415 research outputs found
Exact solution of Schrodinger equation for modified Kratzer's molecular potential with the position-dependent mass
Exact solutions of Schrodinger equation are obtained for the modified Kratzer
and the corrected Morse potentials with the position-dependent effective mass.
The bound state energy eigenvalues and the corresponding eigenfunctions are
calculated for any angular momentum for target potentials. Various forms of
point canonical transformations are applied. PACS numbers: 03.65.-w; 03.65.Ge;
12.39.Fd Keywords: Morse potential, Kratzer potential, Position-dependent mass,
Point canonical transformation, Effective mass Schr\"{o}dinger equation.Comment: 9 page
Transit timing variation analysis of the low-mass brown dwarf KELT-1 b
We investigate whether there is a variation in the orbital period of the short-period brown dwarf-mass KELT-1 b, which is one of the best candidates to observe orbital decay. We obtain 19 high-precision transit light curves of the target using six different telescopes. We add all precise and complete transit light curves from open databases and the literature, as well as the available Transiting Exoplanet Survey Satellite (TESS) observations from sectors 17 and 57, to form a transit timing variation (TTV) diagram spanning more than 10 yr of observations. The analysis of the TTV diagram, however, is inconclusive in terms of a secular or periodic variation, hinting that the system might have synchronized. We update the transit ephemeris and determine an informative lower limit for the reduced tidal quality parameter of its host star of Q ′⋆>(8.5±3.9)×106
assuming that the stellar rotation is not yet synchronized. Using our new photometric observations, published light curves, the TESS data, archival radial velocities, and broadband magnitudes, we also update the measured parameters of the system. Our results are in good agreement with those found in previous analyses
Effective Mass Dirac-Morse Problem with any kappa-value
The Dirac-Morse problem are investigated within the framework of an
approximation to the term proportional to in the view of the
position-dependent mass formalism. The energy eigenvalues and corresponding
wave functions are obtained by using the parametric generalization of the
Nikiforov-Uvarov method for any -value. It is also studied the
approximate energy eigenvalues, and corresponding wave functions in the case of
the constant-mass for pseudospin, and spin cases, respectively.Comment: 12 page
Nitrogenase MoFe-Protein at 1.16 Ã… Resolution: A Central Ligand in the FeMo-Cofactor
A high-resolution crystallographic analysis of the nitrogenase MoFe-protein reveals a previously unrecognized ligand coordinated to six iron atoms in the center of the catalytically essential FeMo-cofactor. The electron density for this ligand is masked in structures with resolutions lower than 1.55 angstroms, owing to Fourier series termination ripples from the surrounding iron and sulfur atoms in the cofactor. The central atom completes an approximate tetrahedral coordination for the six iron atoms, instead of the trigonal coordination proposed on the basis of lower resolution structures. The crystallographic refinement at 1.16 angstrom resolution is consistent with this newly detected component being a light element, most plausibly nitrogen. The presence of a nitrogen atom in the cofactor would have important implications for the mechanism of dinitrogen reduction by nitrogenase
Analytical Solutions of Klein-Gordon Equation with Position-Dependent Mass for q-Parameter Poschl-Teller potential
The energy eigenvalues and the corresponding eigenfunctions of the
one-dimensional Klein-Gordon equation with q-parameter Poschl-Teller potential
are analytically obtained within the position-dependent mass formalism. The
parametric generalization of the Nikiforov-Uvarov method is used in the
calculations by choosing a mass distribution.Comment: 10 page
Exponential Type Complex and non-Hermitian Potentials in PT-Symmetric Quantum Mechanics
Using the NU method [A.F.Nikiforov, V.B.Uvarov, Special Functions of
Mathematical Physics, Birkhauser,Basel,1988], we investigated the real
eigenvalues of the complex and/or - symmetric, non-Hermitian and the
exponential type systems, such as Poschl-Teller and Morse potentials.Comment: 14 pages, Late
Transit timing variation analysis of the low-mass brown dwarf KELT-1Â b
We investigate whether there is a variation in the orbital period of the short-period brown dwarf-mass KELT-1 b, which is one of the best candidates to observe orbital decay. We obtain 19 high-precision transit light curves of the target using six different telescopes. We add all precise and complete transit light curves from open databases and the literature, as well as the available TESS observations from sectors 17 and 57, to form a transit timing variation (TTV) diagram spanning more than 10 years of observations. The analysis of the TTV diagram, however, is inconclusive in terms of a secular or periodic variation, hinting that the system might have synchronized. We update the transit ephemeris and determine an informative lower limit for the reduced tidal quality parameter of its host star of Q′⋆>(8.5±3.9)×106 assuming that the stellar rotation is not yet synchronised. Using our new photometric observations, published light curves, the TESS data, archival radial velocities and broadband magnitudes, we also update the measured parameters of the system. Our results are in good agreement with those found in previous analyses
Approximate Solution of the effective mass Klein-Gordon Equation for the Hulthen Potential with any Angular Momentum
The radial part of the effective mass Klein-Gordon equation for the Hulthen
potential is solved by making an approximation to the centrifugal potential.
The Nikiforov-Uvarov method is used in the calculations. Energy spectra and the
corresponding eigenfunctions are computed. Results are also given for the case
of constant mass.Comment: 12 page
A new approach to the exact solutions of the effective mass Schrodinger equation
Effective mass Schrodinger equation is solved exactly for a given potential.
Nikiforov-Uvarov method is used to obtain energy eigenvalues and the
corresponding wave functions. A free parameter is used in the transformation of
the wave function. The effective mass Schrodinger equation is also solved for
the Morse potential transforming to the constant mass Schr\"{o}dinger equation
for a potential. One can also get solution of the effective mass Schrodinger
equation starting from the constant mass Schrodinger equation.Comment: 14 page
Acute kidney injury prediction for non-critical care patients: a retrospective external and internal validation study
Background: Acute kidney injury (AKI), the decline of kidney excretory
function, occurs in up to 18% of hospitalized admissions. Progression of AKI
may lead to irreversible kidney damage. Methods: This retrospective cohort
study includes adult patients admitted to a non-intensive care unit at the
University of Pittsburgh Medical Center (UPMC) (n = 46,815) and University of
Florida Health (UFH) (n = 127,202). We developed and compared deep learning and
conventional machine learning models to predict progression to Stage 2 or
higher AKI within the next 48 hours. We trained local models for each site (UFH
Model trained on UFH, UPMC Model trained on UPMC) and a separate model with a
development cohort of patients from both sites (UFH-UPMC Model). We internally
and externally validated the models on each site and performed subgroup
analyses across sex and race. Results: Stage 2 or higher AKI occurred in 3%
(n=3,257) and 8% (n=2,296) of UFH and UPMC patients, respectively. Area under
the receiver operating curve values (AUROC) for the UFH test cohort ranged
between 0.77 (UPMC Model) and 0.81 (UFH Model), while AUROC values ranged
between 0.79 (UFH Model) and 0.83 (UPMC Model) for the UPMC test cohort.
UFH-UPMC Model achieved an AUROC of 0.81 (95% confidence interval [CI] [0.80,
0.83]) for UFH and 0.82 (95% CI [0.81,0.84]) for UPMC test cohorts; an area
under the precision recall curve values (AUPRC) of 0.6 (95% CI, [0.05, 0.06])
for UFH and 0.13 (95% CI, [0.11,0.15]) for UPMC test cohorts. Kinetic estimated
glomerular filtration rate, nephrotoxic drug burden and blood urea nitrogen
remained the top three features with the highest influence across the models
and health centers. Conclusion: Locally developed models displayed marginally
reduced discrimination when tested on another institution, while the top set of
influencing features remained the same across the models and sites
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