Metabolism of human insulin after subcutaneous administration: A possible means to uncover insulin misuse

The misuse of insulin for performance enhancement in sport or as toxic agent has frequently been reported in the past. In contrast to synthetic insulin analogues, the administration of recombinant human insulin is hardly recognized by mass spectrometry. The present study was designed to uncover the misuse of recombinant human insulin for doping control purposes as well as for forensic applications. It is hypothesized that an altered metabolite profile of circulating insulin prevails after subcutaneous administration due to exposure of insulin to epidermal proteases.     

Infrared thermographic evaluation of large composite grid parts subjected to axial loading

Many composite parts, such as laminated panels and grid-like shells, operate under high mechanical loading. Evaluation of their structural integrity is crucial to ensure the long-lasting operation of critical components. Since testing a structure under full or “proof” load might be dangerous for personnel, it would be preferable to use a remote, rapid inspection technique. This paper describes a practical application of IR thermography to the inspection of large composite parts used in the aerospace industry. This work has used just one cycle of increasing load from zero load to failure, and this was done for both for tensile and compressive loads. It is shown that, during the formation of micro-defects in polymeric composites, about 40 % of the total dissipated energy is expended for material heating, while about 60 % is related to material damage accompanied by an increase in the defect concentration. Non-uniform composite deformation causes temperature anomalies, whose amplitude may reach 1.5–2.5 °C at a load of about 50–60 % of the limit load.     

Dependency of dynamic interlaminar shear strength of composites on test technique used

Studies are presented on dependency of dynamic interlaminar shear (ILS) strength on the experimental technique used for a typical plain weave E-glass/epoxy composite. Dynamic ILS strength was determined based on two experimental techniques, namely torsional split Hopkinson bar (TSHB) apparatus using thin walled tubular specimens and compressive split Hopkinson pressure bar (SHPB) apparatus using single lap specimens. The results obtained from these techniques are compared. In general, it is observed that dynamic ILS strength for composites obtained by TSHB testing using thin walled tubular specimens is lower than the dynamic ILS strength obtained using single lap specimens in compressive SHPB. The issues involved in TSHB testing of thin walled tubular specimens made of composites are discussed and the reasons for reduced dynamic ILS strength using thin walled tubular specimens are highlighted. Finite element analysis (FEA) of thin walled tubular specimens made of composite and resin subjected to quasi-static torsional loading is presented. Using FEA results, the reasons for lower ILS strength of composite thin walled tubular specimens are substantiated.     

Micromechanical properties of one-step and sequentially crosslinked UHMWPEs for total joint replacements

Microindentation hardness testing was applied to five types of highly-crosslinked ultrahigh molecular weight polyethylenes (UHMWPEs) for total joint replacements. UHMWPE's were crosslinked using the same total radiation dose (75 kGy; γ-radiation) either by the standard, single-step irradiation (one-step crosslinking) or by the newer, several-step irradiation (sequential crosslinking). Each irradiation step was followed by thermal treatment (annealing at 110 °C or remelting at 150 °C) in an inert atmosphere. We showed that: (i) the micromechanical properties were determined by the last thermal treatment step, while the number of irradiation cycles was insignificant and (ii) the values of microhardness, microcreep and microplasticity from the microindentation experiments were in excellent agreement with the changes of UHMWPE structure, characterized by IR and DSC. Statistical evaluation of the results, the agreement with theoretical predictions and the comparison with previous studies on similar systems demonstrated that microindentation was a reliable and sensitive method of UHMWPE characterization.     

Fluorescence Polarization Based Nucleic Acid Testing for Rapid and Cost‐Effective Diagnosis of Infectious Disease

A new nucleic acid detection method was developed for a rapid and cost‐effective diagnosis of infectious disease. This approach relies on the three unique elements: 1) detection probes that regulate DNA polymerase activity in response to the complementary target DNA; 2) universal reporters conjugated with a single fluorophore; and 3) fluorescence polarization (FP) detection. As a proof‐of‐concept, the assay was used to detect and sub‐type Salmonella bacteria with sensitivities down to a single bacterium in less than three hours.     

New PP/PLA/cellulose composites: effect of cellulose functionalization on accelerated weathering behavior (accelerated weathering behavior of new PP/PLA/cellulose composites)

Polylactic acid (PLA) was used as partial replacement for conventional thermoplastic matrix, new composites comprising cellulose, polypropylene (PP), and PLA being realized. In order to obtain a compatible interface between cellulosic pulp and polymeric matrix, two chemical modifications of cellulose with stearoyl chloride and toluene di‐isocyanate (TDI) were performed, structural changes being evidenced by X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The composite materials were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, dynamic scanning calorimetry, impact, tensile and melt rheological tests, surface tension, and dynamic vapor sorption. Because promising results for impact strength and Young modulus were recorded when replacing 15% of PP with PLA in blends of PP with the same cellulosic pulp load, the aim of our study was to assess the behavior to accelerate weathering of composites comprising PP, cellulosic pulp, and PLA. Although the slight decrease in the mechanical properties was recorded after accelerated weathering, the use of functionalized cellulose successfully prevented the deterioration of surface materials, especially for composite comprising stearoyl chloride treated cellulose pulp. Copyright © 2015 John Wiley & Sons, Ltd.     

A centrally cracked thin circular disk, Part I: 3D Elastic–plastic finite element analysis

A full field solution, based on small deformation, three-dimensional elastic–plastic finite element analysis of the centrally cracked thin disk under mode I loading has been performed. The solution for the stresses under small-scale yielding and lo!cally fully plastic state has been compared with the HRR plane stress solution. At the outside of the 3D zone, within a distance of rσ_o/J=18, HRR dominance is maintained in the presence of a significant amount of compressive stress along the crack flanks. Ahead of this region, the HRR field overestimate the stresses. These results demonstrate a completely reversed state of stress in the near crack front compared to that in the plane strain case. The combined effect of geometry and finite thickness of the specimen on elastic–plastic crack tip stress field has been explored. To the best of our knowledge, such an attempt in the published literature has not been made yet. For the qualitative assessment of the results some of the field parameters have been compared to the available experimental results of K, gives a fair estimate of the crack opening stress near the crack front at a distance of order 10⁻² in. On the basis of this analysis, the Linear Elastic Fracture Mechanics approach has been adopted in analyzing the fatigue crack extension experiments performed in the disk (Part II).     

Constitutive equations for martensitic reorientation and detwinning in shape-memory alloys

A crystal-inelasticity-based constitutive model for martensitic reorientation and detwinning in shape-memory alloys (SMAs) has been developed from basic thermodynamics principles. The model has been implemented in a finite-element program by writing a user-material subroutine. We perform two sets of finite-element simulations to model the behavior of polycrystalline SMAs: (1) The full finite-element model where each finite element represents a collection of martensitic microstructures which originated from within an austenite single crystal, chosen from a set of crystal orientations that approximates the initial austentic crystallographic texture. The macroscopic stress-strain responses are calculated as volume averages over the entire aggregate: (2) The Taylor model (J. Inst. Metals 62 (1938) 32) where an integration point in a finite element represents a material point which consist of sets of martensitic microstructures which originated from within respective austenite single-crystals. Here the macroscopic stress-strain responses are calculated through a homogenization scheme.Experiments in tension and compression were conducted on textured polycrystalline Ti-Ni rod initially in the martensitic phase by Xie et al (Acta Mater. 46 (1998) 1989). The material parameters for the constitutive model were calibrated by fitting the tensile stress-strain response from a full finite-element calculation of a polycrystalline aggregate to the simple tension experiment. With the material parameters calibrated the predicted stress-strain curve for simple compression is in very good accord with the corresponding experiment. By comparing the simulated stress-strain response in simple tension and simple compression it is shown that the constitutive model is able to predict the observed tension-compression asymmetry exhibited by polycrystalline Ti-Ni to good accuracy. Furthermore, our calculations also show that the macroscopic stress-strain response depends strongly on the initial martensitic microstructure and crystallographic texture of the material.We also show that the Taylor model predicts the macroscopic stress-strain curves in simple tension and simple compression reasonably well. Therefore, it may be used as a relatively inexpensive computational tool for the design of components made from shape-memory materials.     

基于光学和扫描显微平台的微尺度实验力学检测技术和装置研究

本文基于光学和扫描显微平台,介绍了本研究组在微尺度实验力学检测技术和设备方面的最新研究成果。在检测技术方面涉及显微散斑干涉技术、微标记阵列检测技术、晶粒变形分析技术、光学探针动静态变形分析技术;在检测系统和装置方面介绍了新近开发的双视场薄膜检测系统、散斑微干涉系统、微标记检测平台、AFM和SEM单轴拉伸装置、三维微定位与加载系统、微力传感器及其标定装置、微动平台驱动装置等。探讨了微尺度实验力学检测中的问题和新的检测技术,给出了一些典型的应用和相关装置。     

A review of MEMS-based microscale and nanoscale tensile and bending testing

Thin films at the micrometer and submicrometer scales exhibit mechanical properties that are different than those of bulk polycrystals. Industrial application of these materials requires accurate mechanical characterization. Also, a fundamental understanding of the deformation processes at smaller length scales is required to exploit the size and interface effects to develop new and technologically attractive materials. Specimen fabrication, small-scale force and displacement generation, and high resolution in the measurements are generic challenges in microscale and nanoscale mechanical testing. In this paper, we review small-scale materials testing techniques with special focus on the application of microelectromechanical systems (MEMS). Small size and high force and displacement resolution make MEMS suitable for small-scale mechanical testing. We discuss the development of tensile and bending testing techniques using MEMS, along with the experimental results on nanoscale aluminum specimens.