Application of the work of indentation approach for the characterization of aluminium 2024-T351 and Al cladding by nanoindentation

Nanoindentation has been used to characterize the mechanical properties of aerospace-grade Al2024-T351 with and without a clad layer of pure aluminium. The clad layer is introduced by means of a roll-bonding process which can cause significant work-hardening of the material in the clad layer. The hardness and Young’s modulus of the pure aluminium and the Al2024 have been determined by a number of methods, including the traditional Oliver and Pharr method, and a number of other methods, including direct measurement of the indentation by atomic force microscopy, and evaluation of the work of indentation. The Oliver and Pharr method was found to underestimate the area of contact as it did not include the area of piled-up material around the indentation periphery. This gave a corresponding overestimation of both hardness and modulus. The area of the indentation measured by atomic force microscopy was similarly found to underestimate the contact area owing to relaxation of material around the indent between indentation and imaging. The work of indentation approach was found to give good agreement between the hardness calculated by nanoindentation and those found in the literature

Prevalence of genital Chlamydia trachomatis infection in the general population of Slovenia: serious gaps in control

Methods: Data were collected over 1999–2001 from a probability sample of the general population by face to face interviews and anonymous self administered questionnaires. Respondents were invited to provide a first void urine (FVU) specimen for polymerase chain reaction testing for C trachomatis infection. We compared the results to the equivalent British survey. Results: 1447 individuals contributed FVU specimens (82.6% of survey respondents, 55.3% of those eligible). C trachomatis infection was diagnosed in 3.0% of men and 1.6% of women. Prevalence was highest in men and women aged 18–24 years (4.1% for both). Individuals reporting first heterosexual intercourse before the age of 16, unprotected sexual intercourse with at least one heterosexual partner during the preceding year, concurrent heterosexual relationships during the preceding year, and five or more lifetime heterosexual partners had a higher prevalence. The association was statistically significant only for five or more lifetime partners (adjusted OR 3.0; 95% CI 1.3 to 6.9; p = 0.01). Conclusions: A relatively high prevalence of genital C trachomatis infection among 18–24 year old Slovenians, in the presence of relatively low risk sexual behaviour and low reported incidence rates of chlamydia infection, suggest serious gaps in the diagnosis and treatment of the condition. The results provide support for the introduction of chlamydia screening in Slovenia

Feasibility of testing for Chlamydia trachomatis in a general population sexual behaviour survey in Slovenia.

Our objective was to assess the feasibility of integrating first void urine (FVU) specimens testing for Chlamydia trachomatis genitourinary infection into a general population sexual behaviour survey. A total of 752 randomly selected respondents aged 18 to 54 were enrolled into the survey. Face to face interviewing with self-administered sensitive questions was used. Overall survey response rate was 77.4%. A convenience sub-sample of 83 respondents were invited to provide FVU specimens for confidential testing for C. trachomatis genitourinary infection. Fifty-five complied. This resulted in 66% FVU specimen participation rate among targeted respondents. Two specimens tested positive by Amplicor polymerase chain reaction. High feasibility study overall response rate indicated good acceptability of the survey. It proved feasible to collect FVU specimens for C. trachomatis testing in the small sub-sample. Consequently, we proceeded with integration of testing for C. trachomatis into the ongoing main survey

True Hardness Evaluation of Bulk Metallic Materials in the Presence of Pile Up:Analytical and Enhanced Lobes Method Approaches

In the last few decades, a great deal of attention has been paid to understanding the factors controlling the detailed shape of loading-unloading curves obtained by the Oliver and Pharr’s nanoindentation analysis, to enable us estimate material parameters such as true contact area, Young’s modulus, and hardness. In fact, it is well known that the Oliver and Pharr’s analysis can overestimate hardness, especially in such cases where the material plastically deforms by piling up around the indentation. In recent years, different direct and analytic methods have been proposed. Direct visual methods are based on measurements of the produced indentation by scanning probe microscopy (SPM) or by atomic force microscopy (AFM). Some other analytic methods are based on the work of indentation analysis, that is to say, the analysis of the area of the load-displacement curve. In the case of the current study, DHP-copper hardness measurements using nanoindentation, in both H58 and annealed metallurgical conditions, were investigated by both direct and analytic methods. Three different SPM-based methods and work of indentation analysis methods were used to determine the true hardness. Among the three SPM-based methods, one showed quite a good agreement with the literature data and micro- hardness tests. This method was therefore developed and improved to make it dependent on curve parameters and no longer dependent on SPM or AFM, the measurements of the real contact area. The correlation between the pile-up phenomenon and the m exponent of the P = B(h - h f )^m relationship is also discussed