Dynamic stability evaluation of trunk accelerations during walking in blind and sighted individuals

BACKGROUND

Dynamic stability is a fundamental goal in standing activities. In this regard, monitoring, analysis, and interventions made to improve stability is a research topic investigated in the biomechanics of human movements. Vision has a major role to play in controlling human movement. Nonetheless, little is known about the effects of visual deprivation, especially from birth on dynamic gait stability.

METHODS

The current study was conducted on 20 congenital blind and 10 sighted people (15-38 years). To evaluate the dynamic stability, descriptive data, harmonic ratio (HR), improved harmonic ratio (iHR), and root mean square (RMS), based on trunk acceleration data were measured in three axes: anteroposterior (AP), vertical (V), and mediolateral (ML) while participants walked an eight-meter straight path.

RESULTS

In the comparison of blind and sighted people (eyes open), standard deviation, HR, iHR, and RMS indices were found to be significantly different in both AP and V directions. All the mentioned parameters were significantly lower in blind than in sighted participants. In the comparison of blind people and sighted ones with closed eyes, changes were observed in the maximum, range, standard deviation, and RMS only in the AP axis. In the comparison between eyes open and closed in sighted people, a significant difference was found only in the harmonic ratio of the vertical axis.

CONCLUSION

Visual deprivation led to a decrease in dynamic stability parameters in the AP and V axes. Even the movement of sighted people in unchallenged conditions is dependent on visual information.

Respiratory Function Assessment through Kinematic Analysis of Chest Wall Movements: Effects of Position and Gender

Background

The effect of position and gender on chest movements and respiratory volumes is controversial and investigated in only a few studies.

Objective

This study aimed to investigate the effects of position and gender on the breathing pattern during four different positions in healthy individuals.

Material and Methods

In this cross-sectional study, twenty-eight (14 males, 14 females) healthy individuals participated aged 20-45 years. The optoelectronic plethysmography (OEP) method was used for the three-dimensional evaluation of chest wall motions and the compartmental analysis of the breathing pattern in supine, sitting, standing, and active straight leg raised (ASLR) positions. Volume changes in different parts of the chest wall were also measured.

Results

Position affected total and compartmental respiratory volumes in both genders. Respiratory volumes decreased in the supine position compared to sitting and standing. Total and abdominal respiratory volumes also decreased in females when comparing supine positions with the ASLR. A higher pulmonary rib cage contribution was identified in females, and males exhibited higher abdominal rib cage volume compared with females.

Conclusion

The breathing pattern was affected by position and gender, and the respiratory volumes increased in more upright positions, perhaps due to a greater gravitational load. The ASLR decreases the respiratory volume, which is probably due to increased postural demand.

Evaluation of Contralateral Limb Cross Education and High-Frequency Repetitive Transcranial Magnetic Stimulation on Functional Indices of the Affected Upper Limb in Subacute Phase of Stroke

Background

Stroke is one of the causes of long-term morbidity. Despite rehabilitation strategies, most survivors live with motor deficits in the upper limbs.

Objectives

The aim of the study was to compare the effect of contralateral cross education (CE) and high-frequency repetitive magnetic stimulation (HF-rTMS) on the function of upper extremity in subacute phase of stroke.

Methods

Forty patients were randomly assigned into 4 groups. Group "A" received physical therapy (PT) for 10 sessions, 3 times per week. Group "B" received PT and HF-rTMS as follows: stimulation of 20 Hz for 5 s, intertrain interval for 50 s, 20 trains, 2000 pulses at 90% resting motor threshold, and conventional PT. Group "C" was treated with CE and PT. In group "D," HF-rTMS, CE, and PT were administered.

Results

Significant differences were found in the Fugl-Meyer scale between "A" and "C" (P = 0.01), "A" and "D" (P = 0.02), and "B" and "C" groups (P = 0.01). In the box-block test, there were significant differences between "A" and "B" (P = 0.01), "A" and "C" (P < 0.001), "B" and "D" (P = 0.001), and "B" and "C" groups (P = 0.01). Statistical differences were observed in grip strength between "A" and "B" (P = 0.01) and "A" and "C" groups (P = 0.02).

Conclusions

It is suggested that clinicians select the therapeutic methods in line with their expected goal. When the goal is to improve upper extremity function, CE+PT could be more effective than HF-rTMS+PT. Also, CE+PT and HF-rTMS+PT were more effective than CE+HF-rTMS+PT at improving grip strength. Therefore, combining several methods would not always lead to better results.

Knee Extension Exercise Effects on Physiological and Psychophysical Performance: Normal Weight Versus Obese Office Workers

BACKGROUND

Knee extension exercise is useful and practical for obese and overweight people as this form of exercise is effective in minimizing body weight loading on joints and improving the body's physiological function. This study aimed to compare the physiological and psychophysical parameters of office workers while computer-based working in an active workstation equipped with an active footrest (AFR) prototype with a mechanism for performing knee extension exercises in a sitting position, and also to compare the physiological and psychophysical parameters among normal-weight and obese office workers.

METHODS

In this quasi-experimental study, the physiological parameters of heart rate (HR) and energy expenditure (EE) (measured with the Fitbit Charge HR smartwatch) were measured in two cross-over random sessions for 32 office workers (16 normal-weight and 16 obese) aged 28 to 50 years (M = 42.72, standard deviation [SD] = 4.37) while performing office tasks in sitting and active workstations (equipped with AFR). Perceived physical exertion, comfort, fatigue, and liking were also measured by rating the participants.

FINDINGS

Short-term activity of the participants with AFR performing computer tasks significantly improved physiological and psychophysical parameters compared with the participants in sitting workstations. However, there was no significant difference in the effect of AFR on physiological and psychophysical parameters between normal-weight and obese participants.

CONCLUSIONS/APPLICATION TO PRACTICE

Given the significant increase in EE and HR resulting from exercise with AFR compared with the conventional workstation, the use of AFR can help office workers achieve the minimum standard of physical activity at their workplace.

The hip joint mobilization with movement technique improves muscle activity, postural stability, functional and dynamic balance in hemiplegia secondary to chronic stroke: a blinded randomized controlled trial

BACKGROUND

People with stroke generally experience abnormal muscle activity and develop balance disorder. Based on the important role of the proximal joints of the lower extremity in balance maintenance, hip joint mobilization with movement technique can be applied to enhance normal joint arthrokinematics. Therefore, the present study aimed to investigate the effectiveness of hip joint mobilization with movement technique on stroke patients' muscle activity and balance.

METHODS

Twenty patients aged between 35 and 65 years old with chronic stroke were randomly assigned either to an experimental group (n = 10) or to a control group (n = 10). Both groups participated in a 30-minute conventional physiotherapy session 3 times per week for 4 weeks. The experimental group received an additional 30-minute's session of hip joint mobilization with movement technique on the affected limb. The muscle activity, berg balance scale, time up and go, and postural stability were measured at baseline, 1-day and 2-week follow-up by a blinded assessor.

RESULTS

The experimental group showed a significant improvement in berg balance scale, time up and go, and postural stability (p ≤ 0.05). The rectus femoris, tibialis anterior, biceps femoris, and medial gastrocnemius muscles' activations of the affected limb during static balance test markedly changed along with the biceps femoris, erector spine, rectus femoris, and tibialis anterior muscles during dynamic balance test after hip joint mobilization with movement technique. The mean onset time of rectus abdominus, erector Spine, rectus femoris, and tibialis anterior muscles activity significantly decreased in the affected limb after hip joint mobilization with movement technique compared to the control group (p ≤ 0.05).

CONCLUSIONS

The results of the present study suggest that a combination of hip joint mobilization with movement technique and conventional physiotherapy could improve muscle activity and balance among chronic stroke patients.

TRIAL REGISTRATION NUMBER

The study was registered in the Iranian Registry of Clinical Trials (No; IRCT20200613047759N1). Registration date: 2/08/2020.

Assessment of the effects of white cane variables on step symmetry of blind individuals

BACKGROUND

Step symmetry is an important feature of human gait and is often regarded as a key index of healthy individuals' walking. This study evaluated the effects of height, white cane technique, and cane tip on symmetrical gait in blind individuals.

MATERIALS AND METHODS

Twenty blind and ten sighted subjects, aged 15-38 years, participated in this study. The harmonic ratio (HR) and improved HR (iHR) were measured by trunk accelerometer as gait symmetry index in three axes: anteroposterior (AP), vertical, and mediolateral of the body. These parameters were measured in the sighted group in open-eye conditions and in the blind group in five experimental conditions with different two heights (standard and long), two tips (pencil and roller), and two techniques (two-point touch and constant contact) of white cane when they walked in the 6-m path.

RESULTS

There was a significant difference between HR and iHR of the blind and sighted group, which indicates a significant reduction of symmetry loss in the blind group. Among the five different conditions studied in the group of blind people, an increase was observed in the HR and the iHR on the AP axis during the application of a standard cane with a roller tip, which indicated an increase in symmetry.

CONCLUSION

Based on the results, a long cane with a pencil tip and a standard cane with a roller tip in the constant contact technique can increase step symmetry.

The Use of Cluster Analysis by Partitioning around Medoids (PAM) to Examine the Heterogeneity of Patients with Low Back Pain within Subgroups of the Treatment Based Classification System

Background

Current evidence in low back pain (LBP) focuses on population averages and traditional multivariate analyses to find the significant difference between variables. Such a focus actively obscured the heterogeneity and increased errors. Cluster analysis (CA) addresses the mentioned shortcomings by calculating the degree of similarity among the relevant variables of the different objects.

Objective

This study aims to evaluate the agreement between the treatment-based classification (TBC) system and the equivalent 3 cluster typology created by partitioning around medoids (PAM) analysis.

Material and Methods

In this cross-sectional study, a convenient sample of 90 patients with low back pain (50 males and 40 females) aged 20 to 65 years was included in the study. The patients were selected based on the 21 criteria of 2007 TBC system. An equivalent 3 cluster typology (C3) was applied using PAM method. Cohen's Kappa was run to determine if there was agreement between the TBC system and the equivalent C3 typology.

Results

PAM analysis revealed the evidence of clustering for a C3 cluster typology with average Silhouette widths of 0.12. Cohen's Kappa revealed fair agreement between the TBC system and C3 cluster typology (Percent of agreement 61%, Kappa=0.36, P<0.001). Selected criteria by PAM analysis were different with original TBC system.

Conclusion

Higher probability of chance agreement was observed between two classification methods. Significant inhomogeneity was observed in subgroups of the 2007 TBC system.

Development of an Ergonomic, Portable, Climber-Propelled Date Tree Climbing Device

In the most of main date fruit producer regions, including Iran, date palm crown access operation is still performed traditionally. The date plantation workers need to climb date trees. This may cause an unsafe condition, which increases the risk of fall from height. It is also associated with ergonomic and health problems. The present study aimed to develop a date tree climber device (DTCD) covering all aspects of safety, ergonomics and efficiency. A primary model of the DTCD was structured and modified based on a review of existing devices, a field investigation and an unstructured interview with 20 farmworkers. Participants rated their comfort, perceived pain and discomfort as well as exertion levels when using the DTCD compared to a traditional device (Parband). In total, eight key elements were suggested for the desired device. More than 60% of the participants reported that the DTCD was comfortable/very comfortable compared to Parband. Additionally, DTCD could significantly reduce the pain and discomfort of the back (p < .001), knees (p = .001) and Ankles/feet (p = .01). However, no significant difference was found between devices when the physical exertion was compared through Borg's RPE scale and heart rate analysis. The results of regression analysis showed that the DTCD users perceived lower exertion as the body weight increased (β = -0.18, p = .013). The signs of musculoskeletal disorders, pain and discomfort were strongly reduced among DTCD users and safety aspects improved, generally by reducing discomfort and physical exertion.

Recommended maximum holding time of common static sitting postures of office workers

PURPOSE

A posture maintained for a long period can be harmful to the health of office workers. This study aimed to estimate the recommended ergonomic duration for maintaining different sitting postures.

MATERIALS AND METHODS

Forty healthy male and female students participated in this experiment designed to measure perceived discomfort caused by maintaining common static sitting postures of office workers in a simple ergonomic setup for four minutes. The Borg CR10 scale was given to the participants to assess the discomfort in different body parts, before and after each experiment. Based on the mean group discomfort level of 2, the recommended holding time of each posture was estimated.

RESULTS

The recommended holding time and its discomfort score for each studied posture were tabulated. The shortest holding time of a posture was obtained for the moderate neck flexion (1.61 minutes), and the longest holding time was obtained for legs posture with 90-degree knee flexion (6.45 minutes).

CONCLUSIONS

The recommended holding time in this study may help to assess the risk of Musculoskeletal Disorders in office workers and train the individuals involved in office tasks in proper sitting behavior.

Investigating the effect of background music on cognitive and skill performance: A cross-sectional study

BACKGROUND: Existing studies on the impact of background music in the workplace have reported varying results, from improving production and performance to being known as an annoying factor. Given the lack of evidence of the background music influence on the cognitive factors in the work place in previous studies and the lack of study on the effect of background music on skill performance when gender and personality type is considered, research in this area seems necessary. OBJECTIVE: The purpose of the present study is to investigate the influence of background music on cognitive and skill performance in the work place with regard to gender and personality type. METHODS: This study was conducted with the participation of 52 students (26 males and 26 females) aged between 18–30 years old. Sustained attention, working memory, fine finger and gross manual dexterity skills and personality type were assessed. Participants were randomly tested once when being exposed to classical instrumental music and once again when faced with complete silence RESULTS: Playing background music improved students working memory but had no significant effect on sustained attention. Music also improved skill performance.Overall, memory performance and fine finger dexterity were found significantly better in extroverts when compared to introverts during playing background music. CONCLUSION: Background music improves working memory and speeds up performance in skill tasks, however the role of personality type in influencing background music on cognitive and skill performance needs further investigation.

Effects of an ergonomic intervention program based on the PRECEDE-PROCEED model for reducing work-related health problems and exposure risks among emergency medical dispatchers

OBJECTIVE

To evaluate the effectiveness of an ergonomic intervention program based on the PRECEDE-PROCEED model in terms of improving exposure risks and work-related health problems in emergency medical dispatchers.

METHODS

This quasi-experimental study used an interrupted time series design. Participants were 55 employees working in an Emergency Medical Communications Center in Iran. The intervention program was based on the PRECEDE-PROCEED model and included five face-to-face training sessions and installing auxiliary equipment according to best ergonomic principles. Direct observations of the emergency medical dispatchers' working postures using the Rapid Office Strain Assessment and a survey which included a modified Nordic Questionnaire, Work Ability Score, Visual Fatigue Questionnaire, and a Behavioral Factors Questionnaire were used at three time points: baseline, 1 month post-intervention, and 3 months post-intervention.

RESULTS

The modified Nordic Questionnaire showed significant reductions in pain intensity scores for neck, lower back, knee and ankle after the ergonomic intervention program. In addition, there were considerable post-training improvements in behavioral factors (knowledge and enabling factors) and working postures. No significant changes were observed in Work Ability Scores, or visual symptoms.

CONCLUSIONS

An ergonomic intervention program based on a systematic framework such as the PRECEDE-PROCEED model and on-site interventions can be effective in improving and enhancing the working conditions of emergency medical dispatchers. Therefore, it is suggested that ergonomic interventions be implemented based on standard and valid behavioral change models such as PRECEDE-PROCEED model in other work environments in which musculoskeletal pain and digital eye strain are common.

Investigation of office workers' sitting behaviors in an ergonomically adjusted workstation

Objectives. Common ergonomic office workstations are designed for a few optimum postures. Nonetheless, sitting is a dynamic activity and the ideal sitting posture is rarely maintained in practice. Therefore, the present study aimed to investigate the sitting behavior of office workers in an actual working environment using ergonomically adjusted workstations to examine whether they promote maintaining appropriate sitting postures. Methods. Sitting behaviors (frequency of postures and position changes in different body parts) were explored among 26 office workers during a 60-min sitting duration, using the posture recording and classification method developed by Graf et al. The rapid upper limb assessment (RULA) method was also used to assess postural load. Then, the results of the RULA method were compared with the results from investigating the sitting behavior of office workers. Results. Common ergonomic workstations were effective in eliminating some awkward postures. However, some important risk factors such as holding postures with an inappropriate lumbar spine curve (86% of the observations) and maintaining a posture for a long time (for 7-12 min) were observed in the participants' sitting behaviors, while they were neglected in the RULA method. Conclusions. The common ergonomic workstations could not guarantee the users' appropriate sitting behaviors.

Designing and Usability testing of a New Prototype Active Footrest for Knee Extension Exercise Among Office Workers

OBJECTIVES

The active factor along with light exercise can reduce static muscle work and increase muscle flexibility and endurance. Accordingly, this study aimed to design and prototype a new active footrest, implemented in conventional sitting workstations and to test its usability among office workers.

METHODS

The steps taken to design and prototype the active footrest were a) selection of an exercise appropriate for goals of ergonomic interventions, b) idea development, c) selection of the best conceptual design, d) design with SOLIDWORKS version 2016 software, and e) fabrication of a prototype. Afterward, the usability of the active footrest prototype was assessed among 20 office workers (10 females) using field data by the System Usability Scale.

RESULTS

Upon the completion of the design steps, the active footrest prototype was prototyped by taking into account design criteria (e.g. functionality, inclusive design, easy application, and reduction of additional body movement), anthropometric data and mechanical properties. The participants rated the usability of the active workstation as 89 ± 8.21 (out of 100) and indicating good usability results.

CONCLUSION

In this study, an active footrest was designed and prototyped to perform knee extension exercise with the capability of being implemented in conventional sitting workstations.

Effects of 8 Weeks of Balance Training, Virtual Reality Training, and Combined Exercise on Lower Limb Muscle Strength, Balance, and Functional Mobility Among Older Men: A Randomized Controlled Trial

BACKGROUND

Poor muscle strength, balance, and functional mobility have predicted falls in older adults. Fall prevention guidelines recommend highly challenging balance training modes to decrease falls; however, it is unclear whether certain modes are more effective. The purpose of this study was to determine whether traditional balance training (BT), virtual reality balance training (VR), or combined exercise (MIX) relative to a waitlist control group (CON) would provoke greater improvements in strength, balance, and functional mobility as falls risk factor proxies for falls in older men.

HYPOTHESIS

We hypothesized that 8 weeks of MIX will provoke the greatest improvements in falls risk factors, followed by similar improvements after BT and VR, relative to the CON.

STUDY DESIGN

Single-blinded randomized controlled trial NCT02778841 (ClinicalTrials.gov identifier).

LEVEL OF EVIDENCE

Level 2.

METHODS

In total, 64 community-dwelling older men (age 71.8 ± 6.09 years) were randomly assigned into BT, VR, MIX, and CON groups and tested at baseline and at the 8-week follow-up. The training groups exercised for 40 minutes, 3 times per week, for 8 weeks. Isokinetic quadriceps and hamstrings strength on the dominant and nondominant legs were primary outcomes measured by the Biodex Isokinetic Dynamometer. Secondary outcomes included 1-legged stance on firm and foam surfaces, tandem stance, the timed-up-and-go, and gait speed. Separate one-way analyses of covariance between groups were conducted for each outcome using baseline scores as covariates.

RESULTS

(1) MIX elicited greater improvements in strength, balance, and functional mobility relative to BT, VR, and CON; (2) VR exhibited better balance and functional mobility relative to BT and CON; and (3) BT demonstrated better balance and functional mobility relative to CON.

CONCLUSION

The moderate to large effect sizes in strength and large effect sizes for balance and functional mobility underline that MIX is an effective method to improve falls risk among older adults.

CLINICAL RELEVANCE

This study forms the basis for a larger trial powered for falls.

High-brightness LWIR quantum cascade lasers

Long-wave infrared (LWIR, λ≈8-12µm) quantum cascade lasers (QCLs) are drawing increasing interest, as they provide the possibility of long-distance transmission of light through the atmosphere owing to the reduced water absorption. However, their development has been lagging behind the shorter wavelength QCLs due to much bigger technological challenges. In this Letter, through band structure engineering based on a highly localized diagonal laser transition strategy and out-coupler design using an electrically isolated taper structure, we demonstrate high beam-quality single-mode LWIR QCLs with high-brightness (2.0MWcm^-2sr^-1 for λ≈10µm, 2.2MWcm^-2sr^-1 for λ≈9µm, 5.0MWcm^-2sr^-1 for λ≈8µm) light extraction from a single facet in continuous-wave operation at 15°C. These results mark an important milestone in exploring the lighting capability of inter-sub-band semiconductor lasers in the LWIR spectral range.

Development and validation of a Nurse Station Ergonomics Assessment (NSEA) tool

Background

Nurse stations are one of the primary units for supporting effective functioning of any hospital. They are important working environments that demand adherence to known ergonomic principles for the well-being of both staff and patients. The aim of this study was to develop a psychometrically tested tool for the assessment of the ergonomic conditions of nurse workstations in hospitals.

Methods

Ten hospitals, with a total of 133 nurse stations participated in this mixed-methods research. The domains and items of the tool were developed based on a literature review, an experts’ panel, and interviews with nurses.

Results

The final nurse station ergonomic assessment (NSEA) tool has good psychometric properties. Validity was assessed by face validity and content validity. Reliability was evaluated using inter-rater agreement and test-retest reliability analyses with a four-week interval between assessments. The NSEA is comprised of 64 items across eight domains: layout and location (7 items), workspace (11 items), security-safety (5 items), environmental conditions (8 items), counter (8 items), chair (13 items), desk (9 items), and monitor (3 items).

Conclusions

The NSEA adds to the literature a tool for managers to ensure they comply with legal requirements and support best practice for those working on hospital wards. The NSEA can be used to identify challenges for healthcare professionals who use nurse stations and support the execution of targeted interventions to improve human-environment interactions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12912-021-00600-8.

Proposing a set of ethical guidelines for Iranian physiotherapists: results of a modified Delphi technique

The code of ethical conduct for physiotherapy services must be compatible with the local culture. The ethical guidelines proposed here were developed through a literature review, focus group discussions, and finally a modified Delphi technique to achieve consensus after the data were analysed. At first, the collection of different ethical codes yielded 132 items. In the second stage, repetitive items were discarded, some new items were added, and the various codes were categorised into three domains. Overall, 175 items were considered in the Delphi stage. Subsequently, the items were reduced to 134 in total - 59 in the treatment domain, 41 in research, and 34 in the education domain. The resulting code of ethics will support patients, researchers, students, and teachers in the field of physical therapy with sensitivity to current Iranian legislation and culture.

The Effect of High-Frequency Repetitive Transcranial Magnetic Stimulation on Functional Indices of Affected Upper Limb in Patients with Subacute Stroke

Background:

Repetitive transcranial magnetic stimulation (rTMS) is a novel technique that may improve recovery in patients with stoke, but the role of rTMS as an applied and practical treatment modality for stroke rehabilitation has not been established yet.

Objective:

This study was conducted to determine the effects of a rehabilitation program (RP) in conjunction with rTMS on functional indices of the paretic upper limb in the subacute phase of stroke.

Material and Methods:

In this experimental study, twenty patients in the subacute phase of stroke were randomly assigned into two groups: The high frequency rTMS (HF-rTMS) in conjunction with RP (experimental group), and the RP group (control group). The experimental group received 10 sessions of 20 Hz rTMS on the affected primary motor cortex and the other group received 10 sessions of RP. In experimental group, RP for the paretic hand was conducted following rTMS session. Box and block test (BBT), Fugl-Meyer Motor Assessment for upper limb (FMA-UL), grip strength and pinch strength were used to assess motor function before the first session and after the last session of treatment.

Results:

Significant improvement in BBT, FMA-UL, grip strength and pinch strength was observed in both groups. Improvement of BBT and grip strength was significantly greater in the experimental group rather than the control group (p<0.05). FMA-UL score and the pinch strength were greater in the experimental group, although the differences were not statistically significant.

Conclusion:

HF-rTMS in conjunction with RP is effective to improve the function of upper limb. It seems HF-rTMS is a novel feasible and safe technique for hemiparesis patients in the subacute phase of stroke.

Kinematic cluster analysis of the crouch gait pattern in children with spastic diplegic cerebral palsy using sparse K-means method

BACKGROUND

Crouch gait pattern is a common gait pattern in children with diplegic cerebral palsy with excessive knee flexion throughout stance phase. Few studies have grouped this pattern of gait and usually have examined only the features of gait in the sagittal plane and mostly lower extremities without considering pelvis and trunk behavior. Studies usually categorize the gait pattern according to important variables from the researcher's point of view. Sparse K-means is high dimensional clustering methods that perform clustering and variable selection simultaneously even with low sample size and large number of variables. Our aim was to define existing clusters of crouch gait pattern in children with spastic diplegic cerebral palsy.

METHODS

Cluster analysis was applied on the lower extremity, pelvis and trunk gait kinematics data of 64 limbs of children with crouch gait pattern and 64 limbs of typically developing children. Eighty-nine kinematic variables were used as input variables for clustering.

FINDINGS

Four clusters of crouch gait pattern were defined. Sparse K-means identified influential variables and identified the knee and hip flexion as a major factor in clustering. Kinematic of the trunk, pelvis and ankle was determined in each cluster. Trunk and pelvis kinematic features were strongly correlated with the knee and hip joint flexion severity.

INTERPRETATION

Obtained clusters were confirmed observationally. With increasing knee flexion, the kinematic of the trunk and pelvis were further away from the patterns of typically developing individuals. The clusters ranking appear to be reasonable based on the crouch severity.

A New Clustering Method for Knee Movement Impairments using Partitioning Around Medoids Model

Background:

The movement system impairment (MSI) model is a clinical model that can be used for the classification, diagnosis, and treatment of knee impairments. By using the partitioning around medoids (PAM) clustering method, patients can be easily clustered in homogeneous groups through the determination of the most discriminative variables. The present study aimed to reduce the number of clinical examination variables, determine the important variables, and simplify the MSI model using the PAM clustering method.

Methods:

The present cross-sectional study was performed in Shiraz, Iran, during February-December 2018. A total of 209 patients with knee pain were recruited. Patients’ knee, femoral and tibial movement impairments, and the perceived pain level were examined in quiet standing, sitting, walking, partial squatting, single-leg stance (both sides), sit-to-stand transfer, and stair ambulation. The tests were repeated after correction for impairments. Both the pain pattern and the types of impairment were subsequently used in the PAM clustering analysis.

Results:

PAM clustering analysis categorized the patients in two main clusters (valgus and non-valgus) based on the presence or absence of valgus impairment. Secondary analysis of the valgus cluster identified two sub-clusters based on the presence of hypomobility. Analysis of the non-valgus cluster showed four sub-clusters with different characteristics. PAM clustering organized important variables in each analysis and showed that only 23 out of the 41 variables were essential in the sub-clustering of patients with knee pain.

Conclusion:

A new direct knee examination method is introduced for the organization of important discriminative tests, which requires fewer clinical examination variables.

Electromechanical rolling whiteboard for improving posture and comfort of users in classrooms

BACKGROUND

The prevalence of musculoskeletal disorders is high among teachers. Poor posture when writing on whiteboards is considered among the important causes of these disorders.

OBJECTIVE

The present study aimed to evaluate an electromechanical rolling whiteboard for educational environments as an ergonomic intervention.

METHODS

Thirty university lecturers volunteered to take part in the study. Participants performed a 5-minute writing task on a regular board and on the newly modified whiteboard in random order. The comfort and effectiveness of the boards and the perceived physical effort and posture of the participants were evaluated and compared by applying the verbal rating scale, Borg's rating of physical exertion scale, and rapid entire body assessment, respectively.

RESULTS

A total of 83.2% of participants reported the new whiteboard to be comfortable or more comfortable to use than the regular whiteboard, and 76.6% of them found the new whiteboard to be higher or much higher in effectiveness and usefulness in comparison with the regular whiteboard. The comfort and posture ratings revealed that exertion was significantly less and posture improved while writing on the new board as compared to its counterpart (p < 0.0001).

CONCLUSION

The new whiteboard increased user comfort, reduced physical effort, and improved posture, hopefully leading to a decreased number of work-related musculoskeletal disorders.

Cognitive and skill performance of individuals at sitting versus standing workstations: a quasi-experimental study

Objectives. This study aimed to assess cognitive and skill performance at sitting and standing workstations among students from Shiraz University of Medical Sciences. Methods. Forty students (20 females and 20 males) participated in this quasi-experimental study. Tests were performed among randomly selected participants over two consecutive days: day 1, the Beck depression inventory and Beck anxiety inventory were used to assess the severity of depression and anxiety in the study participants, respectively, and Raven's general intelligence test was used to measure intelligence quotient; day 2, five performance assessment tests (cognitive performance assessment tests 'n-back', 'Stroop' and 'advanced reaction time'; skill performance assessment tests 'two-arm coordination' and 'Purdue pegboard') were randomly selected and presented to individuals at each workstation (sitting and standing workstations). At the end of each sitting and standing position, the comfort of the workstation was measured using a visual analog scale. Results. No statistically significant difference was shown between sitting and standing positions in terms of 'n-back', 'Stroop', 'advanced reaction time', 'two-arm coordination' and 'Purdue pegboard'. Participants were more comfortable in sitting positions and more easily distracted in standing positions. Conclusions. Sitting and standing positions had no significant effects on participants' cognitive and skill performance.

Room temperature quantum cascade lasers with 22% wall plug efficiency in continuous-wave operation

We report the demonstration of quantum cascade lasers (QCLs) with improved efficiency emitting at a wavelength of 4.9 µm in pulsed and continuous-wave (CW) operation. Based on an established design and guided by simulation, the number of QCL-emitting stages is increased in order to realize a 29.3% wall plug efficiency (WPE) in pulsed operation at room temperature. With proper fabrication and packaging, a 5-mm-long, 8-µm-wide QCL with a buried ridge waveguide is capable of 22% CW WPE and 5.6 W CW output power at room temperature. This corresponds to an extremely high optical density at the output facet of ∼35 MW/cm², without any damage.

Work-related Musculoskeletal Symptoms among Agricultural Workers: A Cross-sectional Study in Iran

Objective: In Iran, as in most developing countries, agriculture is considered a hazardous industry. Musculoskeletal disorders (MSD) have been shown to be the most common occupational injury among farmers. The present study was carried out among agricultural workers of Fars province, Iran to determine the prevalence of musculoskeletal symptoms and to assess working postures and ergonomic working conditions to identify the major risk factors associated with MSD. Methods: This cross-sectional study was conducted on 1501 randomly selected Iranian agricultural workers with at least 1 year of job tenure. Data were collected using demographic/occupational questionnaire, Nordic Musculoskeletal Questionnaire (NMQ), Quick Exposure Check (QEC) technique, and ergonomic working conditions checklist. Results: The mean age of the participants was 41.39 ± 13.64 years. The results of NMQ showed the highest prevalence of MSD symptoms was related to lower back (59.3%), knees (36.9%), and upper back (36.6%). Indeed, the QEC score was high or very high (action levels 3 and 4) in 83.1% of the farmers. Moreover, the ergonomic working conditions checklist revealed that the participants' "working postures" index had the lowest mean, indicating poor ergonomic conditions, while "hand tools" had the highest mean, indicating proper ergonomic conditions. Conclusions: The results demonstrated the high prevalence of MSD symptoms among Iranian agricultural workers. Elimination of harmful working postures was recommended to improve working conditions.

Foot hyperpronation alters lumbopelvic muscle function during the stance phase of gait

BACKGROUND

Although altered muscular control of the lumbopelvic region is one of the main risk factors for the development of low back pain and dysfunction, the influence of abnormal foot posture on lumbopelvic muscular function has not been investigated.

RESEARCH QUESTION

To determine possible functional changes due to hyperpronation in the main muscles that control the lumbopelvic segment.

METHODS

Kinematic and kinetic data were collected from 15 persons with hyperpronated feet and compared to a control group of 15 persons with normally aligned feet during the stance phase of gait. A generic OpenSim musculoskeletal model was scaled for each participant. A computed muscle control approach was used to produce a forward dynamic simulation of walking to determine muscle function.

RESULTS

In the hyperpronation group significantly greater peak forces were observed in the erector spinae, iliopsoas and abdominals compared to controls. The former group showed peak latencies for abdominal muscles during early stance, and for erector spinae muscles during both early and late stance. No significant between-group differences were found in gluteus maximus muscle activation in the stance phase of gait.

SIGNIFICANCE

Abnormal foot pronation can change the timing and intensity of lumbopelvic muscle activation. These changes may predispose people to develop secondary dysfunctions.

The effects of playing music during surgery on the performance of the surgical team: A systematic review

BACKGROUND

Music is an economical, advantageous and reliable means of reducing stress or stress-related problems.

OBJECTIVE

The present study aims to evaluate the effects of playing music during surgery on the performance of the surgical team through a systematic review of published studies.

METHODS

The relevant databases of Medline/PubMed, Scopus and Science Direct were searched up to July 2018 to find related articles. The comprehensive literature search was reduced to 19 articles that met inclusion criteria.

RESULTS

The articles comprised 13 studies and reported on the positive effects of music on the performance of the surgical team. The effects included a more relaxing and pleasant environment, more accurate and precise performance of tasks, a decrease in the mental workload and task completion time, increased situation awareness, a reduction in stress and anxiety and improved memory consolidation. Five studies reported on the negative effects of music during surgery as being a negative impact on task completion, poor auditory performance and increased likelihood of having to repeat requests. The remaining article reported no significant differences between groups compared.

CONCLUSIONS

Most studies reported positive effects of music on the surgical team during surgery. These results indicate that it may be possible to improve the performance of the surgical team during surgery while playing controlled music.

Ergonomic Assessment of Exposure to Musculoskeletal Disorders Risk Factors among Dentists of Shiraz, Iran

STATEMENT OF THE PROBLEM

In dental profession, exposure to risk factors of musculoskeletal disorders raises the probability of musculoskeletal injuries in different parts of the body.

PURPOSE

This study aimed to determine the prevalence of musculoskeletal disorders (MSDs), assess the risk of MSDs, and determine the risk factors of musculoskeletal injuries among dentists of Shiraz city.

MATERIALS AND METHOD

In this cross-sectional study, 136 dentists of Shiraz city were randomly selected. The data were collected by Nordic musculoskeletal questionnaire (NMQ). Ergonomic assessment of exposure to MSDs risk factors was carried out by assessment of repetitive tasks (ART) technique. In order to assess dentists' exposure to MSDS risk factors, the method of ART (ART) was adopted. This method has been designed to assess the risk of those tasks that required repetitive motion of upper limb, especially hands and arms. The collected data were analyzed through SPSS software (version. 22). The study regarded p value of <0.05 as significance level.

RESULTS

Mean age of the participants was 35.6±8.7 years. The 12-month prevalence of MSDs among dentists was 91.9%. The results suggested that risk of MSDs among dentists was high. The results of logistic regression analyses indicated that female gender (p< 0.001) and exercise for less than 3 hours per week (p= 0.001) played significant roles in occurrence of MSDs among the study population. Additionally, the results of ART assessment revealed that risk of MSDs in the right side of the subjects' bodies was higher.

CONCLUSION

The findings showed that risk of MSDs and their prevalence in the study population was high with significant association. Based on the results of regression modeling, it seems necessary to pay proper attention to factors associated with MSDs to develop ergonomic solutions to reduce or eliminate musculoskeletal injuries.

Trunk Kinematic Analysis during Gait in Cerebral Palsy Children with Crouch Gait Pattern

BACKGROUND

Deficits in upper body movement have received little attention during gait in cerebral palsy (CP) children with crouch gait pattern (CGP).

OBJECTIVE

Purpose of this research is to describe the correlation of trunk movement with the excessive knee flexion and ankle kinematic in CP children with CGP.

MATERIAL AND METHODS

Gait analysis data from 57 limbs of diplegic CP children with CGP and 26 limbs of normal children was gathered. Kinematic parameters of trunk in relation to the pelvis were extracted in the sagittal, transverse and coronal planes. CP limbs were clustered using K-means cluster analysis according to the knee flexion angle at initial contact and the mean position of ankle joint during the stance phase of gait cycle, to three clusters. Pearson correlation coefficient between knee, ankle and trunk kinematic variables was assessed. Differences between clusters were analyzed with Kruskal-Wallis and post hoc tests.

RESULTS

The results revealed: 1) crouch clusters had more trunk obliquity and rotation mean position than normal; 2) the range of motions of the trunk obliquity and rotation exhibited significant differences between crouch and normal clusters; 3) the level of excessive knee flexion had positive correlation with the trunk mean position in all planes; 4) the ankle kinematic at stance phase was associated with the trunk mean position in all planes.

CONCLUSION

The results revealed the trunk mean position is correlated with the excessive knee flexion severity and ankle joint kinematic in CP children with CGP.

Correlations between core muscle geometry, pain intensity, functional disability and postural balance in patients with nonspecific mechanical low back pain

Patients with low back pain (LBP) have reduced core muscle geometry and impaired postural balance. Impaired trunk control was shown to be associated with poor balance and limited functional mobility in these patients. However, the relationship between muscle geometry and postural balance is unclear. This study aimed to determine the correlation of core muscle geometry with pain intensity, functional disability and postural balance in patients with chronic nonspecific mechanical LBP. Thirty patients aged 20-50 years were enrolled. Ultrasound imaging was used to assess their muscle geometry. The participants completed a numerical rating scale (NRS) for pain severity, and the Persian version of the Roland-Morris Disability Questionnaire (PRMDQ). To estimate static balance, they were asked to perform the single leg stance test. Dynamic balance was assessed with the Y-balance test. Significant correlations were found between NRS scores and bilateral multifidus cross-sectional area during rest (r ≥ - 0.31, P ≤ 0.04) and contraction (r ≥ - 0.37, P ≤ 0.02). NRS scores correlated significantly with bilateral multifidus thickness during rest (r ≥ - 0.31, P ≤ 0.04) and contraction (r ≥ - 0.28, P ≤ 0.04). Significant correlations were also observed for PRMDQ scores with thickness (r ≥ - 0.35, P = 0.04) and cross-sectional area of the multifidus muscles (r ≥ - 0.33, P = 0.04) bilaterally during contraction. A significant correlation was found between Y-balance scores and right abdominal muscle thickness during rest and contraction (r ≥ 0.34, P ≤ 0.04). Core muscle geometry correlated with pain, functional disability indices and dynamic balance in these patients.

The force applied to the knee extensor mechanism differs between flat-footed and normal subjects during walking

Study aim: There is a lack of evidence to show the presence or absence of a relationship between foot morphology and changes of the force applied to the knee extensor mechanism. The purpose of this study was to examine whether the type of foot is a determining factor in the force applied to the extensor mechanism during walking. Materials and methods: Twenty female subjects (18-30 years), 10 with neutrally aligned feet and 10 with functional flat foot, participated in this study. Data were collected by employing a three dimensional motion capture system and a force platform, while the subjects were walking at their preferred speed. Knee extensor mechanism force was measured at sub-phases of gait (heel strike and toe-off). Results: A significant interaction was found between groups and sub-phases of gait for all the variables tested. The subjects with flat foot exhibited a significantly higher extensor mechanism force at toe-off compared to the control group (p < 0.05). Conclusion: It can be concluded that subtalar hyper-pronation would increase the force applied to the knee extensor mecha­nism at toe-off, through increasing the knee sagittal angle, net external flexion moment and extensor mechanism moment arm. Therefore it may increase the possibility of musculoskeletal injuries

Correlation between Trunk-Pelvis Inter-Segmental Coordination Parameters during Walking and Disability Level in Chronic Low Back Pain Patients

BACKGROUND

Chronic low back pain (CLBP) disability has been particularly frustrating because its treatment has been a great therapeutic challenge. Disability has been suggested to depend on different factors that should be found and considered in the medical management. The inter-segmental coordination is often impaired in CLBP subjects; however, to the best of our knowledge, there is no evidence about the relationship between the existence of coordination problems and disability in CLBP patients.

OBJECTIVE

To evaluate the correlation between sagittal plane trunk-pelvis inter-segmental coordination parameters during walking and disability level in CLBP patients.

METHODS

Kinematic data were collected from 16 non-specific CLBP (18-40 years) volunteers during walking. Sagittal plane time-normalized segmental angles and velocities were used to calculate continuous relative phase for each data point. Coordination parameters, mean absolute relative phase (MARP) and deviation phase (DP) were derived to quantify the trunk-pelvis coordination pattern and variability during gait cycles, respectively. The disability level was quantified through Oswestry Disability Index (ODI) questionnaire. Pearson correlation coefficient was used to find the probable correlation between coordination parameters and disability level.

RESULTS

The analysis demonstrated a significant correlation between sagittal plane MARP or DP and disability level (%ODI) in CLBP subjects during walking (r= -0.806 P<0.001 and r= -0.856, P<0.001, respectively).

CONCLUSION

This study demonstrated that the lower the MARP (more in-phase pattern) and DP (less variable pattern) in the CLBP subjects, the more disability existing in such patients. The results suggest that clinicians should look beyond pain management when prescribing rehabilitation for CLBP and consider interventions that target segmental coordination improvement to manage CLBP induced disability.

The influence of foot hyperpronation on pelvic biomechanics during stance phase of the gait: A biomechanical simulation study

Despite the theoretical link between foot hyperpronation and biomechanical dysfunction of the pelvis, the literature lacks evidence that confirms this assumption in truly hyperpronated feet subjects during gait. Changes in the kinematic pattern of the pelvic segment were assessed in 15 persons with hyperpronated feet and compared to a control group of 15 persons with normally aligned feet during the stance phase of gait based on biomechanical musculoskeletal simulation. Kinematic and kinetic data were collected while participants walked at a comfortable self-selected speed. A generic OpenSim musculoskeletal model with 23 degrees of freedom and 92 muscles was scaled for each participant. OpenSim inverse kinematic analysis was applied to calculate segment angles in the sagittal, frontal and horizontal planes. Principal component analysis was employed as a data reduction technique, as well as a computational tool to obtain principal component scores. Independent-sample t-test was used to detect group differences. The difference between groups in scores for the first principal component in the sagittal plane was statistically significant (p = 0.01; effect size = 1.06), but differences between principal component scores in the frontal and horizontal planes were not significant. The hyperpronation group had greater anterior pelvic tilt during 20%–80% of the stance phase. In conclusion, in persons with hyperpronation we studied the role of the pelvic segment was mainly to maintain postural balance in the sagittal plane by increasing anterior pelvic inclination. Since anterior pelvic tilt may be associated with low back symptoms, the evaluation of foot posture should be considered in assessing the patients with low back and pelvic dysfunction.

Posture and discomfort assessment in computer users while using touch screen device as compared with mouse-keyboard and touch pad-keyboard

BACKGROUND

Touch screen computers require significant arm and hand movements. This can result to body discomfort and biomechanical load in users.

OBJECTIVES

This study was carried out to examine posture and users' discomfort while using touch screen device as compared with mouse-keyboard and touch pad-keyboard.

METHODS

Twenty three (23) students participated in this experimental study. The subjects completed pre-defined tasks in three 15 min trials by means of touch screen, touch pad-keyboard and mouse-keyboard as input devices. Postural angles were measured by Qualisys motion capture system. Body discomfort was assessed by a 10-cm visual analog scale. Rating scale was employed to assess the perception of subjects on the posture of body parts while utilizing the three devices.

RESULTS

There was no significant difference in head inclination when using the three types of devices. Nevertheless, the mean of neck (p = 0.005) and trunk (p < 0.0001) inclinations as well as arm angle (p < 0.0001) while using touch screen, differed significantly from the two other devices and were more deviated from neutral posture. The type of input device was found to have significant effect on the right shoulder (p = 0.017), right elbow (p = 0.031), right wrist/hand (p = 0.004) and whole body discomfort (p = 0.026). Touch screen caused more discomfort in the mentioned regions when compared to the other two devices. Friedman test showed that differences of mean ratings for perceived shoulder and elbow postures in the 3 trials were significant (p = 0.005 and p = 0.011, respectively). Touch screen was the most unfavorable input device based on the subjects' judgment.

CONCLUSION

Touch screen caused more deviated postural angles, increased body discomfort and unfavorable postures.

Designing, prototype making and evaluating a mechanical aid device for patient transfer between bed and stretcher

INTRODUCTION

The present study aimed at designing, prototype making and evaluating a new assistive device to improve patient transfer conditions.

METHODS

A new aid device for patient transfer was designed and its prototype was made. Comfort and perceived physical exertion of users and stability and applicability of the device were examined. The test subjects included 37 healthcare workers from a hospital with patient transfer experience. The data collection tools consisted of visual analog scales (VAS) and Borg's rating physical effort scale. The rapid entire body assessment (REBA) method was applied to evaluate working posture.

RESULTS

The results showed that in 70% of the wards, patient transfer was performed manually more than five times per shift. While using the newly designed device, the mean (SD) of the users' comfort, and the clients' comfort and safety, was measured as 8.59 (0.87), 8.46 (0.92) and 8.67 (0.71), respectively, as reported by VAS. The results revealed a significant reduction in the users' rating of perceived exertion (p < 0.001). Additionally, the REBA score was lower in mechanical transfer.

CONCLUSION

The new assistive device increased the users' and the clients' comfort, reduced the users' physical exertion and improved working postures.

A new method for calculating saddle seat height with an emphasis on optimal posture based on trigonometric relations

INTRODUCTION

Based on the literature, the ergonomic saddle chair provides the most appropriate posture for users. Determination of the seat height is critical to establish the proper posture, carried out using various methods of anthropometry. This study aimed to develop a simple and applied method for determining the saddle seat height with an emphasis on appropriate posture.

METHODS

In this study, anthropometric dimensions including weight, body height, popliteal height and seat height at 135° knee angle in 150 male and female dentists were measured. In the laboratory, to determine the 'acetabuloischial number', 25 male and female natural hip bones were measured. The mean saddle-chair height with knee angle of 135° was then compared by two different methods, field measurement and the new calculation method.

RESULTS

The results showed a strong correlation between data gathered from the two different methods, the field measurement and the new calculation method (98%), and Cronbach's α from the intraclass correlation was equal to 0.994 (p < 0.05). This indicated that the two methods produced similar results.

CONCLUSION

The new method can be applied to calculate the optimal height of the saddle seat based on body height and popliteal height.

The Comparison of Genetic Factors Influences on Physical Activity and Health between Classical Medicine and Iranian Traditional Medicine

BACKGROUND

Different factors, especially genetic, effect individual attitude to regular physical activity in Iranian traditional medicine. It was believed that individual physical activity attitude is affected by Mizaj too. Our aim was to conduct a comparative revision and evaluation of the effect of genetic factors on physical activity in classic medicine and Iranian traditional medicine.

METHODS

In this study, we reviewed Persian resources in the research center of traditional medicine at Shiraz University of Medical Sciences. We also evaluated the texts on physical activity and genetics in PubMed and Google Scholar.

RESULTS

The results of classical medicine revision showed the effect of especial genes on obesity and sedentary behavior. It is also derived from Iranian traditional medicine resources that physical activity and sedentary behavior is affected by individual Mizaj.

CONCLUSION

The results showed that those with hot and cold Mizaj have different genetic potentials in sedentary behavior and physical activity. Such categorization would be helpful in identifying illnesses due to sedentary life in special groups of people. It would also allow designing dedicated treatment for each person.

Inter-Segmental Coordination Pattern in Patients with Anterior Cruciate Ligament Deficiency during a Single-Step Descent

Anterior cruciate ligament injury is a debilitating pathology which may alter lower limb coordination pattern in both intact and affected lower extremities during activities of daily living. Emerging evidence supports the notion that kinematic variables may not be a good indicator to differentiate patients with anterior cruciate ligament deficiency during step descent task. The aim of the present study was to examine alterations in kinematics as well as coordination patterns and coordination variability of both limbs of these patients during a single step descent task. Continuous relative phase technique was used to measure coordination pattern and coordination variability between a group of anterior cruciate ligament deficient (n = 23) and a healthy control group (n = 23). A third order polynomial Curve fitting was utilized to provide a curve that best fitted to the data points of coordination pattern and coordination variability of the healthy control group. This was considered as a reference to compare to that of patient group using nonlinear regression analysis. The results of the present study demonstrated an altered coordination pattern of the supporting shank-thigh and the stepping foot-shank couplings in anterior cruciate ligament deficient subjects. It was further noticed that there was an increased coordination variability in foot-shank and shank-thigh couplings of both supporting and stepping legs. There was no significant difference in the hip, knee and ankle joints kinematics in either side of these patients. Anterior cruciate ligament deficient individuals showed altered strategies in both intact and affected legs, with increased coordination variability. Kinematic data did not indicate any significant difference between the two groups. It could be concluded that more sophisticated dynamic approach such as continuous relative phase would uncover discrepancies between the healthy and anterior cruciate ligament deficient individuals.

Assessment of functional parameters and comfort of a new computer mouse as compared with other types of input devices

BACKGROUND

This study was conducted to assess functional parameters and comfort of a new computer mouse (Ergomice) as compared with three other input devices.

MATERIALS AND METHODS

Functional parameters (i.e., task completion time and error rate) of each device were assessed by 10 participants using standardized software based on Standard No. ISO 9241-9:2000. Comfort evaluation was also undertaken for each device using the visual analogue scale technique. Statistical analysis including the Wilcoxon signed-rank test and the Friedman test was performed using SPSS version 16.

RESULTS

The functional parameters of the standard mouse were better than those of the other devices. However, no significant difference was observed between this mouse and Ergomice. Overall comfort evaluation showed that the standard mouse and Ergomice were more comfortable to work with. The comfort level of hand/wrist posture in the Ergomice was higher than that of the other three devices.

CONCLUSION

The design features of Ergomice could improve its functional properties. Hand/wrist posture comfort of Ergomice was judged to be high compared with that of the other devices.

Ultra-broadband quantum cascade laser, tunable over 760 cm(-1), with balanced gain

A heterogeneous quantum cascade laser, consisting of multiple stacks of discrete wavelength quantum cascade stages, emitting in 5.9-10.9 µm, wavelength range is reported. The broadband characteristics are demonstrated with a distributed-feedback laser array, emitting at fixed frequencies at room temperature, covering an emission range of ~760 cm(-1), which is ~59% relative to the center frequency. By appropriate choice of a strained AlInAs/GaInAs material system, quantum cascade stage design and spatial arrangement of stages, the distributed-feedback array has been engineered to exhibit a flat threshold current density across the demonstrated range.

Quantum cascade lasers: from tool to product

The quantum cascade laser (QCL) is an important laser source in the mid-infrared and terahertz frequency range. The past twenty years have witnessed its tremendous development in power, wall plug efficiency, frequency coverage and tunability, beam quality, as well as various applications based on QCL technology. Nowadays, QCLs can deliver high continuous wave power output up to 5.1 W at room temperature, and cover a wide frequency range from 3 to 300 μm by simply varying the material components. Broadband heterogeneous QCLs with a broad spectral range from 3 to 12 μm, wavelength agile QCLs based on monolithic sampled grating design, and on-chip beam QCL combiner are being developed for the next generation tunable mid-infrared source for spectroscopy and sensing. Terahertz sources based on nonlinear generation in QCLs further extend the accessible wavelength into the terahertz range. Room temperature continuous wave operation, high terahertz power up to 1.9 mW, and wide frequency tunability form 1 to 5 THz makes this type of device suitable for many applications in terahertz spectroscopy, imaging, and communication.

GaInN/GaN Multi-Quantum Well Laser Diodes Grown by Low-Pressure Metalorganic Chemical Vapor Deposition

We report the growth, fabrication and characterization of GaInN/GaN multi-quantum well lasers grown on (00·1) sapphire substrates by low pressure metalorganic chemical vapor deposition. The threshold current density of a 1800 μm long cavity length laser was 1.4 kA/cm2 with a threshold voltage of 25 V. These lasers exhibited series resistances of 13 and 14 Ω at 300 and 79 K, respectively.

Designing a new computer mouse and evaluating some of its functional parameters

BACKGROUND

This study aimed to design a new mouse and evaluate some of its functional parameters. The prototype of an ergonomic mouse was made according to design principles.

METHODS

The study was conducted from 2011 to 2013 in the Department of Ergonomics in Shiraz University of Medical Science. Functional parameters including Movement Time (MT) and error rate of the new mouse were evaluated by 10 participants based on ISO 9241-9 standard.

RESULTS

The application of design principles in the new mouse resulted in improving MT and error rate so that they could be comparable to those of a standard mouse. MT, in both the standard and the new mouse was 0.846 and 0.864 s, respectively. Error rate of the standard and the new mouse was reported as 13% and 19%, respectively. Statistical analysis showed no significant difference between the two mice from these perspectives.

CONCLUSIONS

Apparently, the studied functional parameters of the new mouse were similar to those of the standard one. The new mouse could be an appropriate substitution for the standard mouse without losing its positive characteristics.

High performance terahertz quantum cascade laser sources based on intracavity difference frequency generation

We demonstrate high power, room temperature, single-mode THz emissions based on intracavity difference frequency generation from mid-infrared quantum cascade lasers. Dual active regions both featuring giant nonlinear susceptibilities are used to enhance the THz power and conversion efficiency. The THz frequency is lithographically tuned by integrated dual-period distributed feedback gratings with different grating periods. Single mode emissions from 3.3 to 4.6 THz with side-mode suppression ratio and output power up to 40 dB and 65 µW are obtained, with a narrow linewidth of 5 GHz.

Growth of GaN without Yellow Luminescence

We report the growth and photoluminescence characterization of GaN grown on different substrates and under different growth conditions using metalorganic chemical vapor deposition. The deep-level yellow luminescence centered at around 2.2eV is attributed to native defect, most possibly the gallium vacancy. The yellow luminescence can be substantially reduced By growing GaN under Ga-rich condition or doping GaN with Ge or Mg.

AlxGa1-xN-Based Materials and Heterostructures

We present the metalorganic chemical vapor deposition growth, n-type and p-type doping and characterization of AlxGa1-xN alloys on sapphire substrates. We report the fabrication of Bragg reflectors and the demonstration of two dimensional electron gas structures using AlxGa1-xN high quality films. We report the structural characterization of the AlxGa1-xN / GaN multilayer structures and superlattices through X-ray diffraction and transmission electron microscopy. A density of screw and mixed threading dislocations as low as 107 cm-2 was estimated in AlxGa1-xN / GaN structures. The realization of AlxGa1-xN based UV photodetectors with tailored cut-off wavelengths from 365 to 200 nm are presented.

GaAs/GaInP Quantum Well Intersubband Photodetectors for Focal Plane Array Infrared Imaging

We demonstrate long wavelength quantum well infrared photodetectors (QWIP) with GaAs quantum wells and GalnP barriers grown using gas-source molecular beam epitaxy. Wafers were grown with varying well widths. The optimum well width was 75 Å, which resulted in a detection peak at 13 μm and a cutoff wavelength of 15 μm Dark current measurements of the samples with 15 μm cutoff wavelength show low dark current densities. Preliminary focal plane array imaging is demonstrated.

High Resolution X-ray Diffraction of GaN Grown on Sapphire Substrates

X-ray rocking curves are frequently used to assess the structural quality of GaN thin films. In order to understand the information given by the line shape, we need to know the primary mechanism by which the curves are broadened. The GaN films used in this study were grown by low pressure metalorganic chemical vapor deposition (MOCVD) on (00•1) sapphire substrates. GaN films with both broad and very narrow (open detector linewidth of 40 arcseconds for the (00•2) GaN reflection) rocking curves are examined in this work. Reciprocal space maps of both symmetric and asymmetric reciprocal lattice points are used to determine that the cause of the broadening of GaN rocking curves is a limited in-plane coherence length.