Modeling the biomechanics of the lamina cribrosa microstructure in the human eye

Glaucoma is among the leading causes of blindness worldwide that is characterized by irreversible damage to the retinal ganglion cell axons in the lamina cribrosa (LC) region of the optic nerve head (ONH), most often associated with elevated intraocular pressure (IOP). The LC is a porous, connective tissue structure that provides mechanical support to the axons as they exit the eye and the biomechanics of the LC microstructure likely play a crucial role in protecting the axons passing through it. There is a limited knowledge of the IOP-driven biomechanics of the LC microstructure, primarily due to its small size and the difficulty with imaging the LC both in vitro and in vivo. We present finite element (FE) models of three human eye posterior poles that include the LC microstructure and interspersed neural tissues (NT) composed of retinal axons that are constructed directly from segmented, binary images of the LC. These models were used to estimate the stresses and strains in the LC and NT for an acute IOP elevation from 0 to 45 mmHg and compared with identical models except that the LC was represented as a homogenized continuum material with either homogeneous isotropic neo-Hookean properties or heterogeneous properties derived from local connective tissue volume fraction (CTVF) and predominant LC beam orientation. Stresses and strains in the LC and NT microstructure were investigated, and results were compared against those from the models wherein the LC was represented as a homogenized continuum. The regionalized volumetric average stresses and strains showed that the microstructural model yielded similar patterns to our prior approach using an LC continuum representation with mapped LC CTVF/anisotropy, but the microstructural modeling approach allows analysis of the stresses and strains in the LC and NT separately. As expected, the LC beams carried most of the IOP load in the microstructural models but exhibited less strain, while the encapsulated NT exhibited lower stresses and much higher strains. Results also revealed that the continuum models underestimate the maximum strains in the LC beams and NT by a factor of 2-3. Microstructural modeling should provide greater insight into the biomechanical factors driving damage to the axons (NT) and LC connective tissue remodeling that occur in glaucoma. The methods presented are ideal for modeling any structure with a complex microstructure composed of different materials, such as trabecular bone, lung, and tissue engineering scaffolds such as decellularized LC. Matlab code for mesh generation from a segmented image stack of the microstructure is included as Supplemental Material. STATEMENT OF SIGNIFICANCE: Glaucoma is among the leading causes of blindness worldwide that is characterized by axon damage in the lamina cribrosa (LC) region of the eye. We present a new approach for finite element modeling the entire eye-specific 3D LC microstructure and the interspersed neural tissues, incorporated into an eye-specific posterior eye model that provides appropriate boundary and loading conditions. Results are presented for three human donor eyes, showing that prior modeling approaches underestimate the stresses and strains in the laminar microstructure. We constructed models from image stacks of the segmented microstructure (Matlab code included) using an approach that is ideal for modeling any structure with a complex microstructure composed of different materials, such as trabecular bone, lung, and tissue engineering scaffolds.

Prevalence of Ureaplasma urealyticum and Mycoplasma genitalium in men with non-gonococcal urethritis

The study in Teheran, Islamic Republic of Iran, investigated the prevalence of Ureaplasma urealyticum and Mycoplasma species in men with non-gonococcal urethritis. Urethral swab samples were collected from 125 cases and 125 healthy men as a control group. The samples were then investigated by culture methods. The rates of detected bacteria in case and control groups were 19.2% and 7.2% for U. urealyticum, 7.2% and 0.8% for M. genitalium, and 2.4% and 1.6% for M. hominis respectively. Statistical analysis showed a significant difference between case and control groups in the prevalence of U. urealyticum and M. genitalium but not M. hominis. It is concluded that in men, U. urealyticum and M. genitalium may have an etiologic role in non-gonococcal urethritis

Purification and economic analysis of nanoclay from bentonite

Nowadays, due to the most application of montmorillonite, its purification from raw bentonite has great importance. More than 76% of bentonite is composed of montmorillonite, and its industrial applications are related to its montmorillonite content. In this study, the nanoclay was extracted from bentonite by the use of centrifugal force. The results of the field-emission scanning electron microscopy (FE-SEM) analysis show that the nanosized of purified montmorillonite has a sheet structure with a spacing of 22.41 nm and 45.0 nm. The sharp peaks in X-ray diffraction analysis (XRD) illustrated that the montmorillonite purified successfully, and the results of Fourier-transform infrared spectrophotometry (FT-IR) revealed the successful incorporation of the metabolic extraction within the montmorillonite. By comparison of Brunauer-Emmett-Teller (BET) results with IUPAC, it can be realized that the synthesized montmorillonite nanoclay has a microporous structure (< 2 nm) with a surface area of 11.325 m² g^-1. According to IUPAC classification, the BET isotherms of montmorillonite and bentonite indicate a hysteresis loop belonging to the type H3. Finally, the economic analysis results revealed to this method could be the best option for achieving high purity montmorillonite for future applications.

Effects of supplemental fat sources and forage feeding levels on growth performance, nutrient digestibility, ruminal fermentation, and nitrogen utilization in dairy calves

Knowledge regarding the potential interactions between supplemental fat source and fiber level in starter diet of dairy calves is lacking. The aim of the present study was to investigate the effects of supplemental saturated fat [palm fat (PLF) containing 86% palmitic acid (C16:0)] vs. unsaturated fat [soybean oil (SBO) containing 51% linoleic acid (C18:2)] and forage level on feed intake, growth performance, ruminal fermentation, nutrient digestibility, and metabolic traits in dairy calves. Forty newborn Holstein female calves (BW = 39.7 ± 1.8 kg) were assigned to 1 of 4 treatment groups (each consisting of 10 animals) in a 2 × 2 factorial arrangement of fat source [soybean oil vs. palm fat; 3% of starter based on DM basis] and alfalfa hay level (0 vs. 15%, on DM basis): SBO or PLF with (AH) or without (NAH) alfalfa hay. Calves had ad libitum access to water and starters throughout the study and a constant amount of milk was offered among experimental calves during the pre-weaning period. All calves were weaned on day 63 of age and remained in the study until day 73 of age. The results showed that the lowest and the highest starter intake and average daily gain during pre-weaning period was observed when calves received SBO-AH and PLF-AH, respectively. Accordingly, the lowest wither and hip heights at weaning time (day 63) and final wither height (day 73) were observed in SBO-AH group across treatments. Calves received PLF-AH had the highest weaning and final BW compared to other groups. Feed efficiency tended to be higher in PLF groups compared with SBO calves. Calves fed SBO-AH had the lowest digestibility of organic matter and neutral detergent fiber and also total short chain fatty acid concentrations in rumen compared with other groups. The SBO calves had lower urinary allantoin, urinary purine derivatives, and microbial protein synthesis than PLF calves; however, urinary nitrogen increased with SBO supplementation. In summary, the supplementation of SBO rich in C18:2 and AH during the pre-weaning period resulted in negative responses on growth performance, digestibility, and ruminal fermentation profile. Therefore, the inclusion SBO rich in C18:2 along with forage in the starter is not recommendable for young dairy calves.

Evaluation of Heating and Irradiation Methods for Production of Purified Protein Derivative (PPD) of Mycobacterium Tuberculosis

Tuberculin skin test, also known as the tuberculin or purified protein derivative (PPD) test, is an extensively applied diagnostic test for the detection of primary infection with Mycobacterium tuberculosis (Mtb). The production of PPD is accompanied by some difficulties that require a series of modifications in the production and purification processes. The present study aimed to determine the facilitation level of the manufacturing process by modifying evaluation methods for the production of PPD tuberculin. Mtb strains were cultured in Lowenstein-Jensen media, and the cultured strains were inoculated into the Dorset-Henley liquid medium by the biphasic medium of potato-Dorset-Henley. After incubation, flasks containing cultured strain were selected for bacterial inactivation, and the optimal gamma radiation dose(s) was determined. Tuberculoproteins were precipitated by ammonium sulfate (AS) and Trichloroacetic acid (TCA). Protein concentration was determined using the Bradford and Kjeldahl protein assay methods. Finally, the lymphocyte transformation test and potency test were performed. Based on the results, the Dorset-Henley liquid medium is suitable for the massive growth of the bacterium. The transferal of Mtb from solid to liquid medium was directly carried out without intermediate culture. It was found that during tuberculoprotein production, heating at 100&amp;deg;C for 3 h would be safe for killing mycobacterium. Furthermore, the simultaneous use of heating and gamma irradiation (8 kGgy) killed all of the mycobacteria, while doses of 1, 1.5, and 7 kGy decreased a significant number of bacterial cells. The results also indicated that the concentration of tuberculoprotein extracted by TCA precipitation method was higher than that obtained by AS precipitation. The tuberculoproteins which were produced by these two methods in the lymphocyte transformation test were not significantly different in terms of potency (P&amp;gt;0.05). Moreover, due to the high volume of produced protein, the protein measurement was more efficiently carried out by the Kjeldahl method, compared to the Bradford method. Finally, the results of the present study demonstrated that in addition to the novel approach of gamma irradiation, optimum methods are efficient and applicable in the production of PPD tuberculin.

A comparative finite element simulation of locking compression plate materials for tibial fracture treatment

The locking compression plate (LCP) system has several advantages in fracture fixation combining angular stability with the use of locking screws with traditional fixation techniques. However, the system is complex and requiring careful attention to biomechanical principles and good surgical technique. Due to the set of complicate stresses and strains in the LCP system after implantation, the material, which is being used here, is deemed important. However, so far the materials have been limited to the stainless steel (SS) or titanium (Ti). This study was therefore aimed at investigate the biomechanical performance of the internal tibial locked plates at different material properties, including SS, Ti, carbon/polyether ether ketone (PEEK) composite, in treating medial tibial fracture using patient-specific finite element (FE) model of the human tibia. The carbon/PEEK composite materials were used at three different fiber plies configurations. Simulated loading was applied at 60:40 ratios on the medial:lateral aspect. The model was fixed distally in all degrees of freedom. The results revealed the highest stress (307.10 MPa) and the lowest strain (0.14%) at Ti LCP system. The carbon/PEEK LCP system at configuration I and III showed low stress (∼60 MPa) and high strain (0.70%), which are suitable points for designing of an internal LCP system. On the other hand, the highest value of stress in callus region was 4.78 MPa (Carbon PEEK/Configuration I) and the strain variations of callus region were between 1.46% and 3.82% among all materials. These results implied the advantage of carbon/PEEK composite materials in LCP system as they can tolerate higher strains at lower stresses.

A patient-specific finite element analysis of the anterior cruciate ligament under different flexion angles

BACKGROUND

The main responsibility of the anterior cruciate ligament (ACL) is to restore normal knee kinematics and kinetics. Although so far different research has been carried out to measure or quantify the stresses and strains in the ACL experimentally or numerically, there is still a paucity of knowledge in this regard under different flexion angles of the tibiofemoral knee joint.

OBJECTIVE

Understanding the stresses and strains within the ACL under various loading and boundary conditions may have a key asset for the development of an optimal surgical treatment of ACL injury that can better restore normal knee function. This study aimed to calculate the stresses and strains within the ACL under different flexion angles using a patient-specific finite element (FE) model of the human tibiofemoral knee joint.

METHODS

A patient-specific FE model of the human tibiofemoral knee joint was established using computed tomography/magnetic resonance imaging data to calculate the stresses and strains in the ACL under different flexion angles of 0, 10, 20, 30, and 45∘.

RESULTS

Although the role of the flexion angle in the induced stresses and strains of the ACL was insignificant, the highest stress and strain were observed at the flexion angle of 0∘. The concentration of the stresses and strains regardless of the flexion angles were also located at the proximal end of the ACL, where the clinical reports indicated that most ACL tearing occurs there at the femoral insertion site.

CONCLUSIONS

The results have implications not only for understanding the stresses and strains within the ACL under different flexion angles, but also for providing preliminary data for the biomechanical and medical experts in regard of the injuries which may occur to the ACL at relatively higher flexion angles.

Analysis of the effects of finite element type within a 3D biomechanical model of a human optic nerve head and posterior pole

BACKGROUND AND OBJECTIVE

Biomechanical stresses and strains can be simulated in the optic nerve head (ONH) using the finite element (FE) method, and various element types have been used. This study aims to investigate the effects of element type on the resulting ONH stresses and strains.

METHODS

A single eye-specific model was constructed using 3D delineations of anatomic surfaces in a high-resolution, fluorescent, 3D reconstruction of a human posterior eye, then meshed using our simple meshing algorithm at various densities using 4- and 10-noded tetrahedral elements, as well as 8- and 20-noded hexahedral elements. A mesh-free approach was used to assign heterogeneous, anisotropic, hyperelastic material properties to the lamina cribrosa, sclera and pia. The models were subjected to elevated IOP of 45 mmHg after pre-stressing from 0 to 10 mmHg, and solved in the open-source FE package Calculix; results were then interpreted in relation to computational time and simulation accuracy, using the quadratic hexahedral model as the reference standard.

RESULTS

The 10-noded tetrahedral and 20R-noded hexahedral elements exhibited similar scleral canal and laminar deformations, as well as laminar and scleral stress and strain distributions; the quadratic tetrahedral models ran significantly faster than the quadratic hexahedral models. The linear tetrahedral and hexahedral elements were stiffer compared to the quadratic element types, yielding much lower stresses and strains in the lamina cribrosa.

CONCLUSIONS

Prior studies have shown that 20-noded hexahedral elements yield the most accurate results in complex models. Results show that 10-noded tetrahedral elements yield very similar results to 20-noded hexahedral elements and so they can be used interchangeably, with significantly lower computational time. Linear element types did not yield acceptable results.

The effects of the fiber source and xylanase supplementation on production, egg quality, digestibility, and intestinal morphology in the aged laying hen

This study was conducted to evaluate the effects of the fiber source (wheat bran [WB] or sugar beet pulp [SBP]) and xylanase supplementation on production, egg quality, ileal digestibility, intestinal morphology, and gastrointestinal pH in aged laying hens. A total of 540 laying hens (Lohman LSL Lite; 70 wk of lay) were randomized into 10 treatments (6 replicate cages of 9 birds) consisting of a corn soy control supplemented with 0, 3, or 6% WB or SBP with or without xylanase (100 mg of xylanase preparation per kg) for a period of 9 wk in a 5 × 2 factorial arrangement. Hens fed with the diets containing either of the levels of SBP or 6% WB had lower hen-day production, and addition of the enzyme improved hen-day production (P < 0.05), but it could not compensate for the lost production due to the higher levels of either of the fiber sources. Supplementation of 6% SBP to the control diet decreased egg mass (P < 0.05). All fiber-supplemented diets significantly decreased ADFI, which was restored on enzyme addition, with the exception of 3% WB diet. Treatments had no effects on egg weight, feed conversion ratio, egg quality, and serum and carcass traits, except for ileum weight, which was greater in hens fed with the 6% SBP diet (P < 0.05). Adding 3% SBP increased ileal DM digestibility (P < 0.05). Addition of 3% WB improved jejunal villus height, villus height-to-crypt depth ratio, and villus surface area (P < 0.05). Villus surface area, DM, organic matter, and protein digestibility increased as a result of enzyme supplementation (P < 0.05). Cecal pH was reduced on feeding diets containing 3% WB, containing 3% SBP, and with enzyme supplementation (P < 0.05). In conclusion, addition of 3% WB in a corn soy control diet has the potential to improve small intestine morphology in older hens without adverse effects on performance, especially if accompanied by the use of an enzyme, which simultaneously improved morphological traits and nutrient digestibility.

Biomechanics of the keratoconic cornea: Theory, segmentation, pressure distribution, and coupled FE-optimization algorithm

Understanding of the corneal biomechanical properties is of high interest due to its potential application in the early diagnosis of keratoconus (KC). KC by itself is a non-inflammatory eye disorder causes corneal structural and/or compositional anomalies. The biomechanically weakened cornea is no longer able to preserve the normal shape of the cornea against the intraocular pressure (IOP) and gradually starts to bulge outward, invoking a conical shape and subsequent distorted vision. The most popular way to measure the in vivo corneal biomechanical properties is the CorVis-ST, which enables to analyze the dynamic response of the cornea under a temporary air puff pressure. However, the complications, such as the lack of knowledge on the accurate air-puff pressure distribution on the cornea's surface as a function of the distance from the apex of the cornea as well as the time, hinder us to have a reliable estimation of the cornea's mechanical parameters. This study aims to establish patient-specific geometries of the healthy and KC corneas and calculate the pressure distribution on the cornea's surface as a function of both the distance from the apex of the cornea and time, and thereafter, the viscoelastic mechanical properties of both the healthy and KC corneas using a coupled finite element (FE)-optimization algorithm. To do that, the dynamic deformation response of six healthy and six KC corneas were measured via CorVis-ST. The videos of the in vivo deformation of the corneas under the applied air puff pressure were segmented using our segmentation algorithm to determine the anterior and posterior curvatures of the corneas during the dynamic movement of the cornea. The FE model of the corneas were established using the segmented data and subjected to a negative (pre-stress), positive IOP, and air puff pressure while the floating boundary conditions were applied to the two ends of the corneas' FE models. The simulation results were imported into a loop of FE-optimization algorithm and analyzed until the deformation amplitude at the apex of the cornea reaches to its minimum difference compared to the clinical data by CorVis-ST. The results revealed that the pressure distributions found in the literature as a function of the distance from the apex of the cornea and time unable to provide satisfactory results. Therefore, the pressure distributions both as a function of the distance and time were optimized using our coupled FE-optimization algorithm and employed to estimate the viscoelastic properties of the healthy and KC corneas. The mean percentage error (MPE) of 8.45% and 10.79% were found for the healthy and KC corneas compared to the clinical data of CorVis-ST, respectively. The results also revealed a significantly higher short-time shear modulus for the KC (62.33 MPa) compared to the healthy (37.45 MPa) corneas while the long-time shear modulus of both the healthy and KC corneas were almost the same (4.01 vs. 3.91 MPa). The proposed algorithm is a noninvasive technique capable of accurately estimating the viscoelastic mechanical properties of the cornea, which can contribute to understand the mechanism of KC development and improve diagnosis and intervention in KC.

High frequency of BRAF V600E mutation in Iranian population ameloblastomas

Background

Ameloblastoma is a common locally invasive but slow-growing neoplasm of the jaws with an odontogenic origin. Association between BRAF V600E mutation and clinicopathologic features and behavior of ameloblastoma remains controversial. This study aimed to evaluate BRAF V600E gene mutation and expression of its related proteins with clinicopathologic parameters in conventional ameloblastoma.

Material and Methods

50 Formalin-fixed paraffin-embedded blocks were included in this study. Immunohistochemistry was done using rabbit monoclonal BRAF V600E mutation-specific antibody VE1. Quantitative real-time polymerase chain reaction assay was used for evaluating of BRAF V600E mutation.

Results

Expression of BRAF V600E antibody was Positive in 42 out of 50 cases (84%). 46 (92%) out of 50 specimens showed BRAF V600E mutation. There were 13 cases of recurrence (26%). 3 out of 4 cases with negative mutations did not show recurrence.

Conclusions

We report the highest frequency (92%) of BRAF V600E mutation in ameloblastomas in the Iranian population. Although there was not a significant association between BRAF V600E‑positive immunoexpression and recurrence and clinicopathologic parameters, its high frequency could emphasize its role as a therapeutic marker in the future.

Key words:Conventional ameloblastoma, BRAF V600E, recurrence.

A patient-specific fluid–structure interaction model of the cerebrovascular damage in relation to traumatic brain injury

Background

There is a lack of knowledge on the magnitudes of the biomechanical stresses and deformations occurring in the cerebral arterial wall after traumatic brain injury (TBI). Experimental techniques are unable to calculate the stresses and deformations in the cerebral arterial wall after TBI; therefore, the application of numerical simulations, such as finite element modeling, is preferred.

Methods

This study was aimed to calculate the stresses and deformations as well as the alteration in the pressure and velocity of the blood in the cerebrovascular artery using a fluid–structure interaction model.

Results

The results revealed considerable increase in the pressure and velocity of the blood which might lead to cerebrovascular damage followed by hemorrhage. The arterial wall showed the highest deformation of 0.047 mm in the X direction which was higher than that in the Y (0.035–0.050 mm) and Z (0.019–0.030 mm) directions.

Conclusions

These results have implications not only for the understanding of the stresses and deformations in the cerebral artery because of TBI, but also for providing a comprehensive knowledge for biomechanical and medical experts in regard to thresholds of cerebrovascular damage for use in establishing preventive and/or treatment methods.

Investigation into passing behavior at passing zones to validate and extend the use of driving simulators in two-lane roads safety analysis

A passing maneuver allows drivers to maintain their desired speed on two-lane highways. However, it entails a high risk of collision with vehicles travelling in the opposite direction. Investigating drivers' behavior while performing passing maneuvers could provide helpful information on the factors that influence this process. Driving simulators have become important tools for driving behavior research studies as they are safe, facilitate the controlled use of experimental variables, and generate detailed output data. It remains to be seen whether simulator results can be considered representative of real-life driving conditions. With respect to passing maneuvers, no study has made a comprehensive and direct comparison between drivers' passing behavior in the field and driver behavior observed in a simulated environment. In this validation study, a fixed-base interactive simulator was used to collect data from fifty-four participants (eighteen Iranians and thirty-six Italians) involved in several traffic scenarios on a two-lane rural highway segment (obtained by varying the speed of opposing vehicles, lead vehicles and headways in the opposite direction). A 3D model and its environmental characteristics were realized from the real segment which had previously been surveyed with drones to collect videos and derive data on real passing maneuvers. The results for the two-sided K-S test revealed no statistically significant difference in the accepted gap, effective accepted gap, perception reaction time, and time to collision variables between the field and the simulator at the 95 % confidence level. However, when conducting a one-sided K-S test, some statistical directional differences were found in the cases of the accepted gap and perception reaction time variables, which exhibited lower values in the field compared to the simulator again at the 95 % confidence level. Although the passing duration was statistically higher in the simulator than in the field, the shape of the two distributions was not statistically different. Analysis showed that differences in the passing duration are due to the lower passing vehicle speed and lower speed difference with the simulator than in the field, which are caused by truncating headways in the subject direction in the simulator. The cultural background of participants did not result in any discernible difference in passing behavior. The results would support a more extensive use of driving simulators in future passing behavior studies.

Comparative Analysis of Gait Speed Estimation Using Wideband and Narrowband Radars, Thermal Camera, and Motion Tracking Suit Technologies

Research has shown that cognitive and physical functioning of older adults can be reflected in indicators such as walking speed. While changes in cognition, mobility, or health cause changes in gait speed, often gradual variations in walking speed go undetected until severe problems arise. Discrete clinical assessments during clinical consultations often fail to detect changes in day-to-day walking speeds and do not reflect walking speeds in everyday environments, where most of the mobility issues happen. In this paper, we compare four walking speed measurement technologies to a GAITRite mat (gold standard): (1) an ultra wideband radar (covering the band from 3.3 GHz to 10 GHz), (2) a narrow band 24-GHz radar (with a bandwidth of 250 MHz), (3) a perception Neuron Motion Tracking suit, and (4) a thermal camera. Data were collected in parallel using all sensors at the same time for 10 healthy adults for normal and slow walking paces. A comparison of the sensors indicates better performance at lower gait speeds, with offsets (when compared to GAITRite) between 0.1 and 20% for the ultra wideband radar, 1.9 and 17% for the narrowband radar, 0.1 and 38% for the thermal camera, and 1.7 and 38% for the suit. This paper supports the potential of unobtrusive radar-based sensors and thermal camera technologies for ambient autonomous gait speed monitoring for contextual, privacy-preserving monitoring of participants in the community.

Epidemiology and outcome analysis of 3030 burn patients with an ICD-10 approach

The present study aims to document the epidemiologic features and outcomes of burn injuries in Southeastern Iran based on International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10) guidelines. This retrospective cross-sectional study was carried out at Khatam-Al-Anbiya Hospital. Patient demographics, including burn injury data and outcome data were collected from medical records and analyzed through descriptive and analytical statistics using SPSS software. A total of 3,030 burn patients were included in this study. A total of 55% of the subjects were males. The largest age group included patients aged 15-44 (61%). The majority of burns were caused by flame (70.5%), and most of them were third-degree burns (73%). Mean affected total body surface area (TBSA) was 43.98%±30.75% in all subjects and 80.85%±21.41% in the deceased individuals. Most of the burns were accidental (66.2%), and 37% of them occurred in winter. Mean hospital stay was 4.49±4.67 days (within the range of 1-113 days). A quarter of all patients admitted to the hospital died (24.9%). The number of admitted patients, mean length of stay (LOS), and the mortality rate showed a decreasing trend from 2007 to 2016. In contrast, the total mortality rate was high. The significant predictors of mortality included being female, flame burns, longer LOS, a larger TBSA, burns of higher degrees, as well as burn complications. The documentation of burn data, based on ICD-10 directives, standardizes findings from burn injury analyses and leads to the comparability of data at different national and international levels.

Modelling and optimizing of calcium and non-phytate phosphorus requirements of male broiler chickens from 1 to 21 days of age using response surface methodology

The skeleton is the main site of P and Ca deposition; therefore, accurate estimation of Ca and P requirements is necessary to maintaining health and optimum performance of broiler chickens. A response surface methodology (RSM) using a central composite design (CCD) was used for evaluating and optimizing of Ca and non-phytate P (NPP) requirements of broiler chickens for optimal performance, ileal nutrient digestibility and bone mineralization from 1 to 21 days of age. A total of 750 one-day-old male broiler chickens (Ross 308) were randomly distributed into 50 cages including 9 treatments, each replicated 5 times (except central treatment with 10 replicates) and 15 birds in each cage by CCD. The dietary Ca levels of 4.3, 5.6, 8.6, 11.7 and 13.0 g/kg and NPP of 2.5, 2.9, 4.0, 5.0 and 5.4 g/kg were used for nine treatments of CCD. The results indicated that the linear and quadratic effects of NPP, quadratic effects of Ca and Ca × NPP were significant for average weight gain (AWG, P < 0.05), average feed intake (AFI, P < 0.05), feed conversion ratio (FCR, P < 0.05) and Ca and P apparent ileal digestibility (AID, P < 0.05); however, the linear effect of Ca was significant only for FCR (P < 0.05). On the other hand, tibia and toe ash were affected by NPP (linear and quadratic, P < 0.01) and Ca (quadratic, P < 0.01). The second-order polynomial regression model was significant for AWG (R2 = 0.93, P < 0.001), AFI (R2 = 0.88, P < 0.001), FCR (R2 = 0.78, P < 0.001), AID of Ca (R2 = 0.78, P < 0.001) and P (R2 = 0.88, P < 0.001), tibia ash (R2 = 0.86, P < 0.001) and toe ash (R2 = 0.85, P < 0.001). The multi-objective optimization indicated that broiler chickens from 1 to 21 days of age need 7.03 and 4.47 g/kg of Ca and NPP, respectively, to achieve optimal AWG, FCR, tibia and toe ash. However, the dietary Ca and NPP levels can be reduced to 6.57 and 3.95 g/kg with a slight negative impact on performance and bone mineralization, respectively. In conclusion, the findings indicate that using multi-objective optimization model such as RSM provides more information regarding optimum Ca and NPP requirements of broiler chickens, considering the complex interaction between these two minerals. While the NPP levels are in line with current recommended requirements, Ca levels are considerably lower and suggest that current recommended Ca requirements may be in excess of the needs of the broiler.

Efficient removal of 2,4-dinitrophenol from synthetic wastewater and contaminated soil samples using free and immobilized laccases

Among hazardous pollutants, 2,4-Dinitrophenol (2,4-DNP) is considered highly toxic and possesses a remarkable resistance to degradation. Therefore, investigation of the possible mechanisms for removal of such pollutants is important. Laccase enzyme can decompose phenolics despite the fact that its application has been limited due to lack of possibility to reuse it. Immobilization can overcome this problem. In this paper, laccase complexes with montmorillonite K10 and zeolite were used to decompose 2,4-DNP with concentrations of 1.5 mg l^-1 and 50 mg kg^-1 in synthetic wastewater and soil, respectively. The maximum removal of pollutant from wastewater in samples containing laccase-zeolite and laccase-montmorillonite complexes were 99 and 93.3%, respectively, which occurred at 4 h incubation compared with 6 h for free laccase. The maximum removal of pollutant from soil was observed for all treatments after 16 h of incubation. The maximum removal for samples containing free laccase, laccase-zeolite, and laccase-montmorillonite complexes were 98.5%, 98.6%, and 90.4%, respectively. Control sample also showed maximum removal of 35.8%. In general, application of laccase-zeolite complexes in aqueous environment, and these complexes and free laccases in soil was found very effective in degradation of 2,4-DNP. Hence, the use of laccase, especially immobilized laccases, for removal of 2,4-DNP from environment is promising.

Biomechanical role of posterior cruciate ligament in total knee arthroplasty: A finite element analysis

BACKGROUND AND OBJECTIVE

The knee joint is a complex structure which is vulnerable to injury due to various types of loadings as a consequence of walking, running, stair climbing, etc. Total knee arthroplasty (TKA) is a widely used and successful orthopedic procedure which during that the posterior cruciate ligament (PCL) can either be retained or substituted. Different surgical techniques suggest retention or sacrifice of the PCL in TKA for the treatment of osteoarthritis which may alter the post-op outcomes. The objective of this study was to evaluate the biomechanical role of PCL after TKA surgery using finite element (FE) modeling.

METHODS

A three-dimensional (3D) FE model of the prosthetic knee was developed and its validity was compared to available studies in literature. Further, the effect of the retention or removing of the PCL as well as its degradation (i.e. variation in mechanical properties) and angle on knee biomechanics were evaluated during a weight-bearing squatting movement.

RESULTS

The validity of the intact model were confirmed. The results revealed higher stresses in the PCL and tibial insert at higher femoral flexion angles. In addition, the effect of variations in the stiffness of the PCL was found to be negligible at lower while considerable at higher femoral flexion angles. The variations in the elevation angle of the PCL from 89° to 83° at the critical femoral angles of 60° and 120° showed the highest von Mises stresses in the tibial insert.

CONCLUSIONS

The results have implications not only for understanding the stresses in the prosthetic knee model under squat movement but also for providing comprehensive information about the effects of variations in the PCL stiffness and balancing on the induced stresses of the PCL and tibial insert.

Serogroups, and drug resistance of nontyphoidal Salmonella in symptomatic patients with community-acquired diarrhea and chicken meat samples in Tehran

BACKGROUND

Salmonella is considered as a main cause of community-acquired diarrhea in humans, however, sources of the multi-drug resistant (MDR) strains and their link with the disease are not well known.

AIMS

This study aimed to investigate the frequency, serogroup diversity, and antimicrobial susceptibility patterns of Salmonella strains in poultry meat and stool samples of patients with community acquired diarrhea in Tehran.

METHODS

We compared the frequency of non-typhoidal Salmonella serogroups, the similarities of their resistance patterns to 10 antimicrobial compounds, the prevalence of extended spectrum β-lactamase (ESBL) and ampicillinase C (AmpC) genetic determinants, and class 1 and 2 integrons in 100 chicken meat and 400 stool samples of symptomatic patients in Tehran during June 2018 to March 2019.

RESULTS

Salmonella was isolated from 75% and 5.5% of the chicken meats and human stool samples, respectively. The chicken meat isolates mainly belonged to serogroup C (88%, 66/75), while the human stool isolates were mainly related to serogroup D (59.1%, 13/22). The MDR phenotype and the most common rates of resistance to antibiotics, including tetracycline, trimethoprim/sulfamethoxazole (TS) and azithromycin, were detected in 4.5% and 45.3%, 59% and 13.6%, 43% and 9.1%, 42% and 9.1% of the human stool and chicken meat samples, respectively. Carriage of bla _CTX, bla _SHV, and bla _PER genes in the meat isolate with ESBL resistance phenotype and bla _ACC, bla _FOX, and bla _CMY-2 among the 7 meat strains with AmpC resistance phenotype was not confirmed using polymerase chain reaction (PCR). High prevalence of class 1 and 2 integrons was characterized and showed a correlation with resistance to TS and chloramphenicol.

CONCLUSION

These findings showed a lack of association between chicken meats and human isolates due to discrepancy between the characterized serogroups and resistance phenotypes.

A patient-specific numerical modeling of the spontaneous coronary artery dissection in relation to atherosclerosis

The spontaneous coronary artery dissection (SCAD) is a clinical complication of angioplasty leading to an initiation of a tear/crack in the intima layer of the artery. The crack can propagate to the interface of the intima-media layer following by intramural hematoma. The relation between the SCAD and atherosclerosis is a controversial issue, as some studies stated no correlation between them while others showed that a crack can initiate in the intima but cannot propagate into the atrophied media layer. To investigate the relation between the intraluminal crack propagation in the atherosclerotic artery and SCAD, this study numerically investigated the initiation and propagation of a crack in the intraluminal and radial locations of the healthy and atherosclerotic human coronary arterial walls. The energy release rate, namely J-integral, is computed as a numerical derivative of the strain energy with respect to a crack extension using a user-defined virtual crack method (VCE) of extended finite element method (XFEM). Experimental measurements were carried out to calculate the elasto-plastic mechanical properties of the healthy and atherosclerotic human coronary arteries. The experimental data were then assigned to our own established patient-specific FE model of the coronary artery. Cracks were sketched in the intraluminal and radial locations of the arterial wall and allowed to propagate to the virtual interface of the intima-media to form a false lumen. The results revealed a higher stress at the crack tip of the healthy arterial wall compared to the atherosclerotic one. Lower crack tip opening displacement (CTOD) and crack tip opening angle (CTOA) were observed in the intraluminal crack of the atherosclerotic artery. J-integral of the atherosclerotic arterial wall was also found to be higher than the healthy one at the intraluminal crack. The results revealed that although a crack can initiate in the intraluminal of an atherosclerotic artery, it cannot propagate into the media layer due to a relatively higher rate of the strain energy release in the atherosclerotic arterial wall compared to the healthy one.

Effect of a high dose of exogenous phytase and supplementary myo-inositol on mineral solubility of broiler digesta and diets subjected to in vitro digestion assay

This study was conducted to evaluate the effect of microbial phytase and myo-inositol supplementation in low non-phytate phosphorus (nPP) diets on pH and the solubility of minerals in an in vitro digestion procedure (IVDP) and to compare this with digesta from birds fed different diets (grower diets) compared to the in vitro test (starter diets). A total of 660 1-day-old broilers were randomly allotted into 11 dietary treatments and fed a corn-soybean-meal-based diet with recommended nPP (positive control; PC), an nPP-deficient diet (negative control; NC), NC diets supplemented with phytase (500; 1,000; 2,000; 3,000; 4,000; 5,000; and 6,000 FTU/kg), an NC diet plus 0.15% myo-inositol, and an NC diet with reduced Ca level (Ca: nPP ratio same as PC) from 1 to 23 D of age. The pH and Ca solubility of the NC diet was increased compared with the PC when subjected to IVDP (P < 0.05). P solubility in the gizzard and jejunal digesta was reduced in the NC compared with the PC diet and this was also reflected in the IVDP. Phytase addition to the NC diets linearly increased (P < 0.05) the pH value and Ca and P solubilities in both digesta and diets subjected to IVDP. Higher doses of microbial phytase increased (P < 0.05) Zn and Fe solubilities in both digesta and IVDP. Myo-inositol supplementation of the NC diet had no effect on mineral solubility, but decreased (P < 0.05) the pH of the IVDP. Lowering the Ca content of the NC diet decreased (P < 0.05) the pH of the in vitro digested diets and Ca solubility in both broiler digesta and IVDP and also increased (P < 0.05) P solubility in both the jejunal digesta and IVDP. Correlations were noted between the solubility of P in the in vitro assay and that in the gizzard and jejunal digesta, and also with bird performance, confirms the usefulness of in vitro assay.

The Value of Urinary Cystatin C Level to Predict Neonatal Kidney Injury

BACKGROUND

The role of urinary cystatin C to early predict acute kidney injury (AKI) in children and neonates remains uncertain. The present study aimed to assess and compare the level of urinary cystatin C in neonates with and those without AKI.

METHODS

This cross-sectional study was performed on 55 available neonates who were involved by AKI and admitted to the neonatal department at Ali-Asghar hospital in Tehran in 2016. 97 neonates with jaundice and normal serum creatinine level were randomly selected as the control group. In both groups and on admission, the urine levels of cystatin C and creatinine were measured.

RESULTS

The average urinary level of cystatin C was 162.87 ± 56.50 mmol/mole creatinine in the group with AKI and 68.06 ± 57.16 mmol/mole creatinine in the control group that was significantly higher in former group (p < 0.001). The measurement of cystatin C level in urine could predict kidney injury with a sensitivity of 98.2%, a specificity of 39.2%, a positive predictive value of 47.8%, a negative predictive value of 97.4%, and an accuracy of 60.5%. Assessment of the area under the receiver operating characteristic (ROC) analysis showed that measuring urinary cystatin C level could effectively discriminate kidney injury from normal kidney condition in neonates (AUC = 0.868, 95CI: 0.811 - 0.925, P < 0.001). The best cutoff value of urinary cystatin C level to predict kidney injury was shown to be 41.5 mmol/mole creatinine yielding a sensitivity of 98.2% and a specificity of 46.4%.

CONCLUSION

Measurement of cystatin C in urine is an early sensitive method to diagnose neonatal kidney injury.

Urban growth modeling using cellular automata model and AHP (case study: Qazvin city)

Irregular growth in the surrounding lands is one of the most important issues for the city managers and programmers at various levels. Whereas nowadays study the process of land use changes to urban use plays the main role in long time decisions and programs, predicting the process of city growth and its modeling in future with precise methods for management and urban expansion control will be necessary more than other times. One of urban growth modeling is cellular automata model. This model has been used widely in urban studies because of its dynamic nature, ability of Integration with other models, ability to modify the model and required data availability. In this article, to maximize the efficiency of the cellular automata model and its constraints, the integration of the AHP automated cell model and cellular automata model have been used; and its accuracy has been evaluated. This article has been practical because its related principles has been collected in a documentary manner and has been used to analyses the issue in comparative and quantitative methods. Initially, the unplanned growth of Qazvin city has been investigated by Holdern and Shannon model. Then main parameters including distance from roads, land prices, distance from faults, distance from the rivers, soil gender, slope, permission to build land, topography, landscape, view to gardens and forest park as parameters involved in the development of Qazvin city are considered. The input data used in this research are Landsat tm and DEM images of the city of Qazvin in 1996 and 2016. Also, to evaluate the correctness of the model responses, the map of the developed regions in 2016 and the Kappa coefficient have been used. The Kappa coefficient is 92.3%, which is considered significant and appropriate and gave the fact that the Kappa number is acceptable. The Qazvin simulation was made in 2026. The results show that the proposed integrated model is suitable for studying urban growth.

Finite element modeling of the periodontal ligament under a realistic kinetic loading of the jaw system

Purpose

The stresses and deformations in the periodontal ligament (PDL) under the realistic kinetic loading of the jaw system, i.e., chewing, are difficult to be determined numerically as the mechanical properties of the PDL is variably present in different finite element (FE) models. This study was aimed to conduct a dynamic finite element (FE) simulation to investigate the role of the PDL (PDL) material models in the induced stresses and deformations using a simplified patient-specific FE model of a human jaw system.

Methods

To do that, a realistic kinetic loading of chewing was applied to the incisor point, contralateral, and ipsilateral condyles, through the experimentally proven trajectory approach. Three different material models, including the elasto-plastic, hyperelastic, and viscoelastic, were assigned to the PDL, and the resulted stresses of the tooth FE model were computed and compared.

Results

The results revealed the highest von Mises stress of 620.14 kPa and the lowest deformation of 0.16 mm in the PDL when using the hyperelastic model. The concentration of the stress in the elastoplastic and viscoelastic models was in the mid-root and apex of the PDL, while for the hyperelastic model, it was concentrated in the cervical margin. The highest deformation in the PDL regardless of the employed material model was located in the caudal direction of the tooth. The viscoelastic PDL absorbed the transmitted energy from the dentine and led to lower stress in the cancellous bone compared to the elastoplastic and hyperelastic material models.

Conclusion

These results have implications not only for understanding the stresses and deformations in the PDL under chewing but also for providing comprehensive information for the medical and biomechanical experts in regard of the role of the material models being used to address the mechanical behavior of the PDL in other components of the tooth.