Measured Capture Rates Research Articles

Photoconductance Determination of Carrier Capture Cross Sections of Slow Traps in Silicon Through Variable Pulse Filling

The capture cross sections are a key metric to characterize carrier traps in semiconductors. In this article, photoconductance measurements are used to estimate the capture cross sections of traps that are induced by thermal donors in Czochralski-grown silicon wafers. Here, we use a pulse-filling technique with light-emitting diode excitation to measure the capture rate. The measured capture rates are shown to be similar to the values that were measured previously by deep-level transient spectroscopy. Our method allows the contactless measurements of the capture cross sections. The minority carrier cross sections for the two distinct trap states that are studied here are of the order of 10−18 cm2 and the majority carrier cross sections are orders of magnitude smaller. Therefore, it is concluded that the slow traps that are originating from the thermal donors are dominated by the minority carrier trapping.

Impact of curated data on electronic quality measure capture rates within CancerLinQ.

307 Background: Accurate calculation of key quality measures is critical for informing high-quality, value-based cancer care that is consistent with clinical guidelines. The American Society of Clinical Oncology (ASCO)’s CancerLinQ enables oncology organizations around the US to view near-real time quality measure dashboards sourced from structured electronic medical record (EMR) data; however, use of structured data in key fields is highly variable. Unstructured content, such as progress notes, contains important clinical information on treatment and disease status, which can then undergo curation. This process involves trained data abstractors searching for key data elements through a combination of manual review and natural language processing (NLP) to extract structured data from unstructured content. We hypothesize inclusion of curated data substantially augments structured data alone by more accurately representing the patient journey, thus improving validity of quality measures across EMRs. Methods: A total of 96,399 records across 57,232 patients from 4 EMRs vendors were analyzed from 2018-2019 across structured EMR and curated data. Each record represents 1 of 7 key data elements used to calculate the Staging Documented within One Month of First Office Visit quality measure. Structured documentation of these data elements determines if a patient is concordant with the measure, meaning they were staged within 31 days of their first visit after diagnosis, or non-concordant, meaning they were not staged within the appropriate window. Results: More than a quarter of records from patients concordant or non-concordant with the measure (28.85%) had key data elements sourced from curation. In total, 33% of all records among concordant patients were sourced from curation. Relying on structured data alone would show only 67% concordance versus 97.5% concordance among curated records. This demonstrates that appropriate care may often be delivered but documentation may be missing in a significant fraction of structured EMR data, thus limiting accurate reporting capabilities. Conclusions: NLP-assisted curation can meaningfully supplement structured EMR data by providing a more accurate picture of care rendered, which can have substantial impacts on clinical care, quality reporting, and business operations. [Table: see text]

Suspended particle capture by synthetic vegetation in a laboratory flume

AbstractVegetated floodplains and wetlands trap particles, a process that is important for water quality and wetland function and morphology. The rates of particle removal by vegetation remain poorly characterized, especially for small particles and vegetation coated with biofilm. In this study, we measured capture rates of road dust by arrays of grass‐like synthetic vegetation in a laboratory flume. We performed 40 experiments in which stem density, flow velocity, the presence of biofilm, and initial particle concentration varied, and used an in situ particle size analyzer to measure the concentration of a continuous particle size distribution (1.25–250 µm diameter). We fit first‐order decay models to the particle concentration measurements to determine particle capture rates and found that capture rates increased with particle size, stem density, and the presence of biofilm. Capture rates decreased with increasing flow velocity, which suggests that fast flows may resuspend particles from stems. We also calculated percent particle capture efficiencies and fit a new empirical model for capture efficiency to our results. We found that particle capture efficiency was highest for low stem density treatments and propose that stem density affects capture by altering turbulent kinetic energy.

Application of a non-invasive indexing method for introduced Norway rats (Rattus norvegicus) in the Aleutian Islands, Alaska

Island restoration projects that address invasive species issues require measures of invader populations before eradication or control efforts begin, especially for cryptic species such as introduced rodents. To address this need, we tested a non-invasive technique for measuring inter-annual variation in Norway rat (Rattus norvegicus) activity at Kiska Island, Aleutian Islands, Alaska, during 2005-2010. Snap-trapping could not be used at a large mixed colony of small seabirds (auklets, Aethia spp.) at Sirius Point, Kiska, due to the certainty of bird mortality. Away from the colony site at Kiska Harbour, in June 2005, we used snap-traps to measure capture rates, and found a similar corrected trap index (8.5 captures/100 trap nights) to that recorded pre-eradication at Langara Island, British Columbia (8.2 captures/100 trap nights). At Sirius Point, we determined the most effective rat-monitoring method to be a series transects spanning the auklet colony, with detection stations set at 25 m intervals, each including a baited wax block. Rat detections varied nearly 100-fold among years, suggesting high inter-annual variability in the rat population. We found no statistically significant relationship between our rat index and auklet breeding success at Sirius Point with our small sample of years (n = 5, 2006–2010). Nevertheless, we believe rat numbers were much lower at Sirius Point during 2006–2010 than observed qualitatively during 2001–2002 when auklets experienced breeding failure. Our rat activity index protocol is likely applicable to other situations in which introduced rodent numbers needs to be monitored while safeguarding native fauna that could be harmed by snap-trapping.

An update of muon capture on hydrogen

The successful precision measurement of the rate of muon capture on a proton by the MuCap Collaboration allows for a stringent test of the current theoretical understanding of this process. Chiral perturbation theory (χPT), which is a low-energy effective field theory (EFT) that preserves the symmetries and the pattern of symmetry breaking in the underlying theory of QCD, offers a systematic framework for describing μp capture and provides a basic test of QCD at the hadronic level. We describe how this effective theory with no free parameters reproduces the measured capture rate. A recent study has addressed new sources of uncertainties that were not considered in the previous works, and we review to what extent these uncertainties are now under control. Finally, the rationale for studying muon capture on the deuteron and some recent theoretical developments regarding this process are discussed.

High-Bandwidth Protein Analysis Using Solid-State Nanopores

High-bandwidth measurements of the ion current through hafnium oxide and silicon nitride nanopores allow the analysis of sub-30 kD protein molecules with unprecedented time resolution and detection efficiency. Measured capture rates suggest that at moderate transmembrane bias values, a substantial fraction of protein translocation events are detected. Our dwell-time resolution of 2.5 μs enables translocation time distributions to be fit to a first-passage time distribution derived from a 1D diffusion-drift model. The fits yield drift velocities that scale linearly with voltage, consistent with an electrophoretic process. Further, protein diffusion constants (D) are lower than the bulk diffusion constants (D0) by a factor of ∼50, and are voltage-independent in the regime tested. We reason that deviations of D from D0 are a result of confinement-driven pore/protein interactions, previously observed in porous systems. A straightforward Kramers model for this inhibited diffusion points to 9- to 12-kJ/mol interactions of the proteins with the nanopore. Reduction of μ and D are found to be material-dependent. Comparison of current-blockage levels of each protein yields volumetric information for the two proteins that is in good agreement with dynamic light scattering measurements. Finally, detection of a protein-protein complex is achieved.

Quality of Flooded Rice and Fallow Fields as Foraging Habitat for Little Blue Herons and Great Egrets in the Everglades Agricultural Area, USA

Wading birds have been observed foraging in agricultural wetlands worldwide where natural wetlands have become lost, degraded, or seasonally dry, yet the ability of wading birds to satisfy daily energy requirements in agricultural wetlands has been little studied. The ability to meet daily energy requirements for Little Blue Herons (Egretta caerulea) and Great Egrets (Ardea alba) foraging in flooded rice and fallow fields of the Everglades Agricultural Area (EAA) was evaluated during April-June 2008 and 2009. Focal samples were used to measure capture rates (captures/min), identify prey and estimate captured prey size, and calculate energy budgets for both species. Within flooded fields prey density was measured and foraging sites and random locations were compared. Habitat variables did not differ between foraging sites and random locations. Vegetation cover and prey abundance increased in rice fields over time and were greater in rice than fallow fields. Small prey, dominated by fish, were captured by both species and corresponded to prey sampled. Most wading birds in June were observed in newly flooded fallow fields despite lower prey densities. Little Blue Herons met daily energy requirements for both years; but Great Egrets did not, likely due to predominantly small prey, increasing vegetative cover in rice fields, and lower prey densities in newly flooded fallow fields. Although Great Egrets did not meet daily caloric requirements, the EAA may still function as an important transitional habitat at a time when foraging resources in the region are limited.

Shell model study ofCa40muon capture and the(0+,0keV)→(0−,2626keV) axial charge transition

We report results from shell-model studies of muon capture on $^{40}\mathrm{Ca}$ to low-lying levels of $^{40}\mathrm{K}$. We discuss the comparison among calculated capture rates, measured capture rates, and analogous transitions in ($e,{e}^{'}$) scattering in terms of the particle-hole structure of the $^{40}\mathrm{Ca}$-$^{40}\mathrm{K}$ nuclei. We highlight the $^{40}\mathrm{Ca}$$({0}^{+},0)\ensuremath{\rightarrow}$$^{40}\mathrm{K}$$({0}^{\ensuremath{-}},2626)$ axial charge transition and its sensitivity to the induced pseudoscalar coupling ${g}_{p}$ of the proton's weak interaction. In addition, we address the hindrance of unique first-forbidden transitions due to particle-hole interactions and the emergence of allowed Gamow-Teller transitions due to ground-state correlations. Last, we examine the longitudinal alignment of $^{40}\mathrm{K}$ recoils following muon capture and discuss this possibility for independently determining the induced coupling ${g}_{p}$.

Measurement of partial muon capture rates in1s−0dshell nuclei

We report yields for 38 \ensuremath{\gamma}-ray lines and 29 $({\ensuremath{\mu}}^{\ensuremath{-}},\ensuremath{\nu})$ transitions following negative muon capture on ${}^{24}\mathrm{Mg},$ ${}^{28}\mathrm{Si},$ ${}^{31}\mathrm{P},$ and ${}^{32}\mathrm{S}.$ Our results substantially increase the world data set for partial $({\ensuremath{\mu}}^{\ensuremath{-}},\ensuremath{\nu})$ transitions on $1s\ensuremath{-}0d$ shell nuclei. They also resolve a number of inconsistencies between previously published \ensuremath{\gamma}-ray yields and accepted \ensuremath{\gamma}-decay branching ratios. We compare the measured capture rates for the allowed Gamow-Teller (GT) transitions (supplemented with earlier ${}^{23}\mathrm{Na}$ data) with a shell model calculation using the full $1s\ensuremath{-}0d$ space and universal SD interaction. We find a ``best fit'' value of the effective weak axial coupling of ${g}_{a}=\ensuremath{-}{0.91}_{\ensuremath{-}0.17}^{+0.15},$ fair agreement for the per-target summed GT capture rates, but poor agreement for the individual GT capture rates. By replacing the shell model $\ensuremath{\sigma}{\ensuremath{\tau}}^{\ifmmode\pm\else\textpm\fi{}}$ matrix element values with experimentally determined $\ensuremath{\sigma}{\ensuremath{\tau}}^{\ifmmode\pm\else\textpm\fi{}}$ matrix element values, improved predictions for the individual GT capture rates are obtained. Last, we comment on recent determinations of the weak coupling ${g}_{p}$ via muon capture on $1s\ensuremath{-}0d$ shell nuclei.

Preliminary results from the Russian-American Gallium Experiment Cr-neutrino source measurement

The Russian-American Gallium Experiment has been collecting solar neutrino data since early 1990. The flux measurement of solar neutrinos is well below that expected from solar models. We discuss the initial results of a measurement of experimental efficiencies by exposing the gallium target to neutrinos from an artificial source. The capture rate of neutrinos from this source is very close to that which is expected. The result can be expressed as a ratio of the measured capture rate to the anticipated rate from the source activity. This ratio is 0.93 + 0.15, − 0.17 where the systematic and statistical errors have been combined. To first order the experimental efficiencies are in agreement with those determined during solar neutrino measurements and in previous auxiliary measurements. One must conclude that the discrepancy between the measured solar neutrino flux and that predicted by the solar models can not arise from an experimental artifact.

Hyperfine effect in micro- capture on 23Na and gp/ga.

We report measurements of the rates and hyperfine (HF) dependences of ${\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{-}}}$ capture on $^{23}\mathrm{Na}$, and the HF transition rate in Na metal. The measured capture rates are in general agreement with the predictions of the 1s-0d shell model. The measured HF dependences of the 1017 and 1823 keV \ensuremath{\gamma} rays from $^{23}\mathrm{Ne}$ yield ${\mathit{g}}_{\mathit{p}}$/${\mathit{g}}_{\mathit{a}}$=7.6${\ifmmode\pm\else\textpm\fi{}}_{2.5}^{2.1}$ and ${\mathit{g}}_{\mathit{p}}$/${\mathit{g}}_{\mathit{a}}$\ensuremath{\le}7.1(1\ensuremath{\sigma}), consistent with partial conservation of axial-vector current, but in disagreement with claims of an enhancement of ${\mathit{g}}_{\mathit{p}}$/${\mathit{g}}_{\mathit{a}}$ in light nuclei. The measured HF transition rate ${\mathrm{\ensuremath{\Delta}}}_{\mathit{h}}$=15.5\ifmmode\pm\else\textpm\fi{}1.1 \ensuremath{\mu}${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$ is in agreement with the theory of Auger emission but twice the rate previously obtained in NaF (a\ensuremath{\sim}3\ensuremath{\sigma} effect).

Muon capture revisited

The problem of inclusive muon capture in nuclei is studied by calculating the capture rate in asymmetric infinite nuclear matter and using the local density approximation to evaluate the capture rates in nuclei. It is shown that the method is rather reliable and allows one to improve on approximations used in the past. The need for a strong nuclear renormalization is shown, reducing the capture rates by about a factor two in medium and heavy nuclei. By using standard effective interactions in the spin-isospin channel one can account for this renormalization and one finds a remarkable overall agreement with the measured capture rates for a large list of nuclei through the periodic table.

Optical characterization of deep energy levels in semiconductors

Optical techniques for characterizing deep level impurities in semiconductors are discussed, with emphasis on the various physical properties that can be revealed in such studies. The scope is essentially limited to methods for bulk characterization, for the reason that a comprehensive review article devoted to deep level applications seems not to exist for this particular field. One advantage with such techniques is the absence of large electric fields in the investigated part of the sample, such high field may well influence several physical parameters otherwise conveniently studied by space-charge techniques. Further bulk measurements often have the general advantage of probing a large part of the sample, often the entire volume of the crystal. The presentation starts with a description of the recently developed method of constant photoconductivity measurements for deep levels, which turns out to be a very convenient method to measure optical emission rates for deep levels. A brief section on measurements of capture rates for deep levels with a junction space charge capacitance technique is also included. This method actually measures carrier capture in a field free region, and therefore fits into the above-mentioned scope of the article, especially since bulk measurements of capture rates are generally difficult. The remainder of the paper is devoted to a discussion of various photoluminescence techniques, which are useful for determination of many different deep level parameters, mainly for centers giving radiative recombination. Properties revealed by photoluminescence studies are e.g defect identity, energy level position and optical emission rates. There are also methods to measure capture rates and thermal emission rates for deep levels, as will be discussed briefly towards the end. Finally a concluding summary of possible achievements in characterization of different deep level related properties by optical techniques is given.

A transmission method to measure capture rates in fast reactors

A method is described to measure neutron capture rates of materials in a cavity in the center of a fast reactor. The method is based on neutron transmission through a probe of the material to be investigated and can be used also in zero power facilities. Some measurements were done for U-235 and for U-238. On account of the special detector used, it is limited, however, to sufficiently hard neutron energy spectra.

In-situ measurement of the rate of 235U fission induced by lunar neutrons

The depth profile of the neutron-induced fission rate of 235U was directly measured to a depth of 350 g/cm 2 by the Apollo 17 Lunar Neutron Probe Experiment. The fission rate rises sharply from the surface to a broad maximum from 110 to 160 g/cm 2 and drops off at greater depths. The shape of theoretical depth profile of Lingenfelter et al. fits the measured capture rates well at all depths. The absolute magnitude of the experimental fission rates are (11±17)% lower than those calculated theoretically. The excellent agreement between theory and experiment implies that conclusions drawn previously by interpreting lunar sample data with the theoretical capture rates will not require revision. In particular lunar surface processes, rather than uncertainties in the capture rates, are required to explain the relatively low neutron fluences observed for surface soil samples compared to the fluences expected for a uniformly mixed regolith.

The total capture rate of negative muons in4He

Wo have measured the total capture rate of negative muons in4He by exposing the 20 cm liquid helium bubble chamber, operated in a 5 kG magnetic field, to a stopping muon beam. The measured capture rate is (364±46) s−1.

Coupling Constants in Muon Capture

The measured capture rate of muons in ${\mathrm{C}}^{12}$ leading to the ground state of ${\mathrm{B}}^{12}$, in combination with other data, is employed as a basis for a determination of the weak-interaction coupling constants associated with muon capture. The study of this transition has the advantages: (1) that the rate depends only weakly on the vector, induced pseudoscalar, and (possible) tensor coupling constants, but not at all on a possible scalar coupling constant; (2) that empirical information from inelastic electron scattering on ${\mathrm{C}}^{12}$ leading to the excitation of the 15.1-MeV level, the $M1$ lifetime of this level, and the $f{\ensuremath{\tau}}_{\frac{1}{2}}$ value for the beta decay of ${\mathrm{B}}^{12}$ allows one to determine the required nuclear matrix elements of major importance (as well as some of minor importance) in practically a model-independent way. The capture rate can thus be expressed in terms of the axial vector coupling constant and the weak-magnetism coupling constants. Assuming the validity of the conserved-vector-current hypothesis (CVC), and $5l{C}_{p}l28$, one then finds that $\frac{{{F}_{A}}^{\ensuremath{\mu}}}{{{F}_{A}}^{\ensuremath{\beta}}}={{1.04}_{\ensuremath{-}0.10}}^{+0.07}$. On the other hand, if one assumes ${{F}_{A}}^{\ensuremath{\mu}}={{F}_{A}}^{\ensuremath{\beta}}$, one obtains for the isotopic vector magnetic moment of the nucleon (at the appropriate momentum transfer) $\ensuremath{\mu}({\ensuremath{\nu}}^{2})={{5.7}_{\ensuremath{-}1.6}}^{+1.1}$ nuclear magnetons, which is consistent with the CVC prediction of 4.60 nm and can be considered as evidence for weak magnetism in muon capture.

Muon Capture inHe3

The rate has been measured for capture of negative muons on ${\mathrm{He}}^{3}$ to form bound ${\mathrm{H}}^{3}$. The monoenergetic recoil triton was observed in a ${\mathrm{He}}^{3}$ gas scintillation target counter, and the rate was normalized to $\ensuremath{\mu}$-decay electrons observed in surrounding counters. Triton pulses were analyzed in the two dimensions of energy and time with respect to the stopping muon, and with an ultimate energy resolution of 15%, full width at half-maximum, a clean separation could be made between recoil tritons and other muon-associated events. The measured capture rate is 1465\ifmmode\pm\else\textpm\fi{}67 ${\mathrm{sec}}^{\ensuremath{-}1}$, in good agreement with other experiments and with predictions based on the "standard" theory of muon capture. Simultaneous limits were calculated for the vector and induced pseudoscalar coupling constants, $g_{V}^{}{}_{}{}^{\ensuremath{\mu}}$ and $g_{P}^{}{}_{}{}^{\ensuremath{\mu}}$, using the results of this experiment and of the experiments on muon capture in liquid hydrogen. These are $0.7<\frac{g_{V}^{}{}_{}{}^{\ensuremath{\mu}}}{g_{V}^{}{}_{}{}^{\ensuremath{\beta}}}<1.2$ and $1<\frac{g_{P}^{}{}_{}{}^{\ensuremath{\mu}}}{g_{A}^{}{}_{}{}^{\ensuremath{\mu}}}<17$ with central values of 0.99 and 11.6, respectively.