Gas exchange characteristics of wheat stands grown in a closed, controlled environment     

Wheeler RM  Corey KA  Sager JC  Knott WM 《Crop science》1993,33(1):161-168

Information on gas exchange of crop stands grown in controlled environments is limited, but is vital for assessing the use of crops for human life-support in closed habitats envisioned for space. Two studies were conducted to measure gas exchange of wheat stands (Triticum aestivum L. cv. Yecora Rojo) grown from planting to maturity in a large (20 m2 canopy area), closed growth chamber. Daily rates of dark-period respiration and net photosynthesis of the stand were calculated from rates of CO2 build-up during dark cycles and subsequent CO2 drawdown in the light (i.e., a closed-system approach). Lighting was provided as a 20-h photoperiod by high-pressure sodium lamps, with canopy-level photosynthetic photon flux density (PPFD) ranging from 500 to 800 micromoles m-2 s-1 as canopy height increased. Net photosynthesis rates peaked near 27 micromoles CO2 m-2 s-1 at 25 d after planting, which corresponded closely with stand closure, and then declined slowly with age. Similarly, dark-period respiration rates peaked near 14 micromoles CO2 m-2 s-1 at 25 d and then gradually declined with age. Responses to short-term changes in irradiance after canopy closure indicated the stand light compensation point for photosynthesis to be near 200 micromoles m-2 s-1 PPFD. Tests in which CO2 concentration was raised to approximately 2000 micromoles mol-1 and then allowed to draw down to a compensation point showed that net photosynthesis was nearly saturated at > 1000 micromoles mol-1; below approximately 500 micromoles mol-1, net photosynthesis rates dropped sharply with decreasing CO2. The CO2 compensation point for photosynthesis occurred near 50 micromoles mol-1. Short-term (24 h) temperature tests showed net photosynthesis at 20 degrees C > or = 16 degrees C > 24 degrees C, while dark-period respiration at 24 degrees C > 20 degrees C > 16 degrees C. Rates of stand evapotranspiration peaked near Day 25 and remained relatively constant until about Day 75, after which rates declined slowly. Results from these tests will be used to model the use of plants for CO2 removal, O2 production, and water evaporation for controlled ecological life support systems proposed for extraterrestrial environments.  相似文献   

Modeling soil erosion on steep sagebrush rangeland before and after prescribed fire     

Corey A. Moffet  Frederick B. Pierson  Peter R. Robichaud  Kenneth E. Spaeth  Stuart P. Hardegree 《CATENA》2007

Fire in sagebrush rangelands significantly alters canopy cover, ground cover, and soil properties which influence runoff and erosion processes. Runoff can be generated more quickly and in larger volume following fire resulting in increased risk of severe erosion and downstream flooding. The Water Erosion Prediction Project (WEPP) model was developed to predict erosion on cropland, forest, and rangeland. WEPP is a tool that has potential to model the effect of fire on hillslope hydrological processes and help managers address erosion and runoff risks following fire. Experimental results on a steep (35 to 50% slope) sagebrush site suggest that rill erosion is the dominant erosion process following fire and the WEPP parameterization equations related to the rill erosion process need improvements. Rill detachment estimates could be improved by modifying regression-estimated values of rill erodibility. Also, the interactions of rill width and surface roughness on soil shear stress estimates may also need to be modified. In this paper we report the effects of prescribed fire on runoff, soil erosion, and rill hydraulics and compare WEPP estimated erosion for several modeling options with measured erosion.  相似文献   

Comparison of Computed Tomographic Images of Birds Obtained With Sedation vs General Anesthesia     

James Kusmierczyk  Corey R. Wall  Sharman Hoppes  Christine M. Budke  Kathy A. Spaulding 《Journal of Exotic Pet Medicine》2013,22(3):251-257

Computed tomography (CT) is an increasingly available and valuable imaging modality for the diagnosis of companion avian pets. Previously, CT studies of birds required general anesthesia with inhalant anesthetics. Owing to the risks associated with general anesthesia, the authors of this article investigated the effect of sedation on birds during a CT examination. In this study, 10 psittacine birds were imaged using a 40-slice helical CT scanner. Birds were sedated with midazolam and butorphanol and placed in a positioning device. Following the initial study, birds were removed from the device and placed under general anesthesia with isoflurane. A second study was then performed. Two radiologists, blinded to the identity of the birds and partially blinded to the conditions of the study, reviewed the images. Studies were evaluated using a questionnaire consisting of 18 questions. Each question was scored on a Likert scale. A Wilcoxon signed rank test compared scores of sedated and anesthetized birds. A significant difference (P = 0.05) between sedated and anesthetized studies was found for 2 of 18 (11.1%) questions for radiologist 1 and 1 of 18 (5.5%) questions for radiologist 2, with differences identified in the scleral ossicles and the femoral heads. Interrater agreement for all questions using a linearly weighted κ was 0.334 and 0.311 for sedated and anesthetized birds, respectively, indicating fair agreement. The interrater agreement, excluding the head and musculoskeletal system, was 0.381 for sedated animals, indicating fair agreement, and 0.404 for anesthetized birds, indicating moderate agreement. Based on our results, performing CT studies in birds with sedation is a viable alternative to studies performed under general anesthesia.  相似文献   

Spectrophotometric determination of sperm concentration and short‐term cold‐storage of sperm in Atlantic croaker Micropogonias undulatus L. broodstock     

Luca Antoni  Agnès Bardon‐Albaret  Corey R Anderson  Carly R Somerset  Eric A Saillant 《Aquaculture Research》2014,45(8):1283-1294

The objective of this study was to optimize the methodology for spectrophotometric determination of sperm concentration in Atlantic croaker Micropogonias undulatus L. milt and to estimate its potential for short‐term cold‐storage. The spectrophotometric determination of sperm concentration was evaluated using milt samples from six males serially diluted in Hank's balanced salt solution at 200 mOsm kg^?1 (HBSS). The predictive power of regression models between sperm concentration and absorbance was determined from 200 to 500 nm and found to be highest within the visible spectrum despite a peak of milt absorbance at 288 nm. Absorbance reading at 400 nm was selected for further analysis to maximize the absorbance of the sample hence the sensitivity of the method while minimizing the impact of potential sample contamination with blood. The standard‐curve of correlation between sperm absorbance at 400 nm and concentration was validated and held an accuracy ranging between ?7.40% and +4.56% across males. Total sperm motility duration and the proportion of motile spermatozoa were significantly higher in milt samples diluted 1:3 in HBSS than in the undiluted control during up to 30 h of cold‐storage.The methodologies investigated in this study can be applied to optimize sperm usage and achieve predictable artificial fertilization protocols in Atlantic croaker.  相似文献   

Weather Variability and Adaptive Management for Rangeland Restoration     

Stuart P. Hardegree  Jeanne M. Schneider  Corey A. Moffet 《Herpetological Monographs》2012,34(6):53-56

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Technical note: using an automated head chamber system to administer an external marker to estimate fecal output by grazing beef cattle     

Matthew R Beck  Stacey A Gunter  Corey A Moffet  R Ryan Reuter 《Journal of animal science》2021,99(9)

The objective of this experiment was to determine if titanium dioxide (TiO₂) dosed through an automated head chamber system (GreenFeed; C-Lock Inc., Rapid City, SD, USA) is an acceptable method to measure fecal output. The GreenFeed used on this experiment had a 2-hopper bait dispensing system, where hopper 1 contained alfalfa pellets marked with 1% titanium dioxide (TiO₂) and hopper 2 contained unmarked alfalfa pellets. Eleven heifers (BW = 394 ± 18.7 kg) grazing a common pasture were stratified by BW and then randomized to either 1) dosed with TiO₂-marked pellets by hand feeding (HFD; n = 6) or 2) dosed with TiO₂-marked pellets by the GreenFeed (GFFD; n = 5) for 19 d. During the morning (0800), all heifers were offered a pelleted, high-CP supplement at 0.25% of BW in individual feeding stanchions. The HFD heifers also received 32 g of TiO₂-marked pellets at morning feeding, whereas the GFFD heifers received 32 g of unmarked pellets. The GFFD heifers received a single aliquot (32 ± 1.6 g; mean ± SD) of marked pellets at their first visit to the GreenFeed each day with all subsequent 32-g aliquots providing unmarked pellets; HFD heifers received only unmarked pellets. Starting on d 15, fecal samples were collected via rectal grab at feeding and every 12 h for 5 d. A two-one sided t-test method was used to determine agreement and it was determined that the fecal output estimates by HFD and GFFD methods were similar (P = 0.04). There was a difference (P < 0.01; Bartlett’s test for homogenous variances) in variability between the dosing methods for HFD and GFFD (SD = 0.1 and 0.7, respectively). This difference in fecal output variability may have been due to variability of dosing times-of-day for the GFFD heifers (0615 ± 6.2 h) relative to the constant dosing time-of-day for HFD and constant 0800 and 2000 sampling times-of-day for all animals. This research has highlighted the potential for dosing cattle with an external marker through a GreenFeed configured with two (or more) feed hoppers because estimated fecal output means were similar; however, consideration of the increased variability of the fecal output estimates is needed for future experimental designs.  相似文献   

Sequencing of Culex quinquefasciatus establishes a platform for mosquito comparative genomics     

Arensburger P  Megy K  Waterhouse RM  Abrudan J  Amedeo P  Antelo B  Bartholomay L  Bidwell S  Caler E  Camara F  Campbell CL  Campbell KS  Casola C  Castro MT  Chandramouliswaran I  Chapman SB  Christley S  Costas J  Eisenstadt E  Feschotte C  Fraser-Liggett C  Guigo R  Haas B  Hammond M  Hansson BS  Hemingway J  Hill SR  Howarth C  Ignell R  Kennedy RC  Kodira CD  Lobo NF  Mao C  Mayhew G  Michel K  Mori A  Liu N  Naveira H  Nene V  Nguyen N  Pearson MD  Pritham EJ  Puiu D  Qi Y  Ranson H  Ribeiro JM  Roberston HM  Severson DW  Shumway M 《Science (New York, N.Y.)》2010,330(6000):86-88

Culex quinquefasciatus (the southern house mosquito) is an important mosquito vector of viruses such as West Nile virus and St. Louis encephalitis virus, as well as of nematodes that cause lymphatic filariasis. C. quinquefasciatus is one species within the Culex pipiens species complex and can be found throughout tropical and temperate climates of the world. The ability of C. quinquefasciatus to take blood meals from birds, livestock, and humans contributes to its ability to vector pathogens between species. Here, we describe the genomic sequence of C. quinquefasciatus: Its repertoire of 18,883 protein-coding genes is 22% larger than that of Aedes aegypti and 52% larger than that of Anopheles gambiae with multiple gene-family expansions, including olfactory and gustatory receptors, salivary gland genes, and genes associated with xenobiotic detoxification.  相似文献   

Environmental behavior and analysis of agricultural sulfur          下载免费PDF全文

Corey M Griffith  James E Woodrow  James N Seiber 《Pest management science》2015,71(11):1486-1496

Sulfur has been widely used for centuries as a staple for pest and disease management in agriculture. Presently, it is the largest‐volume pesticide in use worldwide. This review describes the sources and recovery methods for sulfur, its allotropic forms and properties and its agricultural uses, including development and potential advantages of nanosulfur as a fungicide. Chemical and microbial reactivity, interactions in soil and water and analytical methods for determination in environmental samples and foodstuffs, including inexpensive analytical methods for sulfur residues in wine, beer and other food/beverage substrates, will be reviewed. The toxicology of sulfur towards humans and agriculturally important fungi is included, with some restrictions on use to promote safety. The review concludes with areas for which more research is warranted. © 2015 Society of Chemical Industry  相似文献   

Feeding Redberry Juniper (Juniperus pinchotii) at Weaning Increases Juniper Consumption by Goats on Pasture     

Timothy H. Dietz  Cody B. Scott  Erika J. Campbell  Corey J. Owens  Charles A. Taylor  Richard Brantely 《Strength and Conditioning Journal》2010,63(3):366-372

Redberry (Juniperus pinchotii Sudw.) and ashe (Juniperus ashei Buchh.) juniper dominate rangelands throughout central Texas. Our objective was to attempt to improve the efficacy of goats as a biological control mechanism for juniper through behavioral training. Conditioning sheep and goats to increase the palatability of chemically defended plants can be a useful tool in brush control. Previous research illustrated that goats can be conditioned to consume more juniper while in individual pens when foraging choices are limited. To test whether this creates a longer-lasting increase in juniper preference, we determined if goats would continue to consume juniper on pasture for one year after being fed juniper in individual pens for 14 d. Female Boer-cross goats (n = 40) were randomly divided into two treatments: conditioned and naive to juniper. At approximately 12 mo of age, conditioned goats were placed in individual pens and fed redberry juniper 1 h daily for 14 d, while naive goats received only alfalfa pellets to meet maintenance requirements. After the pen-feeding phase of the study, goats were placed in one of four pastures (10 goats · pasture^?1) for 12 mo. Two pastures housed conditioned goats, and two pastures housed naive goats at a moderate stocking rate (1 animal unit · yr^?1 · 8 ha^?1). Bite count surveys were conducted twice per month, while herbaceous standing crop and monoterpene levels were measured once per month. Juniper preference varied monthly; however, conditioned goats consistently ate more (P < 0.05) juniper than naive goats except for April, when the study began, and March, when the study ended. When selection of herbaceous forages decreased, conditioned goats increased selection of juniper, while naive goats increased selection of other palatable shrubs. Seasonal changes of monoterpene levels in juniper had no apparent effect on juniper preference. We contend that feeding juniper at weaning will increase use of the plant in grazing situations.  相似文献   

Residual Toxicity of Acid Mine Drainage-Contaminated Sediment to Stream Macroinvertebrates: Relative Contribution of Acidity vs. Metals     

Jean V. Dsa  Kelly S. Johnson  Dina Lopez  Corey Kanuckel  Jennifer Tumlinson 《Water, air, and soil pollution》2008,194(1-4):185-197

Acid mine drainage (AMD), a legacy of coal and mineral extraction, contaminates streams with complex mixtures of acid and heavy metals that are usually partitioned between the water column and substrate. Understanding the conditions under which sediments retain toxicity after the water column is cleared is important for predicting the long term success of remediation efforts. We conducted laboratory and field experiments to evaluate the relative contribution of acidity versus metals to the toxicity of AMD contaminated sediment towards aquatic macroinvertebrates. Laboratory bioassays showed that precipitate-coated substrate from AMD-impacted sites were toxic to Ctenodaphnia magna and reduced growth of mayflies (Ephemeroptera: Heptageniidae). Toxicity correlated more with acidity released from the sediment than with metals. After transplantation to a clean stream, the same Al- and Fe-contaminated substrate were not toxic to daphnia and was readily colonized by benthic macroinvertebrates within 5 weeks.  相似文献