Microscopic origin of granular ratcheting

Numerical simulations of assemblies of grains under cyclic loading exhibit ``granular ratcheting'': a small net deformation occurs with each cycle, leading to a linear accumulation of deformation with cycle number. We show that this is due to a curious property of the most frequently used models of the particle-particle interaction: namely, that the potential energy stored in contacts is path-dependent. There exist closed paths that change the stored energy, even if the particles remain in contact and do not slide. An alternative method for calculating the tangential force removes granular ratcheting.Comment: 13 pages, 18 figure

Biofunctionalization of zinc oxide nanowires for DNA sensory applications

We report on the biofunctionalization of zinc oxide nanowires for the attachment of DNA target molecules on the nanowire surface. With the organosilane glycidyloxypropyltrimethoxysilane acting as a bifunctional linker, amino-modified capture molecule oligonucleotides have been immobilized on the nanowire surface. The dye-marked DNA molecules were detected via fluorescence microscopy, and our results reveal a successful attachment of DNA capture molecules onto the nanowire surface. The electrical field effect induced by the negatively charged attached DNA molecules should be able to control the electrical properties of the nanowires and gives way to a ZnO nanowire-based biosensing device

Hepatocytic expression of human sodium-taurocholate cotransporting polypeptide enables hepatitis B virus infection of macaques

Hepatitis B virus (HBV) is a major global health concern, and the development of curative therapeutics is urgently needed. Such efforts are impeded by the lack of a physiologically relevant, pre-clinical animal model of HBV infection. Here, we report that expression of the HBV entry receptor, human sodium-taurocholate cotransporting polypeptide (hNTCP), on macaque primary hepatocytes facilitates HBV infection in vitro, where all replicative intermediates including covalently closed circular DNA (cccDNA) are present. Furthermore, viral vector-mediated expression of hNTCP on hepatocytes in vivo renders rhesus macaques permissive to HBV infection. These in vivo macaque HBV infections are characterized by longitudinal HBV DNA in serum, and detection of HBV DNA, RNA, and HBV core antigen (HBcAg) in hepatocytes. Together, these results show that expressing hNTCP on macaque hepatocytes renders them susceptible to HBV infection, thereby establishing a physiologically relevant model of HBV infection to study immune clearance and test therapeutic and curative approaches

Surface-enhanced Raman spectroscopy of the endothelial cell membrane

We applied surface-enhanced Raman spectroscopy (SERS) to cationic gold-labeled endothelial cells to derive SERS-enhanced spectra of the bimolecular makeup of the plasma membrane. A two-step protocol with cationic charged gold nanoparticles followed by silver-intensification to generate silver nanoparticles on the cell surface was employed. This protocol of post-labelling silver-intensification facilitates the collection of SERS-enhanced spectra from the cell membrane without contribution from conjugated antibodies or other molecules. This approach generated a 100-fold SERS-enhancement of the spectral signal. The SERS spectra exhibited many vibrational peaks that can be assigned to components of the cell membrane. We were able to carry out spectral mapping using some of the enhanced wavenumbers. Significantly, the spectral maps suggest the distribution of some membrane components are was not evenly distributed over the cells plasma membrane. These results provide some possible evidence for the existence of lipid rafts in the plasma membrane and show that SERS has great potential for the study and characterization of cell surfaces

Classification and Evaluation of Multicast-Based Mobility Support in All-IP Cellular Networks

To solve the IP mobility problem the use of multicast has been proposed in a number of di#erent approaches, applying multicast in di#erent characteristic ways. In this paper we provide a framework to classify such approaches by analyzing requirements, options for using multicast protocols, and mobility functionalities augmenting the multicast

Optimization of Handover Performance by Link Layer Triggers in IP-Based Networks: Parameters, Protocol Extensions and APIs for Implementation

The detection and triggering of handover is an important functionality of handover that has a strong impact on the performance in terms of handover latency and packet loss, in particular in scenarios with frequent handover. It is common to all IP-based mobility solutions that they provide network layer trigger for handover -- for example, based on the lifetime field or the network prefix in Mobile IP advertisements. The technical report covers the following aspects of link layer trigger for handover. First, parameters and their combinations for link-layer triggers are identified. Second, the potential performance gain of link layer triggers in comparison of network layer triggers are quantified for Mobile IP and Hierarchical Mobile IP by means of a simulative study. Third, the interaction of the link layer and the network layer are described for Mobile IPv6 and its hierarchical variant as well as for the fast handover extensions of Mobile IPv6. Fourth, the requirements for an applicationprogramming interface (API) are summarized and existing APIs for interaction between link-layer and network layer are evaluated

Implementation Design of the MOMBASA Software Environment

In this report the implementation of the MOMBASA Software Environment is presented. The MOMBASA Software Environment is an experimental platform to examine multicast-based host mobility in IP networks. The report describes the implementation design of the main components (Mobile Agent, MEP and Gateway), the implementation environment and the necessary modifications of the Linux kernel. Main purpose of the report is to document the current implementation of the MOMBASA Software Environment and particularly, to facilitate its extensibility for use as a generic toolkit for experimentation with multicast-based mobility support