析定性分析化学实验中的“异常”现象

定性分析化学实验是分析实验的重要组成部分,它涉及到的鉴定反应较多,其大部分都具有灵敏、快速之特点.其操作一般采用半微量操作技术.因此,实验中介质变化或是外界环境影响,都有可能引起实验现象'异常'.为了在有限的时间内顺利地完成实验任务,也为了避免错误结论,本文就下述几个实验在正常操作情况下出现的'异常'现象作一简单地分析与阐述,以供实验时参考.

全封闭式NO制取和性质实验

全封闭式ＮＯ制取和性质实验湖北宜昌市葛洲坝一中（４４３００２）周柏洲，李广萍实验原理：１．运用排水集气原理。在简易启普发生器里用钢片与稀硝酸反应制取并贮存ＮＯ．２．运用气体物质分子数减少，庄强降低的原理，将ＮＯ自动导入另一密闭的空容器。内，使其氧化，...

Effects of oxymatrine on experimental hepatic fibrosis and its mechanism in vivo

AIM: Hepatic fibrogenesis has close relation with hepatic stellate cells (HSC)and tissue inhibitors of metalloproteinase (TIMP). Oxymatrine (OM) is a kind of Chinese herb that is found to have some effects on liver fibrosis. We aimed to determine the effects of OM on hepatic fibrosis and explore the possible mechanism. METHODS: Thirty-two rats were randomly divided into four groups; 16 were used to develop hepatic fibrosis by carbon tetrachloride (CCI4) and treated with or without OM, and 16 were used as controls. The expression of tissue inhibitor of metalloproteinase-1 (TIMP-1) and α-smooth muscle actin (α-SMA) in the livers of rats was detected by immunohisto-chemical assay. Liver pathology was determined by H&E staining and reticulum staining. RESULTS: In CCl4-injured rats, the normal structure of lobules was destroyed, and pseudolobules were formed. Hyperplasia of fibers was observed surrounding the lobules. While the degree of fibrogenesis in liver tissues was significantly decreased in those rats with OM-treatment compared with those without OM treatment. The pseudolobules were surrounded by strong, multi-layer reticular fibers, which netted into pseudolobules in CCl4-injured rats, however, there was a significant decrease in reticular fibers in OM-treated rats. The expression of TIMP-1 in hepatic cells was weak in control groups, but strong in CCl4-injured groups, however, the expression of TIMP-1 was significantly inhibited by OM (F = 52.93, P<0.05). There was no significant change in the expression of α-SMA between CCl4-injured rats with or without OM treatment (F= 8.99, P>0.05). CONCLUSION: OM effectively inhibits CCl4-induced fibrogenesis in rat liver tissues, probably by reducing the expression level of TIMP-1.

Experimental and clinical evidence of antioxidant therapy in acute pancreatitis

Oxidative stress has been shown to play an important role in the pathogenesis of acute pancreatitis (AP). Antioxidants, alone or in combination with conventional therapy, should improve oxidative-stress-induced organ damage and therefore accelerate the rate of recovery. In recent years, substantial amounts of data about the efficiency of antioxidants against oxidative damage have been obtained from experiments with rodents. Some of these antioxidants have been found beneficial in the treatment of AP in humans; however, at present there is insufficient clinical data to support the benefits of antioxidants, alone or in combination with conven-tional therapy, in the management of AP in humans. Conflicting results obtained from experimental animals and humans may represent distinct pathophysiological mechanisms mediating tissue injury in different species. Further detailed studies should be done to clarify the exact mechanisms of tissue injury in human AP. Herein I tried to review the existing experimental and clinical studies on AP in order to determine the efficiency of antioxidants. The use of antioxidant enriched nutrition is a potential direction of clinical research in AP given the lack of clues about the efficiency and safety of antioxidant usage in patients with AP.

Development and Lubricating Properties of Rolling Oil for Stainless Steel Cold Rolling

Appropriate base oils and homologous additives such as extreme pressure and anti-wear agents,oiliness agents and antioxidants were selected,and experiments testing the compatibility performance between additive,base oil and other components were carried out to develop the SK and SD series of rolling oils for cold rolling of stainless steel.The developed oils were used in the stainless steel cold rolling lubrication experiments,and were successfully applied in the actual cold rolling operation of stainless steel.Compared with a foreign product,the tribological properties,the thermal oxidation stability,and the rolling lubrication performance of the developed stainless steel cold rolling oils were studied.Test results showed that the tribological properties of the thereby developed rolling oils and the reference one were almost at the same level,and to some extent the performance of rolling was even better than the foreign product,at the same time the stainless steel sheet could retain its well annealed performance.Meanwhile,within a certain range,the lubrication of the rolling oil became better as its viscosity increased at the same level of saponification value,which could provide a lower friction coefficient,so that a higher maximum reduction ratio of the rolled piece through a constant roll gap and a minimum thickness could be secured.Also,similar phenomena appeared as the saponification value increased at a same viscosity level of the rolling oils.

Experimental and Modeling Study on de-NO_x Characteristics of Selective Non-catalytic Reduction in O_2/CO_2 Atmosphere

An experimental study of thermal de-NOx using NH3 as reductant in 02/C02 atmosphere with the effect of S02 and different additives was performed in a drop tube furnace. Results show that the optimum temperature win- dow is 841-1184 ℃, and the optimum reaction temperature is about 900 ℃ with a de-NOx efficiency of 95.4%. A certain amount of S02 has an inhibiting effect on NO reduction. The effect of additives, including Na2C03, C2H5OH and FeCI3, on NO reduction by NH3 is also explored. The addition of Na2CO3 and FeCI3 is useful to widen the tem- perature window and shift the reaction to lower temperature for the efficiency is increased from 30.5% to 74.0% and 67.4% respectively at 800 ℃. Qualitatively, the modeling results using a detailed kinetic modeling mecha- nism represent well most of the process features. The effect of Na2CO3, C2H5OH and FeCI3 addition can be reproduced well by the Na2C03, C2H5OH and Fe（CO）5 sub-mechanism respectively. The reaction mechanism analysis shows that the effects of these additives on NO reduction are achieved mainly by promoting the produc- tion of OH radicals at lower temperature.

Experimental study on performance that carbon dioxide inhibits coal oxidation and spontaneous combustion

Adopting oil-bath temperature programming experiment and gas chromatography, CO2＇s inhibitory performance on spontaneous combustion of Tingnan Coal Mine sample was analyzed. Through temperature rise rate test experiment, the accuracy, stability and reliability of the improved oil-bath temperature programming system applied in this experiment was proved to be superior to the traditional system. Spontaneous combustion characters parameters test of coal sample in pure air was carried out with this system and offered comparison standard for research in next stage. Temperature programming to coal sample was further conducted in oil-bath with different concentration of CO2. Testing results are compared with parameters of concentration of CO, O2, temperature, CO generation rate and O2 consumption rate tested and calculated in previous experiment in pure air. Methods of proportioning between concentration of CO and O2, CO concentration and temperature, CO generation rate and O2 consumption rate were applied to eliminate obstructions from certain external factors such as inlet of CO2; meanwhile influences of CO2 of different concentrations to coal oxidation and spontaneous combustion were investigated. Also CO2 inhibition technique was used in spontaneous combustion prevention in workface No. 106 of Tingnan Coal Mine, data collected from which indicate that CO2 performs well in inhibiting coal oxidation and spontaneous combustion.

Antioxidative potential of a combined therapy of anti TNFα and Zn acetate in experimental colitis

AIM:To evaluate whether combination therapy with antitumour necrosis factor α (TNFα) antibody and Zn acetate is beneficial in dextran sodium sulphate (DSS) colitis.METHODS:Colitis was induced in CD1-Swiss mice with 5% DSS for 7 d.The experimental mice were then randomised into the following subgroups:standard diet + DSS treated (induced colitis group);standard diet + DSS + subcutaneous 25 μg anti-TNFα treated group;Zn acetate treated group + DSS + subcutaneous 25 μg anti-TNFα;standard diet + DSS + subcutaneous 6.25 μg anti-TNFα treated group and Zn acetate treated group + DSS + subcutaneous 6.25 μg anti-TNFα.Each group of mice was matched with a similar group of sham control animals.Macroscopic and histological features were scored blindly.Homogenates of the colonic mucosa were assessed for myeloperoxidase activity as a biochemical marker of inflammation and DNA adducts (8OH-dG) as a measure of oxidative damage.RESULTS:DSS produced submucosal erosions,ulcers,inflammatory cell infiltration and cryptic abscesses which were reduced in both groups of mice receiving either anti-TNFα alone or combined with zinc.The effect was more pronounced in the latter group (vs Zn diet,P < 0.02).Myeloperoxidase activity (vs controls,P < 0.02) and DNA adducts,greatly elevated in the DSS fed colitis group (vs controls,P < 0.05),were significantly reduced in the treated groups,with a more remarkable effect in the group receiving combined therapy (vs standard diet,P < 0.04).CONCLUSION:DSS induces colonic inflammation which is modulated by the administration of anti-TNFα.Combining anti-TNFα with Zn acetate offers marginal benefit in colitis severity.

A Fully Flexible Potential Model for Carbon Dioxide

A fully flexible potential model for carbon dioxide has been developed to predict the vapor-liquid coexistence properties using the NVT-Gibbs ensemble Monte Carlo technique(GEMC).The average absolute deviation between our simulation and the literature experimental data for saturated liquid and vapor densities is 0.3% and 2.0%,respectively.Compared with the experimental data,our calculated results of critical properties(7.39 MPa,304.04 K,and 0.4679 g?cm-3) are acceptable and are better than those from the rescaling the potential parameters of elementary physical model(EPM2).The agreement of our simulated densities of supercritical carbon dioxide with the experimental data is acceptable in a wide range of pressure and temperature.The radial distribution function estimated at the supercritical conditions suggests that the carbon dioxide is a nonlinear molecule with the C O bond length of 0.117 nm and the O C O bond angle of 176.4°,which are consistent with Car-Parrinello molecular-dynamics(CPMD),whereas the EPM2 model shows large deviation at supercritical state.The predicted self-diffusion coefficients are in agreement with the experiments.

Nitric oxide-releasing aspirin but not conventional aspirin improves healing of experimental colitis

AIM:To determine the effect of non-selective cyclooxygenase (COX) inhibitors,selective COX-2 inhibitors and nitric oxide (NO)-releasing aspirin in the healing of ulcerative colitis.METHODS:Rats with 2,4,6 trinitrobenzenesulfonic acid (TNBS)-induced colitis received intragastric (ig) treatment with vehicle,aspirin (ASA) (a nonselective COX inhibitor),celecoxib (a selective COX-2 inhibitor) or NO-releasing ASA for a period of ten days.The area of colonic lesions,colonic blood flow (CBF),myeloperoxidase (MPO) activity and expression of proinflammatory markers COX-2,inducible form of nitric oxide synthase (iNOS),IL-1β and tumor necrosis factor (TNF)-α were assessed.The effects of glyceryl trinitrate (GTN),a NO donor,and 2-(4-carboxyphenyl)-4,5-dihydro-4,4,5,5-tetramethyl-1H-imidazolyl-1-oxy-3-oxide,onopotassium salt (carboxy-PTIO),a NO scavenger,administered without and with ASA or NO-ASA,and the involvement of capsaicin-sensitive afferent nerves in the mechanism of healing the experimental colitis was also determined.RESULTS:Rats with colitis developed macroscopic and microscopic colonic lesions accompanied by a significant decrease in the CBF,a significant rise in colonic weight,MPO activity and plasma IL-1β and TNF-α levels.These effects were aggravated by ASA and 5-(4-chlorophenyl)-1-(4-methoxyphenyl)3-(trifluoromethyl)-1H-pyrazole (SC-560),but not celecoxib and counteracted by concurrent treatment with a synthetic prostaglandin E 2 (PGE 2) analog.Treatment with NO-ASA dose-dependently accelerated colonic healing followed by a rise in plasma NO x content and CBF,suppression of MPO and downregulation of COX-2,iNOS,IL-1β and TNF-α mRNAs.Treatment with GTN,the NO donor,significantly inhibited the ASA-induced colonic lesions and increased CBF,while carboxy-PTIO or capsaicin-denervation counteracted the NO-ASAinduced improvement of colonic healing and the accompanying increase in the CBF.These effects were restored by co-treatment with calcitonin gene related peptide (CGRP) and NO-ASA in capsaicin-denervated animals.CONCLUSION:NO-releasing ASA,in contrast to ASA,COX-1 inhibitors,and SC-560,accelerated the healing of colitis via a mechanism involving NO mediated improvement of microcirculation and activation of sensory nerves releasing CGRP.

Experimental Research on Coke Wastewater Treatment by Hybrid Biological Reactor

Phase hybrid biological reactor （HBR） was used in treating coke wastewater by adding submerging fiber-ball fillers in suspended growth activated sludge. The optimum operation parameters for the highest performance were determined. It was found that the hybrid biological reactor worked well for the coke wastewater treatment in terms of Chemical Oxygen Demand （COD）, NH4＋ -N and other refractory organic compounds removal efficiencies. Compared with conventional activated sludge system, the removal rate of COD and NH4＋ -N and the nitrating rate were higher and more stable in the hybrid biological reactor. COD of effluent was less than 75 mg/L and the removal rate of COD and NH4＋ -N could be up to 95.0% and 92.5% when COD of influent and NH4＋ -N were less than 700 mg/L and 300 rag/L, respectively. In this way, the quality of effluent concentration could reach the first class of integrated wastewater discharge standard （GB8978-1996） （COD ≤100 mg/L）.

Experimental study on zero excess sludge production process with ozonation unit in MBR process

In order to investigate the influence factors of zero excess activated sludge (EAS) process by ozonation, a 100 L membrane bioreactor coupled with a sludge ozonation unit (MBR-SO) was performed for 80 d without EAS wasting. Some mathematical models were developed to elucidate the relationship between process parameters and the operating effects. It is considered that the sludge lysing ratio (ξ), produced COD per unit mass lysed MLSS (η), observed sludge yield coefficient (Yobs) and intrinsic yield coefficient for COD produced by lysed sludge (Y2) significantly affect the flowrate to ozonation unit (q). When q is 0.0067 times of influent flowrate (Q) and ξ is about 0.72 for each batch ozonation, a relatively stable MLSS concentration of 8168 mg/L and zero Yobs are achieved in the MBR-SO system. The calculation of sludge disintegration number indicates that the high ξ can apparently decrease the sludge amount needed for ozonation. At the same ozone dose, the low input ozone concentration and high flowrate can enhance the sludge lysing effects and a low energy consumption of 0.041 Yuan/m3 wastewater is obtained.

One-pot synthesis of cyclic aldol tetramer and ?, β-unsaturated aldol from linear aldehydes using quaternary ammonium combined with sodium hydroxide as catalysts

One-pot synthesis of cyclic aldol tetramer and α, β-unsaturated aldol from C3-C8 linear aldehydes using phase-transfer catalyst（PTC）, quaternary ammonium, combined with sodium hydroxide as catalysts was investigated. Butanal was subjected for detail investigations to study the effect of parameters. It was found that the selectivity of cyclic aldol tetramer depends greatly on the operating conditions of the reaction, especially the PTC/butanal molar ratio. The average selectivity of 2-hydroxy-6-propyl-l, 3, 5-triethyl-3-cyclohexene-1-carboxaldehyde（HPTECHCA） was 54.41% using tetrabutylammonium chloride combined with 14%（mass fraction） Na OH as catalysts at 60 ℃for 2 h with a PTC-to-butanal molar ratio of 0.09：1. Pentanal was more likely to generate cyclic aldol tetramer compared with other aldehydes under the optimum experimental conditions. Recovery of the PTC through water washing followed by adding enough sodium hydroxide from the washings was also demonstrated.

Changes of free iron contents and its correlation with lipid peroxidation after experimental spinal cord injury

Objective: To observe the dynamic changes of fre e iron contents and its relationship to the changes of lipid peroxidation after experimental spinal cord injury (SCI). Methods: Sprague Dawley rats were randomly divided into three g roups: Group A (n=6) received no operation; Group B (n=48) received only laminec tomy (sham); and Group C (n=48) received both laminectomy and traumatic injury ( SCI model). The SCI animal models were made by using an modified Allens weight -drop device (50 g.cm) on T_ 12 . Rats were sacrificed at 0.5 ,1,3,6,12,24 hours after injury. The levels of free iron involved in spinal cord segm ents at different time points were measured by bleomycin assay. The malondialdeh yde (MDA) was also measured by the thiobarbituric acid (TBA). Results: After SCI in Group C,the level of free iron showed a significant increase at 0.5 hour compared to Groups B and A,restored to th e control level at 6 h; the level of MDA was increased at 0.5 hour,peaked a t 3 hours,returned to the control level at 12 hours; the concentrations of free iron and lipid peroxidation in injured rats were significantly and positively c orrelated at 0.5 -3 hours. Conclusions: After SCI the levels of free iron are increased qu ickly and might be a major contributor to lipid peroxidation in injured spinal c ord.