Ge quantum dot arrays grown by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface: nucleation, morphology and CMOS compatibility

Issues of morphology, nucleation and growth of Ge cluster arrays deposited by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface are considered. Difference in nucleation of quantum dots during Ge deposition at low (<600 deg C) and high (>600 deg. C) temperatures is studied by high resolution scanning tunneling microscopy. The atomic models of growth of both species of Ge huts---pyramids and wedges---are proposed. The growth cycle of Ge QD arrays at low temperatures is explored. A problem of lowering of the array formation temperature is discussed with the focus on CMOS compatibility of the entire process; a special attention is paid upon approaches to reduction of treatment temperature during the Si(001) surface pre-growth cleaning, which is at once a key and the highest-temperature phase of the Ge/Si(001) quantum dot dense array formation process. The temperature of the Si clean surface preparation, the final high-temperature step of which is, as a rule, carried out directly in the MBE chamber just before the structure deposition, determines the compatibility of formation process of Ge-QD-array based devices with the CMOS manufacturing cycle. Silicon surface hydrogenation at the final stage of its wet chemical etching during the preliminary cleaning is proposed as a possible way of efficient reduction of the Si wafer pre-growth annealing temperature.Comment: 30 pages, 11 figure

Support for people who use Anabolic Androgenic Steroids: A Systematic Scoping Review into what they want and what they access.

BACKGROUND: Since there is a paucity of research on support for people using Anabolic Androgenic Steroids (AAS), we aimed to identify and synthesise the available evidence in this field. Gaining an understanding of the support both accessed and wanted by recreational AAS users will be of use to professionals who provide services to intravenous substance users and also to those working in the fields of public health and social care, with the aim to increase engagement of those using AAS. METHODS: A systematic scoping review of the literature to explore and identify the nature and scope of information and support both accessed and wanted by non-prescribed AAS users. Any support services or information designed to help people who use AAS were considered. RESULTS: We identified 23 papers and one report for review, which indicated that AAS users access a range of sources of information on: how to inject, substance effectiveness, dosages and side effects, suggesting this is the type of information users want. AAS users sought support from a range of sources including medical professionals, needle and syringe programmes, friends, dealers, and via the internet, suggesting that, different sources were used dependent on the information or support sought. DISCUSSION: AAS users tended to prefer peer advice and support over that of professionals, and access information online via specialist forums, reflecting the stigma that is experienced by AAS users. These tendencies can act as barriers to accessing services provided by professionals. CONCLUSIONS: Support needs to be specific and targeted towards AAS users. Sensitivity to their perceptions of their drug-use and the associated stigma of being classified in the same sub-set as other illicit drug users is relevant to facilitating successful engagement

Does production process influence the mechanical properties of bleached alfa pulpboard?

This study was conducted to determine and analyse the influence of production process on the mechanical properties of bleached alfa pulpboard. Scanning electron microscopy showed that the industrial process currently used to produce the pulpboard causes small-scale and large-scale deformations in the alfa fibres. The same process results in a preferred orientation of the alfa fibres, leading to alignment in the rolling direction and hence there is some variation in the mechanical performance of the pulpboard in the different directions. Indeed, the mechanical properties show that the pulpboard loses its isotropic nature, mainly in the high-deformation regions. The pulpboard does not have the same mechanical characteristics in the longitudinal, 45°, and transverse directions. The samples taken in a longitudinal direction, which corresponds to the rolling direction, have better mechanical performance than in samples taken in the other two directions. Furthermore, the alkali (NaOH) treatment that is used to extract the alfa fibres from the alfa stems did not succeed in removing all of the non-cellulosic materials initially present in the alfa stems

FEA on Grey Cast Iron Assets: A Case Study on Penstocks in the Waste Water System

Penstocks have been used in the water industry for flow control since the Victorian expansion and consolidation of clean and waste water networks. However, the Victorians were the first to use grey cast iron (GCI) castings to manufacture large scale penstocks. Most of these ageing assets are still in operation, however engineering assessments are necessary to determine a structure’s fitness-for-service. Even today, penstocks in the sewer system tend to be made from GCI, due to ease of manufacturing, resistance to corrosion and cost. One characteristic property of grey cast iron is the graphite flake structure in the material, contributing to its low toughness, inconsistency in material strength and brittle behaviour, despite exhibiting slight hardening properties. Finite element analysis (FEA), is a numerical method which allows the analysis of complex structures by splitting it into finite parts and solving them with a computer processor. Despite the versatility of FEA, appropriate considerations and assumptions are necessary due to the difficulty to obtain data from inspection and unique material behaviour of GCI. The article shows concerns for an analysis of GCI penstocks using FEA, which extends into the application of fracture mechanics approaches for defect assessments