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

Spinor-Vector Duality in Heterotic String Orbifolds

The three generation heterotic-string models in the free fermionic formulation are among the most realistic string vacua constructed to date, which motivated their detailed investigation. The classification of free fermion heterotic string vacua has revealed a duality under the exchange of spinor and vector representations of the SO(10) GUT symmetry over the space of models. We demonstrate the existence of the spinor-vector duality using orbifold techniques, and elaborate on the relation of these vacua to free fermionic models.Comment: 20 pages. v2 minor corrections. Version to appear on JHEP. v3 misprints correcte

Spatial cytoskeleton organization supports targeted intracellular transport

The efficiency of intracellular cargo transport from specific source to target locations is strongly dependent upon molecular motor-assisted motion along the cytoskeleton. Radial transport along microtubules and lateral transport along the filaments of the actin cortex underneath the cell membrane are characteristic for cells with a centrosome. The interplay between the specific cytoskeleton organization and the motor performance realizes a spatially inhomogeneous intermittent search strategy. In order to analyze the efficiency of such intracellular search strategies we formulate a random velocity model with intermittent arrest states. We evaluate efficiency in terms of mean first passage times for three different, frequently encountered intracellular transport tasks: i) the narrow escape problem, which emerges during cargo transport to a synapse or other specific region of the cell membrane, ii) the reaction problem, which considers the binding time of two particles within the cell, and iii) the reaction-escape problem, which arises when cargo must be released at a synapse only after pairing with another particle. Our results indicate that cells are able to realize efficient search strategies for various intracellular transport tasks economically through a spatial cytoskeleton organization that involves only a narrow actin cortex rather than a cell body filled with randomly oriented actin filaments

Development of a species-specific coproantigen ELISA for human taenia solium taeniasis

Taenia solium causes human neurocysticercosis and is endemic in underdeveloped countries where backyard pig keeping is common. Microscopic fecal diagnostic methods for human T. solium taeniasis are not very sensitive, and Taenia saginata and Taenia solium eggs are indistinguishable under the light microscope. Coproantigen (CoAg) ELISA methods are very sensitive, but currently only genus (Taenia) specific. This paper describes the development of a highly species-specific coproantigen ELISA test to detect T. solium intestinal taeniasis. Sensitivity was maintained using a capture antibody of rabbit IgG against T. solium adult whole worm somatic extract, whereas species specificity was achieved by utilization of an enzyme-conjugated rabbit IgG against T. solium adult excretory-secretory (ES) antigen. A known panel of positive and negative human fecal samples was tested with this hybrid sandwich ELISA. The ELISA test gave 100% specificity and 96.4% sensitivity for T. solium tapeworm carriers (N = 28), with a J index of 0.96. This simple ELISA incorporating anti-adult somatic and anti-adult ES antibodies provides the first potentially species-specific coproantigen test for human T. solium taeniasis

The value-added tax implications of the temporary change in use adjustments by residential property developers: an international comparative study

Residential property developers sometimes struggle to dispose of newly built residential premises, because of an oversupply of residential property in the market and decreased sales in recent years. Many developers have switched from speculation (when residential properties are built to be sold) to investment (when properties are retained to generate rental income). Some developers only lease out newly constructed dwellings temporarily in anticipation of selling them later at a more favourable price. Units may be held with the ultimate goal of selling them, creating taxable supplies. In South Africa, these changes in the use of residential property have value-added tax (VAT) consequences that result in a negative cash fl ow. In the 2010 Budget Speech, amendments to the harsh VAT legislation were proposed. This study examined the South African VAT legislation applicable to property developers during the period when residential properties are let out. The fi ndings suggest that the current South African VAT legislation relevant to changes in the use of residential properties is harsher than that in New Zealand or Australia, but that the proposed amendments offer some degree of relief. However, even with these amendments, there is insuffi cient relief, and another possible solution is proposed.Key words: value-added tax, residential property, change in use, temporary lettin

Manipulation Strategies for the Rank Maximal Matching Problem

We consider manipulation strategies for the rank-maximal matching problem. In the rank-maximal matching problem we are given a bipartite graph $G = (A \cup P, E)$ such that $A$ denotes a set of applicants and $P$ a set of posts. Each applicant $a \in A$ has a preference list over the set of his neighbours in $G$, possibly involving ties. Preference lists are represented by ranks on the edges - an edge $(a,p)$ has rank $i$, denoted as $rank(a,p)=i$, if post $p$ belongs to one of $a$'s $i$-th choices. A rank-maximal matching is one in which the maximum number of applicants is matched to their rank one posts and subject to this condition, the maximum number of applicants is matched to their rank two posts, and so on. A rank-maximal matching can be computed in $O(\min(c \sqrt{n},n) m)$ time, where $n$ denotes the number of applicants, $m$ the number of edges and $c$ the maximum rank of an edge in an optimal solution. A central authority matches applicants to posts. It does so using one of the rank-maximal matchings. Since there may be more than one rank- maximal matching of $G$, we assume that the central authority chooses any one of them randomly. Let $a_1$ be a manipulative applicant, who knows the preference lists of all the other applicants and wants to falsify his preference list so that he has a chance of getting better posts than if he were truthful. In the first problem addressed in this paper the manipulative applicant $a_1$ wants to ensure that he is never matched to any post worse than the most preferred among those of rank greater than one and obtainable when he is truthful. In the second problem the manipulator wants to construct such a preference list that the worst post he can become matched to by the central authority is best possible or in other words, $a_1$ wants to minimize the maximal rank of a post he can become matched to

Patient empowerment: designing technology that supports people’s coping strategies

Background: Self-management technologies, such as patient-controlled electronic health records (PCEHRs), have the potential to help people manage and cope with disease. Objectives: This study set out to investigate patient families’ lived experiences of working with a PCEHR. Method: We conducted a semi-structured qualitative field study with patient families and clinicians at a children’s hospital in the UK that uses a PCEHR. All families were managing the health of a child with a serious chronic condition, who was typically under the care of multiple clinicians. As data gathering and analysis progressed, it became clear that while much of the literature assumes that patients are willing and waiting to take more responsibility for and control over their health management (for example, with PCEHRs), only a minority of participants in our study responded in this way. Their experiences with the PCEHR were diverse and strongly shaped by their coping styles. Theory on coping identifies a continuum of coping styles, from approach- to avoidance-oriented, and proposes that patients’ information needs depend on their style. Results: Based on themes that emerged from the data analysis, and informed by prior research on coping styles, we identified three groups of patient families and an outlier, distinguished by their coping style and their PCEHR use. We refer to the outlier as controlling (approach-oriented, highly motivated to use PCEHR), and the three groups as collaborating (approach-oriented, motivated to use PCEHR), cooperating (avoidance-oriented, less motivated to use PCEHR) and avoiding (very avoidance-oriented, not motivated to use PCEHR). Conclusions: The PCEHR met the needs of controller and collaborators better than the needs of co-operators and avoiders. We draw on Self-Determination Theory (SDT) to propose ways in which PCEHR design might better meet the needs of avoidance-oriented users. Further, we high-light the need for families to also relinquish control at times, and propose ways in which PCEHR design might support a better distribution of control, based on effective training, ease of use, com-prehensibility of data security mechanisms, timely information provision (recognising people’s dif-ferent needs), personalisation of use, and easy engagement with clinicians through the PCEHR

Optimal solutions to matrix-valued Nehari problems and related limit theorems

In a 1990 paper Helton and Young showed that under certain conditions the optimal solution of the Nehari problem corresponding to a finite rank Hankel operator with scalar entries can be efficiently approximated by certain functions defined in terms of finite dimensional restrictions of the Hankel operator. In this paper it is shown that these approximants appear as optimal solutions to restricted Nehari problems. The latter problems can be solved using relaxed commutant lifting theory. This observation is used to extent the Helton and Young approximation result to a matrix-valued setting. As in the Helton and Young paper the rate of convergence depends on the choice of the initial space in the approximation scheme.Comment: 22 page

Immunisation for refugees in Australia: a policy review and analysis across all States and Territories.

OBJECTIVE: Although people of refugee background are likely to be under-immunised before and after resettlement, no study to date has evaluated refugee specific immunisation policies in Australia. We developed a framework to analyse immunisation policies across Australia to highlight the strengths and gaps so as to inform development of more effective refugee specific immunisation policies. METHODS: We sourced publicly available immunisation policy documents from state and territory government websites. Content analysis of seven policy documents was undertaken using a developed framework comprising crucial policy determinants. RESULTS: Immunisation policy differed substantially across the jurisdictions. While most policies did not highlight the importance of data collection on immunisation for refugees and the public funding of vaccines for refugees, policy determinants such as accessibility and obligations were fulfilled by most jurisdictions. CONCLUSION: Our findings indicate stark differences in immunisation policy for people of refugee background across Australia. Highlighted gaps demonstrate the need to revise current policies so that they are aligned with their intended outcome of enhancing uptake of vaccines and improving immunisation coverage among resettled refugees in Australia. Implications for public health: Immunisation policy development for refugees needs to be robust enough to ensure equitable health services to this group