bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on the Aerodynamic Performance and Internal-External Flow Interaction Effects of Distributed Ducted Fan in the Climbing-Condition
Authors: Gong Tian Yu , Liang Peng Xiang , Wang Zhuo Qi , Yuan Wei
Published: April 2021

Distributed electric propulsion ducted fans play an important role in saving energy and reducing environmental pollution of the airplanes. In this research, unsteady RANS CFD numerical simulations were used to analyse the possible impact of aerodynamic performance and interaction effects of distributed ducted fan in the climbing condition, which is verified with experimental method. Firstly, this paper will explore the effect of internal/external flow interaction on the flow field of the propulsion system at the same time. Secondly, from the perspective of propulsion efficiency and energy consumption, this paper will find the thrust relationship between the maximum continuous working state and the maximum working state and study the performance of the ducted fan. This paper will aim to reduce energy consumption during the propulsion of ducted fans and obtain longer flight time, and find a balance point between power and propulsion efficiency. The results show that the maximum continuous working state is 85% of the maximum thrust state approximately. By combining the aerodynamic interaction phenomena with the aerodynamic performance of the distributed ducted fan, this research provides an important basis and advice for enhancing the flight time of distributed ducted fans and reducing energy consumption during the process of engineering and flow mechanisms.
Variation Law and Experimental Study on Multi-stage Critical Speed of an Aero-engine Power Turbine Rotor
Authors: Nie Weijian , Deng Wangqun , Chen Yanong
Published: April 2021

Finite element method was used to establish the calculation model of the dynamic characteristics of the simulated power turbine rotor, and the dynamic characteristics of the rotor were systematically calculated and analysed. The variation law of the first three stages critical speeds of the rotor with the supporting stiffness and the mass of each disk were revealed. The dynamic characteristics test of the simulated power turbine rotor in the full speed range was completed, and the calculation results and test results were compared and analysed. The results show that the calculation model reflects the dynamic characteristics of the rotor well, and the rationality of the rotor structure design, supporting layout and critical speed distribution were verified. The study provides a theoretical basis for the adjustment of critical speed based on the supporting stiffness and disk’s mass, it also provides technical reference for the real rotor structure design and test.
Simulation study on the relationship between catalyst particle concentration and flow field of a gas turbine
Authors: Liu Guangkui , Sun Sicong , Sha Long , Liang Kui , Yang Xisheng , An Dong , Wen Qi
Published: April 2021

In this paper, the characteristics of the flow field in the gas turbine under different catalyst particle concentrations are simulated and analyzed by FLUENT software. The influences of catalyst particle concentration on the high-temperature smoke flow field, the movement track of catalyst particles and the erosion of the moving blade are studied in detail. The results show that the change of particle concentration has no obvious influence on the high temperature smoke flow field. The erosion wear of moving blade mainly occurs near the leading edge and trailing edge of the blade. The possibility of erosion wear at the leading edge is obviously greater than that at the trailing edge. The concentration of catalyst particles has a great influence on the erosion wear of moving blade. The erosion wear will be aggravated with the increase of catalyst particle concentration.
Rapid Prediction Method of Fan Broadband Noise Based on A Three-dimensional Sound Source Model
Authors: Ye Yang , Liangfeng Wang , Dangguo Yang
Published: April 2021

The fan/compressor broadband noise is an important noise source of civil large bypass ratio turbofan engine.. The empirical method requires massive amounts of test data for support. Adopting the computational aeroacoustic (CAA) method to predict the fan/compressor broadband noise will cost high amounts of computing resources or time. Thus, this study combines flow field calculation with analytical model to study the prediction method of fan/compressor broadband noise, this method can be used for quick and efficient preliminary evaluation and parameter studies. On the basis of the simulation and modeling of the stator – rotor interference phenomenon of fans, rotor wake flow field and the corresponding parameters are obtained. On this basis, the three-dimensional sound source model is used to calculate the blade surface sound source and its propagation under different working conditions. The distribution of sound energy in the duct is obtained. Then, the broadband noise prediction of fan is further acquired. The broadband noise of a typical single-stage TA36 fan is predicted using this method. Study results suggest that (1) turbulence model and turbulence kinetic energy of inlet boundary condition will have an important effect on the prediction results of broadband noise. (2) When the inlet turbulence kinetic energy is small, different turbulence models slightly influence the prediction results of broadband noise; when the inlet turbulence kinetic energy is large, the sound pressure level of sound field obtained by SST model is approximately 5dB larger than that obtained by model. This method can be used in the early stage of fan/compressor design, and the characteristics of blade broadband noise can be rapidly obtained.
A High-Accuracy and Conservative Unstructured Overset Grid data transfer Method for Numerical Simulation of Turbomachinery
Authors: Cui P C , Tang J , Li B , Li H , Wu X J , Ma M S
Published: April 2021

The overset grid method is getting more and more popular in the numerical simulation of turbomachinery, especially in the simulation of wind turbines. Reasonable interpolation between overset grid interfaces is one of the bases to ensure correct calculation of flow fields, non-conservative interpolation is insufficient to guarantee the mass fluxes in the numerical simulation of turbomachinery. This paper develops a conservative interpolation method for hybrid overset mesh based on supermesh technology and centre-based finite volume method. A method to build the local supermesh during overset grid interface by the cell-cut algorithm is presented, and flow field variables could be interpolated conservatively during overset meshes with second-order accuracy via the local supermesh. Numerical results show that the proposed method is strictly conservative for second-order distributed flow variables. Compared with trilinear interpolation method and reverse distance-weighted interpolation method, the method in this paper decreases the numerical errors and the variables are interpolated more accurately. Engineering cases show that the method in this paper is robust and practical for engineering applications.
A digital light processing 3D printed magnetic bioreactor system using silk magnetic bioink
Authors: Ajiteru Olatunji , Choi Kyu Young , Lim Tae Hyeon , Kim Do Yeon , Hong Heesun , Lee Young Jin , Lee Ji Seung , Lee Hanna , Suh Ye Ji , Sultan Md Tipu , Lee Ok Joo , Kim Soon Hee , Park Chan Hum
Published: April 2021

Among various bioreactors used in the field of tissue engineering and regenerative medicine, a magnetic bioreactor is more capable of providing steady force to the cells while avoiding direct manipulation of the materials. However, most of them are complex and difficult to fabricate, with drawbacks in terms of consistency and biocompatibility. In this study, a magnetic bioreactor system and a magnetic hydrogel were manufactured by single-stage three-dimensional (3D) printing with digital light processing (DLP) technique for differentiation of myoblast cells. The hydrogel was composed of a magnetic part containing iron oxide and glycidyl-methacrylated silk fibroin, and a cellular part printed by adding mouse myoblast cell (C2C12) to gelatin glycidyl methacrylate, that was placed in the magnetic bioreactor system to stimulate the cells in the hydrogel. The composite hydrogel was steadily printed by a one-stage layering technique using a DLP printer. The magnetic bioreactor offered mechanical stretching of the cells in the hydrogel in 3D ways, so that the cellular differentiation could be executed in three dimensions just like the human environment. Cell viability, as well as gene expression using quantitative reverse transcription-polymerase chain reaction, were assessed after magneto-mechanical stimulation of the myoblast cell-embedded hydrogel in the magnetic bioreactor system. Comparison with the control group revealed that the magnetic bioreactor system accelerated differentiation of mouse myoblast cells in the hydrogel and increased myotube diameter and length in vitro. The DLP-printed magnetic bioreactor and the hydrogel were simply manufactured and easy-to-use, providing an efficient environment for applying noninvasive mechanical force via FDA-approved silk fibroin and iron oxide biocomposite hydrogel, to stimulate cells without any evidence of cytotoxicity, demonstrating the potential for application in muscle tissue engineering.
Optical behaviour of γ-black CsPbI3 phases formed by quenching from 80 °C and 325 °C
Authors: Valastro Salvatore , Mannino Giovanni , Smecca Emanuele , Sanzaro Salvatore , Deretzis Ioannis , Magna Antonino La , Jena Ajay Kumar , Miyasaka Tsutomu , Alberti Alessandra
Published: April 2021

The orthorhombic γ-black phase of CsPbI3 is well-known to be unstable at room temperature and strategies are needed to counteract its transformation tendency. In this paper we compare γ-black CsPbI3 thin films (∼80 nm) formed via two different routes: a fast quenching of the cubic α-phase from 325 °C (HT-γ) or spontaneously cooling the layer from 80 °C (LT-γ). The successful application of the second procedure is allowed by the use of a mother solution containing Europium with an Eu/Pb ratio as small as 5%. This has been indeed used to form both LT-γ and HT-γ thin films. The phase transition during the heating and cooling pathways is followed in situ by spectroscopic ellipsometry and x-ray diffraction analyses. We demonstrate that both γ-black phases exhibit the same absorption features and critical points as depicted in very details by the dielectric functions. Minor differences can be found in the intensity of the absorption coefficient, assigned to an improved lattice quality in the layer that has experienced the high temperature path. On the other hand, α-black and δ-yellow phases show different critical points in the optical transitions. Besides providing benchmarking optical parameters to discriminates the different phases, we demonstrate that the LT-γ phase closely competes with the HT-γ counterpart during stress tests for stability, with the first one more suited for tandem monolithic architectures that require thermal treatments under 200 °C.
Introduction
Authors: Wallace David
Published: April 2021

This introductory chapter provides an overview of philosophy of physics, which is an interdisciplinary field sitting between physics proper, mainstream philosophy, and the general philosophy of science, and communicating ideas and insights between them. Philosophy of physics is mostly concerned not with physics as a whole but with particular areas within it. Given a field in physics, one can consider the conceptual—that is, philosophical—questions that arise in that field, and the problems in each sub-field are distinctive. The chapter briefly discusses many of these, including some in cutting-edge areas of physics like quantum cosmology, black holes, and string theory. But it notes that the bulk of work in philosophy of physics is concerned with three areas where the physics is reasonably well established: the philosophy of spacetime; the philosophy of statistical mechanics; and the philosophy of quantum mechanics.
Regional scale pressures on reefs
Authors: Sheppard Charles
Published: April 2021

One consequence of the extremely high biodiversity found on reefs is the enormous number of interlocking connections between components. But connections can be destroyed by many kinds of stressors such as pollutants, as can the species themselves. Some species or processes have high redundancy—if destroyed others can fill their role on a reef—while other species or processes may be more or less irreplaceable, in which case when they are destroyed key processes maintaining a healthy reef can be destroyed too. Because so many countries and human communities are dependent on reefs, reef degradation, which is now occurring on a very worrying scale, is of increasing concern. Impacts fall into two main categories: those caused by numerous, usually localized, impacts, such as different forms of pollution and shoreline developments that create large quantities of sediment; and those caused by the more recently recognized, and probably more serious, long-term factors associated with climate change. All of these are ultimately interlinked and all are caused by human activities. Many occur concurrently, each exacerbating the harmful effects of others, and many are synergistic in their impacts. Sewage, nutrient run-off, landfill, dredging, and sedimentation are most important, as are chemicals, pesticides, and metals. Coral diseases are increasing also, commonly as a result. In many areas now too overfishing has become critical and may be the most ecosystem-distorting factor of all.
De Novo Inflammatory Bowel Disease Rarely Occurs During Posttransplant Immunosuppression
Authors: Fang Jiayun M , Lamps Laura , Yeboah-Korang Amoah , Cheng Jerome , Westerhoff Maria
Published: April 2021

Objectives

De novo chronic idiopathic inflammatory bowel disease (CIIBD) is reported to occur at higher rates in posttransplant patients than that of the general population. The previous reports, however, included patients with primary sclerosing cholangitis (PSC), a known association with CIIBD. Hence, we investigated how often posttransplant de novo CIIBD occurs in the absence of PSC.

Methods

We identified 185 posttransplant adults without a history of PSC or CIIBD, who had undergone colonoscopy between July 2013 and June 2020. Biopsies were reviewed and clinical data were gathered.

Results

CIIBD-like colitis accounted for 1.1% (2/185) of our cohort. The 2 affected patients were already taking multiple immunosuppressive therapies. They were initially placed on standard CIIBD maintenance therapy, but then required escalation therapy. One patient had persistent active colitis despite escalation therapy, while the other subsequently had resolution of symptoms and developed quiescent disease.

Conclusions

The incidence of CIIBD-like colitis in our study population was lower than what has been previously described. Both patients had a poor response to standard CIIBD therapy, raising the question whether their diagnosis is truly de novo CIIBD or another immunologic process.
Differences in Hypertension Prevalence and Hypertension Control by Urbanization Among Adults in the United States, 2013–2018
Authors: Ostchega Yechiam , Hughes Jeffery P , Zhang Guangyu , Nwankwo Tatiana , Graber Jessica , Nguyen Duong T
Published: April 2021

Background

To examine the associations between urbanization and hypertension, stage II hypertension, and hypertension control.

Methods

Data on 16,360 US adults aged 18 years or older from the 2013–2018 National Health and Nutrition Examination Survey (NHANES) were used to estimate the prevalence of hypertension (blood pressure (BP) ≥130/80 mm Hg or use of medication for hypertension), stage II hypertension (BP ≥140/90 mm Hg), and hypertension control (BP <130/80 mm Hg among hypertensives) by urbanization, classified by levels of metropolitan statistical areas as large MSAs (population ≥1,000,000), medium to small MSAs (population 50,000–999,999), and non-MSAs (population <50,000).

Results

All prevalence ratios (PRs) were compared with large MSAs and adjusted for demographics and risk factors. The PRs of hypertension were 1.07 (95% confidence interval (CI) = 0.99–1.14) for adults residing in medium to small MSAs and 1.06 (95% CI = 0.99–1.13) for adults residing in non-MSAs. For stage II hypertension, the PRs were higher for adults residing in medium to small MSAs 1.21 (95% CI = 1.06–1.36) but not for adults residing in non-MSAs 1.06 (95% CI = 0.88–1.29). For hypertension control, the PRs were 0.96 (95% CI = 0.91–1.01) for adults residing in medium to small MSAs and 1.00 (95% CI = 0.93–1.06) for adults residing in non-MSAs.

Conclusions

Among US adults, urbanization was associated with stage II hypertension.
Effects of a Collaborative, Community Hospital Network for Antimicrobial Stewardship Program Implementation
Authors: Moehring Rebekah W , Yarrington Michael E , Davis Angelina E , Dyer April P , Johnson Melissa D , Jones Travis M , Spires S Shaefer , Anderson Deverick J , Sexton Daniel J , Dodds Ashley Elizabeth S
Published: April 2021

Background

Individual hospitals may lack expertise, data resources, and educational tools to support antimicrobial stewardship programs (ASP).

Methods

We established a collaborative, consultative network focused on hospital ASP implementation. Services included on-site expert consultation, shared database for routine feedback and benchmarking, and educational programs. We performed a retrospective, longitudinal analysis of antimicrobial use (AU) in 17 hospitals that participated for at least 36 months during 2013–2018. ASP practice was assessed using structured interviews. Segmented regression estimated change in facility-wide AU after a 1-year assessment, planning, and intervention initiation period. Year 1 AU trend (1–12 months) and AU trend following the first year (13–42 months) were compared using relative rates (RR). Monthly AU rates were measured in days of therapy (DOT) per 1000 patient days for overall AU, specific agents, and agent groups.

Results

Analyzed data included over 2.5 million DOT and almost 3 million patient-days. Participating hospitals increased ASP-focused activities over time. Network-wide overall AU trends were flat during the first 12 months after network entry but decreased thereafter (RR month 42 vs month 13, 0.95, 95% confidence interval [CI]: .91–.99). Large variation was seen in hospital-specific AU. Fluoroquinolone use was stable during year 1 and then dropped significantly. Other agent groups demonstrated a nonsignificant downward trajectory after year 1.

Conclusions

Network hospitals increased ASP activities and demonstrated decline in AU over a 42-month period. A collaborative, consultative network is a unique model in which hospitals can access ASP implementation expertise to support long-term program growth.
Epidermal growth factor receptor-dependent maintenance of cardiac contractility
Authors: Guo Shuchi , Okyere Ama Dedo , McEachern Erin , Strong Joshua L , Carter Rhonda L , Patwa Viren C , Thomas Toby P , Landy Melissa , Song Jianliang , Lucchese Ana Maria , Martin Thomas G , Gao Erhe , Rajan Sudarsan , Kirk Jonathan A , Koch Walter J , Cheung Joseph Y , Tilley Douglas G
Published: April 2021

Aims

Epidermal growth factor receptor (EGFR) is essential to the development of multiple tissues and organs and is a target of cancer therapeutics. Due to the embryonic lethality of global EGFR deletion and conflicting reports of cardiac-overexpressed EGFR mutants, its specific impact on the adult heart, normally or in response to chronic stress, has not been established. Using complimentary genetic strategies to modulate cardiomyocyte-specific EGFR expression, we aim to define its role in the regulation of cardiac function and remodelling.

Methods and results

A floxed EGFR mouse model with α-myosin heavy chain-Cre-mediated cardiomyocyte-specific EGFR downregulation (CM-EGFR-KD mice) developed contractile dysfunction by 9 weeks of age, marked by impaired diastolic relaxation, as monitored via echocardiographic, haemodynamic, and isolated cardiomyocyte contractility analyses. This contractile defect was maintained over time without overt cardiac remodelling until 10 months of age, after which the mice ultimately developed severe heart failure and reduced lifespan. Acute downregulation of EGFR in adult floxed EGFR mice with adeno-associated virus 9 (AAV9)-encoded Cre with a cardiac troponin T promoter (AAV9-cTnT-Cre) recapitulated the CM-EGFR-KD phenotype, while AAV9-cTnT-EGFR treatment of adult CM-EGFR-KD mice rescued the phenotype. Notably, chronic administration of the β-adrenergic receptor agonist isoproterenol effectively and reversibly compensated for the contractile dysfunction in the absence of cardiomyocyte hypertrophy in CM-EGFR-KD mice. Mechanistically, EGFR downregulation reduced the expression of protein phosphatase 2A regulatory subunit Ppp2r3a/PR72, which was associated with decreased phosphorylation of phospholamban and Ca2+ clearance, and whose re-expression via AAV9-cTnT-PR72 rescued the CM-EGFR-KD phenotype.

Conclusions

Altogether, our study highlights a previously unrecognized role for EGFR in maintaining contractile homeostasis under physiologic conditions in the adult heart via regulation of PR72 expression.
MEASURING SELECTION COEFFICIENTS AFFECTING THE ALCOHOL DEHYDROGENASE POLYMORPHISM IN DROSOPHILA MELANOGASTER
Authors: Wilson S R , Oakeshott J G , Gibson J B , Anderson P R
Published: April 2021

This paper describes a perturbation experiment on the frequency of the F and S Alcohol dehydrogenase (Adh) alleles of D. melanogaster. Fifty-four isofemale lines set up from three wild populations and with initial F frequencies of either 0.25, 0.50 or 0.75 were maintained on standard laboratory food medium at 22°. At generations 4, 12 and 20 the lines were again scored for Adh gene frequencies. Maximum likelihood procedures were used to estimate selection coefficients for the Adh genotypes. An analysis of deviance was used to compare the coefficients against expectations under the hypotheses of neutrality and of constant values for the three base populations, and for the three initial gene frequency classes. Highly-significant departures from neutrality were observed; over all 54 lines, the set of relative fitnesses for S/S:F/S:F/F was estimated as 1.00:1.08:1.08. In addition, there were significant differences between lines in the outcome of selection which were not attributable to differences between base populations or initial F frequencies. These residual between-line differences, as well as some between-generation, within-line differences are discussed in terms of linkage disequilibria with background genes and electrophoretically cryptic variation at the Adh locus.
PREFERENTIAL MATING IN SYMMETRIC MULTILOCUS SYSTEMS: LIMITS FOR MULTIALLELISM AND FOR MANY LOCI
Authors: Raper J
Published: April 2021

Models in which general forms of preferential mating have been superimposed on the framework of the symmetric heterozygosity selection regime have been examined previously with respect to the existence and local stability of a central polymorphic equilibrium. The results are now extended to produce the limiting form of the stability conditions in two cases: First, where the number of alleles per locus is assumed to be very large; second, where the number of loci affecting the character is very large. It is argued that some type of frequency dependence in the mating pattern must be included, and a particular case is examined in detail. It is shown that multiallelism is ambiguous in its effect on stability, while an increasing number of loci, at least under zero linkage, leads to a simple stability condition which is analogous to the one-locus heterosis principle. Assortative mating appears to be more likely to produce a stable central polymorphism under high levels of allelism than is sexual selection, but is relatively very much weaker than sexual or viability selection if the number of loci involved is large.
DOMINANT MUTATORS IN ESCHERICHIA COLI
Authors: Cox E C , Horner D L
Published: April 2021

In this paper we report on the isolation and genetic analysis of a series of strong mutators mapping at five minutes on the E. coli chromosome. These mutations are dominant and show no evidence of interaction in merodiploids. Cultures grown in broth medium exhibit mutant frequencies five to six orders of magnitude higher than mut+ strains. Cultures propagated in minimal salts media mutate at rates one to three orders higher than wild-type. Three-factor crosses have been used to order these mutators relative to metD, proA, and a Tn10 insertion near five minutes.
EVIDENCE FOR A POLYMORPHISM IN GAMETIC SEGREGATION USING A MALATE DEHYDROGENASE LOCUS IN THE TETRAPLOID TREEFROG HYLA VERSICOLOR
Authors: Danzmann Roy G , Bogart James P
Published: April 2021

Artificial cross combinations of tetraploid Hyla versicolor were analyzed electrophoretically using a polymorphic malate dehydrogenase locus (MDH-1) to determine the mechanism of chromosome segregation. Models for differentiating between disomic and tetrasomic inheritance are presented and tested. In some crosses progeny genotypes fit a disomic mode of segregation. In other crosses there is only evidence for a tetrasomic mode of segregation. Additional crosses produced genotypic ratios which conformed to either a disomic or tetrasomic mode of segregation. The same type of inheritance was demonstrated for any individual when used in multiple cross combinations. These results suggest that there exists in H. versicolor a polymorphism with respect to segregation of gametes, resulting from differences in chromosome pairings during meiosis I.
SUBSTRATE-PREFERENCE POLYMORPHISM AT AN ESTERASE LOCUS OF DROSOPHILA MOJAVENSIS
Authors: Zouros E , van Delden W
Published: April 2021

In a larval esterase of Drosophila mojavensis there are alleles whose products preferentially hydrolyze α-naphthyl esters, whereas the majority of the alleles hydrolyze preferentially β-naphthyl esters. In a collection of laboratory stocks α alleles have a frequency of 15%. Three different mobilities of α alleles were discovered, suggesting a polymorphism rather than a single mutation event. If substrate-preference polymorphisms are common among "multiple-substrate" enzymes (category II of Gillespie and Langley 1974), allozyme variation at these enzyme loci may well be maintained by balancing selection.
ASSOCIATION OF ENDOSPERM REDUCTION WITH PARENTAL IMPRINTING IN MAIZE
Authors: Lin Bor-Yaw
Published: April 2021

Among 38 reciprocal translocations between the maize B chromosome and the proximal region of the long arm of chromosome 10 were six interchanges associated with reduced endosperm development. These six have breakpoints that are the most proximal of the set and constitute a graded series with those broken nearer the centromere which have the most abnormal phenotypes. The group of six defines three major regions that produce the endosperm effects. The remaining 32 translocations reduce kernel size very slightly, suggesting the presence of a fourth region distal to all break-points.—The affected class of kernels lacks a paternally derived representative of that segment of 10L translocated to the B centromeric element (B10 chromosome; 10 10 B10). An accompanying class of kernel in which the paternal B10 chromosome is duplicated in the endosperm (10 10 10B B10 B10) is normal. Kernels of the same endosperm constitution synthesized by introducing both 10 and B10 maternally, however, are defective, resembling 10 10 10B. Maternal B10's are therefore unable to compensate for the absence of a paternal B10. Clearly expression of the 10L genes involved supports normal endosperm growth only following pollen transmission.
TESTING NEUTRALITY IN SUBDIVIDED POPULATIONS
Authors: Slatkin Montgomery
Published: April 2021

Statistical tests of the neutrality hypothesis that are based on the sampling theory of Ewens (1972) require the assumption of panmixia. It is proposed that for a population comprising numerous local populations with weak gene flow among them, tests based on Ewens' theory can be applied separately to samples from each local population. At low levels of gene flow, migration acts primarily like mutation, introducing new alleles to each local population. It is shown with simulation results that, at low levels of migration, correlations in allele frequencies among demes are sufficiently small that the results from the application of Ewens' theory to each deme are statistically independent. It is also shown that, by combining the results of the tests in different demes, some statistical power to detect deviations from neutrality is gained. The method is illustrated with the application to data on a salamander species. At low levels of gene flow, population subdivision must be taken account of in testing neutrality and the proposed test provides one way to do so.
COLD-SENSITIVE CELL-DIVISION-CYCLE MUTANTS OF YEAST: ISOLATION, PROPERTIES, AND PSEUDOREVERSION STUDIES
Authors: Moir Don , Stewart Sue E , Osmond Barbara C , Botstein David
Published: April 2021

We isolated 18 independent recessive cold-sensitive cell-division-cycle (cdc) mutants of Saccharomyces cerevisiae, in nine complementation groups. Terminal phenotypes exhibited include medial nuclear division, cytokinesis, and a previously undescribed terminal phenotype consisting of cells with a single small bud and an undivided nucleus. Four of the cold-sensitive mutants proved to be alleles of CDC11, while the remaining mutants defined at least six new cell-division-cycle genes: CDC44, CDC45, CDC48, CDC49, CDC50 and CDC51.—Spontaneous revertants from cold-sensitivity of four of the medial nuclear division cs cdc mutants were screened for simultaneous acquisition of a temperature-sensitive phenotype. The temperature-sensitive revertants of four different cs cdc mutants carried single new mutations, called Sup/Ts to denote their dual phenotype: suppression of the cold-sensitivity and concomitant conditional lethality at 37°. Many of the Sup/Ts mutations exhibited a cell-division-cycle terminal phenotype at the high temperature, and they defined two new cdc genes (CDC46 and CDC47). Two cold-sensitive medial nuclear division cdc mutants representing two different cdc genes were suppressed by different Sup/Ts alleles of another gene which also bears a medial nuclear division function (CDC46). In addition, the cold-sensitive medial nuclear division cdc mutant csH80 was suppressed by a Sup/Ts mutation yielding an unbudded terminal phenotype with an undivided nucleus at the high temperature. This mutation was an allele of CDC32. These results suggest a pattern of interaction among cdc gene products and indicate that cdc gene proteins might act in the cell cycle as complex specific functional assemblies.
GENETIC ANALYSIS OF CHROMOMERE 3D4 IN DROSOPHILA MELANOGASTER: THE DUNCE AND SPERM-AMOTILE GENES
Authors: Salz Helen K , Davis Ronald L , Kiger John A
Published: April 2021

Both male and female Drosophila that are homozygous deficient for chromomere 3D4 are viable but sterile and lack detectable cAMP-specific phosphodiesterase activity. Two genes have been localized to this region: spermamotile (sam) and dunce (dnc). The sperm-amotile gene is required for male fertility, and the dunce gene is required for normal learning, female fertility, and cAMP-specific phosphodiesterase activity. The sperm-amotile gene maps 0.24 map units to the left of dunce. The expression of the dunce gene seems to be affected by a chromosomal break to the left of sperm-amotile. The fertility of dunce females varies according to changes in the genetic background and the presence or absence of an X-linked suppressor.
DIFFERENCE IN THE RATIO OF DOMINANT-LETHAL MUTATIONS TO HERITABLE TRANSLOCATIONS PRODUCED IN MOUSE SPERMATIDS AND FULLY MATURE SPERM AFTER TREATMENT WITH TRIETHYLENEMELAMINE (TEM)
Authors: Generoso W M , Cain K T , Cornett C V , Russell E W , Hellwig C S , Horton C Y
Published: April 2021

The relative induction of dominant-lethal mutations and heritable translocations in triethylenemelamine-treated male postmeiotic germ cells of mice was determined depending on the stage treated. Males were mated either 11.5–14.5 days after treatment (middle spermatids) or less than 2.5 hours after treatment (fully mature sperm). Results clearly showed that, even though similar levels of dominant-lethal mutations were induced in fully mature sperm and in middle spermatids, the frequency of heritable translocations induced in mature sperm was markedly lower than that induced in middle spermatids. This observation was used, together with earlier ones, to suggest a mechanism by which dominant-lethal mutations and heritable translocations are produced following chemical treatment of male postmeiotic germ cels.
ESTIMATING GENETIC VARIABILITY WITH RESTRICTION ENDONUCLEASES
Authors: Hudson Richard R
Published: April 2021

The estimation of the amount of sequence variation in samples of homologous DNA segments is considered. The data are assumed to have been obtained by restriction endonuclease digestion of the segments, from which the numbers and frequencies of the cleavage sites in the sample are determined. An estimator, p, of the proportion of sites that are polymorphic in the sample is derived without assuming any particular population genetic model for the evolution of the population. The estimator is very close to the Ewens, Spielman and Harris (1981) estimator that was derived with the symmetric Wright-Fisher neutral model. Engels (1981) has also recently proposed an estimator of the same quantity, and he arrived at his estimator without assuming a particular population genetic model. The sampling variance of p and Engels' estimator are derived. It is found that the sampling variance of p is lower than the sampling variance of Engels' estimator. Also, the sampling variance of θ, an estimate of θ (=4Nu) is obtained for the symmetric Wright-Fisher neutral model with free recombination and with no recombination.
THE LOCATION OF A MUTATOR FACTOR IN A STRAIN OF DROSOPHILA MELANOGASTER BY ASSAYING MALE RECOMBINATION
Authors: Scobie Nita N , Schaffer Henry E
Published: April 2021

In a set of "mutation accumulation lines," of Drosophila melanogaster that had originated from two different wild-caught lethal-carrying second chromosomes (Yamaguchi and Mukai 1974; Mukai and Cockerham 1977; Voelkers, Schaffer and Mukai 1980) a correlation exists between high rates of reverse mutation at two visible loci and the ability to induce male recombination (Scobie and Schaffer 1982). The second and third chromosomes were extracted from the lines demonstrating these phenomena and tested for independent ability to induce male recombination. When the wild chromosome being tested was of male origin, extracted second chromosome lines were found to induce moderate to high levels of male recombination and reduced transmission frequency of the wild chromosome (the k value). The recombinants recovered in these crosses also demonstrated a high level of double-crossover recombination without the recovery of the reciprocal double-recombinant types. In addition, identifiable portions of extracted second chromosomes of male origin have been placed on very similar, marked genetic backgrounds and tested for their ability to induce male recombination. Results of this procedure have identified two regions of the second chromosome that induce male recombination and reduce k values. These results are consistent with the hypothesis that there exist two mutator factors on the second chromosome, each associated with a "mutation accumulation line" with an unstable locus.
GENETIC ANALYSIS OF MUTATIONS AT THE GLUED LOCUS AND INTERACTING LOCI IN DROSOPHILA MELANOGASTER
Authors: Harte Peter J , Kankel Douglas R
Published: April 2021

A genetic analysis of the dominant mutation Glued that perturbs the development of the normal axonal architecture of the fly's visual system was undertaken. Ten new alleles at this locus were identified and characterized. TWO complementation groups that were identified failed to complement the original allele, suggesting that it is a double mutant or that it resides at a complex locus. Several of the new alleles display visual-system abnormalities similar to those of the original mutation. Seven of the eight members of one complementation group are embryonic/early larval lethals, like the original mutation. The other allele in this group is temperature sensitive. Homozygous mutant adults exhibit a temperature-sensitive female sterile phenotype. Unsuccessful attempts to recover genetic mosaics carrying clones of cells homozygous for some of these mutations revealed that they are either essential for the viability of individual cells or that they affect some other fundamental cellular function, such as mitosis or the ability to participate in tissue level organization, which prevents them from being recovered in adult mosaics. This also indicates that these mutations do not specifically affect neural cells. A number of X-ray- and EMS-induced partial and complete phenotypic "revertants" of the original allele have also been isolated as material for a comparative analysis of visual system development. All "revertants" that alter the abnormal eye phenotype towards the wild type have similar impact on the organization of the optic lobe.
THE EVOLUTIONARY HISTORY OF DROSOPHILA BUZZATII. III. CYTOGENETIC RELATIONSHIPS BETWEEN TWO SIBLING SPECIES OF THE BUZZATII CLUSTER
Authors: Ruiz A , Fontdevila A , Wasserman M
Published: April 2021

Drosophila buzzatii has been found sympatric in Argentina with a closely-related sibling species, D. serido. The biogeographical, reproductive and chromosomal data allow us to combine these species into an evolutionary unit, the buzzatii cluster. Salivary gland chromosomes also have been used to determine their phylogenetic relationships with other closely related species, showing that the buzzatii cluster species share two inversions—2d  2 and 2s  6—with the species of the martensis cluster. Both clusters arose from South American populations of the ancestor of the mulleri complex, and we propose to include D. buzzatii and D. serido in the mulleri complex of the repleta group.
Dominant suppressors of yeast actin mutations that are reciprocally suppressed.
Authors: Adams A E , Botstein D
Published: April 2021

A gene whose product is likely to interact with yeast actin was identified by the isolation of pseudorevertants carrying dominant suppressors of the temperature-sensitive (Ts) act1-1 mutation. Of 30 independent revertants analyzed, 29 were found to carry extragenic suppressor mutations and of these, 24/24 tested were found to be linked to each other. This linkage group identifies a new gene SAC6, whose product, by several genetic criteria, is likely to interact intimately with actin. First, although act1-1 sac6 strains are temperature-independent (Ts+), 4/17 sac6 mutant alleles tested are Ts in an ACT1+ background. Moreover, four Ts+ pseudorevertants of these ACT1+ sac6 mutants carry suppressor mutations in ACT1; significantly, three of these are again Ts in a SAC6+ background, and are most likely new act1 mutant alleles. Thus, mutations in ACT1 and SAC6 can suppress each other's defects. Second, sac6 mutations can suppress the Ts defects of the act1-1 and act1-2, but not act1-4, mutations. This allele specificity indicates the sac6 mutations do not suppress by simply bypassing the function of actin at high temperature. Third, act1-4 sac6 strains have a growth defect greater than that due to either of the single mutations alone, again suggesting an interaction between the two proteins. The mutant sac6 gene was cloned on the basis of dominant suppression from an act1-1 sac6 mutant library, and was then mapped to chromosome IV, less than 2 cM from ARO1.
Change in chromosome number associated with a double deletion in the Neurospora crassa mitochondrial chromosome.
Authors: Gross S R , Mary A , Levine P H
Published: April 2021

The mitochondrial genome of Neurospora is usually found in a single covalently closed circular 62-kbp DNA molecule. We report here that the mitochondrial genome of a phenotypic revertant of a stopper mutant (stp-ruv) is contained primarily in two separate, nonoverlapping, autonomously replicating circular chromosomes. The circles, one about 21 kbp and the other somewhat less than 36 kbp are derived from the most frequent classes of recombinant chromosomes (21 and 41 kbp) in the chromosomal population of mitochondria in the original stopper mutant. The new, more stable chromosomal configuration, is associated with the deletion of two sequences (1 kbp and 4 kbp) at the splice junctions of the two circles. The data suggest that both deletions are likely to have originated from a single recombinational event involved in generating the 36-kbp circle. Secondary, spontaneously arising derivatives of stp-ruv have been found to yield, at high copy number, short sections of the 21-kbp circle in covalently closed supercoiled circles varying from unit length to very high multimers. The amplified segments span a common segment likely to contain the replication origin of the 21-kbp chromosome.
Haplotype-specific interactions of non-H-2-linked genetic factors controlling the mouse C4 and Slp protein levels.
Authors: Bruisten S M , Skamene E , Demant P
Published: April 2021

The influence of non-H-2 linked genes on the plasma levels of the H-2 S-region encoded proteins C4, Slp, and factor B was tested in Recombinant Inbred (RI) strains. The A X B and B X A RI strains exhibit a continuous range of C4 and Slp levels from very high to very low which reach beyond the levels of their parental strains, C57BL/6J and A/J, indicating involvement of several trans-regulatory (non-H-2-linked) genes. Only limited variation in levels of factor B has been found. No linkage relationship could be established for the trans-regulatory genes, because more than one gene is involved. A complex interaction of H-2 haplotype, genetic background, sex, and possibly maternal effect in determining the C4 and Slp protein plasma levels has been observed. The H-2-dependent sex effect is evident, because males have higher C4 levels than females in RI strains with H-2b but not with H-2a haplotype. This sex effect is also background dependent, because it is present in the H-2b congenic strain on A background (A.BY) but not in C57BL/10 and C57BL/6 (both H-2b). Mice from RI strains with H-2b haplotype have in general higher C4 levels than mice with H-2a haplotype.
A building block model for quantitative genetics.
Authors: Tachida H , Cockerham C C
Published: April 2021

We introduce a quantitative genetic model for multiple alleles which permits the parameterization of the degree, D, of dominance of favorable or unfavorable alleles. We assume gene effects to be random from some distribution and independent of the D's. We then fit the usual least-squares population genetic model of additive and dominance effects in an infinite equilibrium population to determine the five genetic components--additive variance sigma 2 a, dominance variance sigma 2 d, variance of homozygous dominance effects d2, covariance of additive and homozygous dominance effects d1, and the square of the inbreeding depression h--required to treat finite populations and large populations that have been through a bottleneck or in which there is inbreeding. The effects of dominance can be summarized as functions of the average, D, and the variance, sigma 2 D. An important distinction arises between symmetrical and nonsymmetrical distributions of gene effects. With symmetrical distributions d1 = -d2/2 which is always negative, and the contribution of dominance to sigma 2 a is equal to d2/2. With nonsymmetrical distributions there is an additional contribution H to sigma 2 a and -H/2 to d1, the sign of H being determined by D and the skew of the distribution. Some numerical evaluations are presented for the normal and exponential distributions of gene effects, illustrating the effects of the number of alleles and of the variation in allelic frequencies. Random additive by additive (a*a) epistatic effects contribute to sigma 2 a and to the a*a variance, sigma 2/aa, the relative contributions depending on the number of alleles and the variation in allelic frequencies.(ABSTRACT TRUNCATED AT 250 WORDS)
Spatial autocorrelation analysis of migration and selection.
Authors: Sokal R R , Jacquez G M , Wooten M C
Published: April 2021

We test various assumptions necessary for the interpretation of spatial autocorrelation analysis of gene frequency surfaces, using simulations of Wright's isolation-by-distance model with migration or selection superimposed. Increasing neighborhood size enhances spatial autocorrelation, which is reduced again for the largest neighborhood sizes. Spatial correlograms are independent of the mean gene frequency of the surface. Migration affects surfaces and correlograms when immigrant gene frequency differentials are substantial. Multiple directions of migration are reflected in the correlograms. Selection gradients yield clinal correlograms; other selection patterns are less clearly reflected in their correlograms. Sequential migration from different directions and at different gene frequencies can be disaggregated into component migration vectors by means of principal components analysis. This encourages analysis by such methods of gene frequency surfaces in nature. The empirical results of these findings lend support to the inference structure developed earlier for spatial autocorrelation analysis.
Evolutionary Stability for Interactions among Kin under Quantitative Inheritance.
Authors: Harper A B
Published: April 2021

The theory of evolutionarily stable strategies (ESS) predicts the long-term evolutionary outcome of frequency-dependent selection by making a number of simplifying assumptions about the genetic basis of inheritance. I use a symmetrized multilocus model of quantitative inheritance without mutation to analyze the results of interactions between pairs of related individuals and compare the equilibria to those found by ESS analysis. It is assumed that the fitness changes due to interactions can be approximated by the exponential of a quadratic surface. The major results are the following. (1) The evolutionarily stable phenotypes found by ESS analysis are always equilibria of the model studied here. (2) When relatives interact, one of the two conditions for stability of equilibria differs between the two models; this can be accounted for by positing that the inclusive fitness function for quantitative characters is slightly different from the inclusive fitness function for characters determined by a single locus. (3) The inclusion of environmental variance will in general change the equilibrium phenotype, but the equilibria of ESS analysis are changed to the same extent by environmental variance. (4) A class of genetically polymorphic equilibria occur, which in the present model are always unstable. These results expand the range of conditions under which one can validly predict the evolution of pairwise interactions using ESS analysis.