Spacetime perspective of Schwarzschild lensing

We propose a definition of an exact lens equation without reference to a background spacetime, and construct the exact lens equation explicitly in the case of Schwarzschild spacetime. For the Schwarzschild case, we give exact expressions for the angular-diameter distance to the sources as well as for the magnification factor and time of arrival of the images. We compare the exact lens equation with the standard lens equation, derived under the thin-lens-weak-field assumption (where the light rays are geodesics of the background with sharp bending in the lens plane, and the gravitational field is weak), and verify the fact that the standard weak-field thin-lens equation is inadequate at small impact parameter. We show that the second-order correction to the weak-field thin-lens equation is inaccurate as well. Finally, we compare the exact lens equation with the recently proposed strong-field thin-lens equation, obtained under the assumption of straight paths but without the small angle approximation, i.e., with allowed large bending angles. We show that the strong-field thin-lens equation is remarkably accurate, even for lightrays that take several turns around the lens before reaching the observer.Comment: 22 pages, 6 figures, to appear in Phys. Rev.

Virtual power plants : an answer to increasing distributed generation

In the future an adaptive power system is required to integrate the emerging distributed generation (DG) and renewable energy sources (RES). Since most present power systems are based on active controlled transmission network and passive distribution network, the development of smart grids in the distribution network will facilitate and enhance the growth of DG&RES. To develop smart grids, active control of both distribution network and DG&RES is needed. This research employs the virtual power plant (VPP) concept to develop active control of the present and emerging DG&RES. This paper discusses the impact of DG&RES and highlights the advantages of the VPP concept taking major technical, economical and regulatory aspects in consideration

Carrier-envelope phase control over pathway interference in strong-field dissociation of H2+_2^+

The dissociation of an H$_2^+$ molecular-ion beam by linearly polarized, carrier-envelope-phase-tagged 5 fs pulses at 4$\times10^{14}$W/cm$^2$ with a central wavelength of 730 nm was studied using a coincidence 3D momentum imaging technique. Carrier-envelope-phase-dependent asymmetries in the emission direction of H$^+$ fragments relative to the laser polarization were observed. These asymmetries are caused by interference of odd and even photon number pathways, where net-zero photon and 1-photon interference predominantly contributes at H$^+$+H kinetic energy releases of 0.2 -- 0.45 eV, and net-2-photon and 1-photon interference contributes at 1.65 -- 1.9 eV. These measurements of the benchmark H$_2^+$ molecule offer the distinct advantage that they can be quantitatively compared with \textit{ab initio} theory to confirm our understanding of strong-field coherent control via the carrier-envelope phase

Prospects of a virtual power plant to control a cluster of Distributed Generation and Renewable Energy Sources

The integration of distributed generation (DG) and renewable energy sources (RES) in the passive controlled distribution networks leads in present situation to an expansion of the network capacity and thus to excessive investments. If no measures will be taken these expenditures will increase in proportion to the growth of DG&RES. The virtual power plant (VPP) anticipates these challenges and in addition facilitates better dispatching of power and energy from centralized generation to the DG&RES. The VPP offers a concept for the control and management system of DG&RES that responds to the regulatory and socio-economical constraints beside technical challenges. While most VPP concepts are based on active distribution networks, this work uses the VPP concept to transit the present passive distribution networks to the active networks in the future. For that purpose three transition stages are developed after laying of the foundations for a definition of the VPP with the Dutch situation as an example. To anticipate future developments in the electricity infrastructures, the capability of the VPP to combine with the common known control and management concepts is investigate

The microbial and metazoan community associated with colonies of Trichodesmium spp.: a quantitative survey

Association with resource-rich particles may benefit a number of planktonic species in oligotriphic, open-ocean regimes. This study examined communities of microbes and Zooplankton associated with colonies of the cyanobacterium Trichodesmium spp. in the Sargasso Sea. Trichodesmium colonies and seawater controls were collected near Bermuda using SCUBA during September 1995, and June, July and August 1996. Organisms associated with the colonies and those in the surrounding seawater were enumerated using light and fluorescence microscopy. We found that 85% of the Trichodesmium puff and tuft colonies examined harbored associated organisms. Associated organisms included bacteria (rod and coccoid),fungi, pennate diatoms, centric diatoms, heterotrophic and autotriphic dinoflagellates, chrysophytes, hypotrich ciliates, amoebae, hydroids, juveniles and nauplii of harpacticoid copepods, and juvenile decapods. The most common associates (in addition to bacteria) were dinoflagellates (present in 74% of the colonies examined), amoebae (50%), ciliates (24%), and diatoms (24%). Numbers of bacteria per colony volume averaged 8.2x10(8) bacteria ml(-1) (range = 8.1x10(7) -3.5x10(9) bacteria ml(-1)), and the density of associated microzooplankton and metazoans averaged 6.8x10(4) organisms ml(-1) (range = 0-3.6-10(6) organisms ml-1). Associates of Tichodesmium colonies were enriched by two to five orders of magnitude over plankton in the surrounding water. This unique habitat allows for the association of primarily benthic ciliate, diatom and copepod species and could contribute significantly to plankton heterogeneity in the open-ocean. The distribution of associated organisms was affected by sample characteristics such as colony morphology, mucoid matrix structure and colony integrity. The influence of these factors indicates that succession or competition between heterotrophic microorganisms ultimately determines Tichodesmium microcommunity structure. Similar processes could regulate microbial and metazoan communities associated with other resource-rich microenvironments, such as marine snow particles

Privatizing Ecosystem Services: Water Quality Effects from a Carbon Market

Resource /Energy Economics and Policy, Q25,

Outpatient Primary Care Practitioner Access: Sex-Based Preferences

Background: In some innovative outpatient practice models, patients are faced with trade-offs, such as choosing between continuity of care vs quick access to a healthcare practitioner (HCP). Our objective was to assess sex-based differences in visit access preferences at an academic outpatient internal medicine clinic. Methods: A 13-question survey with four discrete choice experiments proposing hypothetical care scenarios was offered to patients over a 6-week period in 2018. Descriptive statistics and chi-squared tests evaluated results by sex for categorical variables, Mann-Whitney rank-sum test for continuous variables, and multivariable models adjusted for age, marital status, education, and income. P-values \u3c 0.05 were statistically significant. Results: A majority of 796 of 1731 (46%) respondents were female (56%) and over age 65 (58.5%). Females were more likely than males to prefer communicating with the same allied health staff (AHS) over receiving a quick response (female 36.3% vs male 28.0%, p=0.0031) Females prioritized seeing their own provider as opposed to scheduling a convenient appointment for routine care (female 90.2% vs male 85.0%, p =0.028). Multivariable analysis found that females were 6% less likely than males to request the same AHS for communication (95% CI 0.62-1.44), 29% less likely to request the same HCP for yearly physicals (95% CI 0.34 – 1.44), but 3% more likely than men to request an acute visit with the same HCP (95% CI 0.68-1.56) and 13% more likely to request the same HCP for virtual visits (95% CI 0.70-1.81). Conclusion: Sex-based differences in access preferences were identified. Women preferred continuity of care with the same HCP and AHS over ease of scheduling or a quick response, though these preferences appear to be moderated by other factors including age and marital status. Further identification of longitudinal and socioeconomic factors influencing preferences is needed in this era of evolving practice models.https://jdc.jefferson.edu/sexandgenderhealth/1029/thumbnail.jp

Inhibition of fungal infection using sulfite pads prior to initiation of callus from Vitis labruscana cv. Concord

Research NoteIncubation of plant material with potassium metabisulfite was found to inhibit fungal infections of explants from grapevines. Grapevine tissue of Vitis labruscana cv. Concord was incubated with sulfite pads containing 0.4 g of potassium metabilsufite for one and two days prior to culturing and evaluated against a control that had been surface sterilized with 0.5 % NaOCI and 70 % ethanol after one week for losses due to microbial contamination. Sulfite fumigation of plant material reduced the incidence of mold infection, particularly in tissue cultures developed from fruit explants which had reductions in contamination as high as 10 fold. Continued attempts to isolate contaminants from cultures intitiated from these explants showed no signs of infection

Disorder-Induced Shift of Condensation Temperature for Dilute Trapped Bose Gases

We determine the leading shift of the Bose-Einstein condensation temperature for an ultracold dilute atomic gas in a harmonic trap due to weak disorder by treating both a Gaussian and a Lorentzian spatial correlation for the quenched disorder potential. Increasing the correlation length from values much smaller than the geometric mean of the trap scale and the mean particle distance to much larger values leads first to an increase of the positive shift to a maximum at this critical length scale and then to a decrease.Comment: Author information under http://www.theo-phys.uni-essen.de/tp/ags/pelster_di