5,383 research outputs found
Poincar\'e's polyhedron theorem for cocompact groups in dimension 4
We prove a version of Poincar\'e's polyhedron theorem whose requirements are
as local as possible. New techniques such as the use of discrete groupoids of
isometries are introduced. The theorem may have a wide range of applications
and can be generalized to the case of higher dimension and other geometric
structures. It is planned as a first step in a program of constructing compact
-surfaces of general type satisfying .Comment: 15 pages, 1 figure, 9 references. Introduction revised. Example 3.16
adde
A Novel Ultrasound-based Measure of the Liver among Diabetes Mellitus Type II Patients
Diabetes mellitus type II (DM II) or adult onset diabetes is due to the inefficient use of insulin, which affects various organs and tissues. Patients with DM II are at risk of suffering non-alcoholic fatty liver disease (NAFLD) that can later develop into more life threating forms such as hepatomegaly, cirrhosis or liver cancer. Following the logic of the non-inferiority trial test, we aim to establish a more accurate anatomical measure of the right liver lobe (RLL) to facilitate close monitoring of liver size with ultrasound (US). We hypothesize that US is not unacceptably worse than computed tomography (CT) or magnetic resonance imaging (MRI) to accurately and reliably measure the size of the RLL when the measure is taken in the midaxillary line and craniocaudal plane (MAL-CC). Therefore, the objective of this study is to conduct a non-inferiority trial to test our novel MAL-CC measure.
To meet this aim, US measure of the RLL was taken from DM II (n=7) and non-DM II (n=5) patients, whom were recruited from 2 endocrinology clinics at SoM-UPR. Preliminary data shows that MAL-CC measure of the RLL from non-DM II patients is 13.99 + 2.53 cm whereas the same measurement among DM II patients is 15.25 + 3.25 cm (Mann-Whitney U test, p= 0.42). It is concluded that there is a non-significant trend for large RLL sizes among DM II patients. Future work aims to increase sample size and to validate our novel measurement with MRI
The effect of primordial non-Gaussianity on the skeleton of cosmic shear maps
(abridged) We explore the imprints of deviations from Gaussian primordial
density fluctuations on the skeleton of the large-scale matter distribution as
mapped through cosmological weak lensing. We computed the skeleton length of
simulated effective convergence maps covering sq. deg each, extracted
from a suite of cosmological body runs with different levels of local
primordial non-Gaussianity. The latter is expected to alter the structure
formation process with respect to the fiducial Gaussian scenario, and thus to
leave a signature on the cosmic web. We found that alterations of the initial
conditions consistently modify both the cumulative and the differential
skeleton length, although the effect is generically smaller than the cosmic
variance and depends on the smoothing of the map prior to the skeleton
computation. Nevertheless, the qualitative shape of these deviations is rather
similar to their primordial counterparts, implying that skeleton statistics
retain good memory of the initial conditions. We performed a statistical
analysis in order to find out at what Confidence Level primordial
non-Gaussianity could be constrained by the skeleton test on cosmic shear maps
of the size we adopted. At 68.3% Confidence Level we found an error on the
measured level of primordial non-Gaussianity of ,
while at 90% Confidence Level it is of . While
these values by themselves are not competitive with the current constraints,
weak lensing maps larger than those used here would have a smaller
field-to-field variance, and thus would likely lead to tighter constraints. A
rough estimate indicates a few tens at 68.3%
Confidence Level for an all-sky weak lensing survey.Comment: 11 pages, 9 figures. Accepted for publication on MNRA
Measurement of the Z/γ∗ forward-backward asymmetry in muon pairs with the ATLAS experiment at the LHC
A study on muon pairs produced through an intermediate Z/γ
∗, in pp collisions at the LHC, at a center-of-mass energy of 7TeV, is presented. After a selection aimed at enhancing the contribution from Z boson decay, the topology of the events is analyzed, and the forward-backward asymmetry is measured. The result is then used to test a method to measure the effective weak mixing angle sin2 θeff W . This note summarizes the results obtained with 2011 data collected by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 4.8 fb−1
Apollo-Soyuz Doppler-tracking experiment MA-089
The Doppler tracking experiment was designed to test the feasibility of improved mapping of the earth's gravity field by the low-low satellite-to-satellite tracking method and to observe variations in the electron density of the ionosphere between the two spacecraft. Data were taken between 1:01 and 14:37 GMT on July 24, 1975. Baseline data taken earlier, while the docking module was still attached to the command and service module, indicated that the equipment operated satisfactorily. The ionospheric data contained in the difference between the Doppler signals at the two frequencies are of excellent quality, resulting in valuable satellite-to-satellite observations, never made before, of wave phenomena in the ionosphere. The gravity data were corrupted by an unexpectedly high noise level of as-yet-undetermined origin, with periods greater than 150 seconds, that prevented unambiguous identification of gravity-anomaly signatures
System engineering study of electrodynamic tether as a spaceborne generator and radiator of electromagnetic waves in the ULF/ELF frequency band
The transmission and generation by orbiting tethered satellite systems of information carrying electromagnetic waves in the ULF/ELF frequency band to the Earth at suitably high signal intensities was examined and the system maintaining these intensities in their orbits for long periods of time without excessive onboard power requirements was investigated. The injection quantity power into electromagnetic waves as a function of system parameters such as tether length and orbital height was estimated. The basic equations needed to evaluate alternataing current tethered systems for external energy requirements are presented. The energy equations to tethered systems with various lengths, tether resistances, and radiation resistances, operating at different current values are applied. Radiation resistance as a function of tether length and orbital height is discussed. It is found that ULF/ELF continuously radiating systems could be maintained in orbit with moderate power requirements. The effect of tether length on the power going into electromagnetic waves and whether a single or dual tether system is preferable for the self-driven mode is discussed. It is concluded that the single tether system is preferable over the dual system
Stellar structures in the outer regions of M33
We present Subaru/Suprime-Cam deep V and I imaging of seven fields in the
outer regions of M33. Our aim is to search for stellar structures corresponding
to extended HI clouds found in a recent 21-cm survey of the galaxy. Three
fields probe a large HI complex to the southeastern (SE) side of the galaxy. An
additional three fields cover the northwestern (NW) side of the galaxy along
the HI warp. A final target field was chosen further north, at a projected
distance of approximately 25 kpc, to study part of the large stellar plume
recently discovered around M33. We analyse the stellar population at R > 10 kpc
by means of V, I colour magnitude diagrams reaching the red clump. Evolved
stellar populations are found in all fields out to 120' (~ 30 kpc), while a
diffuse population of young stars (~ 200 Myr) is detected out to a
galactocentric radius of 15 kpc. The mean metallicity in the southern fields
remains approximately constant at [M/H] = -0.7 beyond the edge of the optical
disc, from 40' out to 80'. Along the northern fields probing the outer \hi
disc, we also find a metallicity of [M/H] = -0.7 between 35' and 70' from the
centre, which decreases to [M/H] = -1.0 at larger angular radii out to 120'. In
the northernmost field, outside the disc extent, the stellar population of the
large stellar feature possibly related to a M33-M31 interaction is on average
more metal-poor ([M/H] = -1.3) and older (> 6 Gyr). An exponential disc with a
large scale-length (~ 7 kpc) fits well the average distribution of stars
detected in both the SE and NW regions from a galactocentric distance of 11 kpc
out to 30 kpc. The stellar distribution at large radii is disturbed and,
although there is no clear correlation between the stellar substructures and
the location of the HI clouds, this gives evidence for tidal interaction or
accretion events.Comment: 13 pages, 13 figures. Accepted for publications in Astronomy and
Astrophysics; minor revisions of the tex
Maxillary nerve block: A comparison between the greater palatine canal and high tuberosity approaches.
Aim: Analgesia and anxiolysis during dental procedures are important for dental care and
patient compliance. This study aims to compare two classical maxillary nerve block (MNB)
techniques: the greater palatine canal (GPC) and the high tuberosity (HT) approaches,
seldom used in routine dental practice.
Methods: The study was conducted on 30 patients, scheduled for sinus lift surgery, who
were randomly divided into 2 groups: the GPC approach to the MNB was used in 15 and the
HT one in the other 15 patients. Anxiolysis was also used, depending on the results of the
pre- preoperative assessment. Patients\u2019 sensations/pain during the procedure, details about
anesthesia, and the dentist\u2019s considerations were all recorded. Data are expressed as mean
\ub1SD. Statistical tests including ANOVA, \u3c72 following Yates correction and linear regression
analysis were carried out. A < 0.05 p value was considered significant.
Results: Study results showed that the anesthesia was effective and constant in the molar
and premolar area. Additional infiltrations of local anesthetics were necessary for vestibular
and palatal areas in the anterior oral cavity, respectively, in the GPC and HT groups. The
two techniques were equally difficult to carry out in the dentist\u2019s opinion. There were
no differences in pain or unpleasant sensations between the two groups, nor were any
anesthesia-related complications reported.
Conclusion: The GPC approach ensures effective anesthesia in the posterior maxillary
region as far as both the dental pulp and the palatal/vestibular mucous membranes are
concerned; the HT approach did not guarantee adequate anesthesia of the pterygopalatine
branch of the maxillary nerve. These regional anesthesia techniques were characterized
by a low incidence of intra and postoperative pain, no noteworthy complications, and high
patient satisfaction
Shadows of Relic Neutrino Masses and Spectra on Highest Energy GZK Cosmic Rays
The Ultra High Energy (UHE) neutrino scattering onto relic cosmic neutrinos
in galactic and local halos offers an unique way to overcome GZK cut-off. The
UHE nu secondary of UHE photo-pion decays may escape the GZK cut-off and travel
on cosmic distances hitting local light relic neutrinos clustered in dark
halos. The Z resonant production and the competitive W^+W^-, ZZ pair production
define a characteristic imprint on hadronic consequent UHECR spectra. This
imprint keeps memory both of the primary UHE nu spectra as well as of the
possible relic neutrino masses values, energy spectra and relic densities. Such
an hadronic showering imprint should reflect into spectra morphology of cosmic
rays near and above GZK 10^{19}-10^{21}eV cut-off energies. A possible neutrino
degenerate masses at eVs or a more complex and significant neutrino mass split
below or near Super-Kamiokande \triangle m_{\nu_{SK}}= 0.1 eV masses might be
reflected after each corresponding Z peak showering, into new twin unexpected
UHECR flux modulation behind GZK energies: E_{p} sim 3(frac{triangle
m_{\nu_{SK}}}/m_{\nu}10^{21}),eV.
Other shadowsof lightest, nearly massless, neutrinos m_{nu_{2K} simeq 0.001eV
simeq kT_{\nu}, their lowest relic temperatures, energies and densities might
be also reflected at even higher energies edges near Grand Unification: E_{p}
\sim 2.2(m_{\nu_{2K}/E_{\nu}})10^{23}, eV .Comment: 14 pages, 6 Figures,Invited Talk Heidelberg DARK 200
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