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• Pb 3 O 4 mixed Li 2 O-SiO 2 :Au 2 O 3 glasses were synthesized and characterized. • Different dielectric parameters viz., ε ′ , M, Z and σ a c were measured as functions of Au 2 O 3 content. • ε′ was decreased with Au 2 O 3 upto 0.04 mol% due to growing presence of PbO 4 units. • Observed dipolar relaxation effects were evaluated using Cole-Cole diagrams. • σ a c exhibited a decreasing trend with Au 2 O 3 content up to 0.04 mol%. • Overall, the presence of red lead was found to reduce the conductivity in these glasses. Studies on dielectric properties viz., ε′ (dielectric permittivity), M, Z and σ ac as functions of frequency and temperature (over wide ranges), of glasses/glass-ceramics give quantitative information on their insulating character. Such studies are also useful for understanding structural aspects of these glasses to a great extent. In this work Pb 3 O 4 mixed Li 2 O-SiO 2 :Au 2 O 3 glasses were synthesized and heat-treated. Analysis of the results of various characterization techniques indicated increased degree of internal augmentation between various structural groups of the glass network. Observed decrease of ε′ with Au 2 O 3 content up to 0.04 mol% was attributed to the decreased magnitude of space charge polarization due to growing presence of PbO 4 units in the glass network. Dipolar relaxation effects of these samples were evaluated using Cole-Cole plots. Variation of conductivity with Au 2 O 3 concentration was analyzed using polaronic tunneling model. Conclusions of these results were found to be in in concurrence with spectroscopic studies. Overall, the presence of Pb 3 O 4 caused reduction the conductivity of these glasses. [ABSTRACT FROM AUTHOR]

• Li2O-HfO2-SiO2 glasses with fixed Sm2O3 and varied content of Au2O3 were prepared. • OA spectra exhibited a broad band in the visible region due to SPR of Au0 particles. • PL spectra of the glasses containing Au0 MPs showed a wide (sp → d) emission band. • PL spectra of Sm3+ doped glasses revealed bright orange and red emission bands. • Role of Au0 particles on improving red emission efficiency of Sm3+ ions was discussed. In this study, Li 2 O-HfO 2 -SiO 2 -Sm 2 O 3 -Au 2 O 3 glasses (doped with fixed concentration of Sm 2 O 3 and varied contents of Au 2 O 3) were synthesized and characterized. The role of Au0 particles on improvisation of red emission of Sm3+ ions was investigated. Optical absorption (OA) spectra of these glasses indicated a number of bands excited from 6H 5/2 of Sm3+ ions. A broad band in the greenish-yellow spectral region due to surface plasmon resonance (SPR) of Au0 nanoparticles was also detected in these spectra. Photoluminescence (PL) spectra of (Sm free glasses) embedded with Au0 metallic particles (MPs) showed a wide band in the visible region ascribed to the transition of electrons from sp → d energy bands. Luminescence spectra of Sm3+ doped glasses revealed bright orange and red emission bands with substantial increased intensities with increased concentration of Au 2 O 3. Effect of Au0 MPs on the red emission efficiency of Sm3+ ions was emphasized with kinetic rate equations. [ABSTRACT FROM AUTHOR]

Lead silicate glasses mixed with 5.0 mol% of Bi 2 O 3 and doped with varying concentrations of CoO have been synthesized. Optical absorption, infrared and photoluminescence spectra and luminescence decay profiles of the prepared glasses were recorded at ambient temperature. Analysis of IR spectral results have indicated that there is increasing proportion of the tetrahedral Co 2+ ions in the glass network with increase in the concentration of CoO. The emission spectra of Bi 2 O 3 free glasses exhibited two significant bands in the orange and red regions when excited at 595 nm. These bands are identified as being due to 4 T 1 ( 4 P)→ 4 A 2 ( 4 F) and 4 T 1 ( 4 P) → 4 T 2 ( 4 F) tetrahedral transitions of Co 2+ ion, respectively. The intensity of orange emission band due to 4 T 1 ( 4 P)→ 4 A 2 ( 4 F) transition is found to be enhanced nearly five times when the glasses are mixed with 5.0 mol% of Bi 2 O 3 . The quantitative analysis of these results indicated that the energy transfer from 3 P 1 → 1 S 0 emission transition of Bi 3+ ions to 4 T 1 ( 4 P)→ 4 A 2 ( 4 F) tetrahedral transition of Co 2+ ion is responsible for the enrichment of this orange emission. [ABSTRACT FROM AUTHOR]

The transparent glasses with composition 30PbO–10GeO 2 –(60−x)SiO 2 −xNb 2 O 5 (mol%) (0 ≤ x ≤ 2.5) are prepared by conventional melt quenching technique. The amorphous nature of the prepared glasses is characterized by XRD. The spectroscopic studies such as optical absorption, FTIR, Raman spectra were carried out at room temperature on these glasses. Besides this electrical properties, like dielectric constant ε ' , loss tan δ , ac conductivity σ a c etc., were also investigated over a moderately wide range of frequency (10 3 –10 6 Hz) and temperature (30–300 °C). The optical absorption spectrum of the prepared glasses has exhibited absorption bands around 325 nm and 340 nm and these are due to the triplet – singlet electronic transition of Ge 2+ state presents in the glass matrix as conversion of GeO 2 into GeO is much easier rather than SiO 2 . From FTIR spectra of as prepared glasses, it is noticed that the intensity of octahedral NbO 6 structural units is found to increase up to 2 mol% of Nb 2 O 5 there after it is observed to decrease. It is also supported by Raman shift of NbO 6 structural units observed around 650 and 930 cm −1 . The analysis of electrical studies is also revealed that the conductivity of prepared glasses is found to increase gradually up to 2 mol% of Nb 2 O 5 beyond this concentration it is observed to decrease. When the spectroscopic investigations are coupled with electrical studies it is concluded that the glass samples doped with 2 mol% of Nb 2 O 5 are found to exhibit good semiconducting nature among the prepared glasses. Such glasses are suitable for fabrication of solid state devices. [ABSTRACT FROM AUTHOR]

This paper reports thermoluminescence (TL) studies on PbO–Al 2 O 3 –SiO 2 : Pr 3+ glasses mixed with varying concentrations of Al 2 O 3 exposed to γ-rays of doses varied between 0 and 5.0 kGy. The TL glow curves of the γ-ray irradiated samples exhibited a dosimetric peak at about 200 °C and the area under the curve increased with increasing Al 2 O 3 and also with the γ-ray dose. The mechanisms responsible for TL emission are quantitatively discussed. The dose response of these glass samples exhibited linear behavior in the medium dose range viz., 1.0–3.0 kGy. Finally, it is observed that the glass mixed with 10 mol% of Al 2 O 3 exhibits highest TL output. The reasons for such larger TL efficiency of these glasses have been identified and discussed quantitatively with the help of the results of optical absorption, IR and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

• PbO-B 2 O 3 -SeO 2 :Er 2 O 3 glass ceramics added with traces of Au 2 O 3 were synthesized. • Characterization studies indicated increasing fraction of defects with Au 2 O 3 content. • Dielectric parameters ε′ , M , Z and σ ac are measured in broad ω temperature T ranges. • ε′ is observed to increase with Au 2 O 3 content due to the space charge polarization. • Mechanism of conduction is analyzed using polaronic tunneling model middle ω region. The variations of M′ and M″ with frequency and temperature of glass ceramic sample EA 75. [Display omitted] The glass ceramics of the composition PbO-B 2 O 3 -SeO 2 :Er 2 O 3 (PBSE) doped with small concentrations of Au 2 O 3 were synthesized. The results of detailed studies on various characterization techniques and also different spectroscopic investigations suggested that these glass ceramics are entrenched with Au 2 (SeO 3) 3 crystal phases and Au0 metallic particles (MPs). These studies further revealed increasing concentration of [SeO 3 ]2- groups and Au0 metallic particles with the increase of Au 2 O 3 content upto 0.075 mol%. Such [SeO 3 ]2- groups are predicted to induce structural imperfections in the glass ceramic. Optical absorption (OA) and photoluminescence (PL) spectral studies also indicated increasing concentration of imperfections with increase of Au 2 O 3 content. The dielectric viz, dielectric permittivity (ε′), electrical modulus (M) , electrical impedance (Z) and a.c. conductivity (σ ac) spectra in the frequency (ω) region 4 Hz to 8 MHz and in the temperature (T) region 303–633 K of these glass ceramic samples were measured as functions of Au 2 O 3 concentration. The dielectric permittivity (ε′) exhibited an increasing trend with Au 2 O 3 concentration and it is ascribed to the increase in the magnitude of the space charge polarization (scp) due to the increase in the concentration of structural defects induced by [SeO 3 ]2- units and Au0 metallic particles. The plots of electric modulus (M) with frequency and temperature exhibited dipolar relaxation phenomena. Such effects were analyzed further using Cole-Cole diagrams and the possible dipoles responsible for these effects were identified. A.C. conductivity (σ ac) exhibited increasing trend with the concentration of Au 2 O 3 (up to 0.075 mol%) and such increase is attributed to the polaronic exchange between different structural groups of selenium oxide. The conduction mechanism is analyzed using polaronic tunneling effect in the middle frequency and high temperature regions, whereas in the lower temperature region QMT model seems to be applicable. Conclusions drawn from dielectric properties were found to be well in accordance with the results of spectroscopic properties. [ABSTRACT FROM AUTHOR]

Abstract: Na2SO4–BaO–P2O5 glasses doped with different concentrations of Fe2O3 were prepared. The valence states of iron ions and their coordination in the glass network have been investigated using optical absorption, ESR, IR and Raman spectroscopy. Electrical and dielectric spectral features have been studied over a wide frequency range (10−2–106 Hz) and within the temperature range from 303 to 523K. The ac and dc conductivities have exhibited maximal effect, whereas the activation energy for the conductivity demonstrated minimum at 1.5mol% of Fe2O3. The ac conductivity in the low temperature region is explained based on quantum mechanical tunneling (QMT) model. The analysis of the dc conductivity indicated that at T>θD/2, the small polaron hopping model is appropriate. The dispersion of real part of dielectric constant ε′(ω), and loss, tan δ, with temperature have been analyzed quantitatively on the basis of space charge and orientation polarization models. [Copyright &y& Elsevier]

Abstract: Sodiumsulpho borophosphate glasses with composition (40− x)Na2SO4–30B2O3–30P2O5: xMnO with x ranging from 0 to 5.0mol% were manufactures. Dielectric spectra have been studied over a wide frequency range of 102–105 Hz and in the temperature range within 30–250°C. The valance states of manganese ions and their ligand coordination in the glass network have been investigated using optical absorption, luminescence and ESR spectroscopy. The analysis of the these results has indicated that the manganese ions exist both in Mn2+ as well as in Mn3+ states and occupy prevailingly octahedral positions and serve as modifiers similarly to Na+ ions The values of dielectric parameters (dielectric constant, ε′(ω), loss tan δ and ac conductivity, σac) were found to increase with increasing MnO content. They play a role of modifiers similarly to Na+ ions, create bonding defects and free ions viz., [SO4]2−, [POO1/2O2]2−, [POO0/2O3]3–, Na+ and (NaSO4)−. The migration of these charge carriers would build up space charge polarization and may be responsible for the enhanced dielectric parameters. The ac conductivity also is enhanced with increasing MnO content. The mechanism responsible for such increase is well explained based on the modifying action of Mn2+ ions. [Copyright &y& Elsevier]

Abstract: A series of Na2SO4–B2O3–P2O5 glasses doped with different concentrations of TiO2 (0 to 1.0mol%) have been synthesized. Dielectric properties (over a range of frequency and temperature) and a variety of spectroscopic (optical absorption, IR, Raman and ESR) properties of these glasses have been investigated. The values of dielectric parameters viz., dielectric constant, loss and ac conductivity at any frequency and temperature are observed to increase with the concentration of TiO2. The optical absorption and ESR spectral studies have pointed out that a part of titanium ions do exist in Ti3+ state in addition to Ti4+ state especially in the samples containing higher concentration of TiO2. The increase of dielectric constant with the concentration of TiO2 is explained on the basis of space charge polarization due to increasing concentration of various bonding defects in the glass network. The dielectric relaxation effects exhibited by these glasses are quantitatively analyzed by pseudo Cole–Cole method and the spreading of relaxation times is established. The ac conductivity is observed to increase with increasing content of TiO2, the mechanism responsible for such increase is well explained based on the modifying action of Ti3+ ions. [Copyright &y& Elsevier]

Abstract: The glasses of the composition 19Na2SO4–20MO–60P2O5: 1.0Ho2O3/1.0Er2O3 (M=Mg, Ca, and Ba) have been synthesized. Optical absorption and fluorescence spectra (in the spectral range 350–2100nm were studied at ambient temperature. The spectra were characterized using Judd–Ofelt theory. From the luminescence spectra, various radiative properties like transition probability A, branching ratio β and the radiative life time τ for blue (B), green (G) and red (R) emission levels of these glasses have been evaluated. The energy transfer between the two rare earth ions (Ho3+ and Er3+) in co-doped Na2SO4–MO–P2O5 glass systems in the visible and NIR regions has also been investigated. Highest intensity, the highest quantum efficiency and maximum energy transfer with low phonon losses of B, G, and R lines has been observed in BaO mixed glasses. The reasons for such higher values of these parameters have been discussed in the light of varying field strengths at the rare earths ion site due to replacement of one modifier oxide with the other. The enhanced intensity of NIR emission (at 2.0μm) has also been discussed in terms of cross relaxation of Er3+ ions from 4I13/2 level to 5I7 of Ho3+ ions. [Copyright &y& Elsevier]

Abstract: LiI–AgI–B2O3 glasses mixed with different concentrations of V2O5 (ranging from 0 to 1.0mol%) were prepared. Electrical and dielectric properties over wide ranges of frequency (10−2–107 Hz) and temperature (173–523K) have been studied. Additionally spectroscopic properties viz., optical absorption and ESR spectra have been investigated. The optical absorption and ESR studies have revealed that vanadium ions do exist in both V4+ and V5+ states and the redox ratio is the highest in the glasses containing 0.8mol% of V2O5. The results of conductivity measurements have indicated that there is a mixed conduction (both ionic and electronic). The ionic conduction seems to be dominant over polaron hopping only in the glasses containing V2O5 more than 0.8mol% of V2O5. The impedance spectra have also indicated that the conduction is predominantly polaronic in nature. The frequency and temperature dependence of the electrical moduli as well as dielectric loss parameters have exhibited relaxation character attributed to the vanadyl complexes. The relaxation effects have been analyzed by the graphical method and from this analysis it has been established that there is a spreading of relaxation times. The results have been further discussed quantitatively in the light of different valance states of vanadium ions with the aid of the data on spectroscopic properties. [Copyright &y& Elsevier]

• Role of Au0 particles on improving PL of Ho3+ ions in a SeO 2 glass ceramic is explored. • Characterization indicated that the samples consist of [SeO 3 ]2− & [SeO 4 ]2− units. • Samples comprising of Au0 particles exhibited sp → d electronic transitional emission. • PL spectra of Au0-Ho3+ codoped samples exhibited intense bands in visible region. • Sensitization by Au0 particles on luminescence output is quantitatively discussed. This study is devoted to investigate the role of Au0 particles on the improvement of luminescence efficiency of Ho3+ ions in a non-conventional lead boroselenate glass ceramic. Characterization by different spectroscopic techniques indicated that the samples consist of [SeO 3 ]2− and [SeO 4 ]2− structural groups. Among them, the fraction of [SeO 3 ]2− groups exhibited an increasing trend with increase of Au 2 O 3 content. These studies have further revealed that a part of Au3+ ions reduced in to gold nano particles during ceramicization process. Optical absorption (OA) spectra of these samples exhibited a wide absorption band with gradual growth with the Au 2 O 3 concentration. This band is attributed to the surface plasmon resonance (SPR) of gold nanoparticles. Additionally, the OA spectra exhibited several characteristic bands of Ho3+ ions in the spectral region of 450–2000 nm. Photoluminescence (PL) spectra of (Ho free samples) containing gold particles exhibited a broad band in the green to red spectral region, identified due to the transition of electrons from sp → d energy bands of gold nanoparticles. PL spectra of co-doped samples exhibited the emission bands in the green, orange and red regions with enhanced intensities as Au 2 O 3 content is increased. OA and PL spectra were characterized using Judd-Ofelt theory and various radiative parameters were estimated. The impact of Au0 particles on the PL efficiency of holmium ions is comprehensively discussed using kinetic rate equations. The crucial role of gold particles as sensitizers in enhancing the luminescence efficiency especially the green emission is quantitatively explained. [ABSTRACT FROM AUTHOR]

In this work, nonlinear optical (NLO) studies of nickel oxide doped (ranging from 0.2 to 1.0 mol %) Li 2 SO 4 –MgO–P 2 O 5 glasses are reported. A combination of femtosecond (fs) laser, as a pumping light source and a high-accuracy polarimeter with low power probing laser, is used to investigate the light-induced optical anisotropy (OA) in these glass materials. The light-induced birefringence (LIB) exhibits slow relaxation tendency up to about 10 s suggesting on anisotropic photorefractive effect evidently dominated fast Kerr effect. This behavior is evaluated in the light of other results reported recently and is explained by the glass polymerization mechanisms. The photorefractive birefringence increases with increase of the quantity of NiO up to 0.8 mol% and it is attributed to the enhanced degree of depolymerization of the glass network due to the hike in the concentration of Ni2+ ions that occupy octahedral (O h) positions. Further increase of NiO content (> 0.8 mol%) causes, however, a certain decrease of the photorefractive birefringence. Notable change in concentration trend is interpreted by rising of phonon losses due to increasing portion of the nickel ions occupying tetrahedral (T h) sites that facilitates the polymerization of the glass network. The doped glasses with the NiO content of about 0.8 mol% may be considered as optimal in the sense of photorefractive efficiency. Relevant samples exhibit largest magnitudes of the photorefractive birefringence and appear to be favorable for potential applications. • Nonlinear optical (NLO) studies of NiO doped Li 2 SO 4 –MgO–P 2 O 5 glasses are studied. • Combination of femtosecond as pumping source and high-accuracy polarimeter is used. • The light-induced birefringence (LIB) exhibits slow relaxation tendency. • This behavior is explained by the glass polymerization mechanisms. • Glasses with 0.8 mol% NiO content exhibited high photorefractive efficiency. [ABSTRACT FROM AUTHOR]

Li 2 SO 4 -MgO-P 2 O 5 glasses doped with varied contents of CuO (from 0- 1.0 mol%) were prepared. The optical birefringence induced by a High Q-2 femtosecond pulsed laser is explored as a function of copper oxide concentration in these glasses. The magnitude of the light-induced birefringence exhibited a gradual decrease with the increase of copper oxide content. The observed behavior is discussed in terms of polymerization of the glass network, the degree of which rises with concentration of Cu+ ions occupying T d sites in the glass matrix. However, the samples containing low content of CuO are dominated by Cu2+ ions that act as modifiers and induce structural imperfections by breaking of P-O-S bonds. Accordingly, the samples mixed with lower content of CuO are more favorable for inducing higher magnitudes of the optical birefringence. This conclusion is corroborated by results of electrical conductivity, positron annihilation and ultrasonic measurements. [ABSTRACT FROM AUTHOR]

• Influence of Ta2O5 on in vitro bioactivity studies of BG is investigated. • Antibacterial activity of Ta2O5-BG against S. aureus & E. coli bacteria is assessed. • XRD and SEM studies proved formation of Ta-HAp crystalline layer on the glasses. • The maximal HAp deposition is observed on BG doped with 2.5 mol% of Ta2O5. • Maximal bacterial killing effect is exhibited by BG doped with 2.5 mol% of Ta2O5. In vitro bioactivity studies (in SBF) and antibacterial activity studies (against S. aureus and E. coli bacteria) of Ta 2 O 5 doped CaF 2 ‒CaO‒B 2 O 3 ‒P 2 O 5 ‒SrO glasses were investigated. XRD and SEM studies indicated formation of Ta-HAp crystalline layer on the samples after immersing in SBF. The studies indicated the maximal content of hydroxyapatite is deposited on the surface of the glasses Ta 2.5. Antibacterial effect against E. coli and S. aureus showed that the samples doped with 2.5 mol% of Ta 2 O 5 are more efficient in killing the bacteria. Such maximal effect is attributed to the presence of the largest concentration of TaO 6 groups that have acted as modifiers in this glass sample. [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]

Glasses of the composition 40Li 2 O‒(60-x)Sb 2 O 3 : xNd 2 O 3 (x = 0.2, 0.4, 0.6, 0.8 and 1.0 mol%) were synthesized by melt quenching technique. The structural and optical characteristics were investigated as a function of Nd 2 O 3 concentration. From the optical absorption spectra J-O intensity parameters (Ω λ , λ = 2,4 and 6) were evaluated; the parameters are found to be in the order: Ω 2 > Ω 6 > Ω 4. The emission spectra recorded at λ exc = 808 nm) exhibited three intense bands at 875 nm, 1053 nm and 1328 nm attributed to4F 3/2 → 4I 9/2 , 11/2 , 13/2 transitions, respectively. The intensity of 4F 3/2 → 4I 11/2 (1.053 μm) emission band is found to be the highest among the three bands. With increasing the concentration of Nd 2 O 3 upto 0.8 mol%, intensity of all emission bands exhibited an increasing trend. Beyond 0.8 mol%, a decrease in the intensity of PL output is observed; this is attributed to concentration quenching losses and increased phonon losses. From emission spectra, various radiative parameters such as transition probability, A R , branching ratio β, and radiative life time, τ R , were evaluated for all glass samples. The analysis of the results indicated glasses mixed with 0.8 mol% of Nd3+exhibited the highest efficiency of 1.053 μm emission. The reasons for such high efficiency were further identified using structural analysis of the host glass using IR spectral studies. [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 study concentration of defects in Li 2 SO 4 −MgO−P 2 O 5 : NiO glass system is estimated. • PAL technique with 22Na positron source (100 kBq) is used for this study. • Glass doped with 0.8 mol% of NiO found to contain maximal concentration of defects. • Higher concentration of defects is ascribed to maximal presence of O h Ni ions in this glass. • Obtained info is found to be in concurrent with inferences drawn by other studies. In this study we have evaluated the concentration of defect centers like voids, their size (up to nanoscale) and the fraction of free volume space integrated in Li 2 SO 4 −MgO−P 2 O 5 :NiO glass system as a function of NiO content. Positron annihilation lifetime (PAL) technique with 22Na positron source of radio activity 100 kBq is used for this study. The size, shape and the concentration of entrenched defects in the glass matrix are predicted to influence profoundly the physical properties of the glass. Cavity radius (R) and the entrenched free volume fraction (f v) are found to be the maximal in the sample doped with 0.8 mol% of NiO. This observation suggested that Ni2+ ions predominantly occupied octahedral positions (acted as modifiers along with SO 4 2– ions) and induced large concentration of structural defects. The obtained information is found to be in concurrent with inferences drawn from dielectrics and spectroscopic studies of these glasses reported earlier. [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]

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]

Luminescence features of samarium ions in non-conventional antimonate oxide glasses added with HfO 2 , Y 2 O 3 and Sc 2 O 3 were investigated. From absorption and luminescence spectra various radiative parameters (associated with orange emission transition viz., 4G 5/2 → 6H 7/2) that give the information on luminescence efficiency of Sm3+ were calculated. The calculated values of radiative parameters are observed to be the largest for hafnia added glasses when compared with those of other two glasses. The infrared spectra have indicated that the trivalent antimony ions take part glass network forming positions with SbO 3 pyramids. The spectra further suggested the maximum concentration ofstructural defects in hafnia mixed glasses. Due to this reason, the vibrational losses (phonon losses) of PL output are expected to be decreased. The observed highest luminescence efficiency of Sm3+ ions in HfO 2 added glasses with respect to that of Y 2 O 3 and Sc 2 O 3 added antimonate glasses is attributed to this reason. • HfO 2 , Y 2 O 3 and Sc 2 O 3 added Sm3+ doped nonconventional Sb 2 O 3 glasses are prepared. • IR spectra suggested maximum concentration structural defects in HfO 2 mixed glasses. • PL spectra exhibited rich orange emission due to 4G 5/2 → 6H 7/2 transition • HfO 2 mixed glasses exhibited highest luminescence efficiency among the three glasses. • Highest luminescence efficiency of HfO 2 glasses is attributed to low phonon losses. [ABSTRACT FROM AUTHOR]

Introduction: The traditional medicinal system of India, Ayurveda, has mentioned Cordia Dichotoma as a potential treatment for various ailments. In the current research, the extracts of Cordia Dichotoma was examined to evaluate their antidepressant potential., Materials and Methods: Here, green leaves of Cordia Dichotoma were used to prepare chloroform, ethanol, and aqueous extracts (referred to as CdCe, CdEe, and CdAe respectively). The research focused on investigating the antidepressant effects of these extracts using behavioral models in experimental animals. Additionally, locomotor activity was assessed as part of the evaluation process., Results: Immobility time was reduced with CdEe Cordia Dichotoma rFST & mTST when at 200 mg/kg and 400 mg/kg body weight. The CdAe showed reduction in immobility time in the repeated rFST) at 400 mg/kg, while in the mTST, significant effects were observed at 200 and 400 mg/kg. Regarding the chloroform extract, it only exhibited a significant reduction in immobility time in the modified Tail Suspension Test (mTST) at a low dose of 200 mg/kg. However, no noticeable change in motor dysfunction was observed with CCl4 and aqueous extracts at doses of 200 and 400 mg/kg. It is worth noting that the chloroform extract (CdCe) did lead to a significant decrease in locomotor activity at the same dosage level. Taken together, these findings suggest that extracts obtained from Cordia Dichotoma leaves may possess antidepressant properties.

The recombinant Yleh from a tropical marine yeast Yarrowia lipolytica NCIM 3589 exhibited a high epoxide hydrolase activity of 9.34 ± 1.80 µmol min -1  mg -1 protein towards 1,2-epoxyoctane (EO), at pH 8.0 and 30 °C. The reaction product was identified as 1,2-Octanediol (OD) by GC-MS using EO and H 2 O 18 as substrate, affirming the functionality of Yleh as an epoxide hydrolase. For EO, the K m , V max , and k cat /K m values were 0.43 ± 0.017 mM, 0.042 ± 0.003 mM min -1 , and 467.17 ± 39.43 mM -1  min -1 , respectively. To optimize the reaction conditions for conversion of racemic EO by Yleh catalyst to enantiopure (R)-1,2-octanediol, initially, Response Surface Methodology was employed. Under optimized reaction conditions of 15 mM EO, 150 µg purified Yleh at 30 °C a maximal diol production of 7.11 mM was attained in a short span of 65 min with a yield of 47.4%. Green technology using deep eutectic solvents for the hydrophobic substrate (EO) were tested as co-solvents in Yleh catalyzed EO hydrolysis. Choline chloride-Glycerol, produced 9.08 mM OD with an increased OD yield of 60.5%. Thus, results showed that deep eutectic solvents could be a promising solvent for Yleh-catalyzed reactions making Yleh a potential biocatalyst for the biosynthesis of enantiopure synthons., (© 2023. The Author(s).)

For quantitative structure-activity relationship (QSAR) modeling in ligand-based drug discovery programs, pseudo-molecular field (PMF) descriptors using intrinsic atomic properties, namely, electronegativity and electron affinity are studied. In combination with partial least squares analysis and Procrustes transformation, these PMF descriptors were employed successfully to develop correlations that predict the activities of target protein inhibitors involved in various diseases (cancer, neurodegenerative disorders, HIV, and malaria). The results show that the present QSAR approach is competitive to existing QSAR models. In order to demonstrate the use of this algorithm, we present results of screening naturally occurring molecules with unknown bioactivities. The pIC 50 predictions can screen molecules that have desirable activity before assessment by docking studies., (© 2021 John Wiley & Sons A/S.)

Phosphate glasses of calcium oxide have been well proved materials for various bio bones and dental implants. However, still there is a lot of scope and demand to produce efficient elastic bio implants and resource. In view of this, Zr x Ca 30-x P 70 phosphate materials are prepared by using melt quenching method. Bio, physical, thermoluminescence and elastic techniques are used to characterize the samples. Additionally, simulated body fluid was prepared and it is used especially for bio techniques. Further, the glasses are taken for different dose (~0, 10, 20 & 50 kGy) of gamma irradiation around half an hour. And again similar techniques are used to characterize the samples. All the findings from bio, physical, thermoluminescence and elastic characterization results are analysed and took for better comparison with previous studies to develop various bio bone (or) bio dental resource. Structural reports suggests that the Zr x Ca 30-x P 70 materials were glassy before immersion in SBF solution and immersed (~720 h) samples are showing partial ceramic nature. The weight loss and pH reports suggests them for alternative bio resource as a bio bones and dental implants. Observed thermal stability, microhardness and elastic modulus evaluations of Zr x Ca 30-x P 70 materials in required standards are also additional advantage. Furthermore, thermoluminiscence (TL) under different γ-irradiation doses is reported for glasses with and without immersing in a simulated body fluid. The glasses lose TL intensity when immersed in simulated body fluid for nearly 720 h. This is useful to modulate bio-behaviour in terms of hydroxyapatite layer growth on the glass surface., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The production of phytase using Aspergillus niger NCIM 563 under submerged fermentation conditions was studied using protein rich chickpea flour as substrate. Employing a hybrid statistical media optimization strategy of Plackett-Burman and Box-Behnken experimental designs in shake-flasks gave an increased phytase activity from an initial 66 IU/mL in 216 h to 160 IU/mL in a reduced time of 132 h. Productivity, thus increased by 3.97 times from 7.3 to 29 IU/mL/day. Using the optimized media, the production was successfully scaled-up further and improved up to 164 IU/mL in 96 h by studies carried out employing 2 and 10-L fermenters. The enzyme supernatant was recovered using centrifugal separation of biomass and the stability of the produced phytase was tested for animal feed applications under gastric conditions. In vitro degradation studies of water soluble monocrotophos, methyl parathion and water insoluble chlorpyrifos, pesticides used extensively in agriculture was carried out. It was observed by HPLC analysis that phytase could degrade 72% of chlorpyrifos at pH 7.0, 35 °C. Comparable results were obtained with monocrotophos and methyl parathion. With chlorpyrifos at higher temperature 50 °C as much as 91% degradation could be obtained. The degradation of chlorpyrifos was further validated by spraying phytase on harvested green chilli (Capsicum annuum L) under normal conditions of pH 7.0, 35 °C and the degradation products obtained analyzed by LCMS. Thus, the present study brings out a potentially novel application of phytase for biodegradation of organophosphorus pesticides.

This article describes the synthesis and characterization of three new Ru(II) polypyridyl complexes including [Ru(phen) 2 (dpphz)] 2+ (1), [Ru(bpy) 2 (dpphz)] 2+ (2) and [Ru(dmb) 2 (dpphz)] 2+ (3) where dpphz = dipyrido[3,2-a:2',3'-c] phenazine-11-hydrazide, phen =1,10-phenanthroline, bpy = 2,2'-bipyridine and dmb = 4,4'-dimethyl2,2'-bipyridine. The binding behaviors of these complexes to calf thymus DNA (CT-DNA) were explored by spectroscopic titrations, viscosity measurements. Results suggest that these complexes can bind to CT-DNA through intercalation. However, their binding strength differs from each other; this may be attributed to difference in the ancillary ligand. The cytotoxicity of 1-3 was evaluated by MTT assay; results indicated that all complexes have significant dose dependent cytotoxicity with HeLa tumor cell line. All complexes exhibited efficient photocleavage of pBR322 DNA upon irradiation. The DNA binding ability of 1-3 was also studied by docking the complexes into B-DNA using docking program.

An efficient inverse problem approach for parameter estimation, state and structure identification from dynamic data by embedding training functions in a genetic algorithm methodology (ETFGA) is proposed for nonlinear dynamical biosystems using S-system canonical models. Use of multiple shooting and decomposition approach as training functions has been shown for handling of noisy datasets and computational efficiency in studying the inverse problem. The advantages of the methodology are brought out systematically by studying it for three biochemical model systems of interest. By studying a small-scale gene regulatory system described by a S-system model, the first example demonstrates the use of ETFGA for the multifold aims of the inverse problem. The estimation of a large number of parameters with simultaneous state and network identification is shown by training a generalized S-system canonical model with noisy datasets. The results of this study bring out the superior performance of ETFGA on comparison with other metaheuristic approaches. The second example studies the regulation of cAMP oscillations in Dictyostelium cells now assuming limited availability of noisy data. Here, flexibility of the approach to incorporate partial system information in the identification process is shown and its effect on accuracy and predictive ability of the estimated model are studied. The third example studies the phenomenological toy model of the regulation of circadian oscillations in Drosophila that follows rate laws different from S-system power-law. For the limited noisy data, using a priori information about properties of the system, we could estimate an alternate S-system model that showed robust oscillatory behavior with predictive abilities., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Multi-component CaF2-Bi2O3-P2O5-B2O3 glasses doped with different concentrations of Cr2O3 were crystallized through heat treatment. The prepared glass ceramic samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and differential thermal analysis (DTA). Spectroscopic studies viz., optical absorption, Fourier transform infrared (FTIR), Raman and electron paramagnetic resonance (EPR) were carried out. The XRD, SEM and DTA studies indicated that the samples contain different crystalline phases. Results of optical absorption and EPR studies pointed out the gradual conversion of chromium ions from Cr(3+) state to Cr(6+) state with an increase of Cr2O3 content from 0.1 to 0.5 mol%. The results of FTIR, Raman and EPR studies revealed that Cr(6+) ions participate in the glass network in tetrahedral positions and seemed to increase the polymerization of the glass ceramics. The quantitative analysis of results of the spectroscopic studies further indicated that the glasses crystallized with low concentration of Cr2O3 are favourable for solid state laser devices., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Combination of statistical optimization and mutagenesis to isolate hypersecretory strains is studied to maximize phytase production from Aspergillus niger NCIM 563 under submerged fermentation. The overall results obtained show a remarkable 5.98-fold improvement in phytase production rates when compared to that using basal medium. Optimization of culture conditions from parent strain is studied first by the Plackett-Burman technique to evaluate the effects of 11 variables for phytase production. The results showed that glucose, MgSO(4), KCl, incubation period, and MnSO(4) are the most significant variables affecting enzyme production. Further optimization in these variables, using a central composite design technique, resulted in 3.74-fold increase in the yield of phytase production to 254,500 U/l when compared with the activity observed with basal media (68,000 U/l) in shake flask. Our experiments show that the phytase from A. niger NCIM 563 exhibits desirable activity in simulated gastric fluid conditions with low pH and also improved thermostability when compared to commercial phytase. The improved yield demonstrates the potential applicability of phytase enzyme as a source of phytase supplement for phosphorus nutrition and environmental protection in animal feed industry. Physical and chemical mutagenesis experiments were carried out in parallel to isolate hypersecretory mutants that could possibly further enhance the enzyme production. Using optimized media conditions of the parent strain, our results show that mutant strain A. niger NCIM 1359 increased the phytase activity by another 1.6-fold to 407,200 U/l.

Phytase production by Aspergillus niger NCIM 563 was optimized by using wheat bran in solid state fermentation (SSF). An integrated statistical optimization approach involving the combination of Placket-Burman design (PBD) and Box-Behnken design (BBD) was employed. PBD was used to evaluate the effect of 11 variables related to phytase production, and five statistically significant variables, namely, glucose, dextrin, NaNO(3), distilled water, and MgSO(4) · 7H(2)O, were selected for further optimization studies. The levels of five variables for maximum phytase production were determined by a BBD. Phytase production improved from 50 IU/g dry moldy bran (DMB) to 154 IU/g DMB indicating 3.08-fold increase after optimization. A simultaneous reduction in fermentation time from 7 to 4 days shows a high productivity of 38,500 IU/kg/day. Scaling up the process in trays gave reproducible phytase production overcoming industrial constraints of practicability and economics. The culture extract also had 133.2, 41.58, and 310.34 IU/g DMB of xylanase, cellulase, and amylase activities, respectively. The partially purified phytase was optimally active at 55°C and pH 6.0. The enzyme retained ca. 75% activity over a wide pH range 2.0-9.5. It also released more inorganic phosphorus from soybean meal in a broad pH range from 2.5 to 6.5 under emulated gastric conditions. Molecular weight of phytase on Sephacryl S-200 was approximately 87 kDa. The K (m) and V (max) observed were 0.156 mM and 220 μm/min/mg. The SSF phytase from A. niger NCIM 563 offers an economical production capability and its wide pH stability shows its suitability for use in poultry feed.

The neuroprotective effect of an ethyl acetate extract of Morinda citrifolia (Rubiaceae) Linn. fruits (EMC, ethyl acetate extract of Morinda citrifolia) at doses of 200 and 400 mg/kg, p.o. was studied on beta-amyloid (25-35) peptide induced cognitive dysfunction in mice. In the step-down inhibitory avoidance, EMC exhibited a significant increase in short-term memory and long-term memory (p < 0.05). A significant decrease (p < 0.01) in escape latency was noticed in the animals in the water maze. A significant increase (p < 0.01) in alteration of behavior was exhibited upon administration of EMC 200 and 400 mg/kg on the Y maze. Exploratory parameters such as line crossings, head dipping and rearing were increased significantly in EMC treated groups in a dose-dependent manner (p < 0.05 and p < 0.01). A significant reduction (p < 0.05) in acetyl cholinesterase activity was noticed in the EMC 200 and 400 mg/kg treated groups. The level of monoamine oxidase-A was decreased by the administration of EMC 200 and 400 mg/kg (p < 0.05 and p < 0.01, respectively). EMC at a dose of 400 mg/kg exhibited a significant increase (p < 0.01) in the levels of serotonin and dopamine. Antioxidant enzymes such as superoxide dismutase, glutathione reductase, glutathione peroxidase and ascorbic acid were decreased significantly in the b-amyloid peptide injected group, whose levels were restored significantly (p < 0.01) by the administration of EMC (400 mg/kg)., ((c) 2009 John Wiley & Sons, Ltd.)