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State‐of‐the‐art photoelectrodes in highly efficient photoelectrochemical (PEC) systems often comprise multilayer architectures where lattice mismatch‐imposed strain at the interfaces can perturb the material's crystalline lattice and electronic structure. Despite its inevitable presence, understanding of strain effects in semiconductor photoelectrodes is lacking, preventing rational exploitation of strain engineering to improve photoelectrode performance. In this work, we combine X‐ray structural characterization with strain tensor decomposition analysis as well as optical/photocurrent spectroscopic methods to demonstrate how volumetric lattice deformations caused by substrate‐imposed hydrostatic strain impact the optoelectronic and PEC properties of BiVO4. Utilizing single‐crystalline, epitaxial BiVO4/indium tin oxide (ITO)/yttrium‐stabilized zirconia (YSZx, x = 8% and 13% mol Y2O3) photoelectrodes as a model platform, we find that tensile hydrostatic strain that causes volumetric lattice dilation in BiVO4 results in slightly enhanced optical absorption, but it is detrimental to the internal quantum efficiencies in BiVO4. We attribute this to localization of photogenerated charge carriers, thereby leading to poor charge separation in the bulk of BiVO4 and increased recombination losses. Finally, we highlight the beneficial effects of compressive hydrostatic strain on enhancing the internal quantum efficiencies in BiVO4. Our results provide a basis for exploiting epitaxial strain engineering to optimize the performance of multilayer photoelectrodes in PEC systems. [ABSTRACT FROM AUTHOR]

The analysis of the photoluminescence of polar light emitting diode (LED) structures with a 25 nm In0.17Ga0.83N quantum well is reported. The observed emission most likely originates from a set of energetically close excited states (ES), while the ground state decays only extremely slowly on a μs‐to‐ms timescale, that is, long‐living charge accumulates there. However, this population can also be quantified spectroscopically by applying short reverse voltage pulses. The emission from ES is effective and nearly exponential with decay time constants of 1.5 and 8 ns at 6 and 300 K, respectively, and is likely dominated by radiative processes. These findings point to a possible route to improved polar device architectures. [ABSTRACT FROM AUTHOR]

The small perturbation frequency‐resolved techniques have been powerful tools in unraveling the kinetic processes governing the operation of perovskite solar cells (PSCs). One such technique is electrochemical impedance spectroscopy (EIS). However, a thorough interpretation of the EIS response of PSCs is still lacking owing to the absence of a uniform electrical equivalent circuit. In this context, intensity‐modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) can be the link between the optical and electrical responses of PSCs and complement the IS technique. In this review, the progress made in interpreting the IMPS/IMVS response of various types of PSCs is summarized and diverse prospects are discussed. First, the basic theory and models present in the literature are discussed. Next, the IMPS/IMVS response of mesoporous and planar PSCs based on various physical parameters is discussed. At last, proposed future prospects for the development of this field are discussed. [ABSTRACT FROM AUTHOR]

Objective of the study: To explain the characteristics and dynamics of resources and recombinations associated with developing products with low and high novelty. Methodology/Approach: The method was an integrative review of the literature on recombinant innovation. It included a creative synthesis that resulted in a theoretical model. Originality/Relevance: The research addresses topics the literature neglects, like explaining which resources and recombinations and why could relate to high or low product novelty. Main results: Certain features of resources (i.e., heterogeneity, specificity, accessibility) with high and low levels may differently influence costs, variety, and frequency of recombinations and, in turn, product novelty. To develop highly novel products, tangible resources, and internally produced new resources may be essential, as knowledge by itself may not be sufficient. Theoretical contributions: Different resource characteristics and their influence on recombinations may help explain whether a product will have low or high novelty. By going beyond the novel recombinations, the research expands the literature's understanding of recombinations and product novelty. Managerial contributions: Companies could assess ex ante which degree of product novelty besides types and costs of recombinations would result from their pools of resources. This assessment would make innovation more efficient for companies with fewer resources, like may occur in emerging markets. [ABSTRACT FROM AUTHOR]

Silicon solar cells with non-uniform and heavily doped emitter region have been investigated. The results show that non-uniform doped solar cells have significantly higher conversion efficiency as compared to the uniformly-doped Si-solar cells. These results were obtained from simulation with the PC1D software. By introducing non-uniform doping profile in the emitter region of a Si solar cell, better performance parameters like improved current-voltage characteristics and higher quantum efficiency was achieved. However, a number of non-ideal effects have been also observed as the doping level increased from certain level. This results into dead layer formation at the front surface of emitter region. The recombinations become significant in which Auger recombination especially reduce lifetime, carrier mobility and tend to decrease the efficiency of solar cell. From the simulations results optimum surface doping level of 1019cm-³ and 1017 cm-3 have been achieved for emitter and base regions, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Significant work has been directed at measuring the exciton diffusion length (LD) in organic semiconductors due to its significance in determining the performance of photovoltaic cells. Several techniques have been developed to measure LD, often probing photoluminescence or charge carrier generation. Interestingly, in this study it is shown that when different techniques are compared, both the diffusive behavior of the exciton and active carrier recombination loss pathways can be decoupled. Here, a planar heterojunction device based on the donor–acceptor pairing of boron subphthalocyanine chloride‐C60 is examined using photoluminescence quenching, photovoltage‐, and photocurrent‐based LD measurement techniques. Photovoltage yields the device relevant LD of both active materials as a function of forward bias subject to geminate recombination losses. These values are used to accurately predict the photocurrent as a function of voltage, suggesting geminate recombination is the dominant mechanism responsible for photocurrent loss. By combining these measurements with photocurrent and photoluminescence quenching, the intrinsic LD, as well as the voltage‐dependent charge transfer state dissociation and charge collection efficiencies are quantitatively determined. The results of this work provide a method to decouple all relevant loss pathways during photoconversion, and establish the factors that can limit the performance of excitonic photovoltaic cells. [ABSTRACT FROM AUTHOR]

Pedigrees are directed acyclic graphs that represent ancestral relationships between individuals in a population. Based on a schematic recombination process, we describe two simple Markov models for sequences evolving on pedigrees-Model R (recombinations without mutations) and Model RM (recombinations with mutations). For these models, we ask an identifiability question: is it possible to construct a pedigree from the joint probability distribution of extant sequences? We present partial identifiability results for general pedigrees: we show that when the crossover probabilities are sufficiently small, certain spanning subgraph sequences can be counted from the joint distribution of extant sequences. We demonstrate how pedigrees that earlier seemed difficult to distinguish are distinguished by counting their spanning subgraph sequences. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present a study on cadmium selenide (CdSe) quantum-dot-sensitized solar cells (QDSSCs) in terms of the evaluation of carrier transport and recombinations using intensity-modulated photovoltage spectroscopy (IMVS) and intensity-modulated photocurrent spectroscopy (IMPS). Using the obtained data through this evaluation, we calculated the electron transport time (τ sc ), electron recombination lifetimes (τ oc ), effective diffusion constants (D eff ), and diffusion lengths (L n ). The QDSSC used in this study show improved fill factors (FF) of ∼60% with a polysulfide (S2−/S x 2−) redox mediator and Pt counter electrode. This result is ascribed to the low series resistances (R s ) of QDSSC that are accessed by electrochemical impedance spectroscopy. In addition, the present study provides information on the sensitization mode of CdSe QDs on TiO2 electrodes, achieved by scanning transmission electron microscopy (STEM) combined with EDS imaging. [Copyright &y& Elsevier]

The HLA-related hemochromatosis mutation C282Y is thought to have originated in Ireland in a person with HLA-A3-B14 and was spread by Vikings. Irish people with two HLA-A3 alleles had a high risk of hemochromatosis. In this study, from west Sweden, we wanted to test these hypotheses. HFE mutations in controls, bone marrow donors with HLA-A3/A3 and patients with hemochromatosis. HLA haplotypes, extended haplotype analysis and pedigree studies. The allelic C282Y frequency 0.04, (CI 0.01-0.07) was lower ( P < 0.001) in Sweden than in Ireland 0.10 (CI 0.08-0.11), and Swedish bone marrow donors with HLA-A3/A3 ( n = 77) had a low risk of hemochromatosis. HLA haplotypes available from 239/262 (91.5%) proband patients homozygous for C282Y showed a dominance of A3-B7 and A3-B14 both in linkage disequilibrium with controls ( P < 0.001). Pedigree studies extended into the 17th century supported a local founder effect of A3-B14 in the county of Bohuslän. The A3-B14 haplotype may well be the original and A3-B7 the result of centromeric recombinations. The haplotype diversity and recombination events were not different from a Celtic series. These findings do not support the hypothesis of the C282Y mutation being of an Irish Celtic origin. Conclusions: The C282Y frequency shows a west to east decline from Ireland through the north of Europe. Vikings may have been involved in the spread of C282Y, but the mutation is probably older and may have been spread in Europe by earlier seafarers. [ABSTRACT FROM AUTHOR]

Background: The haemochromatosis mutation C282Y occurred once in a person who lived in Ireland or Scandinavia and carried either human leucocyte antigen (HLA)-A3-B7 or A3-B14. With time, recombinations are believed to have taken place introducing new HLA haplotypes. This evolution is mainly unknown. In this study, we tried to find a founder, possible recombination events and effect on the phenotype in descendants. Setting: A Swedish mountain population close to Norway, n = 3529, population density <1/km2. Methods: Retrospective genealogy study of HLA haplotypes followed by extended haplotype studies. Results: There were 34 probands (22 men, 12 women) where 31 (91%) shared a common founder origin 12 generations ago. The A3-B14 haplotype was the most common, 39%, in strong linkage disequilibrium ( P < 0.0005) with controls, followed by A3-B7, 20% ( P < 0.005), probably resulting from a centromeric recombination replacing the B14 allele with the common B7. Possible telomeric recombinations took place close to HLA-A and introduced the haplotypes AW19-B7 ( n = 4), AW19-B27 (2), A1-B17 (5) and A2-B12 (4) supported by pedigree studies. Male homozygotes with two copies of HLA-A3 had significantly ( P 0.001) higher mean serum ferritin values than those with one, and liver damage (fibrosis and cirrhosis) was also more common ( P < 0.001) than in a population with a recombinant (A1-B8) haplotype. Conclusions: A3-B14 may well be the ancestral haplotype with A3B7, the result of centromeric recombinations introducing the common B7 allele. Telomeric recombinations were more common than expected. The ancestral HLA-A3 haplotype may be associated with a more severe phenotypic expression. [ABSTRACT FROM AUTHOR]

Abstract: Inter-individual gene copy-number variations (CNVs) probably afford human populations the flexibility to respond to a variety of environmental challenges, but also lead to differential disease predispositions. We investigated gene CNVs for complement component C4 and steroid 21-hydroxylase from the RP-C4-CYP21-TNX (RCCX) modules located in the major histocompatibility complex among healthy Asian-Indian Americans (AIA) and compared them to European Americans. A combination of definitive techniques that yielded cross-confirmatory results was used. The medium gene copy-numbers for C4 and its isotypes, acidic C4A and basic C4B, were 4, 2 and 2, respectively, but their frequencies were only 53–56%. The distribution patterns for total C4 and C4A are skewed towards the high copy-number side. For example, the frequency of AIA-subjects with three copies of C4A (30.7%) was 3.92-fold of those with a single copy (7.83%). The monomodular-short haplotype with a single C4B gene and the absence of C4A, which is in linkage-disequilibrium with HLA DRB1*0301 in Europeans and a strong risk factor for autoimmune diseases, has a frequency of 0.012 in AIA but 0.106 among healthy European Americans (p =6.6×10−8). The copy-number and the size of C4 genes strongly determine the plasma C4 protein concentrations. Parallel variations in copy-numbers of CYP21A (CYP21A1P) and TNXA with total C4 were also observed. Notably, 13.1% of AIA-subjects had three copies of the functional CYP21B, which were likely generated by recombinations between monomodular and bimodular RCCX haplotypes. The high copy-numbers of C4 and the high frequency of RCCX recombinants offer important insights to the prevalence of autoimmune and genetic diseases. [Copyright &y& Elsevier]

Begomoviruses are plant pathogens that caused important losses to crops of economic interest in tropical and subtropical regions in the last decade. In Cuba, nine begomoviruses have been identified affecting tomato, beans, tobacco, pepper, squash, potato and weeds of different botanical families. The intergenic sequence (IR) and the N-terminal regions of the replication associated protein (Rep) of begomoviruses identified in Cuba were analysed using sequence data of gene collections (GeneBank). Statistical programs were used for the alignments, phylogenetic analysis and searching of significant recombination fragments. The detection of possible recombination events was carried out for p=0.05, based on 10000 permutations. Eleven IR recombination event sites between Macroptilium Yellow Mosaic Virus (MaYMV) and Tobacco Leaf Rugose Virus (TLRV), and 15 between Tomato Mottle Taino Virus (TMoTV) and Dicliptera Yellow Mosaic Virus (DiYMoV) were found. Sixteen recombination event sites between MaYMV and Sida Golden Yellow Vein Virus (SiGYVV) were also found in the Rep region. Jatropha Mosaic Virus (JMV) from Jatropha gossipifolia and Tomato Yellow Leaf Curl Virus TYLCV-IL(CU) from tomato and pepper showed base sequences in the alignments that were present in all the polymorphic sites detected and homologous to monomorphic sites. TMoTV and DiYMoV showed 3 and 4 polymorphic sites in the Rep N-terminal region, respectively. All these sites constitute evidences of old recombination events destroyed during the evolution, and they may define the characteristics of the begomovirus species identified. [ABSTRACT FROM AUTHOR]

Abstract: It is known that in the three-dimensional structure of a protein, certain amino acids can interact with each other in order to provide structural integrity or aid in its catalytic function. If these positions are mutated the loss of this interaction usually leads to a non-functional protein. Directed evolution experiments, which probe the sequence space of a protein through mutations in search for an improved variant, frequently result in such inactive sequences. In this work, we address the use of machine learning algorithms, Boolean learning and support vector machines (SVMs), to find such pairs of amino acid positions. The recombination method of imparting mutations was simulated to create in silico sequences that were used as training data for the algorithms. The two algorithms were combined together to develop an approach that weighs the structural risk as well as the empirical risk to solve the problem. This strategy was adapted to a multi-round framework of experiments where the data generated in the present round is used to design experiments for the next round to improve the generated library, as well as the estimation of the interacting positions. It is observed that this strategy can greatly improve the number of functional variants that are generated as well as the average number of mutations that can be made in the library. [Copyright &y& Elsevier]

Expressing two genes in the progeny of stem and progenitor cells that are transduced with a unique viral vector is desirable in certain situations. We tested the ability of two lentiviral vectors to transduce human cells of hematopoietic origin and concomitantly express two reporter genes, either EGFP (enhanced green fluorescent protein) and DsRed2 , or EGFP and EYFP (enhanced yellow fluorescent protein), from two internal promoters. The vectors were generated from the pTRIP deltaU3 EF1alpha EGFP lentiviral vector. Following transduction of hematopoietic and non-hematopoietic cell lines, we performed FACS, PCR and Southern blot analyzes to quantify transduction, integration efficiencies and size of integrated lentiviral vectors, respectively. The detection of DsRed2 fluorescence appeared unexpectedly low in human cells of hematopoietic origin. Alternatively, a modification in the flow cytometry assay allowed us to distinguish between the two overlapping fluorescence signals emitted by EGFP and EYFP, when transduced cells were excited with a 488-nm laser beam. However, the low frequency of double-positive EGFP + EYFP + cells, and the existence of single-positive, mostly EGFP - EYFP + , cells, prompted us to search for recombinations in the vector sequence. Southern blotting of DNA obtained from transduced cells indeed demonstrated that recombination had occurred between the two closely related EGFP and EYFP sequences. These observations suggest that recombination occurred within the EGFP and EYFP genes, which differ by only four amino acids. We conclude that the insertion of two highly homologous sequences into a lentiviral backbone can favor recombination. [ABSTRACT FROM AUTHOR]

This study determines the effects of a water disinfection by-product, 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (also known as mutagen X or MX) and chlorinated tap water on genomic instability in the yeast Saccharomyces cerevisiae. Tap water samples collected from Cherepovets (Russia) and Boston (MA, USA), were extracted using XAD absorption and ethyl acetate elution. MX and these water extracts were then tested for their ability to induce intrachromosomal recombination (deletions or DEL events), interchromosomal recombination (ICR) and aneuploidy (ANEU) using the yeast DEL assay. MX strongly induced DEL, ICR and ANEU events with a positive dose response and no threshold. Cherepovets tap water induced DEL and ICR events while evidence of ANEU induction was weak. The DEL induction potencies were stronger at higher concentrations. The estimated contribution of MX to DEL induction varied from over 50% at low concentrations (which is comparable to a typical contribution of MX to Ames mutagenicity of tap water) to between 2 and 10% at highest concentrations. For Boston tap water, there was only weak evidence of DEL induction and no evidence of ICR and ANEU induction. This is consistent with the results of other studies, which reported much higher concentrations of MX and stronger Ames mutagenicity in Cherepovets tap water than in Boston tap water. [Copyright &y& Elsevier]

Nanocrystalline films of cadmium sulfide sensitized with ruthenium N3 dye show only a feeble photoresponse either in the absorption region of the dye or the band gap excitation of cadmium sulfide. However, when an ultrathin outer shell of magnesium oxide is deposited on the cadmium sulfide crystallites in the film, the photoresponse in both the above regions of the spectrum are greatly enhanced. The result is explained as electron injection from excited dye molecules on the outer magnesium oxide shell to the conduction band of cadmium sulfide and suppression of the leakage of the relaxed electrons to the interface by the magnesium oxide barrier, where they undergo recombinations. Possible applications of this effect in dye-sensitized solar cells are discussed. [Copyright &y& Elsevier]