Femtosecond Visualization of hcp-Iron Strength and Plasticity under Shock Compression.

Iron is a key constituent of planets and an important technological material. Here, we combine in situ ultrafast x-ray diffraction with laser-induced shock compression experiments on Fe up to 187(10) GPa and 4070(285) K at 10^{8} s^{-1} in strain rate to study the plasticity of hexagonal-close-packed (hcp)-Fe under extreme loading states. {101[over ¯]2} deformation twinning controls the polycrystalline Fe microstructures and occurs within 1 ns, highlighting the fundamental role of twinning in hcp polycrystals deformation at high strain rates. The measured deviatoric stress initially increases to a significant elastic overshoot before the onset of flow, attributed to a slower defect nucleation and mobility. The initial yield strength of materials deformed at high strain rates is thus several times larger than their longer-term flow strength. These observations illustrate how time-resolved ultrafast studies can reveal distinctive plastic behavior in materials under extreme environments.

Levels of Mercury in Feathers of Clapper Rails (Rallus crepitans) over 45 Years in Coastal Salt Marshes of New Hanover County, North Carolina.

We sampled clapper rail (Rallus crepitans) feathers from museum specimens collected between 1965 and 2010 to investigate changes in mercury (Hg) availability in coastal marshes of New Hanover County, North Carolina. Stable isotope analysis (δ(13)C and δ(15)N) was conducted to control for dietary shifts that may have influenced Hg exposure. Hg concentrations ranged from 0.96 to 9.22 µg/g (ppm), but showed no significant trend over time; diet (δ(15)N) or foraging habitat (δ(13)C) also provided little to no explanatory power to the variation in Hg concentrations among clapper rails. Our findings suggest the bioavailability of Hg to clapper rails in coastal North Carolina salt marshes has remained consistent over time, despite the global trend of increasing mercury in many other bird species, providing an excellent baseline for any future assessment of Hg availability to salt marsh birds in coastal North Carolina.

Analysis of 101 Mechanical Failures in Distal Femur Fractures Treated with 3 Generations of Precontoured Locking Plates.

OBJECTIVES: To evaluate mechanical treatment failure in a large patient cohort sustaining a distal femur fracture treated with a distal femoral locking plate (DFLP). DESIGN: This retrospective case-control series evaluated mechanical treatment failures of DFLPs. SETTING: The study was conducted at 8 Level I trauma centers from 2010 to 2017. PATIENTS AND PARTICIPANTS: One hundred one patients sustaining OTA/AO 33-A and C distal femur fractures were treated with DFLPs that experienced mechanical failure. INTERVENTION: The intervention included the treatment of a distal femur fracture with a DFLP, affected by mechanical failure (implant failure by loosening or breakage). MAIN OUTCOME MEASURE: The main outcome measures included injury and DFLP details; modes and timing of failure were studied. RESULTS: One hundred forty-six nonunions were found overall (13.4%) including 101 mechanical failures (9.3%). Failures occurred in different manners, locations, and times depending on the DFLPs. For example, 33 of 101 stainless steel (SS) plates (33%) failed by bending or breaking in the working length, whereas no Ti plates failed here ( P < 0.05). Eleven of 12 failures with titanium-Less Invasive Stabilization System (92%) occurred by lost shaft fixation, mostly by the loosening of unicortical screws (91%). Sixteen of 44 variable -angled-LCP failures (36%) occurred at the distal plate-screw junction, whereas only 5 of 61 other DFLPs (8%) failed this way ( P < 0.05). Distal failures occurred on average at 23.7 weeks compared with others that occurred at 38.4 weeks ( P < 0.05). Variable -angled-LCP distal screw-plate junction failures occurred earlier (mean 21.4 weeks). CONCLUSION: Nonunion and mechanical failure occurred in 14% and 9% of patients, respectively, in this large series of distal femur fracture treated with a DFLP. The mode, location, presence of a prosthesis, and timing of failure varied depending on the characteristics of DFLP. This information should be used to optimize implant usage and design to prolong the period of stable fixation before potential implant failures occur in patients with a prolonged time to union. LEVEL OF EVIDENCE: Economic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Clinical Outcomes of Acute Respiratory Failure Associated With Noninvasive and Invasive Ventilation in a Pediatric ICU.

BACKGROUND: It remains unknown if pediatric patients failing initial noninvasive ventilation (NIV) experience worse clinical outcomes than those successfully treated with NIV or those primarily intubated. METHODS: This was a single-center, retrospective review of patients admitted with acute respiratory failure to the University of Michigan pediatric intensive care or cardiothoracic ICUs and receiving NIV or invasive mechanical ventilation as first-line therapy. RESULTS: One hundred seventy subjects met inclusion criteria and were enrolled: 65 NIV success, 55 NIV failure, and 50 invasive mechanical ventilation alone. Of those failing NIV, median time to intubation was 1.8 (interquartile range [IQR] < 1-7) h. On multivariable regression, ICU-free days were significantly different between groups (NIV success: 22.9 ± 6.9 d; NIV failure: 13.0 ± 6.6 d; invasive ventilation: 12.5 ± 6.9 d; P < .001 across all groups). Multivariable regression revealed no difference in ventilator-free days between NIV failure and invasive ventilation groups (15.4 ± 10.1 d vs 15.9 ± 9.7 d, P = .71). Of 64 subjects (37.6%) meeting Pediatric Acute Lung Injury Consensus Conference pediatric ARDS criteria, only 14% were successfully treated with NIV. Ventilator-free days were similar between the NIV failure and invasive ventilation groups (11.6 vs 13.2 d, P = .47). On multivariable analysis, ICU-free days were significantly different across pediatric ARDS groups (P < .001): NIV success: 20.8 + 31.7 d; NIV failure: 8.3 + 23.8 d; invasive alone: 8.9 + 23.9 d, yet no significant difference in ventilator-free days between those with NIV failure versus invasive alone (11.6 vs 13.2 d, P = .47). CONCLUSIONS: We demonstrated that critically ill pediatric subjects unsuccessfully trialed on NIV did not experience increased ICU length of stay or fewer ventilator-free days when compared to those on invasive mechanical ventilation alone, including in the pediatric ARDS subgroup. Our findings are predicated on a median time to intubation of < 2 h in the NIV failure group and the provision of adequate monitoring while on NIV.

In Situ High Pressure Hydrogen Tribological Testing of Common Polymer Materials Used in the Hydrogen Delivery Infrastructure.

High pressure hydrogen gas is known to adversely affect metallic components of compressors, valves, hoses, and actuators. However, relatively little is known about the effects of high pressure hydrogen on the polymer sealing and barrier materials also found within these components. More study is required in order to determine the compatibility of common polymer materials found in the components of the hydrogen fuel delivery infrastructure with high pressure hydrogen. As a result, it is important to consider the changes in physical properties such as friction and wear in situ while the polymer is exposed to high pressure hydrogen. In this protocol, we present a method for testing the friction and wear properties of ethylene propylene diene monomer (EPDM) elastomer samples in a 28 MPa high pressure hydrogen environment using a custom-built in situ pin-on-flat linear reciprocating tribometer. Representative results from this testing are presented which indicate that the coefficient of friction between the EPDM sample coupon and steel counter surface is increased in high pressure hydrogen as compared to the coefficient of friction similarly measured in ambient air.

Outcome of Posterior Tibial Plateau Fixation.

Isolated posterior tibial plateau fractures are rare injuries that encompass a wide variety of fracture patterns. Based on the variation in fracture pattern, the surgical approach varies, with both anterior and posterior approaches described for surgical fixation. Postoperative protocol also varies among studies. The aim of this article is to summarize the outcomes related to posterior column tibial plateau fractures. The papers reviewed, primarily small retrospective case series, showed functional knee range of motion is preserved, a low incidence of wound complications, and patient outcome scores comparable to other reported lower extremity injury outcome scores.

Black art posters, an incentive to increase study enrollment among Blacks in a large cohort study.

OBJECTIVE: Black art posters were offered to replace or augment the established $10 incentive for questionnaire completion in a longitudinal cohort study. METHOD: Eighty-one churches located in the US southern region were divided between two intervention groups, with a control group of 24 churches from the same region. Primary outcome measures were study enrollment rates and questionnaire return rates between December 2003 and July 2004 as a proportion of church goal. RESULTS: 9.3% of participants returning questionnaires selected a poster in preference to $10. Half of participants offered both monetary and art incentives indicated a poster selection. Crude questionnaire return rates were 57.4% for the pooled intervention churches and 38.2% for the control churches. Enrollment rates among those offered both incentives were significantly higher (p<0.01) than when monetary incentives alone were offered after adjustment for church size, promotional dates, and average income of church members. Survey return rates were also higher in the churches offered both incentives (p=0.04). CONCLUSION: These data suggest that the black art posters improved study enrollment and survey return rates. The relatively low rate of poster selection suggests that the art primarily influenced participation indirectly, by creating a more culturally inclusive image of the study.

Understanding organization structures of the college, university, high school, clinical, and professional settings.

Athletes participate at many different levels of competition--from amateur to professional, from backyard sandlot to Yankee Stadium. There are as many different organized structures involved in providing medical care to athletes as there are types of athletes themselves. Although the organizational structures involved in providing medical care for a little league team in a small town are different from those involved in providing care for a professional baseball team, the mission is the same-caring for athletes. This is the central theme of this article. Though there are different organizational structures, there are more common threads than differences in the mission of those who provide medical care for athletes at any level.

Sudden Cardiac Arrest in Athletic Medicine.

OBJECTIVE: To emphasize the importance of decreasing the response time by a trained target responder to increase the survival rate among athletes experiencing sudden cardiac arrest at an athletic event. BACKGROUND: Death due to sudden cardiac arrest that is witnessed is preventable in many cases. However, most people who experience this condition die because of a prolonged response time from onset of the fatal arrhythmia to defibrillation by trained treatment providers. If athletic trainers or other members of the athletic care medical team are trained as target responders and equipped with automated electronic defibrillators, they can immediately treat an athlete who experiences a sudden, life-threatening tachyarrhythmia. This prompt response to the life-threatening emergency should result in a higher survival rate. DESCRIPTION: We review the causes of sudden cardiac arrest during athletic events, note some unusual clinical presentations, discuss improved methods of response and new equipment for treatment, and define the athletic trainer's role as a target responder trained to treat people experiencing sudden cardiac arrest at an athletic event. CLINICAL ADVANTAGES: An athletic care team willing to become part of an emergency response team can help improve the survival rate of athletes experiencing sudden cardiac arrest at an athletic event.

Within-Day Variability of SARS-CoV-2 RNA in Municipal Wastewater Influent During Periods of Varying COVID-19 Prevalence and Positivity

Wastewater surveillance of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA is being used to monitor Coronavirus Disease 2019 (COVID-19) trends in communities; however, within-day variation in primary influent concentrations of SARS-CoV-2 RNA remain largely uncharacterized. In the current study, grab sampling of primary influent was performed every 2 hours over two different 24-hour periods at two wastewater treatment plants (WWTPs) in northern Indiana, USA. In primary influent, uncorrected, recovery-corrected, and pepper mild mottle virus (PMMoV)-normalized SARS-CoV-2 RNA concentrations demonstrated ordinal agreement with increasing clinical COVID-19 positivity, but not COVID-19 cases. Primary influent SARS-CoV-2 RNA concentrations exhibited greater variation than PMMoV RNA concentrations as expected for lower shedding prevalence. The bovine respiratory syncytial virus (BRSV) process control recovery efficiency was low (mean: 0.91%) and highly variable (coefficient of variation: 51% - 206%) over the four sampling events with significant differences between the two WWTPs (p <0.0001). The process control recovery was similar to the independently assessed SARS-CoV-2 RNA recovery efficiency, which was also significantly different between the two WWTPs (p <0.0001). Recovery-corrected SARS-CoV-2 RNA concentrations better reflected within-day changes in primary influent flow rate and fecal content, as indicated by PMMoV concentrations. These observations highlight the importance of assessing the process recovery efficiency, which is highly variable, using an appropriate process control. Despite large variations, both recovery-corrected and PMMoV-normalized SARS-CoV-2 RNA concentrations in primary influent demonstrate potential for monitoring COVID-19 positivity trends in WWTPs serving peri-urban and rural areas.