578 research outputs found
Adsorption of organic molecules at the TiO2(110) surface: the effect of van der Waals interactions
Understanding the interaction of organic molecules with TiO2 surfaces is
important for a wide range of technological applications. While density
functional theory (DFT) calculations can provide valuable insight about these
interactions, traditional DFT approaches with local exchange-correlation
functionals suffer from a poor description of non-bonding van der Waals (vdW)
interactions. We examine here the contribution of vdW forces to the interaction
of small organic molecules (methane, methanol, formic acid and glycine) with
the TiO2 (110) surface, based on DFT calculations with the optB88-vdW
functional. The adsorption geometries and energies at different configurations
were also obtained in the standard generalized gradient approximation (GGA-PBE)
for comparison. We find that the optB88-vdW consistently gives shorter surface
adsorbate-to-surface distances and slightly stronger interactions than PBE for
the weak (physisorbed) modes of adsorption. In the case of strongly adsorbed
(chemisorbed) molecules both functionals give similar results for the
adsorption geometries, and also similar values of the relative energies between
different chemisorption modes for each molecule. In particular both functionals
predict that dissociative adsorption is more favourable than molecular
adsorption for methanol, formic acid and glycine, in general agreement with
experiment. The dissociation energies obtained from both functionals are also
very similar, indicating that vdW interactions do not affect the thermodynamics
of surface deprotonation. However, the optB88-vdW always predicts stronger
adsorption than PBE. The comparison of the methanol adsorption energies with
values obtained from a Redhead analysis of temperature programmed desorption
data suggests that optB88-vdW significantly overestimates the adsorption
strength, although we warn about the uncertainties involved in such
comparisons.Comment: 32 pages, 8 figures; accepted in Surface Scienc
Cluster Variation Approach to the Random-Anisotropy Blume-Emery-Griffiths Model
The random--anisotropy Blume--Emery--Griffiths model, which has been proposed
to describe the critical behavior of He--He mixtures in a porous
medium, is studied in the pair approximation of the cluster variation method
extended to disordered systems. Several new features, with respect to mean
field theory, are found, including a rich ground state, a nonzero percolation
threshold, a reentrant coexistence curve and a miscibility gap on the high
He concentration side down to zero temperature. Furthermore, nearest
neighbor correlations are introduced in the random distribution of the
anisotropy, which are shown to be responsible for the raising of the critical
temperature with respect to the pure and uncorrelated random cases and
contribute to the detachment of the coexistence curve from the line.Comment: 14 pages (plain TeX) + 12 figures (PostScript, appended), Preprint
POLFIS-TH.02/9
Experimental observation and characterization of the magnetorotational instability
Differential rotation occurs in conducting flows in accretion disks and
planetary cores. In such systems, the magnetorotational instability can arise
from coupling Lorentz and centrifugal forces to cause large radial angular
momentum fluxes. We present the first experimental observation of the
magnetorotational instability. Our system consists of liquid sodium between
differentially rotating spheres, with an imposed coaxial magnetic field. We
characterize the observed patterns, dynamics and torque increases, and
establish that this instability can occur from a hydrodynamic turbulent
background.Comment: 4 pages, 5 figures. Final version, accepted for publication in
Physical Review Letter
Integrating Al with NiO nano honeycomb to realize an energetic material on silicon substrate
Nano energetic materials offer improved performance in energy release, ignition, and mechanical properties compared to their bulk or micro counterparts. In this study, the authors propose an approach to synthesize an Al/NiO based nano energetic material which is fully compatible with a microsystem. A two-dimensional NiO nano honeycomb is first realized by thermal oxidation of a Ni thin film deposited onto a silicon substrate by thermal evaporation. Then the NiO nano honeycomb is integrated with an Al that is deposited by thermal evaporation to realize an Al/NiO based nano energetic material. This approach has several advantages over previous investigations, such as lower ignition temperature, enhanced interfacial contact area, reduced impurities and Al oxidation, tailored dimensions, and easier integration into a microsystem to realize functional devices. The synthesized Al/NiO based nano energetic material is characterized by scanning electron microscopy, X-ray diffraction, differential thermal analysis, and differential scanning calorimetry
It\u27s about the patients: Practical antibiotic stewardship in outpatient settings in the United States
Antibiotic-resistant pathogens cause over 35,000 preventable deaths in the United States every year, and multiple strategies could decrease morbidity and mortality. As antibiotic stewardship requirements are being deployed for the outpatient setting, community providers are facing systematic challenges in implementing stewardship programs. Given that the vast majority of antibiotics are prescribed in the outpatient setting, there are endless opportunities to make a smart and informed choice when prescribing and to move the needle on antibiotic stewardship. Antibiotic stewardship in the community, or smart prescribing as we suggest, should factor in antibiotic efficacy, safety, local resistance rates, and overall cost, in addition to patient-specific factors and disease presentation, to arrive at an appropriate therapy. Here, we discuss some of the challenges, such as patient/parent pressure to prescribe, lack of data or resources for implementation, and a disconnect between guidelines and real-world practice, among others. We have assembled an easy-to-use best practice guide for providers in the outpatient setting who lack the time or resources to develop a plan or consult lengthy guidelines. We provide specific suggestions for antibiotic prescribing that align real-world clinical practice with best practices for antibiotic stewardship for two of the most common bacterial infections seen in the outpatient setting: community-acquired pneumonia and skin and soft-tissue infection. In addition, we discuss many ways that community providers, payors, and regulatory bodies can make antibiotic stewardship easier to implement and more streamlined in the outpatient setting
Days to treatment and early retention among patients in treatment for alcohol and drug disorders
a b s t r a c t a r t i c l e i n f o Objectives: Drug and alcohol treatment programs often have long delays between assessment and treatment admission. The study examined the impact of days to treatment admission on the probability of completing four sessions of care within an addiction treatment program implementing improvements in their admission process. Methods: Mixed-effects logistic regression was used to test the effect of wait time on retention in care. Results: Findings demonstrate a strong decrement in the probability of completing four sessions of treatment with increasing time between the clinical assessment and first treatment session
Improved Functional Outcome After Peripheral Nerve Stimulation of the Impaired Forelimb Post-stroke
Lack of blood flow to the brain, i.e., ischemic stroke, results in loss of nerve cells and therefore loss of function in the effected brain regions. There is no effective treatment to improve lost function except restoring blood flow within the first several hours. Rehabilitation strategies are widely used with limited success. The purpose of this study was to examine the effect of electrical stimulation on the impaired upper extremity to improve functional recovery after stroke. We developed a rodent model using an electrode cuff implant onto a single peripheral nerve (median nerve) of the paretic forelimb and applied daily electrical stimulation. The skilled forelimb reaching test was used to evaluate functional outcome after stroke and electrical stimulation. Anterograde axonal tracing from layer V pyramidal neurons with biotinylated dextran amine was done to evaluate the formation of new neuronal connections from the contralesional cortex to the deafferented spinal cord. Rats receiving electrical stimulation on the median nerve showed significant improvement in the skilled forelimb reaching test in comparison with stroke only and stroke with sham stimulation. Rats that received electrical stimulation also exhibited significant improvement in the latency to initiate adhesive removal from the impaired forelimb, indicating better sensory recovery. Furthermore, axonal tracing analysis showed a significant higher midline fiber crossing index in the cervical spinal cord of rats receiving electrical stimulation. Our results indicate that direct peripheral nerve stimulation leads to improved sensorimotor recovery in the stroke-impaired forelimb, and may be a useful approach to improve post-stroke deficits in human patients
Application benchmark results for Big Red, an IBM e1350 BladeCenter Cluster
The purpose of this report is to present the results of benchmark tests with Big Red, an IBM e1350 BladeCenter Cluster. This report is particularly focused on providing details of system architecture and test run results in detail to allow for analysis in other reports and comparison with other systems, rather than presenting such analysis here
Neuronal non-CG methylation is an essential target for MeCP2 function
DNA methylation is implicated in neuronal biology via the protein MeCP2, the mutation of which causes Rett syndrome. MeCP2 recruits the NCOR1/2 co-repressor complexes to methylated cytosine in the CG dinucleotide, but also to sites of non-CG methylation, which are abundant in neurons. To test the biological significance of the dual-binding specificity of MeCP2, we replaced its DNA binding domain with an orthologous domain from MBD2, which can only bind mCG motifs. Knockin mice expressing the domain-swap protein displayed severe Rett-syndrome-like phenotypes, indicating that normal brain function requires the interaction of MeCP2 with sites of non-CG methylation, specifically mCAC. The results support the notion that the delayed onset of Rett syndrome is due to the simultaneous post-natal accumulation of mCAC and its reader MeCP2. Intriguingly, genes dysregulated in both Mecp2 null and domain-swap mice are implicated in other neurological disorders, potentially highlighting targets of relevance to the Rett syndrome phenotype
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