Relative Decay Rates Research Articles

Operational Regime for Maximizing the Durability in Fuel Cell Stacks

Fuel cells have a dichotomy between high performance and long durability, which is further exacerbated by the requirement for high production scale manufacturing. To bridge the aforementioned disconnects, the fuel cell system’s operational controls must be optimized to protect the fuel cell stack from being exposed to conditions that would detrimentally impact the fuel cell stack durability. For instance, Toyota has shown that the fuel cell stack is protected from platinum electrocatalyst oxidation by limiting the upper voltage during idle to 0.85 V (Toyota).[1] The operational controls landscape that must be evaluated as a function of durability are inlet coolant temperature, coolant delta temperature across the stack, coolant temperature cycling and rate, reactant stoichiometry, inlet relative humidity (RH), RH cycling and rate, back pressure, material dependent water back diffusion, cathode catalyst loading, and the load profile and rate.To better understand the impact of the fuel cell operational regime on durability, we evaluate the relative decay rates for multiple short stacks under limited stress tests: (ST1) mid power current density hold, (ST2) elevated coolant temperature/low RH load cycling (GM),[2] and (ST3) concurrently cycling coolant temperature/RH/load. The voltage decay rates are tracked over time to estimate stack lifetime. The stack voltages decrease over the time on test under all three stress test profiles, attributed to initial aging of the cathode catalyst. Polarization curves are used to evaluate decay rates intermittently during the applied stress tests, the decay rates are dependent on current densities in the polarization curve.We find that the voltage decay rate is elevated within the kinetic region of the polarization curve and lower in the mas transport region. The most aggressive stress test is ST3, due to the combined coolant temperature/RH/load cycling. Acknowledgments This material is based upon work supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Hydrogen and Fuel Cell Technologies Office’s FY2020 H2@Scale New Markets FOA, Award Number DE-EE0009248. W. Gibbons (DOE Program Manager), R. Mukunda (LBL), D. Cullen (ORNL), and KC Neyerlin (NREL).Full Legal Disclaimer: “This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.”

Model-independent predictions for decays of double-heavy hadrons into pairs of heavy hadrons

Double-heavy hadrons can decay into pairs of heavy hadrons through transitions from confining Born-Oppenheimer potentials to heavy-hadron-pair potentials with the same Born-Oppenheimer quantum numbers. The states of the double-heavy hadron are constrained by a Born-Oppenheimer exclusion principle from the identical heavy quarks. The states of a pair of identical heavy hadrons are constrained by exclusion principles from identical particles. The transitions are also constrained by conservation of angular momentum and parity. From these constraints, we derive model-independent selection rules for decays of double-heavy hadrons into pairs of heavy hadrons. The coupling potentials are expressed as sums of products of Born-Oppenheimer transition amplitudes and angular-momentum coefficients. If there is a single dominant Born-Oppenheimer transition amplitude, it factors out of the coupling potentials between double-heavy hadrons in the same Born-Oppenheimer multiplet and pairs of heavy hadrons in specific heavy-quark-spin-symmetry multiplets and out of the corresponding partial decay rates. As examples, we discuss the Born-Oppenheimer potentials and multiplets for conventional double-heavy baryons and for double-heavy tetraquark mesons. We also discuss the relative partial decay rates for conventional double-heavy baryons into pairs of heavy hadrons. Published by the American Physical Society 2024

Model-independent predictions for decays of hidden-heavy hadrons into pairs of heavy hadrons

Hidden-heavy hadrons can decay into pairs of heavy hadrons through transitions from confining Born-Oppenheimer potentials to hadron-pair potentials with the same Born-Oppenheimer quantum numbers. The transitions are also constrained by conservation of angular momentum and parity. From these constraints, we derive model-independent selection rules for decays of hidden-heavy hadrons into pairs of heavy hadrons. The coupling potentials are expressed as sums of products of Born-Oppenheimer transition amplitudes and angular-momentum coefficients. If there is a single dominant Born-Oppenheimer transition amplitude, it factors out of the coupling potentials between hidden-heavy hadrons in the same Born-Oppenheimer multiplet and pairs of heavy hadrons in specific heavy-quark-spin-symmetry doublets. If furthermore the kinetic energies of the heavy hadrons are much larger than their spin splittings, we obtain analytic expressions for the relative partial decay rates in terms of Wigner 6j and 9j symbols. We consider in detail the decays of quarkonia and quarkonium hybrids into the lightest heavy-meson pairs. For quarkonia, our model-independent selection rules and relative partial decay rates agree with previous results from quark-pair-creation models in simple cases and give stronger results in other cases. For quarkonium hybrids, we find disagreement even in simple cases. Published by the American Physical Society 2024

Temporal dynamics of ocular torsion and vertical vergence during visual, vestibular, and visuovestibular rotations.

Ocular torsion and vertical divergence reflect the brain's sensorimotor integration of motion through the vestibulo-ocular reflex (VOR) and the optokinetic reflex (OKR) to roll rotations. Torsion and vergence however express different response patterns depending on several motion variables, but research on their temporal dynamics remains limited. This study investigated the onset times of ocular torsion (OT) and vertical vergence (VV) during visual, vestibular, and visuovestibular motion, as well as their relative decay rates following prolonged optokinetic stimulations. Temporal characteristics were retrieved from three separate investigations where the level of visual clutter and acceleration were controlled. Video eye-tracking was used to retrieve the eye-movement parameters from a total of 41 healthy participants across all trials. Ocular torsion consistently initiated earlier than vertical vergence, particularly evident under intensified visual information density, and higher clutter levels were associated with more balanced decay rates. Additionally, stimulation modality and accelerations affected the onsets of both eye movements, with visuovestibular motion triggering earlier responses compared to vestibular motion, and increased accelerations leading to earlier onsets for both movements. The present study showed that joint visuovestibular responses produced more rapid onsets, indicating a synergetic sensorimotor process. It also showed that visual content acted as a fusional force during the decay period, and imposed greater influence over the torsional onset compared to vergence. Acceleration, by contrast, did not affect the temporal relationship between the two eye movements. Altogether, these findings provide insights into the sensorimotor integration of the vestibulo-ocular and optokinetic reflex arcs.

Ground-penetrating radar (GPR) survey and spatial analysis of the George and Addie Giddens Cemetery, Opelika, Alabama

ABSTRACT Interest in locating and preserving the cemeteries of enslaved African Americans has increased the need for new methodologies coupled with efficient, noninvasive geophysical techniques, such as ground-penetrating radar (GPR). The southeast United States, where many of such sites are located, provides many challenges to using GPR due to its humid climate and abundant vegetation, which deteriorates burial remains, disguises burial shafts, and forms physical obstacles to GPR surveys. These challenges make it difficult for GPR alone to locate caskets or burial shafts. To address these issues, this study uses GPR combined with an innovative spatial and observational methodology to locate burials in a humid climate and determine their burial conditions. These mixed methods led to the location of 129 potential graves. Knowing the spatial distribution of burial features provides a context for analyzing the relative burial ages and decay rates within the cemetery site.

The Protective Effect of Virus Capsids on RNA and DNA Virus Genomes in Wastewater.

Virus concentrations measured in municipal wastewater help inform both the water treatment necessary to protect human health and wastewater-based epidemiology. Wastewater measurements are typically PCR-based, and interpreting gene copy concentrations requires an understanding of the form and stability of the nucleic acids. Here, we study the persistence of model virus genomes in wastewater, the protective effects provided by the virus capsids, and the relative decay rates of the genome and infectious viruses. In benchtop batch experiments in wastewater influent at 25 °C, extraviral (+)ssRNA and dsDNA amplicons degraded by 90% within 15-19 min and 1.6-1.9 h, respectively. When encapsidated, the T90 for MS2 (+)ssRNA increased by 424× and the T90 for T4 dsDNA increased by 52×. The (+)ssRNA decay rates were similar for a range of amplicon sizes. For our model phages MS2 and T4, the nucleic acid signal in untreated wastewater disappeared shortly after the viruses lost infectivity. Combined, these results suggest that most viral genome copies measured in wastewater are encapsidated, that measured concentrations are independent of assay amplicon sizes, and that the virus genome decay rates of nonenveloped (i.e., naked) viruses are similar to inactivation rates. These findings are valuable for the interpretation of wastewater virus measurements.

Cleanroom air quality: combined effects of ventilation rate and filtration schemes in a laboratory cleanroom

ABSTRACT Ventilation performance and air quality in cleanrooms are affected by several interconnected parameters, and a change in one component can impact the entire system. Furthermore, occupant interactions with the physical environment can influence particle dispersion, disrupt current airflow by introducing new wakes and ultimately decrease ventilation efficacy. As a result, we set up an experimental study to measure the effects of traffic, flowrate and filtration on ventilation performance while a source of contamination was inside the room. Experiments included three types of occupant movements (i.e., NM, WO, WT) and were performed under two different airflow conditions. Three different metrics, namely relative ventilation efficiency (), decay rate (R) and exposure (γ), were introduced to statistically compare changes in ventilation performance in response to different experimental setups. Decay rates obtained for 0.3-micron particles decreased by up to 50% in the presence of occupants. Lowering cleanroom flowrate due to additional filtering can reduced ventilation effectiveness by almost 50%. Care should be exercised when changing filter efficiency because it can reduce the rate of air supply. These findings are especially intriguing in the context of cleanroom retrofit, as reducing air exchange rates was an unintended consequence of improving filter efficiency.

In-Situ LID and Regeneration of Al-BSF Solar Cells from Different Positions of a B-Doped Cz-Si Ingot

In this paper, five groups of industrial aluminium back-surface-field (Al-BSF) solar cells were made from silicon wafers from different locations of a B-doped Czochralski silicon ingot. Then, we performed the first LID (45 °C, 1 sun, 12 h), regeneration (100 °C, 1 sun, 24 h), and second LID (45 °C, 1 sun, 12 h) treatments on the cells, and measured the in-situ changes of their I-V characteristic parameters by using an I-V tester during the experiment. The cells were also characterized by Suns-Voc measurement, full-area light beam induced current scanning, and external quantum efficiency measurement at the four breakpoints of treatments (before and after the first LID, after regeneration and the second LID). It was found that the LID and regeneration of the Al-BSF solar cells can be explained by the LID and regeneration reaction of B-O defects and the LID caused by dissociation of Fe-B pairs. After regeneration, the relative decay rate of efficiency decreased from 2.75–3.8% during the first LID to 0.42–1.23% during the second LID, indicating that regeneration treatment (100 °C, 1 sun, 24 h) can improve the anti-LID ability of Al-BSF solar cells.

Composition and decomposition of rhizoma peanut (Arachis glabrata Benth.) belowground biomass

Roots and rhizomes can play an important role in nutrient cycling, however, few studies have investigated how their decomposition pattern is affected by defoliation and time of the year. This 2-year study evaluated root-rhizome composition and decomposition of a warm-season rhizomatous perennial legume [rhizoma peanut (RP; Arachis glabrata Benth.)] under continuous stocking or when defoliated by clipping every 56 days. A 168-days incubation trial was performed to determine disappearance of biomass and N and changes in acid detergent fiber (ADF), acid detergent insoluble N (ADIN), and C:N ratio. Additionally, three 56-days incubations were performed each year to evaluate the disappearance coefficient (B0) and relative decay rate (k). There were no treatment differences in any response for the 168-days incubation. After 168 days, 21 and 60% of initial biomass and initial N remained, respectively. Relative decay rate for OM and N were 0.0088 and 0.0035 g g−1 day−1, respectively. Carbon-to-N ratio decreased from 29 at day 0 to 17 at day 168. Concentration of ADIN increased from 6.9 to 19.3 g kg−1, plateauing at day 79. The B0 and k for remaining OM and N were greater in late than early season and could be explained by greater N concentration and lesser C:N ratio. Rapid decomposition, difference in C:N ratio from day 0 to 168, and the increase in ADIN concentration during incubation indicate large amounts of root-rhizome-soluble C at initiation of incubation. These data indicate that RP root-rhizome turnover is more responsive to season than defoliation frequency.

Hydrodynamic attractor in the nonconformal Bjorken flow

Nonconformal attractor behavior is studied by solving nonconformal second-order viscous hydrodynamics with respect to boost-invariant plasmas. Numerical solutions of the relative decay rate of the enthalpy density, the inverse shear and bulk Reynolds numbers all exhibit universal patterns towards an ideal fluid description at late stages, demonstrating the existence of a nonconformal hydrodynamic attractor. However, as a generic feature, the nonconformal hydrodynamic attractor emerges only at late times, which differs drastically from the behavior observed in conformal systems. The absence of the early-time attractor in nonconformal fluids is a consequence of the early-time unstable mode, which arises from a positive-valued eigenmode associated with the free-streaming dynamics. The early-time attractor can be restored in a mixture of the shear and bulk viscous corrections, in which early-time unstable modes cancel approximately. However, to support practical simulations of hydrodynamics in high-energy heavy-ion collisions, for which the early-time nonconformal attractor is approachable in all independent modes, the quadratic coupling between the bulk pressure and the expansion rate should be enhanced by at least a factor of two through the transport coefficient ${\ensuremath{\delta}}_{\mathrm{\ensuremath{\Pi}}\mathrm{\ensuremath{\Pi}}}$.

Alteration of Relative Rates of Biodegradation and Regeneration of Cervical Spine Cartilage through the Restoration of Arterial Blood Flow Access to Rhomboid Fossa: A Hypothesis.

We found the logical way to prove the existence of the mechanism that maintains the rates of biodegradation and regeneration of cervical spine cartilage. We demonstrate, that after we restore access to arterial blood flow through cervical vertebral arteries to rhomboid fossa it causes the prevalence of regeneration over biodegradation. This is in the frames of consideration of the human body as a dissipative structure. Then the recovery of the body should be considered as a reduction of the relative rates of decay below the regeneration ones. Then the recovery of cervical spine cartilage through redirecting of inner dissipative flow depends on the information about oxygen availability that is provided from oxygen detectors in the rhomboid fossa to the cerebellum. Our proposed approach explains already collected data, which satisfies all the scientific requirements. This allows us to draw conclusions that permit reconsidering the way of dealing with multiple chronic diseases.

26 Kasım 2019, ML=6.3, Kuzey Durrës, Arnavutluk Depreminin Artçı Şok Dizisinin Davranışları Üzerine Bir Değerlendirme

A comprehensive assessment of aftershocks occurrence for the November 26th, 2019 earthquake, ML=6.3, 16 km north of Durrës, Albania was achieved. b-value was estimated as 0.88 ±0.07. b-value is close to 1.0 and relatively small b-value may be resulted from the plenty of larger aftershocks with ML4.0. p-value was calculated as 1.23±0.08 with Mmin=3.1 and Tstart=0.0034 days. This high p-value may be a result of the relative fast decay rate of aftershock activity. Dc-value was calculated as 1.74±0.09 and it means that aftershocks are homogeneously distributed at larger scales. The smallest b-values and the largest p-values were observed in the north, northwest and northeast parts of the mainshock. The smaller b-values correlate with the larger stress variations, whereas the larger p-values are related to the maximum slip after mainshock. Consequently, region-time-magnitude analyses of the aftershocks occurrence may supply important clues for the fast evaluations of real time aftershock hazard.

Modelling the Material Resistance of Wood—Part 3: Relative Resistance in above- and in-Ground Situations—Results of a Global Survey

Durability-based designs with timber require reliable information about the wood properties and how they affect its performance under variable exposure conditions. This study aimed at utilizing a material resistance model (Part 2 of this publication) based on a dose–response approach for predicting the relative decay rates in above-ground situations. Laboratory and field test data were, for the first time, surveyed globally and used to determine material-specific resistance dose values, which were correlated to decay rates. In addition, laboratory indicators were used to adapt the material resistance model to in-ground exposure. The relationship between decay rates in- and above-ground, the predictive power of laboratory indicators to predict such decay rates, and a method for implementing both in a service life prediction tool, were established based on 195 hardwoods, 29 softwoods, 19 modified timbers, and 41 preservative-treated timbers.

Evaluation of Selected Accelerated Above-Ground Durability Testing Methods for Wood after Ten Years Exposure

Traditional benchmark wood durability testing methods such as stake tests take many years to give conclusive results, and in-ground tests do not always indicate the efficacy of preservatives in above-ground situations. To find test methods that would shorten the time required for wood evaluation for above-ground end uses, a series of different types of accelerated durability tests were set up. Five types of test: ground proximity, two types of decking, flat panels and double layer, were reassessed after ten years to determine whether the decay rankings given to the various types of preservative had changed over the extended exposure period. Exposure conditions varied between tests, with ground proximity being close to ground, and the double layer test carried out in very wet conditions, while raised decking and flat panel tests were relatively dry. In all of these tests, the preservative retention was 25% of the normal H3 retention. The results indicated that the ground proximity tests gave the fastest and most reliable results. Flat panels contained the next highest decay rates, followed by ground-level decking, double layer and raised decking. The evaluation and comparison of these five test methods after ten years’ field exposure confirmed the trend and relative decay rate that was observed at four-year exposure. The use of a regression model for prediction showed a statistically significant overall relationship between decay scores in 2011 and 2017 (coefficient = 0.14 ± 0.07, d.f. = 345.7, t = 2.038, p = 0.042). When resistance to decay was compared between preservatives, copper-chrome arsenate (CCA)-treated pine and naturally durable spotted gum samples were in better conditions than pine treated with any of the other preservatives.

Fetch effect on the developmental process of aeolian sand transport in a wind tunnel

As the sand mass flux increases from zero at the leading edge of a saltating surface to the equilibrium mass flux at the critical fetch length, the wind flow is modified and then the relative contribution of aerodynamic and bombardment entrainment is changed. In the end the velocity, trajectory and mass flux profile will vary simultaneously. But how the transportation of different sand size groups varies with fetch distance is still unclear. Wind tunnel experiments were conducted to investigate the fetch effect on mass flux and its distribution with height of the total sand and each size group in transportation. The mass flux was measured at six fetch length locations (0.5, 1.2, 1.9, 2.6, 3.4 and 4.1 m) and at three free-stream wind velocities (8.8, 12.2 and 14.5 m/s). The results reveal that the total mass flux and the mass flux of each size group with height can be expressed by q=aexp(−bh), where q is the sand mass flux at height h, and a and b are regression coefficients. The coefficient b represents the relative decay rate. Both the relative decay rates of total mass flux and each size group are independent of fetch length after a quick decay over a short fetch. This is much shorter than that of mass flux. The equilibrium of the relative decay rate cannot be regarded as an equilibrium mass flux profile for aeolian sand transport. The mass fluxes of 176.0, 209.3 and 148.0 μm size groups increase more quickly than that of other size groups, which indicates strong size-selection of grains exists along the fetch length. The maximal size group in mass flux (176.0 μm) is smaller than the maximal size group of the bed grains (209.3 μm). The relative contribution of each size group to the total mass flux is not monotonically decreasing with grain size due to the lift-off of some small grains being reduced due to the protection by large grains. The results indicate that there are complex interactions among different size groups in the developmental process of aeolian sand transport and more attention should be focused on the fetch effect because it has different influences on the total mass flux, the mass flux profile and its relative decay rate.

Optical Control of a Single Nuclear Spin in the Solid State.

We demonstrate a novel method for coherent optical manipulation of individual nuclear spins in the solid state, mediated by the electronic states of a proximal quantum emitter. Specifically, using the nitrogen-vacancy (NV) color center in diamond, we demonstrate control of a proximal ^{14}N nuclear spin via an all-optical Raman technique. We evaluate the extent to which the intrinsic physical properties of the NV center limit the performance of coherent control, and we find that it is ultimately constrained by the relative rates of transverse hyperfine coupling and radiative decay in the NV center's excited state. Possible extensions and applications to other color centers are discussed.

Collagen deamidation in archaeological bone as an assessment for relative decay rates

Attempts to extend methods for dating archaeological bones beyond that of radiocarbon dating, such as amino acid racemization, have met with limited success owing to the dependence on multiple environmental factors and controls. Despite facing similar challenges, deamidation of glutamine has recently been investigated as a potential indicator of ‘thermal age' in archaeological bones, as well as a measure of their preservation quality. In this study, we undertook a series of simulated diagenetic experiments to understand the various factors affecting deamidation. Further, we analysed bones from different Middle Palaeolithic layers from Grotte Mandrin (France), with the results suggesting potential use of deamidation for relative dating, but only in case of extremely well‐preserved layers. The results also suggested the possible use of attenuated total reflectance‐Fourier transform infrared (ATR‐FTIR) spectroscopy as a screening test for soluble collagen before proteomic analysis.

Lifetime-filtered laser-induced exciplex fluorescence for crosstalk-free liquid-vapor imaging.

Laser-induced exciplex fluorescence is a well-established technique for liquid-vapor imaging in evaporating sprays that offers phase-dependent spectrally separated emission. However, the accuracy of this approach is limited by substantial crosstalk from the liquid to vapor phase signals. This Letter shows the use of a combination of spectral and temporal filtering to reduce this crosstalk by three orders of magnitude and eliminate the need for temperature-dependent crosstalk corrections in the N,N-diethylmethylamine/fluorobenzene system. The relative decay rates of the liquid and vapor signals are quantified and show crosstalk-free imaging for monodisperse evaporating droplets over a wide range of exciplex tracer concentrations.

Dynamical control of population and entanglement for open Λ-type atoms by engineering the environment**Project supported by the National Natural Science Foundation of China (Grant No. 11275064), the Specialized Research Fund for the Doctoral Program of Higher Education, China (Grant No. 20124306110003), and the Construct Program of the National Key Discipline, China.

The exactly analytical solution for the dynamics of the dissipative Λ-type atom in the zero-temperature Lorentzian environment is presented. On this basis, we study the evolution of the population and entanglement. We find that the stable populations on the two lower levels of the Λ-type atom can be effectively adjusted by the combination of the relative decay rate and the environmental spectral frequency. However, for the initial Werner-like state, the stable entanglement between the two Λ-type atoms has very little tunability. Furthermore, the stable entanglement for the bilateral environment case is larger than that of the unilateral environmental case. A nonintuitive relation between the stable entanglement and stable population is found.

A statistical space-time-magnitude analysis on the aftershocks occurrence of the July 21th, 2017 MW = 6.5 Bodrum-Kos, Turkey, earthquake

In this study, a detailed space-time-magnitude assessment on the aftershock sequence of July 21th, 2017, MW 6.5, Bodrum-Kos earthquake (Turkey) is carried out by focusing on the analyses of aftershock parameters: b-value, p-value, Dc-value and Mamax. b-value is estimated as 0.90 ± 0.05 with a completeness magnitude Mc = 1.6 and this relatively small b-value may be resulted from the abundance of aftershocks with magnitude ML ≥ 4.0. However, it is well represented by the Gutenberg-Richter law with a typically b ≈ 1.0. p-value is estimated as 1.04 ± 0.02 with a c-value = 0.224 ± 0.039 and is well characterized nearly close to the global p ≈ 1.0. This relatively high p-value may be a result of the relative fast decay rate of the aftershock activity. Dc-value is calculated as 1.74 ± 0.09 and it means that aftershocks are homogeneously distributed. Temporal distribution of b-value shows that small b-values may be due to a stepwise increase in effective stress before the occurrence of larger aftershocks. Regional changes range from 0.5 to 1.2 in b-value, from 0.4 to 1.3 in p-value and from 3.0 to 5.2 in Mamax. The smallest b-values are found in and around mainshock, including Karaada, Bodrum, Akyarlar and Turgutreis, and these regions have high stress as well as coseismic deformation. The largest p-values are found in and around the mainshock epicenter including Karaada, and it is interpreted that this situation may be caused by coseismic deformation. Mamax values larger than 4.4 are observed in and around mainshock epicenter, including Bodrum and Akyarlar, and there is a clear correlation between spatial variations of b-values and Mamax. These results show that stress changes and coseismic deformation seem highly effective on b and p-value variations. Therefore, a special interest needs to be given to these anomaly regions since aftershock hazard is highly associated with these parameters and may be developed considering their space-time-magnitude distribution.