Vietnam has established 1.1 million ha of acacia plantations for wood production, managed on 5-to 10-year rotation cycles. Nearly 50% of the resource is managed by small growers holding 1-5 ha woodlots. Acacia plantations have emerged as an important resource for supporting the rural economy and national export revenue. Given the range of climate, terrain, soils, management inputs and skills, plantation productivity varies from 10 to 25 m 3 ha −1 y −1 . Future growth of this sector will depend on improving and sustaining production from the current land base, much of which is already in its second or third rotation. Although studies on sustainable production are limited, available information suggests good prospects for increasing production and improving soils. Breeding has produced genotypes with potential for increasing growth, but this has not generally been matched by sustainable soil and stand management practices. Several current practices warrant immediate change, based on sustainability principles. Internationally, research has established the need for conserving site resources and other judicious management practices. Vietnam should adopt these principles and develop locally appropriate practices to implement them. Greater efforts are required on surveillance of major diseases and tree breeding to improve disease resistance. Because acacia plantations deliver high economic benefits and there are opportunities for improving productivity, an R&D strategy focused on underpinning sustainable management and application would serve the nation well. Key elements include commitments to adaptive research for achieving impacts, effective partnerships between public and private organisations, fostering an integrated approach to management, and special attention to the needs of smallholder growers.
Under halothane anesthesia five dogs were prepared with both hindlimbs isolated from the systemic circulation to allow intermittent placement on extracorporeal perfusion at constant flow. One limb of each dog was surgically denervated. In this relatively anesthetic-free preparation, graded equivalent doses of alfentanil, fentanyl, and sufentanil were infused over 30 s, and vascular resistance was measured. Increasing opioid administration caused a progressive diminution in peripheral resistance. By the high dose level, alfentanil (500 micrograms/kg), fentanyl (50 micrograms/kg), and sufentanil (6 micrograms/kg) caused equal and significant decreases of 48%, 48%, and 44% in resistance, respectively. There was no difference among the opioids in effects on resistance at equivalent dosages. Neither pretreatment with naloxone nor denervation changed the response to the narcotics. We conclude that the three synthetic opioids produce vasodilation by direct action on the peripheral vascular smooth muscle.
Abstract• The aim of this study was to investigate the effectiveness of using cellulose content, measured by the diglyme-HCl method, as a selection trait in breeding programs for kraft pulp yield in Eucalyptus urophylla.• A total of 275 trees from sixty-two families were sampled from a thinned progeny trial of E. urophylla in northern Vietnam to evaluate cellulose content from breast-height increment cores. Among those, twenty unrelated trees were felled to evaluate cellulose content and pulp yield from breastheight disk samples.• The regression of pulp yield of disk samples on cellulose content was strong either from disks (R 2 = 0.83) or increment cores (R 2 = 0.69). There was no significant difference in cellulose content between the provenances. The narrow-sense within-provenance heritability of cellulose content was 0.50 and the coefficient of additive genetic variation was 3.9%. Genetic correlations between cellulose content and growth (0.28-0.45) or wood basic density (-0.02) were not significantly different from zero.• Breast-height increment core cellulose content measured by diglyme-HCl method is under strong genetic control and can be used to rank trees for pulp yield in E. urophylla plantations. Selection for increased cellulose content would have only minor effects on growth and wood basic density. Mots-clés :teneur en cellulose / Eucalyptus urophylla / corrélation génétique / héritabilité / rendement en pâte Résumé -La teneur en cellulose comme un trait de sélection pour l'amélioration du rendement en pâte kraft d'Eucalyptus urophylla.• L'objectif de cette étude était d'étudier l'efficacité de l'utilisation de la teneur en cellulose, mesuré par la méthode diglyme-HCl, comme un trait de sélection dans les programmes d'amélioration du rendement en pâte kraft chez Eucalyptus urophylla.• Un total de 275 arbres issus de soixante-deux familles ont été échantillonnés, à partir d'un essai de descendance d' E. urophylla dans le nord du Vietnam, pour évaluer la teneur en cellulose de carottes d'accroissement prélevées à hauteur de poitrine. Parmi ces arbres, vingt ont été abattus afin d'évaluer la teneur cellulose et le rendement en pâte de disques échantillons, prélevées à hauteur de poitrine.• La régression de la production de pâte du disques échantillons a été forte sur la teneur en cellulose, soit à partir des disques (R 2 = 0.83) ou des carottes d'accroissement (R 2 = 0.69). Il n'y a pas de différence significative pour la teneur en cellulose entre les provenances. Le sens restreint dans l'héritabilité intra-provenance de la teneur de la cellulose était 0,50 et le coefficient de variation géné-tique additive a été de 3,9 %. Les corrélations génétiques entre la teneur en cellulose et la croissance (0,45) ou l'infra densité du bois (-0,02) ne sont pas significativement différentes de zéro.• La teneur en cellulose des carottes d'accroissement mesurée par la méthode diglyme-HCl est sous contrôle génétique fort et peut être utilisée pour classer les arbres pour le rendement en pâte dans les plantations d'E. ...
We studied the effects of graded exposure to hyperbaric (1,875 mm Hg) oxygen therapy in an acute stroke model prepared by unilateral carotid artery interruption in gerbils. Pentobarbital alone, superoxide dismutase alone, two periods of hyperbaric oxygen alone, and each agent combined with hyperbaric oxygen were administered to investigate possible mechanisms of protection from cerebral ischemia. Survival rates and neurologic deficit scores over 5 days in all treated groups were compared with those in a control group. Survival rates in the groups subjected to 2 (63.9±4.0%) and 4 hours (70.1 ±5.2%) of hyperbaric oxygen alone were significantly higher than in the control group (53.6 ±4.2%). The group treated with pentobarbital alone also demonstrated increased survival (69.8 ±7.0%), but the combination of therapeutic regimens offered no apparent additive protection. By 5 days there were no differences in the neurologic deficit scores of the survivors in the groups. The toxic pulmonary effects of hyperbaric oxygen were assessed in a pilot LD M study. The pressure used caused no mortality during 4 hours of exposure, and the calculated LD M was 7.26 hours. This investigation demonstrates that graded doses of hyperbaric oxygen given after the insult increase survival in a gerbil model of stroke. (Stroke 1990^21:119-123)
A total of 172 clones of Eucalyptus camaldulensis were tested in three clonal tests in northern, north-central and southern Vietnam, with 32 of them planted across all three sites. At age 3-5 years, the clonal repeatabilities were 0.18-0.42 for growth traits, 0.71-0.78 for wood basic density and 0.56-0.66 for pilodyn penetration. Genotypic correlations between growth and density at the three sites were from -0.24 to 0.17, and did not differ significantly from zero. Genotypic correlations between sites were 0.32-0.56 for growth traits at age 3 years, and 0.72-0.88 for density and pilodyn penetration. Selection gains for breast height diameter at individual sites at a selection proportion of 5% were 22-32%, with minor effects on density. Selection for diameter at one site gave indirect responses in diameter at the other two sites that were only 40-60% of the gains obtainable from direct selection at those sites. This study shows that fast-growing E. camaldulensis clones can be selected in Vietnam with only minor effects on density. Selection for growth should be regionally based to maximize selection gain whereas clonal rankings for density will change little across regions.
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