Electronic Structure and Lattice dynamics of NaFeAs

The similarity of the electronic structures of NaFeAs and other Fe pnictides has been demonstrated on the basis of first-principle calculations. The global double-degeneracy of electronic bands along X-M and R-A direction indicates the instability of Fe pnictides and is explained on the basis of a tight-binding model. The de Haas-van Alphen parameters for the Fermi surface (FS) of NaFeAs have been calculated. A $\mathbf{Q}_{M}=(1/2,1/2,0)$ spin density wave (SDW) instead of a charge density wave (CDW) ground state is predicted based on the calculated generalized susceptibility $\chi(\mathbf{q})$ and a criterion derived from a restricted Hatree-Fock model. The strongest electron-phonon (e-p) coupling has been found to involve only As, Na z-direction vibration with linear-response calculations. A possible enhancement mechanism for e-p coupling due to correlation is suggested

Management considerations of massive hemoptysis while on extracorporeal membrane oxygenation.

BACKGROUND: Veno-arterial extracorporeal membrane oxygenation (V-A ECMO) is a life-saving procedure in patients with both respiratory and cardiac failure. Bleeding complications are common since patients must be maintained on anticoagulation. Massive hemoptysis is a rare complication of ECMO; however, it may result in death if not managed thoughtfully and expeditiously. METHODS: A retrospective chart review was performed of consecutive ECMO patients from 7/2010-8/2014 to identify episodes of massive hemoptysis. The management of and the outcomes in these patients were studied. Massive hemoptysis was defined as an inability to control bleeding (\u3e300 mL/day) from the endotracheal tube with conventional maneuvers, such as bronchoscopy with cold saline lavage, diluted epinephrine lavage and selective lung isolation. All of these episodes necessitated disconnecting the ventilator tubing and clamping the endotracheal tube, causing full airway tamponade. RESULTS: During the period of review, we identified 118 patients on ECMO and 3 (2.5%) patients had the complication of massive hemoptysis. One case was directly related to pulmonary catheter migration and the other two were spontaneous bleeding events that were propagated by antiplatelet agents. All three patients underwent bronchial artery embolization in the interventional radiology suite. Anticoagulation was held during the period of massive hemoptysis without any embolic complications. There was no recurrent bleed after appropriate intervention. All three patients were successfully separated from ECMO. CONCLUSIONS: Bleeding complications remain a major issue in patients on ECMO. Disconnection of the ventilator and clamping the endotracheal tube with full respiratory and cardiac support by V-A ECMO is safe. Early involvement of interventional radiology to embolize any potential sources of the bleed can prevent re-hemoptysis and enable continued cardiac and respiratory recovery

The Deschutes Formation: evidence of extension-enhanced explosivity in the early High Cascades

The eruptive history of the Quaternary Cascades arc has been relatively well characterized. However, much less is known about the frequency and sizes of explosive eruptions produced by earlier stages of the arc. The Late Neogene Deschutes Formation of Central Oregon preserves a remarkable record of heightened pyroclastic activity during the initial stages of High Cascades volcanism, following an eastward shift in volcanic activity ~7.5 Ma. Extensive fieldwork, 40Ar 39Ar geochronology, and geochemical analyses allow us to reconstruct this unusually explosive phase of the earliest Central Oregon High Cascades.Plagioclase 40Ar 39Ar ages for eight laterally-extensive marker ignimbrites that stratigraphically bracket the many pyroclastic deposits exposed within the Deschutes Formation, indicate that almost all of these explosive eruptions occurred within only ~800 k.y., between 6.25± 0.07 and 5.45± 0.04 Ma. Combining these age data with multivariate statistical tephra correlation methods, I establish a comprehensive tephrostratigraphy of the Deschutes Formation. These correlations suggest that at least 67 distinct explosive eruptions (possibly as many as 120) occurred within the 800 k.y. explosive pulse.Using a new ArcGIS-based method that I developed for calculating ignimbrite volumes, I find that a total volume of 82 km3 (62 km3 DRE) for just 26 of the ignimbrites deposited distally into the Deschutes Basin. If these ignimbrites also deposited an equal volume to the west and had a tephra fall:flow ratio of betweenii0.5:1 and 1.9:1 (similar to Mount Pinatubo and Valley of Ten Thousand Smokes), the total volume of all 26 eruptions was likely between 246 and 475 km3, or a rate of 6-12 km3 m.y. km. This rate is approximately 2-8 times higher than the production rate of all compositions over the entire Quaternary Cascades and is the highest rate in Oregon over at least the last 17 Ma.The unique timing and location of this pulse, approximately 1 m.y. after an eastward shift of the arc axis, and in a region undergoing extension, may explain the anomalous explosivity recorded in the Deschutes Formation. I suggest that such extension allowed for penetration of hot, low-K tholeiitic basalt magmas into shallow levels of the crust, which induced a period of enhanced shallow crustal melting and the production of large volumes of hot-dry-reduced rhyolites (high Fe, Na, Y, MREE, and low Eu Eu* and Sr). Thus, the anomalously high production of silicic magma and rate of explosive volcanism recorded in the Deschutes Formation is mirrored by the unusual geochemistry of the eruptive products, and are together indicative of magmatic processes driven by extension, that no longer operate during the Quaternary.In addition to constraining changes in geochemistry and style of volcanism through time, I used rigorous statistical methodology to assess the geochemical variability along-arc for the Quaternary Cascades. To do this, I compiled a dataset of over 11,000 samples and utilized a Monte Carlo approach with weighted bootstrap resampling to reduce the bias that over-sampled volcanoes have on overall trends. In in doing so, I assessed regional, rather than local processes. Our study develops a novel approach to assessing along-arc geochemical variability using entirely objective and statistically-based methodology. Using this new approach, I separated the Cascades arc into 5 segments such that the geochemical differences between each is maximized. This new segmentation scheme, which includes the North, Washington, Graben, Mazama, and South Segments is more statistically robust than previous segmentation schemes. By separating the arc into the most statistically distinct regions, one can better assess the spatially disparate processes that lead to geochemical heterogeneity. This, in turn, provides a better understanding of the fundamental processes involved in arc magma generation.Keywords: Cascades Arc, Explosive volcanism, Volcanology, Geochemistry, Tephrochronology, Igneous Petrolog

Iatrogenic pneumatosis intestinalis and pneumatosis hepatis

A term male fetus with meconium-stained liquor was delivered at a peripheral hospital. He developed abdominal distension and bile-stained vomiting shortly after birth. Meconium ingestion was suspected. Gastric lavage was attempted using inappropriately high volumes and concentrations of sodium bicarbonate in this newborn with undiagnosed jejunal atresia. Subsequent abdominal radiographs documented the presence of the jejunal atresia and pneumatosis intestinalis (PI), together with air in both the porta hepatis and liver parenchyma (Figs 1 - 3). The latter features were interpreted as representing necrotising enterocolitis. The child was transferred to Red Cross Children’s Hospital, Cape Town, for corrective surgery

Pressure shift of the superconducting T_c of LiFeAs

The effect of hydrostatic pressure on the superconductivity in LiFeAs is investigated up to 1.8 GPa. The superconducting transition temperature, T_c, decreases linearly with pressure at a rate of 1.5 K/GPa. The negative pressure coefficient of T_c and the high ambient pressure T_c indicate that LiFeAs is the high-pressure analogue of the isoelectronic SrFe_2As_2 and BaFe_2As_2.Comment: 3 pages, 2 figure

Sperm competition, but not major histocompatibility divergence, drive differential fertilization success between alternative reproductive tactics in Chinook salmon

Post-copulatory sexual selection processes, including sperm competition and cryptic female choice (CFC), can operate based on major histocompatibility (MH) genes. We investigated sperm competition between male alternative reproductive tactics (jack (sneaker) and hooknose (guard)) of Chinook salmon (Oncorhynchus tshawytscha). Using a full factorial design, we examined in vitro competitive fertilization success of paired jack and hooknose males at three time points after sperm activation (0, 15 and 60 seconds) to test for male competition, CFC and time effects on male fertilization success. We also examined egg-mediated CFC at two MH genes by examining both the relationship between competitive fertilization success and MH divergence as well as inheritance patterns of MH alleles in resulting offspring. We found that jacks sired more offspring than hooknose males at 0 seconds post-activation; however, jack fertilization success declined over time post-activation, suggesting a trade-off between sperm speed and longevity. Enhanced fertilization success of jacks (presumably via higher sperm quality) may serve to increase sneaker tactic competitiveness relative to dominant hooknose males. We also found evidence of egg-mediated CFC (i.e., female x male interaction) influencing competitive fertilization success, however CFC was not acting on the MH genes as we found no relationship between fertilization success and MH II β1 or MH I α1 divergence and we found no deviations from Mendelian inheritance of MH alleles in the offspring. Our study provides insight into evolutionary mechanisms influencing variation in male mating success within alternative reproductive tactics, thus underscoring different strategies that males can adopt to attain success

Geographic variation in sperm traits reflects predation risk and natural rates of multiple paternity in the guppy

Guppies (Poecilia reticulata) are models for understanding the interplay between natural and sexual selection. In particular, predation has been implicated as a major force affecting female sexual preferences, male mating tactics and the level of sperm competition. When predation is high, females typically reduce their preferences for showy males and engage more in antipredator behaviours, whereas males exploit these changes by switching from sexual displays to forced matings. These patterns are thought to account for the relatively high levels of multiple paternity in high-predation populations compared to low-predation populations. Here, we assess the possible evolutionary consequences of these patterns by asking whether variation in sperm traits reflect differences in predation intensity among four pairs of Trinidadian populations: four that experience relatively low levels of predation from a gape-limited predator and four that experience relatively high levels of predation from a variety of piscivores. We found that males in high-predation populations had faster swimming sperm with longer midpieces compared to males in low-predation populations. However, we found no differences among males in high- and low-predation populations with respect to sperm number, sperm head length, flagellum length and total sperm length