1,455 research outputs found
Trained laser-patterned carbon as high-performance mechanical sensors
We describe the mechanical properties of turbostratically graphitized carbon films obtained by carbon laser-patterning (CLaP) and their application as bending or mechanical pressure sensors. Stable conductive carbonized films were imprinted on a flexible polyethylene terephthalate (PET) substrate by laser-induced carbonization. After initial gentle bending, i.e. training, these sponge-like porous films show a quantitative and reversible change in resistance upon bending or application of pressure in normal loading direction. Maximum response values of ΔR/R0 = 388% upon positive bending (tensile stress) and −22.9% upon negative bending (compression) are implicit for their high sensitivity towards mechanical deformation. Normal mechanical loading in a range between 0 and 500 kPa causes a response between ΔR/R0 = 0 and −15%. The reversible increase or decrease in resistance is attributed to compression or tension of the turbostratically graphitized domains, respectively. This mechanism is supported by a detailed microstructural and chemical high-resolution transmission electron microscopic analysis of the cross-section of the laser-patterned carbon
Dilute ferrimagnetic semiconductors in Fe-substituted spinel ZnGaO
Solid solutions of nominal composition
[ZnGaO][FeO], of the semiconducting spinel
ZnGaO with the ferrimagnetic spinel FeO have been prepared with
= 0.05, 0.10, and 0.15. All samples show evidence for long-range magnetic
ordering with ferromagnetic hysteresis at low temperatures. Magnetization as a
function of field for the = 0.15 sample is S-shaped at temperatures as high
as 200 K. M\"ossbauer spectroscopy on the = 0.15 sample confirms the
presence of Fe, and spontaneous magnetization at 4.2 K. The magnetic
behavior is obtained without greatly affecting the semiconducting properties of
the host; diffuse reflectance optical spectroscopy indicates that Fe
substitution up to = 0.15 does not affect the position of the band edge
absorption. These promising results motivate the possibility of dilute
ferrimagnetic semiconductors which do not require carrier mediation of the
magnetic moment.Comment: 9 pages and 6 figure
DIVERSITY OF STAPHYLOCOCCAL SPECIES CULTURED FROM CAPTIVE LIVINGSTONE’S FRUIT BATS (PTEROPUS LIVINGSTONII) AND THEIR ENVIRONMENT
Livingstone's fruit bats (Pteropus livingstonii) are critically endangered and a captive population has been established as part of the International Union for Conservation of Nature Species Action Plan. The largest colony, in Jersey Zoo, was sampled for staphylococcal carriage and at infection sites, as disease associated with staphylococci had previously been found. Staphylococci were cultured from swabs from 44 bats (skin, oropharynx, mouth ejecta, skin lesions) and from their enclosure. The isolates were identified by matrix-assisted laser desorption-ionization time of flight mass spectrometry; antimicrobial susceptibility testing was performed by disc diffusion and screening for mecA and mecC. Seventeen species of coagulase-negative staphylococci including Staphylococcus xylosus, S. kloosii, S. nepalensis, and S. simiae were isolated. Staphylococcus aureus was identified from both carriage and lesional sites. These findings suggest S. nepalensis may be part of the normal carriage flora of bats. Antimicrobial resistance rates were low and methicillin-resistant Staphylococcus aureus (MRSA) was not identified. Sampling of mouth ejecta for staphylococci may provide results representative for carriage sites
Water formation at low temperatures by surface O2 hydrogenation II: the reaction network
Water is abundantly present in the Universe. It is the main component of
interstellar ice mantles and a key ingredient for life. Water in space is
mainly formed through surface reactions. Three formation routes have been
proposed in the past: hydrogenation of surface O, O2, and O3. In a previous
paper [Ioppolo et al., Astrophys. J., 2008, 686, 1474] we discussed an
unexpected non-standard zeroth-order H2O2 production behaviour in O2
hydrogenation experiments, which suggests that the proposed reaction network is
not complete, and that the reaction channels are probably more interconnected
than previously thought. In this paper we aim to derive the full reaction
scheme for O2 surface hydrogenation and to constrain the rates of the
individual reactions. This is achieved through simultaneous H-atom and O2
deposition under ultra-high vacuum conditions for astronomically relevant
temperatures. Different H/O2 ratios are used to trace different stages in the
hydrogenation network. The chemical changes in the forming ice are followed by
means of reflection absorption infrared spectroscopy (RAIRS). New reaction
paths are revealed as compared to previous experiments. Several reaction steps
prove to be much more efficient (H + O2) or less efficient (H + OH and H2 + OH)
than originally thought. These are the main conclusions of this work and the
extended network concluded here will have profound implications for models that
describe the formation of water in space.Comment: 1 page, 1 figur
Water formation at low temperatures by surface O2 hydrogenation I: characterization of ice penetration
Water is the main component of interstellar ice mantles, is abundant in the
solar system and is a crucial ingredient for life. The formation of this
molecule in the interstellar medium cannot be explained by gas-phase chemistry
only and its surface hydrogenation formation routes at low temperatures (O, O2,
O3 channels) are still unclear and most likely incomplete. In a previous paper
we discussed an unexpected zeroth-order H2O production behavior in O2 ice
hydrogenation experiments compared to the first-order H2CO and CH3OH production
behavior found in former studies on hydrogenation of CO ice. In this paper we
experimentally investigate in detail how the structure of O2 ice leads to this
rare behavior in reaction order and production yield. In our experiments H
atoms are added to a thick O2 ice under fully controlled conditions, while the
changes are followed by means of reflection absorption infrared spectroscopy
(RAIRS). The H-atom penetration mechanism is systematically studied by varying
the temperature, thickness and structure of the O2 ice. We conclude that the
competition between reaction and diffusion of the H atoms into the O2 ice
explains the unexpected H2O and H2O2 formation behavior. In addition, we show
that the proposed O2 hydrogenation scheme is incomplete, suggesting that
additional surface reactions should be considered. Indeed, the detection of
newly formed O3 in the ice upon H-atom exposure proves that the O2 channel is
not an isolated route. Furthermore, the addition of H2 molecules is found not
to have a measurable effect on the O2 reaction channel.Comment: 1 page, 1 figur
Toll-like receptor 4 is a therapeutic target for prevention and treatment of liver failure
Background and aims:
Toll-like receptor 4 (TLR4) plays an essential role in mediating organ injury in acute liver failure (ALF) and acute-on-chronic liver failure (ACLF). Here we assess whether inhibiting TLR4 signaling can ameliorate liver failure and serve as a potential treatment.
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Material and Methods:
Circulating TLR4 ligands and hepatic TLR4 expression was measured in plasma samples and liver biopsies from patients with cirrhosis. TAK-242 (TLR4 inhibitor) was tested in vivo with 10mg/Kg, i.p. in rodent models of ACLF (bile duct ligation + lipopolysaccharide (LPS); carbontetrachloride + LPS) and ALF (Galactosamine + LPS) and in vitro on immortalized human monocytes (THP-1) and hepatocytes (HHL5).. The in vivo therapeutic effect was assessed by coma free survival, organ injury and cytokine release and in vitro by measuring IL6, IL1b or cell injury (TUNEL), respectively.
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Results:
In patients with cirrhosis, hepatic TLR4 expression was upregulated and circulating TLR4 ligands were increased (p<0.001). ACLF in rodents was associated with a switch from apoptotic cell death in ALF to non-apoptotic forms of cell death. TAK-242 reduced LPS induced cytokine secretion and cell death (p=0.002) in hepatocytes and monocytes in vitro. In rodent models of ACLF, TAK-242 administration improved coma free survival, reduced the degree of hepatocyte cell death in liver p<0.001) and kidneys (p=0.048) and reduced circulating cytokine levels (IL1b p<0.001). In a rodent model of ALF TAK-242 prevented organ injury (p<0.001) and systemic inflammation (IL1b p<0.001).
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Conclusion:
This study shows that TLR4 signaling is a key factor in the development of both ACLF and ALF and its inhibition improves severity of organ injury and outcome. TAK-242 may be of therapeutic relevance in patients with liver failure
Proteome-based plasma biomarkers for Alzheimer's disease
Alzheimer's disease is a common and devastating disease for which there is no readily available biomarker to aid diagnosis or to monitor disease progression. Biomarkers have been sought in CSF but no previous study has used two-dimensional gel electrophoresis coupled with mass spectrometry to seek biomarkers in peripheral tissue. We performed a case-control study of plasma using this proteomics approach to identify proteins that differ in the disease state relative to aged controls. For discovery-phase proteomics analysis, 50 people with Alzheimer's dementia were recruited through secondary services and 50 normal elderly controls through primary care. For validation purposes a total of 511 subjects with Alzheimer's disease and other neurodegenerative diseases and normal elderly controls were examined. Image analysis of the protein distribution of the gels alone identifies disease cases with 56% sensitivity and 80% specificity. Mass spectrometric analysis of the changes observed in two-dimensional electrophoresis identified a number of proteins previously implicated in the disease pathology, including complement factor H (CFH) precursor and α-2-macroglobulin (α- 2M). Using semi-quantitative immunoblotting, the elevation of CFH and α- 2M was shown to be specific for Alzheimer's disease and to correlate with disease severity although alternative assays would be necessary to improve sensitivity and specificity. These findings suggest that blood may be a rich source for biomarkers of Alzheimer's disease and that CFH, together with other proteins such as α- 2M may be a specific markers of this illness. © 2006 The Author(s).link_to_subscribed_fulltex
Investigating the genetic and environmental basis of head micromovements during MRI
Introduction Head motion during magnetic resonance imaging is heritable. Further, it shares phenotypical and genetic variance with body mass index (BMI) and impulsivity. Yet, to what extent this trait is related to single genetic variants and physiological or behavioral features is unknown. We investigated the genetic basis of head motion in a meta-analysis of genome-wide association studies. Further, we tested whether physiological or psychological measures, such as respiratory rate or impulsivity, mediated the relationship between BMI and head motion.Methods We conducted a genome-wide association meta-analysis for mean and maximal framewise head displacement (FD) in seven population neuroimaging cohorts (UK Biobank, LIFE-Adult, Rotterdam Study cohort 1-3, Austrian Stroke Prevention Family Study, Study of Health in Pomerania; total N = 35.109). We performed a pre-registered analysis to test whether respiratory rate, respiratory volume, self-reported impulsivity and heart rate mediated the relationship between BMI and mean FD in LIFE-Adult.Results No variant reached genome-wide significance for neither mean nor maximal FD. Neither physiological nor psychological measures mediated the relationship between BMI and head motion.Conclusion Based on these findings from a large meta-GWAS and pre-registered follow-up study, we conclude that the previously reported genetic correlation between BMI and head motion relies on polygenic variation, and that neither psychological nor simple physiological parameters explain a substantial amount of variance in the association of BMI and head motion. Future imaging studies should thus rigorously control for head motion at acquisition and during preprocessing
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