2,043 research outputs found
Analysis of strain and stacking faults in single nanowires using Bragg coherent diffraction imaging
Coherent diffraction imaging (CDI) on Bragg reflections is a promising
technique for the study of three-dimensional (3D) composition and strain fields
in nanostructures, which can be recovered directly from the coherent
diffraction data recorded on single objects. In this article we report results
obtained for single homogeneous and heterogeneous nanowires with a diameter
smaller than 100 nm, for which we used CDI to retrieve information about
deformation and faults existing in these wires. The article also discusses the
influence of stacking faults, which can create artefacts during the
reconstruction of the nanowire shape and deformation.Comment: 18 pages, 6 figures Submitted to New Journal of Physic
CN and HCN in Dense Interstellar Clouds
We present a theoretical investigation of CN and HCN molecule formation in
dense interstellar clouds. We study the gas-phase CN and HCN production
efficiencies from the outer photon-dominated regions (PDRs) into the opaque
cosmic-ray dominated cores. We calculate the equilibrium densities of CN and
HCN, and of the associated species C+, C, and CO, as functions of the
far-ultraviolet (FUV) optical depth. We consider isothermal gas at 50 K, with
hydrogen particle densities from 10^2 to 10^6 cm^-3. We study clouds that are
exposed to FUV fields with intensities 20 to 2*10^5 times the mean interstellar
FUV intensity. We assume cosmic-ray H2 ionization rates ranging from 5*10^-17
s^-1, to an enhanced value of 5*10^-16 s^-1. We also examine the sensitivity of
the density profiles to the gas-phase sulfur abundance.Comment: Accepted for publication in ApJ, 33 pages, 8 figure
Robot-Assisted Prostate Brachytherapy
Abstract: In contemporary brachytherapy procedures, needle placement at the desired target is challenging due to a variety of reasons. A robot-assisted brachytherapy system can potentially improve needle placement and seed delivery, resulting in enhanced therapeutic delivery. In this paper we present a 16 DOF (degrees-of-freedom) robotic system (9DOF positioning module and 7DOF surgery module) developed and fabricated for prostate brachytherapy. Strategies to reduce needle deflection and target movement were incorporated after extensive experimental validation. Provisions for needle motion and force feedback were included into the system for improving robot control and seed delivery. Preliminary experimental results reveal that the prototype system is sufficiently accurate in placing brachytherapy needles
Lithium Decreases Glial Fibrillary Acidic Protein in a Mouse Model of Alexander Disease.
Alexander disease is a fatal neurodegenerative disease caused by mutations in the astrocyte intermediate filament glial fibrillary acidic protein (GFAP). The disease is characterized by elevated levels of GFAP and the formation of protein aggregates, known as Rosenthal fibers, within astrocytes. Lithium has previously been shown to decrease protein aggregates by increasing the autophagy pathway for protein degradation. In addition, lithium has also been reported to decrease activation of the transcription factor STAT3, which is a regulator of GFAP transcription and astrogliogenesis. Here we tested whether lithium treatment would decrease levels of GFAP in a mouse model of Alexander disease. Mice with the Gfap-R236H point mutation were fed lithium food pellets for 4 to 8 weeks. Four weeks of treatment with LiCl at 0.5% in food pellets decreased GFAP protein and transcripts in several brain regions, although with mild side effects and some mortality. Extending the duration of treatment to 8 weeks resulted in higher mortality, and again with a decrease in GFAP in the surviving animals. Indicators of autophagy, such as LC3, were not increased, suggesting that lithium may decrease levels of GFAP through other pathways. Lithium reduced the levels of phosphorylated STAT3, suggesting this as one pathway mediating the effects on GFAP. In conclusion, lithium has the potential to decrease GFAP levels in Alexander disease, but with a narrow therapeutic window separating efficacy and toxicity
Hydrated electron generation by excitation of copper localized surface plasmon resonance
Hydrated electrons are important in radiation chemistry and chargetransfer reactions, with applications that include chemical damage of DNA,
catalysis, and signaling. Conventionally, hydrated electrons are produced by pulsed
radiolysis, sonolysis, two-ultraviolet-photon laser excitation of liquid water, or
photodetachment of suitable electron donors. Here we report a method for the
generation of hydrated electrons via single-visible-photon excitation of localized
surface plasmon resonances (LSPRs) of supported sub-3 nm copper nanoparticles
in contact with water. Only excitations at the LSPR maximum resulted in the
formation of hydrated electrons, suggesting that plasmon excitation plays a crucial
role in promoting electron transfer from the nanoparticle into the solution. The
reactivity of the hydrated electrons was confirmed via proton reduction and
concomitant H2 evolution in the presence of a Ru/ TiO2 catalyst
TIA1 Mutations in Amyotrophic Lateral Sclerosis and Frontotemporal Dementia Promote Phase Separation and Alter Stress Granule Dynamics.
Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are age-related neurodegenerative disorders with shared genetic etiologies and overlapping clinical and pathological features. Here we studied a novel ALS/FTD family and identified the P362L mutation in the low-complexity domain (LCD) of T cell-restricted intracellular antigen-1 (TIA1). Subsequent genetic association analyses showed an increased burden of TIA1 LCD mutations in ALS patients compared to controls (p = 8.7 × 1
How Should Addiction-Related Research at the National Institutes of Health be Reorganized?
The decades-old debate about the optimum organizational structure of the National Institute on Alcohol Abuse and Alcoholism (NIAAA) and National Institute on Drug Abuse (NIDA) has reached a crescendo with the recent deliberations of the Scientific Management Review Board, which, despite the lack of a crisis, proposed a structural reorganization that would dissolve the two institutes and create a new institute for substance use, abuse, and addiction, in hope of new scientific and public health advances (Collins, 2010). For a new institute to succeed, a multitude of potential challenges need to be negotiated effectivel
- …