Laser pulse propagation in a meter scale rubidium vapor/plasma cell in AWAKE experiment

We present the results of numerical studies of laser pulse propagating in a 3.5 cm Rb vapor cell in the linear dispersion regime by using a 1D model and a 2D code that has been modified for our special case. The 2D simulation finally aimed at finding laser beam parameters suitable to make the Rb vapor fully ionized to obtain a uniform, 10 m-long, at least 1 mm in radius plasma in the next step for the AWAKE experiment.Comment: Conference proceeding ,NIMA_EAAC 2015, 6 pages, 7 figure

A Statistical Study of Operating Systems at Harrisburg University

We conducted a survey of 100 students to find out which operating system students are using for their main school laptop. (Class Project

Geospatial variation of ribbed mussel (Geukensia demissa) ecosystem services across the salt marsh landscape

Salt marshes are a hallmark feature of the Atlantic coastline, where they provide a variety of ecosystem services such as: protection from flooding; nutrient and pollutant sequestration; economic uplift from recreational and commercial ventures; and habitat for a variety of finfish, birds, invertebrates, and mammals. Ribbed mussels (Geukensia demissa) are the functionally dominant animals of Gulf and Atlantic salt marshes, living in facultative mutualism with salt marsh cordgrass (Spartina alterniflora). The cordgrass provides habitat and attachment sites for mussels. In turn, the mussels, through the filtration of seston, provide nutrients for plant production through biodeposition. The magnitude of this pelagic-benthic coupling depends on ribbed mussel population density and the quantity and quality of seston. Since mussels are not evenly dispersed across the salt marsh landscape, their ecosystem services are geospatially variable which may have implications for resource managers interested in sustaining or enhancing mussel-mediated benefits. This dissertation’s objective was to quantify the annual variability in particle and nutrient filtration across three habitats of the salt marsh landscape: low marsh habitats along primary tidal channels; intra-marsh creek networks; and vast expanse of high marsh platform. Four representative salt marshes were selected for this study: Dividing Creek, Dennis Creek, and Maurice River in New Jersey along the Delaware Bay; and Coggeshall Cove in Rhode Island in the Narragansett Bay. The relevance of seston filtration data for understanding ecosystem services was demonstrated by estimating the spatial distribution and magnitude of net particulate nitrogen removal and the contribution of biodeposits to vertical marsh accretion. Clearance rates of water by ribbed mussels exhibited little spatial variation, but were dependent on seasonal temperatures. Filtration rates of seston varied with both space and time, since seston quantity and quality was variable at the same scales. Therefore, annual water processing rates can be extrapolated across regions that share similar temperature profiles, but local knowledge regarding seston variability is required to calculate particle filtration services. Annual gross filtration of total suspended solids (TSS) ranged between 4,500 & 11,000 kg ha-1 yr-1 at three locations in New Jersey and 3,800 kg ha-1 yr-1 at one location in Rhode Island. Filtration of particulate nitrogen (PN) ranged between 38 & 92 kg ha-1 yr-1 in New Jersey, assuming 60% of filtered nitrogen was either incorporated into somatic tissue or biodeposited, and 31 kg ha-1 yr-1 in Rhode Island, assuming 43% of filtered nitrogen was either incorporated into somatic tissue or biodeposited. This translated into contributions to vertical accretion between 39 & 93 mm in New Jersey and 26 mm in Rhode Island, if distributed evenly across the salt marsh landscape at the four study sites. The majority of mussel-associated ecosystem services were located in small, mussel-rich, creek networks of both New Jersey (74%) and Rhode Island (69%). However, large discrepancies in mussel density along the primary tidal channels between New Jersey and Rhode Island marshes, resulted in low service provisioning in New Jersey (3%) relative to Rhode Island (28%) in this “shoreline” habitat. The ability to understand the geospatial variation in mussel-mediated services provides natural resource managers with the ability to prioritize areas of high service value for conservation. Additionally, areas where services are underrepresented relative to regional potentials, presumably because of erosion or degradation, can be targeted for restoration or enhancement to maximize ribbed mussel biomass and service potential.Ph.D., Environmental Science -- Drexel University, 201

Erratum to: Sexual Mixing in Shanghai: Are Heterosexual Contact Patterns Compatible With an HIV/AIDS Epidemic?

In the middle of the paragraph just above Figure 6, there is the following sentence: “The range of the mean of the distribution of the proportion infected generated by the simulations is narrow, between 0.5 % and 0.2 % of all nodes.” This should read “between 0.05 % and 0.2 % of all nodes.

Sexual Mixing in Shanghai: Are Heterosexual Contact Patterns Compatible With an HIV/AIDS Epidemic?

China’s HIV prevalence is low, mainly concentrated among female sex workers (FSWs), their clients, men who have sex with men, and the stable partners of members of these high-risk groups. We evaluate the contribution to the spread of HIV of China’s regime of heterosexual relations, of the structure of heterosexual networks, and of the attributes of key population groups with simulations driven by data from a cross-sectional survey of egocentric sexual networks of the general population of Shanghai and from a concurrent respondent-driven sample of FSWs. We find that the heterosexual network generated by our empirically calibrated simulations has low levels of partner change, strong constraints on partner selection by age and education, and a very small connected core, mainly comprising FSWs and their clients and characterized by a fragile transmission structure. This network has a small HIV epidemic potential but is compatible with the transmission of bacterial sexually transmitted infections (STIs), such as syphilis, which are less susceptible to structural breaks in transmission of infection. Our results suggest that policies that force commercial sex underground could have an adverse effect on the spread of HIV and other STIs

Review of Breda Gray, Luigina Ciolfi, and Aparecido de Carvalho, Made to Work: Mobilising Contemporary Worklives,. 2020, Routledge: London.

Book revie

Erratum to: Sexual Mixing in Shanghai: Are Heterosexual Contact Patterns Compatible With an HIV/AIDS Epidemic?

In the middle of the paragraph just above Figure 6, there is the following sentence: “The range of the mean of the distribution of the proportion infected generated by the simulations is narrow, between 0.5 % and 0.2 % of all nodes.” This should read “between 0.05 % and 0.2 % of all nodes.

Continuous Entanglement Distribution from an AlGaAs-on-Insulator Microcomb for Quantum Communications

Using an aluminum gallium arsenide microring resonator, we demonstrate a bright quantum optical microcomb with $>300$ nm bandwidth and more than 20 sets of time-energy entangled modes, enabling spectral demultiplexing with simple, off-the-shelf commercial telecom components. We report high-rate continuous entanglement distribution for two sets of entangled-photon pair frequency modes exhibiting up to $20$ GHz/mW$^2$ pair generation rate. As an illustrative example of entanglement distribution, we perform a continuous-wave time-bin quantum key distribution protocol with 8 kbps raw key rates while maintaining less than 10$\%$ error rate and sufficient two-photon visibility to ensure security of the channel. When the $>$20 frequency modes are multiplexed, we estimate $>$100 kbps entanglement-based key rates or the creation of a multi-user quantum communications network. The entire system requires less than 110 $\mu$W of on-chip optical power, demonstrating an efficient source of entangled frequency modes for quantum communications. As a proof of principle, a quantum key is distributed across 12 km of deployed fiber on the UCSB campus and used to transmit a 21 kB image with $<9\%$ error.Comment: 14 pages, 8 figure

Interferometer-based high-accuracy white light measurement of neutral rubidium density and gradient at AWAKE

The AWAKE experiment requires an automated online rubidium (Rb) plasma density and gradient diagnostic for densities between 1 and 10$\cdot$10$^{14}$ cm$^{-3}$. A linear density gradient along the plasma source at the percent level may be useful to improve the electron acceleration process. Because of full laser ionization of Rb vapor to Rb$^{+}$ within a radius of 1 mm, the plasma density equals the vapor density. We measure the Rb vapor densities at both ends of the source, with high precision using, white light interferometry. At either source end, broadband laser light passes a remotely controlled Mach-Zehnder interferometer built out of single mode fibers. The resulting interference signal, influenced by dispersion in the vicinity of the Rb D1 and D2 transitions, is dispersed in wavelength by a spectrograph. Fully automated Fourier-based signal conditioning and a fit algorithm yield the density with an uncertainty between the measurements at both ends of 0.11 to 0.46 $\%$ over the entire density range. These densities used to operate the plasma source are displayed live in the control room.Comment: 5 pages, 8 figures, EAAC2017 conference proceedin

New Experimental Limits on Macroscopic Forces Below 100 Microns

Results of an experimental search for new macroscopic forces with Yukawa range between 5 and 500 microns are presented. The experiment uses 1 kHz mechanical oscillators as test masses with a stiff conducting shield between them to suppress backgrounds. No signal is observed above the instrumental thermal noise after 22 hours of integration time. These results provide the strongest limits to date between 10 and 100 microns, improve on previous limits by as much as three orders of magnitude, and rule out half of the remaining parameter space for predictions of string-inspired models with low-energy supersymmetry breaking. New forces of four times gravitational strength or greater are excluded at the 95% confidence level for interaction ranges between 200 and 500 microns.Comment: 25 Pages, 7 Figures: Minor Correction