bluuebunny/crossref_metadata_2025 huggingface dataset:
Iron‐Catalyzed Fluoroalkylation of Arylborates with Sulfone Reagents: Beyond the Limitation of Reduction Potential
Authors: Wei Zhiqiang , Miao Wenjun , Ni Chuanfa , Hu Jinbo
Published: March 2021

The iron‐catalyzed alkyl–aryl coupling reaction between sulfones and arylboron compounds has remained a challenge. We report the first iron‐catalyzed radical difluoroalkylation of arylborates with N‐heteroaryl sulfones. The coordination between the iron catalyst and the nitrogen atom of N‐heteroaryl sulfones was identified to be important in overcoming the reduction potential limitation of sulfones in the intermolecular single‐electron‐transfer process, which enables both fluoroalkyl N‐heteroaryl sulfones (with relatively high reduction potentials) and nonfluorinated alkyl N‐heteroaryl sulfones (with low reduction potentials) to serve as powerful alkylation reagents.
Pressure‐Induced Emission toward Harvesting Cold White Light from Warm White Light
Authors: Fu Ruijing , Zhao Wenya , Wang Lingrui , Ma Zhiwei , Xiao Guanjun , Zou Bo
Published: March 2021

The pressure‐induced emission (PIE) behavior of halide perovskites has attracted widespread attention and has potential application in pressure sensing. However, high‐pressure reversibility largely inhibits practical applications. Here, we describe the emission enhancement and non‐doping control of the color temperature in two‐dimensional perovskite (C6H5CH2CH2NH3)2PbCl4 ((PEA)2PbCl4) nanocrystals (NCs) through high‐pressure processing. A remarkable 5 times PIE was achieved at a mild pressure of 0.4 GPa, which was highly associated with the enhanced radiative recombination of self‐trapped excitons. Of particular importance is the retention of the 1.6 times emission of dense (PEA)2PbCl4 NCs upon the complete release of pressure, accompanied by a color change from “warm” (4403 K) to “cold” white light with 14295 K. The irreversible pressure‐induced structural amorphization, which facilitates the remaining local distortion of inorganic Pb‐Cl octahedra with respect to the steric hindrance of organic PEA+ cations, should be greatly responsible for the quenched high‐efficiency photoluminescence.
Organic Tetrabutylammonium Cation Intercalation to Heal Inorganic CsPbI3 Perovskite
Authors: Liu Xiaomin , Wang Xingtao , Zhang Taiyang , Miao Yanfeng , Qin Zhixiao , Chen Yuetian , Zhao Yixin
Published: March 2021

The in situ formation of reduced dimensional perovskite layer via post‐synthesis ion exchange has been an effective way of passivating organic‐inorganic hybrid perovskites. In contrast, cesium ions in Cs‐based inorganic perovskite with strong ionic binding energy cannot exchange with those well‐known organic cations to form reduced dimensional perovskite. Herein, we demonstrate that tetrabutylammonium (TBA+) cation can intercalate into CsPbI3 to effectively substitute the Cs cation and to form one‐dimensional (1D) TBAPbI3 layer in the post‐synthesis TBAI treatment. Such TBA cation intercalation leads to in situ formation of TBAPbI3 protective layer to heal defects at the surface of inorganic CsPbI3 perovskite. The TBAPbI3‐CsPbI3 perovskite exhibited enhanced stability and lower defect density, and the corresponding perovskite solar cell devices achieved an improved efficiency up to 18.32 % compared to 15.85 % of the control one.
Nanoscale supramolecular architectures assembly of copper cyanide, organotin, and 1,10‐phenanthroline coordination polymers: Design and biological applications
Authors: Saleh Dalia I. , Mahmoud Samy F. , Etaiw Safaa Eldin H.
Published: March 2021

The nanosized supramolecular coordination polymers (SCPs)3∞[Cu(μ2CN)2]2.(Me3Sn)2.(phen)2],SCP1,and [Cu2(CN)4(Ph3Sn)2(phen)],SCP2, were prepared utilizing self‐assembly method under ultrasonic irradiation. Single crystal X‐ray diffraction (XRD) of SCP1supports the presence of two anionic [Cu(μ2CN)2]−fragments connected by two (Me3Sn)+cations, while the two phenanthroline (phen) molecules coordinate to the Cu atoms. The two Cu atoms are crystallographically different, while they are chemically identical forming tetrahedral geometry. The structure of SCP2was achieved by calculations using DFT (the density functional theory) and spectroscopic studies. The geometries around the Cu atoms adopt triagonal plane and tetrahedral structure. Spectroscopic data, energy‐dispersive X‐ray spectroscopy (EDX), transmission electron microscopy (TEM), and analytical analysis confirm the chemical formula of SCP2. The nanosized tested compounds1and2are designed to investigate their action on viability and proliferation of five human cancer cell lines. In addition, 2, 2'‐azino‐bis (3‐ethyl benzthiazoline‐6‐sulfonic acid) (ABTS) assay and rate erythrocyte hemolysis were used to test the antioxidant activity of the nanosized SCP1and SCP2. Also, the SCP1and2exhibit good antimicrobial activity keeping them as promising drug candidates for the treatment of bacterial and fungal infections.
Genetic and Epigenetic Fine‐Tuning of TGFB1 Expression Within the Human Osteoarthritic Joint
Authors: Rice Sarah J. , Roberts Jack B. , Tselepi Maria , Brumwell Abby , Falk Julia , Steven Charlotte , Loughlin John
Published: March 2021

Objective

Osteoarthritis (OA) is an age‐related disease characterized by articular cartilage degeneration. It is largely heritable, and genetic screening has identified single‐nucleotide polymorphisms (SNPs) marking genomic risk loci. One such locus is marked by the G>A SNP rs75621460, downstream of TGFB1. This gene encodes transforming growth factor β1, the correct expression of which is essential for cartilage maintenance. This study investigated the regulatory activity of rs75621460 to characterize its impact on TGFB1 expression in disease‐relevant patient samples (n = 319) and in Tc28a2 immortalized chondrocytes.

Methods

Articular cartilage samples from human patients were genotyped, and DNA methylation levels were quantified using pyrosequencing. Gene reporter and electrophoretic mobility shift assays were used to determine differential nuclear protein binding to the region. The functional impact of DNA methylation on TGFB1 expression was tested using targeted epigenome editing.

Results

The analyses showed that SNP rs75621460 was located within a TGFB1 enhancer region, and the OA risk allele A altered transcription factor binding, with decreased enhancer activity. Protein complexes binding to A (but not G) induced DNA methylation at flanking CG dinucleotides. Strong correlations between patient DNA methylation levels and TGFB1 expression were observed, with directly opposing effects in the cartilage and the synovium at this locus. This demonstrated biologic pleiotropy in the impact of the SNP within different tissues of the articulating joint.

Conclusion

The OA risk SNP rs75621460 impacts TGFB1 expression by modulating the function of a gene enhancer. We propose a mechanism by which the SNP impacts enhancer function, providing novel biologic insight into one mechanism of OA genetic risk, which may facilitate the development of future pharmacologic therapies.
The Southern Wide‐Field Gamma‐ray Observatory
Authors: Barres de Almeida Ulisses ,   the SWGO Collaboration
Published: March 2021

The scientific potential of a wide field‐of‐view, and very‐high duty cycle, ground‐based gamma‐ray detector has been demonstrated by the current generation of instruments, such as HAWC and ARGO, and will be further extended in the Northern Hemisphere by LHAASO. Nevertheless, no such instrument exists in the Southern Hemisphere yet, where a great potential lies uncovered for the mapping of Galactic large‐scale emission as well as providing access to the full sky for transient and variable multi‐wavelength and multi‐messenger phenomena. Access to the Galactic Centre and complementarity with the CTA‐South are other key motivations for such a gamma‐ray observatory in the South. There is also significant potential for cosmic ray studies, including investigation of cosmic‐ray anisotropy. In this contribution, I will present the motivations and the concept of the future Southern Wide‐Field Gamma‐ray Observatory (SWGO), now formally established as an international Collaboration and currently in the R&D phase. I will also outline its scientific objectives.
VISTA: A teaching aid to enhance contextual teaching
Authors: Kanika Kanika , Chakraverty Shampa , Chakraborty Pinaki , Madan Manan , Gupta Gaurav , Aggarwal Aditya
Published: March 2021

In this study, an innovative tool for enabling contextual teaching based on visual inputs, named Visual Stimuli‐based Teaching Aid (VISTA), was developed. This system establishes the meaning and significance of concepts that are taught in the classroom within different environmental contexts. The idea of contextual teaching has been deliberated for more than a decade now. Nevertheless, using this in a classroom with limited time and resources has several challenges. VISTA leverages the ubiquitous mobile devices to boost conventional teaching methods with contextual teaching–learning. With VISTA, contextual teaching does not require any specialized device, expensive sensors, or simulated environment. To assess the applicability of VISTA in computer science education, we gathered the responses and experiences from 42 computer science teachers teaching in various universities of India. The responses garnered indicate that contextualization through VISTA is relevant as well as interesting. In total, 86.31% of the teachers found the contextual information provided by VISTA to be significantly related to both the captured images and the concepts presented in the class. These results encourage the use of VISTA as a pedagogical tool for contextual teaching.
Long noncoding RNAs in the regulation of p53‐mediated apoptosis in human cancers
Authors: Chatterjee Manjima , Viswanathan Pragasam
Published: March 2021

Long noncoding RNAs (lncRNAs) are widely known for their regulatory function in transcriptional and posttranscriptional processes. The involvement of such non‐protein‐coding RNAs in nuclear organization and chromatin remodeling is often associated with an increased risk of human malignancies. In cancer, lncRNAs either promote cell survival or may act as a growth suppressor, thus conferring a key regulatory function other than their established role in fundamental cellular processes. Interestingly, lncRNAs interfere with the stages of apoptosis and related pathways involving p53. Many of these molecules either regulate or are regulated by p53 while mounting oncogenic events. Consequently, they may confer both prosurvival or proapoptotic functions depending upon the tissue type. Since the mechanism of cell death is bypassed in many human cancers, it has emerged that the lncRNAs are either overexpressed or knocked down to sensitize cells to apoptotic stimuli. Nonetheless, the abundant expression of lncRNAs in tumor cells renders them suitable targets for anticancer therapies. Although the role of lncRNAs in the p53 network and apoptosis has been independently defined, their interplay in activating p53‐target genes during cell cycle arrest remains unexplored. Thus, we have specifically reviewed the possible involvement of lncRNAs in the p53‐mediated apoptosis of human cancer cells. In particular, we summarize the growing evidence from individual studies and analyze whether lncRNAs are essential to facilitate apoptosis in a p53‐dependent manner. This may lead to the identification of p53‐associated lncRNAs that are suitable therapeutic targets or diagnostic/prognostic markers.
Renal failure and lung hemorrhage as a presentation of COVID‐19 infection, a case report
Authors: Zamani Nazanin , Aloosh Oldooz , Ahsant Samane , Khodabandeloo Niloofar , Ahimahalle Tahere Zarook , Abkhoo Aminreza , Riahi Taghi
Published: March 2021

The concurrent involvement of the lung and kidneys happens in COVID‐19 infection. The patient's respiratory symptoms resolved after hemodialysis. This finding raises the question that if hemodialysis can have a role in the treatment of COVID‐19.
Mass transfer study of butachlor biodegradation using immobilized microbial consortium SMC1 in a packed bed bioreactor
Authors: Mohanty Satya Sundar , Reddy D. Karthik , Jena Hara Mohan
Published: March 2021

In the present study, the effect of external mass transfer on the rate of butachlor biodegradation was studied using calcium alginate immobilized microbial consortium SMC1 in a re‐circulated up‐flow packed bed bioreactor in a batch scale. By assuming the biodegradation kinetics to be first order, the effect of various operational parameters such as feed flow rate, substrate concentration, and the external mass transfer on the bio‐removal of butachlor from the aqueous medium has been explored. Using external film diffusion models and Colburn analogy, the mass transfer correlations at several feed rates were worked out. The correlational analysis obtained in the form of JD = 1.341 was found to predict the experimental data precisely.
A noticeable absence
Authors: Snyder Rebecca A.
Published: March 2021

Coronavirus disease 2019 (COVID‐19) restrictions on visitation policies have created barriers for cancer caregivers and patients. Awareness of the critical role that cancer caregivers play should lead to better integration of the caregiver into clinical care and research after the pandemic ends.
Global sensitivity analysis for assessing the parameters importance and setting a stopping criterion in a biomedical inverse problem
Authors: Rapadamnaba Robert , Ribatet Mathieu , Mohammadi Bijan
Published: March 2021

This paper shows how to obtain in addition to the standard deviations available after a data assimilation procedure based on the ensemble Kalman filter, an apportioning of the total uncertainty in the outputs of a patient‐specific blood flow model into small portions of uncertainty due to input parameters. Statistical indicators generally used for identifying the importance of numerical parameters, namely the Sobol' first order and total indices, are introduced and discussed. These allow the identification of the importance rank of the different input parameters for the patient‐specific blood flow model, as well as the influence of the interactions between these parameters on the model output variance. The results show that knowing the importance rank of the model input parameters during the assimilation procedure is useful to avoid unnecessary over‐solving and to find a suitable stopping criterion in clinical situations where faster diagnosis is always requested. Indeed, the work permits to reduce typically by a factor of six the time to solution and most importantly with very limited extra calculation using already available information.
BMP/TGF‐β signaling as a modulator of neurodegeneration in ALS
Authors: Russo Kathryn , Wharton Kristi A.
Published: March 2021

This commentary focuses on the emerging intersection between BMP/TGF‐β signaling roles in nervous system function and the amyotrophic lateral sclerosis (ALS) disease state. Future research is critical to elucidate the molecular underpinnings of this intersection of the cellular processes disrupted in ALS and those influenced by BMP/TGF‐β signaling, including synapse structure, neurotransmission, plasticity, and neuroinflammation. Such knowledge promises to inform us of ideal entry points for the targeted modulation of dysfunctional cellular processes in an effort to abrogate ALS pathologies. It is likely that different interventions are required, either at discrete points in disease progression, or across multiple dysfunctional processes which together lead to motor neuron degeneration and death. We discuss the challenging, but intriguing idea that modulation of the pleiotropic nature of BMP/TGF‐β signaling could be advantageous, as a way to simultaneously treat defects in more than one cell process across different forms of ALS.
Developing a flexible learning activity on biodiversity and spatial scale concepts using open‐access vegetation datasets from the National Ecological Observatory Network
Authors: Styers Diane M. , Schafer Jennifer L. , Kolozsvary Mary Beth , Brubaker Kristen M. , Scanga Sara E. , Anderson Laurel J. , Mitchell Jessica J. , Barnett David
Published: March 2021

Biodiversity is a complex, yet essential, concept for undergraduate students in ecology and other natural sciences to grasp. As beginner scientists, students must learn to recognize, describe, and interpret patterns of biodiversity across various spatial scales and understand their relationships with ecological processes and human influences. It is also increasingly important for undergraduate programs in ecology and related disciplines to provide students with experiences working with large ecological datasets to develop students’ data science skills and their ability to consider how ecological processes that operate at broader spatial scales (macroscale) affect local ecosystems. To support the goals of improving student understanding of macroscale ecology and biodiversity at multiple spatial scales, we formed an interdisciplinary team that included grant personnel, scientists, and faculty from ecology and spatial sciences to design a flexible learning activity to teach macroscale biodiversity concepts using large datasets from the National Ecological Observatory Network (NEON). We piloted this learning activity in six courses enrolling a total of 109 students, ranging from midlevel ecology and GIS/remote sensing courses, to upper‐level conservation biology. Using our classroom experiences and a pre/postassessment framework, we evaluated whether our learning activity resulted in increased student understanding of macroscale ecology and biodiversity concepts and increased familiarity with analysis techniques, software programs, and large spatio‐ecological datasets. Overall, results suggest that our learning activity improved student understanding of biological diversity, biodiversity metrics, and patterns of biodiversity across several spatial scales. Participating faculty reflected on what went well and what would benefit from changes, and we offer suggestions for implementation of the learning activity based on this feedback. This learning activity introduced students to macroscale ecology and built student skills in working with big data (i.e., large datasets) and performing basic quantitative analyses, skills that are essential for the next generation of ecologists.
Recolonizing carnivores: Is cougar predation behaviorally mediated by bears?
Authors: Engebretsen Kristin N. , Beckmann Jon P. , Lackey Carl W. , Andreasen Alyson , Schroeder Cody , Jackson Pat , Young Julie K.
Published: March 2021

Conservation and management efforts have resulted in population increases and range expansions for some apex predators, potentially changing trophic cascades and foraging behavior. Changes in sympatric carnivore and dominant scavenger populations provide opportunities to assess how carnivores affect one another. Cougars (Puma concolor) were the apex predator in the Great Basin of Nevada, USA, for over 80 years. Black bears (Ursus americanus) have recently recolonized the area and are known to heavily scavenge on cougar kills. To evaluate the impacts of sympatric, recolonizing bears on cougar foraging behavior in the Great Basin, we investigated kill sites of 31 cougars between 2009 and 2017 across a range of bear densities. We modeled the variation in feeding bout duration (number of nights spent feeding on a prey item) and the proportion of primary prey, mule deer (Odocoileus hemionus), in cougar diets using mixed‐effects models. We found that feeding bout duration was driven primarily by the size of the prey item being consumed, local bear density, and the presence of dependent kittens. The proportion of mule deer in cougar diet across all study areas declined over time, was lower for male cougars, increased with the presence of dependent kittens, and increased with higher bear densities. In sites with feral horses (Equus ferus), a novel large prey, cougar consumption of feral horses increased over time. Our results suggest that higher bear densities over time may reduce cougar feeding bout durations and influence the prey selection trade‐off for cougars when alternative, but more dangerous, large prey are available. Shifts in foraging behavior in multicarnivore systems can have cascading effects on prey selection. This study highlights the importance of measuring the impacts of sympatric apex predators and dominant scavengers on a shared resource base, providing a foundation for monitoring dynamic multipredator/scavenger systems.
Tolerance niche expansion and potential distribution prediction during Asian openbill bird range expansion
Authors: Lei Yu , Liu Qiang
Published: March 2021

It is prevalent to use ecological niche models in the analysis of species expansion and niche changes. However, it is difficult to estimate the niche when alien species fail to establish in exotic areas. Here, we applied the tolerance niche concept, which means that niche of species can live and grow but preclude a species from establishing self‐sustaining populations, in such fail‐to‐establish events. Taking the rapidly expanded bird, Asian openbill (Anastomus oscitans), as a model species, we investigated niche dynamics and its potential effects on the population by Niche A and ecospat, predicted potential distribution by biomod2. Results showed that niche expansion has occurred in two non‐native populations caused by the tolerance of colder and wetter environments, and potential distribution mainly concentrated on equatorial islands. Our study suggested that the expanded niche belongs to tolerance niche concept according to the populations' dynamics and GPS tracking evidence. It is essential to consider source populations when we analyze the alien species. We recommended more consideration to the application of tolerance niche in alien species research, and there is still a need for standard measurement frameworks for analyzing the tolerance niche.
Higher temperatures increase growth rates of Rocky Mountain montane tree seedlings
Authors: Carroll Charles J.W. , Knapp Alan K. , Martin Patrick H.
Published: March 2021

Recent observational studies report weak or flat temperature − growth relationships for many tree species in temperate forests. In contrast, distribution limits of trees are strongly shaped by temperature, and studies show marked short‐term temperature effects on leaf‐level ecophysiology. To better determine the effects of warming on trees, we planted one‐year‐old seedlings of one lower montane (ponderosa pine), two upper montane (quaking aspen and lodgepole pine), and one subalpine tree species (subalpine fir) in in situ experimental gardens on an elevation gradient in the Rocky Mountains (USA) which span a 6°C range in temperature but have approximately uniform precipitation. Seedlings were lightly watered the first three growing seasons to facilitate establishment, and growth and survivorship were followed for four years. We expected a trade‐off between growth and survivorship, as seedlings in high temperatures grow faster (e.g., with a longer growing season), but have higher mortality from heat stress. Compared to the coldest site, aspen (+256% wider, +337% taller), ponderosa pine (+234% wider, 270% taller), and lodgepole pine (+235% wider, 283% taller) all had strikingly higher cumulative diameter and height growth in the warmest site by the end of the study. Linear models of cumulative and annual growth in the montane species showed strong, positive relationships with growing‐season temperature, but no significant relationships with growing‐season precipitation. In contrast, growth of subalpine fir did not vary significantly with temperature, but increased slightly with higher growing‐season precipitation. Accelerated growth did not come at the expense of survivorship in the montane species: cumulative four‐year survivorship of the montane species remained robust (71.4–94.4%) in high temperatures, but caused complete mortality of subalpine fir. As long as precipitation remains adequate, these results indicate that warming is likely to strongly increase growth in seedlings of montane species with only modest decreases in survivorship despite higher evapotranspiration, especially in cooler and wetter portions of their current distributions where hydric stress is low. In contrast, warming may negatively affect seedling growth and survival in hotter and drier areas of the Rockies, and warming of +3–6°C may endanger the persistence of subalpine fir over much of its current distribution.
Absence of Non‐Linear Effects Despite Evidence for Catalyst Aggregation
Authors: Geiger Yannick , Achard Thierry , Maisse‐François Aline , Bellemin‐Laponnaz Stéphane
Published: March 2021

An in‐depth study of the catalytic system, consisting of the enantioselective addition of ZnEt2 to benzaldehyde with (1R,2S)‐(−)‐N‐Methylephedrine (NME) as chiral ligand, suggests the presence of dimeric and trimeric aggregates, as deduced from product ee vs. catalyst loading and NMR investigations (1H, DOSY). Formation of catalyst aggregation was excluded in earlier studies as this system displays a linear product ee vs. ligand ee‐correlation, which is usually taken as an indication for the absence of catalyst aggregation. A subsequent theoretical study, using the monomer‐dimer competition model, which we have recently developed, highlights the possible parameter configurations leading to linear product ee vs. ligand ee plots – despite the presence of catalyst dimers. It shows that, while the Kagan and Noyori models allow linearity in very specific cases only, a multitude of scenarios may lead to linearity here, especially if heterochiral dimers are catalytically active.
Elemental geochemistry of surface sediments from Manakudy estuary, south‐west coast of India: Inferences to sources of elements and their accumulation
Authors: Subramanian Muthusamy , Muthumanickam Jayaprakash , Karthikeyan Sivakumar , Senapathi Venkatramanan , Mohan Viswanathan Prasanna , Sekar Selvam , Sabarathinam Chidambaram
Published: March 2021

Manakudy estuary is located in the southernmost tip of the Indian sub‐continent, which is essential to study the sediment geochemistry as it receives limited input of sediments during the rainy season from its catchment zones. The elemental geochemical variation of sediments is to understand the mechanism influencing the estuarine environment, and it becomes baseline data to assess the environmental impact in the near future. Twenty surface sediments samples were collected at different seasons, and the grain size results showed that the estuary sediments were carpeted by the mixture of sand, silt, clay, organic matter (OM), and CaCO3. The seasonal variation of elements is slightly more in the pre‐monsoon than in the post‐monsoon season. Fe showed maximum variation, while Cd showed minimum variation in total heavy metal concentrations of detrital sediments. The order of abundance of metals based on their mean values is as Fe > Mn > Cr > Zn > Cu > Pb > Ni > Co > Cd in pre‐monsoon and Fe > Mn > Zn > Cr > Ni > Co > Cu > Pb > Cd > in post‐monsoon, respectively. Different elemental ratios and enrichment factors were used to assess the abundance of major and trace elements in both seasons. The ecological risk assessment clearly shows the higher concentration of a few metals in the estuarine sediments during post‐ monsoon. Correlation and factor analysis show that from geogenic along with the anthropogenic input of industrial effluents, agriculture, urban, municipal wastes and slum sewage are the major sources for derived metals in the estuarine sediments.
Estimating determinants of healthcare establishment locations with restricted federal administrative data
Authors: Van Sandt Anders , Carpenter Craig Wesley , Dudensing Rebekka , Loveridge Scott
Published: March 2021

We model the locational determinants of nine categories of healthcare services in the contiguous United States using restricted access federal establishment data. These data enable close examination of rural health services, which are subject to suppression in publicly published data sources. After reviewing differences in public and unsuppressed restricted data and testing underlying data generation processes for each healthcare industry, including the Poisson, negative binomial, and their zero‐inflated counterparts, we estimate marginal effects for four categories of independent variables: place‐based factors, financial access, characteristics of population, and industry interdependencies. Findings show establishments are less likely to be found with high concentrations of Medicare and Medicaid recipients, while agglomerations are associated with more establishments. Nonemployer establishments serve a broader spectrum of people, but the rural poor still experience less access to health care.
Neurons including hippocampal spatial view cells, and navigation in primates including humans
Authors: Rolls Edmund T.
Published: March 2021

A new theory is proposed of mechanisms of navigation in primates including humans in which spatial view cells found in the primate hippocampus and parahippocampal gyrus are used to guide the individual from landmark to landmark. The navigation involves approach to each landmark in turn (taxis), using spatial view cells to identify the next landmark in the sequence, and does not require a topological map. Two other cell types found in primates, whole body motion cells, and head direction cells, can be utilized in the spatial view cell navigational mechanism, but are not essential. If the landmarks become obscured, then the spatial view representations can be updated by self‐motion (idiothetic) path integration using spatial coordinate transform mechanisms in the primate dorsal visual system to transform from egocentric to allocentric spatial view coordinates. A continuous attractor network or time cells or working memory is used in this approach to navigation to encode and recall the spatial view sequences involved. I also propose how navigation can be performed using a further type of neuron found in primates, allocentric‐bearing‐to‐a‐landmark neurons, in which changes of direction are made when a landmark reaches a particular allocentric bearing. This is useful if a landmark cannot be approached. The theories are made explicit in models of navigation, which are then illustrated by computer simulations. These types of navigation are contrasted with triangulation, which requires a topological map. It is proposed that the first strategy utilizing spatial view cells is used frequently in humans, and is relatively simple because primates have spatial view neurons that respond allocentrically to locations in spatial scenes. An advantage of this approach to navigation is that hippocampal spatial view neurons are also useful for episodic memory, and for imagery.
Colouring problems for symmetric configurations with block size 3
Authors: Erskine Grahame , Griggs Terry , Širáň Jozef
Published: March 2021

The study of symmetric configurations with block size 3 has a long and rich history. In this paper we consider two colouring problems which arise naturally in the study of these structures. The first of these is weak colouring, in which no block is monochromatic; the second is strong colouring, in which every block is multichromatic. The former has been studied before in relation to blocking sets. Results are proved on the possible sizes of blocking sets and we begin the investigation of strong colourings. We also show that the known and configurations without a blocking set are unique and make a complete enumeration of all nonisomorphic configurations. We discuss the concept of connectivity in relation to symmetric configurations and complete the determination of the spectrum of 2‐connected symmetric configurations without a blocking set. A number of open problems are presented.
Altered expression of serum miR‐106a, miR‐19b, miR‐17, and PTEN in patients with idiopathic membranous nephropathy
Authors: Wu Lina , Zhang Xinpeng , Luo Lin , Li Xiaoying , Liu Yong , Qin Xiaosong
Published: March 2021

Background

To find new diagnostic markers for idiopathic membranous nephropathy (IMN) and also conduct preliminary explorations into the possible pathogenesis of IMN by comparing the expression of microRNA‐451a (miR‐451a), miR‐106a, miR‐19b, miR‐17, and phosphatase and tensin homolog (PTEN) protein in the serum of patients with IMN and healthy controls.

Methods

The expression levels of miR‐451a, miR‐106a, miR‐19b, and miR‐17 in the serum of patients in the IMN group (n = 55, age: 50.2 ± 12.1 years) and the control group (n = 58, age 47.4 ± 13.1 years) were measured by quantitative real‐time polymerase chain reaction (qRT‐PCR), and the concentration of serum PTEN protein was determined by enzyme‐linked immunosorbent assay (ELISA).

Results

Compared with the control group, the expression of miR‐106a, miR‐19b, and miR‐17 was decreased significantly in the IMN group, whereas PTEN protein concentration was increased significantly in the IMN group. The areas under the receiver operating characteristic curve (AUC) of serum miR‐106a, miR‐19b, miR‐17, and PTEN were 0.66 (95% confidence interval [CI], 0.56–0.76), 0.81 (95% CI, 0.73–0.89), 0.69 (95% CI, 0.59–0.79), and 0.86 (95% CI, 0.79–0.93), respectively. The level of serum PTEN protein was negatively correlated with the expression of miR‐106a and miR‐19b. PTEN concentration was positively correlated with serum urea (Urea), creatinine (Crea), cystatin C (Cysc), 24 h urine total protein (24 h‐UP) and negatively correlated with albumin (Alb) and estimated glomerular filtration rate (eGFR).

Conclusions

MiR‐106a, miR‐19b, miR‐17, and PTEN are involved in the pathogenesis of IMN and may become new biomarkers for the diagnosis of IMN.
Magnetic resonance imaging findings of the posterior fossa in 47 patients with mucopolysaccharidoses: A cross‐sectional analysis
Authors: Reichert Roberta , Pérez Juliano A. , Dalla‐Corte Amauri , Pinto e Vairo Filippo , de Souza Carolina F. M. , Giugliani Roberto , Isolan Gustavo R. , Stefani Marco Antonio
Published: March 2021

Background

Mucopolysaccharidoses (MPS) is a group of hereditary multisystemic lysosomal disorders. Most neuroimaging studies in MPS have focused on the supratentorial compartment and craniocervical junction abnormalities, and data regarding posterior fossa findings are scarce in the literature. Thus, our purpose is to describe posterior fossa findings on magnetic resonance imaging (MRI) of MPS patients.

Methods

We reviewed routine MRI scans of MPS patients being followed up at our institution (types I, II, III, IV, and VI), focusing on posterior fossa structures.

Results

Forty‐seven MPS patients were included. MRI‐visible perivascular spaces were commonly found in the midbrain and adjacent to the dentate nuclei (85% and 55% of patients, respectively). White‐matter lesion was not identified in most cases. Its most frequent localizations were in the pons and cerebellum (34% and 30% of patients, respectively). Enlargement of cerebrospinal fluid (CSF) spaces in the posterior fossa was present in 55% of individuals and was more frequent in neuronopathic patients (73% vs 40%; P = .02). Cerebellar volume was classified as normal, apparent macrocerebellum, atrophic, and hypoplastic in 38%, 38%, 21%, and 3% of patients, respectively. A depression of the posterior fossa floor in the midline sagittal plane was found in 22 patients (47%), which was statistical significantly associated with enlargement of CSF spaces (P = .02) and with apparent macrocerebellum (P = .03).

Conclusion

The present study compiled the main posterior fossa findings in MPS patients. Classically described in the supratentorial compartment, MRI‐visible perivascular spaces, white matter lesions, and enlarged perivascular spaces were also found in the posterior fossa. However, atrophy, which commonly affects cerebral hemispheres, was not the most frequent cerebellar morphology found in our study. Moreover, potential findings for future research were described.
Visualization of Human Aortic Valve Dynamics Using Magnetic Resonance Imaging with Sub‐Millisecond Temporal Resolution
Authors: Zhong Zheng , Sun Kaibao , Dan Guangyu , Luo Qingfei , Farzaneh‐Far Afshin , Karaman Meryem Muge , Zhou Xiaohong Joe
Published: March 2021

Background

Visualization of aortic valve dynamics is important in diagnosing valvular diseases but is challenging to perform with magnetic resonance imaging (MRI) due to the limited temporal resolution.

Purpose

To develop an MRI technique with sub‐millisecond temporal resolution and demonstrate its application in visualizing rapid aortic valve opening and closing in human subjects in comparison with echocardiography and conventional MRI techniques.

Study Type

Prospective.

Population

Twelve healthy subjects.

Field Strength/Sequence

3 T; gradient‐echo‐train‐based sub‐millisecond periodic event encoded imaging (get‐SPEEDI) and balanced steady‐state free precession (bSSFP).

Assessment

Images were acquired using get‐SPEEDI with a temporal resolution of 0.6 msec. get‐SPEEDI was triggered by an electrocardiogram so that each echo in the gradient echo train corresponded to an image at a specific time point, providing a time‐resolved characterization of aortic valve dynamics. For comparison, bSSFP was also employed with 12 msec and 24 msec temporal resolutions, respectively. The durations of the aortic valve rapid opening (Tro), rapid closing (Trc), and the maximal aortic valve area (AVA) normalized to height were measured with all three temporal resolutions. M‐mode echocardiograms with a temporal resolution of 0.8 msec were obtained for further comparison.

Statistical Test

Parameters were compared between the three sequences, together with the echocardiography results, with a Mann–Whitney U test.

Results

Significantly shorter Tro (mean ± SD: 27.5 ± 6.7 msec) and Trc (43.8 ± 11.6 msec) and larger maximal AVA/height (2.01 ± 0.29 cm2/m) were measured with get‐SPEEDI compared to either bSSFP sequence (Tro of 56.3 ± 18.8 and 63.8 ± 20.2 msec; Trc of 68.2 ± 16.6 and 72.8 ± 18.2 msec; maximal AVA/height of 1.63 ± 0.28 and 1.65 ± 0.32 cm2/m for 12 msec and 24 msec temporal resolutions, respectively, P < 0.05). In addition, the get‐SPEEDI results were more consistent with those measured using echocardiography, especially for Tro (29.0 ± 4.1 msec, P = 0.79) and Trc (41.6 ± 4.3 msec, P = 0.16).

Data Conclusion

get‐SPEEDI allows for visualization of human aortic valve dynamics and provided values closer to those measured using echocardiography than the bSSFP sequences.

Level of Evidence

1

Technical Efficacy Stage

1
Long‐term cardiac reverse remodeling after cardiac resynchronization therapy
Authors: Alvarez‐Alvarez Belén , García‐Seara Javier , Martínez‐Sande Jose L. , Rodríguez‐Mañero Moisés , Fernández López Xesús A. , González‐Melchor Laila , Iglesias‐Alvarez Diego , Gude Francisco , Díaz‐Louzao Carla , González‐Juanatey José R.
Published: March 2021

Introduction

The benefit of cardiac resynchronization therapy (CRT) in heart failure (HF) patients with reduced left ventricular ejection fraction (LVEF) have been observed in the first year. However, there are few data on long‐term follow‐up and the effect of changes of LVEF on mortality. This study aimed to assess the LV remodeling after CRT implantation and the probable effect of changes in LVEF with repeated measures on mortality over time in a real‐world registry.

Methods

Among our cohort of 328 consecutive CRT patients, mixed model effect analysis have been made to describe the temporal evolution of LVEF and LVESV changes over time up with several explanatory variables. Besides, the effect of LVEF along time on the probability of mortality was evaluated using joint modeling for longitudinal and survival data.

Results

The study population included 328 patients (253 men; 70.2 ± 9.5 years) in 4.2 (2.9) years follow‐up. There was an increase in LVEF of 11% and a reduction in LVESV of 42 mL during the first year. These changes are more important during the first year, but slight changes remain during the follow‐up. The largest reduction in LVESV occurred in patients with left bundle branch block (LBBB) and the smallest reduction in patients with NYHA IV. The smallest increase in LVEF was an ischemic etiology, longer QRS, and LV electrode in a nonlateral vein. Besides, the results showed that the LVEF profiles taken during follow‐up after CRT were associated with changes in the risk of death.

Conclusion

Reverse remodeling of the left ventricle is observed especially during the first year, but it seems to be maintained later after CRT implantation in a contemporary cohort of patients. Longitudinal measurements could give us additional information at predicting the individual mortality risk after adjusting by age and sex compared to a single LVEF measurement after CRT.
Dynamic analysis of meteorological time series in Hong Kong: A nonlinear perspective
Authors: Yan Bowen , Chan Pak Wai , Li Qiusheng , He Yuncheng , Shu Zhenru
Published: March 2021

Many meteorological systems are chaotic in nature, which inevitably limits its predictability. Accurate prediction of meteorological variables depends primarily on properly diagnosing the complex underlying dynamics. Nonlinear dynamic analysis has shown to be particularly useful for such purpose. In this study, the concept of recurrence analysis was extended to investigate and characterize the underlying dynamics of meteorological time series (i.e., wind speed, temperature, pressure and relative humidity) based on daily observation in Hong Kong during a period from 1998 to 2018. The existence of chaos was clearly identified based on the phase space reconstruction diagram and the recurrence plot. It was shown that the underlying dynamics associated with wind speed appears to indicate higher level of complexity as compared to those of pressure and temperature, which, in consequence, may lead to more irregular time‐dependent behaviour and lower predictability. Moreover, season‐to‐seasonal variability in the dynamics of meteorological time series was evident, particularly for wind speed and temperature. Overall, this study shows that the recurrence analysis can be well applied as a useful diagnostic tool to investigate the dynamics of meteorological systems, which is expected to provide a new avenue regarding the modelling and prediction of the behaviour of meteorological parameters.
qModeL: A plug‐and‐play model‐based reconstruction for highly accelerated multi‐shot diffusion MRI using learned priors
Authors: Mani Merry , Magnotta Vincent A. , Jacob Mathews
Published: March 2021

Purpose

To introduce a joint reconstruction method for highly undersampled multi‐shot diffusion weighted (msDW) scans.

Methods

Multi‐shot EPI methods enable higher spatial resolution for diffusion MRI, but at the expense of long scan‐time. Highly accelerated msDW scans are needed to enable their utilization in advanced microstructure studies, which require high q‐space coverage. Previously, joint k‐q undersampling methods coupled with compressed sensing were shown to enable very high acceleration factors. However, the reconstruction of this data using sparsity priors is challenging and is not suited for multi‐shell data. We propose a new reconstruction that recovers images from the combined k‐q data jointly. The proposed qModeL reconstruction brings together the advantages of model‐based iterative reconstruction and machine learning, extending the idea of plug‐and‐play algorithms. Specifically, qModeL works by prelearning the signal manifold corresponding to the diffusion measurement space using deep learning. The prelearned manifold prior is incorporated into a model‐based reconstruction to provide a voxel‐wise regularization along the q‐dimension during the joint recovery. Notably, the learning does not require in vivo training data and is derived exclusively from biophysical modeling. Additionally, a plug‐and‐play total variation denoising provides regularization along the spatial dimension. The proposed framework is tested on k‐q undersampled single‐shell and multi‐shell msDW acquisition at various acceleration factors.

Results

The qModeL joint reconstruction is shown to recover DWIs from 8‐fold accelerated msDW acquisitions with error less than 5% for both single‐shell and multi‐shell data. Advanced microstructural analysis performed using the undersampled reconstruction also report reasonable accuracy.

Conclusion

qModeL enables the joint recovery of highly accelerated multi‐shot dMRI utilizing learning‐based priors. The bio‐physically driven approach enables the use of accelerated multi‐shot imaging for multi‐shell sampling and advanced microstructure studies.
Short‐term effect of low‐dose rituximab on myasthenia gravis with muscle‐specific tyrosine kinase antibody
Authors: Zhou Yufan , Yan Chong , Gu Xinyu , Zhou Lei , Lu Jun , Zhu Wenhua , Huan Xiao , Luo Sushan , Zhong Huahua , Lin Jie , Lu Jiahong , Zhao Chongbo , Xi Jianying
Published: March 2021

Introduction/Aims

The study aims to investigate the short‐term efficacy of low‐dose rituximab and its effect on immunological biomarker levels in myasthenia gravis (MG) patients with antibodies against muscle‐specific tyrosine kinase (MuSK‐MG).

Methods

Twelve MuSK‐MG patients were enrolled in this prospective, open‐label, self‐controlled pilot study. Clinical severity was evaluated at baseline and 6 mo after a single rituximab treatment (600 mg). B lymphocyte subtypes, MuSK antibody titers, together with levels of immunoglobulins, serum B‐cell activating factor (BAFF), a proliferation‐inducing ligand (APRIL), soluble CD40L, and four exosomal microRNAs were evaluated. A correlation matrix to reveal pairwise relationships among above variables was also generated.

Results

The single rituximab treatment significantly lowered the clinical severity scores and reduced daily dosage of prednisone (P = .032) at 6 mo. MuSK antibody titers decreased (P = .035) without significant changes in immunoglobulin levels. Serum BAFF level increased (P = .010), which negatively correlated with the percentages of B cells in lymphocytes as well as clinical severity. Additionally, serum exosomal miR‐151a‐3p showed a reduction of 28.1% (P = .031).

Discussion

We confirmed the clinical efficacy of low‐dose rituximab in MuSK‐MG, accompanied by a decrease in MuSK antibody titers and an increase in serum BAFF. Serum BAFF levels negatively correlated with B‐cell counts as well as clinical severity.
Effect of contact resistance in organic field‐effect transistors
Authors: Shi Yanjun , Liu Jie , Hu Yuanyuan , Hu Wenping , Jiang Lang
Published: March 2021

Contact resistance (RC) is universally present in organic field‐effect transistors (OFETs) and the performance of OFETs can be easily affected by RC, which will result in poor performances such as low mobility (μ), large threshold voltage (VT), and non‐ideal transfer/output characteristics. In this article, we provide a comprehensive review on the effects of RC in OFETs. We start with a brief introduction of the origin of RC and its effects on OFETs, followed by the commonly used methods for extraction of RC. Then, methods for reducing RC are thoroughly discussed. Especially, fabricating monolayer molecular crystal (MMC) OFETs is highlighted as one of the key solutions to reduce RC effectively. The final section describes the challenges in MMCs preparation and concludes with an outlook for further reducing RC to enhance the performances of OFETs.