Optical gas sensor based on the combination of a QD photoluminescent probe and a QD photodetector

We report on a sensor architecture for detection of hazardous gases. The proposed device is based on the integration of a solid-state quantum dot (QD) photoluminescent probe with a QD photodetector on the same substrate. The effectiveness of the approach is demonstrated by developing a compact optical sensor for trace detection of explosives in air. The proposed architecture is very simple and consists of a silicon substrate with both surfaces coated with QD films. The upper layer acts as photoluminescent probe, pumped by a blue LED. The change of photoluminescence intensity associated to the interaction between the QDs and the target analyte is measured by the QD photodetector fabricated on the opposite side of the substrate. The sensor is mounted into a small chamber provided with the LED and the front-end electronics. The device is characterized by using nitrobenzene as representative nitroaromatic compound. Extremely low concentrations (down to 0.1 ppm) can be detected by the proposed device, with a theoretical detection limit estimated to be as low as 2 ppb. Results are repeatable and no ageing effect is observed over a 70 d period. The proposed architecture may provide a promising solution for explosive detection in air as well as other sensing applications, thanks to its sensitivity, simple fabrication process, practical usability and cost effectiveness.

Colloidal Bismuth Chalcohalide Nanocrystals

Here we present a colloidal approach to synthesize bismuth chalcohalide nanocrystals (BiEX NCs, in which E=S, Se and X=Cl, Br, I). Our method yields orthorhombic elongated BiEX NCs, with BiSCl crystallizing in a previously unknown polymorph. The BiEX NCs display a composition‐dependent band gap spanning the visible spectral range and absorption coefficients exceeding 10⁵ cm⁻¹. The BiEX NCs show chemical stability at standard laboratory conditions and form colloidal inks in different solvents. These features enable the solution processing of the NCs into robust solid films yielding stable photoelectrochemical current densities under solar‐simulated irradiation. Overall, our versatile synthetic protocol may prove valuable in accessing colloidal metal chalcohalide nanomaterials at large and contributes to establish metal chalcohalides as a promising complement to metal chalcogenides and halides for applied nanotechnology.

The dynamic surface chemistry of colloidal metal chalcogenide quantum dots

The chemical species (ligands) at the surface of colloidal inorganic semiconductor nanocrystals (QDs) mediate their interactions with the surroundings. The solvation of the QDs reflects a subtle interplay between ligand-solvent and ligand-ligand interactions, which eventually compete with the coordination of the ligands at the QD surface. The QD surface coordination and solvation are indeed fundamental to preserve their optoelectronic properties and to foster the effective application of QD-based inks and nanocomposites. Here we investigate such ligand interactions by exploiting diffusion ordered NMR spectroscopy (DOSY), which is suggested as an essential complement to spectral line width analysis. To this end, we use colloidal metal chalcogenide (CdS, CdSe, and PbS) QDs with (metal-)oleate ligands at their surface in several solvents exhibiting different viscosities and polarities. We demonstrate that the ligand shell is dynamically bound to the metal chalcogenide QDs, and is thus in equilibrium between the QD surface and the surrounding solvent. Such dynamic equilibria depend on ligand-solvent interactions, which are more prominent in aliphatic, rather polar solvents that favor the solvation of the ligands and, as a consequence, their displacement from the QD surface. In addition, the ligand-ligand interactions, which are more relevant for larger QDs, contribute to the stabilization of the ligand bonding at the QD surface.

Stable Ligand Coordination at the Surface of Colloidal CsPbBr3 Nanocrystals

Ruling over the surface chemistry of metal halide perovskite nanocrystals (NCs) is crucial to access reliable luminophores. Here, we provide an atomic-level description of the surface of colloidal CsPbBr₃ NCs, achieving an effective passivation strategy that leads to near-unity photoluminescence quantum yield. To this end, we used two different types of CsPbBr₃ NCs, which had been synthesized with an outer shell of either oleylammonium bromide ion pairs or Cs-oleate complexes. We perturbed the dynamic equilibria at the NCs' surface with ligands from a comprehensive library, including amines (and their conjugated acids) with different basicities, chain lengths, and steric encumbrances. We demonstrate that control of both ligand binding affinity and ligand-to-NC molar ratio is essential to attain thermodynamically stable coordination of the NC surface. We thus present a reliable protocol for managing the surface chemistry of colloidal CsPbBr₃ NCs and for selectively addressing their ligand-induced morphological (and structural) transformations.

Central administration of NPY or an NPY-Y5 selective agonist increase in vivo extracellular monoamine levels in mesocorticolimbic projecting areas

Selective NPY-Y5 antagonists are known to reduce NPY-evoked increase of food intake under free feeding conditions and drug-reinforced operant responding in rodents suggesting that NPY-Y5 receptors can regulate reinforcers, potentially by modulating the hypothalamic-limbic reward system. However, evidence published to date has revealed a limited expression of NPY-Y5 in the limbic areas. Thus, the first aim of the present study was to investigate the distribution of NPY-Y5 receptor binding sites in rat mesocorticolimbic projection areas such as the nucleus accumbens (NAc), medial prefrontal cortex (mPFC), and lateral hypothalamus (LH). Since mesocorticolimbic release of monoamines has been typically associated to the rewarding and motivational significance of reinforcers, we then compared the ability of NPY and an NPY-Y5 selective agonist, [cPP1-7,NPY19-23,Ala31,Aib32,Gln34]hPP, to evoke changes in extracellular monoamines from these brain regions using in vivo microdialysis techniques. Intracerebral doses of each compound were selected on the basis of those previously demonstrated to trigger food intake in a separate set of animals. We found that NPY-Y5 receptors were widely distributed in both the NAc and mPFC but not in the LH nuclei. Central administration of either NPY (4.5 nmol/rat) or the NPY-Y5 agonist (0.6 nmol/rat) induced a significant increase of dopamine (DA) output of up to 150% of basal values in the NAc. In addition, NPY induced a stepped increase of norepinephrine (NE) outflow in the NAc area. Also extracellular levels of NE levels were increased by both treatments in the mPFC (150% vs basal concentration). Hypothalamic monoamine levels were unaffected by both treatments. Extracellular serotonin (5-HT) levels were also unchanged in all regions. Given the NPY-Y5 agonist paralleled the in vivo ability of NPY to increase DA, these data suggest that the release of NPY may modulate behaviours associated to accumbal DA release such reward and reinforcement by, at least in part, acting on mesocorticolimbic NPY-Y5 receptors.

[Evaluation of the effectiveness of occupational safety and health inspections of construction sites in the Piedmont region from 2001 to 2005]

OBJECTIVES

To assess the effectiveness of safety inspections in the construction industry in Piedmont in terms of exposure to risk and injuries.

METHODS

We conducted a retrospective analysis of the surveillance activities carried out in Piedmont between 2001 and 2005: to this purpose, we used a logical framework and we identified indicators to evaluate the process and its impact on exposure and injuries.

PROCESS

fixed standards involving the number of safety inspections and the type of constructions under control were respected; there was always sufficient diversity among the public works under control, although local health units used different working methods. Impact on exposure and injuries: injury rates in the construction industry in Piedmont showed a decreasing trend and systematically lower values compared to national rates. Injury rates in the "roads and railways" sector showed an increasing trend owing to the great number of public works under construction. In this case, the effect of preventive measures seems less noticeable, but this mainly depends on methodological limits, such as mismatch between numerator and denominator, difficulties in estimating the number of workers actually present on the sites, underreporting of minor events.

CONCLUSIONS

Despite the limitations of a retrospective analysis, the Piedmont safety inspection programme for the construction industry showed coherence with the objectives and had a positive impact on injury rates.

[Working conditions and health problems among call-centre operators: a study on self-reported data in the Piedmont Region (Italy)]

BACKGROUND

Currently, about 250,000 workers are employed in the call-centre sector in Italy. The nature and the organization of the work exposes workers to a variety of psychosocial and ergonomic hazards, with a potential impact on physical and psychological health.

OBJECTIVE

The aim of the study was to investigate working conditions and health status among call-centre operators, in order to estimate the prevalence of exposure to psychosocial and ergonomic risk factors, and of potentially work-related health problems.

METHODS

Workers from seven call-centres operating in the Torino area were invited to participate in the survey. During the period 2005-2006, 775 subjects working in telecommunications (70%), telemarketing (14%) and finance (16%) completed a standardized questionnaire on socio-demographics and lifestyle, working conditions, symptoms and diseases.

RESULTS

Poor microclimatic conditions, elevated noise, high levels of exposure to psychosocial factors and a high prevalence of unfavourable ergonomic working conditions were observed With regard to health conditions, the mental health index was lower than that expected for the Italian population. Overall, 60%, of the subjects reported headache, 57% musculoskeletal symptoms and 46% voice disorders, for which they consulted a physician and/or took medication.

CONCLUSION

A high proportion of call-centre operators were exposed to organizational and psychosocial risk factors, while the self-reported prevalence of potentially work-related health conditions was also high, as has been reported by other authors. Although further epidemiological studies are needed to meaningfully evaluate these associations, it also appears necessary to implement interventions on the most frequently encountered hazards in this sector.

[Injury rates and severity during the construction of High Speed Train Track Torino-Novara: which are the expected risks?]

BACKGROUND

Construction of the Torino-Novara High Speed Train Track (TAV) provided a unique opportunity to describe the magnitude of accidents on a major construction project for which complete data were available for 123 companies with over 10,000 employees.

OBJECTIVES

To describe the rate and severity of accidents during the construction of TAV and to compare this with national indexes. The limits and critical points of the national surveillance system are discussed and solutions for responding to public occupational safety and health service needs are proposed.

METHODS

1,691 injuries with more than 3 lost work days were recorded between 2003 and 2005 by the TAV Surveillance System (Orme-TAV). Accident rate and severity indexes (Orme indexes) by year and occupation, were compared with indexes for Piedmont and Italy for the period 2002-04 provided by INAIL (National Institute for Insurance against Occupational Accidents and Diseases) for the Construction sector and the Road and Railway Construction sub-sector. A comparison with the accident rate of the same 123 firms calculated for all construction yards in Italy in 2003-04 (national indexes) was also made.

RESULTS

Accident rates decreased from 152 in 2003 to 72 in 2005 per 1,000 workers, but were higher than the national indexes (the Orme indexes/national indexes ratio was 1.75 in 2003 and 1.67 in 2004). Accident severity indexes were lower than the national figures.

DISCUSSION

Complete reporting, facilitated by the existence of a Surveillance System, yielded accident rates that were more reliable than those previously reported. Data suggest that the discrepancy is due to both underreporting and exposed worker assessment difficulties. The burden of on-site work-related accidents in the construction sector appears to be higher and more costly than what has been desumed from national data.

Tolerance to nicotine in mice lacking alpha7 nicotinic receptors

RATIONALE

Previous studies have suggested that a knockout of the gene coding for alpha7 nicotinic receptor subunits influences the behaviour of undrugged mice but not the acute effect of nicotine on locomotor activity.

OBJECTIVES

The present studies extend these observations to nicotine tolerance assessed by means of schedule-controlled behaviour.

METHODS

Groups of alpha7-/- and alpha7+/+ mice were trained to press levers under an FR20 schedule of food reinforcement. The acute response rate-depressant effects of nicotine were determined in both genotypes and the mice were then subdivided into groups treated daily with nicotine (1.2 mg/kg/day) or saline. After 39 days of exposure to this regimen, the dose-response curves were re-determined.

RESULTS

Knockout of the alpha7 gene had no consistent effect on the lever-pressing behaviour of undrugged mice and did not influence the acute, dose-related, response rate-depressant effect of nicotine (0.2-1.2 mg/kg). When dose-response curves for nicotine (0.4-2.0 mg/kg) were re-determined after daily dosing with the drug, both wild-type and knockout mice developed similar tolerance to nicotine, as shown by approximately 2.5-fold shifts to the right of the dose-response curves.

CONCLUSIONS

Nicotinic receptors containing the alpha7 subunit do not play a significant role in the regulation of the lever-pressing behaviour studied or in the acute behavioural depressant effect of nicotine and the development of tolerance to that effect. Such results contrast with previous reports suggesting profound impairments in sensitivity to nicotine in nicotinic receptor beta2-/- mice.

[Healthy life expectancy in the occupied segment of the Turin population]

BACKGROUND

The indicators of healthy life expectancy measure differences in health among various population subgroups more sensitively than do indicators of mortality.

OBJECTIVES

The aim of the study was to analyze some of the above indicators to evaluate the differences among occupational categories in Turin.

METHODS

Mortality tables by occupation were calculated on Turin residents, aged 18-64 years in 1991, using the Turin Longitudinal Study which combines personal, census, and health information for the residents of the city. Longitudinal assessments of health expectancy were obtained by means of record-linkage with the Cancer Registry, the Diabetes Registry, and hospital discharge records. In addition, prevalence estimates of good health, disability, and chronic illness, obtained from ISTAT (Central Statistics Institute) investigations in 1999-2000 were combined with mortality data using Sullivan's algorithm.

RESULTS

Among men there was a systematic disadvantage in almost all indicators of health expectancy for some manual occupations, while jobs requiring more qualifications were more advantaged. The health profile for women was more controversial, with an overall disadvantage among women who were professional consultants, although this group showed substantial variability: the legal professions had the lowest life and health expectancies, with approximately 3 years of life less than the health professions, which were among the most advantaged.

DISCUSSION

The various indicators gave results which were at times conflicting, especially because the information obtained from the available sources had major limitations. The development of indicators needs to aim for greater homogeneity between mortality and health data to ensure maximum comparability.

[Differences of perceived health and lifestyle by occupational groups in the Italian ISTAT (Central Statistic Institute) health survey]

BACKGROUND

Little is known about the distribution by occupation of chronic illness, disability, morbidity, and lifestyles which put health at risk.

OBJECTIVES

To provide a map of the social inequalities in various dimensions of health and lifestyle by social class and for specific occupational groups. To formulate a hypothesis about the mechanisms which generate these inequalities.

METHODS

Prevalence rate ratios and prevalence odds ratios of perceived health, chronic illness, disability, absenteeism, trauma, smoking, and obesity calculated with data from the 1999-2000 Italian ISTAT (Central Statistics Institute) health survey; the study population includes adults (aged over 18 years) employed, or searching for a job, or withdrawn from the workforce.

RESULTS

Among workers in manual unskilled labour, construction and agriculture are noted for worse health and more unhealthy lifestyles than average. For example, perceived bad health is more widespread among agricultural labourers (OR = 1.63), masons and construction machine operators (OR = 1.75), transport drivers (OR = 1.40), male caretakers, custodians, janitors and domestic help (OR = 1.46), electro-technicians (OR = 1.44), leatherworkers and shoemakers (OR = 3.58), miners and quarrymen (OR = 2.60), earthenware and stone workers (OR = 2.14), garment and furnishings workers (OR = 1.86); in female workers excess risk for perceived bad health was present among agricultural labourers (OR = 2.08), caretakers, custodians, janitors and domestic helpers (OR = 1.49), waitresses, cooks and bartenders, (OR = 1.44), and textile workers (OR = 1.67). Smoking was more widespread among chemical workers (OR = 1.41), and in miners and quarrymen (OR = 1.30). An excess risk of smoking of 20-25% was evident in spinners, weavers and finishers; masons, (and) builders; waiters, cooks and bartenders; garment and furnishings workers; porters and warehouse workers. The risk was 10% higher among foundry workers and forgers, plumbers, carpenters and welders, and transport drivers. Among women the propensity to smoke was higher among waitresses, cooks and bartenders (OR = 1.37), cleaners, commerce and service workers (OR = 1.22). Other occupational groups with an increased smoking prevalence, where women were less represented, included: chemical workers (OR = 2.25), butchers (OR = 1.97), postwomen (OR = 1.58), plastics workers (OR = 1.56), shippers (OR = 1.37).

CONCLUSIONS

It can be hypothesized on the one hand that there are factors and mechanisms common to the various occupational groups belonging to the same social class; on the other, there are factors and mechanisms specific to certain occupational categories. The latter can generate specific health subcultures. A greater integration between qualitative and quantitative research is recommended, which would yield better explanations of the observed inequalities.

SCH 58261 (an adenosine A(2A) receptor antagonist) reduces, only at low doses, K(+)-evoked glutamate release in the striatum

The aim of the present work was to determine whether systemic administration of the adenosine A(2A) receptor antagonist, SCH 58261 (7-(2-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2,4,triazolo[1,5-c]pyrimidine), could modulate striatal glutamate outflow in the rat. Microdialysis experiments were performed in male Wistar rats implanted with microdialysis probes in the striatum. Pretreatment (15 min before) with SCH 58261 (0.01 and 0.1, but not 1 mg/kg intraperitoneally) significantly prevented K(+)-stimulated glutamate release. These results suggest that SCH 58261 could possess neuroprotective effects in the low dose range, while, at higher doses, the occurrence of additional mechanisms may limit the neuroprotective potential of this drug.

The mGlu5 receptor agonist CHPG stimulates striatal glutamate release: possible involvement of A2A receptors

The intrastriatal perfusion of the selective metabotropic glutamate (mGlu)5 receptor agonist (RS)-2-chloro-5-hydroxy-phenylglycine (CHPG, 1000 microM) significantly increased (approximately + 100%, p < 0.05) glutamate extracellular levels with respect to basal values. The potentiating effect of CHPG was prevented by the selective mGlu5 receptor antagonist 2-methyl-6(phenyl-ethynyl)-pyridine (MPEP, 250 microM)) and by the adenosine A2A receptor antagonist SCH 58261 (2 mg/kg, i.p.). The results show that mGlu5 receptors are involved in the regulation of striatal glutamate release and suggest an involvement of adenosine A2A receptors in mGlu5 receptor-mediated effects.