Eutectic Colony Formation: A Stability Analysis

Experiments have widely shown that a steady-state lamellar eutectic solidification front is destabilized on a scale much larger than the lamellar spacing by the rejection of a dilute ternary impurity and forms two-phase cells commonly referred to as `eutectic colonies'. We extend the stability analysis of Datye and Langer for a binary eutectic to include the effect of a ternary impurity. We find that the expressions for the critical onset velocity and morphological instability wavelength are analogous to those for the classic Mullins-Sekerka instability of a monophase planar interface, albeit with an effective surface tension that depends on the geometry of the lamellar interface and, non-trivially, on interlamellar diffusion. A qualitatively new aspect of this instability is the occurence of oscillatory modes due to the interplay between the destabilizing effect of the ternary impurity and the dynamical feedback of the local change in lamellar spacing on the front motion. In a transient regime, these modes lead to the formation of large scale oscillatory microstructures for which there is recent experimental evidence in a transparent organic system. Moreover, it is shown that the eutectic front dynamics on a scale larger than the lamellar spacing can be formulated as an effective monophase interface free boundary problem with a modified Gibbs-Thomson condition that is coupled to a slow evolution equation for the lamellar spacing. This formulation provides additional physical insights into the nature of the instability and a simple means to calculate an approximate stability spectrum. Finally, we investigate the influence of the ternary impurity on a short wavelength oscillatory instability that is already present at off-eutectic compositions in binary eutectics.Comment: 26 pages RevTex, 14 figures (28 EPS files); some minor changes; references adde

Barriers for introducing HIV testing among tuberculosis patients in Jogjakarta, Indonesia: a qualitative study

<p>Abstract</p> <p>Background</p> <p>HIV and HIV-TB co-infection are slowly increasing in Indonesia. WHO recommends HIV testing among TB patients as a key response to the dual HIV-TB epidemic. Concerns over potential negative impacts to TB control and lack of operational clarity have hindered progress. We investigated the barriers and opportunities for introducing HIV testing perceived by TB patients and providers in Jogjakarta, Indonesia.</p> <p>Methods</p> <p>We offered Voluntary Counselling and Testing (VCT) to TB patients in parallel to a HIV prevalence survey. We conducted in-depth interviews with 33 TB patients, 3 specialist physicians and 3 disease control managers. We also conducted 4 Focus Group Discussions (FGDs) with nurses. All interviews and FGDs were recorded and data analysis was supported by the QSR N6^®software.</p> <p>Results</p> <p>Patients' and providers' knowledge regarding HIV was poor. The main barriers perceived by patients were: burden for accessing VCT and fear of knowing the test results. Stigma caused concerns among providers, but did not play much role in patients' attitude towards VCT. The main barriers perceived by providers were communication, patients feeling offended, stigmatization and additional burden.</p> <p>Conclusion</p> <p>Introduction of HIV testing among TB patients in Indonesia should be accompanied by patient and provider education as well as providing conditions for effective communication.</p

India's Revised National Tuberculosis Control Programme: looking beyond detection and cure.

SETTING: Pune District, Maharashtra State, India. OBJECTIVES: To examine delays experienced by patients in accessing directly observed treatment. DESIGN: Data were collected from 117 new sputum-positive patients using a semi-structured interview schedule. RESULTS: Patient delays as well as diagnostic and treatment delays, which reflect the performance of a National TB Programme, were minimal. Provider delays, however, contributed significantly to delayed entry into India's Revised National TB Control Programme (RNTCP). Patients had to resort to multiple contacts with providers due to limitations of these providers in diagnosing or directing patients to the RNTCP. Patients who consulted a private provider participating in the public-private mix (PPM) were more likely to be suspected (OR 2.63, 90% CI 1.04-6.64) and referred (OR 6.8, 95%CI 2.08-22.21) to the RNTCP. Once the patients entered the RNTCP, the response of the system was rapid, with diagnosis offered and treatment initiated within on average 7 days. CONCLUSION: Interventions aimed at providers to encourage early suspicion and referral to the RNTCP, such as the PPM, are more important in improving patient access to TB care than those focusing on reducing patient delays

Daylight Fading of Dyes in Mixture on Polyamide-6 Fibre

75-78<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:"times="" roman";mso-ansi-language:en-us;="" mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">Nylon-6 has been dyed with single and binary mixtures of dyes. The light fastness of the dyed material exposed to daylight has been evaluated visually using the standard Blue Scale. The concentration of dye on the material has been estimated spectrophotometrically before and after exposure to light. It appears that the observed catalytic fading of dyes in mixture is at times an optical effect and not a catalytic degradation.</span

Studies in the reaction of formaldehyde with cellulose

This article does not have an abstract

Production and Characterization of Nylon-6 Filaments Containing Carbon Black

126-132<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:"times="" roman";mso-ansi-language:en-us;="" mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">Nylon-6 filament yarns containing up to 1.5% carbon black have been prepared using two different methods, viz. (1) incorporating carbon black in disperse form during polymerization and melt spinning, and (2) blending the chips containing 1.5% carbon black, prepared as in (1), with chips without any carbon black (blank) and melt spinning. The filaments thus produced were examined for their structure and properties. It has been observed that the samples prepared by method (1) are more homogeneous and have more uniform properties.</span