bluuebunny/crossref_metadata_2025 huggingface dataset:
Time‐Restricted Feeding Improves Glucose Tolerance in Men at Risk for Type 2 Diabetes: A Randomized Crossover Trial
Authors: Hutchison Amy T. , Regmi Prashant , Manoogian Emily N.C. , Fleischer Jason G. , Wittert Gary A. , Panda Satchidananda , Heilbronn Leonie K.
Published: April 2019

Objective

This study aimed to assess the effects of 9‐hour time‐restricted feeding (TRF), early (TRFe) or delayed (TRFd), on glucose tolerance in men at risk for type 2 diabetes.

Methods

Fifteen men (age 55 ± 3 years, BMI 33.9 ± 0.8 kg/m2) wore a continuous glucose monitor for 7 days of baseline assessment and during two 7‐day TRF conditions. Participants were randomized to TRFe (8 am to 5 pm) or TRFd (12 pm to 9 pm), separated by a 2‐week washout phase. Glucose, insulin, triglycerides, nonesterified fatty acids, and gastrointestinal hormone incremental areas under the curve were calculated following a standard meal on days 0 and 7 at 8 am (TRFe) or 12 pm (TRFd).

Results

TRF improved glucose tolerance as assessed by a reduction in glucose incremental area under the curve (P = 0.001) and fasting triglycerides (P = 0.003) on day 7 versus day 0. However, there were no mealtime by TRF interactions in any of the variables examined. There was also no effect of TRF on fasting and postprandial insulin, nonesterified fatty acids, or gastrointestinal hormones. Mean fasting glucose by continuous glucose monitor was lower in TRFe (P = 0.02) but not TRFd (P = 0.17) versus baseline, but there was no difference between TRF conditions.

Conclusions

While only TRFe lowered mean fasting glucose, TRF improved glycemic responses to a test meal in men at risk for type 2 diabetes regardless of the clock time that TRF was initiated.
Hybrid‐permeability model evaluation through concepts of tortuosity and resistance rate: Properties of manufactured hybrid laminate
Authors: Monticeli Francisco Maciel , da Silva Monte Vidal Dielly Cavalcanti , Shiino Marcos Yutaka , Voorwald Herman Jacobus Cornelis , Cioffi Maria Odila Hilário
Published: April 2019

The mechanical properties of composite structures depend on the preform impregnation and a successful impregnation can be achieved using the permeability relation in the case of an infusion process. The objective of this study is to develop an analytical model to predict the permeability K of carbon and glass fabrics through hybrid laminate using different stacking sequence, applying an average‐permeability model. Preforms permeabilities were evaluated through tortuosity and void‐volume fraction. The model allows the analysis of different stacking sequence combinations (interleaved and in block), measuring the contribution of each material type. As a result, hybrid average‐permeability model was validated through experimental permeability tests, dimensionless permeability, and tortuosity results, besides enabling predictions of the flow front behavior with <10% of deviation. Carbon fiber preforms exhibited higher flow resistance, which is explained via tortuosity concept. A combination of carbon/glass preforms presented an increased permeability, which means a synergy that provides higher value of K. In addition, the use of hybrid preforms, especially Hybrid 2 stacking sequence, reduce the injection time and void formation, ensuring composite impregnation quality. POLYM. ENG. SCI., 59:1215–1222 2019. © 2019 Society of Plastics Engineers
Complex macromolecular structures from stable radical containing block copolymers
Authors: Kocaarslan Azra , Yilmaz Gorkem , Liedel Clemens , Yagci Yusuf
Published: April 2019

A novel synthetic strategy for the synthesis of graft copolymers is reported. Block copolymers containing segments with stable nitroxyl radicals side groups were first prepared by anionic polymerization, which were then used as a precursor for the subsequent nitroxide‐mediated radical polymerization (NMRP) of styrene. This way, block–graft copolymers with polystyrene side chains grafted from one of the blocks were successfully synthesized in a controlled manner. In addition, block–graft copolymers with grafted polystyrene chains and a poly(tert‐butyl methacrylate) block were subjected to hydrolysis to yield the corresponding amphiphilic polymers. The structures and the molecular weight characteristics of the polymers were characterized by spectral and chromatographic analyses. The surface morphology of thus obtained polymers was also investigated by microscopic techniques. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 62–69
Biogenesis, quality control, and structural dynamics of proteins as explored in living cells via site‐directed photocrosslinking
Authors: Fu Xinmiao , Chang Zengyi
Published: April 2019

Protein biogenesis and quality control are essential to maintaining a functional pool of proteins and involve numerous protein factors that dynamically and transiently interact with each other and with the substrate proteins in living cells. Conventional methods are hardly effective for studying dynamic, transient, and weak protein–protein interactions that occur in cells. Herein, we review how the site‐directed photocrosslinking approach, which relies on the genetic incorporation of a photoreactive unnatural amino acid into a protein of interest at selected individual amino acid residue positions and the covalent trapping of the interacting proteins upon ultraviolent irradiation, has become a highly efficient way to explore the aspects of protein contacts in living cells. For example, in the past decade, this approach has allowed the profiling of the in vivo substrate proteins of chaperones or proteases under both physiologically optimal and stressful (e.g., acidic) conditions, mapping residues located at protein interfaces, identifying new protein factors involved in the biogenesis of membrane proteins, trapping transiently formed protein complexes, and snapshotting different structural states of a protein. We anticipate that the site‐directed photocrosslinking approach will play a fundamental role in dissecting the detailed mechanisms of protein biogenesis, quality control, and dynamics in the future.
Relative sensitivities of simulated rainfall to fixed shape parameters and collection efficiencies
Authors: Freeman Sean W. , Igel Adele L. , van den Heever Susan C.
Published: April 2019

Rainfall prediction by weather forecasting models is strongly dependent on the microphysical parametrization being utilized within the model. As forecasting models have become more advanced, they are more commonly using double‐moment bulk microphysical parametrizations. While these double‐moment schemes are more sophisticated and require fewer a priori parameters than single‐moment parametrizations, a number of parameter values must still be fixed for quantities that are not Prognosed or diagnosed. Two such parameters, the width of the rain drop size distribution and the choice of collection efficiencies between liquid hydrometeors, are examined here. Simulations of deep convective storms were performed in which the collection efficiency dataset and the a priori width of the rain drop size distribution (RSD) were individually and simultaneously modified. Analysis of the results show that the a priori width of the RSD was a larger control on the total accumulated precipitation (a change of up to 75% over the typical values tested in this article) than the choice of collection efficiency dataset used (a change of up to 10%). Changing the collection efficiency dataset produces most of the impacts on precipitation rates through changes in the warm rain process rates. On the other hand, the decrease in precipitation with narrowing RSDs occurs in association with the following processes: (a) decreased rain production due to increased evaporation, (b) decreased rain production due to decreased ice melting, and (c) slower raindrop fall speed which leads to longer residency times and changes in rain self‐collection. These results add to the growing body of work showing that the representation of hydrometeor size distributions is critically important, and suggests that more work should be done to better represent the width of the RSD in models, including further development of triple‐moment and bin schemes.
Triimide‐Functionalized n‐Type Polymer Semiconductors Enabling All‐Polymer Solar Cells with Power Conversion Efficiencies Approaching 9%
Authors: Wang Yingfeng , Yan Zhenglong , Uddin Mohammad Afsar , Zhou Xin , Yang Kun , Tang Yumin , Liu Bin , Shi Yongqiang , Sun Huiliang , Deng Aiying , Dai Junfeng , Woo Han Young , Guo Xugang
Published: April 2019

Two triimide‐functionalized n‐type acceptor polymers are designed and synthesized, which show narrower bandgap, lower‐lying frontier molecular orbital energy levels, and improved film morphology than the diimide‐functionalized analogue polymers. When blended with a p‐type donor polymer semiconductor PTB7‐Th, an outstanding power conversion efficiency of 8.98% with a remarkable open‐circuit voltage of 1.03 V is attained. This efficiency is among the highest values in all‐polymer solar cells (all‐PSCs) reported till today, surpassing that (6.85%) of the diimide‐functionalized analogue polymers by a big margin and even higher than that (8.69%) of the fullerene‐based solar cells. The results demonstrate that the triimide‐functionalized f‐BTI3 is an excellent building block for developing n‐type polymer semiconductors, and the polymer f‐BTI3‐T is among the best‐performing n‐type polymers for applications in all‐PSCs. The structure–property correlations of these imide‐functionalized polymer semiconductors offer important guides for developing high‐performance n‐type polymer semiconductors.
Peer gender and educational choices
Authors: Schøne Pål , Simson Kristine von , Strøm Marte
Published: April 2019

We use idiosyncratic variation in gender composition across cohorts within Norwegian lower secondary schools to analyze the impact of female peers on students’ educational choices. We find that having more female peers in lower secondary school increases the probability of choosing STEM over language subjects in upper secondary school for both girls and boys. It also increases the probability of choosing a vocational track instead of an academic track. Registry data and survey evidence suggest that potential mechanisms are related to relative performance in STEM subjects, as well as less gender discrimination for girls and increased willingness to compete for boys.
The dynamics of self-control: within-participant modeling of binary food choices and underlying decision processes as a function of restrained eating
Authors: Georgii Claudio , Schulte-Mecklenbeck Michael , Richard Anna , Van Dyck Zoé , Blechert Jens
Published: April 2019

Successful self-control during food choice might require inhibition of impulses to avoid indulging in tempting but calorie-dense foods, and this might particularly apply to individuals restraining their food intake. Adopting a novel within-participant modeling approach, we tested 62 females during a mouse-tracking based binary food choice task. Subsequent ratings of foods on palatability, healthiness, and calorie density were modeled as predictors for both decision outcome (choice) and decision process (measures of self-control conflict) while considering the moderating role of restrained eating. Results revealed that individuals higher on restrained eating were less likely to choose more high-calorie foods and showed less self-control conflict when choosing healthier foods. The latter finding is in contrast with the common assumption of self-control as requiring effortful and conscious inhibition of temptation impulses. Interestingly, restrained eaters rated healthy and low-calorie foods as more palatable than individuals with lower restrained eating scores, both in the main experiment and an independent replication study, hinting at an automatic and rather effortless mechanism of self-control (palatability shift) that obviates effortful inhibition of temptation impulses.
Circularity Brokers: Digital Platform Organizations and Waste Recovery in Food Supply Chains
Authors: Ciulli Francesca , Kolk Ans , Boe-Lillegraven Siri
Published: April 2019

In recent years, researchers and practitioners have increasingly paid attention to food waste, which is seen as highly unethical given its negative environmental and societal implications. Waste recovery is dependent on the creation of connections along the supply chain, so that actors with goods at risk of becoming waste can transfer them to those who may be able to use them as inputs or for their own consumption. Such waste recovery is, however, often hampered by what we call ‘circularity holes’, i.e., missing linkages between waste generators and potential receivers. A new type of actor, the digital platform organization, has recently taken on a brokerage function to bridge circularity holes, particularly in the food supply chain. Yet, extant literature has overlooked this novel type of brokerage that exploits digital technology for the transfer and recovery of discarded resources between supply chain actors. Our study investigates this actor, conceptualized as a ‘circularity broker’, and thus unites network research and circular supply chain research. Focusing on the food supply chain, we adopt an interpretive inductive theory-building approach to uncover how platform organizations foster the recovery of waste by bridging circularity holes. We identify and explicate six brokerage roles, i.e., connecting, informing, protecting, mobilizing, integrating and measuring, and discuss them in relation to extant literature, highlighting novelties compared to earlier studies. The final section reflects on contributions, implications, limitations and areas for further research.
Early-life Chronic Stressors, Rumination, and the Onset of Vulvodynia
Authors: Khandker Maheruh , Brady Sonya S. , Rydell Sarah A. , Turner Rachel M. , Schreiner Pamela J. , Harlow Bernard L.
Published: April 2019

Introduction

Vulvodynia is a debilitating, chronic vulvar pain condition. Community-based case-control studies have consistently shown associations between early-life chronic stressors and vulvodynia onset.

Aim

We examined rumination as a specific stress response involved in the psychobiological mechanism of vulvodynia.

Methods

A psychosocial survey with questions specific to early-life traumatic events and rumination were administered to 185 matched case-control pairs of women with and without vulvodynia. Conditional logistic regression was used to examine associations between rumination constructs (ie, total rumination, emotion-focused, instrumental, and searching for meaning) and vulvodynia onset. Conditional logistic regression was also used to determine whether these associations depended on early-life stressors (ie, severity of childhood abuse and of self-reported antecedent traumatic events). Age at interview, antecedent pain disorders, any childhood abuse, and antecedent psychiatric morbidity were included as covariates.

Main Outcome Measures

We estimated the odds of rumination in relation to the onset of vulvodynia within a community-based and clinically confirmed sample of women with and without vulvodynia.

Results

Vulvodynia was associated with the highest tertile of emotion-focused (odds ratio [OR] = 2.1; 95% CI = 1.2, 3.2) and instrumental (OR = 2.1; 95% CI = 1.1, 4.0) rumination. These associations were attenuated after additional adjustment for antecedent psychiatric morbidity. Among women who reported rumination about early-life stressors before vulvar pain in cases or matched reference age in control subjects, those with vulvodynia were >2 times more likely to report the highest tertile of total rumination (OR = 2.3; 95% CI = 1.1, 5.0) compared with those without vulvodynia.

Clinical Implications

Healthcare providers may be able to identify subsets of women who could benefit from preventive measures before the development of vulvodynia.

Strength & Limitations

This is the first study to use a community-based and clinically confirmed sample of women with and without vulvodynia to examine the associations between rumination about early-life trauma and the onset of vulvodynia. However, as with all retrospective studies, the reporting of information (eg, traumatic events) was subject to recall bias and misclassification.

Conclusion

Our findings indicate that a prolonged cognitive stress response (ie, rumination) may be 1 important mechanism by which early-life chronic stressors contribute to the onset vulvodynia. Prospective studies are recommended to examine whether and how cognitive, affective, and physiological components of prolonged stress responses interact to influence the development of vulvodynia. Understanding both the psychobiological and behavioral mechanisms may help in addressing and treating individuals to potentially reverse the development of vulvodynia.
“If Everyone Else is Having This Talk with Their Doctor, Why Am I Not Having This Talk with Mine?”: The Experiences of Sexuality and Sexual Health Education of Young Women with Spina Bifida
Authors: Streur Courtney S. , Schafer Christine L. , Garcia Valerie P. , Quint Elisabeth H. , Sandberg David E. , Wittmann Daniela A.
Published: April 2019

Introduction

Women with spina bifida are sexually active, but most never discuss this topic with providers.

Aim

To determine what women with spina bifida understand about their sexual health, how they learned about it, what questions they have, and their experiences with their sexuality.

Methods

For this qualitative study, women with spina bifida ages 16 and older without marked developmental delay were individually interviewed. 25 women with spina bifida participated (mean age 27.1 years, range 16–52). Interviews were independently coded for themes by 3 reviewers, using Grounded Theory, with disagreements resolved by consensus.

Main Outcome Measures

We identified overlapping themes regarding the women’s perception and experience of their sexuality and sexual health education.

Results

17 of the 25 (68%) participants had been or were currently sexually active. 5 themes emerged regarding their understanding of their sexuality and their sexual experiences: (i) being perceived as asexual, (ii) sources for sex education, (iii) need for spina bifida–specific sex education, (iv) impact of spina bifida–specific features on sexual encounters, and (v) perceived relationship between low sexual self-confidence and risk for sexual assault.

Clinical Implications

Women with spina bifida are sexual beings, but they are perceived as asexual by providers, which prevents them from getting adequate sexual health education and leaves them with misconceptions and unanswered questions, as well as vulnerable to sexual abuse.

Strength & Limitations

The strengths of this study include the diversity of women interviewed, including their age, severity of disability, and experiences with their sexuality, as well as the ability to reach thematic saturation. The limitation of this study is that most women received treatment at a single Midwestern tertiary referral center in the United States.

Conclusion

Including sexual health discussions in the usual care of women with spina bifida is critical to enhancing their sexual confidence and experience and preventing sexual abuse.
MIM2019 conference report: Worldwide confidence persists
Authors: Capus Joseph
Published: April 2019

The MIM2019 conference celebrated its 30th anniversary on an upbeat note with positive outlooks for the industry from around the World. Technical sessions reviewed developments in materials and processes. The convergence of MIM and Additive Manufacturing was seen to provide new opportunities for MIM parts producers. A selection of presentations is summarized in this report.
International Stem Cell Corporation V. Comptroller General of Patents, Designs and Trade Marks (C.J.E.U.)
Authors: Plomer Aurora
Published: April 2019

On December 18, 2014, the Grand Chamber of the Court of Justice of the European Union (CJEU) issued its judgment in International Stem Cell Corporation v. Comptroller General of Patents, Designs and Trade Marks. The Court held that the term “human embryo” does not cover unfertilized human eggs produced by parthenogenesis (parthenotes).
Paris Agreement
Authors: Horowitz Cara A.
Published: April 2019

The Paris Agreement sets forth a new international legal regime aimed at strengthening the global response to climate change. It was adopted in December 2015 at the annual gathering of parties to the United Nations Framework Convention on Climate Change. The Paris Agreement sits within and implements the Convention.
Seismologists Search for the Indian Ocean’s “Missing Mass”
Authors: Ningthoujam Lachit , Negi Sanjay , Pandey Dhananjai
Published: April 2019

An Indian scientific team set out to sea last year to find clues to the source of an unusually weak gravitational potential in the middle of the Indian Ocean.
A United Europe Benefits Global Science, Say EU Geoscientists
Authors: Cartier Kimberly
Published: April 2019

“You are the stakeholders of European integration,” former Italian prime minister Mario Monti told an assembly of geoscientists.
Plastic Fragments Found for the First Time on a Glacier
Authors: Kornei Katherine
Published: April 2019

The discovery, made in the Italian Alps, confirms the ubiquity of plastic pollution worldwide.
AGU Honored with the First Clean Energy DC Award
Authors: McEntee Chris
Published: April 2019

AGU aspires to lead by demonstrating that a building on a tight urban footprint can operate on a net-zero energy basis while providing a productive and healthy place to work and meet.
Author Correction: The chromosome-level quality genome provides insights into the evolution of the biosynthesis genes for aroma compounds of Osmanthus fragrans
Authors: Yang Xiulian , Yue Yuanzheng , Li Haiyan , Ding Wenjie , Chen Gongwei , Shi Tingting , Chen Junhao , Park Min S. , Chen Fei , Wang Lianggui
Published: April 2019

Since the publication of this article, the authors have noticed that the NCBI accession number is missing from article.
Author Correction: The complexity of the Fragaria x ananassa(octoploid) transcriptome by single-molecule long-read sequencing
Authors: Yuan Huazhao , Yu Hongmei , Huang Tao , Shen Xinjie , Xia Jin , Pang Fuhua , Wang Jing , Zhao Mizhen
Published: April 2019

Since the publication of this article, the authors have noticed that the part of acknowledgement is missing from article. Here is the acknowledgement:
A novel compound heterozygous variant of ECHS1 identified in a Japanese patient with Leigh syndrome
Authors: Uchino Shumpei , Iida Aritoshi , Sato Atsushi , Ishikawa Keiko , Mimaki Masakazu , Nishino Ichizo , Goto Yu-ichi
Published: April 2019

Leigh syndrome (LS) is a heterogeneous neurodegenerative disorder caused by mitochondrial dysfunction. Certain LS cases have mutations in ECHS1, which encodes a short-chain enoyl-CoA hydratase involved in the metabolism of fatty acids and branched-chain amino acids in mitochondria. Using exome sequencing, we diagnosed a Japanese patient with LS and identified the patient as a compound heterozygote for a novel variant of ECHS1, consisting of NM_004092.4:c.23T>C (p.Leu8Pro) and NM_004092.4:c.176A>G (p.Asn59Ser).
A novel regulatory circuit between p53 and GFI1 controls induction of apoptosis in T cells
Authors: Vadnais Charles , Chen Riyan , Fraszczak Jennifer , Hamard Pierre-Jacques , Manfredi James J. , Möröy Tarik
Published: April 2019

Here we demonstrate a mode of reciprocal regulation between GFI1 and p53 that controls the induction of apoptosis in T cells. We show that GFI1 prevents induction of p53 dependent apoptosis by recruiting LSD1 to p53, which leads to the demethylation of its C-terminal domain. This is accompanied by a decrease of the acetylation of lysine 117 within the core domain of the murine p53 protein, which is required for transcriptional induction of apoptosis. Our results support a model in which the effect of GFI1’s regulation of methylation at the c-terminus of p53 is ultimately mediated through control of acetylation at lysine 117 of p53. We propose that GFI1 acts prior to the occurrence of DNA damage to affect the post-translational modification state and limit the subsequent activation of p53. Once activated, p53 then transcriptionally activates GFI1, presumably in order to re-establish the homeostatic balance of p53 activity. These findings have implications for the activity level of p53 in various disease contexts where levels of GFI1 are either increased or decreased.
Enhanced nonlinear magneto-optical rotation in cold atoms: A theoretical study
Authors: Ghaderi Goran Abad Mohsen , Valinezhad Mitra , Mahmoudi Mohammad
Published: April 2019

We theoretically investigate magneto-optical rotation (MOR) of a linearly polarized probe field in the four-level N-type cold atoms. By applying a static magnetic field and a weak coupling field, it is shown that the birefringence enhancement is induced in the system. Moreover, we show that the static magnetic field has a major role in switching the dichroism to enhanced birefringence in the system. We also obtain a large intensity for the output field with nearly perpendicular MOR angle by 88 degrees with subnatural width. It is demonstrated that Doppler broadening has a destructive effect on the MOR of the polarization direction of the probe field. The results of our study can be used for selecting narrow band of wavelengths and polarization converter for efficient switching of TM/TE polarization modes in optical communication, the depolarization backscattering lidar, polarization spectroscopy and precision measurements.
Examination of novel 4-aminoquinoline derivatives designed and synthesized by a hybrid pharmacophore approach to enhance their anticancer activities
Authors: Solomon V. Raja , Pundir Sheetal , Lee Hoyun
Published: April 2019

In an attempt to develop effective and potentially safe anticancer agents, thirty-six 4-aminoquinoline derived sulfonyl analogs were designed and synthesized using a hybrid pharmacophore approach. The cytotoxicity of these compounds was determined using three breast tumor cell lines (MDA-MB231, MDA-MB468 and MCF7) and two matching non-cancer breast epithelial cell lines (184B5 and MCF10A). Although most of the compounds were quite effective on the breast cancer cells, the compound 7-chloro-4-(4-(2,4-dinitrophenylsulfonyl)piperazin-1-yl)quinoline (13; VR23) emerged as potentially the most desirable one in this series of compounds. Data from the NCI-60 cancer panel screening show that compound 13 is effective on a wide range of different cancers. Importantly, compound 13 is needed up to 17.6-fold less doses to achieve the same IC50 against cancer than non-cancer cells (MDA-MB468 vs MCF10A), suggesting that it can potentially be less toxic to normal cells. Cancer cells formed multiple centrosomes in the presence of compound 13, resulting in the cell cycle arrest at prometa-meta phase. This abnormality leads to eventual cell demise with sub-G1 DNA content typically shown with apoptotic cells. In addition, compound 13 also causes an increase in lysosomal volume in cancer but not in non-cancer cells, which may contribute at least in part to its preferential cancer cell-killing. The cancer cell-killing effect of compound 13 is highly potentiated when combined with either bortezomib or monastrol.
Simulation and analysis of electro-optic tunable microring resonators in silicon thin film on lithium niobate
Authors: Han Huangpu , Xiang Bingxi
Published: April 2019

Silicon thin film on lithium niobate combines the advantages of electronic properties of silicon and optical properties of lithium niobate, making it an ideal platform for high-density integrated optics. In this paper, we present an electro-optic tunable microring resonator in silicon thin film on lithium niobate operating at wavelengths of approximately 1.55 μm. The single-mode conditions, optical power distribution, mode profiles, and propagation losses of silicon waveguides are discussed and compared systematically. Quality factor, free spectral range, and bending losses of silicon microring resonators as different radii for different gap sizes between channel and ring waveguides are analyzed in detail. The bending loss and free spectral range decreased with increasing bending radius while the quality factor increased with increasing radius and gap size. The transmission spectrum of microring with radius R = 10 μm was tuned using the electro-optic effect. The key issues affecting the electro-optic effect, such as silicon film thickness and electric field strength, are discussed. This study is helpful for the understanding of microring structures in silicon thin film on lithium niobate, as well as for the fabrication of high-performance and multifunctional photonic integrated devices.
Interaction of the simple carbene c-C3H2with H2: potential energy surface and low-energy scattering
Authors: Ben Khalifa M. , Wiesenfeld L. , Hammami K.
Published: April 2019

Cyclopropenylidene, c-C3H2, is a simple hydrocarbon, ubiquitous in astrophysical gases, and possessing a permanent electric dipole moment.
Organocatalytic asymmetric synthesis of both cis- and trans-configured pyrano[2,3-b]chromenes via different dehydration pathways
Authors: Lv Xue-Jiao , Zhao Wei-Wei , Chen Ying-Han , Wan Sheng-Biao , Liu Yan-Kai
Published: April 2019

The enamine-catalyzed [3 + 3]-cycloaddition between chroman-2-ols and β,γ-unsaturated α-ketoesters is developed to access both enantiomers of cis- and trans-fused pyrano[2,3-b]chromene derivatives.
Asymmetric total synthesis of (+)-astellatol and (−)-astellatene
Authors: Zhao Nan , Xie Shengling , Tian Peilin , Tong Rongbiao , Ning Chengqing , Xu Jing
Published: April 2019

Here we describe the full account of the total synthesis of (+)-astellatol, as well as the first total synthesis of (−)-astellatene.
An excellent OER electrocatalyst of cubic SrCoO3−δ prepared by a simple F-doping strategy
Authors: Wang Wanhua , Yang Yi , Huan Daoming , Wang Likun , Shi Nai , Xie Yun , Xia Changrong , Peng Ranran , Lu Yalin
Published: April 2019

Cubic perovskite SrCoO3−δ was successfully prepared through simple anion F-doping and demonstrated great OER performance.
Tailoring exciton diffusion and domain size in photovoltaic small molecules by annealing
Authors: Sajjad Muhammad T. , Zhang Yiwei , Geraghty Paul B. , Mitchell Valerie D. , Ruseckas Arvydas , Blaszczyk Oskar , Jones David J. , Samuel Ifor D. W.
Published: April 2019

Annealing is shown to increase both exciton diffusion and domain size in two organic photovoltaic materials. This enables both efficient light harvesting and efficient charge extraction.
Spectral analysis of the dipping LMXB system XB 1916-053
Authors: Gambino A. F. , Iaria R. , Di Salvo T. , Mazzola S. M. , Marino A. , Burderi L. , Riggio A. , Sanna A. , D’Amico N.
Published: April 2019

Context. XB 1916-053 is a low mass X-ray binary system (LMXB) hosting a neutron star (NS) and showing periodic dips. The spectrum of the persistent emission was modeled with a blackbody component having a temperature between 1.31 and 1.67 keV and with a Comptonization component with an electron temperature of 9.4 keV and a photon index Γ between 2.5 and 2.9. The presence of absorption features associated with highly ionized elements suggested the presence of partially ionized plasma in the system.

Aims. In this work we performed a study of the spectrum of XB 1916-053, which aims to shed light on the nature of the seed photons that contribute to the Comptonization component.

Methods. We analyzed three Suzaku observations of XB 1916-053: the first was performed in November 2006 and the others were carried out in October 2014. We extracted the persistent spectra from each observation and combined the spectra of the most recent observations, obtaining a single spectrum with a higher statistic. We also extracted and combined the spectra of the dips observed during the same observations.

Results. On the basis of the available data statistics, we infer that the scenario in which the corona Comptonizes photons emitted both by the innermost region of the accretion disk and the NS surface is not statistically relevant with respect to the case in which only photons emitted by the NS surface are Comptonized. We find that the source is in a soft spectral state in all the analyzed observations. We detect the Kα absorption lines of Fe XXV and Fe XXVI, which have already been reported in literature, and for the first time the Kβ absorption lines of the same ions. We also detect an edge at 0.876 keV, which is consistent with a O VIII K absorption edge. The dip spectrum is well described by a model that considers material in different ionization states covering the persistent spectrum and absorbing part of the rear radiation. From this model we rescale the distance of the absorber to a distance that is lower than 1 × 1010 cm.
The Universe at extreme magnification
Authors: Diego J. M.
Published: April 2019

Extreme magnifications of distant objects by factors of several thousand have recently become a reality. Small, very luminous compact objects, such as supernovae (SNe), giant stars at z = 1 − 2, Pop III stars at z >  7, and even gravitational waves (GWs) from merging binary black holes near caustics of gravitational lenses can be magnified many thousands or even tens of thousands of times thanks to their small size. We explore the probability of such extreme magnifications in a cosmological context and include the effect of microlenses near critical curves. We show how the presence of microlenses near the critical curve sets a limit on the maximum magnification. We use a combination of state of the art halo mass functions, high-resolution analytical models for the density profiles, and inverse ray tracing to estimate the probability of magnification near caustics. We estimate the rate of highly magnified events in the case of SNe, GWs, and very luminous stars including Pop III stars. Our findings reveal that future observations will increase the number of events at extreme magnifications, and will open the door not only to studying individual sources at cosmic distances, but also to constraining compact dark matter candidates.
The evolution of ultra-massive white dwarfs
Authors: Camisassa María E. , Althaus Leandro G. , Córsico Alejandro H. , De Gerónimo Francisco C. , Miller Bertolami Marcelo M. , Novarino María L. , Rohrmann René D. , Wachlin Felipe C. , García-Berro Enrique
Published: April 2019

Ultra-massive white dwarfs are powerful tools used to study various physical processes in the asymptotic giant branch (AGB), type Ia supernova explosions, and the theory of crystallization through white dwarf asteroseismology. Despite the interest in these white dwarfs, there are few evolutionary studies in the literature devoted to them. Here we present new ultra-massive white dwarf evolutionary sequences that constitute an improvement over previous ones. In these new sequences we take into account for the first time the process of phase separation expected during the crystallization stage of these white dwarfs by relying on the most up-to-date phase diagram of dense oxygen/neon mixtures. Realistic chemical profiles resulting from the full computation of progenitor evolution during the semidegenerate carbon burning along the super-AGB phase are also considered in our sequences. Outer boundary conditions for our evolving models are provided by detailed non-gray white dwarf model atmospheres for hydrogen and helium composition. We assessed the impact of all these improvements on the evolutionary properties of ultra-massive white dwarfs, providing updated evolutionary sequences for these stars. We conclude that crystallization is expected to affect the majority of the massive white dwarfs observed with effective temperatures below 40 000 K. Moreover, the calculation of the phase separation process induced by crystallization is necessary to accurately determine the cooling age and the mass-radius relation of massive white dwarfs. We also provide colors in the Gaia photometric bands for our H-rich white dwarf evolutionary sequences on the basis of new model atmospheres. Finally, these new white dwarf sequences provide a new theoretical frame to perform asteroseismological studies on the recently detected ultra-massive pulsating white dwarfs.
Reaction of NH+, NH2+, and NH3+ ions with H2 at low temperatures
Authors: Rednyk S. , Roučka Š. , Kovalenko A. , Tran T. D. , Dohnal P. , Plašil R. , Glosík J.
Published: April 2019

Aims. We present an experimental investigation of the exothermic reactions of NH+, NH2+, and NH3+ ions with H2 at temperatures relevant for interstellar clouds.

Methods. The reactions were studied using a variable-temperature 22-pole radio frequency ion trap instrument.

Results. The temperature dependences of rate coefficients of these reactions have been obtained at temperatures from 15 up to 300 K. The reaction of NH+ with H2 has two channels, which lead to NH2+ ( ∼ 97%) and H+3 ( ∼ 3%) with nearly constant reaction rate coefficients (kaNH+(17 K) = 1.0 × 10−9 cm3 s−1 and kbNH+(17 K) = 4.0 × 10−11 cm3 s−1, respectively). The reaction of NH2+ with H2 produces only NH3+ ions. The measured rate coefficient monotonically decreases with increasing temperature from kNH2+(17 K) = 6 × 10−10 cm3 s−1 to kNH2+(300 K) = 2 × 10−10 cm3 s−1. The measured rate coefficient of the reaction of NH3+ with H2, producing NH+4, increases with decreasing temperature from 80 K down to 15 K, confirming that the reaction proceeds by tunnelling through a potential barrier.
Source number counts at high energies: Swift versus NuSTAR
Authors: Akylas A. , Georgantopoulos I.
Published: April 2019

The hard X-ray sky at energies above 10 keV has been extensively explored by the Swift/Gehrels and the NuSTAR missions in the 14−195 keV and the 3−24 keV bands. respectively. The main population of the hard X-ray detected sources are active galactic nuclei (AGN). A discrepancy has been reported between the number count distributions of the two missions in the sense that the extrapolation of the Swift/Gehrels number counts in the flux regime sampled by NuSTAR lies significantly below the NuSTAR counts. We explore this aspect anew by comparing the number count distributions derived from the Swift/Gehrels 105-month catalogue with those from the serendipitous NuSTAR source catalogue. We use a novel number count distribution estimator that makes use of the C-statistic on the unbinned data. In the 14−195 keV band, the Swift/BAT counts follow a Euclidean slope with α = 1.51 ± 0.10 (90% confidence level). The NuSTAR counts in the 8−24 keV band present a steeper slope with α = 1.71 ± 0.20 because of an upturn at fluxes below ∼2 × 10−13 erg cm−2 s−1. The same upturn is observed in the soft (3−8 keV) NuSTAR number counts, which generally also present a steep slope with α = 1.82 ± 0.15. Only the bright part of the NuSTAR 3−8 keV counts agrees with the Chandra number counts in the 2−10 keV band, while the fainter part (below ∼7 × 10−13 erg cm−2 s−1) of the soft NuSTAR counts is in marked disagreement with the Chandra counts. Next, we compare the derived number counts in the different bands using our X-ray AGN population synthesis models. The comparison between the Chandra and the Swift/BAT number counts shows a very good agreement for the standard AGN spectrum with a power-law slope Γ = 1.9, a high-energy cut-off at ∼130 keV and a 2−10 keV reflection component of 3%. On the other hand, using this standard AGN spectral model, only the bright part of the NuSTAR 8−24 keV and 3−8 keV number counts agrees with the model predictions. It is therefore most likely that the disagreement between the X-ray number counts in the different bands is caused by the faint NuSTAR number counts. We discuss various possibilities for the origin of this disagreement.
Uncertainties in gas kinematics arising from stellar continuum modeling in integral field spectroscopy data: the case of NGC 2906 observed with VLT/MUSE
Authors: Bellocchi E. , Ascasibar Y. , Galbany L. , Sánchez S. F. , Ibarra–Medel H. , Gavilán M. , Díaz Á.
Published: April 2019

Context. Integral field spectroscopy (IFS) provides detailed information about galaxy kinematics at high spatial and spectral resolution, and the disentanglement of the gaseous and stellar components is a key step in the analysis of the data.

Aims. We study how the use of several stellar-subtraction methods and line fitting approaches can affect the derivation of the main kinematic parameters (velocity and velocity dispersion fields) of the ionized gas component.

Methods. The target of this work is the nearby galaxy NGC 2906, observed with the MUSE instrument at the Very Large Telescope (VLT). A sample of twelve spectra is selected from the inner (nucleus) and outer (spiral arms) regions, characterized by different ionization mechanisms. We compare three different methods to subtract the stellar continuum (FIT3D, STARLIGHT and pPXF), combined with one of the following stellar libraries: MILES, STELIB and GRANADA+MILES.

Results. The choice of the stellar-subtraction method is the most important ingredient affecting the derivation of the gas kinematics, followed by the choice of the stellar library and by the line-fitting approach. In our data, typical uncertainties in the observed wavelength and width of the Hα and [NII] lines are of the order of ⟨δλ⟩rms ∼ 0.1 Å and ⟨δσ⟩rms ∼ 0.2 Å (i.e., ∼5 and 10 km s−1, respectively). The results obtained from the [NII] line seem to be slightly more robust, as it is less affected by stellar absorption than Hα. All methods considered yield statistically consistent measurements once a mean systemic contribution Δλ¯ = Δσ¯ = 0.2 ΔMUSE is added in quadrature to the line-fitting errors, where ΔMUSE = 1.1 Å ∼50 km s−1, which denotes the instrumental resolution of the MUSE spectra.

Conclusions. Although the subtraction of the stellar continuum is critical in order to recover line fluxes, any method (including none) can be used to measure the gas kinematics, as long as an additional component, Δλ¯ = Δσ¯ = 0.2 ΔMUSE, is added to the error budget.
Stellar cusp and warm dust at the heart of NGC 1068
Authors: Rouan D. , Grosset L. , Gratadour D.
Published: April 2019

Aims. Establishing precisely how stars and interstellar medium distribute within the central 100 pc area around an AGN, down to the pc scale, is key to understanding the late stages of transfer of matter onto the accretion disc.

Methods. Using adaptive optics-assisted (SPHERE-VLT) near-IR images in the H band, Ks band, and several narrow bands of the Seyfert 2 galaxy NGC 1068, we analysed the radial distribution of brightness in the central r <  100 pc area down to the pc scale. The median-averaged radial profiles are fitted by a cusp (power law) plus a central point source. A simple radiative transfer model is also used to interpret the data.

Results. We find that the fit of radial brightness profiles beyond 10 pc is done quite precisely at Ks band by a cusp of exponent −2.0 plus a central point source and by a cusp of exponent −1.2 at H. The difference of exponents between H band and Ks band can be explained by differential extinction, provided that the distribution of dust is itself cuspy, with an exponent −1.0. However, the derived stellar density is found to follow a r−4 cusp, which is much steeper than any other cusp, either theoretically predicted around a massive black hole, or observed in the centre of early- and late-type galaxies or in mergers. Introducing a segregation in the stellar population with a central excess of giant stars leads to a somewhat less steep exponent; however, the de-reddened luminosity of the stellar cusp, as well as the mass of dust and gas all appear much too high to be realistic. An alternative scenario, where the Ks-band profile is well fitted by a combination of radiation from a stellar cusp identical to the H-band profile and thermal emission of warm/hot dust heated by the central engine appears much more satisfactory. NGC 1068 is shown to satisfy a relationship between half-light radius, cusp luminosity, and exponent that we established using a sample of luminous infrared galaxies (LIRGs) and ultraluminous infrared galaxies ULIRGs. This suggests that the cusp is the remnant of a recent starburst. We identify the central point-like source with the very hot dust at the internal wall of the putative torus and derive an intrinsic luminosity that requires a central extinction AK ≈ 8, a value consistent with predictions by several torus models.

Conclusions. The overall picture revealed by this study is closely consistent with the scheme of a central rather steep stellar cusp, embedded in a diluted medium of warm dust, while a compact and dense structure identified with the putative torus is required to interpret a highly reddened point-like central source of very hot dust.
Radial abundance gradients in the outer Galactic disk as traced by main-sequence OB stars
Authors: Bragança G. A. , Daflon S. , Lanz T. , Cunha K. , Bensby T. , McMillan P. J. , Garmany C. D. , Glaspey J. W. , Borges Fernandes M. , Oey M. S. , Hubeny I.
Published: April 2019

Context. Elemental abundance gradients in galactic disks are important constraints for models of how spiral galaxies form and evolve. However, the abundance structure of the outer disk region of the Milky Way is poorly known, which hampers our understanding of the spiral galaxy that is closest to us and that can be studied in greatest detail. Young OB stars are good tracers of the present-day chemical abundance distribution of a stellar population and because of their high luminosities they can easily be observed at large distances, making them suitable to explore and map the abundance structure and gradients in the outer regions of the Galactic disk.

Aims. Using a sample of 31 main-sequence OB stars located between galactocentric distances 8.4−15.6 kpc, we aim to probe the present-day radial abundance gradients of the Galactic disk.

Methods. The analysis is based on high-resolution spectra obtained with the MIKE spectrograph on the Magellan Clay 6.5-m telescope on Las Campanas. We used a non-NLTE analysis in a self-consistent semi-automatic routine based on TLUSTY and SYNSPEC to determine atmospheric parameters and chemical abundances.

Results. Stellar parameters (effective temperature, surface gravity, projected rotational velocity, microturbulence, and macroturbulence) and silicon and oxygen abundances are presented for 28 stars located beyond 9 kpc from the Galactic center plus three stars in the solar neighborhood. The stars of our sample are mostly on the main-sequence, with effective temperatures between 20 800−31 300 K, and surface gravities between 3.23−4.45 dex. The radial oxygen and silicon abundance gradients are negative and have slopes of −0.07 dex kpc−1 and −0.09 dex kpc−1, respectively, in the region 8.4 ≤ RG ≤ 15.6 kpc.

Conclusions. The obtained gradients are compatible with the present-day oxygen and silicon abundances measured in the solar neighborhood and are consistent with radial metallicity gradients predicted by chemodynamical models of Galaxy Evolution for a subsample of young stars located close to the Galactic plane.