6,399 research outputs found
The external benefits of higher education
The private market benefits of education are widely studied at the micro level, although the magnitude of their macroeconomic impact is disputed. However, there are additional benefits of education, which are less well understood. In this paper the macroeconomic effects of external benefits of higher education are estimated using the “micro-to-macro” simulation approach. Two types of externalities are explored: technology spillovers and productivity spillovers in the labour market. These links are illustrated and the results suggest they could be very large. However, this is qualified by the dearth of microeconomic evidence, for which we hope to encourage further work
An In-Depth Analysis of the Slingshot Interconnect
The interconnect is one of the most critical components in large scale
computing systems, and its impact on the performance of applications is going
to increase with the system size. In this paper, we will describe Slingshot, an
interconnection network for large scale computing systems. Slingshot is based
on high-radix switches, which allow building exascale and hyperscale
datacenters networks with at most three switch-to-switch hops. Moreover,
Slingshot provides efficient adaptive routing and congestion control
algorithms, and highly tunable traffic classes. Slingshot uses an optimized
Ethernet protocol, which allows it to be interoperable with standard Ethernet
devices while providing high performance to HPC applications. We analyze the
extent to which Slingshot provides these features, evaluating it on
microbenchmarks and on several applications from the datacenter and AI worlds,
as well as on HPC applications. We find that applications running on Slingshot
are less affected by congestion compared to previous generation networks.Comment: To be published in Proceedings of The International Conference for
High Performance Computing Networking, Storage, and Analysis (SC '20) (2020
K Corrections For Type Ia Supernovae and a Test for Spatial Variation of the Hubble Constant
Cross-filter K corrections for a sample of "normal" Type Ia supernovae (SNe)
have been calculated for a range of epochs. With appropriate filter choices,
the combined statistical and systematic K correction dispersion of the full
sample lies within 0.05 mag for redshifts z<0.7. This narrow dispersion of the
calculated K correction allows the Type Ia to be used as a cosmological probe.
We use the K corrections with observations of seven SNe at redshifts 0.3 < z
<0.5 to bound the possible difference between the locally measured Hubble
constant (H_L) and the true cosmological Hubble constant (H_0).Comment: 6 pages, 3 Postscript figures, uuencoded uses crckapb.sty and
psfig.sty. To appear in Thermonuclear Supernovae (NATO ASI), eds. R. Canal,
P. Ruiz-LaPuente, and J. Isern. Postscript version is also available at
http://www-supernova.lbl.gov
Cosmology from Type Ia Supernovae
This presentation reports on first evidence for a
low-mass-density/positive-cosmological-constant universe that will expand
forever, based on observations of a set of 40 high-redshift supernovae. The
experimental strategy, data sets, and analysis techniques are described. More
extensive analyses of these results with some additional methods and data are
presented in the more recent LBNL report #41801 (Perlmutter et al., 1998;
accepted for publication in Ap.J.), astro-ph/9812133 .
This Lawrence Berkeley National Laboratory reprint is a reduction of a poster
presentation from the Cosmology Display Session #85 on 9 January 1998 at the
American Astronomical Society meeting in Washington D.C. It is also available
on the World Wide Web at http://supernova.LBL.gov/ This work has also been
referenced in the literature by the pre-meeting abstract citation: Perlmutter
et al., B.A.A.S., volume 29, page 1351 (1997).Comment: 9 pages, 8 color figs. Presented at Jan '98 AAS Meeting, also cited
as BAAS,29,1351(1997). Archived here in response to requests; see more
extensive analyses in ApJ paper (astro-ph/9812133
Implications For The Hubble Constant from the First Seven Supernovae at z >= 0.35
The Supernova Cosmology Project has discovered over twenty-eight supernovae
(SNe) at 0.35 <z < 0.65 in an ongoing program that uses Type Ia SNe as
high-redshift distance indicators. Here we present measurements of the ratio
between the locally observed and global Hubble constants, H_0^L/H_0^G, based on
the first 7 SNe of this high-redshift data set compared with 18 SNe at z <= 0.1
from the Calan/Tololo survey. If Omega_M <= 1, then light-curve-width corrected
SN magnitudes yield H_0^L/H_0^G < 1.10 (95% confidence level) in both a
Lambda=0 and a flat universe. The analysis using the SNe Ia as standard candles
without a light-curve-width correction yields similar results. These results
rule out the hypothesis that the discrepant ages of the Universe derived from
globular clusters and recent measurements of the Hubble constant are
attributable to a locally underdense bubble. Using the
Cepheid-distance-calibrated absolute magnitudes for SNe Ia of Sandage (1996},
we can also measure the global Hubble constant, H_0^G. If Omega_M >= 0.2, we
find that H_0^G < 70 km/s/Mpc in a Lambda=0 universe and H_0^G < 78 km/s/Mpc in
a flat universe, correcting the distant and local SN apparent magnitudes for
light curve width. Lower results for H_0^G are obtained if the magnitudes are
not width corrected.Comment: 13 pages, 2 Postscript figures. Preprint also available at
http://www-supernova.lbl.gov . To appear in ApJ Letter
Surface code quantum computing by lattice surgery
In recent years, surface codes have become a leading method for quantum error
correction in theoretical large scale computational and communications
architecture designs. Their comparatively high fault-tolerant thresholds and
their natural 2-dimensional nearest neighbour (2DNN) structure make them an
obvious choice for large scale designs in experimentally realistic systems.
While fundamentally based on the toric code of Kitaev, there are many variants,
two of which are the planar- and defect- based codes. Planar codes require
fewer qubits to implement (for the same strength of error correction), but are
restricted to encoding a single qubit of information. Interactions between
encoded qubits are achieved via transversal operations, thus destroying the
inherent 2DNN nature of the code. In this paper we introduce a new technique
enabling the coupling of two planar codes without transversal operations,
maintaining the 2DNN of the encoded computer. Our lattice surgery technique
comprises splitting and merging planar code surfaces, and enables us to perform
universal quantum computation (including magic state injection) while removing
the need for braided logic in a strictly 2DNN design, and hence reduces the
overall qubit resources for logic operations. Those resources are further
reduced by the use of a rotated lattice for the planar encoding. We show how
lattice surgery allows us to distribute encoded GHZ states in a more direct
(and overhead friendly) manner, and how a demonstration of an encoded CNOT
between two distance 3 logical states is possible with 53 physical qubits, half
of that required in any other known construction in 2D.Comment: Published version. 29 pages, 18 figure
Immune or genetic-mediated disruption of CASPR2 causes pain hypersensitivity due to enhanced primary afferent excitability
Human autoantibodies to contactin-associated protein-like 2 (CASPR2) are often associated with neuropathic pain, and CASPR2 mutations have been linked to autism spectrum disorders, in which sensory dysfunction is increasingly recognized. Human CASPR2 autoantibodies, when injected into mice, were peripherally restricted and resulted in mechanical pain-related hypersensitivity in the absence of neural injury. We therefore investigated the mechanism by which CASPR2 modulates nociceptive function. Mice lacking CASPR2 (Cntnap2 ) demonstrated enhanced pain-related hypersensitivity to noxious mechanical stimuli, heat, and algogens. Both primary afferent excitability and subsequent nociceptive transmission within the dorsal horn were increased in Cntnap2 mice. Either immune or genetic-mediated ablation of CASPR2 enhanced the excitability of DRG neurons in a cell-autonomous fashion through regulation of Kv1 channel expression at the soma membrane. This is the first example of passive transfer of an autoimmune peripheral neuropathic pain disorder and demonstrates that CASPR2 has a key role in regulating cell-intrinsic dorsal root ganglion (DRG) neuron excitability
The Type Ia Supernova Rate at z ~ 0.4
We present the first measurement of the rate of Type Ia supernovae at high
redshift. The result is derived using a large subset of data from the Supernova
Cosmology Project as described in more detail at this meeting by Perlmutter et
al. (1996). We present our methods for estimating the numbers of galaxies and
the number of solar luminosities to which the survey is sensitive, the
supernova detection efficiency and hence the control time. We derive a
rest-frame Type Ia supernova rate at z~0.4 of 0.82^+0.54_-0.37 ^+0.42_-0.32 h^2
SNu where the first uncertainty is statistical and the second includes
systematic effects.Comment: 9 pages, 3 Postscript figures, uuencoded uses crckapb.sty and
psfig.sty. To appear in Thermonuclear Supernovae (NATO ASI), eds. R. Canal,
P. Ruiz-LaPuente, and J. Isern. Postscript version is also available at
http://www-supernova.lbl.gov
Scheduled Discoveries of 7+ High-Redshift Supernovae: First Cosmology Results and Bounds on q_0
Our search for high-redshift Type Ia supernovae discovered, in its first
years, a sample of seven supernovae. Using a "batch" search strategy, almost
all were discovered before maximum light and were observed over the peak of
their light curves. The spectra and light curves indicate that almost all were
Type Ia supernovae at redshifts z = 0.35 -- 0.5. These high-redshift supernovae
can provide a distance indicator and "standard clock" to study the cosmological
parameters q_0, Lambda, Omega_0, and H_0. This presentation and the following
presentations of Kim et al. (1996), Goldhaber et al. (1996), and Pain et al.
(1996) will discuss observation strategies and rates, analysis and calibration
issues, the sources of measurement uncertainty, and the cosmological
implications, including bounds on q_0, of these first high-redshift supernovae
from our ongoing search.Comment: 15 pages, 6 Postscript figures, uuencoded uses crckapb.sty and
psfig.sty. To appear in Thermonuclear Supernovae (NATO ASI), eds. R. Canal,
P. Ruiz-LaPuente, and J. Isern. Postscript version is also available at
http://www-supernova.lbl.gov
The Type Ia Supernova Rate at z
We present the first measurement of the rate of Type Ia supernovae at high
redshift. The result is derived using a large subset of data from the Supernova
Cosmology Project. Three supernovae were discovered in a surveyed area of 1.7
square degrees. The survey spanned a week baseline and used images
with limiting magnitude of . We present our methods for
estimating the numbers of galaxies and the number of solar luminosities to
which the survey is sensitive, and the supernova detection efficiency which is
used to determine the control time, the effective time for which the survey is
sensitive to a Type Ia event. We derive a rest-frame Type Ia supernova rate at
of SNu (1 SNu
= 1 SN per century per \Lbsun), where the first uncertainty is
statistical and the second includes systematic effects. For the purposes of
observers, we also determine the rate of SNe, per sky area surveyed, to be SNe\ for SN magnitudes in
the range .Comment: 33 pages, To be published in December 10, 1996 issue of ApJ Vol 47
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