A 128K-bit CCD buffer memory system

A prototype system was implemented to demonstrate that CCD's can be applied advantageously to the problem of low power digital storage and particularly to the problem of interfacing widely varying data rates. 8K-bit CCD shift register memories were used to construct a feasibility model 128K-bit buffer memory system. Peak power dissipation during a data transfer is less than 7 W., while idle power is approximately 5.4 W. The system features automatic data input synchronization with the recirculating CCD memory block start address. Descriptions are provided of both the buffer memory system and a custom tester that was used to exercise the memory. The testing procedures and testing results are discussed. Suggestions are provided for further development with regards to the utilization of advanced versions of CCD memory devices to both simplified and expanded memory system applications

Baryon phase-space density in heavy-ion collisions

The baryon phase-space density at mid-rapidity from central heavy-ion collisions is estimated from proton spectra with interferometry and deuteron coalescence measurements. It is found that the mid-rapidity phase-space density of baryons is significantly lower at the SPS than the AGS, while those of total particles (pion + baryon) are comparable. Thermal and chemical equilibrium model calculations tend to over-estimate the phase-space densities at both energies.Comment: 5 pages, 2 tables, no figure. RevTeX style. Accepted for publication in Phys. Rev. C Rapid Communicatio

The leaching of natural colloids from forest surface soils and their role for the P transfer

Soil nanoparticles (d<100nm) and colloids (d<1µm) exert a decisive control on the mobilisation of strongly sorbing compounds such as phosphorus (P). We investigated the nanoparticles and colloids present in forest soil leachates examining their role for the P fixation and for the vertical P transfer in forest soils. Mesocosm experiments with three German forest soils (upper 20 cm) were conducted. The mesocosms were irrigated with artificial rain for 22 months and the nanoparticles and colloids were characterised in the soil leachates with special attention to P. The field flow fractionation (FFF) technique coupled online to UV- and DLS- detectors and inductively coupled plasma mass spectrometry (ICP-MS) or to an organic carbon detector (OCD) enabled a size resolved characterization and quantification of the nanoparticulate and colloidal fractions and their elemental composition (P, Corg, Fe, A, Si, Ca. Mn). To visualise and better characterise the particles present in the leachates, transmission electron microscopy with energy-dispersive x-ray spectroscopy (TEM-EDX) measurements were performed. The translocated particles exhibited sizes up to 350 nm. Using FFF we separated the colloids in three size fractions i) 3-20 nm ii) 20-70 nm and iii) 70-350 nm. The particle fractions showed different chemical compositions. However their composition and characteristics were similar between the three forest sites and comparable to the natural nanoparticles and colloids from soils (“water dispersible colloids”) and streams described in literature. Up to 90% (on average ~45 %) of the leached P was associated with the nanoparticles and colloids. Our qualitative and quantitative analysis of the soil leachates showed that nanoparticles and colloids are crucial vectors controlling the P fluxes in forest ecosystems and could be a significant, but as yet still poorly quantified P loss factor

Incorporating Radial Flow in the Lattice Gas Model for Nuclear Disassembly

We consider extensions of the lattice gas model to incorporate radial flow. Experimental data are used to set the magnitude of radial flow. This flow is then included in the Lattice Gas Model in a microcanonical formalism. For magnitudes of flow seen in experiments, the main effect of the flow on observables is a shift along the $E^*/A$ axis.Comment: Version accepted for publication in Phys. Rev. C, Rapid Communicatio

A unified description for nuclear equation of state and fragmentation in heavy ion collisions

We propose a model that provides a unified description of nuclear equation of state and fragmentations. The equation of state is evaluated in Bragg-Williams as well as in Bethe-Peierls approximations and compared with that in the mean field theory with Skyrme interactions. The model shows a liquid-gas type phase transition. The nuclear fragment distributions are studied for different densities at finite temperatures. Power law behavior for fragments is observed at critical point. The study of fragment distribution and the second moment $S_2$ shows that the thermal critical point coincides with the percolation point at the critical density. High temperature behavior of the model shows characteristics of chemical equilibrium.Comment: 20 pages in RevTex, 11 figures (uuencoded ps files), to appear in Phys. Rev.

Accurate calibration of test mass displacement in the LIGO interferometers

We describe three fundamentally different methods we have applied to calibrate the test mass displacement actuators to search for systematic errors in the calibration of the LIGO gravitational-wave detectors. The actuation frequencies tested range from 90 Hz to 1 kHz and the actuation amplitudes range from 1e-6 m to 1e-18 m. For each of the four test mass actuators measured, the weighted mean coefficient over all frequencies for each technique deviates from the average actuation coefficient for all three techniques by less than 4%. This result indicates that systematic errors in the calibration of the responses of the LIGO detectors to differential length variations are within the stated uncertainties.Comment: 10 pages, 6 figures, submitted on 31 October 2009 to Classical and Quantum Gravity for the proceedings of 8th Edoardo Amaldi Conference on Gravitational Wave

Bringing the Fuzzy Front End into Focus

Technology planning is relatively straightforward for well-established research and development (R and D) areas--those areas in which an organization has a history, the competitors are well understood, and the organization clearly knows where it is going with that technology. What we are calling the fuzzy front-end in this paper is that condition in which these factors are not well understood--such as for new corporate thrusts or emerging areas where the applications are embryonic. While strategic business planning exercises are generally good at identifying technology areas that are key to future success, they often lack substance in answering questions like: (1) Where are we now with respect to these key technologies? ... with respect to our competitors? (2) Where do we want or need to be? ... by when? (3) What is the best way to get there? In response to its own needs in answering such questions, Sandia National Laboratories is developing and implementing several planning tools. These tools include knowledge mapping (or visualization), PROSPERITY GAMES and technology roadmapping--all three of which are the subject of this paper. Knowledge mapping utilizes computer-based tools to help answer Question 1 by graphically representing the knowledge landscape that we populate as compared with other corporate and government entities. The knowledge landscape explored in this way can be based on any one of a number of information sets such as citation or patent databases. PROSPERITY GAMES are high-level interactive simulations, similar to seminar war games, which help address Question 2 by allowing us to explore consequences of various optional goals and strategies with all of the relevant stakeholders in a risk-free environment. Technology roadmapping is a strategic planning process that helps answer Question 3 by collaboratively identifying product and process performance targets and obstacles, and the technology alternatives available to reach those targets

Discovery and Follow-up of Rotating Radio Transients with the Green Bank and LOFAR Telescopes

We have discovered 21 Rotating Radio Transients (RRATs) in data from the Green Bank Telescope (GBT) 350-MHz Drift-scan and the Green Bank North Celestial Cap pulsar surveys using a new candidate sifting algorithm. RRATs are pulsars with sporadic emission that are detected through their bright single pulses rather than Fourier domain searches. We have developed {\tt RRATtrap}, a single-pulse sifting algorithm that can be integrated into pulsar survey data analysis pipelines in order to find RRATs and Fast Radio Bursts. We have conducted follow-up observations of our newly discovered sources at several radio frequencies using the GBT and Low Frequency Array (LOFAR), yielding improved positions and measurements of their periods, dispersion measures, and burst rates, as well as phase-coherent timing solutions for four of them. The new RRATs have dispersion measures (DMs) ranging from 15 to 97 pc cm$^{-3}$, periods of 240 ms to 3.4 s, and estimated burst rates of 20 to 400 pulses hr$^{-1}$ at 350 MHz. We use this new sample of RRATs to perform statistical comparisons between RRATs and canonical pulsars in order to shed light on the relationship between the two populations. We find that the DM and spatial distributions of the RRATs agree with those of the pulsars found in the same survey. We find evidence that slower pulsars (i.e. $P>200$ ms) are preferentially more likely to emit bright single pulses than are faster pulsars ($P<200$ ms), although this conclusion is tentative. Our results are consistent with the proposed link between RRATs, transient pulsars, and canonical pulsars as sources in various parts of the pulse activity spectrum.Comment: 18 pages, 13 figures, 5 tables, published in Ap

Continuum corrections to the level density and its dependence on excitation energy, n-p asymmetry, and deformation

In the independent-particle model, the nuclear level density is determined from the neutron and proton single-particle level densities. The single-particle level density for the positive-energy continuum levels is important at high excitation energies for stable nuclei and at all excitation energies for nuclei near the drip lines. This single-particle level density is subdivided into compound-nucleus and gas components. Two methods were considered for this subdivision. First in the subtraction method, the single-particle level density is determined from the scattering phase shifts. In the Gamov method, only the narrow Gamov states or resonances are included. The level densities calculated with these two methods are similar, both can be approximated by the backshifted Fermi-gas expression with level-density parameters that are dependent on A, but with very little dependence on the neutron or proton richness of the nucleus. However, a small decrease in the level-density parameter was predicted for some nuclei very close to the drip lines. The largest difference between the calculations using the two methods was the deformation dependence on the level density. The Gamov method predicts a very strong peaking of the level density at sphericity for high excitation energies. This leads to a suppression of deformed configurations and, consequently, the fission rate predicted by the statistical model is reduced in the Gamov method.Comment: 18 pages 24 figure

Equation of state of asymmetric nuclear matter and collisions of neutron-rich nuclei

The ratio of pre-equilibrium neutrons to protons from collisions of neutron-rich nuclei is studied as a function of their kinetic energies. This ratio is found to be sensitive to the density dependence of the nuclear symmetry energy, but is independent of the compressibility of symmetric nuclear matter and the in-medium nucleon-nucleon cross sections. The experimental measurement of this ratio thus provides a novel means for determining the nuclear equation of state of asymmetric nuclear matter.Comment: 11 pages + 3 postscript figures, Phys. Rev. Lett. (1997) in pres