Temporal Degradation Research Articles

Development of a quantitative PCR-based method for studying temporal DNA degradation in waterlogged bone.

While several studies have examined temporal DNA degradation in bones collected from terrestrial environments, studies on temporal DNA degradation in bones collected from aquatic environments are limited and mostly based on case studies. The objective of this study was to assess the impact of long-term submersion, aquatic environment, bone type and DNA extraction method on DNA quality and quantity. Bone samples (scapulae and ribs), collected every ~1000 ADD from a freshwater lake and river, underwent DNA extraction via ChargeSwitch® gDNA Plant Kit and organic phenol-chloroform methods, and DNA quantitation using both TaqMan and SYBR Green-based quantitative PCR (qPCR) methods. Results suggest that in both bone types, quality of recovered DNA (i.e., degradation index) declined significantly with increase in submersion time. Among two bone types, quality of recovered DNA from scapulae declined faster than rib samples. There was no significant difference in recovered DNA quantity between bone types, DNA extraction methods, or locations but various interactions between these variables showed significant difference. Overall, it can be concluded that DNA can be extracted from waterlogged bone in sufficient quantity to generate an STR profile up to 4000 ADD.

X-Ray Computed Tomography Visualization of Electrode Morphology Changes during Start-up/Shut-Down Cycling in Polymer Electrolyte Fuel Cells

Optimization of polymer electrolyte fuel cells can be achieved with detailed characterization of the operational behavior of the catalyst layer (CL). Moreover, understanding its operational degradation due to the changes to its multi-scale, composite structure is important for durability improvements and retaining high fuel cell performance over time. Start-up/shut-down (SU/SD) cycles are known to induce temporarily high, oxidizing potentials at the cathode electrode due to a propagating hydrogen-air front along the anode active area. These high potentials cause carbon corrosion and catalyst layer degradation [1], which can be observed during the lifetime of a test cell using advanced imaging techniques. Scanning electron microscopy (SEM) has typically been used to characterize the CL structure since it provides high contrast and high-resolution imaging [2]. However, SEM requires considerable sample handling, sample is destroyed during preparation, is limited to 2D visualization, and can suffer from edge effects, which makes segmentation and interpretation of CL lifetime degradation studies difficult.In contrast, the use of X-ray computed tomography (XCT) allows 3D and 4D non-intrusive imaging. This virtual dataset allows visualization of internal fuel cell components, such as the CL, over the test lifetime. To date, XCT studies on CL degradation have investigated changes instigated by voltage cycling accelerated stress testing; as well as in-operando imaging to obtain water distribution [3,4]. The objective of the present work is to assess temporal and local morphological electrode degradation effects caused by SU/SD cycling via 4D identical-location micro-XCT imaging with a custom, small scale fuel cell fixture. The results are compared against the equivalent case for voltage cycling in order to elucidate any differences in the specific degradation phenomena. In addition, impacts of gas flow distribution and anode/cathode channel alignment on local degradation is being investigated.Physical changes in the cathode-CL were periodically measured from beginning of life (BOL) to end of life (EOL), as shown in Figure 1, and correlated to the corrosion of the carbon support structure and platinum dissolution. The resultant data indicates a gradual degradation of the cathode-CL. Furthermore, the subsequent morphological changes were in good agreement with the losses in fuel cell performance and the deterioration of the electrochemical surface area. A similar degradation trend was observed in the voltage-cycling degradation study reported previously by our team [3]. However, a variance in the degradation of landing versus channel regions between these two studies exists. Where in this work more degradation was observed under the channel region, whereas, more degradation in the channel was observed in the voltage-cycling study. This contrast can be resolved when one considers that the cell voltage in the voltage-cycling study was applied uniformly under constant gas flow, while the degradation from the SU/SD cycling is influenced by the movement of the reacting gases along the anode active area.At BOL, the studied cathode-CL featured local variations in thickness with mud-cracks randomly distributed across the active area. Upon SU/SD cycling, the most corrosion of the carbon support structure and platinum dissolution was observed at thin cathode-CL regions along pre-existing crack formations. In addition, the gas flow distribution impacts with reduced channel reactant flow and reduced anode/cathode landing alignment were investigated. It was found that an overall increased cathode-CL degradation by SU/SD cycling occurred in the flow channel with reduced reactant flow, while misalignment of the anode/cathode landing did not influence the CCL degradation, compared to the regular aligned cells. Overall, the in situ electrochemical diagnostics and micro-XCT results showed direct relationships between carbon corrosion, platinum dissolution and electrode capacitance loss from SU/SD cycling. These morphological observations are thus believed to be responsible for much of the performance degradation during SU/SD cycling. Acknowledgements This research was supported by Natural Sciences and Engineering Research Council of Canada, Canada Foundation for Innovation, British Columbia Knowledge Development Fund, Automotive Partnership Canada, Ballard Power Systems, Canada Research Chairs, Western Economic Diversification Canada, and Simon Fraser University

A Learning-Based Framework for Circuit Path Level NBTI Degradation Prediction

Negative bias temperature instability (NBTI) has become one of the major causes for temporal reliability degradation of nanoscale circuits. Due to its complex dependence on operating conditions, it is a tremendous challenge to the existing timing analysis flow. In order to get the accurate aged delay of the circuit, previous research mainly focused on the gate level or lower. This paper proposes a low-runtime and high-accuracy machining learning framework on the circuit path level firstly, which can be formulated as a multi-input–multioutput problem and solved using a linear regression model. A large number of worst-case path candidates from ISCAS’85, ISCAS’89, and ITC’99 benchmarks were used for training and inference in the experiment. The results show that our proposed approach achieves significant runtime speed-up with minimal loss of accuracy.

Electrothermal transport induced material reconfiguration and performance degradation of CVD-grown monolayer MoS2 transistors

Device and material reliability of 2-dimensional materials, especially CVD-grown MoS2, has remained un-addressed since 2011 when the first TMDC transistor was reported. For its potential application in next generation electronics, it is imperative to update our understanding of mechanisms through which MoS2 transistors’ performance degrades under long-term electrical stress. We report, for CVD-grown monolayer MoS2, results on temporal degradation of material and device performance under electrical stress. Both low and high field regimes of operation are explored at different temperatures, gate bias and stress cycles. During low field operation, current is found to saturate after hundreds of seconds of operation with the current decay time constant being a function of temperature and stress cycle. High field operation, especially at low temperature, leads to impact ionization assisted material and device degradation. It is found that high field operation at low temperature results in amorphization of the channel and is verified by device and kelvin probe force microscopy (KPFM) analyses. In general, a prolonged room temperature operation of CVD-grown MoS2 transistors lead to degraded gate control, higher OFF state current and negative shift in threshold voltage (VT). This is further verified, through micro-Raman and photoluminescence spectroscopy, which suggest that a steady state DC electrical stress leads to the formation of localized low resistance regions in the channel and a subsequent loss of transistor characteristics. Our findings unveil unique mechanism by which CVD MoS2 undergoes material degradation under electrical stress and subsequent breakdown of transistor behavior. Such an understanding of material and device reliability helps in determining the safe operating regime from device as well as circuit perspective.

Sensitivity of snow models to the accuracy of meteorological forcings in mountain environments

Abstract. Snow models are usually evaluated at sites providing high-quality meteorological data, so that the uncertainty in the meteorological input data can be neglected when assessing model performances. However, high-quality input data are rarely available in mountain areas and, in practical applications, the meteorological forcing used to drive snow models is typically derived from spatial interpolation of the available in situ data or from reanalyses, whose accuracy can be considerably lower. In order to fully characterize the performances of a snow model, the model sensitivity to errors in the input data should be quantified. In this study we test the ability of six snow models to reproduce snow water equivalent, snow density and snow depth when they are forced by meteorological input data with gradually lower accuracy. The SNOWPACK, GEOTOP, HTESSEL, UTOPIA, SMASH and S3M snow models are forced, first, with high-quality measurements performed at the experimental site of Torgnon, located at 2160 m a.s.l. in the Italian Alps (control run). Then, the models are forced by data at gradually lower temporal and/or spatial resolution, obtained by (i) sampling the original Torgnon 30 min time series at 3, 6, and 12 h, (ii) spatially interpolating neighbouring in situ station measurements and (iii) extracting information from GLDAS, ERA5 and ERA-Interim reanalyses at the grid point closest to the Torgnon site. Since the selected models are characterized by different degrees of complexity, from highly sophisticated multi-layer snow models to simple, empirical, single-layer snow schemes, we also discuss the results of these experiments in relation to the model complexity. The results show that, when forced by accurate 30 min resolution weather station data, the single-layer, intermediate-complexity snow models HTESSEL and UTOPIA provide similar skills to the more sophisticated multi-layer model SNOWPACK, and these three models show better agreement with observations and more robust performances over different seasons compared to the lower-complexity models SMASH and S3M. All models forced by 3-hourly data provide similar skills to the control run, while the use of 6- and 12-hourly temporal resolution forcings may lead to a reduction in model performances if the incoming shortwave radiation is not properly represented. The SMASH model generally shows low sensitivity to the temporal degradation of the input data. Spatially interpolated data from neighbouring stations and reanalyses are found to be adequate forcings, provided that temperature and precipitation variables are not affected by large biases over the considered period. However, a simple bias-adjustment technique applied to ERA-Interim temperatures allowed all models to achieve similar performances to the control run. Regardless of their complexity, all models show weaknesses in the representation of the snow density.

Degradation prediction of encapsulant-glass adhesion in the photovoltaic module under outdoor and accelerated exposures

Maintaining good encapsulant-glass adhesion is important to ensure the long-term durability of photovoltaic (PV) modules. An exposure dose based model was used in this study to predict the temporal and spatial degradation of encapsulant-glass adhesion inside the PV module under hygrothermal exposure. The exposure dose is a single parameter that combines the exposure temperature, humidity and time using an exponential relation that is governed by a degradation activation energy. Peel tests were used to measure degradation in ethylene–vinyl acetate (EVA)-glass adhesion in PV module laminates that are aged under various constant temperature and humidity environments. An optimization technique applied to fit an exponential relation between the degraded adhesion strength and exposure dose gave the degradation activation energy as 59.4 kJ/mol.The model was used to study EVA-glass adhesion degradation for glass-glass and glass-backsheet based PV modules exposed to 5 year outdoor (Delhi, India), damp heat, humidity freeze and thermal cycling environments. The spatial and temporal distribution of relative humidity at the EVA-glass interface inside the PV module was predicted considering Fickian diffusion in the backsheet and EVA. The predicted humidity is used to estimate the exposure dose, which is further used to predict adhesion degradation. The highest degradation in all exposures occurs at the edge for the glass-glass module, whereas near the gap between cells for the glass-backsheet module. The integrity of the interface near the exposed boundary can be assessed by the damp heat exposure, but the integrity away from the boundary cannot be assessed by the accelerated exposures.

Spatio-temporal immunolocalization of extensin protein and hemicellulose polysaccharides during olive fruit abscission.

Immunocytochemical and molecular analyses reveal that the disassembly of the cell wall may be mediated by changes in the level and subcellular location of extensin protein and hemicelluloses during olive-fruit abscission. Although cell-wall modification is believed to underlie the changes in organ abscission, information concerning the changes in cell-wall proteins and hemicellulose polysaccharides is still limited. The aim of this work was to analyze the spatio-temporal patterns of the distribution of different extensin proteins and hemicelluloses in the abscission zone (AZ) during natural ripe-fruit abscission in olive (Olea europaea L.). In this study, we employed immunogold labeling in the ripe-fruit AZ during olive AZ cell separation, using an expanded set of monoclonal antibodies that recognize different types of hemicelluloses (LM11, LM15, and LM21), callose (anti-(1,3)-β-D-glucan) and extensin (JIM19) epitopes, and transmission electron microscopy imaging. Our data demonstrate that AZ cell separation was accompanied by a loss of the JIM19 extensin epitopes and a reduction in the detection of the LM15 xyloglucan epitopes in AZ cell walls, whereas AZ cells were found to be enriched with respect to the xylan and callose levels of the cell wall during olive ripe-fruit abscission. By contrast, AZ cell-wall polysaccharide remodeling did not involve mannans. Moreover, in ripe-fruit AZ, quantitative RT-PCR analysis revealed that OeEXT1, OeEXT2, OeXTH9, and OeXTH13 genes were downregulated during abscission, whereas the expression of OeXTH1, OeXTH5, and OeXTH14 genes increased during abscission. Taken together, the results indicate that AZ cell-wall dynamics during olive ripe-fruit abscission involves extensin protein and hemicellulose modifications, as well as related expressed genes. This is the first study available demonstrating temporal degradation of extensin protein and hemicelluloses in the AZ at the subcellular level.

Dark Lock-in Thermography Identifies Solder Bond Failure as the Root Cause of Series Resistance Increase in Fielded Solar Modules

Correlating the electrical performance of photovoltaic modules to the spatially resolved photoluminescence, electroluminescence, and dark lock-in thermography (DLIT) images is an important long-term goal for developing solar cell technology. These images offer highly sophisticated and detailed information about the spatial distribution and (if imaged at successive time intervals) temporal degradation of local series and shunt resistances. There have been extensive studies to correlate these imaging techniques to local characteristics at the cell level. However, it has been difficult to extract and quantify module-level information from the techniques. In this study, we interpret module current-voltage (I-V) measurements along with corresponding DLIT images within a module-scale simulation framework, demonstrating that series resistance degradation of the module I-V characteristics, in this case, can be attributed to solder bond failures. Our simulations highlight how current crowding associated with a failed solder joint (or a section of the solder pad) translates to the characteristic point-like (asymmetric doublet) heating pattern in neighboring solder joints (or the neighboring regions of the solder pad). The correlation between series resistance and solder joint degradation could inform expedited diagnosis of field degradation of solar modules.

On Optimal Condition of Plant–Microbial Remediation of Petroleum Hydrocarbon Polluted Soil

ABSTRACT At present, plant–microbial remediation of soil petroleum pollution has been widely used, but the study of using models to predict remediation effect and find optimal remediation conditions is still very lacking. In this paper, on the basis of the numerical model of previous research, the effects of Suaeda salsa–microbial remediation technique on soil petroleum hydrocarbon pollution were simulated under different soil initial pollutant concentration, soil moisture content and tillage depth. The spatial and temporal degradation of petroleum hydrocarbons and the corresponding degradation rate were studied. The results showed that under different remediation conditions, the degradation rate of microbes, plant and plant–microbial of petroleum hydrocarbon is in the range of 12.70%–24.70%, 4.14%–54.58% and 29.32%–67.28% in 180 days, respectively. It was found that the degradation rate of petroleum hydrocarbons was significantly affected by soil initial pollutant concentration, soil moisture content and tillage depth. The optimal application conditions of S. salsa–microbial remediation technology were found for the remediation of soil petroleum hydrocarbon pollution.

Measurement and Modeling of Ambient-Air-Induced Degradation in Organic Thin-Film Transistor

The lifetime of organic thin-film transistors (OTFTs) is known to be significantly shorter than that of silicon MOSFETs. It is therefore important to be able to predict their degradation early in the design phase. In this paper, OTFT current characteristic variation is studied in measurements of fabricated devices. In addition, we propose a drain-current simulation model that incorporates temporal parameter variation. The proposed model expresses parameter degradations as changes in threshold voltage and carrier mobility. With the extracted parameters, our proposed model successfully reproduces the temporal performance degradation observed in fabricated devices. We compared our proposed model with existing parameter variation models by fitting with measurement results. Root mean square errors (RMSEs) were calculated for each model. Our proposed model achieved an RMSE of 2.26% whereas that of the existing model was 9.80%. Oscillation frequency degradation in an organic ring oscillator (RO) circuit was also simulated to compare with the measurement results. The simulation results adequately captured the degradation trend observed in the measured results.

Temporal physicochemical changes and transformation of biochar in a rice paddy: Insights from a 9-year field experiment

Biochar application to soil has attracted extensive attention worldwide due to its carbon (C) sequestration and fertility-enhancing properties. However, the lack of biochar accumulation in highly disturbed agroecosystems challenges the perceived long-term stability of biochars in soil. This 9-year field experiment was conducted in rice paddy fields to understand the temporal degradation of biochars produced from two contrasting feedstocks (rice straw vs. bamboo) at a high temperature (600 °C). Obvious physical alterations, surface oxidation, and transformation of condensed aromatic C occurred in biochars in the disturbed paddy field with frequent redox cycles. Increase in O/C atomic ratio, levels of high-temperature-sensitive degradable components, H/C ratio, and linear alkyl-C content were observed, which were indicative of time-dependent molecular changes and degradative transformation of biochars. Biochar degradation was characterized by the loss of labile C at an early stage and the degradation of aromatic C at a later stage. Based on the massive loss of C content in biochars (10.3–11.8%) and considerable degradation of aromatic C (5.0–8.7%) in 9 years, we argue that current biphasic C dynamic models probably overestimate the stability of biochars in agroecosystems such as rice paddy fields. Long-term field experiments (>5 years) are required to assess biochar's potential for C sequestration. This study provides long-term field data regarding the temporal changes in biochar physicochemical properties, which may facilitate the development of a robust assessment scheme on the long-term persistence of biochars in agroecosystems.

Forecast uncertainty‐based performance degradation diagnosis of solar PV systems

In this study, the authors are interested in estimating how much a PV system underperforms than expected by exploiting forecast uncertainty. For this, they first study a forecast accuracy-related forecast uncertainty metric using the ensemble method based on the dropout technique, which is widely used in deep learning forecasting models. Given the forecast accuracy-related uncertainty metric, the rationale of the authors' approach is that forecast accuracy is likely to decrease compared to the normal case of similar uncertainty metric values if any performance degradation happens. It is because similar uncertainty metric values are likely to show similar forecast accuracy. Therefore, they generate a standard table by simulating possible performance degradation cases and conduct the performance degradation diagnosis by looking up the standard table based on the uncertainty metric. From the experiments, in the case of persistent degradation, they show that their approach estimates the performance degradation with the estimation error of around 1% while an uncertainty-unaware approach shows the estimation error of up to 5%. In the case of temporal degradation, their approach shows the estimation error of around 3%, while the uncertainty-unaware approach does not show meaningful result.

Spatial and temporal distribution, degradation, and metabolism of three neonicotinoid insecticides on different parts, especially pests' target feeding parts of apple tree.

Neonicotinoid insecticides (NIs) have been recently banned in some countries because of increased pest resistance and deleterious risks to non-target organisms. Recent studies considered all parts of crops as a whole part in plant protection. However, there are few reports focused on the distribution and metabolic trends of NIs on target feeding sites of different pests in apple orchards. The spatial and temporal distribution, absorption, degradation, and metabolism of three NIs, imidacloprid, acetamiprid, and thiamethoxam, on different parts of apple trees were studied under foliar spray and root irrigation treatments. In the spray treatment, the initial average concentration ratios (TCRs) were 31.6% for lower shoots, 23.3% for upper leaves, 23.2% for upper shoots, 21.0% for lower leaves, and 0.5% and 0.4% for upper and lower fruits, respectively. The average half-lives of the three NIs were 2.9 days for shoots, 7.4 days for leaves, and 10.8 days for fruits. The degradation rate of shoots was 2.5 times that of leaves, and 3.6 times that of fruits. Imidacloprid olefin and N-methyl acetamiprid were two of the main metabolites. In the root treatment, both roots and soils had high TCRs during the whole sampling period. Only imidacloprid was transmitted to above-ground parts of the plants, with TCRs of 0.38-50.94%. This study found significant differences in spatial and temporal distribution, degradation, metabolism, and trends of NIs on different pest target sites of apple trees. The data obtained may help promote scientific control of target pests and evaluation of safety for non-target species in orchards. © 2020 Society of Chemical Industry.

Climate change impact assessment on a carbonate aquifer under semi-arid climate: example of the Cenomanian-Turonian aquifer within Meskala-Ouazzi region (Essaouira Basin, Morocco)

This study aims to assess the climate change impact on water resources of the Essaouira Basin (Morocco). The rainfall index shows a significant interannual variability which is organized in an alternation of the excess period (1940–1956), two deficit periods (1956–1986 and 1998–2015) separated by a normal period (1986–1998). The statistical approach reveals the presence of a break in 1956 with a rainfall deficit of 14.45% and that the temperatures show a general upward trend with a warming of 2.3 °C for mean and minimum temperature and of 2.8 °C for maximum and this for the period 1987–2014. Flow rates show a slight upward trend that could be explained by a short and intense rainfall that characterizes our semi-arid environment. Concerning the piezometric approach, it shows a general descent in piezometric surface for the period of observation (reached 12 m in some wells). The downward evolution of piezometric surface due to the decrease of precipitation has resulted in the spatial and temporal degradation of the groundwater quality. A decrease in nitrate levels has been noted; this could be explained by the downward trend in precipitation by favoring the retention of nitrates in the superficial parts of the soil and by limiting their infiltration to the aquifer.

Intensifying vehicular proton exchange membrane fuel cells for safer and durable, design and operation

The explosion in a proton exchange membrane fuel cell (PEMFC) powered forklift in Louisiana, USA in May 2018 and the resulting fatality highlights the need for the improved safety of this technology. Apart from the safety concerns, PEMFC durability has been an important issue towards its further commercialization. Both the safety and durability concerns associated with this technology can be attributed to the temporal degradation of its components. In this study, we have developed a mathematical model that relates the microscale PEMFC degradation to the probability of a macroscale explosion in a Fuel Cell Electric Vehicle (FCEV). Using the model and the inherent safety principle of intensification, it was observed that increasing the operating temperature of the PEMFC system can significantly improve both its safety and durability while intensifying membrane design parameters i.e. membrane thickness and membrane conductivity do not provide any significant improvements. A key inference from this study is that the durability (expressed in voltage loss) and safety (expressed in explosion probability) of a PEMFC system are not perfectly correlated.

Land Resources Usage Constraints and Their Temporal Change in Bale Eco-Region, Southeast Ethiopia

Usage of land resources to meet the demands of human being has an impact on the land resources. The purpose of the study was to investigate the land resource usage constraints and their temporal change in Bale Eco Region, Southeast Ethiopia. Both qualitative and quantitative cross sectional study designs were employed. Data was collected using HH survey, in depth interview, focus group discussion and field observation. Data analysis, descriptive and inferential statistics were implemented by using SPSS software version 20. Chi-Square test, frequencies and percentage were used to compare differences among variables with respect to the three agro-ecologies and statistical significance was decreased at P ≤ 0.05. Qualitative data was first transcribed to texts in local language then retranslated to English for writing the report. Data analysis was done after categorizing the transcripts. The information obtained from quantitative and qualitative sources were triangulated to ensure the relevance of the results of the study. Based on the finding of the study trends of land holding probability (p=0.00) and land productivities= (0.00), were significantly difference. Physical, technological and extension services were among the constraints that are identified to influence land and other natural resources utilization in the three agro-ecologies of BER. Lack of technology and lack of science based knowledge were among of the critical constraints that reported by majority of the respondents that limit them from utilizing their land resources. Almost in all agro-ecologies, low and erratic rainfall, climate variability, drought, inaccessibility, lack of water sources was the common constraints of. It is recommended that concerned bodies should minimize constraints of responsible land resource utilizations and temporal natural resources degradation in BER.

Spatial and Temporal Corrosion Degradation Modelling with A Lévy Process based on ILI (In-Line) Inspections

Corrosion defects affect the structural integrity of onshore pipelines making them prone to a Loss of Containment (LOC). LOCs may trigger significant consequences over the surrounding people and environment. Therefore, In-Line (ILI) inspections are commonly implemented to measure indicators of the metal loss along the pipe due to corrosion to support future intervention decisions. However, ILI tools are subject to detection uncertainties that hide the real number of defects because of the accuracy of the technique and the complexity of the spatially distributed corrosion degradation. This paper presents a framework in which a corroding pipeline is assessed spatially and temporally based on ILI measurements. This framework includes new defects generated over time, which are clustered with those already detected, degraded, and assessed regarding the reliability. To this end, the number of new defects is estimated with a Homogeneous Poisson Process. The defects are clustered with the DNV RP-F101 criterion, and their degradation is predicted using Levy processes. Finally, reliability is assessed temporally and spatially using Monte Carlo simulations based on a dynamic segmentation and a failure region. Following a real case study, the approach results allow us to identify critical segments of the pipeline.

Picosecond contrast degradation by surface imperfections in chirped-pulse-amplification stretchers.

In this paper, we propose a study of the picosecond temporal contrast degradation of ultrashort laser pulses by surface defects in pulse stretchers. In a chirped-pulse-amplification stretcher or compressor, dust and damages on the surface of an optical element lead to a spectral amplitude modulation. Furthermore, surface figure errors of optical elements happening where the pulse is spatially dispersed yield a modulation of the spectral phase. The influence of both amplitude and phase noise effects is numerically investigated using a hybrid ray-tracing method that enables treating separately the influence of noise sources, whether noise occurs in the near field or the far field. We show that the main issue in terms of picosecond contrast degradation is a combined effect of surface pattern distortion in the far field and phase-amplitude coupling caused by spatial frequency filters. Temporal domains can be defined, where the temporal contrast is dominated by different noise effects. The algorithm used in this paper is compared to the cross-correlation trace of a pulse. The conclusions emerging from the presented analysis are universally applicable to known grating stretcher geometries.

Water quality response to river flow regime at three major rivers in Alberta

AbstractBoth anthropogenic activities and natural factors affect river water in quantity and quality, while anthropogenic activities have been often blamed to cause water quality temporal degradation. In addition, riverine water quality displays intra-annual/seasonal variations, which are often more prominent than inter-annual variations. The intra-annual variations in water quality, which are attracting the attention of managers and policy-makers, beg the question of how to better manage riverine water quality at a finer time resolution. The natural factors, in particular, the hydro-meteorological variables, could be the primary drivers of the intra-annual variations of riverine water quality. Therefore, this paper examined the association between riverine water quality and one hydro-meteorological variable (flow) with the focus on their relationship at the intra-annual timescale on three selected rivers in Alberta, Canada. The results demonstrated that flow drives intra-annual variation of riverine water quality in general. Moreover, some water quality parameters responded to flow distinctively at three flow regimes (low, medium, and high flows). Water quality parameters were categorized into eight groups according to their responses to flow at the flow regimes. These implied the challenges in water quality management while providing insight into how to formulate more effective water management strategies.

Cyclin A2 degradation during the spindle assembly checkpoint requires multiple binding modes to the APC/C

The anaphase-promoting complex/cyclosome (APC/C) orchestrates cell cycle progression by controlling the temporal degradation of specific cell cycle regulators. Although cyclin A2 and cyclin B1 are both targeted for degradation by the APC/C, during the spindle assembly checkpoint (SAC), the mitotic checkpoint complex (MCC) represses APC/C’s activity towards cyclin B1, but not cyclin A2. Through structural, biochemical and in vivo analysis, we identify a non-canonical D box (D2) that is critical for cyclin A2 ubiquitination in vitro and degradation in vivo. During the SAC, cyclin A2 is ubiquitinated by the repressed APC/C-MCC, mediated by the cooperative engagement of its KEN and D2 boxes, ABBA motif, and the cofactor Cks. Once the SAC is satisfied, cyclin A2 binds APC/C-Cdc20 through two mutually exclusive binding modes, resulting in differential ubiquitination efficiency. Our findings reveal that a single substrate can engage an E3 ligase through multiple binding modes, affecting its degradation timing and efficiency.