An in Situ Technique for Elemental Analysis of Lunar Surfaces

An in situ analytical technique that can remotely determine the elemental constituents of solids has been demonstrated. Laser-Induced Breakdown Spectroscopy (LIBS) is a form of atomic emission spectroscopy in which a powerful laser pulse is focused on a solid to generate a laser spark, or microplasma. Material in the plasma is vaporized, and the resulting atoms are excited to emit light. The light is spectrally resolved to identify the emitting species. LIBS is a simple technique that can be automated for inclusion aboard a remotely operated vehicle. Since only optical access to a sample is required, areas inaccessible to a rover can be analyzed remotely. A single laser spark both vaporizes and excites the sample so that near real-time analysis (a few minutes) is possible. This technique provides simultaneous multielement detection and has good sensitivity for many elements. LIBS also eliminates the need for sample retrieval and preparation preventing possible sample contamination. These qualities make the LIBS technique uniquely suited for use in the lunar environment

High-level Cryptographic Abstractions

The interfaces exposed by commonly used cryptographic libraries are clumsy, complicated, and assume an understanding of cryptographic algorithms. The challenge is to design high-level abstractions that require minimum knowledge and effort to use while also allowing maximum control when needed. This paper proposes such high-level abstractions consisting of simple cryptographic primitives and full declarative configuration. These abstractions can be implemented on top of any cryptographic library in any language. We have implemented these abstractions in Python, and used them to write a wide variety of well-known security protocols, including Signal, Kerberos, and TLS. We show that programs using our abstractions are much smaller and easier to write than using low-level libraries, where size of security protocols implemented is reduced by about a third on average. We show our implementation incurs a small overhead, less than 5 microseconds for shared key operations and less than 341 microseconds (< 1%) for public key operations. We also show our abstractions are safe against main types of cryptographic misuse reported in the literature

Spin Relaxation in a Quantum Dot due to Nyquist Noise

We calculate electron and nuclear spin relaxation rates in a quantum dot due to the combined action of Nyquist noise and electron-nuclei hyperfine or spin-orbit interactions. The relaxation rate is linear in the resistance of the gate circuit and, in the case of spin-orbit interaction, it depends essentially on the orientations of both the static magnetic field and the fluctuating electric field, as well as on the ratio between Rashba and Dresselhaus interaction constants. We provide numerical estimates of the relaxation rate for typical system parameters, compare our results with other, previously discussed mechanisms, and show that the Nyquist mechanism can have an appreciable effect for experimentally relevant systems.Comment: v2: New discussion of arbitrary gate setups (1 new figure), more Comments on experiments; 6 pages, 4 figure

Transport in an inhomogeneous interacting one--dimensional system

Transport through a one--dimensional wire of interacting electrons connected to semi--infinite leads is investigated using a bosonization approach. An incident electron is transmitted as a sequence of partial charges. The dc conductance is found to be entirely determined by the properties of the leads. The dynamic nonlocal conductivity is rigorously expressed in terms of the transmission. For abrupt variations of the interaction parameters at the junctions the central wire acts as a Fabry--Perot resonator. When one of the connected wires has a tendency towards superconducting order, partial Andreev reflection of an incident electron occurs.Comment: 11 pages, RevTeX 3.0, 1 postscript figure, everything in a uuencoded fil

Is It Time For An Exchange Traded Futures Contract Based On A Housing Price Index?

There is not a good hedging instrument to absorb housing price risk. An exchange traded futures contract based on a hedonic or repeat sale housing price index would help homeowners, originators, home builders, and others hedge housing price risk, but it does not exist, yet. We discuss the need and why it may be time for its introduction

First Results from the Transit Ephemeris Refinement and Monitoring Survey (TERMS)

Transiting planet discoveries have yielded a plethora of information towards understanding the structure and atmospheres of extra-solar planets. These discoveries have been restricted to the short-period or low-periastron distance regimes due to the bias inherent in the geometric transit probability. Through the refinement of planetary orbital parmaters, and hence reducing the size of transit windows, long-period planets become feasible targets for photometric follow-up. Here we describe the TERMS project which is monitoring these host stars at predicted transit times

Multiple-quasiparticle agglomerates at \nu=2/5

We investigate the dynamics of quasiparticle agglomerates in edge states of the Jain sequence for \nu=2/5. Comparison of the Fradkin-Lopez model with the Wen one is presented within a field theoretical construction, focusing on similarities and differences. We demonstrate that both models predict the same universal role for the multiple-quasiparticle agglomerates that dominate on single quasiparticles at low energy. This result is induced by the presence of neutral modes with finite velocity and is essential to explain the anomalous behavior of tunneling conductance and noise through a point contact.Comment: 6 pages, in press Physica E as proceedings of FQMT0

Categorisation and Detection of Dark Matter Candidates from String/M-theory Hidden Sectors

We study well-motivated dark matter candidates arising from weakly-coupled hidden sectors in compactified string/$M$-theory. Imposing generic top-down constraints greatly restricts allowed candidates. By considering the possible mechanisms for achieving the correct dark matter relic density, we compile categories of viable dark matter candidates and annihilation mediators. We consider the case where supersymmetry breaking occurs via moduli stabilisation and is gravitationally mediated to the visible and other hidden sectors, without assuming sequestering of the sector in which supersymmetry is broken. We find that in this case, weakly-coupled hidden sectors only allow for fermionic dark matter. Additionally, most of the mechanisms for obtaining the full relic density only allow for a gauge boson mediator, such as a dark $Z'$. Given these considerations, we study the potential for discovering or constraining the allowed parameter space given current and future direct detection experiments, and direct production at the LHC. We also present a model of a hidden sector which would contain a satisfactory dark matter candidate.Comment: 29 pages, 10 figure

Arginine-rich peptides destabilize the plasma membrane, consistent with a pore formation translocation mechanism of cell penetrating peptides

Recent molecular dynamics simulations (Herce and Garcia, PNAS, 104: 20805 (2007)) have suggested that the arginine-rich HIV Tat peptides might be able to translocate by destabilizing and inducing transient pores in phospholipid bilayers. In this pathway for peptide translocation, arginine residues play a fundamental role not only in the binding of the peptide to the surface of the membrane but also in the destabilization and nucleation of transient pores across the bilayer, despite being charged and highly hydrophilic. Here we present a molecular dynamics simulation of a peptide composed of nine arginines (Arg-9) that shows that this peptide follows the same translocation pathway previously found for the Tat peptide. We test this hypothesis experimentally by measuring ionic currents across phospholipid bilayers and cell membranes through the pores induced by Arg-9 peptides. We find that Arg-9 peptides, in the presence of an electrostatic potential gradient, induce ionic currents across planar phospholipid bilayers, as well as in cultured osteosarcoma cells and human smooth muscle cells freshly isolated from the umbilical artery. Our results suggest that the mechanism of action of Arg-9 peptide involves the creation of transient pores in lipid bilayers and cell membranes.Comment: This is an extended version of the published manuscript, which had to be shortened before publication to fit within the number of pages required by the journa