bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Simulation of the Influence of Design Parameters on Gas-liquid Transport Characteristics of Centrifugal Pump
Authors: He L , Zhang J Y , Zhang Z M , Meng L , Zhu H W , Li T Y
Published: January 2021

Traditional centrifugal pumps have obvious advantages for transporting pure liquidmedia, but the existence of gas phase will cause the decline of head and efficiency, and even air blockage. Therefore, it is strongly necessary to design a gas-liquid pump with superior performance. There are various parameters that can affect the multiphase centrifugal pump performance and energy consumption. The blade outlet angle and blade number are the most critical. In this paper, CFD method is used to study the influence of outlet angle and blade number on gas-liquid transport of centrifugal pump. The results show that the boosting pressure of centrifugal impeller decreases with the increases of gas volume fraction and the boosting pressure for impeller of lower outlet angle decreases to a greater degree when the gas volume faction increases. The hydraulic performance of impeller with blade number of 6 and 8 is compared, which shows impeller with blade number of 8 has higher boosting pressure and higher efficiency than blade number of 6 under the same gas-liquid working condition. This paper will provide reference for the design of multi-phase pump to meet the requirements of gas-liquid flow.
Numerical prediction of sediment erosion in reference Francis turbine for complete operating range
Authors: Lama Ram , Gautam Saroj , Neopane Hari Prasad , Thapa Biraj Singh , Chitrakar Sailesh , Ghimire Amul
Published: January 2021

Erosive and abrasive wear affect the overall performance of hydro-turbines. Hard and excessive sediment particles are unavoidable in power plants of Himalayan basins. However, modifying the design of turbine components to have a minimum impact of the sediments could be one of the viable solutions. Past studies have shown possibilities of minimizing the erosion in turbine components by changing the blade angle distribution of the runner. The optimizations were based on the designed condition, i.e. at the Best Efficiency Point (BEP) of the turbine. The turbines are however, operated in various conditions, which might produce a different erosion scenario compared to BEP. Hence, the optimization process should also take these off-designed points under consideration. This paper presents a case study of Jhimruk hydropower plant of Nepal, whose turbine components get severely eroded due to sediments. Steady state numerical simulations for 4 guide vanes and 3 runner blade passages are done for the predictions of efficiency and percentile sediment erosion rate density (PSERD) on runner blades for 11 operating conditions including BEP. Apart from the conventional efficiency hill chart diagram, this paper focuses on the development of a hill diagram of PSERD, such that the prediction of the erosion in turbines can be done similar to the efficiency. Introduction of such PSERD hill diagrams could be a standard mean for the design optimization of turbines in sediment laden water.
Numerical Analysis of Rotor Dynamics of Dredge Pump Shafting
Authors: Zhai L M , Cao L , Cao J W , Lei H M , Ahn S H , Chen F N , Luo Y Y , Xiao Y X , Wang Z W
Published: January 2021

The operating condition of dredge pump is highly complicated, a technical issue is the shaft vibration problems, which has great effects on the operation safety and stability of pumps. This paper introduces a mathematical model of rotor dynamics for the dredge pump, which is used to numerically investigate critical speeds and mode shapes of the pump shaft under different bearing stiffness and damping. The effects of bearing stiffness and damping on shafting vibration characteristics are considered. The results show that the stiffness has great effect on 1st and 3rd order critical speed and the damping effect can be ignored. The stiffness has little effect on shafting axial and torsional natural frequency, but has great effect on lateral natural frequency. The analysis method of rotor dynamics dealt with in this paper can provide a foundation for the design of dredge pump shafting.
Configuration Comparison of Municipal Waste Incineration Plant in County Area of Henan Province
Authors: Yao He , Yao Weiguo
Published: January 2021

Based on the status of county-level domestic waste treatment in Henan Province, this paper compares the system configuration, land occupation, technical parameters, operational flexibility and initial investment for 1 × 600t/d and 2 × 300t/d incineration lines and recommendations are proposed in the end. A single incineration line has a lower initial investment, and is suggested on the premise that temporary waste transfer and storage space can be reserved. Otherwise double incineration lines should be used for operation flexibility.
Synthesis of NiSiO@NiAlFe by Hydrothermal method and removal of Cs+ in water
Authors: Hu Yuying , Pan Cheng , Zheng Xiaohuan , Liu Susu , Peng Xiaoming
Published: January 2021

In this work, novel NiSiO@NiAlFe layered double hydroxides (LDHs) hollow spheres were prepared by hydrothermal method. It could be observed that the grafting of LDHs towards NiSiO hollow spheres could avoid the LDHs’ aggregation, and thus enhance the material’s adsorption capacity. Furthermore, The effect of pH on adsorption Cs, kinetics and isotherm models were studied. Results indicated that NiSiO@NiAlFe LDHs hollow spheres had sufficient adsorption capability towards Cs+. The adsorption kinetics satisfied the pseudo-second-order adsorption model, Temkin model and Langmuir isotherm model. The adsorption process was efficient at the alkaline condition (pH=10). The adsorption kinetics indicated that the adsorption process could reach the equilibrium in only 20 minutes. The maximum adsorption capacity of Cs+ towards NiSiO@NiAlFe hollow spheres were estimated to be 61.5 mgg-1. Thus, NiSiO@NiAlFe hollow spheres presented a broad potential for treating cesium containing wastewater.
Study on the Sustainable Development Model of Industrial Heritage
Authors: Li Qijun
Published: January 2021

As crucial urban resources, industrial heritage occupies an important geographic location of the city, and it is generally of historical value, social value, technological or scientific value, economic value, and aesthetic value. The paper selected TESTBED2 as the case to study for it is the typical light industrial remains after the industrial revolution in Chongqing. This paper tried to discuss conservation of industrial heritage from multi-sensory marketing and Sustainable development. The paper evaluated the industrial heritage TESTBED2, and provided new methods for the reform of the industrial wasteland, and brought new landscape forms and looked forward to the model and tracks for the protection and reuse for the industrial industry, so as to realize the sustainable development of the industrial heritage.
Visibility Variation in Zhengzhou from 2008–2017
Authors: Zou Junchen , Lu Jinyu , Wang Yanling , Li Jianpeng , Liu Huiyuan , Wang Lin , Liu Xiuxiu , Ma Zhenqi , Xu Xueqiong , Liu Wensi
Published: January 2021

Visibility is closely related to air quality and is therefore a source of concern. Using data from the National Basic Weather Station (NBWS), this study measured visibility variation in Zhengzhou from 2008 to 2017. The effects of PM2.5 and meteorological parameters on visibility were also assessed. Results indicated that the mean annual visibility fluctuated between 8.07 km and 14.02 km, decreasing during the period from 2008 to 2013 and then increasing slightly after 2013. The seasonal mean visibility was 11.69 km in spring (the highest value), 11.37 km in summer, 9.42 km in autumn, and 8.98 km in winter (the lowest value). The mean annual concentrations of PM2.5 from 2015 to 2017 were 90.83 μg m-3, 79.89 μg m-3, and 66.69 μg m-3, respectively. These were 159.51%, 128.26%, and 90.54% higher than 35 μg m-3 of the second grade of China National Ambient Air Quality Standards (CNAAQS). Additionally, direct radiation, total radiation, temperature, and relative humidity were positively correlated with visibility, whereas PM2.5 mass concentration, scattered radiation, and wind velocity were negatively correlated with visibility. Further research is needed to analyse the effect of PM2.5 on visibility and the mechanism through which this occurs.
Research and Application of the technology of Forced Ventilation Diversion to Control and Reduce Dust in Comprehensive Excavation Face
Authors: Yang Junlei
Published: January 2021

In order to solve the problem of dust pollution in the comprehensive excavation face, the matching relationship between the long forced ventilation and the short dust removal sucking was grasped, and reasonable control dust removal process parameters were obtained. In this paper, the 3-1 coal return air roadway in Hongliulin Coal Mine is taken as the research object. By establishing the working face physical model and adopting the numerical simulation method, the different axial diameter outward air ratio is compared and analyzed. Combined with the field measurement, it is verified to obtain the optimal range of dust axial diameter outward air ratio. The application results show that a swirl air curtain is formed along the sidewall of the roadway after the adoption of the attached air duct, and a dust control air curtain pointing to the head is gradually formed after entering the section of the roadheader. When the axial diameter outward wind ratio is 1:2∼1:3, the breathing dust at the driver's position can be controlled within 17 mg/m3, and the dust removal efficiency can be increased to more than 93%, which greatly improves the working environment and ensures the occupational health and safety of workers.
Improvement of Sensitivity of Capacitive Micromachined Ultrasound Transducer
Authors: Wang Yifan , Liu Shuo
Published: January 2021

CMUT (Capacitive Micromachined Ultrasonic Transducer) has a wild range of applications in medical detecting and imaging fields. However, operating under self-generating-self-receiving (SGSR) method usually results in poor sensitivity. But the sensitivity cannot be improved simply by increasing the resonant frequency since the frequency of a specific kind of CMUT is designed for specific usage. In this paper, based on one specific type of CMUT, a mechanical model is built and the simulation analysis is demonstrated. A brand-new method one-generating-multiple-receiving (OGMR) is introduced and a special circuit model has been designed to improve the signal to thermal noise ratio. By increasing the number of receiving capacitors from 1 to 8, we increased the signal-noise ratio to 2.83 times.
A preliminary analysis on mechanical characteristics of transmission conductors in the vicinity of suspension clamps
Authors: Zhao Guoliang , Rui Xiaoming
Published: January 2021

Overhead transmission conductors are prone to wire strands breaking under the conditions of breeze vibration, and many broken strands occur in the vicinity of suspension clamps. In order to research the stress distribution characteristics of the conductor in the vicinity of suspension clamps, a relatively effective Finite Element (FE) model was proposed. Preliminary verification of model rationality through comparative analysis of theoretical calculation and simulation, and use this model to study the mechanical characteristics of the cross-section of the conductor in the key position of the conductor-clamp system. The research conclusions are as follows: a new concept of equivalent bending stiffness and equivalent diameter is proposed, which is used to calculate the alternating bending stress of conductors under breeze vibration conditions. The alternating bending stress of the wire strands follow the bending amplitude (Y
b) increases with increasing. Under the complex load, the Equivalent (Von-Mises) stress of the aluminum wire strands at the Last Point of Contact (LPC) of the conductor and the clamp shows a decreasing trend from the outside to the inside, and the maximum Von-Mises stress occurs at the contact position between the outermost wire strands and the clamp.
Study on Thermal Runaway Process of LiFePO4/C Batteries
Authors: Gao Fei , Fan Maosong , Wang Congjie , Liu Wei , Zhu Yanli
Published: January 2021

The LiFePOVC battery has been widely used in many fields, and its safety problems are gradually attracting widespread concern. In this paper, two kinds of LiFePO4/C batteries with 25 Ah and 200 Ah were taken as research objects. The thermal runaway phenomena of two batteries were analyzed, and the difference of thermal runaway phenomena between two batteries were compared. The results show that the safety valve of the 200 Ah battery ruptures earlier and the thermal runaway occurs earlier under the same overcharge rate. The work provides a reference for the protection design of LiFePO4/C batteries.
Advances of numerical simulation research on the emulsion flow field of wet skin-pass mill
Authors: Qiao Haijun
Published: January 2021

Anti-rust agents are used as emulsion liquids to spray the roll gaps for wet skin-pass of cold-rolled steel strips. The wet-skin strip steel has a good shape, fewer surface defects, good anti-rust effect, higher strength, low roller consumption, and high work efficiency. Some research advances on the numerical simulation of the emulsion flow field in the wet skin-pass mill are discussed, including simplified two-dimensional nozzle models such as straight or convergent, high-pressure jets and conical converging nozzles to provide a theoretical reference for the numerical simulation of the emulsion flow field in the wet skin-pass mill.
Genomic exclusion and other micronuclear anomalies are common in genetically defective clones of tetrahymena thermophila.
Authors: Pitts R A , Doerder F P
Published: January 2021

Genomic exclusion (GE) is an abnormal form of conjugation which has previously been described in detail for three hypodiploid strains of Tetrahymena thermophila. These strains cannot form gametic nuclei and by failing to participate in normal reciprocal fertilization their genes are excluded from exconjugants. To determine whether GE is a general property of infertile strains, we surveyed genetically and cytogenetically 19 additional strains of T. thermophila to determine why they failed to contribute genes to sexual progeny. Crosses to genetically marked tester strains showed that seventeen of these strains undergo GE. In each case GE appears to be due to the failure of the defective partner to form functional gametic nuclei. The normal conjugant, however, contributes to its defective partner a haploid nucleus identical to its own, and following diploidization of the unfertilized nuclei, the conjugants separate retaining the old macronuclei. Cytofluorimetric measurement of micronuclear DNA content in 18 strains suggests that aneuploidy is the proximate cause of GE; eleven strains were hypodiploid, five were diploid and three were hyperdiploid. Many irregular cytogenetic events were observed in conjugants presumably not undergoing GE, including, in some instances, abnormal meiosis in the normal partner. Since genomic exclusion was found in both wildtype and mutant clones, the results suggest that it should be possible by appropriate crosses to identify genomic exclusion strains of any genotype.
Molecular evolution of the Escherichia coli chromosome. I. Analysis of structure and natural variation in a previously uncharacterized region between trp and tonB.
Authors: Stoltzfus A , Leslie J F , Milkman R
Published: January 2021

We present the sequence of a 3500-bp region of the Escherichia coli strain K12 chromosome lying between the tryptophan operon and the tonB gene. Analysis of the sequence yields six open reading frames that have properties characteristic of genes for proteins. The reading frames are closely spaced, and putative transcription units and control sites compose over 95% of the DNA. The sequences of several wild strains of E. coli have been determined for a large segment of the region described. Comparison of these sequences reveals the effects of base substitutions, DNA rearrangements, and recombination. In the regions presumably expressed as polypeptides, most of the natural variation results from synonymous substitutions. However, the DNA rearrangements identified have end points within the open reading frames and disrupt them in a variety of ways. The effects of genetic recombination between strains, recently found to be significant on a large scale in E. coli, are also apparent in the region between trp and tonB.
The effect of sequence homozygosity on the frequency of X-chromosomal exchange in Drosophila melanogaster females.
Authors: Rutherford S L , Carpenter A T
Published: January 2021

The repair of mismatched heteroduplex DNA has been implicated in the normal resolution of meiotic exchange events. Although sequence microheterogeneity over defined intervals of homologous chromosomes has been correlated with local effects on recombination, this correlation has not previously been extended to effects on chromosomal levels of exchange. In order to determine the role of microheterogeneity in normal exchange between homologs, a system was devised for monitoring exchange between isogenic X chromosomes. Lack of microheterogeneity did not significantly alter the frequency of exchange along the isogenic X chromosomes relative to controls or to previously reported values. There were, however, characteristic levels of exchange intrinsic to the cloned X chromosomes in each of the lines tested.
Genetic and molecular mapping of chromosome region 85A in Drosophila melanogaster.
Authors: Jones W K , Rawls J M
Published: January 2021

Chromosome region 85A contains at least 12 genetic complementation groups, including the genes dhod, pink and hunchback. In order to better understand the organization of this chromosomal segment and to permit molecular studies of these genes, we have carried out a genetic analysis coupled with a chromosome walk to isolate the DNA containing these genes. Complementation tests with chromosomal deficiencies permitted unambiguous ordering of most of the complementation groups identified within the 85A region. Recombinant bacteriophage clones were isolated that collectively span over 120 kb of 85A DNA and these were used to produce a molecular map of the region. The breakpoint sites of a number of 85A chromosome rearrangements were localized on the molecular map, thereby delimiting regions of the DNA that contain the various genetic complementation groups.
Rex-induced recombination implies bipolar organization of the ribosomal RNA genes of Drosophila melanogaster.
Authors: Robbins L G , Swanson E E
Published: January 2021

Rex-induced mitotic recombination was used to determine whether nucleolus organizers can pair in both inverted and noninverted orientations. Two target chromosomes, each duplicated for the rDNA region, were exposed to maternal Rex activity. Recombination in one orientation should yield deletion of the material between the two nucleolus organizers, recombination in the other orientation should yield inversion of the same material. Both products were recovered from both target chromosomes. The generality of using Rex-mediated recombination for analysis of the rDNA is considered.
IN SUPPORT OF THE TELOMERE CONCEPT
Authors: Roberts Paul A
Published: January 2021

The frequency of recovered X-ray-induced (4000R) rearrangements that, in all probability, mimic terminal deletions of the X chromosome was only one of, roughly, 105  X chromosomes screened for tip deficiencies. Although the single exception looks terminally deleted, it is probably capped by a very short or nonpolytene telomeric segment. It is apparent from these data that the probability of "healing" or stabilization of a terminally deleted X in the zygotic nucleus or developing embryo of Drosophila melanogaster is vanishingly small. The telomeric caps in two obviously interstitial deficiencies that were recovered represent, roughly, 1/500 of the length of a mitotic chromosome. These findings give some indication of the extreme difficulty of detecting short telomeric segments capping either deleted polytene chromosomes or deleted metaphase chromosomes of, for example, humans.
DIRECT RESPONSE TO SELECTION FOR POSTWEANING GAIN IN THE RAT
Authors: Baker R L , Chapman A B , Wardell R T
Published: January 2021

The effectiveness of selection for 3–9-week gain was examined in a population of rats with a history of past selection for high 3–9-week gain. Lines were selected for high (U line) and low (D line) 3–9-week gain with two replicates of each line. Two randomly selected lines were also kept, one originating from the same base population as the two selected lines (R line) and the other originating from a population that had been randomly mated for the previous 27 generations (C line). Two replicates of each of these lines were kept. After seven generations of selection, a randomly selected line (relaxed line) was formed from each of the two upward- and each of the two downward-selected lines. Results have been presented for 13 generations of selection. The environmental trend for 3–9-week gain, as indicated by the randomly selected R and C lines, was consistently negative in all four lines. Realized heritabilities calculated by deviating the response to selection from the trend in the R or C lines resulted in non-significantly higher values in the D lines than the U lines. Six generations of relaxation of selection indicated no effect of natural selection in the U lines or the D lines. The relative magnitude of the drift, error and common environmental variances were estimated by the methods given by Hill (1971). The estimates of these parameters then led to calculation of the degree of bias in the sampling variances of the realized heritability estimates. As was predicted by Hill (1971), estimates of the variance of realized heritabilities obtained by using standard regression techniques were less than those obtained using Hill's formulae. The results are discussed in relation to other similar studies with rats and mice.
CORRELATED RESPONSES TO SELECTION FOR POSTWEANING GAIN IN THE RAT
Authors: Baker R L , Chapman A B
Published: January 2021

Evidence for correlated responses to selection was investigated in lines of rats selected for 13 generations for high (U line) and low (D line) 3–9-week gain in comparison with random-bred control lines (R and C lines). The increase in 3–9-week gain in the U lines was shown to be due largely to an increase in 9-week weight, although 3-week weight also increased in these lines. In the D lines, where a marked decrease in 3–9-week gain was observed, this was found to be due to a large decrease in 9-week weight and no detectable change in 3-week weight. The average 2-week litter weight, a measure of the lactational performance of the dam, was significantly greater in the U lines than in the D lines. Selection for 3–9-week gain in these lines of rats led to changes of litter size at birth in the same direction as that of selection. This resulted in a significantly higher litter size in the U lines than in the D lines. The number of rats alive at 2 and 9 weeks of age and the percentage of mated females pupping were similar in the U and D lines but lower in these lines than the random bred C lines, providing evidence for a reduction of "fitness" in the selected lines. Carcass composition was studied for all lines at the 11th generation of selection. Carcass composition, in terms of water, fat, ash and protein, was similar in the R and C lines. The U lines had more water and less fat than the R or C line. The D lines had similar carcass composition to the R and C lines. It is suggested that these selected and random-bred lines of rats are potentially useful animals to investigate further the developmental and physiological mechanisms which control growth.
DESIGNING ARTIFICIAL SELECTION EXPERIMENTS FOR SPECIFIC OBJECTIVES
Authors: Bohren B B
Published: January 2021

The observed genetic gain (∆P) from selection in a finite population is the possible expected genetic gain E(∆G) minus the difference in inbreeding depression effects in the selected and control lines. The inbreeding depression can be avoided by crossing the control and selected ♂ and ♀ parents to unrelated mates and summing the observed gains. The possible expected gain will be reduced by an amount D from the predicted gain because of the effects of the genetic limit and random genetic drift, the magnitude of which is a function of effective population size, N. The expected value of D is zero in unselected control populations and in the first generation for selected populations. Therefore, this source of bias can be reduced by increasing N in the selected populations and can be avoided by selecting for a single generation. To obtain observed responses which are unbiased estimates of the predicted response from which to estimate the realized heritability (or regression) in the zero generation, or to test genetic theory based on infinite population size, single-generation selection with many replications would be most efficient. To measure the "total" effect or genetic efficiency of a selection criterion or method, including the effect of different selection intensities, effective population sizes, and space requirements, more than one generation of selection is required to estimate the expected response in breeding values. The efficiency, in the sense of minimum variance, of estimating the expected breeding values at any generation t will decline as the number of generations t increases. The variance of either the estimated mean gain or the regression of gain on selection differential can be reduced more by increasing the number of replicates K than by increasing the number of generations t. Also the general pattern of the response over t can be estimated if the N's are known. Therefore, two- or not more than three-generation selection experiments with many replications would be most efficient.
ISOLATION AND STUDY OF MUTANTS LACKING A DEREPRESSIBLE PHOSPHATASE IN CHLAMYDOMONAS REINHARDI
Authors: Matagne R F , Loppes R
Published: January 2021

In the green alga Chlamydomonas reinhardi, removal of inorganic phosphate from the culture medium results in the increase of phosphatase activity (derepression) in the wild-type (WT) strain as well as in a double mutant (P2Pa) lacking the two main constitutive acid phosphatases. Following treatment of WT and P2Pa with N-methyl-N′-nitro-N-nitrosoguanidine (MNNG), mutants were recovered which display very low phosphatase activities when grown in the absence of phosphate; as shown by electrophoresis, they lack one non-migrating phosphatase (PD mutants). This enzyme is active over a wide range of pH with an optimum at pH 7.5. The comparison of electropherograms from WT and mutants grown on media with or without phosphate allowed us to provide a tentative definition of the pool of derepressible phosphatases in Chlamydomonas : in addition to the neutral phosphatase lacking in PD mutants, Chlamydomonas produces two electrophoretic forms of alkaline phosphatase showing an optimal activity at pH 9.5.
THE GENETICS OF DROSOPHILA SUBOBSCURA POPULATIONS. V. A STUDY OF LINKAGE DISEQUILIBRIUM IN NATURAL POPULATIONS BETWEEN GENES AND INVERSIONS OF THE E CHROMOSOME
Authors: Loukas M , Krimbas C B
Published: January 2021

The genetics of Hk and Est-9 complex gene have been studied in Drosophila subobscura. While Hk alleles mendelize normally, Est-9 is a complex locus consisting of several very closely linked genes with active and silent alleles. Both genes are located on chromosome E; a detailed genetic map was constructed with the help of visible markers and inversions. Both Hk and Est-9 are included in or are very near to inversions of the E chromosome. While Hk does not show linkage disequilibrium either with Est-9 or inversions, Est-9 does show disequilibrium in two ways: both with inversions and between different Est-9 genes. All natural populations studied show the same kind of association between Est-9 gene combinations and inversions. It is argued that these results are better explained by selection than by neutrality.
GEOGRAPHIC VARIATION IN GENETIC DOMINANCE OF THE COLOR MORPHS OF THE RED-BACKED SALAMANDER, PLETHODON CINEREUS
Authors: Highton Richard
Published: January 2021

Female parent-offspring phenotypic data on color morph frequencies in the red-backed salamander, Plethodon cinereus, were obtained from two Virginia localities (164 broods from Greene County and 97 broods from Giles County). The color morph data indicate that the striped morph is genetically dominant in Giles County and recessive in Greene County. It is suggested that epistatic interaction of two or more loci is responsible for the difference between the localities.
MODIFICATION AND INHERITANCE OF PLEIOTROPIC CROSS RESISTANCE AND COLLATERAL SENSITIVITY IN SACCHAROMYCES CEREVISIAE
Authors: Rank G H , Robertson A J , Phillips K L
Published: January 2021

A meiotic segregant (oliPR1) was isolated with a phenotype of multiple cross resistance and collateral sensitivity. Strain oliPR1 has increased sensitivity to ethidium bromide, dequalinium chloride, acriflavin, paromomycin and neomycin, and increased resistance to oligomycin, rutamycin, venturicidin, triethyltin bromide, antimycin, carbonylcynamide-m-chlorophenylhydrazone, tetra-N-butylammonium bromide, dibenzyldimethylammonium chloride, triphenylmethylphosphonium bromide, chloramphenicol, carbomycin, tetracycline, triton-X-165 and cycloheximide. Single gene inheritance of the cross resistance and collateral sensitivity was shown by 2:2 parental ditype segregation and reversion of the complete phenotype by a spontaneous revertant. The locus conferring the oliPR1 phenotype was mapped 11.7 units from an unspecified centromere. Antibiotic resistance showed incomplete dominance, with the level of hybrid resistance dependent upon the inhibitor tested. Resistant diploids that produced four resistant ascospores were the result of mitotic recombination prior to meiosis. A partial revertant phenotype (sensitive to all inhibitors except oligomycin, antimycin and carbonylcyanide-m-chlorophenylhydrazone) was shown to be due to a single nuclear gene causing partial suppression of oliPR1. Anaerobic pretreatment, 37° and 0.5 M KCl were observed to reduce the growth of oliPR1 when challenged with seven diverse inhibitors (antimycin, carbonylcyanide-m-chlorophenylhydrazone,-chloramphenicol, cycloheximide, oligomycin, triethyltin bromide, and triphenylmethylphosphonium bromide). Resistance to cycloheximide was not altered by the [rho—] state. A revertant of oliPR1 (sensitive to the above inhibitors but resistant to ethidium bromide, paromycin and neomycin) showed anaerobic and temperature sensitization to ethidium bromide, paromomycin and neomycin. Continuous monitoring of oxygen uptake by the revertant after anaerobic pretreatment revealed that anaerobiosis sensitized respiratory adaptation of the revertant to neomycin. It is proposed that oliPR1 is a mutation resulting in the alteration of plasma membrane premeability to many diverse inhibitors.
RIBOSOMAL GENE LOCALIZATION AND DISTRIBUTION (ARRANGEMENT) WITHIN THE NUCLEOLAR ORGANIZER REGION OF ZEA MAYS
Authors: Ramirez Samuel A , Sinclair John H
Published: January 2021

Cytogenetic and molecular hybridization techniques were used to examine the arrangement of rRNA genes at the nucleolar organizer region (NOR) of maize. TB-6a stocks involving a reciprocal translocation between a B chromosome and the NOR of chromosome 6 were used. The amount of rDNA in the different stocks used varied from 1.5 to 4 NOR equivalents depending on the number of B6 choromosomes present. Cytological measurements show that the medial break through the NOR results in an equal partitioning of the heterochromatic knob (the NOR) between chromosome 6 and the B chromosome to which it was translocated. DNA-rRNA hybridization experiments show a linear relationship between the amount of rRNA capable of hybridizing with DNA and the number of NOR equivalents present. The data confirm McClintock's conclusion that the heterochromatic knob, rather than the constricted portion, is the true NOR region. Further, they show that the number of ribosomal genes is correlated with the amount of cytologically visible NOR, suggesting a uniform distribution of genes throughout the locus.
GENETIC LOADS IN HETEROGENEOUS ENVIRONMENTS
Authors: Taylor Charles E
Published: January 2021

A model of population structure in heterogeneous environments is described with attention focused on genetic variation at a single locus. The existence of equilibria at which there is no genetic load is examined.—The absolute fitness of any genotype is regarded as a function of location in the niche space and the population density at that location. It is assumed that each organism chooses to live in that habitat in which it is most fit ("optimal habitat selection").—Equilibria at which there is no segregational load ("loadless equilibria") may exist. Necessary and sufficient conditions for the existence of such equilibria are very weak. If there is a sufficient amount of dominance or area in which the alleles are selectively neutral, then there exist equilibria without segregational loads. In the N, p phase plane defined by population size, N, and gene frequency, p, these equilibria generally consist of a line segment which is parallel to the p axis. These equilibria are frequently stable.
CHROMOSOMAL BASIS OF THE MEROZYGOSITY IN A PARTIALLY DIPLOID MUTANT OF PNEUMOCOCCUS
Authors: Ledbetter Mary Lee S , Hotchkiss Rollin D
Published: January 2021

A sulfonamide-resistant mutant of pneumococcus, sulr-c, displays a genetic instability, regularly segregating to wild type. DNA extracts of derivatives of the strain possess transforming activities for both the mutant and wild-type alleles, establishing that the strain is a partial diploid. The linkage of sulr-c to strr-61, a stable chromosomal marker, was established, thus defining a chromosomal locus for sulr-c. DNA isolated from sulr-c cells transforms two mutant recipient strains at the same low efficiency as it does a wild-type recipient, although the mutant property of these strains makes them capable of integrating classical "low-efficiency" donor markers equally as efficiently as "high efficiency" markers. Hence sulr-c must have a different basis for its low efficiency than do classical low efficiency point mutations. We suggest that the DNA in the region of the sulr-c mutation has a structural abnormality which leads both to its frequent segregation during growth and its difficulty in efficiently mediating genetic transformation.
EFFECTS OF GLUCOSE REPRESSION ON THE TRANSMISSION AND RECOMBINATION OF MITOCHONDRIAL GENES IN YEAST (SACCHAROMYCES CEREVISIAE)
Authors: Birky C William
Published: January 2021

Matings of a number of Saccharomyces cerevisiae stocks give different output ratios of mitochondrial genotypes depending on whether the cells are glucose-repressed or derepressed. The effects of glucose repression are independent of cellular mating type and mitochondrial genotype, and take place at least in part after zygotes are formed. An explanation is proposed in terms of changes in the relative numbers of mitochondrial DNA molecules contributed by the a and α parents, modified by selective replication or destruction of molecules inside the zygote.
PARASEXUAL GENETIC ANALYSIS OF THE CELLULAR SLIME MOLD DICTYOSTELIUM DISCOIDEUM A3
Authors: Rothman Frank G , Alexander Ellen T
Published: January 2021

Haploid strain A3 of the cellular slime mold Dictyostelium discoideum is valuable for biochemical studies because it is capable of axenic growth. Mutants of A3 temperature-sensitive for growth and resistant to the drugs cycloheximide, acriflavin, or methanol were isolated.—Heterozygous diploid recombinants, formed at low frequency by cell and nuclear fusion, were isolated by selecting temperature-resistant progeny of mixed cultures of two nonallelic temperature-sensitive haploids (Loomis 1969). Each drug-resistant mutation was found to be recessive. Two independently isolated methanol-resistant mutants were in one complementation group.—Diploids of A3 heterozygous for drug resistance formed drug-resistant segregants with a frequency of approximately 10-4. Segregants selected for resistance to a single drug were either haploid or diploid; the fraction which was haploid varied from 0.11 to 0.86, depending on the selected marker. Segregants selected for resistance to two or three drugs were almost all haploid.—Using this parasexual cycle of diploid formation and haploidization, linkage of these temperature-sensitive and drug-resistance mutations to each other and to mutations studied by Katz and Sussman (1972) and by Williams, Kessin and Newell (1974b) was analyzed. The methanol-resistant mutants were found to be partially resistant to acriflavin, and unlinked to the mutant selected for acriflavin resistance, which was methanol-sensitive. Of the expected seven linkage groups in D. discoideum, five, and a possible sixth, have been marked.—Linkage analysis of a mutant abnormal in morphogenesis showed that its phenotype results from two unlinked chromosomal mutations
First insight into the whole genome shotgun sequence of the endangered noble pen shell Pinna nobilis: a giant bivalve undergoing a mass mortality event
Authors: Bunet Robert , Prévot Jean-Marc , Vicente Nardo , García-March José Rafa , Martinović Rajko , Tena-Medialdea José , Joksimovic Danijela , Bonnefont Jean-Luc , Coupé Stéphane
Published: January 2021

The noble pen shell Pinna nobilis is a Mediterranean endemic and emblematic giant bivalve. Already considered by the late 20th century to be an endangered species, it is facing a dramatic and rapidly expanding epizooty that has decimated populations since mid-2016. The ecological importance of P. nobilis has prompted important investigations for conservation purposes. Here, we report a first analysis of the whole genome sequencing of this animal. This was performed on an Illumina HiSeq X platform using a single paired-end library of short fragments (2 × 150 bp). The de novo contig assembly had a total size of 584 Mb (96,738 contigs, N50 = 7.6 kb, with 0.4% of ambiguous nucleotides), representing 77.5% of the predicted genome size of 754 Mb. The P. nobilis genome is highly AT-rich, with a GC content of 35.6%. At 1%, heterozygosity was in the range of other bivalves with sequenced genomes. Over one-third (36.2%) of the genome consisted of repeated elements with a surprising larger number of short interspersed nuclear elements compared to other molluscan genomes. We were also able to reconstruct the full mitochondrial genome (c. 19 kb, with 12 protein-coding genes, 2 rRNA and 22 tRNA genes). In the context of the epizootic outbreak affecting P. nobilis, a first insight into the innate immune and stress-related genes found in the sequence is provided.
Cometary records revise Eastern Mediterranean chronology around 1240 CE
Authors: Murata Koji , Ichikawa Kohei , Fujii Yuri I , Hayakawa Hisashi , Cheng Yongchao , Kawamoto Yukiko , Sano Hidetoshi
Published: January 2021

Eirene Laskarina, Empress of John III Batatzes of the exiled Byzantine Empire of Nicaea (1204–1261 CE), was an important Eastern Mediterranean figure in the first half of the thirteenth century. We reassess the death day of Eirene, which has been variously dated during the years between the end of 1239 and 1241, with the understanding that narrowing the range in which this event occurred contributes much to understanding the political situation in the area around 1240. George Akropolites, a famous official of the Empire, gives an account that connects Eirene's death to a comet that appeared “six months earlier,” thus pointing to two comet candidates that were visible from the Eastern Mediterranean during the years 1239 and 1241, one recorded on “1239 June 3” and the other on “1240 January 31.” Recent historians prefer the former, based on historical circumstances and without a critical assessment of the comet records. We revisit the historical records and reveal that the “1239 June 3” candidate was not a comet. On the other hand, the other candidate was a comet, as supported by multiple historical records in multiple regions, and is also a good fit with Akropolites’ narrative. Therefore, we conclude that Eirene died six months after the comet that was seen on 1240 January 31, which places her death in the summer of 1240. Given that her death day is crucial for determining some other contemporary events across the Eastern Mediterranean, our results offer a solid basis for further research on the thirteenth-century Eastern Mediterranean.
Exploring intentional medication non-adherence in patients with systemic lupus erythematosus: the role of physician–patient interactions
Authors: Leung Jerik , Baker Elizabeth A , Kim Alfred H J
Published: January 2021

Objective

Medication non-adherence contributes to worse health outcomes among SLE patients. The underlying mechanisms that drive medication non-adherence are poorly understood. The purpose of this study was to explore possible mechanisms of medication non-adherence by eliciting patient experiences.

Methods

Consented adult patients with ACR- or SLICC-classified SLE were recruited. Ten semi-structured interviews were conducted across six participants. Interviews were audio recorded, transcribed, and analysed using an iterative process. The findings were presented to an interactive public forum with SLE patients, family members and friends of patients, and health-care professionals to assess validity and for elaboration of the concepts developed.

Results

The following three interrelated themes emerged from the interviews. First, why do rheumatologists not know more about lupus or share what they do know with their patients? Second, why do I have to take so many drugs and why do the drugs not work? Third, if my rheumatologist cannot communicate with me, why should I follow the prescribed medication regimen?

Conclusion

Our exploratory findings lay out a possible underlying logic by which patients might choose intentionally to engage with medication non-adherence behaviours. Patients suggested that poor communication with their rheumatologists along with a lack of validation of their symptoms contributed to them not valuing the recommendations of physicians. This also contributed to development of a cynical outlook and little belief that medication would improve their condition. Although further work is needed to validate these findings, our preliminary work suggests that interventions focusing on the development of communication skills among both patients and rheumatologists are necessary to reduce medication non-adherence.
Synthesis of libraries and multi-site mutagenesis using a PCR-derived, dU-containing template
Authors: Meinke Gretchen , Dalda Nahide , Brigham Benjamin S , Bohm Andrew
Published: January 2021

Directed DNA libraries are useful because they focus genetic diversity in the most important regions within a sequence. Ideally, all sequences in such libraries should appear with the same frequency and there should be no significant background from the starting sequence. These properties maximize the number of different sequences that can be screened. Described herein is a method termed SLUPT (Synthesis of Libraries via a dU-containing PCR-derived Template) for generating highly targeted DNA libraries and/or multi-site mutations wherein the altered bases may be widely distributed within a target sequence. This method is highly efficient and modular. Moreover, multiple distinct sites, each with one or more base changes, can be altered in a single reaction. There is very low background from the starting sequence, and SLUPT libraries have similar representation of each base at the positions selected for variation. The SLUPT method utilizes a single-stranded dU-containing DNA template that is made by polymerase chain reaction (PCR). Synthesis of the template in this way is significantly easier than has been described earlier. A series of oligonucleotide primers that are homologous to the template and encode the desired genetic diversity are extended and ligated in a single reaction to form the mutated product sequence or library. After selective inactivation of the template, only the product library is amplified. There are no restrictions on the spacing of the mutagenic primers except that they cannot overlap.
An Ebola virus disease model with fear and environmental transmission dynamics
Authors: Juga M.L. , Nyabadza F. , Chirove F.
Published: January 2021

Recent Ebola virus disease (EVD) outbreaks have been limited not only to the interactions between humans but also to the complex interplay of the environment, human and socio-economic factors. Changes in human behaviour as a result of fear can also affect disease transmission dynamics. In this paper, a compartmental model is used to study the dynamics of EVD incorporating fear and environmental transmission. We formulate a fear dependent contact rate function to measure the rate of person to person, as well as pathogen to person transmissions. The epidemic threshold and the model equilibria are determined and, their stabilities are analysed. The model is validated by fitting it to data from the 2019 and 2020 EVD outbreaks in the Democratic Republic of Congo. Our results suggest that the fear of death from EVD may reduce the transmission and aid the control of the disease, but it is not sufficient to eradicate the disease. Policymakers need to also implement other control measures such as case finding, media campaigns, Quarantine and increase in the number of beds in the Ebola treatment centers, good laboratory services, safe burials and social mobilisation, to eradicate the disease.

Highlights

Due to its high case fatality rate, EVD undoubtedly instills fear in the inhabitants of any affected community.

We propose an Ebola model with fear, which considers the pathogens in the environment to quantify the effect of fear and environmental transmission on the EVD disease dynamics.

The fear of death from Ebola is proportional to the Ebola disease transmission rate.

At high levels of fear, the number of EVD cases decrease.