bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Description of Vibrational Modes in Hexaphyrins: Understanding the Aromaticity Reversal in the Lowest Triplet State
Authors: Sung Young Mo , Oh Juwon , Naoda Koji , Lee Taegon , Kim Woojae , Lim Manho , Osuka Atsuhiro , Kim Dongho 
Published: August 2016

AbstractAromaticity reversal in the lowest triplet state, or Baird's rule, has been postulated for the past few decades. Despite numerous theoretical works on aromaticity reversal, experimental study is still at a rudimentary stage. Herein, we investigate the aromaticity reversal in the lowest excited triplet state using a comparable set of [26]‐ and [28]hexaphyrins by femtosecond time‐resolved infrared (IR) spectroscopy. Compared to the relatively simple IR spectra of [26]bis(rhodium) hexaphyrin (R26H), those of [28]bis(rhodium) hexaphyrin (R28H) show complex IR spectra the region for the stretching modes of conjugated rings. Whereas time‐resolved IR spectra of R26H in the excited triplet state are dominated by excited state IR absorption peaks, while those of R28H largely show ground state IR bleaching peaks, reflecting the aromaticity reversal in the lowest triplet state. These contrasting IR spectral features serve as new experimental aromaticity indices for Baird's rule.
Total Synthesis of 11‐Saxitoxinethanoic Acid and Evaluation of its Inhibitory Activity on Voltage‐Gated Sodium Channels
Authors: Wang Chao , Oki Mana , Nishikawa Toru , Harada Daisuke , Yotsu‐Yamashita Mari , Nagasawa Kazuo 
Published: August 2016

Abstract11‐Saxitoxinethanoic acid (SEA) is a member of the saxitoxin (STX) family of paralytic shellfish poisons, and contains an unusual C−C bond at the C11 position. Reported herein is a total synthesis of SEA. The key to our synthesis lies in a Mukaiyama aldol condensation reaction of silyl enol ether with glyoxylate in the presence of an anhydrous fluoride reagent, [Bu4N][Ph3SnF2], which directly constructs the crucial C−C bond at the C11 position in SEA. The NaVCh‐inhibitory activities of SEA and its derivatives were evaluated by means of cell‐based assay. SEA showed an IC50 value of (47±12) nm, which is approximately twice as potent as decarbamoyl‐STX (dcSTX).
Photoswitchable NIR‐Emitting Gold Nanoparticles
Authors: Bonacchi Sara , Cantelli Andrea , Battistelli Giulia , Guidetti Gloria , Calvaresi Matteo , Manzi Jeannette , Gabrielli Luca , Ramadori Federico , Gambarin Alessandro , Mancin Fabrizio , Montalti Marco 
Published: August 2016

AbstractPhoto‐switching of the NIR emission of gold nanoparticles (GNP) upon photo‐isomerization of azobenzene ligands, bound to the surface, is demonstrated. Photophysical results confirm the occurrence of an excitation energy transfer process from the ligands to the GNP that produces sensitized NIR emission. Because of this process, the excitation efficiency of the gold core, upon excitation of the ligands, is much higher for the trans form than for the cis one, and t→c photo‐isomerization causes a relevant decrease of the GNP NIR emission. As a consequence, photo‐isomerization can be monitored by ratiometric detection of the NIR emission upon dual excitation. The photo‐isomerization process was followed in real‐time through the simultaneous detection of absorbance and luminescence changes using a dedicated setup. Surprisingly, the photo‐isomerization rate of the ligands, bound to the GNP surface, was the same as measured for the chromophores in solution. This outcome demonstrated that excitation energy transfer to gold assists photo‐isomerization, rather than competing with it. These results pave the road to the development of new, NIR‐emitting, stimuli‐responsive nanomaterials for theranostics.
Amyloid Aggregates Arise from Amino Acid Condensations under Prebiotic Conditions
Authors: Greenwald Jason , Friedmann Michael P. , Riek Roland 
Published: August 2016

AbstractCurrent theories on the origin of life reveal significant gaps in our understanding of the mechanisms that allowed simple chemical precursors to coalesce into the complex polymers that are needed to sustain life. The volcanic gas carbonyl sulfide (COS) is known to catalyze the condensation of amino acids under aqueous conditions, but the reported di‐, tri‐, and tetra‐peptides are too short to support a regular tertiary structure. Here, we demonstrate that alanine and valine, two of the proteinogenic amino acids believed to have been among the most abundant on a prebiotic earth, can polymerize into peptides and subsequently assemble into ordered amyloid fibers comprising a cross‐β‐sheet quaternary structure following COS‐activated continuous polymerization of as little as 1 mm amino acid. Furthermore, this spontaneous assembly is not limited to pure amino acids, since mixtures of glycine, alanine, aspartate, and valine yield similar structures.
Cold Sintering: A Paradigm Shift for Processing and Integration of Ceramics
Authors: Guo Jing , Guo Hanzheng , Baker Amanda L. , Lanagan Michael T. , Kupp Elizabeth R. , Messing Gary L. , Randall Clive A. 
Published: August 2016

AbstractThis paper describes a sintering technique for ceramics and ceramic‐based composites, using water as a transient solvent to effect densification (i.e. sintering) at temperatures between room temperature and 200 °C. To emphasize the incredible reduction in sintering temperature relative to conventional thermal sintering this new approach is named the “Cold Sintering Process” (CSP). Basically CSP uses a transient aqueous environment to effect densification by a mediated dissolution–precipitation process. CSP of NaCl, alkali molybdates and V2O5 with small concentrations of water are described in detail, but the process is extended and demonstrated for a diverse range of chemistries (oxides, carbonates, bromides, fluorides, chlorides and phosphates), multiple crystal structures, and multimaterial applications. Furthermore, the properties of selected CSP samples are demonstrated to be essentially equivalent as samples made by conventional thermal sintering.
Bicontinuous Nanoporous Frameworks: Caged Longevity for Enzymes
Authors: Bae Jae‐Sung , Jeon Eunkyung , Moon Su‐Young , Oh Wangsuk , Han Sun‐Young , Lee Jeong Hun , Yang Sung Yun , Kim Dong‐Myung , Park Ji‐Woong 
Published: August 2016

AbstractThe preparation of bicontinuous nanoporous covalent frameworks, which are promising for caging active enzymes, is demonstrated. The frameworks have three‐ dimensionally continuous, hydrophilic pores with widths varying between 5 and 30 nm. Enzymes were infiltrated into the bicontinuous pore by applying a pressured enzyme solution. The new materials and methods allowed the amount of caged proteins to be controlled precisely. The resulting enzyme‐loaded framework films could be recycled many times with nearly no loss of catalytic activity. Entropic trapping of proteins by a bicontinuous pore with the right size distribution is an unprecedented strategy toward facile in vitro utilization of biocatalysts.
Palladium‐Catalyzed Defluorinative Coupling of 1‐Aryl‐2,2‐Difluoroalkenes and Boronic Acids: Stereoselective Synthesis of Monofluorostilbenes
Authors: Thornbury Richard T. , Toste F. Dean 
Published: August 2016

AbstractThe palladium‐catalyzed defluorinative coupling of 1‐aryl‐2,2‐difluoroalkenes with boronic acids is described. Broad functional‐group tolerance arises from a redox‐neutral process by a palladium(II) active species which is proposed to undergo a β‐fluoride elimination to afford the products. The monofluorostilbene products were formed with excellent diastereoselectivity (≥50:1) in all cases, and it is critical, as traditional chromatographic techniques often fail to separate monofluoroalkene isomers. As a demonstration of this method's unique combination of reactivity and functional‐group tolerance, a Gleevec® analogue, using a monofluorostilbene as an amide isostere, was synthesized.
Enhanced Electrochemical Kinetics on Conductive Polar Mediators for Lithium–Sulfur Batteries
Authors: Peng Hong‐Jie , Zhang Ge , Chen Xiang , Zhang Ze‐Wen , Xu Wen‐Tao , Huang Jia‐Qi , Zhang Qiang 
Published: August 2016

AbstractLithium–sulfur (Li–S) batteries have been recognized as promising substitutes for current energy‐storage technologies owing to their exceptional advantage in energy density. The main challenge in developing highly efficient and long‐life Li–S batteries is simultaneously suppressing the shuttle effect and improving the redox kinetics. Polar host materials have desirable chemisorptive properties to localize the mobile polysulfide intermediates; however, the role of their electrical conductivity in the redox kinetics of subsequent electrochemical reactions is not fully understood. Conductive polar titanium carbides (TiC) are shown to increase the intrinsic activity towards liquid–liquid polysulfide interconversion and liquid–solid precipitation of lithium sulfides more than non‐polar carbon and semiconducting titanium dioxides. The enhanced electrochemical kinetics on a polar conductor guided the design of novel hybrid host materials of TiC nanoparticles grown within a porous graphene framework (TiC@G). With a high sulfur loading of 3.5 mg cm−2, the TiC@G/sulfur composite cathode exhibited a substantially enhanced electrochemical performance.
Tungsten(VI) Carbyne/Bis(carbene) Tautomerization Enabled by N‐Donor SBA15 Surface Ligands: A Solid‐State NMR and DFT Study
Authors: Bendjeriou‐Sedjerari Anissa , Sofack‐Kreutzer Julien , Minenkov Yury , Abou‐Hamad Edy , Hamzaoui Bilel , Werghi Baraa , Anjum Dalaver H. , Cavallo Luigi , Huang Kuo‐Wei , Basset Jean‐Marie 
Published: August 2016

AbstractDesigning supported well‐defined bis(carbene) complexes remains a key challenge in heterogeneous catalysis. The reaction of W(≡CtBu)(CH2tBu)3 with amine‐modified mesoporous SBA15 silica, which has vicinal silanol/silylamine pairs [(≡SiOH)(≡SiNH2)], leads to [(≡SiNH2−)(≡SiO−)W(≡CHtBu)(CH2tBu)2] and [(≡SiNH2−)(≡SiO−)W(=CHtBu)2(CH2tBu). Variable temperature, 1H–1H 2D double‐quantum, 1H–13C HETCOR, and HETCOR with spin diffusion solid‐state NMR spectroscopy demonstrate tautomerization between the alkyl alkylidyne and the bis(alkylidene) on the SBA15 surface. Such equilibrium is possible through the coordination of W to the surface [(≡Si−OH)(≡Si−NH2)] groups, which act as a [N,O] pincer ligand. DFT calculations provide a rationalization for the surface–complex tautomerization and support the experimental results. This direct observation of such a process shows the strong similarity between molecular mechanisms in homogeneous and heterogeneous catalysis. In propane metathesis (at 150 °C), the tungsten bis(carbene) tautomer is favorable, with a turnover number (TON) of 262. It is the highest TON among all the tungsten alkyl‐supported catalysts.
Direct Observation of Aggregation‐Induced Backbone Conformational Changes in Tau Peptides
Authors: Jiji A. C. , Shine A. , Vijayan Vinesh 
Published: August 2016

AbstractIn tau proteins, the hexapeptides in the R2 and R3 repeats are known to initiate tau fibril formation, which causes a class of neurodegenerative diseases called the taupathies. We show that in R3, in addition to the presence of the hexapeptides, the correct turn conformation upstream to it is also essential for producing prion‐like fibrils that are capable of propagation. A time‐dependent NMR aggregation assay of a slow fibril forming R3‐S316P peptide revealed a trans to cis equilibrium shift in the peptide‐bond conformation preceding P316 during the growth phase of the aggregation process. S316 was identified as the key residue in the turn that confers templating capacity on R3 fibrils to accelerate the aggregation of the R3‐S316P peptide. These results on the specific interactions and conformational changes responsible for tau aggregation could prove useful for developing an efficient therapeutic intervention in Alzheimer's disease.
Gold‐Induced Fibril Growth: The Mechanism of Surface‐Facilitated Amyloid Aggregation
Authors: Gladytz Anika , Abel Bernd , Risselada Herre Jelger 
Published: August 2016

AbstractThe question of how amyloid fibril formation is influenced by surfaces is crucial for a detailed understanding of the process in vivo. We applied a combination of kinetic experiments and molecular dynamics simulations to elucidate how (model) surfaces influence fibril formation of the amyloid‐forming sequences of prion protein SUP35 and human islet amyloid polypeptide. The kinetic data suggest that structural reorganization of the initial peptide corona around colloidal gold nanoparticles is the rate‐limiting step. The molecular dynamics simulations reveal that partial physisorption to the surface results in the formation of aligned monolayers, which stimulate the formation of parallel, critical oligomers. The general mechanism implies that the competition between the underlying peptide–peptide and peptide–surface interactions must strike a balance to accelerate fibril formation.
Two‐Dimensional Skyrmion Lattice Formation in a Nematic Liquid Crystal Consisting of Highly Bent Banana Molecules
Authors: Kang Sungmin , Lee Eun‐Woo , Li Tianqi , Liang Xiaobin , Tokita Masatoshi , Nakajima Ken , Watanabe Junji 
Published: August 2016

AbstractWe synthesized a novel banana‐shaped molecule based on a 1,7‐naphthalene central core that exhibits a distinct mesomorphism of the nematic‐to‐nematic phase transition. Both the X‐ray profile and direct imaging of atomic force microscopy (AFM) investigations clearly indicates the formation of an anomalous nematic phase possessing a two‐dimensional (2D) tetragonal lattice with a large edge (ca. 59 Å) directed perpendicular to the director in the low‐temperature nematic phase. One plausible model is proposed by an analogy of skyrmion lattice in which two types of cylinders formed from left‐ and right‐handed twist‐bend helices stack into a 2D tetragonal lattice, diminishing the inversion domain wall.
Dermal Fibroblasts from Different Layers of Pig Skin Exhibit Different Profibrotic and Morphological Characteristics
Authors: Zuo Yanhai , Yu Xiaoping , Lu Shuliang 
Published: August 2016

ABSTRACTIn vitro studies of human dermal fibroblast (DF) heterogeneity have long been reported, yet in vivo studies and related research on animals are rare. The objectives of the study were to determine whether the DFs of pigs exhibit heterogeneity and to identify an animal model for the in vivo study of DF heterogeneity. The skin of three female red Duroc pigs (FRDPs) was separated into six layers, and the second and fifth layers (i.e., the superficial and deep dermis) were used in the establishment of wound models and cell cultures. To create the wound models, 54 tongue‐shaped flaps were created on one side of the dorsum, and the underlying dermis was then fully replaced with the superficial or deep dermis (the superficial and deep groups, respectively). Skin samples were harvested at postoperative weeks 1, 2, and 3 for measurements of the normal and wounded skin thicknesses. Cells cultured from the superficial and deep dermis (i.e., superficial and deep DFs) were subjected to quantitative estimation of collagen and electron microscopy. The wounded skin thickness in the deep group was significantly greater than that in the superficial group. In contrast with the long deep DFs, the superficial DFs were short and exhibited microvilli‐like cell surface projections. Compared with the superficial DFs, the deep DFs exhibited a greater density of rough endoplasmic reticulum and produced significantly more collagen. Similar to humans, FRDPs exhibit DF heterogeneity and should thus be a good animal model for in vivo studies of DF heterogeneity. Anat Rec, 299:1585–1599, 2016. © 2016 Wiley Periodicals, Inc.
Tailoring Size and Coverage Density of Silver Nanoparticles on Monodispersed Polymer Spheres as Highly Sensitive SERS Substrates
Authors: Hu Yougen , Zhao Tao , Zhu Pengli , Zhu Yu , Liang Xianwen , Sun Rong , Wong Ching‐Ping 
Published: August 2016

AbstractSilver nanoparticles (AgNPs) were deposited onto the monodispersed carboxylic polystyrene (CPS) spheres by an improved in situ reduction method. The size and coverage density of the AgNPs on the surface of CPS spheres could be easily tailored by tuning the concentrations of carboxylic functional groups and silver precursor. The morphologies and structures of the resulting CPS/Ag hybrid particles were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), UV‐Vis‐NIR spectrometer and X‐ray photoelectron spectroscopy (XPS), etc. The surface enhanced Raman scattering (SERS) performances of the resulting uniform CPS/Ag hybrid particles were investigated using 4‐aminobenzenethiol (4‐ABT) as the probe molecule. The optimized CPS/Ag hybrid particles show high enhancement factor (EF) of 2.71×107, low limit of detection (LOD) of 10−10 m and good reproducibility with relative standard deviation (RSD) of 9.64 %. The good SERS improvement properties demonstrate these hybrid particles could be employed as simple and effective substrates in the SERS spectroscopy.
Stability of Local On‐Ramp Metering Control Laws
Authors: Alvarez‐Icaza Luis , Rosas‐Jaimes Oscar , Lárraga María Elena 
Published: August 2016

AbstractA framework for stability analysis of local on‐ramp metering control strategies based on the cell transmission model is presented. Within this framework, it is possible to formulate Lyapunov and input‐state stability results for on‐ramp metering control strategies in an open section of highway with on‐ramps. Using this analysis, recommendations for the design of on‐ramp metering control laws set points are derived. Two examples on the use of such analysis are presented. One deals with the stability analysis of a local on‐ramp metering control law and the other with the design of a disturbance observer that, used in combination with the local on‐ramp metering control law, provides a more robust response to traffic regulation. Simulation results are included that confirm the possibility of using this framework to test the impact of local on‐ramp metering control strategies.
Features of vortex split MSSWs that are problematic to forecast
Authors: Taguchi Masakazu 
Published: August 2016

AbstractA companion paper demonstrated that it is more difficult to forecast major stratospheric sudden warmings (MSSWs) of the vortex split type on medium range time scales of about 2 weeks than other MSSWs. As its extension, this study further investigates more specific features of planetary waves for the greater difficulty through a composite analysis using the Japanese 55‐year reanalysis data and the Japan Meteorological Agency 1‐month hindcast data. Results show that the hindcast data of about two week lead times to the MSSWs largely underestimate the vortex stretching and split at 10 hPa, and the forcing and propagation of planetary wave of zonal wavenumber 2 to the stratosphere. The underestimation in the wave forcing largely reflects a deficiency in simulating a nonlinear, or quadratic, term in wave anomalies (meridional wind and temperature) from the climatology.
Bauwerksprüfung unterstützt durch neuartige Besichtigungstechniken – Erste Erfahrungen
Authors: Holst Ralph , Sperber Martin , Gößmann Rainer 
Published: August 2016

AbstractDie Straßenverkehrsinfrastruktur ist durch steigende Belastungen und zunehmende Durchschnittsalter mittlerweile vielfach am Rande der Leistungsfähigkeit angelangt. In Zukunft werden Baumaßnahmen in erheblichem Umfang durchzuführen sein. Damit diese Erhaltungsmaßnahmen technisch und wirtschaftlich optimal durchgeführt werden können, ist es notwendig, frühzeitig und umfassend über den aktuellen Zustand, vor allem der Brücken, informiert zu sein. Hierfür ist es notwendig, den Zustand dieser zu erfassen, neue innovative Techniken zur Unterstützung der Bauwerksprüfung nach DIN 1076 sollen hinsichtlich ihrer Eignung überprüft werden.Unbemannte Fluggeräte bzw. UAS (Unmanned Aerial System) bieten vielfältige Möglichkeiten zur Bilderfassung und können als unterstützendes technisches Hilfsmittel bei der Bauwerksprüfung zum Einsatz kommen. Im Rahmen eines Forschungsprojekts wurden drei Brücken mithilfe von UAS beflogen, wodurch Schäden identifiziert werden konnten. Insbesondere die Möglichkeit zur Befliegung schwer zugänglicher Stellen, Zeitersparnis während einer Prüfung und die automatisierte Schadenserkennung machen diese Technologie für die Brückenprüfung interessant. Durch die gezielte Anwendung der UAS‐Technologie kann eine Reduzierung der Nutzungseinschränkung des Bauwerks verbunden mit einer Qualitätssteigerung der Ergebnisse erreicht werden.
Parsimonious mixtures of multivariate contaminated normal distributions
Authors: Punzo Antonio , McNicholas Paul D. 
Published: August 2016

A mixture of multivariate contaminated normal distributions is developed for model‐based clustering. In addition to the parameters of the classical normal mixture, our contaminated mixture has, for each cluster, a parameter controlling the proportion of mild outliers and one specifying the degree of contamination. Crucially, these parameters do not have to be specifieda priori, adding a flexibility to our approach. Parsimony is introduced via eigen‐decomposition of the component covariance matrices, and sufficient conditions for the identifiability of all the members of the resulting family are provided. An expectation‐conditional maximization algorithm is outlined for parameter estimation and various implementation issues are discussed. Using a large‐scale simulation study, the behavior of the proposed approach is investigated and comparison with well‐established finite mixtures is provided. The performance of this novel family of models is also illustrated on artificial and real data.
Triboluminescence and crystal structure of the complex [Eu(NО3)3(HMPA)3]: role of cleavage planes
Authors: Bukvetskii B. V. , Mirochnik A. G. , Zhikhareva P. A. 
Published: August 2016

AbstractThe atomic structure of crystals of the [Eu(NО3)3(HMPA)3] [hexamethylphosphotriamide (HMPA)] complex characterized by an intensive luminescence and triboluminescence was determined using X‐ray structural analysis. Noncentrosymmetric crystals have a monoclinic syngony: a = 16.0686 (3), b = 11.0853 (2), c = 20.9655 Å (4), β = 93.232° (1), space group P21, Z = 4, ρcalc = 1.560 g/cm3. The crystal structure is represented by individual С18Н54EuN12O12P3 complexes linked through van der Waals interactions with clearly expressed cleavage planes. The Eu(III) atom coordination polyhedron reflected the state of a distorted square antiprism. Structural aspects of the suggested model, including formation of triboluminescence properties, were considered and the role of the cleavage planes was discussed.
Resonant and non‐resonant energy transfer from Ce3+ → X (X = Tb3+, Eu3+ or Dy3+) in NaMgSO4F material
Authors: Choubey S. R. , Gedam S. C. , Dhoble S. J. 
Published: August 2016

AbstractAn inorganic NaMgSO4F fluoride material was prepared by the wet chemical method and studied for its photoluminescence (PL) and resonant–non‐resonant energy transfer (RET and NORET) capabilities between Ce3+ → Tb3+, Ce3+ → Eu3+ and Ce3+ → Dy3+ rare earth ions. The Tb3+ emission for Ce3+ → Tb3+ transfers under ultraviolet (UV) wavelengths peaked at 491, 547, and 586 nm, for excitation at 308 nm due to 5D4 → 7FJ (J = 4, 5, 6) transitions. Eu emission spectra were observed at 440 nm (Eu2+), 593 nm and 616 nm (Eu3+) recorded for different concentrations of materials, whereas Dy3+ emission from Ce3+ → Dy3+ transfer under UV wavelengths peaked at 485 nm and 577 nm due to 4F9/2 → 6H15/2 and 6H13/2 transitions. The purpose of the present study is to understand the RET and NORET effects of Tb3+, Eu3+ and Dy3+ co‐doping in a NaMgSO4F:Ce3+ luminescent material, which could be used as a green‐emitting material for lamp phosphors.