Second Dissociation Constant of Bis-[(2-hydroxyethyl)amino]acetic Acid (BICINE) and pH of Its Buffer Solutions from 5 to 55 °C

The values of the second dissociation constant, K ₂, and related thermodynamic quantities of the ampholyte bis[(2-hydroxyethyl)amino]acetic acid (BICINE) have been determined at temperatures from 5 to 55 ^∘C. The pH values of six equimolal buffer solutions, and four buffer solutions having ionic strengths (I = 0.16 mol⋅kg⁻¹) similar to those in blood plasma, have been evaluated at 12 temperatures from 5 to 55 ^∘C using the Bates–Guggenheim convention. The liquid junction potentials (E _j ) between the buffer solutions of BICINE and saturated KCl solution of the calomel electrode at 25 and 37 ^∘C have been estimated by measurement with a flowing junction cell. These values of E _j have been used to ascertain the operational pH values at 25 and 37 ^∘C. The pK ₂ values at 25 and 37 ^∘C are 8.333 and 8.156, respectively. The thermodynamic quantities associated with the second acid dissociation have been calculated from the values of pK ₂ as a function of temperature. The zwitterionic buffer BICINE was shown to be useful as a pH standard in the region close to that of blood serum.     

缓冲剂对镀镍过程作用机理的研究

缓冲剂对镀镍过程作用机理的研究①高灿柱鹿玉理刘汝涛陈方（山东大学环境工程系济南２５０１００）李树本（中国科学院兰州化学物理研究所兰州７３００００）电镀镍是量大面广的镀种，它作为镀铬、贵金属、仿金、枪黑、黑镍的底层，用途非常广泛［１］．在镀镍过程中，...     

Proactive heuristic procedures for robust project scheduling: An experimental analysis

Solution-robust project scheduling is a growing research field aiming at constructing proactive schedules to cope with multiple disruptions during project execution. When stochastic activity durations are considered, including time buffers between activities is a proven method to improve the stability of a baseline schedule.     

Buffer Standards for pH Measurement of N-(2-Hydroxyethyl)piperazine-N′-2-ethanesulfonic Acid (HEPES) for I=0.16 mol⋅kg−1 from 5 to 55 °C

The values of the second dissociation constant, pK ₂, of N-(2-hydroxyethyl) piperazine-N′-2-ethanesulfonic acid (HEPES) have been reported at twelve temperatures over the temperature range 5 to 55 °C, including 37 °C. This paper reports the results for the pa _H of eight isotonic saline buffer solutions with an I=0.16 mol⋅kg⁻¹ including compositions: (a) HEPES (0.01 mol⋅kg⁻¹) + NaHEPES (0.01 mol⋅kg⁻¹) + NaCl (0.15 mol⋅kg⁻¹); (b) HEPES (0.02 mol⋅kg⁻¹) + NaHEPES (0.02 mol⋅kg⁻¹) + NaCl (0.14 mol⋅kg⁻¹); (c) HEPES (0.03 mol⋅kg⁻¹) + NaHEPES (0.03 mol⋅kg⁻¹) + NaCl (0.13 mol⋅kg⁻¹); (d) HEPES (0.04 mol⋅kg⁻¹) + NaHEPES (0.04 mol⋅kg⁻¹) + NaCl (0.12 mol⋅kg⁻¹); (e) HEPES (0.05 mol⋅kg⁻¹) + NaHEPES (0.05 mol⋅kg⁻¹) + NaCl (0.11 mol⋅kg⁻¹); (f) HEPES (0.06 mol⋅kg⁻¹) + NaHEPES (0.06 mol⋅kg⁻¹) + NaCl (0.10 mol⋅kg⁻¹); (g) HEPES (0.07 mol⋅kg⁻¹) + NaHEPES (0.07 mol⋅kg⁻¹) + NaCl (0.09 mol⋅kg⁻¹); and (h) HEPES (0.08 mol⋅kg⁻¹) + NaHEPES (0.08 mol⋅kg⁻¹) + NaCl (0.08 mol⋅kg⁻¹). Conventional pa _H values, for all eight buffer solutions from 5 to 55 °C, have been calculated. The operational pH values with liquid junction corrections, at 25 and 37 °C have been determined based on the NBS/NIST standard between the physiological phosphate standard and four buffer solutions. These are recommended as pH standards for physiological fluids in the range of pH = 7.3 to 7.5 at I=0.16 mol⋅kg⁻¹.     

Use of different buffers for detection and separation in determination of physio‐active components in oolong tea infusion by CZE with amperometric detection

With a view of simultaneous determination of physio‐active ingredients in oolong tea infusion: sugars, amino acids, epigallocatechin gallate and ascorbic acid, a novel CZE with amperometric detection method was studied. Operated in a wall‐jet configuration, 100 mmol/L NaOH was used in detecting cell to lead the electrocatalysis oxidation behaviors of the analytes on a 300 μm diameter copper‐disc electrode (working electrode), while in separating capillary, a mild alkaline running buffer consisting in a mixture of 30 mmol/L borate and 40 mmol/L phosphates charged and carried analytes to detecting end. The methodology research was performed for system stability and suitability. Under the optimal CE conditions, analytes could be separated within moderate time period. Good linearity between peak area and concentration existed over three orders of magnitude; lower RSD and LOD were achieved. The oolong tea infusion was assayed and result was satisfactory.     

基于流量门限的提前预留竞争解决机制(英文)

基于小尺寸缓存的提前预留机制是有效的竞争解决方案.为支持区分服务,本文研究了两优先级提前预留机制的阻塞模型,分析了变化缓存尺寸与载荷比率条件下光突发交换网络核心节点的阻塞性能.为降低两优先级提前预留机制的突发丢弃率,提出一种基于流量门限的提前预留机制.数值分析确定了合理的缓存尺寸与流量门限,实现了高、低优先级间的缓存使用平衡.仿真结果表明:与原有提前预留机制相比,基于流量门限的提前预留机制保持了全流量状态范围内的阻塞性能,并明显降低了中、低流量状态内的突发丢弃率.     

Buffer Standards for the Physiological pH of the Zwitterionic Compound,DIPSO, from 5 to 55 °C

The values of the second dissociation constant, pK ₂, and related thermodynamic quantities of 3-[N,N-bis (2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) have already been reported over the temperature range 5 to 55 °C including 37 °C. This paper reports the pH values of four NaCl-free buffer solutions and four buffer composition containing NaCl salt at I=0.16 mol⋅kg⁻¹. Conventional pa _H values are reported for all eight buffer solutions. The operational pH values have been calculated for four buffer solutions recommended as pH standards, at 25 and 37 °C after correcting the liquid junction potentials with the flowing junction cell.     

Buffer Standards for the Physiological pH of Zwitterionic Compounds,MOBS and TABS from 5 to 55°C

The values of the second dissociation constant, pK₂, and related thermodynamic quantities of 4-(N-morpholino)butanesulfonic acid (MOBS) and N-tris(hydroxymethyl)-4-aminobutanesulfonic acid (TABS) have already been reported over the temperature range 5–55°C including 37{°}C. This paper reports the pH values of twelve equimolal buffer solutions at designated pH (s) with the following compositions: (a) mixtures of MOBS (0.05 mol-kg^–1) + NaMOBS (0.05 mol-kg^–1); (b) MOBS (0.08 mol-kg^–1) + NaMOBS (0.08 mol-kg^–1); (c) MOBS (0.08 mol-kg^–1) + NaMOBS (0.08 mol-kg^–1) + NaCl (0.08 mol-kg^–1); (d) TABS (0.05 mol-kg^–1) + NaTABS (0.05 mol-kg^–1); and (e) TABS (0.08 mol-kg^–1) + NaTABS (0.08 mol-kg^–1); and (f) TABS (0.08 mol-kg^–1) + NaTABS (0.08 mol-kg^–1) + NaCl (0.08 mol-kg^–1). Two buffer solutions have ionic strengths I= 0.05 mol-kg^–1, another two have I=0.08 mol-kg^–1, and the remaining two buffer solutions have I= 0.16 mol-kg^–1, which is close to that of the clinical fluids (blood serum). These buffers have been recommended as a useful pH standard for the measurements of physiological solutions. Conventional pH values of all six buffer solutions from 5–55°C, as well as those obtained from the liquid junction potential correction at 25 and 37{°}C have been calculated. The flowing-junction calomel cell has been utilized to measure E_j, the liquid junction potential.     

Buffer Standards for the Physiological pH of the Zwitterionic Compound, TAPS, From 5 to 55 ∘C

The values of the second dissociation constant, pK ₂, and related thermodynamic quantities of N-[tris(hydroxymethyl)methyl-3-amino]propanesulfonic acid (TAPS) have already been reported at 12 temperatures over the temperature range 5–55 ^∘C, including 37 ^∘C. This paper reports the results for the pH of five equimolal buffer solutions with compositions: (a) TAPS (0.03 mol⋅kg⁻¹) + NaTAPS (0.03 mol⋅kg⁻¹); (b) TAPS (0.04 mol⋅ kg⁻¹) + NaTAPS (0.04 mol⋅kg⁻¹); (c) TAPS (0.05 mol⋅kg⁻¹) + NaTAPS (0.05 mol⋅kg⁻¹); (d) TAPS (0.06 mol⋅kg⁻¹) + NaTAPS (0.06 mol⋅kg⁻¹); and (d) TAPS (0.08 mol⋅kg⁻¹) + NaTAPS (0.08 mol⋅kg⁻¹). The remaining eight buffer solutions consist of saline media of the ionic strength I = 0.16 mol⋅kg⁻¹, matching closely to that of the physiological sample. The compositions are: (f) TAPS (0.04 mol-kg⁻¹) + NaTAPS (0.02 mol-kg⁻¹) + NaCl (0.14 mol⋅kg⁻¹); (g) TAPS (0.05 mol⋅kg⁻¹) + NaTAPS (0.04 mol⋅kg⁻¹) + NaCl (0.12 mol⋅kg⁻¹); (h) TAPS (0.6 mol⋅kg⁻¹) + NaTAPS (0.04 mol⋅kg⁻¹) + NaCl (0.12 mol⋅kg⁻¹); (i) TAPS (0.08 mol⋅kg⁻¹) + NaTAPS (0.06 mol⋅kg⁻¹) + NaCl (0.10 mol⋅kg⁻¹); (j) TAPS (0.04 mol⋅ kg⁻¹) + NaTAPS (0.04 mol⋅kg⁻¹) + NaCl (0.12 mol⋅kg⁻¹); (k) TAPS (0.05 mol⋅kg⁻¹) + NaTAPS (0.05 mol⋅kg⁻¹) + NaCl (0.11 mol⋅kg⁻¹); (l) TAPS (0.06 mol⋅kg⁻¹) + NaTAPS (0.06 mol⋅kg⁻¹) + NaCl (0.10 mol⋅kg⁻¹); and (m) TAPS (0.08 mol⋅kg⁻¹) + NaTAPS (0.08 mol⋅kg⁻¹) + NaCl (0.08 mol⋅kg⁻¹). These buffers are recommended as a pH standard for clinical measurements in the range of physiological application. Conventional pH values, designated as pH(s), for all 13 buffer solutions from 5 to 55 ^∘C have been calculated. The operational pH values with liquid junction corrections, at 25 and 37 ^∘C for buffer solutions, designated above as (b), (c), (d), (e), (j), (l), and (m); have been determined based on the difference in the values of the liquid junction potentials between the accepted phosphate standard and the buffer solutions under investigation.     

Scheduling batches in flowshop with limited buffers in the shampoo industry

In this paper we address the problem of planning a temporary storage area in a real production system. This temporary storage area is composed of parallel temporary storage units with distinct capacities. The storage operation of a job, also called a batch, has to answer time restrictions such as release dates, due dates, restricted family dependent setup times and time lags, and also a space constraint which is the capacity of the temporary storage unit. The goal is to schedule the batches on the storage units in order to minimize the total setup times and the maximum lateness. First, we model the problem on a single storage unit as a two-machine flowshop problem with a limited buffer capacity and we show that it is NP-hard. We also show that the particular case in which no lateness is allowed is solvable in polynomial time under special conditions on the buffer capacity, both for single or parallel temporary storage units. Next we provide three heuristics: a greedy algorithm, a hybrid heuristic based on Ant Colony Optimization and Simulated Annealing and finally a dedicated heuristic. The latter strongly exploits the structural properties shown in this paper. We provide experimental results which highlight the efficiency of the dedicated heuristic in comparison with the two other heuristics.