Measurements of jet structure and fragmentation from full jet reconstruction in heavy ion collisions at RHIC

Measurements of inclusive hadron suppression and di-hadron azimuthal correlations have provided important insights into jet quenching in hot QCD matter. However, they do not provide access to the energy of the hard scattering and are limited in their sensitivity since they can be affected by biases toward hard fragmentation and small energy loss. Full jet reconstruction in heavy-ion collisions enables a complete study of the modification of jet structure due to energy loss, but is challenging due to the high-multiplicity environment. We present measurements of fully reconstructed di-jets at mid-rapidity in 200 GeV p+p and central Au+Au collisions performed with the STAR detector. We compare fragmentation functions measured in 200 GeV p+p and central Au+Au collisions and assess the systematic uncertainties of their ratio.Comment: Proceedings of Quark Matter 09 Conferenc

Modulation of the extracellular matrix patterning of thrombospondins by actin dynamics and thrombospondin oligomer state

Thrombospondins (TSPs) are evolutionarily-conserved, secreted glycoproteins that interact with cell surfaces and extracellular matrix (ECM) and have complex roles in cell interactions. Unlike the structural components of the ECM that form networks or fibrils, TSPs are deposited into ECM as arrays of nanoscale puncta. The cellular and molecular mechanisms for the patterning of TSPs in ECM are poorly understood. In the present study, we investigated whether the mechanisms of TSP patterning in cell-derived ECM involves actin cytoskeletal pathways or TSP oligomer state. From tests of a suite of pharmacological inhibitors of small GTPases, actomyosin-based contractility, or actin microfilament integrity and dynamics, cytochalasin D and jasplakinolide treatment of cells were identified to result in altered ECM patterning of a model TSP1 trimer. The strong effect of cytochalasin D indicated that mechanisms controlling puncta patterning depend on global F-actin dynamics. Similar spatial changes were obtained with endogenous TSPs after cytochalasin D treatment, implicating physiological relevance. Under matched experimental conditions with ectopically-expressed TSPs, the magnitude of the effect was markedly lower for pentameric TSP5 and Drosophila TSP, than for trimeric TSP1 or dimeric Ciona TSPA. To distinguish between the variables of protein sequence or oligomer state, we generated novel, chimeric pentamers of TSP1. These proteins accumulated within ECM at higher levels than TSP1 trimers, yet the effect of cytochalasin D on the spatial distribution of puncta was reduced. These findings introduce a novel concept that F-actin dynamics modulate the patterning of TSPs in ECM and that TSP oligomer state is a key determinant of this process

A Coupled Analysis of Atmospheric Mass Loss and Tidal Evolution in XUV Irradiated Exoplanets: The TRAPPIST-1 Case Study

Exoplanets residing close to their stars can experience evolution of both their physical structures and their orbits due to the influence of their host stars. In this work, we present a coupled analysis of dynamical tidal dissipation and atmospheric mass loss for exoplanets in X-ray and ultraviolet (XUV) irradiated environments. As our primary application, we use this model to study the TRAPPIST-1 system and place constraints on the interior structure and orbital evolution of the planets. We start by reporting on an ultraviolet continuum flux measurement (centered around ~1900 Å) for the star TRAPPIST-1, based on 300 ks of Neil Gehrels Swift Observatory data, and which enables an estimate of the XUV-driven thermal escape arising from XUV photodissociation for each planet. We find that the X-ray flaring luminosity, measured from our X-ray detections, of TRAPPIST-1 is 5.6 × 10⁻⁴ L*, while the full flux including non-flaring periods is 6.1 × 10⁻⁵ L*, when L* is TRAPPIST-1's bolometric luminosity. We then construct a model that includes both atmospheric mass loss and tidal evolution and requires the planets to attain their present-day orbital elements during this coupled evolution. We use this model to constrain the ratio Q′ = 3Q/2k₂ for each planet. Finally, we use additional numerical models implemented with the Virtual Planet Simulator VPLanet to study ocean retention for these planets using our derived system parameters

Overview on jet results from STAR

Full jet reconstruction allows access to the parton kinematics over a large energy domain and can be used to constrain the mechanisms of energy loss in heavy-ion collisions. Such measurements are challenging at RHIC, due to the high-multiplicity environments created in heavy-ion collisions. In these proceedings, we report an overview of the results on full jet reconstruction obtained by the STAR experiment. Jet measurements in 200 GeV p+p show that jets are calibrated pQCD probes and provide a baseline for jet measurements in Au+Au collisions. Inclusive differential jet production cross sections and ratios are reported for central 200 GeV Au+Au collisions and compared to p+p. We also present measurements of fully reconstructed di-jets at mid-rapidity, and compare spectra and fragmentation functions in p+p and central Au+Au collisions.Comment: Proceedings for the 26th WWND conferenc

New insights into the role of atmospheric transport and mixing on column and surface concentrations of NO2 at a coastal urban site

We use a multi-year record of Pandora-derived NO2 total column abundance in Boston to examine the influence of atmospheric transport on column NO2 and its surface concentrations during the warm season in a coastal urban environment. We derive tropospheric NO2 estimates from the total column with a measurement-model fusion approach using near-real-time estimates of stratospheric NO2 from NASA’s GEOS-CF model system and find the average influence of stratospheric NO2 at this urban site can be 30-70% depending on season and time of day. Sea breeze days tend to exhibit rapid temporal variability in the column that which can go in the opposite direction of changes in surface NO2 concentrations. By comparing tropospheric NO2 with surface concentrations, we constrain the role of boundary layer entrainment processes in the evolution of surface NO2 concentrations, while highlighting the value of column measurements in identifying sea breeze frontal dynamics. We estimate an apparent equal mixing layer height of NO2 and infer that surface NOx emissions remain concentrated near the surface regardless of atmospheric stability regime. When comparing the Pandora- to TROPOMI-derived column NO2 measurements, we find that sea breeze days present a unique challenge likely due to higher spatial heterogeneity in NO2 and the meteorology involved that is not well represented in operational retrieval inputs. Our observations provide new insights into column and surface variability of NO2 which will be relevant to interpreting geostationary observations, especially in coastal urban locations.80NSSC18K0745 - NASAFirst author draf

Discretization of variational regularization in Banach spaces

Consider a nonlinear ill-posed operator equation $F(u)=y$ where $F$ is defined on a Banach space $X$. In general, for solving this equation numerically, a finite dimensional approximation of $X$ and an approximation of $F$ are required. Moreover, in general the given data \yd of $y$ are noisy. In this paper we analyze finite dimensional variational regularization, which takes into account operator approximations and noisy data: We show (semi-)convergence of the regularized solution of the finite dimensional problems and establish convergence rates in terms of Bregman distances under appropriate sourcewise representation of a solution of the equation. The more involved case of regularization in nonseparable Banach spaces is discussed in detail. In particular we consider the space of finite total variation functions, the space of functions of finite bounded deformation, and the $L^\infty$--space

ACUMEN: Amplifying Control and Understanding of Multiple ENtities

In virtual environments, the control of numerous entities in multiple dimensions can be difficult and tedious. In this paper, we present a system for synthesizing and recognizing aggregate movements in a virtual environment with a high-level (natural language) interface. The principal com- ponents include: an interactive interface for aggregate con- trol based on a collection of parameters extending an exist- ing movement quality model, a feature analysis of aggregate motion verbs, recognizers to detect occurrences of features in a collection of simulated entities, and a clustering algorithm that determines subgroups. Results based on simulations and a sample instruction application are shown