1,721,035 research outputs found
Mesh Locking Effects in the Finite Volume Solution of 2-D Anisotropic Diffusion Equations
No full textStrongly anisotropic diffusion equations require special techniques to overcome or reduce the mesh locking phenomenon. We present a finite volume scheme that tries to approximate with the best possible accuracy the quantities that are of importance in discretizing anisotropic fluxes. In particular, we discuss the crucial role of accurate evaluations of the tangential components of the gradient acting tangentially to the control volume boundaries, that are called into play by anisotropic diffusion tensors. To obtain the sought characteristics from the proposed finite volume method, we employ a second-order accurate reconstruction scheme which is used to evaluate both normal and tangential cell-interface gradients. The experimental results on a number of different meshes show that the scheme maintains optimal convergence rates in both L(2) and H(1) norms except for the benchmark test considering full Neumann boundary conditions on non-uniform grids. In such a case, a severe locking effect is experienced and documented. However, within the range of practical values of the anisotropy ratio, the scheme is robust and efficient. We postulate and verify experimentally the existence of a quadratic relationship between the anisotropy ratio and the mesh size parameter that guarantees optimal and sub-optimal convergence rate
Efficient generation of restriction matrices for exploiting partial or complete symmetries in 2D and 3D problems
No full textA Three terminal varactor for RF ICs in standard CMOS technology
No full textA three terminal metal-oxide-silicon varactor operated between accumulation and deep depletion is proposed for RF IC's. Prototypes, realized in a 0.35 μm standard CMOS technology, show a 3.1:1 capacitance tuning. The corresponding minimum Q is 23 at 1800 MHz. The proposed varactor lends itself as tuning element of VCO's in highly integrated CMOS transceiver
Patch testing with nickel sulfate: comparison between 2 nickel sulfate preparations and 2 different test sites on the back
No full textAmong patients routinely undergoing patch testing for suspected allergic contact dermatitis (ACD), nickel is the most frequently sensitizing hapten, with a clear predominance in the female population. However, some patients who report the appearance of dermatitis upon exposure to metal objects show negative patch test results to a nickel sulfate 5% pet. application. In some cases, a positive response to nickel can be observed simply by repeating the patch test. The objective of our study was to assess if, during routine patch testing, positive responses to nickel sulfate are missed owing to contingent problems, referring to application site, patch test execution or variations in skin reactivity. To this end, we applied 2 different patch test materials containing nickel sulfate 5% pet. to 3040 consecutive patients, undergoing patch testing for suspected allergic contact dermatitis, during the same session. The role of the lest site was also investigated by applying the preparation on 2 different sites of the back in 30 patients. Of the whole, 612 patients (20%) showed positive patch test responses. The 2 nickel materials were almost equivalent: 78% of nickel-sensitive patients had positive reactions to both, whereas 11% showed a positive response to 1 preparation alone. No variations in patch test responses in relation to application site were observed. Our data show that false-negative patch test responses to nickel are frequent. The use of 2 different preparations during the same patch test session increases the response rate by 10%
Patch Testing With Pollens Of Gramineae In Patients With Atopic-Dermatitis And Mucosal Atopy
No full textn
Pretreatment of the test area with 1-day occlusion improves the response rate to NiSo4 5% pet. - Patch tests in subjects with a positive history of nickel allergy
No full textA group of 58 women, aged 18 to 51 years, with a clinical history of nickel allergy, who exhibited equivocal or negative reactions to nickel sulfate 5% pet. patch tests performed on the skin of the back, were recruited consecutively from the patch test clinic from September 1993 to June 1994. In order to improve the response rate to NiSO4 5% pet. patch tests, a testing procedure utilizing pretreatment of the test area by 1-day (24-h) occlusion was introduced. Patients underwent 2 patch tests on adjacent sites of the volar surface of both forearms. 3 of the patch tests were performed with 40 mg nickel sulfate 5% pet., whereas a control test was carried out by occluding with an empty chamber. 2 of the nickel sulfate test sites were pretreated with 1-day occlusion performed with an empty chamber. A visual grading system and echographic measurement were used to quantify the responses 30-40 min after patch test removal. Echographic evaluations were carried out using a 20 MHz B-scanner. Measurement of skin thickness and determination of the hypoechogenic dermal area, both considered to be parameters of inflammation, were used to evaluate the intensity of the allergic reaction. At the 3-day (72-h) evaluation, 19 subjects out of 58 clearly showed positive reactions to nickel sulfate 5% pet. at pre-occluded skin sites. Moreover, values of skin thickness and of 0-30 areas at positive pre-occluded nickel test areas were higher in respect to control test areas, confirming clinical evidence of increased response to NiSO4 after occlusion
Contact Sensitization To Textile Dyes - Description Of 100 Subjects
No full textWe have described 100 subjects sensitized to textile dyes. Of these, 16 had clinically been suspected of having a textile dermatitis from among 1145 patients referred for patch testing. 41 patients were identified from among 861 consecutive subjects tested with the GIRDCA (Italian Research Group on Contact and Environmental Dermatitis) standard series supplemented with 4 disperse dyes (Disperse Blue 124, Disperse Red 1, Disperse Yellow 3, Disperse Orange 3). The remaining 43 patients were identified from among 746 subjects tested with the GIRDCA standard series, supplemented with the 4 disperse dyes mentioned above and a further series of 12 other textile dyes. The clinical picture was extremely variable: most patients had a typical eczematous dermatitis, but we also observed persistent erythematous-wheal-type reactions, a transient urticarial dermatitis and an erythema-multiforme-like eruption. Among these textile dyes, Disperse Blue 124 caused most reactions. With the addition of the 4 disperse dyes to the GIRDCA standard series, we identified 4.8% sensitized to textile dyes, a much higher figure than the 1.4% observed among patients being patch tested on the basis of their history and the clinical findings; the addition of a further 12 textile dyes to the series further increased the detection rate to 5.8%. We stress the importance of routinely patch testing with textile dyes, which can help to elucidate the cause of certain kinds of atypical dermatitis
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
