519 research outputs found
Supporting Treatment Adherence Readiness through Training (START) for patients with HIV on antiretroviral therapy: study protocol for a randomized controlled trial.
BackgroundFew HIV antiretroviral adherence interventions target patients before they start treatment, assess adherence readiness to determine the timing of treatment initiation, or tailor the amount of adherence support. The Supporting Treatment Adherence Readiness through Training (START) intervention, based on the information-motivation-behavioral skills model of behavior change, is designed to address these gaps with the inclusion of (1) brief pill-taking practice trials for enhancing pretreatment adherence counseling and providing a behavioral criterion for determining adherence readiness and the timing of treatment initiation and (2) a performance-driven dose regulation mechanism to tailor the amount of counseling to the individual needs of the patient and conserve resources. The primary aim of this randomized controlled trial is to examine the effects of START on antiretroviral adherence and HIV virologic suppression.Methods/designA sample of 240 patients will be randomized to receive START or usual care at one of two HIV clinics. Primary outcomes will be optimal dose-taking adherence (>85 % prescribed doses taken), as measured with electronic monitoring caps, and undetectable HIV viral load. Secondary outcomes will include dose-timing adherence (>85 % prescribed doses taken on time) and CD4 count. Primary endpoints will be month 6 (short-term effect) and month 24 (to test durability of effect), though electronic monitoring will be continuous and a fully battery of assessments will be administered every 6 months for 24 months.DiscussionIf efficacious and cost-effective, START will provide clinicians with a model for assessing patient adherence readiness and helping patients to achieve and sustain readiness and optimal treatment benefits.Trial registrationClinicalTrials.gov identifier NCT02329782 . Registered on 22 December 2014
A microscopic Ginzburg--Landau theory and singlet ordering in SrRuO
The long-standing quest to determine the superconducting order of
SrRuO (SRO) has received renewed attention after recent nuclear
magnetic resonance (NMR) Knight shift experiments have cast doubt on the
possibility of spin-triplet pairing in the superconducting state. As a putative
solution, encompassing a body of experiments conducted over the years, a
-wave order parameter caused by an accidental near-degeneracy has been
suggested [S. A. Kivelson et al., npj Quantum Materials , 43 (2020)].
Here we develop a general Ginzburg--Landau theory for multiband
superconductors. We apply the theory to SRO and predict the relative size of
the order parameter components. The heat capacity jump expected at the onset of
the second order parameter component is found to be above the current threshold
deduced by the experimental absence of a second jump. Our results tightly
restrict theories of order, and other candidates caused by a
near-degeneracy, in SRO. We discuss possible solutions to the problem.Comment: 13 pages, 8 figure
Skyrmions in Twisted Bilayer Graphene: Stability, Pairing, and Crystallization
We study the excitations that emerge upon doping the translationally invariant correlated insulating states in magic-angle twisted bilayer graphene at various integer filling factors ν. We identify parameter regimes where these are excitations associated with skyrmion textures in the spin or pseudospin degrees of freedom, and explore both short-distance pairing effects and the formation of long-range ordered skyrmion crystals. We perform a comprehensive analysis of the pseudospin skyrmions that emerge upon doping insulators at even ν, delineating the regime in parameter space where these are the lowest-energy charged excitations by means of self-consistent Hartree-Fock calculations on the interacting Bistritzer-MacDonald model. We explicitly demonstrate the purely electron-mediated pairing of skyrmions, a key ingredient behind a recent proposal of skyrmion superconductivity. Building upon this, we construct hopping models to extract the effective masses of paired skyrmions, and discuss our findings and their implications for skyrmion superconductivity in relation to experiments, focusing on the dome-shaped dependence of the transition temperature on the twist angle. We also investigate the properties of spin skyrmions about the quantized anomalous Hall insulator at ν=+3. In both cases, we demonstrate the formation of robust spin or pseudospin skyrmion crystals upon doping to a finite density away from integer filling
Coulomb-driven band unflattening suppresses -phonon pairing in moir\'e graphene
It is a matter of current debate whether the gate-tunable superconductivity
in twisted bilayer graphene is phonon-mediated or arises from electron-electron
interactions. The recent observation of the strong coupling of electrons to
so-called -phonon modes in angle-resolved photoemission spectroscopy
experiments has resuscitated early proposals that -phonons drive
superconductivity. We show that the bandwidth-enhancing effect of interactions
drastically weakens both the intrinsic susceptibility towards pairing as well
as the screening of Coulomb repulsion that is essential for the phonon
attraction to dominate at low temperature. This rules out purely
-phonon-mediated superconductivity with the observed transition temperature
of K. We conclude that the unflattening of bands by Coulomb
interactions challenges any purely phonon-driven pairing mechanism, and must be
addressed by a successful theory of superconductivity in moir\'e graphene.Comment: 8 pages, 2 figures (+16 pages, 8 figures supplement
Electron-phonon coupling and competing Kekul\'e orders in twisted bilayer graphene
Recent scanning tunneling microscopy experiments [K.P. Nuckolls et al.,
arXiv:2303.00024] have revealed the ubiquity of Kekul\'e charge-density wave
order in magic-angle twisted bilayer graphene. Most samples are moderately
strained and show `incommensurate Kekul\'e spiral' (IKS) order involving a
graphene-scale charge density distortion uniaxially modulated on the scale of
the moir\'e superlattice, in accord with theoretical predictions. However,
ultra-low strain samples instead show graphene-scale Kekul\'e charge order that
is uniform on the moir\'e scale. This order, especially prominent near filling
factor , is unanticipated by theory which predicts a time-reversal
breaking Kekul\'e current order at low strain. We show that including the
coupling of moir\'e electrons to graphene-scale optical zone-corner (ZC)
phonons stabilizes a uniform Kekul\'e charge ordered state at with a
quantized topological (spin or anomalous Hall) response. Our work clarifies how
this phonon-driven selection of electronic order emerges in the strong-coupling
regime of moir\'e graphene.Comment: 5+4 page
A perpetual switching system in pulmonary capillaries
Of the 300 billion capillaries in the human lung, a small fraction meet normal oxygen requirements at rest, with the remainder forming a large reserve. The maximum oxygen demands of the acute stress response require that the reserve capillaries are rapidly recruited. To remain primed for emergencies, the normal cardiac output must be parceled throughout the capillary bed to maintain low opening pressures. The flow-distributing system requires complex switching. Because the pulmonary microcirculation contains contractile machinery, one hypothesis posits an active switching system. The opposing hypothesis is based on passive switching that requires no regulation. Both hypotheses were tested ex vivo in canine lung lobes. The lobes were perfused first with autologous blood, and capillary switching patterns were recorded by videomicroscopy. Next, the vasculature of the lobes was saline flushed, fixed by glutaraldehyde perfusion, flushed again, and then reperfused with the original, unfixed blood. Flow patterns through the same capillaries were recorded again. The 16-min-long videos were divided into 4-s increments. Each capillary segment was recorded as being perfused if at least one red blood cell crossed the entire segment. Otherwise it was recorded as unperfused. These binary measurements were made manually for each segment during every 4 s throughout the 16-min recordings of the fresh and fixed capillaries (>60,000 measurements). Unexpectedly, the switching patterns did not change after fixation. We conclude that the pulmonary capillaries can remain primed for emergencies without requiring regulation: no detectors, no feedback loops, and no effectors-a rare system in biology. NEW & NOTEWORTHY The fluctuating flow patterns of red blood cells within the pulmonary capillary networks have been assumed to be actively controlled within the pulmonary microcirculation. Here we show that the capillary flow switching patterns in the same network are the same whether the lungs are fresh or fixed. This unexpected observation can be successfully explained by a new model of pulmonary capillary flow based on chaos theory and fractal mathematics
Building crystalline topological superconductors from Shiba lattices
Localized or propagating Majorana boundary modes are the key feature of
topological superconductors. While being a rarity in natural compounds, the
tailored manipulation of quantum matter offers novel opportunities for their
realization. Specifically, lattices of Shiba bound states that arise when
magnetic adatoms are placed on the surface of a conventional superconductor can
be used to create topological minibands within the superconducting gap of the
substrate. Here, we exploit the possibilities of scanning tunneling microscopy
to create and probe adatom lattices with single atom precision to create
topological crystalline superconductors. Their topological character and
boundary modes are protected by the spatial symmetries of the adatom lattice.
We combine scanning probe spectroscopy, spin-sensitive measurements, first
principle calculations, and theoretical modeling to to reveal signatures
consistent with the realization of two types of mirror-symmetry protected
topological superconductors: (i) with full bulk gap and topological edge as
well as higher-order corner states and (ii) with symmetry-protected bulk nodal
points. Our results show the immense versatility of Shiba lattices to design
the topology and sample geometry of 2D superconductors.Comment: Published in Nature Physics
(https://doi.org/10.1038/s41567-023-02104-5
Geodetic VLBI Observations of EGRET Blazars
We present VLBI observations of the EGRET quasars 0202+149, CTA 26, and
1606+106, as well as additional analysis of VLBI observations of 1156+295
presented in Piner & Kingham (1997b). We have produced 8 and 2 GHz VLBI images
at 11 epochs, 8 epochs, and 12 epochs, spanning the years 1989 to 1996, of
0202+149, CTA 26, and 1606+106 respectively. The VLBI data have been taken from
the Washington VLBI correlator's geodetic database. We have measured the
apparent velocities of the jet components and find that CTA 26 and 1606+106 are
superluminal sources, with average apparent speeds of 8.9 and 2.9 h^{-1}c
respectively (H_{0}=100h km s^{-1} Mpc^{-1}, q_{0}=0.5). The components in
0202+149 are stationary, and we identify this source as a compact F double.
These sources all have apparently bent jets, and we detected non-radial motion
of components in CTA 26 and 1156+295. We have not yet detected any components
emerging subsequent to the gamma-ray flares in CTA 26, 1156+295, and 1606+106,
and we derive lower limits on the ejection times of any such components. The
misalignment angle distribution of the EGRET sources is compared to the
distribution for blazars as a whole, and we find that EGRET sources belong
preferentially to neither the aligned nor the misaligned population. We also
compare the average values for the apparent velocities and Doppler beaming
factors for the EGRET and non-EGRET blazars, and find no significant
differences. We thus find no indication, within the measurement errors, that
EGRET blazars are any more strongly beamed than their counterparts which have
not been detected in gamma-rays.Comment: 47 pages, including 13 figures; accepted for publication in the
Astrophysical Journa
- …