bluuebunny/crossref_metadata_2025 huggingface dataset:
WATER CONTENT AND SOIL CORE VOLUME ON BROOKSTON CLAY LOAM
Authors: STONE J. A. , WIRES K. C.
Published: March 2010

Soil core volumes, from a long-term fertility experiment on Brookston clay loam, were adjusted for soil water content at sampling to explain large year-to-year fluctuations in bulk density and porosity. Adjusting the long-term soil core data decreased values of bulk density, total porosity, and air-filled porosity and reduced the variation between years. However, the year-to-year variation remained highly significant. Year-to-year fluctuations in bulk density and porosity on Brookston clay loam soil do not appear to be solely the result of changes in soil volume due to differences in soil water content at the time of sampling. Key words: Shrinkage, bulk density, porosity
TRACE ELEMENTS IN AGRICULTURAL SOILS OF NORTHWESTERN ALBERTA
Authors: SOON Y. K. , ABBOUD S.
Published: March 2010

Fifty-two surface soils and 11 subsoils collected from agricultural soils of the Peace River region of northwestern Alberta were analyzed for total and extractable contents of Cd, Cr, Cu, Mn, Ni, Pb and Zn. The purpose of this survey was to build up a data base on trace element contents of agricultural and environmental concerns for soils of this region. Extractable amounts were determined by DTPA-ammonium bicarbonate, 0.05 M EDTA, 0.1 M HCl and saturation extractions. Total Cd, Cr, Cu, Mn and Pb concentrations were similar to average values for "world" soils; Ni was less than and Zn greater than "world" average. Total Cr was higher and total Pb lower than average values reported for Canadian soils. Total Cd, Cu, Ni, Pb and Zn were similar in surface and subsurface soils. Extractable Cd, Mn, Ni and Zn tended to be greater in surface soils compared to subsoils; Cu and Pb were higher in the clay-enriched subsoils. Among the surface soils, soils with higher amounts of organic matter contained greater amounts of total and extractable metals with few exceptions. Clay content was also closely correlated with the distribution and content of Cu, Pb and Cr. Few, if any, of the soils would be expected to be deficient in Cu, Mn or Zn for the production of crops. Key words: Cadmium, copper, chromium, manganese, nickel, lead, zinc
ION-SELECTIVE ELECTRODE DETERMINATION OF SOLUTION K IN SOIL SUSPENSIONS AND ITS SIGNIFICANCE IN KINETIC STUDIES
Authors: WANG F. L. , HUANG P. M.
Published: March 2010

The feasibility of using a K ion-selective electrode (K-ISE) to monitor changes in solution K concentration in soil suspensions with time, under shaking conditions, was investigated and its significance in kinetics studies of K adsorption was discussed. Factors that affect the efficiency of the K-ISE method include the response time of the electrode, influence of suspended soil particles, shaking speed, and ionic strength of the system. The response time of the K-ISE decreased with increasing K concentration. Moreover, for a system with a solution K concentration greater than 10 mg K L−1, errors resulting from response delays were negligible when, under shaking conditions, observation time intervals were greater than 30 s. The influence of suspended soil particles on the K-ISE method was negligible for soil suspensions with a solution/soil ratio of 50:1 (vol/wt). Shaking significantly influenced K-ISE determination of solution K concentration. The degree of the influence of shaking on the determination of solution K appeared to be related to ionic factors of the systems. Shaking had much less influence on the soil suspensions, the filtrates and mixed CaCl2-KCl solutions than on pure KCl solutions. Satisfactory results were obtained by taking into account the response time, suspended soil particle and shaking speed factors and by adjusting the ionic strength of the calibration system (KCl standard solution series). Key words: Potassium ion-selective PVC membrane electrode, batch technique, kinetics, calibration system, electrode response time, suspended soil particle, shaking speed, ionic strength
SOIL EROSION EFFECTS ON SOIL QUALITY AND YIELD
Authors: VERITY G. E. , ANDERSON D. W.
Published: March 2010

This study examines the cumulative effect of erosion on soil properties that are important to productivity, and estimates the effect of erosion on grain yields. Experiments were located in central Saskatchewan on Dark Brown soils of the Weyburn Association. The relationship between yields and relative distance down eroded hillslopes was described best by a third-order polynominal equation. Grain yields were lowest on the upper slopes and increased steadily through mid-slopes to maximum values that were often double the upper slope yield on the lower or foot slope, then decreased again in the more level parts of the fields away from the slope. The impact of varying degrees of erosion on productivity was estimated by adding back incremental depths of topsoil to eroded knolls. Grain yields were increased by 45–58% by adding 50 mm of topsoil, with additional topsoil (100 or 150 mm) generally increasing yields slightly, but at a decreasing rate. Changes in soil quality with increasing erosion were measured on otherwise similar soils on eroded knolls, with the period of cultivation ranging from 0 (native) to 75 yr. Reductions in the amount of 137Cs in surface horizons with increasing period of cultivation indicated the cumulative effects of erosion, with general soil losses of 20 to 30 Mg ha−1 yr−1. Consistent reductions in silt plus very fine sand fractions with time suggested that wind erosion had been dominant. Organic C and P, total N and S decreased with increasing erosion. Potentially mineralizable N descreased at a faster rate than total N. The CaCO3 content of surface horizons increased, and inorganic P remained constant with increasing degree of erosion. Key words: Nutrients, soil productivity, soil quality, eroded, catena.
ELEMENTAL SULFUR OXIDATION AS INFLUENCED BY PLANT GROWTH AND DEGREE OF DISPERSION WITHIN SOIL
Authors: JANZEN H. H.
Published: March 2010

Controlled environment studies were conducted to characterize the effects of cropping treatment and degree of particle dispersion on S oxidation rate. In two soils (a Chernozem and a Luvisol), S oxidation rates were not greatly affected by cropping treatment (barley, beans, canola, or fallow). In a second experiment, S oxidation was shown to approach maximum rates at a dispersion level of 1000 g soil g−1 S. Key words: Sulfur, placement, rhizosphere, fertilizer, elementals
THE USE OF FLUORESCENCE SPECTROSCOPY TO STUDY HERBICIDE-HUMIC ACID INTERACTIONS: PRELIMINARY OBSERVATIONS
Authors: OLSON B. M.
Published: March 2010

Fluorescence spectroscopy was used to study the interaction of humic acid with Cu+2, paraquat and simetryn. Paraquat and Cu+2 quenched the fluorescence of humic acid (HA) by as much as 74 and 89%, respectively. Simetryn did not quench the fluorescence of HA, even at pH 4 under which conditions simetryn would have carried a positive charge due to protonation. Key words: Fluorescence spectroscopy, simetryn, paraquat, copper, humic acid
COMPARISON OF TWO SAMPLE OXIDATION METHODS FOR QUANTITATIVE MEASUREMENT OF 12C AND 14C IN PLANT AND SOIL
Authors: WINTER J. P. , GREGORICH E. G. , VORONEY R. P. , KACHANOSKI R. G.
Published: March 2010

Two methods for determining total C and 14C in plant and soil were compared. One method involved wet oxidation of samples in concentrated acid and measuring evolved 12/14CO2 captured in NaOH. The other method oxidized samples in an induction furnace, measured total CO2-C by thermal conductivity, then 14CO2-C collected in a NaOH solution. Over a range of carbon contents and including both plant and soil samples, the wet and dry oxidation methods were highly correlated (r2 = 0.99) and the slope of the regression wet on dry methods (±SE) was 1.00 ± 0.01 and 1.05 ± 0.01 for total-C and 14C, respectively. However, the dry oxidation method may not be as accurate as the wet method for soil samples especially at low levels of C, less than 5 mg C g−1 sample. Key words: Total carbon, carbon-14, high-temperature induction furnace, acid digestion
EFFETS D'APPORT D'AMENDEMENTS LIGNEUX FRAIS ET HUMIFIES SUR LA PRODUCTION DE POMME DE TERRE ET SUR LA DISPONIBILITE DE L'AZOTE EN SOL SABLEUX
Authors: BEAUCHEMIN SUZANNE , LAVERDIÈRE MARC R. , N'DAYEGAMIYE ADRIEN
Published: March 2010

Intensive potato cropping has been reported as a major cause of degradation of sandy soils. Wood residues from tree clipping applied to soils can substitute for crop residues to maintain adequate organic matter levels and crop productivity. However, this ligneous material presents a C:N ratio varying from 50 to 175 and, when applied in large quantities, may induce N immobilization at the expense of the crop. The objectives of this study were to quantify the importance of this N immobilization following addition of residues and its effect on yield and quality of potato crops. Fresh or humified residues (50 t ha−1) were applied to the soil and incorporated. The third treatment received no residue. Each treatment was subdivided into subtreatments which received either 0, 150, 200 or 250 kg N ha−1. P, K, Mg and S were applied at the same rate on all treatments. Following the application of wood residues in 1987, 46 kg N ha−1 were immobilized in amended plots. N recovery from fertilizer was 51%. To obtain comparable yields of similar quality to those measured on unamended plots, an additional 1.9 kg N t−1 residues added or 100 kg N ha−1 were required. In 1988, N immobilization was considerably reduced; yield and quality of potato tubers in plots that received wood residues the previous year were comparable to those of the unamended plots with appropriate fertilization. Water retention was significantly improved in plots that received wood residues. Partial decomposition of the residues for 1 yr prior to application on the soil did not significantly improve plant growth compared to fresh residues. Key words: Wood residues, tree clippings, potato yield, dry matter content, nitrogen immobilization, soil water content
EFFECTS OF HISTORICAL LAND CLEARING ON ORGANIC MATTER AND NITROGEN LEVELS IN SOILS OF THE FRASER LOWLAND OF BRITISH COLUMBIA, CANADA AND WASHINGTON, U.S.A.
Authors: GOLDIN ALAN , LAVKULICH L. M.
Published: March 2010

Two soils derived from glacial deposits and one from alluvium were examined for changes in organic matter (OM) and nitrogen levels between 1943 and 1983 across the international boundary in the Fraser Lowland of western North America. Duplicate samples were collected from the upper 0.2 m from 60 randomly selected sites on the five land clearing periods (1943–1955, 1955–1966, 1966–1976, 1976–1983, uncleared) on each of three parent materials: glacial outwash, alluvium, and glacialmarine deposits in the United States and Canada. The land clearing periods were determined from medium scale aerial photographs taken in 1943, 1955, 1966, 1976, and 1983. Cultivation results in a 20% loss of OM after 35 yr on all soils. The largest loss is in the first 15 yr on all soils. Changes in N levels on the three parent materials is irregular. C:N narrows on all soils from about 15:1 to about 12:1. Key words: Organic matter, nitrogen, Fraser Lowland, land clearing, air photo interpretation, parent material
EVALUATION OF SOIL EXTRACTANTS FOR THE PREDICTION OF PLANT-AVAILABLE POTASSIUM IN ONTARIO SOILS
Authors: LIU LIANGXUE , BATES THOMAS E.
Published: March 2010

The effectiveness of five extractants, NaCl, AB-DTPA, NH4OAc, Mehlich 3 and HNO3 was evaluated on 72 Ontario soils for prediction of plant-available K to alfalfa (Medicago sativa L.) grown in a greenhouse. Total K uptake by four cuts of alfalfa was used to measure plant available soil K. The average amounts of K extracted were in ascending order: AB-DTPA < NaCl < = NH4OAc < Mehlich 3 < HNO3. The highest simple correlation with K uptake by alfalfa was obtained with HNO3 (r = 0.76) and the lowest with NaCl (r2 = 0.61). The K uptake by alfalfa was used as the dependent variable to develop predictive models using stepwise regression, with extractable soil K, exchangeable Mg and Ca, soil pH, organic matter, cation exchange capacity (CEC), and contents of silt and clay as independent variables. The best prediction of K uptake with extracted soil K and its square was AB-DTPA (R2 = 0.84), followed by HNO3 (0.81), NH4OAc (0.81), NaCl (0.78) and Mehlich 3 (0.77). Inclusion of soil properties improved the effectiveness of prediction. The models developed with the different extractants differ in the number of variables which contributed significantly at 5% probability. Based on the final R2 and ease of measurement of variables, the NH4OAc model is one of the best as a predictor of availability of K in Ontario soils when used along with other soil properties such as plant-available nonexchangeable K and soil organic matter. Key words: Potassium extractants, plant-available K, alfalfa
SIMPLE MICROWAVE DIGESTION TECHNIQUE FOR ELEMENTAL ANALYSIS OF MINERAL SOIL SAMPLES
Authors: WARREN C. J. , XING B. , DUDAS M. J.
Published: March 2010

A new, rapid, and inexpensive method is described for digestion and dissolution of mineral soil and clay samples for determination of total elemental abundance. Standard soil samples were dissolved using HF and HNO3 in 60 mL Teflon bombs. Dissolution was complete after 7 min using a household microwave oven operating at 350 W. Addition of H3BO3 stabilized the digests against loss of silicon. Precise and accurate results were obtained for digests analyzed by inductively coupled plasma atomic emission spectrometry for total content of Si, Al, Fe, Mg, Ca, Na, K, and Mn. Key words: Elemental composition, standard soils, soil analysis
SOIL MICROARTHROPODS IN LONG-TERM NO-TILLAGE AND CONVENTIONAL TILLAGE CORN PRODUCTION
Authors: WINTER J. P. , VORONEY R. P. , AINSWORTH D. A.
Published: March 2010

Cultivation is known to reduce the number and diversity of microarthropod (Acarina and Collembola) populations from levels observed under natural forest or grassland vegetation. Under no-tillage crop production, the soil remains relatively undisturbed and plant litter decomposes at the soil surface, much like in natural soil ecosystems. The objective of this study was to investigate whether microarthropod populations under long-term (19 yr) continuous corn (Zea mays L.) production were increased by no-tillage (NT) vs. conventional tillage (CT; moldboard plow and harrowing) management. Numbers of microarthropods were also obtained from a soil managed as the CT treatment for 15 yr until seeding to bromegrass (Bromus inermus L.) hay for the last 4 yr. During the growing seasons over 2 yr, soil cores were taken every 2–3 wk and extracted for microarthropods using a high gradient extractor. The surface 5 cm of soil was sampled during the first year. All three treatments were different (P < 0.05), with bromegrass, NT and CT soils containing respectively, 15.9, 12.4, and 5.8 microarthropods × 1000 m−2 of which 84, 69, and 70% were Acarina. In the second year, the surface 15 cm was sampled and the number of microarthropods in the corn soils was similar (P < 0.05), containing 33.6 microarthropods × 1000 m−2, 92–98% of which were Acarina. However, microarthropods and soil organic-C were more concentrated in the surface 5 cm of soil in NT than CT. The soil under bromegrass contained 1.3 times more microarthropods (99% were Acarina) than under continuous NT and CT corn. Thus, when examined to a depth of 15 cm, 19 yr of NT corn did not increase the size of the microarthropod populations compared to CT, whereas production of bromegrass hay for 3–4 yr following long-term continuous CT corn did increased microarthropod numbers. Key words: Microarthropods, Collembola, Acarina, Zea mays, Bromus inermus, no-tillage, conservation tillage, soil carbon
SOIL DEVELOPMENT IN A 100-YEAR-OLD DIKE NEAR GRAND PRÉ, NOVA SCOTIA
Authors: BEKE G. J.
Published: March 2010

The morphology and composition were studied of a pair of soil profiles that had developed in a dike which was constructed 100 yr ago from marine sediments of silty clay loam texture. Both profiles had a weakly expressed A-B-C horizon sequence and strong structural development. They had Bm horizons and their exchange complex was dominated by magnesium ions. Organic carbon had accumulated in the surface mineral horizon at a maximum rate of 26.3 g m−2 yr−1. Adverse climatic conditions, typical for this and similar site locations, appeared to impose a limit on soil development. Key words: Soil formation, marine sediments, maritime climate
EFFECT OF MOLYBDENUM APPLICATIONS ON PLANT MOLYBDENUM CONCENTRATION AND CROP YIELDS ON SPHAGNUM PEAT SOILS
Authors: GUPTA UMESH C. , LEBLANC P. V. , CHIPMAN E. W.
Published: March 2010

Studies were conducted on peat soils to determine the effect of Mo application on crop yields and plant tissue Mo concentrations. In a greenhouse experiment Mo applications resulted in highest crop yield increases for cauliflower with lesser increases for onions and red clover. Plant tissue Mo levels of less than 0.06, 0.04, and 0.03 mg kg−1 in onions, cauliflower, and red clover, respectively were in the deficiency range. Sufficiency levels for Mo were 0.1 mg kg−1 for onions, 0.07 mg kg−1 for cauliflower, and 0.27 mg kg−1 for red clover. No response to Mo was found on carrots even at plant tissue Mo concentrations as low as 0.04 and 0.15 mg kg−1 under greenhouse and field experiments, respectively. In the field study liming and Mo both increased carrot leaf Mo concentrations but only liming increased carrot yields. Key words: Molybdenum concentration, vegetables, red clover, sphagnum peat, liming
THE USE OF CALCIUM NITRATE TO REDUCE PHYTOTOXIN ACCUMULATION DURING CROP RESIDUE DECOMPOSITION
Authors: FARQUHARSON B. J. , VORONEY R. P. , BEAUCHAMP E. G. , VYN T. J.
Published: March 2010

This study examined the effects of calcium carbonate, calcium oxide and calcium nitrate on the production and accumulation of volatile fatty acids (VFAs) and phenolic compounds (PCs) during soybean residue decomposition. Soil amended with calcium compounds, residue and water was incubated for 7 d at 25 °C. Measurements were made of VFAs, PCs, ammonium-N, nitrate-N and pH in a soil water extract. Accumulations of VFAs were significantly reduced by calcium nitrate amendment whereas both calcium carbonate and calcium oxide increased their accumulation. Accumulation of PCs followed the same trend but were not significantly different. The nitrate in the calcium nitrate amendment is suspected of promoting the oxidation of the products of residue decomposition via denitrification, by providing electron acceptors. In addition there was evidence of dissimilatory nitrate reduction to ammonium, which would have contributed to soil buffering capacity and to detoxify accumulations of nitrite. Key words: Volatile fatty acids, phenolic compounds, phytotoxicity, denitrification, dissimilatory nitrate reduction
FATE OF LABELLED FERTILIZER NITROGEN IN COMMERCIAL LOWBUSH BLUEBERRY STANDS
Authors: EATON LEONARD J. , PATRIQUIN DAVID G.
Published: March 2010

Labelled fertilizer nitrogen (15N) was applied to four commercial lowbush blueberry stands in order to assess the fate of fertilizer N. Thirteen weeks after application, 45 and 64% of the labelled fertilizer N was recovered from blueberry plants at Debert and Pigeon Hill, respectively. This suggests rapid uptake of fertilizer N by blueberry plants. Sixteen months after application, an average of 67% of the fertilizer N was recovered from the four sites. The results of this study support other evidence suggesting that lowbush blueberry systems conserve fertilizer N. Key words: Blueberry, 15N, fertilizer
RELATIONS BETWEEN AGGREGATE STABILITY AND ORGANIC COMPONENTS FOR A SILT LOAM SOIL
Authors: PERFECT E. , KAY B. D.
Published: March 2010

Rates of change in wet-aggregate stability under different cropping systems have been reported. These data were used to infer rates of change in the amount of stabilizing materials present. Increases in wet-aggregate stability did not correlate with increases in total organic carbon content, suggesting that some components of the organic carbon pool are more actively involved in stabilizing aggregates than others. Assuming a linear relation between these active components and wet-aggregate stability, the amount of stabilizing materials present should increase exponentially with time when forages are introduced onto soil previously used for row crop production. Key words: Soil structure, wet-aggregate stability, organic matter, corn, forages
Malaria Parasitemia and CD4 T Cell Count, Viral Load, and Adverse HIV Outcomes Among HIV-Infected Pregnant Women in Tanzania
Authors: Franke Molly F. , Spiegelman Donna , Ezeamama Amara , Aboud Said , Msamanga Gernard I. , Mehta Saurabh , Fawzi Wafaie W.
Published: March 2010

We examined the cross-sectional relationships between malaria parasitemia and CD4 T cell count and viral load among human immunodeficiency virus (HIV)-infected pregnant women. We then followed women to investigate whether or not baseline parasitemia predicted CD4 T cell counts or viral loads > 90 days post-baseline or predicted time to HIV disease stage 3 or 4 or acquired immune deficiency syndrome (AIDS)-related death (ARD). Parasitemia level was nonlinearly associated with viral load at baseline and among measurements taken > 90 days post-baseline; women with low baseline parasitemia, versus none, had higher viral loads at both time points. Any baseline parasitemia predicted an increased rate of ARD among women with baseline CD4 T cell counts ≥ 500 cells/µL (ratio rate [RR] = 2.6; 95% confidence interval [CI] = 1.1–6.0; P test for heterogeneity = 0.05). Further study is warranted to determine whether or not parasitemia is especially detrimental to individuals with lower levels of immunosuppression or chronic low parasitemia.
Toxoplasma gondii Seropositivity and Co-Infection with TORCH Pathogens in High-Risk Patients from Qatar
Authors: Abu-Madi Marawan A. , Behnke Jerzy M. , Dabritz Haydee A.
Published: March 2010

Testing of patients who are deemed to be at high risk for TORCH pathogens, e.g., pregnant women, their fetuses, neonates, and acquired immunodeficiency syndrome (AIDS) patients, is important so that specific treatment can be initiated. This study included 1,857 such patients between 2005 and 2008. Logistic regression was used to evaluate factors associated with Toxoplasma gondii seropositivity. Among 823 women of childbearing age, 35.1% and 5.2% tested positive for T. gondii IgG and IgM, respectively. Three infants ≤ 6 months of age (0.8% of 353) were congenitally infected. Factors associated with T. gondii IgG seropositivity included older age, East Mediterranean or African nationality, positive cytomegalovirus (CMV) and herpes simplex virus (HSV)-1 serostatus, and negative rubella IgG results. The decreasing prevalence of IgM antibodies between 2005 and 2008 suggested that exposure to T. gondii from food or environmental sources declined over this period in Qatar. Population-based studies of newborns would be helpful to accurately estimate incidence of congenital toxoplasmosis.
A New Approach to Postpartum Rounds: Patient-Centered Collaborative Care Improves Efficiency
Authors: Segel Sally , Hashima Jason , Gregory William Thomas , Edelman Alison , Li Hong , Guise Jeanne-Marie
Published: March 2010

Objective

At our institution, traditional postpartum rounds were time consuming and inefficient with a low percentage (approximately 12%) of patients meeting the goal of being discharged by 11:00 am. A patient-centered collaborative care (PCCC) initiative was implemented to improve discharge efficiency, staff communication, and patient satisfaction. We investigated whether this paradigm shift to PCCC could improve clinical inefficiencies and timely discharge.

Methods

The PCCC rounding system was created by a representative group of physicians, residents, nurses, case managers, and social workers. An intervention study was conducted to examine the impact of PCCC during which physicians, residents, medical students, nurses, case managers, and social workers made rounds together. Efficiency data were collected for patients whose infants were delivered by the obstetric service for a 1-month period before and 6 months after implementing PCCC. Comparisons were made on the time of discharge and whether Foley catheter removal affected discharge time. χ2 test, Wilcoxon 2-sample test, and Pearson correlation coefficient were used where appropriate.

Results

Three hundred five patients were included in this analysis, of which 156 participated in traditional postpartum rounds and 149 in PCCC rounds. Discharge efficiency significantly improved with PCCC rounds, with 20.8% of patients being discharged by 11:00 am as compared to 11.5% for traditional postpartum rounds (P  =  .03). Early Foley catheter removal was significantly associated with time to discharge order (Pearson correlation coefficient, 0.22; P  =  .01) and discharge time (Pearson correlation coefficient, 0.28; P  =  .002).

Conclusions

Patient-centered collaborative care rounds improve the efficiency of postpartum care and discharge time.
A Simplified Observation Tool for Residents in the Outpatient Clinic
Authors: Gigante Joseph , Swan Rebecca
Published: March 2010

Background

The Accreditation Council for Graduate Medical Education promotes direct observation of residents as a key assessment tool for competency in patient care, professionalism, and communication skills. Although tools exist, validity and reliability have not been demonstrated for most, and many tools may have limited feasibility because of time constraints and other reasons. We conducted a study to measure feasibility of a simplified observation tool to evaluate these competencies and provide timely feedback.

Methods

In the pediatric resident continuity clinic of a large children's hospital, we used a direct observation form with a 3-point scale for 16 items in the domains of patient care, professionalism, and communication skills. The form was divided by portion of visit, with specific items mapped to 1 or more of the competencies, and was used to provide direct oral feedback to the resident. Faculty and residents completed surveys rating the process (ease of use, satisfaction, and self-assessed usefulness) on a 5-point Likert scale.

Results

The study encompassed 89 surveys completed by attending physicians; 98% (87 of 89) of the time the form was easy to use, 99% (88) of the time its use did not interfere with patient flow, and 93% (83) of the observations provided useful information for resident feedback. Residents completed 70 surveys, with the majority (69%, 48) reporting they were comfortable about being observed by an attending physician; 87% (61) thought that direct observation did not significantly affect their efficiency. Ninety-seven percent of the time (68) residents reported that direct observation provided useful feedback.

Conclusion

The data suggest the form was well-received by both faculty and residents, and enabled attending physicians to provide useful feedback.
Efficacy and Efficiency of Webcast Orientations Versus Live Resident Orientations: Results of a 2-Year Survey
Authors: Andolsek Kathryn M. , Murphy Gwen , Pinheiro Sandro , Petrusa Emil , Tuck Tammy , Weinerth John
Published: March 2010

Background

Beginning a graduate medical education training program is associated with a steep learning curve for incoming residents.

Objective

To compare the efficacy and efficiency of live versus webcast formats for Institutional Orientation.

Methods

This 2-year non-blinded study, with a nonrandomized cohort, compares outcomes for trainees oriented Summer 2005 in a ‘‘live-lecture’’ format with trainees oriented Summer 2006 using a webcast format. Outcomes include posttest success, the time required, presentation quality and utility, and cost.

Results

In 2005, 249 trainees attended the live orientation. Of the 211 who completed the posttest; 132 (63%) passed it within 3 attempts. Of the 241 trainees in 2006, 236 completed the posttest. Of these, 215 (91%) passed it within 3 attempts. Compared to the live-lecture cohort, the webcast cohort rated the posttest as more difficult. Despite performing better, significantly fewer trainees in the webcast cohort rated the posttest as “appropriate” (χ2 =  5 28.57, df 5 1, P , .001). There were no significant differences between the 2 groups on their perceptions of quality and utility of the presentations. While the first year cost of the webcast exceeded that of live lectures, the amortized cost was nearly identical to the live-lecture costs.

Discussion

As corroborated by resident comments, the web-based approach was more effective because it provided trainees flexibility regarding when to study, options on how to view the material, and opportunities to review it if needed for mastery. We plan to continue using the webcast strategy, revising the content as needed.
Deep Standing Internal Waves in California Basins1
Authors: EMERY K. O.
Published: March 2010

Periodic variations of the water temperature observed at depths of 700, 850, and 1000 m in the Catalina Basin (sill at 982 m, bottom at 1357 m) lead to the inferred existence of deep standing internal waves having an amplitude of 130 to 200 m. The presence of such waves may account for the prior observation of bottom currents as great as 18 cm/sec, of suspended sediment near the basin floors, of a virtual absence of gradients of oxygen and nutrients near the bottom, of locally coarser sediments at basin sills than at their bottoms, and of replacement of basin water so rapidly that oxygen does not become deficient nor do regenerated nutrients become abnormally concentrated in the basin waters.
The “Stress‐drop Jet” in Lake Mendota
Authors: BRYSON REID A. , BUNQE W. W.
Published: March 2010

Under certain conditions a rapid increase of current velocity is observed at the bottom of the epilimnion. This phenomenon seems to be associated with a rapid decrease of wind stress on the lake surface. It is postulated that the energy for this “jet” is stored in the solenoid field set up by the preceding wind. It must then represent the first swing of an internal seiche.
Primary Production in Lakes
Authors: VERDUIN JACOB
Published: March 2010

The mean photosynthetic rate of lake phytoplankton under optimal light (natural conditions) is about 0.5 micromoles of O2 evolved or CO2 consumed per microliter of organisms per hour; 1–2 micromoles per milligram ash‐free dry weight per hour; and 0.2 micromoles per microgram of chlorophyll per hour. Simple equations are presented for computing photosynthetic yield per square meter of water surface. Computations for several lakes yielded values mostly lying between 150–200 millimoles per square meter per day. A year‐round study under completely natural conditions in western Lake Erie showed winter yields of about 40 millimoles per square meter per day and summer maxima of about 300. The annual curve followed the solar radiation curve closely. It is estimated that 28 days are required for a gram of phytoplankton (ash‐free dry weight) to produce an additional gram of glucose available for reproduction; 80 per cent of the photosynthate produced is required to support phytoplankton respiration.
The Heat Budget of a Body of Water of Varying Volume1
Authors: SAUR J. F. T. , ANDERSON E. R.
Published: March 2010

When the heat budget is applied to determine the evaporation from a lake of varying volume, the water budget must be considered. Using the continuity of the system a modified equation for evaporation from the heat budget has been developed. The modified equation has a term in the denominator that includes a base temperature used in the calculations. This equation is flexible in use and permits minimizing errors due to unknown quantities in the water budget.
The Distribution of Neomysis americana in the Estuary of the Delaware River1
Authors: HULBURT EDWARD M.
Published: March 2010

Observations on the planktonic shrimp, Neomysis americana (Smith), in the Delaware River estuary were carried out over a period of two years. It was found that Neomysis was far more abundant in the deep water of the estuary than in the near‐surface or shallow water. Moreover, it was more abundant within the estuary than in the coastal waters at the mouth of Delaware Bay. Measurements of the length of the animal showed increase in size from the ocean toward the river end of the estuary. These features are interpreted in light of the probable circulation of the estuary to show that the animals became older during their “up‐estuary” drift in deep water. Furthermore, they tended to accumulate within the estuary due to their avoidance of the out‐flowing surface waters. A principal source for Neomysis in the coastal waters outside the Bay is thus suggested. During spring and summer, however, reproduction within the Bay contributed to the stock of animals there. The up‐estuary extent of Neomysis was related to the 4‰ isohaline, and the partial exclusion from surface waters was attributed to their avoidance of excessive light.
Studies on the Mass Culture of Phaeodactylum
Authors: RAYMONT J. E. G. , ADAMS M. N. E.
Published: March 2010

Mass cultures of Phaeodactylum varying from 15 to 2,400 L have been successfully grown in covered tanks outside the laboratory. The maximum concentration obtained was 32,000 cells/mm3. Light has been shown to be a severely limiting factor in dense cultures. On the exponential phase of growth, under maximal light conditions, the highest division rate was 1 division in just under 24 hours. Addition of CO2 has a markedly beneficial effect on maximum cell densities. Phosphate was taken up with extreme rapidity in dense mass cultures; repeated addition of N and P prolonged growth, provided CO2 was added. A flagellate (Monas sp.) occurred regularly and became a predator in aging Phaeodactylum cultures. The monad multiplied only slowly in rapidly growing Phaeodactylum cultures. Some estimates are given of the dry weight of crop.
The Limnology of Canyon Ferry Reservoir
Authors: WRIGHT JOHN C.
Published: March 2010

Phytoplankton and zooplankton standing crop, gross and net primary production were measured. From these data the daily rate of loss of phytoplankton from the euphotic zone was calculated. The phytoplankton loss correlated well with zooplankton during September and with vertical water movement during October. A grazing coefficient was calculated (G = 1.064 L water/mg dry wt. zooplankton/day). By use of this coefficient the loss of phytoplankton by zooplankton grazing was calculated for the period of study and averaged 0.255 mg glucose/L/day. Zooplankton assimilation averaged 0.216 mg glucose/L/day, indicating a digestive efficiency of 85%. Gross and net primary production from September 6 to October 17 amounted to 137.2 and 114.0 g glucose/m2, respectively. Zooplankton assimilation was estimated to be 85% of net primary production. The ratio of zooplankton net production to zooplankton assimilation was 10.5%.
Lake Water and Sediment1
Authors: HAYES F. R. , REID B. L. , CAMERON M. L.
Published: March 2010

Redox potentials of mud cores from seven lakes, including acid bog, unproductive, and productive types, were measured with Mortimer’s multiple electrode. A break existed below the surface, but variation in measurement was too great to characterize its depth within ±30–50%. Accuracy of potential measurement is limited by lack of poise, so that the scatter of units of the multiple electrode increases as a standard solution or a natural mud is diluted with distilled water. With the muds studied the scatter was ±50 mv. In poorly poised systems the area of platinum is also important, so that potentials of 0.01 to 0.42 volts were obtained on the same sample with electrodes of different sizes. The presence of H2S causes a voltage drop, e.g., 20‐min. bubbling of a reduced solution with H2S caused the voltage to fall from 0.63 to 0.17 v. Production of H2S in nature is abolishedby O2. As a further difficulty the sediments of some lakes are able to deposit a sulphide plating on submerged platinum. Evidence is presented that the real oxidized layer is one mm or less thick, and that the reported break in the electrode curve at about one cm is caused by factors other than oxidation of iron salts, e.g., turbulent stirring of the sediment by wind‐induced currents, and presence of sulphide.
Primary Production of Continental Shelf Waters off New York1
Authors: RYTHER JOHN H. , YENTSCH CHARLES S.
Published: March 2010

The chlorophyll‐radiation method of measuring primary production, described earlier by the authors, was employed on six oceanographic cruises during 1956–7, each occupying 25 stations across the continental shelf off New York. The relationship photosynthesis/ hour (opt. light):chlorophyll a, using the oxygen production method, was found to agree with that determined earlier from culture and harbor water experiments, despite wide variations of temperature, nutrients, and the abundance of phytoplankton. The same ratio, with photosynthesis measured by C14 uptake, was extremely variable and usually lower than that obtained by oxygen‐production photosynthesis values.

Estimates of daily production beneath a square meter of sea surface by the chlorophyll‐radiation method and in situ C14 values agreed within reasonable limits in 75% of the measurements; for the remainder of the times the C14 values were consistently lower.

Daily production throughout the year ranged roughly from 0.20 to 1.00 g carbon/m2/day within the whole area studied. Estimated annual production decreased in a seaward direction from 160 g carbon/m2/year in the shallow coastal waters to 100 g carbon/m2/year on the continental slope. These values are intermediate between Riley’s estimates for Long Island Sound and the Sargasso Sea.
Sun‐Orientation and Homing in Fishes1
Authors: HASLER A. D. , HORRALL R. M. , WISBY W. J. , BRAEMER W.
Published: March 2010

The white bass, Roccus chrysops, has two principal spawning grounds 1.6 km apart on the northern shore of Lake Mendota. Fish displaced from these spawning grounds return faithfully to their respective spawning sites, and of 1366 fish marked and displaced to mid‐lake, a distance of 2.4 km, 181 were recaptured in fyke nets and less than 9% erred by being recaptured at the net on the other spawning ground. Fish released at the spawning ground were not recaptured in greater percentage than those displaced and released in mid‐lake.

Fish to which floats were attached for direct tracing moved generally north from the center of the lake when released on clear days. Moreover, fish released between the two spawning grounds also moved north on clear days. On cloudy days, however, or if blinded with eyecaps, they moved at random. Unexplained is how they differentiate between the two spawning areas; apparently it is by means other than with the aid of the sun.

A laboratory analysis of the sun‐compass mechanism was made. An immature specimen of Lepomis macrochirus was trained, at a specific time of day, to find cover in one of sixteen boxes of a circular tank. When trained, the fish entered the training box in a consistent compass‐direction at any time of day. Under an overcast sky the choices were completely unoriented. When tested under an artificial sun, (light bulb), this fish responded as though it were the real sun, at that time of day and sought cover in the “artificial” direction, reaffirming the presence of a biological clock. White bass were also successfully trained to a compass‐direction under the natural sun.

Lepomis gibbosus was tested with another method. It too has a sun‐compass mechanism.

These field and laboratory experiments suggest strongly that the sun serves as the point of reference, and that the animal compensates for its movement by a biological chronometer.
Annual Fluctuations in Sulphate and Bicarbonate Hardness in Ponds
Authors: MANN K. H.
Published: March 2010

In four ponds studied, sulphate in solution was high in spring, low in autumn, while bicarbonate was low in spring, high in autumn. The fall in sulphate was probably due to reduction to sulphide which became locked up in the mud as ferrous sulphide. The fluctuation in bicarbonate was partly due to the removal of CO2 during photosynthesis and partly to the action of sulphuric acid when the sulphide was oxidized in winter.
Determinations of the Solubility of Oxygen in Pure Water1
Authors: STEEN H.
Published: March 2010

A recently published revision of the absorption coefficients for oxygen in water has prompted a reinvestigation of the subject by a new microgasometric technique. A known volume of gas‐free water (approximately 1 ml) was brought into contact with oxygen at constant pressure and temperature. The oxygen uptake and the amount of water were measured with a micrometer burette. The results obtained at 6°, 12°, 18°, and 24° C confirm the standard handbook values of Winkler and Fox to within ±1% of a.
The Production of Extracellular Carbohydrates by Some Marine Flagellates1
Authors: GUILLARD ROBERT R. L. , WANGERSKY PETER J.
Published: March 2010

Extracellular carbohydrate production during the growth of bacteria‐free cultures of the marine flagellates Isochrysis galbana, Monochrysis lutheri, Prymnesium parvum, Dunaliella euchlora, Pyraminomonas sp., Rhodomonas (?) sp., and Chlamydomonas sp. was followed by the N‐ethyl carbazole method.

Carbohydrate production did not parallel cell numbers during exponential growth of any of these organisms; maximum concentrations during this phase were under 3 mg/L. Carbohydrates accumulated in all stationary cultures (having 106–107 cells/ml), to the greatest extent in Prymnesium cultures, which attained 123 mg/L. Isochrysis and Monochrysis produced 25 and 16 mg/L, respectively, while the others had under 10 mg/L even when cell disintegration was evident.

Aging cultures (not all bacteria‐free) of 4 diatoms, 2 dinoflagellates, 2 additional green algae, and a cyanophyte were assayed. Concentrations ranged from 1.5 to 60 mg/L.

This suggests that the organisms studied contribute significant free carbohydrates only during late bloom conditions, when algae are abundant and under physiological circumstances resembling stationary or declining culture.
The Distribution of the Planktonic Chaetognatha in the Pacific and their Relationship to the Water Masses1
Authors: BIERI ROBERT
Published: March 2010

The geographic extents of 27 species of Chaetognatha in the Pacific have been inferred from analyses of 2,900 plankton samples taken at more than 900 stations.

Two species of chaetognaths—Sagitta elegans and S. maxima—are found in the Pacific only in the Subarctic Water Mass. Four species—Sagitta enflata, S. hexaptera, S. pacifica, and Pterosagitta draco—occur in the Pacific Equatorial and Central Water Masses. Seven species—Sagitta robusta, S. regularis, S. ferox, Krohnitta pacifica, Sagitta bedoti, S. neglecta, and S. pulchra—occur in the Equatorial and Western Central Water Masses. The latter three species appear to be disjunct equatorial species that are absent from the central equatorial Pacific. Sagitta pseudoserratodentata occupies the North Pacific Central Water Mass. S. californica, essentially a warm‐water cosmopolite, is very rare in the Equatorial Water Mass. The Peru and California Currents are inhabited by Sagitta friderici. A close relative, S. crassa, lives in the coastal waters of Japan. Sagitta minima, Sagitta species (serratodentata group), Sagitta decipiens, S. lyra, and Krohnitta subtilis, species which have their maximum abundance at about 200 meters (somewhat deeper than all of the preceding), appear to be limited in the north at about 45° N. Lat. Sagitta planctonis, S. macrocephala, and Eukrohnia fowleri, living primarily at depths of 500 meters and greater, have been taken in the present study as far north as 55° N. Lat., both in the Bering Sea and Gulf of Alaska. The very deep living species, Heterokrohnia mirabilis, was taken at a single station in the Eastern Equatorial Pacific. The sharpest chaetognath boundary yet found in the Pacific occurs in the Eastern Pacific at 18° to 20° N. Lat. and is associated with pronounced temperature, oxygen, and probably salinity gradients.

Species distributions analogous to those of the Chaetognatha are found in the euphausiids, copepods, and dinoflagellates among other groups of organisms.
The Summer Standing Crop of Fish on a Shallow Bermuda Reef1
Authors: BARDACH JOHN E.
Published: March 2010

Repeated estimates of reef fishes by visual counts were made on a shallow isolated Bermuda reef with a surface of approximately one hectare (2.5 acres). A standing crop of 490 kg was found in midsummer.

Comparisons between the fish fauna of this reef and more extended reef areas indicate that carnivorous reef fishes predominate on isolated reefs, while herbivores become more prevalent on large browsing areas. Available information on the yearly growth rates of Bermuda reef fishes suggests a relatively high overall efficiency of utilization of incident solar energy (ca. 0.0014%). The similarity of isolated reefs to ponds is discussed.
1100‐Meter Dive in the Bathyscaph Trieste
Authors: DIETZ ROBERT S.
Published: March 2010

This paper describes a dive made in the bathyscaph trieste on July 3, 1957, with the writer as the scientific observer and Jaques Piccard as the pilot. This was the fifth dive of a series of twenty‐eight dives made during 1957 and sponsored by the U. S. Office of Naval Research. The dive lasted 2 hours and 31 minutes, with 36 minutes spent on the bottom.
An Investigation of the Circulation over Second Point Bar, Lake Mendota
Authors: CLARKE DAVID B. , BRYSON REID A.
Published: March 2010

The flow of water in the middle and surface layers around and over a lake bar was examined in terms of horizontal and vertical velocities, and divergence. These quantities were mapped and the patterns correlated with the general current velocity, wind conditions, and obstruction by the bar.

1) The bar caused two types of flow around it. In the unstratified layer above the thermocline the flow continued right over the bar, although the exact pattern of motion depended upon the current speed and the geography of the bar.

2) In the thermocline there was a strong tendency for the water to flow around the bar, although considerable upwelling and sinking of the layer occurred. Helical rotors appeared on either side of the bar.

3) Internally consistent and detailed patterns of circulation were observed on a small scale without excessive expenditure of time or money.