bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of magnetic anisotropy in a Co thin film on a flexible substrate by applying biaxial tensile strain
Authors: Matsumoto H. , Ota S. , Koyama T. , Chiba D.
Published: January 2021

We have demonstrated a reversible control of magnetic anisotropy in Pt/Co and Pd/Co structures formed on a polyethylene naphthalate flexible substrate by stretching the substrate biaxially. Compared with the case of the uniaxial tensile strain, which has been previously studied, the in-plane biaxial tensile strain produces much larger compressive strain normal to the plane, resulting in the significant modulation of the perpendicular magnetic anisotropy. We found the magnetic easy axis switching from in-plane to out-of-plane by applying up to 2% biaxial strain. In-plane magnetic anisotropy induced by the biaxial tensile strain is also investigated.
Depolarization field tuning of nanoscale ferroelectric domains in (001)PbZr0.4Ti0.6O3/SrTiO3/PbZr0.4Ti0.6O3 epitaxial heterostructures
Authors: Govinden V. , Zhang Q. , Sando D. , Valanoor N.
Published: January 2021

The effect of tuning the depolarization field in (001)-oriented ultrathin epitaxial PbZr0.4Ti0.6O3/SrTiO3/PbZr0.4Ti0.6O3 ferroelectric heterostructures is investigated. The thickness of the dielectric spacer (SrTiO3) is maintained constant at 2 unit cells. The ferroelectric layer thickness in the heterostructure (each PbZr0.4Ti0.6O3) layer varied from 8 to 15 nm is exploited as the parameter to tune the depolarization field. Piezoresponse force microscopy reveals a domain evolution from continuous labyrinthine domains to individual nanoscale bubble domains under the influence of an increasing depolarization field. A statistical analysis of the domain features (i.e., domain wall length and domain fraction) reveals that this change in domain morphology also affects the wall roughness and its associated disorder. The local coercive voltage obtained using switching spectroscopy piezoresponse force microscopy finds the 15 nm film to have the lowest coercive voltage. This is attributed to both a strain-induced increase in tetragonality and the depolarization field-induced changes in the domain morphology.
All-optical and microwave-free detection of Meissner screening using nitrogen-vacancy centers in diamond
Authors: Paone D. , Pinto D. , Kim G. , Feng L. , Kim M.-J. , Stöhr R. , Singha A. , Kaiser S. , Logvenov G. , Keimer B. , Wrachtrup J. , Kern K.
Published: January 2021

Microscopic studies on thin film superconductors play an important role for probing non-equilibrium phase transitions and revealing dynamics at the nanoscale. However, magnetic sensors with nanometer scale spatial and picosecond temporal resolution are essential for exploring these. Here, we present an all-optical, microwave-free method that utilizes the negatively charged nitrogen-vacancy (NV) center in diamond as a non-invasive quantum sensor and enables the spatial detection of the Meissner state in a superconducting thin film. We place an NV implanted diamond membrane on a 20nm thick superconducting La2−xSrxCuO4 (LSCO) thin film with Tc of 34K. The strong B-field dependence of the NV photoluminescence allows us to investigate the Meissner screening in LSCO under an externally applied magnetic field of 4.2mT in a non-resonant manner. The magnetic field profile along the LSCO thin film can be reproduced using Brandt’s analytical model, revealing a critical current density jc of 1.4×108A/cm2. Our work can be potentially extended further with a combination of optical pump probe spectroscopy for the local detection of time-resolved dynamical phenomena in nanomagnetic materials.
The relaxation dynamics of single flow-stretched polymers in semidilute to concentrated solutions
Authors: Tyagi Neha , Cherayil Binny J.
Published: January 2021

Recent experiments on the return to equilibrium of solutions of entangled polymers stretched by extensional flows [Zhou and Schroeder, Phys. Rev. Lett. 120, 267801 (2018)] have highlighted the possible role of the tube model’s two-step mechanism in the process of chain relaxation. In this paper, motivated by these findings, we use a generalized Langevin equation (GLE) to study the time evolution, under linear mixed flow, of the linear dimensions of a single finitely extensible Rouse polymer in a solution of other polymers. Approximating the memory function of the GLE, which contains the details of the interactions of the Rouse polymer with its surroundings, by a power law defined by two parameters, we show that the decay of the chain’s fractional extension in the steady state can be expressed in terms of a linear combination of Mittag-Leffler and generalized Mittag-Leffler functions. For the special cases of elongational flow and steady shear flow, and after adjustment of the parameters in the memory function, our calculated decay curves provide satisfactory fits to the experimental decay curves from the work of Zhou and Schroeder and earlier work of Teixeira et al. [Macromolecules 40, 2461 (2007)]. The non-exponential character of the Mittag-Leffler functions and the consequent absence of characteristic decay constants suggest that melt relaxation may proceed by a sequence of steps with an essentially continuous, rather than discrete, spectrum of timescales.
A simplified charge projection scheme for long-range electrostatics in ab initio QM/MM calculations
Authors: Pan Xiaoliang , Nam Kwangho , Epifanovsky Evgeny , Simmonett Andrew C. , Rosta Edina , Shao Yihan
Published: January 2021

In a previous work [Pan et al., Molecules 23, 2500 (2018)], a charge projection scheme was reported, where outer molecular mechanical (MM) charges [>10 Å from the quantum mechanical (QM) region] were projected onto the electrostatic potential (ESP) grid of the QM region to accurately and efficiently capture long-range electrostatics in ab initio QM/MM calculations. Here, a further simplification to the model is proposed, where the outer MM charges are projected onto inner MM atom positions (instead of ESP grid positions). This enables a representation of the long-range MM electrostatic potential via augmentary charges (AC) on inner MM atoms. Combined with the long-range electrostatic correction function from Cisneros et al. [J. Chem. Phys. 143, 044103 (2015)] to smoothly switch between inner and outer MM regions, this new QM/MM-AC electrostatic model yields accurate and continuous ab initio QM/MM electrostatic energies with a 10 Å cutoff between inner and outer MM regions. This model enables efficient QM/MM cluster calculations with a large number of MM atoms as well as QM/MM calculations with periodic boundary conditions.
Effect of chemical substitution on polytypes and extended defects in chalcopyrites: A density functional theory study
Authors: Park Kanghyeon , Jeong Byeong-Hyeon , Lim Hui Yeor , Park Ji-Sang
Published: January 2021

In ternary semiconductors, both stacking disorder and cation disorder can cause the formation of polytypes and extended defects. We perform density functional theory calculations to investigate the stability of polytypes in six ternary sulfides, such as CuInS2, CuGaS2, CuAlS2, AgInS2, AgGaS2, and AgAlS2. The formation energy of polytypes generated by stacking disorders is used to generate the anisotropic next-nearest neighbor Ising models. The estimated stacking fault energy by the model is in good agreement with the calculated stacking fault energy. The incorporation of Ga and Ag tends to suppress and promote the formation of stacking faults, respectively. On the other hand, the electronic bandgap of the polytypes generated by cation disorder is negatively correlated with the formation energy, resulting in the trapping of charge carriers at antisite domain boundaries. The formation of antisite domain boundaries can be suppressed by the incorporation of Ag and Ga.
On the impingement of free, thin sheets of liquids—A photographic study of the impingement zone
Authors: Demyanovich Robert J.
Published: January 2021

The impingement zone created by the impingement of two free, thin sheets of liquids was studied using photographic techniques. The experimental parameters studied were the impingement angle, single-sheet velocity, single-sheet thickness at impingement, liquid surface tension, and liquid viscosity. Momentum balances of the impingement are in good agreement with observations that a critical mixed sheet velocity must be achieved in order for the liquid to flow in the backward direction of the mixed sheet. The critical mixed sheet velocity for backflow was found to correlate well with the Taylor–Culick velocity. However, if all of the kinetic energy associated with the single-sheet component velocity that is destroyed upon impingement is dissipated into the mixed sheet, then that critical velocity cannot be achieved, and there will be no backflow from the backward part of the mixed sheet. An unusual result of the study is that the projection of the single sheets onto the mixed sheet at impingement presents as a “skin” that can be clearly seen in photographs or a video. This “skin” feature potentially allows for the use of macro photography to measure the thickness of the single sheet at impingement.
The 3-
O
-sulfation of heparan sulfate modulates protein binding and lyase degradation
Authors: Chopra Pradeep , Joshi Apoorva , Wu Jiandong , Lu Weigang , Yadavalli Tejabhiram , Wolfert Margreet A. , Shukla Deepak , Zaia Joseph , Boons Geert-Jan
Published: January 2021

Significance

Although heparan sulfate (HS) modified by a 3-
O
-sulfate (3-OS) has been implicated in many biological processes, there is only a rudimentary understanding of ligand requirements of HS-binding proteins requiring this type of modification. We developed a modular synthetic approach that provided a structurally diverse collection of HS oligosaccharides with and without 3-OS. The compounds were printed as a glycan microarray to determine ligand requirements of HS-binding proteins, which revealed specific HS sequons for binding, and led to the discovery of proteins needing 3-OS for binding. The compounds made it possible to determine receptor requirements of herpes simplex virus, and substrate specificities of heparin lyases. The platform provides an important means to examine the biology of 3-OS−modified HS.
Bayesian estimation of SARS-CoV-2 prevalence in Indiana by random testing
Authors: Yiannoutsos Constantin T. , Halverson Paul K. , Menachemi Nir
Published: January 2021

Significance

Infection with the novel coronovirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in a worldwide pandemic of COVID-19 disease. Efforts to design local, regional, and national responses to the virus are constrained by a lack of information on the extent of the epidemic as well as inaccuracies in newly developed diagnostic tests. In this study we analyze data from testing randomly selected Indiana state residents for infection or previous exposure to SARS-CoV-2 and derive estimates of the statewide COVID-19 prevalence in an attempt to address potential biases arising from nonresponse and diagnostic testing errors.
Rootstocks.
Authors: Durner Ed , Durner Ed Rutgers
Published: January 2021

Plants of many horticultural crops consist of multiple genetic systems, two or more distinct genotypes joined together as a single plant. The components are identified as the rootstock, interstem and scion. Grafting and budding are the processes that combine these components to establish vascular continuity between them to produce a single plant. Grafting may be natural or human initiated, forced grafting. This datasheet will mainly consider forced grafting with only a brief discussion of natural grafting. The rootstock is that component of the plant that fuses with the scion and provides the plants root system. Other terms used to describe this lower portion of the plant include stock and understock. Stock is synonymous with both rootstock and understock. Understock implies that the lower portion of the plant provides both the root system and some of the trunk while rootstock or stock implies that only the root system is provided by the lower piece. When grafting is performed high on the rootstock, the rootstock may also provide scaffold limbs. The scion is the plants shoot system. It is the component that produces the desired commodity in most cases, which are usually flowers or fruit. In perennials, the scion is nearly always vegetatively propagated. In grafted vegetables, the scion is usually propagated via seed. An interstem is a third genetic component of some grafted plants and is often selected to provide compatibility between the rootstock and the scion. Both grafting and budding combine dissimilar genotypes into one plant. Budding is a form of grafting where a single vegetative bud is used as the scion or interstem. Grafting refers to the condition where more than one bud on a common stem piece are combined with the rootstock or interstem. Perennial ornamental and fruit crops are the grafted crops that are familiar to most horticulturists. Annual vegetable crops are increasingly being grown as grafted plants and interest in using them in commercial production is rising steeply. Short lists of common rootstocks for a number of ornamental, fruit, nut and vegetable crops are presented in Tables 1-3 (at the bottom of this article). These lists are by no means complete, but provide an insight into the large number of rootstocks available in modern horticultural production. Specific recommendations for an area should be obtained from local experts. Good rootstocks should possess as many of the following crop appropriate characteristics as possible: affordable, long term graft compatible, easily propagated, promotes precocity and productivity, controls scion vigour, conveys pest resistance, improves stress tolerance, and has minimal suckering.
Plant factories - closed plant production systems (CPPS).
Authors: Morgan Lynette
Published: January 2021

A plant factory is an indoor, enclosed, crop cultivation system where the growing environment is precisely controlled to maximise production. This control over all aspects of plant growth includes light, temperature, humidity, air movement, carbon dioxide (CO2) and nutrition. This is largely achieved through soilless (hydroponic) cultivation techniques. The term plant factory has previously included high intensity production systems such as greenhouses reliant on natural light only or natural light supplemented with horticultural lighting, as well as those utilising only artificial lighting. More recently, 'plant factory' has come to represent a CPPS (closed plant production system) or termed PFAL (plant factory with artificial lighting) where no natural sunlight is required. Plant factories may also be referred to as 'indoor vertical farms' or 'indoor vertical cropping' in the USA and other countries, based on the multi-level nature of the systems which aim to maximise growing space. With a high level of environmental control, plant factories can produce vegetables two to four times faster than by typical outdoor cultivation (Luna-Maldonao et al., 2016), and with the use of vertical systems, optimise yields per unit of floor area. In addition to higher levels of production, plant factories are becoming increasingly sustainable as less water, fertilizers, pesticides and labour are consumed during cultivation (Hu et al., 2014).
Heterogeneous disease-propagating stem cells in juvenile myelomonocytic leukemia
Authors: Louka Eleni , Povinelli Benjamin , Rodriguez-Meira Alba , Buck Gemma , Wen Wei Xiong , Wang Guanlin , Sousos Nikolaos , Ashley Neil , Hamblin Angela , Booth Christopher A.G. , Roy Anindita , Elliott Natalina , Iskander Deena , de la Fuente Josu , Fordham Nicholas , O’Byrne Sorcha , Inglott Sarah , Norfo Ruggiero , Salio Mariolina , Thongjuea Supat , Rao Anupama , Roberts Irene , Mead Adam J.
Published: January 2021

Juvenile myelomonocytic leukemia (JMML) is a poor-prognosis childhood leukemia usually caused by RAS-pathway mutations. The cellular hierarchy in JMML is poorly characterized, including the identity of leukemia stem cells (LSCs). FACS and single-cell RNA sequencing reveal marked heterogeneity of JMML hematopoietic stem/progenitor cells (HSPCs), including an aberrant Lin−CD34+CD38−CD90+CD45RA+ population. Single-cell HSPC index-sorting and clonogenic assays show that (1) all somatic mutations can be backtracked to the phenotypic HSC compartment, with RAS-pathway mutations as a “first hit,” (2) mutations are acquired with both linear and branching patterns of clonal evolution, and (3) mutant HSPCs are present after allogeneic HSC transplant before molecular/clinical evidence of relapse. Stem cell assays reveal interpatient heterogeneity of JMML LSCs, which are present in, but not confined to, the phenotypic HSC compartment. RNA sequencing of JMML LSC reveals up-regulation of stem cell and fetal genes (HLF, MEIS1, CNN3, VNN2, and HMGA2) and candidate therapeutic targets/biomarkers (MTOR, SLC2A1, and CD96), paving the way for LSC-directed disease monitoring and therapy in this disease.
Effects of dietary restriction on neuroinflammation in neurodegenerative diseases
Authors: Fontana Luigi , Ghezzi Laura , Cross Anne H. , Piccio Laura
Published: January 2021

Recent and accumulating work in experimental animal models and humans shows that diet has a much more pervasive and prominent role than previously thought in modulating neuroinflammatory and neurodegenerative mechanisms leading to some of the most common chronic central nervous system (CNS) diseases. Chronic or intermittent food restriction has profound effects in shaping brain and peripheral metabolism, immunity, and gut microbiome biology. Interactions among calorie intake, meal frequency, diet quality, and the gut microbiome modulate specific metabolic and molecular pathways that regulate cellular, tissue, and organ homeostasis as well as inflammation during normal brain aging and CNS neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, and multiple sclerosis, among others. This review discusses these findings and their potential application to the prevention and treatment of CNS neuroinflammatory diseases and the promotion of healthy brain aging.
Initial TCV operation with a baffled divertor
Authors: Reimerdes H. , Duval B.P. , Elaian H. , Fasoli A. , Février O. , Theiler C. , Bagnato F. , Baquero-Ruiz M. , Blanchard P. , Brida D. , Colandrea C. , De Oliveira H. , Galassi D. , Gorno S. , Henderson S. , Komm M. , Linehan B. , Martinelli L. , Maurizio R. , Moret J.-M. , Perek A. , Raj H. , Sheikh U. , Testa D. , Toussaint M. , Tsui C.K. , Wensing M. , TCV team the , EUROfusion MST1 team the
Published: January 2021

The Tokamak à Configuration Variable (TCV) tokamak is in the midst of an upgrade to further its capability to investigate conventional and alternative divertor configurations. To that end, modular and removable gas baffles have been installed to decrease the coupling between the divertor and the plasma core. The baffles primarily seek to suppress the transit of recycling neutrals to closed flux surfaces. A first experimental campaign with the gas baffles has shown that the baffled divertor remains compatible with a wide range of configurations including snowflake and super-X divertors. Plasma density ramp experiments reveal an increase of the neutral pressure in the divertor by up to a factor ×5 compared to the unbaffled divertor and thereby qualitatively confirm simulations with the SOLPS-ITER code that were used to guide the baffle design. Together with a range of new and upgraded divertor diagnostics, the baffled TCV divertor is now used to validate divertor models for ITER and next step devices with particular emphasis on geometric variations.
On basic and Bass quaternion orders
Authors: Chari Sara , Smertnig Daniel , Voight John
Published: January 2021

A quaternion order

O

\mathcal {O}

over a Dedekind domain

R
R

is Bass if every

R
R

-superorder is Gorenstein, and

O

\mathcal {O}

is basic if it contains an integrally closed quadratic

R
R

-order. In this article, we show that these conditions are equivalent in local and global settings: a quaternion order is Bass if and only if it is basic. In particular, we show that the property of being basic is a local property of a quaternion order.
Fast multi-precision computation of some Euler products
Authors: Ettahri S. , Ramaré O. , Surel L.
Published: January 2021

For every modulus

q
≥
3

q\ge 3

, we define a family of subsets

A

\mathcal {A}

of the multiplicative group

(

Z

/

q

Z

)
×

(\mathbb {Z}/q\mathbb {Z})^\times

for which the Euler product

∏

p
+
q

Z

∈

A

(
1
−

p

−
s

)

\prod _{p+q\mathbb {Z}\in \mathcal {A}}(1-p^{-s})

can be computed with high numerical precision, where

s
>
1

s>1

is some given real number. We provide a Sage script to do so, and extend our result to compute Euler products
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="product Underscript p plus q double-struck upper Z element-of script upper A Endscripts upper F left-parenthesis 1 slash p Superscript s Baseline right-parenthesis slash upper H left-parenthesis 1 slash p Superscript s Baseline right-parenthesis">

∏

p
+
q

Z

∈

A

F
(
1

/

p
s

)

/

H
(
1

/

p
s

)

\prod _{p+q\mathbb {Z}\in \mathcal {A}}F(1/p^s)/H(1/p^s)

where

F
F

and

H
H

are polynomials with real coefficients, when this product converges absolutely. This enables us to give precise values of several Euler products occurring in number theory.
Effective bounds for Huber’s constant and Faltings’s delta function
Authors: Avdispahić Muharem
Published: January 2021

By a closer inspection of the Friedman-Jorgenson-Kramer algorithm related to the prime geodesic theorem on cofinite Fuchsian groups of the first kind, we refine the constants therein. The newly obtained effective upper bound for Huber’s constant is in the modular surface case approximately

74000
74000

-times smaller than the previously claimed one. The degree of reduction in the case of an upper bound for Faltings’s delta function ranges from

10

8

10^{8}

to

10

16

10^{16}

.
A nonlinear Schrödinger equation with fractional noise
Authors: Deya Aurélien , Schaeffer Nicolas , Thomann Laurent
Published: January 2021

We study a stochastic Schrödinger equation with a quadratic nonlinearity and a space-time fractional perturbation, in space dimension

d
≤
3

d\leq 3

. When the Hurst index is large enough, we prove local well-posedness of the problem using classical arguments. However, for a small Hurst index, even the interpretation of the equation needs some care. In this case, a renormalization procedure must come into the picture, leading to a Wick-type interpretation of the model. Our fixed-point argument then involves some specific regularization properties of the Schrödinger group, which allows us to cope with the strong irregularity of the solution.
Spatial variation of microtubule depolymerization in large asters
Authors: Ishihara Keisuke , Decker Franziska , Caldas Paulo , Pelletier James F. , Loose Martin , Brugués Jan , Mitchison Timothy J.
Published: January 2021

We systematically measure plus-end dynamics in large microtubule asters and find evidence for spatial regulation of depolymerization rate.
What is the relationship between validated frailty scores and mortality for adults with COVID-19 in acute hospital care? A systematic review
Authors: Cosco Theodore D , Best John , Davis Daniel , Bryden Daniele , Arkill Suzanne , van Oppen James , Riadi Indira , Wagner Kevin R , Conroy Simon
Published: January 2021

Background and Aim

The aim of this systematic review was to quantify the association between frailty and COVID-19 in relation to mortality in hospitalised patients.

Methods

Medline, Embase, Web of Science and the grey literature were searched for papers from inception to 10 September 2020; the search was re-run in Medline up until the 9 December 2020. Screening, data extraction and quality grading were undertaken by two reviewers. Results were summarised using descriptive statistics, including a meta-analysis of overall mortality; the relationships between frailty and COVID-19 mortality were summarised narratively.

Results

A total of 2,286 papers were screened resulting in 26 being included in the review. Most studies were from Europe, half from the UK, and one from Brazil; the median sample size was 242.5, median age 73.1 and 43.5% were female. In total, 22/26 used the Clinical Frailty Scale; reported mortality ranged from 14 to 65%. Most, but not all studies showed an association between increasing frailty and a greater risk of dying. Two studies indicated a sub-additive relationship between frailty, COVID-19 and death, and two studies showed no association.

Conclusions

Whilst the majority of studies have shown a positive association between COVID-19-related death and increasing frailty, some studies suggested a more nuanced understanding of frailty and outcomes in COVID-19 is needed. Clinicians should exert caution in placing too much emphasis on the influence of frailty alone when discussing likely prognosis in older people with COVID-19 illness.
The ‘Wish to Die’ in later life: prevalence, longitudinal course and mortality. Data from TILDA
Authors: Briggs Robert , Ward Mark , Kenny Rose Anne
Published: January 2021

Background

‘Wish to Die’ (WTD) involves thoughts of or wishes for one’s own death or that one would be better off dead.

Objective

To examine the prevalence, longitudinal course and mortality-risk of WTD in community-dwelling older people.

Design

Observational study with 6-year follow-up.

Setting

The Irish Longitudinal Study on Ageing, a nationally representative cohort of older adults.

Subjects

In total, 8,174 community-dwelling adults aged ≥50 years.

Methods

To define WTD, participants were asked: ‘In the last month, have you felt that you would rather be dead?’ Depressive symptoms were measured using the CES-D. Mortality data were compiled by linking administrative death records to individual-level survey data from the study.

Results

At Wave 1, 3.5% of participants (279/8,174) reported WTD. Both persistent loneliness (OR 5.73 (95% CI 3.41–9.64)) and depressive symptoms (OR 6.12 (95% CI 4.33–8.67)) were independently associated with WTD.

Of participants who first reported WTD at Wave 1 or 2, 72% did not report WTD when reassessed after 2 years, and the prevalence of depressive symptoms (−44%) and loneliness (−19%) was more likely to decline in this group at follow-up.

Fifteen per cent of participants expressing WTD at Wave 1 died during a 6-year follow-up.

Conclusions

WTD amongst community-dwelling older people is frequently transient and is strongly linked with the course of depressive symptoms and loneliness. An enhanced focus on improving access to mental health care and addressing social isolation in older people should therefore be a public health priority, particularly in the current context of the Covid-19 pandemic.
III—The Wonder Of Signs
Authors: Haddock Adrian
Published: January 2021

Anscombe (1956) raises a difficulty for the very idea of quotation. Davidson (1979) seeks to dissolve this difficulty. But the difficulty is real. And its lesson is that, in quotation, language takes itself as its topic in a non-objectifying manner. The idea of a non-objectifying manner of being a topic is crucial, not merely for understanding quotation, but for understanding the distinctive form of sensory consciousness in which language is perceived.
Pyramidal Cells in Olfactory Cortex
Authors: Brunjes Peter C
Published: January 2021

The neocortex and olfactory cortices share many features including their laminar organization, developmental sequences, and cell types. Previous work indicates that neocortical pyramidal cells exhibit a gradient of dendritic size: cells involved in the initial processing of information are less complex than those in subsequent, higher processing areas. Results presented here confirm that the same is true for the olfactory cortex: pyramidal cells in the region closest to the olfactory bulb, the anterior olfactory nucleus, have smaller total dendritic length and occupy less neural space than those in the posterior piriform cortex. These findings add to the evidence for general rules of development, organization, and function across forebrain cortices.
Cardiac operations and interventions during the COVID-19 pandemic: a nationwide perspective
Authors: Leyva Francisco , Zegard Abbasin , Okafor Osita , Stegemann Berthold , Ludman Peter , Qiu Tian
Published: January 2021

Aims 

The COVID-19 pandemic has led to a decline in hospitalizations for non-COVID-19-related conditions. We explored the impact of the COVID-19 pandemic on cardiac operations and interventions undertaken in England.

Methods and results 

An administrative database covering hospital activity for England, the Health Episodes Statistics, was used to assess a total of 286 697 hospitalizations for cardiac operations and interventions, as well as 227 257 hospitalizations for myocardial infarction (MI) and 453 799 for heart failure (HF) from 7 January 2019 to 26 July 2020. Over the 3 months of ‘lockdown’, total numbers and mean reductions in weekly rates [n (−%)], compared with the same time period in 2019, were: coronary artery bypass grafting [−2507 (−64%)]; percutaneous coronary intervention [−5245 (−28%)]; surgical [−1324 (−41%)] and transcatheter [−284 (−21%)] aortic valve replacement; mitral valve replacement; implantation of pacemakers [−6450 (−44%)], cardiac resynchronization therapy with [−356 (−42%)] or without [−491 (−46%)] defibrillation devices, and implantable cardioverter-defibrillators [−501 (−45%)]; atrial fibrillation ablation [−1902 (−83%)], and other ablations [−1712 (−64%)] (all P < 0.001). Over this period, there were 21 038 fewer procedures than in the reference period in 2019 (P < 0.001). These changes paralleled reductions in hospitalizations for MI [−10 794 (−27%)] and HF [−63 058 (−28%)] (both P < 0.001).

Conclusions 

The COVID-19 pandemic has led to substantial reductions in the number of cardiac operations and interventions undertaken. An alternative strategy for healthcare delivery to patients with cardiac conditions during the COVID-19 pandemic is urgently needed.
Linkage and the maintenance of heritable variation by mutation-selection balance.
Authors: Bürger R
Published: January 2021

The role of linkage in influencing heritable variation maintained through a balance between mutation and stabilizing selection is investigated for two different models. In both cases one trait is considered and the interactions within and between loci are assumed to be additive. Contrary to most earlier investigations of this problem no a priori assumptions on the distribution of genotypic values are imposed. For a deterministic two-locus two-allele model with recombination and mutation, related to the symmetric viability model, a complete nonlinear analysis is performed. It is shown that, depending on the recombination rate, multiple stable equilibria may coexist. The equilibrium genetic and genic variances are calculated. For a polygenic trait in a finite population with a possible continuum of allelic effects a simulation study is performed. In both models the equilibrium genetic and genic variances are roughly equal to the house-of-cards prediction or its finite population counterpart as long as the recombination rate is not extremely low. However, negative linkage disequilibrium builds up. If the loci are very closely linked the equilibrium additive genetic variance is slightly lower than the house-of-cards prediction, but the genic variance is much higher. Depending on whether the parameters are in favor of the house-of-cards or the Gaussian approximation, different behavior of the genetic system occurs with respect to linkage.
Arrest of micronuclear DNA replication during genomic exclusion in Tetrahymena produces haploid strains.
Authors: Kaczanowski A , Gornicka I , Cleffmann G
Published: January 2021

Diploid cells of Tetrahymena thermophila were crossed to strain A*V, whose micronucleus is defective, to induce the unilateral transfer of gametic nuclei from the diploid cells to the A*V cells (round I of genomic exclusion). These haploid nuclei presumably undergo one endomitotic cycle and then become diploid with a G1 (2C) DNA content. However, further DNA replication from 2C to 4C was transiently arrested until the pairs separated. When endomitosis was blocked by treatment with cycloheximide during 6-8 hours of conjugation, the exconjugants of round I of genomic exclusion remained haploid. Competence for diploidization is apparently limited to some period of time after nuclear transfer. Blocking of diploidization during round I of genomic exclusion can be used as an efficient way to induce haploid strains in Tetrahymena.
Genes that implement the hermaphrodite mode of dosage compensation in Caenorhabditis elegans.
Authors: Plenefisch J D , DeLong L , Meyer B J
Published: January 2021

We report a genetic characterization of several essential components of the dosage compensation process in Caenorhabditis elegans. Mutations in the genes dpy-26, dpy-27, dpy-28, and the newly identified gene dpy-29 disrupt dosage compensation, resulting in elevated X-linked gene expression in XX animals and an incompletely penetrant maternal-effect XX-specific lethality. These dpy mutations appear to cause XX animals to express each set of X-linked genes at a level appropriate for XO animals. XO dpy animals are essentially wild type. Both the viability and the level of X-linked gene expression in XX animals carrying mutations in two or more dpy genes are the same as in animals carrying only a single mutation, consistent with the view that these genes act together in a single process (dosage compensation). To define a potential time of action for the gene dpd-28 we performed reciprocal temperature-shift experiments with a heat sensitive allele. The temperature-sensitive period for lethality begins 5 hr after fertilization at the 300-cell stage and extends to about 9 hr, a point well beyond the end of cell proliferation. This temperature-sensitive period suggests that dosage compensation is functioning in XX animals by mid-embryogenesis, when many zygotically transcribed genes are active. While mutations in the dpy genes have no effect on the sexual phenotype of otherwise wild-type XX or XO animals, they do have a slight feminizing effect on animals whose sex-determination process is already genetically perturbed. The opposite directions of the feminizing effects on sex determination and the masculinizing effects on dosage compensation caused by the dpy mutations are inconsistent with the wild-type dpy genes acting to coordinately control both processes. Instead, the feminizing effects are most likely an indirect consequence of disruptions in dosage compensation caused by the dpy mutations. Based on the cumulative evidence, the likely mechanism of dosage compensation in C. elegans involves reducing X-linked gene expression in XX animals to equal that in XO animals via the action of the dpy genes.
Definition of cis-acting elements regulating expression of the Drosophila melanogaster ninaE opsin gene by oligonucleotide-directed mutagenesis.
Authors: Mismer D , Rubin G M
Published: January 2021

We have analyzed the cis-acting regulatory sequences of the Rh1 (ninaE) gene in Drosophila melanogaster by P-element-mediated germline transformation of indicator genes transcribed from mutant ninaE promoter sequences. We have previously shown that a 200-bp region extending from -120 to +67 relative to the transcription start site is sufficient to obtain eye-specific expression from the ninaE promoter. In the present study, 22 different 4-13-bp sequences in the -120/+67 promoter region were altered by oligonucleotide-directed mutagenesis. Several of these sequences were found to be required for proper promoter function; two of these are conserved in the promoter of the homologous gene isolated from the related species Drosophila virilis. Alteration of a conserved 9-bp sequence results in aberrant, low level expression in the body. Alteration of a separate 11-bp sequence, found in the promoter regions of several photoreceptor-specific genes of Drosophila, results in an approximately 15-fold reduction in promoter efficiency but without apparent alteration of tissue-specificity. A protein factor capable of interacting with this 11-bp sequence has been detected by DNaseI footprinting in embryonic nuclear extracts. Finally, we have further characterized two separable enhancer sequences previously shown to be required for normal levels of expression from this promoter.
Molecular genetic variation in the centromeric region of the X chromosome in three Drosophila ananassae populations. I. Contrasts between the vermilion and forked loci.
Authors: Stephan W , Langley C H
Published: January 2021

We have surveyed three natural populations of Drosophila ananassae for restriction map variation at the forked (f) and vermilion (v) loci, using 6-cutter restriction enzymes. Both loci are located in the centromeric region of the X chromosome. Two major conclusions can be drawn from the data. First, we found strong evidence for population subdivision, i.e., significant differences in the frequency distributions of polymorphisms and/or haplotypes between the Burma, India, and Brazil populations. Secondly, the pattern of DNA sequence variation between the two loci is unexpectedly different. The level of nucleotide variation in the v locus region is reduced (relative to f), especially in the Burma population. Furthermore, in contrast to v, we found no insertions/deletions larger than 700 bp and no significant linkage disequilibrium at f. The genetic differentiation among subpopulations can readily be attributed to restricted migration as the predominant evolutionary force. According to population genetics theory, the differences in DNA polymorphisms between the two loci are in qualitative agreement with the hypothesis that recombination is reduced in the v locus region ("centromere effect") but not at f. In order to test this hypothesis directly, we determined the cytogenetic positions of several loci in the centromeric region by in situ hybridization and found by comparison with the genetic map that recombination at v is indeed very low, much lower than at f.
Escherichia coli mutator mutD5 is defective in the mutHLS pathway of DNA mismatch repair.
Authors: Schaaper R M
Published: January 2021

We have previously reported that the Escherichia coli mutator strain mutD5 was defective in the correction of bacteriophage M13mp2 heteroduplex DNA containing a T.G mismatch. Here, this defect was further investigated with regard to its interaction with the mutHLS pathway of mismatch repair. A set of 15 different M13mp2 heteroduplexes was used to measure the mismatch-repair capability of wild-type, mutL and mutD5 cells. Throughout the series, the mutD5 strain proved as deficient in mismatch repair as the mutL strain, indicating that the repair defect is similar in the two strains in both extent and specificity. [One exception was noted in the case a T.G mispair that was subject to VSP (Very Short Patch) repair. VSP repair was abolished by mutL but not by mutD.] Variation in the dam-methylation state of the heteroduplex molecules clearly affected repair in the wild-type strain but had no effect on either the mutD or mutL strain. Finally, mutDmutL or mutDmutS double-mutator strains were no more deficient in mismatch repair as were the single mutator strains. The combined results strongly argue that the mismatch-repair deficiency of mutD5 cells resides in the mutH,L,S-dependent pathway of mismatch repair and that the high mutation rate of mutD strains derives in part from this defect.
Mechanisms of mutagenesis by chloroacetaldehyde.
Authors: Jacobsen J S , Perkins C P , Callahan J T , Sambamurti K , Humayun M Z
Published: January 2021

A number of bifunctional chemical mutagens induce exocyclic DNA lesions. For example, 2-chloroacetaldehyde (CAA), a metabolite of vinyl chloride, readily reacts with single-stranded DNA to predominantly form etheno lesions. Here, we report on in vivo mutagenesis caused by CAA treatment of DNA in vitro. These experiments used partially duplex phage M13AB28 replicative form DNA in which a part of the lacZ gene sequence was held in single-stranded form to direct reaction with CAA. CAA-treated partial duplex DNA was transfected into Escherichia coli, and the induced base changes were defined by DNA sequencing. These experiments suggested that CAA treatment induced mutations at cytosines, much less efficiently at adenines, but not at guanines or thymines. Among mutations targeted to cytosine, 80% were C-to-T transitions and 20% were C-to-A transversions. Application of a post-labeling method detected dose-dependent formation of ethenoadenine and ethenocytosine in CAA treated DNA. These data indicate that ethenocytosine is a highly efficient mutagen with properties suggestive of a non-instructional DNA lesion in vivo. Paradoxically, ethenoadenines are efficiently bypassed by a mechanism which appears to be largely nonmutagenic.
Meiosis in Mesostoma ehrenbergii ehrenbergii. IV. Recombination nodules in spermatocytes and a test of the correspondence of late recombination nodules and chiasmata.
Authors: Croft J A , Jones G H
Published: January 2021

Male meiosis in Mesostoma ehrenbergii ehrenbergii (2x = 10) is characterized by extreme restriction of chiasma formation; 3 pairs of chromosomes form bivalents at metaphase I which are associated by single very distally localized chiasma, while two pairs of chromosomes remain as unpaired univalents. Electron microscopical three-dimensional reconstruction analysis of serial sections has been applied to 20 pachytene spermatocyte nuclei. In each nucleus three short stretches of synaptonemal complex (SC) were found, confined to a localized branched lobe of the nucleus, confirming the findings of an earlier study. The majority of reconstructed nuclei show that each of the three SC segments has a single prominent recombination nodule ("late" RN) associated with it. Late RNs in this system therefore show an excellent correspondence with metaphase I chiasmata, in contrast to a previous report. M.e. ehrenbergii is therefore not an exception to the hypothesis that meiotic exchange requires a functional late RN. A few nuclei had two, one or no RNs; these presumably represent nuclei that are not at the stage of maximum RN presence. Although M. e. ehrenbergii shows pronounced chiasma localization at the light microscope level, at the ultrastructural level RNs are widely distributed along the 5-10 microns of SC formed in each bivalent, indicating that genetic exchange are not restricted to particular localized sites but occur at a large number of DNA sequence.
The ash-1, ash-2 and trithorax genes of Drosophila melanogaster are functionally related.
Authors: Shearn A
Published: January 2021

Mutations in the ash-1 and ash-2 genes of Drosophila melanogaster cause a wide variety of homeotic transformations that are similar to the transformations caused by mutations in the trithorax gene. Based on this similar variety of transformations, it was hypothesized that these genes are members of a functionally related set. Three genetic tests were employed here to evaluate that hypothesis. The first test was to examine interactions of ash-1, ash-2 and trithorax mutations with each other. Double and triple heterozygotes of recessive lethal alleles express characteristic homeotic transformations. For example, double heterozygotes of a null allele of ash-1 and a deletion of trithorax have partial transformations of their first and third legs to second legs and of their halteres to wings. The penetrance of these transformations is reduced by a duplication of the bithorax complex. The second test was to examine interactions with a mutation in the female sterile (1) homeotic gene. The penetrance of the homeotic phenotype in progeny from mutant mothers is increased by heterozygosis for alleles of ash-1 or ash-2 as well as for trithorax alleles. The third test was to examine the interaction with a mutation of the Polycomb gene. The extra sex combs phenotype caused by heterozygosis for a deletion of Polycomb is suppressed by heterozygosis for ash-1, ash-2 or trithorax alleles. The fact that mutations in each of the three genes gave rise to similar results in all three tests represents substantial evidence that ash-1, ash-2 and trithorax are members of a functionally related set of genes.
Patterns of variation in the rDNA cistron within and among world populations of a mosquito, Aedes albopictus (Skuse).
Authors: Black W C , McLain D K , Rai K S
Published: January 2021

A restriction map was constructed of the ribosomal cistron in a mosquito, Aedes albopictus (Skuse). The 18s, 28s and nontranscribed spacer (NTS) regions were subcloned and used to probe for intraspecific variation. Seventeen populations were examined throughout the world range of the species. No variation was detected in the coding regions but extensive and continuous variation existed in the NTS. The NTS consisted of two nonhomologous regions. The first region contained multiple 190-bp AluI repeats nested within larger XhoI repeats of various sizes. There was a large number of length variants in the AluI repeat region of the NTS. No repeats were found in the second region and it gave rise to relatively fewer variants. An analysis of NTS diversity in individual mosquitoes indicated that most of the diversity arose at the population level. Discriminant analysis was performed on spacer types in individual mosquitoes and demonstrated that individuals within a population carried a unique set of spacers. In contrast with studies of the NTS in Drosophila populations, there seems to be little conservation of spacers in a population. The importance of molecular drive relative to drift and selection in the generation of local population differentiation is discussed.
Molecular population genetics of mtDNA size variation in crickets.
Authors: Rand D M , Harrison R G
Published: January 2021

Nucleotide sequence analysis of a region of cricket (Gryllus firmus) mtDNA showing discrete length variation revealed tandemly repeated sequences 220 base pairs (bp) in length. The repeats consist of 206 bp sequences bounded by the dyad symmetric sequence 5'GGGGGCATGCCCCC3'. The sequence data showed that mtDNA size variation in this species is due to variation in the number of copies of tandem repeats. Southern blot analysis was used to document the frequency of crickets heteroplasmic for two or more different-sized mtDNAs. In New England populations of G. firmus and a close relative Gryllus pennsylvanicus approximately 60% of the former and 45% of the latter were heteroplasmic. From densitometry of autoradiographs the frequencies of mtDNA size classes were determined for the population samples and are shown to very different in the two species. However, in populations where hybridization between the two species has occurred, the frequencies of size classes and cytoplasmic genotypes in each species' distinct mtDNA lineage were shifted in a manner suggesting nuclear-cytoplasmic interactions. The data were applied to reported diversity indices and hierarchical statistics. The hierarchical statistics indicated that the greatest proportion of variation for mtDNA size was due to variation among individuals in their cytoplasmic genotypes (heteroplasmic or homoplasmic state). The diversity indices were used to estimate a per-generation mutation rate for size variants of 10(-4). The data are discussed in light of the relationship between genetic drift and mutation in maintaining variation for mtDNA size.