419 research outputs found
Rutger's CAM2000 chip architecture
This report describes the architecture and instruction set of the Rutgers CAM2000 memory chip. The CAM2000 combines features of Associative Processing (AP), Content Addressable Memory (CAM), and Dynamic Random Access Memory (DRAM) in a single chip package that is not only DRAM compatible but capable of applying simple massively parallel operations to memory. This document reflects the current status of the CAM2000 architecture and is continually updated to reflect the current state of the architecture and instruction set
Content addressable memory project
A parameterized version of the tree processor was designed and tested (by simulation). The leaf processor design is 90 percent complete. We expect to complete and test a combination of tree and leaf cell designs in the next period. Work is proceeding on algorithms for the computer aided manufacturing (CAM), and once the design is complete we will begin simulating algorithms for large problems. The following topics are covered: (1) the practical implementation of content addressable memory; (2) design of a LEAF cell for the Rutgers CAM architecture; (3) a circuit design tool user's manual; and (4) design and analysis of efficient hierarchical interconnection networks
The Geological Context of Middle Pleistocene Crater Lake Deposits and Fossil Birds at Ulupau Head, Oahu, Hawaiian Islands
Els dipòsits pleistocènics Llacunars del cràter Ulupau, a Oahu, contenen les restes fòssils més antigues d' ocells conegudes a les Illes Hawaïi. Aquests fòssils són importants per documentar les taxes evolutives a una varietat de línies d'ocells terrestres i aquàtics de les illes. Lanàlísí estratigràfic detallat revela diferents cicles deposicionals que comporten dipòsits llacunars interestratificats, colluvium i paleosòls. La conca volcànica va ser oberta per l'erosió marina prèvia al pic del darrer interglacial (estadi isotòpic marí, o 'MIS' Se), fa 125 ka, restringint l'edat dels sediments del Llac al Pleistocè Mitjà. Els tres cicles de deposició (Unitats III, IV i V) semblen estar estretament lligats a pujades interglacials amb una ciclicitat de 100 ka. Donada la complexitat de la successió dels sediments del cràter i el temps requerit per a la seva formació, és probable que la conca deillac s'omplís al Llarg de diferents interglacials, assolint una extensió màxima de més de 50 ha durant l'estadi MIS 11, fa W1S 400 ka. Aquesta és també la màxima edat probable de les capes fossilíferes més riques de la Unitat III, però no es pot excloure que siguin del MIS 9 (fa 300 ka). Els requeriments d'hàbitat probables de diferents elements de l'avifauna donen llum sobre la paleoecologia de la localitat durant el Pleistocè Mitjà.Summary Pleistocene lake deposits in Ulupau Crater on Oahu contain the oldest fossil bird remains known from the Hawaiian Islands. These fossils are important for docwnenting evolutionary rates in a variety of lineages of land and water birds from the islands. Detailed stratigraphic analysis reveals distinct cycles of deposition involving interbedded lacustrine deposits, coLluviwn, and paleosols. The volcanic basin was breached by marine erosion prior to the peak of the last interglaciation (marine isotope stage or 'MIS' Se) over 125 ky ago, constraining the age of the lake sediments to the middle Pleistocene. The three cycles of deposition (Units III, Iv; and V) appear to be closely linked with interglacial highstands with 100 ky cyclicity. Given the complexity of the succession of crater sediments and the time required for their formation, it is probable that the lake basin filled over several interglacials, reaching a maximwn extent of over 50 ha during MIS 11, about 400 ky ago. This is also the likely maximum age of the richest fossil beds in Unit Iv; but MIS 9 (300 ky) also remains a possibility. Probable habitat requirements of the various elements of the avifauna provide insights into the paleoecology of the site during the middle Pleistocene
Stratigraphy and Whole-Rock Amino Acid Geochronology of Key Holocene and Last Interglacial Carbonate Deposits in the Hawaiian Islands
We evaluated the utility of whole-rock amino acid racemization
as a method for the stratigraphic correlation and dating of carbonate sediments
in the Hawaiian Islands. D-alloisoleucine/L-isoleucine (A/I) ratios were determined
for carbonate sand and sandstone samples from 25 localities in the archipelago.
The superposition of A/I ratios within stratigraphic sections and the regional
concordance of ratios within geological formations support the integrity
of the method. To correlate the A/I ratios with an absolute chronology, comparisons
were made with previously published uranium series dates on corals
and with 14C dates on carbonate sand and organic material, including several
new dates reported herein. The A/I mean from four marine isotope stage (MIS)
5e U-series calibration sites was 0.505 ± 0.027 (n = 11), and 12 "test sites" of
previously uncertain or speculative geochronological age yielded an A/I mean
of 0.445 ± 0.058 (n = 17). Similarly, extensive Holocene dunes on Moloka'i
and Kaua'i were correlated by a mean A/I ratio of 0.266 ± 0.022 (n = 8) and
equated with a 14C bulk sediment mean age of 8600 yr B.P. Our results indicate
that the eolian dunes currently exposed in various localities in the Islands originated
primarily during two major periods of dune formation, the last interglacial
(MIS 5e) and the early Holocene (MIS 1). MIS 5e and MIS 1 A/I ratios
from the Hawaiian Islands show close agreement with previous whole-rock
studies in Bermuda and the Bahamas. We discuss these results in terms of their
relevance to models of lithospheric flexure and to imposing constraints on the
time frame for the extinction of fossil birds
Prodromus of Vertebrate Paleontology and Geochronology of Bermuda
Les fluctuacions pleistocèniques del nivell de la mar han estat el primer determinant de la deposició geològica i l'evolució biòtica a Bermuda. Lilla està composta d'arenes carbonatades dipositades sobre el cim erosionat d'un volcà submarí durant el decurs de nivells de la mar elevats dels períodes interglacials. A partir de les arenisques interglaciars s'han obtingut unes poques restes de vertebrats, principalment d'edat pleístocènica mitja. Els intervals glacials estan marcats per sols vermells, derivats principalment de la pols atmosfèrica. Els vertebrats fòssils d'edat glacial no es troben preservats a la superfície i només es coneixen de coves i rebliments de fissures. A Bermuda es coneixen faunes fòssils dels darrers dos episodis glacials, però no dels anteriors. Es coneixen extincions certes o probables de vertebrats correlacionades amb, com a minim, quatre pujades interglacials del nivell de la mar (estadis isotòpics marins, MIS, 11,9,5 i 1). Es revisa la història de la paleontologia de vertebrats a Bermuda i s'allisten i es descriuen breument les localitats de vertebrats fòssils.Pleistocene sea-level fluctuations were the primary determinant of geological deposition and biotic evolution on Bermuda. The island is composed of carbonate sand deposited on the eroded summit of a submarine volcano during elevated sea-levels of interglacial periods. A few vertebrate remains have been recovered directly from interglacial sandstones, mainly of mid-Pleistocene age. Glacial intervals are marked by red soils derived mainly from atmospheric dust. Vertebrate fossils of glacial age are not preserved at the surface and are known only from caves and fissure fills. Fossil faunas are known on Bermuda from the last two glacial episodes but none of the earlier ones. Certain or probable extinctions of vertebrates are correlated with at least four interglacial rises in sea-level--Marine Isotope Stages (MIS) 11,9,5, and 1. The history ofvertebrate paleontology on Bermuda is reviewed and fossil vertebrate localities are listed and briefly described
65 Cybele in the thermal infrared: Multiple observations and thermophysical analysis
We investigated the physical and thermal properties of 65 Cybele}, one of the
largest main-belt asteroids. Based on published and recently obtained thermal
infrared observations, including ISO measurements, we derived through
thermophysical modelling (TPM) a size of 302x290x232 km (+/- 4 %) and an
geometric visible albedo of 0.050+/-0.005. Our model of a regolith covered
surface with low thermal inertia and "default" roughness describes the
wavelengths and phase angle dependent thermal aspects very well. Before/after
opposition effect and beaming behaviour can be explained in that way. We found
a constant emissivity of 0.9 at wavelengths up to about 100 micron and lower
values towards the submillimetre range, indicating a grain size distribution
dominated by 200 micron particle sizes. The spectroscopic analysis revealed an
emissivity increase between 8.0 and 9.5 micron. We compared this emissivity
behaviour with the Christiansen features of carbonaceous chondrite meteorites,
but a conclusive identification was not possible. A comparison between the
Standard Thermal Model (STM) and the applied TPM clearly demonstrates the
limitations and problems of the STM for the analysis of multi-epoch and
-wavelengths observations. While the TPM produced a unique diameter/albedo
solution, the calculated STM values varied by +/-30 % and showed clear trends
with wavelength and phase angle. Cybele can be considered as a nice textbook
case for the thermophysical analysis of combined optical and thermal infrared
observations.Comment: 11 pages, 8 figures, accepted for publication by A&
Below the Lyman Edge: UV Polarimetry of Quasars
The Lyman edge at 912 \AA is an important diagnostic region for studying
quasi-stellar objects (QSOs). In particular, it reveals a great deal about the
physical conditions within the atmospheres of accretion disks, a ubiquitous
component of QSO theories. A robust prediction of accretion disk models is a
significant polarization due to electron scattering just longward (in
wavelength) of the Lyman edge because of the wavelength dependence of the
Hydrogen absorption opacity. Observations of the Lyman edge regions of QSOs
have shown scant evidence for the predicted features-few QSOs show the broad,
partial Lyman edges expected to be common according to most theories, and none
show the high polarizations expected longward of the Lyman edge. Still,
polarization spectra of a small number of QSOs have shown a rising polarization
(up to 20%) at wavelengths shortward of the Lyman edge. We have now doubled our
sample of intermediate-redshift QSOs observed with the HST/FOS
spectropolarimeter to determine the amount of polarization on both sides of the
Lyman limit. For this new sample of six objects, polarizations are low and
mostly consistent with zero below the Lyman edge.
Another important result of the new data is that it strengthens the
conclusion that quasars are generally not polarized significantly just longward
of the Lyman edge at $\sim 1000 \AA. There is no significant statistical
wavelength dependence to the polarization longward of the Lyman edge indicating
that simple plane-parallel atmospheres with scattering-dominated opacity are
not significant sources of UV flux in quasars.Comment: Accepted to Ap.J., 30 pages, 8 figure
The NICMOS Snapshot Survey of nearby Galaxies
We present ``snapshot'' observations with the NearInfrared Camera and
MultiObject Spectrometer (NICMOS) on board the Hubble Space Telescope (HST) of
94 nearby galaxies from the Revised Shapley Ames Catalog. Images with 0.2 as
resolution were obtained in two filters, a broad-band continuum filter (F160W,
roughly equivalent to the H-band) and a narrow band filter centered on the
Paschen alpha line (F187N or F190N, depending on the galaxy redshift) with the
51x51 as field of view of the NICMOS camera 3. A first-order continuum
subtraction is performed, and the resulting line maps and integrated Paschen
alpha line fluxes are presented. A statistical analysis indicates that the
average Paschen alpha surface brightness {\bf in the central regions} is
highest in early-type (Sa-Sb) spirals.Comment: Original contained error in flux calibration. Table 1 now has correct
Paschen Alpha fluxes. 14 pages LaTeX with JPEG and PS figures. Also available
at http://icarus.stsci.edu/~boeker/publications.htm
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