184 research outputs found
On Integrable Backgrounds Self-dual under Fermionic T-duality
We study the fermionic T-duality symmetry of integrable Green-Schwarz
sigma-models on AdS backgrounds with Ramond-Ramond fluxes in various
dimensions. We show that sigma-models based on supercosets of PSU supergroups,
such as AdS_2 \times S^2 and AdS_3 \times S^3 are self-dual under fermionic
T-duality, while supercosets of OSp supergroups such as non-critical AdS_2 and
AdS_4 models, and the critical AdS_4 \times CP^3 background are not. We present
a general algebraic argument to when a supercoset is expected to have a
fermionic T-duality symmetry, and when it will fail to have one.Comment: LaTeX, 27 pages, no figures, JHEP3 style; v2: references added; v3: a
comment in subsection 3.3 and a reference added; v4: fixed typos, published
versio
Coherent manipulation of nuclear spins in the strong driving regime
Spin-based quantum information processing makes extensive use of spin-state
manipulation. This ranges from dynamical decoupling of nuclear spins in quantum
sensing experiments to applying logical gates on qubits in a quantum processor.
Here we present an antenna for strong driving in quantum sensing experiments
and theoretically address challenges of the strong driving regime. First, we
designed and implemented a micron-scale planar spiral RF antenna capable of
delivering intense fields to a sample. The planar antenna is tailored for
quantum sensing experiments using the diamond's nitrogen-vacancy (NV) center
and should be applicable to other solid-state defects. The antenna has a broad
bandwidth of 22 MHz, is compatible with scanning probes, and is suitable for
cryogenic and ultrahigh vacuum conditions. We measure the magnetic field
induced by the antenna and estimate a field-to-current ratio of
G/A, representing a x6 increase in efficiency compared to the state-of-the-art.
We demonstrate the antenna by driving Rabi oscillations in H spins of an
organic sample on the diamond surface and measure H Rabi frequencies of
over 500 kHz, i.e., -pulses shorter than 1 - faster than
previously reported in NV-based nuclear magnetic resonance (NMR). Finally, we
discuss the implications of driving spins with a field tilted from the
transverse plane in a regime where the driving amplitude is comparable to the
spin-state splitting, such that the rotating wave approximation does not
describe the dynamics well. We present a recipe to optimize pulse fidelity in
this regime based on a phase and offset-shifted sine drive, that may be
optimized without numerical optimization procedures or precise modeling of the
experiment. We consider this approach in a range of driving amplitudes and show
that it is particularly efficient in the case of a tilted driving field
On the fermionic T-duality of the AdS_4 \times CP^3 sigma-model
In this note we consider a fermionic T-duality of the coset realization of
the type IIA sigma-model on AdS_4 \times CP^3 with respect to the three flat
directions in AdS_4, six of the fermionic coordinates and three of the CP^3
directions. We show that the Buscher procedure fails as it leads to a singular
transformation and discuss the result and its implications.Comment: LaTeX2e, 9 pages, no figures, JHEP style; v2: minor clarifications;
v3: typos fixed, matches the published versio
The phosphoproteome of toll-like receptor-activated macrophages
First global and quantitative analysis of phosphorylation cascades induced by toll-like receptor (TLR) stimulation in macrophages identifies nearly 7000 phosphorylation sites and shows extensive and dynamic up-regulation and down-regulation after lipopolysaccharide (LPS).In addition to the canonical TLR-associated pathways, mining of the phosphorylation data suggests an involvement of ATM/ATR kinases in signalling and shows that the cytoskeleton is a hotspot of TLR-induced phosphorylation.Intersecting transcription factor phosphorylation with bioinformatic promoter analysis of genes induced by LPS identified several candidate transcriptional regulators that were previously not implicated in TLR-induced transcriptional control
Analysis of the transcriptional networks underpinning the activation of murine macrophages by inflammatory mediators
Macrophages respond to the TLR4 agonist LPS with a sequential transcriptional cascade controlled by a complex regulatory network of signaling pathways and transcription factors. At least two distinct pathways are currently known to be engaged by TLR4 and are distinguished by their dependence on the adaptor molecule MyD88. We have used gene expression microarrays to define the effects of each of three variables-LPS dose, LPS versus IFN-beta and -gamma, and genetic background-on the transcriptional response of mouse BMDMs. Analysis of correlation networks generated from the data has identified subnetworks or modules within the macrophage transcriptional network that are activated selectively by these variables. We have identified mouse strain-specific signatures, including a module enriched for SLE susceptibility candidates. In the modules of genes unique to different treatments, we found a module of genes induced by type-I IFN but not by LPS treatment, suggesting another layer of complexity in the LPS-TLR4 signaling feedback control. We also observe that the activation of the complement system, in common with the known activation of MHC class 2 genes, is reliant on IFN-gamma signaling. Taken together, these data further highlight the exquisite nature of the regulatory systems that control macrophage activation, their likely relevance to disease resistance/susceptibility, and the appropriate response of these cells to proinflammatory stimuli
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