A BiCMOS dynamic carry lookahead adder circuit for VLSIimplementation of high-speed arithmetic unit

A BiCMOS dynamic carry lookahead circuit that is free from race problems is presented. A 16 b full-adder test circuit, which has been designed based on a 2 μm BiCMOS technology, shows a more than five times improvement in speed as compared to the CMOS Manchester carry lookahead (MCLA) circuit. The speed advantage of the BiCMOS dynamic carry lookahead circuit is even greater in a 32- or 64-b adder     

Influence of doping on the electronic structure of (La,Sr)2CuO4

High-statistics (>4 × 10⁸ counts), room-temperature measurements of the electron-positron momentum density of La_2?x Sr _x CuO₄ have been performed for samples with Sr concentrations of x=0.0, 0.1, 0.13, and 0.2. These spectra have been analyzed in conjunction with theoretical calculations of the electron-positron momentum density. The metallic samples show features consistent with the presence of a Fermi surface, but its evolution with increasing Sr concentration does not follow the predictions of band theory. These results may indicate the effects of electron-electron correlation on the electron momentum distribution in the Cu-O plane.     

The domain composition method applied to Poisson's equation in two dimensions

Domain composition, a recently described method for formulating continuum field problems, removes certain restrictions on the construction of finite element models such that it is possible to solve a finite element problem without using a global compatible mesh. The domain composition method couples or otherwise constrains meshes in local regions to obtain a solution equivalent to that produced by conventional finite element methods. In particular, the domain composition method enables finite element models to be formulated with overlapping elements. Several advantages come from this, including an ability to automatically generate a finite element model from a solid geometric model, an ability to use a variety of element types in a single finite element model and an ability to exactly match element boundaries to the local geometry. This paper shows in detail a finite element formulation of Poisson's equation using domain composition and presents certain key algorithms that incorporate the domain composition method into well-established finite element procedures.     

Abnormal behavioral responses to fenfluramine in patients with affective and personality disorders. Correlation with increased serotonergic responsivity

Serotonergic responsivity was assessed in 20 psychiatric patients by the prolactin response to a fenfluramine challenge test. During the fenfluramine challenge 6 of 20 patients (30%) spontaneously reported psychopathologic reactions that included: increased anxiety/agitation, psychotic symptoms, illusions, mood elevation, and anergia. The time of peak behavioral symptoms (2.5 +/- 0.8 hrs) corresponded closely to the time of peak increase in prolactin levels (3.0 +/- 1.1 hr). Abnormal behavioral responders had statistically significant greater increases in prolactin 1 to 4 hr after fenfluramine when compared to normal responders. Patients who developed an abnormal psychopathologic response to fenfluramine were characterized by higher levels of anxiety and agitation at the time of admission to the hospital but otherwise were not distinguishable on the basis of severity of other psychiatric symptoms. This study suggests that increased serotonergic transmission may trigger anxiety, psychosis, and mood elevation in specific vulnerable individuals, whereas other patients with similar psychiatric illnesses are not affected.     

Inhibitory effect of bifemelane on superoxide generation by activated neutrophils measured using a simple chemiluminescence method

We evaluated the effect of 4-(2-benzylphenoxy)-N-methylbutylamine hydrochloride (bifemelane hydrochloride) on superoxide production by human neutrophils using an MCLA-dependent chemiluminescence assay. Bifemelane hydrochloride dose-dependently inhibited superoxide production by neutrophils stimulated with phorbol myristate acetate, opsonized zymosan, or N-formyl-methionyl-leucyl-phenylalanine, while it had no effect on superoxide production by a hypoxanthine-xanthine oxidase system. These results indicate that bifemelane hydrochloride does not have a scavenging effect, but has an inhibitory effect on superoxide generation by neutrophils. Although this drug is commonly used for treating chronic cerebral infarction, it may also have a protective effect on acute ischemia/reperfusion injury.     

Electrical coupling and impulse propagation in anatomically modeledventricular tissue

Computer simulations were used to study the role of resistive couplings on flat-wave action potential propagation through a thin sheet of ventricular tissue. Unlike simulations using continuous or periodic structures, this unique electrical model includes random size cells with random spaced longitudinal and lateral connections to simulate the physiologic structure of the tissue. The resolution of the electrical model is ten microns, thus providing a simulated view at the subcellular level. Flat-wave longitudinal propagation was evaluated with an electrical circuit of over 140,000 circuit elements, modeling a 0.25 mm by 5.0 mm sheet of tissue. An electrical circuit of over 84,000 circuit elements, modeling a 0.5 mm by 1.5 mm sheet was used to study flat-wave transverse propagation. Under normal cellular coupling conditions, at the macrostructure level, electrical conduction through the simulated sheets appeared continuous and directional differences in conduction velocity, action potential amplitude and V˙_max were observed. However, at the subcellular level (10 μm) unequal action potential delays were measured at the longitudinal and lateral gap junctions and irregular wave-shapes were observed in the propagating signal. Furthermore, when the modeled tissue was homogeneously uncoupled at the gap junctions conduction velocities decreased as the action potential delay between modeled cells increased. The variability in the measured action potential was most significant in areas with fewer lateral gap junctions, i.e., lateral gap junctions between fibers were separated by a distance of 100 μm or more     

Wideband HEMT MMIC low-noise amplifier with temperaturecompensation

A wideband low-noise pseudomorphic HEMT MMIC variable-gain amplifier has been designed and fabricated. The amplifier has a nominal gain of 13 dB across the band 2-20 GHz, with gain flatness better than ±0.4 dB. The noise figure is less than 3 dB across the band 6-16 GHz. An on-chip temperature-sensing diode is used to provide a linear temperature correction which has been used to reduce the gain variation of the amplifier by a factor of 2 across the temperature range -50°C to +95°C     

Performance of asynchronous DS-CDMA system with long and shortspreading codes

The effect of spreading code length on the BER performance of an asynchronous DS-CDMA system is studied by means of Monte Carlo simulation. The probability of the crosscorrelation value between segments of long sequences is also discussed. Results indicate that the system performance with very long codes is ~1 dB worse compared to that of short CDMA codes