Simultaneous Spectrophotometric Determination of 2-Thiouracil and 2-Mercaptobenzimidazole in Animal Tissue Using Multivariate Calibration Methods: Concerns and Rapid Methods for Detection

ABSTRACT: Two multivariate calibration methods, partial least squares (PLS) and principal component regression (PCR), were applied to the spectrophotometric simultaneous determination of 2-mercaptobenzimidazole (MB) and 2-thiouracil (TU). A genetic algorithm (GA) using partial least squares was successfully utilized as a variable selection method. The concentration model was based on the absorption spectra in the range of 200 to 350 nm for 25 different mixtures of MB and TU. The calibration curve was linear across the concentration range of 1 to 10 μg mL⁻¹ and 1.5 to 15 μg mL⁻¹ for MB and TU, respectively. The values of the root mean squares error of prediction (RMSEP) were 0.3984, 0.1066, and 0.0713 for MB and 0.2010, 0.1667, and 0.1115 for TU, which were obtained using PCR, PLS, and GA-PLS, respectively. Finally, the practical applicability of the GA-PLS method was effectively evaluated by the concurrent detection of both analytes in animal tissues. It should also be mentioned that the proposed method is a simple and rapid way that requires no preliminary separation steps and can be used easily for the analysis of these compounds, especially in quality control laboratories.     

第三代无线通信系统的设计与验证

首先讨论传统的设计方法在设计无线通信系统物理层基带部分时的弊端。然后展示一个具有可行性的设计流程，它基于使用信号处理工作系统（ＳＰＷ）作为系统和硬件工程师的通用设计平台。     

Seismic motion response and fragility analyses of cantilever retaining walls with cohesive backfill

The seismic motion response of a cantilever retaining wall with cohesive and cohesionless backfill materials was evaluated using fully dynamic analysis based on finite difference method. The dynamic analysis was validated based on experimental test results and then compared to analytical and empirical correlations based on Newmark sliding block method. Seven different earthquake events and the backfills with low to high levels of cohesion were considered. Nonlinear regression analyses were carried out to provide correlations between free-field peak ground acceleration (PGA) and maximum relative displacement of the retaining wall. These results were compared to results from empirical and analytical methods. Furthermore, fragility analyses were conducted to determine the probability of damage to the retaining wall for different free-field PGAs and backfill cohesions. It is demonstrated to what extent a small amount of cohesion in backfill material can influence displacement of the retaining wall and probability of damage in seismic conditions.     

Mechanism of the reversibility of asphaltene precipitation in crude oil

Asphaltene precipitation and deposition occur in petroleum reservoirs as a change in pressure, temperature and liquid phase composition and reduce the oil recovery considerably. In addition to these, asphaltene precipitates may deposit in the pore spaces of reservoir rock and form plugging, which is referred to as a type of formation damage, i.e. permeability reduction. In all cases above, it is of great importance to know under which conditions the asphaltenes precipitate and to what extent precipitated asphaltenes can be re-dissolved. In other words, to what extent the process of asphaltene precipitation is reversible with respect to change in thermodynamic conditions. In present work, a series of experiments was designed and carried out to quantitatively distinguish the reversibility of asphaltene precipitation upon the change in pressure, temperature and liquid composition. Experiments were conducted in non-porous media. Generally it was observed that the asphaltene precipitation is a partial reversible process for oil under study upon temperature change with hysteresis. However, the precipitation of asphaltene as a function of mixture composition and pressure is nearly reversible with a little hysteresis.     

Evaluation of a permeability–porosity relationship in a low-permeability creeping material using a single transient test

A method is presented for the evaluation of the permeability–porosity relationship in a low-permeability porous material using the results of a single transient test. This method accounts for both elastic and non-elastic deformations of the sample during the test, and is applied to a hardened class G oil well cement paste. An initial hydrostatic undrained loading is applied to the sample. The generated excess pore pressure is then released at one end of the sample while monitoring the pore pressure at the other end and the radial strain in the middle of the sample during the dissipation of the pore pressure. These measurements are back-analysed to evaluate the permeability and its evolution with porosity change. The effect of creep of the sample during the test on the measured pore pressure and volume change is taken into account in the analysis. This approach permits to calibrate a power law permeability–porosity relationship for the tested hardened cement paste. The porosity sensitivity exponent of the power–law is evaluated equal to 11, and is shown to be mostly independent of the stress level and of the creep strains.     

Effective stress law for the permeability of a limestone

The effective stress law for the permeability of a limestone is studied experimentally by performing constant-head permeability tests in a triaxial cell with different conditions of confining pressure σ and pore pressure p_f. Test results show that a pore pressure increase and a confining pressure decrease both result in an increase of the permeability, and that the effect of the pore pressure change on the variation of the permeability is more important than the effect of a change of the confining pressure. A power law is proposed for the variation of the permeability with the effective stress (σ′=σ–n_kp_f). The permeability-effective stress coefficient n_k increases linearly with the differential pressure and is greater than unity as soon as the differential pressure exceeds few bars. The test results are well reproduced using the proposed permeability-effective stress law. A conceptual pore-shell model based on a detailed observation of the microstructure of the studied limestone is proposed. This model is able to explain the experimental observations on the effect of the total stress and of the pore pressure on the permeability of the limestone. Effective stress coefficients for the stress-dependent permeability which are greater than one are obtained. It is shown that the controlling factor is the ratio of the different bulk moduli of the various constituents of the rock. This ratio is studied experimentally by performing microhardness tests.     

Improved impossible differential and biclique cryptanalysis of HIGHT

HIGHT is a lightweight block cipher introduced in CHES 2006 by Hong et al as a block cipher suitable for low‐resource applications. In this paper, we propose improved impossible differential and biclique attacks on HIGHT block cipher both exploiting the permutation‐based property of the cipher's key schedule algorithm as well as its low diffusion. For impossible differential attack, we found a new 17‐round impossible differential characteristic that enables us to propose a new 27‐round impossible differential attack. The total time complexity of the attack is 2^120.4 where an amount of 2^59.3 chosen plaintext‐ciphertext pairs and 2^107.4 memory are required. We also instantiate a new biclique cryptanalysis of HIGHT, which is based on the new idea of splitting each of the forward and backward keys into 2 parts where the computations associated to each one are performed independently. The time complexity and data complexity of this attack are 2^125.7 and 2⁴², respectively. To the best of our knowledge, this is the fastest biclique attack on full‐round HIGHT.     

Selective laser melting raw material commoditization: impact on comparative competitiveness of additive manufacturing

The paper analyses the impact of cheaper metal powder supplies on the comparative competitiveness of additive manufacturing (AM). By utilising two case studies, we compare the economic impact of an innovative titanium extraction method on Selective Laser Melting (SLM) and conventional methods of machining and casting. A switch-over analysis identifies the production quantities above which conventional manufacturing is more cost competitive than additive manufacturing. This analysis is performed for current raw material as well as cheaper raw material supply. The results illustrate the improved comparative competitiveness of SLM as the titanium supply is commoditised and more readily available in powder form. The responsiveness of the supply chain is improved as the switch-over point between SLM and conventional methods increases. Moreover, as the raw material supply chain for titanium is transformed through the use of this novel extraction method, the manufacturing supply chain is simplified.     

Influence of preparation procedure and ferric oxide nanoparticles addition on transport properties of homogeneous cation-exchange SPPO/SPVC membrane

Homogeneous cation-exchange membranes were prepared through evaporation and phase inversion methods using sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) and sulfonated polyvinylchloride as binders. The effect of polymers blend’s ratio and preparation method on structure and electrochemical properties of the prepared membranes were evaluated. The microstructures of the membranes were investigated by scanning electron microscopy (SEM) and the sulfonation of polyvinylchloride was confirmed by elemental analyses. Moreover, the membranes performance was evaluated by ion-exchange capacity (IEC), fixed ion concentration, membrane potential, transport number, permselectivity, areal resistance, ionic permeability, flux of ions, current efficiency, membrane oxidative stability, mechanical properties and water content tests. The results indicated that IEC and water content were affected by the SPPO content and microstructures of the membranes. The results showed increased efficiency and suitable electrochemical properties for membranes prepared by the evaporation method in comparison with others. Also, \(\hbox {Fe}_{2}\hbox {O}_{3}\) nanoparticles were synthesized at room temperature by a simple sonochemical reaction between ferric chloride and NaOH. The results revealed that the addition of different amounts of \(\hbox {Fe}_{2}\hbox {O}_{3}\) nanoparticles to the polymeric matrix could affect the hydrophilicity and transport properties of ion-exchange membranes.     

Numerical Assessment of the Film Cooling Through Novel Sister-Shaped Single-Hole Schemes

In the present paper, a numerical investigation is conducted on film cooling performance from novel sister-shaped single-hole schemes. Based on the sister hole film cooling technique, shaped holes are formed by merging discrete sister holes to a primary hole. Simulations are performed at four blowing ratios of 0.25, 0.5, 1, and 1.5. The novel-shaped holes resulted in a significant reduction in the jet liftoff effect in comparison with a cylindrical and a forward-diffused shaped hole. Moreover, film cooling effectiveness is notably increased at the high blowing ratios of 1 and 1.5.