Javi Garcia - Academia.edu (original) (raw)
Papers by Javi Garcia
Arid Land Research and Management, 2007
Long-term interactions between vegetation succession and soil quality in alfalfa fields were inve... more Long-term interactions between vegetation succession and soil quality in alfalfa fields were investigated in the semi-arid Loess Plateau of China. The successional ecosystem is composed of six different planting-year alfalfa fields (namely, 3–5–9–15–21–25 years). The yield, cover, and height of alfalfa increased from 194 g dry hay m−2, 55.6%, and 52.8 cm in the 3-year stage to 406 g dry hay m−2, 85.5%, and 72.5 cm in the 9-year stage, respectively. Subsequently, they tended to decrease and reached their respective minimum levels at the 25-year stage. The density of alfalfa continued to decrease but the plant species richness increased with successional age. Microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass C-to-N ratio and soil basal respiration (BR) at 0–20 cm soil depth decreased steadily from 3 years to 9 years, but increased from 15 years to 25 years. The values for metabolic quotient (qCO2) were the opposite of the above four parameters along the succession gradient. Principal component analysis of soil microbial activity and respiration data in relation to soil physical and chemical properties demonstrated the variable trend in soil quality along the gradient. Generally, soil quality worsened within the 9-year stage while alfalfa production increased, but it tended to recover in the following stages while alfalfa production decreased. Soil quality and vegetation variables differed with growing seasons and soil depths. Our experiment showed that alfalfa fields should be plowed down after alfalfa has been grown for more than 9 years when soil water and fertility conditions are favorable for the production of follow-up crops in this area.
Applied Physics A-materials Science & Processing, 1993
A study of the gas-phase parameters involved in ArF laser induced chemical vapour deposition of s... more A study of the gas-phase parameters involved in ArF laser induced chemical vapour deposition of silicon-oxide thin films is presented. A complete set of experiments has been performed showing the influence of the concentration of the precursor gases, N2O and SiH4, and their influence on total and partial pressures on film growth and properties. In this paper we demonstrate the ability of this LCVD method to deposit silicon oxide films of different compositions and densities by appropriate control of gas composition and total pressure. Moreover, a material specific calibration plot comprising data obtained using different preparation techniques is presented, allowing determination of the stoichiometry of SiO x films by using FTIR spectroscopy independently of the deposition method. For the range of processing conditions examined, the experimental results suggest that chemical processes governing deposition take place mainly in the gas phase.
Journal of Non-crystalline Solids, 1995
Hydrogenated amorphous silicon nitride films have been prepared by laser-induced chemical vapour ... more Hydrogenated amorphous silicon nitride films have been prepared by laser-induced chemical vapour deposition from NH3SiH4Ar gas mixtures, heated by the gas-phase absorption of CO2 laser radiation. Samples have been characterized by ellipsometry (λ = 632 nm) and Fourier transform infrared spectroscopy to determine refractive index, thickness and bond composition. With regard to the power density effect, there is a non-linear
Current Vascular Pharmacology, 2005
One of the most important features of liver cirrhosis is the splanchnic and systemic arterial vas... more One of the most important features of liver cirrhosis is the splanchnic and systemic arterial vasodilation, related to an increase in vascular capacity and an active vasodilation. This arterial vasodilation seems to be the consequence of the excessive generation of vasodilating substances, which also contributes to a lower than normal pressor response to circulating nervous or humoral substances. The following review analyzes the mechanisms responsible for the vascular hyporesponse to vasoconstrictors observed in the experimental models of liver cirrhosis. It has become increasingly clear that, among the great variety of substances studied, nitric oxide (NO) seems to be one of the main contributors to this vascular alteration, since elimination of the endothelium or inhibition of its synthesis corrects it. The mechanism by which NO interferes with the contractile apparatus in smooth muscle cells seems to be related to a direct effect on calcium entry from the extracellular space and release from the internal stores.
Arid Land Research and Management, 2007
Long-term interactions between vegetation succession and soil quality in alfalfa fields were inve... more Long-term interactions between vegetation succession and soil quality in alfalfa fields were investigated in the semi-arid Loess Plateau of China. The successional ecosystem is composed of six different planting-year alfalfa fields (namely, 3–5–9–15–21–25 years). The yield, cover, and height of alfalfa increased from 194 g dry hay m−2, 55.6%, and 52.8 cm in the 3-year stage to 406 g dry hay m−2, 85.5%, and 72.5 cm in the 9-year stage, respectively. Subsequently, they tended to decrease and reached their respective minimum levels at the 25-year stage. The density of alfalfa continued to decrease but the plant species richness increased with successional age. Microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass C-to-N ratio and soil basal respiration (BR) at 0–20 cm soil depth decreased steadily from 3 years to 9 years, but increased from 15 years to 25 years. The values for metabolic quotient (qCO2) were the opposite of the above four parameters along the succession gradient. Principal component analysis of soil microbial activity and respiration data in relation to soil physical and chemical properties demonstrated the variable trend in soil quality along the gradient. Generally, soil quality worsened within the 9-year stage while alfalfa production increased, but it tended to recover in the following stages while alfalfa production decreased. Soil quality and vegetation variables differed with growing seasons and soil depths. Our experiment showed that alfalfa fields should be plowed down after alfalfa has been grown for more than 9 years when soil water and fertility conditions are favorable for the production of follow-up crops in this area.
Applied Physics A-materials Science & Processing, 1993
A study of the gas-phase parameters involved in ArF laser induced chemical vapour deposition of s... more A study of the gas-phase parameters involved in ArF laser induced chemical vapour deposition of silicon-oxide thin films is presented. A complete set of experiments has been performed showing the influence of the concentration of the precursor gases, N2O and SiH4, and their influence on total and partial pressures on film growth and properties. In this paper we demonstrate the ability of this LCVD method to deposit silicon oxide films of different compositions and densities by appropriate control of gas composition and total pressure. Moreover, a material specific calibration plot comprising data obtained using different preparation techniques is presented, allowing determination of the stoichiometry of SiO x films by using FTIR spectroscopy independently of the deposition method. For the range of processing conditions examined, the experimental results suggest that chemical processes governing deposition take place mainly in the gas phase.
Journal of Non-crystalline Solids, 1995
Hydrogenated amorphous silicon nitride films have been prepared by laser-induced chemical vapour ... more Hydrogenated amorphous silicon nitride films have been prepared by laser-induced chemical vapour deposition from NH3SiH4Ar gas mixtures, heated by the gas-phase absorption of CO2 laser radiation. Samples have been characterized by ellipsometry (λ = 632 nm) and Fourier transform infrared spectroscopy to determine refractive index, thickness and bond composition. With regard to the power density effect, there is a non-linear
Current Vascular Pharmacology, 2005
One of the most important features of liver cirrhosis is the splanchnic and systemic arterial vas... more One of the most important features of liver cirrhosis is the splanchnic and systemic arterial vasodilation, related to an increase in vascular capacity and an active vasodilation. This arterial vasodilation seems to be the consequence of the excessive generation of vasodilating substances, which also contributes to a lower than normal pressor response to circulating nervous or humoral substances. The following review analyzes the mechanisms responsible for the vascular hyporesponse to vasoconstrictors observed in the experimental models of liver cirrhosis. It has become increasingly clear that, among the great variety of substances studied, nitric oxide (NO) seems to be one of the main contributors to this vascular alteration, since elimination of the endothelium or inhibition of its synthesis corrects it. The mechanism by which NO interferes with the contractile apparatus in smooth muscle cells seems to be related to a direct effect on calcium entry from the extracellular space and release from the internal stores.