FOREST STRUCTURE AND REGENERATION PATTERN OF BETULA UTILIS D. DON IN MANASLU CONSERVATION AREA, NEPAL

Forest structure and regeneration of Betula utilis (D. Don) was studied in birch forestlocated in Samagaun valley (3500 – 4000 m) of Manaslu Conservation Area. Vegetationsampling was done by quadrat method. Altogether 40 quadrats were sampled to determinethe Importance Value Index (IVI) of tree species, and distribution pattern of seedlings andsaplings. Regeneration was assessed by density - diameter curve. Four tree species wererecorded from the forest. Betula utilis was the dominant tree species with the highestImportance Value Index (173.22) in mixed Betula forest and 262.96 in pure Betula forestand Abies spectabilis was the co – dominant species (65.95) in mixed Betula forest whileRhododendron campanulatum was the co-dominant species (37.03) in pure Betula forest.Density of Betula utilis increased with increase in elevation where as density of other treespecies decreased with increase in elevation. Mixed Betula forest at lower elevation wasyoung. The density diameter curve of the tree population of Betula utilis, both on mixed andpure forests, deviated slightly from the typical reverse J shaped structure and hence did notshow the sustainable regeneration. The sapling density was higher than seedling density.The distribution of seedlings and saplings were not uniform among the sampling plots.DOI: http://dx.doi.org/10.3126/eco.v20i0.11472ECOPRINT An International Journal of EcologyVol. 20, 2013page: 107-113

The Optimization on Tread Profile Based on Wheel-Rail Match

The matching status of wheel/rail affect the driving stability and safety directly. It could improve the dynamic behaviors by optimizing the matching status of wheel/rail. Taking the wheel rim tread named LMa as an object, the wheel diameter curve method was used to optimize the profile of tread LMa. Then the dynamic behaviors of the optimized profile (LMa-G) were obtained by the dynamic analysis. The results obtained indicate that the profile of tread LMa - G showing better contact performance.

Determinants of terminal mesenteric artery resistance during the first postnatal month

Experiments were conducted to delineate the vascular effector systems that contribute to setting mesenteric vascular tone in swine during the first postnatal month. Terminal mesenteric arteries (TMA), which function as resistance vessels, were studied in vitro with a microvascular perfusion system allowing independent pressure and flow manipulation. When pressure was varied 0–100 mmHg in the absence of flow, TMA from 1-day-old animals demonstrated myogenic vasoconstriction, whereas TMA from 40-day-old animals did not. In 1- but not 40-day-old TMA, the endothelin A (ETA) receptor antagonist BQ-610 shifted the pressure-diameter curve upward, whereas the ETB receptor antagonist BQ-788 and the l-arginine analog N G-monomethyl-l-arginine (l-NMMA) shifted the curve downward; in all instances, myogenic vasoconstriction was preserved. Flow eliminated myogenic vasoconstriction in 1-day-old TMA, i.e., diameter increased as a function of pressure. The effect of BQ-610 was lost under flow conditions; however, BQ-788 and N-acyl-l-Trp-3,5-bis-(trifluoromethyl) benzyl ester, an antagonist specific to the substance P neurokinin-1 (NK1) receptor, shifted the pressure-diameter curve downward in the presence of flow, whereas l-NMMA restored myogenic vasoconstriction. Adding flow had no effect on the pressure-diameter relationship in 40-day-old TMA. Other blocking agents, including prazosin, losartan, indomethacin, and charybdotoxin, had no effect on the pressure-diameter relationship in either age group under flow or no-flow conditions. Constitutive production of nitric oxide (NO) and endothelin-1 participates in setting resistance in 1-day-old TMA, and important stimulants to NO production include flow and activation of ETB and NK1 receptors. In contrast, 40-day-old TMA act as passive conduits in which the elastic properties of the vessel are the primary determinant of diameter.

Myogenic responses of isolated rat skeletal muscle venules: modulation by norepinephrine and endothelium

The pressure-induced myogenic response of large venules of skeletal muscle and its possible interactions with adrenergic receptor activation and endothelial factors have not yet been elucidated. Therefore, first-order venules of rat gracilis muscle were isolated, cannulated, and placed in an organ chamber. Changes in internal diameter of the vessels as a function of perfusion pressure (PP) were obtained. In response to increases in PP (0.5-17.5 mmHg), the diameter of venules increased from 197.1 +/- 23.96 to 369 +/- 14.1 microns. In passive conditions (in Ca(2+)-free solution), the pressure-diameter curve of venules shifted significantly upward. In the presence of norepinephrine (NE; 10(-6) M) in the bath solution, the pressure-diameter curve of active venules shifted significantly downward, and in the pressure-normalized diameter curve, a negative slope developed (-6.1 +/- 4.6). In both the absence and presence of NE, removal of endothelium significantly reduced venular diameters in the pressure ranges of 3-5 and 2-5 mmHg, respectively, but did not change significantly the characteristics of the pressure-diameter curves. These findings indicate that the smooth muscle of venules actively responds to changes in intraluminal pressure. This response is greatly facilitated by NE and modulated by the endothelium. The myogenic response of skeletal muscle venules, especially in the presence of NE, could have a role in the regulation of the resistance and capacitance of venules and, consequently, blood flow and tissue exchange in skeletal muscle.

New application of a polynomial curve to plot volume estimation

This paper presents a new method of plot volume estimation using a limited sample of heights. It requires measurement of all diameters in the plot and a limited number of height measurements per plot within a plot-specific diameter class predefined by the method. It also requires a diameter-based description of tree form. The method utilizes a polynomial curve to relate heights and diameters, but does not provide information on the plot height structure in the form of a traditional height–diameter curve. The approach was examined using data from north-central Ontario jack pine (Pinusbanksiana Lamb.) stands. The developed method of stand volume estimation is precise and unbiased with respect to height measurements; it reduces laborious height measurements compared with traditional methods utilizing a height–diameter curve.

Effect of enalaprilat on splanchnic vascular capacitance during acute ischemic heart failure in dogs

This study investigates the effect of angiotensin-converting-enzyme inhibition by intravenous enalaprilat (100 micrograms/kg) on splanchnic vascular capacitance during acute left ventricular failure induced by coronary microembolization in alpha-chloralose/urethan anesthetized dogs. Changes in hepatic and splenic vascular volumes were determined from organ diameters (sonomicrometry) at 15, 30, and 45 min after enalaprilat injection. Changes in vascular capacitance were assessed from organ pressure-diameter curves obtained during transient hepatic outflow occlusion. Thirty minutes after enalaprilat, hepatic volume was increased by 52 +/- 14 ml (P < 0.01), and portal and hepatic vein pressures were decreased from 10.2 +/- 0.9 to 8.7 +/- 0.8 mmHg (P < 0.01) and from 3.9 +/- 1.6 to 3.1 +/- 0.7 mmHg (P < 0.05), respectively. Splenic volume did not change. Enalaprilat shifted the hepatic pressure-diameter curve upward, resulting in a larger hepatic volume at any given pressure. Curve intercept was increased, suggesting an increase in unstressed vascular volume. Curve slope was unchanged. In conclusion, enalaprilat increased hepatic vascular volume during acute left ventricular failure in dogs. The pressure-diameter curve shift suggests a reduction in the smooth muscle tone of hepatic capacitance vessels.

HEIGHT SAMPLING IN RED PINE AND WHITE SPRUCE PLANTATIONS

Greater height variability in plantations of white spruce necessitates taking more observations for mean height estimates than are required for red pine. Height/diameter curves can provide reliable estimates of mean or dominant height. A parabolic expression of the height/diameter curve has advantages over a free-hand curve for volume estimates in demanding only objective preparation and requiring fewer height observations, but is less accurate for dominant height estimates.

NUMBER OF RHYACIONIA BUOLIANA (SCHIFF.) PER PINE SHOOT AS A POPULATION INDEX, WITH A RAPID DETERMINATION METHOD OF THIS INDEX AT LOW POPULATION LEVELS

The number of R. buoliana per shoot is a good index of its abundance in a pine stand; but the determination of the index at low population levels involves counting large numbers of shoots. However, for the conspicuous third instar larvae and older stages it can be determined rapidly by counting the number of individuals present on a tree and estimating the number of shoots by measuring the stem diameter and referring to a predetermined shoot-diameter curve for the stand.