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.

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.

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).

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.

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.

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.

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.

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.

CSF somatostatin and abnormal response to dexamethasone administration in schizophrenic and depressed patients.

Low levels of cerebrospinal fluid (CSF) somatostatin and abnormal response to dexamethasone are two neuroendocrine disturbances reported to appear in depression and other neuropsychiatric disorders. We measured the levels of CSF somatostatin in patients with schizophrenia (n = 44) and depression (n = 19). In view of in vitro and animal evidence of the ability of somatostatin to inhibit stimulated corticotropin secretion, we also administered the dexamethasone suppression test to a subgroup of the patients with schizophrenia (n = 16) and the total depressed group. Lower levels of CSF somatostatin were found in dexamethasone nonsuppressors regardless of diagnosis and were negatively correlated with maximum postdexamethasone cortisol level in the total and depressed patient groups. These data suggest a functional relationship between hypothalamic-pituitary-adrenal axis hyperactivity and reduced CSF somatostatin level.

Cerebrospinal fluid monoamine and monoamine metabolite levels and the dexamethasone suppression test in depression. Relationship to life events.

The cerebrospinal fluid levels of norepinephrine and six monoamine metabolites were measured in 23 patients meeting DSM-III criteria for major depressive episode, 15 of whom also met criteria for melancholia. Life events during the six-month period before the onset of depression were recorded using Paykel's method. There was no difference in Hamilton depression ratings between patients with life events and those without. However, depressed patients who did not have a life event in the six months before the onset of depression had significantly lower levels of the dopamine metabolite homovanillic acid and the serotonin metabolite 5-hydroxyindoleacetic acid than those with life events. The incidence of nonsuppression on the dexamethasone suppression test was also greater in patients with a major depressive episode who did not have an undesirable life event than in those who did. Thus, the presence or absence of life events led to a separation into biologically distinct groups.

Clinical and biochemical effects of verapamil administration to schizophrenic patients.

We administered verapamil hydrochloride, a calcium channel antagonist, to seven chronically ill schizophrenic patients for five weeks under double-blind, placebo-controlled conditions. No therapeutic effect was noted. Worsening in hostile and uncooperative behaviors and a syndrome of heightened emotional tone was observed during verapamil treatment and during the postverapamil placebo period. Verapamil produced significant increases in cerebrospinal fluid (CSF) and plasma levels of homovanillic acid and in plasma levels of prolactin, as well as significant decreases in plasma levels of 3-methoxy-4-hydroxyphenethyleneglycol. Verapamil and its active metabolite, norverapamil, were partitioned into CSF with CSF/plasma ratios of 0.06 and 0.04, respectively. The lack of therapeutic effects of verapamil in schizophrenic patients differs from earlier reports of its usefulness in treating manic patients. The biochemical and clinical data from our study suggest the possibility that verapamil exerts behaviorally relevant central nervous system activity in schizophrenic patients.

Circadian variation of plasma homovanillic acid levels is attenuated by fluphenazine in patients with schizophrenia.

Plasma homovanillic acid (HVA) levels were measured hourly for a 24-hour period in 10 patients with schizophrenia during treatment with placebo and fluphenazine. Ten age- and sex-matched normal volunteers were similarly studied. Diet and activity were carefully controlled and monitored in both patients and controls. A circadian rhythm of the plasma HVA level was found in controls with a nadir in the afternoon and peak values in the early morning hours; when the patients were free from drugs, they showed a similar rhythm with lower amplitudes. Fluphenazine treatment significantly reduced the plasma concentrations of HVA and abolished the 24-hour rhythm. These data suggest that a 24-hour rhythm of the plasma HVA level exists in humans and that the amplitude of this rhythm may be less pronounced in patients with schizophrenia. Treatment with neuroleptic drugs reduces both the absolute levels and the normal circadian rhythm of the plasma HVA level.

The diurnal variation in plasma homovanillic acid level persists but the variation in 3-methoxy-4-hydroxyphenylglycol level is abolished under constant conditions.

Plasma concentrations of homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) were determined every two hours for two consecutive days in seven depressed patients and seven matched normal controls. On the first day subjects followed their regular ward routine. On the second day they were placed on a regimen in which activity, posture, diet, and wakefulness were held constant. There were significant diurnal variations in both MHPG and HVA concentrations on the baseline day, whereas on the constant routine, a diurnal variation was present only in HVA. We conclude that diurnal variations in plasma MHPG are evoked by changes in physical activity, posture, or other factors controlled on the constant routine, and that a major component of the diurnal variation in plasma HVA concentrations is regulated by a circadian oscillator that is independent of sleep or activity.

Alprazolam augmentation of the antipsychotic effects of fluphenazine in schizophrenic patients. Preliminary results.

Alprazolam was added, under double-blind conditions, to stable fluphenazine hydrochloride regimens in 12 symptomatic, chronically ill inpatients with schizophrenia. The addition of alprazolam was associated with significant, albeit modest, reductions in global psychosis, thought disorder, and paranoia ratings, with a return to pretreatment levels on discontinuation of alprazolam treatment. Improvement in "negative symptoms" such as emotional withdrawal paralleled the changes in "positive symptoms" but did not, in itself, reach statistical significance. There were no significant changes in group mean plasma levels of homovanillic acid or 3-methoxy-4-hydroxyphenylglycol during alprazolam treatment, although group mean serum cortisol levels were significantly decreased by alprazolam treatment. Patients who responded favorably to alprazolam treatment were significantly more psychotic or anxious before treatment, were older, showed significant alprazolam-associated reductions in plasma levels of homovanillic acid, and had significantly more prominent prefrontal cortex atrophy on computed tomographic scans than patients in whom alprazolam was without therapeutic effect. These preliminary data, based on a small sample, suggest that some patients with schizophrenia who are only partially responsive to standard neuroleptic treatment may benefit from the addition of triazolobenzodiazepines, such as alprazolam.

Longitudinal measurement of plasma homovanillic acid levels in schizophrenic patients. Correlation with psychosis and response to neuroleptic treatment.

The plasma levels of homovanillic acid (HVA), a major circulating dopamine (DA) metabolite, were measured in schizophrenic patients during five weeks each of double-blind placebo-controlled neuroleptic treatment (N = 16) and withdrawal (N = 11). Both neuroleptic treatment and withdrawal were associated with time-dependent changes in the plasma levels of HVA; treatment was associated with decreases and withdrawal with increases. The levels of plasma HVA measured longitudinally during both conditions were highly correlated with psychosis ratings. Moreover, changes in individual mean weekly levels of plasma HVA were predictive of treatment response, including changes in both positive and negative symptoms of schizophrenia. These data are consistent with the suggestion that the mechanisms of action of antipsychotic drugs involve, in addition to short-term DA receptor blockade, a slowly developing decrease in presynaptic DA activity.

The effects of dexamethasone on plasma homovanillic acid and 3-methoxy-4-hydroxyphenylglycol. Evidence for abnormal corticosteroid-catecholamine interactions in major depression.

We investigated the possible interactions between corticosteroids and catecholamines in depression by studying the effects of the synthetic glucocorticoid dexamethasone on plasma levels of homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) in a group of depressed patients and normal controls. In comparison with metabolite levels on a control day, normal controls showed a significant dexamethasone-induced increase in the plasma HVA level and a trend toward a decrease in the plasma MHPG level at 4 PM following dexamethasone administration (1 mg orally at 11 PM). Conversely, depressed patients, particularly those with psychotic features, showed a significant dexamethasone-induced increase in the plasma MHPG level and a blunting of the plasma HVA response relative to the normal controls. Dexamethasone-induced increases in the plasma MHPG level were directly correlated with the severity of depressive symptoms and with postdexamethasone cortisol levels in the depressed patients. These data suggest abnormal corticosteroid-catecholamine interactions in depression and, specifically, in depressed patients with psychotic features.

Prednisone effects on neurochemistry and behavior. Preliminary findings.

To evaluate the neurochemical, neuroendocrine, and behavioral effects of exogenous corticosteroids in humans, we administered prednisone (80 mg/d orally for 5 days) in a double-blind manner to 12 medically healthy volunteers. Behavioral measures were assessed before, during, and after prednisone administration in all 12 subjects, and cerebrospinal fluid biochemistry was assessed before and during prednisone administration in 9 of the subjects. Prednisone administration was associated with decreases in cerebrospinal fluid levels of corticotropin, norepinephrine, beta-endorphin, beta-lipotropin, and somatostatinlike immunoreactivity. No significant changes were noted in cerebrospinal fluid levels of alpha-melanocyte-stimulating hormone, corticotropin-releasing hormone, 3-methoxy-4-hydroxyphenylglycol, homovanillic acid, or 5-hydroxyindoleacetic acid. No consistent or significant group mean changes were observed in structured behavioral ratings, although 9 (75%) of the volunteers studied reported mild behavioral changes while receiving prednisone. Correlations between the neurochemical and behavioral changes are discussed.