358 research outputs found
Environment as a Witness: Selective Proliferation of Information and Emergence of Objectivity in a Quantum Universe
We study the role of the information deposited in the environment of an open
quantum system in course of the decoherence process. Redundant spreading of
information -- the fact that some observables of the system can be
independently ``read-off'' from many distinct fragments of the environment --
is investigated as the key to effective objectivity, the essential ingredient
of ``classical reality''. This focus on the environment as a communication
channel through which observers learn about physical systems underscores
importance of quantum Darwinism -- selective proliferation of information about
``the fittest states'' chosen by the dynamics of decoherence at the expense of
their superpositions -- as redundancy imposes the existence of preferred
observables. We demonstrate that the only observables that can leave multiple
imprints in the environment are the familiar pointer observables singled out by
environment-induced superselection (einselection) for their predictability.
Many independent observers monitoring the environment will therefore agree on
properties of the system as they can only learn about preferred observables. In
this operational sense, the selective spreading of information leads to
appearance of an objective ``classical reality'' from within quantum substrate.Comment: New figures, to appear in PR
Cops & No Counselors: How the Lack of School Mental Health Staff Is Harming Students
This report examines data provided by the U.S. Department of Education\u27s Office of Civil Rights to better understand the prevalence of school-based mental health (SBMH) professionals in schools. Asserting that access to emotional, behavioral, and mental health supports are part of accessing a Free and Appropriate Education and are a civil right, Dr. Mann and her collaborators at the ACLU examine the impact of a lack of appropriate SBMH supports in schools. The report authors also examine the consequences of hardening of schools including the proliferation of law enforcement in schools
Objective properties from subjective quantum states: Environment as a witness
We study the emergence of objective properties in open quantum systems. In
our analysis, the environment is promoted from a passive role of reservoir
selectively destroying quantum coherence, to an active role of amplifier
selectively proliferating information about the system. We show that only
preferred pointer states of the system can leave a redundant and therefore
easily detectable imprint on the environment. Observers who--as it is almost
always the case--discover the state of the system indirectly (by probing a
fraction of its environment) will find out only about the corresponding pointer
observable. Many observers can act in this fashion independently and without
perturbing the system: they will agree about the state of the system. In this
operational sense, preferred pointer states exist objectively.Comment: 5 pages, 1 figure, extensive changes, presentation improve
Lessons Learned from Preparing OSIRIS-REx Spectral Analog Samples for Bennu
NASA\u27s OSIRIS-REx sample return mission launched on September 8th, 2016 to rendezvous with B-type hide asteroid (101955) Bennu in 2018. Type C and B asteroids have been linked to carbonaceous chondrites because of their similar visible - to - near infrared (VIS-NIR) spectral properties [e.g., 1,2]. The OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) and the Thermal Emission Spectrometer (OTES) will make spectroscopic observations of Bennu during the encounter. Constraining the presence or absence of hydrous minerals (e.g., Ca-carbonate, phyllosilicates) and organic molecules will be key to characterizing Bennu [3] prior to sample site selection. The goal of this study was to develop a suite of analog and meteorite samples and obtain their spectral properties over the wavelength ranges of OVIRS (0.4- 4.3 micrometer) and OTES (5.0-50 micrometer). These spectral data were used to validate the mission science-data processing system. We discuss the reasoning behind the study and share lessons learne
Asteroids Were Born Big
How big were the first planetesimals? We attempt to answer this question by
conducting coagulation simulations in which the planetesimals grow by mutual
collisions and form larger bodies and planetary embryos. The size frequency
distribution (SFD) of the initial planetesimals is considered a free parameter
in these simulations, and we search for the one that produces at the end
objects with a SFD that is consistent with asteroid belt constraints. We find
that, if the initial planetesimals were small (e.g. km-sized), the final SFD
fails to fulfill these constraints. In particular, reproducing the bump
observed at diameter D~100km in the current SFD of the asteroids requires that
the minimal size of the initial planetesimals was also ~100km. This supports
the idea that planetesimals formed big, namely that the size of solids in the
proto-planetary disk ``jumped'' from sub-meter scale to multi-kilometer scale,
without passing through intermediate values. Moreover, we find evidence that
the initial planetesimals had to have sizes ranging from 100 to several 100km,
probably even 1,000km, and that their SFD had to have a slope over this
interval that was similar to the one characterizing the current asteroids in
the same size-range. This result sets a new constraint on planetesimal
formation models and opens new perspectives for the investigation of the
collisional evolution in the asteroid and Kuiper belts as well as of the
accretion of the cores of the giant planets.Comment: Icarus (2009) in pres
Changing dental caries and periodontal disease patterns among a cohort of Ethiopian immigrants to Israel: 1999–2005
Dental profile of patients with Gaucher disease
BACKGROUND: This study was conducted to determine whether patients with Gaucher disease had significant dental pathology because of abnormal bone structure, pancytopenia, and coagulation abnormalities. METHODS: Each patient received a complete oral and periodontal examination in addition to a routine hematological evaluation. RESULTS: Gaucher patients had significantly fewer carious lesions than otherwise healthy carriers. Despite prevalence of anemia, there was no increase in gingival disease; despite the high incidence of thrombocytopenia, gingival bleeding was not noted; and despite radiological evidence of bone involvement, there was no greater incidence loss of teeth or clinical tooth mobility. CONCLUSIONS: These data represent the first survey of the oral health of a large cohort of patients with Gaucher disease. It is a pilot study of a unique population and the results of the investigation are indications for further research. Based on our findings, we recommend regular oral examinations with appropriate dental treatment for patients with Gaucher disease as for other individuals. Consultation between the dentist and physician, preferably one with experience with Gaucher disease, should be considered when surgical procedures are planned
Stellar Diameters and Temperatures VI. High angular resolution measurements of the transiting exoplanet host stars HD 189733 and HD 209458 and implications for models of cool dwarfs
We present direct radii measurements of the well-known transiting exoplanet
host stars HD 189733 and HD 209458 using the CHARA Array interferometer. We
find the limb-darkened angular diameters to be theta_LD = 0.3848 +/- 0.0055 and
0.2254 +/- 0.0072 milliarcsec for HD 189733 and HD 209458, respectively. HD
189733 and HD 209458 are currently the only two transiting exoplanet systems
where detection of the respective planetary companion's orbital motion from
high resolution spectroscopy has revealed absolute masses for both star and
planet. We use our new measurements together with the orbital information from
radial velocity and photometric time series data, Hipparcos distances, and
newly measured bolometric fluxes to determine the stellar effective
temperatures (T_eff = 4875 +/- 43, 6093 +/- 103 K), stellar linear radii (R_* =
0.805 +/- 0.016, 1.203 +/- 0.061 R_sun), mean stellar densities (rho_* = 1.62
+/- 0.11, 0.58 +/- 0.14 rho_sun), planetary radii (R_p = 1.216 +/- 0.024, 1.451
+/- 0.074 R_Jup), and mean planetary densities (rho_p = 0.605 +/- 0.029, 0.196
+/- 0.033 rho_Jup) for HD 189733 b and HD 209458 b, respectively. The stellar
parameters for HD 209458, a F9 dwarf, are consistent with indirect estimates
derived from spectroscopic and evolutionary modeling. However, we find that
models are unable to reproduce the observational results for the K2 dwarf, HD
189733. We show that, for stellar evolutionary models to match the observed
stellar properties of HD 189733, adjustments lowering the solar-calibrated
mixing length parameter from 1.83 to 1.34 need to be employed
The impact of hospital market structure on patient volume, average length of stay, and the cost of care
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