Titania powder modified sol-gel process for photocatalytic applications

Thick films of TiO₂ were prepared on glass and stainless steel substrates using an alkoxide sol-gel process modified by addition of Degussa P-25 powder. The prepared films were characterized by SEM, EDS, XRD and other methods. The TiO₂ films obtained from the powder modified sol were compared to films obtained from the alkoxide sol-gel without modification. The films obtained from the modified sol-gel were about ten times thicker for a single dip coating/heat treatment cycle than the films obtained from the sol without powder addition. The prepared thick films were smooth and free of macrocracking, fracture or flaking. The grain size of these films was uniform and in the range 100–150 nm and the films were a mixture of anatase and rutile TiO₂. The films obtained from the powder modified sol on the stainless steel substrate were also much harder compared to the films obtained from sols without modification and displayed excellent adhesion to the substrate.     

New non-dipolar structures with significant quadratic hyperpoiarizabilites

‘Octupolar’ molecules are of particular interest in the field of nonlinear optics due to their potentially large quadratic nonlinearities. Within this framework, we have designed organic chromophores of tetrahedral symmetry and investigated their quadratic nonlinearities by performing harmonic light scattering (HLS) experiments in solutions. Issues related to the molecular engineering of the nonlinearity-transparency trade-off have been addressed. As a result, molecules combining significant quadratic hyperpolarizabilities and excellent transparency have been identified.     

Relation of deranged neonatal cerebral oxidative metabolism with neurodevelopmental outcome and head circumference at 4 years

Cerebral oxidative metabolism was studied using phosphorus magnetic resonance spectroscopy during the first week of life and neurodevelopmental outcome was assessed at 4 years in 62 infants who had clinical and/or biochemical evidence consistent with birth asphyxia (critically impaired intrapartum gas exchange). Twenty-one died and the neurodevelopmental status of the 41 who survived was assessed by a range of tests at age 4 years. The minimum recorded values for the cerebral phosphocreatine:inorganic phosphate concentration ratio (an index of oxidative metabolism) were related to outcome. The results showed significant relations between the extent of derangement of neonatal oxidative metabolism and a range of adverse outcomes, including death, and at 4 years reduced head growth and the presence and severity of neuromotor impairments, overall neurodevelopmental impairments, and cognitive functioning. Strong correlations between the extent of derangement of neonatal oxidative metabolism and outcome at 1 and 4 years were also shown. We conclude that the severities of adverse outcomes at 1 and 4 years of age were closely related to the extent of cerebral energy derangement in the first week of life, and we also conclude that primary intrapartum hypoxic-ischaemic cerebral injury was generally responsible for the events that led to death, microcephaly, and impaired     

Microstructure and microtexture evolution with aging treatment in an Al–Mg–Si alloy severely deformed by HPT

Experiments were conducted on an Al–0.6 % Mg–0.4 % Si alloy to evaluate the effect of different preliminary thermal treatments on the evolution of microstructure and microtexture during processing by High-Pressure Torsion (HPT). Disks of the alloy were solution-treated, then some disks were briefly aged at 473 K, and other disks were briefly aged at 523 K before processing by HPT for up to 20 complete revolutions. The processing by HPT refined the microstructure to an average grain size as small as ~0.25 μm in the solution-treated alloy after 20 turns but preliminary aging led to slightly larger average grain sizes of ~0.35–0.40 μm after 20 turns. For all processing conditions, there was a high fraction of high-angle grain boundaries after HPT and it is shown that aging introduces changes in the microtexture intensities.     

Vibrotactile perception thresholds in four non-exposed populations of working age

The purpose of this study was to establish a basis for the use of a device for measuring vibrotactile perception thresholds for epidemiological purposes on a series of non-exposed populations. Vibrotactile perception thresholds (VPTs) were measured with a vibrometer in 218 men and 160 women belonging to two non-exposed male blue collar populations, one white-collar population and one age and gender stratified sample of the general population. VPTs were measured on the middle and the little finger of the dominant hand at 31.5 and 125 Hz. The VPTs were expressed in dB and the effect of a series of factors including the population, age, gender and digital temperature was assessed in a regression analysis weighted by the inverse variance of the measurements. Adjusted for age, no significant difference between the VPTs in the four male populations was observed. At frequency 125 Hz, the effect of age (0.3 dB per year) was more important than at frequency 31.5 Hz (0.2 dB per year). In the two female populations, the results were less stable than among males and the VPTs were higher than among males. However, the age-dependence was similar among males and females. The within-test variance is a valuable indicator of the quality of the VPT measurements. Weighting by its inverse improved the fit of the regression models. Normal values for VPTs in non-exposed populations were obtained, which were reproducible in four separate populations.     

Ecological risk assessment of pesticides in the Mediterranean region. The need for crop-specific scenarios

The risk assessment procedures of pesticides in the European Union are mostly based on worst-case scenarios developed for central and northern European conditions. From the point of view of Mediterranean conditions, these assessment procedures are not always appropriate, and therefore the development of specific scenarios is required. There are differences not only in meteorological data (temperature, solar irradiation, or rainfall volume and annual distribution) between these countries, but also in farm distribution, crop characteristics, soil or sediment properties and surface or groundwater characteristics. These differences are more evident for the typical crops of the southern countries, such as olive groves, vineyards, citrus or rice fields, and in these cases more realistic estimates of exposure are required. Our proposal includes the development of new criteria to improve the ecological risk assessment process for the conditions of the Mediterranean region, and the justification of this need.     

Annealing temperature and environment effects on ZnO nanocrystals embedded in SiO2: a photoluminescence and TEM study

We report on efficient ZnO nanocrystal (ZnO-NC) emission in the near-UV region. We show that luminescence from ZnO nanocrystals embedded in a SiO₂ matrix can vary significantly as a function of the annealing temperature from 450°C to 700°C. We manage to correlate the emission of the ZnO nanocrystals embedded in SiO₂ thin films with transmission electron microscopy images in order to optimize the fabrication process. Emission can be explained using two main contributions, near-band-edge emission (UV range) and defect-related emissions (visible). Both contributions over 500°C are found to be size dependent in intensity due to a decrease of the absorption cross section. For the smallest-size nanocrystals, UV emission can only be accounted for using a blueshifted UV contribution as compared to the ZnO band gap. In order to further optimize the emission properties, we have studied different annealing atmospheres under oxygen and under argon gas. We conclude that a softer annealing temperature at 450°C but with longer annealing time under oxygen is the most preferable scenario in order to improve near-UV emission of the ZnO nanocrystals embedded in an SiO₂ matrix.     

Specifying receiver IP2 and IP3 based on tolerance to modulated blockers

This paper provides an analysis of the impact of amplitude modulated blocking signals on receiver performance due to device nonlinearity. Using a standard polynomial model of nonlinearity, we derive limitations on the receiver SNR capabilities, depending on the blocking signal modulation statistical properties. The phenomena that we focus on are cross-modulation due to odd-order nonlinearity and amplitude demodulation due to even-order nonlinearity. The results are then detailed for two types of blocking signal modulations: GSM/EDGE modified 8PSK and UTRA/FDD uplink HPSK.