Implementation of P-type black silicon with high aspect ratio for optoelectronics applications

Black Silicon (BSi) is a semiconductor with a surface modified to get a very low reflectivity and correspondingly high absorption of visible light. P-type <100> silicon wafers were used to prepare very low reflecting samples. These samples may use as substrates in optoelectronic applications. Electrochemical etching at different etching current, and time were applied. B-silicon is chemically equal to normal silicon, differs in surface treatment that changes a morphology. This special morphology is demanded for absorption enhancement which involves maximum light absorption. Surface roughness is done by texturing or trenching a silicon wafer surface. As these structures are in place, and as they are small enough, incident light will be more absorbed and less reflected, this is what gives black silicon its name. BSi was characterized by (FESEM), structural analysis indicates that BS layers were formed. The porosity was in the range of (10–40) % and it is dependent on etching time and etching current value. Etching density is 0.1073/mm2. Reflection analysis shows satisfying minimum reflectivity spectrum with the intensity of peaks decrease and red shifted with increasing the etching current. A peak of the Photoluminescence ranges about 360 nm, PL peaks are blue shifted and proportional to etching current. The band gap energy ranged from 2 to 3.4 eV, it is affected with porous morphology and directly proportional to etching current values

Spindle cell variant of medullary thyroid carcinoma: a clinicopathologic study of four cases

BackgroundMedullary thyroid carcinoma (MTC) is a malignant tumor derived from C cells. It accounts for about 10% of all thyroid malignancies. More than 14 histological variants have been described. Among them, spindle cell variant is extremely rare.Case presentationHere we describe 4 cases of spindle cell variant of MTC collected from 2012 to 2019. Ultrasound showed solid and hypoechoic nodules. Three patients underwent total thyroidectomy and regional lymph node dissection, and 1 patient underwent thyroid mass resection. Histologically, the tumors showed spindle shaped cells in bundles or interlaced arrangement, separated by hyalinised fibrous stroma that contained amyloid deposits. Immunohistochemistry showed that the tumor cells were positive for calcitonin, chromogranin A, synaptophysin, CD56, and TTF-1, but negative for other lineage-specific markers.ConclusionsWe report 4 rare cases of spindle cell variant of MTC. Due to its rarity and special morphology, the diagnosis of spindle cell variant MTC relies on its morphology and immunohistochemical markers to avoid misdiagnosis.

Recent Advances in the Preparation and Catalytic Performance of Mn-based Oxide Catalysts with Special Morphology for the Removal of Air Pollutants

Air pollutants result in serious environmental pollution and cause harm to human health, which has led to air pollutions gaining attention. At present, the catalytic oxidation technology is one of...

Collective training on individual programs: worldview, concept and practices

The author proposes to consider the relationship of social and individual in the form of a triangle with vertices: «loneliness among others,» «all as one» («system»), «complex cooperation of personalities». Individual and truly collective are in a relationship of unity and harmony, and do not confront each other. There is a danger of choosing from two evils: the pole of absolute autonomy or the pole of personal-social unification. Meaningful socialization has two alternatives: «system» and «collective». The need to build educational communities on a collectivist basis is due to political, socio-pedagogical and psychological reasons. The worldviews of pedagogical activity in the system of collective education are revealed, in particular, the value principle «Man is the main goal and the main means of a fruitful educational environment», the activity principle «Everyone is the goal, everyone is the means», the principle of joint existence «Cooperation is the leading type of relationship». The individual educational program is interpreted as the student's ideas about his upcoming educational activities, formed by him in collaboration with other students and teachers. An individual program differs from a «single» program, compiled by a student individually or paired with a tutor, and then implemented autonomously or according tothe principle of a supermarket. In the individual program, educational, club and production blocks are allocated. Conceptual provisions on the system of collective education are disclosed: specific principles of training organization; basic processes (educational, club, production, reflexive-planning); structural units – temporary cooperation of students and teachers, permanent detachments of students, a council of commanders, teacher cooperation, a general gathering of the team; special morphology of teachers – subject, «duty» teacher, didacto-technician, assistant. Four levels of organization of collective education are distinguished: samples, alternating training, constant training in individual segments of an educational institution and collective training throughout the institution. Practical options are called, in particular, a subject-methodological vacation school, multi-day immersion, a «day» without classes and lessons, a different-age group on one subject, a different-age group in the afternoon, a different-age team of a full day.

Preparation and Photocatalytic Water Splitting Hydrogen Production of Titanium Dioxide Nanosheets

Improving the efficiency of photocatalytic water splitting to produce hydrogen is currently a hot topic in research. TiO2 nanosheets are a good carrier of photocatalytic materials and have become attractive materials in the new century because of their high active surface exposure characteristics and special morphology. Considering the advantages and disadvantages of conventional chemical and physical methods that are used for preparing TiO2 nanosheets, an optimized scheme for the preparation of TiO2 nanosheets via hydrothermal calcination was proposed. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and UV-visible diffuse reflection absorption spectra (DRS) were used to characterize the structure and morphology of the TiO2 nanosheets, and differences in the photocatalytic water splitting hydrogen production activity of the different calcination temperatures were compared. The suitable calcination temperature of the TiO2 nanosheets was 400°C, and the hydrogen production rate was 270 μmol/h, which indicated that the sheet structure was beneficial for improving the photocatalytic water splitting hydrogen production performance of the material. It is hoped that this work will support the regulation of the surface morphology and surface modification of nanomaterials.

The formation of the thumb requires direct modulation of Gli3 transcription by Hoxa13

In the tetrapod limb, the digits (fingers or toes) are the elements most subject to morphological diversification in response to functional adaptations. However, despite their functional importance, the mechanisms controlling digit morphology remain poorly understood. Here we have focused on understanding the special morphology of the thumb (digit 1), the acquisition of which was an important adaptation of the human hand. To this end, we have studied the limbs of the Hoxa13 mouse mutant that specifically fail to form digit 1. We show that, consistent with the role of Hoxa13 in Hoxd transcriptional regulation, the expression of Hoxd13 in Hoxa13 mutant limbs does not extend into the presumptive digit 1 territory, which is therefore devoid of distal Hox transcripts, a circumstance that can explain its agenesis. The loss of Hoxd13 expression, exclusively in digit 1 territory, correlates with increased Gli3 repressor activity, a Hoxd negative regulator, resulting from increased Gli3 transcription that, in turn, is due to the release from the negative modulation exerted by Hox13 paralogs on Gli3 regulatory sequences. Our results indicate that Hoxa13 acts hierarchically to initiate the formation of digit 1 by reducing Gli3 transcription and by enabling expansion of the 5′Hoxd second expression phase, thereby establishing anterior−posterior asymmetry in the handplate. Our work uncovers a mutual antagonism between Gli3 and Hox13 paralogs that has important implications for Hox and Gli3 gene regulation in the context of development and evolution.

Three-dimensional assemblies of carbon nitride tubes as nanoreactors for enhanced photocatalytic hydrogen production

Three-dimensional assembly of carbon nitride tube was obtained from supramolecular precursor. The special morphology and triazole ring group modification endowed materials' enhanced photocatalytic hydrogen evolution property (71 mmol g−1 h−1).

The Difference between Hot and Cold Deformation and its Effect on Microstructure and Mechanical Properties of Near Beta Titanium Alloy

An investigation of cold and hot deformation and the subsequent heat treatment including the annealing at the (α+β)- field temperature and ageing of VST55531 alloy showed that the material after the cold drawing without the heat treatment has the extremely low values of uniform elongation and during the tensile test the strain becomes localized at a neck upon 0.2 % strain. The ageing of coldworked material improves the strength and increases a limit of uniform deformation and generally has a beneficial effect on a strengthto-ductility ratio of alloy probably due to achieving a special morphology of secondary α-phase. The obtained values of the combination of strength and ductility in the cold-worked material at 50% strain reduction degree are 1 625 MPa for UTS, 8% - El, 36% - RA, that exceed significantly the values obtained for the hot-worked and as-annealed material, and are attractive for application in products that require the increased strength and ductile characteristics.