On Shear Rheology of Gel Propellants

Selected fuel, oxidizer and simulant gels were prepared and rheologically characterized using a rotational rheometer. For fuel gelation both organic and inorganic gellants were utilized, whereas oxidizers and simulants were gelled with addition of silica and polysaccharides, respectively. The generalized Herschel‐Bulkley constitutive model was found to most adequately represent the gels studied. Hydrazine‐based fuels, gelled with polysaccharides, were characterized as shear‐thinning pseudoplastic fluids with low shear yield stress, whereas inhibited red‐fuming nitric acid (IRFNA) and hydrogen peroxide oxidizers, gelled with silica, were characterized as yield thixotropic fluids with significant shear yield stress. Creep tests were conducted on two rheological types of gels with different gellant content and the results were fitted by Burgers‐Kelvin viscoelastic constitutive model. The effect of temperature on the rheological properties of gel propellant simulants was also investigated. A general rheological classification of gel propellants and simulants is proposed.     

Infinitesimal displacement analysis of a parallel manipulator with circular guide via the differentiation of constraint equations

This paper considers several subproblems associated with solving the forward and inverse position and speed problems and defining singular configurations for a parallel robot with six degrees of freedom and six kinematic chains that move along a circular guide (rotopod). The solution of these subproblems is necessary for analyzing the topological features of the parallel robot and employing the results of such analysis in control algorithms design.     

New Perspectives in Reducing Amyloid Aggregation and Toxicity

One of the fundamental biochemical characteristics of Alzheimer′s Disease (AD) is the intercellular accumulation of amyloid beta (Aβ) peptide plaques in the brain. Although there is not yet a cure for AD, major efforts have been made to identify antiamyloidogenic agents and therapeutic strategies to treat this disease and related conditions. Our group focuses on inhibiting the aggregation and toxicity of Aβ using two distinct approaches. The first involves covalently attaching the sequence-derived core amyloidogenic amino acid fragment KLVFF to the surfaces of serum albumin microspheres. These particles bind soluble Aβ with high affinity, inhibit its aggregation, reduce its toxicity, and decrease the inflammation induced by its aggregates. Microsphere-bound Aβ stimulates microglia and is phagocytosed via a different mechanism from that used for Aβ removal, so enabling its clearance even by defective cells. Our second approach utilizes self-assembled cyclic D,L-α-peptides as conformational mimics of the amyloid fibril architecture that inhibit the aggregation and cytotoxicity of Aβ. Here, we review these strategies and their mechanisms of action.     

低温液体储槽夹套下封头开裂原因分析

一台低温液体储槽使用了近8个月夹套下封头就发生开裂。设备返厂维修时，通过宏观检验、内简耐压试验、材质理化检验等分析，找出了封头开裂的主要原因是设备安装不合理，全部支座焊接固定，不能自由膨胀。     

一种验证电梯初装时测试的平衡系数的方法

电梯“溜梯”是指电梯在非电动运行的情况下,由于轿厢与对重之间的质量差造成曳引轮转矩超过制动力矩或者破坏曳引条件而引起轿厢上升或下降的现象。平衡系数的变化可能引起电梯“溜梯”事故。电梯在安装验收完成后,在使用中如果轿厢进行过度装饰或对重块发生变化,都会带来平衡系数的改变。因此,如何验证电梯初装时测试的平衡系数是否有效成了人们关注的一个问题。除了电梯自检记录和验收检验记录中测试的电流载荷曲线图可以为平衡系数的有效性提供证据之外,在本文中,笔者提出一种验证电梯初装时测试的平衡系数有效性的方法,与业界人士探讨。     

Effect of chloride salts on protein extraction and interfacial protein film formation in meat batters

Six comminuted chicken breast meat mixes and six meat batters were made with isoionic NaCl (25 g kg^?1), MgCl₂, CaCl₂, KCl, LiCl (IS = 0.43) and 15 g kg^?1 NaCl (IS = 0.26). The quantity and type of proteins extracted and used for interfacial protein film (IPF) formation was determined and related to batter stability. The monovalent salts produced IPF which differed in individual protein content between salts but which all contained significantly larger amounts of protein (P < 0.01) than those using divalent salts. MgCl₂ extracted more protein than CaCl₂ and produced a different protein profile in the IPF. However, MgCl₂ formed unstable raw batters whereas CaCl₂ did not. In addition, a simple, rapid method for extracting and quantifying proteins from meat batters was developed to assist in direct determination of the actual soluble protein uptake by the fat phase during comminution.     

SNAP-Tag-Targeted MRI-Fluorescent Multimodal Probes

Magnetic resonance imaging (MRI) is a powerful imaging modality, widely employed in research and clinical settings. However, MRI images suffer from low signals and a lack of target specificity. We aimed to develop a multimodal imaging probe to detect targeted cells by MRI and fluorescence microscopy. We synthesized a trifunctional imaging probe consisting of a SNAP-tag substrate for irreversible and specific labelling of cells, cyanine dyes for bright fluorescence, and a chelated Gd^III molecule for enhancing MRI contrast. Our probes exhibit specific and efficient labelling of genetically defined cells (expressing SNAP-tag at their membrane), bright fluorescence and MRI signal. Our synthetic approach provides a versatile platform for the production of multimodal imaging probes, particularly for light microscopy and MRI.     

Polyharmonic smoothing splines and the multidimensional Wiener filtering of fractal-like signals.

Motivated by the fractal-like behavior of natural images, we develop a smoothing technique that uses a regularization functional which is a fractional iterate of the Laplacian. This type of functional was initially introduced by Duchon for the approximation of nonuniformily sampled, multidimensional data. He proved that the general solution is a smoothing spline that is represented by a linear combination of radial basis functions (RBFs). Unfortunately, this is tedious to implement for images because of the poor conditioning of RBFs and their lack of decay. Here, we present a much more efficient method for the special case of a uniform grid. The key idea is to express Duchon's solution in a fractional polyharmonic B-spline basis that spans the same space as the RBFs. This allows us to derive an algorithm where the smoothing is performed by filtering in the Fourier domain. Next, we prove that the above smoothing spline can be optimally tuned to provide the MMSE estimation of a fractional Brownian field corrupted by white noise. This is a strong result that not only yields the best linear filter (Wiener solution), but also the optimal interpolation space, which is not bandlimited. It also suggests a way of using the noisy data to identify the optimal parameters (order of the spline and smoothing strength), which yields a fully automatic smoothing procedure. We evaluate the performance of our algorithm by comparing it against an oracle Wiener filter, which requires the knowledge of the true noiseless power spectrum of the signal. We find that our approach performs almost as well as the oracle solution over a wide range of conditions.