InGaN epilayer characterization by microfocused x-ray reciprocal space mapping

We report the use of microfocused three-dimensional x-ray reciprocal space mapping to study InGaN epilayers with average InN content 20%-22%. Analysis of the full volume of reciprocal space, while probing samples on the microscale with a focused x-ray beam, allowed us to gain valuable information about the nanostructure of InN-rich InGaN epilayers. It is found that “seed” InGaN mosaic nanocrystallites are twisted with respect to the ensemble average and strain-free. The initial stages of InGaN-on-GaN epitaxial growth, therefore, conform to the Volmer-Weber growth mechanism with “seeds” nucleated on strain fields generated by the a-type edge dislocations

Characterization of InGaN and InAlN epilayers by microdiffraction X-Ray reciprocal space mapping

We report a study of InGaN and InAlN epilayers grown on GaN/Sapphire substrates by microfocused three-dimensional X-ray Reciprocal Space Mapping (RSM). The analysis of the full volume of reciprocal space, while probing samples on the microscale with a focused X-ray beam, allows us to gain uniquely valuable information about the microstructure of III-N alloy epilayers. It is found that “seed” InGaN mosaic nanocrystallites are twisted with respect to the ensemble average and strain free. This indicates that the growth of InGaN epilayers follows the Volmer-Weber mechanism with nucleation of “seeds” on strain fields generated by the a-type dislocations which are responsible for the twist of underlying GaN mosaic blocks. In the case of InAlN epilayer formation of composition gradient was observed at the beginning of the epitaxial growth

A clinical case of neonatal diabetes caused by INS gene mutation

Neonatal diabetes mellitus (NDM) is a severe endocrine pathology diagnosed in children during the first months of life. It comprises rare (1:300 000–1:400 000 newborns) metabolic disorders with postnatal pancreatic β-cell dysfunction, manifested by hyperglycaemia and hypoinsulinaemia. It is currently established that molecular genetic diagnosis of neonatal diabetes forms can influence treatment and prognosis. Interestingly, most identified mutations in the insulin gene are not inherited, but are sporadic. There is evidence that, in addition to heterozygous INS mutations, NDM can be caused by homozygous or compound-heterozygous mutations. The present article presents the clinical case of a girl with NDM associated with an INS gene mutation. INS gene mutations cause permanent diabetes and require children to undergo genetic examination, especially patients with type 1 diabetes in the absence of antibodies. Currently, there are no data that allow to determine a phenotypic and genotypic ‘portrait’ of NDM forms or to explain the factors determining their occurrence. Further studies of clinical cases of neonatal diabetes are therefore required to determine the characteristics of NDM subtypes with subsequent disease prognosis

Vitamin D Status Among Children With Juvenile Idiopathic Arthritis: A Multicenter Prospective, Non-randomized, Comparative Study

BackgroundJuvenile idiopathic arthritis (JIA) is a chronic autoimmune disease characterized by destructive and inflammatory damage to the joints. The aim in this study was to compare vitamin D levels between children and adolescents, 1–18 years of age, with juvenile idiopathic arthritis (JIA) and a health control group of peers. We considered effects of endogenous, exogenous, and genetic factors on measured differences in vitamin D levels among children with JIA.MethodsOur findings are based on a study sample of 150 patients with various variants of JIA and 277 healthy children. The blood level of vitamin D was assessed by calcidiol level. The following factors were included in our analysis: age and sex; level of insolation in three regions of country (center, south, north); assessment of dietary intake of vitamin D; effect of prophylactic doses of cholecalciferol; a relationship between the TaqI, FokI, and BsmI polymorphisms of the VDR gene and serum 25(OH)D concentration.ResultsWe identified a high frequency of low vitamin D among children with JIA, prevalence of 66%, with the medial level of vitamin D being within the range of “insufficient” vitamin D. We also show that the dietary intake of vitamin D by children with JIA is well below expected norms, and that prophylactic doses of vitamin D supplementation (cholecalciferol) at a dose of 500–1,000 IU/day and 1,500–2,000 IU/day do not meet the vitamin D needs of children with JIA. Of importance, we show that vitamin D levels among children with JIA are not affected by clinical therapies to manage the disease nor by the present of VDR genetic variants.ConclusionProphylactic administration of cholecalciferol and season of year play a determining role in the development of vitamin D deficiency and insufficiency

Tensile strain mapping in flat germanium membranes

Scanning X-ray micro-diffraction has been used as a non-destructive probe of the local crystalline quality of a thin suspended germanium (Ge) membrane. A series of reciprocal space maps were obtained with ∼4 μm spatial resolution, from which detailed information on the strain distribution, thickness, and crystalline tilt of the membrane was obtained. We are able to detect a systematic strain variation across the membranes, but show that this is negligible in the context of using the membranes as platforms for further growth. In addition, we show evidence that the interface and surface quality is improved by suspending the Ge

Role of the endocrine disorders in pregnancy in the pathogenesis of intrauterine and postnatal developmental disorders in children: modern view within the concept of nutritional programming (literature review)

Due to the growth of non-infectious morbidity of the world’s child and adult population, the concept of nutritional programming connecting cardiovascular and certain endocrine diseases with the fetoplacental complex disorders in the antenatal period has been developed over the past 25 years. An increase in the prevalence of obesity and gestational diabetes in pregnant women lays the groundwork for an increase in the prevalence of glucose metabolism disorders and the risk of endocrine pathology in children. Both low weight and overweight at birth evidence the unfavourable course of the intrauterine period. The review discusses the factors contributing to the fetal organs and systems growth retardation, hypovitaminosis D, insulin resistance and possible mechanisms for their development. The authors present the analysis of the data available in the modern literature on the mechanism of the obesity and GDM programming effect on the diseases in new-borns and children

High quality single crystal Ge nano-membranes for opto-electronic integrated circuitry

A thin, flat, and single crystal germanium membrane would be an ideal platform on which to mount sensors or integrate photonic and electronic devices, using standard silicon processing technology. We present a fabrication technique compatible with integrated-circuit wafer scale processing to produce membranes of thickness between 60 nm and 800 nm, with large areas of up to 3.5 mm2. We show how the optical properties change with thickness, including appearance of Fabry-Pérot type interference in thin membranes. The membranes have low Q-factors, which allow the platforms to counteract distortion during agitation and movement. Finally, we report on the physical characteristics showing sub-nm roughness and a homogenous strain profile throughout the freestanding layer, making the single crystal Ge membrane an excellent platform for further epitaxial growth or deposition of materials

Hormonal-metabolic patterns disorders of bone tissue mineralization in children with celiac disease

The review presents information about the pathophysiological mechanisms underlying disorders of the processes of mineralization of bone tissue in patients with celiac disease. The attention is focused on the role of vitamin D and its active metabolite calcitriol, and also parathyroid hormone in regulating calcium-phosphorus metabolism, which is carried out in target organs  – small intestine, kidney, bone tissue. Atrophy of the intestinal mucosa in celiac disease is accompanied not only by malabsorption of calcium, and increased resorption of bone due to increased concentration of PTG. According to various studies on the background of developing the osteoporosis in celiac disease, the risk of bone fractures is significantly increased in patients. Strict adherence to a gluten-free diet allows to normalize both the absorption of calcium, and impaired hormonal mechanisms in bone remodeling in the acute phase, and can reduce the risks of osteoporosis and pathological fractures in patients with celiac disease