Enhancement of steric repulsion with temperature in oriented lipid multilayers

We have studied the temperature dependence of the stacking periodicity, d, of oriented phospholipid multilayers using grazing angle neutron scattering techniques. d is found to increase substantially at higher temperatures, just before the bilayers peel off from the substrate. Although we do not observe thermal unbinding, our results are consistent with the notion that the unbinding transition is driven by steric repulsion arising from thermal fluctuations of the membranes, in contrast to those of a recent study by Vogel et al. [Phys. Rev. Lett. 84, 390 (2000)]

Carbon radio recombination lines from gigahertz to megahertz frequencies towards Orion A

Context. The combined use of carbon radio recombination lines (CRRLs) and the 158 $\mu$m-[CII] line is a powerful tool for the study of the energetics and physical conditions (e.g., temperature and density) of photodissociation regions (PDRs). However, there are few observational studies that exploit this synergy. Aims. Here we explore the relation between CRRLs and the 158 $\mu$m-[CII] line in light of new observations and models. Methods. We present new and existing observations of CRRLs in the frequency range 0.15--230 GHz with ALMA, VLA, the GBT, Effelsberg 100m, and LOFAR towards Orion~A (M42). We complement these observations with SOFIA observations of the 158 $\mu$m-[CII] line. We studied two PDRs: the foreground atomic gas, known as the Veil, and the dense PDR between the HII region and the background molecular cloud. Results. In the Veil we are able to determine the gas temperature and electron density, which we use to measure the ionization parameter and the photoelectric heating efficiency. In the dense PDR, we are able to identify a layered PDR structure at the surface of the molecular cloud to the south of the Trapezium cluster. There we find that the radio lines trace the colder portion of the ionized carbon layer, the C$^{+}$/C/CO interface. By modeling the emission of the $158$~$\mu$m-[CII] line and CRRLs as arising from a PDR we derive a thermal pressure $>5\times10^{7}$ K cm$^{-3}$ and a radiation field $G_{0}\approx10^{5}$ close to the Trapezium. Conclusions. This work provides additional observational support for the use of CRRLs and the 158 $\mu$m-[CII] line as complementary tools to study dense and diffuse PDRs, and highlights the usefulness of CRRLs as probes of the C$^{+}$/C/CO interface.Comment: 18 pages, 16 figures, accepted for publication in A&

Evidence for Infanticide in Bottlenose Dolphins of the Western North Atlantic

Nine bottlenose dolphin (Tursiops truncatus) calves that stranded in Virginia in 1996 and 1997 died of severe blunt-force trauma. Injuries were concentrated on the head and chest and multiple rib fractures, lung lacerations, and soft tissue contusions were prominent. Skeletal and/or soft tissue trauma occurred bilaterally in all of the calves. One had a bite wound across the left mandible that exhibited deep punctures consistent with the tooth placement in an adult bottlenose dolphin. The lesions were not compatible with predation, boat strike, fisheries interactions, rough-surf injury, or blast injury. However, they were similar to traumatic injuries described in stranded bottlenose dolphin calves and harbor porpoises (Phocoena phocoena) in Great Britain attributed to violent dolphin interactions. The evidence suggests that violent dolphin behavior was the cause of the trauma in the nine calves reported here and that infanticide occurs in bottlenose dolphins of the western North Atlantic

Discontinuous unbinding of lipid multibilayers

We have observed a discontinuous unbinding transition of lipid bilayer stacks composed of phosphatidylethanolamine and phosphatidylglycerol using X-ray diffraction. The unbinding is reversible and coincides with the main (Lβ→Lα) transition of the lipid mixture. Interbilayer interaction potentials deduced from the diffraction data reveal that the bilayers in the Lβ phase are only weakly bound. The unbinding transition appears to be driven by an abrupt increase in steric repulsion resulting from increased thermal undulations of the bilayers upon entering the fluid Lαphase

Heterogeneity within AML with CEBPA mutations; only CEBPA double mutations, but not single CEBPA mutations are associated with favourable prognosis

CCAAT/enhancer binding protein alpha (CEBPA) mutations in AML are associated with favourable prognosis and are divided into N- and C-terminal mutations. The majority of AML patients have both types of mutations. We assessed the prognostic significance of single (n=7) and double (n=12) CEBPA mutations among 224 AML patients. Double CEBPA mutations conferred a decisively favourable overall (P=0.006) and disease-free survival (P=0.013). However, clinical outcome of patients with single CEBPA mutations was not different from CEBPA wild-type patients. In a multivariable analysis, only double – but not single – CEBPA mutations were identified as independent prognostic factors. These findings indicate heterogeneity within AML patients with CEBPA mutations

The free volume of poly(vinyl methylether) as computed in a wide temperature range and at length scales up to the nanoregion

14 páginas, 12 figuras.In the present work, we focus on the free volume evaluations from different points of view, including the aspect of probe sizes, temperature, and cavity threshold. The free volume structure is analyzed on structures of poly(vinyl methylether) prepared by fully atomistic molecular dynamics. At first, the temperature behavior of an overall free volume and a free volume separated into individual cavities is shown. The origin of large free volume cavities is explained. A complex view on the cavity number is provided, while a complicated behavior previously observed is now explained. The number of large cavities remained almost constant with the temperature. Oppositely, the number of small cavities related to the atomic packing changes with temperature in a distinct way for glassy and supercooled regions. The cavity number maxima determine a percolation threshold according to percolation theory. The change in polymer properties with temperature can be related to a percolation of the free volume according to the free volume theory, when proper probe radii ∼0.8 Å are used for its observation. A construction of probabilistic distribution of free volume sizes is suggested. The free volume distributions reported here are bimodal. The bimodal character is explained by two different packings—atomic and segmental—forming a prepeak and a main peak on the distribution. Further attention is dedicated to comparisons of the computed free volume sizes and the ortho-positronium (o-Ps) lifetimes. The prepeak of the free volume distribution is probably unseen by o-Ps because of a cavity threshold limit. The effect of the shape factor on the computed o-Ps lifetimes is tested. The quasicavities obtained by redistributing the free volume maintain the ratio of the main dimensions with temperature. Finally, novel data on the cavity environment are provided, while it is suggested how these can be useful with the recent developments in the positron annihilation methods. The coordination number of large cavities with the polymer segments is around 1, as predicted in the free volume theory. Similarly to the percolation and the cavity number, the coordination number exhibits a change when explored by a suitable probe radius ∼0.8 Å. The insightful visualizations showed properties of interest investigated within the actual work.This work was supported by Project No. MAT2007– 63681 (Spanish Ministry of Education) and Grant No. IT- 436–07 (Basque Government). Support from Spanish Ministry of Education Grant No. CSD2006-53 is also acknowledged.Peer reviewe

Prevalence of High Resilience in Old Age and Association with Perceived Threat of COVID-19—Results from a Representative Survey

Little is known about resilience in old age and its manifestation during the COVID-19 pandemic. This study aims to estimate the prevalence of high resilience in the German old age population. We further examine the socio-demographic correlates and whether high resilience reflects on older adults’ perception of the threat posed by COVID-19. The data were derived from a representative telephone survey of n = 1005 older adults (≥65 years) during the first COVID-19 lockdown. Assessments included socio-demographic variables, the perceived threat of COVID-19, and high resilience (Brief Resilience Scale; cutoff: ≥4.31). The association between high resilience and threat from COVID-19 was analyzed using ordinal logistic regression. The study sample had a mean age (SD) of 75.5 (7.1) years, and n = 566 (56.3%) were female. The estimated prevalence of high resilience was 18.7% (95% CI = [16.3; 21.2]). High resilience was more prevalent in the younger age group and participants with higher education levels. High resilience was significantly associated with a lower perception of threat from COVID-19. The results of the representative survey in the German old age population showed that one out of five adults aged 65 years and older had high resilience. Older adults with high resilience tended to feel less threatened by COVID-19. Further research on resilience in old age is needed to support vulnerable groups in the context of care

Magainin 2 and PGLa in bacterial membrane mimics III : membrane fusion and disruption

We previously speculated that the synergistically enhanced antimicrobial activity of Magainin 2 and PGLa is related to membrane adhesion, fusion, and further membrane remodelling. Here, we combined computer simulations with time-resolved in vitro fluorescence microscopy, cryogenic electron microscopy (cryo-EM), and small-angle X-ray scattering (SAXS) to interrogate such morphological and topological changes of vesicles at nanoscopic and microscopic length scales in real time. Coarse-grained simulations revealed the formation of an elongated and bent fusion zone between vesicles in the presence of equimolar peptide mixtures. Vesicle adhesion and fusion was observed to occur within few seconds by cryo-EM and corroborated by SAXS measurements. The latter experiments further indicated continued and time-extended structural remodelling also for individual peptides or chemically-linked peptide heterodimers, but with different kinetics. Fluorescence microscopy further captured peptide-dependent adhesion, fusion, and occasional bursting of giant unilamellar vesicles already few seconds after peptide addition. The synergistic interactions between the peptides shorten the time response of vesicles and enhance membrane fusogenic and disrupting properties of the equimolar mixture compared to the individual peptides