A natural functionally graded biocomposite coating--human enamel

Human enamel has been found to be a coating with excellent mechanical performance, and has undergone extensive investigation and discussion. However, most of the reported studies consider the enamel as a homogeneous anisotropic biocomposite. The current study illustrated the graded properties of the biocomposite from its functional load-bearing direction. Within the thickness of the enamel, from the outer surface towards the enamel-dentin junction (EDJ), the elastic modulus (E(x)) and hardness (H(x)) of enamel exist in an exponential relationship with normalized thickness (x) as E(x)=111.64x(0.18) (R(2)=0.94) and H(x)=4.41x(0.16) (R(2)=0.87) GPa, respectively. Moreover, the creep ability of enamel increases towards the EDJ. The graded properties of the biocomposite can be explained by both microstructural and compositional changes along the thickness of the material towards the EDJ. Finite element analysis indicates that the graded properties of enamel have important roles in reducing the enamel-dentin interface stresses and maintaining the integrity of the multilayer tooth structure. The results provide a new angle to understand the excellent mechanical behaviour of the multilayer tooth structure and may inspire the development of new functionally graded materials and coating structures.

Assessment of workload during pediatric trauma resuscitation

BACKGROUND

Trauma resuscitations are high-pressure, time-critical events during which health care providers form ad hoc teams to rapidly assess and treat injured patients. Trauma team members experience varying levels of workload during resuscitations resulting from the objective demands of their role-specific tasks, the circumstances surrounding the event, and their individual previous experiences. The goal of this study was to determine factors influencing workload experienced by trauma team members during pediatric trauma resuscitations.

METHODS

Workload was measured using the National Aeronautics and Space Administration Task Load Index (TLX). TLX surveys were administered to four trauma team roles: charge nurse, senior surgical resident (surgical coordinator), emergency medicine physician, and junior surgical resident or nurse practitioner (bedside clinician). A total of 217 surveys were completed. Univariate and multivariate statistical techniques were used to examine the relationship between workload and patient and clinical factors.

RESULTS

Bedside clinicians reported the highest total workload score (208.7), followed by emergency medicine physicians (156.3), surgical coordinators (144.1), and charge nurses (129.1). Workload was higher during higher-level activations (235.3), for events involving intubated patients (249.0), and for patients with an Injury Severity Score greater than 15 (230.4) (p, 0.001 for all). When controlling for potential confounders using multiple linear regression, workload was increased during higher level activations (79.0 points higher, p = 0.01) and events without previous notification (38.9 points higher, p = 0.03). Workload also remained significantly higher for the bedside clinician compared with the other three roles (p ≤ 0.005 for all).

CONCLUSION

Workload during pediatric trauma resuscitations differed by team role and was increased for higher-level activations and events without previous notification. This study demonstrates the validity of the TLX as a tool to measure workload in trauma resuscitation.

LEVEL OF EVIDENCE

Prognostic study, level II.

Risk of injury in basketball, football, and soccer players, ages 15 years and older, 2003-2007

CONTEXT

A major challenge in the field of sports injury epidemiology is identifying the appropriate denominators for injury rates.

OBJECTIVE

To characterize risk of injury from participation in basketball, football, and soccer in the United States, using hours of participation as the measure of exposure, and to compare these rates with those derived using population estimates in the denominator.

DESIGN

Descriptive epidemiology study.

SETTING

United States, 2003-2007.

PARTICIPANTS

People ages 15 years and older who experienced an emergency department-treated injury while playing basketball, football, or soccer.

MAIN OUTCOME MEASURE(S)

Rates of emergency department-treated injuries resulting from participation in basketball, football, or soccer. Injury rates were calculated for people ages 15 and older for the years 2003-2007 using the U.S. population and hours of participation as the denominators. The risk of injury associated with each of these sports was compared for all participants and by sex.

RESULTS

From 2003 through 2007, annual injury rates per 1000 U.S. population were as follows: 1.49 (95% confidence interval [CI] = 1.30, 1.67) in basketball, 0.93 (95% CI = 0.82, 1.04) in football, and 0.43 (95% CI = 0.33, 0.53) in soccer. When the denominator was hours of participation, the injury rate in football (5.08 [95% CI = 4.46, 5.69]/10 000 hours) was almost twice as high as that for basketball (2.69 [95% CI = 2.35, 3.02]/10 000 hours) and soccer (2.69 [95% CI = 2.07, 3.30]/10 000 hours).

CONCLUSIONS

Depending on the choice of denominator, interpretation of the risk of an emergency department-treated injury in basketball, football, or soccer varies greatly. Using the U.S. population as the denominator produced rates that were highest in basketball and lowest in soccer. However, using hours of participation as a more accurate measure of exposure demonstrated that football had a higher rate of injury than basketball or soccer for both males and females.

FTIR imaging of brain tissue reveals crystalline creatine deposits are an ex vivo marker of localized ischemia during murine cerebral malaria: general implications for disease neurochemistry

Phosphocreatine is a major cellular source of high energy phosphates, which is crucial to maintain cell viability under conditions of impaired metabolic states, such as decreased oxygen and energy availability (i.e., ischemia). Many methods exist for the bulk analysis of phosphocreatine and its dephosphorylated product creatine; however, no method exists to image the distribution of creatine or phosphocreatine at the cellular level. In this study, Fourier transform infrared (FTIR) spectroscopic imaging has revealed the ex vivo development of creatine microdeposits in situ in the brain region most affected by the disease, the cerebellum of cerebral malaria (CM) diseased mice; however, such deposits were also observed at significantly lower levels in the brains of control mice and mice with severe malaria. In addition, the number of deposits was observed to increase in a time-dependent manner during dehydration post tissue cutting. This challenges the hypotheses in recent reports of FTIR spectroscopic imaging where creatine microdeposits found in situ within thin sections from epileptic, Alzheimer's (AD), and amlyoid lateral sclerosis (ALS) diseased brains were proposed to be disease specific markers and/or postulated to contribute to the brain pathogenesis. As such, a detailed investigation was undertaken, which has established that the creatine microdeposits exist as the highly soluble HCl salt or zwitterion and are an ex-vivo tissue processing artifact and, hence, have no effect on disease pathogenesis. They occur as a result of creatine crystallization during dehydration (i.e., air-drying) of thin sections of brain tissue. As ischemia and decreased aerobic (oxidative metabolism) are common to many brain disorders, regions of elevated creatine-to-phosphocreatine ratio are likely to promote crystal formation during tissue dehydration (due to the lower water solubility of creatine relative to phosphocreatine). The results of this study have demonstrated that although the deposits do not occur in vivo, and do not directly play any role in disease pathogenesis, increased levels of creatine deposits within air-dried tissue sections serve as a highly valuable marker for the identification of tissue regions with an altered metabolic status. In this study, the location of crystalline creatine deposits were used to identify whether an altered metabolic state exists within the molecular and granular layers of the cerebellum during CM, which complements the recent discovery of decreased oxygen availability in the brain during this disease.

Compliance with barrier precautions during paediatric trauma resuscitations

PURPOSE

Barrier precautions protect patients and providers from blood-borne pathogens. Although barrier precaution compliance has been shown to be low among adult trauma teams, it has not been evaluated during paediatric resuscitations in which perceived risk of disease transmission may be low. The purpose of this study was to identify factors associated with compliance with barrier precautions during paediatric trauma resuscitations.

METHODS

Video recordings of resuscitations performed on injured children (<18 years old) were reviewed to determine compliance with an established policy requiring gowns and gloves. Depending on activation level, trauma team members included up to six physicians, four nurses, and a respiratory therapist. Multivariate logistic regression was used to determine the effect of team role, resuscitation factors, and injury mechanism on barrier precaution compliance.

RESULTS

Over twelve weeks, 1138 trauma team members participated in 128 resuscitations (4.7% penetrating injuries, 9.4% highest level activations). Compliance with barrier precautions was 81.3%, with higher compliance seen among roles primarily at the bedside compared to positions not primarily at the bedside (90.7% vs. 65.1%, p<0.001). Bedside residents (98.4%) and surgical fellows (97.6%) had the highest compliance, while surgical attendings (20.8%) had the lowest (p<0.001). Controlling for role, increased compliance was observed during resuscitations of patients with penetrating injuries (OR=3.97 [95% CI: 1.35-11.70], p=0.01), during resuscitations triaged to the highest activation level (OR=2.61 [95% CI: 1.34-5.10], p=0.005), and among team members present before patient arrival (OR=4.14 [95% CI: 2.29-7.39], p<0.001).

CONCLUSIONS

Compliance with barrier precautions varies by trauma team role. Team members have higher compliance when treating children with penetrating and high acuity injuries and when arriving before the patient. Interventions integrating barrier precautions into the workflow of team members are needed to reduce this variability and improve compliance with universal precautions during paediatric trauma resuscitations.

Markers of inflammation, metabolic risk factors, and incident heart failure in American Indians: the Strong Heart Study

Inflammation may play a role in increased risk of heart failure (HF) that is associated with obesity, metabolic syndrome (MS), and diabetes. This study investigated associations between inflammatory markers, MS, and incident HF in a population with a high prevalence of diabetes, obesity, and MS. The cohort consisted of 3098 American Indians without prevalent cardiovascular disease who had C-reactive protein (CRP) and fibrinogen measured at the Strong Heart Study phase II examination. Independent associations between inflammatory markers, MS, and HF were analyzed by Cox hazard models. During a mean follow-up of 11 years, 218 participants developed HF. After the adjustment for cardiovascular risk factors, fibrinogen, (hazard ratio [HR], 1.36; 95% confidence interval [CI], 1.15-1.59) but not CRP (HR, 1.25; 95% CI, 0.97-1.32) remained a significant HF predictor. In individuals without diabetes, concomitant presence of MS and elevated CRP or fibrinogen increased HF risk (for MS and CRP: HR, 2.02; 95% CI, 0.95-4.31; for CRP and fibrinogen: HR, 1.75; 95% CI, 0.83-3.72). In a population with a high prevalence of obesity, MS, and diabetes, elevated CRP and fibrinogen increased HF risk. These associations are attenuated by the adjustments for conventional risk factors suggesting that inflammation acts in concert with metabolic and clinical risk factors in increasing HF risk.

A Raman spectroscopic study of a fulgurite

A Raman microspectroscopic study of several fulgurites has been undertaken. A fulgurite is an amorphous mineraloid, a superheated glassy solid that is formed when a lightning bolt hits a sandy or rocky ground and thermal energy is transferred. The Raman spectra revealed several forms of crystalline and fused silica and also the presence of polyaromatic hydrocarbons found in an interfacial zone of a glass bubble. This, together with the presence of anatase, a low-temperature polymorph of TiO(2), suggested that some regions of the fulgurite specimen were not subjected to temperatures of 1800 degrees C, which are attained when lightning hits the surface of sand or a rock.

Relationship between glycemic control and depression among American Indians in the Strong Heart Study

OBJECTIVES

To examine the relationship between depression and glycemic control in the Strong Heart Study (SHS), a longitudinal study of cardiovascular disease in American Indians.

METHODS

This cross-sectional analysis focused on the relationship between depression, diabetes and glycemic control among 2832 individuals aged > or =15 years. Depression was measured by the Center for Epidemiologic Studies of Depression Scale and diabetes by American Diabetes Association criteria. An ordered logit regression model was used to assess whether diabetes was related to level of depression (none, mild, moderate, severe). Multiple logistic regression was used to explore the relationship between A1c and severe depression in participants with diabetes.

RESULTS

Rates of depression were higher in men and women with diabetes when compared to those without diabetes, respectively (P<.05). For every 1-U increase in A1c, the odds of severe depression increased by 22% (OR 1.22, 95% CI: 1.05-1.42). Female sex (OR 2.97, 95% CI: 1.32-6.69) and body mass index (BMI) (OR 1.04, 95% CI: 1.00-1.08) also were significantly associated with increased risk for severe depression. Although BMI appears to be significantly associated with increased risk for severe depression, the magnitude of this effect was small.

CONCLUSIONS

Individuals with diabetes have higher rates of depression than those without diabetes, consistent with other populations. There is a positive relationship between severity of depression and A1c levels; men and women with severe depression have higher A1c levels than those with moderate-to-no depression.

Vibrational spectroscopic mapping and imaging of tissues and cells

Vibrational spectroscopic mapping (point-by-point measurement) and imaging of biological samples (cells and tissues) covering Fourier-transform infrared (FTIR) and Raman spectroscopies has opened up many exciting new avenues to explore biochemical architecture and processes within healthy and diseased cells and tissues, including medical diagnostics and drug design.

Fatty acid consumption and metabolic syndrome components: the GOCADAN study

Fatty acids (FAs) have been related to changes in glucose and lipid metabolism. In this article, the authors assess the association between intake of specific FAs and components of the metabolic syndrome (MS) in adult Eskimos. A total of 691 Inupiat Eskimos (325 men and 366 women), aged 34 to 75 years, were examined as part of the Genetics of Coronary Artery Disease in Alaska Natives (GOCADAN) study. The investigation included a physical examination, blood pressure measurements, blood sampling under fasting conditions, 2-hour oral glucose tolerance test, and a personal interview including a validated food frequency questionnaire. Components of MS were defined according to the Third Report of the National Cholesterol Education Program Adult Treatment Panel criteria. Consumption of individual FAs showed associations with MS components. Long-chain omega-3 FAs, from fish and sea mammals, were associated with lower blood pressure, serum triglycerides, and 2-hour glucose and higher high-density lipoprotein cholesterol, fasting insulin, and homeostasis model assessment. Saturated fat consumption was associated with higher triglyceride levels and blood pressure. Trans-FA consumption was associated with higher blood pressure. Consumption of long-chain omega-3 FAs from marine sources may improve certain MS components, and thus may reduce risk for cardiovascular disease. High consumption of saturated FAs and trans-FAs may have an adverse effect on MS.

The Rio Tinto Mars analogue site: an extremophilic Raman spectroscopic study

The Rio Tinto site is recognised as a terrestrial Mars analogue because of the presence of jarosite and related sulfates which have recently been identified by the NASA Mars Exploration Rover "Opportunity" in the El Capitan region of Meridiani Planum on Mars. It has long been known that acidophilic microbial action is responsible for the deep blood-red colour of the water in Rio Tinto, where the pH varies from about 1.5 to 3.0 and the water is rich in iron and sulfur. Following recent Raman spectroscopic characterisation of the mineral phases of the Rio Tinto system, we report here a study of the biological components found in several specimens of deposited minerals and near the waterside that were collected during a GeoRaman VI Conference organized field trip in 2006. Key biosignatures were found for carotenoids, scytonemin and mycosporine-like amino acids, which are indicative of the biological colonisation of exposed mineral substrates; information from this study will be useful for targeting Martian sites using a miniaturized Raman instrument where the biosignatures of relict or extant life could remain in the geological record.

Characterization of nanoindentation-induced residual stresses in human enamel by Raman microspectroscopy

The objective of this research was to investigate nanoindentation-induced residual stresses in human enamel using Raman microspectroscopy and establish if this approach can be used as a stress meter. Healthy human premolars and sintered hydroxyapatite samples were embedded, cut, and the surfaces were polished finely with a 0.05 microm polishing paste before Berkovich and spherical indentations were made with a force of 100 mN. Spectra were collected using a Renishaw Raman InVia reflex microscope equipped with an air-cooled charge-coupled device (CCD) camera. Sample excitation was achieved using either an argon ion laser emitting at 514.5-nm or a NIR diode laser emitting at 830-nm. The residual micro stresses within and surrounding the indentation impressions were monitored by mapping the position of the nu(1)(PO(4)) band of (crystalline) hydroxyapatite. The Raman maps coincided well with the optical micrographs of the samples. Despite the presence of a fluorescence background from the organic component of human enamel, spectra collected using 514.5-nm excitation exhibited more significant shifts in the position of the nu(1)(PO(4)) band than spectra collected using 830-nm excitation. This implies that the former excitation may be a more appropriate excitation for stress detection. It was concluded that Raman microspectroscopy provides a novel high-resolution and non-destructive method for exploring the role of microstructure on the residual stress distribution within natural biocomposites.

Descriptive epidemiology of collegiate women's lacrosse injuries: National Collegiate Athletic Association Injury Surveillance System, 1988-1989 through 2003-2004

OBJECTIVE

To review 16 years of National Collegiate Athletic Association injury surveillance data for women's lacrosse and identify potential areas for injury prevention initiatives.

BACKGROUND

Women's lacrosse is a fast-paced, primarily noncontact sport. Participation in collegiate women's lacrosse almost doubled between the 1988-1989 and 2003-2004 seasons. Lacrosse equipment consists of sticks made of wood or a synthetic material and a hard rubber ball. Until recently, mouth guards were the only required protective equipment.

MAIN RESULTS

Collegiate women's lacrosse game injury rates increased over the 16-year study period. More than 60% of all severe game injuries were lower extremity sprains and strains and knee internal derangements, most frequently the result of noncontact incidents. The most common injury scenarios by injury mechanism and player activity were no contact while ball handling (16.4%) and contact from a stick while ball handling (10.5%). Contact from a stick or a ball accounted for 5.6% and 5.2% of injuries sustained during shooting activities, respectively. Approximately 22% of all game and 12% of all practice injuries involved the head and neck. Contact from a stick accounted for the majority (56.0%) of above-the-neck injuries in games; contact from the ball accounted for 20.0% of these injuries. Participants had 5 times the risk of sustaining a concussion in a game as in a practice (0.70 versus 0.15 injuries per 1000 athletic-exposures, rate ratio = 4.7, 95% confidence interval = 3.8, 6.5).

RECOMMENDATIONS

To reduce the lower extremity injuries that comprise the greatest injury burden in women's lacrosse, future researchers should evaluate proprioceptive, plyometric, and balance training interventions designed specifically for female players. Other research areas of great interest involve determining whether protective eyewear (mandated in 2004) reduces injuries to the eye, orbit, and nasal area and identifying any unintended consequences of the mandate, such as increased risk of injuries to other areas of the face or more aggressive play.

Cross-sectional relationship of reported fatigue to obesity, diet, and physical activity: results from the third national health and nutrition examination survey

STUDY OBJECTIVES

Reported daytime fatigue may be influenced by modifiable risk factors. We hypothesized that daytime fatigue is associated with less-favorable lifestyle factors, including high body mass index, higher intake of dietary fat, and limited physical activity.

DESIGN

Cross-sectional analysis.

SETTING

Population-based survey.

PARTICIPANTS

Participants aged 20 to 59 years in the Third National Health and Nutrition Examination Survey.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

We examined relationships between responses to the question, "Right now would you say you are feeling energetic, fresh, average, tired or exhausted?" and body mass index, waist circumference, leisure time physical activity, and macronutrient intake. Analyses included only people who reported getting their usual amount of sleep the night before the evaluation and controlled for age, sex, and ethnicity; 5.6%, 14.6%, 58.3%, 19.5%, and 2.0% reported that they felt "energetic," "fresh," "average," "tire d," and "ex hausted" respectively. There was a U-shaped association across the categories of fatigue for physical activity, body mass index, and waist circumference, with the healthiest lifestyle factors being associated with reporting feeling "fresh." Relative to the fresh group, average, tired and exhausted participants were 1.6, 1.9, and 3.8 times more likely to report insufficient physical activity, all statistically different from the fresh group. This pattern was also observed for body mass index and waist circumference and persisted after adjustment for covariates and exclusion of individuals with depression.

CONCLUSIONS

In adults aged 20 to 59 years in the United States, self-reported fatigue is associated with higher body mass index, higher waist circumference, and a reduced likelihood of getting recommended levels of physical activity.