Abstract Supersonic isothermal turbulence is a common process in astrophysical systems. In this work, we explore the energy in such systems. We show that the conserved energy is the sum of the kinetic energy (K) and Helmholtz free energy (F). We develop analytic predictions for the probability distributions,P(F) andP(K), as well as their nontrivial joint distribution,P(F,K). We verify these predictions with a suite of driven turbulence simulations, finding excellent agreement. The turbulence simulations were performed at Mach numbers ranging from 1 to 8, and three modes of driving: purely solenoidal, purely compressive, and mixed. We find thatP(F) is discontinuous atF= 0, with the discontinuity increasing with Mach number and compressive driving.P(K) resembles a lognormal with a negative skew. The joint distribution,P(F,K), shows a bimodal distribution, with gas either existing at highFand highKor at lowFand lowK.
more »
« less
Toward Single Photon Detection using Nanophotonic Parametric Amplifiers
Ultra-intense parametric amplification can be used for amplifying single photons to macroscopic levels. We experimentally detected coherent states with 〈N〉=4.86 with 17% efficiency and 2.5% dark count probability.
more »
« less
- Award ID(s):
- 1846273
- PAR ID:
- 10544734
- Publisher / Repository:
- Optica Publishing Group
- Date Published:
- ISBN:
- 978-1-957171-25-8
- Page Range / eLocation ID:
- FTh3A.5
- Format(s):
- Medium: X
- Location:
- San Jose, CA
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The influence of climate feedbacks on regional hydrological changes under warming is poorly understood. Here, a moist energy balance model (MEBM) with a Hadley Cell parameterization is used to isolate the influence of climate feedbacks on changes in zonal‐mean precipitation‐minus‐evaporation (P − E) under greenhouse‐gas forcing. It is shown that cloud feedbacks act to narrow bands of tropicalP − Eand increaseP − Ein the deep tropics. The surface‐albedo feedback shifts the location of maximum tropicalP − Eand increasesP − Ein the polar regions. The intermodel spread in theP − Echanges associated with feedbacks arises mainly from cloud feedbacks, with the lapse‐rate and surface‐albedo feedbacks playing important roles in the polar regions. TheP − Echange associated with cloud feedback locking in the MEBM is similar to that of a climate model with inactive cloud feedbacks. This work highlights the unique role that climate feedbacks play in causing deviations from the “wet‐gets‐wetter, dry‐gets‐drier” paradigm.more » « less
-
Summary Evolutionarily conserved DEK domain‐containing proteins have been implicated in multiple chromatin‐related processes, mRNA splicing and transcriptional regulation in eukaryotes.Here, we show that two DEK proteins, DEK3 and DEK4, control the floral transition inArabidopsis. DEK3 and DEK4 directly associate with chromatin of related flowering repressors,FLOWERING LOCUS C(FLC), and its two homologs,MADS AFFECTING FLOWERING4(MAF4) andMAF5, to promote their expression.The binding of DEK3 and DEK4 to a histone octamerin vivoaffects histone modifications atFLC,MAF4andMAF5loci. In addition, DEK3 and DEK4 interact with RNA polymerase II and promote the association of RNA polymerase II withFLC,MAF4andMAF5chromatin to promote their expression.Our results show that DEK3 and DEK4 directly interact with chromatin to facilitate the transcription of key flowering repressors and thus prevent precocious flowering inArabidopsis.more » « less
-
Abstract Buffelgrass [Pennisetum ciliare(L.) Link] is an invasive C4perennial bunchgrass that is a threat to biodiversity in aridlands in the Americas and Australia. Topography influencesP. ciliareoccurrence at large spatial scales, but further investigation into the relationship between local-scale topography andP. ciliaregrowth and reproduction would be beneficial. Further, density-dependent effects onP. ciliaregrowth and reproduction have been demonstrated in greenhouse experiments, but the extent to which density dependence influencesP. ciliarein natural populations warrants further investigation. Here we present a study on the relationships between local-scale topography (aspect and slope gradient) and vegetation characteristics (shrub cover,P. ciliarecover, andP. ciliaredensity) and their interactions on individualP. ciliareplant size and reproduction. We measured slope gradient, aspect, shrub cover,P. ciliarecover,P. ciliaredensity, and the total number of live culms and reproductive culms of 10P. ciliareplants in 33 4 by 4 m plots located in 11 transects at the Desert Laboratory at Tumamoc Hill, Tucson, AZ, USA. We modeled the relationships at the local scale of (1)P. ciliarecover and density with aspect and slope gradient and (2)P. ciliaresize and reproduction with abiotic (slope gradient and aspect) and biotic (P. ciliarecover and density and native shrub and cacti cover) characteristics. Aspect and slope gradient were poor predictors ofP. ciliarecover and density in already invaded sites at the scale of our plots. However, aspect had a significant relationship withP. ciliareplant size and reproduction.Pennisetum ciliareplants on south-facing aspects were larger and produced more reproductive culms than plants on other aspects. Further, we found no relationship betweenP. ciliaredensity andP. ciliareplant size and reproduction. Shrub cover was positively correlated withP. ciliarereproduction. South-facing aspects are likely most vulnerable to fast spread and infilling by newP. ciliareintroductions.more » « less
-
ABSTRACT ObjectiveNeighborhood perceptions are associated with physical and mental health outcomes; however, the biological associates of this relationship remain to be fully understood. Here, we evaluate the relationship between neighborhood perceptions and amygdala activity and connectivity with salience network (i.e., insula, anterior cingulate, thalamus) nodes. MethodsForty-eight older adults (mean age = 68 [7] years, 52% female, 47% non-Hispanic Black, 2% Hispanic) without dementia or depression completed the Perceptions of Neighborhood Environment Scale. Lower scores indicated less favorable perceptions of aesthetic quality, walking environment, availability of healthy food, safety, violence (i.e., more perceived violence), social cohesion, and participation in activities with neighbors. Participants separately underwent resting-state functional magnetic resonance imaging. ResultsLess favorable perceived safety (β= −0.33,pFDR= .04) and participation in activities with neighbors (β= −0.35,pFDR= .02) were associated with higher left amygdala activity, independent of covariates including psychosocial factors. Less favorable safety perceptions were also associated with enhanced left amygdala functional connectivity with the bilateral insular cortices and the left anterior insula (β= −0.34,pFDR= .04). Less favorable perceived social cohesion was associated with enhanced left amygdala functional connectivity with the right thalamus (β =−0.42,pFDR= .04), and less favorable perceptions about healthy food availability were associated with enhanced left amygdala functional connectivity with the bilateral anterior insula (right:β= −0.39,pFDR= .04; left:β= −0.42,pFDR= .02) and anterior cingulate gyrus (β= −0.37,pFDR= .04). ConclusionsTaken together, our findings document relationships between select neighborhood perceptions and amygdala activity as well as connectivity with salience network nodes; if confirmed, targeted community-level interventions and existing community strengths may promote brain-behavior relationships.more » « less
An official website of the United States government

