2,056 research outputs found
The nucleus of 103P/Hartley 2, target of the EPOXI mission
103P/Hartley 2 was selected as the target comet for the Deep Impact extended
mission, EPOXI, in October 2007. There have been no direct optical observations
of the nucleus of this comet, as it has always been highly active when
previously observed. We aimed to recover the comet near to aphelion, to a)
confirm that it had not broken up and was in the predicted position, b) to
provide astrometry and brightness information for mission planning, and c) to
continue the characterisation of the nucleus. We observed the comet at
heliocentric distances between 5.7 and 5.5 AU, using FORS2 at the VLT, at 4
epochs between May and July 2008. We performed VRI photometry on deep stacked
images to look for activity and measure the absolute magnitude and therefore
estimate the size of the nucleus. We recovered the comet near the expected
position, with a magnitude of m_R = 23.74 \pm 0.06 at the first epoch. The
comet had no visible coma, although comparison of the profile with a stellar
one showed that there was faint activity, or possibly a contribution to the
flux from the dust trail from previous activity. This activity appears to fade
at further epochs, implying that this is a continuation of activity past
aphelion from the previous apparition rather than an early start to activity
before the next perihelion. Our data imply a nucleus radius of \le 1 km for an
assumed 4% albedo; we estimate a ~6% albedo. We measure a colour of (V-R) = 0.
26 \pm 0.09.Comment: 5 pages, 4 figures, accepted for publication in A&
The Performance of Adults of Various Grade Levels on Specific Mental Functions
Test items designed to measure general intelligence, mechanical information and personality balance were selected from the Motor Vehicle Test, Series I, Revised, of Iowa State College, and administered to 220 Civilian Conservation Corps enrollees
Solar-insolation-induced changes in the coma morphology of comet 67P/Churyumov-Gerasimenko. Optical monitoring with the Nordic Optical Telescope
Context. 67P/Churyumov-Gerasimenko (67P/C-G) is a short-period Jupiter family comet with an orbital period of 6.55 years. Being
the target comet of ESA’s Rosetta mission, 67P/C-G has become one of the most intensively studied minor bodies of the Solar System.
The Rosetta Orbiter and the Philae Lander have brought us unique information about the structure and activity of the comet nucleus,
as well as its activity along the orbit, composition of gas, and dust particles emitted into the coma. However, as Rosetta stayed in very
close proximity to the cometary nucleus (less than 500 km with a few short excursions reaching up to 1500 km), it could not see the
global picture of a coma at the scales reachable by telescopic observations (103 - 105 km).
Aims. In this work we aim to connect in-situ observations made by Rosetta with the morphological evolution of the coma structures monitored by the ground-based observations. In particular, we concentrate on causal relationships between the coma morphology and evolution observed with the Nordic Optical Telescope (NOT) in the Canary Islands, and the seasonal changes of the insolation and the activity of the comet observed by the Rosetta instruments.
Methods. Comet 67P/C-G was monitored with the NOT in imaging mode in two colors. Imaging optical observations were performed roughly on a weekly basis, which provides good coverage of short- and long-term variability. With the three dimensional modeling of the coma produced by active regions on the Southern Hemisphere, we aim to qualify the observed morphology by connecting it to the activity observed by Rosetta.
Results. During our monitoring program, we detected major changes in the coma morphology of comet 67P/C-G. These were longterm and long-lasting changes. They do not represent any sudden outburst or short transient event, but are connected to seasonal changes of the surface insolation and the emergence of new active regions on the irregular shaped comet nucleus. We have also found significant deviations in morphological changes from the prediction models based on previous apparitions of 67P/C-G, like the time delay of the morphology changes and the reduced activity in the Northern Hemisphere. According to our modeling of coma structures and geometry of observations, the changes are clearly connected with the activity in the Southern Hemisphere observed by the Rosetta spacecraft
Differential rotation measurement of soft X-Ray corona
The aim of this paper is to study the latitudinal variation in the solar
rotation in soft X-ray corona. The time series bins are formed on different
latitude regions of the solar full disk (SFD) images that extend from 80 degree
South to 80 degree North. These SFD images are obtained with the soft X-ray
telescope (SXT) on board the Yohkoh solar observatory. The autocorrelation
analyses are performed with the time series that track the SXR flux modulations
in the solar corona. Then for each year, extending from 1992 to 2001, we obtain
the coronal sidereal rotation rate as a function of the latitude. The present
analysis from SXR radiation reveals that; (i) the equatorial rotation rate of
the corona is comparable to the rotation rate of the photosphere and the
chromosphere, (ii) the differential profile with respect to the latitude varies
throughout the period of the study; it is more in the year 1999 and least in
1994 and (iii) the equatorial rotation period varies systematically with
sunspot numbers and indicates its dependence on the phases of the solar
activity cycle.Comment: 9 Pages, 4 Figures, Accepted for Publication in MNRA
Frozen to death? -- Detection of comet Hale-Bopp at 30.7 AU
Comet Hale--Bopp (C/1995 O1) has been the single most significant comet
encountered by modern astronomy, still having displayed significant activity at
25.7 AU solar distance in late 2007. It is a puzzling question when and where
this activity will finally cease. Here we present new observations with the ESO
2.2m telescope at La Silla to check the activity of Hale--Bopp at 30.7 AU solar
distance. On 2010-12-04, 26 CCD images were taken with 180 s exposure times for
photometry and morphology. The comet was detected in R and had a total
brightness of 23.3+-0.2 mag, referring to an absolute brightness of
R(1,1,0)=8.3. The profile of the coma was star-like at a seeing of 1.9",
without any evidence of a coma or tail extending farther than 2.5" (=55,000 km
in projection) and exceeding 26.5 mag/arcs^2 surface brightness. The measured
total brightness corresponds to a relative total reflecting surface, a_RC, of
485 km^2, nine times less than three years before. The calculated a_RC value
would imply a nucleus with 60--65 km radius assuming 4% albedo. This size
estimate is in significant contradiction with the previous results scattering
around 35 km. Therefore we suggest that the comet may still be in a low-level
activity, despite the lack of a prominent coma. Alternatively, if the nucleus
is already dormant, the albedo should be as high as 13%, assuming a radius of
35 km. With this observation, Hale--Bopp has been the most distant comet ever
observed, far beyond the orbit of Neptune.Comment: 4 pages, accepted by A&
A Comprehensive Survey of Brane Tilings
An infinite class of gauge theories can be engineered on
the worldvolume of D3-branes probing toric Calabi-Yau 3-folds. This kind of
setup has multiple applications, ranging from the gauge/gravity correspondence
to local model building in string phenomenology. Brane tilings fully encode the
gauge theories on the D3-branes and have substantially simplified their
connection to the probed geometries. The purpose of this paper is to push the
boundaries of computation and to produce as comprehensive a database of brane
tilings as possible. We develop efficient implementations of brane tiling tools
particularly suited for this search. We present the first complete
classification of toric Calabi-Yau 3-folds with toric diagrams up to area 8 and
the corresponding brane tilings. This classification is of interest to both
physicists and mathematicians alike.Comment: 39 pages. Link to Mathematica modules provide
Spitzer Space Telescope Observations of the Nucleus of Comet 103P/Hartley 2
We have used the Spitzer Space Telescope InfraRed Spectrograph (IRS) 22-μm peakup array to observe thermal emission from the nucleus and trail of comet 103P/Hartley 2, the target of NASA’s Deep Impact Extended Investigation (DIXI). The comet was observed on UT 2008 August 12 and 13, while 5.5 AU from the Sun. We obtained two 200 frame sets of photometric imaging over a 2.7 hr period. To within the errors of the measurement, we find no detection of any temporal variation between the two images. The comet showed extended emission beyond a point source in the form of a faint trail directed along the comet’s antivelocity vector. After modeling and removing the trail emission, a NEATM model for the nuclear emission with beaming parameter of 0.95 ± 0.20 indicates a small effective radius for the nucleus of 0.57 ± 0.08 km and low geometric albedo 0.028 ± 0.009 (1σ). With this nucleus size and a water production rate of 3 × 10^(28) molecules s^(-1) at perihelion, we estimate that ~100% of the surface area is actively emitting volatile material at perihelion. Reports of emission activity out to ~5 AU support our finding of a highly active nuclear surface. Compared to Deep Impact’s first target, comet 9P/Tempel 1, Hartley 2’s nucleus is one-fifth as wide (and about one-hundredth the mass) while producing a similar amount of outgassing at perihelion with about 13 times the active surface fraction. Unlike Tempel 1, comet Hartley 2 should be highly susceptible to jet driven spin-up torques, and so could be rotating at a much higher frequency. Since the amplitude of nongravitational forces are surprisingly similar for both comets, close to the ensemble average for ecliptic comets, we conclude that comet Hartley 2 must have a much more isotropic pattern of time-averaged outgassing from its nuclear surface. Barring a catastrophic breakup or major fragmentation event, the comet should be able to survive up to another 100 apparitions (~700 yr) at its current rate of mass loss
Long-term persistency and costs associated with the use of iron chelation therapies in the treatment of Sickle cell disease within Medicaid programs.
OBJECTIVE: This retrospective study evaluated iron chelating therapy (ICT) discontinuation and costs in Sickle cell disease (SCD) Medicaid recipients using healthcare claims from 2006-2010.
METHODS: Patients with ≥1 SCD diagnosis claim, ≥2 claims for deferoxamine (DFO) or deferosirox (DFX), and continuous enrollment ≥6 months prior to and 18 months following ICT initiation were included. Outcomes included treatment discontinuation, persistence (i.e., refill gaps ≥6 weeks), and total healthcare costs.
RESULTS: The average age among 404 SCD patients meeting study inclusion criteria was 18.7 (±11.0) years, with 45.8% being males and 66.7% being Blacks. Switches or combinations from DFO at index occurred in 124 (74.7%) patients compared to 10 (4.2%) with DFX at index. The Cox regression model that assessed long-term medication persistence indicated a 1.30-times higher likelihood of treatment discontinuation with DFO compared to DFX (95% CI: 1.06-1.61). Some 19.7% of patient remained on DFX relative to 4.8% on DFO. Both inpatient and total costs were similar in DFX and DFO treatment groups. Following 1 year of treatment, 37.4% remained on DFX compared to 15.7% on DFO. Meaningful differences in treatment discontinuation between the two treatment groups did not occur until 220+ days during the study period. At 18-months, treatment discontinuation rates were high in both groups; 95% for DFO and 80% for DFX.
CONCLUSION: This study of SCD Medicaid patients found more therapeutic switches from DFO to DFX and a higher medication persistency rate with DFX than DFO. The conclusions are limited by the study\u27s retrospective nature, which depends on multivariate statistics to account for patient heterogeneity and risk factors
P/2010 A2 LINEAR II: dynamical dust modelling
P/2010 A2 is an object on an asteroidal orbit that was observed to have an
extended tail or debris trail in January 2010. In this work, we fit the
outburst of P/2010 A2 with a conical burst model, and verify previous
suspicions that this was a one--time collisional event rather than an sustained
cometary outburst, implying that P/2010 A2 is not a new Main Belt Comet driven
by ice sublimation. We find that the best--fit cone opening angle is about 40
to 50 degrees, in agreement with numerical and laboratory simulations of
cratering events. Mapping debris orbits to sky positions suggests that the
distinctive arc features in the debris correspond to the same debris cone
inferred from the extended dust. From the velocity of the debris, and from the
presence of a velocity maximum at around 15 cm/s, we infer that the surface of
A2 probably has a very low strength (<1 kPa), comparable to lunar regolith.Comment: 14 pages, 25 figures; accepted by Astronomy and Astrophysic
The impact of a community pharmacist conducted comprehensive medication review (CMR) on 30-day re-admission rates and increased patient satisfaction scores: A pilot study
Objective: To determine the impact of pharmacist conducted Comprehensive Medication Review (CMR) follow-up within seven days after discharge on (1) readmission rates, (2) detection of drug related problems, (3) and changes in Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS) scores.
Design: Rates of re-admission for pneumonia, congestive heart failure (CHF), or myocardial infarction (MI), within 30 days of discharge are compared between patients receiving a CMR from the pharmacist to a historical control group not receiving the service. The CMR documentation is reviewed to classify any detected drug related problems. Overall HCAHPS scores for the hospital are compared for the three months prior to instituting this service and the three months during the service.
Setting: Patients were discharged from a 101-bed acute care hospital located in rural West Virginia. The community pharmacist worked with the hospital to contact patients after discharge to demonstrate a partnership between inpatient and outpatient care.
Patients: Patients were included if they had a discharge diagnosis of pneumonia, congestive heart failure (CHF), or myocardial infarction (MI), and were returning to self-care or family-care. If discharged between 10/12/2012 and 12/11/2012 they were included in the historical control group. If discharged between 12/12/2012 and 2/12/2012 they were offered the CMR service and included in the intervention group.
Intervention: Patients received a telephone call two to seven days following discharge from a pharmacist who conducted the Comprehensive Medication Review (CMR)
Results: Patients who participated in a CMR via the telephone had decreased 30-day readmission rates compared to the historical control group (16% v 33%). Overall 22 significant drug therapy problems were identified among patients. HCAHPS scores for the questions "Did you receive communication regarding your medications" increased during the study time period (65% vs 72%).
Conclusion: The mixed results of available data from previous studies on pharmacist inclusion in the discharge process focuses heavily on counseling before the patient is discharged. Results of this study show community pharmacist partnership in discharge follow-up can also assist in decreasing readmissions, detecting drug related problems, and increasing patient satisfaction.
Type: Original Researc
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