Whole-pattern profile fitting of powder diffraction data collected in parallel-beam flat-plate asymmetric reflection geometry

Abstract: A simple, physically based model that allows the whole-pattern profile fitting of diffraction data collected in parallel-beam flat-plate asymmetric reflection geometry is presented. In this arrangement, there is a fixed angle between the incident beam and the sample, resulting in a fixed-length beam footprint. The use of a wide-angle detector for the simultaneous detection of the data precludes the use of any diffracted beam optics. Therefore, the observed peak widths are a function of the length of the beam footprint on the sample. The model uses up to three refinable parameters, depending on the intensity profile of the beam, to calculate the effect of diffraction angle on the width of all diffracted peaks. The use of this model reduces the total number of parameters required to fit the observed peak widths and shapes, hence leading to increased stability in the profile analysis. Implementations of the model are provided for both fundamental parameters and empirical approaches

Simulation of electronic and transport properties in carbon nanotubes from second principles

RESUMEN: La quiralidad es una propiedad intrínseca que presentan algunos materiales cuando no son superponibles con su imagen especular. Esta ruptura de simetría da lugar a compuestos que aparecen en dos fases distintas, con la misma estructura electrónica, pero distinta respuesta ante perturbaciones externas variables en el tiempo. En este trabajo se va a llevar a cabo un estudio computacional de propiedades electrónicas y de transporte de carga en nanotubos de carbono. Existen muchos tipos de nanotubos que pueden clasificarse sistemáticamente a partir del plegamiento entorno a un eje de una lámina de grafeno. Presentan gran interés tanto teórico como desde el punto de vista de las aplicaciones, por tratarse de materiales con periodicidad unidimensional que presentan, en muchos casos, quiralidad. Para estudiar el efecto de la quiralidad en el transporte en los nanotubos de carbono, en primer lugar se va a plantear un modelo de segundos principios para el grafeno, basado en un modelo de enlace fuerte. Se realizará una comparativa con los resultados obtenidos para el estado fundamental mediante técnicas de Teoría Funcional de la Densidad (DFT). Después se realizará un análisis de la estructura electrónica de los nanotubos a partir de la obtenida para el grafeno mediante la aproximación de Zone-Folding. Esto permite relacionar la naturaleza metálica o semiconductora de los nanotubos con la dirección de plegamiento de la lámina de grafeno, así como el tamaño del gap entre las bandas de valencia y de conducción, la presencia de conos de Dirac (dispersión lineal de la energía en el espacio recíproco) o el comportamiento de las singularidades de Van-Hove, características de la periodicidad unidimensional de los nanotubos. También, se va a realizar una división en coordenadas cilíndricas, de la corriente local generada en cada átomo de carbono por un campo eléctrico constante, paralelo al eje del nanotubo; analizando la dependencia de cada una de ellas con la geometría de los nanotubos (radio y quiralidad). Se va a tratar de relacionar el transporte de electrones con la dirección de los enlaces químicos del material y justificar con ello la presencia de una corriente tangencial, que permitirá distinguir a la pareja de imágenes especulares, en función del sentido de rotación de la misma. Finalmente, se va a dar un orden de magnitud al campo magnético generado en el interior del nanotubo, utilizando para ello la aproximación clásica de un solenoide infinito.ABSTRACT: Chirality is an intrinsic property of some materials that occurs when they are non superimposable with its mirror image. This symmetry breaking gives rise to compounds that can exist in two difierent phases, having the same electronic structure, but different response to time dependent external perturbations. In this project, a computational study of electronic and transport properties of carbon nanotubes will be carried out. There are many kinds of nanotubes according to how they are created by folding a graphene sheet around a particular axis. They have a great interest from both the theorical and from the application point of view, since they are materials with unidimensional periodicity that display chirality in several cases. In order to study the effect of chirality over the transport properties of carbon nanotubes, a second principles model for graphene, based on a tight binding model, will be considered first. A comparison of the results will be made with the ground state from Density Functional Theory techniques of first principles (DFT). An analysis of the electronic structure of the nanotubes will be carried out from that obtained for graphene by the Zone-Folding approximation. This will allow to relate the metallic or semiconductor nature of the nanotubes with the direction of folding of the graphene sheet, as well as the size of the gap between the valence and conduction bands, the presence of Dirac cones (linear energy dispersion in the reciprocal space) or the behaviour of the Van-Hove singularities, characteristics of the nanotubes' one-dimensional periodicity. Also, a division in cylindrical coordinates of the local current generated in each carbon atom by a constant electric field, parallel to the axis of the nanotube will be performed, in order to analyze the dependence that each of them have with the geometry of the nanotubes (radius and chirality). The transport of electrons is tried to be related with the direction of the chemical bonds of the material and justify with it the presence of a tangential current, which will allow us to distinguish the pair of mirror images, depending on their direction of rotation. Finally, an order of magnitude of the magnetic field generated inside the nanotube is going to be computed using the classical approximation of an infinite solenoid.Grado en Físic

Preliminary Report on Resting Spores of Dinophyceae found in Sea Bottom Mud and Sea Water collected from Fukuyama Area

1. 花紛分析学の手法により赤潮多発水域の一つである福山地先の海域の底泥,海水から渦鞭毛藻類の休眠胞子を検出することを試みた。 2. その結果,田尻港で採取した底泥からは1gあたり約2.5個体,仙酔島の靹水産実験所で採取した海水の沈降物からは海水100lあたり約3個体の休眠胞子が得られた。 3. これらの休眠胞子は,謂わゆるhystrichosphere,游泳体類似の体制を有するものを含め14の形態に分けることができたが,現段階ではこれらのうち一部がGonyaulaxやPeridiniumの休眠胞子であることが解ったのみで,游泳体との関係を充分明確にするには至っていない。 4. 本論文ではこれらの諸形態を,仮に形態I,形態II等として取り扱いその形態的特徴を記載した。1. We tried to find resting spores of Dinophyceae in sea bottom mud and sea water collected from Fukuyama area, where red water often break out, with ordinary palynological method. 2. As the result of this trial, we could obtain 2.5 cells of spores from 1 gram of wet mud and 3 cells from 100 l of sea water. 3. These spores could be distinguished into 14 forms, containing so-called hystrichospheres and swarmer-like forms, but could not be correlated with their corresponding swarmers, except a few forms which were identified with the cysts of Gonyaulax or Peridinium in this preliminary study. 4. All forms were tentatively treated as Form I, Form II and so on, and their morphological features were described in this paper

Powder-Pattem-Fitting Methods in Structure Determination

The Rietveld method is a well known powder-pattem-fitting method which consists in adjusting the complete theoretical diffraction pattern, calculated on the basis of the model for the sample crystal structure, to the experimental powder diffraction pattern. In the fitting procedure, the structure model is being refined. The Rietveld method also enables determination of some other structural properties of the material, like crystallite size and strains, and the quantitative phase analysis of a multicomponent mixture. Complementary fitting methods to the Rietveld method are the individual profile fitting method and the whole-powder-pattern decomposition method, which do not require structural models. The individual profile fitting method enables decomposition of the overlapping diffraction lines in a small range of the powder pattern, while the whole-powder-pattern decomposition method simultaneously decomposes the whole powder pattern into individual lines and refines the unit-cell parameters of the sample. Although the powder-pattern-fitting methods are not methods for direct structure determination, they are very powerful tools in the course of structure determination when the sample is not available in a single crystal form. Several examples of the application of the described methods in structure determination are presented

大型藻類の微量金属の含有量ととりこみに関する研究 : II. アオノリ,アマノリの金属添加海水での培養に関する研究

自然状態で生育するアオノリ,アマノリの金属含有量が海水の金属含有量により異なってくるかを調べるため,海水に金属を添加し,葉体中の金属含有濃度を調べた。アサクサノリ等の細胞層一層のParenchyma組織では,細胞部を中心にその両側に細胞充間物質とクチクル層の五層からなり,成分的には三層よりなっている。したがってとりかこまれた金属が葉体のどの部位に存在するか葉体を三層に分離し層別の金属含有濃度を調査した。添加金属はFe,Mn,Cdの3種で海水中の各金属濃度は対照海水の金属濃度10, 250, 1000倍とした。葉体の金属添加海水での培養時間は24×3時間,明期・暗期12×4時間とした。 アオノリの対照海水中の培養では各金属含有濃度はFe:478μg/g, Mn:116μg/g, Cd:Trace,24時間後の金属添加海水ではFe:1340μg/g, Mn:698μg/g, Cd: 58.5μg/gであった。 アマノリでは対照海水中での各金属の含有濃度はFe:200～300μg/g,Mn:50～60,Cd:0.5～1.5であった。金属添加海水では葉体中のFe濃度はあまり大きな増加はみとめられなかったが,Mn,Cdについては高濃度海水において葉体中の金属含有濃度は培養時間と比例的関係が認められた。アマノリ葉体の部位別金属含有濃度について,Feはどの部位にも平均的に分布し,Mnでは細胞部に少なく表層と中層に高い含有濃度を示した。また,とりこみについても中層部が強く,表層部でもとりこまれた。Cdの場合は細胞部の濃度は海水中のCd濃度が高くなっても変化は少なく,中層部へのとりこみが非常に多かった。明期暗期別の金属のとりこみについては,Feでは明白な傾向が認められなかったが,Mn,Cdについては興味ある結果が得られた。すなわち,Mn,は明期にとりこまれ,暗期にはとりこまれない。Cdは明・暗期に関係なく培養時間と比例的にとりこみが行なわれることが明白になった。1. In the culture of Porphyra in the sea water supplemented with metals, the uptakes of Mn and Cd were relatively high and increased in proportion to culture time when the metal concentration in water was high. 2. Fe distributed evenly in all the three parts of fronds. Mn was concentrated in surface and middle layer, while Cd was accumulated mainly in the middle layer and a little in the surface layer. In general the uptake was high in the middle layer. 3. In the uptake of Mn there was a clear distinction between light and dark conditions, that is, Mn was absorbed only during light period. While, Cd was absorbed regardless of light and dark periods

大型藻類の微量金属の含有量ととりこみに関する研究 : I. アマノリに含有する微量金属元素の測定方法と自然状態アマノリの微量金属の含有状態

海藻中の微量金属に関する研究は陸上植物の無機成分や海藻中の有機成分にくらべて,はなはだ少ない。海藻の形態的構造は陸上植物と異なり比較的簡単で,根,茎,葉などの特別な器官の揃っているものは少ない。ただ他物に付着する組織だけをもち,養分等の吸収については体の全表面で行うのが普通である。また,生活史の一時期を除けば海藻はほとんど付着生活である。それ故,海藻の生活環境である海水の影響を当然考えなくてはならない。潮間帯付近に生育する海藻にとっては海水の成分はもちろん,その底泥や懸濁物までも海藻に与える影響は大きいものと考えなければならない。したがって海藻中の微量金属の含有量は海藻の種類,季節,生育する場所(水平,垂直的)に大いに異なると予想される。 自然状態におけるアマノリ属の微量金属の含有量を調べるため,福山地先のノリ養殖場において1972年11月から1973年4月に至るまで半月ごとに岸寄りの河口付近から沖合にかけて三定点を設け,ノリを採取した。アマノリ試料は硝酸－過塩素酸－塩酸で分解し,Fe,Zn,Mn,Cu,Pb,Cdの6種の元素について原子吸光分光分析法により測定した。また同時に葉体のクロロフィルa量についても測定した。 原子吸光分光分析法による測定法で各元素とも95%以上の回収率が得られた。三定点におけるアマノリの微量金属含有量の変動はFe:100～1000μg/g, Zn:100～200, Mn:20～70, Cu:9～30, Pb:1～4, Cd:0.1～0.5であった。一般的に必須微量元素であるFe,Zn,Mn,Cnは葉体が若いときに含有濃度が高く,成熟期に減少し,Pb,Cdは反対に葉体が若いとき少なく除々に増加する傾向を示した。クロロフィルa量の季節的変動はFe含有濃度の季節的変動によく似た傾向を示した。当初予想した葉体中の微量元素の季節的,地域的変動があまり明確にならなかった。l. Trace metals in Porphyra were recovered for more than 95% by the treatment of the alga with HNO3 -HClO4 -HCl. 2. Ten to 20% of the standard deviations were obtained by the analyses of the alga. 3. The trace metals in Porphyra could be divided into two groups according to their tendencies of seasonal and regional variations, one is the group of Fe, Zn, Mn, and Cu and the other group is Pb and Cd. 4. The variation of chlorophyll a content was quite similar to that of Fe. 5. The content of metals was different in Porphyra collected from regions other than the fixed stations

Production of 2-butanol through meso-2,3-butanediol consumption in lactic acid bacteria

2-Butanol has been an issue of industries in many areas, for example, biofuel production (as an advanced alternate fuel), fermented beverages, and food (as taste-altering component). Thus, its source of production, the biological pathway, and the enzymes involved are of high interest. In this study, 42 different isolates of lactic acid bacteria from nine different species were screened for their capability to consume meso-2,3-butanediol and produce 2-butanol. Lactobacillus brevis was the only species that showed any production of 2-butanol. Five of ten tested isolates of L.brevis were able to convert meso-2,3-butanediol to 2-butanol in a synthetic medium (SM2). However, none of them showed the same capability in a complex medium such as MRS indicating that the ability to produce 2-butanol is subject to some kind of repression mechanism. Furthermore, by evaluating the performance of the enzymes required to convert meso-2,3-butanediol to 2-butanol, that is, the secondary alcohol dehydrogenase and the diol dehydratase, it was shown that the latter needed the presence of a substrate to be expressed