Artisanal canoe fishing industry of the Rivers State: its economic viability and investment potentials

Consequent upon the present national call in Nigeria for all to go back to agriculture including fishing, most retrenched workers and unemployed youths from the riverine areas are taking up fishing as a legitimate and gainful livelihood. To sustain this tempo and attract more investment, the economic viability of such projects must be known. This study is an attempt to document the profitability and investment potential of artisanal canoe fishing. Socio-economic information including catches, operational cost and returns were obtained through a personal interview questionnaire survey of 240 randomly selected artisanal canoe fishermen from Bonny, Brass and Degema Local Government Areas (LGA) of the State and analyzed. With an investment cost of about 8,135, 8,490 and 6,571 and operation cost of 750, 776 and 627, the analysis showed an average monthly gross income of 1,869, 3,221 and 1,775 for the three local government areas respectively. A benefit-cost-ratio of 1:8, net present value of 400, 603 and internal rate of return greater than 50% were obtained. Since capital invested in fisheries is not tied up for long before benefits start flowing, coupled with the high IRR, it is concluded that artisanal canoe fishing would be an economically viable venture if well managed

不同功率下的飞秒激光在水中形成的脉冲压缩和超连续谱

本文研究了飞秒激光脉冲在水中的传输情况.通过改变不同的激光输入功率进行模拟，我们发现从输入功率略高于到远远高于发生自聚焦的临界功率,分别是群速度色散和多光子电离多光子吸收阻止了自聚焦导致的脉冲塌陷，当多光子电离和多光子吸收主导传输时，脉冲能被压缩到几个光学周期.在频域，多光子电离能引起很强的蓝移,而多光子吸收能对这种蓝移起到抑制作用。

Constitutive plasma membrane targeting and microdomain localization of Dok5 studied by single-molecule microscopy

In the present study, single-molecule fluorescence microscopy was used to examine the characteristics of plasma membrane targeting and microdomain localization of enhanced yellow fluorescent protein (eYFP)-tagged wild-type Dok5 and its variants in living Chinese hamster ovary (CHO) cells. We found that Dok5 can target constitutively to the plasma membrane, and the PH domain is essential for this process. Furthermore, single-molecule trajectories analysis revealed that Dok5 can constitutively partition into microdomain on the plasma membrane. Finally, the potential mechanism of microdomain localization of Dok5 was discussed. This study provided insights into the characteristics of plasma membrane targeting and microdomain localization of Dok5 in living CHO cells. (C) 2008 Elsevier B.V. All rights reserved.

Ab initio study of anharmonicity in high pressure Cmca-4 metallic hydrogen

Hydrogen is the only atom for which the Schr odinger equation is solvable. Consisting only of a proton and an electron, hydrogen is the lightest element and, nevertheless, is far from being simple. Under ambient conditions, it forms diatomic molecules H2 in gas phase, but di erent temperature and pressures lead to a complex phase diagram, which is not completely known yet. Solid hydrogen was rst documented in 1899 [1] and was found to be isolating. At higher pressures, however, hydrogen can be metallized. In 1935 Wigner and Huntington predicted that the metallization pressure would be 25 GPa [2], where molecules would disociate to form a monoatomic metal, as alkali metals that lie below hydrogen in the periodic table. The prediction of the metallization pressure turned out to be wrong: metallic hydrogen has not been found yet, even under a pressure as high as 320 GPa. Nevertheless, extrapolations based on optical measurements suggest that a metallic phase may be attained at 450 GPa [3]. The interest of material scientist in metallic hydrogen can be attributed, at least to a great extent, to Ashcroft, who in 1968 suggested that such a system could be a hightemperature superconductor [4]. The temperature at which this material would exhibit a transition from a superconducting to a non-superconducting state (Tc) was estimated to be around room temperature. The implications of such a statement are very interesting in the eld of astrophysics: in planets that contain a big quantity of hydrogen and whose temperature is below Tc, superconducting hydrogen may be found, specially at the center, where the gravitational pressure is high. This might be the case of Jupiter, whose proportion of hydrogen is about 90%. There are also speculations suggesting that the high magnetic eld of Jupiter is due to persistent currents related to the superconducting phase [5]. Metallization and superconductivity of hydrogen has puzzled scientists for decades, and the community is trying to answer several questions. For instance, what is the structure of hydrogen at very high pressures? Or a more general one: what is the maximum Tc a phonon-mediated superconductor can have [6]? A great experimental e ort has been carried out pursuing metallic hydrogen and trying to answer the questions above; however, the characterization of solid phases of hydrogen is a hard task. Achieving the high pressures needed to get the sought phases requires advanced technologies. Diamond anvil cells (DAC) are commonly used devices. These devices consist of two diamonds with a tip of small area; for this reason, when a force is applied, the pressure exerted is very big. This pressure is uniaxial, but it can be turned into hydrostatic pressure using transmitting media. Nowadays, this method makes it possible to reach pressures higher than 300 GPa, but even at this pressure hydrogen does not show metallic properties. A recently developed technique that is an improvement of DAC can reach pressures as high as 600 GPa [7], so it is a promising step forward in high pressure physics. Another drawback is that the electronic density of the structures is so low that X-ray di raction patterns have low resolution. For these reasons, ab initio studies are an important source of knowledge in this eld, within their limitations. When treating hydrogen, there are many subtleties in the calculations: as the atoms are so light, the ions forming the crystalline lattice have signi cant displacements even when temperatures are very low, and even at T=0 K, due to Heisenberg's uncertainty principle. Thus, the energy corresponding to this zero-point (ZP) motion is signi cant and has to be included in an accurate determination of the most stable phase. This has been done including ZP vibrational energies within the harmonic approximation for a range of pressures and at T=0 K, giving rise to a series of structures that are stable in their respective pressure ranges [8]. Very recently, a treatment of the phases of hydrogen that includes anharmonicity in ZP energies has suggested that relative stability of the phases may change with respect to the calculations within the harmonic approximation [9]. Many of the proposed structures for solid hydrogen have been investigated. Particularly, the Cmca-4 structure, which was found to be the stable one from 385-490 GPa [8], is metallic. Calculations for this structure, within the harmonic approximation for the ionic motion, predict a Tc up to 242 K at 450 GPa [10]. Nonetheless, due to the big ionic displacements, the harmonic approximation may not su ce to describe correctly the system. The aim of this work is to apply a recently developed method to treat anharmonicity, the stochastic self-consistent harmonic approximation (SSCHA) [11], to Cmca-4 metallic hydrogen. This way, we will be able to study the e ects of anharmonicity in the phonon spectrum and to try to understand the changes it may provoque in the value of Tc. The work is structured as follows. First we present the theoretical basis of the calculations: Density Functional Theory (DFT) for the electronic calculations, phonons in the harmonic approximation and the SSCHA. Then we apply these methods to Cmca-4 hydrogen and we discuss the results obtained. In the last chapter we draw some conclusions and propose possible future work.

Defects in LPE-grown beta-barium borate (beta-BaB2O4) thin films

Morphological defects in beta-barium borate (beta-BBO) thin films grown on Sr2+ -doped alpha-BBO substrates by liquid phase epitaxy (LPE) technique were studied by scanning electron micrograph (SEM), atomic force microscopy (AFM) and optical spectroscopy. The present results indicate that the main defects exit in beta-BBO thin films are microcracks and hollow structure. The formation of microcrack is due to the lattice mismatch and the difference of thermal expansion coefficients between substrate and film. The hollow structure might be caused during the combination of islands, which formed in the initial stage. (C) 2006 Elsevier GmbH. All rights reserved.

Efeito da terapia farmacológica anti-hipertensiva sobre densidade capilar e função endotelial microcirculatória

Hipertensos têm rarefação capilar e disfunção endotelial microcirculatória, tornando-se mais vulneráveis a lesões em órgãos-alvo. O estudo buscou avaliar o efeito de seis meses de tratamento farmacológico sobre densidade capilar e reatividade microvascular a estímulos fisiológicos e farmacológicos em hipertensos de baixo risco cardiovascular. Secundariamente testou-se a existência de diversidade nas respostas a diferentes estratégias anti-hipertensivas. Foram recrutados 44 pacientes, com 46,71,3 anos e 20 normotensos com 48,01,6 anos. Avaliaram-se dados antropométricos e laboratoriais e dosaram-se no soro o fator de crescimento vascular endotelial (VEGF), receptor Flt-1 para VEGF e óxido nítrico (NO). A contagem capilar foi por microscopia intravital, captando-se imagens da microcirculação no dorso da falange do dedo médio e contando os capilares com programa específico. Repetia-se o procedimento após hiperemia reativa pós-oclusiva (HRPO) para avaliar o recrutamento capilar. A reatividade vascular foi testada por fluxometria Laser Doppler, iontoforese de acetilcolina (Ach), HRPO e hiperemia térmica local (HTL). Os pacientes foram distribuídos aleatoriamente para dois grupos de tratamento: succinato de metoprolol titulado a 100 mg diários ou olmesartana medoxomila titulada a 40 mg diários, empregando-se, se necessário, a hidroclorotiazida. Os controles seguiram o mesmo protocolo inicial e após seis meses todos os testes foram repetidos nos hipertensos. As variáveis clínicas e laboratoriais basais eram semelhantes em comparação aos controles e entre os dois grupos de tratamento. Após seis meses, havia pequenas diferenças entre os grupos na relação cintura-quadril e HDL. A densidade capilar antes do tratamento era significativamente menor que no grupo controle (71,31,5 vs 80,61,8 cap/mm2 p<0,001 e HRPO 71,71,5 vs 79,52,6 cap/mm2 p<0,05) e, com o tratamento, aumentou para 75,41,1 cap/mm2 (p<0,01) no estado basal e para 76,81,1 cap/mm2 à HRPO (p<0,05). À reatividade vascular, a condutância vascular cutânea (CVC) em unidades de perfusão (UP)/mmHg era similar à HTL nos controles e hipertensos e aumentou com o tratamento nos dois subgrupos (metoprolol:1,730,2 a 1,900,2 p<0,001 e olmesartana:1,490,1 a 1,870,1 p<0,001). A CVC máxima à HRPO era menor nos hipertensos: 0,30(0,22-0,39) que nos controles: 0,39(0,31-0,49) com p<0,001. Após tratamento, aumentou para 0,41(0,29-0,51) com p<0,001. O aumento foi significativo apenas no grupo olmesartana (0,290,02 a 0,420,04 p<0,001). A diferença entre o tempo para atingir o fluxo máximo à HRPO aumentou no grupo metoprolol após tratamento 3,0 (-0,3 a 8,8) segundos versus olmesartana 0,4 (-2,1 a 2,4) segundos p<0,001. À iontoforese, a área sob a curva de fluxo (AUC) era similar nos grupos e aumentou com o tratamento, de 6087(3857-9137) para 7296(5577-10921) UP/s p=0,04. O VEGF e receptor não diferiam dos controles nem sofreram variações. A concentração de NO era maior nos hipertensos que nos controles: 64,9 (46,8-117,6) vs 50,7 (42-57,5) M/dl p=0,02 e não variou com tratamento. Em conclusão, hipertensos de baixo risco têm menor densidade e menor recrutamento capilar e ambos aumentam com tratamento. Apresentam também disfunção endotelial microcirculatória que melhora com a terapia.

Formação in vitro de biofilme de Candida albicans em materiais usados no preenchimento dos acessos aos parafusos das próteses sobre implantes

Os orifícios de acesso aos parafusos de retenção devem ser preenchidos para que o parafuso não seja danificado caso seja necessária a remoção da prótese. Dentre os materiais mais utilizados estão o algodão, a fita de politetrafluoretileno e a guta percha. O objetivo deste estudo é avaliar a formação de biofilme de Candida albicans nos materiais anteriormente descritos, buscando estabelecer um parâmetro que contribua para a escolha do tipo de material mais adequado a ser utilizado clinicamente. Foram utilizados UCLAs, análogos e parafusos sextavados, todos de titânio. Os conjuntos foram montados com torque de 32N. Os materiais foram condensados no interior dos UCLAs e colocados em meio de cultura com uma suspensão de 3x106 células/ml de Candida albicans. O sistema foi armazenado à 37C com agitação, por 15 dias e o meio foi renovado a cada 48 horas. A quantificação de biofilme foi realizada pelo ensaio de MTT e leitura à 490nm, resultando em diferentes valores de densidade óptica. A normalidade (p=0,304 - Kolmogorov-Smirnov) e a igualdade de variâncias (p=0,721 - Scheffe) foram testadas primeiramente. O teste de análise de variância demonstrou diferença significativa entre os grupos (p<0,001) e com o Holm-Sidak foi observada diferença significativa entre os grupos algodão e guta (p<0,05) e algodão e fita de politetrafluoetileno (p<0,05); não houve diferença significativa entre os grupos guta e fita de politatrafluoretileno (p>0,05), apesar dos valores da fita de politetrafluoetileno terem sido maiores. Considerando-se as limitações deste estudo in vitro, podemos concluir que tanto a guta-percha quanto a fita de politetrafluoretileno apresentaram menor formação de biofilme, não havendo diferença estatisticamente significativa entre os materiais. O algodão apresentou um nível de formação de biofilme significativamente maior que a fita de politetrafluoretileno e a guta percha. Diante disso, serão necessários novos estudos para confirmar as limitações que este tipo de material pode apresentar quando usado como material de preenchimento do acesso do parafuso da prótese sobre implante.

Distribution, growth, and mortality of sailfish (Istiophorus platypterus) larvae in the northern Gulf of Mexico

Ichthyoplankton surveys were conducted in shelf and slope waters of the northern Gulf of Mexico during the months of May–September in 2005 and 2006 to investigate the potential role of this region as spawning and nursery habitat of sailfish (Istiophorus platypterus). During the two-year study, 2426 sailfish larvae were collected, ranging in size from 2.0 to 24.3 mm standard length. Mean density for all neuston net collections (n=288) combined was 1.5 sailfish per 1000 m2, and maximum density was observed within frontal features created by hydrodynamic convergence (2.3 sailfish per 1000 m2). Sagittal otoliths were extracted from 1330 larvae, and otolith microstructure analysis indicated that the sailfish ranged in age from 4 to 24 days after hatching (mean=10.5 d, standard deviation [SD]=3.2 d). Instantaneous growth coefficients (g) among survey periods (n=5) ranged from 0.113 to 0.127, and growth peaked during July 2005 collections when density within frontal features was highest. Daily instantaneous mortality rates (Z) ranged from 0.228 to 0.381, and Z was indexed to instantaneous weight-specific growth (G) to assess stage-specific production potential of larval cohorts. Ratios of G to Z were greater than 1.0 for all but one cohort examined, indicating that cohorts were gaining biomass during the majority of months investigated. Stage-specific production potential, in combination with catch rates and densities of larvae, indicates that the Gulf of Mexico likely represents important spawning and nursery habitat for sailfish.

Identification of damping: Part 4, error analysis

In previous papers (S. Adhikari and J. Woodhouse 2001 Journal of Sound and Vibration 243, 43-61; 63-88; S. Adhikari and J. Woodhouse 2002 Journal of Sound and Vibration 251, 477-490) methods were proposed to obtain the coefficient matrix for a viscous damping model or a non-viscous damping model with an exponential relaxation function, from measured complex natural frequencies and modes. In all these works, it has been assumed that exact complex natural frequencies and complex modes are known. In reality, this will not be the case. The purpose of this paper is to analyze the sensitivity of the identified damping matrices to measurement errors. By using numerical and analytical studies it is shown that the proposed methods can indeed be expected to give useful results from moderately noisy data provided a correct damping model is selected for fitting. Indications are also given of what level of noise in the measured modal properties is needed to mask the true physical behaviour.