Rationalizing Graphene-ZnO Composites for Gas Sensing via Functionalization with Amines

The rational design of composites based on graphene/metal oxides is one of the pillars for advancing their application in various practical fields, particularly gas sensing. In this study, a uniform distribution of ZnO nanoparticles (NPs) through the graphene layer was achieved, taking advantage of amine functionalization. The beneficial effect of amine groups on the arrangement of ZnO NPs and the efficiency of their immobilization was revealed by core-level spectroscopy, pointing out strong ionic bonding between the aminated graphene (AmG) and ZnO. The stability of the resulting Am-ZnO nanocomposite was confirmed by demonstrating that its morphology remains unchanged even after prolonged heating up to 350 °C, as observed by electron microscopy. On-chip multisensor arrays composed of both AmG and Am-ZnO were fabricated and thoroughly tested, showing almost tenfold enhancement of the chemiresistive response upon decorating the AmG layer with ZnO nanoparticles, due to the formation of p-n heterojunctions. Operating at room temperature, the fabricated multisensor chips exhibited high robustness and a detection limit of 3.6 ppm and 5.1 ppm for ammonia and ethanol, respectively. Precise identification of the studied analytes was achieved by employing the pattern recognition technique based on linear discriminant analysis to process the acquired multisensor response.

Alcohol Vapor Sensor Based on Quasi-2D Nb2O5 Derived from Oxidized Nb2CTz MXenes

MXenes are two-dimensional (2D) materials with a great potential for sensor applications due to their high aspect ratio and fully functionalized surface that can be tuned for specific gas adsorption. Here, we demonstrate that the Nb2CTz-based sensor exhibits high performance towards alcohol vapors at temperatures up to 300-350 °C, with the best sensitivity towards ethanol. We attribute the observed remarkable chemiresistive effect of this material to the formation of quasi-2D Nb2O5 sheets as the result of the oxidation of Nb-based MXenes. These findings are supported by synchrotron X-ray photoelectron spectroscopy studies together with X-ray diffraction and electron microscopy observations. For analyte selectivity, we employ a multisensor approach where the gas recognition is achieved by linear discriminant analysis of the vector response of the on-chip sensor array. The reported protocol demonstrates that MXene layers are efficient precursors for the derivation of 2D oxide architectures, which are suitable for developing gas sensors and sensor arrays.

Effects of Plasma Treatment on the Surface and Photocatalytic Properties of Nanostructured SnO2-SiO2 Films

In this work, we study the effects of treating nanostructured SnO₂-SiO₂ films derived by a sol-gel method with nitrogen and oxygen plasma. The structural and chemical properties of the films are closely investigated. To quantify surface site activity in the films following treatment, we employed a photocatalytic UV degradation test with brilliant green. Using X-ray photoelectron spectroscopy, it was found that treatment with oxygen plasma led to a high deviation in the stoichiometry of the SnO₂ surface and even the appearance of a tin monoxide phase. These samples also exhibited a maximum photocatalytic activity. In contrast, treatment with nitrogen plasma did not lead to any noticeable changes in the material. However, increasing the power of the plasma source from 250 W to 500 W led to the appearance of an SnO fraction on the surface and a reduction in the photocatalytic activity. In general, all the types of plasma treatment tested led to amorphization in the SnO₂-SiO₂ samples.

Adaptive Peptide Molecule as the Promising Highly-Efficient Gas-Sensor Material: In Silico Study

Gas sensors are currently employed in various applications in fields such as medicine, ecology, and food processing, and serve as monitoring tools for the protection of human health, safety, and quality of life. Herein, we discuss a promising direction in the research and development of gas sensors based on peptides-biomolecules with high selectivity and sensitivity to various gases. Thanks to the technique developed in this work, which uses a framework based on the density-functional tight-binding theory (DFTB), the most probable adsorption centers were identified and used to describe the interaction of some analyte molecules with peptides. The DFTB method revealed that the physical adsorption of acetone, ammonium, benzene, ethanol, hexane, methanol, toluene, and trinitrotoluene had a binding energy in the range from -0.28 eV to -1.46 eV. It was found that peptides may adapt to the approaching analyte by changing their volume up to a maximum value of approx. 13%, in order to confine electron clouds around the adsorbed molecule. Based on the results obtained, the prospects for using the proposed peptide configurations in gas sensor devices are good.

Nanocomposite Co3O4-ZnO Thin Films for Photoconductivity Sensors

Thin nanocomposite films based on zinc oxide (ZnO) added with cobalt oxide (Co₃O₄) were synthesized by solid-phase pyrolysis. According to XRD, the films consist of a ZnO wurtzite phase and a cubic structure of Co₃O₄ spinel. The crystallite sizes in the films increased from 18 nm to 24 nm with growing annealing temperature and Co₃O₄ concentration. Optical and X-ray photoelectron spectroscopy data revealed that enhancing the Co₃O₄ concentration leads to a change in the optical absorption spectrum and the appearance of allowed transitions in the material. Electrophysical measurements showed that Co₃O₄-ZnO films have a resistivity up to 3 × 10⁴ Ohm∙cm and a semiconductor conductivity close to intrinsic. With advancing the Co₃O₄ concentration, the mobility of the charge carriers was found to increase by almost four times. The photosensors based on the 10Co-90Zn film exhibited a maximum normalized photoresponse when exposed to radiation with wavelengths of 400 nm and 660 nm. It was found that the same film has a minimum response time of ca. 26.2 ms upon exposure to radiation of 660 nm wavelength. The photosensors based on the 3Co-97Zn film have a minimum response time of ca. 58.3 ms versus the radiation of 400 nm wavelength. Thus, the Co₃O₄ content was found to be an effective impurity to tune the photosensitivity of radiation sensors based on Co₃O₄-ZnO films in the wavelength range of 400-660 nm.

Toward On-Chip Multisensor Arrays for Selective Methanol and Ethanol Detection at Room Temperature: Capitalizing the Graphene Carbonylation

The artificial olfaction units (or e-noses) capable of room-temperature operation are highly demanded to meet the requests of society in numerous vital applications and developing Internet-of-Things. Derivatized 2D crystals are considered as sensing elements of choice in this regard, unlocking the potential of the advanced e-nose technologies limited by the current semiconductor technologies. Herein, we consider fabrication and gas-sensing properties of On-chip multisensor arrays based on a hole-matrixed carbonylated (C-ny) graphene film with a gradually changed thickness and concentration of ketone groups of up to 12.5 at.%. The enhanced chemiresistive response of C-ny graphene toward methanol and ethanol, of hundred ppm concentration when mixing with air to match permissible exposure OSHA limits, at room-temperature operation is signified. Following thorough characterization via core-level techniques and density functional theory, the predominant role of the C-ny graphene-perforated structure and abundance of ketone groups in advancing the chemiresistive effect is established. Advancing practice applications, selective discrimination of the studied alcohols is approached by linear discriminant analysis employing a multisensor array's vector signal, and the fabricated chip's long-term performance is shown.

Paper-Based Humidity Sensors as Promising Flexible Devices, State of the Art, Part 2: Humidity-Sensor Performances

This review article covers all types of paper-based humidity sensor, such as capacitive, resistive, impedance, fiber-optic, mass-sensitive, microwave, and RFID (radio-frequency identification) humidity sensors. The parameters of these sensors and the materials involved in their research and development, such as carbon nanotubes, graphene, semiconductors, and polymers, are comprehensively detailed, with a special focus on the advantages/disadvantages from an application perspective. Numerous technological/design approaches to the optimization of the performances of the sensors are considered, along with some non-conventional approaches. The review ends with a detailed analysis of the current problems encountered in the development of paper-based humidity sensors, supported by some solutions.

Application of Titanium Carbide MXenes in Chemiresistive Gas Sensors

The titanium carbide MXenes currently attract an extreme amount of interest from the material science community due to their promising functional properties arising from the two-dimensionality of these layered structures. In particular, the interaction between MXene and gaseous molecules, even at the physisorption level, yields a substantial shift in electrical parameters, which makes it possible to design gas sensors working at RT as a prerequisite to low-powered detection units. Herein, we consider to review such sensors, primarily based on Ti₃C₂T_x and Ti₂CT_x crystals as the most studied ones to date, delivering a chemiresistive type of signal. We analyze the ways reported in the literature to modify these 2D nanomaterials for (i) detecting various analyte gases, (ii) improving stability and sensitivity, (iii) reducing response/recovery times, and (iv) advancing a sensitivity to atmospheric humidity. The most powerful approach based on designing hetero-layers of MXenes with other crystals is discussed with regard to employing semiconductor metal oxides and chalcogenides, noble metal nanoparticles, carbon materials (graphene and nanotubes), and polymeric components. The current concepts on the detection mechanisms of MXenes and their hetero-composites are considered, and the background reasons for improving gas-sensing functionality in the hetero-composite when compared with pristine MXenes are classified. We formulate state-of-the-art advances and challenges in the field while proposing some possible solutions, in particular via employing a multisensor array paradigm.

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 (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 °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.

Modeling Interfacial Interaction between Gas Molecules and Semiconductor Metal Oxides: A New View Angle on Gas Sensing

With the development of internet of things and artificial intelligence electronics, metal oxide semiconductor (MOS)-based sensing materials have attracted increasing attention from both fundamental research and practical applications. MOS materials possess intrinsic physicochemical properties, tunable compositions, and electronic structure, and are particularly suitable for integration and miniaturization in developing chemiresistive gas sensors. During sensing processes, the dynamic gas-solid interface interactions play crucial roles in improving sensors' performance, and most studies emphasize the gas-MOS chemical reactions. Herein, from a new view angle focusing more on physical gas-solid interactions during gas sensing, basic theory overview and latest progress for the dynamic process of gas molecules including adsorption, desorption, and diffusion, are systematically summarized and elucidated. The unique electronic sensing mechanisms are also discussed from various aspects including molecular interaction models, gas diffusion mechanism, and interfacial reaction behaviors, where structure-activity relationship and diffusion behavior are overviewed in detail. Especially, the surface adsorption-desorption dynamics are discussed and evaluated, and their potential effects on sensing performance are elucidated from the gas-solid interfacial regulation perspective. Finally, the prospect for further research directions in improving gas dynamic processes in MOS gas sensors is discussed, aiming to supplement the approaches for the development of high-performance MOS gas sensors.

Toward a Selective Analysis of Heavy Metal Salts in Aqueous Media with a Fluorescent Probe Array

Detection of heavy meals in aqueous media challenges worldwide research in developing particularly fast and affordable methods. Fluorescent sensors look to be an appropriate instrument for such a task, as recently they have been found to have made large progress in the detection of chemical analytes, primarily in the environment, along with biological fluids, which still suffer from not enough selectivity. In this work, we propose a new fluorescent method to selectively recognize heavy metals in an aqueous solution via employing an array of several fluorescent probes: acridine yellow, eosin, and methylene blue, which were taken as examples, being sensitive to a microsurrounding of the probe molecules. The exemplary sensor array generated six channels of spectral information through the use of various combinations of excitation and detection wavelengths. Following the known multisensor approach, we applied a linear discriminant analysis to selectively distinguish the vector signals from the sensor array from salts of heavy metals-Cu, Pb, Zn, Cd, and Cz-at the concentration ranges of 2.41 × 10^-6-1.07 × 10^-5 M, 2.8 × 10^-5-5.87 × 10^-4 M, 1.46 × 10^-6-6.46 × 10^-6 M, 1.17 × 10^-8-5.2 × 10^-8 M, and 2.11 × 10^-6-9.33 × 10^-6 M, respectively. The suggested approach was found to be promising due to it employing only one cuvette containing the test solution, simplifying a sample preparation when compared to preparing a variety of solutions in tests with single fluorescence probes.

A Blueprint for the Synthesis and Characterization of Thiolated Graphene

Graphene derivatization to either engineer its physical and chemical properties or overcome the problem of the facile synthesis of nanographenes is a subject of significant attention in the nanomaterials research community. In this paper, we propose a facile and scalable method for the synthesis of thiolated graphene via a two-step liquid-phase treatment of graphene oxide (GO). Employing the core-level methods, the introduction of up to 5.1 at.% of thiols is indicated with the simultaneous rise of the C/O ratio to 16.8. The crumpling of the graphene layer upon thiolation without its perforation is pointed out by microscopic and Raman studies. The conductance of thiolated graphene is revealed to be driven by the Mott hopping mechanism with the sheet resistance values of 2.15 kΩ/sq and dependable on the environment. The preliminary results on the chemiresistive effect of these films upon exposure to ethanol vapors in the mix with dry and humid air are shown. Finally, the work function value and valence band structure of thiolated graphene are analyzed. Taken together, the developed method and findings of the morphology and physics of the thiolated graphene guide the further application of this derivative in energy storage, sensing devices, and smart materials.

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 Mo₂ CT_x flakes with high aspect ratio are successfully synthesized. The chemiresistive effect in a sub-µm MXene multilayer for different organic vapors and humidity at 10¹ -10⁴  ppm in dry air is studied. Reasonably, the low-noise resistance signal allows the detection of H₂ O down to 10 ppm. Moreover, humidity suppresses the response of Mo₂ CT_x 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 -10⁶  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 Mo₂ CT_x chemiresistance is mainly originating from electron transport through interflake potential barriers with heights up to 0.2 eV. Density functional theory calculations, elucidating the Mo₂ C surface interaction with organic analytes and H₂ O, explain the experimental data as an energy shift of the density of states under the analyte's adsorption which induces increasing electrical resistance.

Microplotter-Printed On-Chip Combinatorial Library of Ink-Derived Multiple Metal Oxides as an "Electronic Olfaction" Unit

Information about the surrounding atmosphere at a real timescale significantly relies on available gas sensors to be efficiently combined into multisensor arrays as electronic olfaction units. However, the array's performance is challenged by the ability to provide orthogonal responses from the employed sensors at a reasonable cost. This issue becomes more demanded when the arrays are designed under an on-chip paradigm to meet a number of emerging calls either in the internet-of-things industry or in situ noninvasive diagnostics of human breath, to name a few, for small-sized low-powered detectors. The recent advances in additive manufacturing provide a solid top-down background to develop such chip-based gas-analytical systems under low-cost technology protocols. Here, we employ hydrolytically active heteroligand complexes of metals as ink components for microplotter patterning a multioxide combinatorial library of chemiresistive type at a single chip equipped with multiple electrodes. To primarily test the performance of such a multisensor array, various semiconducting oxides of the p- and n-conductance origins based on pristine and mixed nanocrystalline MnO_x, TiO₂, ZrO₂, CeO₂, ZnO, Cr₂O₃, Co₃O₄, and SnO₂ thin films, of up to 70 nm thick, have been printed over hundred μm areas and their micronanostructure and fabrication conditions are thoroughly assessed. The developed multioxide library is shown to deliver at a range of operating temperatures, up to 400 °C, highly sensitive and highly selective vector signals to different, but chemically akin, alcohol vapors (methanol, ethanol, isopropanol, and n-butanol) as examples at low ppm concentrations when mixed with air. The suggested approach provides us a promising way to achieve cost-effective and well-performed electronic olfaction devices matured from the diverse chemiresistive responses of the printed nanocrystalline oxides.

Light-Tuned DC Conductance of Anatase TiO₂ Nanotubular Arrays: Features of Long-Range Charge Transport

Experimental results related to the photoactivated dc conductance of anatase TiO₂ nanotubular arrays (aTNTAs) under pulsed irradiation by a laser light inside and outside the fundamental absorption band are presented. It is found that the mobility and diffusion coefficients of charge carriers in the examined aTNTA are extremely low due to a strong charge-phonon coupling, abundance of shallow traps, and hopping conductivity between adjacent nanotubes. We consider that the confining electric field appeared within the array structure due to the difference in the local concentrations of excess electrons and holes at large values of the dc conductance suppresses the drift current. In this case, the dc conductance of such aTNTAs is mainly matured by the diffusion of mobile carriers. A recurrent kinetic model for evolution of the dc conductance of aTNTAs under laser irradiation has been proposed to interpret the experimental results.

The Room-Temperature Chemiresistive Properties of Potassium Titanate Whiskers versus Organic Vapors

The development of portable gas-sensing units implies a special care of their power efficiency, which is often approached by operation at room temperature. This issue primarily appeals to a choice of suitable materials whose functional properties are sensitive toward gas vapors at these conditions. While the gas sensitivity is nowadays advanced by employing the materials at nano-dimensional domain, the room temperature operation might be targeted via the application of layered solid-state electrolytes, like titanates. Here, we report gas-sensitive properties of potassium titanate whiskers, which are placed over a multielectrode chip by drop casting from suspension to yield a matrix mono-layer of varied density. The material synthesis conditions are straightforward both to get stable single-crystalline quasi-one-dimensional whiskers with a great extent of potassium replacement and to favor the increase of specific surface area of the structures. The whisker layer is found to be sensitive towards volatile organic compounds (ethanol, isopropanol, acetone) in the mixture with air at room temperature. The vapor identification is obtained via processing the vector signal generated by sensor array of the multielectrode chip with the help of pattern recognition algorithms.

Potassium polytitanate gas-sensor study by impedance spectroscopy

Nanocrystalline potassium polytitanates K2O·nTiO2·mH2O represent a new type of semiconducting compounds which are characterized by a high specific surface that makes them promising for use in gas sensors. In this work, we have studied potassium polytitanate mesoporous nanoparticle agglomerates placed over a SiO2/Si substrate equipped with multiple coplanar electrodes to measure the electrical response to various organic vapors, 1000 ppm of concentration, mixed with air by impedance spectrometry in range of the 10(-2)-10(6) Hz. The recorded impedance data for each sensor segment are associated with RC components of an equivalent circuit which are applied to selectively recognize the test vapors exploiting a "multisensor array" approach.

Single-nanobelt electronic nose: engineering and tests of the simplest analytical element

Electronic instruments mimicking the mammalian olfactory system are often referred to as "electronic noses" (E-noses). Thanks to recent nanotechnology breakthroughs the fabrication of mesoscopic and even nanoscopic E-noses is now feasible in the size domain where miniaturization of the microanalytical systems encounters principal limitations. Here we describe probably the simplest and yet fully functioning E-nose made of an individual single-crystal metal oxide quasi-1D nanobelt. The nanobelt was indexed with a number of electrodes in a way that each segment of the nanobelt between two electrodes defines an individual sensing elemental "receptor" of the array. The required diversity of the sensing elements is "encoded" in the nanobelt morphology via longitudinal width variations of the nanobelt realized during its growth and via functionalization of some of the segments with Pd catalyst. The proposed approach represents the combined bottom-up/top-down technologically viable route to develop robust and sensitive analytical systems scalable down to submicrometer dimensions.

A gradient microarray electronic nose based on percolating SnO(2) nanowire sensing elements

Fabrication, characterization, and tests of the practical gradient microarray electronic nose with SnO(2) nanowire gas-sensing elements are reported. This novel device has demonstrated an excellent performance as a gas sensor and e-nose system capable of promptly detecting and reliably discriminating between several reducing gases in air at a ppb level of concentration. It has been found that, in addition to the temperature gradient across the nanowire layer, the density and morphological inhomogeneities of nanowire mats define the discriminating power of the electronic nose.

Toward the nanoscopic "electronic nose": hydrogen vs carbon monoxide discrimination with an array of individual metal oxide nano- and mesowire sensors

The array of chemiresistors made of individual pristine SnO2, surface doped (Ni)-SnO2 nanowires, and TiO2 and In2O3 mesoscopic whiskers was fabricated on a Si/SiO2 wafer. Their conductance was measured under pulses of H2 and CO reducing gases in oxygen as background gas. The nanostructures were shown to be n-type semiconductors possessing high sensitivity to the target gases. Following the "electronic nose" concept, correlation analysis of response of three-chemiresistor array is shown to be sufficient to discriminate between H2 and CO signals.

[The effect of temperature on the growth of the promastigotes of different species of Leishmania]

The specific growth rate (r), the time of reduplication (T), reproduction rates (k) and the duration of the exponential phase (E) of L.major (L.m.), L.turanica (L.t.), and L.gerbilli (L.g.) are different from one another. It is shown that they differently depend on the temperature. Temperature has the greatest influence on L.g and the least on L.m. and its intermediate influence on L.t. The growth of long-term cultivation strains depends on the temperature than that short-term ones. It is associated with the adaptation rate of leishmania promastigotes to the growth in the nutrient medium. The optimum temperatures are defined for reproduction of the three species.

[A comparison of the growth of Leishmania major, L. turanica and L. gerbilli on NNN medium]

Leishmania promastigotes grew in the NNN medium with medium-199 as a liquid phase. The NNN medium was prepared with agar bases of the following firms: Sigma, Oxoid, Difco, Medbioprom (Russia). Growth characteristics were examined with the following indices: specific growth rate (r), reduplication time (T), reproductive rate (k). The investigations have shown that the kind of agar base has the most influence on the r and T of L.turanica and L.gerbelli and on the k of L.major. The greatest differences of the r and T of 3 species were found when the Sigma agar base was used. The kinds of agar bases were selected for long-term cultivation and biomass growing. The ways of Leishmania adaptation to growth in different media were discussed.

[The isoenzyme identification of Leishmania isolates taken from greater gerbils, sandflies and human patients in foci of zoonotic cutaneous leishmaniasis in Turkmenistan]

In 1991-1992, 230 isolates were obtained in the Tedzhen oasis and its adjacent desert areas: 172 isolates from great gerbils, 39 from P. papatasi, and 19 from human cutaneous leishmaniasis patients. All the isolates were identified by the isoenzyme polyacrylamide gel electrophoresis by 8 enzymes. The characteristics of Leishmania circulation in the hyperendemic foci of Turkmenistan were similar to those previously studied in the mesoendemic areas of Uzbekistan and Kazakhstan. L. turanica which is non-pathogenic for man prevailed among infected great gerbils in winter, spring, and early summer, making the natural foci epidemiologically safe in that period of time. It was only in August-September that the great gerbil infection rate by L. major appeared to increase, occasionally reaching 100%. Epizootics due to L. major are developing in the presence of L. turanica, therefore most isolates are clone mixtures of L. major and L. turanica. P. papatasi is the only vector in the Tedzhen oasis; there has been strong evidence for its transmission of both L. major and L. turanica, which makes the concept inconsistent that P. papatasi is associated only with L. major. The overall analysis of recent findings of the distribution of L. major in the populations of great gerbils makes it possible to limit the former endemic zoonotic cutaneous leishmaniasis areas to 40 degrees N latitude and the southern borders of Turkmenistan and Uzbekistan. Within this area, the distribution of L. major is uneven and associated basically with rivers, valleys, oases, and foothill desert plains.

[The identification of marker strains of Leishmania major, L. turanica and L. gerbilli by the polymer chain reaction with a universal primer]

The Leningrad Nuclear Physics Institute, Academy of Science of the USSR, and Martsinovskiĭ Institute of Medical Parasitology and Tropical Medicine, USSR Ministry of Health, developed polymerase chain reaction (PCR) technique with universal primer 3-2 for Leishmania identification. The primers were patented in the USSR (Patent No 4757254, 1989). Reference strains of three Leishmania species were identified: L. major--MRHO/SU/59/Neal P; L. gerbilli--MRHO/CN/60/gerbilli; L. turanica--MRHO/SU/80/Cl 3720 and MRHO/SU/83/KD 051. Each Leishmania species is specific and different in its PCR pattern whereas the two L. turanica strains have identical PCR patterns of the given primer.

[Occurrence of atypical histamine H2 receptors in the wall of the frog subclavian vein]

Selective H2-histamine agonist dimaprit was shown to produce relaxation of the isolated frog subclavian vein, with it persisting under the effect of selective H2-histamine antagonist cimetidine. Possible nonspecific mechanisms of relaxation produced by histamine are discussed. The data presented do not exclude that there are atypical H2-histamine receptors in subclavian vein of frogs, the activation of which initiates the attenuation of the active tension.

[Effect of activation of alpha- and beta-adrenergic receptors, M-cholinergic receptors and H1-histamine receptors on mechanical tension in the frog subclavian vein]

The effects of adrenaline, noradrenaline, isoproterenol, dopamine, histamine, acetylcholine, and serotonin on the wall tension in the isolated frog subclavian vein and modification of these effects by appropriate antagonists were examined. The existence of alpha- and beta-adreno-, M-choline- and H1-histamine receptors was demonstrated. Stimulation of alpha-adreno- and H1-histamine receptors augments and that of beta-adreno- and M-cholinoreceptors diminishes active wall tension in the vein.