On Periodic Matrix-Valued Weyl-Titchmarsh Functions

We consider a certain class of Herglotz-Nevanlinna matrix-valued functions which can be realized as the Weyl-Titchmarsh matrix-valued function of some symmetric operator and its self-adjoint extension. New properties of Weyl -Titchmarsh matrix-valued functions as well as a new version of the functional model in such realizations are presented. In the case of periodic Herglotz-Nevanlinna matrix-valued functions we provide a complete characterization of their realizations in terms of the corresponding functional model. We also obtain properties of a symmetric operator and its self-adjoint extension generating periodic Weyl-Titchmarsh matrix-valued function. We study pairs of operators (a symmetric operator and its self-adjoint extension) with constant Weyl-Titchmarsh matrix-valued functions and establish connections between such pairs of operators and representations of the canonical commutation relations for unitary groups of operators in Weyl's form. As a consequence of such an approach we obtain the Stone-von Neumann theorem for two unitary groups of operators satisfying the commutation relations as well as some extension and refinement of the classical functional model for generators of those groups. Our examples include multiplication operators in weighted spaces, first and second order differential operators, as well as the Schr\"odinger operator with linear potential and its perturbation by bounded periodic potential

Exact Inference for the Linear Model with Groupwise Heteroscedasticity

Exact inference on a single coefficient in a linear regression model, as introduced by Bekker (1997), is elaborated for the case of normally distributed heteroscedastic disturbances. Instead of approximate inference based on feasible generalized least squares, exact confidence sets are formulated based on partial rotational invariance of the distribution of the vector of disturbances. The approach is applied to the random-effects and fixed-effects models for panel data.

Parodies of whiteness: Die Antwoord and the politics of race, gender, and class in South Africa

The dramatic reconfiguration of the social, political, and ideological order in South Africa since 1990/1994 has demanded a concomitant reconceptualization of (white) Afrikaner notions of self and belonging in the (new) nation. In this article, we draw on recent developments in the study of varidirectional voicing (polyphony), performance, and mediatization to examine how the South African rap-rave group Die Antwoord makes use of parody and metaparody in their music to critique emerging ‘new Afrikaner’ identities and the racial, class, and gender configurations on which they are based. We also discuss the structural limits of these critiques and the political potential of (meta)parodic performance more generally

Digging into Lipid Membrane Permeation for Cardiac Ion Channel Blocker d-Sotalol with All-Atom Simulations.

Interactions of drug molecules with lipid membranes play crucial role in their accessibility of cellular targets and can be an important predictor of their therapeutic and safety profiles. Very little is known about spatial localization of various drugs in the lipid bilayers, their active form (ionization state) or translocation rates and therefore potency to bind to different sites in membrane proteins. All-atom molecular simulations may help to map drug partitioning kinetics and thermodynamics, thus providing in-depth assessment of drug lipophilicity. As a proof of principle, we evaluated extensively lipid membrane partitioning of d-sotalol, well-known blocker of a cardiac potassium channel Kv11.1 encoded by the hERG gene, with reported substantial proclivity for arrhythmogenesis. We developed the positively charged (cationic) and neutral d-sotalol models, compatible with the biomolecular CHARMM force field, and subjected them to all-atom molecular dynamics (MD) simulations of drug partitioning through hydrated lipid membranes, aiming to elucidate thermodynamics and kinetics of their translocation and thus putative propensities for hydrophobic and aqueous hERG access. We found that only a neutral form of d-sotalol accumulates in the membrane interior and can move across the bilayer within millisecond time scale, and can be relevant to a lipophilic channel access. The computed water-membrane partitioning coefficient for this form is in good agreement with experiment. There is a large energetic barrier for a cationic form of the drug, dominant in water, to cross the membrane, resulting in slow membrane translocation kinetics. However, this form of the drug can be important for an aqueous access pathway through the intracellular gate of hERG. This route will likely occur after a neutral form of a drug crosses the membrane and subsequently re-protonates. Our study serves to demonstrate a first step toward a framework for multi-scale in silico safety pharmacology, and identifies some of the challenges that lie therein

Nutritional status, quality of life and CD4 cell count of adults living with HIV/AIDS in the Ga-Rankuwa area (South Africa)

Objective: To determine if there was a relationship between CD4 cell count, nutritional status and self-reported quality of life (QoL) in HIV-infected adults.Design: Descriptive study in the quantitative research domain.Setting: The out-patient antiretroviral (ARV) clinic at Dr George Mukhari Hospital (Ga-Rankuwa) (institutional).Subjects: The study group (n = 90) consisted of male (n = 34) and female patients (18–50 years) diagnosed with HIV/AIDS. Convenience sampling was used.Outcome measures: Anthropometry (weight, height, BMI, MUAC, TSF),  dietary intake (habitual food intake recall) and QoL (WHOQoL-HIV questionnaire) were assessed. Data collection was done from January–April 2007.Results: Significant, but poor, positive correlation was found for the  following anthropometrical parameters and the CD4 cell count: weight(r = 0.37; ρ = 0.00), BMI (r = 0.39; ρ = 0.00), and MUAC (r = 0.36; ρ = 0.00). The study group had a poor dietary quality. Significant correlation with the CD4 cell count was found for the following domains of the QoL: physical activity (r = 0.27; ρ = 0.01), psychological (r = 0.27; ρ = 0.01), level of independence (r = 0.36; ρ = 0.00), and environmental (r = 0.27; ρ = 0.01). The overall QoL assessment was average, according to the WHOQoL-HIV questionnaire score. Conclusion: Significant positive relationships existed between specific anthropometry and the CD4 cell count, and also between certain QoL domains and the CD4 cell count. Strategies for increasing dietary diversity and QoL ought to be identified and implemented in communities.Recommendation: A longitudinal study would give better understanding of the relationship between nutritional status, the CD4 cell count and Qo