Spin coating behavior of polyimide precursor solutions

Experimental data confirm the utility of the following simple equation in predicting the spin coating behavior of polyimide precursor solutions: in which .     

Inhomogeneous Density in Die Compaction: Experiments and Finite-Element Calculations

X-ray density measurements and two-color powder displacement observations were used to determine the reliability of the cylindrical test cell as a source of data for a plasticity model of granular materials. Calculations with such a model agree well with the experimental density distribution, for the cylindrical test cell itself and for a cylindrical die, compacted from one side by means of a profiled plunger .     

Proline versus charge concept for protein stabilization against proteolytic attack

The virtue of the so-called ‘proline concept’ andthe ‘charge concept’ for stabilizing protease-susceptibleregions of a protein structure was compared on bovine pancreaticribonuclease A. Alanine 20 and serine 21, both of whichare located in a loop that is susceptible to the unspecificproteases subtilisin Carlsberg, subtilisin BPN', proteinaseK and elastase, were replaced with proline or lysine by site-directedmutagenesis. The rate constant of proteolysis was decreasedby up to three orders of magnitude for the proline mutants dependingon the site of the mutation and the protease used. In contrast,substitution by lysine increased the proteolytic resistanceby only one order of magnitude characterizing the ‘prolineconcept’ as superior to the ‘charge concept’.Although the four applied proteases are considered to be unspecific,the degree of stabilization of the ribonuclease molecule variedconsiderably, indicating the impact of individual differencesin their substrate specificity on the proteolytic resistanceand degradation pathway of the target protein. Received May 12, 2003; revised October 23, 2003; accepted October 30, 2003     

Protein design for non-aqueous solvents

Improving protein stability in unnatural and suboptimal environmentsis a promising application of protein engineering technology.Carefully designed amino acid alterations may lead to dramaticpositive effects on the stability of proteins under highly perturbingconditions, such as in non-aqueous solvents. Applications ofbiocatalysts and proteins with specific binding capabilitiesin the chemical industry have been severely limited by constraintsplaced on the solvent environment. With the advent of convenientmethods for altering the amino acid composition and even synthesizingentirely new protein molecules, it is worthwhile to considerengineering proteins for stability in non-aqueous solvents.In order to identify the features that a protein would needfor stability in organic media, we have been studying the structureand properties of the hydrophobic protein crambin. Crambin isunique in that it is soluble and stable in very high concentrationsof polar organic solvents. Crambin and its water-soluble homologsoffer a powerful demonstration of protein engineering for non-aqueoussolvents. This paper describes the structural features thatcontribute to crambin's special properties. Based on these observationsand consideration of how non-aqueous solvents affect the interactionsimportant in protein folding, a set of rules for designing non-aqueoussolvent-stable proteins is proposed.     

A corpus of Schlieren photography of speech production: potential methodology to study aerodynamics of labial,nasal and vocalic processes

Language Resources and Evaluation - This report presents a corpus of articulations recorded with Schlieren photography, a recording technique to visualize aeroflow dynamics for two purposes. First,...     

周志宏对魏氏组织及马氏体的形成和形貌的早期金相研究

关于铁合金中相变的详尽显微组织方面的早期研究之一是由艾伯特·苏佛教授的学生周志宏（哈佛大学博士，１９２８年）完成的。该项研究描述了铁碳合金中魏氏组织和马氏体的形成，所用合金具有宽的碳含量范围，热处理时采用的冷却速率范围也是宽的。还描述了一种独特的汞浴淬火方法。此研究工作从未完全发表过。本文援引该博士论文中的一些原始显微组织照片和部分原文，并试图用我们现今对于铁合金相变的理解来阐明和重新诠释。文中还包括中国引进现代工业和科学的历史背景，以及周志宏对苏佛教授的个人回忆。     

Convergence of generalized-$\boldsymbol{\alpha}$ time integration for nonlinear systems with stiff potential forces

Generalized-\(\alpha\) time integration schemes, originally developed for application in structural dynamics, are increasingly popular throughout many branches of multibody system simulation. Their simple implementation and the opportunity to control the numerical dissipation make them highly appealing for use in broad fields of application.Initially introduced for the solution of linear ordinary differential equations, there have been several extensions to nonlinear structural dynamics and constrained multibody systems in various formulations.In the present paper, we consider the application to systems with very stiff potential forces (singular singularly perturbed systems) whose solution approaches in the limit case that of a constrained system (index-3 differential–algebraic equation). We give a convergence analysis comparing the highly oscillatory solutions of the stiff system to those of the associated constrained one and show that the classical second order convergence result holds for position coordinates as well as for appropriately projected errors on the velocity level.The theoretical results are verified by numerical experiments for a simple test example.     

Static Strategies for Worksharing with Unrecoverable Interruptions

One has a large workload that is “divisible”—its constituent work’s granularity can be adjusted arbitrarily—and one has access to p remote worker computers that can assist in computing the workload. How can one best utilize the workers? Complicating this question is the fact that each worker is subject to interruptions (of known likelihood) that kill all work in progress on it. One wishes to orchestrate sharing the workload with the workers in a way that maximizes the expected amount of work completed. Strategies are presented for achieving this goal, by balancing the desire to checkpoint often—thereby decreasing the amount of vulnerable work at any point—vs. the desire to avoid the context-switching required to checkpoint. Schedules must also temper the desire to replicate work, because such replication diminishes the effective remote workforce. The current study demonstrates the accessibility of strategies that provably maximize the expected amount of work when there is only one worker (the case p=1) and, at least in an asymptotic sense, when there are two workers (the case p=2); but the study strongly suggests the intractability of exact maximization for p≥2 computers, as work replication on multiple workers joins checkpointing as a vehicle for decreasing the impact of work-killing interruptions. We respond to that challenge by developing efficient heuristics that employ both checkpointing and work replication as mechanisms for decreasing the impact of work-killing interruptions. The quality of these heuristics, in expected amount of work completed, is assessed through exhaustive simulations that use both idealized models and actual trace data.     

Error bounds for initial value problems by optimization

The computation of the error bounds for approximate solutions of initial value problems for ordinary differential equations has a long and successful history. This paper presents a new scheme to compute such bounds with uncertain initial conditions using preconditioned defect estimates and optimization techniques. These bounds are based on the newly developed concept of conditional differential inequalities. The scheme is implemented in MATLAB and AMPL. The resulting enclosures are compared with the packages VALENCIA-IVP, VNODE-LP and VSPODE for bounding solutions of ODEs. The current prototype uses heuristics to solve the global optimization subproblems. Hence the bounds obtained in the numerical experiments are not fully rigorous. The latter can be achieved by using rigorous global optimization and rounding error control, but the effect on the bounds is likely to be marginal only.