Study of Concentration Quenching and Energy Transfer Mechanism in Ce Doped Y2O3 Nanomaterials.

We study concentration quenching and energy transfer mechanisms of yttrium oxide (Y2O3) nanomaterials doped with different concentrations (0-5 mol%) of cerium (Ce). Photoluminescence (PL) spectra recorded under an excitation wavelength of 350 nm show a broad emission band at ∼ 406 nm and a feeble emission band at ∼ 463 nm in the undoped Y2O3 sample. The doping of Ce in Y2O3 induced multiple PL peaks within the blue-green region of the spectrum in all the doped samples with the peak at ∼ 466 nm being notably the prominent one. This prominent emission band exhibits a decrease in intensity with increasing Ce concentration due to concentration quenching. Analysis of Time-resolved photoluminescence (TRPL) spectra reveal that the average emission lifetime of Ce-doped Y2O3 is shorter than that of the undoped Y2O3 sample. The concentration quenching effect and the decrease of average emission lifetime of the dominant emission band are explained on the basis of energy transfer from the host Y2O3 to the Ce3+ ion centres. The critical quenching concentration of Ce3+ ion in Y2O3:Ce phosphor was identified to be 1 mol% and the critical transfer distance was estimated to be 23.74 Å. Analysis reveal that the concentration quenching mechanism involves nearest-neighbour interaction.

Luminescence Dynamics of BaAl2O4:Eu2+ Phosphor.

We studied steady-state and time-resolved photoluminescence of Eu doped BaAl2O4 phosphor. The undoped BaAl2O4 sample shows a dominant blue emission band at ~ 428 nm and two secondary maxima at ~ 405 and 456 nm due to F-centre and aggregate defects such as F2 -centre. The samples after doping of Eu at 1-5% show additional emission bands at ~ 485 and 518 nm due to Eu2+ centre and a red emission band at ~ 657 nm is attributed to Eu3+ centre. The sample doped with 2% of Eu shows anomalous emission having the dominant peak at ~ 494 nm. The average luminescence lifetime of the emission band at ~ 428 nm in the undoped sample was estimated to be (3.29 ± 0.91) ns. The average luminescence lifetime of this emission band after doping of Eu was found to increase by 102 orders of magnitude. The intensity of the 428 nm blue emission band was found to quench after doping of Eu beyond 3%. The concentration quenching effect was attributed to dipole-quadrupole interaction. Further, a non-radiative fluorescence energy transfer mechanism from an extrinsic Eu2+ centre to an intrinsic F-centre is proposed to describe the luminescence dynamics of the samples.

Sensitivity of ZnO Film-Based X-ray Sensors: A Comprehensive Study on the Effect of Thickness of ZnO Layer.

For all types of photosensors, efficient absorption of photons of particular interest is very essential. We report the effect of thickness of the ZnO layer in ZnO film-based X-ray sensors. A set of five samples Z1, Z2, Z3, Z4, and Z5 is developed by varying the thickness of the ZnO layer between 10 and 73 µm. The dark I-V characteristics of the sensors show a "pseudorectifying" type nature. A quantitative analysis of the dark currents reveals that the dark I-V characteristics are affected by space charge limited current (SCLC) due to intrinsic defects present in the ZnO films. The effect of the SCLC is prominent in the thicker films in comparison to the thinner ones. The sensors show high signal-to-noise (S/N) ratio below 5.0 V bias voltage. The S/N ratio is found to increase with the thickness of the ZnO layer due to efficient absorption of X-ray photons. The photoresponse characteristics of the sensors against dose rate are sublinear between 0.015 and 0.234 Gy/s. The photoresponse time of the sensors are found to be nearly 1 s. The sensitivities of Z1, Z2, Z3, Z4, and Z5 sensors at 4.5 V bias voltage for 0.234 Gy/s dose rate are estimated to be 55.51, 337.08, 312.01, 152.81, and 103.52 µC/Gy cm3, respectively. The sensitivity of the device is found to increase with increase in thickness of the ZnO layer and reaches an optimum level for the thickness of about 19-26 µm. Beyond this range, the sensitivity is found to decrease due to the Schubweg effect.

Optical properties of blue-light-emitting Y2 O3 :Ce nanophosphor for solid-state lighting application.

The structural, surface morphological, optical absorption and emission features of Y2 O3 :Ce (0%-5%) were studied. The samples had a body-centred cubic crystal structure. The undoped sample had a crystallite size of 29.03 nm, and it varied after doping with Ce. The grain size of the samples varied from 23.00 to 50.78 nm. All the samples exhibited a strong absorption band at 206 nm due to F-centre absorption and absorption involving the delocalised bands. In addition, the doped samples exhibited a secondary band at ~250 nm due to 4f → 5d transitions of Ce3+ ions. The optical bandgap of the undoped sample was found to be ~5.37 eV, and it decreased to 5.20 eV with an increase in Ce concentration to 5%. The undoped sample under 350-nm excitation exhibited a broad photoluminescence (PL) emission band with the maxima at 406 nm and a secondary band at 463 nm. In contrast, multiple PL peaks were centred at ~397, 436, 466, 488 and 563 nm in all the doped samples. The average lifetime of the emission band at 406 nm was 1.05 ns and that of the emission band at ~466 nm was 1.63 ns. The material has potential for solid-state lighting applications.

Phototransferred thermoluminescence characteristics of microcline (KAlSi3O8) under 470 nm blue- and 870 nm infrared-light illumination.

We report phototransferred thermoluminescence (PTTL) induced in microcline by 470 nm blue- and 870 nm infrared-light. A conventional thermoluminescence (TL) glow curve measured from a sample irradiated to 40 Gy produces five composite TL glow peaks P1, P2, P3, P4 and P5 at 90, 123, 166, 298 and 391 °C respectively. The sample produces PTTL peaks also identified as P1, P2, P3 and P4 following illumination by blue or infrared light after irradiation to 40 Gy and preheating to 400 °C. Step-annealing suggests the presence of deep electron traps associated with a signal beyond 500 °C. However, preheating to 500 °C and exposure to blue or infrared light does not produce significant PTTL peaks. For doses between 40 Gy and 100 Gy, the maximum PTTL is emitted within 60 and 150 s of blue light illumination. On the other hand, the same feature under the infrared light illumination occurs within 100-200 s of illumination. PTTL peaks P1, P2, P3 and P4 reproduced under blue light illumination have a linear dose response between 10 Gy and 100 Gy and those reproduced under infrared light illumination have a superlinear dose response between 10 and 100 Gy. In contrast, donor peak P5 in both cases follows sublinear dose response within the same dose range. Fading of PTTL peaks P1, P2, P3 and P4 as well as the donor peak P5 are negligibly small under blue light illumination compared to that of infrared light illumination. PTTL glow curves are also found to be properly reproducible.

Complications of tuberculous meningitis and their effect on outcome in a tertiary care cohort.

BACKGROUND: To report the frequency and severity of complications, and their effect on the outcome of tuberculous meningitis (TBM).METHODS: In this retrospective cohort study, the following TBM complications were observed: status epilepticus (SE), hydrocephalus, paradoxical clinical worsening (PCW), hyponatremia, drug-induced hepatitis (DIH), infarction and mechanical ventilation (MV). These were recorded and correlated with stage of meningitis and outcome.RESULTS: A total of 144 patients with TBM (median age 26 years, range 12-75) were included. There were 76 (52.8%) females. The patients were in Stage I (n = 33), Stage II (n = 82) and Stage III (n = 29); 58 had definite TBM. Complications occurred in 128 (88.9%); complications included hydrocephalus (n = 58, 40.3%), hyponatremia (n = 70, 48.6%), infarction (n = 48, 33.3%), DIH (n = 42, 29.2%), SE (n = 16, 18.0%), MV (n = 43, 29.9%) and PCW (n = 24, 16.7%), with variable overlap. By 6 months, 33 patients had died. Death was related to PCW (P = 0.016), hyponatremia (P = 0.03), MV (P = 0.02), infarction (P = 0.03) and the number of complications. Except PCW, most complications occurred during the first month.CONCLUSIONS: In TBM, complications occurred in 128 (88.9%) patients, mainly in the early stages, with variable overlap. Infarction, PCW, hyponatremia and MV were predictive of poor outcome.

Impaired Autophagy Flux is Associated with Proinflammatory Microglia Activation Following Japanese Encephalitis Virus Infection.

Role of autophagy in Japanese encephalitis viral (JEV) infection is not well known. In the present study, we reported the role of autophagy flux in microglia activation, neurobehavioral function and neuronal death using a mouse model of JEV. Markers for autophagy (LC3-II/I, SQSTM1/P62, phos-Akt, phos-AMPK), and neuronal death (cleaved caspase 12, H2Ax, polyubiquitin) were investigated by western blot at 1, 3 and 7 days post inoculation. Cathepsin D was measured in cerebral cotex of JEV infected mice spectrophotometrically. Microglia activation and pro-inflammatory cytokines (IL1ß, TNF-α, IFNγ, IL6) were measured by immunohistochemistry, western blot and qPCR analysis. In order to determine the neuroinflammatory changes and autophagy mediated neuronal cell death, BV2-microglia and N2a-neuronal cells were used. Autophagy activation marker LC3-II/I and its substrate SQSTM1/P62 were significantly increased while cathepsin D activity was decreased on day 7 post inoculation in cerebral cortex. Microglia in cortex were activated and showed higher expression of proinflammatory mRNA of IL1ß, TNF-α, IFNγ and IL6, with increased DNA damage (H2AX) and neuronal cell death pathways in hippocampus and neurobehavioral dysfunction. Similar observations on JEV infection mediated autophagy flux inhibition and neuronal cell death was found in N2a neuronal cell. Collectively, our study provides evidence on the role of autophagy regulation, microglial activation and neurodegeneration following JEV infection.

Thermoluminescence and infrared light stimulated luminescence of limestone (CaCO3) and its dosimetric features.

Thermoluminescence (TL) and infrared light stimulated luminescence (IRSL) of limestone (CaCO3) collected from the Mawsmai Cave, India is reported. Structural and compositional analyses show that the sample has a rhombohedral crystal structure and contains 33.45% of CaO. TL measured at 1 °C/s from a sample irradiated to 600 Gy produces three composite glow peaks P1, P2 and P3 at 92, 165 and 239 °C respectively. The nature of the glow peaks is suggestive of the presence of a continuum trap distribution with activation energy between 0.40 eV and 1.12 eV. As regards to dose response, the TL intensity of P1 increases at a uniform rate with dose between 10 and 1000 Gy. Interestingly, the intensity of P3 increases with dose through two uniform regions, one within 10-100 Gy and the other between 100 and 1000 Gy. The IRSL measurement produces ill-shaped decay curves. The IRSL intensity also increases with dose at two different uniform rates within 10-100 Gy and 100-1000 Gy. Residual TL recorded after each IRSL measurement shows similar dose response as that under the conventional TL. Regarding fading, P1 fades by 88% and P3 by 14% within 12 h of irradiation.

The effect of pre-dose on thermally and optically stimulated luminescence from α-Al2O3:C,Mg and α-Al2O3:C.

We report the effect of pre-dose on the thermoluminescence (TL) and optically stimulated luminescence (OSL) dose response of α-Al2O3:C,Mg and α-Al2O3:C. Before any luminescence measurement, the samples were irradiated with different doses, namely 100, 500 and 1000 Gy to populate the deep electron traps. This is the pre-dose. The results from TL and OSL studies are compared with results from samples used without any pre-measurement dose. The TL glow curves and OSL decay curves of α-Al2O3:C,Mg recorded after pre-doses of 100, 500 and 1000 Gy are identical to those from a sample used without any pre-dose. Further, the TL and OSL dose response of all α-Al2O3:C,Mg samples are similar regardless of pre-dose. In comparison, the TL glow curves and OSL decay curves of α-Al2O3:C are influenced by pre-dose. We conclude that the differences in the TL and OSL dose response of various pre-dosed samples of α-Al2O3:C are due to the concentration of charge in the deep traps. On the other hand, owing to the lower concentration of such deep traps in α-Al2O3:C,Mg, the TL or OSL dose responses are not affected by pre-dose in this material.

Hypovolemia due to cerebral salt wasting may contribute to stroke in tuberculous meningitis.

BACKGROUND: Both stroke and cerebral salt wasting (CSW) are common in tuberculous meningitis (TBM), but there is paucity of studies evaluating their combined effect. AIM: The present study has been undertaken to evaluate the spectrum of stroke in TBM and its relation to CSW. DESIGN: Hospital-based prospective cohort study. METHODS: Eighty-one patients with TBM diagnosed on the basis of clinical, cerebrospinal fluid and magnetic resonance imaging (MRI) criteria were prospectively included. Stroke was diagnosed on the basis of clinical, MRI findings or both. Stroke risk factors were noted. Patients with hyponatremia were categorized into CSW and other causes. Three and 6 months outcome was defined using modified Rankin Scale (mRS) as good (<2) or poor (≥2). RESULTS: Out of 81 patients with TBM, 32 (39.5%) had ischemic stroke. CSW was the commonest cause of hyponatremia and occurred in 34 (42%) patients. Stroke occurred in tubercular zone in 10, ischemic zone in 15 and both in 7 patients. The patients with ischemic zone infarction were older and had stroke risk factors such as diabetes mellitus, hypertension and hyperlipidemia. Out of 16 (47%) patients with CSW, 10 (62.5%) had stroke during the polyuric phase. The patients with CSW had more frequent deep white matter infarcts (P = 0.01) which were in internal border zone in 4 (40%). CONCLUSION: In TBM, stroke occurred in 39.5% of the patients, 50% of whom had CSW. Volume contraction due to CSW may contribute to stroke.

A study of atrial and brain natriuretic peptides in tuberculous meningitis and acute encephalitis.

OBJECTIVE: To report atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) levels in patients with tuberculous meningitis (TBM) and acute encephalitis syndrome (AES), and evaluate their relationship with hyponatraemia. METHODS: Consecutive patients with TBM and AES were included in the study. Hyponatraemia was categorised as cerebral salt wasting (CSW), syndrome of inappropriate secretion of antidiuretic hormone (SIADH) and a miscellaneous group based on clinical and laboratory criteria. Serum ANP and BNP levels were measured upon hospital admission, at the time of diagnosis of hyponatraemia and upon correction of hyponatraemia. Outcome at 3 months was assessed using the modified Rankin scale (mRS) as good (mRS 2) and poor (mRS >2). RESULTS: There were 67 patients with TBM and 77 with AES. Hyponatraemia was more common in TBM than in AES (65.7% vs. 27%, P < 0.01). Forty-one (63.1%) patients had CSW, 6 (9.2%) SIADH and 18 (27.7%) had miscellaneous causes of hyponatraemia. During hyponatraemia, ANP (180 ± 45 vs. 106 ± 32 pg/ml, P < 0.01) and BNP (263 ± 118 vs. 163 ± 91 pg/ml, P  0.01) levels were significantly increased compared with baseline, and remained high even after Na+ correction. CONCLUSION: ANP and BNP levels were increased during hyponatraemia and remained high even after correction of hyponatraemia in TBM and AES, especially in patients with CSW. However, ANP and BNP levels could not be used to differentiate CSW from SIADH.

Detecting protein complexes based on a combination of topological and biological properties in protein-protein interaction network.

Protein complexes are known to play a major role in controlling cellular activity in a living being. Identifying complexes from raw protein protein interactions (PPIs) is an important area of research. Earlier work has been limited mostly to yeast. Such protein complex identification methods, when applied to large human PPIs often give poor performance. We introduce a novel method called CSC to detect protein complexes. The method is evaluated in terms of positive predictive value, sensitivity and accuracy using the datasets of the model organism, yeast and humans. CSC outperforms several other competing algorithms for both organisms. Further, we present a framework to establish the usefulness of CSC in analyzing the influence of a given disease gene in a complex topologically as well as biologically considering eight major association factors.

Pontomesencephalic Atrophy and Postural Instability in Wilson Disease.

BACKGROUND AND PURPOSE: The MR Parkinsonism index helps in differentiating progressive supranuclear palsy from Parkinson disease and multisystem atrophy. Pontomesencephalic involvement is common in neurologic Wilson disease, but there is no prior study evaluating the MR Parkinsonism index and its indices in Wilson disease. We report the MR Parkinsonism index and its indices in Wilson disease and correlate these changes with clinical severity and postural reflex. MATERIALS AND METHODS: Thirteen individuals with neurologic Wilson disease were included, and their clinical details, including neurologic severity, postural reflex abnormality, and location of signal changes on MR imaging, were noted. The 3D BRAVO T1 sequence was used for measurement of the MR Parkinsonism index and its indices. The MR Parkinsonism index and its indices were also obtained in 6 age- and sex-matched controls. The morphometric parameters in Wilson disease were compared with those in with healthy controls and among the patients with and without abnormal postural reflex. RESULTS: The midbrain area was reduced in patients with Wilson disease compared with controls (112.08 ± 27.94 versus 171.95 ± 23.66 mm2, P = .002). The patients with an abnormal postural reflex had an increased MR Parkinsonism index and pons-to-midbrain ratio compared with controls, whereas these parameters were equivalent in patients with normal postural reflex and controls. The patients with abnormal postural reflex had more severe illness, evidenced by higher Burke-Fahn-Marsden scores (51.0 ± 32.27 versus 13.75 ± 12.37, P = .04) and neurologic severity grades (2.57 ± 0.53 versus 1.67 ± 0.82, P = .04). CONCLUSIONS: An increase in the MR Parkinsonism index in Wilson disease is mainly due to midbrain atrophy and it correlates with neurologic severity and abnormal postural reflex.

A COMPARATIVE STUDY OF THE DOSIMETRIC FEATURES OF α-Al2O3:C,Mg AND α-Al2O3:C.

A comparative study of the dosimetric features of α-Al2O3:C,Mg and α-Al2O3:C relevant to thermoluminescence dosimetry is reported. A glow curve of α-Al2O3:C,Mg measured at 1°C/s after beta irradiation to 1 Gy shows two subsidiary peaks at 42°C (labelled as I) and 72°C (II) and the main peak at 161°C (III) whereas a glow curve of α-Al2O3:C measured under the same conditions shows the main peak at 178°C (II') and a lower intensity peak at 48°C (I'). Apart from these ones, there are several other peaks at temperatures beyond that of the main peak in both α-Al2O3:C,Mg and α-Al2O3:C. However, the latter are not included in this study. We report a comparative quantitative analysis of dose response and fading of peaks I, II and III of α-Al2O3:C,Mg and peaks I' and II' of α-Al2O3:C. Analysis shows that the dose response of peaks I and III is sublinear within 1-10 Gy whereas that of peak II is superlinear within 1-4 Gy followed by a sublinear region within 4-10 Gy. In comparison, the dose response of peak I' is superlinear within 1-4 Gy followed by a sublinear region within 4-10 Gy whereas that of peak II' is sublinear within 1-4 Gy followed by a superlinear region within 4-10 Gy. As regards to fading corresponding to 1 Gy, peak I is very unstable and fades within 300 s, peak II is more stable and takes up to 43200 s to fade. In comparison, peak III fades down to 30% of its initial intensity within 2400 s. Interestingly, between 2400 and 800 s, the intensity fades by 17% only. Regarding fading in α-Al2O3:C, peak I' fades within 600 s whereas peak II' shows an inverse fading behaviour up to 64800 s. The rate of fading for peaks I, II and III in α-Al2O3:C,Mg was found to decrease with increase in dose. However, no such behaviour was observed in α-Al2O3:C. The fading in both samples is discussed on the basis of a charge hopping mechanism.

Spectrum of hyperosmolar hyperglycaemic state in neurology practice.

BACKGROUND & OBJECTIVES: Hyperosmolar hyperglycaemic state (HHS) is a medical emergency, but there is a paucity of studies reporting the spectrum of neurological manifestations of HHS. We, therefore, report the neurological spectrum, triggering factors and outcome of HHS in general neurology practice. METHODS: The records of the patients with HHS were extracted from computerized hospital information system and those managed currently were prospectively included. The demographic, clinical manifestations, duration of diabetes and precipitating events such as infection, stress and stroke were noted. Patients with HHS were categorized into seizure, movement disorder and encephalopathy groups. Their electroencephalography, magnetic resonance imaging (MRI) findings and outcome were noted. RESULTS: There were 17 patients with HHS (age range 40 and 75 yr) and seven were females. Seven patients were diabetic for five years, one for four years, one for one year and four were diagnosed after the occurrence of HHS. Four patients had epilepsia partialis continua persisting for 72-360 h, one patient had focal seizures and his MRI revealed T2 hyperintensity in frontal region in one patient and cerebellar vermian hyperintensity in another. All the five patients improved, but two had neurological deficits on discharge. Nine patients had encephalopathy which was precipitated by stroke in six patients, urinary infections in two and meningitis in one. Three females had hemichorea-hemiballismus syndrome, which was triggered by infections. Abnormal movements lasted 5-10 days and responded to correction of hyperosmolarity. Nine out of 17 patients improved completely whereas the remaining eight had partial recovery, these patients had stroke, ventilator-related complications or meningoencephalitis. INTERPRETATION & CONCLUSIONS: The most common presentation of HHS was encephalopathy (9) followed by seizure (5) and hemichorea-hemiballismus syndrome (3) which responded to the correction of hyperosmolar state.

Spectrum and outcome of acute infectious encephalitis/encephalopathy in an intensive care unit from India.

PURPOSE: To evaluate the spectrum of acute infectious encephalitis/encephalopathy syndrome (AIES) in intensive care unit (ICU) and the predictors of mechanical ventilation (MV) and outcome of these patients. METHODS: AIES patients diagnosed on the basis of fever, altered sensorium, seizure and cerebrospinal fluid pleocytosis admitted to the neurology ICU were prospectively included. The demographic and clinical details, hematological, biochemical, MRI and etiological findings of the patients were noted. Need of MV, death in hospital and 3-month functional outcome were analyzed. RESULTS: One hundred sixty-four out of 258 (64%) AIES patients needed ICU admission. Their median age was 35 (2-85) years and 71 (43%) were females. The etiology was viral in 44 (herpes and Japanese encephalitis in 12 each, dengue in 17, mumps, measles and varicella in 1 patient each), non-viral in 64 (scrub typhus in 48, falciparum malaria in 6, leptospira in 3 and bacterial in 7) and undetermined etiology in 56 (34%) patients. Sixty-nine (42%) patients needed MV. On multivariate analysis, Glasgow Coma Scale (GCS) score, Sequential Organ Failure Assessment (SOFA) score and raised intracranial pressure were independent predictors of MV. Forty-three (26%) patients died, and all were in the MV group. Higher SOFA score and untreatable etiology were independent predictors of mortality. At 3-month follow-up, 14% had poor and 86% had good outcome. Low GCS score, focal weakness and status epilepticus independently predicted poor outcome. CONCLUSION: Twenty-six percent patients with AIES died in ICU, and 86% had good recovery at 3 months. Admission SOFA scores and untreatable etiology predicted mortality.

Possible role of transforming growth factor ß in tuberculous meningitis.

BACKGROUND: Transforming growth factor ß (TGF-ß) is an anti-inflammatory cytokine and its role in hydrocephalus and stoke has been suggested. Tuberculous meningitis (TBM) is associated with exudates, stroke, hydrocephalus and tuberculoma, but the role of TGF-ß has not been evaluated in relation to these changes. AIM: To evaluate the cerebrospinal fluid (CSF) TGF-ß level in the patients with TBM, and correlate these with clinical findings, MRI changes, paradoxical response and outcome at 6months. METHODS: TBM patients diagnosed on the basis of clinical, CSF and MRI criteria were prospectively included. The clinical details including duration of illness, seizures, focal motor deficit, Glasgow Coma Scale (GCS) score and stage of TBM were noted. Presence of exudate, hydrocephalus, tuberculoma and infarction in MRI was also noted. MRI was repeated at 3months and presence of paradoxical response was noted. Cerebrospinal fluid TGF-ß was measured using ELISA on admission and repeated at 3months and these were compared with 20 controls. RESULTS: TGF-ß level was significantly higher in TBM compared to the controls (385.76±249.98Vs 177.85±29.03pg/ml, P<0.0001). TGF-ß correlated with motor deficit, infarction and tuberculoma on admission but did not correlate with CSF abnormalities, drug induced hepatitis, paradoxical response and outcome. TGF-ß level at 3months was significantly lower than the baseline but remained higher than the controls. CONCLUSION: CSF TGF-ß levels are elevated in TBM and correlate with infarction and tuberculoma.

Temperature assisted radiative and non-radiative recombination mechanisms in sillimanite (Al2SiO5) mineral.

Temperature assisted luminescence in sillimanite (Al2SiO5) mineral was studied using thermoluminescence (TL). TL characteristics were studied in un-annealed and different annealed samples. Analysis showed that in the un-annealed sample, there was four electron trapping sites at depths ~0.56, 0.87, 1.08, 1.32eV and a hole trapping site at depth ~3.63eV from the conduction band acting as a recombination center. Further analysis on the annealed samples showed that the 0.56eV trapping site was a pressure induced surface trap and it disappeared after annealing. However, the other trapping and recombination sites were found to be stable under thermal treatment. Due to this trap distribution, three partially overlapping glow peaks were observed. The glow peaks were found to be affected by thermal quenching. The thermal quenching parameters were evaluated from the composite glow curves by using Computerized Resolved Peak (CRP) technique. The activation energies for thermal quenching (W) estimated from the three peaks were found to be ~0.69±0.05, 0.92±0.06 and 1.15±0.03eV respectively and the pre-exponential factors (C) were ~1.12×108, 2.65×1010 and 9.23×1011 respectively. Based on the analysis, a band model was proposed and the whole radiative and non-radiative recombination mechanisms were discussed.