Efficient Immunization Strategies for Computer Networks and Populations

We present an effective immunization strategy for computer networks and populations with broad and, in particular, scale-free degree distributions. The proposed strategy, acquaintance immunization, calls for the immunization of random acquaintances of random nodes (individuals). The strategy requires no knowledge of the node degrees or any other global knowledge, as do targeted immunization strategies. We study analytically the critical threshold for complete immunization. We also study the strategy with respect to the susceptible-infected-removed epidemiological model. We show that the immunization threshold is dramatically reduced with the suggested strategy, for all studied cases.Comment: Revtex, 5 pages, 4 ps fig

Experimental Studies Towards a DC-DC Conversion Powering Scheme for the CMS Silicon Strip Tracker at SLHC

The upgrade of the CMS silicon tracker for the Super-LHC presents many challenges. The distribution of power to the tracker is considered particularly difficult, as the tracker power consumption is expected to be similar to or higher than today, while the operating voltage will decrease and power cables cannot be exchanged or added. The CMS tracker has adopted parallel powering with DC-DC conversion as the baseline solution to the powering problem. In this paper, experimental studies of such a DC-DC conversion powering scheme are presented, including system test measurements with custom DC-DC converters and current strip tracker structures, studies of the detector susceptibility to conductive noise, and simulations of the effect of novel powering schemes on the strip tracker material budget

Nuclear quantum optics with x-ray laser pulses

The direct interaction of nuclei with super-intense laser fields is studied. We show that present and upcoming high-frequency laser facilities, especially together with a moderate acceleration of the target nuclei, do allow for resonant laser-nucleus interaction. These direct interactions may be utilized for the optical measurement of nuclear properties such as the transition frequency and the dipole moment, thus opening the field of nuclear quantum optics. As ultimate goal, one may hope that direct laser-nucleus interactions could become a versatile tool to enhance preparation, control and detection in nuclear physics.Comment: 5 pages, 3 eps figures, revised versio

Radio-Frequency Spectroscopy

Contains reports on three research projects

The nuclear AC-Stark shift in super-intense laser fields

The direct interaction of super-intense laser fields in the optical frequency domain with nuclei is studied. As main observable, we consider the nuclear AC-Stark shift of low-lying nuclear states due to the off-resonant excitation by the laser field. We include the case of accelerated nuclei to be able to control the frequency and the intensity of the laser field in the nuclear rest frame over a wide range of parameters. We find that AC-Stark shifts of the same order as in typical quantum optical systems relative to the respective transition frequencies are feasible with state-of-the-art or near-future laser field intensities and moderate acceleration of the target nuclei. Along with this shift, we find laser-induced modifications to the proton root-mean-square radii and to the proton density distribution. We thus expect direct laser-nucleus interaction to become of relevance together with other super-intense light-matter interaction processes such as pair creation.Comment: 10 pages, 2 eps figure

A new online database of nuclear electromagnetic moments

Nuclear electromagnetic (EM) moments, i.e., the magnetic dipole and the electric quadrupole moments, provide important information of nuclear structure. As in other types of experimental data available to the community, measurements of nuclear EM moments have been organized systematically in compilations since the dawn of nuclear science. However, the wealth of recent moments measurements with radioactive beams, as well as earlier existing measurements, lack an online, easy-to-access, systematically organized presence to disseminate information to researchers. In addition, available printed compilations suffer a rather long life cycle, being left behind experimental measurements published in journals or elsewhere. A new, online database (http://magneticmoments.info) focusing on nuclear EM moments has been recently developed to disseminate experimental data to the community. The database includes non–evaluated experimental data of nuclear EM moments, giving strong emphasis on frequent updates (life cycle is 3 months) and direct connection to the sources via DOI and NSR hyperlinks. It has been recently integrated in IAEA LiveChart [1], but can also be found as a standalone webapp [2]. A detailed review of the database features, as well as plans for further development and expansion in the near future is discussed

Variational Monte Carlo Study of Spin-Gapped Normal State and BCS-BEC Crossover in Two-Dimensional Attractive Hubbard Model

We study properties of normal, superconducting (SC) and CDW states for an attractive Hubbard model on the square lattice, using a variational Monte Carlo method. In trial wave functions, we introduce an interspinon binding factor, indispensable to induce a spin-gap transition in the normal state, in addition to the onsite attractive and intersite repulsive factors. It is found that, in the normal state, as the interaction strength $|U|/t$ increases, a first-order spin-gap transition arises at $|U_{\rm c}|\sim W$ ($W$: band width) from a Fermi liquid to a spin-gapped state, which is conductive through hopping of doublons. In the SC state, we confirm by analysis of various quantities that the mechanism of superconductivity undergoes a smooth crossover at around |U_{\ma{co}}|\sim |U_{\rm c}| from a BCS type to a Bose-Einstein condensation (BEC) type, as $|U|/t$ increases. For |U|<|U_{\ma{co}}|, quantities such as the condensation energy, a SC correlation function and the condensate fraction of onsite pairs exhibit behavior of $\sim \exp(-t/|U|)$, as expected from the BCS theory. For |U|>|U_{\ma{co}}|, quantities such as the energy gain in the SC transition and superfluid stiffness, which is related to the cost of phase coherence, behave as $\sim t^2/|U|\propto T_{\rm c}$, as expected in a bosonic scheme. In this regime, the SC transition is induced by a gain in kinetic energy, in contrast with the BCS theory. We refer to the relevance to the pseudogap in cuprate superconductors.Comment: 14 pages, 22 figures, submitted to Journal of the Physical Society of Japa

Safety of the 2D/3D direct-acting antiviral regimen in HCV-induced Child-Pugh A cirrhosis – A pooled analysis

AbstractBackground & aimsChronic hepatitis C virus (HCV)-infected patients with cirrhosis are a high-priority population for treatment. To help inform the benefit–risk profile of the all-oral direct-acting antiviral (DAA) combination regimen of ombitasvir, paritaprevir, and ritonavir, with or without dasabuvir (OBV/PTV/r ± DSV) in patients with Child-Pugh A cirrhosis, we undertook a comprehensive review of AbbVie-sponsored clinical trials enrolling patients with Child-Pugh A cirrhosis.MethodsTwelve phase II or III clinical trials of the 2-DAA regimen of OBV/PTV/r ± ribavirin (RBV) or the 3-DAA regimen of OBV/PTV/r + DSV ± RBV that included patients with Child-Pugh A cirrhosis were reviewed; patients who completed treatment by November 16, 2015 were included in a pooled, post hoc safety assessment. The number and percentage of patients with treatment-emergent adverse events (TEAEs), serious TEAEs, and TEAEs consistent with hepatic decompensation were reported.ResultsIn 1066 patients with Child-Pugh A cirrhosis, rates of serious TEAEs and TEAEs leading to study drug discontinuation were 5.3% (95% CI: 4.1–6.8) and 2.2% (95% CI: 1.4–3.2), respectively. Thirteen patients (1.2%; 95% CI: 0.7–2.1) had a TEAE that was consistent with hepatic decompensation. The most frequent TEAEs consistent with hepatic decompensation were ascites (n=8), esophageal variceal hemorrhage (n=4), and hepatic encephalopathy (n=2).ConclusionsThis pooled analysis in 1066 HCV-infected patients with Child-Pugh A cirrhosis confirms the safety of OBV/PTV/r ± DSV ± RBV in this population. These results support the use of OBV/PTV/r ± DSV ± RBV in this high-priority population.Lay summaryThis pooled safety analysis in 1066 HCV-infected patients with compensated cirrhosis, receiving treatment with ombitasvir, paritaprevir, and ritonavir with or without dasabuvir, with or without ribavirin, shows that the rate of hepatic decompensation events was comparable to rates from historical reports for untreated patients