双螺杆挤压机螺杆元件类型对扭矩和压力的影响

以食用脱脂低温豆粕为原料,以Brabender DSE-25型双螺杆挤压膨化实验室工作站为加工设备,研究了不同几何参数的输送元件、捏合块和齿型盘6种螺杆元件对挤压过程中扭矩和压力的影响。结果表明:螺杆元件对扭矩和压力有显著影响;对扭矩影响的主次顺序为反向输送元件;齿型盘、捏合块、正向输送元件;有反向螺旋角或错裂角或对物料剪切强度大的元件能够显著增加扭矩;元件对压力的影响规律不明显。对系统稳定性的初步分析认为,错列角为45°和90°的捏合块具有较好的混炼效果,而齿型盘和错列角为-45°的捏合块的混炼效果较差。     

Abatement of High Concentrated Ammonia Loaded Waste Gases in Compost Biofilters

The performance of lab-scale compostbiofilters for the purification of waste gasescontaining high (>70 mg m^-3) ammoniaconcentrations was studied. When using fresh compostmaterial, no effect of inoculating the compostmaterial with a nitrifying culture was observed sincehigh elimination capacities (up to 350 gNH₃ m^-3 d^-1) were obtained in both theinoculated and the non-inoculated biofilter. Due tothe physico-chemical interaction of NH₃ with thecompost material at the start of the experiment, nomicrobiological start-up period was observed and highremoval efficiencies were obtained from the first dayon. Next to this, no NH₃-toxicity was observedeven at concentrations up to 550 mg NH₃ m^-3.About 50% of the NH₃-removal was found to benitrified, while the other 50% remained in thebiofilter as NH ⁺₄ . As a result of this, noacidification of the carrier material was observed andNH₄NO₃ accumulated in the biofilter. Due toosmotic effects, however, a complete inhibition innitrification and NH₃-removal was obtained at ameasured NH₄NO₃-concentration in the compostmaterial of 6–7 g N kg^-1, corresponding to acumulative NH₃-removal in the biofilter of ±6000 g m^-3. Finally, it was illustrated that theremoval of the odorant dimethyl sulfide (Me₂S) ina Hyphomicrobium MS3-inoculated compostbiofilter is completely inhibited due toNH₃-toxicity at a waste gas concentration of 100 mg NH₃ m^-3. Next to this, theNH ⁺₄ - and NO ^?₃ -concentrations inthe compost material that were shown to inhibit thenitrification, also strongly affected theMe₂S-degrading activity of Hyphomicrobium MS3.

     

Modeling vertical movement of organic matter in a soil incubated for 41 years with C labeled straw

The distribution of organic matter (OM) in the soil profile reflects the balance between inputs and decomposition at different depths as well as transport of OM within the profile. In this study we modeled movement of OM in the soil profile as a result of mechanisms resulting in dispersive and advective movement. The model was used to interpret the distribution of ¹⁴C in the soil profile 41 years after the labeling event. The model fitted the observed distribution of ¹⁴C well (R²=0.988, AIC_c=−82.6), with a dispersion constant of D=0.71 cm² yr⁻¹ and an advection constant of v=0.0081 cm yr⁻¹. However, the model consistently underestimated the amount of OM in the soil layers from 27 to 37 cm depth. A possible explanation for this is that different fractions of OM are transported by different mechanisms. For example, particulate OM, organomineral colloids and dissolved OM are not likely to be transported by the same mechanisms. A model with two OM fractions, one moving exclusively by dispersive processes (D=0.26 cm² yr⁻¹) and another moving by both dispersive (D=0.99 cm² yr⁻¹) and advective (v=0.23 cm yr⁻¹) processes provided a slightly better fit to the data (R²=0.995, AIC_c=−83.6). More importantly, however, this model did not show the consistent underestimation from 27 to 37 cm soil depth. This corroborates the assumption that differing movement mechanisms for different OM fractions are responsible for the observed distribution of ¹⁴C in the profile. However, varying dispersion, advection, and decay of OM with depth are also possible explanations.     

Biological activity and organic matter mineralization of soils amended with biowaste composts

This study aims to elucidate the significance of compost and soil characteristics for the biological activity of compost‐amended soils. Two agricultural soils (Ap horizon, loamy arable Orthic Luvisol and Ah horizon, sandy meadow Dystric Cambisol) and a humus‐free sandy mineral substrate were amended with two biowaste composts of different maturity in a controlled microcosm system for 18 months at 5 °C and 14 °C, respectively. Compost application increased the organic matter mineralization, the C_mic : C_org ratio, and the metabolic quotients significantly in all treatments. The total amount of C_org mineralized ranged from < 1 % (control plots) to 20 % (compost amended Dystric Cambisol). Incubation at 14 °C resulted in 2.7‐ to 4‐fold higher cumulative C_org mineralization compared to 5 °C. The C_mic : C_org ratios of the compost‐amended plots declined rapidly during the first 6 months and reached a similar range as the control plots at the end of the experiment. This effect may identify the compost‐derived microbial biomass as an easily degradable C source. Decreasing mineralization rates and metabolic quotients indicated a shift from a compost‐derived to a soil‐adapted microbial community. The C_org mineralization of the compost amended soils was mainly regulated by the compost maturity and the soil texture (higher activity in the sandy textured soils). The pattern of biological activity in the compost‐amended mineral substrate did not differ markedly from that of the compost‐amended agricultural soils, showing that the turnover of compost‐derived organic matter dominated the overall decay process in each soil. However, a priming effect occurring for the Dystric Cambisol indicated, that the effect of compost application may be soil specific.     

ULTRASONOGRAPHIC EXAMINATION OF THE THYROID GLAND OF HYPERTHYROID CATS: COMPARISON TO 99mTcO−4 SCINTIGRAPHY

High-resolution ultrasonography was evaluated as an alternative to ^99mTcO^-₄ scintigraphy for examining size and appearance of thyroid glands in hyperthyroid cats. Thyroid ultrasound examinations were performed on 6 normal cats and 14 cats with hyperthyroidism. Thyroid lobe volume was estimated from ultrasound images using the equation for a prolate ellipsoid, π/6 (length * height * width). Total thyroid volume was estimated by adding the volume estimations of the left and right lobes. Thyroid lobes of hyperthyroid cats were considered abnormal if estimated volume exceeded the 99% confidence interval for normal thyroid volume determined from the control group. Scintigraphic examinations performed on hyperthyroid cats were evaluated for unilateral versus bilateral disease and for the presence of ectopic activity. Mean thyroid lobe volume and total thyroid volume for normal cats was 85 and 169 mm³, respectively. Mean thyroid lobe volume and total thyroid volume for hyperthyroid cats was 578 and 889 mm³. There was a significant difference in mean estimated total thyroid volume of normal and hyperthyroid cats. Thyroid lobes with greater than normal TcO^-₄ uptake on scintigraphy were larger and had variable homogeneity, echogenicity, and margination on ultrasound examination. There also was an 85.7% agreement of scintigraphy and ultrasonography in differentiating normal from abnormal thyroid lobes. A fair correlation between estimated total thyroid volume of hyperthyroid cats and most recent pretherapy serum thyroxine values were also found. This preliminary study indicates that thyroid ultrasound examination may provide information that is useful for diagnosis and treatment of feline hyperthyroidism. Although ultrasound provides accurate evaluation of the thyroid glands, it cannot replace ^99mTcO^-₄ scintigraphy for screening of metastatic lesions and ectopic glands.     

Effect of replacing soybean protein with protein from porcupine joint vetch (Aeschynomene histrix BRA 9690) and stylo (Stylosanthes guianensis Composite) leaf meal on growth performance of native (Moo Lath) Lao pigs

The effect of replacing soybean crude protein (CP) with legume leaf meal (LLM) CP on feed intake, growth performance and carcass traits was studied in native female Moo Lath Lao pigs. The diets comprised one traditional diet (T) without soybean meal, one control diet (C) with soybean meal and six diets iso-nitrogenous with diet C in which soybean protein was replaced (33, 66 and 100 % of CP) with LLM CP from porcupine joint vetch (PLM) or Stylosanthes (SLM). Feed and water were offered ad libitum. Replacing soybean CP with LLM CP reduced (P?<?0.05) intake of dry matter (DMI), CP (CPI), metabolisable energy (MEI), final body weight (BW) and average daily gain (ADG), but had no effect (P?>?0.05) on feed conversion ratio (FCR). Increasing the replacement rate of soybean CP with LLM CP had a negative linear effect (P?<?0.001) on DMI, CPI, MEI, final BW and ADG, and on all carcass traits except lean meat percentage. There were no differences in dressing percentage or organ weight and length between treatments. Supplementing diet T with soybean meal resulted in higher (P?<?0.05) DMI, CPI and MEI, lower (P?<?0.05) FCR, and higher (P?<?0.05) final BW and ADG. Slaughter weight, hot carcass weight, eye muscle thickness, back fat, fat in carcass and lean meat were lower (P?<?0.05) with diet T than diet C. In conclusion, LLM from stylo and porcupine joint vetch can be used as a CP source to partially replace soybean meal CP in the diet of growing native female Moo Lath Lao pigs.     

Prevalence and risk factors of Coxiella burnetii seropositivity in Danish beef and dairy cattle at slaughter adjusted for test uncertainty

Antibodies to Coxiella burnetii have been found in the Danish dairy cattle population with high levels of herd and within herd seroprevalences. However, the prevalence of antibodies to C. burnetii in Danish beef cattle remains unknown. The objectives of this study were to (1) estimate the prevalence and (2) identify risk factors associated with C. burnetii seropositivity in Danish beef and dairy cattle based on sampling at slaughter.