一种新型浸金剂的应用试验研究

对"绿金牌"新型环保浸金剂进行了全泥炭浆提金工艺条件研究及工业应用试验。其结果表明,该"绿金牌"新型浸金药剂与氰化钠的浸出效果基本一致,工业试验中金的浸出率可以达到92%以上。对尾渣的有害性分析结果表明,该药剂的干排尾渣中氰化物含量远远低于氰化浸出工艺的干排尾渣,符合环保标准。     

Feasibility study of the new rutile extraction process from natural ilmenite ore based on the oxidation reaction

Phase relations in the Fe₂O₃-FeTiO₃-TiO₂ system were investigated by equilibrating synthetic samples in evacuated sealed quartz tubes at a temperature of 1373 K. The equilibrium partial pressure of oxygen was measured by the electromotive force (EMF) method in the temperature range of 1273 to 1373 K. The phase diagram and oxygen partial pressure diagram in the titanium-iron-oxygen ternary system were then constructed at 1373 K. Rutile extraction from natural ilmenite ore was discussed from the thermodynamic viewpoint. It is found that rutile can be produced from common natural ilmenite ores not only by the reduction as the conventional titanium-rich slag process but also by an oxidation. Then, the oxidation experiment was conducted in air using Australian ilmenite ore to obtain rutile as one of the coexistent phases. Magnetic separation and leaching experiments for synthesized pseudobrookite and reagent rutile were conducted to confirm the possibility of separation of rutile from pseudobrookite. A new rutile extraction process was then proposed.     

Molecular biological access to the chemistry of unknown soil microbes: a new frontier for natural products

Cultured soil microorganisms have provided a rich source of natural-product chemistry. Because only a tiny fraction of soil microbes from soil are readily cultured, soil might be the greatest untapped resource for novel chemistry. The concept of cloning the metagenome to access the collective genomes and the biosynthetic machinery of soil microflora is explored here.     

The sensitivity of biological tissue to ultrasound

Plasminogen activators are serine proteases which play a key role in morphogenesis and tissue remodelling. Two different molecular types, tissue-type and urokinase-type, were identified and they were postulated to play a role in neural development. The developing chick optic lobe plays a central role in processing visual information. In previous studies we demonstrated the occurrence of high levels of plasminogen activator activity in this model. The aim of the present paper is to study the temporal pattern of expression of this activity and characterize the type of plasminogen activator expressed in the developing optic lobe. Using soluble fractions derived by ultracentrifugation from Triton X-100-treated membrane fractions we measured the protease activity with a radial fibrinolytic assay. Employing different inhibitors of fibrinolytic activity and a zymographic assay, we showed that the developing optic lobe expresses only one type of plasminogen activator which corresponds to an urokinase-type of 70 kDa. Our results indicate that peaks of protease activity temporally correlate with massive neuronal migration, neurite outgrowth and synapse formation and maturation. This suggests that a plasminogen activator could play a role in these developmental events. This consistent pattern of variability strongly suggests that it is developmentally regulated and, if so, it could be a reliable parameter to study neural plastic changes induced by modifications in the environmental stimulation.     

TWIP950在某新车型前纵梁的应用可行性研究

本文对第二代AHSS典型钢种TWIP950的机械性能包括拉伸强度、n值、r值和烘烤硬化性进行了试验.采用1.5 mm厚度TWIP950替代1.6 mm厚度DC05进行轻量化设计的前纵梁正碰仿真结果表明,使用TWIP钢在减重6.25%的同时具有更佳的吸能效果.通过冲压仿真和现场试制对两种材料的冲压成形性进行了比较,结果表明TWIP950在具有更好成形性的同时也面临更大的回弹.总之,在模具设计时进行有效的回弹控制并保证钢板理想的边缘状态,TWIP950具备在前纵梁的轻量化应用可行性.     

改变药剂配方降耗增效的试验研究及生产实践

玲珑选冶厂通过改变药剂配方，降耗增效效果明显，年综合经济效益可达到１５０万元以上。     

Calibration and standardization of microwave ovens for fixation of brain and peripheral nerve tissue

BACKGROUND: The role of the inhibitory neurotransmitter gamma aminobutyric acid (GABA) in schizophrenia has previously been investigated using postmortem material. Recently, using single photon emission tomography (SPET) with the selective benzodiazepine antagonist 123I-Iomazenil as the radioligand, we have demonstrated an in vivo relationship between reduced GABAA/benzodiazepine receptor binding and the severity of positive symptomatology in schizophrenia. The present study aimed to build on this using the same in vivo scanning techniques, and relating findings to cognitive functioning. METHODS: Ten nonpsychiatric control subjects and 15 schizophrenic patients, matched for age and handedness, were scanned. A battery of neuropsychologic tests was also administered. RESULTS: Correlational analysis revealed a pattern of increased correlations between GABAA/benzodiazepine receptor binding and task performance, in the schizophrenic group compared to the control group. CONCLUSIONS: Findings are preliminary but suggest a relationship between reduced GABAA/benzodiazepine receptor binding and poorer cognitive functioning, involving memory and visual attention processes, in the schizophrenic group but not in the control group. A role for GABA in the pathophysiology of schizophrenia is suggested. Limitations of the present study and suggestions for future research are discussed.     

Feasibility study of vascular-endoscopic valvuloplasty. Using a laser and flexible endoscope

Percutaneous balloon valvuloplasty is generally accepted, but post procedural complications limit its efficacy and reduce long-term success. To eliminate these risks, the authors explored the feasibility of cardioscopy guided percutaneous laser valvuloplasty in an experimental setting. The combined working model consisted of a separate balloon tipped thin fiber optic endoscope, laser balloon catheter, and a Nd-YAG laser transmitter. A porcine pulmonary valve was used as our in vivo target of laser ablation in a beating heart. Under general anesthesia, the endoscopic catheter is delivered into the pulmonary valve area through either the internal jugular or femoral vein under fluoroscopy. Positioning the pulmonary apparatus coaxial to the endoscopic visual field by manipulation of the catheter allowed for targeting and ablation of the commissure of the pulmonary valve under endoscopic view through the balloon filled with saline solution. The ablation energy was 15-30 W, 0.5-1.0 sec, and 2,000-3,000 J total. The animal was then killed and histopathologic study of the ablated area was done. The commissure of the pulmonary valve was smoothly ablated in 4 cases, and the entire ablation procedure was successfully witnessed through endoscopy. The authors encountered some difficulty in laser targeting, limitations to the endoscopic field of vision, and difficulty in holding the position of the apparatus in the beating heart. These are the barriers to overcome for future clinical application of this procedure. However, these results indicate the clear possibility of future use of cardioscopy guided percutaneous laser valvuloplasty in a clinical setting.     

Radiofrequency volumetric tissue reduction for treatment of turbinate hypertrophy: a pilot study

BACKGROUND: Apoptosis maintains cell homeostasis. Altered apoptosis is involved in carcinogenesis. It was our aim to investigate whether reflux esophagitis may alter apoptosis in the esophageal mucosa and whether antireflux surgery may restore normal apoptosis. METHODS: Apoptosis was studied preoperatively and postoperatively in esophageal biopsies of 39 patients with various grades of reflux esophagitis and in Barrett's mucosa using the TUNEL method. Biopsies were also taken from lesions of the squamous epithelium adjacent to the Barrett's mucosa. RESULTS: Apoptosis increased with the severity of esophagitis. Apoptosis was low in Barrett's epithelium. Squamous epithelium adjacent to Barrett's mucosa showed increased apoptosis. After surgery apoptosis decreased in squamous epithelium, and it remained low in Barrett's epithelium. CONCLUSIONS: Apoptosis in reflux esophagitis may be protective against increased proliferation. Low apoptosis following antireflux surgery indicates that surgery is effective to prevent reflux-induced cell proliferation. Inhibition of apoptosis in Barrett's may promote carcinogenesis. This may not change following surgery.     

Feasibility study of CPR in the water

More than 8000 drownings occur each year in the United States alone. With the increased popularity of scuba diving for commercial and sport purposes, one would predict an increase in related deaths or accidents. Yet procedures to administer first aid are limited to mouth-to-mouth, and external cardiac compressions must await moving the victim to a firm surface. This study discusses the technique of placing a victim upon the rescuer's chest and initiating full cardiopulmonary resuscitation (CPR) immediately on the site. During emergency regulator resuscitation (E.R.R.), ventilations are administered by use of a slightly modified, factory-calibrated scuba regulator. The techniques were tested on an instrumented aquatic CPR mannequin and found to meet the published criteria for successful CPR.     

ArF-excimer laser-induced secondary radiation in photoablation of biological tissue

Secondary radiation, emitted during and after the irradiation of corneal, dermal, and dental tissue by an ArF-excimer laser (193 nm), was qualitatively and quantitatively characterized. Emission of secondary radiation was found in the range of 200-800 nm. The intensity of secondary radiation in the range of 200-315 nm (UVC and UVB) is approximately 20% of the total intensity at high laser fluences (> 2 J/cm2), and approximately 50% at moderate laser fluences (< 500 mJ/cm2); 10 muJ/cm2 in the UVC and UVB were measured at the sample surface, at fluences (< 1J/cm2) which are of relevance for clinical procedures on soft tissues. In dental tissue processing, very high fluences (> 5 J/cm2) are required. As a consequence, laser-induced plasma formation can be observed. Secondary radiation can be used as a visible guide for selective removal of carious altered tissue. The data we have found might be of assistance in estimating potential hazards for future mutagenic studies in the field.     

Post-insertion peri-implant tissue assessment: a longitudinal study

The peri-implant gingivae act as a biological barrier that prevents the ingress of plaque bacteria, oral debris, and saliva components into the internal environment of the jaw. The integrity of this barrier around a total of 163 Steri-Oss HA-coated threaded root-form implants placed in 48 patients was examined at six-month intervals over a 42-month time period, beginning at the time of final prosthetic placement. Five clinical parameters for tissue assessment were used: Mean Implant Sulcus Readings (MISR), Mühlemann Sulcus Bleeding Index (SBI), Miller's Mobility Index (MI), bone loss readings (BL), and gingival condition (GI). Bone loss and mobility were negligible throughout the 42-month study period. At six months post-insertion, 58.6% of the Mean Implant Sulcus Readings exceeded 4 mm. Gingival conditions and bleeding response also were non-ideal in a significant number of cases (52.9 and 62.1%, respectively). However, all three of these assessments later showed dramatic improvement. Patients' inability to "deplaque" their newly acquired implant prostheses effectively may be a factor contributing to the high incidence of undesirable pocket depths and non-optimal gingival appearance at the first six-month assessment point. Attainment of the necessary skills may account for the improved readings at the later evaluations.     

Modeling of intraluminal heating of biological tissue: implications for treatment of benign prostatic hyperplasia

A computer model for predicting the thermal response of a biological tissue to different intraluminal heating modalities is presented. A practical application of the model is to calculate the temperature distributions during thermal coagulation of prostate by contact heating and radiative heating. The model uses a two-dimensional axisymmetric diffusion approximation method to calculate the light distribution during radiative heating. The traditional Pennes' bio-heat equation is used to calculate the temperatures in the presence of blood flow. An implicit finite difference scheme with nonuniform grid spacings is used to solve the diffusion equation for light distribution and the bio-heat equation. Model results indicate that the radiative heating of prostate by Nd:YAG (1064 mm) and diode (810 mm) lasers can be a more effective and efficient means of coagulating a large volume of prostate, as compared to contact heating of the tissue. Blood perfusion is shown to provide a considerable heat sink as the laser exposure time is increased. Surface cooling by irrigation during the laser irradiation of tissue is shown to be an effective method for delaying tissue explosion and obtaining a large volume of coagulated tissue. The model also shows that the volume of the coagulated tissue is appreciably altered by a change in the rate of energy deposition.     

Efficient Monte Carlo simulation of confocal microscopy in biological tissue

A variance-reduction technique is described that greatly improves the efficacy of Monte Carlo simulations of reflection-mode confocal microscopy in anisotropically scattering media. The efficiency gain is large enough that the performance of confocal microscopes probing as deep as 5 scattering lengths can be simulated with a desktop computer. We use the technique to simulate the response of a true confocal microscope probing biological tissue, a problem that has been impractical to undertake by using conventional Monte Carlo methods. Our most important finding is that operation of a confocal microscope in the true confocal mode enables much more effective rejection of undesired scattered light than operation in the partially coherent mode, but the maximum probing depths of microscopes operated in either mode are similar (2-3) scattering lengths) in practice because of sensitivity limitations.     

Behavior of SCN-lesioned chipmunks in natural habitat: a pilot study

The necessity of a circadian pacemaker, the suprachiasmatic nuclei (SCN), for survival was evaluated in a population of approximately 65 wild eastern chipmunks, Tamias striatus. The research involved over 3000 h of field-work between May 1995 and October 1997 on a study site at Mountain Lake Biological Station, Virginia. The 28 chipmunks randomly designated as project animals included 10 SCN-lesioned chipmunks, 5 surgical controls (sham-lesioned), and 13 intact controls. Visual observation, live trapping, and radio telemetric tracking were used to assess 6 aspects of survival and reproduction. Upon release after surgery, every animal returned to its den site and was able to maintain its home territory. In warm months from May through October, all chipmunks were active above ground with a strictly day-active pattern. During the remaining cold months, they were normothermic but relatively torpid in their underground dens for extended periods of time. Short-term mortality for the initial 3 months included only a single intact control chipmunk; loss for the extended period from August 1995 to October 1996 was 40% for the SCN-lesioned animals, 0% for surgical controls, and 15.4% for the intact controls. Survival differences were not significant between surgical control and intact control groups but were significant (alpha = .10) between SCN-lesioned and pooled control groups. Annual body weight patterns were similar for both groups. Most individuals in both SCN-lesioned and control groups were reproductively active in the spring and fall breeding periods. Lack of major differences may be attributable to the exceptionally favorable conditions for survival such as a very abundant fall acorn crop, medium population size, and absence of heavy predation.     

Performance characteristics of a new synthetic APTT reagent

The question of whether the use of a teaching strategy employing simulation influences attitudes toward disabled persons over time was addressed in this quasi-experimental intervention study. The experimental group participated in "Sensitivity Day" which incorporated a simulation activity. A total of 77 undergraduate baccalaureate nursing students completed the Attitudes Toward Disabled Persons scale four times: presimulation, immediate postsimulation, six week delayed postsimulation and six month delayed postsimulation. In general, the nursing students had relatively positive scores on the Attitudes Toward Disabled Persons scale in each testing period. The best indicator of postsimulation attitude scores was the presimulation attitude score. Personal and prior nursing experience had no statistical effects on attitude. Improvement that was significant at p = .07 level was noted in the experimental group at the six weeks delayed postsimulation when compared with the presimulation attitude scores. This study supplies data that is useful in constructing learning activities and contributes to the body of knowledge about simulation and attitudes toward persons with disabilities.     

Polyglucosan bodies in brain tissue: a systematic study

The relation between age, sex and presence of polyglucosan bodies in the brain has been systematically studied in 64 patients who did not suffer from neurological brain disorders and in 2 cases with Lafora's disease. In the normal brain the number of polyglucosan bodies is related to increasing age. Under the age of 40, polyglucosan bodies can be found sporadically in cases without a neurological disorder, but in the cases of Lafora's disease their number is uncomparatively higher. A sex relation has not been found.     

A preliminary study of the fixation mechanism of collagen reaction with a polyepoxy fixative

A new biomaterial has been developed by fixing native collagens with a polyepoxy compound (PC) fixative. Prior studies have shown that this biomaterial has comparable properties as compared to collagen fixed with glutaraldehyde (GA) and thus has a great promise for use as an implantable bioprosthesis. The purpose of this study was to understand the mechanism of the amino acids-PC reactions in the fixation process. Bovine arteries were fixed with PC under various pH, concentration and temperature conditions as a function of fixation time. Individual amino acid components in the fresh and the fixed arteries were assayed using a Beckman amino acid analyzer to determine the degree of tanning. The denaturation temperature (Td) was also measured on each sample. Since the denaturation temperature is a direct indication of cross-linking of individual amino acids with the fixative, the difference in the degree of tanning for the same increase in Td may be indicative of the quantity of the masked, non-cross-linked amino acids. The fixation reaction data indicated that not all amino acids were cross-linked upon contacting the PC fixative. Masking appeared to be more substantial with a fixation at higher pH values.