Double-diffusive magnetic buoyancy instability in a quasi-two-dimensional Cartesian geometry

Magnetic buoyancy, believed to occur in the solar tachocline, is both an important part of large-scale solar dynamo models and the picture of how sunspots are formed. Given that in the tachocline region the ratio of magnetic diffusivity to thermal diffusivity is small it is important, for both the dynamo and sunspot formation pictures, to understand magnetic buoyancy in this regime. Furthermore, the tachocline is a region of strong shear and such investigations must involve structures that become buoyant in the double-diffusive regime which are generated entirely from a shear flow. In a previous study, we have illustrated that shear-generated doublediffusive magnetic buoyancy instability is possible in the tachocline. However, this study was severely limited due to the computational requirements of running three-dimensional magnetohydrodynamic simulations over diffusive time-scales. A more comprehensive investigation is required to fully understand the double-diffusive magnetic buoyancy instability and its dependency on a number of key parameters; such an investigation requires the consideration of a reduced model. Here we consider a quasi-two-dimensional model where all gradients in the x direction are set to zero. We show how the instability is sensitive to changes in the thermal diffusivity and also show how different initial configurations of the forced shear flow affect the behaviour of the instability. Finally, we conclude that if the tachocline is thinner than currently stated then the double-diffusive magnetic buoyancy instability can more easily occur

19F-labeling of the adenine H2-site to study large RNAs by NMR spectroscopy

In comparison to proteins and protein complexes, the size of RNA amenable to NMR studies is limited despite the development of new isotopic labeling strategies including deuteration and ligation of differentially labeled RNAs. Due to the restricted chemical shift dispersion in only four different nucleotides spectral resolution remains limited in larger RNAs. Labeling RNAs with the NMR-active nucleus [superscript 19]F has previously been introduced for small RNAs up to 40 nucleotides (nt). In the presented work, we study the natural occurring RNA aptamer domain of the guanine-sensing riboswitch comprising 73 nucleotides from Bacillus subtilis. The work includes protocols for improved in vitro transcription of 2-fluoroadenosine-5′-triphosphat (2F-ATP) using the mutant P266L of the T7 RNA polymerase. Our NMR analysis shows that the secondary and tertiary structure of the riboswitch is fully maintained and that the specific binding of the cognate ligand hypoxanthine is not impaired by the introduction of the [superscript 19]F isotope. The thermal stability of the [superscript 19]F-labeled riboswitch is not altered compared to the unmodified sequence, but local base pair stabilities, as measured by hydrogen exchange experiments, are modulated. The characteristic change in the chemical shift of the imino resonances detected in a 1H,15N-HSQC allow the identification of Watson–Crick base paired uridine signals and the [superscript 19]F resonances can be used as reporters for tertiary and secondary structure transitions, confirming the potential of [superscript 19]F-labeling even for sizeable RNAs in the range of 70 nucleotides.Deutsche Forschungsgemeinschaft (collaborative research center: SFB902

NACA Research Memorandums

Report presenting a study of static wind-tunnel data on the effects of external stores like tanks, torpedoes, bombs, and radar domes on the stability of military airplanes. The results are focused on longitudinal and lateral stability. Static longitudinal stability is affected at various Mach numbers, but the data was not sufficient to estimate the effect on the lateral stability

Age-related differences in emotional reactivity, regulation, and rejection sensitivity in adolescence

Although adolescents’ emotional lives are thought to be more turbulent than those of adults, it is unknown whether this difference is attributable to developmental changes in emotional reactivity or emotion regulation. Study 1 addressed this question by presenting healthy individuals aged 10–23 with negative and neutral pictures and asking them to respond naturally or use cognitive reappraisal to down-regulate their responses on a trial-by-trial basis. Results indicated that age exerted both linear and quadratic effects on regulation success but was unrelated to emotional reactivity. Study 2 replicated and extended these findings using a different reappraisal task and further showed that situational (i.e., social vs. nonsocial stimuli) and dispositional (i.e., level of rejection sensitivity) social factors interacted with age to predict regulation success: young adolescents were less successful at regulating responses to social than to nonsocial stimuli, particularly if the adolescents were high in rejection sensitivity. Taken together, these results have important implications for the inclusion of emotion regulation in models of emotional and cognitive development.National Science Foundation (U.S.) (Award BCS-0224342)National Institutes of Health (U.S.) (Award MH076137)National Institutes of Health (U.S.) (Award HD069178)National Institutes of Health (U.S.) (Award MH094056

Alpha effect due to buoyancy instability of a magnetic layer

A strong toroidal field can exist in form of a magnetic layer in the overshoot region below the solar convection zone. This motivates a more detailed study of the magnetic buoyancy instability with rotation. We calculate the alpha effect due to helical motions caused by a disintegrating magnetic layer in a rotating density-stratified system with angular velocity Omega making an angle theta with the vertical. We also study the dependence of the alpha effect on theta and the strength of the initial magnetic field. We carry out three-dimensional hydromagnetic simulations in Cartesian geometry. A turbulent EMF due to the correlations of the small scale velocity and magnetic field is generated. We use the test-field method to calculate the transport coefficients of the inhomogeneous turbulence produced by the layer. We show that the growth rate of the instability and the twist of the magnetic field vary monotonically with the ratio of thermal conductivity to magnetic diffusivity. The resulting alpha effect is inhomogeneous and increases with the strength of the initial magnetic field. It is thus an example of an "anti-quenched" alpha effect. The alpha effect is nonlocal, requiring around 8--16 Fourier modes to reconstruct the actual EMF based on the actual mean field.Comment: 14 pages, 19 figures 3 tables (submitted to A & A

Photo collage-based photograph display system on mobile computing platform

In the last few decades, mobile computing platform technology has grown rapidly, as observed from smart phones that have quickly become ubiquitous. The mobile computing platform is the most widely used platform in our life today, and digital photographs captured through these devices have become routine for most people. In this study, we propose a novel artistic method for displaying photographs in mobile devices as a photo collage. Using our system, users can view a representative photograph as a collage of photographs associated with a certain event and access each of photographs individually. To implement this, we employ centroidal Voronoi diagram to obtain an even distribution of tiles, and use the sites as the location of tiles. We use the edge avoidance technique to prevent tiles from being located across the edges. To obtain the direction of tiles that follow near a strong edge, we employ the Edge tangent Flow field and use the field as the directions of tiles. Finally, we search for photographs that best match the tiles calculated above by using a thumbnail difference metric

Phenotypic and functional characteristics of highly differentiated CD57 +NKG2C + NK cells in HIV-1- infected individuals

Natural killer (NK) cells are important anti-viral effector cells. The function and phenotype of the NK cells that constitute an individual’s NK cell repertoire can be influenced by ongoing and/or previous viral infections. Indeed, infection with human cytomegalovirus (HCMV) drives the expansion of a highly differentiated NK cell population characterized by expression of CD57 and the activating NKG2C receptor. This NK cell population has also been noted to occur in HIV-1-infected individuals. We evaluated the NK cells of HIV-1-infected and –uninfected individuals to determine the relative frequency of highly differentiated CD57 +NKG2C + NK cells and characterize these cells for their receptor expression and responsiveness to diverse stimuli. Highly differentiated CD57 +NKG2C + NK cells occurred at higher frequencies in HCMV-infected donors relative to HCMV-uninfected donors and were dramatically expanded in HIV-1/HCMV co-infected donors. The expanded CD57 +NKG2C + NK cell population in HIV-1-infected donors remained stable following antiretroviral therapy. CD57 +NKG2C + NK cells derived from HIV-1-infected individuals were robustly activated by antibody-dependent stimuli that contained anti-HIV-1 antibodies or therapeutic anti-CD20 antibody, and these NK cells mediated cytolysis through NKG2C. Lastly, CD57 +NKG2C + NK cells from HIV-1-infected donors were characterized by reduced expression of the inhibitory NKG2A receptor. The abundance of highly functional CD57 +NKG2C + NK cells in HIV-1-infected individuals raises the possibility that these NK cells could play a role in HIV-1 pathogenesis or serve as effector cells for therapeutic/cure strategies

The 25th Anniversary of the Baby Doe Rules: Perspectives from the Fields of Law, Health Care, Ethics, and Disability Policy

A highly publicized and controversial case involving the withholding of medical treatment from a “Baby Doe” with Down syndrome gave rise in 1984 to the federal law known as the Baby Doe Rules, which went into effect the following year. The law conditions the grant of federal funds for any state’s child protective services program on the state’s assurance that it can respond to reports of medical neglect, which may include the withholding of medical treatment from disabled infants with life-threatening conditions. Leading scholars and practitioners from the fields of health care, law, ethics, and disability policy who are experts in the field of neonatal medicine and decision-making involving very premature and other medically at-risk infants gathered to provide thoughtful commentary and debate on the occasion of the 25th Anniversary of the Baby Doe Rules. The Georgia State University Law Review will publish a symposium volume on the topic in Fall 2009

The 25th Anniversary of the Baby Doe Rules: Perspectives from the Fields of Law, Health Care, Ethics, and Disability Policy

A highly publicized and controversial case involving the withholding of medical treatment from a “Baby Doe” with Down syndrome gave rise in 1984 to the federal law known as the Baby Doe Rules, which went into effect the following year. The law conditions the grant of federal funds for any state’s child protective services program on the state’s assurance that it can respond to reports of medical neglect, which may include the withholding of medical treatment from disabled infants with life-threatening conditions. Leading scholars and practitioners from the fields of health care, law, ethics, and disability policy who are experts in the field of neonatal medicine and decision-making involving very premature and other medically at-risk infants gathered to provide thoughtful commentary and debate on the occasion of the 25th Anniversary of the Baby Doe Rules. The Georgia State University Law Review will publish a symposium volume on the topic in Fall 2009