Competition for shared resources increases dependence on initial population size during coalescence of gut microbial communities.

The long-term success of introduced populations depends on their initial size and ability to compete against existing residents, but it remains unclear how these factors collectively shape colonization. Here, we investigate how initial population (propagule) size and resource competition interact during community coalescence by systematically mixing eight pairs of in vitro microbial communities at ratios that vary over six orders of magnitude, and we compare our results to a neutral ecological model. Although the composition of the resulting co-cultures deviated substantially from neutral expectations, each co-culture contained species whose relative abundance depended on propagule size even after ~40 generations of growth. Using a consumer-resource model, we show that this dose-dependent colonization can arise when resident and introduced species have high niche overlap and consume shared resources at similar rates. This model predicts that propagule size will have larger, longer-lasting effects in diverse communities in which niche overlap is higher, and we experimentally confirm that strain isolates show stronger dose dependence when introduced into diverse communities than in pairwise co-culture. This work shows how neutral-like colonization dynamics can emerge from non-neutral resource competition and have lasting effects on the outcomes of community coalescence.

Prolonged delays in human microbiota transmission after a controlled antibiotic perturbation.

Humans constantly encounter new microbes, but few become long-term residents of the adult gut microbiome. Classical theories predict that colonization is determined by the availability of open niches, but it remains unclear whether other ecological barriers limit commensal colonization in natural settings. To disentangle these effects, we used a controlled perturbation with the antibiotic ciprofloxacin to investigate the dynamics of gut microbiome transmission in 22 households of healthy, cohabiting adults. Colonization was rare in three-quarters of antibiotic-taking subjects, whose resident strains rapidly recovered in the week after antibiotics ended. In contrast, the remaining antibiotic-taking subjects exhibited lasting responses, with extensive species losses and transient expansions of potential opportunistic pathogens. These subjects experienced elevated rates of commensal colonization, but only after long delays: many new colonizers underwent sudden, correlated expansions months after the antibiotic perturbation. Furthermore, strains that had previously transmitted between cohabiting partners rarely recolonized after antibiotic disruptions, showing that colonization displays substantial historical contingency. This work demonstrates that there remain substantial ecological barriers to colonization even after major microbiome disruptions, suggesting that dispersal interactions and priority effects limit the pace of community change.

A tungsten external heater for BX90 diamond anvil cells with a range up to 1700 K.

Resistive heating of a sample in a diamond anvil cell (DAC) can generate a homogeneous temperature field across the sample chamber with reliable temperatures measured by a thermocouple. It is of importance in experiments aiming at exploring phase diagrams and quantifying thermoelastic properties of materials. Here, we present a ring-heater design developed for BX90 diamond anvil cells (DACs). It is made of a ring-shaped aluminum oxide holder hosting a tungsten wire coil inside and coupled with Ar + 2% H2 gas to prevent oxidation during experiment. This modular plug-and-play design enables in situ studies of samples via x-ray diffraction up to a temperature of 1700 K. Temperature in the BX90 sample volume as measured through a thermocouple was calibrated using the melting point of gold. As an application of this design, we report the thermal expansion coefficient of MgO at 9.5(1) GPa.

Effect of Cuff Pressure on Blood Flow during Blood Flow-restricted Rest and Exercise.

PURPOSE: This study investigated the relationship between blood flow restriction (BFR) cuff pressure and blood flow at rest and during exercise, with the aim of determining if lower cuff pressures will provide an ischemic stimulus comparable to higher pressures. METHODS: The relationship between blood flow and cuff pressure at rest was determined by measuring blood flow (Doppler Ultrasound) through the superficial femoral artery (SFA) in 23 adults across a range of pressures (0%-100% Arterial Occlusion Pressure at rest [rAOP]). The interplay between cuff pressure, blood flow and exercise was assessed by determining AOP at rest and during plantar flexion exercise (eAOP) and subsequently measuring the blood flow response to plantar flexion exercise with BFR cuff pressure set to either 40% rAOP or 40% eAOP. RESULTS: At rest, a nonlinear relationship between cuff pressure and blood flow through the SFA exhibited a plateau at moderate pressures, with nonsignificant differences in blood flow (~9%, P = 1.0) appearing between pressures ranging from 40% to 80% rAOP. While eAOP was greater than rAOP (229 ± 1.5 mm Hg vs 202 ± 1.5 mm Hg, P < 0.01), blood flow during plantar flexion exercise did not significantly differ (P = 0.49) when applying 40% rAOP or 40% eAOP. CONCLUSIONS: Blood flow through the SFA exhibits a nonlinear relationship with cuff pressure, such that cuff pressures in the range of 40% to 80% rAOP reduce blood flow to approximately the same degree. The BFR interventions opting for lower (e.g., 40% AOP), more comfortable pressures will likely provide an ischemic stimulus comparable to that of higher (80% AOP), less-comfortable pressures.

Hartmann characterization of the PEEM-3 aberration-corrected X-ray photoemission electron microscope.

Aberration correction by an electron mirror dramatically improves the spatial resolution and transmission of photoemission electron microscopes. We will review the performance of the recently installed aberration corrector of the X-ray Photoemission Electron Microscope PEEM-3 and show a large improvement in the efficiency of the electron optics. Hartmann testing is introduced as a quantitative method to measure the geometrical aberrations of a cathode lens electron microscope. We find that aberration correction leads to an order of magnitude reduction of the spherical aberrations, suggesting that a spatial resolution of below 100 nm is possible at 100% transmission of the optics when using x-rays. We demonstrate this improved performance by imaging test patterns employing element and magnetic contrast.

Compact low power infrared tube furnace for in situ X-ray powder diffraction.

We describe the development and implementation of a compact, low power, infrared heated tube furnace for in situ powder X-ray diffraction experiments. Our silicon carbide (SiC) based furnace design exhibits outstanding thermal performance in terms of accuracy control and temperature ramping rates while simultaneously being easy to use, robust to abuse and, due to its small size and low power, producing minimal impact on surrounding equipment. Temperatures in air in excess of 1100 °C can be controlled at an accuracy of better than 1%, with temperature ramping rates up to 100 °C/s. The complete "add-in" device, minus power supply, fits in a cylindrical volume approximately 15 cm long and 6 cm in diameter and resides as close as 1 cm from other sensitive components of our experimental synchrotron endstation without adverse effects.

Correlation-Driven Insulator-Metal Transition in Near-Ideal Vanadium Dioxide Films.

We use polarization- and temperature-dependent x-ray absorption spectroscopy, in combination with photoelectron microscopy, x-ray diffraction, and electronic transport measurements, to study the driving force behind the insulator-metal transition in VO_{2}. We show that both the collapse of the insulating gap and the concomitant change in crystal symmetry in homogeneously strained single-crystalline VO_{2} films are preceded by the purely electronic softening of Coulomb correlations within V-V singlet dimers. This process starts 7 K (±0.3 K) below the transition temperature, as conventionally defined by electronic transport and x-ray diffraction measurements, and sets the energy scale for driving the near-room-temperature insulator-metal transition in this technologically promising material.

Tailoring the topology of an artificial magnetic skyrmion.

Despite theoretical predictions, it remains an experimental challenge to realize an artificial magnetic skyrmion whose topology can be well controlled and tailored so that its topological effect can be revealed explicitly in a deformation of the spin textures. Here we report epitaxial magnetic thin films in which an artificial skyrmion is created by embedding a magnetic vortex into an out-of-plane aligned spin environment. By changing the relative orientation between the central vortex core polarity and the surrounding out-of-plane spins, we are able to control and tailor the system between two skyrmion topological states. An in-plane magnetic field is used to annihilate the skyrmion core by converting the central vortex state into a single domain state. Our result shows distinct annihilation behaviour of the skyrmion core for the two different skyrmion states, suggesting a topological effect of the magnetic skyrmions in the core annihilation process.

Assessing metabolic syndrome in people with ID (intellectual disabilities) on antipsychotic medication.

Aims To identify whether clinical information routinely collected and recorded on clinical files is available for the identification of metabolic syndrome and to assess the prevalence of risk factors for the syndrome in a sample of people with intellectual disabilities (ID) and mental illness treated with antipsychotic medication. METHODS: A retrospective analysis was performed for 76 adults with ID and comorbid mental illness, for whom treatment with antipsychotic medication was established. Statistical analysis was performed using SPSS 16.0. The Student t-test for parametric data and χ 2-test for non-parametrical data were used. RESULTS: Five of the six criteria for metabolic syndrome were available in all or a high proportion of the files, however no measurement for waist circumference was recorded in any of the files. Aripiprazole appears to be the least risky antipsychotic for metabolic syndrome. CONCLUSION: It is important to develop a systematic protocol to record diagnostic variables for metabolic syndrome in at risk populations such as those with ID and mental illness treated with regular antipsychotics.

Modeling and validating chronic pharmacological manipulation of circadian rhythms.

Circadian rhythms can be entrained by a light-dark (LD) cycle and can also be reset pharmacologically, for example, by the CK1δ/ε inhibitor PF-670462. Here, we determine how these two independent signals affect circadian timekeeping from the molecular to the behavioral level. By developing a systems pharmacology model, we predict and experimentally validate that chronic CK1δ/ε inhibition during the earlier hours of a LD cycle can produce a constant stable delay of rhythm. However, chronic dosing later during the day, or in the presence of longer light intervals, is not predicted to yield an entrained rhythm. We also propose a simple method based on phase response curves (PRCs) that predicts the effects of a LD cycle and chronic dosing of a circadian drug. This work indicates that dosing timing and environmental signals must be carefully considered for accurate pharmacological manipulation of circadian phase.CPT: Pharmacometrics & Systems Pharmacology (2013) 2, e57; doi:10.1038/psp.2013.34; published online 17 July 2013.

Imaging the first-order magnetic transition in La0.35Pr0.275Ca0.375MnO3.

The nature of the ferromagnetic, charge, orbital, and antiferromagnetic order in La0.35Pr0.275Ca0.375MnO3 on the nano- and microscale was investigated by photoemission electron microscopy (PEEM) and resonant elastic soft x-ray scattering (RSXS). The structure of the ferromagnetic domains around the Curie temperature T(C) indicates that they nucleate under a high degree of lattice strain, which is brought about by the charge, orbital, and antiferromagnetic order. The combined temperature-dependent PEEM and RSXS measurements suggest that the lattice distortions associated with charge and orbital order are glassy in nature and that phase separation is driven by the interplay between it and the more itinerant charge carriers associated with ferromagnetic metallic order, even well below T(C).

Stability and antimicrobial effectiveness of treprostinil sodium in Sterile Diluent for Flolan.

INTRODUCTION: Long-term intravenous infusion of epoprostenol and treprostinil for treatment of pulmonary arterial hypertension (PAH) via a central venous catheter is associated with the risk of bloodstream infection (BSI). While several potential explanations exist for possible differences in BSI incidence among intravenous prostanoids, one hypothesis suggests that the alkaline pH of epoprostenol in Sterile Diluent for Flolan (SDF) has greater antimicrobial activity compared with the neutral pH of other common diluents such as sterile saline or water, which have been used for treprostinil. METHODS: The chemical stability and antimicrobial activity of 4 microg/ml and 130 microg/ml treprostinil in SDF were assessed according to United States and European Pharmacopeia. RESULTS: At both concentrations, treprostinil in SDF remained stable after incubation at 40 degrees C and ambient relative humidity for up to 52 h. Solution pH also remained stable (range 10.4-10.6), and the solutions were essentially free of particulate at all time points examined. Antimicrobial activity was measured using an antimicrobial effectiveness test after inoculation with five species of bacteria, yeast and mould. The antimicrobial activity of both concentrations of treprostinil met United States Pharmacopeia requirements. Further, the antimicrobial activity of treprostinil in SDF against gram-negative bacteria (> 4 log(10) reductions) exceeded that previously described for treprostinil in sterile saline. CONCLUSION: These results suggest that dilution of treprostinil with the alkaline solution SDF may reduce the risk of infection from inadvertent patient contamination compared with dilution of treprostinil in sterile saline.

X-ray damage in protein-metal hybrid structures: a photoemission electron microscopy study.

Bacterial surface layer protein sheets (S layer) coated with an ultrathin cobalt or silver film were studied by means of laterally resolved near-edge X-ray absorption fine structure spectroscopy performed by photoemission electron microscopy. Comparison with results obtained on pristine S layers allowed us to characterize both chemical interaction and X-ray damage in these protein-metal hybrid systems. In particular, we found that besides direct damage upon exposure to X-ray radiation the biomolecules experience additional contribution of the deposited metals, by low-energy electron generation in the metal particles.

Vapour-phase activities of essential oils against antibiotic sensitive and resistant bacteria including MRSA.

AIMS: To determine whether essential oil (EO) vapours could reduce surface and airborne levels of bacteria including methicillin-resistant Staphylococcus aureus (MRSA). METHODS AND RESULTS: The antibacterial activity of geranium and lemongrass EO individually and blended were evaluated over a range of concentrations by direct contact and vapour diffusion. The EO were tested in vitro against a selection of antibiotic-sensitive and -resistant bacteria, including MRSA, vancomycin-resistant Enterococci (VRE), Acinetobacter baumanii and Clostridium difficile. An EO blend containing lemongrass and geranium was used to formulate BioScent that was dispersed into the environment using the ST Pro machine. The effects were variable depending on the methods used. In a sealed box environment, MRSA growth on seeded plates was reduced by 38% after 20 h exposure to BioScent vapour. In an office environment, the ST Pro machine dispersing BioScent effected an 89% reduction of airborne bacteria in 15 h, when operated at a constant output of 100%. CONCLUSIONS: EO vapours inhibited growth of antibiotic-sensitive and -resistant bacteria in vitro and reduced surface and airborne levels of bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: Results suggest that EO vapours, particularly Bioscent, could be used as a method of air disinfection.

Guidelines for the prevention of central venous catheter-related blood stream infections with prostanoid therapy for pulmonary arterial hypertension.

Intravenous prostanoids are the backbone of therapy for advanced pulmonary arterial hypertension (PAH) and have improved long-term outcome and quality of life. Currently, two prostanoids are approved by the US Food and Drug administration for parenteral administration: epoprostenol (Flolan) and treprostinil (Remodulin). Chronic intravenous therapy presents considerable challenges for patients and caregivers who must learn sterile preparation of the medication, operation of the pump, and care of the central venous catheter. Patients are routinely counseled and advised regarding the risks of CR-BSIs and catheter care before central line insertion. Central line infections as well as bacteremia are well documented risks of chronic intravenous therapy and may significantly contribute to morbidity and mortality. Recent reports have suggested a possible increase in CR-BSI; therefore, the Scientific Leadership Council of the Pulmonary Hypertension Association decided to provide guidelines for good clinical practice regarding catheter care. Although data exits regarding patients with central venous catheters and the risk of blood stream infections in patients with cancer or other disorders, there is little data regarding the special needs of patients with pulmonary arterial hypertension requiring central venous access. These guidelines are extrapolated from the diverse body of literature regarding central venous catheter care.

Magnetic bubble domain phase at the spin reorientation transition of ultrathin Fe/Ni/Cu(001) film.

Magnetic domain phases of ultrathin Fe/Ni/Cu(001) are studied using photoemission electron microscopy at the spin reorientation transition (SRT). We observe a new magnetic phase of bubble domains within a narrow SRT region after applying a nearly in-plane magnetic field pulse to the sample. By applying the magnetic field pulse along different directions, we find that the bubble domain phase exists only if the magnetic field direction is less than approximately 10 degrees relative to the sample surface. A temperature dependent measurement shows that the bubble domain phase becomes unstable above 370 K.

Electrical control of antiferromagnetic domains in multiferroic BiFeO3 films at room temperature.

Multiferroic materials, which offer the possibility of manipulating the magnetic state by an electric field or vice versa, are of great current interest. In this work, we demonstrate the first observation of electrical control of antiferromagnetic domain structure in a single-phase multiferroic material at room temperature. High-resolution images of both antiferromagnetic and ferroelectric domain structures of (001)-oriented multiferroic BiFeO3 films revealed a clear domain correlation, indicating a strong coupling between the two types of order. The ferroelectric structure was measured using piezo force microscopy, whereas X-ray photoemission electron microscopy as well as its temperature dependence was used to detect the antiferromagnetic configuration. Antiferromagnetic domain switching induced by ferroelectric polarization switching was observed, in agreement with theoretical predictions.

Magnetic stripe domains in coupled magnetic sandwiches.

Magnetic stripe domains in the spin reorientation transition region are investigated in (Fe/Ni)/Cu(001) and Co/Cu/(Fe/Ni)/Cu(001) using photoemission electron microscopy. For (Fe/Ni)/Cu(001), the stripe domain width decreases exponentially as the Fe/Ni film approaches the spin reorientation transition point. For Co/Cu/(Fe/Ni)/Cu(001), the Fe/Ni stripe orientation is aligned with the Co in-plane magnetization, and the stripe domain width decreases exponentially with increasing the interlayer coupling between the Fe/Ni and Co films. By considering magnetic stripes within an in-plane magnetic field, we reveal a universal dependence of the stripe domain width on the magnetic anisotropy and on the interlayer coupling.

Vortex core-driven magnetization dynamics.

Time-resolved x-ray imaging shows that the magnetization dynamics of a micron-sized pattern containing a ferromagnetic vortex is determined by its handedness, or chirality. The out-of-plane magnetization in the nanometer-scale vortex core induces a three-dimensional handedness in the planar magnetic structure, leading to a precessional motion of the core parallel to a subnanosecond field pulse. The core velocity was an order of magnitude higher than expected from the static susceptibility. These results demonstrate that handedness, already well known to be important in biological systems, plays an important role in the dynamics of microscopic magnets.

Magnetic phase transition in Co/Cu/Ni/Cu(100) and Co/Fe/Ni/Cu(100).

Magnetic phase transitions in coupled magnetic sandwiches of Cu/Co/Cu/Ni/Cu(100) and Cu/Co/Fe/Ni/Cu(100) are investigated by photoemission electron microscopy. Element-specific magnetic domains are taken at room temperature to reveal the critical thickness at which the magnetic phase transition occurs. The results show that a coupled magnetic sandwich undergoes three types of magnetic phase transitions depending on the two ferromagnetic films' thickness. A phase diagram is constructed and explained in the process of constructing Monte Carlo simulations, which corroborate the experimental results.