Polystyrene-based nanocomposites with different fillers: fabrication and mechanical properties

The paper presents a comprehensive analysis of elastic properties of polystyrene-based nanocomposites filled with different types of inclusions: small spherical particles (SiO2 and Al2O3), alumosilicates (montmorillonite, halloysite natural tubules and Mica) and carbon nanofillers (carbon black and multi-walled carbon nanotubes). Composites were fabricated by melt technology. The analysis of composite melts showed that the introduction of Montmorillonite, Multi-walled carbon nanotubes, and Al2O3 particles provided an increase in melt viscosity by an average of 2 to 5 orders of magnitude over the pure polystyrene. Block samples of composites with different filler concentrations were prepared, and their linear and nonlinear elastic properties were studied. The introduction of more rigid particles led to a more profound increase in the elastic modulus of the composite, with the highest rise of about 80% obtained with carbon fillers. Carbon black particles provided also an enhanced strength at break of about 20% higher than that of pure polystyrene. The nonlinear elastic moduli of composites were shown to be more sensitive to addition of filler particles to the polymer matrix than the linear ones. The nonlinearity coefficient $\beta$ comprising the combination of linear and nonlinear elastic moduli of a material demonstrated considerable changes correlating with changes of the Young's modulus. The absolute value of $\beta$ showed rise in 1.5-1.6 times in the CB- and HNT-containing composites as compared to that of pure PS. The changes in nonlinear elasticity of fabricated composites were compared with measurements of the parameters of bulk nonlinear strain waves in them. Variations of wave velocity and decay decrement correlated with observed enhancement of materials nonlinearity

Single-cell and neuronal network alterations in an in vitro model of Fragile X syndrome

The Fragile X mental retardation protein (FMRP) is involved in many cellular processes and it regulates synaptic and network development in neurons. Its absence is known to lead to intellectual disability, with a wide range of comorbidities including autism. Over the past decades, FMRP research focused on abnormalities both in glutamatergic and GABAergic signaling, and an altered balance between excitation and inhibition has been hypothesized to underlie the clinical consequences of absence of the protein. Using Fmrp knockout mice, we studied an in vitro model of cortical microcircuitry and observed that the loss of FMRP largely affected the electrophysiological correlates of network development and maturation but caused less alterations in single-cell phenotypes. The loss of FMRP also caused a structural increase in the number of excitatory synaptic terminals. Using a mathematical model, we demonstrated that the combination of an increased excitation and reduced inhibition describes best our experimental observations during the ex vivo formation of the network connections

Low-Impedance 3D PEDOT:PSS Ultramicroelectrodes

The technology for producing microelectrode arrays (MEAs) has been developing since the 1970s and extracellular electrophysiological recordings have become well established in neuroscience, drug screening and cardiology. MEAs allow monitoring of long-term spiking activity of large ensembles of excitable cells noninvasively with high temporal resolution and mapping its spatial features. However, their inability to register subthreshold potentials, such as intrinsic membrane oscillations and synaptic potentials, has inspired a number of laboratories to search for alternatives to bypass the restrictions and/or increase the sensitivity of microelectrodes. In this study, we present the fabrication and in vitro experimental validation of arrays of PEDOT:PSS-coated 3D ultramicroelectrodes, with the best-reported combination of small size and low electrochemical impedance. We observed that this type of microelectrode does not alter neuronal network biological properties, improves the signal quality of extracellular recordings and exhibits higher selectivity toward single unit recordings. With fabrication processes simpler than those reported in the literature for similar electrodes, our technology is a promising tool for study of neuronal networks. \ua9 Copyright \ua9 2020 Jones, Moskalyuk, Barthold, Gut\uf6hrlein, Heusel, Schr\uf6ppel, Samba and Giugliano

ВИЗНАЧЕННЯ ТОКСИЧНОСТІ НОВОГО ДЕЗІНФІКУЮЧОГО ЗАСОБУ ТДС

The article presents the parameters of acute toxicity and side effects of new acid–detergent disinfectant TDS, which is used to sanitize dairy liquid. It was established that the figures DL50 native solution (concentrate) disinfectant is more than 2500 mg/kg. According to its toxic properties owned disinfectant according to GHS (globally harmonized system of classification and hazard labeling of chemicals) to the V class of toxicity – low toxic substance has weak skin–irritating properties and strong locally irritating action.The working preparation solution (0,5 % concentration) for its toxic properties not classified by GHS, because DL50  is larger that 10,000 mg / kg. Working solution has no skin–irritant properties, and locally irritant effect is 24–48 hours.В статье приведены параметры острой токсичности и побочного действия нового кислотного моюще–дезинфицирующего средства ТДС, который применяется для санитарной обработки молочной посуды. Установлено, что показатели DL50 нативного раствора (концентрата) дезинфектанта — больше 2500 мг/кг. По своим токсичным свойствам дезинфектант принадлежит, согласно СГС (согласованная на глобальном уровне система классификации опасности и маркировки химической продукции), к V классу токсичности – малотоксичные вещества, обладает слабыми кожно–раздражающими свойствами и сильным местно–раздражающим действием. Рабочий раствор препарата (0,5 % концентрации) по своим токсичным свойствам не квалифицируется по СГС, поскольку его DL50 является больше 10000 мг/кг. Рабочий раствор не обладает кожно–раздражающими свойствами, а местно–раздражающее действие проявляется в течение 24–48 часов.У статті наведено параметри гострої токсичності та побічної дії нового кислотного мийно–дезінфікуючого засобу ТДС, що застосовується для санітарної обробки молочного посуду. Встановлено, що показник DL50 нативного  (розчину концентрату) дезінфектанту є більшим як 2500 мг/кг. За своїми токсичними властивостями дезінфектант належить, згідно з УГС (узгоджена на глобальному рівні система класифікації небезпеки та маркування хімічної продукції ), до V класу токсичності – малотоксичні речовини, володіє слабкими шкірно–подразнюючими властивостями та сильною місцево–падразнюючою дією.Робочий розчин препарату у 0,5 % концентрації за своїми токсичними властивостями не кваліфікується за УГС, оскільки DL50  його є більшим, ніж 10000 мг/кг. Робочий розчин не володіє шкірно–подразнюючими властивостями, а місцево–подразнююча дія проявляється протягом 24–48 годин

Comparative Evaluation of Biomechanical Characteristics of Acellular Dermal Matrix for Hernioplasty

Background. With the introduction of synthetic mesh implants into clinical practice, the recurrence rate of postoperative ventral hernias was signifi cantly reduced. The extensive use of synthetic implants led to the development of specifi c complications. The development of biological implants, based on extensively purifi ed decellularized collagen matrix of xenogeneic origin is highly relevant due to the fact that, unlike synthetic analogues, they have a biological origin and biodegrade in a natural way, gradually being replaced with newly formed connective tissue. The use of bioprostheses reduces the risk of complications.Objectives. To conduct a comparative evaluation of the biomechanical characteristics of acellular dermal matrix, obtained by detergent-enzymatic decellularization, and commercially distributed Permacol™ matrix.Methods. Acellular dermal matrix (ADM) was created by using samples of native skin of pig of Landras breed aged 4 months. The dermis was processed by means of detergent-enzymatic method. In order to evaluate and compare the mechanical properties of acellular dermal matrix, the biological samples were divided into 2 groups of 15 samples each. The fi rst group included acellular dermal matrix samples, the second group — native samples of pigs unprocessed dermis. The control group consisted of samples of PermacolTM Surgical Implant, xenotransplant for hernioplasty approved for use in the Russian Federation (Covidien, France). All samples were tested wet using universal testing instrument Instron 1122. MedCalc Statistical Software (Belgium) was used for statistical processing of the study results.Results. In the present study, pig dermis was processed using a detergent-enzymatic method to produce ADM. Routine histological examination confi rmed the removal of all cellular elements, and at the same time it was proven that the native structure of the dermis remained intact during its processing. The mechanical characteristics of xenogenic ADM were further determined. Its tensile strength was 9.1 ± 0.6 MPa (910 N/cm2 ), elongation to break was 21.1 ± 2.3%, and elastic modulus was 50.0 ± 1.6 MPa. These characteristics largely corresponded to the strength characteristics of native pig dermis and far exceeded the necessary physiological parameters. PermacolTM control was tested in two directions (longitudinal and transverse). In the longitudinal direction, the sample had higher mechanical characteristics: strength — 12.0 ± 1.7 MPa, elongation to break — 29.7 ± 2.4%, stiffness modulus — 47.2 ± 6.5 MPa. In the transverse direction, all indicators were 1.5–2 times lower.Conclusion. The developed xenogeneic biological implant in the form of ADM demonstrates rather good characteristics of plasticity, tensile strength and elasticity, to be used as a biological endoprosthesis for plasty of hernia defects of the abdominal wall of any size and shape

Study of air conditioning systems for storage and display of art works

The article describes technical characteristics of modern air conditioning systems that are of use to ensure the ambient conditions required for storage and display of art works in art museums. The author performs comparison analysis of centralized and autonomous air conditioning systems. The article includes an inference about how important it is to combine elements of both systems according to the design tasks and features of the integrated museum and exhibition platform (Museum Quarter in Krasnoyarsk), which includes historical buildings and new modern exhibition areas

Резистентность к антибактериальным препаратам и бактериофагам изолятов Klebsiella pneumoniae, выделенных от детей разного возраста с кишечными инфекциями

The aim is to study the antibiotic and phage resistance of K. pneumoniae strains isolated from children with acute intestinal infections. Materials and methods. 490 K. pneumoniae strains isolated by the bacteriological method from feces from patients with intestinal infections of various etiologies aged from 1 month to 18 years in the period 2019—2021 were studied. The diagnosis of intestinal infection caused by K. pneumoniae was established taking into account the detection of the pathogen at a concentration of at least 5 lg CFU/g (n = 283; 57.8%). Children with Klebsiella seeding, made up three age groups: from 1 to 12 months of life (n = 245; 50%); from 1 to 3 years (n = 131; 26.7%); from 3 to 18 years (n = 114; 23.3%). Results. A higher frequency of K. pneumoniae seeding in high concentrations from fecal samples of children with intestinal infections aged from 1 to 12 months was established (?2 = 14.24; p < 0.001). Analysis of the frequency of K. pneumoniae resistance to antimicrobials revealed its increase to ampicillin/sulbactam from 4.2 ± 1.6% to 9.7 ± 1.9% and to gentamicin from 3.0 ± 1.3% to 7.6 ± 1.7% (p < 0.05) with an increase in the concentration of the pathogen from 3—4 to 5—6 lg CFU/ml. In K. pneumoniae strains isolated in low concentrations, resistance to polyvalent anti-klebsiella bacteriophage was significantly higher than to monovalent bacteriophage. Conclusion. Children of the first year of life belong to the risk group for the development of klebsiella intestinal infection. An increase in the frequency of K. pneumoniae resistance to ampicillin/sulbactam and gentamicin correlates with an increase in the concentration of the pathogen in fecal samples.Цель — совершенствование этиотропной терапии бактериальных ОКИ у детей различных возрастных групп на основе определения резистентности штаммов Klebsiella рneumoniae внебольничного происхождения к антибиотикам и бактериофагам. Материалы и методы. Исследованы 490 штаммов K. pneumoniae, выделенных бактериологическим методом из фекалий от больных кишечными инфекциями различной этиологии в возрасте от 1 месяца до 18 лет в период 2019—2021 гг. Диагноз кишечной инфекции, вызванной K. pneumoniae, устанавливали при обнаружении возбудителя в концентрации не менее 5 lg КОЕ/г (n = 283; 57,8%). Дети с высевом клебсиелл составили три возрастные группы: от 1 до 12 месяцев (n = 245; 50%); от 1 до 3 лет (n = 131; 26,7%); от 3 до 18 лет (n = 114; 23,3%). Результаты. Установлена более высокая частота высевов K. pneumoniae в высоких концентрациях из фекальных проб детей с кишечными инфекциями в возрасте от 1 до 12 месяцев (χ2 = 14,24; p < 0,001). Анализ частоты резистентности K. pneumoniae к антимикробным препаратам выявил ее нарастание к ампициллину/сульбактаму с 4,2 ± 1,6% до 9,7 ± 1,9% и к гентамицину с 3,0 ± 1,3% до 7,6 ± 1,7% (p < 0,05) с повышением концентрации возбудителя от 3—4 до 5—6 lg КОЕ/мл. У штаммов K. pneumoniae, выделенных в низкой концентрации, резистентность к поливалентному антиклебсиеллезному бактериофагу, была значимо выше, чем к моновалентному бактериофагу. Заключение. Дети первого года жизни относятся к группе риска по развитию клебсиеллезной кишечной инфекции. Нарастание частоты резистентности K. pneumoniae к ампициллину/сульбактаму и к гентамицину коррелирует с повышением концентрации возбудителя в пробах фекалий

Linear and Nonlinear Elastic Properties of Polystyrene-Based Nanocomposites with Allotropic Carbon Fillers and Binary Mixtures

We report measurements of linear and nonlinear elastic properties of polystyrene-based nanocomposites with six types of nanofillers, including single and binary mixtures of allotropic carbon nanoparticles. Composite samples were fabricated by the same technology and contained the same filler concentration (5% wt.), which allowed for a direct comparison of their properties. It was shown that the most significant variations of linear and nonlinear elastic properties occur in different nanocomposites. In particular, the most pronounced enhancements of linear elastic moduli (in about 50%) obtained in tensile and flexural tests and in dynamic mechanical analysis were recorded in the sample filled with spherical fullerene nanoparticles. While the most profound rise of absolute values of nonlinear elastic moduli (tens of times) was obtained in the sample filled with the mixture of carbon nanotubes and graphene. The observed tendencies demonstrated the synergistic effect of fillers of different dimensionality on the elastic properties of nanocomposites

Study of air conditioning systems for storage and display of art works

The article describes technical characteristics of modern air conditioning systems that are of use to ensure the ambient conditions required for storage and display of art works in art museums. The author performs comparison analysis of centralized and autonomous air conditioning systems. The article includes an inference about how important it is to combine elements of both systems according to the design tasks and features of the integrated museum and exhibition platform (Museum Quarter in Krasnoyarsk), which includes historical buildings and new modern exhibition areas