bluuebunny/crossref_metadata_2025_split huggingface dataset:
Total content of kaurene diterpenes in Annona vepretorum stems via 1H qNMR: A method for speeding the identification of bioactive extracts
Authors: de Souza Araújo Camila , de Oliveira Ana Paula , da Conceição Santos Alan Diego , Guimarães Amanda Leite , dos Santos Silva Naiane Darklei , Queiroz Mário Adriano Ávila , da Cruz Araújo Edigênia Cavalcante , da Silva Almeida Jackson Roberto Guedes 
Published: August 2018

AbstractIntroductionKaurene diterpenes (KDs) constitute a chemical class often found in the genus Annona with interesting biological activities. To date, chromatographic tools have been mostly used to determine KDs. Quantitative nuclear magnetic resonance (qNMR) has distinguished itself in quantitative estimation of natural products and is an interesting choice to assess total KD contents.ObjectiveTo establish a 1H qNMR method for determining the total KD contents in extracts and fractions obtained from Annona vepretorum stems.MethodologyStems were extracted with hexane and methanol, resulting in the hexane extract (HEX‐E) and the methanol extract (MeOH‐E). The former was partitioned with the acid–base method to obtain the total alkaloid fraction (TA‐F) and the neutral dichloromethane fraction (NDM‐F). 1H qNMR measurements were performed on 400 MHz with samples solubilized in deuterated dimethyl sulfoxide. Quantification was carried out using the signals at 4.71 and 4.78 ppm related to hydrogens of the exocyclic double bond of the basic skeleton of KDs and gallic acid as the standard reference. The selectivity, intra‐ and inter‐day precision, reproducibility, limit of detection, limit of quantification, and robustness of the methodology were evaluated.ResultsUsing the newly developed method, the total KD contents (in μg/mg) were 653.80 ± 12.15 (HEX‐E), 458.90 ± 25.94 (NDM‐F), 375.60 ± 27.52 (TA‐F), and 315.10 ± 19.20 (MeOH‐E). For determining the most promising bioactive sample, the KD contents and the sample discriminations obtained by principal component analysis were correlated to the antibacterial activity. Such approach pointed out HEX‐E as a potential source of KDs.ConclusionThe developed method offers a fast and simple way of determining total KD contents.
A Sequential Debonding Fracture Model for Hydrogen‐Bonded Hydrogels
Authors: Xin Hai , Oveissi Farshad , Naficy Sina , Spinks Geoffrey M. 
Published: August 2018

ABSTRACTHydrogen bonds are known to play an important role in prescribing the mechanical performance of certain hydrogels such as polyether‐based polyurethanes. The quantitative contribution of hydrogen bonds to the toughness of polymer networks, however, has not been elucidated to date. Here, a new physical model is developed to predict the threshold fracture energies of hydrogels physically crosslinked via hydrogen bonds. The model is based on consecutive and sequential dissociation of hydrogen‐bonded crosslinks during crack propagation. It is proposed that the scission of hydrogen bonds during crack propagation allows polymer strands in the deformation zone to partially relax and release stored elastic energy. The summation of these partial chain relaxations leads to amplified threshold fracture energies which are 10–45 times larger than those predicted by the classical Lake–Thomas theory. Experiments were performed on a hydrophilic polyurethane hydrogel where urea additions were used to control the density of hydrogen bonds. The measured fracture energies were in good agreement with the calculated values. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1287–1293
Nanocomposite smart hydrogels with improved responsiveness and mechanical properties: A mini review
Authors: Liu Zhuang , Faraj Yousef , Ju Xiao‐Jie , Wang Wei , Xie Rui , Chu Liang‐Yin 
Published: August 2018

ABSTRACTResponsive hydrogels have the ability to change their volume, transparency, or other properties in response to external chemical and/or physical stimuli. The responsiveness properties including responsive rate and degree, as well as mechanical properties such as Young's modulus, toughness, breaking strength, and breaking strain are crucial parameters of the smart hydrogels that determine the scope of hydrogel applications such as soft actuators, artificial muscles, and tissue engineering scaffolds. In this paper, the development of the nanocomposite smart hydrogels, which can achieve both improved responsiveness and mechanical properties, is reviewed. First, the fabrication approaches for building the nanocomposite networks by doping organic or inorganic nanomaterials via crosslinking or blending strategies are introduced. Then, the mechanisms used to improve both responsiveness and mechanical properties of nanocomposite responsive hydrogels are discussed. Finally, the perspectives as well as current challenges of such nanocomposite responsive hydrogels are addressed. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1306–1313
Quantitative chest computerized tomography and FEV1equally identify pulmonary exacerbation risk in children with cystic fibrosis
Authors: Sanders Don B. , Li Zhanhai , Parker‐McGill Katelyn , Farrell Philip , Brody Alan S. 
Published: August 2018

AbstractBackgroundChest computerized tomography (CT) scores are associated with the frequency of future pulmonary exacerbations in people with cystic fibrosis (CF). However, cut‐off values to identify children with mild lung disease with different risks for frequent future pulmonary exacerbations have not been identified.MethodsChest CT scans were assessed using the Brody score for participants of the Pulmozyme Early Intervention Trial (PEIT) and Wisconsin Randomized Clinical Trial of CF Newborn Screening (WI RCT). We determined the area under the receiver operating characteristic (ROC) curve for Brody scores and forced expiratory volume in 1 s (FEV1) to compare with the frequency of pulmonary exacerbations up to 10 years later.ResultsThere were 60 participants in the PEIT with mean (SD) age 10.6 (1.7) years at the time of the CT and 81 participants in the WI RCT with mean age 11.5 (3.0) years. The Brody score cut‐off that best identified children at‐risk for ≥0.3 annual pulmonary exacerbations was 3.6 in the PEIT and 2.1 in the WI RCT. There were no statistical differences between ROC curves for the Brody CT score and FEV1% predicted in either study (P ≥ 0.4).ConclusionsCT score cut‐off values that identify children with CF with mild lung disease at different risks for frequent pulmonary exacerbations over an extended follow up period are similar in separate cohorts. Brody scores and FEV1% predicted have similar abilities to identify these children, suggesting that FEV1% predicted alone may be adequate for predicting future frequency of pulmonary exacerbations.
Dative bonds versus electron solvation in tri‐coordinated beryllium complexes: Be(CX)3 [X = O, S, Se, Te, Po] and Be(PH3)3 versus Be(NH3)3
Authors: Ariyarathna Isuru R. , Miliordos Evangelos 
Published: August 2018

AbstactThe formation mechanism and bonding scheme for the titled molecules is proposed based on high‐level theoretical calculations. All species are formed via three dative bonds from the ligands to Be. For Be(CX)3 [X = O, S, Se, Te, Po] species and Be(PH3)3 the two electrons of beryllium are promoted from 2s to 2p facilitating these bonds. At the same time, electronic density is donated toward the ligands via the π‐frame. In contrast, ammonia partly solvates the valence 2s electrons of Be, which are delocalized in the periphery of the molecule. Based on the proton affinity of all of these complexes and their derivatives, we found that they are strong Lewis bases. For example, Be(PMe3)3 is stronger than ammonia and its ethyl substituted analogue and could serve as the basis of more efficient frustrated Lewis pairs.
Coupled cluster theory with the polarizable continuum model of solvation
Authors: Caricato Marco 
Published: August 2018

AbstractThe environment may significantly affect molecular properties. Thus, it is desirable to account explicitly for these effects on the wave function and its derivatives, especially when the latter are evaluated with accurate methods, such as those belonging to coupled cluster (CC) theory. In this tutorial review, we discuss how to combine CC methods with the polarizable continuum model of solvation (PCM). We describe useful approximations that include the solvent response to the correlation and excited state equations while maintaining the computational cost comparable to in vacuo calculations. Although applied to PCM, the theoretical framework presented in this review is general and can be used with any polarizable embedding model. Representative applications of the CC‐PCM method to ground and excited state properties of solvated molecules are presented, and comparisons with experiment, and between the full and approximate schemes are discussed.
High‐sensitivity sulfur isotopic measurements for Antarctic ice core analyses
Authors: Takahashi Kazuya , Nakai Yoichi , Motizuki Yuko , Ino Toshiyuki , Ito Shigeru , Ohkubo Satoru B. , Minami Takeshi , Takaku Yuichi , Yamaguchi Yoshitaka , Tanaka Miho , Motoyama Hideaki 
Published: August 2018

RationaleSulfur is widely distributed in nature, and sulfur isotopic measurements have been applied to elucidate the origin and transport of sulfuric compounds in the lithosphere, biosphere, and atmosphere. Analyses of samples containing small amounts of sulfur, such as the Antarctic ice core samples analyzed herein, require a high‐sensitivity analytical method.MethodsWe developed a high‐sensitivity sulfur isotopic ratio (δ34S value) analytical system equipped with an elemental analyzer, a cryo‐flow device, and an isotope ratio mass spectrometer, and established a measurement and calibration procedure.ResultsUsing this system, we precisely measured the δ34S values of samples containing 5–40 nmol sulfate. Test runs were performed on samples from the Antarctic shallow ice core DF01, and the data obtained were consistent with those obtained by previous studies that reported δ34S values for Antarctic snow and ice samples of more than 200 g (containing more than 150 nmol sulfate). Among the analyzed samples, one showed a peak sulfate concentration in its depth profile that is considered to have resulted from a large volcanic eruption. The δ34S value obtained at that depth in the sample was distinct from values at other depths and consistent with reported values for volcanic sulfates.ConclusionsThe analytical system developed herein is a powerful tool for trace sulfur isotopic analyses. The results obtained from the DF01 ice core samples are the first step towards elucidating high‐time‐resolution (less than 1 year) paleo‐environmental changes by sulfur isotopic analyses.
MRI‐guided frameless biopsy robotic system with the inclusion of unfocused ultrasound transducer for brain cancer ablation
Authors: Giannakou Marinos , Yiallouras Christos , Menikou Georgios , Ioannides Cleanthis , Damianou Christakis 
Published: August 2018

AbstractBackgroundA magnetic resonance image (MRI) guided robotic system dedicated for brain biopsy was developed. The robotic system carries a biopsy needle and a small rectangular unfocused, single element, planar ultrasonic transducer which can be potentially utilized to ablate small and localized brain cancer.Materials and MethodsThe robotic device includes six computer‐controlled axes. An agar‐based phantom was developed which included an olive that mimics brain target. A rectangular ultrasonic transducer operated at 4 MHz was used.ResultsThe functionality of the robotic system was assessed by means of ultrasound imaging, MRI imaging, and MR thermometry, demonstrating effective targeting. The heating capabilities of the ultrasonic transducer were also evaluated.ConclusionsA functional MRI‐guided robotic system was produced which can perform frameless brain biopsy. In the future, if a tumour is proven malignant, the needle can be pulled‐out and a small ultrasonic transducer can be inserted to ablate the tumour.
Rotavirus: Genetics, pathogenesis and vaccine advances
Authors: Sadiq Asma , Bostan Nazish , Yinda Kwe Claude , Naseem Saadia , Sattar Sadia 
Published: August 2018

SummarySince its discovery 40 years ago, rotavirus (RV) is considered to be a major cause of infant and childhood morbidity and mortality particularly in developing countries. Nearly every child in the world under 5 years of age is at the risk of RV infection. It is estimated that 90% of RV‐associated mortalities occur in developing countries of Africa and Asia. Two live oral vaccines, RotaTeq (RV5, Merck) and Rotarix (RV1, GlaxoSmithKline) have been successfully deployed to scale down the disease burden in Europe and America, but they are less effective in Africa and Asia. In April 2009, the World Health Organization recommended the inclusion of RV vaccination in national immunization programs of all countries with great emphasis in developing countries. To date, 86 countries have included RV vaccines into their national immunization programs including 41 Global Alliance for Vaccines and Immunization eligible countries. The predominant RV genotypes circulating all over the world are G1P[8], G2P[4], G3P[8], G4P[8], and G9P[8], while G12[P6] and G12[P8] are emerging genotypes. On account of the segmented genome, RV shows an enormous genetic diversity that leads to the evolution of new genotypes that can influence the efficacy of current vaccines. The current need is for a global RV surveillance program to monitor the prevalence and antigenic variability of new genotypes to formulate future vaccine development planning. In this review, we will summarize the previous and recent insights into RV structure, classification, and epidemiology and current status of RV vaccination around the globe and will also cover the status of RV research and vaccine policy in Pakistan.
Adaptive trajectory tracking control for VTOL‐UAVs with unknown inertia, gyro‐bias, and actuator LOE
Authors: Benrezki Rabie Riadh , Tayebi Abdelhamid , Tadjine Mohamed 
Published: August 2018

SummaryThis paper proposes an adaptive controller for the trajectory tracking problem of vertical take‐off and landing unmanned aerial vehicles with unknown inertia and gyro‐bias, in the presence of external disturbances and actuator loss of effectiveness. To achieve our control objective, first, an a priori bounded virtual control law, providing an a priori bounded thrust and desired attitude, is designed for the translational dynamics. Thereafter, the torque input is designed for the rotational dynamics to track the desired orientation derived in the first stage. The stability of the overall hierarchical closed‐loop system and the global convergence of the tracking errors to zero are rigorously established. Finally, numerical simulations are performed to validate the effectiveness of the proposed control scheme.
Sliding mode adaptive control for a class of nonlinear time‐varying systems
Authors: Meza‐Aguilar Marco , Loukianov Alexander G. , Rivera Jorge 
Published: August 2018

SummaryIn this work, the problem of designing a control scheme capable of controlling dynamical systems with unknown time‐varying parameters and disturbances is proposed. In contrast with other works, based on two techniques, ie, adaptive backstepping and sliding modes, an improved method that guarantees the output asymptotic tracking of a smooth reference signal, the stability of the closed‐loop system, and the identification errors' boundedness is developed. By means of sliding mode observers, the adaptation errors' required information is extracted and injected to adaptive laws. The behavior of the proposed control scheme is analyzed by the Lyapunov method. The performance of the proposed system is verified with an academic example.
Using United States Geological Survey stream gages to predict flow and temperature conditions to maintain freshwater mussel habitat
Authors: Cole Jeffrey C. , Townsend Philip A. , Eshleman Keith N. , St. John White Barbara , Galbraith Heather S. , Lellis William A. 
Published: August 2018

AbstractHabitat conditions necessary to support freshwater mussels can be difficult to characterize and predict, particularly for rare or endangered species such as the federally endangered dwarf wedgemussel, Alasmidonta heterodon. In this study, we evaluate flow and temperature conditions in three areas of the mainstem Delaware River known to consistently support A. heterodon, and we develop predictive models using the U.S. Geological Survey (USGS) stream gages and thermal stations in order to identify conditions under which habitat alteration could threaten the species. Flow and temperature prediction models based on nearby existing USGS gage and thermal stations were predictive for all three sites. Both discharge prediction and water depth profile models indicate one location (Site 3) was the most vulnerable to low‐flow conditions as it requires the highest discharge rate (26.3 cms) at the USGS Callicoon gage to maintain both the full wetted perimeter (Pfull) and minimal wetted perimeter (Pmin) and prevent occlusion of areas that contain A. heterodon. Flow management targets aimed at protecting Site 3 should also protect Sites 1 and 2. Although analyses indicated significant benthic habitat available in all three sites even under low discharge rates, specific mussel locations could be vulnerable to dewatering and thermal stress if only Pmin values were maintained. Results indicate the magnitude of site temperature deviations from thermal stations varied by site and river temperature. In general, our results suggest that existing temperature and stream gage infrastructure may be used predictively to evaluate the effects of different flow targets on mainstem Delaware River A. heterodon habitat.
Photoelectron emission characteristics of iron surfaces scratched in different environments: Dependence on photon energy irradiation methods
Authors: Momose Yoshihiro , Sakurai Takao , Nakayama Keiji 
Published: August 2018

The characteristics of photoelectron emission (PE) and X‐ray photoelectron spectroscopy of iron surfaces scratched in different environments were investigated. The scratching environments were air, water, and organic liquids. The PE quantum yields (emitted electrons/photon), YFD and Ys, were obtained in 2 ways of irradiation of the surface with photon energies: during the light wavelength scan in the range of 300 to 200 nm at 25°C, 200°C, and 339°C and during temperature increase and subsequent decrease scans in the range of 25°C to 339°C under 210‐nm‐light irradiation, respectively. The equation YFD = αA (Ep − ϕ)2/2kB2, where αA is called the electron photoemission probability, A is identical to the Richardson constant, Ep is the incident photon energy, and ϕ is the photothreshold, was applied to the wavelength scan data to obtain αA and ϕ. Additionally, the emission intensity at 210‐nm wavelength (I210) and the total number of emitted electrons (NT) were obtained during the wavelength scan. Arrhenius activation energies obtained for αA, I210, and NT were ΔEαA = 0.113 to 0.074 eV, ΔE210 = 0.085 to 0.054 eV, and ΔENT = 0.088 to 0.053 eV, respectively. The ΔE210 and ΔENT increased with ΔEαA. The dependence of ΔE210, ΔENT, and ΔEαA on the environments was completely different from that of ΔEaUp1 values for the Ys during the temperature increase scan (Up1 scan), which were previously reported to be in the 0.212‐ to 0.035‐eV range. The PE characteristics were explained from the dependence on the O1s component ratio of ZO = O2−/(OH− + O2−) and the acid‐base interaction between the surface Fe −OH groups and the molecules of the liquid environments.
Nanomechanics of Extracellular Vesicles Reveals Vesiculation Pathways
Authors: Sorkin Raya , Huisjes Rick , Bošković Filip , Vorselen Daan , Pignatelli Silvia , Ofir‐Birin Yifat , Freitas Leal Joames K. , Schiller Jürgen , Mullick Debakshi , Roos Wouter H. , Bosman Giel , Regev‐Rudzki Neta , Schiffelers Raymond M. , Wuite Gijs J. L. 
Published: August 2018

AbstractExtracellular vesicles (EVs) are emerging as important mediators of cell–cell communication as well as potential disease biomarkers and drug delivery vehicles. However, the mechanical properties of these vesicles are largely unknown, and processes leading to microvesicle‐shedding from the plasma membrane are not well understood. Here an in depth atomic force microscopy force spectroscopy study of the mechanical properties of natural EVs is presented. It is found that several natural vesicles of different origin have a different composition of lipids and proteins, but similar mechanical properties. However, vesicles generated by red blood cells (RBC) at different temperatures/incubation times are different mechanically. Quantifying the lipid content of EVs reveals that their stiffness decreases with the increase in their protein/lipid ratio. Further, by maintaining RBC at “extreme” nonphysiological conditions, the cells are pushed to utilize different vesicle generation pathways. It is found that RBCs can generate protein‐rich soft vesicles, possibly driven by protein aggregation, and low membrane–protein content stiff vesicles, likely driven by cytoskeleton‐induced buckling. Since similar cortical cytoskeleton to that of the RBC exists on the membranes of most mammalian cells, our findings help advancing the understanding of the fundamental process of vesicle generation.
Nanoconfined Nickel@Carbon Core–Shell Cocatalyst Promoting Highly Efficient Visible‐Light Photocatalytic H2 Production
Authors: Zhang Ke , Ran Jingrun , Zhu Bicheng , Ju Huanxin , Yu Jiaguo , Song Li , Qiao Shi‐Zhang 
Published: August 2018

AbstractThe realization of large‐scale solar hydrogen (H2) production relies on the development of high‐performance and low‐cost photocatalysts driven by sunlight. Recently, cocatalysts have demonstrated immense potential in enhancing the activity and stability of photocatalysts. Hence, the rational design of highly active and inexpensive cocatalysts is of great significance. Here, a facile method is reported to synthesize Ni@C core–shell nanoparticles as a highly active cocatalyst. After merging Ni@C cocatalyst with CdS nanorod (NR), a tremendously enhanced visible‐light photocatalytic H2‐production performance of 76.1 mmol g−1 h−1 is achieved, accompanied with an outstanding quantum efficiency of 31.2% at 420 nm. The state‐of‐art characterizations (e.g., synchrotron‐based X‐ray absorption near edge structure) and theoretical calculations strongly support the presence of pronounced nanoconfinement effect in Ni@C core–shell nanoparticles, which leads to controlled Ni core size, intimate interfacial contact and rapid charge transfer, optimized electronic structure, and protection against chemical corrosion. Hence, the combination of nanoconfined Ni@C with CdS nanorod leads to significantly improved photocatalytic activity and stability. This work not only for the first time demonstrates the great potential of using highly active and inexpensive Ni@C core–shell structure to replace expensive Pt in photocatalysis but also opens new avenues for synthesizing cocatalyst/photocatalyst hybridized systems with excellent performance by introducing nanoconfinement effect.