TRULY BALANCED PULSE GENERATOR USING MICROWAVE TRANSISTOR AND SRD

A novel efficient circuit for Ultra-WideBand(UWB) balanced sub-nanosecond monocycle pulse generation is presented.The pulse generator employs wideband bipolar transistor,step recovery diodes,Schottky diodes,and simple charging and discharging circuitry.Simple transient analysis and design of the circuit are presented along with their operating principle.The pulse generator produces truly balanced monocycle pulse with 500 ps pulse-width and 800 mV peak voltage.The generated monocycle pulse also has very symmetrical positive and negative portions and low ringing level.The presented pulse generator can be used as both a transmitter feeding UWB balanced antennas without broadband baluns and a balanced switching pulse generator that used in UWB receiver.

Substituent Effect on Infrared Spectra and Thermodynamic Properties of Polynitroamino Substituted Cyclopentane and Cyclohexane

Density functional theory method was employed to study the effect of the nitroamino group as a substituent in cyclopentane and cyclohexane, which usually construct polycyclic or caged nitramines. Based on the optimized molecular structures of two groups of monocyclic nitramines at the B3LYP/6-31G^＊＊ level, the infrared （IR） spectra were obtained and assigned by harmonic vibrational analysis. The calculated results agree reasonably with the available experimental data. According to the principles of statistic thermodynamics, thermodynamic properties were derived from the IR spectra, which were linearly correlated with the number of nitroamino groups as well as the temperature. The contributions of nitroamino groups to thermodynamic properties are in accord with the group additivity.

Wilt Disease of Tara (<i>Caesalpinia spinose</i>Molina Kuntz) in Nursery in the Inter Andean Valley of Cochabamba, Bolivia

Tara (Caesalpinia spinose Molina Kuntz) is a native plant of the Bolivian Andes. A number of projects have promoted the cultivation of this species over the last 20 years, in efforts to make use of its medicinal, food and industrial properties. However, as tara plantations have grown, so too has the incidence of disease affecting the species, leading to economic losses. The aim of the present work was to identify the causal agent of wilting in tara, and to determine the incidence of the disease in nursery-grown plants. Three experimental plots (R1-R3) were established in plantlet production bedsat the ESFOR nursery in order to assess the incidence of wilting. Plant spacing was 1 × 1 m. At the two leaf stage, samples of diseased and apparently healthy plants were taken to the laboratory for the isolation of pathogens. Both the apparently healthy and diseased plants gave rise to the same kinds of fungal colony on PDA. Microscopic examination revealed microconidia, macroconidia, phialides and chlamydospores suggesting the causal agent to be Fusarium oxysporum. Over the (up to) 84-day period following thinning, the incidence of wilting for 2010 was R1 = 2.56%, R2 = 3.15% and R3 = 2.22% per 14 days, and for 2013 it was R1 = 1.24%, R2 = 2.45% and R3 = 2.13% per 14 days;the apparent infection rates for 2010 were rR1 = 0.0003/day, rR2 = 0.0003/day and rR3 = 0.0003/day, and for 2013 they were rR1 = 0.0003/day, rR2 = 0.0004/day and rR3 = 0.0003/day. These values are characteristic of monocyclic epiphytic fungi such as F. oxysporum.

Enumeration of Stereoisomers of Chiral and Achiral Derivatives of Monocyclic Cycloalkanes Having Heteromorphous Alkyl Substituents with Distinct Length <i>k</i>

A combinatorial method based on the determination of the averaged weight of permutations controlling the chirality/achirality fittingness of 2n substitution sites of the monocyclic cycloalkane allows to obtain generalized functional equations for direct enumeration of enantiomers pairs and achiral skeletons of any derivatives of monocyclic cycloalkanes having heteromorphic alkyl substituents with the distinct length k with the empirical formula , wherein at least two alkyl groups??of the distinct size ?each. ?is the number of alkyl radicals ?of the system??verifying the relation . The integer sequences of enantiomer pairs and achiral skeletons are given for substituted derivatives of monocyclic cycloalkane for n = 3, 4 and k = 3, 4, 5. The composite stereoisomerism of this particular compound is also highlighted.

Pulse Generation and Compression Techniques for Microwave Electronics and Ultrafast Systems

Ultrabroadband systems and ultrafast electronics require the generation,transmission,and processing of high-quality ultrashort pulses rang-ing from nanoseconds(ns)to picoseconds(ps),which include well-established and emerging applications of time-domain reflectometry,arbitrary wave-form generation,sampling oscilloscopes,frequency synthesis,through-wall radar imaging,indoor communication,radar surveillance,and medical radar detection.Impulse radar advancements in industrial,scientific,and medical(ISM)domains are,for example,driven by ns-scale-defined ultrawideband(UWB)technologies.Nevertheless,the generation of ultrashort ps-scale pulses is highly desired to achieve unprecedented performances in all these ap-plications and future systems.However,due to the variety and applicability of different pulse generation and compression techniques,the selection of optimum or appropriate pulse generators and compressors is difficult for practitioners and users.To this end,this article aims to provide a comprehen-sive overview of ultrashort ns and ps pulse generation and compression techniques.The proposed and developed pulse generators available in the litera-ture and on the market,which are characterized by their corresponding pros and cons,are also explored.The theoretical analysis of pulse generation us-ing a nonlinear transmission line(NLTL)presented in the literature is briefly explained as well.Additionally,a holistic overview of these pulse genera-tors from the perspective of applications is given to describe their utilization in practical systems.All of these techniques are well summarized and com-pared in terms of fundamental pulse parameters,and research gaps in specified areas are highlighted.A thorough discussion of previous research work on various topologies and techniques is presented,and potential future directions for technical advancement are examined.

Atmospheric gaseous aromatic hydrocarbons in eastern China based on mobile measurements:Spatial distribution,secondary formation potential and source apportionment

Monocyclic aromatic hydrocarbons(MAHs)and polycyclic aromatic hydrocarbons(PAHs)are both well known as hazardous air pollutants and also important anthropogenic precursors of tropospheric ozone(O3)and secondary organic aerosols(SOA).In recent years,there have been intensive studies covering MAHs emission from various sources and their behavior under stimulated photochemical conditions.Yet in-situ measurements of PAHs presence and variations in ambient air are sparse.Herein we conducted large geometrical scale mobile measurements for 16 aromatic hydrocarbons(AHs,including 7 MAHs and 9 PAHs)in eastern China between October 27 and November 8,2019.This unique dataset has allowed for some insights in terms of AHs concentration variations,accompanying chemical composition,source contributions and spatial distributions in eastern China.In general,AHs showed a clear concentration variability between the south and the north of the Yangtze River Delta(YRD).The concentrations of PAHs were approximately 9%of AHs,but contributed 23%of SOA formation potential.Source apportionment via positive matrix factorization(PMF)model revealed that industrial processes as the largest source(44%)of observed AHs,followed by solvent usage(21%),vehicle exhaust(19%),coal combustion(11%)and coking processes(6%).In the perspective of PAHs sources,coal combustion emissions were identified as the dominating factor of a share of 41%–52%in eastern China.Our findings complemented the simultaneously monitoring information of PAHs and MAHs in eastern China,revealed the importance of PAHs to SOA formation and highlighted the necessity of formulating strategies to reduce emissions from anthropogenic sources and reduce risks to human health.

Substituent effect on the molecular stability,group interaction,detonation performance,and thermolysis mechanism of nitroamino-substituted cyclopentanes and cyclohexanes

Density functional theory (DFT) method has been employed to study the effect of nitroamino group as a substituent in cyclopentane and cyclohexane, which usually construct the polycyclic or caged nitra-mines. Molecular structures were investigated at the B3LYP/6-31G** level, and isodesmic reactions were designed for calculating the group interactions. The results show that the group interactions ac-cord with the group additivity, increasing with the increasing number of nitroamino groups. The dis-tance between substituents influences the interactions. Detonation performances were evaluated by the Kamlet-Jacobs equations based on the predicted densities and heats of formation, while thermal stability and pyrolysis mechanism were studied by the computations of bond dissociation energy (BDE). It is found that the contributions of nitroamino groups to the detonation heat, detonation velocity, detonation pressure, and stability all deviate from the group additivity. Only 3a, 3b, and 9a-9c may be novel potential candidates of high energy density materials (HEDMs) according to the quantitative cri-teria of HEDM (ρ≈ 1.9 g/cm3, D ≈ 9.0 km/s, P ≈ 40.0 GPa). Stability decreases with the increasing number of N-NO2 groups, and homolysis of N-NO2 bond is the initial step in the thermolysis of the title com-pounds. Coupled with the demand of thermal stability (BDE > 20 kcal/mol), only 1,2,4-trinitrotriazacy-clohexane and 1,2,4,5-tetranitrotetraazacyclohexane are suggested as feasible energetic materials. These results may provide basic information for the molecular design of HEDMs.

Tagetones A and B, new cytotoxic monocyclic diterpenoids from flowers of Tagetes minuta

Tagetones A(1) and B(2), two new monocyclic diterpenoids were isolated from the n-hexane fraction of fresh flowers of Tagetes minuta L.(Asteraceae). Their structures were established by multiple spectroscopic methods(IR, HR-ESI-MS, and 1D-, and 2D-NMR), in addition to comparison with literature data. Compound 1 showed cytotoxic activity towards MCF7 and A549 cancer cells with IC_(50) values being 4.68 and 4.24 μmol·L^(-1), respectively, compared to doxorubicin(IC_(50) 0.13 and 1.12 μmol·L^(-1), respectively). Compound 2 also exhibited significant activity against HCT116 cancer cells(IC_(50), 6.30 μmol·L^(-1)).

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Density functional theory (DFT) method has been employed to study the effect of nitroamino group as a substituent in cyclopentane and cyclohexane, which usually construct the polycyclic or caged nitra-mines. Molecular structures were investigated at the B3LYP/6-31G** level, and isodesmic reactions were designed for calculating the group interactions. The results show that the group interactions ac-cord with the group additivity, increasing with the increasing number of nitroamino groups. The dis-tance between substituents influences the interactions. Detonation performances were evaluated by the Kamlet-Jacobs equations based on the predicted densities and heats of formation, while thermal stability and pyrolysis mechanism were studied by the computations of bond dissociation energy (BDE). It is found that the contributions of nitroamino groups to the detonation heat, detonation velocity, detonation pressure, and stability all deviate from the group additivity. Only 3a, 3b, and 9a-9c may be novel potential candidates of high energy density materials (HEDMs) according to the quantitative cri-teria of HEDM (ρ ≈ 1.9 g/cm3, D ≈ 9.0 km/s, P ≈ 40.0 GPa). Stability decreases with the increasing number of N-NO2 groups, and homolysis of N-NO2 bond is the initial step in the thermolysis of the title com-pounds. Coupled with the demand of thermal stability (BDE > 20 kcal/mol), only 1,2,4-trinitrotriazacy-clohexane and 1,2,4,5-tetranitrotetraazacyclohexane are suggested as feasible energetic materials. These results may provide basic information for the molecular design of HEDMs.