4,258 research outputs found
Thermal Analysis of Infrared Irradiation-Assisted Nanosecond-Pulsed Tumor Ablation
Nanosecond Pulsed Electric Fields (nsPEF) have the potential to treat a variety of cancer types including melanoma, pancreatic and lung squamous cancers. Recent studies show that nsPEF-based cancer therapy may be improved further with the assistance of moderate heating of the target. A feedbacklooped heating system, utilizing a 980-nm fiber optic laser, was integrated into nsPEF electrodes for tumor ablation. The laser beam profile was determined to be Gaussian using a knife-edge technique. Thermal properties of the biological target were evaluated based on the treatment area, penetration depth and thermal distribution due to laser irradiation with or without nsPEF. Synergistic effects between nsPEF and the moderately elevated temperature at the target was observed, resulting in enhanced overall survival tumor regression up to 50% in the treatment of lung squamous cell cancer in mice
A Bayesian Evidence Synthesis Approach to Estimate Disease Prevalence in Hard-To-Reach Populations: Hepatitis C in New York City
Existing methods to estimate the prevalence of chronic hepatitis C (HCV) in
New York City (NYC) are limited in scope and fail to assess hard-to-reach
subpopulations with highest risk such as injecting drug users (IDUs). To
address these limitations, we employ a Bayesian multi-parameter evidence
synthesis model to systematically combine multiple sources of data, account for
bias in certain data sources, and provide unbiased HCV prevalence estimates
with associated uncertainty. Our approach improves on previous estimates by
explicitly accounting for injecting drug use and including data from high-risk
subpopulations such as the incarcerated, and is more inclusive, utilizing ten
NYC data sources. In addition, we derive two new equations to allow age at
first injecting drug use data for former and current IDUs to be incorporated
into the Bayesian evidence synthesis, a first for this type of model. Our
estimated overall HCV prevalence as of 2012 among NYC adults aged 20-59 years
is 2.78% (95% CI 2.61-2.94%), which represents between 124,900 and 140,000
chronic HCV cases. These estimates suggest that HCV prevalence in NYC is higher
than previously indicated from household surveys (2.2%) and the surveillance
system (2.37%), and that HCV transmission is increasing among young injecting
adults in NYC. An ancillary benefit from our results is an estimate of current
IDUs aged 20-59 in NYC: 0.58% or 27,600 individuals
Influence of diffraction on the spectrum and wavefunctions of an open system
In this paper, we demonstrate the existence and significance of diffractive
orbits in an open microwave billiard, both experimentally and theoretically.
Orbits that diffract off of a sharp edge of the system are found to have a
strong influence on the transmission spectrum of the system, especially in the
regime where there are no stable classical orbits. On resonance, the
wavefunctions are influenced by both classical and diffractive orbits. Off
resonance, the wavefunctions are determined by the constructive interference of
multiple transient, nonperiodic orbits. Experimental, numerical, and
semiclassical results are presented.Comment: 27 pages, 29 figures, and 3 tables. Submitted to Physical Review E. A
copy with higher resolution figures is available at
http://monsoon.harvard.edu/~hersch/papers.htm
Ground reaction force estimation in football using inertial measurement units during alternate lateral bounding
Ground reaction force (GRF) is of interest to understand the mechanics of football shoe-surface interactions and the consequences for athletic performance (Luo & Stefanyshyn, 2011 Luo, G., & Stefanyshyn, D. (2011). Identification of critical traction values for maximum athletic performance. Footwear Science, 3, 127–138. doi:10.1080/19424280.2011.639807
[Taylor & Francis Online] , [Google Scholar]
; Pedroza, Fernandez, Heidt, & Kaeding, 2010 Pedroza, A., Fernandez, S., Heidt, R., & Kaeding, C. (2010). Evaluation of the shoe-surface interaction using an agility maneuver. Medicine and Science in Sports and Exercise, 42, 1754–1759.
[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]
). Force platforms (FP) are the gold standard for measuring GRF; however, they are expensive devices, athletes may adjust their movements to target a specific area and installation is difficult outside the laboratory under football specific surfaces. Potential candidates to overcome these limitations and estimate GRFs in-field are inertial measurement units (IMU)
Tidal Venuses: Triggering a Climate Catastrophe via Tidal Heating
Traditionally stellar radiation has been the only heat source considered
capable of determining global climate on long timescales. Here we show that
terrestrial exoplanets orbiting low-mass stars may be tidally heated at high
enough levels to induce a runaway greenhouse for a long enough duration for all
the hydrogen to escape. Without hydrogen, the planet no longer has water and
cannot support life. We call these planets "Tidal Venuses," and the phenomenon
a "tidal greenhouse." Tidal effects also circularize the orbit, which decreases
tidal heating. Hence, some planets may form with large eccentricity, with its
accompanying large tidal heating, and lose their water, but eventually settle
into nearly circular orbits (i.e. with negligible tidal heating) in the
habitable zone (HZ). However, these planets are not habitable as past tidal
heating desiccated them, and hence should not be ranked highly for detailed
follow-up observations aimed at detecting biosignatures. Planets orbiting stars
with masses <0.3 solar masses may be in danger of desiccation via tidal
heating. We apply these concepts to Gl 667C c, a ~4.5 Earth-mass planet
orbiting a 0.3 solar mass star at 0.12 AU. We find that it probably did not
lose its water via tidal heating as orbital stability is unlikely for the high
eccentricities required for the tidal greenhouse. As the inner edge of the HZ
is defined by the onset of a runaway or moist greenhouse powered by radiation,
our results represent a fundamental revision to the HZ for non-circular orbits.
In the appendices we review a) the moist and runaway greenhouses, b) hydrogen
escape, c) stellar mass-radius and mass-luminosity relations, d) terrestrial
planet mass-radius relations, and e) linear tidal theories. [abridged]Comment: 59 pages, 11 figures, accepted to Astrobiology. New version includes
an appendix on the water loss timescal
Prioritising between direct observation of therapy and case-finding interventions for tuberculosis: use of population impact measures
BACKGROUND: Population impact measures (PIMs) have been developed as tools to help policy-makers with locally relevant decisions over health risks and benefits. This involves estimating and prioritising potential benefits of interventions in specific populations. Using tuberculosis (TB) in India as an example, we examined the population impact of two interventions: direct observation of therapy and increasing case-finding. METHODS: PIMs were calculated using published literature and national data for India, and applied to a notional population of 100 000 people. Data included the incidence or prevalence of smear-positive TB and the relative risk reduction from increasing case finding and the use of direct observation of therapy (applied to the baseline risks over the next year), and the incremental proportion of the population eligible for the proposed interventions. RESULTS: In a population of 100 000 people in India, the directly observed component of the Directly Observed Treatment, Short-course (DOTS) programme may prevent 0.188 deaths from TB in the next year compared with 1.79 deaths by increasing TB case finding. The costs of direct observation are (in international dollars) I4839 or I2703 per life saved respectively. CONCLUSION: Increasing case-finding for TB will save nearly 10 times more lives than will the use of the directly observed component of DOTS in India, at a smaller cost per life saved. The demonstration of the population impact, using simple and explicit numbers, may be of value to policy-makers as they prioritise interventions for their populations
Zero temperature string breaking in lattice quantum chromodynamics
The separation of a heavy quark and antiquark pair leads to the formation of
a tube of flux, or "string", which should break in the presence of light
quark-antiquark pairs. This expected zero-temperature phenomenon has proven
elusive in simulations of lattice QCD. We study mixing between the string state
and the two-meson decay channel in QCD with two flavors of dynamical sea
quarks. We confirm that mixing is weak and find that it decreases at level
crossing. While our study does not show direct effects of internal quark loops,
our results, combined with unitarity, give clear confirmation of string
breaking.Comment: 20 pages, 7 figures. With small clarifications and two additions to
references. Submitted to Phys. Rev.
Science and the Liberal Arts at Ursinus College
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Quenched hadron spectroscopy with improved staggered quark action
We investigate light hadron spectroscopy with an improved quenched staggered
quark action. We compare the results obtained with an improved gauge plus an
improved quark action, an improved gauge plus standard quark action, and the
standard gauge plus standard quark action. Most of the improvement in the
spectroscopy results is due to the improved gauge sector. However, the improved
quark action substantially reduces violations of Lorentz invariance, as
evidenced by the meson dispersion relations.Comment: New references adde
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