A REVIEW OF THE CHEMICAL VAPOR DEPOSITION (CVD) OF THE REFRACTORY COMPOUNDS OF TITANIUM - A UNIQUE FAMILY OIF COATINGS

This paper is a review of a unique family of refractory compounds comprising the boride, carbide and nitride of titanium. These materials are characterized by high hardness, high wear resistance and chemical inertness. They are obtained as coatings by chemical vapor deposition (CVD) on a variety of substrates such as tool steel, cemented carbides, graphite and many others. Promising deposition techniques are plasma-CVD and metallo-organic CVD. Major applications of these coatings are found in wear, erosion and corrosion protection and in cutting tools     

A 160-MHz analog equalizer for magnetic disk read channels

This paper presents a 160-MHz five-tap adaptive analog equalizer for magnetic recording disk drive read channels. The design is based on a direct form finite impulse response (FIR) architecture which includes four key features: signal shuffling in the analog domain to improve noise performance, use of a master sample-and-hold stage to improve the dynamic performance and clock jitter of the clock recovery loop, use of an additional sample-and-hold stage to accommodate settling time requirements and reduce power, and use of a time interleaved sign-sign LMS algorithm which permits coefficient adaptation at low power and area. This equalizer occupies 1.36 mm² and consumes only 240 mW with 5-V supply voltage. It is fabricated in BiCMOS technology with 0.8-μm CMOS and 0.72-μm² NPN, 3LM, and DP capacitor     

Pulsed-field gel electrophoresis genomic fingerprinting of hospital Escherichia coli bacteraemia isolates

To study the effects of massive weight loss on insulin secretion, we analysed the oscillations of fasting peripheral insulin levels in obese patients who underwent vertical banded gastroplasty as treatment for morbid obesity. Patients were studied before and 6 months after surgery. Serial measurements of plasma free insulin levels were obtained in duplicates from 0 to 60 min at one-minute intervals. Insulin levels were then analysed by autocorrelation and Fourier transformation. In normal controls and obese patients, the first oscillatory insulin component was detected between 10 and 14 min. Compared to obese controls (n = 4), overt Type 2 diabetic patients (n = 4) had reduced amplitudes of insulin pulses and no oscillatory component. These defects were not as pronounced in patients with impaired glucose tolerance (IGT) after an oral glucose tolerance test (OGTT) (n = 5). When detected, the periodicity of the oscillations occurred at different periods. In 3/5 IGT patients, the first positive peak of correlation was found at 13.3 +/- 2.3 min. Weight loss (mean +/- SD) after 6 months was 24.3 +/- 3.7 for subjects with normal glucose tolerance (NGT), 37.9 +/- 9 for those with IGT and 29.8 +/- 5 kgs for Type 2 diabetic subjects. After weight loss, insulin oscillatory activity was detected in 4/5 IGT patients, with a period of 13 +/- 3 min. Weight loss did not reverse the defects observed in obese diabetic patients despite a significant reduction in peripheral insulin levels from 28.6 +/- 6 to 15.6 +/- 6 mU/l (p < 0.05). Insulin values remained higher than in obese controls (7.82 +/- 2, p < 0.05), and Type 2 patients remained mildly hyperglycaemic. These findings indicate that beta-cell activity is abnormal in Type 2 diabetic patients. The absence of modification after weight loss suggests that inherent beta-cell defects may contribute to hyperglycaemia.     

The stethoscope. A potential source of nosocomial infection?

OBJECTIVE: To determine the relation between epidural injectate volume (ml/kg of body weight) and its craniad migration in calves and pigs. ANIMALS: 23 neonatal calves and 26 feeder pigs. PROCEDURE: Animals were randomly assigned to receive different volumes of new methylene blue (NMB, 1.2 mg/ml in 0.9% saline solution). Injections were made into the sacrococcygeal intervertebral space in calves and the lumbosacral intervertebral space in pigs, immediately after euthanasia. Sagittal sections of the spine were made at necropsy, and craniad migration of NMB was determined and rounded to the nearest intervertebral space. RESULTS: In calves treated with 0.05, 0.1, or 0.15 ml of NMB/kg, mean +/- SEM number of stained spinal segments was 5 +/- 0.3, 8 +/- 0.6, and 8 +/- 0.6, respectively. Craniad migration of NMB was significantly greater for 0.15 and 0.1 ml/kg volumes versus 0.05 ml/kg. In pigs treated with 0.05, 0.1, 0.2, of 0.3 ml of NMB/kg, mean number of stained spinal segments was 8 +/- 1.1, 8 +/- 0.9, 10 +/- 1.2, and 18 +/- 2.0. Craniad dye migration was significantly greater in the 0.3 ml/kg group versus the 3 lower volume groups. Linear regression performed on both sets of data after logarithmic transformation of spaces migrated to correct for non-normality was significant (P < 0.05), and R2 values of 0.49 and 0.55 were obtained for calves and pigs, respectively. CONCLUSIONS: There is a significant correlation between volume (ml/kg) of NMB injected in the epidural space and its craniad migration in calves and pigs. CLINICAL RELEVANCE: Results provide a basis for determination of volume of injectate to be given to reach a minimal desired level and should be a useful baseline for future investigations of epidural drug administration.     

Beginnings and endings: keys to better engineering technicalwriting

Engineers face many technical writing tasks that have many features in common: title, abstract, introduction, problem formulation, methods, results, and conclusions. But it is often very difficult to actually write these segments in the same order they appear in the finished product. Instead of this linear approach, we recommend a modular approach starting with the core sections, the methods and results that researchers know best, and working backward and forward to pick up the beginnings and endings. We show how the beginning and ending sections build on the core sections and offer strategies to improve them     

Thermal design and simulation of bipolar integrated circuits

Keeping device operating temperatures within reasonable limits is necessary for reliability of all ICs and important for achieving the expected performance for many ICs. GaAs heterojunction bipolar transistors (HBTs) offer high speed and good device matching characteristics that are attractive for many high-speed circuits, but they are more susceptible than other IC technologies to the unexpected generation of very high junction temperatures. The reasons for this tendency are discussed, and an HBT sample-and-hold (S/H) circuit that had device temperature rises of over 300°C is described. To address this problem, a new thermal simulation tool called ThCalc was created. ThCalc calculates the temperature profile of an IC and runs fast enough to allow calculations on a whole chip. ThCalc was used to redesign the S/H IC to reduce the largest temperature rise by a factor of 2.7 with a minimal impact on circuit size     

A 6-b, 4 GSa/s GaAs HBT ADC

A GaAs-AlGaAs heterojunction bipolar transistor (HBT) process was developed to meet the speed, gain, and yield requirements for analog-to-digital converters (ADC's). The HBT has current gain of over 100 and f_T and f_MAX of over 50 GHz. A 6-b, 4 GSa/s (4 giga-samples/s) ADC was designed and fabricated in this process. The ADC uses an analog folding architecture, includes an on-chip master-slave track-and-hold (T/H) circuit, and provides Gray-encoded digital outputs. The ADC achieves 5.6 effective bits at 4 GSa/s, a faster clock rate than any noninterleaved semiconductor ADC reported to date. It has a resolution bandwidth (the frequency at which effective bits has dropped by 0.5 b) of 1.8 GHz at 4 GSa/s, higher than any published ADC. The chip operates at up to 6.5 GSa/s. GaAs HBT IC's are especially prone to high operating temperatures. This led to reliability problems that were overcome by the use of a fast DC thermal simulator written for this project. A SPICE model for self-heating effects is also described     

Magnetic resonance imaging of bovine ovaries in vitro

A sample of 20 bovine ovaries were imaged in vitro using nuclear magnetic resonance (NMR) techniques to determine the visibility of various physiologic structures. In particular, the possibility of using NMR imaging to differentiate atretic follicles from physiologically selected and ovulatory follicles was examined. Five of the 20 ovaries were preserved in formalin, whereas the remaining 15 were preserved in a saline solution and imaged within 18 hours of death. Images weighted by T₁ and T₂ proton spin relaxation rates were obtained along with some three-dimensional (3-D) data sets acquired via a fast imaging with steady-state precession technique. Physiologically different structures were easily identified in the images from their morphology, especially in the 3-D images. Weighting by T₁ and T₂ was able to separate structures in the fresh ovaries in the following manner. Atretic and cohort follicles appear dark in T₁-weighted images and bright in T₂-weighted images. Ovulatory follicles appear bright in both T₁-and T₂-weighted images, whereas prephysiologic selection follicles present an intermediate brightness in T₁-weighted images and appear dark in T₂-weighted images. The corpus luteum appears bright in T₁-weighted images and dark in T₂-weighted images, whereas cysts in the corpus luteum appear dark in T₁-weighted images and bright in T₂-weighted images. The varying brightness of the follicles at different stages of development is hypothesized to be related to different hormone and protein concentrations in the follicular fluid. For example, it is known that physiologically selected preovulatory follicles contain high concentrations of estrogens in a viscous follicular fluid. The increased viscosity may occur only when the follicle fluid contains high concentrations of estrogen and contributes to bright T₁-weighted images. The possibility of using nuclear relaxation-weighted NMR imaging for the study of follicular dynamics and other ovarian biology therefore shows great promise.     

Sudden deaths in yearling feedlot cattle

A survey of the causes for fatal diseases of yearling feedlot cattle was conducted on more than 407,000 cattle during a 14-month period. Of the 4,260 (1%) cattle that died during this period, 1,358 (32%) were categorized as cases of "sudden death syndrome." Of the 11 most frequent causes of the syndrome, as determined at necropsy, only 4--bloat, pulmonary aneurysms, riding injury, and hemopericardium--were considered as short-course problems and true causes of sudden death. The largest number of cases of sudden death were attributed to pneumonia (113 animals). Consequently, the sudden death syndrome is a misnomer for many long-course diseases and, in some instances, a mask for neglect because, as clinically used, the name frequently includes cattle that have been sick, often with pneumonia, for several days.