Suitable Buffer Research Articles

Simultaneous determination of dihydroxybenzene and phenylenediamine positional isomers using capillary zone electrophoresis coupled with amperometric detection

In general capillary zone electrophoresis (CZE) separation models, o-, m-, and p-phenylenediamine isomers can be separated in a weak acidic running buffer for their pK(a) values being 4.52, 5.64, 6.04, respectively, while o-, m-, and p-dihydroxybenzene isomers can be separated in a weak basic buffer for their pK(a) values being 9.40, 9.40 and 10.04, respectively. So, it is hard to find a suitable running buffer at a fixed pH in normal CZE for simultaneous separation of these two groups of positional isomers. In this paper, a novel method based on alternately running two different pH buffers in CZE coupled with amperometric detection (CZE-AD) was designed to simultaneously determine these two groups of positional isomers. It is found that when two different pH running buffers were employed alternately under appropriate order and time, the six analytes could be separated perfectly in less than 20 min and the detection limits were as low as 10(-7) mol/L. Furthermore, the effects of working electrode potential, pH and concentration of running buffer, separation voltage and injection time on CZE-AD were investigated. Experimental results demonstrated that the introduced method was practical to simultaneously determine two groups of positional isomers with different pK(a) and had some advantages of high sensitivity, good repeatability and small sample requirement.

A Study on the Advanced Surface Characteristic of Yttria (Y<sub>2</sub>O<sub>3</sub>) Ceramic by Using Optimal Design of Process

Since a fine ceramic is possessed of creditable physical and chemical material properties: high thermal resistance, chemical inertness and frictional wear resistance, its applications have been increasing in various industrial fields. Yttria(Y2O3) ceramic, which is formed of cubic crystal structure, has been considered as a light-transmitting material for an optical application and suitable buffer layer in the electronic industry. And its other applications have been increasing recently. For the effective applications of Yttria ceramic, it needs to improve a surface characteristic such as the waviness and surface roughness. The lapping process with in-process electrolytic dressing(IED) method has been performed in the surface machining of high hard-brittle material. IED method is able to overcome the surface machining defects caused by worn grains and unstable chip discharge during conventional lapping process. However, the machining control should be carefully conducted and investigated about each material because its material properties are different each other and exceedingly sensitive. Taguchi method, called robust design, is a useful method for engineering productivity elevation. It is able to search a powerful factor, which influences optimal process design, in accordance with considering noise factors reduction. When diverse factors influence a result according to complex actions each other, it needs to search optimal condition of factors. Response surface design has been widely used in various industrial fields. It helps to solve process design problems in accordance with robust design of process condition.

A molecular-based fast method to determine the extent of DNA damages in higher plants and fungi

Comet assay also called ‘single cell gel electrophoresis is a technique for the detection of DNA damage and repair at the level of single cells, which is one of the most advanced techniques introduced to the agricultural sciences in recent years. The assay is one of the most popular tests of DNA damage detection (e.g. single and double-strand breaks, oxidative-induced base damage and DNA-DNA/DNAprotein cross linking) by electrophoresis. The assay is very sensitive, rapid, easy to handle, noninvasive, visual and inexpensive compared to most conventional techniques to detect DNA damage, there is also little amount of cell samples required and it is applicable for most eukaryotic cells, thus, it has rapidly gained importance in the fields of genetic toxicology, medicine, environmental studies and agriculture. Isolated DNA from cells are embedded in a thin agarose gel on a microscope slide and unwound in a suitable buffer and exposed to a weak electric field to attract broken, negatively-charged DNA towards the anode. After electrophoresis, migrated DNA fragments stained with a fluorescent dye would resemble a shape of a comet observed by a fluorescence microscopy. The extent of comet-like shapes would indicate the level of DNA damage in cells. The intensity of comet tail relative to the head would also reflect the extent of DNA damage in numerical.

Validation of a sensitive ion chromatography method for determination of monoethylsulfate in Indinavir sulfate drug substance

The present study relates to the optimization of an ion chromatography method to determine the content of monoethylsulfate at very low levels in Indinavir sulfate drug substance, and subsequent validation of the method to prove its suitability, reliability and sensitivity. Monoethylsulfate is a potential impurity of Indinavir sulfate, and may forms during the preparation as well as during storage. The ion chromatography method was developed in such a way that to enhance the detection level by introducing suppressor, and minimizing acquisition time by using suitable buffer of 3.2 mmole of sodium carbonate and 1 mmole of sodium hydrogen carbonate in water as eluent. The retention time of monoethylsulfate was about 9.5 min and the total acquisition time was 25 min. The optimized method was validated to prove its performance characteristics by demonstrating selectivity, sensitivity (limit of detection and quantification), linearity, precision and accuracy. The established limit of detection and quantification of monoethylsulfate in Indinavir sulfate by this method was found to be 24 ng/ml and 74 ng/ml respectively, and the overall percent accuracy (recovery) of samples evaluated at different concentration levels was found to be 97.1, indicating the sensitivity and accuracy of this optimized ion chromatography method.

Buffer Interference with Protein Dynamics: A Case Study on Human Liver Fatty Acid Binding Protein

Selection of suitable buffer types is often a crucial step for generating appropriate protein samples for NMR and x-ray crystallographic studies. Although the possible interaction between MES buffer (2-( N-morpholino)ethanesulfonic acid) and proteins has been discussed previously, the interaction is usually thought to have no significant effects on the structures of proteins. In this study, we demonstrate the direct, albeit weak, interaction between MES and human liver fatty acid binding protein (hLFABP). Rather than affecting the structure of hLFABP, we found that the dynamics of hLFABP, which were previously proposed to be relevant to its functions, were significantly affected by the binding of hLFABP with MES. Buffer interference with protein dynamics was also demonstrated with Bis-Tris buffer, which is quite different from MES and fatty acids in terms of their molecular structures and properties. This result, to our knowledge, is the first published report on buffer interference with protein dynamics on a microsecond to millisecond timescale and could represent a generic problem in the studies of functionally relevant protein dynamics. Although being a fortuity, our finding of buffer-induced changes in protein dynamics offers a clue to how hLFABP accommodates its ligands.

An Adaptive Data Aggregation Algorithm in Wireless Sensor Network with Bursty Source

The Wireless Sensor network is distributed event based systems that differ from conventional communica-tion network. Sensor network has severe energy constraints, redundant low data rate, and many-to-one flows. Aggregation is a technique to avoid redundant information to save energy and other resources. There are two types of aggregations. In one of the aggregation many sensor data are embedded into single packet, thus avoiding the unnecessary packet headers, this is called lossless aggregation. In the second case the sensor data goes under statistical process (average, maximum, minimum) and results are communicated to the base station, this is called lossy aggregation, because we cannot recover the original sensor data from the received aggregated packet. The number of sensor data to be aggregated in a single packet is known as degree of ag-gregation. The main contribution of this paper is to propose an algorithm which is adaptive to choose one of the aggregations based on scenarios and degree of aggregation based on traffic. We are also suggesting a suitable buffer management to offer best Quality of Service. Our initial experiment with NS-2 implementa-tion shows significant energy savings by reducing the number of packets optimally at any given moment of time.

Mechanistic Insight into Site-Restricted Monoubiquitination of FANCD2 by Ube2t, FANCL, and FANCI

A key step in the Fanconi anemia (FA) tumor suppressor pathway is the site-specific monoubiquitination of the FANCD2 protein. Genetic studies indicate that this crucial modification requires eight known FA gene products and the E2-conjugating enzyme Ube2t. Here, we minimally reconstitute this monoubiquitination reaction with Ube2t and the FANCL protein, revealing that monoubiquitination is stimulated by a conserved RWD-like domain in FANCL. Furthermore, addition of the FANCI protein enhances monoubiquitination and also restricts it to the in vivo substrate lysine residue on FANCD2. This work therefore establishes a system that provides mechanistic insight into the functions of FANCL and FANCI in the catalysis of FANCD2 monoubiquitination.

Stability of vitamin C derivatives in topical formulations containing lipoic acid, vitamins A and E

The stability of ascorbyl palmitate, sodium ascorbyl phosphate and magnesium ascorbyl phosphate in topical formulations was investigated by direct reverse phase high performance liquid chromatography after sample dilution with a suitable buffer - organic solvent mixture. Ascorbyl palmitate, sodium ascorbyl phosphate and magnesium ascorbyl phosphate are derivatives of ascorbic acid which differ in hydrolipophilic properties. They are widely used in cosmetic and pharmaceutical preparations. According to the results, ascorbyl esters showed significant differences: sodium ascorbyl phosphate and magnesium ascorbyl phosphate are more stable derivatives of vitamin C than ascorbyl palmitate and may be easily used in cosmetic products.

Field‐amplified on‐line sample stacking for simultaneous enantioseparation and determination of some β‐blockers using capillary electrophoresis

A capillary electrophoresis method using carboxymethyl-beta-cyclodextrin as the chiral selector and mixture of methanol and ethanol as the organic additive was successfully developed for the simultaneous enantioseparation and determination of six beta-blockers, namely, carteolol, atenolol, sotalol, metoprolol, esmolol and propranolol in this paper. The most suitable running buffer for enantioseparation was found to be the solution of 20 mmol/L NaH(2)PO(4)-Na(2)HOP(4) (pH 5.5) containing 1.5% w/v carboxymethyl-beta-cyclodextrin, 5% v/v methanol and 5% v/v ethanol. Furthermore, field-amplified sample injection as an on-line sample stacking method was developed in order to increase the detection sensitivity. The experimental conditions for both simultaneous enantioseparation and the field-amplified sample injection method had been investigated in detail. Under the optimum conditions, the detection limits (defined as S/N=3) of this method were 0.01, 0.05, 0.05, 0.05, 0.05 and 0.5 microg /mL for (+/-) carteolol, (+/-) atenolol, (+/-) sotalol, (+/-) metoprolol, (+/-) esmolol and (+/-) propranolol, respectively, which were much lower than those of the conventional methods. The enhancement factors were greatly improved by 25-fold for the enantiomers of the beta-blockers except five-fold for (+/-) propranolol. Eventually, the proposed method has been applied for the analysis of human serum sample.

Dynamic riparian buffer widths from potential non-point source pollution areas in forested watersheds

Efforts to manage National Forests in the USA for wood production, while protecting water quality, are currently constrained by models that do not address the temporal dynamics of variable non-point source (NPS) areas. NPS areas are diffuse sources of contaminants contributed mostly by runoff as a result of different land use activities. Riparian vegetative buffers are often used to control contaminants from NPS areas but defining suitable widths require different policy considerations. In this study, the approach for defining suitable buffer widths is to apply a distributed process-based model that predicts potential NPS areas prone to generating runoff in relation to overland flow distances. A case study of the concept was applied to the 72 km 2 Pete King watershed located in the Clearwater National Forest (CNF) in central Idaho, USA. This grid modeling approach is based on a Geographic Information System (GIS) and it integrates the soil moisture routing (SMR) model with probabilistic analysis. The SMR model is a daily water balance model that simulates the hydrology of forested watersheds using real or stochastically generated climate data, a digital elevation model, soil, and land use data. The probabilistic analysis incorporates the variability of soil depth and accounts for uncertainties associated with the prediction of NPS areas using Monte Carlo simulation. A 1-year simulation for the case study location was performed to examine the spatial and temporal changes in NPS areas prone to generating runoff. The results of the simulation indicate that the seasonal variability of saturated areas determines the spatial dynamics of the potential NPS pollution. Use of this model for the design of riparian buffer widths would increase the effectiveness of decision-making in forest management and planning by mapping or delineating NPS areas likely to transport contaminants to perennial surface water bodies.

Substrate characteristics beneath self-aligned carbon-nanotube forests

The catalyst has been examined before and after heating as well as after forest removal. This has revealed the importance of FeO and an additional role for a SiO2 buffer layer in the production of higher-quality faster-growing carbon-nanotube (CNT) forests. Our results, together with the literature, show that oxidation during heating (even when an inert gas is used) breaks up the Fe layer into small Fe2O3 islands. A suitable SiO2 buffer layer (either deposited or formed during the process) acts to inhibit Fe2O3 reduction past FeO, even in the presence of hydrogen from catalytic breakdown of the hydrocarbon during CNT growth. It is suggested that FeO is a more active catalyst than Fe and is more strongly bound to the surface. The interaction appears crucial for faster-growing, self-aligned forests and also for avoiding tip growth, disoriented layers, and included metal particles, which would be toxic in biomedical applications.

Simultaneous determination of flavonoids in chrysanthemum by capillary zone electrophoresis with running buffer modifiers

Despite the separation efficiency of capillary electrophoresis (CE) is much higher than other chromatographic methods, it is sometimes difficult to perfectly separate the complex ingredients in biological samples. One possible and simple way to develop the separation effect in CE is to add some modifiers in the running buffer. In this paper, the suitable running buffer modifiers were explored to simultaneously separate and detect six typical flavonoids (apigenin, luteolin, kaempferol, quercetin, (+)-catechin and (−)-epicatechin) which are the main active ingredients in chrysanthemum by capillary zone electrophoresis with amperometric detection (CZE-AD). It was found that when β-cyclodextrin (β-CD) and the mixture of methanol and ethanol were used as running buffer modifiers, a baseline separation of the six analytes could be accomplished in less than 20 min and the detection limits were as low as 10 −7 or 10 −8 g ml −1. Other factors affecting the CZE separation, such as working potential, pH value and ionic strength of running buffer, separation voltage and sample injection time were extensively investigated. Under the optimum conditions, a successful practical application on the determination of chrysanthemum samples confirmed the validity and practicability of this method.

IN2S3:Ag, an ideal buffer layer for thin film solar cells

Silver diffusion enhanced the properties of Indium sulfide (In2S3) films making it highly suitable buffer layer for photovoltaic applications. Thin layer of silver deposited over In2S3 films diffused into In2S3 films in ‘as-deposited’ condition itself creating doping effect. A significant enhancement in crystallinity and grain size could be obtained up to an optimum percentage of doping concentration. This optimum value showed dependence on thickness and atomic ratio of indium and sulfur in the film. Band gap decreased up to the optimum value of doping and thereafter it increased. Electrical studies showed a decrease in resistivity due to doping. Sample having the optimum doping was found to be more photosensitive and low resistive when compared with the pristine sample. These results proved that silver diffused indium sulfide surpasses pristine sample for crystallinity and photosensitivity. Doping β-In2S3 film with optimum amount of silver modified the structural and electrical properties of the films favorably so that the Ag electrodes given to the ITO/CuInS2/In2S3 cell structure itself acted as a doping agent for the In2S3 layer, enhancing the cell efficiency to 9.5% (John et al. Sol Energy Mater Sol Cells 89:27, 2005).

Three-way partial least-squares/residual bilinearization study of second-order lanthanide-sensitized luminescence excitation-time decay data: Analysis of benzoic acid in beverage samples

Lanthanide-sensitized luminescence excitation-time decay matrices were employed for achieving the second-order advantage using as chemometric algorithms parallel factor analysis (PARAFAC) and multidimensional partial least-squares with residual bilinearization (N-PLS/RBL). The second-order data were measured for a calibration set of samples containing the analyte benzoic acid in the concentration range from 0.00 to 5.00 mg L −1, for a validation set containing the analyte and the potential interferent saccharin (in the range 0.00–6.00 mg L −1), and for real samples of beverages containing benzoic acid as preservant, saccharin, and other potentially interfering compounds. All samples were treated with terbium(III), trioctylphosphine oxide as a synergistic ligand, and contained a suitable imidazol buffer, in order to ensure maximum intensity of the luminescence signals. The results indicate a slightly better predictive ability of the newly introduced N-PLS/RBL procedure over standard PARAFAC, both in what concerns the comparison with nominal analyte concentrations in the validation sample set and with results provided by the reference high-performance liquid chromatographic technique for the real sample set.

Al-oxynitride interfacial layer investigations for PrXOY on SiC and Si

We investigate the dielectric properties of Praseodymium based oxides PrXOY by preparing MIS (metal insulator semiconductor) structures consisting of PrXOY as a high-k insulating layer and silicon (Si) or silicon carbide (SiC) as semiconductor substrates. The use of a buffer layer between PrXOY and the semiconductor is necessary as we found deleterious reactions between these materials such as silicate and graphite formation. Possessing a higher permittivity value (εr) than silicon dioxide (SiO2) and good lattice matching in conjunction with similar thermal expansion coefficient to SiC, we focus on aluminum oxynitride (AlON) as a suitable buffer layer for this high-k/wide-bandgap system. In our spectroscopic investigations we found a decrease or indeed prevention of silicon diffusion into the oxide and an increased Pr2O3 fraction after deposition. In electrical characterizations of PrXOY/AlON stacks we found considerable improvements in the leakage current by several orders on both substrates, especially on silicon where we obtain values down to 10−7A/cm2 at a CET (capacitance equivalent thickness) of 4nm. We observed interface state densities in the range of 5 × 1011-1 × 1012/eVcm2 and 1-5 × 1012/eVcm2 on Si and SiC, respectively.

Improving interaction responsiveness of multimedia presentations

The Management of user interactions in distributed multimedia presentations requires addressing new challenging issues. In this paper, we revue the semantic of VCR-like interactions. We argue that using VCR commands in the same way as it is done with video data (accelerating the presentation) is not suitable. Furthermore, those interactions are semantically linked to the content of the presentation; the final objective of users is to quickly browse and access a certain content. Firstly, we define a novel adequate semantic of VCR-like interactions for multimedia presentations. It considers human understanding of accelerated multimedia presentation, as the most important criterion to be taken into account. Secondly, we propose an integrated preloading and replacement strategy, named Content-based Prefetching Strategy (CPS) as a suitable buffer management strategy for those VCR-like functionalities. Finally, we show by multiple series of experimentations that CPS observes minimum response time for VCR-like interactions.

Investigation of Solid‐Phase Buffers for Sulfur‐Oxidizing Autotrophic Denitrification

This paper investigates biological denitrification using autotrophic microorganisms that use elemental sulfur as an electron donor. In this process, for each gram of nitrate-nitrogen removed, approximately 4.5 g of alkalinity (as calcium carbonate) are consumed. Because denitrification is severely inhibited below pH 5.5, and alkalinity present in the influent wastewaters is less than the alkalinity consumed, an external buffer was needed to arrest any drop in pH from alkalinity consumption. A packed-bed bioreactor configuration is ideally suited to handle variations in flow and nitrate loading from decentralized wastewater treatment systems, as it is a passive system and thus requires minimal maintenance; therefore, a solid-phase buffer packed with the elemental sulfur in the bioreactor is most suitable. In this research, marble chips, limestone, and crushed oyster shells were tested as solid-phase buffers. Bench- and field-scale studies indicated that crushed oyster shell was the most suitable buffer based on (1) the rate of dissolution of buffer and the buffering agent released (carbonate, bicarbonate, or hydroxide), (2) the ability of the buffer surface to act as host for microbial attachment, (3) turbidity of the solution upon release of the buffering agent, and (4) economics.

Effect of a full-grown vegetative filter strip on herbicide runoff: Maintaining of filter capacity over time

Narrow vegetative filter strips (VFS) proved to effectively reduce herbicide runoff from cultivated fields mainly due to the ability of vegetation to delay surface runoff, promote infiltration and adsorb herbicides. Since VFS are dynamic systems, their performance would not remain constant over the years indicating the need to define suitable buffer management. In order to evaluate the performance of different five and six year-old VFS, the runoff of the herbicides metolachlor and terbuthylazine was monitored in 2002 and 2003 in an experimental site in northern Italy. The structure of the herbaceous cover in the buffers changes over time. When rows of trees are present, the grass cover is decreased by the shading action of the trees, but the leaf litter gains importance. In VFS with grass cover only, the cover composition changes because of the substitution of grass by broadleaf species. Six metres wide VFS are very effective in reducing runoff volume and concentration during both wet and dry years. Classification analysis showed that runoff concentration and volume are linked to the characteristics of the rainfall event, buffer, source of herbicides and time after application. Regression analysis showed that the significant predictors for runoff volume are rainfall amount and intensity, total vegetal cover in the VFS, crop leaf area index and time after treatment; for concentration they are rainfall intensity, crop leaf area index and total vegetal cover in the VFS. The role of VFS is complex, so appropriate management is required to maintain its increasing filtering capacity over time.

A hybrid cycle bandwidth allocation scheme with differentiated services support in Ethernet passive optical networks

The Ethernet passive optical network (EPON) has emerged as one of the most promising solutions for next generation broadband access networks. Designing an efficient upstream bandwidth allocation scheme with differentiated services (DiffServ) support is a crucial issue for the successful deployment of EPON, carrying heterogeneous traffic with diverse quality of service (QoS) requirements. In this article, we propose a new hybrid cycle scheme (HCS) for bandwidth allocation with DiffServ support. In this scheme, the high-priority traffic is transmitted in fixed timeslots at fixed positions in a cycle while the medium- and low-priority traffic are transmitted in variable timeslots in an adaptive dynamic cycle. A suitable local buffer management scheme is also proposed to facilitate QoS implementation. We develop a novel feature providing potentially multiple transmission opportunities (M-opportunities) per-cycle for high-priority traffic. This feature is significant in improving delay and delay-variation performance. The HCS provides guaranteed services in a short-cycle scale for delay and jitter sensitive traffic while offering guaranteed throughput in a moderately long-time scale for bandwidth sensitive traffic and at the same time maximizing throughput for non-QoS demanding best-effort traffic. We develop analytical performance analysis on the deterministic delay bound for high-priority traffic and minimum throughput guarantees for both high- and medium-priority traffic. On the other hand, we also conduct detailed simulation experiments. The results show a close agreement between analytical approach and simulation. In addition, the simulation results show that the HCS scheme is able to provide excellent performance in terms of average delay, delay-variation, and throughput as compared with previous approaches.

Enhanced performance of overlap flow-shop scheduling involving reworking and a time buffer

This study presents an overlap scheduling solution to enhance system performance for branched-line flow-shop operations that involve reworking and a time buffer. In scheduling the branched-line operations involving reworking and a time buffer, two mutual inter-dependent problems must be solved: one is to determine the appropriate job schedule, and the other is to find a suitable time buffer at the right position of the system. Analysis results indicate that arranging a job sequence using a meta-search, of which the genetic algorithm-based best-fit search is the simplest, most effective, and least costly way for improving overlap flow-shop scheduling performance. In determining the job schedule involving reworking and a time buffer for branched-line operations, we propose a genetic algorithm-based overlap scheduling heuristic to perform the best-fit search using a pre-determined time buffer. Having found a suitable time buffer, we build a scheduling simulator to measure the performance for the job schedule that is determined by the genetic algorithm when a time buffer is added.