bluuebunny/crossref_metadata_2025_split huggingface dataset:
Training sets based on uncertainty estimates in the cluster-expansion method
Authors: Kleiven David , Akola Jaakko , Peterson Andrew A , Vegge Tejs , Chang Jin Hyun 
Published: April 2021

AbstractCluster expansion (CE) has gained an increasing level of popularity in recent years, and its applications go far beyond its original root in binary alloys, reaching even complex crystalline systems often used in energy materials research. Similar to other modern machine learning approaches in materials science, many strategies have been proposed for training and fitting the CE models to first-principles calculation results. Here, we propose a new strategy for constructing a training set based on their relevance in Monte Carlo sampling for statistical analysis and reduction of the expected error. The CE model constructed from the proposed approach has lower dependence on the specific details of the training set, thereby increasing the reproducibility of the model. The same method can be applied to other machine learning approaches where it is desirable to sample relevant configurational space with a small set of training data, which is often the case when they consist of first-principles calculations.
Arrhythmogenesis in the aged heart following ischaemia–reperfusion: role of transient receptor potential vanilloid 4
Authors: Peana Deborah , Polo-Parada Luis , Domeier Timothy L 
Published: April 2021

Abstract

Aims
Cardiomyocyte Ca2+ homoeostasis is altered with ageing and predisposes the heart to Ca2+ intolerance and arrhythmia. Transient receptor potential vanilloid 4 (TRPV4) is an osmotically activated cation channel with expression in cardiomyocytes of the aged heart. The objective of this study was to examine the role of TRPV4 in Ca2+ handling and arrhythmogenesis following ischaemia–reperfusion (I/R), a pathological scenario associated with osmotic stress.

Methods and results
Cardiomyocyte membrane potential was monitored prior to and following I/R in Langendorff-perfused hearts of Aged (19–28 months) male and female C57BL/6 mice ± TRPV4 inhibition (1 μM HC067047, HC). Diastolic resting membrane potential was similar between Aged and Aged HC at baseline, but following I/R Aged exhibited depolarized diastolic membrane potential vs. Aged HC. The effects of TRPV4 on cardiomyocyte Ca2+ signalling following I/R were examined in isolated hearts of Aged cardiac-specific GCaMP6f mice (±HC) using high-speed confocal fluorescence microscopy, with cardiomyocytes of Aged exhibiting an increased incidence of pro-arrhythmic Ca2+ signalling vs. Aged HC. In the isolated cell environment, cardiomyocytes of Aged responded to sustained hypoosmotic stress (250mOsm) with an increase in Ca2+ transient amplitude (fluo-4) and higher incidence of pro-arrhythmic diastolic Ca2+ signals vs. Aged HC. Intracardiac electrocardiogram measurements in isolated hearts following I/R revealed an increased arrhythmia incidence, an accelerated time to ventricular arrhythmia, and increased arrhythmia score in Aged vs. Aged HC. Aged exhibited depolarized resting membrane potential, increased pro-arrhythmic diastolic Ca2+ signalling, and greater incidence of arrhythmia when compared with Young (3–5 months).

Conclusion
TRPV4 contributes to pro-arrhythmic cardiomyocyte Ca2+ signalling, electrophysiological abnormalities, and ventricular arrhythmia in the aged mouse heart.
Understanding students’ motivation in L2 collaborative writing
Authors: Chen Wenting 
Published: April 2021

Abstract
Although research about the potential learning outcome of collaborative writing in L2 or foreign language education has proliferated in the last few decades, little is known about students’ motivation in collaborative writing. This case study seeks to explore higher-proficiency (HP) students’ motivation in L2 collaborative writing, as well as factors influencing their motivation. The findings reveal that students with similar proficiency (HP) could have different levels of motivation, which may affect their participation. This study also found that knowledge of collaborative writing, previous beliefs and experiences of pair/group work, and perceived value of the role in the partnership were three major factors that influence students’ motivation in collaborative writing. This study makes several recommendations from a motivational perspective about how best to implement collaborative writing tasks in L2 classes.
POLYMORPHISM FOR DIMERIZING ABILITY AT THE ESTERASE-5 LOCUS IN DROSOPHILA PSEUDOOBSCURA
Authors: Cobbs Gary 
Published: April 2021

ABSTRACT
Three new alleles are reported at the esterase-5 locus of Drosophila pseudoobscura. All three of these alleles are different from those previously reported in their ability to dimerize. One allele will not form heterodimers or homodimers and exists only as a monomer. A second allele does form heterodimers but will not form homodimers. The third allele forms both hetero- and homodimers as well as forming monomers. Estimates of the frequency of these alleles in a natural population are given. The existence of these is discussed with respect to recently proposed models for a molecular mechanism for heterosis.
TERMINAL REDUNDANCY HETEROZYGOTES INVOLVING THE FIRST-STEP-TRANSFER REGION OF THE BACTERIOPHAGE T5 CHROMOSOME
Authors: Fischhoff David , MacNeil Douglas , Kleckner Nancy 
Published: April 2021

ABSTRACT
Individual progeny of two-factor crosses between A1am and A2am T5 phages give rise to bursts containing more than one type of plaque. The simplest explanation for these mixed bursts is that the A1 and A2 genes are located within the terminally repeated portion of the T5 genome and that the mixed bursts are made by "terminal redundancy heterozygotes". The observation of genetic heterozygosity means that the A1 and A2 genes are repeated intact. This implies that the terminal segments of T5 are genetically interchangeable.
UV MUTAGENESIS IN RADIATION-SENSITIVE STRAINS OF YEAST
Authors: Lawrence Christopher W , Christensen Roshan 
Published: April 2021

ABSTRACT
The yeast Saccharomyces cerevisiae appears to possess a single mutagenic or "error prone" pathway for the repair of UV damage, probably involving the functions of at least seven genes; rev1, rev2, rev3 (Lemontt 1971a), rad6, rad8, rad9 and rad18 (Lawrence et al. 1974; present results). Strains carrying rad6 are the most sensitive to the lethal effects of UV light in this group and double mutants carrying rad6 and either rev1, rev3, rad9 or rad18 are no more sensitive than this single mutant strain. rev3 rad6 double mutant diploids failed to show any UV-induced reversion of the normally highly revertible ochre allele cyc1-9, even though a total of more than 2.5 × 109 viable cells was examined, suggesting that strains of this kind are entirely UV-immutable; spontaneous revertants could be recovered, however.—The rad6 and rev3 gene products would appear to be necessary for all kinds of mutagenic events at all sites within the genome, but the products of the other genes that act in the "errorprone" pathway hage a more restricted role and are involved in the production of only some kinds of mutations. It is suggested that such selectivity arises from the interaction of some repair enzymes with specific nucleotide sequences.
THE UNIT OF SELECTION IN DROSOPHILA MERCATORUM I. THE INTERACTION OF SELECTION AND MEIOSIS IN PARTHENOGENETIC STRAINS
Authors: Templeton Alan R , Sing Charles F , Brokaw Barbara 
Published: April 2021

ABSTRACT
An important problem in population genetics is the determination of the level of genetic organization to which fitness measures can be ascribed that yield an adequate description or prediction of the outcome of selection in populations. To study this problem, we used two strains of Drosophila merca torum (S-1-Im and O-3-Im) that are capable of both sexual and parthenogenetic reproduction, a feature that allows us to experimentally control many factors which affect genetic variability. Both S and O reproduce parthenogenetically by "pronuclear duplication," a mechanism that retains normal meiosis (and hence crossing over and assortment) but results in homozygosity for all loci in a single generation. Since an isozyme survey indicated that S and O differ at a third of their loci, we hypothesized that S and O have adapted in genetically distinct fashions to the genetic environment of total homozygosity. This is tested by breeding females that are S-O hybrids for 100%, 60% and 40% of their genetic backgrounds, and scoring their respective parthenogenetic progenies for four isozyme and two visible markers. The data collected gave evidence for a coadaptation to total homozygosity involving non-additive and non-multiplicative interactions between non-alleles. As the perturbation of the parental coadapted genotypes by meiosis increases (i.e., the greater the degree of S-O hybridity), the level of genetic material which behaves as an additive/multiplicative fitness unit becomes larger. Selective neutrality of genetic variation may be an artifact of our failure to measure the proper genetic unit of selection.
TWO CHROMOSOMAL GENES REQUIRED FOR KILLING EXPRESSION IN KILLER STRAINS OF SACCHAROMYCES CEREVISIAE
Authors: Wickner Reed B , Leibowitz Michael J 
Published: April 2021

ABSTRACT
The killer character of yeast is determined by a 1.4 × 106 molecular weight double-stranded RNA plasmid and at least 12 chromosomal genes. Wild-type strains of yeast that carry this plasmid (killers) secrete a toxin which is lethal only to strains not carrying this plasmid (sensitives). —— We have isolated 28 independent recessive chromosomal mutants of a killer strain that have lost the ability to secrete an active toxin but remain resistant to the effects of the toxin and continue to carry the complete cytoplasmic killer genome. These mutants define two complementation groups, kex1 and kex2. Kex1 is located on chromosome VII between ade5 and lys5. Kex2 is located on chromosome XIV, but it does not show meiotic linkage to any gene previously located on this chromosome. —— When the killer plasmid of kex1 or kex2 strains is eliminated by curing with heat or cycloheximide, the strains become sensitive to killing. The mutant phenotype reappears among the meiotic segregants in a cross with a normal killer. Thus, the kex phenotype does not require an alteration of the killer plasmid. —— Kex1 and kex2 strains each contain near-normal levels of the 1.4 × 106 molecular weight double-stranded RNA, whose presence is correlated with the presence of the killer genome.
THE POPULATION GENETICS OF PARTHENOGENETIC STRAINS OF DROSOPHILA MERCATORUM. II. THE CAPACITY FOR PARTHENOGENESIS IN A NATURAL, BISEXUAL POPULATION
Authors: Templeton Alan R , Carson Hampton L , Sing Charles F 
Published: April 2021

ABSTRACT
Drosophila mercatorum is a bisexual species, but certain strains are capable of parthenogenetic reproduction in the laboratory. We investigated the parthenogenetic capacity of the virgin daughters of females captured from a natural, bisexual population in Hawaii. An isozyme survey indicated the natural population is polymorphic at about 50% of its loci, and its individuals heterozygous at 18% of their loci. The predominant mode of parthenogenesis in D. mercatorum causes homozygosity for all loci in a single generation. Despite this radical change in genetic state, 23% of the virgin female lines produced adult parthenogenetic progeny, and 16% produced parthenogenetic progeny themselves capable of parthenogenetic reproduction. The parthenogenetic rate as measured by the number of parthenogenetic progeny themselves capable of parthenogenesis divided by the number of eggs laid is around 10-5 for the virgin female lines. We argue that one of the major reasons for this low rate is that very few of the impaternate zygotes have a genotype that can survive and reproduce under the genetic conditions imposed by parthenogenetic reproduction. This intense selective bottleneck can be passed in a single generation if enough unfertilized eggs are laid, and once passed is accompanied by a large (perhaps a thousandfold) increase in the rate of parthenogenesis and by modifications in many phenotypic traits such as morphology and behavior.
HIDDEN ALLELES AT THE α-GLYCEROPHOSPHATE DEHYDROGENASE LOCUS IN COLIAS BUTTERFLIES
Authors: Johnson George B 
Published: April 2021

ABSTRACT
By varying polyacrylamide gel pore size, the α-glycerophosphate dehydrogenase locus of Colias butterflies is shown to contain at least five alleles, rather than the two which had been reported previously. Two of the alleles have the same apparent net charge, and presumably are detected electrophoretically because of conformational differences. Additional variation occurs in the isoelectric points of the proteins. It is suggested that electrophoresis employing a single gel of intermediate pore size will fail to discriminate between many alleles, and that the concept of electrophoretic alleles as differing simply in charge may not always be appropriate.
"How does one know what it is one believes
When it's so difficult to know what it is one knows?"
—Jumpers (Stoppard, 1972)
ON THE NATURE OF CIS-ACTING REGULATORY PROTEINS AND GENETIC ORGANIZATION IN BACTERIOPHAGE: THE EXAMPLE OF GENE Q OF BACTERIOPHAGE Λ
Authors: Echols Harrison , Court Donald , Green Linda 
Published: April 2021

ABSTRACT
We note the existence of a "partially cis-acting" regulatory protein of bacteriophage λ: the product of the phage Q gene. We suggest that there may be a complete spectrum from "all cis" to "all trans" for such regulatory proteins. This behavior might arise because a DNA-binding protein either acts at a nearby (cis) site soon after synthesis or becomes "lost" for its trans activity on another genome through nonspecific interactions with DNA. Our proposed explanation provides one evolutionary basis for the linkage of genes for regulatory proteins and the sites at which such proteins act; it also suggests a possible rationale for the "metabolic instability" of certain regulatory proteins.
A POLLEN SELECTION SYSTEM FOR ALCOHOL-DEHYDROGENASE-NEGATIVE MUTANTS IN PLANTS
Authors: Schwartz Drew , Osterman John 
Published: April 2021

ABSTRACT
Exposure of freshly shed maize pollen to allyl alcohol vapors allows selective fertilization by mutant alcohol-dehydrogenase-negative grains. Wild-type pollen grains are killed by the enzymatic conversion of allyl alcohol to the highly toxic acrylaldehyde.
INTERCONVERSION OF YEAST MATING TYPES I. DIRECT OBSERVATIONS OF THE ACTION OF THE HOMOTHALLISM (HO) GENE
Authors: Hicks James B , Herskowitz Ira 
Published: April 2021

ABSTRACT
The HO gene promotes interconversion between a and α mating types. As a consequence, homothallic diploid cells are formed by mating between siblings descended from a single α HO or a HO spore. In order to determine the frequency and pattern of the mating-type switch, we have used a simple technique by which the mating phenotype can be assayed without losing the cell to the mating process itself. Specifically, we have performed pedigree analysis on descendants of single homothallic spores, testing these cells for sensitivity to α-factor.
The switch from α to a and vice versa is detectable after a minimum of two cell divisions. 50% of the clones tested showed switching by the four-cell stage. Of the four cells descended from a single cell, only the oldest cell and its immediate daughter are observed to change mating type. This pattern suggests that one event in the switching process has occurred in the first cell division cycle. Restriction of the switched mating-type to two particular cells may reflect the action of the homothallism system followed by nonrandom segregation of DNA strands in mitosis.
The mating behavior of cells which have sustained a change in mating type due to the HO gene is indistinguishable from that of heterothallic strains.
F' PLASMIDS FROM HfrH AND HfrC IN recA- ESCHERICHIA COLI
Authors: Ou Jonathan T , Anderson Thomas F 
Published: April 2021

ABSTRACT
We have isolated and characterized a number of clones resulting from matings of HfrH and HfrC cultures of Escherichia coli with auxotrophic recA- E. coli. As in Low's (1968) experiments, the recA- marker prevented integration of F′ episomes into the vegetative chromosomes of the host. Both F′H F′C plasmids contained a great variety of non-selected nutritional markers. However, more F′H plasmids seemed to have expressed F+ characteristics than did F′C plasmids. These characteristics include (i) the presence of F-pili as determined by susceptibility to male-specific phages; (ii) fertility as determined by the merozygote's ability to transfer nutritional markers to an auxotrophic F- strain of E. coli; and (iii) a high degree of inheritability as estimated by the proportion of F′ bacteria to F- bacteria in clones grown in a non-selective medium like broth. This proportion is seen to be affected by both factors that determine the probabilities that daughters of F′ bacteria inherit the episome and from physiological factors that determine the rates of growth of F′ and F- bacteria.
GENETIC CONTROL OF GENE EXPRESSION: INDEPENDENT LOCATION OF Flt(3) AND ITS INTERACTIONS WITH THE MUTABLE V LOCUS IN NICOTIANA
Authors: Sand Seaward A 
Published: April 2021

ABSTRACT
New information has resulted from studies comparing the genetic behavior of two experimental cultures, termed variegated-3 and variegated-1, which arose earlier following an interspecific cross. Phenotypic expression in the plant material involves distinctive variegation patterns of anthocyanin distribution in floral tissues.—The data are consistent with the hypothesis that the genetic constitution of variegated-3 includes a unique and independently segregating regulator component, Flt(3), in addition to the v locus element held in common with variegated-1. Flt(3) has not been generated anew within the variegated-1 genotypes among more than 10,000 observed progeny. Presence of Flt(3) modifies the timing of somatic sectoring events, and is correlated with the capability to produce, in germ cell lines of phenotypically flecked plants, frequent changes at the v locus to a stable, non-variegating, dominant allelic form, V.—The latter process is of special interest because progeny tests of mutant individuals, containing newly-arisen V alleles, fail to reveal continued presence of Flt(3). Thus the mechanism generating V from v appears to be correlated invariably with loss or inactivation of the controllingelementinducing this class of mutations, which is located initially on a different chromosome from that bearing v.
GENETIC MODELS FOR THE ANALYSIS OF DATA FROM THE FAMILIES OF IDENTICAL TWINS
Authors: Nance Walter E , Corey Linda A 
Published: April 2021

ABSTRACT
Genetic models are described which exploit the unique relationships that exist within the families of identical twins to obtain weighted least squares estimates of additive, dominance and epistatic components of genetic variance as well as estimates of the contributions of X-linked genes, maternal effects and three sources of environmental variation. Since all of the relationships required to achieve a resolution of these variance components are contained within each family unit, the model would appear to be superior to previous approaches to the analysis of quantitative traits in man.
EVOLUTION OF HAWAIIAN DROSOPHILIDAE. II. PATTERNS AND RATES OF CHROMOSOME EVOLUTION IN AN ANTOPOCERUS PHYLOGENY
Authors: Yoon J S , Richardson R H 
Published: April 2021

ABSTRACT
The phylogenetic relationships of seven species of the genus Antopocerus (Family Drosophilidae) have been determined by means of a study of the metaphase configurations and polytene chromosomes. Based on biogeographical, behavioral and cytogenetic information, A. longiseta from Molokai is tentatively identified as the primitive species of the genus. The metaphase karyotypes of all Antopocerus species are either five pairs of rod chromosomes and a pair of dots (5R1D), or six rods (6R). Heterochromatin additions converted the dots to rods. Chromosome breakpoints for inversions also are clustered at heterochromatic loci. The chromosome segments between heterochromatic loci may represent sets of functionally related loci, evolving as a unit. The rate of chromosomal inversion substitution is estimated in the origin of the taxon (probably a subgenus of Drosophila rather than a separate genus). It averages no greater than one substitution per 1,000 years, or one per 5,000 generations. The average genetic death rate per generation of one individual per hundred is required to achieve this substitution rate. The rate of inversion substitution during radiation of this taxon may be only 4.4 × 10-3 times as fast as that present in forming the taxon. Alternatively, radiation may have required only 250,000 years if rates of substitution are the same as in the origination of the taxon. Average rates of substitution reflect genetic accidents, selection pressures and rates of adaptation to new niches, as well as the rate of encountering new niches. Rate of adaptation probably is much greater in this instance than rate of encountering new niches. Therefore, the average rate of evolution reflects more nearly biogeographic and ecological factors than genetic factors.
GENETIC VARIATION IN HETEROGENEOUS ENVIRONMENTS
Authors: Taylor Charles E 
Published: April 2021

ABSTRACT
A model of population structure in heterogeneous environments is described and conditions sufficient for maintaining a polymorphism are derived.
The absolute fitness of any genotype is regarded as a function of location in the niche space and the population density at that location. Two modes of habitat selection are examined: (1) organisms are distributed uniformly over the environment; and (2) each organism selects to occupy that habitat in which it is most fit ("optimal habitant selection").—Sufficient conditions for maintenance of genetic polymorphisms are derived for both models. In populations which do not practice habitat selection heterozygote superiority averaged over the environment is sufficient to guarantee the existence of polymorphisms. Comparable conditions for populations which practice optimal habitat selection are much less restrictive. If the heterozygotes are superior to one homozygote in any one part of the niche and to the other homozygote in any other part of the niche then a polymorphism will be defined.—A positive correlation between genetic and environmental variation follows from the model with habitat selection, but not from the other. The adaptive significance of polymorphisms thus depends on how animals behave.
SELECTION FOR INCREASED NUMBERS OF EXTRA HETEROCHROMATIC CHROMOSOMES IN THE TOMATO
Authors: Quiros Carlos F 
Published: April 2021

ABSTRACT
Crossing two parental plants carrying two types of extra chromosomes, 2n+2(5L•7S) by 2n+3(2S•2S) permitted effective selection for individuals with up to eight 2S•2S chromosomes in later generations. The crossing of 2n + 3(2S•2S) by 2n+1(8S•8L) and by the wild tomato relative, diploid L. pimpinellifolium, produced plants with up to four extra chromosomes. The tolerance of 2S•2S chromosomes through both gametophytes is at least four extras. The presence of two to eight extra 2S•2S chromosomes decreased pollen fertility between 82 to 41%. Progeny tests reveal that 2S•2S chromosomes tend to be lost in transmission. Progenies of self-pollinated individuals with 25, 26, 27, 28, 29 and 30 chromosomes averaged 24.3, 25.1, 25.5, 27.1, 28.2 and 27.9 chromosomes respectively. The offspring of crosses between diploid and extrachromosomal plants showed similar tendencies. Evidently tomato 2S•2S chromosomes lack the mechanisms for accumulation characteristic of some plant species with naturally occurring accessory chromosomes.—Extra 2S•2S chromosomes are very stable mitotically and are not eliminated from the somatic tissue of unmodified plants. Severe pruning of certain plants induced loss or gain of these chromosomes.—The importance of accumulating two to 18 nucleolar organizer regions in a cell by addition of 2S•2S chromosomes is discussed.