Showing papers by "Colorado State University published in 1978"

Kinematical studies of the flows around free or surface-mounted obstacles; applying topology to flow visualization

Abstract: In flows around three-dimensional surface obstacles in laminar or turbulent streamsthere are a number of points where the shear stress or where two or more component,s of the mean velocity are zero. In the first part of this paper we summarize and extend the kinematical theory for the flow near these points, particularly by emphasizing the topological classification of these points as nodes or saddles. We show that the zero-shear-stress points on the surface and on the obstacle must be such that the sum of the nodes ΣN and the sum of the saddles Σs satisfy \[ \Sigma_N -\Sigma_S = 0. \] If the obstacle has a hole through it, such as a passageway under a building, \[ \Sigma_N -\Sigma_S =-2. \] If the surface is a junction between two pipes, \[ \Sigma_N -\Sigma_S =-1. \] We also consider, in two-dimensional plane sections of the flow, the points where the components of the mean velocity parallel to the planes are zero, both in the flow and near surfaces cutting the sections. The latter points are half-nodes N′ or half-saddles S′. We find that \[ (\Sigma_N +{\textstyle\frac{1}{2}}\Sigma_{N^{\prime}}-(\Sigma_{S^{\prime}}+{\textstyle\frac{1}{2}}\Sigma_{S^{\prime}}) = 1-n, \] where n is the connectivity of the section of the flow considered.In the second part new flow-visualization studies of laminar and turbulent flows around cuboids and axisymmetric humps (i.e. model hills) are reported. A new method of obtaining a high resolution of the surface shear-stress lines was used. These studies show how enumerating the nodes and saddle points acts as a check on the inferred flow pattern.Two specific conclusions drawn from these studies are that: for all the flows we observed, there are no closed surfaces of mean streamlines around the separated flows behind three-dimensional surface obstacles, which con-tradicts most of the previous suggestions for such flows (e.g. Halitsky 1968);the separation streamline on the centre-line of a three-dimensional bluff obstacle does not, in general, reattach to the surface.

Estimates on the production of CO and H2 from the oxidation of hydrocarbon emissions from vegetation

Abstract: Extrapolating from extensive field measurements on foliar emissions in the U.S. approximate global inputs of isoprene and terpenes of 3.5 times 10 to the 14th power and 4.8 times 10 to the 14th power g(C)/yr, respectively, are obtained. The oxidation of these hydrocarbons could contribute in an important way to the atmospheric sources of CO (4.2-13.3 times 10 to the 14th power g/yr) and H2 (10-35 times 10 to the 12th power g/yr), and to organic species soluble in rainwater

Sapwood water storage: its contribution to transpiration and effect upon water conductance through the stems of old‐growth Douglas‐fir

Abstract: Enough water is stored in the sapwood of large Douglas-fir to significantly contribute to transpiration. Sapwood water content falls through the season, causing the wood's conductivity to fall. This leads to low leafwater potentials, stomatal closure, and reduced photosynthesis by the trees. The amount of water stored in the sapwood of Douglasfir 50-60 m tall, growing in the Cascade Mountains of Oregon, was estimated periodically over two seasons from measurements of sapwood relative water content (Rs). The relationship between Rs and volume of water contained in the sapwood was determined in the laboratory, and an equation describing the variation of relative conductivity (K) with Rs was derived from the literature. Stomatal conductance (ks) and leaf water potentials were measured in the field. The relative conductivity of the sapwood was calculated from estimates of the flow rate through the tree and differences in water potential between dawn and the time of comparison. Flow rate was assumed to equal transpiration rate, calculated from the Penman-Monteith equation using measured ks values. A sixfold decrease in K during the summer was attributed to changes in Rs. The maximum observed diurnal variation in K would require a change in RS estimated at 25%. About 270 m3 ha−1 (27 mm) of water were stored in sapwood, and 75% of that was in the stemwood. Withdrawal from this store reached 1.7 mm day−1 on clear days after cloudy or rainy weather. Recharge could be almost as fast (up to 1.6 mm day−1) after rain, but was very slow if the foliage remained wet.

The origin of ozone in the troposphere

Abstract: Examination of the distribution of tropospheric ozone indicates that surface destruction in the Northern Hemisphere (NH) should be about three times larger than in the Southern Hemisphere (SH). If, according to the traditional understanding of ozone, this species were a passive tracer in the troposphere, a threefold larger flux out of the stratosphere should exist in the NH than in the SH. However, meteorological analyses fail to support such pronounced hemispheric differences in stratosphere-troposphere exchange. Alternatively, therefore, it is hypothesized that photochemical synthesis of ozone in the troposphere may be particularly important in the NH because of asymmetries in the sources and distribution of carbon monoxide, hydrocarbons and nitric oxide.

Applicability of kinematic and diffusion models.

Abstract: The applicability of the kinematic and diffusion models of open channel flow is assessed by comparing the propagation characteristics of sinusoidal perturbations to the steady uniform flow for the kinematic, diffusion, and dynamic models (the dynamic model is that based on the complete Saint Venant equations). The comparison allows the determination of inequality criteria that need to be satisfied if the kinematic or diffusion models are to simulate the physical phenomena within a prescribed accuracy. It is shown that bed slope and wave period (akin to wave duration in waves of shape other than sinusoidal) are the important physical characteristics in determining the applicability of the approximate models. Larger bed slopes or long wave periods, or both, will satisfy the inequality criteria. In practice, larger bed slopes are those of overland flow, and long wave periods are those corresponding to slow-rising flood waves.

Aromatic side-chain contributions to the far ultraviolet circular dichroism of peptides and proteins

Abstract: The rotational strength of the La transition in phenylalanine and tyrosine side chains has been calculated for dipeptides with various backbone and side-chain conformations. Similar calculations have also been performed for tripeptides in the β-turn conformation with aromatic residues at the corners of the turn. The interaction of the aromatic ring with neighboring peptides generates rotational strengths in the La transition of the order of 0.1 Debye-Bohr magneton. When the preferred backbone and side-chain conformations are considered, it is found that the most probable conformations have positive La bonds. This result accounts for the observation that the N-acyl amino acid amides of L-Tyr and LPhe have positive La bands. It also suggests that, although other interactions may affect the numerical value and even the sign, there will be a significant positive contribution to the rotational strength of aromatic residues in globular proteins from nearest-neighbor interactions. Calculations on proteins of known conformation at the nearest-neighbor level confirm the tendency toward positive La contributions for Phe and Tyr residues. This contribution can be of the order of 10% of the observed CD even in proteins with rather strong amide contributions. In some proteins, such as the gene 5 protein from bacteriophage fd and many snake-venom toxins, side-chain contributions from Tyr and Trp residues manifest themselves as positive CD bands in the 225–250-nm region. The magnitude of the nearest-neighbor contributions and the trend toward positive contributions are consistent with the observation of such CD bands in globular proteins. No special stacking interaction among aromatic side chains needs to be invoked.

The effects of water- and nitrogen-induced stresses on plant community structure in a semiarid grassland.

Abstract: A replicated factorial experiment was designed to test the hypothesis that manipulating inputs of water and mineral nitrogen to a semiarid grassland would disrupt existing interactions resulting in alteration of the structure of the primary producer community. Alteration of community structure was measured as either changes in growing season average biomass of 6 functional groups of plants or their relative contribution to total biomass.Additions of water greatly increased total biomass and resulted in the replacement of one of the dominant functional groups by a subordinate group. The water plus nitrogen treatment resulted in large biomass increases in two of the dominant functional groups, elimination of succulents as an important component of community structure, and establishment of several introduced weedy species. Continuation of the experiment will likely result in complete dominance of the water plus nitrogen treatment by these introduced species.Despite the large changes in community structure observed as a result of water- and nitrogen-induced stresses we conclude that the shortgrass prairie in northcentral Colorado is asymptotically stable with respect to these influences.

Muskingum-Cunge Method with Variable Parameters

Abstract: The Muskingum-Cunge method in which the parameters K and X are allowed to vary in time and space is investigated A three-point approach and an iterative four-point approach to the calculation of the variable parameters are shown to be sufficiently accurate in the simulation of flood flows A two-point approach is shown to be inaccurate in the calculation of peak discharge and travel time Furthermore, the two-point method results in a significant loss of mass

Flow Resistance of Large-Scale Roughness

Abstract: A theory of the resistance to flow in rivers with large-scale roughness is developed and a resistance equation is constructed using data from the upper River Tees, England. The theoretical analysis shows that, in channels with large values of relative roughness, resistance to flow depends mainly on the size, shape, spacing, and size distribution of the boundary roughness elements. Channel geometry is important only in its effect on the drag of the elements. This theory is illustrated using data from field sites at which roughness shape and size distribution were similar and roughness spacing could be directly related to relative roughness. In the resistance equation (which is specific to the field sites) the resistance coefficient varies with just relative roughness and a parameter of channel geometry.

A microprocessor system for multifunctional control of upper-limb prostheses via myoelectric signal identification

Abstract: The paper deals with the problem of controlling artificial limbs in cases where several limb functions require control. These situations are of importance, especially to above-elbow upper-extremity amputees. Here, classical EMG (myoelectric) controllers have failed in the past, since they were based on only determining existence or nonexistence of an EMG signal. Recent work by Lyman et al. at UCLA has approached this multifunctional (MF) control problem via using a large number of electrodes, though still considering only a limited part of the EMG spectrum. The present approach is based on earlier work by Graupe et al. [4], considering the whole spectrum of the EMG signal via identifying its time series model such that several limb functions can be controlled from a single signal site. However, the present work subsequently employs parallel filtering to discriminate between the various limb functions of interest to achieve fast discrimination and control as required for practical applications, since this allows the identification itself to be performed off line. Real-time on-line results are presented in the paper, as recently obtained from tests carried out on a 1969 Vietnam above-elbow amputee who had most severe (90 percent) nerve and muscle loss at his stump, and could therefore not use more than one or two electrode pairs. The results, where complete discrimination was achieved within 0.15 to 0.2 seconds using 8-bit Intel 8080 microprocessors at double precision (incorporating hardware multipliers), have yielded an 85 percent success rate in discrimination between four to five limb functions using a single electrode pair. It is noted that the amputee mentioned had no previous EMG actuation training whatsoever.

Simple phenol and phenolic compounds in food flavor

Abstract: Simple phenol and phenolic compounds occur in a vast portion of our diet. This review attempts to discuss their occurrences relative to our food supply. In addition, their chemical, nutritional, and sensory properties are explored, as well as methods for their isolation, identification, and quantitation.

Serum Melatonin Concentrations During Different Stages of the Annual Reproductive Cycle in Ewes

Abstract: To determine the effect of reproductive status on photo-induced alterations in serum concentrations of melatonin, samples of blood were collected at 2 h intervals for 96 h from ewes during estrous cycles, anestrus, the transition from estrus to anestrus and the transition from anestrus to estrus. Two groups of ewes were sampled during the normal breeding season. One group was sampled during the luteal phase of the estrous cycle (Days 8-11 of a 16 day cycle) and the other group was sampled during the follicular and estrual phases of the cycle (Days 15, 16, 1, 2). At each of the 4 times of the year sampled, there was a distinct circadian rhythm in peripheral concentrations of melatonin. Average night-time concentrations (297 ± 46.5, S.E.M., pg/mI) were 2-3 times greater than average day-time concentrations (140 ± 16.8, S.E.M., pg/mI). Concentrations of melatonin remained constant throughout the dark phase. Due to alterations in duration of the photoperiod, the duration of elevated melatonin concentrations was longest when ewes were exhibiting estrous cycles and shortest when ewes were exhibiting anestrus. Mean concentrations of melatonin during the day or during the night did not differ significantly during different reproductive states. To determine precisely how serum melatonin concentrations reflect light-dark transitions, melatonin concentrations were quantified in samples of blood collected at 1 mm intervals from 3 ewes during the mid-luteal phase of the estrous cycle. Lights were left on 2 h into the normal night, turned off 1 h and then turned on. Sampling was initiated 30 mm before the initial light-dark transition and was terminated 30 mm after the return to light. When ewes were exposed to light, plasma concentrations of melatonin remained at baseline levels of 10-100 pg/mI. Upon initiation of darkness, there was a short lag (5-10 mm) after which melatonin concentrations elevated to levels of 150-300 pg/mi. This elevation occurred over a 2 mm interval in 2 ewes and over a 10 mm interval in the third. Upon return to light, melatonin concentrations declined to baseline levels within 5-10mm.

The Generation of Secondary Ice Particles in Clouds by Crystal–Crystal Collision

Abstract: The number of fragments generated by crystal collisions in a cloud is a product of the number of fragments produced per collision and the collision frequency. The first term, called the fragment generation function, was obtained experimentally by taking high-speed photographs of collisions of natural ice crystals with a fixed plate. The number of fragments in a collision was found as a function of the change in momentum on impact with a fixed plate and as a function of crystal type and degree of rime. The difference in the change in momentum for collisions in a cloud compared to the fixed plate is treated theoretically and developed into a mathematical model. The collision frequency is incorporated into the model and rates of fragment generation studied for different crystal combinations, sizes and concentrations. The generation of secondary particles by mechanical fracturing does not explain the presence of large concentrations of ice crystals in relatively warm clouds. The additional crystals g...

Cryptosporidiosis in immunodeficient Arabian foals.

Abstract: Five of six immunodeficient Arabian foals that died of adenoviral infection were found to be infected with an intestinal coccidian of the genus Cryptosporidium. Various developmental stages of the ...

Molybdenum toxicity and hypocuprosis in ruminants: a review.

Abstract: Elevated Mo intakes depress Cu availability and may produce a physiological Cu deficiency in ruminants. Total sulfur or sulfate in the ration generally potentiates the effect of Mo. The ratio of Cu to Mo in feed is important regardless of the absolute amount of each. For this reason, and because of the importance of the S content of the diet, it is impossible to define safe dietary limits for Cu and Mo. Physiological Cu deficiencies are produced by four classes of feeds: (1) high Mo, generally above 100 ppM, (2) low Cu:Mo ratio, 2:1 or less, (3) Cu deficiency, below 5 ppM, and (4) high protein, 20 to 30% protein in fresh forage. The latter situation probably results from higher levels of sulfide produced from sulfur amino acids during rumen fermentation. Copper sulfide is largely unabsorbed. Future instances of hypocuprosis in the US are most likely to occur from marginal copper deficiencies in forages.

Catecholamine-induced stimulation of progesterone and adenosine 3',5'-monophosphate production by dispersed ovine luteal cells.

Abstract: Epinephrine (E), isoproterenol (ISO), and norepinephrine (NE) as well as LH and N,O-dibutyryl cAMP [(Bu)2cAMP] stimulated progesterone production by enzymatically dispersed cells of the ovine corpus luteum. cAMP synthesis was also stimulated by LH and the catecholamines. The hormonally induced stimulation of progesterone and cAMP synthesis was inhibited by the β-adrenergic antagonist propranolol at a concentration (3 × 10-4 M) at which the drug acts nonspecifically on plasma membranes. At a concentration where propranolol acts as a competitive inhibitor of β-adrenergic receptors (6 × 10-6 M), propranolol did not block LH or (Bu)2cAMP-induced steroidogenesis but continued to inhibit the stimulatory effect of the catecholamines. Catecholamines might exert an indirect effect on steroidogenesis by stimulating fibroblasts or erythrocytes to produce cAMP which could then diffuse into granulosa and thecal cells to stimulate progesterone production. However, incubation of isolated small cells (fibroblasts and ery...

Anxiety management training for pattern A behavior.

Abstract: During a 3-week period, seven subjects were treated with Anxiety Management Training (AMT) while seven subjects served as a wait-list control. Pattern A behaviors, measured by the Jenkins Activity Survey (JAS), self-report of anxiety, as measured by the Spielberger state (STAI-S) and trait (STAI-T) anxiety inventories, and indices of blood pressure, cholesterol, and triglycerides were obtained before and after treatment. Results indicate that treated subjects compared to controls showed significant reductions in the Hard-Driving component of pattern A behavior, showed lower posttest STAI-A and STAI-T scores, but failed to evidence a statistically significant reduction in systolic and diastolic blood pressure or cholesterol and triglyceride levels. The implications of these data to theoretical and practical conceptualizations of stress management are discussed.

Ion beam divergence characteristics of three-grid accelerator systems

Abstract: The first comprehensive experimental investigation of two-grid accelerator systems is presented. A wide range of geometrical grid parameters and grid set operating conditions were investigated for their effect on ion beam divergence. Ion beam divergence was found to depend most strongly on normalized perveance per hole, grid separation ratio, net-to-total accelerating voltage ratio, and discharge-to-total accelerating voltage ratio variations. The graphical results contained herein provide guidelines for the design of ion accelerator systems. A general ion beam divergence angle correlation was developed to permit approximate beam divergence estimates, at parametric values other than those tested, of present grid set designs. Although argon was the main test gas used in this study, it is shown that the results are applicable to other propellants as well.

Route of Melatonin Secretion in Sheep

Abstract: To determine the proportion of the total melatonin output which is secreted directly into the third ventricle of sheep, samples of blood from the jugular vein and of cerebrospinal fluid (CSF) from the cisterna magna were obtained during 128-min intervals on three consecutive nights from four ewes. Blood was withdrawn continuously at a rate of 3 ml/min and pooled into 1-min fractions. Simultaneously with the collection of blood, 0.5-ml samples of CSF were obtained from the cisterna magna every 4 min. Melatonin concentrations were quantified in all samples by radioimmunoassay. During the sampling interval of the first night, lights were left on for 32 min, turned off for 64 min, and then turned back on for an additional 32 min. These samples were utilized to obtain the concentration profiles of melatonin in jugular blood and cisternal CSF during an endogenous surge of melatonin secretion. Plasma concentrations of melatonin remained between 10 and 100 pg/ml in two Corriedale crossbred ewes and between 200 an...