Adsorption-Induced Deformation of Mesoporous Solids

The Derjaguin - Broekhoff - de Boer theory of capillary condensation is employed to describe deformation of mesoporous solids in the course of adsorption-desorption hysteretic cycles. We suggest a thermodynamic model, which relates the mechanical stress induced by adsorbed phase to the adsorption isotherm. Analytical expressions are derived for the dependence of the solvation pressure on the vapor pressure. The proposed method provides a description of non-monotonic hysteretic deformation during capillary condensation without invoking any adjustable parameters. The method is showcased drawing on the examples of literature experimental data on adsorption deformation of porous glass and SBA-15 silica.Comment: 21 pages, 3 figure

Analysis of Transient Processes in a Radiophysical Flow System

Transient processes in a third-order radiophysical flow system are studied and a map of the transient process duration versus initial conditions is constructed and analyzed. The results are compared to the arrangement of submanifolds of the stable and unstable cycles in the Poincare section of the system studied.Comment: 3 pages, 2 figure

Discrete Nonholonomic LL Systems on Lie Groups

This paper applies the recently developed theory of discrete nonholonomic mechanics to the study of discrete nonholonomic left-invariant dynamics on Lie groups. The theory is illustrated with the discrete versions of two classical nonholonomic systems, the Suslov top and the Chaplygin sleigh. The preservation of the reduced energy by the discrete flow is observed and the discrete momentum conservation is discussed.Comment: 32 pages, 13 figure

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

Active Spatial Perception in the Vibrissa Scanning Sensorimotor System

Haptic perception is an active process that provides an awareness of objects that are encountered as an organism scans its environment. In contrast to the sensation of touch produced by contact with an object, the perception of object location arises from the interpretation of tactile signals in the context of the changing configuration of the body. A discrete sensory representation and a low number of degrees of freedom in the motor plant make the ethologically prominent rat vibrissa system an ideal model for the study of the neuronal computations that underlie this perception. We found that rats with only a single vibrissa can combine touch and movement to distinguish the location of objects that vary in angle along the sweep of vibrissa motion. The patterns of this motion and of the corresponding behavioral responses show that rats can scan potential locations and decide which location contains a stimulus within 150 ms. This interval is consistent with just one to two whisk cycles and provides constraints on the underlying perceptual computation. Our data argue against strategies that do not require the integration of sensory and motor modalities. The ability to judge angular position with a single vibrissa thus connects previously described, motion-sensitive neurophysiological signals to perception in the behaving animal

A template-free and low temperature method for the synthesis of mesoporous magnesium phosphate with uniform pore structure and high surface area

Mesoporous phosphates are a group of nanostructured materials with promising applications, particularly in biomedicine and catalysis. However, their controlled synthesis via conventional template-based routes presents a number of challenges and limitations. Here, we show how to synthesize a mesoporous magnesium phosphate with a high surface area and a well-defined pore structure through thermal decomposition of a crystalline struvite (MgNH4PO4·6H2O) precursor. In a first step, struvite crystals with various morphologies and sizes, ranging from a few micrometers to several millimeters, had been synthesized from supersaturated aqueous solutions (saturation index (SI) between 0.5 and 4) at ambient pressure and temperature conditions. Afterwards, the crystals were thermally treated at 70-250 °C leading to the release of structurally bound water (H2O) and ammonia (NH3). By combining thermogravimetric analyses (TGA), scanning and transmission electron microscopy (SEM, TEM), N2 sorption analyses and small- and wide-angle X-ray scattering (SAXS/WAXS) we show that this decomposition process results in a pseudomorphic transformation of the original struvite into an amorphous Mg-phosphate. Of particular importance is the fact that the final material is characterized by a very uniform mesoporous structure with 2-5 nm wide pore channels, a large specific surface area of up to 300 m2 g-1 and a total pore volume of up to 0.28 cm3 g-1. Our struvite decomposition method is well controllable and reproducible and can be easily extended to the synthesis of other mesoporous phosphates. In addition, the so produced mesoporous material is a prime candidate for use in biomedical applications considering that magnesium phosphate is a widely used, non-toxic substance that has already shown excellent biocompatibility and biodegradability