822 research outputs found
Visualizing Rank Deficient Models: A Row Equation Geometry of Rank Deficient Matrices and Constrained-Regression
Situations often arise in which the matrix of independent variables is not of full column rank. That is, there are one or more linear dependencies among the independent variables. This paper covers in detail the situation in which the rank is one less than full column rank and extends this coverage to include cases of even greater rank deficiency. The emphasis is on the row geometry of the solutions based on the normal equations. The author shows geometrically how constrained-regression/generalized-inverses work in this situation to provide a solution in the face of rank deficiency
Association Between Public Reporting of Outcomes With Procedural Management and Mortality for Patients With Acute Myocardial Infarction
AbstractBackgroundPublic reporting of procedural outcomes may create disincentives to provide percutaneous coronary intervention (PCI) for critically ill patients.ObjectivesThis study evaluated the association between public reporting with procedural management and outcomes among patients with acute myocardial infarction (AMI).MethodsUsing the Nationwide Inpatient Sample, we identified all patients with a primary diagnosis of AMI in states with public reporting (Massachusetts and New York) and regionally comparable states without public reporting (Connecticut, Maine, Maryland, New Hampshire, Rhode Island, and Vermont) between 2005 and 2011. Procedural management and in-hospital outcomes were stratified by public reporting.ResultsAmong 84,121 patients hospitalized with AMI, 57,629 (69%) underwent treatment in a public reporting state. After multivariate adjustment, percutaneous revascularization was performed less often in public reporting states than in nonreporting states (odds ratio [OR]: 0.81, 95% confidence interval [CI]: 0.67 to 0.96), especially among older patients (OR: 0.75, 95% CI: 0.62 to 0.91), those with Medicare insurance (OR: 0.75, 95% CI: 0.62 to 0.91), and those presenting with ST-segment elevation myocardial infarction (OR: 0.63, 95% CI: 0.56 to 0.71) or concomitant cardiac arrest or cardiogenic shock (OR: 0.58, 95% CI: 0.47 to 0.70). Overall, patients with AMI in public reporting states had higher adjusted in-hospital mortality rates (OR: 1.21, 95% CI: 1.06 to 1.37) than those in nonreporting states. This was observed predominantly in patients who did not receive percutaneous revascularization in public reporting states (adjusted OR: 1.30, 95% CI: 1.13 to 1.50), whereas those undergoing the procedure had lower mortality (OR: 0.71, 95% CI: 0.62 to 0.83).ConclusionsPublic reporting is associated with reduced percutaneous revascularization and increased in-hospital mortality among patients with AMI, particularly among patients not selected for PCI
Intensive HST, RXTE and ASCA Monitoring of NGC 3516: Evidence Against Thermal Reprocessing
During 1998 April 13-16, NGC 3516 was monitored almost continuously with HST
for 10.3 hr in the UV and 2.8 d in the optical, and simultaneous RXTE and ASCA
monitoring covered the same period. The X-rays were strongly variable with the
soft (0.5-2 keV) showing stronger variations (~65% peak-to-peak) than the hard
(2-10 keV; ~50% peak-to-peak). The optical continuum showed much smaller but
highly significant variations: a slow ~2.5% rise followed by a faster ~3.5%
decline. The short UV observation did not show significant variability.
The soft and hard X-ray light curves were strongly correlated with no
significant lag. Likewise, the optical continuum bands (3590 and 5510 A) were
also strongly correlated with no measurable lag above limits of <0.15 d.
However no significant correlation or simple relationship could be found for
the optical and X-ray light curves. These results appear difficult to reconcile
with previous reports of correlations between X-ray and optical variations and
of measurable lags within the optical band for some other Seyfert 1s.
These results also present serious problems for "reprocessing" models in
which the X-ray source heats a stratified accretion disk which then reemits in
the optical/ultraviolet: the synchronous variations within the optical would
suggest that the emitting region is <0.3 lt-d across, while the lack of
correlation between X-ray and optical variations would indicate, in the context
of this model, that any reprocessing region must be >1 lt-d in size. It may be
possible to resolve this conflict by invoking anisotropic emission or special
geometry, but the most natural explanation appears to be that the bulk of the
optical luminosity is generated by some other mechanism than reprocessing.Comment: 23 pages including 6 figures, accepted for publication in Ap
FIRST J102347.6+003841: The First Radio-Selected Cataclysmic Variable
We have identified the 1.4 GHz radio source FIRST J102347.6+003841 (hereafter
FIRST J1023+0038) with a previously unknown 17th-mag Galactic cataclysmic
variable (CV). The optical spectrum resembles that of a magnetic (AM Herculis-
or DQ Herculis-type) CV. Five nights of optical CCD photometry showed
variations on timescales of minutes to hours, along with rapid flickering. A
re-examination of the FIRST radio survey data reveals that the radio detection
was based on a single 6.6 mJy flare; on two other occasions the source was
below the ~1 mJy survey limit. Several other magnetic CVs are known to be
variable radio sources, suggesting that FIRST J1023+0038 is a new member of
this class (and the first CV to be discovered on the basis of radio emission).
However, FIRST J1023+0038 is several optical magnitudes fainter than the other
radio-detected magnetic CVs. It remains unclear whether the source simply had a
very rare and extraordinarily intense radio flare at the time of the FIRST
observation, or is really an unusually radio-luminous CV; thus further
observations are urged.Comment: 4 pages, 3 figures; accepted for December 2002 issue of Publications
of the Astronomical Society of the Pacifi
EVM and Achievable Data Rate Analysis of Clipped OFDM Signals in Visible Light Communication
Orthogonal frequency division multiplexing (OFDM) has been considered for
visible light communication (VLC) thanks to its ability to boost data rates as
well as its robustness against frequency-selective fading channels. A major
disadvantage of OFDM is the large dynamic range of its time-domain waveforms,
making OFDM vulnerable to nonlinearity of light emitting diodes (LEDs). DC
biased optical OFDM (DCO-OFDM) and asymmetrically clipped optical OFDM
(ACO-OFDM) are two popular OFDM techniques developed for the VLC. In this
paper, we will analyze the performance of the DCO-OFDM and ACO-OFDM signals in
terms of error vector magnitude (EVM), signal-to-distortion ratio (SDR), and
achievable data rates under both average optical power and dynamic optical
power constraints. EVM is a commonly used metric to characterize distortions.
We will describe an approach to numerically calculate the EVM for DCO-OFDM and
ACO-OFDM. We will derive the optimum biasing ratio in the sense of minimizing
EVM for DCO-OFDM. Additionally, we will formulate the EVM minimization problem
as a convex linear optimization problem and obtain an EVM lower bound against
which to compare the DCO-OFDM and ACO-OFDM techniques. We will prove that the
ACO-OFDM can achieve the lower bound. Average optical power and dynamic optical
power are two main constraints in VLC. We will derive the achievable data rates
under these two constraints for both additive white Gaussian noise (AWGN)
channel and frequency-selective channel. We will compare the performance of
DCO-OFDM and ACO-OFDM under different power constraint scenarios
At Sea Test 2 recovery cruise : Cruise 206 on board R/V Knorr April 10 - 15, 2012 Woods Hole - Woods Hole, MA
The R/V Knorr, on Cruise 206, carried out the recovery of three moorings for the Coastal
and Global Scale Nodes (CGSN) Implementing Organization of the NSF Ocean
Observatories Initiative. These three moorings are prototypes of the moorings to be used
by CGSN at the Pioneer, Endurance, and Global Arrays. Knorr departed from Woods
Hole, Massachusetts on April 10, 2012 and steamed south to the location of the mooring
deployments on the shelf break. Over five days, April 10-15, Knorr surveyed the bottom
at the planned mooring sites, recovered the moorings, and carried out preliminary
investigations of mechanical and electrical functionality on the recovered moorings and
mooring hardware, including observations of biofouling and corrosion. Knorr returned to
Woods Hole on April 15, 2012.Funding was provided by the National Science Foundation contract #SA9-10 through the
Consortium for Ocean Leadershi
At Sea Test 2 deployment cruise : cruise 475 on board R/V Oceanus September 22 – 26, 2011 Woods Hole –Woods Hole, MA
The R/V Oceanus, on Cruise 475, carried out the deployment of three moorings for the
Coastal and Global Scale Nodes (CGSN) Implementing Organization of the NSF Ocean
Observatories Initiative. These three moorings are prototypes of the moorings to be used
by CGSN at the Pioneer, Endurance, and Global Arrays. Oceanus departed from Woods
Hole, Massachusetts on September 22, 2011 and steamed south to the location of the
mooring deployments on the shelf break. Over three days, September 23-25, Oceanus
surveyed the bottom at the planned mooring sites, deployed the moorings, and carried out
on site verification of the functioning of the moorings and moored hardware. Oceanus
returned to Woods Hole on September 26, 2011.Funding was provided by the National Science Foundation
through the Consortium for Ocean Leadershi
Effects of an active warm-up on variation in bench press and back squat (upper and lower body measures).
The present study investigated the magnitude of diurnal variation in back squat and bench press using the MuscleLab linear encoder over three different loads and assessed the benefit of an active warm-up to establish whether diurnal variation could be negated. Ten resistance-trained males underwent (mean ± SD: age 21.0 ± 1.3 years, height 1.77 ± 0.06 m, and body mass 82.8 ± 14.9 kg) three sessions. These included control morning (M, 07:30 h) and evening (E, 17:30 h) sessions (5-min standardized warm-up at 150 W, on a cycle ergometer), and one further session consisting of an extended active warm-up morning trial (ME, 07:30 h) until rectal temperature (Trec) reached previously recorded resting evening levels (at 150 W, on a cycle ergometer). All sessions included handgrip, followed by a defined program of bench press (at 20, 40, and 60 kg) and back squat (at 30, 50, and 70 kg) exercises. A linear encoder was attached to an Olympic bar used for the exercises and average force (AF), peak velocity (PV), and time to peak velocity (tPV) were measured (MuscleLab software; MuscleLab Technology, Langesund, Norway) during the concentric phase of the movements. Values for Trec were higher in the E session compared to values in the M session (Δ0.53 °C, P  0.05) to increase from M to E levels. Therefore, MuscleLab linear encoder could detect meaningful differences between the morning and evening for all variables. However, the diurnal variation in bench press and back squat (measures of lower and upper body force and power output) is not explained by time-of-day oscillations in Trec
Delivery of Dark Material to Vesta via Carbonaceous Chondritic Impacts
NASA's Dawn spacecraft observations of asteroid (4) Vesta reveal a surface
with the highest albedo and color variation of any asteroid we have observed so
far. Terrains rich in low albedo dark material (DM) have been identified using
Dawn Framing Camera (FC) 0.75 {\mu}m filter images in several geologic
settings: associated with impact craters (in the ejecta blanket material and/or
on the crater walls and rims); as flow-like deposits or rays commonly
associated with topographic highs; and as dark spots (likely secondary impacts)
nearby impact craters. This DM could be a relic of ancient volcanic activity or
exogenic in origin. We report that the majority of the spectra of DM are
similar to carbonaceous chondrite meteorites mixed with materials indigenous to
Vesta. Using high-resolution seven color images we compared DM color properties
(albedo, band depth) with laboratory measurements of possible analog materials.
Band depth and albedo of DM are identical to those of carbonaceous chondrite
xenolith-rich howardite Mt. Pratt (PRA) 04401. Laboratory mixtures of Murchison
CM2 carbonaceous chondrite and basaltic eucrite Millbillillie also show band
depth and albedo affinity to DM. Modeling of carbonaceous chondrite abundance
in DM (1-6 vol%) is consistent with howardite meteorites. We find no evidence
for large-scale volcanism (exposed dikes/pyroclastic falls) as the source of
DM. Our modeling efforts using impact crater scaling laws and numerical models
of ejecta reaccretion suggest the delivery and emplacement of this DM on Vesta
during the formation of the ~400 km Veneneia basin by a low-velocity (<2
km/sec) carbonaceous impactor. This discovery is important because it
strengthens the long-held idea that primitive bodies are the source of carbon
and probably volatiles in the early Solar System.Comment: Icarus (Accepted) Pages: 58 Figures: 15 Tables:
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Personalized Genetic Risk Counseling to Motivate Diabetes Prevention: A randomized trial
OBJECTIVE To examine whether diabetes genetic risk testing and counseling can improve diabetes prevention behaviors. RESEARCH DESIGN AND METHODS We conducted a randomized trial of diabetes genetic risk counseling among overweight patients at increased phenotypic risk for type 2 diabetes. Participants were randomly allocated to genetic testing versus no testing. Genetic risk was calculated by summing 36 single nucleotide polymorphisms associated with type 2 diabetes. Participants in the top and bottom score quartiles received individual genetic counseling before being enrolled with untested control participants in a 12-week, validated, diabetes prevention program. Middle-risk quartile participants were not studied further. We examined the effect of this genetic counseling intervention on patient self-reported attitudes, program attendance, and weight loss, separately comparing higher-risk and lower-risk result recipients with control participants. RESULTS The 108 participants enrolled in the diabetes prevention program included 42 participants at higher diabetes genetic risk, 32 at lower diabetes genetic risk, and 34 untested control subjects. Mean age was 57.9 ± 10.6 years, 61% were men, and average BMI was 34.8 kg/m2, with no differences among randomization groups. Participants attended 6.8 ± 4.3 group sessions and lost 8.5 ± 10.1 pounds, with 33 of 108 (30.6%) losing ≥5% body weight. There were few statistically significant differences in self-reported motivation, program attendance, or mean weight loss when higher-risk recipients and lower-risk recipients were compared with control subjects (P > 0.05 for all but one comparison). CONCLUSIONS Diabetes genetic risk counseling with currently available variants does not significantly alter self-reported motivation or prevention program adherence for overweight individuals at risk for diabetes
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