Impact of Electron-Electron Cusp on Configuration Interaction Energies

The effect of the electron-electron cusp on the convergence of configuration interaction (CI) wave functions is examined. By analogy with the pseudopotential approach for electron-ion interactions, an effective electron-electron interaction is developed which closely reproduces the scattering of the Coulomb interaction but is smooth and finite at zero electron-electron separation. The exact many-electron wave function for this smooth effective interaction has no cusp at zero electron-electron separation. We perform CI and quantum Monte Carlo calculations for He and Be atoms, both with the Coulomb electron-electron interaction and with the smooth effective electron-electron interaction. We find that convergence of the CI expansion of the wave function for the smooth electron-electron interaction is not significantly improved compared with that for the divergent Coulomb interaction for energy differences on the order of 1 mHartree. This shows that, contrary to popular belief, description of the electron-electron cusp is not a limiting factor, to within chemical accuracy, for CI calculations.Comment: 11 pages, 6 figures, 3 tables, LaTeX209, submitted to The Journal of Chemical Physic

Singlet Oxygen Delivery Through the Porous Cap of a Hollow-Core Fiber Optic Device

The development of the first photosensitizer/fiber optic device is reported. An oxygen-flowing, fiber-capped configuration is used for the application of heterogeneous, spatially confined singlet oxygen delivery in aqueous media. This is a unique device, unlike other heterogeneous photosensitizers, in which local concentrations of singlet oxygen can be delivered via introduction and withdrawal of the fiber tip

Increased efficiency of direct nanoimprinting on planar and curved bulk titanium through surface modification

In this work the direct transfer of nanopatterns into titanium is demonstrated. The nanofeatures are imprinted at room temperature using diamond stamps in a single step. We also show that the imprint properties of the titanium surface can be altered by anodisation yielding a significant reduction in the required imprint force for pattern transfer. The anodisation process is also utilised for curved titanium surfaces where a reduced imprint force is preferable to avoid sample deformation and damage. We finally demonstrate that our process can be applied directly to titanium rods

Illicit drug use and cerebral microbleeds in stroke and transient ischemic attack patients

Background: Cerebral microbleeds (CMB) signal cerebral small vessel disease and are associated with ischemic stroke (IS) incidence, recurrence, and complications. While illicit drug use (IDU) is associated with cerebral small vessel disease, the association between CMB and IDU is understudied. We sought to delineate differences in vascular risk factors between IDU and CMB and determine the effect of this relationship on outcomes in IS/transient ischemic attack (TIA) patients. Methods: We included 2001 consecutive IS and TIA patients (years 2009-2018) with a readable T2*gradient-echo MRI sequence. CMB rating followed standardized guidelines and CMB were grouped topographically into lobar, deep or infratentorial. IDU data (history and/or urine toxicology) was available for 1746 patients. The adverse composite outcome included pneumonia, urinary tract infection, deep venous thrombosis or death during hospitalization. Good functional outcome was defined as modified Rankin scale score < 3 and ambulatory on discharge. Univariate analysis was used to assess vascular risk factors and multivariable logistic regression was used to characterize the IDU/CMB relationship on outcomes. Results: We observed IDU in 13.8 % (n=241), and CMB in 32.9% (n=575, 53.8% lobar, 27.3% deep and 18.8% infratentorial). Patients with IDU and at least one CMB were older (53.6±10.5 vs. 56.9±11.5, p=0.04), had a lower BMI (28.1±5.9 vs. 26.6±4.4, p=0.04), and were more likely to have had a previous IS/TIA (25.1% vs. 41.9%, p=0.01). IDU trended higher for those with severe CMB (10+) compared with those without CMB and 1-9 CMB (25% [n=9] vs 14.3% [n=1171] and 12.1% [n=65] respectively; p=0.07) without individual drug deviations from this pattern. Adverse and good functional outcomes were observed in 177 and 905 total patients, respectively. No significant interaction was observed between IDU and CMB with either adverse or functional composite outcomes. Conclusion: IDU prevalence was high in our urban study population, and showed a borderline association with increasing CMB burden. Patients with CMB and IDU history were older and more likely to have had a previous IS/TIA. Further studies are required to clarify the clinical consequences related to the relationship between IDU and CMB.Author Disclosures: B. Petrie: None. H. Lau: None. F. Cajiga-Pena: None. S. Abbas: None. B. Finn: None. K. Dam: None. A. Cervantes-Arslanian: None. T.N. Nguyen: None. H. Aparicio: None. D. Greer: None. J.R. Romero: Speakers' Bureau; Modest; Received speaker honoraria from Ferrer Group

Singlet Oxygen Chemistry in Water. 2. Photoexcited Sensitizer Quenching by O2 at the Water−Porous Glass Interface

Insight into the O2 quenching mechanism of a photosensitizer (static or dynamic) would be useful for the design of heterogeneous systems to control the mode of generation of 1O2 in water. Here, we describe the use of a photosensitizer, meso-tetra(N-methyl-4-pyridyl)porphine (1), which was adsorbed onto porous Vycor glass (PVG). A maximum loading of 1.1 × 10−6 mol 1 per g PVG was achieved. Less than 1% of the PVG surface was covered with photosensitizer 1, and the penetration of 1 reaches a depth of 0.32 mm along all faces of the glass. Time-resolved measurements showed that the lifetime of triplet 1*-ads was 57 μs in water. Triplet O2 quenched the transient absorption of triplet 1*-ads; for samples containing 0.9 × 10−6−0.9 × 10−8 mol 1 adsorbed per g PVG, the Stern−Volmer constant, KD, ranged from 23 700 to 32 100 M−1. The adduct formation constant, KS, ranged from 1310 to 510 M−1. The amplitude of the absorption at 470 nm decreased slightly (by about 0.1) with increased O2 concentrations. Thus, the quenching behavior of triplet 1*-ads by O2 was proposed to be strongly dependent on dynamic quenching. Only ∼10% of the quenching was attributed to the static quenching mechanism. The quenching of triplet 1*-ads was similar to that observed for photosensitizers in homogeneous solution which are often quenched dynamically by O2

UV photon-counting CCD detectors that enable the next generation of UV spectroscopy missions: AR coatings that can achieve 80-90% QE

We describe recent progress in the development of anti-reflection coatings for use at UV wavelengths on CCDs and other Si-based detectors. We have previously demonstrated a set of coatings which are able to achieve greater than 50% QE in 4 bands from 130nm to greater than 300nm. We now present new refinements of these AR-coatings which will improve performance in a narrower bandpass by 50% over previous work. Successful test films have been made to optimize transmission at 190nm, reaching 80% potential transmission