570 research outputs found
The DLV System for Knowledge Representation and Reasoning
This paper presents the DLV system, which is widely considered the
state-of-the-art implementation of disjunctive logic programming, and addresses
several aspects. As for problem solving, we provide a formal definition of its
kernel language, function-free disjunctive logic programs (also known as
disjunctive datalog), extended by weak constraints, which are a powerful tool
to express optimization problems. We then illustrate the usage of DLV as a tool
for knowledge representation and reasoning, describing a new declarative
programming methodology which allows one to encode complex problems (up to
-complete problems) in a declarative fashion. On the foundational
side, we provide a detailed analysis of the computational complexity of the
language of DLV, and by deriving new complexity results we chart a complete
picture of the complexity of this language and important fragments thereof.
Furthermore, we illustrate the general architecture of the DLV system which
has been influenced by these results. As for applications, we overview
application front-ends which have been developed on top of DLV to solve
specific knowledge representation tasks, and we briefly describe the main
international projects investigating the potential of the system for industrial
exploitation. Finally, we report about thorough experimentation and
benchmarking, which has been carried out to assess the efficiency of the
system. The experimental results confirm the solidity of DLV and highlight its
potential for emerging application areas like knowledge management and
information integration.Comment: 56 pages, 9 figures, 6 table
Phase transition close to room temperature in BiFeO3 thin films
BiFeO3 (BFO) multiferroic oxide has a complex phase diagram that can be
mapped by appropriately substrate-induced strain in epitaxial films. By using
Raman spectroscopy, we conclusively show that films of the so-called
supertetragonal T-BFO phase, stabilized under compressive strain, displays a
reversible temperature-induced phase transition at about 100\circ, thus close
to room temperature.Comment: accepted in J. Phys.: Condens. Matter (Fast Track Communication
An embedding scheme for the Dirac equation
An embedding scheme is developed for the Dirac Hamiltonian H. Dividing space
into regions I and II separated by surface S, an expression is derived for the
expectation value of H which makes explicit reference to a trial function
defined in I alone, with all details of region II replaced by an effective
potential acting on S and which is related to the Green function of region II.
Stationary solutions provide approximations to the eigenstates of H within I.
The Green function for the embedded Hamiltonian is equal to the Green function
for the entire system in region I. Application of the method is illustrated for
the problem of a hydrogen atom in a spherical cavity and an Au(001)/Ag/Au(001)
sandwich structure using basis sets that satisfy kinetic balance.Comment: 16 pages, 5 figure
Gemini Near Infrared Spectrograph - Distant Quasar Survey: Prescriptions for Calibrating UV-Based Estimates of Supermassive Black Hole Masses in High-Redshift Quasars
The most reliable single-epoch supermassive black hole mass ()
estimates in quasars are obtained by using the velocity widths of
low-ionization emission lines, typically the H line.
Unfortunately, this line is redshifted out of the optical band at ,
leaving estimates to rely on proxy rest-frame ultraviolet (UV)
emission lines, such as C IV or Mg II , which
contain intrinsic challenges when measuring, resulting in uncertain estimates. In this work, we aim at correcting estimates
derived from the C IV and Mg II emission lines based on estimates derived from
the H emission line. We find that employing the equivalent width of C IV
in deriving estimates based on Mg II and C IV provides values that
are closest to those obtained from H. We also provide prescriptions to
estimate values when only C IV, only Mg II, and both C IV and Mg
II are measurable. We find that utilizing both emission lines, where available,
reduces the scatter of UV-based estimates by when
compared to previous studies. Lastly, we discuss the potential of our
prescriptions to provide more accurate and precise estimates of
given a much larger sample of quasars at , where
both Mg II and H can be measured in the same near-infrared spectrum.Comment: 19 pages (AASTeX 6.3.1), 9 figures, accepted for publication in Ap
Ordered arrays of multiferroic epitaxial nanostructures
Epitaxial heterostructures combining ferroelectric (FE) and ferromagnetic (FiM) oxides are a possible route to explore coupling mechanisms between the two independent order parameters, polarization and magnetization of the component phases. We report on the fabrication and properties of arrays of hybrid epitaxial nanostructures of FiM NiFe2O4 (NFO) and FE PbZr0.52Ti0.48O3 or PbZr0.2Ti0.8O3, with large range order and lateral dimensions from 200 nm to 1 micron
Understanding the user experience of location based services:five principles of perceptual organisation applied
Gemini Near Infrared Spectrograph -- Distant Quasar Survey: Augmented Spectroscopic Catalog and a Prescription for Correcting UV-Based Quasar Redshifts
Quasars at most often have redshifts measured from rest-frame
ultraviolet emission lines. One of the most common such lines, C IV
, shows blueshifts up to , and in
rare cases even higher. This blueshifting results in highly uncertain redshifts
when compared to redshift determinations from rest-frame optical emission
lines, e.g., from the narrow [O III] feature. We present
spectroscopic measurements for 260 sources at
having
mag from the Gemini Near Infrared
Spectrograph - Distant Quasar Survey (GNIRS-DQS) catalog, augmenting the
previous iteration which contained 226 of the 260 sources whose measurements
are improved upon in this work. We obtain reliable systemic redshifts based on
[O III] for a subset of 121 sources which we use to calibrate
prescriptions for correcting UV-based redshifts. These prescriptions are based
on a regression analysis involving C IV full-width-at-half-maximum intensity
and equivalent width, along with the UV continuum luminosity at a rest-frame
wavelength of 1350 A. Applying these corrections can improve the accuracy and
the precision in the C IV-based redshift by up to
and , respectively, which correspond to
Mpc and Mpc in comoving distance at . Our prescriptions
also improve the accuracy of the best available multi-feature redshift
determination algorithm by , indicating that the
spectroscopic properties of the C IV emission line can provide robust redshift
estimates for high-redshift quasars. We discuss the prospects of our
prescriptions for cosmological and quasar studies utilizing upcoming large
spectroscopic surveys.Comment: 20 pages (AASTeX 6.3.1), 8 figures, accepted for publication in Ap
Differential expression of HSPA1 and HSPA2 proteins in human tissues; tissue microarray-based immunohistochemical study
In the present study we determined the expression pattern of HSPA1 and HSPA2 proteins in various normal human tissues by tissue-microarray based immunohistochemical analysis. Both proteins belong to the HSPA (HSP70) family of heat shock proteins. The HSPA2 is encoded by the gene originally defined as testis-specific, while HSPA1 is encoded by the stress-inducible genes (HSPA1A and HSPA1B). Our study revealed that both proteins are expressed only in some tissues from the 24 ones examined. HSPA2 was detected in adrenal gland, bronchus, cerebellum, cerebrum, colon, esophagus, kidney, skin, small intestine, stomach and testis, but not in adipose tissue, bladder, breast, cardiac muscle, diaphragm, liver, lung, lymph node, pancreas, prostate, skeletal muscle, spleen, thyroid. Expression of HSPA1 was detected in adrenal gland, bladder, breast, bronchus, cardiac muscle, esophagus, kidney, prostate, skin, but not in other tissues examined. Moreover, HSPA2 and HSPA1 proteins were found to be expressed in a cell-type-specific manner. The most pronounced cell-type expression pattern was found for HSPA2 protein. In the case of stratified squamous epithelia of the skin and esophagus, as well as in ciliated pseudostratified columnar epithelium lining respiratory tract, the HSPA2 positive cells were located in the basal layer. In the colon, small intestine and bronchus epithelia HSPA2 was detected in goblet cells. In adrenal gland cortex HSPA2 expression was limited to cells of zona reticularis. The presented results clearly show that certain human tissues constitutively express varying levels of HSPA1 and HSPA2 proteins in a highly differentiated way. Thus, our study can help designing experimental models suitable for cell- and tissue-type-specific functional differences between HSPA2 and HSPA1 proteins in human tissues
Characterization of SABRE crystal NaI-33 with direct underground counting
Ultra-pure NaI(Tl) crystals are the key element for a model-independent
verification of the long standing DAMA result and a powerful means to search
for the annual modulation signature of dark matter interactions. The SABRE
collaboration has been developing cutting-edge techniques for the reduction of
intrinsic backgrounds over several years. In this paper we report the first
characterization of a 3.4 kg crystal, named NaI-33, performed in an underground
passive shielding setup at LNGS. NaI-33 has a record low K contamination
of 4.30.2 ppb as determined by mass spectrometry. We measured a light
yield of 11.10.2 photoelectrons/keV and an energy resolution of 13.2%
(FWHM/E) at 59.5 keV. We evaluated the activities of Ra and Th
inside the crystal to be Bq/kg and Bq/kg,
respectively, which would indicate a contamination from U and
Th at part-per-trillion level. We measured an activity of 0.510.02
mBq/kg due to Pb out of equilibrium and a quenching factor of
0.630.01 at 5304 keV. We illustrate the analyses techniques developed to
reject electronic noise in the lower part of the energy spectrum. A cut-based
strategy and a multivariate approach indicated a rate, attributed to the
intrinsic radioactivity of the crystal, of 1 count/day/kg/keV in the
[5-20] keV region
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