Ab initio studies of two-photon absorption of some stilbenoid chromophores

Two-photon absorption of a series of donor-acceptor trans-stilbene derivatives is studied by means of density functional theory applied to second-order response function. Several important issues in modeling are highlighted which must be addressed for a reliable reproduction of the experimental results. It is evident that the correct order of magnitude of calculated two-photon absorption cross sections can only be obtained if proper account is taken of vibrational broadening of the absorption profiles. A comparison of the theoretical results with the experimental ones indicates that the computed two-photon absorption cross sections are in rough agreement with our previous report, although the observed systematic increase of the cross sections with the electron acceptor strength is not well reproduced. It is suggested that this disagreement may be due not only to the deficiencies of the computations but also to a variety of factors contributing to the experimental value of the effective two-photon absorption cross section, which are not taken into account in the ab initio calculations

Negative refractivity assisted optical power limiting

We propose an approach for achieving optical power limiting (OPL) using planar multilayered media. The approach involves the use of multiple bilayer structures that consist of a negative index (NIM) layer followed by a nonlinear two-photon absorbing (TPA) layer. The NIM layers refocus light in the TPA layers to increase intensity and nonlinear absorption. We perform parametric two-dimensional finite difference time domain simulations and compute the power transmittance of the media as a function of the incident light intensity, the number of layers, the layer thickness, and the material properties. Our analysis demonstrates proof-of-concept and indicates that the TPA-based OPL can be enhanced and optimized using NIM focusing.This work was in part supported by a grant from the office of Vice-President for Research at the University at Buffalo and in part by the Chemistry and Life Sciences Directorate of the Air Force Office of Scientific Research

Research of Geopolymer Foam Concrete on the Base of the Wastes Produced By Kemerovo Heat and Power Enterprises

The article shows the results of the research on geopolymer foam concrete production on the base of the wastes of Kemerovo heat and power enterprises. Relationships between the compression strength and average density of geopolymer foam concrete and the alkaline activator amount, alkaline concentration, foaming agent amount and duration of the blend mechanical activation were determined. It was found out that being in its optimal composition the material obtained has strength 2.0-3.5 MPa under density from 350 up to 500 kg/m3. Infusion of the developed construction material on the basis of the industrial wastes will allow to change more expensive construction materials on the cement base and provide the utilization of the industrial wastes

TLM modeling and system identification of optimized antenna structures

The transmission line matrix (TLM) method in conjunction with the genetic algorithm (GA) is presented for the bandwidth optimization of a low profile patch antenna. The optimization routine is supplemented by a system identification (SI) procedure. By the SI the model parameters of the structure are estimated which is used for a reduction of the total TLM simulation time. The SI utilizes a new stability criterion of the physical poles for the parameter extraction

Asymmetric properties between the forward and backward stimulated emission generated by ultrafast three- and four-photon excitation

This paper presents the observation of asymmetric behavior between the forward and backward stimulated emission, generated in multiphoton active dye solutions, through three- or four-photon excitation of subpicosecond laser pulses. At a pump energy level considerably higher than the lasing threshold value, the peak wavelengths of the forward stimulated emission are 20–30-nm shorter than those of the backward stimulated emission for the two investigated stilbazolium dye solutions (PRL-L3 and PRL-L10). This obvious spectral asymmetry can be explained by the following three considerations: (i) the difference of spatial/temporal sequences between the forward and backward stimulated emission pulses; (ii) blueshift of the peak wavelength of transient gain experienced by the forward stimulated emission pulse; and (iii) saturation of reabsorption at the forward lasing wavelength range. These proposed explanations are verified by a specially designed pump-probe experiment, utilizing a white-light continuum as the probe beam and the ∼1300-nm laser radiation as the pump beam for three-photon excitation. The experimental results have clearly shown the existence of the saturation effect of reabsorption and the gain-peak blueshift effect as well as their transient features

Improving the Efficiency of Using Smalldistributed Generation Systems through Mechanisms of Demand Management for Electricity and Gas

The article is devoted to the development of a model and a set of methods for improving the efficiency of using small-distributed generation systems. The basis of the developed model is the integration of methods of price-dependent demand management for electricity and natural gas with a system of small-distributed power generation. The developed management model allows electricity consumers to reduce the cost of purchasing energy resources in comparison with the cost of electricity supplied from energy companies, based on the analysis of price indicators for the supply of electricity from regional energy markets and the terms of natural gas supply. The article presents the results of the pricing principles analysis for all components of the electricity and natural gas cost. The possibility of complex price-dependent demand management for the consumption of electric power is demonstrated through the management of electricity generation schedules by a small-generation system and schedules of gas consumption spent on electricity generation by a system of small-distributed generation. The complex of methods of price-dependent power consumption developed by the authors, taking into account the use of the system of small-distributed generation, can be adapted to the use by various types of electricity consumers that purchase electricity in the energy markets of various countries of the world.The work was supported by Act 211 Government of the Russian Federation, contract No 02.A03.21.0011

ChloroMitoSSRDB 2.00: More genomes, more repeats, unifying SSRs search patterns and on-the-fly repeat detection

© The Author(s) 2015. Published by Oxford University Press. Organelle genomes evolve rapidly as compared with nuclear genomes and have been widely used for developing microsatellites or simple sequence repeats (SSRs) markers for delineating phylogenomics. In our previous reports, we have established the largest repository of organelle SSRs, ChloroMitoSSRDB, which provides access to 2161 organelle genomes (1982 mitochondrial and 179 chloroplast genomes) with a total of 5838 perfect chloroplast SSRs, 37 297 imperfect chloroplast SSRs, 5898 perfect mitochondrial SSRs and 50 355 imperfect mitochondrial SSRs across organelle genomes. In the present research, we have updated ChloroMitoSSRDB by systematically analyzing and adding additional 191 chloroplast and 2102 mitochondrial genomes. With the recent update, ChloroMitoSSRDB 2.00 provides access to a total of 4454 organelle genomes displaying a total of 40 653 IMEx Perfect SSRs (11 802 Chloroplast Perfect SSRs and 28 851 Mitochondria Perfect SSRs), 275 981 IMEx Imperfect SSRs (78 972 Chloroplast Imperfect SSRs and 197 009 Mitochondria Imperfect SSRs), 35 250 MISA (MIcroSAtellite identification tool) Perfect SSRs and 3211 MISA Compound SSRs and associated information such as location of the repeats (coding and non-coding), size of repeat, motif and length polymorphism, and primer pairs. Additionally, we have integrated and made available several in silico SSRs mining tools through a unified web-portal for in silico repeat mining for assembled organelle genomes and from next generation sequencing reads. ChloroMitoSSRDB 2.00 allows the end user to perform multiple SSRs searches and easy browsing through the SSRs using two repeat algorithms and provide primer pair information for identified SSRs for evolutionary genomics

Обратное рассеяние ультразвуковых волн как основа метода контроля структуры и физико-механических свойств чугунов

Increasing the reliability of control of cast iron structure and its physical and mechanical characteristics is an important scientific and technical task of the machine-building industry. The paper studies the possibilities of controlling the structure of cast irons using structural noise created by ultrasonic scattering on graphite inclusions of different shapes. The subject of the present studies was such characteristics of structural noise as amplitude-temporal A(t) and as root mean square value of the amplitude of the ultrasonic waves backscattering field AN, compared with the data on ultrasonic velocity and strength or tensile strength of cast iron samples. As a result of the studies, a significant difference between the amplitude parameters of the AN structural noise obtained for samples with different shapes of graphite inclusions at 5 MHz was revealed for the first time. So, for example, for samples of gray cast iron (Russian: СЧ10, СЧ15, СЧ20, СЧ25), having predominantly plate-like form of graphite inclusions, the value of AN on 14–15 dB exceeds that measured in high-strength specimens of the cast iron with the prevailing form of spherical graphite inclusions ВЧ50 (Russian), etc. At the same time growth of longitudinal ultrasonic velocity amounted to 20–25 %. The method of rejection of gray cast iron from high-strength cast iron according to the data of amplitude parameters of structural noise AN at unilateral and local sounding of the object without using an additional reference signal reflected from its oppositional wall is suggested.Повышение надёжности контроля структуры чугунов и их физико-механических характеристик является важной научно-технической задачей машиностроительной промышленности. В работе изучены возможности контроля структуры чугунов, используя структурный шум, создаваемый рассеянием ультразвуковых колебаний на графитовых включениях разной формы. Предметом настоящих исследований являлись такие характеристики структурного шума как амплитудновременные А(t) и среднеквадратичные амплитуды AN волн рассеяния, сопоставляемые с данными по скорости ультразвуковых колебаний, а также прочностью или временным сопротивлением на растяжение образцов чугунов. В результате исследований впервые выявлено существенное различие между амплитудными параметрами структурного шума AN, полученными для образцов с разной формой графитовых включений на частоте 5 МГц. Так, например, для образцов серого чугуна (СЧ10, СЧ15, СЧ20, СЧ25), имеющих преимущественно пластинчатую форму графитовых включений, величина AN на 14–15 дБ превышает ту, что измерена в высокопрочных чугунах с превалирующей формой включений графита шаровидной формы – ВЧ50. При этом, рост продольной скорости ультразвука с увеличением временного сопротивления составил ≈ 20–25 %. Предложен метод отбраковки серого чугуна от высокопрочного по данным амплитудных параметров структурного шума AN при одностороннем и локальном прозвучивании объекта без использования дополнительного опорного сигнала, отражённого от его оппозитной стенки

Backscattering of Ultrasonic Waves as the Basis of the Method of Control of Structure and Physicо-Mechanical Properties of Cast Irons

Increasing the reliability of control of cast iron structure and its physical and mechanical characteristics is an important scientific and technical task of the machine-building industry. The paper studies the possibilities of controlling the structure of cast irons using structural noise created by ultrasonic scattering on graphite inclusions of different shapes. The subject of the present studies was such characteristics of structural noise as amplitude-temporal A(t) and as root mean square value of the amplitude of the ultrasonic waves backscattering field AN, compared with the data on ultrasonic velocity and strength or tensile strength of cast iron samples. As a result of the studies, a significant difference between the amplitude parameters of the AN structural noise obtained for samples with different shapes of graphite inclusions at 5 MHz was revealed for the first time. So, for example, for samples of gray cast iron (Russian: СЧ10, СЧ15, СЧ20, СЧ25), having predominantly plate-like form of graphite inclusions, the value of AN on 14–15 dB exceeds that measured in high-strength specimens of the cast iron with the prevailing form of spherical graphite inclusions ВЧ50 (Russian), etc. At the same time growth of longitudinal ultrasonic velocity amounted to 20–25 %. The method of rejection of gray cast iron from high-strength cast iron according to the data of amplitude parameters of structural noise AN at unilateral and local sounding of the object without using an additional reference signal reflected from its oppositional wall is suggested