bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elucidating Mechanisms of Diffusion‐Based Calcium Carbonate Synthesis Leads to Controlled Mesocrystal Formation
Authors: Ihli Johannes , Bots Pieter , Kulak Alexander , Benning Liane G , Meldrum Fiona C 
Published: November 2012

AbstractAggregation‐based crystal growth often gives rise to crystals with complex morphologies which cannot be generated via classical growth processes. Despite this, understanding of the mechanism is rather poor, particularly when organic additives or amorphous precursor phases are present. In this work, advantage is taken of the observation that aggregation‐based growth of calcium carbonate, and indeed many other minerals, is most often observed using diffusion‐based synthetic methods. By fully characterizing the widely used ammonia diffusion method (ADM)–which is currently used as a “black box”–the solution and supersaturation conditions which accompany CaCO3 precipitation using this method are identified and insight is gained into the nucleation and growth processes which generate calcite mesocrystals. This reveals that the distinguishing feature of the ADM is that the initial nucleation burst consumes only a small quantity of the available ions, and the supersaturation then remains relatively constant, and well above the solubility of amorphous calcium carbonate (ACC), until the reaction is almost complete. New material is thus generated over the entire course of the precipitation, a feature which appears to be fundamental to the formation of complex, aggregation‐based morphologies. Finally, the importance of this understanding is demonstrated using the identified carbonate and supersaturation profiles to perfectly replicate CaCO3 mesocrystals through slow addition of reagents to a bulk solution. This approach overcomes many of the inherent problems of the ADM by offering excellent reproducibility, enabling the synthesis of such CaCO3 structures in large‐scale and continuous‐flow systems, and ultimately facilitating in situ studies of assembly‐based crystallization mechanisms.
Organocatalytic Enantioselective Aza‐Michael Addition of Purine Bases to α,β‐Unsaturated Ketones
Authors: Wu Hao , Tian Zhiqing , Zhang Lili , Huang Yaodong , Wang Yongmei 
Published: November 2012

AbstractThe first organocatalytic enantioselective aza‐Michael addition of purine bases to α,β‐unsaturated ketones has been developed, affording Michael adducts in moderate to high yields (up to 96% yield) and high to excellent enantioselectivities (up to >99% ee). A wide range of α,β‐unsaturated ketones including aliphatic and aromatic enones are tolerated in this process, generally demonstrating good reactivity, regioselectivity and enantioselectivity. The aromatic α,β‐unsaturated ketones showing quite low reactivity in the reported catalytic systems, were first successfully employed as Michael acceptors in this transformation, yielding high enantioselectivities (up to 94% ee). The utility of this method was also applied for the synthesis of enantioenriched non‐natural nucleoside analogues with potential biological activities.
Poly(styrene) Resin‐Supported Cobalt(III) Salen Cyclic Oligomers as Active Heterogeneous HKR Catalysts
Authors: Kahn Michael G. C. , Stenlid Joakim H. , Weck Marcus 
Published: November 2012

AbstractA cross‐linked poly(styrene) support functionalized with cobalt(III) salen cyclic oligomers that can be used as a catalyst for the hydrolytic kinetic resolution (HKR) of terminal epoxides is reported. This catalyst is the most active heterogeneous catalyst to date for the HKR of terminal epoxides and can be recycled more than six times with excellent enantioselectivities for the HKR of epichlorohydrin. A 3‐fold rate enhancement was observed when conducting the HKR reaction with 6 equivalents of water compared to 0.6 equivalents. We hypothesize that this rate enhancement is due to water sequestration of the diol product from the organic phase, thereby maintaining a high local concentration of epoxides and catalyst in the organic phase.
Calcium Carbonate Polyamorphism and Its Role in Biomineralization: How Many Amorphous Calcium Carbonates Are There?
Authors: Cartwright Julyan H. E. , Checa Antonio G. , Gale Julian D. , Gebauer Denis , Sainz‐Díaz C. Ignacio 
Published: November 2012

AbstractAlthough the polymorphism of calcium carbonate is well known, and its polymorphs—calcite, aragonite, and vaterite—have been highly studied in the context of biomineralization, polyamorphism is a much more recently discovered phenomenon, and the existence of more than one amorphous phase of calcium carbonate in biominerals has only very recently been understood. Here we summarize what is known about polyamorphism in calcium carbonate as well as what is understood about the role of amorphous calcium carbonate in biominerals. We show that consideration of the amorphous forms of calcium carbonate within the physical notion of polyamorphism leads to new insights when it comes to the mechanisms by which polymorphic structures can evolve in the first place. This not only has implications for our understanding of biomineralization, but also of the means by which crystallization may be controlled in medical, pharmaceutical, and industrial contexts.
Polymerization‐induced phase separation and resulting thermomechanical properties of thermosetting/reactive nonlinear polymer blends: A review
Authors: Liu Yuhong 
Published: November 2012

AbstractThermosets, which have a highly crosslinked structure, play a pivotal role in high‐performance composite materials because of their excellent mechanical properties, including their high modulus, high strength, and high glass‐transition temperature. In general, however, thermosets are brittle materials with a toughness and elongation at break that are unsatisfactory for many applications, especially at high temperatures. The key factor that can greatly influence the toughness of a thermoset material is its cured microstructure or nanostructure. Recently, it has been revealed that the introduction of a reactive modifier into a multicomponent thermosetting prepolymer is a versatile way to finely tune the polymerization‐induced phase separation (PIPS) and the microstructure and thermomechanical properties of the resulting thermosets. This review focuses first on the advancement of the methods used to study the PIPS of thermosetting prepolymers. I go on to discuss factors influencing the thermodynamic and the kinetic behavior of PIPS and the resulting morphology and thermomechanical properties of thermosetting blends obtained when nonlinear reactive modifiers are incorporated. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Eu3+‐activated Y2MoO6: a narrow band red‐emitting phosphor with strong near‐UV absorption
Authors: He Xianghong , Bian Danping , Wang Hao , Xu Jian 
Published: November 2012

ABSTRACTNear‐UV excited narrow line red‐emitting phosphors, Eu3+‐activated Y2MoO6 systems, were synthesized using a simple molten salt reaction. The structure and photoluminescence characteristics were investigated using X‐ray powder diffraction, UV–Vis absorption and fluorescent spectrophotometry. The excitation spectra show strong broad‐band absorptions in the near‐UV to blue light regions which match the radiation of near‐UV light‐emitting diode chips well. Under excitation of either near‐UV or blue light, intense red emission with a main peak of 611 nm is observed, ascribed to the 5D0–7F2 transition of Eu3+ ions; the optimal doping concentration is 20 mol%. The chromaticity coordinates (x = 0.65, y = 0.34) of the as‐obtained phosphor are very close to the National Television Standard Committee standard values (x = 0.67, y = 0.33). All these characteristics suggest that this material is a promising red‐emitting phosphor candidate for white‐LEDs based on near‐UV LED chips. Copyright © 2012 John Wiley & Sons, Ltd.
Flavin Conjugates for Delivery of Peptide Nucleic Acids
Authors: Marlin Fanny , Simon Philippe , Bonneau Stéphanie , Alberti Patrizia , Cordier Céline , Boix Charlotte , Perrouault Loïc , Fossey Aurélie , Saison‐Behmoaras Tula , Fontecave Marc , Giovannangeli Carine 
Published: November 2012

AbstractOligonucleotides and their analogues, such as peptide nucleic acids (PNAs), can be used in chemical strategies to artificially control gene expression. Inefficient cellular uptake and inappropriate cellular localization still remain obstacles in biological applications, however, especially for PNAs. Here we demonstrate that conjugation of PNAs to flavin resulted in efficient internalization into cells through an endocytic pathway. The flavin–PNAs exhibited antisense activity in the sub‐micromolar range, in the context of a treatment facilitating endosomal escape. Increased endosomal release of flavin conjugates into the cytoplasm and/or nucleus was shown by chloroquine treatment and also—when the flavin–PNA was conjugated to rhodamine, a mild photosensitizer—upon light irradiation. In conclusion, an isoalloxazine moiety can be used as a carrier and attached to a cargo biomolecule, here a PNA, for internalization and functional cytoplasmic/nuclear delivery. Our findings could be useful for further design of PNAs and other oligonucleotide analogues as potent antisense agents.
Type II Ligands as Chemical Auxiliaries To Favor Enzymatic Transformations by P450 2E1
Authors: Ménard Amélie , Fabra Camilo , Huang Yue , Auclair Karine 
Published: November 2012

AbstractThe remarkable ability of P450 enzymes to oxidize inactivated CH bonds and the high substrate promiscuity of many P450 isoforms have inspired us and others to investigate their use as biocatalysts. Our lab has pioneered a chemical‐auxiliary approach to control the promiscuity of P450 3A4 and provide product predictability. The recent realization that type II ligands are sometimes also P450 substrates has prompted the design of a new generation of chemical auxiliaries with type II binding properties. This approach takes advantage of the high affinity of type II ligands for the active site of these enzymes. Although type II ligands typically block P450 activity, we report here that type II ligation can be harnessed to achieve just the opposite, that is, to favor biocatalysis and afford predictable oxidation of small hydrocarbon substrates with P450 2E1. Moreover, the observed predictability was rationalized by molecular docking. We hope that this approach might find future use with other P450 isoforms and yield complimentary products.
Catalytic Electron‐Transfer Oxygenation of Substrates with Water as an Oxygen Source Using Manganese Porphyrins
Authors: Fukuzumi Shunichi , Mizuno Takuya , Ojiri Tetsuya 
Published: November 2012

AbstractManganese(V)–oxo–porphyrins are produced by the electron‐transfer oxidation of manganese–porphyrins with tris(2,2′‐bipyridine)ruthenium(III) ([Ru(bpy)3]3+; 2 equiv) in acetonitrile (CH3CN) containing water. The rate constants of the electron‐transfer oxidation of manganese–porphyrins have been determined and evaluated in light of the Marcus theory of electron transfer. Addition of [Ru(bpy)3]3+ to a solution of olefins (styrene and cyclohexene) in CH3CN containing water in the presence of a catalytic amount of manganese–porphyrins afforded epoxides, diols, and aldehydes efficiently. Epoxides were converted to the corresponding diols by hydrolysis, and were further oxidized to the corresponding aldehydes. The turnover numbers vary significantly depending on the type of manganese–porphyrin used owing to the difference in their oxidation potentials and the steric bulkiness of the ligand. Ethylbenzene was also oxidized to 1‐phenylethanol using manganese–porphyrins as electron‐transfer catalysts. The oxygen source in the substrate oxygenation was confirmed to be water by using 18O‐labeled water. The rate constant of the reaction of the manganese(V)–oxo species with cyclohexene was determined directly under single‐turnover conditions by monitoring the increase in absorbance attributable to the manganese(III) species produced in the reaction with cyclohexene. It has been shown that the rate‐determining step in the catalytic electron‐transfer oxygenation of cyclohexene is electron transfer from [Ru(bpy)3]3+ to the manganese–porphyrins.
Multiscale observations of snow accumulation and peak snowpack following widespread, insect‐induced lodgepole pine mortality
Authors: Biederman Joel A. , Brooks P. D. , Harpold A. A. , Gochis D. J. , Gutmann E. , Reed D. E. , Pendall E. , Ewers B. E. 
Published: November 2012

ABSTRACTSeasonal snowpack in forested lands is the primary source of fresh water in western North America, where mountain pine beetle (MPB) infestation has resulted in rapid and extensive tree die‐off. Forests significantly influence the amount and spatial distribution of peak seasonal snowpack, but the impacts of large‐scale tree mortality on the processes controlling peak snowpack are not well understood. We evaluate the effects of widespread tree mortality on winter snow accumulation and peak seasonal snowpack across multiple spatial scales and several levels of MPB impact in the Central Rocky Mountains. Observations for winters 2010 and 2011 include continuous snow depths in 20 plots, distributed snow surveys at peak accumulation and climate observations above and below canopy including precipitation, temperature, humidity, wind and shortwave radiation. Stable water isotopes were observed for fresh snowfall and for snowpack. Plot‐scale snowfall observations showed 20% lower interception (p < 0.05) in grey‐phase stands (needles lost) than in unimpacted stands. However, distributed snow surveys found no differences in peak seasonal snow water equivalent between unimpacted and grey‐phase stands. Water isotopes of snowpack from MPB‐killed stands indicated kinetic fractionation; enriched values demonstrated higher winter snowpack sublimation in MPB‐killed forest. Following MPB infestation, reduced canopy sublimation of intercepted snow appeared to be compensated by increased snowpack sublimation, consistent with observations of higher snowpack insolation. Consequently, the effects of widespread tree mortality on peak seasonal snowpack, which is crucial for downstream water resources, will be influenced by compensation for lower interception by higher snowpack sublimation. Copyright © 2012 John Wiley & Sons, Ltd.
Hybridization in Materials Science – Evolution, Current State, and Future Aspirations
Authors: Drisko Glenna L. , Sanchez Clément 
Published: November 2012

AbstractWe introduce this themed issue of the European Journal of Inorganic Chemistry with a short overview of hybrid inorganic–organic materials. Hybrid materials have been used in society since antiquity, in fact the creative musings regarding hybridization began in ancient mythology. Now hybrid materials are ubiquitous, and so for clarity they have been divided into different classes and subgroups. These are explained and illustrated with notable synthetic and natural examples. The second half of this overview is devoted to some speculation about the future potential of hybrid materials based on some of the most exciting areas of development, such as artificial photosynthetic leaves, metamaterials, molecular machines, theranostics, 3D printing, nuclear waste storage, and the exploration of life's extraordinary evolutionary origins.
Hierarchical Macro‐mesoporous Pt Deposits on Gold Microwires for Efficient Methanol Oxidation
Authors: Heim Matthias , Wattanakit Chularat , Reculusa Stéphane , Warakulwit Chompunuch , Limtrakul Jumras , Ravaine Serge , Kuhn Alexander 
Published: November 2012

AbstractHierarchically ordered macro‐mesoporous Pt films have been synthesized on gold microwires by filling the void space of a colloidal crystal template with mesoporous Pt through electrodepositing the metal in the presence of self‐assembled surfactant molecules, followed by a dissolution of the template. The network of interconnected macro‐ and mesopores in the homogeneous films was characterized using microscopy (SEM, TEM) and electrochemical techniques. The active surface areas of the porous wires increased by more than three orders of magnitude compared to nonporous samples. These high surface‐to‐volume ratios resulted in a high electrocatalytic activity for methanol oxidation.
Response‐only modal identification of structures using strong motion data
Authors: Ghahari S. F. , Abazarsa F. , Ghannad M. A. , Taciroglu E. 
Published: November 2012

SUMMARYDynamic characteristics of structures — viz. natural frequencies, damping ratios, and mode shapes — are central to earthquake‐resistant design. These values identified from field measurements are useful for model validation and health‐monitoring. Most system identification methods require input excitations motions to be measured and the structural response; however, the true input motions are seldom recordable. For example, when soil–structure interaction effects are non‐negligible, neither the free‐field motions nor the recorded responses of the foundations may be assumed as ‘input’. Even in the absence of soil–structure interaction, in many instances, the foundation responses are not recorded (or are recorded with a low signal‐to‐noise ratio). Unfortunately, existing output‐only methods are limited to free vibration data, or weak stationary ambient excitations. However, it is well‐known that the dynamic characteristics of most civil structures are amplitude‐dependent; thus, parameters identified from low‐amplitude responses do not match well with those from strong excitations, which arguably are more pertinent to seismic design. In this study, we present a new identification method through which a structure's dynamic characteristics can be extracted using only seismic response (output) signals. In this method, first, the response signals’ spatial time‐frequency distributions are used for blindly identifying the classical mode shapes and the modal coordinate signals. Second, cross‐relations among the modal coordinates are employed to determine the system's natural frequencies and damping ratios on the premise of linear behavior for the system. We use simulated (but realistic) data to verify the method, and also apply it to a real‐life data set to demonstrate its utility. Copyright © 2012 John Wiley & Sons, Ltd.
Saliva levels of 3‐methoxy‐4‐hydroxyphenylglycol and clinical efficacy of mirtazapine or selective serotonin reuptake inhibitors in patients with major depression
Authors: Egami Maki , Imamura Yoshiomi , Nabeta Hiromi , Mizoguchi Yoshito , Yamada Shigeto 
Published: November 2012

ObjectiveThis study compared saliva levels of 3‐methoxy‐4‐hydroxyphenylglycol (sMHPG) in patients with major depressive disorder (MDD) to levels in healthy controls and explored whether sMHPG levels in patients with MDD were a predictive marker for antidepressant efficacy.MethodssMHPG levels were compared in 53 patients with MDD and 275 age‐matched healthy controls. Patients' depressive symptoms were assessed by the 17‐item Hamilton Rating Scale for Depression at baseline and 4 weeks after treatment with selective serotonin reuptake inhibitors (SSRIs, n = 23) or mirtazapine (n = 30), followed by saliva sampling. The mirtazapine group included nine patients who had been treated with an SSRI for more than 4 weeks without any improvement. sMHPG levels were measured by gas chromatography–mass spectrometry.ResultssMHPG levels in MDD patients were significantly higher than in controls. The responder rate to drug treatment at 4 weeks was 62% for mirtazapine (13/21), 57% for SSRIs (13/23), and 89% (8/9) for SSRI plus mirtazapine. sMHPG at baseline in 13 responders treated with SSRIs, but not mirtazapine, was significantly higher than that in non‐responder group and showed consequent reduction 4 weeks after treatment. The area under the receiver operating characteristic (ROC) curves of sMHPG for discrimination of SSRI responders and non‐responders was 0.86 ± 0.10 (95% confidence interval: 0.64–1.0, p = 0.005). In contrast, the ROC curve of sMHPG levels for discrimination of mirtazapine responders and non‐responders was not significant. Adjunctive treatment with mirtazapine to SSRI non‐responders was effective, regardless of baseline sMHPG levels.ConclusionsMHPG in patients with MDD was higher than in healthy controls. High baseline sMHPG levels in patients with MDD maybe a predictive marker for SSRI response. Copyright © 2012 John Wiley & Sons, Ltd.
Surface modification of the conducting polymer, polypyrrole, via affinity peptide
Authors: Nickels Jonathan D. , Schmidt Christine E. 
Published: November 2012

AbstractA novel strategy for affinity‐based surface modification of the conducting polymer, polypyrrole, (PPy), has been developed. A 12‐amino acid peptide (THRTSTLDYFVI, hereafter denoted T59) was previously identified via the phage display technique. This peptide noncovalently binds to the chlorine‐doped conducting polymer polypyrrole (PPyCl). Studies have previously shown that conductive polymers have promising application in neural electrodes, sensors, and for improving regeneration and healing of peripheral nerves and other tissues. Thus, the strong and specific attachment of bioactive molecules to the surface of PPy using the T59 affinity peptide is an exciting new approach to enhance the bioactivity of electrically active materials for various biomedical applications. We demonstrate this by using T59 as a tether to modify PPyCl with the laminin fragment IKVAV to enhance cell interactions, as well as with the so‐called stealth molecule poly(ethylene glycol; PEG) to decrease cell interactions. Using these two modification strategies, we were able to control cell attachment and neurite extension on the PPy surface, which is critical for different applications (i.e., the goal for tissue regeneration is to enhance cell interactions, whereas the goal for electrode and sensor applications is to reduce glial cell interactions and thus decrease scarring). Significantly, the conductivity of the PPyCl surface was unaffected by this surface modification technique, which is not the case with other methods that have been explored to surface modify conducting polymers. Finally, using subcutaneous implants, we confirmed that the PPyCl treated with the T59 peptide did not react in vivo differently than untreated PPyCl. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.
Protein Kinase A phosphorylates NCoR to enhance its nuclear translocation and repressive function in human prostate cancer cells
Authors: Choi Hyo‐Kyoung , Yoo Jung‐Yoon , Jeong Mi‐Hyeon , Park Soo‐Yeon , Shin Dong‐Myoung , Jang Sung‐Wuk , Yoon Ho‐Geun , Choi Kyung‐Chul 
Published: November 2012

AbstractProtein Kinase A (PKA) phosphorylates diverse protein substrates to modulate their function. In this study, we found that PKA specifically phosphorylates the RD1 (Repression Domain 1) domain of nuclear receptor corepressor (NCoR). We demonstrated that the Serine‐70 of NCoR is identified the critical amino acid for PKA‐dependent NCoR phosphorylation. Importantly, we found that PKA‐dependent phosphorylation enhances the nuclear translocation of NCoR. More importantly, the activation of PKA enhanced the repressive activity of NCoR in a reporter assay and potentiated the antagonist activity in the Androgen Receptor (AR)‐mediated transcription. Taken together, these results uncover a regulatory mechanism by which PKA positively modulates NCoR function in transcriptional regulation in prostate cancer. J. Cell. Physiol. 228: 1159–1165, 2013. © 2012 Wiley Periodicals, Inc.