Bio-inspired gas sensing: boosting performance with sensor optimization guided by "machine learning".

The performance of existing gas sensors often degrades in field conditions because of the loss of measurement accuracy in the presence of interferences. Thus, new sensing approaches are required with improved sensor selectivity. We are developing a new generation of gas sensors, known as multivariable sensors, that have several independent responses for multi-gas detection with a single sensor. In this study, we analyze the capabilities of natural and fabricated photonic three-dimensional (3-D) nanostructures as sensors for the detection of different gaseous species, such as vapors and non-condensable gases. We employed bare Morpho butterfly wing scales to control their gas selectivity with different illumination angles. Next, we chemically functionalized Morpho butterfly wing scales with a fluorinated silane to boost the response of these nanostructures to the vapors of interest and to suppress the response to ambient humidity. Further, we followed our previously developed design rules for sensing nanostructures and fabricated bioinspired inorganic 3-D nanostructures to achieve functionality beyond natural Morpho scales. These fabricated nanostructures have embedded catalytically active gold nanoparticles to operate at high temperatures of ≈300 °C for the detection of gases for solid oxide fuel cell (SOFC) applications. Our performance advances in the detection of multiple gaseous species with specific nanostructure designs were achieved by coupling the spectral responses of these nanostructures with machine learning (a.k.a. multivariate analysis, chemometrics) tools. Our newly acquired knowledge from studies of these natural and fabricated inorganic nanostructures coupled with machine learning data analytics allowed us to advance our design rules for sensing nanostructures toward the required gas selectivity for numerous gas monitoring scenarios at room and high temperatures for industrial, environmental, and other applications.

[Parasitic disease of urinary tract system (on the example of schistosomiasis)].

INTRODUCTION: The globalization observed in the modern world contributes to the increasing rate of the delivery of "exotic" bacterial and parasitic infections from the tropic countries to Russia and the European countries. AIM: To analyze the modern early diagnostic tools of premalignant changes and malignant tumors of urinary bladder of schistosome origin in the residents of endemic areas. MATERIALS AND METHODS: The current study included an analysis of examination and treatment of 181 patients with bladder schistosomiasis who lived in Benguela province in Angola. In 39 cases (21.5%) bladder cancer associated with schistosomiasis was detected. All patients were undergone to surgical treatment. 142 patients (78.5%) were divided into two groups. In Group 1 (n=74) patients had uncomplicated bladder schistosomiasis and in Group II (n=68) the patients with granulomatous inflammatory changes in the urinary bladder were included. RESULTS: The patients with bladder schistosomiasis (n=142) were undergone to outpatient examination. In 38 cases (26.8%) the cytologic study of urinary sediment (CSUS) revealed the schistosomes eggs. With ultrasound study, the specific granulomatous changes in the mucous membrane of urinary bladder were detected in 28 cases (19.7%) while hydronephrosis, calcifications and thickening of bladder wall was diagnosed in 7 (4.9%), 10 (7%) and 99 (69.7%) patients, respectively. During cystoscopy the granulomatous changes in the bladder were found in 68 cases (47.9%). In Group I patients received "Praziquantel" in combination with oral antibiotic therapy, which resulted in resolution of gross hematuria and dysuria. All patients in Group II (n=68) were also administered antibacterial and antiprotozoal therapy. An additional 35 patients (24.6%) were undergone to transurethral bladder resection. Of 33 patients in Group II (23.2%) who received only antibacterial and antiprotozoal therapy the granulomas persisted in 7 cases (4.9%) and, therefore, TURB was performed. The subsequent studies showed the regression of the lesions in these patients. CONCLUSION: CSUS and ultrasound study are not sufficient for diagnosis of bladder schistosomiasis. Cystoscopy is recommended for all patients, since it allows to evaluate bladder volume and to determine the indications for TURB in addition to antiprotozoal and antibacterial therapy.

Multi-environment Nanocalorimeter with Electrical Contacts for Use in the Scanning Electron Microscope.

We have developed a versatile nanocalorimeter sensor which allows imaging and electrical measurements of samples under different gaseous environments using the scanning electron microscope (SEM) and can simultaneously measure the sample temperature and associated heat of reaction. This new sensor consists of four independent heating/sensing elements for nanocalorimetry and eight electrodes for electrical measurements, all mounted on a 50 nm thick, 250 µm × 250 µm suspended silicon nitride membrane. This membrane is highly electron transparent and mechanically robust enabling in situ SEM observation under realistic temperatures, environmental conditions and pressures up to one atmosphere. To demonstrate this new capability, we report here on 1) in situ SEM-nanocalorimetry study of melting and solidification of polyethylene oxide, 2) the temperature dependence of conductivity of a nanowire; 3) the electron beam induced current measurements (EBID) of a nanowire in vacuum and air. Furthermore, the sensor is easily adaptable to operate in liquid environment and is compatible with most existing SEM. This versatile platform couples nanocalorimetry with in situ SEM imaging under various gaseous and liquid environments and is applicable to materials research, nanotechnology, energy, catalysis and biomedical applications.

Age-related features of expression of cell renewal factors in the intestinal Peyer's patches.

Immunohistochemical study with markers of proapoptotic protein P53 and proliferation protein Ki-67 revealed an age-related decrease in proliferative activity of lymphocyte in the intestinal Peyer's patches and an increase in the ratio of apoptotic cells in humans. These changes aggravate atrophy and involution of the intestinal epithelium during aging.

Neuroendocrine and proliferative potential of human intestinal cells during aging.

A population of neuroendocrine cells secreting chromogranin A was verified in the intestine of subjects aged over 60 years. The count of intestinal cells expressing chromogranin A and Ki-67 proliferation protein increases with aging. More intensive expression of chromogranin A and Ki-67 protein in senile age and in long-livers is presumably a compensatory mechanism aimed at the gastrointestinal function maintenance during its age-associated involution.

Symmetry relationship and strain-induced transitions between insulating M1 and M2 and metallic R phases of vanadium dioxide.

The ability to synthesize VO2 in the form of single-crystalline nanobeams and nano- and microcrystals uncovered a number of previously unknown aspects of the metal-insulator transition (MIT) in this oxide. In particular, several reports demonstrated that the MIT can proceed through competition between two monoclinic (insulating) phases M1 and M2 and the tetragonal (metallic) R phase under influence of strain. The nature of such phase behavior has been not identified. Here we show that the competition between M1 and M2 phases is purely lattice-symmetry-driven. Within the framework of the Ginzburg-Landau formalism, both M phases correspond to different directions of the same four-component structural order parameter, and as a consequence, the M2 phase can appear under a small perturbation of the M1 structure such as doping or stress. We analyze the strain-controlled phase diagram of VO2 in the vicinity of the R-M2-M1 triple point using the Ginzburg-Landau formalism and identify and experimentally verify the pathways for strain-control of the transition. These insights open the door toward more systematic approaches to synthesis of VO2 nanostructures in desired phase states and to use of external fields in the control of the VO2 phase states. Additionally, we report observation of the triclinic T phase at the heterophase domain boundaries in strained quasi-two-dimensional VO2 nanoplatelets, and theoretically predict phases that have not been previously observed.

Copper phthalocyanine quasi-1D nanostructures: growth morphologies and gas sensing properties.

The growth conditions of meso- and nanoscopic copper phthalocyanine quasi-1D structures, single crystalline whiskers and "nanowebs" were investigated on various technologically important substrates and were compared to existing literature. The synthesized morphologies were used to fabricate organic conductometric gas-sensing devices, and their sensitivity and selectivity toward NOx were investigated. The obtained results demonstrate excellent sensitivity and selectivity of these quasi-1D chemiresistors. Both the response time of the quasi-1D CuPc sensors and their overall gas sensing performance can be further enhanced by reducing the surface-to-bulk ratio of these nano- and meso-structures.

Application of spectromicroscopy tools to explore local origins of sensor activity in quasi-1D oxide nanostructures.

We have tested a range of imaging and spectroscopic techniques to address their ability to locally explore the interplay between surface reactivity and transport properties of the metal oxide nanostructure wired as a chemiresistor and chemi-FET. In particular, we used scanning surface potential microscopy (SSPM) to monitor the spatial and temporal particularities of the dc potential distributions in an operating device. We also successfully implemented synchrotron radiation-based photoelectron emission microscopy (PEEM) to explore submicron lateral compositional and electronic (work function) inhomogeneity on the surface of an individual nanowire sensor. These results open new avenues to visualize and spectroscopically address the chemical phenomena on an individual quasi-1D nanostructure both in real time and at nano- and mesoscopic level.

Enhanced gas sensing by individual SnO2 nanowires and nanobelts functionalized with Pd catalyst particles.

The sensing ability of individual SnO(2) nanowires and nanobelts configured as gas sensors was measured before and after functionalization with Pd catalyst particles. In situ deposition of Pd in the same reaction chamber in which the sensing measurements were carried out ensured that the observed modification in behavior was due to the Pd functionalization rather than the variation in properties from one nanowire to another. Changes in the conductance in the early stages of metal deposition (i.e., before metal percolation) indicated that the Pd nanoparticles on the nanowire surface created Schottky barrier-type junctions resulting in the formation of electron depletion regions within the nanowire, constricting the effective conduction channel and reducing the conductance. Pd-functionalized nanostructures exhibited a dramatic improvement in sensitivity toward oxygen and hydrogen due to the enhanced catalytic dissociation of the molecular adsorbate on the Pd nanoparticle surfaces and the subsequent diffusion of the resultant atomic species to the oxide surface.

Electronic control of chemistry and catalysis at the surface of an individual tin oxide nanowire.

Tin oxide single nanowires configured as field effect transistors were shown to be operable and tunable alternately as gas sensors or as catalysts under a gaseous atmosphere that simulated realistic ambient conditions. The unusually large surface-to-volume ratio available with nanowires causes adsorption or desorption of donor or acceptor molecules on the nanowire's surface to greatly alter its bulk electron density at relatively small values of the gate voltage. This process can be sensitively monitored as changes in the nanowire's conductivity. The potentially radical change in carrier density can lead to significant changes in the nanowire's sensitivity as a sensor or reciprocally as a catalyst in reactions that involve charge exchange across the nanowire's surface. This leads to the prospect of tuning catalysis or other surface reactions entirely through electronic means.

[Activities of a consultation and diagnostic polyclinic for AIDS and AIDS-related infections]. / O rabote konsul'tativno-diagnosticheskoi polikliniki "SPID i SPID-indikatornye infektsii.

The analysis of curative and diagnostic work of AIDS counselling and diagnostic units (CDU) showed that during a year and a half 15,000 people had been screened, 27 of these were identified as persons infected with human immunodeficiency virus (HIV) and 4 persons identified at other places, were registered for followup. It was found that 51.3 percent of people were screened anonymously, reason for screening being epidemiological indications--history of blood transfusions, homosexual contacts, irregular sexual intercourse. The rest did not observe anonymity, 10.7 percent of these persons were screened by clinical indications. The in-depth clinical screening of patients who sought care in CDU, patients infected with HIV and persons who had contacts with them, required the consultative services of different specialists--dermatovenerologists, gynaecologists, sexologists, stomatologists and some others. It determined the necessity of establishing an outpatient department of "AIDS and AIDS-indicatory infections" which represented a new organizational form of AIDS service.