Theoretical study of electronic damage in single particle imaging experiments at XFELs for pulse durations 0.1 - 10 fs

X-ray free-electron lasers (XFELs) may allow to employ the single particle imaging (SPI) method to determine the structure of macromolecules that do not form stable crystals. Ultrashort pulses of 10 fs and less allow to outrun complete disintegration by Coulomb explosion and minimize radiation damage due to nuclear motion, but electronic damage is still present. The major contribution to the electronic damage comes from the plasma generated in the sample that is strongly dependent on the amount of Auger ionization. Since the Auger process has a characteristic time scale on the order of femtoseconds, one may expect that its contribution will be significantly reduced for attosecond pulses. Here, we study the effect of electronic damage on the SPI at pulse durations from 0.1 fs to 10 fs and in a large range of XFEL fluences to determine optimal conditions for imaging of biological samples. We analyzed the contribution of different electronic excitation processes and found that at fluences higher than $10^{13}$-$10^{15}$ photons/$\mu$m$^2$ (depending on the photon energy and pulse duration) the diffracted signal saturates and does not increase further. A significant gain in the signal is obtained by reducing the pulse duration from 10 fs to 1 fs. Pulses below 1 fs duration do not give a significant gain in the scattering signal in comparison with 1 fs pulses. We also study the limits imposed on SPI by Compton scattering.Comment: 35 pages, 9 figures, 1 table, 2 appendixes, 45 reference

The Experiences of Social Workers in Corporate America

The purpose of this study was to explore the experiences of social workers in Corporate America, including their role in corporate social responsibility (CSR). The data collected was from four semi-structured interviews that lasted between 20 to 45 minutes each. Each participant was employed by or consulted for a large corporation and had roles in a variety of departments, including government affairs, internal consulting, talent and change management and leadership development. None of the participants had direct CSR responsibilities, however, each participant had experience with their CSR programs and valued them in their organizations. The study explored the participants’ responsibilities in their organization, and how their social work practice and skills were incorporated in their work. Themes from the data indicated that social workers are most valued in their organizations for their abilities to build relationships, effectively implement change and see things in a different perspective from their co-workers. Participants reported that they used their social work skills in their daily work even within their business roles, and believed that corporations could benefit from having more individuals with the social work perspective in their organizations. The findings in this study fill a gap in the current literature and may have implications for social work in corporate settings, in social work education, and in future social work research

The Experiences of Social Workers in Corporate America

The purpose of this study was to explore the experiences of social workers in Corporate America, including their role in corporate social responsibility (CSR). The data collected was from four semi-structured interviews that lasted between 20 to 45 minutes each. Each participant was employed by or consulted for a large corporation and had roles in a variety of departments, including government affairs, internal consulting, talent and change management and leadership development. None of the participants had direct CSR responsibilities, however, each participant had experience with their CSR programs and valued them in their organizations. The study explored the participants\u27 responsibilities in their organization, and how their social work practice and skills were incorporated in their work. Themes from the data indicated that social workers are most valued in their organizations for their abilities to build relationships, effectively implement change and see things in a different perspective from their co-workers. Participants reported that they used their social work skills in their daily work even within their business roles, and believed that corporations could benefit from having more individuals with the social work perspective in their organizations. The findings in this study fill a gap in the current literature and may have implications for social work in corporate settings, in social work education, and in future social work research

Effects of interspecific competition, salinity, and hurricanes on the success of an invasive fish, the Rio Grande cichlid (Herichthys cyanoguttatus)

The Rio Grande cichlid (Herichthys cyanoguttatus) has been established in the Greater New Orleans Metropolitan Area (GNOMA) for at least 20 years. It is often the most common fish species in urban canals and has also been found in natural waterways outside of the GNOMA. The effects and potential for further spread of H. cyanoguttatus is uncertain. My research addressed how extensive the cichlids spread in the GNOMA, how H. cyanoguttatus interacted with L. macrochirus, a native fish, and what salinity tolerance this species has. Surveys on Lake Pontchartrain and in the GNOMA indicated that H. cyanoguttatus is well established in urban habitats. These surveys also indicate that H. cyanoguttatus has spread rapidly into Bayou Saint John and City Park in recent years and that H. cyanoguttatus populations were relatively unaffected by Hurricanes Katrina and Rita. There is little evidence that H. cyanoguttatus has become established outside of the GNOMA, but this lack of persistence cannot be explained by abiotic variables I measured. Salinity may be a factor and this was measured in growth trials of H. cyanoguttatus. Salinities up to 16 ppt, however, had no significant effect on H. cyanoguttatus growth. Interspecific behavioral experiments were conducted to examine potential biotic interactions with native fish species. Prior resident trials indicated that H. cyanoguttatus was aggressive whether holding territory or not, and that native bluegill (Lepomis macrochirus) was only aggressive while holding territory. Feeding experiments were performed to examine biotic interactions between H. cyanoguttatus and L. macrochirus. Lepomis macrochirus grew faster than H. cyanoguttatus when inter- and intraspecific trials were compared; however, no significant growth differences were seen when trials were structured with L. macrochirus as prior residents. The major findings of my research are a high salinity tolerance of H. cyanoguttatus, a potential mechanism for H. cyanoguttatus affecting native fishes through aggression as residents and invaders, and the presence of H. cyanoguttatus throughout the GNOMA, before and after the hurricanes

On the Cholesky Decomposition for electron propagator methods: General aspects and application on C60

To treat the electronic structure of large molecules by electron propagator methods we developed a parallel computer program called P-RICD$\Sigma$. The program exploits the sparsity of the two-electron integral matrix by using Cholesky decomposition techniques. The advantage of these techniques is that the error introduced is controlled only by one parameter which can be chosen as small as needed. We verify the tolerance of electron propagator methods to the Cholesky decomposition threshold and demonstrate the power of the P-RICD$\Sigma$ program for a representative example (C60). All decomposition schemes addressed in the literature are investigated. Even with moderate thresholds the maximal error encountered in the calculated electron affinities and ionization potentials amount to a few meV only, and the error becomes negligible for small thresholds.Comment: 30 pages, 6 figures submitted to J.Chem. Phy

Quantum techniques using continuous variables of light

We present schemes for the generation and evaluation of continuous variable entanglement of bright optical beams and give a brief overview of the variety of optical techniques and quantum communication applications on this basis. A new entanglement-based quantum interferometry scheme with bright beams is suggested. The performance of the presented schemes is independent of the relative interference phase which is advantageous for quantum communication applications.Comment: 11 pages, 5 figures; minor correction, accepted versio

Thermal Conductivity and Specific Heat of the Spin-Ice Compound Dy2_2Ti2_2O7_7: Experimental Evidence for Monopole Heat Transport

Elementary excitations in the spin-ice compound Dy$_2$Ti$_2$O$_7$ can be described as magnetic monopoles propagating independently within the pyrochlore lattice formed by magnetic Dy ions. We studied the magnetic-field dependence of the thermal conductivity {\kappa}(B) for B || [001] and observe clear evidence for magnetic heat transport originating from the monopole excitations. The magnetic contribution {\kappa}_{mag} is strongly field-dependent and correlates with the magnetization M(B). The diffusion coefficient obtained from the ratio of {\kappa}_{mag} and the magnetic specific heat is strongly enhanced below 1 K indicating a high mobility of the monopole excitations in the spin-ice state.Comment: 5 pages, 4 figure