bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of reduced graphene oxide on the sunlight-driven photocatalytic activity of rGO/h-MoO3 nanocomposites
Authors: Ramar Venkadeshkumar , Karthikeyan Balasubramanian
Published: January 2021

In this present work, we explore the preparation of h-molybdenum oxide/reduced graphene oxide (h-MoO3/rGO) nanocomposites via a simple precipitation technique to enhance the photocatalytic activity of h-MoO3 under direct sunlight illumination. The phase formation h-MoO3 was confirmed by x-ray diffraction studies, Fourier transform infrared spectroscopy and Raman spectroscopic studies revealed the formation of rGO/h-MoO3 nanocomposites. The surface morphologies of the synthesized samples were analyzed through field-emission scanning electron microscopy. Moreover, the hazardous methylene blue dye degradation was studied to evaluate the photocatalytic activity of the prepared materials under direct sunlight illumination. The comparative results show that the rGO/h-MoO3 composites exhibited higher catalytic activity than the bare h-MoO3. The reason behind the enhancement of the photocatalytic activity was discussed in great detail. Moreover, in situ scavenger studies were carried out to probe the mechanism of photocatalysis.
Development of a model for registration and notification of accidents and incidents in nuclear medicine
Authors: Rodrigues Marlon Da Silva Brandão , Oliveira Susie Medeiros , de Sá Lidia Vasconcellos
Published: January 2021

Nuclear medicine (NM) is a medical speciality that uses unsealed radioactive sources involving several handling procedures with some critical points before, during, and after the examination and therapies performed, requiring special attention to the occurrence of a possible accident or incident over the course of the clinical routine. The accidents and incidents in NM can involve actors such as workers, patients, the public or caregivers, and even the environment. Although expected, the number of occurrences and their nature are not well understood due to the absence of a Brazilian reporting tool for incidents or accidents. This paper aims to develop a web-based NM incident and accident notification system named SINMED (NM Notification System). Specific forms were developed in an offline system in html5 language with an online system interface according to the Google Forms platform. The developed forms were based on existing international notification templates from the the perspective of NM services in operation applying Brazilian regulations.
Limiting regimes for electron-beam induced deposition of copper from aqueous solutions containing surfactants
Authors: Esfandiarpour Samaneh , Hastings J Todd
Published: January 2021

Focused electron beam induced deposition of pure materials from aqueous solutions has been of interest in recent years. However, controlling the liquid film in partial vacuum is challenging. Here we modify the substrate to increase control over the liquid layer in order to conduct a parametric study of copper deposition in an environmental scanning electron microscope. We identified the transition from electron to mass-transport limited deposition as well as two additional regimes characterized by aggregated and high-aspect ratio deposits. We observe a high deposition efficiency of 1–10 copper atoms per primary electron that is consistent with a radiation chemical model of the deposition process.
Fusion performance of spherical and conventional tokamaks: implications for compact pilot plants and reactors
Authors: Costley A E , McNamara S A M
Published: January 2021

Spherical tokamaks (STs) have features that make them a potentially attractive option for fusion power production compared to conventional tokamaks (CTs) including operation at high beta and high self-driven ‘bootstrap’ current. The thermal energy confinement time (τ
Ε) also typically has a stronger dependence on toroidal magnetic field and a weaker dependence on plasma current, but so far it has not been established how this difference impacts performance under reactor conditions. This aspect is explored in this paper. Using empirical data from NSTX and MAST, and from multiple CTs, we investigate analytically and by using established fusion codes the potential fusion performance, characterised by the fusion triple product, nTτ
Ε, and fusion power gain, Q
fus, where n and T are the density and temperature respectively. We find that for similar values of field and fusion power, but smaller volume, STs can have nTτ
Ε up to a factor of three higher and Q
fus an order of magnitude higher than CTs. We identify the origin of this enhanced performance and outline a measurement to advance this finding. Potentially our results open an alternative and faster route to fusion power based on relatively small, low power STs.
Time-dependent shape of bistable unsymmetric carbon fibers-epoxy thin laminates
Authors: Nicassio Francesco , Lionetto Francesca , Scarselli Gennaro , Maffezzoli Alfonso
Published: January 2021

Carbon fiber-epoxy thin laminates, manufactured adopting a [0/90] non-symmetric lay-up, are characterized by two stable curved shapes, so being bistable. These composite thin laminates are attracting great interest for their potential application as novel morphing structures and power harvesting devices in many engineering fields. The curvature changes of rectangular bistable plates were monitored at room temperature by a laser scanner system over a time span of 10 d. These changes were ascribed to the relaxation of thermal stresses over time. Anisotropic stress relaxation behavior was then studied looking at the matrix dominated properties, such as the transverse modulus in accelerated high temperature experiments and the moisture absorption. Then, a simple viscoelastic model was proposed together with a finite element analysis of the distortion arising from laminate cooling at the end of high temperature cure process. The experimental and numerical results showed that the transverse elastic modulus and the hygroscopic effect are the main factors affecting the shape relaxation of bistable laminates.
Effect on microstructure and corrosion resistance of semi-solid slurry of 7A04 aluminum alloy by electromagnetic stirring
Authors: Zhu Yanli , Xu Xiaolong , Zhao Junwen , Hu Guangzhong
Published: January 2021

The microstructures and corrosion resistance of electromagnetic stirring (EMS) semi-solid slurry and as-cast 7A04 aluminum alloy were compared in this work. The results show that the primary microstructure of the as-cast 7A04 aluminum alloy is mainly dendritic and columnar dendrite with obvious elements segregation. In contrast, semi-solid processing can effectively form homogeneous and round primary α-Al grains, and significantly reducing element segregation. In addition, the main phases of the two forming methods (as-cast and semi-solid) both involved α-Al, η-MgZn2, θ-Al2Cu. With the decrease of solidification temperature, the semi-solid alloy formed by electromagnetic stirring increases the precipitation of brittle phase S-Al2CuMg. The self-corrosion potential of the semi-solid alloy is greater than that of the as-cast alloy, and the polarization curve has obvious passivation characteristics. Semi-solid processing could improve corrosion resistance of 7A04 aluminum alloy obviously.
Recrystallization and diffusion mechanisms of segregation improvement in cast billets by high temperature reduction pretreatment
Authors: Liu Hongqiang , Cheng Zhicheng , Yu Wei , Cai Qingwu
Published: January 2021

Controlling the segregation of alloying elements in steel can improve the uniformity of the structure and properties of the material. High Temperature Reduction Pretreatment (HTRP) is an effective technique to improve the internal quality of steel by generating plastic deformation in the core and providing the recrystallization energy. Comparative analysis was conducted to illustrate the effect of the HTRP on the internal quality of 42CrMo cast billets. To quantitatively analyze the recrystallization and diffusion mechanisms, the tested samples were measured using Scanning Electron Microscopy (SEM), Original Position Statistic Distribution Analysis (OPA) and Electron Probe Microanalysis (EPMA). The results show that the plastic deformation prompts the austenite to recrystallize. As the deformation of the HTRP sample increases, the recrystallized austenite grain size decreases significantly. It is also found that the statistical macro-segregation and micro-segregation ratios of substitutional elements Si, Mn, Cr and Mo decrease. The increase in austenite grain boundaries enables the increase in diffusion coefficient of the solid solution elements, which is the main reason for improving the segregation of the cast billet.
Reaction mechanism of metakaolin materials prepared by calcining coal gangue
Authors: Jiu Shaowu , Cheng Simeng , Li Hui , Wang Lei
Published: January 2021

Metakaolin-based auxiliary cementitious materials fabricated by coal gangue were achieved. The temperature and time required for the preparation of metakaolin materials from the calcination of coal gangue were optimized based on the analysis of the reaction characteristics and kinetics during the calcination of coal gangue. The phase, microstructures, and activity analysis of the products were performed, and the effect of calcination conditions on the activity of the product was ascertained. The results of thermal analysis-infrared spectra combined experiments indicated that the dehydroxylation of kaolinite was a one-step reaction during the calcination of coal gangue within a temperature range of 379.8 °C–737.3 °C. According to the General Integration, Flynn-Wall-Ozawa and Kissinger methods, the activation energy E of dehydroxylation of kaolinite is 181.62 kJ·mol−1 and pre-index factor A is 109.27 s−1 for calculating the calcination time of metakaolin. The experimental results show that high-activity metakaolin products, that with a dissolution rate of 64.79–71.57 wt% of activated alumina and with an effective dissolution rate of 68.82–94.35 wt% of activated silica, are prepared under the condition of calcination for 15 min and the temperature of 700 °C–825 °C. The kinetic model simulation results for the calcination time at different temperatures correspond to the experimental results.
Sm3+ driven enhancement in photocatalytic degradation of hazardous dyes and photoluminescence properties of hexagonal-ZnO nanocolumns
Authors: Dash Debasrita , Panda N R , Sahu Dojalisa
Published: January 2021

Samarium doped ZnO (Sm-ZnO) nanocolumns were grown by wet chemical method and the doping effect of Sm3+ on visible light photocatalytic (PC) and photoluminescence (PL) properties of ZnO was investigated. Methylene blue (MB) and methyl orange (MO) were considered for the degradation study as a step initiated towards the remediation of industrial wastewater. Subsequent characterization studies by x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) enumerate that the hexagonal-wurtzite structured Sm-ZnO is highly crystalline in nature and possesses hexagonal column like nano-architectures. Although, a charge imbalance exists between the ions, the substitutional effects of Sm3+ at Zn2+ sites have been observed from the XRD spectra and discussed by suitable mechanisms. FTIR measurement gives the information on the evolution of peaks related to metal-oxygen bond in Sm-ZnO which may be linked with Sm ions. PC measurement shows that the degradation efficiency of 95% can be achieved by Sm-ZnO photocatalysts in degrading MB and 91% for MO. Sm doping induces high charge separation efficiency and generation of OH ions in ZnO leading to such improvisation in degradation efficiency. The prepared Sm-ZnO nanocatalysts possess high degree of photostability and reusability even after fourth cycle of photodegradation. PL spectra show the suppression of the sharp and intense excitonic emission band of ZnO in Sm-ZnO due to low rated direct recombination of carriers. Incorporation of Sm3+ ends up with intrinsic defect mediated enhancement in the visible emissions especially in the blue, yellow and red region of light spectrum.
Compactness of iso-resonant potentials for Schrödinger operators in dimensions one and three
Authors: Hislop Peter , Wolf Robert
Published: January 2021

We prove compactness of a restricted set of real-valued, compactly supported potentials

V
V

for which the corresponding Schrödinger operators

H
V

H_V

have the same resonances, including multiplicities. More specifically, let

B
R

(
0
)

B_R(0)

be the ball of radius

R
>
0

R > 0

about the origin in

R

d

\mathbb {R}^d

, for

d
=
1
,
3

d=1,3

. Let

I

R

(

V
0

)

\mathcal {I}_R (V_0)

be the set of real-valued potentials in

C
0
∞

(

B
¯

R

(
0
)
;

R

)

C_0^\infty ( \overline {B}_R(0); \mathbb {R})

so that the corresponding Schrödinger operators have the same resonances, including multiplicities, as

H

V
0

H_{V_0}

, for a fixed, but arbitrary, potential

V
0

∈

C
0
∞

(

B
¯

R

(
0
)
;

R

)

V_0 \in C_0^\infty ( \overline {B}_R(0); \mathbb {R})

. We prove that the set

I

R

(

V
0

)

\mathcal {I}_R (V_0)

is a compact subset of

C
0
∞

(

B
¯

R

(
0
)
)

C_0^\infty (\overline {B}_R(0))

in the

C
∞

C^\infty

-topology. An extension to Sobolev spaces of less regular potentials is discussed.
Blood Pressure in Childhood and Adolescence
Authors: Hardy Shakia T , Urbina Elaine M
Published: January 2021

Elevated blood pressure (BP) and hypertension commonly occur in children and adolescents and increase the risk of cardiovascular disease in adulthood. The purpose of this review is to summarize recent research in pediatric hypertension including changes in defining hypertension, BP measurement techniques, hypertension epidemiology, risk factors, treatment, and BP-related target organ damage. Defining pediatric hypertension using the 2017 American Academy of Pediatrics’ updated Clinical Practice Guideline resulted in a larger proportion of children being classified as having elevated BP or hypertension compared with prior guidelines. Trends in the distribution of BP among US children and adolescents suggest that BP levels and the prevalence of hypertension may have increased from 2011–2014 to 2015–2018. Factors including a family history of hypertension, obesity, minority race/ethnicity, physical inactivity, high dietary intake of sodium, and poor sleep quality are associated with an increased prevalence of elevated BP and hypertension. Evidence of a linear relationship between systolic BP and target organ damage indicates that BP levels currently considered normal could increase the risk of target organ damage in childhood. Lifestyle changes, such as adhering to the Dietary Approaches to Stop Hypertension diet, are a central component of effectively reducing BP and have been shown to reduce target organ damage. Pharmacologic treatment using angiotensin-converting enzyme inhibitors and angiotensin receptor blockers is an effective and safe method for reducing BP among children with uncontrolled BP after implementing lifestyle changes. Research gaps in the prevention, detection, classification, and treatment of hypertension in children demonstrate opportunities for future study.
Alignment-free Genomic Analysis via a Big Data Spark Platform
Authors: Ferraro Petrillo Umberto , Palini Francesco , Cattaneo Giuseppe , Giancarlo Raffaele
Published: January 2021

Motivation

Alignment-free distance and similarity functions (AF functions, for short) are a well-established alternative to pairwise and multiple sequence alignments for many genomic, metagenomic and epigenomic tasks. Due to data-intensive applications, the computation of AF functions is a Big Data problem, with the recent literature indicating that the development of fast and scalable algorithms computing AF functions is a high-priority task. Somewhat surprisingly, despite the increasing popularity of Big Data technologies in computational biology, the development of a Big Data platform for those tasks has not been pursued, possibly due to its complexity.

Results

We fill this important gap by introducing FADE, the first extensible, efficient and scalable Spark platform for alignment-free genomic analysis. It supports natively eighteen of the best performing AF functions coming out of a recent hallmark benchmarking study. FADE development and potential impact comprises novel aspects of interest. Namely, (i) a considerable effort of distributed algorithms, the most tangible result being a much faster execution time of reference methods like MASH and FSWM; (ii) a software design that makes FADE user-friendly and easily extendable by Spark non-specialists; (iii) its ability to support data- and compute-intensive tasks. About this, we provide a novel and much needed analysis of how informative and robust AF functions are, in terms of the statistical significance of their output. Our findings naturally extend the ones of the highly regarded benchmarking study, since the functions that can really be used are reduced to a handful of the eighteen included in FADE.

Availabilityand implementation

The software and the datasets are available at https://github.com/fpalini/fade.

Supplementary information

Supplementary data are available at Bioinformatics online.
Comparison of management and outcomes of ST-segment elevation myocardial infarction patients in Estonia, Hungary, Norway, and Sweden according to national ongoing registries
Authors: Blöndal Mai , Ainla Tiia , Eha Jaan , Lõiveke Piret , Marandi Toomas , Saar Aet , Veldre Gudrun , Edfors Robert , Lewinter Christian , Jernberg Tomas , Jortveit Jarle , Halvorsen Sigrun , Becker Dávid , Csanádi Zoltán , Ferenci Tamas , Andréka Péter , Jánosi András
Published: January 2021

Aims

Describe the characteristics, management and outcomes of hospitalized ST-segment elevation myocardial infarction (STEMI) patients according to national ongoing myocardial infarction registries in Estonia, Hungary, Norway, and Sweden.

Methods and results

Country-level aggregated data was used to study baseline characteristics, use of in-hospital procedures, medications at discharge, in-hospital complications, 30-day and 1-year mortality for all patients admitted with STEMI during 2014–2017 using data from EMIR (Estonia; n = 4584), HUMIR (Hungary; n = 23 685), NORMI (Norway; n = 12 414, data for 2013–2016), and SWEDEHEART (Sweden; n = 23 342). Estonia and Hungary had a higher proportion of women, patients with hypertension, diabetes, and peripheral artery disease compared to Norway and Sweden. Rates of reperfusion varied from 75.7% in Estonia to 84.0% in Sweden. Rates of recommendation of discharge medications were generally high and similar. However, Estonia demonstrated the lowest rates of dual antiplatelet therapy (78.1%) and statins (86.5%). Norway had the lowest rates of beta-blockers (80.5%) and angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers (61.5%). The 30-day mortality rates ranged between 9.9% and 13.4% remaining lowest in Sweden. One-year mortality rates ranged from 14.8% in Sweden and 16.0% in Norway to 20.6% in Hungary and 21.1% in Estonia. Age-adjusted lethality rates were highest for Hungary and lowest for Sweden.

Conclusion

This inter-country comparison of data from four national ongoing European registries provides new insights into the risk factors, management and outcomes of patients with STEMI. There are several possible reasons for the findings, including coverage of the registries and variability of baseline-characteristics’ definitions that need to be further explored.
Concurrent use of P-glycoprotein or Cytochrome 3A4 drugs and non-vitamin K antagonist oral anticoagulants in non-valvular atrial fibrillation
Authors: Sandhu Roopinder K , Islam Sunjidatul , Dover Douglas C , Andrade Jason G , Ezekowitz Justin , McAlister Finlay A , Hawkins Nathaniel M , Kaul Padma
Published: January 2021

Aim

To determine the concurrent use of P-glycoprotein (P-gp) or Cytochrome (CYP) 3A4 drugs and non-vitamin K antagonist oral anticoagulants (NOACs) among non-valvular AF (NVAF) patients in clinical practice.

Methods and results

Administrative databases identified all adults (≥18 years) with incident or prevalent NVAF who initiated a NOAC in an outpatient or inpatient setting, between July 2012 and March 2019 in Alberta, Canada. Concurrent use was defined as a P-gp or CYP3A4 dispensation in the 100 days prior to and overlapping NOAC dispensation. The P-gp and CYP3A4 drugs were categorized into three groups and drug-drug interactions classified according to the 2018 European Heart Rhythm Association practical guide. Time-varying Cox models calculated the crude hazard ratio (HR) of outcomes at 1-year. A total of 642 255 NOAC dispensations occurred for 36 566 NVAF patients. Of these, 71 643 (11.2%) had a concurrent dispensation of an interacting P-gp or CYP3A4 drug. Overall, the drug–drug interaction was defined as contraindicated in 2.5%, avoid/caution in 2.3%, and for another 6.7% should require a dose adjustment. When all drug–drug interactions were considered, inappropriate NOAC prescribing occurred in 63% (n = 45 080) of dispensations. There was a significantly higher risk of death (HR 1.58, 1.47–1.70) for a drug–drug interaction but not for stroke (P = 0.89) or major bleeding risk (P = 0.13).

Conclusions

The concurrent use of P-gp or CYP3A4 drugs and NOACs was uncommon but important since almost two-thirds of patients with drug–drug interactions had inappropriate NOAC dosing and a higher risk of death. More attention to this issue is needed.
Future burden of cardiovascular disease in Australia: impact on health and economic outcomes between 2020 and 2029
Authors: Marquina Clara , Talic Stella , Vargas-Torres Sandra , Petrova Marjana , Abushanab Dina , Owen Alice , Lybrand Sean , Thomson David , Liew Danny , Zomer Ella , Ademi Zanfina
Published: January 2021

Aims

To estimate the health and economic burden of new and established cardiovascular disease from 2020 to 2029 in Australia.

Methods and results

A two-stage multistate dynamic model was developed to predict the burden of the incident and prevalent cardiovascular disease, for Australians 40–90 years old from 2020 to 2029. The model captured morbidity, mortality, years of life lived, quality-adjusted life years, healthcare costs, and productivity losses. Cardiovascular risk for the primary prevention population was derived using Australian demographic data and the Pooled Cohort Equation. Risk for the secondary prevention population was derived from the REACH registry. Input data for costs and utilities were extracted from published sources. All outcomes were annually discounted by 5%. A number of sensitivity analyses were undertaken to test the robustness of the study. Between 2020 and 2029, the model estimates 377 754 fatal and 991 375 non-fatal cardiovascular events. By 2029, 1 061 756 Australians will have prevalent cardiovascular disease (CVD). The population accrued 8 815 271 [95% uncertainty interval (UI) 8 805 083–8 841 432] years of life lived with CVD and 5 876 975 (5 551 484–6 226 045) QALYs. The total healthcare costs of CVD were projected to exceed Australian dollars (AUD) 61.89 (61.79–88.66) billion, and productivity losses will account for AUD 78.75 (49.40–295.25) billion, driving the total cost to surpass AUD 140.65 (123.13–370.23) billion.

Conclusion

Cardiovascular disease in Australia has substantial impacts in terms of morbidity, mortality, and lost revenue to the healthcare system and the society. Our modelling provides important information for decision making in relation to the future burden of cardiovascular disease.
EVIDENCE FOR EXTENSIVE GENETIC DIFFERENTIATION BETWEEN THE SEX-RATIO AND THE STANDARD ARRANGEMENT OF DROSOPHILA PSEUDOOBSCURA AND D. PERSIMILIS AND IDENTIFICATION OF HYBRID STERILITY FACTORS
Authors: Wu Chung-I , Beckenbach Andrew T
Published: January 2021

This study deals with sex-ratio genes tightly linked within the Sex-Ratio inversion. By taking advantage of the fact that the Sex-Ratio chromosome of Drosophila persimilis [SR(B)] is homosequential to the Standard chromosome of D. pseudoobscura [ST(A)], we carried out two reciprocal introgression experiments. Individual segments of SR(B) or ST(A) were introgressed into the genome of D. pseudoobscura or D. persimilis, respectively. Males possessing a hybrid SR(B)-ST(A) X chromosome and a genetic background derived from either of the two species were tested for fertility and sex-ratio expression.—It was found that, in terms of the meiotic drive genes, the Sex-Ratio chromosome differs extensively from the Standard chromosome. Because recombinations of these genes result in a complete loss of sex-ratio expression, this finding lends strong support to the hypothesis of gene coadaptation. Coadaptation, in this context, is the advantage of being transmitted preferentially. In light of this finding, the evolution of the sex-ratio system in these two sibling species is discussed.—Introgression experiments also yielded information about hybrid sterility. With reciprocal introgression, sterility interactions were found to be "asymmetric." The asymmetry is fully expected from the viewpoint of evolution of postmating reproductive isolation.
SELECTION AND ENDPOINT DISTRIBUTION OF BACTERIAL INVERSION MUTATIONS
Authors: Schmid Molly B , Roth John R
Published: January 2021

This paper describes the isolation and characterization of spontaneous inversion mutants of Salmonella typhimurium. The mutants are selected by demanding that an unexpressed hisD gene acquire a new promoter. Chromosome rearrangements that juxtapose the hisD gene and a foreign promoter are obtained by this selection. Although a number of inversions are found, the frequency was lower than expected. The breakpoints of these inversions are not distributed randomly either in the his operon or on the chromosome. The his breakpoint lies in the hisG-hisD intercistronic region, a sequence known to occur at several places on the bacterial chromosome. In most of the inversions, the "non-his" breakpoint lies across the chromosome, so that the inverted region includes the origin or terminus of DNA replication. The significance of these results is discussed.
GENETIC LINKAGE IN THE HORSE. II. DISTRIBUTION OF MALE RECOMBINATION ESTIMATES AND THE INFLUENCE OF AGE, BREED AND SEX ON RECOMBINATION FREQUENCY
Authors: Andersson Leif , Sandberg Kaj
Published: January 2021

n the present study an extensive amount of data, comprising more than 30,000 offspring in total, was analyzed to evaluate the influence of age and sex on the recombination frequency in the K-PGD segment of the equine linkage group (LG) I and the influence of age, breed and sex on recombination in the Al-Es segment of LG II. A highly significant sex difference is reported for both segments. Male and female recombination values in the K-PGD segment were estimated at 25.8 ± 0.8 and 33.3 ± 2.5%, respectively. Similarly, recombination was less frequent in the male (36.6 ± 0.7%) than in the female (46.6 ± 1.2%) in the Al-Es segment. Comparison of data from two Swedish horse breeds revealed no significant breed differences in either sex for recombination in the Al-Es segment. No evidence of an age effect was found in any segment or sex. The distribution of individual male recombination estimates was also investigated, and a significant heterogeneity among stallions was revealed in the K-PGD segment. The results are discussed in relation to previous studies on factors affecting recombination in mammals.
AN ANALYSIS OF REGIONAL CONSTRAINTS ON EXCHANGE IN DROSOPHILA MELANOGASTER USING RECOMBINATION-DEFECTIVE MEIOTIC MUTANTS
Authors: Szauter Paul
Published: January 2021

The frequency of crossing over per unit of physical distance varies systematically along the chromosomes of Drosophila melanogaster. The regional distribution of crossovers in a series of X chromosomes of the same genetic constitution, but having different sequences, was compared in the presence and absence of normal genetically mediated regional constraints on exchange. Recombination was examined in Drosophila melanogaster females homozygous for either normal sequence X chromosomes or any of a series of X chromosome inversions. Autosomally, these females were either (1) wild type, (2) homozygous for one of several recombination-defective meiotic mutations that attenuate the normal regional constraints on exchange or (3) heterozygous for the multiply inverted chromosome TM2. The results show that the centromere, the telomeres, the heterochromatin and the euchromatic-heterochromatic junction do not serve as elements that respond to genic determinants of the regional distribution of exchanges. Instead, the results suggest that there are several elements sparsely distributed in the X chromosome euchromatin. Together with the controlling system affected by recombination-defective meiotic mutations, these elements specify the regional distribution of exchanges. The results also demonstrate that the alteration in the distribution of crossovers caused by inversion heterozygosity (the interchromosomal effect) results from the response of a normal controlling system to an overall increase in the frequency of crossing over, rather than from a disruption of the system of regional constraints on exchange that is disrupted by meiotic mutations. The mechanisms by which regional constraints on exchange might be established are discussed, as is the possible evolutionary significance of this system.
DISTRIBUTION OF NONSTRUCTURAL VARIATION ALONG THREE CHROMOSOME ARMS BETWEEN WHEAT CULTIVARS CHINESE SPRING AND CHEYENNE
Authors: Crossway Anne , Dvořák Jan
Published: January 2021

Metaphase I (MI) pairing of wheat homologous chromosomes is usually reduced in hybrids between cultivars relative to the parental inbred lines. Previous work suggested that this phenomenon is caused by polymorphism in nucleotide sequences (nonstructural chromosome variation) among wheat cultivars. The present work investigated the distribution of this variation along three selected chromosome arms between cultivars Chinese Spring and Cheyenne. Chinese Spring ditelosomics 3Aq, 6Ap and 6Bp were crossed with disomic substitutions of Cheyenne chromosomes 3A, 6A and 6B in Chinese Spring, respectively. The resulting F1 plants, called substituted monotelodisomics, were crossed with the respective Chinese Spring monosomics, producing potentially "recombinant" substituted monosomics. When these "recombinant" chromosomes were combined with the parental Chinese Spring telosomes, marked reductions in mean telosome-pairing frequency were found compared with the corresponding Chinese Spring monotelodisomics. The mean pairing frequencies of the "recombinant" chromosomes showed a continuous distribution between those of the substituted and Chinese Spring monotelodisomics. The results suggest that the nonstructural variation that reduces MI pairing between chromosomes of different wheat cultivars is not localized in a specific site but distributed along each chromosome arm. Little variation was found among monotelodisomics for either the number of ring bivalents per cell or the number of univalents other than those constituting the heteromorphic pair. This implies that the reductions in MI pairing between the Cheyenne and Chinese Spring chromosomes are caused by something residing within these specific chromosomes that does not affect the pairing of the remaining Chinese Spring chromosomes in the same cell. Furthermore, the absence of parental types among the "recombinant"-substituted monotelodisomics suggests that the sequences involved in the variation studied here are capable of converting heterohomologous chromosomes to something intermediate in nature in the span of only a single generation.
THE GENETIC ANALYSIS OF A CHROMOSOME-SPECIFIC MEIOTIC MUTANT THAT PERMITS A PREMATURE SEPARATION OF SISTER CHROMATIDS IN DROSOPHILA MELANOGASTER
Authors: Gethmann Richard C
Published: January 2021

mei-G87 is a recessive meiotic mutant that increases second chromosome nondisjunction in both males and females. A significant proportion of the diplo-2 exceptions are equational. In females, diplo-2 reductional exceptions are usually noncrossovers, but, in equational exceptions, crossover frequency and distribution are the same as that found in the haplo-2 controls. The frequencies of nondisjunction are relatively low: 0.6% in females and 1.3% in males. Nondisjunction frequency is affected by environmental conditions (possibly humidity). The defect in mei-G87, as in other "second division" mutants, appears to be a failure to maintain sister-chromatid cohesion. mei-G87 increases nondisjunction of only the second chromosome. This may indicate either a weak mutant with only the second chromosome being sensitive enough to misbehave or it may indicate that chromosome-specific regions responsible for sister-chromatid cohesion exist.
R-STIPPLED MAIZE AS A TRANSPOSABLE ELEMENT SYSTEM
Authors: Williams W M , Satyanarayana K V , Kermicle J L
Published: January 2021

The I-R element at the R locus destabilizes kernel pigmentation giving the variegated pattern known as stippled (R-st). In trans linkage phase with R-st the element was shown to act as a modifier of stippled, intensifying seed spotting in parallel with effects of the dominant linked modifier M-st. Presence of I-R in the genome was, therefore, shown to be detectable as a modifier of R-st. When this test was used, new modifiers resembling M-st were often detected following mutations of R-st to the stable allele R-sc. Such mutations evidently occurred by transposition of I-R away from the R locus to a site where it was identifiable as a modifier. M-st may be such a transposed I-R. Analysis of mutations to R-sc during the second (sperm-forming) mitosis in pollen grains showed that some of the transposed I-R elements were linked with R, whereas others assorted independently. Their strengths varied from barely discernible to a level equal to M-st. Overreplication frequently accompanied transposition at the sperm-forming mitosis, leading to transposed I-R elements in both the mutant and nonmutant sperm.
CYTOGENETIC ANALYSIS OF A SEGMENT OF THE Y CHROMOSOME OF DROSOPHILA MELANOGASTER
Authors: Hardy Robert W , Lindsley Dan L , Livak Kenneth J , Lewis Barbara , Siversten Annegrethe L , Joslyn Geoffrey L , Edwards Jacqueline , Bonaccorsi Silvia
Published: January 2021

Males carrying a large deficiency in the long arm of the Y chromosome known to delete the fertility gene kl-2 are sterile and exhibit a complex phenotype: (1) First metaphase chromosomes are irregular in outline and appear sticky; (2) spermatids contain micronuclei; (3) the nebenkerns of the spermatids are nonuniform in size; (4) a high molecular weight protein ordinarily present in sperm is absent; and (5) crystals appear in the nucleus and cytoplasm of spermatocytes and spermatids. In such males that carry Ste  + on their X chromosome the crystals appear long and needle shaped; in Ste males the needles are much shorter and assemble into star-shaped aggregates. The large deficiency may be subdivided into two shorter component deficiencies. The more distal is male sterile and lacks the high molecular weight polypeptide; the more proximal is responsible for the remainder of the phenotype. Ste males carrying the more proximal component deficiency are sterile, but Ste  + males are fertile. Genetic studies of chromosome segregation in such males reveal that (1) both the sex chromosomes and the large autosomes undergo nondisjunction, (2) the fourth chromosomes disjoin regularly, (3) sex chromosome nondisjunction is more frequent in cells in which the second or third chromosomes nondisjoin than in cells in which autosomal disjunction is regular, (4) in doubly exceptional cells, the sex chromosomes tend to segregate to the opposite pole from the autosomes and (5) there is meiotic drive; i.e., reciprocal meiotic products are not recovered with equal frequencies, complements with fewer chromosomes being recovered more frequently than those with more chromosomes. The proximal component deficiency can itself be further subdivided into two smaller component deficiencies, both of which have nearly normal spermatogenic phenotypes as observed in the light microscope. Meiosis in Ste  + males carrying either of these small Y deficiencies is normal; Ste males, however, exhibit low levels of sex chromosome nondisjunction with either deficient Y. The meiotic phenotype is apparently sensitive to the amount of Y chromosome missing and to the Ste constitution of the X chromosome.
ORGANIZATION AND MAPPING OF A SEQUENCE ON THE DROSOPHILA MELANOGASTER X AND Y CHROMOSOMES THAT IS TRANSCRIBED DURING SPERMATOGENESIS
Authors: Livak Kenneth J
Published: January 2021

The D. melanogaster DNA segment in the recombinant phage λDm2L1 contains at least eight copies of a tandemly repeated 1250-base pair (bp) sequence (henceforth called the 2L1 sequence). Testes from XO D. melanogaster males contain an abundant 800-base RNA species that is homologous to a 520-bp region of the 2L1 sequence. Blotting experiments show that the 2L1 sequence is repeated in the D. melanogaster genome and is present on both the X and Y chromosomes. With the use of X-Y translocations, the 2L1 sequence has been mapped to a region between kl-1 and kl-2 on the long arm of the Y chromosome. In Oregon-R wild type there are an estimated 200 copies of the 2L1 sequence on the X chromosome and probably at least 80 copies on the Y chromosome. In some other strains the repetition frequency on the Y chromosome is about the same, but the copy number on the X chromosome is much reduced. On the basis of the five strains investigated, there is a correlation between copy number of the 2L1 sequence on the X chromosome and the presence of a particular allele of the Stellate locus (Ste; 1-45.7). It seems that low copy number corresponds to Ste  + and high copy number corresponds to Ste. The Ste locus determines whether single or star-shaped crystals are observed in the spermatocytes of XO males. Studies using D. simulans and D. mauritiana DNA show that the 2L1 sequence is homologous to restriction fragments in male DNA but not female DNA, indicating that this sequence is present only on the Y chromosome in these two species. In DNA derived from D. erecta, D. teissieri and D. yakuba, there is very little, if any, hybridization with the 2L1 sequence probe.
MUTATIONS AND CHROMOSOMAL REARRANGEMENTS AFFECTING THE EXPRESSION OF SNAIL, A GENE INVOLVED IN EMBRYONIC PATTERNING IN DROSOPHILA MELANOGASTER
Authors: Grau Yves , Carteret Cathie , Simpson Pat
Published: January 2021

Mutants at the snail locus are zygotically acting embryonic lethals that affect dorsoventral patterning. A comparison of seven mutant alleles shows considerable variation in expressivity and a graded effect along the dorsoventral axis: more extreme alleles result in the abnormal development of the dorsally derived ectoderm as well as the ventrally derived mesoderm, whereas weaker alleles affect only development of the mesoderm. Animals transheterozygous for different mutant alleles occasionally survive to adulthood; they frequently have missing halteres and more rarely are hemithorax. The mutant phenotype of snail is shown here to be enhanced zygotically by haploidy of two nearby regions on the second chromosome: the elbow to no-ocelli region and the interval defined by l(2)br36 and l(2)br37. It is concluded that the products of all of these genes function together in the process of specification of pattern in the embryo.
TIME OF RECOMBINATION IN THE DROSOPHILA MELANOGASTER OOCYTE. III. SELECTION AND CHARACTERIZATION OF TEMPERATURE-SENSITIVE AND -INSENSITIVE, RECOMBINATION-DEFICIENT ALLELES IN DROSOPHILA
Authors: Grell R F
Published: January 2021

The procedure for the selection of a temperature-sensitive recombination mutant in Drosophila is described. Use of this procedure has led to the recovery of three alleles at a new recombination locus called rec-1, located within the region of chromosome 3 circumscribed by Deficiency(3R)sbd  105. One allele, rec-1  26, is temperature sensitive, and the other two alleles, rec-1  6 and rec-1  16, are temperature insensitive. Gene dosage studies reveal rec-1  26 to be a leaky mutant with greater recombination activity in two doses than in one. The other two alleles show no dose response, implying that they may be null mutants. The temperature response curves of rec-1  26 as a homozygote and in heteroallelic combination with rec-1  16 suggest that the sharp decrease in recombination between 28° and 31° indicates temperature denaturation of an enzyme or other protein specified by the mutant and associated with the recombination process. The ability of small changes in temperature to reverse or abolish polarity in recombination along the X chromosome arm in rec-1  26/rec-1  16 females brings into question the use of the "polarity" criterion to partition mutants into two functional types, i.e., precondition mutants that display polarity and exchange mutants that do not. Evidence that rec-1 may be part of a complex locus residing in a chromosome segment harboring a variety of recombination-related genes is presented.
DOES CHI GIVE OR TAKE?
Authors: Stahl Franklin W , Lieb M , Stahl Mary M
Published: January 2021

In lytic cycle crosses with Red-Gam-λ phage, particles were examined that had undergone an Int-mediated exchange. It was assumed that this exchange dimerized the circular λ, making it packageable. Among these Int-mediated recombinants, particles were identified that had, in addition, enjoyed a close double exchange mediated by the RecBC pathway. Such close double exchanges indicate localized negative interference and are analogous to eukaryotic conversions that have retained parental configuration of flanking markers. These events are stimulated by Chi, a recombinator specific to the RecBC pathway. When Chi is present in only one parent in the cross, the complementary double exchange recombinants are Chi stimulated to the same degree. This behavior of Chi contrasts with that of characterized eukaryotic recombinators.
TISSUE-SPECIFIC AND PRETRANSLATIONAL CHARACTER OF VARIANTS OF THE ROSY LOCUS CONTROL ELEMENT IN DROSOPHILA MELANOGASTER
Authors: Clark S H , Daniels S , Rushlow C A , Hilliker A J , Chovnick A
Published: January 2021

Prior reports from this laboratory have described the experimental basis for our understanding of the genetic organization of the rosy locus (ry:3-52.0) of Drosophila melanogaster, as a bipartite genetic entity consisting of a structural element that codes for the xanthine dehydrogenase (XDH) peptide and a contiguous, cis-acting control element. The present report describes our progress in the analysis of the control element and its variants. Characterization of the control element variants reveals that, with respect to late third instar larval tissue distribution of XDH activity and cross-reacting material, i409H is associated with a large, tissue-specific increase in fat body which is not observed in malpighian tubules. Further data are presented in support of the inference that this differential expression must reflect differential production of XDH-specific RNA transcripts.—Gel blot analyses are described which demonstrate (1) that the phenotypic effects associated with variation in the rosy locus control element relate to differences in accumulation of XDH-specific poly-A+ RNA and (2) do not relate to differences in rosy DNA template numbers.—Experiments are described that provide for unambiguous mapping of control element sites through the use of half-tetrad recombination experiments and the recovery and phenotypic characterization of the reciprocal products of exchange between control element site variants. Thus, we are able to order the sites as follows: kar-i1005 i409-ry.
POLYANDRY IN HONEY BEES (APIS MELLIFERA L.): SPERM UTILIZATION AND INTRACOLONY GENETIC RELATIONSHIPS
Authors: Laidlaw Harry H , Page Robert E
Published: January 2021

Sperm usage by queen honey bees was examined by progeny analyses using six phenotypically distinct genetic markers. No evidence was found for sperm displacement or precedence. All queens used the sperm of all males that inseminated them during all sampling periods. Sperm usage, as measured by phenotypic frequencies, did fluctuate nonrandomly but did not result in abnormally high representation of a single phenotype or the elimination of other phenotypes as has often been suggested. The genetic relationships of workers within honey bee colonies are estimated from the data presented. Average genetic relatedness is shown to be low among colony nestmates and probably approaches 0.25 in colonies with naturally mated queens. There is no evidence for elevated relatedness among colony subfamilies due to nonrandom fluctuations in sperm usage by queens or for numerical dominance of any subfamilies.
STABLE EQUILIBRIA AT TWO LOCI IN POPULATIONS WITH LARGE SELFING RATES
Authors: Hastings Alan
Published: January 2021

The equilibrium structure of two-locus, two-allele models with very large selfing rates is found using perturbation techniques. For free recombination, r = ½, the following results hold. If the heterozygotes do not have at least an approximate 30% advantage in fitness relative to homozygotes, a stable equilibrium with all alleles present is possible only if all of the homozygote fitnesses differ at most by approximately the outcrossing rate, t, and all stable polymorphic equilibria have disequilibrium values, D, that are at most on the order of the outcrossing rate. Once the heterozygote fitnesses are above the threshold, there are stable equilibria possible with D near its maximum possible value. The results show that the observed disequilibria in highly selfed plant populations are not likely to result from selection leading to an equilibrium.
MEIOTIC RECOMBINATION BETWEEN DUPLICATED GENETIC ELEMENTS IN SACCHAROMYCES CEREVISIAE
Authors: Jackson Jennifer A , Fink Gerald R
Published: January 2021

We have studied the meiotic recombination behavior of strains carrying two types of duplications of an 18.6-kilobase HIS4 BamHI fragment. The first type is a direct duplication of the HIS4 BamHI fragment in which the repeated sequences are separated by Escherichia coli plasmid sequences. The second type, a tandem duplication, has no sequences intervening between the repeated yeast DNA. The HIS4 genes in each region were marked genetically so that recombination events between the duplicated segments could be identified. Meiotic progeny of the strains carrying the duplication were analyzed genetically and biochemically to determine the types of recombination events that had occurred. Analysis of the direct vs. tandem duplication suggests that the E. coli plasmid sequences are recombinogenic in yeast when homozygous. In both types of duplications recombination between the duplicated HIS4 regions occurs at high frequency and involves predominantly interchromosomal reciprocal exchanges (equal and unequal crossovers). The striking observation is that intrachromosomal reciprocal recombination is very rare in comparison with interchromosomal reciprocal recombination. However, intrachromosomal gene conversion occurs at about the same frequency as interchromosomal gene conversion. Reciprocal recombination events between regions on the same chromatid are the most infrequent exchanges. These data suggest that intrachromosomal reciprocal exchanges are suppressed.