Long-term Failure Rate Research Articles

A High Reliability High Sensitivity Lightwave Receiver for the SL Undersea Lightwave System

Undersea lightwave systems need receivers with the utmost in both reliability and sensitivity. Our design has evolved from the type which we provided for an earlier deep-sea trial. The primary features of our present receiver are an InGaAs planar p-i-n photodiode with passivation and antireflection coating and a Si bipolar integrated circuit, both encapsulated in a special chip carrier. Both the photodiode and the amplifier are placed in the same carrier so that a direct chip-to-chip wire bond can minimize stray capacitance, which helps to maximize sensitivity. The back-illuminated structure of the photodiode allows the InP substrate to serve as a window in the hermetically sealed carrier. Since both active devices are in a separate package from the passive components, they can undergo the high temperature bake-out and hermetic seal followed by the high temperature high bias. purge necessary to assure the reliability of the semiconductors. This optical chip carrier is then mounted inside another hermetic package which contains the passive components, including the optical fiber pigtail, which must undergo bake-out and seal at more moderate temperatures. Within the constraints of reliability, bandwidth, and dynamic range, the physical structure of the integrated circuit and its bias conditions have been chosen to maximize sensitivity. The design of the circuit enables us to select those devices from a production lot which will achieve the highest sensitivity in a completed receiver. This receiver is used in systems operating with NRZ data from 140 to 440 Mbit/s. At 1.3 μm and 296 Mbit/s the mean sensitivity achieved was an average optical power \bar{P} = -35.6 dBm for a 10-9bit error rate (BER), with a best value of -36.3 dBm. This receiver is physically robust, being able to withstand stresses well in excess of those encountered in actual use. Preliminary aging data indicate that a long-term failure rate of less than 2.5 in 109device hours can be achieved.

Intraoperative balloon-catheter dilatation in the treatment of coronary artery disease

Intraoperative balloon angioplasty has been employed as an adjunct to conventional coronary artery bypass techniques for arteriosclerotic obstructions in areas difficult to expose. In 14 patients having repeat cardiac catheterization prior to discharge from the hospital, an average preoperative stenosis of 50% was reduced to 26% in 14 arteries subjected to angioplasty. In four patients, improvement was less than 20%. There were no known complications, and time to perform the procedure was less than 10 minutes per angioplasty. Intraoperative angioplasty is indicated when normal sequential or multiple grafting procedures cannot be performed, but the procedure may have a significantly higher long-term failure rate than coronary artery bypass alone.

Long-term failure rate and morphologic correlations in porcine bioprosthetic heart valves

To ascertain relations among site, incidence, and mechanisms of clinically evident failure of porcine bioprosthetic heart valves, the frequency of failure of 1,110 valves in 1,001 adult operative survivors from January 1972 to January 1982 was reviewed and correlated with the pathologic features of 22 consecutive dysfunctional valves. There were 373 mitral, 519 aortic, and 109 double replacements, yielding for study 482 mitral and 628 aortic valves at risk. Infective endocarditis occurred in 1.9% (8 mitral, 7 aortic, and 4 double). Twenty-three valves (13 mitral and 10 aortic) with documented primary dysfunction were explanted, a mean of 55 months (range 9 to 94) after surgery. The primary dysfunction rate for the 333 valves implanted for greater than or equal to 5 years was 6.8% (11 of 161) for mitral and 4.1% (7 of 172) for aortic valves. Valves implanted for less than 5 years had a failure rate of 0.7%. The actuarially determined freedom from primary valve failure was 98 +/- 1% for mitral and 98 +/- 1% for aortic valves at 5 years and 79 +/- 7% for mitral and 91 +/- 4% for aortic valves at 10 years. Recovered valves (12 mitral and 10 aortic) with detailed morphologic analysis were functioning for a mean duration of 52 months (range 12 to 87). Causes of failure included calcification-related tears in 7 (4 mitral and 3 aortic, mean 66 months), tear without calcium deposits in 4 (4 mitral, mean 44 months), cuspal stiffening without tear but with calcium deposits in 2 (1 mitral and 1 aortic, mean 80 months) and thrombosis in 1 (aortic). Late primary dysfunction was most frequently a result of degenerative processes, especially calcification, often with secondary tears, but cuspal tears in the absence of calcium deposits and thrombosis predominated at shorter intervals.

Long-term failure rate and morphologic correlations in porcine bioprosthetic heart valves

Long-term failure rate and morphologic correlations in porcine bioprosthetic heart valves

The pathology of invasive breast cancerA Syllabus Derived from Findings of the National Surgical Adjuvant Breast Project (Protocol No. 4)

The inter-relationships of 32 pathologic and 7 clinical parameters encountered in the study of 1000 examples of invasive breast carcinoma have been presented. In some instances the biological significance of these associations is at present unclear. In others it is to be noted that there is no information provided as to the rank of their significance. Nevertheless, the associations that were encountered not only help further characterize the various forms of breast cancer but also provide information regarding the possible biological significance of some of their features. Although it is not our intention to minimize the possible significance of the inter-relationships of pathologic parameters, most emphasis in the summarizing statements which follow has been placed upon those correlations which may relate to prognosis. In this regard reference has been made to short-term treatment failure, vis a vis local recurrence and/or metastases, which may not necessarily accurately reflect patient survival, although generally such a relationship exists. Information in this regard as well as to the rank of the significance of these pathologic features shall be forthcoming when sufficient time has elapsed since the inception of this study to allow for such conclusions, i.e. survival or long-term treatment failure rates. Lastly, it becomes evident that the guidelines followed in the examination of these specimens appear to represent at least the minimum requirements necessary for a meaningful pathologic evaluation of breast carcinoma.

The relationship between blood-flow and failure of femoropopliteal reconstructive arterial surgery.

Abstract Blood-flow measured at operation in 80 limbs was found to be significantly related to the patency of the reconstruction 12 months later. The incidence of failure was 14 per cent when the flow exceeded 100 ml. per minute and was 54 per cent when the flow was less than this figure. Although blood-flow was significantly lower in patients with obstructed distal arteries, there were wide variations in flow between limbs with similar degrees of obstruction. There was, however, a significant increase in the failure rate with increasing arterial obstruction, and where two or all three of the tibial arteries were obstructed the long-term failure rate was 48 per cent.

Long-term results of reconstructive aortoiliac surgery

The records of sixty-three patients undergoing successful surgery for aortoiliac occlusive disease have been reviewed. The patients were divided into two groups according to the distribution of their disease at the time of the original operation. Group I consisted of forty-two patients who had both aortoiliac and distal disease. Group II consisted of twenty-one patients in whom the disease was localized to the aortoiliac region. The over-all long-term failure rate for the reconstruction was 29 per cent and although the patency rate in group II was slightly higher than that in group I, no statistical differences were detected between the two groups. In addition, when the resuits of endarterectomy were compared with the results obtained with the grafting procedures, the patients undergoing endarterectomy did slightly better, although the differences noted were not found to be significant. In terms of disease progression, there were marked differences between the two groups. Patients with disease confined to the aortoiliac area at the time of operation had only a 14 per cent incidence of disease progression. This is in contrast to results in group I in which 38 per cent of the patients developed new occlusive disease during the follow-up period. Most of the new disease occurred in the superficial femoral artery and about half the lesions noted in group I required surgery. None of the lesions noted in group II required operative therapy. The results suggest that there is a biologic difference between patients with a solitary aortoiliac lesion and those with additional occlusive disease in other sites. The outlook as far as new disease formation is concerned is better in those patients with localized lesions.