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Crystal structure and spectroscopic properties of Na2K6(VO)(2)(SO4)7  

DEFF Research Database (Denmark)

Red-brown crystals of a new mixed alkali oxo sulfato vanadium(V) compound Na2K6(VO)(2)(SO4)(7), suitable for X-ray determination, have been obtained from the catalytically important binary molten salt system M2S2O7-V2O5 (M = 80% K and 20% Na). By slow cooling of a mixture with the mole fraction X-V2O5 = 0.24 from 325 degreesC, i.e., just below the liquidus temperature, to the solidus temperature of around 300 degreesC, a dark reddish amorphous phase was obtained containing crystals of the earlier described V(V)-V(IV) mixed valence compound K-6(VO)(4)(SO4)(8) and Na2K6-(VO)(2)(SO4)(7) described here. This compound crystallizes in the tetragonal space group P4(3)2(1)2 (No. 96) with a = 9.540(3) Angstrom, c = 29.551(5) Angstrom at 20 degreesC and Z = 4. It contains a distorted VO6 octahedron with a short V-O bond of 1.552(6) Angstrom, a long one of 2.276(5) Angstrom trans to this, and four equatorial V-O bonds in the range 1.881(6)-1.960-(6) A. The deformation of the VO6 octahedron is less pronounced compared tothat of the known oxo sulfato V(V) compounds. Each VO3+ group is coordinated to five sulfate groups of which two are unidentately coordinated and three are bidentate bridging to neighboring VO3+ groups. The length of the S-O bonds in the S-O-V bridges of the two unidentately coordinated sulfato groups are 1.551(6) Angstrom and 1.568(6) Angstrom, respectively, which are unusually long compared to our earlier measurements of sulfate groups in other V(111), V(IV), and V(V) compounds.

Nielsen, Kurt; Eriksen, Kim Michael

2002-01-01

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AC conductivity and dielectric behavior of polyaniline/sodium metavenadate (PANI/NaVO3) composites  

International Nuclear Information System (INIS)

The conducting polyaniline/sodium metavenadate (PANI/NaVO3) composites were synthesized by single step in situ polymerization technique by placing finely grinded powder of NaVO3 during the polymerization of aniline. The formation of mixed phases of the polymer together with the conducting emeraldine salt phase was confirmed by spectroscopic techniques like FTIR. SEM images indicated a systematic morphological variation of particles aggregated in the composite matrix as compared to the pristine PANI. AC conductivity and dielectric behavior of these composites were investigated in the frequency range 50 Hz to 5 MHz. It is found that AC conductivity obeyed the power law index and the variation of conductivity with wt% of NaVO3 could be related to conductivity relaxation phenomenon. These composites have shown high dielectric constant, which is related to polarization. It is seen that both dielectric constant and dielectric loss decrease with increase in frequency. Variations in measured parameters of AC response with increasing frequency of these composites are found to follow systematic trends that are similar to those observed with temperature and doping.

2009-11-15

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The dependence of the oxidation state of vanadium on the oxygen pressure in melts of VO sub x Na sub 2 O-VO sub x and CaO-S sub 1 O sub 2 -VO sub x  

Energy Technology Data Exchange (ETDEWEB)

The oxidation state of vanadium has been determined as a function of oxygen pressure in pure VO{sub {ital x}} melts at 808{degrees}C to 1000{degrees}C, in Ha{sub 2}O-VO{sub {ital x}} melts with the initial molar rations Na{sub 2}O/V{sub 2}O{sub 5} = 0.2, 0.5, and 1.0 at 1000{degrees}C, and in CaO-SiO{sub 2}-VO{sub {ital x}} melts with the molar ratios CaO/SiO{sub 2} = 0.71, 1.00, and 1.36 at 1600{degrees}C. In the VO{sub {ital x}} melts, {ital x} is close to 2.5 in the range of oxygen pressure from {ital p}{sub O{sub 2}} = 10{sup {minus} 3} to 0.94 atm. The deviation, {delta} from stoichiometric V{sub 2}O{sub 5} ({delta} = 2.5 {minus} {ital x}) varies approximately proportionally to {ital p}{sub O{sub 2}}{sup {minus} 1/4}, indicting an equilibrium between V{sup 4 +} and V{sub 5 +} ions. In the Na{sub 2}O-VO{sub {ital x}} and CaO-SiO{sub 2}-VO{sub {ital x}} melts, {ital x} varies with log {ital p}{sub O{sub 2}} according to an S-shaped function, with {ital x} approaching 1.5 at low and 2.5 at high oxygen pressures. At given oxygen pressures, {ital x} increases with Na{sub 2}O or CaO content, respectively. Hence, these oxides stabilize the higher valent vanadium ions. For the CaO-SiO{sub 2}-VO{sub {ital x}} system, the determined {ital x-p}{sub O{sub 2}} dependence can be interpreted quantitatively in terms of V{sup 4 +}/V{sup 5 +} and V{sup 3+}/V{sup 4+} equilibria.

Mittelstadt, R.; Schwerdtfeger, K. (Inst. fur Allgemeine Metallurgie, Technische Universitat Clausthal, Robert Koch Str. 42, D-3392 Claustal-Zellerfeld (DE))

1990-02-01

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Neutron and X-ray diffraction studies on the high temperature phase of Mn3(VO4)2, the new isostructural compound NaMn4(VO4)3 and their mixed crystals NaxMn4.5?x/2(VO4)3 (0?x?1)  

International Nuclear Information System (INIS)

This paper presents a detailed structure analysis (combined Rietveld analysis of X-ray and neutron powder diffraction data as well as quantum mechanical calculations) of the high temperature phase of Mn3(VO4)2 (space group I4¯2d). Special attention is directed to the analysis of the local coordination around Mn2+ ions or vacancies within a stella quadrangula configuration of anions. Furthermore, the new compound NaMn4(VO4)3 is described as well as a range of mixed crystals between NaMn4(VO4)3 and Mn3(VO4)2 (described by the formula NaxMn4.5-x/2(VO4)3, 0?x?1) which were synthesized by a solid state route. All compounds were shown to be isostructural to the high temperature phase Mn3(VO4)2. - Graphical abstract: The crystal structure of the new compound NaMn4(VO4)3. Highlights: ? We present neutron and X-ray diffraction studies on high temperature-Mn3(VO4)2. ? Structural details of partly filled stellae quadrangulae positions are discussed. ? Refined structural parameters and theoretical calculations are compared. ? We investigate the mixed crystal system Mn3(VO4)2–NaMn4(VO4)3.

2012-10-01

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Hot corrosion behaviour of Fe-Al based intermetallic in molten NaVO3 salt  

International Nuclear Information System (INIS)

The hot corrosion of sprayed Fe-40 (at.%)Al intermetallic alloy with additions of boron and alumina whiskers in molten NaVO3 at 700 deg. C has been evaluated by potentiodynamic polarization curves and electrochemical impedance spectroscopy, EIS, techniques. For short exposure times, the corrosion mechanism under these conditions was observed to be controlled by an activation process, whereas for longer exposure times, the corrosion process was under diffusion control due to the growing of an Al2O3 oxide scale, which made the diffusion of both reducing and oxidizing species through the scale to the alloy or scale surfaces more difficult. Equivalent electric model used to simulate the EIS data showed that a finite length Warburg diffusion could properly characterize the diffusion process, which confirmed the formation of a compact corrosion product scales containing rich aluminium oxide. Thus, the corrosion process was under diffusion control of aggressive ions through the formed scale. The electrochemical study was complemented by scanning electronic microscopy characterization and micro chemical analysis.

2009-06-01

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AC conductivity and dielectric behavior of polyaniline/sodium metavenadate (PANI/NaVO{sub 3}) composites  

Energy Technology Data Exchange (ETDEWEB)

The conducting polyaniline/sodium metavenadate (PANI/NaVO{sub 3}) composites were synthesized by single step in situ polymerization technique by placing finely grinded powder of NaVO{sub 3} during the polymerization of aniline. The formation of mixed phases of the polymer together with the conducting emeraldine salt phase was confirmed by spectroscopic techniques like FTIR. SEM images indicated a systematic morphological variation of particles aggregated in the composite matrix as compared to the pristine PANI. AC conductivity and dielectric behavior of these composites were investigated in the frequency range 50 Hz to 5 MHz. It is found that AC conductivity obeyed the power law index and the variation of conductivity with wt% of NaVO{sub 3} could be related to conductivity relaxation phenomenon. These composites have shown high dielectric constant, which is related to polarization. It is seen that both dielectric constant and dielectric loss decrease with increase in frequency. Variations in measured parameters of AC response with increasing frequency of these composites are found to follow systematic trends that are similar to those observed with temperature and doping.

Machappa, T. [Department of Physics, Gulbarga University, Gulbarga 585 106, Karnataka (India); Ambika Prasad, M.V.N., E-mail: Prasad1_Amb@rediffmail.co [Department of Materials Science, Gulbarga University, Gulbarga 585 106, Karnataka (India)

2009-11-15

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On the soft magnetic properties of the compounds of the series Na(x)Mn(4.5-x/2)(VO4)3 and the magnetic structure of h.t.-Mn3(VO4)2 (x = 1).  

Science.gov (United States)

The high temperature phase of manganese vanadate h.t.-Mn3(VO4)2 and the solid solution with NaMn4(VO4)3 (Na(x)Mn(4.5-x/2)(VO4)3) were shown to order ferrimagnetically below 55 K for x dodecahedron). This coordination can be understood as two penetrating oxygen coordination tetrahedra, one showing shorter and one showing longer Mn-O distances. The magnetic moments of the Mn(2+) ions on the 4b site are aligned parallel to the ones on 8d and antiparallel to the ones on 8c, being in good agreement with the GKA rules. The local exchange interactions between the Mn(2+) ions on the 4b to those on the 8c/8d sites are likely to be similar in strength and competitive and therefore probably contribute to the soft magnetic properties. PMID:23380831

Clemens, Oliver; Wright, Adrian J; Knight, Kevin S; Slater, Peter R

2013-06-14

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Cinética do consumo de oxigênio e tempo limite na vvo2max: comparação entre homens e mulheres Oxygen uptake kinetics and threshold time at the vVO2max: tomparison between men and women  

Directory of Open Access Journals (Sweden)

Full Text Available Foi investigada a influência do gênero no tempo limite (Tlim e na cinética do VO2 durante corrida na velocidade associada ao VO2max (vVO2max em nove homens e nove mulheres, todos adultos, jovens e sedentários, com idades entre 20 e 30 anos. Homens e mulheres realizaram dois testes em esteira rolante, sendo um teste incremental para determinar VO2max (42,66 ± 4,50 vs. 32,92 ± 6,03mL.kg-1.min-1 e vVO2max (13.2 ± 1.5 vs. 10,3 ± 2,0km.h-1, respectivamente. Um segundo teste com carga constante na vVO2max até a exaustão. O Tlim e a cinética do VO2 foram determinados. Não houve diferença significante entre homens e mulheres para constante de tempo (? (35,76 ± 21,03 vs. 36,5 ± 6,21s, respectivamente; P = 0,29; Tlim (308 ± 84,3 vs. 282,11 ± 57,19s, respectivamente; P = 0,68, tempo para atingir o VO2max (TAVO2max (164,48 ± 96,73 vs. 167,88 ± 28,59s, respectivamente; P = 0,29, tempo para atingir o VO2max em percentual do Tlim (%Tlim (50,24 ± 16,93 vs. 62,63 ± 16,60%, respectivamente; P = 0,19, tempo mantido no VO2max (TMVO2max (144,08 ± 42,55 vs. 114,23 ± 76,96s, respectivamente; P = 0,13. Estes resultados sugerem que a cinética do VO2 e o Tlim são similares entre homens e mulheres sedentários na vVO2max.The aim of this study was to investigate the influence of gender on Tthre and VO2 response during running exercise performed at vVO2max. Therefore, eighteen untrained individuals (9 male and 9 female with normal weight and aged between 20 - 30 years (VO2max = 42.66 ± 4.50 vs 32.92 ± 6.03 mL.kg-1.min-1 and vVO2max = 13.2 ± 1.5 vs 10.3 ± 2.0 km.h-1, for male and female, respectively were assessed. Subjects performed two exercise tests on treadmill. First one was an incremental test to determine VO2max, velocity at VO2max (vVO2max and second test was performed at steady velocity - vVO2max - until exhaustion. The threshold time (Tthre and VO2 kinetics response was determined. No significant differences were observed between men and women for time constant (? (35.76 ± 21.03 vs 36.5 ± 6.21s, respectively; P = 0.29; Tthre (308 ± 84.3 vs 282.11 ± 57.19s, respectively; P = 0.68, time to achieve VO2max (TAVO2max (164.48 ± 96.73 vs 167.88 ± 28.59s, respectively; P = 0.29, time to achieve VO2max in Tthre percentage (%Tthre (50.24 ± 16.93 vs 62.63 ± 16.60%, respectively; P = 0.19; time maintained at VO2max (TMVO2max (144.08 ± 42.55 vs 114.23 ± 76.96s, respectively; P = 0.13. These results suggest that the VO2 kinetics response and Tthre is similar between untrained men and women at the vVO2max.

Paulo Henrique Silva Marques de Azevedo

2010-08-01

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VO2 pico e inclinação VE/VCO2 na era dos betabloqueadores na insuficiência cardíaca: uma experiência brasileira Peak VO2 and VE/VCO2 slope in betablockers era in patients with heart failure: a brazilian experience  

Directory of Open Access Journals (Sweden)

Full Text Available FUNDAMENTO: Estudos têm demonstrado que o consumo de oxigênio de pico (VO2 pico e a inclinação VE/VCO2 são preditores de sobrevida em pacientes com insuficiência cardíaca (IC. Entretanto, com a adição do betabloqueador no tratamento da IC, os valores de prognóstico do VO2 pico e da Inclinação VE/VCO2 não estão totalmente estabelecidos. OBJETIVO: Avaliar o efeito dos betabloqueadores no valor de prognóstico do VO2 pico e da inclinação VE/VCO2 em pacientes com IC. MÉTODOS: Estudamos 391 pacientes com insuficiência cardíaca, com idade de 49 ± 14 anos e fração de ejeção do ventrículo esquerdo de 38 ± 10%. Total de pacientes que usavam (grupo I - GI e não usavam (grupo II - GII betabloqueadores: 229 e 162, respectivamente. Todos os pacientes foram submetidos a teste de esforço cardiopulmonar, em esteira, usando o protocolo de Naughton. RESULTADOS: O VO2 pico 16 ml.kg-1.min-1 categorizaram pacientes com melhor prognóstico em médio prazo. A faixa do VO2 pico entre > 10 e BACKGROUND: Studies have demonstrated that peak oxygen consumption (peak VO2 and the VE/VCO2 slope are predictors of survival in patients with heart failure (HF. However, with the advent of betablockers in the treatment of HF, the prognostic values of peak VO2 and VE/VCO2 slope have not been fully established. OBJECTIVE: To evaluate the effect of betablocker use on the prognostic value of peak VO2 and VE/VCO2 slope in patients with HF. METHODS: We studied 391 patients with heart failure, aged 49 ± 14 years and presenting a left ventricular ejection fraction of 38 ± 10%. The total number of patients that used (Group I - GI or did not use (Group II - GII betablockers was 229 and 162, respectively. All patients were submitted to a cardiopulmonary stress test on a treadmill, using the Naughton protocol. RESULTS: A peak VO2 16 ml.kg-1.min-1 categorizes patients with a better mid-term prognosis. Peak VO2 values between > 10 and < 16 ml.kg-1.min-1 indicated moderate risk for cardiac event in four years of follow up. The betablocker use significantly reduced the VE/VCO2 slope in patients with HF. The prognostic value of the VE/VCO2 slope < 34 in the group using betablocker can reflect the impact of the drug on this cardiorespiratory variable. CONCLUSION: A low peak VO2 and an elevated VE/VCO2 slope are strong and independent predictors of cardiac events in HF. Thus, both variables remain important survival predictors in patients with HF, especially at the age of betablockers.

Guilherme Veiga Guimarães

2008-07-01

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VO2 pico e inclinação VE/VCO2 na era dos betabloqueadores na insuficiência cardíaca: uma experiência brasileira / Peak VO2 and VE/VCO2 slope in betablockers era in patients with heart failure: a brazilian experience  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese FUNDAMENTO: Estudos têm demonstrado que o consumo de oxigênio de pico (VO2 pico) e a inclinação VE/VCO2 são preditores de sobrevida em pacientes com insuficiência cardíaca (IC). Entretanto, com a adição do betabloqueador no tratamento da IC, os valores de prognóstico do VO2 pico e da Inclinação VE/V [...] CO2 não estão totalmente estabelecidos. OBJETIVO: Avaliar o efeito dos betabloqueadores no valor de prognóstico do VO2 pico e da inclinação VE/VCO2 em pacientes com IC. MÉTODOS: Estudamos 391 pacientes com insuficiência cardíaca, com idade de 49 ± 14 anos e fração de ejeção do ventrículo esquerdo de 38 ± 10%. Total de pacientes que usavam (grupo I - GI) e não usavam (grupo II - GII) betabloqueadores: 229 e 162, respectivamente. Todos os pacientes foram submetidos a teste de esforço cardiopulmonar, em esteira, usando o protocolo de Naughton. RESULTADOS: O VO2 pico 16 ml.kg-1.min-1 categorizaram pacientes com melhor prognóstico em médio prazo. A faixa do VO2 pico entre > 10 e Abstract in english BACKGROUND: Studies have demonstrated that peak oxygen consumption (peak VO2) and the VE/VCO2 slope are predictors of survival in patients with heart failure (HF). However, with the advent of betablockers in the treatment of HF, the prognostic values of peak VO2 and VE/VCO2 slope have not been fully [...] established. OBJECTIVE: To evaluate the effect of betablocker use on the prognostic value of peak VO2 and VE/VCO2 slope in patients with HF. METHODS: We studied 391 patients with heart failure, aged 49 ± 14 years and presenting a left ventricular ejection fraction of 38 ± 10%. The total number of patients that used (Group I - GI) or did not use (Group II - GII) betablockers was 229 and 162, respectively. All patients were submitted to a cardiopulmonary stress test on a treadmill, using the Naughton protocol. RESULTS: A peak VO2 16 ml.kg-1.min-1 categorizes patients with a better mid-term prognosis. Peak VO2 values between > 10 and

Guimarães, Guilherme Veiga; Silva, Mário Sérgio Vaz da; d' Avila, Veridiana Moraes; Ferreira, Silvia Moreira Ayub; Silva, Christiano Pereira; Bocchi, Edimar Alcides.

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DISTANCE LEARNING IN SLOVAKIA AND IN THE CHOSEN COUNTRIES OF EUROPEAN UNION / Dištan?né vzdelávanie na Slovensku a vo vybraných krajinách EÚ  

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Full Text Available Authors refer to the theme of distance learning and its application in Slovak republic and in the chosen countries of European Union. In the article there is a brief history of distance learning usage.Autori sa v príspevku venujú problematike využitia dištan?ného vzdelávania ako na Slovensku, tak aj vo vybraných krajinách Európskej únie. V príspevku uvádzajú stru?ný historický preh?ad používania dištan?ného vzdelávania a jednej z jeho foriem - e-learningu.

Lan?ari? Drahoš

2008-10-01

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Resonant Soft X-Ray Emission Spectroscopy of V2O3, VO2 and NaV2O5  

Science.gov (United States)

Resonant soft X-ray emission (RSXE) spectra of V2O3, VO2 and NaV2O5 were recorded for a series of excitation energies at resonances of the V L- and O K-absorption band. The V L- and O K-emission in these vanadium oxide bands possess considerable overlap. By resonant excitation we can tune the energy to the absorption thresholds, thereby eliminating this overlap. Hereby we obtain the V 3d and O 2p projected density-of-states of the valence band. Resonant inelastic X-ray scattering (RIXS) is found to be weak in V2O3, which we explain as being due to its metallic character at room temperature. Vanadium dioxide (VO2), semiconducting at room temperature, shows considerable RIXS features only at the O K-emission band. Distinct RIXS structures are visible in the RSXE spectra of the insulator NaV2O5. In the emission spectra excited at the V L-thresholds of this ternary vanadium oxide, dd-excitations of the V dxy subband at an energy loss of -1.7 eV are observed. Our observation, that RIXS is stronger for insulators than for metals, should be taken advantage of for studying insulator-to-metal transitions in vanadium compounds in the future.

Schmitt, T.; Duda, L.-C.; Augustsson, A.; Guo, J.-H.; Nordgren, J.; Downes, J. E.; McGuinness, C.; Smith, K. E.; Dhalenne, G.; Revcolevschi, A.; Klemm, M.; Horn, S.

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Resonant soft x-ray emission spectroscopy of V2O3, VO2 and NaV2O5  

International Nuclear Information System (INIS)

Resonant soft X-ray emission (RSXE) spectra of V2O3, VO2 and NaV2O5 were recorded for a series of excitation energies at resonances of the V L- and O K-absorption band. The V L- and O K-emission in these vanadium oxide bands possess considerable overlap. By resonant excitation we can tune the energy to the absorption thresholds, thereby eliminating this overlap. Hereby we obtain the V 3d and O 2p projected density-of-states of the valence band. Resonant inelastic X-ray scattering (RIXS) is found to be weak in V2O3, which we explain as being due to its metallic character at room temperature. Vanadium dioxide (VO2), semiconducting at room temperature, shows considerable RIXS features only at the O K-emission band. Distinct RIXS structures are visible in the RSXE spectra of the insulator NaV2O5. In the emission spectra excited at the V L-thresholds of this ternary vanadium oxide, dexcitations of the V dxy subband at an energy loss of -1:7 eV are observed. Our observation, that RIXS is stronger for insulators than for metals, should be taken advantage of for studying insulator-to-metal transitions in vanadium compounds in the future

2004-01-01

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A detailed study of the dehydration process in synthetic strelkinite, Na[(UO{sub 2})(VO{sub 4})] . nH{sub 2}O (n = 0, 1, 2)  

Energy Technology Data Exchange (ETDEWEB)

Synthetic strelkinite Na[(UO{sub 2})(VO{sub 4})] . nH{sub 2}O (n = 0, 1, 2) was systematically investigated by single crystal X-ray diffraction and thermoanalytical methods. The anhydrous form and two hydrates were isolated as single crystals and the structures of these phases solved: Na[(UO{sub 2})(VO{sub 4})], monoclinic, P2{sub 1}/c, a = 6.0205(1) Aa, b = 8.3365(1) Aa, c = 10.4164(2) Aa, {beta} = 100.466(2) , V = 514.10(1) Aa{sup 3}, R{sub 1} = 0.0337; Na[(UO{sub 2})(VO{sub 4})] . H{sub 2}O, monoclinic, P2{sub 1}/c, a = 7.722(2) Aa, b = 8.512(1) Aa, c = 10.480(4) Aa, {beta} = 113.18(3) , V = 633.3(3) Aa{sup 3}, R{sub 1} = 0.1658; Na[(UO{sub 2})(VO{sub 4})] . 2 H{sub 2}O, monoclinic, P2{sub 1}/n, a = 16.2399(5) Aa, b = 8.2844(2) Aa, c = 10.5011(2) Aa, {beta} = 97.644(2) , V = 1400.24(6) Aa{sup 3}, R{sub 1} = 0.0776. A possible mechanism of the structural transformation processes during dehydration is proposed based on the structures of the anhydrous phase and the hydrates. (orig.)

Suleimanov, Evgeny V.; Somov, Nikolay V.; Chuprunov, Evgeny V.; Mayatskikh, Ekaterina F. [Nizhny Novgorod State Univ. (Russian Federation); Depmeier, Wulf [Kiel Univ. (Germany). Inst. fuer Geowissenschaften; Alekseev, Evgeny V. [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Energie- und Klimaforschung (IEK-6)

2012-11-01

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Predição da potência aeróbia (VO2máx) de crianças e adolescentes em teste incremental na esteira rolante / Prediction of aerobic power (VO2max) of children and adolescents during an incremental treadmill test  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese O consumo máximo de oxigênio (VO2máx) é a quantidade máxima de energia que pode ser produzida pelo metabolismo aeróbio em determinada unidade de tempo, podendo ser determinado direta ou indiretamente através de equações preditivas. O objetivo deste trabalho foi elaborar uma equação preditiva específ [...] ica para determinar o VO2máx de meninos de 10 a 16 anos. Quarenta e dois meninos realizaram teste ergoespirométrico de corrida em esteira rolante com velocidade inicial de 9 km/h até exaustão voluntária. Através da regressão linear múltipla foi possível desenvolver a seguinte equação para a determinação indireta do VO2máx: VO2máx (ml/min) = -1574,06 + (141,38 x Vpico) + (48,34 * Massa corporal), com erro padrão de estimativa = 191,5 ml/min (4,10 ml/kg/min) e o coeficiente de determinação = 0,934. Sugerimos que esta é uma fórmula adequada para predizer o VO2máx para esta população. Abstract in english The maximal oxygen uptake (VO2max) is the maximal quantity of energy that can be produced by the aerobic metabolism in certain time unity. It can be determined direct or indirectly by predictive equations. The objective of this study was to make a specific predictive equation to determine the VO2max [...] from boys aged 10-16 years-old. Forty-two boys underwent a treadmill running ergospirometric test, with the initial velocity set at 9 km/h, until voluntary exhaustion. By the multiple linear regression was possible to develop the following equation for the indirect determination of the VO2max: VO2max (ml/min) = -1574.06 + (141.38 x Vpeak) + (48.34 * Body mass), with standard error of estimate = 191.5 ml/min (4.10 ml/kg/min) and coefficient of determination = 0.934. We suggest that this formula is appropriate to predict VO2max for this population.

Fabiana Andrade, Machado; Benedito Sérgio, Denadai.

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VoIP Security  

Digital Repository Infrastructure Vision for European Research (DRIVER)

VOIP or Voice Over Internet Protocol is a common term for phone service over IP based networks. There are much information about VoIP and some of how VoIP can be secured. There is however no standard for VoIP and no general solution for VoIP Security. The security in VoIP systems today are often non existing or in best case weak and often based on proprietary solutions. This master thesis investigates threats to VoIP system and describes existing alternatives for securing VoIP as it is today....

Fontanini, Piero

2008-01-01

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PRETRATAMIENTOS DE LA CELULOSA Y BIOMASA PARA LA SACARIFICACIÓN  

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Full Text Available La biomasa celulósica se ha vuelto un producto interesante para ser aprovechada como materia prima en la fabricación de biocombustibles, especialmente el etanol. El paso crítico en su conversión a etanol, implica la degradación de los polisacáridos a azúcares fermentables, en un proceso denominado sacarificación. La celulosa, el componente principal de la biomasa, es un polisacárido de difícil degradación en condiciones de tratamiento moderadas. Las investigaciones más recientes en el campo de los biorecursos, se han enfocado hacia el desarrollo de ciertos pretratamientos de la biomasa o la celulosa bajo los cuales se logra que estos materiales sean de más fácil degradación a azúcares fermentables. El presente artículo resume los resultados más sobresalientes, sin ser exhaustivos, de los pretaratimentos de la celulosa y la biomasa para su conversión a productos fermentables por la ruta etanólica.

ANDERSON GUARNIZO FRANCO

2009-01-01

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Synthesis, X-ray crystal structure, and EPR study of [Na(H 2O) 2] 2[VO(H 2O) 5][SiW 12O 40]·4H 2O  

Science.gov (United States)

The vanadyl salt [Na(H 2O) 2] 2[VO(H 2O) 5][SiW 12O 40]·4H 2O has been synthesized in mild conditions by cationic exchanges from dodecasilicotungstic acid. Structural determination and EPR study have been achieved on single crystals. They are tetragonal, space group P4/ n with a=14.7759(1), c=10.4709(2) Å, V=2286(1) Å 3 and Z=2. A three-dimensional framework built from Keggin anions [SiW 12O 40] 4- linked by sodium cations in (110) and ( 1 1¯0 ) planes generates channels along the c axis in which are localized aquo vanadyl complexes [VO(H 2O) 5] 2+ and water molecules. Single crystal EPR spectra show eight hyperfine lines of the vanadium atom ( I=7/2) which are split into 1:2:1 pattern when the magnetic field is parallel to the c axis. The triplet pattern may be attributed to weak dipolar interactions between the nearest-neighbor vanadium atoms which are 10.47 Å apart in the infinite chain. A ring model was used to simulate the spectrum, and a very small antiferromagnetic exchange interaction was determined accurately . The EPR parameters determined are gx= gy=1.980, gz=1.9336, Ax= Ay=0.0072 cm -1, and Az=0.01805 cm -1, J=-0.00025 cm -1.

Tézé, André; Marchal-Roch, Catherine; So, Hyunsoo; Fournier, Michel; Hervé, Gilbert

2001-03-01

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A three-dimensional structure of vanadium malonate: synthesis, characterization and X-ray structure of [Na 2VO(C 3H 2O 4) 2(H 2O) 2] n  

Science.gov (United States)

A three-dimensional structure [Na 2VO(C 3H 2O 4) 2(H 2O) 2] n was synthesized from the aqueous solution of V 2O 5, malonic acid and HCl. The compound crystallizes in orthorhombic system, space group C222 1 with a=7.2472(9) Å, b=15.9465(2) Å, c=10.3672(1) Å, V=1198.1(3) Å 3, Z=4, and R1=0.0242 for 1027 observed reflections. Single crystal X-ray diffraction reveals that the vanadium atom is coordinated by six oxygen atoms in an octahedral geometry. It is more interesting that one sodium ion is coordinated by two ? 3-OH 2 and six carboxyl oxygen atoms, which exhibits an unusual coordination mode. The malonato-vanadium units are linked up by two sodium ions to an extended network

Zhang, Quan-Zheng; Lu, Can-Zhong; Yang, Wen-Bin; Chen, Shu-Mei; Yu, Ya-Qin

2004-05-01

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ESTIMACIÓN DE BIOMASA AÉREA EN CULTIVOS CON SENSORES REMOTOS  

Directory of Open Access Journals (Sweden)

Full Text Available Para estimar la producción de biomasa aérea en cultivos utilizando sensores remotos se realizaron análisis de la producción de biomasa e información espectral en cinco cultivos medidos en campo, durante una campaña de muestreo en el Valle del Yaqui, Sonora. La información espectral fue procesada hasta la obtención del índice de vegetación iso-suelo (IVIS. Los análisis multitemporales muestran un comportamiento similar entre el desarrollo de los cultivos y el valor del IVIS, por lo que se obtuvo una relación lineal entre ellos. De manera similar fueron analizados el índice de cosecha y su relación con el IVIS. Los resultados mostraron que el IVIS es un índice adecuado para la estimación de biomasa y rendimiento en cultivos.

Fermu00EDn Pascual-Ramu00EDrez

2012-01-01

 
 
 
 
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ECUACIONES ALOMÉTRICAS PARA ESTIMAR BIOMASA Y CARBONO EN Quercus magnoliaefolia  

Directory of Open Access Journals (Sweden)

Full Text Available En el ejido El Zapote de la Reserva de la Biosfera "Sierra de Huautla", estado de Morelos, México, se seleccionaron doce árboles de Quercus magnoliaefolia Née y se determinó su biomasa en la parte aérea. El modelo alométrico quedó expresado como: B = 0.0345 * DAP2.9334 en donde B es la biomasa (kg y DAP es el diámetro a la altura del pecho (cm, con un coeficiente de determinación (R2= 0.98; P<0.001. Adicionalmente, se estimó la biomasa mediante una regresión lineal múltiple que consideró el área basal (AB, la densidad específica de la madera (DEM y la altura de los árboles (H. Una alta proporción de la varianza de la biomasa fue explicada solamente por el área basal. La DEM y H no incrementaron significativamente la precisión de los modelos. El porcentaje promedio de carbono en los árboles de Q. magnoliaefolia fue de 47.14 con valores de 46.29 % para el fuste, 46.83 % para las ramas y 48.31 % para el follaje. La proporción promedio de los componentes de la especie estudiada fue de 2.5 % para el fuste, 27.8 % para las ramas y 9.6 % para el follaje.

Jesu00FAs D. Gu00F3mez-Du00EDaz

2011-01-01

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EFECTO DEL CARBONATO DE POTASIO EN LA EVOLUCIÓN DE LOS GRUPOS FUNCIONALES DE LOS BIOCRUDOS DE CONVERSIÓN HIDROTÉRMICA DE BIOMASA LIGNOCELULÓSICA ALREDEDOR DEL PUNTO CRÍTICO DEL AGUA / POTASSIUM CARBONATE EFFECT ON BIOCRUDE FUNCTIONAL GROUPS EVOLVING FROM LIGNOCELLULOSIC BIOMASS UNDERGOING HYDROTHERMAL CONVERSION CLOSE TO THE CRITICAL POINT OF WATER / EFEITO DO CARBONATO DE POTÁSSIO NA FORMAÇÃO DOS GRUPOS FUNCIONAIS DOS BIOPETRÓLEOS OBTIDOS POR CONVERSÃO HIDROTÉRMICA DE BIOMASSA LENHOCELULÓSICA PRÓXIMO DO PONTO CRÍTICO DA ÁGUA  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in portuguese Um tipo de biomassa pobre em lenhina, do género Pennisetum, foi submetido ao processo de conversão hidrotérmica na presença de carbonato de potássio como catalisador. As reacções foram conduzidas em condições próximas do ponto crítico da água. Os produtos de reacção não aquosos (biopetróleo) foram s [...] eparados por decantação e analisados por espectroscopia de infravermelho. Os biopetróleos obtidos contêm compostos com funcionalidades aromáticas, olefínicas, hidroxiladas, éteres e, no caso do biopetróleo obtido sob condição subcrítica, funções carbonilo. A fracção gasosa e a quantidade de biopetróleo aumentam na presença de carbonato de potássio. Abstract in spanish Un tipo de biomasa pobre en lignina, del género Pennisetum, fue sometida al proceso de conversión hidrotérmica en presencia de carbonato de potasio como catalizador. Las reacciones se llevaron a cabo en ambientes cercanos al punto crítico del agua. Los productos de reacción no acuosos (biocrudo) se [...] separaron por decantación y se analizaron por espectrometría infrarroja. Los biocrudos obtenidos contienen compuestos con funcionalidades aromáticas, olefínicas, hidroxiladas, éteres, y para el caso del biocrudo obtenido bajo la condición subcrítica funciones carbonilo. La fracción gaseosa y el biocrudo aumentan en presencia del carbonato de potasio. Abstract in english A type of poor-lignin biomass (Pennisetum sp.) was hydrothermally converted in the presence of potassium carbonate as catalyst. The reactions were carried out close to the critical point of the water. The non-aqueous (biocrude) reaction products were separated by decantation and were analyzed by inf [...] rared spectrometry. The biocrude products so obtained contained compounds having aromatic, olephinic, hydroxylated and ether functionalities; sub-critical biocrude had carbonyl functions. The gaseous and biocrude fractions increased in the presence of potassium carbonate.

Alejandro A, Castro; Andrés, Anzola; Iván, Cagua; Luis I, Rodríguez; Yazmín, Agámez; Orlando, Hernández; José de J, Díaz.

23

Enriquecimiento de biomasa de levadura con micronutrientes esenciales  

Directory of Open Access Journals (Sweden)

Full Text Available Se estudian las potencialidades de enriquecimiento de la biomasa de levaduras GRAS a partir de medios de cultivo ricos en micronutrientes de interés, básicamente, cromo y selenio. La levadura tiene la propiedad de incorporar a su biomasa cantidades elevadas de componentes del medio aún cuando no se utilicen metabólicamente. Las dietas diarias actuales, incluso en los países desarrollados, son regularmente deficitarias en Se y Cr, elementos esenciales para el comportamiento metabólico estable. El Cr es un componente del Factor de Tolerancia a la Glucosa (GTF que facilita las funciones de la insulina. Por medio de las técnicas del batch incrementado se puede llegar a concentraciones de Cr y Se de hasta 1000 ppm. Los productos puede ser empleado en la prevención y profilaxis de la Diabetes mellitus, en su variante senil, en tanto que el Se juega un rol antioxidante primordial.

Miguel A. Otero

2008-01-01

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Generación eléctrica a partir de biomasa en una destilería diversificada  

Directory of Open Access Journals (Sweden)

Full Text Available La instalación de una destilería de etanol diversificada, como una vía de generación de energía renovable integrada a la producción de alimentos, muestra relevantes ventajas en comparación con las destilerías tradicionales. En particular, para el caso de una planta de producción de etanol de este tipo, de 1200 hL/d, la generación de electricidad, con la biomasa que esta industria genera, alcanza el valor de 15,92 MW de potencia eléctrica excedente para el Sistema Electroenergético Nacional. Constituye un polo de desarrollo económico, social y estratégico, atendiendo al concepto de autosustentación dado por el Protocolo de Kyoto. El concepto de diversificación alcanza a todo el sector productivo. En las destilerías tradicionales la diversificación es incipiente. La biomasa constituye una de las principales fuentes de generación de energía limpia y barata, pasando de ser un subproducto, a un eslabón fundamental del proceso productivo.

Pedro A. Rodru00EDguez

2007-01-01

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Cambios en la biomasa de raíces y micorrizas arbusculares en cultivos itinerantes del Amazonas Venezolano / Changes in root biomass and arbuscular mycorrhizae in shifting crops of the Venezuelan Amazon / Mudanças na biomassa de raízes e micorrizas arbusculares em cultivos itinerantes do Amazonas Venezolano  

Scientific Electronic Library Online (English)

Full Text Available SciELO Venezuela | Language: Spanish Abstract in portuguese A designação de biomassa a produção de raízes finas em plantas terrestres e a formação de associações simbióticas micorrízico arbusculares (MA) constituem adaptações de importância em condições de baixa fertilidade. Em um mosaico de agricultura itinerante, conformado por duas áreas de cultivo (parce [...] las), duas áreas de 2-4 e de 4-6 anos de abandono depois de ser cultivadas (pousios) e uma área de bosque chuvoso pouco perturbado, se compararam a biomassa de raízes finas (diâmetro Abstract in spanish La asignación de biomasa a la producción de raíces finas en plantas terrestres y la formación de asociaciones simbióticas micorrízico arbusculares (MA) constituyen de importantes adaptaciones en condiciones de baja fertilidad. En un mosaico de agricultura itinerante, conformado por dos áreas de cult [...] ivo (conucos), dos áreas de 2-4 y de 4-6 años de abandono después de ser cultivadas (barbechos) y un área de bosque lluvioso poco perturbado, se compararon la biomasa de raíces finas (diámetro Abstract in english The allocation of biomass to the production of fine roots in terrestrial plants and arbuscular mycorrhizal (AM) symbiotic partnerships are important adaptations under conditions of low fertility. In a mosaic of shifting cultivation, comprising two growing areas (conucos) and two 2-4 and 4-6 years de [...] serted areas after being cultivated (fallow), and a little disturbed rain forest area, differences in fine root biomass (diameter

Carolina, Kalinhoff; Alicia, Cáceres; Leonardo, Lugo.

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Cuantificación de ácidos grasos a partir de biomasa microalgal  

Directory of Open Access Journals (Sweden)

Full Text Available Long chain polyunsaturated fatty acids are focusing the interest of researchers as long as analytical techniques are being improved. The Lepage and Roy direct transesterification method is being widely used to measure fatty acid content of microalgae which are proposed as potential sources of these products. In this paper, the physical state of the biomass to be analyzed is studied. Comparison has been stated between lyophilized biomass and wet biomass just harvested. Furthermore, the amount of sample and the number of methyl ester extractions have also been studied. From the statistical analysis carried out, wet biomass to fatty acid determination and the adequate range of sample are proposed. Three methyl ester extractions improve the resolution of GC analysis.

El interés creciente por los ácidos grasos poliinsaturados de cadena larga viene favorecido por la mejora de las técnicas de análisis. La metodología de transesterificación directa propuesta por Lepage y Roy está siendo ampliamente utilizada para la determinación del contenido en ácidos grasos de microalgas, consideradas como potenciales fuentes de estos productos. En el presente trabajo, se analiza la influencia del estado físico de la biomasa analizada, seca, normalmente por liofilización, o húmeda recién cosechada del cultivo. Asimismo, se analiza el efecto de la cantidad de biomasa empleada y del número de extracciones de los esteres metílicos obtenidos. Del estudio estadístico realizado se pone de manifiesto la importancia del estado físico de la muestra, aconsejándose el uso de biomasa directamente obtenida del cultivo. Se proponen los intervalos de cantidad de biomasa para metilación, así como la conveniencia de realizar tres extracciones previas a la inyección en el cromatógrafo, que favorece la resolución del análisis.

García Sánchez, J. L.

1993-12-01

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La biomasa en la producción de electricidad en España  

Directory of Open Access Journals (Sweden)

Full Text Available The generation of electricity using biomass began in Spain in the mid-1990s. In this paper, we examine the combustible products used in the generation of this type of electricity, the legal framework protecting its production, the evolution of the installed power and its territorial distribution, the environmental impact of biomass as a renewable energy, the energy policy supporting this technology and the problems for the development of biomass as a energy source in Spain.

[es] La producción de electricidad con biomasa comienza su desarrollo en España a mediados de los años noventa. En este artículo se analizan los productos combustibles de biomasa destinados a la generación de electricidad, el marco legal que protege esta producción, la evolución de la potencia instalada y su distribución territorial, el impacto ambiental de la biomasa como energía renovable, la política energética de apoyo a esta tecnología, y los problemas para el desarrollo de la biomasa como fuente energética en España. [fr] La biomasse dans la production d´électricité en Espagne. La production d'électricité avec biomasse commence son développement en Espagne vers le milieu des années quatre-vingt-dix. Dans cet article nous analysons les produits combustibles de biomasse destines à engendrer de l'électricité, le cadre légal qui protégé cette production, l'évolution de la puissance installée, la répercussion de l'environnement de la biomasse comme énergie renouvelable, la politique énergétique de soutien à cette technologie et les problèmes pour le développement de la biomasse comme source énergétique en Espagne.

Espejo Marín, Cayetano

2005-06-01

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Estudio técnico y económico para la sustitución del gasóleo por biomasa térmica en edificios urbanos  

Digital Repository Infrastructure Vision for European Research (DRIVER)

La finalidad del proyecto consiste en realizar la sustitución de calderas de gasóleo por calderas de biomasa para suministrar calefacción a edificios urbanos. En primer lugar, se ha hecho un estudio de la demanda calorífica de los edificios, y posteriormente se ha estudiado el ciclo completo de la biomasa, incluyendo el suministro y tipo de biomasa, dimensiones de los equipos y espacios necesarios para la instalación. Después de estudiar la viabilidad técnica y económica, podemos conc...

2012-01-01

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Remoción y recuperación de cromo (III de soluciones acuosas por biomasa de sorgo  

Directory of Open Access Journals (Sweden)

Full Text Available En este trabajo se investigó la capacidad de la biomasa de ?desecho de sorgo? para remover y recuperar iones de cromo(III de soluciones acuosas, tanto en sistemas en lote como en flujo continuo. Los resultados muestran que los iones de cromo(III se unen preferentemente a la biomasa de sorgo a pH 4.5-5, después de 15 minutos de contacto, con una capacidad de saturación de aproximadamente 10 mg/g de biomasa seca. La biomasa inmovilizada fue capaz de remover y recuperar eficientemente iones de cromo(III en flujo continuo y en varios ciclos de remoción-recuperación.

I. Cano Rodru00EDguez

2002-01-01

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VoWiFi Roaming  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Freedom is human’s natural instinct, which was limited by Ethernet and Fixed Telephony Era. With the emergence of new technologies like wireless fidelity (WiFi) and voice over IP (VoIP) humans once again have freedom of movement; which at the very same time provides enough reasons to change the market dynamics of communication industry. The buzz of Voice over WiFi (VoWiFi) in recent years indicates that VoWiFi is shaping up as the next big challenge to traditional telephony, not only due to...

Muhammad Ali, Syed

2006-01-01

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Accessing the VO with Python  

Science.gov (United States)

We introduce two products for accessing the VO from Python: PyVO and VOClient. PyVO is built on the widely-used Astropy package and is well suited for integrating automated access to astronomical data into highly customizable scripts and applications for data analysis in Python. VOClient is built on a collection of C-libraries and is well suited for integrating with multi-language analysis packages. It also provides a framework for integrating legacy software into the Python environment. In this demo, we will run through several examples demonstrate basic data discovery and retrieval of data. This includes finding archives containing data of interest (VO registry), retrieving datasets (SIA, SSA), and exploring (Cone Search, SLAP). VOClient features some extended capabilities including the ability to communicate to other desktop applications from a script using the SAMP protocol.

Plante, R.; Fitzpatrick, M.; Graham, M.; Tody, D.; Young, W.

2014-05-01

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Synthesis, characterization and catalytic activity of two novel cis-dioxovanadium(v) complexes: [VO2(L)] and [VO2(Hlox)  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Dois novos complexos [VO2(L)] e [VO2(HLox)] foram sintetizados e caracterizados por espectroscopias no IV, UV-Vis e RMN, voltametria cíclica, análise elementar e difração de raios X. A síntese do ligante inédito H2Lox também é descrita. Os complexos 1 e 2 foram obtidos pela reação de [VO(acac)2] com [...] os respectivos ligantes HL e H2Lox. Alternativamente, 2 foi preparado a partir da reação de HL com [VO(acac)2] na presença de hidroxilamina, e através da reação de 1 com hidroxilamina. Dados cristalográficos mostram que 1 e 2 apresentam estruturas moleculares similares, onde o centro de vanádio(V) cis-dioxo encontra-se coordenado em um ambiente octaédrico distorcido formado pelos ligantes L- e HLox-, respectivamente. A atividade catalítica destes compostos foi avaliada na oxidação do cicloexano, utilizando H2O2 e t-BuOOH como oxidantes. Ambos apresentam seletividade > 70% para formação de cicloexilidroperóxido. Cálculos B3LYP/6-31G(d) foram empregados na otimização da geometria e para auxiliar na atribuição do espectro eletrônico. Abstract in english Two novel complexes, [VO2(L)] (1) and [VO2(HLox)] (2), were synthesized and characterized by IV, UV-Vis and NMR spectroscopy, cyclic voltammetry, elemental analysis and X-ray diffraction. The synthesis of a new ligand, H2Lox, is also described. Complexes 1 and 2 were obtained by the reaction of [VO( [...] acac)2] with the ligands HL and H2Lox, respectively. Alternatively, 2 was also obtained by the reaction of HL with [VO(acac)2] in the presence of hydroxylamine, and by the reaction of 1 with hydroxylamine. Crystallographic data show that complexes 1 and 2 have similar molecular structures, in which the cis-dioxovanadium(V) center is coordinated to L- or HLox-, respectively, in a distorted octahedral environment. The catalytic activity of these compounds towards cyclohexane oxidation was evaluated using H2O2 and t-BuOOH as oxidants. Both complexes presented > 70% selectivity for cyclohexylhydroperoxide formation. B3LYP/6-31G(d) calculations were used to confirm the geometry and to help assign the electronic spectra.

Natália M. L., Silva; Carlos B., Pinheiro; Eluzir P., Chacon; Jackson A. L. C., Resende; José Walkimar de M., Carneiro; Tatiana L., Fernández; Marciela, Scarpellini; Mauricio, Lanznaster.

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VO for Education: Archive Prototype  

Science.gov (United States)

The number of remote control telescopes dedicated to education is increasing in many countries, leading to correspondingly larger and larger amount of stored educational data that are usually available only to local observers. Here we present the project for a new infrastructure that will allow teachers using educational telescopes to archive their data and easily publish them within the Virtual Observatory (VO) avoiding the complexity of professional tools. Students and teachers anywhere will be able to access these data with obvious benefits for the realization of grander scale collaborative projects. Educational VO data will also be an important resource for teachers not having direct access to any educational telescopes. We will use the educational telescope at our observatory in Trieste as a prototype for the future VO educational data archive resource. The publishing infrastructure will include: user authentication, content and curation validation, data validation and ingestion, VO compliant resource generation. All of these parts will be performed by means of server side applications accessible through a web graphical user interface (web GUI). Apart from user registration, that will be validated by a natural person responsible for the archive (after having verified the reliability of the user and inspected one or more test files), all the subsequent steps will be automated. This means that at the very first data submission through the webGUI, a complete resource including archive and published VO service will be generated, ready to be registered to the VO. The efforts required to the registered user will consist only in describing herself/himself at registration step and submitting the data she/he selects for publishing after each observation sessions. The infrastructure will be file format independent and the underlying data model will use a minimal set of standard VO keywords, some of which will be specific for outreach and education, possibly including VO field identification (astronomy, planetary science, solar physics). The VO published resource description will be suggested such as to allow selective access to educational data by VO aware tools, differentiating them from professional data while treating them with the same procedures, protocols and tools. The whole system will be very flexible, scalable and with the objective to leave as less work as possible to humans.

Ramella, M.; Iafrate, G.; De Marco, M.; Molinaro, M.; Knapic, C.; Smareglia, R.; Cepparo, F.

2014-05-01

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AJUSTE DE ECUACIONES DE BIOMASA PARA Pinus durangensis (Martínez M. EN LA REGIÓN DE EL SALTO, DURANGO  

Directory of Open Access Journals (Sweden)

Full Text Available El objetivo del presente estudio fue ajustar ecuaciones lineales y no lineales para estimar biomasa por componente de hojas, ramas, fuste y total, para árboles con edades entre tres y diez años, en la región de El Salto, Dgo. Los resultados indican que las ecuaciones se ajustan mejor a nivel individual, el componente total muestra los mejores estadísticos de ajuste, mientras que las mayores variaciones se detectan en las ramas y en el fuste. Adicionalmente se analizan porcentajes de biomasa por componente donde se observa que el fuste aporta 46.9 % de la biomasa, las hojas 35.6 % y las ramas solamente 17.3 % de la biomasa total. Así mismo, dentro del rango de edad analizado, la biomasa en el fuste aumenta anualmente 2.96 %; la biomasa en las hojas disminuye 3.13 % y la biomasa en las ramas aumenta 0.17 %.

E. Montes de Oca-Cano

2009-01-01

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Estimación de biomasa por métodos alométricos, nutrimentos y carbono en plantaciones de palmito en Costa Rica  

Directory of Open Access Journals (Sweden)

Full Text Available El agroecosistema de palmito (Bactris gasipaes es un sistema de producción sostenible en los trópicos húmedos. Los métodos alométricos permiten predecir la producción de biomasa en forma no destructiva en cualquier momento y a partir de este dato determinar las fases de crecimiento del cultivo, los componentes de la biomasa y los nutrimentos asociados a cada componente, así como el rendimiento económico esperado de una plantación. Los objetivos generales del presente trabajo fueron obtener y validar funciones de predicción de la biomasa seca y de palmitos producidos en plantaciones comerciales, para correlacionarlos con la biomasa y la producción comercial de palmitos en las mismas. De esta manera, en varias fincas de la región Atlántica de Costa Rica se cosechó plantas de palmito y se separó sus componentes: follaje, pecíolos y tallos. Se utilizó modelos de regresión no lineales para calcular en forma independiente los coeficientes de las ecuaciones y así estimar los componentes de la biomasa y de la biomasa total. El diámetro basal fue una variable más efectiva para predecir la producción de biomasa que la altura hasta la hoja candela, la altura total y el número de

Adrián Ares

2002-01-01

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BIOMASA DE RAÍCES EN UN BOSQUE TEMPLADO CON Y SIN MANEJO FORESTAL EN HIDALGO, MÉXICO  

Directory of Open Access Journals (Sweden)

Full Text Available Las raíces son buenos indicadores funcionales del ecosistema ya que constituyen gran parte de la biomasa viva del suelo y ejercen un control sobre los procesos de pedogénesis, la producción de materia orgánica y la dinámica de los nutrientes. En este trabajo se comparó la biomasa de raíces gruesas y finas entre un bosque conservado y un bosque con manejo forestal de corte selectivo. La biomasa promedio de raíces no difirió significativamente entre sitios (P = 0.185. La biomasa en el bosque con manejo forestal fue de 3.05 Mg•ha-1 (E. E. = 0.25 y de 3.39 Mg•ha-1 (E. E. = 0.24 en el bosque conservado. Las raíces finas ocuparon el mayor porcentaje de la biomasa en ambos tipos de bosque, aunque sus valores no difirieron significativamente entre sitios (P = 0.095. De acuerdo con los resultados, al parecer, el manejo forestal de tipo de corte selectivo mantiene las condiciones ambientales y en particular del suelo, lo que permite contener una biomasa similar a la de un bosque conservado bajo condiciones naturales.

Numa P. Pavu00F3n

2012-01-01

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BIOMASA AÉREA Y FACTORES DE EXPANSIÓN DE ESPECIES ARBÓREAS EN BOSQUES DEL SUR DE NUEVO LEÓN  

Directory of Open Access Journals (Sweden)

Full Text Available El objetivo de este estudio fue la estimación de biomasa y el cálculo de factores de expansión de Pinus pseudostrobus, Pinus teocote, y Quercus spp., en bosques del Sur de Nuevo León, México. Se derribaron de 8 a 16 árboles por especie, se determinó el peso húmedo en campo, se extrajeron muestras para determinar la relación Peso seco-Peso húmedo (Ps/Ph, con la que se calculó el peso seco total de cada árbol. Se ajustaron modelos de biomasa. La ecuación que mejor se ajustó presentó la forma y = a(Eb/D +1.3 , donde y es la biomasa aérea, E exponencial, D diámetro normal, a, b parámetros y 1.3 constante. En todos los casos el coeficiente de determinación (R2 fue mayor a 0.89 y el error estándar porcentual (Sx% menor a 30.9. Se estimó la biomasa por tipo de bosque de acuerdo a los datos de 1,053 árboles obtenidos en las parcelas de muestreo de 400 m2, obteniéndose para el bosque de pino 125.333 toneladas de biomasa por hectárea (tB·ha-1, el de encino-pino 112.593 tB·ha-1 y el de pino-encino 96.688 tB·ha-1. Se calcularon factores de expansión de biomasa (Fexp, los valores promedio obtenidos fueron 1,373 para Pinus pseudostrobus, 1,394 para P. teocote y 1,511 para Quercus spp.

G. Domu00EDnguez-Cabrera

2009-01-01

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Obtención de etanol a partir de biomasa lignocelulósica  

Directory of Open Access Journals (Sweden)

Full Text Available Se muestra el estado de la literatura en cuanto a la obtención de etanol a partir de hidrolizados lignocelulósicos, una alternativa muy estudiada en la actualidad en el mundo con vistas a disminuir el costo del etanol combustible. Se reportan los materiales lignocelulósicos que están en estudio siendo el bagazo de caña de azúcar y los derivados del maíz los más utilizados. Se presentan los métodos de pre-tratamiento, purificación del hidrolizado, fraccionamiento de la celulosa, obtención de microorganismos geneticamente modificados y producción a nivel de planta piloto e industrial. Los métodos de pretratamiento por explosión por vapor y de purificación por "overliming" son los más estudiados con resultados satisfactorios. Entre los métodos de fraccionamiento de la celulosa, la sacarificación y fermentación simultáneas (SSF se reporta como el proceso más novedoso y eficiente para la obtención de etanol a partir de biomasa aunque a nivel de planta piloto e industrial se continúa trabajando con el sistema de hidrólisis ácida. Se muestran algunos resultados obtenidos con microorganismos genéticamente modificados como la levadura Saccharomyces y la bacteria Escherichia coli.

Mabel Viu00F1als-Verde

2012-01-01

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Biomasa acumulada e indicadores de calidad nutritiva en cebadilla chaqueña (Bromus auleticus Trinius ex Nees  

Directory of Open Access Journals (Sweden)

Full Text Available Bromus auleticus (cebadilla chaqueña es considerada uno de los recursos forrajeros más promisorios delCono Sur. Presenta variación entre poblaciones que ha sido determinada para diversos caracteres vegetativos, lo cual podría traducirse en diferencias de producción y calidad de forraje. El objetivo del presente estudio fue evaluar dos procedencias de cebadilla chaqueña (Argentina y Uruguay para biomasa acumulada e indicadores de calidad nutritiva en dos períodos del año (verano-otoño y otoño-primavera. Se compararon cinco clones uruguayos (U y cinco argentinos (A, dispuestos al azar en surcos distanciados a 1 m entre sí, con 10 plantas cada uno. Se determinó biomasa acumulada por planta (B y calidad, midiendo Fibra Detergente Neutra (FDN, Proteína Bruta (PB y Digestibilidad de la Materia Seca (DMS en dos momentos del año. En general, la biomasa fue de baja calidad debido al momento en que se realizaron los cortes, lo que limita elalcance de los resultados. Sin embargo, las diferencias observadas entre los clones en este estado de desarrollo podrían indicar la existencia de variación entre genotipos de cebadilla chaqueña U y A en biomasa y calidad nutritiva. En biomasa acumulada no se observó efecto significativo de origen. En todas las variablesde calidad evaluadas en verano-otoño, se encontraron diferencias significativas entre orígenes. En otoñoprimavera, las diferencias entre orígenes fueron significativas para DMS. Los clones U presentaron mayor PB, menor FDN y mayor DMS. Dentro de cada origen, los argentinos presentaron menos diferencias que los uruguayos, tanto en biomasa acumulada como en calidad. Para ninguno de los clones A o U se encontró coincidencia entre mayor biomasa y mayor calidad.

BUSTAMANTE, E.G.R.

2012-06-01

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Performance of VoIP on HSDPA  

DEFF Research Database (Denmark)

This paper provides packet scheduler design and performance simulations for running VoIP services over high-speed downlink packet access (HSDPA) in WCDMA. The main challenge of supporting VoIP service on HSDPA is the tight delay requirement combined with the small VoIP packet size. A packet scheduler design incorporating VoIP packet aggregation and user multiplexing is proposed and the VoIP capacity is studied for a macro-cellular environment. Results are obtained for different delay budgets and packet scheduling settings, using either blind round robin or a slightly modified version of proportional fair scheduling. For proportional fair scheduling with code-multiplexing of 4-users, the downlink VoIP cell capacity on HSDPA is found to be in the range 72-104 users depending on whether the delay budget for the Node-B scheduling and user reception equals 80 ms or 150 ms, respectively.

Wang, Bang; Pedersen, Klaus I.

2005-01-01

 
 
 
 
41

Interaction of RNase A with VO3- and VO2+ ions. Metal ion binding mode and protein secondary structure.  

Science.gov (United States)

Some of vanadyl complexes have shown potential to inhibit RNase activity by acting as transition state analogue, while at the same time not inhibiting DNase. To gain an insight into the interaction of protein with vanadate (VO3-) and vanadyl (VO2+) ions, the present study was designed to examine the binding of ribonuclase A (RNase A) with NaVO3 and VOSO4 in aqueous solution at physiological pH with metal ion concentrations of 0.001 mM to 1 mM, and protein concentration of 2% w/v. Absorption spectra and Fourier transform infrared (FTIR) spectroscopy with self-deconvolution and second derivative resolution enhancement were used to determine the cation binding mode, association constant and the protein secondary structure in the presence of vanadate and vanadyl ions in aqueous solution. Spectroscopic results show that an indirect metal ion interaction occurs with the polypeptide C = O, C-N (via H2O) with overall binding constants of K(VO3-) = 3.93x10(2) M(-1) and K(VO2+) = 4.20x10(3) M(-1). At high metal ion concentrations, major protein secondary structural changes occur from that of the alpha-helix 29% (free enzyme) to 23-24%; beta-sheet (pleated and anti) 50% (free enzyme) to 64-66% and turn 21% (free enzyme) to 10-12% in the metal-RNase complexes. The observed structural changes indicate a partial protein unfolding in the presence of high metal ion concentration. PMID:10636082

Purcell, M; Novetta-Delen, A; Arakawa, H; Malonga, H; Tajmir-Riahi, H A

1999-12-01

42

Electrochemical reduction of silver vanadium phosphorous oxide, Ag2VO2PO4: the formation of electrically conductive metallic silver nanoparticles  

Digital Repository Infrastructure Vision for European Research (DRIVER)

As a cathode material, silver vanadium phosphorous oxide (Ag2VO2PO4) displays several notable electrochemical properties: large capacity, high current capability, and an effective delivery of high current pulses. These cell performance characteristics can be attributed to the presence of silver nanoparticles formed in-situ during the electrochemical reduction of Ag2VO2PO4. Specifically, changes in the composition and structure of Ag2VO2PO4 with reduction, especially the formation of silver na...

Takeuchi, Esther S.; Marschilok, Amy C.; Tanzil, Kevin; Kozarsky, Eric S.; Zhu, Shali; Takeuchi, Kenneth J.

2009-01-01

43

VO2 films as active infrared shutters  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An active optical shutter for infrared light (3-5 ?m) has been designed, exploiting the phase transition in thermochromic vanadium dioxide (VO2). A spin coating processing route for VO2 films has been adapted to manufacture reproducible depositions onto sapphire (Al2O3) substrates. The VO2 films have been characterized by X-ray powder diffraction (XRPD) and infrared spectroscopy (FTIR), showing 55 % transmittance in the open mode and 0.1 % in the closed mode. The VO2 film temperature determi...

Johansson, Daniel

2006-01-01

44

Conversión hidrotérmica suscritica de residuos orgánicos y biomasa. Mecanismos de reacción  

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Full Text Available La conversión hidrotérmica es un procedimiento que emula el proceso natural de conversión de la materia orgánica en un biocrudo con propiedades fisicoquímicas similares a las del petróleo. La transformación artificial de biomasa requiere conocer previamente las rutas de reacción y productos prevalentes. En la conversión de celulosa, el principal componente de la biomasa, se presenta despolimerización por hidrólisis y se obtienen oli- gosacaridos, los cuales presentan deshidratación y condensación retro-aldol, para transformarse en furfurales y ácidos carboxIlicos. Otros componentes de la biomasa como lignina, proteInas y ésteres grasos, presentan rutas de reacción en las que coexisten la hidrólisis y la pirólisis. Dada la presencia de carbohidratos en la biomasa, los principales productos de su conversión hidrotérmica subcrItica y de sus residuos seran analogos a los que presenta la celulosa. Dichas sustancias tienen un valor agregado que supera considerablemente los costos de adquisición de la materia prima. Al representar en un grafico las relaciones molares O/C, H/C de los principales productos de conversión hidrotérmica de biomasa reportados en la literatura, se evidencia que la trayectoria de evolución para los productos de conversión hacia biocrudos se traslapa con la evolución geológica de los combustibles fósiles.

Alejandro Amadeus Castro Vega

2010-04-01

45

New phases in the system LiMnVO4-Mn3(VO4)2  

International Nuclear Information System (INIS)

The synthesis of orthorhombic Mn3(VO4)2 via a simple solid state route as well as the description of a new tetragonal high temperature phase are reported in this paper. Additionally, the system LiMnVO4-Mn3(VO4)2 (=Mn1.5VO4), described by the formula LixMn1.5-x/2VO4, is investigated in detail, showing that substitution of one Mn2+ in Mn1.5VO4 by two Li+ ions favors the formation of the tetragonal high temperature phase for x?0.22. This substitution is facilitated by the statistical half occupancy of the 4b site by Mn2+ in tetragonal Mn1.5VO4, whereas additional crystallographic sites would have to be occupied in the orthorhombic phase. The inverse substitution of Li by Mn in orthorhombic LiMnVO4 is also shown to be possible in the range 0.72?x?1. For 0.22?x?0.72, there is a large miscibility gap with a two phase mixture of the tetragonal Mn1.5VO4 type and orthorhombic LiMnVO4 type phases. - Graphical Abstract: The unusual coordination of Mn in the form of a stella quadrangula with the surrounding vanadate groups. Highlights: ? First synthesis of orthorhombic Mn3(VO4)2 via a simple solid state route. ? The crystal chemistry of the phases involved is rather complicated and it depends on the amount of Li that is incorporated. ? System LiMnVO4-Mn3(VO4)2 (=Mn1.5VO4), described by the formula LixMn1.5-x/2VO4, is investigated in detail.

2011-10-01

46

Phase relations and optoelectronic characteristics in the NdVO4–BiVO4 system  

International Nuclear Information System (INIS)

Studies performed on the NdVO4–BiVO4 system showed the existence of the BixNd1?xVO4 homogeneity range for x ? 0.49(1). Extended X-ray absorption fine structure and X-ray diffraction analyses confirmed that Bi3+ is incorporated onto the Nd site in the NdVO4 crystal structure with some distortion of the local structure. Surprisingly, the unit cell volume decreases with the increase in the content of the larger Bi3+ ion. On the other side of the NdVO4–BiVO4 system, Nd3+ does not enter the BiVO4 structure but forms the NdVO4-based secondary phase. Ultraviolet–visible spectroscopy showed that the band gap of NdVO4 can be reduced to below 3.1 eV by the Bi doping. New emissions that do not exist for NdVO4 have been found in the 650–675 nm range of BixNd1?xVO4 photoluminescence spectra. The observed chemical and optoelectronic properties were explained on the basis of the hybridization of Bi 6s2 and O 2p orbitals

2013-02-01

47

Hydrothermal Synthesis and Photocatalytic Properties of Cu-doped BiVO4 Microsheets  

Directory of Open Access Journals (Sweden)

Full Text Available Using Bi(NO33·5H2O, NaVO3 and Cu(NO32·3H2O as raw materials, Cu-doped BiVO4 microsheets were synthesized by ultrasonic-hydrothermal process with cetyltrimethyl ammonium bromide (CTAB as template. The as-prepared samples were investigated by XRD, XPS, SEM, HRTEM, UV-Vis and BET tests. The results reveal that uniform and well crystallized Cu/BiVO4 microsheets in monoclinic crystal structure, with length of 1.0–2.0 ?m, width of 0.5–2.0 ?m and thickness of 200–300 nm, could be obtained via an ultrasonic-hydrothermal route assisted by 2.0 g CTAB. Compared with BiVO4 particles, Cu/BiVO4 nanosheets show a little red shift in the absorption band, resulting in a narrowed band gap (<2.4 eV. For 5.0wt% Cu/ BiVO4 microsheet, its photodegradation rate constant K is5.89 ×10–2 /min and the best photocatalytic activity is found with a 100% degradation of methylene blue (MB with 10 mg/L concentration under visible-light irradiation for 60 min.

LIU Guo-Cong, JING Zhen, ZHANG Xi-Bing, LI Xian-Feng, LIU Hong

2013-03-01

48

Selective Synthesis of Mesoporous and Nanorod CeVO4 without Template  

International Nuclear Information System (INIS)

A simple and efficient method has been established for the selective synthesis of mesoporous and nanorod CeVO4 with different precursors by sonochemical method. CeVO4 nanorod can be simply synthesized by ultrasound irradiation of Ce(NO3)3 and NH4VO3 in aqueous solution without any surfactant or template. While mesoporous CeVO4 with high specific surface area can be prepared with Ce(NO3)3, V2O5 and NaOH in the same way. Mesoporous CeVO4 has a specific surface area of 122 m2 g-1 and an average pore size of 5.2 nm; CeVO4 nanorods have a diameter of about 5 nm, and a length of 100-150 nm. The ultrasound irradiation and ammonia in the reactive solution are two key factors in the formation of such rod-like products. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG) and differential thermal analyses (DTA), UV/vis absorption spectroscopy and Brunauer-Emmett-Teller (BET) were applied for characterization of the as-prepared products

2007-04-01

49

Selección de una levadura para la producción de biomasa: crecimiento en suero de queso  

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Full Text Available El presente proyecto se realizó con el objetivo de recomendar una especie de levadura para la producción de biomasa, utilizando como sustrato el suero de leche del proceso de elaboración de queso blanco tipo Turrialba. Se compararon las especies Kluyveromyces marxianus, Candida kefyr y Saccharomyces cerevisiae por medio de su crecimiento en un sistema de fermentación por lotes. Se determinó el tiempo de fermentación, la productividad total y el contenido de proteína de la biomasa. Al comparar la variación en el tiempo según la levadura utilizada, se obtuvo diferencias significativas (p ? 0,05. Las levaduras K. marxianus y C. kefyr presentaron un tiempo de 19 y 18 horas, respectivamente y S. cerevisiae, un tiempo de 24 horas. Con respecto a la productividad total de biomasa, la especie K. marxianus presentó un valor de 0,22 g/lxh, resultando significativamente diferente (p ? 0,05 a las especies C. kefyr y S. cerevisiae, para las cuales se obtuvieron productividades de 0,14 y 0,13 g/lxh. La variación en el contenido de proteína de acuerdo con la levadura utilizada no resultó significativo (p ? 0,05. Para la especie K. marxianus se obtuvo un contenido de proteína de 32%, 34% para C. kefyr y 35% para S. cerevisiae. Se seleccionó la especie de levadura Kluyveromyces marxianus para la producción de proteína unicelular, por presentar un menor tiempo de fermentación, mayor productividad e igual contenido proteico de la biomasa que las otras levaduras, además de facilidades de utilización

Eric Wong-González

2006-01-01

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Biomasa, proteína, taninos y rendimiento en haba en función del nitrógeno  

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Full Text Available El haba (Vicia faba L. es un cultivo de importancia en el altiplano mexicano por su alto consumo de semilla fresca, seca y forraje. La producción de haba está en función del genotipo y el manejo del cultivo. Dentro de éste se incluye la fertilización nitrogenada, determinante en el rendimiento. Los estudios sobre la influencia del nitrógeno (N en las estructuras de la planta relacionados con la producción de biomasa, el rendimiento y la calidad del mismo son limitados. Así, el objetivo del presente trabajo fue determinar el efecto del N sobre la biomasa, los componentes del rendimiento, el rendimiento y la concentración de taninos en pericarpio, testa y cotiledones de haba. La siembra de haba, cultivar Cochinera, se realizó durante el verano de 1998 con tratamientos de 0 y 100 kg ha-1 de N y una densidad de 4 plantas m-2. La aplicación de N no afectó la fenología del cultivo. Así, la emergencia ocurrió 13 días después de la siembra (DDS; la floración, 60 DDS; y la madurez fisiológica, 125 DDS. El N no afectó la distribución o asignación (% de biomasa en las estructuras de la planta, pero incrementó la acumulación total de biomasa en cada estructura, el número de vainas m-2, el número de semillas m-2 y, en consecuencia, el rendimiento y la concentración de proteína. La concentración de taninos en haba no fue afectada por la aplicación de N.

Antioco Guadarrama Quiroz

2007-01-01

51

Biomasa y densidad de dos especies de pastos marinos en el sur de Quintana Roo, México  

Directory of Open Access Journals (Sweden)

Full Text Available La biomasa y productividad de una comunidad de pastos marinos es útil para determinar el estado ecológico de la costa. Se comparó la biomasa foliar y la densidad de vainas en praderas de Thalassia testudinum Banks & Sol. ex K. D. Koenig, en dos ambientes de la costa del Caribe mexicano (N= 6 cuadrantes/sitio en Noviembre de 1998. Los valores de vainas y biomasa foliar fueron más bajos en la pradera asociada al manglar, que en la pradera establecida en una laguna arrecifal. Esto probablemente se deba a que las hojas del manglar tuvieron porcentaje más alto de epífitas. Por otro lado, T. testudinum tuvo mayor biomasa que Syringodium filiforme Kütz en la laguna arrecifal.The biomass and productivity of a seagrass community are useful for determining the ecological status of the coast. Leaf biomass and shoot density in beds of Thalassia testudinum Banks & Sol. ex K. D. Koenig, were compared for two environments in the Mexican Caribbean coast (N= 6 quadrants/site in November 1998. Shoot and leaf biomass values were lower in the mangrove-associated meadow than in the reef lagoon meadow. This could be related to the higher percentage of epiphytes on mangrove leaves. In addition, T. testudinum had more biomass than Syringodium filiforme Kütz in the reef lagoon.

Martha Angélica Gutiérrez-Aguirre

2000-06-01

52

Acumulación de biomasa y nutrimentos en plantaciones de palmito en Guápiles, Costa Rica  

Directory of Open Access Journals (Sweden)

Full Text Available Se cuantificó la producción de biomasa y nutrimentos en 2 plantaciones de pejibaye para palmito (Bactris gasipaes Kunth de 4 y 8 años, mediante la estimación mensual del peso seco de palmitos cosechados y sus residuos (hojas, cáscaras, rebrotes, durante un período de 52 semanas consecutivas en Guápiles, Costa Rica. Adicionalmente, se determinó la extracción de N, P, K, Ca y Mg en todos los componentes de la planta en cada muestreo mensual. También se realizó un muestreo destructivo al final de las 52 semanas para estimar la biomasa aérea y remanente y su contenido de nutrimentos. A pesar de que hubo diferencias estacionales en la producción de palmitos y rebrotes durante el año, ambas plantaciones presentaron rendimientos acumulativos de número de palmitos y producción de biomasa muy similares al final de los 12 meses. Con base en el promedio de las 2 plantaciones, la producción de materia seca cosechada fue de 13,1 t ha-1, y sólo el 11% fue removido del campo, con la producción de 11214 palmitos y sus cáscaras. Al comparar la biomasa en la vegetación remanente con lo cosechado en forma acumulada se encontró que el

Thomas J. Smyth

2002-01-01

53

Biomasa, rendimiento, eficiencia en el uso del agua y nitrógeno en girasol de humedad residual  

Directory of Open Access Journals (Sweden)

Full Text Available Durante 1987 y 1988, se realizó un estudio para determinar la influencia genotípica y de la fertilización nitrogenada (150 y 300 kg N ha-1 sobre la producción de biomasa, rendimiento y eficiencia en el uso del agua (EUA del girasol (Helianthus annuus L., cultivado en condiciones de humedad residual. Los resultados indican que las condiciones ambientales variaron principalmente con relación a la precipitación, que fue de 531 mm y de 709 mm. Esto influyó sobre la producción del girasol, la cual en ambos años mostró diferencias genotípicas y diferente respuesta a la aplicación de N. Sungro 380 (genotipo tardío mostró mayor producción de biomasa, un índice de cosecha y rendimiento más bajo que Arbung E-353 (ABE353, genotipo precoz, en particular en el año más seco. En 1987, el N incrementó la biomasa en 17 y 29% y el rendimiento en 14 y 12% en ABE353 y Sungro 380, respectivamente. En 1988, el incremento en biomasa fue 76 y 64%, y de 51 y 29% en rendimiento de grano para los genotipos respectivos. Dichos incrementos fueron producto de una mayor EUA. Para lograr una mayor producción de girasol en estas regiones, se recomienda la siembra de genotipos precoces y fertilización nitrogenada.

J. Alberto Escalante Estrada

2001-01-01

54

MODELOS MATEMÁTICOS PARA LA ESTIMACIÓN DE BIOMASA DE ÓRGANOS AÉREOS DE LIMÓN 'PERSA' (Citrus latifolia Tan.  

Directory of Open Access Journals (Sweden)

Full Text Available En muchos de los estudios de crecimiento de las plantas se requiere evaluar la biomasa, lo cual normalmente implica la destrucción de los árboles. En el presente trabajo se generaron modelos matemáticos de alta confiabilidad que estiman la cantidad de biomasa de órganos aéreos de limón 'Persa' con base en otras variables que no requieren la destrucción del material vegetal y además son de fácil medición. Para ello, se separaron ramas, hojas y frutos de los árboles y se les midió la cantidad de biomasa además del área foliar de las hojas y otras características morfológicas inherentes a cada tipo de órgano. Se encontró que la cantidad de biomasa de cada órgano se encuentra estrechamente relacionada con las siguientes características: para las ramas, el volumen calculado por las fórmulas del cono y cono truncado, en los casos de las ramas no podadas y podadas, respectivamente; para los frutos, el diámetro ecuatorial, y para las hojas, la longitud de la lámina y su ancho máximo. Se generaron modelos para cada órgano con coeficientes de determinación muy elevados (entre 0.9528 y 0.9981 y C(p aceptable (entre 1.6696 y 16.3685, para modelos de 2 a 4 variables.

G. Almaguer-Vargas

2007-01-01

55

Biomasa y densidad de dos especies de pastos marinos en el sur de Quintana Roo, México  

Scientific Electronic Library Online (English)

Full Text Available SciELO Costa Rica | Language: Spanish Abstract in spanish La biomasa y productividad de una comunidad de pastos marinos es útil para determinar el estado ecológico de la costa. Se comparó la biomasa foliar y la densidad de vainas en praderas de Thalassia testudinum Banks & Sol. ex K. D. Koenig, en dos ambientes de la costa del Caribe mexicano (N= 6 cuadran [...] tes/sitio) en Noviembre de 1998. Los valores de vainas y biomasa foliar fueron más bajos en la pradera asociada al manglar, que en la pradera establecida en una laguna arrecifal. Esto probablemente se deba a que las hojas del manglar tuvieron porcentaje más alto de epífitas. Por otro lado, T. testudinum tuvo mayor biomasa que Syringodium filiforme Kütz en la laguna arrecifal. Abstract in english The biomass and productivity of a seagrass community are useful for determining the ecological status of the coast. Leaf biomass and shoot density in beds of Thalassia testudinum Banks & Sol. ex K. D. Koenig, were compared for two environments in the Mexican Caribbean coast (N= 6 quadrants/site) in [...] November 1998. Shoot and leaf biomass values were lower in the mangrove-associated meadow than in the reef lagoon meadow. This could be related to the higher percentage of epiphytes on mangrove leaves. In addition, T. testudinum had more biomass than Syringodium filiforme Kütz in the reef lagoon.

Gutiérrez-Aguirre, Martha Angélica; de la Fuente-Betancourt, María Gabriela; Cervantes-Martínez, Adrián.

56

Fuzzing dans la sphère VoIP  

Digital Repository Infrastructure Vision for European Research (DRIVER)

La voix sur IP (VoIP) s'impose aujourd'hui comme l'une des technologies clefs de l'Internet actuel et futur. Dans cet article, nous partageons l'expérience pratique acquise ces deux dernières années par notre équipe de recherche sur l'automatisation des processus de découverte de vulnérabilités dans le monde VoIP. Nous dressons un portrait relativement sombre de la sécurité actuelle de la sphère VoIP en présentant les vulnérabilités les plus dangereuses capables d'aboutir à la c...

Abdelnur, Humberto; Festor, Olivier; State, Radu

2008-01-01

57

Digital Forensics in VoIP networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

With VoIP being deployed on large scale, forensic analysis of captured VoIP traffic is of major practical interest. In this paper, we present a new fingerprinting approach that identifies the types of devices (name, version, brand, series) in captured VoIP traffic. We focus only on the signaling plane and discard voice related data. Although we consider only one signaling protocol for the illustration, our tool relies on structural information trees and can easily be adapted to any protocol o...

2010-01-01

58

Comprehensive Comparison of VoIP SIP Protocol Problems and Cisco VoIP System  

Directory of Open Access Journals (Sweden)

Full Text Available Voice over IP (VoIP, use of the packet switched internet for telephony, has improved substantially in the past few years. On the other hand, VoIP has many challenges that do not exist in the public switched telephone network (PSTN, a circuit switched system. VoIP is an application running on the internet, and therefore inherits the internet’s security issues. It is important to realise that VoIP is a relatively young technology, and with any new technology, security typically improves with maturity. This paper provides a comprehensive comparison of a VoIP SIP protocol and CISCO VoIP system. The comparison involves the investigation of the vulnerabilities that target both systems and how secure each system is. With this comparison we present our conclusion on which system is more secure.

TALAL AL-KHAROBI

2012-08-01

59

ESTIMACIÓN DE BIOMASA Y CARBONO EN UN BOSQUE DE Abies religiosa  

Directory of Open Access Journals (Sweden)

Full Text Available Se generaron dos ecuaciones para determinar biomasa y carbono en Abies religiosa (H.B.K. Schl. et Cham. Tales ecuaciones son de la forma Y = b Xk, donde Y es el contenido de biomasa o de carbono, y X el diámetro normal (DN. Para estimar los valores b y k del modelo se utilizaron datos de 26 árboles de un área en aprovechamiento forestal, con diámetro normal entre 6.5 y 79 cm del predio -El Innominado- en San Felipe Hidalgo Nanacamilpa, Tlaxcala, México. A cada árbol se le determinó la biomasa de sus componentes (fuste, ramas y follaje; de este material se seleccionaron al azar 10 submuestras de fuste, 10 de ramas y 6 de follaje, y todas se analizaron para determinar su concentración de carbono. La concentración de carbono en el fuste fue de 46.6 %, en las ramas fue de 46 % y en follaje 46.1 %, y la concentración promedio de carbono por árbol fue de 46.5 %. El mayor porcentaje de biomasa (84.5 % se encontró en el fuste incluido el tocón, mientras que en las ramas y el follaje hubo 6.9 y 8.6 %, respectivamente. Con la biomasa y el DN de los 26 árboles se obtuvo el ajuste de los parámetros b y k del modelo propuesto (B = 0.0713 DN2.5104. Para establecer las variables del modelo predictivo de carbono acumulado por árbol (CAA en función del DN, se usó un procedimiento idéntico al anterior, cuyo resultado fue CAA = 0.0332 DN2.5104. Los parámetros para ambas ecuaciones fueron estimados con un coeficiente de determinación (R2 de 0.99.

Dulce Ma. Avendau00F1o Hernandez

2009-01-01

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Biorefinery Technologies for Biomass Conversion Into Chemicals and Fuels Towards Zero Emissions (Review) / Nulles Emisiju Princips Biomasas Konversijas Tehnolo?ij?s Aizst?jot Fosilos Resursus (P?rskata Raksts)  

Science.gov (United States)

Exhausting of world resources, increasing pollution, and climate change are compelling the shift of the world economy from continuous growth to a kind of economy based on integration of technologies into zero emissions production systems. Transition from non-renewable fossil resources to renewable resources provided by solar radiation and the current processes in biosphere is seen in the bio-refinery approach - replacing crude oil refineries by biomass refineries. Biotechnology and nano-technologies are getting accepted as important players along with conventional biomass refinery technologies. Systems design is a significant element in the integration of bio-refinery technologies in clusters. A number of case-studies, steam explosion auto-hydrolysis (SEA) in particular, are reviewed to demonstrate conversion of biomass into value-added chemicals and fuels. Analysis of energy flows is made as part of modelling the SEA processes, the eMergy (energy memory) approach and sustainability indices being applied to assess environmental impacts. Resursu izs?kums, vides pies?r?ojums un glob?la m?roga klimatisk?s izmai?as ir civiliz?cijas izdz?vošanai b?tiski faktori, kas virza pasaules ekonomikas p?rmai?as, atsakoties no nep?rtrauktas izaugsmes idejas par labu t?dai ekonomikai, kas balst?s uz atjaunojošamies resursiem un daž?du tehnolo?iju integr?cijemisiju principam atbilstoš?s ražošanas sist?m?s. Saules radi?cijas ierosin?tajos plan?tas biosf?r? notiekošajos procesos rad?to organisko vielu p?rstr?des kompleksi, kas oper? iev?rojot sabalans?tu nulles emisiju principu, tiek uzl?koti k? t?s ekonomisk?s (ražošanas) strukt?ras, kur?m j?nodrošina p?reja uz atjaunojošos resursu izmantošanu, aizst?jot esoš?s fosilo resursu (naftas, og?u) p?rstr?des r?pn?cas. L?dz?s jau apg?taj?m biomasas rafin?šanas tehnolo?ij?m svar?ga un pieaugoša loma ekonomisk?s sist?mas resursu b?zes nomai?? ir bio- un nanotehnolo?ij?m, bet ražošanas sist?mu projekt?šanai - biomasas konversijas tehnolo?iju klasteriz?cij?. Apl?kojot virkni konkr?tu tehnolo?isko risin?jumu, TSA - biomasas autohidrol?zi tvaika spr?dzien? tai skait?, iztirz?tas ar biomasas konversiju, izmantošanu un augstas pievienot?s v?rt?bas produktiem - ??miskiem savienojumiem un degviel?m, saist?t?s ekololo?isk?s un energoefektivit?tes probl?mas. Uzsverot biomasas TSA pirmapstr?des univers?lo noz?mi daž?do tehnolo?isko kompleksu strukt?r?, apl?kota TSA ietekme uz vidi, demonstr?jot eMer?ijas (ener??tisk?s atmi?as) pieeju un „ilgtsp?jas" indeksu izmantošanu. Lai gan pie sasniegt? tehnolo?isk?s att?st?bas l?me?a un patreiz?jiem fosilo ener?ijas nes?ju pat?ri?a tempiem nav iesp?jams tos piln?b? aizst?t ar bioener?iju, bioener?ijas sektora tehnolo?iju pilnveidošana ir svar?ga ar? bioresursu racion?las izmantošanas un citos aspektos. Latvijas ener??tisk?s neatkar?bas kontekst? b?tiska noz?me ir tradicion?lo bioener?ijas resursu izmantošanas efektivit?tes celšanai un inovat?vo bioener?ijas tehnolo?iju valstiskam atbalstam.u nulles

Gravitis, J.; Abolins, J.

2013-10-01

 
 
 
 
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LACK - a VoIP Steganographic Method  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The paper presents a new steganographic method called LACK (Lost Audio PaCKets Steganography) which is intended mainly for VoIP. The method is presented in a broader context of network steganography and of VoIP steganography in particular. The analytical results presented in the paper concern the influence of LACK's hidden data insertion procedure on the method's impact on quality of voice transmission and its resistance to steganalysis.

Mazurczyk, Wojciech; Lubacz, Jozef

2008-01-01

62

Condicionantes económicos del aprovechamiento de biomasa forestal con fines energéticos. Una revisión de las estimaciones para el norte de España  

Directory of Open Access Journals (Sweden)

Full Text Available Este artículo presenta una revisión de los estudios y ensayos disponibles sobre los costes de producción de biomasa forestal en el norte de España, particularmente, los de la denominada biomasa forestal primaria residual. Se analiza el papel de la biomasa en la economía forestal, así como las características de la oferta y la demanda del incipiente mercado ligado al aprovechamiento energético de este tipo de biomasa. Se discuten los principales factores determi-nantes de sus costes de producción y, en función de éstos y los precios de mercado, se analizan las condiciones de viabilidad económica de la explotación del recurso. El análisis de estas condiciones puede ser útil para la planifica-ción forestal y energética.

JAVIER BLANCO GONZu00C1LEZ

2013-01-01

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COMPUTER SIMULATION IN THE ELECTRONICS EDUCATION FOCUSED TO INCREASE THE SPECIAL HIGH SCHOOL STUDENTS MOTIVATION II. / Po?íta?ové modelovanie vo výu?be elektroniky zamerané na zvýšenie motivácie žiakov SOŠ II  

Directory of Open Access Journals (Sweden)

Full Text Available The authors interpret the particular results of their research in this contribution. It is focused to the impact of computer model on education. Anticipated result is the higher efficiency of special education here. This aim is achieved by application of motivation relations in coherence with exploitation easy reached free software. At the same time here is the latest technology, based on the computer design of circuits, applied here.Tento príspevok je pokra?ovaním prvej ?asti, ktorá bola zameraná na zvýšenie motivácie prostredníctvom bezplatne získate?ného softvéruzo siete internet. Obsahom druhej ?asti príspevku je súbor ukážok jednosmernej, striedavej a transiert analýzy elektronických obvodov.

Arpáš Július

2008-02-01

64

Synthesis of epitaxial rutile-type VO2 and VO2(B) polymorph films  

Science.gov (United States)

We exploit epitaxial relationships of rutile-type VO2 with (0001) Al2O3, (111) LaAlO3, (10?10) Al2O3, and (10?12) Al2O3 to achieve high-quality VO2 thin-film synthesis. We show that the deposition temperature can be lowered when these substrates are employed compared to one with no preferred crystallographic relationship with VO2, such as Si. We also report the first thin-film synthesis of the metastable VO2(B) polymorph on (001) LaAlO3 with a strongly preferred (001) out-of-plane orientation. These results are of interest for integrating VO2 films with other oxides in optoelectronic and reconfigurable device structures.

Wong, Franklin J.; Ramanathan, Shriram

2014-03-01

65

Lattice relaxation and ferromagnetic character of (LaVO3)m/SrVO3superlattices  

Science.gov (United States)

The experimental observation that vanadate superlattices (LaVO3)m/SrVO3 show ferromagnetism up to room temperature (Lüders U. et al., Phys. Rev. B, 80 (2009) 241102(R)) is investigated by means of density functional theory, and the band structure for m = 5 and 6 is calculated. A buckling of the interface VO2 layers is found in both cases, but subtle differences in bond length lead to very different properties for even and odd values of m: in the even case, the two interface VO2 layers effectively decouple from the adjacent LaO layers due to a strong bond length enhancement. This results into a local inversion of the orbital occupancy and to the confinement of the charge carriers. In the odd case, the amplitude of the bond length variation is smaller, so that the charge carriers spill into the deeper-lying VO2 layers, and spin-polarised interfaces are obtained.

Schuster, Cosima; Lüders, Ulrike; Frésard, Raymond; Schwingenschlögl, Udo

2013-08-01

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DENSIDAD Y BIOMASA DE MACROINVERTEBRADOS ACUÁTICOS DERIVANTES EN UNA QUEBRADA TROPICAL DE MONTAÑA (BOGOTÁ, COLOMBIA  

Directory of Open Access Journals (Sweden)

Full Text Available Se estimó la variación en la densidad de deriva de macroinvertebrados acuáticos y suaporte de materia orgánica en términos de biomasa de diferentes estados inmadurose imagos, en un tramo de una quebrada tropical de montaña ubicada en los cerrosorientales de Bogotá – Colombia y durante eventos de altas y bajas precipitaciones.Se colectó un total de 96 taxones de los cuales el más abundante fue Simulium con194 individuos (abundancia total. La densidad de deriva al igual que el aporte debiomasa de los macroinvertebrados acuáticos, fue mayor durante el período de bajasprecipitaciones. Los dípteros (quironómidos y los ácaros presentaron la mayordensidad de deriva mientras que los tricópteros (Triplectides aportaron las mayoresbiomasas a la deriva. En la escala temporal de un día, no se presentaron diferenciasen la densidad y la biomasa en la deriva entre el día y la noche.

RODRÍGUEZ-BARRIOS JAVIER

2007-12-01

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Predicción del contenido intracelular de trehalosa en el proceso de producción de biomasa de Saccharomyces cerevisiae  

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Full Text Available La trehalosa es un carbohidrato dimérico componente de la levadura de panificación Saccharomyces cerevisiae, y es considerado como indicador de la capacidad fermentativa y de la viabilidad de las células. En procesos de producción de levadura, se busca inducir una acumulación intracelular de trehalosa. Por ser un compuesto citoplásmico, la cuantificación de la trehalosa requiere de tomas de muestra y de métodos analíticos posteriores. Así, el conocimiento del contenido citoplásmico de trehalosa es siempre ulterior al desarrollo del proceso de producción de biomasa, y esto dificulta el ajuste en tiempo real de parámetros de operación para incrementar la cantidad de trehalosa en la biomasa. Por tanto, se requiere de alguna alternativa para estimación de la trehalosa intracelular en tiempo real. Este trabajo presenta una opción de predicción basada tanto en el metabolismo celular implicado durante la biosíntesis de trehalosa, como en un algoritmo de redes neuronales dinámicas para la estimación de la concentración intracelular del carbohidrato.

J. S. Aranda

2008-01-01

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LA BIOMASA MICROBIANA EN SUELOS DE MONTAÑA CON DIFERENTES USOS: UN ESTUDIO DE LABORATORIO  

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Full Text Available El uso agrícola de los suelos del Parque Nacional Nevado de Toluca (PNTT, conlleva prácticas como la utilización creciente de agroquímicos. Para investigar el efecto de la aplicación de fertilizantes nitrogenados y biocidas de uso generalizado en la zona de estudio sobre la biomasa microbiana y la mineralización del carbono (C, se realizó una incubación de suelos del PNNT con diferentes usos: bosque (bajo la copa de oyamel (Abies religiosa, destinados al pastoreo (pradera y cultivado con maíz. Con los siguientes tratamientos: sulfato deamonio (585.36 kg ha-1, urea (250 kg ha-1, 2, 4-D (1 L ha-1, captan (2 kg ha-1 y suelos sin aplicación. La mineralización del C, el nitrógeno de la biomasa microbiana (NBM y el carbono de la biomasa microbiana (CBM se midieron a los 56 días de incubación. Los resultados mostraron que el cambio de uso de suelo de bosque a cultivo disminuye la biomasa microbiana, la proporción de CBM y NBM en los suelos de cultivo fue menor en más del 55% en comparación con los suelos de bosque. Los tratamientos 2, 4-D y captan dieron lugar al decremento significativo del CBM en los suelos de bosque, hasta en un 40 %, con respecto al suelo sin aplicación. La aplicación de captan favoreció el incremento del CBM en los suelos de pradera y cultivo. El NBM aumentó en los tres suelos con diferente uso al aplicar urea. La adición de sulfato de amonio, urea, 2, 4-D amina o captan causa efectos diferenciados en los suelos de bosque, pradera y cultivo indicando que el impacto de los biocidas y fertilizantes está relacionado con la degradación de los mismos.

A. Cruz Ruiz

2012-01-01

69

EFECTO DEL ÁCIDO SALICÍLICO SOBRE BIOMASA, ACTIVIDAD FOTOSINTÉTICA, CONTENIDO NUTRICIONAL Y PRODUCTIVIDAD DEL CHILE JALAPEÑO  

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Full Text Available El uso de biorreguladores del crecimiento es una práctica para mejorar el rendimiento y calidad de los cultivos. Actualmente se ha considerado al ácido salicílico un biorregulador del crecimiento de las plantas. El objetivo del presente trabajo fue estudiar el efecto de las diferentes dosis de ácido salicílico (AS sobre la acumulación de biomasa, concentración de pigmentos, actividad fotosintética, contenido nutricional y productividad del chile jalapeño (Capsicum annuum L. cv. Chichimeca. El AS fue aplicado a la solución nutritiva en dosis crecientes: 0.025 mM, 0.05 mM, 0.1 mM, 0.2 mM, 0.4 mM y 0.8 mM, más un control (sin aplicación de AS. Los resultados indican que la aplicación de AS a las plantas de chile jalapeño cv. Chichimeca aumentaron significativamente la producción de biomasa foliar, en raíz y total, principalmente en las dosis de 0.1 y 0.2 mM. Por otro lado, los tratamientos de 0.1 y 0.2 mM de AS tuvieron un efecto positivo en la producción de frutos. Asimismo, la actividad fotosintética presentó un comportamiento similar a la acumulación de biomasa y producción de frutos por planta, sobresaliendo los tratamientos 0.1 y 0.2 mM de AS con la máxima actividad fotosintética. En relación al análisis nutricional, se observó que a una mayor acumulación de biomasa y producción por planta se presentó una menor acumulación de nutrientes, debido probablemente al efecto de dilución. Se concluye que los tratamientos con 0.1 y 0.2 mM de AS cumplen un papel de biorregulador del crecimiento en chile jalapeño.

Damaris Leopoldina Ojeda-Barrios

2011-01-01

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DOSIS DE NITRÓGENO Y SU EFECTO EN LA PRODUCCIÓN Y DISTRIBUCIÓN DE BIOMASA DE ALGODÓN TRANSGÉNICO  

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Full Text Available El objetivo del presente estudio fue determinar el efecto de la dosis de nitrógeno (N en la producción y asignación de biomasa y en los indicadores del crecimiento de la variedad transgénica NuCot 35B de algodón (Gossypium hirsutum L.. Las dosis evaluadas fueron 0, 80 y 160 kg ha-1 de N, las cuales se distribuyeron en un diseño de bloques al azar con seis repeticiones. La siembra se realizó en el sistema de producción de surcos estrechos (0.76 m entre surcos y distancia de 0.20 m entre plantas para una población de 65 500 plantas ha-1. Para determinar el efecto del N en la dinámica de crecimiento y eficiencia en la producción y distribución de biomasa se realizaron cuatro muestreos destructivos a 69, 82, 105 y 124 días después de la siembra (DDS. En cada muestreo se colectaron dos plantas por parcela para determinar área foliar, peso seco total y peso seco de órganos vegetativos y reproductivos. Con los datos de área foliar y peso de biomasa seca se estimó la tasa de crecimiento del cultivo (TCC, tasa de asimilación neta (TAN, índice de área foliar (IAF, relación de área foliar (RAF, área foliar específica (AFE y relación de peso foliar (RPF. El N aplicado no afectó la tasa de producción y distribución de biomasa, ni los indicadores de la magnitud de fotosíntesis. A 124 DDS los órganos reproductivos acumulaban 60%del peso seco total de la planta. La mayor TCC (22.1 g m-2 d-1 se presentó entre 69 y 105 DDS. La dosis deN tampoco afectó RAF,AFE y RPF, lo cual indica que, en todas las fases de crecimiento, las plantas acumularon la misma cantidad de fotoasimilados en sus hojas. La RPF obtenida indica que, independientemente de la cantidad de N aplicado, las plantas asignan elmismo porcentaje de fotoasimilados a su estructura foliar.

Jorge A. Orozco-Vidal

2008-01-01

71

Factores del manejo para estabilizar la producción de biomasa con leguminosas en el trópico  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Este material tiene como objetivo abundar acerca de aquellos factores del manejo que conduzcan a estabilizar la producción de biomasa en sistemas ganaderos en el trópico. Es obvio que los sistemas mejorados y bien manejados de pasturas de gramíneas y leguminosas, en cualquiera de sus alternativas, son opciones para lograr la sostenibilidad. Una concepción más amplia y profunda es la relativa a los estudios de pasturas mixtas; éstos, deben ten...

2006-01-01

72

PRODUCCIÓN DE BIOMASA DE Artemia franciscana Kellogg 1906 UTILIZANDO DIFERENTES DIETAS  

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Full Text Available Se realizó el cultivo semiintensivo de Artemia franciscana, cepa Perú, utilizando diferentes dietas en base a microalgas e insumos alimenticios que forman parte de algunos ingredientes que se utilizan para preparar alimento formulado de peces y crustáceos, con el fin de determinar la factibilidad del uso de estos para la obtención de biomasa de adultos. El estudio se ejecutó en base a un diseño experimental completamente aleatorio con 7 tratamientos y 3 réplicas cada uno, aplicándose a los datos obtenidos un Análisis de Varianza de una vía (ANOVA y la prueba de Tukey para establecer diferencias significativas entre los tratamientos. Los resultados del análisis próximal de las dietas, mostraron que la harina de soya presentó la cantidad de proteínas requerida por A. franciscana durante su crecimiento (34.33 %, igualmente con esta dieta se obtuvo la mejor tasa de crecimiento (0.19, biomasa más alta (113.33 g y el mejor Factor de Conversión Alimenticia (1.4. Así mismo la biomasa de A. franciscana producida con harina de soya, presentó un nivel de proteínas adecuado para la maduración de reproductores de crustáceos (53.38 %.

Enrique Vinatea

2009-01-01

73

Biomasa y composición nutricional de la asociación Cenchrus ciliaris - Gliricidia sepium al establecimiento  

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Full Text Available Se asoció Cenchrus ciliaris (Cc y Gliricidia sepium (Gs para evaluar la producción de biomasa y la composición química de los forrajes en la fase de establecimiento, en el estado de Morelos, México, en condiciones de trópico seco. Se empleó un análisis de varianza con diseño en bloques al azar, en donde T1 fue pasto solo, T2 Cc más Gs con 5,000 plantas ha-1 y el T3 Cs más Gs con 14,285 plantas ha-1. Se midió la producción de forraje individual y asociado con materia seca (t MS/Ha, la altura (A en cm, la proteína cruda (PC%, las fracciones de fibra (FDN% y FDA% y la digestibilidad in vitro de la materia seca (DIVMS%. El T3 tuvo una mejor producción de biomasa (P0.05. La asociación de 14,285 plantas ha-1 de G. sepium con pasto Cenchrus ciliaris mejoró la producción de biomasa y la disponibilidad total de nutrientes por superficie cultivada al establecimiento

J. L. Valle

2004-01-01

74

Asignación de biomasa y rendimiento de girasol con relación al nitrógeno y densidad de población  

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Full Text Available Se realizó un estudio con girasol (Helianthus annuus L., bajo condiciones de temporal, en Montecillo, México, para determinar el efecto de la aplicación de 0 y 100 kg de N ha-1 y 57 000 (80*25 cm y 114 000 (40*25 cm plantas ha-1 sobre la producción de biomasa, su distribución en la planta, el rendimiento y sus componentes. El N y 100 kg ha-1 de P2O5 se aplicaron a todo el experimento al momento de la siembra. El diseño experimental fue en bloques completos al azar con arreglo en parcelas divididas y cuatro repeticiones. El N y el aumento en densidad de población no afectaron la distribución (% de materia seca en los órganos de la planta. Por otra parte, la acumulación de materia seca (g m-2 en cada estructura de la planta se incrementó al aplicar N y con el uso de poblaciones altas. Esto condujo a una mayor producción de biomasa, rendimiento y un número más alto de semillas m-2 (NSMC. El NSMC fue el componente de mayor correlación con el rendimiento. El peso de 100 semillas (P100S no registró cambios significativos por efecto de los tratamientos. Además, al combinar el N con densidad alta, se logró una mayor producción de biomasa y rendimiento.

Ricardo Vega Muu00F1oz

2001-01-01

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Efecto de rastrojos en el nitrógeno de biomasa microbiana en un agroecosistema arrocero inundado  

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Full Text Available Del año 2002 al 2004 se investigó en un agroecosistema arrocero inundado a fin de evaluar cambios en la actividad de la biomasa microbiana y su contenido de nitrógeno ?N?, durante cuatro ciclos consecutivos del cultivo. Se comparó la tendencia del contenido de nitrógeno de la biomasa microbiana ?NBM? en los sistemas siembra directa sobre rastrojos ?SDR? y labranza mecanizada convencional ?LMC?. Durante el tercer ciclo de arroz se evaluó el efecto de los rastrojos de mucuna ?Mucuna deeringiana (Bort. Merr?; se comparó la materia orgánica del suelo ?MOS? y el NBM. Adicionalmente, durante el cuarto ciclo de arroz del estudio, fueron contrastados cambios en la actividad de la biomasa microbiana en tres diferentes etapas de crecimiento del cultivo. En los primeros 5 cm del perfil del suelo la cantidad de NBM siempre fue mayor en SDR. En esta capa del suelo, la combinación de rastrojos de arroz acumulados durante tres ciclos con rastrojos de mucuna del ciclo previo, permitió una mayor estratificación de la MOS. Se observó un incremento de la MOS de 2,3 a 4,1%, mientras que el NBM fue casi cuatro veces mayor. La respiración de los microorganismos del suelo y la mineralización del N fue afectada principalmente por la presencia continua de una lámina de agua sobre el suelo. Se concluyó que la SDR es un sistema capaz de complementar la fertilización química e incrementar los rendimientos del arroz mediante la gradual liberación de N y otros nutrimentos derivados de la descomposición de los rastrojos

Carlos Ramírez-Martínez

2006-01-01

76

DISTRIBUCIÓN DE BIOMASA Y ACUMULACIÓN DE PLOMO EN CALABACITA (Cucurbita pepo L. CULTIVADA EN SUELO CONTAMINADO  

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Full Text Available Se estudió el efecto del suelo contaminado con plomo en el híbrido experimental de calabacita (Cucurbita pepo L. denominado 'Termo'. Se cultivó calabacita en bolsas negras de polietileno, a cielo abierto. Se evaluaron las variables distribución de la producción de biomasa, altura de planta, contenido de clorofila y acumulación de plomo en raíz, tallo, hoja, flor y fruto. Los tratamientos fueron 0, 65, 300 y 1000 ppm de plomo aplicado al suelo a través de Pb(NO32. Se utilizó un diseño experimental de bloques completos al azar con seis repeticiones, y la unidad experimental fue una bolsa negra de polietileno con dos plantas. Las evaluaciones se hicieron 50 días después del trasplante para altura de planta y contenido de clorofila, y a los 52 días para peso fresco, peso seco y acumulación de plomo. Se observó que la altura de planta fue significativamente menor cuando se aplicó plomo a cualquier dosis. También se observó que la mayor acumulación de biomasa en raíz y tallo fue producida con la dosis 300 ppm y en fruto con 65 ppm de plomo, en tanto que la biomasa total y las unidades SPAD (clorofila no resultaron afectadas. De las estructuras comestibles, la flor presentó una mayor acumulación del metal que el fruto. A bajas dosis de plomo, la flor fue la estructura que más lo acumuló. Esto sugiere que es conveniente evaluar el contenido de metales pesados en productos agrícolas para consumo humano, aun cuando provengan de suelos contaminados sin intención.

Maru00EDa Teresa Colinas-Leu00F3n

2012-01-01

77

Drowning in Data : VO to the rescue  

CERN Document Server

Astronomical datasets are growing in size and diversity, posing severe technical problems. At the same time scientific goals increasingly require the analysis of very large amounts of data, and data from multiple archives. The Virtual Observatory (VO) initiative aims to make multiwavelength science and large database science as seamless as possible. It can be seen as the latest stage of a long term trend towards standardisation and collectivisation in astronomy. Within this inevitable trend, we can avoid the high energy style of building large fixed hierarchical teams, and keep the individualist style of astronomical research, if the VO is used to build a facility class data infrastructure. I describe how the VO works and how it may change in the Web 2.0 era.

Lawrence, A

2009-01-01

78

Biomasa acumulada e indicadores de calidad nutritiva en cebadilla chaqueña (Bromus auleticus Trinius ex Nees)  

Scientific Electronic Library Online (English)

Full Text Available SciELO Argentina | Language: Spanish Abstract in spanish Bromus auleticus (cebadilla chaqueña) es considerada uno de los recursos forrajeros más promisorios del Cono Sur. Presenta variación entre poblaciones que ha sido determinada para diversos caracteres vegetativos, lo cual podría traducirse en diferencias de producción y calidad de forraje. El objetiv [...] o del presente estudio fue evaluar dos procedencias de cebadilla chaqueña (Argentina y Uruguay) para biomasa acumulada e indicadores de calidad nutritiva en dos períodos del año (verano-otoño y otoño-primavera). Se compararon cinco clones uruguayos (U) y cinco argentinos (A), dispuestos al azar en surcos distanciados a 1 m entre sí, con 10 plantas cada uno. Se determinó biomasa acumulada por planta (B) y calidad, midiendo Fibra Detergente Neutra (FDN), Proteína Bruta (PB) y Digestibilidad de la Materia Seca (DMS) en dos momentos del año. En general, la biomasa fue de baja calidad debido al momento en que se realizaron los cortes, lo que limita el alcance de los resultados. Sin embargo, las diferencias observadas entre los clones en este estado de desarrollo podrían indicar la existencia de variación entre genotipos de cebadilla chaqueña U y A en biomasa y calidad nutritiva. En biomasa acumulada no se observó efecto significativo de origen. En todas las variables de calidad evaluadas en verano-otoño, se encontraron diferencias significativas entre orígenes. En otoñoprimavera, las diferencias entre orígenes fueron significativas para DMS. Los clones U presentaron mayor PB, menor FDN y mayor DMS. Dentro de cada origen, los argentinos presentaron menos diferencias que los uruguayos, tanto en biomasa acumulada como en calidad. Para ninguno de los clones A o U se encontró coincidencia entre mayor biomasa y mayor calidad. Abstract in english Bromus auleticus (“chaqueña” bromegrass) may be considered as one of the most valuable forage species for the Southern Cone. This species shows variation among populations, determined in diverse vegetative characters, which could result in differences in production and forage quality. The objective [...] of this study was to evaluate two origins of Bromus auleticus (Argentina and Uruguay) for characters of biomass accumulated and quality in two periods of the year (Summer-Autumn and Autumn-Spring). Five Uruguayan (U) and Argentine (A) clones were compared, it were randomly arranged in rows spaced one meter of each other, with 10 plants each one. Biomass accumulated per plant (B) and biomass quality were determined in two times of the year measuring neutral detergent fiber (NDF), crude protein (CP) and dry mater digestibility (DMD). In general, quality of biomass was poor due to time cuttings, limiting the scope of the results. However, differences between the clones in this stage of development could be indicating the presence of variation among genotypes of “chaqueña” prairie grass U and A in biomass and nutritional quality. Significant effect of origin for B was not observed. In all biomass quality variables evaluated in Summer-Autumn, significant differences between origins were found. In Autumn-Spring, differences between origins were significant in DMD. U clones showed more CP, less NDF and higher DMD. Within each origin, A showed less differences than U both in B and quality. Concerning A or U clones, no coincidence between high biomass and high quality was found.

E.G.R, Bustamante; M.A, Ruiz; E, Morici; F.J, Babinec; A.B, Pordomingo.

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VO2 max in an Indian population: a study to understand the role of factors determining VO2 max.  

Science.gov (United States)

VO2 max is the maximum amount of oxygen a person can consume and the value does not change despite an increase in workload. There is lack of data evaluating the impact of factors, which could affect VO2 max measurement, particularly in Indian population. The objectives of the present study were (i) to estimate VO2 max in a young healthy Indian population and to compare it with available prediction equations for Indian population (ii) to correlate time to achieve VO2 max with the relative VO2 max (iii) to assess the factors affecting the time to achieve VO2 max measurement (body composition and physical activity level). Twenty healthy adult males (18-30 years) underwent detailed anthropometry, physical activity level and modified Bruce protocol for VO2 max assessment. Breath by breath VO2, VCO2, oxygen saturation, heart rate, blood pressure were measured continuously and following exercise protocol. There was an internal validity between the estimated VO2 max and the maximum heart rate (MHR) (r = 0.51, P < 0.05). Respiratory rate and tidal volume significantly correlated with VO2 max P < 0.01). Linear regression analysis indicated physical activity level (PAL) was a strong predictor of time to reach VO2 max. Out of the 3 prediction equations computed to estimate VO2 max, 2 equations significantly overestimated VO2 max. In Conclusion, physical activity level emerged to be a strong predictor of time to VO2 max. Time to achieve VO2 max is an important factor to be considered when determining VO2 max. There was an overestimation in the VO2 max values derived from predicted equations. PMID:24617157

Nitin, Y M; Sucharita, S; Madhura, M; Thomas, T; Sandhya, T A

2013-01-01

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From hollow olive-shaped BiVO4 to n-p core-shell BiVO4@Bi2O3 microspheres: controlled synthesis and enhanced visible-light-responsive photocatalytic properties.  

Science.gov (United States)

In this study, hollow olive-shaped BiVO(4) and n-p core-shell BiVO(4)@Bi(2)O(3) microspheres were synthesized by a novel sodium bis(2-ethylhexyl)sulfosuccinate (AOT)-assisted mixed solvothermal route and a thermal solution of NaOH etching process under hydrothermal conditions for the first time, respectively. The as-obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy, Brunauer-Emmett-Teller surface area, and UV-vis diffuse-reflectance spectroscopy in detail. The influence of AOT and solvent ratios on the final products was studied. On the basis of SEM observations and XRD analyses of the samples synthesized at different reaction stages, the formation mechanism of hollow olive-shaped BiVO(4) microspheres was proposed. The photocatalytic activities of hollow olive-shaped BiVO(4) and core-shell BiVO(4)@Bi(2)O(3) microspheres were evaluated on the degradation of rhodamine B under visible-light irradiation (? > 400 nm). The results indicated that core-shell BiVO(4)@Bi(2)O(3) exhibited much higher photocatalytic activities than pure olive-shaped BiVO(4). The mechanism of enhanced photocatalytic activity of core-shell BiVO(4)@Bi(2)O(3) microspheres was discussed on the basis of the calculated energy band positions as well. The present study provides a new strategy to enhancing the photocatalytic activity of visible-light-responsive Bi-based photocatalysts by p-n heterojunction. PMID:21171642

Guan, Mei-Li; Ma, De-Kun; Hu, Sheng-Wei; Chen, Yan-Jun; Huang, Shao-Ming

2011-02-01

 
 
 
 
81

Electron paramagnetic resonance and optical absorption study of VO2+-doped sodium zinc sulfate tetrahydrate single crystals  

Science.gov (United States)

Single-crystal electron paramagnetic resonance (EPR) studies of VO2+ doped in sodium zinc sulfate tetrahydrate (Na2Zn(SO4)2·4H2O) have been carried out at room temperature. The results show the presence of three magnetically inequivalent VO2+ sites with different populations. The VO2+ impurity ions take up substitutional positions in the host lattice replacing Zn2+ ions. The angular variation of EPR spectra in three mutually orthogonal planes, bc, a*c and ba*, are used to determine the spin-Hamiltonian parameters. The optical absorption spectrum of VO2+ ions doped in the crystal lattice is also recorded at room temperature in the wavelength range 325-1100 nm. This is utilized to study the energy level structure of the VO2+ ion. By correlating the EPR and optical data, various molecular orbital coefficients of the VO2+ ion with its ligands are evaluated and the nature of bonding in the crystal is discussed.

Kripal, Ram; Shukla, Santwana

2012-01-01

82

Synthesis, structures and magnetic properties of the new vanadates AgMnVO4 and RbMnVO4  

International Nuclear Information System (INIS)

The new compounds, AgMnVO4 and RbMnVO4 have been synthesized by solid state reaction route. Their crystal structures were determined from single-crystal X-ray diffraction data for RbMnVO4 and powder X-ray diffraction data for AgMnVO4. AgMnVO4 crystallizes with the maricite-type structure in space group Pnma, a=9.5778(6) A, b=6.8518(4) A, c=5.3734(3) A and Z=4. RbMnVO4 crystallizes in space group P63 with a stuffed tridymite-type structure, a=11.2584(3), c=8.9893(13) A and Z=8. A merohedral twinning was taken into account for its structural refinement. To our knowledge this is the first vanadate showing this structural type. AgMnVO4 and RbMnVO4 were characterized by magnetic susceptibility and specific heat measurements. AgMnVO4 is antiferromagnetic with a Neel temperature of 12.3 K determined by specific heat measurements. RbMnVO4 exhibits canted antiferromagnetism with a Neel temperature of 6.5 K. - Graphical Abstract: The new vanadates AgMnVO4 and RbMnVO4 have been synthesized by solid state reaction. They crystallize with a maricite-type and a stuffed tridymite-type structure, respectively. Antiferromagnetic interactions were observed in both compounds

2008-11-01

83

Produccion de Biomasa de Scenedesmus Obliquus en diferentes medios de cultivo.  

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Full Text Available Los nutrientes son factores fundamentales que afectan el rendimiento de los cultivos de microalgas, de ahí la importancia de llevar a cabo estudios a escala de laboratorio con cepas de interés científico y comercial. El objetivo del trabajo fue investigar la producción de biomasa de Scenedesmus obliquus en diferentes medios de cultivo. Se utilizaron dos reactores tipo columnas de 2 L de capacidad empleando medio Extracto de Suelo, y medio Albañal Sintético respectivamente, a los cuales se les adicionó el inóculo del cultivo (1%, en la fase logarítmica de crecimiento. Para mantener agitado y homogéneo el sistema, se suministró aire a razón de 100 L/h, que fue medido con un regulador de flujo y se colocaron en un local cuya temperatura media era de 29,7 o C. Los reactores trabajaron en modo discontinuo (batch. Se mantuvieron con un régimen de luz/oscuridad de 8/16 horas durante 18 días. Para seguir el comportamiento del cultivo se determinó la Densidad óptica, la clorofila a, los sólidos suspendidos volátiles, se midió el pH y la producción de biomasa en el sistema. La velocidad de crecimiento específico fue ¿ = 0,16 d-1 para el cultivo en el medio Agar extracto de suelo y ¿ = 0,33 d-1 para el cultivo en medio Albañal sintético. El tiempo de duplicación fue de 4,33 d'-1 para el cultivo en medio AES y 2,10 d-1 para el medio de Albañal Sintético. Se alcanzaron los valores más altos en la producción de biomasa en el medio Albañal, lo que demostró un mejor desarrollo de la microalga investigada en este medio.

V. Martu00EDnez

2005-01-01

84

Factores del manejo para estabilizar la producción de biomasa con leguminosas en el trópico  

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Full Text Available Este material tiene como objetivo abundar acerca de aquellos factores del manejo que conduzcan a estabilizar la producción de biomasa en sistemas ganaderos en el trópico. Es obvio que los sistemas mejorados y bien manejados de pasturas de gramíneas y leguminosas, en cualquiera de sus alternativas, son opciones para lograr la sostenibilidad. Una concepción más amplia y profunda es la relativa a los estudios de pasturas mixtas; éstos, deben tener un enfoque más biológico por lo que, además de considerar el ambiente en el cual se desarrollan y crecen, hay que incluir la forma en que los componentes vegetales se manifiestan en las especies implicadas del agroecosistema. Aquí no podemos olvidar el efecto del animal. Los problemas asociados con la persistencia se reconocen cada vez más como una preocupación real. Los diversos factores que controlan la permanencia de las especies forrajeras se agrupan en aquellos que pueden ser manejados y controlados por el productor, así como en los que éste no puede intervenir. Es por ello que las producciones animales y de otro tipo, derivados de estos sistemas, varían positivamente en el tiempo, en la medida en que se va consolidando la relación suelo /planta /animal. De esta correspondencia no puede quedar excluido el papel interactuante y modificador del hombre con los elementos antes señalados. La producción de biomasa es una actividad multidisciplinaria; de ahí que el éxito de su funcionamiento esté condicionado al conocimiento de las interacciones entre sus componentes, así como entre éstos y el medio ambiente, lo cual permitirá la generación de estrategias de manejo acordes con la ecología que conduzcan a mejorar la productividad y la sostenibilidad del agroecosistema. Por tanto, la producción de biomasa constituye un elemento determinante en el éxito y la eficiencia de los sistemas con leguminosas.

T. E. Ruiz

2006-01-01

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Estimativa das contribuições dos sistemas anaeróbio lático e alático durante exercícios de cargas constantes em intensidades abaixo do VO2max / Estimation of contributions of the anaerobic lactic and alactic systems during constant-load exercises at intensities below the VO2max  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese O objetivo do estudo foi estimar as contribuições do metabolismo anaeróbio lático (MAL) e alático (MAA) em intensidades abaixo do consumo máximo de oxigênio (VO2max). Dez homens (23 ± 4 anos, 176,4 ± 6,8 cm, 72,4 ± 8,2 kg, 12,0 ± 4,5 % de gordura corporal) realizaram um teste progressivo até a exaus [...] tão voluntária para identificação do VO2max, da potência correspondente ao VO2max (WVO2max) e do segundo limiar ventilatório (LV2). Na segunda e na terceira visita foram realizados seis testes de cargas constantes (três testes por sessão) com intensidades abaixo do VO2max. Houve uma predominância do MAL sobre o MAA durante os exercícios submáximos a partir da intensidade correspondente ao LV2, sendo significativamente maior em 90% VO2max (p Abstract in english The purpose this study was that estimated contributions of the anaerobic lactic (MAL) and alactic (MAA) metabolism during constant load exercises at intensities below the maximal oxygen capacity uptake (VO2max). Ten males (23 ± 4 years, 176.4 ± 6.8 cm, 72.4 ± 8.2 kg, 12.0 ± 4.5 % of fat body) perfor [...] med in the first visit a progressive test until exhaustion to identification of VO2max, power output corresponding to the VO2max (WVO2max) and second ventilatory threshold (LV2). On the second and third visit, the participants performed six constant workload tests (3 per session) with intensities below VO2max. There was a predominance of MAL about MAA during the exercises sub-maximal from intensity corresponding to the LV2, being significantly higher at 90% VO2max (p

Marcos David, Silva-Cavalcante; Renata Gonçalves, Silva; Rodrigo Poles, Urso; Rogério Carvalho, Silva; Carlos Rafaell, Correia-Oliveira; Victor Gustavo Ferreira, Santos; Adriano Eduardo, Lima-Silva; Rômulo, Bertuzzi.

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Estimativa das contribuições dos sistemas anaeróbio lático e alático durante exercícios de cargas constantes em intensidades abaixo do VO2max Estimation of contributions of the anaerobic lactic and alactic systems during constant-load exercises at intensities below the VO2max  

Directory of Open Access Journals (Sweden)

Full Text Available O objetivo do estudo foi estimar as contribuições do metabolismo anaeróbio lático (MAL e alático (MAA em intensidades abaixo do consumo máximo de oxigênio (VO2max. Dez homens (23 ± 4 anos, 176,4 ± 6,8 cm, 72,4 ± 8,2 kg, 12,0 ± 4,5 % de gordura corporal realizaram um teste progressivo até a exaustão voluntária para identificação do VO2max, da potência correspondente ao VO2max (WVO2max e do segundo limiar ventilatório (LV2. Na segunda e na terceira visita foram realizados seis testes de cargas constantes (três testes por sessão com intensidades abaixo do VO2max. Houve uma predominância do MAL sobre o MAA durante os exercícios submáximos a partir da intensidade correspondente ao LV2, sendo significativamente maior em 90% VO2max (p The purpose this study was that estimated contributions of the anaerobic lactic (MAL and alactic (MAA metabolism during constant load exercises at intensities below the maximal oxygen capacity uptake (VO2max. Ten males (23 ± 4 years, 176.4 ± 6.8 cm, 72.4 ± 8.2 kg, 12.0 ± 4.5 % of fat body performed in the first visit a progressive test until exhaustion to identification of VO2max, power output corresponding to the VO2max (WVO2max and second ventilatory threshold (LV2. On the second and third visit, the participants performed six constant workload tests (3 per session with intensities below VO2max. There was a predominance of MAL about MAA during the exercises sub-maximal from intensity corresponding to the LV2, being significantly higher at 90% VO2max (p < 0.05. Thus, these results may help coaches to implement training loads appropriate to their athletes, according to the metabolic demand of the competition.

Marcos David Silva-Cavalcante

2013-01-01

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Quemador de Doble Turbulizador Estático (QDTE: una tecnología para la combustión de biomasa en el proceso de secado agroindustrial  

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Full Text Available El trabajo realiza el análisis de factibilidad técnico-económico y ambiental de la introducción de un Quemador de Doble Turbulizador Estático (QDTE para el secado agroindustrial del arroz en el secadero «Emilio Lastre», en el mismo se expone todo el procedimiento de cálculo térmico, aerodinámico e hidrodinámico utilizado durante el diseño del quemador, a partir de la realización de una búsqueda bibliográfica actualizada. El QDTE fundamenta su principio de funcionamiento en la combustión en suspensión total de las partículas de arroz (y otras biomasas, de manera tal que la biomasa combustible quema durante su recorrido por el volumen de la cámara de combustión. Pero, este quemador tiene como característica innovadora distintiva el perfeccionamiento del proceso aerodinámico donde se determinan tres conceptos novedosos: escalonamiento (distribución del aire en: primario y secundario, la turbulización de dos corrientes aerodinámicas: primaria y secundaria y la co? combustión de biomasa con combustible fósil (Diesel.

Bienvenido Sarru00EDa Lu00F3pez

2007-01-01

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VO2 kinetics during submaximal exercise following simulated weightlessness  

Science.gov (United States)

A study is presented of the effects of deconditioning following 7 days of continuous head-down (-6 degrees) bedrest on changes in steady-state VO2, O2, and recovery VO2 during the performance of constant-load exercises. The deconditioning effects of bedrest on the physical working capacity were manifested in the subjects by significant changes in VO2 kinetics following the 7 days of head-down bedrest. While the subjects demonstrated the ability to attain similar steady-state VO2, simulated weightlessness using head-down bedrest resulted in a reduction of total VO2 capacity and an increase in the O2 deficit and VO2 halftime during submaximal constant-load exercise. It is concluded that this change in VO2 kinetics was induced by reexposure of the cardiovascular system to the +1 Gz (upright) environment.

Convertino, V. A.; Sandler, H.

1982-01-01

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Recuperación de la biomasa mediante la sucesión secundaria, Cordillera Central de los Andes, Colombia  

Scientific Electronic Library Online (English)

Full Text Available SciELO Costa Rica | Language: Spanish Abstract in spanish En bosques secundarios premontanos tropicales es escasa la información sobre el tiempo requerido para recuperar la biomasa aérea y subterránea de los primarios. Por lo tanto, establecimos 33 parcelas de 0.1ha entre 550 y 1 700m en bosques secundarios que cubrían estadios serales de 3 a 36 años y est [...] imamos la biomasa de las plantas y de las raíces gruesas con ecuaciones locales. Así como la biomasa de las pasturas y barbechos por cosecha de 54 y 18 parcelas, respectivamente. También se calculó la edad de las parcelas con informantes locales, sensores remotos, C14 y anillos de crecimiento. En cada parcela medimos la biomasa aérea viva por hectárea (Bav) y la de las raíces gruesas por hectárea (Brg). Modelamos la Bav y Brg en función de la edad mediante la ecuación de von Bertalanfy con asíntotas de 247t/ha (Bav) y 66t/ha (Brg) resultantes de la medición de 33 parcelas de 0.1ha en los bosques primarios. Con la razón Brg/Bav=f(t) estimamos 87 años para que los bosques secundarios recuperen la Bav existente en los primarios y 217 años para recuperar la Brg. La tasa máxima de crecimiento instantáneo de la Bav fue 6.95t/ha/año a los 10 años y la tasa media máxima de crecimiento 6.26t/ha/año a los 17 años. La media ponderada de la tasa de crecimiento absoluto de la Bav alcanzó 4.57t/ha/año y la relativa 10% anual. La razón Brg/Bav inicialmente aumenta muy aceleradamente hasta 4-5 años (25%), luego disminuye hasta 25 años (18%) para luego incrementar hasta 26.7 Abstract in english Biomass recovery through secondary succession in the Cordillera Central de los Andes, Colombia. Estimations on biomass recovery rates by secondary tropical forests are needed to understand the complex tropical succession, and their importance on CO2 capture, to offset the warming of the planet. We c [...] onducted the study in the Porce River Canyon between 550 and 1 700m.a.s.l. covering tropical and premontane moist belts. We established 33 temporary plots of 50mx20m in secondary forests, including fallows to succesional forests, and ranging between 3 and 36 years old; we measured the diameter at breast height (D) of all woody plants with D?5cm. In each one of these plots we established five 10mx10m subplots, in which we measured the diameter betweem 1cm?D

Jorge Ignacio, del Valle; Héctor Iván, Restrepo; Mónica María, Londoño.

90

Estudio de la oxidación a elevada temperatura de ocho aleaciones en atmósferas de combustión de biomasa  

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Full Text Available The combustion of biomass, especially wheat straw, generates very corrosive media particularly near the superheater tubes. Chlorine is known to be the main corrosive agent in biomass-fired plants. This paper focuses on the study of the corrosivity of such environments composed of gases and ashes, at high temperature, on eight commercial alloys with different chromium and nickel contents. These have been: AISI 347 CG (1.4550, AISI 347 FG(1.4550, AISI 316LN (1.4910, ESSHETE 1250 (1.4982, AC 66 (1.4877, X20CrMoV12:1 (1.4922 and AISI 347 coated with Inconel 625 and Inconel 686. Corrosion tests in the boiler have been performed during 8.000 h and 15.000 h at temperatures between 500 °C y 550 °C in the biomass plant of Sangüesa (Navarra, Spain. Experimental results showed an unacceptable behaviour far the martensitic steel, acceptable far the austenitics and good far the inconels. The appearance of the corrosion attack was also investigated to obtain understanding of the corrosion mechanism. The corrosion mechanism by molten salts has been rejected. The active oxidation corrosion mechanism has been proposed as the most probable in order to interpretate the corrosion behaviour of these materials in these environments.

La combustión de biomasa, especialmente de paja de cereal, genera un ambiente muy corrosivo, particularmente, cerca de los tubos sobrecalentadores. El cloro es el principal agente corrosivo en las plantas de biomasa. Este trabajo se centra en comprobar el comportamiento de ocho aleaciones comerciales en una ambiente de combustión de biomasa. Los materiales estudiados han sido las siguientes: AISI 347 CG (1.4550, AISI 347 FG (1.4550, AISI 316LN (1.4910, ESSHETE 1250 (1.4982, AC 66 (1.4877, X20CrMoV12:1 (1.4922 y AISI 347 recubiertos con Inconel 625 e Inconel 686. Los ensayos se han realizado en la caldera de la planta de biomasa de Sangüesa (Navarra, España durante 8.000 y 15.000 h a una temperatura de 500-550 °C. Los resultados indican un buen comportamiento de los aceros inoxidables austeníticos y de las aleaciones de Inconel, mientras que el del acero martensítico no ha sido aceptable. Se ha propuesto el mecanismo conocido como “oxidación activa” para interpretar el comportamiento a la corrosión de estos materiales en estos medios.

Berlanga-Labari, C.

2008-08-01

91

Biomassa de rotíferos em ambientes dulcícolas: Revisão de métodos e fatores influentes / Rotifer biomass in freshwater environments: Review of methods and influencing factors / Biomasa de rotíferos en ambientes dulciacuícolas: Revisión de métodos y factores influyentes  

Scientific Electronic Library Online (English)

Full Text Available SciELO Venezuela | Language: Portuguese Abstract in portuguese A biomassa de uma comunidade aquática fornece informações quantitativas da matéria orgânica disponível nos diferentes níveis tróficos. As dificuldades metodológicas para se estimar a biomassa zooplanctônica explicam os poucos estudos existentes, principalmente no Brasil. Neste estudo objetiva-se des [...] crever as metodologias mais utilizadas na estimativa da biomassa de rotíferos, analisar suas vantagems e desvantagems, comparar resultados obtidos com cada técnica, e investigar alguns fatores que influenciam sua biomassa. A estimativa mais utilizada é a determinação do volume, a partir de dimensões lineares. Estudos apontam que os valores estimados da biomassa de rotíferos podem variar de acordo com as metodologias de amostragem, preservação dos indivíduos, características limnológicas dos ambientes e genotípicas dos indivíduos, predação, disponibilidade de alimento, além da sazonalidade. Todos esses fatores evidenciam a necessidade de se estimar a biomassa ao invés da utilização de equações já descritas na literatura, bem como a importância de se descrever detalhadamente a metodologia utilizada em cada amostragem, e algumas características limnológicas dos ambientes estudados. Abstract in spanish La biomasa de una comunidad acuática provee información cuantitativa de la materia orgánica disponible en los diferentes niveles tróficos. Las dificultades metodologías en la estimación de la biomasa zooplanctónica explican los pocos estudios existentes, principalmente en Brasil. Se describen los mé [...] todos más utilizados en la estimación de la biomasa de rotíferos, se analizan sus ventajas y desventajas, se comparan los resultados obtenidos con cada técnica, y se discuten algunos factores que influyen en su biomasa. El método más utilizado es la determinación del biovolumen, obtenido a partir de las dimensiones lineales de los rotíferos. La mayor parte de los estudios sugieren que la biomasa de rotíferos varía de acuerdo con los métodos de muestreo, la conservación de los individuos, la depredación y la disponibilidad de alimentos, además de la estacionalidad. Todos estos factores evidencian la necesidad de estimar la biomasa en lugar de utilizar ecuaciones ya descritas en la literatura, así como la importancia de describir el método utilizado en cada muestreo y algunas características limnológicas de los ambientes estudiados. Abstract in english The biomass of an aquatic community provides quantitative information from available organic matter in different trophic levels. The methodological difficulties in estimating zooplankton biomass explain the scarcity of existing studies, particularly in Brazil. The most used methodologies for rotifer [...] biomass estimation are described and their advantages and disadvantages analyzed. Results obtained with the different techniques are compared and some factors influencing the biomass are discussed. The most commonly used methodology is the biovolume, calculated from rotifer linear dimensions. Studies point out that rotifers biomass vary according to sampling methodologies, individual preservation, environments limnological characteristics, individual genotypical characteristics, predation, food resource availability and seasonality. All these factors emphasize the importance of estimating biomass instead of using equations already described in the literature, as well as the importance to describe in detail the methodology employed in each sampling and some limnological features of the studied environments.

Dayane, Christian Rossa; Claudia, Costa Bonecker; Leandro, Junio Fulone.

92

Slovenské parlamentné vo?by 2010: nacionálna agenda na ústupe?  

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Full Text Available The 2010 Slovak Parliamentary Elections: National Agenda on Retreat? In the Slovak parliamentary elections of 2010, the reformist centre-right parties defeated the left-nationalist coalition government led by Robert Fico. The election results brought some other surprises – the Movement for a Democratic Slovakia and its leader, three-times Prime Minister Vladimír Me?iar, as well as the Party of Hungarian Coalition were eliminated from the national parliament. Moreover, the election outcome of the radical right-wing Slovak National Party declined significantly. On the other hand, two new parties entered parliament. All in all, the election outcomes show the weakening of the nationalist agenda and the nationalist vote. The paper examines why this has happened and raises the question of to what extent it is sustainable.

Olga Gyarfášová

2011-04-01

93

CARNIVORE: an open source VO registry  

Science.gov (United States)

Registries are the keystone of service oriented astronomy, facilitating the publication, resolution and discovery of astronomical resources inherent in using the VO. CARNIVORE is a fully-featured open source VO registry developed at Caltech. It supports publishing, searching and harvesting, and is fully compliant with the IVOA Registry Interface specification. It utilizes the latest XML technologies - XForms, XQuery and a native XML database - to provide a complete end-to-end XML solution for resource metadata: this provides the efficiency and flexibility that relational model-based solutions lack. It is also easily extensible with infrastructure generated directly from XML Schema. CARNIVORE is designed primarily to offer data and service providers who want to set up their own registry the functionality they require in an off-the-shelf implementation: they avoid the hassle of designing a system from scratch and functionality can easily be added or tailored to address specific needs.

Graham, M. J.; Williams, R. D.

2006-07-01

94

Steganography of VoIP streams  

CERN Multimedia

In this paper, we circumscribe available steganographic techniques that can be used for creating covert channels for VoIP (Voice over Internet Protocol) streams. Apart from characterizing existing steganographic methods we provide new insights by presenting two new techniques. First one is network steganography solution and exploits free/unused fields of the RTCP (Real-Time Control Protocol) and RTP (Real-Time Transport Protocol) protocols. The second method provides hybrid storage-timing covert channel by utilizing delayed audio packets. The results of the experiment, that was performed, regardless of steganalysis, to estimate a total amount of data that can be covertly transferred in VoIP RTP stream during the typical call, are also included in this article.

Mazurczyk, Wojciech

2008-01-01

95

What are suspicious VoIP delays?  

CERN Document Server

Voice over IP (VoIP) is unquestionably the most popular real-time service in IP networks today. Recent studies have shown that it is also a suitable carrier for information hiding. Hidden communication may pose security concerns as it can lead to confidential information leakage. In VoIP, RTP (Real-time Transport Protocol) in particular, which provides the means for the successful transport of voice packets through IP networks, is suitable for steganographic purposes. It is characterised by a high packet rate compared to other protocols used in IP telephony, resulting in a potentially high steganographic bandwidth. The modification of an RTP packet stream provides many opportunities for hidden communication as the packets may be delayed, reordered or intentionally lost. In this paper, to enable the detection of steganographic exchanges in VoIP, we examined real RTP traffic traces to answer the questions, what do the "normal" delays in RTP packet streams look like? and, is it possible to detect the use of know...

Mazurczyk, Wojciech; Szczypiorski, Krzysztof

2010-01-01

96

The GIRAFFE Archive : Database and VO access  

Science.gov (United States)

GIRAFFE is an intermediate and high resolution multi-fibre spectrograph installed at VLT/UT2 (ESO) since 2003. It produces 1D spectra in its multi-object configuration and 3D spectra using its integral field unit configurations. The raw data collected by the instrument (science and calibrations) are part of the ESO archive (http://archive.eso.org). The GIRAFFE Archive, developed in Paris Observatory, provides reduced spectra from the observations made by the instrument once they are publicly available. These spectra are automatically reduced using the ESO GIRAFFE data reduction pipeline. The reduced spectra can be accessed via the web interface of the database (giraffe-archive.obspm.fr'>http://giraffe-archive.obspm.fr), which offers a large range of selection criteria, including individual target positions, magnitudes, signal-to-noise ratios, together with an interactive quick look of the reduced spectra. They also can be accessed in the Virtual Observatory via the SSA web service of VO-Paris Data Centre (http://voparis-srv.obspm.fr/portal/). Two collections are available in the VO: the 1D spectra (summed in the case of integral field observations) and the 3D field observations. These latter products can be explored using the VO Paris Euro3D Client (http://voplus.obspm.fr/ chil/Euro3D/).

Royer, F.; Jégouzo, I.; Tajahmady, F.; Normand, J.

2012-09-01

97

Moessbauer effect studies on modified VO2  

International Nuclear Information System (INIS)

Moessbauer experiments are made on modified VO2 of exactly determined iron concentration with precise structural characterization. The following compositions are investigated: Vsub(1-x)Fesub(x)O2 with x up to 0.022, Vsub(1-x)Fesub(x)Osub(2-y) (x = 0.002 and 0.011), and Vsub(0.99-z)Fesub(0.01)Mosub(z)O2 with z up to 0.04. For the M1 phase of stoichiometric Fe-doped samples only a single doublet with low quadrupole splitting is found. The Moessbauer spectra of the T phase confirm its character as a transitional phase between M1 and M2. The behaviour of the Fe-doped VO2 is discussed with the assumption of Fe3+-V4+ bonds on the paired cation sites. The Moessbauer spectra of the oxygen deficient samples and of the Fe-Mo doped VO2 show a single doublet with larger quadrupole splitting compared with the stoichiometric M1 phase. This result can be accounted for by the effect of the electronic defects present in these samples. (author)

1978-01-01

98

RESERVAS DE BIOMASA DE ÁRBOLES DISPERSOS EN POTREROS Y MITIGACIÓN AL CAMBIO CLIMÁTICO  

Directory of Open Access Journals (Sweden)

Full Text Available El presente estudio tuvo como objetivo determinar la contribución de los árboles en potreros a la mitigación al cambio climático mediante la estimación de las reservas de carbono in Costa Rica y Nicaragua. Entre los años 2002 y 2003, 17 783 árboles fueron inventariados en potreros de 59 fincas ubicadas en zonas de bosque tropical seco, húmedo y seco con transición a húmedo. El valor promedio de las reservas de biomasa de los árboles en los potreros fue de 10,7±1,1 Mg/ha con un valor mínimo de 5,3±1 Mg/ha en Rivas y un máximo de 13,5±3,5 Mg/ha en Matiguás. Existe relación entre la biomasa arriba del suelo de los potreros con la densidad árboles y el área basal, lo que permitió desarrollar ecuaciones simples para predecir dichos cambios. El diseño de políticas que incentiven la conservación y manejo de árboles en potreros, será un aspecto clave a ser incorporado dentro de las estrategias de cambio climático de los países.

Mario Chacu00F3n-Leu00F3n

2013-01-01

99

BIOMASA, PROLINA Y PARÁMETROS NITROGENADOS EN PLÁNTULAS DE NOGAL BAJO ESTRÉS HÍDRICO Y FERTILIZACIÓN NITROGENADA  

Directory of Open Access Journals (Sweden)

Full Text Available Se realizó un estudio cuyo objetivo fue medir la respuesta de los procesos fisiológicos bajo las condiciones de estrés hídrico y concentración de nitrógeno (N en plantas de nogal pecanero [Carya illinoinensis (Wangenh C. Koch]. El experimento consistió en la siembra, crecimiento y desarrollo de plantas a partir de semillas de nogal pecanero Western Schley; las cuales fueron sometidas a diferentes manejos: aportación de riego y N, aportación de riego sin N, estrés hídrico y adición de N y finalmente bajo estrés hídrico y ausencia de N. Fueron evaluadas las siguientes variables: altura de planta, diámetro de tronco, concentración de clorofila (unidades SPAD y metanol, número de hojas e índice de área foliar, prolina y biomasa. Los resultados demostraron que, las plántulas con aportación de N y estrés hídrico redujeron la concentración de Nt y N-NO3 - en 21.73 y 61.84 % respectivamente, área foliar y diámetro de tronco en un 53.4 y 36.5 %, respectivamente, incrementándose el contenido de prolina en 39.41 %. Con riego y en ausencia de N se disminuyó el contenido de clorofila en 20 % y la biomasa de tallo en 58.34 %, finalmente el contenido relativo de agua (CRA de tallo y raíz decreció en 61.54 y 60.17 % respectivamente.

Ofelia Adriana Hernu00E1ndez-Rodru00EDguez

2011-01-01

100

Análisis Exergético de la Gasificación de Biomasa Exergy Analysis of Biomass Gasification  

Directory of Open Access Journals (Sweden)

Full Text Available El objetivo de este estudio fue realizar el análisis exergético de la gasificación de biomasa residual con la finalidad de obtener energía útil. Se desarrolló un modelo para la gasificación de biomasa basado en el equilibrio químico de las reacciones. Este modelo permite predecir la evolución de la composición del gas de síntesis en función de la temperatura, las presiones y la composición elemental de los residuos del proceso de extracción de aceite de palma y orujo de lavado de uva (hidrogeno, oxigeno, carbono y nitrógeno, como también hacer un análisis exergético. Se encontró que independiente del agente gasificante, la concentración de monóxido de carbono e hidrógeno tienden a incrementar significativamente a altas presiones y elevadas temperaturas. Además, se muestra que la eficiencia exergética incrementa con la temperatura y disminuye con el aumento de la relación aire/combustible.This paper shows the exergy analysis applied to the gasification process of residual biomass with the purpose of obtaining useful energy. A model for the biomass gasification based on chemical equilibrium of the reactions is proposed. The model allows predicting the syngas composition as a function of temperature, pressure and ultimate analysis of palm oil and grapevine pruning waste (determining hydrogen, oxygen, carbon and nitrogen. It was found that the carbon monoxide and hydrogen concentration significantly increase at high pressure and temperature independently of the gasifying agent. Furthermore, it was also noticed that the exergy efficiency increases as temperature increases, and decreases as the relative fuel/air ratio increases.

Jorge M Mendoza

2012-01-01

 
 
 
 
101

Avaliação da biomassa de microcrustáceos em ambientes aquáticos continentais / Microcrustacean biomass estimation in continental aquatic environments / Evaluación de la biomasa de microcrustáceos en ambientes acuáticos continentales  

Scientific Electronic Library Online (English)

Full Text Available SciELO Venezuela | Language: Portuguese Abstract in portuguese As metodologias para a estimativa da biomassa são variadas. Entretanto, o método mais difundido para obter a biomassa de microcrustáceos zooplanctônicos é a partir da obtenção de equações de regressão linear, considerando a relação peso seco-comprimento dos indivíduos. Esta metodologia é de uso gene [...] ralizado, quase o 75% dos trabalhos pesquisados neste estudo. Em relação aos ambientes estudados, 52% correspondem a trabalhos feitos em regiões temperadas. Nessa região também foi elaborada a maioria das regressões disponíveis na literatura para as diferentes espécies. É necessário desenvolver mais estudos e construir equações para as diferentes espécies presentes nas regiões subtropicais e tropicais. A maioria dos autores citados não especificam se usou indivíduos fixados e não fixados. Tampoco especificam o critério adotado na medição nem quantos indivíduos foram utilizados em cada classe de comprimento. Esto acontece para a elaboração das equações e para o uso das equações já elaboradas, sendo muitas veces estos critérios assumidos como arbitrário. As fórmulas de regressão não devem ser aplicadas universalmente sem reservas. As equações feitas para uma mesma espécie podem variar tanto nos valores da intercepção como na inclinação da reta, pois depende do ambiente onde foram realizadas. Embora, os usuários dessas regressões devem atestar para as variações que as mesmas possam sofrer em função de fatores que afetam a relação peso-comprimento. Conclui-se que, para o cálculo da biomassa por equações peso seco-comprimento, é necessário padronizar os critérios de medição do comprimento, técnicas de preservação, número de indivíduos por classe de comprimento, e tempo e temperatura de secagem. Abstract in spanish Las metodologías para estimación de biomasa son variadas. El método más difundido para el cálculo de la biomasa de microcrustáceos zooplanctónicos parte de la obtención de ecuaciones de regresión lineal, considerando la relación peso seco-longitud de los individuos. Esta metodología es de uso genera [...] lizado, siendo usada en casi 75% de las publicaciones analizadas en el presente estudio. En relación a los diferentes ambientes analizados, 52% corresponden a regiones templadas, donde también fueron realizadas la mayoría de las regresiones disponibles para diferentes especies. Es necesario, por ello, desarrollar más estudios y elaborar ecuaciones para las diferentes especies presentes en ambientes tropicales y subtropicales. La mayoría de los autores citados no especifica el uso de individuos fijados o no, ni especifican el criterio para la medición o cuántos individuos fueron utilizados en cada clase de longitud. Esto ocurre para la elaboración de las ecuaciones y para el uso de ecuaciones elaboradas en otros estudios. Estos criterios son asumidos como arbitrarios, dificultando e impidiendo el uso de estas ecuaciones, por lo que las fórmulas no deben ser aplicadas universalmente sin reservas. Las ecuaciones pueden variar, aun para una misma especie, en los valores de intersección y pendiente de la recta, dependiendo del ambiente donde fueron realizadas. Los usuarios de estas regresiones deben considerar las variaciones que las mismas pueden sufrir en función de factores que afectan la relación peso seco-longitud. Se concluye que, para calcular biomasa por ecuaciones peso seco-longitud, es necesario estandarizar los criterios de medición de la longitud de los individuos, técnicas de preservación, número de individuos por clase de longitud, así como tiempo y temperatura de secado. Abstract in english There are several methodologies for biomass estimation. The most common for microcrustacean zooplanktonic biomass determination are based on linear regression equations relating individual dry weight and length. Almost 75% of the papers reviewed in the present stydy have used this methodology, and 5 [...] 2% of them refer to studies ca

Martín C, M. Blettler; Cláudia, Cósta Bonecker.

102

Characterization of nano-InVO4 powders synthesized by the hydrothermal process on various In/V molar ratio and soaking conditions  

International Nuclear Information System (INIS)

Various hydrothermal parameters such as the In/V ratio of starting materials, soaking time and additives were conducted to examine the resulting phase formation and particle morphology of InVO4. The possible reaction during InVO4 formation was proposed. The powders were characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy and BET (Brunauer-Emmett-Teller) surface area measurement. Optical properties were investigated by UV-vis and Fourier transform infrared spectroscopy. The XRD patterns indicated a single InVO4 phase formed at the starting In/V ratio of 1/2 and In(OH)3, Na2V6O16 coexisted with InVO4 when the In/V ratio was 1/1 and 1/3, respectively. For the vanadium-rich samples (In/V = 1/3), the second phase of Na2V6O16 increased with the increasing soaking time and demonstrated significant absorption in UV-vis spectra than pure InVO4. The size and shape of InVO4 particles could be tailored from rod-like into rounded square particles by PVP additives, acting as structure-directing-agent (SDA), up to 0.3 wt%.

2009-07-29

103

Respuesta al déficit hídrico en pinus leiophylla: acumulación de biomasa, desarrollo de hojas secundarias y mortandad de plántulas  

Directory of Open Access Journals (Sweden)

Full Text Available Se establecieron dos ensayos para determinar la respuesta al déficit hídrico de plántulas de 11 poblaciones de Pinus leiophylla Schl. et Cham. catalogadas en dos grupos (?agotador y ahorrador? en función de su consumo de agua. En el primer ensayo, se evaluó el incremento en biomasa y el desarrollo de hojas secundarias en plantas de nueve meses de edad, sometidas a tres niveles de humedad (S0 ?control?, S1 ?déficit moderado?, S2 ?déficit severo? durante dos meses (periodo de sequía, seguido por un periodo de recuperación de cuatro meses. En el segundo ensayo, se suspendió el riego 12 días y dos meses después se evaluaron la mortandad y el daño en el brote terminal de las plantas. La acumulación de biomasa se redujo hasta 80% durante el periodo de sequía en el nivel S2; en cambio, durante el periodo de recuperación la acumulación de biomasa fue similar en los tres niveles de humedad. Las poblaciones ?ahorradoras? de humedad fueron más sensibles al déficit hídrico, pero durante el periodo de recuperación acumularon mayor biomasa que las poblaciones ?agotadoras?. El déficit hídrico severo también ocasionó un retraso en el desarrollo de hojas secundarias, siendo más notorio el efecto en el grupo ?ahorrador?. Asociado a su menor consumo de agua, el grupo ?ahorrador? presentó menor mortandad y daño al brote terminal que el grupo ?agotador?, por lo que en condiciones de sequía ese tipo de poblaciones podría ser útil en la restauración de sitios donde exista una baja disponibilidad de agua.

T. Martu00EDnez Trinidad

2002-01-01

104

RELACIÓN ENTRE LA BIOMASA Y ALGUNAS CARACTERÍSTICAS MORFOLÓGICAS DE LAS BROMELIAS FITOTELMATAS DE UN BOSQUE ALTO ANDINO COLOMBIANO  

Directory of Open Access Journals (Sweden)

Full Text Available Se evaluaron algunas características morfológicas para seis especies de bromelias fitotelmata (Guzmania gloriosa, Racinaea tetrantha, Tillandsia biflora, T. complanata, T. fendleri y T. turneri con el fin de establecer cuales características podrían utilizarse como estimadores indirectos de la biomasa total de la planta. El estudio se realizó en un bosque alto andino de la Sabana de Bogotá, Colombia, ubicado a 2900 m de altitud. Para cada especie se recolectaron entre 32 y 64 individuos en diferentes estadios de crecimiento, a cada uno de los cuales se le registró: 1 el número de hojas por roseta; 2 el perímetro de la base de la roseta; 3 la cobertura de la planta; 4 el largo de la lámina foliar; 5 la altura de la roseta; y 6 la biomasa total. Los resultados de la prueba Wilcoxon muestran que la cobertura fue la variable que más se relacionó con la biomasa. Una prueba de ajuste de curva mostró que la línea recta es la que más explica la relación entre la cobertura y la biomasa, permitiendo hacer estimaciones a partir de la ecuación sin ser necesario un muestreo destructivo.

Isaza Carolina

2009-06-01

105

Intrusion detection mechanisms for VoIP applications  

CERN Document Server

VoIP applications are emerging today as an important component in business and communication industry. In this paper, we address the intrusion detection and prevention in VoIP networks and describe how a conceptual solution based on the Bayes inference approach can be used to reinforce the existent security mechanisms. Our approach is based on network monitoring and analyzing of the VoIP-specific traffic. We give a detailed example on attack detection using the SIP signaling protocol.

Nassar, M E B; Festor, O; Nassar, Mohamed El Baker; State, Radu; Festor, Olivier

2006-01-01

106

Proceso de gasificación de biomasa: una revisión de estudios teórico- experimentales / Biomass gasification process: theoretical and experimental studies a review  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in spanish La situación energética y medioambiental mundial hace que la generación de energía mediante sistemas basados en energías renovables tome cada vez una mayor relevancia. Estos sistemas tienen una doble ventaja ya que posibilitan la diversificación energética y reducen la dependencia del petróleo a la [...] vez que se disminuyen las emisiones globales de CO2. La biomasa es uno de los recursos energéticos con mayor potencial tanto en países desarrollados como emergentes pero sigue sin sufrir el desarrollo esperado. La gasificación de biomasa es uno de los sistemas con gran potencial ya que permite la generación tanto de energía térmica como eléctrica, mediante tecnologías de bajo costo como los gasificadores de lecho fijo (potencias medias- bajas), o reactores de lecho fluidizado con tecnología más exigente y con mayor capacidad de generación. La transformación de la biomasa en un combustible gaseoso, aprovechable en motores de combustión interna alternativos o en turbinas de gas como combustible, exige que la biomasa atraviese varios procesos termoquímicos, compuestos por reacciones endotérmicas (secado, devolatilización y reducción) y exotérmicas (oxidación de volátiles y carbón). La selección de un gasificador requiere conocer las propiedades de la biomasa, mientras que el diseño del mismo exige conocer el fenómeno termoquímico por completo. El objetivo de este trabajo es presentar una revisión actualizada de los diferentes planteamientos tanto teóricos como experimentales desarrollados para estudiar el proceso de gasificación de biomasa, tanto en lecho fijo como en lecho fluidizado, con miras a diseñar gasificadores de biomasa. Abstract in english Each day the energy systems relying on renewable resources are more relevant in the world energy politics due to the fossil energy and environmental crisis. These systems increase energy resources of countries, reduce the oil dependency, and diminish CO2 global emissions. Biomass is one of the renew [...] able resources with higher potential in developing and developed countries. Biomass gasification has huge possibilities to be developed. Such as fixed bed gasifiers, or fluidized bed reactors with more technology demanding and more power capacity. Biomass transformation in a gaseous fuel to be used in a reciprocating internal combustion engine or gas turbines requires that biomass passes through several thermochemical stages. Endothermic reactions (drying, pyrolysis and reduction) and exothermic process (volatiles and carbon oxidation). To select a specific gasifier it is necessary to know biomass properties (chemical and physical), whereas to design a reactor it is necessary to know and understand the complete phenomena. The aim of this work is to show an actualized review about different theoretical and experimental approaches to study biomass gaification process in fixed and fluidized bed reactors in order to design biomass gasifiers.

Pérez, Juan; Borge, David; Agudelo, John.

107

Photoemission study of TiO2/VO2 interfaces  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We have measured photoemission spectra of two kinds of TiO$_2$-capped VO$_2$ thin films, namely, that with rutile-type TiO$_2$ (r-TiO$_2$/VO$_2$) and that with amorphous TiO$_2$ (a-TiO$_2$/VO$_2$) capping layers. Below the Metal-insulator transition temperature of the VO$_2$ thin films, $\\sim 300$ K, metallic states were not observed for the interfaces with TiO$_2$, in contrast with the interfaces between the band insulator SrTiO$_3$ and the Mott insulator LaTiO$_3$ in spite...

Maekawa, K.; Takizawa, M.; Wadati, H.; Yoshida, T.; Fujimori, A.; Kumigashira, H.; Oshima, M.; Muraoka, Y.; Nagao, Y.; Hiroi, Z.

2006-01-01

108

The Astrophysical Virtual Observatory to EURO-VO Transition  

CERN Document Server

The Astrophysical Virtual Observatory (AVO) initiative, jointly funded by the European Commission and six European organisations, had the task of creating the foundations of a regional scale infrastructure by conducting a research and demonstration programme on the VO scientific requirements and necessary technologies. The AVO project is now formally concluded. I highlight AVO's main achievements and then describe its successor, the EURO-VO project. With its three new interlinked structures, the Data Centre Alliance, the Facility Centre, and the Technology Centre, the EURO-VO is the logical next step for the deployment of an operational VO in Europe.

Padovani, P

2005-01-01

109

Evaluation of VoIP Security for Mobile Devices  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Market research reports by In-Stat, Gartner, and the Swedish Post and Telecom Agency (PTS) reveal a growing worldwide demand for Voice over IP (VoIP) and smartphones. This trend is expected to continue over the coming years and there is wide scope for mobile VoIP solutions. Nevertheless, with this growth in VoIP adoption come challenges related with quality of service and security. Most consumer VoIP solution, even in PCs, analog telephony adapters, and home gateways, do not yet support media...

Nakarmi, Prajwol Kumar

2011-01-01

110

Componente lento do VO2 em crianças durante exercício pesado de corrida: análise com base em diferentes modelos matemáticos Componente lento de VO2 en niños durante ejercicio arduo de carrera: análisis con base en diferentes modelos matemáticos Slow component of VO2 in children during running exercise performed at heavy intensity domain: analysis with different mathematical models  

Directory of Open Access Journals (Sweden)

Full Text Available O objetivo deste estudo foi verificar e quantificar a magnitude do componente lento do consumo de oxigênio (CL em crianças submetidas a exercícios de corrida em esteira rolante, com cargas constantes de intensidade acima do limiar de lactato (75%D, utilizando para isso dois modelos de análise: a modelo matemático com três termos exponenciais; e b modelo deltaVO2 6-3min. Participaram do estudo oito crianças do sexo masculino (11,92 ± 0,63 anos; 44,06 ± 13,01kg; 146,63 ± 7,25cm; e níveis de maturação sexual 1 e 2, aparentemente saudáveis, não treinadas, que realizaram em diferentes dias: 1 teste incremental na esteira rolante para a determinação do consumo de oxigênio de pico (VO2pico e do limiar de lactato (LL; e 2 dois testes de carga constante em esteira rolante durante seis minutos na intensidade de 75%delta [75%delta = LL + 0,75 x (VO2pico - LL]. Para determinação do CL utilizaram-se: a modelo matemático de três termos (Exp3; e b a diferença no VO2 entre o sexto e o terceiro minuto de exercício (deltaVO2 6-3min. O CL foi expresso em valores absolutos (ml/min e também como a contribuição percentual do CL para o aumento do VO2 no final do exercício (%CL. O CL determinado pelo modelo Exp3 (129,69 ± 75,71ml/min e 8,4 ± 2,92% foi significantemente maior do que o obtido pelo modelo deltaVO2 6-3min (68,69 ± 102,54ml/min e 3,6 ± 7,34%. Portanto, os valores de CL obtidos em crianças durante o exercício de corrida realizado no domínio pesado (75%delta são dependentes do modelo de análise (Exp3 x deltaVO2 6-3min.El objetivo de este estudio ha sido el de verificar y cuantificar la magnitud del componente lento del consumo de oxígeno (CL en niños, sometidos a ejercicios de carrera en cinta rodante, con cargas constantes de intensidad por encima del límite de lactato (75%delta, utilizando para esto dos modelos de análisis: a modelo matemático con tres términos exponenciales; y b modelo deltaVO2 6-3 min. Participaron del estudio 8 niños del sexo masculino (11,92 ± 0,63 años; 44,06 ± 13,01 kg; 146,63 ± 7,25 cm; y niveles de madurez sexual 1 y 2, aparentemente saludables, no entrenados, que realizaron en diferentes días: 1 Test incremental en la cinta rodante para determinar el consumo de oxígeno de pico (VO2pico y del límite de lactato (LL; y 2 Dos tests de carga constante en cinta rodante durante seis minutos a intensidad de 75%delta [75%delta = LL + 0,75 x (VO2pico - LL]. Para determinar el CL usamos: a modelo matemático de tres términos (Exp3; y b la diferencia en el VO2 entre el sexto y el tercer minuto de ejercicio (deltaVO2 6-3 min. El CL fue expresado en valores absolutos (ml/min y también como contribución porcentual de CL para el aumento de VO2 al final del ejercicio (%CL. El CL determinado por el modelo Exp3 (129,69 ± 75,71 ml/min y 8,4 ± 2,92% fue significativamente mayor al que fue obtenido por el modelo deltaVO2 6-3 min (68,69 ± 102,54 ml/min y 3,6 ± 7,34%. Por tanto, los valores de CL obtenidos en niños durante el ejercicio de carrera realizado en dominio pesado (75%delta son dependientes del modelo de análisis (Exp3 x deltaVO2 6-3 min.The purpose of this study was to identify and quantify the magnitude of the slow component of VO2 (SC in children during running exercise, performed at heavy intensity domain (75%delta, using two different mathematical models: a three-exponential model and; b deltaVO2 6-3 min. Eight healthy male children (11.92 ± 0.63 years; 44.06 ± 13.01 kg; 146.63 ± 7.25 cm; and sexual maturity levels 1 and 2, not trained, performed in different days the following tests: 1 incremental running treadmill test to determine the peak oxygen uptake (VO2peak and the lactate threshold (LT; and 2 two transitions from baseline to 75%delta [75%D = LT + 0.75 x (VO2 peak - LT] for six minutes on treadmill. The SC was deter mined by two models: a three-exponential model (Exp3; and b the VO2 difference between the sixth and the third exercise minute (deltaVO2 6-3min. The SC was expressed as the absolute (ml/min and percent contribution

Fabiana Andrade Machado

2006-12-01

111

Bioadsorción de Cadmio (II en Solución Acuosa por Biomasas Fúngicas Biosorption of Cadmium (II in Aqueous Solutions by Fungal Biomass  

Directory of Open Access Journals (Sweden)

Full Text Available Se determinó la bioadsorción de Cadmio (II en solución por la biomasa celular de quince hongos, por el método colorimétrico de la ditizona. La biomasa de Mucor rouxii IM-80 fue más eficiente en la remoción de Cadmio (II en solución (8.2 mg/g seguida de M. rouxii mutante (7.1 mg/g, A. flavus I (5.9 mg/g y Helminthosporium sp (5.4 mg/g. Para la biomasa de M. rouxii-IM-80, la mayor bioadsorción fue a pH= 5.0-6.0, a 28ºC durante 40 horas con 1.0 mg/200 mL de concentración inicial de Cadmio (II y 80 mg/200 mL de biomasa celular. Se concluye que algunas biomasas fúngicas remueven eficientemente Cadmio (II en solución y pueden utilizarse para descontaminar nichos acuáticos contaminados con este metalThe biosorption of dissolved Cadmium (II using cellular biomass of 15 fungi, using a dithizone colorimetric method, was determined. The Mucor rouxii IM-80 biomass was more efficient in removing Cadmium (II from solution (8.2 mg/g, followed by the M. rouxii mutant (7.1 mg/g, Aspergillus flavus I (5.9 mg/g and Helminthosporium sp (5.4 mg/g biomasses. The highest biosorption for M. rouxii IM-80 was at pH 5.0-6.0, at 28ºC for 40 h employing 1.0 mg/200mL of Cadmium (II as initial concentration, and 80 mg/200 mL of fungal biomass. It was concluded that some fungal biomass efficiently removed Cadmium (II from solution and could be used for decontamination of aquatic habitats polluted with this metal

Ismael Acosta

2007-01-01

112

Bioadsorción de Cadmio (II) en Solución Acuosa por Biomasas Fúngicas / Biosorption of Cadmium (II) in Aqueous Solutions by Fungal Biomass  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish Se determinó la bioadsorción de Cadmio (II) en solución por la biomasa celular de quince hongos, por el método colorimétrico de la ditizona. La biomasa de Mucor rouxii IM-80 fue más eficiente en la remoción de Cadmio (II) en solución (8.2 mg/g) seguida de M. rouxii mutante (7.1 mg/g), A. flavus I (5 [...] .9 mg/g) y Helminthosporium sp (5.4 mg/g). Para la biomasa de M. rouxii-IM-80, la mayor bioadsorción fue a pH= 5.0-6.0, a 28ºC durante 40 horas con 1.0 mg/200 mL de concentración inicial de Cadmio (II) y 80 mg/200 mL de biomasa celular. Se concluye que algunas biomasas fúngicas remueven eficientemente Cadmio (II) en solución y pueden utilizarse para descontaminar nichos acuáticos contaminados con este metal Abstract in english The biosorption of dissolved Cadmium (II) using cellular biomass of 15 fungi, using a dithizone colorimetric method, was determined. The Mucor rouxii IM-80 biomass was more efficient in removing Cadmium (II) from solution (8.2 mg/g), followed by the M. rouxii mutant (7.1 mg/g), Aspergillus flavus I [...] (5.9 mg/g) and Helminthosporium sp (5.4 mg/g) biomasses. The highest biosorption for M. rouxii IM-80 was at pH 5.0-6.0, at 28ºC for 40 h employing 1.0 mg/200mL of Cadmium (II) as initial concentration, and 80 mg/200 mL of fungal biomass. It was concluded that some fungal biomass efficiently removed Cadmium (II) from solution and could be used for decontamination of aquatic habitats polluted with this metal

Acosta, Ismael; Moctezuma-Zárate, María de Guadalupe; Cárdenas, Juan F; Gutiérrez, Conrado.

113

COMPORTAMIENTO DE LA ACUMULACIÓN Y DISTRIBUCIÓN DE BIOMASA EN GENOTIPOS DE PAPA ESTABLECIDOS EN CONDICIONES DE SECANO  

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Full Text Available El estudio se realizó durante el periodo de secano de 1996, en Metepec, México, para determinar el comportamiento de la acumulación y distribución de biomasa en los diferentes órganos y en la planta completa de cinco genotipos de papa; éstos fueron establecidos en surcos de 90 cm de anchura y 30 cm de distancia entre plantas de un sólo tallo. Después de la emergencia, a intervalos de 7±1 días, fueron cosechadas cinco plantas en competición completa y disecadas la parte aérea (hojas, tallo principal y tallo de ramas y subterránea (raíces, estolones, tubérculos y sección enterrada del tallo principal. Posteriormente fueron puestas a secar en una estufa con aire forzado a 75 °C por 72 h hasta alcanzar su peso seco constante. El comportamiento de la acumulación y distribución de biomasa hacia los diferentes órganos de la planta estuvo asociada, en la mayoría de los casos, con el hábito de crecimiento de los genotipos: determinado en 'Alpha', 'Norteña' y 'C-771A11', o indeterminado en 'Puebla' y 'C-676014'. Las curvas de acumulación fueron similares entre genotipos y su tendencia general se ajustó a modelos de tipo logístico o polinomial. A partir de los 45 a 50 días después la emergencia, la acumulación de biomasa en la parte subterránea y la planta completa fue casi paralela. La duración de la etapa de tuberización afectó la acumulación de biomasa en los tubérculos de manera que los genotipos de ciclo intermedio, como 'Norteña' y 'C-676014', fueron más eficientes (272 y 294 g·planta-1 que los precoces o tardíos. Entre los órganos aéreos, las hojas acumularon más biomasa (40-53 y 79-81 g·planta-1, independientemente del hábito de crecimiento de los genotipos.

H. Lozoya-Saldau00F1a

2005-01-01

114

ESTUDIOS TOXICOLOGICOS COMO HERRAMIENTA PARA EVALUAR EL DESEMPENO DE UN REACTOR ANAEROBIO DE BIOMASA INMOVILIZADA  

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Full Text Available Los efluentes de la Industria de Papel y Celulosa son usualmente tóxicos y mutagénicos. Esa característica se deriva principalmente por la presencia de compuestos xenobióticos formados durante el proceso. Los parámetros globales para el análisis de la calidad del agua como, demanda química de oxigeno, carbón orgánico total, entre otros, no permiten identificar si el potencial toxicológico es remediado después de los tratamientos. El objetivo de este trabajo fue evaluar el desempeño de un reactor anaerobio horizontal de biomasa inmovilizada (RAHBI tratando un efluente real de blanqueamiento de celulosa Kraft, por medio de ensayos de toxicidad (Daphnia similis Ceriodaphnia silvestrii , mutagenicidad y citotoxicidad (Allium cepa L. . Los resultados mostraron alta sensibilidad de todos los organismos estudiados y buena capacidad del reactor anaerobio para remover compuestos que ejercen efectos tóxicos y mutagénicos. Los bioensayos estudiados representan una alternativa interesante para el análisis de la calidad del agua y para la evaluación del desempeño de tratamientos.

EDUARDO CLETO PIRES

2010-01-01

115

The Effect of Habitual Smoking on VO2max  

Science.gov (United States)

VO2max is associated with many factors, including age, gender, physical activity, and body composition. It is popularly believed that habitual smoking lowers aerobic fitness. PURPOSE: to determine the effect of habitual smoking on VO2max after controlling for age, gender, activity and BMI. METHODS: 2374 men and 375 women employed at the NASA/Johnson Space Center were measured for VO2max by indirect calorimetry (RER>=1.1), activity by the 11 point (0-10) NASA Physical Activity Status Scale (PASS), BMI and smoking pack-yrs (packs day*y of smoking). Age was recorded in years and gender was coded as M=1, W=0. Pack.y was made a categorical variable consisting of four levels as follows: Never Smoked (0), Light (1-10), Regular (11-20), Heavy (>20). Group differences were verified by ANOVA. A General Linear Models (GLM) was used to develop two models to examine the relationship of smoking behavior on VO2max. GLM #1(without smoking) determined the combined effects of age, gender, PASS and BMI on VO2max. GLM #2 (with smoking) determined the added effects of smoking (pack.y groupings) on VO2max after controlling for age, gender, PASS and BMI. Constant errors (CE) were calculated to compare the accuracy of the two models for estimating the VO2max of the smoking subgroups. RESULTS: ANOVA affirmed the mean VO2max of each pack.y grouping decreased significantly (pBMI were independently related with VO2max (R2 = 0.642, SEE = 4.90, pBMI the effect of habitual smoking on reducing VO2max is minimal, about 0.85 ml/kg/min, until the habit exceeds 20 pack.y at which point an additional decrease of 1.71 ml/kg/min is noted. Adding pack.y data improves the accuracy of predicting the VO2max of smokers.

Wier, Larry T.; Suminski, Richard R.; Poston, Walker S.; Randles, Anthony M.; Arenare, Brian; Jackson, Andrew S.

2008-01-01

116

¿Controla la biomasa de pastos marinos la densidad de los peracáridos (Crustacea: Peracarida) en lagunas tropicales?  

Scientific Electronic Library Online (English)

Full Text Available SciELO Costa Rica | Language: Spanish Abstract in spanish Se analizó la variación en tiempo y espacio de los crustáceos peracáridos que habitan las praderas de Ruppia maritima del sistema lagunar de Alvarado, Veracruz, Golfo de México. El muestreo de esta asociación de crustáceos se realizó de diciembre de 1992 a noviembre de 1994. Los organismos se obtuvi [...] eron de 108 muestras recolectadas en seis sitios con R. maritima. La asociación de crustáceos incluyó 11 especies. Ocho especies en Amphipoda (Hourstonius laguna, Cerapus benthophilus, Apocorophium louisianum, Grandidierella bonnieroides, Leptocheirus rhizophorae, Gammarus mucronatus, Melita longisetosa y Haustorius sp.), una en Isopoda (Cassidinidea ovalis) y dos en Tanaidacea (Discapseudes holthuisi and Leptochelia savignyi). La taxocenosis, la densidad y la biomasa de estos organismos mostraron pulsos estacionales relacionados positivamente con la variación de la biomasa de R. maritima, la salinidad, los afluentes epicontinentales y las bocas de comunicación. Las especies C. ovalis, G. mucronatus, A. louisianum y D. holthuisi fueron componentes dominantes en la asociación de peracáridos. Abstract in english Does sea-grass biomass control the density of peracarids (Crustacea: Peracarida) in tropical lagoons? We analyzed the time-space variation of the peracarid crustaceans that inhabit seagrasses of the Alvarado Lagoon System, Veracruz, Gulf of Mexico. The organisms were collected from 108 samples in si [...] x sites with Ruppia maritima beds (December 1992 to November 1994). The assemblage was composed of 11 species. Eight species of Amphipoda (Hourstonius laguna, Cerapus benthophilus, Apocorophium louisianum, Grandidierella bonnieroides, Leptocheirus rhizophorae, Gammarus mucronatus, Melita longisetosa and Haustorius sp.), one of Isopoda (Cassidinidea ovalis) and two of Tanaidacea (Discapseudes holthuisi and Leptochelia savignyi) were identified. Taxocoenosis, density and biomass of peracarids showed seasonal pulses related to R. maritima biomass, salinity variation, epicontinental affluent and inlets. The species C. ovalis, G. mucronatus, A. louisianum and D. holthuisi were dominant. Rev. Biol. Trop. 55 (1): 43-53. Epub 2007 March. 31.

Ignacio, Winfield; Sergio, Cházaro-Olvera; Fernando, Álvarez.

117

Análisis Exergético de la Gasificación de Biomasa / Exergy Analysis of Biomass Gasification  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish El objetivo de este estudio fue realizar el análisis exergético de la gasificación de biomasa residual con la finalidad de obtener energía útil. Se desarrolló un modelo para la gasificación de biomasa basado en el equilibrio químico de las reacciones. Este modelo permite predecir la evolución de la [...] composición del gas de síntesis en función de la temperatura, las presiones y la composición elemental de los residuos del proceso de extracción de aceite de palma y orujo de lavado de uva (hidrogeno, oxigeno, carbono y nitrógeno), como también hacer un análisis exergético. Se encontró que independiente del agente gasificante, la concentración de monóxido de carbono e hidrógeno tienden a incrementar significativamente a altas presiones y elevadas temperaturas. Además, se muestra que la eficiencia exergética incrementa con la temperatura y disminuye con el aumento de la relación aire/combustible. Abstract in english This paper shows the exergy analysis applied to the gasification process of residual biomass with the purpose of obtaining useful energy. A model for the biomass gasification based on chemical equilibrium of the reactions is proposed. The model allows predicting the syngas composition as a function [...] of temperature, pressure and ultimate analysis of palm oil and grapevine pruning waste (determining hydrogen, oxygen, carbon and nitrogen). It was found that the carbon monoxide and hydrogen concentration significantly increase at high pressure and temperature independently of the gasifying agent. Furthermore, it was also noticed that the exergy efficiency increases as temperature increases, and decreases as the relative fuel/air ratio increases.

Jorge M, Mendoza; Antonio J, Bula; Rafael D, Gómez; Lesmes A, Corredor.

118

¿Controla la biomasa de pastos marinos la densidad de los peracáridos (Crustacea: Peracarida en lagunas tropicales?  

Directory of Open Access Journals (Sweden)

Full Text Available Se analizó la variación en tiempo y espacio de los crustáceos peracáridos que habitan las praderas de Ruppia maritima del sistema lagunar de Alvarado, Veracruz, Golfo de México. El muestreo de esta asociación de crustáceos se realizó de diciembre de 1992 a noviembre de 1994. Los organismos se obtuvieron de 108 muestras recolectadas en seis sitios con R. maritima. La asociación de crustáceos incluyó 11 especies. Ocho especies en Amphipoda (Hourstonius laguna, Cerapus benthophilus, Apocorophium louisianum, Grandidierella bonnieroides, Leptocheirus rhizophorae, Gammarus mucronatus, Melita longisetosa y Haustorius sp., una en Isopoda (Cassidinidea ovalis y dos en Tanaidacea (Discapseudes holthuisi and Leptochelia savignyi. La taxocenosis, la densidad y la biomasa de estos organismos mostraron pulsos estacionales relacionados positivamente con la variación de la biomasa de R. maritima, la salinidad, los afluentes epicontinentales y las bocas de comunicación. Las especies C. ovalis, G. mucronatus, A. louisianum y D. holthuisi fueron componentes dominantes en la asociación de peracáridos.Does sea-grass biomass control the density of peracarids (Crustacea: Peracarida in tropical lagoons? We analyzed the time-space variation of the peracarid crustaceans that inhabit seagrasses of the Alvarado Lagoon System, Veracruz, Gulf of Mexico. The organisms were collected from 108 samples in six sites with Ruppia maritima beds (December 1992 to November 1994. The assemblage was composed of 11 species. Eight species of Amphipoda (Hourstonius laguna, Cerapus benthophilus, Apocorophium louisianum, Grandidierella bonnieroides, Leptocheirus rhizophorae, Gammarus mucronatus, Melita longisetosa and Haustorius sp., one of Isopoda (Cassidinidea ovalis and two of Tanaidacea (Discapseudes holthuisi and Leptochelia savignyi were identified. Taxocoenosis, density and biomass of peracarids showed seasonal pulses related to R. maritima biomass, salinity variation, epicontinental affluent and inlets. The species C. ovalis, G. mucronatus, A. louisianum and D. holthuisi were dominant. Rev. Biol. Trop. 55 (1: 43-53. Epub 2007 March. 31.

Ignacio Winfield

2007-03-01

119

Efeito do tempo de intervalo da amostra ventilatória na variabilidade do consumo máximo de oxigênio (VO2 máx) em jogadores de futebol profissional / Effect of time intervals of ventilatory sampling in the variability of maximum oxygen uptake in professional soccer players  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese O propósito deste estudo foi verificar, em futebolistas profissionais, o impacto de sete intervalos de tempo sobre a variável fisiológica consumo máximo de oxigênio (VO2 máx). Dezoito jogadores de futebol com média de idade de 24 ± 4 anos (18-31), peso de 72,5 ± 5,9kg (62-83) e estatura de 176,5 ± 7 [...] ,0cm (164-188) foram submetidos a teste ergométrico máximo em esteira rolante, utilizando-se protocolo escalonado contínuo. A resposta de freqüência cardíaca (FC) foi registrada por meio de um eletrocardiógrafo computadorizado de 12 derivações simultâneas. A ventilação pulmonar (V E), o consumo de oxigênio (VO2), a produção de dióxido de carbono (VCO2) e a razão de troca respiratória (RER) foram calculadas a partir de valores medidos por um sistema espirométrico computadorizado. Os resultados deste estudo demonstraram que houve variabilidade significante do VO2 máx (p Abstract in english The purpose of this investigation was to verify the impact of seven ventilatory time intervals on the maximum oxygen uptake (VO2 max) in professional soccer players. Eighteen male soccer players aged 24.4 ± 4 (18-31), weight 72.5 ± 5.9 kg (62-83) and height 176.5 ± 7 cm (164-188) were submitted to a [...] maximum exercise test on treadmill, using the continuous protocol. The heart rate response was recorded by means of computerized ECG with 12 leads, simultaneously. The respiratory exchange ratio, carbon dioxide production, oxygen uptake and pulmonary ventilation were calculated by means of the spirometric computerized system. The results of this study demonstrated that there was significant variability (p

Silva, Paulo Roberto Santos; Romano, Angela; Visconti, Ana Maria; Teixeira, Alberto Alves de Azevedo; Roxo, Carla Dal Maso Nunes; Machado, Gilberto da Silva; Rebello, Luciana Collet Winther; Sousa, Jorge Mendes de.

120

Evolution of the spectral weight in the Mott-Hubbard series SrVO3-CaVO3-LaVO3-YVO3  

International Nuclear Information System (INIS)

The Mott-Hubbard series SrVO3-CaVO3-LaVO3-YVO3 present a distinct metal-insulator transition. The microscopic origin of this transition can be related to the correlation effects in the electronic structure. The valence band photoemission results show very interesting trends across these Mott-Hubbard series. These results suggest that the O 2p states play an important role in the Mott-Hubbard transition. Some of the changes in the spectra are unexpected and cannot be explained by the current Mott-Hubbard theories (author)

2008-01-01

 
 
 
 
121

Componente lento do VO2 em crianças durante exercício pesado de corrida: análise com base em diferentes modelos matemáticos / Slow component of VO2 in children during running exercise performed at heavy intensity domain: analysis with different mathematical models / Componente lento de VO2 en niños durante ejercicio arduo de carrera: análisis con base en diferentes modelos matemáticos  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese O objetivo deste estudo foi verificar e quantificar a magnitude do componente lento do consumo de oxigênio (CL) em crianças submetidas a exercícios de corrida em esteira rolante, com cargas constantes de intensidade acima do limiar de lactato (75%D), utilizando para isso dois modelos de análise: a) [...] modelo matemático com três termos exponenciais; e b) modelo deltaVO2 6-3min. Participaram do estudo oito crianças do sexo masculino (11,92 ± 0,63 anos; 44,06 ± 13,01kg; 146,63 ± 7,25cm; e níveis de maturação sexual 1 e 2), aparentemente saudáveis, não treinadas, que realizaram em diferentes dias: 1) teste incremental na esteira rolante para a determinação do consumo de oxigênio de pico (VO2pico) e do limiar de lactato (LL); e 2) dois testes de carga constante em esteira rolante durante seis minutos na intensidade de 75%delta [75%delta = LL + 0,75 x (VO2pico - LL)]. Para determinação do CL utilizaram-se: a) modelo matemático de três termos (Exp3); e b) a diferença no VO2 entre o sexto e o terceiro minuto de exercício (deltaVO2 6-3min). O CL foi expresso em valores absolutos (ml/min) e também como a contribuição percentual do CL para o aumento do VO2 no final do exercício (%CL). O CL determinado pelo modelo Exp3 (129,69 ± 75,71ml/min e 8,4 ± 2,92%) foi significantemente maior do que o obtido pelo modelo deltaVO2 6-3min (68,69 ± 102,54ml/min e 3,6 ± 7,34%). Portanto, os valores de CL obtidos em crianças durante o exercício de corrida realizado no domínio pesado (75%delta) são dependentes do modelo de análise (Exp3 x deltaVO2 6-3min). Abstract in spanish El objetivo de este estudio ha sido el de verificar y cuantificar la magnitud del componente lento del consumo de oxígeno (CL) en niños, sometidos a ejercicios de carrera en cinta rodante, con cargas constantes de intensidad por encima del límite de lactato (75%delta), utilizando para esto dos model [...] os de análisis: a) modelo matemático con tres términos exponenciales; y b) modelo deltaVO2 6-3 min. Participaron del estudio 8 niños del sexo masculino (11,92 ± 0,63 años; 44,06 ± 13,01 kg; 146,63 ± 7,25 cm; y niveles de madurez sexual 1 y 2), aparentemente saludables, no entrenados, que realizaron en diferentes días: 1) Test incremental en la cinta rodante para determinar el consumo de oxígeno de pico (VO2pico) y del límite de lactato (LL); y 2) Dos tests de carga constante en cinta rodante durante seis minutos a intensidad de 75%delta [75%delta = LL + 0,75 x (VO2pico - LL)]. Para determinar el CL usamos: a) modelo matemático de tres términos (Exp3); y b) la diferencia en el VO2 entre el sexto y el tercer minuto de ejercicio (deltaVO2 6-3 min). El CL fue expresado en valores absolutos (ml/min) y también como contribución porcentual de CL para el aumento de VO2 al final del ejercicio (%CL). El CL determinado por el modelo Exp3 (129,69 ± 75,71 ml/min y 8,4 ± 2,92%) fue significativamente mayor al que fue obtenido por el modelo deltaVO2 6-3 min (68,69 ± 102,54 ml/min y 3,6 ± 7,34%). Por tanto, los valores de CL obtenidos en niños durante el ejercicio de carrera realizado en dominio pesado (75%delta) son dependientes del modelo de análisis (Exp3 x deltaVO2 6-3 min). Abstract in english The purpose of this study was to identify and quantify the magnitude of the slow component of VO2 (SC) in children during running exercise, performed at heavy intensity domain (75%delta), using two different mathematical models: a) three-exponential model and; b) deltaVO2 6-3 min. Eight healthy male [...] children (11.92 ± 0.63 years; 44.06 ± 13.01 kg; 146.63 ± 7.25 cm; and sexual maturity levels 1 and 2), not trained, performed in different days the following tests: 1) incremental running treadmill test to determine the peak oxygen uptake (VO2peak) and the lactate threshold (LT); and 2) two transitions from baseline to 75%delta [75%D = LT + 0.75 x (VO2 peak - LT)] for six minutes on treadmill. The SC was deter mined by two models: a) three-exponential m

Machado, Fabiana Andrade; Guglielmo, Luiz Guilherme Antonacci; Greco, Camila Coelho; Denadai, Benedito Sérgio.

122

Preparation and crystal structure of a new bismuth vanadate, Bi3.33(VO4)2O2  

International Nuclear Information System (INIS)

Graphical abstract: Crystal structure of Bi3.33(VO4)2O2. Solid lines indicate the unit cell. Highlights: ? We can prepare a new bismuth vanadate, Bi3.33(VO4)2O2 by hydrothermal reaction using a hydrated sodium bismuthate. ? We clarify that the crystal structure is composed by four bismuth atoms with the coordination number of 6 or 8 and two VO4 tetrahedra. ? This compound exhibited photocatalytic behavior for decomposition of phenol under visible light irradiation. -- Abstract: Single crystals of a new bismuth vanadate, Bi3.33(VO4)2O2 was prepared by hydrothermal reaction using a hydrated sodium bismuthate, NaBiO3.nH2O as one of the starting compounds. The crystal structure was determined by using single crystal X-ray diffraction data. This compound crystallizes in the triclinic space group P1-bar (no. 2) with a = 7.114(1), b = 7.844(2), c = 9.372(2) A, ? = 106.090(7), ? = 94.468(7) and ? = 112.506(8)o, Z = 2 and the final R factors are R1 = 0.052 and wR2 = 0.14 for 2085 unique reflections. The crystal structure is composed by four bismuth atoms with the coordination number of 6 or 8 and two VO4 tetrahedra, and one of four bismuth atoms is statistically distributed in the splitting sites with the distance of 0.83 A. This compound exhibited photocatalytic behavior for decomposition of phenol under visible light irradiation and its activity was less than that of monoclinic BiVO4.

2011-06-01

123

BiVO(4)/CuWO(4) heterojunction photoanodes for efficient solar driven water oxidation.  

Science.gov (United States)

BiVO(4)/CuWO(4) heterojunction electrodes were prepared using spray deposition of a highly porous bismuth vanadate film onto the surface of an electrodeposited three dimensional network connected copper tungstate. Bilayer BiVO(4)/CuWO(4)/fluorine doped tin oxide glass (FTO) electrodes demonstrated higher photocurrent magnitudes than either with BiVO(4)/FTO or CuWO(4)/FTO electrodes in 1.0 M Na(2)SO(4) electrolyte buffered at pH 7. The photocurrent is enhanced by the formation of the heterojunction that aids charge carrier collection brought about by the band edge offsets. When the pH 7 buffered electrolytes contained 1.0 M bicarbonate is employed instead of 1.0 M sulfate, the charge transfer resistance was decreased. This led to nearly 1.8 times the photocurrent density at 1.0 V vs. Ag/AgCl. The photocurrent was stable over 24 hours in bicarbonate electrolyte. PMID:23348367

Pilli, Satyananda Kishore; Deutsch, Todd G; Furtak, Thomas E; Brown, Logan D; Turner, John A; Herring, Andrew M

2013-03-01

124

The Effect of Habitual Smoking on VO2max  

Science.gov (United States)

VO2max is associated with many factors, including age, gender, physical activity, and body composition. It is popularly believed that habitual smoking lowers aerobic fitness. PURPOSE: to determine the effect of habitual smoking on VO2max after controlling for age, gender, activity and BMI. METHODS: 2374 men and 375 women employed at the NASA/Johnson Space Center were measured for VO2max by indirect calorimetry (RER>=1.1), activity by the 11 point (0-10) NASA Physical Activity Status Scale (PASS), BMI and smoking pack-yrs (packs day*y of smoking). Age was recorded in years and gender was coded as M=1, W=0. Pack.y was made a categorical variable consisting of four levels as follows: Never Smoked (0), Light (1-10), Regular (11-20), Heavy (>20). Group differences were verified by ANOVA. A General Linear Models (GLM) was used to develop two models to examine the relationship of smoking behavior on VO2max. GLM #1(without smoking) determined the combined effects of age, gender, PASS and BMI on VO2max. GLM #2 (with smoking) determined the added effects of smoking (pack.y groupings) on VO2max after controlling for age, gender, PASS and BMI. Constant errors (CE) were calculated to compare the accuracy of the two models for estimating the VO2max of the smoking subgroups. RESULTS: ANOVA affirmed the mean VO2max of each pack.y grouping decreased significantly (psmoking exposure increased. GLM #1 showed that age, gender, PASS and BMI were independently related with VO2max (R2 = 0.642, SEE = 4.90, pSmoked, the effects on VO2max from Light and Regular smoking habits were -0.83 and -0.85 ml.kg- 1.min-1 respectively (psmoking on VO2max was -2.56 ml.kg- 1.min-1 (psmoking group in GLM #2 was smaller than the CE s of the smoking group counterparts in GLM #1. CONCLUSIONS: After accounting for the effects of gender, age, PASS and BMI the effect of habitual smoking on reducing VO2max is minimal, about 0.85 ml/kg/min, until the habit exceeds 20 pack.y at which point an additional decrease of 1.71 ml/kg/min is noted. Adding pack.y data improves the accuracy of predicting the VO2max of smokers.

Wier, Larry T.; Suminski, Richard R.; Poston, Walker S.; Randles, Anthony M.; Arenare, Brian; Jackson, Andrew S.

2008-01-01

125

The Effect of Habitual Smoking on VO2max  

Science.gov (United States)

VO2max is associated with many factors, including age, gender, physical activity, and body composition. It is popularly believed that habitual smoking lowers aerobic fitness. PURPOSE: to determine the effect of habitual smoking on VO2max after controlling for age, gender, activity and BMI. METHODS: 2374 men and 375 women employed at the NASA/Johnson Space Center were measured for VO2max by indirect calorimetry (RER>=1.1), activity by the 11 point (0-10) NASA Physical Activity Status Scale (PASS), BMI and smoking pack-yrs (packs day*y of smoking). Age was recorded in years and gender was coded as M=1, W=0. Pack.y was made a categorical variable consisting of four levels as follows: Never Smoked (0), Light (1-10), Regular (11-20), Heavy (>20). Group differences were verified by ANOVA. A General Linear Models (GLM) was used to develop two models to examine the relationship of smoking behavior on VO2max. GLM #1(without smoking) determined the combined effects of age, gender, PASS and BMI on VO2max. GLM #2 (with smoking) determined the added effects of smoking (pack.y groupings) on VO2max after controlling for age, gender, PASS and BMI. Constant errors (CE) were calculated to compare the accuracy of the two models for estimating the VO2max of the smoking subgroups. RESULTS: ANOVA affirmed the mean VO2max of each pack.y grouping decreased significantly (psmoking exposure increased. GLM #1 showed that age, gender, PASS and BMI were independently related with VO2max (R2 = 0.642, SEE = 4.90, pSmoked, the effects on VO2max from Light and Regular smoking habits were -0.83 and -0.85 ml.kg- 1.min-1 respectively (peffect of Heavy smoking on VO2max was -2.56 ml.kg- 1.min-1 (psmoking group in GLM #2 was smaller than the CE s of the smoking group counterparts in GLM #1. CONCLUSIONS: After accounting for the effects of gender, age, PASS and BMI the effect of habitual smoking on reducing VO2max is minimal, about 0.85 ml/kg/min, until the habit exceeds 20 pack.y at which point an additional decrease of 1.71 ml/kg/min is noted. Adding pack.y data improves the accuracy of predicting the VO2max of smokers.

Wier, Larry T.; Suminski, Richard R.; Poston, Walker S.; Randles, Anthony M.; Arenare, Brian; Jackson, Andrew S.

2008-01-01

126

Nanoscale Thermal Mapping of VO2  

Science.gov (United States)

We present a method for nanoscale thermal imaging of insulating thin films. We image the local temperature of the metal-insulator transition in a VO2 film, and investigate the role of Joule heating in two-terminal geometry. By sweeping the voltage applied to a conducting atomic force microscope tip in contact mode, we locally trigger and detect the transition to the metallic phase. By fitting the Poole-Frenkel conduction regime immediately preceding the transition, we extract the local temperature. Finally, we find grains displaying two electronic transitions, consistent with a locally stable intermediate insulating phase.[4pt] We acknowledge financial support from Harvard's Nanoscale Science and Engineering Center, funded by NSF grant PHY 01-17795 and the Sloan Fellowship. Adam Pivonka acknowledges the support of the New York Community Trust--George Merck Fund. Magdalena Huefner acknowledges the support of the Deutsche Forschungsgemeinschaft (HU 1960/11).

Pivonka, Adam; Huefner, Magdalena; Ko, Changhyun; Frenzel, Alex; O'Connor, Kevin; Ramanathan, Shriram; Hudson, Eric; Hoffman, Jennifer

2013-03-01

127

Reproducibility of maximum aerobic power (VO2max) among soccer players using a modified heck protocol / Reprodutibilidade da potência aeróbia máxima (VO2max) em jogadores de futebol utilizando o protocolo de heck modificado  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese OBJETIVO: Determinar o grau de reprodutibilidade do consumo máximo de oxigênio (VO2max) em jogadores de futebol utilizando o protocolo de Heck modificado. MÉTODOS: Foram avaliados por duas vezes, com intervalo de 15 dias entre os testes, 11 futebolistas masculinos. Todos eram de alto nível, treinava [...] m em média 10 horas por semana subdivididos em treinamentos físicos, técnicos, táticos e jogos competitivos, totalizando cinco vezes por semana e na fase em que foram avaliados se encontravam em pleno período competitivo realizando um jogo por semana. Os futebolistas foram avaliados em esteira ergométrica (1,2 km.h-1) a cada dois minutos e inclinação fixa durante o teste em 3%. O VO2max foi medido diretamente utilizando analisador metabólico de análise de gases expirados respiração-a-respiração. RESULTADOS: A velocidade máxima de corrida e o VO2max atingido nos dois testes foram respectivamente: (15,6 ± 1,1 vs. 15,7 ± 1,2 km.h-1; [p = 0,78]) e (54,5 ± 3,9 vs. 55,2 ± 4,4 ml.kg-1.min-1; [P = 0,88]). Houve correlação significante e alta do VO2max entre os dois testes após 15 dias de intervalo [r = 0,97; P Abstract in english OBJECTIVE: To determine the degree of reproducibility of maximum oxygen consumption (VO2max) among soccer players, using a modified Heck protocol. METHODS: 2 evaluations with an interval of 15 days between them were performed on 11 male soccer players. All the players were at a high performance leve [...] l; they were training for an average of 10 hours per week, totaling 5 times a week. When they were evaluated, they were in the middle of the competitive season, playing 1 match per week. The soccer players were evaluated on an ergometric treadmill with velocity increments of 1.2 km.h-1 every 2 minutes and a fixed inclination of 3% during the test. VO2max was measured directly using a breath-by-breath metabolic gas analyzer. RESULTS: The maximum running speed and VO2max attained in the 2 tests were, respectively: (15.6 ± 1.1 vs. 15.7 ± 1.2 km.h-1; [P = .78]) and (54.5 ± 3.9 vs. 55.2 ± 4.4 ml.kg-1.min-1; [P = .88]). There was high and significant correlation of VO2max between the 2 tests with a 15-day interval between them [r = 0.97; P

Paulo Roberto, Santos-Silva; Alfredo José, Fonseca; Anita Weigand de, Castro; Júlia Maria D' Andréa, Greve; Arnaldo José, Hernandez.

128

Polymorphism of Ag{sub 3}VO{sub 4}  

Energy Technology Data Exchange (ETDEWEB)

The polymorphism of Ag{sub 3}VO{sub 4} was investigated with temperature dependent synchrotron powder diffraction, and differential scanning calorimetry in the temperature range 295 K {<=} T {<=} 893 K. Three crystal structures of Ag{sub 3}VO{sub 4} were identified and determined from powder diffraction data: a-Ag{sub 3}VO{sub 4} (T = 295 K, C2/c, a = 10.2672(2) Aa, b = 4.9814(1) Aa, c = 10.2240(2) Aa, {beta} = 116.0(1) , V = 470.0(2) Aa{sup 3}), {beta}-Ag{sub 3}VO{sub 4} (T = 423 K, I anti 42m, a = 4.9968(1) Aa, c = 9.6911(3) Aa, V = 241.97(1) Aa{sup 3}), and {gamma}-Ag{sub 3}VO{sub 4} (T = 703 K, Fm anti 3m, a = 7.8386(1) Aa, V = 481.62(1) Aa{sup 3}). The crystal structures of all three phases of Ag{sub 3}VO{sub 4} can be described as cubic closed packed arrangements of [VO{sub 4}]{sup 3-} anions with the silver cations occupying all octahedral and tetrahedral voids. (orig.)

Dinnebier, R.E.; Jansen, M. [Max-Planck-Inst. for Solid State Research, Stuttgart (Germany); Reichert, H. [Max-Planck-Inst. for Metal Research, Stuttgart (Germany); Kowalevsky, A.

2007-07-01

129

Reinvestigation of the synthesis of LiFeVO4  

International Nuclear Information System (INIS)

Highlights: ? We reinvestigated the synthesis of the LiFeVO4 compound. ? We demonstrate that the recently reported LiFeVO4 phase is not a pure phase. ? We proved by Rietveld refinement that LiFeVO4 is a mixture ofLiVO3 and Fe2O3. ? We noticed some attempts to fraud (modification of the powder pattern) . - Abstract: The synthesis of LiFeVO4 composition has been performed in air starting from Li2CO3, Fe2O3, and V2O5 and using the standard solid-state reaction route reported by Refs. . Identical X-ray diffraction pattern has been obtained, however our careful analysis with MDI Jade 5.0 software does not agree with previously reported pure LiFeVO4 samples. The powder pattern has been perfectly indexed using the single crystal data of LiVO3 (C2/c, a = 10.16718 A, b = 8.415725 A, c = 5.884155 A and ? = 110.489o) and ?-Fe2O3 (R-3c, a = 5.035 A, c = 13.75 A).

2011-07-15

130

Biomasa y producción primaria en una pradera de Thalassia Testudinum en la Bahía de Neguange, parque Tayrona. Mar Caribe, Colombia  

Directory of Open Access Journals (Sweden)

Full Text Available A seagrass meadow in Neguange Bay, Parque Natural Tayrona, was sampled twice in september, 1994, in order to determine biomass, primary productivity and elongation rate of Thalassia testudinum. The average biomass was 1337,69 prps/m2, the average weight of the leaves 131,21 prps/m2 and the
average dry weight 5,93 mg/cm2. The daily growth in lenght of the leaves was 4,66 mm. The average rate of renovation was 33,38 days. The primary productivity was 25,3 g.m-2.day-'.En una pradera de pasto marino de la Bahía de Neguange, parque natural Tayrona, se realizaron dos muestreos durante el mes de septiembre de 1994, con el propósito de determinar la biomasa y producción primaria, así como la tasa de elongación de la fanerógama marina Thalassia testudinum. La biomasa promedio fue 1337,69 gps/m2, el promedio de peso de las hojas 131,21 gps/m2, y el promedio de peso seco por área fue 5,93 mg/cm2. Las hojas tuvieron un crecimiento diario promedio de 4,66 mm. La tasa de renovación promedio de la pradera se calculó en 33,38 días. La biomasa producida aproximada fue 25, 3 g.m-2.día-'.

Herrera Martínez Yimy

1995-11-01

131

EFECTO DEL VERMIABONO EN CRECIMIENTO Y ACUMULACIÓN DE BIOMASA EN Aeschynomene americana L. EN BANCOS DE MINERÍA A CIELO ABIERTO  

Directory of Open Access Journals (Sweden)

Full Text Available Se evaluó el efecto del vermiabono en el establecimiento y crecimiento de Aeschynomene americana en bancos de material abandonados como estrategia para su restauración, para lo cual se instauraron parcelas de 1 m2 a las que se les adicionó 1 kg m-2 de vermiabono (compost de lombriz Eisenia foetida y se compararon con un testigo al cual no se le aplicó vermiabono. Después de un ciclo de cultivo se observó que no existieron diferencias en la sobrevivencia de las plantas (10 y 16%, pero sí en la tasa de crecimiento, debido a que las plantas tratadas con vermiabono lograron alturas ocho veces mayores que el tratamiento testigo. Esta diferencia también se observó en la acumulación de biomasa al final del ciclo de vida de la planta (120 días, puesto que las plantas tratadas acumularon 21.7 g m-2 de materia seca; de los cuales 7 g m-2 se destinaron a la producción del fruto, en contraste con las plantas del tratamiento testigo que acumularon 1.5 g m-2 de biomasa y sólo 0.2 g m-2 se asignaron a los frutos, por lo que estas plantas no produjeron semillas. Las plantas tratadas con vermiabono formaron menos raíz respecto a la biomasa total en comparación con el tratamiento testigo, por lo cual se concluye que la aplicación de compost de lombriz promueve el desarrollo de A. americana hasta formar semillas.

Rosa de Lourdes Romo Campos

2009-01-01

132

K3VO2(V2As2O12  

Directory of Open Access Journals (Sweden)

Full Text Available A new potassium vanadium arsenate, tripotassium trivanadium bis(arsenate hexaoxide, K3VO2(V2As2O12, was synthesized by a solid-state reaction at 743?K. The structure is built up from VO5 pyramids, VO4 tetrahedra (.m. symmetry and AsO4 tetrahedra linked together by corner-sharing to form a three-dimensional framework. The two crystallographically independent K+ cations, one of which has .m. symmetry, are located in the interconnected tunnels running along the a and b directions.

Ahmed Driss

2009-05-01

133

Optical properties for the Mott transition in VO2  

Directory of Open Access Journals (Sweden)

Full Text Available The relationship between the first-order metal-insulator transition (MIT and the structural phase transition (SPT in VO2 film is analyzed by dielectric function, optical conductivity, plasma energy, and electrical conductivity. The MIT and SPT temperatures in VO2 films were approximately 68 and 75 °C, respectively, with an intermediate phase existing between 68 and 75 °C. The optical and electrical results indicate that the first-order MIT in VO2 films is not driven by the SPT.

Manil Kang

2012-03-01

134

K3VO2(V2As2O12)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new potassium vanadium arsenate, tripotassium trivanadium bis(arsenate) hexaoxide, K3VO2(V2As2O12), was synthesized by a solid-state reaction at 743?K. The structure is built up from VO5 pyramids, VO4 tetrahedra (.m. symmetry) and AsO4 tetrahedra linked together by corner-sharing to form a three-dimensional framework. The two crystallographically independent K+ cations, one of which has .m. symmetry, are located in the interconnected tunnels running along the a and b directions.

Safa Ezzine; Mohamed Faouzi Zid; Ahmed Driss

2009-01-01

135

Recuperación de la biomasa mediante la sucesión secundaria, Cordillera Central de los Andes, Colombia  

Directory of Open Access Journals (Sweden)

Full Text Available En bosques secundarios premontanos tropicales es escasa la información sobre el tiempo requerido para recuperar la biomasa aérea y subterránea de los primarios. Por lo tanto, establecimos 33 parcelas de 0.1ha entre 550 y 1 700m en bosques secundarios que cubrían estadios serales de 3 a 36 años y estimamos la biomasa de las plantas y de las raíces gruesas con ecuaciones locales. Así como la biomasa de las pasturas y barbechos por cosecha de 54 y 18 parcelas, respectivamente. También se calculó la edad de las parcelas con informantes locales, sensores remotos, C14 y anillos de crecimiento. En cada parcela medimos la biomasa aérea viva por hectárea (Bav y la de las raíces gruesas por hectárea (Brg. Modelamos la Bav y Brg en función de la edad mediante la ecuación de von Bertalanfy con asíntotas de 247t/ha (Bav y 66t/ha (Brg resultantes de la medición de 33 parcelas de 0.1ha en los bosques primarios. Con la razón Brg/Bav=f(t estimamos 87 años para que los bosques secundarios recuperen la Bav existente en los primarios y 217 años para recuperar la Brg. La tasa máxima de crecimiento instantáneo de la Bav fue 6.95t/ha/año a los 10 años y la tasa media máxima de crecimiento 6.26t/ha/año a los 17 años. La media ponderada de la tasa de crecimiento absoluto de la Bav alcanzó 4.57t/ha/año y la relativa 10% anual. La razón Brg/Bav inicialmente aumenta muy aceleradamente hasta 4-5 años (25%, luego disminuye hasta 25 años (18% para luego incrementar hasta 26.7Biomass recovery through secondary succession in the Cordillera Central de los Andes, Colombia. Estimations on biomass recovery rates by secondary tropical forests are needed to understand the complex tropical succession, and their importance on CO2 capture, to offset the warming of the planet. We conducted the study in the Porce River Canyon between 550 and 1 700m.a.s.l. covering tropical and premontane moist belts. We established 33 temporary plots of 50mx20m in secondary forests, including fallows to succesional forests, and ranging between 3 and 36 years old; we measured the diameter at breast height (D of all woody plants with D?5cm. In each one of these plots we established five 10mx10m subplots, in which we measured the diameter betweem 1cm?D<5cm of all woody plants. We estimated the biomass of pastures by harvesting 54 plots of 2mx2m, and of shrubs in the fallows by harvesting the biomass in 18 plots of 5mx2m. We modeled Bav (above ground live biomass of woody plants and Brg (coarse root biomass as a function of succesional age (t with the growth model of von Bertalanffy, using 247t/ha and 66t/ha as asymptote, respectively. Besides, we modeled the ratios brg/bav=f(D and Brg/Bav=f(t. The model estimated that 87 years are required to recover the existing Bav of primary forests through secondary succession, and 217 years for the Brg of the primary forest. The maximum instantaneous growth rate of the Bav was 6.95 t/ha/yr at age 10. The maximum average growth rate of the Bav was 6.26 t/ha/yr at age 17. The weighted average of the absolute growth rate of the Bav reached 4.57t/ha/yr and the relative growth rate 10% annually. The ratio brg/bav decreases with increasing D. The ratio Brg/Bav initially increases very rapidly until age 5 (25%, then decreases to reach 25 years (18% and increases afterwards until the ratio reaches the asymptote (26.7%. Rev. Biol. Trop. 59 (3:1337-1358. Epub 2011 September 01.

Jorge Ignacio del Valle

2011-09-01

136

Consideraciones sobre la producción de etanol a partir de la biomasa lignocelulósica  

Directory of Open Access Journals (Sweden)

Full Text Available En los últimos años, como consecuencia del aumento de los precios del petróleo y las exigencias ecológicas, ha crecido el interés por la producción de bioetanol como combustible de vehículos automotores. En Brasil y EEUU, los principales productores, se estima una producción por cada país en el 2006 de alrededor de los 19 mil millones de litros. Brasil planea aumentar la producción hasta 26.5 mil millones en el 2016 mientras que para esa misma fecha EEUU pretende alcanzar los 45,4 mil millones de litros. Las materias primas más empleadas son maíz y caña de azúcar. Sería de interés incluir entre éstas a la biomasa lignocelulósica que se obtiene como subproductos agrícolas y forestales (pajas de cereales, bagazo, aserrín y virutas de madera que no son aptos para el consumo humano y por su composición química son susceptibles de ser sacarificados por hidrólisis química o enzimática. Se analizan críticamente las posibles vías para desarrollar la producción de alcohol a partir de estos materiales, en especial la vía química, cuya perspectiva de éxito se encuentra estrechamente vinculada al desarrollo de reactores continuos. De esta manera, se pueden intensificar las condiciones de reacción que permitan incrementar la productividad del proceso, mediante la obtención de los máximos rendimientos de azúcares con el empleo de los menores volúmenes del equipamiento, sin descuidar la disminución de la concentración de sustancias inhibidoras de la fermentación en el sistema.

Josu00E9 C. Villar

2008-01-01

137

Velocidad de acumulación de biomasa en la dosificación de la fertirrigación ecológica del tomate en organopónico  

Directory of Open Access Journals (Sweden)

Full Text Available En condiciones de organopónico, fueron determinadas las curvas de materia seca sobre biomasa aérea total, por períodos de crecimiento definidos en el cultivo de tomate Vita, tomándose como criterio para determinar la dosis más oportuna de aplicación de Fitomás E. en la fertirrigación. Se utilizaron dos tratamientos del biofertilizante y un tratamiento testigo, los cuales mostraron diferencia significativa desde los primeros períodos de crecimiento. La curva de materia seca, de mejor resultado en la dosis de fertilizante fue comparada con un modelo teórico generado para estimar la acumulación diaria de materia seca, teniendo en cuenta las proporciones referidas al período de crecimiento, además los datos observados y los estimados fueron relacionados mediante una regresión lineal cuya ecuación resultó altamente significativa (R2=0.99, P< 0.01, por lo que puede señalarse que la función logística que simula la acumulación de materia seca es válida. Fueron evaluados además, los rendimientos frescos de los frutos y algunos aspectos de la calidad interna, coincidiendo con igual tendencia a la mantenida en la materia seca foliar.

Osvaldo Campos Piedra

2009-01-01

138

Density functional theory study of rutile VO2 surfaces  

CERN Document Server

We present the results of a density functional theory (DFT) investigation of the surfaces of rutile-like vanadium dioxide, VO2(R). We calculate the surface energies of low Miller index planes, and find that the most stable surface orientation is the (110). The equilibrium morphology of a VO2(R) particle has an acicular shape, laterally confined by (110) planes and topped by (011) planes. The redox properties of the (110) surface are investigated by calculating the relative surface free energies of the non-stoichiometric compositions as a function of oxygen chemical potential. It is found that the VO2(110) surface is oxidized with respect to the stoichiometric composition, not only at ambient conditions but also at the more reducing conditions under which bulk VO2 is stable in comparison with bulk V2O5. The adsorbed oxygen forms surface vanadyl species much more favorably than surface peroxo species.

Mellan, Thomas A

2012-01-01

139

Depressed Phase Transition in Solution-Grown VO2 Nanostructures  

Energy Technology Data Exchange (ETDEWEB)

The first-order metal-insulator phase transition in VO{sub 2} is characterized by an ultrafast several-orders-of-magnitude change in electrical conductivity and optical transmittance, which makes this material an attractive candidate for the fabrication of optical limiting elements, thermochromic coatings, and Mott field-effect transistors. Here, we demonstrate that the phase-transition temperature and hysteresis can be tuned by scaling VO{sub 2} to nanoscale dimensions. A simple hydrothermal protocol yields anisotropic free-standing single-crystalline VO{sub 2} nanostructures with a phase-transition temperature depressed to as low as 32 C from 67 C in the bulk. The observations here point to the importance of carefully controlling the stochiometry and dimensions of VO{sub 2} nanostructures to tune the phase transition in this system.

Whittaker, L.; Jaye, C; Fu, Z; Fischer, D; Banerjee, S

2009-01-01

140

Tunable waveguiding in electrically programmable VO2-based photonic crystals  

Science.gov (United States)

The feasibility of electrically programmable waveguiding in a photonic crystal (PC) is explored based on the metal-insulator transition of vanadium dioxide (VO2). Unlike the ordinary PCs, wave propagation in the desired structure may be switched on/off or redirected by applying an electrical bias on the selective electrodes by taking advantage of the electrically induced VO2 phase transition and subsequent modulation of dielectric properties. The characteristics of the two-dimensional VO2-based PCs with line defects are analyzed using the iterative plane wave and finite difference time domain methods. Particularly, the influence of the Drude relaxation on waveguiding is examined as the high rate typical for metallic VO2 can lead to the signal loss. An optimized structure is proposed to minimize the loss and simplify the fabrication.

Xiao, D.; Kim, K. W.; Lazzi, G.; Zavada, J. M.

2006-06-01

 
 
 
 
141

Nonreciprocal switching of VO2 thin films on microstructured surfaces  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We demonstrate that the combination of near-field focusing and a switchable oxide layer permits construction of a modulator with different optical switching thresholds in two opposing directions. For that purpose VO2 layers are deposited onto spherical micrometer-sized particles. The phase transition in VO2 is induced by a nanosecond-pulsed Nd:YAG laser from two different directions. The measured thresholds differ by a factor of 2.4, consistent with calculated differences in the intensities i...

Karakurt, Ismail; Adams, Charles H.; Leiderer, Paul; Boneberg, Johannes; Haglund, Richard F.

2010-01-01

142

Evaluación de dos métodos para la estimación de biomasa arbórea a través de datos Landsat TM en Jusnajab La Laguna, Chiapas, México: estudio de caso  

Directory of Open Access Journals (Sweden)

Full Text Available Se evaluaron dos métodos para estimar biomasa arbórea con apoyo en sensores remotos (LANDSAT TM. El primer método se realizó con base en una clasificación supervisada multiespectral con seis bandas Se utilizaron tipos de vegetación identificados a partir de la composición de biomasa de ¡os géneros dominantes y de la altura promedio estimada del dosel, habiéndose distinguido ocho clases de vegetación. Se obtuvo una biomasa total de 1 073 x 10 3t (902 x 10 3t a 1 220 x 10 3t En el segundo método se utilizaron índices diferenciados de vegetación (NDVI de las bandas TM4/TM3; TM4/TM5 y TM4/TM7. Se aplicó un modelo de regresión que relaciona la biomasa promedio con los valores digitales (VD de los NDVI. El modelo exponencial fue el de mejor ajuste para los tres NDVl con una p 0.01. Los valores de los NVDl fueron TM4/ TM3. R2=0 611, TM4/TM5. R2=0.671 y TM4/TM7: R2=0.676. La biomasa total estimada con cada NDVI fue de 1 164 x 10 3t (490 x 10 3t a 2 409 x 10 3t para TM4/TM3; de 515x10 3t (331 x 10 3 t a 757 x 1 0 3 t p a r a TM/TM5 y d e 726 x 1 0 3 t ( 3 9 8 x 1 0 3 t a 1 210 x 10 3t para TM4/TM7. El resultado de la biomasa total calculada por el método de clasificación multiespectral, comparado con los valores estimados por el método de ordenamiento exponencial, mostró mayor similitud con el valor máximo del NDVl que relaciona las bandas TM4/TM7 (de mayor ajuste estadístico y con el valor promedio del NDVl TM4/TM3 (de menor ajuste estadístico. Utilizando el NDVl TM4/TM5, todos los valores de biomasa resultaron más bajos. De este estudio se concluye que es posible asociar razonablemente la biomasa de vegetación arbolada de pino-encino y reservorios de carbono con los índices de vegetación. A través del uso de sensores remotos se podrían predecir cambios de biomasa en escalas temporales y espaciales.

Jorge Escandón Calderón

1999-01-01

143

Partición de biomasa aérea en procedencias de Pinus greggii plantadas en el sur de México / Aboveground biomass allocation of Pinus greggii provenances planted in southern México  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish La asignación de biomasa en los órganos del árbol puede ser influenciada por factores climáticos y edafológicos, competencia lumínica, y por diferencias genéticas de los árboles. El objetivo fue estimar los componentes de biomasa aérea en 13 procedencias mexicanas de Pinus greggii Engelm. plantadas [...] en 1997 en el sur de México. Se utilizaron datos de biomasa obtenidos en 2011 de 106 muestras aleatorias de ramas, 60 árboles medidos en pie y datos generales de la plantación establecida bajo un diseño experimental de bloques al azar. Se encontraron diferencias significativas (P ? 0.05) entre procedencias en acumulación de biomasa en acículas y madera con corteza. La mayor biomasa foliar fue para las procedencias del centro del país, El Piñón y Molango (5.1 t ha-1), mientras que la procedencia norteña, Los Lirios, acumuló la mayor cantidad de biomasa en madera con corteza (19.4 t ha-1). No hubo diferencias en biomasa de ramas cuyo promedio fue de 9.5 t ha-1, ni en la biomasa aérea total acumulada que fue de 25.6 t ha-1, en árboles de 14 años de edad para todas las procedencias. La biomasa se distribuyó 52.0, 33.6 y 14.4 % para madera con corteza, ramas y follaje, respectivamente. Abstract in english Biomass allocation on the tree may be influenced by climate, soil conditions, light competition and genetic differences among trees. Aboveg-round biomass components were estimated in 13 Mexican provenances of Pinus greggii Engelm. planted in 1997 in Southern México. Biomass data were collected in 20 [...] 11 from 106 random samples of branches and 60 standing trees. Data sampling was distributed under a randomized block design. Significant differences (P ? 0.05) among provenances in biomass accumulation of needles and wood + bark were found. The highest leaf biomass accumulation was for provenances from Central México, El Piñón y Molango (5.1 t ha-1). Among the northern provenances, Los Lirios accumulated the highest biomass in wood + bark (19.4 t ha-1). No differences among provenances were found in branch biomass, with an average of 9.5 t ha-1, and neither in total accumulated biomass which was 25.6 t ha-1, for 14 year-old trees. Total biomass was distributed 52.0, 33.6 and 14.4 % for wood + bark, branches and leaves, respectively.

Villegas-Jiménez, Daniel E.; Rodríguez-Ortiz, Gerardo; Velasco-Velasco, Vicente A.; Ruiz-Luna, Judith; Carrillo-Rodríguez, José C.; Ramírez-Sánchez, Susana E..

144

VO2 Kinetics and Metabolic Contributions Whilst Swimming at 95, 100, and 105% of the Velocity at VO2?max  

Science.gov (United States)

A bioenergetical analysis of swimming at intensities near competitive distances is inexistent. It was aimed to compare the transient VO2 kinetics responses and metabolic contributions whilst swimming at different velocities around VO2max?. 12 trained male swimmers performed (i) an incremental protocol to determine the velocity at VO2max? (vVO2max?) and (ii) three square wave exercises from rest to 95, 100, and 105% of vVO2max?. VO2 was directly measured using a telemetric portable gas analyser and its kinetics analysed through a double-exponential model. Metabolic contributions were assessed through the sum of three energy components. No differences were observed in the fast component response (?1—15, 18, and 16 s, A1—36, 34, and 37?mL · kg?1 · min??1, and Gain—32, 29, and 30?mL · min??1 at 95, 100, and 105% of the vVO2max?, resp.) but A2 was higher in 95 and 100% compared to 105% intensity (480.76?±?247.01, 452.18?±?217.04, and 147.04?±?60.40?mL · min??1, resp.). The aerobic energy contribution increased with the time sustained (83?±?5, 74?±?6, and 59?±?7% for 95, 100, and 105%, resp.). The adjustment of the cardiovascular and/or pulmonary systems that determine O2 delivery and diffusion to the exercising muscles did not change with changing intensity, with the exception of VO2 slow component kinetics metabolic profiles.

Sousa, Ana C.; Vilas-Boas, Joao P.; Fernandes, Ricardo J.

2014-01-01

145

Neutron diffraction study of YVO3, NdVO3, and TbVO3  

CERN Document Server

The structural and magnetic properties of YVO3, NdVO3 and TbVO3 were investigated by single-crystal and powder neutron diffraction. YVO3 shows a structural phase transition at 200 K from an orthorhombic structure with the space group Pbnm to a monoclinic one with the space group P21/b. But supplementary high-resolution synchrotron diffraction experiments showed that the monoclinic distortion is extremely small. A group theoretical analysis shows that this magnetic state in the monoclinic phase is incompatible with the lattice structure, unless terms of higher than bilinear order in the spin operators are incorporated in the spin Hamiltonian. This observation is discussed in the light of recent theories invoking unusual many-body correlations between the vanadium t2g orbitals. A structural phase transition back to the orthorhombic space group Pbnm is observed upon cooling below 77 K. This transition is accompanied by a rearrangement of the magnetic structure into a mode compatible with the lattice structure. T...

Reehuis, M; Pattison, P; Ouladdiaf, B; Rheinstädter, M C; Ohl, M; Regnault, L P; Miyasaka, M; Tokura, Y; Keimer, B

2006-01-01

146

Flujos de biomasa y estructura de un ecosistema de surgencia tropical en La Guajira, Caribe colombiano  

Scientific Electronic Library Online (English)

Full Text Available SciELO Costa Rica | Language: Spanish Abstract in spanish La Guajira es un ecosistema de surgencia explotado en la costa del Caribe colombiano. Con el propósito de integrar la información disponible sobre el sistema se construyó un modelo trófico de 27 grupos funcionales usando el programa Ecopath 5.0 Beta. Se obtuvo una base cuantitativa para compararlo c [...] on otros sistemas de surgencia. La Guajira presenta una biomasa total de 68 t/km²/año, la producción primaria neta del sistema es de 1 248.51 t/km²/año y las transferencias totales del sistema son de 3 275 t/km²/año, lo que indica un ecosistema con una surgencia moderada comparada con otros sitios. Las mayores transferencias de energía se dan del nivel trófico I-II (68.93 %), aunque existe una importante proporción de flujos al detritus (32 %). Los resultados en los atributos de madurez del sistema sugieren que La Guajira es un ecosistema inmaduro debido a que la relación P/R excede a 1 y está en desarrollo debido a la baja ascendencia (33.7 %) y alta capacidad de desarrollo (66.3 %) como ocurre con otras surgencias donde se presentan valores de ascendencia entre 20 % y 35 %. Aunque los datos básicos de entrada en el modelo fueron buenos, gracias a las investigaciones que se han elaborado entre 1995 y 2000, existen algunos grupos donde no se encuentra aún información adecuada; especialmente en los valores de biomasa del fitoplancton, invertebrados, bagres, peces depredadores pelágicos, así como estimaciones de producción en invertebrados, peces depredadores pelágicos y peces pequeños pelágicos. No existe una cuantificación de las poblaciones de mamíferos y aves en el área de estudio, los cuales constituyen depredadores superiores y hacen parte esencial en sistemas de surgencia Abstract in english Biomass flow and structure of a tropical upwelling ecosystem in La Guajira, Colombian Caribbean. La Guajira is an exploited tropical upwelling ecosystem in the Colombian Caribbean coast. A trophic model of 27 functional groups was constructed using the ECOPATH 5.0 Beta software to integrate the avai [...] lable information on the ecosystem. The model allowed a comparison with other trophic flow models of upwelling ecosystems. Total system biomass (68 t/km²/year), net system production (1248.5 t/km²/year), and total system throughput (3 275 t/km²/year) make La Guajira moderate when compared with other systems. The largest amount of energy throughput is achieved from trophic level I to II (68.93 %), although an important proportion of the total flow originates from detritus (32 %). The production/respiration ratio exceeds 1, suggesting that La Guajira is an immature ecosystem and is in development, as determined by its low ascendency (33.7 %) and high development capacity (66.3 %), similar to other upwellings that have values of ascendency between 20 % and 35 %. Although the basic input data were good and covered 1995 to 2000, appropriate information is still not available on some trophic groups such as biomass (for phytoplankton, invertebrates, catfishes and pelagic predator fishes), secondary production data (invertebrates, pelagic predator fishes, and small pelagic fishes), and seabird and mammal populations, which are top trophic levels and an essential part of upwelling ecosystems. Rev. Biol. Trop. 54 (4): 1257-1282. Epub 2006 Dec. 15

Criales-Hernández, Maria Isabel; B. García, Camilo; Wolff, Matthias.

147

Flujos de biomasa y estructura de un ecosistema de surgencia tropical en La Guajira, Caribe colombiano  

Directory of Open Access Journals (Sweden)

Full Text Available La Guajira es un ecosistema de surgencia explotado en la costa del Caribe colombiano. Con el propósito de integrar la información disponible sobre el sistema se construyó un modelo trófico de 27 grupos funcionales usando el programa Ecopath 5.0 Beta. Se obtuvo una base cuantitativa para compararlo con otros sistemas de surgencia. La Guajira presenta una biomasa total de 68 t/km²/año, la producción primaria neta del sistema es de 1 248.51 t/km²/año y las transferencias totales del sistema son de 3 275 t/km²/año, lo que indica un ecosistema con una surgencia moderada comparada con otros sitios. Las mayores transferencias de energía se dan del nivel trófico I-II (68.93 %, aunque existe una importante proporción de flujos al detritus (32 %. Los resultados en los atributos de madurez del sistema sugieren que La Guajira es un ecosistema inmaduro debido a que la relación P/R excede a 1 y está en desarrollo debido a la baja ascendencia (33.7 % y alta capacidad de desarrollo (66.3 % como ocurre con otras surgencias donde se presentan valores de ascendencia entre 20 % y 35 %. Aunque los datos básicos de entrada en el modelo fueron buenos, gracias a las investigaciones que se han elaborado entre 1995 y 2000, existen algunos grupos donde no se encuentra aún información adecuada; especialmente en los valores de biomasa del fitoplancton, invertebrados, bagres, peces depredadores pelágicos, así como estimaciones de producción en invertebrados, peces depredadores pelágicos y peces pequeños pelágicos. No existe una cuantificación de las poblaciones de mamíferos y aves en el área de estudio, los cuales constituyen depredadores superiores y hacen parte esencial en sistemas de surgenciaBiomass flow and structure of a tropical upwelling ecosystem in La Guajira, Colombian Caribbean. La Guajira is an exploited tropical upwelling ecosystem in the Colombian Caribbean coast. A trophic model of 27 functional groups was constructed using the ECOPATH 5.0 Beta software to integrate the available information on the ecosystem. The model allowed a comparison with other trophic flow models of upwelling ecosystems. Total system biomass (68 t/km²/year, net system production (1248.5 t/km²/year, and total system throughput (3 275 t/km²/year make La Guajira moderate when compared with other systems. The largest amount of energy throughput is achieved from trophic level I to II (68.93 %, although an important proportion of the total flow originates from detritus (32 %. The production/respiration ratio exceeds 1, suggesting that La Guajira is an immature ecosystem and is in development, as determined by its low ascendency (33.7 % and high development capacity (66.3 %, similar to other upwellings that have values of ascendency between 20 % and 35 %. Although the basic input data were good and covered 1995 to 2000, appropriate information is still not available on some trophic groups such as biomass (for phytoplankton, invertebrates, catfishes and pelagic predator fishes, secondary production data (invertebrates, pelagic predator fishes, and small pelagic fishes, and seabird and mammal populations, which are top trophic levels and an essential part of upwelling ecosystems. Rev. Biol. Trop. 54 (4: 1257-1282. Epub 2006 Dec. 15

Maria Isabel Criales-Hernández

2006-12-01

148

USO DE LA LEVADURA TORULA (TORULOPSIS UTILIS) EN LA OBTENCIÓN DE BIOMASA DE ARTEMIA  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in spanish Se llevaron a cabo estudios para determinar la factibiíidad del uso de la levadura torula (Torulopsis utilis), como fuente de alimento en cultivos intensivos de Artemia. Se alcanzaron rendimientos máximos de biomasa de 5.14 g/l y 8.43 mm de largo medio total en la variante de mejores resultados. Con [...] centraciones de levadura de 1 g/l/día en el período inicial de 6 días pueden considerarse adecuadas para el crecimiento de la Artemia, mientras que concentraciones de 3.5 y 7 g/l/día son excesivas. A partir del séptimo día 3 g/l/día constituye una concentración apropiada de alimento mientras que 1 g/l/día es insuficiente para obtener un crecimiento satisfactorio en esta etapa. Las ecuaciones de crecimiento para este cultivo en las condiciones descritas son las siguientes: variante de 1 g/l/día, L = -0.5214 + 0.4837 T; variante de 3 g/l/día, L = -1.1707 + 0.738 T. Abstract in english Studies were carried out to determine the possibilities of use torula yeast (Torulopsis utilis), as a source of feed in intensive cultured Artemia, Maximum biomass yields of 5.14 g/l and 8.43 mm of average total length were obtained for the treatment with the best results. Yeast concentration of 1 g [...] /l/day in the initial 6 days period, can be considered adequate for Artemia growth while the concentration of 1 g/l/day is insufficient to obtain a satisfactory growth. The growth equations in the described culture conditions were as follow: treatment 1 g/l/day, L= -0.5214 + 0.4837 T; treatment 3 g/l/day, L = -1.1707 + 0.738 T.

Rafael, Tizol Correa.

149

Enfermedad pulmonar obstructiva crónica por exposición al humo de biomasa / Chronic obstructive pulmonary disease by biomass smoke exposure  

Scientific Electronic Library Online (English)

Full Text Available SciELO Public Health | Language: Spanish Abstract in spanish En este artículo se discute la relación existente entre la enfermedad pulmonar obstructiva crónica (EPOC) y el humo de biomasa. Más de la mitad de la población utiliza biomasa como combustible principal, sobre todo en áreas rurales y en países en vías de desarrollo donde su uso llega hasta el 80%. L [...] a inhalación del humo de biomasa crea un estado inflamatorio crónico, que se acompaña de una activación de metaloproteinasas y una reducción de la movilidad mucociliar. Esto podría explicar la gran asociación existente entre la exposición a biomasa y EPOC, revelada por estudios observacionales y epidemiológicos provenientes de países en vías de desarrollo y de países desarrollados. En esta revisión exploramos también las diferencias entre la EPOC causada por tabaco y por biomasa, y encontramos que, a pesar de las diferencias fisiopatológicas, la mayoría de las características clínicas, calidad de vida y mortalidad fueron parecidas. En los últimos diez años se han realizado intervenciones para disminuir la exposición a biomasa mediante el uso de cocinas mejoradas y combustibles limpios, sin embargo, estas estrategias todavía no han sido exitosas debido a su incapacidad para reducir los niveles de contaminación a niveles recomendados por la Organización Mundial de la Salud, y por su falta de uso. Por lo tanto, hay una necesidad urgente de ensayos de campo aleatorios, cuidadosamente realizados, para determinar la verdadera gama de reducciones de contaminación potencialmente alcanzables, la probabilidad de su uso y los beneficios a largo plazo en la reducción de la gran carga mundial de EPOC Abstract in english In this article, the relationship between chronic obstructive pulmonary disease (COPD) and biomass smoke will be discussed. More than half of the world population uses biomass for fuel, especially in rural areas and in developing countries where usage reaches 80%. Biomass smoke inhalation creates an [...] inflammatory chronic state, which is accompanied by metalloproteinases activation and mucociliary mobility reduction. This could explain the existing association between biomass exposure and COPD, revealed by observational and epidemiological studies from developing and developed countries. In this review, the differences between COPD caused by tobacco and biomass were explored. It was found that despite the pathophysiological differences, most of the clinical characteristics, quality of life and mortality were similar. In the last ten years there have been interventions to reduce the biomass smoke exposure by using improved stoves and cleaner fuels. However, these strategies have not yet been successful due to inability to reduce contamination levels to those recommended by the World Health Organization as well as due to the lack of use. Therefore, there is an urgent need for carefully conducted, randomized field trials to determine the actual range of potentially reachable contamination reductions, the probability of use and the long term benefits of reducing the global burden of COPD

Matías, Lopez; Nicole, Mongilardi; William, Checkley.

150

Enfermedad pulmonar obstructiva crónica por exposición al humo de biomasa / Chronic obstructive pulmonary disease by biomass smoke exposure  

Scientific Electronic Library Online (English)

Full Text Available SciELO Peru | Language: Spanish Abstract in spanish En este artículo se discute la relación existente entre la enfermedad pulmonar obstructiva crónica (EPOC) y el humo de biomasa. Más de la mitad de la población utiliza biomasa como combustible principal, sobre todo en áreas rurales y en países en vías de desarrollo donde su uso llega hasta el 80%. L [...] a inhalación del humo de biomasa crea un estado inflamatorio crónico, que se acompaña de una activación de metaloproteinasas y una reducción de la movilidad mucociliar. Esto podría explicar la gran asociación existente entre la exposición a biomasa y EPOC, revelada por estudios observacionales y epidemiológicos provenientes de países en vías de desarrollo y de países desarrollados. En esta revisión exploramos también las diferencias entre la EPOC causada por tabaco y por biomasa, y encontramos que, a pesar de las diferencias fisiopatológicas, la mayoría de las características clínicas, calidad de vida y mortalidad fueron parecidas. En los últimos diez años se han realizado intervenciones para disminuir la exposición a biomasa mediante el uso de cocinas mejoradas y combustibles limpios, sin embargo, estas estrategias todavía no han sido exitosas debido a su incapacidad para reducir los niveles de contaminación a niveles recomendados por la Organización Mundial de la Salud, y por su falta de uso. Por lo tanto, hay una necesidad urgente de ensayos de campo aleatorios, cuidadosamente realizados, para determinar la verdadera gama de reducciones de contaminación potencialmente alcanzables, la probabilidad de su uso y los beneficios a largo plazo en la reducción de la gran carga mundial de EPOC Abstract in english In this article, the relationship between chronic obstructive pulmonary disease (COPD) and biomass smoke will be discussed. More than half of the world population uses biomass for fuel, especially in rural areas and in developing countries where usage reaches 80%. Biomass smoke inhalation creates an [...] inflammatory chronic state, which is accompanied by metalloproteinases activation and mucociliary mobility reduction. This could explain the existing association between biomass exposure and COPD, revealed by observational and epidemiological studies from developing and developed countries. In this review, the differences between COPD caused by tobacco and biomass were explored. It was found that despite the pathophysiological differences, most of the clinical characteristics, quality of life and mortality were similar. In the last ten years there have been interventions to reduce the biomass smoke exposure by using improved stoves and cleaner fuels. However, these strategies have not yet been successful due to inability to reduce contamination levels to those recommended by the World Health Organization as well as due to the lack of use. Therefore, there is an urgent need for carefully conducted, randomized field trials to determine the actual range of potentially reachable contamination reductions, the probability of use and the long term benefits of reducing the global burden of COPD

Matías, Lopez; Nicole, Mongilardi; William, Checkley.

151

Biomasa fúngica y bacteriana como indicadoras del secuestro de C en suelos de sabanas sustituidos por pinares en Uverito, Venezuela  

Directory of Open Access Journals (Sweden)

Full Text Available Cualquier transformación de un ecosistema natural a un sistema agrícola o forestal conduce a una modificación importante no sólo del pool del carbono total, sino también del carbono asociado con la biomasa microbiana. Su cuantificación es importante en la determinación del impacto de las prácticas agrícolas y el cambio de uso de la tierra sobre la calidad del suelo. El objetivo de este estudio fue determinar, a través del método de inhibición selectiva, la biomasa fúngica y bacteriana y la relación (H:B en suelos de sabana nativa sustituidos por pinares (Pinus caribaea var. hondurensis, para establecer si éstos parámetros son indicadores sensibles de cambios en el contenido de carbono en suelos de Uverito, Venezuela. La relación de aditividad del inhibidor (RAI y la inhibición total por efecto combinado del inhibidor (ITC se llevaron a cabo para determinar, si los inhibidores microbianos tuvieron actividad sobre otros organismos para los cuales éstos no estaban destinados. La cuantificación de la biomasa fúngica y bacteriana se llevó a cabo mediante el uso de la cycloheximida como inhibidor fúngico, y la estreptomicina y el cloranfenicol como inhibidores bacterianos. Esta investigación evidencia que este cambio de uso de la tierra ejerció un efecto significativo sobre la biomasa microbiana del suelo, y muestra que en el sistema de pinares existe una dominancia del componente fúngico, en contraste con la sabana nativa, en la cual domina la biomasa bacteriana. La sustitución de la sabana nativa por plantaciones de pino en Uverito, promueve un mayor secuestro del carbono en el suelo. Los valores de la relación de aditividad del inhibidor (RAI tanto para la sabana nativa como para el sistema de pinares, resultaron ambos >1.0. La inhibición total combinada (ITC resultó menor en el sistema de pinares; a partir de lo cual, es posible inferir que una elevada proporción de la biomasa microbiana fue afectada por la combinación de los inhibidores.Fungal and bacterial biomass as indicators of soil C sequestration in savannas soils substituted by pine plantations. A transformation of any natural ecosystem to an agricultural or forest system leads to an important soil modification, not only in the total carbon pool, but also in the carbon associated to the microbial biomass. This way, carbon quantification on soil quality is important for the determination of impacts of agricultural practices and land use changes. The aim of this study was to the determine, through the selective inhibition technique, the fungal and bacterial biomass, and fungal-to-bacterial ratio (F:B in pine plantations (Pinus caribaea var. hondurensis, to establish if these parameters are sensible indicators of changes in the carbon content in Uverito soils (Venezuela. Furthermore, the inhibitor additivity ratio (IAR and total combined inhibition (TCI were carried out to determine if the antibiotics caused non-target inhibition. The quantification of fungal and bacterial biomass was carried out by using of cyloheximide as fungal inhibitor, and streptomycin and chloranphenicol as specific bacterial inhibitors. This research evidences that this land use change exerted a significant effect on soil microbial biomass, and shows that in pine plantations there is a dominance of the fungal component, in contrast to the native savanna, in which the bacterial biomass dominates. The substitution of native savanna by pine plantation in Uverito promotes a major soil carbon sequestration. The values of the inhibitor additivity ratio (IAR as for native savanna as pine system, were both>1.0. The total combined inhibition (TCI was smaller in the pine systems, from which it is possible to infer that a high proportion of microbial biomass was affected by the combination of the inhibitors. Rev. Biol. Trop. 58 (3: 977-989. Epub 2010 September 01.

Magalis Zabala

2010-09-01

152

Spectroscopic Analysis in the Virtual Observatory Environment with SPLAT-VO  

CERN Document Server

SPLAT-VO is a powerful graphical tool for displaying, comparing, modifying and analyzing astronomical spectra, as well as searching and retrieving spectra from services around the world using Virtual Observatory (VO) protocols and services. The development of SPLAT-VO started in 1999, as part of the Starlink StarJava initiative, sometime before that of the VO, so initial support for the VO was necessarily added once VO standards and services became available. Further developments were supported by the Joint Astronomy Centre, Hawaii until 2009. Since end of 2011 development of SPLAT-VO has been continued by the German Astrophysical Virtual Observatory, and the Astronomical Institute of the Academy of Sciences of the Czech Republic. From this time several new features have been added, including support for the latest VO protocols, along with new visualization and spectra storing capabilities. This paper presents the history of SPLAT-VO, it's capabilities, recent additions and future plans, as well as a discussi...

Skoda, Petr; Neves, Margarida Castro; Andresic, David; Jenness, Tim

2014-01-01

153

COMPETENCIA POR SUSTRATO DURANTE EL DESARROLLO DE BIOMASA SULFATORREDUCTORA A PARTIR DE UN LODO METANOGÉNICO EN UN REACTOR UASB  

Directory of Open Access Journals (Sweden)

Full Text Available En este trabajo se estudió la competencia entre microorganismos metanogénicos y sulfatorreductores utilizando un reactor anaerobio de lecho de lodo granular con flujo ascendente (UASB a escala laboratorio, el cual fue usado para el enriquecimiento de biomasa sulfatorreductora a partir de un lodo granular de origen metanogénico. El reactor se alimentó con una mezcla de etanol y acetato, la carga orgánica se incrementó de 0.5 a 2 g de demanda química de oxígeno (DQO/L-d a pH de 7.0. El consumo de DQO fue mayor a 90 % y la alcalinidad producida por la oxidación del sustrato incrementó el pH en el efluente hasta 8.0. A partir de los 50 días de operación, el reactor se alimentó con lactato y sulfato para promover la sulfatorreducción. La carga orgánica se aumentó de 1 a 3 g DQO/L-d con una relación DQO/Sulfato de 0.67 a un tiempo de retención hidráulico de un día. A los 194 días de operación del reactor el máximo consumo de DQO y sulfato obtenido fue de 94 y 22 %, respectivamente. La concentración total del sulfuro alcanzada fue de 310 mg S2-/L y la actividad sulfatorreductora de la biomasa fue de 0.29 g DQO-H2S/g SSV-d, lo que mostró el desarrollo de biomasa sulfatorreductora. La actividad metanogénica que se obtuvo fue de 0.35 g DQO-CH4/g SSV-d, estos resultados mostraron que los organismos metanogénicos no fueron desplazados por las bacterias sulfatorreductoras, coexistiendo ambos tipos de microorganismos en el lodo granular anaerobio al final de la operación del reactor.

Elías RAZO-FLORES

2010-01-01

154

EVALUACIÓN DE LA BIOMASA Y MANEJO DE Lemna gibba (LENTEJA DE AGUA EN LA BAHÍA INTERIOR DEL LAGO TITICACA, PUNO  

Directory of Open Access Journals (Sweden)

Full Text Available Uno de los mayores problemas que enfrenta la ciudad de Puno es la presencia de la lenteja de agua (Lemna gibba en la bahía interior del Lago Titicaca, debido al proceso de eutrofización que sufre a causa del mal tratamiento de las aguas residuales de la ciudad de Puno. Muchas de las estrategias planteadas hasta ahora no han dado resultados positivos en la reducción de la biomasa de Lemna gibba, debido a que estos planes están direccionados a la exterminación de este organismo. En lugar de ello se debe pensar en la forma más sostenible de hacer uso de la lenteja. Es por eso que los objetivos fueron: (a estimar la biomasa (kg/m² de lenteja de agua de la bahía interior del lago Titicaca y, (b plantear una estrategia de manejo de la lenteja de agua de la bahía interior del lago Titicaca. El promedio de la biomasa de la lenteja de agua en la bahía interior fue de 6.94 kg/m², mientras que los promedios de pH y temperatura del agua fueron de 6.3 y 13.8°C, respectivamente. Esto prueba la eficacia de este organismo para crecer en condiciones difíciles (además hay altos niveles de N, P y metales pesados, por lo que su manejo puede ser una alternativa para disminuir el proceso de eutrofización del lago. Las estrategias de manejo de lenteja estuvieron enmarcadas dentro de un plano social, económico y ambiental, lo que permite su sostenibilidad en beneficio de la población de Puno y del ecosistema del lago Titicaca.

Ángel Canales-Gutiérrez

2010-01-01

155

Cambios en el porcentaje de sodio intercambiable (PSI y la relación de absorción de sodio (RAS de un suelo y su influencia en la actividad y biomasa microbiana  

Directory of Open Access Journals (Sweden)

Full Text Available

Con el objetivo de evaluar los cambios en el PSI, la RAS y su influencia en la actividad y  biomasa  microbiana  del suelo,  se aplicaron  diversas  concentraciones  de vinaza  como enmienda procedente de la industria de alcohol carburante, sobre un suelo afectado por sodicidad con severas limitaciones en las condiciones físicas, químicas y biológicas. Se aplicó un diseño en bloques completos al azar que incluye cuatro tratamientos y tres repeticiones, y muestreos de suelo al inicio y final del proceso a tres profundidades (0-20, 20-40 y 40-60 cm, cuyas variables de respuesta a medir fueron  la respiración, C- biomasa microbiana, MO%, pH, CIC, CE, RAS y PSI. La actividad biológica (CO2 y el C-biomasa microbiana mostraron

incrementos significativos en el rango ideal para el establecimento del cultivo de caña.

Torrente Trujillo Armando

2011-03-01

156

Utilización del medio de cultivo UIT-A en la obtención de biomasa para la identificación bioquímica micobacteriana  

Directory of Open Access Journals (Sweden)

Full Text Available Se compara el medio de cultivo sólido UIT-A con el Lowenstein Jensen, para la obtención de biomasa en el montaje del test bioquímico de identificación de micobacterias "no tuberculosas" (MNT, con el objetivo de valorar la posibilidad de utilización como medio de cultivo para el montaje y análisis de dichas pruebas bioquímicas. Los resultados obtenidos en los 2 medios de cultivo utilizados fueron iguales, por lo que se recomienda el uso del medio de cultivo UIT-A fundamentalmente para aquellas cepas con crecimiento pobre o escaso.

LILIAN M. MEDEROS CUERVO

1995-12-01

157

The Effect of Habitual Smoking on VO2max  

Science.gov (United States)

VO2max is associated with many factors, including age, gender, physical activity, and body composition. It is popularly believed that habitual smoking lowers aerobic fitness. PURPOSE: to determine the effect of habitual smoking on VO2max after controlling for age, gender, activity and BMI. METHODS: 2374 men and 375 women employed at the NASA/Johnson Space Center were measured for VO2max by indirect calorimetry (RER>=1.1), activity by the 11 point (0-10) NASA Physical Activity Status Scale (PASS), BMI and smoking pack-yrs (packs day*y of smoking). Age was recorded in years and gender was coded as M=1, W=0. Pack.y was made a categorical variable consisting of four levels as follows: Never Smoked (0), Light (1-10), Regular (11-20), Heavy (>20). Group differences were verified by ANOVA. A General Linear Models (GLM) was used to develop two models to examine the relationship of smoking behavior on VO2max. GLM #1(without smoking) determined the combined effects of age, gender, PASS and BMI on VO2max. GLM #2 (with smoking) determined the added effects of smoking (pack.y groupings) on VO2max after controlling for age, gender, PASS and BMI. Constant errors (CE) were calculated to compare the accuracy of the two models for estimating the VO2max of the smoking subgroups. RESULTS: ANOVA affirmed the mean VO2max of each pack.y grouping decreased significantly (p<0.01) as the level of smoking exposure increased. GLM #1 showed that age, gender, PASS and BMI were independently related with VO2max (R2 = 0.642, SEE = 4.90, p<0.001). The added pack.y variables in GLM #2 were statistically significant (R2 change = 0.7%, p<0.01). Post hoc analysis showed that compared to Never Smoked, the effects on VO2max from Light and Regular smoking habits were -0.83 and -0.85 ml.kg- 1.min-1 respectively (p<0.05). The effect of Heavy smoking on VO2max was -2.56 ml.kg- 1.min-1 (p<0.001). The CE s of each smoking group in GLM #2 was smaller than the CE s of the smoking group counterparts in GLM #1. CONCLUSIONS: After accounting for the effects of gender, age, PASS and BMI the effect of habitual smoking on reducing VO2max is minimal, about 0.85 ml/kg/min, until the habit exceeds 20 pack.y at which point an additional decrease of 1.71 ml/kg/min is noted. Adding pack.y data improves the accuracy of predicting the VO2max of smokers.

Wier, Larry T.; Suminski, Richard R.; Poston, Walker S.; Randles, Anthony M.; Arenare, Brian; Jackson, Andrew S.

2008-01-01

158

Análisis de biomasa del vuelo de un rodal adulto de Pinus radiata Analysis of aboveground biomass in a mature stand of Pinus radiata  

Directory of Open Access Journals (Sweden)

Full Text Available Se realizó un estudio de biomasa en árboles de Pinus radiata D. Don de 42 años, obtenidos de un rodal ubicado entre las ciudades de Santa Juana y Nacimiento, VIII Región, Chile. El rodal se diferenció en tres clases de copa: dominante, codominante e intermedio. En cada clase de copa se obtuvieron valores de biomasa para cada componente (madera, corteza, ramas, ramillas y acículas; la madera resultó ser el componente que más aportó a la biomasa total sobre el suelo (88,9%, seguido de la corteza (8,2% y ramas (1,5%. Con los valores de biomasa obtenidos, se ajustaron funciones de biomasa por componente, relacionando estos valores con variables del árbol; el dap (diámetro a la altura del pecho y el dbc (diámetro en la base de la copa viva fueron las variables que mostraron mayor correlación con los valores de biomasa por componente y menores errores de estimación.A study of biomass in Pinus radiata D. Don with 42 years old was made, the trees were obtained of a stand placed between the cities of Santa Juana and Nacimiento, VIII Region, Chile. Three classes of top were differentiated in the stand: dominant, codominant and intermediate. The value of the mass for each component (wood, bark, branches, branchlets and needle was obtained from each class of top; the wood resulted as the most important component in the total biomass of the tree (88.9%, then the bark (8.2% and branches (1.5%. Obtained the values of biomass, the function of biomass for each component was obtained, related this values with the variables of the tree; the variables that showed greater correlation with the values of biomass by component and minors estimation errors are dbh (breast height diameter and dbc (base of live crown diameter.

CLAUDIO MUÑOZ RIVEROS

2005-12-01

159

Determinación de las reservas de carbono de la biomasa aérea, en diferentes sistemas de uso de la tierra en San Martín, Perú  

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Full Text Available Se determinó la biomasa aérea en diferentes sistemas de uso de la tierra en la región de San Martín-Perú, con la finalidad de conocer el potencial de captura de carbono. Los sistemas de uso de la tierra evaluados fueron: Bosque primario, Bosque secundario de diferentes edades, sistemas agrícolas locales maíz (Zea maiz, arroz (Oriza Sativa, pastos (Brachiaria y sistemas agroforestales con café (Coffea arabica bajo sombra y cacao (Cacao sp.. También se comparó este potencial con otros sistemas de uso de la tierra de otras regiones del Perú y se monitoreó la pérdida de reservas de carbono después del corte de la foresta y su reemplazo por cultivos. En cada uno de éstos sistemas se establecieron al azar cinco transectos donde se evaluó la biomasa arbórea. Dentro de éstos transectos se establecieron cuadrados también al azar para cuantificar la biomasa herbácea y la biomasa de hojarasca. El carbono total en el bosque primario fue de 485 tm C ha-1, superando ampliamente las reservas del bosque secundario de 50 años y de bosque descremado de 20 años. Con relación al bosque primario se observa una reducción de reservas en más de 50% del bosque secundario de 50 años (234 tm C ha-1. El bosque descremado de 20 años perdió más del 80% de reservas (62 tm C ha-1. El nivel de reservas de carbono en la biomasa de hojarasca de los sistemas boscosos, no es significativo al compararlo con el total de las reservas de carbono de la biomasa aérea; sin embargo si es significativo para sistemas agroforestales. Los sistemas agroforestales secuestraron entre 19 a 47 tm C ha-1, dependiendo de la cantidad de especies forestales, tipo de cultivo, edad y tipo de suelo y recuperan el potencial de captura en forma productiva. Los sistemas agrícolas capturaron poco C (5 tm C ha-1, además generan fugas de gases efecto invernadero (GEI cuando se usan agroquímicos y quema de rastrojos, entre otros.

Tatiana Lapeyre

2004-01-01

160

Controlled synthesis of VO2(R), VO2(B), and V2O3 vanadium-oxide nanowires  

International Nuclear Information System (INIS)

Vanadium-oxide nanowires (NWs) V2O5, VO2(R), VO2(B), and V2O3 are deposited on a substrate to study their field-emission properties. V2O5 NWs are prepared by thermal evaporation via vapor transport of a vanadium-oxide complex under mild conditions. Films of VO2 and V2O3 wires are subsequently prepared by reducing V2O5 one-dimensional nanocrystals at 450 °C with hydrogen gas. The composition of the flowing H2/Ar mixture and the duration of reduction are utilized to control the formation of VO2(R) or VO2(B) NWs. The crystallinity and morphology of products as prepared are characterized using several techniques, including powder X-ray diffraction, a scanning electron microscope, and a transmission electron microscope. The field-emission properties of the vanadium-oxide NWs as prepared exhibit a turn-on field of 4.56–7.65 V/?m and an emission current density up to 3.68–8.36 mA/cm2. These features indicate that vanadium-oxide NWs have potential FE emitter applications.Graphical AbstractV2O5, VO2(R), VO2(B), and V2O3 NWs were synthesized via thermal evaporation and controlled reduction process. Field-emission properties of these NWs exhibited turn-on fields of 4–8 V/?m, an emission current density up to 3.5 mA/cm2

2013-07-01

 
 
 
 
161

Structural characterization of PrVO3 epitaxial thin films  

CERN Document Server

Rare earth perovskite oxides constitute a wide family of materials presenting functional proper- ties strongly coupled to their crystalline structure. Here, we report on the experimental results on epitaxial PrVO3 deposited on SrTiO3 single crystal substrates by pulsed laser deposition. By com- bining advanced structural characterization tools, we have observed that the PVO unrelaxed film structure grown on STO, is characterized by two kinds of oriented domains whose epitaxial relations are: (i) PrVO3[110]o//SrTiO3[001]c and PrVO3[001]o//SrTiO3[100]c, (ii) PrVO3[110]o//SrTiO3[001]c and PrVO3[001]o//SrTiO3[010]c. We have also measured reciprocal space maps. From these results, we have determined that the PVO film epitaxy on STO imposes a lowering of the PVO structure symmetry from orthorhombic (Pbnm) to monoclinic (P21/m). We show, the nominal strain induced by the substrate being constant, that the obtained film structure depends on both growth oxygen and temperature. Thus, by finely controlling the depositio...

Copie, O; Boullay, P; Morales, M; Pautrat, A; David, A; Mercey, B; Pravarthana, D; Infante, I C; Janolin, P -E; Prellier, W

2014-01-01

162

Electrical switching and Mott transition in VO2  

Science.gov (United States)

In this paper the problem of the Mott metal-insulator transition in vanadium dioxide driven by an external electric field is considered. Delay time (td) measurements have shown that the experimental value of td is almost three orders of magnitude lower than the theoretical value, calculated in a simple electrothermal model. This suggests that under non-equilibrium conditions (in high electric fields) electron correlation effects contribute to the development of the insulator to metal transition. The extra-carrier injection from Si into VO2 was carried out in the structures Si-SiO2-VO2 on p-type silicon with ? = 0.1 ? cm and a SiO2 thickness 70 nm. It has been shown that the metal-insulator transition in VO2 can be initiated by injection, i.e. by the increase of the electron density. The value of the critical density was found to be of the order of the electron density in VO2 in the semiconducting phase, approximately 1018-1019 cm-3. This confirms that the metal-insulator transition in VO2 is the purely electronic Mott-Hubbard transition.

Stefanovich, G.; Pergament, A.; Stefanovich, D.

2000-10-01

163

One-step hydrothermal conversion of VO2(B) into W-doped VO2(M) and its phase transition and optical switching properties  

Science.gov (United States)

W-doped monoclinic vanadium dioxide VO2(M) nanobelts have been transformed from VO2(B) nanobelts in the presence of tungstic acid by a facile one-step hydrothermal route for the first time. The as-prepared samples were characterized by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and variable-temperature infrared spectroscopy (IR). The results show that W atoms are doped into the crystal lattice of VO2(M) matrix, and the morphology and size of the as-obtained VO2(M) nanobelts are dependent on that of the precursor VO2(B). The phase transition temperature (Tc) of W-doped VO2(M) can be tuned by W doping. The variable-temperature IR reveals that the as-synthesized W-doped VO2(M) nanobelts have outstanding thermochromic characters and optical switching properties.

Zhang, Yifu; Zhang, Xiongzhi; Huang, Yu; Huang, Chi; Niu, Fei; Meng, Changgong; Tan, Xiaoyu

2014-02-01

164

Efecto de lixiviados del raquis de plátano sobre la actividad y biomasa microbiana en floración y cosecha del tomate  

Directory of Open Access Journals (Sweden)

Full Text Available Se utilizaron cinco tratamientos: el testigo (T0 y cuatro concentraciones de lixiviados (T1= 100%, T2= 75%, T3= 50% y T4= 25% aplicados 15, 30 y 60 días después del trasplante. La actividad microbiana se determinó con la metodología del CAB y la biomasa microbiana con el método de fumigación-extracción. En la actividad microbiana se encontraron diferencias significativas entre los tratamientos, presentando la aplicación del lixiviado a la menor concentración (25% la mayor actividad (56.76 mgCO2g suelo-1. La actividad fue mayor en floración en todos los tratamientos. Para biomasa microbiana no se presentaron diferencias significativas entre los tratamientos ni entre épocas. ABSTRACT The effect of leaching from rachis on soil microbial biomass and activity during tomato flowering and harvesting period. Field trail comprised five treatments of different leaching concentrations (T0= test, T1= 100%, T2= 75%, T3=50%, and T4=25% sprinkled on soil 15, 30 and 60 days after tomato transplanting. Microbial activity was measured with CAB method and microbial biomass was recorded with fumigation - extraction method. The average microbial activity with sprinking of 25% of leaching was higher (56.76 mgCO2g suelo-1. No significant difference in order to treatments and periods in microbial biomass were observed. These observations showed leaching sprinkling in low concentration influence en microbial activity for the conditions of this experiment. Key words: Soil biology, biomass, leaching, Lycopersicum sculentun.

Muñoz V. Rosa Elvira

2005-03-01

165

Efecto del brasinoesteroide y densidad de población en la acumulación de biomasa y rendimiento de ayocote (Phaseolus coccineus L.  

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Full Text Available Se estudió el efecto del regulador de crecimiento brasinoesteroide en la acumulación de materia seca y en el rendimiento de grano de ayocote (Phaseolus coccineus L. variedad Blanco Tlaxcala. La siembra se realizó el 3 de mayo del 2000 bajo condiciones de temporal en Tetelco, Tláhuac, D. F., México. Las densidades de siembra estudiadas fueron 60, 75, 90 105 y 120 mil plantas por hectárea. Se aplicaron 40 mg·ha-1 del brasinoesteroide (solución cuya concentración fue 1 mg·ml-1 en tres partes: 10 mg·ha-1 a los 30 días después de la siembra (dds, 10 mg·ha-1 a los 60 dds y 20 mg·ha-1 90 dds. El brasinoesteroide incrementó la biomasa total y por órganos en la mayoría de las densidades en estudio. En densidades de 105 y 120 mil plantas por hectárea el incremento de biomasa total se triplicó en comparación con las demás densidades. El brasinoesteroide incrementó el rendimiento en un 68 % en la densidad de 90 mil plantas por hectárea

M. L. P. Vargas-Vu00E1zquez

2005-01-01

166

PRODUCCIÓN DE PROTEÍNA Y BIOMASA PROBIÓTICA DE Lactobacillus casei LIOFILIZADAS A PARTIR DE SUERO DE LECHE DE CABRA  

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Full Text Available En este trabajo se documenta la factibilidad técnica de obtención de dos productos de valor agregado a partir de suero de leche de cabra: (a proteína liofilizada y (b biomasa probiótica liofilizada de Lactobacillus casei. Se presentan resultados de experimentos de ultrafiltración de suero de leche de cabra (SLC, del cual se retiene proteína con una alta relación proteína/lactosa. En su forma liofilizada, esta proteína presentó características de solubilidad superiores a productos comerciales similares. El permeado resultante del ultrafiltrado de SLC fue utilizado como medio de cultivo para el crecimiento del microorganismo probiótico L. casei. Se reportan resultados de experimentos de fermentación de suero de leche por lote y lote alimentado para la producción de biomasa. La cinética de crecimiento de L. casei en SLC desproteinizado no suplementado es analizada a partir de datos de experimentos por lotes. Se observa un marcado efecto inhibitorio del crecimiento bacteriano asociado a la producción de ácido láctico. Las estrategias por lote alimentado aquí reportadas resultan en productividades superiores, concentraciones de sustrato residual menores y viabilidades más altas del producto respecto a procesos por lote.

E. J. Aguirre-Ezkauriatza

2009-01-01

167

Phase Transformation of VO2 Nanoparticles Assisted by Microwave Heating  

Science.gov (United States)

The microwave assisted synthesis nowadays attracts a great deal of attention. Monoclinic phase VO2 (M) was prepared from NH4VO3 and H2C2O4 · 2H2O by a rapid microwave assisted technique. The synthesis parameters, microwave irradiation time, microwave power, and calcinations temperature were systematically varied and their influences on the structure and morphology were evaluated. The microwave power level has been carried out in range 180–600?W. TEM analysis demonstrated nanosized samples. The structural and morphological properties were measured using XRD, TEM, and thermal analyses. The variations of vanadium phase led to thermochromic properties.

Sikong, Lek.

2014-01-01

168

Phase transformation of VO2 nanoparticles assisted by microwave heating.  

Science.gov (United States)

The microwave assisted synthesis nowadays attracts a great deal of attention. Monoclinic phase VO2 (M) was prepared from NH4VO3 and H2C2O4 · 2H2O by a rapid microwave assisted technique. The synthesis parameters, microwave irradiation time, microwave power, and calcinations temperature were systematically varied and their influences on the structure and morphology were evaluated. The microwave power level has been carried out in range 180-600 W. TEM analysis demonstrated nanosized samples. The structural and morphological properties were measured using XRD, TEM, and thermal analyses. The variations of vanadium phase led to thermochromic properties. PMID:24688438

Phoempoon, Phatcharee; Sikong, Lek

2014-01-01

169

Infrared-sensitive electrochromic device based on VO2  

Science.gov (United States)

The field-effect transistor (FET) provides an electrical switching function of current flowing through a channel surface by external voltage. Here, we report on a field-effect device that enables electrical switching of optical transmittance as well as conventional electrical current. We investigated optical properties of vanadium dioxide (VO2) thin film under the presence of electric field generated at the interface between VO2 and ionic liquid in a FET geometry, and found that the device exhibits clear electrochromic effect with large ON/OFF contrast only in the infrared region, potentially beneficial for energy-saving smart window applications as a voltage-tunable transparent heat-cutting filter.

Nakano, M.; Shibuya, K.; Ogawa, N.; Hatano, T.; Kawasaki, M.; Iwasa, Y.; Tokura, Y.

2013-10-01

170

Hydrogen dynamics and metallic phase stabilization in VO2  

Science.gov (United States)

Experimental doping of VO2 with hydrogen has been shown to trigger the semiconductor-to-metal phase transition below room temperature. Here, we report the results of density functional calculations showing that hydrogen-induced lattice distortion stabilizes the metallic phase. We also show that hydrogen diffuses preferentially along the rutile [001] direction whereby surface orientations can be tailored for optimal transport. Finally, we show that hydrogen doping is energetically favored, but there is a 1.6 eV barrier for dissociation of hydrogen molecules on a (100) monoclinic surface. These results give insight into the effect of hydrogen on the properties and phase transition of VO2.

Warnick, Keith H.; Wang, Bin; Pantelides, Sokrates T.

2014-03-01

171

Lattice effects in HoVo{sub 3} single crystal  

Energy Technology Data Exchange (ETDEWEB)

We report the study of lattice effects in the Mott insulator HoVO{sub 3} performed by means of linear thermal expansion on a single crystal in the temperature range 10-290 K. The holmium orthovanadate HoVO{sub 3} reveals gradual orbital ordering (OO) below T {sub OO}=200 K and orders antiferromagnetically at T {sub N}=113 K. A first-order structural phase transition takes place at T {sub S}{approx}38 K, which is probably accompanied by change of the OO type and hence the type of antiferromagnetic spin ordering.

Sikora, M. [Instituto de Ciencia de Materiales de Aragon, CSIC-Universidad de Zaragoza, Facultad de Ciencias, Zaragoza 50009 (Spain); Solid State Physics Department, AGH University of Science and Technology, 30-059 Cracow (Poland); Marquina, C. [Instituto de Ciencia de Materiales de Aragon, CSIC-Universidad de Zaragoza, Facultad de Ciencias, Zaragoza 50009 (Spain)]. E-mail: clara@unizar.es; Ibarra, M.R. [Instituto de Ciencia de Materiales de Aragon, CSIC-Universidad de Zaragoza, Facultad de Ciencias, Zaragoza 50009 (Spain); Nugroho, A.A. [Solid State Chemistry Laboratory, Materials Science Center, University of Groningen, Nijenborg 4 9747 AG Groningen (Netherlands); Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132 (Indonesia); Palstra, T.T.M. [Solid State Chemistry Laboratory, Materials Science Center, University of Groningen, Nijenborg 4 9747 AG Groningen (Netherlands)

2007-09-15

172

Accuracy of the VO2peak prediction equation in firefighters  

Science.gov (United States)

Background A leading contributing factor to firefighter injury and death is lack of fitness. Therefore, the Fire Service Joint Labor Management Wellness-Fitness Initiative (WFI) was established that includes a focus on providing fitness assessments to all fire service personnel. The current fitness assessment includes a submaximal exercise test protocol and associated prediction equation to predict individual VO2peak as a measure of fitness. There is limited information on the accuracy, precision, and sources of error of this prediction equation. This study replicated previous research by validating the accuracy of the WFI VO2peak prediction equation for a group of firefighters and further examining potential sources of error for an individual firefighters’ assessment. Methods The sample consisted of 22 firefighters who completed a maximal exercise test protocol similar to the WFI submaximal protocol, but the test was terminated when firefighters reached a maximal level of exertion (i.e., measured VO2peak). We then calculated the predicted VO2peak based on the WFI prediction equation along with individual firefighters’ body mass index (BMI) and 85% of maximum heart rate. The data were analyzed using paired samples t-tests in SPSS v. 21.0. Results The difference between predicted and measured VO2peak was -0.77?±?8.35 mL•kg-1•min-1. However, there was a weak, statistically non-significant association between measured VO2peak and predicted VO2peak (R2?=?0.09, F(1,21)?=?2.05, p?=?0.17). The intraclass correlation coefficient (ICC?=?0.215, p?>?0.05) and Pearson (r?=?0.31, p?=?0.17) and Spearman (??=?0.28, p?=?0.21) correlation coefficients were small. The standard error of the estimate (SEE) was 8.5 mL•kg-1•min-1. Further, both age and baseline fitness level were associated with increased inaccuracy of the prediction equation. Conclusions We provide data on the inaccuracy and sources of error for the WFI VO2peak prediction equation for predicting fitness level in individual firefighters, despite apparently accurate predictions for a group of firefighters. These results suggest that the WFI prediction equation may need to be reevaluated as a means of precisely determining fitness for individual firefighters, which may affect employment status, duty assignment, and overall life safety of the firefighter.

2014-01-01

173

Lightweight security mechanism for PSTN-VoIP cooperation  

CERN Multimedia

In this paper we describe a new, lightweight security mechanism for PSTN-VoIP cooperation that is based on two information hiding techniques: digital watermarking and steganography. Proposed scheme is especially suitable for PSTN-IP-PSTN (toll-by-passing) scenario which nowadays is very popular application of IP Telephony systems. With the use of this mechanism we authenticate end-to-end transmitted voice between PSTN users. Additionally we improve IP part traffic security (both media stream and VoIP signalling messages). Exemplary scenario is presented for SIP signalling protocol along with SIP-T extension and H.248/Megaco protocol.

Mazurczyk, W; Mazurczyk, Wojciech; Kotulski, Zbigniew

2006-01-01

174

Reproducibility of maximum aerobic power (VO2max among soccer players using a modified heck protocol Reprodutibilidade da potência aeróbia máxima (VO2max em jogadores de futebol utilizando o protocolo de heck modificado  

Directory of Open Access Journals (Sweden)

Full Text Available OBJECTIVE: To determine the degree of reproducibility of maximum oxygen consumption (VO2max among soccer players, using a modified Heck protocol. METHODS: 2 evaluations with an interval of 15 days between them were performed on 11 male soccer players. All the players were at a high performance level; they were training for an average of 10 hours per week, totaling 5 times a week. When they were evaluated, they were in the middle of the competitive season, playing 1 match per week. The soccer players were evaluated on an ergometric treadmill with velocity increments of 1.2 km.h-1 every 2 minutes and a fixed inclination of 3% during the test. VO2max was measured directly using a breath-by-breath metabolic gas analyzer. RESULTS: The maximum running speed and VO2max attained in the 2 tests were, respectively: (15.6 ± 1.1 vs. 15.7 ± 1.2 km.h-1; [P = .78] and (54.5 ± 3.9 vs. 55.2 ± 4.4 ml.kg-1.min-1; [P = .88]. There was high and significant correlation of VO2max between the 2 tests with a 15-day interval between them [r = 0.97; P OBJETIVO: Determinar o grau de reprodutibilidade do consumo máximo de oxigênio (VO2max em jogadores de futebol utilizando o protocolo de Heck modificado. MÉTODOS: Foram avaliados por duas vezes, com intervalo de 15 dias entre os testes, 11 futebolistas masculinos. Todos eram de alto nível, treinavam em média 10 horas por semana subdivididos em treinamentos físicos, técnicos, táticos e jogos competitivos, totalizando cinco vezes por semana e na fase em que foram avaliados se encontravam em pleno período competitivo realizando um jogo por semana. Os futebolistas foram avaliados em esteira ergométrica (1,2 km.h-1 a cada dois minutos e inclinação fixa durante o teste em 3%. O VO2max foi medido diretamente utilizando analisador metabólico de análise de gases expirados respiração-a-respiração. RESULTADOS: A velocidade máxima de corrida e o VO2max atingido nos dois testes foram respectivamente: (15,6 ± 1,1 vs. 15,7 ± 1,2 km.h-1; [p = 0,78] e (54,5 ± 3,9 vs. 55,2 ± 4,4 ml.kg-1.min-1; [P = 0,88]. Houve correlação significante e alta do VO2max entre os dois testes após 15 dias de intervalo [r = 0,97; P< 0,001]. CONCLUSÃO: O protocolo de Heck modificado foi reprodutível e o intervalo de quinze dias entre os testes ergoespirométricos não foi suficiente para modificar significativamente o VO2max dos jogadores de futebol.

Paulo Roberto Santos-Silva

2007-01-01

175

Effects of electrical stimulation on VO2 kinetics and delta efficiency in healthy young men  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Objective: To determine the effects of electrical stimulation (ES) on oxygen uptake (VO2) kinetics and delta efficiency (DE) during gradual exercise. The hypothesis was that ES would attenuate the VO2-workload relation and improve DE.

Perez, M.; Lucia, A.; Santalla, A.; Chicharro, J.

2003-01-01

176

Producción de Biomasa en el Mejillon verde de localidad de la Península de Araya, Venezuela.  

Scientific Electronic Library Online (English)

Full Text Available SciELO Venezuela | Language: Spanish Abstract in portuguese O mexilhão verde Perna viridis, originário do Indo-Pacifico foi identificado e relatado no Golfo de Paria em 1993, causando por sua abundancia grande impacto nas comunidades costeiras. A produção específica dos componentes da biomassa individual de P. viridis foi determinada em uma população natural [...] em Guayacán, estado Sucre, Venezuela. Amostras mensais se realizaram entre agosto '02 e agosto '03, e as biomassas (peso seco) de gônada, músculo adutor, resto de tecidos somáticos e matriz orgânica da concha foram avaliadas utilizando equações mensais longitude-peso seco e um modelo de crescimento local. Nas amostras se determinaram temperatura da água, salinidade, O2 dissolvido e disponibilidade de alimento (clorofila a). O maior peso seco gônada (pg) se observou em agosto de ambos anos, com mínimos em julho para as idades maiores, com três prováveis períodos de desove. O resto de tecido somático (prt) apresentou máximo em setembro e mínimo em junho, e o músculo (pm) máximo em agosto '03 e mínimo em maio. A produção de tecido somático (Prt), músculo adutor (Pm) e matéria orgânica da concha (Pc) foram máximas aos 12 meses, diminuindo posteriormente. A produção de gônadas (Pg) nos períodos de desove aumentou de 0,10g aos 6 meses até 1,15g a 2,5 anos. A produção total (P) aumentou com a idade, mas a relação P/B diminuiu. O esforço reprodutivo (Pg/P) aumentou de 0,13g até 0,71g aos 2,5 anos, revelando uma estratégia populacional de alta produtividade de gônadas que garante o alto potencial biótico da espécie. Abstract in spanish El mejillón verde Perna viridis, originario del Indo-Pacifico fue reportado en el Golfo de Paria en 1993, causando por su abundancia gran impacto en las comunidades costeras. La producción específica de los componentes de la biomasa individual de P. viridis fue determinada en una población natural e [...] n Guayacán, estado Sucre, Venezuela. Muestreos mensuales se realizaron entre agosto ?02 y agosto ?03, y las biomasas (peso seco) de gónada, músculo aductor, resto de tejidos somáticos y matriz orgánica de la concha fueron evaluadas utilizando ecuaciones mensuales longitud-peso seco y un modelo de crecimiento local. En los muestreos se determinaron temperatura del agua, salinidad, O2 disuelto y disponibilidad de alimento (clorofila a). El mayor peso seco gonadal (pg) se observó en agosto de ambos años, con mínimos en julio para las edades mayores, con tres probables periodos de desove. El resto de tejido somático (prt) presentó máximo en setiembre y mínimo en junio, y el músculo (pm) máximo en agosto ?03 y mínimo en mayo. La producción de tejido somático (Prt), músculo aductor (Pm) y materia orgánica de la concha (Pc) fueron máximas a los 12 meses, disminuyendo posteriormente. La producción de gónadas (Pg) en los periodos de desove aumentó de 0,10g a los 6 meses hasta 1,15g a 2,5 años. La producción total (P) aumentó con la edad, pero la relación P/B disminuyó. El esfuerzo reproductivo (Pg/P) aumentó de 0,13g hasta 0,71g a los 2,5 años, revelando una estrategia poblacional de alta productividad de gónadas que garantiza el alto potencial biótico de la especie. Abstract in english The green mussel Perna viridis, native of the Indo-Pacific, was reported in the Gulf of Paria in 1993, causing large impact in the local coastal communities due to their abundance. Specific production of individual biomass components in a natural population of P. viridis was determined in Guayacan, [...] Sucre state, Venezuela. The Monthly samplings were carried out between August ?02 and August ?03 and the biomass (dry weight) of gonad, adductor muscle, remaining somatic tissues and shell organic material were evaluated using monthly length-dry weight equations and a model of local population growth. In the samplings, water temperature, salinity, dissolved O2 and food availability (chlorophyll a) were determined. The largest dry weight gonadal tissue (pg)

Malavé, Carmen J; Prieto Arcas, Antulio S.

177

Oxygen pressure dependent VO2 crystal film preparation and the interfacial epitaxial growth study  

International Nuclear Information System (INIS)

High quality VO2 crystal films have been prepared on sapphire substrates by pulsed laser deposition method and the effects of oxygen pressure on the crystal phase structure are investigated. Results indicate that the phases and microstructures of VO2 films are strongly sensitive to oxygen pressure. High oxygen pressure tends to form coarse B-VO2 nanocrystals while low pressure favors a flat M1-VO2 film epitaxial growth. X-ray diffraction ?-scan patterns confirm the [020] epitaxial growth orientation of the M1-VO2 film and the in-plane lattice epitaxial relationship at the interface is also examined. Raman spectra indicate that M1-VO2 phase has much stronger Raman scattering modes than B-VO2, and the clear phonon modes further confirm the idea stoichiometry of VO2 crystal film. Infrared transmittance spectra as the function of temperature are recorded and the results show that M1-VO2 crystal films undergo a distinct infrared transmittance variation across metal insulator transition boundary, while B-VO2 exhibits negligible thermochromic switching properties in the temperature range concerned. The pronounced phase transition behavior of the M1-VO2 crystal film makes it a promising candidate for optical filter/switch and smart window applications in the future. - Highlights: ? High quality VO2 films with different phase structures were obtained by PLD method. ? High oxygen pressure tends to form B-VO2 while low pressure favors M1-VO2 film. ? ?-scan XRD confirms the [020] epitaxial growth orientation of the M1-VO2 film. ? The epitaxial relationship is explained based on domain matching theory. ? M1-VO2 film shows excellent optical property in infrared range.

2012-07-31

178

A Novel Protocol Design and Collaborative Forensics Mechanism for VoIP Services  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The simplicity and low cost of Voice over Internet Protocol (VoIP) services has made these services increasingly popular as the Internet has grown. Unfortunately, these advantages of VoIP are attractive to both legitimate and nefarious users, and VoIP is often used by criminals to communicate and conduct illegal activities (such as fraud or blackmail) without being intercepted by Law Enforcement Agencies (LEAs). However, VoIP can also increase the efficiency ...

2012-01-01

179

Componente lento da cinética do VO2: determinantes fisiológicos e implicações para o desempenho em exercícios aeróbios / Slow component of VO2 kinetics: physiological determinants and implications for performance in aerobic exercises  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese A cinética do consumo de oxigênio (VO2) e a resposta do lactato sanguíneo durante o exercício de carga constante em diferentes intensidades permitem caracterizar os domínios moderado, pesado e severo do exercício. Em exercício de intensidade constante, o perfil da resposta do VO2, analisada por ajus [...] tes exponenciais, apresenta as fases cardiodinâmica, fundamental e lenta. A ocorrência do componente lento (CL) tem sido associada a fatores como recrutamento de fibras do tipo II e acúmulo de metabólitos, como lactato, íons H+, fosfato inorgânico e ADP. O CL expressa uma redução da eficiência muscular e tem sido associado à menor tolerância de exercícios aeróbios de intensidade alta. O presente estudo teve por objetivo detalhar a fundamentação teórica sobre sua ocorrência, a influência na tolerância ao exercício, bem como prover os diferentes procedimentos adotados em sua quantificação. Abstract in english Oxygen uptake (VO2) kinetics and blood lactate response during constant workload exercise at different intensities allow characterizing the moderate, heavy and severe exercise domains. In constant-intensity exercise, the VO2 response profile, analyzed by exponential fits, shows the cardiodynamic, fu [...] ndamental and slow phases. The occurrence of the slow component (SC) has been associated with factors such as the recruitment of type II fibers and the accumulation of metabolites such as lactate, ions H+, inorganic phosphate and adenosine diphosphate. The SC expresses a reduction of muscular efficiency and has been associated with lower tolerance to high-intensity aerobic exercise. The present study aimed to detail the theoretical framework of its occurrence and its influence on exercise tolerance, as well as providing the different procedures used in its quantification.

Renato Aparecido Correa, Carita; Dalton Muller, Pessoa Filho; Luis Fabiano, Barbosa; Camila Coelho, Greco.

180

ESTUDIO CINÉTICO DEL PROCESO DE DEVOLATILIZACIÓN DE BIOMASA LIGNOCELULÓSICA MEDIANTE ANÁLISIS TERMOGRAVIMÉTRICO PARA TAMAÑOS DE PARTÍCULA DE 2 A 19 mm  

Directory of Open Access Journals (Sweden)

Full Text Available Con el objetivo de proporcionar herramientas que mejoren el diseño de los sistemas de gasificación/combustión de biomasa, y los modelos cinético-químicos de dichos procesos, se presenta un estudio de la cinética química asociada al proceso de devolatilización de biomasa mediante pruebas de termogravimetría utilizando tamaños de partícula que varían de 2 a 19 mm, y tasas de calentamiento de 10, 15 y 20 K/min. El desarrollo de este trabajo se justifica debido a que no hay resultados disponibles en la bibliografía que estudien tamaños superiores a 1 mm. Mediante el ajuste de los puntos experimentales utilizando un modelo de primer orden se determinan los parámetros de las constantes cinéticas (forma de Arrhenius. El estudio muestra que la energía de activación es directamente proporcional a la tasa de calentamiento y al tamaño de partícula, se comprueba que el proceso de descomposición térmica de la biomasa se da a temperaturas más altas con el aumento del tamaño de las partículas, debido a la importancia que toman los procesos de transferencia calor y masa. Los parámetros cinéticos calculados pueden ser utilizados en los modelos dimensionales del proceso de gasificación-combustión de biomasa, considerando el tamaño de las partículas intrínseco en la cinética.

ANDRÉS MELGAR

2008-01-01

 
 
 
 
181

Remoción de Cromo (VI en Solución Acuosa por la Biomasa Celular de Paecilomyces sp. Removal of Chromium (VI from Aqueous Solutions by Fungal Biomass of Paecilomyces sp.  

Directory of Open Access Journals (Sweden)

Full Text Available El objetivo de este trabajo fue determinar la remoción de Cromo (VI en solución por la biomasa celular del hongo contaminante ambiental Paecilomyces sp. por el método colorimétrico de la difenilcarbazida. La mayor bioadsorción fue a pH= 1.0±0.2, a 50ºC durante 16 horas con 7.2 mg/200 mL de concentración inicial de Cromo (VI y 80 mg/200 mL de biomasa celular. Se concluye que la biomasa fúngica remueve adecuadamente Cromo (VI en solución y puede utilizarse para descontaminar nichos acuáticos contaminados, ya que 1 g de biomasa fúngica remueve 100 mg/200 mL del metal a las tres horas de incubación.The objective of this work was to determine the removal of Chromium (VI on the Paecilomyces sp.; fungal biomass, spectrophotometrically using diphenylcarbazide as the complexing agent. The highest adsorption was obtained at pH= 1.0±0.2, at 50ºC after 16 hours of incubation, with 7.2 mg/200 mL of initial concentration of Chromium (VI and 80 mg/200 mL of cellular biomass. It was concluded that application of this biomass on the removal of Cr (VI in aqueous solutions can be used since 1 g of fungal biomass remove 100 mg/200 mL of this metal after three hours of incubation.

Ismael Acosta

2008-01-01

182

Remoción de Cromo (VI) en Solución Acuosa por la Biomasa Celular de Paecilomyces sp. / Removal of Chromium (VI) from Aqueous Solutions by Fungal Biomass of Paecilomyces sp.  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish El objetivo de este trabajo fue determinar la remoción de Cromo (VI) en solución por la biomasa celular del hongo contaminante ambiental Paecilomyces sp. por el método colorimétrico de la difenilcarbazida. La mayor bioadsorción fue a pH= 1.0±0.2, a 50ºC durante 16 horas con 7.2 mg/200 mL de concentr [...] ación inicial de Cromo (VI) y 80 mg/200 mL de biomasa celular. Se concluye que la biomasa fúngica remueve adecuadamente Cromo (VI) en solución y puede utilizarse para descontaminar nichos acuáticos contaminados, ya que 1 g de biomasa fúngica remueve 100 mg/200 mL del metal a las tres horas de incubación. Abstract in english The objective of this work was to determine the removal of Chromium (VI) on the Paecilomyces sp.; fungal biomass, spectrophotometrically using diphenylcarbazide as the complexing agent. The highest adsorption was obtained at pH= 1.0±0.2, at 50ºC after 16 hours of incubation, with 7.2 mg/200 mL of in [...] itial concentration of Chromium (VI) and 80 mg/200 mL of cellular biomass. It was concluded that application of this biomass on the removal of Cr (VI) in aqueous solutions can be used since 1 g of fungal biomass remove 100 mg/200 mL of this metal after three hours of incubation.

Acosta, Ismael; Cárdenas, Juan F; Alvarado-Hernández, Diana; Moctezuma-Zárate, María G.

183

Comportamiento de la disponibilidad de biomasa y la composición química en 23 accesiones de Leucaena spp. / Performance of biomass availability and chemical composition of 23 Leucaena spp. accessions  

Scientific Electronic Library Online (English)

Full Text Available SciELO Cuba | Language: Spanish Abstract in spanish Se realizó un estudio con 23 accesiones de Leucaena spp. en un área que tenía seis años de sembrada. El objetivo fue determinar, en las plantas establecidas, la biomasa total, la biomasa comestible, la biomasa leñosa, el grosor del tallo y el número de ramas de cada accesión, y su composición bromat [...] ológica en condiciones de pastoreo simulado. La investigación se realizó en la EEPF "Indio Hatuey" durante dos años, en un suelo Ferralítico Rojo lixiviado, húmico nodular ferruginoso hidratado. Se utilizaron parcelas sencillas de 3 m x 6 m. En la biomasa comestible y sus componentes (hojas y tallos tiernos) existieron diferencias significativas (P Abstract in english A study was conducted with 23 Leucaena spp. accessions in an area which had been planted six years before. The objective was to determine, in the established plants, total biomass, edible biomass, ligneous biomass, stem diameter and number of branches in each accession, and its bromatological compos [...] ition under simulated grazing conditions. The research was conducted at the EEPF "Indio Hatuey" during two years, on a hydrated ferruginous nodular humic lixiviated Ferralitic Red soil. Simple 3 m x 6 m plots were used. In the edible biomass and its components (leaves and fresh stems), there were significant differences (P

Wencomo, Hilda B; Ortiz, R.

184

Estimation of VO2 Max: A Comparative Analysis of Five Exercise Tests.  

Science.gov (United States)

Thirty-eight healthy females measured maximal oxygen uptake (VO2max) on the cycle ergometer and treadmill to compare five exercise tests (run, walk, step, and two tests using heart-rate response on the bicycle ergometer) in predicting VO2max. Results indicate that walk and run tests are satisfactory predictors of VO2max in 30- to 39-year-old…

Zwiren, Linda D.; And Others

1991-01-01

185

Magnetic properties of lanthanoid-VO{sub 3}  

Energy Technology Data Exchange (ETDEWEB)

The magnetization and magnetic susceptibility were measured for Ln-VO{sub 3}, except for lanthanoids Ln=Pm{sup 3+} and Tb{sup 3+}. The paramagnetic behaviors and the magnetic phase transition above 77 K were discussed on the basis of the contributions of Ln{sup 3+} and V{sup 3+} magnetic moments. ((orig.)).

Kimishima, Y. [Department of Physics, Faculty of Engineering, Yokohama National University, Tokiwadai 156, Hodogaya-ku, Yokohama 240 (Japan); Takahashi, M. [Department of Physics, Faculty of Engineering, Yokohama National University, Tokiwadai 156, Hodogaya-ku, Yokohama 240 (Japan); Okada, K. [Department of Physics, Faculty of Engineering, Yokohama National University, Tokiwadai 156, Hodogaya-ku, Yokohama 240 (Japan); Ishikawa, H. [Department of Physics, Faculty of Engineering, Yokohama National University, Tokiwadai 156, Hodogaya-ku, Yokohama 240 (Japan); Ichiyanagi, Y. [Computer Room, Faculty of Education, Yokohama National University, Tokiwadai 156, Hodogaya-ku, Yokohama 240 (Japan)

1995-02-09

186

Structure and magnetism of epitaxial PrVO3 films.  

Science.gov (United States)

The interplay between charge, spin, orbital and lattice degrees of freedom in transition metal oxides has motivated extensive research aiming to understand the coupling phenomena in these multifunctional materials. Among them, rare earth vanadates are Mott insulators characterized by spin and orbital orderings strongly influenced by lattice distortions. Using epitaxial strain as a means to tailor the unit cell deformation, we report here on the first thin films of PrVO3 grown on (001)-oriented SrTiO3 substrate by pulsed laser deposition. An extensive structural characterization of the PrVO3 films, combining x-ray diffraction and high-resolution transmission electron microscopy studies, reveals the presence of oriented domains and a unit cell deformation tailored by the growth conditions. We have also investigated the physical properties of the PrVO3 films. We show that, while PrVO3 exhibits an insulating character, magnetic measurements indicate low-temperature hard-ferromagnetic behavior below 80 K. We discuss these properties in view of the thin-film structure. PMID:24214665

Copie, O; Rotella, H; Boullay, P; Morales, M; Pautrat, A; Janolin, P-E; Infante, I C; Pravathana, D; Lüders, U; Prellier, W

2013-12-11

187

Synthesis and characterization of FeVO4 nanoparticles  

International Nuclear Information System (INIS)

Highlights: ? Simple co-precipitation method were employed for the synthesis of FeVO4. ? The calcination temperature and the reaction time were optimized. ? The effect of surfactants on the structural, morphological and magnetic properties was studied. ? The shape of the particles changes due to the effect of surfactant. ? Enhancement of magnetic orderings on the addition of surfactant. -- Abstract: Iron vanadate (FeVO4) nanoparticles were synthesized by simple co-precipitation method using various surfactants such as ethylene glycol, polyethylene glycol 200 and polyethylene glycol 400 as the structure directing agents. Systematic investigations on the structural, morphological and magnetic properties of the materials have been studied. The lattice constants of the triclinic structure of FeVO4 were calculated from the X-ray diffraction (XRD) analyses. The average grain size was estimated to be around 35 nm, which increased with increasing the calcination temperature. The stretching and bending vibrations of Fe-O were evaluated from the FT-IR spectra. Using VSM magnetometer, magnetic property was investigated through magnetic susceptibility and magnetization measurements. FeVO4 exhibits two magnetic ordering temperatures at T ? 20 K and 14 K, which is due to two different chemical environments of Fe ligands such as octahedral FeO6 and trigonal bipyramidal FeO5 in a six-column doubly bent chain, respectively.

2011-10-01

188

Covert Channels in SIP for VoIP signalling  

CERN Multimedia

In this paper, we evaluate available steganographic techniques for SIP (Session Initiation Protocol) that can be used for creating covert channels during signaling phase of VoIP (Voice over IP) call. Apart from characterizing existing steganographic methods we provide new insights by introducing new techniques. We also estimate amount of data that can be transferred in signalling messages for typical IP telephony call.

Mazurczyk, Wojciech

2008-01-01

189

Fabrication and Electrical Properties of Pure VO2 Phase Films  

CERN Document Server

We have grown VO2 thin films by laser ablation for electronic device applications. In obtaining the thin films of the pure VO2 phase, oxygen partial pressure is a critical parameter because vanadium oxides have several phases with the oxygen concentration. It is found that the pure VO2 films are grown on Al2O3 substrate in the narrow ranges of 55-60 mTorr in an Ar+10% O2 ambient, and that the mixed phase films are synthesized when the deposition pressure slightly deviates from the optimum pressure. The (100) oriented VO2 films undergo an abrupt metal-insulator transition (MIT) with resistance change of an order of 104 at 338K. In the films of mixed phases, the small change of the resistance is observed at the same temperature. The polycrystalline films are grown on SiO2/Si substrate, and undergo a broaden MIT of the resistance. This may be attributed to mixed phases generated in the films because of a coarse interface states. Furthermore, the abrupt MIT and collective current motion appearing in metal are obs...

Chae, B G; Kim, H T; Maeng, S Y; Kang, K Y

2003-01-01

190

Matching of Male and Female Subjects Using VO2 Max.  

Science.gov (United States)

The increasing use of various VO2 max expressions as test measures is a problem because the magnitude of sex difference varies considerably with each expression. A valid match of male and female test subjects would consider physical activity history and the amount of endurance exercise done in the previous year. (Author/FG)

Cureton, Kirk J.

1981-01-01

191

Collective orbital excitations in GdVO{sub 3}  

Energy Technology Data Exchange (ETDEWEB)

In the vanadates (RVO{sub 3}) orbital interactions are expected to be especially strong. In the compounds YVO{sub 3} and HoVO{sub 3} these interactions lead to two different phases of orbital ordering (OO), one in an intermediate temperature range with G-type OO and one low-temperature phase with C-type OO. In these orbitally ordered states, one expects novel collective excitations, so called orbitons, which are analogous to spin waves in a magnetically ordered state. Previous optical measurements of YVO{sub 3} and HoVO{sub 3} have shown a striking feature at 0.4 eV with polarization E parallel c in the intermediate phase which is interpreted as bi-orbiton excitation. Furthermore a second interesting feature at 0.55 eV with polarization E parallel a is observed. The interpretation of this feature is still a puzzle. We show the optical conductivity {sigma}({omega}) of GdVO{sub 3} single crystals for the mid-infrared range and temperatures from 10 K to 300 K. In GdVO{sub 3}, G-type OO (the intermediate phase of YVO{sub 3}) extends down to the lowest temperatures, offering additional information on the excitations discussed above.

Voigt, Michael; Maeder, Luis; Shportko, Konstantin; Grueninger, M. [Universitaet Koeln (Germany); Blake, Graeme R.; Mufti, Nandang; Palstra, Thomas T.M. [University of Groningen (Netherlands); Nugroho, Agustinus A. [University of Groningen (Netherlands); Institut Teknologi Bandung (Indonesia)

2011-07-01

192

A novel two-dimensional mixed molybdenum vanadium polyoxometalate: Synthesis, magnetic property and characterization of [PMo8VIMo4VO(VO){Co(phen)}](HO)[PMo4VIMo8VO(VO){Co(phen)(HO)}  

Science.gov (United States)

A new compound [PMo8VIMo4VO(VO)2{Co(phen)2}2](HO)2[PMo4VIMo8VO(VO)2{Co(phen)2(HO)}2]1 (phen = phenanthroline) has been synthesized under hydrothermal conditions and characterized by IR, TG analysis and single-crystal X-ray diffraction. The study of the magnetic property of compound 1 exhibits the presence of antiferromagnetic interactions. Compound 1 crystallizes in the monoclinic system, space group P2 1/ c, a = 21.843(4) Å, b = 16.566(3) Å, c = 21.025(4) Å, ? = 90°, ? = 100.26(3)°, ? = 90°, V = 7486(3) Å 3, Z = 2. The basic building unit in compound 1 is the [PMo 12V 2O 42] cluster. The most remarkable structural feature of 1 is that there exist two distinct [PMo 12V 2O 42] clusters. One is covalently linked by [Co(phen) 2] complexes to form 2D covalent layer, the other supports two [Co(phen) 2(H 2O)] complexes forming a 2D supramolecular network. Such two different kinds of layers are further stacked to form a novel 3D supramolecular framework.

Dai, Limei; Ma, Ying; Wang, Enbo; Wang, Xinlong; Lu, Ying; Wang, Xiaolan

2007-03-01

193

"Kogda emotsii vo mne bezuderzhno põlajut..." : [luuletused] / Jevgenia Brodneva  

Index Scriptorium Estoniae

Sisu: "Kogda emotsii vo mne bezuderzhno põlajut..." ; "Võ menja nikogda ne vstretite..." ; "Kogda nastupit vremja rasstavanja..." ; "Prosti za lozh i za obidu..." ; "Ja v plenu svoihh sobstvennõhh tshuvstv..." ; "Ot nego nelzja otkazatsja..." ; "Mne b rukoi do tebja dotjanutsja..." ; "Ja potshti, ja potshti v tebja vljublena..." ; "Ja po tebe skutshaju..."

Brodneva, Jevgenia

2003-01-01

194

PRODUCCIÓN DE BIOMASA Y EXOPOLISACÁRIDOS DE Grifóla frondosa BAJO CULTIVO SUMERGIDO UTILIZANDO FUENTES DE CARBONO NO CONVENCIONALES  

Directory of Open Access Journals (Sweden)

Full Text Available Grifóla frondosa es un hongo Basidiomycete comestible y medicinal que produce polisacáridos tipo glucanos (?-1,6 y ?-1,3 con actividad antitumoral e inmunomoduladora. Para el presente trabajo, el objetivo fue evaluar la incidencia de diferentes fuentes de carbono (FC en la producción de biomasa y exopolisacári-dos (EPS, bajo condiciones de cultivo sumergido, utilizando un diseño estadístico factorial con dos factores: fuente de carbono (FC(1-7 y medio (MB y MS. La máxima producción de biomasa micelial (21,10 ± 0,82 g/l y la máxima producción de EPS (6,53 ± 0,14 g/l se logró utilizando el medio MB suplementado con FC4. Además de lo anterior, se logró desarrollar un medio de cultivo que cumple con el objetivo de disminuir costos, de Col $18.455 a $656 por litro de medio, produciendo (14,14 ± 0,82 g/l de biomasa y (5,16 ± 0,14 g/l de EPS, utilizando el medio MS suplementando con FC4. Estos resultados abren nuevas alternativas y posibilidades en nuestro país para el desarrollo de productos a partir de esta especie con costos que estén al alcance de la población.Grifóla frondosa is a Basidiomycete fungus edible and medicinal, it produces polysaccharides such a glucans (?-1,6 and ?-1,3 with anti-tumor and inmuno-stimulating activity. For this work, the aim was evaluate the incidence of different carbon sources (FC in biomass and exo-polymer (EPS production, under submerged culture conditions, by using a factorial statistical design with two factors: carbon source (FC(1-7 and medium (MB and MS. The maximal yield of mycelial biomass (21,10 ± 0,82 g/l and the maximal yield in EPS (6,53 ± 0,14 g/l was achieved by using the MB medium supplemented with FC4. Besides, it was possible to develop a medium that fulfills the objective of reducing costs from $18.455 to $656 Colombian pesos for each liter of medium used, which produces (14,14 ± 0,82 g/l of biomass and (5,16 ± 0,14 g/l of EPS, using the MS medium supplemented with FC4. This result opens new alternatives and possibilities in our country for developing products of this species with cost that can be reached by population.

Paula Zapata

2007-06-01

195

LA SUSTITUCIÓN DE LA SABANA NATIVA POR PLANTACIONES DE PINO Y LA VARIABILIDAD TEMPORAL EN LA BIOMASA MICROBIANA Y LA MINERALIZACIÓN DEL CARBONO Y NITRÓGENO EN EL SUELO  

Directory of Open Access Journals (Sweden)

Full Text Available El cambio de uso de la tierra y la variabilidad temporal característica de los llanos orientales de Venezuela, son factores que tienen impacto ecológico sobre las poblaciones y actividades microbianas. Específicamente, en esta región, una gran extensión de sabanas nativas, ha sido reemplazada por plantaciones de Pinus caribaea var. hondurensis; sin embargo, se conoce poco sobre el impacto que este cambio de uso de la tierra produce en la calidad de los suelos. Este estudio investiga la magnitud en la cual la biomasa microbiana y los parámetros involucrados en las actividades mineralizadoras del carbono (C y el nitrógeno (N son afectados por el cambio de uso de la tierra y la variabilidad temporal. El estudio se realizó durante los períodos de sequía y lluvias. La biomasa microbiana se determinó a través del método de la fumigación-extracción (FE. La actividad mineralizadora del C no se realizó determinando la actividad de la ¿-glucosidasa, y la mineralización del N a través de la amonificación de la arginina (AA y la actividad de la proteasa-N¿-benzoil- L-arginamida (proteasa-BAA. Los resultados evidenciaron que estos parámetros son indicadores de variaciones en la calidad del suelo. El cambio de uso de la tierra afectó la biomasa microbiana y la tasa de mineralización del C y el N. La mayor biomasa microbiana presente en la plantación de pino, así como la menor actividad ineralizadora del C y el N en esta plantación, sugieren, que una mayor preservación de estos nutrientes ocurre en pinares; lo cual favorece la calidad del suelo. La dinámica temporal de la biomasa microbiana en la sabana nativa y en la plantación de pino no está acoplada a la variación temporal de la mineralización del C y el N de estos sistemas.

Yrma Gu00F3mez

2010-01-01

196

Influencia de la aplicación de vinaza en actividad y biomasa microbiana en un Entic Dystropept y un Fluventic haplustoll del Valle del Cauca, Colombia  

Directory of Open Access Journals (Sweden)

Full Text Available Con la aplicación de vinaza, residuo de la producción de alcohol carburante a partir de la caña de azúcar, se evaluó el efecto sobre la actividad y biomasa microbiana del suelo y el suministro de K+ al cultivo de maíz dulce (Zea Mays en un Entic Dystropept y un Fluventic Haplustoll del Valle del Cauca, Colombia. Se utilizó un diseño completamente al azar con cuatro tratamientos y cinco repeticiones: T1 (100% requerimiento de K+ con KCl, T2 (100% requerimiento de K+ con vinaza, T3 (50% requerimiento de K+ con KCl +50% con vinaza y T4 (25% requerimiento de K+ con KCl +75% con vinaza. Se estimó biomasa microbiana por el método de fumigación-extracción. Se realizó análisis de varianza, prueba de comparación de medias, regresiones y correlaciones (SAS. Se presentaron diferencias significativas en la actividad y biomasa microbiana por época de muestreo y entre los diferentes muestreos; al final del cultivo el Entic Dystropept presentó el contenido más alto de biomasa microbiana-C en el T2, mientras que en el Fluventic Haplustoll fue en el T1. El menor qCO2 fue para el T2 del Entic Distropept y T1 del Fluventic Haplustoll, estos tratamientos presentaron mayor acumulación de biomasa en cada suelo respectivamente T2 (30 450 kg ha-1 y T1 (21 015.6 kg ha-1.

Bonilla Correa Carmen Rosa

2009-03-01

197

Determinación de las reservas de carbono en la biomasa aérea de sistemas agroforestales de theobroma cacao l. en el departamento de San Martìn, Perú  

Directory of Open Access Journals (Sweden)

Full Text Available En este estudio se evaluó la biomasa aérea en seis diferentes sistemas agroforestales de cacao (Theobroma cacao L. asociado con especies forestales maderables y frutales; con el propósito de conocer el potencial de captura de carbono por cada sistema. El estudio se realizó en dos diferentes sitios ubicados en la región San Martín (provincias de San Martín y Mariscal Cáceres. Los sistemas agroforestales estimados presentaron edades de 5, 12 y 20 años. En cada sistema se establecieron aleatoriamente cinco cuadrantes de 100 m2 cada uno, evaluándose la biomasa vegetal total existente. Para evaluar la ecuación alométrica del cacao se muestrearon 7 plantas cuyas edades variaron de 01 hasta 22 años. Loas resultados en captura de carbono en cada sistema agroforestal varían desde 26.2 t C ha-1para el sistema de Pachiza de 5 años hasta 45.07 t C ha-1del sistema agroforestal de Pachiza de 12 años; Así mismo, la captura de carbono en biomasa arbórea de los árboles vivos, osciló desde 12.09 t ha-1 hasta 35.5 t ha-1, seguido por la biomasa de hojarasca que presentaron valores desde 4 t ha-1 hasta 9.97 t ha-1; mientras la biomasa de árboles muertos en pie y caídos muertos presentaron valores muy variables y bajos. Los sistemas agroforestales de 12 y 20 años representan el 66.7% de los sistemas que presentan reservas de carbono por encima de los 40 t C ha-1; mientras que los sistemas de 5 años se encuentran con reservas de carbono por debajo de los 30 t C ha-1. Los sistemas agroforestales de 5 años ubicados en Juanjui y Pachiza presentaron el mayor flujo de carbono anual, generando el mayor beneficio económico con créditos por CO2 equivalente

Vicente Pocomucha

2007-01-01

198

VO2: Orbital competition, magnetism, and phase stability  

Science.gov (United States)

The relative phase stability of VO2 is one of the most fundamental issues concerning the metal-insulator transition in this material but has been so far largely unexplored theoretically. We investigate the relative stability of various phases of VO2 using different levels of energy functionals within density functional theory (DFT). It is found that straightforward applications of several popular energy functionals, including the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional, result in a wrong prediction for the ground state of VO2. In particular, although the HSE and DFT+U methods are able to produce a band gap in the M1 phase, they strongly favor the formation of local magnetic moments, a result that clearly disagrees with experiments. We also examine the effect of the occupation and the redistribution of the d derived t2g (i.e., dxz, dyz, and dx2-y2) orbitals of V atoms on the calculated relative phase stability of VO2. We find that a small change in d occupation can result in a drastically different theoretical prediction. With the introduction of an orbital-dependent potential, a complete separation between the dx2-y2 derived valence band and dxz and dyz derived conduction bands in the M1 phase is achieved, resulting in a slight redistribution of the d occupation and a more faithful account of the polarization of the t2g orbitals. This slight rearrangement of the d occupation also leads to a relative phase stability of VO2 (including structural and magnetic phases) that agrees well with experiment.

Yuan, Xun; Zhang, Yubo; Abtew, Tesfaye A.; Zhang, Peihong; Zhang, Wenqing

2012-12-01

199

Identifying the active site in nitrogen-doped graphene for the VO2+/VO2(+) redox reaction.  

Science.gov (United States)

Nitrogen-doped graphene sheets (NGS), synthesized by annealing graphite oxide (GO) with urea at 700-1050 °C, were studied as positive electrodes in a vanadium redox flow battery. The NGS, in particular annealed at 900 °C, exhibited excellent catalytic performance in terms of electron transfer (ET) resistance (4.74 ± 0.51 and 7.27 ± 0.42 ? for the anodic process and cathodic process, respectively) and reversibility (?E = 100 mV, Ipa/Ipc = 1.38 at a scan rate of 50 mV s(-1)). Detailed research confirms that not the nitrogen doping level but the nitrogen type in the graphene sheets determines the catalytic activity. Among four types of nitrogen species doped into the graphene lattice including pyridinic-N, pyrrolic-N, quaternary nitrogen, and oxidic-N, quaternary nitrogen is verified as a catalytic active center for the [VO](2+)/[VO2](+) couple reaction. A mechanism is proposed to explain the electrocatalytic performance of NGS for the [VO](2+)/[VO2](+) couple reaction. The possible formation of a N-V transitional bonding state, which facilitates the ET between the outer electrode and reactant ions, is a key step for its high catalytic activity. PMID:23647240

Jin, Jutao; Fu, Xiaogang; Liu, Qiao; Liu, Yanru; Wei, Zhiyang; Niu, Kexing; Zhang, Junyan

2013-06-25

200

Porous peanut-like Bi2O3-BiVO4 composites with heterojunctions: one-step synthesis and their photocatalytic properties.  

Science.gov (United States)

For the first time, porous peanut-like Bi(2)O(3)-BiVO(4) composites with heterojunctions have been synthesized by a one-step mixed solvothermal method with the assistance of a l-lysine template. A mixture of ethylene glycol (EG) and H(2)O (volume ratio of EG-H(2)O = 3:1) is used as the solvent. Unlike the traditional methods, no concentrated HNO(3) and/or NaOH are involved in diluting Bi and V sources in the adopted approach. The as-synthesized peanut-like samples are rough and porous on the surface and to some extent are interior-hollow. The degradation of methylene blue (MB) is employed to evaluate the photocatalytic activity of the Bi(2)O(3)-BiVO(4) composite. It is observed that the composite performs much better than Bi(2)O(3) and BiVO(4), plausibly due to heterojunctions formed between Bi(2)O(3) and BiVO(4). To investigate the relationship between structure and performance, the as-synthesized samples are characterized by XRD, XPS, SEM, TEM (HRTEM), UV-vis DRS, PL and nitrogen adsorption-desorption methods. Additionally, a possible growth mechanism of this hollow peanut-like structure and the separation process of photogenerated electron-hole pairs on the heterojunctions have been discussed. PMID:22751937

Chen, Lang; Zhang, Qiang; Huang, Rui; Yin, Shuang-Feng; Luo, Sheng-Lian; Au, Chak-Tong

2012-08-21

 
 
 
 
201

Validade de equações de predição em estimar o VO2max de brasileiros jovens a partir do desempenho em corrida de 1.600m / Predictive equations validity in estimating the VO2max of young Brazilians from performance in a 1600 m run  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese O objetivo deste estudo foi analisar a validade da equação proposta por Cureton et al. (1995) "VO2peak = -8.41 (MRW) + 0.34 (MRW)2 + 0.21 (Age x Gender) -0.84 (BMI) + 108.94" em estimar o VO2max de brasileiros jovens a partir de um teste de 1.600 metros, e sugerir uma equação de predição que seja es [...] pecífica para essa população. Participaram do estudo 30 homens fisicamente ativos (23 ± 3,1anos; 74,8 ± 5,8kg; 1,78 ± 0,05m; 49,8 ± 6,5mL.kg-¹.min-1) que foram submetidos a um teste incremental máximo (TI) em esteira e um teste de desempenho em corrida de 1.600 metros. Os indivíduos foram divididos em dois grupos: G1 - para gerar uma equação de predição específica para VO2max de brasileiros jovens e G2 - para aplicar ambas as equações a fim de analisar suas validades. Diferenças estatisticamente significativas foram observadas entre o VO2max determinado diretamente no TI (50,1 ± 7,1mL.kg-¹.min-¹) e os valores de VO2max obtidos pela equação proposta por Cureton et al. (44,2 ± 6,5mL.kg-¹.min-¹) com baixa correlação entre elas (r = 0,21). A relação entre VO2max e velocidade em corrida de 1.600m obtidos no G1 resultou na seguinte equação de predição: (VO2max = 0,177 * 1.600Vm(m.min-1) + 8,101). Quando essa nova equação foi aplicada nos participantes do G2, o VO2max predito (50,1 ± 7,2mL.kg-¹.min-¹) não diferiu do VO2max determinado diretamente (50,1 ± 7,1mL.kg-¹.min-¹) com alta correlação entre eles (r = 0,81). Assim, concluímos que a equação de Cureton et al. (1995), elaborada a partir de resultados de amostra norte-americana, subestimou o VO2max de brasileiros jovens e fisicamente ativos. Por outro lado, a equação proposta no presente estudo se mostrou válida para estimar o VO2max através do teste de desempenho de 1.600 metros para a população estudada. Abstract in english The aim of the present study was to analyze the validity of predictive equation proposed by Cureton et al. (1995) for VO2peak = -8.41 (MRW) + 0.34 (MRW) 2 + 0.21 (Age x Gender) -0.84 (BMI) + 108.94" on estimating the VO2max of young Brazilians from a 1600-m running performance, and to suggest a pred [...] ictive equation specific for this population. 30 physically active young men (23±3.1age; 74.8±5.8kg; 1.78±0.05m; 49.8±6.5mL.kg-¹.min-1) who were submitted to an incremental exercise test (IT) on treadmill until exhaustion with gas analysis participated in this study. Subjects also performed a 1600-m running track test as fast as possible. The volunteers were randomly sorted in two groups: G1 - to generate a specific predictive equation for VO2max, and G2 - to apply both predictive equations (actual and from Cureton et al.) to evaluate their validity on estimating VO2max in a Brazilian population sample. Significant differences were observed between VO2max directly identified on IT through gas analysis (50.1±7.1 mL.kg-¹.min-¹) in relation to the results obtained by the predictive equation proposed by Cureton et al. (1995) (44.2±6.5mL.kg-¹.min-¹) with a weak relationship between them (r = 0.21). The relationship between the VO2max on IT and the running velocity on 1600-m as obtained for G1 resulted in the following predictive equation: (VO2max = 0.177*1600Vm(m.min-1) + 8,101). When this new equation was applied on the participants of G2, the predicted VO2max (50.1±7.2mL.kg-¹.min-¹) did not differ from VO2max determined directly on IT (50.1±7.1mL.kg-¹.min-¹) with a high correlation between them (r = 0.81). Thus, it was concluded that the Cureton et al. predictive equation developed with a North Americanpopulation sample as grounding, underestimated the VO2max of physically active young Brazilians. On the other hand, the predictive equation proposed on the present study was considered valid for this purpose through the 1600-m running performance for our participants.

Almeida, Jeeser Alves de; Campbell, Carmen S. G.; Pardono, Emerson; Sotero, Rafael da Costa; Magalhães, Guilherme; Simões, Herbert Gustavo.

202

La biomasa de los cultivos en el oecosistema. Sus beneficios agroecológicos / The biomass of the cultivations in the agroecosistema. Its benefits agroecological  

Scientific Electronic Library Online (English)

Full Text Available SciELO Cuba | Language: Spanish Abstract in spanish La biomasa es el resultado de la transformación de la energía solar en energía química. El hombre a través de la historia la ha utilizado no solo para su alimentación sino también para la alimentación de sus animales. Los avances de la ciencia promovieron el desarrollo agrario basado en la revolució [...] n verde, la cual solo promueve la producción de alimentos ya sea de uso humano o animal, marginando la importancia de la biomasa como enriquecedor del recurso suelo al disponerse de los insumos necesarios para sustituir su fertilidad natural. En la actualidad la producción y conservación de la biomasa de cualquier cultivo cobra una importancia trascendente; por que ello contribuye, además, a la protección medioambiental a través de la captura de carbono. El presente trabajo tuvo como objetivo demostrar la importancia que proporciona la biomasa generalmente no alimenticia para los humanos, a fin de emplearla no solo como alimento animal, sino también como enriquecedora del recurso natural suelo. Las investigaciones realizadas en Cuba sobre el tema es pobre, aun cuando en la actualidad resulta de gran importancia encontrar variantes que permitan profundizar en la producción de biomasa en su relación con el medio ambiente. Finalmente se exponen los resultados preliminares sobre producción de biomasa a partir de la agrobiodiversidad presente en los escenarios productivos, a la vez que se reflexiona sobre la importancia del tema para futuras investigaciones. Abstract in english Biomass is the result of the transformation of solar energy into chemical energy. The man throughout history has used not only for food but also for feeding their animals. The progress of science promoted agricultural development based on the green revolution, which only promotes the production of e [...] ither food or feed, marginalizing the importance of biomass as enriching the soil resources available inputs needed to replace their fertility natural. At present the production and preservation of any crop biomass becomes transcendent importance, because it also contributes to environmental protection through carbon sequestration. This study aimed to show the importance of providing non-food biomass generally for humans to use it not only as animal feed but also as a natural resource rich soil. Research in Cuba on the subject is poor, even though today is very important to find alternatives to deepen in the production of biomass in relation to the environment. Finally, we present preliminary results on the production of biomass from agricultural biodiversity present in production scenarios, while reflecting on the important question for future research.

Martínez Romero, Anirebis; Leyva Galán, Angel.

203

Efecto de nutrientes sobre la producción de biomasa del hongo medicinal Ganoderma lucidum / Effect of nutrients in the biomass production of the medicinal mushroom Ganoderma lucidum  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in spanish El hongo Ganoderma lucidum, en los constituyentes de su biomasa, tiene compuestos con propiedades benéficas para la salud; es por esto que el conocimiento de las condiciones nutricionales adecuadas para su crecimiento permitirá su producción industrial y a bajo costo. En este trabajo se evaluó a niv [...] el de matraz el efecto de la relación C/N, y la presencia de diferentes fuentes de carbono, nitrógeno y micronutrientes sobre la producción de biomasa. Empleando glucosa y peptona como fuentes de carbono y nitrógeno, respectivamente, se encontró una relación C/N óptima de 16,7:1 para la cual la máxima producción de biomasa fue de 25 g/L. Manteniendo esta relación C/N, y sustituyendo la glucosa por lactosa o harina de cebada y la peptona por extracto de levadura, la producción de biomasa se incrementó a 35 g/L. En presencia de harina de cebada la adición al medio de cultivo de sales de Mg y K, y de tiamina, no generó un mayor incremento en la producción de biomasa. La producción de biomasa de G. lucidum se ve favorecida por la presencia en el medio de cultivo de relaciones C/N cercanas a las reportadas conforme a la composición típica de los hongos, así como por la presencia de sustratos complejos como la harina de cebada que le aportan además de la fuente de carbono micronutrientes necesarios para su desarrollo. Abstract in english Ganoderma lucidum fungus has some biomass components with beneficial health properties. The knowledge about its nutritionals requirements for growing will favor its industrial production at lower cost. In this work, the effect of C/N ratio, the presence of different carbon, nitrogen and micronutrien [...] ts sources, on fungal biomass production, were evaluated. Using glucose and peptone as carbon and nitrogen sources, respectively, an optimal C/N ratio of 16,7:1 was found, for which the maximal biomass production was 25 g/L. Replacing glucose by lactose or barley flour and peptone by yeast extract at the same C/N ratio, the biomass production was enhanced to 35 g/L. With barley flour in the culture medium, the presence of Mg and K salts and thiamine did not turn out into a major increase of biomass. The G. lucidum biomass production is promoted by C/N ratios in the culture medium nearly equivalent to that found in the fungus, as well as the presence of complex substrates as barley flour which, additionally, contributes with important micronutrients along with the carbon source.

Ana María, Torres López; Juan Carlos, Quintero Díaz; Lucía, Atehortua Garcés.

2011-07-01

204

Synergy Between Archives, VO, and the Grid at ESAC  

Science.gov (United States)

Over the years, in support to the Science Operations Centers at ESAC, we have set up two Grid infrastructures. These have been built: 1) to facilitate daily research for scientists at ESAC, 2) to provide high computing capabilities for project data processing pipelines (e.g., Herschel), 3) to support science operations activities (e.g., calibration monitoring). Furthermore, closer collaboration between the science archives, the Virtual Observatory (VO) and data processing activities has led to an other Grid use case: the Remote Interface to XMM-Newton SAS Analysis (RISA). This web service-based system allows users to launch SAS tasks transparently to the GRID, save results on http-based storage and visualize them through VO tools. This paper presents real and operational use cases of Grid usages in these contexts

Arviset, C.; Alvarez, R.; Gabriel, C.; Osuna, P.; Ott, S.

2011-07-01

205

Epitaxial growth of VO2 by periodic annealing  

Science.gov (United States)

We report the growth of ultrathin VO2 films on rutile TiO2 (001) substrates via reactive molecular-beam epitaxy. The films were formed by the cyclical deposition of amorphous vanadium and its subsequent oxidation and transformation to VO2 via solid-phase epitaxy. Significant metal-insulator transitions were observed in films as thin as 2.3 nm, where a resistance change ?R/R of 25 was measured. Low angle annular dark field scanning transmission electron microscopy was used in conjunction with electron energy loss spectroscopy to study the film/substrate interface and revealed the vanadium to be tetravalent and the titanium interdiffusion to be limited to 1.6 nm.

Tashman, J. W.; Lee, J. H.; Paik, H.; Moyer, J. A.; Misra, R.; Mundy, J. A.; Spila, T.; Merz, T. A.; Schubert, J.; Muller, D. A.; Schiffer, P.; Schlom, D. G.

2014-02-01

206

VO2: a two-fluid incoherent metal?  

CERN Document Server

We present {\\it ab initio} LDA+DMFT results for the many-particle density of states of $VO_{2}$ on the metallic side of the strongly first-order ($T$-driven) insulator-metal transition. In strong contrast to LDA predictions, there is {\\it no} remnant of even correlated Fermi liquid behavior in the correlated metal. Excellent quantitative agreement with published photoemission and X-ray absorption experiments is found in the metallic phase. We argue that the absence of FL-quasiparticles provides a natural explanation for the bad-metallic transport for $T > 340 K$. Based on this agreement, we propose that the I-M transition in $VO_{2}$ is an orbital-selective Mott transition, and point out the relevance of orbital resolved one-electron and optical spectroscopy to resolve this outstanding issue.

Laad, M S; Müller-Hartmann, E

2004-01-01

207

Gate-tunable gigantic lattice deformation in VO2  

Science.gov (United States)

We examined the impact of electric field on crystal lattice of vanadium dioxide (VO2) in a field-effect transistor geometry by in-situ synchrotron x-ray diffraction measurements. Whereas the c-axis lattice parameter of VO2 decreases through the thermally induced insulator-to-metal phase transition, the gate-induced metallization was found to result in a significant increase of the c-axis length by almost 1% from that of the thermally stabilized insulating state. We also found that this gate-induced gigantic lattice deformation occurs even at the thermally stabilized metallic state, enabling dynamic control of c-axis lattice parameter by more than 1% at room temperature.

Okuyama, D.; Nakano, M.; Takeshita, S.; Ohsumi, H.; Tardif, S.; Shibuya, K.; Hatano, T.; Yumoto, H.; Koyama, T.; Ohashi, H.; Takata, M.; Kawasaki, M.; Arima, T.; Tokura, Y.; Iwasa, Y.

2014-01-01

208

VO? thermochromic smart window for energy savings and generation.  

Science.gov (United States)

The ability to achieve energy saving in architectures and optimal solar energy utilisation affects the sustainable development of the human race. Traditional smart windows and solar cells cannot be combined into one device for energy saving and electricity generation. A VO2 film can respond to the environmental temperature to intelligently regulate infrared transmittance while maintaining visible transparency, and can be applied as a thermochromic smart window. Herein, we report for the first time a novel VO2-based smart window that partially utilises light scattering to solar cells around the glass panel for electricity generation. This smart window combines energy-saving and generation in one device, and offers potential to intelligently regulate and utilise solar radiation in an efficient manner. PMID:24157625

Zhou, Jiadong; Gao, Yanfeng; Zhang, Zongtao; Luo, Hongjie; Cao, Chuanxiang; Chen, Zhang; Dai, Lei; Liu, Xinling

2013-01-01

209

Electron Spin Resonance of VO2 thin films  

Science.gov (United States)

The metal-insulator transition present in chromium doped VO2 nanoscale film has been observed by electron spin resonance (ESR) spectroscopy. VO2 is a highly correlated electron system with numerous practical applications pertaining to this transition, including ultra-fast optical switching and smart windows. We use Cr^3+ transition metal ions with concentration of order one percent as a probe in a 140 nm film to detect this transition. The film exhibited a four-fold decrease in chromium intensity as temperature increased through the transition temperature (˜67^o C). ESR signal intensities were also used to characterize the hysteretic behavior of this particular transition; these results are in agreement with hysteresis observed through optical means. A discussion of how changes in ESR relaxation times affect signal intensities, as monitored through the transition, will be presented.

Maynes, K. C.; Bunton, P. H.; Baker, D. B.; Hartman, Kenneth; Haglund, R. F., Jr.; Lopez, R.; Habalica, A.

2006-03-01

210

VO2 thermochromic smart window for energy savings and generation  

Science.gov (United States)

The ability to achieve energy saving in architectures and optimal solar energy utilisation affects the sustainable development of the human race. Traditional smart windows and solar cells cannot be combined into one device for energy saving and electricity generation. A VO2 film can respond to the environmental temperature to intelligently regulate infrared transmittance while maintaining visible transparency, and can be applied as a thermochromic smart window. Herein, we report for the first time a novel VO2-based smart window that partially utilises light scattering to solar cells around the glass panel for electricity generation. This smart window combines energy-saving and generation in one device, and offers potential to intelligently regulate and utilise solar radiation in an efficient manner.

Zhou, Jiadong; Gao, Yanfeng; Zhang, Zongtao; Luo, Hongjie; Cao, Chuanxiang; Chen, Zhang; Dai, Lei; Liu, Xinling

2013-10-01

211

Green VoIP : A SIP Based Approach  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This master thesis presents, examines, designs, implements, and evaluates with respect to energy efficiency a secure and robust VoIP system. This system utilizes a Session Initiation Protocol (SIP) infrastructure assisted by a cloud service, specifically focusing on small to medium sized enterprises (SME) and homes. This research focuses on using inexpensive, flexible, commodity embedded hardware (specifically a Linksys WRT54GL wireless router for the local site with a customized operating sy...

Talaganov, Goce

2012-01-01

212

Accuracy of peak VO2 assessments in career firefighters  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background Sudden cardiac death is the leading cause of on-duty death in United States firefighters. Accurately assessing cardiopulmonary capacity is critical to preventing, or reducing, cardiovascular events in this population. Methods A total of 83 male firefighters performed Wellness-Fitness Initiative (WFI) maximal exercise treadmill tests and direct peak VO2 assessments to volitional fatigue. Of the 83, 63 completed WFI sub-maximal exerc...

Drew-Nord Dana C; Myers Jonathan; Nord Stephen R; Oka Roberta K; Hong OiSaeng; Froelicher Erika S

2011-01-01

213

Topotactic insertion of lithium in the layered structure Li4VO(PO4)2: The tunnel structure Li5VO(PO4)2  

International Nuclear Information System (INIS)

A new V(III) lithium phosphate Li5VO(PO4)2 has been synthesized by electrochemical insertion of lithium into Li4VO(PO4)2. This phase, which crystallizes in the space group I4/mcm, exhibits a tunnel structure closely related to the layered structure of Li4VO(PO4)2 and to the tunnel structure of VO(H2PO4)2. The topotactic reactions that take place during lithium exchange and intercalation, starting from VO(H2PO4)2 and going to the final phase Li5VO(PO4)2 are explained on the basis of the flexible coordinations of V4+ and V3+ species. The electrochemical and magnetic properties of this new phase are also presented and explained on the basis of the structure dimensionality. - Graphical abstract: Electrochemical synthesis of a new 3D V(III) lithium phosphate, Li5VO(PO4)2. Starting from the 2D Li4VO(PO4)2, the topotactic reaction that take place during lithium intercalation is explained on the basis of the flexible coordinations of V4+ and V3+ species

2008-04-01

214

Structural and morphology comparison between m-LaVO4 and LaVO3 compounds prepared by sol-gel acrylamide polymerization and solid state reaction  

International Nuclear Information System (INIS)

We contrast the production of LaVO3 polycrystalline samples obtained by reduction of m-LaVO4 prepared by sol-gel acrylamide polymerization (SGAP) and solid state reaction (SSR). For SGAP the formation of m-LaVO4 occurs at 400 deg. C, for SSR at 1400 deg. C. For m-LaVO4-SGAP we observe a homogeneous morphology with needle-shaped grains of 50 nm average size. The SSR presents a broader size distribution in the micrometer range. Both m-LaVO4 samples were reduced into LaVO3 using a Zr rod at 850 deg. C in vacuum. LaVO3-SGAP presents a homogeneous grain distribution with an average size of 745 nm. LaVO3-SSR has an average size of 3.45 ?m. The stoichiometry of all compounds was confirmed by energy dispersive X-ray spectroscopy. X-ray powder diffraction and transmission electron microscopy give crystal structures in agreement with those reported in the literature.

2009-06-24

215

Synthesis and properties of the double perovskites La2NiVO6, La2CoVO6, and La2CoTiO6  

International Nuclear Information System (INIS)

The double perovskites La2CoVO6, La2CoTiO6, and La2NiVO6, are described. Rietveld fitting of neutron and powder X-ray diffraction data show La2NiVO6 and La2CoVO6 to have a disordered arrangement of B-cations whereas La2CoTiO6 shows ordering of the B-cations (with ?5% Co/Ti inversion). Curie-Weiss fits to the linear region of the 1/? plots reveal Weiss temperatures of -107, -34.8, and 16.3 K for La2CoVO6, La2CoTiO6, and La2NiVO6, respectively, and magnetic transitions are observed. La2CoTiO6 prepared by our method differs from material prepared by lower-temperature routes. A simple antiferromagnetic spin model is consistent with the data for La2CoTiO6. These compounds are semiconductors with bandgaps of 0.41 (La2CoVO6), 1.02 (La2CoTiO6) and 0.45 eV (La2NiVO6). - Graphical abstract: The antiferromagnetic structure of La2CoTiO6 as prepared by high-temperature routes with spins showing the P2/m' magnetic symmetry

2007-01-01

216

CyberSKA Radio Imaging Metadata and VO Compliance Engineering  

Science.gov (United States)

The CyberSKA project has written a specification for the metadata encapsulation of radio astronomy data products pursuant to insertion into the VO-compliant Common Archive Observation Model (CAOM) database hosted by the Canadian Astronomy Data Centre (CADC). This specification accommodates radio FITS Image and UV Visibility data, as well as pure CASA Tables Imaging and Visibility Measurement Sets. To extract and engineer radio metadata, we have authored two software packages: metaData (v0.5.0) and mddb (v1.3). Together, these Python packages can convert all the above stated data format types into concise FITS-like header files, engineer the metadata to conform to the CAOM data model, and then insert these engineered data into the CADC database, which subsequently becomes published through the Canadian Virtual Observatory. The metaData and mddb packages have, for the first time, published ALMA imaging data on VO services. Our ongoing work aims to integrate visibility data from ALMA and the SKA into VO services and to enable user-submitted radio data to move seamlessly into the Virtual Observatory.

Anderson, K. R.; Rosolowsky, E.; Dowler, P.

2013-10-01

217

RELATIONSHIP BETWEEN %HEART RATE RESERVE AND %VO2 RESERVE DURING ELLIPTICAL CROSSTRAINER EXERCISE  

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Full Text Available The primary purpose of the study was to determine the relationships between %HRR vs. %VO2R and %HRR vs. %VO2max during maximal elliptical crosstrainer (ECT exercise. A secondary aim was to compare the %HRR vs. %VO2R and %HRR vs. %VO2max relationships between maximal ECT and treadmill (TM exercise. Adult subjects (n = 48 completed a maximal exercise test on the ECT, with a subgroup (N = 24 also performing a maximal exercise test on the TM. Continuous HR and VO2 data were analyzed via linear regression to determine y-intercept and slope values for %HRR vs. %VO2R and %HRR vs. %VO2max. Student t-tests were used to determine whether the mean y-intercept and slope values differed from the line of identity (y-intercept = 0, slope = 1. For each group, both the y-intercept and slope for %HRR vs. %VO2R fit the line of identity. Conversely, for all groups both the y-intercept and slope for %HRR vs. %VO2max were significantly different (p 0.05 for either y-intercept (ECT = 0.3 vs. TM = -0.3, p = 0.435 or slope (ECT = 1.01 vs. TM = 1.00, p = 0.079 values. In agreement with previous research on TM and cycle exercise, it was found that %HRR is more closely aligned with %VO2R, rather than %VO2max during ECT exercise. Additionally, it was found that the regressions of %HRR vs. %VO2R and %HRR vs. %VO2max were equivalent between the ECT and TM

Lance C. Dalleck

2006-12-01

218

Pulmonary and leg VO2 during submaximal exercise: implications for muscular efficiency  

Science.gov (United States)

Insights into muscle energetics during exercise (e.g., muscular efficiency) are often inferred from measurements of pulmonary gas exchange. This procedure presupposes that changes of pulmonary O2 (VO2) associated with increases of external work reflect accurately the increased muscle VO2. The present investigation addressed this issue directly by making simultaneous determinations of pulmonary and leg VO2 over a range of work rates calculated to elicit 20-90% of maximum VO2 on the basis of prior incremental (25 or 30 W/min) cycle ergometry. VO2 for both legs was calculated as the product of twice one-leg blood flow (constant-infusion thermodilution) and arteriovenous O2 content difference across the leg. Measurements were made 3-5 min after each work rate imposition to avoid incorporation of the VO2 slow component above the lactate threshold. For all 17 subjects, the slope of pulmonary VO2 (9.9 +/- 0.2 ml O2.W-1.min-1) was not different (P greater than 0.05) from that for leg VO2 (9.2 +/- 0.6 ml O2.W-1.min-1). Estimation of "delta" efficiency (i.e., delta work accomplished divided by delta energy expended, calculated from slope of VO2 vs. work rate and a caloric equivalent for O2 of 4.985 cal/ml) using pulmonary VO2 measurements (29.1 +/- 0.6%) was likewise not significantly different (P greater than 0.05) from that made using leg VO2 measurements (33.7 +/- 2.4%). These data suggest that the net VO2 cost of metabolic "support" processes outside the exercising legs changes little over a relatively broad range of exercise intensities. Thus, under the conditions of this investigation, changes of VO2 measured from expired gas reflected closely those occurring within the exercising legs.

Poole, D. C.; Gaesser, G. A.; Hogan, M. C.; Knight, D. R.; Wagner, P. D.

1992-01-01

219

E-LEARNING SOLUTIONS IN EDUCATION OF PEDAGOGIC EMPLOYEES / E-learningové riešenia vo vzdelávaní pedagogických zamestnancov  

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Full Text Available According to the requirements on qualitative forms and methods of education, Methodical-pedagogical centre, has prepared a project supporting teaching with use of modern educaton methods with sponzorship from ESF For providing such an extensive project the Methodical-pedagogical centre used e-learning environment. The first part of article emphasizes the importance of teachers education in the new socio-economical conditions. It defines the needs of teachers in the field of using ICT during the education process. It describes forms and methods suitable for gaining new competencies. The second part of the article gives us the information abouth e-learning portal of the project „Functional literacy of teachers in information technologies - use of ICT in subjects". The modules are using the different possibilities of MOODLE interface. Author evaluates the interest of teachers for e-learning and the feedback from lectu-trers. The third part of the article presents first experience of using videoconference in the field of education of teachers, on example of a conference aimed to use of ICT in the work of elementary and high school teachers (in the preparation for teaching and also in the teaching process itself.Na základe potreby zvyšovania k?ú?ových kompetencií pedagogických zamestnancov bol s finan?nou podporou ESF pripravený projekt na podporu vyu?ovania s využitím moderných vyu?ovacích metód. Na zabezpe?enie rozsiahleho projektu v oblasti využívania informa?ných technológií a na zvýšenie efektívnosti vzdelávania pedagogických zamestnancov využilo Metodicko-pedagogické centrum v Tren?íne e-learningové prostredie. Príspevok v prvej ?asti poukazuje na význam vzdelávania u?ite?ov v nových spolo?ensko-eko-nomických podmienkach. Definuje potreby u?ite?ov v oblasti využívania IKT na vyu?ovaní a predstavuje formy a metódy vhodné na získanie nových kompetencií. V druhej ?asti príspevku je predstavený e-learningový portál projektu Funk?ná gramotnos? u?ite?ov v informa?ných technológiách - využitie IKT vo vyu?ovacích predmetoch. Jednotlivé vzdelávacie moduly rozli?nou mierou využívajú možnosti prostredia MOODLE. Autor vyhodnocuje záujem pedagógov o e-learningové vzdelávanie a skúsenosti lektorov zo vzdelávania. V tretej ?asti príspevku sú predstavené prvé skúsenosti využitia videokonferencie v oblasti vzdelávania pedagógov na príklade konferencie zameranej na využívanie informa?ných technológií v práci pedagógov základných a stredných škôl - v príprave na vyu?ovanie i vo vlastnom vyu?ovacom procese.

Jakubeková Miroslava

2008-06-01

220

Acumulación y distribución de biomasa en Leucaena leucocephala (lam) de Wit., durante la fase de establecimiento. I. Repartición de biomasa / Accumulation and distribution of biomass in Leucaena leucocephala (Lam.) de wit during the phase of establishment. II. Repartitioning of biomass  

Scientific Electronic Library Online (English)

Full Text Available SciELO Venezuela | Language: Spanish Abstract in spanish En el presente estudio se comparó el patrón de acumulación de biomasa aérea y radical durante los primeros 110 días después de la germinación (DDG), en tres líneas de Leucaena leucocephala (CIAT 7984, 9438, 18477). El cv. Perú se utilizó como testigo con fines de comparación. El experimento se llevó [...] a cabo en condiciones de invernadero, cultivándose las plantas en tubos de PVC de 1 m de alto por 0.20 m de ancho. El diseño del experimento fue un completamente aleatorizado, en un arreglo factorial de 4 líneas x 5 cosechas (15, 30, 45, 60 y 110 DDG) x 5 repeticiones. Los datos fueron analizados por vía no paramétrica. Para estimar el patrón de acumulación y distribución de biomasa se midió en cada cosecha el peso seco acumulado de hojas (MSh), tallos (MSt) y raíces (MSr). A los 110 DDG, todas las líneas en general destinaron una mayor proporción de asimilados en producir hojas a expensa de tallos y raíces. La MSh no fue diferente (P Abstract in english In the present study, dry matter accumulation and the pattern of distribution between aerial and bellow-ground biomass were studied in three accessions (CIAT 7984, 9438, 18477) of Leucaena leucocephala during 110 days after germination (DAG). Cv. Perú was used as a control plant. The experiment was [...] carried out under glasshouse conditions, where plants were grown in PVC pots (1 m height x 0.20 m diameter). A completed randomized designed was used, in a factorial arrangement of 4 plant materials x 5 harvests (ie. 15, 30, 45, 60 and 110 DAG) x 5 replicates. To estimate biomass accumulation and assimilates distribution within the plant, harvests of individual plants were performed and the dry weight of leaf (LDM), stems (SDM) and root (DMR) at different depths was recorded. Initially, all accessions diverted a high proportion of the available energy in producing root biomass, while by the end of the establishment period relatively more photosynthetic material was used to increase leaf and stem biomass. The MSh was not different (P

Eunice, Guevara; Orlando, Guenni.

 
 
 
 
221

REDUCCIÓN DE LA BIOMASA DEL PINO CARRASCO (PINUS HALEPENSIS EN UN ÁREA DEL SURESTE SEMIÁRIDO PENINSULAR COMO ESTRATEGIA PARA EVITAR EL ESTRÉS HÍDRICO  

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Full Text Available En las épocas de fuertes sequías, la vegetación mediterránea sufre un estado de estrés hídrico prolongado que le obliga a adoptar diversas estrategias de supervivencia, entre las que fi guran, como último recurso, y antes de llegar a superar su capacidad de resilencia, la reducción de la biomasa de hojas. En este trabajo se pone de manifi esto como algunos ejemplares de Pinus halepensis existentes en el área de estudio (el campo experimental de El Ardal, Murcia, redujeron apreciablemente su biomasa aérea en respuesta a la sequía, que se manifestó en un importante aumento de la producción de hojarasca. La producción de hojarasca se relaciona además de con la precipitación registrada en el periodo de estudio, con la humedad del suelo, parámetro clave en la supervivencia de la vegetación en ambientes secos.

Francisco Belmonte Serrato

2008-01-01

222

Comportamiento de la disponibilidad de biomasa y la composición química en 23 accesiones de Leucaena spp. Performance of biomass availability and chemical composition of 23 Leucaena spp. accessions  

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Full Text Available Se realizó un estudio con 23 accesiones de Leucaena spp. en un área que tenía seis años de sembrada. El objetivo fue determinar, en las plantas establecidas, la biomasa total, la biomasa comestible, la biomasa leñosa, el grosor del tallo y el número de ramas de cada accesión, y su composición bromatológica en condiciones de pastoreo simulado. La investigación se realizó en la EEPF "Indio Hatuey" durante dos años, en un suelo Ferralítico Rojo lixiviado, húmico nodular ferruginoso hidratado. Se utilizaron parcelas sencillas de 3 m x 6 m. En la biomasa comestible y sus componentes (hojas y tallos tiernos existieron diferencias significativas (PA study was conducted with 23 Leucaena spp. accessions in an area which had been planted six years before. The objective was to determine, in the established plants, total biomass, edible biomass, ligneous biomass, stem diameter and number of branches in each accession, and its bromatological composition under simulated grazing conditions. The research was conducted at the EEPF "Indio Hatuey" during two years, on a hydrated ferruginous nodular humic lixiviated Ferralitic Red soil. Simple 3 m x 6 m plots were used. In the edible biomass and its components (leaves and fresh stems, there were significant differences (P<0,05 between the seasons of the two years. It could be observed that production was higher in the rainy season than in the dry season, although there were no differences among the mean biomass production of the accessions; in the case of total biomass no significant differences were found between seasons. To continue the studies is recommended, to determine, in the long term, the effect of the evaluated indicators on the availability and persistence of the tree.

Hilda B Wencomo

2012-03-01

223

Biomasa acumulada e intercambio gaseoso en maíz proveniente de semilla de diferente tamaño bajo humedad favorable y restringida: (con 3 tablas)  

Scientific Electronic Library Online (English)

Full Text Available SciELO Argentina | Language: Spanish Abstract in spanish Se evaluó la velocidad de germinación y el crecimiento de plántulas de maíz provenientes de semilla de dos diferentes tamaños para determinarlas diferencias en la producción de biomasa durante la etapa vegetativa y estimar los efectos de una condición diferente de disponibilidad de humedad sobre el [...] estatus fisiológico de la plántula. Una mayor cantidad de biomasa en el endospermo y en el embrión de las semillas permitió una mayor disponibilidad de reservas durante la etapa posterior a la germinación y anterior a la emergencia, dando como resultado un mayor vigor inicial en las plántulas evaluadas, y en consecuencia una mayor acumulación de biomasa, tanto radical como aérea, durante la etapa vegetativa. La presencia de una restricción de humedad durante la germinación y la etapa vegetativa de estas plantas provocó un decremento de 72.6% en la acumulación de biomasa en la parte aérea, tanto en plantas provenientes de semilla grande como chica, como consecuencia de una disminución de diversos procesos fisiológicos como son la conductancia estomática, transpiración y tasa fotosintética. Abstract in english The germination speed and seedling growth of maize seed of two different sizes was evaluated. To determine the differences in the biomass production during the vegetative stage from different seed size, considering the effects of humidity on seedling physiological status. A larger amount of biomass [...] in endosperm and embryo allowed greater availability of reserves during the later stage of the germination; previous to emergency resulting in a high seedling vigor and a most accumulation of as much radical biomass as aerial during the vegetative stage, the water restriction during the germination and the vegetative stage of these plants caused a decrement of 72,6% in the aerial biomass accumulation in big and small seed plants, due to a diminution from diverse physiological processes such as stomatic conductance, transpiration and photosynthetic rate.

López-Santillán, José Alberto; Castro-Nava, Sergio; Trejo-López, Carlos; Mendoza-Castillo, Ma. Del Carmen; Ortiz-Cereceres, Joaquín.

224

Producción de biomasa de Saccharomyces cerevisiae y Candida utilis usando residuos de pulpa de Coffea arabica L  

Scientific Electronic Library Online (English)

Full Text Available SciELO Venezuela | Language: Spanish Abstract in spanish Los avances en biotecnología industrial ofrecen oportunidades potenciales para la utilización económica de residuos agro-industriales tales como la pulpa de café, material mucilaginoso, fibroso (producto secundario) obtenido durante el proceso húmedo o seco del beneficio de las cerezas de café. El p [...] ropósito de este trabajo fue utilizar los residuos de la pulpa de café, rico en materia orgánica, como sustrato para la producción de biomasa de levaduras por procesos de fermentación aeróbica. Los residuos de café se sometieron a hidrólisis con una solución de ácido sulfúrico al 2%, en una relación 10:1 (líquido:sólido), con un tamaño de partícula ? 2 mm., operando a presión atmosférica, ebullición a reflujo, durante 4 horas. El extracto ácido se filtró y se ajustó a pH 4,5 y luego se esterilizó a 120 ºC por 15 minutos. La fermentación se realizó con Saccharomyces cerevisiae y Candida utilis, medio de producción extracto de café enriquecido con sales nutritivas. Se formularon diferentes medios de producción (1,2,3 y 4), siendo el N°3, enriquecido con extracto de café hidrolizado, 1L; urea, 3g/L; fosfato ácido de potasio, 2g/L; extracto de malta, 1,3g/L y melaza, 30g/L, el cual aportó los mejores resultados. El tiempo total de fermentación fue de 8 horas. Se obtuvo 10g/L de biomasa con un incremento proteico de 7,39 a 42,5%. Se puede concluir que la pulpa de café constituye un sustrato adecuado para obtener biomasa o proteína unicelular, que podría ser destinada como suplemento en formulaciones para alimentación animal Abstract in english The advances in industrial biotechnology offer potential opportunities for the economic use of agro-industrial remainders such as the coffee pulp, mucilagenous, fibrous material (secondary product) obtained during the humid or dry process of the benefit of the coffee cherries. The intention of this [...] work was to use the remainders of the pulp of coffee, rich in organic matter, like substrate for the production of biomass of leavenings by processes of aerobic fermentation. The coffee remainders were put under hydrolysis with a sulfuric acid solution to 2%, in a 10:1 relation (liquid: solid), with a size of particle ? 2 mm, operating to atmospheric pressure, boiling to ebb tide, during 4 hours. The acid extract filtered and it adjusted to pH 4,5 and then it sterilize to 120 ºC by 15 minutes. The fermentation was made with Saccharomyces cerevisiae and Candida utilis, the production means: extract of coffee enriched with nutritious salts. Different means from production were formulated (1,2,3 and 4), being the N°3, enriched with extract of hydrolyzed coffee, 1L; urea, 3g/L; acid potassium phosphate, 2g/L; extract of Malta, 1,3g/L and molasses, 30g/L, which contributed the best results. The total time of fermentation was of 8 hours. 10g/L of biomass with a protein increase from 7.39 to 42.5% was obtained. It is possible to be concluded that the coffee pulp constitutes an suitable substrate to obtain biomass or unicellular protein, that could be destined like supplement in formulations for feeding animal

Gualtieri A, María J; Villalta R, Carolina; Díaz T, Lorena E; Medina, Gerardo; Lapenna, Elisa; Rondón, María E.

225

Building a VO-compliant Radio Astronomical DAta Model for Single-dish radio telescopes (RADAMS)  

CERN Document Server

The Virtual Observatory (VO) is becoming the de-facto standard for astronomical data publication. However, the number of radio astronomical archives is still low in general, and even lower is the number of radio astronomical data available through the VO. In order to facilitate the building of new radio astronomical archives, easing at the same time their interoperability with VO framework, we have developed a VO-compliant data model which provides interoperable data semantics for radio data. That model, which we call the Radio Astronomical DAta Model for Single-dish (RADAMS) has been built using standards of (and recommendations from) the International Virtual Observatory Alliance (IVOA). This article describes the RADAMS and its components, including archived entities and their relationships to VO metadata. We show that by using IVOA principles and concepts, the effort needed for both the development of the archives and their VO compatibility has been lowered, and the joint development of two radio astronom...

Santander-Vela, J D; Leon, S; Espigares, V; Ruiz, J E; Verdes-Montenegro, L; Solano, E

2012-01-01

226

Variaciones de abundancia y biomasa del zooplancton en un embalse tropical oligo-mesotrófico del norte de Venezuela  

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Full Text Available La abundancia del zooplancton en los embalses está determinada principalmente por la velocidad y el contenido del agua, pero se sabe relativamente poco sobre los embalses tropicales. Se estudió la distribución temporal y espacial de la abundancia y la biomasa del zooplancton en el eje longitudinal del embalse de Clavellinos, en el norte de Venezuela, entre octubre 2006 y septiembre 2007. El zooplancton fue recolectado en el estrato oxigenado con una red de plancton. Un total de 16 taxones fueron identificados: Copepoda, Cladocera, Rotifera, Ostracoda y Diptera. Thermocyclops decipiens (Copepoda, Cyclopoida dominó la comunidad, mientras que los rotíferos fueron los más diversos, con 10 especies. La abundancia del zooplancton varió de 31 a 101ind/l en E1, 36 a 84ind/l en E2, y, de 30 a 250ind/L en el E3. La biomasa varió de 97,4 a 1406.3?g/l en E1, 108,5 a 397.2?g/l en E2, y de 25,9 a 763.9?g/l en el E3. Esta comunidad de zooplancton pareci? responder a las variaciones ambientales en el embalse, m?s que a las variaciones en la disponibilidad de recursos.Variations of zooplankton abundance and biomass in a tropical oligo-mesotrophic reservoir in Northern Venezuela. Zooplankton abundance in reservoirs is mainly determined by the speed and content of the water, but relatively little is known regarding tropical reservoirs. We studied the seasonal and spatial distribution of zooplankton abundance and biomass along the longitudinal axis of Clavellinos reservoir, northern Venezuela, from October 2006 to September 2007. Zooplankton was collected from the oxygenated layer using a plankton net. A total of 16 taxa were identified: Copepoda, Cladocera, Rotifera, Ostracoda and Diptera. Thermocyclops decipiens (Copepoda, Cyclopoida dominated the community, while rotifers were the most diverse, with 10 species. Zooplankton abundance varied from 31 to 101ind/L in E1, 36 to 84ind/L in E2, and, from 30 to 250ind/L in E3. Biomass varied from 97.4 to 1406.3?g/l in E1, 108.5 to 397.2?g/l in E2, and from 25.9 to 763.9?g/l in E3. This zooplankton community seems to respond to environmental variations in the reservoir, rather than to variations in resource availability. Rev. Biol. Trop. 58 (2: 603-619. Epub 2010 June 02.

Sandra Merayo

2010-06-01

227

Variaciones de abundancia y biomasa del zooplancton en un embalse tropical oligo-mesotrófico del norte de Venezuela  

Scientific Electronic Library Online (English)

Full Text Available SciELO Costa Rica | Language: Spanish Abstract in spanish La abundancia del zooplancton en los embalses está determinada principalmente por la velocidad y el contenido del agua, pero se sabe relativamente poco sobre los embalses tropicales. Se estudió la distribución temporal y espacial de la abundancia y la biomasa del zooplancton en el eje longitudinal d [...] el embalse de Clavellinos, en el norte de Venezuela, entre octubre 2006 y septiembre 2007. El zooplancton fue recolectado en el estrato oxigenado con una red de plancton. Un total de 16 taxones fueron identificados: Copepoda, Cladocera, Rotifera, Ostracoda y Diptera. Thermocyclops decipiens (Copepoda, Cyclopoida) dominó la comunidad, mientras que los rotíferos fueron los más diversos, con 10 especies. La abundancia del zooplancton varió de 31 a 101ind/l en E1, 36 a 84ind/l en E2, y, de 30 a 250ind/L en el E3. La biomasa varió de 97,4 a 1406.3?g/l en E1, 108,5 a 397.2?g/l en E2, y de 25,9 a 763.9?g/l en el E3. Esta comunidad de zooplancton pareci? responder a las variaciones ambientales en el embalse, m?s que a las variaciones en la disponibilidad de recursos. Abstract in english Variations of zooplankton abundance and biomass in a tropical oligo-mesotrophic reservoir in Northern Venezuela. Zooplankton abundance in reservoirs is mainly determined by the speed and content of the water, but relatively little is known regarding tropical reservoirs. We studied the seasonal and s [...] patial distribution of zooplankton abundance and biomass along the longitudinal axis of Clavellinos reservoir, northern Venezuela, from October 2006 to September 2007. Zooplankton was collected from the oxygenated layer using a plankton net. A total of 16 taxa were identified: Copepoda, Cladocera, Rotifera, Ostracoda and Diptera. Thermocyclops decipiens (Copepoda, Cyclopoida) dominated the community, while rotifers were the most diverse, with 10 species. Zooplankton abundance varied from 31 to 101ind/L in E1, 36 to 84ind/L in E2, and, from 30 to 250ind/L in E3. Biomass varied from 97.4 to 1406.3?g/l in E1, 108.5 to 397.2?g/l in E2, and from 25.9 to 763.9?g/l in E3. This zooplankton community seems to respond to environmental variations in the reservoir, rather than to variations in resource availability. Rev. Biol. Trop. 58 (2): 603-619. Epub 2010 June 02.

Sandra, Merayo; Ernesto J, González.

228

Efecto de fertilización nitrogenada en la producción de biomasa y calidad de aceite esencial en Lippia alba (Miller, Pronto alivio.  

Directory of Open Access Journals (Sweden)

Full Text Available En el Campo Experimental de la Universidad Nacional de Colombia sede Palmira (CEUNP se realizó un ensayo para evaluar el efecto de la fertilización nitrogenada, aplicando dos fuentes (gallinaza y urea en dos niveles (50 y 100 kg/ha de nitrógeno y dos frecuencias de corte (dos y cuatro meses. En el lote experimental se situaron 15 parcelas, en un diseño de bloques completos al azar, con cinco tratamientos y tres repeticiones. Para el análisis de la información se utilizó el programa estadístico SAS. El máximo rendimiento de biomasa y aceites esenciales se obtuvo con la aplicación de 100 kg/ha de nitrógeno en forma de urea y la frecuencia de corte cada dos meses. Los niveles de extracción de Lippia alba en nitrógeno variaron entre 79.7 y 128.5; fósforo entre 24.5 y 30.5; potasio entre 114.6 y 138.8 y calcio entre 100 y 150 kg/ha. El aceite esencial estuvo compuesto mayoritariamente por carvona y limoneno. Palabras claves: Fertilización nitrogenada, Lippia alba, Rendimientos biomasa, aceites esenciales, pronto alivio. ABSTRACT Nitrogenous fertilization effects in the Lippia alba production and quality. In the Experimental Center of the National University of Colombia-Palmira (CEUNP a experiment was realized to evaluate the effect of the nitrogenous fertilization, using two sources (gallinaza and urea at two levels (50 and 100 kg/ha of nitrogen and two cutting frequencies (each two and four months. In the experimental area 15 plots were planted, in a randomized Complete Blocks design random (RCBD with five treatments and three repetitions to measure the following variables: production of fresh matter, content of dry matter, nutrients extraction and content of essential oils. The analysis of variance used the statistical program SAS. The maximum yield of biomass and essential was obtained oils combining the fertilization with 100 kg/ha of nitrogen as urea and the cutting frequency every of two months. The levels of nutrients extraction of Lippia alba varied between 79.7 and 128.5 kg/ha of nitrogen, 24.5 and 30.5 kg/ha of phosphorus, 114.6 and 138.8 Kg/ha of potassium and between 100 y 150 kg/ha of Calcium. The phytochemical analyses showed that the essential oil was mainly composed by carvona and limoneno. Key words: Nitrogenous Fertilization, Lippia alba, yields, biomass, essential oils.

Sánchez O. M.

2004-04-01

229

Effects of aluminum substitution on photocatalytic property of BiVO4 under visible light irradiation  

International Nuclear Information System (INIS)

Graphical abstract: Visible-light-driven Al/BiVO4 photocatalyst was prepared by a hydrothermal process. After introducing Al, the BiVO4 particles retain monoclinic scheelite structures and the ability of visible light absorption is enhanced. XPS and FTIR results reveal that the Al ions influence the local structure of the BiVO4. The photocatalytic experiments demonstrate that the Al species incorporation can effectively enhance the photocatalytic activity of BiVO4 due to the existence of distorted VO43? tetrahedron and the stronger optical absorption intensity. Highlights: ? The visible-light-driven Al/BiVO4 photocatalysts are first prepared in our study. ? It is found that Al is introduced into the BiVO4 lattice successfully. ? The Al-doped BiVO4 shows a far higher photocatalytic activity than undoped BiVO4. ? One of the reason for the higher activity is the distorted VO43? tetrahedron. ? Another reason for the higher activity is the strong optical absorption intensity. -- Abstract: Novel visible-light-driven Al/BiVO4 photocatalysts were synthesized via a facile hydrothermal method for the first time. The samples were characterized by X-ray diffraction, N2-sorption, UV–vis diffuse reflectance spectra, scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transformed infrared spectra and X-ray photoelectron spectroscopy. The photocatalytic activity of the samples was evaluated by the decomposition of methylene blue under visible light irradiation (400 nm 4. The results revealed that the introduction of Al can improve photocatalytic performance greatly and different concentration of Al resulted in different photocatalytic activity. The highest activity is obtained by the sample with a doping concentration of 12 at%. The reason for the enhanced photocatalytic activities of Al/BiVO4 samples was also discussed in this paper.

2012-03-01

230

Comparative Study of VoIP over WiMax and WiFi  

Digital Repository Infrastructure Vision for European Research (DRIVER)

VoIP is a technology in great demand these days. Its interactive nature makes it very appealing for users and today it is one of the most dominant technologies for communication. With the growth over wireless networks the option to have voice communication over wireless has been considered - the choices are VoIP over WiFi or VoIP over WiMax. This paper studies and compares the two options and summarizes the results.

Atif Qureshi, M.; Arjumand Younus; Muhammad Saeed; Farhan Ahmed Sidiqui; Nasir Touheed; Shahid Qureshi, M.

2011-01-01

231

High-pressure synthesis of BaVO3: A new cubic perovskite  

Science.gov (United States)

A new cubic perovskite BaVO3 was synthesized by high-pressure synthesis at 15 GPa, and 1350 °C. Contrary to our expectations that lattice expansion by Ba substitution for Sr would lead to non-centrosymmetric tetragonal distortion, BaVO3 preserved its cubic crystal structure with a=3.94288(3) Å at room temperature and had Fermi-liquid characteristics as SrVO3 down to the lowest temperature.

Nishimura, Kousuke; Yamada, Ikuya; Oka, Kengo; Shimakawa, Yuichi; Azuma, Masaki

2014-06-01

232

Optimization of thermochromic VO2 based structures with tunable thermal emissivity  

Science.gov (United States)

In this paper, we design and simulate VO2/metal multilayers to obtain a large tunability of the thermal emissivity of infrared (IR) filters in the typical mid wave IR window of many infrared cameras. The multilayer structure is optimized to realise a low emissivity filter at high temperatures useful for military purposes. The values of tunability found for VO2/metal multilayers are larger than the value for a single thick layer of VO2.

Voti, R. Li; Larciprete, M. C.; Leahu, G.; Sibilia, C.; Bertolotti, M.

2012-08-01

233

Validity of 20-MST for predicting VO2max of adult Singaporean athletes.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This investigation compared the results of direct and indirect measurements of maximum oxygen uptake (VO2max) of an Asian population. Twenty subjects (16 male, 4 female), all of whom were physical education students, were assessed directly using laboratory treadmill running to determine VO2max. The indirect estimation of VO2max was obtained using a modified form of the Leger and Lambert 20-m multistage shuttle run test (20-MST). Heart rates were recorded throughout both tests. Pearson product...

Sproule, J.; Kunalan, C.; Mcneill, M.; Wright, H.

1993-01-01

234

Impact of VoIP and QoS on Open and Distance Learning  

Science.gov (United States)

Voice over Internet Protocol (VoIP) is becoming a reality in many organizations. The potential for mobility in voice over wi-fi networks will derive demand for the technology. Wireless VoIP is poised to rival VoIP as an alternative telephony tool. Internet has been used to transport data in the form of packet. In the past, Internet did not support…

Saxena, P. C.; Jasola, Sanjay; Sharma, Ramesh C.

2006-01-01

235

Processing Facilitation Strategies in OV and VO Languages: A Corpus Study  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The present corpus study aimed to examine whether Basque (OV) resorts more often than Spanish (VO) to certain grammatical operations, in order to minimize the number of arguments to be processed before the verb. Ueno & Polinsky (2009) argue that VO/OV languages use certain grammatical resources with different frequencies in order to facilitate real-time processing. They observe that both OV and VO languages in their sample (Japanese, Turkish and Spanish) have a similar fre...

Luis Pastor; Itziar Laka

2013-01-01

236

A importância do limiar anaeróbio e do consumo máximo de oxigênio (VO2 máx. em jogadores de futebol The importance of the anaerobic threshold and maximum oxygen uptake (VO2 PEAK for soccer players  

Directory of Open Access Journals (Sweden)

Full Text Available O objetivo deste estudo foi fazer uma abordagem sobre a importância do limiar anaeróbio (LA e o consumo máximo de oxigênio (VO2máx. em jogadores de futebol e comparar os resultados encontrados em nossos futebolistas com os da literatura especializada. Foram avaliados 18 jogadores de futebol profissional, com média de idade de 24 ± 4 anos, peso de 72,5 ± 5,9kg; estatura de 176,5 ± 7,0cm e superfície corpórea de 1,91 ± 0,15m². Todos os atletas foram avaliados após um período de dois meses de treinamentos. Os futebolistas foram submetidos a teste máximo em esteira ergométrica, utilizando-se protocolo escalonado e contínuo. A resposta de freqüência cardíaca (FC foi registrada por meio de um eletrocardiógrafo (HeartWare de 12 derivações simultâneas e, a pressão arterial (PA, por meio de método auscultatório. A ventilação pulmonar (V E, o consumo de oxigênio (VO2, a produção de dióxido de carbono (VCO2 e a razão de troca respiratória (RER foram avaliados por método espirométrico computadorizado respiração-a-respiração (MedGraphics Corporation [MGC]. Os seguintes resultados foram verificados: no (LA: [FC = 173,6 ± 8,6bpm; VO2 = 55,78 ± 5,93ml.kg.-1.min-1; velocidade = 14,6 ± 1,0km.h-1]; no exercício máximo [FC = 189,5 ± 11,4bpm; V E = 134,1 ± 15,9L.min-1; VO2máx. = 63,75 ± 4,93ml.kg.-1.min-1; velocidade = 17,8 ± 1,0km.h-1; Borg = 18,3 ± 1,3 pontos]. Concluindo: Os resultados, comparados com os da literatura especializada na modalidade futebol, demonstraram que os índices de LA e VO2máx. foram semelhantes e, até mesmo, superiores a vários de estudos publicados sobre essas duas variáveis em jogadores de futebol profissional. Entretanto, considerando as posições dos jogadores, não há um consenso definido sobre os índices mais adequados de LA e VO2máx. em futebolistas, mas, sim, sugestões.The aim of this study was to make an approach on the importance of the anaerobic threshold (AT and the peak oxygen uptake in soccer players, and compare the results found in players to those existing in the specialized literature. An evaluation was made in 18 professional soccer players aged 24 ± 4; weight 72.5 ± 5.9 kg; height 176.5 ± 7.0 cm, and body surface 1.91 ± 0.15 m². Every athlete was evaluated after a 2 month training period. The soccer players were submitted to a maximum exercise test on treadmill, using incremental continuous protocol. The heart rate (HR was recorded by means of an electrocardiograph (HeartWare with 12 simultaneous leads and the arterial blood pressure (BP by auscultation method. The pulmonary ventilation (V E, the oxygen uptake (VO2, the carbon dioxide production (VCO2 and the respiratory exchange rate (RER were evaluated by means of the breath-by-breath spirometric computerized method (MedGraphics Corporation-MGC. The following results were verified in the AT: HR = 173.6 ± 8.6 bpm; VO2 = 55.78 ± 5.93 mlO2.kg-1.min-1; running velocity = 14.6 ± 1.0 km.h-1; maximum exercise: HR = 189.5 ± 11.4 bpm; V E = 134.1 ± 15.9 L.min-1; VO2 peak = 63.75 ± 4.93 mlO2.kg-1.min-1; maximum velocity = 17.8 ± 1.0 km.h-1; Borg scale = 18.3 ± 1.3 points. In conclusion, the results, when compared to those of specialized literature, proved the rate of AT and VO2 peak to be similar and even superior to several results published about such two variables in professional soccer players. Considering, however, the players' position, there is no definite consensus on the most adequate AT rates and VO2 peak in soccer players, but only suggestions.

Paulo Roberto Santos Silva

1999-12-01

237

A importância do limiar anaeróbio e do consumo máximo de oxigênio (VO2 máx.) em jogadores de futebol / The importance of the anaerobic threshold and maximum oxygen uptake (VO2 PEAK) for soccer players  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese O objetivo deste estudo foi fazer uma abordagem sobre a importância do limiar anaeróbio (LA) e o consumo máximo de oxigênio (VO2máx.) em jogadores de futebol e comparar os resultados encontrados em nossos futebolistas com os da literatura especializada. Foram avaliados 18 jogadores de futebol profis [...] sional, com média de idade de 24 ± 4 anos, peso de 72,5 ± 5,9kg; estatura de 176,5 ± 7,0cm e superfície corpórea de 1,91 ± 0,15m². Todos os atletas foram avaliados após um período de dois meses de treinamentos. Os futebolistas foram submetidos a teste máximo em esteira ergométrica, utilizando-se protocolo escalonado e contínuo. A resposta de freqüência cardíaca (FC) foi registrada por meio de um eletrocardiógrafo (HeartWare) de 12 derivações simultâneas e, a pressão arterial (PA), por meio de método auscultatório. A ventilação pulmonar (V E), o consumo de oxigênio (VO2), a produção de dióxido de carbono (VCO2) e a razão de troca respiratória (RER) foram avaliados por método espirométrico computadorizado respiração-a-respiração (MedGraphics Corporation [MGC]). Os seguintes resultados foram verificados: no (LA): [FC = 173,6 ± 8,6bpm; VO2 = 55,78 ± 5,93ml.kg.-1.min-1; velocidade = 14,6 ± 1,0km.h-1]; no exercício máximo [FC = 189,5 ± 11,4bpm; V E = 134,1 ± 15,9L.min-1; VO2máx. = 63,75 ± 4,93ml.kg.-1.min-1; velocidade = 17,8 ± 1,0km.h-1; Borg = 18,3 ± 1,3 pontos]. Concluindo: Os resultados, comparados com os da literatura especializada na modalidade futebol, demonstraram que os índices de LA e VO2máx. foram semelhantes e, até mesmo, superiores a vários de estudos publicados sobre essas duas variáveis em jogadores de futebol profissional. Entretanto, considerando as posições dos jogadores, não há um consenso definido sobre os índices mais adequados de LA e VO2máx. em futebolistas, mas, sim, sugestões. Abstract in english The aim of this study was to make an approach on the importance of the anaerobic threshold (AT) and the peak oxygen uptake in soccer players, and compare the results found in players to those existing in the specialized literature. An evaluation was made in 18 professional soccer players aged 24 ± 4 [...] ; weight 72.5 ± 5.9 kg; height 176.5 ± 7.0 cm, and body surface 1.91 ± 0.15 m². Every athlete was evaluated after a 2 month training period. The soccer players were submitted to a maximum exercise test on treadmill, using incremental continuous protocol. The heart rate (HR) was recorded by means of an electrocardiograph (HeartWare) with 12 simultaneous leads and the arterial blood pressure (BP) by auscultation method. The pulmonary ventilation (V E), the oxygen uptake (VO2), the carbon dioxide production (VCO2) and the respiratory exchange rate (RER) were evaluated by means of the breath-by-breath spirometric computerized method (MedGraphics Corporation-MGC). The following results were verified in the AT: HR = 173.6 ± 8.6 bpm; VO2 = 55.78 ± 5.93 mlO2.kg-1.min-1; running velocity = 14.6 ± 1.0 km.h-1; maximum exercise: HR = 189.5 ± 11.4 bpm; V E = 134.1 ± 15.9 L.min-1; VO2 peak = 63.75 ± 4.93 mlO2.kg-1.min-1; maximum velocity = 17.8 ± 1.0 km.h-1; Borg scale = 18.3 ± 1.3 points. In conclusion, the results, when compared to those of specialized literature, proved the rate of AT and VO2 peak to be similar and even superior to several results published about such two variables in professional soccer players. Considering, however, the players' position, there is no definite consensus on the most adequate AT rates and VO2 peak in soccer players, but only suggestions.

Silva, Paulo Roberto Santos; Romano, Angela; Teixeira, Alberto Azevedo Alves; Visconti, Ana Maria; Roxo, Carla Dal Maso Nunes; Machado, Gilberto Silva; Vidal, José Roberto Rivelino; Inarra, Luís Antonio.

238

QoS-guaranteed burst transmission for VoIP service over optical burst switching networks  

Science.gov (United States)

We propose a burst transmission method that guarantees the voice over Internet protocol (VoIP) service. The proposed method consists of three techniques: round-robin burst assembly with slotted scheduling, priority control with void filling, and hop-based preemption. Each technique is utilized so that the burst loss probability and the burst transmission delay satisfy VoIP quality of service (QoS). We evaluate by simulation the performance of the proposed method in NSFNET with 14 nodes. Numerical examples show that our proposed method is effective for guaranteeing the VoIP QoS while accommodating a large number of VoIP users.

Tachibana, Takuji; Kasahara, Shoji

2007-08-01

239

Evaporation and condensation of LnVO4 orthovanadates in vacuum  

International Nuclear Information System (INIS)

Processes of electron-beam evaporation and condensation in vacuum of lanthanide orthovanadates have been investigated. It is shown that high-temperature evaporation in vacuum of lanthanide orthovanadates results in their dissociation. VO+,VO2+, LnO+(Yb+) ions are the main ones in vapour mass-spectra under quasiequilibrium conditions. Disproportionation of LnVO4 under the effect of electron beam in vacuum causes the absence of rare earth ions in the condensate composition and the presence of vanadium ions in reduced state, also in the form of metal and oxides of the system V-VO with low oxidation state

1990-01-01

240

Time limit at VO2max velocity in elite crawl swimmers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

he purpose of this study is to assess, with elite crawl swimmers, the time limit at the minimum velocity corresponding to maximal oxygen consumption (TLim-vVO2max), and to characterize its main determinants. Eight subjects performed an incremental test for vVO2max assessment and, forty-eight hours later, an all-out swim at vVO2max until exhaustion. VO2 was directly measured using a telemetric portable gas analyzer and a visual pacer was used to help the swimmers keeping the predetermined velo...

Ricardo Fernandes; Kari Keskinen; Paulo Colaço; Ana Querido; Leandro Machado; Pedro Morais; Daniel Novais; Daniel Marinho; João Paulo Vilas Boas Soares Campos

2008-01-01

 
 
 
 
241

Nanostructured VO2 film with high transparency and enhanced switching ratio in THz range  

Science.gov (United States)

We investigated the terahertz (THz) transmission characteristics of semiconductor VO2 film and its THz suppression behavior after the phase transition. The VO2 films were deposited by the sol-gel method, and an in situ growth with surface nanocrystallization occurring in the films with increasing thickness was presented. Morphology-induced percolation leads to high THz transparency in the semiconductor VO2 film, and the more compact nanostructure could account for the enhanced THz switching ratio in the metallic film. These results may offer insights into the artificial design of VO2 films for THz device applications.

Shi, Qiwu; Huang, Wanxia; Lu, Tiecheng; Zhang, Yaxin; Yue, Fang; Qiao, Shen; Xiao, Yang

2014-02-01

242

IAX-Based Peer-to-Peer VoIP Architecture  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Nowadays, Voice over IP (VoIP) constitutes a privileged field of service innovation. One benefit of the VoIP technology is that it may be deployed using a centralized or a distributed architecture. One of the most efficient approaches used in the deployment of centralized VoIP systems is based on the use of IAX (Inter-Asterisk Exchange), an open-source signaling/data exchange protocol. Even though they are currently widely used, client-server VoIP systems suffer from many we...

Lazzez, Amor; Fredj, Ouissem Ben; Slimani, Thabet

2013-01-01

243

Optimization of thermochromic VO2-based structures with tunable thermal emissivity  

International Nuclear Information System (INIS)

In this paper we design and simulate VO2/metal multilayers to obtain a large tunability of the thermal emissivity of IR filters in the typical MWIR window of many infrared cameras. The multilayer structure is optimized to realise a low-emissivity filter at high temperatures useful for military purposes. The values of tunability found for VO2/metal multilayers are larger than the value for a single thick layer of VO2. Innovative SiO2/VO2 synthetic opals are also investigated to enhance the optical tunability by combining the properties of a 3D periodic structure and the specific optical properties of vanadium dioxide.

2013-01-01

244

Direct fabrication of organic carbon coated VO2(B) (VO2(B)-C) core–shell structured nanobelts by one step hydrothermal route and its formation mechanism  

International Nuclear Information System (INIS)

Highlights: ? VO2(B)-C core–shell nanobelts were synthesized by a one-step hydrothermal route. ? The effect of glucose and reaction time was briefly discussed. ? Glucose played a dual role, namely as a reductant and as a carbon precursor. ? The possible formation mechanism of VO2(B)-C was proposed. - Abstract: Organic carbon coated vanadium dioxide (VO2(B)-C) core–shell structured nanobelts were successfully synthesized using V2O5 and glucose solution as the starting materials by a facile one-step hydrothermal route. The as-obtained core–shell materials were characterized by scanning electron microscope, transmission electron microscopy, X-ray powder diffraction, energy-dispersive X-ray spectrometer, elemental analysis, Fourier transform infrared spectroscopy and Raman measurements. Some parameters, such as, the concentration of glucose and the reaction time, were briefly discussed to disclose the formation process of VO2(B)-C core–shell structured nanobelts. Glucose played a dual role in the hydrothermal process, namely as a reductant to reduce V2O5 to VO2(B), and as a carbon precursor for the organic carbon shell. The proper quantity of glucose (i.g.: 0.27 g) was beneficial for the fabrication of VO2(B)-C. Furthermore, the possible formation mechanism of VO2(B)-C core–shell structured nanobelts was proposed.

2012-12-15

245

Biosorción de iones cobre con biomasa de algas y orujos deshidratados  

Directory of Open Access Journals (Sweden)

Full Text Available They were carried out experiments of biosorption batch and in continuous to remove copper from aqueous solutions using as adsorbent green algae and olive residues under virgins conditions and chemically activated. The results of batch biosorption indicate that the algae present mayor elimination capacities than the waste of olives, with uptakes of copper of the order of 96 % using activated algae with dissolution of Na2SO4 under the optimum conditions. The results of the columns tests show that the virgin algae permits the removal of more copper ions than the activate algae, with removal efficiency of 98 % during the firth 20 min, a breakthrough time of 240 min and a saturation at time of 600 min. In the second cycle the regenerated biomass showed a best performance indicating that they can be used for another biosorption cycle.

Se realizaron experimentos de biosorción batch y en continuo para remover cobre desde soluciones acuosas usando como adsorbentes algas verdes y residuos de aceituna en condiciones vírgenes y activadas químicamente. Los resultados de la biosorción a escala batch indican que las algas presentan mayor capacidad de eliminación que los orujos, alcanzándose captaciones de cobre del orden de 96 % con algas activadas con disoluciones de Na2SO4 bajo condiciones óptimas de las variables estudiadas. Los resultados de los ensayos en columna muestran que las algas vírgenes captan más iones cobre que las activadas con Na2SO4, con eficacias de eliminación del 98 % durante los primeros 20 min, con un tiempo de ruptura de 240 min y una saturación a los 600 min. Al ser sometidas a un segundo ciclo de biosorción, las algas regeneradas muestran un mejor rendimiento lo que indica que pueden ser usadas en otro ciclo de eliminación.

Romero, L.

2011-02-01

246

Distribución de biomasa de Barleria lupulina Lindl. en respuesta a tres regímenes de riego / Biomass distribution of Barleria lupulina Lindl. in response to three watering regimes  

Scientific Electronic Library Online (English)

Full Text Available SciELO Venezuela | Language: Spanish Abstract in spanish Barleria lupulina es un planta con propiedades medicinales potenciales, cuya acumulación de fitomasa, a nivel de sus órganos, ha sido poco investigada. Se determinó la distribución de biomasa de B. lupulina Lindl. en respuesta a tres regímenes de riego. Se diseñaron, por triplicado, tres tratamiento [...] s de riego: cada 2 (RI), 5 (RII) y 15 (RIII) días. Se realizaron mediciones del contenido relativo de agua (CRA), el potencial hídrico, y determinaciones de área foliar y biomasa seca a los seis meses después de la emergencia de las plántulas. El área foliar disminuyó un 88%, y la biomasa total 60% en estrés más severo (RIII), en concordancia con la disminución en el contenido relativo de agua y el potencial hídrico, pero las inflorescencias y el número de semillas incrementaron. Asimismo, el régimen de riego menos frecuente (RIII) afectó la distribución de asimilados puesto que los valores calculados a través de los índices como: la relación raíz/vástago (R/V), la relación de área foliar (RAF) y el área foliar específica (AFE) disminuyeron con dicho tratamiento. Se concluye que los efectos producidos por la disminución en la disponibilidad de agua comprenden reducción en la biomasa radical, cambios en la distribución de biomasa, variación del área foliar y aumento en las estructuras reproductivas. Abstract in english Barleria lupulina is a vascular plant with potential medicinal properties, which phytomass accumulation at the organ's level, has been poor investigated. Biomass distribution of Barleria lupulina Lindl. in response to three watering regimes was determined. Three treatment, in triplicate, of watering [...] were designed: every 2 (RI), 5 (RII) and 15 (RIII) days. The relative water content (RWC), leaf water potentials, leaf area and dry biomass were measured six months later the emergency of the seedlings. Leaf area decreased 88% and total biomass 60%, with the more severe water stress (RIII), and corresponding with a decrease in RWC and water potential, but inflorescens and seeds were greatest. The less frequent watering regimes (RIII) affected assimilate distribution because the value calculations in: root/shoot (R/S), leaf area ratio (LAR) and specific leaf area (SLA) decreased. We concluded that the effects produced by the reduction in water availability include a decrease in root biomass, changes in biomass distribution, variation in leaf area and increases in reproductive structures.

V, Paz; A, Vera; A, Páez.

247

Distribución de biomasa de Barleria lupulina Lindl. en respuesta a tres regímenes de riego Biomass distribution of Barleria lupulina Lindl. in response to three watering regimes  

Directory of Open Access Journals (Sweden)

Full Text Available Barleria lupulina es un planta con propiedades medicinales potenciales, cuya acumulación de fitomasa, a nivel de sus órganos, ha sido poco investigada. Se determinó la distribución de biomasa de B. lupulina Lindl. en respuesta a tres regímenes de riego. Se diseñaron, por triplicado, tres tratamientos de riego: cada 2 (RI, 5 (RII y 15 (RIII días. Se realizaron mediciones del contenido relativo de agua (CRA, el potencial hídrico, y determinaciones de área foliar y biomasa seca a los seis meses después de la emergencia de las plántulas. El área foliar disminuyó un 88%, y la biomasa total 60% en estrés más severo (RIII, en concordancia con la disminución en el contenido relativo de agua y el potencial hídrico, pero las inflorescencias y el número de semillas incrementaron. Asimismo, el régimen de riego menos frecuente (RIII afectó la distribución de asimilados puesto que los valores calculados a través de los índices como: la relación raíz/vástago (R/V, la relación de área foliar (RAF y el área foliar específica (AFE disminuyeron con dicho tratamiento. Se concluye que los efectos producidos por la disminución en la disponibilidad de agua comprenden reducción en la biomasa radical, cambios en la distribución de biomasa, variación del área foliar y aumento en las estructuras reproductivas.Barleria lupulina is a vascular plant with potential medicinal properties, which phytomass accumulation at the organ's level, has been poor investigated. Biomass distribution of Barleria lupulina Lindl. in response to three watering regimes was determined. Three treatment, in triplicate, of watering were designed: every 2 (RI, 5 (RII and 15 (RIII days. The relative water content (RWC, leaf water potentials, leaf area and dry biomass were measured six months later the emergency of the seedlings. Leaf area decreased 88% and total biomass 60%, with the more severe water stress (RIII, and corresponding with a decrease in RWC and water potential, but inflorescens and seeds were greatest. The less frequent watering regimes (RIII affected assimilate distribution because the value calculations in: root/shoot (R/S, leaf area ratio (LAR and specific leaf area (SLA decreased. We concluded that the effects produced by the reduction in water availability include a decrease in root biomass, changes in biomass distribution, variation in leaf area and increases in reproductive structures.

V Paz

2003-07-01

248

Conversión hidrotérmica subcrítica de residuos orgánicos y biomasa: Mecanismos de reacción / Subcritical hydrothermal conversion of organic wastes and biomass: Reaction pathways  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in spanish La conversión hidrotérmica es un procedimiento que emula el proceso natural de conversión de la materia orgánica en un biocrudo con propiedades físico-químicas similares a las del petróleo. La transformación artificial de biomasa requiere conocer previamente las rutas de reacción y productos prevale [...] ntes. En la conversión de celulosa, el principal componente de la biomasa, se presenta despolimerización por hidrólisis y se obtienen oligosacáridos, los cuales presentan deshidratación y condensación retro-aldol, para transformarse en furfurales y ácidos carboxílicos. Otros componentes de la biomasa como lignina, proteínas y ésteres grasos, presentan rutas de reacción en las que coexisten la hidrólisis y la pirólisis. Dada la presencia de carbohidratos en la biomasa, los principales productos de su conversión hidrotérmica subcrítica y de sus residuos serán análogos a los que presenta la celulosa. Dichas sustancias tienen un valor agregado que supera considerablemente los costos de adquisición de la materia prima. Al representar en un gráfico las relaciones molares O/C, H/C de los principales productos de conversión hidrotérmica de biomasa reportados en la literatura, se evidencia que la trayectoria de evolución para los productos de conversión hacia biocrudos se traslapa con la evolución geológica de los combustibles fósiles. Abstract in english Hydrothermal conversion is a procedure which emulates organic matter?s natural conversion into bio-crude having physical and chemical properties analogous to petroleum. The artificial transformation of biomass requires previous knowledge of the main reaction routes and product availability. The main [...] component of biomass (depolymerisation by hydrolysis) is presented in hydrothermal cellulose conversion, producing oligosaccharides which exhibit dehydration and retro-aldol condensation reactions for transforming into furfurals and carboxylic acids. Other biomass components (such as lignin, proteins, and fat esters) present both hydrolysis and pyrolysis reaction routes. As long as biomass mainly contains carbohydrates, subcritical hydrothermal conversion products and their wastes will be fundamentally analogous to those displaying cellulose. These substances have added-value by far surpassing raw material?s acquisition cost. When the main hydrothermal conversion products? O/C, H/C molar ratios as reported in literature are plotted, an evolutionary trajectory for conversion products appears to be closely or even overlapped with fossil fuels? geological evolution.

Castro Vega, Alejandro Amadeus; Rodríguez Varela, Luis Ignacio; Díaz Velásquez, José de Jesús.

249

Intestinal absorption and secretion of radioactive vanadium (_4_8VO"-"3) in rats and effect of Al(OH)"3  

International Nuclear Information System (INIS)

Sprague-Dawley rats (180-300 g) were fasted overnight and gavaged with 5 ?mol Na"3VO"4 in 1.0 ml 0.9% NaCl containing 1 ?Ci _4_8V. Control animals (n = 12) simultaneously received 1.0 ml diluent and experimental animals (n = 12) received 1 ml Al(OH)"3. Diluent and Al(OH)"3 were then given daily for 4 d. Urine and feces were collected separately each day. In control animals total _4_8V recovery (stool and urine) over 4 d was 86.6 +/- 2.4% of the administered dose. Although Al(OH)"3 insignificantly increased total _4_8V recovery (93.6 +/- 3.2%), it markedly increased excretion of _4_8V in the stool as compared to the urine (control:stool, 69.1 +/- 1.8%; urine, 12.5 +/- 1.3%; Al(OH)"3:stool, 85.7 +/- 1.5%; urine, 7.9 +/- 1.8%). Animals were then sacrificed and tissue uptake of tracer measured. The pattern of unexcreted _4_8V in tissues of both groups was kidney > bone > liver > intestine > muscle, but the tissue levels were uniformly higher in controls than in Al(OH)"3-treated animals. The ability of Al(OH)"3 to remove endogenous VO"-"3 was also examined. _4_8V was injected ip (n = 20). Half of the animals received diluent and half received 1.0 ml Al(OH)"3 by gavage daily for 4 d. There were no differences in the pattern of _4_8V tissue distribution and excretion. It is concluded that Al(OH)"3 may prevent tissue accumulation of VO"-"3 from dietary sources by reducing intestinal VO"-"3 absorption

1982-01-01

250

Carbono en biomasa microbiana y carbono soluble como indicadores de calidad de Vertisoles cultivados con caña azucarera  

Directory of Open Access Journals (Sweden)

Full Text Available El objetivo del presente estudio fue identificar propiedades biológicas, químicas y físicas del suelo, como el carbono de la biomasa microbiana (Cbio, el carbono orgánico soluble (COS, el pH, la materia orgánica (MO, la capacidad de intercambio catiónico (CIC y la densidad parente (Dap, como indicadores de calidad del cambio de uso del suelo de selva a cultivo de caña de azúcar en la Chontalpa, Tabasco. Se muestreó un Vertisol de selva y cuatro Vertisoles cultivados con caña de azúcar durante cinco, 10 y 20 y más de 30 años. Se encontró que ocurren cambios significativos en las propiedades del suelo cuando una selva se transforma en suelo cultivado con caña de azúcar. El Cbio, el COS y la MO disminuyeron conforme aumentó el tiempo dedicado al cultivo. El cambio en las propiedades del suelo de los diferentes sitios se atribuye al manejo agrícola que año con año se lleva a cabo en el suelo, así como a la falta de prácticas agronómicas que contribuyan a conservar la fertilidad del suelo cañero.

Liliana Armida-Alcudia

2005-01-01

251

Uso de la biomasa como fuente de energía para el secado agroindustrial del café: estudio de caso  

Directory of Open Access Journals (Sweden)

Full Text Available El trabajo trata sobre el análisis de siete variantes de calentamiento del aire que se emplea en el proceso de secado del café, teniendo en cuenta los aspectos térmicos, hidrodinámicos, energéticos, exergéticos y económicos, con la singularidad de que la biomasa se quema en un Horno de Capa Cónica Deslizante (HCCD. Se concluye que la variante número seis reúne las condiciones más atractivas para su utilización en el proceso de calentamiento del aire, utilizado en el secado del café, pues en ella se incrementa la temperatura del aire desde 25 oC hasta 400 oC, lográndose la máxima eficiencia en el proceso de transferencia de calor en el Calentador de Aire Tubular (CAT (10,5 %, la máxima eficiencia de la instalación (43,3 %, así como el máximo rendimiento exergético global (15,2 %. Se comprueba la factibilidad de ejecutar la inversión de la instalación que se propone debido a las ventajas económicas evidentes que la misma presenta.

Yusleidis Cisnero Reyna

2005-01-01

252

Comprehensive picture of VO2 from band theory  

The structural, electronic, and magnetic features of the metal-insulator transition from the tetragonal rutile (R) to the monoclinic (M1) phase of VO2 are well reproduced by band theory using the modified Becke-Johnson exchange potential. Based on this description, we identify a tendency for monoclinic charge ordering in the R phase due to electronic correlations as the origin of the phase transition. Whereas, the structural changes are crucial for the gap opening in the M1 phase, spin degeneracy in both phases is stabilized by correlation-induced delocalization of the V3d electrons.

Zhu, Zhiyong

2012-08-28

253

Japanese Virtual Observatory (JVO): implementation of VO standard protocols  

Science.gov (United States)

We developed the third prototype towards a Japanese Virtual Observatory (JVO). IVOA standards, such as Simple Image Access and ADQL, were adapted to the system for the first time. We also constructed an OAI-PMH publishing registry, a web service based searchable registry, and VO data services based on SIA and SkyNode protocols. Most of the components were built on open software, except for an XML database used for searchable registry. This paper describes the JVO proto 3 system and results of a performance measurement.

Shirasaki, Y.; Tanaka, M.; Honda, S.; Kawanomoto, S.; Yasuda, N.; Masunaga, Y.; Ishihara, Y.; Tsutsumi, J.; Nakamoto, H.; Kobayashi, Y.

2006-07-01

254

VoIP Steganography and Its Detection - A Survey  

CERN Document Server

Steganography is an ancient art that encompasses various techniques of information hiding, the aim of which is to secret information into a carrier message. Steganographic methods are usually aimed at hiding the very existence of the communication. Due to the rise in popularity of IP telephony, together with the large volume of data and variety of protocols involved, it is currently attracting the attention of the research community as a perfect carrier for steganographic purposes. This paper is a survey of the existing VoIP steganography (steganophony) methods and their countermeasures.

Mazurczyk, Wojciech

2012-01-01

255

IP Telephony Deploying VoIP Protocols and IMS Infrastructure  

CERN Multimedia

All you need to know about deploying VoIP protocols in one comprehensive and highly practical reference - Now updated with coverage on SIP and the IMS infrastructure. This book provides a comprehensive and practical overview of the technology behind Internet Telephony (IP), providing essential information to Network Engineers, Designers, and Managers who need to understand the protocols. Furthermore, the author explores the issues involved in the migration of existing telephony infrastructure to an IP - based real time communication service. Assuming a working knowledge of IP and networking, i

Hersent, Olivier

2010-01-01

256

Analysis of VoIP Traffic with Multiple Packet Transfer  

Directory of Open Access Journals (Sweden)

Full Text Available Voice over Internet Protocol (VoIP is a form of voice communication. Today Wireless LANs are providing a cost effective alternative for the voice communication. Initially the wireless access protocols are not suitable for the voice communication. Subsequently, new techniques are developed for the real time voice communication. In voice communication the delay is an important factor. In this paper a new technique is proposed for the voice over IEEE 802.11 WLANs. The proposed technique is compared with Modified ICF

Tara Chand, Vishal Srivastava

2012-06-01

257

Electron spin resonance of FeVO4  

Science.gov (United States)

We report on electron spin resonance (ESR) investigations of a FeVO4 single crystal. Temperature and angular dependences of ESR resonance positions were measured and calculated in temperature range of 35-100 K. The spectra show rich angular dependences of the linewidth, the shape and the resonance field. They consist of a single broad line with asymmetric distortion. Due to the low symmetry of the crystal lattice this distortion can be explained by taking into account the influence of non diagonal dynamic susceptibility.

Bojanowski, Bohdan; Kaczmarek, S?awomir Maksymilian

2014-05-01

258

Bulk sensitive core-level photoemission spectroscopy of VO2  

International Nuclear Information System (INIS)

We have studied electronic structures of VO2 by soft and hard X-ray synchrotron core-level photoelectron spectroscopy. In our measurements, temperature and photon energy dependences of the V 2p core-level spectra are observed. Remarkable spectral changes are observed across the metal-insulator transition (MIT) at T=340K. A clear shoulder structure is observed on the lower binding energy side of the V 2p3/2 peak in the metallic phase. This shoulder structure, being stronger for larger h?, is interpreted as the well-screened feature by bulk conduction electrons

2007-03-01

259

The DaCHS Multi-protocol VO Server  

Science.gov (United States)

GAVO's Data Center Helper Suite (DaCHS) is a suite of tools for publishing data to the Virtual Observatory. It implements all major VO protocols (SCS, SIAP, SSAP, TAP, OAI-PMH). The integrated management and ingestion component allow defining metadata, structure, and services once and re-use the definition throughout the publication cycle from initial metadata aquisition to registry record generation. It has been driving GAVO's data center since 2008 and is now deployed in multiple locations around the globe. This poster briefly describes the design of the system as well as a bird's-eye view of data publishing with DaCHS.

Demleitner, M.

2014-05-01

260

Efecto de la poda en el rendimiento de biomasa de 20 accesiones de especies arbóreas Effect of pruning on the biomass yield of 20 accessions of tree species  

Directory of Open Access Journals (Sweden)

Full Text Available Se evaluó el comportamiento de 20 accesiones de arbóreas ante la poda, durante cinco años, para lo cual se utilizó un diseño de bloques al azar con ocho repeticiones. Se determinó la biomasa comestible, la biomasa leñosa y la biomasa total, así como la composición bromatológica y el número de rebrotes. En el período lluvioso manifestaron un mejor comportamiento, en cuanto al rendimiento de biomasa, L. macrophylla CIAT-17240 y L. leucocephala CIAT-17498 (3,02 y 3,15 kg de MS/árbol como promedio. El número de rebrotes osciló entre 7 y 24 y la de mejor resultado fue L. leucocephala CIAT-17498 (24 rebrotes por planta. Sin embargo, en el período poco lluvioso la producción de biomasa comestible fluctuó entre 0,10 y 1,25 kg de MS/árbol, y se destacó de nuevo L. leucocephala CIAT-17498. Un comportamiento similar al del período lluvioso se constató en los indicadores restantes. Se concluye que los mejores resultados en cuanto a la producción de biomasa comestible se encontraron en el período lluvioso; se destacó L. leucocephala CIAT-17498 en este indicador y en el número de rebrotes para ambas épocas del año. Los contenidos de materia seca, fibra bruta y proteína bruta de la biomasa comestible de las plantas, tuvieron poca variación por el efecto de la época dentro de la misma especie, tendencia que se comprobó también para los minerales. Las accesiones demostraron ser una importante alternativa para la alimentación de los rumiantes, por sus altos contenidos de proteína bruta.The performance of 20 tree accessions when pruned was evaluated during five years, for which a randomized block design with eight repetitions was used. The edible, ligneous and total biomass, as well as the bromatological composition and number of regrowths were determined. In the rainy season L. macrophylla CIAT-17240 and L. leucocephala CIAT-17498 showed a better performance, regarding biomass yield (3,02 and 3,15 kg DM/tree as average. The number of regrowths varied between 7 and 24 and the best result was observed in L. leucocephala CIAT-17498 (24 regrowths per plant. Nevertheless, in the dry season the edible biomass production fluctuated between 0,10 and 1,25 kg DM/tree, and L. leucocephala CIAT-17498 stood out again. A performance similar to that of the rainy season was observed in the other indicators. The best results regarding edible biomass production were concluded to be found in the rainy season; L. leucocephala CIAT-17498 stood out in this indicator and in the number of regrowths for both seasons. The dry matter, crude fiber and crude protein contents of the edible biomass of the plants, had little variation due to the effect of the season within the same species, a trend that was also observed for minerals. The accessions proved to be an important alternative for feeding ruminants, because of their high contents of crude protein.

Odalys C Toral

2007-09-01

 
 
 
 
261

Equation for estimating tree biomass in tropical forests of Costa Rica Ecuación para estimar la biomasa arbórea en los bosques tropicales de Costa Rica  

Directory of Open Access Journals (Sweden)

Full Text Available One of the most relevant measures for climate change mitigation is the conservation and regeneration of forests in our countries. The amount of stored carbon in the forest biomass becomes a relevant variable for public policy. The present article analyses the association of some dasometric variables, easily obtained, with tree biomass with the purpose of indirectly estimating it, given that direct measurement of tree biomass is a complex and very expensive task. The general objective of this study was to analyze the pattern shown by dasometric variables, easily obtained, with tree biomass to estimate it by using data from two tropical forests in Costa Rica, with the purpose of analyzing its potential general application in tropical forests in the entire country. The bibliographic review helped to identify four possible models which estimate biomass in tropical forests. 907 trees were used with diameter at breast height (dbh greater than 10 cm in two tropical forests in Costa Rica (Corcovado National Park at the SW of the country, and Fila Carbón at the SE part, Caribbean slope, generating a biomass estimate as precise as possible. Dasometric variables (wood density, total height and dbh were used to analyze their relationship with biomass with the objective of finding a model that could predict it. The final model uses, as independent variables, dbh and density. Dbh has a high correlation with tree total height, which is very difficult to obtain in the field, therefore it was not used. The variable density is very important as it varies between trees having the same structure but of different species. To estimate the model, a segmented regression technique was used as well as weighted mean squares to solve for heteroscedasticity. The final model met all statistical assumptions for a linear model according to the residual and parametric analysis. The determination coefficient resulted in 0,992. As a conclusion, the study proposes a methodological approach to estimate forest biomass, which is very useful to support decision-making on carbon storage in tropical forests. Biomass determination in the field in future plots is going to help the calibration of this approach to estimate biomass stored in tropical forests.Una de las medidas más relevantes para la mitigación del cambio climático es la conservación y regeneración del bosque en nuestros países.  La cantidad de carbono que se almacena en la biomasa arbórea pasa a ser una medida relevante para la política pública. El presente trabajo analiza la asociación que tienen algunas variables dasométricas, fácilmente medibles, asociadas a la biomasa, con el propósito de estimarla indirectamente, dado que la medición directa de la biomasa arbórea es un trabajo complejo y tiene un costo muy elevado.  El objetivo general del estudio fue hacer un análisis del comportamiento de las variables dasométricas fácilmente medibles para predecir biomasa arbórea con datos de dos bosques tropicales de Costa Rica, con el propósito de analizar su posible aplicación generalizada en los bosques tropicales de todo el país. Mediante una revisión bibliográfica, se determinaron cuatro posibles modelos que estiman biomasa en bosques tropicales. Se evaluaron 907 árboles con diámetro a la altura de pecho (dap mayor a 10 cm en dos bosques tropicales de Costa Rica (Parque Nacional Corcovado en el suroeste y Fila Carbón en el sureste, vertiente del Caribe, generando una estimación de biomasa lo más precisa posible. Se realizó un análisis de las variables de los árboles (densidad específica de la madera, altura total y dap y su biomasa, con el fin de desarrollar el modelo que facilitara la predicción de esta. El modelo final utiliza como variables independientes el dap y la densidad.  Con el dap se da el hecho de que existe una alta correlación con la altura total, la cual es muy difícil de obtener en el campo, de modo que se decidió no utilizarla. La variable densidad es importante, ya que dos árboles con la misma estructura pero distinta densid

Shu Wei-Chou

2013-06-01

262

Microtwinning in highly nonstoichiometric VO{sub x} thin films  

Energy Technology Data Exchange (ETDEWEB)

Both pulsed-DC biased and commercial ion-beam sputtered VO{sub x} thin films maintain a face-centered-cubic nanocrystalline phase, even for stoichiometries of x > 1.5, which is well outside the bulk equilibrium solubility range for cubic VO{sub x}. Many of these highly nonstoichiometric films exhibit a high density of microtwins, which give rise to unusual fine structure in the selected-area electron diffraction patterns, namely: an additional defect ring; a significant broadening of the {l_brace}2 0 0{r_brace} ring; pairs of parallel rod features which are tangent to the additional defect ring; and additional fine-structure features between the {l_brace}2 0 0{r_brace} and {l_brace}2 2 0{r_brace} rings. The formation of the microtwins is correlated with the coalescence of vanadium vacancies along the {l_brace}1 1 1{r_brace} twin planes in the crystalline lattice.

Li Jing [Materials Research Institute, Pennsylvania State University, University Park, PA 16802 (United States); Gauntt, Bryan D. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Dickey, Elizabeth C., E-mail: ecd10@psu.edu [Materials Research Institute, Pennsylvania State University, University Park, PA 16802 (United States)] [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States)

2010-09-15

263

Elastic properties of VO2 from first-principles calculation  

Science.gov (United States)

We used first-principles methods to calculate the elastic properties of rutile (R) structure and monoclinic (M1: space group P21/c, M2: space group C2/m) structure VO2, including single-crystal elastic constants cij's, polycrystalline bulk modulus, shear modulus, Young's modulus and elastic anisotropy ratio. We found that the energy difference among the R, M1 and M2 phases is small, indicating that it is easy to transit among them under a perturbation. Furthermore, from the pressure dependence of cij's, we also found that the structural instability (or phase transition) will occur when the volumes of the three phases are slightly smaller than their equilibrium volumes. Additionally, the R and M2 phases are predicted to be harder than the M1 phase, indicated by their larger bulk moduli and shear moduli. The elastic anisotropy of the M2 phase is larger than the M1 and R phases. The presently predicted elastic properties of VO2 provide helpful guidance for the strain energy estimation and stress analysis in nano-electronic devices.

Dong, Huafeng; Liu, Hongfei

2013-08-01

264

Generation of gas-phase VO2+, VOOH+, and VO2+-nitrile complex ions by electrospray ionization and collision-induced dissociation.  

Science.gov (United States)

Cationic metal species normally function as Lewis acids, accepting electron density from bound electron-donating ligands, but they can be induced to function as electron donors relative to dioxygen by careful control of the oxidation state and ligand field. In this study, cationic vanadium(IV) oxohydroxy complexes were induced to function as Lewis bases, as demonstrated by addition of O2 to an undercoordinated metal center. Gas-phase complex ions containing the vanadyl (VO2+), vanadyl hydroxide (VOOH+), or vanadium(V) dioxo (VO2+) cation and nitrile (acetonitrile, propionitrile, butyronitrile, or benzonitrile) ligands were generated by electrospray ionization (ESI) for study by multiple-stage tandem mass spectrometry. The principal species generated by ESI were complexes with the formula [VO(L)n]2+, where L represents the respective nitrile ligands and n=4 and 5. Collision-induced dissociation (CID) of [VO(L)5]2+ eliminated a single nitrile ligand to produce [VO(L)4]2+. Two distinct fragmentation pathways were observed for the subsequent dissociation of [VO(L)4]2+. The first involved the elimination of a second nitrile ligand to generate [VO(L)3]2+, which then added neutral H2O via an association reaction that occurred for all undercoordinated vanadium complexes. The second [UO(L)4]2+ fragmentation pathway led instead to the formation of [VOOH(L)2]+ through collisions with gas-phase H2O and concomitant losses of L and [L+H]+. CID of [VOOH(L)2]+ caused the elimination of a single nitrile ligand to generate [VOOH(L)]+, which rapidly added O2 (in addition to H2O) by a gas-phase association reaction. CID of [VONO3(L)2]+, generated from spray solutions created by mixing VOSO4 and Ba(NO3)2 (and precipitation of BaSO4), caused elimination of NO2 to produce [VO2(L)2]+. CID of [VO2(L)2]+ produced elimination of a single nitrile ligand to form [VO2(L)]+, a V(V) analogue to the O2-reactive V(IV) species [VOOH(L)]+; however, this V(V) complex was unreactive with O2, which indicates the requirement for an unpaired electron in the metal valence shell for O2 addition. In general, the [VO2(L)2]+ species required higher collisions energies to liberate the nitrile ligand, suggesting that they are more strongly bound than the [VOOH(L)2]+ counterparts. PMID:17034156

Parsons, Zack; Leavitt, Chris; Duong, Thanh; Groenewold, Gary S; Gresham, Garold L; Van Stipdonk, Michael J

2006-10-19

265

Non-Exercise Estimation of VO[subscript 2]max Using the International Physical Activity Questionnaire  

Science.gov (United States)

Non-exercise equations developed from self-reported physical activity can estimate maximal oxygen uptake (VO[subscript 2]max) as well as sub-maximal exercise testing. The International Physical Activity Questionnaire is the most widely used and validated self-report measure of physical activity. This study aimed to develop and test a VO[subscript…

Schembre, Susan M.; Riebe, Deborah A.

2011-01-01

266

Submaximal Treadmill Exercise Test to Predict VO[subscript 2]max in Fit Adults  

Science.gov (United States)

This study was designed to develop a single-stage submaximal treadmill jogging (TMJ) test to predict VO[subscript 2]max in fit adults. Participants (N = 400; men = 250 and women = 150), ages 18 to 40 years, successfully completed a maximal graded exercise test (GXT) at 1 of 3 laboratories to determine VO[subscript 2]max. The TMJ test was completed…

Vehrs, Pat R.; George, James D.; Fellingham, Gilbert W.; Plowman, Sharon A.; Dustman-Allen, Kymberli

2007-01-01

267

Effects of porous nano-structure on the metal–insulator transition in VO2 films  

International Nuclear Information System (INIS)

Graphical abstract: The picture shows the morphology and hysteresis loop of porous VO2 film: porous nano-structure with small nanoparticles is obtained, transition temperature is reduced to 56 °C and hysteresis width is increased to 36 °C. Highlights: ? VO2 films with small nanoparticles and homogeneous pores are obtained. ? Tt of porous nano-structure VO2 film is reduced to 56 °C and ?T is increased to 36 °C. ? Systematic study of CTAB concentration on morphology and MIT properties of the VO2 films is conducted. - Abstract: In this work, we confirmed experimentally that the porous nano-structure of vanadium dioxide (VO2) films had significant effects on the features of the metal–insulator transition. Porous VO2 films had been synthesized on mica substrates via a simple solution process with inorganic precursor and cetyltrimethyl ammonium bromide (CTAB). SEM images showed a combination of homogenously distributed pores and VO2 nanoparticles. Metal to insulator transition (MIT) characteristics measurements revealed that, the porous nano-structure VO2 films had low transition temperature, wide hysteresis width and gentle slopes of hysteresis loop. Morphologies and MIT characteristics of the films could be controlled by simply varying CTAB concentration, which is of great importance in achieving practical applications.

2012-10-15

268

MAXIMAL OXIGEN UPTAKE (VO2 MAX AS THE INDICATOR OF PHYSICAL WORKING CAPACITY IN SPORTSMEN  

Directory of Open Access Journals (Sweden)

Full Text Available The term “aerobic capacity” represents the sum of aerobic metabolic processes in human organism. It is the basis of the physical working capacity. Value of the maximal oxygen uptake (VO2max is the best indicator for the aerobic capacity evaluation.The purpose of this study was to check the possibility of using VO2max as the indicator of aerobic capacity in sportsmen and to check differences in VO2max values in regard to non-sportsmen.The goals were: 1.Analyses of the VO2max values in sportsmen of various sports 2. Comparison of values of sportsmen with the values of non-sportsmen.This study included 67 sportsmen (rowers, football players and judoists and 28 nonsportsmen. VO2max was measured by using a direct method.The results obtained show statistically higher VO2max values in rowers (4,52 L/min - 55,8 mL/kg/min in regard to football players (4,2 L/min – 53,6 mL/kg/min, judoists (3,58 L/min - 47,2 mL/ kg/min and non-sportsmen (3,28 L/min – 42,3 mL/kg/min. Successful rowing requires high anaerobic capacity and, therefore, high VO2max.These results show higher values of VO2max in sportsmen in regard to non-sportsmen, which is the result of training only.

Zvezdana Rajkovaca

2005-12-01

269

One step synthesis of monoclinic VO2 (B) bundles of nanorods: Cathode for Li ion battery  

International Nuclear Information System (INIS)

One of the metastable phases of vanadium dioxide, VO2(B) bundles of nanorods and microspheres have been synthesized through a simple hydrothermal method by dispersing V2O5 in aqueous quinol. The obtained products were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and electrochemical discharge–charge test for lithium battery. It was found that the morphologies of the obtained VO2(B) can be tuned by manipulating the relative amount of quinol. The electrochemical test found that the bundles of nanorods exhibit an initial discharge capacity of 171 mAh g?1 and its almost stabilized capacity was reached to 108 mAh g?1 after 47 cycles at a current density of 0.1 mA g?1. The formation mechanism of the VO2(B) bundles of nanorods and microspheres was also discussed. - Highlights: ? VO2(B) bundles of nanorods and microspheres were prepared by hydrothermal route at 180 °C for 1 day. ? In this method for the synthesis of VO2(B), we are the first to use quinol as a reducing agent. ? Morphologies of the obtained VO2(B) can be tuned by manipulating the relative amount of quinol. ? VO2(B) exhibits an initial capacity of 171 mAh g?1 and reached to 108 mAh g?1 after 47 cycles. ? The formation mechanism of the VO2(B) bundles of nanorods and microspheres is also discussed.

2012-06-01

270

Effect of Toe Clips During Bicycle Ergometry on VO2 max.  

Science.gov (United States)

Eight men participated in three randomized maximal oxygen uptake tests to investigate the hypothesis that the use of toe clips on bicycle ergometers produced a higher VO2 max. No significant difference in mean VO2 max or performance time was observed. (Author/MT)

Moffat, Roger S.; Sparling, Phillip B.

1985-01-01

271

Transient VO2 Characteristics in Children at the Onset of Steady-Rate Exercise.  

Science.gov (United States)

Transient oxygen uptake (VO2) was studied in 28 children ranging in age from seven to fourteen. It was found that the VO2 halftime is similar to that of adults and that younger children attained a steady rate quicker than older children. (Authors/FG)

Freedson, Patty S.; And Others

1981-01-01

272

VO2-WO3 nanocomposite thin films synthesized by pulsed laser deposition technique  

International Nuclear Information System (INIS)

Pure VO2 and VO2-WO3 composite thin films were grown on quartz substrate by pulsed laser deposition (PLD) technique. The influence of varying WO3 molar concentration in the range from x = 0.0 to x = 0.4 on structural, electrical and optical properties of VO2-WO3 nanocomposite thin films has been systematically investigated. X-ray diffraction studies reveal the single crystalline monoclinic VO2 phase (m-VO2) up to 10% of WO3 content whereas both m-VO2 as well as h-WO3 (hexagonal WO3) phases were present at higher WO3 content (0.2 ? x ? 0.4). Optical transmittance spectra of the films showed blue shift in the absorption edge with increase in WO3 content. Temperature dependence of resistivity (R-T) measurements indicates significant variation in metal-insulator transition temperature, width of the hysteresis, and shape of the hysteresis curve. Cyclic Voltammetry measurements were performed on VO2-WO3 thin films. A direct correlation between V/W ratio and structure-property relationship was established. The present investigations reveal that doping of WO3 in VO2 is effective to increase the optical transmittance and to reduce the semiconductor to metal phase transition temperature close to room temperature.

2011-08-15

273

Localization of 3d electrons in VO/sub 2/+Ar solid solutions  

Energy Technology Data Exchange (ETDEWEB)

Electroconductivity sigma, transmission spectra t, light reflection R and optical conductivity sigmasub(opt) in the temperature range T from 77.8 to 400 K for VO/sub 2/ samples and VO/sub 2/+Ar solid solutions on their base are measured. Preparation of the latter has been realized by the ion implantation method in the implantation dose range from 0 to 6.10/sup 16/ cm/sup -2/. At implantation doses higher than 10/sup 16/ cm/sup -2/ the transition into isolator state at high T, has been found, the transformation of R and sigmasub(opt) spectra in the process of this transition is analogous to their variation at ''temperature'' phase transition metal-isolator in VO/sub 2/ crystals. The found effect is related to increase of average distances between lattice atoms of VO/sub 2/ in the VO/sub 2/+Ar system leading to 3d-electron localization or Mott transition into isolator state. Discussion of 3d-electron properties in VO/sub 2/ is presented and considerations on the character of conformity of isolator state in the VO/sub 2/+Ar system to isolator state in low-temperature monoclinic VO/sub 2/ crystal phase are set forth.

Mokerov, V.G.; Iegishev, A.R.; Ignat' ev, A.S.

1981-04-01

274

Localization of 3d electrons in VO_2+Ar solid solutions  

International Nuclear Information System (INIS)

Electroconductivity ?, transmission spectra t, light reflection R and optical conductivity ?sub(opt) in the temperature range T from 77.8 to 400 K for VO_2 samples and VO_2+Ar solid solutions on their base are measured. Preparation of the latter has been realized by the ion implantation method in the implantation dose range from 0 to 6.10"1"6 cm"-"2. At implantation doses higher than 10"1"6 cm"-"2 the transition into isolator state at high T, has been found, the transformation of R and ?sub(opt) spectra in the process of this transition is analogous to their variation at ''temperature'' phase transition metal-isolator in VO_2 crystals. The found effect is related to increase of average distances between lattice atoms of VO_2 in the VO_2+Ar system leading to 3d-electron localization or Mott transition into isolator state. Discussion of 3d-electron properties in VO_2 is presented and considerations on the character of conformity of isolator state in the VO_2+Ar system to isolator state in low-temperature monoclinic VO_2 crystal phase are set forth

1981-04-01

275

Pt/VO{sub 2} double-layered films combining thermochromic properties with low emissivity  

Energy Technology Data Exchange (ETDEWEB)

This study involves the optical properties of Pt/VO{sub 2} composite films, with a Pt top layer and a VO{sub 2} bottom layer. VO{sub 2} and Pt films were grown on fused silica substrates by polymer-assisted deposition and sputtering, respectively. These Pt/VO{sub 2} films were characterized by scanning electron microscopy, UV-visible-NIR spectrophotometry, Fourier transform infrared spectrometry, four-point probe and Raman spectroscopy. The results indicate that these Pt/VO{sub 2} films can enhance the infrared reflectivity while retaining their thermochromic properties. Although the visible transmittance is depressed by these Pt layers, the addition of antireflection coatings boosts the transmittance from 25.1% to 37.9% at 0.55 {mu}m. In addition, the semiconductor-metal (S-M) transition temperatures of Pt/VO{sub 2} films shift to lower temperatures in the heating semicycle (T{sub c,h}), from 67.8 C for a pure VO{sub 2} film to 58.5 C for a VO{sub 2} film covered with a 9 nm Pt layer. This work provides an important prototype structure for the development of new smart windows that combine thermochromic properties with low emissivity. (author)

Kang, Litao; Du, Jing; Zhang, Zongtao [Research Center for Industrial Ceramics, Shanghai Institute of Ceramics (SIC), Chinese Academy of Sciences (CAS), Dingxi 1295, Changning, Shanghai 200050 (China); Graduate University of Chinese Academy of Sciences, Yuquanlu 19, Beijing 100049 (China); Gao, Yanfeng; Luo, Hongjie [Research Center for Industrial Ceramics, Shanghai Institute of Ceramics (SIC), Chinese Academy of Sciences (CAS), Dingxi 1295, Changning, Shanghai 200050 (China); Chen, Zhang [Research Center for Industrial Ceramics, Shanghai Institute of Ceramics (SIC), Chinese Academy of Sciences (CAS), Dingxi 1295, Changning, Shanghai 200050 (China); School of Materials Science and Engineering, Shaanxi University of Science and Technology, Xi' an 710021 (China)

2010-12-15

276

Equações para a previsão da potência aeróbia (VO2) de jovens adultos brasileiros Equations for predicting aerobic power (VO2) of young Brazilian adults  

Digital Repository Infrastructure Vision for European Research (DRIVER)

FUNDAMENTO: O VO2 pode ser previsto, com base em parâmetros antropométricos e fisiológicos, para determinadas populações. OBJETIVO: Propor modelos preditivos do VO2 submáximo e máximo para jovens adultos brasileiros. MÉTODOS: Os 137 voluntários (92 homens) foram submetidos ao teste progressivo de esforço máximo (GXT) no ciclo ergômetro (Monark®, Br). Medidas de trocas gasosas e ventilatórias foram realizadas em circuito aberto (Aerosport® TEEM 100, EUA). Em outro grupo, 13 volu...

2010-01-01

277

Textured metastable VO2 (B) thin films on SrTiO3 substrates with significantly enhanced conductivity  

Science.gov (United States)

Textured metastable VO2 (B) thin films with a layered structure were grown on SrTiO3 (001) by pulsed laser deposition. The X-ray diffraction and transmission electron microscopy results indicate that VO2 (B) films exhibit c-axis out-of-plane, while the films have 4 possible in-plane matching relations. In addition, a small amount of VO2 (M) phase can co-grow in the VO2 (B) phase when the film thickness exceeds a threshold. The thick VO2 films on STO exhibit a sharp metal-insulator transition with an increase of electrical conductivity in two orders of magnitude. This study may provide an alternative approach to enhance the performance of insulating VO2 (B) based batteries with increased electrical conductivity by incorporating VO2 (M) phase in the VO2 (B) phase layered network.

Chen, Aiping; Bi, Zhenxing; Zhang, Wenrui; Jian, Jie; Jia, Quanxi; Wang, Haiyan

2014-02-01

278

Adsorption-controlled growth of BiVO4 by molecular-beam epitaxy  

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Full Text Available Single-phase epitaxial films of the monoclinic polymorph of BiVO4 were synthesized by reactive molecular-beam epitaxy under adsorption-controlled conditions. The BiVO4 films were grown on (001 yttria-stabilized cubic zirconia (YSZ substrates. Four-circle x-ray diffraction, scanning transmission electron microscopy (STEM, and Raman spectroscopy confirm the epitaxial growth of monoclinic BiVO4 with an atomically abrupt interface and orientation relationship (001BiVO4 ? (001YSZ with [100]BiVO4 ? [100]YSZ. Spectroscopic ellipsometry, STEM electron energy loss spectroscopy (STEM-EELS, and x-ray absorption spectroscopy indicate that the films have a direct band gap of 2.5 ± 0.1 eV.

S. Stoughton

2013-10-01

279

Self-Assembly and Horizontal Orientation Growth of VO2 Nanowires.  

Science.gov (United States)

Single-crystalline vanadium dioxide (VO2) nanostructures have attracted an intense research interest recently because of their unique single-domain metal-insulator phase transition property. Synthesis of these nanostructures in the past was limited in density, alignment, or single-crystallinity. The assembly of VO2 nanowires (NWs) is desirable for a "bottom-up" approach to the engineering of intricate structures using nanoscale building blocks. Here, we report the successful synthesis of horizontally aligned VO2 NWs with a dense growth mode in the [1-100]quartz direction of a polished x-cut quartz surface using a simple vapor transport method. Our strategy of controlled growth of VO2 NWs promisingly paves the way for designing novel metal-insulator transition devices based on VO2 NWs. PMID:24965899

Cheng, Chun; Guo, Hua; Amini, Abbas; Liu, Kai; Fu, Deyi; Zou, Jian; Song, Haisheng

2014-01-01

280

Photon band hysteresis in VO2 photonic crystal under semiconductor-metal phase transition  

International Nuclear Information System (INIS)

The VO2-based photonic crystals possessing the semiconductor-metal phase transition in temperature range of 55-75 deg C were synthesized by infiltration of opal matrices with VO2 and subsequent etching out SiO2 from opal-VO2 composites. It was found that crystals had broad photon forbidden band in the visible spectral range, whose energy location changes drastically under the phase transition. A temperature-induced displacement and thermal hysteresis of the photon forbidden band position due to the phase transition in VO2 were observed. A theoretical model of the periodic layer medium was proposed to describe quantitatively the reflection spectra of the synthesized photonic crystals of opal and VO2

2002-09-01

 
 
 
 
281

Self-Assembly and Horizontal Orientation Growth of VO2 Nanowires  

Science.gov (United States)

Single-crystalline vanadium dioxide (VO2) nanostructures have attracted an intense research interest recently because of their unique single-domain metal-insulator phase transition property. Synthesis of these nanostructures in the past was limited in density, alignment, or single-crystallinity. The assembly of VO2 nanowires (NWs) is desirable for a “bottom-up” approach to the engineering of intricate structures using nanoscale building blocks. Here, we report the successful synthesis of horizontally aligned VO2 NWs with a dense growth mode in the [1-100]quartz direction of a polished x-cut quartz surface using a simple vapor transport method. Our strategy of controlled growth of VO2 NWs promisingly paves the way for designing novel metal-insulator transition devices based on VO2 NWs.

Cheng, Chun; Guo, Hua; Amini, Abbas; Liu, Kai; Fu, Deyi; Zou, Jian; Song, Haisheng

2014-01-01

282

Prepaid and Postpaid VoIP Service Enhancements and Hybrid Network Performance Measurement  

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Full Text Available This study focuses on prepaid and postpaid VoIP technology service enhancement. The aims are to i merge wireless technology in rural areas with wired technologies and services in urban areas. It intends to investigate the minimum requirement needs by wireless and wired technology in using of telco connectivity. It is also to define which technology will achieve a low operating cost and good performance. In addition, the most apparent benefit of implementing prepaid/postpaid VoIP network in rural areas is that to achieve a robust fault tolerance and load-balancing voice traffic between urban and rural areas. ii Merging of WAP and VoIP network to provide Information-on-Demand (IoD services to prepaid and postpaid VoIP users. It is to provide value added services for prepaid and postpaid VoIP users. WAP and other similar technologies will continue to play an important role in the development of Information-on-Demand (IoD services in future. In addition, the most apparent benefit of implementing WAP technology with prepaid/postpaid VoIP network architecture is that to achieve WAP enabled mobile to access this facility during travelling, meeting, seminar and conference. Integration of WAP technology with prepaid/postpaid VoIP network architecture can achieve efficiency end-to-end information services between service providers (ISPs/ITSPs and WAP mobile phone users. Therefore, prepaid and postpaid VoIP service enhancement can improve and obtain high efficiency network, technical, business and customer-care aspects in contributing the robust prepaid/postpaid VoIP network architecture for prepaid/postpaid VoIP users.

Mohd Nazri Ismail

2006-01-01

283

PRELIMINARY ANALYSIS OF BIOMASS POTENTIALLY USEFUL FOR PRODUCING BIODIESEL / ANALISIS PRELIMINAR DE BIOMASA POTENCIALMENTE ÚTIL PARA PRODUCIR BIODIESEL  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: English Abstract in spanish Considerando que el biodiesel se está convirtiendo en una solución viable para algunos problemas energéticos y medioambientales, la investigación de materias primas para su producción es un tema de creciente interés. Este estudio presenta los resultados de una investigación dedicada al análisis prel [...] iminar de varias especies vegetales (biomasa), potencialmente útiles para producir biodiesel. La zona de bioprospección es una región de la costa pacifica colombiana. Las especies promisorias recolectadas fueron sometidas a diferentes pruebas normalizadas ASTM para definir propiedades que faciliten su evaluación. Algunas de las especies fueron sometidas a un proceso de transesterificación. Adicionalmente, se realiza una comparación entre las propiedades termo-físicas de los biodiesel y las propiedades del diesel comercial. Las pruebas de rendimiento de estos biocombustibles en los motores de encendido por compresión, particularmente la eficiencia, el consumo y la potencia a diferentes RPM del motor, se presentan en este trabajo. Abstract in english Given that biodiesel is emerging as a viable solution for some energy and environmental problems, research on raw materials appropriate for its production is a matter of growing interest. In this study we present the results of research devoted to preliminary analysis on several vegetable (biomass) [...] species potentially useful for producing biodiesel. The bioprospection zone is a region on the Colombian Pacific coast. The candidate species collected underwent different standardized ASTM tests in order for us to define properties that facilitate their evaluation. Some of the species underwent a transesterification process. Comparisons between the thermo-physical properties of the biofuels obtained and the properties of commercial diesel were carried out. Also, performance tests for these biofuels were conducted in compression ignition engines, particularly evaluating efficiency, fuel consumption, and potency at different RPMs.

GERARDO, CABRERA CIFUENTES; JUAN CARLOS, BURBANO JARAMILLO; JOSÉ ISIDRO, GARCIA MELO.

284

MODELOS DE REGRESIÓN PARA ESTIMAR ÁREA DE LA HOJA Y BIOMASA DE ÓRGANOS EN ÁRBOLES JÓVENES DE MANZANO  

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Full Text Available Se generaron modelos matemáticos empíricos de aplicación general con técnicas de regresión lineal múltiple, para estimar el área de la hoja y la biomasa aérea en manzano "Agua Nueva II" / M-7, útiles en estudios de crecimiento, relaciones fuente-demanda y productividad. Los modelos obtenidos tienen alta precisión, (R2 > 0.969. El área (AFE, el peso seco de la lámina de la hoja (PSL y el peso seco de pecíolo (PSP pueden ser estimados con los modelos: AFE= -3.24140(AL + 0.67616(AL2 + 1.63287(AL (LL/AL; PSL= 0.02699(AFE + 0.00021917(AFE2; y PSP= 0.00384(AFE - 0.04432 (LL/AL + 0.02291(LL/AL, respectivamente, donde AL y LL son ancho máximo y largo de la lámina de la hoja, respectivamente. Se mide la longitud, el diámetro proximal o basal y el diámetro distal o apical de cada rama, tallo y tronco. Estas medidas se utilizan para calcular el volumen en fresco (V de cada uno de esos órganos como un cono truncado. El volumen se utilizó para los modelos: PST= 0.6688(V, PSTP= 0.55902(V, lnPSRG= 0.77462[ln(V], PSRM= 0.49349(V y PSRP= 0.57297(V; éstos estiman los pesos secos del tronco (PST, del tallo principal (PSTP, de ramas grandes (PSRG, medianas (PSRM y pequeñas o dardos (PSRP de cada planta. EL modelo del peso seco para el sistema radical (PSRZ está en función de la longitud (LPT y diámetro distal del tronco: PSRZ= 10.80747(LPT(DDT + (-01.37171 (DDT2. Las longitudes y los diámetros se expresan en centímetros, el área en centímetros cuadrados, el volumen en centímetros cúbicos y los pesos en gramos.

J. P. Cruz-Hernu00E1ndez

2007-01-01

285

Biomasa, rendimiento, eficiencia en el uso del agua y de la radiación solar del agrosistema girasol-frijol  

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Full Text Available El estudio se realizó durante el verano de 2002 Los tratamientos consistieron en la siembra en unicultivo y combinación de frijol Canario 107, Bayomex (hábito de crecimiento determinado, Michoacán (hábito de crecimiento indeterminado y girasol cv. Victoria. La siembra se realizó el 25 de mayo de 2002 a la densidad de población de 4.2 y 8.3 plantas m-2 de girasol y frijol, respectivamente, en un suelo de textura arcillosa, con un pH de 7.8 y se fertilizó con 100-100-00 de NPK. El diseño experimental fue bloques al azar con cuatro repeticiones. El sistema de siembra no afectó la fenología, el requerimiento térmico y la evapotranspiración de ambos cultivos. Las unidades calor (UC y la evapotranspiración (ETc de los cultivos de la siembra a la madurez fisiológica fueron 1521 UC y 279.6 mm para el cv. Victoria, 658 UC y 201.3 mm para Canario 107, 811 UC y 213.7 mm para Bayomex y 1041 UC y 241.7 mm para Michoacán. El agrosistema combinado de girasol y frijol fue más eficiente en el uso de los insumos para la producción agrícola. La combinación de girasol Victoria y frijol Michoacán mostró la eficiencia en el uso del agua (EUA y eficiencia en el uso de la radiación (EUR más alta y, en consecuencia, una mayor producción de biomasa y rendimiento. El uso equivalente de la tierra (UET para el rendimiento de semilla obtenido con la combinación de Victoria más Canario 107, Victoria más Michoacán y Victoria más Bayomex fue de 1.6, 1.9 y 3.0, respectivamente, y muestra una ventaja en el rendimiento de los cultivos combinados sobre los unicultivos de 60, 90 y 200%, respectivamente.

Edgar J. Morales-Rosales

2006-01-01

286

Estimación de biomasa y carbono en dos especies de bosque mesófilo de montaña Biomass and carbon assessment in two tree species in a cloudy forest  

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Full Text Available La generación de ecuaciones alométricas es importante para determinar la biomasa y el carbono en las especies arbóreas. Esta información es útil en los estudios de cambio climático. En el presente estudio se generaron ecuaciones alométricas para dos especies de importancia ecológica en el bosque mesófilo de montaña: Clethra mexicana DC y Alnus arguta (Schltdl Spach. Las ecuaciones que se determinaron son de la forma Y= bXk; donde: Y= contenido de biomasa o de carbono (kg; y X= diámetro normal (DN en centímetros. Para estimar los valores b y k del modelo para cada especie, se realizó un muestreo de quince árboles de Clethra mexicana y 22 de Alnus arguta. En Clethra mexicana el mayor porcentaje de biomasa 45.2 % se encontró en el fuste incluido el tocón, mientras que en las ramas y el follaje estaba 36.3% y 18.6%, respectivamente. Con la biomasa y el DN de los árboles se determinaron los parámetros b y k del modelo propuesto (B= 0.4632 DN1.8168, R²= 0.946. Para Alnus arguta el mayor porcentaje de biomasa (60.6%, se encontró en el fuste incluido el tocón, mientras que en las ramas y el follaje presentó 27.4 y 12%, respectivamente. Al igual que el caso anterior con la biomasa y el DN, se obtuvieron los parámetros b y k del modelo propuesto (B= 0.1649 DN2.2755, R²= 0.968. Después de analizar el contenido de carbono en las muestra de cada especie, se ajustaron las ecuaciones para Clethra mexicana C= 22.49DN1.8168, con R²= 0.946, mientras que para Alnus arguta C= 0.0809DN2.2782 con R²= 0.968.The generation of allometric equations is important to determine biomass and carbon in tree species. This information is useful in climate change studies. In this paper, allometric equations were generated for two species of ecological importance in the cloud forest: Clethra mexicana DC and Alnus arguta (Schltdl Spach. Equations determined are of the form Y= bXk; where: Y= biomass or carbon content (kg; and X= normal diameter (ND in centimeters. To estimate model values of b and k for each species, a sampling was performed in fifteen Clethra mexicana and 22 of Alnus arguta trees. In Clethra mexicana the highest percentage of biomass 45.2% was found in the trunk including the stump, while branches and foliage had 36.3% and 18.6% respectively. With the biomass and ND of the tress, b and k parameters were determined from the proposed model (B= 0.4632 DN1.8168, R²= 0.946. For Alnus arguta the highest percentage of biomass (60.6% was found in the trunk including the stump, while branches and foliage had 27.4 and 12% respectively. Like the previous case with biomass and ND, b and k parameters were obtained from the proposed model (B= 0.1649 DN2.2755, R²= 0.968. After analyzing carbon content in each species samples, equations were adjusted for Clethra mexicana C= 22.49DN1.8168, with R²= 0.946, whereas for Alnus arguta C= 0.0809DN2.2782 with R² = 0.968.

Miguel Acosta Mireles

2011-08-01

287

E-LEARNING - INNOVATIONS IN EDUCATION OF NURSES / E-learning - inovácie vo vzdelávaní sestier  

Directory of Open Access Journals (Sweden)

Full Text Available The present requirements in nursing education lead educational institutions to preparation of the flexible forms of education, in full-time or part-time study. One of the main objectives of the university education of nurses is to provide available and relevant education for the applicants for the chosen profession to improve the personal and professional quality. In 2008/2009 the Department of Nursing at Faculty of Social Sciences and Health Care, Constantine the Philosopher University in Nitra, provides the distant form of education in applied fields of nursing through the on-line courses.Sú?asné požiadavky vo vzdelávaní sestier vedú vzdelávacie inštitúcie k príprave flexibilných foriem vzdelávania, ?i už v internom alebo externom štúdiu. K hlavným cie?om vysokoškolského vzdelávania sestier patrí poskytnutie dostupného a relevantného vzdelávania záujemcom pre danú profesiu, k preh?beniu osobných a profesionálnych kvalít. V akademickom roku 2008/2009 na Katedre ošetrovate?stva Fakulty sociálnych vied a zdravotníctva UKF v Nitre realizujeme dištan?nú formu vzdelávania v aplikovaných odborov ošetrovate?stva prostredníctvom on-line kurzov.

Solgajová Andrea

2008-10-01

288

Relative Aerial Biomass Yield of Intercroped Alfalfa with Winter Forage Cereals Rendimiento Relativo de Biomasa Aérea en Intercultivos de Alfalfa con Cereales Forrajeros de Invierno  

Directory of Open Access Journals (Sweden)

Full Text Available In the tropical regions of the world, intercropping is mostly associated with food grain production, whereas it is receiving increased attention in temperate regions as a means of efficient forage production. The aim of this work was to determine the relative yield of aerial biomass in alfalfa or lucerne (Medicago sativa L. and winter forage cereals intercrops. These were done in eight systems resulting from the combination of species sown at different dates. The biomass was measured in three situations: alfalfa and cereal sole-crop and alfalfa-cereal intercrops, the relative biomass yields were calculated by the relative yield index (RYI. The field experiment was conducted as a bifactorial array in a randomized complete block design of two replicates. The alfalfa-cereal intercrops provided RYI values ranging from 0.71 to 0.83. This showed that it is possible to produce, in the same area, between 71 and 83% of the biomass that both crops would produce in separate ones.En las regiones tropicales del mundo, el intercultivo está asociado con la producción de granos para la alimentación, mientras que en áreas templadas recibe mayor atención como medio de producción eficiente de forraje. El objetivo de este experimento fue determinar el rendimiento relativo de biomasa aérea en intercultivos de alfalfa (Medicago sativa L. y cereales forrajeros de invierno. Se establecieron ocho sistemas producto de la combinación con especies de cereales con distintas fechas de siembra. Las mediciones de biomasa se realizaron en tres situaciones: monocultivo de alfalfa, monocultivo de cereales e intercultivo de alfalfa-cereal, calculándose el rendimiento relativo del intercultivo (RRI. Se empleó un diseño con arreglo bifactorial y dos repeticiones en bloques completos al azar. Los intercultivos de alfalfa-cereal generaron valores de RRI entre 0,71 y 0,83, lo que indicó que en una misma superficie es posible producir entre el 71 y 83% de la biomasa que ambos cultivos producirían en superficies separadas.

Telmo Pereyra

2008-09-01

289

Evaluación de dos métodos para la estimación de biomasa arbórea a través de datos LANDSAT TM en Jusnajab La Laguna, Chiapas, México: estudio de caso  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish Se evaluaron dos métodos para estimar biomasa arbórea con apoyo en sensores remotos (LANDSATTM). El primer método se realizó con base en una clasificación supervisada multiespectral con seis bandas Se utilizaron tipos de vegetación identificados a partir de la composición de biomasa de los géneros d [...] ominantes y de la altura promedio estimada del dosel habiéndose distinguido ocho clases de vegetación. Se obtuvo una biomasa total de 1 073 x 10³t (902 x 10³t a 1220 x 10³t). En el segundo método se utilizaron índices diferenciados de vegetación (NDVI) de las bandas TM4/TM3; TM4/TM5 y TM4/TM7. Se aplicó un modelo de regresión que relaciona la biomasa promedio con los valores digitales (VD) de los NDVI. El modelo exponencial fue el de mejor ajuste para los tres NDVI con una p ? 0.01 Los valores de los NVDI fueron TM4/TM3: R²=0.611; TM4/TM5: R²=0.671 y TM4/TM7: R²=0.676. La biomasa total estimada con cada NDVI fue de 1 164 x 10³t (490 x 10³t a 2 409 x 10³) para TM4/TM3; de 515 x 10³1 (331 x 10³t a 757 x 10³t) para TM4/TM5 y de 726 x 10ª t (398 x 10³1 a 1 210 x 10³1) para TM4/TM7. El resultado de la biomasa total calculada por el método de clasificación multiespectral, comparado con los valores estimados por el método de ordenamiento exponencial, mostró mayor similitud con el valor máximo del NDVI que relaciona las bandas TM4/TM7 (de mayor ajuste estadístico) y con el valor promedio del NDVI TM4/TM3 (de menor ajuste estadístico). Utilizando el NDVI TM4/TM5, todos los valores de biomasa resultaron más bajos. De este estudio se concluye que es posible asociar razonablemente la biomasa de vegetación arbolada de pino-encino y reservorios de carbono con los índices de vegetación A través del uso de sensores remotos se podrían predecir cambios de biomasa en escalas temporales y espaciales. Abstract in english Two approaches to estimate arboreal biomass with remote sensing (LANDSAT TM) are evaluated In the first approach a multi-spectral supervised classification with six bands was applied The classification of the vegetation types is based on biomass composition of the dominant tree species and canopy he [...] ight. Eight vegetation types could be distinguished. According to this approach the total tree biomass amounted to 1 073 x 10³ t (902 to 1 220 x 10³t). In the second approach a Normal Differentiated Vegetation Index (NDVI) of the band combinations TM4/TM3, TM4/TM5 and TM4/TM7 was used, A regression equation was developed to relate arboreal biomass with NDVI. Using these equations, the total biomass was estimated at 1 164 x 10³ T (490 to 2 409 x 10³T) for TM4/TM3; at 515 x 10³t (331 to 757 x 10³t) for TM4/TM5 and 726 x 10³t (398 to 1 210 x 10³t) for TM4/TM7. The average biomass estimation of the NDVI using TM4rTM3 is similar to the estimation using the classification approach, but the 95% confidence Interval is wider. Meanwhile, the biomass estimation of the NDVI using TM4/TMI5 and TM4/TM7 was lower than the biomass estimation from the classification approach, but both showed a narrow 95% confidence interval. The results of this study Indicate that it is possible to estimate within a reasonable confidence interval the tree biomass of pine-oak forest using an ordination approach with NDVI As such, remote sensing could be used to estimate temporal and spatial changes in aboveground biomass.

Escandón Calderón, Jorge; Jong, Ben H. J. de; Ochoa Gaona, Susana; March Mifsut, Ignacio; Castillo, Miguel Angel.

290

Determinación de carbono orgánico total presente en el suelo y la biomasa de los páramos de las comunidades de chimborazo y shobol llinllin en Ecuador  

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Full Text Available En la determinación del contenido de carbono orgánico total presente en el suelo y la biomasa (cobertura vegetal de los páramos de las comunidades de Chimborazo, con 210ha de páramo cuya ubicación es 746667UTM-9825400UTM, y Shobol Llinllín, con 350 ha de páramo, 754680UTM–9854678UTM, pertenecientes a San Juan en Ecuador, se seleccionaron 9 puntos de muestreo de acuerdo a la variación, características y altitud del suelo, repartidos para este estudio en tres pisos altitudinales comprendidos, para el páramo de la comunidad Chimborazo, entre 3600-3900 msnm y, en el caso de Shobol Llinllín, entre 3600-3950 msnm.

M. Echeverría

2013-01-01

291

Estimación de la biomasa foliar de Prosopis flexuosa mediante relaciones alométricas Estimation of leaf biomass in Prosopis flexuosa by means of allometric relationships  

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Full Text Available La estimación alométrica de la biomasa foliar arbórea es necesaria para determinar la producción primaria y para analizar algunas de las interacciones ecológicas entre los árboles y los demás componentes de la vegetación. El objetivo del trabajo fue ajustar y seleccionar modelos para estimar la biomasa foliar de Prosopis flexuosa a partir de variables dendrométricas. Se apearon seis árboles, se midió su diámetro y se calculó el área de albura de muestras transversales de leño, en cuatro niveles: en los órdenes de ramificación dentro de la copa viva (ramas secundarias, terciarias y cuaternarias agrupadas, en el extremo distal de las ramas primarias y en los extremos distal y basal del fuste. Se recolectaron las hojas correspondientes a cada nivel y se obtuvo el peso seco. El área de albura fue la mejor variable predictora de biomasa foliar, aunque el diámetro tuvo buen ajuste en ramas dentro de la copa viva y en ramas primarias. Los modelos calculados con variables de fuste tuvieron menor ajuste. Se concluye que para la estimación no destructiva de la biomasa foliar de plantas adultas de Prosopis flexuosa es recomendable utilizar el modelo basado en el diámetro distal de las ramas primarias.The estimation of leaf biomass, usually performed by alometric relations, is important for the interpretation of primary production and for the assessment of ecological interactions between trees and the rest of the components in a wood vegetation. The goal for the present work was to adjust and to select allometric models for the estimation of leaf biomass Prosopis flexuosa based on dendrometric variables. Six trees were surveyed. The diameter and sapwood area of transversal samples of wood were determined at four different levels: in the orders of ramification within living crown (secondary, tertiary and quaternary grouped branches, at the distal portions of primary branches and in the apical and basal portions of bole. The leaves were collected according to each level and dry mass was obtained. The sapwood area was the best predictor of leaf biomass, although diameter provided accurate estimations within crown and at the distal portions of primary branches. The models based on trunk dimensions were less precise. It is concluded that the obtained regression model based on the diameter of the distal portions of primary branches can be applied for the non-destructive estimation of leaf biomass in Prosopis flexuosa adult trees.

M. Ledesma

2010-12-01

292

High quality diesel fuels by VO-LSGO hydrotreatment  

Energy Technology Data Exchange (ETDEWEB)

The aim of the paper is to obtain a high quality Diesel fuel by hydro-deoxigenation of vegetable oils (VO) mixed with a low sulfur gasoil (LSGO). The process is possible by using a bi-functional catalyst Ni-Mo supported by an activated Al{sub 2}O{sub 3} containing 2% Ultrastable Y-zeolite. The experimental conditions were: T =340 - 380 C, Pressure = 50 bar, LHSV = 1,5 h{sup -1}, H{sub 2}/Feed ratio = 15 mole H{sub 2} /mole liquid feed. The liquid product was separated in two fractions: a light distillate (similar to gasoline) and a heavy distillate (boiling point > 200 C) with very good characteristics for Diesel engines. The reaction chemistry is very complex, but the de-oxygenation process is decisive for the chemical structure of hydrocarbons from final product. Finally, a schema for the reaction mechanism is proposed. (orig.)

Stanica-Ezeanu, Dorin; Juganaru, Traian [Petroleum and Gas Univ. of Ploiesti (Romania)

2013-06-01

293

Zircon to monazite phase transition in CeVO4  

CERN Document Server

X-ray diffraction and Raman-scattering measurements on cerium vanadate have been performed up to 12 and 16 GPa, respectively. Experiments reveal that at 5.3 GPa the onset of a pressure-induced irreversible phase transition from the zircon to the monazite structure. Beyond this pressure, diffraction peaks and Raman-active modes of the monazite phase are measured. The zircon to monazite transition in CeVO4 is distinctive among the other rare-earth orthovanadates. We also observed softening of external translational Eg and internal B2g bending modes. We attributed it to mechanical instabilities of zircon phase against the pressure-induced distortion. We additionally report lattice-dynamical and total-energy calculations which are in agreement with the experimental results. Finally, the effect of non-hydrostatic stresses on the structural sequence is studied and the equations of state of different phases are reported.

Panchal, V; Santamaria-Perez, D; Errandonea, D; Manjon, F J; Rodriguez-Hernandez, P; Munoz, A; Achary, S N; Tyagi, A K

2011-01-01

294

A structured approach to VO reconfigurations through Policies  

CERN Document Server

One of the strength of Virtual Organisations is their ability to dynamically and rapidly adapt in response to changing environmental conditions. Dynamic adaptability has been studied in other system areas as well and system management through policies has crystallized itself as a very prominent solution in system and network administration. However, these areas are often concerned with very low-level technical aspects. Previous work on the APPEL policy language has been aimed at dynamically adapting system behaviour to satisfy end-user demands and - as part of STPOWLA - APPEL was used to adapt workflow instances at runtime. In this paper we explore how the ideas of APPEL and STPOWLA can be extended from workflows to the wider scope of Virtual Organisations. We will use a Travel Booking VO as example.

Reiff-Marganiec, Stephan

2012-01-01

295

Influence of dimensionality on phase transition in VO2 nanocrystals  

Directory of Open Access Journals (Sweden)

Full Text Available Hydrothermally synthesized one-dimensional and two-dimensional nanocrystals of VO2 undergo phase transition around 65°C, where temperature and mechanism of phase transition are dependent on dimensionality of nanocrystals. Both nanocrystalline samples exhibit depression of phase transition temperature compared to the bulk material, the magnitude of which depends on the dimensionality of the nanocrystal. One-dimensional nanoribbons exhibit lower phase transition temperature and higher values of apparent activation energy than two-dimensional nanosheets. The phase transition exhibits as a complex process with somewhat lower value of enthalpy than the phase transition in the bulk, probably due to higher proportion of surface atoms in the nanocrystals. High values of apparent activation energy indicate that individual steps of the phase transition involve simultaneous movement of large groups of atoms, as expected for single-domain nanocrystalline materials. [Projekat Ministarstva nauke Republike Srbije, br. 142015

Blagojevi? V.A.

2013-01-01

296

Orbital-assisted metal-insulator transition in VO$_{2}$  

CERN Document Server

We found direct experimental evidence for an orbital switching in the V 3d states across the metal-insulator transition in VO$_{2}$. We have used soft-x-ray absorption spectroscopy at the V $L_{2,3}$ edges as a sensitive local probe, and have determined quantitatively the orbital polarizations. These results strongly suggest that, in going from the metallic to the insulating state, the orbital occupation changes in a manner that charge fluctuations and effective band widths are reduced, that the system becomes more 1-dimensional and more susceptible to a Peierls-like transition, and that the required massive orbital switching can only be made if the system is close to a Mott insulating regime.

Haverkort, M W; Tanaka, A; Reichelt, W; Streltsov, S V; Korotin, M A; Anisimov, V I; Hsieh, H H; Lin, H J; Chen, C T; Khomskii, D I; Tjeng, L H

2005-01-01

297

Variação diurna e resposta da cinética do VO2 de ciclistas durante exercício muito intenso Diurnal variation and Vo2 kinetic response of cyclists during heavy exercis e  

Directory of Open Access Journals (Sweden)

Full Text Available O objetivo do presente estudo foi avaliar a influência da hora do dia nos parâmetros da cinética do consumo de oxigênio de ciclistas durante exercício muito intenso. Nove voluntários do sexo masculino realizaram exercícios de carga constante às 08:00, 13:00 e 18:00 h, em dias diferentes. Estes exercícios foram realizados duas vezes em cada visita, com um intervalo de 1 h entre eles. A intensidade usada foi de 75%? (75% da diferença entre o VO2 no limiar de lactato e o VO2max. A amplitude do componente primário do VO2 (2597 ± 273 ml.min-1, 2513 ± 268 ml.min-1 e 2609 ± 370 ml.min-1, a constante de tempo do componente primário do VO2 (19.3 ± 2.5 s, 18.4 ± 3.0 s e 19.7 ± 3.9 s, o componente lento do VO2 (735 ± 81 ml.min-1, 764 ± 99 ml.min-1 e 680 ± 121 ml.min-1 e o tempo de resposta média (51.8 ± 4.2 s, 51.2 ± 4.2 s e 51.4 ± 3.4 s não apresentaram diferenças significativas entre os diferentes horários do dia (08:00, 13:00 e 18:00 h, assim como os demais parâmetros da cinética do VO2. Estes resultados sugerem que a resposta da cinética do VO2 de ciclistas durante exercício muito intenso (75%? não é influenciada pela hora do dia.The objective of the present study was to evaluate the influence of the time of day on the parameters of oxygen uptake kinetics of trained cyclists during high intensity exercise. Nine male volunteers repeated bouts at constant loads at 08:00, 13:00 and 18:00 h on different days. These exercise bouts were performed twice on each occasion, with an interval of 1 h between them. The load intensity used was 75%? (75% of the difference between the VO2 at the lactate threshold and the VO2max. The primary VO2 amplitude (2597 ± 273 ml.min-1, 2513 ± 268 ml.min-1 and 2609 ± 370 ml.min-1, the primary VO2 time constant (19.3 ± 2.5 s, 18.4 ± 3.0 s and 19.7 ± 3.9 s, the VO2 slow component (735 ± 81 ml.min-1, 764 ± 99 ml.min-1 and 680 ± 121 ml.min-1 and the mean response time (51.8 ± 4.2 s, 51.2 ± 4.2 s and 51.4 ± 3.4 s did not present significant differences at the different times (08:00, 13:00 and 18:00 h, neither did the other parameters of the VO2 kinetics. These results suggest that the response of the VO2 kinetics of cyclists exercising at high intensity (75%? is not influenced by the time of day.

Marcos G. Santana

2008-06-01

298

Un modelo simple para describir la dinámica de la biomasa del camarón nailon Heterocarpus reedi en Coquimbo, Chile A simple model for describing the biomass dynamics of the nylon shrimp Heterocarpus reedi at Coquimbo, Chile  

Directory of Open Access Journals (Sweden)

Full Text Available RESUMEN. Entre septiembre de 1997 y agosto de 2000 se realizó un seguimiento diario de la dinámica espacial y temporal de la CPUE (ton·lance-1 de camarón nailon por parte de la flota arrastrera con puerto base en Coquimbo. Se construyó un modelo de remoción de biomasa modificado para explicar las variaciones temporales de la CPUE basado en los conceptos de abundancia (biomasa total poblacional y disponibilidad (biomasa que puede ser potencialmente capturada. Ambas cantidades fueron calculadas por ecuaciones, cuyas diferencias (positivas o negativas indicaron los cambios en la disponibilidad de la biomasa a través del tiempo y el reclutamiento (magnitud y temporalidad. El modelo modificado indicó dos períodos anuales de distinta longitud en la disponibilidad de biomasa al arte de pesca. También indicó una tasa de reducción más acelerada para la biomasa que para la CPUE. Los resultados pueden influir en la determinación de la época óptima para la realización de las evaluaciones directas del recurso con fines de determinar cuotas de capturaA daily record of space/time dynamics was carried out on CPUE (ton·trawl-1 for the nylon shrimp trawl fishery based at Coquimbo, Chile, between September 1997 and August 2000. A modified biomass depletion model was constructed to analyze the temporal variations in CPUE based on the concepts of abundance (total population biomass and availability (potential biomass capture. Both quantities were calculated by equations whose differences (positive and negative indicated the changes in availability of biomass over time, as well as recruitmernt (magnitude and seasonality. The modified model suggested there were two periods annually, of different lengths, and different biomasses available with the fishing gear. The model also indicated a more rapid rate of reduction in biomass than did the CPUE. The results could influence the determination of the best season for carrying out direct resource evaluations aimed at determining catch quotas

Eduardo P. Pérez

2005-11-01

299

Controlled synthesis of VO{sub 2}(R), VO{sub 2}(B), and V{sub 2}O{sub 3} vanadium-oxide nanowires  

Energy Technology Data Exchange (ETDEWEB)

Vanadium-oxide nanowires (NWs) V{sub 2}O{sub 5}, VO{sub 2}(R), VO{sub 2}(B), and V{sub 2}O{sub 3} are deposited on a substrate to study their field-emission properties. V{sub 2}O{sub 5} NWs are prepared by thermal evaporation via vapor transport of a vanadium-oxide complex under mild conditions. Films of VO{sub 2} and V{sub 2}O{sub 3} wires are subsequently prepared by reducing V{sub 2}O{sub 5} one-dimensional nanocrystals at 450 Degree-Sign C with hydrogen gas. The composition of the flowing H{sub 2}/Ar mixture and the duration of reduction are utilized to control the formation of VO{sub 2}(R) or VO{sub 2}(B) NWs. The crystallinity and morphology of products as prepared are characterized using several techniques, including powder X-ray diffraction, a scanning electron microscope, and a transmission electron microscope. The field-emission properties of the vanadium-oxide NWs as prepared exhibit a turn-on field of 4.56-7.65 V/{mu}m and an emission current density up to 3.68-8.36 mA/cm{sup 2}. These features indicate that vanadium-oxide NWs have potential FE emitter applications.Graphical AbstractV{sub 2}O{sub 5}, VO{sub 2}(R), VO{sub 2}(B), and V{sub 2}O{sub 3} NWs were synthesized via thermal evaporation and controlled reduction process. Field-emission properties of these NWs exhibited turn-on fields of 4-8 V/{mu}m, an emission current density up to 3.5 mA/cm{sup 2}.

Ke, Jhih-Syuan; Weng, Sheng-Feng; Wu, Ming-Cheng; Lee, Chi-Shen, E-mail: chishen@mail.nctu.edu.tw [National Chiao Tung University, Department of Applied Chemistry (China)

2013-07-15

300

Physiochemical studies on the composition and stability of the complexes of VO(II) and UO2(II) with L-lysinemono-hydrochloride  

International Nuclear Information System (INIS)

The VO(II) and UO2(II) form 1:1 and 1:2 complexes with L-lysine monohydrochloride [NH2(CH2)4 CH(NH2) COOH HCl]. Calvin and Melchior's extension of Bjerrum method as modified by Irving and Rossotti have been used for the determination of stability constant at 30 degC and 40 degC at a constant ionic strength (?=0.1M NaClO4). These values were further refined by 'Least Square Method' and 'Schroder's Convergence Formula'. The thermodynamic parameters DELTAG, DELTAH and DELTAS have been also evaluated and their importance in complexation has been discussed. (author)

1981-01-01

 
 
 
 
301

o-Iminobenzosemiquinonate and o-imino-p-methylbenzosemiquinonate anion radicals coupled VO2+ stabilization.  

Science.gov (United States)

The diamagnetic VO(2+)-iminobenzosemiquinonate anion radical (L(R)(IS)(•-), R = H, Me) complexes, (L(-))(VO(2+))(L(R)(IS)(•-)): (L(1)(-))(VO(2+))(L(H)(IS)(•-))•3/2MeOH (1•3/2MeOH), (L(2)(-))(VO(2+))(L(H)(IS)(•-)) (2), and (L(2)(-))(VO(2+))(L(Me)(IS)(•-))•1/2 L(Me)(AP) (3•1/2 L(Me)(AP)), incorporating tridentate monoanionic NNO-donor ligands {L = L(1)(-) or L(2)(-), L(1)H = (2-[(phenylpyridin-2-yl-methylene)amino]phenol; L(2)H = 1-(2-pyridylazo)-2-naphthol; L(H)(IS)(•-) = o-iminobenzosemiquinonate anion radical; L(Me)(IS)(•-) = o-imino-p-methylbenzosemiquinonate anion radical; and L(Me)(AP) = o-amino-p-methylphenol} have been isolated and characterized by elemental analyses, IR, mass, NMR, and UV-vis spectra, including the single-crystal X-ray structure determinations of 1•3/2MeOH and 3•1/2 L(Me)(AP). Complexes 1•3/2MeOH, 2, and 3•1/2 L(Me)(AP) absorb strongly in the visible region because of intraligand (IL) and ligand-to-metal charge transfers (LMCT). 1•3/2MeOH is luminescent (?(ext), 333 nm; ?(em), 522, 553 nm) in frozen dichloromethane-toluene glass at 77 K due to ?(diimine?)?(diimine)* transition. The V-O(phenolato) (cis to the V?O) lengths, 1.940(2) and 1.984(2) Å, respectively, in 1•3/2MeOH and 3•1/2 L(Me)(AP) are consistent with the VO(2+) description. The V-O(iminosemiquinonate) (trans to the V?O) lengths, 2.1324(19) in 1•3/2MeOH and 2.083(2) Å in 3•1/2 L(Me)(AP), are expectedly ?0.20 Å longer due to the trans influence of the V?O bond. Because of the stronger affinity of the paramagnetic VO(2+) ion to the L(H)(IS)(•-) or L(Me)(IS)(•-), the V-N(iminosemiquinonate) lengths, 1.908(2) and 1.921(2) Å, respectively, in 1•3/2MeOH and 3•1/2 L(Me)(AP), are unexpectedly shorter. Density functional theory (DFT) calculations using B3LYP, B3PW91, and PBE1PBE functionals on 1 and 2 have established that the closed shell singlet (CSS) solutions (VO(3+)-amidophenolato (L(R)(AP)(2-)) coordination) of these complexes are unstable with respect to triplet perturbations. But BS (1,1) M(s) = 0 (VO(2+)-iminobenzosemiquinonate anion radical (L(R)(IS)(•-)) coordination) solutions of these species are stable and reproduce the experimental bond parameters well. Spin density distributions of one electron oxidized cations are consistent with the [(L(-))(VO(2+))(L(R)(IQ))](+) descriptions [VO(2+)-o-iminobenzoquinone (L(R)(IQ)) coordination], and one electron reduced anions are consistent with the [(L(•2-))(VO(3+))(L(R)(AP)(2-))](-) descriptions [VO(3+)-amidophenolato (L(R)(AP)(2-)) coordination], incorporating the diimine anion radical (L(1)(•2-)) or azo anion radical (L(2)(3-)). Although, cations and anions are not isolable, but electro-and spectro-electrochemical experiments have shown that 3(+) and 3(-) ions are more stable than 1(+), 2(+) and 1(-), 2(-) ions. In all cases, the reductions occur with simultaneous two electron transfer, may be due to formation of coupled diimine/azo anion radical-VO(2+) species as in [(L(•2-))(VO(2+))(L(R)(AP)(2-))](2-). PMID:21348449

Roy, Amit Saha; Saha, Pinaki; Adhikary, Nirmal Das; Ghosh, Prasanta

2011-03-21

302

Reinvestigation of the synthesis of LiFeVO{sub 4}  

Energy Technology Data Exchange (ETDEWEB)

Highlights: {yields} We reinvestigated the synthesis of the LiFeVO{sub 4} compound. {yields} We demonstrate that the recently reported LiFeVO{sub 4} phase is not a pure phase. {yields} We proved by Rietveld refinement that LiFeVO{sub 4} is a mixture ofLiVO{sub 3} and Fe{sub 2}O{sub 3}. {yields} We noticed some attempts to fraud (modification of the powder pattern) . - Abstract: The synthesis of LiFeVO{sub 4} composition has been performed in air starting from Li{sub 2}CO{sub 3}, Fe{sub 2}O{sub 3}, and V{sub 2}O{sub 5} and using the standard solid-state reaction route reported by Refs. . Identical X-ray diffraction pattern has been obtained, however our careful analysis with MDI Jade 5.0 software does not agree with previously reported pure LiFeVO{sub 4} samples. The powder pattern has been perfectly indexed using the single crystal data of LiVO{sub 3} (C2/c, a = 10.16718 A, b = 8.415725 A, c = 5.884155 A and {beta} = 110.489{sup o}) and {alpha}-Fe{sub 2}O{sub 3} (R-3c, a = 5.035 A, c = 13.75 A).

Yahia, Hamdi Ben, E-mail: benyahia.hamdi@aist.go.jp [Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan); Shikano, Masahiro; Tatsumi, Kuniaki [Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan)

2011-07-15

303

BiVO4–graphene catalyst and its high photocatalytic performance under visible light irradiation  

International Nuclear Information System (INIS)

Highlights: ? A facile strategy is designed to deposit leaf-like BiVO4 lamellas on graphene sheet. ? Graphene oxide is reduced to graphene in the hydrothermal reaction process. ? BiVO4–graphene system shows high catalytic effects under visible light irradiation. - Abstract: A BiVO4–graphene photocatalyst was prepared by a facile one-step hydrothermal method and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectra (XPS), and transmission electron microscopy (TEM) techniques. The results show that the graphene sheets in this catalyst are exfoliated and decorated by leaf-like BiVO4 lamellas. In comparison with the pure BiVO4 catalyst, the BiVO4–graphene system reveals much higher photocatalytic activity for degradation of methyl orange (MO), methylene blue (MB), Rhodamine B (RhB) and active black BL-G in water under visible light irradiation due to the concerted effects of BiVO4 and graphene sheets or their integrated properties.

2011-12-15

304

Experimental Analysis of VoIP over Wireless Local Area Networks  

Directory of Open Access Journals (Sweden)

Full Text Available

VoIP is a rapidly growing technology that enables the transport of voice over data networks such asthe public Internet. VoIP became a viable alternative to the public switched telephone networks (PSTNs. In parallel, a dramatic increase is happening in the deployment of Wireless Local Areas Networks (WLAN in buildings and corporate campuses. Nowadays, WLAN is mostly used for ordinary data services such as web browsing, file transfer and electronic mail. However, with the emerging usage of VoIP telephony, WLAN are sought to be used as an access infrastructure for enabling such applications. One of the issues of using VoIP over WLAN is the effects caused by users roaming within and between WLAN subnets during a VoIP session. The latency and the jitter are greatly impacted when the control of the mobile node is handed over from one access point (AP to another one. This poses a challenge to providing and preserving QoS for VoIP users in WLAN environments. In this paper, we propose to study and measure the effect of the handover for both intra and inter mobility for VoIP traffic.

Mohammed Boulmalf

2007-06-01

305

Effects of erythrocyte infusion on VO2max at high altitude  

DEFF Research Database (Denmark)

This study investigated whether autologous erythrocyte infusion would ameliorate the decrement in maximal O2 uptake (VO2max) experienced by lowlanders when they ascend to high altitude. VO2max was measured in 16 men (treadmill running) at sea level (SL) and on the 1st (HA1) and 9th (HA9) days of high-altitude (4,300 m) residence. After VO2max was measured at SL, subjects were divided into two matched groups (n = 8). Twenty-four hours before ascent to high altitude, the experimental group received a 700-ml infusion of autologous erythrocytes and saline (42% hematocrit), whereas the control group received only saline. The VO2max of erythrocyte-infused [54 +/- 1 (SE) ml.kg-1.min-1] and control subjects (52 +/- 2 ml.kg-1.min-1) did not differ at SL before infusion. The decrement in VO2max on HA1 did not differ between groups, averaging 26% overall, despite higher (P <0.01) arterial hematocrit, hemoglobin concentration, and arterial O2 content in the erythrocyte-infused subjects. By HA9, there were no longer any differences in hematocrit, hemoglobin concentration, or arterial O2 content between groups. No change in VO2max occurred between HA1 and HA9 for either group. Thus, despite increasing arterial O2-carrying capacity, autologous erythrocyte infusion did not ameliorate the decrement in VO2max at 4,300-m altitude.

Young, Jette Feveile; Sawka, M N

1996-01-01

306

EPR and UV studies of VO2+ ions in potassium D-gluconate monohydrate single crystals  

International Nuclear Information System (INIS)

Electron paramagnetic resonance (EPR) of VO2+ doped potassium hydrogen D-gluconate single crystals and powder have been examined at room temperature. Single crystal rotations in each of the three mutually orthogonal crystalline planes namely ac, ba and ca indicate two different VO2+ complexes. Each complex is located in different chemical environments, each environment containing two magnetically inequivalent VO2+ sites in distinct orientations occupying substitutional positions in the lattice and showing a very large angular dependence. The powder spectrum also clearly indicates four different VO2+ complexes, confirming the single crystal analysis. Crystalline field around the VO2+ ion is nearly axial. The optical absorption spectrum of VO2+ ions in the crystal lattice is also studied at room temperature. The characteristic spectrum of the VO2+ ions has two absorption bonds. The bond positions are at 17 857 and 11 235 cm-1. Spin Hamiltonian parameters and molecular orbital coefficients are calculated from the EPR and the optical data, and results are discussed.

2009-11-01

307

EPR and UV studies of VO 2+ ions in potassium D-gluconate monohydrate single crystals  

Science.gov (United States)

Electron paramagnetic resonance (EPR) of VO 2+ doped potassium hydrogen D-gluconate single crystals and powder have been examined at room temperature. Single crystal rotations in each of the three mutually orthogonal crystalline planes namely ac, ba and ca indicate two different VO 2+ complexes. Each complex is located in different chemical environments, each environment containing two magnetically inequivalent VO 2+ sites in distinct orientations occupying substitutional positions in the lattice and showing a very large angular dependence. The powder spectrum also clearly indicates four different VO 2+ complexes, confirming the single crystal analysis. Crystalline field around the VO 2+ ion is nearly axial. The optical absorption spectrum of VO 2+ ions in the crystal lattice is also studied at room temperature. The characteristic spectrum of the VO 2+ ions has two absorption bonds. The bond positions are at 17 857 and 11 235 cm -1. Spin Hamiltonian parameters and molecular orbital coefficients are calculated from the EPR and the optical data, and results are discussed.

Yarba??, Zeynep; Karabulut, Bünyamin; Karabulut, Abdulhalik

2009-11-01

308

Handover Management for VoWLAN Based on Estimation of AP Queue Length and Frame Retries  

Science.gov (United States)

Switching a communication path from one Access Point (AP) to another in inter-domain WLANs is a critical challenge for delay-sensitive applications such as Voice over IP (VoIP) because communication quality during handover (HO) is more likely to be deteriorated. To maintain VoIP quality during HO, we need to solve many problems. In particular, in bi-directional communication such as VoIP, an AP becomes a bottleneck with the increase of VoIP calls. As a result, packets queued in the AP buffer may experience a large queuing delay or packet losses due to increase in queue length or buffer overflow, thereby causing the degradation of VoIP quality for the Mobile Nodes (MNs) side. To avoid this degradation, MNs need to appropriately and autonomously execute HO in response to the change in wireless network condition, i.e., the deterioration of wireless link quality and the congestion state at the AP. In this paper, we propose an HO decision strategy considering frame retries, AP queue length, and transmission rate at an MN for maintaining VoIP quality during HO. Through simulation experiments, we then show that our proposed method can maintain VoIP quality during HO by properly detecting the wireless network condition.

Niswar, Muhammad; Kashihara, Shigeru; Tsukamoto, Kazuya; Kadobayashi, Youki; Yamaguchi, Suguru

309

Pacing strategy and VO2 kinetics during a 1500-m race.  

Science.gov (United States)

We investigated the oxygen uptake response (V.O (2)) to a 1500-m test conducted using a competition race strategy. On an outdoor track, eleven middle-distance runners performed a test to determine V.O (2max), velocity associated with V.O (2max) (v-V.O (2max)) and a supramaximal 1500-m running test (each test at least two days apart). V.O (2max) response was measured with the use of a miniaturised telemetric gas exchange system (Cosmed, K4, Roma, Italy). The 1500-m running test was performed at a mean velocity of 107. 6 + 2 % v-V.O (2max). The maximal value of oxygen uptake recorded during the 1500-m test (V.O (2peak)) was reached by subjects at 75.9 + 7.5 s (mean + SD) (i.e., 459 +/- 59 m). The time to reach V.O (2max) (TV.O (2peak)) and the start velocity (200- to 400-m after the onset of the 1500 m) expressed in % v-V.O (2max) were negatively and significantly correlated (p < 0.05), but our results indicate that a fast start does not necessarily induce a good performance. These results suggest that V.O (2max) is reached by all the subjects at the onset of a simulated 1500-m running event and are therefore in contrast with previous results obtained during treadmill running. PMID:17990206

Hanon, C; Leveque, J-M; Thomas, C; Vivier, L

2008-03-01

310

Facile fabrication of an efficient BiVO4 thin film electrode for water splitting under visible light irradiation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An efficient BiVO4 thin film electrode for overall water splitting was prepared by dipping an F-doped SnO2 (FTO) substrate electrode in an aqueous nitric acid solution of Bi(NO3)3 and NH4VO3, and subsequently calcining it. X-ray diffraction of the BiVO4 thin film revealed that a photocatalytically active phase of scheelite-monoclinic BiVO4 was obtained. Scanning electron microscopy images showed that the surface of an FTO substrate was uniformly coated with the BiVO4 film with 300–400 nm o...

2012-01-01

311

The substitution of cations by magnesium in the structure K3Ho(VO4)2  

International Nuclear Information System (INIS)

The cation substitutions in the crystal lattice of binary potassium-holmium vanadate (V) K3Ho(VO4)2 by magnesium have been studied using various types of chemical solid state reactions. It was shown that in the presence of the quasi-ternary system K3VO4-Mg3(VO4)2-HoVO4 at 700 C there a compound defined as K3Ho(VO4)2 with a narrow homogeneity range where K and Ho are partially substituted by Mg in accordance with various schemes. (orig.)

1998-07-24

312

Epitaxial growth and characterization of CaVO3 thin films  

International Nuclear Information System (INIS)

Epitaxial thin films of CaVO3 were synthesized on SrTiO3, LaAlO3 and (La0.27Sr0.73)(Al0.65Ta0.35)O3 substrates by pulsed laser deposition. All CaVO3 films, independent of epitaxial strain, exhibit metallic and Pauli paramagnetic behavior as CaVO3 single crystals. X-ray absorption measurements confirmed the 4+ valence state for Vanadium ions. With prolonged air exposure, an increasing amount of V3+ is detected and is attributed to oxygen loss in the near surface region of the films.

2009-09-01

313

Predictability of VO2 max from submaximal cycle ergometer and bench stepping tests.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The predictability of the maximal oxygen uptake (VO2 max) was studied using progressive and steady state protocols for cycle ergometry and bench stepping. The subjects were 12 healthy men, 23-58 years old. Prediction of VO2 max was made by extrapolation of the heart rate and O2 uptake at several sub-maximal work-loads using the least squares regression technique. The four sub-maximal procedures underestimated the measured VO2 max by between 0.13-0.55 l.min-1. The differences between the measu...

Fitchett, M. A.

1985-01-01

314

Intermediate metallic phase in VO2 observed with scanning tunneling spectroscopy.  

Science.gov (United States)

This investigation focuses on the formation of nanoscale puddles of an intermediate metallic phase (IMP) in the metal-insulator transition (MIT) temperature regime of single-crystalline vanadium dioxide (VO2) nanowires. The electronic structure of VO2 nanowires was examined with scanning tunneling spectroscopy. The evolution of the local density of states of individual nanowires throughout the MIT regime is presented with differential tunneling conductance spectra and images measured as the temperature was increased. Our results show that the formation of an IMP plays an important role in the MIT of intrinsic VO2. PMID:24909228

Hatch, John Byron; Whittaker-Brooks, Luisa; Wu, Tai-Lung; Long, Gen; Zeng, Hao; Sambandamurthy, G; Banerjee, Sarbajit; Luo, Hong

2014-07-21

315

Influence of prior exercise on VO2 kinetics subsequent exhaustive rowing performance.  

Science.gov (United States)

Prior exercise has the potential to enhance subsequent performance by accelerating the oxygen uptake (VO2) kinetics. The present study investigated the effects of two different intensities of prior exercise on pulmonary VO2 kinetics and exercise time during subsequent exhaustive rowing exercise. It was hypothesized that in prior heavy, but not prior moderate exercise condition, overall VO2 kinetics would be faster and the VO2 primary amplitude would be higher, leading to longer exercise time at VO2max. Six subjects (mean ± SD; age: 22.9±4.5 yr; height: 181.2±7.1 cm and body mass: 75.5±3.4 kg) completed square-wave transitions to 100% of VO2max from three different conditions: without prior exercise, with prior moderate and heavy exercise. VO2 was measured using a telemetric portable gas analyser (K4b(2), Cosmed, Rome, Italy) and the data were modelled using either mono or double exponential fittings. The use of prior moderate exercise resulted in a faster VO2 pulmonary kinetics response (?1?=?13.41±3.96 s), an improved performance in the time to exhaustion (238.8±50.2 s) and similar blood lactate concentrations ([La(-)]) values (11.8±1.7 mmol.L(-1)) compared to the condition without prior exercise (16.0±5.56 s, 215.3±60.1 s and 10.7±1.2 mmol.L(-1), for ?1, time sustained at VO2max and [La(-)], respectively). Performance of prior heavy exercise, although useful in accelerating the VO2 pulmonary kinetics response during a subsequent time to exhaustion exercise (?1?=?9.18±1.60 s), resulted in a shorter time sustained at VO2max (155.5±46.0 s), while [La(-)] was similar (13.5±1.7 mmol.L(-1)) compared to the other two conditions. Although both prior moderate and heavy exercise resulted in a faster pulmonary VO2 kinetics response, only prior moderate exercise lead to improved rowing performance. PMID:24404156

Sousa, Ana; Ribeiro, João; Sousa, Marisa; Vilas-Boas, João Paulo; Fernandes, Ricardo J

2014-01-01

316

Theoretical investigation of the optical and EPR parameters for VO 2+ion in some complexes  

Science.gov (United States)

The molecular orbital coefficients and the EPR parameters of trisodium citrate dihydrate, sodium hydrogen oxalate monohydrate, potassium d-gluconate monohydrate and L-Alanine vanadyl complexes are calculated theoretically. Two d-d transition spectra and EPR parameters for the VO 2+ complex are calculated theoretically by using crystal-field theory. The calculated g and A paramaters have indicated that paramagnetic center is axially symmetric. Having the relations of g?A? for VO 2+ ions, it can be concluded that VO 2+ ions are located in distorted octahedral sites (C 4 v) elongated along the z-axis and the ground state of the paramagnetic electron is dxy.

Kalfao?lu, Emel; Karabulut, Bünyamin

2012-04-01

317

Synthesis and characterization of VO2-based thermochromic thin films for energy-efficient windows  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Thermochromic VO2 thin films have successfully been grown on SiO2-coated float glass by reactive DC and pulsed-DC magnetron sputtering. The influence of substitutional doping of V by higher valence cations, such as W, Mo, and Nb, and respective contents on the crystal structure of VO2 is evaluated. Moreover, the effectiveness of each dopant element on the reduction of the intrinsic transition temperature and infrared modulation efficiency of VO2 is discussed. In summary, all the dopant elemen...

Batista, C.; Ribeiro, R. M.; Teixeira, Vasco M. P.

2011-01-01

318

Morphology-dependent photocatalytic removal of NO by hierarchical BiVO4 microboats and microspheres under visible light  

Science.gov (United States)

In this study, hierarchical monoclinic BiVO4 three-dimensional (3D) superstructures with two kinds of morphologies, namely BiVO4 microboats and BiVO4 microspheres, have been controllably synthesized by adjusting reaction time in the template-free hydrothermal process using ethylene glycol as solvent. The nucleation, growth, and self-assembly of the BiVO4 superstructures could be readily controlled with reaction time, which brought different morphologies to the final product. The as-prepared BiVO4 superstructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption experimentation, and UV-vis diffuse reflectance spectra (UV-vis DRS). The monoclinic 3D BiVO4 catalysts are composed of two-dimensional (2D) nanoplates which intercross with each other. Nanoplates were firstly formed by aggregation of primary nanocrystallites and then self-assembly converted to microboats and microspheres via the oriented attachment mechanism. The prepared BiVO4 3D catalysts can respond to visible light and their optical and photocatalytic properties are relevant to their morphologies. The BiVO4 microspheres showed superior photocatalytic activity on removal of gaseous NO compared to the BiVO4 microboats. The morphology-dependent photocatalytic property of the BiVO4 superstructures is discussed. This work suggests that the synthesized BiVO4 micropheres are promising photocatalyst for environmental remediation.

Ai, Zhihui; Lee, Shuncheng

2013-09-01

319

Study on Thermochromic VO2 Films Grown on ZnO-Coated Glass Substrates for “Smart Windows”  

Science.gov (United States)

Vanadium dioxide (VO2) is one of the most attractive thermochromic materials, which show large changes in optical and electrical properties at the transition temperature (Tt) close to the atmospheric temperature (approximately 340 K). We already reported for VO2 deposition by rf magnetron sputtering using V2O3 or V2O5 targets that VO2 films thicker than 400 nm showed high thermochromic performance, whereas the VO2 films thinner than 200 nm did not show such performance because of their poor crystallinity and off-stoichiometry. In this study, very thin thermochromic VO2 films with thicknesses of about 50 nm were successfully deposited using highly -preferred oriented ZnO polycrystalline films as a buffer layer between the VO2 film and glass substrate (VO2/ZnO/glass) because of the heteroepitaxial growth of VO2 polycrystalline films. W-doped VO2 films were also deposited on the ZnO-coated glass substrates (ZnO/glass) by cosputtering. It was confirmed that W doping for thin VO2 films deposited on the ZnO/glass can decrease Tt systematically. Such very thin VO2 films should have high potential for application in “smart windows”.

Kato, Kazuhiro; Song, Pung Keun; Odaka, Hidehumi; Shigesato, Yuzo

2003-10-01

320

Producción de biomasa y rendimiento de semilla en la asociación girasol (Helianthus annuus L.-frijol (Phaseolus vulgaris L. en función del nitrógeno y fósforo  

Directory of Open Access Journals (Sweden)

Full Text Available En 2003 se realizó un estudio en Montecillo, Estado de México, para determinar el efecto de la aplicación de nitrógeno (0, 40 y 80 kg ha?1 y fósforo (0, 30 y 60 kg P2O5 ha?1 en la siembra combinada de girasol (cv. Victoria y frijol (cv. Michoacán. Con el suministro de 80 kg N ha?1 (80 ? 00 ? 00 se incrementó la producción de biomasa y rendimiento de semilla superando al testigo sin fertilizante en 32% y 35%. Cuando se adicionaron 60 kg P2O5 ha?1 (00 ? 60 ? 00 se obtuvo una producción de materia seca y rendimiento de semilla superior al testigo en 24 y 27%, respectivamente. Aunque la interacción nitrógeno x fósforo no fue significativa, existió una tendencia positiva a medida de que se incrementaron los niveles de nitrógeno y fósforo (80 ? 60 ? 00, alcanzando los máximos valores en la producción de biomasa (2667.9 g m?2 y rendimiento de semilla (644.6 g m?2, los cuales superaron en 49 y 50% al testigo sin fertilizante.

J. Antonio López Sandoval

2007-01-01

 
 
 
 
321

Método basado en teledetección para estimar la emisión de gases efecto invernadero por quema de biomasa A remote sensing method to estimate greenhouse gas emissions from biomass burning  

Directory of Open Access Journals (Sweden)

Full Text Available La quema de biomasa es una fuente importante de gases efecto invernadero en países en vías de desarrollo. En Colombia, el cambio de uso del suelo, la silvicultura y el sector agropecuario superan el 50% de las emisiones totales de efecto invernadero. El fuego se utiliza con frecuencia como un mecanismo para cambiar el uso del suelo. Los Llanos orientales y la Amazonía colombiana están sometidos todos los años a la quema de biomasa, especialmente entre enero y marzo. Los estudios en la distribución espacial y temporal de las emisiones son importantes de cara a los informes en el ámbito nacional. Este artículo de revisión describe el método para hacer estas estimaciones utilizando teledetección y algunos de los resultados disponibles para Colombia.Biomass burning is a major source of greenhouse gas emissions in developing countries. In Colombia, land use change, forestry and agriculture are responsible for more than 50% of the total greenhouse gas emissions. Fire is commonly used as a mechanism for land use change. In Colombia the Llanos Orientales and the Amazonia are subject to biomass burning every year during the dry season, especially from January to March. Studies of the spatial and temporal distribution of emissions are required for emissions report at a national level. The goal of this state of the art article is to describe a method to estimate emissions with a remote sensing approach and to present some of the variables already measured in Colombia.

Jesús Adolfo Anaya Acevedo

2011-01-01

322

Predictors of VO2Peak in children age 6- to 7-years-old  

DEFF Research Database (Denmark)

This study investigated the predictors of aerobic fitness (VO2PEAK) in young children on a population-base. Participants were 436 children (229 boys and 207 girls) aged 6.7 ± 0.4 yrs. VO2PEAK was measured during a maximal treadmill exercise test. Physical activity was assessed by accelerometers. Total body fat and total fat free mass were estimated from skinfold measurements. Regression analyses indicated that significant predictors for VO2PEAK per kilogram body mass were total body fat, maximal heart rate, sex, and age. Physical activity explained an additional 4-7%. Further analyses showed the main contributing factors for absolute values of VO2PEAK were fat free mass, maximal heart rate, sex, and age. Physical activity explained an additional 3-6%.

Hermansen, Bianca; Bugge, Anna

2011-01-01

323

LaVo4: Eu Phosphor Films with Enhanced Eu Solubility  

Energy Technology Data Exchange (ETDEWEB)

Eu doped rare-earth orthovanadates are known to be good red phosphor materials. In particular, LaVO{sub 4}:Eu is a promising candidate due to the low Eu-site point symmetry, and thus high dipole transition probability within Judd-Ofelt theory. However, the low solubility limit (< 3 mol %) of Eu in LaVO{sub 4} prevents its efficient use as a phosphor. We present optical evidence of enhanced Eu solubility as high as 10 mol % in LaVO{sub 4}:Eu thin films grown by pulsed laser deposition and postannealing. The photoluminescent intensity exceeded that of YVO{sub 4}:Eu thin films when excited below the host bandgap, indicating stronger direct emission of Eu in LaVO{sub 4}.

Hwang, Harold

2011-08-11

324

Effects of porous nano-structure on the metal-insulator transition in VO2 films  

Science.gov (United States)

In this work, we confirmed experimentally that the porous nano-structure of vanadium dioxide (VO2) films had significant effects on the features of the metal-insulator transition. Porous VO2 films had been synthesized on mica substrates via a simple solution process with inorganic precursor and cetyltrimethyl ammonium bromide (CTAB). SEM images showed a combination of homogenously distributed pores and VO2 nanoparticles. Metal to insulator transition (MIT) characteristics measurements revealed that, the porous nano-structure VO2 films had low transition temperature, wide hysteresis width and gentle slopes of hysteresis loop. Morphologies and MIT characteristics of the films could be controlled by simply varying CTAB concentration, which is of great importance in achieving practical applications.

Xu, Yuanjie; Huang, Wanxia; Shi, Qiwu; Zhang, Yang; Zhang, Yubo; Song, Linwei; Zhang, Yaxin

2012-10-01

325

The characteristics of Au:VO2 nanocomposite thin film for photo-electricity applications  

Science.gov (United States)

Au nanoparticles have been fabricated on normal glass substrates using nanosphere lithography (NSL) method. Vanadium dioxide has been deposited on Au/glass by reactive radio frequency (rf) magnetron sputtering. The structure and composition were determined by X-ray diffraction and X-ray photoelectron spectroscope. Electrical and optical properties of bare VO2 and Au:VO2 nanocomposite thin films were measured. Typical hysteresis behavior and sharp phase transition were observed. Nanopartical Au could effectively reduce the transition temperature to 40 °C. The transmittance spectrum for both Au:VO2 nanocomposite thin film shows high transmittance under transition temperature and low transmittance above transition temperature. The characteristics present the Au:VO2 nanocomposite thin film can be used for applications, such as “smart window” or “laser protector”.

Zhu, Yabin; Na, Jie; He, Fan; Zhou, Yueliang

2013-08-01

326

Photothermal optical modulation of ultra-compact hybrid Si-VO? ring resonators.  

Science.gov (United States)

We demonstrate photothermally induced optical switching of ultra-compact hybrid Si-VO? ring resonators. The devices consist of a sub-micron length ~70 nm thick patch of phase-changing VO? integrated onto silicon ring resonators as small as 1.5 ?m in radius. The semiconductor-to-metal transition (SMT) of VO? is triggered using a 532 nm pump laser, while optical transmission is probed using a tunable cw laser near 1550 nm. We observe optical modulation greater than 10dB from modest quality-factor (~10³) resonances, as well as a large -1.26 nm change in resonant wavelength ??, resulting from the large change in the dielectric function of VO? in the insulator-to-metal transition achieved by optical pumping. PMID:22714350

Ryckman, Judson D; Diez-Blanco, V; Nag, Joyeeta; Marvel, Robert E; Choi, B K; Haglund, Richard F; Weiss, Sharon M

2012-06-01

327

Study of Insulator-Metal transition of VO2 thin films with ultrafast optical pulses  

Science.gov (United States)

VO2 has been a popular material to study in the past few decades as it has a reversible insulator-metal transition (IMT) when heated past 340K or stimulated with an ultrafast optical pulse. The resistance and optical properties change by several orders of magnitude, making it an attractive candidate for low loss plasmonic devices, ultrafast switches, or smart windows. We study the dynamics of the transition of VO2 thin films on different substrates with femtosecond pulses in a pump-probe experiment in order to better understand the mechanisms behind the transition. We have measured the IMT at several different temperatures to investigate any change in the dynamics of the transition. We also study the Raman spectroscopy of VO2 thin films heated through the transition. The effects of the different substrates on the transition of the VO2 thin film will be discussed.

Radue, Elizabeth; Wang, Lei; Crisman, Evan; Wincheski, Russell; Kittiwatanakul, S.; Lu, J.; Wolf, S. A.; Lukaszew, Rosa; Novikova, Irina

2013-03-01

328

Experimental Analysis of VoIP over Wireless Local Area Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

VoIP is a rapidly growing technology that enables the transport of voice over data networks such asthe public Internet. VoIP became a viable alternative to the public switched telephone networks (PSTNs). In parallel, a dramatic increase is happening in t...

Abderrahmane Lakas; Mohammed Boulmalf

2007-01-01

329

Cardiac output distribution in miniature swine during locomotory exercise to VO/sub 3max/  

International Nuclear Information System (INIS)

Distribution of cardiac output (CO) was studied in miniature swine (22 +/- 1 kg) during level treadmill exercise up to the speed (17.7 km/hr) that elicited maximal oxygen consumption (VO/sub 2max/) (60 +/- 4 m1/min/kg). COs and tissue blood flows (BFs) were measured with the radiolabelled microsphere technique. CO increased from a preexercise value of 2.1 +/- 0.5 1/min up to 9.9 +/- 0.5 1/min at VO/sub 2max/. In preexercise standing 43% of CO went to skeletal muscle, which comprised 36 +/- 1% of body mass, 42% to viscera (12 +/- 1% mass), 5% to brain, heart, and lungs (2% +/- 0.1% mass), and 10% to skin and skeleton (35 +/- 2% mass). Preexercise could not be considered resting because of the animals' excitability. Skeletal muscle BF increased progressively with speed up to VO/sub 2max/, both in absolute terms and in percent CO. At VO/sub 2max/, 88% of CO went to muscle, 3% to viscera, 8% to brain, heart and lungs, and 1% to skin and skeleton. Thus, at VO/sub 2max/ only 4% of CO went to the inactive tissues, which constituted 47% of body mass. In 2 pigs that ran at speeds above 17 km/hr, total muscle BF leveled off at VO/sub 2max/. These findings demonstrate that muscle BF progressively increases up to VO/sub 2max/, and that VO_2 levels off at the same intensity as muscle flow

1986-03-01

330

QoS Analysis for Signaling in VoIP Client and Server Communication for Multicore  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Due to the cost-effective solutions provided by Voice over Internet Protocol (VoIP) technology to enterprises and individuals, the growth has been significantly high in this area during the past and current decade. The growing demand has resulted in the escalating number of users who need secure, reliable and efficient communication systems. The deployment of multicore hardware has been solving the computational complexity problems. A multicore hardware/software model for VoIP is the key rese...

Adnan, Muhammad

2012-01-01

331

Prepaid and Postpaid VoIP Service Enhancements and Hybrid Network Performance Measurement  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study focuses on prepaid and postpaid VoIP technology service enhancement. The aims are to i) merge wireless technology in rural areas with wired technologies and services in urban areas. It intends to investigate the minimum requirement needs by wireless and wired technology in using of telco connectivity. It is also to define which technology will achieve a low operating cost and good performance. In addition, the most apparent benefit of implementing prepaid/postpaid VoIP network in r...

Mohd Nazri Ismail; Asaad Abusin

2006-01-01

332

Analysis of a procedure for inserting steganographic data into VoIP calls  

CERN Document Server

The paper concerns performance analysis of a steganographic method, dedicated primarily for VoIP, which was recently filed for patenting under the name LACK. The performance of the method depends on the procedure of inserting covert data into the stream of audio packets. After a brief presentation of the LACK method, the paper focuses on analysis of the dependence of the insertion procedure on the probability distribution of VoIP call duration.

Mazurczyk, Wojciech

2008-01-01

333

Unraveling Metal-insulator Transition Mechanism of VO2 Triggered by Tungsten Doping  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Understanding the mechanism of W-doping induced reduction of critical temperature (TC) for VO2 metal-insulator transition (MIT) is crucial for both fundamental study and technological application. Here, using synchrotron radiation X-ray absorption spectroscopy combined with first-principles calculations, we unveil the atomic structure evolutions of W dopant and its role in tailoring the TC of VO2 MIT. We find that the local structure around W atom is intrinsically symmetric with a tetragonal-...

Tan, Xiaogang; Yao, Tao; Long, Ran; Sun, Zhihu; Feng, Yajuan; Cheng, Hao; Yuan, Xun; Zhang, Wenqing; Liu, Qinghua; Wu, Changzheng; Xie, Yi; Wei, Shiqiang

2012-01-01

334

Simulated swimming: a useful tool for evaluation the VO2 max of swimmers in the laboratory.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study was designed to develop a simulated swimming exercise (SS) so that peak VO2 would be assessed on swimmers in a laboratory setting. The subjects assumed a prone position on an incline bench and performed arm cranking on a Monark Rehab Trainer while performing a flutter kick against tension supplied by elastic cords. The SS test was compared to four peak VO2 tests: treadmill running (RN), tethered swimming (TW), bicycle ergometry (B), and arm cranking (AC). Eleven male varsity swimme...

Kimura, Y.; Yeater, R. A.; Martin, R. B.

1990-01-01

335

Unwanted Traffic and Information Disclosure in VoIP Networks : Threats and Countermeasures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The success of the Internet has brought significant changes to the telecommunication industry. One of the remarkable outcomes of this evolution is Voice over IP (VoIP), which enables realtime voice communications over packet switched networks for a lower cost than traditional public switched telephone networks (PSTN). Nevertheless, security and privacy vulnerabilities pose a significant challenge to hindering VoIP from being widely deployed. The main object of this thesis is to define and ela...

Zhang, Ge

2012-01-01

336

Voltage-controlled switching and thermal effects in VO2 nano-gap junctions  

Science.gov (United States)

Voltage-controlled switching in lateral VO2 nano-gap junctions with different gap lengths and thermal properties was investigated. The effect of Joule heating on the phase transition was found to be strongly influenced by the device geometry, the contact material, and the current. Our results indicate that the VO2 phase transition was likely initiated electronically, which was sometimes followed by a secondary thermally induced transition.

Joushaghani, Arash; Jeong, Junho; Paradis, Suzanne; Alain, David; Stewart Aitchison, J.; Poon, Joyce K. S.

2014-06-01

337

Equações para a previsão da potência aeróbia (VO2 de jovens adultos brasileiros Equations for predicting aerobic power (VO2 of young Brazilian adults  

Directory of Open Access Journals (Sweden)

Full Text Available FUNDAMENTO: O VO2 pode ser previsto, com base em parâmetros antropométricos e fisiológicos, para determinadas populações. OBJETIVO: Propor modelos preditivos do VO2 submáximo e máximo para jovens adultos brasileiros. MÉTODOS: Os 137 voluntários (92 homens foram submetidos ao teste progressivo de esforço máximo (GXT no ciclo ergômetro (Monark®, Br. Medidas de trocas gasosas e ventilatórias foram realizadas em circuito aberto (Aerosport® TEEM 100, EUA. Em outro grupo, 13 voluntários foram submetidos ao GXT e a um teste de onda quadrada (SWT, para avaliar a validade externa das fórmulas do ACSM, de Neder et al e do nomograma de Åstrand-Ryhming. Adotou-se o delineamento experimental de validação cruzada e o nível de significância de p BACKGROUND: VO2 may be predicted with base on anthropometric and physiological parameters for determined populations. OBJECTIVE: To propose models for submaximal and maximal VO2 prediction in young Brazilian adults. METHODS: A total of 137 volunteers (92 men underwent graded maximal exercise test (GXT in a cycle ergometer (MonarkTM, Br. Gas exchange and respiratory measurements were performed in an open circuit (AerosportTM TEEM 100, USA. In another group, 13 volunteers underwent GXT and a square wave test (SWT in order to evaluate the external validity of Neder et al's formula, ACSM's formula, and of Åstrand-Ryhming nomogram. The study design chosen was a cross-validation and the significance level was set at p < 0.05. RESULTS: For men during submaximal exercises, a mathematical model was deduced with base on workload, body mass, and age, which explained 89% of the VO2 variation, with SEE (standard error of the estimate = 0.33 l.min-1. For the maximum load in the male group, another model with the same variables explained 71% of VO2 variation, with SEE = 0.40 l.min-1. For women, 93% of VO2 variation could be explained, with SEE = 0.17 l.min-1, both in submaximal and maximal exercise, with only one equation by use e of the same independent variables. CONCLUSION: The models derived in the present study proved to be accurate to predict submaximal and maximal VO2 in young Brazilian adults. (Arq Bras Cardiol. 2010; [online]. ahead print, PP.0-0

Paula Magrani

2010-06-01

338

Improving BiVO4 photoanodes for solar water splitting through surface passivation.  

Science.gov (United States)

BiVO4 has shown great potential as a semiconductor photoanode for solar water splitting. Significant improvements made during recent years allowed researchers to obtain a photocurrent density of up to 4.0 mA cm(-2) (AM1.5 sunlight illumination, 1.23 VRHE bias). For further improvements of the BiVO4 photoelectrodes, a deep understanding of the processes occurring at the BiVO4-H2O interface is crucial. Employing an electrochemical loading and removal process of NiOx, we show here that carrier recombination at this interface strongly affects the photocurrents. The removal of NiOx species by electrochemical treatment in a phosphate electrolyte leads to significantly increased photocurrents for BiVO4 photoelectrodes. At a bias of 1.23 VRHE, the Incident Photon-to-Current Efficiency (IPCE) at 450 nm reaches 43% for the passivated BiVO4 electrode under back side illumination. A model incorporating heterogeneity of NiOx centers on the BiVO4 surface (OER catalytic centers, recombination centers, and passivation centers) is proposed to explain this improved performance. PMID:24845546

Liang, Yongqi; Messinger, Johannes

2014-05-28

339

Visible light photocatalytic activity of BiVO4 particles with different morphologies  

Science.gov (United States)

Bismuth vanadate (BiVO4) particles with different morphologies were synthesized by a one-step hydrothermal process and their optical and photocatalytic properties were investigated. Their crystal structure and microstructures were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). XRD patterns demonstrate that the as-prepared samples are monoclinic cell. FESEM shows that BiVO4 crystals can be fabricated in different morphologies by simply manipulating the reaction parameters of hydrothermal process. The UV-visible diffuse reflectance spectra (UV-vis DRS) reveal that the band gaps of BiVO4 photocatalysts are about 2.07-2.21 eV. The as-prepared BiVO4 photocatalysts exhibit higher photocatalytic activities in the degradation of rhodamine B (Rh B) under visible light irradiation (? > 420 nm) compared with traditional N-doped TiO2 (N-TiO2). Furthermore, wheat like BiVO4 sample reveals the highest photocatalytic activity. Up to 100% Rh B is decolorized after visible light irradiation for 180 min. The reason for the difference in the photocatalytic activities for BiVO4 samples obtained at different conditions were systematically studied based on their shape, size and the variation of local structure.

Lin, Xue; Yu, Lili; Yan, Lina; Li, Hongji; Yan, Yongsheng; Liu, Chunbo; Zhai, Hongju

2014-06-01

340

ENDOR-determined solvation structure of VO2+ in frozen solutions  

International Nuclear Information System (INIS)

The solvation structure of the vanadyl ion (VO2+) in methanol and in water-methanol mixtures has been investigated by application of /sup 1H/ and 13C electron nuclear double resonance (ENDOR) spectroscopy. The ligand origins of the proton ENDOR resonances have been assigned with use of materials selectively enriched with 2H. The principal hyperfine coupling (hfc) components of both 1H and 13C in solvent molecules coordinated to the VO2+ ion have been determined by analysis of the H0 dependence of the ENDOR spectra. The ENDOR results provide unambiguous evidence that in water-methanol mixtures only VO(H2O)52+ and [VO(H2O)4(CH3OH)]2+ species are formed. In pure methanol the VO(CH3OH)52+ species is observed. The coordination geometries of the VO2+ complexes are deduced from ENDOR estimates of metal-nucleus distances by using computer-based molecular graphics. It is shown on the basis of molecular modeling that the ENDOR-determined metal-nucleus distances are best accounted for by complexes of tetragonal-pyramidal geometry. 29 references, 9 figures, 7 tables

1988-09-21

 
 
 
 
341

Body fat, abdominal fat and body fat distribution related to VO(2PEAK) in young children  

DEFF Research Database (Denmark)

Abstract Objective. Aerobic fitness, defined as maximum oxygen uptake (VO(2PEAK)), and body fat measurements represent two known risk factors for disease. The purpose of this study was to investigate the relationship between VO(2PEAK) and body fat measurements in young children at a population-based level. Methods. Cross-sectional study of 225 children (128 boys and 97 girls) aged 8-11 years, recruited from a population-based cohort. Total lean body mass (LBM), total fat mass (TBF), and abdominal fat mass (AFM) were measured by dual-energy x-ray absorptiometry. Body fat was also calculated as a percentage of body mass (BF%) and body fat distribution as AFM/TBF. VO(2PEAK) was assessed by indirect calorimetry during maximal exercise test. Results. Significant relationships existed between body fat measurements and VO(2PEAK) in both boys and girls, with Pearson correlation coefficients for absolute values of VO(2PEAK) (0.22-0.36, P<0.05), and for VO(2PEAK) scaled by body mass (-0.38 - -0.70, P

Andersen, Lars Bo

2011-01-01

342

The performance model of dynamic virtual organization (VO) formations within grid computing context  

International Nuclear Information System (INIS)

Grid computing aims to enable 'resource sharing and coordinated problem solving in dynamic, multi-institutional virtual organizations (VOs)'. Within the grid computing context, successful dynamic VO formations mean a number of individuals and institutions associated with certain resources join together and form new VOs in order to effectively execute tasks within given time steps. To date, while the concept of VOs has been accepted, few research has been done on the impact of effective dynamic virtual organization formations. In this paper, we develop a performance model of dynamic VOs formation and analyze the effect of different complex organizational structures and their various statistic parameter properties on dynamic VO formations from three aspects: (1) the probability of a successful VO formation under different organizational structures and statistic parameters change, e.g. average degree; (2) the effect of task complexity on dynamic VO formations; (3) the impact of network scales on dynamic VO formations. The experimental results show that the proposed model can be used to understand the dynamic VO formation performance of the simulated organizations. The work provides a good path to understand how to effectively schedule and utilize resources based on the complex grid network and therefore improve the overall performance within grid environment.

2009-05-30

343

VO2 (A): Reinvestigation of crystal structure, phase transition and crystal growth mechanisms  

Science.gov (United States)

Well crystallized VO2 (A) microrods were grown via a single step hydrothermal reaction in the presence of V2O5 and oxalic acid. With the advantage of high crystalline samples, we propose P4/ncc as an appropriate space group at room temperature. From morphological studies, we found that the oriented attachment and layer by layer growth mechanisms are responsible for the formation of VO2 (A) micro rods. The structural and electronic transitions in VO2 (A) are strongly first order in nature, and a marked difference between the structural transition temperatures and electronic transitions temperature was evidenced. The reversible intra- (LTP-A to HTP-A) and irreversible inter- (HTP-A to VO2 (M1)) structural phase transformations were studied by in-situ powder X-ray diffraction. Attempts to increase the size of the VO2 (A) microrods are presented and the possible formation steps for the flower-like morphologies of VO2 (M1) are described.

Rao Popuri, Srinivasa; Artemenko, Alla; Labrugere, Christine; Miclau, Marinela; Villesuzanne, Antoine; Pollet, Michaël

2014-05-01

344

Microemulsion-mediated hydrothermal synthesis and characterization of zircon-type LaVO4 nanowires  

International Nuclear Information System (INIS)

The zircon-type tetragonal (t-) LaVO4 nanowires were controlled synthesized by a new approach, a microemulsion-mediated hydrothermal method, in which the aqueous cores of sodium dodecyl sulfate (SDS)/cyclohexane/n-hexanol/water microemulsion were used as constrained microreactors for a controlled growth of t-LaVO4 nanocrystals under hydrothermal conditions. The microemulsion exists stably just at room temperature and not under hydrothermal conditions, in addition, the as-obtained nanowires are much larger than the microemulsion droplets, so that the microemulsion does not simply act as a template, but rather directs crystal growth into nanowires presumably by interacting with the surface of the growing crystal. A series of experimental results indicated that several experimental parameters, such as the SDS concentration, the species and content of the cosurfactant play important roles in the morphological control of the t-LaVO4 nanocrystals. Possible formation mechanism of t-LaVO4 nanowires is also discussed. - Graphical abstract: The zircon-type tetragonal (t-) LaVO4 nanowires were controlled synthesized by a microemulsion-mediated hydrothermal method, in which the aqueous cores of SDS/cyclohexane/n-hexanol/water microemulsion were used as constrained microreactors for a controlled growth of t-LaVO4 nanocrystals under hydrothermal conditions

2007-01-01

345

[Solvothermal synthesis and optical properties of LiVO4 : Dy3+ nanorod].  

Science.gov (United States)

Using La2O3, Dy2O3, NH4VO3, HNO3 as materials, solvothermal synthesis method was adopted to prepare LaVO4 : Dy3+ nanorods through adjusting the pH values of ethanol-water mixing solution. The as-prepared samples were characterized by X-ray diffraction, transmission electron microscope, infrared spectrum, UV-Vis absorption spectra and fluorescence spectra. The results show that the phase transition from m- to t -LaVO4 : Dy3+ can be found when the pH value changes from 2 to 4. With the increase of the pH value of the mixing solution, the grain size of the sample becomes smaller and the shape of LaVO4 : Dy3+ crystal changes from irregular nanoparticle to one dimension nanorod. Besides, the band gap of the sample decrease from 3.68 (pH 2) to 3.43 eV (pH 10). It is found from FL that the excitation spectra of LaVO4 : Dy3+ nanorods have a little red shift in comparison with irregular nanoparticle. Furthermore, the LaVO4 : Dy3+ nanorod exhibits the strongest yellow emission (4F9/2-6 H13/2) and blue emission(4F9/2-6H15/2), and it possesses the largest Y/B value (1.039). PMID:23427562

Wei, Qing-Min; Lu, Jian-Ping; Liu, Guo-Cong; Liang, Da-Wen

2012-12-01

346

Monoclinic BiVO{sub 4} with regular morphologies: Hydrothermal synthesis, characterization and photocatalytic properties  

Energy Technology Data Exchange (ETDEWEB)

Monoclinic bismuth vanadate (BiVO{sub 4}) samples with regular morphologies were prepared by a facile hydrothermal process with Bi{sub 2}O{sub 3} and NH{sub 4}VO{sub 3} as starting materials. The physical and photophysical properties of the as-prepared samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), infrared spectroscopy (IR), and UV-vis diffuse reflectance spectroscopy (UV-vis). It was found that cuboid-like, square plate-like and flower-like BiVO{sub 4} could be readily obtained by tailoring the pH values of the reaction suspensions in the presence of CTAB. Both pH value and CTAB played crucial roles in the morphology evolution of the as-prepared samples. The bandgaps (E{sub g}) of cuboid-like, square plate-like and flower-like BiVO{sub 4} were 2.39 eV, 2.40 eV and 2.46 eV, respectively. The photocatalytic performance of the as-prepared BiVO{sub 4} was much better than that of P25 for photodegradation of methyl orange under sunlight irradiation. The photocatalytic activities of BiVO{sub 4} samples were highly related to their crystallinities and shapes.

Li Haibin [School of Materials Science and Engineering, Central South University, Changsha 410083 (China)], E-mail: coastllee@hotmail.com; Liu Guocong [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Department of Chemistry, Yulin Normal University, Yulin 537000 (China); Duan Xuechen [School of Materials Science and Engineering, Central South University, Changsha 410083 (China)

2009-05-15

347

Processing Facilitation Strategies in OV and VO Languages: A Corpus Study  

Directory of Open Access Journals (Sweden)

Full Text Available The present corpus study aimed to examine whether Basque (OV resorts more often than Spanish (VO to certain grammatical operations, in order to minimize the number of arguments to be processed before the verb. Ueno & Polinsky (2009 argue that VO/OV languages use certain grammatical resources with different frequencies in order to facilitate real-time processing. They observe that both OV and VO languages in their sample (Japanese, Turkish and Spanish have a similar frequency of use of subject pro-drop; however, they find that OV languages (Japanese, Turkish use more intransitive sentences than VO languages (English, Spanish, and conclude this is an OV-specific strategy to facilitate processing. We conducted a comparative corpus study of Spanish (VO and Basque (OV. Results show (a that the frequency of use of subject pro-drop is higher in Basque than in Spanish; and (b Basque does not use more intransitive sentences than Spanish; both languages have a similar frequency of intransitive sentences. Based on these findings, we conclude that the frequency of use of grammatical resources to facilitate the processing does not depend on a single typological trait (VO/OV but it is modulated by the concurrence of other grammatical features.

Luis Pastor

2013-08-01

348

Synthesis and characterization of VO2-based thermochromic thin films for energy-efficient windows  

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Full Text Available Abstract Thermochromic VO2 thin films have successfully been grown on SiO2-coated float glass by reactive DC and pulsed-DC magnetron sputtering. The influence of substitutional doping of V by higher valence cations, such as W, Mo, and Nb, and respective contents on the crystal structure of VO2 is evaluated. Moreover, the effectiveness of each dopant element on the reduction of the intrinsic transition temperature and infrared modulation efficiency of VO2 is discussed. In summary, all the dopant elements--regardless of the concentration, within the studied range-- formed a solid solution with VO2, which was the only compound observed by X-ray diffractometry. Nb showed a clear detrimental effect on the crystal structure of VO2. The undoped films presented a marked thermochromic behavior, specially the one prepared by pulsed-DC sputtering. The dopants effectively decreased the transition of VO2 to the proximity of room temperature. However, the IR modulation efficiency is markedly affected as a consequence of the increased metallic character of the semiconducting phase. Tungsten proved to be the most effective element on the reduction of the semiconducting-metal transition temperature, while Mo and Nb showed similar results with the latter being detrimental to the thermochromism.

Batista Carlos

2011-01-01

349

Synthesis and characterization of VO2-based thermochromic thin films for energy-efficient windows  

Science.gov (United States)

Thermochromic VO2 thin films have successfully been grown on SiO2-coated float glass by reactive DC and pulsed-DC magnetron sputtering. The influence of substitutional doping of V by higher valence cations, such as W, Mo, and Nb, and respective contents on the crystal structure of VO2 is evaluated. Moreover, the effectiveness of each dopant element on the reduction of the intrinsic transition temperature and infrared modulation efficiency of VO2 is discussed. In summary, all the dopant elements--regardless of the concentration, within the studied range-- formed a solid solution with VO2, which was the only compound observed by X-ray diffractometry. Nb showed a clear detrimental effect on the crystal structure of VO2. The undoped films presented a marked thermochromic behavior, specially the one prepared by pulsed-DC sputtering. The dopants effectively decreased the transition of VO2 to the proximity of room temperature. However, the IR modulation efficiency is markedly affected as a consequence of the increased metallic character of the semiconducting phase. Tungsten proved to be the most effective element on the reduction of the semiconducting-metal transition temperature, while Mo and Nb showed similar results with the latter being detrimental to the thermochromism.

Batista, Carlos; Ribeiro, Ricardo M.; Teixeira, Vasco

2011-12-01

350

Mechanochemical synthesis of nanostructured BiVO{sub 4} and investigations of related features  

Energy Technology Data Exchange (ETDEWEB)

Highly crystalline monoclinic bismuth vanadate (BiVO{sub 4}) nanopowders with crystallite sizes less than 50 nm were obtained by mechanical milling of a stoichiometric mixture of bismuth oxide (Bi{sub 2}O{sub 3}) and vanadium pentoxide (V{sub 2}O{sub 5}). Different synthesized batches were obtained by varying the preparation times and the number of the tungsten carbide balls (BPR) while keeping constant the jar rotation speed. Annealing treatments were performed on the obtained nanopowders in order to improve the crystalline order and the BiVO{sub 4} nanoparticles surface states. Characterizations methods, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) equipped with X-ray energy dispersive spectrometer (EDS), Raman spectrometry, FTIR and UV-Vis diffuse reflectance techniques were used to shed light on the structure, morphologies and composition of the obtained nanopowders. Even if monoclinic BiVO{sub 4} crystalline structure was stabilized in samples after appropriate annealing, shifts of Raman peak positions after such treatments revealed the occurrence of symmetry distortions in the local structure of the monoclinic phase. -- Graphical abstract: Art Work - BiVO{sub 4} Synthesis and Structures. Highlights: Black-Right-Pointing-Pointer Synthesis by ball-milling of original nanostructures of BiVO{sub 4}. Black-Right-Pointing-Pointer Stabilizing a monoclinic BiVO{sub 4} polytype with nanoparticle sizes about 20 nm. Black-Right-Pointing-Pointer Investigations of annealing effects on structures, vibration and optical features.

Venkatesan, R. [Nanoscience and Nanotechnology program, CINVESTAV-IPN, Zacatenco, Av IPN 2508, Col Zacatenco, D.F., C.P. 07360 (Mexico); Institute of Molecules and Materials of Le Mans (IMMM) UMR CNRS, Universite du Maine, 72085 Le Mans (France); Velumani, S., E-mail: velu@cinvestav.mx [Nanoscience and Nanotechnology program, CINVESTAV-IPN, Zacatenco, Av IPN 2508, Col Zacatenco, D.F., C.P. 07360 (Mexico); Department of Electrical Engineering (SEES), CINVESTAV-IPN, Zacatenco, Av IPN 2508, Col Zacatenco, D.F., C.P. 07360 (Mexico); Kassiba, A., E-mail: kassiba@univ-lemans.fr [Institute of Molecules and Materials of Le Mans (IMMM) UMR CNRS, Universite du Maine, 72085 Le Mans (France)

2012-08-15

351

Influencia de la variabilidad edafica en la producción de biomasa del cultivo de la uña de gato uncaria tomentosa (willd d.c. en la cuenca del río aguaytia, region Ucayali -Perú  

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Full Text Available En Mayo 2003 se instalaron cuatro plantaciones de uña de gato Uncaria tomentosa (Willd D.C a lo largo de la Cuenca del Río Aguaytia en Ucayali Perú. Las plantas correspondieron al clon 11, propagadas in vitro, y procedentes del Instituto de Biotecnología (IBT de la Universidad Nacional Agraria La Molina (UNALM. El estudio se basó en la determinación de la influencia edáfica en la producción de biomasa de esta especie como cultivo. Las áreas experimentales se encuentran a diferentes niveles altitudinales desde los 136 hasta los 884 msnm. En Junio 2005 se realizó la primera poda y el muestreo de suelos a dos profundidades, de 0 a 15 y de 15 a 30 cm del suelo.La textura arcillosa en los suelos fueron las que correlacionaron mejor con la producción de la biomasa del clon; siendo las ecuaciones más representativas: a Biomasa = 27.329(% Arena - 51.875 y b Biomasa = -32.247(arcilla ? 2169.8. Los indicadores mas significativos de la fertilidad del suelo en el proceso de adaptación de esta especie como cultivo fueron: los contenidos de fósforo (P, materia orgánica (M.O., nitrógeno (N total, saturación de aluminio (% Al, potasio (K, magnesio (Mg y el pH

Gilberto Domínguez

2007-01-01

352

Aprovechamiento de Biomasa Peletizada en el Sector Ladrillero en Bogotá-Colombia: Análisis Energético y Ambiental Use of Pelleted Biomass in the Brick Industry in Bogota-Colombia: Energy and Environmental Analysis  

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Full Text Available En este estudio se compara el desempeño energético y ambiental del uso de combustibles a partir de dos tipos de biomasas peletizadas: residuos de madera, provenientes de podas y residuos de la producción de muebles, principalmente aserrín. La biomasa proveniente de residuos de madera es uno de los materiales más adecuados para utilizar como combustible alternativo. El sector ladrillero tiene una gran demanda energética para sus procesos de secado y cocción y el uso de combustibles alternativos a partir de biomasa permite obtener reducciones importantes en emisiones atmosféricas y no afecta las condiciones técnicas del proceso de producción de ladrillos. La biomasa con mejor desempeño, tanto en las variables energéticas como ambientales evaluadas, fue el aserrín.This study compared the energy and environmental performance of fuels from two types of pelleted biomass: wood waste from pruning and waste from furniture production, mainly sawdust. Wood residues biomass is one of the most suitable materials for using as an alternative fuel. The brick manufacture sector has a high energy demand for its drying and firing processes and the use of alternative fuels from biomass allows significant reductions in emissions and does not affect the technical conditions of the process of brick production. The biomass with better performance was sawdust, which presented the optimum energy and environmental variables.

César A García-Ubaque

2013-01-01

353

Two-step hydrothermal process for synthesis of F-doped BiVO4 spheres with enhanced photocatalytic activity  

International Nuclear Information System (INIS)

Highlights: •F-doped BiVO4 spheres were synthesized by a simple two step hydrothermal process. •F? ions might restrain the recombination of photogenerated electron–hole pairs. •The as-obtained F-doped BiVO4 spheres exhibit higher photocatalytic activity. -- Abstract: F-doped BiVO4 spheres were synthesized by a simple two step hydrothermal process. The effects of F ions on the microstructure and photocatalytic activity of BiVO4 were investigated in detail. The undoped BiVO4 solid spheres with smooth surface are chemically etched by corrosive F? ions, which result in the F-doped BiVO4 spheres with large pores on the surface. The substitution of O2? ions by F? ions could result in the decrease of the BiVO4 lattice parameters, influence the chemical environment surrounding the Bi, V and O elements, cause the red-shifted of the adsorption edge and modify the absorption abilities in visible light region. F-doped BiVO4 spheres exhibited higher photocatalytic activity than undoped BiVO4 under visible light irradiation because an appropriate amount of F? ions introduced into BiVO4 crystal lattice might effectively restrain the recombination of photogenerated electron–hole pairs

2013-12-25

354

VO-KOREL: A Fourier disentangling service of Virtual Observatory  

CERN Document Server

VO-KOREL is a web service exploiting the technology of Virtual Observatory for providing the astronomers with the intuitive graphical front-end and distributed computing back-end running the most recent version of Fourier disentangling code KOREL. The system integrates the ideas of the e-shop basket, conserving the privacy of every user by transfer encryption and access authentication, with features of laboratory notebook, allowing the easy housekeeping of both input parameters and final results, as well as it explores a newly emerging technology of cloud computing. While the web-based front-end allows the user to submit data and parameter files, edit parameters, manage a job list, resubmit or cancel running jobs and mainly watching the text and graphical results of a disentangling process, the main part of the back-end is a simple job queue submission system executing in parallel multiple instances of FORTRAN code KOREL. This may be easily extended for GRID-based deployment on massively parallel computing cl...

Škoda, Petr; Fuchs, Jan

2011-01-01

355

EPR and UV/VIS spectroscopic investigations of VO2+ complexes and compounds formed in alkali pyrosulfates  

DEFF Research Database (Denmark)

The catalytically important molten salt-gas system M2S2O7-M2SO4-V2O5/SO2(g) (M = Na. K, Rb, Cs) has been investigated by X- and Q-band EPR spectroscopy. In order to obtain information about the V(IV) complex formation in the melts, samples rather dilute in V2O5 were quenched from the molten state at 450-460degreesC to 0degreesC. EPR spectra of the quenched samples were recorded on samples with alkali to vanadium (M/V) ratios 40, 80 and 160. The spectra show that two V(IV) complexes dominate in the melt regardless of the type of alkali metal ion. In systems with low activity of sulfate a paramagnetic V(IV) complex with g(parallel to) = 1.915, g(perpendicular to) = 1,978 and line widths 5-15 Gauss is observed. In systems saturated with M2SO4 the obtained EPR spectra show a paramagnetic complex with the g-tensors g(parallel to) = 1.930, g(perpendicular to) = 1.980 and line widths 20-60 Gauss. These results fit very well with the assumption that the species VO(SO4)(2)(2-) and SO42- are in equilibrium with VO(SO4)(3)(4-). It has also been shown for the system M2S2O7-M2SO4(sat)-V2O5/SO42-(g) that the line widths in the system increase with higher cation radius, and depend linearly on the volume fraction of the sample occupied by the cation. This indicates that spin-spin relaxation effects are the major contribution to line broadening. Combining information from UV/VIS and EPR spectra shows that the VO2+ unit in the molten salt solvent exhibits electronic properties close to aqueous solutions of V(IV).

Rasmussen, Søren Birk; Eriksen, Kim Michael

2002-01-01

356

Synthesis, structure, and reactivity of dinuclear nickel amino-thiophenolate complexes bearing bridging VO2(OH)2- and VO2(OR)2- coligands.  

Science.gov (United States)

A series of novel mixed ligand dinickel complexes of the type [Ni(II)(2)L(?-L')](+), where L' is a tetrahedral oxo-alkoxo vanadate (L' = [O(2)V(V)(OR)(2)](-), R = H or alkyl) and L a macrocyclic N(6)S(2) supporting ligand, have been prepared, and their esterification reactivity has been studied. The orthovanadate complex [Ni(2)L(?-O(2)V(OH)(2))](+) (2), prepared by reaction between [Ni(2)L(?-Cl)]ClO(4) with Na(3)VO(4) and a phase transfer reagent in CH(3)CN, reacts smoothly with MeOH and EtOH forming the vanadate diesters [Ni(2)L(?-O(2)V(OMe)(2))](+) (3) and [Ni(2)L(?-O(2)V(OEt)(2))](+) (4). The dialkyl orthovanadate esters in 3 and 4 are readily transesterified with mono- and difunctional alcohols. Complex 3 can also be generated from 4 by transesterification with MeOH. Complexes 3 and 4 react with diols (ethylene glycol, propylene glycol and diethylene glycol) as well to afford the complexes [Ni(2)L(?-O(2)V(OH)(OCH(2)CH(2)OH))](+) (5), [Ni(2)L(?-O(2)V(OCH(2))(2)CH(2))](+) (6), and [Ni(2)L(?-O(2)V(OCH(2)CH(2))(2)O)] (7). The crystal structures of the tetraphenylborate salts of complexes 3-7 reveal in each case four-coordinate O(2)V(V)(OR)(2)(-) groups bonded in a ?(1,3)-bridging mode to generate trinuclear complexes with a central N(3)Ni(?-S)(2)(?(1,3)-O(2)V(OR)(2))NiN(3) core. The stabilization of the four-coordinate V(V)O(2)(OR)(2)(-) moieties is a consequence of both the two-point coordinative fixation to and the steric protection of the bowl-shape binding pocket of the [Ni(2)L](2+) fragment. Cyclic voltammetry experiments reveal that the encapsulated vanadate esters are not reduced in a potential window of -2.0 to +2.5 V vs SCE. The spins of the nickel(II) (S(i) = 1 ions) in 3 are weakly ferromagnetically coupled (J = +23 cm(-1), (H = -2JS(1)S(2))) to produce an S = 2 ground state. PMID:22530886

Lozan, Vasile; Lach, Jochen; Kersting, Berthold

2012-05-01

357

EFICIENCIA EN EL USO DE LOS INSUMOS AGRÍCOLAS EN LA PRODUCCIÓN DE BIOMASA Y EL RENDIMIENTO DEL SISTEMA COMBINADO GIRASOL - FRIJOL EN FUNCIÓN DEL NITRÓGENO  

Directory of Open Access Journals (Sweden)

Full Text Available La eficiencia en el uso de los insumos ha sido la principal razón por la cual los cultivos asociados se siguen utilizando en la actualidad. El suministro de nitrógeno (N en los cultivos combinados, donde se incluye una leguminosa, debe considerarse, ya que existe evidencia de que una aplicación mínima o excesiva de N podría modificar, de manera significativa, la respuesta de dichos agrosistemas a la adición de este elemento. Por tal motivo, se realizó un estudio cuyo objetivo fue determinar el efecto de distintos niveles de N sobre la eficiencia en el uso de agua y radiación, la producción de biomasa y el rendimiento de semilla en la siembra combinada de girasol y frijol. La investigación se realizó durante el verano de 2003, en Montecillo, Estado de México. Los tratamientos consistieron en la aplicación de 40, 80, 120 y 160 kg ha-1 de N y un testigo, sin fertilizante. Como fuente de N se utilizó urea (46% de N: la mitad se aplicó en el momento de la siembra y el resto en la primera escarda. La siembra se realizó el 22 de mayo de 2003, con la densidad de población de 8.3 plantas m-2 (15 x 80 cm, alternando una planta de frijol y una de girasol. El diseño experimental fue de bloques al azar con cuatro repeticiones. En la asociación, se determinó la fenología, la evapotranspiración y las unidades calor; a la madurez fisiológica, se estimó la producción de biomasa, el rendimiento de semilla, el índice de cosecha, la eficiencia en el uso del agua y la radiación. Con excepción de 160 kg ha-1 de N, la aplicación de N incrementó el índice de área foliar y la radiación interceptada, así como la eficiencia en el uso del agua y radiación y, en consecuencia, la producción de biomasa y rendimiento de semilla. En ese sentido, a medida que se incrementa la cantidad de N por hectárea, los demás nutrimentos deben estar en cantidades adecuadas, ya que si esto no ocurre, el efecto de la aplicación de N se reduce.

Edgar J. Morales Rosales

2007-01-01

358

Synthesis, characterization and catalytic activity of two novel cis - dioxovanadium(V) complexes: [VO{sub 2}(L)] and [VO{sub 2}(HLox)  

Energy Technology Data Exchange (ETDEWEB)

Two novel complexes, [VO{sub 2}(L)] (1) and [VO{sub 2}(HLox)] (2), were synthesized and characterized by IV, UV-Vis and NMR spectroscopy, cyclic voltammetry, elemental analysis and X-ray diffraction. The synthesis of a new ligand, H{sub 2}Lox, is also described. Complexes 1 and 2 were obtained by the reaction of [VO(acac){sub 2}] with the ligands HL and H{sub 2}Lox, respectively. Alternatively, 2 was also obtained by the reaction of HL with [VO(acac)2] in the presence of hydroxylamine, and by the reaction of 1 with hydroxylamine. Crystallographic data show that complexes 1 and 2 have similar molecular structures, in which the cis-dioxovanadium(V) center is coordinated to L- or HLox{sup -}, respectively, in a distorted octahedral environment. The catalytic activity of these compounds towards cyclohexane oxidation was evaluated using H{sub 2}O{sub 2} and t-BuOOH as oxidants. Both complexes presented > 70% selectivity for cyclohexylhydroperoxide formation. B3LYP/6.31G(d) calculations were used to confirm the geometry and to help assign the electronic spectra. (author)

Silva, Natalia M.L.;