Permeation of urea through various polyurethane membranes

BACKGROUND: Controlled‐release systems using polymer membranes are very important in agriculture for labour‐saving and effective delivery of pesticides and other agents. Polymer‐coated granules are one of the most useful formulations, and a study of the factors for polymer design is necessary to achieve various release patterns. A permeation study using plain membranes was carried out in order to clarify parameters, and the results were compared with the release from polymer‐coated granules. RESULTS: The permeation coefficient of urea through a plain polyurethane membrane decreased significantly as the urethane and alkyl side chain content increased. The glass transition temperature and crosslink density of the polyurethanes hardly influenced its permeability. The release rate from polyurethane‐coated granules was also reduced by alkyl side chains. However, it was faster than that through a plain membrane because of capsule expansion by continuous water penetration and structural changes in the membrane. CONCLUSION: The release rate of urea through a polyurethane plain membrane and from polyurethane‐coated granules can be controlled by changing the chemical properties of the membrane. In addition, physical properties such as the glass transition temperature T_g or crosslink density should be considered to assess the release profile from polyurethane‐coated granules. Copyright © 2009 Society of Chemical Industry     

两种功能高分子材料对沙土物理性质影响的比较

采用SEM,透水系数法、加压板法等现代测试手段,观察与分析高分子吸水树脂、固沙植被多功能高分子复合材料表面微观结构形态,比较高分子吸水树脂与固沙植被多功能高分子复合材料改良沙土后沙土的透水、保水等特性及沙土水分的有效利用情况.实验结果证明固沙植被多功能高分子复合材料比高分子吸水树脂改良沙土的效果好,使沙土的气、液、固三相比有利植物的生长,能保持高的水有效利用率.本实验结果为固沙植被多功能高分子复合材料的应用提供了新的依据.     

An enzyme-linked immunosorbent assay using canine coronavirus-infected CRFK cells as antigen for detection of anti-coronavirus antibody in cat

From the reasons that canine coronavirus (CCV) grows more efficiently than feline coronavirus in a cell culture and they are mutually related in their antigenicities, an enzyme-linked immunosorbent assay (ELISA) using CCV-infected feline kidney (CRFK) cells as substrate antigens was developed for detection of anti-coronavirus antibodies in cats. It was indispensable for generating coronavirus-specific ELISA antibody activities that the sample was applied to the mock-infected, normal CRFK cells in parallel with the CCV-infected cells and then the optical density values given by the mock-infected cell antigen were subtracted from those given by the virus-infected cell antigen. On the basis of ELISA antibody titers obtained in sera from the cats experimentally infected with CCV and from the spontaneous feline infectious peritonitis (FIP) cases, the ELISA described in the present study was found to be applicable as a simple and easy serologic test which was able to detect anti-coronavirus antibodies as efficiently as the indirect immunofluorescence assay with homologous FIP virus.     

Response changes with growth in the gustatory receptors of young yellowtails (Seriola quinqueradiata)

SUMMARY: Laboratory-hatched juvenile yellowtails (mean fork length, 9.3 cm) were reared for 2 months in two groups on different kinds of food, mysid and squid in one group and fish in the other, and the gustatory neural responses to seven chemicals (adenosine-5'-monophosphate, alanine, arginine, betaine, proline, tryptophan, and valine) were recorded in fish before and after the 2-month rearing period. Large variances in the responses to some chemicals were noticed in the juveniles before the rearing experiment. Mann–Whitney U -tests on the neural responses indicated significant changes in the magnitude of the responses to valine and some other chemicals relative to that for proline or tryptophan between the pre- and the two post-rearing groups. No significant differences in the response magnitude for the seven chemicals were observed for the two post-rearing groups suggesting that the response changes during the 2-month rearing might have been intrinsic and not due to specific food items in the diet. The dose–response relationship for some chemicals was also examined in the juveniles before and after the 2-month rearing. A slight lowering of threshold was noticed for alanine and valine after the rearing. Data on the responses of wild yellowtails were in support of the changing responsiveness of gustatory receptors during development of juvenile yellowtails.     

Role of homestead forests in household economy and factors affecting forest production: a case study in southwest Bangladesh

Empirical information regarding the role of homestead forests in household economy is essential in understanding the importance of these resources. Identification of the factors that affect homestead forest production and understanding forest owners' attitudes toward key forest management issues have great significance in making appropriate policy responses to manage these resources on a sustainable basis. In Bangladesh, homestead forests are claimed to play an important economic role in rural livelihoods, but no reliable quantitative information exists. This study was undertaken to investigate the role of homestead forests in the household economy, examine if forest production and income vary across landholding size classes, to explore the relationships of homestead forest production with species richness, education level, and household size, and to assess the attitude of homestead forest owners toward key forest management issues. Results show that homestead forests contribute 15.9% of the household income and generate 51.4 man-days of employment per household per year. Production of homestead forests significantly varies across landholding size classes. It was observed that forest production depends significantly on species richness of homestead forests and the education level of forest owners. However, no such relationship was found between forest production and household size. The study revealed that farming families depend more on forest income than nonfarming families. Attitudes of forest owners toward key forest management issues differ significantly across landholding size classes. For example, although the majority of the forest owners prefer fruit species to timber species, the percentage of respondents decreased as the landholding size class increased, while the opposite trend was observed for timber species. The findings of this study suggest that diversification of forests and extension of education amongst forest owners would improve forest production. Furthermore, forest policy should address the concerns of the forest owners in different landholding classes and focus on their specific requirements to enhance sustainable forest management.     

Carcinogen-induced Thyroid Proliferative Lesions in Wistar Hannover GALAS Rats with Thyroid Dysplasia

Incidences and morphological features of thyroid proliferative lesions induced by carcinogens in Wistar Hannover GALAS rats (GALAS rats) showing normal growth with or without thyroid dysplasia were examined. All thyroid tissue samples were obtained from our recently conducted study using male GALAS rats treated with 5 carcinogens according to the medium-term multiorgan carcinogenicity bioassay protocol (called DMBDD treatment). In the DMBDD-treated rats, thyroid dysplasia was found in 9 out of 114 rats. Follicular cell adenomas were found in 5 out of 9 rats with thyroid dysplasia and in 7 out of 105 rats without thyroid dysplasia. The incidence of adenoma was significantly increased in rats with thyroid dysplasia (55.6%) compared with that in rats without thyroid dysplasia (6.7%). Adenomas in rats with thyroid dysplasia were observed as single or multiple nodules, well demarcated and composed of variously sized vacuolated cells or unvacuolated cells. These histopathological features and staining profiles of luminal colloid for PAS and thyroglobulin, together with PCNA-positive cells, were fundamentally similar to those of rats without thyroid dysplasia. On the other hand, the luminal colloid in adenomas of rats with thyroid dysplasia had a tendency to be poorly stained for T(4) compared with that of rats without thyroid dysplasia. From these findings, it appears that dysplastic thyroids of rats showing normal growth are more sensitive to carcinogens than normal thyroids. In addition, the morphological features of carcinogen-induced thyroid proliferative lesions in GALAS rats with thyroid dysplasia were fundamentally similar to those of rats without thyroid dysplasia, except for the vacuoles and T(4) staining profile.     

Minimum alveolar concentration for blunting adrenergic responses (MAC-BAR) of sevoflurane in dogs

It is well known that heart rate or arterial blood pressure may increase in response to surgical stimulation despite the absence of a purposeful movement. However, there is limited information regarding anesthetic requirement for blunting adrenergic response in dogs. This study was designed to compare the minimum alveolar concentrations of sevoflurane required to prevent autonomic response (MAC-BAR) and purposeful movement (MAC) in dogs. Sevoflurane MAC-BAR and MAC were determined in 5 beagle dogs by judging dogs' response to a noxious electrical stimulus applied to the gingiva. The sevoflurane MAC-BAR was significantly higher than MAC (3.33 ± 0.48 vs 2.10 ± 0.28%, P=0.005). These results suggested that autonomic responses occurred at sevoflurane anesthetic concentrations at which purposeful movements were absent.