905 research outputs found
Doping density, not valency, influences catalytic metal-assisted plasma etching of silicon
Metal-assisted plasma etching (MAPE) of silicon (Si) is an etching technique driven by the catalytic activity of metals such as gold in fluorine-based plasma environments. In this work, we investigated the role of the Si substrate by examining the effects of dopant concentration in both n- and p-type Si and dopant atom type in n-type Si in SF6/O2 mixed gas plasma. At the highest dopant concentrations, both n- and p-type Si initially exhibit inhibition of the MAPE-enhanced etching. As the etch progresses, MAPE initiates, resulting in catalytic etching of the underlying Si at the metal-Si interface. Interestingly, MAPE-enhanced etching increases with decreasing doping concentrations for both n-and type Si substrates, distinct from results for the similar but divergent, metal-assisted chemical etching of silicon in liquid. Our findings show that the metal-Si interface remains essential to MAPE, and surface enrichment of the dopant atoms or other surface chemistries and the size of metal nanoparticles can play roles in modulating catalytic activity
Recommended from our members
The Adoption and Use of Electronic Information Resources by a Non-Traditional User Group: Automotive Service Technicians.
The growing complexity of machines has led to a concomitant increase in the amount and complexity of the information needed by those charged with servicing them. This, in turn, has led to a need for more robust methods for storing and distributing information and for a workforce more sophisticated in its use of information resources. As a result, the service trades have "professionalized," adopting more rigorous academic standards and developing ongoing certification programs. The current paper deals with the acceptance of advanced electronic information technology by skilled service personnel, specifically, automotive service technicians. The theoretical basis of the study is Davis' technology acceptance model. The purpose of the study is to determine the effects of three external factors on the operation of the model: age, work experience, and education/certification level. The research design is in two parts, beginning with an onsite observation and interviews to establish the environment. During the second part of the research process a survey was administered to a sample of automotive service technicians. Results indicated significant inverse relationships between age and acceptance and between experience and acceptance. A significant positive relationship was shown between education, particularly certification, and acceptance
Anagen hair follicles transplanted into mature human scars remodel fibrotic tissue
Despite the substantial impact of skin scarring on patients and the healthcare system, there is a lack of strategies to prevent scar formation, let alone methods to remodel mature scars. Here, we took a unique approach inspired by how healthy hairbearing skin undergoes physiological remodelling during the regular cycling of hair follicles. In this pilot clinical study, we tested if hair follicles transplanted into human scars can facilitate tissue regeneration and actively remodel fibrotic tissue, similar to how they remodel the healthy skin. We collected full-thickness skin biopsies and compared the morphology and transcriptional signature of fibrotic tissue before and after transplantation. We found that hair follicle tranplantation induced an increase in the epidermal thickness, interdigitation of the epidermal-dermal junction, dermal cell density, and blood vessel density. Remodelling of collagen type I fibres reduced the total collagen fraction, the proportion of thick fibres, and their alignment. Consistent with these morphological changes, we found a shift in the cytokine milieu of scars with a long-lasting inhibition of pro-fibrotic factors TGFÎČ1, IL13, and IL-6. Our results show that anagen hair follicles can attenuate the fibrotic phenotype, providing new insights for developing regenerative approaches to remodel mature scars
Spatial Heterogeneity Can Lead to Substantial Local Variations in COVID-19 Timing and Severity
Standard epidemiological models for COVID-19 employ variants of compartment
(SIR) models at local scales, implicitly assuming spatially uniform local
mixing. Here, we examine the effect of employing more geographically detailed
diffusion models based on known spatial features of interpersonal networks,
most particularly the presence of a long-tailed but monotone decline in the
probability of interaction with distance, on disease diffusion. Based on
simulations of unrestricted COVID-19 diffusion in 19 U.S cities, we conclude
that heterogeneity in population distribution can have large impacts on local
pandemic timing and severity, even when aggregate behavior at larger scales
mirrors a classic SIR-like pattern. Impacts observed include severe local
outbreaks with long lag time relative to the aggregate infection curve, and the
presence of numerous areas whose disease trajectories correlate poorly with
those of neighboring areas. A simple catchment model for hospital demand
illustrates potential implications for health care utilization, with
substantial disparities in the timing and extremity of impacts even without
distancing interventions. Likewise, analysis of social exposure to others who
are morbid or deceased shows considerable variation in how the epidemic can
appear to individuals on the ground, potentially affecting risk assessment and
compliance with mitigation measures. These results demonstrate the potential
for spatial network structure to generate highly non-uniform diffusion behavior
even at the scale of cities, and suggest the importance of incorporating such
structure when designing models to inform healthcare planning, predict
community outcomes, or identify potential disparities
Parton cascade description of relativistic heavy-ion collisions at CERN SPS energies ?
We examine Pb+Pb collisions at CERN SPS energy 158 A GeV, by employing the
earlier developed and recently refined parton-cascade/cluster-hadronization
model and its Monte Carlo implementation. This space-time model involves the
dynamical interplay of perturbative QCD parton production and evolution, with
non-perturbative parton-cluster formation and hadron production through cluster
decays. Using computer simulations, we are able to follow the entwined
time-evolution of parton and hadron degrees of freedom in both position and
momentum space, from the instant of nuclear overlap to the final yield of
particles. We present and discuss results for the multiplicity distributions,
which agree well with the measured data from the CERN SPS, including those for
K mesons. The transverse momentum distributions of the produced hadrons are
also found to be in good agreement with the preliminary data measured by the
NA49 and the WA98 collaboration for the collision of lead nuclei at the CERN
SPS. The analysis of the time evolution of transverse energy deposited in the
collision zone and the energy density suggests an existence of partonic matter
for a time of more than 5 fm.Comment: 16 pages including 7 postscript figure
Unraveling the Pharmacokinetic Interaction of Ticagrelor and MEDI2452 (Ticagrelor Antidote) by Mathematical Modeling
The investigational ticagrelor-neutralizing antibody fragment, MEDI2452, is developed to rapidly and specifically reverse the antiplatelet effects of ticagrelor. However, the dynamic interaction of ticagrelor, the ticagrelor active metabolite (TAM), and MEDI2452, makes pharmacokinetic (PK) analysis nontrivial and mathematical modeling becomes essential to unravel the complex behavior of this system. We propose a mechanistic PK model, including a special observation model for post-sampling equilibration, which is validated and refined using mouse in vivo data from four studies of combined ticagrelor-MEDI2452 treatment. Model predictions of free ticagrelor and TAM plasma concentrations are subsequently used to drive a pharmacodynamic (PD) model that successfully describes platelet aggregation data. Furthermore, the model indicates that MEDI2452-bound ticagrelor is primarily eliminated together with MEDI2452 in the kidneys, and not recycled to the plasma, thereby providing a possible scenario for the extrapolation to humans. We anticipate the modeling work to improve PK and PD understanding, experimental design, and translational confidence
Simulation of Light Antinucleus-Nucleus Interactions
Creations of light anti-nuclei (anti-deuterium, anti-tritium, anti-He3 and
anti-He4) are observed by collaborations at the LHC and RHIC accelerators. Some
cosmic ray experiments are aimed to find the anti-nuclei in cosmic rays. To
support the experimental studies of the anti-nuclei a Monte Carlo simulation of
anti-nuclei interactions with matter is implemented in the Geant4 toolkit. The
implementation combines practically all known theoretical approaches to the
problem of antinucleon-nucleon interactions.Comment: 8 pages, 5 figure
Synergistic and antagonistic effects of land use and nonânative species on community responses to climate change
Climate change, landâuse change and introductions of nonânative species are key determinants of biodiversity change worldwide. However, the extent to which anthropogenic drivers of environmental change interact to affect biological communities is largely unknown, especially over longer time periods. Here, we show that plant community composition in 996 Swedish landscapes has consistently shifted to reflect the warmer and wetter climate that the region has experienced during the second half of the 20th century. Using community climatic indices, which reflect the average climatic associations of the species within each landscape at each time period, we found that species compositions in 74% of landscapes now have a higher representation of warmâassociated species than they did previously, while 84% of landscapes now host more species associated with higher levels of precipitation. In addition to a warmer and wetter climate, there have also been large shifts in land use across the region, while the fraction of nonânative species has increased in the majority of landscapes. Climatic warming at the landscape level appeared to favour the colonization of warmâassociated species, while also potentially driving losses in coolâassociated species. However, the resulting increases in community thermal means were apparently buffered by landscape simplification (reduction in habitat heterogeneity within landscapes) in the form of increased forest cover. Increases in nonânative species, which generally originate from warmer climates than Sweden, were a strong driver of communityâlevel warming. In terms of precipitation, both landscape simplification and increases in nonânatives appeared to favour species associated with drier climatic conditions, to some extent counteracting the climateâdriven shift towards wetter communities. Anthropogenic drivers can act both synergistically and antagonistically to determine trajectories of change in biological communities over time. Therefore, it is important to consider multiple drivers of global change when trying to understand, manage and predict biodiversity in the future
Measurements of knee rotation-reliability of an external device in vivo
<p>Abstract</p> <p>Background</p> <p>Knee rotation plays an important part in knee kinematics during weight-bearing activities. An external device for measuring knee rotation (the Rottometer) has previously been evaluated for validity by simultaneous measurements of skeletal movements with Roentgen Stereometric Analysis (RSA). The aim of this study was to investigate the reliability of the device.</p> <p>Method</p> <p>The within-day and test-retest reliability as well as intertester reliability of the device in vivo was calculated. Torques of 3, 6 and 9 Nm and the examiner's apprehension of end-feel were used at 90°, 60° and 30° of knee flexion. Intraclass Correlation Coefficient <sub>2,1 </sub>(ICC <sub>2,1</sub>), 95% confidence interval (CI) of ICC and 95% CI between test trials and examiners were used as statistical tests.</p> <p>Result</p> <p>ICC<sub>2,1 </sub>ranged from 0.50 to 0.94 at all three flexion angles at 6 and 9 Nm as well as end-feel, and from 0.22 to 0.75 at 3 Nm applied torque.</p> <p>Conclusion</p> <p>The Rottometer was a reliable measurement instrument concerning knee rotation at the three different flexion angles (90°, 60° and 30°) with 6 and 9 Nm applied torques as well as the examiner's apprehension of end-feel. Three Nm was not a reliable torque. The most reliable measurements were made at 9 Nm applied torque.</p
- âŠ