Relevance of the antibody response against human immunodeficiency virus type 1 envelope to vaccine design

Understanding the antibody response in HIV-1 infection is important to vaccine design. We have studied the antibody response to HIV-1 envelope at the molecular level and determined the characteristics of neutralizing and non-neutralizing antibodies. These antibodies were isolated from phage display libraries prepared from long-term seropositive asymptomatic individuals. The HIV-1 envelope is presented to the immune system in several antigenically distinct configurations: unprocessed gp160, gp120 and gp41 subunits and native envelope, each of which may be important in eliciting an antibody response in HIV-1 infection. The antibodies tested characteristically had poor affinities for native envelope as expressed on the surface of virions or infected cells, but had high affinities against non-native forms of HIV-1 envelope (viral debris). An exceptionally potent neutralizing antibody in contrast, bound native envelope with equivalent or somewhat higher affinity than this. This indicates that the antibody response in HIV-1 infection is principally elicited by viral debris rather than virions, and that these antibodies bind and neutralize viruses sub-optimally. Potential vaccines should be designed to elicit responses against native envelope.     

Implementation of an Aerostat Positioning System With Cable Control

The capabilities of a multi-tethered aerostat positioning system are investigated using experimental and simulation results. The system consists of a platform supported by a helium-filled aerostat and attached to three anchored ground tethers actuated using computer-controlled winches. The experimental system was designed to perform a proof-of-concept study of a novel large-scale radio telescope requiring a receiver to be positioned accurately at an altitude of up to 500 m. Results from a series of flight tests are presented with a comparison between the passive response of the system and the response using proportional, integral, and derivative (PID) controllers with a position feedback. The motion of the platform is smaller for all cases using the feedback control. To improve on the PID results, a dynamics model of the system is used to develop and simulate optimal and feedforward (FF) control strategies. The optimal linear quadratic Gaussian (LQG) controller offers a 50% improvement over the PID controller, and both the LQG and the PID feedback controllers were shown to benefit considerably from the addition of a FF control term that exploits the measurements of the system's main disturbance force     

Dynamic resource allocation in OFDM systems: an overview of cross-layer optimization principles and techniques

Recently, a lot of research effort has been spent on cross-layer system design. It has been shown that cross-layer mechanisms (i.e., policies) potentially provide significant performance gains for various systems. In this article we review several aspects of cross-layer system optimization regarding wireless OFDM systems. We discuss basic optimization models and present selected heuristic approaches realizing cross-layer policies by means of dynamic resource allocation. Two specific areas are treated separately: models and dynamic approaches for single transmitter/receiver pairs (i.e., a point-to-point communication scenario) as well as models and approaches for point-to-multipoint communication scenarios (e.g., the downlink of a wireless cell). This article provides basic knowledge in order to investigate future OFDM cross-layer-optimization issues     

Cloning, nucleotide sequence, and expression in Escherichia coli of levansucrase genes from the plant pathogens Pseudomonas syringae pv. glycinea and P. syringae pv. phaseolicola

Plant-pathogenic bacteria produce various extracellular polysaccharides (EPSs) which may function as virulence factors in diseases caused by these bacteria. The EPS levan is synthesized by the extracellular enzyme levansucrase in Pseudomonas syringae, Erwinia amylovora, and other bacterial species. The lsc genes encoding levansucrase from P. syringae pv. glycinea PG4180 and P. syringae pv. phaseolicola NCPPB 1321 were cloned, and their nucleotide sequences were determined. Heterologous expression of the lsc gene in Escherichia coli was found in four and two genomic library clones of strains PG4180 and NCPPB 1321, respectively. A 3. 0-kb PstI fragment common to all six clones conferred levan synthesis on E. coli when further subcloned. Nucleotide sequence analysis revealed a 1,248-bp open reading frame (ORF) derived from PG4180 and a 1,296-bp ORF derived from NCPPB 1321, which were both designated lsc. Both ORFs showed high homology to the E. amylovora and Zymomonas mobilis lsc genes at the nucleic acid and deduced amino acid sequence levels. Levansucrase was not secreted into the supernatant but was located in the periplasmic fraction of E. coli harboring the lsc gene. Expression of lsc was found to be dependent on the vector-based Plac promoter, indicating that the native promoter of lsc was not functional in E. coli. Insertion of an antibiotic resistance cassette in the lsc gene abolished levan synthesis in E. coli. A PCR screening with primers derived from lsc of P. syringae pv. glycinea PG4180 allowed the detection of this gene in a number of related bacteria.     

Visual specialization and brain evolution in primates

Several theories have been proposed to explain the evolution of species differences in brain size, but no consensus has emerged. One unresolved question is whether brain size differences are a result of neural specializations or of biological constraints affecting the whole brain. Here I show that, among primates, brain size variation is associated with visual specialization. Primates with large brains for their body size have relatively expanded visual brain areas, including the primary visual cortex and lateral geniculate nucleus. Within the visual system, it is, in particular, one functionally specialized pathway upon which selection has acted: evolutionary changes in the number of neurons in parvocellular, but not magnocellular, layers of the lateral geniculate nucleus are correlated with changes in both brain size and ecological variables (diet and social group size). Given the known functions of the parvocellular pathway, these results suggest that the relatively large brains of frugivorous species are products of selection on the ability to perceive and select fruits using specific visual cues such as colour. The separate correlation between group size and visual brain evolution, on the other hand, may indicate the visual basis of social information processing in the primate brain.     

Reality: a cousin twice removed [object technology]

Reasoning too much in terms of the real world can actually be detrimental to software quality. What matters is not how closely we model today's reality but how extensible and reusable our software is, so it can be adapted to a new or changed reality. The paper considers how reusability and extensibility are object technology's central goals. Object technology is not about modeling the real world. Object technology is about producing quality software, and the way to obtain this is to devise the right abstractions, whether or not they model what someone sees as the reality     

Hypertension in Haitians: results of a pilot survey of a public teaching hospital multispecialty clinic

Little is known about hypertension in Haitians. We performed a pilot survey of ambulatory Haitian patients in a multispecialty clinic at a large public teaching hospital. Approximately 10% of the clinic population was of Haitian origin. Clinical data were collected on 88 consecutive Haitian patients. Of these 88, 77 (87.5%) were hypertensive (SBP > or = 140 or DBP > or = 90 mm Hg or taking antihypertensive medication). The characteristics of the hypertensive patients were: age 54.1 +/- 13.0 (s.d.) years; 27 men, 50 women; 12/64 (19%) smoked; 7/63 (11%) used alcohol. Diabetes was present in 21/77 (27%). In patients for whom height and weight were available, obesity was present in 52%. Using JNC V criteria, 18 (23%) had Stage 1, 16 (21%) Stage 2, 18 (23%) Stage 3, and 25 (33%) Stage 4 hypertension. Despite 63/77 (82%) being treated for hypertension, only 20 (26%) were controlled (< 140/< 90 mm Hg). Of those under treatment, 29 were taking one drug; 18 (two drugs); 12 (three drugs); and four (four drugs). Target organ damage was evident in 37 (48%), including coronary artery disease (8), CHF (6), chronic renal failure (15), stroke (9), and LVH by ECG (19). There was evidence of severe noncompliance in 32 (42%). We conclude that in this clinic sample, hypertension was highly prevalent and unusually severe in terms of blood pressure (BP) level, refractoriness to treatment, and target organ consequences. Further studies are indicated.     

Intermodulation Distortion in CMOS Attenuators and Switches

Gain control elements are widely used in communication systems both to limit the incident power to the circuitry and to control the amplitude of the transmitted signal. Attenuators are one way of controlling the signal amplitude. The distortion performance of common CMOS attenuator topologies is investigated in this work. CMOS device equations that model the device in different regions of operation and which also model short channel effects are used for calculating distortion performance. Calculated distortion is compared with simulation results and experimental data, and qualitative explanations of the distortion curves as well as the deviation between different sources of data are given. Potential improvements in linearity performance of attenuators via circuit design techniques have also been discussed