Different Behavior of Magnetic Impurities in Crystalline and Ammorphous States of Superconductors

It has been observed that the effect of magnetic impurities in a superconductor is drastically different depending on whether the host superconductor is in a crystalline or an amorphous state. Based on the recent theory of Kim and Overhauser (KO), it is shown that as the system is getting disordered, the initial slope of the $T_{c}$ depression is decreasing by a factor $\sqrt{\ell/\xi_{0}}$, when the mean free path $\ell$ becomes smaller than the BCS coherence length $\xi_{0}$, which is in agreement with experimental findings. In addition, for a superconductor in a crystalline state in the presence of magnetic impurities the superconducting transition temperature $T_{c}$ drops sharply from about 50% of $T_{c0}$ (for a pure system) to zero near the critical impurity concentration. This {\sl pure limit behavior} was indeed found by Roden and Zimmermeyer in crystalline Cd. Recently, Porto and Parpia have also found the same {\sl pure limit behavior} in superfluid He-3 in aerogel, which may be understood within the framework of the KO theory.Comment: 7 figures, 20 pages, latex, to appear in Superconductor Science and Technolog

The HIV epidemic in Botswana and gender inequalities: a way forward

The Botswana HIV/AIDS epidemic started in the early 1990s, with the proportion of the overall population infected with HIV (prevalence) rapidly escalating to 28.2% by the year 2000. Today, HIV prevalence has decreased to 23%, yet Botswana has the third highest percentage of HIV infected population in the world. The HIV epidemic in Botswana is in need of attention, but prevalence alone does not represent the full picture. HIV incidence (the rate of new infections and a critical indicator of success of HIV prevention programs) peaked in Botswana around 1996 at 5.7% and has declined to about 2.72% today. Botswana's two most effective programs in its response to the epidemic have been provision of universal HIV treatment and prevention of mother-to-child-transmission (PMTCT) programs, which have achieved over 95% coverage for all eligible patients. These two programs largely account for Botswana's rapid decline in HIV prevalence and incidence rates. However, females have continually had higher rates of prevalence and incidence than males throughout the course of Botswana's epidemic. In order to continue these declining rates of infection, Botswana may consider redoubling its efforts around HIV prevention. Women and young adolescent girls have not been the main beneficiaries of prevention programs. Women are more susceptible to HIV infection biologically and more vulnerable to infection due to social determinants, most notably their lack of empowerment and control in sexual partnerships. The main social drivers of the HIV epidemic in Botswana have been concurrent partnerships, sexual assault, cross-generational sex, and transactional sex. These drivers increase risk of HIV infection particularly for women. Botswana has implemented promising national prevention programs focused on HIV counseling and testing, consistent condom use, decreased concurrent partnerships, and male circumcision. However, the Botswana legal system reinforces gender inequalities, further increasing women's risk for HIV infection. In Botswana's law, martial rape, domestic violence, and intimate partner violence are not criminalized. Further, sex with minors and sexual assault are not strictly enforced. Sex work is illegal and stigmatized, and thus sex workers are not receiving appropriate support in HIV prevention. This high-risk population accounts for only 1.65% of the general population but will account for 6.38% of new HIV infections. The HIV treatment and PMTCT programs have decreased HIV incidence, but Botswana may consider increasing its behavioral prevention programs to regard gender norms and reforming legislation to protect women and young girls. This paper recommends behavioral prevention programs through increased youth education programs, women empowerment programs, access to sexual and reproductive health care, and male involvement in sexual and reproductive health. Further, it is recommended that policy makers focus on reforming civil legislation and bolstering enforcement of existing laws that protect women from violence. The key to successful scale-up of behavioral prevention in Botswana will be community-driven HIV initiatives and strong leadership from community leaders and members of parliament, including women

Impurity scattering in a d-wave superconductor

The influence of (non-magnetic and magnetic) impurities on the transition temperature of a d-wave superconductor is studied anew within the framework of BCS theory. Pairing interaction decreases linearly with the impurity concentration. Accordingly $T_{c}$ suppression is proportional to the (potential or exchange) scattering rate, $1/\tau$, due to impurities. The initial slope versus $1/\tau$ is found to depend on the superconductor contrary to Abrikosov-Gor'kov type theory. Near the critical impurity concentration $T_{c}$ drops abruptly to zero. Because the potential scattering rate is generally much larger than the exchange scattering rate, magnetic impurities will also act as non-magnetic impurities as far as the $T_{c}$ decrease is concerned. The implication for the impurity doping effect in high $T_{c}$ superconductors is also discussed.Comment: 12 pages and 1 figure, PlainTex, submitted to Mod. Phys. Lett. B, For more information, please see "http://taesan.kaist.ac.kr/~yjkim

Efficacy of inducible protein 10 as a biomarker for the diagnosis of tuberculosis

SummaryObjectiveThis study evaluated inducible protein 10 (IP-10) as a diagnostic biomarker for specific tuberculosis (TB) infection and evaluated the ability of IP-10 to distinguish between active TB and latent TB infection (LTBI).MethodsForty-six patients with active pulmonary TB, 22 participants with LTBI, and 32 non-TB controls were enrolled separately. We measured IP-10 in serum and in supernatants from whole blood stimulated with TB-specific antigens.ResultsTB antigen-dependent IP-10 secretion was significantly increased in the active TB patients and LTBI subjects compared with controls, but did not differ significantly between the active TB patients and LTBI subjects. Serum IP-10 levels were higher in active TB than in LTBI (174.9 vs. 102.7pg/ml, p=0.002). The respective rates of positive responders of TB antigen-dependent IP-10 were 97.8%, 90.9%, and 12.5% in active TB, LTBI, and non-TB controls, respectively. For serum IP-10, 87.5%, 45.5%, and 9.5% of responders were positive in the respective groups.ConclusionsThe IP-10 response to TB antigen may constitute a specific biomarker for TB infection, but does not by itself distinguish between active TB and LTBI. Serum IP-10 may enhance the diagnostic performance when used in combination with another marker