Rates For Capture Research Articles

Autonomous Control Method for Object Grasping of Logistics Sorting Manipulator Considering Changes in Lighting Environment

The autonomous grasping operation is the key to the intelligent logistics sorting manipulators. Since the current logistics sorting manipulators mostly use visual sensors to identify objects, they are extremely vulnerable to the changes in the lighting environment. Therefore, the research considers the influence of complex lighting environment on the autonomous grasping of logistics sorting manipulators. Furthermore, it verifies the effectiveness of SAC-AE-ICM algorithm through simulations and experiments. The experimental results show that SAC-AE-ICM algorithm can quickly achieve convergence in many experiments and can obtain global optimization. In the process of automatic capture, the success rate of SAC-AE-ICM algorithm can reach 90%, which is 25% higher than that of the method without ICM and has better convergence. The success rate was as high as 77% for unknown or irregular targets. In practical experiments, SAC-AE-ICM can effectively capture under good lighting conditions. However, under low light conditions, the probability of capturing unknown targets is about 72.5%. Overall, the success rates for single-object and multi-object capture are 88% and 85%, respectively.

Onset of zooplanktivory and optimal water flow rates for prey capture in newly settled polyps of ten Caribbean coral species

Zooplanktivory is an important source of nutrients in corals, providing up to 35% of daily metabolic energy requirements in some species. However, little is known about coral zooplanktivory shortly after larval settlement and metamorphosis. In most species it is unclear if, when and under which conditions newly settled polyps are able to capture and ingest prey. This remains a critical knowledge gap, as zooplanktivory could allow coral settlers to replenish energy reserves shortly after metamorphosis, possibly improving settler condition during one of their most vulnerable life stages. Here, we documented the onset of prey (Artemia salina nauplii) capture in ten Caribbean coral species and assessed optimal water flow rates (WFR) for prey capture in five of these species. All species initiated zooplanktivory within six days following metamorphosis, with the exception of Acropora palmata which was never observed capturing nauplii during our 20-day study. Optimal WFR for prey capture varied among species, with Favia fragum displaying maximum prey capture rates in zero flow and Diploria labyrinthiformis most effectively capturing nauplii under WFR of 5–20 cm s−1. Under each species’ optimum WFR, prey capture abilities varied considerably, with F. fragum capturing up to one nauplius every two minutes compared to one nauplius every nine minutes in Colpophyllia natans. Using these findings, we make species-specific recommendations to optimize coral husbandry and larval-based restoration practices for these ten coral species.

Astrophysical reaction rates with realistic nuclear level densities

Realistic nuclear level densities (NLDs) obtained within the spectral distribution method (SDM) are employed to study nuclear processes of astrophysical interest. The merit of SDM lies in the fact that the NLDs corresponding to many body shell model Hamiltonian consisting of residual interaction can be obtained for the full configurational space without recourse to the exact diagnolization of huge matrices. We calculate NLDs and s-wave neutron resonance spacings which agree reasonably well with the available experimental data. By employing these NLDs, we compute reaction cross-sections and astrophysical reaction rates for radiative neutron capture in few Fe-group nuclei, and compare them with experimental data as well as with those obtained with NLDs from phenomenological and microscopic mean-field models. The results obtained for the NLDs from SDM are able to explain the experimental data quite well. These results are of particular importance since the configuration mixing through the residual interaction naturally accounts for the collective excitations. In the mean-field models, the collective effects are included through the vibrational and rotational enhancement factors and their NLDs are further normalized at low energies with neutron resonance data.

The suitability of high throughput automated patch clamp for physiological applications.

Although automated patch clamp (APC) devices have been around for many years and have become an integral part of many aspects of drug discovery, high throughput instruments with gigaohm seal data quality are relatively new. Experiments where a large number of compounds are screened against ion channels are ideally suited to high throughput APC, particularly when the amount of compound available is low. Here we evaluate different APC approaches using a variety of ion channels and screening settings. We have performed a screen of 1920 compounds on GluN1/GluN2A NMDA receptors for negative allosteric modulation using both the SyncroPatch 384 and FLIPR. Additionally, we tested the effect of 36 arthropod venoms on NaV 1.9 using a single 384-well plate on the SyncroPatch 384. As an example for mutant screening, a range of acid-sensing ion channel variants were tested and the success rate increased through fluorescence-activated cell sorting (FACS) prior to APC experiments. Gigaohm seal data quality makes the 384-format accessible to recording of primary and stem cell-derived cells on the SyncroPatch 384. We show recordings in voltage and current clamp modes of stem cell-derived cardiomyocytes. In addition, the option of intracellular solution exchange enabled investigations into the effects of intracellular Ca2+ and cAMP on TRPC5 and HCN2 currents, respectively. Together, these data highlight the broad applicability and versatility of APC platforms and also outlines some limitations of the approach. KEY POINTS: High throughput automated patch clamp (APC) can be used for a variety of applications involving ion channels. Lower false positive rates were achieved using automated patch clamp versus a fluorometric imaging plate reader (FLIPR) in a high throughput compound screen against NMDA receptors. Genetic variants and mutations can be screened on a single 384-well plate to reduce variability of experimental parameters. Intracellular solution can be perfused to investigate effects of ions and second messenger systems without the need for excised patches. Primary cells and stem cell-derived cells can be used on high throughput APC with reasonable success rates for cell capture, voltage clamp measurements and action potential recordings in current clamp mode.

Extracting capture from transfer reactions

Indirect reaction techniques are very important in astrophysics as they provide information that is complementary to direct measurements or that otherwise cannot be obtained directly. It is then critical to have a reliable reaction theory that can connect the reaction measurement with the astrophysical information desired. This is a brief report on the progress made in the theory for transfer reactions when used to determine neutron capture rates for r-process and proton capture for rp-process nuclei. We will discuss the different types of experiments and their connection to astrophysics. An overview of the current status of the theory will be provided, with emphasis on several recent theory developments, including transfer to continuum, the improvement of the optical potential and uncertainty quantification. Applications to a couple of neutron rich and proton rich cases will be discussed.

Inert and Reactive Oxide Particles for High-Temperature Thermal Energy Capture and Storage for Concentrating Solar Power

Oxide particles have potential as robust heat transfer and thermal energy storage (TES) media for concentrating solar power (CSP). Particles of low-cost, inert oxides such as alumina and/or silica offer an effective, noncorrosive means of storing sensible energy at temperatures above 1000 °C. However, for TES subsystems coupled to high-efficiency, supercritical-CO2 cycles with low temperature differences for heat addition, the limited specific TES (in kJ kg−1) of inert oxides requires large mass flow rates for capture and total mass for storage. Alternatively, reactive oxides may provide higher specific energy storage (approaching 2 or more times the inert oxides) through adding endothermic reduction. Chemical energy storage through reduction can benefit from low oxygen partial pressures (PO2) sweep-gas flows that add complexity, cost, and balance of plant loads to the TES subsystem. This paper compares reactive oxides, with a focus on Sr-doped CaMnO3–δ perovskites, to low-cost alumina-silica particles for energy capture and storage media in CSP applications. For solar energy capture, an indirect particle receiver based on a narrow-channel, counterflow fluidized bed provides a framework for comparing the inert and reactive particles as a heat transfer media. Low-PO2 sweep gas flows for promoting reduction impact the techno-economic viability of TES subsystems based on reactive perovskites relative to those using inert oxide particles. This paper provides insights as to when reactive perovskites may be advantageous for TES subsystems in next-generation CSP plants.

Structure and Decay at Rapid Proton Capture Waiting Points

We investigate the region of the nuclear chart around $A \simeq 70$ from a three-body perspective, where we compute reaction rates for the radiative capture of two protons. One key quantity is here the photon dissociation cross section for the inverse process where two protons are liberated from the borromean nucleus by photon bombardment. We find a number of peaks at low photon energy in this cross section where each peak is located at the energy corresponding to population of a three-body resonance. Thus, for these energies the decay or capture processes proceed through these resonances. However, the next step in the dissociation process still has the option of following several paths, that is either sequential decay by emission of one proton at a time with an intermediate two-body resonance as stepping stone, or direct decay into the continuum of both protons simultaneously. The astrophysical reaction rate is obtained by folding of the cross section as function of energy with the occupation probability for a Maxwell-Boltzmann temperature distribution. The reaction rate is then a function of temperature, and of course depending on the underlying three-body bound state and resonance structures. We show that a very simple formula at low temperature reproduces the elaborate numerically computed reaction rate.

Collision rates for rare cell capture in periodic obstacle arrays strongly depend on density of cell suspension

Recently, computational modelling has been successfully used for determination of collision rates for rare cell capture in periodic obstacle arrays. The models were based on particle advection simulations where the cells were advected according to velocity field computed from two dimensional Navier–Stokes equations. This approach may be used under the assumption of very dilute cell suspensions where no mutual cell collisions occur. We use the object-in-fluid framework to demonstrate that even with low cell-to-fluid ratio, the optimal geometry of the obstacle array significantly changes. We show computational simulations for ratios of 3.5, 6.9 and 10.4% determining the optimal geometry of the periodic obstacle arrays. It was already previously demonstrated that cells in periodic obstacle arrays follow trajectories in two modes: the colliding mode and the zig–zag mode. The colliding mode maximizes the cell-obstacle collision frequency. Our simulations reveal that for dilute suspensions and for suspensions with cell-to-fluid ratio 3.5%, there is a range of column shifts for which the cells follow colliding trajectories. However we showed, that for 6.9 and 10.4%, the cells never follow colliding trajectories.

Measurement and calculation of U and Th reaction rates in uranium mock assemblies

The conceptual blanket based on a subcritical reactor for a fusion–fission hybrid energy reactor with magnetic confinement fusion is being studied. To validate nuclear data and code of neutronics calculation for the blanket design, measurement of reaction rates for U and Th is performed by integral experiments. Based on the fission blanket, the uranium mock assemblies are established, and include the depleted uranium shell, the depleted-uranium/polyethylene/graphite shell and the natural uranium cube. A depleted-uranium/polyethylene/graphite assembly of 131mm in inner radius and 365mm in outer radius consists of three layers of depleted uranium shells, two layers of polyethylene shells and a graphite shell, and these shells are arranged alternatively. A D–T fusion neutron source is centered of the spherical assemblies. The U reaction rates for capture, fission and ratio of capture to fission in the assemblies are measured by depleted uranium foils and an HPGe gamma spectrometer. The 232Th reaction rates for capture, fission and ratio of capture to fission are measured by ThO2 foils put into the depleted uranium shell. The measured results are compared to the calculated ones by using MCNP code with ENDF/B-VII.0 library data.

Integrated Black Liquor Gasification Polygeneration System with CO2 Capture in Pulp and Paper Mills to Produce Methanol and Electricity

Based on KAMa pulp and paper mill, a polygeneration system integrated with a black liquor gasifier is proposed. The effects of CO2 captured by oxygen-fuel combustion and Selexol absorption on the performance of the polygeneration system are studied in terms of both thermodynamic performance and cost assessment. Using the Aspen Plus simulator, the performance of the studied polygeneration systems are analyzed from the perspectives of the first and second laws of thermodynamics. Compared with the reference system, the first law efficiency of the polygeneration system increased from 15.7% to 29.3%, with an investment increment of 17.9%. The investment incremental rates for CO2 capture by oxyfuel combustion and Selexol absorption are 15.1% and 16.7%, respectively. Energy penalty due to CO2 capture and compression is 0.61 MJ electricity/kg CO2, avoided in the oxygen-fuel method at a cost of $29.6/tonne CO2. However, energy penalty can reach 1.03 MJ product (electricity and methanol) per kg CO2, avoided in the Selexol absorption CO2 capture process at a cost of $46.0/tonne CO2.

Cansolv CO2 capture: The value of integration

Abstract If CO2 emissions are to be reduced to control global warming, many large scale projects will need to be executed on a short term that capture and sequester the CO2. Most studies to date have focused on CO2 capture from power plant flue gas and concluded that the cost of CO2 scrubbing is in itself expensive and that more mature and efficient technologies are needed. CO2 emission control is also complicated by the need to provide SO2 and NOx emission control as well. Burner modifications can be used to control NOx, but other scrubbing technologies are needed to control SO2 emissions. For high sulfur coals, limestone scrubbing is generally applied, adding to the cost of power through purchases of limestone reagent and disposal of by-product gypsum. Cansolv has evolved amine based regenerable technologies that capture SO2 and CO2 and that release them in a water wet, nearly pure condition. SO2 can be converted to sulfuric acid and CO2 can be dried, compressed and sequestered without further treatment. Most importantly, energy used to capture SO2 can be recycled to help capture CO2, reducing the net energy demand of the CO2 process. The use of these two technologies together allows power companies to use higher sulfur, lower cost fuels and reduce energy consumption rates for CO2 capture. By-product sulfuric acid from the SO2 scrubbing system also provides a ready source of revenue to offset scrubbing costs. Cansolv has proven its SO2 scrubbing technologies in commercial applications since 2002. It has operated CO2 pilot plants at several different locations, logging over 6,000 hours of operation. The two technologies will come together in an integrated system, in a plant designed to generate 50 tons per day of CO2, which will start up in 2009. This paper presents important design and performance advantages of these systems.

A continuous time version and a generalization of a Markov-recapture model for trapping experiments

Wileyto et al. [E.P. Wileyto, W.J. Ewens, M.A. Mullen, Markov-recapture population estimates: a tool for improving interpretation of trapping experiments, Ecology 75 (1994) 1109] propose a four-state discrete time Markov process, which describes the structure of a marking–capture experiment as a method of population estimation. They propose this method primarily for estimation of closed insect populations. Their method provides a mark–recapture estimate from a single trap observation by allowing subjects to mark themselves. The estimate of the unknown population size is based on the assumption of a closed population and a simple Markov model in which the rates of marking, capture, and recapture are assumed to be equal. Using the one step transition probability matrix of their model, we illustrate how to go from an embedded discrete time Markov process to a continuous time Markov process assuming exponentially distributed holding times. We also compute the transition probabilities after time t for the continuous time case and compare the limiting behavior of the continuous and discrete time processes. Finally, we generalize their model by relaxing the assumption of equal per capita rates for marking, capture, and recapture. Other questions about how their results change when using a continuous time Markov process are examined.

Weak interactions in hot nucleon matter

The reaction rates for electron capture, neutrino absorption, and neutrino scattering in hot asymmetric nuclear matter are calculated with two-body effective interactions and one-body effective weak operators obtained from realistic models of nuclear forces by use of correlated basis theory. The infinite system is modeled in a box with periodic boundary conditions, and the one-quasiparticle quasi-hole response functions are calculated with a large microcanonical sample and the Tamm-Dancoff approximation. Results for matter at a temperature of 10 MeV, proton fraction 0.4, and densities $\ensuremath{\rho}=(\frac{1}{2},1,\frac{3}{2}){\ensuremath{\rho}}_{0}$, where ${\ensuremath{\rho}}_{0}$ is the equilibrium density of symmetric nuclear matter, are presented to illustrate the method. In general, the strength of the response is shifted to higher-energy transfers when compared with that of a noninteracting Fermi gas. The shift in the response and the weakness of effective operators as compared with the bare operators significantly reduce the cross sections for electron capture and neutrino scattering by factors of $~2.5$--$3.5$. In contrast, the symmetry energy enhances the neutrino absorption reaction rate relative to the Fermi gas. However, this reaction rate is still quite small because of Pauli blocking.

The 8Li( [formula omitted]) 9Li reaction and astrophysical 8B( [formula omitted]) 9C reaction rate

Angular distribution of the Li 8 ( d , p ) Li g.s. 9 reaction at E cm = 7.8 MeV was measured in inverse kinematics. The square of asymptotic normalization coefficient (ANC) for the virtual decay Li 9 → Li 8 + n was derived to be 1.33 ± 0.33 fm −1 through distorted wave Born approximation (DWBA) analysis, for the first time. According to charge symmetry, (ANC) 2 for C 9 → B 8 + p was then extracted to be 1.14 ± 0.29 fm −1 . We have deduced the astrophysical S-factors and reaction rates for direct capture in B 8 ( p , γ ) C 9 at energies of astrophysical relevance using the ANC for C 9 → B 8 + p extracted from the mirror system.

Cost‐optimal contaminant plume management with a combination of pump‐and‐treat and physical barrier systems

AbstractThe economic potential of combining hydraulic barriers and pump‐and‐treat systems to manage contaminant plumes is investigated by means of a comparative cost analysis. The analysis is based on a preceding study on the hydraulic performance of barrier‐supported and conventional pump‐and‐treat systems, which revealed the efficiency of accurately positioned barriers in reducing pumping rates for contaminant plume capture. In the present paper, we examine whether the application of physical barriers like slurry walls or sheet piles also leads to economic benefits, i.e., whether the reduction of the operational costs outweighs the capital costs associated with the construction of the barriers. An economic model is presented that quantifies remediation costs by the use of cost functions relating costs to site‐specific and system‐specific parameters. The model is applied to a hypothetical remediation scenario. The results clearly demonstrate that physical barriers may yield significant savings in the total costs, particularly if unit costs for on‐site treatment are high. Furthermore, as barriers tend to reduce the uncertainty about the pumping rate required to capture a plume, they smooth the trade‐off curves between total remediation costs and system reliability.

Many-body theory of carrier capture and relaxation in semiconductor quantum-dot lasers

In quantum-dot laser devices containing a quasi-two-dimensional wetting layer, a pump process initially populates the wetting-layer states. The scattering of carriers from these spatially-extended quasi-two-dimensional states into the quantum-dot states as well as the relaxation of carriers between the quantum-dot levels are studied theoretically. Based on the wave functions for the coupled quantum-dot/wetting-layer system interaction matrix elements are calculated for carrier-carrier Coulomb interaction and carrier-phonon interaction. Scattering rates for various capture and relaxation processes are evaluated under quasiequilibrium conditions. For elevated carrier densities in the wetting layer, Coulomb scattering provides processes with capture (relaxation) times typically faster than $10\phantom{\rule{0.3em}{0ex}}\mathrm{ps}\phantom{\rule{0.3em}{0ex}}(1\phantom{\rule{0.3em}{0ex}}\mathrm{ps})$. When energy conservation allows for interaction with LO phonons, comparable rates are obtained.

Dynamics of DNA Loop Capture by the SfiI Restriction Endonuclease on Supercoiled and Relaxed DNA

The SfiI endonuclease is a prototype for DNA looping. It binds two copies of its recognition sequence and, if Mg 2+ is present, cuts both concertedly. Looping was examined here on supercoiled and relaxed forms of a 5.5 kb plasmid with three SfiI sites: sites 1 and 2 were separated by 0.4 kb, and sites 2 and 3 by 2.0 kb. SfiI converted this plasmid directly to the products cut at all three sites, though DNA species cleaved at one or two sites were formed transiently during a burst phase. The burst revealed three sets of doubly cut products, corresponding to the three possible pairings of sites. The equilibrium distribution between the different loops was evaluated from the burst phases of reactions initiated by adding MgCl 2 to SfiI bound to the plasmid. The short loop was favored over the longer loops, particularly on supercoiled DNA. The relative rates for loop capture were assessed after adding SfiI to solutions containing the plasmid and MgCl 2. On both supercoiled and relaxed DNA, the rate of loop capture across 0.4 kb was only marginally faster than over 2.0 kb or 2.4 kb. The relative strengths and rates of looping were compared to computer simulations of conformational fluctuations in DNA. The simulations concurred broadly with the experimental data, though they predicted that increasing site separations should cause a shallower decline in the equilibrium constants than was observed but a slightly steeper decline in the rates for loop capture. Possible reasons for these discrepancies are discussed.

Electron capture rates on nuclei and implications for stellar core collapse.

Supernova simulations to date have assumed that during core collapse electron captures occur dominantly on free protons, while captures on heavy nuclei are Pauli blocked and are ignored. We have calculated rates for electron capture on nuclei with mass numbers A=65-112 for the temperatures and densities appropriate for core collapse. We find that these rates are large enough so that, in contrast to previous assumptions, electron capture on nuclei dominates over capture on free protons. This leads to significant changes in core collapse simulations.

Presupernova Evolution with Improved Rates for Weak Interactions

Recent shell-model calculations of weak-interaction rates for nuclei in the mass range A = 45-65 have resulted in substantial revisions to the hitherto standard set of Fuller, Fowler, & Newman (FFN). In particular, key electron-capture rates, such as that for 60Co, are much smaller. We consider here the effects of these revised rates on the presupernova (post-oxygen burning) evolution of massive stars in the mass range 11-40 M☉. Moreover, we include, for the first time in models by our group, the effects of modern rates for beta decay in addition to electron capture and positron emission. Stars of 15, 25, and 40 M☉ are examined in detail using both the full FFN rate set and the revised rates. An additional finely spaced (in mass) grid of 34 models is also calculated in order to give the systematics of iron core and silicon core masses. Values for the central electron mole number at the time of iron core collapse in the new models are typically larger, by ΔYe = 0.005-0.015, than those of Woosley & Weaver, with a tendency for the more massive models to display larger differences. About half of this change is a consequence of including beta decay; the other half, the result of the smaller rates for electron capture. Unlike what might be expected solely on basis of the larger Ye values, the new iron core masses are systematically smaller owing to a decrease in the entropy in the outer iron core. The changes in iron core mass range from zero to 0.1 M☉ (larger changes for high-mass stars). It would be erroneous however to estimate the facility of exploding these new models based solely upon their iron core mass since the entire core structure is altered and the density change is not so different as the adjustments in composition might suggest. We also observe, as predicted by Aufderheide et al., a tendency toward beta equilibrium just prior to the collapse of the core, and the subsequent loss of that equilibrium as core collapse proceeds. This tendency is more pronounced in the 15 M☉ model than in the heavier stars. We discuss the key weak reaction rates, both beta decay and electron capture, responsible for the evolution of Ye and make suggestions for future measurements.

Plasmon dispersion effects for surface plasmon mediated proton neutralization at Mg surfaces

Transition rates for surface plasmon-assisted electron capture by H+ ions interacting with Mg surfaces have been calculated. We show that the plasmon dispersion and the representation of the initial metal state significantly change the transition rates with respect to previous calculations. In particular, the ion perturbation on the initial state greatly increases the transition rates at large ion–surface distances which is consistent with the results obtained by other authors for the Auger process.