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# crystal

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#1
Jingjie He, Zhan Kang
This paper presents a study on topology optimization of novel material microstructural configurations to achieve directional elastic wave propagation through maximization of partial band gaps. A waveguide incorporating a periodic-microstructure material may exhibit different propagation properties for the plane elastic waves incident from different inlets. A topology optimization problem is formulated to enhance such a property with a gradient-based mathematical programming algorithm. For alleviating the issue of local optimum traps, the random morphology description functions (RMDFs) are introduced to generate random initial designs for the optimization process...
July 12, 2017: Ultrasonics
#2
Roberto L Moreira, Ricardo P S M Lobo, Anderson Dias
A comprehensive set of optical vibrational modes of monoclinic taurine crystals was determined by Raman scattering, and infrared reflectivity and transmission spectroscopies. By using appropriate scattering/reflection geometries, the vibrational modes were resolved by polarization and the most relevant modes of the crystal could be assigned. In particular, we were able to review the symmetry of the gerade modes and to resolve ambiguities in the literature. Owing to the non-orthogonal character of Bu modes in monoclinic crystals (lying on the optic axial plane), we carried out a generalized Lorentz dispersion analysis consisting of simultaneous adjust of infrared-reflectivity spectra at various light polarization angles...
July 14, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
#3
REVIEW
Yaqiang Wang, Juli Feigon
Telomerase is an RNP that synthesizes the 3' ends of linear chromosomes and is an important regulator of telomere length. It contains a single long non-coding telomerase RNA (TER), telomerase reverse transcriptase (TERT), and other proteins that vary among organisms. Recent progress in structural biology of telomerase includes reports of the first cryo-electron microscopy structure of telomerase, from Tetrahymena, new crystal structures of TERT domains, telomerase RNA structures and models, and identification in Tetrahymena telomerase holoenzyme of human homologues of telomere-associated proteins that have provided a more unified view of telomerase interaction at telomeres as well as insights into the role of telomerase RNA in activity and assembly...
July 18, 2017: Current Opinion in Structural Biology
#4
Yan Li, Ran Andy Mei, Zhongqiang Yang
This study demonstrates a new process for preparation of oil-in-water (O/W) emulsion using the high gravity technique. This involves a mixture of oil and water that are passed through a rotating packed bed, under a high shear force, from which oil is emulsified into tiny droplets and subsequently dispersed in water. The process is cycled in order to break the droplets repeatedly and achieve an emulsion with small size and low polydispersity index (PDI). The advantage of the high gravity technique is that the emulsions with a desired size and polydispersity can be rapidly obtained by tuning experimental parameters, such as relative centrifugal force (RCF), cycle times (CT), liquid flow rate (VL) and surfactant concentration (Csurfactant)...
June 13, 2017: Journal of Colloid and Interface Science
#5
Dan Wang, Weizhong Chen, Shanqing Huang, Yafeng He, Xichun Liu, Qingyuan Hu, Tianbiao Wei, Hong Shang, Jianhua Gan, Hao Chen
Pseudomonas aeruginosa (P. aeruginosa) is a major opportunistic human pathogen, causing serious nosocomial infections among immunocompromised patients by multi-determinant virulence and high antibiotic resistance. The CzcR-CzcS signal transduction system in P. aeruginosa is primarily involved in metal detoxification and antibiotic resistance through co-regulating cross-resistance between Zn(II) and carbapenem antibiotics. Although the intracellular regulatory pathway is well-established, the mechanism by which extracellular sensor domain of histidine kinase (HK) CzcS responds to Zn(II) stimulus to trigger downstream signal transduction remains unclear...
July 21, 2017: PLoS Pathogens
#6
Lei Jia, Yaxiong Sun
Chemical stability is a major concern in the development of protein therapeutics due to its impact on both efficacy and safety. Protein "hotspots" are amino acid residues that are subject to various chemical modifications, including deamidation, isomerization, glycosylation, oxidation etc. A more accurate prediction method for potential hotspot residues would allow their elimination or reduction as early as possible in the drug discovery process. In this work, we focus on prediction models for asparagine (Asn) deamidation...
2017: PloS One
#7
Hui Liu, Jun Chen, Longlong Fan, Yang Ren, Zhao Pan, K V Lalitha, Jürgen Rödel, Xianran Xing
High-performance piezoelectric materials constantly attract interest for both technological applications and fundamental research. The understanding of the origin of the high-performance piezoelectric property remains a challenge mainly due to the lack of direct experimental evidence. We perform in situ high-energy x-ray diffraction combined with 2D geometry scattering technology to reveal the underlying mechanism for the perovskite-type lead-based high-performance piezoelectric materials. The direct structural evidence reveals that the electric-field-driven continuous polarization rotation within the monoclinic plane plays a critical role to achieve the giant piezoelectric response...
July 7, 2017: Physical Review Letters
#8
Pablo M Piaggi, Omar Valsson, Michele Parrinello
Crystallization is a process of great practical relevance in which rare but crucial fluctuations lead to the formation of a solid phase starting from the liquid. As in all first order first transitions, there is an interplay between enthalpy and entropy. Based on this idea, in order to drive crystallization in molecular simulations, we introduce two collective variables, one enthalpic and the other entropic. Defined in this way, these collective variables do not prejudge the structure into which the system is going to crystallize...
July 7, 2017: Physical Review Letters
#9
Wen Wei Ho, Soonwon Choi, Mikhail D Lukin, Dmitry A Abanin
We analyze the quantum dynamics of periodically driven, disordered systems in the presence of long-range interactions. Focusing on the stability of discrete time crystalline (DTC) order in such systems, we use a perturbative procedure to evaluate its lifetime. For 3D systems with dipolar interactions, we show that the corresponding decay is parametrically slow, implying that robust, long-lived DTC order can be obtained. We further predict a sharp crossover from the stable DTC regime into a regime where DTC order is lost, reminiscent of a phase transition...
July 7, 2017: Physical Review Letters
#10
Natalia Bedoya Martínez, Benedikt Schrode, Andrew O F Jones, Tommaso Salzillo, Christian Ruzié, Nicola Demitri, Yves Henri Geerts, Elisabetta Venuti, Raffaele Guido Della Valle, Egbert Zojer, Roland Resel
A combined experimental and theoretical approach, consisting of lattice phonon Raman spectroscopy and density functional theory (DFT) calculations, is proposed as a tool for lattice dynamics characterization and polymorph phase identification. To illustrate the reliability of the method, the lattice phonon Raman spectra of two polymorphs of the molecule 2,7-dioctyloxy[1]benzothieno[3,2-{\it b}]benzothiophene are investigated. We show that DFT calculations of the lattice vibrations based on the known crystal structures, including many body dispersion van der Waals (MBD-vdW) corrections, predict experimental data within an accuracy of $\ll$ 5 \ru{} ($\ll$ 0...
July 21, 2017: Journal of Physical Chemistry Letters
#11
Agnès Joncour, Nicolas Desroy, Christopher Housseman, Xavier Bock, Natacha Bienvenu, Laëtitia Cherel, Virginie Labeguere, Christophe Peixoto, Denis Annoot, Luce Lepissier, Jörg Heiermann, Willem Jan Hengeveld, Gregor Pilzak, Alain Monjardet, Emanuelle Wakselman, Veronique Roncoroni, Sandrine Le Tallec, René Galien, Christelle David, Nele Vandervoort, Thierry Christophe, Katja Conrath, Mia Jans, Alexandre Wohlkonig, Robert Touitou, Damien Fleury, Lionel Vercheval, Patrick Mollat, Nicolas Triballeau, Ellen Van der Aar, Reginald Brys, Bertrand Heckmann
Autotaxin (ATX) is a secreted enzyme playing a major role in the production of lysophosphatidic acid (LPA) in blood through hydrolysis of lysophosphatidyl choline (LPC). The ATX-LPA signaling axis arouses a high interest in the drug discovery industry as it has been implicated in several diseases including cancer, fibrotic diseases and inflammation among others. An imidazo[1,2-a]pyridine series of ATX inhibitors was identified out of a high throughput screening (HTS). A co-crystal structure with one of these compounds and ATX revealed a novel binding mode with occupancy of the hydrophobic pocket and channel of ATX but no interaction with zinc ions of the catalytic site...
July 21, 2017: Journal of Medicinal Chemistry
#12
Zong-Jun Li, Sisi Wang, Shu-Hui Li, Tao Sun, Wei-Wei Yang, Kazutaka Shoyama, Takafumi Nakagawa, Il Jeon, Xiaoniu Yang, Yutaka Matsuo, Xiang Gao
C60 o-quinodimethane bisadducts (C60(QM)2) are promising electron acceptors for the bulk heterojuction (BHJ) organic solar cells (OSCs). However, previous production of C60(QM)2 often resulted in excessive regioisomers, which were difficult to purify and might consequently obscure the structure-performance study of the organofullerene acceptors. Herein, the electrosynthesis of C60(QM)2 is reported. The reaction exhibits a strong regiocontrol with generation of less regioisomers. Single regioisomers of cis-2, trans-3 and e C60(QM)2 are obtained, and the structures are solved with single crystal X-ray diffraction...
July 21, 2017: Journal of Organic Chemistry
#13
Gengwen Tan, Xinping Wang
Since the pioneering work by Thiele and Chichibabin, who synthesized the first diradicals bridged by phenylene and biphenylene groups in 1904 and 1907, respectively, numerous efforts have been devoted to synthesizing stable diradicals during the last few decades, and several strategies have been developed to stabilize these highly reactive diradicals. In this Account, we describe the synthesis and characterization of isolable bis(triarylamine) dications, nitrogen analogues of Thiele's, Chichibabin's, and Müller's hydrocarbons, which represent facilely accessible, stable diradicals by replacing carbinyl centers with isoelectronic aminium centers...
July 21, 2017: Accounts of Chemical Research
#14
Jack Kay Clegg, Aidan Brock, Katrina Jolliffe, Simon Parsons, Leonard Lindoy, Peter Tasker, Fraser White
A unique pressure-induced Cu-N bond breaking/bond forming reaction is reported. The variation of pressure on a single crystal of a one-dimensional copper(II)-containing coordination polymer (Cu2L2(1-methylpiperazine)2]n, where H2L is 1,1'-(1,3-phenylene)-bis(4,4-dimethylpentane-1,3-dione)), was monitored using single crystal X-ray diffraction with the aid of a diamond anvil cell. At a very low elevated pressure (~0.05 GPa) a remarkable reversible phase change was observed. The phase change results in the depolymerization of the material through the cleavage and formation of axial Cu-N bonds as well as "ring flips" of individual axially coordinated 1-methylpiperazine ligands...
July 21, 2017: Chemistry: a European Journal
#15
Eseosa T Ighodaro, Peter T Nelson, Walter A Kukull, Frederick A Schmitt, Erin L Abner, Allison Caban-Holt, Shoshana H Bardach, Derrick C Hord, Crystal M Glover, Gregory A Jicha, Linda J Van Eldik, Alexander X Byrd, Anita Fernander
Blacks/African Americans have been reported to be ∼2-4 times more likely to develop clinical Alzheimer's disease (AD) compared to Whites. Unfortunately, study design challenges (e.g., recruitment bias), racism, mistrust of healthcare providers and biomedical researchers, confounders related to socioeconomic status, and other sources of bias are often ignored when interpreting differences in human subjects categorized by race. Failure to account for these factors can lead to misinterpretation of results, reification of race as biology, discrimination, and missed or delayed diagnoses...
July 19, 2017: Journal of Alzheimer's Disease: JAD
#16
Mary X Wang, Jeffrey D Brodin, Jaime A Millan, Soyoung E Seo, Martin Girard, Monica Olvera de la Cruz, Byeongdu Lee, Chad A Mirkin
Colloidal crystal engineering with DNA can be used to realize precise control over nanoparticle (NP) arrangement. Here, we investigate a case of DNA-based assembly where the properties of DNA as a polyelectrolyte brush are employed to alter a hybridization-driven NP crystallization pathway. Using the coassembly of DNA-conjugated proteins and spherical gold nanoparticles (AuNPs) as a model system, we explore how steric repulsion between noncomplementary, neighboring NPs due to overlapping DNA shells can influence their ligand-directed behavior...
July 21, 2017: Nano Letters
#17
Wenhan He, Maksim Y Livshits, Diane A Dickie, Zhen Zhang, Luis E Mejiaortega, Jeffrey J Rack, Qin Wu, Yang Qin
We report the synthesis, characterization and detailed comparison of a series of novel Pt-bisacetylide containing conjugated small molecules possessing an unconventional "roller-wheel" shaped structure that is distinctly different from the "dumbbell" designs in traditional Pt-bisacetylide containing conjugated polymers and small molecules. The relationship between the chemical nature and length of the "rollers" and the electronic and physical properties of the materials are carefully studied by steady state spectroscopy, cyclic voltammetry, differential scanning calorimetry, single-crystal X-ray diffraction, transient absorption spectroscopy, theoretical calculation and device application...
July 21, 2017: Journal of the American Chemical Society
#18
Vivekanand Sharma, Dinesh De, Sanchari Pal, Prithwidip Saha, Parimal K Bharadwaj
The solvothermal reaction of Zn(NO3)2·6H2O and a linear dicarboxylate ligand H2L, in the presence of urotropine in N,N'-dimethylformamide (DMF), gives rise to a new porous two-dimensional (2D) coordination network, {[Zn3(L)3(urotropine)2]·2DMF·3H2O}n (1), with hxl topology. Interestingly, framework 1 exhibits excellent emission properties owing to the presence of naphthalene moiety in the linker H2L, that can be efficiently suppressed by subtle quantity of nitro explosives in aqueous medium. Furthermore, presence of urotropine molecules bound to the metal centers, 1 is found to be an excellent heterogeneous catalyst meant for atom-economical C-C bond-forming Baylis-Hillman reactions...
July 21, 2017: Inorganic Chemistry
#19
Naihua Miao, Bin Xu, Nicholas C Bristowe, Jian Zhou, Zhimei Sun
Atomically thin two-dimensional (2D) materials have received considerable research interest due to their extraordinary properties and promising applications. Here we predict the mono-layered indium triphosphide (InP3) as a new semiconducting 2D material with a range of favourable functional properties by means of ab initio calculations. The 2D InP3 crystal shows high stability and promise of experimental synthesis. It possesses an indirect band-gap of 1.14 eV and a high electron mobility of 1919 cm(2)V(-1)s(-1), which can be strongly manipulated with applied strain...
July 21, 2017: Journal of the American Chemical Society
#20
Chad R Simmons, Fei Zhang, Tara MacCulloch, Nour Eddine Fahmi, Nicholas Stephanopoulos, Yan Liu, Nadrian C Seeman, Hao Yan
The foundational goal of structural DNA nanotechnology-the field that uses oligonucleotides as a molecular building block for the programmable self-assembly of nanostructured systems-was to use DNA to construct three-dimensional (3D) lattices for solving macromolecular structures. The programmable nature of DNA makes it an ideal system for rationally constructing self-assembled crystals, and immobilizing guest molecules in a repeating 3D array through their specific stereospatial interactions with the scaffold...
July 21, 2017: Journal of the American Chemical Society
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