1,848 research outputs found
Practical Schemes For Privacy & Security Enhanced RFID
Proper privacy protection in RFID systems is important. However, many of the
schemes known are impractical, either because they use hash functions instead
of the more hardware efficient symmetric encryption schemes as a efficient
cryptographic primitive, or because they incur a rather costly key search time
penalty at the reader. Moreover, they do not allow for dynamic, fine-grained
access control to the tag that cater for more complex usage scenarios.
In this paper we investigate such scenarios, and propose a model and
corresponding privacy friendly protocols for efficient and fine-grained
management of access permissions to tags. In particular we propose an efficient
mutual authentication protocol between a tag and a reader that achieves a
reasonable level of privacy, using only symmetric key cryptography on the tag,
while not requiring a costly key-search algorithm at the reader side. Moreover,
our protocol is able to recover from stolen readers.Comment: 18 page
Study of the and reactions close to threshold
Two--kaon production in proton--deuteron collisions has been studied at three
energies close to threshold using a calibrated magnetic spectrograph to measure
the final He and a vertex detector to measure the pair.
Differential and total cross sections are presented for the production of
--mesons, decaying through , as well as for prompt
production. The prompt production seems to follow phase space in both
its differential distributions and in its energy dependence. The amplitude for
the {He} reaction varies little for excess energies below 22
MeV and the value is consistent with that obtained from a threshold
measurement. The angular distribution of the decay pair shows that
near threshold the --mesons are dominantly produced with polarization
along the initial proton direction. No conclusive evidence for
production is found in the data.Comment: 13 figure
Automatic rebuilding and optimization of crystallographic structures in the Protein Data Bank
Motivation: Macromolecular crystal structures in the Protein Data Bank (PDB) are a key source of structural insight into biological processes. These structures, some >30 years old, were constructed with methods of their era. With PDB_REDO, we aim to automatically optimize these structures to better fit their corresponding experimental data, passing the benefits of new methods in crystallography on to a wide base of non-crystallographer structure users
Frauenforschung in der Soziologie - quo vadis?
It is widely accepted that the devastating consequences of spinal cord injury are due to the failure of lesioned CNS axons to regenerate. The current study of the spontaneous tissue repair processes following dorsal hemisection of the adult rat spinal cord demonstrates a phase of rapid and substantial nerve fibre in‐growth into the lesion that was derived largely from both rostral and caudal spinal tissues. The response was characterized by increasing numbers of axons traversing the clearly defined interface between the lesion and the adjacent intact spinal cord, beginning by 5 days post operation (p.o.). Having penetrated the lesion, axons became associated with a framework of NGFr‐positive non‐neuronal cells (Schwann cells and leptomeningeal cells). Surprisingly few of these axons were derived from CGRP‐ or SP‐immunoreactive dorsal root ganglion neurons. At the longest survival time (56 days p.o.), there was a marked shift in the overall orientation of fibres from a largely rostro‐caudal to a dorso‐ventral axis. Attempts to identify which recognition molecules may be important for these re‐organizational processes during attempted tissue repair demonstrated the widespread and intense expression of the cell adhesion molecules (CAM) L1 and N‐CAM. Double immunofluorescence suggested that both Schwann cells and leptomeningeal cells contributed to the pattern of CAM expression associated with the cellular framework within the lesion
Upper limits for a narrow resonance in the reaction p + p -> K^+ + (Lambda p)
The reaction pp -> K^+ + (Lambda p) has been measured at T_p = 1.953 GeV and
\Theta = 0 deg with a high missing mass resolution in order to study the Lambda
p final state interaction. Narrow S = -1 resonances predicted by bag model
calculations are not visible in the missing mass spectrum. Small structures
observed in a previous experiment are not confirmed. Upper limits for the
production cross section of a narrow resonance are deduced for missing masses
between 2058 and 2105 MeV/c^2.Comment: 8 pages, 5 figure
Geo‐Hydromorphological Assessment of Europe’s Southernmost Blanket Bogs
Blanket bogs are a globally rare type of ombrotrophic peatland internationally recognised for long‐term terrestrial carbon storage, the potential to serve as carbon sinks, habitat provision and for their palaeoenvironmental archive. This habitat is protected in the European Union under the Habitats Directive (92/43/EEC), but a number of blanket bogs located in the Cantabrian Mountains (northern Spain), representing the southernmost known edge‐of‐range for this habitat in Europe, are currently not recognised and are at increased threat of loss.
Using climatic data, topography, aerial photography and peat depth surveys, this study has identified ten new areas of blanket bog located between the administrative regions of Cantabria and Castilla y León. Peat depth data and topography were used to provide a detailed geomorphological description and hydromorphological classification (mesotope units) of these currently unrecognised areas of blanket bog.
Maximum peat depth measured across the ten sites ranged from 1.61 m to 3.78 m covering a total area of 18.6 ha of blanket bog (> 40 cm peat depth). The volume of peat accumulated across the sites was determined to be more than 216,000 m3 and is estimated to hold 19.89 ± 3.51kt C. Twenty‐four individual hydrological mesotope units were described indicating a diverse assemblage of blanket bogs in this region.
The peatlands identified in this research extend the known limit of blanket bogs in Europe farther south than previously recorded and combined with four other unprotected blanket bogs recently identified in the Cantabrian Mountains, these peatlands represent 10.5% of blanket bog currently recognised and protected in Spain. The range of anthropogenic pressures currently acting on peatlands in the Cantabrian Mountains indicates that without protection these important landforms and carbon stored may be lost. An urgent update of European peatland inventories is thus required to preserve these valuable carbon stores and potential carbon sinks
Cross section of the reaction close to threshold
We have measured inclusive data on -meson production in collisions
at COSY J\"ulich close to the hyperon production threshold and determined the
hyperon-nucleon invariant mass spectra. The spectra were decomposed into three
parts: , and . The cross section for the
channel was found to be much smaller than a previous measurement in
that excess energy region. The data together with previous results at higher
energies are compatible with a phase space dependence.Comment: accepted by Phys. lett. B some typos correcte
- …