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The boomerang returns? Accounting for the impact of uncertainties on the dynamics of remanufacturing systems
Recent years have witnessed companies abandon traditional open-loop supply chain structures in favour of closed-loop variants, in a bid to mitigate environmental impacts and exploit economic opportunities. Central to the closed-loop paradigm is remanufacturing: the restoration of used products to useful life. While this operational model has huge potential to extend product life-cycles, the collection and recovery processes diminish the effectiveness of existing control mechanisms for open-loop systems. We systematically review the literature in the field of closed-loop supply chain dynamics, which explores the time-varying interactions of material and information flows in the different elements of remanufacturing supply chains. We supplement this with further reviews of what we call the three ‘pillars’ of such systems, i.e. forecasting, collection, and inventory and production control. This provides us with an interdisciplinary lens to investigate how a ‘boomerang’ effect (i.e. sale, consumption, and return processes) impacts on the behaviour of the closed-loop system and to understand how it can be controlled. To facilitate this, we contrast closed-loop supply chain dynamics research to the well-developed research in each pillar; explore how different disciplines have accommodated the supply, process, demand, and control uncertainties; and provide insights for future research on the dynamics of remanufacturing systems
The Bivariate Brightness Function of Galaxies and a Demonstration of the Impact of Surface Brightness Selection Effects on Luminosity Function Estimations
In this paper we fit an analytic function to the Bivariate Brightness
Distribution (BBD) of galaxies. It is a combination of the classical Schechter
Function convolved with a Gaussian distribution in surface brightness: thus
incorporating the luminosity-surface brightness correlation as seen in many
recent datasets. We fit this function to a recent measurement of the BBD based
on 45,000 galaxies from the two-degree field Galaxy Redshift Survey (Cross et
al. 2001).
Using a BBF we explore the impact of the limiting detection isophote on
classical measures of the galaxy luminosity distribution. If Gaussian corrected
magnitudes are used these change to mags, and for mag
arcsec. Hence while the faint-end slope, , appears fairly robust
to surface brightness issues, both the and values are highly
dependent. The range over which these parameters were seen to vary is fully
consistent with the scatter in the published values, reproducing the range of
observed luminosity densities (Mpc
see Cross et al. 2001). We conclude that surface brightness selection effects
are primarily responsible for this variation. After due consideration of these
effects, we derive a value of Mpc.Comment: 10 pages, 7 figures, Accepted by MNRA
Validating canopy clumping retrieval methods using hemispherical photography in a simulated Eucalypt forest
The so-called clumping factor (Ω) quantifies deviation from a random 3D distribution of material in a vegetation canopy and therefore characterises the spatial distribution of gaps within a canopy. Ω is essential to convert effective Plant or Leaf Area Index into actual LAI or PAI, which has previously been shown to have a significant impact on biophysical parameter retrieval using optical remote sensing techniques in forests, woodlands, and savannas. Here, a simulation framework was applied to assess the performance of existing in situ clumping retrieval methods in a 3D virtual forest canopy, which has a high degree of architectural realism. The virtual canopy was reconstructed using empirical data from a Box Ironbark Eucalypt forest in Eastern Australia. Hemispherical photography (HP) was assessed due to its ubiquity for indirect LAI and structure retrieval. Angular clumping retrieval method performance was evaluated using a range of structural configurations based on varying stem distribution and LAI. The CLX clumping retrieval method (Leblanc et al., 2005) with a segment size of 15° was the best performing clumping method, matching the reference values to within 0.05 Ω on average near zenith. Clumping error increased linearly with zenith angle to > 0.3 Ω (equivalent to a 30% PAI error) at 75° for all structural configurations. At larger zenith angles, PAI errors were found to be around 25–30% on average when derived from the 55–60° zenith angle. Therefore, careful consideration of zenith angle range utilised from HP is recommended. We suggest that plot or site clumping factors should be accompanied by the zenith angle used to derive them from gap size and gap size distribution methods. Furthermore, larger errors and biases were found for HPs captured within 1 m of unrepresentative large tree stems, so these situations should be avoided in practice if possible
The Hubble Space Telescope Wide Field Camera 3 Early Release Science data: Panchromatic Faint Object Counts for 0.2-2 microns wavelength
We describe the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) Early
Release Science (ERS) observations in the Great Observatories Origins Deep
Survey (GOODS) South field. The new WFC3 ERS data provide calibrated, drizzled
mosaics in the UV filters F225W, F275W, and F336W, as well as in the near-IR
filters F098M (Ys), F125W (J), and F160W (H) with 1-2 HST orbits per filter.
Together with the existing HST Advanced Camera for Surveys (ACS) GOODS-South
mosaics in the BViz filters, these panchromatic 10-band ERS data cover 40-50
square arcmin at 0.2-1.7 {\mu}m in wavelength at 0.07-0.15" FWHM resolution and
0.090" Multidrizzled pixels to depths of AB\simeq 26.0-27.0 mag (5-{\sigma})
for point sources, and AB\simeq 25.5-26.5 mag for compact galaxies.
In this paper, we describe: a) the scientific rationale, and the data taking
plus reduction procedures of the panchromatic 10-band ERS mosaics; b) the
procedure of generating object catalogs across the 10 different ERS filters,
and the specific star-galaxy separation techniques used; and c) the reliability
and completeness of the object catalogs from the WFC3 ERS mosaics. The
excellent 0.07-0.15" FWHM resolution of HST/WFC3 and ACS makes star- galaxy
separation straightforward over a factor of 10 in wavelength to AB\simeq 25-26
mag from the UV to the near-IR, respectively.Comment: 51 pages, 71 figures Accepted to ApJS 2011.01.2
Local-Group tests of dark-matter Concordance Cosmology: Towards a new paradigm for structure formation
(abridged) Predictions of the Concordance Cosmological Model (CCM) of the
structures in the environment of large spiral galaxies are compared with
observed properties of Local Group galaxies. Five new most probably
irreconcilable problems are uncovered. However, the Local Group properties
provide hints that may lead to a solution of the above problems The DoS and
bulge--satellite correlation suggest that dissipational events forming bulges
are related to the processes forming phase-space correlated satellite
populations. Such events are well known to occur since in galaxy encounters
energy and angular momentum are expelled in the form of tidal tails, which can
fragment to form populations of tidal-dwarf galaxies (TDGs) and associated star
clusters. If Local Group satellite galaxies are to be interpreted as TDGs then
the sub-structure predictions of CCM are internally in conflict. All findings
thus suggest that the CCM does not account for the Local Group observations and
that therefore existing as well as new viable alternatives have to be further
explored. These are discussed and natural solutions for the above problems
emerge.Comment: A and A, in press, 25 pages, 9 figures; new version contains minor
text adjustments for conformity with the published version and additional
minor changes resulting from reader's feedback. The speculation on a dark
force has been added. Also, the Fritz Zwicky Paradox is now included to agree
with the published versio
Sterile neutrinos: the dark side of the light fermions
The discovery of neutrino masses suggests the likely existence of gauge
singlet fermions that participate in the neutrino mass generation via the
seesaw mechanism. The masses of the corresponding degrees of freedom can range
from well below the electroweak scale to the Planck scale. If some of the
singlet fermions are light, the sterile neutrinos appear in the low-energy
effective theory. They can play an important role in astrophysics and
cosmology. In particular, sterile neutrinos with masses of several keV can
account for cosmological dark matter, which can be relatively warm or cold,
depending on the production mechanism. The same particles can explain the
observed velocities of pulsars because of the anisotropy in their emission from
a cooling neutron star born in a supernova explosion. Decays of the relic
sterile neutrinos can produce a flux of X-rays that can affect the formation of
the first stars. Existing and future X-ray telescopes can be used to search for
the relic sterile neutrinos.Comment: 54 page
A blind HI survey in the Canes Venatici region
We have carried out a blind HI survey using the Westerbork Synthesis Radio
Telescope to make an inventory of objects with small HI masses (between 10^6
and 10^8 Msol) and to constrain the low-mass end of the HI mass function. The
survey has been conducted in a part of the volume containing the nearby Canes
Venatici groups of galaxies. The surveyed region covers an area on the sky of
about 86 square degrees and a range in velocity from about -450 to about 1330
km/s. We find 70 sources in the survey by applying an automated searching
algorithm. Two of the detections have not been catalogued previously, but they
can be assigned an optical counterpart, based on visual inspection of the
second generation Digital Sky Survey images. Only one of the HI detections is
without an optical counterpart. This object is detected in the vicinity of
NGC4822 and it has been already detected in previous HI studies. Nineteen of
the objects have been detected for the first time in the 21-cm emission line in
this survey. The distribution of the HI properties of our detections confirms
our ability to find low mass objects. 86% of the detections have profile widths
less than 130 km/s and can be considered dwarf galaxy candidates. The HI fluxes
measured imply that this survey goes about 10 times deeper than any previous
blind HI survey. The HI mass function and the optical properties of the
detected sources will be discussed in future papers.Comment: 46 pages, 15 figures (including the atlas of HI observations);
accepted for publication in MNRAS; the high resolution pdf available at
http://www.exp-astro.phys.ethz.ch/kovac/public/WSRTCVn
Mendelian randomization provides support for obesity as a risk factor for meningioma.
Little is known about the causes of meningioma. Obesity and obesity-related traits have been reported in several epidemiological observational studies to be risk factors for meningioma. We performed an analysis of genetic variants associated with obesity-related traits to assess the relationship with meningioma risk using Mendelian randomization (MR), an approach unaffected by biases from temporal variability and reverse causation that might have affected earlier investigations. We considered 11 obesity-related traits, identified genetic instruments for these factors, and assessed their association with meningioma risk using data from a genome-wide association study comprising 1,606 meningioma patients and 9,823 controls. To evaluate the causal relationship between the obesity-related traits and meningioma risk, we consider the estimated odds ratio (OR) of meningioma for each genetic instrument. We identified positive associations between body mass index (odds ratio [ORSD] = 1.27, 95% confidence interval [CI] = 1.03-1.56, P = 0.028) and body fat percentage (ORSD = 1.28, 95% CI = 1.01-1.63, P = 0.042) with meningioma risk, albeit non-significant after correction for multiple testing. Associations for basal metabolic rate, diastolic blood pressure, fasting glucose, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, systolic blood pressure, total cholesterol, triglycerides and waist circumference with risk of meningioma were non-significant. Our analysis provides additional support for obesity being associated with an increased risk of meningioma
Innovation and growth in the UK pharmaceuticals: the case of product and marketing introductions
New drug introductions are key to growth for pharmaceutical firms. However, not all innovations are the same and they may have differential effects that vary by firm size. We use quarterly sales data on UK pharmaceuticals in a dynamic panel model to estimate the impact of product (new drugs) and marketing (additional pack varieties) innovations within a therapeutic class on a firm’s business unit growth. We find that product innovations lead to substantial growth in both the short and long run, whereas a new pack variety only produces short-term effects. The strategies are substitutes but the marginal effects are larger for product innovations relative to additional packs, and the effects are larger for smaller business units. Nonetheless, pack introductions offer a viable short-term growth strategy, especially for small- and medium-sized businesses
Influence of obesity-related risk factors in the aetiology of glioma
BACKGROUND: Obesity and related factors have been implicated as possible aetiological factors for the development of glioma in epidemiological observation studies. We used genetic markers in a Mendelian randomisation framework to examine whether obesity-related traits influence glioma risk. This methodology reduces bias from confounding and is not affected by reverse causation. METHODS: Genetic instruments were identified for 10 key obesity-related risk factors, and their association with glioma risk was evaluated using data from a genome-wide association study of 12,488 glioma patients and 18,169 controls. The estimated odds ratio of glioma associated with each of the genetically defined obesity-related traits was used to infer evidence for a causal relationship. RESULTS: No convincing association with glioma risk was seen for genetic instruments for body mass index, waist-to-hip ratio, lipids, type-2 diabetes, hyperglycaemia or insulin resistance. Similarly, we found no evidence to support a relationship between obesity-related traits with subtypes of glioma-glioblastoma (GBM) or non-GBM tumours. CONCLUSIONS: This study provides no evidence to implicate obesity-related factors as causes of glioma
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