42 research outputs found
Hybrid gold single crystals incorporating amino acids
Composite hybrid gold crystals are of profound interest in various research
areas ranging from materials science to biology. Their importance is due to
their unique properties and potential implementation, for example in sensing or
in bio-nanomedicine. Here we report on the formation of hybrid organic-metal
composites via the incorporation of selected amino acids histidine, aspartic
acid, serine, glutamine, alanine, cysteine, and selenocystine into the crystal
lattice of single crystals of gold. We used electron microscopy, chemical
analysis and high-resolution synchrotron powder X ray diffraction to examine
these composites. Crystal shape, as well as atomic concentrations of occluded
amino acids and their impact on the crystal structure of gold, were determined.
Concentration of the incorporated amino acid was highest for cysteine, followed
by serine and aspartic acid. Our results indicate that the incorporation
process probably occurs through a complex interaction of their individual
functional groups with gold atoms. Although various organic gold composites
have been prepared, to the best of our knowledge this is the first reported
finding of incorporation of organic molecules within the gold lattice. We
present a versatile strategy for fabricating crystalline nanohybrid composite
gold crystals of potential importance for a wide range of applications
Lattice parameter of polycrystalline diamond in the low-temperature range
The lattice parameter for polycrystalline diamond is determined as a function of temperature in the 4–300 K
temperature range. In the range studied, the lattice parameter, expressed in angstrom units, of the studied
sample increases according to the equation a = 3.566810(12) + 6.37(41) × 10−14T
4
(approximately, from 3.5668
to 3.5673 Å). This increase is larger than that earlier reported for pure single crystals. The observed dependence
and the resulting thermal expansion coefficient are discussed on the basis of literature data reported for diamond
single crystals and polycrystal
Capecitabine from X-ray powder synchrotron data
In the title compound [systematic name 5-deoxy-5-fluoro-N-(pentyloxycarbonyl)cytidine], C15H22FN3O6, the pentyl chain is disordered over two positions with refined occupancies of 0.53 (5) and 0.47 (5). The furan ring assumes an envelope conformation. In the crystal, intermolecular N—H⋯O hydrogen bonds link the molecules into chains propagating along the b axis. The crystal packing exhibits electrostatic interactions between the 5-fluoropyrimidin-2(1H)-one fragments of neighbouring molecules as indicated by short O⋯C [2.875 (3) and 2.961 (3) Å] and F⋯C [2.886 (3) Å] contacts
Targeting the mesolithic: Interdisciplinary approaches to archaeological prospection inthe Brown Bank area, southern North Sea
YesThis paper describes some results of the research undertaken over the Brown Bank area during recent (2018/2019) geoarchaeological surveys in the North Sea which included seismic imaging, shallow (vibro)coring and dredging. It examines the benefits of simultaneous high-resolution (0.5 – 1m) and ultra-high-resolution (10 – 20cm) seismic survey techniques and a staged approach to resolving the submerged Holocene landscape in the highest possible detail for the purpose of targeted prospecting for archaeological material from the Mesolithic landscape of Doggerland. The materials recovered from such surveys offer significantly greater information due to an enhanced understanding of the context in which they were recovered. The importance of this information cannot be understated archaeologically, as few locations on land provide the opportunity to recover archaeological finds in situ within preserved landscapes. Moreover, it allows offshore areas of potential human activity to be prospected with some certainty of success.ER
Simultaneous large optical and piezoelectric effects induced by domain reconfiguration related to ferroelectric phase transitions
Electrical switching of ferroelectric domains and subsequent domain wall motion promotes strong piezoelectric activity; however, light scatters at refractive index discontinuities such as those found at domain wall boundaries. Thus, simultaneously achieving large piezoelectric effect and high optical transmissivity is generally deemed infeasible. Here, it is demonstrated that the ferroelectric domains in perovskite Pb(In1/2Nb1/2)O3 Pb(Mg1/3Nb2/3)O3-PbTiO3 domain-engineered crystals can be manipulated by electrical field and mechanical stress to reversibly and repeatably, with small hysteresis, transform the opaque poly-domain structure into a highly transparent mono-domain state. This control of optical properties can be achieved at very low electric fields (less than 1.5 kV cm−1) and is accompanied by a large (>10000 pm V−1) piezoelectric coefficient that is superior to that of linear state-of-the-art materials by a factor of three or more. The coexistence of tunable optical transmissivity and high piezoelectricity paves the way for a new class of photonic devices
Finishing the euchromatic sequence of the human genome
The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead
Résolution des structures cristallines par diffraction des rayons X et neutrons sur poudres en utilisant les méthodes d'optimisation globale
Ce travail de thèse s'articule autour la résolution des structures cristallines par diffraction des rayons X et neutrons sur poudres en utilisant les méthodes d'optimisation globale. Le premier sujet concerne les phénomènes d'ordre-désordre observés dans certains solides moléculaires organiques de type globulaire. Le deuxième est centré sur la famille des neuropeptides opiacés. Ces neurotransmetteurs régulent, au sein du système nerveux central, les fonctions sensitives telles que la douleur et la respiration. Le but de notre étude était de déterminer la structure cristalline de la Leu-enkephaline, sous sa forme complète ou fragmentée. Enfin, le troisième sujet d'étude est la localisation d'une molécule de benzène adsorbée sur des zéolithes X au sodium de structure déjà connue. Ce résultat a été obtenu par simulation et l'utilisation de cartes d'entropie maximale.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF