Metal-ligand bifunctional catalysis for asymmetric hydrogenation

Chiral diphosphine/1,2-diamine-Ru(II) complexes catalyse the rapid, productive and enantioselective hydrogenation of simple ketones. The carbonyl-selective hydrogenation takes place via a non-classical metal-ligand bifunctional mechanism. The reduction of the C=O function occurs in the outer coordination sphere of an 18e trans-RuH2(diphosphine)(diamine) complex without interaction between the unsaturated moiety and the metallic centre. The Ru atom donates a hydride and the NH2 ligand delivers a proton through a pericyclic six-membered transition state, directly giving an alcoholic product without metal alkoxide formation. The enantiofaces of prochiral ketones are differentiated on the chiral molecular surface of the saturated RuH2 species. This asymmetric catalysis manifests the significance of 'kinetic' supramolecular chemistry.     

Gold nanoparticles quench fluorescence by phase induced radiative rate suppression

The fluorescence quantum yield of Cy5 molecules attached to gold nanoparticles via ssDNA spacers is measured for Cy5-nanoparticle distances between 2 and 16 nm. Different numbers of ssDNA per nanoparticle allow to fine-tune the distance. The change of the radiative and nonradiative molecular decay rates with distance is determined using time-resolved photoluminescence spectroscopy. Remarkably, the distance dependent quantum efficiency is almost exclusively governed by the radiative rate.     

On the development of colloidal nanoparticles towards multifunctional structures and their possible use for biological applications

In this Review, we describe the synthesis of high-quality colloidal nanoparticles in organic solvents, the mechanisms by which they can be transferred into aqueous solution, and some of their applications in biology. In particular, we will place emphasis on the creation of multifunctional nanoparticles or nanoparticle assemblies.     

基于轮廓合成的人耳图像边缘检测

人耳识别技术作为一种新的研究在生物特征识别领域提出一种新思路.边缘检测是图像特征分析识别的基础,检测质量直接影响系统识别率.本文针对人耳图像的局部特征和识别要求提出一种基于轮廓合成的边缘检测方法.该算法对采集到的图像预处理,将Sobel算子与阈值法得出的边缘图像合成,最后根据统计结果用去除干扰技术处理非边缘.这种方法得出的耳朵边缘图像清晰完整无干扰,比单一采用其他方法效果好,为后续特征提取及识别提供较好基础.     

Hot Deformation Behavior and Physically Based Constitutive Modeling of Low Activation Martensitic Steel

The hot-deformation behaviors of low activation martensitic steel were investigated in temperature range of 850-950 ℃ and strain rate range of 0.001-1 s^-1 by Gleeble-3500 thermal simulation machine. The constitutive equation was established and its predictive ability of flow behaviors was evaluated. Hot processing maps of low activation martensitic steel at different strains were established. The results show that the material exhibits the characteristics of dynamic recrystallization at higher deformation temperature and lower strain rate. The prediction results of constitutive equation are in good agreement with the experimental results. The optimal parameter combinations for hot processing at true strain of 0.4 and 0.6 are determined as the interval of temperature of 870-930 ℃ and strain rate of 0.001-0.01 s^-1, and the interval of temperature of 920-950 ℃ and strain rate of 0.3-0.1 s^-1, respectively.     

Forward-bias impedance of GaAs1-xPx LED's

The forward bias impedance characteristics of GaAs_1-xP_x LED's have been determined. In all cases, the equivalent parallel capacitance reaches a maximum and then either saturates (x = 0.4) or becomes negative at certain frequencies (x = 0.85 and x = 1). The current densities at which C_p maxima are reached are below typical values for display, multiplexing or optical emitters applications (i.e. J_F = 1 A/cm² for x = 0.85). It is suggested large series resistances for x = 0.4, and conductivity modulation effects for x > 0.4 are responsible for the above impedance behavior.     

A small domain (6.5 kDa) of bacterial protein G inhibits C3 covalent binding to the Fc region of IgG immune complexes

Attachment of the complement component C3 to antigen-antibody (Ag-Ab) complexes (immune complexes, IC) is the key molecular event responsible for the elimination of many Ag in the form of Ag-Ab-C3b. The CH1 domain and the Fc region of the Ab, which have previously been involved in the binding of C3b, are also the targets of several bacterial IgG-binding proteins, particularly proteins G and A. Here we describe the ability of a small recombinant protein G domain (B2; 6.5 kDa) to inhibit the covalent binding of C3b to the Fc portion of IgG without affecting the binding to the Fab part. Protein G (B2 domain) produced a remarkable inhibition of covalent binding of C3b to IC formed with rabbit IgG, but none with the F(ab')2 fragment, indicating that B2 interferes with the C3b binding to the Fc region. A weak inhibition was observed with IC formed with mouse IgG2b which preferentially binds B2 domain on the CH1 domain of the Fab. To confirm these data, recombinant single-chain Ab devoid of CH1 domains (scAb), and including the rabbit or human Fc portion (hinge-CH2-CH3), were produced and used to form IC. Protein G-B2 domain inhibited C3b binding to IC formed with scAb of either human or rabbit constant regions, supporting the view of a specific blockade of C3b binding to the Fc region. A similar inhibition of C3b binding was observed using protein A instead of protein G B2 domain and the same set of IC. On the CH1 domain, C3b and B2 bind on opposite faces, and therefore do not interfere with each other in their binding. However, B2 domain bound to the inter-CH2-CH3 region impedes the C3b binding to the Fc. This inhibition clarifies the specificity of C3b for the different regions of IgG and explains how bacterial IgG-binding proteins provide the bacteria with a mechanism of evasion from the opsonizing action of complement and contribute to the virulence. This could be a general mechanism of escape because protein G binds the majority of mammalian Ig.     

Sympathetic reflex dystrophy: an uncommon illness in childhood]

We measured activities of dynorphin-converting enzyme (DCE), substance P endopeptidase (SPE) and angiotensin-converting enzyme (ACE) in cerebrospinal fluid (CSF) in 13 patients with rhizopathic pain from an herniated lumbar disc, in 9 patients with pain from coxarthrosis and in 11 control patients without pain. In the patients with disc hernia and coxarthrosis, another sample of CSF was analyzed 3-12 months after treatment, when pain had subsided. The DCE activity in the patients was higher than that in both the control patients and the patients with pain from coxarthrosis (nociceptive pain). Similarly, the activity of SPE was lower in the patients with herniated lumbar disc than in controls and in the patients with coxarthrosis. After treatment, the difference in activity compared to controls was lower, but still significant in patients with herniated discs. The ACE activity did not differ from controls in patients with ischialgia, while it was increased in patients with coxarthrosis. This increase also remained after arthroplasty with pain relief. In conclusion, measurements of neuropeptides may be useful for evaluating neuropathic pain.