979 research outputs found
Isochoric, isobaric and ultrafast conductivities of aluminum, lithium and carbon in the warm dense matter (WDM) regime
We study the conductivities of (i) the equilibrium isochoric state
(), (ii) the equilibrium isobaric state (),
and also the (iii) non-equilibrium ultrafast matter (UFM) state () with the ion temperature less than the the electron temperature
. Aluminum, lithium and carbon are considered, being increasingly complex
warm dense matter (WDM) systems, with carbon having transient covalent bonds.
First-principles calculations, i.e., neutral-pseudoatom (NPA) calculations and
density-functional theory (DFT) with molecular-dynamics (MD) simulations, are
compared where possible with experimental data to characterize and . The NPA are
closest to the available experimental data when compared to results from
DFT+MD, where simulations of about 64-125 atoms are typically used. The
published conductivities for Li are reviewed and the value at a temperature of
4.5 eV is examined using supporting X-ray Thomson scattering calculations. A
physical picture of the variations of with temperature and density
applicable to these materials is given. The insensitivity of to
below 10 eV for carbon, compared to Al and Li, is clarified.Comment: 10 figure
Ion-ion dynamic structure factor, acoustic modes and equation of state of two-temperature warm dense aluminum
The ion-ion dynamical structure factor and the equation of state of warm
dense aluminum in a two-temperature quasi-equilibrium state, with the electron
temperature higher than the ion temperature, are investigated using
molecular-dynamics simulations based on ion-ion pair potentials constructed
from a neutral pseudoatom model. Such pair potentials based on density
functional theory are parameter-free and depend directly on the electron
temperature and indirectly on the ion temperature, enabling efficient
computation of two-temperature properties. Comparison with ab initio
simulations and with other average-atom calculations for equilibrium aluminum
shows good agreement, justifying a study of quasi-equilibrium situations.
Analyzing the van Hove function, we find that ion-ion correlations vanish in a
time significantly smaller than the electron-ion relaxation time so that
dynamical properties have a physical meaning for the quasi-equilibrium state. A
significant increase in the speed of sound is predicted from the modification
of the dispersion relation of the ion acoustic mode as the electron temperature
is increased. The two-temperature equation of state including the free energy,
internal energy and pressure is also presented
Nasal Carriage of Staphylococcus aureus in Australian (pre-clinical and clinical) Medical Students
The nasal carriage of Staphylococcus aureus in 808 Australian medical students was studied. Five groups of students experienced varying degrees of clinical exposure in a hospital environment ranging from 0 to 42 months. The overall percentage of carriers among the five groups did not vary. However, with increasing clinical exposure there was a decrease in the percentage of isolates sensitive to all antibiotics tested, and an increase in the carriage of S. aureus resistant to three or more antibiotics. No carriers of methicillin-resistant S. aureus (MRSA) were detected. The comparative rates of S. aureus carriage between female and male students varied. The relevance of medical students as nasal carriers of S. aureus in the hospital environment today is discussed
Mutation in VPS35 associated with Parkinson's disease impairs WASH complex association and inhibits autophagy
Endosomal protein sorting controls the localization of many physiologically important proteins and is linked to several neurodegenerative diseases. VPS35 is a component of the retromer complex, which mediates endosome-to-Golgi retrieval of membrane proteins such as the cation-independent mannose 6-phosphate receptor. Furthermore, retromer is also required for the endosomal recruitment of the actin nucleation promoting WASH complex. The VPS35 D620N mutation causes a rare form of autosomal-dominant Parkinson’s disease (PD). Here we show that this mutant associates poorly with the WASH complex and impairs WASH recruitment to endosomes. Autophagy is impaired in cells expressing PD-mutant VPS35 or lacking WASH. The autophagy defects can be explained, at least in part, by abnormal trafficking of the autophagy protein ATG9A. Thus, the PD-causing D620N mutation in VPS35 restricts WASH complex recruitment to endosomes, and reveals a novel role for the WASH complex in autophagosome formation
Recommended from our members
The effect of gamma irradiation of the volatility and redox state of simulated DWPF high-level nuclear waste glasses
Gamma-induced volatility of simulated DWPF high-level nuclear waste glasses is highly dependent upon the redox state of the glass. For oxidized glasses with an Fe[sup 2+]/(Fe[sup 2+] + Fe[sup 3+]) ratio < 0.1, no volatility was detected after gamma irradiation. Since the projected DWPF high-level radioactive waste glasses will be oxidized, no significant gamma-induced volatility is expected for these glasses upto the glass transition temperature. For larger pieces of highly-reduced DWPF simulated waste glass, no volatility was observed (using [approximately]100 mg pieces in the TGA) after gamma irradiation. However, for powdered samples of this reduced glass, volatility changes upon gamma radiation were detected at 350 and 475[degree]C. The volatility at 350[degree]C was due to changes at the glass surface whereas the change in volatility at 475[degree]C were due to interactions of gamma irradiation within the bulk of the glass. The glass transition temperatures of both oxidized and reduced glasses were unaffected by gamma irradiation but did increase upon a second heat cycle. Results are also presented which reveal that no significant change in redox level within the glass occurred as a result of gamma irradiation
Molecular Electroporation and the Transduction of Oligoarginines
Certain short polycations, such as TAT and polyarginine, rapidly pass through
the plasma membranes of mammalian cells by an unknown mechanism called
transduction as well as by endocytosis and macropinocytosis. These
cell-penetrating peptides (CPPs) promise to be medically useful when fused to
biologically active peptides. I offer a simple model in which one or more CPPs
and the phosphatidylserines of the inner leaflet form a kind of capacitor with
a voltage in excess of 180 mV, high enough to create a molecular electropore.
The model is consistent with an empirical upper limit on the cargo peptide of
40--60 amino acids and with experimental data on how the transduction of a
polyarginine-fluorophore into mouse C2C12 myoblasts depends on the number of
arginines in the CPP and on the CPP concentration. The model makes three
testable predictions.Comment: 15 pages, 5 figure
Cough-generated aerosols of Pseudomonas aeruginosa and other Gram-negative bacteria from patients with cystic fibrosis
Background: Pseudomonas aeruginosa is the most common bacterial pathogen in cystic fibrosis (CF) patients. Current infection control guidelines aim to prevent transmission via contact and respiratory droplet routes and do not consider the possibility of airborne transmission. We hypothesized that with coughing, CF subjects produce viable, respirable bacterial aerosols. Methods: Cross-sectional study of 15 children and 13 adults with CF, 26 chronically infected with P. aeruginosa. A cough aerosol sampling system enabled fractioning of respiratory particles of different size, and culture of viable Gram negative non-fermentative bacteria. We collected cough aerosols during 5 minutes voluntary coughing and during a sputum induction procedure when tolerated. Standardized quantitative culture and genotyping techniques were used. Results: P. aeruginosa was isolated in cough aerosols of 25 (89%) subjects of whom 22 produced sputum samples. P. aeruginosa from sputum and paired cough aerosols were indistinguishable by molecular typing. In 4 cases the same genotype was isolated from ambient room air. Approximately 70% of viable aerosols collected during voluntary coughing were of particles ≤ 3.3 microns aerodynamic diameter. P. aeruginosa, Burkholderia cenocepacia Stenotrophomonas maltophilia and Achromobacter xylosoxidans were cultivated from respiratory particles in this size range. Positive room air samples were associated with high total counts in cough aerosols (P=0.003). The magnitude of cough aerosols were associated with higher FEV1 (r=0.45, P=0.02) and higher quantitative sputum culture results (r=0.58, P=0.008). Conclusion: During coughing, CF patients produce viable aerosols of P. aeruginosa and other Gram negative bacteria of respirable size range, suggesting the potential for airborne transmission
- …