Search

Atomic force microscopy techniques (conductive-AFM, I-V spectroscopy and PFM) were used for characterisation of the local electrical properties of bilayer polyaniline-polystyrene/P(VDF-TrFE) polymer nanocomposite. Observed hysteresis of current-voltage characteristics confirms its memristive properties. It was caused by the influence of the ferroelectric polarization of P(VDF-TrFE) layer, the domain structure of which was visualised by piezoelectric force microscopy on the transport of charge carriers at the interface.

Results of the study of rheological characteristics of dispersion-filled polymer composition materials (DFPCMs) based on low-density polyethylene (LDPE) and glass beads of ShSO-30 brand are given. Rheological properties of dispersion-filled polymer composition materials are considered for the first time in context of formation of the disperse phase in the system of functional division of polymer matrix (φp = θ + B + M), which are described within the lattice theory (HL, IC, TL, and CL) and generation of disperse systems possessing various structures (DS, LFS, MFS, and HFS) in terms of generalized and reduced parameters (θ, aav/d, θ/B, and θ/Sf). A relationship of rheological characteristics of DFPCMs to generalized parameters and types of disperse structure according to their classification (DS, LFS, MFS, and HFS) is shown for the first time. Such approach allows one to predict the rheological properties of all DFPCMs upon generation of various types of disperse structures using the disperse phase (filler) with known geometrical sizes (d), particle shape (ke), specific surface (Ssp), and maximum packing density (content (kpacking and φm)) and specified polymer matrix.

A study of the effect of holding the cast iron melt at temperatures of 1,300, 1,450 and 1,600 °C for 20, 55 and 90 minutes on the structure and properties of cast iron in a liquid state and after crystallization was carried out. The studies were carried out on samples with a diameter of 30 mm; cast iron containing 3.61–3.75 % carbon, 1.9–2.4 % silicon, 0.03 % manganese, 0.081–0.084 % phosphorus, 0.031–0.039 % sulfur was poured into green-sand molds. The samples were cast from the original cast iron (unmodified), modified with ferrosilicon 75 GOST 1415-93 (FS75), rare-earth metals (REM) and together with the REM+FS75 complex. The structure of cast iron was investigated by optical metallography, electron microscopy and X-ray structural analysis. An increase in the holding temperature and time of the cast iron melt leads to an increase in its hardness. An increase in temperature at a short holding time leads to an increase in strength in the entire investigated temperature range (1,300–1,600 °С). Holding for 90 minutes at a temperature of 1,450 °C corresponds to an extremum, after which, with a further increase in temperature, a sharp drop in strength is observed. The change in the toughness of cast iron is characterized in a similar way

Abstract It is well known that the propagation of traditional combustion and detonation waves was determined by the branched chain reactions discovered by Academician N.N. Semenov. This article discusses a new type of detonation waves initiated by chemical condensation processes. Chemical condensation waves arise as a result of the heat released during the explosive condensation of a highly supersaturated carbon vapor formed as a result of the dissociation of the initial carbon-containing molecules behind the front of the initiating shock wave. Unlike traditional combustion and detonation waves, the mechanism of chemical condensation does not include branched chain reactions; nevertheless, the laws of propagation of detonation waves of condensation are clearly described by the Zel’dovich–Neumann–Döring theory.

Here, the synthesis of holey carbonylated (C-ny) graphene derivative and its application for gas sensing is demonstrated. The carbonylation of graphene oxide leads to the 3-fold increase in the concentration of carbonyl groups’ up to 9 at.% with a substantial elimination of other oxygen functionalities. Such a chemical modification is accompanied by the perforation of the graphene layer with the appearance of matrices of nanoscale holes, leading to corrugation of the layer and its sectioning into localized domains of the π-conjugated network. Combined with the predominant presence of carbonyls, granting the specificity in gas molecules adsorption, these features result in the enhanced gas sensing properties of C-ny graphene at room temperature with a selective response to NH3. Opposite chemiresistive response towards ammonia when compared to other analytes, such as ethanol, acetone, CO2, is demonstrated for the C-ny graphene layer both in humid and dry air background. Moreover, a selective discrimination of all of the studied analytes is further approached by employing a vector signal generated by C-ny multielectrode chip. Comparing the experimental results with the calculations performed in framework of density functional theory, we clarify the effect of partial charge transfer caused by water and ammonia adsorption on the chemiresistive response.

Three-component semiconductors open up new possibilities for creating semiconductor devices.One of the promising three-component semiconductors is indium-gallium nitride InxGa1-xN, which is considered as a solid alloy of binary compounds - indium nitride InN and gallium nitride GaN.Prediction of the prospects for creating devices based on InxGa1-xN is possible with a thorough study of the electrical properties of its binary nitrides; indium nitride and gallium nitride.In the scientific literature, for these nitrides, studies of the Hall mobility predominate, the temperature dependence of which is described in a narrow range of impurity concentration values and the correspondence of the simulation results to the experimental ones is obtained by introducing correction factors.The aim of this work is to calculate the temperature dependence of the electron drift mobility forInNand GaN in a wide range of the degree of doping of semiconductors and to choice the initial parameters of the materials that make it possible to obtain the best agreement with the experimental results.For the nitrides under study, numerical modeling of scattering processes for typical types of impurity (on neutral atoms and impurity ions) and phonon (acoustic, polar optical, intervalley) mechanisms was carried out; momentum scattering rates were calculated and analyzed.For the first time for indium and gallium nitrides, a temperature dependence of the electron drift mobility was calculated in a wide range of values of the dopant concentration. The simulation results were verified.The field-velocity characteristics were calculated by the method of relaxation equations and compared with the results obtained by the Monte-Carlo method.For the nitrides under study, initial parameters are proposed that ensure agreement with experimental data when simulating the transport properties of electrons in a weak electric field mode.The results of numerical simulations indicate that it is promising to create highly efficient, high-speed, powerful devices for various purposes based on indium nitride and gallium nitride.

Influence of thermal treatment in H2 atmosphere on magnetic and dielectric properties of nanocrystalline BaTiO3 samples was studied. It was found that increase of the concentration of oxygen vacanc...

In this work, the local current-voltage characteristics of nanocomposite phase boundaries in the form of a poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) (70/30) matrix filled with conductive polyaniline (PANI) particles are studied by conductive atomic force microscopy. At negative external bias voltages, these dependencies are shown to have an interval with a negative differential resistance. This fact is caused by the switching of ferroelectric polarization of individual nanocrystallites PVDF-TrFE located near the phase boundaries in the amorphous matrix volume. The obtained results confirm assumptions about the memristive properties of the investigated nanocomposites.

Petroleum coke is one of the waste products generated in the oil refining industry that can be used as fuel in energetics. However, the low volatile matter content and graphite-like structure of petroleum coke are the reasons for its high ignition temperature and combustion complexity. In this research, petroleum coke combustion and oxidation kinetics in the presence of metal catalysts were investigated. To evaluate the effect of the catalyst on the ignition temperature and the apparent activation energy, a new approach of a “fixed fluidized bed” was proposed. In this mode, petroleum coke particles spaced from each other by inert quartz powder kind of “freeze” in the porous layer. This regime allows us to determine the ignition temperature of petroleum coke particles in the static mode by differential thermography and calculate the activation energy by gas analysis. Organic and inorganic salts of copper, iron, and cerium are used as catalysts for petroleum coke combustion. A series of experiments were carried out in the porous media thermo-effect cell (PMTEC) and on a thermogravimetric (TG) analyzer. The kinetics of the combustion processes was calculated by Kissinger–Akahira–Sunose and Ozawa–Flynn–Wall methods. The results obtained in the “fixed bed” mode showed that the ignition temperature and the average apparent activation energy significantly decreased in the presence of CuCl2 and FeCl3. The results obtained by the new approach were compared with the results of the thermogravimetric analysis.

An experimental study of the kinetics of oxidation of dimethyl ether, n-butanol, and methane was carried out using emission and atomic resonance absorption spectroscopy. All experiments were performed in a shock tube behind reflected shock wave in a wide temperature range from 1890 to 3250 K at a pressure of 2.4 ± 0.4 bar. In all investigated conditions, the peaks of nonequilibrium UV radiation of electronically excited carbon monoxide CO(a3Πr) were observed. Besides, the resonant absorption profiles of atomic oxygen in the ground electronic state O(3P) converted to O-atom concentration profiles were for the first time measured at this temperature range. For simulating the CO(a3Πr) radiation experimental profiles a kinetic mechanism of its formation and consumption was developed. This mechanism was implemented into existing comprehensive detailed kinetic models (such as Ranzi et al. (2014), Vasu and Sarathy (2013), NUIG Mech 56.54 (2013), GRI-Mech 3.0 (1999) and Alviso et al. (2018)), which were then tested on the obtained experimental profiles of atomic oxygen and electronically excited carbon monoxide. It was shown that the proposed CO(a3Πr) sub-mechanism nearly correct describes the ongoing reaction processes, however, complete compliance was not achieved. To elucidate reactions responsible for the differences observed, a sensitivity analysis was performed. As a result, the most important elementary reactions were determined.

Nanocomposite in the form of a porous matrix SiO2 with average pore size of 320 nm filled with barium titanate nanoparticles in paraelectric cubic phase was obtained. Shift of the stretching vibration of Si–O–Si to higher frequencies caused by increased strengthening of the network in the matrices has been observed. Also demonstrated that decrease in the intensity of the absorption relating to Si–O(H) stretching vibration relative to Si-O(−Si) stretching vibration. Raman scattering spectra demonstrate the presence of both a cubic and a tetragonal ferroelectric crystalline phase in the filler nanoparticles. Thus, the mechanical deformation of nanoparticles in the pores of the matrix can lead to a change in the crystalline phase of the filler.

Microbubbles are the most commonly used imaging contrast agent in ultrasound. However, due to their size, they are limited to vascular compartments. These microbubbles can be condensed or formulated as perfluorocarbon nanodroplets (PFCnDs) that are small enough to extravasate and then be triggered acoustically at the target site. These nanoparticles can be further enhanced by including an optical absorber such as near infrared organic dye or nanoparticles (e.g., copper sulfide nanoparticles or gold nanoparticles/nanorods). Optically tagged PFCnDs can be vaporized through laser irradiation in a process known as optical droplet vaporization (ODV). This process of activation enables the use of high boiling point perfluorocarbon cores, which cannot be vaporized acoustically under the maximum mechanical index threshold for diagnostic imaging. Higher boiling point cores result in droplets that will recondense after vaporization, resulting in "blinking" PFCnDs that briefly produce contrast after vaporization before condensing back into nanodroplet form. This process can be repeated to produce contrast on demand, allowing for the background free imaging, multiplexing, super-resolution, and contrast enhancement through both optical and acoustic modulation. This article will demonstrate how to synthesize optically-triggerable, lipid shell PFCnDs utilizing probe sonication, create polyacrylamide phantoms to characterize the nanodroplets, and acoustically modulate the PFCnDs after ODV to improve contrast.

A brief review of the results of research on reducing the flammability of modified materials based on polycarbonate, the effect of flame retardants and additives that reduce dropping, as well as affecting the complex of properties of polycarbonate is presented. The optimal concentrations of modifying additives for obtaining fire-resistant compositions with high optical characteristics have been determined. It is shown that to achieve the maximum flammability category (PV-0 at a thickness of 2 mm) and oxygen index (42.3%) for thin-walled products, it is necessary to use a high- viscosity grade of polycarbonate (MFI 2.5±1.0 g/10 min), alkali metal sulfonates as a fire retardant and an anti-dripping additive.

A numerical analysis of the recently discovered promoting of the growth of condensed carbon nanoparticles during the thermal decomposition of acetylene in the presence of methane additives has been performed. Calculations carried out using the modern kinetic mechanism, describing the growth of carbon nanoparticles during hydrocarbon pyrolysis and combustion, have confirmed a significant acceleration of the growth of polyaromatic hydrocarbons and nanoparticles, as well as temperature and pressure during shock wave pyrolysis of acetylene with the addition of 10% methane. The results indicate a possible decrease in threshold pressure and acceleration of the development of acetylene detonation in the presence of methane additions.

In the pyrolysis of different hydrocarbon/carbon suboxid fuels formation of carbon particles with the special view to their structures was examined. For this, the following three very different pyrolysis systems were investigated experimentally i) a pyrolysis reactor, ii) a shock tube and iii) a plasma reactor with respect to the influence of varying reaction parameters on the carbonaceous nanoparticles. The particles formed in these reaction systems were studied in view of their morphology and state of crystallization by use of electron microscopy (Philips CM30) at low- and high resolution combined with micro-diffraction measurements. As to be seen at low resolution of the transmission electron microscopy studies, the particle sizes in the pyrolysis reactor and shock tube do not differ significantly, but distinguished considerably from those particle sizes obtained in the plasma reactor. While the particles obtained in the pyrolysis reactor and shock-tube had particle diameters of about d ≈ 30 nm, the particles in the plasma reactor consisted of fluffy-like units, and their sizes were about d ≈ 4 nm. The various carbon layers consisted of different polyaromatic hydrocarbon units with variable sizes arranged to diverse states in the course of graphitization.

Photoacoustic visualization of nanoparticles is capable of high contrast imaging at depth greater than that of traditional optical imaging techniques. Identifying the impact of various parameters on the photoacoustic signal is crucial in the design of effective medical imaging and diagnostics. Here, we develop a complete model of Fourier heat conduction incorporating the interfacial thermal resistance and photoacoustic equation for core-shell nanospheres in a fluid under nanosecond pulsed laser illumination. An analytical solution is obtained, elucidating the contribution of each region (core, shell, or the fluid) in the generation of the photoacoustic signal. The model reveals that the sharper the laser pulse temporal waveform is, the higher the sensitivity of the generated photoacoustic signal will be to the interfacial thermal resistance, and, thus, the higher the possibility of photoacoustic signal amplification will be using silica-coating. The comprehensive model and adopted analytical solution reveal the underlying physics of the photoacoustic signal generation form core-shell nanosphere systems. Photoacoustic imaging of colloidal nanosystems is a useful tool for biological applications, yet current models of the photo-induced thermal processes contain un-physical assumptions. Here, the authors propose a model capable of disentangling the role of the nanoparticle, shell, surrounding material, and laser pulse properties.

Catalyst-free chemical vapor deposition is used to form thin (1–2 nm) carbon layers on the surface of alumina nanofibers resulting in carbon-alumina nanocomposites. Thermal analysis, X-ray fluorescent microanalysis, Raman spectroscopy, and electrical resistance measurements of these composites show that increasing of synthesis time not only increases the amount of carbon on alumina surface, but also the ordering and density of the carbon layers. Nitrogen adsorption data reveal the decrease of total pore volume with increasing the synthesis time. The obtained composite material could be employed for the preparation of ion-selective membranes with switchable ion transport, electroconductive ceramics, and electrochemical sensors.

Influence of thermal treatment on magnetic and dielectric properties of nanostructured BaTiO3 samples, sintered at 700, 1000 and 1200 °C was studied. The sample sintered at 700 °C is not ferroelect...

Multilayer (14 layers, 115–122 nm thick each) BiFeO3/CoFe2O4/substrate (BFO/CFO) and CoFe2O4/BiFeO3/substrate (CFO/BFO) nanocomposites were obtained by the method of sol-gel synthesis. It i...

Phase-change perfluorohexane nanodroplets (PFHnDs) are a new class of recondensable submicrometer-sized contrast agents that have potential for contrast-enhanced and super-resolution ultrasound imaging with an ability to reach extravascular targets. The PFHnDs can be optically triggered to undergo vaporization, resulting in spatially stationary, temporally transient microbubbles. The vaporized PFHnDs are hyperechoic in ultrasound imaging for several to hundreds of milliseconds before recondensing to their native, hypoechoic, liquid nanodroplet state. The decay of echogenicity, i.e., the dynamic behavior of the ultrasound signal from optically triggered PFHnDs in ultrasound imaging, can be captured using high-frame-rate ultrasound imaging. We explore the possibility to manipulate the echogenicity dynamics of optically triggered PFHnDs in ultrasound imaging by changing the phase of the ultrasound imaging pulse. Specifically, the ultrasound imaging system was programmed to transmit two imaging pulses with inverse polarities. We show that the imaging pulse phase can affect the amplitude and the temporal behavior of PFHnD echogenicity in ultrasound imaging. The results of this study demonstrate that the ultrasound echogenicity is significantly increased (about 78% improvement) and the hyperechoic timespan of optically triggered PFHnDs is significantly longer (about four times) if the nanodroplets are imaged by an ultrasound pulse starting with rarefactional pressure versus a pulse starting with compressional pressure. Our finding has direct and significant implications for contrast-enhanced ultrasound imaging of droplets in applications such as super-resolution imaging and molecular imaging where detection of individual or low-concentration PFHnDs is required.

The influence of calcite on crude oil combustion was studied using high-pressure differential scanning calorimetry (HP-DSC). Calcite had a small effect on the low-temperature oxidation (LTO), but i...

In photoacoustic imaging, the second near-infrared (NIR-II) window is where tissue generates the least background signal. However, the large size of the few available contrast agents in this spectral range impedes their pharmacokinetics and decreases their thermal stability, leading to unreliable photoacoustic imaging. Here, we report the synthesis of miniaturized gold nanorods absorbing in the NIR-II that are 5–11 times smaller than regular-sized gold nanorods with a similar aspect ratio. Under nanosecond pulsed laser illumination, small nanorods are about 3 times more thermally stable and generate 3.5 times stronger photoacoustic signal than their absorption-matched larger counterparts. These unexpected findings are confirmed using theoretical and numerical analysis, showing that photoacoustic signal is not only proportional to the optical absorption of the nanoparticle solution but also to the surface-to-volume ratio of the nanoparticles. In living tumour-bearing mice, these small targeted nanorods display a 30% improvement in efficiency of agent delivery to tumours and generate 4.5 times greater photoacoustic contrast. Miniaturized gold nanorods are reliable NIR-II photoacoustic agents, showing higher photothermal stability, enhanced photoacoustic signal and more efficient agent-to-tumour delivery compared with their larger counterparts.

The growth of carbon particles was studied in heated flows of a burnt-gas flow reactor containing mixtures of N2/C2H2, and N2/C2H2 with addition of H2 or CH4 surrounded by a rich C2H4/air flame. Soot particle sizes and volume fractions were measured by laser-induced incandescence (LII) between 50 and 130 mm above the nozzle exit. The measurements indicate a soot-inhibiting effect of adding H2 to the C2H2/N2 flow on both, particle sizes and soot volume fractions. The effect of CH4 addition to the C2H2/N2 flows was ambivalent, depending on the methane-to-acetylene ratio. At gas mixtures with N2:CH4:C2H2 = 0.42:0.35:0.23 and 0.39:0.32:0.29 by volume at fixed total flow rates, the measured soot volume fractions were substantially increased in presence of CH4, while the mean diameters of the particles were slightly decreased. Gas temperatures were measured by a generalized line-reversal method with Abel transformation. Temperatures of the surrounding C2H4/air flame were around 1600 K, and temperatures of the inner flows, where soot formation was measured, were between 1550 and 1630 K. Plug-flow reactor calculations provided a qualitative understanding of the influence of CH4 on the soot particle growth.

Influence of surface modification of barium titanate nanoparticles of spherical shape with the average size of 200 nm in ferroelectric tetragonal crystal phase on the value of piezoelectric response by piezoelectric force microscopy has been studied. It has been found that the modification of the surface of nanoparticles with organic molecules for the increasing of biocompatibility leads to a decrease in the value of effective piezo response from 150 to 48–60 pm/V. At the same time, it is possible to switch polarization in the investigated samples. This allows to consider the mentioned nanocomposites to be promising materials for diagnostics and treatment of cancer tumors, as well as creation of new generation implants accelerating the osteogenesis process.

The fabrication of planar junctions in carbon nanomaterials is a promising way to increase the optical sensitivity of optoelectronic nanometer-scale devices in photonic connections, sensors, and photovoltaics. Utilizing a unique lithography approach based on direct femtosecond laser processing, a fast and easy technique for modification of single-walled carbon nanotube (SWCNT) optoelectronic properties through localized two-photon oxidation is developed. It results in a novel approach of quasimetallic to semiconducting nanotube conversion so that metal/semiconductor planar junction is formed via local laser patterning. The fabricated planar junction in the field-effect transistors based on individual SWCNT drastically increases the photoresponse of such devices. The broadband photoresponsivity of the two-photon oxidized structures reaches the value of 2 × 107 A W−1 per single SWCNT at 1 V bias voltage. The SWCNT-based transistors with induced metal/semiconductor planar junction can be applied to detect extremely small light intensities with high spatial resolution in photovoltaics, integrated circuits, and telecommunication applications.

Summary We detected large values of the complex electrical conductivity of four kimberlite samples based on laboratory measurements carried out when saturating the samples with brines with the electrical conductivity ranging between 200 and 30 000 S/cm. Both the real surface conductivity and the quadrature conductivity were found much larger than that of common volcanic rocks and sediments. Based on measurements of petrophysical properties of these cores as well as on optical microscopic images we argued that this anomalous conductivity is explained by highly conductive and polarizable clayey matrix, which shows an abundance of the saponite, a mineral of smectite group. These new data confirms usability of electrical (resistivity, and especially Induced Polarization) and electromagnetic methods in kimberlite exploration.

Perovskite solar cells represent a highly promising third-generation photovoltaic technology. However, their practical implementation is hindered by low device operational stability, mostly related to facile degradation of the absorber materials under exposure to light and elevated temperatures. Improving the intrinsic stability of complex lead halides is a big scientific challenge, which might be addressed using various &ldquo, molecular modifiers&rdquo, These modifiers are usually represented by some additives undergoing strong interactions with the perovskite absorber material, resulting in enhanced solar cell efficiency and/or operational stability. Herein, we present a derivative of 1,4,6,10-tetraazaadamantane, NAdCl, as a promising molecular modifier for lead halide perovskites. NAdCl spectacularly improved both the thermal and photochemical stability of methylammonium lead iodide (MAPbI3) films and, most importantly, prevented the formation of metallic lead Pb0 as a photolysis product. NAdCl improves the electronic quality of perovskite films by healing the traps for charge carriers. Furthermore, it strongly interacts with the perovskite framework and most likely stabilizes undercoordinated Pb2+ ions, which are responsible for Pb0 formation under light exposure. The obtained results feature 1,4,6,10-tetraazaadamantane derivatives as highly promising molecular modifiers that might help to improve the operational lifetime of perovskite solar cells and facilitate the practical implementation of this photovoltaic technology.

Graphical abstract, In molecular and cellular photoacoustic imaging with exogenous contrast agents, image contrast is plagued by background resulting from endogenous absorbers in tissue. By using optically modulatable nanoparticles, we develop ultra-sensitive photoacoustic imaging by rejecting endogenous background signals and drastically improving signal contrast through time-delayed pump-probe pulsed laser illumination. Gated by prior pump excitation, modulatable photoacoustic (mPA) signals are recovered from unmodulatable background through simple, real-time image processing to yield background-free photoacoustic signal recovery within tissue mimicking phantoms and from ex-vivo tissues. Inherently multimodal, the fluorescence and mPA sensitivity improvements demonstrate the promise of Synchronously Amplified Photoacoustic Image Recovery (SAPhIRe) for PA imaging in diagnosis and therapy.

Early stage cancer detection technologies can provide functional information and potentially decrease the mortality rate caused by cervical cancer. In our previous work, a miniaturized ultrasound and photoacoustic endoscopic system has been developed to image the cervical tissue through the cervical canal to fulfills the need for a safe, low-cost, and high-resolution functional diagnostic system. However, the miniaturized size of endoscope and American National Standards Institute safety limits cause constraints of using high-intensity illumination during imaging. In addition, the strong light scattering of tissues limits the light penetration depth. Fortunately, the cervix anatomy allows for the delivery of additional light from the ectocervix by using an external illumination system. Here we propose a dual, co-planar illumination system, which can provide adequate illumination to the cervical tissue via combined internal and external light delivery strategies. Therefore, an increase in the area of light-tissue interaction allows us to raise the laser light energy while keeping fluence under safety limits. Thus, a reliable PA imaging can be obtained for the whole cervical tissue thickness. The system performance was tested using a Monte Carlo simulation, and laser-light fluence was calculated and compared at different depths within a simulated cervical-tissue model. The results indicated a higher and more uniform fluence in the Monte Carlo simulations. In addition, the photoacoustic imaging of the proposed system was evaluated by two cervical tissue-mimicking phantoms with human blood and graphite rods as inclusions inside it. In accordance with the simulations, the phantom study revealed a more reliable photoacoustic signal for the entire depth of the phantoms with an improved contrast to noise ratio and signal to noise ratio, and a higher coverage ratio of the imaging field of view. In summary, the dual-mode illumination system can provide more realistic information of inclusions within the tissue while considering safety limits, which can lead to more accuracy in biomarker detection for cervical cancer diagnostics.

Modern comprehensive kinetic mechanisms for modeling the oxidation of hydrocarbon mixtures in the high-temperature range do not consider possible excited states of radicals and molecules that can affect combustion processes at certain time intervals.

The high mortality rate of cervical cancer can be minimized by early-stage cancer detection or providing functional information about the tissue to provide an effective treatment. Such clinical procedures require the need for a safe, low-cost, and high-resolution functional diagnostic system. Previously, we proposed a dual-modal ultrasound and photoacoustic imaging endoscope with a miniaturized footprint for imaging the cervical tissue through the cervical canal. Since the light delivery system in our endoscope can carry a limited amount of light fluence (restricted to ANSI safety limits), we proposed to develop a dual, co-planar illumination system to irradiate cervical tissue both from inside and outside. The proposed endoscopic system was developed by coupling the external illumination system to the developed US/PA imaging endoscope. The external illumination system can provide additional illumination to the cervical tissue through the vaginal fornix area. The total diameter of the external illumination system is 4.2 mm and comprises of seven optical fibers. The performance of the system was evaluated through a tissue-mimicking phantom. Results indicated that the combined dual-illumination system enabled PA imaging to provide a higher consistent signal amplitude. In addition, an enhanced signal to noise ratio and contrast to noise ratio was achieved throughout the whole mimicked tissue phantom thickness while complying with the safety limits for light fluence.

Two generation mechanisms—optical perturbation and acoustic radiation force (ARF)—were investigated where high frame rate ultrasound imaging was used to track the propagation of induced SAWs. We compared ARF-induced SAWs with laser-induced SAWs generated by laser beam irradiation of the uniformly absorbing tissue-like viscoelastic phantom, where light was preferentially absorbed at the surface. We also compared the frequency content of SAWs generated by ARF versus pulsed laser light, using the same duration of excitation. Differences in the SAW bandwidth were expected because, in general, laser light can be focused into a smaller area. Finally, we compared wave generation and propagation when the wave’s origin was below the surface. We also investigated the relationship between shear wave amplitude and optical fluence. The investigation reported here can potentially extend the applications of laser-induced SAW generation and imaging in life sciences and other applications.

In this work, we report a novel method of mask-less doping of graphene channel in field-effect transistor configuration by local inkjet printing of organic semiconducting molecules. Graphene-based transistor was fabricated via large-scale technology, allowing for upscaling electronic device fabrication and lowering the device cost. The altering of functionalization of graphene was performed through local inkjet printing of semiconducting molecules: N,N′-Dihexyl- 3,4,9,10-perylenedicarboximide (PDI-C6), 5,5′′′-Dihexyl-2,2′:5′,2′′:5′′,2′′′-quaterthiophene (HEX-4T-HEX) and polyalanine (PANI). We found the effect of UV treatment on fabrication of graphene/organic junctions because of change in graphene hydrophobic properties. We demonstrated the high resolution (about 50 μm) and accurate printing of organic ink on UV treated chemical vapor deposited (CVD) graphene. The PANI/graphene junction demonstrate more stable photoresponse characteristic for 470 nm diode illumination. The characteristics of PDI/graphene junction demonstrate the saturation for high diode power because of organic crystals degradation. The photoresponse of 1 mA/W was demonstrated for PANI/graphene junction at 0.3 V bias voltage. The developed method opens the way for local functionalization of on-chip array of graphene by inkjet printing of different semiconducting organic molecules for photonics and electronics application.

The kinetics of reaction of C2H5OH with N2O behind shock waves is studied. The quantitative measurements of the time profiles of concentration of O atoms were carried out by the method of atomic resonance absorption spectroscopy (ARAS) using resonance vacuum-ultraviolet line of O-atom at 130.5 nm. For the calibration of absorption intensity of oxygen atoms depending on its concentration, the special series of experiments in the mixture containing different amounts of N2O in Ar was carried out at T = 2100 ± 50 K when molecule of N2O is completely dissociated. An experimental study of the appearance and consumption of oxygen atoms during the reaction of ethanol with oxygen in mixture 10 ppm N2O + (10 ... 0.1) ppm C2H5OH + Ar at temperatures of 16002300 K and pressures of 200-300 kPa have been carried out. A kinetic analysis of obtained data was performed using the Chemkin package.

We present the results on development of the 3D imaging platform combining photoacoustic tomography and fluorescence (PAFT) for preclinical and biological research. This combined multimodal imaging instrument addresses known deficiencies in sensitivity, spatial resolution, and anatomical registration of the individual imaging components. Multiangle photoacoustic projections, excited by an OPO operating in the near-infrared window, of a live anesthetized animal are used to reconstruct large volumes (30 cm3) that show deep anatomical vasculature and blood-rich tissues with resolutions exceeding 150 μm. A sCMOS camera is used for simultaneous co-registered multi-angle optical imaging. The images of a fluorescent dual-contrast agent are then reconstructed into a 3D volume using a tomographic algorithm. A separate 532-nm low-energy pulsed laser excitation is used for skin topography and imaging of superficial vasculature. All three imaging channels can be combined to produce spatially accurate in vivo volumes showing an animal’s skin, deep anatomical structures, and distribution of photosensitive molecular contrast agents. PAFT’s photoacoustic sensitivity was assessed using contrast agents in a phantom study. We demonstrate biomedical imaging application of PAFT’s combined imaging modalities by observing biodistribution of a dual-contrast agent injected intravenously to in vivo preclinical murine models.

In this work, γ-Fe2O3 nanoparticles were synthesized by co-precipitation method and characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, dynamic light scattering, X-ray diffraction, and Mossbauer spectroscopy techniques. By co-precipitation method, ultrafine γ-Fe2O3 quasi-spherical individual nanoparticles with the average diameter of 9.1 nm and the surface free of capping ligands were successfully synthesized. The catalytic effect of the synthesized γ-Fe2O3 nanoparticles upon the combustion performance and kinetic of heavy oil combustion was studied by porous medium thermo-effect cell (PMTEC) together with isoconversional kinetic analysis using Ozawa-Flynn-Wall method. The results show that the combustion performance of heavy oil was substantially increased by γ-Fe2O3 nanoparticles. The reaction intervals of low temperature oxidation (LTO) and high temperature oxidation (HTO) were shifted to lower temperature with an obvious increase in temperature caused the exothermic oxidation reactions. In addition, the fingerprint of the dependence of effective activation energy on conversion degree shows that the effective activation energy was reduced by about 20–35 kJ/mol during the whole combustion process. These observed improvements make γ-Fe2O3 nanoparticle a promising catalyst for catalyzing heavy oil combustion.

An optical wavelength selection method based on the stability of the absorption cross-section matrix to improve spectroscopic photoacoustic (sPA) imaging was recently introduced. However, spatially-varying chromophore concentrations cause the wavelength- and depth-dependent variations of the optical fluence, which degrades the accuracy of quantitative sPA imaging. This study introduces a depth-optimized method that determines an optimal wavelength set minimizing an inverse of the multiplication of absorption cross-section matrix and fluence matrix to minimize the errors in concentration estimation. This method assumes that the optical fluence distribution is known or can be attained otherwise. We used a Monte Carlo simulation of light propagation in tissue with various depths and concentrations of deoxy-/oxy-hemoglobin. We quantitatively compared the developed and current approaches, indicating that the choice of wavelength is critical and our approach is effective especially when quantifying deeper imaging targets. Keywords: Spectroscopic photoacoustic imaging, Oxygen saturation estimation, Optimal wavelength selection, Spectral unmixing

OBJECTIVES Intravascular photoacoustic (IVPA) imaging is being developed to image atherosclerotic plaques, a leading cause of morbidity and mortality in the United States. However, the safety of this imaging modality, which requires repeated irradiation with short laser pulses, has not yet been investigated. This study has two objectives. First, determine in vitro the limit of cumulative fluence that can be applied to cells before death at IVPA relevant wavelengths. Second, evaluate if high single pulse fluences are a potential cause of cell death during IVPA imaging. MATERIALS AND METHODS Experiments were conducted using endothelial cells, macrophages, and smooth muscle cells. The cumulative fluence experiments were conducted at 1064 and 1197 nm, using a high pulse repetition frequency laser. Cells were irradiated with a wide range of cumulative fluences and evaluated for cell death. The thresholds for death were compared to the maximum expected clinical cumulative fluence. To evaluate the effect of single pulse fluences, cells were irradiated at 1064, 1210, and 1720 nm. Light was delivered at a range of pulse energies to emulate the fluences that cells would be exposed to during clinical IVPA imaging. RESULTS At 1064 nm, all three cell types remained viable at cumulative fluences above the maximum expected clinical cumulative fluence, which is calculated based on common IVPA imaging protocols. At 1197 nm, cells were viable near or just below the maximum expected clinical cumulative fluence, with some cell type to cell type variation. All three cell types remained viable after irradiation with high single pulse fluences at all three wavelengths. CONCLUSION The cumulative fluence experiments indicate that safety considerations are likely to put constraints on the amount of irradiation that can be used in IVPA imaging protocols. However, this study also indicates that it will be possible to use IVPA imaging safely, since cumulative fluences could be reduced by as much as two orders of magnitude below the maximum expected clinical cumulative fluence by varying the imaging protocol, albeit at the expense of image quality. The single pulse fluence experiments indicate that cell death from single pulse fluence is not likely during IVPA imaging. Thus, future studies should focus on heat accumulation as the likely mechanism of tissue damage. Lasers Surg. Med. © 2018 Wiley Periodicals, Inc.

Air injection is a promising method for enhanced oil recovery (EOR) in both conventional and unconventional oil sources. It is widely accepted that oxidation reactions between oil and injected air determine the success of an air injection process. In this study, electron paramagnetic resonance (EPR) was introduced as a new route to investigate the occurrence of low-temperature oxidation (LTO) and its behavior by monitoring the signals of free radicals. The EPR experiments were conducted for the different crude oil samples (light, medium and heavy) heated in both static air and flow air (air-bubbling) conditions under different temperatures from 25 °C to 180 °C. The results showed that the free-radical concentrations exhibited a good correspondence on the heating temperature. Furthermore, nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) experiments were carried out to help to analyze the oxidation process and verify the EPR results. It turned out that the EPR results can be well supported by NMR, FTIR and DSC data, which indicates that proposed EPR monitoring method can be applied as a fast and low-cost technique to investigate LTO under mild reaction conditions. Simultaneously, the combination of EPR, NMR, FTIR and DSC can help to better understand the LTO mechanism and to monitor the application of in-situ combustion technique in the field.

A coherency of photoacoustic and ultrasound waves is dependent on the accuracy of the speedof- sound. This study evaluates the feasibility of a speed-of-sound estimation method for dual photoacoustic and ultrasound waves using laser-activated phase-change perfluorohexane nanodroplets (PFHnDs). The proposed method demonstrates that the estimated speed-of-sound (ESS) is close to the expected speed-of-sound for the medium (deviation = 0.3%), so it is useful for phase aberration correction in dual ultrasound and photoacoustic imaging.

Single and few-layer graphene photodetectors have attracted much attention in the past few years. Pristine graphene shows a very weak response to visible light; hence, fabrication of complex graphe...

Subject: due to a wide spread in construction practice of castellated beams with the rhomb-shaped perforation of the web, influence of parameters of such openings on beam’s deflections was investigated. Currently, in the Design Codes, both domestic and international, and also in Eurocode 3, the recommendations on determination of deflections of such beams are absent although they contain regulatory requirements. Research objectives: elaboration of analytical relationship, convenient for engineering calculations, for estimation of deflections of castellated beams with rhombic perforation of the web. Materials and methods: derivation of the deflection formula was carried out using one of the efficient methods for calculating deformations of perforated I-beams, based on the use of the theory of compound bars. Several numerical coefficients included in the expression for the stiffness coefficient of the elastic layer, formed by web-posts, were refined by means of finite element calculations. As a criterion for reliability of the analytical expression for deflections, the results of the finite element analysis of the beam, obtained with the ANSYS software complex, are used. Results: results of the study constitute the analytical relation for engineering calculations of deflections of castellated beams with the rhombic perforation of the web. The applicability of the proposed dependence to the calculation of deflections for beams with different shapes of rhombic perforation is verified by varying both the height of the openings and the width of the web-posts. In all cases, only the angle of inclination of the hexagonal sides, taken equal to 60°, remains fixed. An example of analysis of a perforated beam according to the method considered is given. For beams made by wasteless technology, when the width of the web-posts is equal to the horizontal side of the opening, for a rhomb-shaped perforation with a constant relative height of the openings, the total cut-out area remains practically unchanged for any width of the web-posts. A consequence of this is the weak influence of the relative width of the web-posts on deflections of beams with a fixed height of the openings. Conclusions: obtained engineering relationship will certainly be of practical interest to designers and can be recommended for including into the Design Codes of the Russian Federation.

To develop technologies for the reuse of alloy powders obtained from cobalt-chrome wastes and to evaluate the effectiveness of their use, complex theoretical and experimental studies are required. The main advantage of the proposed technology is the use of waste as raw materials, which is much cheaper than the pure components used in traditional technologies. The purpose of this work was to perform X-ray spectral microanalysis of sintered samples from cobalt-chrome powders obtained for additive technologies by electroerosive dispersion. For the implementation of the planned studies, wastes of the cobalt-chrome alloy of the brand KHMS 'CELLIT' were chosen. For the production of cobalt-chrome powders, a device for electro-erosive dispersion of conductive materials was used. As a working fluid, butyl alcohol was used. The powders are consolidated by the method of spark plasma sintering using the system of spark plasma sintering SPS 25-10. Using the energy-dispersive X-ray analyzer from EDAX, built into the scanning electron microscope QUANTA 200 3D, spectra of characteristic X-ray radiation were obtained at various points on the surface of the sample. It has been experimentally established that Co and Cr are mainly contained in cobalt-chrome powder-alloys on the surface.

Using copper stearate as catalysts, catalytic in-situ combustion (ISC) of heavy oil was studied by porous medium thermo-effect cell (PMTEC) and combustion tube experiments. Significant acceleration of combustion was observed in porous media in PMTEC when copper stearate was added. Copper stearate promoted fuel deposition and its combustion and made them occur easier in low temperature, thus shifting both low-temperature oxidation (LTO) and high-temperature oxidation (HTO) into lower temperatures, and even totally merge HTO into LTO in some conditions. We found that the promotion on fuel deposition by catalysts might be related to the change of H/C ratio in fuel. The improvement in the performance of ISC by copper stearate in combustion tube experiments mainly manifests in lower ignition temperature, lower H/C ratio, increased air/fuel ratio, higher oil recovery, and higher level of in-situ oil upgrading, which makes copper stearate a good candidate for catalyzing ISC in field application.

The fabrication processes for narrow-spectrum photosensitive structures based on J-aggregates of cyanine dyes are studied. Two technological approaches are proposed: the electrokinetic deposition of single J-aggregates in the planar electrode configuration and the fabrication of multilayer structures with a sensitive layer of cyanine dye J-aggregates and a transparent electrode made of a conductive carbon nanotube network on a flexible polyethylene naphthalate substrate.

Using atomic resonance absorption spectroscopy, we measure the temporal profiles of Cl atom concentration at interaction with acetylene behind shock waves. We used CCl4 thermal decay as the chlorine atom source. We used a 30 ppm of CCl4 and 300 ppm of C2H2 in argon mixture for the experiments, at 1400–2300 K and pressures of about 2 bar. For experimental results, we determine the rate constant of the chlorine atom consumption in the Cl + C2H2 = C2H + HCl reaction. The experimental data show essentially lower activation energy than the results of the theoretical calculations performed earlier, possibly due to the acetylene molecule vibrational energy contributing to overcoming the reaction barrier.

Improvement of solar cell efficiency beyond the Shockley–Queisser limit requires introduction of new physical concepts. One such concept is hot carrier solar cell, proposed more than three decades ago and still not impressively demonstrated in experiment. Here we show that hot carrier solar cell may be considered as thermoelectric device based on Seebeck effect. This enables one to describe the operation of hot carrier solar cell in a simple way. We fabricated a prototype of the hot carrier solar cell showing open circuit voltage at room temperature larger than the band gap in the absorber material. Extrapolation of open circuit voltage to absolute zero temperature results in barrier height depending on light intensity, interpreted by splitting of quasi-Fermi levels between the regions of different carrier temperature. Properties of the prototype solar cell may be described by kinetic transport theory as well as from the point of view of the thermoelectric theory.

Purpose This study introduces a real-time contrast-enhanced ultrasound imaging method with recently developed laser-activated nanodroplets (LANDs), a new class of phase-change nanometer-scale contrast agents that provides perceptible, sustained high-contrast with ultrasound. Methods In response to pulsed laser irradiation, the LANDs-, which contain liquid perfluorohexane and optical fuses-blink (vaporize and recondense). That is, they change their state from liquid nanodroplets to gas microbubbles, and then back to liquid nanodroplets. In their gaseous microbubble state, the LANDs provide high-contrast ultrasound, but the microbubbles formed in situ typically recondense in tens of milliseconds. As a result, LAND visualization by standard, real-time ultrasound is limited. However, the periodic optical triggering of LANDs allows us to observe corresponding transient, periodic changes in ultrasound contrast. This study formulates a probability function that measures how ultrasound temporal signals vary in periodicity. Then, the estimated probability is mapped onto a B-scan image to construct a LAND-localized, contrast-enhanced image. We verified our method through phantom and in vivo experiments using an ultrasound system (Vevo 2100, FUJIFILM VisualSonics, Inc., Toronto, ON, Canada) operating with a 40-MHz linear array and interfaced with a 10 Hz Nd:YAG laser (Phocus, Opotek Inc., Carlsbad, CA, USA) operating at the fundamental 1064 nm wavelength. Results From the phantom study, the results showed improvements in the contrast-to-noise ratio of our approach over conventional ultrasound ranging from 129% to 267%, with corresponding execution times of 0.10 to 0.29 s, meaning that the developed method is computationally efficient while yielding high-contrast ultrasound. Furthermore, in vivo sentinel lymph node (SLN) imaging results demonstrated that our technique could accurately identify the SLN. Conclusions The results indicate that our approach enables efficient and robust LAND localization in real time with substantially improved contrast, which is essential for the successful translation of this contrast agent platform to clinical settings.