乙硫氨酯选矿药剂合成新工艺研究

乙硫氨酯是十分重要的一类有色金属浮选捕收剂，对硫化铜矿的浮选有很好的成效。随着选矿企业对新型酯类药剂乙硫氨酯的逐步认可，国内外选矿厂对乙硫氨酯的需求量越来越大。国内生产厂家普遍采用的氯乙酸法生产乙硫氨酯所产生的大量副产物巯基乙酸钠因为市场需求量过小，严重制约了乙硫氨酯的产能释放。用自制的黄原酸苄基酯与一乙胺反应合成了乙硫氨酯和苄基硫醇两个产品，所得产品为两个独立的产品，无需进行蒸馏分离，经辽宁某铜矿矿石浮选验证，所合成的乙硫氨酯与氯乙酸法合成的产品浮选效果相当。而另一产物苄基硫醇可用作有机合成中间体和农药用原料，为乙硫氨酯的合成提供了一个新思路。     

紫外固化金属涂料用丙烯酸环氧酯制备及应用

以双酚A型环氧树脂与丙烯酸反应,合成用于紫外光固化金属涂料的丙烯酸环氧酯低聚物．研究了反应温度、催化剂、阻聚剂、投料比等因素对合成反应的影响．通过正交试验确定了丙烯酸环氧酯低聚物合成反应的最优条件．合成产物的红外光谱分析结果表明,光敏性的碳碳双键基团被引入到环氧树脂结构中,涂层固化完全．用合成出的低聚物制备了紫外光固化涂料,初步研究了此涂料对钢铁基材的防护性能．研究结果表明,涂层具有良好的耐化学腐蚀性及防护性能．     

二氯异氰尿酸钠的研制

异氰尿酸的氯化产品由美国化学家Chattowax和Wadmore于 190 2年首次合成 ,产品在工业和民事领域得到了广泛应用。尽快地研究开发这类产品已是当务之急。本文介绍了二氯异氰尿酸钠的试验过程、试验结果以及结果讨论等方面内容     

n-NdF3制备、表征及对尿酸的电化学检定

采用水热法合成稀土纳米材料NdF₃（n-NdF₃）,并用于构建生物传感器实现对尿酸的电化学检定.首先利用扫描电子显微镜（SEM）、X-射线衍射（XRD）以及能谱分析（EDS）对所制备的材料进行结构表征和组成分析,并通过循环伏安（CV）和电化学阻抗（EIS）技术对修饰过程进行表征.详细研究尿酸在不同电极上的电化学行为.随后将生物传感器用于对多巴胺和尿酸的同时检定时,结果表明,在两者共存的情况下出现分离效果较好的2个氧化峰.这说明所制备的n-NdF3对尿酸具有高的灵敏性和好的催化活性.生物传感器能用于对多巴胺和尿酸的同时检定.      

用于制备浮选捕收剂苯甲酰基硫氨酯的中间体苯甲酰基异硫氰酸酯的合成研究

苯甲酰基硫氨酯是一种新型的硫化矿浮选捕收剂，它的合成方法大多是使用中间体苯甲酰基异硫氰酯与醇反应合成。介绍了以硫氰酸钠与苯甲酰氯为原料，以水为溶剂，采用组合催化剂DP，催化合成苯甲酰基异硫氰酸酯的方法。该方法获得的中间体苯甲酰基异硫氰酸酯产品纯度、收率等指标较为理想。该合成方法较有机溶剂法具有反应速度快、反应条件温和、工艺简单、成本低等优点，其合成中间体可以直接用于捕收剂苯甲酰基硫氨酯的制备。     

甲基磺酸亚铈催化合成柠檬酸三(2-乙基)己酯的研究

合成了甲基磺酸亚铈,研究了以甲基磺酸亚铈催化柠檬酸和2-乙基己醇的酯化反应,考察了反应温度、催化剂用量、醇酸摩尔比等因素对反应结果的影响,对合成的产品进行了红外光谱分析.实验结果表明,甲基磺酸亚铈催化合成柠檬酸三(2-乙基) 己酯的最佳反应条件为:n (2-乙基己醇):n(柠檬酸)＝3.60:1,催化剂用量0.25% (以酸的物质的量计),反应温度120℃～130℃,负压操作.在最佳反应条件下,柠檬酸三(2-乙基)己酯收率在98.0%以上.反应结束后,催化剂通过简单的相分离即可重复使用.甲基磺酸亚铈重复使用5 次后,其催化活性无明显下降,产品收率仍可达到90%以上.     

尿素对前驱物及氮化铝粉末粒度形貌的影响

以硝酸铝、葡萄糖为原料,用碳热还原法制备氮化铝粉末,研究尿素对前驱物及其氮化反应产物的组成和显微形貌的影响,发现尿素不仅可以影响前驱物的组成和显微形貌,还对氮化反应产物的显微形貌有重要影响。在溶液里添加尿素后,它与硝酸铝发生了低温燃烧合成反应,生成了比表面积高的泡沫状前驱物,该过程中碳由于燃烧损失较大,在没有添加尿素的溶液中,没有燃烧反应发生,碳的损失小,生成的前驱物团聚现象严重,比表面积低,两种前驱物保留了前驱物的形貌特征,对于不添加尿素合成的前驱物,在其氮化反应后所生成的氮化铝粉末板结严重;而添加尿素合成的前驱物的氮化反应产物是由球形颗粒组成的软团聚体。利用XRD,SEM等分析方法对粉末进行了表征。     

钛在尿素生产中的应用

1材料使用简介尿素是一种中性高效氮肥，又是重要的工业原料．尿素合成反应按下式分两步进行：zwll。＋CO、xll－AfXIWh氨基甲酸铁N‘H：vvvNHrtNHapNH。＋HP尿素氨基甲酸饮转化成尿素的反应是不完全的，需要从含有尿素、过五氢和水的混合物溶液中分离出去．氨基甲酸镀是一种强腐蚀性介质，对使用的材料提出了相应的要求．目前，国内外尿素工厂广泛使用AISI316L型不锈钢作为主要注腐蚀材料，但使用效果不甚满意，主要存在以下几个问题．（l）使用温度不能过高316L作村里的尿素合成塔使用温度在185℃～190℃左右，如果长期趋温使用…     

硫氨酯捕收剂的制备及浮选性能

为解决硫氨酯捕收剂制备过程中副产品处理困难、存在污染等问题，设计了四种新工艺制备乙硫氨酯（IPETC），分别联产对叔丁基苄基硫醇（BBSH）、苄基三硫代碳酸盐（BTTC）、苄硫基乙基黄药（SBEX）、二苄基二硫醚。在优化的合成工艺条件下，合成IPETC联产BBSH，得到含IPETC和BBSH的复合捕收剂，其中IPETC的质量分数为51%，BBSH的质量分数为41%，IPETC和BBSH的收率达到95%；合成IPETC联产BTTC，IPETC和BTTC的收率分别达到94%和95%，纯度分别为91%和82%；合成IPETC联产SBEX，IPETC的收率和纯度分别达到89%和95%，SBEX的收率和纯度分别为93%和91%；合成IPETC联产二苄基二硫醚，IPETC的收率和纯度分别达到93%和92%，二苄基二硫醚的收率和纯度分别达到95%和94%。考察了制备的复合捕收剂（IPETC与BBSH）对铜钼矿的浮选性能，结果表明，复合捕收剂对铜钼矿表现出良好的捕收性能。联产的新型捕收剂SBEX、BTTC对黄铜矿的捕收力略强于异丁基黄药，对黄铁矿具有较好的选择性，可替代异丁基黄药浮选硫化铜矿。红外光谱和X射线光电子能谱分析结果表明，SBEX、BTTC与黄铜矿作用时，捕收剂分子中的C=S和C—S与矿物表面的金属Cu作用，生成捕收剂与铜的表面络合物吸附在黄铜矿的表面。      

相转移催化合成乙氧羰基异硫氰酸酯

乙氧羰基异硫氰酸酯是一种非常重要的有机合成中间产物,可用于合成多种乙氧基烷基类硫氨酯及多种杂环化合物。本文叙述了用水做溶剂情况下,以某复合催化剂催化合成乙氧羰基异硫氰酸酯的方法,并对反应温度进行了具体的研究试验。特别研究了催化剂对反应时间及产率的影响,探讨了溶剂对反应的影响。在催化及低温条件下,工业合成乙氧羰基异硫氰酯的方法,达到了提高产品质量和降低催化剂污染的目的。     

Phagocytotic activity of macrophages separated from corpus lutea of pseudopregnant rabbits

Isocyanates are used extensively in the polyurethane industry. Pulmonary and dermal sensitization resulting from exposure to diisocyanates has frequently been reported, but the potential effects of polyisocyanates on health are less well known. Thus, since 1978, occupational exposure limits have been established for diisocyanates only. Nevertheless, respiratory diseases and dermatitis have been reported in the polyurethane industry after accidental isocyanate contact during spills or splashes. The aim of this experimental work was to assess the dermal hypersensitivity of guinea pigs to some polyisocyanate prepolymers by means of a well-conducted standard predictive Buehler test. Our results showed that dicyclohexylmethane 4,4'-diisocyanate (HMDI), toluylene 2,4-diisocyanate (TDI), TDI adduct triol, TDI isocyanurate, 1,6-hexamethylene diisocyanate (HDI), HDI isocyanurate, HDI biuret and isophorone diisocyanate (IPDI) induced dermal sensitization while IPDI isocyanurate did not. In conclusion, the dermal hypersensitivity of guinea pigs to some polyisocyanates was similar to those of their corresponding monomers except for IPDI isocyanurate, suggesting that the results from diisocyanate monomers could not be a valuable approach for the detection of the sensitization potency of the corresponding prepolymers.     

Urea kinetics in humans at two levels of exercise intensity

A primed constant infusion of [15N2]urea was used to quantify the response of urea production to exercise at 40 and 70% maximal oxygen consumption on a treadmill. Total urea production, urea production from recycled N, urea production from nonrecycled N, and urea N recycled back into body protein were calculated. Most components of urea kinetics were unaffected by exercise at either intensity. The rate of urea reincorporated into protein was significantly increased during exercise and recovery at both levels of exercise. We conclude that exercise does not stimulate urea production but that there may be an accelerated reincorporation of urea N back into body protein.     

RNA editing of the barley (Hordeum vulgare) mitochondrial ATP synthase subunit 9

1. Single Comb White Leghorn adult cockerels were fed on 50 g/kg protein diet, 200 g/kg protein diet or 50 g/kg protein diet plus urea and in vitro ammoniagenesis from urea and uric acid in the caeca was determined. 2. Four-fold protein intake caused about 4.6-fold increase in caecal ammonia production from urea (P < 0.05), and tended to increase it from uric acid as compared with 50 g/kg protein-fed birds. 3. Dietary urea significantly increased caecal ammonia production from urea and uric acid by about 2 and 3 times as much as those of control birds, respectively (P < 0.05). 4. It is concluded that increased protein intake and the feeding of urea are able to induce ammoniagenesis from urea and uric acid in the caeca of fowls.     

Electrophysiological elucidation of pathways of intrinsic horizontal connections in rat visual cortex

In single pass perfused rat liver, rapid osmotic water shifts across the plasma membrane in response to hyperosmolar urea were followed by monitoring liver mass and transient concentrating or diluting effects on Na+ concentration in effluent perfusate. Sudden addition or removal of hyperosmolar urea (200mM, resulting in a step change of the perfusate osmolarity from 305 to 505 mosmol/l) had little effect on liver mass or Na+ activity in the effluent perfusate, suggesting that urea equilibrated at a rate similar to that of water across the liver plasma membrane. When, however, phloretin (0.2mM) was present, sudden addition (removal) of urea (200mM) induced within seconds a marked and transient decrease (increase) of both liver mass and effluent Na+ concentration, suggestive of transient osmotic water shifts out of/into the cells. Although to a lesser extent, comparable effects were induced when urea was added/removed in the presence of the phloretin-related phenol compounds 2,4,6-trihydroxyacetophenone (5mM) and 2,4,5-trihydroxybutyrophenone (5mM). Phloretin-induced inhibition of urea export from livers preloaded with [14C]urea was reversible, and no saturation of urea transport was found at concentrations up to 200mM. In contrast to [14C]urea transport, [3H]water transport across the plasma membrane was not affected by phloretin. The data indicate that urea export across the hepatocyte plasma membrane is almost as fast as water export. The urea transport mechanism is sensitive to phloretin and other phenol compounds, works with high capacity and is distinct from the water-transporting system. The regulation of this putative transport mechanism and its relevance for hepatic nitrogen metabolism remain to be established.     

Active sodium-urea counter-transport is inducible in the basolateral membrane of rat renal initial inner medullary collecting ducts

Rat inner medullary collecting ducts (IMCD3s) possess a luminal Na+-dependent, active urea secretory transport process, which is upregulated by water diuresis. In this study of perfused IMCDs microdissected from base (IMCD1), middle (IMCD2), or tip (IMCD3) of the inner medulla, we tested whether furosemide diuresis alters active urea transport. Rats received furosemide (10 mg/d s.c. for 3-4 d) and were compared with pair-fed control rats. Furosemide significantly decreased urine osmolality and urea clearance, and increased blood urea nitrogen. IMCD3s from furosemide-treated rats had significantly lower rates of active urea secretion than IMCD3s from control rats. IMCD2s showed no active urea transport in control or furosemide-treated rats. IMCD1s from control rats had no active urea transport, but IMCD1s from furosemide-treated rats expressed significant rates of active urea reabsorption. In IMCD1s, this active urea reabsorptive transport process was inhibited by: (i) 0. 25 mM phloretin (bath); (ii) 1 mM ouabain (bath); and (iii) replacing bath Na+ with NMDG+; it was stimulated by 10 nM bumetanide (bath). In summary, we found that furosemide decreased active urea secretion in IMCD3s and induced active urea reabsorption in IMCD1s. The new Na+- dependent, active urea reabsorptive transport process may be a basolateral Na+-urea antiporter.     

Milk urea nitrogen as a tool to monitor the protein nutrition of dairy cows

The relationship between protein nutrition and milk urea N was investigated in three experiments with a total of 125 cows. After 4 wk of pretreatment, cows received 1 of 13 diets with different ratios of protein to energy for 16 wk. Milk was sampled individually for urea analyses during pretreatment and during wk 1, 5, 10, and 15 of treatment. Results were compared with N losses estimated from rumen fermentation and with N losses of metabolic origin. The mean milk urea N concentration was 12.6 mg/100 ml of milk (range, 9.0 to 18.3 mg). For bulk samples especially, the rumen efflux of crude protein intake was the main determinant of the variation in milk urea N (r2 = 0.81; residual SD = 1.1). However, N losses from the rumen explained only about 50% of the variation in the milk urea N content of samples from individual cows. The N losses of metabolic origin, which, in these experiments, were responsible for 47 to 100% of urinary N losses, were not related to milk urea N. Results showed that regular measurement of milk urea N in bulk samples can be used to monitor N losses from rumen fermentation. However, the value does not give an indication of the efficiency with which the absorbed protein is utilized.     

Refolding of urea-denatured tubulin: recovery of nativelike structure and colchicine binding activity from partly unfolded states

Tubulin unfolding in urea proceeds via the formation of a partially unfolded intermediate state, stable in 2 M urea, that unfolds further in higher urea concentrations. The intermediate state had spectroscopic properties reminiscent of a molten globule and negligible colchicine binding activity. Refolding of totally unfolded tubulin in 8 M urea yielded an intermediatelike state characterized by partial burial of tryptophans and partial recovery of secondary and tertiary structures, although colchicine-binding activity of the protein was not regained. Further folding of this intermediatelike state, toward the native conformation, with respect to both structural and functional parameters did not occur. However, a significant percentage of colchicine binding activity and nativelike tertiary structure was recovered when refolding was initiated from partially denatured protein samples, viz., from <1.2 M urea. Thus, although high concentration of urea induced loss of structure and activity was irreversible, the conformational changes induced in restricted regions of tubulin by lower concentrations of urea, which are probably crucial for its various functional properties, could be reversed.     

Plasma urea in hypertensive patients

The annual increase in plasma urea was measured in 253 hypertensive patients. On average there was a significant increase in plasma urea with time which did not depend on the sex of the patient or the type of hypertension. It did, however, depend on the initial level of plasma urea. A table giving the upper limits for expected annual increment may prove useful in clinical assessment. The relation between plasma urea and presenting blood pressure and age was examined in 1217 patients seen at the Hammersmith Hospital hypertension clinic from 1952 to 1967. The plasma urea was significantly related to both age and diastolic and systolic blood pressure. It was higher in men than in women up to 60 years of age, but not above that age, and it increased with presenting mean blood pressure in both sexes, but the increase was greater in men. There was a quadratic relation between age and plasma urea in both men and women. In both sexes the plasma urea increased between the ages of 60 and 80.     

Treatment with crystalline ultra-pure urea reduces the aggregation of integral membrane proteins without inhibiting N-terminal sequencing

We have demonstrated that N-terminal sequencing can be performed successfully despite boiling protein samples in the presence of urea under precise conditions, before loading them onto SDS-PAGE and transfer to polyvinylidene difluoride membrane. Using myoglobin as a test protein, we found that its ability to undergo N-terminal sequencing was not affected by the presence of urea provided "ultra-pure" urea was used. Consistent with this result, we verified that urea did not carbamylate myoglobin since its molecular mass was measured by mass spectrometry after electroelution of the protein band from the gel. These observations are useful for the study of integral membrane proteins, in particular to study their topology from proteolysis experiments, since heating in the presence of urea before SDS-PAGE reduces membrane protein aggregation [Soulié, S., Mo/ller, J.V., Falson, P., and le Maire, M. (1996) Anal. Biochem. 236, 363-364]. We show that the sequencing yield of a hydrophobic peptide from reticulum Ca2+-ATPase was more than doubled in the presence of urea in accord with the quantification of the Coomassie Blue staining of the gel and of the amount present on the polyvinylidene difluoride membrane. For three peptides of the gastric H+K+-ATPase, the sequencing yield after urea treatment increased almost threefold.     

Purification by column chromatographies of beta-amyloid precursor proteins and their association with other 95 kDa protein in rat brain

For verifying catabolic states in insulin-dependent patients and dogs the method estimating urea production rates with 13C and with doubly 15N labeled urea, respectively, has been established. For a fast steady state of urea tracer dilution, a prime of 600 times the continuous infusion rate had to be injected. Urea was isolated from plasma samples by protein precipitation and cation exchange chromatography with a consecutive derivatization of the dried urea fraction (trimethylsilyl derivatives). The masses of the fragment ions m/z 189 (14N14N), 190 (14N15N) and 191 (15N15N) urea are monitored to estimate the [15N2] urea frequency in the overall body urea pool in mol percent excess (MPE). 1 to 15 ng of derivatized urea were measured efficiently. An excellent correlation between expected standard and measured MPE (r = 0.9977) was achieved from solutions containing 1 to 7% [15N2]urea. The interassay coefficient of variation amounted to < 10% for a [15N2]urea portion of > or = 3%. Normoglycemic diabetic patients who were treated with insulin overnight showed significantly higher urea production compared to healthy controls (9.22 +/- 2.07 vs. 5.4 +/- 0.32 mumol.kg-1.min-1; p < 0.05). Measurements in chronic diabetic dogs proved an increased rate of amino acid catabolism (+20% urea production) in systemic versus portal application of insulin in paired studies. This increased nitrogen load in diabetics may accelerate progression of diabetic nephropathy. Thus, the established stable isotope technique may serve as a sensitive and useful indicator of amino acid catabolism in clinical and experimental research.