Potential long-term growth gains from early clump thinning of coppice-regenerated oak stands

A study was established in the Missouri Ozarks to evaluate coppice regeneration of oak. Five years after a 32-year-old stand was clearcut and regenerated naturally through stump sprouts, the dominant sprout on each stump was identified based upon height. Treated plots were thinned to the single dominant sprout on each stump whereas control plots were not thinned. Twenty-five years later the largest 247, 371, 494, and 618 stems per ha were examined and height of the dominant sprout at age 5 was found to be strongly related to dbh at age 30 in both thinned and unthinned plots. However, in the thinned plots, the largest 494 stems per ha were on average 11%, 28%, and 58% greater, respectively, in height, dbh, and volume compared to similar dominant sprouts in unthinned plots. Logistic regression analysis was used to develop curves for the evaluation of potential gains from clump thinning. In this analysis, the average height of a stand at age 5 was used to estimate thinning gains at age 30.     

A motorized grinder for making soil thin sections

A small hand-held device is described which enables an operator to grind soil thin sections very rapidly as compared to conventional hand grinding. The apparatus is relatively inexpensive and easy to construct as it comprises only a simple motorized grinder and grit impregnated discs 2.5 cm in diameter.     

Dentate gyrus NMDA receptors mediate rapid pattern separation in the hippocampal network

Forming distinct representations of multiple contexts, places, and episodes is a crucial function of the hippocampus. The dentate gyrus subregion has been suggested to fulfill this role. We have tested this hypothesis by generating and analyzing a mouse strain that lacks the gene encoding the essential subunit of the N-methyl-d-aspartate (NMDA) receptor NR1, specifically in dentate gyrus granule cells. The mutant mice performed normally in contextual fear conditioning, but were impaired in the ability to distinguish two similar contexts. A significant reduction in the context-specific modulation of firing rate was observed in the CA3 pyramidal cells when the mutant mice were transferred from one context to another. These results provide evidence that NMDA receptors in the granule cells of the dentate gyrus play a crucial role in the process of pattern separation.     

Regulation of blood and lymphatic vascular separation by signaling proteins SLP-76 and Syk

Lymphatic vessels develop from specialized endothelial cells in preexisting blood vessels, but the molecular signals that regulate this separation are unknown. Here we identify a failure to separate emerging lymphatic vessels from blood vessels in mice lacking the hematopoietic signaling protein SLP-76 or Syk. Blood-lymphatic connections lead to embryonic hemorrhage and arteriovenous shunting. Expression of slp-76 could not be detected in endothelial cells, and blood-filled lymphatics also arose in wild-type mice reconstituted with SLP-76-deficient bone marrow. These studies reveal a hematopoietic signaling pathway required for separation of the two major vascular networks in mammals.     

影响烟草特有亚硝胺积累的因素

把Ｎｉｃｏｔｉａｎａ ｐｌｕｍｂａｇｉｎｉｆｏｌｉａ的基因突变种子和普通种子发芽后嫁接在Ｗｅｓｃｏｎｓｉｎ３８烟株上,与温室条件下正常盆栽生长的Ｎｉｃｏｔｉａｎａ ｐｌｕｍｂａｇｉｎｉｆｏｌｉａ和母体Ｗｅｓｃｏｎｓｉｎ３８分析比较,试验结果得出：Ｗｅｓｃｏｎｓｉｎ３８上嫁接Ｎｉｃｏｔｉａｎａ ｐｌｕｍｂａｇｉｎｉｆｏｌｉａ基因突变种子还原酶活性最高,晾制后烟叶中烟草特有的亚硝胺含量次之;温室盆栽的     

Comment on "Absence of cooling in New Zealand and the adjacent ocean during the Younger Dryas chronozone"

Barrows et al. (Reports, 5 October 2007, p. 86) presented cosmogenic exposure dates and data from an ocean sediment core that challenge evidence for glacier advance in New Zealand during the Younger Dryas event. We use modeling of geomorphic processes to argue that their cosmogenic exposure dates are inconclusive.     

Percolation Theory, Thermoelasticity, and Discrete Hydrothermal Venting in the Earth's Crust

As hydrothermal fluid ascends through a network of cracks into cooler crust, heat is transferred from the fluid to the adjacent rock. The thermal stresses caused by this heating close cracks that are more or less vertical. This heating may affect network connections and destroy the permeable crack network. Thermoelastic stresses caused by a temperature difference of approximately 1000 degrees C can decrease the interconnectivity of a crack network to the percolation threshold. If the temperature is slightly less, thermoelastic stresses may focus the discharge in hydrothermal systems into discrete vents.     

Population changes in Phytophthora infestans in Taiwan associated with the appearance of resistance to metalaxyl

In recent years, late blight, caused by Phytophthora infestans (Mont) De Bary, has increased in severity in many parts of the world, and this has been associated with migrations which have introduced new, arguably more aggressive, populations of the pathogen. In Taiwan, late blight has been endemic on outdoor tomato crops grown in the highlands since the early 1900s, but recent epidemics have been more damaging. To ascertain the present status of the Taiwanese population of P infestans, 139 isolates of the pathogen collected and maintained by the Asian Vegetable Research and Development Center (AVRDC) were characterized using mating type, metalaxyl sensitivity, allozyme genotype, mitochondrial haplotype and RFLP fingerprinting. Up to 1997, all isolates were found to belong to the old clonal lineage of P infestans (US-1 and variants), but in isolates from 1998 a new genotype appeared, and by 2000 this had apparently completely displaced the old population. This new genotype was an A1 mating type and has the dilocus allozyme genotype 100/100/111, 100/100 for the loci coding for glucose-6-phosphate isomerase and peptidase, respectively. These characters, together with RG57 fingerprinting, indicated that these isolates belonged to the US-11 clonal lineage, a minority (11%) being a previously unreported variant of US-11. Whereas metalaxyl-resistant isolates were not detected in the old population, 96% of the new genotypes proved resistant, with the remainder being intermediate in sensitivity. It may be inferred from this sudden, marked change in the characteristics of the Taiwanese P infestans that a new population of the pathogen was introduced around 1997-98 and that this may well have already been metalaxyl-resistant when it arrived, although a role for in situ selection cannot be excluded.