2,663 research outputs found
A deep learning approach to diabetic blood glucose prediction
We consider the question of 30-minute prediction of blood glucose levels
measured by continuous glucose monitoring devices, using clinical data. While
most studies of this nature deal with one patient at a time, we take a certain
percentage of patients in the data set as training data, and test on the
remainder of the patients; i.e., the machine need not re-calibrate on the new
patients in the data set. We demonstrate how deep learning can outperform
shallow networks in this example. One novelty is to demonstrate how a
parsimonious deep representation can be constructed using domain knowledge
How do methanol masers manage to appear in the youngest star vicinities and isolated molecular clumps?
General characteristics of methanol (CH3OH) maser emission are summarized. It
is shown that methanol maser sources are concentrated in the spiral arms. Most
of the methanol maser sources from the Perseus arm are associated with embedded
stellar clusters and a considerable portion is situated close to compact HII
regions. Almost 1/3 of the Perseus Arm sources lie at the edges of optically
identified HII regions which means that massive star formation in the Perseus
Arm is to a great extent triggered by local phenomena. A multiline analysis of
the methanol masers allows us to determine the physical parameters in the
regions of maser formation. Maser modelling shows that class II methanol masers
can be pumped by the radiation of the warm dust as well as by free-free
emission of a hypercompact region hcHII with a turnover frequency exceeding 100
GHz. Methanol masers of both classes can reside in the vicinity of hcHIIs.
Modelling shows that periodic changes of maser fluxes can be reproduced by
variations of the dust temperature by a few percent which may be caused by
variations in the brightness of the central young stellar object reflecting the
character of the accretion process. Sensitive observations have shown that the
masers with low flux densities can still have considerable amplification
factors. The analysis of class I maser surveys allows us to identify four
distinct regimes that differ by the series of their brightest lines.Comment: 8 pages, 4 figures, invited presentation at IAU242 "Astrophysical
Masers and their environments
Direct -body code on low-power embedded ARM GPUs
This work arises on the environment of the ExaNeSt project aiming at design
and development of an exascale ready supercomputer with low energy consumption
profile but able to support the most demanding scientific and technical
applications. The ExaNeSt compute unit consists of densely-packed low-power
64-bit ARM processors, embedded within Xilinx FPGA SoCs. SoC boards are
heterogeneous architecture where computing power is supplied both by CPUs and
GPUs, and are emerging as a possible low-power and low-cost alternative to
clusters based on traditional CPUs. A state-of-the-art direct -body code
suitable for astrophysical simulations has been re-engineered in order to
exploit SoC heterogeneous platforms based on ARM CPUs and embedded GPUs.
Performance tests show that embedded GPUs can be effectively used to accelerate
real-life scientific calculations, and that are promising also because of their
energy efficiency, which is a crucial design in future exascale platforms.Comment: 16 pages, 7 figures, 1 table, accepted for publication in the
Computing Conference 2019 proceeding
Experimental studies and nuclear model calculations on (p,xn) and (p,pxn) reactions on 85Rb from their threshold up to 100 MeV
Excitation functions were measured by the stacked-foil technique for the reactions Rb-85(p, pxn)Rb-89m,Rb-g83,Rb-82m.81 from their thresholds up to 100MeV. Nuclear model calculations were performed using the code ALICE-IPPE both on (p, xn) reactions reported earlier and (p, pxn) reactions described here. The experimental excitation curves and the results of nuclear model calculations were found to be qualitatively in agreement. With the exception of the (p, n) reaction above 40MeV, the theory appears to reproduce all the experimental data within deviations of about 50%. The cross section ratios for the isomeric pairs Sr-85m,Sr-g and Rb-84m,Rb-g are discussed qualitatively in terms of the spins of the states involved and the increasing projectile energy
English medium of instruction: A situation analysis
The majority of learners in southern Africa receive their education through the medium of a second language, English. Although teachers of English play a crucial role in helping learners to acquire language skills in the medium of instruction, we argue that subject content teachers' lack of attention to the teaching of the four language skills may be a raison d'être for learners' lack of academic achievement. A situation analysis conducted among three study populations examined the extent to which subject content teachers took responsibility for the teaching of language skills in the content classroom, as well as possible reasons for not doing so. It also shed some light on the amount of language teaching that actually took place in a content classroom. The aim of the situation analysis was to determine whether there was a need for a specialised training course for English second language medium of instruction teachers.South African Journal of Education Vol. 27 (1) 2007: pp. 69-8
On the Identification of High Mass Star Forming Regions using IRAS: Contamination by Low-Mass Protostars
We present the results of a survey of a small sample (14) of low-mass
protostars (L_IR < 10^3 Lsun) for 6.7 GHz methanol maser emission performed
using the ATNF Parkes radio telescope. No new masers were discovered. We find
that the lower luminosity limit for maser emission is near 10^3 Lsun, by
comparison of the sources in our sample with previously detected methanol maser
sources. We examine the IRAS properties of our sample and compare them with
sources previously observed for methanol maser emission, almost all of which
satisfy the Wood & Churchwell criterion for selecting candidate UCHII regions.
We find that about half of our sample satisfy this criterion, and in addition
almost all of this subgroup have integrated fluxes between 25 and 60 microns
that are similar to sources with detectable methanol maser emission. By
identifying a number of low-mass protostars in this work and from the
literature that satisfy the Wood & Churchwell criterion for candidate UCHII
regions, we show conclusively for the first time that the fainter flux end of
their sample is contaminated by lower-mass non-ionizing sources, confirming the
suggestion by van der Walt and Ramesh & Sridharan.Comment: 8 pages with 2 figures. Accepted by Ap
Methanol masers : Reliable tracers of the early stages of high-mass star formation
The GLIMPSE and MSX surveys have been used to examine the mid-infrared
properties of a statistically complete sample of 6.7 GHz methanol masers. The
GLIMPSE point sources associated with methanol masers are clearly distinguished
from the majority, typically having extremely red mid-infrared colors, similar
to those expected of low-mass class 0 young stellar objects. The intensity of
the GLIMPSE sources associated with methanol masers is typically 4 magnitudes
brighter at 8.0 micron than at 3.6 micron. Targeted searches towards GLIMPSE
point sources with [3.6]-[4.5] > 1.3 and an 8.0 micron magnitude less than 10
will detect more than 80% of class II methanol masers. Many of the methanol
masers are associated with sources within infrared dark clouds (IRDC) which are
believed to mark regions where high-mass star formation is in its very early
stages. The presence of class II methanol masers in a significant fraction of
IRDC suggests that high-mass star formation is common in these regions.
Different maser species are thought to trace different evolutionary phases of
the high-mass star formation process. Comparison of the properties of the
GLIMPSE sources associated with class II methanol masers and other maser
species shows interesting trends, consistent with class I methanol masers
tracing a generally earlier evolutionary phase and OH masers tracing a later
evolutionary phase.Comment: 45 pages, 19 figures, accepted for publication in Ap
New Periodic 6.7 GHz Class II Methanol Maser Associated with G358.460-0.391
Eight new class II methanol masers selected from the 6.7 GHz Methanol
Multibeam survey catalogues I and II were monitored at 6.7 GHz with the 26m
Hartebeesthoek Radio Astronomy Observatory (HartRAO) radio telescope for three
years and seven months, from February 2011 to September 2014. The sources were
also observed at 12.2 GHz and two were sufficiently bright to permit
monitoring. One of the eight sources, namely G358.460-0.391, was found to show
periodic variations at 6.7 GHz. The period was determined and tested for
significance using the Lomb-Scargle, epoch-folding and Jurkevich methods, and
by fitting a simple analytic function. The best estimate for the period of the
6.7 GHz class II methanol maser line associated with G358.460-0.391 is 220.0
0.2 day.Comment: 8 pages, 11 figures, accepted for publication in MNRAS. The appendix
of 4 pages (with 16 figures) will be published as online versio
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