698 research outputs found
Considerations in the design of large space structures
Several analytical studies of topics relevant to the design of large space structures are presented. Topics covered are: the types and quantitative evaluation of the disturbances to which large Earth-oriented microwave reflectors would be subjected and the resulting attitude errors of such spacecraft; the influence of errors in the structural geometry of the performance of radiofrequency antennas; the effect of creasing on the flatness of tensioned reflector membrane surface; and an analysis of the statistics of damage to truss-type structures due to meteoroids
Classification of Construction Projects
The final publication is available at World Academy of Science via https://waset.org/Publication/classification-of-construction-projects/10001697 © 2015, This unmodified version is made available under the CC BY-SA 2.0 https://creativecommons.org/licenses/by-sa/2.0/In order to address construction project requirements and specifications, scholars and practitioners need to establish taxonomy according to a scheme that best fits their need. While existing characterization methods are continuously being improved, new ones are devised to cover project properties which have not been previously addressed. One such method, the Project Definition Rating Index (PDRI), has received limited consideration strictly as a classification scheme. Developed by the Construction Industry Institute (CII) in 1996, the PDRI has been refined over the last two decades as a method for evaluating a project's scope definition completeness during front-end planning (FEP). The main contribution of this study is a review of practical project classification methods, and a discussion of how PDRI can be used to classify projects based on their readiness in the FEP phase. The proposed model has been applied to 59 construction projects in Ontario, and the results are discussed
The Opacity of Spiral Galaxy Disks VIII: Structure of the Cold ISM
The quantity of dust in a spiral disk can be estimated using the dust's
typical emission or the extinction of a known source. In this paper, we compare
two techniques, one based on emission and one on absorption, applied on
sections of fourteen disk galaxies. The two measurements reflect, respectively
the average and apparent optical depth of a disk section. Hence, they depend
differently on the average number and optical depth of ISM structures in the
disk. The small scale geometry of the cold ISM is critical for accurate models
of the overall energy budget of spiral disks. ISM geometry, relative
contributions of different stellar populations and dust emissivity are all free
parameters in galaxy Spectral Energy Distribution (SED) models; they are also
sometimes degenerate, depending on wavelength coverage. Our aim is to constrain
typical ISM geometry. The apparent optical depth measurement comes from the
number of distant galaxies seen in HST images through the foreground disk. We
measure the IR flux in images from the {\it Spitzer} Infrared Nearby Galaxy
Survey in the same section of the disk that was covered by HST. A physical
model of the dust is fit to the SED to estimate the dust surface density, mean
temperature, and brightness in these disk sections. The surface density is
subsequently converted into the average optical depth estimate. The two
measurements generally agree. The ratios between the measured average and
apparent optical depths of the disk sections imply optically thin clouds in
these disks. Optically thick disks, are likely to have more than a single cloud
along the line-of-sight.Comment: 31 pages, 5 figures, 4 tables, accepted for publication in A
Pillared two-dimensional metal-organic frameworks based on a lower-rim acid appended calix[4]arene
Solvothermal reactions of the lower-rim functionalized diacid calix[4]arene 25,27-bis(methoxycarboxylic acid)-26,28-dihydroxy-4-tert-butylcalix[4]arene (LH₂) with Zn(NO₃)₂•6H₂O and the dipyridyl ligands 4,4/-bipyridyl (4,4/-bipy), 1,2-di(4-pyridyl)ethylene (DPE) or 4,4/-azopyridyl (4,4/-azopy) afforded a series of 2-D structures of the formulae {[Zn(4,4/-bipy)(L)]•2¼DEF}n (1), {[Zn₂(L)(DPE)]•DEF}n (2) and {[Zn(OH₂)₂(L)(4,4/-azopy)]•DEF}n (3) (DEF = diethylformamide)
Topological mechanochemistry of graphene
In view of a formal topology, two common terms, namely, connectivity and
adjacency, determine the quality of C-C bonds of sp2 nanocarbons. The feature
is the most sensitive point of the inherent topology of the species so that
such external action as mechanical deformation should obviously change it and
result in particular topological effects. The current paper describes the
effects caused by uniaxial tension of a graphene molecule in due course of a
mechanochemical reaction. Basing on the molecular theory of graphene, the
effects are attributed to both mechanical loading and chemical modification of
edge atoms of the molecule. The mechanical behavior is shown to be not only
highly anisotropic with respect to the direction of the load application, but
greatly dependent on the chemical modification of the molecule edge atoms thus
revealing topological character of the graphene deformation.Comment: 9 pages, 10 figures, 1 table. arXiv admin note: text overlap with
arXiv:1301.094
The ROSAT All-Sky Survey: a Catalog of Clusters of Galaxies in a Region of 1 Ster around the South Galactic Pole
A field of 1.013 ster in the ROSAT all-sky survey (RASS), centered on the
south galactic pole (SGP), has been searched in a systematic, objective manner
for clusters of galaxies. The procedure relied on a correlation of the X-ray
positions and properties of ROSAT sources with the distribution of galaxies in
the COSMOS digitised data base, which was obtained by scanning the plates of
the UK Schmidt IIIa-J optical southern sky survey. The study used the second
ROSAT survey data base (RASS-2) and included several optical observing
campaigns to measure redshifts. The search, a precursor to the larger REFLEX
survey of the whole southern sky, reached the detection limits of the RASS and
the COSMOS data, and yielded a catalog of 186 clusters in which the lowest flux
is 1.5e-12 erg/cm2/s in the 0.1-2.4 keV band. Of these 157 have measured
redshifts. Using a limit of 3.0e-12 erg/cm2/s a complete subset of 112 clusters
was obtained, of which 110 have measured redshifts. The spatial distribution of
the X-ray clusters out to z = 0.15 shows an extension of the Local Supercluster
to the Pisces-Cetus supercluster (z<~0.07), and a more distant orthogonal
structure at 0.07<z<0.15.Comment: To be published in ApJ Supplements in February 2002: 53 pages: 18
figure
Probing the Intrinsic Shape and Alignment of Dark Matter Haloes using SDSS Galaxy Groups
We study the three-dimensional and projected shapes of galaxy groups in the
Sloan Digital Sky Survey Data Release 4, and examine the alignment between the
orientation of the central galaxy and the spatial distribution of satellite
galaxies. The projected ellipticity of a group is measured using the moments of
the discrete distribution of its member galaxies. We infer the
three-dimensional and projected axis ratios of their dark matter haloes by
comparing the measured ellipticity distributions with those obtained from Monte
Carlo simulations of projected, triaxial dark matter haloes with different axis
ratios. We find that the halo shape has a strong dependence on the halo mass.
While the haloes of low-mass groups are nearly spherical, those of massive
groups tend to be prolate. For groups containing at least four members, the
statistical distribution of their measured ellipticities does not have a strong
dependence on the colors of their central galaxies. Our analysis further shows
that the average three-dimensional axis ratio for haloes with is about , resulting in a
projected axis ratio of . Our results for the alignment between the
orientation of the central galaxy of a group and the distribution of their
satellite galaxies are in broad agreement with those obtained by Yang et al.
The distribution of satellite galaxies preferentially aligns with the major
axis of the central galaxy, with a clear dependence on both halo mass and
galaxy colors. (abridged)Comment: 13 pages, 10 figures and 2 tables. Accepted for publication in MNRA
The incidence, aetiology, and coagulation management of massive postpartum haemorrhage: a two-year national prospective cohort study
Introduction
Between 2017 and 2018 a national quality improvement initiative was introduced incorporating point-of-care viscoelastic haemostatic assays (VHA) to guide blood product transfusion. Laboratory coagulation profiles, use and results of VHA, and administration of blood products were investigated.
Methods
A two-year prospective cohort study of maternal outcomes of women experiencing massive postpartum haemorrhage (PPH) >1000 mL in Wales. In this study, cases of massive PPH (≥2500 mL and/or ≥5 units red blood cell (RBC) transfusion) were identified.
Results
Massive PPH occurred in 349 of 60 914 maternities (rate 5.7 per 1000). There were no deaths from PPH. Intensive care unit admission and/or hysterectomy occurred in 34/311 (10.9%) and 16/347 (4.6%), respectively. The leading cause of massive PPH was genital tract trauma (107/349, 30.6%). Two hundred and seventy-nine (80.6%) required RBC transfusion and 79/345 (22.9%) received at least one blood coagulation product. Results of VHA were recorded in 245/349 (70.2%), with 44/98 (44.9%) women tested in the first six months vs 63/77 (81.8%) in the final six months. Hypofibrinogenaemia (Clauss fibrinogen 1.5×reference range in 10/293 (3.4%).
Conclusion
In Wales, the use of VHA in cases of massive PPH increased over time, enabling clinicians to adopt a targeted, patient-specific approach to blood product administration, with only 22.9% of women receiving blood coagulation products and 17.1% having a documented clotting abnormality
Water safety plans and climate change mitigation
[Excerpt] Definition
Quality water at affordable prices for all is a key
condition for the promotion of public health, environmental sustainability, and quality and safety of
life. In a context of growing external uncertainties
arising from changes in the climate and the environment, ensuring these conditions is an upward
concern and is of utmost relevance to increase
scientific research on the impacts of climate
change on water quality modification and in minimization/mitigation strategies
Carcinoid Tumour of the Appendix: An Analysis of 1,485 Consecutive Emergency Appendectomies
Aim: The aim of this study is to conduct a retrospective analysis of the incidence and long-term results of carcinoid tumours of the appendix in emergency appendectomies. Methods: A retrospective review of 1,485 appendectomies was performed in two centres from January 2000 until January 2006. Demographic data, clinical presentation, histopathology, operative reports and survival were scored and compared with the literature. Results: In three women and four men, carcinoid tumours were identified (0.47%). The mean age was 32.7 years (range, 20-59 years). The clinical presentation was resembling the symptoms of acute appendicitis in all cases. Laparoscopic appendectomy was the treatment of choice in five patients; in one of these patients, a conversion to laparotomy was necessary. The other two patients underwent primary open appendectomy. Five patients underwent additional surgery after the pathology report became available. Four patients underwent ileocecal resection; one other patient underwent right hemicolectomy. In none of the re-operation specimens was residual carcinoid tumour detected. After a mean follow-up of 65 months (range, 25-92), all patients were alive and disease- and symptom-free. Conclusion: Carcinoid tumours of the appendix most often present as acute appendicitis. It also emphasises the value of histopathological analysis of every removed appendix. The long-term prognosis of incidentally found carcinoids of the appendix is good
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