Rate In July Research Articles

Oxygen use by nitrification in the hypolimnion and sediments of Lake Erie

Nitrification is an oxygen consumptive process, consuming 2mol of oxygen per mol of ammonium oxidized. Hypolimnion and sediment samples were collected during the summers of 2008–2010 in Lake Erie to determine the total oxygen consumption and oxygen consumption from nitrification by blocking nitrification with selective inhibitors. Oxygen consumption by nitrification in the hypolimnion was 3.7±2.9(mean±1 SD)μmolO2/L/d, with nitrification accounting for 32.6±22.1% of the total oxygen consumption. Nitrification in the hypolimnion contributed more to oxygen consumption in the eastern sites than western sites and was lowest in September. The nitrification rate did not correlate with environmental factors such as oxygen, nitrate or ammonium, or nitrifier numbers. Oxygen consumption by nitrification in sediment slurries was 7.1±5.8μmolO2/g/d, with nitrification accounting for 27.0±19.2% of the total oxygen consumption with the lowest rates in July and the lowest percentages in June. Oxygen consumption by nitrification in intact sediment cores was 682±61.1μmolO2/m/d with nitrification accounting for 30.4±10.7% of the total oxygen consumption. Nitrification rates in intact cores were generally highest in September. The proportion of oxygen consumed by nitrification corresponds closely with what would be predicted from complete oxidation of a Redfield molecule (23%). While nitrification is unlikely to be the dominant oxygen consumptive process, the rates observed in Lake Erie were sufficient to theoretically deplete a large portion of the hypolimnetic oxygen pool during the stratified period.

Photosynthetic Characteristics of Resistance and Susceptible Lines to High Temperature Injury in Panax ginseng Meyer

In this study, photosynthetic parameters such as the net photosynthesis rate, stomatal conductance, intercellular CO2 concentration, and transpiration rate were examined in selected ginseng varieties and/or lines that are resistant (Yunpoong, HTIR 1, HTIR 2, and HTIR 3) and susceptible (Chunpoong) to high temperature injury (HTI). The net photosynthesis rate increased with the increase in the light intensity in all the HTI-resistant and -susceptible ginseng lines with a light saturation point of 200 μmol m-2s-1, except for Yunpoong that had a light saturation point of 400 μmol m-2s-1. At the light saturation point, the net photosynthesis rate in July was highest in HTIR 3, at 4.2 μmol CO2 m-2s-1, and was lowest in Yunpoong, HTIR 1, Chunpoong, and HTIR 2, in that order, at 1.9 to 3.7 μmol CO2 m-2s-1. The net photosynthesis rate in August was highest in Yunpoong at 5.9 μmol CO2 m-2s-1, and lowest in HTIR 1 and HTIR 3 (4.5 μmol CO2 m-2s-1) and in other lines, in that order, at 2.8 to 2.9 μmol CO2 m-2s-1. The stomatal conductance in July was highest in HTIR 3 (0.055 mol H2O m-2s-1) and Yunpoong, Chunpoong, HTIR 1, and HTIR 2 were 0.038, 0.037, 0.031, and 0.017 in that orders. In August, meanwhile, HTIR 1 showed the highest as 0.075, and followed by HTIR 3, Chungpoong, and HTIR 2 with 0.070, 0.047, and 0.023, respectively. The intercellular CO2 concentration at the light saturation point in July and August was much lower in HTIR 2 at 139 and 185 μmol mol-1 than in the other ginseng lines at 217 to 257 and 274 to 287 μmol mol-1, respectively. The transpiration rate in July and August was higher in the HTI-resistant lines of Yunpoong, HTIR 1, and/or HTIR 3 at 0.83 to 1.03 and 1.67 to 2.10 mol H2O m-2s-1 than in the other ginseng lines at 0.27 to 0.79 mol H2O m-2s- 1 and 0.51-1.65 mol H2O m-2s-1, respectively. Conclusively, all the photosynthetic parameters that were examined in this study were generally higher in the HTI-resistant ginseng lines than in the HTI-susceptible lines, except for HTIR 2, and were much higher in August than in July, especially in the resistant ginseng lines. All these results can be used to provide basic information for the selection of HTI-resistant ginseng lines and the application of cultural practices that are efficient for ginseng growth, based on the photosynthetic characteristics of the lines.

Effects of elevated carbon dioxide and temperature on photosynthesis and fruit characteristics of ‘Niitaka’ pear (Pyrus pyrifolia Nakai)

The effects of global warming and CO2 level were investigated on tree growth and fruit characteristics of ‘Niitaka’ pear. The treatments consisted of ambient temperature and 390 μL·L−1 CO2 (control group), ambient temperature + 4°C and 390 μL·L−1 CO2 (elevated temperature group), ambient temperature and 700 μL·L−1 CO2 (elevated CO2 group), and ambient temperature + 4°C and 700 μL·L−1 CO2 (elevated climate group). Fruit weight was the highest in elevated CO2 group (543.0 g), but lowest in elevated temperature group (394.3 g). Flesh firmness at harvest was the highest in elevated temperature group. For fruit skin color, Hunter L* and b* values were not significantly different among treatments, while Hunter a* value was higher on those treated with higher temperature and CO2 concentration. Photosynthetic rate in July and August was high in plants under elevated CO2 concentration. In contrast, the elevated temperature and elevated climate groups showed relatively high photosynthetic rate in early July, then became far lower than those of the control and the elevated CO2 group in late August. Rapid increase in fruit diameter was observed on fruits grown under elevated climate, then slowed down after the middle fruit growth stage. Soluble solids content increased at harvest time in groups with elevated CO2.

Multifractal detrended cross-correlations between the Chinese exchange market and stock market

Based on the daily price data of the Chinese Yuan (RMB)/US dollar exchange rate and the Shanghai Stock Composite Index, we conducted an empirical analysis of the cross-correlations between the Chinese exchange market and stock market using the multifractal cross-correlation analysis method. The results demonstrate the overall significance of the cross-correlation based on the analysis of a statistic. Multifractality exists in cross-correlations, and the cross-correlated behavior of small fluctuations is more persistent than that of large fluctuations. Moreover, using the rolling windows method, we find that the cross-correlations between the Chinese exchange market and stock market vary with time and are especially sensitive to the reform of the RMB exchange rate regime. The previous reduction in the flexibility of the RMB exchange rate in July 2008 strengthened the persistence of cross-correlations and decreased the degree of multifractality, whereas the enhancement of the flexibility of the RMB exchange rate in June 2010 weakened the persistence of cross-correlations and increased the multifractality. Finally, several relevant discussions are provided to verify the robustness of our empirical analysis.

Primary production throughout austral fall, during a time of decreasing daylength in the western Antarctic Peninsula

Antarctic phytoplankton is characterized by a pronounced seasonality in abundance, driven mainly by changes in sunlight. We combined measurements and modeling to describe the influence of changing daylength on fall and winter phytoplankton production in coastal waters of the western Antarctic Peninsula (wAP) in 2001 and 2002. The model was parameterized with field observations from the Palmer Long-Term Ecological program in the wAP during summer and early fall and from the Southern Ocean Global Ecosystems Dynamics program fall and winter cruises to Marguerite Bay and shelf waters. Shorter daylength and a deepening of the mixed layer account for most of the decrease in primary production during March, April, and May. At this time, biomass decreases by an order of magnitude and remains low and constant until the end of August. An additional loss rate was added to the primary production model to fit output to obser- vations. This loss rate, estimated at ~0.1 to 0.15 d �1 , is due to physical, chemical, and biological processes such as scavenging by sea ice, zooplankton grazing, cell lysis, and cell sedimentation, which are expected to be high at this time of year. Growth and loss rates of phytoplankton popu- lations are similar on 1 March, with growth decreasing rapidly over time while the loss rates remain constant. By the beginning of winter (1 June), growth is low, with minimum rates in July and increasing towards September. During a period of diminishing food supply, preliminary esti- mates of grazing indicate that fall biomass could support existing macrozooplankton populations, but the timing and concentration of food supply is variable and expected to affect health of zoo- plankton as they enter the winter.

Abstract 33: Seasonal Patterns in Risk-Standardized Mortality after Ischemic Stroke: A Winter and July Effect

Background: A recent systematic review found that mortality rates were higher and efficiency of care lower in hospitals coincident with the introduction of new trainees in July, but there was significant heterogeneity in study quality, and none of the included studies focused on stroke care. Purpose: To assess seasonal variation in 30-day risk-standardized mortality rates (RSMRs) for elderly ischemic stroke patients from 1999 to 2006 and determine whether patterns differ for patients discharged from teaching versus non-teaching hospitals. Methods: The study cohort included all fee-for-service Medicare beneficiaries aged 65 years and older discharged with an ischemic stroke (ICD-9 primary codes 433, 434, 436) from 1999 to 2006 in the United States. A hierarchical logistic regression model fitted annual data to estimate the 30-day RSMR, adjusted for demographic and clinical characteristics. The annual datasets were combined and reconstructed to time series analyses, with month as a unit. The time series analysis included 96 months; RSMRs were calculated for each month. The unobserved components modeling approach was used to fit the time series data with risk-adjusted mortality as an outcome to compare seasonal patterns by month for teaching and non-teaching hospitals. Results: Of 2,824,694 ischemic stroke discharges, 51.7% were from teaching hospitals. The 30-day RSMR decreased steadily from 1999 to 2006 in teaching hospitals ( Figure 1 A). Seasonal patterns were present within each calendar year, with the highest 30-day RSMR occurring in the winter (January) and the lowest RSMR in the summer, with a secondary peak in July (p=0.004; Figure 1 B). The same patterns were also seen for non-teaching hospitals (not shown). Conclusions: Thirty-day risk-standardized mortality rates after ischemic stroke in the elderly have decreased between 1999 to 2006. Seasonal patterns are evident, with the highest RSMR in January, and a secondary peak in July. Because these patterns were similar for teaching and non-teaching hospitals, the July peak can not be explained based on the introduction of new trainees. The reasons for these seasonal patterns, including higher mortality rates in July, are unclear.

Structure of mortality from cardiovascular and respiratory diseases during abnormal weather in summer, 2010, in Moscow

Summary. Mortality rate in July – August, 2010, according to findings of the pathomorphological department of Clinical hospital N57 in Moscow has been analyzed and compared with the appropriate period of 2009. During abnormally hot weather and air pollution (smog), mortality from cardiovascular and respiratory diseases has significantly increased in Moscow. The most prominent growth in mortality rate was seen among patients with ischaemic heart disease and congestive heart failure and among patients with bronchial asthma complicated with status asthmaticus.

High failure rate of the dissolution tests for 500-mg amoxicillin capsules sold in Cambodia: is it because of the product or the test method?

During the survey of substandard medicines in Cambodia in 2007, it was found that more than 90% of 500-mg amoxicillin (AMPC) capsules failed the United States Pharmacopeia (USP) 30 TEST 1 dissolution test. In the USP, several monographs provide multiple methods for performing the dissolution test. By using the 500-mg AMPC capsule as an example, we aimed to identify the problems and implications of the USP methods adopted for the dissolution test as a global standard. All AMPC samples were collected from the Cambodian market in 2007. For the quantitative test, we referred to USP 30. We performed the USP 28 and USP 30 TEST 2 dissolution tests and compared these results with those of the USP 30 TEST 1. All 500-mg AMPC capsules used for the comparison passed the quantitative test. Samples that passed the USP 28 and USP 30 TEST 2 dissolution tests were identical, and the pass rate was 97.1% (34/35), whereas the pass rate with the USP 30 TEST 1 was 8.6% (3/35). The difference in the dissolution results between the three methods was significant (P<0.0001). This study revealed that many users would select the most stringent method when multiple methods exist in the USP. This may lead to a high failure rate of the tests. Because USP is a global standard, we recommend that it take into consideration the developing countries and create a more detailed user-friendly manual for selection for appropriate methods.

Sources of new nitrogen in the Vietnamese upwelling region of the South China Sea

In the South China Sea, the southwest monsoon between June and September induces upwelling off the southern central Vietnamese coast. During field campaigns in July 2003 and 2004 we evaluated the importance of nitrate and nitrogen fixation as sources of new nitrogen for phytoplankton primary productivity, both in the actual upwelling zone and in the oligotrophic area farther offshore. Complementary to rate measurements of primary productivity, nitrate uptake, and nitrogen fixation, we determined vertical nitrate fluxes by Ekman upwelling (upwelling zone) and turbulent diffusion (offshore waters). Because of the influence of El Niño, upwelling was weaker in July 2003, with an average primary productivity of 28 ± 18 mmol C m−2 d−1, compared to 103 ± 25 mmol C m−2 d−1 in July 2004. Calculated upwelling nitrate fluxes of 17 ± 2 mmol N m−2 d−1 in July 2004 are consistent with N demands of primary productivity, if Redfield stoichiometry is assumed. In July 2003 upwelling fluxes of 14 ± 2 mmol N m−2 d−1 exceeded N demands, indicating that new production was not fully realized. Diffusive nitrate fluxes in offshore waters were determined in July 2003 and are of the order of 2.3 ± 0.6 mmol N m−2 d−1, based on the maximal diffusivities of 1 cm2 s−1 in the nitracline. Nitrogen fixation was a significant N source in offshore waters, but at lower rates in July 2003 (22–119 μmol N m−2 day−1) than in July 2004 (37–375 μmol N m−2 day−1), equaling 1%–5% and probably 2%–25% of the diffusive nitrate fluxes, respectively.

MEASUREMENT OF IN SITU SPECIFIC GROWTH RATES OF MICROCYSTIS (CYANOBACTERIA) FROM THE FREQUENCY OF DIVIDING CELLS(1).

Diel changes in the frequency of dividing cells (FDC) of three Microcystis species were investigated in a small eutrophic pond from July to October 2005. The representative species was M. aeruginosa (Kütz.) Kütz., constituting 57%-86% of the Microcystis population throughout the study period, and the remainder were M. viridis (A. Braun) Lemmerm. and M. wesenbergii (Komárek) Komárek. The FDC of M. aeruginosa and M. wesenbergii increased in the daytime and fell in the nighttime in July and August, but this regular variation was not observed in September or October. The in situ specific growth rates of Microcystis species were estimated based on the assumption that the specific growth rate can be given as an absolute value of the derivative of FDC with respect to time. The calculated values were similar among species-0.15-0.38 · d(-1) for M. aeruginosa, 0.14-0.63 · d(-1) for M. viridis, and 0.18-0.61 · d(-1) for M. wesenbergii. The specific growth rates in July and August slightly exceeded those in September and October. The analysis of the in situ specific growth rate of Microcystis indicated that recruitment of the benthic population or morphological change, rather than massive growth, was at least partly responsible for the dominance of M. aeruginosa in the study pond.

Distribution and activity of Bacteria and Archaea in the different water masses of the Tyrrhenian Sea

Abstract This study examines the abundance of the Bacteria, Crenarchaeota and Euryarchaeota and bulk activities (phosphatase and aminopeptidase activities, heterotrophic prokaryotic production and dark CO2 fixation) in the major water masses of the Tyrrhenian Sea (from surface to bottom: Modified Atlantic Water (MAW); Levantine Intermediate Water (LIW) and Tyrrhenian Deep Water (TDW)) in July and December 2005. Data from the catalyzed reporter deposition coupled with fluorescence in situ hybridization (CARD-FISH) analyses indicate that the percentage of Bacteria was always higher than the percentage of Crenarchaeota and Euryarchaeota throughout the water column. While the percentage of Euryarchaeota was relatively homogeneous (∼10%) through the water column, the percentage of Crenarchaeota increased with depth (from 5% to 14% in July and from 7% to 17% in December in MAW and TDW, respectively). Regarding differences between July and December 2005, the percentage of Bacteria in the MAW was lower in July than in December (25% versus 43%, respectively) while quite constant (∼40%) in the TDW. The pattern of phosphatase and aminopeptidase activity varied according to the stations considered, but both ectoenzyme activities showed higher maximum velocity rates in July than in December in the deep-sea waters. Particularly, specific activity of phosphatase in the deep-sea waters (TDW) was 7 times higher (median value) than in surface waters (MAW). Prokaryotic production, aminopeptidase and phosphatase activity measurements were always higher under in situ pressure conditions than after decompression. For the first time, the measurement of the dark CO2 fixation was investigated under in situ pressure conditions and its decompressed counterparts. These data give new information to understanding the role of prokaryotes (Bacteria and Archaea) in biogeochemical cycles of the meso- and batypelagic waters of the oceans.

CO 2 efflux under different grazing managements on subalpine meadows of Shangri-La, Northwest Yunnan Province, China

Soil carbon stored on the Tibetan Plateau appears to be stable under current temperature, but it may be sensitive to global warming. In addition, different grazing systems may alter carbon emission from subalpine meadow ecosystems in this region. Using a chamber-closed dynamic technique, we measured ecosystem respiration (ER) and soil respiration (SR) rates with an infrared gas analyzer on a perennial grazing meadow (PM) and a seasonal grazing meadow (SM) of Shangri-La in the Hengduan Mountain area. Both PM and SM showed strong unimodal seasonal variations, with the highest rates in July and the lowest in January. Significant diurnal variations in respiration were also observed on PM, affected mainly by air and soil temperatures, with the highest rates at 14:00 and the lowest before dawn. Both ER and SR rates were higher on PM than on SM from June to October, suggesting that the higher grazing pressure on PM increased respiration rates on subalpine meadows. The exponential model F = ae bT of soil temperature ( T) explained the variation in respiration better than the model of soil moisture ( W) ( R 2 = 0.50–0.78, P < 0.0001), while the multiple model F = ae bT W c gave better simulations than did single-factor models ( R 2 = 0.56–0.89, P < 0.0001). Soil respiration was the major component of ER, accounting for 63.0%–92.7% and 47.5%–96.4% of ER on PM and SM, respectively. Aboveground plant respiration varied with grass growth. During the peak growing season, total ecosystem respiration may be dominated by this above-ground component. Long-term (annual) Q 10 values were about twice as large as short-term (one day) Q 10. Q 10 at different time scales may be controlled by different ecological processes. The SM had a lower long-term Q 10 than did the PM, suggesting that under increased temperature, soil carbon may be more stable with reduced grazing pressure.

A study on the application of neural network to the interrelationship among Renminbi and foreign currencies

Due to the apparent advantages such as huge market and low labor cost, which increase worldwide manufacturers and investors more interest into the emerging economy of Chinese market in this decade. To understand the exchange rate among international currencies is one of the key issues for successful foreign invests. Since Chinese authorities changed the fixed exchange rate into floating exchange rate in July 2005, the fluctuation of Renminbi (Chinese Dollar) has become the main contention of all investors The fluctuation of exchange rates is affected by complicate economical and governmental factors which become hardly to predict. This study takes the rises and falls of exchange rate of Renminbi as the subject of the research without considering the factors of other economic indexes or bank interest rates. This study adoptsartificial intelligence neural network as a tool for verifying hypotheses with the historical data of past exchanges rates of foreign currencies. In order to differ from the past economic and statistic models that have been explored fore many times, a variety of economic indexes or bank interest rates will not be taken into account as factor in this paper. Furthermore, the foreign currencies exchange rates published by Federal Reserve Bank of New York are adopted as a factor. This paper tries to figure out a simpler method to predict the fluctuation of Renminbi

WEDDELL SEAL UNDERWATER CALLING RATES DURING THE WINTER AND SPRING NEAR MAWSON STATION, ANTARCTICA

AbstractUnderwater vocalization monitoring and surveys, both on ice and underwater, were used to determine if Weddell seals (Leptonychotes weddellii) near Mawson Station, Antarctica, remain under the fast ice during winter within close range of breeding sites. Daytime and nighttime underwater calling rates were examined at seven breeding sites during austral winter and spring to identify seasonal and diel patterns. Seals rarely hauled out at any of the sites during winter, although all cohorts (adult males, females, and juveniles) were observed underwater and surfacing at breathing holes throughout winter (June–September) and spring (October–December). Seal vocalizations were recorded during each sampling session throughout the study (n= 102 daytime at seven sites collectively, and n= 5 24‐h samples at each of two sites). Mean daytime calling rate was low in mid‐winter (July) (mean = 18.9 ± 7.1 calls/min) but increased monthly, reaching a peak during the breeding season (November) (mean = 62.6 ± 15.7 calls/min). Mean nighttime calling rate was high throughout the winter and early spring (July–October) with mean nocturnal calling rate in July (mean = 61.8 ± 35.1 calls/min) nearly equal to mean daytime calling rate in November (during 24‐h daylight). Reduced vocal behavior during winter daylight periods may result from animals utilizing the limited daylight hours for nonvocal activities, possibly feeding.

Water table fluctuations under three riparian land covers, Iowa (USA)

AbstractWater table depth is known to play an important role in nitrogen cycling in riparian zones, but little detailed monitoring of water table fluctuations has been reported. In this study, results of high‐resolution water table monitoring under three common riparian land covers (forest, cool season grass, corn) were analysed to gain a better understanding of the relation of vegetation cover to water table depth. Three riparian wells located at the Neal Smith National Wildlife Refuge in Jasper County, Iowa, were instrumented with data loggers to record hourly water table behaviour from July to December 2004. Water table depth under the forest showed a diurnal pattern of rising and falling water levels, whereas the grass and corn exhibited a stepped pattern of greater drawdown during the day and less drainage at night. Clear daytime and night‐time water table signals were related to daily plant water demands and lateral groundwater flow. Using two estimates of specific yield, hourly and daily ET rates were estimated to be higher under the forest cover than the grass and corn, with peak ET rates in July ranging from 5·02 to 6·32 mm day−1 for forest and from 1·81 to 4·13 mm day−1 for corn and grass. Following plant senescence in October, water table declines were associated with lateral flow to Walnut Creek. The results from this study suggest that consideration should be given to monitoring water table behaviour more frequently to capture daily and seasonal patterns related to riparian vegetation type. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Nationwide data confirms absence of ‘July phenomenon’ in obstetrics: it's safe to deliver in July

To determine whether operator-dependent obstetric complications occur at higher rates in July at teaching hospitals using a large, nationwide sample of deliveries. Data for this study were obtained from an administrative dataset, the Nationwide Inpatient Sample, for the years 1998 to 2002. Singleton deliveries and singleton livebirth admissions among Medicaid patients at teaching hospitals with OB/GYN residents working on the Labor and Delivery ward were identified. Outcomes for various complications for these patients in the month of July were compared to those occurring in the months from August to June. The 26,546 women in our cohort who delivered in July were compared to the 272,584 women delivering during August to June. There were no statistically significant differences in the rates of cesarean delivery, urethral/bladder injury, third or fourth degree lacerations, wound complications, postpartum hemorrhage, transfusion, shoulder dystocia, chorioamnionitis or anesthesia-related complications. The 26,175 singleton livebirth admissions in July were compared to 266,158 such admissions in August to June. There were no statistically significant differences in the rates of brachial plexus injury (0.2 vs 0.2%, P=0.824) or birth asphyxia (0.1 vs 0.1%, P=0.643). This study shows no increased rate of operator-dependent complications of delivery at teaching hospitals nationwide in the month of July.

Seasonal variation in metabolism of cultured Pacific oyster, Crassostrea gigas, in Sanggou Bay, China

Rates of respiration and excretion of the Pacific oyster, Crassostrea gigas, were measured seasonally from June 2002 to July 2003 under ambient conditions of food, water temperature, pH, and salinity in Sanggou Bay, an important mariculture coast in north China. The aim of this study is to obtain fundamental data for further establishing an energy budget model and assessing the carrying capacity for cultivation of C. gigas in north China. Oysters were collected monthly or bimonthly from the integrated culture areas of bivalve and kelp in the bay. Oxygen consumption and ammonium and phosphorus excretion rates were measured, and ratios of O/N and N/P were calculated. One-way ANOVA was applied to determine differences among these parameters that act as a function of seasonal variation. All the physiological parameters yielded highly significant variations with season ( P < 0.01). The rate of respiration varied seasonally, with the highest oxygen consumption rate in July and the lowest rate in January, ranging from 0.07 to 2.13 mg O 2 h − 1 g − 1dry tissue weight (DW). Maximum and minimum ammonium excretion rates were recorded in August and January, respectively, ranging from 0.51 to 5.40 μmol NH 4–N h − 1g − 1 DW. Rates of phosphorus excretion varied from 0.11 (in January) to 0.64 (in July) μmol PO 4–P h − 1g − 1 DW. The O/N and N/P ratios changed from 9.2 (in January) to 59.8 (in July) and from 4.6 (in January) to 10.9 (in August), respectively. For each season, the allometric relationship between the physiological response (e.g., rate of oxygen consumption, ammonium and phosphorus excretion) and DW of the animal was estimated using the formula: Y = a × DW b .

A Study on Seasonal Variations of Indoor Gamma Dose in Bangladesh

Monthly variation of gamma dose rate measured in indoor air of buildings of Bangladesh was found to vary cosinusoidally through a period of 1 year. Significant seasonal variations were observed. Maximum dose rate, however, was observed in January and a minimum in July. Dose rate in January was 32% higher than the annual average, whereas dose rate in July was 50% lower. Seasonally varied ventilation and air exchange rates of the houses might play an important role in the observed variation. The average reduction with respect to winter dose was 59% in summer. Because of lower ventilation and air exchange rates between indoor and outdoor atmosphere, it is expected that the indoor dose rate would be higher in basements than that of upper floors. Monthly dose rate was also found to be influenced by the meteorological conditions. Correlations between dose rate and temperature (r2=0.85), rainfall (r=-0.83) and atmospheric pressure (r=0.92) were obtained, but no significant correlation (r=-0.45) was seen between dose rate and humidity. The results show that the seasonal variations of indoor dose rates should be taken into account to estimate annual effective dose equivalent.

Evaporation determined by the energy‐budget method for Mirror Lake, New Hampshire

Evaporation was determined by the energy‐budget method for Mirror Lake during the open water periods of 1982–1987. For all years, evaporation rates were low in spring and fall and highest during the summer. However,the times of highest evaporation rates varied during the 6 yr. Evaporation reached maximum rates in July for three of the years, in June for two of the years, and in August for one of the years. The highest evaporation rate during the 6‐yr study was 0.46 cm d−1 during 27 May–4 June 1986 and 15–21 July 1987. Solar radiation and atmospheric radiation input to the lake and long‐wave radiation emitted from the lake were by far the largest energy fluxes to and from the lake and had the greatest effect on evaporation rates. Energy advected to and from the lake by precipitation, surface water, and ground water had little effect on evaporation rates. In the energy‐budget method, average evaporation rates are determined for energy‐budget periods, which are bounded by the dates of thermal surveys of the lake. Our study compared evaporation rates calculated for short periods, usually ~1 week, with evaporation rates calculated for longer periods, usually ~2 weeks. The results indicated that the shorter periods showed more variability in evaporation rates, but seasonal patterns, with few exceptions, were similar.

Lysis of plankton in the non-stratified southern North Sea during summer and autumn 2000

Abstract An improved esterase method was used to measure the lysis rate of natural phytoplankton in the non-stratified southern part of the North Sea during July and September 2000. Low nutrient concentrations indicated that phytoplankton was controlled by nutrients in July. The average values for silicate, phosphate, ammonium, nitrite, and nitrate were 1.75 ± 1.2, 0.072 ± 0.06, 0.73 ± 0.56, 0.04 ± 0.03, and 0.35 ± 0.44 μM, respectively (n = 24). The average underwater irradiance of the water column was 355 ± 133 Wh m–2 d–1. In autumn (cruise from 11 to 22 September 2000), the phytoplankton grew under light-control. In this period, the average water column irradiance was much lower (i.e. 90 ± 36 Wh m–2 d–1) than during summer because of lower incident irradiance levels and higher turbidity of the water column. Major dissolved inorganic nutrients were higher in September than in July: the average values for silicate, phosphate, ammonium, nitrite, and nitrate were 2.24 ± 1.03, 0.22 ± 0.05, 1.13 ± 0.65, 0.16 ± 0.32, and 0.68 ± 0.85 μM, respectively (n = 24). The average specific lysis rate of plankton was relatively low in September (0.04 ± 0.02 d–1, n = 24), and high in July (i.e. 0.20 ± 0.10 d–1, n = 24). Within each season, the plankton lysis rate correlates with the prevailing average underwater irradiance level at the various stations. The specific lysis rate of plankton was correlated with the total viral abundance (6 × 106–32 × 106 ml–1) in September. The virus density was lowest in turbid waters. In July, viruses were more abundant (20 × 106–48 × 106 ml–1). However, the substantially higher lysis rates in July could not be explained exclusively on the basis of enhanced virus abundance. It is concluded that nutrient-limitation during summer is a stress factor that causes losses to plankton communities by lysis of cells, additional to viral infection.