Tracer monitored titrations: measurement of total alkalinity

We introduce a new titration methodology, tracer monitored titration (TMT), in which analyses are free of volumetric and gravimetric measurements and insensitive to pump precision and reproducibility. Spectrophotometric monitoring of titrant dilution, rather than volume increment, lays the burden of analytical performance solely on the spectrophotometer. In the method described here, the titrant is a standardized mixture of acid-base indicator and strong acid. Dilution of a pulse of titrant in a titration vessel is tracked using the total indicator concentration measured spectrophotometrically. The concentrations of reacted and unreacted indicator species, derived from Beer's law, are used to calculate the relative proportions of titrant and sample in addition to the equilibrium position (pH) of the titration mixture. Because the method does not require volumetric or gravimetric additions of titrant, simple low-precision pumps can be used. Here, we demonstrate application of TMT for analysis of total alkalinity (A(T)). High-precision, high-accuracy seawater A(T) measurements are crucial for understanding, for example, the marine CaCO3 budget and saturation state, anthropogenic CO2 penetration into the oceans, calcareous phytoplankton blooms, and coral reef dynamics. We present data from 286 titrations on three types of total alkalinity standards: Na2CO3 in 0.7 mol kg x soln(-1) NaCl, NaOH in 0.7 mol kg x soln(-1) NaCl, and a seawater Certified Reference Material (CRM). Based on Na2CO3 standards, the accuracy and precision are +/-0.2 and +/-0.1% (4 and 2 micromol kg x soln(-1) for A(T) approximately 2100-2500 micromol kg x soln(-1), n = 242), using low-precision solenoid pumps to introduce sample and titrant. Similar accuracy and precision were found for analyses run 42 days after the initial experiments. Excellent performance is achieved by optimizing the spectrophotometric detection system and relying upon basic chemical thermodynamics for calculating the equivalence point. Although applied to acid-base titrations in this paper, the approach should be generally applicable to other types of titrations.     

Universal tracer monitored titrations

Titrations, while primarily known as the chemical rite of passage for fledgling science students, are still widely used for chemical analysis. With its many years of existence and improvement, the method would seem an unlikely candidate for innovation, yet it is desirable, in this age of autonomous sensing where analyzers may be sent into space or to the bottom of the ocean, to have a simplified titrimetric method that does not rely upon volumetric or gravimetric measurement of sample and titrant. In previous work on the measurement of seawater alkalinity, we found that use of a tracer in the titrant eliminates the need to measure mass or volume. Here, we show the versatility of the method for diverse types of titrations and tracers. The results suggest that tracers may be employed in all types of titrations, opening the door for greatly simplified laboratory and field-based chemical analysis.     

Continuous on-line true titrations by feedback-based flow ratiometry. The principle of compensating errors

We introduce a new concept for continuous on-line titrations based on feedback-controlled flow ratiometry and the principle of compensating errors. The system has been thoroughly tested by applying it to acid-base neutralization titrations with indicator-based end point detection. In a typical case, the total flow (FT, consisting of the sample and the titrant flows) is held constant while the titrant (e.g., a standard base containing an indicator) flow FB varies linearly in response to a controller output voltage. The sample (e.g., an acidic solution to be titrated) flow FA constitutes the makeup and thus also varies (FA = FT - FB). The status of the indicator color in the mixed stream is monitored by an optical detector and used either for governing the controller output or for interpreting the results of the titration. Three methods (PID based control, fixed triangular wave control, and feedback-based triangular wave control implemented on a PC) were examined. In the last and the most successful approach, the titrant flow is initially ramped upward linearly. At the instant a change in the color is sensed by the detector, the titrant flow rate FH is higher than the true equivalence flow rate FE because of the lag time between the first compositional change and its detection. The sensing of the change in color causes the system output to immediately reverse its ramp direction such that the titrant flow now goes down linearly at the same rate. At the instant a change in color, in the opposite direction this time, is again sensed, the titrant flow rate FL is lower than FE by exactly the same amount that FH was higher than FE. This principle of compensating errors (FE = (FH + FL)/2) allows true titrations with excellent reproducibility and speed (0.6% RSD at 3 s/titration and 0.2% RSD at 10 s/titration) and titrant volume consumption as little as 12 microL/titration and solves an old conceptual problem in flow based titrations.     

Top management team diversity,ambidextrous innovation and the mediating effect of top team decision-making processes

Until now, the amount of evidences for and discussions of how a top management team (TMT)’s composition influences ambidextrous innovation are very limited. This article develops and tests a model that connects task-related TMT diversity and TMT decision-making processes to explain the heterogeneity in a firm’s strategic focus on ambidextrous innovation. The paper is based on a questionnaire survey/analysis with sample of 179 TMTs from high-tech firms in China. The conclusion exhibits that TMT task-related diversity has a strong effect on a firm’s strategic focus on ambidextrous innovation through strategic decision-making activities. The findings suggest that the TMT debate and decision comprehensiveness can mediate the relationship between TMT task-related diversity and a firm’s strategic focus on ambidextrous innovation. Overall, these results suggest that involvement in debate and comprehensiveness of strategic decision activities may bring out the potential of a TMT’s diversity in enabling them to focus on ambidextrous innovation strategy.     

IMPROVEMENT OF FATIGUE LIFE OF 1080 STEEL BY THERMOMECHANICAL PROCESSING

Abstract— Many thermomechanical treatments (TMT) have been applied in the past to alloys in order to improve the balance between various static mechanical properties. The current research has applied a given type of TMT to the improvement of fatigue behavior in eutectoid steel. The TMT involved the cold rolling of annealed eutectoid steel to a reduction in thickness of 75% followed by rapid heating in liquid lead to a temperature just above the A ₁ temperature for a short time period and an air cool to room temperature. This type of TMT produces very oriented cementite in recrystallized ferrite. Plane bending cantilever fatigue tests with constant maximum load were run at 30 Hz and zero mean stress ( R =−1·0). In terms of S–N fatigue curves the annealed condition is inferior to both the TMT and cold rolled conditions, however, there is no apparent advantage of the TMT over the cold rolled condition. There is, however, a considerable advantage in the TMT which becomes evident with normalization of all S–N curves with respect to the ultimate tensile strength. One thus finds that the TMT is quite superior, on an equivalent strength basis, to both the cold rolled and annealed conditions. The same was true on a basis of hardness normalization. This means that by TMT one can produce fatigue properties in a material of much higher formability which are equivalent to or better than those in a cold rolled material. Samples oriented in the cross-roll direction had total fatigue lives longer than for those oriented in the roll direction. This is explained in terms of mechanical fibering of pearlite colonies and inclusions, and by a crystallographic texturing of the ferrite matrix. TMT strength is a result of austenite grain size refinement, reduction of interlamellar spacing, fiber strengthening and both solid solution and precipitate hardening.     

铝合金形变热处理工艺研究进展

综述了过去40年铝合金形变热处理工艺的发展过程和最新的研究动态,介绍了形变热处理对铝合金组织与性能的影响及其在工业上的应用.通过分析铝合金形变热处理工艺研究中存在的一些问题,说明继续深入地开展铝合金形变热处理的试验研究仍然十分必要;而针对具体合金,简化和优化其形变热处理工艺使之能够在工业化生产条件下广泛应用更是当务之急.     

Evaluation and optimization of ion-current ratio measurements by selected-ion-monitoring mass spectrometry

Stable isotopically labeled compounds are regularly used as internal standards in quantitation and as tracers of in vivo metabolism. In both applications, the ratio of unlabeled to labeled analogues is determined from an ion-current ratio measured by a mass spectrometer. The precision of the ion-current ratio measurement defines the detection limit for quantitation and for tracer enrichment measurement. We have used standard models of noise to develop a method that evaluates ion-current ratio noise (i) that varies with the signal intensity and (ii) that is signal independent. This model produces a simple equation that defines the ion-current ratio precision using constants that can be evaluated empirically from the measurement of two ion-current ratios from a single standard measured multiple times. We demonstrate that our approach can predict the effect of signal intensity, ion-current ratio magnitude, and internal standard or tracer choice on the measurement precision. The standard deviations predicted by our method are shown to equal standard deviations of samples measured experimentally. This method allows a simple evaluation of a mass spectrometry system and can define the precision of new quantitation and tracer methods.     

非水溶剂电位滴定法测量碱基纯度

建立了在非水溶剂中电位滴定测定纯度标准物质胞嘧啶(Cyt)和腺嘌呤(Ade)含量的方法。通过实验对非水溶剂、滴定剂种类、滴定剂浓度、滴定终点进行了选择,确定了溶剂为冰醋酸HAc,滴定剂为高氯酸HClO₄,滴定剂浓度为0.05 mo1／L,终点为电位曲线的等当点,实验用电位滴定曲线准确确定了滴定终点。通过15次测定,测得Ade的纯度为99.40%,不确定度度为0.38%(k=2);测得Cyt纯度为99.58%,不确定度0.42%(k=2)。     

In at the Deep End of Firm Internationalization

• The purpose of this research is to examine the consequences of top management team (TMT) internationalization: why and under what conditions can TMT nationality diversity be beneficial?
• On the basis of the upper echelons theory from the strategic leadership literature, the relationship between the TMT nationality diversity and firm performance in the strategic context of firm internationalization is investigated in moderated multiple regressions models (MMR) for a sample of Dutch, Swiss, and UK companies.
• The study findings suggest that the TMT nationality diversity becomes advantageous only in firms with high degree of internationalization. Companies have to be strongly committed to foreign markets so that the benefits of the TMT nationality diversity can materialize.
• The arising managerial implication is that the TMT nationality diversity can be a powerful tool in building a firm’s competitive advantage, provided that companies are strongly exposed to the international environment. The study also provides corroborative evidence that the search for moderating and mediating variables in the TMT demography research represents a step in the right direction.

     

How do top management team characteristics affect digital orientation? Exploring the internal driving forces of firm digitalization

The top management team (TMT) plays a key role in the process of the firm digital transformation. However, few studies have focused on the impact of TMT characteristics on the digital orientation of firms. In this paper, we simultaneously explore the impact of the dispersion, aggregation, and background characteristics of TMT on the digital orientation of firms. Based on the upper echelons theory and strategic orientation theory, we propose that the diversity and average education level of TMT positively impact firms' digital orientation. The average age and tenure of TMT have a negative impact on the digital orientation of firms. The overseas and financial backgrounds of TMT members have a positive impact on the digital orientation of firms. Our hypothesis was tested using large-scale longitudinal data and computer-aided text analysis methods from Chinese listed companies. This paper provides useful supplements to early research on digital driving factors and digital orientation in emerging economies, and also provides more universal suggestions for digital practices in firms.     

粒子图像测速技术测量精度影响因素分析

对基于粒子图像测速(PIV)技术的瞬时全流场测量方法进行了综述.系统介绍了 PIV的工作原理、技术的关键环节(获取图像的品质)和影响测量精度主要因素(示踪粒子性能、光源性能、背景噪声、成像畸变、同步器时间分辨率及图像处理算法).基于这些分析,给出了示踪粒子性能的保障、成像组件的选择以及图像处理方法确定的具体建议.     

Titration without Mixing or Dilution: Sequential Injection of Chemical Sensing Membranes

A novel, miniaturized titration was developed using beads 35 μm in diameter as semisolid aqueous titrant retained in a nonaqueous sample stream. Agarose beads with internally bound pH indicator served as a pH sensing membrane material swollen with aqueous NaOH titrant. The indicator monitored the remaining titrant within the agarose beads during perfusion with H(2)SO(4) in 1-butanol samples. Irreversible reaction of 2 mg bead layers was made possible by automated packing and disposal in a flow cell. This strategy substituted membrane advantages for the burdens of mixing and unnecessary dilution under laminar flow conditions. The agarose environment was conditioned with NaCl to tolerate dissolved salt in the sample. Transmittance measurements were made via fiber optics through FEP PTFE optical windows. A simple inverse relationship held between endpoint volume and acid concentration so that calibration curves were linear, R(2) = 0.9980.     

Planar measurement of three-component velocity by streaked-particle-imaging velocimetry

A streaked-particle-imaging-velocimetry (SPIV) technique for the instantaneous planar measurement of three-component velocity has been developed and demonstrated. In this system a camera images the scattered light from two laser sheets onto the same recording medium. One of the laser sheets, double pulsed with short pulse duration, freezes the tracer particle motion and records a pair of images from each tracer. The other laser sheet, cw, provides tracer trajectories whose length is controlled by the sheet thickness. The recorded image from each tracer is then its streak trajectory superimposed on its frozen paired particle image. The planar two components of velocity are deduced from the distance between image pairs and the time separation of the double light pulses. This information, combined with the tracer trajectory streak length, determines the trace particle staying time within the laser sheet. The tracer velocity normal to the laser sheet is then calculated from this staying time and the laser sheet thickness that can be calibrated from the measurements. The resultant SPIV technique was demonstrated with a free jet seeded with small particles, and the derived velocity was reported.     

High-Resolution Enabled TMT 8-plexing

Isobaric mass tag-based quantitative proteomics strategies such as iTRAQ and TMT utilize reporter ions in the low-mass range of tandem MS spectra for relative quantification. The number of samples that can be compared in a single experiment (multiplexing) is limited by the number of different reporter ions that can be generated by differential stable isotope incorporation ((15)N, (13)C) across the reporter and the mass balancing parts of the reagents. Here, we demonstrate that a higher multiplexing rate can be achieved by utilizing the 6 mDa mass difference between (15)N- and (13)C-containing reporter fragments, in combination with high-resolution mass spectrometry. Two variants of the TMT127 and TMT129 reagents are available; these are distinguished by the position and the nature of the incorporated stable isotope in the reporter portions of the labels (TMT127L, (12)C(8)H(16)(15)N(1)(+); TMT127H, (12)C(7)(13)C(1)H(16)(14)N(1)(+); TMT129L, (12)C(6)(13)C(2)H(16)(15)N(1)(+); and TMT129H, (12)C(5)(13)C(3)H(16)(14)N(1)(+)). We demonstrate that these variants can be baseline-resolved in Orbitrap Elite higher-energy collision-induced dissociation spectra recorded with a 96 ms transient enabling comparable dynamic range, precision, and accuracy of quantification as 1 Da spaced reporter ions. The increased multiplexing rate enabled determination of inhibitor potencies in chemoproteomic kinase assays covering a wider range of compound concentrations in a single experiment, compared to conventional 6-plex TMT-based assays.     

Increasing the Multiplexing Capacity of TMTs Using Reporter Ion Isotopologues with Isobaric Masses

Quantitative mass spectrometry methods offer near-comprehensive proteome coverage; however, these methods still suffer with regards to sample throughput. Multiplex quantitation via isobaric chemical tags (e.g., TMT and iTRAQ) provides an avenue for mass spectrometry-based proteome quantitation experiments to move away from simple binary comparisons and toward greater parallelization. Herein, we demonstrate a straightforward method for immediately expanding the throughput of the TMT isobaric reagents from 6-plex to 8-plex. This method is based upon our ability to resolve the isotopic shift that results from substituting a (15)N for a (13)C. In an accommodation to the preferred fragmentation pathways of ETD, the TMT-127 and -129 reagents were recently modified such that a (13)C was exchanged for a (15)N. As a result of this substitution, the new TMT reporter ions are 6.32 mDa lighter. Even though the mass difference between these reporter ion isotopologues is incredibly small, modern high-resolution and mass accuracy analyzers can resolve these ions. On the basis of our ability to resolve and accurately measure the relative intensity of these isobaric reporter ions, we demonstrate that we are able to quantify across eight samples simultaneously by combining the (13)C- and (15)N-containing reporter ions. Considering the structure of the TMT reporter ion, we believe this work serves as a blueprint for expanding the multiplexing capacity of the TMT reagents to at least 10-plex and possibly up to 18-plex.     

Top management team’s innovation-related characteristics and the firm’s explorative R&D: an analysis based on patent data

This study investigates the relationship between characteristics of the firm’s top management team (TMT) and its research and development (R&D) activities. Specifically, this research analyzes how observable characteristics of the TMT, such as functional experiences or educational background, and average tenure affect the firm’s proportion of explorative R&D activities. From the perspective of the upper-echelon theory, we hypothesize that the TMT’s functional experiences with R&D or science or engineering educational backgrounds increase the firm’s tendency towards explorative R&D. Moreover, we propose that the average tenure of TMT members with innovation-related experiences would have a positive moderation effects on these relationships. The hypotheses are tested using a dataset containing biographical information of the TMT members, financial, and patent data of 89 firms in U.S. high-tech industries from 2006 to 2009. Firm’s explorative R&D activities are analyzed using data on patent citations, patent classes, and non-patent references. The empirical analysis shows that the top managers’ educational background in science or engineering as well as their previous functional experiences with R&D have a positive effect on the firm’s explorative innovation activities. We also find that the size of these effects increases with a longer tenure of these TMT members. Our findings provide implications related to the effects of organizational characteristics on the establishment of a R&D strategy and highlight the role of TMT members with innovative experiences in directing a firm’s R&D activities and outcomes.     

Chasing equilibrium: measuring the intrinsic solubility of weak acids and bases

A novel procedure is described for rapid (20-80 min) measurement of intrinsic solubility values of organic acids, bases, and ampholytes. In this procedure, a quantity of substance was first dissolved at a pH where it exists predominantly in its ionized form, and then a precipitate of the neutral (un-ionized) species was formed by changing the pH. Subsequently, the rate of change of pH due to precipitation or dissolution was monitored and strong acid and base titrant were added to adjust the pH to discover its equilibrium conditions, and the intrinsic solubility of the neutral form of the compound could then be determined. The procedure was applied to a variety of monoprotic and diprotic pharmaceutical compounds. The results were highly repeatable and had a good correlation to available published values. Data collected during the procedure provided good diagnostic information. Kinetic solubility data were also collected but provided a poor guide to the intrinsic solubility.     

TMT(5-巯基-1,3,4-噻二唑-2-硫代乙酸)的合成

TMT是一种重要的照相有机物中间体，可用于合成成色剂、防灰务剂、预灰化剂、稳定剂、增感剂、显影剂等方面，近年又广泛应用于医药、染料、农药等工业，本文介绍其合成方法。以二硫化碳、水合肼为原料，两步法合成5-巯基-1，3，4-噻二唑-2-硫代乙酸，该反应条件温和，操作简单，收率达到80％，适合工业化生产。并利用红外、质谱、液相色谱、元素分析对其进行了鉴定。     

Enhanced sample multiplexing for nitrotyrosine-modified proteins using combined precursor isotopic labeling and isobaric tagging

Current strategies for identification and quantification of 3-nitrotyrosine (3NT) post-translationally modified proteins (PTM) generally rely on biotin/avidin enrichment. Quantitative approaches have been demonstrated which employ isotopic labeling or isobaric tagging in order to quantify differences in the relative abundances of 3NT-modified proteins in two or potentially eight samples, respectively. Here, we present a novel strategy which uses combined precursor isotopic labeling and isobaric tagging (cPILOT) to increase the multiplexing capability of quantifying 3NT-modified proteins to 12 or 16 samples using commercially available tandem mass tags (TMT) or isobaric tags for relative and absolute quantification (iTRAQ), respectively. This strategy employs "light" and "heavy" labeled acetyl groups to block both N-termini and lysine residues of tryptic peptides. Next, 3NT is reduced to 3-aminotyrosine (3AT) using sodium dithionite followed by derivatization of light and heavy labeled 3AT-peptides with either TMT or iTRAQ multiplex reagents. We demonstrate the proof-of-principle utility of cPILOT with in vitro nitrated bovine serum albumin (BSA) and mouse splenic proteins using TMT(0), TMT(6), and iTRAQ(8) reagents and discuss limitations of the strategy.     

Top management Team's cognitive diversity and the Firm's ambidextrous innovation capability: The mediating role of ambivalent interpretation

The top management team (TMT) diversity has received considerable attention in literature, especially due to its influence on an organization's innovation strategy. While previous studies have considered diversity in terms of education, experience, skills, functionality, and gender, little is known about the TMT's cognitive diversity. We contribute to the literature by examining the influence of the TMT's cognitive diversity on an organization's ambidextrous innovation capability; i.e., its incremental and radical innovation capability. Results from 50 TMTs involved in the electronics industry support our hypothesized mediating role of ambivalent interpretation; that the TMT cogitative diversity positively influences ambivalent interpretation, and this, in turn, positively influences both radical and incremental innovation capability. These findings have important implications for how a firm's decision makers (i.e., the TMT) with their diverse cognitive styles support building the firm's ambidextrous capability through ambivalent interpretation.