1,635 research outputs found
Sub-matrix updates for the Continuous-Time Auxiliary Field algorithm
We present a sub-matrix update algorithm for the continuous-time auxiliary
field method that allows the simulation of large lattice and impurity problems.
The algorithm takes optimal advantage of modern CPU architectures by
consistently using matrix instead of vector operations, resulting in a speedup
of a factor of and thereby allowing access to larger systems and
lower temperature. We illustrate the power of our algorithm at the example of a
cluster dynamical mean field simulation of the N\'{e}el transition in the
three-dimensional Hubbard model, where we show momentum dependent self-energies
for clusters with up to 100 sites
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Self-care habits among people who inject drugs with skin and soft tissue infections: a qualitative analysis.
BACKGROUND:Injection drug use is on the rise in the USA, and skin and soft tissue infections (SSTI) are a common complication, resulting in significant morbidity and mortality. Due to structural barriers to care-seeking, many people who inject drugs avoid formal care and resort to self-care techniques, but little is known about the nature of these techniques, or more generally about the accuracy or breadth of this population's knowledge of SSTIs. METHODS:Semi-structured qualitative interviews were conducted with 12 people who inject heroin in two metropolitan areas: Sacramento and Boston, USA. RESULTS:These interviews reveal a robust and accurate knowledge base regarding skin infections, including the progression from simple cellulitis to an abscess, and acknowledgment of the possibility of serious infections. Nonetheless, there remains a reticence to seek care secondary to past traumatic experiences. A step-wise approach to self-care of SSTI infections was identified, which included themes of whole-body health, topical applications, use of non-prescribed antibiotics, and incision and drainage by non-medical providers. CONCLUSIONS:The reported SSTI self-care strategies demonstrate resilience and ingenuity, but also raise serious concerns about inappropriate antibiotic consumption and complications of invasive surgical procedures performed without proper training, technique, or materials. Harm reduction agencies and health care providers should work to obviate the need for these potentially dangerous practices by improving healthcare access for this population. In the absence of robust solutions to meet the needs of this population, education materials should be developed to optimize the efficacy and minimize the harms of these practices, while empowering and supporting the autonomy of people who use drugs and providing clear guidance on when self-care should be abandoned in favor of formal medical care
A century-long record of plant evolution reconstructed from a coastal marsh seed bank
Evidence is mounting that climate-driven shifts in environmental conditions can elicit organismal evolution, yet there are sparingly few long-term records that document the tempo and progression of responses, particularly for plants capable of transforming ecosystems. In this study, we āresurrectedā cohorts of a foundational coastal marsh sedge (Schoenoplectus americanus) from a time-stratified seed bank to reconstruct a century-long record of heritable variation in response to salinity exposure. Common-garden experiments revealed that S. americanus exhibits heritable variation in phenotypic traits and biomass-based measures of salinity tolerance. We found that responses to salinity exposure differed among the revived cohorts, with plants from the early 20th century exhibiting greater salinity tolerance than those from the mid to late 20th century. Fluctuations in salinity tolerance could reflect stochastic variation but a congruent record of genotypic variation points to the alternative possibility that the loss and gain in functionality are driven by selection, with comparisons to historical rainfall and paleosalinity records suggesting that selective pressures vary according to shifting estuarine conditions. Because salinity tolerance in S. americanus is tightly coupled to primary productivity and other vital ecosystem attributes, these findings indicate that organismal evolution merits further consideration as a factor shaping coastal marsh responses to climate change
Retinoic acid modulates chromatin to potentiate tumor necrosis factor alpha signaling on the DIF2 promoter
Transcriptional activation by nuclear hormone receptors is well characterized, but their cooperation with other signaling pathways to activate transcription remains poorly understood. Tumor necrosis factor alpha (TNFĪ±) and all-trans retinoic acid (RA) induce monocytic differentiation of acute promyelocytic leukemia (APL) cells in a synergistic manner. We used the promoter of DIF2, a gene involved in monocytic differentiation, to model the mechanism underlying the cooperative induction of target genes by RA and TNFĪ±. We show a functional RA response element in the DIF2 promoter, which is constitutively bound by PML/RARĪ± in APL cells. RA stimulates release of corepressors and recruitment of chromatin modifying proteins and additional transcription factors to the promoter, but these changes cause only a modest induction of DIF2 mRNA. Co-stimulation with RA plus TNFĪ± facilitates binding of NF-ĪŗB to the promoter, which is crucial for full induction of transcription. Furthermore, RA plus TNFĪ± greatly enhanced the level of RNA Pol II phosphorylation on the DIF2 promoter, via synergistic recruitment of TFIIH. We propose that RA mediates remodeling of chromatin to facilitate binding of transcription factors, which cooperate to enhance Pol II phosphorylation, providing a mechanism whereby nuclear receptors interact with other signaling pathways on the level of transcription
Cardiovascular Adaptations to Long Duration Head-Down Tilt Bed Rest
INTRODUCTION: Orthostatic hypotension is a serious risk for crewmembers returning from spaceflight. Numerous cardiovascular mechanisms have been proposed to account for this problem, including vascular and cardiac dysfunction, which we studied during bed rest. METHODS: Thirteen subjects were studied before and during bed rest. Statistical analysis was limited to the first 49-60 days of bed rest, and compared to pre-bed rest data. Ultrasound data were collected on vascular and cardiac structure and function. Tilt testing was conducted for 30 minutes or until presyncopal symptoms intervened. RESULTS: Plasma volume was significantly reduced by day 7 of bed rest. Flow-mediated dilation in the leg was significantly increased at bed rest day 49. Arterial responses to nitroglycerin differed in the arm and leg, but did not change as a result of bed rest. Intimal-medial thickness markedly decreased at bed rest days 21, 35 and 49. Several cardiac functional parameters including isovolumic relaxation time, ejection time and myocardial performance index were significantly increased (indicating a decrease in cardiac function) during bed rest. There was a trend for decreased orthostatic tolerance following 60 days of bed rest. DISCUSSION: These data suggest that 6 head-down tilt bed rest alters cardiovascular structure and function in a pattern similar to short duration spaceflight. Additionally, the vascular alterations are primarily seen in the lower body, while vessels of the upper body are unaffected. KEY WORDS: spaceflight, orthostatic intolerance, hypotension, fluid-shift, plasma volum
Moons Are Planets: Scientific Usefulness Versus Cultural Teleology in the Taxonomy of Planetary Science
We argue that taxonomical concept development is vital for planetary science
as in all branches of science, but its importance has been obscured by unique
historical developments. The literature shows that the concept of planet
developed by scientists during the Copernican Revolution was theory-laden and
pragmatic for science. It included both primaries and satellites as planets due
to their common intrinsic, geological characteristics. About two centuries
later the non-scientific public had just adopted heliocentrism and was
motivated to preserve elements of geocentrism including teleology and the
assumptions of astrology. This motivated development of a folk concept of
planet that contradicted the scientific view. The folk taxonomy was based on
what an object orbits, making satellites out to be non-planets and ignoring
most asteroids. Astronomers continued to keep primaries and moons classed
together as planets and continued teaching that taxonomy until the 1920s. The
astronomical community lost interest in planets ca. 1910 to 1955 and during
that period complacently accepted the folk concept. Enough time has now elapsed
so that modern astronomers forgot this history and rewrote it to claim that the
folk taxonomy is the one that was created by the Copernican scientists.
Starting ca. 1960 when spacecraft missions were developed to send back detailed
new data, there was an explosion of publishing about planets including the
satellites, leading to revival of the Copernican planet concept. We present
evidence that taxonomical alignment with geological complexity is the most
useful scientific taxonomy for planets. It is this complexity of both primary
and secondary planets that is a key part of the chain of origins for life in
the cosmos.Comment: 68 pages, 16 figures. For supplemental data files, see
https://www.philipmetzger.com/moons_are_planets
High stakes and low bars: How international recognition shapes the conduct of civil wars
When rebel groups engage incumbent governments in war for control of the state, questions of international recognition arise. International recognition determines which combatants can draw on state assets, receive overt military aid, and borrow as sovereignsāall of which can have profound consequences for the military balance during civil war. How do third-party states and international organizations determine whom to treat as a state's official government during civil war? Data from the sixty-one center-seeking wars initiated from 1945 to 2014 indicate that military victory is not a prerequisite for recognition. Instead, states generally rely on a simple test: control of the capital city. Seizing the capital does not foreshadow military victory. Civil wars often continue for many years after rebels take control and receive recognition. While geopolitical and economic motives outweigh the capital control test in a small number of important cases, combatants appear to anticipate that holding the capital will be sufficient for recognition. This expectation generates perverse incentives. In effect, the international community rewards combatants for capturing or holding, by any means necessary, an area with high concentrations of critical infrastructure and civilians. In the majority of cases where rebels contest the capital, more than half of its infrastructure is damaged or the majority of civilians are displaced (or both), likely fueling long-term state weakness
Doing gender locally: The importance of āplaceā in understanding marginalised masculinities and young menās transitions to āsafeā and successful futures
Observable anxieties have been developing about the position of boys and young men in contemporary society in recent years. This is expressed as a crisis of masculinity, in which place is often implicitly implicated, but is rarely considered for its role in the shaping of young menās practices, trajectories and aspirations. Drawing on research conducted with young people who accessed a range of social care support services, this article argues that transition means different things for young men in different locales and that local definitions of masculinity are required to better understand young menās lives and the opportunities available to them. The authors argue that home life, street life, individual neighbourhoods, regions and nations all shaped the young menās identities and the practices they (and the staff working with them) drew on in order to create successful futures and āsafeā forms of masculinity. It is suggested that this place-based approach has the potential to re-shape the ācrisisā discourse surrounding masculinity and the anxieties associated with young men
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