A mathematical characterization and analysis of a feedforward circuit for CDMA applications

Feedforward is known to be one of the best methods for power amplifier linearization due to its superior linearization performance albeit with relatively poor power efficiency. Here we present the derived closed-form expressions, which relate the main channel power and distortion products at the output of a simple feedforward circuitry to the circuit parameters. Consequently, a mathematical handy tool is achieved toward specifying the circuit parameters rapidly for optimum linearity performance and efficiency. The main and error amplifiers used in the feedforward are assumed to have a third-order AM/AM nonlinearity. The derived expressions are verified by simulation. The conditions for the validity of the model choice are highlighted. For the matched and lossless case, a compact relationship is obtained, which clearly demonstrates the tradeoff between nonlinearities of main and error amplifier for a given system linearity and output power. Delay mismatch is also included in the analysis.     

Characterization of event related potentials using information theoretic distance measures

Analysis of event-related potentials (ERPs) using signal processing tools has become extremely widespread in recent years. Nonstationary signal processing tools such as wavelets and time-frequency distributions have proven to be especially effective in characterizing the transient phenomena encountered in event-related potentials. In this paper, we focus on the analysis of event-related potentials collected during a psychological experiment where two groups of subjects, spider phobics and snake phobics, are shown the same set of stimulus: A blank stimulus, a neutral stimulus and a spider stimulus. We introduce a new approach, based on time-frequency distributions, for analyzing the ERPs. The difference in brain activity before and after a stimulus is presented is quantified using distance measures as adapted to the time-frequency plane. Three different distance measures, including a new information theoretic distance measure, are applied on the time-frequency plane to discriminate between the responses of the two groups of subjects. The results illustrate the effectiveness of using distance measures combined with time-frequency distributions in differentiating between the two classes of subjects and the different regions of the brain.     

Role of apoptosis in the regulation of virus-induced T cell responses, immune suppression, and memory

The binding of several biotinylated biologic probes was determined in sections of 20 surgical specimens of prostate cancer and of 21 biopsy specimens of hyperplastic prostate. Whereas neither the immunomodulatory, galactoside-specific lectin from Viscum album nor the human beta-galactoside-specific lectin (M(r) 14 kd) or its specific antibody discerned any remarkable differences, the lectin from Urtica dioica (UDA) and interleukin-2, the in vitro production of which is enhanced by this lectin, exhibited obvious preference for hyperplastic cells. In addition, the presence of binding sites for chemically synthesized blood group determinants was tested. Carcinoma cases revealed a higher percentage of binding of synthetic blood group trisaccharide H than hyperplasia cases. Due to these differences, diverse parameters, derived from measurement of integrated optical density (IOD) and from syntactic structure analysis, were correlated with the extent of binding of these biologic probes for the tumor cases. Primarily, parameters that are related to computation of a minimum spanning tree were significantly different in positive and negative cases for both UDA and interleukin-2. For the binding of blood group trisaccharide H the 5C exceeding rate, the 2CV deviation index and the distance of neighboring tumor cells with an IOD > 5 were clearly dissimilar. Our results thus suggest an extension of the panel of biologic probes for prostate cancer and substantiate the usefulness of correlations of binding of selected biologic probes to features derived from the assessment of IOD and syntactic structure analysis.     

Shrinking pleuritis with atelectasis

During a 10-year period 28 patients with shrinking pleuritis with atelectasis (SPA) were observed and operated upon. This lesion has been given different names in the literature, for instance rounded atelectasis, pleuroma, pulmonary pseudotumour, and lung folding. All patients except two were operated upon because of a diagnosis of pulmonary tumour. However, at operation no tumour was found. The aetiology and pathogenesis of SPA are discussed on the basis of X-ray, operative, and histopathological findings.     

A new selenium-based RAFT agent for surface-initiated RAFT polymerization of 4-vinylpyridine

A new selenium-based reversible addition-fragmentation chain transfer (RAFT) agent, 4-cyanopentanoic acid diselenobenzoate (RAFT-Se), was synthesized and utilized in the surface-initiated RAFT polymerization of 4-vinylpyridine (4VP) on silicon substrate. The results indicate that the RAFT-Se can control the surface-initiated RAFT polymerization, as evidenced by the number-average molecular weight that increase linearly with monomer conversion, molecular weights that agreed well with the predicted values, and the relatively low polydispersity indexes. The surface-initiated RAFT polymerization with the RAFT-Se was the same polymerization mechanism as its analog, 4-cyanopentanoic acid dithiobenzoate (RAFT-S). The grafting density of the poly(4-vinylpyridine) brushes prepared in the presence of RAFT-Se (σ_RAFT-Se) and RAFT-S (σ_RAFT-S) was estimated to be about 0.51 and 0.66 chains/nm², respectively. In addition, the end of polymer chains on silicon substrate contains selenium element which may be useful in biosensor applications.     

Dietary Sources of Fiber Intake and Its Association with Socio-Economic Factors among Flemish Preschool Children

The objectives were to assess total dietary fiber intake, identify the major sources of dietary fiber, and examine its association with socio-economic factors among Flemish preschoolers. Three-day estimated dietary records were collected from a representative sample of preschoolers 2.5-6.5 years old (n = 661; 338 boys, 323 girls). The mean dietary fiber intake (13.4 g/d) was lower than the intake level recommended by the Belgian Superior Health Council (70% boys and 81% girls below the guidelines). The most important contributor was the group of bread and cereals (29.5%), followed by fruits (17.8%), potatoes and grains (16.0%), energy-dense, low-nutritious foods (12.4%), and vegetables (11.8%). Multiple linear regression analyses showed that total fiber intake was associated with maternal education and parents' employment. Overall, fiber intakes from high-nutritious foods (vegetables and fruits) were higher in preschoolers of higher educated mothers and those with one or both parents being employed. In conclusion, the majority of the preschoolers had dietary fiber intakes below the recommended level. Hence, dietary fiber should be promoted among parents of preschoolers and low socio-economic status families should be addressed in particular.