bluuebunny/crossref_metadata_2025 huggingface dataset:
Quality Changes during Storage of Burkina (a Millet and Milk-based) Drink
Authors: Jerry Ampofo-Asiama , Hafusatu Mamudu , Emeruwa Helen Oluchi , Kant Owusu Fokuo , Bright Quaye
Published: April 2020

Burkina, a drink prepared from millet and milk, is gaining economic attention in Ghana due to its perceived nutritious nature and high energy content. The drink which is produced on a small-scale is usually vended without proper control of storage conditions leading to rapid loss of quality. The objective of this study was to investigate the effect of storing burkina at different temperatures (4 and 30°C) on the microbial and physicochemical (pH, titratable acidity, brix and phenolic content) quality of the drink. The pH, titratable acidity, brix and phenolic content of freshly prepared burkina were 3.65, 0.49%, 2.05 and 0.26 mg GAE/100 g, respectively. Although, changes were observed, storage temperature did not have a significant effect on the physicochemical quality of burkina. The initial load of aerobic mesophiles, lactic acid bacteria, Enterobacteriaceae, and yeast and moulds in the freshly prepared Burkina were 6.45, 5.49, 2.58 and 4.45 log cfu/mL, respectively. Storage at the higher temperature resulted in an increased microbial load within 48 h, leading to faster spoilage, with only marginal increases observed at the lower storage temperature.
Comparative Evaluation of the Influence of Organic and Inorganic Fertilizers on Growth Performance of Tetrapleura tetraptera
Authors: Edem U. L. , Ekerette E. E.
Published: April 2020

The continuous destruction of our rainforest has threatened the existence of many useful and multipurpose plant species such as Tetrapleura tetraptera. To revert this situation, efforts must be made towards its sustainable use by encouraging reforestation which entails raising of seedlings for mass propagation of this crop. This study was aimed at comparing the effects of organic (chicken litter) and inorganic (NPK 15:15:15) fertilizers on seedling growth in four accessions of Tetrapleura tetraptera and hence determining fertilizer preference for this forest species. The Complete Randomized Design (CRD) was used in a factorial arrangement with four accessions and three fertilizer types in eight replicates. One month after transplanting, the fertilizers (organic and inorganic) were uniformly applied at the rate of 45 kg/hectare according to the experimental design. Data were collected monthly for a period of three months on plant height, stem diameter, leaf area, leaf length, member of branches, number of leaves, primary and secondary internode length per plant. Data on seedling emergence were also taken. Data collected were subjected to a two-way analysis of variance. Least significant difference (LSD) was used to separate significant means at p = 0.05. Result obtained revealed that the soil was rich in calcium, phosphorus and organic matter but low in nitrogen and potassium which were adequately complemented in mean days to seedling emergence in four accessions studied. Our findings also revealed that the organic (chicken litter) fertilizer did better (P<0.05) in all accessions than inorganic (NPK 15:15:15) fertilizer for all morphological traits studied. The performance of Cross River accession was outstanding as illustrated by the significant interaction obtained in most parameters. With chicken, litter fertilizer, Cross River accession produced the tallest plant (27.38 cm), largest leaf area (1.99 cm2), highest number of branches (20.13), highest number of leaves (66.75), longest stem diameter (0.93 cm), longest leaf length (1.94 cm), lowest primary (0.80) and lowest secondary (0.83) internode length. The use of organic fertilizers is therefore recommended for improved seedling growth of Tetrapleura tetraptera.
Employee Deviance as By-product of Psychological Contract: The Moderating Effects of Power Distance among Employees in Insurance Companies in Nigeria
Authors: Etodike Chukwuemeka N. , Joe-Akunne Chiamaka O. , Obibuba Ijeoma M.
Published: April 2020

Employees have expectations from their organizations; whether they are written, contractual, or not, these expectations have an equally employee outcome such as employee deviance. Indices indicate that employee deviance is on the increase especially in the organized private sector; thus, this study evaluated employee deviance as by-product of psychological contract and power distance among a sample of employees (289) from insurance organizations in Nigeria with an average age of 34.50 years and standard deviation of 3.50. The study sought to ascertain the relationship between psychological contract and employee deviance and whether perceptions of power distance moderated this relationship. Psychological contract inventory (PCI), Power distance scale adapted from CVSCALE Five-dimensional scale of individual cultural values and Workplace deviant behaviour scale were utilized for data collection.  The result of data analysis indicated that the adjusted R2 for step 1 is .24 at F(42.06) p < .01. In the second model, the adjusted R2 is .26 and R change is .002.  This R change was significant at F (33.76), df = 285 p < .01. The Beta coefficient for model 2 shows that psychological contract significantly and negatively predicted employee deviant behaviours at Beta value, thus, the first hypothesis was confirmed at β = -.68, p < .01. Similarly, power distance significantly and positively predicted employee deviant behaviour at β coefficient value of .34, p < .01, thus, the second hypothesis was also confirmed. Also, the third hypothesis where power distance moderated the relationship between psychological contract and employee deviant behaviour was confirmed at β =.27, p < .01. The study concludes that organizations whose interests do not account for the expectations of their employees are at risk of higher levels of employees’ deviance either as byproduct of psychological contract violations or as a retaliatory behaviour.
The International Code of Marketing of Breastmilk Substitutes: Are Implementers in Southern Nigeria Adequately Informed?
Authors: Nte Alice R. , Eke Gracia K. , Onuora Ngozi
Published: April 2020

Background: The knowledge about the International Code of Marketing of Breastmilk Substitutes and relevant subsequent World Health Assembly (WHA) Resolutions (the Code), its implementation and enforcement are essential in promoting, protecting and supporting breastfeeding, especially exclusive breastfeeding for the first six months of life and optimal infant and young child feeding. Violations by various stakeholders remain a perennial problem within and outside Nigeria with the main reason being lack of information of the Code and its relevance to child survival, growth and development.

Aims: To share the findings from data collected during the sensitization of stakeholders on the International Code of Marketing of Breastmilk Substitutes in four States in the UNICEF Rivers Field Office, southern Nigeria.

Study Design: Prospective study.

Place and Duration of Study: September-October 2017, Southern, Nigeria.

Methodology: Stakeholders from 4 southern States in Nigeria attended the sensitization meetings. A pre- and post-tests were administered to assess the knowledge they acquired from the workshops. Results were analysed using percentages and test of significance. 

Results: The two-day meeting for each State held in September and October 2017 for a total of 296 participants out of whom data on 237 (80%) participants were analysed for presentation. Over 95% respondents had not read the Code and the Nigerian Regulations 2005, did not know the contents and their responsibility towards its implementation before the meeting. At the post test, the performance of the participants significantly improved (p<0.05) on all test items. All participants now owned the Code, the Nigerian Regulations and other relevant documents to sustain their knowledge and commitment to the implementation of the Code.

Conclusion: Ignorance and lack of ownership of copies of the Code contributed to the level of its violations and poor implementation. Improved compliance with the Code requires creation of awareness about it among stakeholders.
Rubber-tip Design Improvement for Die Crack Elimination at Diebond Process
Authors: Rodriguez Rennier S. , Gomez Frederick Ray I.
Published: April 2020

The paper focused on the elimination of die crack occurrence at the diebond process. Design of experiment (DOE) was done on the pick and place rubber-tip design and an improved design was finalized. The improved rubber-tip configuration with smaller vacuum design and full contact surface eventually resolved the die crack issues, improving the manufacturability of thin silicon die during diebond process. For future works, the configuration could be applied for packages with similar requirement.
Optimization of the Extraction Procedure of Apixaban from Dried Rat Plasma Spots
Authors: Aksenova L. V. , Koval V. V. , Chernonosov A. A.
Published: April 2020

Aims: Apixaban is an anticoagulant used to treat and prevent blood clots, as well as to prevent stroke in people with atrial fibrillation. The dried spot analyses, including dried blood spots and dried plasma spots, are used to simplify techniques for determining drug concentrations in blood and plasma. In this case, equipment with highly sensitive detector is required, for example, mass spectrometer, as well as a high level of drug extraction from the dried spot. In this work, apixaban extraction from dried plasma spots (DPS) was studied in order to determine the optimal parameters of the extraction method.

Study Design: Short Research Articles.

Place and Duration of Study: Core Facility of Mass Spectrometric Analysis, Institute of Chemical Biology and Fundamental Medicine SB RAS, between September 2019 and February 2020.

Methodology: The organic extraction method was chosen for evaluation as the most suitable for LC-MS assay. Several parameters: percentage of organic solvent, presence or absence of 0.1% formic acid (FA), time, volume and temperature of extraction were investigated to find the best combination for recovery of apixaban from DPS for further LC-MS analysis.

Results: The results showed that the main influence on the extraction is the composition of the solvent, volume of solvent, as well as temperature and time of extraction. Pure acetonitrile is the worst solvent for extracting apixaban from DPS. Solvents: MeOH:H2O (100:0, v: v), MeOH: 0.1% FA in H2O (80:20, v:v), ACN: 0.1% FA in H2O (90:10, v:v) or ACN:MeOH (90:10, v:v) provide better recovery of apixaban. The optimum extraction parameters were as follows: 90% acetonitrile concentration, extraction temperature of 40°C, extraction time of 15 min, and solvent volume of 100
Stacking‐Order‐Driven Optical Properties and Carrier Dynamics in ReS2
Authors: Zhou Yongjian , Maity Nikhilesh , Rai Amritesh , Juneja Rinkle , Meng Xianghai , Roy Anupam , Zhang Yanyao , Xu Xiaochuan , Lin Jung‐Fu , Banerjee Sanjay K. , Singh Abhishek K. , Wang Yaguo
Published: April 2020

Two distinct stacking orders in ReS2 are identified without ambiguity and their influence on vibrational, optical properties and carrier dynamics are investigated. With atomic resolution scanning transmission electron microscopy (STEM), two stacking orders are determined as AA stacking with negligible displacement across layers, and AB stacking with about a one‐unit cell displacement along the a axis. First‐principles calculations confirm that these two stacking orders correspond to two local energy minima. Raman spectra inform a consistent difference of modes I & III, about 13 cm−1 for AA stacking, and 20 cm−1 for AB stacking, making a simple tool for determining the stacking orders in ReS2. Polarized photoluminescence (PL) reveals that AB stacking possesses blueshifted PL peak positions, and broader peak widths, compared with AA stacking, indicating stronger interlayer interaction. Transient transmission measured with femtosecond pump–probe spectroscopy suggests exciton dynamics being more anisotropic in AB stacking, where excited state absorption related to Exc. III mode disappears when probe polarization aligns perpendicular to b axis. The findings underscore the stacking‐order driven optical properties and carrier dynamics of ReS2, mediate many seemingly contradictory results in the literature, and open up an opportunity to engineer electronic devices with new functionalities by manipulating the stacking order.
Reducing the Singlet−Triplet Energy Gap by End‐Group π−π Stacking Toward High‐Efficiency Organic Photovoltaics
Authors: Han Guangchao , Hu Taiping , Yi Yuanping
Published: April 2020

To improve the power conversion efficiencies for organic solar cells, it is necessary to enhance light absorption and reduce energy loss simultaneously. Both the lowest singlet (S1) and triplet (T1) excited states need to energertically approach the charge‐transfer state to reduce the energy loss in exciton dissociation and by triplet recombination. Meanwhile, the S1 energy needs to be decreased to broaden light absorption. Therefore, it is imperative to reduce the singlet−triplet energy gap (ΔEST), particularly for the narrow‐bandgap materials that determine the device T1 energy. Although maximizing intramolecular push−pull effect can drastically decrease ΔEST, it inevitably results in weak oscillator strength and light absorption. Herein, large oscillator strength (≈3) and a moderate ΔEST (0.4−0.5 eV) are found for state‐of‐the‐art A−D−A small‐molecule acceptors (ITIC, IT‐4F, and Y6) owing to modest push−pull effect. Importantly, end‐group π−π stacking commonly in the films can substantially decrease the S1 energy by nearly 0.1 eV, but the T1 energy is hardly changed. The obtained reduction of ΔEST is crucial to effectively suppress triplet recombination and acquire small exciton dissociation driving force. Thus, end‐group π−π stacking is an effective way to achieve both small energy loss and efficient light absorption for high‐efficiency organic photovoltaics.
Deterministic Realization of Quasicrystal Surface Relief Gratings on Thin Azopolymer Films
Authors: Salvatore Marcella , Borbone Fabio , Oscurato Stefano Luigi
Published: April 2020

Spatially structured UV–visible light fields generate topographic modulations on the surface of films of azobenzene‐containing polymers. The geometry of the surface reliefs depends on the spatiotemporal distribution of light over the sample. If multistep sequential irradiations are used, even illumination configurations as simple as the interference of two linearly polarized beams produce complex surface textures. This is the case of the quasicrystal geometries, obtainable as the superposition of multiple sinusoidal surface relief gratings oriented in different directions over the surface. The quantitative relief design would require a comprehensive theoretical description of the light‐induced relief formation mechanism, which is still elusive for azopolymers. Here, despite limiting the description at a phenomenological level, the deterministic design of the quasicrystal surface reliefs obtained in sequential light exposures of an azopolymer film is demonstrated. The model provides an excellent agreement between simulated and experimental relief textures, predicting also the dependence of relief structural features on illumination parameters as the number of exposure steps and the beam interference angle. The deterministic texture design allows the controlled tailoring of surface functionalities related to the relief geometry like light diffraction properties of the samples, which are here exploited to manipulate, split, and trap diffracted light.
Flexible Generation of Multi‐Aqueous Core Hydrogel Capsules Using Microfluidic Aqueous Two‐Phase System
Authors: Wang Hui , Liu Haitao , He Fan , Chen Wenwen , Zhang Xu , Zhao Mengqian , Wang Li , Qin Jianhua
Published: April 2020

Hydrogel capsules are widely applied in materials science, pharmaceutical science, and tissue engineering due to their tunable nature, defined core–shell architecture, and proper biocompatibility. Specially, multi‐core capsules are highly functional carriers with notable advantages for co‐encapsulation of diverse incompatible components without cross‐contamination. However, current approaches for generating such capsules are limited by using gas/oil‐water‐oil systems, leading to poor biocompatibility and functions due to the gas/oil cores. Herein, a simple and new approach is proposed for flexible fabrication of multi‐aqueous core hydrogel capsules (MACHC) using microfluidic aqueous two‐phase system (µATPS). In this system, a flow‐focusing microfluidic device is designed to create a stable laminar flow with two immiscible liquids composed of polyethylene glycol and dextran, which is sheared by oil phase to further effectively produce MACHC. The volume and components of each core can be well tailored by precisely adjusting the distinct flows, while the number of cores is determined by the orifice design of microfluidic chip. The MACHC are successfully used to co‐encapsulate heterogeneous hepatic and endothelial cells, indicating good biocompatibility and multi‐functionality of the multi‐core carriers. The proposed µATPS‐based approach is stable and convenient, holding promise for generation of multi‐responsive materials, tissue engineering, and co‐delivery of diverse drugs.
Atomic Layer Deposition Assisted Encapsulation of Quantum Dot Luminescent Microspheres toward Display Applications
Authors: Fang Fan , Liu Mengjia , Chen Wei , Yang Hongcheng , Liu Yizun , Li Xiang , Hao Junjie , Xu Bing , Wu Dan , Cao Kun , Lei Wei , Müller‐Buschbaum Peter , Sun Xiao Wei , Chen Rong , Wang Kai
Published: April 2020

Quantum dots (QDs) are promising for being used in advanced displays due to their outstanding emission properties. Herein, a novel encapsulation method for QDs is reported and ultra‐stable QDs@SiO2@Al2O3 luminescent microspheres (QLuMiS) are obtained by combining a sol–gel method for the intermediate SiO2 layer with a fluidized powder atomic layer deposition (ALD) for the outer Al2O3 layer. The rich hydroxyl coverage on the QDs@SiO2 surface provides abundant chemisorption sites, which are beneficial for the deposition of Al2O3 in the ALD process. Simultaneously, the water‐oxygen channels in the SiO2 layer are blocked by the Al2O3 layer, which protects the QDs against deterioration. Consequently, the QLuMiS exhibit an excellent stability with 86% of the initial light conversion efficiency after 1000 h of blue light aging under a light power density of 2000 mW cm−2. Such stability is significantly better than that of QDs@Al2O3 and QDs@SiO2 samples. Moreover, under this strong irradiation aging condition with blue light, the extrapolated lifetime (L50) of QLuMiS is 4969 h, which is ten times longer than that of QDs@SiO2 and is the best record as far as is known. Finally, a prototype of a QLuMiS‐based cellphone screen with a wide color gamut of 115% NTSC is demonstrated.
Growth trajectories of wheat–maize intercropping with straw and plastic management in arid conditions
Authors: Yin Wen , Yu Aizhong , Guo Yao , Fan Hong , Hu Falong , Fan Zhilong , Zhao Cai , Chai Qiang , Coulter Jeffrey A.
Published: April 2020

Interspecific interactions in intercropping can affect the yield of component crops, but little attention has been given to the dynamics of interspecific competition based on biomass accumulation in various management practices. A field experiment with wheat (Triticum aestivumL.)–maize (Zea maysL.) intercropping was conducted to evaluate the interspecific competition with four types of straw management for wheat (no‐tillage with straw standing or mulched soil and conventional tillage with straw incorporation or no straw retained) and two methods of plastic mulching for maize (no‐tillage with residual plastic mulching [i.e., new at the beginning of the previous crop, old plastic mulched in season] and conventional tillage with annual new plastic mulching). Aboveground biomass of intercrops was sampled throughout the growing season and fit to a logistic growth model. Compared with sole‐cropping, intercropping significantly increased maximum biomass and maximum growth rate of wheat but suppressed vegetative and maximum growth rates of maize. Maize growth recovered after wheat was harvested when maize was blister kernel stage (R2). Straw mulching in wheat strips and residual plastic mulching in maize strips produced greater maximum biomass amount or rates of wheat and maize than that with conventional intercropping (conventional tillage with no straw retention in wheat strips and annual new plastic mulching in maize strips). Straw mulching in wheat strips and residual plastic mulching in maize strips enhanced total grain yields by 14.9% compared with conventional intercropping. Straw mulching in wheat strips and residual plastic mulch in maize strips are suitable for coordinating interspecies interactions and increasing the productivity of wheat–maize intercropping.
The health of restaurant work: A historical and social context to the occupational health of food service
Authors: Lippert Julia , Rosing Howard , Tendick‐Matesanz Felipe
Published: April 2020

The United States currently has over one million restaurants, making food service one of the largest workforces and industry sectors in the nation's economy. Historically, concern for the health of early restaurant workers was tied largely to the hygiene of the food and thus the wellbeing of the customer rather than the individuals preparing the food. The landscape of occupational illness and injury that resulted is fraught with some of the starkest health disparities in wages, discrimination, benefits, injuries, and illness seen among US laborers. These disparities have consistently been associated with social class and economic position. Conditions identified during the early years of restaurant work, before the introduction of occupational safety and health protections, persist today largely due to tipped wages, dependence on customer discretion, and the management structure. Research and intervention efforts to control occupational health hazards should be directed toward the socioeconomic and structural roots of health problems among food service workers in the United States. Such efforts have important implications for enhancing worker protections, improving wages, and restructuring working conditions for restaurant and food service workers. They also suggest opportunities for occupational health practitioners and researchers to contribute to system‐level change analysis to address centuries‐old occupational health challenges still facing one of the largest sectors of workers in the country.
Cryogenic Correlative Single‐Particle Photoluminescence Spectroscopy and Electron Tomography for Investigation of Nanomaterials
Authors: Dahlberg Peter D. , Perez Davis , Su Zhaoming , Chiu Wah , Moerner W. E.
Published: April 2020

Cryogenic single‐particle photoluminescence (PL) spectroscopy has been used with great success to directly observe the heterogeneous photophysical states present in a population of luminescent particles. Cryogenic electron tomography provides complementary nanometer scale structural information to PL spectroscopy, but the two techniques have not been correlated due to technical challenges. Here, we present a method for correlating single‐particle information from these two powerful microscopy modalities. We simultaneously observe PL brightness, emission spectrum, and in‐plane excitation dipole orientation of CdSSe/ZnS quantum dots suspended in vitreous ice. Stable and fluctuating emitters were observed, as well as a surprising splitting of the PL spectrum into two bands with an average energy separation of 80 meV. In some cases, the onset of the splitting corresponded to changes in the in‐plane excitation dipole orientation. These dynamics were assigned to structures of individual quantum dots and the excitation dipoles were visualized in the context of structural features.
Progress of Organic Electrodes in Aqueous Electrolyte for Energy Storage and Conversion
Authors: Huang Jianhang , Dong Xiaoli , Guo Zhaowei , Wang Yonggang
Published: April 2020

Aqueous batteries using inorganic compounds as electrode materials are considered a promising solution for grid‐scale energy storage, while wide application is limited by the short life and/or high cost of electrodes. Organics with carbonyl groups are being investigated as the alternative to inorganic electrode materials because they offer the advantages of tunable structures, renewability, and they are environmentally benign. Furthermore, the wide internal space of such organic materials enables flexible storage of various charged ions (for example, H+, Li+, Na+, K+, Zn2+, Mg2+, and Ca2+, and so on). We offer a comprehensive overview of the progress of organics containing carbonyls for energy storage and conversion in aqueous electrolytes, including applications in aqueous batteries as solid‐state electrodes, in flow batteries as soluble redox species, and in water electrolysis as redox buffer electrodes. The advantages of organic electrodes are summarized, with a discussion of the challenges remaining for their practical application.
CoII Complexes as Liposomal CEST Agents
Authors: Abozeid Samira M. , Asik Didar , Sokolow Gregory E. , Lovell Jonathan F. , Nazarenko Alexander Y. , Morrow Janet R.
Published: April 2020

Three paramagnetic CoII macrocyclic complexes containing 2‐hydroxypropyl pendant groups, 1,1′,1′′,1′′′‐(1,4,8,11‐tetraazacyclotetradecane‐1,4,8,11‐tetrayl)tetrakis‐ (propan‐2‐ol) ([Co(L1)]2+, 1,1′‐(4,11‐dibenzyl‐1,4,8,11‐tetraazacyclotetradecane‐1,8‐diyl)bis(propan‐2‐ol) ([Co(L2)]2+), and 1,1′‐(4,11‐dibenzyl‐1,4,8,11‐tetraazacyclotetradecane‐1,8‐diyl)bis(octadecan‐2‐ol) ([Co(L3)]2+) were synthesized to prepare transition metal liposomal chemical exchange saturation transfer (lipoCEST) agents. In solution, ([Co(L1)]2+) forms two isomers as shown by 1H NMR spectroscopy. X‐ray crystallographic studies show one isomer with 1,8‐pendants in cis‐configuration and a second isomer with 1,4‐pendants in trans‐configuration. The [Co(L2)]2+ complex has 1,8‐pendants in a cis‐configuration. Remarkably, the paramagnetic‐induced shift of water 1H NMR resonances in the presence of the [Co(L1)]2+ complex is as large as that observed for one of the most effective LnIII water proton shift agents. Incorporation of [Co(L1)]2+ into the liposome aqueous core, followed by dialysis against a solution of 300 mOsm L−1 produces a CEST peak at 3.5 ppm. Incorporation of the amphiphilic [Co(L3)]2+ complex into the liposome bilayer produces a more highly shifted CEST peak at −13 ppm. Taken together, these data demonstrate the feasibility of preparing CoII lipoCEST agents.
Incorporating Rare‐Earth Terbium(III) Ions into Cs2AgInCl6:Bi Nanocrystals toward Tunable Photoluminescence
Authors: Liu Ying , Rong Ximing , Li Mingze , Molokeev Maxim S. , Zhao Jing , Xia Zhiguo
Published: April 2020

The incorporation of impurity ions or doping is a promising method for controlling the electronic and optical properties and the structural stability of halide perovskite nanocrystals (NCs). Herein, we establish relationships between rare‐earth ions doping and intrinsic emission of lead‐free double perovskite Cs2AgInCl6 NCs to impart and tune the optical performances in the visible light region. Tb3+ ions were incorporated into Cs2AgInCl6 NCs and occupied In3+ sites as verified by both crystallographic analyses and first‐principles calculations. Trace amounts of Bi doping endowed the characteristic emission (5D4→7F6‐3) of Tb3+ ions with a new excitation peak at 368 nm rather than the single characteristic excitation at 290 nm of Tb3+. By controlling Tb3+ ions concentration, the emission colors of Bi‐doped Cs2Ag(In1−xTbx)Cl6 NCs could be continuously tuned from green to orange, through the efficient energy‐transfer channel from self‐trapped excitons to Tb3+ ions. Our study provides the salient features of the material design of lead‐free perovskite NCs and to expand their luminescence applications.
Thoughts on What Chemists Can Contribute to Fighting SARS‐CoV‐2 – A Short Note on Hand Sanitizers, Drug Candidates and Outreach
Authors: Opatz Till , Senn‐Bilfinger Joerg , Richert Clemens
Published: April 2020

The SARS‐CoV‐2 outbreak causing the respiratory disease COVID‐19 has left many chemists in academia without an obvious option to contribute to fighting the pandemic. Some of our recent experiences indicate that there are ways to overcome this dilemma. A three‐pronged approach is proposed.
Topology‐Templated Synthesis of Crystalline Porous Covalent Organic Frameworks
Authors: Jin Enquan , Geng Keyu , Lee Ka Hung , Jiang Weiming , Li Juan , Jiang Qiuhong , Irle Stephan , Jiang Donglin
Published: April 2020

A strategy is presented for the synthesis of crystalline porous covalent organic frameworks via topology‐templated polymerization. The template is based on imine‐linked frameworks and their (001) facets seed the C=C bond formation reaction to constitute 2D sp2carbon‐conjugated frameworks. This strategy is applicable to templates with different topologies, enables designed synthesis of frameworks that cannot be prepared via direct polymerization, and creates a series of sp2carbon frameworks with tetragonal, hexagonal, and kagome topologies. The sp2carbon frameworks are highly luminescent even in the solid state and exhibit topology‐dependent π transmission and exciton migration; these key fundamental π functions are unique to sp2carbon‐conjugated frameworks and cannot be accessible by imine‐linked frameworks, amorphous analogues, and 1D conjugated polymers. These results demonstrate an unprecedented strategy for structural and functional designs of covalent organic frameworks.
Artificial Splitting of a Non‐Ribosomal Peptide Synthetase by Inserting Natural Docking Domains
Authors: Kegler Carsten , Bode Helge B.
Published: April 2020

The interaction in multisubunit non‐ribosomal peptide synthetases (NRPSs) is mediated by docking domains that ensure the correct subunit‐to‐subunit interaction. We introduced natural docking domains into the three‐module xefoampeptide synthetase (XfpS) to create two to three artificial NRPS XfpS subunits. The enzymatic performance of the split biosynthesis was measured by absolute quantification of the products by HPLC‐ESI‐MS. The connecting role of the docking domains was probed by deleting integral parts of them. The peptide production data was compared to soluble protein amounts of the NRPS using SDS‐PAGE. Reduced peptide synthesis was not a result of reduced soluble NRPS concentration but a consequence of the deletion of vital docking domain parts. Splitting the xefoampeptide biosynthesis polypeptide by introducing docking domains was feasible and resulted in higher amounts of product in one of the two tested split‐module cases compared to the full‐length wild‐type enzyme.
A Concise Total Synthesis of (+)‐Waihoensene Guided by Quaternary Center Analysis
Authors: Peng Cheng , Arya Piyush , Zhou Zhiyao , Snyder Scott A.
Published: April 2020

The four contiguous all‐carbon quaternary centers of waihoensene, coupled with the absence of any traditional reactive functional groups other than a single alkene, render it a particularly challenging synthetic target among angular triquinane natural products. Here, we show that its polycyclic frame can be assembled concisely by using a strategically chosen quaternary center to guide the formation of the other three through judiciously selected C−C bond formation reactions. Those events, which included a unique Conia‐ene cyclization and a challenging Pauson–Khand reaction, afforded a 17‐step synthesis of the molecule in enantioenriched form.
SLIM: A Short‐Linked, Highly Redox‐Stable Trityl Label for High‐Sensitivity In‐Cell EPR Distance Measurements
Authors: Fleck Nico , Heubach Caspar A. , Hett Tobias , Haege Florian R. , Bawol Pawel P. , Baltruschat Helmut , Schiemann Olav
Published: April 2020

The understanding of biomolecular function is coupled to knowledge about the structure and dynamics of these biomolecules, preferably acquired under native conditions. In this regard, pulsed dipolar EPR spectroscopy (PDS) in conjunction with site‐directed spin labeling (SDSL) is an important method in the toolbox of biophysical chemistry. However, the currently available spin labels have diverse deficiencies for in‐cell applications, for example, low radical stability or long bioconjugation linkers. In this work, a synthesis strategy is introduced for the derivatization of trityl radicals with a maleimide‐functionalized methylene group. The resulting trityl spin label, called SLIM, yields narrow distance distributions, enables highly sensitive distance measurements down to concentrations of 90 nm, and shows high stability against reduction. Using this label, the guanine‐nucleotide dissociation inhibitor (GDI) domain of Yersinia outer protein O (YopO) is shown to change its conformation within eukaryotic cells.
Metal‐Deficient Supramolecule Based on a Fivefold‐Symmetric Building Block
Authors: Schiller Jana , Peresypkina Eugenia , Virovets Alexander V. , Scheer Manfred
Published: April 2020

An unprecedented cationic supramolecule [(Cp′′Fe(η5‐P5))12{CuNCMe}8]8+ 2.66 nm in diameter was selectively isolated as a salt of the weakly coordinating anion [Al{OC(CF3)3}4]− for the first time and characterized by X‐ray structure analysis, PXRD, NMR spectroscopy, and mass spectrometry. Its metal‐deficient core contains the lowest possible number of Cu atoms to connect 12 pentaphosphaferrocene units, providing a supramolecule with fullerene topology which, topologically, also represents the simplest homologue in the family of metal‐deficient pentaphosphaferrocene‐based supramolecules [{CpRFe(η5‐P5)}12(CuX)20−n]. The 12 vacant metal sites between the cyclo‐P5 rings, the largest number attained to date, make this compound a facile precursor for potential inner and outer modifications of the core as well as for functionalization via the substitution of labile acetonitrile ligands.
3D numerical simulation of radionuclides atmospheric dispersion in Chinese nuclear safety regulation
Authors: Wang Xuan , Wang Yichuan , Liao Yunxuan , Wang Dezhong , Du Fenglei , Ma Yuanwei , Wang Bo
Published: April 2020

For increasing the regulation accuracy and efficiency, commercial computational fluid dynamics (CFD) software Fluidyn‐PANACHE was induced to assist in the analysis of typical radionuclides atmospheric diffusion for the Chinese nuclear safety regulation. The atmospheric dispersion simulation system that used three‐dimensional CFD methods, combined three‐dimensional GIS, and multiple technical methods, such as boundary values calculation, body‐fitting mesh generation, and refinement, was established to simulate and discuss the local wind field characteristics, pollutant transportation, and spatial distribution patterns under spot or constant meteorological conditions following unsteady (real time) or steady methods, respectively. This method can be used to reasonably simulate the turbulent and circumferential flow around large cooling towers in the inland nuclear power plant, compensating the shortage in subtleness of the standard Gaussian model, as well as shortage in realizing multiwind direction simulation in the calculation by the traditional CFD model. The calculation results of annual average atmospheric dispersion factor under normal operation indicated the seasonal differences, with maximum average dispersion factor in autumn, which were consistent with those suggested by Gaussian mixture model. Consequently, it is reasonable to avoid refueling overhauling in autumn to diminish pollution. The CFD numerical simulation method, which has a high agreement with the results of physical tests such as wind tunnel test, provides a new reference for the nuclear safety review of inland nuclear facilities in China.
The effects of modified zinc oxide nanoparticles on the mechanical/thermal properties of epoxy resin
Authors: Baghdadi Yasmine N. , Youssef Lucia , Bouhadir Kamal , Harb Mohammad , Mustapha Samir , Patra Digambara , Tehrani‐Bagha Ali R.
Published: April 2020

Characterized by its strength, durability, and thermal properties, epoxy resin has been widely used as an adhesive, paint, and coating in many applications in the aerospace, civil and automotive industries. Despite this, the thermoset polymer resin has been known for its brittleness and low fracture resistance. This study focuses on the reinforcement of an epoxy resin system (diglycidyl ether of bisphenol A) with zinc oxide (ZnO) nanoparticles in their pristine form and a further modified form. The modification took place in two ways: coating with polydopamine (PDA) and covalently functionalizing them with (3‐aminopropyl)triethoxysilane (APTES) and (3‐glycidoxypropyl)trimethoxysilane (GPTMS). Therefore, four different types of nanoparticles were used: pristine ZnO, ZnO/PDA, ZnO/GPTMS, and ZnO/APTES aiming to improve the interfacial bonding between the polymeric matrix and the reinforcement. Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy, and scanning electron microscopy characterization and imaging techniques were used to prove that the ZnO nanoparticles were successfully modified prior to manufacturing the epoxy composites. While tensile testing showed that using pristine ZnO increases the composite's strength by 32.14%, the fracture toughness of the resin was improved by 9.40% when reinforced with ZnO functionalized with APTES. TGA showed that the addition of functionalized nanoparticles increases the material's degradation temperature by at most 7.31 ± 4.9°C using ZnO/APTES. Differential scanning calorimetry and dynamic mechanical analysis testing proved that the addition of any type of nanoparticles increases the resin's glass transition temperature by as much as 7.83°C (ZnO/APTES).
Glycosylation as a tool for rational vaccine design
Authors: Hariharan Vivek , Kane Ravi S.
Published: April 2020

The discovery of broadly neutralizing antibodies that can neutralize multiple strains or subtypes of a pathogen has renewed interest in the development of broadly protective vaccines. To that end, there has been an interest in designing immunofocusing strategies to direct the immune response to specific, conserved regions on antigenic proteins. Modulation of glycosylation is one such immunofocusing strategy; extensive glycosylation is often exploited by pathogens for immune evasion. Masking epitopes on protein immunogens with “self” glycans can also shield the underlying protein surface from humoral immune surveillance. We review recent advances in applying glycosylation as an immunofocusing tool. We also highlight recent interesting work in the HIV‐1 field involving the identification and elicitation of broadly neutralizing antibodies that incorporate glycans into their binding epitopes.
The effect of positioning on maternal anatomy and hemodynamics during late pregnancy
Authors: Humphries Aimee , Thompson John M. D. , Stone Peter , Mirjalili Seyed Ali
Published: April 2020

Introduction

Supine positioning during late pregnancy causes dramatic compression of maternal abdominal vasculature and is a risk factor for stillbirth. The azygos vein has been shown to provide collateral circulation in this scenario. There are many well‐known anatomical differences in abdominal vasculature between the left and right sides of the body. However, the effect of left and right positioning in pregnancy has not been well studied.

Materials and Methods

After obtaining ethics approval, 10 women with uncomplicated pregnancies between 34 and 38 weeks gestation underwent magnetic resonance imaging in the left and right lateral positions. Phase contrast images were evaluated to measure blood flow through the abdominal aorta, inferior vena cava, and azygos vein.

Results

No significant differences between left and right lateral positions were found in blood flow through the IVC at its formation (mean difference −0.15 L/min [CI −0.47, 0.18], p = .34) or through the azygos vein (mean difference 0.02 L/min [CI −0.22, 0.26], p = .87). Blood flow through the IVC just above the level of the renal veins was found to be reduced by 35% in the right lateral position when compared to the left (mean difference 1.01 L/min [CI 0.25, 1.43], p = .03). There were no significant differences in cardiac output or blood flow through the abdominal aorta.

Conclusions

While it was noted that blood flow through the IVC immediately above the level of the renal veins was reduced in the right lateral position, this did not appear to impact significantly on maternal cardiac output or blood flow through the azygos vein.
Synergistic Interactions Are Prevalent in Catalytic Amyloids
Authors: Marshall Liam R. , Jayachandran Megha , Lengyel‐Zhand Zsofia , Rufo Caroline M. , Kriews Austin , Kim Min‐Chul , Korendovych Ivan V.
Published: April 2020

Interactions between multiple functional groups are key to catalysis. Previously, we reported synergistic interactions in catalytic amyloids formed by mixtures of heptameric peptides that lead to significant improvements in esterase activity. Herein, we describe the in‐depth investigation of synergistic interactions within a family of amyloid fibrils, exploring the results of functional group interactions, the effects of chirality and the use of mixed enantiomers within fibrils. Remarkably, we find that synergistic interactions (either positive or negative) are found in the vast majority of binary mixtures of catalytic amyloid‐forming peptides. The productive arrangements of functionalities rapidly identified by mixing different peptides will undoubtedly lead to the development of more active catalysts for a variety of different transformations.
Bimetallic Co/Mo2C Nanoparticles Embedded in 3D Hierarchical N‐doped Carbon Heterostructures as Highly Efficient Electrocatalysts for Water Splitting
Authors: Zhang Jinxu , Sun Xueping P. , Wei Peng , Lu Gongchang , Sun Shixiong X. , Xu Yue , Fang Chun , Li Qing , Han Jiantao T.
Published: April 2020

Modulating intrinsic electronic and geometric structures of bimetallic electrocatalysts has been regarded as a promising strategy to effectively solve the sluggish kinetics and large overpotential of OER (Oxygen evolution reaction) and HER (Hydrogen evolution reaction) involved in future large‐scale electricity‐to‐hydrogen generation. Here, the bifunctional Co/Mo2C electrocatalysts encapsulated in 3D hierarchical nitrogen‐doped carbon nanofibers synchronously rooted with abundant carbon nanotubes (Co/Mo2C‐NCNTs) were successfully fabricated by a facile electrospinning method. Due to the unique heterostructures and strong synergetic effects between Co and Mo2C nanoparticles to improve OH− affinity, moderate Mo−H bonds, and expose more active sites, the Co/Mo2C‐NCNTs displayed a tiny overpotential for OER (η10=310 mV) and HER (η10=170 mV) and stably operated for 24 h. Moreover, the results of a water electrolysis device demonstrated that the faradaic efficiency was close to 100 %, which further proved that this method was feasible and effective to fabricate high‐efficiency bifunctional non‐noble electrocatalysts for water splitting.
Metallic Glass Films with Nanostructured Periodic Density Fluctuations Supported on Si/SiO2as an Efficient Hydrogen Sorber
Authors: Sarac Baran , Ivanov Yurii P. , Karazehir Tolga , Putz Barbara , Greer A. Lindsay , Sarac A. Sezai , Eckert Jürgen
Published: April 2020

Nanostructured metallic glass films (NMGF) can exhibit surface and intrinsic effects that give rise to unique physical and chemical properties. Here, a facile synthesis and electrochemical, structural, and morphologic characterization of Pd‐Au‐Si based MGs of approximately 50 nm thickness supported on Si/SiO2is reported. Impressively, the maximum total hydrogen charge stored in the Pd‐Au‐Si nanofilm is equal to that in polycrystalline Pd films with 1 μm thickness in 0.1 mH2SO4electrolyte. The same NMGF has a volumetric desorption charge that is more than eight times and 25 % higher than that of polycrystalline PdNF and Pd‐Cu‐Si NMGF with the same thickness supported on Si/SiO2, respectively. A significant number of nanovoids originating from PdHxcrystals, and an increase in the average interatomic spacing is detected in Pd‐Au‐Si NMGF by high‐resolution TEM. Such a high amount of hydrogen sorption is linked to the unique density fluctuations without any chemical segregation exclusively observed for this NMGF.
Simultaneous measurement of optical rotation dispersion and absorption spectra for chiral substances
Authors: Liu Xing , Yang Jinlong , Geng Zhihao , Jia Hongzhi
Published: April 2020

We present a new method based on optical null methods for simultaneously measuring the optical rotatory dispersion (ORD) and absorption spectra of chiral substances. The optical rotation angle at a specific wavelength can be obtained from the optical nulls of the Malus curves with and without the sample. We use the optical nulls of the two curves as benchmark points and the readings to the right of the benchmark points by a certain angular offset to eliminate the influence of the analyzer on the light intensity and obtain the absorbance of the chiral substance at a specific wavelength. The 4096 pixels of the line scan CCD can measure multiple wavelengths simultaneously so that continuous ORD and absorption spectra can be obtained. The experimental results show that the standard deviation of the specific optical rotation is 0.11 deg mL g−1 dm−1, the standard deviation of the maximum absorption wavelength is 0.45 nm, and that absorbance of the sample varies linearly with the concentration. This method is helpful for simplifying the experiment and has a profound influence on the analysis of the contents and molecular configurations of chiral substances in the future.
In situ Surface Charge Density Visualization of Self‐assembled DNA Nanostructures after Ion Exchange
Authors: Møller Sønderskov Steffan , Hyldgaard Klausen Lasse , Amland Skaanvik Sebastian , Han Xiaojun , Dong Mingdong
Published: April 2020

The charge density of DNA is a key parameter in strand hybridization and for the interactions occurring between DNA and molecules in biological systems. Due to the intricate structure of DNA, visualization of the surface charge density of DNA nanostructures under physiological conditions was not previously possible. Here, we perform a simultaneous analysis of the topography and surface charge density of DNA nanostructures using atomic force microscopy and scanning ion conductance microscopy. The effect of in situ ion exchange using various alkali metal ions is tested with respect to the adsorption of DNA origami onto mica, and a quantitative study of surface charge density reveals ion exchange phenomena in mica as a key parameter in DNA adsorption. This is important for structure‐function studies of DNA nanostructures. The research provides an efficient approach to study surface charge density of DNA origami nanostructures and other biological molecules at a single molecule level.