Regrowth of ryegrass swards subject to different cutting regimes and stocking densities

A cutting experiment was carried out on a sward of S23 perennial ryegrass to study the effect of different defoliation regimes on regrowth and the factors affecting regrowth. The defoliation frequencies and intensities encompassed the range commonly found on continuously stocked pastures. The defoliation regimes produced swards of contrasting growth form with regrowth characteristics which differed in respect of senescence loss, fall in water-soluble carbohydrate concentration, residual leaf area index, photosynthesis per unit leaf area index and photosynthesis per unit area of land. Regrowth was most closely related to the latter. These results were used to interpret data for net canopy photosynthesis of continuously grazed pastures.     

热处理对水牛乳稳定特性的影响

为比较不同热处理条件对水牛乳稳定性的影响,实验采用不同条件热处理后的pH缓冲容量、总溶解固体（total dissolved solids,TDS）、蛋白沉淀量及表观黏度等指标研究杂交高代水牛乳样品。结果表明：与未经处理的水牛乳样品相比,水牛乳经不同条件热处理后,其pH缓冲容量、TDS、蛋白沉淀量及表观黏度皆发生显著变化。其中水牛乳分别在经121℃/15 min和95℃/5 min处理后,其pH缓冲容量、TDS、蛋白沉淀量及表观黏度分别达到最大值和最小值。因此,认为在本实验研究范围内,水牛乳经121℃/15 min及95℃/5 min处理后,对其稳定性影响最大。     

Nasopharyngeal cryptococcosis

Naturally occurring cryptococcosis in five cats, a dog and a koala is described. Involvement of the nasopharynx was documented in all patients, and nasopharyngeal mass lesions accounted for the major presenting complaints in four. Signs referable to nasopharyngeal disease included snoring, stertor, inspiratory dyspnoea and aerophagia. Diagnoses were made by caudal rhinoscopy using a retroverted flexible endoscope, vigorous orthograde flushing with saline, or at necropsy. Concurrent cryptococcal rhinitis was present in all cases, although involvement appeared limited to the caudal nasal cavity in most cases. Typical signs of nasal cavity disease, such as sneezing and nasal discharge, were often absent. Treatment of nasopharyngeal cryptococcosis should include physical dislodgement or debulking of lesion(s) to provide immediate alleviation of upper airway obstruction, followed by systemic antifungal therapy to eliminate residual infection from the nasal cavity. Infections caused by Cryptococcus neoformans var gattii accounted for a disproportionately large number of these cases.     

An epidemiological study of Fasciola hepatica in the Netherlands

Summary

Transmission of F.hepatica under natural conditions was analysed in a three year programme. The variables used were the indirect haemagglutination (IHA) technique, worm establishment in tracer lambs and the population dynamics, infection rate and shedding pattern of Lymnaea truncatula.

It is concluded that fluke eggs, infected snails and metacercariae on herbage can survive the winter in the Netherlands. Metacercarial availability was positively correlated to the amount of rainfall in the grazing period. The role of developed eggs that survive the winter is important, because this results in earlier infections in the herd.

The use of the serological diagnosis method IHA is important to detect F. hepatica infection in an early stage. Use of cellophane paper on floats is a useful method for determining the shedding pattern of cercariae from L. truncatula. It is concluded that collection of metacercariae on cellophane floats, inventarization of L. truncatula and its infection level are useful tools for the prediction of liverfluke infections.     

牧草新品种黔草1号高羊茅的选育

黔草1号高羊茅是利用贵州地方野生资源作亲本,采用改良混合选择法,经10余年的选育研究育成的新品种。该品种抗逆性强、适应性广、坪用性好、耐践踏、持续性好、绿期长,返青期比引进品种凌志提前7 d,枯黄期晚3 d;种子成熟期集中,种子平均产量比对照品种高20%以上。适应我国长江中下游低山、丘陵等地区种植,是运动场草坪、环境绿化、生态治理的优良草种。     

Nanocapillarity and Chemistry in Carbon Nanotubes

Open carbon nanotubes were filled with molten silver nitrate by capillary forces. Only those tubes with inner diameters of 4 nanometers or more were filled, suggesting a capillarity size dependence as a result of the lowering of the nanotube-salt interface energy with increasing curvature of the nanotube walls. Nanotube cavities should also be less chemically reactive than graphite and may serve as nanosize test tubes. This property has been illustrated by monitoring the decomposition of silver nitrate within nanotubes in situ in an electron microscope, which produced chains of silver nanobeads separated by high-pressure gas pockets.     

Growth and carbon economy of nodulated white clover in the presence and absence of combined nitrogen

An investigation of the carbon economy of single S184 white clover plants nodulated with an effective strain of Rhizobium trifolii growing on N-free nutrient solution and supplied with 150 parts/10⁶ N as NH₄NO₃ has shown that 10% more of the C fixed per day is available for growth in the plants supplied with combined N. The difference between the two groups of plants is a result of higher respiratory activity in the roots of plants growing exclusively on N₂. In terms of shoot growth, however, the difference in growth rate is likely to be less than 10%, because the rate of root growth is greater in the plants supplied with a moderate level of combined N. There is no evidence that NO^-₃ and CO₂ compete for photosynthetically produced reductant in the leaves of plants grown on N₂+NH₄NO₃, since no reduction in net photosynthesis was observed in plants assimilating combined N. An experiment carried out on detached leaflets of white clover grown on N₂ and on N₂+ NH₄NO₃ has shown that NO^-₃ -reducing activity is present in the leaflets of plants grown on N₂+ NH₄NO₃ but not in plants grown on N₂ and that the activity is light-dependent. Measurements of ¹⁴CO₂ respired in the light and dark by leaflets previously allowed to photosynthesize ¹⁴CO₂ showed that the ratio of ¹⁴CO₂ output in the light to ¹⁴CO₂ output in the dark was no higher in plants grown on N₂+ NH₄NO₃ than in plants grown on N₂. This observation is consistent with the finding that N source does not affect net photosynthesis in whole plants.     

Effect of Leptin on In Vivo Goat Embryo Production

The aim of this study was to evaluate the effect of leptin administration during superovulation on in vivo goat embryo production. Ten mature does were superovulated with 133 mg follicle‐stimulating hormone (FSH) i.m. in six descending doses at 12‐h intervals. The goats received 4.8 μg/kg human recombinant leptin s.c. (leptin group, n = 5) or phosphate‐buffered saline (PBS) (control group, n = 5) with the first and second FSH doses. The does were mated and subjected to embryo collection by transcervical technique 6 days later. The total number of cells per embryo and the number of cells with fragmented DNA were assessed in selected blastocysts by combining Hoechst 33342 and terminal dUTP nick‐end labelling (TUNEL) staining. Plasma concentrations of oestradiol (E₂) and progesterone (P₄) were determined by electrochemiluminescence from the day of FSH treatment, on the day of superovulatory oestrus and on the day before embryo collection. Compared with the control group, the does that received leptin had a higher number of transferable embryos (p < 0.005), fewer embryos classified as degenerated (p < 0.001) and fewer TUNEL‐positive cells/blastocyst (p < 0.001). The number of transferable embryos was positively correlated with E₂ concentrations on day of oestrus (r = 0.562; p < 0.01) and P₄ concentrations on the day of embryo collection (r = 0.912; p < 0.001). We concluded that in vivo leptin administration during FSH treatment improved embryo quality and affected ovarian steroidogenesis in superovulated goats.     

Influence of soil physicochemical properties, particle size fractions and mineralogy on the leaching potentials of arsenic and antimony in abandoned mine soils

At abandoned mine sites, arsenic (As)- and antimony (Sb)-enriched soils are often disposed of through onsite burial or capping. In highly weathered mine sites, the mobility of As and Sb is typically controlled by iron (Fe)(Ⅲ)/Fe(Ⅱ) phases; thus, the suitability of such disposal methods and appropriate testing techniques are questionable. In the present study, leaching potentials of As and Sb were examined using the toxicity characteristic leaching procedure (TCLP), waste extraction test (WET), and WET-extended procedure (WET-EXT) at three abandoned mine site soils in Australia. The leached concentration of As regularly exceeded USEPA criteria (5 mg L^-1). The highest leached concentrations of As and Sb were observed in the finest particle size fraction (< 0.053 mm) by WET-EXT (1 040 mg L^-1 for As and 21.10 mg L^-1 for Sb) followed by WET (800 mg L^-1 for As and 20.90 mg L^-1 for Sb). The TCLP method resulted in the lowest concentrations of leached As (0.000 9 mg L^-1) and Sb (0.000 3 mg L^-1). Crystalline and amorphous As-bearing Fe oxides were the main phases in the soils studied. However, the best correlations of leached As determined by TCLP (0.832), WET (0.944), and WET-EXT (0.961) were found with the non-specifically sorbed (NS1) As fraction. The mineralogical and sequential extraction data clearly indicate the dominant role of Fe geochemistry in controlling leachability of As and Sb. The TCLP method was unlikely to be suitable for assessing leachability, as it exhibited no relationship with leachable Fe and substantially lower leached As and Sb than the other two methods. Given the high to extremely high leachable As and Sb concentrations, most of the soil samples would not be recommended for placement in capping works, old shafts, or reduction systems (e.g., collection in drainage basins).