Phase Transformation Introduced by Mechanical and Chemical Surface Preparations of Tetragonal Zirconia Polycrystals

Cutting of Y2O3-doped TZP rods by a low-speed diamond saw introduces an unidentified, metastable phase X (x-ZrO2) coexisting with the tetragonal (t-ZrO2) and the monoclinic (m-ZrO2) phases initially present in the sample. Further mechanical deformation of the cut surface by indentation or polishing sustains the x-ZrO2. Chemical etching removes the x-ZrO2 and increases the m-ZrO2content.

Synthesis and Isolation of 5,6-Dihydro-4H-1,3-Oxazine Hydrobromides by Autocyclization of N-(3-Bromopropyl)amides

5,6-Dihydro-4H-1,3-oxazine hydrobromides have been synthesized by the nucleophilic autocyclo-O-alkylation of N-(3-bromopropyl)amides under neutral conditions in chloroform. It is found that electron-donating amide alpha-substituents influence the autocyclization efficiency.

Synthesis of Functionalized Dihydrothiophenes from Doubly Activated Cyclopropanes Using Tetrathiomolybdate as the Sulfur Transfer Reagent

A number of doubly activated cyclopropanes were synthesized starting from various substituted bromosulfonium bromides in good yield. Regioselective ring-opening of cyclopropanes with tetrathiomolybdate as the sulfur transfer reagent gave dihydrothiophenes in excellent yield.

Effect of Short Duration of Load increment on the Compressibility of Soils

This study concerns the effect of duration of load increment (up to 24 h) on the consolidation properties of expansive black cotton soil (liquid limit = 81%) and nonexpansive kaolinite (liquid limit = 49%). It indicates that the amount and rate of compression are not noticeably affected by the duration of loading for a standard sample of 25 mm in height and 76.2 mm in diameter with double drainage. Hence, the compression index and coefficient of consolidation can be obtained with reasonable accuracy even if the duration of each load increment is as short as 4 h. The secondary compression coefficient (C-alpha epsilon) for kaolinite can be obtained for any pressure range with 1/2 h of loading, which, however, requires 4 h for black cotton soil. This is because primary consolidation is completed early in the case of kaolinite. The paper proves that the conventional consolidation test can be carried out with much shorter duration of loading (less than 4 h) than the standard specification of 24 h or more even for remolded fine-grained soils.

Isolation and characterization of proteolytic enzymes from the latex of Synadenium grantii Hook, 'f'

Two fractions showing proteolytic enzymes have been obtained from the latex of Synadenium grantii Hook, 'f', using gel-filtration and anion-exchange chromatographic techniques. Both these proteases have the same molecular mass of 76+/-2 kDa each. They exhibit maximal activity at pH 7.0 and at a temperature of 60 degreesC. They display stability over a pH range from 5-10 and are also highly thermostable. Irreversible inhibition by PMSF indicates that they are serine proteases. In addition, histidine residues also appear to play an important role in catalysis as evidenced by inhibition with DEPC. They also exhibit similarity with respect to pH and temperature optima, kinetic properties and thermal stability. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.

Biochemistry of water-logged soils. Part IV. Carbon and nitrogen transformations

1. During the fermentation of water-logged soil containing added substances with different carbon-nitrogen ratios, the reaction first turns slightly acid, but soon returns to the original hydrogen-ion concentration (pH 7·6). 2. The quantities of ammonia present in the medium increase up to a point, after which there is steady decrease. 3. There is nitrification only in the case of substances with narrow C/N ratios. The production of nitrate generally commences only after about a month, when the vigour of the initial fermentation has subsided and fairly large quantities of ammonia have accumulated in the medium. 4. The extent of mineralisation of nitrogen is determined chiefly by the C/N ratio, though in the cases of substances like mahua and lantana the presence of other constituents may also influence the processes. The quantities of mineralised nitrogen present in the soil system generally tend to decrease after about two months.

Effect of Input Source Energy on SASW Evaluation of Cement Concrete Pavement

A series of spectral analyses of surface waves (SASW) tests were conducted on a cement concrete pavement by dropping steel balls of four different values of diameter (D) varying between 25.4 and 76.2 mm. These tests were performed (1) by using different combinations of source to nearest receiver distance (S) and receiver spacing (X), and (2) for two different heights (H) of fall, namely, 0.25 and 0.50 m. The values of the maximum wavelength (lambda(max)) and minimum wavelength (lambda(min)) associated with the combined dispersion curve, corresponding to a particular combination of D and H, were noted to increase almost linearly with an increase in the magnitude of the input source energy (E). A continuous increase in strength and duration of the signals was noted to occur with an increase in the magnitude of D. Based on statistical analysis, two regression equations have been proposed to determine lambda(max) and lambda(min) for different values of source energy. It is concluded that the SASW technique is capable of producing nearly a unique dispersion curve irrespective of (1) diameters and heights of fall of the dropping masses used for producing the vibration, and (2) the spacing between different receivers. The results presented in this paper can be used to provide guidelines for deciding about the input source energy based on the required exploration zone of the pavement. (C) 2014 American Society of Civil Engineers.

Colecta y establecimiento de banco de germoplasma en coleccion viva e In vitro del genero Xanthosoma en Nicaragua

Con el objetivo de conservar in vitro y en colección viva la variabilidad del género Xanthosoma se realizaron colectas en 27 sitios de tres regiones de Nicaragua entre julio y 2006 Oc tubre 2007. El banco de germoplasma in vitro se estableció mediante el cultivo de meristemos y colección viva utilizando la técnica de reproducción acelerada de semilla. Se elaboró un herbario de las accesiones. Catorce descriptores de colecta se utilizaro n para el análisis de agrupamiento (AA) preliminar del parentesco y dispersión entre las accesiones. Se colectaron 63 accesiones de 6 especies, 18 X. violaceum , 8 X. sagittifolium (ambas comestibles), 1 X. robustum , 6 X . wendlandii , 6 X. mexicanum , 2 X. at rovirens monstrosum (ornamental) y 22 X . spp (sin identificar). 74.6 % provienen de la Región Central, 19.0 % del Pacifico y 6.3 % del Caribe, la menos explorada. 76.2 % de las accesiones tienen hoja lisa sagitada, 1.6 % entera ondulada, 9.5% pubescente sa gitada, 3.2 % con ápice en forma de cono y 9.5 % lobulada lisa. 96.8 % de las hojas son verde y 3.2 % variegada ( X. atrovirens monstrosum ) . El 27 % de las accesiones producen estolones y 73 % cormelos. 61.5 % presentan seudotallo color verde, 28.6 % púrp ura y 9.5 % jaspeado. E n e l AA preliminar las accesiones formaron 2 grupos ( silvestres y cultivados ). 63 % de la variación total lo provocan un componente de 4 variables, y dos de 2 variables. El banco de germoplasma in vitro , la colección viva y el herbar io evidencian la variabilidad de Xanthosoma en Nicaragua.

Atomistic simulations of crack nucleation and intergranular fracture in bulk nanocrystalline nickel

We report large scale molecular dynamics simulations of dynamic cyclic uniaxial tensile deformation of pure, fully dense nanocrystalline Ni, to reveal the crack initiation, and consequently intergranular fracture is the result of coalescence of nanovoids by breaking atomic bonds at grain boundaries and triple junctions. The results indicate that the brittle fracture behavior accounts for the transition from plastic deformation governed by dislocation to one that is grain-boundary dominant when the grain size reduces to the nanoscale. The grain-boundary mediated plasticity is also manifested by the new grain formation and growth induced by stress-assisted grain-boundary diffusion observed in this work. This work illustrates that grain-boundary decohesion is one of the fundamental deformation mechanisms in nanocrystalline Ni.

Classical correlated imaging from the perspective of coherent-mode representation

We use coherent-mode representation of partially coherent fields to analyze correlated imaging with classical light sources. This formalism is very useful to study the imaging quality. By decomposing the unknown object as the superposition of different coherent modes, the components corresponding to small eigenvalues cannot be well imaged. The generated images depend crucially on the distribution of the eigenvalues of the coherent-mode representation of the source and the decomposition coefficients of the objects. Three kinds of correlated imaging schemes are analyzed numerically.

A study of the ^9 Be nucleus

The reaction ⁷Li(³He, p)⁹Be has been used to measure excitations and intrinsic widths of levels in ⁹Be below the ⁷Li + d threshold. Previously unreported levels have been found at excitations of (13.78 ± .03) MeV and (16.671 ± .008) MeV with widths of (590 ± 60) keV and (41 ± 4) keV respectively. Two overlapping levels have been found at (11.81 ± .02) MeV and (11.29 ± .03) MeV with widths of (400 ± 30) keV and (620 ± 70) keV respectively. Branching ratios from ⁹Be levels populated in this reaction to the ground and first excited states of ⁸Be have been measured by observing the associated protons in coincidence with the decay neutrons. Branching ratios were found to be:

Excitation in ⁹Be .... Branching Ratio.......... Final Nucleus.........

(MeV) .......................... (percent) .....................................

.. 2.43 ........................... 7.5 ± 1.5 .............. ⁸Be(g.s.)

.. 3.03 ........................... 87 ± 13......................................

.. 4.65 ........................... 13 ± 4.......................................

.. 6.76 .............................. ≤ 2 ......................................

.. 11.29 ...............................≤ 2 ......................................

.. 11.81 ...............................≤ 3 ......................................

.. 6.76 ........................... .41 ≤ B.R. ≤ .69 ....... ⁸Be(2⁺)

.. 11.29 ........................... 14 ± 4 .......................................

.. 11.81 ........................... 12 ± 4 .......................................

Corresponding reduced widths for neutron emission are calculated and a comparison of the results with the expectations of current nuclear models is made. In particular the measured branching ratio to ⁸Be(g.s.) from ⁹Be(2.43 MeV) corresponds to an f-wave reduced with θ²_f = 2.1 x 10^-2, in units of ħ²/mR², with R = 4.35 fm. A comparison of this value with that predicted by a Nilsson model calculation, in which ⁹Be is taken to be a deformed nucleus, is discussed. The measured value for θ²_f is found to be consistent with that expected on the basis of measured E2-transition rates between rotational levels in ⁹Be.

Efeitos da associação entre dieta hiperlipídica e ovariectomia sobre aspectos comportamentais, lipídeos séricos e o desenvolvimento corporal de ratas adultas

O aumento da longevidade evidenciou nas mulheres os efeitos deletérios da deficiência ovariana como, a obesidade central e as doenças neurodegenerativas. Os hábitos alimentares modernos favorecem o consumo excessivo de gorduras, que contribuem para efeitos adversos sobre a saúde, incluindo alteração da composição corporal e da função nervosa. Assim, objetivamos estudar como a dieta hiperlipídica (DH), contendo óleo de soja, associada à perda da função gonadal influenciam o comportamento e o desenvolvimento corporal de ratas adultas. Ratas Wistar adultas foram ovariectomizadas (OVX) ou pseudo-operadas (C) e após 7d passaram a receber dieta contendo 4%(normo) ou 19%(hiperlípidica) de óleo de soja: C4 (n=29), OVX4 (n=30), C19 (n=30), OVX19 (n=30). Foram avaliados a massa e o comprimento corporais e a ingestão alimentar, e aspectos comportamentais de ansiedade, através de teste no Labirinto em Cruz Elevado (LCE); de busca pela novidade, por testes no Campo Vazado (CV); e aprendizagem/memória avaliada no labirinto aquático radial de 8 braços (LAROB). Ao final dos testes, os animais foram anestesiados, exsanguinados e o tecido adiposo intra-abdominal foi coletado e pesado. O soro foi utilizado para dosagens de triglicerídeo (TG), VLDL-c, colesterol (COL), HDL-c e estradiol. A ingestão alimentar média e o comprimento corporal não diferiram entre os grupos, mas o grupo OVX19 mostrou ganho significativo (13,6%) de massa corporal mais precocemente que os demais. O mesmo padrão foi observado quanto à massa de tecido adiposo, que foi 86% maior no OVX19. Os TG, VLDL e COL aumentaram cerca de 28% no OVX19, porém sem alteração de HDL-c (33,762,2 mg/dl). A DH e a ovariectomia se mostraram ansiogênicos e quando associados, a DH parece reverter o efeito ansiogênico da castração. Padrão similar de resposta foi observado na resposta ao teste de busca por novidade. No teste de aprendizagem/memória o OVX4 apresentou maior tempo de latência no primeiro dia, e todos responderam de forma semelhante nos demais dias. Conclui-se que a deficiência de estradiol acompanhada da ingestão de dieta hiperlipídica mantém o desempenho cognitivo, o comportamento emocional e a motivação, embora prejudique a adiposidade e o metabolismo lipídico.

菊科蒿属与邻近属植物的研究

该成果系作者经近20年的研究，结合《中国植物志》第76卷2分册的编研，先后在全国大多数省区采集标本4000余号，在国内外标本馆参考鉴定标本4万多份，并以形态分类研究为主，结合形态解剖学、细胞学、孢粉学、谱系分支分析等多学科研究，将菊科春黄菊族区分为9大自然群，首次发表了“菊科蒿属演化系统”及“蒿属与邻近属间的亲缘关系”的新观点；首次系统的研究报导了中国蒿属植物186种，44变种，绢蒿属31种，3变种的系统分类、分布与主要经济用途等，发表了1新属、1新亚属、6新组、41新种、22新变种、38新组合种，64中国新分布记录种或变种；纠正前人错误鉴定或混乱35种；首次指出“蒿属自然群起源中心”在亚洲北方，“现代分布中心”在北温带及亚热带地区，而“现代分布区密集中心”在亚洲中部及东部地区的观点，首次报导了蒿属及邻近属在我国形成极为独特的“三斜带密集带谱”的分布规律和“横断山脉——喜马拉雅山脉”地区是一独特的区系分区，该地区既是蒿属植物冰期“避难所”，又是冰后期该属新分化衍生的次生种类的“次生起源中心”、“次生分化中心”及蒿属“第二个现代分布区密集中心”等独特见解。还分别报导亚、欧、非三洲蒿属区系含10亚区、28地区成份；绢蒿属含5亚区、8地区成份。从化学分类证实了原始组的种类多含“单萜类化合物”，略为进化组的种类多含“倍半萜类化合物”，而在进化组的种类则含苯环类化合物。研究成果达国际领先水平。

水生植物凤眼莲的种内基因型差异与入侵模式

原产于亚马逊河流域的水生植物凤眼莲（Eichhornia crassipes）在花部结构上有三种花型（L、M和S），故其配殖系统（mating system）为典型的三型花柱（tristyly）。但在入侵地区，它却常只有M和L两种花型，其中尤以M型占据绝对优势，使有性繁殖水平大为下降。为了解释凤眼莲在入侵过程中，花型频率为何发生变化以及该变化对其在入侵地的适应性进化上有何影响，作者在中国西南的两个居群中连续两年开展了野外生长和人工授粉实验，对比分析水面和泥地两类不同生境中M和L在克隆生长、生物量积累以及有性繁殖水平等方面的异同，并利用RAPD、 ISSR片段比较了具M型和L型花植物个体间的遗传变异水平。对三型花柱这一长期引人注目的遗传模式的分子位点也尝试了连锁片段的克隆和测序。 克隆生长的对比实验发现，在2004年，漂浮生长的M个体平均克隆分株数为25.37，L为21.20，前者显示较强的克隆生长能力（t＝2.252， P< 0.05）;2005年的实验再次证实M（每个个体19.83个分株）比L（每个个体15.53分株）表现出了显著较强的克隆优势（t＝2.631，P<0.001）。M较L多产生克隆约24%。 但在岸边泥地上固着生长时，2004年L个体平均克隆分株为16.20，M 为10.17个分株。L表现出了更强的克隆生长能力（t＝4.788，p<0.001），与漂浮生长状况下的情形恰恰相反，暗示M与L个体可能存在一定的生态位分化。这种分化可能是在入侵过程中形成的，也可能反映了原产地亚马孙流域旱涝交替造成的固着生长与漂浮生长交替发生的种内适应性。 生物量（干重）的对比分析发现，M个体在漂浮生长和固着生长的情况下都比L有着更高的生物量积累（漂浮生长实验：t＝6.173，p<0.005（2004年）;t＝6.99，p<0.001（2005年）。固着生长实验：t＝4.029，p<0.001）。生物量对凤眼莲的竞争和过冬有着一定的作用，因此较大的生物量积累可能是M个体在当地气候和环境中逐渐适应的一个结果。 有性繁殖的实验包括了实验个体的花序数与花朵数、自交与异交人工授粉的结实情况以及种子萌发率等方面的对比分析。结果表明，虽然M和L个体在花序数和花朵数上不存在显著差异，但是M个体在自交和异交的种子产量上比L略高，尤其是自交的种子产量，M显著高于L（M平均每个蒴果的自交种子产量为139.8，L为76.2）。以各100粒种子进行萌发实验，发现两花型之间在种子萌发率上不存在显著差异。对于M而言，其自交种子产量远大于异交种子产量 （139.8 vs. 93.3），且种子萌发率也略大于异交的种子萌发率（自交种子萌发率45.47％，异交种子萌发率 30.73％）。结合以上的实验结果，本文认为M基因型优势的形成可能与M个体与当地环境长期适应导致的生长与繁殖 上的优势有关。M的本地适应性是建立在特定的遗传背景上时，异交反而会破坏这种遗传组合，造成远交衰退。 对40个M和30个L个体进行20个RAPD引物和20个ISSR引物的遗传分析时发现，所有个体在RAPD表型上没有区别，但是在M中出现了3个ISSR表型，在L中出现了2个ISSR表型。本文还尝试利用RAPD技术扫描与三型花柱的遗传位点连锁的DNA片段。在146个RAPD随机引物中，初步发现两个候选片段，一个750bp，另一个2 000bp;已对它们进行了克隆、测序。 这些初步实验表明凤眼莲在我国的入侵可能伴随着基因型的差异表现和居群遗传分化，这种基因型的差异表现对该植物的成功入侵具有作用。其中，花型为M的个体的优势生长解释了该花型在中国分布区内的主导地位。推测该生长优势的遗传基础可能来源于基因组内较高的杂合子水平和在入侵地较长的适应历史，但最终结论尚有待进一步的实验证据。