bluuebunny/crossref_metadata_2025 huggingface dataset:
Recovery efficiency of two glove-sampling methods
Authors: Lyons Amanda K. , Rose Laura J. , Noble-Wang Judith
Published: March 2021

Two methods to sample pathogens from gloved hands were compared: direct imprint onto agar and a sponge-wipe method. The sponge method was significantly better at recovering Clostridiodes difficile spores, and no difference was observed between the methods at 101 inoculum for carbapenemase-producing KPC+ Klebsiella pneumoniae, methicillin-resistant Staphylococcus aureus, and Acinetobacter baumannii.
New monitoring confirms regular breeding of the Mediterranean monk seal in Northern Cyprus
Authors: Beton Damla , Broderick Annette C. , Godley Brendan J. , Kolaç Emre , Ok Meltem , Snape Robin T. E.
Published: March 2021

The Endangered Mediterranean monk seal Monachus monachus is one of the most threatened marine mammals. Across Cyprus, suitable habitat and presence of monk seals is well documented and, recently, camera-trap surveys in Southern Cyprus found there to be pupping. We present results of the first camera-trap surveys in Northern Cyprus spanning the pupping period. Four adult/subadults and three pups were identified in three of eight caves monitored with camera traps. One site on the north-west of the island supported at least three adult/subadult seals and pupping occurred there in 3 consecutive years. The breeding and resting sites identified require urgent conservation to manage threats of disturbance, coastal development and fisheries bycatch. To determine the size of this population, a long-term survey with greater and more continuous coverage is required.
Late effects of early weaning on food preference and the dopaminergic and endocannabinoid systems in male and female rats
Authors: Soares Patricia Novaes , Miranda Rosiane Aparecida , Bertasso Iala Milene , Pietrobon Carla Bruna , Rodrigues Vanessa Silva Tavares , de Oliveira Elaine , Manhães Alex Christian , de Moura Egberto Gaspar , Lisboa Patricia Cristina
Published: March 2021

Early weaning (EW) is associated with obesity later in life. Here, using an EW model in rats, we investigated changes in feeding behavior and the dopaminergic and endocannabinoid systems (ECS) in the adult offspring. Lactating Wistar rats were divided into two groups: EW, dams were wrapped with a bandage to interrupt suckling during the last 3 days of breastfeeding; CONT; dams fed the pups throughout the period without hindrances. EW animals were compared with CONT animals of the same sex. At PN175, male and female offspring of both groups could freely self-select between high-fat and high-sugar diets (food challenge test). EW males preferred the high-fat diet at 30 min and more of the high-sugar diet after 12 h compared to CONT males. EW females did not show differences in their preference for the palatable diets compared to CONT females. Total intake of standard diet from PN30-PN180 was higher in both male and female EW animals, indicating hyperphagia. At PN180, EW males showed lower type 2 dopamine receptor (D2r) in the nucleus accumbens (NAc) and dorsal striatum, while EW females had lower tyrosine hydroxylase in the ventral tegmental area and NAc, D1r in the NAc, and D2r in the prefrontal cortex. In the lateral hypothalamus, EW males had lower fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase, whereas EW females showed lower N-arachidonoyl-phosphatidylethanolamine phospholipase-D and increased FAAH. Early weaning altered both the dopaminergic and ECS parameters at adulthood, contributing to the eating behavior changes of the progeny in a sex-dependent manner.
GSK3B induces autophagy by phosphorylating ULK1
Authors: Ryu Hye Young , Kim Leah Eunjung , Jeong Hyeonjeong , Yeo Bo Kyoung , Lee Ji-Won , Nam Hyeri , Ha Shinwon , An Hyun-Kyu , Park Hyunhee , Jung Seonghee , Chung Kyung Min , Kim Jiyea , Lee Byung-Hoon , Cheong Heesun , Kim Eun-Kyoung , Yu Seong-Woon
Published: March 2021

Unc-51-like autophagy activating kinase 1 (ULK1), a mammalian homolog of the yeast kinase Atg1, has an essential role in autophagy induction. In nutrient and growth factor signaling, ULK1 activity is regulated by various posttranslational modifications, including phosphorylation, acetylation, and ubiquitination. We previously identified glycogen synthase kinase 3 beta (GSK3B) as an upstream regulator of insulin withdrawal-induced autophagy in adult hippocampal neural stem cells. Here, we report that following insulin withdrawal, GSK3B directly interacted with and activated ULK1 via phosphorylation of S405 and S415 within the GABARAP-interacting region. Phosphorylation of these residues facilitated the interaction of ULK1 with MAP1LC3B and GABARAPL1, while phosphorylation-defective mutants of ULK1 failed to do so and could not induce autophagy flux. Furthermore, high phosphorylation levels of ULK1 at S405 and S415 were observed in human pancreatic cancer cell lines, all of which are known to exhibit high levels of autophagy. Our results reveal the importance of GSK3B-mediated phosphorylation for ULK1 regulation and autophagy induction and potentially for tumorigenesis.
PPAR-gamma induced AKT3 expression increases levels of mitochondrial biogenesis driving prostate cancer
Authors: Galbraith Laura C. A. , Mui Ernest , Nixon Colin , Hedley Ann , Strachan David , MacKay Gillian , Sumpton David , Sansom Owen J. , Leung Hing Y. , Ahmad Imran
Published: March 2021

Peroxisome Proliferator-Activated Receptor Gamma (PPARG) is one of the three members of the PPAR family of transcription factors. Besides its roles in adipocyte differentiation and lipid metabolism, we recently demonstrated an association between PPARG and metastasis in prostate cancer. In this study a functional effect of PPARG on AKT serine/threonine kinase 3 (AKT3), which ultimately results in a more aggressive disease phenotype was identified. AKT3 has previously been shown to regulate PPARG co-activator 1 alpha (PGC1α) localisation and function through its action on chromosome maintenance region 1 (CRM1). AKT3 promotes PGC1α localisation to the nucleus through its inhibitory effects on CRM1, a known nuclear export protein. Collectively our results demonstrate how PPARG over-expression drives an increase in AKT3 levels, which in turn has the downstream effect of increasing PGC1α localisation within the nucleus, driving mitochondrial biogenesis. Furthermore, this increase in mitochondrial mass provides higher energetic output in the form of elevated ATP levels which may fuel the progression of the tumour cell through epithelial to mesenchymal transition (EMT) and ultimately metastasis.
Transition of children with life-limiting conditions to adult care and healthcare use: a systematic review
Authors: Jarvis Stuart W. , Roberts Daniel , Flemming Kate , Richardson Gerry , Fraser Lorna K.
Published: March 2021

Background

Improved survival has led to increasing numbers of children with life-limiting conditions transitioning to adult healthcare services. There are concerns that transition may lead to a reduction in care quality and increases in emergency care. This review explores evidence for differences in health or social care use post- versus pre-transition to adult services.

Methods

MEDLINE, EMBASE, CINAHL, PsychINFO and Social Science Citation Index were searched. Studies published in English since 1990 including individuals with any life-limiting condition post- and pre-transition and reporting a health or social care use outcome were included. Data were extracted and quality assessed by one reviewer with 30% checked by an independent reviewer.

Results

Nineteen papers (18 studies) met the inclusion criteria. There was evidence for both increases and decreases (post- versus pre-transition) in outpatient attendance, inpatient admissions, inpatient bed days and health service costs; for increases in Emergency Department visits and for decreases in individuals receiving physiotherapy.

Conclusions

Evidence for changes in healthcare use post- versus pre-transition is mixed and conflicting, although there is evidence for an increase in Emergency Department visits and a reduction in access to physiotherapy. More high-quality research is needed to better link changes in care to the transition.

Impact

Evidence for changes in healthcare use associated with transition to adult services is conflicting.

Emergency Department visits increase and access to physiotherapy decreases at transition.

There are marked differences between care patterns in the United States and Canada.
Low maternal vitamin A intake increases the incidence of teratogen induced congenital diaphragmatic hernia in mice
Authors: Rocke Ayanna W. , Clarke Tianna G. , Dalmer Timothy R. A. , McCluskey Sydney A. , Rivas Juan F. Garcia , Clugston Robin D.
Published: March 2021

Background

Congenital diaphragmatic hernia (CDH) is a severe birth defect associated with high perinatal mortality and long-term morbidity. The etiology of CDH is poorly understood although abnormal retinoid signaling has been proposed to contribute to abnormal diaphragm development. Existing epidemiological data suggest that inadequate dietary vitamin A intake is a risk factor for developing CDH.

Methods

Using a mouse model of teratogen-induced CDH, the objective of this study was to test the hypothesis that low maternal vitamin A intake contributes to abnormal diaphragm development. To test this hypothesis, we optimized a model of altered maternal dietary vitamin A intake and a teratogenic model of CDH in mice that recapitulates the hallmark features of posterolateral diaphragmatic hernia in humans.

Results

Our data uniquely show that low maternal dietary vitamin A intake and marginal vitamin A status increases the incidence of teratogen-induced CDH in mice.

Conclusion

Low dietary vitamin A intake and marginal vitamin A status lead to an increased incidence of teratogen-induced CDH in mice, highlighting the importance of adequate dietary vitamin A intake and CDH risk.

Impact

This study describes and validates a mouse model of altered maternal and fetal vitamin A status.

This study links existing epidemiological data with a mouse model of teratogen-induced congenital diaphragmatic hernia, highlighting the importance of low maternal vitamin A intake as a risk factor for the development of congenital diaphragmatic hernia.

This study supports the Retinoid Hypothesis, which posits that the etiology of congenital diaphragmatic hernia is linked to abnormal retinoid signaling in the developing diaphragm.
Experimental identification and in silico prediction of bacterivory in green algae
Authors: Bock Nicholas A , Charvet Sophie , Burns John , Gyaltshen Yangtsho , Rozenberg Andrey , Duhamel Solange , Kim Eunsoo
Published: March 2021

While algal phago-mixotrophs play a major role in aquatic microbial food webs, their diversity remains poorly understood. Recent studies have indicated several species of prasinophytes, early diverging green algae, to be able to consume bacteria for nutrition. To further explore the occurrence of phago-mixotrophy in green algae, we conducted feeding experiments with live fluorescently labeled bacteria stained with CellTracker Green CMFDA, heat-killed bacteria stained with 5-(4,6-dichlorotriazin-2-yl) aminofluorescein (DTAF), and magnetic beads. Feeding was detected via microscopy and/or flow cytometry in five strains of prasinophytes when provided with live bacteria: Pterosperma cristatum NIES626, Pyramimonas parkeae CCMP726, Pyramimonas parkeae NIES254, Nephroselmis pyriformis RCC618, and Dolichomastix tenuilepis CCMP3274. No feeding was detected when heat-killed bacteria or magnetic beads were provided, suggesting a strong preference for live prey in the strains tested. In parallel to experimental assays, green algal bacterivory was investigated using a gene-based prediction model. The predictions agreed with the experimental results and suggested bacterivory potential in additional green algae. Our observations underline the likelihood of widespread occurrence of phago-mixotrophy among green algae, while additionally highlighting potential biases introduced when using prey proxy to evaluate bacterial ingestion by algal cells.
Risk of hematologic malignancies after breast ductal carcinoma in situ treatment with ionizing radiation
Authors: Wang Kang , Li Zhuyue , Chen Xingxing , Zhang Jianjun , Xiong Yongfu , Zhong Guochao , Shi Yang , Li Qing , Zhang Xiang , Li Hongyuan , Xiang Tingxiu , Foukakis Theodoros , Radivoyevitch Tomas , Ren Guosheng
Published: March 2021

The increased incidence of secondary hematologic malignancies (SHM) is a well-known, potentially fatal, complication after cancer treatment. It is unknown if patients with ductal carcinoma in situ (DCIS) of the breast treated with external beam radiotherapy (RT) and who survive long-term have increased risks of secondary hematologic malignancies (SHM), especially for low/intermediate-risk subsets with limited benefits from RT. DCIS patients in Surveillance, Epidemiology, and End Results (SEER) registries (1975–2016) were identified. Relative risks (RR), hazard ratio (HR), and standardized incidence ratios (SIR) were calculated to assess the SHM risk and subsequent survival times. SHM development, defined as a nonsynchronous SHM occurring ≥1 year after DCIS diagnosis, was our primary endpoint. Of 184,363 eligible patients with DCIS, 77,927 (42.3%) in the RT group, and 106,436 (57.7%) in the non-RT group, 1289 developed SHMs a median of 6.4 years (interquartile range, 3.5 to 10.3 years) after their DCIS diagnosis. Compared with DCIS patients in the non-RT group, RT was associated with increased early risk of developing acute lymphoblastic leukemia (ALL; hazard ratio, 3.15; 95% CI, 1.21 to 8.17;P = 0.02), and a delayed risk of non-Hodgkin lymphoma (NHL; hazard ratio, 1.33; 95% CI, 1.09 to 1.62;P < 0.001). This increased risk of ALL and NHL after RT was also observed in subgroup analyses restricted to low/intermediate-risk DCIS. In summary, our data suggest that RT after breast conserving surgery for DCIS patients should be cautiously tailored, especially for low and intermediate-risk patients. Long-term SHM surveillance after DCIS diagnosis is warranted.
Levetiracetam treatment leads to functional recovery after thoracic or cervical injuries of the spinal cord
Authors: Lima Rui , Gomes Eduardo D. , Cibrão Jorge R. , Rocha Luís A. , Assunção-Silva Rita C. , Rodrigues Cláudia S. , Neves-Carvalho Andreia , Monteiro Susana , Salgado António J. , Silva Nuno A.
Published: March 2021

Spinal cord injury (SCI) leads to dramatic impairments of motor, sensory, and autonomic functions of affected individuals. Following the primary injury, there is an increased release of glutamate that leads to excitotoxicity and further neuronal death. Therefore, modulating glutamate excitotoxicity seems to be a promising target to promote neuroprotection during the acute phase of the injury. In this study, we evaluated the therapeutic effect of a FDA approved antiepileptic drug (levetiracetam-LEV), known for binding to the synaptic vesicle protein SV2A in the brain and spinal cord. LEV therapy was tested in two models of SCI—one affecting the cervical and other the thoracic level of the spinal cord. The treatment was effective on both SCI models. Treated animals presented significant improvements on gross and fine motor functions. The histological assessment revealed a significant decrease of cavity size, as well as higher neuronal and oligodendrocyte survival on treated animals. Molecular analysis revealed that LEV acts by stabilizing the astrocytes allowing an effective uptake of the excess glutamate from the extracellular space. Overall, our results demonstrate that Levetiracetam may be a promising drug for acute management of SCI.
Anomalous structure transition in undercooled melt regulates polymorphic selection in barium titanate crystallization
Authors: Ge Xuan , Hu Qiaodan , Yang Fan , Xu Jun , Han Yanfeng , Lai Pingsheng , Qin Jingyu , Li Jianguo
Published: March 2021

The crystallization processes of titanates are central to the fabrication of optical and electrical crystals and glasses, but their rich polymorphism is not fully understood. Here, we show when and how polymorphic selection occurs during the crystallization of barium titanate (BaTiO3, BT) using in situ high energy synchrotron X-ray diffraction and ab initio molecular dynamic simulation. An anomalous structure transition is found in molten BT during cooling across the cubic-hexagonal transition temperature, which enables nucleation selection of BT by manipulating the undercooling: a cubic phase is preferred if nucleation is triggered at large undercooling, whereas a hexagonal phase is promoted at small undercooling. We further reveal that the nucleation selection between the cubic and the hexagonal phase is regulated by the intrinsic structure property of the melt, in particular, the degree of polymerization between Ti-O polyhedra. These findings provide an innovative perspective to link the polymorphic crystallization to the non-isomorphic structure transition of the melt beyond the conventional cognition of structural heredity.
Mizoroki–Heck type reactions and synthesis of 1,4-dicarbonyl compounds by heterogeneous organic semiconductor photocatalysis
Authors: Khamrai Jagadish , Das Saikat , Savateev Aleksandr , Antonietti Markus , König Burkhard
Published: March 2021

We report the synthesis of 1,4-dicarbonyl compounds and substituted alkenes (Mizoroki–Heck type coupling) starting from secondary and tertiary alkyl halides and vinyl acetate or styrene derivatives using visible-light photocatalysis.
A titanium dioxide–carbon nanotube hybrid to simultaneously achieve the mechanical enhancement of natural rubber and its stability under extreme frictional conditions
Authors: Wan Le , Deng Cong , Zhao Ze-Yong , Zhao Hai-Bo , Wang Yu-Zhong
Published: March 2021

Titanium oxide-carbon nanotube hybrids may efficiently promote the stability of nature rubber under extreme frictional conditions.
A fast and direct iodide-catalyzed oxidative 2-selenylation of tryptophan
Authors: Gao Yu-Ting , Liu Shao-Dong , Cheng Liang , Liu Li
Published: March 2021

We have developed a novel methodology for the synthesis of valuable 2-selenylated tryptophans from diselenides under the catalysis of iodide.
β-Cyclodextrin-conjugated phthalocyanines as water-soluble and recyclable sensitisers for photocatalytic applications
Authors: Chen Xiao-Fei , Ng Dennis K. P.
Published: March 2021

β-Cyclodextrin-conjugated phthalocyanines immobilised on adamantane-modified silica nanoparticles can serve as photostable and recyclable sensitisers for photocatalytic applications.
Gold(i) bridged dimeric and trimeric heterometallic {Cr7Ni}-based qubit systems and their characterization
Authors: Asthana Deepak , Lockyer Selena J. , Nawaz Selina , Woolfson Robert J. , Timco Grigore A. , Muryn Christopher A. , Vitorica-Yrezabal Iñigo J. , Collison David , Burton Neil A. , Winpenny Richard E. P.
Published: March 2021

Gold(i) bridged dimeric and trimeric structures of a ground state spin S = 1/2 heterometallic {Cr7Ni} wheel have been prepared and studied by continuous wave (CW) and pulsed wave EPR spectrometry.
Development of sterically hindered siloxide-functionalized polyoxotungstates for the complexation of 5d-metals
Authors: Auvray Thomas , Nachtigall Olaf , Brennessel William W. , Jones William D. , Matson Ellen M.
Published: March 2021

Organosilyl-functionalized trivacant Keggin polyoxotungstates [PW9O34(RSiOH)3]3− and their Hf alkoxide complexes have been prepared and characterized to study the influence of the varied steric hindrance from aryl and aliphatic silanol substituents.
Synthetically facile organic solar cells with >4% efficiency using P3HT and a silicon phthalocyanine non-fullerene acceptor
Authors: Grant Trevor M. , Dindault Chloé , Rice Nicole A. , Swaraj Sufal , Lessard Benoît H.
Published: March 2021

We demonstrate organic photovoltaic devices with extremely low synthetic complexity by pairing poly(3-hexithiophene) (P3HT) with a novel non-fullerene acceptor (NFA) bis(tri-n-propylsilyl oxide) silicon phthalocyanine ((3PS)2-SiPc).
Tuning the NLO response of bis-cyclometalated iridium(iii) complexes by modifying ligands: experimental and structural DFT analysis
Authors: Akhtar Mansoor , Arif Ali Muhammad , Ullah Khan Shifa , Shan Guo-Gang , Xu Hong-liang , Su Zhong-Min
Published: March 2021

DFT calculations have been carried out to investigate two synthesized iridium(iii) complexes with substituted Phbd (1-phenyl-2-(pyridin-2-yl)-1H-benzo[d]imidazole) and Crbd (9-(4-(2-(pyridin-2-yl)-1H-benzo[d]imidazol-1-yl)phenyl)-9H-carbazole) as ancillary ligands.
Rational manufacture of yolk–shell and core–shell metal oxide double layers from silica-templated coordination polymer double layers
Authors: Yeo Jian , Lee Gihyun , Lee Sujeong , Oh Moonhyun
Published: March 2021

Yolk–shell and core–shell hybrid metal oxide double layers with varied metal compositions are rationally constructedviasimple calcination of silica-templated coordination polymer double layers.
Zeolite-mediated production of cyclic organic carbonates: reaction of CO2 with styrene oxide on zeolite Y impregnated with metal halides
Authors: Ozorio Leonardo P. , Henrique Fábio J. S. , Comerford James W. , North Michael , Mota Claudio J. A.
Published: March 2021

Zeolites impregnated with metal halides as efficient catalysts for cyclic organic carbonate production.
FoxA2 and RNA Pol II mediate human islet amyloid polypeptide turnover in ER-stressed pancreatic β-cells
Authors: Chatterjee Bhowmick Diti , Burnett Lydia , Kudaibergenova Zhanar , Jeremic Aleksandar M.
Published: March 2021

Here, we investigated transcriptional and trafficking mechanisms of human islet amyloid polypeptide (hIAPP) in normal and stressed β-cells. In high glucose-challenged human islets and rat insulinoma cells overexpressing hIAPP, cell fractionation studies revealed increased accumulation of hIAPP. Unexpectedly, a significant fraction (up to 22%) of hIAPP was found in the nuclear soluble and chromatin-enriched fractions of cultured human islet and rat insulinoma cells. The nucleolar accumulation of monomeric forms of hIAPP did not have any adverse effect on the proliferation of β-cells nor did it affect nucleolar organization or function. However, intact nucleolar organization and function were essential for hIAPP expression under normal and ER-stress conditions as RNA polymerase II inhibitor, α-amanitin, reduced hIAPP protein expression evoked by high glucose and thapsigargin. Promoter activity studies revealed the essential role of transcription factor FoxA2 in hIAPP promoter activation in ER-stressed β-cells. Transcriptome and secretory studies demonstrate that the biosynthetic and secretory capacity of islet β-cells was preserved during ER stress. Thus, the main reason for increased intracellular hIAPP accumulation is its enhanced biosynthesis under these adverse conditions.
Flute oscillations of cooling coronal loops with variable cross-section
Authors: Shukhobodskaia Daria , Shukhobodskiy Alexander A. , Erdélyi Robert
Published: March 2021

We consider fluting oscillations in a thin straight expanding magnetic flux tube in the presence of a background flow. The tube is divided into a core region that is wrapped in a thin transitional region, where the damping takes place. The method of multiple scales is used for the derivation of the system of governing equations. This system is applicable to study both standing and propagating waves. Furthermore, the system of equations is obtained for magnetic tubes with a sharp boundary. An adiabatic invariant is derived using the Wentzel-Kramer-Brillouin method for a magnetic flux tube with slowly varying density, and the theoretical results are then used to investigate the effect of cooling on flute oscillations of a curved flux tube semi-circlular in shape. We have analysed numerically the dependencies of the dimensionless amplitude for a range of values of the expansion factor and the ratio of internal to external plasma densities at an initial time. We find that the amplitude increases due to cooling and is higher for a higher expansion factor. Higher values of the wave number lead to localisation of the oscillation closer to the boundary. Finally, we show that the higher the value of the ratio of internal to external plasma densities, the higher the amplification of oscillation due to cooling. Therefore, we conclude that the wave number, density ratio, and the variation of tube expansion are all relevant parameters in the cooling process of an oscillating flux tube.
Decompression: a first-intention treatment for “large” non-syndromic odontogenic keratocysts
Authors: Muret Marjorie , Malthiéry Eve , Casenave Théo , Costes-Martineau Valérie , Torres Jacques-Henri
Published: March 2021

Though odontogenic keratocysts (OKCs) are benign lesions, they have a high recurrence rate. Because of their aggressive behavior, they have been classified as tumors by the WHO until 2017. Main differential diagnoses are amelobastoma and dentigerous cyst. Anatomopathological examination can reach a final diagnosis. Several treatments have been proposed: curettage, resection, enucleation (alone or together with peripheral ostectomy) and decompression. Decompression aims to decrease the volume of the lesion of “large” OKCs, in order to prevent surgery-related fractures and to preserve the surrounding important anatomical structures such as the inferior alveolar nerve. It could lead to a complete regression. If not, secondary enucleation can be performed in better conditions: a reduced volume to remove, a thicker epithelium to detach, a lower risk to damage neighboring anatomic structures and a lower recurrence rate. Long-term follow-up however remains necessary. Nowadays, minimally invasive surgery prevails. And since OKC was returned into the odontogenic cysts group in the WHO classification, decompression should be considered as the first intention treatment. The purpose of this paper is to provide an update about OKC features and biological mechanisms, to review the different treatment options and to provide a step-by-step protocol for decompression.
Transport of coupled particles in rough ratchet driven by Lévy noise
Authors: Song Yao , Ning Lijuan
Published: March 2021

This paper studies the transport of coupled particles in a tilted rough ratchet potential. The relationship between particles transport and roughness, noise intensity, external force, coupling strength, and free length is explored numerically by calculating the average velocity of coupled particles. Related investigations have found that rough potential can accelerate the process of crossing the barrier by increasing the particles velocity compared with smooth potential. It is based on the fact that the roughness on the potential surface is like a “ladder,” which helps particles climb up and blocks them from sliding down. Moreover, superimposing an appropriate external force on the coupled particles or strengthening the Lévy noise leads to the particles velocity to increase. It is worth emphasizing that when the external force is selected properly, an optimal roughness can be found to maximize the particles velocity. For a given roughness, an optimal coupling coefficient is discovered to match the maximum velocity. And once the coupling coefficient is greater than the optimal value, the particles velocity drops sharply to zero. Furthermore, our results also indicate that choosing an appropriate free length between particles can also speed up transport.
Capturing multifractality of pressure fluctuations in thermoacoustic systems using fractional-order derivatives
Authors: Varghese Alan J. , Chechkin Aleksei , Metzler Ralf , Sujith R. I.
Published: March 2021

The stable operation of a turbulent combustor is not completely silent; instead, there is a background of small amplitude aperiodic acoustic fluctuations known as combustion noise. Pressure fluctuations during this state of combustion noise are multifractal due to the presence of multiple temporal scales that contribute to its dynamics. However, existing models are unable to capture the multifractality in the pressure fluctuations. We conjecture an underlying fractional dynamics for the thermoacoustic system and obtain a fractional-order model for pressure fluctuations. The data from this model has remarkable visual similarity to the experimental data and also has a wide multifractal spectrum during the state of combustion noise. Quantitative similarity with the experimental data in terms of the Hurst exponent and the multifractal spectrum is observed during the state of combustion noise. This model is also able to produce pressure fluctuations that are qualitatively similar to the experimental data acquired during intermittency and thermoacoustic instability. Furthermore, we argue that the fractional dynamics vanish as we approach the state of thermoacoustic instability.
Deciphering the role of temperature in Li+ co-dopant occupancy in BaYF5:Yb3+,Er3+ up-converting nanocrystals and its structure–property relationship
Authors: Devi Suman , Luwang Meitram Niraj
Published: March 2021

Precision engineering of defects in luminescent nanoscale crystalline materials with lesser controls to design is an area of interest in engineering materials with desired properties. Li+ co-doped BaYF5 nanocrystals were engineered, and temperature as controls for determining the co-dopant occupancies in the host lattice is studied. An observed enhancement in the up-conversion photoluminescence results from the co-dopant occupancy at Ba2+ sites via substitution through the hot injection method, whereas for samples prepared using co-precipitation, photoluminescence quenching was observed, which can be correlated with the Li+ occupancy at the interstitial site near Er3+ and also due to the incorporation of OH−. The crystal lattice deformation as a result of doping and the mechanism for the observed enhancement/quenching of luminescence are studied using x-ray diffraction, x-ray photoelectron spectroscopy, and energy transfer mechanism. Cytotoxicity assay and photoluminescence studies of the synthesized nanocrystals confirm that the material is biocompatible.
Multi-pulse time resolved gamma ray spectroscopy of the advanced radiographic capability using gas Cherenkov diagnostics
Authors: Meaney K. D. , Kerr S. , Williams G. J. , Geppert-Kleinrath H. , Kim Y. , Herrmann H. W. , Kalantar D. H. , Mackinnon A. , Bowers M. , Pelz L. , Alessi D. , Martinez D. , Prantil M. , Herriot S. , Hermann M. R. , Lanier T. E. , Hamamoto M. , Di Nicola J. M. , Yang S. , Williams W. , Widmayer C. , Lowe-Webb R.
Published: March 2021

The advanced radiographic capability located at the National Ignition Facility (NIF) uses high intensity, short pulse lasers to create bright photon sources for diagnosing high energy density experiments. There are radiographic needs for a multi-frame time-resolved MeV gamma diagnostic for experiments on the NIF with sub-nanosecond resolution. A series of experiments demonstrated measurements of MeV x-ray spectra resolved with a time separation of a few nanoseconds through the use of gas Cherenkov detectors. A two-pulse radiographic experiment found a 30% reduction in > 2.8 MeV photon flux compared to the first frame exposure.
Particle–particle particle–mesh algorithm for electrolytes between charged dielectric interfaces
Authors: Yuan Jiaxing , Antila Hanne S. , Luijten Erik
Published: March 2021

Ionic distributions near charged interfaces control processes from colloidal aggregation to solvent flow in nanodevices. Such interfaces are often characterized by a jump in the permittivity, which gives rise to the surface polarization charge. This induced charge may significantly affect the ionic distributions so that efficient methods for modeling spatially varying dielectrics are needed. We formulate a method with O(N⁡log⁡N) scaling for electrolytes between charged planar interfaces with asymmetric dielectric contrasts. Our approach, which builds on earlier work, is based on combining image charges with the particle–particle particle–mesh algorithm and representing uniform surface charges via an electric field. This enables simulations of complex dielectric interactions that outperform most alternative methods in speed and accuracy. To make the method practically useful, we provide guidelines—based upon careful tests—for choosing optimal simulation parameters. Explicit expressions for the electrostatic forces are given to facilitate the implementation of our algorithm in standard molecular dynamics packages.
Aerodynamic interaction of bristled wing pairs in fling
Authors: Kasoju Vishwa T. , Santhanakrishnan Arvind
Published: March 2021

Tiny flying insects of body lengths under 2 mm use the “clap-and-fling” mechanism with bristled wings for lift augmentation and drag reduction at a chord-based Reynolds number (Re) on O(10). We examine the wing–wing interaction of bristled wings in fling at Re = 10 as a function of initial inter-wing spacing (δ) and degree of overlap between rotation and linear translation. A dynamically scaled robotic platform was used to drive physical models of bristled wing pairs with the following kinematics (all angles relative to vertical): (1) rotation about the trailing edge to angle θr, (2) linear translation at a fixed angle (θt), and (3) combined rotation and linear translation. The results show that (1) the cycle-averaged drag coefficient decreased with increasing θr and θt and (2) decreasing δ increased the lift coefficient owing to increased asymmetry in the circulation of leading and trailing edge vortices. A new dimensionless index, reverse flow capacity (RFC), was used to quantify the maximum possible ability of a bristled wing to leak the fluid through the bristles. The drag coefficients were larger for smaller δ and θr despite larger RFC, likely due to the blockage of inter-bristle flow by shear layers around the bristles. Smaller δ during early rotation resulted in the formation of strong positive pressure distribution between the wings, resulting in an increased drag force. The positive pressure region weakened with increasing θr, which in turn reduced the drag force. Tiny insects have been previously reported to use large rotational angles in fling, and our findings suggest that a plausible reason is to reduce drag forces.
Falling balls in a viscous fluid with contact: Comparing numerical simulations with experimental data
Authors: von Wahl Henry , Richter Thomas , Frei Stefan , Hagemeier Thomas
Published: March 2021

We evaluate a number of different finite-element approaches for fluid–structure (contact) interaction problems against data from physical experiments. This consists of trajectories of single particles falling through a highly viscous fluid and rebounding off the bottom fluid tank wall. The resulting flow is in the transitional regime between creeping and turbulent flows. This type of configuration is particularly challenging for numerical methods due to the large change in the fluid domain and the contact between the wall and the particle. In the finite-element simulations, we consider both rigid body and linear elasticity models for the falling particles. In the first case, we compare the results obtained with the well-established Arbitrary Lagrangian–Eulerian (ALE) approach and an unfitted moving domain method together with a simple and common approach for contact avoidance. For the full fluid–structure interaction (FSI) problem with contact, we use a fully Eulerian approach in combination with a unified FSI-contact treatment using Nitsche's method. For higher computational efficiency, we use the geometrical symmetry of the experimental setup to reformulate the FSI system into two spatial dimensions. Finally, we show full three-dimensional ALE computations to study the effects of small perturbations in the initial state of the particle to investigate deviations from a perfectly vertical fall observed in the experiment. The methods are implemented in open-source finite element libraries, and the results are made freely available to aid reproducibility.
Ordering, phase behavior, and correlations of semiflexible polymers in confinement
Authors: Nikoubashman Arash
Published: March 2021

Semiflexible polymers are ubiquitous in biological systems, e.g., as building blocks of the cytoskeleton, and they also play an important role in various materials due to their ability to form liquid-crystalline order. These rigid macromolecules are characterized by numerous (hierarchical) length-scales that define their static and dynamic properties. Confinement can promote uniform order, e.g., through capillary nematization in narrow slits, but it can also introduce long-ranged disruptions of the nematic ordering field through (unavoidable) topological defects in spherical containers. This Perspective concentrates on the theoretical description and computational modeling of such confined systems, with the focus on spherical containers that play an important role in the injection/ejection of double-stranded DNA from viral capsids and the fabrication of nematic droplets. Basic principles and recent developments are reviewed, followed by a discussion of open questions and potential directions for future research in this field.
Experimental characterization of air-saturated porous material via low-frequencies ultrasonic transmitted waves
Authors: Sadouki Mustapha
Published: March 2021

An improved acoustic method is proposed for measuring the tortuosity and the viscous and thermal characteristic lengths of air-saturated porous materials via low-frequency ultrasonic transmitted waves (70 kHz–110 kHz). The equivalent fluid model is considered. The interaction between the saturated fluid and the structure is taken into account in two frequency response factors: the dynamic tortuosity of the medium and the dynamic compressibility of the air which are described by their high-frequency expansion in powers of the viscous and thermal skin depth, either limiting the expansion to the first two leading terms or the first three leading terms with the introduction of two new viscous and thermal shape factors. These two new factors play an important role in stabilizing and improving the inverted parameters of the tortuosity and the viscous and thermal characteristic lengths in the frequency band considered. The inverse problem is solved numerically in the frequency domain by minimizing the spectrum of simulated and experimental transmitted signals. Optimized parameters of tortuosity, viscous and thermal characteristic lengths, and viscous and thermal shape factors are obtained simultaneously. The tests are carried out with three samples of plastic foam. The results obtained by the two procedures are discussed and compared to those given in the literature.
X-ray phase contrast and absorption imaging for the quantification of transient cavitation in high-speed nozzle flows
Authors: Karathanassis I. K. , Heidari-Koochi M. , Zhang Q. , Hwang J. , Koukouvinis P. , Wang J. , Gavaises M.
Published: March 2021

High-flux synchrotron radiation has been employed in a time-resolved manner to characterize the distinct topology features and dynamics of different cavitation regimes arising in a throttle orifice with an abrupt flow-entry contraction. Radiographs obtained though both x-ray phase-contrast and absorption imaging have been captured at 67 890 frames per second. The flow lies in the turbulent regime (Re = 35 500), while moderate (CN = 2.0) to well-established (CN = 6.0) cavitation conditions were examined encompassing the cloud and vortical cavitation regimes with pertinent transient features, such as cloud-cavity shedding. X-ray phase-contrast imaging, exploiting the shift in the x-ray wave phase during interactions with matter, offers sharp-refractive index gradients in the interface region. Hence, it is suitable for capturing fine morphological fluctuations of transient cavitation structures. Nevertheless, the technique cannot provide information on the quantity of vapor within the orifice. Such data have been obtained utilizing absorption imaging, where beam attenuation is not associated with scattering and refraction events, and hence can be explicitly correlated with the projected vapor thickness in line-of-sight measurements. A combination of the two methods is proposed as it has been found that it is capable of quantifying the vapor content arising in the complex nozzle flow while also faithfully illustrating the dynamics of the highly transient cavitation features.
A harmonic oscillator model to study the intensification of microwave radiation by a subwavelength uniform plasma discharge
Authors: Laffont Adrien , Pascaud Romain , Callegari Thierry , Liard Laurent , Pascal Olivier , Adam Jean-Pierre
Published: March 2021

A harmonic oscillator model is proposed to study the intensification of microwave radiation of an electrically small antenna when surrounded by a subwavelength plasma discharge. This model describes the oscillations of free electrons in a spherical plasma when it is excited by an incident electromagnetic wave. It shows that at resonance, these charge oscillations lead to a significant volume current and, thus, to an enhancement of the radiation. Depending on the electron density of the plasma, this radiation enhancement may occur in the microwave range. The proposed model is compared with the Mie scattering theory with perfect agreement when the electrical size ka of the spherical plasma remains smaller than 0.1. Despite its apparent simplicity, this model unveils the main mechanism that stands behind the intensification of microwave radiation by a subwavelength plasma discharge.
Analysis of the water flow inside tire grooves of a rolling car using refraction particle image velocimetry
Authors: Cabut D. , Michard M. , Simoens S. , Mees L. , Todoroff V. , Hermange C. , Le Chenadec Y.
Published: March 2021

In order to better understand the hydroplaning phenomenon, local velocity measurements of water flow are performed inside the tire grooves of a real car rolling through a water puddle. Velocity fields are obtained by combining refraction Particle Image Velocimetry (r-PIV) illumination, seeding fluorescent particles, and either the classical two dimensional two components or the two dimensional three components stereoscopic recording arrangements. The presence of some bubble columns inside the grooves is highlighted by separate visualization using the fluorescent contrast technique evidencing two phase flow characteristics. A simple predictive model is proposed supporting the r-PIV analysis. It provides useful information to adjust the focusing distance and to understand the effect of the bubble column presence on the recorded r-PIV images, especially for the seeding particles located in the upper part of the grooves, as fluorescent light is attenuated by the bubbles. Also, the predictions provided by the model are compatible with the measurements. The velocity fields inside the grooves are analyzed using ensemble averaging performed over a set of independent snapshots, recorded with the same operating parameters. The variability of the longitudinal velocity distribution measured in a groove for several independent runs is explained by different mechanisms, like the random position of fluorescent seeding particles at various heights of the groove, the hydrodynamic interactions between longitudinal and transverse grooves, and the random location of the transverse grooves from one run to another. Three velocity components in cross sections of the longitudinal grooves are obtained using the stereoscopic arrangement. They are compatible with the presence of some longitudinal vortices assumed in the literature. The number of vortices is shown to be dependent on the aspect ratio characterizing a groove's rectangular cross section. We demonstrate, from measurements performed for several car velocities, that the velocity distribution inside longitudinal grooves shows self-similarity when using specific dimensionless length and velocity scales. Hydrodynamic interactions between longitudinal and transverse grooves are discussed on the basis of a mass budget; a fluid/structure interaction mechanism is proposed in order to correlate the overall direction of the flow in a transverse groove with its location inside the contact zone. Finally, some physical mechanisms are suggested for the birth of longitudinal vortices.
Consistency study of Lattice-Boltzmann schemes macroscopic limit
Authors: Farag G. , Zhao S. , Chiavassa G. , Boivin P.
Published: March 2021

Owing to the lack of consensus about the way Chapman–Enskog should be performed, a new Taylor-expansion of lattice-Boltzmann models is proposed. In contrast to the Chapman–Enskog expansion, recalled in this manuscript, the method only assumes a sufficiently small time step. Based on the Taylor expansion, the collision kernel is reinterpreted as a closure for the stress-tensor equation. Numerical coupling of lattice-Boltzmann models with other numerical schemes, also encompassed by the method, is shown to create error terms whose scalings are more complex than those obtained via Chapman–Enskog. An athermal model and two compressible models are carefully analyzed through this new scope, casting a new light on each model's consistency with the Navier–Stokes equations.
Operation analysis of the wideband high-power microwave sources based on the gyromagnetic nonlinear transmission lines
Authors: Cui Yancheng , Meng Jin , Huang Liyang , Yuan Yuzhang , Wang Haitao , Zhu Danni
Published: March 2021

The wideband High-Power Microwave (HPM) sources, which combine the advantages of narrowband and ultrawideband sources, have drawn much attention. As a kind of wideband source, the gyromagnetic nonlinear transmission lines (GNLTLs) can directly modulate the incident pulses into radio frequency pulses without relying on the interaction between e-beam and microwaves. Due to the special working mechanism of gyromagnetic precession, the center frequency of the GNLTL can also be adjusted in a certain range. Based on classical magnetism and a simplified model of the GNLTL, this paper semi-quantitatively and theoretically analyzed the generation mechanism of HPM and illustrated the influences of the variations of parameters on the output microwaves. Then, a simple simulation based on 1-dimensional transmission line modeling method was carried out to study the performance of the GNLTL quantitatively, with the coupling of 1D telegraphist equations and the 3D Landau–Lifshitz–Gilbert equation. Simulation results preliminarily verified the conclusions derived from the theoretical analysis, and some working characteristics of the GNLTL were also obtained. This paper may help to understand the special working mechanism of the GNLTL and provide certain guidance for related simulations and experiments.
Logistic map trajectory distributions: Renormalization-group, entropy, and criticality at the transition to chaos
Authors: Diaz-Ruelas A. , Baldovin F. , Robledo A.
Published: March 2021

We study the evolution of the probability density of ensembles of iterates of the logistic map that advance toward and finally remain at attractors of representative dynamical regimes. We consider the mirror families of superstable attractors along the period-doubling cascade and of chaotic-band attractors along the inverse band-splitting cascade. We examine also their common aperiodic accumulation point. The iteration time progress of the densities of trajectories is determined via the action of the Frobenius–Perron (FP) operator. As a difference with the study of individual orbits, the analysis of ensembles of positions offers a viewpoint from which the nonlinear dynamical features of this iconic model can be better characterized in statistical-mechanical terms. The scaling of densities along the considered families of attractors conforms to a renormalization-group (RG) structure, while their entropies are seen to attain extrema at the fixed points of the RG flows. Additionally, this entropy as a function of the map control parameter displays the characteristic features of an equation of state of a thermal system undergoing a second-order phase transition. We discuss our results.