四聚乙醛的谱学行为及燃烧特性研究

为研究四聚乙醛的燃烧特性,利用差热分析仪、红外光谱仪和光纤光谱仪测试了该物质的谱学行为。基于热谱,提出了四聚乙醛的热解反应历程及燃烧发光机理,并利用燃烧光谱予以验证。结果表明:四聚乙醛的热谱包括升华和热分解两个阶段,热解后的剩余产物为凝聚态的C。结合四聚乙醛的热解反应历程,提出了其燃烧发光机理,分析得出四聚乙醛燃烧时发出黄色火焰,这是由于凝聚态的碳燃烧产生的,燃烧火焰光谱在591.35nm处黄光区出现最大峰支持了这一结论的正确性。     

AMOPLACE treatment of intermediate-grade and high-grade malignant lymphoma: a Cancer and Leukemia Group B study

To address the question of whether complete seizure relief has a positive effect on psychosocial functioning in patients with temporal lobe epilepsy, a follow-up study was conducted at the Montreal Neurological Institute. The approach was one of "before-after" study, with focus on the successfully operated patients, those in whom complete seizure relief was obtained. The Washington Psychosocial Seizure Inventory, specifically developed and validated for use with epilepsy patients, was used for psychosocial assessments. Of 30 surgically treated patients screened for the study, 15 gained complete relief from seizures. At 1-year postoperative follow-up, they showed reductions in their problems scores on all but one of eight psychosocial scales; the average reduction ranged from 24% in Vocational Adjustment to 60% in Adjustment to Seizures. In the areas of Emotional Adjustment and Interpersonal Adjustment reductions were 37 and 48%, respectively. Among the component items, improvement was greatest in ability to concentrate and make decisions, confidence in interpersonal skills, ability to express personal opinions, and perception by others. No appreciable changes occurred in the 15 patients who did not gain complete relief of seizures; indeed, on six of the eight scales they showed a modest increase in their problem scores. This study provides evidence that complete relief from seizures leads to appreciable improvements in psychosocial well-being, manifest as early as 1-year postoperatively, in young adult patients.     

基于压缩感知子空间的时延估计算法

现有单快拍条件下子空间类时延估计算法由于降低有效带宽导致估计精确度下降,多快拍条件下压缩感知类算法由于多次采样具有相似稀疏结构也导致了性能下降。针对以上条件下2种算法鲁棒性不强的问题,提出一种在单快拍与多快拍条件下均具有较高精确度的基于压缩感知子空间的时延估计算法。该算法首先判定快拍数与多径数的关系,在快拍数大于等于多径数时通过求解谱峰的目标函数得到时延估计,在快拍数小于多径数时先重构得到改进的噪声子空间,再求解谱峰的目标函数得到时延估计。仿真结果表明,该算法在单快拍与多快拍条件下具有较高的估计精确度,与子空间类算法和压缩感知类算法相比具有更好的鲁棒性。     

Evaporative heat transfer characteristics of industrial safety helmets

Thermal discomfort is one of the major complaints from the wearers of industrial safety helmets. While studies have been reported on dry heat transfer (conduction, convection and radiation) in safety helmets, the investigation of wet heat dissipating (evaporation) properties has not been found in the literature. To evaluate experimentally the evaporative heat transfer characteristics of industrial safety helmets, a method was developed to simulate sweating of a human head on a thermal head manikin, and to use this manikin to assess the wet heat transfer of five industrial safety helmets. A thermal head manikin was covered with a form-fitting cotton stocking to simulate 'skin'. The skin was wetted with distilled water to simulate 'sweating'. A form-fitting perforated polyethylene film was used to cover the wetted stocking to control the skin wettedness at two levels, 0.64 and 1.0. Experiments were conducted in a climatic chamber, under the following conditions: the ambient temperature = head manikin surface temperature = 34 +/- 0.5 degrees C; ambient relative humidity 30% and 60%. Also, the effects of wind and a simulated solar heat load were investigated. The five helmets showed statistically significant difference in evaporative heat transfer under the experimental conditions. Skin wettedness, ambient humidity, wind and solar heat showed significant effects on evaporative heat transfer. These effects were different for the different helmets.     

Laser-machining experiment with an excimer laser and a kinoform

We have used a kinoform to increase the beam-power utilization in an excimer-laser-machining experiment. The kinoform creates the pattern to be machined. Thus less power is wasted on the blocking parts of a shadow mask. To achieve as smooth an intensity profile as possible, the kinoform was also used together with a microlens-array beam homogenizer. We discuss the intensity distributions of the patterns created by the kinoform with and without the beam homogenizer as well as the design of the kinoform and the homogenizer, with emphasis on the relation to the coherence properties of the laser beam.     

Evidence for flavin movement in the function of p-hydroxybenzoate hydroxylase from studies of the mutant Arg220Lys

The isoalloxazine ring system of the FAD cofactor of p-hydroxybenzoate hydroxylase must be secluded from solvent at specific stages of catalysis in order to form and stabilize a flavin C4a-hydroperoxide. This species may then react with the activated phenolate of p-hydroxybenzoate. A number of crystal structures of the enzyme with alterations to active site substituents or complexes with analogue benzoates have revealed an alternate position for the isoalloxazine (Gatti et al. (1994) Science 266, 110-114; Schreuder et al. (1994) Biochemistry 33, 10161-10170). This new flavin conformation is 7 A "out" toward solvent and may open a passage for substrate entry to the active site. Arginine 220 is one of the few residues in the structure to demonstrate conformational changes when the flavin is "out". In this study we have made the Arg220Lys mutant to test the significance of this residue in flavin movement. The R220K mutation has brought about dramatic alterations to all aspects of catalysis. Stopped flow kinetic characterization of the mutant has revealed that, while the effector role for the substrate is maintained, there exists an order of magnitude decrease in the limiting rate of reduction, even though there is 40-fold increase in association with NADPH. The mutant enzyme has only a fraction of its reductive half-reaction coupled to product formation, and the hydroxylation process is slow. This occurs despite a higher proportion of the more activated substrate phenolate in the active site. Many of the observed changes can be attributed to a decrease in the stability of the "in" conformation of the flavin during the catalysis and indicate a role for flavin conformational states in many of the catalytic processes of the enzyme.     

Radioimmunotherapy with a 64Cu-labeled monoclonal antibody: a comparison with 67Cu

67Cu (t1/2 = 62 h) has demonstrated potential as a radionuclide for radioimmunotherapy, but limited availability severely restricts its widespread use. 64Cu (t1/2 = 12.8 h) has been shown to have comparable effectiveness in vitro and in vivo. The present study was undertaken to examine the therapeutic potential of 64Cu- and 67Cu-bromoacetamidobenzyl-1,4,8,11-tetraazacyclotetradeca ne-N, N',N",N"'-tetraacetic acid (BAT)-2-iminothiolane (2IT)-1A3 (1A3 is a mouse anti-human colorectal cancer mAb) for treatment of GW39 human colon carcinoma carried in hamster thighs. Hamsters were injected with 64Cu- or 67Cu-BAT-2IT-1A3 or Cu-labeled nonspecific IgG (MOPC) or saline. Hamsters were killed 6-7 months after therapy or when tumors were > or = 10 g. Of the hamsters with small tumors (mean weight 0.43 +/- 0.25 g), 87.5% were disease-free 7 months after treatment with 2 mCi (1 Ci = 37 GBq) of 64Cu-BAT-2IT-1A3 or 0.4 MCi of 67Cu-BAT-2IT-1A3. The mean tumor doses at these activities of 64Cu- and 67Cu-BAT-2IT-1A3 were 586 and 1269 rad (1 rad = 0.01 Gy), respectively. In contrast, 76% of hamsters treated with 2 mCi of 64Cu-BAT-2IT-MOPC or 0.4 mCi of 67Cu-BAT-2IT-MOPC had to be killed before 6 months because of tumor regrowth. When hamsters with larger tumors (mean weight 0.66 +/- 0.11 g) were treated with 64Cu- or 67Cu-BAT-2IT-1A3, survival was extended compared with controls, but only one animal remained tumor-free to 6 months. These results demonstrate that 64Cu- and 67Cu-BAT-2IT-1A3 given in a single administered dose can eradicate small tumors without significant host toxicity, but additional strategies to deliver higher tumor doses will be needed for larger tumors.     

Flavin conformational changes in the catalytic cycle of p-hydroxybenzoate hydroxylase substituted with 6-azido- and 6-aminoflavin adenine dinucleotide

Crystallographic studies have demonstrated two flavin conformations for p-hydroxybenzoate hydroxylase (PHBH) [Gatti, D. L., Palfey, B. A. , Lah, M. S., Entsch, B., Massey, V., Ballou, D. P., & Ludwig, M. L. (1994) Science 266, 110-114. Schreuder, H. A., Mattevi, A., Obmolova, G., Kalk, K. H., Hol, W. G. J., van der Bolt, F. J. T., & van Berkel, W. J. H. (1994) Biochemistry 33, 10161-10170]. The isoalloxazine ring system of one conformation (the "out" conformation) is significantly more exposed to solvent and is not in position for necessary catalytic reactions, but when the natural substrate is bound to the enzyme, the isoalloxazine is in the correct position (the "in" conformation) for its chemical function. In this study, several aspects of the function of the conformational change in catalysis were explored using the wild-type and Tyr222Phe forms of PHBH substituted with 6-azido FAD. This flavin served as both a spectral probe and a photolabel. The enzyme containing 6-azido FAD was a relatively effective catalyst for the hydroxylation of p-hydroxybenzoate. However, the intermediate reduced 6-azido enzyme was chemically unstable, and a small fraction converted to 6-amino PHBH by the elimination of N2 during each catalytic cycle. The reduction of 6-azido FAD PHBH by NADPH was almost as fast as the reduction of the natural enzyme. The characteristic spectral change caused by NADPH binding prior to hydride transfer strongly suggests that flavin movement from the "in" to the "out" conformation precedes flavin reduction. Irradiation of 6-azido PHBH with visible light covalently labeled proline 293, an active site residue, under conditions in which the flavin adopted the "in" conformation, while no protein labeling occurred under conditions in which the flavin was "out". The labeled protein exchanged substrate and was reduced by NADPH much more slowly than before photolysis. It is therefore concluded that isoalloxazine movement is required for pyridine nucleotide to gain access to the active site and for the exchange of aromatic ligands.     

Lysine 194 is functional in isocitrate lyase from Escherichia coli

BACKGROUND: Peritoneal involvement by Wilms' tumor indicates stage III disease. CT is the single preferred modality in determining the extent and staging of Wilms' tumor; however, the CT appearances of Wilms' tumor involvement of the peritoneum have not been specifically addressed in the literature. OBJECTIVE: The objective of this study was to demonstrate the CT manifestations when there is involvement of the peritoneum, mesentery and/or omentum in Wilms' tumor. MATERIALS AND METHODS: Four cases of Wilms' tumor form the basis of this report. They were examined on Elscint CT scanners. RESULTS: Masses ("dropped metastases") in the pelvis were present in all four patients. Three patients had masses in the mesentery of the small bowel and sigmoid colon. Infiltration of the greater omentum was identified in two patients as a mantle of tumor separating bowel from the anterior abdominal wall. Ascites was present in two patients. In one patient broad-based solid masses of varying sizes were noted on the parietal and on the visceral surfaces of the peritoneum, and in a different patient a discrete mass was noted in the lesser omentum. CONCLUSION: The peritoneal spaces, recesses, ligaments and folds are invisible unless invaded by disease which is well demonstrated on CT.