Showing papers by "Colorado State University published in 1994"

A genetic algorithm tutorial

Abstract: This tutorial covers the canonical genetic algorithm as well as more experimental forms of genetic algorithms, including parallel island models and parallel cellular genetic algorithms. The tutorial also illustrates genetic search by hyperplane sampling. The theoretical foundations of genetic algorithms are reviewed, include the schema theorem as well as recently developed exact models of the canonical genetic algorithm.

Nanomaterials: a membrane-based synthetic approach.

Abstract: Materials with nanoscopic dimensions not only have potential technological applications in areas such as device technology and drug delivery but also are of fundamental interest in that the properties of a material can change in this regime of transition between the bulk and molecular scales. In this article, a relatively new method for preparing nanomaterials, membrane-based synthesis, is reviewed. This method entails synthesis of the desired material within the pores of a nanoporous membrane. Because the membranes used contain cylindrical pores of uniform diameter, monodisperse nanocylinders of the desired material, whose dimensions can be carefully controlled, are obtained. This "template" method has been used to prepare polymers, metals, semiconductors, and other materials on a nanoscopic scale.

Dendritic spines: cellular specializations imparting both stability and flexibility to synaptic function.

Abstract: Dendritic spines, the tiny protrusions that stud the surface of many neurons, are the location of over 90% of all excitatory synapses that occur in the CNS. Their small size has, in large part, made them refractory to conventional experimental approaches. Yet their widespread occurrence and likely involvement in learning and memory has motivated extensive efforts to obtain quantitative descriptions of spines in both steady state and dynamic onditions. Since the seminal mathematical analyses of D’Arcy Thompson (1992), the power of quantitatively establishing key parameters of structure has become recognized as a foundation of successful biological inquiry. For dendritic spines, highly precise determinations of structure and its variation are again proving to be essential for establishing a valid concept of function. The recent conjunction of high quality information about the structure, function, and theoretical implications of dendritic spines has, in fact, produced a flurry of

Phylogeny of hard- and soft-tick taxa (Acari: Ixodida) based on mitochondrial 16S rDNA sequences

Abstract: Ticks are parasitiform mites that are obligate hematophagous ectoparasites of amphibians, reptiles, birds, and mammals. A phylogeny for tick families, subfamilies, and genera has been described based on morphological characters, life histories, and host associations. To test the existing phylogeny, we sequenced approximately 460 bp from the 3' end of the mitochondrial 16S rRNA gene (rDNA) in 36 hard- and soft-tick species; a mesostigmatid mite, Dermanyssus gallinae, was used as an outgroup. Phylogenies derived using distance, maximum-parsimony, or maximum-likelihood methods were congruent. The existing phylogeny was largely supported with four exceptions. In hard ticks (Ixodidae), members of Haemaphysalinae were monophyletic with the primitive Amblyomminae and members of Hyalomminae grouped within the Rhipicephalinae. In soft ticks (Argasidae), the derived phylogeny failed to support a monophyletic relationship among members of Ornithodorinae and supported placement of Argasinae as basal to the Ixodidae, suggesting that hard ticks may have originated from an Argas-like ancestor. Because most Argas species are obligate bird octoparasites, this result supports earlier suggestions that hard ticks did not evolve until the late Cretaceous.

A general model for soil organic matter dynamics: sensitivity to litter chemistry, texture and management.

Abstract: Different conceptual and simulation models of soil organic matter (SOM) have been developed during the last 20 yr. Jenkinson and Rayners (1977) developed the first widely used SOM model. This model divided soil C into active, slow and passive pools that have different turnover times (1 yr, 30 yr, and 1500 yr, respectively). This conceptual framework has been used in many of the recently developed SOM models (van Veen & Paul, 1981; Parton et aI., 1987; Jenkinson, 1990). van Veen and Paul (1981) improved on Jenkinson and Rayners (1977) model by including concepts of physical and chemical protection, and factors such as soil erosion and soil cultivation. Parton et al. (1987) added the impact of soil texture on SOM dynamics and developed generalized nutrient cycling submodels which simultaneously simulate soil C and inorganic and organic N, P and S dynamics (Parton et aI., 1988). Jenkinson's most recent model (Jenkinson, 1990) also includes soil physical protection by clay. Many of the concepts used in the different SOM models have been incorporated into the nutrient cycling models that are linked to crop plant production models [Erosion-Productivity Impact Calculator (EPIC), Williams et aI., 1985; Nitrogen-Tillage-Residue Management (NTRM), Shaffer, 1985; DeNitrification and DeComposition Model (DNDC), Li

Development of a driving anger scale

Abstract: A cluster analysis of responses from more than 1500 college students to 53 potentially angering driving-related situations yielded a 33-item driving anger scale (alpha reliability = .90) with six reliable subscales involving hostile gestures, illegal driving, police presence, slow driving, discourtesy, and traffic obstructions. Subscales all correlated positively, suggesting a general dimension of driving anger as well as anger related to specific driving-related situations. Men were more angered by police presence and slow driving whereas women were more angered by illegal behavior and traffic obstructions, but differences compensated so there were no gender differences on total score. A 14-item short form (alpha reliability = .80) was developed from scores more highly correlated (r = .95) with scores on the long form. Driving anger may have potential value for research on accident prevention and health psychology.

A global 1° by 1° NDVI data set for climate studies. Part 2: The generation of global fields of terrestrial biophysical parameters from the NDVI

Abstract: A satellite-based 1° by 1° normalized difference vegetation index (NDVI) data set has been processed to derive land surface parameters for general circulation models of the atmosphere (GCMs). Prior to calculation of the land surface parameters, corrections were applied to the source NDVI data set to account for (i) obvious anomalies in the data time-series, (ii) the effect of variations in solar zenith angle, (iii) data dropouts in cold regions where a temperature threshold procedure designed to screen for clouds also eliminates cold land surface points, and (iv) persistent cloud cover in the tropics. An outline of the procedures for calculating land surface parameters from the corrected NDVI data set is given, and a brief description is provided of source material that was used in addition to the NDVI data. The data sets summarized in this paper should represent improvements over prescriptions currently used in land surface parameterizations in that the spatial and temporal dynamics of key land ...

Demonstration of a discharge pumped table-top soft-x-ray laser

Abstract: We report the first observation of large soft-x-ray amplification ($gl=7.2$) in a discharge-created plasma. A fast, \ensuremath{\sim}40 kA, current pulse from a compact discharge was used to excite plasma columns up to 12 cm in length in 4-mm channels, producing population inversion in the $J=0\ensuremath{-}1$ line of Ne-like Ar and resulting in a gain of 0.6 ${\mathrm{cm}}^{\ensuremath{-}1}$ at 46.9 nm. The beam divergence was measured to be 9 mrad.

Long- and short-term effects of fire on nitrogen cycling in tallgrass prairie

Abstract: Fires in the tallgrass prairie are frequent and significantly alter nutrient cycling processes. We evaluated the short-term changes in plant production and microbial activity due to fire and the long-term consequences of annual burning on soil organic matter (SOM), plant production, and nutrient cycling using a combination of field, laboratory, and modeling studies. In the short-term, fire in the tallgrass prairie enhances microbial activity, increases both above-and belowground plant production, and increases nitrogen use efficiency (NUE). However, repeated annual burning results in greater inputs of lower quality plant residues causing a significant reduction in soil organic N, lower microbial biomass, lower N availability, and higher C:N ratios in SOM. Changes in amount and quality of below-ground inputs increased N immobilization and resulted in no net increases in N availability with burning. This response occurred rapidly (e.g., within two years) and persisted during 50 years of annual burning. Plant production at a long-term burned site was not adversely affected due to shifts in plant NUE and carbon allocation. Modeling results indicate that the tallgrass ecosystem responds to the combined changes in plant resource allocation and NUE. No single factor dominates the impact of fire on tallgrass plant production.

Long river profiles, tectonism, and eustasy: A guide to interpreting fluvial terraces

Abstract: Along three rivers at the Mendocino triple junction, northern California, strath, cut, and fill terraces have formed in response to tectonic and eustatic processes. Detailed surveying and radiometric dating at multiple sites indicate that lower reaches of the rivers are dominated by the effects of oscillating sea level, primarily aggradation and formation of fill terraces during sea level high stands, alternating with deep incision during low stands. A eustasy-driven depositional wedge extends tens of kilometers upstream on all rivers (tapering to zero thickness). This distance is greater than expected from studies of the effects of check dams on much smaller streams elsewhere, due in part to the large size of these rivers. However, the change in gradient is nearly identical to other base level rise studies: the depositional gradient is about half that of the original channel. Middle to upper reaches of each river are dominated by the effects of long-term uplift, primarily lateral and vertical erosion and formation of steep, unpaired strath terraces exposed only upstream of the depositional wedge. Vertical incision at a rate similar to that of uplift has occurred even during the present sea level high stand along rivers with highest uplift rates. Strath terraces have steeper gradients than the modern channel bed and do not merge with marine terraces at the river mouth; consequently, they cannot be used to determine altitudes of sea level high stands. Strath formation is a continuous process of response to long-term uplift, and its occurrence varies spatially along a river depending on stream power, and hence position, upstream. Strath terraces are found only along certain parts of a coastal stream: upstream of the aggradational effects of oscillating sea level, and far enough downstream that stream power is in excess of that needed to transport the prevailing sediment load. For a given size river, the greater the uplift rate, the greater the rate of vertical incision and, consequently, the less the likelihood of strath terrace formation and preservation.

Medically important arboviruses of the United States and Canada.

Abstract: Of more than 500 arboviruses recognized worldwide, 5 were first isolated in Canada and 58 were first isolated in the United States. Six of these viruses are human pathogens: western equine encephalitis (WEE) and eastern equine encephalitis (EEE) viruses (family Togaviridae, genus Alphavirus), St. Louis encephalitis (SLE) and Powassan (POW) viruses (Flaviviridae, Flavivirus), LaCrosse (LAC) virus (Bunyaviridae, Bunyavirus), and Colorado tick fever (CTF) virus (Reoviridae, Coltivirus). Their scientific histories, geographic distributions, virology, epidemiology, vectors, vertebrate hosts, transmission, pathogenesis, clinical and differential diagnoses, control, treatment, and laboratory diagnosis are reviewed. In addition, mention is made of the Venezuelan equine encephalitis (VEE) complex viruses (family Togaviridae, genus Alphavirus), which periodically cause human and equine disease in North America. WEE, EEE, and SLE viruses are transmitted by mosquitoes between birds; POW and CTF viruses, between wild mammals by ticks; LAC virus, between small mammals by mosquitoes; and VEE viruses, between small or large mammals by mosquitoes. Human infections are tangential to the natural cycle. Such infections range from rare to focal but are relatively frequent where they occur. Epidemics of WEE, EEE, VEE, and SLE viruses have been recorded at periodic intervals, but prevalence of infections with LAC and CTF viruses typically are constant, related to the degree of exposure to infected vectors. Infections with POW virus appear to be rare. Adequate diagnostic tools are available, but treatment is mainly supportive, and greater efforts at educating the public and the medical community are suggested if infections are to be prevented.

Intracellular trafficking in Mycobacterium tuberculosis and Mycobacterium avium-infected macrophages.

Abstract: Despite the potential role of the macrophage in the eradication of invading microbes, Mycobacterium species have evolved mechanisms to ensure their survival and replication inside the macrophage. Particles phagocytosed by macrophages normally will be delivered into acid lysosomal compartments for degradation. Mycobacterium must, in some way, avoid this fate by modulation of their phagosome. Immunoelectron microscopy of macrophages infected with Mycobacterium avium or Mycobacterium tuberculosis indicates that the vacuolar membrane surrounding the bacilli possesses the late endosomal/lysosomal marker, LAMP-1 (lysosomal-associated membrane protein-1), but lacks the vesicular proton-ATPase. Analysis of the intersection of the bacteria-containing vacuoles with the endocytic network of the macrophage supports previous studies indicating that these bacilli restrict the fusion capability of their intracellular compartments. The occurrence of vesicles containing lipoarabinomannan, discrete from those containing Mycobacterium, indicate that material does traffic out from the mycobacterial vacuole. To compensate for this loss of membrane, the vacuole must remain dynamic and fuse with LAMP-1-containing vesicles to maintain the density of this marker.

Lamarckian Evolution, The Baldwin Effect and Function Optimization

Abstract: We compare two forms of hybrid genetic search. The first uses Lamarckian evolution, while the second uses a related method where local search is employed to change the fitness of strings, but the acquired improvements do not change the genetic encoding of the individual. The latter search method exploits the Baldwin effect. By modeling a simple genetic algorithm we show that functions exist where simple genetic algorithms without learning as well as Lamarckian evolution converge to the same local optimum, while genetic search utilizing the Baldwin effect converges to the global optimum. We also show that a simple genetic algorithm exploiting the Baldwin effect can sometimes outperform forms of Lamarckian evolution that employ the same local search strategy.

The global impact of land-use change

Abstract: creased by 25% to greater than 350 ppm. Water quality and soil fertility in many regions of the world have been severely degraded, and the biotic system has been dissected, depleted, and endangered by increasing human demands (Ojima et al. 1991). To understand the cause and the effect of global change, the scientific community must focus greater attention on the social context (i.e., cultural, political, demographic, and economic factors) influencing human impact on the global environ-

Functional significance of different human CYPlAl genotypes

Abstract: At least two different polymorphisms in the human CYP1A1 gene have been associated with an increased risk for tobacco-related lung cancer; however, the functional significance of these polymorphisms has not been determined. We measured CYP1A1 genotypes, gene expression levels and enzymatic activity levels in mitogen-stimulated lymphocytes to determine whether genetic polymorphisms in CYP1A1 alter transcriptional and/or post-transcriptional regulation of the gene. Genotypes were determined at two sites previously associated with lung cancer: a point mutation in exon 7 near the catalytic region of the enzyme and an Msp1 RFLP in the 3' non-coding region of the gene. Variant genotypes at the Msp1 site had no effect on CYP1A1 gene induction, however, variant genotypes at the exon 7 site were significantly associated with increased CYP1A1 gene inducibility. We also observed a significant interaction between the exon 7 polymorphism and smoking on mRNA levels. There was a 3-fold elevation in CYP1A1 enzymatic activity in exon 7 variant genotypes. When Msp1 and exon 7 genotypes were combined, there was an increased CYP1A1 inducibility and enzymatic activity in subjects with the exon 7 polymorphism, and in subjects with both polymorphisms.

Ecology of alpine streams

Abstract: SUMMARY 1. This review examines ecological conditions and zoobenthic communities of kryal, krenal and rhithral streams of the alpine zone. Altitudinal and biogeographical faunal patterns are also analysed. 2. Kryal segments, fed by glacial meltwater, are characterized by low temperatures (Tmax4°C) and large diel flow fluctuations in summer. The water may be clear or turbid from suspended rock flour. Fishes and higher plants are absent. The macroalga Hydrurus foetidus may be abundant in kryal and other alpine stream types of the Holarctic. The highly restricted cosmopolitan fauna of glacial brooks consists of diamesine chironomids, sometimes accompanied by simuliids. Sparse food resources include algae and allochthonous (aeolian) organic matter. 3. Rhithral segments in alpine catchments are characterized by soft water, a hydrograph dominated by an extended period of snowmelt runoff, and a broader temperature range than kryal or krenal biotopes. Bryophytes, macroalgae (chrysophytes, chlorophytes, cyanophytes, rhodophytes) and epiphytic and epilithic diatoms constitute the flora. A relatively diverse zoobenthos includes four orders of insects (Flecoptera, Ephemeroptera, Trichoptera, Diptera), turbellarians, acarines, oligochaetes and nematodes. 4. Krenal segments, fed by groundwater, are typically calcareous with summer-cool and winter-warm thermal conditions, high water clarity, and constant flow regimes. Bryophytes and macroafgae are accompanied by a rich diatom flora. The zoobenthos consists of a composite of kryal and rhithral elements with few crenobionts. Zoobenthos species richness values are intermediate between those of kryal and rhithral segments, whereas densities in perennial, well-oxygenated springbrooks far exceed those in other alpine stream types. 5. Downstream faunal changes are most predictable in kryal segments where chironomids of the genus Diamesa are the predominant, if not sole, members of the zoobenthos in the upper zone of glacial brooks, the metakryal. Where Tmax exceeds about 2°C the transition to the hypokryal occurs and Diamesa is co-dominant with simuliids. These largely stenozonal headwater forms decline downstream where Tmax exceeds about 4°C, concomitant with a marked increase in the euryzonal mountain fauna. 6. Species occurring in alpine rhithral biotopes tend to be euryzonal forms at their upper alrirudinal limits, whereas the lower elevation mountain stream fauna consists of species with narrower distribution limits. There is, however, a precipitous drop in mean altitudinal range from the alpine rhithral to the kryat because of the stenozonal nature of the glacial brook fauna. 7. The view that effects of temperature on generation time and mutation rate determine the speed at which selection proceeds is consistent with altitudinal species richness patterns exhibited by zoobenthos along the alrirudinal gradient and may provide an evolutionary explanation for the low faunal diversity in alpine headwaters. 8. With increasing altitude, mountain ‘islands’ become progressively insular as area decreases and isolation increases. For a cold-adapted stream fauna the insular nature of mountain tops is greatest in the tropics. Nonetheless, alpine stream faunas generally

Synthesis of polymeric microcapsule arrays and their use for enzyme immobilization

Abstract: Current methods for immobilizing enzymes for use in bioreactors and biosensors include adsorption on or covalent attachment to a support, micro-encapsulation, and entrapment within a membrane/film or gel. The ideal immobilization method should employ mild chemical conditions, allow for large quantities of enzyme to be immobilized, provide a large surface area for enzyme-substrate contact within a small total volume, minimize barriers to mass transport of substrate and product, and provide a chemically and mechanically robust system. Here we describe a method for enzyme immobilization that satisfies all of these criteria. We have developed a template-based synthetic method that yields hollow polymeric microcapsules of uniform diameter and length. These microcapsules are arranged in a high-density array in which the individual capsules protrude from a surface like the bristles of a brush. We have developed procedures for filling these microcapsules with high concentrations of enzymes. The enzyme-loaded microcapsule arrays function as enzymatic bioreactors in both aqueous solution and organic solvents.

Dietary polyunsaturated fatty acid regulation of gene transcription.

Abstract: We have known for nearly 30 years that dietary polyenoic (n-6) and (n-3) fatty acids potentially inhibit hepatic fatty acid biosynthesis. The teleological explanation for this unique action of PUFAs resides in their ability to suppress the synthesis of (n-9) fatty acids. By inhibiting fatty acid biosynthesis, dietary PUFAs reduce the availability of substrate for delta 9 desaturase (7, 22, 34, 36) and in turn reduce the availability of (n-9) fatty acids for incorporation into plasma membranes. In this way, essential biological processes dependent on essential fatty acids (e.g. reproduction and trans-dermal water loss) continue to operate normally. Therefore, if essential fatty acid intake did not regulate (n-9) fatty acid synthesis, the survival of the organism would be threatened. During the past 20 years, we have gradually elucidated the cellular and molecular mechanisms by which dietary PUFAs modulate fatty acid biosynthesis and (n-9) fatty acid availability. Central to this mechanism has been our ability to determine that dietary PUFAs regulate the transcription of genes coding for lipogenic enzymes (12, 40). The potential mechanisms by which PUFAs govern gene transcription are numerous, and it is unlikely that any one mechanism can fully elucidate the nuclear actions of PUFA. The difficulty in providing a unifying hypothesis at this time stems from: (a) the many metabolic routes taken by PUFAs upon entering the hepatocyte (Figure 1); and (b) the lack of identity of a specific PUFA-regulated trans-acting factor. However, the studies described above indicate that macronutrients, like PUFA, are not only utilized as fuel and structural components of cells, but also serve as important mediators of gene expression (12, 14, 40). As regulators of gene expression, PUFAs (or metabolites) are thought to affect the activity of transcription factors, which in turn target key cis-linked elements associated with specific genes. Whether this targeting involves DNA-protein interaction or the interaction of PUFA-regulated factors is unclear. A better understanding of the nuclear actions of PUFA will clarify the role of these compounds in lipid metabolism and lead to a better understanding of the role of PUFAs in disease processes such as insulin-resistant diabetes and certain forms of cancer.

Metastable phase formation and enhanced diffusion in f.c.c. alloys under high dose, high flux nitrogen implantation at high and low ion energies

Abstract: The use of elevated target temperatures near 400 °C during high flux ion implantation of N2+ at energies ranging from 60 keV to 0.4 keV leads to a metastable, f.c.c. high nitrogen solid solution phase induced in austenitic (f.c.c.) Cr-containing stainless steels. This phase has not been produced in an f.c.c. Ni-Fe alloy containing no Cr. Penetration depths of the N are significantly larger than expected on the basis of known diffusion coefficients of N in Cr-containing stainless steels or in pure f.c.c.-Fe. X-ray diffraction data suggest unusual differences in N penetration and concentration depending on the f.c.c. grain orientation. Consideration is given to possible residual stresses induced by N expansion of the lattice and to the anisotropic elastic constants for austenitic stainless steels. The amount of N in interstitial solid solution approaches 40 at.% under the lower energy, higher flux conditions, but only in the (200) crystallographic planes parallel to the surface. The N-expanded f.c.c. phase with the highest amount of N is found by conversion electron Mossbauer spectroscopy to be magnetic in AISI 304 and 310 stainless steels. A comparison of our results with those from related methods such as conventional plasma ion nitriding and pulsed plasma ion implantation is made to demonstrate that the observed metastable solid solution phase is often produced by other methods provided that appropriate temperatures and processing times are used. The similar penetration depths of N in the f.c.c. Cr-containing stainless steels for the various methods are consistent with thermal diffusion and metastable solubility that are enhanced by the Cr. The metastability is associated with the low Cr mobility below about 450 °C and the strong N-Cr bond. Evidence for vacancy-enhanced diffusion is not found and we see at present no advantage to using ion energies higher than about 2 keV at these elevated temperatures for producing surfaces with optimized tribological behavior based on the extremely high strength, metastable, N solid solution phase.

Measuring functional cohesion

Abstract: We examine the functional cohesion of procedures using a data slice abstraction. Our analysis identifies the data tokens that lie on more than one slice as the "glue" that binds separate components together. Cohesion is measured in terms of the relative number of glue tokens, tokens that lie on more than one data slice, and super-glue tokens, tokens that lie on all data slices in a procedure, and the adhesiveness of the tokens. The intuition and measurement scale factors are demonstrated through a set of abstract transformations. >

Ecosystem and physiological controls over methane production in northern wetlands

Abstract: Peat chemistry appears to exert primary control over methane production rates in the Canadian Northern Wetlands Study (NOWES) area. We determined laboratory methane production rate potentials in anaerobic slurries of samples collected from a transect of sites through the NOWES study area. We related methane production rates to indicators of resistance to microbial decay (peat C: N and lignin: N ratios) and experimentally manipulated substrate availability for methanogenesis using ethanol (EtOH) and plant litter. We also determined responses of methane production to pH and temperature. Methane production potentials declined along the gradient of sites from high rates in the coastal fens to low rates in the interior bogs and were generally highest in surface layers. Strong relationships between CH4 production potentials and peat chemistry suggested that methanogenesis was limited by fermentation rates. Methane production at ambient pH responded strongly to substrate additions in the circumneutral fens with narrow lignin: N and C: N ratios (delta CH4/delta EtOH = 0.9-2.3 mg/g) and weakly in the acidic bogs with wide C: N and lignin: N ratios (delta CH4/delta EtOH = -0.04-0.02 mg/g). Observed Q(sub 10) values ranged from 1.7 to 4.7 and generally increased with increasing substrate availability, suggesting that fermentation rates were limiting. Titration experiments generally demonstrated inhibition of methanogenesis by low pH. Our results suggest that the low rates of methane emission observed in interior bogs during NOWES likely resulted from pH and substrate quality limitation of the fermentation step in methane production and thus reflect intrinsically low methane production potentials. Low methane emission rates observed during NOWES will likely be observed in other northern wetland regions with similar vegetation chemistry.

Contributions of tryptophan side chains to the far-ultraviolet circular dichroism of proteins

Abstract: It has often been assumed that the role of aromatic side chains in the far-ultraviolet region of protein circular dichroism (CD) is negligible. However, some proteins have positive CD bands in the 220-230 nm region which are almost certainly due to aromatic side chains. The contributions to the CD of interactions between tryptophan side chains and the nearest neighbor peptide groups have been studied, focusing on the indole Bb transition which occurs near 220 nm. Calculations on idealized peptide conformations show that the CD depends strongly on both backbone and side-chain conformation. Because of the low symmetry of indole, rotation about the C beta C gamma bond (dihedral angle chi 2) by 180 degrees generally leads to large changes in the CD, often causing the Bb band to reverse sign. When side-chain conformational preferences are taken into account, there is no strong bias for either positive or negative Bb rotational strengths. The observation that simple tryptophan derivatives such as N-acetyl-L-tryptophan methylamide have positive CD near 220 nm implies either that these derivatives prefer the alpha R region over the beta region, or that there is little preference for chi 2 180 degrees. Nearest-neighbor-only calculations on individual tryptophans in 15 globular proteins also reveal a small bias toward positive Bb bands. Rotational strengths of the Bb transition for some conformations can be as large as approximately 1.0 Debye-Bohr magnetons in magnitude, corresponding to maximum molar ellipticities greater than 10(5) deg cm2/dmol. Although a substantial amount of cancellation occurs in most of the examples considered here, such CD contributions could be significant, especially in proteins of low helix content.

Multidimensional assignment formulation of data association problems arising from multitarget and multisensor tracking

Abstract: The ever-increasing demand in surveillance is to produce highly accurate target and track identification and estimation in real-time, even for dense target scenarios and in regions of high track contention. The use of multiple sensors, through more varied information, has the potential to greatly enhance target identification and state estimation. For multitarget tracking, the processing of multiple scans all at once yields high track identification. However, to achieve this accurate state estimation and track identification, one must solve an NP-hard data association problem of partitioning observations into tracks and false alarms in real-time. The primary objective in this work is to formulate a general class of these data association problems as multidimensional assignment problems to which new, fast, near-optimal, Lagrangian relaxation based algorithms are applicable. The dimension of the formulated assignment problem corresponds to the number of data sets being partitioned with the constraints defining such a partition. The linear objective function is developed from Bayesian estimation and is the negative log posterior or likelihood function, so that the optimal solution yields the maximum a posteriori estimate. After formulating this general class of problems, the equivalence between solving data association problems by these multidimensional assignment problems and by the currently most popular method of multiple hypothesis tracking is established. Track initiation and track maintenance using anN-scan sliding window are then used as illustrations. Since multiple hypothesis tracking also permeates multisensor data fusion, two example classes of problems are formulated as multidimensional assignment problems.

Long‐Term Effects of Residue Management in Wheat‐Fallow: I. Inputs, Yield, and Soil Organic Matter

Abstract: Soil organic matter (SOM) is valuable, because of both its beneficial effect on soil quality and crop productivity and its potential to sequester C. Long-term experiments provide an opportunity to identify crop management practices that enhance or degrade soil quality. This study was initiated in 1931 to determine residue management effects on crop yield and SOM (organic C and N) in a winter wheat (Triticum aestivum L.)-fallow system. The soil is a coarse-silty, mixed, mesic Typic Haploxeroll. Treatments include (units ha⁻¹ crop⁻¹) 22.4 Mg manure, 2.24 Mg pea vine residue, 0, 45, and 90 kg N with and without spring burning of straw, and 0 kg N with fall burning of straw. Yearly C and N inputs and removals have been determined since 1976, and calculated for prior periods. Soil C and N have been determined at ≈ 11-yr intervals. Manure, which supplies 111 kg N ha⁻¹ crop⁻¹, has consistently produced the highest yield and maintained the highest soil C and N contents. Other treatments initially yielded from 80 to 90% of the manure treatment, but have progressively declined in direct relation to decreasing soil N content. Low-fertility treatments currently yield from 43 to 57% of the manure treatment. The change in soil C and N with time is nearly linear for all treatments, and highly correlated with residue input. Treatment effects on soil C and N have been confined to the top 30 cm of soil, but there has been a slow steady decline in C and N in the 30- to 60-cm zone that is not related to residue management. Oregon State Univ. Agric. Exp. Stn. Technical Paper no. 10 132.

Poly(Pro)II Helixes in Globular Proteins: Identification and Circular Dichroic Analysis

Abstract: A method to identify poly(L-proline)-type (PII) conformation in crystal structures of globular proteins is presented. Short segments of PII structure were identified in globular protein structures, and these form a significant fraction of the residues which are not assigned to alpha-helix, beta-sheet, and beta-turns. The fractions of alpha-helix, beta-sheet, beta-turns, PII, and unordered, identified in conjunction with the Kabsch and Sander method [(1983) Biopolymers 22, 2577], were incorporated in the analysis of circular dichroism (CD) spectra of proteins. The separation of PII fraction from the fraction of residues not assigned to alpha-helix or beta-sheet or -turns resulted in a distinctive PII CD spectrum and an unusual CD spectrum corresponding to the residual unassigned structures. The quality of prediction of PII fraction from CD spectra of proteins was comparable to that of beta-sheet and -turns.

Competition, facilitation, seed distribution and the origin of patches in a Patagonian steppe

Abstract: The Pataxonian steppe is composed mainly of shrubs and tussock grasses organized in two types of patches: scattered grass tussocks in a matrix of bare soil and shrubs, each surrounded by a dense ring of grass tussocks. We analyzed the variation of competition, facilitation, and seed distribution through space and time as major driving forces in the development of this patch structure. Emergence and survival of grass seedlings increased with distance from shrubs when the ring of grasses was left intact. On the contrary, when the ring of grasses was experimentally removed, seedling survival decreased with distance from the shrub. Differences in root density, soil water potential, and evaporation accounted for these patterns (...)