Exploring the low temperature tempering range of low alloy quenched and tempered steels

Abstract It is well known that quenched and tempered alloy steel components with ultimate tensile strength in excess of 1400 MPa are seldom employed as mechanical components, due to their not adequate ductility, as ascertained by multiple researches performed during World War II and soon after. Nevertheless, use of low temperature tempered steels in some niche applications, as well as researches performed on surface heat treated high carbon steels and on their behavior upon tempering in the vicinity of 200°C have stemmed into renewed interest in quenched and low temperature tempered low alloy steels. Application to 36NiCrMo16 steel bars is examined here, by means of tensile and hardness tests and fractographic and metallographic examinations after quenching and tempering in the 160 to 440 °C temperature range

Modeling of Mid-IR Amplifier Based on an Erbium-Doped Chalcogenide Microsphere

An optical amplifier based on a tapered fiber and an Er3+-doped chalcogenide microsphere is designed and optimized. A dedicated 3D numerical model, which exploits the coupled mode theory and the rate equations, is used. The main transitions among the erbium energy levels, the amplified spontaneous emission, and the most important secondary transitions pertaining to the ion-ion interactions have been considered. Both the pump and signal beams are efficiently injected and obtained by a suitable design of the taper angle and the fiber-microsphere gap. Moreover, a good overlapping between the optical signals and the rare-earth-doped region is also obtained. In order to evaluate the amplifier performance in reduced computational time, the doped area is partitioned in sectors. The obtained simulation results highlight that a high-efficiency midinfrared amplification can be obtained by using a quite small microsphere

Metallo-Dielectric Multilayer Structure for Lactose Malabsorption Diagnosis through H2 Breath Test

A metallo-dielectric multilayer structure is proposed as a novel approach to the analysis of lactose malabsorption. When lactose intolerance occurs, the bacterial overgrowth in the intestine causes an increased spontaneous emission of H2 in the human breath. By monitoring the changes in the optical properties of a multilayer palladium-polymeric structure, one is able to detect the patient's disease and the level of lactose malabsorption with high sensitivity and rapid response

Wide-band optical field concentrator for low-index core propagation

We propose a novel chirped structure consisting of a low index polymer core bounded by modulated multilayer claddings, to realize an optical field concentrator with virtually zero propagation losses in a wide spectral range, independent of wave polarization. In spite of the absence of the total internal reflection mechanism, properly designed multilayer claddings ensure the achievement of unitary transmittance in a wide spectral range, including the widely used wavelengths for optical communications. Several cladding geometries obtained by varying the thicknesses of the cladding layers are reported and discussed.Comment: submitted to the Journal of the European Optical Societ

Chagas disease in the United Kingdom: A review of cases at the hospital for Tropical Diseases London 1995-2018. The current state of detection of Chagas disease in the UK

Background: Chagas disease (CD), is a parasitic disease endemic in Latin America. Presentation in non-endemic areas is either in the asymptomatic indeterminate phase or the chronic phase with cardiac and/or gastrointestinal complications. Methods: The Hospital for Tropical Diseases (HTD) based in central London, provides tertiary care for the management of CD. We reviewed all cases managed at this centre between 1995 and 2018. Results: Sixty patients with serologically proven CD were identified. Most were female (70%), with a median age at diagnosis of 41 years. Three quarters of the patients were originally from Bolivia. 62% of all patients were referred to the HTD by their GP. Nearly half of the patients were asymptomatic (47%). Twelve patients had signs of cardiac involvement secondary to CD. Evidence of gastrointestinal damage was established in three patients. Treatment was provided at HTD for 31 patients (47%). Most patients (29) received benznidazole, five of them did not tolerate the course and were switched to nifurtimox. Of the seven patients receiving this second line drug, five completed treatment, whilst two interrupted it due to side effects. Conclusions: Despite the UK health system having all the resources required to diagnose, treat and follow up cases, there is lack of awareness of CD, such that the vast majority of cases remain undiagnosed and therefore do not receive treatment. We propose key interventions to improve the detection and management of this condition in the UK, especially in pregnant women and neonates

Simultaneous Detection of FISH Signals and Bromo-Deoxyuridine Incorporation in Fixed Tissue Cultured Cells

FISH (Fluorescence in situ hybridization) is a powerful technique that detects and localises specific DNA sequences on metaphase chromosomes, interphase nuclei or chromatin fibres. When coupled to BrdU (5-Bromo 2-deoxy-uridine) labeling of newly replicated DNA, the replication properties of different DNA sequences can be analysed. However, the technique for the detection of BrdU incorporation is time consuming, and relies on acidic pH buffer treatments, that prevent use of pH sensitive fluorochromes such as FITC (Fluoro-isothiocianate) during FISH. In this work, we describe a simplified protocol that allows the simultaneous detection of FISH signals and BrdU incorporation. Since the technique does not involve paraformaldehyde for cell fixation, or formamide for denaturation of the target DNA and in post-hybridisation washes, it represents a safer alternative to classical FISH techniques

Compositional Genome Contexts Affect Gene Expression Control in Sea Urchin Embryo

Gene expression is widely perceived as exclusively controlled by the information contained in cis-regulatory regions. These are built in a modular way, each module being a cluster of binding sites for the transcription factors that control the level, the location and the time at which gene transcription takes place. On the other hand, results from our laboratory have shown that gene expression is affected by the compositional properties (GC levels) of the isochores in which genes are embedded, i.e. the genome context. To clarify how compositional genomic properties affect the way cis-regulatory information is utilized, we have changed the genome context of a GFP-reporter gene containing the complete cis-regulatory region of the gene spdeadringer (spdri), expressed during sea urchin embryogenesis. We have observed that GC levels higher or lower than those found in the natural genome context can alter the reporter expression pattern. We explain this as the result of an interference with the functionality of specific modules in the gene's cis-regulatory region. From these observations we derive the notion that the compositional properties of the genome context can affect cis-regulatory control of gene expression. Therefore although the way a gene works depends on the information contained in its cis-regulatory region, availability of such information depends on the compositional properties of the genomic context