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This article reviews the importance of multiple stakeholders in program development, including the essential role of university and community partnerships.Yakima Valley College—a two-year, Hispanic-serving institution—partnered with four-year universities, agricultural centers, businesses, and federal and state agencies to develop a streamlined undergraduate research experience in which students work closely with a faculty mentor in a STEM field on summer projects of 120 hours each.

Grasslands managed for grazing are the largest land-use category globally, with a significant proportion of these grasslands occurring in semiarid and arid regions. In such dryland systems, the effect of grazing on native plant diversity has been equivocal, some studies suggesting that grazing reduces native plant diversity, others that grazing increases or has little impact on diversity. One impediment toward generalizing grazing effects on diversity in this region is that high levels of interannual variation in precipitation may obfuscate vegetative response patterns. By analyzing a long-term data set collected over a 20-yr period in a semiarid grassland, we explicitly evaluated the role of climate in regulating the effect of cattle grazing on plant communities, finding that climate interacted with grazing intensity to shape grassland communities. Community composition of plots that were intensively grazed varied considerably in response to climatic variation and native species richness was low relative to ungrazed and moderately grazed plots. Following a severe drought in 2002, exotic species richness rapidly increased in the high-intensity grazing plots. While this pattern was mirrored in the other treatments, exotic species richness increased to a greater extent and was slower to return to pre-drought levels in the high-intensity grazing plots. Overall, moderate grazing, even compared to grazing cessation, stabilized grassland communities through time, increased resilience to drought, and maintained the highest levels of native plant diversity and lowest levels of exotic diversity. These findings suggest that grazing, at moderate levels, may support grassland resilience to climate change in semiarid regions. However, grazing that exceeds tolerances, particularly in combination with extreme climatic events, like drought, can alter plant composition over relatively long timescales and possibly increase invasibility by nonnative species.

Digital mucoid cysts have a tendency for recurrence after operative intervention. Several procedures are in use.Retrospective evaluation for effectiveness, safety and patient satisfaction by using a questionnaire after treatment for digital mucoid cysts with targeted surgical excision and closure by flap-design.All patients treated with surgical excision for digital mucoid cysts at the Dermatology Department of the Ludwigshafen City Hospital between 2007 and 2011 were evaluated using a specially designed questionnaire.We evaluated 31 patients. The patient group consisted of 65% women, the median age was 61 years. Seventy-eight percent of patients with nail involvement had a marked improvement or complete resolution of this complaint after surgery. A few complications (e.g., redness, pain or hematoma) were observed after treatment, but no patients required oral antibiotics. Patient evaluation of cosmetic outcome revealed high satisfaction with the procedure, nevertheless recurrence of the digital mucoid cysts was observed in 22.5% of all cases.Surgical excision in treatment of digital mucoid cysts was shown to be effective and safe. However, possible advantages and disadvantages of this treatment option should be discussed with the patients before a decision on the kind of therapy is reached.

Management of domesticated ungulates on grasslands has the potential to affect ecosystem function at landscape to global scales. In the southwestern United States, introduction of livestock in the 1800s corresponded with grassland degradation and dramatic shifts in vegetation, including the rapid spread of invasive plant species. In contemporary grasslands, however, evidence increasingly suggests that responsible grazing may enhance plant diversity in the region, though positive effects on diversity may or may not offer corresponding benefits to ecosystem function. Here, we examined the effects of grazing on land cover and functional composition of a semiarid grassland over a 20-year period. We found that high intensity grazing increased exposed soil and shifted community composition toward a greater proportion of annual and exotic species. This was particularly apparent following a severe drought event that initiated a significant loss of perennial plant cover, especially forbs, and was followed by a nearly 4-fold expansion of exotic species. Plots that were grazed at moderate levels consistently exhibited the lowest proportion of exotic species and were similar in functional group composition to exclosure plots. However, moderate grazing did increase soil exposure relative to exclosure plots. These findings suggest that moderate grazing could provide benefits to grassland ecosystem diversity and correlated ecosystem services like invasive species control and pollination services, while simultaneously increasing erosion, reducing water infiltration and altering nutrient cycling, due to increased soil exposure and disturbance. The potential for grazing to exert antagonistic effects on ecosystem services, depending on site conditions and grazing intensity, suggests that livestock management decisions should be tailored to individual management and conservation goals that address the inherent spatiotemporal variability of arid grasslands. Keywords: Plant functional groups, Climate change, Southwestern United States, Exotic species, Ecosystem services, Livestock management

Surgical approaches for melanocytic nevi and malignant melanoma of the umbilicus differ in the extent of the procedures. Whenever appropriate, umbilical nevi should be removed with minimal trauma and preservation of the tissue for unimpaired histological investigation. Simple strategies for successful outpatient procedures will be introduced. In the rare case of a proven umbilical melanoma, surgery has to be extensive to ensure necessary margins. Since accidental opening of the abdomen can be a risk after previous surgery or occult umbilical hernia, strict hygiene has to be guaranteed and necessary precautions should to be taken.

The ecological benefits of changing cattle grazing practices in the western United States remain controversial, due in part to a lack of experimentation. In 1997 we initiated an experimental study of two rangeland alternatives, cattle removal and high-impact grazing, and compared grassland community responses with those with more conventional, moderate grazing practices. The study was conducted in a high-elevation, semiarid grassland near Flagstaff, Arizona (U.S.A.). We conducted annual plant surveys of modified Whittaker plots for 8 years and examined plant composition shifts among treatments and years. High-impact grazing had strong directional effects that led to a decline in perennial forb cover and an increase in annual plants, particularly the exotic cheatgrass (Bromus tectorum L.). A twofold increase in plant cover by exotic species followed a severe drought in the sixth year of the study, and this increase was greatest in the high-impact grazing plots, where native cover declined by one-half. Cattle removal resulted in little increase in native plant cover and reduced plant species richness relative to the moderate grazing control. Our results suggest that some intermediate level of cattle grazing may maintain greater levels of native plant diversity than the alternatives of cattle removal or high-density, short-duration grazing practices. Furthermore, episodic drought interacts with cattle grazing, leading to infrequent, but biologically important shifts in plant communities. Our results demonstrate the importance of climatic variation in determining ecological effects of grazing practices, and we recommend improving conservation efforts in arid rangelands by developing management plans that anticipate this variation. Resumen: Los beneficios ecologicos del cambio de practicas de pastoreo de ganado en el oeste de Estados Unidos aun son controversiales, en parte por la falta de experimentacion. En 1997 iniciamos un estudio experimental de dos alternativas, remocion de ganado y pastoreo de alto impacto, y comparamos las respuestas de la comunidad de pastizal con las de practicas de pastoreo moderadas, mas convencionales. El estudio se llevo a cabo en un pastizal semiarido, de alta elevacion, cerca de Flagstaff, Arizona (E.U.A.). Durante 8 anos realizamos muestreos anuales de plantas en parcelas Whittaker modificadas y examinamos los cambios en la composicion de plantas entre tratamientos y anos. El pastoreo de alto impacto tuvo dos efectos direccionales que llevaron a una declinacion en la cobertura de hierbas perennes y al incremento de plantas anuales, particularmente de pasto exotico Bromus tectorum L. Despues de una sequia severa la cobertura de especies exoticas incremento al doble en el sexto ano del estudio, y este incremento fue mayor en las parcelas de pastoreo de alto impacto, en las que la cobertura de especies nativas declino a la mitad. La remocion de ganado resulto en un leve incremento en la cobertura de plantas nativas y redujo la riqueza de especies de plantas en relacion con el control con pastoreo moderado. Nuestros resultados sugieren que algun nivel intermedio de pastoreo puede mantener mayores niveles de diversidad de plantas nativas que las alternativas de remocion de ganado o de practicas de pastoreo de alta densidad y corta duracion. Mas aun, las sequias episodicas interactuan con el pastoreo de ganado, conduciendo a cambios, poco frecuentes pero biologicamente importantes, en las comunidades de plantas. Nuestros resultados demuestran la importancia de la variacion climatica en la determinacion de los efectos ecologicos de las practicas de pastoreo, y recomendamos el mejoramiento de los esfuerzos de conservacion en llanuras aridas mediante el desarrollo de planes de gestion que anticipen esta variacion.

Wilhelm et al. have recently called attention to the unidentified broad emission features near 117 nm in the solar spectrum. They discuss the observed properties of these features in detail but do not identify the source of this emission. We show that the broad autoionizing transitions of neutral sulfur are responsible for these emission features. Autoionizing lines of \ion{S}{i} occur throughout the spectrum between Lyman alpha and the Lyman limit. Sulfur is a normal contributor to stellar spectra. We use non-LTE chromospheric model calculations with line data from the Kurucz 2004 \ion{S}{i} line list to simulate the solar spectrum in the range 116 to 118 nm. We compare the results with SUMER disk-center observations from Curdt et al. and limb observations from Wilhelm et al. Our calculations generally agree with the SUMER observations of the broad autoionizing \ion{S}{i} emission features, the narrow \ion{S}{i} emission lines, and the continuum in this wavelength region, and agree with basic characteristics of the center-to-limb observations. In addition to modeling the average spectrum, we show that a change of $\pm$ 200 K in the temperature distribution causes the intensity to change by a factor of 4. This exceeds the observed intensity variations 1) with time in quiet regions at these wavelengths, and 2) with position from cell centers to bright network. These results do not seem compatible with current dynamical models that have temporal variations of 1000 K or more in the low chromosphere., 5 pages, 4 figures, 1 table (Accepted for Astronomy & Astrophysics)

Riparian spider abundance is influenced by the extent and architecture of litter, which is greatly influenced by flood regime. Flood-deposited clumps of intertwined plant material and inorganic debris (“litter hovels”) attached to trees and elevated above the ground by past high water events present a unique, persistent, and unstudied habitat type for spiders. We investigated spider use of litter hovels along an unregulated reach of West Clear Creek, Arizona, USA dominated by native riparian vegetation. Ninety two percent of litter hovels were occupied by at least one spider, with a mean occupancy of 4.5 spiders per hovel. Spider abundance and diversity at the family level were positively correlated with litter hovel size. Furthermore, spiders were non-randomly distributed among litter hovels in three areas of this riparian system: the vegetated floodplain, creek edges, and islands within the creek channel. Overall spider diversity was two-fold greater on creek islands than in the vegetated floodplain, and spider abundance also varied by predation guild among the three habitat types. Running and web-building spiders were most abundant on creek islands, while stalking and ambushing spiders were two-fold more abundant along creek edges in comparison with other habitats. For this riparian system, we estimate that spider densities could reach 270,000/ha in hovels alone, and therefore alteration of flood regimes through stream management may have important implications for arthropod dynamics. Current efforts to restore natural flood regimes and native vegetation in Southwestern streams are likely to benefit spider populations, their predators, and the regulation of herbivorous arthropods.

Cattle grazing is often implicated as a factor that reduces vegetative cover and the abundance of important forage plants for wildlife. Recent declines in northern Arizona populations of pronghorn (Antilocapra americana Ord) have focused public and scientific attention on the factors contributing to low fawn recruitment and the potential benefits of cattle removal. To further understandtheeffectsofcattlegrazing,westudiedthepotentialhidingcoverprovidedbystandingliveanddeadherbaceousmatter as well as forb richness and canopy cover following 5 years of cattle removal. Cattle removal increased horizontal hiding cover by 8% at a distance of 5 m (P ¼ 0.025), but had no statistically significant effect on the potential hiding cover at distances of 10 m (P ¼ 0.105) or 25 m (P ¼ 0.746). Forb species richness was 16% lower in exclosures than in an adjacent grazed pasture in 2001 (P ¼ 0.036), but no differences were observed in 2002 (P ¼ 0.636). The canopy cover of forbs was generally unaffected by cattle removal. These results suggest that curtailing or removing cattle is unlikely, by itself, to lead to rapid improvements in the hiding cover or forb availability for pronghorn on similar rangelands in northern Arizona. In this region, where immediate improvements in fawn survival and recruitment are important to population persistence, additional management actions should be considered.

Mammalian spermatozoa undergo the acrosome reaction (AR) in response to the interaction of a carbohydrate-recognizing molecule(s) on the sperm plasma membrane (sperm surface receptor) and its complementary glycan (ligand) moiety(ies) on the zona pellucida (ZP). Previously, we demonstrated that a hexose (mannose) or two amino sugars (glucosaminyl or galactosaminyl residues) when covalently conjugated to a protein backbone (neoglycoproteins) mimicked the mouse ZP3 glycoprotein and induced the AR in capacitated mouse spermatozoa (Loeser and Tulsiani, Biol Reprod 1999; 60:94-101). To elucidate the mechanism underlying sperm-neoglycoprotein interaction and the induction of the AR, we have examined the effect of several AR blockers on neoglycoprotein-induced AR. Our data demonstrate that two known L-type Ca(2+) channel blockers prevented the induction of the AR by three neoglycoproteins (mannose-BSA, N-acetylglucosamine-BSA, and N-acetylgalactosamine-BSA). The fact that the L-type Ca(2+) channel blockers (verapamil, diltiazem) had no inhibitory effect on sperm surface galactosyltransferase or alpha-D-mannosidase, two carbohydrate-recognizing enzymes thought to be sperm surface receptors, suggests that the reagents block the AR by a mechanism other than binding to the active site of the enzymes.

Capacitated acrosome-intact mouse spermatozoa bind to the egg's zona pellucida in a receptor-ligand-mediated manner. Mouse zona pellucida 3 (mZP3) is a glycoprotein that functions as a primary ligand and inducer of the acrosome reaction (AR). Multiple sugar residues on mZP3 are thought to be recognized by complementary sugar binding enzymes (glycosidases or glycosyltransferases) or sugar binding lectin-like proteins on the sperm surface. To elucidate the nature of the sugar residues involved in sperm-egg recognition, several neoglycoproteins (ngps) were tested for their ability to induce the AR. Ngps are synthetic glycoproteins with a known monosaccharide conjugated to BSA. Capacitated mouse spermatozoa were treated in the absence or presence of several concentrations of ngps. A significantly greater number of spermatozoa underwent the AR in the presence of mannose-BSA, N-acetylglucosamine-BSA, and N-acetylgalactosamine-BSA than in their absence. Glucose-BSA or galactose-BSA had no effect on the AR. Inclusion of millimolar concentrations of unconjugated sugars (mannose, N-acetylglucosamine, or N-acetylgalactosamine) neither induced the AR nor blocked induction of the AR by ngps. These results demonstrate that some sugar residues can induce the AR, but only when conjugated to a protein backbone. Glucosaminyl-BSA (but not mannosyl-BSA or galactosaminyl-BSA) was a substrate for sperm-surface galactosyltransferase (GT), an enzyme thought to function as a receptor by binding to complementary glucosaminyl residues on mZP3. These data suggest a possible interaction between protein-conjugated glucosaminyl residues and sperm GT in the induction of the AR.

An on-line purification system for a large-scale low-background liquid scintillation detector has been tested with the 5 t liquid scintillation detector, the Counting Test Facility at Gran Sasso. Counter-current water extraction removes polar and charged impurities such as ions and metal salts. Vacuum distillation of the entire scintillator has been applied to remove both radioactive impurities and chemical impurities that affect the optical properties of the scintillator. Filtration with a 0.05 μm particulate filter removed suspended dust particles that may contain U, Th and K. Nitrogen stripping was employed to remove dissolved water and noble gases (e.g. 85 Kr) from the scintillator. The system has effectively reduced the internal back in the 5 t liquid scintillation detector from 470±90 events/d to the detection limit of the detector (±45 events/d) in the energy window 250 E

The emission lines of Mg I at 7.4, 12.2, and 12.3 μm are now known to be formed in the upper photosphere; the line emission is due to collisional coupling of higher levels with the continuum together with radiative depopulation of lower levels. These combined effects cause the line source functions of high-lying transitions to exceed the corresponding Planck functions. However, there are uncertainties in a) the relevant atomic data, particularly the collisional rates and ultraviolet photoionization rates, and b) the sensitivity of the calculated results to changes in atmospheric temperature and density. These uncertainties are examined by comparing twelve calculated Mg I line profiles in the range 2.1-12.3 μm with ATMOS satellite observations. We show results based on different rates, and using different atmospheric models representing a range of dark and bright spatial features. The calculated Mg profiles are found to be relatively insensitive to atmospheric model changes, and to depend critically on the choice of collisional and photoionization rates. We find better agreement with the observations using collision rates from van Regemorter (1962) rather than from Seaton (1962). We also compare twelve calculated hydrogen profiles in the range 2.2-12.4 μm with ATMOS observations. The available rates and cross sections for hydrogen seem adequate to account for the observed profiles, while the calculated lines are highly sensitive to atmospheric model changes. These lines are perhaps the best available diagnostics of the temperature and density structure of the photosphere and low chromosphere. Further calculations based on these infrared hydrogen lines should lead to greatly improved models of the solar atmosphere.

As collaborative groups gain popularity as an alternative means for addressing conflict over management of public lands, the need for methods to evaluate their effectiveness in achieving ecological and social goals increases. However, frameworks that examine both effectiveness of the collaborative process and its outcomes are poorly developed or altogether lacking. This paper presents and evaluates the utility of the holistic ecosystem health indicator (HEHI), a framework that integrates multiple ecological and socioeconomic criteria to evaluate management effectiveness of collaborative processes. Through the development and application of the HEHI to a collaborative in northern Arizona, the Diablo Trust, we present the opportunities and challenges in using this framework to evaluate the ecological and social outcomes of collaborative adaptive management. Baseline results from the first application of the HEHI are presented as an illustration of its potential as a co-adaptive management tool. We discuss lessons learned from the process of selecting indicators and potential issues to their long-term implementation. Finally, we provide recommendations for applying this framework to monitoring and adaptive management in the context of collaborative management.

Oocytes of rabbits and mice, successfully cultured in vitro in the first half of the twentieth century, laid the foundation for assisted reproductive techniques decades later. In vitro fertilization (IVF) studies in rabbits resulted in the first birth of a normal offspring in 1959. Since then, advances in experimental reproductive technology, leading to new insights into sperm capacitation, oocyte maturation and sperm-egg interaction, have tremendously increased our knowledge about the fertilization process in humans.

In this paper we have extended our previous modeling of energy balance in the chromosphere-corona transition region to cases with particle and mass flows. The cases considered here are quasi-steady, and satisfy the momentum and energy balance equations in the transition region. We include in all equations the flow velocity terms and neglect the partial derivatives with respect to time. We present a complete and physically consistent formulation and method for solving the non-LTE and energy balance equations in these situations, including both particle diffusion and flows of H and He. Our results show quantitatively how mass flows affect the ionization and radiative losses of H and He, thereby affecting the structure and extent of the transition region. Also, our computations show that the H and He line profiles are greatly affected by flows. We find that line shifts are much less important than the changes in line intensity and central reversal due to the effects of flows. In this paper we use fixed conditions at the base of the transition region and in the chromosphere because our intent is to show the physical effects of flows and not to match any particular observations. However, we note that the profiles we compute can explain the range of observed high spectral and spatial resolution Lyman alpha profiles from the quiet Sun. We suggest that dedicated modeling of specific sequences of observations based on physically consistent methods like those presented here will substantially improve our understanding of the energy balance in the chromosphere and corona., 50 pages + 20 figures; submitted to ApJ 9/10/01; a version with higher resolution figures is available at http://cfa-www.harvard.edu/~avrett/

Matrix Gla protein (MGP) is an inhibitor of calcification of the arterial wall but the mechanism of inhibition has not been resolved. Since chondrogenesis has been identified in calcified arteries from MPG null mice, we hypothesized that locally produced MGP might inhibit calcification by neutralizing the known effect of bone morphogenetic proteins (BMPs) as promotors of chondrogenesis and bone formation. As the first step to test this hypothesis, we demonstrate that MGP is a binding protein for 125I-BMP-2. Optimal binding is dependent on metals which suggests that the metal binding Gla region in MGP is involved. MGP is shown to undergo a Ca++ induced conformational change despite the presence of the gamma-carboxylase binding site being part of the mature protein sequence. The data propose that MGP matures earlier in the secretory pathway than other vitamin K-dependent proteins. Antibodies were used in an attempt to identify MGP in bovine serum. Conformational specific MGP antibodies were shown to also recognize the Gla region in prothrombin and factor X but did not identify MGP in serum. This finding is supported by electrophoresis data which demonstrate the absence of MGP among Ba-citrate absorbed vitamin K-dependent serum proteins. We conclude that MGP does not exist in normal bovine serum.

Mammalian spermatozoa undergo the acrosome reaction (AR) in response to the interaction of a carbohydrate-recognizing molecule(s) on the sperm plasma membrane (sperm surface receptor) and its complementary glycan (ligand) moiety(ies) on the zona pellucida (ZP). Previously, we demonstrated that a hexose (mannose) or two amino sugars (glucosaminyl or galactosaminyl residues) when covalently conjugated to a protein backbone (neoglycoproteins) mimicked the mouse ZP3 glycoprotein and induced the AR in capacitated mouse spermatozoa (Loeser and Tulsiani, Biol Reprod 1999; 60:94-101). To elucidate the mechanism underlying sperm-neoglycoprotein interaction and the induction of the AR, we have examined the effect of several AR blockers on neoglycoprotein-induced AR. Our data demonstrate that two known L-type Ca(2+) channel blockers prevented the induction of the AR by three neoglycoproteins (mannose-BSA, N-acetylglucosamine-BSA, and N-acetylgalactosamine-BSA). The fact that the L-type Ca(2+) channel blockers (verapamil, diltiazem) had no inhibitory effect on sperm surface galactosyltransferase or alpha-D-mannosidase, two carbohydrate-recognizing enzymes thought to be sperm surface receptors, suggests that the reagents block the AR by a mechanism other than binding to the active site of the enzymes.

Capacitated acrosome-intact mouse spermatozoa bind to the egg's zona pellucida in a receptor-ligand-mediated manner. Mouse zona pellucida 3 (mZP3) is a glycoprotein that functions as a primary ligand and inducer of the acrosome reaction (AR). Multiple sugar residues on mZP3 are thought to be recognized by complementary sugar binding enzymes (glycosidases or glycosyltransferases) or sugar binding lectin-like proteins on the sperm surface. To elucidate the nature of the sugar residues involved in sperm-egg recognition, several neoglycoproteins (ngps) were tested for their ability to induce the AR. Ngps are synthetic glycoproteins with a known monosaccharide conjugated to BSA. Capacitated mouse spermatozoa were treated in the absence or presence of several concentrations of ngps. A significantly greater number of spermatozoa underwent the AR in the presence of mannose-BSA, N-acetylglucosamine-BSA, and N-acetylgalactosamine-BSA than in their absence. Glucose-BSA or galactose-BSA had no effect on the AR. Inclusion of millimolar concentrations of unconjugated sugars (mannose, N-acetylglucosamine, or N-acetylgalactosamine) neither induced the AR nor blocked induction of the AR by ngps. These results demonstrate that some sugar residues can induce the AR, but only when conjugated to a protein backbone. Glucosaminyl-BSA (but not mannosyl-BSA or galactosaminyl-BSA) was a substrate for sperm-surface galactosyltransferase (GT), an enzyme thought to function as a receptor by binding to complementary glucosaminyl residues on mZP3. These data suggest a possible interaction between protein-conjugated glucosaminyl residues and sperm GT in the induction of the AR.

The mammalian spermatozoon undergoes continuous modifications during spermatogenesis, maturation in the epididymis, and capacitation in the female reproductive tract. Only the capacitated spermatozoa are capable of binding the zona-intact egg and undergoing the acrosome reaction. The fertilization process is a net result of multiple molecular events which enable ejaculated spermatozoa to recognize and bind to the egg's extracellular coat, the zona pellucida (ZP). Sperm-egg interaction is a species-specific event which is initiated by the recognition and binding of complementary molecule(s) present on sperm plasma membrane (receptor) and the surface of the ZP (ligand). This is a carbohydrate-mediated event which initiates a signal transduction cascade resulting in the exocytosis of acrosomal contents. This step is believed to be a prerequisite which enables the acrosome reacted spermatozoa to penetrate the ZP and fertilize the egg. This review focuses on the formation and contents of the sperm acrosome as well as the mechanisms underlying the induction of the acrosome reaction. Special emphasis has been laid on the synthesis, processing, substrate specificity, and mechanism of action of the acid glycohydrolases present within the acrosome. The hydrolytic action of glycohydrolases and proteases released at the site of sperm-zona binding, along with the enhanced thrust generated by the hyperactivated beat pattern of the bound spermatozoon, are important factors regulating the penetration of ZP. We have discussed the most recent studies which have attempted to explain signal transduction pathways leading to the acrosomal exocytosis.

One-dimensional hydrostatic-equilibrium models are shown here for faint, average, and bright components of the quiet Sun, and for a plage region, describing in each case how the atmosphere is stratified through the photosphere, chromosphere, and transition region up to a temperature of 105 K. The observed coronal line radiation is assumed to be the inward incident radiation at the 105 K boundary. This coronal radiation penetrates into the upper chromosphere causing sufficient helium ionization to populate the lower level of the He I 10830 A line, producing optically-thin absorption of the photospheric continuum at 10830A. The amount of absorption, which is proportional to the optical thickness of the upper chromosphere in the 10830 line, depends on 1) the strength of the coronal lines at wavelengths in the He I 504 A ionizing continuum, and 2) the density and geometrical thickness of the upper chromosphere. The computed 10830 A line is shown for the four atmospheric models and for three values of the coronal illumination. The calculated off-limb 10830 intensity distribution shows a minimum in the low chromosphere and a maximum at roughly 2000 km above the photosphere, in general agreement with observations, indicating that this is the predominant height of the transition region over most of the solar surface.

The emission lines of Mg I at 7.4, 12.2, and 12.3 µm are now known to be formed in the upper photosphere; the line emission is due to collisional coupling of higher levels with the continuum together with radiative depopulation of lower levels. These combined effects cause the line source functions of high-lying transitions to exceed the corresponding Planck functions. Rowever, there are uncertainties in a) the relevant atomic data, particularly the collisional rates and ultraviolet photoionization rates, and b) the sensitivity of the calculated results to changes in atmospheric temperature and density. These uncertainties are examined by comparing twelve calculated Mg I line profiles in the range 2.1–12.3 µm with ATMOS satellite observations. We show results based on different rates, and using different atmospheric models representing a range of dark and bright spatial features. The calculated Mg profiles are found to be relatively insen-tive to atmospheric model changes, and to depend critically on the choice of collisional and hotoionization rates. We find better agreement with the observations using collision rates from van Regemorter (1962) rather than from Seaton (1962). We also compare twelve calculated hydrogen profiles in the range 2.2–12.4 µm with ATMOS observations. The available rates and cross Sections for hydrogen seem adequate to account for the observed profiles, while the calculated lines are highly sensitive to atmospheric model changes. These lines are perhaps the best available diagnostics of the temperature and density structure of the photosphere and low chromosphere. purther calculations based on these infrared hydrogen lines should lead to greatly improved models df the solar atmosphere.

In light of the continuing debate regarding overcompensation we studied the responses of above-ground biomass in a high-elevation, semi-arid grassland to defoliation, defoliation history, and livestock grazing. The above-ground annual net primary productivity (ANPP) was measured over 2 years in one-hundred twenty, 1-m2 plots that were exposed to single- and multi-year defoliation and grazing treatments. Plant communities showed an average increase in ANPP of 31%–45% due to a single defoliation event. The most conservative estimate of average ANPP of defoliated subplots was 29.4 g m−2 greater than the non-defoliated controls. A history of defoliation, due to clipping or grazing, lessened the magnitude of the compensatory response, but above-ground overcompensation of biomass was still observed, ranging on average from 17% to 26%. One dominant species, squirreltail grass [Elymus elymoides (Raf.) Swezeyi], accounted for nearly one-third of the community-level increases in ANPP. In contrast to above-...

In our previous papers we described the mathematical formalism and the computed results for energy-balance hydrostatic models of the solar transition region. In this paper we discuss in some detail the limitations of the hydrostatic and one-dimensional assumptions used. Then we analyze the determination of helium emission when diffusion is included. We use transport coefficients estimated from kinetic theory to determine the helium departures from local ionization balance. We calculate the helium spectra for each of our models and evaluate the role of helium in the energy transport. Also, we investigate the effects of coronal illumination on the structure of the transition region and upper chromosphere, and show how coronal illumination affects various EUV lines and the He I 10830 A line. Comparing with both absolute intensities and detailed line profiles, we show that our models are consistent not only with the observed hydrogen spectra but also with the available helium spectra.

A non-LTE radiative transfer investigation of the emission lines is conducted at 7 and 12 microns using a realistic atomic model for neutral magnesium. An average quiet sun atmospheric model is used to calculate emission-line profiles that resemble the observed ones, i.e., broad absorption troughs with narrow central emission, and significant limb brightening. The charge exchange rates are found to be significant, but the effects of high-n coupling between Mg and Mg(+) together with radiative low-n transitions are of greater importance. It is confirmed that the emission cores are formed no higher than the temperature minimum region, and that the emission is caused by non-LTE effects rather than by the chromospheric temperature rise. It is inferred from the model calculations that the line core is sensitive to magnetic fields located almost 400 km above those measured in ordinary magnetograms; the gas pressure decreases 20-fold between these two heights.

The radiation of energy by hydrogen lines and continua in hydrostatic energy-balance models of the transition region between the solar chromosphere and corona is studied using models which assume that mechanical or magnetic energy is dissipated in the hot corona and is then transported toward the chromosphere down the steep temperature gradient of the transition region. These models explain the average quiet sun and also the entire range of variability of the Ly-alpha lines. The relations between the downward energy flux, the pressure of the transition region, and the different hydrogen emission are described.

The energy balance in the lower transition region is analyzed by constructing theoretical models which satisfy the energy balance constraint. The energy balance is achieved by balancing the radiative losses and the energy flowing downward from the corona. This energy flow is mainly in two forms: conductive heat flow and hydrogen ionization energy flow due to ambipolar diffusion. Hydrostatic equilibrium is assumed, and, in a first calculation, local mechanical heating and Joule heating are ignored. In a second model, some mechanical heating compatible with chromospheric energy-balance calculations is introduced. The models are computed for a partial non-LTE approach in which radiation departs strongly from LTE but particles depart from Maxwellian distributions only to first order. The results, which apply to cases where the magnetic field is either absent, or uniform and vertical, are compared with the observed Lyman lines and continuum from the average quiet sun. The approximate agreement suggests that this type of model can roughly explain the observed intensities in a physically meaningful way, assuming only a few free parameters specified as chromospheric boundary conditions.

Line fluxes and profiles are computed for a sequence of spherically symmetric T Tauri wind models. The calculations indicate that the H-alpha emission of T Tauri stars arises in an extended and probably turbulent circumstellar envelope at temperatures above about 8000 K. The models predict that Mg II resonance line emission should be strongly correlated with H-alpha fluxes; observed Mg II/H-alpha ratios are inconsistent with the models unless extinction corrections have been underestimated. The models predict that most of the Ca II resonance line and IR triplet emission arises in dense layers close to the star rather than in the wind. H-alpha emission levels suggest mass loss rates of about 10 to the -8th solar mass/yr for most T Tauri stars, in reasonable agreement with independent analysis of forbidden emission lines. These results should be useful for interpreting observed line profiles in terms of wind densities, temperatures, and velocity fields.

Detailed performance evaluations are presented for six ACM algorithms: quicksort (No. 64), Shellsort (No. 201), stringsort (No. 207), “ TREESORT3 ” (No. 245), quickersort (No. 271), and qsort (No. 402). Algorithms 271 and 402 are refinements of algorithm 64, and all three are discussed in some detail. The evidence given here demonstrates that qsort (No. 402) requires many more comparisons than its author claims. Of all these algorithms, quickersort requires the fewest comparisons to sort random arrays.

We describe a representation procedure that is useful for the evaluation of certain basic types of integrals and for the solution of certain integral equations. Several numerical examples are given.

We describe a method for solving the line-transfer equations for a two-component atmosphere consisting of an array of columns, characterized by a particular variation of temperature with height, which are embedded in a medium in which the temperature is a different function of height. Radiative interaction between the two regions is taken into account, and the opacity is allowed to vary arbitrarily with depth. Some calculations that correspond to the solar Ca K-line are described.

An enzyme-linked immunosorbent assay for anticardiolipin (ACL) antibody was performed on 250 consecutive antinuclear antibody (ANA) or anticytoplasmic antibody (ACA) positive sera and 50 consecutive ANA/ACA negative sera submitted to a rheumatology reference laboratory for ANA testing. Of the 250 ANA/ACA positive sera, 33 (13%) were found to be ACL antibody positive. This compared with only 2 (4%) ACL antibody positive samples among the 50 ANA/ACA negative controls. Chart review revealed only one documented case of thrombosis in ACL antibody positive patients. We conclude that among ANA/ACA positive patients, ACL antibody is a frequent finding. ACL antibody in the population studied is not associated with thrombosis. ACL antibody in this group appears to more accurately reflect immune reactivity than a thrombotic state.

The Newtonian equations of motion of N bodies are integrated by expanding the positions and velocities in Taylor series in the time. In the method presented here, the coefficients of the Taylor series (i.e., the time derivatives of the accelerations) are given analytically as explicit functions of the current positions and velocities. This method uses no past information and thus is tailored for variable time steps. We compare the efficiency of this explicit scheme with that of a differencing scheme (which also uses variable time steps) for a variety of solar-system configurations. When the time step changes rapidly, as in an elliptic orbit of high eccentricity, the longer time required to compute the explicit coefficients is more than compensated by the ability to take longer time steps.

A nine-level atomic model is presented for C I lines synthesis in the sun. All the atomic parameters are based on recent experimental and theoretical data. Profiles of the multiplets at 1561 and 1657 A are computed from a model of the solar chromosphere. The sensitivity of the results to changes in the atomic parameters is examined. Partial frequency redistribution must be included in these lines to obtain agreement between calculated and observed profiles.

Semiempirical model atmospheres are presented for the darkest parts of large sunspot umbrae, regions have called umbral cores. The approach is based on general-purpose computational procedures that are applicable to different types of stellar atmospheres. It is shown that recent umbral intensity measurements of the spectral energy distribution may be accounted for by an umbral core atmospheric model that varies with time during the solar cycle; the observed center-limb variation can be accounted for by the properties of the model. Three umbral core models are presented, corresponding to the early, middle, and late phases of the solar cycle. These three models also may be regarded as having the properties of dark, average, and bright umbral cores respectively. The effects of atomic, opacity, and abundance data uncertainties on the model calculations are briefly discussed. For comparison, a new reference model for the average quiet solar photosphere is given.

The accuracy of the simplifying approximations usually made to avoid solving in detail the equations of radiative transfer from broad emission line regions of quasi-stellar objects is examined. Starting with a pure hydrogen model, the effects are considered of including heavy-element cooling, helium and X-ray opacity, X-ray heating, Lyman continuum transfer replacing on-the-spot approximation, and line transfer with Lyman-alpha partial redistribution replacing escape probabilities. The hydrogen statistical equilibrium equations are solved in detail. 40 references.