Precision instrumentation for rolling element bearing characterization.

This article describes an instrument to measure the error motion of rolling element bearings. This challenge is met by simultaneously satisfying four requirements. First, an axial preload must be applied to seat the rolling elements in the bearing races. Second, one of the races must spin under the influence of an applied torque. Third, rotation of the remaining race must be prevented in a way that leaves the radial, axial/face, and tilt displacements free to move. Finally, the bearing must be fixtured and measured without introducing off-axis loading or other distorting influences. In the design presented here, an air bearing reference spindle with error motion of less than 10 nm rotates the inner race of the bearing under test. Noninfluencing couplings are used to prevent rotation of the bearing outer race and apply an axial preload without distorting the bearing or influencing the measurement. Capacitive displacement sensors with 2 nm resolution target the nonrotating outer race. The error motion measurement repeatability is shown to be less than 25 nm. The article closes with a discussion of how the instrument may be used to gather data with sufficient resolution to accurately estimate the contact angle of deep groove ball bearings.

Growth of tungsten oxide nanorods with carbon caps.

Hybrid nanostructures consisting of tungsten oxide nanorods with mushroom-shaped carbon caps were grown on electrochemically etched tungsten tips by thermal chemical vapor deposition with methane and argon. These nanorods grow along the radial direction and are very straight and smooth. Electron microscopy revealed a dominant diameter and length of approximately 50 nm and approximately 0.6 microm, respectively. High-resolution transmission electron microscopy (HRTEM), and electron energy loss spectroscopy (EELS) revealed the presence of crystalline monoclinic W18O49 in the nanorods, and the cap was entirely amorphous carbon. A plausible growth mechanism involves the reduction of tungsten oxide WO3, present on the tungsten surface, by methane at 900 degrees C.

Grey-scale ultrasonic imaging of the kidney.

The ultrasonic appearances of the kidney in images which contain grey shades corresponding to the detected echo-pulse heights have been examined. These "greyscale" images were obtained using a standard Nuclear Enterprises Diasonograph 4102B and a Varian 620/L digital computer interfaced to this Diasonograph. The computer was used to analyse and display the ultrasonograms with 16 grey shades. Both kidneys of 36 subjects were examined and compared with IVU findings. This group included patients with normal kidneys, polycystic kidneys, hydronephrosis, glomerulonephritis and neoplastic tumours. It was found possible to make sharp, grey-shaded ultrasonograms which were very useful to the diagnostician. In particular, the grey shade of the renal parenchyma was used as a standard to compare other grey-shaded structures. Also the grey shading was useful in defining the renal pelvis in transverse scans and the renal poles in axial scan.

Diagnosis and decision making in lumbar disc prolapse and nerve entrapment.

This prospective study of 185 patients undergoing first-time lumbar surgery compared how accurately clinical criteria and water-soluble myelography predicted the operative findings. Clinical diagnostic criteria of nerve root pain, root irritation signs, and neurologic signs of root compression supplemented by myelography were shown to be much more accurate than myelography alone, both in predicting the presence or absence of nerve root involvement and in distinguishing disc prolapse from bony entrapment. Provided the clinical criteria were clearly defined, patients with three or more of the four criteria were usually found to have a disc prolapse while bony entrapment could frequently be identified with one or two criteria. It is concluded that although lumbar disc prolapse is well-recognized, in practice clinical assessment and diagnostic criteria need to be defined more clearly to match increasingly sophisticated radiology.

Stiffness of desiccating insect wings.

The stiffness of insect wings is typically determined through experimental measurements. Such experiments are performed on wings removed from insects. However, the wings are subject to desiccation which typically leads to an increase in their stiffness. Although this effect of desiccation is well known, a comprehensive study of the rate of change in stiffness of desiccating insect wings would be a significant aid in planning experiments as well as interpreting data from such experiments. This communication presents a comprehensive experimental analysis of the change in mass and stiffness of gradually desiccating forewings of Painted Lady butterflies (Vanessa cardui). Mass and stiffness of the forewings of five butterflies were simultaneously measured every 10 min over a 24 h period. The averaged results show that wing mass declined exponentially by 21.1% over this time period with a time constant of 9.8 h, while wing stiffness increased linearly by 46.2% at a rate of 23.4 µN mm(-1) h(-1). For the forewings of a single butterfly, the experiment was performed over a period of 1 week, and the results show that wing mass declined exponentially by 52.2% with a time constant of 30.2 h until it reached a steady-state level of 2.00 mg, while wing stiffness increased exponentially by 90.7% until it reached a steady-state level of 1.70 mN mm(-1).

Parametric structural modeling of insect wings.

Insects produce thrust and lift forces via coupled fluid-structure interactions that bend and twist their compliant wings during flapping cycles. Insight into this fluid-structure interaction is achieved with numerical modeling techniques such as coupled finite element analysis and computational fluid dynamics, but these methods require accurate and validated structural models of insect wings. Structural models of insect wings depend principally on the shape, dimensions and material properties of the veins and membrane cells. This paper describes a method for parametric modeling of wing geometry using digital images and demonstrates the use of the geometric models in constructing three-dimensional finite element (FE) models and simple reduced-order models. The FE models are more complete and accurate than previously reported models since they accurately represent the topology of the vein network, as well as the shape and dimensions of the veins and membrane cells. The methods are demonstrated by developing a parametric structural model of a cicada forewing.

Triple therapy in early active rheumatoid arthritis: a randomized, single-blind, controlled trial comparing step-up and parallel treatment strategies.

OBJECTIVE: The Tight Control of Rheumatoid Arthritis study previously demonstrated that an intensive step-up disease-modifying antirheumatic drug (DMARD) treatment strategy targeting persistent disease activity was superior to routine care in the management of early rheumatoid arthritis (RA). We undertook this study to test the hypothesis that early parallel triple therapy achieves better outcomes than step-up therapy within an intensive disease management regimen. METHODS: Ninety-six patients with early RA (mean disease duration 11.5 months) were randomized to receive step-up therapy (sulfasalazine [SSZ] monotherapy, then after 3 months, methotrexate [MTX] was added, and when the maximum tolerated dosage of MTX was reached, hydroxychloroquine [HCQ] was added) or parallel triple therapy (SSZ/MTX/HCQ). All patients were assessed monthly for 12 months. If their disease activity score in 28 joints (DAS28) was > or =3.2, the dosage of DMARDs was increased according to protocol, and swollen joints were injected with triamcinolone acetonide (maximum dosage 80 mg per month). A metrologist who was blinded to the treatment allocation performed assessments every 3 months. The primary outcome measure was the mean decrease in the DAS28 score at 12 months. RESULTS: Both groups showed substantial improvements in disease activity and functional outcome. At 12 months, the mean decrease in the DAS28 score was -4.0 (step-up therapy group) versus -3.3 (parallel therapy group) (P = 0.163). No significant differences in the percentages of patients with DAS28 remission (step-up therapy group 45% versus parallel triple therapy group 33%), DAS28 good response (60% versus 41%, respectively), or American College of Rheumatology criteria for 20% improvement (ACR20) (77% versus 76%, respectively), ACR50 (60% versus 51%, respectively), or ACR70 (30% versus 20%, respectively) responses were seen. Radiologic progression was similar in both groups. CONCLUSION: This study confirms that highly effective control of disease activity can be achieved using conventional DMARDs as part of an intensive disease management strategy. Within this setting, step-up therapy is at least as effective as parallel triple therapy.

Prevalence of proximal faecal stasis in active ulcerative colitis.

Proximal faecal stasis may occur when faecal matter accumulates in the uninflamed colon above an area of active ulcerative colitis. This phenomenon is thought to be the cause of symptoms in some patients with distal disease. It is not known, however, how often patients with active distal colitis exhibit slow colonic transit. Fifty two consecutive patients with active ulcerative colitis each ingested 10 radio-opaque markers nightly for 14 days. Minimum colonic transit times were derived from counts of retained markers shown by plain abdominal radiography on the 15th day. The transit times for each patient were related to their disease extent and bowel frequency. Four patients had colonic transit times greater than one week and two others had evidence of relative stasis. The results indicate that approximately 10% of attacks of distal colitis are associated with faecal stasis.

Immediate CT pneumocolon for failed colonoscopy; comparison with routine pneumocolon.

AIM: To assess the role and reliability of 2D CT pneumocolon in the diagnosis of colonic malignancy, and compare feasibility of referral sources. MATERIALS AND METHODS: A prospective study of 50 patients with suspected large bowel malignancy. Patients underwent bowel cleansing, rectal air insufflation and contrast enhanced CT with 5 mm collimation, 3 mm reconstruction and a pitch of 1.4. Subsequent correlation was with pathology (16), colonoscopy (13), barium enema (5), ERCP (1) and clinical follow-up alone (8). RESULTS: Diagnostic images were obtained in 43/50 patients (86% feasibility). Follow-up was obtained in 35/43 patients (one patient died of an unrelated cause, and seven patients were deemed unfit for further investigation). Seventeen colonic carcinomas were diagnosed (three false-positives: one ischaemic colitis, one diverticular stricture and one faecal mass), one diverticular stricture, one fistula, one pancreatic carcinoma and one ovarian malignancy. The remaining 14 were negative. Overall sensitivity was 100% (for lesions >1.5 cm) with a specificity of 94% for structural abnormalities, but only 82% for the correct identification of malignancy. CONCLUSION: Computed tomography (CT) pneumocolon is a reliable alternative to barium enema where colonoscopy is incomplete, with the advantage of extraluminal screening, and examination of the proximal bowel. In the frail elderly or young unfit patient, it is a valuable additional diagnostic tool.

An analysis of 200 patients with negative small bowel enemas.

Clinical, operative and pathological findings were used to assess the ability of the small bowel enema to exclude organic disease in the small intestine. On the basis of 200 patients with negative small bowel enemas it is concluded that there was a very low incidence of false negative results on clinical grounds and in 36 patients coming to surgery or autopsy, 25 (69%) had no evidence of intrinsic or extrinsic small bowel disease while 11 (31%) had various lesions which are discussed. Review of the radiology in these patients indicated a number of technical problems.

Recurrent varicose veins: a radiological approach to investigation.

Superficial venography was used in nine lower limbs of eight patients with recurrent varicose veins occurring after high ligation or stripping. This technique demonstrated four different types of recurrence and identified the cause in individual patients. The most common type of recurrence was not a missed tributary of the long saphenous or a missed perforating vein, but a tortuous leash of recanalised vein reconnecting the long saphenous and femoral veins. Implications for treatment of primary varicose veins are discussed.

Vascular complications of osteochondroma.

Apart from trauma, symptoms arising from peripheral arteries are very unusual in adolescents and young adults. Three cases of osteochondroma associated with rare vascular complications are presented, together with a review of the literature. The development of pain in relation to osteochondroma does not necessarily imply trauma or the onset of malignancy and vascular complications should be considered, particularly if the bone lesion occurs around the knee. In this situation, arteriography is considered essential in planning surgical treatment and the importance of angiography in two planes is emphasised.

Arterio-venous shunting complicating occlusive atherosclerotic peripheral vascular disease.

Three cases of severe occlusive peripheral vascular disease are described in which spontaneous arterio-venous fistulae at the site of atheromatous occlusion have been demonstrated by angiography during the arterial phase. Although none of these patients exhibited specific clinical signs of an arterio-venous fistula, this phenomenon is considered to have been a clinically significant factor in the patients' peripheral ischaemia. In one case both the superficial femoral artery stenosis and the spontaneous shunts were effectively treated by percutaneous angioplasty.

Subsynovial vascular abnormality causing recurrent hemarthrosis in an 84-year-old man.

We describe a patient with recurrent hemarthrosis of one knee. Investigation demonstrated a vascular abnormality of the synovium as the likely cause. Structural abnormalities of the synovial vasculature should be considered, in the absence of a systemic cause, as a potential source of bleeding in older patients with recurrent hemarthrosis.

Spinal and general anaesthesia in total hip replacement: frequency of deep vein thrombosis.

Subarachnoid block (SAB) or general anaesthesia (GA) was induced in 85 patients undergoing total hip replacement. The frequency of deep vein thrombosis (DVT), assessed by fibrinogen uptake studies and venography, was 29% in those patients receiving SAB and 54% in the GA group. Total blood loss (intra-operative and post-operative wound suction drainage) in SAB group was 66% and total transfusion volume 52% of that of GA group. No morbidity attributable to SAB or to the associated arterial hypotension was detected.

Case report: pancreatic mediastinal pseudocyst--an unusual cause of palpitations.

We describe a case of pancreatic mediastinal pseudocyst which presented atypically with palpitations due to marked cardiac compression. Computed tomography (CT) showed a large abdominal pseudocyst extending through the diaphragm into the posterior mediastinum. Surgical drainage produced rapid symptomatic relief and the pseudocyst resolved completely within 2 months.

Unbuffered highly acidic gastric juice exists at the gastroesophageal junction after a meal.

BACKGROUND & AIMS: Gastroesophageal reflux typically occurs after meals. During dual gastric and esophageal pH monitoring, we observed that postprandial refluxate was often more acidic than the gastric contents. This study aimed to investigate this phenomenon. METHODS: Dual gastric and esophageal pH tracings were analyzed from 40 dyspeptic patients. Dual pH electrode pull-through studies were performed in healthy volunteers to document regional variation in intragastric pH under both fasting and postprandial conditions. The squamocolumnar junction was identified using radio-opaque endoscopic clips. We also examined in vitro partitioning of gastric juice added to a homogenized fatty meal. RESULTS: The dual pH traces confirmed that esophageal refluxate was frequently more acidic than the body of the stomach after meals but not during fasting. The pull-through studies showed a pocket of acid at the gastroesophageal junction that escaped the buffering effect of meals, remaining highly acidic (median pH 1.6) compared with the body of the stomach (pH 4.7; P < 0.001). This proximal acid pocket extended from the cardia across the squamocolumnar junction 1.8 cm into the distal esophagus. The in vitro studies showed that acidic gastric juice could partition on top of a homogenized fatty meal. CONCLUSIONS: After eating, highly acidic unbuffered gastric juice is present at the gastroesophageal squamocolumnar junction and is likely to contribute to the high prevalence of disease at this site.