Search

We describe a protocol for flow cytometry analysis of cell cycle in plants using indirect immunolabelling staining and Vicia faba, Pisum sativum and Zea mays root tip cells as model systems. The protocol is based on simultaneous analysis of two fluorescent signals. The first, obtained after staining with propidium iodide, is used to quantify total nuclear DNA content. The second, obtained after indirect immunofluorescent staining of bromodeoxyuridine (BrdUrd), is used to quantify the amount of BrdUrd incorporated into nuclear DNA. In an attempt to standardize the procedure, the effects of various conditions for partial DNA denaturation using HCl, as well as of BrdUrd concentration and incorporation time on flow cytometry DNA / BrdUrd content analysis have been studied. Maximum BrdUrd-linked fluorescence was observed after a 30 min pulse with 10 μM BrdUrd and after DNA denaturation with 1.5 N HCl (final concentration) for 30 min at 25 °C. Under these conditions, DNA content histograms with relatively small coefficient of variation (< 4%, full peak) could be obtained. To avoid non-specific staining of cytoplasm and cell walls, the protocol involves the use of nuclei isolated from formaldehyde-fixed tissues. Fixed isolated nuclei are stable and may be stored in hexylene glycol 0.75 M at 4 °C for prolonged periods prior to actual staining and analysis.

Several drugs previously tested in clinical trials and approved for different indications have been repurposed for bipolar disorder. We carried out a systematic meta-review of meta-analyses of randomized placebo-controlled trials investigating repurposed drugs as adjunctive treatments for mania and bipolar depression. We performed a critical appraisal using ‘A MeaSurement Tool to Assess systematic Reviews’ Version 2 (AMSTAR 2). We synthesized results on efficacy, tolerability, and safety, assessing evidence quality according to the ‘Grading of Recommendations, Assessment, Development and Evaluations’ (GRADE) approach. Our systematic search identified nine eligible studies investigating 12 drugs, four for mania and eight for bipolar depression. The quality of reporting was heterogeneous according to AMSTAR 2. In mania, allopurinol (for symptoms reduction and remission at 4–8 weeks) and tamoxifen (for response and symptoms reduction at 4–6 weeks) showed higher efficacy than placebo, with low and very low quality of evidence, respectively. Concerning bipolar depression, modafinil/armodafinil (for response, remission, and symptoms reduction at 6–8 weeks) and pramipexole (for response and symptoms reduction at 6 weeks) were superior to placebo, despite the low quality of evidence. Results on the efficacy of celecoxib and N-acetylcysteine were of low quality and limited to certain outcomes. Overall, the lack of evidence of high and moderate quality does not allow us to draw firm conclusions on the clinical utility of repurposed drugs as adjunctive treatments for mania and bipolar depression, highlighting the need for additional research.

Single crystals of PbMoO 4 were studied by means of light-induced electron paramagnetic resonance (EPR) and wavelength resolved thermally stimulated luminescence (TSL). The work is focused on the electron self-trapped at the (MoO 4 ) 2- complex. Detailed analysis of the EPR spectra of this complex allowed to determine a set of spin-Hamiltonian parameters including g factor and the 95,97 Mo, 207 Pb hyperfine tensors further used in calculations performed in terms of crystal field and LCAO-MO theories. They have shown a significant overlap of the Mo 5 d 1 and 6 s 6 p ligand lead orbitals. The contributions of oxygen and lead to the molecular orbitals with an electron trapped at the (MoO 4 ) 3- complex were about 14% and 38%, respectively. The decay of the molybdenum center EPR intensity with annealing temperature provided information about thermal stability of the center, which thermally destroys already at 40 K. Trap depth and frequency factor, E t = 0.05 eV, and f 0 = 10 4 s −1 , have been determined. The TSL glow curve displays two overlapping peaks in the 40–50 K temperature region, corresponding to the disappearance of the EPR signal from the (MoO 4 ) 3- center. By partial cleaning technique and initial rise method it is shown that the lower temperature peak is related to a trap with thermal parameters similar to those determined for the (MoO 4 ) 3- center. This allows to correlate it to the thermal destruction of the (MoO 4 ) 3- center. The obtained results are discussed in a broader frame of charge trapping mechanism in all the family of tungstate and molybdate-based single crystals.

International audience; The recent trends in scintillator technologies stimulate research efforts toward the development of novel materials morphologies, such as nanoparticles, able to efficiently convert ionizing radiations into light. For example, scintillating nanoparticles attract great interest in medical oncological therapies. In this work, the structural and morphological properties of HfO2:Ti nanoparticles with Ti concentrations from 0.03 to 10 mol% and subjected to calcination up to 1000 °C are thoroughly characterized; moreover, X‐ray photoelectron spectroscopy reveals the incorporation of Ti in both Ti (III) and Ti (IV) chemical states in as prepared samples, while the exclusive presence of Ti(IV) is unambiguously identified in calcined nanoparticles. The optical emission under X‐ray excitation evidences an intense Ti (IV)‐related luminescence at 2.5 eV in high temperature calcined samples with a few microseconds scintillation lifetime, and efficiency comparable to that of Bi4Ge3O12 reference scintillator. Finally, the competitive role of defects in charge carriers capture is demonstrated by the monotonic increase of the 2.5 eV band during prolonged X‐ray irradiation, more evident for nanoparticles with titanium concentration below 1 mol%. HfO2:Ti may also find application in X‐ray triggered oncological therapies by using the Ti (IV)‐related bright radioluminescence to excite photosensitizer molecules for singlet oxygen generation.

Oxygen vacancies play an important role in the luminescence processes of inorganic scintillator materials. In order to study the effects of oxygen vacancies on the luminescence properties of Na3LuSi3O9:Ce3+, these phosphors were prepared using a high temperature solid-state reaction method under different atmosphere and raw materials. It was found that oxygen vacancy had great influence on the absorption, photoluminescence and decay curves of Na3LuSi3O9:Ce3+. The luminescence intensity and peak position showed a regular change when synthesizing atmosphere changed. Na3LuSi3O9:Ce3+ with more oxygen vacancies showed much stronger luminescence intensity at high temperature than that without vacancies. And it was also found that the decreasing of oxygen vacancies can quicken the photoluminescence decay of Ce3+ in Na3LuSi3O9. The existence of oxygen vacancies in Na3LuSi3O9:Ce3+ was confirmed by Zr4+ doping and thermoluminescence emission spectra. At last, emission bands of Ce3+ and oxygen vacancies were well distinguished under X-ray excitation and probable cause of the formation of oxygen vacancies was discussed.

International audience; In this work, we investigate the optical properties of hafnium dioxide nanocrystals, upon X-ray irradiation, looking for spectral evolution following thermal treatments in air up to 1000 °C that modify the crystal size as well as their point defect concentrations. Radio-luminescence measurements from 10 K up to room temperature reveal a rich and evolving picture of the optical features. A complete spectral analysis of the broad luminescence spectra reveals the presence of several emission components in the visible and UV regions. The lower energy components peaking at 2.1, 2.5, and 2.9 eV are characterized by a thermal quenching energy of 0.08 eV, while the corresponding value for the UV bands at 4.1 and 4.7 eV is close to 0.23 eV. We tentatively assign the components ranging from 2 to 3 eV to the presence of optically active defects of an intrinsic nature, together with the occurrence of titanium impurities; conversely, the bands at higher energies are likely to be of an excitonic nature. The comparison with previous photo-luminescence studies allows evidencing characteristic differences between the features of luminescence emissions caused by intra-centre excitation and those occurring under ionizing irradiation. Finally, scintillation measurements in the visible range reveal the existence of a fast decay in the nanosecond time scale for the smallest hafnia nanocrystals. This study offers a clear description of HfO2 luminescence characteristics upon excitation by X-rays and can lead to a better comprehension of the structure–property relationship at the nanoscale in metal oxides.

International audience; The influence of Ca codoping on the optical absorption, photo‐, radio‐, and thermo‐luminescence properties of YAlO3:Ce (YAP:Ce) crystals has been studied for four different calcium concentrations ranging from 0 to 500 ppm. Ca codoping results in a partial oxidation of Ce3+ into Ce4+, The luminescence time response under pulsed X‐ray excitation of the Ce3+/Ce4+ admixure clearly demonstrates the role of hole migration on both the rise time and the generally observed slow components. From an application point of view, Ca codoping significantly improves the timing performances, but the induced presence of Ce4+ ions is also the cause of a reduction in scintillation efficiency.

Structural and optical properties of sol–gel silica based glassceramics doped with 0.1 mol% Ce and codoped with Gd at high concentrations, from 5 mol% up to 40 mol%, are investigated and compared to those of analogous samples doped only with Ce. Raman scattering, transmission electron microscopy, and x-ray diffraction reveal the formation of Gd apatite-like silicate (Gd4.67O(SiO4)3) and of Gd pyrosilicate (Gd2Si2O7) nanophases whose morphology and crystallinity depend on the Gd concentration and thermal treatments. Optical absorption measurements demonstrate the role of the densification atmosphere in modifying the charge state of Ce ions. The incorporation of Ce3+ ions in the nanophases is put in evidence by photo- and radio-luminescence results.

Single -crystal growth of Tm3+-doped Y2O3, Sc2O3, and Lu2O3 sesquioxides, with a melting point around 2400 °C, by the micropulling down technique is reported. Crystal quality and composition of the crystals were evaluated by rocking curve and energy-dispersive X-ray (EDX) analyses, respectively. Optical properties including optical transmittance and photoluminescence decay profiles were also examined. Furthermore, scintillation performance of the crystals including pulse height spectra and radio-luminescence spectra under alfa-ray and gamma-ray excitation was evaluated. © 2011 American Chemical Society.

The growth of Y 2 O 3 , Sc 2 O 3 , and Lu 2 O 3 single crystals using the micro-pulling-down method is reported. Crystallinity, optical transmittance, and scintillation characteristics including emission spectra, pulse height spectra, and decay kinetics under α-ray excitation of the grown crystals were studied. The light yields of Y 2 O 3 , Sc 2 O 3 , and Lu 2 O 3 crystals were estimated from the pulse height spectra excited by 241 Am 5.5 MeV α-rays, in about 920±92 ph/5.5 MeVα, 370±37 ph/5.5 MeVα, and 150±15 ph/5.5 MeVα, respectively. The scintillation decay times of Y 2 O 3 , Sc 2 O 3 , and Lu 2 O 3 crystals were estimated with following fast/slow parameters 30.1/184, 14.6/51.3, and 16.7 ns, respectively. Furthermore, α-ray imaging was performed using Y 2 O 3 crystal.

The effect of sintering atmosphere on the optical and structural properties of Cerium doped sol-gel silica was investigated. Two sets of xerogels with Ce concentration from 0 to 10 mol% were prepared and densified in different conditions. The effect of a post-densification rapid thermal treatment was also considered. Optical absorption measurements evidenced that in oxidizing conditions Cerium is preferably incorporated inside the silica matrix as Ce4+ while the trivalent state is favoured by reducing conditions. Transmission electron microscopy images show rare-earth clusters formation whose nature was investigated by means of Raman, EDS and microdiffraction measurements. In order to evaluate the efficiency of the glasses as scintillating materials radio-luminescence measurements were carried out. A numerical fit of RL spectra showed the presence of two components peaking at 2.7 and 3.1 eV. After RTT, the relative intensity of the 3.1 eV component increases with Ce concentration. © 2009 Elsevier B.V. All rights reserved.

Photon beams produced by a cobalt-60 Unit and a 6 MV linear accelerator equipped with stereotactic collimators were used to investigate some dosimetric properties of a radioluminescent dosimeter based on a Ce-doped optical fibre. The stability of the signal with increasing the irradiation time, enabled a reliable and real-time measurement of the dose rate. The methods, recently developed, of optical coupling, light collection and signal processing allowed to achieve a satisfactory signal to noise ratio, a good reproducibility and a linear dose-response. The punctual dimension of the doped fibre diameter was exploited in the characterization of stereotactic fields, providing results in agreement with those obtained using a micro-ionization chamber. © 2008 Elsevier Ltd. All rights reserved.

We present a study of the optical properties of Gd-doped sol-gel silica glasses densified at different temperatures (from 450 up to 1050 °C) by means of optical absorption (OA) and radio luminescence (RL). The effect of a post-densification rapid thermal treatment (RTT) at approximately 1800 °C is also considered. Room temperature OA and RL measurements have revealed a slight low-energy shift of Gd3+ absorption/emission lines by densification temperature increasing accompanied by a parallel increase of Gd3+ RL intensities, especially strong after RTT. These effects are interpreted on the basis of structural modifications of the silica matrix and of the removal of non-radiative channels competing with Gd3+ emission. Moreover, RL spectra of fully densified samples display high-energy shoulders on the 6P7/2-8S Gd3+ emission possibly related to crystal field splitting of the 6P7/2 state. This interpretation is supported by the temperature dependence of RL spectra, investigated in the 10-320 K temperature interval: an increase of the intensity of high-energy components vs. temperature has been observed, which can be interpreted as due to thermally assisted excitation of electrons belonging to the lower 6P7/2 state to higher crystal field states and their subsequent radiative recombination. © 2006 Elsevier B.V. All rights reserved.

A set of terbium-doped silicate glasses densified up to 1050 °C was prepared by the sol-gel method. A broad range of dopant concentrations (0.001-10 mol%) was considered together with an undoped sample as a reference. The effects of a high-temperature (1600-1800 °C) post-densification rapid thermal treatment (RTT) on the luminescence properties of the samples were investigated. RTT enhances the scintillating efficiency of the samples increasing the radio-luminescence intensity up to two orders of magnitude. The relevant effects induced by RTT on radio- and photo-luminescence spectra (RL, PL) and on PL decay curves indicate the occurrence of modifications of the surroundings of Tb3 + luminescence centres. © 2007 Elsevier Ltd. All rights reserved.

Phosphorescence emitted by a new dosimetric system based on a SiO2 optical fibre doped with Ce3+ ions was investigated. The defects in the matrix that, acting as electron traps, originate the phosphorescence signal were studied by means of thermally stimulated luminescence in the temperature interval 313-533 K. A continuous trap distribution with activation energies extending from 0.8 to 1.5 eV was observed. On the basis of these findings, the temperature dependence of the shape of isothermal phosphorescence decay was analysed and the corresponding spectrum was compared with that of radioluminescence. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Decesari, S. ... et. al.-- 24 pages, 15 figures, 4 tables, the supplement related to this article is available online https://doi.org/10.5194/acp-14-12109-2014-supplement, The use of co-located multiple spectroscopic techniques can provide detailed information on the atmospheric processes regulating aerosol chemical composition and mixing state. So far, field campaigns heavily equipped with aerosol mass spectrometers have been carried out mainly in large conurbations and in areas directly affected by their outflow, whereas lesser efforts have been dedicated to continental areas characterised by a less dense urbanisation. We present here the results obtained at a background site in the Po Valley, Italy, in summer 2009. For the first time in Europe, six state-of-the-art spectrometric techniques were used in parallel: aerosol time-of-flight mass spectrometer (ATOFMS), two aerosol mass spectrometers (high-resolution time-of-flight aerosol mass spectrometer - HR-ToF-AMS and soot particle aerosol mass spectrometer - SP-AMS), thermal desorption aerosol gas chromatography (TAG), chemical ionisation mass spectrometry (CIMS) and (offline) proton nuclear magnetic resonance (1H-NMR) spectroscopy. The results indicate that, under high-pressure conditions, atmospheric stratification at night and early morning hours led to the accumulation of aerosols produced by anthropogenic sources distributed over the Po Valley plain. Such aerosols include primary components such as black carbon (BC), secondary semivolatile compounds such as ammonium nitrate and amines and a class of monocarboxylic acids which correspond to the AMS cooking organic aerosol (COA) already identified in urban areas. In daytime, the entrainment of aged air masses in the mixing layer is responsible for the accumulation of low-volatility oxygenated organic aerosol (LV-OOA) and also for the recycling of non-volatile primary species such as black carbon. According to organic aerosol source apportionment, anthropogenic aerosols accumulating in the lower layers overnight accounted for 38% of organic aerosol mass on average, another 21% was accounted for by aerosols recirculated in residual layers but still originating in northern Italy, while a substantial fraction (41 %) was due to the most aged aerosols imported from transalpine areas. The different meteorological regimes also affected the BC mixing state: in periods of enhanced stagnation and recirculation of pollutants, the number fraction of the BC-containing particles determined by ATOFMS was 75% of the total, while in the days of enhanced ventilation of the planetary boundary layer (PBL), such fraction was significantly lower (50 %) because of the relative greater influence of non-BC-containing aerosol local sources in the Po Valley. Overall, a full internal mixing between BC and the nonrefractory aerosol chemical components was not observed during the experiment in this environment. © Author(s) 2014, This work was funded by European integrated project on aerosol cloud climate and air quality interactions (no. 036833-2, EUCAARI). The ERA-Interim data were kindly provided by Silvio Davolio (CNR-ISAC). Data analysis was co-funded by the project PEGASOS (EC FP7-ENV-2010-265148) and by the project SUPERSITO of Region Emilia-Romagna. ACCENTC is also gratefully acknowledged. Finally, Emanuela Finessi (CNR-ISAC, now at University of York) is also gratefully acknowledged for the precious work in aerosol filter collection in the field. Manuel Dall’Osto and Roy M. Harrison thank the UK National Centre for Atmospheric Science for financial support

LiCaAlF6 (LiCAF) crystals doped with two different ions (europium and lead) have been investigated as potential new dosimetric materials. The stability of thermally stimulated luminescence (TSL) glow peaks in LiCAF:Eu was evaluated by means of the initial rise technique. The decay times at room temperature of the traps related to the dosimetric glow peaks were found to range between 40 and 2 × 104 years confirming the good dosimetric characteristics of this crystal. The glow curve of LiCAF:Pb is dominated by a peak at approximately 300 °C emitting in the UV region ( 3P0,1-1S0 transition of Pb 2+) superimposed to a very broad structure at lower temperature (20-200 °C) featuring recombination at an intrinsic defect centre. The anomalous behavior of the low temperature structure during thermal cleaning procedures prevented any reliable numerical analysis of the TSL glow peak at 300 °C. © 2009 Elsevier Ltd. All rights reserved.

International audience; For the next generation of calorimeters, designed to improve the energy resolution of hadrons and jets measurements, there is a need for highly granular detectors requiring peculiar geometries. Heavy inorganic scintillators allow compact homogeneous calorimeter designs with excellent energy resolution and dual-readout abilities. These scintillators are however not usually suited for geometries with a high aspect ratio because of the important losses observed during the light propagation. Elongated single crystals (fibers) of Lutetium Aluminium garnet (LuAG, Lu3Al5O12) were successfully grown with the micropulling-down technique. We present here the results obtained with the recent fiber production and we discuss how the light propagation could be enhanced to reach attenuation lengths in the fibers better than 0.5 m.

We study trapping states of Ce 3+ -doped SrHfO 3 by thermally stimulated luminescence in a wide temperature range (10–730 K). We determine characteristic parameters of the traps by the initial rise technique. We also determine the energy of thermal ionization of the excited state of Ce 3+ in SrHfO 3 host by purely optical method based on the study of UV illumination-induced thermoluminescence. The method provides a value of the thermal ionization energy of about 0.25 eV.

We study defect states in Pr3+-doped Lu2Si2O7 crystal by wavelength resolved thermally stimulated luminescence both below and above room temperature. We identify the TSL peaks, analyze them by the initial rise technique and calculate the characteristic parameters of the corresponding traps. The role of tunnelling of charge carriers between traps and recombination centers up to RT is observed and discussed. The TSL spectra show that the charge carrier recombination predominantly occurs at Pr3+ centers. We also provide some comparison with the LPS:Ce3+ crystal prepared by the same method. (C) 2011 Elsevier B.V. All rights reserved.

The optical and structural properties of terbium doped sodium gadolinium phosphate glasses of three different compositions subjected to a crystallization process were studied and compared with those of the parent glassy samples. The structural characteristics of the glassy and crystallized phases were determined by Raman spectroscopy and the results showed a remarkable reduction in the full width at half maximum of the Raman peaks after crystallization. Radio-luminescence measurements revealed the emissions of both Gd3+ and Tb3+ ions. Their intensities strongly increased and their intensity ratio was modified by the crystallization. The luminescence temperature dependence investigated by radio-luminescence measurements in the temperature interval from 10 to 310K became more complicated after crystallization. The role of free carrier trapping phenomena in the modification of the radio-luminescence efficiency was also studied by thermally stimulated luminescence. © 2009 IOP Publishing Ltd.

We study lutetium hafnate, Lu4Hf3O12, prepared by acetate and citrate combustion in the form of nanometric powders. Optical properties including X-ray excited luminescence, steady-state and time resolved photoluminescence as well as thermally stimulated luminescence are investigated for undoped as well as Eu3+ and Tb3+ doped samples. We identify recombination centers in the host matrix and we tentatively associate the principal emission with a radiative transition of the F + center. We also demonstrate that athermal tunneling of charge carriers between traps and recombination centers is the predominant mechanism of delayed radiative recombination following irradiation by ionizing radiation. © 2011 Elsevier B.V. All rights reserved.

Fourier transform absorption spectroscopy in the 500-6000 cm- 1 and 9-300 K ranges is applied to monitor the effects produced by Eu3+ incorporation into sol-gel silica samples doped with concentration increasing from 0.001 to 10 mol%. The aim is to investigate the formation of aggregates by exploiting the Eu3+ crystal-field transitions. Complementary microreflectance and Raman spectra are also measured in the range of silica intrinsic vibrational modes to confirm the hypothesis of matrix modification induced by increasing doping levels. Evidences of clustering are found for high Eu3+ concentrations. Up to 3 mol% the crystal-field line intensities gradually increase and the OH- content smoothly decreases. A further increase to 10 mol% causes drastic, remarkable changes, i.e. sharp crystal-field lines appear which narrow by lowering the temperature. Furthermore, the OH - related bands are no longer detectable. For concentrations up to 3 mol% the aggregates are amorphous as the silica matrix, while for the Eu 3+ 10 mol% sample they show a rather ordered structure. © 2011 Elsevier B.V. All rights reserved.

We use acetate–citrate combustion to prepare SrHfO3 powders both undoped and doped with Ce3+ and Pb2+ ions in several concentrations, from 0.01 up to 3 mol%. The evolution of their morphological and structural features during the sintering process is studied by scanning electron microscopy, X-ray diffraction, and Raman experiments. We discuss the dependence of the optical properties, investigated by radioluminescence and time resolved luminescence, on sintering conditions and material structure.

We study defect states in undoped and Eu3+-doped Lu 3GaxAl5-xO12 (x = 0-5) garnet crystals by wavelength resolved thermally stimulated luminescence above room temperature. Eu3+ ions act not only as recombination centres but also as high temperature traps, as testified by the presence of a TSL peak at 450 °C correlated with Eu3+-doping. With increasing gallium content all glow peaks are shifted to lower temperatures. This trend is confirmed also for powder samples prepared by sol-gel technique. The observed low temperature shift of the glow peaks can be considered as a consequence of the band gap reduction following the increase of Ga3+ concentration. The comparison with the glow curve of a Ce3+-doped crystal is also shown. © 2010 Elsevier B.V. All rights reserved.

The chemoselective addition of tetraallyltin to dialkyl, alkenyl– alkyl, and alkynyl–alkyl ketones can be performed with high yields in N-methyl-N-butylpyrrolidinium trifuoromethansulfonate (MBP-Tf). Other room temperature ionic liquids (RTILs) can also be successfully employed if some sulfonic acid is added. The reaction is very sensitive to the electronic properties of the substrate. Aryl alkyl ketones bearing electron-withdrawing substituents behave like dialkyl ketones and react promptly; on the contrary, electron-rich aryl alkyl ketones react sluggishly, which allows selective competitive allylation of dialkyl substrates to occur. The ionic liquid solvent can be easily recycled, which meets the green chemistry principles of selectivity and reuse of chemicals. NMR spectroscopic data support the formation of tin-triflate catalysts in situ.

A thorough study was performed on Gd-doped sol-gel silica glasses, in the concentration range 0-8 mol% Gd. The analyses were carried out as a function of Gd content, before and after a post-densification thermal treatment. Different results concerning optical, vibrational, magnetic, and structural features were gathered in correlated experiments. The presence of Gd-rich nanoclusters was revealed. The size of nanoclusters increases by increasing the dopant concentration and by performing a rapid thermal treatment (RTT) at 1800 °C in air, which causes also a remarkable intensity increase of the 6P7/2 →8S7/2 radioluminescence transition of Gd3+. Nanoclusters are amorphous, possibly close to a Gd2SiO5 stoichiometry as suggested by fast Fourier transform infrared spectroscopy (FTIR). FTIR studies revealed also the presence of Gd-dimers interacting with OH- groups. Moreover, the presence of isolated Gd3+ ions was detected by electron paramagnetic resonance investigations. Based on the results obtained with different techniques, the Gd-incorporation in silica glass host and the resulting optical properties are discussed. © 2008 Elsevier B.V. All rights reserved.

In typical CMOS process flows, critical oxides are often exposed to damaging treatments such as ion implantation and oxygen plasma ashing, commonly used during resist removal or pre-etch treatments. These processes can induce major modifications in SiO2 bulk and surface structure. As a consequence wet etch rate of the material is impacted and wet cleaning steps have to be tuned. In this work we have studied the effect of oxygen plasmas on an ion implanted oxide layers using surface charge, HF etch rate profiling [1] and thermo-luminescence techniques. A thermally grown silicon dioxide, about 250A thick, was boron implanted with energies from 40 to 300KeV using a dose in the 10 at/cm2 range. After ion implantation, wafers were treated with a resist removal sequence (dry and wet steps) to reproduce a common CMOS process flow. Some samples were then processed in oxygen plasma in RF, microwave and TCP (Transformer Coupled Plasma) reactors. Etch rate of a thermal oxide in hydrofluoric acid is proportional to the damaging level in the layer: the higher is the number of oxygen vacancies, the faster is the oxide etching. The depth of the damage from RF and TCP plasmas was found to be proportional to the RF power because of the higher energy of the oxygen plasma ions induced. In case of 400W RF power, plasma damage affects 30÷40A oxide from the top surface and the etch rate is about 4.5 times respect to reference oxide. Using a power of 200W and 300W or using the TCP process, surface damage is limited to the topmost 20÷30A with a relative etch rate of 3÷3.5. We also observed a damage recovery effect of RF and TCP plasmas in the bulk of the oxide, up to 200A depth. When 100W RF plasma power is used we observed by surface charge measurement a large spread in charging potential, because of the poor plasma uniformity at such low power [Figure 1]: surface charging varies from 2 to 8V. As a consequence of the poor plasma uniformity even the etch rate was found to be strongly non-uniform across the wafer: in low charging areas (e.g. point 8 in Figure 2) the ion implantation damage is almost completely recovered while in other areas (e.g. point 11 in Figure 2) the damage is increased. Thermo-luminescence measurements show the presence of different kind of point defects whose quantity and nature is modulated by the plasma. In case of the sample treated with 100W RF plasma, we obtained different thermo-luminescence glow curves in high charging areas and low charging areas [Figure 3] after 30KeV X-ray irradiation of the samples. TCP oxygen plasma was also confirmed by this technique to have the lowest amount of defects among the measured samples. Figure 1: Charging map of 250A thermal oxide treated with 100W RF plasma

FTIR spectroscopy is applied to monitor the effects caused by fluorinated precursors (1-10 mol%) in the sol-gel synthesis of silica glasses, either pure or doped with Ce and Er. In pure samples the Si-OH level is heavily reduced to ∼3 × 10-3 mol%. In doped samples the effect is more limited. The presence of residual fluorine, proved by the Si-F vibrational absorption at ∼950 cm-1, causes deep changes in the rare-earth (RE) crystal field spectra, which are characterized by narrow absorption lines. The lines broaden if the temperature is increased from 9 to 300 K. The result is discussed in terms either of local ordering around the rare earth ion or by its partial decoupling from the disordered host matrix, due to the creation of network terminating sites. © 2007 Elsevier B.V. All rights reserved.

In this study we investigate the role of traps on radio- and photo-luminescence properties of terbium doped silica. The investigation is motivated by the promising characteristics of rare-earth doped silica obtained by the sol-gel technique as scintillating material. We focus on those phenomena that can be responsible for problematic properties such as the increase of radio-luminescence sensitivity following repeated irradiations. A set of terbium doped silica with different terbium concentrations (0.03 mol%, 0.1 mol% and 10 mol%) prepared by the sol-gel technique and densified at 1050 °C in oxidizing atmosphere has been considered. The effect of a post-densification rapid thermal treatment on the RL and PL properties has also been investigated. This treatment improved the scintillation characteristics of the samples reducing their RL instability under prolonged irradiation. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The optical properties of Yb-doped sol-gel silica glasses were studied by optical absorption and radio-luminescence (RL) measurements, that revealed the typical absorption and emission pattern of Yb3+ ions. Moreover, RL bands in the 1.5-3.5 eV interval were also observed, and related to defects of the silica matrix. The RL intensity temperature dependence, investigated in the 10-320 K interval, evidenced the presence of the SiO2 self-trapped exciton emission at 2.2 eV, whose intensity was rapidly quenched by temperature increasing. At variance, the Yb3+ emission intensity increased markedly by temperature increasing. This phenomenon is interpreted by considering a competitive role of point defects in free carrier trapping, evidenced by parallel wavelength resolved thermally stimulated luminescence measurements. © 2007 Elsevier B.V. All rights reserved.

In this paper different sol gel syntheses strategies are adopted in order to produce Ce - doped silica - glasses scintillators with improved properties. Variations on the synthesis procedure are adopted to reduce the hydroxyl content of the sol gel glass; to this purpose, a fluorine derivative of silicon alkoxide was added in the sol gel reaction. Since a drawback of Ce - doped sol gel glasses is the partial oxidation of Ce 3+ to Ce 4+ in the matrix probably occurring during the sintering procedure, both Ce - doped xerogel and fluorinated xerogel were treated under reducing atmosphere (H 2 :Ar) instead of the usual oxidizing atmosphere. Glasses obtained in such ways are compared with commercial synthetic glasses and with previously produced sol gel samples by spectroscopic IR absorption measurements, and by radio-luminescence experiments.

Background: Homocysteinemia (Hcy) increase and risk factors in HIV-positive patients are not clear yet. Methods: HIV-positive patients on stable highly active antiretroviral therapy (HAART) regimens for at least 6 months were enrolled in this cross-sectional study. Among other factors, vitamin B12, folate and length of exposure to protease inhibitors (PIs) were evaluated for their possible correlation with hyper-Hcy (>13 µmol/l in females; >15 µmol/l in males) by logistic regression analysis. Results: Ninety-eight HIV-positive patients were recruited. Twenty-eight (28.6%) had hyper-Hcy. Length of exposure to antiretroviral therapy and PIs did not result to be significantly associated with hyper-Hcy risk. Normal folate level was the only factor associated with the outcome, resulting protective from hyper-Hcy, either at univariate (OR = 0.22; CI 95% = 0.06–0.86; p = 0.029) and multivariable (OR = 0.24; CI 95% = 0.06–0.94; p = 0.04) logistic regression analysis. Folate predictive value of hyper-Hcy risk was driven by levels in the lowest quartiles of the study population (i.e. Conclusions: No significant correlations were observed between hyper-Hcy and length of exposure to antiretroviral therapy or PIs. Folate could be a confounding factor in the association between hyper-Hcy and PI exposure found by others. The potential value of folate supplementation, in those who are deficient and in those with hyper-Hcy, merits study.

Thermally stimulated luminescence (TSL) properties of cerium and terbium doped SiO2 sol-gel glasses were studied after X-ray irradiation in the temperature range 10-700 K. The role of Ce3+ and Tb3+ as recombination centers was shown. The existence of a distribution of trap levels was observed; the activation energies of such a distribution were calculated to extend from about 8 x 10(-3) eV up to 1.8 eV for both cerium and terbium doped sol-gel glasses. The effect of a post-densification thermal treatment on TSL properties was also analyzed. (c) 2005 Elsevier B.V. All rights reserved.

In the blue colored sapphires of metamorphic origin and Verneuil synthetic studied here, the absorption-emission properties in the VIS-NIR range are largely determined by Cr3+ and Ti3+, as we have been able to demonstrate recently. In that work a sharp radioluminescence band occurring at 870 nm in Verneuil blue sapphires was left unattributed: here we give evidence for the attribution of that band to the E-2 emission transition of V2+, and for the existence of such an emission also in natural samples of metamorphic origin. After such a result, we accurately evaluated by EDXRF the V concentrations in various samples and found the ion more ubiquitous than foreseen. We then searched for and found, weak but diagnostic spin forbidden transitions and phonon sequencies in the absorption spectra of samples sufficiently rich in V. The experimental results just mentioned allowed us to discuss the effects of the overlap of V3+ and Cr3+ spin-allowed absorption bands on the spectrum of the varieties of corundum under study. To complete the updating of the interpretation, we spent a further effort to strengthen the attribution of the absorption band at 14500 cm(-1) (currently interpreted as an IVCT (Fe2+ -> Fe3+)) to the E-5 -> T-5(2) transitions of Cr2+.

Optical absorption and luminescence spectra of yellow corundum have been analyzed, both in magmatic and metamorphic materials, looking at the role of localized electronic transitions of transition metal ions at substituted Al sites. By the aid of energy dispersed x-ray fluorescence (EDXRF) elemental analysis and electron paramagnetic resonance (EPR) measurements, the results confirm that Fe3+ is the dominant impurity ion. However, the results also evidence that Cr3+ and Ti3+ contribute in determining the optical absorption and emission properties of this variety of gem-quality corundum, as we have recently found in Type 1 blue sapphires of metamorphic origin. Furthermore, preferentially but not exclusively in samples of metamorphic origin, Mn plays a role never evaluated up to now. Here we show how few ppm of Mn - below the detection limit of EDXRF, not revealed in the optical absorption spectra, but barely detected by EPR spectroscopy as Mn2+ ion -are active in photoluminescence, showing up with the characteristic emissions of Mn2+, Mn3+ and Mn4+.

Doubly-doped BaY2F8:Tm, Nd scintillation crystals were grown by modified micro-pulling-down method. Nd co-doping was chosen to enhance the energy transfer from the host lattice to the Nd3+ luminescence center via the 5d-levels of Tm3+, due to the overlap of Tm3+ 5d-4f emission spectrum with the Nd3+ 4f-5d absorption. The energy transfer was clearly evidenced in the BaY2F8: Tm, Nd. This process is not complicated by an energy migration to killer centers and/or cross-relaxation. The radioluminescence process is complicated by an energy transfer from the host lattice exciton states to the lower f-levels of Tm3+ ion.

The optical emission from the 5d – 4f allowed transition of Pr3+ ions embedded in sol-gel silica is investigated for High Energy Physics applications requiring fast scintillating materials. A complete and detailed characterization of the optical, scintillation and radiation hardness properties of Pr-doped silica is carried out employing different experimental techniques including steady-state and time-resolved photo-luminescence, radio- and thermo-luminescence, scintillation and optical absorption. Optical absorption measurements, performed after X-ray irradiation sequences up to 1 kGy, evidence the formation of radiation-induced absorption bands related to point defects acting as color centers. Spontaneous partial recovery of the radiation-induced defects at room temperature, as well as after thermal treatments, is also disclosed. Particular attention is paid to the comparison between bulk silica, both before and after a melting process, and fibers. The results reveal the presence of a lower concentration of optically active defects in melted glass. Such comparison highlights a role of the fiber drawing in modifying the glass defectiveness, consisting in the occurrence of a structural reorganization of the amorphous network during the process.