Activating a zymogen without proteolytic processing: mutation of Lys15 and Asn194 activates trypsinogen

The zymogen and mature enzyme forms of trypsin-like serine proteases exhibit a wide range of activities. The prototypical trypsinogen-trypsin system is an example of a minimally active zymogen and a maximally active mature protease. The present work identifies several features of trypsinogen which govern its activity. Our results indicate that rat trypsin is 10(8)-fold more active than rat trypsinogen. Rat trypsinogen appears to be less active than bovine trypsinogen. His40 is believed to be an important determinant of zymogen activity. We are unable to verify this role for His40 in trypsinogen since the mutation of His40 to Phe appears to change the trypsin-substrate interface. Deletion of the N-terminal Ile16 from trypsin is expected to produce a trypsinogen-like protein since the Ile16-Asp194 salt bridge cannot form. Such mutants have higher activity and BPTI affinity than trypsinogen, which indicates that the activation peptide stabilizes the inactive trypsinogen conformation. The mutation of Lys15 to Ala increases the BPTI affinity and activity of trypsinogen to an even greater extent; thus, removal of Lys15 can account for the effect of the loss of the activation peptide. These results suggest that Lys15 is an important determinant of zymogen activity. The mutation of Asp194 to Asn also increases the BPTI affinity and activity of trypsinogen. This result suggests that in addition to stabilizing the active conformation of trypsin via the Ile16-Asp194 salt bridge, Asp194 also maintains the inactive conformation of trypsinogen. A correlation exists between the values of kcat/Km and BPTI affinity of mutant trypsinogens and trypsins. However, the slope of this correlation is 0.64, which indicates that different "active" conformations are involved in BPTI binding and substrate hydrolysis. DeltaI16V17 trypsinogen is the lone outlier; its BPTI affinity is higher than would be expected based on the value of kcat/Km. We show that the rate of BPTI association is slower for DeltaI16V17 trypsinogen than for a mutant trypsinogen with a similar BPTI affinity. This observation suggests that BPTI binds to an "active" trypsinogen conformation that is not kinetically accessible to substrates.     

An advanced computer code for single-tuned harmonic filter design

The objective of this paper is to present a novel approach for limiting harmonic and improving reactive compensation for industrial power systems using single-tuned filters. The unique feature of the developed power distribution model is that it incorporates both the filter capacity and resonant point as design parameters. The model also considers the detuning effects due to temperature and frequency variations, as well as manufacturing tolerances. The proposed approach was implemented as a PC-based computer code, and it was integrated with a user-friendly graphical user interface. The developed analysis tool was employed to solve the harmonic problems of several industrial plants, and the results all showed great improvements after using this computer tool     

Calculations of fracture criteria by classical mechanics I — Pellini's Duplex Rule

In a previous paper we presented a relaxation method to compute the elastic strain concentration of a crack. It was also shown, based on this method and in conjunction with the Rule of Sliding, that the plastic strain concentration curve can be calculated. In the current paper, we present the calculations of static load fracture using the relaxation method that we have previously proposed and the fracture criterion, f, of the second strength theory. Our results are in good agreement with those predicted by Pellini's Duplex Rule. We thus provide a theoretical basis for the Fracture Arrest Diagram of Pellini.     

The interactions between In-Sn solders and an electroless Ni-P deposit upon heat treatment

The interactions between In-Sn solders and an electroless Ni-P deposit within the multilayer combinations comprised of In-Sn/electroless Ni-P/Al were investigated with the aid of heat treatments at various temperatures and durations. The main reaction product was identified with X-ray diffractometry (XRD) as In₃Ni₂ regardless of the In-contents of the In-Sn solders. The formation of this In₃Ni₂ compound occurred through the diffusion of Ni towards the In-Sn solder. The intermetallic compound layer achieved its maximum thickness within 100 h upon heat treatment at 60 C; the thickness of the compound layer did not increase upon extending heat treatment. Sn tended to dissolve in the In₃Ni₂ compound.     

Formulating and solving a class of optimization problems for high-performance gray world automatic white balance

This paper provides new insights into methods performing automatic white balance for a digitally captured image. It is shown that automatic white balance may be formulated as an optimization problem with explicit definition of objective function, decision variables, and constraints. Three alternative methods of formulating the optimization problem are proposed. It is also shown that fuzzy inference rules, commonly utilized in existing literatures to evaluate to what degree an image satisfying the gray world assumption, may be incorporated into the objective function of the optimization problem. A two-stage adjustment law with constrained search direction is then proposed to update the decision variables. A gradient descent algorithm is employed to numerically solve the problem, which guarantees the convergence and that optimal white balance effort is achieved for most images. Experimental results and a comparative study justify that the proposed methods are preferable to existing methods with regard to the execution time, the algorithmic complexity, and the performance.     

WCDMA直放站数字下变频的FPGA实现

数字下变频器（Digital Down Converter,DDC）是WCDMA直放站的重要组成部分,它将高速采样的数字中频信号下变频到基带,然后进行抽取,低通滤波。重点研究了数字下变频器的数控振荡器NCO和半带滤波器的原理和硬件设计仿真,通过FPGA芯片Virtex-6 XC6VLX75T设计实现了适用于WCDMA直放站的数字下变频器,并对其进行硬件仿真与验证。     

Comparison of approaches based on optimization and algebraic iteration for binary tomography

Binary tomography represents a special category of tomographic problems, in which only two values are possible for the sought image pixels. The binary nature of the problems can potentially lead to a significant reduction in the number of view angles required for a satisfactory reconstruction, thusly enabling many interesting applications. However, the limited view angles result in a severely underdetermined system of equations, which is challenging to solve. Various approaches have been proposed to address such a challenge, and two categories of approaches include those based on optimization and those based on algebraic iteration. However, the relative strengths, limitations, and applicable ranges of these approaches have not been clearly defined in the past. Therefore, it is the main objective of this work to conduct a systematic comparison of approaches from each category. This comparison suggested that the approaches based on algebraic iteration offered both superior reconstruction fidelity and computation efficiency at low (two or three) view angles, and these advantages diminished at high view angles. Meanwhile, this work also investigated the application of regularization techniques, the selection of optimal regularization parameter, and the use of a local search technique for binary problems. We expect the results and conclusions reported in this work to provide valuable guidance for the design and development of algorithms for binary tomography problems.     

Side-effect localization for lazy, purely functional languages via aspects

Many side-effecting programming activities, such as profiling and tracing, can be formulated as crosscutting concerns and be framed as side-effecting aspects in the aspect-oriented programming paradigm. The benefit gained from this separation of concerns is particularly evident in purely functional programming, as adding such aspects using techniques such as monadification will generally lead to crosscutting changes. This paper presents an approach to provide side-effecting aspects for lazy purely functional languages in a user transparent fashion. We propose a simple yet direct state manipulation construct for developing side-effecting aspects and devise a systematic monadification scheme to translate the woven code to monadic style purely functional code. Furthermore, we present a static and dynamic semantics of the aspect programs and reason about the correctness of our monadification scheme with respect to them.     

采用职责链模式实现多语言系统的程序设计

国际通用的应用程序需要不同语言的软件界面.介绍一种采用职责链设计模式实现多语言系统程序设计的解决方案,并结合具体实例说明了实现该解决方案的过程.实践结果表明,这种方法开发周期短,应用程序所有的语言版本可以同时发布,减少了软件的升级和维护的工作量.