CVD diamond sensors for charged particle detection

CVD diamond material was used to build position-sensitive detectors for single-charged particles to be employed in high-intensity physics experiments. To obtain position information, metal contacts shaped as strips or pixels are applied to the detector surface for one- or two-dimensional coordinate measurement. Strip detectors 2×4 cm² in size with a strip distance of 50 μm were tested. Pixel detectors of various pixel sizes were bump bonded to electronics chips and investigated. A key issue for the use of these sensors in high intensity experiments is the radiation hardness. Several irradiation experiments were carried out with pions, protons and neutrons exceeding a fluence of 10¹⁵ particles/cm². The paper presents an overview of the results obtained with strip and pixel detectors in high-energy test beams and summarises the irradiation studies.     

Seismic response of box-type tunnels in soft soil: Experimental and numerical investigation

A series of dynamic centrifuge tests were carried out at the geotechnical centrifuge facility of IFSTTAR in Nantes, to investigate the response of box-type tunnels embedded in dry sand under sinusoidal and seismic excitation, as affected by soil-tunnel relative flexibility and soil-structure interface rugosity. The system under investigation was analyzed by means of full dynamic time history analyses, implementing rigorous finite element models. The numerical models were calibrated on the basis of back analysis of tests, while the numerical predictions were compared with experimental data, in terms of soil and tunnel horizontal acceleration, soil shear strains and tunnel deformations. The validated numerical models were then employed to further investigate several aspects of the system seismic response. Results indicate a rocking deformation mode coupled with the well-known racking distortion of box-type tunnels under seismic shaking. The effect of the soil-tunnel interface characteristics and soil yielding on the racking deformation of the tunnel, the dynamic earth pressures and shear stresses around the tunnel, as well as on dynamic lining forces is also reported. Soil yielding leads to post-shaking, residual, dynamic earth pressures, shear stresses and lining forces, especially in the case of flexible tunnels, while interface characteristics affect the distributions of these response parameters around the perimeter of the tunnel section. The ability of simplified seismic design methods for tunnels to predict the response is finally discussed, by comparing their predictions with the recorded data and the numerical results.     

Analysis of lateral earth pressure on a vertical circular shaft considering the 3D arching effect

The lateral earth pressure on a vertical circular shaft is investigated using both experiments and numerical analyses. The study focused on quantifying the magnitude and distribution of the lateral earth pressure, which was measured by considering the three-dimensional arching effect. A framework for determining distribution of the earth pressure based on centrifuge model tests and 2D FE analysis is introduced. The FE modelling techniques and the constitutive relationships of the soil are presented in detail. Parametric analyses showed that the arching effect on the lateral earth pressure is highly dependent on the diameter and height of the shaft, the internal friction angle and the cohesion value of the soil, the end-bearing conditions and the flexural modulus of the shaft. The study found that when the arching effect is considered, the lateral earth pressure on a vertical circular shaft is approximately 80% less than that calculated using Rankine’s theory. The study also found that the arching effect of the soil is more significant for flexible vertical shafts than for rigid vertical shafts embedded in weathered soil.     

Enhancing fiber/matrix bonding in polypropylene fiber reinforced cementitious composites by microbially induced calcite precipitation pre-treatment

In fiber reinforced cementitious composites (FRCC), bonding between the fibers and matrix governs many important properties, including strengths, fracture energy, ductility, and energy absorption capacities. This study explores the application of a microbiological process of microbially induced calcite precipitation (MICP) to pre-treating surface of polypropylene (PP) fibers for enhancing the interfacial boning strength. This technique utilizes MICP process to produce calcium carbonate that binds onto the fiber surface, leading to increased interfacial bond area and strength. Laboratory tests indicate that MICP modification could increase the post-cracking resistance and energy absorption capacity of the FRCC beam specimens by 58% and 69.3%, respectively. Microstructure analysis reveals that PP fibers after MICP treatment were coated with a layer of CaCO₃ with thickness around 20–50 μm depending on the degree of deposition. Results acknowledged a significant role of MICP pre-treatment in enhancing the fiber-matrix bonding properties of FRCC and the corresponding mechanical performance.     

Improvement of optical properties of Nd:YAG transparent ceramics by post-annealing and post hot isostatic pressing

The Nd:YAG transparent ceramics were fabricated by vacuum sintering. The Nd:YAG samples were annealed at 1450 °C for 20 h in air and followed by hot isostatic pressing (HIP) at 1700 °C for 2 h in 200 MPa Ar and then re-annealed at 1250–1450 °C for 10 h in air. The experimental results showed that the optical properties of Nd:YAG samples varied markedly with different post treatments. After air annealing at 1450 °C for 20 h and HIP at 1700 °C for 2 h under 200 MPa of Ar and then air re-annealing at 1250 °C for 10 h, the transmittances of the samples increased from 51.2% to 77.2% (at 400 nm) and 78.4% to 83.6% (at 1064 nm), respectively. The annealing and HIP are effective post treatments to reduce oxygen vacancies and intergranular pores respectively in Nd:YAG transparent ceramics.     

Advances in DNA typing in the agro-food supply chain

BackgroundDNA typing is increasingly being applied to assess the genetic origin and authenticity of products entering and exiting the food supply chain. The growing interest in DNA typing has arisen from an expanding array of contexts, such as the need to protect manufacturers, ensure compliance with food regulations, validate labels, fight misbranding, evaluate product ingredients and defend consumers' rights and freedom of choice.Scope and approachThis review presents current practices and emerging technologies about the genetic traceability in the agro-food chain, providing an overview of the specificity and challenges related to the analysis of commercial products of plant origin. We also discuss unsolved needs and specific features of DNA testing in the agro-food supply chain. These include the biochemical and physical variability of the samples under investigation, the possible DNA degradation, and the necessity to distinguish among plant varieties and not only different species.Key findings and conclusionsWe acknowledge that a number of DNA typing systems have been successfully used, and the vast majority are based on the PCR technique. Advances in next-generation sequencing technologies are expected to greatly expand data range and the amount of information accessible to a DNA analysis. The evaluation and implementation of novel technologies and tools, along with concerted efforts to increase information sharing and to establish standard operating protocols, are main priorities of genetic typing in the agro-food chain.     

On the adsorption of aliphatic alcohols on gold

The reversible adsorption of primary and secondary aliphatic alcohols from neutral solution on gold has been studied by measuring differential capacity vs potential curves. The calculated free energies of adsorption ΔG_ad increase with increasing length of the alcohol molecule. Their correlation with the results of studies of the anodic oxidation of the alcohols at the gold electrode in alkaline solution yields further support of the oxidation mechanism proposed earlier.     

全国辐射环境监测网络环境γ辐射剂量率测量比对

2013年12月,环境保护部辐射环境监测技术中心在四川省凉山彝族自治州组织了全国辐射监测网络的环境γ辐射剂量率和宇宙射线响应测量比对。共有32家成员单位的47台仪器设备参与了7个环境测点的比对测量,比对结果统一到γ空气吸收剂量率,采用Z比分数值分别对不同型号仪器的测量结果进行评价。比对结果显示,闪烁计数器测量数据的离散性较高压电离室大。除宇宙射线响应测点外,两类仪器的测量结果保持着较好的线性。     

选煤厂酸性煤泥水的处理工艺改造

马兰矿选煤厂的煤泥水呈酸性且泥化现象严重,现有处理工艺不能实现清水洗煤、闭路循环,为此对煤泥水的处理工艺进行了改造,实现了洗煤废水闭路循环,废水零排放,最终达到节约运行成本和保护环境的目的,改造后可节省药剂费用约为53万元/a.     

Effect of geosynthetic component characteristics on the potential for GCL internal erosion

Experiments quantifying GCL permittivity and the ultimate water head the GCLs can sustain before the initiation of internal erosion when underlain by a 50 mm angular to subangular gravel subgrade are conducted. The influence of different geotextiles over the subgrade, water heads, hydration periods before testing, masses per unit area of bentonite within the GCL, and ionic strengths of the solution (cation exchange) are considered. Test results show that GCL with the scrim-reinforced nonwoven geotextile over the subgrade has the best hydraulic performance against internal erosion, followed by the woven geotextile coated with a 110 g/m² polypropylene film. A woven or nonwoven is the least useful for preventing internal erosion, with the corresponding threshold water head initiating internal erosion >39 m for scrim-reinforced nonwoven, 21 m for lightly coated woven, 4–5 m for woven and nonwoven alone, respectively. Cation exchange, length of hydration, and mass per unit area of bentonite do not notably affect the threshold water head for the subgrade examined. Once internal erosion occurs, there is a 3-order of magnitude increase in permittivity. The practical implications are discussed.