In Situ Observations of the Deformation Behavior and Fracture Mechanisms of Ti-45Al-2Nb-2Mn+0.8 vol pct TiB₂

The deformation and fracture mechanisms of a nearly lamellar Ti-45Al-2Nb-2Mn (at. pct) + 0.8 vol pct TiB₂ intermetallic, processed into an actual low-pressure turbine blade, were examined by means of in situ tensile and tensile-creep experiments performed inside a scanning electron microscope (SEM). Low elongation-to-failure and brittle fracture were observed at room temperature, while the larger elongations-to-failure at high temperature facilitated the observation of the onset and propagation of damage. It was found that the dominant damage mechanisms at high temperature depended on the applied stress level. Interlamellar cracking was observed only above 390 MPa, which suggests that there is a threshold below which this mechanism is inhibited. Failure during creep tests at 250 MPa was controlled by intercolony cracking. The in situ observations demonstrated that the colony boundaries are damage nucleation and propagation sites during tensile creep, and they seem to be the weakest link in the microstructure for the tertiary creep stage. Therefore, it is proposed that interlamellar areas are critical zones for fracture at higher stresses, whereas lower stress, high-temperature creep conditions lead to intercolony cracking and fracture.The authors are grateful to Industria de Turbo Propulsores, S.A. for supplying the intermetallic blades. Funding from the Spanish Ministry of Science and Innovation through projects MAT2009-14547-C02-01 and MAT2009-14547-C02-02 is acknowledged. The Madrid Regional Government supported this project partially through the ESTRUMAT grant P2009/MAT-1585. C.J.B. acknowledges the support from Grant SAB2009-0045 from the Spanish Ministry of Education for his sabbatical stage in Madrid.Publicad

Multiple juvenile xanthogranuloma in an adult patient: a case report

Background: Juvenile xanthogranuloma is a benign, normolipemic, dendrocytic histiocytosis that usually affects young children. It presents clinically as single or multiple yellow-brown papulonodular lesions in the upper part of the body, especially the head and neck. In adults, xanthogranuloma is not common and usually presents as a single lesion. Multiple xanthogranuloma in adults is rare. For the most part, cutaneous lesions are self-limited and seldom necessitate treatment. Here we report an adult patient with multiple xanthogranuloma.Case: A 45-year-old woman presented with multiple papulonodular lesions around the eyes and over her breasts and back. Biopsy showed giant cells with a wreath-like arrangement of nuclei (Touton giant cell) and diagnosis of juvenile xanthogranuloma was made.Conclusion: Although juvenile xanthogranuloma is a disease of children, it can rarely occur in adults. These patients should be evaluated for involvement of other organs to prevent complications. With ocular involvement, the risk of morbidity is high, and complications can include glaucoma, retinal detachment, cataract, vascular occlusion, hyphema, and corneal blood staining.&nbsp

Cryoscopy: a novel enhancing method of in vivo skin imaging.

BACKGROUND: It is a common observation that superficial freezing of normal skin and skin tumors may create a transient superficial whitening effect. In this respect, cryoscopy refers to the direct observation by dermoscopy, with or without digital recording, of the visual alterations of the frozen tissues. AIMS: To define the optimal method of cryoscopy and to describe the cryoscopy patterns of normal skin and selected skin lesions. MATERIALS AND METHODS: The influence of (a) different cryogenic sources [solid carbon dioxide (-78.5 degrees C), liquid nitrogen (N(2), -196 degrees C), and a mixture of dimethyl ether and propane (-57 degrees C)], (b) various application methods (spraying, cotton chill tips, copper plate), and (c) freezing time was assessed with regard to clinical feasability, visualization quality, and persistance time of the whitening effect. Cryoscopy patterns of normal skin, callosities and of histologically proven seborrheic keratoses, verrucous hamartomas, molluscum contagiosum, keratoacanthomas, viral warts, condylomas, actinic keratoses, dermatofibromas, skin tags, basal cell carcinomas, angiomas, and melanocytic naevi were assessed. RESULTS: The cryoscopy images of skin highlighted the skin lines. They appeared similar regardless of the freezing source and the application method. The aspects differed according to the nature of the lesions. The cotton chill tip method provided a longer whitening period compared with the other cold sources, both in normal and lesional skin. Hence, it represented the most convenient way for performing digital recording cryoscopy. On normal skin, cryoapplication was limited to about 1.5 s due to pain, resulting in whitening times ranging from 6 to 9 s, which was too short for easy digital recording. On all studied skin tumors, a 10-s N(2) freezing time was not experienced as painful, and blanching time persisted for 20-34 s, allowing easy digital recording. The whitening time was longer with increasing freezing time on both normal and lesional skin. Every single examined normal skin site and all the skin lesions showed a strong whitening effect, except heavily cornified structures, including some keratoses, callosities, and viral warts. Increased contrast of the skin surface texture was observed in almost every studied lesion. CONCLUSION: The N(2) cotton chill tip technique appeared to be the most convenient technique for cryoscopy and provided longer whitening periods compared with the other freezing sources. Pain prevented its use on normal skin, but a series of exophytic skin lesions was conveniently accessible to cryoscopy. The differences in whitening periods of various epidermal components resulted in increased visual contrast, creating typical cryoscopy images for the different exophytic skin tumors. Cryoscopy represents a novel in vivo skin imaging technique that is rapid, non-invasive, cost-effective, and easily performed. It shows both investigative and diagnostic potentials. It is remarkable that cryoscopy pictures closely resemble those yielded by skin capacitance imaging

The Efficacy Of Low-Dose Oral Corticosteroids In The Treatment Of Vitiligo Patients

Background: Vitiligo is an acquired pigmentary disorder that affects 1% of population. It presents as depigmented patches. One of the most probable theories regarding the pathogenesis of vitiligo is autoimmunity. Systemic corticosteroids may arrest the progression of vitiligo and lead to repigmentation by suppressing immune system. The objective of this study is to assess the clinical efficacy of low-dose oral corticosteroids in actively progressing vitiligo. Materials and Methods: Seventy four patients with vitiligo were evaluated. The patients took daily doses of oral prednisolone (0.3 mg/kg) initially for 2 months. Then the dosage was halved monthly, for the five subsequent months of treatment. The effects of treatment were evaluated using photography's before and after the study. Side effects were assessed at the first, second, third and fourth month of the treatment. Results: Arrested progression of vitiligo and repigmentation were noted in 74.3% and 62.1% of patients respectively. The mean pigmentation was 26.8%. The localized form, lower age of disease onset, no hair whiteness on the lesions and less affliction percent showed increased repigmentation with statistical significance. There was no significant difference between sexes and positive family history of vitiligo in patients. The best therapeutic results were obtained for facial lesions and the worst for mucosal lesions. The side effects of treatment were minimal and did not affect the course of the treatment. Conclusion: Low-dose oral corticosteroids are effective and have few serious side effects in preventing the progression of actively progressing vitiligo but regimentation is not significant and this regimen is effective in patients who are refractory to topical corticosteroids or phototherapy

Cryotherapy in the treatment of pyogenic granuloma

Background: Pyogenic granuloma is a benign, acquired, proliferative vascular lesion of the skin and mucous membranes. Many different treatments have been used for pyogenic granuloma with variable success rates. Objectives: To evaluate the efficacy of cryotherapy in the treatment of pyogenic granuloma. Methods: In a prospective observational study, 135 patients with pyogenic granuloma were treated with cryotherapy using liquid nitrogen. The patients were followed up every 3 weeks until 3 months after disappearance of the lesion. Results: Complete resolution of the pyogenic granuloma was achieved in all patients after a mean of 1.58 treatments (range, 1-4 treatments). At the end of follow-up period, there was a flat imperceptible scar, smaller than the treated lesion, in 16 patients (11.8). A hypertrophic scar, 3 mm in diameter, was observed in one patient. Hypopigmentation was observed in seven patients (5.1). No other complication or side-effect was recorded in the study. Conclusions: We believe that pyogenic granuloma can be treated simply and effectively with cryotherapy. © 2006 European Academy of Dermatology and Venereology

Interests and limitations of nanoindentation for bulk multiphase material identification: Application to the β phase of Ti-5553

This paper focuses on the numerical modeling of nanoindentation tests. The first goal of this study is to collect essential material parameters and boundary conditions from the literature and to complete the data required to accurately model nanoindentation tests. The second goal of this study consists in validating the material parameters identified from macroscopic tensile tests of the body-centered cubic b phase of Ti-5553, a new generation of titanium alloy. This validation is performed looking at experimental and numerical nanoindentation curves obtained for different grain orientations