The long way down--are carbon and oxygen isotope signals in the tree ring uncoupled from canopy physiological processes?     

Offermann C  Ferrio JP  Holst J  Grote R  Siegwolf R  Kayler Z  Gessler A 《Tree physiology》2011,31(10):1088-1102

The carbon (δ(13)C) and oxygen (δ(18)O) stable isotope composition is widely used to obtain information on the linkages between environmental drivers and tree physiology over various time scales. The tree-ring archive can especially be exploited to reconstruct inter- and intra-annual variation of both climate and physiology. There is, however, a lack of information on the processes potentially affecting δ(13)C and δ(18)O on their way from assimilation in the leaf to the tree ring. As a consequence, the aim of this study was to trace the isotope signals in European beech (Fagus sylvatica L.) from leaf water (δ(18)O) and leaf assimilates (δ(13)C and δ(18)O) to tree-ring wood via phloem-transported compounds over a whole growing season. Phloem and leaf samples for δ(13)C and δ(18)O analyses as well as soil water, xylem water, leaf water and atmospheric water vapour samples for δ(18)O analysis were taken approximately every 2 weeks during the growing season of 2007. The δ(13)C and δ(18)O samples from the tree rings were dated intra-annually by monitoring the tree growth with dendrometers. δ(18)O in the phloem organic matter and tree-ring whole wood was not positively related to leaf water evaporative enrichment and δ(18)O of canopy organic matter pools. This finding implies a partial uncoupling of the tree-ring oxygen isotopic signal from canopy physiology. At the same time, internal carbon storage and remobilization physiology most likely prevented δ(13)C in tree-ring whole wood from being closely related to intra-annual variation in environmental drivers. Taking into account the post-photosynthetic isotope fractionation processes resulting in alterations of δ(13)C and δ(18)O not only in the tree ring but also in phloem carbohydrates, as well as the intra-annual timing of changes in the tree internal physiology, might help to better understand the meaning of the tree-ring isotope signal not only intra- but also inter-annually.  相似文献   

Vacuum Squeezing of Solids: Macroscopic Quantum States Driven by Light Pulses     

GA Garrett  AG Rojo  AK Sood  JF Whitaker  R Merlin 《Science (New York, N.Y.)》1997,275(5306):1638-1640

Femtosecond laser pulses and coherent two-phonon Raman scattering were used to excite KTaO3 into a squeezed state, nearly periodic in time, in which the variance of the atomic displacements dips below the standard quantum limit for half of a cycle. This nonclassical state involves a continuum of transverse acoustic modes that leads to oscillations in the refractive index associated with the frequency of a van Hove singularity in the phonon density of states.  相似文献   

Sorption and Degradation of Selected Fungicides in the Turfgrass Canopy     

Sigler  William V.  Reicher  Zachary  Throssell  Clark  Bischoff  Marianne  Turco  Ronald F. 《Water, air, and soil pollution》2003,142(1-4):311-326

Microbial degradation of fungicides on leaf surfaces after repeated applications to turfgrass was investigated. Prior andcurrent work in our laboratory has identified two characteristicsof the turfgrass leaf system that may contribute to the enhanceddegradation of fungicides after repeated application to turfgrass:(1) The leaf surface is rich in microorganisms (～10⁸ g^-1 dr wt leaf), and (2) Leaf surface microorganisms may respond to repeated fungicide applications in a manner consistentwith the phenomena of enhanced biodegradation. Field studies wereconducted on ‘Penncross' creeping bentgrass with four fungicidesrepresenting three chemical families applied either two or eight times in one growing season. Biodegradation was estimated using data from both a field study and a parallel laboratory study thatfollowed the fate of ¹⁴C-labelled fungicides. For the laboratory incubations, the locations of the residual ¹⁴C fungicides were estimated using a sequential extraction protocolthat fractionated the materials into three pools: available,retained and bound. Data from both the field and laboratory studyrefuted our hypothesis that enhanced biodegradation would developfollowing repeated applications of the fungicides onto the leafsurface. Our studies support a conclusion that a two-stagephysical sorption process leads to plant incorporation and thiscontrols most of the fungicide's fate. Thus, our data suggestthat microbial activity plays a less important part in theprocess than would be indicated by considering the size of themicrobial population on the leaves.  相似文献   

Evaluation of an enzyme-linked immunosorbent assay for detection of Eperythrozoon suis antibodies in swine.   总被引：17，自引：0，他引：17  

F S Hsu  M C Liu  S M Chou  J F Zachary  A R Smith 《American journal of veterinary research》1992,53(3):352-354

An ELISA was developed and tested to detect antibodies to Eperythrozoon suis in swine. Results were compared with those of the indirect hemagglutination (IHA) test. Antigen isolated from swine heavily infected with E suis was used for both tests. Comparison of the ELISA with the IHA test revealed a significant (P less than 0.001) correlation between results. Of 114 samples obtained from 9 swine infected with E suis, 87.7% were seropositive (titer greater than or equal to 200) via the ELISA, and 80.7% were seropositive (titer greater than or equal to 20) via the IHA test. The sensitivity of the ELISA was greater than that of the IHA test. All blood samples obtained from specific-pathogen-free swine tested negative for E suis antibody. Cross-reactions were not observed between E suis antigen and antisera against various swine and cattle disease agents using ELISA. We concluded that the ELISA may be used for rapid and effective diagnosis of infection with E suis in swine.  相似文献   

Hydrops foetalis in dwarf calves associated with twinning     

PAW HARPER  MR LATTER  JF WILKINS 《Australian veterinary journal》1995,72(6):236-238

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Correlation of plasma concentrations of progesterone and oestradiol with ultrasound characteristics of the uterus and duration of oestrous behaviour in the cycling mare   总被引：1，自引：0，他引：1  

JF Pycock  S. Dieleman  P. Drifjhout  Y. van der  Brug  C. Oei  GC van der  Weijden 《Reproduction in domestic animals》1995,30(4):224-227

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The Epidemiology of Mountain Bike Park Injuries at the Whistler Bike Park,British Columbia (BC), Canada     

Zachary Ashwell  Mary Pat McKay  Jeffery R. Brubacher  Annie Gareau 《The Forestry Chronicle》2012,23(2):140-145

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Effects of oral isosorbide and glycerol on intraocular pressure,serum osmolality,and blood glucose in normal dogs     

Neal T. Wasserman  Gavin Kennard  Zachary N. Cochrane  Lisa M. Felchle 《Veterinary ophthalmology》2013,16(1):20-24

Objective To evaluate and compare the effects of oral isosorbide and glycerol on intraocular pressure (IOP), serum osmolality (SOSM), and blood glucose (BG) in normal dogs. Methods Ten normal dogs were administered an oral dose of either isosorbide (1.5 g/kg), glycerol (1.5 g/kg) or control (water, 2 mL/kg) in a double blind protocol. Prior to dosing, baseline IOP, SOSM, and BG were measured in all dogs. IOP was subsequently evaluated every 30 min for 6 h post‐dosing. BG and SOSM were reassessed at times 1, 2, 4, and 6 h post‐dosing. After 1‐week washout periods, every dog was subject to each of the three treatments. The dogs were held NPO for 4 h after dosing. Results The maximal decrease in IOP was 17% by 1 h and 13.5% by 30 min after glycerol and isosorbide administration, respectively. However, the overall changes in IOP were not significant when compared to the controls. SOSM increased above baseline after dosing with glycerol but decreased after isosorbide, which difference was significant at 1, 2, and 4 h post‐administration. BG significantly increased after administration of glycerol relative to the control but was not significantly affected by isosorbide. Conclusions Neither glycerol nor isosorbide significantly affected IOP when compared to the control. However, glycerol induced significant elevations in both BG relative to the control and SOSM relative to isosorbide.  相似文献   

Evaluation of Methods to Determine Sperm Density for the European eel,Anguilla anguilla     

SR Sørensen  V Gallego  L Pérez  IAE Butts  J Tomkiewicz  JF Asturiano 《Reproduction in domestic animals》2013,48(6):936-944

European eel, Anguilla anguilla, is a target species for future captive breeding, yet best methodology to estimate sperm density for application in in vitro fertilization is not established. Thus, our objectives were to evaluate methods to estimate European eel sperm density including spermatocrit, computer‐assisted sperm analysis (CASA) and flow cytometry (FCM), using Neubauer Improved haemocytometer as benchmark. Initially, relationships between spermatocrit, haemocytometer counts and sperm motility were analysed, as well as the effect of sperm dilution on haemocytometer counts. Furthermore, accuracy and precision of spermatocrit, applying a range of G‐forces, were tested and the best G‐force used in method comparisons. We found no effect of dilution on haemocytometer sperm density estimates, whereas motility associated positively with haemocytometer counts, but not with spermatocrit. Results from all techniques, spermatocrit, CASA and FCM, showed significant positive correlations with haemocytometer counts. The best correlation between spermatocrit and haemocytometer counts was obtained at 6000 ×  g (r = 0.68). Of two CASA variants, one or three photographic fields (CASA‐1 and CASA‐2), CASA‐2 showed a very high accuracy to haemocytometer counts (r  =  0.93), but low precision (CV: CASA‐2 = 28.4%). FCM was tested with and without microfluorospheres (FCM‐1 and FCM‐2), and relationships to haemocytometer counts were highly accurate (FCM‐1: r  =  0.94; FCM‐2: r  =  0.88) and precise (CV: FCM‐1 = 2.5; FCM‐2 = 2.7%). Overall, CASA‐2 and FCM‐1 feature reliable methods for quantification of European eel sperm, but FCM‐1 has a clear advantage featuring highest precision and accuracy. Together, these results provide a useful basis for gamete management in fertilization protocols.  相似文献   

Long-Term Cropping System, Tillage, and Poultry Litter Application Affect the Chemical Properties of an Alabama Ultisol     

Zhongqi HE  Irenus A. TAZISONG  Xinhua YIN  Dexter B. WATTS  Zachary N. SENWO  Henry Allen TORBERT 《土壤圈》2019,29(2):180-194

Sustainable agricultural practices have been steadily increasing in the last couple of decades. These management practices frequently involve cover crops, less or no-tillage, and organic fertilization. In this study, we evaluated the effects of cropping systems,tillage and no-tillage, and the application of poultry litter(PL) on selected soil physicochemical properties and soil test nutrients. Soil samples were collected from the topmost surface(0–5 cm) and subsurface(5–10 cm) layers. The general effect trend was PL application no-tillage cover crop cropping type. There were more statistically significant(P ≤ 0.05) correlations between the 18 soil attributes at the topmost surface than at the subsurface. This could be due to the accumulation of external C inputs and nutrients by crop residues and PL application as well as the retaining effects of no-tillage on less mobile nutrient components. Because of their high mobility and volatile nature, total nitrogen(N), ammonia-N(NH_4~+-N), and nitrate-N(NO_3~--N) levels varied greatly(high standard deviations), showing no consistent patterns among the treatments. Compared to the soybean cropping system, corn, especially with the wheat cover crop, contributed more to the total carbon(C) and sulfur(S) in the topmost surface soils(0–5 cm). Poultry litter application greatly increased pH, cation exchange capacity(CEC), base saturation, magnesium(Mg), phosphorus(P), calcium(Ca),sodium(Na), potassium(K), manganese(Mn), copper(Cu), and zinc(Zn) in both soil layers. Contrast comparisons revealed that PL application had more of an effect on these soil chemical properties than no-tillage and cropping systems. These results will shed light on developing better nutrient management practices while reducing their runoff potentials.  相似文献