Showing papers by "University of Ioannina published in 1999"

Additional nucleon current contributions to neutrinoless double β decay

Abstract: We have examined the importance of momentum-dependent-induced nucleon currents such as weak-magnetism and pseudoscalar couplings to the amplitude of neutrinoless double beta decay $(0\ensuremath{ u}\ensuremath{\beta}\ensuremath{\beta}$ decay) in the mechanisms of light and heavy Majorana neutrino, as well as in that of Majoron emission. Such effects are expected to occur in all nuclear models in the direction of reducing the light neutrino matrix elements by about $30%.$ To test this we have performed a calculation of the nuclear matrix elements of the experimentally interesting nuclei $A=76, 82, 96, 100, 116, 128, 130, 136,$ and 150 within the proton-neutron renormalized quasiparticle random-phase approximation. We have found that indeed such corrections vary somewhat from nucleus to nucleus, but in all cases they are greater than $25%.$ In the case of a heavy neutrino the effect is much larger (up to a factor of 6). Combining our results with the best presently available experimental limits on the half-life of the $0\ensuremath{ u}\ensuremath{\beta}\ensuremath{\beta}$ decay, we have extracted new limits on the effective neutrino mass (light and heavy) and the effective Majoron coupling constant.

Lung involvement in primary Sjögren's syndrome is mainly related to the small airway disease

Abstract: OBJECTIVE To evaluate lung involvement in patients with primary Sjogren’s syndrome. METHODS Sixty one consecutive, non-smoking patients, 58 women and three men, were evaluated clinically, physiologically, and radiologically. A bronchial and/or transbronchial biopsy was performed on 13 of the patients. Physiological data were compared with that of a control group of 53 healthy non-smoking subjects matched for age and sex. RESULTS In 41% of the patients the main symptom was dry cough. Physiological studies revealed that the patients presented significantly lower expiratory flow values (% pred) when compared with those of the control group: the forced expiratory volume in one second (FEV 1 ) (mean (SD)) was 96% (16) v 111% (13) (p 50 ) was 72% (24) v 103% (17) (p 25 ) was 49% (25) v 98 % (20) (p 2 ) correlated significantly with MEF 50 ( r =0.35, p 25 ( r =0.33, p CONCLUSION The airway epithelia seem to be the main target of the inflammatory lesion of the lung in patients with primary Sjogren’s syndrome. It seems to be common, subclinically leading to obstructive small airway physiological abnormalities.

Singularity free cosmological solutions in quadratic gravity

Abstract: We study a general field theory of a scalar field coupled to gravity through a quadratic Gauss-Bonnet term $\ensuremath{\xi}(\ensuremath{\varphi}{)R}_{\mathrm{GB}}^{2}.$ The coupling function has the form $\ensuremath{\xi}(\ensuremath{\varphi})={\ensuremath{\varphi}}^{n},$ where n is a positive integer. In the absence of the Gauss-Bonnet term, the cosmological solutions for an empty universe and a universe dominated by the energy-momentum tensor of a scalar field are always characterized by the occurrence of a true cosmological singularity. By employing analytical and numerical methods, we show that, in the presence of the quadratic Gauss-Bonnet term, for the dual case of even n, the set of solutions of the classical equations of motion in a curved FRW background includes singularity-free cosmological solutions. The singular solutions are shown to be confined in a part of the phase space of the theory allowing the non-singular solutions to fill the rest of the space. We conjecture that the same theory with a general coupling function that satisfies certain criteria may lead to non-singular cosmological solutions.

Pooling research results: benefits and limitations of meta-analysis.

Abstract: Article-at-a-Glance Background Meta-analysis, the systematic and quantitative synthesis of evidence, has developed considerably in the 1990s and is emerging as an important methodology in medical decision making. As a research methodology, meta-analysis has benefits and limitations that must be acknowledged in its application. Examples of benefits The benefits of meta-analysis include the ability to improve the power of small or inconclusive studies to answer questions and the ability to identify sources of diversity across various types of studies. Meta-analysis may reveal how heterogeneity among populations affects the effectiveness of medical interventions in different settings and in different patients. It can also help detect biases, such as publication bias and "Tower of Babel" bias, as well as deficiencies in the design, conduct, analysis, and interpretation of research. In this way, it can also stimulate improvements in the quality of the data needed to optimize medical care. Examples of limitations Meta-analysis cannot improve the quality or reporting of the original studies. Other limitations come from misapplications of the method, such as when study diversity is ignored or mishandled in the analysis or when the variability of patient populations, the quality of the data, and the potential for underlying biases are not addressed. Conclusions Meta-analysis has promoted the sense that obtaining evidence is a global enterprise and that complete information needs to be evaluated and synthesized to obtain the most unbiased results. Analyzing sources of bias and diversity is essential to performing, understanding, and using meta-analyses in medical care.

Implicit-explicit multistep methods for quasilinear parabolic equations

Abstract: Efficient combinations of implicit and explicit multistep methods for nonlinear parabolic equations were recently studied in [1]. In this note we present a refined analysis to allow more general nonlinearities. The abstract theory is applied to a quasilinear parabolic equation.

Current Advances and Changes in Treatment Strategy May Improve Survival and Quality of Life in Patients With Potentially Curable Gastric Cancer

Abstract: Background: The treatment strategy for gastric cancer is determined by the stage of disease. Advances in diagnostic techniques such as endoscopic ultrasound (EUS) and in staging have increased the accuracy of pretreatment staging. Correct staging is a prerequisite for the optimal treatment of gastric cancer patients. Long-term expected survival and quality of life (QOL) are the major criteria determining the therapeutic strategy.

N=1 supersymmetric SU(4)xSU(2)LxSU(2)R effective theory from the weakly coupled heterotic superstring

Abstract: In the context of the free-fermionic formulation of the heterotic superstring, we construct a three generation N=1 supersymmetric SU(4)xSU(2)LxSU(2)R model supplemented by an SU(8) hidden gauge symmetry and five Abelian factors. The symmetry breaking to the standard model is achieved using vacuum expectation values of a Higgs pair in (4bar,2R)+(4,2R) at a high scale. One linear combination of the Abelian symmetries is anomalous and is broken by vacuum expectation values of singlet fields along the flat directions of the superpotential. All consistent string vacua of the model are completely classified by solving the corresponding system of F- and D-flatness equations including non-renormalizable terms up to sixth order. The requirement of existence of electroweak massless doublets further restricts the phenomenologically viable vacua. The third generation fermions receive masses from the tree-level superpotential. Further, a complete calculation of all non-renormalizable fermion mass terms up to fifth order shows that in certain string vacua the hierarchy of the fermion families is naturally obtained in the model as the second and third generation fermions earn their mass from fourth and fifth order terms. Along certain flat directions it is shown that the ratio of the SU(4) breaking scale and the reduced Planck mass is equal to the up quark ratio m_c/m_t at the string scale. An additional prediction of the model, is the existence of a U(1) symmetry carried by the fields of the hidden sector, ensuring thus the stability of the lightest hidden state. It is proposed that the hidden states may account for the invisible matter of the universe.

A kurtosis-based dynamic approach to Gaussian mixture modeling

Abstract: We address the problem of probability density function estimation using a Gaussian mixture model updated with the expectation-maximization (EM) algorithm. To deal with the case of an unknown number of mixing kernels, we define a new measure for Gaussian mixtures, called total kurtosis, which is based on the weighted sample kurtoses of the kernels. This measure provides an indication of how well the Gaussian mixture fits the data. Then we propose a new dynamic algorithm for Gaussian mixture density estimation which monitors the total kurtosis at each step of the EM algorithm in order to decide dynamically on the correct number of kernels and possibly escape from local maxima. We show the potential of our technique in approximating unknown densities through a series of examples with several density estimation problems.

Mobile agents for WWW distributed database access

Abstract: The popularity of the Web as a universal access mechanism for network information has created the need for developing Web based DBMS client/server applications. However, the current commercial applet based methodologies for accessing database systems offer limited flexibility, scalability and robustness. We propose a new framework for Web based distributed access to database systems based on Java based mobile agents. The framework supports lightweight, portable and autonomous clients as well as operation on slow or expensive networks. The implementation of the framework shows that its performance is comparable to, and in some cases outperforms, the current approach. In fact, in wireless and dial-up environments and for average size transactions, a client/agent/server adaptation of the framework provides a performance improvement of approximately a factor of ten. For the fixed network, the gains are about 40% and 30% respectively.

Proton induced thick target γ-ray yields of light nuclei at the energy region Ep=1.0–4.1 MeV

Abstract: Excitation function measurements of thick target c-ray yields were taken for the elements Li, B, F, Na, Mg, Al, Si and P after bombardment with protons at the energy interval Epa 1.0‐4.1 MeV. The yields of all c-rays emitted at Epa 1.77 and 4.0 MeV are tabulated and discussed. ” 1999 Elsevier Science B.V. All rights reserved.

Nerve and vessel injuries during high tibial osteotomy combined with distal fibular osteotomy: a clinically relevant anatomic study.

Abstract: Based on our clinical experience and an anatomical study, we examined the conditions under which injury to the popliteal artery, tibial nerve or peroneal nerve and its branches may occur during high tibial osteotomy. In 250 high tibial osteotomies performed in our department, we observed the following intraoperative complications. (1) The popliteal artery was severed in 1 patient and repaired by the same surgical team using a microsurgical technique. (2) A tibial nerve paresis also occurred in 1 patient. (3) In 3 patients, temporary palsy of the anterior tibialis muscle was documented. (4) In 4 other patients, palsy of the extensor hallucis longus occurred. To investigate the causes of these complications in the popliteal artery, tibial nerve and branches of the peroneal nerve, we dissected the neurovascular structures surrounding the area of the osteotomy in 10 cadaveric knees and performed a high tibial osteotomy in another 13 cadaveric knees. We concluded the following. (1) The popliteal artery and tibial nerve are protected, at the level of the osteotomy, behind the popliteus and tibialis posterior muscles. Damage can occur only by placing the Hohman retractor behind the muscles. The insertion of the muscles is very close to the periosteum and can be separated only with a scalpel. (2) The tibialis anterior muscle is innervated by a group of branches arising from the deep branch of the peroneal nerve. In two-thirds of the dissected knees, we found a main branch close to the periosteum, which can be damaged by dividing the muscle improperly or due to improper placement and pressure of the Hohman retractor. This may explain the partially reversible muscle palsy. (3) The extensor hallucis longus is also innervated by 2–3 thin branches, arising from the deep branch of the peroneal nerve, but in 25% of the specimens, only one large branch was found. This branch is placed under tension by manipulating the distal tibia forward. Thus, it may be damaged by the Hohman retractor during distal screw fixation, tensioned by hyperextension or directly injured during midshaft fibular osteotomy.

Synthetic Analogues for Oxovanadium(IV)–Glutathione Interaction: An EPR, Synthetic and Structural Study of Oxovanadium(IV) Compounds with Sulfhydryl‐Containing Pseudopeptides and Dipeptides

Abstract: Valuable analogues of the VIVO2‡ ± glutathione complex have been synthesized and characterized. The reaction of [VO(CH3COO)2(phen)] (phenˆ 1,10-phenanthroline) with the sulfhydryl-containing pseudopeptides (scp) N-(2mercaptopropionyl)cysteine (H4m2pc), and N-(3-mercaptopropionyl)cysteine (H4m3pc) in the presence of triethylamine gives the oxovanadium(iv) compounds [(Et3NH)2][VO(m2pc)] (1) and [(Et3NH)2][VO(m3pc)] (2), while reaction of [VOCl2(phen)] with the scp N-(2mercaptopropionyl)glycine (H3mpg) and the dipeptides glycylglycine (H2glygly) and glycyl-l-alanine (H2glyala) in the presence of triethylamine results in the formation of the compounds [Et3NH][VO(mpg)(phen)] (3), [VO(glygly)(phen)] ́ 2 CH3OH (4 ́ 2 CH3OH), and [VO(glyala)(phen)] ́ CH3OH (5 ́ CH3OH). Complex [VOCl2(phen)(CH3OH)] (7) was prepared by the reaction of [VOCl2(thf)2] with phen in a methanolic solution. The X-ray structure of 3 shows that the vanadium(iv) atom is ligated to a tridentate mpg3ÿ ligand at the Sthiolato, Npeptide and Ocarboxylato atoms. The X-ray structure of 7 is also reported. The optical, infrared, magnetic, electron paramagnetic resonance, and electrochemical properties of compounds 1 ± 5 ́ CH3OH and 7 were studied. Combination of the correlation plots of the EPR parameters gz versus Az , or the groundstate orbital population (b*)2 versus Az , together with the additivity relationship, Az,calcdˆSniAzi/4, were shown to provide a powerful tool for probing the equatorial donor atoms in an oxovanadium(iv) compound and consequently in biomolecules. Thus, these methods provide valuable evidence for the assignment of the equatorial donor atoms for the VIVO2‡ center of the VIVO2‡ ± glutathione system at various pH values. Model NMR studies (interaction of vanadium(v) with H3mpg) showed that there is a possibility of vanadium(v) ligation to glutathione. The contribution of a deprotonated peptide(amide) nitrogen to Az is not a fixed quantity (it varies from 29 to 43 10ÿ4 cmÿ1), but is influenced by the presence of the three other donor atoms in the equatorial plane and, in particular, their charge.

Aggregation of hsp70 and hsc70 in vivo is distinct and temperature-dependent and their chaperone function is directly related to non-aggregated forms.

Abstract: We used non-denaturing gradient analysis of cell extracts before and after heat treatment of the cells and showed that hsp70 and hsc70 aggregate in vivo in a temperature-dependent fashion. Their aggregation profiles were found to be clearly distinguishable and sensitive to ATP depletion. Pore exclusion limit electrophoresis showed that these two proteins are mainly found in autoaggregated forms including dimers, trimers and oligomers. The addition of denatured luciferase to the cell extracts reversed the aggregation of both proteins towards their non-aggregated forms. Immunoprecipitation and Western-blot analysis showed that the non-aggregated form is the only one bound to denatured luciferase. Our results suggest that aggregated hsp70 and hsc70 represent predominantly self-associated molecules unable to exert chaperone activity. The cochaperone hsp40 was also found to be aggregated and, on addition of denatured luciferase, its aggregation was reversed to a non-aggregated state. Immunoprecipitation analysis indicated that hsp40 forms a complex with the non-aggregated form of hsc70 and denatured luciferase. These results confirm previous in vitro studies and support the suggestion that in vivo cytosolic hsp70 and hsc70 exist mainly in an oligomer–monomer equilibrium which is dependent on the environmental temperature, the levels of ATP and the presence of denatured proteins.

Evaluation of collateral sprouting after end-to-side nerve coaptation using a fluorescent double-labeling technique.

Abstract: The mechanism of end-to-side neurorrhaphy is believed to be by collateral sprouting, although evidence for this is lacking. This study validates whether axonal sprouting originates from the donor intact nerve by collateral sprouting with the use of a fluorescent double-labeling technique. End-to-side neurorrhaphy was performed on adult female Sprague-Dawley rats. Eight and 12 months postoperatively, animals were injected with true blue and diamidino yellow into the tibialis anterior and/or gastrocnemius muscles and were transcardially perfused with fixative after 7 days of retrograde transport. The lumbar enlargement and the dorsal root ganglia from L3 to L6 were harvested and serial sectioning and fluorescent microscopy were performed. No double-labeling neurons were observed in control animals, but a group of neurons that were greenish or yellowish in color were seen with single labeling. Double-labeling neurons, however, were seen in animals treated with end-to-side neurorrhaphy whether or not perineurotomy was performed. These results demonstrate that one parent nerve fiber can emanate another axon by collateral sprouting following end-to-side neurorrhaphy. We hypothesize that the causes of collateral sprouting might result from “switching signals” and/or “switching factors.” © 1999 Wiley-Liss, Inc. MICROSURGERY 19:281–286 1999

Ecological risk assessment of agrochemicals in European estuaries

Abstract: The Fluxes of Agrochemicals into the Marine Environment (FAME) project, which was funded by the European Union, studied the presence and fate of pesticides in major European river/estuary systems. As part of the cooperation within FAME, samples from four rivers were sent to all participants. Each laboratory analyzed the samples with a range of techniques, thus creating a database that could not have been developed through individual efforts. In the present study, compounds are identified that are important to the contamination of the marine environment on the basis of their environmental concentrations and toxicological properties. Two risk assessment methods are used. The toxic unit method, which provides a first indication of the relative contribution of compounds to the total toxicity of a sample, and the inverse method of Van Straalen and Denneman, which has been used to assess the ecological risk of a selected set of compounds (i.e., atrazine, simazine, alachlor, and metolachlor). Environmental concentrations of these target compounds were determined at different seasons during a period of at least 1 year and, hence, variations in ecological risk patterns for different European river/estuary systems could be identified. The application of the risk assessment procedures is hampered by a lack of toxicological data. It is concluded, however, that pesticides exert a significant pressure on the aquatic system. To our knowledge, this is the first joint study in which the ecological risks of modern pesticides related to different European river/estuary systems are compared.

Automated management of nutrient solutions based on target electrical conductivity, ph, and nutrient concentration ratios

Abstract: An algorithm to automatically formulate the composition and prepare nutrient solutions for soilless cultures based on desired characteristics given as target values is proposed To formulate the complete ionic composition of a nutrient solution, standard recommendations referring to the following solution characteristics should be available: (i) electrical conductivity (EC), (ii) pH, (iii) concentration ratios of macronutrients (meq basis), and (iv) micronutrient concentrations Moreover, the mineral composition of the water used to prepare the nutrient solution should be taken into account To develop the main steps of the algorithm, the total salt concentration (meq L‐1) of the nutrient solution is related to the desired electrical conductivity The target pH indicates the concentration of HCO3 − in the nutrient solution, whereas the absolute concentration of each macronutrient is derived from the desired concentration ratios and the total salt concentration The necessary calculations are stan