Exceedingly Small Gadolinium Oxide Nanoparticles with Remarkable Relaxivities for Magnetic Resonance Imaging of Tumors

Gd chelates have occupied most of the market of magnetic resonance imaging (MRI) contrast agents for decades. However, there have been some problems (nephrotoxicity, non‐specificity, and low r₁) that limit their applications. Herein, a wet‐chemical method is proposed for facile synthesis of poly(acrylic acid) (PAA) stabilized exceedingly small gadolinium oxide nanoparticles (ES‐GON‐PAA) with an excellent water dispersibility and a size smaller than 2.0 nm, which is a powerful T₁‐weighted MRI contrast agent for diagnosis of diseases due to its remarkable relaxivities (r₁ = 70.2 ± 1.8 mM^?1 s^?1, and r₂/r₁ = 1.02 ± 0.03, at 1.5 T). The r₁ is much higher and the r₂/r₁ is lower than that of the commercial Gd chelates and reported gadolinium oxide nanoparticles (GONs). Further ES‐GON‐PAA is developed with conjugation of RGD2 (RGD dimer) (i.e., ES‐GON‐PAA@RGD2) for T₁‐weighted MRI of tumors that overexpress RGD receptors (i.e., integrin α_vβ₃). The maximum signal enhancement (ΔSNR) for T₁‐weighted MRI of tumors reaches up to 372 ± 56% at 2 h post‐injection of ES‐GON‐PAA@RGD2, which is much higher than commercial Gd‐chelates (<80%). Due to the high biocompatibility and high tumor accumulation, ES‐GON‐PAA@RGD2 with remarkable relaxivities is a promising and powerful T₁‐weighted MRI contrast agent.     

On the linear stability of eccentrically stiffened functionally graded annular spherical shell on elastic foundations

The study deals with the formulation of governing equations of eccentrically stiffened functionally graded materials annular spherical shells resting on elastic foundations and based upon the classical shell theory and the smeared stiffeners technique taking into account geometrical nonlinearity in Von Karman-Donnell sense. The annular spherical shells are reinforced by eccentrically longitudinal and transversal stiffeners made of full metal or full ceramic depending on situation of stiffeners at metal-rich side or ceramic-rich side of the shell respectively. Approximate solutions are assumed to satisfy the simply supported boundary condition and Galerkin method is applied to obtain closed-form relations of bifurcation type of buckling loads. Numerical results are given to evaluate effects of inhomogeneous, dimensional parameters, outside stiffeners and elastic foundations to the buckling of structures.     

Tunable Ferromagnetism and Thermally Induced Spin Flip in Vanadium-Doped Tungsten Diselenide Monolayers at Room Temperature

The outstanding optoelectronic and valleytronic properties of transition metal dichalcogenides (TMDs) have triggered intense research efforts by the scientific community. An alternative to induce long-range ferromagnetism (FM) in TMDs is by introducing magnetic dopants to form a dilute magnetic semiconductor. Enhancing ferromagnetism in these semiconductors not only represents a key step toward modern TMD-based spintronics, but also enables exploration of new and exciting dimensionality-driven magnetic phenomena. To this end, tunable ferromagnetism at room temperature and a thermally induced spin flip (TISF) in monolayers of V-doped WSe₂ are shown. As vanadium concentration increases, the saturation magnetization increases, which is optimal at ≈4 at% vanadium; the highest doping level ever achieved for V-doped WSe₂ monolayers. The TISF occurs at ≈175 K and becomes more pronounced upon increasing the temperature toward room temperature. The TISF can be manipulated by changing the vanadium concentration. The TISF is attributed to the magnetic-field- and temperature-dependent flipping of the nearest W-site magnetic moments that are antiferromagnetically coupled to the V magnetic moments in the ground state. This is fully supported by a recent spin-polarized density functional theory study. The findings pave the way for the development of novel spintronic and valleytronic nanodevices and stimulate further research.     

非自由场地的动力沉降估计

重点研究了地层成层性对非自由场动力沉降的影响。为了简化分析上部结构对于地层的附加作用，引入了动力锥传力机制，建立了非均质地基模型。根据地基或结构变形与沉降的不同成因，在总结自由场地研究成果的基础上，将建筑物非均质地基地震荷载或其他动力荷载引起的动力沉降分解为以下几部分：循环剪切荷载导致的土壤体积压缩；上部结构的反射或散射的动力剪切荷载引起的附加沉降；地基土壤动力非线性过程中由于材料的刚度退化引起的变形等沉降。以砂土地基为例，给出了求解的过程和步骤。     

矩形箍筋对钢筋混凝土短柱承载力提高的分析

建立了钢筋混凝土轴心受压短柱非线性有限元模型 ,分析了含箍特征值 λv 和箍筋间距 s对矩形箍筋柱的受压承载力的影响 ,得到了柱的受压承载力的提高随不同强度的混凝土、不同λv的箍筋的变化规律     

Enteric pathogens in flood-related waters in urban areas of the Vietnamese Mekong Delta: a case study of Ninh Kieu district,Can Tho city

ABSTRACT

This paper investigates the contamination of floodwaters in the urban center of Can Tho city, Vietnam. We sampled water from sewers, surface water bodies, and flood, before, during, and after specific flooding events. Total nucleic acid was extracted from the samples and subjected to a quantitative polymerase chain reaction (qPCR) to detect specific enteric pathogens. The difference between pathogen concentrations in floodwater and sewer water was compared by using the Mann Whitney U test. Correlations between the different pathogens were determined using the non-parametric Spearman test. E. coli and Rotavirus-A were the most prevalent pathogens in floodwater. We observed a weak association between E. coli and Rotavirus in flood-related waters (r < 0.5). Floodwater quality showed no difference to sewer water quality in terms of the E. coli and Rotavirus A concentrations (p > 0.05). Our results indicate that floodwater poses a significant urban public health risk due to the presence of enteric pathogens.     

New generation photon-counting cameras: algol and CPNG

Algol and Comptage de Photons Nouvelle Génération (CPNG) are new generation photon counting cameras developed for high angular resolution in the visible by means of optical aperture synthesis and speckle interferometry and for photon noise limited fast imaging of biological targets. They are intensified CCDs. They have been built to benefit from improvements in photonic commercial components, sensitivity, and personal computer workstations processing power. We present how we achieve optimal performances (sensitivity and spatiotemporal resolution) by the combination of proper optical and electronics design, and real-time elaborated data processing. The number of pixels is 532 x 516 and 1024(2) read at a frame rate of 262 and 100 Hz for CPNG and Algol, respectively. The dark current is very low: 5.5 x 10(-4) e(-) .pixel(-1). s(-1). The saturation flux is approximately 7 photon events /pixel/s. Quantum efficiencies reach up to 36% and 26% in the visible with the GaAsP photocathodes and in the red with the GaAs ones, respectively, thanks to the sensitivity of the photocathodes and to the photon centroiding algorithm; they are likely the highest values reported for intensified CCDs.     

New Raman spectrometer using a digital micromirror device and a photomultiplier tube detector for rapid on-line industrial analysis. Part II: Choice of analytical methods

In this paper, the performances of four improved analytical methods (backward stepwise selection of peak intensities, sum of characteristic peaks of a component, moving window partial least squares, and genetic algorithms) using wavelength selection for the analysis of xylene mixtures by Raman spectroscopy are tested for further use on the new "digital micromirror device associated with a photomultiplier tube" Raman spectrometer. It is shown that the errors of prediction using only a few selected points (from 4 to 49 depending on the method) are almost the same as when using the whole spectral range (1050 points). Compared to the last two methods, the "backward stepwise selection of peak intensities" and "sum of characteristic peaks of a component" methods are robust under industrial conditions and appear to be well suited for chemical quantitative analysis with the new Raman spectrometer, which allows the measurements of the total intensity to be made simultaneously for a number of pre-selected frequencies. Results show that the errors of prediction can be near to or even lower than 2%.     

The effect of graphite addition on the mechanical and tribological properties of pitch-based granular carbon composites

The present work deals with the effect of graphite addition on selected mechanical and tribological properties of pitch-based granular carbon composites. Three pitches (a commercial impregnating coal tar pitch, an air-blown pitch and a thermally treated coal tar pitch) and anthracite particles as reinforcing material were used to prepare carbon composites to be tested as carbon brake pads. These carbon composites show good compression strength (from 25.8 to 94.2 MPa) but unstable and high friction coefficients (>0.5). Experimental results have showed that small amounts of graphite addition (2.5 and 5.0 wt%) lead to carbon materials with more stable and lower friction coefficient (<0.3). So, graphite addition promoted the reduction in the wear rate. Finally, compressive strength of carbon composites prepared with modified pitches significantly increases after addition of small amounts of graphite with values from 94 to 128.8 MPa.