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Polyurethanes (PURs) synthesized using hexamethylene diisocyanate (HDI) and polyethylene glycol with molecular weights of 400 g mol−1 and 600 g mol−1 (PUR 400 HDI and PUR 600 HDI) or polyoxypropylene diol (POPD) of molecular weights 1002 g mol−1 and 2002 g mol−1 (PUR 1002 HDI and PUR 2002 HDI) were used as modifiers for diglycidyl ether of bisphenol A. It was found that maximum improvement in impact strength and critical stress intensity factor (KC) values was obtained for compositions containing 15% PUR 400 and 5% PUR 1002. Such improvement in the resistance to crack propagation due to PUR incorporation might be related with the soft segments of polyethylene glycol and POPD. The critical stress intensity factor (KC) values increased from 1.7 MPa m1/2 (virgin epoxy) to 2.5 MPa m1/2 with the addition of 10% PUR 400. Fourier transform infrared spectra confirmed the formation of an interpenetrating polymer network structures with polymeric modifier. Scanning electron micrographs of epoxy resins (EPs) modified with PUR with longer chains (PUR 1002 and PUR 2002) exhibited a deformed leaf-like morphology with larger plastic deformation zones with the presence of microcracks. However, EP/PUR based on polyethylene glycol showed less deformed structure. [ABSTRACT FROM PUBLISHER]

The present work deals with the effect of the sonication amplitude and the mixing time on the mechanical and thermal properties of an epoxy (EP) resin modified with 1 wt% nanoclay. It was confirmed that the mechanical properties of the EP matrix were dependent on the dispersion of nanoclays which in turn are affected by the mixing parameters. At short mixing times, the impact strength (IS) increased with increasing amplitude. Maximum IS and flexural properties values were obtained with ultrasonic amplitude of 260 μm and a mixing time of 10 min. The effect of mixing time was more pronounced on the deflection temperature under load than the sonication amplitude. Moreover, it was shown that longer mixing times resulted in a smoother nanocomposite fracture surface with only few cracks. The fracture surfaces of the EP nanocomposites were rough with significant plastic deformations and several microcracks with nanoparticles embedded in the polymer matrix. [ABSTRACT FROM PUBLISHER]

The title compound(tetrazol-5-yl)acetic acid (TA) is an interestingmolecule that contains both a carboxylic group and its isostere tetrazolylgroup. Out of nine theoretically predicted stable structures of TA,three appeared to be present in solid argon. Thermal decompositionof the species aided by water molecules was studied in detail bothexperimentally using FTIR matrix isolation technique and theoreticallyat the B3LYP/6-311++G(2d,2p) level. Experimentally, it was found thatthe decarboxylation process appeared at the presence of water tracesin the system. Theoretically, it was shown that the energy barrierof the water assisted process was lower by ca. 30 kJ mol–1comparing to the process without water participation. The UV photolysisof the TA/Ar system was studied using both broad-band and narrow-bandsources. The main photoproducts appeared to be carbodiimidylaceticacid and (1H-diaziren-3-yl)acetic acid. The progressof the reactions induced was followed by FTIR spectroscopy, whereasinterpretation of the results was supported by quantum chemical calculations(DFT, TD-DFT). [ABSTRACT FROM AUTHOR]

The present work investigates the effect of epoxy resin (EP) modification with polyurethanes (PURs) based on polyethylene glycol and two different diisocyanates: 4,4′-diphenylmethane diisocyanate (MDI) and 2,4-toluene diisocyanate (TDI). The impact strength of the material based on 15 wt% PUR with TDI was enhanced by 130%, while the critical stress intensity factor and the flexural strength of epoxy composition based on 5 wt% PUR with MDI increased by approximately 140% in comparison with unmodified EP. Fourier transform infrared spectroscopy confirmed the occurrence of chemical reaction between the hydroxyl groups of EP and isocyanate groups of PUR, explaining the improvement in the mechanical properties of EP. Moreover, scanning electron micrographs showed a rough surface with plastic yielding and several microcracks in the compositions containing TDI-based PUR and deformed leaf-like morphology with more elongated structure for the EP modified with MDI-based PUR. [ABSTRACT FROM PUBLISHER]

Abstract: The (tetrazol-5-yl)acetic acid crystal was characterized by the X-ray diffraction and FTIR spectroscopic methods. The analysis of the crystal structure reveals that the compound exists in the solid state as 1H-tautomer. The molecules are linked by two types of the intermolecular hydrogen bonds forming an infinite two-dimensional network in the (101) plane. Intramolecular NO hydrogen bonds are also formed in the crystal. The analysis of the FTIR spectra of the crystalline sample and its deuterated analogue, based on the B3LYP/6-311++G(2d,2p) frequency calculations of two model tetramers, has been performed in relation to the obtained crystal structure data. [Copyright &y& Elsevier]

The present study investigates the effect of the ultrasonic amplitude and the mixing time on the impact strength (IS) and the flexural properties of an epoxy resin containing 1wt% nanoclay. The results showed that the amplitude and the mixing time had a significant effect on the IS but a smaller effect on the flexural strength and the flexural strain at break of the epoxy resin. Maximum IS and flexural properties were obtained with a maximum ultrasonic amplitude of 260µm (100%) and a mixing time of 10 min due to better nanoparticles dispersion. The utility function was found to be the highest at lower mixing times and higher amplitudes for both considered cases of satisfactory mechanical properties values. It was confirmed that under optimum mixing conditions, the fracture surfaces of epoxy composites were rougher with significant plastic deformations with nanoparticles embedded in the polymer matrix, explaining thus the improvement of the mechanical properties of the polymer matrix. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus is one of the most interesting microbial species in clinical studies. It is characterized by a wide extent of strain diversity, first of all, due to variability in virulence and pathogenicity. The aim of this study was to test the method of rapid Staphylococcus strain differentiation by a certain sign based on registration of characteristics features of MALDI mass spectra accumulated during direct protein profiling of the bacterial cell. The model signs registered as strain differences included production of β-lactamase and α-hemolysin encoded by blaZ and hla genes, respectively. The mathematical analysis of MALDI mass spectra accumulated for 53 S. aureus isolates using the clustering genetic algorithm resulted in generation of two independent classification models, which could differentiate the strains by the considered features. Using statistical contribution of each mass peak to the model, the most significant peaks (masses), which could be considered as the markers of Staphylococcus strain differences, were found. The generated diagnostic models were characterized by the following sensitivity and specificity coefficients: 97.5 and 82.5%, respectively, for strain differentiation by β-lactamase production and 90.0 and 88.7% by the presence of α-hemolysin. [ABSTRACT FROM AUTHOR]

The identification of Salmonella sp. in stool samples usually takes 2 days when employing routine procedures. Fast approaches are necessary in order to shorten the analysis time. The aim of this work was the development of a rapid procedure for the detection of Salmonella sp. from clinical stool samples. Spiked stool samples were cultured in selective selenite enrichment broth. Identifications were directly performed from the liquid broth by the MALDI Biotyper. After the evaluation of this method, the same procedure was applied to clinical samples. Coevally, the samples were streaked on Hektoen agar and single colonies were analyzed by the MALDI Biotyper. For comparison, the liquid broth was plated according to the standard laboratory procedure. A total of 4,847 samples were analyzed for Salmonella sp. In total, 108 Salmonella sp.-positive samples were identified; 66 of these were identified after the streaking of stool samples on Hektoen agar and subsequent MALDI Biotyper analysis of Salmonella sp. suspicious colonies. These and a further 34 samples were detected as Salmonella sp.-positive directly from the selenite enrichment broth on day one. Eight Salmonella sp.-positive samples were not detected before plating of the selenite broth and subsequent MALDI Biotyper analysis on day two. The combination of MALDI Biotyper analysis and selective selenite enrichment broth identification delivers positive results for the majority of the samples already after one day. [ABSTRACT FROM AUTHOR]

Abstract: The most stable conformers of 2-(tetrazol-1-yl)-, 3-(tetrazol-1-yl)- and 2-(tetrazol-5-yl)pyridines undergo photolysis in Ar matrices at cryogenic temperatures to yield pyridin-2-ylcarbodiimide or pyridin-3-ylcarbodiimide. Spectroscopic evidence of carbon-to-nitrogen rearrangement in the case of the 2-(tetrazol-5-yl)pyridine molecule is provided. For the latter molecule a second pathway leads to the 1-cyclopenta-2,4-dienylketenimine formation. The experimental findings are supported by extensive B3LYP/6-311++G(2d,2p) calculations. [Copyright &y& Elsevier]

This work investigates the effect of polycarbonate (PC) and montmorillonite (MMT) content on the properties and morphology of epoxy resin (EP). Izod impact strength (IS), flexural strength and critical stress intensity factor (KC) were estimated as function of modifiers content. The values of IS and KC parameters increased by respectively 150% and 90% with the addition of 5 wt % PC. Hybrid compositions containing 1 wt % MMT and 5 wt % PC exhibited the best mechanical properties. Indeed, the addition of 1 wt % MMT to EP modified with 5 wt % PC caused enhancement of IS values by 100% in comparison with neat EP. SEM micrographs revealed that the enhancement mechanism of mechanical properties might be due to extensive yielding of EP associated with the formation of stratified elongated structures. Moreover, differential scanning calorimetry analysis revealed that the addition of nanoclay to EP resulted in a decrease of the glass transition temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

The present work investigates the mechanical properties of conventional and hybrid composites based on epoxy resin. Diglycidyl ether of bisphenol A was used as the matrix and triethylenetetramine was used as the curing agent. Polyurethane (PUR) used was based on polyether and toluene diisocyanate. Impact strength (IS), critical stress intensity factor (Kc), tensile strength (TS) and flexural strength were evaluated as function of modifiers content. It is shown that IS is increased by approximately 120% and 200% with the addition of respectively 10 phr of glass beads (GB) or 10 phr PUR, in comparison with IS of the unmodified epoxy resin. Moreover, Kc was increased by approximately 20% with 10 phr GB and 35% with 10 phr PUR. The addition of 15 phr PUR gave compositions with 30% enhanced TS and 40% increased tensile strain at break. However, the strain at break decreased with increasing amount of GB. Hybrid composition containing 10 phr PUR and 15 phr GB exhibited the maximum tensile energy to break corresponding to 80% and 85% improvement respectively in relation to the energy at break of the virgin epoxy resin and composition with only 10 phr PUR. Infrared spectra analysis of the compositions containing PUR revealed the formation of an interpenetrating polymer network structure between the modifier and the polymer matrix [ABSTRACT FROM PUBLISHER]

Epoxy resin was modified with polyurethane having different isocyanate index. Impact strength, tensile strength, elongation at break and flexural strength were estimated as functions of polyurethane content and isocyanate index. Hardness, linear expansion coefficient and the deflection temperature under load were estimated for selected compositions. Infrared spectroscopy was carried out for unmodified epoxy resin and compositions with improved mechanical properties. Maximum improvement in the fracture toughness was reached with polyurethane with highest content of isocyanate. Hardness was not affected but elastic modulus decreased, implying a softening of epoxy-based compositions. The infrared spectra indicated that an excess of isocyanate groups leads to a grafting process between the modifier and the matrix, explaining the toughening of the latter. [ABSTRACT FROM AUTHOR]

Abstract: A flat, compressed elastic film on a viscous layer is unstable. The film can form wrinkles to reduce the elastic energy. In this paper, we are interested in the two-dimensional models for thin films bonded to a viscous layer and in particular we focus on generic instabilities evidenced in this context by Suo and coworkers [Huang, Z., Hong, W., Suo, Z., . Non linear analyses of wrinkles in a film bonded to a compliant substrate. J. Mech. Phys. Solids 53, 2101–2118; Lo, Y.H., 1991. New approach to grow pseudomorphic structures over the critical thickness. Appl. Phys. Lett. 59, 2311–2320]. We present a rigorous linear perturbation analysis for anisotropic materials, that allows the prediction of both the orientation of the corrugations of the thin film, and the wavelength that maximize the growth velocity. Finally, we compare our theoretical estimates to experimental results for a alloy constraint to InP. [Copyright &y& Elsevier]

Currently, data for 107 sclerotherapy procedures in patients (mean age, 52.4 years) who have undergone renal sclerotherapy up until August 2017 has been analyzed (high-dose STS = 62; low-dose STS = 45). Target kidney volume decrease as measured on MRI was greater in patients who received high-dose STS (high-dose STS = 387 CC, low-dose STS = 178 CC; P <0.05). There was no statistically significant difference between the two groups in terms of total adverse events (high-dose STS = 14, low-dose STS = 5); however, post procedure pain was more frequent in patients receiving high-dose STS group (high-dose STS = 9, low-dose STS = 1 P <0.05). [Extracted from the article]

Abstract: We bonded quantum well InP dies on a photonic layer transferred on silicon CMOS processed wafer using direct molecular bonding. This approach is suitable for new applications, viz., photonics on silicon, 3D packaging and integrated sensors. The chips are diced from a bulk substrate and bonded directly onto a silicon substrate without any organic nor metallic adhesive layer. A thin silicon dioxide layer can be added on both assembled surfaces to enhance bonding quality. After bonding, the dies can mechanically be thinned down to 20μm and chemically etched. The InAsP quantum well stack of the InP dies keeps its optoelectronics features and performances after being transferred onto a silicon substrate. [Copyright &y& Elsevier]

[Display omitted] • Five isomers of 3-aminopyrazine-2-carboxylic acid detected and characterized in solid argon. • UV-laser induced conformational and amino-imino transformations uncovered. • Decarboxylation and pyrazine ring cleavage observed upon irradiation. • Potential energy surfaces explored using the B3LYP/6–311++G(2d,2p). The UV-induced photochemistry and molecular structure of 3-aminopyrazine-2-carboxylic acid were studied in argon matrices by Fourier-transform infrared spectroscopy and B3LYP/6–311++G(2d,2p) calculations. Out of seventeen possible isomers of this molecule located on the singlet potential energy surface the most stable one, APA1 comprising intramolecular O–H···N and N–H···O hydrogen bonds, was detected experimentally in the matrix after deposition. Two new conformers APA2 and APA3 were generated upon irradiation with λ = 280 nm by trans/cis -COOH isomerization and at λ = 360 nm by COOH group rotamerization, respectively, whereas an amino-imino tautomerization leading to IPA1 and IPA2 structures occurred at λ = 305 nm. The reverse reactions were also observed upon irradiation of the matrices at 265, 230 and 400 nm. Simultaneously with the photoisomerizations, a cleavage of the pyrazine ring along with CO 2 elimination was observed leading to the formation of carbodiimide and cyanamide derivatives. [ABSTRACT FROM AUTHOR]

• Four isomers of 2-aminonicotinic acid detected and characterized in solid argon. • UV-laser induced conformational and amino-imino transformations uncovered. • Potential energy surfaces explored using the DFT and XMS-CASPT2 methods. • Amino-imino tautomerization due to proton transfer in the vibrationally hot S 0 state. The structure and phototransformations of 2-aminonicotinic acid (ANA) induced by tunable UV laser were studied in low-temperature argon matrices with the use of Fourier-transform infrared (FTIR) spectroscopy. After the deposition of the argon matrix, two amino isomers (ANA-1 and ANA-2) were detected, with populations of 96 % and 4 %, respectively. Electronic structure calculations confirm these to be the two most stable isomers of ANA. The irradiation of the amino isomers gives rise to an intricate system of photoinduced reactions, which involves amino-imino phototautomerism, and rotations of the carboxylic group. Following irradiation at 350 nm, a rotation of the carboxylic group of ANA-1 was detected leading to increase of the ANA-2 form. In turn, at 310 nm two new imino forms (INA-1 and INA-2) of 2-aminonicotinic acid were generated indicating that UV-induced hydrogen atom transfer between ANA and INA tautomeric forms took place. The corresponding reverse photorotamerizations were also detected at 390 nm, resulting in the recovery of the initial ANA-1 and ANA-2 isomers. On the basis of electronic structure calculations, we hypothesize that ANA-INA phototautomerization takes place in the vibrationally hot electronic ground state. Its occurrence appears to be contingent on the molecule being able to access a conical intersection between the lowest singlet excited state and the ground state. [ABSTRACT FROM AUTHOR]

• SeO 2 based glasses of composition 39PbO-(60- x)B 2 O 3 - x SeO 2 :1.0 Er 2 O 3 were synthesized. • IR/Raman spectra suggested growth of [SeO 3 ]2−/[SeO 4 ]2− units' ratio with SeO 2 content. • Analysis of OA spectra indicated J-O parameters to follow the order: Ω 2 > Ω 6 > Ω 4. • Green and NIR PL emission bands exhibited significant growth with SeO 2 content. • PL spectra quantitatively analysed using kinetic rate equations. • Gain co-efficient G(λ) of 4I 13/2 →4I 15/2 transition indicated its lasing behaviour. In this work we have studied impact of SeO 2 concentration on luminescence properties of 39PbO-(60- x)B 2 O 3 - x SeO 2 :1.0 Er 2 O 3 (10 ≤ x ≤ 50) glass system. The structural analysis of the samples carried out by XRD, SEM indicated that the prepared samples are in amorphous phase. IR, Raman and XPS studies revealed increasing presence of isolated selenite [SeO 3 ]2−groups and decreasing concentration of [SeO 4 ]2−(selenate) groups with increasing content of SeO 2 in the glass network. Optical absorption (OA) spectra revealed absorption bands due to 4I 15/2 → 4F 7/2 , 9/2 , 2H 11/2 , 4S 3/2 , 4I 9/2 , 11/2 , 13/2 transitions of Er3+ ions. Using J-O theory, the spectra were characterized and the evaluated Ω λ parameters are found to be in the order: Ω 2 > Ω 4 > Ω 6. The PL spectra recorded at λ exc = 378 nm exhibited the emission bands due to 2H 11/2 →4I 15/2 (B), S 3/2 →4I 15/2 (G), 4F 9/2 →4I 15/2 (O) and 4I 13/2 →4I 15/2 (NIR) transitionsof Er3+ ions. With the gradual increase SeO 2 content, the PL emission bands (especially green and NIR bands) have exhibited significant growth. The spectra were quantitatively analysed using kinetic rate equations and the causes for enhancement of PL emission were recognised and discussed. From the gain co-efficient G(λ) of the 4I 13/2 →4I 15/2 transition, its lasing behaviour is detected for a population inversion of nearly 50%. [ABSTRACT FROM AUTHOR]

This study is devoted to investigate the effect of Cu ions on the concentration of defect centres like free volume elements (which influence the physical properties of the glasses to a large extent), integrated in exotic lithium magnesium sulphophosphate glasses using positron (e+) annihilation lifetime spectroscopy (PAL) technique. Glasses of a particular composition viz., 20Li 2 SO 4 –20MgO–(60-x) P 2 O 5 : x CuO (0 ≤ x ≤ 1.0 in mol%) were prepared by traditional melt-quenching technique. The analysis of the glass structure by means of spectroscopic studies, indicated that there is a gradual increasing fraction of Cu+ ions with increase of CuO content. The analysis further suggested that Cu2+ ions acted as modifiers in the glass network while Cu+ ions took part network forming position and increased the rigidity of the glass network. Later, positron annihilation decay profiles in the samples were recorded. 22Na isotope (0.1 MBq) was used as the positron source for this study. The obtained decay profiles were resolved in to three components and the corresponding intensity (I) and lifetime (τ) parameters were estimated and their variations with the concentration of CuO were plotted. The plots suggested that among the three intensity components, the third component (even though its contribution to the total intensity is small) exhibited the largest lifetime and further exhibited a decreasing trend with increase of CuO content. Moreover, radius of the cavity (R) and the fraction free volume (f v) entrenched in the glass matrix are found to decrease with increase of CuO concentration. The analysis of results of these studies in combination with the conclusions drawn from dielectric and related studies suggested a gradual decreasing concentration of O h Cu2+ ions which induce free volume defects by acting as modifiers. Overall analysis of the results of PAL studies suggested increasing content of CuO facilitates the increasing rigidity or increasing corrosion resistance of lithium sulphophosphate glasses. • Free volume fraction in CuO doped lithium sulphophosphate glass system is evaluated. • Positron annihilation technique with a positron source of 0.1 MBq is used for this. • Lithium sulphophosphate glass with CuO (1.0 mol%) revealed minimal defect concentration. • Lower concentration of defects is attributed to high content of Cu+ ions in the glass. • Results were found to be in synchronization with conclusions drawn by other studies. [ABSTRACT FROM AUTHOR]

In this investigation we have estimated the fraction of free volume defects and also their size (to the nanoscale) entrenched in V 2 O 5 doped PbO added Bi 2 O 3 –SiO 2 glass system (by means of positron annihilation spectroscopy (PAS) studies) with a view to understand the influence of such defects on several physical properties of this glass system. The glasses of the chemical composition viz., 30PbO–5Bi 2 O 3 ‒ (65- x) SiO 2 : x V 2 O 5 (0 ≤ x ≤ 0.6, insteps of 0.1) are used in this study. Glasses were prepared by traditional melt quenching technique. PAS studies were perormed using 22Na (0.1 MBq) positron radioactive source. Positron annihilation lifetime is found to be significantly affected by the concentrations of V 2 O 5 dopant. The third component I 3 of positrons is found to be feeble in all the glasses. For this reason, initially, we have used a simple two component positron trapping model (ignoring the third component) to calculate annihilation parameters viz., the bulk average positron lifetime (τ b), positron trapping rate in defect (κ d), fraction of trapped positrons (η), the average lifetime for all the positrons (τ avg) and defect-related time (τ d). The calculations were repeated with three component positron model. The results of positron annihilation studies have indicated that concentration of free volume nano sized defects, the fraction (f v) of volume defects and their radius (R) are the lowest for the glass V 3. Such minimal value of defect concentration is ascribed to dominant existence of vanadium ions in V5+ valence state that involves in glass network forming with VO 5 structural units. Whereas, the observed increased value of f v with increase of V 2 O 5 from 0.3 to 0.6 mol% is attributed to growing concentration of vanadyl complexes (VO)2+ that have acted as modifiers. Quantitative information obtained on dependence of concentration of free volume imperfections on V 2 O 5 content in the studied glass is observed to be in good agreement with the inferences drawn from several macroscopic properties that include electrical properties reported earlier. • PbO–Bi 2 O 3 –SiO 2 glasses doped with different concentrations of V 2 O 5 were synthesized. • Concentration of free volume defects trapped in glasses estimated by PAS technique. • Radius of voids is found to be the lowest in the glass doped with 0.3 mol% of V 2 O 5. • Change in free volume defect concentration is correlated with VO2+ ion concentration. [ABSTRACT FROM AUTHOR]

• Influence of V 2 O 5 on dielectric features of bismuth silicate glasses is investigated. • Spectroscopic studies revealed increasing disorder of the glass network with V 2 O 5 content. • σ ac exhibited maximal value for the glass with 0.6 mol% of V 2 O 5 content. • In the glasses doped with >0.3 mol% of V 2 O 5 ionic contribution to σ ac is dominant. V 2 O 5 doped lead bismuth silicate glasses were prepared by melt quenching technique. Initially, the spectroscopic investigations viz., optical absorption (OA) and EPR spectral studies were performed; the results of these studies suggested reduction of a part of V5+ ions into V4+ ions (that are identified to form vanadyl complexes viz., VO2+). The results further indicated the largest concentration of such complexes in the glass doped with 0.6 mol% of V 2 O 5. Infrared spectral (IR) results suggested a progressive disintegration of the augmented glass network with increase of V 2 O 5 concentration beyond 0.3 mol%. Later, extensive investigations on dielectric properties were carried out. Values of dielectric permittivity, ε′(ω), loss tangent and a.c. conductivity, σ ac , observed to be minimal for the glass containing 0.3 mol% of V 2 O 5 (V 3 glass) and found to be increased for further increase of V 2 O 5 content at any frequency and temperature. The electric moduli components exhibited dipolar relaxation effects. Relaxation time τ for dipoles estimated from the spectra of electric moduli showed a decreasing trend as the V 2 O 5 content increased up to 0.3 mol% and beyond that τ is found to be increased. The complexes of V4+ and Bi3+ ions with oxygen ions were predicted to be the possible dipoles responsible for the dipolar effects. A.c. conductivity variation with V 2 O 5 concentration indicated the minimum for V 3 glass and exhibited increasing trend as the content of V 2 O 5 raised from 0.3 to 0.6 mol%. Quantitative analysis of this result indicated polaronic contribution to the conductivity (ascribed to mutual transfer of polarons between V4+and V5+ ions) is prevalent in these glasses. [ABSTRACT FROM AUTHOR]

We have investigated a family with severe X-linked spastic paraplegia and assigned the disease locus to Xq11.2-q23 by linkage and haplotype analysis. This region harbors the gene coding for proteolipid protein, which is mutated in one of the two established forms of X-linked spastic paraplegia, i.e., SPG2. We have performed extensive mutation analysis of this gene. Our failure to detect a mutation in this family suggests a third locus in X-linked recessive spastic paraplegia. [ABSTRACT FROM AUTHOR]

In this study we have investigated the influence of MnO content on electrical characteristics (viz., dielectric properties including impedance spectra over wide ranges of continuous frequencies and temperatures, a.c and d.c. conductivities) of lead zirconium silicate glass ceramic with a view to assess its insulating character. Such assessment is crucial for using the material in different electronic devices, for example, as insulating sheets in the display panels. The variations of ε, tan δ (measured at different temperatures and frequencies) observed with the concentration of MnO are analysed in terms of structural transformations taking place in the glass ceramics. Although, the dielectric constant and loss tangent with temperature and frequency have not exhibited any distinct dipolar relaxation effects, the electric moduli (evaluated using real and imaginary parts of dielectric constant) have exhibits such effects clearly. Moreover, the variation of relaxation time (evaluated from electric moduli spectra) indicated multiple relaxation times for dipoles. Relaxation effects were ascribed to the complexes of octahedral Mn2+ ions. The conductivity (both ac and dc) with concentration of MnO exhibited the minima at 0.6 mol% of MnO. This effect is attributed to predominant presence of Mn ions in tetrahedral positions that were assumed to alternate with SiO 4 units in the glass network. In the studied samples, both ionic and polaronic components are predicted to contribute to the conductivity. The polaronic component (arises due to exchange of polarons between Mn2+ ↔ Mn3+ ions) seemed to be gradually dominating over the ionic component with progressive insertion of MnO content up to 0.6 mol% in the bulk glass ceramic sample. The near temperature invariant part of σ ac behaviour (in the low temperature range) is analysed using both quantum mechanical tunnelling (QMT) model and the concentration of defect energy states near the Fermi level (N(E F), evaluated in this range of temperatures, was found to be the minimal for the sample M 6. Analysis of dc conductivity results suggested the small polaron hoping (SPH) model holds good in the high temperature region; however, for the low temperature part of dc conductivity variable range hopping (VRH) model seems to be more appropriate. Finally, with the increase of MnO concentration up to 0.6 mol% in the titled glass ceramics, the conductivity decreases and leads to increase in the insulating strength of the material. This unique functionality may also make the investigated glass ceramic material perspective for medical applications in addition to their usage as insulating sheets in the display panels. • Dielectric properties of MnO mixed lead zirconium silicate glass ceramics investigated. • Electrical moduli spectra exhibited relaxation effects due to octahedral Mn2+ ions. • Glass ceramic samples mixed with 0.6 mol% of MnO exhibited the lowest conductivity. • Dc conductivity variation in the lower temperature region is explained using VRH model. [ABSTRACT FROM AUTHOR]

This study consists of comprehensive investigations on dielectric permittivity (ε′), electric moduli (M′, M″), impedance (Z), and conductivity (σac) spectra over broad regions of frequency and temperature of lead zirconium silicate glass ceramics mixed with different concentrations of Fe2O3. The observed increase in dielectric permittivity with the content of Fe2O3 is attributed to the increasing presence of iron ions in octahedral positions. Electric moduli plots with frequency (ω) and temperature (T) exhibit dipolar effects. These effects are quantitatively analyzed by Cole–Cole plots; the analysis indicates the distribution of relaxation times. Probable dipoles for these effects are identified and discussed. AC conductivity (σac) shows a rising trend with an increase in Fe2O3 beyond 0.2 mol%, and this increase is attributed to the polaron exchange among Fe2+ and Fe3+ ions. The conduction mechanism is well explained using a polaron tunneling model in the middle‐frequency and high‐temperature regions. [ABSTRACT FROM AUTHOR]