Nonlinear dynamics of femtosecond optical solitary wave propagationat the zero dispersion point

A perturbed nonlinear Schrodinger equation, describing nonlinear pulse propagation of femtosecond duration in optical fibers at the zero dispersion point, is considered. This equation is reduced to an ordinary differential equation, which is treated by means of Hamiltonian dynamics techniques. Conditions for solitary wave formation, as well as the solutions themselves, namely, a bright soliton, a rarefaction soliton, and a pair of dark solitons, are derived analytically. The shifts of the solitary wave velocity, the angular frequency, and the wavenumber, as well as the peak power required to launch a bright soliton are also obtained. The connection among the point initial conditions of the pulse and the type of solitary wave that can be excited is finally presented     

Silicon bipolar chipset for SONET/SDH 10 Gb/s fiber-opticcommunication links

High-speed multiplexers, demultiplexers, frequency dividers, mixers, and amplifiers are key electronic components in high-speed fiber-optic communications systems such as SONET/SDH. In this paper, we present several important digital and analog integrated circuits (IC) which have been developed for use in SONET/SDH 10 Gb/s optical communication links. The circuits have been fabricated in MOSAIC 5E, an advanced silicon bipolar technology (f_T=26 GHz). The resulting chipset which amounts to a total of 10 IC's consists of multiplexers, demultiplexers, a regenerative frequency divider (2:1), a dual output limiting amplifier, and two different types of mixers for clock extraction. Specifically, the design and performance of these IC's and a hybrid clock recovery module are discussed. The high performance and potential low cost of this research chipset show that advanced silicon bipolar circuit technology can play an important role in future multigigabit fiber-optic communication systems     

Endoplasmic reticulum Ca(2+)-ATPase in microsomal vesicles isolated from bovine retinae

Active Ca2+ transport was measured in microsomal vesicles prepared from bovine retinae and was compared with that in disk membranes of the photoreceptor cells of the same retina. The 45Ca uptake was dependent on the presence of Mg(2+)-ATP and was inhibited by vanadate or when GTP substituted for ATP. The dependence of calcium uptake on the external free Ca2+ concentration gave a KM = 13 microM or a KM = 0.1 microM for disks and microsomal vesicles, respectively. A phosphorylated intermediate (E-P) of Ca(2+)-ATPase of about 100 kDa was isolated in microsomal vesicles. The E-P formation was strongly inhibited by thapsigargin and partially by 2,5-di-(-butyl)benzohydroquinone. Digestion of disks or microsomes with calpain had no effect on the phosphorylated intermediate, while digestion with trypsin produced two fragments of approximately 55 kDa and 35 kDa. These results suggest that bovine retinal microsomes contain a calcium pump belonging to the SERCA family.     

Layout-synthesis techniques for yield enhancement

Several yield-enhancement techniques are proposed for the last two stages of VLSI design, i.e., topological/symbolic and physical layout synthesis. Our approach is based on modifications of the symbolic/physical layout to reduce the sensitivity of the design to random point defects without increasing the area, rather than fault tolerance techniques. A layout compaction algorithm is presented and the yield improvement results of some industrial layout examples are shown. This algorithm has been implemented in a commercial CAD framework. Some routing techniques for wire length and via minimization are presented, and the results of wire length reduction in benchmark routing examples are shown. We demonstrate through topological optimization for PLA-based designs that yield enhancement can be applied even at a higher level of design abstraction. Experimental results show that it is possible to achieve significant yield improvements without increasing the layout area by applying the proposed techniques during layout synthesis     

Differential class III and glibenclamide effects on action potential duration in guinea-pig papillary muscle during normoxia and hypoxia/ischaemia

1. Microelectrode recording techniques were used to study the effects of several potassium channel blockers which are considered to be Class III antiarrhythmic compounds. The effects of (+)-sotalol, UK-66,914, UK-68,798 and E-4031 on action potential duration (APD) were determined in guinea-pig isolated papillary muscles. The compounds were evaluated under normoxic or hypoxic/ischaemic conditions at 36.5 degrees C and compared to glibenclamide, which is considered to be a blocker of ATP-dependent potassium channels. Prolongation of action potential duration at 90% repolarization (APD90) was taken as an indirect measure of potassium channel blockade. 2. Under normoxic conditions, the Class III compounds prolonged APD in a concentration-dependent manner. According to EC15 values, the order of potency of the Class III compounds was found to be UK-68,798 > E-4031 > UK-66,914 > (+)-sotalol. Glibenclamide did not significantly prolong APD90 under normoxic conditions. 3. Perfusion with an experimental hypoxic or ischaemic bathing solution produced qualitatively similar effects on action potentials. Over a period of 20-25 min in either of the experimental solutions, there was a small decrease in action potential amplitude (APA) and a prominent shortening of APD. The ischaemic solution also depolarized the resting membrane potential by about 15 mV. 4. (+)-Sotalol and UK-66,914 did not reverse the shortening of APD induced by perfusion with hypoxic Krebs solution. High concentrations of glibenclamide (10 microM) and UK-68,798 (30 and 60 microM) partially reversed the hypoxia-shortened APD. Glibenclamide was more potent and exhibited a greater time-dependent action than UK-68,798. 5. During experimental ischaemia, the Class III compound E-4031 (10 microM, n = 7) produced small, but significant, increases in the APD90 (11 +/-3 ms after 20 min) which were not clearly time-dependent(14 +/- 4 ms after 30 min). UK-68,798 (10 microM) also produced a small, but insignificant, increase in APD90(12 =/-6 ms at 20 min, n = 4). Higher concentrations of UK-68,798 (30 and 60 microM, n = 4) did not produce a consistently significant increase in APD90 during ischaemia: significance was only attained after 20 min in the presence of 60 microM UK-68,798 (24 +/- 12 ms). However, in marked contrast to the effects of the Class III compounds, glibenclamide (10 microM) produced large time-dependent increases in ischaemic APD90 (34 +/- 11 ms at 7 min, n = 9) which were significant 15 min or more after drug addition(52 +/- 12 ms at 20 min, n = 7; 74 +/- 5 ms at 30 min, n = 6).6. The present microelectrode data suggest that blockers of ATP-dependent potassium channels, such as glibenclamide, might prove to be more effective than Class III compounds against ischaemia-induced shortening of cardiac action potentials.     

Kinetics of saturation of liquid metal flow with gases

An analysis of the kinetics of gas dissolution in a liquid metal flow is performed. It is shown that due to a high pouring rate and specific surface of the flow, the flow in the arc of molten filler metal, as distinct from the flow of liquid metal during its pouring, leads to intense saturation of the melt with gas.Volgograd Branch of the Novocherkassk Polytechnic Institute. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 64, No. 4, pp. 414–420, April, 1993.     

Alpha blockaders--first or second line antihypertensive agents?

Alpha-receptor blockers reduce blood pressure by blocking of the alpha 1-receptors in the smooth muscle cells in the arteriolar walls. The heart pump function is not disturbed. Most studies have shown that the alpha-receptor blockers induce a reduction in plasma-triglycerides and an increase in the ratio between HDL- and LDL-cholesterol. They do not interfere with the metabolism of electrolytes, glucose or uric acid and have no negative effect on pulmonary function. Although long-term use does not induce a permanent increase in heart rate, some patients respond to initial therapy with faster heart rate and palpitations. The alpha-receptor blockers should not be used in patients with coronary heart disease if the patient is not on chronic beta-blockade. When these precautions are followed, the alpha-blockers can be used as first-line treatment--just like ACE-inhibitors and calcium-antagonists.