Catalytic constants enable the emergence of bistability in dual phosphorylation

Dual phosphorylation of proteins is a principal component of intracellular signalling. Bistability is considered an important property of such systems and its origin is not yet completely understood. Theoretical studies have established parameter values for multistationarity and bistability for many types of proteins. However, up to now no formal criterion linking multistationarity and bistability to the parameter values characterizing dual phosphorylation has been established. Deciding whether an unclassified protein has the capacity for bistability, therefore requires careful numerical studies. Here, we present two general algebraic conditions in the form of inequalities. The first employs the catalytic constants, and if satisfied guarantees multistationarity (and hence the potential for bistability). The second involves the catalytic and Michaelis constants, and if satisfied guarantees uniqueness of steady states (and hence absence of bistability). Our method also allows for the direct computation of the total concentration values such that multistationarity occurs. Applying our results yields insights into the emergence of bistability in the ERK–MEK–MKP system that previously required a delicate numerical effort. Our algebraic conditions present a practical way to determine the capacity for bistability and hence will be a useful tool for examining the origin of bistability in many models containing dual phosphorylation.     

Proton Conductivity in Solid Solution 0.7(CaWO4)–0.3(La0.99Ca0.01NbO4) and Ca(1−x)LaxW(1−y)TayO4

The conductivity of nominal CaWO₄, CaW_0.99Ta_0.01O_4–δ, 0.7(CaWO₄)–0.3(La_0.99Ca_0.01NbO_4–δ), and Ca_0.9La_0.1WO_4+δ has been studied by means of a.c. impedance measurements. Proton conductivity was observed for CaW_0.99Ta_0.01O_4–δ, which displayed exothermic hydration with enthalpy and entropy of –82 kJ/mol and –120 J/molK, respectively. The proton mobility in CaW_0.99Ta_0.01O_4–δ was low, with enthalpy and preexponential factor of mobility of 82 kJ/mol and 0.7 cm²K/Vs. The high enthalpy of mobility is interpreted to reflect association between the acceptor dopant and protonic defects, whereas the low preexponential factor of mobility may reflect a lower proton concentration than assumed. Rietveld refinement indicated low solubilities of La on Ca‐site and Ta on W‐site. Proton conductivity was also observed in undoped CaWO₄, however, not in Ca_0.9La_0.1WO_4+δ. The conductivity of 0.7(CaWO₄)–0.3(La_0.99Ca_0.01NbO_4–δ) behaved much like that of undoped LaNbO₄, likely due to a very low acceptor dopant concentration.     

宁要模糊的正确，不要明确的错误：石油勘探和开采行业的新决策方法

本文讨论了运用整体综合方法评价不确定性对油气投资决策影响的必要性。我们认为，仅对于投资决策评价各种要素的综合性常规精确模型增添处理不确定性的功能，是不能有效达到上述目的的。此外我们还认为，这种方法即使是可行的，也并不是人们所期望的。因此我们提出了在决策支持系统中引入整体和概率评价方法的概念。这种整体分析方法有两种要素。一种是技术要素，它综合了各种评价和决策工具。另一种是模拟思路要素，它全面考虑了不确定性的广度和规模。为了更全面、准确和严格地评价不确定性对投资决策过程的影响，这种方法要牺牲一部分技术精度和细节。这种系统的基本组成主要有各领域的简化要素模型、蒙特卡罗模拟工具以及模拟语言，可用于满足用户的特殊要求、综合不同要素之间的相互依赖关系、执行决策逻辑以及作为学习结果更新信息。文中说明了这种系统如何识别哪种不确定性对决策影响最大、如何评价信息采集（数据、技术分析）的价值以及如何在缓解和／或利用不确定性的下一步计划中促进灵活性。其他应用还有优化开发情景、评价真实的选择情景以及为投资组合分析的输入数据生成统一的风险现金流。这种系统的应用已通过其综合技术决策和经营决策的能力，使多学科资产管理团队的工作实现了真正的以价值驱动为重点。     

High-Temperature Proton Conductivity in Acceptor-Substituted Rare-Earth Ortho-Tantalates, LnTaO4

The electrical properties of 1 mol% Ca-doped LnTaO₄ (Ln=La, Nd, Gd, Er) have been characterized by AC impedance spectroscopy and by the EMF transport number technique as a function of the oxygen pressure and the water vapor pressure from 300° to 1200°C. Protons, oxide ions, electron holes, and electrons contribute to the total conductivity, depending on the conditions. Ionic conductivity predominates under reducing and weakly reducing conditions, with protons prevailing in wet atmospheres up to temperatures of around 1000°C. p -type electronic conductivity prevails at high temperatures under oxidizing conditions. The conductivity behavior has been interpreted according to a point-defect model where protons and oxygen vacancies charge compensate the acceptor doping. Thermodynamic and transport parameters have been extracted based on the changes in total conductivity upon variations in the conditions. The hydration enthalpy becomes increasingly negative with increasing oxide ion density from LaTaO₄ to ErTaO₄.     

Comparison of composition, enzyme activity and selected functional properties of potato proteins isolated from potato juice with two different expanded bed resins

Protein concentrates prepared by expanded bed adsorption (EBA) chromatography from industrial potato juice (PJ) were analysed for chemical composition, color, enzyme activities, thermal properties and selected functional properties (solubility and emulsifying stability). Two EBA multi-modal resins, MIMO I-45 and MIMO 1300 (UpFront Chromatography), were employed under various pH conditions resulting in four potato protein concentrates, A-D. Concentrate B contained an electrophoretically pure protease inhibitor fraction (20-21 kDa), whereas concentrate A, C and D contained both patatin (41 kDa) and protease inhibitors. The potato protein concentrates were explored for the presence of transitions from native to denatured states using differential scanning calorimetry (DSC). Concentrate C had lower heat of transition (ΔH) and T-onset than the other concentrates. The concentrate containing protease inhibitors exhibited the highest denaturation temperature and enthalpy. All concentrates differed significantly (P < 0.05) in color brightness, with concentrate B and D emerging as the brightest. The solubility of the concentrates was evaluated at pH 6 and pH 4.5. All concentrates had lower solubility at pH 4.5 than at pH 6 (70-80%). The stability of emulsions (1% protein, 20% oil, 0.08% xanthan gum) against creaming was analysed with a new method based on the Single electrode Capacitance Probe (SeCaP) technology. Small differences among concentrates were observed by the new SeCaP method.     

Untersuchung über den Durchschlag und die Vorgänge bei elektrischer Beanspruchung in Isolierölen verschiedener Festigkeit

Zusammenfassung Die vorliegende Untersuchung befaßt sich mit dem Verhalten eines Isolieröles in den Festigkeitsgrenzen von 25 bis 245 kV/cm bei elektrischer Beanspruchung durch Gleich- und Wechselspannung. Das Isolieröl wird zwischen Plattenelektroden in zwei zueinander senkrechten Richtungen auf Durchschlag und Stromdurchgang geprüft.Bei Beobachtung der Vorgänge in dem elektrisch beanspruchten Isolieröl mit einer Festigkeit von 50 bis 180 kV/cm durch optische Vergrößerung kann neben bereits bekannten Vorgängen zwischen den Elektroden im abgedunkelten Raum deutlich ein Glimmen beobachtet werden, das den Öldurchschlag einleitet. Dieses Glimmen wird zurückgeführt auf Ionisation in adsorbierten Luftbläschen und in mit Luft gefüllten Hohlräumen der im Öl schwimmenden Fasern.Es ergibt sich aber auch für dieses Öl bei einer Festigkeit von 50 bis 180 kV/cm ein Unterschied in der Höhe der Durchschlagsspannung zwischen senkrechter und waagerechter Beanspruchung, während diese Unterschiede im Öl unterhalb und oberhalb dieser Festigkeitsgrenzen nicht festgestellt werden können. Analoge Beziehungen gelten auch für die mit der Schering-Brücke ermittelten Werte für die Stromaufnahme. Der größte Unterschied zeigt sich bei einer Durchbruchfeldstärke des Öles von 120 kV/cm, wo die Durchschlagsspannung bei waagerechter Beanspruchungsrichtung um 18 bis 20% über der Durchschlagsspannung in senkrechter Beanspruchungsrichtung liegt. Die Stromaufnahme in senkrechter Beanspruchungsrichtung ist dagegen bei Öl von 120 kV/cm um etwa 50% größer als in waagerechter Beanspruchungsrichtung. Die festgestellten Unterschiede zwischen senkrechter und waagerechter Beanspruchungsrichtung werden auf Wärmeentwicklung im Öl, die durch das beobachtete Glimmen verursacht werden, zurückgeführt. Damit findet die Theorie des verschleierten Gasdurchschlages eine Bestätigung für das untersuchte Isolieröl mit einer Festigkeit von 50 bis 180 kV/cm. In Öl unterhalb der Festigkeitsgrenze von 50 kV/cm scheinen die Theorie des reinen Faserdurchschlags und oberhalb einer Festigkeit von 180 kV/cm die Theorie des reinen Ionisationsvorganges ausschlaggebend zu sein. Die drei Gebiete des reinen Faserdurchschlages, des verschleierten Gasdurchschlages und des Ionisationsvorganges sind jedoch nicht streng gegeneinander abzugrenzen, sondern überlagern sich je nach der Festigkeit des untersuchten Öles.     

Freezing patterns in quench frozen,freeze-dried polyvinylpyrrolidone (PVP)

An SEM investigation of the effects of freezing and freeze-drying on 2 mm diameter columns as well as on 10 mm diameter thick discs of PVP was carried out using standard techniques of quench freezing and cryofracturing followed by freeze-drying. Quench freezing in liquid Freon 12 or liquid propane led to patterns of ice formation that depended on the position in the sample, the orientation of the fracture plane observed relative to the geometry of the sample and the concentration of PVP. Vitrification did not occur. Quench freezing in liquid N₂ resulted in larger ice crystals and the pattern of the crystals was much less predictable.     

An ultrastructural study of cryofractured myocardial cells with special attention to the relationship between mitochondria and sarcoplasmic reticulum

A comparative study of various cryofracturing techniques has been conducted on the mammallian myocardial cell. Quench freezing of fresh or fixed tissue in melting Freon 22 resulted in severe cellular damage due to ice crystallization. Fixation with Karnovsky's fixative prior to quenching had no modifying effect on the size and distribution of the ice crystals. The crystals were orientated primarily in the direction of the long axis of the myofibrils, manifested as empty tube-like structures in the scanning electron microscope (SEM). Regular cross-bridging often seen at the Z-band levels indicated that ice crystals, at least in some portions of the cells, were confined within the sarcomere. Within the same cell the size of the ice crystals could vary considerably. Treatment of the tissue with polyvinylpyrrolidone (PVP) prior to rapid freezing had no noticeable cryoprotective effect. The surface of the thin layer of PVP surrounding the freeze dried tissue appeared amorphous in the SEM. However, the first evidence of ice crystallization was found a few micrometres under the surface. The freezing artefacts were completely circumvented if the cryofracturing was carried out on ethanol-impregnated or on critical point dried material. While the first method resulted in a smooth fracture plane passing through the cell structures, the intracellular fracture plane of the critical point dried material followed the surface of the cell organelles. Separation of the cell organelles caused by freezing or by critical point drying revealed thread-like structures extending from the mitochondrial surface. Re-examination of SEM-processed material in the transmission electron microscope (TEM) revealed that these structures were part of the sarcoplasmic reticulum (SR), and that a close contact between the SR and the outer mitochondrial membrane existed. TEM of conventional prepared material revealed that strands of electron-dense material, here named ‘mito-reticular junctional fibres’, bridged the narrow gap between the mitochondrial surface and the SR. It is suggested that these fibres have a specific anchoring function.     

Impact of noise and nonlinear distortion due to clipping on the BERperformance of a 64-QAM signal in hybrid AM-VSB/QAM optical fibertransmission system

Experimental BER measurements of a 64-QAM signal in a hybrid AM-VSB/QAM optical fiber transmission system are shown to be in good agreement with a corrected and reinterpreted theory of impulsive and Gaussian noise based on Middleton's class B impulsive noise model. Fiber dispersion induced distortion of the chirped laser output is also shown to adversely affect the QAM signal