8,046 research outputs found
Multisite Microprobes for Electrochemical Recordings in Biological Dynamics
For over 30 years, techniques have been developed that allow for the microscale (10-30 /mum) measurement of chemical signals with high temporal resolution (1-200 Hz). Such measurements, called in vivo electrochemical recordings, allow for the direct determination of neurotransmitter molecules and related compounds in biological systems. Multiple recordings, simultaneously performed at different, closely spaced, well defined locations throughout a three-dimensional tissue volume in the brain, are of interest in neuroscience. Developments in microelectronic techniques enable the fabrication of multi-electrode microprobes for recording extracellular action potentials generated by individual neurons simultaneously. A high-yield microfabrication process has been successfully developed for the fabrication of a novel semiconductor based, four-site silicon microprobe that involves a three-mask process and standard UV photolithography. A plasma process has been developed for dry etching of the gold electrodes and conducting lines. The electrochemical behavior of the microprobe is investigated by a high-speed computer-based in vitro electrochemical recording system. The electrochemical signals are measured at 5 Hz and varying gain. It is found that a selectivity of over 500:1 is achieved, and the signal to noise ratio of the recorded signal is particularly suitable for in vivo recordings
Radio Frequency Energy Harvesting and Management for Wireless Sensor Networks
Radio Frequency (RF) Energy Harvesting holds a promising future for
generating a small amount of electrical power to drive partial circuits in
wirelessly communicating electronics devices. Reducing power consumption has
become a major challenge in wireless sensor networks. As a vital factor
affecting system cost and lifetime, energy consumption in wireless sensor
networks is an emerging and active research area. This chapter presents a
practical approach for RF Energy harvesting and management of the harvested and
available energy for wireless sensor networks using the Improved Energy
Efficient Ant Based Routing Algorithm (IEEABR) as our proposed algorithm. The
chapter looks at measurement of the RF power density, calculation of the
received power, storage of the harvested power, and management of the power in
wireless sensor networks. The routing uses IEEABR technique for energy
management. Practical and real-time implementations of the RF Energy using
Powercast harvesters and simulations using the energy model of our Libelium
Waspmote to verify the approach were performed. The chapter concludes with
performance analysis of the harvested energy, comparison of IEEABR and other
traditional energy management techniques, while also looking at open research
areas of energy harvesting and management for wireless sensor networks.Comment: 40 pages, 9 figures, 5 tables, Book chapte
Graphene Transport at High Carrier Densities using a Polymer Electrolyte Gate
We report the study of graphene devices in Hall-bar geometry, gated with a
polymer electrolyte. High densities of 6 are
consistently reached, significantly higher than with conventional back-gating.
The mobility follows an inverse dependence on density, which can be correlated
to a dominant scattering from weak scatterers. Furthermore, our measurements
show a Bloch-Gr\"uneisen regime until 100 K (at 6.2 ),
consistent with an increase of the density. Ubiquitous in our experiments is a
small upturn in resistivity around 3 , whose origin is
discussed. We identify two potential causes for the upturn: the renormalization
of Fermi velocity and an electrochemically-enhanced scattering rate.Comment: 13 pages, 4 figures, Published Versio
BaFe2As2 Surface Domains and Domain Walls: Mirroring the Bulk Spin Structure
High-resolution scanning tunneling microscopy (STM) measurements on
BaFe2As2-one of the parent compounds of the iron-based superconductors-reveals
a (1x1) As-terminated unit cell on the (001) surface. However, there are
significant differences of the surface unit cell compared to the bulk: only one
of the two As atoms in the unit cell is imaged and domain walls between
different (1x1) regions display a C2 symmetry at the surface. It should have
been C2v if the STM image reflected the geometric structure of the surface or
the orthorhombic bulk. The inequivalent As atoms and the bias dependence of the
domain walls indicate that the origin of the STM image is primarily electronic
not geometric. We argue that the surface electronic topography mirrors the bulk
spin structure of BaFe2As2, via strong orbital-spin coupling
Candidemia from a Urinary Tract Source: Microbiological Aspects and Clinical Significance
Twenty-six cases of candidemia associated with a well-defined urinary tract source were retrospectively identified and reviewed. Urinary tract abnormalities were present in 23 of 26 patients (88%), 19 (73%) of whom had urinary tract obstruction. Nineteen patients had undergone urinary tract procedures before the onset of candidemia. Episodes of candidemia were brief and low-grade in intensity (median duration, 1 day; median colony count, 1.5 cfu/10 mL of blood). Only eight patients (31%) received ⩾500 mg of amphotericin B. There were five in-hospital deaths (19%); two of these deaths were attributed to candidiasis. No late complications of candidemia were documented for the surviving patients. Patients with urologic pathology and candiduria who undergo surgery or manipulation of the urinary tract are at significant risk for candidemia, and further studies should examine the issue of administration of prophylaxis to this grou
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Prevalence of established and emerging biomarkers of immune checkpoint inhibitor response in advanced hepatocellular carcinoma.
The clinical deployment of immune checkpoint inhibitors (ICIs) has created a tandem drive for the identification of biomarkers linked to benefit. Comprehensive genomic profiling was performed to evaluate the frequency of genomic biomarkers of ICI response in 755 patients with advanced hepatocellular carcinoma (HCC). Median age was 62 years' old, 73% were male, 46% had extrahepatic disease, 107 had documented hepatitis C, 96 had hepatitis B and 4 patients were coinfected. Median tumor mutation burden (TMB) was 4 mutations/Mb and only 6 tumors (0.8%) were TMB-high. Out of 542 cases assessed for microsatellite instability (MSI), one (0.2%) was MSI-high and TMB-high. Twenty-seven (4%) patients had POLE/D alterations. One patient had a pathogenic POLE R762W mutation but TMB was 4 mutations/Mb. Forty percent had DNA damage response gene alterations. In a small case series (N=17) exploring the relationship between biomarkers and ICI response, one patient (TMB 15 mutations/Mb, MSI-low) had a sustained complete response to nivolumab lasting > 2 years. Otherwise there were no significant genomic or TMB differences between responders, progressors, and those with stable disease. Overall, markers of genomic instability were infrequent in this cohort. Larger clinically annotated datasets are needed to explore genomic and non-genomic determinants of ICI response in HCC
Long-term effectiveness of a digital therapeutic intervention for smoking cessation: a randomized controlled trial
Introduction: The present study evaluated the long-term effectiveness of Quit Genius (QG), an extended digital smoking cessation intervention. Methods: Participants were adult smokers (N=556) recruited between January and November of 2019 via social media and referrals from primary care practices who were given nicotine replacement therapy and randomly assigned to Quit Genius (QG) (n=277), a cognitive behavioral therapy (CBT) based digital intervention or Very Brief Advice (VBA) (n=279), a face-to-face control intervention. Primary analyses (N=530), by intention-to-treat, compared QG and VBA on biochemically verified continuous 7-day abstinence at 4, 26, and 52 weeks post-quit date. Secondary outcomes included sustained abstinence, quit attempts, self-efficacy and mental well-being. Results: Seven-day point prevalence abstinence from weeks 4 through 52 ranged from 27% to nearly 45% among those who received QG, and from 13% to 29% for those in VBA. Continuous 7-day abstinence at 26 and 52 weeks occurred in 27.2% and 22.6% of QG participants, respectively, relative to 16.6% and 13.2% of VBA participants; QG participants were more likely to remain abstinent than those in VBA (Relative Risk [RR]= 1.71, 95% CI 1.17-2.50; p=0.005). Conclusions: This study provides evidence for the long-term effectiveness of an extended digital therapeutic intervention. Implications The long-term effectiveness of digital smoking cessation interventions has not been well-studied. This study established the long-term effectiveness of an extended CBT-based intervention; results may inform implementation of scalable, cost-effective approaches to smoking cessation in the health system
Sensitivity analysis methods for uncertainty budgeting in system design
Quantification and management of uncertainty are critical in the design of engineering systems, especially in the early stages of conceptual design. This paper presents an approach to defining budgets on the acceptable levels of uncertainty in design quantities of interest, such as the allowable risk in not meeting a critical design constraint and the allowable deviation in a system performance metric. A sensitivity-based method analyzes
the effects of design decisions on satisfying those budgets, and a multi-objective optimization formulation permits the designer to explore the tradespace of uncertainty reduction activities while also accounting for a cost budget. For models that are computationally costly to evaluate, a surrogate modeling approach based on high dimensional model representation (HDMR) achieves efficient computation of the sensitivities. An example problem in aircraft conceptual design illustrates the approach.United States. National Aeronautics and Space Administration. Leading Edge Aeronautics Research Program (Grant NNX14AC73A)United States. Department of Energy. Applied Mathematics Program (Award DE-FG02-08ER2585)United States. Department of Energy. Applied Mathematics Program (Award DE-SC0009297
Correlated two-pion exchange and large-N(C) behavior of nuclear forces
The effect of correlated scalar-isoscalar two-pion exchange (CrTPE) modes is
considered in connection with central and spin-orbit parts of the NN force. The
two-pion correlation function is coupled directly to the scalar form factor of
the nucleon which we calculate in the large-N(C) limit where the nucleon can be
described as a soliton of an effective chiral theory. The results for the
central NN force show a strong repulsive core at short internucleon distances
supplemented by a moderate attraction beyond 1 fm. The long-range tail of the
central NN potential is driven by the the pion-nucleon sigma term and
consistent with the effective meson exchange. The spin-orbit part of
the NN potential is repulsive. The large-N(C) scaling behavior of the
scalar-isoscalar NN interaction is addressed. We show that the spin-orbit part
is O(1/N^2(C)) in strength relative to the central force resulting in the ratio
suggested by the 1/N(C) expansion for N(C)=3. The latter is in
agreement with our numerical analysis and with the Kaplan-Manohar large-N(C)
power counting. Unitarization of the scattering amplitude plays here
an important role and improves the tree level results. Analytical
representations of the CrTPE NN potential in terms of elementary functions are
derived and their chiral content is discussed.Comment: 29 pages, 7 figure
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