Combinatorial Bounds and Characterizations of Splitting Authentication Codes

We present several generalizations of results for splitting authentication codes by studying the aspect of multi-fold security. As the two primary results, we prove a combinatorial lower bound on the number of encoding rules and a combinatorial characterization of optimal splitting authentication codes that are multi-fold secure against spoofing attacks. The characterization is based on a new type of combinatorial designs, which we introduce and for which basic necessary conditions are given regarding their existence.Comment: 13 pages; to appear in "Cryptography and Communications

The Location of the Nucleus of NGC 1068 and the Three-dimensional Structure of Its Nuclear Region

The HST archival UV imaging polarimetry data of NGC 1068 is re-examined. Through an extensive estimation of the observational errors, we discuss whether the distribution of the position angles (PAs) of polarization is simply centrosymmetric or not. Taking into account the effect of a bad focus at the time of the observation, we conclude that, within the accuracy of HST/FOC polarimetry, the PA distribution is completely centrosymmetric. This means that the UV polarization originates only from scattering of the radiation from a central point-like source. However, our analysis shows that the most probable location of the nucleus is only ~0.''08 (~6pc) south from the brightest cloud called ``cloud B''. The error circle of 99% confidence level extends to cloud B and to ``cloud A'' which is about 0.''2 south of cloud B. By this FOC observation, Cloud B is only marginally rejected as the nucleus. Assuming that the UV flux is dominated by electron-scattered light, we have also derived a three-dimensional structure of the nuclear region. The inferred distribution suggests a linear structure which could be related to the radio jet.Comment: 19 pages, 14 figures, to be published in the Astrophysical Journa

Maximizing phonon thermal conductance for ballistic membranes

At low temperatures, phonon scattering can become so weak that phonon transport becomes ballistic. We calculate the ballistic phonon conductance G for membranes using elasticity theory, considering the transition from three to two dimensions. We discuss the temperature and thickness dependence and especially concentrate on the issue of material parameters. For all membrane thicknesses, the best conductors have, counter-intuitively, the lowest speed of sound.Comment: 4 pages, 4 figures, proceedings to phonons 2007 conferenc

A Practical Guide to Operator/ Surface-Owner Disputes and the Current State of the Accommodation Doctrine

This Article provides an overview of the operator\u27s rights and a practical guide to the procedures available to enforce them. Of particular emphasis, this Article will discuss how an operator can use injunctive relief to prevent surface-owner interference, and will specifically provide a checklist of sorts for how an operator can obtain a temporary restraining order. This Article will also address how the operator\u27s rights can be limited by the accommodation doctrine. In this regard, this Article will examine how the accommodation doctrine is triggered, what the surface owner must prove when asserting the accommodation doctrine, and whether the accommodation doctrine provides a mechanism for the surface owner to recover damages from the operator for unreasonable surface use

Role of Endovascular Grafts in Combined Vascular and Skeletal Injuries of the Lower Extremity: a Preliminary Report

Background: A gunshot wound to the lower extremity with combined skeletal and vascular injuries can be difficult to manage. In clinical practice, it is not always possible to assemble a multispecialty team to work seamlessly to attain this goal, and the end result may be unnecessary prolonged ischemic time. A covered endovascular stent (EVS) can be used initially to restore perfusion without need of a time-consuming temporary shunt in select cases. Objectives: The objective of this study is to compare novel methods of repairing the superficial femoral artery to the traditional three-step operative approach in patients that have a concomitant femur fracture. Patients and Methods: All patients with combined vascular and skeletal injuries to the lower extremity were reviewed retrospectively. Patients were divided into three groups: Group 1: EVS placed percutaneously. Group 2: EVS placed with a hybrid combination of open and endovascular technique. Group 3: Placement of temporary shunt followed by skeletal stabilization and definitive vascular repair. Results: There were 16 patients identified. Group 1 = three, Group 2 = six, Group 3 = seven. EVS can shorten time to revascularization and prevents a second episode of vascular interruption at the time of the final vascular repair. The structural stability of the EVS was strong enough to withstand the skeletal manipulation without deformation of the stent. Conclusions: EVS is comparable to open repair and has the strength to withstand orthopedic manipulation in the short term when used in combined vascular and skeletal injuries to the lower extremity. Ischemic time is reduced significantly if final revascularization is accomplished at the onset with an EVS and the process is more efficient if the trauma surgeon is able to repair the vascular injury. With increasing sophistication of endovascular devices, this offers an appealing approach to vascular injuries that will decrease ischemic and total operative times when compared to the more traditional three-stage repair

Optical Pulse-Phased Photopolarimetry of PSR B0656+14

We have observed the optical pulse profile of PSR B0656+14 in 10 phase bins at a high signal-to-noise ratio, and have measured the linear polarization profile over 30% of the pulsar period with some significance. The pulse profile is double-peaked, with a bridge of emission between the two peaks, similar to gamma-ray profiles observed in other pulsars. There is no detectable unpulsed flux, to a 1-sigma limit of 16% of the pulse-averaged flux. The emission in the bridge is highly (~ 100%) polarized, with a position angle sweep in excellent agreement with the prediction of the Rotating Vector Model as determined from radio polarization observations. We are able to account for the gross features of the optical light curve (i.e., the phase separation of the peaks) using both polar cap and outer gap models. Using the polar cap model, we are also able to estimate the height of the optical emission regions.Comment: 27 pages, 11 figures, accepted by ApJ (scheduled v597 n2, November 10, 2003

Evolution of the bilayer nu = 1 quantum Hall state under charge imbalance

We use high-mobility bilayer hole systems with negligible tunneling to examine how the bilayer nu = 1 quantum Hall state evolves as charge is transferred from one layer to the other at constant total density. We map bilayer nu = 1 state stability versus imbalance for five total densities spanning the range from strongly interlayer coherent to incoherent. We observe competition between single-layer correlations and interlayer coherence. Most significantly, we find that bilayer systems that are incoherent at balance can develop spontaneous interlayer coherence with imbalance, in agreement with recent theoretical predictions.Comment: 4 pages, 4 figure