Horizontal supergranule-scale motions inferred from TRACE ultraviolet observations of the chromosphere

We study horizontal supergranule-scale motions revealed by TRACE observation of the chromospheric emission, and investigate the coupling between the chromosphere and the underlying photosphere. A highly efficient feature-tracking technique called balltracking has been applied for the first time to the image sequences obtained by TRACE (Transition Region and Coronal Explorer) in the passband of white light and the three ultraviolet passbands centered at 1700 {\AA}, 1600 {\AA}, and 1550 {\AA}. The resulting velocity fields have been spatially smoothed and temporally averaged in order to reveal horizontal supergranule-scale motions that may exist at the emission heights of these passbands. We find indeed a high correlation between the horizontal velocities derived in the white-light and ultraviolet passbands. The horizontal velocities derived from the chromospheric and photospheric emission are comparable in magnitude. The horizontal motions derived in the UV passbands might indicate the existence of a supergranule-scale magnetoconvection in the chromosphere, which may shed new light on the study of mass and energy supply to the corona and solar wind at the height of the chromosphere. However, it is also possible that the apparent motions reflect the chromospheric brightness evolution as produced by acoustic shocks which might be modulated by the photospheric granular motions in their excitation process, or advected partly by the supergranule-scale flow towards the network while propagating upward from the photosphere. To reach a firm conclusion, it is necessary to investigate the role of granular motions in the excitation of shocks through numerical modeling, and future high-cadence chromospheric magnetograms must be scrutinized.Comment: 5 figures, accepted by Astronomy & Astrophysic

Humanized Rag1−/−γc−/− Mice Support Multilineage Hematopoiesis and Are Susceptible to HIV-1 Infection via Systemic and Vaginal Routes

Several new immunodeficient mouse models for human cell engraftment have recently been introduced that include the Rag2−/−γc−/−, NOD/SCID, NOD/SCIDγc−/− and NOD/SCIDβ2m−/− strains. Transplantation of these mice with CD34+ human hematopoietic stem cells leads to prolonged engraftment, multilineage hematopoiesis and the capacity to generate human immune responses against a variety of antigens. However, the various mouse strains used and different methods of engrafting human cells are beginning to illustrate strain specific variations in engraftment levels, duration and longevity of mouse life span. In these proof-of-concept studies we evaluated the Balb/c-Rag1−/−γ−/− strain for engraftment by human fetal liver derived CD34+ hematopoietic cells using the same protocol found to be effective for Balb/c-Rag2−/−γc−/− mice. We demonstrate that these mice can be efficiently engrafted and show multilineage human hematopoiesis with human cells populating different lymphoid organs. Generation of human cells continues beyond a year and production of human immunoglobulins is noted. Infection with HIV-1 leads to chronic viremia with a resultant CD4 T cell loss. To mimic the predominant sexual viral transmission, we challenged humanized Rag1−/−γc−/− mice with HIV-1 via vaginal route which also resulted in chronic viremia and helper T cell loss. Thus these mice can be further exploited for studying human pathogens that infect the human hematopoietic system in an in vivo setting

Outage-Optimized Multicast Beamforming with Distributed Limited Feedback

We consider a slowly fading multicast channel with one T -antenna transmitter and K single-antenna receivers with the goal of minimizing channel outage probability using quantized beamforming. Our focus is on a distributed limited feedback scenario where each receiver can only quantize and send feedback information regarding its own receiving channels. A classical result in point-to-point quantized beamforming is that a necessary and sufficient condition for full diversity is to have log2 T bits from the receiver with an appropriate quantizer. We first generalize this result to multicast beamforming systems and show that a necessary and sufficient condition to achieve full diversity for all receivers is to have log2T bits from each receiver with an appropriate quantizer. Achievable diversity gains with a long-term power constraint are also discussed. Moreover, for a two-receiver system and with R feedback bits per receiver, we show that the outage performance with quantized beamforming is within O\left(2-R32T2right) dBs to the performance with full channel state information at the transmitter (CSIT). This constitutes, in the context of multicast channels, the first example of a distributed limited feedback scheme whose performance can provably approach the performance with full CSIT. Numerical simulations confirm our analytical findings

Outage-Optimized Multicast Beamforming with Distributed Limited Feedback

We consider a slowly fading multicast channel with one T -antenna transmitter and K single-antenna receivers with the goal of minimizing channel outage probability using quantized beamforming. Our focus is on a distributed limited feedback scenario where each receiver can only quantize and send feedback information regarding its own receiving channels. A classical result in point-to-point quantized beamforming is that a necessary and sufficient condition for full diversity is to have log T bits from the receiver with an appropriate quantizer. We first generalize this result to multicast beamforming systems and show that a necessary and sufficient condition to achieve full diversity for all receivers is to have log T bits from each receiver with an appropriate quantizer. Achievable diversity gains with a long-term power constraint are also discussed. Moreover, for a two-receiver system and with R feedback bits per receiver, we show that the outage performance with quantized beamforming is within O\left(2-R32T2right) dBs to the performance with full channel state information at the transmitter (CSIT). This constitutes, in the context of multicast channels, the first example of a distributed limited feedback scheme whose performance can provably approach the performance with full CSIT. Numerical simulations confirm our analytical findings. 2

Depoliticizing adaptation: a critical analysis of EU climate adaptation policy

The ways in which climate adaptation is understood in the European Union isexamined via three key policy documents: the Strategy on adaptation and theGreen and White Papers that preceded it. Drawing on PoststructuralistDiscourse Theory, light is shed on the implicit values and assumptions thatunderpin this recent policy initiative. The findings demonstrate a tensionbetween the declared ambition to act on adaptation and implicit suggestionsthat nothing really has to change, and the challenge can be addressed bymarket and technological innovations, and by mainstreaming adaptation intoexisting sectoral policies. The policy discourse effectively serves to depoliticizechoices societies make in response to climate change, presenting adaptationas a non-political issue. Insight into European adaptation discourse enablesdeeper understanding of recent policy developments and opens up possibleentry points for critique

A humanized mouse-based HIV-1 viral outgrowth assay with higher sensitivity than in vitro qVOA in detecting latently infected cells from individuals on ART with undetectable viral loads.

Assays that can verify full viral eradication are essential in the context of achieving a cure for HIV/AIDS. In vitro quantitative viral out growth assays (qVOA) are currently the gold standard for measuring latent HIV-1 but these assays often fail to detect very low levels of replication-competent virus. Here we investigated an alternative in vivo approach for sensitive viral detection using humanized mice (hmVOA). Peripheral blood CD4+ T cell samples from HIV subjects on stable ART with undetectable viral loads by RT-PCR were first assayed by in vitro qVOA. Corresponding patient samples in which no virus was detected by qVOA were injected into humanized mice to allow viral outgrowth. Of the five qVOA virus negative samples, four gave positive viral outgrowth in the hmVOA assay suggesting that it is more sensitive in detecting latent HIV-1