Geological Mapping of the Debussy Quadrangle (H-14) Preliminary Results

Geological mapping of Mercury is crucial to build an understanding of the history of the planet and to set the context for BepiColombo’s observations [1]. Geo-logical mapping of the Debussy quadrangle (H-14) is now underway as part of a program to map the entire planet at a scale of 1:3M using MESSENGER data [2]. The quadrangle is located in the southern hemisphere of Mercury at 0o – 90o E and 22.5o – 65o S. This will be the first high resolution map of the quadrangle as it was not imaged by Mariner 10

Agate Fossil Beds National Monument Fish Inventory

The Niobrara River flows through Agate Fossil Beds National Monument (AGFO) maintaining about 18-km of riverine habitat. The lack of large-scale human alterations like impoundment and channelization to the Niobrara River within AGFO make this stretch of river an ideal location to support native fish communities. However, concern for native fishes in the Niobrara River in and around AGFO has grown because non-native brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss have been actively stocked in the region. Other species like largemouth bass Micropterus salmoides, bluegill Lepomis macrochirus, and northern pike Esox lucius may have also established populations from stocking activities above or below the AGFO property

Structural Behavior of Tc and I Ions in Nuclear Waste Glass

AbstractTechnetium-99 (Tc) and iodine-129 (I) are two long-lived fission products of high volatility, which makes their study in glass structure challenging. Both technetium and iodine have broad ranging multivalent chemistry and complex reactivity dependent on redox conditions; technetium and iodine redox may vary from Tc0 to Tc7+ and from I- to I7+. Relatively few studies have been done on their speciation in glass, in part because of their low retention at the temperatures required for glass melting. To better understand the redox and structural behavior of Tc and I in various nuclear waste glasses, a series of technetium- and iodine-containing borosilicate glasses of varied chemistry were prepared at scales ranging from a few grams to hundreds of kilograms. Technetium was included in both high-level and low-level nuclear waste glass formulations under a variety of redox conditions at concentrations ranging from 0.003 wt% to 0.06 wt%. Non-radioactive iodine glass samples were prepared in crucible melts using excess amounts of sodium or potassium iodide salts or ammonium iodate that resulted in concentrations ranging from 0.04 to 1.27 wt% iodine. These samples were also compared to glasses prepared in pilot-scale experiments in which the overall retentions reached 48% and 34% for technetium and iodine, respectively. Tc and I speciation in the resulting glasses were determined by X-ray absorption spectroscopy (XAS). While technetium was found as Tc0, Tc4+, and Tc7+, only I- was identified in these glasses. Previous studies of Tc local environment information inferred from K-edge XAS and Raman spectroscopy identified pertechnetate tetrahedra surrounded by network-modifying cations in oxidized glasses and octahedral TcO6 units in glasses prepared under reducing conditions. Conversely, iodine K-edge XAS of all glasses studied indicate iodide environments with lithium or sodium nearest-neighbors resembling disordered versions of octahedral sites in crystalline lithium or sodium iodide

Optimal Quantum Clocks

A quantum clock must satisfy two basic constraints. The first is a bound on the time resolution of the clock given by the difference between its maximum and minimum energy eigenvalues. The second follows from Holevo's bound on how much classical information can be encoded in a quantum system. We show that asymptotically, as the dimension of the Hilbert space of the clock tends to infinity, both constraints can be satisfied simultaneously. The experimental realization of such an optimal quantum clock using trapped ions is discussed.Comment: 4 pages, revtex, 1 figure, revision contains some new result

Undergraduate work placements: an analysis of the effects on career progression

Combining work experience with degree-level study is seen as a key differentiator for securing employment upon graduation in a competitive employment market. The positive benefits of sandwich courses, where up to twelve months is spent working in industry, are widely acknowledged in academic literature though data analysis tends to focus on cohorts in single subject areas with course-based factors possibly influencing outcomes. This paper explores the benefits of work placements on a cross-cohort basis with an institutional level study empirically analysing over three academic years the outcomes for placement students in comparison to non-placement students. The study found that completing a sandwich work placement is associated with improved academic performance in the final year of study. Placement students are also more likely to secure appropriate graduate-level work and higher starting salaries upon completion of their degree in comparison to non-placement students

Phase Operator for the Photon Field and an Index Theorem

An index relation $dim\ ker\ a^{\dagger}a - dim\ ker\ aa^{\dagger} = 1$ is satisfied by the creation and annihilation operators $a^{\dagger}$ and $a$ of a harmonic oscillator. A hermitian phase operator, which inevitably leads to $dim\ ker\ a^{\dagger}a - dim\ ker\ aa^{\dagger} = 0$, cannot be consistently defined. If one considers an $s+1$ dimensional truncated theory, a hermitian phase operator of Pegg and Barnett which carries a vanishing index can be defined. However, for arbitrarily large $s$, we show that the vanishing index of the hermitian phase operator of Pegg and Barnett causes a substantial deviation from minimum uncertainty in a characteristically quantum domain with small average photon numbers. We also mention an interesting analogy between the present problem and the chiral anomaly in gauge theory which is related to the Atiyah-Singer index theorem. It is suggested that the phase operator problem related to the above analytic index may be regarded as a new class of quantum anomaly. From an anomaly view point ,it is not surprising that the phase operator of Susskind and Glogower, which carries a unit index, leads to an anomalous identity and an anomalous commutator.Comment: 32 pages, Late