Preparation of polycrystalline FeTe1−xSx (x = 0.00–0.30) via solid-state reaction method at ambient pressure

Polycrystalline samples with nominal composition FeTe1−x S x (x = 0.00–0.30) were synthesized via solid state reaction method with intermittent grinding in argon gas flow. X-ray diffraction (XRD) patterns revealed the tetragonal structure (space group P4/nmm) of the samples with the presence of impurities Fe3O4 and FeTe2. By substitution with S, the a and c lattice parameters shrink probably due to the smaller ionic radius of S2− compared to Te2−. Scanning electron microscopy images showed that the samples developed plate-like grains with increasing S substitution. Substitution of Te with S suppresses the structural transition of the parent compound FeTe as shown by both the temperature dependence of resistance and magnetic moment measurements. All of the S-substituted samples showed a rapid drop of resistance at around 9–10 K but zero resistance down to 4 K was not observed. In addition, negative magnetic moment corresponds to diamagnetism was detected in the samples for x = 0.25 and 0.30 suggesting the coexistence of magnetic and superconducting phase in these samples. The magnetization hysteresis loops measured at room temperature showed ferromagnetic behavior for the pure and S substituted samples. However, the magnetization, rentivity and coercivity decreased with S content

Room temperature dielectric properties of polycrystalline FeTe1−xSex (x = 0.0–0.5)

In this work, frequency-dependent dielectric properties of polycrystalline samples with nominal compositions FeTe1−x Se x (x = 0.0–0.5) were investigated. The samples were synthesized via solid-state reaction method with intermittent grinding at ambient pressure. The phase formation, lattice properties and chemical compositions of the samples were analysed. Dielectric constants (ε′, ε′′), dielectric loss (tan δ) and alternating current (AC) conductivity (σ ac) as a function of frequency ranging from 100 Hz to 10 MHz were measured at room temperature. X-ray diffraction (XRD) data showed the presence of impurity phases of Fe3O4, FeTe2 and hexagonal FeSe/Fe7Se8. Both a and c lattice parameters decreased with the substitution of Se. Energy-dispersive x-ray spectroscopy confirmed the increasing ratio of Se/Te with x. The measured negative values of real dielectric constant (ε′) for x = 0.0–0.5 indicate the conductive nature of these samples. As the Se content was increased, the ε′ became more negative as a result of better grain connectivity as shown by the higher AC conductivity and dielectric loss

Synthesis of bulk FeTe1−xSex (x = 0.1−0.5) at ambient pressure

In this study, polycrystalline samples with nominal composition FeTe1−xSe x (x=0.1−0.5) were synthesized by solid-state reaction method at ambient pressure. In order to minimize oxidation, argon gas flow was maintained throughout the heat treatment. The phase formation of FeTe1−xSe x samples was checked by X-ray diffraction (XRD). The polycrystalline FeTe1−xSe x samples were indexed to a tetragonal structure with space group of P4/nmm. The lattice parameters a- and c-axes shrink significantly with the substitution of Se. As shown by the scanning electron microscope (SEM) images, the samples developed a plate-like grain structure gradually with the increase of Se concentration. Measurements of temperature dependence of magnetic moment showed that the onset of superconducting transition temperature, T c, increased with Se concentration. The T c is about 10.6 and 13.5 K for x= 0.1 and 0.5, respectively. All the samples exhibit ferromagnetic behavior as shown by the field-dependent magnetization measured at room temperature

Report of the third Asian Prostate Cancer study meeting.

The Asian Prostate Cancer (A-CaP) study is an Asia-wide initiative that was launched in December 2015 in Tokyo, Japan, with the objective of surveying information about patients who have received a histopathological diagnosis of prostate cancer (PCa) and are undergoing treatment and clarifying distribution of staging, the actual status of treatment choices, and treatment outcomes. The study aims to clarify the clinical situation for PCa in Asia and use the outcomes for the purposes of international comparison. Following the first meeting in Tokyo in December 2015, the second A-CaP meeting was held in Seoul, Korea, in September 2016. This, the third A-CaP meeting, was held on October 14, 2017, in Chiang Mai, Thailand, with the participation of members and collaborators from 12 countries and regions. In the meeting, participating countries and regions presented the current status of data collection, and the A-CaP office presented a preliminary analysis of the registered cases received from each country and region. Participants discussed ongoing challenges relating to data input and collection, institutional, and legislative issues that may present barriers to data sharing, and the outlook for further patient registrations through to the end of the registration period in December 2018. In addition to A-CaP-specific discussions, a series of special lectures were also delivered on the situation for health insurance in the United States, the correlation between insurance coverage and PCa outcomes, and the outlook for robotic surgery in the Asia-Pacific region. Members also confirmed the principles of authorship in collaborative studies, with a view to publishing original articles based on A-CaP data in the future

Quantitative analysis of the expression of p53 gene in colorectal carcinoma by using real-time PCR

Colorectal carcinoma ranks third among ten leading causes of cancer in Malaysia. The colorectal carcinoma tumourigenesis involves the inactivation of tumour suppressor genes, and activation of proto-oncogenes. The p53 is one of the tumour suppressor genes that is involved in the colorectal carcinogenesis. The p53 gene is located on human chromosome 17p13.1 and comprises of 11 exons. Deficiencies in the p53 gene can cause the cancerous cells to spread to distant organs such as liver, lungs, lymph nodes, spine and bone. The most common p53 abnormalities that can lead to the metastasis of colorectal tumours are mutation and deregulation of the gene. In this study, nine colorectal carcinoma samples were used to establish a simple and sensitive strategy in the study on in vivo p53 expression by using realtime LightCycler SYBR Green I technology

A QCL model with integrated thermal and stark rollover mechanisms

There is a need for a model that accurately describes dynamics of a bound-to-continuum terahertz quantum cascade laser over its full range of operating temperatures and bias conditions. In this paper we propose a compact model which, through the inclusion of thermal and Stark effects, accurately reproduces the light-current characteristics of an exemplar bound-to-continuum terahertz quantum cascade laser. Through this model, we investigate the dynamics of this laser with a view to applications in high-speed free space communications

Multi-spectral terahertz sensing: proposal for a coupled-cavity quantum cascade laser based optical feedback interferometer

We propose a laser feedback interferometer operating at multiple terahertz (THz) frequency bands by using a pulsed coupled-cavity THz quantum cascade laser (QCL) under optical feedback. A theoretical model that contains multi-mode reduced rate equations and thermal equations is presented, which captures the interplay between electro-optical, thermal, and feedback effects. By using the self-heating effect in both active and passive cavities, self-mixing signal responses at three different THz frequency bands are predicted. A multi-spectral laser feedback interferometry system based on such a coupled-cavity THz QCL will permit ultra-high-speed sensing and spectroscopic applications including material identification

Laser Feedback Interferometry as a Tool for Analysis of Granular Materials at Terahertz Frequencies: Towards Imaging and Identification of Plastic Explosives

We propose a self-consistent method for the analysis of granular materials at terahertz (THz) frequencies using a quantum cascade laser. The method is designed for signals acquired from a laser feedback interferometer, and applied to non-contact reflection-mode sensing. Our technique is demonstrated using three plastic explosives, achieving good agreement with reference measurements obtained by THz time-domain spectroscopy in transmission geometry. The technique described in this study is readily scalable: replacing a single laser with a small laser array, with individual lasers operating at different frequencies will enable unambiguous identification of select materials. This paves the way towards non-contact, reflection-mode analysis and identification of granular materials at THz frequencies using quantum cascade lasers

A Preliminary Study Of Differentially Expressed Genes In Malaysian Colorectal Carcinoma Cases

Presently, the complete genetic mechanisms for the progression of adenoma to carcinoma for colorectal carcinoma (CRC) remain largely unclear. In order to obtain genetic information of this cancer pathway, we searched for differentially expressed genes in tumours of CRC. Gene expression profiles from CRC cases were assessed via the DNA microarray system. We report up-regulation and down-regulation of 819 and 98 genes respectively, in the tumours relative to their normal controls. The differential expression patterns of 121 genes were persistent in all tumours. Thirty three of these are ribosomal proteins (RPs) genes. Comparison of the 121 genes with a public domain gene expression database, the Cancer Gene Expression Database (CGEP), revealed 47 genes to be consistently differentially expressed in colorectal tumours. Among these, 22 are RP genes. Among all RP genes identified in this study the over-expression pattern for six of them is consistent with literature. The up-regulation of RP L32 in CRC tumours was demonstrated for the first time in this study and it was also verified via reverse transcription-polymerase chain reaction (RT-PCR) analysis. Non-RP genes worth noting are the tumour susceptibility gene (TSG101) and the 20-kDa myosin light chain (MLC-2). Albeit small sample size (n = 2 for microarray analysis), our preliminary studies revealed many genes that are brought into the context of CRC tumourigenesis for the first time, thus providing new clues to the genetic events during colorectal carcinogenesis

Optomechanical response with nanometer resolution in the self-mixing signal of a terahertz quantum cascade laser

Owing to their intrinsic stability against optical feedback (OF), quantum cascade lasers (QCLs) represent a uniquely versatile source to further improve self-mixing interferometry at mid-infrared and terahertz (THz) frequencies. Here, we show the feasibility of detecting with nanometer precision, the deeply subwavelength ($\lt \lambda /6000$<λ/6000) mechanical vibrations of a suspended ${{\rm Si}_3}{{\rm N}_4}$Si3N4 membrane used as the external element of a THz QCL feedback interferometer. Besides representing an extension of the applicability of vibrometric characterization at THz frequencies, our system can be exploited for the realization of optomechanical applications, such as dynamical switching between different OF regimes and a still-lacking THz master-slave configuration