bluuebunny/crossref_metadata_2025 huggingface dataset:
The Anterior Cingulate and Error Avoidance
Authors: Magno Elena , Foxe John J. , Molholm Sophie , Robertson Ian H. , Garavan Hugh
Published: May 2006

The precise role of the anterior cingulate cortex in monitoring, evaluating, and correcting behavior remains unclear despite numerous theories and much empirical data implicating it in cognitive control. The present event-related functional magnetic resonance imaging study was able to separate monitoring from error-specific functions by allowing subjects to reject a trial so as to avoid errors. Cingulate and left dorsolateral prefrontal activity was greatest on rejection trials but comparable for correct and error trials, whereas an error-specific response was observed in bilateral insula. A dissociation was also observed between the cingulate and the nucleus accumbens with the latter more active for error than reject trials. These results reveal that the functional role of the cingulate is not particular to errors but instead is related to an evaluative function concerned with on-line behavioral adjustment in the service of avoiding losses.
Dynamics of Suppression in Macaque Primary Visual Cortex
Authors: Smith Matthew A. , Bair Wyeth , Movshon J. Anthony
Published: May 2006

The response of a neuron in primary visual cortex (V1) to an optimal stimulus in its classical receptive field (CRF) can be reduced by the presence of an orthogonal mask, a phenomenon known as cross-orientation suppression. The presence of a parallel stimulus outside the CRF can have a similar effect, in this case known as surround suppression. We used a novel stimulus to probe the time course of cross-orientation suppression and found that it is very fast, starting even before the response to optimal excitatory stimuli. However, it occurs with some delay after the offset response, considered to be a measure of the earliest excitatory signals that reach the CRF. We also examined the time course of response to a stimulus presented outside the CRF and found that cross-orientation suppression begins substantially earlier than surround suppression measured in the same cells. Together, these findings suggest that cross-orientation suppression is attributable to either direct feedforward signal paths to V1 neurons or a circuit involving fast local interneurons within V1. Feedback from higher cortical areas is implicated in surround suppression, but our results make this an implausible mechanism for cross-orientation suppression. We conclude that suppression from inside and outside the CRF occur through different mechanisms.
Murine homologues of the Drosophila gustavus gene are expressed in ovarian granulosa cells
Authors: Xing Yan , Gosden Roger , Lasko Paul , Clarke Hugh
Published: May 2006

Mammalian homologues of genes that control oogenesis in other organisms may play similar roles in mammalian ovarian development. In Drosophila melanogaster, GUSTAVUS (GUS) protein physically interacts with and is necessary for the proper posterior localization of VASA protein, and thus is required for specification of germ cells. We identified two mouse genes, SSB-1 and SSB-4 (SPRY domain SOCS box protein), whose protein products share 75% identity and are each approximately 70% identical to Drosophila GUS. Both SSB-1 and SSB-4 mRNA were detectable in mouse ovaries by Northern blotting of total and poly(A) + RNA, but were expressed in few other tissues. SSB-1 was detectable in testes, although the 3′-untranslated region of the mRNA was considerably shorter than the ovarian mRNA. In situ hybridization and RT-PCR analysis of ovaries revealed that both genes were expressed in granulosa cells at all stages of follicular development. In contrast, expression was barely detectable in in oocytes. Immunoblotting analysis revealed that SSB-1 protein was present in follicles at different stages of growth, and immunocytochemistry confirmed that SSB-1 and SSB-4 were detectable in granulosa cells of primary and subsequent stage follicles and that they were present in both mural and cumulus granulosa cells of antral follicles. These results establish that GUS-related proteins, which in Drosophila are restricted to the germ cells, are in the mouse instead expressed in the granulosa cells and are present throughout folliculogenesis. Based on their tissue-restricted pattern of expression and apparent abundance in granulosa cells, we propose that SSB-1 and SSB-4 play key roles in regulating granulosa cell physiology.
High-speed photography of the development of microdamage in trabecular bone during compression
Authors: Thurner Philipp J. , Erickson Blake , Schriock Zachary , Langan John , Scott Jeff , Zhao Maria , Weaver James C. , Fantner Georg E. , Turner Patricia , Kindt Johannes H. , Schitter Georg , Morse Daniel E. , Hansma Paul K.
Published: May 2006

The mechanical properties of healthy and diseased bone tissue were extensively studied in mechanical tests. Most of this research was motivated by the immense costs of health care and social impacts due to osteoporosis in post-menopausal women and the aged. Osteoporosis results in bone loss and change of trabecular architecture, causing a decrease in bone strength. To address the problem of assessing local failure behavior of bone, we combined mechanical compression testing of trabecular bone samples with high-speed photography. In this exploratory study, we investigated healthy, osteoarthritic, and osteoporotic human vertebral trabecular bone compressed at high strain rates. Apparent strains were found to transfer into to a broad range of local strains. Strained trabeculae were seen to whiten with increasing strain. Comparison of whitened regions seen in high-speed photography sequences with scanning electron micrographs showed that the observed whitening was due to the formation of microcracks. From the results of a motion energy filter applied to the recorded movies, we saw that the whitened areas are, presumably, also areas of high deformation. In summary, high-speed photography allows the detection of microdamage in real time, leading toward a better understanding of the local processes involved in bone failure.
Effect of initial preform porosity on solid-state foaming of titanium
Authors: Murray N.G.D. , Dunand D.C.
Published: May 2006

Titanium foams were produced by the expansion of pressurized argon pores trapped within a preform during a previous powder-consolidation step. Compared with creep expansion at 903 °C, superplastic expansion (induced by a 830–980 °C cycling around the allotropic temperature of titanium) increases foaming rate and final porosity. The pore size and fraction in the preforms were varied by using a range of initial titanium powder sizes and argon pressures. As initial preform porosity increases from 0.06 to 2.7%, foaming rate increases in the early stages of creep and superplastic foaming. However, at a later stage, foaming ceases prematurely for preforms with high initial porosity, as pores connect to the surface, allowing the escape of the pressurized argon. Preforms with 0.40% initial porosity result in foams with an optimal combination of high foaming rate, high final porosity (up to 47%), tailorable open or closed porosity, and Young's modulus as low as 23 GPa.
Nanomechanical properties of nacre
Authors: Katti Kalpana S. , Mohanty Bedabibhas , Katti Dinesh R.
Published: May 2006

Nacre, the inner iridescent layer of seashells is a model biomimetic system composed of 95% of inorganic (aragonite) phase and 5% of organic phase. Nacre exhibits an interlocked layered “brick and mortar” structure where the bricks are made up of aragonitic calcium carbonate and mortar is an organic phase. Here, we report the role of indentation load and penetration depth on measurement of nanomechanical properties of nacre. A range of loads from 10 μN to 10,000 μN were applied to obtain the response from different depths of nacre. The values of hardness and elastic modulus decrease with increasing load (i.e., increase in penetration depth). The variation in these values is significant at lower loads and decreases with increase in indentation load. From our results, it appears that the nanoindentation tests done at lower loads are highly influenced by micro and nanostructure in nacre. The indentation experiments performed at low loads indicate an elastic modulus of about 15 GPa for the organic phase. The low load, low penetration experiments appear to be better indicators of nanomechanical behavior. Also, we have observed a step-like behavior in the load-displacement curves at high load indentations on nacre. These features are attributed to the organic layer between the aragonite platelets. The indentation tests with penetration depths more than ∼250-300 nm often disrupt the organic layer and the behavior is not recovered in the unloading part of the curve. The microarchitecture and the composition of nacre contribute to the decrease in hardness values with increasing depth along with the indentation size effects.
Energy absorption of a polyacrylic acid partial sodium salt-modified nanoporous system
Authors: Surani Falgun B. , Qiao Yu
Published: May 2006

We experimentally investigated the pressure-induced infiltration of a nanoporous silica-based energy absorption system modified by polyacrylic acid partial sodium salt (sodium polyacrylate). Under ambient conditions, sodium polyacrylate forms a soft matter with water. As the hydrostatic pressure increases, the dehydration of the soft matter occurs and the nanopores are filled by water molecules, accompanied by a significant energy dissipation. This result has fundamental scientific interest for understanding behaviors of confined liquids and great technological importance for developing advanced solid-like protective/damping materials.
In situ synthesis of nano-sized cobalt ferrite particle/organic hybrid
Authors: Nakamura Satoshi , Sakamoto Wataru , Yogo Toshinobu
Published: May 2006

A CoFe2O4 particle/organic hybrid was synthesized using in situ processing of metalorganics of cobalt and iron below 100 °C. A mixture of cobalt (II) acetylacetonate (CA) and iron (III) 3-allylacetylacetonate (IAA) was hydrolyzed and polymerized yielding cobalt ferrite particle/organic hybrid. The crystallinity of cobalt ferrite depended upon the hydrolysis conditions of cobalt acetylacetonate-iron 3-allylacetylacetonate (CA-IAA). Nanocrystalline cobalt ferrite particles were uniformly dispersed in the organic matrix. The saturation magnetization of hybrid increased with increasing crystallinity of cobalt ferrite particles in the organic matrix. The hybrid showed a magnetization-applied field (BH) curve with no coercive force at room temperature. The magnetization versus H/T curves from 150 to 300 K were superimposed on the same curve and satisfied the Langevin equation. The hybrid revealed a saturation magnetization of 33.7 emu/g and a coercivity of 11 kOe at 4.2 K.
Victimization, Substance Use, and HIV Risk Behaviors Among Gay/Bisexual/Two-Spirit and Heterosexual American Indian Men in New York City
Authors: Simoni Jane M. , Walters Karina L. , Balsam Kimberly F. , Meyers Seth B.
Published: May 2006

Objectives.secondary aims included describing condom-use attitudes, beliefs about HIV/AIDS in the Indian community, HIV knowledge, HIV status, and preference for and access to HIV prevention services in this population.

Methods. A survey was mailed to all members of an American Indian community organization in New York City.

Results. The 20 men self-identifying as gay, two-spirit, or bisexual (hereafter, “two-spirit”) were more likely to report being victimized and engaging in HIV risk behaviors than the 51 heterosexual respondents, although they reported comparable levels of recent substance use. Overall, victimization was associated with lifetime HIV risk behaviors (even after control for sexual orientation) but not with substance use or unsafe sex in the past 12 months. The percentage of HIV infection was surprisingly high (10% of two-spirit men and 6% of heterosexual men).

Conclusions. Two-spirit men are a vulnerable population whose victimization must be understood within an appropriate historical and political context.
Blood Transfusions in the Early Years of AIDS in Sub-Saharan Africa
Authors: Schneider William H. , Drucker Ernest
Published: May 2006

Blood transfusions transmit HIV more effectively than other means, yet there has been little examination of their role in the origins and early course of AIDS in sub-Saharan Africa. We review historical data in archives, government reports, and medical literature from African and European sources documenting the introduction, establishment, use, and growth of blood transfusions in sub-Saharan Africa. These data allow estimation of the geographic diffusion and growth of blood transfusions between 1940 and 1990.

By 1955, 19 African colonies and countries reported transfusion programs—with national rates of 718 to 1372 per 100 000 by 1964, and urban rates similar to those in developed countries. We estimated 1 million transfusions per year in sub-Saharan Africa by 1970 and 2 million per year by the 1980s, indicating that transfusions were widely used throughout sub-Saharan Africa during the crucial period of 1950–1970, when all epidemic strains of HIV first emerged in this region.
Longitudinal Relationships Between Use of Highly Active Antiretroviral Therapy and Satisfaction With Care Among Women Living With HIV/AIDS
Authors: Burke-Miller Jane K. , Cook Judith A. , Cohen Mardge H. , Hessol Nancy A. , Wilson Tracey E. , Richardson Jean L. , Williams Pete , Gange Stephen J.
Published: May 2006

Objectives. We used longitudinal data to examine the roles of 4 dimensions of patient satisfaction as both predictors and outcomes of use of highly active antiretroviral therapy (HAART) among women in the United States with HIV/AIDS.

Methods. Generalized estimating equations were used to analyze time-lagged satisfaction–HAART relationships over 8 years in the Women’s Interagency HIV Study.

Results. Multivariate models showed that, over time, HAART use was associated with higher patient satisfaction with care in general, with providers, and with access/convenience of care; however, patient satisfaction was not associated with subsequent HAART use. Symptoms of depression and poor health-related quality of life were associated with less satisfaction with care on all 4 dimensions assessed, whereas African American race/ethnicity, illegal drug use, and fewer primary care visits were associated with less HAART use.

Conclusions. Our findings suggest that dissatisfaction with care is not a reason for underuse of HAART among women with HIV and that providers should not be discouraged from recommending HAART to dissatisfied patients. Rather, increasing women’s access to primary care could result in both increased HAART use and greater patient satisfaction.
HIV Testing Among Young Adults in the United States: Associations with Financial Resources and Geography
Authors: Nguyen Trang Quyen , Ford Carol A. , Kaufman Jay S. , Leone Peter A. , Suchindran Chirayath , Miller William C.
Published: May 2006

We estimated prevalence and odds ratios for self-reported HIV testing among sexually experienced young adults using nationally representative data obtained from Wave III of the National Longitudinal Study of Adolescent Health (Add Health). The prevalence of testing in the past year was 18.8%.

Young adults who had private or no health insurance were less likely to report testing than were young adults who had public health insurance, particularly in the South. Respondents with functional income were less likely to report testing than were those without functional income, particularly in the South and Northeast. Variable HIV testing based on finances and insurance should be addressed.
Perpetration of Intimate Partner Violence Associated With Sexual Risk Behaviors Among Young Adult Men
Authors: Raj Anita , Santana M. Christina , La Marche Ana , Amaro Hortensia , Cranston Kevin , Silverman Jay G.
Published: May 2006

Objective. We assessed the association between intimate partner violence (IPV) perpetration and sexual risk behaviors and fatherhood (having fathered children) among young men.

Methods. Sexually active men aged 18 to 35 years who visited an urban community health center and who reported having sexual intercourse with a steady female partner during the past 3 months (N = 283) completed a brief self-administered survey about sexual risk behaviors, IPV perpetration, and demographics. We conducted logistic regression analyses adjusted for demographics to assess associations between IPV and sexual risk behaviors and fatherhood.

Results. Participants were predominantly Hispanic (74.9%) and Black (21.9%). Participants who reported IPV perpetration during the past year (41.3%) were significantly more likely to report (1) inconsistent or no condom use during vaginal and anal sexual intercourse, (2) forcing sexual intercourse without a condom, (3) having sexual intercourse with other women, and (4) having fathered 3 or more children.

Conclusion. IPV perpetration was common among our sample and was associated with increased sexual risk behaviors. Urban community health centers may offer an important venue for reaching this at-risk population.
Radioisotope Turnover and Energy Flow in Terrestial Isopod Populations
Authors: Reichle David E.
Published: May 2006

Radiocesium turnover rates in terrestrial isopod populations were used to measure food consumption and metabolism under natural and laboratory—simulated field conditions. Four old—field and forest species were studied: Armadillidium vulgare (Latreille), Armadillidium nasatum Budde—Lund, Cylisticus convexus (DeGeer), and Metoponorthus pruinosus (Brandt). Uptake, body burden equilibria, and elimination rates for 134Cs were related to environmental temperatures (Q10°2). dietary supplements of stable Na, K, and Cs salts produced no effect upon 134Cs elimination rates. Assimilation fractions from food were 60 to 64% for digestible dry matter, 70 to 73% for caloric intake, and 70 to 87% for radiocesium. Body equilibrium concentrations and biological half—lives of radiocesium in each species permitted estimates of food consumption comparable to gravimetric determinations. Food intake varied between different species and ranged from 1.5 to 3.5% of dry body weight per day. Bomb calorimetry and respirometry measurements were used to partition the total energy budgets, caloric inputs required for maintenance, production, and growth were determined. Radiocesium elimination rates were correlated with the metabolic rates of individual species, and radionuclide turnover rates in tagged individuals were demonstrated to be a practicable means of determining the activity and metabolism of species in the natural habitats.
Influence of Temperature on the Dormancy of Some Spring Emphemerals
Authors: Risser Paul , Cottam Grant
Published: May 2006

The effect of temperature on the breaking of dormancy was examined in five species of spring ephemerals, Claytonia virginica, Erythronium albidum, E. americanum, Dicentra cucullaria, and D. canadensis. All species except Claytonia required cold treatment to imitate growth. Dormancy was not broken in D. canadensis under the experimental conditions. Generally, with increasing lengths of cold treatment, the time for subsequent emergence decreased, the time the plants remained green decreased, and up to a point, the size of the resulting plants increased.
A Possible Recycling Mechanism in Tropical Forrest
Authors: Young Frank N.
Published: May 2006

The abundance of noterid beetles in root mats along many miles of swift streams in Columbia suggests that they play a role in carrying nutrients back into the surrounding forests.
Studies of Behavior of the Tribolium Flour Beetles. II. Distributions in Depth of T. Castaneum and T. Confusum in Fractionable Shell Vials
Authors: Ghent Arthur W.
Published: May 2006

Flour beetle distributions, in depth, were studied with plastic replicas of the shell vials employed in the Chicago Tribolium competition model (10—mm rings of Plexiglas tubing, held together with mending tape). No differences were found between distributions of male and female T. castaneum, both of which were found distributed roughly uniformly throughout fresh flour after 10 hr. Less than 2% of T. castaneum imagoes were found on the surface at that time. In contrast, 88% of male T. confusum, and 33% of females, were still on the surface after 10 hr. Mixed populations became stratified during this same period, with the more slowly entering T. confusum imagoes evidently forcing T. castaneum into the lower halves of the vials. In these mixtures, male T. confusum entered four more rapidly than in the controls, evidently in response to its more rapid conditioning with T. castaneum present. The average depth of T. castaneum imagoes was well below that of T. confusum during the first 4 days, but these population centers crossed each other on day 5. Thereafter T. confusum, shown in part 1 to prefer conditioned flour, predominated below the surface, and T. castaneum, shown in part 1 to prefer fresh four, predominated on the surface. After 26 days at 29°C, 70% relative humidity, T. castaneum had produced three times as many larvae as T. confusum, these being also from two to four times larger than the T. confusum larvae, depending on the flour level examined. The numbers of T. castaneum larvae reaching the prepupal and pupal stages also greatly exceeded those of T. confusum. More T. confusum eggs were found, however, and for both species the egg distributions appeared negatively correlated with the larval distributions. This suggests the importance of egg cannibalism by larvae. The roles that imago and larval behavior may play in determining the outcome of competition, and the relevance of the notion of ecological similarity to the Chicago competition model and to evolutionary theory, are discussed.
Ecology of a Red Pine (Pinus Resinosa) Plantation in Michigan
Authors: Gysel Leslie W.
Published: May 2006

A savanna—like area of 1,302 acres in northern Michigan was planted from 1919 to 1923 with red pine (Pinus resinosa), a species not common in local plant communities at that time. Its high survival resulted in marked changes in plant species composition and cover. The plantation could be considered an artificial community. On a designated natural or unplanted area of 122 acres adjacent to the pine plantation, jack pine (P. banksiana) and northern pin oak (Quercus ellipsoidalis) developed as the dominant tree species. The structure and composition of this community, other than the tree overstory, are similar to that of the red pine plantation. Many areas remained open after the planting; in 1938, 15% of the total area was open and in 1963, 8% remained open. Lichens form a large part of the cover in these openings; a few species of grasses, sedges, and shrubs have a high frequency but form a small amount of plant cover. Animal and bird species commonly found in northern Michigan are sparse in the plantation and in the unplanted area. Populations of white—tailed deer, snowshoe hare, and ruffed grouse have decreased during the development of the plantation.
The Effects of Subfreezing Temperatures on the Longevity and Fecundity of Oncopeltus Fasciatus (Dallas)
Authors: Saint R. S. , Chiang H. C.
Published: May 2006

Adults of the milkweed bug Oncopeltus fasciatus, 2 to 3 days old, were exposed to –35°C for 3, 7, and 12 min. These exposures produced mortalities of 16.0, 48.5, and 79.5% respectively 72 hr after the exposure. In general, the mean postexposure longevity, as well as the length of the reproductive period, was inversely proportional to the length of the exposure. The detailed analysis of the survivorship curves indicated that the females of the 7— and 12—min exposures suffered a higher mortality in the first half of the life span, and that the ones which survived tended to live longer than those in the control series. The fecundity, as indicated by both the daily oviposition and the total oviposition, was higher in the survivors of the 3— and 7—min exposures than in the control series. The implications of these findings in population ecology, organic evolution, and insect control are discussed.
Effects of Seed Origin on Drought Resistance of Douglas‐Fir (Pseudotsuga Menziesii) (Mirb.) Franco
Authors: Ferrell William K. , Woodard E. Steve
Published: May 2006

Douglas—fir seedlings from a number of seed origins were subjected to drought conditions in the greenhouse and laboratory. Interior mountain seedlings showed significantly greater drought resistance than seedlings from origins west of the Cascade Mountains. Differences were also found within each of these groupings. In the Corvallis, Oregon, area seedlings produced from seed on a south slope had more drought resistance than those from a short distance away of a north slope. Differences in drought resistance may involve either drought hardiness or drought avoidance, or both.
An Ecological Significance of Evergreenness
Authors: Monk Carl D.
Published: May 2006

Percentage of evergreenness in 158 forest stands from seven community types in north—central Florida ranged from 0 to 100. In general, the evergreen species are more important on dry sterile sites and the deciduous species on mesic fertile sites. Nine environmental variables or combinations of variables accounted for approximately 51% of the variation in stand evergreenness. The segregation of evergreen species to dry sterile sites may be related to the gradual return of nutrients to the soil or the establishment of a more closed mineral cycle through (1) the leaching of nutrients from leaves and (2) year—round leaf fall.
Patterns of Photosynthesis under Natural Environmental Conditions
Authors: Hodges John D.
Published: May 2006

Net photosynthesis in six different conifers was studies under various natural environmental conditions. Changes in the pattern of photosynthesis on clear days, especially the midday decrease, are apparently primarily controlled by changes in leaf water potential. In noble fir and Scots pine, water potential probably acts mainly through its influence on stomatal movement. In grand fir, Douglas—fir, hemlock ,and Sitka spruce, however, some other mechanism, probably mesophyll resistance to CO2 diffusion, seems to play a more important role. Both mechanisms probably operate concurrently in all species. Daily variations in leaf water potential seem to occur primarily in response to changes in atmospheric moisture, or, more precisely, vapor pressure gradient from leaf to atmosphere. Variation in carbohydrate content, through its influence on solute concentration, may also influence leaf water potential.
Influence of Daylength on the Photosynthetic Capacity of Stone Pine (Pinus Cembra L.)
Authors: Bamberg Samuel , Schwarz Werner , Tranquillini Walter
Published: May 2006

The effects of constant and varying daylengths on the photosynthetic capacity of some pine, the major tree forming timberline in the Eastern Alps, were studied from fall to spring on plants in the open under natural conditions and in the greehouse at 2,000 m altitude (timberline). CO2 uptake was measured using a CO2 gas analyzer on plants in a climatized wind canal under standardized optimal conditions. Photosynthetic capacity of plants in the open rapidly decreased in the fall, reaching zero in the early December, became positive in mid—March, and slowly increased in the spring. Plants in the greenhouse under natural day—length and photoperiods of 12 and 8 hr also had a definite midwinter depression in photosynthetic capacity. This winter depression is attributed to either an endogeneous rhythm in physiological activity, or to an induced change before the start of the test, or to the effect of changing quality and quantity of light in the wintertime.
Studies of Subtidal Marine Vegetation in Western Washington
Authors: Neushul M.
Published: May 2006

Objectively defined, benthic plant associations in the Puget Sound region are compared with associations recorded by other workers, in this and other areas. A shallow Laminaria association, an Agarum dominated region at mid—depths and a red algal association of Rhodoptilum, Callophyllis, and hydroids near the lower (17 to 20 m) limits of plant distribution, are described. Variation in community composition at similar depths is attributed mainly to substrate differences. Algal community structure is shown to be influenced by variation with season, depth and water movement. The descriptive details obtained in this study provide a basis for further inquiry into the environmental conditions that define these under—sea plant associations.
A Rapid Method for Estimating Arboreal Canopy Cover
Authors: Emlen John T.
Published: May 2006

The per cent of a tract of savannah or woodland that is covered by tree canopy is measured by point quadrat sampling along a series of straight line transects using a vertical viewing tube.
Plant Communities and Environmental Interrelationship in a Portion of the Tillamook Burn, Northwestern Oregon
Authors: Bailey Arthur W. , Poulton Charles E.
Published: May 2006

Major post—burn communities were characterized and environmental relationships investigated on an area burned by forest fires in 1933, 1939, and 1945. Results that seral vegetation developing after three forest fires is classifiable, and the communities show consistent relationships to environmental factors. Both shade—intolerant, early seral species and shade—tolerant, late seral or climax species revealed specific environmental requirements for growth and survival. Species composition and dominance data were recorded in 42 stands. Six associes were recognized. The Alnus rubra/Polystichum numitum associes occurs predominantly below 1,200 ft elevation, on north—facing, lower slope positions. These stands usually occupy the stony phase of the Hembre or the Astoria soil series. The Alnus rubra/Rubus parviflorus associes is found on steep, north—facing slopes usually at slightly higher elevations than the Alnus/Polystichum associes. These stands are predominantly associated with the stony phase of the Hembre soil series. The Acer circinatum/Polystichum munitum associes, found on all aspects between 700 and 1,200 ft, was arbitrarily classified into xeric and mesic phases. However, the community is usually associated with steep, lower slope positions. It is also found on the stony phase of the Hembre or the Astoria soil series. The Rubus parviflorus/Trientalis latifolia associes is found on all aspects, on steep, upper slope positions and above 1,200 ft elevation. It occurs predominantly on the Kilchis soil series. Stands of the Pteridium aquilinum/Lotus crassifolius associes usually occupy gentle, middle, and upper slope positions on all aspects above 1,200 ft elevation. It is found on the deep, stone—free Hembre soil series. The Vaccinium parvifolium/Gaultheria shallon associes is found on south—facing, convex slopes or ridgetops from 700 to 2,100 ft. It occurs to some degree on all soil series in the area. Two provisional associes were recognized: the Acer macrophyllum/Symphoricarpos mollis associes occupying partially—vegetated, south—facing, rock outcroppings and talus slopes, and the Acer macrophyllum/Alnus rubra associes limited to stream bottoms. Some of the cause of vegetation heterogeneity are discussed, and a dichotomous key to the vegetation is presented.
Effect of Environment and Heredity on the Root‐Growth Pattern of Red Pine
Authors: Merritt Clair
Published: May 2006

Observations were made on the seasonal root activity of 2—0 seedlings of red pine (Pinus resinosa Ait.) growing in controlled environments. Portions of the growth pattern conformed closely to the seasonal pattern commonly reported for field environments even though environmental variation was minimized in the controlled experiment. The nature of this pattern was determined by varying temperature, photoperiod, and soil moisture. It was concluded that the gross pattern of root activity is endogenously controlled although environmental variation may induce significant quantitative changes in activity and influence the timing of events.
Site Selection by Larval Water Mites Parasitic on the Damselfly Cercion Hieroglyphicum Brauer
Authors: Mitchell Rodger
Published: May 2006

Two species of Arrenurus commonly parasitize a population of the damselfly Cercion hieroglyphicum. The incidence of the thoracic parasite, A. mitoensis Imamura and Mitchell, is low. Mite larvae preferentially clump together on the host mesothorax and at peaks of mite abundance may kill hosts. The abdominal parasite, A. agrionicolus Uchida, is abundant and locates 98% of the hosts. Larvae attach to the venter of the abdomen; the first mite usually attaches 0.50 mm anterior to the tip of segment 7 and subsequent attachments are anterior to this point with the mites usually keeping 0.10 mm apart. Responses to crowding cause mites to move to new sites, which tends to produce equal numbers on the two sides of the host abdomen, as well as forcing mites to more anterior attachment sites. These two parasites show the contrasting adaptations of a clumped parasite versus those of a more uniformly distributed parasite that is usually abundant enough to show intraspecfic competition for host resources.
Microseston Dynamics in a Simple Sierra Nevada Lake‐Stream System
Authors: Maciolek J. A. , Tunzi M. G.
Published: May 2006

Suspended organic particles in a small, precipitous drainage were studied primarily in regard to trophic ecology. Headwater and seepage sources in the 6.5—km (4—mile) system contained minimal quantities (<2 gcal/liter or 0.5 mg/liter dry wt) mainly of organic detritus. Maximum concentration (>12 gcal/liter or nearly 3 mg/liter dry wt) appeared in the stream as effluent phytoplankton from the single lake located near the headwaters. A progressive decrease in cellular microseston below the lake was accompanied by an increase in detritus. The cell loss was due mostly to trophic uptake by filter—feeding simuliid larvae which were capable of removing 60% of the suspended algae within a 0.4—km section of stream. Downstream gain of organic detritus resulted from external contributions (e.g. streamside vegetation), abetted by decompositional processes within the stream, including digestion by aquatic invertebrates. Autochthonous material was considerably less important quantitatively as seston than allochthonous (lacustrine and terrestrial). Sedimentation and physiochemical loss were secondary to trophic uptake in seston removal. Destruction of cellular material by turbulent flow was directly proportional to stream gradient and was clearly evident only where a prolonged gradient existed in excess of 5%. Because all loss—causing factors operate selectively on cellular material, organic detritus would be expected as the chief microseston component of streams isolated from lake outflow.
Some Factors Affecting Drift Rates of Baetis and Simuliidae in a Large River
Authors: Pearson William D. , Franklin Donald R.
Published: May 2006

Effects of eight factors on the drift rates of Baetis nymphs and Simuliidae larvae were tested with multiple regression analyses. Illumination, population density of all other organisms and temperature had significant influences on drift rates of both organisms. Turbidity and water—level fluctuations were related to changes in drift rates indirectly through influence upon light penetration and population density, respectively. Dissolved—oxygen concentration, calendar date, and depth of water at the sample site did not clearly affect drift rates of either organism. In areas where population densities were high, the eight factors tested accounted for 65% to 81% of the variability observed in drift rates. Maximum drift rates were 170 x 106 Baetis sp. nymphs (63.2 kg) and 10.9 x 106 Simuliidae larvae (5.4 kg) per day.
Ecology and Activity of Himalayan Foothill Rhesus Monkeys (Macaca Mulatta)
Authors: Neville Melvin K.
Published: May 2006

Himalayan foothill rhesus monkeys were studied for a year at three forest habitats and in the town of Haldwani in Uttar Pradesh, India. Food supplies in the forest diminished both in abundance and variety as altitude increased during the ascent from tropical forests at the base of the foothills to subtropical pine and temperate oak forests at elevations of 5000 ft or more. Home range, day range, population density, and activity patterns also varied with altitude: monkey troops in the less favorable areas had larger home ranges and day ranges and were more often on the move during the day, while the lower elevations had a higher population density of monkeys. Increased mobility was a characteristic of one subtropical pine forest troop lacking any adult male. Both the abundance of food in Haldwani and the limited tolerance of the human inhabitants limited home ranges there to about 0.02 mi2, approximately 1/20 that of the smallest forest troop home range. Activity patterns were more stereotyped in the town than in the forest. The population density of the occupied portion of town was much more than in the forests, but less than on Cayo Santiago. Night time activity is probably greater in town.
Selection of Pupation Site by Drosophila Melanogaster and D. Simulans
Authors: Sameoto D. D. , Miller Richard S.
Published: May 2006

Drosophila melanogaster and D. simulans larvae were tested to determine their choice of pupation site in relation to larval density and moisture content of the medium. A dry medium produced a change in pupation behavior in D. simulans but not in D. melanogaster populations. Both species responded to a medium with high water content as follows: (1) a higher proportion of pupae were found on the sides of the vials rather than on the medium, (2) there was an increase in the total number of pupae produced, (3) there was an increase in pupal mortality, and (4) the total number of adults produced was not affected by moisture content of the medium.
Contribution of Shrubs to the Nitrogen Economy of a Desert‐Wash Plant Community
Authors: Garcia-Moya Edmondo , McKell Cyrus M.
Published: May 2006

Total nitrogen incorporated in the shrubs of a low—fertility desert plant community (principally Acacia Gregii, Cassia armata, and Larrea divaricata) was estimated from the nitrogen content of plant parts, the total weight of plants and proportional weight of roots, stems, and leaves, and the number of plants per unit area. The average nitrogen content of shrub leaves, stems, and roots was 1.31%, .87%, and .80%, respectively. Shrub cover occupied 20% of the ground surface and contained an average of 29 kg nitrogen/ha. Legume shrubs were not significantly greater in nitrogen content than nonlegume shrubs. Soil nitrogen content decreased significantly as a function of radial distance from the center of the shrub canopy. Areas between shrubs averaged 0.19% nitrogen in the surface inch of soil. Soil nitrogen content decreased significantly from the surface to 90—cm depth and was closely related to shrub species and their root—distribution patterns.
Influence of Meadow Mouse Populations on California Grassland
Authors: Batzli George O. , Pitelka Frank A.
Published: May 2006

The influence of meadow mouse (Microtus californicus) populations on grass—land ecosystems was studied at two sites with similar densities of Microtus, but in different types of grassland–a coastal prairie and an inland valley grassland. Height of vegetation, volume of standing crop, and percentage cover were greater at the dry inland site where the annual grass Bromus rigidus was dominant. At the milder coastal site the annual grass Lolium multiflorum and the perennial bunchgrass Danthonia californica were dominant; forbs and other perennial grasses were more important. During a year with high rainfall and moderate densities of Microtus (1967) total standing crop, average height of vegetation, and weight of seed crop at the coastal site increased. Although 1966 and 1968 were both dry years, standing crop, seed production, and volume and cover of vegetation were less in 1968, when the meadow mouse population was high, than in 1966, when it was low. Exclosure studies demonstrated that these vegetation changes resulted from changes in Microtus density. Major food plants for the mice contributed 85% less volume to the vegetation on unexclosed areas after a high density of 395 Microtus per hectare (160/acre). Seed fall from preferred grasses was diminished 70% on grazed areas.
Sequence and Timing of Bee Foraging in Flowers of Ipomoea and Aniseia (Convolulaceae)
Authors: Schlising Robert A.
Published: May 2006

Flowers of Ipomoea triloba, I. Setifera, I. battatas, and Aniseia martinicensis growing in three areas of disturbed vegetation in Costa Rica were visited by a large number of foraging insects during the dry—season moths of February and March 1967. The commonest foragers collecting pollen or nectar, or both, were bees in the families Anthophoridae, Apidae, Colletidae, and Halictidae. The species of bees varied with the locality and with the species of plant, but an ordered and predictable sequence in groups of foragers was seen throughout the few hours in the morning that the flowers remained open. Each species of bee had a foraging period for a definite portion of the morning, and the peak activity was often at a different time for each species of bee, usually in mid—or late morning. The average time of an individual bee visit to a flower varied also, and the longest individual visits were early in the morning in at least four genera. The average number of insect visits to 106 flowers was about 20, but ranged from 1 to 142. These flowers seemed morphologically well suited for cross pollination, and the bees foraging in them doubtless served as effective pollen vectors.
Caloric Values of Pinus Virginiana as Affected by Time of Sampling, Tree Age, and Position in Stand
Authors: Madgwick H. A. I.
Published: May 2006

Caloric values of new needles, twigs, and first—year cones increased throughout the growing season. Values for older tissues were more stable though cones decreased in caloric values during the second year. In young stands, suppressed trees had lower caloric values for needles than dominants, but this trend reversed with stand age. Branches on suppressed trees had higher caloric values than those on dominants. Bole—wood values were unaffected by position in stand. Stand age did not affect stand averages of caloric values of needles, branches, wood, or bark. Caloric values for Pinus virginiana increased in the order boles, branches, mature needles irrespective of tree age, stand density, and time of year. Values for P. Virginiana were similar to values for other Pinus spp. found in the literature.
Ecology of Red‐Tailed Hawk Predation in Alberta
Authors: Luttich Stuart , Rusch Donald H. , Meslow E. Charles , Keith Lloyd B.
Published: May 2006

The Red—tailed Hawk population on a 60—mile2 (156—km2) area in central Alberta was studied during 1965—68. This migratory population was present from early April to September each year. Breeding red—tails occupied open and forested habitats with equal facility, taking prey species from all cover types associated with nesting sites. Mammals, chiefly Richardson's ground squirrels and snowshoe hares, comprised 66% of total prey biomass taken by red—tails; waterfowl comprised 18%. Representation of meadow voles in the red—tail diet reflected annual variations in vole densities, but there was no consistent relationship between snowshoe hare and Ruffed Grouse densities and their utilization by red—tails. Numbers of adult red—tails resident on the study area varied little from year to year, and nesting success was not directly related to changes in cyclic hare and grouse populations. Red—tails took between 1.9 and 7.0% of the adult hares, and 0.3—0.8% of the juveniles on the study area during mid—April through August, 1966—68. Estimates of red—tail predation on Ruffed Grouse over this same period were 1.4 to 5.1% of adults, and 0.9 to 2.2% of juveniles. Calculated losses of Richardson's Ground squirrels to Red—tailed Hawks during 1967 and 1968 ranged from 22 to 60% in three populations. Losses of adults were especially high, and may have exceeded 90% in one instance. Adult male ground squirrels were significantly more vulnerable than adult females.
Production, Mineral Accumulation and Pigment Concentrations in Typha Latifolia and Scirpus Americanus
Authors: Boyd Claude E.
Published: May 2006

Shoot productivity was measured for Typha latifolia and Scirpus americanus. Samples were also subjected to chemical analyses. Tissue concentrations of chlorophylls a and b, carotenoids and most macronutrients declined as the plants aged. Net accumulation of these constituents per square meter usually continued during periods of dry matter increase, even though tissue concentrations were diminishing. Dry matter standing crop was the decisive factor determining quantities of chemical constituents per square meter. Uptake rates for macronutrients were generally not proportional to productivity rates. The most rapid uptake of several nutrients occurred earlier than maximum growth rates.
A Regression Method for Mark‐Recapture Estimation of Population Size with Unequal Catchability
Authors: Marten Gerald G.
Published: May 2006

The assumption of equal catchability of marked and unmarked animals in mark—recapture sampling is examined. Violation of this assumption may come from two basic sources, heterogeneity or contagion, and both produce a bias in the estimate of population size. Two approaches to this problem are discussed. First, it is noted that bias can be avoided by statistically independent sampling procedures for marking and recapturing. Second, a new regression method is presented for multiple captures on a closed population, which combines mark—recapture with "simulated" removal and tests whether the assumption of equal catchability holds, regardless of the source of bias. Furthermore, if the ratio of catchabilities between unmarked and marked animals is constant over at least two successive samples, the method provides an estimate of population size even if the assumption of equal catchability does not hold. Two suggestions are made to supplement the regression method. First, noncapture sampling to obtain the ratio of unmarked to marked animals has several advantages over trapping. Second, a subclass of the marked animals may satisfy the constant ratio assumption even when all marked animals do not. A worked example is provided to illustrate the method.
Factors Influencing Shoot Production and Mineral Nutrient Levels in Typha Latifolia
Authors: Boyd Cluade E. , Hess Lloyd W.
Published: May 2006

Shoot standing crops for Typha latifolia ranged from 428 to 2,252 g dry wt/m2. Standing crops were positively correlated with concentrations of dilute acid soluble phosphorus in hydrosoils and dissolved phosphorus in the waters. Except for a weak0 correlation for dissolved calcium, additional site fertility parameters were not correlated with standing crop. Tissue nutrient levels varied considerably, maximum values for most minerals being three or four times as great as the smallest values. Correlations between environmental levels of several nutrients and tissue concentrations were significant, but not very strong. Tissue concentrations of most nutrients were positively correlated with nitrogen content. Despite variations in tissue levels of nutrients, standing crop was the decisive factor determining quantities of nutrients per unit area of stand.