Application of X-ray Computed Tomography in Characterization Microstructure Changes of Cement Pastes in Carbonation Process

The microstructure characteristics and meso-defect volume changes of hardened cement paste before and after carbonation were investigated by three-dimensional （3D） X-ray computed tomograpby （XCT）, where three types water-to-cement ratio of 0.53, 0.35 and 0.23 were considered. The high-resolution 3D images of microstructure and filtered defects were reconstructed by an XCT VG Studio MAX 2.0 software, The meso- defect volume fractions and size distribution were analyzed based on 3D images through add-on modules of 3D defect analysis. The 3D meso-defects volume fractions before carbonation were 0.79%, 0.38% and 0.05% corresponding to w/c ratio=0.53, 0.35 and 0.23, respectively. The 3D meso-defects volume fractions after carbonation were 2.44%, 0.91% and 0.14% corresponding to w/c ratio=0.53, 0.35 and 0.23, respectively. The experimental results suggest that 3D meso-defects volume fractions after carbonation for above three w/c ratio increased significantly. At the same time, meso-cracks distribution of the carbonation shrinkage and gray values changes of the different w/c ratio and carbonation reactions were also investigated.

Dual-phase coexistence enables to alleviate resistance drift in phase-change films

The amorphous phase-change materials with spontaneous structural relaxation leads to the resistance drift with the time for phase-change neuron synaptic devices. Here, we modify the phase change properties of the conventional Ge_2Sb_2Te_5(GST) material by introducing an SnS phase. It is found that the resistance drift coefficient of SnS-doped GST was decreased from 0.06 to 0.01. It can be proposed that the origin originates from the precipitation of GST nanocrystals accompanied by the precipitation of SnS crystals compared to single-phase GST compound systems. We also found that the decrease in resistance drift can be attributed to the narrowed bandgap from 0.65 to 0.43 eV after SnS-doping. Thus, this study reveals the quantitative relationship between the resistance drift and the band gap and proposes a new idea for alleviating the resistance drift by composition optimization, which is of great significance for finding a promising phase change material.

The Role of Chest X-Ray in Monitoring Lung Changes among COVID-19 Patients in Gaza Strip

Objective: To investigate the time course and findings severity of COVID-19 infection at chest radiography based on a 6-point radiological severity score, and correlates these with patients’ age and gender. Methods: This is a retrospective study of COVID-19 patients who were admitted at European Gaza Hospital and evaluated between October 6, 2020, and November 30, 2020. Baseline and serial chest radiographs, up to 4 images per patient, were reviewed and assessed for predominant pattern, side, and location of lung opacity. Utilized a 6-point scoring system, which divides the chest X-ray into 6 zones, to assess chest X-ray changes and correlate them with the severity of infection, age, and gender of patients. Results: The study included 136 COVID-19 patients: (51/136, 37%) were males and (85/136, 62.5%) were females, while age ranged from 7 months to 90 years with a mean age of 41.7 ± (19.5) years. Negative Chest x-rays were more observed than positive images. Ground-glass opacity was the most frequent pattern with a decreasing trend from 1st to 4th chest X-ray (from 33.8% to 3.7%), followed by consolidation (from 16.2% to 2.9%). Also, the commonest pattern of opacity was seen in peripheral areas (27/136, 19.9%), lower zone location (23/136, 16.9%), and bilateral opacity involvement (43/136;31.6%). No significant correlation was noticed between the patient’s gender, age, and severity score (P > 0.05). Conclusions: The 6-point chest X-ray severity score as a predictive tool in assessing the severity due to provide an assessment of the progression or regression pathway.

Gamma induced changes in Makrofol/CdSe nanocomposite films

We applied an ex-situ casting procedure to prepare a nanocomposite(NCP)from Makrofol polycarbonate(PC)and CdSe nanoparticles.The CdSe nanoparticles were prepared by a thermolysis procedure in the presence of N_(2) gas flow.Rietveld refinement of x-ray data illustrated that the CdSe adopts a cubic zinc blend structure of 6.057 A lattice parameter and 2 nm typical grain size.Samples from the prepared NCP were exposed to γ dosages(20 kGy-250 kGy).The modifications induced in the NCP films owing to γ dosages have been studied.Theγirradiation(50 kGy-250 kGy)causes crosslinks that reduce the optical bandgap from 4.15 eV to 3.81 eV,associated with an increase in dielectric parameters and refractive index.This is attributed to an increase in the mass fraction of the disordered regions as specified by x-ray diffraction.The PC-CdSe NCP was found to have a reaction to color modification which makes it suitable for saleable reproduction on a printing press.

Ultrafast structural dynamics using time-resolved x-ray diffraction driven by relativistic laser pulses

Based on a femtosecond laser plasma-induced hard x-ray source with a high laser pulse energy(>100 mJ)at 10 Hz repetition rate,we present a time-resolved x-ray diffraction system on an ultrafast time scale.The laser intensity is at relativistic regime(2×10^(19)W/cm^(2)),which is essential for effectively generating K_(α)source in high-Z metal material.The produced copper K_(α)radiation yield reaches to 2.5×10^(8)photons/sr/shot.The multilayer mirrors are optimized for monochromatizating and two-dimensional beam shaping of Kαemission.Our experiment exhibits its ability of monitoring the transient structural changes in a thin film SrCoO_(2.5)crystal.It is demonstrated that this facility is a powerful tool to perform dynamic studies on samples and adaptable to the specific needs for different particular applications with high flexibility.

Crystal structure and thermochemical properties of bis(1-octylammonium) tetrachlorochromate phase change materials

A new crystalline complex （C8H17NH3）2CdCI4（s） （abbreviated as CsCd（s）） is synthesized by liquid phase reaction. The crystal structure and composition of the complex are determined by single crystal X-ray diffraction, chemical analysis, and elementary analysis. It is triclinic, the space group is P-1 and Z = 2. The lattice potential energy of the title complex is calculated to be UpoT （CsCd（s））=978.83 kJ.mol^-1 from crystallographic data. Low-temperature heat capacities of the complex are measured by using a precision automatic adiabatic calorimeter over a temperature range from 78 K to 384 K. The temperature, molar enthalpy, and entropy of the phase transition for the complex are determined to be 307.3±0.15 K, 10.15±0.23 kJ.mol^-1, and 33.054-0.78 J.K^-1.mol^-1 respectively for the endothermic peak. Two polynomial equations of the heat capacities each as a function of temperature are fitted by using the leastsquare method. Smoothed heat capacity and thermodynamic functions of the complex are calculated based on the fitted polynomials.

Quantification of changes in zero valent iron morphology using X-ray computed tomography

Morphological changes within the porous architecture of laboratory scale zero valent iron （ZVI） permeable reactive barriers （PRBs）, after exposure to different groundwater conditions, have been quantified experimentally for different ZVI/sand ratios （10%, 50% and 100%, W/W） with the aim of inferring porosity changes in field barriers. Column studies were conducted to simulate interaction with different water chemistries, a synthetic groundwater, acidic drainage and deionised （DI） water as control. Morphological changes, in terms of pore size and distribution, were measured using X-ray computed tomography （CT）. CT image analysis revealed significant morphological changes in columns treated with different water chemistries. For example, 100% ZVI （W/W） columns had a higher frequency of small pores （0.6 mm） was observed in ZVI grains reacted with typical groundwater, resulting in a porosity of 27%, compared to 32% when exposed to DI water. In comparison, ZVI grains treated with the acidic drainage had higher porosity （44%） and larger average pore size （2.8 mm）. 10% ZVI PRB barrier material had the highest mean porosity （56%） after exposure to any water chemistry whilst 100% ZVI （W/W） columns always had the lowest （34%） with the 50% ZVI （W/W） in between （40%）. These results agree with previously published PRB field data and simultaneously conducted geochemical monitoring and mass balance calculation, indicating that both the geochemical and hydraulic environment of the PRB play an important role in determining barrier lifespan. This study suggests that X-ray CT image analysis is a powerful tool for studying the detailed inter pores between ZVI grains within PRBs.

大骨节病病区学龄前儿童骨干骺端X线改变调查

目的探讨大骨节病的发病机理及大骨节病病区学龄前儿童骨关节部位X线表现。方法纳入大骨节病病区四川省金川县河西乡乃当村1-6岁学龄前儿童，拍摄手、膝关节X光片，盲法读片。结果全村共22名学龄前儿童，除外2例仍在哺乳、3例外出未归者后，纳入17例，另有3例6-8岁学龄儿童因家长发现其关节肿大也应要求纳入检查。结果发现该20例受检儿童均有尺和／或桡骨、股骨和／或胫骨干骺端X线改变。结论轻型大骨节病病区金川县河西乡乃当村学龄前儿童普遍存在骨干骺端改变，符合“脱碘酶功能障碍假说”关于大骨节病病区低龄儿童可能存在软骨发育障碍的推论。

Magnetocaloric effect of (Gd_(1-x)Ce_x)Co_2 compounds in low magnetic fields

The phases in the compounds （Gd1-xCex）Co2 with x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 were investigated by X-ray diffraction, and the magnetocaloric effect for x = 0-0.4 was studied by magnetization measurements. The samples are almost single phase with a cubic MgCu2-type structure for x = 0-0.5. The magnetization decreases with an increase in Ce content. There is almost no magnetic transition for x = 0.5 at 100-350 K. The Curie temperature （To） of the （Gd1-xCex）Co2compounds with x from 0.1 to 0.4 are 350, 344, 340, and 338 K respectively. The maximum magnetic entropy change is 2.34 J·kg^-1·K^-1 when x = 0.3. The results of Arrott plots show that the magnetic phase transition is second-order magnetic phase transition in these compounds.

Mineral chemistry and 3D tomography of a Chang’E 5 high-Ti basalt:implication for the lunar thermal evolution history

In December 2020, Chang’E-5(CE-5), China’s first lunar sample return mission, successfully collected samples totaling 1731 g from the northern Oceanus Procellarum. The landing site was located in a young mare plain, a great distance from those of Apollo and Luna missions. These young mare basalts bear critical scientific significance as they could shed light on the nature of the lunar interior(composition and structure) as well as the recent volcanism on the Moon. In this article, we investigated a CE-5 basalt sample(CE5 C0000 YJYX065) using a combination of state-of-art techniques, including high resolution X-ray tomographic microscopy(HR-XTM), energy dispersive X-ray spectroscopy(EDS)-based scanning electron microscope(SEM), and electron probe microanalysis(EPMA) to reveal its 3 D petrology and minerology.Our results show that this sample has a fine-to medium-grained subophitic texture, with sparse olivine phenocrysts setting in the groundmass of pyroxene, plagioclase, ilmenite and trace amounts of other phases. It has an extremely high ilmenite modal abundance(17.8 vol%) and contains a significant amount(0.5 vol%) of Ca-phosphate grains. The mineral chemistry is in excellent agreement with that of Apollo and Luna high-Ti basalts. The major phase pyroxenes also display strong chemical zoning with compositions following the trends observed in Apollo high-Ti basalts. Based on current data, we came to the conclusion that CE5 C0000 YJYX065 is a high-Ti mare basalt with a rare earth element(REE) enriched signature. This provides a rigid ground-truth for the geological context at the CE-5 landing site and clarifies the ambiguity inferred from remote sensing surveys.

CHANGE OF STRUCTURAL CHARACTERISTICS IN IODINE INTERCALATED Bi-Sr-Ca-Cu-O SINGLE CRYSTAL

Ⅰ. INTRODUCTIONX. D. Xiang et al. have reported the preliminary structural characteristics of the iodine intercalated Bi_2Sr_2Ca_1Cu_2O_y high T_c superconductors. The cell dimension along c direction is expanded from 30.80 to 37.78 after iodine is intercalated. They suggested that an iodinelayer addition with 3.5 thickness is inserted into the host crystal perpendicular to c direction. The transition temperature of the host superconductor is ranged from 82 to 90 K.

Valency and Its Change Process of Samarium Ion in Samarium Fluoride System

Nonstoichiometric series SmF_x (2.0≤x≤3.0) have been synthesized by reduction of samarium trifluoride with hydrogen for several times, and the stoichiometric samarium difluoride has been obtained. The structure of nonstoichiometric samarium fluoride series and the valency of samarium ion are briefly discussed. The valent change process of samarium ion at high temperatures in different atmospheres is investigated.