Buffer Behavior Research Articles

DNA Strand Buffers.

A buffer reaction actively resists changes to the concentration of a chemical species. Typically, buffering reactions have only been able to regulate the concentration of hydronium (i.e., pH) and other ions. Here, we develop a new class of buffers that regulate the concentrations of short sequences of DNA (i.e., oligonucleotides). A buffer's behavior is determined by its set point concentration, capacity to resist disturbances, and response time after a disturbance. We provide simple mathematical formulas for selecting rate constants to tune each of these properties and show how to design DNA sequences and concentrations to implement the desired rate constants. We demonstrate several oligonucleotide buffers that maintain oligonucleotide set point concentrations between 10 and 80 nM in the presence of disturbances of 50 to 500 nM, with response times of less than 10 min to 1.5 h. Multiple buffers can regulate different sequences of DNA in parallel without crosstalk. Oligonucleotide buffers could stabilize and restore reactant concentrations in DNA circuits or in self-assembly processes, allowing such systems to operate reliably for extended durations. These buffers might also be coupled to other reactions to buffer molecules other than DNA. In general, an oligonucleotide buffer can be viewed as a chemical "battery" that maintains the total chemical potential of a buffered species in a closed system.

Linking bank regulatory capital buffer to business cycle fluctuations

PurposeThe purpose of this paper is to assist bank regulators in Africa who are currently considering the implementation of Basel III countercyclical capital buffer (CCB) requirement.Design/methodology/approachUsing a panel data set of 129 commercial banks operating in 14 African countries over the period 2004–2014, this paper estimates the system generalized method of moments regression to examine the impact of business cycle on banks’ regulatory capital buffers and attempts to identify the influence of bank revenue diversification, market power and cost of funding (CF) on bank regulatory capital buffers. It further carries out some robustness analyses using a panel data set of 257 commercial banks in 23 African countries over the period 2004–2014.FindingsThe results show that higher regulatory capital buffers are associated with higher market power, higher revenue diversification and higher CF. Additionally, the results show significant evidence of procyclical behavior of bank capital buffers (BUFs) in the sampled countries.Practical implicationsThe results of this study suggest that African banking systems are not exposed to contagion and systemic risks arising from countercyclical movements of BUFs to the real economy. Therefore, this study does not support the implementation of the Basel III CCB requirement in the sampled African countries.Originality/valueConsidering that the results of existing studies on the cyclical behavior of BUFs are inconclusive, there is value in studying the cyclical movements of bank regulatory capital buffers in a set of countries that has not been analyzed before. Toward this direction, this is the first empirical study focusing on the cyclical behavior of bank regulatory capital buffers in Africa. Besides examining the cyclical behavior of bank regulatory capital buffers, this paper further investigates the effects of bank revenue diversification, market power and CF on bank regulatory capital buffers.

Three dimensional thermo-hydraulic modelling for KBS-3H alternative

The KBS-3H disposal alternative is composed by horizontally placed supercontainers comprising the canisters with the spent nuclear fuel surrounded in both drift axis and radial directions by compacted bentonite blocks (buffer) enclosed in a perforated shell. The different internal gaps between the supercontainer components and the one between the buffer blocks and the host rock have direct effects on the buffer behaviour. This paper presents a Thermo-Hydraulic (TH) Three-Dimensional (3D) numerical model developed to analyse a particular geometry assuming three different gap state conditions and providing results of the temperature, liquid pressure, and evolution of the degree of saturation.The material parameters, constitutive models, and assumptions made were carefully selected with regards to laboratory measurements reported in directly-related bibliography. The modelling settles the importance of understanding the groundwater flow through the rock mass and from fractures in the rock in order to achieve reliable predictions regarding buffer saturation, since it is known that the saturation times could range from few years to one thousand years depending on the hydrogeological conditions in the rock. The obtained results lead to full saturation times of 50 to 100 years. In addition to the rock hydraulic conductivity and fracture transmissivity, the saturation process was directly affected by the material properties of the buffer and gap presence between the buffer blocks and the host rock. Finally, in connection with thermal evolution, the thermal conductivity of repository components and the behaviour of air gaps in the buffer were key variables.

Low-pH cement mortar-bentonite perturbations in a small-scale pilot laboratory experiment

ABSTRACTA novel method to perform small-scale laboratory experiments that reproduce concrete–bentonite and concrete–groundwater interactions has been developed. Such interfaces will prevail in engineered barrier systems used for isolation of nuclear waste. With the goal of optimizing the experimental method, this work has analysed the geochemical interaction of distilled water, low-pH cement mortar and FEBEX-bentonite for 75 days. Limited but evident reactivity between the materials was observed, mainly decalcification in cement mortar, carbonation at the interface with bentonite and Mg enrichment in bentonite. These results are consistent with the state-of-the-art literature and were used to validate this small-scale pilot laboratory experiment to establish the basis for further studies comparing the behaviour of different buffer and cement materials.

Relationship of Adverse Family Experiences to Resilience and School Engagement Among Vermont Youth.

Adverse childhood experiences (ACEs) are associated with a range of health outcomes and risk behaviors. In 2011-2012, the National Survey of Children's Health (NSCH) included questions about adverse family experiences (AFEs). AFE survey questions are similar to ACE questions, except there are no questions about emotional/physical/sexual trauma, and questions are asked of parents rather than children. Although the relationship between ACEs and work/school absenteeism has been studied, the relationships between AFEs of school-aged children, school performance, and buffering behaviors have not been explored in depth. We examined AFEs and measures of resilience and school engagement among 1330 Vermont children (6-17years) included in the NSCH, using descriptive, bivariate, and multivariable analyses. The most prevalent AFEs were divorce/separation of parents; family income hardship; substance use problems; and mental illness, suicidality, or severe depression. Adjusting for sex, age, special health care needs, poverty level, and maternal physical/mental-emotional health status, children who had three or more AFEs had lower odds of completing all required homework [adjusted odds ratio (AOR) 3.3, 95% confidence interval (CI) 1.7-6.3] and higher odds of failing to exhibit resilience (AOR 2.1, 95% CI 1.2-3.8), compared to children having no AFEs. Children with three or more AFEs had difficulty engaging in school and completing homework, though poor outcomes were buffered when children showed resilience. Parents, school-based mental health professionals, and teachers could help identify children who may be less resilient and have difficulties completing homework assignments. Preventive approaches to children's emotional problems (e.g., promoting family health, using family-based approaches to treat emotional/behavioral problems) could be applied in schools and communities to foster resilience and improve school engagement of children.

Natural evolution of alkaline characteristics in bauxite residue

Bauxite residue, a highly alkaline solid waste, is extremely hazardous to the surrounding environment and current research approaches have largely focused on the removal and separation of alkaline substances. Natural weathering processes may be a step forward in terms of their regeneration. In this study, natural evolution of basic alkalinity, electrical conductivity, exchangeable ions and acid neutralizing capacity of residue in the disposal areas was discussed. Minerals, exchangeable cations and alkaline anions were analyzed by X-ray powder diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and titration, respectively. Acid neutralizing capacity was carried out by batch neutralization experiments. Basic alkalinity, electrical conductivity, cation exchange capacity and exchangeable sodium percentage decreased with increasing disposal duration. Sodium was the predominant exchangeable cation in fresh residue but its concentration significantly decreased with increasing time from initial disposal. The acid neutralizing capacity of bauxite residue was investigated by incubation with hydrochloric acid. Acid neutralizing capacity curves changed with disposal duration and each revealed a characteristic buffering behavior that could be controlled by its alkaline components.

Playout buffer and DRX aware scheduling scheme for video streaming over LTE system

In this study, a playout buffer and discontinuous reception (DRX) aware scheduling scheme (PBDAS) is proposed to improve the video streaming transmission over the long term evolution systems by considering the characteristics of both the DRX mechanism and the HTTP streaming. First, to reconcile the three mechanisms, the metric called remaining playout time (RPT) is proposed, which can be used to estimate the playout status of the clients. With the RPT, the scheduler can accurately differentiate the urgency among the clients. Then, a two level resource allocation schemes is proposed. In the scheduler, the upper level is responsible for determining the scheduling set, while the lower level will be in charge of allocating the resource to the user equipments (UEs) in the set. With the scheduling set, the priority of the UEs can be accurately distinguished. For different scheduling set, different forms of metrics are designed, with which both the efficiency of the radio resource and the playout continuity can be significantly improved. In addition, a playout buffer level estimation method is given to improve the feasibility of the implementation of PBDAS. By analysing the behaviour of the playout buffer, the buffer level can be estimated with the cumulative serving rate and the HTTP streaming information, which can be obtained in the eNodeB and from the quality of experience reports, respectively. The simulation results show that PBDAS can shorten the total interruption duration of the existing schemes by about 50% as well as keep the power consumption at a low level.

New Rapid Evaluation for Long-Term Behavior in Deep Geological Repository by Geotechnical Centrifuge—Part 2: Numerical Simulation of Model Tests in Isothermal Condition

In high-level radioactive waste disposal repositories, there are long-term complex thermal, hydraulic, and mechanical (T–H–M) phenomena that involve the generation of heat from the waste, the infiltration of ground water, and swelling of the bentonite buffer. The ability to model such coupled phenomena is of particular importance to the repository design and assessments of its safety. We have developed a T–H–M-coupled analysis program that evaluates the long-term behavior around the repository (called “near-field”). We have also conducted centrifugal model tests that model the long-term T–H–M-coupled behavior in the near-field. In this study, we conduct H–M-coupled numerical simulations of the centrifugal near-field model tests. We compare numerical results with each other and with results obtained from the centrifugal model tests. From the comparison, we deduce that: (1) in the numerical simulation, water infiltration in the rock mass was in agreement with the experimental observation. (2) The constant-stress boundary condition in the centrifugal model tests may cause a larger expansion of the rock mass than in the in situ condition, but the mechanical boundary condition did not affect the buffer behavior in the deposition hole. (3) The numerical simulation broadly reproduced the measured bentonite pressure and the overpack displacement, but did not reproduce the decreasing trend of the bentonite pressure after 100 equivalent years. This indicates the effect of the time-dependent characteristics of the surrounding rock mass. Further investigations are needed to determine the effect of initial heterogeneity in the deposition hole and the time-dependent behavior of the surrounding rock mass.

Buffer Behaviour in Massive MIMO Systems

Buffer Behaviour in Massive MIMO Systems

Anchoring Relationships at Work: High‐Quality Mentors and Other Supportive Work Relationships as Buffers to Ambient Racial Discrimination

Applying a unifying theoretical framework of high‐quality work relationships, we conducted a set of 3 complementary studies that examined whether high‐quality mentoring relationships can buffer employees from the negative effects of ambient discrimination at work. Integrating relational mentoring with relational systems theory, we first examined whether the presence of a high‐quality mentoring relationship buffers employees in a sample of 3,813 workers. In support of the “mentors‐as‐buffers” hypothesis, we found that employees who witnessed or were aware of racial discrimination at work had lower organizational commitment than those not exposed, but employees with high‐quality mentoring relationships experienced less loss of commitment than those lacking mentors. We then examined the specific buffering behaviors used by mentors in high‐quality relationships and whether these behaviors were effective for other work relationships and outcomes. Applying Kahn's typology, we developed and validated a measure of high‐quality relational holding behaviors in a sample of 262 workers. Using this measure in a third sample of 557 workers, we found that mentors buffer by providing holding behaviors, but we did not find this buffering effect when supervisors or coworkers provided holding behaviors. This potent mentor buffering effect held across a range of outcomes, including organizational commitment, physical symptoms of stress, insomnia, and stress‐related absenteeism. These studies suggest that mentoring may be a singularly effective relationship that offers a safe harbor for employees faced with ambient discrimination at work.

Transient boundary conditions in the frame of THM-processes at nuclear waste repositories

In nuclear waste repositories, initially unsaturated buffer is subjected to constant heat emitted by waste canister in conjunction with peripheral hydration through water from host rock. The transient hydration process can be potraied as transformation of initial heterogeneity towards homogeneity as final stage. In this context, this paper addresses the key issue of hydro mechanical behaviour of compacted buffer in context of clay microstructure and its evolution under repository relevant loading paths and material heterogeneity. This paper also introduces a unique column experiment facility available at Ruhr Universitat Bochum, Germany. The facility has been designed as a forerunner of field scale testing program to simulate the transient hydration process of compacted buffer as per German reference disposal concept. The device is unique in terms of having proficiency to capture the transient material response under various possible repository relevant loading paths with higher precision level by monitor the key parameters like temperature, total suction, water content and axial & radial swelling pressure at three different sections along the length of compacted soil sample. In general, a larger spectrum of loading paths/scenarios, which may arise in the nuclear repository, can be covered precisely with existing device.

Business Cycle, Banking Market Structure and Capital Buffer

Based on the panel data of 40 Chinese commercial banks from 2004 to 2014, this paper tests empirically the relationship among business cycle, banking market structure and capital buffer using the method of GMM. The results show that in China: capital buffers fluctuate over the business cycles countercyclicality, and market concentration shows a negative relationship with the capital buffers. The decrease of market concentration enforces the countercyclical behavior of capital buffers.

Investigation on chemical effects on GMZ bentonite used as buffer materials

GMZ bentonite has been selected as a buffer/backfill material for the design of Chinese HLW repository due to its suitable properties. Investigations have been conducted on this material to have a better understanding of its engineering behavior. In this paper, a review of the studies on the chemical effects in GMZ bentonite is presented. The adsorption of radionuclides Ni(II), Cr(III) and Eu(III) etc. on GMZ bentonite is investigated and the influences of external chemical agents are assessed. Some modifications on GMZ bentonite have been implemented to improve its adsorption properties. In the meantime, the influences of NaOH solutions with variations in concentration and pH values on hydraulic conductivity, mechanical behavior and mineralogy of GMZ bentonite are investigated with consideration of temperature. Effects of salt solutions are also assessed in different studies using solutions of Na+ and Ca2+ , which are the predominant cations in the groundwater of Beishan area. It is observed that both cations influence the buffering behavior of bentonite at a different degree. Further investigations should be done for better understanding the influences of coupling factors and time on the chemical behavior of material.

Visualization of Buffer Capacity with 3-D “Topo” Surfaces: Buffer Ridges, Equivalence Point Canyons and Dilution Ramps

BufCap TOPOS is free software that generates 3-D topographical surfaces (“topos”) for acid–base equilibrium studies. It portrays pH and buffer capacity behavior during titration and dilution procedures. Topo surfaces are created by plotting computed pH and buffer capacity values above a composition grid with volume of NaOH as the x axis and overall system dilution as the y axis. What emerge are surface features that correspond to pH and buffer behaviors in aqueous solutions. Topo surfaces are created for pH, log buffer capacity, and linear buffer capacity. Equivalence point breaks become pH cliffs and logarithmic buffer capacity canyons that grow shallower with dilution. Areas of high buffer capacity become rounded ridges. Dilution alone generates 45° ramps. Example systems include hydrochloric acid, HCl (a strong acid); acetic acid, CH3COOH (a weak monoprotic acid); oxalic acid, HOOCCOOH (a weak diprotic acid); and l-glutamic acid hydrochloride, C5H9NO4·HCl (a weak triprotic acid). The Supporting Information includes a copy of the interactive BufCap TOPOS program, macro-enabled spreadsheets that quickly generate surfaces for any mono-, di-, or triprotic acid. Only acid dissociation constants, Ka values, need be changed. Other materials include teaching slides for lectures, plus worksheets and laboratory activities for first-year college courses and third-year or graduate analytical chemistry courses.

Modeling the Moisture Buffering Behavior of a Coated Biobased Building Material by Including Hysteresis

To investigate the influence of plastering on the moisture buffering behavior of hemp concrete, experiments are performed on two samples, one uncoated and one coated with less hygroscopic lime-based plasters. Global mass variations were monitored and results indicate in this case that coating reduces the MBV of hemp concrete. In addition, local temperatures and relative humidities are also measured at several depths within the samples in the view of validating a heat and mass transfer model. Results show that including the hysteretic behavior of each layer (hemp concrete and plasters) leads to a better agreement between numerical and experimental results, but also plays a significant role in the prediction of stored energy.

Experimental measurements of U60 nanocluster stability in aqueous solution

In this study, the aqueous behavior of isolated U60 nanoclusters (K16Li25[UO2(O2)OH]60)−19 was studied under several pH conditions and nanocluster concentrations to determine if the nanoclusters exhibit solid phase buffering behavior or if they exhibit behavior more like aqueous complexes. U60 is a cage cluster consisting of 60 (UO2)(O2)2(OH)2 uranyl polyhedral which share OH and O2 groups with their neighboring uranyl polyhedral, resulting in negatively charged cage clusters whose charge is at least partially offset by K+ and Li+ in the aqueous phase. Batch experiments to monitor nanocluster stability were conducted for 16days at pH 7.5, 8.0 and 8.5 at nanocluster suspension concentrations of 1.4, 2.8 and 6.0g/L. The aqueous concentrations of U, Li, and K, determined after 10kDa molecular weight filtration, achieved steady-state with the nanoclusters within 24h. The steady-state aqueous U, Li, and K concentrations were independent of solution pH, however they increased with increasing nanocluster concentration, indicating that the nanoclusters do not buffer the aqueous activities as a bulk solid phase would, but exhibit behavior that is more characteristic of dissolved aqueous complexes. The ion activity product (I.A.P.) value was calculated using two approaches: (1) treating the nanoclusters as a solid phase with an activity of one, and (2) treating the nanoclusters as aqueous complexes with a non-unit activity equal to their concentration in solution. The I.A.P. values that were calculated with non-unit activity for the nanoclusters exhibited significantly less variation as a function of nanocluster concentration compared to the I.A.P. values calculated with a nanocluster activity of one. The results yield a calculated log dissociation constant for the U60 nanoclusters of 9.2+0.2/−0.3 (1σ). Our findings provide a better understanding of the thermodynamic stability and behavior of U60 nanoclusters in aqueous systems, and can be used to estimate the dissociation behavior of nanoclusters under a range of aqueous conditions.

The Behavior of Australian Banks’ Capital Buffers: Pro- or Counter-Cyclical?

This paper investigates the behavior of capital buffers of Australian banks to changes in the business cycle. More particularly, whether there is a behavioral difference between big and small banks, and whether the 2008-09 global financial crisis influenced bank behavior with respect to capital buffers. Applying the Generalized Method of Moments technique, we find the evidence to support pro-cyclical behavior of large banks, but counter-cyclical of small banks. Our results also show that banks with large size, large risky portfolio, and high lending growth rate tend to hold less capital than their peers. Finally, our results suggest that the latest financial crisis did induce banks to hold more capital.

Experimental demonstration of a microdisk resonator filter/buffer utilizing two-mode interference.

We have experimentally demonstrated a microdisk-resonator (MDR)-based filter for filtering and buffering applications utilizing two-mode interference. Optical filtering or buffering behavior can be generated by the coherent interference between two orthogonal whispering-gallery modes (WGMs) in a MDR symmetrically coupled to two bus waveguides. MDRs were fabricated using nanofabrication processes on a silicon-on-insulator platform. Multiple resonances of WGMs are excited in a MDR and unique filter characteristics have been observed for two spectrally nearby resonances. The measured results agree well with the theoretical simulation. Bandpass filtering is achieved with a 3 dB bandwidth of 0.66 nm and an in-band ripple of less than 1 dB when the two resonances are detuned, while the filter can function as an optical buffer with an insertion loss of 5.85 dB and a predicted time delay of 15 ps when the two resonances are approximately aligned. Furthermore, the influence of resonance spacing is analyzed on the performance of this filter.

Groundwater in hard rocks of Benin: Regional storage and buffer capacity in the face of change

Groundwater plays a major role in supplying domestic water to millions of people in Africa. In the future, the ability to increase reliable water supplies for domestic and possibly irrigation purposes will depend on groundwater development. Groundwater storage is a key property because it controls the buffering behavior of the aquifer as it is subjected to time-varying conditions such as increased pumping or land-use change. However, quantitative knowledge of groundwater storage in Africa is very limited. This lack of knowledge is a major concern in hard rocks, which cover about 40% of the surface area of Africa. This paper presents a unique quantitative assessment of groundwater storage in different types of hard rocks and a first estimate of the capacity of hard rock aquifers to buffer changes in climatic and anthropogenic conditions. Our study area in Benin (West Africa) is composed of various grades of metamorphic rocks. We used the latest developments in the application of the magnetic resonance geophysical method to confront the methodological difficulty of quantifying groundwater storage. We successfully conducted 38 magnetic-resonance measurements in eight (8) different geological units; each measurement was quantitatively interpreted in terms of groundwater storage. We determined the groundwater storage of our study area to be 440 mm ± 70 mm (equivalent water thickness). To assess the buffer capacity of aquifers, we compared groundwater storage to groundwater discharge. Groundwater discharge is the sum of natural discharge plus human abstraction. We estimated natural discharge (i.e. deep drainage plus evapotranspiration) from water table fluctuations monitored in six (6) piezometers. Human abstraction was calculated based on the number of operating boreholes and their average daily abstraction. We found that human abstraction (0.34 mm/year ± 0.07 mm) is far less than natural discharge (108 mm/year ± 58 mm). We conclude that increased abstraction due to population growth will probably have a smaller impact on storage than observed land-use change, which may lead to a change in the evapotranspiration rate. We calculated buffer capacity as the ratio of current storage to total discharge, and obtained a result of 6 years ± 47 months. This buffer capacity confirms groundwater’s ability to buffer changes. Finally, our study is intended to promote a more quantitative approach to assessing groundwater resources in Africa and to support our ability to adapt to current and future changes.

Surface complexation modeling of proton and metal sorption onto graphene oxide

The objective of this investigation was to develop a surface complexation modeling approach to account for proton and metal (Cd, Pb) binding onto many-layered graphene oxide (MLGO) across a range of pH and ionic strength conditions. MLGO particles exhibit large buffering capacities between pH 3 and pH 10 and the buffering behavior is only nominally influenced by ionic strength. In contrast, batch metal sorption experiments illustrate that the striking capacity of MLGO to sorb metals substantially diminishes with increases in ionic strength. X-ray absorption spectroscopy measurements were used to establish reaction stoichiometries and indicate that both Cd and Pb associate with single sites on the MLGO surface. The difference in sorption behaviors for protons and metals is best modeled using a 4-site non-electrostatic surface complexation model that accounts for ionic strength effects as a competition between Na from the background electrolyte and Cd/Pb for available MLGO sorption sites. Using this approach, titration data are used to constrain the site concentrations and pKa values for MLGO binding sites. The pKa values (±1σ) are calculated as 4.55 (±0.91), 6.52 (±0.49), 8.48 (±0.21), and 9.98 (±0.21). We then use these parameters and the metal sorption data to determine thermodynamic stability constants for each important Cd– and Pb–MLGO surface complex. The site concentrations and equilibrium constants provided herein are critical for developing and testing remediation strategies for specific water chemistries.