John B. Delos is a retired professor of physics, now manager of a research company. He is author of about 140 papers, guided 12 postdocs, and directed PhD dissertations of 18 graduate students. s. He held research grants from National Science Foundation, Office of Naval Research and National Institutes of health. He is Fellow of the American Physical Society (APS), was named Outstanding Scientist of Virginia (1990), and was elected Chair of the Division of Atomic, Molecular and Optical Physics of American Physical Society. For seven years he taught a Freshman Seminar titled “Ethical Issues in Men’s Lives” Supervisors: S.M. Blinder, undergraduate advisor. W.R. Thorson, PhD advisor.
Three quantum-mechanical computational techniques based on energy moments, μk= ∫ dqψ*(q)Hkψ(q), a... more Three quantum-mechanical computational techniques based on energy moments, μk= ∫ dqψ*(q)Hkψ(q), and semimoments, νk(q′)=[Hkψ(q)]q=q′, are formulated. The μ method, which employs the μk, is connected to the method of moments in probability theory, to the variational method, and to eigenvalue spectroscopy. The ν and λ methods, which employ semimoments, are related to local energy methods using one and several configuration points, respectively. An Nth-order calculation, requiring 2N moments or semimoments, yields N approximate eigenvalues and eigenfunctions. In accordance with a conjectured convergence criterion, exact eigenstates are approached in the limit N→∞. From quantities obtained in a moments calculation, a lower bound on the ground-state eigenvalue can also be determined using a refinement of Weinstein's criterion. A computational method for generating moments and semimoments is given and the μ method is applied to the linear harmonic oscillator.
ABSTRACT Total electron-detachment cross sections sigmae for collisions of F-, Cl-, Br-, and I- w... more ABSTRACT Total electron-detachment cross sections sigmae for collisions of F-, Cl-, Br-, and I- with atomic hydrogen have been measured for relative collision energies E ranging from 0.1 to 20 eV. For F-, Cl-, and Br-, sigmae is found to decrease with increasing E and is fairly well described by a simple orbiting model in which an effective polarizability is used to describe the interaction of the anion with atomic hydrogen at small internuclear separations. For the system I-+H, sigmae increases with increasing collision energy. The measured sigmae for Cl-+H is also found to agree well with calculations based on an effective-range approximation. Charge-transfer cross sections have been measured for F-, Cl-, and I-+H and are found to be small.
Objective This study aimed to evaluate the role of an objective physiologic biomarker, arterial b... more Objective This study aimed to evaluate the role of an objective physiologic biomarker, arterial blood pressure variability, for the early identification of adverse short-term electroencephalogram (EEG) outcomes in infants with hypoxic-ischemic encephalopathy (HIE). Study Design In this multicenter observational study, we analyzed blood pressure of infants meeting these criteria: (1) neonatal encephalopathy determined by modified Sarnat exam, (2) continuous mean arterial blood pressure (MABP) data between 18 and 27 hours after birth, and (3) continuous EEG performed for at least 48 hours. Adverse outcome was defined as moderate–severe grade EEG at 48 hours. Standardized signal preprocessing was used; the power spectral density was computed without interpolation. Multivariate binary logistic regression was used to identify which MABP time and frequency domain metrics provided improved predictive power for adverse outcomes compared with standard clinical predictors (5-minute Apgar scor...
Near-threshold photodetachment from negative atomic ions provides a virtually pointlike source of... more Near-threshold photodetachment from negative atomic ions provides a virtually pointlike source of electrons, and is ideally suited to study electron dynamics in externally applied electric and magnetic fields. These fields govern the motion of the emitted electron wave, and lead to characteristic modulations both in the total photocurrent and in the spatial electron distribution. These changes have been predicted and
Three quantum-mechanical computational techniques based on energy moments, μk= ∫ dqψ*(q)Hkψ(q), a... more Three quantum-mechanical computational techniques based on energy moments, μk= ∫ dqψ*(q)Hkψ(q), and semimoments, νk(q′)=[Hkψ(q)]q=q′, are formulated. The μ method, which employs the μk, is connected to the method of moments in probability theory, to the variational method, and to eigenvalue spectroscopy. The ν and λ methods, which employ semimoments, are related to local energy methods using one and several configuration points, respectively. An Nth-order calculation, requiring 2N moments or semimoments, yields N approximate eigenvalues and eigenfunctions. In accordance with a conjectured convergence criterion, exact eigenstates are approached in the limit N→∞. From quantities obtained in a moments calculation, a lower bound on the ground-state eigenvalue can also be determined using a refinement of Weinstein's criterion. A computational method for generating moments and semimoments is given and the μ method is applied to the linear harmonic oscillator.
ABSTRACT Total electron-detachment cross sections sigmae for collisions of F-, Cl-, Br-, and I- w... more ABSTRACT Total electron-detachment cross sections sigmae for collisions of F-, Cl-, Br-, and I- with atomic hydrogen have been measured for relative collision energies E ranging from 0.1 to 20 eV. For F-, Cl-, and Br-, sigmae is found to decrease with increasing E and is fairly well described by a simple orbiting model in which an effective polarizability is used to describe the interaction of the anion with atomic hydrogen at small internuclear separations. For the system I-+H, sigmae increases with increasing collision energy. The measured sigmae for Cl-+H is also found to agree well with calculations based on an effective-range approximation. Charge-transfer cross sections have been measured for F-, Cl-, and I-+H and are found to be small.
Objective This study aimed to evaluate the role of an objective physiologic biomarker, arterial b... more Objective This study aimed to evaluate the role of an objective physiologic biomarker, arterial blood pressure variability, for the early identification of adverse short-term electroencephalogram (EEG) outcomes in infants with hypoxic-ischemic encephalopathy (HIE). Study Design In this multicenter observational study, we analyzed blood pressure of infants meeting these criteria: (1) neonatal encephalopathy determined by modified Sarnat exam, (2) continuous mean arterial blood pressure (MABP) data between 18 and 27 hours after birth, and (3) continuous EEG performed for at least 48 hours. Adverse outcome was defined as moderate–severe grade EEG at 48 hours. Standardized signal preprocessing was used; the power spectral density was computed without interpolation. Multivariate binary logistic regression was used to identify which MABP time and frequency domain metrics provided improved predictive power for adverse outcomes compared with standard clinical predictors (5-minute Apgar scor...
Near-threshold photodetachment from negative atomic ions provides a virtually pointlike source of... more Near-threshold photodetachment from negative atomic ions provides a virtually pointlike source of electrons, and is ideally suited to study electron dynamics in externally applied electric and magnetic fields. These fields govern the motion of the emitted electron wave, and lead to characteristic modulations both in the total photocurrent and in the spatial electron distribution. These changes have been predicted and
Uploads
Papers by John Delos