Structural and optical properties of nanoparticles (V, Al) co-doped ZnO synthesized by sol–gel processes

ZnO, Zn0.9V0.1O and Zn0.89V0.1Al0.01O nanoparticles have been prepared by a sol–gel method and their structural and optical properties have been investigated. The obtained nanopowder was characterised by various techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. After thermal treatment at 500 C in air, the powder of Zn0.89V0.1Al0.01O with an average particle size of 25 nm presents a strong luminescence band in the visible range. The PL band energy position presents a small blue shift with the increase of measurement temperature. Different possible attributions of this emission band will be discussed

Sol–gel synthesis, structural and luminescence properties of MT-doped SiO2/Zn2SiO4 nanocomposites

The sol–gel method is used for the preparation of undoped, Mn and V-doped Zn2SiO4 particles embedded in SiO2 host matrix. The phase purity and morphological features were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) investigations. The obtained SiO2/Zn2SiO4 nanocomposite, exhibits a strong photoluminescence (PL) band centered at around 760nm, attributed to energy transfer occurs from Zn2SiO4 particles to NBOHs interfaces defects. In addition, the PL spectrum for the SiO2/Zn2SiO4:Mn nanocomposite showed that a dominant peak at 525nm appeared, which originated from the 4T1–6A1 transitions of Mn2+ ions. In the case of SiO2/Zn2SiO4:V, the PL reveals a band centered at about 540nm attributed to the effect of the V5+ in the host matrix nanocomposite

the significant effect of size and concentrations of iron oxide nanoparticles on magnetic resonance imaging contrast enhancement

In this study, iron oxide (γ-Fe2O3) nanoparticles (IONs) were successfully synthesized using sol-gel method, and characterized by XRD and VSM. The potential application of the differently sized IONs (22 nm and 30 nm) as magnetic resonance imaging (MRI) contrast agents was investigated. The relaxation time (T2) of the IONs was measured at room temperature and concentration range of 9–84 µg/ml using fast spin echo sequence with six echoes. The size was found to affect the contrast enhancement of the MRI image, with the T2 for 22 nm sized γ-Fe2O3 nanoparticles exhibiting a shorter dephasing compared to the 30 nm sized γ-Fe2O3 nanoparticles. The T2 relaxivity also decreased with increasing concentration (9–84 µg/ml) of the γ-Fe2O3 nanoparticles. Based on the T2-weighted analysis, a better signal (i.e. brighter image) was achieved for the 30 nm sized γ-Fe2O3 nanoparticles. Thus, the use of IONs to enhance MR image contrast is dependent on the nanoparticle size and concentration of the IONs. In general, the results indicate that the synthesized γ-Fe2O3 nanoparticles are promising materials for use as MRI contrast agents. Keywords: Magnetic resonance imaging, Iron oxides nanoparticles, T2 relaxivity, XRD, VS

CO sensing characteristics of In-doped ZnO semiconductor nanoparticles

Abstract A study on the CO sensing characteristics of In-doped ZnO semiconductor nanoparticles (IZO NPs) prepared by a modified sol–gel technique is reported. The morphological and microstructural features of IZO NPs with various dopant concentrations (1 at.%, 2 at.%, 3 at.%, and 5 at.% In) were investigated by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The influence of indium doping on defect characteristics of ZnO was also investigated by photoluminescence (PL). A thick film of IZO NPs was deposited by screen printing on an alumina substrate provided with a pair of Pt interdigitated electrodes to fabricate a simple conductometric sensor platform. The as fabricated In-doped ZnO sensors showed enhanced sensitivity to CO gas with respect to pure ZnO one. Sensors with low dopant loading (1 at.% and 2 at.% In) were found to be more sensitive with shorter response and recovery times than those with high dopant loading

In vivo evolution of tumour cells after the generation of double-strand DNA breaks

In vitro, the ratio of single- to double-strand DNA breaks (DSB) and their absolute values determine the cell death pathway. The consequences of the generation of various numbers of DSB generated in vivo in tumour cells have been analysed in two different experimental tumour models. Synchronisation of DSB generation and control of their number have been achieved using different doses of bleomycin (BLM) and tumour cell permeabilisation by means of locally delivered electric pulses. According to BLM dose, different cell death pathways are observed. At a low therapeutic dose, a mitotic cell death pathway is detected. It is characterised by the appearance of 'atypical mitosis', TUNEL and caspase-3 positive, 24 h after the treatment, and later by the presence of typical apoptotic figures, mainly TUNEL positive but caspase-3 negative. Caspase-3 is thus an early marker of apoptosis. Mitotic cell death is also followed by lymphocytic infiltration reaction. At high doses of BLM, pseudoapoptosis is detected within a few minutes after the treatment. These cell death pathways are discussed as a function of the number of DSB generated, by comparison with previous results obtained in vitro using BLM or ionising radiation

Diasporic virginities: social representations of virginity and identity formation amongst British arab muslim women

This study compares how practising and non-practising British Arab Muslim women position themselves in relation to representations of virginity. Overall, in our qualitative study, we found that representations of culture and religion influenced social practices and social beliefs in different ways: non-practising Muslim women felt bound by culture to remain virgins, while practising Muslim women saw it as a religious obligation but were still governed by culture regarding the consequences of engaging in premarital sex. Interestingly, some practising Muslim participants used Mut’a (a form of temporary ‘marriage’) to justify premarital sex. This, however, did not diminish the importance of virginity in their understanding and identification as Arab women. In fact, this study found that virginity, for the British Arabs interviewed, embodied a sense of ‘Arabness’ in British society. Positioning themselves as virgins went beyond simply honour; it was a significant cultural symbol that secured their sense of cultural identity. In fact this cultural identity was often so powerful that it overrode their Islamic identities, prescribing their behaviour even if religion was seen as more ‘forgiving’

Normative and self-perceived orthodontic treatment need of a Peruvian university population

BACKGROUND: Previous studies on orthodontic treatment need in young adults have shown that up to 50% had malocclusions that needed orthodontic treatment. The aims of this study were to assess the normative and self-perceived need for orthodontic treatment using the Index of Orthodontic Treatment Need (IOTN) and to determine if the treatment need levels were influenced by sex, age and socio-economic status (SES) in a sample of Peruvian young adults. METHODS: 281 first-year students (157 male and 124 female students) with a mean age of 18.1 +/- 1.6 years were randomly selected and evaluated through the Dental Health Component (DHC) and Aesthetic Component (AC) of the IOTN. Structured interview and clinical examination were used to assess the students. Descriptive statistics and Chi-square tests were used for data analysis with statistical significance set at P < 0.05. RESULTS: An intra-examiner reliability of 0.89 was obtained (weighted Kappa). The percentage of students according to SES was 51.2%, 40.6% and 8.2% corresponding to low, medium and high SES respectively. The percentage of students with DHC grades 4–5 was 29.9% whereas the percentage of students with AC grades 8–10 was 1.8%. There were no significant differences in the distribution of normative and self-perceived orthodontic treatment need based on sex, age and SES comparisons. CONCLUSION: Normative orthodontic treatment need was not matched by a similar level of self-perceived treatment need in these young adults. Sex, age and SES were non-significant factors associated with levels of treatment need

Systematics of Inclusive Photon Production in 158 AGeV Pb Induced Reactions on Ni, Nb, and Pb Targets

The multiplicity of inclusive photons has been measured on an event-by-event basis for 158 AGeV Pb induced reactions on Ni, Nb, and Pb targets. The systematics of the pseudorapidity densities at midrapidity (rho_max) and the width of the pseudorapidity distributions have been studied for varying centralities for these collisions. A power law fit to the photon yield as a function of the number of participating nucleons gives a value of 1.13+-0.03 for the exponent. The mean transverse momentum, , of photons determined from the ratio of the measured electromagnetic transverse energy and photon multiplicity, remains almost constant with increasing rho_max. Results are compared with model predictions.Comment: 16 pages including 4 figure