bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rhodium(III)‐Catalyzed Alkenylation–Annulation of closo‐Dodecaborate Anions through Double B−H Activation at Room Temperature
Authors: Zhang Yuanbin , Sun Yuji , Lin Furong , Liu Jiyong , Duttwyler Simon 
Published: November 2016

Abstract1,2,3‐Trisubstituted closo‐dodecaborates with B−O, B−N, and B−C bonds as well as a fused borane oxazole ring have been synthesized by rhodium‐catalyzed direct cage B−H alkenylation and annulation of ureido boranes in the first reported example of regioselective B−H bond functionalization of the [B12H12]2− cage by transition‐metal catalysis. This reaction proceeded at room temperature under ambient conditions and exhibited excellent selectivity for efficient monoalkenylation with good functional‐group tolerance. The urea moiety enabled B−H activation by acting as a directing group, was incorporated in the oxazole ring in situ, and also avoided multiple alkenylation. A possible mechanism is proposed on the basis of the isolation of a rhodium agostic intermediate and control experiments.
Practical Photocatalytic Trifluoromethylation and Hydrotrifluoromethylation of Styrenes in Batch and Flow
Authors: Straathof Natan J. W. , Cramer Sten E. , Hessel Volker , Noël Timothy 
Published: November 2016

AbstractStyrenes represent a challenging class of substrates for current radical trifluoromethylation and hydrotrifluoromethylation methods due to a myriad of potential side reactions. Herein, we describe the development of mild, selective and broadly applicable photocatalytic trifluoromethylation and hydrotrifluoromethylation protocols for these challenging substrates. The methods use fac‐Ir(ppy)3, visible light and inexpensive CF3I and can be applied to a diverse set of vinylarene substrates. The use of continuous‐flow photochemical reaction conditions allowed to reduce the reaction time and increase the reaction selectivity.
Symmetry‐Breaking Charge Transfer and Hydrogen Bonding: Toward Asymmetrical Photochemistry
Authors: Dereka Bogdan , Rosspeintner Arnulf , Krzeszewski Maciej , Gryko Daniel T. , Vauthey Eric 
Published: November 2016

AbstractSymmetry‐breaking charge transfer upon photoexcitation of a linear A‐π‐D‐π‐A molecule (D and A being electron donating and accepting groups) could be visualized using ultrafast time‐resolved infrared spectroscopy by monitoring the CN stretching modes on the A units. Whereas in apolar solvents, the S1 state remains symmetric and quadrupolar, symmetry breaking occurs within ca. 100 fs in polar solvents as shown by the presence of two CN bands, instead of one in apolar solvents, with a splitting that increases with polarity. In protic solvents, symmetry breaking is significantly amplified by H‐bonding interactions, which are the strongest at the CN group with the highest basicity. In strongly protic solvents, the two CN bands transform in about 20 ps into new bands with a larger splitting, and the lifetime of the S1 state is substantially reduced. This is attributed to the formation of an excited asymmetric tight H‐bond complex.
Macroscopic Hexagonal Tubes of 3 d–4 f Metallocycles
Authors: Wu Jianfeng , Zhao Lang , Zhang Li , Li Xiao‐Lei , Guo Mei , Powell Annie K. , Tang Jinkui 
Published: November 2016

AbstractThe self‐assembly of three giant hexagonal 3d–4f metallocycles with inner diameters of 16.4, 16.5, and 16.4 Å, is described. Hexagonal metallocycles were stacked along the crystallographic c axis, producing unique hexagonal macroscopic tubular single crystals. The assembly mechanism of the tubular crystals was investigated. Remarkably, all three hexagonal metallocycles show typical single‐molecule magnet behavior, benefiting from the ferromagnetic couplings between the 3d and 4f ions.
Short Enantioselective Total Synthesis of Tatanan A and 3‐epi‐Tatanan A Using Assembly‐Line Synthesis
Authors: Noble Adam , Roesner Stefan , Aggarwal Varinder K. 
Published: November 2016

AbstractShort and highly stereoselective total syntheses of the sesquilignan natural product tatanan A and its C3 epimer are described. An assembly‐line synthesis approach, using iterative lithiation–borylation reactions, was applied to install the three contiguous stereocenters with high enantio‐ and diastereoselectivity. One of the stereocenters was installed using a configurationally labile lithiated primary benzyl benzoate, resulting in high levels of substrate‐controlled (undesired) diastereoselectivity. However, reversal of selectivity was achieved by using a novel diastereoselective Matteson homologation. Stereospecific alkynylation of a hindered secondary benzylic boronic ester enabled completion of the synthesis in a total of eight steps.
Explaining the Size Dependence in Platinum‐Nanoparticle‐Catalyzed Hydrogenation Reactions
Authors: Bai Licheng , Wang Xin , Chen Qiang , Ye Yifan , Zheng Haoquan , Guo Jinghua , Yin Yadong , Gao Chuanbo 
Published: November 2016

AbstractHydrogenation reactions are industrially important reactions that typically require unfavorably high H2 pressure and temperature for many functional groups. Herein we reveal surprisingly strong size‐dependent activity of Pt nanoparticles (PtNPs) in catalyzing this reaction. Based on unambiguous spectral analyses, the size effect has been rationalized by the size‐dependent d‐band electron structure of the PtNPs. This understanding enables production of a catalyst with size of 1.2 nm, which shows a sixfold increase in turnover frequency and 28‐fold increase in mass activity in the regioselective hydrogenation of quinoline, compared with PtNPs of 5.3 nm, allowing the reaction to proceed under ambient conditions with unprecedentedly high reaction rates. The size effect and the synthesis strategy developed herein may provide a general methodology in the design of metal‐nanoparticle‐based catalysts for a broad range of organic syntheses.
Aluminum Hydride Catalyzed Hydroboration of Alkynes
Authors: Bismuto Alessandro , Thomas Stephen P. , Cowley Michael J. 
Published: November 2016

AbstractAn aluminum‐catalyzed hydroboration of alkynes using either the commercially available aluminum hydride DIBAL‐H or bench‐stable Et3Al⋅DABCO as the catalyst and H‐Bpin as both the boron reagent and stoichiometric hydride source has been developed. Mechanistic studies revealed a unique mode of reactivity in which the reaction is proposed to proceed through hydroalumination and σ‐bond metathesis between the resultant alkenyl aluminum species and HBpin, which acts to drive turnover of the catalytic cycle.
Experimental and Computational Studies of the Copper Borate Complexes [(NHC)Cu(HBEt3)] and [(NHC)Cu(HB(C6F5)3)]
Authors: Collins Lee R. , Rajabi Nasir A. , Macgregor Stuart A. , Mahon Mary F. , Whittlesey Michael K. 
Published: November 2016

AbstractThe synthesis of the Cu‐borate complexes [(6Mes)Cu(HBR3)] featuring the unusual [HBEt3]− (5) and [HB(C6F5)3]− (6) ligands is described. Experimental and computational studies show both compounds feature a direct Cu–H interaction, but that while 5 is two‐coordinate, 6 displays an additional, stabilizing Cu–Cipso(C6F5) interaction.
Hollow Nanotubes of N‐Doped Carbon on CoS
Authors: Chen Yuming , Li Xiaoyan , Park Kyusung , Zhou Limin , Huang Haitao , Mai Yiu‐Wing , Goodenough John B. 
Published: November 2016

AbstractLow‐cost, single‐step synthesis of hollow nanotubes of N‐doped carbon deposited on CoS is enabled by the simultaneous use of three functionalities of polyacrylonitrite (PAN) nanofibers: 1) a substrate for loading active materials, 2) a sacrificial template for creating hollow tubular structures, and 3) a precursor for in situ nitrogen doping. The N‐doped carbon in hollow tubes of CoS provides a high‐capacity anode of long cycle life for a rechargeable Li‐ion or Na‐ion battery cell that undergoes the conversion reaction 2 A++2 e−+CoS →Co+A2S with A=Li or Na.
A Hyperpolarizable 1H Magnetic Resonance Probe for Signal Detection 15 Minutes after Spin Polarization Storage
Authors: Roy Soumya S. , Norcott Philip , Rayner Peter J. , Green Gary G. R. , Duckett Simon B. 
Published: November 2016

AbstractNuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) are two extremely important techniques with applications ranging from molecular structure determination to human imaging. However, in many cases the applicability of NMR and MRI are limited by inherently poor sensitivity and insufficient nuclear spin lifetime. Here we demonstrate a cost‐efficient and fast technique that tackles both issues simultaneously. We use the signal amplification by reversible exchange (SABRE) technique to hyperpolarize the target 1H nuclei and store this polarization in long‐lived singlet (LLS) form after suitable radiofrequency (rf) pulses. Compared to the normal scenario, we achieve three orders of signal enhancement and one order of lifetime extension, leading to 1H NMR signal detection 15 minutes after the creation of the detected states. The creation of such hyperpolarized long‐lived polarization reflects an important step forward in the pipeline to see such agents used as clinical probes of disease.
Rhodium‐Catalyzed Diastereoselective Cyclization of Allenyl‐Sulfonylcarbamates: A Stereodivergent Approach to 1,3‐Aminoalcohol Derivatives
Authors: Spreider Pierre A. , Haydl Alexander M. , Heinrich Marc , Breit Bernhard 
Published: November 2016

AbstractA diastereoselective and stereodivergent rhodium‐catalyzed intramolecular coupling of sulfonylcarbamates with terminal allenes is described and it provides selective access to 1,3‐aminoalcohol derivatives, scaffolds found in bioactive compounds. The reaction is compatible with a large range of different functional groups, thus furnishing products with high diastereoselectivities and yields. Moreover, multigram scale reactions, as well as the application of suitable product transformations were demonstrated.
Organocatalytic Enantioselective Vinylogous Pinacol Rearrangement Enabled by Chiral Ion Pairing
Authors: Wu Hua , Wang Qian , Zhu Jieping 
Published: November 2016

AbstractAn enantioselective pinacol rearrangement of functionalized (E)‐2‐butene‐1,4‐diols was developed. In the presence of a catalytic amount of a chiral BINOL‐derived N‐triflyl phosphoramide, these 1,4‐diols rearranged to β,γ‐unsaturated ketones in excellent yields and enantioselectivities. The formation of a chiral ion pair between the intermediary allylic cation and the chiral phosphoramide anion was postulated to be responsible for the highly efficient chirality transfer. These chiral building blocks were further converted into enantioenriched polysubstituted tetrahydrofuran and tetrahydronaphthalene derivatives.
Wall slip velocity measurement of molten polypropylene in capillary flow based on length‐corrected Mooney technique
Authors: Ren Zhong , Huang Xingyuan , Liu Hesheng 
Published: November 2016

ABSTRACTIn this study, to measure wall slip velocity of molten polypropylene (PP) by using different length‐to‐diameter (L/D) ratios of capillary dies with fixed diameter, a length‐corrected Mooney technique was proposed. Moreover, the effects of pressure, temperature, and L/D ratio were considered to better represent wall slip mechanism. To verify the feasibility of the length‐corrected Mooney technique, a series of capillary rheological experiments for molten PP were carried out. Meanwhile, the power‐law quantitative equations of slip velocity were established by shear stress. Moreover, the effects of L/D ratio and temperature on rheological properties of PP were investigated. In addition, numerical simulations for slip velocity and rheological properties of PP were performed. Numerical results validated that the length‐corrected Mooney technique, and the power‐law quantitative equations of slip velocity were available. Results showed that wall slip velocity of molten PP decreased with the capillary die's L/D ratio, but increased with the temperature and shear rate. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44589.
Development of release methods for captive‐bred freshwater pearl mussels (Margaritifera margaritifera
Authors: Kyle Rebecca , Reid Neil , O'Connor Nessa , Roberts Dai 
Published: November 2016

Abstract

Biodiversity loss is a global problem with freshwater bivalves considered among the most endangered biota. The freshwater pearl mussel, Margaritifera margaritifera, is declining throughout its range owing to habitat degradation and overexploitation. In most of its range, populations are regarded as reproductively non‐functional, which has led to the development of captive breeding programmes.
A novel method of releasing M. margaritifera was tested, with captive‐bred juveniles being released into the rivers caged in ‘mussel silos’ (protective concrete domes with ventilation creating upwelling to ensure water through‐flow).
In total, 240 juvenile mussels were released and survival and growth rates were monitored for 18 months after release for three size classes: A (13.01–20.00 mm); B (10.01–13.00 mm); and C (4.01–10.00 mm).
Two experimental treatments were tested: one in which sediment was added to each silo (allowing mussels to orientate and burrow) and one without sediment. Survival by the end of the experiment at month 18 was significantly higher for the largest size class at 97% (although growth was lowest in this cohort), and lowest for the smallest size class, at 61% (although growth was highest in this cohort). Survival and growth were unaffected by the experimental treatment suggesting that adding sediment offered no advantage. Growth was positively correlated both with water temperature and with particle size of suspended solids (both of which were collinear, peaking in summer).
There are many ex situ breeding programmes for freshwater pearl mussels throughout Europe and the results of this study suggest that the use of mussel silos may be a useful tool to protect juvenile mussels, allowing them to be released at a relatively early stage of development and minimizing the risk of domestication.
Copyright © 2016 John Wiley & Sons, Ltd.
Betwixt and Between: Intracranial Perspective on Zygomatic Arch Plasticity and Function in Mammals
Authors: Franks Erin M. , Holton Nathan E. , Scott Jeremiah E. , McAbee Kevin R. , Rink Jason T. , Pax Kazune C. , Pasquinelly Adam C. , Scollan Joseph P. , Eastman Meghan M. , Ravosa Matthew J. 
Published: November 2016

ABSTRACTThe zygomatic arch is morphologically complex, providing a key interface between the viscerocranium and neurocranium. It also serves as an attachment site for masticatory muscles, thereby linking it to the feeding apparatus. Though morphological variation related to differential loading is well known for many craniomandibular elements, the adaptive osteogenic response of the zygomatic arch remains to be investigated. Here, experimental data are presented that address the naturalistic influence of masticatory loading on the postweaning development of the zygoma and other cranial elements. Given the similarity of bone‐strain levels among the zygoma and maxillomandibular elements, a rabbit and pig model were used to test the hypothesis that variation in cortical bone formation and biomineralization along the zygomatic arch and masticatory structures are linked to increased stresses. It was also hypothesized that neurocranial structures would be minimally affected by varying loads. Rabbits and pigs were raised for 48 weeks and 8 weeks, respectively. In both experimental models, CT analyses indicated that elevated masticatory loading did not induce differences in cortical bone thickness of the zygomatic arch, though biomineralization was positively affected. Hypotheses were supported regarding bone formation for maxillomandibular and neurocranial elements. Varying osteogenic responses in the arch suggests that skeletal adaptation, and corresponding variation in performance, may reside differentially at one level of bony architecture. Thus, it is possible that phenotypic diversity in the mammalian zygoma is due more singularly to natural selection (vs. plasticity). These findings underscore the complexity of the zygomatic arch and, more generally, determinants of skull form. Anat Rec, 299:1646–1660, 2016. © 2016 Wiley Periodicals, Inc.
A GIS‐based method to identify cost‐effective routes for rural deviated fixed route transit
Authors: Yang Hongtai , Cherry Christopher R. , Zaretzki Russell , Ryerson Megan S. , Liu Xiaobo , Fu Zhijian 
Published: November 2016

SummaryDeviated fixed route transit (DFRT) service connecting rural and urban areas is a growing transportation mode in the USA. Little research has been done to develop frameworks for route design. A methodology to explore the most cost‐effective DFRT route is presented in this paper. The inputs include potential DFRT demand distribution and a road network. A heuristic is used to build possible routes by starting at urban cores and extending in all network directions in certain length increments. All the DFRT routes falling in the length range desired by the users are selected. The cost effectiveness of those routes, defined by operating cost per passenger trip, is compared. The most cost‐effective route is selected and presented in a GIS map. A case study illustrates the methodology in several Tennessee metropolitan regions. The most cost‐effective route length is case specific; some routes (e.g. those out of our Nashville case) are most cost effective when short, while others (e.g. those out of Memphis) are most cost effective when long. Government agencies could use the method to identify routes with the lowest operating cost per passenger given a route length or an operating cost budget. Copyright © 2016 John Wiley & Sons, Ltd.
Metabolite profiling of whole murine embryos reveals metabolic perturbations associated with maternal valproate‐induced neural tube closure defects
Authors: Akimova Darya , Wlodarczyk Bogdan J. , Lin Ying , Ross M. Elizabeth , Finnell Richard H. , Chen Qiuying , Gross Steven S. 
Published: November 2016

BackgroundValproic acid (VPA) is prescribed therapeutically for multiple conditions, including epilepsy. When taken during pregnancy, VPA is teratogenic, increasing the risk of several birth and developmental defects including neural tube defects (NTDs). The mechanism by which VPA causes NTDs remains controversial and how VPA interacts with folic acid (FA), a vitamin commonly recommended for the prevention of NTDs, remains uncertain. We sought to address both questions by applying untargeted metabolite profiling analysis to neural tube closure (NTC) stage mouse embryos.MethodsPregnant SWV dams on either a 2 ppm or 10 ppm FA supplemented diet were injected with a single dose of VPA on gestational day E8.5. On day E9.5, the mouse embryos were collected and evaluated for NTC status. Liquid chromatography coupled to mass spectrometry metabolomics analysis was performed to compare metabolite profiles of NTD‐affected VPA‐exposed whole mouse embryos with profiles from embryos that underwent normal NTC from control dams.ResultsNTDs were observed in all embryos from VPA‐treated dams and penetrance was not diminished by dietary FA supplementation. The most profound metabolic perturbations were found in the 10ppm FA VPA‐exposed mouse embryos, compared with the other three treatment groups. Affected metabolites included amino acids, nucleobases and related phosphorylated nucleotides, lipids, and carnitines.ConclusionMaternal VPA treatment markedly perturbed purine and pyrimidine metabolism in E9.5 embryos. In combination with a high FA diet, VPA treatment resulted in gross metabolic changes, likely caused by a multiplicity of mechanisms, including an apparent disruption of mitochondrial beta‐oxidation. Birth Defects Research 109:106–119, 2017. © 2016 Wiley Periodicals, Inc.
Core–shell structured CdTe/CdS@SiO2@CdTe@SiO2 composite fluorescent spheres: Synthesis and application for Cd2+ detection
Authors: Liu Fang , Li Shujia , Hu Ruoxin , Shao Na 
Published: November 2016

AbstractCore–shell structured quantum dot (QD)–silica fluorescent nanoparticles have attracted a great deal of attention due to the excellent optical properties of QDs and the stability of silica. In this study, core–shell structured CdTe/CdS@SiO2@CdTe@SiO2 fluorescent nanospheres were synthesized based on the Stöber method using multistep silica encapsulation. The second silica layer on the CdTe QDs maintained the optical stability of nanospheres and decreased adverse influences on the probe during subsequent processing. Red‐emissive CdTe/CdS QDs (630 nm) were used as a built‐in reference signal and green‐emissive CdTe QDs (550 nm) were used as a responding probe. The fluorescence of CdTe QDs was greatly quenched by added S2−, owing to a S2−‐induced change in the CdTe QDs surface state in the shell. Upon addition of Cd2+ to the S2−‐quenched CdTe/CdS@SiO2@CdTe@SiO2 system, the responding signal at 550 nm was dramatically restored, whereas the emission at 630 nm remained almost unchanged; this response could be used as a ratiometric ‘off–on’ fluorescent probe for the detection of Cd2+. The sensing mechanism was suggested to be: the newly formed CdS‐like cluster with a higher band gap facilitated exciton/hole recombination and effectively enhanced the fluorescence of the CdTe QDs. The proposed probe shows a highly sensitive and selective response to Cd2+ and has potential application in the detection of Cd2+ in environmental or biological samples.
Online measurement of viscosity for biological systems in stirred tank bioreactors
Authors: Schelden Maximilian , Lima William , Doerr Eric Will , Wunderlich Martin , Rehmann Lars , Büchs Jochen , Regestein Lars 
Published: November 2016

ABSTRACTOne of the most critical parameters in chemical and biochemical processes is the viscosity of the medium. Its impact on mixing, as well as on mass and energy transfer is substantial. An increase of viscosity with reaction time can be caused by the formation of biopolymers like xanthan or by filamentous growth of microorganisms. In either case the properties of fermentation broth are changing and frequently non‐Newtonian behavior are observed, resulting in major challenges for the measurement and control of mixing and mass transfer. This study demonstrates a method for the online determination of the viscosity inside a stirred tank reactor. The presented method is based on online measurement of heat transfer capacity from the bulk medium to the jacket of the reactor. To prove the feasibility of the method, fermentations with the xanthan producing bacterium Xanthomonas campestris pv. campestris B100 as model system were performed. Excellent correlation between offline measured apparent viscosity and online determined heat transfer capacity were found. The developed tool should be applicable to any other process with formation of biopolymers and filamentous growth. Biotechnol. Bioeng. 2017;114: 990–997. © 2016 Wiley Periodicals, Inc.