一种衡量机构传动质量的新指标——兼论机构的压力角

长期以来,在凸轮机构中用压力角α;在连杆机构中用传动角γ(因为丨90°-γ丨=α,实质上仍是压力角)作为衡量机构传动质量的指标和设计依据。本文通过分析,指出了压力角作为这种指标的缺陷和提出了新的机构传动质量指标Ψ'=tga'tgφ',其中α'为实际压力角,φ'为从动件与机架间的当量摩擦角。文章还阐述了新指标在机构分析和综合上的应用。     

Microparticles from stored red blood cells promote a hypercoagulable state in a murine model of transfusion

Background

Red blood cell-derived microparticles are biologically active, submicron vesicles shed by erythrocytes during storage. Recent clinical studies have linked the duration of red blood cell storage with thromboembolic events in critically ill transfusion recipients. In the present study, we hypothesized that microparticles from aged packed red blood cell units promote a hypercoagulable state in a murine model of transfusion.

Postbypass Treatment

Ischemia induced by cross-clamping the aorta during open-heart operations initiates progressive metabolic derangement. If the duration of ischemia is short, these derangements are easily reversed by restoring the flow of blood containing oxygen and substrate. If ischemia is prolonged, treatment designed to ameliorate ischemic damage may be necessary. Three problems are discussed: (1) loss of adenine nucleotides, particularly adenosine triphosphate, (2) impairment of calcium sequestration, and (3) formation of microemboli in coronary vessels. The rationale for postbypass treatment is presented.     

Protection of the Myocardium with High-Energy Solutions

An approach to intraoperative protection of the myocardium is described that attempts to increase glucose utilization by infusion of high-energy solutions during aortic cross-clamping. Infusion of hypertonic glucose or glucose plus insulin prior to aortic cross-clamping has enhanced contractility and increased high-energy phosphate moieties in animals with induced ischemia. Recent pilot experiments in our laboratory suggest that infusions of creatine may result in increased production of creatine phosphate, which in turn induces phosphorylation of adenosine diphosphate to adenosine triphosphate, possibly enhancing myocardial contractility. The intraoperative clinical benefits of these infusions remain to be proved, however.     

Biochemical Changes of Ischemia

Normothermic ischemic arrest by aortic cross-clamping, a widely used clinical technique, is associated with metabolic changes in the myocardium that are incompletely understood. The effects of aortic cross-clamping on glycolytic pathways as well as associated morphological changes are discussed. Emphasis is placed on the conservation of high-energy phosphate moieties during the period of cross-clamping as well as during reperfusion. A marked reduction in total high-energy phosphates (62%) and glycogen (63%) and an increase in lactate production (243%) denote a shift to anaerobic metabolism during the period of arrest. Despite reperfusion, total high-energy nucleotides remained depressed. The data suggest that persistent abnormal myocardial carbohydrate metabolism and low levels of high-energy nucleotides prevent recovery of contractility following normothermic ischemic arrest and reperfusion.     

In vitro technique for isolating prostatic cells from blood.

An in vitro technique for isolating prostatic cells from blood has been applied to the study of circulating prostatic cells during a transurethral resection of the prostate. Our findings indicate that prostatic cells that are added to the blood in vitro can be isolated by the technique described and that cells resembling prostatic cells can be isolated from the blood of the patient undergoing transurethral resection of the prostate. Furthermore, the results of our study suggest that (i) in selected patients, needle biopsy of the prostate should be carried out prior to transurethral resection of the prostate and that (ii) patients who have multifocal adenocarcinoma diagnosed at the time of transurethral resection of the prostate may not be suitable candidates for future prostatectomy.     

Delayed flank approach to isolated renal trauma in children.

Seven cases of delayed operation for renal trauma are presented. The only kidney lost would have been lost with early operation. No undue friability of the renal tissue was found. The flank approach in delayed procedures for renal trauma has certain advantages over the transabdominal approach.     

微机控制集成运放参数的自动测试

TP—801控制集成运放参数的自动测试系统具有自动测试、自动分档、计数、显示、打印等功能。速度快、结构简单、测试简便、可靠与成本低是系统的主要特点。本文介绍了硬件框图、软件结构和主程序流程图。通过介绍一个测试过程、调试与整定方法,简述计算方法、测试范围与测试精度等问题。     

Clinical results with a new acoustic device to identify the epidural space

Fifty patients scheduled for surgery under lumbar epidural anaesthesia were included in a study to evaluate the possibility of localising the epidural space solely by means of an acoustic signal. With an experimental set-up, the pressure generated during the epidural puncture procedure was translated into a corresponding acoustic signal. One anaesthetist held the epidural needle with both hands and detected the epidural space by means of this acoustic signal. At the same time, a second anaesthetist applied the loss of resistance technique and functioned as control. In all patients the epidural space was located with the acoustic signal. This was confirmed by conventional loss of resistance in 49 (98%) of the patients; in one patient (2%) it was not. We conclude that it is possible to locate the epidural space using an acoustic signal alone.     

Multiple level injuries of the cervical spine

In a group of 105 patients admitted to hospital with injuries of the cervical spine, the incidence of injuries at multiple levels was 24 per cent. Multi-level injuries occurred in 17 out of 54 patients (31 per cent) sustaining a noteworthy neurological injury and in 8 out of 51 when such an injury was absent. This incidence is higher than previously reported, probably due to increasingly elaborate investigations. In the majority of cases, treatment of the dominant injury was unchanged by the demonstration of injuries at other levels, but in a small number, serious errors in treatment arose or could have arisen. Careful multi-level assessment, including assessment of the cervicothoracic junction, is indicated before selecting management. While conventional or computerized axial tomography may occasionally be necessary to achieve this, good conventional radiography remains the most important investigation. Computerized axial tomography is particularly useful in establishing the anatomy of complex injuries in the upper cervical spine.     

Thyroid abscess in a 14-month-old child

Suppurative thyroiditis occurring in childhood is rare. Progression to abscess formation is an even more uncommon occurrence. Only four thyroid abscesses occurring in children under 15 yr of age have been reported in the past 20 yr.^1–4A 14-mo-old white girl developed an enlarging mass in the anterior neck. Two weeks previously she was treated for otitis media by her local physician and subsequently was observed to develop a mass in the area of the thyroid gland. Her febrile course was not altered by antibiotics. Physical examination was entirely within normal limits except for the thyroid which was firm and hard with a 4-cm movable mass in the region of the left lobe of the thyroid. There was no associated erythema or apparent tenderness.Laboratory studies included a hemoglogin of 11.6 g/100 ml, hematocrit of 33.5 vol %, white blood cell count of 16,700/ml³ with a differential count of 65 neutrophils, 30 lymphocytes, and 5 monocytes. A urinalysis revealed no abnormalities. Stool culture grew normal enteric flora. A throat culture grew non-Group A beta hemolytic streptococci. A chest film revealed no abnormalities. Studies of thyroid function included a T-3 (30.4%) within normal limits and a T-4 (10.1 μg) in the high euthyroid range.The child received erythromycin 125 mg orally at 6-hr intervals without cessation of fever for 4 days. At this time, it was felt that the fever was related to the thyroid mass which appeared unchanged from the time of admission.At operation, an abscess cavity was noted in the superion of the left lobe of the thyroid gland. Approximately 10 cc of purulent material was removed from the cavity and a Penrose drain was placed in the abscess cavity. A biopsy specimen revealed inflammation and fibrosis consistent with the wall of the abscess. Bacterial, fungal, and acid-fast cultures of the pus were negative.The child became afebrile within 24 hr after operation. The postoperative course was uncomplicated except for the occurrence of a skin abscess at the site of the operative incision. Drainage of this abscess yielded 4 cc of purulent material from which staphylococcus epidermidis was grown. Subsequently the child has not experienced any further difficulty and remains euthyroid.     

Exposure of the circumflex coronary artery

A simplified method of obtaining exposure of the circumflex coronary artery using a mesh envelope is described. The device is constructed of readily available materials. Its construction, use, and clinical application are presented.     

Topical povidone-iodine reduces mortality from bacterial peritonitis

The efficacy of topical 10 and 1.5% povidone-iodine was assessed in a rat fecal peritonitis model. Both solutions were bactericidal in vitro. An LD₉₀ preparation of fecal peritonitis in the rat was then assessed and rats were assigned to control or four treatment groups consisting of lavage with saline, 10% povidone-iodine (2.5 ml/kg), povidone-iodine plus saline (600 ml/kg), or 1% cephalothin (600 ml/kg). Twenty-four-hour mortality rates were recorded. Quantitative peritoneal cultures were obtained before and 3 and 6 hr after lavage. Lavage was effective only with 1.5% povidone-iodine or when cephalothin was added. Each of these lavage solutions significantly reduced mortality (P < 0.05). Delayed intravenous cephalothin (200 mg/kg) reduced mortality significantly following 10 or 1.5% povidone-iodine. Failure of povidone irrigation is due to uncontrolled infection rather than to drug toxicity.     

Metabolic evidence that regional hypothermia induced by cold saline protects the heart during ischemic arrest

The rationale for cold saline induced hypothermic myocardial protection during ischemic cardioplegia has been limited for the most part to empiric and contractility observations. The aim of this study was to evaluate the degree of metabolic protection afforded by this procedure. In 21 dogs (C) placed on total cardiopulmonary bypass, normothermic ischemic arrest was induced for 60 min followed by 30 min of reperfusion. In 8 other dogs (CS), similarly treated, the heart was continuously cooled with saline at 5°C before and during the ischemia. Myocardial biopsies analyzed for ATP, ADP, creatine phosphate (CP), lactate and glycogen (Gly), were obtained before cross clamping at 15, 30, 45 and 60 min of ischemia and after 30 min of reperfusion.Significantly higher levels of ATP, CP and Gly were found in the CS hearts during and following the cross clamp period. These data indicate that local hypothermia slows the breakdown of high energy phosphate moieties during ischemic arrest. However, despite the protection afforded, ATP remains significantly depressed following reperfusion.