Preparation of composite tubular grafts for vascular repair via electrospinning

A novel type of composite vascular graft was developed via electrospinning in the present investigation.Collagen and chitosan were blended to form the inner and outer layer.Poly(1-lactide-co-caprolacto...     

High reproducibility and sensitivity of bifacial copper nanowire array for detection of glucose

The ordered bifacial copper nanowire array (Cu BNWA) was synthesized by a template assisted electrochemical deposition method. The morphology and structure of the as-prepared samples were investigated by field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). The results show that the ordered Cu nanowire array with uniform geometrical dimensions covered both side of the Cu substrate. When used as the electrode for glucose detection, the minimum detectable concentration of glucose can be reached as low as 0.2 mM. Impressively, the sample still showed high sensitivity and stability for glucose detection after two months placement in ambient environment. These excellent performances of the Cu BNWA make it a promising non-enzyme glucose detection sensor for various applications.     

Influence of semisolid forging ratio on the microstructure and mechanical properties of Ti14 alloy

The present work is focused on the microstructure and mechanical properties of Ti14 alloy with different semisolid deformation ratios during forging tests. The results revealed that the forging ratio had a significant effect on the precipitation of the alloy. Fewer plate-shaped Ti₂Cu tended to precipitate on grain boundaries with higher forging ratios, and finally the plate-shaped Ti₂Cu formed precipitate-free zones along grain boundaries with a forging ratio of 75%. The precipitation on grain boundaries was found to be controlled by a peritectic reaction. Large forging ratios accelerated the extrusion of liquid and resulted in less liquid along the prior grain boundaries, which reduced the peritectic precipitation in this region and formed precipitate-free zones during re-solidification. In addition, increasing the forging ratio could accelerate dynamic recrystallization, which is favorable for improving the semisolid formability. The tensile ductility increased with increasing forging ratio, and a mixed fracture mode, involving both cleavage and dimple fracture, was observed after forging with a forging ratio of 75%, which is attributed to the presence of precipitate-free zones formed along grain boundaries during semisolid processing.     

Multi-genetic events collaboratively contribute to Pten-null leukaemia stem-cell formation

Cancer stem cells, which share many common properties and regulatory machineries with normal stem cells, have recently been proposed to be responsible for tumorigenesis and to contribute to cancer resistance. The main challenges in cancer biology are to identify cancer stem cells and to define the molecular events required for transforming normal cells to cancer stem cells. Here we show that Pten deletion in mouse haematopoietic stem cells leads to a myeloproliferative disorder, followed by acute T-lymphoblastic leukaemia (T-ALL). Self-renewable leukaemia stem cells (LSCs) are enriched in the c-Kit(mid)CD3(+)Lin(-) compartment, where unphosphorylated beta-catenin is significantly increased. Conditional ablation of one allele of the beta-catenin gene substantially decreases the incidence and delays the occurrence of T-ALL caused by Pten loss, indicating that activation of the beta-catenin pathway may contribute to the formation or expansion of the LSC population. Moreover, a recurring chromosomal translocation, T(14;15), results in aberrant overexpression of the c-myc oncogene in c-Kit(mid)CD3(+)Lin(-) LSCs and CD3(+) leukaemic blasts, recapitulating a subset of human T-ALL. No alterations in Notch1 signalling are detected in this model, suggesting that Pten inactivation and c-myc overexpression may substitute functionally for Notch1 abnormalities, leading to T-ALL development. Our study indicates that multiple genetic or molecular alterations contribute cooperatively to LSC transformation.     

Neural network approach for modification and fitting of digitized data in reverse engineering

Reverse engineering in the manufacturing field is a process in which the digitized data are obtained from an existing object model or a part of it, and then the CAD model is reconstructed. This paper presents an RBF neural network approach to modify and fit the digitized data. The centers for the RBF are selected by using the orthogonal least squares learning algorithm. A mathematically known surface is used for generating a number of samples for training the networks. The trained networks then generated a number of new points which were compared with the calculating points from the equations. Moreover, a series of practice digitizing curves are used to test the approach. The results showed that this approach is effective in modifying and fitting digitized data and generating data points to reconstruct the surface model.     

Experimental demonstration of five-photon entanglement and open-destination teleportation

Quantum-mechanical entanglement of three or four particles has been achieved experimentally, and has been used to demonstrate the extreme contradiction between quantum mechanics and local realism. However, the realization of five-particle entanglement remains an experimental challenge. The ability to manipulate the entanglement of five or more particles is required for universal quantum error correction. Another key process in distributed quantum information processing, similar to encoding and decoding, is a teleportation protocol that we term 'open-destination' teleportation. An unknown quantum state of a single particle is teleported onto a superposition of N particles; at a later stage, this teleported state can be read out (for further applications) at any of the N particles, by a projection measurement on the remaining particles. Here we report a proof-of-principle demonstration of five-photon entanglement and open-destination teleportation (for N = 3). In the experiment, we use two entangled photon pairs to generate a four-photon entangled state, which is then combined with a single-photon state. Our experimental methods can be used for investigations of measurement-based quantum computation and multi-party quantum communication.     

Influence of isothermal aging on σ precipitation in super duplex stainless steel

The time-temperature-transformation (TTT) curve of the 00Cr25Ni7Mo4N duplex stainless steel was obtained with a Formastor-digital thermal dilatometer, and the influence of isothermal aging on σ precipitation was studied by metallographic observation, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results show that the decomposition of ferrite phase is accompanied by the formation of σ phase at 750–1000℃, especially in the range of 800–900℃. The longer the aging time, the higher the amount of σ precipitation. The area fraction of various phases remains at a certain value upon the completion of ferrite deformation. The temperature of 850℃ is the most sensitive transaction temperature, the incubation time for the formation of σ precipitation is less than 1 min, and aging for 20 min leads to the complete transformation of ferrite. The σ phase is formed preferentially at the α/α/γ junction, and then grows along the α/α boundary in the matrix.     

The structural basis for autonomous dimerization of the pre-T-cell antigen receptor

The pre-T-cell antigen receptor (pre-TCR), expressed by immature thymocytes, has a pivotal role in early T-cell development, including TCR β-selection, survival and proliferation of CD4(-)CD8(-) double-negative thymocytes, and subsequent αβ T-cell lineage differentiation. Whereas αβTCR ligation by the peptide-loaded major histocompatibility complex initiates T-cell signalling, pre-TCR-induced signalling occurs by means of a ligand-independent dimerization event. The pre-TCR comprises an invariant α-chain (pre-Tα) that pairs with any TCR β-chain (TCRβ) following successful TCR β-gene rearrangement. Here we provide the basis of pre-Tα-TCRβ assembly and pre-TCR dimerization. The pre-Tα chain comprised a single immunoglobulin-like domain that is structurally distinct from the constant (C) domain of the TCR α-chain; nevertheless, the mode of association between pre-Tα and TCRβ mirrored that mediated by the Cα-Cβ domains of the αβTCR. The pre-TCR had a propensity to dimerize in solution, and the molecular envelope of the pre-TCR dimer correlated well with the observed head-to-tail pre-TCR dimer. This mode of pre-TCR dimerization enabled the pre-Tα domain to interact with the variable (V) β domain through residues that are highly conserved across the Vβ and joining (J) β gene families, thus mimicking the interactions at the core of the αβTCR's Vα-Vβ interface. Disruption of this pre-Tα-Vβ dimer interface abrogated pre-TCR dimerization in solution and impaired pre-TCR expression on the cell surface. Accordingly, we provide a mechanism of pre-TCR self-association that allows the pre-Tα chain to simultaneously 'sample' the correct folding of both the V and C domains of any TCR β-chain, regardless of its ultimate specificity, which represents a critical checkpoint in T-cell development. This unusual dual-chaperone-like sensing function of pre-Tα represents a unique mechanism in nature whereby developmental quality control regulates the expression and signalling of an integral membrane receptor complex.     

铜川贫煤中氮赋存形态的红外光谱研究

目的 研究煤中氮的有机形态及煤转化利用过程中含氮污染物排放规律。方法 利用红外光谱法对铜川原煤及其干燥后的煤样进行了分析。结果 得到不同工况下煤样的FTIR谱图。3040cm^-1附近的吸收峰是煤中羟基与吡啶环上N原子形成的氢键振动，对比干燥前后煤样的红外谱图，发现吡咯环上N与H形成的氢键在3400cm^-1附近引起中强峰；同时，芳族伯胺基团、腈类物质中C≡N键也可以利用红外谱图检测到。结论 铜川贫煤中氮元素主要以吡啶、吡咯及氨基的形式存在，并存在腈类C≡N键的结构形式。