Electrochemistry and ion-sensing properties of calix[4]arene derivatives

The cyclic voltammetric properties of several substituted calix[4]arenes were examined in acetonitrile and dichloromethane. The compounds that contained one phenolic group in the macrocyclic cavity were able to be electrochemically oxidised at positive potentials. In acetonitrile, cyclic voltammetry experiments indicated that the phenolic compounds were oxidised in a two-electron (one-proton) process over all measured scan rates (up to 50 V s⁻¹), while in dichloromethane, the oxidation process occurred by one-electron at scan rates ≥5 V s⁻¹, to most likely form the radical cations. In both solvents, longer timescale (minutes to hours) controlled potential coulometry experiments indicated that the oxidation process occurred by two-electrons per molecule, to form reactive diamagnetic cations that could not be reduced back to the starting materials under electrolysis conditions. The ion-sensing properties of the compounds were investigated in polymer membrane ion-selective electrodes and it was found that they responded reversibly in a Nernstian fashion to Groups 1 and 2 metals and had the highest selectivity to the cesium cation.     

Evaluating applicants to emergency medicine residency programs

This article reviews the pertinent literature related to the selection process of medical students to emergency medicine residency programs. The impact that academic performance in medical school, the interview, letters of recommendation, and other achievements have on the performance of the future resident are reviewed. All articles identified by an English language MEDLINE search were reviewed by the authors as to significance to the subject. Review of relevant literature indicates that no precise correlation can be made between performance in medical school and achievements during the residency, although there seems to be a correlation between academic performance in medical school and similar performance on board certification examinations.     

Transudative vs exudative pleural effusions: differentiation using Gd-DTPA-enhanced MRI

A 57-year-old female who had been performed mitral valve replacement (MVR) using 31 mm prosthetic valve 32 months before entered the hospital for the evaluation of long standing severe hemolytic anemia without infectious sign. Transesophageal echocardiogram revealed a moderate sized vegetation on the atrial site of the prosthetic valve. The size and number of the vegetation were increased after deterioration of infectious illness. Blood culture grew serratia marcessans and alpha-hemolytic Streptococcus. Re-MVR was carried out with the diagnosis of prosthetic valve endocarditis (PVE). As the symptom of PVE, hemolytic anemia without infectious sign is a rare condition. TEE is an useful method to make diagnosis of PVE by detecting the vegetations and evaluating their change of size and methods and to evaluate the effectiveness of the treatment.     

MHC class II molecules bind indiscriminately self and non-self peptide homologs: effect on the immunogenicity of non-self peptides

Synthetic peptides spanning the entire sequence of both human and mouse beta 2-microglobulin (beta 2M) have been tested for their capacity to bind to three different mouse (I-Ad, I-Ed, and I-Ak) or human (DR1, DR2, and DR5) class II molecules. The results demonstrate that class II molecules do not discriminate between self and non-self peptides. When the immunogenicity of the human beta 2M peptides was measured by their ability to prime H-2d mice for in vitro T cell proliferation, it was found that peptides incapable of binding class II molecules in vitro were also non-immunogenic in vivo. Interestingly, however, several binders, including the human beta 2M peptide 1-16, the best binder in this series to Iad molecules, were found to be non-immunogenic. Since the corresponding mouse beta 2M peptide 1-16 was also capable of binding to Iad molecules, this suggested that lack of responsiveness to the non-self peptide could arise either from central or peripheral tolerance induced by the self homolog. Alternatively, lack of responsiveness could arise from other mechanisms, such as negative selection by other non-homolog sequences or lack of suitable T cell receptor genes. To discriminate between these possibilities, H-2d mice with disrupted beta 2M genes were immunized with the human beta 2M peptide 1-16. This peptide also failed to prime for T cell responsiveness in beta 2M-negative mice, suggesting that a hole in the T cell repertoire for this antigen was not mediated by negative selection or peripheral tolerance induced by self beta 2M peptides.     

44-ns Continuously Tunable Dispersionless Optical Delay Element Using a PPLN Waveguide With Two-Pump Configuration, DCF, and a Dispersion Compensator

This letter presents an optically controlled, continuously tunable, dispersionless optical delay element in fiber based on a selective wavelength converter using a periodically poled lithium-niobate waveguide with two-pump configuration, dispersion-compensated fiber, and a dispersion compensator. Optical phase information is preserved in this technique, and there is no fundamental limitation on pulsewidth or bit rate. A Continuous optical delay up to 44-ns is shown for 10-Gb/s nonreturn-to-zero applications, which is equal to a 440-bit slot     

COMBINING MULTI‐AGENT PARADIGM AND MEMETIC COMPUTING FOR PERSONALIZED AND ADAPTIVE LEARNING EXPERIENCES

Learning is a critical support mechanism for industrial and academic organizations to enhance the skills of employees and students and, consequently, the overall competitiveness in the new economy. The remarkable velocity and volatility of modern knowledge require novel learning methods offering additional features as efficiency, task relevance and personalization. Computational Intelligence methodologies can support e‐Learning system designers in two different aspects: (1) they represent the most suitable solution able to support learning content and activities, personalized to specific needs and influenced by specific preferences of the learner and (2) they assist designers with computationally efficient methods to develop “in time” e‐Learning environments. This article attempts to achieve both results by exploiting an ontological representations of learning environment and memetic approach of optimization, integrated into a cooperative distributed problem solving framework. This synergy enables multi‐island memetic approach managing a collection of models and processes for adapting an e‐Learning system to the learner expectations and to formulate objectives in an effective and dynamic intelligent way. More precisely, our proposal exploits ontological representations of learning environment and a memetic distributed problem‐solving approach to generate the best learning presentation and, at the same time, minimize the computational efforts necessary to compute optimal learning experiences.     

Theory of relativistic optical harmonic generation

We present a theoretical model of optical harmonic generation excited by laser beams sufficiently intense that relativistic effects are important. This model shows that, under relativistic conditions, third-harmonic generation can be excited with comparable efficiency by either linear or circularly polarized light. This result is to be contrasted with experience from traditional (nonrelativistic) nonlinear optics, where group-theoretical arguments show that third-harmonic emission cannot occur under circularly polarized excitation. These results are in good agreement with the observed polarization dependence of the third-harmonic emission reported recently in an experiment conducted under conditions such that relativistic effects are important. Our theoretical model also predicts that all even and odd harmonies of the fundamental laser frequency are emitted in the near-forward direction with an intensity that increases with that of the incident laser field     

Parametric fault tree for the dependability analysis of redundant systems and its high-level Petri net semantics

In order to cope efficiently with the dependability analysis of redundant systems with replicated units, a new, more compact fault-tree formalism, called Parametric Fault Tree (PFT), is defined. In a PFT formalism, replicated units are folded and indexed so that only one representative of the similar replicas is included in the model. From the PFT, a list of parametric cut sets can be derived, where only the relevant patterns leading to the system failure are evidenced regardless of the actual identity of the component in the cut set. The paper provides an algorithm to convert a PFT into a class of High-Level Petri Nets, called SWN. The purpose of this conversion is twofold: to exploit the modeling power and flexibility of the SWN formalism, allowing the analyst to include statistical dependencies that could not have been accommodated into the corresponding PFT and to exploit the capability of the SWN formalism to generate a lumped Markov chain, thus alleviating the state explosion problem. The search for the minimal cut sets (qualitative analysis) can be often performed by a structural T-invariant analysis on the generated SWN. The advantages that can be obtained from the translation of a PFT into a SWN are investigated considering a fault-tolerant multiprocessor system example.