翻耕短期内对草原土壤呼吸的影响

以呼伦贝尔草甸草原为研究对象,研究不同翻耕深度(10cm和20cm)对土壤呼吸的影响。结果表明:翻耕短期内明显加速土壤呼吸速率,且随着翻耕深度的增加而增加。在翻耕后15d内,翻耕10cm和翻耕20cm处理的土壤呼吸速率平均值分别为3.79μmol CO2/m2/s和4.78μmol CO2/m2/s,分别是天然草地的1.33和1.68倍,这种影响持续一段时间后趋于稳定。在翻耕30d后,不同处理的土壤呼吸速率间差距明显减小,天然草地、翻耕10cm和翻耕20cm处理的土壤呼吸速率,在翻耕后第30~47d内测定的平均值分别为2.23μmol CO2/m2/s、1.90μmol CO2/m2/s、2.14μmol CO2/m2/s。     

EFFECT OF REGION OF INTEREST SELECTION AND UPTAKE MEASUREMENT ON GLOMERULAR FILTRATION RATE MEASURED BY 99mTc-DTPA SCINTIGRAPHY IN DOGS

Determinations of different methods of measurement of uptake of 99mTc-DTPA using scintigraphy of glomerular filtration rate (GFR) were made from 29 studies on 10 healthy beagle dogs. GFR was measured by calculating the percentage dose uptake (integral method) and rate of uptake (slope method) of 99mTc-DTPA using manual kidney regions of interest (ROI) and automatic kidney and background ROIs at different time periods of the uptake phase. These results were compared using linear regression analysis to the GFR obtained from 99mTc-DTPA plasma clearance using multiple blood samples. The best correlation coefficient between percentage DTPA uptake and GFR by DTPA clearance (r = 0.84, P < 0.001) was derived from time intervals between 30s-120s with a perirenal background ROI at 1 or 2 pixels out from the kidney ROI using automatic kidney ROI at 20% threshold. With the slope method, the best correlation coefficient (r = 0.85, P < 0.001) was obtained from time intervals between 30s-peak with the background ROI at 2 pixels out from the kidney ROI using automatic ROI at 35% threshold. The offset was higher, and the correlation varied more with different ROIs and the method was unreliable at time intervals extending beyond the peak radioactivity. Manual kidney ROIs with automatic background ROIs had slightly lower correlations. With DTPA renography both integral and slope uptake method with automatic kidney and background ROIs are accurate methods to estimate the GFR, but that the integral method is much more stable to variations in ROI size and the duration of the uptake phase of the renogram.     

狗牙根草茎建植成坪质量的施肥和播种研究

本研究试图探明狗牙根草茎在不同播种深度和施肥方法下对高尔夫草坪备草区建植生长的影响。采用二因素随机区组设计,在高尔夫草坪备草区大田中对不同播种深度(1,2和3 cm)和施肥措施(底肥和追肥)进行比较分析。结果表明,生长成坪期间草坪草的盖度、种群密度和株高随着播种深度的增加而增加,但是在成坪后期播深2和3 cm对草坪质量的影响差异不显著;追肥比底肥效果好。在狗牙根草茎高尔夫草坪备草区建植生长中,播种深度是首要因素,其次是施肥方法;两因素交互作用显著。结合建植成本和工期,在生产实践中推荐采用播种深度应为2 cm,播后1周内追肥,并建议施用速效肥。     

Comparison of Seven Digital Cameras for Digitizing Radiographs

The purpose of this study was to evaluate seven digital cameras for their ability to adequately capture quality radiographic images and their relative cost effectiveness. Radiographs of line pair (LP) phantoms (ranging from 0.6 to 16.6 LP/mm) and a 20-step contrast phantom were photographed at a near distance of 30.0 cm and a far distance (determined for each camera) at which a full 14 x 17 in film filled the viewfinder. Of the seven cameras tested, the Canon EOS-D30 consistently performed the best in LP/mm resolved (7.7 at close distance, 1.4 at far distance) and in contrast latitude (all 20 steps at both close and far distances). The Canon EOS-D30, determined to be the best camera used in this study for photographing radiographic images, is also the most expensive camera that was used. Two cameras, the Nikon Coolpix 995 and the Sony DSC-F707, were very close to the Canon in performance at considerably less cost. Certain inexpensive cameras may not be acceptable choices for teleradiology.     

Screening for periodontal disease in research dogs - a methodology study

Background

It has been shown that the prevalence of both clinical attachment loss (CAL) ≥1 mm and pocket probing depth (PPD) ≥4 mm is relatively high even in younger dogs, but also that only a minority of the dogs have such clinical signs of periodontal disease (PD) in more than a few teeth. Hence, a minority of dogs carry the major PD burden. These epidemiological features suggest that screening for PD in larger groups of dogs, allowing for rapid assessment of treatment planning, or for the selection of dogs with or without PD prior to be included in experimental trials, should be possible. CAL is the central variable in assessing PD extent and severity while PPD is the central variable used in treatment planning which make these two variables obvious in a screening protocol with the dual aim of disease identification and treatment planning. The main purpose of the present study in 98 laboratory Beagle dogs was to construct a fast, simple and accurate screening tool, which is highly sensitive for the identification of dogs with PD.

Results

Examination of the maxillary P4, P3, P2, I1 and C would, in this population, result in the identification of 85.5% of all dogs and 96% of all teeth positive for CAL ≥1 mm, and 58.9% of all dogs and 82.1% of all teeth positive for PD ≥4 mm.Examination of tooth pairs, all C’s, maxillary I2, M2 and the mandibular P4 would, in this population result in identification of 92.9% of all dogs and 97.3% of all teeth positive for PD ≥4 mm, and 65.5% of all dogs and 83.2% of all teeth positive for CAL ≥1 mm. The results presented here only pertain to the present study population.

Conclusions

This screening protocol is suitable for examination of larger groups of laboratory Beagle dogs for PD and our findings indicate that diseased dogs are identified with a high degree of sensitivity. Before this screening can be used in clinical practice, it has to be validated in breeds other than Beagle dogs and in populations with larger age variation.     

青海省海北州不同草地利用方式土壤基本理化性状研究

为探索土地利用方式变化对土壤理化性状的影响,以青藏高原青海省海北州原生矮嵩草(Kobresia humil)草甸、原生灌丛草甸、退化矮嵩草草甸、退化灌丛草草甸、人工草地、农田地为研究对象,对各利用方式下土壤的基本理化性状进行研究.结果表明:退化导致0～10 cm土层土壤容重增大,而对下层土壤容重没有明显影响,2种退化草地0～10 cm土层的土壤容重均大于10～20 cm土层,其中退化灌丛草甸与原生灌丛草甸之间差异显著(P＜0.05),人工种植也导致表层土壤容重有升高的趋势,人工种草和开垦均导致0～20 cm土层土壤容重的变异消失.草地退化和开垦均导致土壤有机碳和全氮含量降低,草地退化还导致土壤     

滴头埋设深度对土壤水分运移及草坪草生长的影响

草坪地下滴灌与喷灌相比,具有节水、方便管理等优点。为了掌握滴灌中滴头的适宜埋设深度,通过模拟及实地试验,对地下滴灌土壤水分分布及其对草坪生长的影响进行了观测分析。结果表明:在流量和灌水时间一定的情况下,随着埋深的增加,湿润锋在水平方向的运移距离减小,在垂直方向上增大;相同埋深时,滴头两侧的含水率分布对称。在高羊茅((Festuca arundinacea Schreb. cv. Pixie))生长旺季,不同埋深处理对地上生物量影响显著(P<0.05),埋深20cm显著高于其他处理(P<0.05);不同埋深处理植株密度差异不显著;不同埋设深度对高羊茅根系分布有一定的影响,在每个滴头附近的根系密度和重量明显增加。     

高寒草地凋落物覆盖对狼毒生长微环境及种苗定居的影响

种子萌发和幼苗定居是植物生活史中最为脆弱的两个阶段.为了探明高寒草地狼毒(Stellera chamaejasme)种苗定居的生境选择,本研究在其原生境下通过人工控制试验,研究凋落物覆盖对土壤微环境(温、湿度)的影响以及狼毒种子在不同生境条件下的出苗和定居表现.结果表明:凋落物覆盖总体上能够降低土壤温度,提高土壤含水量...     

To sea or not to sea? Multiple lines of evidence reveal the contribution of non‐diadromous recruitment for supporting endemic fish populations within New Zealand's longest river

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施氮深度对‘黄金梨’树氮素吸收、分配及利用效率的影响

以7年生‘黄金梨’树为试材,采用~(15)N示踪技术研究了3个施氮深度[0(表面施氮)、20和40 cm]处理下不同器官对氮素的吸收、分配及利用效率,并探讨了氮素在土壤中的残留及损失。结果表明,梨果实成熟期,果实的Ndff值最高,其他器官的Ndff值均表现为20 cm施氮深度处理显著高于其他处理。各施氮深度处理,~(15)N的分配率均为贮藏器官最高,生殖器官最低。20 cm施氮深度处理的梨树N利用率最高(26.23%),40 cm施氮深度处理最低(15.65%)。N损失率以表面施氮处理最高(54.21%),20 cm施氮深度最低;0~80 cm土层的N残留率以40 cm施氮深度处理最高(31.73%),表面施氮处理最低。因此,本研究中,20 cm深度施氮处理能提高梨树各器官对N肥的吸收征调能力,氮素损失少。