Highly responsive and selective ozone sensor based on Ga doped ZnS-ZnO composite sprayed films.

Ozone detection is currently the subject of wide scientific and technological research, motivated by its harmful impact on human safety, environment and health. With the aim of searching for new highly sensitive materials for ozone detection, Ga-doped ZnS and ZnS-ZnO films were deposited by a spray pyrolysis technique. The obtained films were annealed at 400 °C for two hours. The ozone sensing properties were investigated by measuring the sensor resistance for several ozone concentrations ranging from 30 to 120 ppb. The sensor response reveals a dependence on the gallium concentration. The best response was obtained with 4% doping gallium. The sensitivity is 4.5 ppb-1 at 260 °C and the response to 30 ppb ozone is 150. Moreover, the sensor shows high performance such as good selectivity and fast rapidity.

Annealing effect on the physical properties of TiO2 thin films deposited by spray pyrolysis.

Titanium dioxide (TiO2) thin films were deposited on glass substrates at 350 °C using the spray pyrolysis technique. As deposited and annealed thin films were characterized by X-ray diffraction, scanning electron microscopy, UV-VIS spectroscopy, and photodetection. Unlike the as deposited samples which were amorphous, annealed samples show an anatase phase. Films were absorbent in the UV region and the band gap energy decreases from 3.78 eV to 3.4 eV with annealing. The photoresponse of TiO2 photodetectors was recorded under UV (λ1 = 365 nm, λ2 = 254 nm) and visible light illumination by reversible switching (ON/OFF) cycles using DC electrical characterization. Photosensitive properties such as reproducible photosensitivity, responsivity, and detectivity were also studied.

Chemical VOC sensing mechanism of sol-gel ZnO pellets and linear discriminant analysis for instantaneous selectivity.

This work reports on the integration of ZnO pellets for use as a virtual sensor array (VSA) of volatile organic compounds (VOCs). ZnO pellets consist of nano-powder prepared using a sol-gel technique. The microstructure of the obtained samples was characterized by XRD and TEM methods. The response to VOCs at different concentrations was measured over a range of operating temperatures (250-450 °C) using DC electrical characterization. The ZnO based sensor showed a good response towards ethanol, methanol, isopropanol, acetone and toluene vapors. We note that the highest sensitivity (0.26 ppm-1) is obtained with ethanol while the lowest one (0.041 ppm-1) corresponds to methanol. Consequently, the limit of detection (LOD) estimated analytically reached 0.3 ppm for ethanol and 2.0 ppm for methanol at an operating temperature of 450 °C. The sensing mechanism of the ZnO semiconductor was developed on the basis of the reaction between the reducing VOCs with the chemisorbed oxygen. We verify through the Barsan model that mainly O- ions in the layer react with VOC vapor. Furthermore, dynamic response was investigated to construct mathematical features with distinctly different values for each vapor. Basic linear discrimination analysis (LDA) shows a good job of separating two groups by combining features. In the same way we have shown an original reason embodying the distinction between more than two volatile compounds. With relevant features and VSA formalism, the sensor is clearly selective towards individual VOCs.

Thickness effect on VOC sensing properties of sprayed In2S3 films.

This work reports the thickness effect on the sensing performances of In2S3 material for some Volatile Organic Compounds (VOCs). In2S3 films were deposited on glass substrates by the spray pyrolysis technique. Different samples were prepared via changing the spray time in the range of 10-90 min. The film thickness varies from 0.8 µm to 6.1 µm. The X-ray diffraction results demonstrate that the In2S3 films are polycrystalline in nature and exhibit a cubic structure. Additionally, Scanning Electron Microscopy (SEM) and 3D profilometry examinations show that the surface roughness increases with the rising spray time. On the other hand, the oxygen adsorption versus working temperature was investigated. Sensing measurements with ethanol, methanol and acetone gases were carried out by a dynamic control of the current passing through the sensitive layers. The best sensitivity was obtained for the film matching a 70 min deposit time. An understanding of the detection mechanism based on the oxidation reaction between reduced vapors and chemisorbed oxygen was confirmed. The selectivity of the sensor was analyzed for several volatile organic compounds (VOCs).

Investigation of the effect of S/In molar ratio on physical properties of sprayed In2S3 thin films.

Indium sulfide (In2S3) thin films have been synthesized on glass substrates using the spray technique (CSP). The S : In molar ratio was varied from 1 to 4 in the starting solution. The Raman analysis confirms the formation of the ß-In2S3 material and the absence of a secondary phase. The EDS analysis reveals that our layers are pure. The thin film surface is free of cracks, as observed in AFM images. Optical transmission achieved 80% in the visible and near infrared region. The refractive index (n) is affected by the changes in the S/In molar ratio. The optical parameters, single oscillator energy (E 0), dispersion energy (E d) and high frequency dielectric constant (ε ∞), are calculated via the Wemple-DiDomenico model. In addition, the photoconductivity kinetics in In2S3 films for S/In = 2 were investigated and analyzed. The I-V characteristics and the photoresponse were also studied.

[Contribution of the cryosurgery in the management of xeroderma pigmentosum]. / L'apport de la cryochirurgie dans la prise en charge du xeroderma pigmentosum.

BACKGROUND: Basal cell carcinoma (BCC) occurs frequently in young patients with xeroderma pigmentosum (XP). Because tumours are multiple and usually found on the face, alternatives to surgery are proposed. The purpose of this study was to evaluate the efficacy of cryosurgery for BCC in XP patients. PATIENTS AND METHODS: This was a retrospective study that included all instances of BCC occurring in XP patients treated by cryosurgery between January 2002 and October 2008. RESULTS: Forty-five cases of primary facial BCC and one case of relapsing BCC (16 on the cheeks, 11 on the nose, six on the face and five on the inner edge of the eye area) were treated by cryosurgery in 18 XP patients (average age: 18.7 years; sex ratio: 0.5). Mean carcinoma size was 10mm. Thirty-six tumours were nodular and 10 were nodular and ulcerated. Follow-up ranged from 16 to 60 months (mean: 30 months). Complications were rare. Cosmetic results were satisfactory. We noted 10 cases of hypopigmentation (21.7%) and one notch on the nose following treatment for recurrent BCC on a radiotherapy scar. Relapse occurred in one case (2.17%). CONCLUSION: Because of its simplicity, its good safety, its sparing of skin and its reliability of oncological outcome, cryosurgery is the treatment of choice for CBC in XP patients.

[Skin aging]. / Le vieillissement cutané.

The skin aging is the result of the association of seven factors; chronological factor, genetic factors, exposure to ultraviolet rays (photodamage), behaviour factors, endocrinous, catabolics and mechanics factors. The treatment combine sun protection measures, topical treatment, dermatological and surgical techniques (peelings, resurfacing laser, injections of collagen, botulic toxin...). The authors intend to study clinical and anatomy-physiology aspect of skin aging, as well as different treatments.

[Cutaneous lymphoma in Tunisia: clinical profile and therapeutic results]. / Lymphomes cutanés en Tunisie: profil clinique et résultats thérapeutiques.

PURPOSE: The aim of this retrospective study was to investigate therapeutic result of cutaneous lymphoma in Tunisia. PATIENTS AND METHODS: Between January 1969 and June 1994, 100 patients with cutaneous lymphoma were referred either to Salah Azaiz Institute or the other University Hospitals of Tunisia. Fifty-one patients had epidermotropic lymphoma and 49 non-epidermotropic lesions. Eighty-seven patients received complete treatment. Puvatherapy and other local dermatologic treatments were used for early stage mycosis fungoïdes. Thirty-two patients benefited from radiotherapy, with curative dose in 28 cases. Chemotherapy including anthracyclin agents was used for high grade lymphoma. Thirteen patients had association of radiotherapy and chemotherapy. RESULTS: Five-year survival rates were 50% for patients with epidermotropic lesions and 56% for patients with non-epidermotropic cutaneous lymphoma. Statistical study has not identified any significant prognosis factor. CONCLUSION: Radiotherapy and chemotherapy are both effective. Treatment should depend on stage and histologic type.

[Giant cell fibroblastoma associated with Darier-Ferrand dermatofibrosarcoma in an adult]. / Association d'un fibroblastome à cellules géantes et d'un dermatofibrosarcome de Darier-Ferrand chez un adulte.

INTRODUCTION: Giant cell fibroblastoma is a rare mesenchyma tumor of childhood having many similarities with dermatofibrosarcoma protuberans in adults. OBSERVATION: We report the case of a 28-year-old woman presenting a subcutaneous inter-mammary mass associating both tumors. Immunohistochemistry showed an expression of CD 34 only by dermatofibrosarcoma protuberans cells. DISCUSSION: It is important to stress: the rarity of this association, the difficulty to confirm the diagnosis and to establish the links between these two tumors: simple association (as in our case), transformation or recurrence of giant cell fibroblastoma in dermatofibrosarcoma protuberans.

[Oral desensitization to antitubercular agents]. / Désensibilisation orale aux anti-tuberculeux.

We report a case of hypersensitivity reaction to majors antituberculosis drugs. We have successfully performed oral desensitization to "Rifater *". We present our protocol that we compare to those proposed in the literature.