bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluating escalation in oil pollution and its framing: approaches used by the print media for coverage
Authors: Odoemelam Chika Ebere , Hasan Nik Norma Nik
Published: January 2021

Oil pollution incidents have become a reoccurring decimal in most countries during the last twenty decades. The controversy about who is responsible for the massive oil pollution experienced globally in certain oil-producing countries has amplified tensions between significant stakeholders in those countries. For example, oil pollution in Nigeria and Ghana has triggered ecosystem degradation, the devastation of local communities’ means of livelihood, and the death of aquatic organisms such as fish. This paper discusses the escalation in oil pollution and the print media’s coverage through a content analysis method. Our report evaluates news approaches developed by Semetko and Valkenburg (2000a, 2000b) and differences and similarities in the distribution of news frames among three Nigerian newspapers; The Daily Sun, The Guardian, and The Punch from 2014–2018. Our findings show that The Daily Sun used more of the frames of responsibility, economic consequences, and human interest in their oil pollution reports in the Niger-Delta region. This is probably because journalists at The Daily Sun often chose to be objective and on the people’s side by reporting the whole truth irrespective of the consequences to their job and news organization. This was in harmony with the quantitative content analysis results, where 57.7%, 63.3%, and 55.6% of oil pollution coverage were framed as responsibility, economic consequences, and human interest. In contrast, The Guardian and The Punch newspapers used less of these frames, perhaps due to the two papers’ laissez-faire attitude towards holding the oil companies accountable despite glaring evidence of the negative consequences of oil pollution on the livelihood of oil-bearing communities and the environment. However, our result also indicates that the morality frame was the least used among the three selected newspapers, as journalists find it challenging to give moral messages while maintaining journalistic neutrality.
On the failure and fracture of hydrogels for cartilage replacement
Authors: Cook Robert F , Oyen Michelle L
Published: January 2021

The failure and fracture properties of hydrogels and hydrogel composites are considered in the contexts of applicable fracture mechanics and biomaterials engineering. Distinction is made between material failure properties, characterized by a work of failure independent of mechanism, and fracture properties, characterized by fracture resistance that requires clear identification of crack propagation. Although advanced hydrogels can exhibit very large works of failure relative to conventional single-network hydrogels, they do so only at large strains and are not well characterized by fracture properties alone. The large failure strains are not obviously relevant to many biomaterial applications such as cartilage replacement, for which the engineering requirements involve limited physiological strains. An example is given of fiber-reinforced hydrogel composites that demonstrate increased work of failure at small strains.
Exciton band structure of molybdenum disulfide: from monolayer to bulk
Authors: Fugallo Giorgia , Cudazzo Pierluigi , Gatti Matteo , Sottile Francesco
Published: January 2021

Exciton band structures analysis provides a powerful tool to identify the exciton character of materials, from bulk to isolated systems, and goes beyond the mere analysis of the optical spectra. In this work, we focus on the exciton properties of molybdenum sisulfide (MoS2) by solving the ab initio many-body Bethe–Salpeter equation, as a function of momentum, to obtain the excitation spectra of both monolayer and bulk MoS2. We analyse the spectrum and the exciton dispersion on the basis of a model excitonic Hamiltonian capable of providing an efficient description of the excitations in the bulk crystal, starting from the knowledge of the excitons of a single layer. In this way, we obtain a general characterization of both bright and darks excitons in terms of the interplay between the electronic band dispersion (i.e. interlayer hopping) and the electron–hole exchange interaction. We identify for both the 2D and the 3D limiting cases the character of the lowest-energy excitons in MoS2, we explain the effects and relative weights of both band dispersion and electron–hole exchange interaction and finally we interpret the differences observed when changing the dimensionality of the system.
Fundamental aspects of graphene and its biosensing applications
Authors: Tade Rahul Shankar , Nangare Sopan Namdev , Patil Pravin Onkar
Published: January 2021

The worldwide frontiers of research have experienced a flood of developments in advanced nanomaterials. Among these, graphene, a member of the carbon family, has now replaced many traditional materials and broadened the horizons of material chemistry, analytical chemistry, pharmaceutics, and other multidisciplinary fields. Owing to the exceptional properties of graphene, it has been widely utilized in various nanocomposites as a reinforcing material and for biosensing components. The present review serves as a familiarization for budding researchers in the materials science and analytical fields, where the use of graphene in biosensing-related applications had long been foreseen. Furthermore, we also offer a brief review of graphene’s tunable properties for biosensing. This article describes the actual mechanisms of interfaces that interact with graphene, such as immunogenic agents, bacteria, and other biomolecules. We also discuss the application of graphene-based materials to the biosensing of a range of analytes, and the challenges and future perspectives of graphene. Thus, this review gives a detailed insight into biosensing with graphene, graphene’s fundamental properties, and application perspectives.
Evaluation of mechanical performance on a developed AA 6061matrix-Mg/0.9-Si/0.68 reinforced with B4C based composites
Authors: Singh Hartaj , Singh Gagandeep , Singh Kapil , Vardhan Sachit
Published: January 2021

Aluminum matrix composites are chosen for electronic, aircraft, and automobile components due to the lightness of their weight and high specific strength. High-quality aluminum-based composites are well known for their microhardness and high refractoriness performance in aerospace with the advantage of structural applications. The boron carbide ceramic as a reinforcement plays an outstanding function in the base matrix to enhance the mechanical behavior of the composites. The present effort revealed that the synthesized composites were fabricated by the stir casting process and B4C having a particulate size of 50 µm were reinforced from 1% to 15% in the AA 6061 by varying weight percentages. Microhardness such as Brinell and Rockwell hardness moreover impact testing was performed experimentally. The mechanical characterization of fabricated composites with high mechanical performance-based composites has been investigated in this research work. Using microstructural characterization by scanning electron microscopy and x-ray diffraction we examinded high mechanical performance-based composites.
Computational phase transitions: benchmarking Ising machines and quantum optimisers
Authors: Philathong Hariphan , Akshay Vishwa , Samburskaya Ksenia , Biamonte Jacob
Published: January 2021

While there are various approaches to benchmark physical processors, recent findings have focused on computational phase transitions. This is due to several factors. Importantly, the hardest instances appear to be well-concentrated in a narrow region, with a control parameter allowing uniform random distributions of problem instances with similar computational challenge. It has been established that one could observe a computational phase transition in a distribution produced from coherent Ising machine(s). In terms of quantum approximate optimisation, the ability for the quantum algorithm to function depends critically on the ratio of a problems constraint to variable ratio (called density). The critical density dependence on performance resulted in what was called, reachability deficits. In this perspective we recall the background needed to understand how to apply computational phase transitions in various bench-marking tasks and we survey several such contemporary findings.
Planted hitting set recovery in hypergraphs
Authors: Amburg Ilya , Kleinberg Jon , Benson Austin R
Published: January 2021

In various application areas, networked data is collected by measuring interactions involving some specific set of core nodes. This results in a network dataset containing the core nodes along with a potentially much larger set of fringe nodes that all have at least one interaction with a core node. In many settings, this type of data arises for structures that are richer than graphs, because they involve the interactions of larger sets; for example, the core nodes might be a set of individuals under surveillance, where we observe the attendees of meetings involving at least one of the core individuals. We model such scenarios using hypergraphs, and we study the problem of core recovery: if we observe the hypergraph but not the labels of core and fringe nodes, can we recover the ‘planted’ set of core nodes in the hypergraph? We provide a theoretical framework for analyzing the recovery of such a set of core nodes and use our theory to develop a practical and scalable algorithm for core recovery. The crux of our analysis and algorithm is that the core nodes are a hitting set of the hypergraph, meaning that every hyperedge has at least one node in the set of core nodes. We demonstrate the efficacy of our algorithm on a number of real-world datasets, outperforming competitive baselines derived from network centrality and core-periphery measures.
Health Selection Into Eviction: Adverse Birth Outcomes and Children’s Risk of Eviction Through Age 5 Years
Authors: Schwartz Gabriel L , Leifheit Kathryn M , Berkman Lisa F , Chen Jarvis T , Arcaya Mariana C
Published: January 2021

Adverse birth outcomes put children at increased risk of poor future health. They also put families under sudden socioeconomic and psychological strain, which has poorly understood consequences. We tested whether infants experiencing an adverse birth outcome—low birthweight or prematurity, as well as lengthy hospital stays—were more likely to be evicted in early childhood, through age 5 years. We analyzed 5,655 observations contributed by 2,115 participants in the Fragile Families and Child Wellbeing Study—a national, randomly sampled cohort of infants born in large US cities between 1998 and 2000—living in rental housing at baseline. We fitted proportional hazards models using piecewise logistic regression, controlling for an array of confounders and applying inverse probability of selection weights. Having been born low birthweight or preterm was associated with a 1.74-fold increase in children’s hazard of eviction (95% confidence interval: 1.02, 2.95), and lengthy neonatal hospital stays were independently associated with a relative hazard of 2.50 (95% confidence interval: 1.15, 5.44) compared with uncomplicated births. Given recent findings that unstable housing during pregnancy is associated with adverse birth outcomes, our results suggest eviction and health may be cyclical and co-constitutive. Children experiencing adverse birth outcomes are vulnerable to eviction and require additional supports.
Evolution of floral scent in relation to self-incompatibility and capacity for autonomous self-pollination in the perennial herbArabis alpina
Authors: Petrén Hampus , Toräng Per , Ågren Jon , Friberg Magne
Published: January 2021

Background and Aims

The transition from outcrossing to selfing is a frequent evolutionary shift in flowering plants and is predicted to result in reduced allocation to pollinator attraction if plants can self-pollinate autonomously. The evolution of selfing is associated with reduced visual floral signalling in many systems, but effects on floral scent have received less attention. We compared multiple populations of the arctic–alpine herb Arabis alpina (Brassicaceae), and asked whether the transition from self-incompatibility to self-compatibility has been associated with reduced visual and chemical floral signalling. We further examined whether floral signalling differ between self-compatible populations with low and high capacity for autonomous self-pollination, as would be expected if benefits of signalling decrease with reduced dependence on pollinators for pollen transfer.

Methods

In a common garden we documented flower size and floral scent emission rate and composition in eight self-compatible and nine self-incompatible A. alpina populations. These included self-compatible Scandinavian populations with high capacity for autonomous self-pollination, self-compatible populations with low capacity for autonomous self-pollination from France and Spain, and self-incompatible populations from Italy and Greece.

Key Results

The self-compatible populations produced smaller and less scented flowers than the self-incompatible populations. However, flower size and scent emission rate did not differ between self-compatible populations with high and low capacity for autonomous self-pollination. Floral scent composition differed between self-compatible and self-incompatible populations, but also varied substantially among populations within the two categories.

Conclusions

Our study demonstrates extensive variation in floral scent among populations of a geographically widespread species. Contrary to expectation, floral signalling did not differ between self-compatible populations with high and low capacity for autonomous self-pollination, indicating that dependence on pollinator attraction can only partly explain variation in floral signalling. Additional variation may reflect adaptation to other aspects of local environments, genetic drift, or a combination of these processes.
m6A regulator-mediated methylation modification patterns and characteristics of immunity and stemness in low-grade glioma
Authors: Du Jianyang , Ji Hang , Ma Shuai , Jin Jiaqi , Mi Shan , Hou Kuiyuan , Dong Jiawei , Wang Fang , Zhang Chaochao , Li Yuan , Hu Shaoshan
Published: January 2021

m6A RNA methylation is an emerging epigenetic modification, and its potential role in immunity and stemness remains unknown. Based on 17 widely recognized m6A regulators, the m6A modification patterns and corresponding characteristics of immune infiltration and stemness of 1152 low-grade glioma samples were comprehensively analyzed. Machine-learning strategies for constructing m6AScores were trained to quantify the m6A modification patterns of individual samples. Here, we reveal a significant correlation between the multi-omics data of regulators and clinicopathological parameters. We identified two distinct m6A modification patterns (an immune-activated differentiation pattern and an immune-desert dedifferentiation pattern) and four regulatory patterns of m6A methylation on immunity and stemness. We show that the m6AScores can predict the molecular subtype of low-grade glioma, the abundance of immune infiltration, the enrichment of signaling pathways, gene variation and prognosis. The concentration of high immunogenicity and clinical benefits in the low-m6AScore group confirmed the sensitive response to radio-chemotherapy and immunotherapy in patients with high-m6AScore. The results of the pan-cancer analyses illustrate the significant correlation between m6AScore and clinical outcome, the burden of neoepitope, immune infiltration and stemness. The assessment of individual tumor m6A modification patterns will guide us in improving treatment strategies and developing objective diagnostic tools.
Bowel preparation in colorectal surgery: the day of reckoning is here
Authors: Alverdy J C
Published: January 2021

Before the use of mechanical bowel preparation is either eliminated or subjected to a clinical trial, its scientific premise should be reconsidered, and consensus of its redesign discussed by a panel of experts including surgeons, infectious disease specialists, microbiome scientists, and clinical trialists.
Litigation in breast surgery: unique insights from the English National Health Service experience
Authors: O’Connell R L , Patani N , Machin J T , Briggs T W R , Irvine T , MacNeill F A
Published: January 2021

Background

The increase in medical negligence claims against the National Health Service (NHS) over the past decade has had a detrimental impact on limited financial and human resources that could otherwise be available for direct clinical care. The aim of this study was to review litigation claims in breast surgery as part of the national Getting It Right First Time quality improvement initiative, with the aim of identifying opportunities to improve clinical practice and patient safety.

Methods

All general and plastic surgical claims notified to NHS Resolution between April 2012 and April 2018 were reviewed. Claims related specifically to breast surgery were retrieved manually, and case summaries were analysed independently by two breast surgeons.

Results

From 6915 claims, 449 relating to breast surgery were identified and reviewed. The mean(s.d.) claimant age was 46(13) years. The median number of claims over the 6-year period per NHS trust was 2 (range 0–22). The most frequent causes of litigation were dissatisfaction with cosmetic outcome (121 claims, 26.9 per cent) and patient-reported delays in diagnosis (121, 26.9 per cent). A large proportion of claims related to breast implant surgery (78, 17.4 per cent), and issues regarding consent/communication were common (69, 15.4 per cent). The estimated annual cost of breast surgery litigation claims ranged from £5.57 to £9.59 million (€6.35–11.02 million).

Conclusion

Patient-reported delays in diagnosis and dissatisfaction with cosmetic outcome are the most common causes of litigation related to breast surgery. These key themes should be the focus for workforce learning, with the aim of improving patient care and experience.
Interventions to prevent and treat sarcopenia in a surgical population: a systematic review and meta-analysis
Authors: Tomassini S , Abbasciano R , Murphy G J
Published: January 2021

Background

The aim of this systematic review was to summarize the results of trials evaluating interventions for the reduction of sarcopenia in patients undergoing surgery.

Methods

Searches were conducted using the Cochrane Central Register of Controlled Trials, MEDLINE and Embase. RCTs evaluating exercise, dietary or pharmacological interventions to address sarcopenia in the perioperative period were included. Treatment effect estimates were expressed as standardized mean differences (MDs) with confidence intervals, and heterogeneity was expressed as I2 values.

Results

Seventy trials including 3402 participants were selected for the data synthesis. Exercise interventions significantly increased muscle mass (MD 0.62, 95 per cent c.i. 0.34 to 0.90; P < 0.001), muscle strength (MD 0.55, 0.39 to 0.71; P < 0.001), measures of gait speed (MD 0.42, 0.05 to 0.79; P = 0.03), and reduced time for completion of set exercises (MD −0.76, −1.12 to −0.40; P < 0.001) compared with controls. Subgroup analysis showed that interventions in the early postoperative period were more likely to have a positive effect on muscle mass (MD 0.71, 0.35 to 1.07; P < 0.001) and timed tests (MD −0.70, −1.10 to −0.30; P = 0.005) than preoperative interventions. Treatment effects on muscle mass (MD 0.09, −0.31 to 0.49; P = 0.66) and strength (MD 0.46, −0.01 to 0.92; P = 0.05) were attenuated by the presence of cancer. Results of analyses restricted to nine trials at low risk of allocation concealment bias and fourteen trials at low risk of attrition bias were comparable to those of the primary analysis. Risk-of-bias assessment showed that most trials were at high risk of incomplete outcome and attrition bias, thus reducing the estimate of certainty of the evidence according to the GRADE assessment tool.

Conclusion

Exercise interventions appear beneficial in reducing the impact of sarcopenia. Because of the high risk of bias and low certainty of the current evidence, large RCTs using standardized measures of muscle mass should be undertaken.
Randomized clinical trial and meta-analysis of the impact of a fibrin sealant patch on pancreatic fistula after distal pancreatectomy: CPR trial
Authors: Mungroop T H , van der Heijde N , Busch O R , de Hingh I H , Scheepers J J , Dijkgraaf M G , Groot Koerkamp B , Besselink M G , van Eijck C H
Published: January 2021

Background

Postoperative pancreatic fistula (POPF) remains the main cause of morbidity in patients after distal pancreatectomy. The objective of this study was to investigate whether an absorbable fibrin sealant patch could prevent POPF after distal pancreatectomy.

Methods

A multicentre, patient-blinded, parallel-group randomized superiority trial was performed in seven Dutch hospitals. Allocation was done using a computer-generated randomization list with a 1 : 1 allocation ratio and concealed varying permuted block sizes. Pancreatic stump closure with a fibrin patch was compared with standard treatment in patients undergoing distal pancreatectomy. The primary endpoint was the development of grade B/C POPF. A systematic review and meta-analysis was performed which combined the present findings with all available evidence.

Results

Between October 2010 and August 2017, 247 patients were enrolled. Fifty-four patients (22.2 per cent) developed a POPF, 25 of 125 patients in the patch group versus 29 of 122 in the control group (20.0 versus 23.8 per cent; P = 0·539). No related adverse effects were observed. In the meta-analysis, no significant difference was seen between the patch and control groups (19.7 versus 22.0 per cent; odds ratio 0.89, 95 per cent c.i. 0.60 to 1.32; P = 0·556).

Conclusion

Application of a fibrin patch to the pancreatic stump does not reduce the incidence of POPF in distal pancreatectomy. Future studies should focus on alternative fistula mitigation strategies, considering pancreatic neck thickness and duct size as risk factors. Trial registration number NL5876 (Netherlands Trial Registry).
Behavioral and Physiological Evidence of a favored Hand Posture in the Body Representation for Action
Authors: Romano Daniele , Mioli Alessandro , D’Alonzo Marco , Maravita Angelo , Di Lazzaro Vincenzo , Di Pino Giovanni
Published: January 2021

Motor planning and execution require a representational map of our body. Since the body can assume different postures, it is not known how it is represented in this map. Moreover, is the generation of the motor command favored by some body configurations? We investigated the existence of a centrally favored posture of the hand for action, in search of physiological and behavioral advantages due to central motor processing. We tested two opposite hand pinch grips, equally difficult and commonly used: forearm pronated, thumb-down, index-up pinch against the same grip performed with thumb-up. The former revealed faster movement onset, sign of faster neural computation, and faster target reaching. It induced increased corticospinal excitability, independently on pre-stimulus tonic muscle contraction. Remarkably, motor excitability also increased when thumb-down pinch was only observed, imagined, or prepared, actually keeping the hand at rest. Motor advantages were independent of any concurrent modulation due to somatosensory input, as shown by testing afferent inhibition. Results provide strong behavioral and physiological evidence for a preferred hand posture favoring brain motor control, independently by somatosensory processing. This suggests the existence of a baseline postural representation that may serve as an a priori spatial reference for body–space interaction.
Assessing the redistributive impact of the 2013 CAP reforms: an EU-wide panel study
Authors: Hanson Aaron
Published: January 2021

This paper analyses the effects of the 2013 Common Agricultural Policy reforms on the distribution of direct payments across the European Union (EU) member states. The differential implementation of two key redistributive policies across countries from 2014 onwards enables the use of a generalised difference-in-differences strategy to estimate their distributional effects. Using data on EU-wide direct payment recipients reveals a substantial negative impact on the largest payment recipients and significant redistribution towards smaller farmers. A disaggregated analysis suggests that of the two instruments, capping, though still an attractive option for policymakers, is less effective at redistributing subsidies towards smaller farmers than the Redistributive Payment Scheme.
Archaeal tyrosine recombinases
Authors: Badel Catherine , Da Cunha Violette , Oberto Jacques
Published: January 2021

The integration of mobile genetic elements into their host chromosome influences the immediate fate of cellular organisms and gradually shapes their evolution. Site-specific recombinases catalyzing this integration have been extensively characterized both in bacteria and eukarya. More recently, a number of reports provided the in-depth characterization of archaeal tyrosine recombinases and highlighted new particular features not observed in the other two domains. In addition to being active in extreme environments, archaeal integrases catalyze reactions beyond site-specific recombination. Some of these integrases can catalyze low-sequence specificity recombination reactions with the same outcome as homologous recombination events generating deep rearrangements of their host genome. A large proportion of archaeal integrases are termed suicidal due to the presence of a specific recombination target within their own gene. The paradoxical maintenance of integrases that disrupt their gene upon integration implies novel mechanisms for their evolution. In this review, we assess the diversity of the archaeal tyrosine recombinases using a phylogenomic analysis based on an exhaustive similarity network. We outline the biochemical, ecological and evolutionary properties of these enzymes in the context of the families we identified and emphasize similarities and differences between archaeal recombinases and their bacterial and eukaryal counterparts.
In vitroinfection models to study fungal–host interactions
Authors: Last Antonia , Maurer Michelle , S. Mosig Alexander , S. Gresnigt Mark , Hube Bernhard
Published: January 2021

Fungal infections (mycoses) affect over a billion people per year. Approximately, two million of these infections are life-threatening, especially for patients with a compromised immune system. Fungi of the genera Aspergillus, Candida, Histoplasma and Cryptococcus are opportunistic pathogens that contribute to a substantial number of mycoses. To optimize the diagnosis and treatment of mycoses, we need to understand the complex fungal–host interplay during pathogenesis, the fungal attributes causing virulence and how the host resists infection via immunological defenses. In vitro models can be used to mimic fungal infections of various tissues and organs and the corresponding immune responses at near-physiological conditions. Furthermore, models can include fungal interactions with the host–microbiota to mimic the in vivo situation on skin and mucosal surfaces. This article reviews currently used in vitro models of fungal infections ranging from cell monolayers to microfluidic 3D organ-on-chip (OOC) platforms. We also discuss how OOC models can expand the toolbox for investigating interactions of fungi and their human hosts in the future.
Ten-year estimation of Oriental beech (Fagus orientalisLipsky) volume increment in natural forests: a comparison of an artificial neural networks model, multiple linear regression and actual increment
Authors: Bayat Mahmoud , Bettinger Pete , Hassani Majid , Heidari Sahar
Published: January 2021

Determining forest volume increment, the potential of wood production in natural forests, is a complex issue but is of fundamental importance to sustainable forest management. Determining potential volume increment through growth and yield models is necessary for proper management and future prediction of forest characteristics (diameter, height, volume, etc.). Various methods have been used to determine the productive capacity and amount of acceptable harvest in a forest, and each has advantages and disadvantages. One of these methods involves the artificial neural network techniques, which can be effective in natural resource management due to its flexibility and potentially high accuracy in prediction. This research was conducted in the Ramsar forests of the Mazandaran Province of Iran. Volume increment was estimated using both an artificial neural network and regression methods, and these were directly compared with the actual increment of 20 one-hectare permanent sample plots. A sensitivity analysis for inputs was employed to determine which had the most effect in predicting increment. The actual average annual volume increment of beech was 4.52 m3ha−1 yr−1, the increment was predicted to be 4.35 and 4.02 m3ha−1 yr−1 through the best models developed using an artificial neural network and using regression, respectively. The results showed that an estimate of increment can be predicted relatively well using the artificial neural network method, and that the artificial neural network method is able to estimate the increment with higher accuracy than traditional regression models. The sensitivity analysis showed that the standing volume at the beginning of the measurement period and the diameter of trees had the greatest impact on the variation of volume increment.
TEMPERATURE-SENSITIVE DNA SYNTHESIS MUTANTS OF BACILLUS SUBTILIS—APPENDIX: THEORY OF DENSITY TRANSFER FOR SYMMETRIC CHROMOSOME REPLICATION
Authors: White Kalpana , Sueoka Noboru
Published: January 2021

A simple method for characterizing temperature-sensitive DNA synthesis mutants is described. The method uses density transfer and transformation techniques and is based on expected theoretical behavior of the chromosome population. A direct proof of inhibition of initiation of DNA replication is provided. The mutant dna-I, showing quick inhibition of initiation, is further characterized and mapped. An independent method for mapping genetic markers close to the origin, based on their transfer behavior after inhibition of initiation, is presented.
REPAIR OF UV-INDUCED PYRIMIDINE DIMERS IN DROSOPHILA MELANOGASTER CELLS IN VITRO
Authors: Trosko James E , Wilder Kathy
Published: January 2021

Tissue culture cells of Drosophila melanogaster were given various doses of ultraviolet light. The results indicate that Drosophila cells do have a darkrepair excision mechanism which is not sensitive to caffeine. Pyrimidine dimers were destroyed by photoreactivating illumination in these cells and this destruction probably represents monomerization of the pyrimidine dimers.
APPARENT DIFFERENTIAL SELECTION AT AN ISOZYME LOCUS BETWEEN QUEENS AND WORKERS OF THE ANT APHAENOGASTER RUDIS
Authors: Crozier R H
Published: January 2021

The frequencies of two alleles at a cathodal malate dehydrogenase locus in populations of A. rudis were studied in 47 colonies from three localities in Georgia and one in New Jersey. The male gene frequencies of the New Jersey and one Georgia locality differ significantly. All the queens at one Georgia locality were heterozygotes. This genotypic distribution differs strongly from that of the workers, in which approximately equal numbers of heterozygotes and homozygotes were found. The heterozygote excess among queens but not their worker progeny suggests differential selection between these castes. This study also shows that rudis colonies consist of a single, once-mated queen and her worker progeny.
TEMPERATURE-SENSITIVE MUTATIONS IN DROSOPHILA MELANOGASTER XII. THE GENETIC AND DEVELOPMENTAL EFFECTS OF DOMINANT LETHALS ON CHROMOSOME 3
Authors: Holden Jeanette J , Suzuki David T
Published: January 2021

Out of 25,000 EMS-treated third chromosomes examined, ten dominant temperature-sensitive (DTS) lethal mutations which are lethal when heterozygous at 29°C but survive at 22°C were recovered. Seven of the eight mutations mapped were tested for complementation; these mutants probably define eight loci. Only DTS-2 survived in homozygous condition at 22°C; homozygous DTS-2 females expressed a maternal effect on embryonic viability. Two of the mutant-bearing chromosomes, DTS-1 and DTS-6, exhibited dominant phenotypes similar to those associated with Minutes. Each of the seven mutants examined exhibited a characteristic phenotype with respect to the time of death at 29°C and the temperature-sensitive period during development. Only DTS-4 exhibited dominant lethality in triploid females.
SELECTION FOR A THRESHOLD CHARACTER IN DROSOPHILA IV. CHROMOSOMAL ANALYSES OF PLATEAUED POPULATIONS
Authors: Latter B D H
Published: January 2021

Chromosome substitution and intra-chromosomal recombination techniques have been employed to determine the genetic basis of limits to selection in lines selected for high scutellar bristle number from the Canberra population. Three observations indicate the presence of an upper threshold affecting some component traits, which is not readily discernible at the level of the selected phenotype:

(1) The variance of the number of anterior + interstitial + posterior bristles is progressively reduced as the mean approaches a total of eight at these sites. Total bristle number, which includes apicals in addition to the above three components, and which was the trait subject to selection, shows little evidence of this phenomenon;

(2) the effect of a given chromosome substitution is also greatly reduced as the mean approaches eight anterior + interstitial + posterior bristles, by comparison with its effect in genotypes of lower mean;

(3) chromosome substitutions show some evidence of negative interaction as this level is approached, in contrast to the positive interactions evident at higher means. All chromosomes except IV are involved in progress beyond the proposed upper threshold. However, chromosome III has the most important effect, due primarily to a major gene located at approximately 61 cM, which also markedly increases dorsocentral and postvertical bristle numbers.
SOMATIC CROSSING OVER IN GLYCINE MAX (L.) MERRILL: EFFECT OF SOME INHIBITORS OF DNA SYNTHESIS ON THE INDUCTION OF SOMATIC CROSSING OVER AND POINT MUTATIONS
Authors: Vig B K
Published: January 2021

Glycine max (soybean) is the only known higher plant with a definitely established occurrence of somatic crossing over. This material lends itself to the analysis of somatic crossing over, gross chromosomal aberrations and mutations, all of which may be induced by the same treatment of the mutagen given to seeds. This is made possible because gene Y11 for chlorophyll development in the variety L65-1237 is incompletely dominant over its allele y11, so that twin or double spots composed of a dark green (Y 11 Y 11)and a yellow (Y 11 Y 11) component can be observed adjacent to and as mirror images of each other on the light green Y 11 Y 11 leaves in the areas of complementary exchange for these genes. Lack of growth of either component of this double spot as well as several types of chromosomal disturbances give rise to single spots resembling phenotypes of Y 11 Y 11 or Y 11 Y 11 leaves. Point mutations can be studied by looking for green sectors originating from Y 11 Y 11 genotype on the Y 11 Y 11 plants. Seeds obtained from heterozygous plants were treated with caffeine, cytosine arabinoside, actinomycin D and 5-fluoro-deoxyuridine, all known inhibitors of DNA synthesis, and puromycin, an inhibitor of synthesis of proteins. The treatments with caffeine and actinomycin D increased the frequency of somatic crossing over as measured by the frequency of double spots on Y 11 Y 11 leaves, but cytosine arabinoside, 5-fluorodeoxyuridine and puromycin did not. Thus somatic crossing over was induced only by those chemicals which are known to allow rejoining of chromosomes, thereby suggesting a correlation between the two phenomena. These observations indicate that it is not the mere inhibition of DNA synthesis, but some rather more specific event in DNA repair which is responsible for complementary exchanges. Some of these results differ from studies carried out with fungi. The main effect of all chemicals tested, except caffeine and actinomycin D, was inferred to be the production of deletions in Y 11 Y 11 plants which raised the frequency of single (dark green or yellow) spots relative to the doubles. Caffeine was the only chemical which constantly increased the frequency of specific point mutations. In the control material, the great majority of spots are found on the upper surface of the leaf. This picture could not be changed in any of the treated materials, thus indicating uniform resistance of spongy mesophyll tissue to the mutagens applied.
EXPERIMENTAL EVALUATION OF RELATIONSHIPS AMONG POPULATIONS RESULTING FROM INTERGRADATION AMONG CULTIVARS OF ZEA MAYS L
Authors: Hanson W D , Moll R H
Published: January 2021

Populations were developed as intergradations among three maize cultivars, two adapted to North Carolina and one to Mexico, with the objective of testing whether diallel information could be used to identify the relationships among populations. The data substantiated theoretical observations that the technique would identify relationships among populations resulting from recent intergradations.
GENETICS OF HEADING TIME IN WHEAT (TRITICUM AESTIVUM L.). I. THE INHERITANCE OF PHOTOPERIODIC RESPONSE
Authors: Klaimi Y Y , Qualset C O
Published: January 2021

The inheritance of photoperiodic response was studied in crosses involving four spring wheats (Sonora 64, Pitic 62, Justin and Thatcher) and three winter wheats (Blackhull, Early Blackhull and Extra Early Blackhull). The parental cultivars were classified into a photoperiod-sensitive group (Justin, Thatcher, Blackhull and Early Blackhull) and a relatively photoperiod-insensitive group (Sonora 61, Pitic 62 and Extra Early Blackhull) based on their heading response when vernalized and grown under different daylength regimes.—F1 data indicated that daylength insensitivity is not always dominant over daylength sensitivity and that the dominance relationship with respect to photoperiodic response depends on the alleles present in the parents. The heading patterns after vernalization and growth under short days of F1, F2, F3 and backcross generations of a 4-parent diallel cross involving Justin, Sonora 64, Extra Early Blackhull and Blackhull could be satisfactorily explained on the basis of two major loci with three alleles at each locus. The genotype for each parent was suggested in terms of these loci. Genes with minor effects also influenced the photoperiodic response in a quantitative manner.—Diallel cross analysis of the number of days to heading (log scale) indicated significant additive and dominance genetic variances, a high average degree of dominance for earliness (photoperiod insensitivity) and a preponderance of recessive alleles in the parents acting in the direction of lateness (photoperiod sensitivity). Estimation of the genetic components of variation contained in the generation means of individual crosses (untransformed data) showed that, besides additivity and dominance, epistasis was also an important factor in the genetic control of photoperiodic response in wheat.
DISTRIBUTION OF GENE FREQUENCY AS A TEST OF THE THEORY OF THE SELECTIVE NEUTRALITY OF POLYMORPHISMS
Authors: Lewontin R C , Krakauer Jesse
Published: January 2021

The variation in gene frequency among populations or between generations within a population is a result of breeding structure and selection. But breeding structure should affect all loci and alleles in the same way. If there is significant heterogeneity between loci in their apparent inbreeding coefficients F=sp2/p(1-p), this heterogeneity may be taken as evidence for selection. We have given the statistical properties of F and shown how tests of heterogeneity can be made. Using data from human populations we have shown highly significant heterogeneity in F values for human polymorphic genes over the world, thus demonstrating that a significant fraction of human polymorphisms owe their current gene frequencies to the action of natural selection. We have also applied the method to temporal variation within a population for data on Dacus oleae and have found no significant evidence of selection.
THE GENETIC BASIS FOR MUCOIDY AND RADIATION SENSITIVITY IN capR (lon) MUTANTS OF E. coli K-12
Authors: Bush John W , Markovitz Alvin
Published: January 2021

CapR mutants of E. coli K-12 overproduce capsular polysaccharide (mucoid phenotype) and enzymes involved in capsular polysaccharide synthesis, and they are sensitive to radiation. It has been uncertain whether both properties are mediated by damage to a single cistron or by a polar effect on a second cistron in the same operon. Introduction of a polarity suppressor caused no change in the overproduction of polysaccharide, in the enzymes of polysaccharide synthesis or in radiation sensitivity of the capR mutant. Thus mucoidy and radiation sensitivity resulting from capR (lon) mutations are both the consequences of impairment of the same cistron. The experiments demonstrate the advantage of the use of polarity suppressors (over conventional nonsense suppressors) in determining whether pleiotropic effects of a mutation are the result of polarity.
UV SENSITIVITY OF SEVERAL GENETIC MARKERS OF HAEMOPHILUS INFLUENZAE DNA
Authors: Chevallier M R , Greth M L
Published: January 2021

Studies on inactivation by UV of several genetic markers of the streptomycin and novobiocin resistance regions of H. influenzae DNA have shown that two kinds of markers may be found with respect to frequency of integration, UV sensitivity and reactivability. One class of markers has high integration frequency and low UV sensitivity, which can be partly explained by the reactivability of the irradiated markers. The second class of markers has low integration frequency and high UV sensitivity. Markers of each class have been found in the novobiocin region.—In one recipient strain with decreased transformability the difference in integration frequency between the two classes is enhanced.
EXTRACHROMOSOMAL ELEMENT DELTA IN DROSOPHILA MELANOGASTER. IX. INDUCTION OF DELTA-RETAINING CHROMOSOME LINES BY MUTATION AND GENE MAPPING
Authors: Minamori Sumio , Sugimoto Kinue
Published: January 2021

[Delta b], symbolized as [δb], is retained by Sb chromosome lines and transmitted through the females to their progeny. Transmission through the males is not directly demonstrable (Minamori 1969a). [delta r], symbolized as [δr], is retained by Sr chromosome lines and transmitted biparentally (Minamori 1971). The multiplication of delta is suppressed at low temperature. All descendant lines derived from Sb-carrying or Sr-carrying flies in which the presence of delta cannot be demonstrated gradually accumulate their specific delta factors over many generations (Minamori 1969b, 1972). The delta factors and the sensitive chromosomes are inseparably associated. This observation led to the assumption that delta may be a copy of a chromosomal gene or a certain agent integrated into the chromosome (Minamori 1972). This assumption was examined in the present study by experiments designed to induce delta-retaining sensitive chromosomes, and to map the gene(s) responsible for delta-retention and/or for sensitivity to the killing action of delta factor. One sensitive chromosome which retained [δb] (Sb chromosome) was obtained in the presence of [δb] out of 2492 insensitive chromosomes which retained no delta; in addition one Sb chromosome was obtained in the presence of [δr] out of 2131 insensitives. The latter finding suggests that Sb might be induced by a mutation caused by [δb] or [δr], but not by integration of either delta into the chromosome. Four Sb chromosomes and one sensitive chromosome which retained [δr] (Sr chromosome) were obtained out of 1970 insensitives when males carrying the chromosome were fed an alkylating mutagen, ethyl methane sulfonate (EMS). The location of delta-retaining genes was examined by crossing-over experiments employing eight Sb and five Sr chromosomes. The genes on these chromosomes were found to be located in the same region or near one another. The gene for [δb], symbolized as Dab, and the gene for [δr], symbolized as Dar, are assumed to be multiple alleles of a locus at 2-24.9. The sensitivity of the chromosomes was modified appreciably by recombination; hence, the genes controlling this trait are assumed to be a polygenic system. The findings obtained in this study lead to the hypothesis that delta may be produced by a chromosomal gene (Da) and transmitted extrachromosomally.
GENETIC POLYMORPHISM AND EVOLUTION IN PARTHENOGENETIC ANIMALS. I. POLYPLOID CURCULIONIDAE
Authors: Suomalainen Esko , Saura Anssi
Published: January 2021

The genetic variability at enzyme loci in different triploid and tetraploid parthenogenetic weevil populations has been elucidated by starch gel electrophoresis. The overall genotype of individual weevils belonging to different populations has been determined for over 25 loci. The results are compared with those obtained for diploid bisexual races of either the same or closely related species. The variation within a parthenogenetic population differs from that in diploid, sexually reproducing populations, i.e. the allele frequencies are not in a Hardy-Weinberg equilibrium. The results indicate that apomictic parthenogenetic populations can differentiate genetically. The genotypes within a population resemble each other more than genotypes belonging to different populations. It is evident that evolution still continues-even if slowed down—in parthenogenetic weevils. A comparison between the allele relationships in geographically isolated polyploid parthenogenetic populations and related diploid bisexual forms does not support the hypothetical hybrid origin of parthenogenesis and polyploidy in weevils. Parthenogenesis within a parthenogenetic weevil species is evidently monophyletic.
ISOLATION OF SUPPRESSIVE SENSITIVE MUTANTS FROM KILLER AND NEUTRAL STRAINS OF SACCHAROMYCES CEREVISIAE
Authors: Somers J M
Published: January 2021

Dominant sensitive mutants were isolated from a killer and a neutral strain of Saccharomyces cerevisiae by treatment with nitrosomethylurethane. Genetic studies suggest that these sensitives arose by mutation of the wild-type cytoplasmic genetic determinants (k) or (n) to a mutant form (s). (s) determinants lack wild-type (k) and (n) activity but are retained in the cell and suppress the replication or activity of the wild-type determinants, converting killer and neutral cells to the sensitive phenotype. These mutants show an obvious similarity in behavior to suppressive petite mutants of yeast.
THE INHERITANCE OF ENZYME VARIANTS FOR TYROSINE AMINOTRANSFERASE, NADP-DEPENDENT MALATE DEHYDROGENASE, NADP-DEPENDENT ISOCITRATE DEHYDROGENASE, AND TETRAZOLIUM OXIDASE IN TETRAHYMENA PYRIFORMIS, SYNGEN 1
Authors: Borden D , Miller E T , Nanney D L , Whitt G S
Published: January 2021

The isozymic patterns of tyrosine aminotransferase, NADP malate dehydrogenase, NADP isocitrate dehydrogenase, and tetrazolium oxidase were examined by starch-gel electrophoresis in Tetrahymena pyriformis, syngen 1. The genetics of the alleles controlling these enzymes was studied through a breeding program. Each enzyme locus was shown to assort vegetatively, as do other loci in this organism. A detailed analysis of the assortment process for the tyrosine aminotransferase locus indicated that the rate of stabilization of heterozygotes into pure types was essentially identical to previously-reported rates for other loci.