bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical modeling results of vibroseismic monitoring of volcanic structures with different shape of the magma chamber
Authors: Sapetina A F , Glinskiy B M , Martynov V N
Published: January 2021

The paper considers the possibility of active monitoring of volcanic structures based on the simulation of vibroseismic transmission using the dynamical theory of elasticity. A solution method, a parallel algorithm, and a program system based on a finite-difference approach together with CFS-PML method of absorbing boundaries are developed. Different variations of a magmatic stratovolcano approximate model are considered, comparative numerical calculations are carried out. The calculated wave field inside the volcanic structure has a compound structure depending on the geometry of studied objects and their rheological characteristics. Based on the studies, it may be concluded that monitoring of the considered type of volcanoes using precision vibroseismic sources and seismic observation systems is possible. A variant of vibroseismic monitoring of Elbrus volcano using the observation system in the tunnel of the Baksan Neutrino Observatory is proposed.
Iterative methods for solving Riccati differential equations
Authors: Ogundile O. P. , Edeki S. O. , Olaniregun D. G.
Published: January 2021

This work considers the approximate solution of the Riccati differential equations (RDEs). For ease of computation, the iterative methods applied are the Daftardar-Gejji and Jafari Method (DJM) and the Picard Iteration Method (PIM). The results obtained via the DJM are compared with those from PIM. The comparison shows that both methods are in agreement with the corresponding exact form. The Picard approach transforms the differential equation into an interconnected form; though, Lipschitz’s criterion of consistency but satisfied.
Remarks on the solution of a one-dimensional heat model with axial symmetry using decomposition method
Authors: Edeki S. O. , Abolarinwa A. , Ogundile O. P. , Ogunniyi P. O.
Published: January 2021

This paper explores the use of a new decomposition method termed-Natural Decomposition Method (NDM) on a one-dimensional heat model-equation with axial symmetry for analytical solutions. The series solutions of the sampled cases are obtained by the proposed method with ease and high precision for less computational time. Hence, this indicates the feasibility of the proposed approach.
Factors affecting the study time of first and final year students of a world class university
Authors: Okagbue Hilary I. , Odetunmibi Oluwole A. , Ezenkwe Adaeze M. , Anene Glory N. , Boluwajoko Anjoreoluwa E. , Offiah Ifeanyi B. , Akinsola Boluwatife E.
Published: January 2021

Many activities compete for the time students spent on academic activities, but few works have been done on the factors affecting the study times of first and final year students. Questionnaires were given to 150 first and final year students from four colleges of a world-class university located in Ogun State, Nigeria and the aim is to investigate the factors affecting their study time. Ninety-eight representing 65.3% of the students study between 1 and 4 hours per day. Gender, age, level and college affiliation are not associated with their perceived desired results. In the same vein, it was observed that gender and age are not associated with hours of study. However, there are significant associations between the duo of level and college and study hours. Also, there is no significant association (i) Between the number of hours spent on sleeping and the number of hours spent on studying and (ii). The hours spent on study and the desired result. In conclusion, strategies are needed to be crafted and deployed to increase the hours spent on studying by the first and final year students which are likely to give them their desired results and improve the art of learning. Logistic regression on the desired results was predicted by the 3 moderation variables, namely; the gender and level, age and college, and level and college. Intervention programmes are to be incorporated into the curriculum to motivate students in achieving their desired results. Tutorial classes, investment in learning tools, promotion of discussion groups, counselling are recommended for first and final year students to stimulate their interests in their chosen course of study and to prepare them for successful careers.
The relevance of the internet of things to the real estate profession
Authors: Akindele N. A. , Ogundile O. P. , Ogunniyi P. O.
Published: January 2021

This paper examines the relevance of the Internet of Things to the Real Estate profession. Questionnaires were distributed, and the interview was also conducted on the Estate Surveyors and Valuers in Akure metropolis. The paper adopts a quantitative method of data analysis. Descriptive techniques were adopted; it includes the tabular analysis of data using percentages and frequencies. A bar chart and Pie chart were also used. From table 4 and figure one (1) (bar chart), it was discovered that most of the respondents are aware of the existence of the Internet of Things as the majority of them indicated their awareness. Table 5 and figure 2 (Pie chart) also show that a high percentage of the respondents agreed that the Internet of Things is relevant to the Real Estate profession.
Enhanced Numerov Method for the Numerical Solution of Second Order Initial Value Problems
Authors: Akinlabi G. O. , Bishop S. A. , Edeki S. O.
Published: January 2021

Numerov method is a multistep numerical method that is used in solving second order differential equations. In this work, we apply this method as a Boundary Value Method (BVM) for the numerical approximation of both linear and nonlinear second order initial value problems. This is achieved by constructing the Numerov method via interpolation and collocation process while utilizing data at off-step points and implementing it as a BVM. On comparing the results obtained from the solved problems, it shows that the method is accurate with high level of convergence to their exact forms and performs better than results from literature.
Trend Analysis of the Variations of Ambient Temperature Using Mann-Kendall Test and Sen’s Estimate in Calabar, Southern Nigeria
Authors: Agbo E P , Ekpo C M
Published: January 2021

Studies have been made to understand the fluctuations of temperature in regions around the world because of an ever changing variation due mostly to man’s anthropogenic activities. This study is focused on analysing the temperature variations in Calabar, Southern Nigeria for 20 years (1998 – 2018) using the Mann-Kendall trend test and Sen’s slope estimator. Results from the Mann-Kendall test shows that the annual trends of the maximum and average ambient temperature are both increasing after showing positive Kendall Z-values (1.04 and 0.10 respectively). The minimum ambient temperature annual trend was observed to be decreasing after having a negative Kendall Z-value (-0.32); the estimations from Sen’s slope agreed with these results. The p-values were calculated to be 0.745, 0.299, and 0.922 for the minimum, maximum, and average ambient temperature trend respectively; these values were all found to be less than all significant levels used 0.1% (0.001), 1% (0.01), 5% (0.05), and 10% (0.1). This shows that the trends were not increasing or decreasing significantly, hence there is “no significant trend”. This may be due to the almost unchanging weather condition in the region arising from its closeness to the Atlantic Ocean.
The effect of residence time and temperature on product yields during the pyrolysis of coconut husks
Authors: Adeyemo K. K. , Efemwenkiekie U. K. , Badmus F. O. , Ogundile O. P. , Akinpelu A. , Itabiyi E. O.
Published: January 2021

This study explains the effect of residence time and temperature on product yield obtained from Coconut husks’ pyrolysis. The husk of the coconut was prepared in the required sizes for the experiment. The experiment was carried out on eighteen different coconut husks at different temperature ranges and varying residence time. The coconut husk pyrolysis was confirmed to give three product yields: char (solid), tar (liquid), and the gaseous fuel, while a polynomial regression model was developed using the Response surface methodology (RSM) to create a polynomial regression model. The effect of pyrolysis temperature level change and its product yield duration was investigated using Full Factorial Design (FFD). Generally, during the pyrolysis process, it can be observed that temperature and reaction time have a strong outcome on the product yields. When the pyrolysis temperature increases at constant residence time, the biogas production increases, and vice versa.
Experimental investigation on light non-aqueous phase liquids removal from groundwater using steam injection technique
Authors: Ojo B. S. , Babaremu K. O. , Adegbola A. A. , Ademosun O. T. , Ogundile O. P.
Published: January 2021

Groundwater pollution by Non-Aqueous Phase Liquids (NAPLs) has become an increasing threat. This article studied the steam injection efficiency in the groundwater remediation contaminated with non-aqueous phase liquid (diesel) through a bench-scale laboratory experiment. The experimental set up consists of a steam boiler and sandbox. Steam, which was generated from the steam boiler was supplied to the sandbox at injection rate of 0.14m3/s, pressure of 1.5bar and temperature of 150°C. The initial volume of diesel used was 500ml. At the supply of the steam to the sandbox, it was observed that the mixture of groundwater and diesel was heated and at a temperature above their boiling points, the mixture change phase and vaporized from the chamber through the outlet or recovery side into the condenser and were separated on cooling using phase separator. The remediation time was from 0 to 6 hours and it was showed that as the time increases, the recovered volume of diesel increases as 66.04% of diesel was recovered after the allowed 6hours. Therefore, it was evident that the steam injection technique is efficient in the removal of light non-aqueous phase liquids in groundwater.
Rain-fed pulses of methane from East Africa during 2018–2019 contributed to atmospheric growth rate
Authors: Lunt Mark F , Palmer Paul I , Lorente Alba , Borsdorff Tobias , Landgraf Jochen , Parker Robert J , Boesch Hartmut
Published: January 2021

East Africa is a key location for wetland emissions of methane (CH4), driven by variations in rainfall that are in turn influenced by sea-surface temperature gradients over the Indian Ocean. Using satellite observations of CH4 and an atmospheric chemistry-transport model, we quantified East African CH4 emissions during 2018 and 2019 when there was 3-σ anomalous rainfall during the long rains (March–May) in 2018 and the short rains (October–December) in 2019. These rainfall anomalies resulted in CH4 emissions of 6.2 ± 0.3 Tg CH4 and 8.6 ± 0.3 Tg CH4, in each three month period, respectively, and represent a 10% and 37% increase compared to the equivalent season in the opposite year, when rainfall was close to the long-term seasonal mean. We find the additional short rains emissions were equivalent to over a quarter of the growth in global emissions in 2019, highlighting the disproportionate role of East Africa in the global CH4 budget.
A Magnetohydrodynamic (MHD) Power Generating System: A Technical Review
Authors: Bera Tushar Kanti
Published: January 2021

A magnetohydrodynamic (MHD) power generation technique is a nonconventional electric power harvesting modality in which the electricity is generated from an ionised fluid flow under a magnetic field. The ionized fluid moving under a magnetic field works as a moving electrical conductor and the MHD generator generates electrical energy according to the Faraday’s electromagnetic principle. The concept of MHD based electric power generation was first time introduced by Michael Faraday in 1832, and since then the MHD power generation method has been studied by several groups of researcher. In this paper the MHD technique has been discussed in details followed by a discussion on its components and instrumentation. A technical review on the research works conducted on MHD power generation has been presented and the major developments have been highlighted. The present scenario and the future trends are also discussed along with the challenges of the technology.
Electrical Impedance Spectroscopy (EIS) for Photovoltaic Materials: Possibilities and Challenges
Authors: Bera Tushar Kanti
Published: January 2021

Electrical Impedance Spectroscopy (EIS) is a noninvasive material characterization technique which provides the frequency response of the electrical impedance of materials under test as the signature of the material properties. EIS injects constant amplitude AC electrical currents and measures the developed potentials at different frequency points to calculate the complex electrical impedance. In EIS, the electrical impedance profile of a material is correlated with its structure and composition for material testing either online or offline. EIS is found as a fast, portable, user-friendly, and noninvasive technique and hence, it has been utilized for material characterization in a number of engineering fields and applied science areas. In the past few decades, EIS has also been used to characterize the photovoltaic materials. This paper reviews the possibilities and challenges of EIS technique applied for the characterization of the photovoltaic materials. The paper presents a brief discussion about the EIS technology, applications of EIS on PV materials along with the advantages and limitations of the technology. The paper concludes with the highlight of the recent trends of EIS based PV material characterization process mentioning the challenges of the technique.
Uveal melanoma cells use ameboid and mesenchymal mechanisms of cell motility crossing the endothelium
Authors: Onken Michael D. , Blumer Kendall J. , Cooper John A.
Published: January 2021

Uveal melanoma is highly metastatic and only disseminates hematogenously, so that transendothelial migration is vital to metastasis. Uveal melanoma cells switch from amoeboid to mesenchymal motility, controlled by the Rho and Rac pathways, which act downstream of the oncogenic Gq/11 that drives tumor formation.
Appreciation of Social Norms in Agenesis of the Corpus Callosum
Authors: Brown Warren S , Burnett Karissa A , Vaillancourt Ashley , Paul Lynn K
Published: January 2021

Objective

Anecdotal reports regarding high-functioning adults with agenesis of the corpus callosum (AgCC) suggest that they often lack psychosocial insight. We attempted to determine whether adults with AgCC are able to correctly identify appropriate behaviors within social contexts using the Social Norms Questionnaire.

Method

The Social Norms Questionnaire measures knowledge of norms and judgments of what is appropriate to do in particular contexts. It was administered online to individuals with AgCC and control participants.

Results

Individuals with AgCC scored significantly lower in understanding social norms than controls, tending to over-adhere to social norms significantly more than controls. There was no significant difference regarding breaking of social norms.

Conclusion

Results suggest that adults with AgCC have deficient judgment regarding the nuances of appropriate behaviors in social contexts. They adhere to social norms concretely, lacking the ability to integrate context in social scenarios to make appropriately nuanced judgments.
Anticancer peptides prediction with deep representation learning features
Authors: Lv Zhibin , Cui Feifei , Zou Quan , Zhang Lichao , Xu Lei
Published: January 2021

Anticancer peptides constitute one of the most promising therapeutic agents for combating common human cancers. Using wet experiments to verify whether a peptide displays anticancer characteristics is time-consuming and costly. Hence, in this study, we proposed a computational method named identify anticancer peptides via deep representation learning features (iACP-DRLF) using light gradient boosting machine algorithm and deep representation learning features. Two kinds of sequence embedding technologies were used, namely soft symmetric alignment embedding and unified representation (UniRep) embedding, both of which involved deep neural network models based on long short-term memory networks and their derived networks. The results showed that the use of deep representation learning features greatly improved the capability of the models to discriminate anticancer peptides from other peptides. Also, UMAP (uniform manifold approximation and projection for dimension reduction) and SHAP (shapley additive explanations) analysis proved that UniRep have an advantage over other features for anticancer peptide identification. The python script and pretrained models could be downloaded from https://github.com/zhibinlv/iACP-DRLF or from http://public.aibiochem.net/iACP-DRLF/.
Advancing Landscape and Seascape Ecology from a 2D to a 3D Science
Authors: Lepczyk Christopher A , Wedding Lisa M , Asner Gregory P , Pittman Simon J , Goulden Tristan , Linderman Marc A , Gang Jeanne , Wright Rosalie
Published: January 2021

Landscape ecology has fundamentally changed the way ecologists view the world through a greater understanding of the links between spatial patterns and ecological processes. Until recently, landscape ecology has been largely a two-dimensional (2D) science focused on the spatial patterning of 2D planar surfaces rather than three-dimensional (3D) structures. Advances in high-resolution remote sensing technologies, such as laser altimetry, acoustic sensors, and photogrammetry now provide the capability to map complex ecosystem structure in three dimensions, creating more structurally realistic models of the environment. In the present article, we focus on high-resolution 3D structure, using terrestrial and marine examples to illustrate how state-of-the-art advances in landscape ecology achieved through novel data fusion, spatial analysis, and geovisualization of environmental data can provide new ecological insights. These examples provide a look to the future in landscape and seascape ecology, where continued progress toward a multidimensional science will fundamentally shift the way we view, explore, and conceptualize the world.
Experimental near-infrared spectroscopy-guided minimally invasive segmental artery occlusion
Authors: von Aspern Konstantin , Haunschild Josephina , Heier Marcus , Ossmann Susann , Mohr Friedrich W , Borger Michael A , Etz Christian D
Published: January 2021

OBJECTIVES

Minimally invasive staged segmental artery (SA) coil- and plug embolization is a new method for paraplegia prevention associated with extensive aortic procedures. Near-infrared spectroscopy of the paraspinal collateral network (cnNIRS) has emerged as a non-invasive method for spinal cord monitoring. The aim of this study was to evaluate cnNIRS to guide minimally invasive SA occlusion.

METHODS

In a chronic large animal experiment, 18 juvenile pigs underwent two-stage minimally invasive staged SA coil- and plug embolization for complete SA occlusion. Coil-embolization was performed either by SA main stem occlusion (characteristic of pig anatomy) or separately for the left- and right SA. Lumbar cnNIRS was recorded during and after the procedure. Neurological status was assessed up to 3 days after complete SA occlusion.

RESULTS

Mean time from SA coil embolization to minimum cnNIRS values was 11 ± 5 min with an average decrease from 101 ± 2% to 78 ± 8% of baseline (difference: −23 ± 9, P < 0.001). Lumbar cnNIRS demonstrated significant differences between left and right when SAs were occluded separately in all cases (−7 ± 4%, 1 min after first SA occlusion; P = 0.001). Permanent paraplegia occurred in 2 (11%) and any kind of neurological deficit—temporary or permanent—in 7 animals (39%). Association between lumbar cnNIRS and neurological outcome after minimally invasive staged SA coil- and plug embolization suggests positive correlation (R = 0.5, P = 0.052).

CONCLUSIONS

Lumbar cnNIRS independently reacts to unilateral SA occlusion. cnNIRS-guided SA occlusion is feasible and may become a useful adjunct facilitating adequate and complete vessel occlusion.
Nasal ventilation and rapid maxillary expansion (RME): a randomized trial
Authors: Iwasaki Tomonori , Papageorgiou Spyridon N , Yamasaki Youichi , Ali Darendeliler M , Papadopoulou Alexandra K
Published: January 2021

Objective

To assess three rapid maxillary expansion (RME) appliances in nasal ventilation.

Trial design

Three-arm parallel randomized clinical trial.

Methods

Sixty-six growing subjects (10–16 years old) needing RME as part of their orthodontic treatment were randomly allocated (1:1:1 ratio) to three groups of 22 patients receiving Hyrax (H), Hybrid-Hyrax (HH), or Keles keyless expander (K). The primary outcome of nasal ventilation (pressure and velocity) and secondary outcomes (skeletal, dental, soft tissue, and nasal obstruction changes) were blindly assessed on the initial (T0) and final (T1, 6 months at appliance removal) cone-beam computed tomography (CBCT) data by applying computational fluid dynamics (CFD) method. Differences across groups were assessed with crude and adjusted for baseline values and confounders (gender, age, skeletal maturation, expansion amount, mucosal/adenoid hypertrophy, nasal septum deviation) regression models with alpha = 5%.

Results

Fifty-four patients were analysed (19H, 21HH, 14K). RME reduced both nasal pressure (H: −45.8%, HH: −75.5%, K: −63.2%) and velocity (H: −30%, HH: −58.5%, K: −35%) accompanied with nasal obstruction resolution (H: 26%, HH: 62%, K: 50%). Regressions accounting for baseline severity indicated HH expander performing better in terms of post-expansion maximum velocity (P = 0.03) and nasal obstruction resolution (P = 0.04), which was robust to confounders. Mucosal/adenoid hypertrophy and nasal septum deviation changes were variable, minimal, and similar across groups. The HH resulted in significantly greater increase in the nasal cross-sectional area (62.3%), anterior (14.6%), and posterior (10.5%) nasal widths. Nasal obstruction resolution was more probable among younger (P = 0.04), skeletally immature (P = 0.03), and male patients (P = 0.02) without pre-treatment mucosal hypertrophy (P = 0.04), while HH was associated with marginal greater probability for obstruction resolution.

Conclusions

RME resulted in improvement of nasal skeletal parameters and simulated ventilation with the former being in favour of the HH and the latter not showing significant differences among the three appliances.

Limitation

Attrition in the K group due to blocked activation rods possibly leading to limited sample to identify any existing group differences.

Harms

Replacement of blocked Keles expanders for finalizing treatment.

Protocol

The protocol was not published before the trial commencement.

Registration

Australian and New Zealand Clinical Trial Registry; ACTRN12617001136392.
A WIDESPREAD SILENT POLYMORPHISM OF HUMAN CARBONIC ANHYDRASE III (31 ILE ↔ VAL): IMPLICATIONS FOR EVOLUTIONARY GENETICS
Authors: Hewett-Emmett David , Welty Rosalind J , Tashian Richard E
Published: January 2021

During amino acid sequence studies of carbonic anhydrase (CA) III, purified from a pool of human skeletal muscles, an electrophoretically undetectable (silent) variation was found at residue 31 which was either valine and/or isoleucine. To distinguish a simple allelic polymorphism from more complex models involving gene duplication, 11 separate CA III samples were purified from individuals of different age and racial backgrounds. Peptide mapping by high performance liquid chromatography and sequencing indicated that four were homozygous for 31-Val, three homozygous for 31-Ile and four were apparent heterozygotes. Since the ratio of Val/Ile at residue 31 was approximately 1.0 in the heterozygotes, the present observations are consistent with a simple allelic polymorphism model. Despite the small sample size, there are preliminary indications that the gene frequencies may differ among racial groups. The finding of this silent allelic polymorphism together with the finding of an electrophoretically detectable polymorphism of CA II permits us to test the linkage of the CA II and CA III genes which appear to have been formed by gene dupliction more than 300 million years ago. The possibility that the Val/Ile variation may represent a neutral mutation is discussed.
AN AUTOSOMAL GENE THAT AFFECTS X CHROMOSOME EXPRESSION AND SEX DETERMINATION IN CAENORHABDITIS ELEGANS
Authors: Meneely Philip M , Wood William B
Published: January 2021

Recessive mutant alleles at the autosomal dpy-21 locus of C. elegans cause a dumpy phenotype in XX animals but not in XO animals. This dumpy phenotype is characteristic of X chromosome aneuploids with higher than normal X to autosome ratios and is proposed to result from overexpression of X-linked genes. We have isolated a new dpy-21 allele that also causes partial hermaphroditization of XO males, without causing the dumpy phenotype. All dpy-21 alleles show hermaphroditization effects in XO males that carry a duplication of part of the X chromosome and also partially suppress a transformer (tra-1) mutation that converts XX animals into males. Experiments with a set of X chromosome duplications show that the defects of dpy-21 mutants can result from interaction with several different regions of the X chromosome. We propose that dpy-21 regulates X chromosome expression and may be involved in interpreting X chromosome dose for the developmental decisions of both sex determination and dosage compensation.
ASSOCIATION OF CHROMOSOME AND ENZYME POLYMORPHISMS IN NATURAL AND CAGE POPULATIONS OF DROSOPHILA MELANOGASTER
Authors: Inoue Yutaka , Tobari Yoshiko N , Tsuno Kendo , Watanabe Takao K
Published: January 2021

The frequencies of a polymorphic inversion, In(2L)t, and of Adh and αGpdh alleles were analyzed in three natural populations of Drosophila melanogaster from Japan. Significant positive correlations between the frequencies of In(2L)t and AdhS or ?GpdhF were detected due to tight linkage. An analysis of correlation with latitude showed that the negative cline of AdhS frequency could be explained entirely by its linkage with In(2L)t; the frequency of AdhS on the standard chromosome did not show a latitudinal cline. To the contrary, the cline of αGpdhF frequency itself was positive, and its linkage with In(2L)t makes the positive cline unclear. These results suggest that the two allozymes themselves respond to latitudinal natural selection in different ways. When these populations were transferred to laboratory cages and maintained for a long time, they lost the chromosomal polymorphism but retained stable enzyme polymorphisms, although allele frequencies in the cage were not the same as in nature. The frequencies of Adh and αGpdh alleles were close to those in earlier cage populations of the same geographical origin.
DISTRIBUTION OF NONSTRUCTURAL VARIATION BETWEEN WHEAT CULTIVARS ALONG CHROMOSOME ARM 6Bp: EVIDENCE FROM THE LINKAGE MAP AND PHYSICAL MAP OF THE ARM
Authors: Dvořák Jan , Chen Kuey-Chu
Published: January 2021

Metaphase I (MI) pairing of homologous chromosomes in wheat intercultivar hybrids (heterohomologous chromosomes) is usually reduced relative to that within the inbred parental cultivars (euhomologous chromosomes). It was proposed elsewhere that this phenomenon is caused by polymorphism in nucleotide sequences (nonstructural chromosome variation) among wheat cultivars. The distribution of this polymorphism along chromosome arm 6Bp (=6BS) of cultivars Chinese Spring and Cheyenne was investigated. A population of potentially recombinant chromosomes derived from crossing over between telosome 6Bp of Chinese Spring and Cheyenne chromosome 6B was developed in the isogenic background of Chinese Spring. The approximate length of the Chinese Spring segment present in each of these chromosomes was assessed by determining for each chromosome the interval in which crossing over occurred (utilizing the rRNA gene region, a distal C-band and the gliadin gene region as markers). The MI pairing frequencies of these chromosomes (only the complete chromosomes were used) with the normal Chinese Spring telosome 6Bp were determined. These were directly proportional to the length of the euhomologous segment. The longer the incorporated euhomologous segment the better was the MI pairing. This provided evidence that the heterohomologous chromosomes are differentiated from each other in numerous sites distributed throughout the arm.—The comparison of the physical map of arm 6Bp with the linkage map showed a remarkable distortion of the linkage map; no crossing over was detected in the proximal 68% of the arm. A population of 49 recombinant chromosomes was assayed for recombination within the rRNA gene region, but none was detected. No new length variants of the nontranscribed spacer separating the 18S and 26S rRNA genes were detected either.
MUTANTS OF S. CEREVISIAE DEFECTIVE IN THE MAINTENANCE OF MINICHROMOSOMES
Authors: Maine Gregory T , Sinha Pratima , Tye Bik-Kwoon
Published: January 2021

We have isolated yeast mutants that are defective in the maintenance of circular minichromosomes. The minichromosomes are mitotically stable plasmids, each of which contains a different ARS (autonomously replicating sequence), a centrometeric sequence, CEN5, and two yeast genes, LEU2 and URA3. Forty minichromosome maintenance-defective (Mcm-) mutants were characterized. They constitute 16 complementation groups. These mutants can be divided into two classes, specific and nonspecific, by their differential ability to maintain minichromosomes with different ARSs. The specific class of mutants is defective only in the maintenance of minichromosomes that carry a particular group of ARSs irrespective of the centromeric sequence present. The nonspecific class of mutants is defective in the maintenance of all minichromosomes tested irrespective of the ARS or centromeric sequence present. The specific class may include mutants that do not initiate DNA replication effectively at specific ARSs present on the minichromosomes; the nonspecific class may include mutants that are affected in the segregation and/or replication of circular plasmids in general.
POLYMORPHIC SITES AND THE MECHANISM OF EVOLUTION IN HUMAN MITOCHONDRIAL DNA
Authors: Cann Rebecca L , Brown Wesley M , Wilson Allan C
Published: January 2021

Twelve restriction enzymes were used to screen for the presence or absence of cleavage sites at 441 locations in the mitochondrial DNA of 112 humans from four continents. Cleavage maps were constructed by comparison of DNA fragment sizes with those expected from the published sequence for one human mtDNA. One hundred and sixty-three of the sites were polymorphic, i.e., present in some individuals but absent from others, 278 sites being invariant. These polymorphisms probably result from single base substitutions and occur in all functional regions of the genome.—In 77 cases, it was possible to specify the exact nature and location (within a restriction site) of the mutation responsible for the absence of a restriction site in a known human mtDNA sequence and its presence in another human mtDNA. Fifty-two of these 77 gain mutations occur in genes coding for proteins, 34 being silent and 18 causing amino acid replacements; moreover, nine of the replacements are radical.—Notable also is the anomalous ratio of transitions to transversions required to account for these 77 restriction site differences between the known human mtDNA sequences and other human mtDNAs. This ratio is lower for most groups of restriction sites than has been reported from sequence comparisons of limited parts of the mtDNA genome in closely related mammals, perhaps indicating a special functional role or sensitivity to mutagenesis for palindromic regions containing high levels of guanine and cytosine.—From the genomic distribution of the 163 polymorphic sites, it is inferred that the level of point mutational variability in tRNA and rRNA genes is nearly as high as in protein-coding genes but lower than in noncoding mtDNA. Thus, the functional constraints operating on components of the protein-synthetic apparatus may be lower for mitochondria than for other systems. Furthermore, the mitochondrial genes for tRNAs that recognize four codons are more variable than those recognizing only two codons.—Among the more variable of the human mitochondrial genes coding for proteins is that for subunit 2 of cytochrome oxidase; this polypeptide appears to have been evolving about five times faster in primates than in other mammals. Cytochrome c, a nuclearly encoded protein that interacts directly with the oxidase 2 subunit in electron transport, has also evolved faster in primates than in rodents or ungulates. This example, along with that for the mitochondrial rRNA genes and the nuclear genes coding for mitochondrial ribosomal proteins, provides evidence for coevolution between specific nuclear and mitochondrial genes.
CONTROL OF ANTHOCYANIN SYNTHESIS IN PETUNIA HYBRIDA BY MULTIPLE ALLELIC SERIES OF THE GENES An1 AND An2
Authors: Gerats Anton G M , Farcy Eliane , Wallroth Marco , Groot Steven P C , Schram André
Published: January 2021

A mutable allele of the An1 locus in Petunia hybrida has given rise to a multiple series of stable derivative alleles. Anthocyanin concentration in mature flowers of these mutants (an1  +/p/an1) decreases from the wild-type red to the recessive white in a continuous series. Anthocyanin composition changes regularly: the ratio of peonidin to cyanidin is 3.5 for an an1  +/+/an1 and 1.2 for an an1  +/p5/an1 mutant. Analysis of anthocyanins during flower development indicates that these differences in composition are due to the specific state of the An1 locus and not to anthocyanin concentration. Anthocyanin concentration in flowers of the allelic series for An1 correlates with the activity of the enzymes UDP-glucose: flavonoid-3-O-glucosyltransferase and SAM: anthocyanin-3′-O-methyltransferase. The same correlations were found for members of a comparable allelic series at the An2 locus. The possibility that the correlation between the enzyme activities is due to the occurrence of a multienzyme complex is discussed.
POPULATION GENETICS OF DROSOPHILA AMYLASE. V. GENETIC BACKGROUND AND SELECTION ON DIFFERENT CARBOHYDRATES
Authors: Powell Jeffrey R , Amato George D
Published: January 2021

Frequency changes in amylase allozymes and patterns of tissue-specific expression of amylase have been monitored in laboratory populations of Drosophila pseudoobscura maintained on media in which the only carbohydrate source was maltose or starch. Nonrandom changes occurred in patterns of expression, whereas no patterns in allozyme frequency changes were discernible. The nature of the pattern changes was similar to an identical study done on populations derived from a natural population several hundred miles from the population used in the present experiments. However, in the previous study nonrandom changes in allozyme frequencies were also noted. Evidently, selection on the Drosophila amylase system differs depending upon the genetic background of the population. Furthermore, the evolutionary dynamics of structural gene variants and those regions controlling its expression may be independent, a result consistent with DNA sequence data.
ANALYSIS OF DYSGENESIS-INDUCED LETHAL MUTATIONS ON THE X CHROMOSOME OF A Q STRAIN OF DROSOPHILA MELANOGASTER
Authors: Simmons Michael J , Raymond John D , Culbert Timothy P , Laverty Todd R
Published: January 2021

The Q strain known as v  6 was tested for its ability to induce X-linked lethal mutations in male and female hybrids from crosses with M strains in the P-M system of hybrid dysgenesis. All measurements of the mutation rate were made on the X chromosome derived from the v  6 strain. The lethal rate for young hybrid males from the cross M female x v  6 male was 1.11% per chromosome. For older males, it was only 0.44%, suggesting that there is less mutational or more repair activity in the germ cells of the older males or that mutant cells are selectively eliminated as the hybrid males age. The lethal rate for hybrid females from comparable crosses was approximately the same for both ages that were tested. However, it was substantially less than the rate for the hybrid males—only 0.26% per chromosome. Genetically identical hybrid females from reciprocal crosses also showed a low mutation rate, 0.13% per chromosome. Again, there was no difference between young and old flies.—Mapping experiments established that most of the lethal mutations that were recovered from the male and female hybrids were located in two regions on the X chromosome, one between bands 14B13 and 15A9, the other between bands 19A1 and 20A, which encompasses the maroonlike locus. More refined mapping of the lethals in the maroonlike region demonstrated that the vast majority of these affected a single gene located in band 19C4. Cytological analysis of the lethal chromosomes revealed that several carried rearrangements, including inversions, duplications and deficiencies. Chromosome breakage occurred primarily in bands 14D1-3 and 18F-20A, and most of the breaks in the latter segment were located in 19C. However, rearrangements involving 19C and mutations of the gene in 19C4 were mutually exclusive events. In situ hybridization of a P element probe to the chromosomes of v  6 demonstrated that P elements reside at a minimum of five sites on the X chromosome. These P element sites correspond to the mutational and breakage hot spots on that chromosome. The combined genetic and cytological data imply that most of the X-linked lethal mutations that occur in M × v  6 hybrids are due to local P element action. Consideration of these and other data suggest that v  6 is a weak P strain in the P-M system of hybrid dysgenesis and that other Q strains might also be regarded in this way.
GENETIC CONTROL OF L-A AND L-(BC) dsRNA COPY NUMBER IN KILLER SYSTEMS OF SACCHAROMYCES CEREVISIAE
Authors: Ball Steven G , Tirtiaux Catherine , Wickner Reed B
Published: January 2021

M dsRNA in yeast encodes a toxin precursor and immunity protein, whereas L-A dsRNA encodes the 81,000-dalton major protein of the intracellular particles in which both L-A and M are found. L-(BC) dsRNA(s) are found in particles with different coat proteins. We find that M dsRNA lowers the copy number of L-A, but not L-(BC). The SKI gene products lower the copy number of L-(BC), L-A, M1 and M2. This is the first known interaction of L-(BC) with any element of the killer systems. The MAK3, MAK10 and PET18 gene products are necessary for L-A maintenance and replication, but mutations in these genes do not affect L-(BC) copy number. Mutations in MAK1, MAK4, MAK7, MAK17 and MAK24 do not detectably affect copy number of L-(BC) or L-A.
GENOTYPIC CORRELATION AND REGRESSION IN SOCIAL GROUPS: MULTIPLE ALLELES, MULTIPLE LOCI AND SUBDIVIDED POPULATIONS
Authors: Pamilo Pekka
Published: January 2021

Genotypic correlations and regressions can be estimated from multiallelic data sets either by weighting the allelic effects additively or by specifically weighting the genotypic interactions. Both methods can be extended to multiple loci, but they do not fully take into account the joint segregation patterns at the loci. These genotypic statistics have a great importance in sociobiological contexts, as they can be used for genetic descriptions of social structures. In this paper I examine the two estimation methods and show how the genotypic correlation and regression coefficients from genotypic interactions are connected to other statistics of standard population genetics; special emphasis is given to the sample-size correction when intracolony correlations from small samples were estimated. I also show how genotypic correlation and regression can be estimated in subdivided populations, both in continuous populations with isolation by distance and in populations divided into separate subpopulations. The latter analysis is an example of a more general hierarchic correlation analysis.
CYTOGENETIC MAPPING OF ENZYME LOCI ON CHROMOSOMES J AND U OF DROSOPHILA SUBOBSCURA
Authors: Pinsker W , Sperlich D
Published: January 2021

Enzyme loci located on chromosome J and U were mapped cytologically by means of a Y translocation technique. A linkage map of the two chromosomes was established in a parallel experiment and the recombination frequency in different regions of the chromosomes determined. A comparison of the cytogenetic localization of the enzyme genes in D. subobscura and D. melanogaster indicates that many paracentric inversions must have taken place in the course of divergent evolution. However, no displacements of genes from one element to another due to pericentric inversions, reciprocal translocations or transposing elements can be observed. In spite of the large number of structural rearrangements that have occurred in the phylogeny of the genus Drosophila, gross similarities of banding pattern in homologous regions of the chromosomes of the two species become apparent.
MISMATCH REPAIR MUTATIONS OF ESCHERICHIA COLI K12 ENHANCE TRANSPOSON EXCISION
Authors: Lundblad Victoria , Kleckner Nancy
Published: January 2021

Excision of the prokaryotic transposon Tn 10 is a host-mediated process that occurs in the absence of recA function or any transposon-encoded functions. To determine which host functions might play a role in transposon excision, we have isolated 40 mutants of E. coli K12, designated tex, which increase the frequency of Tn 10 precise excision. Three of these mutations (texA) have been shown to qualitatively alter RecBC function. We show that 21 additional tex mutations with a mutator phenotype map to five genes previously identified as components of a methylation-directed pathway for repair of base pair mismatches: uvrD, mutH, mutL, mutS and dam. Previously identified alleles of these genes also have a Tex phenotype.—Several other E. coli mutations affecting related functions have been analyzed for their effects on Tn10 excision. Other mutations affecting the frequency of spontaneous mutations (mutT, polA, ung), different excision repair pathways (uvrA, uvrB) or the state of DNA methylation (dcm) have no effect on Tn 10 excision. Mutations ssb-113 and mutD5, however, do increase Tn 10 excision.—The products of the mismatch correction genes probably function in a coordinated way during DNA repair in vivo. Thus, mutations in these genes might also enhance transposon excision by a single general mechanism. Alternatively, since mutations in each gene have qualitatively and quantitatively different effects on transposon excision, defects in different mismatch repair genes may enhance excision by different mechanisms.
CIRCADIAN RHYTHMS IN NEUROSPORA CRASSA: INTERACTIONS BETWEEN CLOCK MUTATIONS
Authors: Lakin-Thomas Patricia L , Brody Stuart
Published: January 2021

Mutations at four loci in Neurospora crassa that alter the period of the circadian rhythm have been used to construct a series of double mutant strains in order to detect interactions between these mutations. Strains carrying mutations at three of these loci have altered periods on minimal media: prd-1, several alleles at the olir (oligomycin resistance) locus and four alleles at the frq locus. A mutation at the fourth locus, cel, which results in a defect in fatty acid synthesis, also leads to lengthening of the period when the medium is supplemented with linoleic acid (18:2). The cel mutation was crossed into strains carrying the frq, prd-1 and olir mutations, and the periods of the double mutant strains with and without 18:2 supplementation were determined. In addition, data from the literature for other combinations of loci and/or chemical effects on the period have been reanalyzed.—It was found that (1) both prd-1 and olir are epistatic to the effects of 18:2 on cel; (2) in the series of cel frq double mutant strains, the period-lengthening effect of 18:2 is inversely proportional to the period of the frq parent, indicating an interaction between frq and cel; (3) period effects reported in the literature can be described as changes by a fixed ratio or percentage of the period rather than by a fixed number of hours, and the data, therefore, can support a multiplicative as well as an additive model.—Several biochemical interpretations of these interactions are discussed, based on simple chemical kinetics, enzyme inhibition kinetics and the control of flux through metabolic pathways.
TEMPORAL VARIATION OF THE MATING SYSTEM IN A NATURAL POPULATION OF JACK PINE
Authors: Cheliak W M , Dancik B P , Morgan K , Yeh F C H , Strobeck C
Published: January 2021

Mating system parameters of a northern conifer, Pinus banksiana Lamb., were estimated from allozyme polymorphisms. Seeds analyzed were obtained from serotinous cones of 30 individuals and represented four independent fertilizations in 1975, 1976, 1977 and 1978. Results indicated that a mixed mating system model, with a mean effective outcrossing rate of 88 ± 0.047%, described the mating system of this stand. However, there was an approximately linear increase in the apparent selfing rate from the oldest (1975) to the newest (1978) crop. Two hypotheses could account for these observations. First, there may have been changes in the mating system during the 4-yr period, but linearity of the differences observed in this study may have been due to chance. These changes were, however, independent of the variability of the observed pollen pool. This indicated that they were not a result of different proportions of outcrossed zygotes directly observed. Second, there could have been a more or less constant amount of selfing, followed by a differential loss of viability of selfed and outcrossed zygotes during the period of storage in the cones. Under this hypothesis, selfed zygotes are at a selective disadvantage relative to outcrossed zygotes. No differences in the mating system could be demonstrated among the three crown strata of this stand. There was significant interlocus heterogeneity in the filial generation genotypic distributions and in the estimated outcrossing rates, reflecting the complex nature of forces that can affect single-locus estimates. There was evidence of some additional inbreeding, possibly due to family structures in the stand; however, this was a minor component of the total inbreeding.
GENE INTERACTIONS AFFECTING MUSCLE ORGANIZATION IN CAENORHABDITIS ELEGANS
Authors: Brown Susan J , Riddle Donald L
Published: January 2021

Revertants of unc-15(e73)I, a paralyzed mutant with an altered muscle paramyosin, include six dominant and two recessive intragenic unc-15 revertants, two new alleles of the previously identified suppressor gene, sup-3 V, and a new suppressor designated sup-19(m210)V. The recessive intragenic unc-15 revertants exhibit novel alterations in paramyosin paracrystal structure and distribution, and these alterations are modified by interaction with unc-82(e1220)IV, another mutation that affects paramyosin. A strain containing both unc-15 and a mutation in sup-3 V that restores movement was mutagenized, and paralyzed mutants resembling unc-15 were isolated. Twenty mutations that interfere with suppression were divided into three classes (nonmuscle, sus-1, and mutations within sup-3) based on phenotype, genetic map position and dominance. The nonmuscle mutations include dumpy and uncoordinated types that have no obvious direct effect on muscle organization. Two recessive mutations define a new gene, sus-1 III. These mutations modify the unc-15(e73) phenotype to produce a severely paralyzed, dystrophic double mutant that is not suppressed by sup-3. Five semidominant, intragenic sup-3 antisuppressor mutations, one of which occurred spontaneously, restore the wild-type sup-3 phenotype of nonsuppression. However, reversion of these mutants generated no new suppressor alleles of sup-3, suggesting that the sup-3 antisuppressor alleles are not wild type but may be null alleles.