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Several spaceborne altimeters have been built and flown, and others are being developed, to provide measurements of ocean and ice sheet topography. Until the launch of TOPEX (Ocean Topography Experiment), altimeters were single-frequency systems that were incapable of removing the effects of ionospheric delay on the radar pulse. With the current state-of-the-art in satellite altimetry, the ionosphere causes the largest single error when using single-frequency altimeters. Ionospheric models provide the only recourse short of adding a second frequency to the altimeter. Unfortunately, measurements of the ionosphere are lacking over the oceans or ice sheets where they are most needed. A possible solution to the lack of data density may result from an expanded use of the Global Positioning System (GPS). This paper discusses how the reflection of the GPS signal from the ocean can be used to extend ionospheric measurements by simply adding a GPS receiver and downward-pointing antenna to satellites carrying singl...

We compared the strength of a new step-cut technique for flexor tendon repair with that of the widely used Kessler-Tajima technique, giving special attention to the relative contributions of the core and epitendinous sutures. 36 flexor digitorum profundus tendons from human cadavers were used. Corresponding digits from the same donor were paired, and the two tendons of each pair were placed in the Kessler-Tajima and step-cut groups, respectively. Each group had three subcategories of repair: (1) core repair alone; (2) epitendinous repair alone; and (3) full repair. In the Kessler-Tajima repair, the core stitch contributed more to ultimate tensile strength, while the epitendinous stitch contributed more to gap formation resistance. In the step-cut repair, however, the epitendinous stitch contributed more to both measures of strength. The full step-cut repair was 65% stronger in resisting gap formation and had 84% more ultimate tensile strength than the full Kessler-Tajima repair. We attribute the greater strength of the step-cut repair to the additional number of epitendinous loops, which lie perpendicular to the long axis of the tendon.

Early excision and allografting of massive burns is beneficial. However, chronic immunosuppression, utilized to prolong allograft survival, increases the potential risk of infection. We have previously shown long-term skin allograft survival in mice with a 30% total body surface area (TBSA) burn by inducing donor-specific tolerance (DST) using only perigrafting administration of antithymocyte globulin (ATG) and donor bone marrow (DBM). Chronic immunosuppression is avoided. This study tests whether induction of DST compromises host resistance to infection. Resistance to a septic challenge created by cecal ligation and puncture (CLP) 10 days after a 30% TBSA burn was investigated in the following groups of mice: Group Mortality ∗ I. CLP, eschar intact ( n = 18 ) 83% II. CLP, burn excision, isograft ( n = 14 ) 43% III. CLP, burn excision, allograft, ATG ( n = 15 ) 40% IV. CLP, burn excision, allograft, ATG, DBM ( n = 14 ) 50% Positive blood cultures were documented for 97% of mortalities. Burn excision and grafting significantly ( P ⩽ 0.05) decreased mortality. No increased mortality was seen in allografted mice receiving ATG or ATG and DBM compared to isografted mice receiving no immunosuppression. These studies suggest that skin allografting with DST may permit the benefits of burn excision without the risks of infection seen with chronic immunosuppression.

These studies demonstrate clearly that the creation of donor-specific tolerance in animals permits the long-term survival of incompatible skin grafts placed following a burn with early eschar excision. Furthermore, the studies demonstrate graphically that such replacement can be done without any increase in the septic mortality in these animals and strongly suggest that such a treatment would be potentially efficacious as a therapy for large body burns that could not be successfully covered with autografts. When animals were observed either in the potentially septic milieu of a large 30% body burn or in a situation of a deliberate attempt to create a septic state using the septic challenge of CLP, the placement of a full-thickness skin graft that survived was clearly beneficial to the animal in reducing mortality. In addition, the donor-specific tolerance technique described permits long-term survival of these skin grafts, which in some of the earlier laboratory studies were able to survive permanently and might well achieve permanent survival in a clinical situation. However, a prolonged graft survival of 90 to 100 days, considering the ability to develop new split thickness skin grafts providing dermal cover at 20- to 25-day intervals, would provide opportunity for a least four "croppings" of the skins. Thus, for example, a small area of remaining autograft skin of 20% in an 80% burn patient could potentially be cropped four times to achieve close to 80% coverage. Coverage would be easier and more successful in the more common burns of less than 70% of TBSA. It is of interest to us that there is virtually no well-developed literature on the use of donor-specific tolerance to aid skin graft survival. There would seem to be a reasonable rationale for considering such therapy since septic problems should not be significantly increased during induction of skin graft tolerance. Once the skin grafting has produced a significant increase in functionally covered skin, the risk of sepsis should decrease markedly. Because sepsis is currently the major factor in 75% of burn deaths, donor-specific tolerance for skins grafts appears to be eminently reasonable for future consideration. Expanded animal studies are probably necessary before clinical trials are undertaken, although skin grafting with immunosuppression has already been tried in patients.

Two methods of surveillance for nosocomial infection--routine notification and active case finding--were compared during three consecutive months at the high risk newborn unit of the Hospital de Base of the Federal District, involving 66 newborns, which represented 93% of the total patient population referred to that unit for specialized care. Our purpose was to measure the efficiency of routine notification. While this method involved infection notification forms routinely filled by the physician at discharge time, active surveillance consisted of physical examination and chart review of all the newborns, carried out, independently, twice a week: routine notification estimated a 27.3 per cent prevalence rate, versus a 30.3 per cent by active-case finding, considered by the authors a superior surveillance method. Although infection rates were similar, routine surveillance resulted in many false-positive and false-negative notifications, reaching a sensitivity of 60.0 per cent and a specificity of 86.9 per cent. The resulting positive predictive value was 66.7 per cent and negative, 83.3 per cent. The data collected by routine notification was often incomplete and inconsistent. In conclusion, the results seem to indicate that control programs based solely on routine surveillance could be producing inaccurate nosocomial infection rates and, consequently inadequate control measures.

The development of transmission networks and magnetic components for the L5 system represents the largest network development project of its type ever undertaken within the Bell System. Over 200 different coded designs of networks, requiring in excess of 40 man-years of effort, were required to meet the frequency-selective and signal-shaping requirements of the system. Despite this effort, neither systems requirements nor systems schedules could have been met without significant contributions from allied technologies. This article identifies those technologies and describes design techniques that have advanced the state-of-the-art capabilities in transmission network and magnetic component design.

Reversed-phase high-pressure liquid chromatography (HPLC) was utilized to determine the stability of tetrahydropapaveroline (THP) and salsolinol at two ambient temperatures and over varying time intervals of up to 27 hr. Although ascorbate, an antioxidant, was shown to retard the temporally contingent degradation of THP at both 22°C and 37°C, the breakdown of the tetrahydrosoquinoline product was more pronounced at 37°C. Salsolinol was virtually stable under all conditions. The formation of detectable by-products of THP was demonstrated by the presence of secondary peaks in the THP-water assay which were strikingly absent in the THP-ascorbate aliquots. Finally, the HPLC profiles of five THP samples obtained from four different sources revealed the presence of similar secondary peaks which varied considerably in shape and peak height from one sample to another. The implications of this lack of uniformity of THP for pharmacological studies of addictive processes is discussed.

The E6 repeater is a low-cost, transistorized, voice-frequency, two-way repeater for use in the exchange area plant, including use in trunks between local offices and between local and toll offices. It permits both types of trunks to be operated at low net loss, while meeting the impedance requirements placed on trunks between local and toll offices. These features are possible because of a unique method of repeater design, in which the impedance-matching function and the gain function are allocated to separate portions of the repeater and are separately adjustable. The impedance-matching function is accomplished by means of a line building-out network, which permits any cable pair associated with the repeater to be built out and made to match the impedance of the toll office. The gain unit presents the same image impedance, which is essentially independent of gain adjustment. Changes in gain are controlled by two resistive, adjustable artworks — one in the series-connected negative impedance converter, and the other in the shunt-connected converter. In previous designs of negative impedance repeaters, complex impedance networks were required for adjustment of both gain and impedance match. The E6 repeater also incorporates novel mechanical features, with transistorization resulting in low power drain and less heat dissipation in the telephone central office. Power is derived from the existing 48-volt central office battery.

The line repeaters of the L-4 system represent a hierarchy of repeaters of increasing complexity: basic, regulating, and equalizing repeaters. Based on a building block philosophy, each of the more complex repeaters performs all of the functions of the less complex types plus additional functions of its own. The simplest, the basic repeater, is a plug-in unit with a shaped gain-frequency characteristic that compensates for the transmission loss of two miles of cable. The regulating repeater includes all of the components of the basic repeater plus two dynamic gain-regulating circuits and a deviation equalizer. Both repeaters include line building-out networks to compensate for departures from the nominal two-mile spacing. This paper develops the building block philosophy of the line repeaters and considers those aspects of the basic and regulating repeaters that contribute to load carrying capacity, reliability, noise figure, and modulation performance. It emphasizes the design features of the line repeaters that contribute to a fully-hardened system.