Cascaded, stagger-tuned, broadband, low-ripple optical amplifiers

We show theoretically that the gain spectrum obtained by cascading two or more semiconductor optical amplifiers can have a ripple amplitude that is significantly smaller than that currently attainable with a single stage of optical amplification. For example, by cascading two stagger-tuned amplifiers, each having 10 dB of coupling loss and facet reflectivities of 10(-3), one can achieve a net (fiber-to-fiber) gain of 30 dB with less than 2 dB of ripple amplitude. We also show that, under some conditions, simple cascading of optical amplifiers, without the stagger tuning and associated control, can lead to low-ripple, high-gain optical amplification.

Hemostasis in hypertensive disorders of pregnancy

We studied parameters of hemostasis reported to be altered with "pure" preeclampsia in hypertensive disorders of pregnancy. Plasma fibronectin, antithrombin, and alpha-2 antiplasmin were measured in normal pregnancies (N = 26) and in pregnancies complicated by preeclampsia (N = 19), hypertension (N = 11), and chronic hypertension with superimposed preeclampsia (N = 11). Preeclampsia, both pure and superimposed, was associated with high fibronectin (P less than .001), low antithrombin III (P less than .001), and low alpha-2 antiplasmin (P less than .05) levels, suggesting endothelial injury, clotting, and fibrinolysis, respectively. Alpha-2 antiplasmin was increased with chronic hypertension (P less than .001), regardless of whether there was superimposed preeclampsia. Fibronectin appeared to be more closely linked with preeclampsia than antithrombin III or alpha-2 antiplasmin and may prove valuable in detecting preeclampsia when evaluating hypertension in pregnancy.

Effect of some recent analgesics on labor pain and maternal and fetal blood gases and pH

This study attempts to determine the analgesic properties of nalbuphine, pentazocine and butorphanol during labor and their potential effects on maternal and fetal blood gases and pH. Butorphanol analgesia was superior to either nalbuphine or pentazocine in relieving labor pain. The studied analgesics caused significant maternal respiratory acidosis and fetal metabolic acidosis. These acidotic changes were most marked with pentazocine, moderate with nalbuphine and minimal with butorphanol.

Preeclampsia, delivery, and the hemostatic system

To determine the effects of preeclampsia and delivery, the hemostatic system was evaluated before and 24 to 48 hours after delivery in 59 nulliparous patients without clinical signs of disseminated intravascular coagulation. Fifteen patients with mild preeclampsia and 18 with severe preeclampsia were compared with 26 pregnant control patients. Preeclampsia was associated with high fibronectin (p less than 0.001), low antithrombin III (p less than 0.001), and low alpha 2-antiplasmin (p less than 0.005), suggesting endothelial injury, clotting, and fibrinolysis, respectively. After delivery, fibronectin decreased only in preeclamptic patients (p less than 0.005); alpha 2-antiplasmin increased in all groups (p less than 0.001). Endothelial injury in preeclampsia appeared to resolve soon after delivery, which could contribute to the rapid clinical improvement noted in the early puerperium.

Mechanisms for reduced colloid osmotic pressure in preeclampsia

The determinants of plasma colloid osmotic pressure were studied in 32 patients with preeclampsia and their matched control subjects. Although plasma colloid osmotic pressure was significantly related to preeclampsia, its severity, and proteinuria, it was most highly correlated with an elevated fibronectin level, suggesting that endothelial injury, rather than proteinuria, is the major mechanism of reduced colloid osmotic pressure in preeclampsia.

Potential anticancer agents, XI. X-ray structure determination of acantholide

The X-ray structure of acantholide, a melampolide sesquiterpene lactone from Acanthospermum glabratum (DC.) Willd. was determined by the aid of direct methods. The compound was cytotoxic but displayed no antitumor activity. Evaluation of the X-ray and NMR data indicated that the same conformation exists in the solid state as in solution.

Oncogenic and tumor-promoting Spermatophytes and Pteridophytes and their active principles

A survey and discussion are presented of plants classified as Spermatophyta and Pteridophyta, extracts of which have been shown to be oncogenic or tumor-promoting in animals. The active oncogenic and tumor-promoting principles, where known, have been identified. They represent tannins; pyrrolizidine, indole, tropolone, quinoline, purine, and benzophenanthridine alkaloids; nitroso compounds; triterpene glycosides; lignans; isoflavans; allyl benzenoids; simple (nu-pyrenes; and carbocyclic hydroxy acids. A total of 28 compounds of known structure have been identified as oncogens and several phorbol esters as tumor-promoters. Plants known to contain any of the 28 oncogens (excluding shikimic acid and caffeine) have been tabulated; they represent at least 454 species, 110 genera, and 34 families of Spermatophyta and Pteridophyta.

Modification of diffusion rates of benzocaine from topical vehicles using sodium salicylate as complexing agent

The release of benzocaine from various topical vehicles containing benzocaine, alone and in the presence of a complexing agent, sodium salicylate, was measured at 37 degrees using dialysis through a cellulose membrane. Sodium salicylate had a marked effect on the release of benzocaine, depending upon the the type of vehicle, with the largest increase observed for the water-miscible base, polyethylene glycol (macrogol ointment BPC). The amount of drug released from preparations containing 1% (w/w) and 2% (w/w) benzocaine in this vehicle depended upon the sodium salicylate concentration. Results are discussed in terms of the differing physical properties of the complexes formed.

Guidance of surface waves by multilayer coatings

A periodic sequence of layers with alternately high and low refractive indices can guide loosely bound surface waves parallel to the layers. Most of the power flows in free space, and, thus, the losses may be considerably smaller than the bulk losses of the dielectric materials used. Possible applications are briefly discussed.