Solution of the Synthesis Problem of Boundary Optimal Control of a Rod Cooling Process with a Heat Conductive Viscosity

The problem of synthesis of the boundary optimal control of the cooling process of media with heat conductive viscosity is investigated. In addition to the distributed parameters, the concentrated parameters act on the system. This is due to the fact that the temperature of the external environment is unknown and varies according to a given law. As a result, the process is described by a system of partial differential equations and ordinary differential equations. In this case, heat transfer occurs at the right end of the rod. This complicates the obtaining of a solution of this boundary-value problem in an explicit form. But it is possible to establish the existence and uniqueness of the solution of the corresponding boundary-value problem for concrete admissible controls.The criterion of quality is a quadratic functional and it is required to build control in the form of feedback. First by the Fourier method, the problem under consideration is formulated in an infinite-dimensional phase space. As a result, the problem of synthesis of optimal control in a functional space is obtained. To solve this problem, the dynamic programming method is used. To do this, let's introduce the Bellman functional and obtain the Bellman equation, which this functional satisfies. The solution of this equation allows to find the control parameter in the form of a functional defined on the set of the state function. Further, by introducing the corresponding functions, feedback control is constructed for the original problem. Unlike program control, this allows to influence the behavior of the system at any time, that is, to ensure the self-regulation of the process. However, let's note that the difficulties in solving this problem are connected with the justification of the proposed method. This is established by the investigation of a closed system

The Origin of Doping in Quasi-Free Standing Graphene on Silicon Carbide

We explain the robust p-type doping observed for quasi-free standing graphene on hexagonal silicon carbide by the spontaneous polarization of the substrate. This mechanism is based on a bulk property of SiC, unavoidable for any hexagonal polytype of the material and independent of any details of the interface formation. We show that sign and magnitude of the polarization are in perfect agreement with the doping level observed in the graphene layer. With this mechanism, models based on hypothetical acceptor-type defects as they are discussed so far are obsolete. The n-type doping of epitaxial graphene is explained conventionally by donor-like states associated with the buffer layer and its interface to the substrate which overcompensate the polarization doping.Comment: 10 pages, 1 figur

Heparin Mimetic Peptide Nanofibers Promote Angiogenesis

Cataloged from PDF version of article.New blood vessel formation (angiogenesis) is one of the most important processes required for functional tissue formation. Induction of angiogenesis is usually triggered by growth factors released by cells. Glycosaminoglycans (e.g., heparan sulphates) in the extracellular matrix aid in proper functioning of these growth factors. Therefore, exogeneous heparin or growth factors were required for promoting angiogenesis in previous regenerative medicine studies. Here we report for the first time induction of angiogenesis by a synthetic nanofibrous peptide scaffold without the addition of any exogenous growth factors or heparin. We designed and synthesized a self-assembling peptide amphiphile molecule that is functionalized with biologically active groups to mimic heparin. Like heparin, this molecule has the ability to interact with growth factors and effectively enhance their bioactivity. The nanofibers formed by these molecules were shown to form a 3D network mimicking the structural proteins in the extracellular matrix. Because of heparin mimicking capabilities of the peptide nanofibers, angiogenesis was induced without the addition of exogenous growth factors in vitro. Bioactive interactions between the nanofibers and the growth factors enabled robust vascularization in vivo as well. Heparin mimetic peptide nanofibers presented here provide new opportunities for angiogenesis and tissue regeneration by avoiding the use of heparin and exogenous growth factors. The synthetic peptide nanofiber scaffolds enriched with proper chemical functional groups shown in this study can be used to induce various desired physiological responses for tissue regeneration. © 2011 American Chemical Society

Traumatic upper cervical esophageal perforation in childhood with door handle

Cervical esophageal rupture due to trauma in childhood is an extremely rare entity associated with a high rate of morbidity and mortality if misdiagnosed. There is still no consensus on the assessment and elective management of children with trauma and esophageal rupture. Surgical primary repair is usually not feasible in patients with delayed diagnosis, especially if the period extends over 48 h. We report a case of an 8-year-old boy who suffered a posterior oropharyngeal and cervical esophageal perforation after accidental intraoral penetration of a door handle. Primary repair was avoided because of late presentation of the patient. In nearly 1½ months, the perforation resolved completely without surgical intervention to the primary site.Keywords: childhood, esophageal perforation, traum

Self-induced penetrating rectal perforation by foreign body: an unusual event in childhood

Traumatic rectal perforation is a very rare and dangerous emergency in childhood. We present a case of rectal perforation due to self-induced transanal impalement.Keywords: children, foreign body, rectal perforatio

Study of Catalytic Properties of the HoxMg1-xAl2O4 Modified HZSM-5 Zeolite in Conversion of Methanol to C2-C4 Alkenes and p-Xylene

Selective conversion of methanol to C2-C4 alkenes and p-xylene is one of the appealing chemical routes. Currently, there are no effective catalysts for the co-production of C2-C4 alkenes and p-xylene from methanol. To date, modified medium-pore ZSM-5 zeolites are considered one of the excellent candidates for the development of selective catalysts for the conversion of methanol to lower alkenes and aromatic hydrocarbons. In this paper, nanosized (30-33nm) powders of HoхMg1-хAl2O4 spinel structure were obtained by the method of combustion of nitrate solutions of aluminium, magnesium, holmium, diethylmalonate and hydrazine monohydrate with the further calcination of nanopowders at 1000 °C. Obtained nanopowders used in the preparation of a solid-phase catalytic composition of HoхMg1-хAl2O4-HZSM-5. Various physico-chemical properties of the catalytic composition were investigated using X-ray diffraction (XRD), pyridine adsorption (BİO-RAD FTS 3000 MX) and low-temperature nitrogen adsorption (BET) techniques. The textural properties and acidity of the catalysts were altered by adjusting the nanopowder concentration (1.0-5.0 wt.%) in the catalytic composition. The conversion of methanol in the presence of the catalytic compositions was carried out in flow-type fixed-bed catalytic reactor at 400 °C, in the presence of nitrogen carrier gas with 1.0 h-1 flow rate. A correlation between the selectivity to C2-C4 alkenes and p-xylene with a ratio of Lewis (L) and Brønsted (B) acid sites and the volume of the catalyst pore, the amount of the modifier in the catalytic system has been established. As the amount of HoхMg1-хAl2O4 nanopowder increases, the ratio of B/L acid sites and the volume of the catalyst pore decrease, which play a significant role in the increase of the selectivity to C2-C4 alkenes and p-xylene. Maximum yield of C2-C4 alkenes (31.6%) and selectivity to p-xylene (80.5%) is achieved on a catalytic composition containing 5.0 wt.% HoxMg1-xAl2O4. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Characterization of ancient ceramic shreds: Insights into firing conditions and manufacturing technology

Four ancient ceramic shreds from the archaeological site Leletepe in the Fizuli region of the Republic of Azerbaijan and two local raw ceramic pastes were characterized by powder X-ray diffraction (PXRD) and thermal analysis (TG-DTG) techniques. XRD analysis of ceramic sherds reveals that all investigated samples contain similar minerals: quartz, feldspar, and clay. Three samples out of four contain calcite. Based on the traditional approach, it has been assumed that the firing process in these samples stopped before 700 °C. The mass loss ratios of samples of ancient ceramics also indicate that reversible dehydroxylation took place in all four samples, thus indicating the initial mild firing conditions. The summary of all the applied methods indicates that the ceramic samples were made using a similar manufacturing technology. According to XRD analysis, samples N1 and N4 contain diopside, and samples N2 and N3 contain maghemite, indicating the different origins of the ceramic shreds. Analysis of the raw ceramic mass also did not reveal the presence of these minerals, which may indicate a discrepancy between the origin of ancient ceramic sherds and modern ones

Bronchogenic Cysts Located in Neck Region: An Uncommon Entity with a Common Reason for Misdiagnosis

Herein we present a child with a bronchogenic cyst, which was located at the right side of the cervical oesophagus displacing it to the left. At operation we found that the cyst had a common wall with the oesophagus, which was completely excised. Preoperative diagnosis was esophageal duplication, however, histopathological analysis confirmed the diagnosis of bronchogenic cyst. As accurate preliminary diagnosis is difficult in bronchogenic cysts, we assume to have this pathology in mind in the differential diagnosis, presenting at atypical locations in the neck regionIndex Word: Bronchogenic cyst, neck, sternum

Traumatic neuroma after torticollis surgery: a rare occurrence

We report a 15 years old girl who admitted to our hospital with signs of recurrent torticollis after two failed operations and consistent pain at the side of surgery. The past operations were performed at 1 and 6 years of age and she has been suffering pain from previous incisions with neck movements. At physical examination, the sternocleidomastoid (SCM) muscle behaved like a fibrous band, restricting the neck movements and resulting in pain. The operation was indicated for the fibrotic SCM. At operation two separate incisions were performed on each end of the SCM to remove all of the fibrotic muscle. The histopathological examination demonstrated a traumatic neuroma which respectively correlates with the pain symptoms. The patient discharged on the second postoperative day and physiotherapy was started. The patient is symptom free one year after the surgery. This case demonstrates a rare occurrence of traumatic neuroma after torticollis surgery, which can manifest with pain.Keywords: neuroma, torticollis, traum

Electrostatic effects on nanofiber formation of self-assembling peptide amphiphiles

Cataloged from PDF version of article.Self-assembling peptide amphiphile molecules have been of interest to various tissue engineering studies. These molecules self-assemble into nanofibers which organize into three-dimensional networks to form hydrocolloid systems mimicking the extracellular matrix. The formation of nanofibers is affected by the electrostatic interactions among the peptides. In this work, we studied the effect of charged groups on the peptides on nanofiber formation. The self-assembly process was studied by pH and zeta potential measurements, FT-IR, circular dichroism, rheology, atomic force microscopy, scanning electron microscopy and transmission electron microscopy. The aggregation of the peptides was triggered upon neutralization of the charged residues by pH change or addition of electrolyte or biomacromolecules. Understanding the controlled formation of the hydrocolloid gels composed of peptide amphiphile nanofibers can lead us to develop in situ gel forming bioactive collagen mimetic nanofibers for various tissue engineering studies including bioactive surface coatings. (C) 2010 Elsevier Inc. All rights reserved