Effective Recombination Rate Research Articles

Ultrahigh-Frequency Heterodyne Lock-In Carrierography for Large-Scale Quantitative Multi-Parameter Imaging of Colloidal Quantum Dot Solar Cells

Ultrahigh-frequency heterodyne lock-in carrierography (UHF-HeLIC) is a new near-IR dynamic photoluminescence (PL) camera-based large-area imaging technique. It is specifically developed for investigating dynamic optoelectronic events that occur at very fast diffusion-wave rates (> = 10 kHz), above which conventional camera imaging cannot be achieved. The nonlinear combination of two-frequency-modulated photogenerated carrier density waves (CDWs) with a 10 Hz beat frequency was used to generate HeLIC images in the UHF range (up to 270 kHz) above the effective CDW recombination rate. Using sequences of these high-frequency images and UHF-HeLIC theory, carrier lifetime, diffusivity, and diffusion and drift length images were reconstructed from colloidal quantum dot solar cells and used for studying the influence of surface and interface trap states on photocarrier transport processes. The new non-destructive UHF-HeLIC imaging methodology shows excellent potential for industrial in-line photovoltaic device characterization, fundamental optoelectronic physical process studies, and various other photoelectronic applications.

Phylotranscriptomics of Pristionchus Nematodes Reveals Parallel Gene Loss in Six Hermaphroditic Lineages

Mutation and recombination are main drivers of phenotypic diversity, but the ability to create new allelic combinations is strongly dependent on the mode of reproduction. While most animals are dioecious (i.e., separated male and female sexes), in a number of evolutionary lineages females have gained the ability to self-fertilize [1, 2], with drastic consequences on effective recombination rate, genetic diversity, and the efficacy of selection [3]. In the genus Caenorhabditis, such hermaphroditic or androdioecious lineages, including C.briggsae and C.tropicalis, display a genome shrinkage relative totheir dioecious sister species C.nigoni and C.brenneri, respectively [4, 5]. However, common consequences of reproductive modes on nematode genomes remain unknown, because most taxa contain single or few androdioecious species. One exception is the genus Pristionchus, with seven androdioecious species. Pristionchus worms are found in association with scarab beetles in worldwide samplings, resulting in deep taxon sampling and currently 39 culturable and available species. Here, we use phylotranscriptomics of all 39 Pristionchus species to provide a robust phylogeny based on an alignment of more than 2,000 orthologous clusters, which indicates that the seven androdioecious species represent six independent lineages. We show that gene loss is more prevalent in all hermaphroditic lineages than in dioecious relatives and that the majority of lost genes evolved recently in the Pristionchus genus. Further, we provide evidence that genes with male-biased expression are preferentially lost in hermaphroditic lineages. This supports a contribution of adaptive gene loss to shaping nematode genomes following the evolution of hermaphroditism.

Persistent seed banking as eco-evolutionary determinant of plant nucleotide diversity: novel population genetics insights.

Contents Summary 725 I. Introduction 725 II. Seed banks decrease the population extinction rate 726 III. Seed banks define the effective population size 727 IV. Seed banks affect the mutation rate 728 V. Seed banks affect the effective recombination rate 728 VI. Seed banks influence the rate and signatures of natural selection 729 VII. Conclusion 729 Acknowledgements 729 References 729 SUMMARY: Long-term persistent seed banking is a common temporal bet-hedging strategy in plants to adapt to unpredictable environments. The population genomics perspective developed in this article suggests that seed banking determines plant nucleotide diversity by decreasing the rate of genetic drift and the effect of linked selection while increasing mutational input. As a result, persistent seed banks are important factors determining the magnitude of the discrepancy between the census size of the above-ground plant population and its genetic diversity, an effect known as the Lewontin paradox. The theoretical population genetics predictions presented here can be tested by combining genome-wide polymorphism data with ecological studies of dormancy.

Stationary afterglow apparatus with CRDS for study of processes in plasmas from 300 K down to 30 K.

A cryogenic stationary afterglow apparatus equipped with a near-infrared cavity-ring-down-spectrometer (Cryo-SA-CRDS) for studies of electron-ion recombination processes in the plasma at temperatures 30-300 K has been designed, constructed, tested, and put into operation. The plasma is generated in a sapphire discharge tube that is contained in a microwave cavity. The cavity and the tube are attached to the second stage of the cold head of the cryocooler system, and they are inserted to an UHV chamber with mirrors for CRDS and vacuum windows on both ends of the tube. The temperature of the discharge tube can be made as low as 25 K. In initial test measurements, the discharge was ignited in He/Ar/H2 or He/H2 gas mixtures and the density of H3+ ions and their kinetic and rotational temperatures were measured during the discharge and afterglow. From the measured decrease in the ion density, during the afterglow, effective recombination rate coefficients were determined. Plasma relaxation was studied in He/Ar gas mixtures by monitoring the presence of highly excited argon atoms. The spectroscopic measurements demonstrated that the kinetic temperature of the ions is equal to the gas temperature and that it can be varied from 300 K down to 30 K.

Synthesis and characterization of Sb3+-doped Ag/AgCl with enhanced visible-light photocatalytic activity

Novel Sb3+-doped Ag/AgCl photocatalysts containing different fractions of Sb3+ were synthesized by a simple coprecipitation method and systematically characterized by many techniques. The activity was maximized at the dosage of 2 wt% Sb3+ in methyl orange (MO) photodegradation experiments, and was reserved after three cycles. The photocatalytic activity was decided by the effective separation and low recombination rate of photogenerated electron–hole pairs. The high activities theoretically contributed to the Sb3+-induced formation of chloride dangling bonds and vacancies. The activity of Sb3+-doped Ag/AgCl (2 wt%) maximized to 98% after 14 min, which was much higher than the 50% of pure Ag/AgCl. Electron spin resonance and photoluminescence spectrum showed ·OH was the main active species during the MO oxidation over Sb3+-doped Ag/AgCl.

Effects of partial selfing on the equilibrium genetic variance, mutation load, and inbreeding depression under stabilizing selection.

The mating system of a species is expected to have important effects on its genetic diversity. In this article, we explore the effects of partial selfing on the equilibrium genetic variance Vg , mutation load L, and inbreeding depression δ under stabilizing selection acting on a arbitrary number n of quantitative traits coded by biallelic loci with additive effects. When the U/n ratio is low (where U is the total haploid mutation rate on selected traits) and effective recombination rates are sufficiently high, genetic associations between loci are negligible and the genetic variance, mutation load, and inbreeding depression are well predicted by approximations based on single-locus models. For higher values of U/n and/or lower effective recombination, moderate genetic associations generated by epistasis tend to increase Vg , L, and δ, this regime being well predicted by approximations including the effects of pairwise associations between loci. For yet higher values of U/n and/or lower effective recombination, a different regime is reached under which the maintenance of coadapted gene complexes reduces Vg , L, and δ. Simulations indicate that the values of Vg , L, and δ are little affected by assumptions regarding the number of possible alleles per locus.

Origin of C. latifolia and C. aurantiifolia triploid limes: the preferential disomic inheritance of doubled-diploid 'Mexican' lime is consistent with an interploid hybridization hypothesis.

Two main types of triploid limes are produced worldwide. The 'Tahiti' lime type (Citrus latifolia) is predominant, while the 'Tanepao' type (C. aurantiifolia) is produced to a lesser extent. Both types result from natural interspecific hybridization involving a diploid gamete of C. aurantiifolia 'Mexican' lime type (itself a direct interspecific C. micrantha × C. medica hybrid). The meiotic behaviour of a doubled-diploid 'Mexican' lime, the interspecific micrantha/medica recombination and the resulting diploid gamete structures were analysed to investigate the possibility that 'Tahiti' and 'Tanepao' varieties are derived from natural interploid hybridization. A population of 85 tetraploid hybrids was established between a doubled-diploid clementine and a doubled-diploid 'Mexican' lime and used to infer the genotypes of 'Mexican' lime diploid gametes. Meiotic behaviour was studied through combined segregation analysis of 35 simple sequenbce repeat (SSR) and single nucleotide polymorphismn (SNP) markers covering the nine citrus chromosomes and cytogenetic studies. It was supplemented by pollen viability assessment. Pollen viability of the doubled-diploid Mexican lime (64 %) was much higher than that of the diploid. On average, 65 % of the chromosomes paired as bivalents and 31.4 % as tetravalents. Parental heterozygosity restitution ranged from 83 to 99 %. Disomic inheritance with high preferential pairing values was deduced for three chromosomes. Intermediate inheritances, with disomic trend, were found for five chromosomes, and an intermediate inheritance was observed for one chromosome. The average effective interspecific recombination rate was low (1.2 cM Mb-1). The doubled-diploid 'Mexican' lime had predominantly disomic segregation, producing interspecific diploid gamete structures with high C. medica/C. micrantha heterozygosity, compatible with the phylogenomic structures of triploid C. latifolia and C. aurantiifolia varieties. This disomic trend limits effective interspecific recombination and diversity of the diploid gamete population. Interploid reconstruction breeding using doubled-diploid lime as one parent is a promising approach for triploid lime diversification.

Electron-ion recombination in low temperature hydrogen/deuterium plasma

The stationary afterglow with cavity ring down spectrometer (SA-CRDS) was used to study the recombination of H3 + , H2 D+ , HD2 + and D3 + ions with electrons in low temperature (77–300 K) plasmas in He/Ar/H2 /D2 gas mixtures. By measuring effective recombination rate coefficients (α eff ) in plasma with mixtures of ions and their dependences on temperature and partial densities of He, H2 and D2 , α eff (T , [He],[H2 ],[D2 ]), we determined binary (α binH3 , α binH2D , α binHD2 , α binD3 ) and ternary (K H3 , K H2D , K HD2 , K D3 ) recombination rate coefficients for H3 + , H2 D+ , HD2 + and D3 + ions. For all four ions we observed very efficient He assisted ternary recombination which is comparable with binary recombination already at [He] =1 × 1017 cm−3 . The removal of excited particles in afterglow plasma was monitored to obtain the plasma thermalisation rate at given experimental conditions. The inferred deexcitation rates for reaction of helium metastable atoms with D2 are k D2 (300 K)=(2.1 ± 0.3) × 10−10 cm3 s−1 and k D2 (140 K)=(1.3 ± 0.3) × 10−10 cm3 s−1 .

Charge States of Krypton and Xenon in the Solar Wind

We calculate charge state distributions of Kr and Xe in a model for two different types of solar wind using the effective ionization and recombination rates provided from the OPEN_ADAS data base. The charge states of heavy elements in the solar wind are essential for estimating the efficiency of Coulomb drag in the inner corona. We find that xenon ions experience particularly low Coulomb drag from protons in the inner corona, comparable to the notoriously weak drag of protons on helium ions. It has been found long ago that helium in the solar wind can be strongly depleted near interplanetary current sheets, whereas coronal mass ejecta are sometimes strongly enriched in helium. We argue that if the extraordinary variability of the helium abundance in the solar wind is due to inefficient Coulomb drag, the xenon abundance must vary strongly. In fact, a secular decrease of the solar wind xenon abundance relative to the other heavier noble gases (Ne, Ar, Kr) has been postulated based on a comparison of noble gases in recently irradiated and ancient samples of ilmenite in the lunar regolith. We conclude that decreasing solar activity and decreasing frequency of coronal mass ejections over the solar lifetime might be responsible for a secularly decreasing abundance of xenon in the solar wind.

Fizychni vlastyvosti kremniyevykh sensornykh struktur z fotoelektrychnym pryntsypom peretvorennya na osnovi “hlybokoho” p–n-perekhodu

A capability to produce effective sensor structures on the basis of “deep”silicon junction has been substantiated. If the incident light is strongly absorbed by this junction, the photocurrent through it is shown to substantially depend on the recombination characteristics and the charge state of the illuminated surface, provided that the junction parameters are optimal. The depth of the illuminated region is demonstrated to exceed the diffusion length of minority charge carriers. It is found that the larger diffusion length of minority charge carriers corresponds to stronger changes of the photocurrent generated by the illuminated surface area. A possibility to transform the junction from a photodetector into an effective chemical sensor is verified by numerical calculations. The physical mechanisms relating the changes in the effective surface recombination rate and the absorption of polar molecules are discussed. The sensor properties of suggested silicon junctions are analyzed for a number of analytes. Their suitability for the creation of selective chemical sensors (electronic noses) is demonstrated experimentally.

Simulation of beam-induced plasma in gas-filled rf cavities

Processes occurring in a radio-frequency (rf) cavity, filled with high pressure gas and interacting with proton beams, have been studied via advanced numerical simulations. Simulations support the experimental program on the hydrogen gas-filled rf cavity in the Mucool Test Area (MTA) at Fermilab, and broader research on the design of muon cooling devices. SPACE, a 3D electromagnetic particle-in-cell (EM-PIC) code with atomic physics support, was used in simulation studies. Plasma dynamics in the rf cavity, including the process of neutral gas ionization by proton beams, plasma loading of the rf cavity, and atomic processes in plasma such as electron-ion and ion-ion recombination and electron attachment to dopant molecules, have been studied. Through comparison with experiments in the MTA, simulations quantified several uncertain values of plasma properties such as effective recombination rates and the attachment time of electrons to dopant molecules. Simulations have achieved very good agreement with experiments on plasma loading and related processes. The experimentally validated code SPACE is capable of predictive simulations of muon cooling devices.

Stationary afterglow measurements of the temperature dependence of the electron–ion recombination rate coefficients of and in He/Ar/H2/D2 gas mixtures at T = 80–145 K

We report measurements of the binary and ternary recombination rate coefficients of deuterated isotopologues of . A cavity ring-down absorption spectrometer was used to monitor the fractional abundances of , , and during the decay of a plasma in He/Ar// mixtures. A dependence of the measured effective recombination rate coefficients on the helium buffer gas density was observed and hence both the binary and the ternary recombination rate coefficients for and were obtained in the temperature range 80–145 K.

Фотоелектричне перетворення сигналу в глибокому p-n- переході як засіб детектування карбонових нанотрубок з адсорбованим сульфанолом у водному розчині

The possibility of using the principle of photoelectric conversion in structures with a deep p-n junction to control the content of carbon nanotubes with adsorbed surfactant (SDBS) in an aqueous solution was shown. Experimental studies of the analyte influence on the change in the photocurrent through a deep p-n junction were carried out. A shift in the dependence of the photocurrent on the voltage applied to the surface of the sensor structure due to the presence of carbon nanotubes in the solution was recorded. The change in the effective recombination rate, which corresponds to the distribution of the photocurrent at the surface, can be attributed to a change in the near-surface band bending.

Consequences of genetic linkage for the maintenance of sexually antagonistic polymorphism in hermaphrodites

When selection differs between males and females, pleiotropic effects among genes expressed by both sexes can result in sexually antagonistic selection (SA), where beneficial alleles for one sex are deleterious for the other. For hermaphrodites, alleles with opposing fitness effects through each sex function represent analogous genetic constraints on fitness. Recent theory based on single-locus models predicts that the maintenance of SA genetic variation should be greatly reduced in partially selfing populations. However, selfing also reduces the effective rate of recombination, which should facilitate selection on linked allelic combinations and expand opportunities for balancing selection in a multilocus context. Here, I develop a two-locus model of SA selection for simultaneous hermaphrodites, and explore the joint influence of linkage, self-fertilization, and dominance on the maintainance of SA polymorphism. I find that the effective reduction in recombination caused by selfing significantly expands the parameter space where SA polymorphism can be maintained relative to single-locus models. In particular, linkage facilitates the invasion of male-beneficial alleles, partially compensating for the "female-bias" in the net direction of selection created by selfing. I discuss the implications of accounting for linkage among SA loci for the maintenance of SA genetic variation and mixed mating systems in hermaphrodites.

Synthesis of novel Cd2P2O7/Ag3PO4 photocatalyst with enhanced visible-light photocatalytic performance and the enhancement mechanism

Novel Cd2P2O7/Ag3PO4 photocatalysts containing different mass fractions of Cd2P2O7 were synthesized by a hydrothermal method. The photocatalysts were characterized by X-ray diffractometry, transmission electron microscopy, X-ray photoelectron spectroscopy, Electron spin resonance (ESR), Fourier transform infrared spectrometry, ultraviolet–visible absorption spectroscopy and photoluminescence spectroscopy. Photocatalytic activity was decided by the effective separation and low recombination rate of photogenerated electron-hole pairs. During the experiments, the Cd2P2O7/Ag3PO4 composites possessed fierce electron- hole separation capacity. In particular, the 1wt% Cd2P2O7/Ag3PO4 catalyst displayed higher photocatalytic performance than pure Ag3PO4 under visible-light irradiation (λ>420nm). The ESR spectrum showed the main active species during the methyl orange degradation were ·OH and ·O2−.

Monitoring the removal of excited particles in He/Ar/H2low temperature afterglow plasma at 80–300 K

Stationary afterglow (SA) experiments with cavity ring down absorption spectrometer (cw-CRDS) have been used to study recombination of H 3 + ions with electrons. To characterize the plasma during the afterglow we monitored the time evolution of density of He 2 excited dimers ( a 3 Ʃ u + ) in plasmas in pure helium and in helium with small admixture of Ar and H 2 . By monitoring the plasma decay and its dependence on [H 2 ] and [Ar] in the afterglow in pure He and in He/Ar/H 2 mixture we estimated the rate of plasma thermalization in the temperature range of 80–300 K. The inferred deexcitation rate coefficients for reaction of helium metastable atoms with H 2 were (0.9 ± 0.3) × 10 −10 cm 3 s −1 , (1.9 ± 0.2) × 10 −10 cm 3 s −1 and (2.7 ± 0.2) × 10 −10 cm 3 s −1 at 80 K, 140 K and 300 K, respectively. The effective recombination rate coefficients for H 3 + were evaluated from the decay of the electron number density. We propose the lower estimate for the saturation of the effective recombination rate coefficient in H 3 + and D 3 + dominated plasma.

Noble-metal-free cobalt phosphide modified carbon nitride: An efficient photocatalyst for hydrogen generation

Photocatalytic hydrogen generation from water is an important solar-to-chemical conversion process, and is also a sustainable and environment-friendly generation approach for energy source of hydrogen. Herein, for the first time, we report the noble-metal-free CoP/g-C3N4 hybrid as a photocatalyst for the highly efficient hydrogen generation by water splitting under visible light irradiation, whose hydrogen generation rate is ∼131 times higher than that of pure g-C3N4, and is even better than that of Pt/g-C3N4. Based on the detailed analyses of photoluminescence (PL) spectra, UV–vis diffuse reflectance spectroscopy (UV–vis DRS), photocurrent-time (i-t) curves, and electrochemical impedance spectroscopy (EIS) Nyquist plots, the reason for the high efficiency of CoP/g-C3N4 is found to be its good absorption ability of visible light, highly effective separation and low recombination rate of photo-generated electron-hole pairs due to the addition of CoP to g-C3N4.

Improved catalytic activity of Pt/rGO counter electrode in In2O3-based DSSC

A platinum/reduced graphene oxide (Pt/rGO) nanocomposite acting as a counter electrode (CE) was fabricated using a chemical bath deposition method for In2O3-based dye-sensitized solar cell (DSSC) via sol-gel technique. The report analyzes the morphological and electrochemical impedance spectroscopy of the annealing Pt/rGO films at 350, 400, and 450 °C. Micrograph images obtained from field emission scanning electron microscopy demonstrated the annealed films are highly porous. The energy-dispersive X-ray results show that the carbon atoms were homogeneously distributed on the film annealed at 400 °C. A good photovoltaic performance was exhibited with high photocurrent density of 8.1 mA cm−2 and power conversion efficiency (η) of 1.68 % at the Pt/rGO CE annealed at 400 °C. The employed electrochemical impedance spectroscopy analysis quantifies that the Pt/rGO films annealed at 400 °C provide more efficient charge transfer with the lowest effective recombination rate and high electron life time, hence improving the performance of Pt/rGO CE.

Morphological and electron mobility studies in nanograss In2O3 DSSC incorporating multi-walled carbon nanotubes

In2O3and In2O3-MWCNTs, thin films were prepared by means of sol-gel spin coating technique for dye-sensitized solar cells (DSSCs). The morphological characteristics of In2O3 and In2O3-MWCNT thin films were studied via atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The porous and rough surface structure of nanograss In2O3 increased the surface area for improved dye loading. The low photovoltage issue in In2O3-based DSSCs was addressed by the incorporation of MWCNTs. The bandgap decreased when In2O3 was incorporated with MWCNTs. The presence of MWCNTs in the thin film caused the fermi level (EF) to shift upward and this leads to a larger energy gap between EF and the iodine redox level (EREDOX) that results in higher photovoltage. The In2O3-MWCNT-based DSSCs exhibited better photovoltaic performance than In2O3-based DSSC with photovoltaic efficiency of 1.29 and 0.14 %, respectively. The electrochemical impedance spectroscopy (EIS unit) supported the photovoltaic performance by quantifying that the In2O3-MWCNT thin films provide more efficient charge transfer with the lowest effective recombination rate and high electron lifetime, hence improving the performance of DSSCs.

Interactions between Genetic and Ecological Effects on the Evolution of Life Cycles.

Sexual reproduction leads to an alternation between haploid and diploid phases, whose relative length varies widely across taxa. Previous genetical models showed that diploid or haploid life cycles may be favored, depending on dominance interactions and on effective recombination rates. By contrast, niche differentiation between haploids and diploids may favor biphasic life cycles, in which development occurs in both phases. In this article, we explore the interplay between genetical and ecological factors, assuming that deleterious mutations affect the competitivity of individuals within their ecological niche and allowing different effects of mutations in haploids and diploids (including antagonistic selection). We show that selection on a modifier gene affecting the relative length of both phases can be decomposed into a direct selection term favoring the phase with the highest mean fitness (due to either ecological differences or differential effects of mutations) and an indirect selection term favoring the phase in which selection is more efficient. When deleterious alleles occur at many loci and in the presence of ecological differentiation between haploids and diploids, evolutionary branching often occurs and leads to the stable coexistence of alleles coding for haploid and diploid cycles, while temporal variations in niche sizes may stabilize biphasic cycles.