Anomalous Microwave Surface Resistance of CeCu6

We present surface resistance measurements of the archetypical heavy-fermion compound CeCu6 for frequencies between 3.7 and 18 GHz and temperatures from 1.2 to 6 K. The measurements were performed with superconducting stripline resonators that allow simultaneous measurements at multiple frequencies. The surface resistance of CeCu6 exhibits a pronounced decrease below 3 K, in consistence with dc resistivity. The low-temperature frequency dependence of the surface resistance follows a power law with exponent 2/3. While for conventional metals this would be consistent with the anomalous skin effect, we discuss the present situation of a heavy-fermion metal, where this frequency dependence might instead stem from the influence of electronic correlations.Comment: 6 pages, 3 figures, proceedings of SCES 201

CePdAl - a Kondo lattice with partial frustration

Magnetic frustration, which is well-defined in insulating systems with localized magnetic moments, yields exotic ground states like spin ices, spin glasses, or spin liquids. In metals magnetic frustration is less well defined because of the incipient delocalization of magnetic moments by the interaction with conduction electrons, viz., the Kondo effect. Hence, the Kondo effect and magnetic frustration are antithetic phenomena. Here we present experimental data of electrical resistivity, magnetization, specific heat and neutron diffraction on CePdAl, which is one of the rare examples of a geometrically frustrated Kondo lattice, demonstrating that the combination of Kondo effect and magnetic frustration leads to an unusual ground state.Comment: 8 pages, 6 figure

Application of a functional model for the modernization of devices designed to eliminate emergency oil spills

The article describes the stages of creation and composition of the functional model, which can be used for the design of oil spill response devices. The principle of operation of the functional model given in the article and it's graphical scheme are show

Spatiotemporal controlled delivery of nanoparticles to injured vasculature

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2010.Cataloged from PDF version of thesis. Vita.Includes bibliographical references.Complex multimodal nanoparticles (NP) that target and deliver therapeutic agents to a site of disease are a promising direction in modem medicine. As a starting point for innovation, we designed a hybrid NP system combining the benefits of liposomes and polymeric NPs. These particles have a polymeric surface which displays targeting ligands while avoiding macrophage uptake. A liposome-like layer provides in vivo biocompatibility and a hydrophobic core allows for high-capacity small molecule drug delivery. Targeting ligands that bind injured vasculature were discovered and optimized by screening an M13 bacteriophage library (109 independent clones) against collagen IV, the major component of the basement membrane. Relative binding affinities using ELISA identified the lead targeting candidate, which bound with 900-fold greater relative affinity to collagen IV when compared with the unselected library. The selected peptide sequence was synthesized and tested for its ability to actively target the hybrid NP system. Paclitaxel, an anti-proliferative drug, was chosen as the delivered pharmaceutical. Drug release was modified through a slow-eluting paclitaxel conjugate using controlled ester hydrolysis (drug release -10-12 days in vitro). To test these targeted NPs, injured vasculature was approximated using an aortic smooth muscle culture embedded on a collagen IV matrix. In this setting, the hybrid NPs showed clear evidence of increased potency using the selected ligands. In experimental animal models of surgery-induced vascular injury, targeted NPs showed a four-fold improved retention at angioplastied aortas over intact aortas ex vivo. Targeted NPs were tested as intraarterially delivered therapy to angioplastied carotid arteries in vivo and showed a two-fold better localization at injury sites versus scrambled-peptide and non-targeted NPs. Targeted NPs were also tested using a systemic, intravenous infusion administered postprocedure on Day I and 6 and resulted in lower neointima-to-media (N/M) scores at two weeks compared to FDA-approved Taxol@ and injury-only groups (N/Msham= -249 + 0.046, vs. N/MTaxol=0.837 ± 0.087, N/MNP=0.749 ± 0.136 and N/MPep-NP=0.662 ± 0.169, all P < 0.01 vs. injury-only, mean ± SEM, n=5). These findings indicate that complex, multilayered NPs can functionally target and treat injured vasculature, a clinical problem of primary importance.by Juliana Maria Chan.Ph.D

Identification of regulatory variants associated with genetic susceptibility to meningococcal disease.

Non-coding genetic variants play an important role in driving susceptibility to complex diseases but their characterization remains challenging. Here, we employed a novel approach to interrogate the genetic risk of such polymorphisms in a more systematic way by targeting specific regulatory regions relevant for the phenotype studied. We applied this method to meningococcal disease susceptibility, using the DNA binding pattern of RELA - a NF-kB subunit, master regulator of the response to infection - under bacterial stimuli in nasopharyngeal epithelial cells. We designed a custom panel to cover these RELA binding sites and used it for targeted sequencing in cases and controls. Variant calling and association analysis were performed followed by validation of candidate polymorphisms by genotyping in three independent cohorts. We identified two new polymorphisms, rs4823231 and rs11913168, showing signs of association with meningococcal disease susceptibility. In addition, using our genomic data as well as publicly available resources, we found evidences for these SNPs to have potential regulatory effects on ATXN10 and LIF genes respectively. The variants and related candidate genes are relevant for infectious diseases and may have important contribution for meningococcal disease pathology. Finally, we described a novel genetic association approach that could be applied to other phenotypes

Under the Rule of the Snake Kings: Uxul in the 7th and 8th centuries

Since 2009, the University of Bonn is conducting archaeological investigations at Uxul, a medium sized classic Maya city in the extreme south of the Mexican state of Campeche. The project's research goal is to investigate the expansion and disintegration of hegemonic power in the Maya area, concentrating on the core area of the Maya Lowlands and especially on Uxul's close relation to the powerful Kaan dynasty at Calakmul. New evidence strengthens the hypothesis that Uxul was under the control of Calakmul since the early 7th century. Also, our data suggest that the downfall and abandonment of Uxul were closely related to the fateful defeats of Calakmul's rulers Yukno'm Yich'aak K'ahk' and Yukno'm Took' K'awiil at the hands of Tikal in AD 695 and 736. When the central authority collapsed during the mid-8th century, the shrinking population of Uxul was not able to maintain the social cohesion to protect even the most vitally important of infrastructures: its water management system.Desde el 2009, la Universidad de Bonn efectúa trabajos arqueológicos en el sitio de Uxul, una ciudad maya del Clásico en el extremo sur del estado de Campeche. El objetivo del proyecto es investigar la expansión y desintegración de los poderes hegemónicos en el área maya, con un enfoque en la zona central de las Tierras Bajas y específicamente en la estrecha relación de Uxul con los gobernantes de la poderosa dinastía Kaan de Calakmul. Evidencia novedosa confirma las hipótesis de que Uxul estuvo bajo control de Calakmul en el siglo VII y de que su caída se puede relacionar directamente con las derrotas de los gobernantes Yukno'm Yich'aak K'ahk' y Yukno'm Took' K'awiil a cargo de Tikal en 695 y 736 d. C., respectivamente. Cuando las autoridades centrales colapsaron en la segunda mitad del siglo VIII, la población de Uxul ni siquiera fue capaz de mantener la infraestructura más importante para sobrevivir: aquella relacionada con el manejo del agua

Investigating usability and user experience of individually verifiable internet voting schemes

Internet voting can afford more inclusive and inexpensive elections. The flip side is that the integrity of the election can be compromised by adversarial attacks and malfunctioning voting infrastructure. Individual verifiability aims to protect against such risks by letting voters verify that their votes are correctly registered in the electronic ballot box. Therefore, voters need to carry out additional tasks making human factors crucial for security. In this article, we establish a categorization of individually verifiable Internet voting schemes based on voter interactions. For each category in our proposed categorization, we evaluate a voting scheme in a user study with a total of 100 participants. In our study, we assessed usability, user experience, trust, and further qualitative data to gain deeper insights into voting schemes. Based on our results, we conclude with recommendations for developers and policymakers to inform the choices and design of individually verifiable Internet voting schemes