Near Room-Temperature Intrinsic Exchange Bias in an Fe Intercalated ZrSe2 Spin Glass.

Some magnetic systems display a shift in the center of their magnetic hysteresis loop away from zero field, a phenomenon termed exchange bias. Despite the extensive use of the exchange bias effect, particularly in magnetic multilayers, for the design of spin-based memory/electronics devices, a comprehensive mechanistic understanding of this effect remains a longstanding problem. Recent work has shown that disorder-induced spin frustration might play a key role in exchange bias, suggesting new materials design approaches for spin-based electronic devices that harness this effect. Here, we design a spin glass with strong spin frustration induced by magnetic disorder by exploiting the distinctive structure of Fe intercalated ZrSe2, where Fe(II) centers are shown to occupy both octahedral and tetrahedral interstitial sites and to distribute between ZrSe2 layers without long-range structural order. Notably, we observe behavior consistent with a magnetically frustrated and multidegenerate ground state in these Fe0.17ZrSe2 single crystals, which persists above room temperature. Moreover, this magnetic frustration leads to a robust and tunable exchange bias up to 250 K. These results not only offer important insights into the effects of magnetic disorder and frustration in magnetic materials generally, but also highlight as design strategy the idea that a large exchange bias can arise from an inhomogeneous microscopic environment without discernible long-range magnetic order. In addition, these results show that intercalated TMDs like Fe0.17ZrSe2 hold potential for spintronic technologies that can achieve room temperature applications.

Selective nitrogen adsorption via backbonding in a metal-organic framework with exposed vanadium sites.

Industrial processes prominently feature π-acidic gases, and an adsorbent capable of selectively interacting with these molecules could enable important chemical separations1-4. Biological systems use accessible, reducing metal centres to bind and activate weakly π-acidic species, such as N2, through backbonding interactions5-7, and incorporating analogous moieties into a porous material should give rise to a similar adsorption mechanism for these gaseous substrates8. Here, we report a metal-organic framework featuring exposed vanadium(II) centres capable of back-donating electron density to weak π acids to successfully target π acidity for separation applications. This adsorption mechanism, together with a high concentration of available adsorption sites, results in record N2 capacities and selectivities for the removal of N2 from mixtures with CH4, while further enabling olefin/paraffin separations at elevated temperatures. Ultimately, incorporating such π-basic metal centres into porous materials offers a handle for capturing and activating key molecular species within next-generation adsorbents.

Selective, High-Temperature O2 Adsorption in Chemically Reduced, Redox-Active Iron-Pyrazolate Metal-Organic Frameworks.

Developing O2-selective adsorbents that can produce high-purity oxygen from air remains a significant challenge. Here, we show that chemically reduced metal-organic framework materials of the type AxFe2(bdp)3 (A = Na+, K+; bdp2- = 1,4-benzenedipyrazolate; 0 < x ≤ 2), which feature coordinatively saturated iron centers, are capable of strong and selective adsorption of O2 over N2 at ambient (25 °C) or even elevated (200 °C) temperature. A combination of gas adsorption analysis, single-crystal X-ray diffraction, magnetic susceptibility measurements, and a range of spectroscopic methods, including 23Na solid-state NMR, Mössbauer, and X-ray photoelectron spectroscopies, are employed as probes of O2 uptake. Significantly, the results support a selective adsorption mechanism involving outer-sphere electron transfer from the framework to form superoxide species, which are subsequently stabilized by intercalated alkali metal cations that reside in the one-dimensional triangular pores of the structure. We further demonstrate O2 uptake behavior similar to that of AxFe2(bdp)3 in an expanded-pore framework analogue and thereby gain additional insight into the O2 adsorption mechanism. The chemical reduction of a robust metal-organic framework to render it capable of binding O2 through such an outer-sphere electron transfer mechanism represents a promising and underexplored strategy for the design of next-generation O2 adsorbents.

Association between Prehospital CPR Quality and End-Tidal Carbon Dioxide Levels in Out-of-Hospital Cardiac Arrest.

INTRODUCTION: International Guidelines recommend measurement of end-tidal carbon dioxide (EtCO2) to enhance cardiopulmonary resuscitation (CPR) quality and optimize blood flow during CPR. Numerous factors impact EtCO2 (e.g., ventilation, metabolism, cardiac output), yet few clinical studies have correlated CPR quality and EtCO2 during actual out-of-hospital cardiac arrest (OHCA) resuscitations. The purpose of this study was to describe the association between EtCO2 and CPR quality variables during OHCA. METHODS: This is an observational study of prospectively collected CPR quality and capnography data from two EMS agencies participating in a statewide resuscitation quality improvement program. CPR quality and capnography data from adult (≥18 years) cardiac resuscitation attempts (10/2008-06/2013) were collected and analyzed on a minute-by-minute basis using RescueNet™ Code Review. Linear mixed effect models were used to evaluate the association between (log-transformed) EtCO2 level and CPR variables: chest compression (CC) depth, CC rate, CC release velocity (CCRV), ventilation rate. RESULTS: Among the 1217 adult OHCA cases of presumed cardiac etiology, 925 (76.0%) had a monitor-defibrillator file with CPR quality data, of which 296 (32.0%) cases had >1 minute of capnography data during CPR. After capnography quality review, 66 of these cases (22.3%) were excluded due to uninterpretable capnography, resulting in a final study sample of 230 subjects (mean age 68 years; 69.1% male), with a total of 1581 minutes of data. After adjustment for other CPR variables, a 10 mm increase in CC depth was associated with a 4.0% increase in EtCO2 (p < 0.0001), a 10 compression/minute increase in CC rate with a 1.7% increase in EtCO2 (p = 0.02), a 10 mm/second increase in CCRV with a 2.8% increase in EtCO2 (p = 0.03), and a 10 breath/minute increase in ventilation rate with a 17.4% decrease in EtCO2 (p < 0.0001). CONCLUSION: When controlling for known CPR quality variables, increases in CC depth, CC rate and CCRV were each associated with a statistically significant but clinically modest increase in EtCO2. Given the small effect sizes, the clinical utility of using EtCO2 to guide CPR performance is unclear. Further research is needed to determine the practicality and impact of using real-time EtCO2 to guide CPR delivery in the prehospital environment.

Exchange Bias in a Layered Metal-Organic Topological Spin Glass.

The discovery of conductive and magnetic two-dimensional (2D) materials is critical for the development of next generation spintronics devices. Coordination chemistry in particular represents a highly versatile, though underutilized, route toward the synthesis of such materials with designer lattices. Here, we report the synthesis of a conductive, layered 2D metal-organic kagome lattice, Mn3(C6S6), using mild solution-phase chemistry. Strong geometric spin frustration in this system mediates spin freezing at low temperatures, which results in glassy magnetic dynamics consistent with a rare geometrically frustrated (topological) spin glass. Notably, we show that this geometric frustration engenders a large, tunable exchange bias of 1625 Oe in Mn3(C6S6), providing the first example of exchange bias in a coordination solid or a topological spin glass. Exchange bias is a critical component in a number of spintronics applications, but it is difficult to rationally tune, as it typically arises due to structural disorder. This work outlines a new strategy for engineering exchange bias systems using single-phase, crystalline lattices. More generally, these results demonstrate the potential utility of geometric frustration in the design of new nanoscale spintronic materials.

Exchange biased anomalous Hall effect driven by frustration in a magnetic kagome lattice.

Co[Formula: see text]Sn[Formula: see text]S[Formula: see text] is a ferromagnetic Weyl semimetal that has been the subject of intense scientific interest due to its large anomalous Hall effect. We show that the coupling of this material's topological properties to its magnetic texture leads to a strongly exchange biased anomalous Hall effect. We argue that this is likely caused by the coexistence of ferromagnetism and geometric frustration intrinsic to the kagome network of magnetic ions, giving rise to spin-glass behavior and an exchange bias.

Subscapularis Peel for Open Reduction and Internal Fixation of Proximal Humerus Fractures With a Head Split.

Proximal humerus fractures involving an articular head split are rare and complex injuries. In the elderly population, arthroplasty is the optimal treatment, whereas in younger patients, the utility of arthroplasty procedures is limited by concerns of long-term implant survival. As a result, open reduction and internal fixation is still often the first-line treatment option for head-splitting injuries. The traditionally described deltopectoral or anterolateral surgical approaches to the proximal humerus rely on indirect reduction and limited visualization of the articular fragments. We present a case series of younger patients with head-split proximal humerus fractures treated with open reduction and internal fixation through a deltopectoral approach with a subscapularis peel to improve humeral head visualization, reduction, and fixation. The improved reduction may lead to better long-term outcomes and reduce the need for additional surgical procedures. In addition, there were no cases of avascular necrosis in this series.

Telephone CPR Instructions in Emergency Dispatch Systems: Qualitative Survey of 911 Call Centers.

INTRODUCTION: Out-of-hospital cardiac arrest (OHCA) is a leading cause of death. The 2010 American Heart Association Emergency Cardiovascular Care (ECC) Guidelines recognize emergency dispatch as an integral component of emergency medical service response to OHCA and call for all dispatchers to be trained to provide telephone cardiopulmonary resuscitation (T-CPR) pre-arrival instructions. To begin to measure and improve this critical intervention, this study describes a nationwide survey of public safety answering points (PSAPs) focusing on the current practices and resources available to provide T-CPR to callers with the overall goal of improving survival from OHCA. METHODS: We conducted this survey in 2010, identifying 5,686 PSAPs; 3,555 had valid e-mail addresses and were contacted. Each received a preliminary e-mail announcing the survey, an e-mail with a link to the survey, and up to three follow-up e-mails for non-responders. The survey contained 23 primary questions with sub-questions depending on the response selected. RESULTS: Of the 5,686 identified PSAPs in the United States, 3,555 (63%) received the survey, with 1,924/3,555 (54%) responding. Nearly all were public agencies (n=1,888, 98%). Eight hundred seventy-eight (46%) responding agencies reported that they provide no instructions for medical emergencies, and 273 (14%) reported that they are unable to transfer callers to another facility to provide T-CPR. Of the 1,924 respondents, 975 (51%) reported that they provide pre-arrival instructions for OHCA: 67 (3%) provide compression-only CPR instructions, 699 (36%) reported traditional CPR instructions (chest compressions with rescue breathing), 166 (9%) reported some other instructions incorporating ventilations and compressions, and 92 (5%) did not specify the type of instructions provided. A validation follow up showed no substantial difference in the provision of instructions for OHCA by non-responders to the survey. CONCLUSION: This is the first large-scale, nationwide assessment of the practices of PSAPs in the United States regarding T-CPR for OHCA. These data showing that nearly half of the nation's PSAPs do not provide T-CPR for OHCA, and very few PSAPs provide compression-only instructions, suggest that there is significant potential to improve the implementation of this critical link in the chain of survival for OHCA.