bluuebunny/crossref_metadata_2025_split huggingface dataset:
2‐Methoxypyridine as a Thymidine Mimic in Watson–Crick Base Pairs of DNA and PNA: Synthesis, Thermal Stability, and NMR Structural Studies
Authors: Novosjolova Irina , Kennedy Scott D. , Rozners Eriks 
Published: August 2017

AbstractThe development of nucleic acid base‐pair analogues that use new modes of molecular recognition is important both for fundamental research and practical applications. The goal of this study was to evaluate 2‐methoxypyridine as a cationic thymidine mimic in the A–T base pair. The hypothesis was that including protonation in the Watson–Crick base pairing scheme would enhance the thermal stability of the DNA double helix without compromising the sequence selectivity. DNA and peptide nucleic acid (PNA) sequences containing the new 2‐methoxypyridine nucleobase (P) were synthesized and studied by using UV thermal melting and NMR spectroscopy. Introduction of P nucleobase caused a loss of thermal stability of ≈10 °C in DNA–DNA duplexes and ≈20 °C in PNA–DNA duplexes over a range of mildly acidic to neutral pH. Despite the decrease in thermal stability, the NMR structural studies showed that P–A formed the expected protonated base pair at pH 4.3. Our study demonstrates the feasibility of cationic unnatural base pairs; however, future optimization of such analogues will be required.
Recent Advances on Computational Investigations of N‐Heterocyclic Carbene Catalyzed Cycloaddition/Annulation Reactions: Mechanism and Origin of Selectivities
Authors: Wang Yang , Wei Donghui , Zhang Wenjing 
Published: August 2017

AbstractThe developments of theoretical studies on NHC‐catalyzed [n+2] (n=2, 3, 4) and other cycloaddition/annulation reactions have been summarized in this review. The detailed mechanisms, role of NHC, and origin of chemo‐ and stereoselectivity of these kinds of reactions were illustrated to provide valuable insights for rational design of new NHC‐catalyzed cycloaddition/annulation reactions with high selectivities. Moreover, computational and theoretical methods commonly used were also mentioned to open the door for deep exploration of the general principle for NHC‐catalyzed reactions within theoretical chemistry.
Microscopic Insights on the Multiferroic Perovskite‐Like [CH3NH3][Co(COOH)3] Compound
Authors: Mazzuca Lidia , Cañadillas‐Delgado Laura , Fabelo Oscar , Rodríguez‐Velamazán J. Alberto , Luzón Javier , Vallcorba Oriol , Simonet Virginie , Colin Claire V. , Rodríguez‐Carvajal Juan 
Published: August 2017

AbstractThe characterization of the crystal structure, phase transitions, magnetic structure and dielectric properties has been carried out on [CH3NH3][Co(COOH)3] (1) perovskite‐like metal–organic compound through variable‐temperature single‐crystal and powder neutron and X‐ray diffraction and relative permittivity measurements. The paraelectric to antiferroelectric‐like phase transition observed at around 90 K is triggered by a structural phase transition; the structural studies show a change from Pnma space group at RT (1A) to P21/n space group at low temperature (1B). This phase transition involves the occurrence of small distortions in the framework and counterions. Neutron diffraction studies have shown a magnetic order showing spontaneous magnetization below 15 K, due to the occurrence of a non‐collinear antiferromagnetic structure with a weak ferromagnetic component, mainly due to the single‐ion anisotropy of the CoII ions.
General Synthesis of Transition‐Metal Oxide Hollow Nanospheres/Nitrogen‐Doped Graphene Hybrids by Metal–Ammine Complex Chemistry for High‐Performance Lithium‐Ion Batteries
Authors: Chen Jiayuan , Wu Xiaofeng , Gong Yan , Wang Pengfei , Li Wenhui , Mo Shengpeng , Peng Shengpan , Tan Qiangqiang , Chen Yunfa 
Published: August 2017

AbstractWe present a general and facile synthesis strategy, on the basis of metal–ammine complex chemistry, for synthesizing hollow transition‐metal oxides (Co3O4, NiO, CuO‐Cu2O, and ZnO)/nitrogen‐doped graphene hybrids, potentially applied in high‐performance lithium‐ion batteries. The oxygen‐containing functional groups of graphene oxide play a prerequisite role in the formation of hollow transition‐metal oxides on graphene nanosheets, and a significant hollowing process occurs only when forming metal (Co2+, Ni2+, Cu2+, or Zn2+)–ammine complex ions. Moreover, the hollowing process is well correlated with the complexing capacity between metal ions and NH3 molecules. The significant hollowing process occurs for strong metal–ammine complex ions including Co2+, Ni2+, Cu2+, and Zn2+ ions, and no hollow structures formed for weak and/or noncomplex Mn2+ and Fe3+ ions. Simultaneously, this novel strategy can also achieve the direct doping of nitrogen atoms into the graphene framework. The electrochemical performance of two typical hollow Co3O4 or NiO/nitrogen‐doped graphene hybrids was evaluated by their use as anodic materials. It was demonstrated that these unique nanostructured hybrids, in contrast with the bare counterparts, solid transition‐metal oxides/nitrogen‐doped graphene hybrids, perform with significantly improved specific capacity, superior rate capability, and excellent capacity retention.
Mechanism of the Catalytic Carboxylation of Alkylboronates with CO2 Using Ni−NHC Complexes: A DFT Study
Authors: Delarmelina Maicon , Marelli Enrico , de M. Carneiro José Walkimar , Nolan Steven P. , Bühl Michael 
Published: August 2017

AbstractA new mechanism is proposed for the Ni‐catalyzed carboxylation of organoboronates with CO2. DFT investigations at the PBE0‐D3 level have shown that direct CO2 addition to the catalysts [Ni(NHC)(Allyl)Cl] (1NHC, NHC=IMe, IPr, SIPr and IPr*) is kinetically disfavored and formation of the Aresta‐type intermediate is unlikely to occur. According to the mechanism proposed here, the carboxylation process starts with addition of the borate species to 1NHC, followed by transmetalation, CO2 cycloaddition and carboxylation. The rate‐determining step was identified as being the transmetalation process, with computed relative free energy barriers of 34.8, 36.8, and 33.5 kcal mol−1 for 1IPr, 1SIPr and 1IPr*, respectively.
Molecular Simulations of Thermodynamic Properties for the Systemα‐Cyclodextrin/Alcohol in Aqueous Solution
Authors: Markthaler Daniel , Gebhardt Julia , Jakobtorweihen Sven , Hansen Niels 
Published: August 2017

AbstractFree‐energy calculations based on molecular simulations provide access to a wide range of thermodynamic properties such as the solubility and partitioning of a molecule in and between various phases. It is demonstrated how molecular dynamics free‐energy simulations may be used to obtain the solubilities of primary alcohols andn‐alkanes in water and binding affinities of primary alcohols toα‐cyclodextrin. The equivalence of two distinct routes to calculate binding free energies is shown leading to the conclusion that host‐guest binding affinities may be used to probe the underlying molecular force field.
Effect of sulphur deposition on well performance in a sour gas reservoir
Authors: Hu Jinghong , Lei Zhengdong , Chen Zhangxin , Ma Zhanguo 
Published: August 2017

AbstractSulphur deposition has been the centre of attention in sour gas reservoir development. While Roberts's solubility model is widely used in sour reservoir damage to describe elemental sulphur precipitation and deposition in a near‐wellbore area, this model cannot accurately predict a change in sulphur solubility. A productivity prediction model, with consideration of sulphur deposition, is also not complete, particularly for modelling sulphur deposition and fractured horizontal wells. In this study, based on the unsteady percolation mechanics theory and superposition principle, we develop a new numerical model to quantify fractured horizontal well production by combining various sulphur solubility models. We examine the effects of sulphur deposition on permeability, porosity, and production performance. The results show that sulphur deposition damages reservoirs and thus decreases well production in later stages. These results also show that the permeability and porosity reduction using Roberts's sulphur solubility model is greater than that using Hu et al.'s sulphur solubility model. The damage degree is relatively smaller when using Hu et al.'s sulphur solubility model, and the effect of sulphur deposition on a production performance curve is negligible. Moreover, Hu et al.'s model is closer to actual production data. The results can guide reservoir engineers to optimize development plans in sour gas reservoirs.
Dual‐pH/Magnetic‐Field‐Controlled Drug Delivery Systems Based on Fe3O4@SiO2‐Incorporated Salecan Graft Copolymer Composite Hydrogels
Authors: Hu Xinyu , Wang Yongmei , Zhang Liangliang , Xu Man , Zhang Jianfa , Dong Wei 
Published: August 2017

AbstractSalecan is a water‐soluble extracellular β‐glucan and has excellent physicochemical and biological properties for hydrogel preparation. In this study, a new pH/magnetic field dual‐responsive hydrogel was prepared by the graft copolymerization of salecan with 4‐pentenoic acid (PA) and N‐hydroxyethylacrylamide (HEAA) in the presence of Fe3O4@SiO2 nanoparticles for doxorubicin hydrochloride (DOX) release. Integration of Fe3O4@SiO2 nanoparticles in salecan‐g‐poly(PA‐co‐HEAA) copolymers afforded magnetic sensitivity to the original material. DOX‐loaded hydrogels exhibited a clear capacity for pH/magnetic field dual‐responsive controlled drug release. Lowering the pH to acidic conditions or introducing an external magnetic field caused an enhancement in DOX release. This salecan‐g‐poly(PA‐co‐HEAA)/Fe3O4@SiO2 composite hydrogel is a promising drug carrier for magnetically targeted drug delivery with enhanced DOX cytotoxicity against A549 cells.
Flow features and device‐induced blood trauma in CF‐VADs under a pulsatile blood flow condition: A CFD comparative study
Authors: Chen Zengsheng , Jena Sofen K. , Giridharan Guruprasad A. , Koenig Steven C. , Slaughter Mark S. , Griffith Bartley P. , Wu Zhongjun J. 
Published: August 2017

AbstractIn this study, the flow features and device‐associated blood trauma in 4 clinical ventricular assist devices (VADs; 2 implantable axial VADs, 1 implantable centrifugal VAD, and 1 extracorporeal VAD) were computationally analyzed under clinically relevant pulsatile flow conditions. The 4 VADs were operated at fixed pump speed at a mean rate of 4.5 L/min. Mean pressure difference, wall shear stress, volume distribution of scalar shear stress (SSS), and shear‐induced hemolysis index (HI) were derived from the flow field of each VAD and were compared. The computationally predicted mean pressure difference across the 3 implantable VADs was ~70 mmHg, and the extracorporeal VAD was ~345 mmHg, which matched well with their reported pressure‐flow curves. The axial VADs had higher mean wall shear stress and SSS compared with the centrifugal VADs. However, the residence time of the centrifugal VADs was much longer compared with the axial VADs because of the large volume of the centrifugal VADs. The highest SSS was observed in one axial VAD, and the longest exposure time was observed in 1 centrifugal VAD. These 2 VADs generated the highest HI. The shear‐induced HI varied as a function of flow rate within each cardiac cycle. At fixed pump speed, the HI was greatest at low flow rate due to longer exposure time to shear stress compared with at high flow rate. Subsequently, we hypothesize that to reduce the risk of blood trauma during VAD support, shear stress magnitude and exposure time need to be minimized.
Formation, Structure, and Composition of Methylaluminoxane
Authors: Linnolahti Mikko , Collins Scott 
Published: August 2017

AbstractThe structurally ill‐characterized methylaluminoxane (MAO) is the activator of choice in olefin polymerization catalysis. We have carried out large scale and systematic quantum chemical calculations to simulate the thermodynamics of its formation by controlled hydrolysis of trimethylaluminum (TMA), extending the studies up to 25 Al atoms, and thus, to the real size domain of MAO. In agreement with previous postulates on its structure, MAO is shown to favor cage‐like structures, which commonly contain associated TMA, regardless of size or shape. The sites containing associated TMA are reactive, and explain the function of MAO as a catalyst activator. The compositions of MAOs show overall agreement with experiments, and exhibit structural transitions from chains to rings to sheets to eventually cages as a function of size. The most stable cage structure is obtained for a composition of (MeAlO)16(Me3Al)6, which is in precise agreement with mass spectrometric studies of corresponding anions, and adapts a tubular molecular structure with a molecular weight of 1360 g mol−1. Our mass spectrometric measurements enable detection of both major and minor anion species.
Tracking and understanding phase progression in Lisa's case
Authors: Ferreira Joana F. , Vasco António B. , Basseches Michael , Conceição Nuno , Vaz‐Velho Catarina , Goldman Rhonda 
Published: August 2017

This study adds a phase‐by‐phase perspective to the well‐known, and thoroughly analysed on a moment‐by‐moment basis, case of Lisa. The aim is to see whether this phase‐by‐phase analysis adds anything valuable to the understanding of the processes of change in this case and the therapeutic processes in general.In this good‐outcome case study, a team of raters integrated the temporal sequencing phase component of the Paradigmatic Complementarity Metamodel (PCM) with a moment‐by‐moment tracking method—the Developmental Analysis of Psychotherapy Process Method (DAPP)—to analyse what occurred along the process that could explain the phase transitions and consolidations observed and how the therapist facilitated them.We illustrate and explain the therapeutic progression with therapeutic interactions from the dyad. The results suggest that Lisa evolved in accordance with the sequence of phases proposed by the PCM until phase 4 (out of 7). However, only phase 2 gains show evidence of structural consolidation.The sequence of phases proposed by the PCM seems to represent a natural progression for patients throughout the therapeutic process, and the consideration of a phase‐by‐phase map in analysing and thinking of therapeutic cases may be a valuable tool regarding clinical decision making.
Prevalence of apical periodontitis and frequency of root‐filled teeth in an adult Sudanese population
Authors: Ahmed I. , Ali R.W. , Mudawi A.M. 
Published: August 2017

AbstractThe aim of this study was to estimate the prevalence of teeth with apical periodontitis (AP) and root‐filled (RF) teeth in an adult Sudanese population. Panoramic and periapical radiographs were obtained for 200 patients over 18 years of age seeking routine dental care and attending the dental clinics (University of Khartoum) and the dental hospital (University of Science and Technology) for the first time. The periapical status of all teeth (except third molars) was categorized on the basis of the presence or absence of radiographic signs of AP. In addition, the frequency of RF teeth was recorded. Data were analyzed using the chi‐square test and odds ratio (OR).The periapical status of 4,967 teeth was assessed. AP in one or several teeth was identified in 95 (47%) patients and in 3.3% of the teeth. The prevalence of AP was higher in molar teeth (7.3%) than in premolar (3.5%) and anterior teeth (0.9%, p ≤ .001). There were 80 (1.6%) RF teeth in 42 (21%) patients. The probability of root‐filling in molar and premolar teeth was almost twice that of anterior teeth (OR with 95% confidence intervals: 1.06 < 1.91 < 3.44, p ≤ .05).The prevalence of RF teeth increased with age (OR of 48 ± year = 3.06, p ≤ .001). Statistical analysis showed that the probability of radiological detection of AP in RF teeth was 17‐fold higher than in nonfilled ones (OR with 95% confidence intervals: 9.87 < 16.83 < 28.25, p ≤ .001).Therefore, the probability of AP, RF teeth with or without AP, and missing teeth was high in molar teeth than in anterior or premolar teeth. The frequency of RF teeth was low compared to that demonstrated in most other epidemiological studies. This highlights the need to focus on improving the quality of restorations and the procedure by which root canal is shaped and disinfected.
Wide‐band dual‐resonance capacitive cross‐coupled divide‐by‐5 injection‐locked frequency divider
Authors: Jang Sheng‐Lyang , Lu Kei‐Wu , Huang Yi‐Ru 
Published: August 2017

SummaryA wide locking range divide‐by‐5 injection‐locked frequency divider (ILFD) is proposed and was implemented in the TSMC 0.18‐μm 1P6M CMOS process. Conventional divide‐by‐5 ILFD has limited locking range. The proposed divide‐by‐5 ILFD is based on a capacitive cross‐coupled voltage‐controlled oscillator (VCO) with a dual‐resonance resonator, which is implemented in the divide‐by‐5 ILFD to obtain a wide overlapped locking range. At the drain‐source bias VDD of 0.9 V and at the incident power of 0 dBm, the measured locking range of the divide‐by‐5 ILFD is 3.2 GHz, from the incident frequency 9.4 to 12.6 GHz, the percentage is 29.09%. The core power consumption is 2.98 mW. The die area is 0.987 × 1.096 mm2.
The effect of trypan blue treatment on autofluorescence of fixed cells
Authors: Shilova Olga N. , Shilov Evgeny S. , Deyev Sergey M. 
Published: August 2017

AbstractControlling background fluorescence remains an important challenge in flow cytometry, as autofluorescence can interfere with the detection of chromophores. Furthermore, experimental procedures can also affect cellular fluorescence in certain regions of the emission spectrum. In this work, the effects of fixation, permeabilization, and heating on cellular autofluorescence are analyzed in various spectral regions, along with the influence of trypan blue as a quenching dye for these treatments. The impact of these procedures on the staining of SK‐BR‐3 cells with a dim green fluorophore, a miniSOG (mini Singlet Oxygen Generator) flavoprotein in the form of the recombinant protein DARPin‐miniSOG, is also evaluated. The data presented here indicate that fixation of certain types of cells leads to noticeable increase of the autofluorescence. Our results also suggest that trypan blue should be used as an autofluorescence quencher only with bright green emitters since it interferes with the fluorescent signal in a longer‐wavelength region of the spectrum and as a result causes reduction of the signal from dim green fluorescent agents. © 2017 International Society for Advancement of Cytometry
Resolution ofR‐(−)andS‐(+)‐enantiomers of clenbuterol in pharmaceutical preparations and black‐market products using liquid chromatography–tandem mass spectrometry
Authors: Velasco‐Bejarano Benjamín , Bautista Jahir , Noguez Ma. Olivia , Camacho Evangelina , Rodríguez Martha E. , Rodríguez Leonardo 
Published: August 2017

Several banned substances are illegally used by athletes in racemic mixtures for performance enhancement. These include clenbuterol, methyl hexaneamine, methamphetamines, and amphetamines. Clenbuterol is present in a large number of doping samples from Olympic and non‐Olympic athletes that have adverse analytical findings (AAFs). In some cases, the presence of these substances could be the result of consumption of meat contaminated with clenbuterol. In other cases, the origin is not clear. In this study, 27 products with racemic clenbuterol were evaluated using a new analytical methodology for the resolution ofR‐(−) andS‐(+)‐enantiomers of clenbuterol by liquid chromatography–tandem mass spectrometry (LC–MS/MS) using a chiral column in 15 min with good separation. The method developed can also be used for the analysis of other biological matrices such as urine, serum, and meat. The resolution between two peaks' (Rs) value obtained using chromatographic data was 1.03. Both clenbuterol enantiomers were present in all products analyzed and the ratio was nearly 1. The origin of the product was not important for determining the presence of one or both enantiomers. All products displayed a 50:50 ratio of clenbuterol enantiomers. To the best of our knowledge, clenbuterol ratio determination of a large number of pharmaceutical preparations and black‐market products has not been reported previously. The information shown could be used by national anti‐doping organizations and the athletes with AAFs attributed to clenbuterol. Copyright © 2017 John Wiley & Sons, Ltd.
Riverine fish diversity varies according to geographical isolation and land use modification
Authors: Nicol Elizabeth , Stevens Jamie R. , Jobling Susan 
Published: August 2017

AbstractUnderstanding the environmental factors driving species‐genetic diversity correlations (SGDCs) is critical for designing appropriate conservation and management strategies to protect biodiversity. Yet, few studies have explored the impact of changing land use patterns on SGDCs specifically in aquatic communities. This study examined patterns of genetic diversity in roach (Rutilus rutilus L.) together with fish species composition across 19 locations in a large river catchment, spanning a gradient in land use. Our findings show significant correlations between some, but not all, species and genetic diversity end points. For example, genetic and species differentiation showed a weak but significant linear relationship across the Thames catchment, but additional diversity measures such as allelic richness and fish population abundance did not. Further examination of patterns in species and genetic diversity indicated that land use intensification has a modest effect on fish diversity compared to the combined influence of geographical isolation and land use intensification. These results indicate that environmental changes in riparian habitats have the potential to amplify shifts in the composition of stream fish communities in poorly connected river stretches. Conservation and management strategies for fish populations should, therefore, focus on enhancing connectivity between river stretches and limit conversion of nearby land to arable or urban use to maintain current levels of biodiversity.
Marine protected area restricts demographic connectivity: Dissimilarity in a marine environment can function as a biological barrier
Authors: Sato Masaaki , Honda Kentaro , Uy Wilfredo H. , Baslot Darwin I. , Genovia Tom G. , Nakamura Yohei , Bernardo Lawrence Patrick C. , Kurokochi Hiroyuki , Pantallano Allyn Duvin S. , Lian Chunlan , Nadaoka Kazuo , Nakaoka Masahiro 
Published: August 2017

AbstractThe establishment of marine protected areas (MPAs) can often lead to environmental differences between MPAs and fishing zones. To determine the effects on marine dispersal of environmental dissimilarity between an MPA and fishing zone, we examined the abundance and recruitment patterns of two anemonefishes (Amphiprion frenatus and A. perideraion) that inhabit sea anemones in different management zones (i.e., an MPA and two fishing zones) by performing a field survey and a genetic parentage analysis. We found lower levels of abundance per anemone in the MPA compared to the fishing zones for both species (n = 1,525 anemones, p = .032). The parentage analysis also showed that lower numbers of fishes were recruited from the fishing zones and outside of the study area into each anemone in the MPA than into each anemone in the fishing zones (n = 1,525 anemones, p < .017). However, the number of self‐recruit production per female did not differ between the MPA and fishing zones (n = 384 females, p = .516). Because the ocean currents around the study site were unlikely to cause a lower settlement intensity of larvae in the MPA, the ocean circulation was not considered crucial to the observed abundance and recruitment patterns. Instead, stronger top‐down control and/or a lower density of host anemones in the MPA were potential factors for such patterns. Our results highlight the importance of dissimilarity in a marine environment as a factor that affects connectivity.