Risk factors for retinal detachment following cataract surgery: the impact of posterior capsular rupture

AIM

To investigate risk factors for retinal detachment (RD) after cataract surgery, particularly posterior capsular rupture (PCR) with or without vitreous loss.

METHODS

Single centre electronic medical record database study of 18 065 consecutive first eye cataract operations performed between 2005 and 2014. Survival analysis was performed with Kaplan-Meier curves and a Cox proportional hazard regression analysis to calculate HRs with respect to RD.

RESULTS

The RD rate at 3 months and 7 years was 0.067% and 0.30%, respectively, with a median time to RD of 15 months (mean: 18 months, range: 0-84 months). Men had a higher RD risk (HR 2.00; 95% CI 1.03 to 3.88; p=0.03) in the univariate model. Patients <60 years and those >80 years had an HR of 5.12 (95% CI 2.60 to 10.07; p<0.001) and 0.16 (95% CI 0.38 to 0.69; p=0.01), respectively, compared with patients 60-80 years of age. Eyes longer than 25 mm had an HR of 3.98 (95% CI 1.93 to 8.20; p<0.001) compared with eyes 23-25 mm. PCR occurred in 400 (2.2%) eyes. The HR for RD was 12.83 (95% CI 5.62 to 29.30; p<0.001) for PCR with vitreous loss. There were no RD events in eyes with PCR without vitreous loss.

CONCLUSIONS

The risk for RD after cataract surgery is higher in younger patients and eyes with longer axial length or PCR with vitreous loss during surgery.

Pressure-induced phase transformation in zircon-type orthovanadate SmVO4 from experiment and theory

The compression behavior of zircon-type samarium orthovanadate, SmVO4, has been investigated using synchrotron-based powder x-ray diffraction and ab initio calculations of up to 21 GPa. The results indicate the instability of ambient zircon phase at around 6 GPa, which transforms to a high-density scheelite-type phase. The high-pressure phase remains stable up to 21 GPa, the highest pressure reached in the present investigations. On pressure release, the scheelite phase is recovered. The crystal structure of the high-pressure phase and the equations of state for the zircon- and scheelite-type phases have been determined. Various compressibilities, such as the bulk, axial and bond compressibilities, estimated from the experimental data are found to be in good agreement with the results obtained from theoretical calculations. The calculated elastic constants show that the zircon structure becomes mechanically unstable beyond the transition pressure. Overall there is good agreement between the experimental and theoretical findings.

A chemical method for stabilizing a new series of solid solution Pr1-xCexScO3 (0.0 ≤x≤ 1.0) systems

A new series of Pr1-xCexScO3 (0.0 ≤x≤ 1.0) compounds was synthesized by a two-step synthesis route, involving a combustion reaction followed by reduction while heating in a low partial pressure of O2, generated by a zirconium sponge that acts as an oxygen getter. For the first time, perovskite solid solution formation was observed in this series in the entire homogeneity range. These compounds were characterized using XRD, Raman spectroscopy and DRUV-visible spectroscopy. Rietveld refinement was carried out on the XRD data to determine unit cell parameters, bond lengths, bond angles along with the tilt angles for ScO6 octahedra. The analyses of the Raman shift were also in agreement with the XRD data. All compounds in this series showed a decreasing trend in the bandgap from 4.74 to 2.91 eV as a function of increasing Ce(3+) concentration.

Effect of grain size and microstructure on radiation stability of CeO2: an extensive study

To investigate the variation in the radiation stability of ceria with microstructure under the electronic excitation regime, ceria samples sintered under different conditions were irradiated with high energy 100 MeV Ag ions. The ceria nanopowders were synthesized and sintered at 800 °C (S800), 1000 °C (S1000) and 1300 °C (S1300), respectively. The samples with widely varying grain size, densities and microstructure were obtained. The pristine and irradiated samples were studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). None of the samples amorphized up to the highest fluence of 1 × 10(14) ions per cm(2) employed in this study. XRD and Raman studies showed that the sample with lowest grain size suffered maximum damage while the sample with largest grain size was most stable and showed little change in crystallinity. Raman spectroscopy indicated the enhanced formation of Ce(3+) and related defects in the sample with larger grain size after irradiation. The most intriguing result was the absence of Ce(3+)-related defects in the sample with lowest grain size which actually showed maximum damage upon irradiation. The XPS studies on S800 and S1300 provided concrete evidence for the presence of Ce(3+) and oxygen ion vacancies in S1300. The grain boundaries and grain size dependent stability have been discussed.

Bifunctional Li and Co Doped ZnO Nanostructures Synthesized by Solvothermal Method: Stabilizer Controlled Shape and Size Tuning

1D nanostructures of ZnO, Zn0.95Co0.05O and Zn0.85Co0.05Li0.10 were synthesized by a solvothermal chemical method with and without using oleic acid as a stabilizer. We report a very interesting observation of both room temperature ferromagnetism and photoluminescence properties along with development of different morphological transformation of these nanostructures on doping Co and Li in ZnO in the presence and absence of oleic acid. Zn0.95Co0.05O sample prepared in the presence of oleic acid showed increased saturation magnetization value (~ 4.1 emu/g and) compared to Zn0.95Co0.05O prepared without oleic acid (~ 1.1 emu/g). In both the cases it is observed that Li incorporation further enhances the room temperature ferromagnetic (RTFM) behavior and saturation magnetization values (~ 6 emu/g) of luminescent Zn0.95Co0.05 nanostructures. These results are significant, as the luminescent 1 D RTFM materials will have implications in photo magnetic devices like magneto-optical switches and sensors.

Association of novel SNPs in the candidate genes affecting caprine milk fatty acids related to human health

In the present investigation, 618 milk samples of Sirohi breed of goat were collected, and analyzed for conjugated linoleic acid (CLA, C18:2) and other fatty acids. The CLA in studied goat milk samples was 4.87 mg/g of milk fat and C18:2 cis-9, trans-11 contributes 2.9 mg/g of milk fat and trans10 cis12 contributes 0.82 mg/g of milk fat. The saturated fatty acids in the milk accounted for 69.55% and unsaturated fatty acid accounted for 28.50%. The unsaturated fatty acid was constituted by monounsaturated fatty acid (24.57%) and polyunsaturated fatty acids (3.96%.). The major contribution (45.56%) in total fatty acid was of C12:0, C14:0 and C16:0. C18:0 and short chain ones (C4:0, C6:0, C8:0, and C10:0) have a neutral or cholesterol-decreasing effect. The DNA sequence analysis of the genes (DGAT1, SCAP, PPARG, OLR, FABP3 and PRL) in a random panel of 8 Sirohi goats revealed 38 SNPs across the targeted regions. Out of the studied SNPs (38) across these genes, 22 SNPs had significant effect on one or a group of fatty acids including CLA. The genotypes at these loci showed significant differences in the least square means of a particular fatty acid or a group of fatty acids including CLA and its isomers.

Efficacy of contrast enhanced grey scale ultrasound in characterisation of hepatic focal lesions: A pilot study

BACKGROUND

Contrast enhanced ultrasound (CEUS) has recently gained widespread acceptance as an adjunct to conventional grey scale ultrasound. The present pilot study was undertaken to evaluate the efficacy of this technique in characterisation of hepatic focal lesions.

METHODS

Adult patients who had at least one focal liver lesion underwent ultrasound evaluation in regular and contrast mode before and after intravenous administration of sulphur hexafluoride. The diagnoses were confirmed by comparison with a reference standard (multidetector CT), response to treatment or pathological correlation.

RESULTS

The rate of correct diagnosis for unenhanced ultrasound was 54%, CEUS was 72% and multidetector CT (MDCT) was 92%. A comparison of unenhanced ultrasound versus CEUS using the McNemar test yielded a p value of 0.0704 (>0.05). However, comparison of CEUS versus MDCT using the McNemar test yielded a p value of 0.0265 (<0.05). Additionally, comparison of unenhanced ultrasound versus MDCT using the McNemar test yielded a p value of <0.0001.

CONCLUSION

CEUS increases diagnostic efficacy over unenhanced ultrasound but does not have any significant advantages over MDCT. Currently it may be used as a problem solving tool in atypical haemangiomas, echogenic focal liver lesions, contrast sensitivity and to avoid multiple studies utilising ionising radiation.

Nanomechanical and optical properties of yttrium thin films by magnetron sputtering

This Letter reports on nanomechanical and optical properties of yttrium thin films deposited on an Si (100) wafer. Elemental depth profiling by a secondary ion mass spectrometer revealed absence of formation of yttrium hydride, both on the surface and beneath. The optical properties were investigated by spectroscopic ellipsometry, and the refractive indices extracted after suitable modeling were found to be 2.51 at 546 nm. Hardness and elastic modulus of these films were found to be 7 and 142 GPa, respectively. These studies indicate that yttrium thin films are suitable for x-ray mirrors, photocathode emitters in e-beam lithography, electron microscopes, and free-electron lasers.

The association of cytochrome P450 genetic polymorphisms with sulfolane formation and the efficacy of a busulfan-based conditioning regimen in pediatric patients undergoing hematopoietic stem cell transplantation

Cytochrome P450 enzymes (CYPs) and flavin-containing monooxygenases (FMOs) likely have a role in the oxidation of intermediate metabolites of busulfan (Bu). In vitro studies to investigate the involvement of these enzymes are cumbersome because of the volatile nature of the intermediate metabolite tetrahydrothiophene (THT) and the lack of sensitive quantitation methods. This study explored the association between the CYP2C9, CYP2C19, CYP2B6 and FMO3 genotypes and sulfolane (Su, a water soluble metabolite of Bu) plasma levels in children undergoing hematopoietic stem cell transplantation (HSCT). The relationship between these genotypes and the effectiveness of myeloablative conditioning was also analyzed. Sixty-six children receiving an intravenous Bu-based myeloablative conditioning regimen were genotyped for common functional variant alleles in CYP2C9 (*2 and *3), CYP2C19 (*2 and *17), FMO3 (rs2266780, rs2266782 and rs1736557) and CYP2B6 (*5 and *9). The plasma levels of Bu and its metabolite Su were measured after the ninth Bu dose in a subset of 44 patients for whom plasma samples were available. The ratio of Bu to Su was considered the metabolic ratio (MR) and was compared across the genotype groups. Higher MRs were observed in CYP2C9*2 and *3 allele carriers (mean±s.d.: 7.8±3.6 in carriers vs 4.4±2.2 in non-carriers; P=0.003). An increased incidence of graft failure was observed among patients with an MR>5 compared with those with MR values <5 (20% vs 0%; P=0.02). In contrast, a significantly higher incidence of relapse and graft failure (evaluated as event-free survival) was observed in patients with malignant disease who carried CYP2B6 alleles with reduced function on both chromosomes compared with carriers of at least one normal allele (100% vs 40%; P=0.0001). These results suggest that CYP2C9 has a role in the oxidation reactions of THT and indicate that it may be possible to predict the efficacy of Bu-based myeloablative conditioning before HSCT on the basis of CYP genotypes and Bu MRs.

Physico-chemical processes and kinetics of sunlight-induced hydrophobic ↔ superhydrophilic switching of transparent N-doped TiO₂ thin films

Sunlight-responsive anatase N-doped TiO2 thin films undergoing reversible and switchable hydrophobic to superhydrophilic transition were synthesized by ultrasonic spray pyrolysis in a single step. Film thickness, roughness, surface morphology, crystal structure, composition, band gap, and wetting properties were studied using surface profilometry, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis spectroscopy, and water contact angle measurements, respectively. Surface X-ray photoelectron spectroscopy before and after sunlight irradiation revealed the major physicochemical process responsible for the hydrophobic → hydrophilic transition as surface hydroxylation and that responsible for hydrophilic → superhydrophilic transition as destruction of surface adsorbed organic species. The kinetic rates of the hydrophobic → superhydrophilic transition under sunlight and superhydrophilic → hydrophobic transition when kept under dark are found to be 0.215 min(-1) and 2.03 × 10(-4) min(-1), respectively.

Phonons and colossal thermal expansion behavior of Ag3Co(CN)6 and Ag3Fe(CN)6

Recently colossal volume thermal expansion has been observed in the framework compounds Ag(3)Co(CN)(6) and Ag(3)Fe(CN)(6). We have measured phonon spectra using neutron time-of-flight spectroscopy as a function of temperature and pressure. Ab initio calculations were carried out for the sake of analysis and interpretation. Bonding is found to be very similar in the two compounds. At ambient pressure, modes in the intermediate frequency part of the vibrational spectra in the Co compound are shifted slightly to higher energies as compared to the Fe compound. The temperature dependence of the phonon spectra gives evidence for a large explicit anharmonic contribution to the total anharmonicity for low-energy modes below 5 meV. We have found that modes are mainly affected by the change in size of the unit cell, which in turn changes the bond lengths and vibrational frequencies. Thermal expansion has been calculated via the volume dependence of phonon spectra. Our analysis indicates that Ag phonon modes within the energy range 2-5 meV are strongly anharmonic and major contributors to thermal expansion in both systems. The application of pressure hardens the low-energy part of the phonon spectra involving Ag vibrations and confirms the highly anharmonic nature of these modes.

Hybrid multiferroic nanostructure with magnetic-dielectric coupling

The development of methods to economically synthesize single wire structured multiferroic systems with room temperature spin-charge coupling is expected to be important for building next-generation multifunctional devices with ultralow power consumption. We demonstrate the fabrication of a single nanowire multiferroic system, a new geometry, exhibiting room temperature magnetodielectric coupling. A coaxial nanotube/nanowire heterostructure of barium titanate (BaTiO(3), BTO) and cobalt (Co) has been synthesized using a template-assisted method. Room temperature ferromagnetism and ferroelectricity were exhibited by this coaxial system, indicating the coexistence of more than one ferroic interaction in this composite system.

Reappearance of ferroelectric soft modes in the paraelectric phase of Pb(1-x)Ca(x)TiO3 at high pressures: Raman and x-ray diffraction studies

High pressure Raman spectroscopy and x-ray diffraction measurements have been carried out on Pb(1-x)Ca(x)TiO(3) (x = 0.10 and 0.30). Using high pressure Raman spectroscopic data, it is observed that the phonon instability responsible for the ferroelectric phase reappears in the paraelectric phase after a critical pressure. The observed critical pressures in the Ca(2+) doped PbTiO(3) system are much lower than the unique pressures suggested for PbTiO(3) based materials. A suitable explanation is given to explain this lowering of critical pressure. It is also shown that the ferroelectric phase which stabilizes in the paraelectric phase has a tetragonal symmetry with space group I4cm.

Synthesis of uniform gold nanoparticles using non-pathogenic bio-control agent: evolution of morphology from nano-spheres to triangular nanoprisms

Green synthesis of gold nanospheres with uniform diameter and triangular nanoprisms with optically flat surface was carried out using a non-pathogenic bio-control agent Trichoderma asperellum for reduction of HAuCl(4). Kinetics of the reaction was monitored by UV-Vis absorption spectroscopy. No additional capping/complexing agent was used for stabilizing the gold nanoparticles. Evolution of morphology from pseudospherical nanoparticles to triangular nanoprisms was studied by transmission electron microscopy (TEM). It revealed that three or more pseudospheres fused to form nanoprisms of different shapes and sizes. Slow rate of reduction of HAuCl(4) by constituents of cell-free fungal extract was instrumental in producing such exotic morphologies. Isolation of gold nanotriangles from the reacting masses was achieved by differential centrifugation.

Pollen-specific expression of Oryza sativa indica pollen allergen gene (OSIPA) promoter in rice and Arabidopsis transgenic systems

Earlier, a pollen-specific Oryza sativa indica pollen allergen gene (OSIPA), coding for expansins/pollen allergens, was isolated from rice, and its promoter--upon expression in tobacco and Arabidopsis--was found active during the late stages of pollen development. In this investigation, to analyze the effects of different putative regulatory motifs of OSIPA promoter, a series of 5' deletions were fused to β-glucuronidase gene (GUS) which were stably introduced into rice and Arabidopsis. Histochemical GUS analysis of the transgenic plants revealed that a 1631 bp promoter fragment mediates maximum GUS expression at different stages of anther/pollen development. Promoter deletions to -1272, -966, -617, and -199 bp did not change the expression profile of the pollen specificity. However, the activity of promoter was reduced as the length of promoter decreased. The region between -1567 and -199 bp was found adequate to confer pollen-specific expression in both rice and Arabidopsis systems. An approximate 4-fold increase in the GUS activity was observed in the pollen of rice when compared to that of Arabidopsis. As such, the OSIPA promoter seems promising for generation of stable male-sterile lines required for the production of hybrids in rice and other crop plants.

Sm(2-x)Dy(x)Zr2O7 pyrochlores: probing order-disorder dynamics and multifunctionality

The present work involves the synthesis of a series of Sm(2-x)Dy(x)Zr(2)O(7) compounds (0.0 ≤ x ≤ 2.0) by a controlled gel combustion process. The powders were thoroughly analyzed by powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, and diffuse-reflectance UV-visible spectroscopy. The powder XRD studies revealed the system to be single-phasic throughout with retention of pyrochlore-type ordering until 40 mol % of Dy(3+), beyond which the pyrochlore lattice gives way to the defect fluorite structure. Interestingly, Raman spectroscopic studies (as against XRD studies) showed retention of pyrochlore-type ordering throughout the homogeneity range of the compositions studied. This is perhaps the first study that reports retention of a weak pyrochlore-type superstructure in the Dy(2)Zr(2)O(7) system, which was otherwise known to crystallize in the defect fluorite system. The ionic conductivity measurements showed an increase in the activation energy (E(a)) with an increase in the mole percent of Dy(3+) owing to the decreased mobility with an increase in the degree of disorder. The system possesses a tunable band gap with varying amounts of Dy(3+). First-principles calculations were performed to support a decrease in the band gap of the doped system with an increase in the Dy(3+) content. The potential as photocatalysts of some of these compositions was explored, and they exhibited high photocatalytic activity for degradation of xylenol orange, with t(1/2) increasing from pure Sm(2)Zr(2)O(7) to pure Dy(2)Zr(2)O(7).

White light emission from spin coated Gd2O3:Dy nano phosphors synthesized using polyol technique

Water dispersible Gd2O3:Dy3+ (2%) nanophosphors were synthesized through a facile polyol process and characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), Dynamic Light Scattering (DLS) and photoluminescence (PL) spectrophotometry. The results of XRD, TEM and DLS show that resultant nanoparticles are single phasic and have spherical shape with 17 to 22% dispersibility. An efficient energy transfer was observed from host to the dopant ions. Characteristic blue and yellow emissions from Dy3+ ions were observed. The CIE coordinates of the nanophosphor lie in the white light region of the chromaticity diagram. Spin coating of the nanophosphor was done on quartz substrate. Bright white luminescence of this film was observed under ultraviolet light with lamda exc = 310 nm.

Crucial role of the reaction conditions in isolating several metastable phases in a Gd-Ce-Zr-O system

A series of samples with composition Gd(2-y)Ce(y)Zr(2)O(7) (0.0 ≤ y ≤ 2.0) were prepared by the gel combustion method followed by high-temperature reduction. The details of the structural variations as a function of the composition, temperature, and oxygen stoichiometry have been investigated by X-ray diffraction (XRD), high-temperature XRD (HT-XRD), and thermogravimetry. A complete solubility of Gd(3+) in Ce(2)Zr(2)O(7) and Ce(2)Zr(2)O(8) could be achieved by this adaptive preparative method. Analysis of the XRD data revealed a sequential variation of the structural features with oxygen stoichiometry as well as Gd(3+) contents in these compositions. The variation in the unit cell parameter along the compositions has a strong influence on the oxygen uptake behavior in the Gd(2-y)Ce(y)Zr(2)O(7) system, as observed from the thermogravimetric and HT-XRD studies. The preparation and stability of various metastable phases in Gd-Ce-Zr-O have been addressed in detail. The details of the study will be useful for the design and application of a potential redox catalyst and an oxygen storage capacitor.

Zinc oxide epitaxial thin film deposited over carbon on various substrate by pulsed laser deposition technique

Zinc Oxide (ZnO) is a promising candidate material for optical and electronic devices due to its direct wide band gap (3.37 eV) and high exciton binding energy (60 meV). For applications in various fields such as light emitting diode (LED) and laser diodes, growth of p-type ZnO is a prerequisite. ZnO is an intrinsically n-type semiconductor. In this paper we report on the synthesis of Zinc Oxide-Carbon (ZnO:C) thin films using pulsed laser deposition technique (PLD). The deposition parameters were optimized to obtain high quality epitaxial ZnO films over a carbon layer. The structural and optical properties were studied by glazing index X-ray diffraction (GIXRD), photoluminescence (PL), optical absorption (OA), and Raman spectroscopy. Rutherford backscattering spectroscopy (RBS), scanning electron microscopy with energy dispersive spectroscopy (SEMEDS) and atomic force microscopy (AFM) were employed to determine the composition and surface morphology of these thin films. The GIXRD pattern of the synthesized films exhibited hexagonal wurtzite crystal structure with a preferred (002) orientation. PL spectroscopy results showed that the emission intensity was maximum at -380 nm at a deposition temperature of 573 K. In the Raman spectra, the E2 phonon frequency around at 438 cm(-1) is a characteristic peak of the wurtzite lattice and could be seen in all samples. Furthermore, the optical direct band gap of ZnO films was found to be in the visible region. The growth of the epitaxial layer is discussed in the light of carbon atoms from the buffer layer. Our work demonstrates that the carbon is a novel dopant in the group of doped ZnO semiconductor materials. The introduction of carbon impurities enhanced the visible emission of red-green luminescence. It is concluded that the carbon impurities promote the zinc related native defect in ZnO.

Pneumocystis jirovecii dihydropteroate synthase (DHPS) genotypes in non-HIV-immunocompromised patients: a tertiary care reference health centre study

Studies on Pneumocystis jirovecii dihydropteroate synthase (DHPS) genotypes among non-HIV immunocompromised patients from developing countries are rare. In the present prospective investigation, 24 (11.8%) cases were found to be positive for Pneumocystis jirovecii out of 203 non-HIV patients with a clinical suspicion of Pneumocystis pneumonia (PCP). Dihydropteroate synthase (DHPS) genotype 1 (Thr55+Pro57) was noted in 95.8% P. jirovecii isolates in the present study in contrast to only 4.1% of patients with DHPS genotype 4 (Thr55Ala + Pro57Ser).

jefA (Rv2459), a drug efflux gene in Mycobacterium tuberculosis confers resistance to isoniazid & ethambutol

BACKGROUND & OBJECTIVES

Drug efflux pumps have been contributing factor(s) in the development of multidrug resistance in various clinically relevant bacteria. During efflux pump gene expression studies on mycobacteria, we have found a previously uncharacterized open reading frame (ORF) Rv2459 to be overexpressed in drug stressed conditions. The objective of the present study was to investigate the role of this ORF as a drug efflux pump, which might add new information in our understanding about the alternative mechanisms of drug resistance in mycobacteria.

METHODS

The open reading frame Rv2459 of Mycobacterium tuberculosis encoding a probable drug efflux protein has been cloned using pSD5 E.coli-Mycobacterium shuttle vector and overexpressed in M. tuberculosis H(37)Rv. This ORF was named as jefA. Overexpression of this gene in clones has been verified by real-time reverse transcription PCR. Minimum inhibitory concentrations (MICs) of recombinant as well as non-recombinant clones were determined by resazurin microtitre assay plate method (REMA) with and without efflux pump inhibitors carbonyl cyanide m-chlorophenylhydrazone (CCCP) and verapamil.

RESULTS

In recombinant strains of M. tuberculosis, the overexpression of this gene led to an increase in MIC of anti-tubercular drugs isoniazid and ethambutol when tested by REMA. In the presence of CCCP and verapamil, the recombinant strains showed decrease in MIC for these drugs. Bioinformatic analysis has shown a close relation of JefA protein with drug efflux pumps of other clinically relevant bacteria. In homology derived structure prepared from nearest available model, it was observed that amino acids forming TMH 1, 8 and 11 participated in ethambutol specificity and those forming TMH 2, 7 and 10 participated in isoniazid specificity in JefA.

INTERPRETATION & CONCLUSION

The increased transcription of jefA leads to increased resistance to ethambutol and isoniazid in M. tuberculosis via efflux pump like mechanism and contributes in the development of resistance to these drugs. JefA amino acid sequence is well conserved among clinically important bacterial genera, which further provides evidence of being a potent drug efflux pump. The involvement in drug resistance and very little homology with any of the human proteins makes JefA important to be included in the list of potential drug targets.

Experimental and theoretical investigations on magnetic behavior of (Al,Co) co-doped ZnO nanoparticles

We present the structural and magnetic properties of Zn(0.95-x)Co(0.05)Al(x)O (x = 0.0 to 0.1) nanoparticles, synthesized by a novel sol-gel route followed by pyrolysis. Powder X-ray diffraction data confirms the formation of a single phase wurtzite type ZnO structure for all the compositions. The Zn(0.95)Co(0.05)O nanoparticles show diamagnetic behavior at room temperature. However, when Al is co-doped with Co with x = 0.0 to 0.10 in Zn(0.95-x)Co(0.05)Al(x)O, a systematic increase in ferromagnetic moment is observed up to x = 0.07 at 300 K. Above x = 0.07 (e.g. for x = 0.10) a drastic decrease in ferromagnetic nature is observed which is concomitant with the segregation of poorly crystalline Al rich ZnO phase as evidenced from TEM studies. Theoretical studies using density functional calculations on Zn(0.95-x)Co(0.05)Al(x)O suggest that the partial occupancy of S2 states leads to an increased double exchange interaction favoring the ferromagnetic ground states. Such ferromagnetic interactions are favorable beyond a threshold limit. At a high level doping of Al, the exchange splitting is reduced, which suppresses the ferromagnetic ordering.

Effect of doping on the morphology and multiferroic properties of BiFeO3 nanorods

In this study we report the synthesis of BiFeO(3) nanorods using a sonochemical technique. The nanorods had a diameter of 20-50 nm, a length of 100-500 nm and exhibit aspect ratios in the range of 5-10. However, after doping, the TEM images of Bi(0.9)Ba(0.1)Fe(0.9)Mn(0.1)O(3) and Bi(0.9)Ca(0.1)Fe(0.9)Cr(0.1)O(3) samples show that the aspect ratios of both the double doped samples have reduced considerably, while retaining the crystallinity of the particles. BiFeO(3) nanorods show a weak ferromagnetic order at room temperature, which is quite different from the linear M-H relationship reported for bulk BiFeO(3). The saturation magnetization of these BiFeO(3) nanostructures has been found to increase on doping with various metal ions (Ba(2+), Ca(2+), Mn(2+), Cr(3+)), reaching a maximum value of 1.35 emu g(-1) for the Bi(0.9)Ba(0.1)Fe(0.9)Mn(0.1)O(3) nanostructures. However, saturation of electric polarization was observed only in case of the Bi(0.9)Ca(0.1)Fe(0.9)Cr(0.1)O(3) nanostructures.

Nanoceria-PAN composite-based advanced sorbent material: a major step forward in the field of clinical-grade 68Ge/68Ga generator

The (68)Ge/(68)Ga generator has high potential for clinical positron emission tomography (PET) imaging. However, because of the unavailability of a suitable sorbent material, the commercially available (68)Ge/(68)Ga generators are not directly adaptable for the preparation of (68)Ga-labeled radiopharmaceuticals. In view of this, a new nanoceria-polyacrylonitrile (PAN) composite sorbent has been synthesized by decomposition of a cerium oxalate precursor to cerium oxide and its subsequent incorporation in PAN matrix for the development of a clinical grade (68)Ge/(68)Ga generator. The X-ray diffraction (XRD) studies and BET nitrogen adsorption technique revealed that nanocrystalline ceria had an average particle size of approximately 10 nm, surface area of 72 +/- 3 m(2)/g and an average pore size of 3.8 +/- 0.1 A. Investigation of the distribution ratio (K(d)) values for the prepared sorbent in 0.01 N HCl medium revealed the suitability of the sorbent for the quantitative retention of (68)Ge and efficient elution of clinical grade (68)Ga. A 370 MBq (10 mCi) (68)Ge/(68)Ga chromatographic generator was developed using this sorbent. (68)Ga could be regularly eluted from this generator with >80% elution yield. The eluted (68)Ga possess high radionuclidic purity (<1 x 10(-5)% of (68)Ge impurity), chemical purity (<0.1 ppm of Ce, Fe and Mn ions) and was amenable for the preparation of (68)Ga-labeled radiopharmaceuticals. The generator gave a consistent performance with respect to the elution yield and purity of (68)Ga over an extended period of 7 months.