81 research outputs found
Regulation of stress-strain state and calculation of deformations of continuous foundations under increased multiple loads
The analysis of design and operation experience of grain elevators is executed. Metal silos of high capacity are representatives of structures with continuous foundations that perceive increased and multiple loads. Methods of regulating the stress-strain state with the help of creation of artificial bases are considered in detail. A technique for estimating the stress-strain state and calculating the deformations of continuous foundations is proposed
Ecological indices of manufacture of Portland cement clinker and production of the dolomite clinker
The Multisensor Array Based on Grown-On-Chip Zinc Oxide Nanorod Network for Selective Discrimination of Alcohol Vapors at Sub-ppm Range
We discuss the fabrication of gas-analytical multisensor arrays based on ZnO nanorods grown via a hydrothermal route directly on a multielectrode chip. The protocol to deposit the nanorods over the chip includes the primary formation of ZnO nano-clusters over the surface and secondly the oxide hydrothermal growth in a solution that facilitates the appearance of ZnO nanorods in the high aspect ratio which comprise a network. We have tested the proof-of-concept prototype of the ZnO nanorod network-based chip heated up to 400 °C versus three alcohol vapors, ethanol, isopropanol and butanol, at approx. 0.2–5 ppm concentrations when mixed with dry air. The results indicate that the developed chip is highly sensitive to these analytes with a detection limit down to the sub-ppm range. Due to the pristine differences in ZnO nanorod network density the chip yields a vector signal which enables the discrimination of various alcohols at a reasonable degree via processing by linear discriminant analysis even at a sub-ppm concentration range suitable for practical applications
UV-Light-Tunable p-/n-Type Chemiresistive Gas Sensors Based on Quasi-1D TiS\u3csub\u3e3\u3c/sub\u3e Nanoribbons: Detection of Isopropanol at ppm Concentrations
The growing demand of society for gas sensors for energy-efficient environmental sensing stimulates studies of new electronic materials. Here, we investigated quasi-one-dimensional titanium trisulfide (TiS3) crystals for possible applications in chemiresistors and on-chip multisensor arrays. TiS3 nanoribbons were placed as a mat over a multielectrode chip to form an array of chemiresistive gas sensors. These sensors were exposed to isopropanol as a model analyte, which was mixed with air at low concentrations of 1–100 ppm that are below the Occupational Safety and Health Administration (OSHA) permissible exposure limit. The tests were performed at room temperature (RT), as well as with heating up to 110 oC, and under an ultraviolet (UV) radiation at λ = 345 nm. We found that the RT/UV conditions result in a n-type chemiresistive response to isopropanol, which seems to be governed by its redox reactions with chemisorbed oxygen species. In contrast, the RT conditions without a UV exposure produced a p-type response that is possibly caused by the enhancement of the electron transport scattering due to the analyte adsorption. By analyzing the vector signal from the entire on-chip multisensor array, we could distinguish isopropanol from benzene, both of which produced similar responses on individual sensors. We found that the heating up to 110 oC reduces both the sensitivity and selectivity of the sensor array
UV-Light-Tunable p-/n-Type Chemiresistive Gas Sensors Based on Quasi-1D TiS3 Nanoribbons: Detection of Isopropanol at ppm Concentrations
The growing demand of society for gas sensors for energy-efficient environmental sensing stimulates studies of new electronic materials. Here, we investigated quasi-one-dimensional titanium trisulfide (TiS(3)) crystals for possible applications in chemiresistors and on-chip multisensor arrays. TiS(3) nanoribbons were placed as a mat over a multielectrode chip to form an array of chemiresistive gas sensors. These sensors were exposed to isopropanol as a model analyte, which was mixed with air at low concentrations of 1–100 ppm that are below the Occupational Safety and Health Administration (OSHA) permissible exposure limit. The tests were performed at room temperature (RT), as well as with heating up to 110 °C, and under an ultraviolet (UV) radiation at λ = 345 nm. We found that the RT/UV conditions result in a n-type chemiresistive response to isopropanol, which seems to be governed by its redox reactions with chemisorbed oxygen species. In contrast, the RT conditions without a UV exposure produced a p-type response that is possibly caused by the enhancement of the electron transport scattering due to the analyte adsorption. By analyzing the vector signal from the entire on-chip multisensor array, we could distinguish isopropanol from benzene, both of which produced similar responses on individual sensors. We found that the heating up to 110 °C reduces both the sensitivity and selectivity of the sensor array
2D Molybdenum Carbide MXenes for Enhanced Selective Detection of Humidity in Air
2D transition metal carbides and nitrides (MXenes) open up novel opportunities in gas sensing with high sensitivity at room temperature. Herein, 2D Mo2CTx flakes with high aspect ratio are successfully synthesized. The chemiresistive effect in a sub-mu m MXene multilayer for different organic vapors and humidity at 10(1)-10(4) ppm in dry air is studied. Reasonably, the low-noise resistance signal allows the detection of H2O down to 10 ppm. Moreover, humidity suppresses the response of Mo2CTx to organic analytes due to the blocking of adsorption active sites. By measuring the impedance of MXene layers as a function of ac frequency in the 10(-2)-10(6) Hz range, it is shown that operation principle of the sensor is dominated by resistance change rather than capacitance variations. The sensor transfer function allows to conclude that the Mo2CTx chemiresistance is mainly originating from electron transport through interflake potential barriers with heights up to 0.2 eV. Density functional theory calculations, elucidating the Mo2C surface interaction with organic analytes and H2O, explain the experimental data as an energy shift of the density of states under the analyte's adsorption which induces increasing electrical resistance
Anthropometric characteristics of patients suffering from chronic cystitis
Introduction. With a depressingly high prevalence of chronic cystitis (it is believed that half of women suffer from acute cystitis at least once in their lives), there is still no clarity on this disease. We were unable to find any studies on the anthropometric characteristics of patients with chronic cystitis either in the domestic or in the English literature.Objective. To assess the anthropometric characteristics of patients with chronic recurrent cystitis.Material & methods. A prospective multicenter cohort study included 91 patients with symptoms of acute cystitis. All underwent anthropometric measurements, analyzed complaints, studied anamnesis morbi et vitae, performed a study on a gynecological chair; urine was sent for general analysis and bacteriological examination for nonspecific microflora with the determination of the sensitivity of the isolated pathogen to antimicrobial drugs. The patients answered questions about the Russian version of the Acute Cystitis Symptom Score (ACSS). A urethra and cervical canal smear was studied using the polymerase chain reaction method to identify the causative agents of sexually transmitted infections. The diagnosis was considered confirmed in the presence of leukocyturia, bacteriuria, and the sum of symptoms on the ACSS scale was 6 or more.Results. The duration of chronic recurrent cystitis was averaged at 7.1 ± 4.2 years. The age of the patients ranged from 18 to 49 years, averaging 28.9 ± 3.9 years. The height ranged from 150 cm to 178 cm, on average 165.9 ± 7.1 cm. The average weight was within the normal range: 64.2 ± 6.1 kg. However, the spread in the cohort by body weight was two-fold: from 42 to 86 kg. Overweight was found in five (5.5%) patients; two patients (2.2%), on the contrary, had a body weight deficit. When analyzing anthropometric indicators, along with the obvious ones (direct dependence of the duration of the disease on the age of the patient; direct dependence of the quality of life on the severity of symptoms), other statistically significant correlations were established: a positive relationship between age and weight, weight and duration of the disease.Conclusion. The analysis showed that overweight women respond to treatment worse, they have a longer history of cystitis. Neither typical symptoms nor ACSS score correlated with any of the anthropometric measures
The impact of life events on later life: A latent class analysis of the English longitudinal study of ageing
Objectives: Inequalities in life events can lead to inequalities in older age. This research aimed to explore associations between life events reported by older people and quality of life (QoL) and functional ability. Study Design: A latent class analysis (LCA) of the English Longitudinal Study of Ageing wave 3. Methods: Participants were grouped according to eight life events: parental closeness, educational opportunities in childhood, financial hardship, loss of an unborn child, bereavement due to war, involvement in conflict, violence, and experiencing a natural disaster. Linear and logistic regression were used to explore associations between these groups and the main outcomes of functional ability and QoL. Results: 7,555 participants were allocated to four LCA groups: “Few life events” (n=6,250), “Emotionally cold mother” (n=724), “Violence in combat” (n=274) and “Many life events” (n=307). Reduced QoL was reported in the “many life events” (coefficient -5.33, 95%CI -6.61 to -4.05), “emotionally cold mother” (-1.89, -2.62 to 1.15) and “violence in combat” (-1.95, -3.08 to -0.82) groups, compared to the “few life events” group. The “many life events” group also reported more difficulty with activities of daily living. Conclusions: Policies aimed at reducing inequalities in older age should consider events across the life course
The hypothesis about the influence of electrical phenomena on geological processes and global disasters
Global Warming is officially recognized as one of the aspects to the Earth’s climate change; and its major factor is a sharp anthropogenic increase in concentration of greenhouse gases, especially carbon dioxide (CO2). However many scientists do not agree with this view and do not consider the anthropogenic factor as its basic reason, thus regarding measures for limiting greenhouse gas emissions as useless. The authors believe that a real reason is lack of unequivocal ideas in the framework of the Earth Science. The objective of the research presented in the article is to establish true reasons for global catastrophes, global warming, their rapid increase of recent decades, and their hazard level, as well as to reveal their nature and actual mechanisms. The authors critically analyzed and compared the existing data on global processes and catastrophes on Earth from ancient times to nowadays, revealed their actual mechanisms on the basis of Submicroand Macrocolloid Chemistry and Physical-Chemical Mechanics of Earth, a new science on Earth set up by the authors. The authors demonstrated that the motive power of all global phenomena and processes on Earth is the electric force, conditioned by the surplus negative electric charge of Earth, and the reason of the approaching global catastrophe is an abnormal increase of the charge in recent decades. The article deals with critical analysis of experimental data on dynamics of global catastrophes, among them the change in Earth’s temperature and level of ocean, a greater amount of carbon gas and atmosphere dust
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