1,978 research outputs found
An analytically solvable three-body problem
The problem of three particles interacting through harmonic forces is
discussed within the Newtonian formalism. By means of a didactic approach, an
exact analytical solution is found, and ways to extend it to the N-body case
are pointed out.Comment: In Portuguese. To appear in Revista Brasileira de Ensino de Fisica
(RBEF
The Stellar Content of Obscured Galactic Giant HII Regions. VI: W51A
We present K-band spectra of newly born OB stars in the obscured Galactic
giant H II region W51A and ~ 0.8'' angular resolution images in the J, H and
K_S-bands. Four objects have been spectroscopically classified as O-type stars.
The mean spectroscopic parallax of the four stars gives a distance of 2.0 \pm
0.3 kpc (error in the mean), significantly smaller than the radio recombination
line kinematic value of 5.5 kpc or the values derived from maser propermotion
observations (6--8 kpc). The number of Lyman continuum photons from the
contribution of all massive stars (NLyc ~ 1.5 x 10^{50} s^{-1}) is in good
agreement with that inferred from radio recombination lines (NLyc = 1.3 x
10^{50} s^{-1}) after accounting for the smaller distance derived here.
We present analysis of archival high angular resolution images (NAOS CONICA
at VLT and T-ReCS at Gemini) of the compact region W51 IRS2. The K_S--band
images resolve the infrared source IRS~2 indicating that it is a very young
compact HII region. Sources IRS2E was resolved into compact cluster (within 660
AU of projected distance) of 3 objects, but one of them is just bright extended
emission. W51d1 and W51d2 were identified with compact clusters of 3 objects
(maybe 4 in the case of W51d1) each one. Although IRS~2E is the brightest
source in the K-band and at 12.6 \micron, it is not clearly associated with a
radio continuum source. Our spectrum of IRS~2E shows, similar to previous work,
strong emission in Br and HeI, as well as three forbidden emission
lines of FeIII and emission lines of molecular hydrogen (H_2) marking it as a
massive young stellar object.Comment: 31 pages and 9 figures, submitted to A
Leveraging Previous Facial Action Units Knowledge for Emotion Recognition on Faces
People naturally understand emotions, thus permitting a machine to do the
same could open new paths for human-computer interaction. Facial expressions
can be very useful for emotion recognition techniques, as these are the biggest
transmitters of non-verbal cues capable of being correlated with emotions.
Several techniques are based on Convolutional Neural Networks (CNNs) to extract
information in a machine learning process. However, simple CNNs are not always
sufficient to locate points of interest on the face that can be correlated with
emotions. In this work, we intend to expand the capacity of emotion recognition
techniques by proposing the usage of Facial Action Units (AUs) recognition
techniques to recognize emotions. This recognition will be based on the Facial
Action Coding System (FACS) and computed by a machine learning system. In
particular, our method expands over EmotiRAM, an approach for multi-cue emotion
recognition, in which we improve over their facial encoding module
NiO-nanoflowers decorating a plastic electrode for the non-enzymatic amperometric detection of H2O2 in milk: old issue, new challenge
In food supply chain, there are regulatory limitations on the use of chemicals for cleaning processing lines
since the healthiness of the commodities must be guaranteed if accidentally traces of these detergents and
sanitizers pass to them. Hydrogen peroxide, is a commonly used sanitizer in the cleaning of the food
processing lines having both bactericidal and bacteriostatic properties, however, it produces inflammatory
effects on the human body. The availability of rapid systems to detect its accidental presence is therefore
useful to speed up the control and apply corrective actions. In the present work, a drop casting and easily
prepared plastic graphite / PVC electrode decorated with NiO nanostructures has been investigated as
electrochemical sensor for the non-enzymatic amperometric determination of H2O2. 24 The catalytic activity,
dispersion, and stability of NiO nanostructures mixed with plastic nanocomposite electrode have been studied
in detail. The preparation method, particularly the precipitating agents used in the synthesis of NiO
nanostructures strongly influenced their morphology and porosity. Further, the electrochemical response of
NiO-PE electrodes towards H2O2 resulted to be morphology-dependent. The non-enzymatic electrochemical
sensor was optimized for the rapid and sensitive detection of H2O2 present in milk with no sample pre-
treatments. NiO nanoflowers showed the best catalytic activity towards H2O2, a linear range that extends up
to 4 mM and a LOD of 5 μM (3sd of the blank signal) were obtained
Incidence of, predictors for, and mortality associated with malignant ventricular arrhythmias in non-ST elevation myocardial infarction patients.
BACKGROUND: The incidence of non-ST elevation myocardial infarction (NSTEMI) is increasing. Although life-threatening ventricular arrhythmias have been well-documented in patients with ST elevation MI (STEMI), their incidence and importance in NSTEMI have not been examined in similar detail. We examined the incidence, predictors, and mortality rates of ventricular arrhythmias in a cohort of NSTEMI patients undergoing an early invasive strategy.
METHODS: Consecutive patients admitted with NSTEMI who underwent cardiac catheterization within 48 h of admission were identified by chart review. Presence and type of ventricular arrhythmias and 30-day mortality were recorded. Malignant arrhythmias were defined as sustained ventricular tachycardia (VT, \u3e100 beats/min lasting \u3e30 s) or fibrillation (VF). Clinical risk factors, laboratory values, findings on electrocardiogram, echocardiogram, cardiac catheterization, and revascularization procedure data were recorded.
RESULTS: VT/VF occurred in 21 (7.6%) of 277 NSTEMI patients. Sixty percent of these events occurred within the first 48 h after hospital admission, with a median occurrence at 72 h. Twelve patients (4.3%) required defibrillation. Troponin levels were higher and left ventricular ejection fraction was lower in the VT/VF group. Multivariable analysis also identified the presence of left bundle branch block and need for urgent coronary artery bypass grafting as significant predictors of malignant ventricular arrhythmias. Thirty-day mortality was significantly higher in NSTEMI patients with malignant ventricular arrhythmias than without (38 vs. 3%, P\u3c0.001).
CONCLUSION: Despite an early invasive strategy, malignant ventricular arrhythmias are frequent in NSTEMI patients and are associated with increased 30-day mortality
Distribution of left ventricular ejection fraction in angina patients with severe coronary artery disease not amenable to revascularization.
BACKGROUND: As the number of angina patients with severe coronary artery disease not amenable to revascularization increases, new therapies will be developed. How patients with depressed compared to normal left ventricular ejection fraction (LVEF) will respond to new therapies may differ.
HYPOTHESIS: We conducted a retrospective chart review to determine the distribution of LVEF in angina patients with severe coronary artery disease (three-vessel disease with \u3e50% stenosis major epicardial vessels or \u3e50% stenosis left main) not amenable to revascularization.
METHODS: Patients underwent cardiac catheterization between 2004 and 2009. LVEF, measured by echocardiography, nuclear-gated imaging or radioventriculography within 6 months of catheterization, was recorded. Demographics, symptoms, risk factors, past myocardial infarction, catheterization results, medications, and the Duke Coronary Artery Jeopardy Score were recorded.
RESULTS: Eight thousand six hundred and ninety-nine patient charts were reviewed; 124 met criteria. There was a continuous, and not bimodal, distribution of LVEF. Fifty-eight patients (47%) in the normal LVEF group were compared to 66 patients (53%) in the abnormal LVEF group (
CONCLUSION: There is a wide distribution of LVEF among angina patients not amenable to revascularization. A novel finding of this study showed that mortality was high regardless of LVEF. As new therapies for angina are developed, attention will need to be paid to how such therapies affect these two patient groups
Stereotyping and the treatment of missing data for drug and alcohol clinical trials
Stigma and stereotyping of marginalized groups often is insidious and shows up in unlikely places, for instance in how clinical trials consider dropouts in treatment research. A surprising number of studies presume that people who do not complete the study protocol relapse and code their data as if they had been observed. There is no good statistical rationale for this treatment of missing data and numerous and more defensible alternative methods are available. We need to be mindful about our attitudes and preconceptions about the people we are intending to help. There is no good reason to continue to support science built on this scientifically indefensible stereotyping, however unintentional
- …