358 research outputs found
A matrix-less and parallel interpolation–extrapolation algorithm for computing the eigenvalues of preconditioned banded symmetric Toeplitz matrices
No full textIn the past few years, Bogoya, Boettcher, Grudsky, and Maximenko obtained the precise asymptotic expansion for the eigenvalues of a Toeplitz matrix
T_n(f), under suitable assumptions on the generating function f , as the matrix size n goes to infinity. On the basis of several numerical experiments, it was conjectured by Serra-Capizzano that a completely analogous expansion also holds for the eigenvalues of the preconditioned Toeplitz matrix T_n(u)^{-1}*T_n(v), provided f = v/u is monotone and further conditions on u and v are satisfied. Based on this expansion, we here propose and analyze an interpolation–extrapolation algorithm for computing the eigenvalues of T_n(u)^{−1}*T_n(v). The algorithm is suited for parallel implementation and it may be called “matrix-less” as it does not need to store the entries of the matrix. We illustrate the performance of the algorithm through numerical experiments and
we also present its generalization to the case where f = v/u is non-monotone
The molecular electric quadrupole moment and electric-field-gradient induced birefringence (Buckingham effect) of Cl2
No full textAn ab initio investigation of the molecular properties rationalizing the electric-field-gradient induced birefringence
(Buckingham effect) for Cl2 is presented. The quadrupole moment is determined using hierarchies of basis sets and wavefunction
models. The electric dipole polarizability, the dipole – dipole – quadrupole and dipole – dipole – magnetic dipole
hyperpolarizabilities are determined exploiting a Coupled Cluster Singles and Doubles (CCSD) response approach. The properties
are zero-point vibrationally averaged, and the contribution of excited ro-vibrational states accounted for. To this end, the
interatomic 1Σ+g ground state potential has been computed at CCSD plus perturbative triples – CCSD(T) – level employing a
large augmented correlation consistent basis set. The effect of relativity is estimated at the Dirac-Hartree-Fock level. Our best
value for the quadrupole moment of Cl2 is (2.327 ± 0.010) au and it is in excellent agreement with experiment which, after
revision and dependent on the procedure employed for correcting the original estimate of (2.24 ± 0.04) au of Graham et al.,
[Mol. Phys., 93, 49, (1998)], ranges from (2.31 ± 0.04) au to (2.36 ± 0.04) au
The molecular electric quadrupole moment and electric-field-gradientinduced birefringence (Buckingham effect) of Cl2
No full textEigenvalue Isogeometric Approximations Based on B-Splines: Tools and Results
No full textIn this note, we focus on the spectral analysis of large matrices coming from isogeometric approximations based on B-splines of the eigenvalue problem (Formula Presented) where u(0) and u(1) are given. When considering the collocation case, global distribution results for the eigenvalues are available in the literature, despite the nonsymmetry of the related matrices. Here we complement such results by providing precise estimates for the extremal eigenvalues and hence for the spectral conditioning of the resulting matrices. In the Galerkin setting, the matrices are symmetric and positive definite and a more complete analysis has been conducted in the literature. In the latter case we furnish a further procedure that gives a highly accurate estimate of all the eigenvalues, starting from the knowledge of the spectral distribution symbol. The techniques involve dyadic decomposition arguments, tools from the theory of generalized locally Toeplitz sequences, and basic extrapolation methods
Probing the potential energy surface by high-resolution x-ray absorption spectroscopy: The umbrella motion of the core-excited CH3 free radical
No full textA detailed study of the umbrellalike vibration in inner-shell spectroscopy is presented. The high-resolution
x-ray absorption spectrum for the lowest lying core excitation of the CH3 free radical was recorded. High
quality potential energy surfaces PES for the initial and final states of the transition were calculated as a
function of the symmetrical stretching and the umbrella deformation coordinates. The strong anharmonicity
along the umbrella coordinate in the double-well region of the PES of the core excited state has a strong effect
on the bending vibrational progressions. The excellent agreement between the experiment and theory allows an
accurate spectroscopic characterization of the vibrational structure of the electronic transition, and the estimation
of the umbrella inversion time of 149 fs
The umbrella motion of core-excited CH3 and CD3 methyl radicals
No full textAn accurate experimental and theoretical study of the lowest core excitation of CH3 and CD3 methyl
radicals is presented. The complex vibrational structure of the lowest band of the x-ray absorption
spectrum XAS is due to the large variation of the molecular geometry, which is planar in the
ground state and pyramidal in the core-excited state. The XAS spectra of the two radicals were
recorded at high resolution and assigned by theoretical simulations of the spectra, taking into
account the coupling of symmetrical stretching and symmetrical bending umbrellalike
deformations of the radicals. An excellent agreement between experimental and theoretical spectral
profiles allowed us to accurately characterize the vibrational structure of the electronic transition.
The similarities, as well as the differences, of the peculiar vibrational progression observed for the
two radicals are explained by the strong anharmonicity along the umbrella coordinate and by the
isotopic variation, leading to a different probing of the double-well potential energy surface of the
core excited state during the nuclear motion
Corrigendum: The Body Odor Disgust Scale (BODS): Development and validation of a novel olfactory disgust assessment [Chem. Senses, (2016) (1-10)] doi: 10.1093/chemse/bjw107
No full textIn "The Body Odor Disgust Scale (BODS): Development and Validation of a Novel Olfactory Disgust Assessment" by Marco Tullio Liuzza et al., the sentence in section "Confirmatory factor analysis", "One hundred sixty-eight participants (49.6%) defined themselves as female." should be "One hundred twenty-eight participants (49.6%) defined themselves as female.". This has been corrected in print and online. The author regrets this error
Substance Use Disorder Relapse and Readmission
No full textabstract: According to the National Institute on Drug Abuse (NIDA), tobacco, alcohol, and illicit drugs accounted for 820 billion dollars in costs related to crime, lost work productivity, and health care services. Nearly 20 million Americans suffer from substance misuse, but only 3.7 million received treatment. Of those who receive treatment, the risk of relapse is high, ranging from 40-60% within a year of treatment. Improvement in the treatment of substance use disorders (SUD)
is necessary to improve the health of our society. Current literature demonstrates that individualized recovery plans and follow-up care are effective in reducing relapse and readmission. Costs to the individual, institution, and healthcare system can be reduced. This project aimed to decrease the risk for relapse and readmission with recovery plan reviews at 72hrs, and two-weeks, post-discharge. The risk of relapse was measured by the Time-To-Relapse questionnaire and the UCLA loneliness scale. The project took place in a residential treatment facility in Phoenix, Arizona. There were five participants initially; two were lost at the two-week follow-up. Pre and post-test results were compared to measure potential predictability of relapse. The two-tailed paired samples t-test was performed to compare the means of the scores but yielded insignificant results. All participants maintained sobriety. Qualitative data via interview showed positive results demonstrated by statements from the participants. Recovery plan review
with follow-up care is a promising evidence-based practice that can be implemented to help individuals maintain sobriety. Additional research is recommended to examine further the impact on the maintenance of sobriety over time
The Effect of Chess Training on the Development of Cognitive Abilities
No full textIstraživanjem se željelo utvrditi hoće li sustavna šahovska poduka utjecati na razvoj kognitivnih sposobnosti kod učenika nižih razreda osnovne škole. Neki raniji autori su nakon uvođenja šahovske poduke pronašli poboljšanje na mjerama pamćenja, vizualno-spacijalnih sposobnosti, numeričkih vještina, opće inteligencije te drugih sposobnosti. U istraživanju je sudjelovao 51 učenik drugog i trećeg razreda u dvije osnovne škole iz grada Zagreba. Eksperimentalnu skupinu (N=21) činili su učenici koji su početkom školske godine 2008./2009. po prvi put upisali školu šaha kao izvannastavnu aktivnost, a kontrolnu skupinu (N=30) činili su njihovi razredni kolege koji se nisu bavili šahom. Provedena su dva mjerenja u razmaku od godine i pol dana. Korišteni su Test identičnih slika i Test rotacije karata iz baterije French Kit (French, Ekstrom i Price, 1963.) te zadaci za mjerenje opsega kratkoročnog pamćenja i radnog pamćenja. Rezultati su pokazali da eksperimentalna skupina u drugom mjerenju nije pokazala statistički značajno veći napredak u odnosu na prvo mjerenje u usporedbi s kontrolnom skupinom, iako su se razlike među skupinama u odnosu na prvo mjerenje povećale.The aim of this study was to determine whether systematic chess training could influence the development of elementary school pupils’ cognitive abilities. Some earlier authors have found an improvement in visuospatial abilities, numerical skills, general intelligence and other abilities after introducing chess training. 51 second and third grade pupils from two elementary schools in the city of Zagreb participated in the study. The experimental group (N=21) was formed of pupils who enrolled in chess course as an extracurricular activity for the first time in school year 2008/2009, and the control group was formed of their classmates who did not study chess. Data was collected twice during one and a half years, using Identical Pictures Test and Card Rotations Test from the French Kit (French, Ekstrom and Price, 1963) and tasks for measuring short-term memory and working memory. The results showed that the experimental group did not show statistically significant improvement over the control group in the second measuring compared to the first, although the differences between the two groups had increased in the second measuring
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