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Allan Hills 12073: A metal-rich eucrite
No full textRecovery: Allan Hills 12073 is a 500 mg meteorite fragment, partially covered by fresh fusion crust, recovered
from the Near Western Allan Hills ice field, during the 2012-2013 campaign of the Italian Programma Nazionale di
Ricerche in Antartide (PNRA).
Sampling and Methods: ALH 12073 was split into three fragments. One fragment (~150 mg) was used to prepare
a thin section for petrographic description and EMP analysis. A second fragment of about 150 mg, devoid of
fusion crust, was split in two smaller chips. The larger one, of about 105 mg, was prepared for solution ICP-MS
analysis. The smaller one was ground and homogenized for triple oxygen isotope measurements. The third fragment
was embedded in resin, sectioned and polished for bulk Hand-Held XRF analysis. Three pyroxene crystals, of about
300 microns in size each, were selected for X-ray single-crystal diffraction and structure refinement. Two plagioclases
of about 4 mg in mass were extracted for 39Ar-40Ar dating (the plagioclases are under irradiation at the writing
of this abstract, May 2016).
Petrography: In thin section, ALH 12073 shows unbrecciated, inequigranular, medium- to fine-grained subophitic
texture. It maily consists of subhedral plagioclase (46 vol%) and low-Ca pyroxene (34 vol%), plus minor euhedral
tridymite (7 vol%), high-Ca pyroxene (4 vol%), Fe,Ni metal (4 vol%), sulfide (3 vol%), phosphates (2 vol%)
and traces of chromite.
Mineral Chemistry: The low-Ca pyroxene is orthopyroxene (En63.1, Fs33.9, Wo3.1) with a relatively uniform
composition, and average Fe/Mn ratio of 26. It hosts few, local, fine-exolved Ca-rich lamellae. The plagioclase is
anorthite (An92.4, Ab7.5, Or0.2). The high-Ca pyroxene is augite (En 43.3, Fs 16.1, Wo 40.5). It is exolved and displays
two systems of Ca-poor lamellae. The chromite is Mg-rich with an average Mg# of 10%. The Fe,Ni metals are
divided in low Ni-phase (kamacite) and high Ni-phase (taenite).
Thermospeedometric constraints: Opx-Cpx pairs provide an average equilibrium crystallization temperatures
of T = 961 ± 21 °C; the closure temperature of the Fe-Mg cation ordering in three orthopyroxenes (Fs36) determined
through the calibration curve by [1], Tc, are 891 ± 23, 968 ± 22 and 979 ± 27 °C.
Oxygen isotope composition: Triple oxygen isotope composition of ALH 12073 (δ18O = 4.4 ± 0.15‰; δ17O =
2.09 ± 0.15‰) is, within uncertainty, in the range of HED meteorites.
Bulk composition: Major element bulk data indicate that ALH 12073 is a sub-alkaline basalt (SiO2 = 49.44
wt%; Na2O+K2O = 0.16 wt%). Compared with literature data for eucrites [2] ALH 12073 has on average higher
Al2O3 (15% relative) and FeO (50% relative) content. These differences are indicative of higher modal proportion of
plagioclase and metals.
The REE pattern is flat with relatively unfractionated La/Yb ratio (La/YbN=0.8) and a large positive Eu anomaly
(Eu/Eu*=3.8) indicative of plagioclase accumulation. The concentration of incompatible lithophile trace elements
such as Ba, Sr, Zr, Nb, Hf, Th, U and Rb exhibits striking similarities with cumulate eucrites. In turn, when compared
to whole rock literature data, the siderophile elements (Ni, Co) plot far off the field of HED meteorites, towards
higher concentrations.
Discussion: On the basis of pyroxene Fe/Mn ratio and oxygen isotope composition, the ALH 12073 basalt belongs
to the HED family, i.e. it is an eucrite. The relatively high δ18O value could reflect the high modal plagioclase
content of the rock [3]. Pyroxene thermospeedometric data indicate quenching after equilibrium crystallization at
temperatures of about 1000 °C. This is consistent with the occurrence of tridymite. The high metal and bulk siderophile
element content are anomalous for eucrites and needs explanations. Several possibilities can be proposed: 1)
introduction of foreign metal by impact [4]. 2) Change of ƒ(O2) during crystallization. 3) Increase of sulfur partial
pressure during heating and subsequent reduction [5]. 4) Kinship with metal-rich meteorites. All of these options
will be discussed at the meeting
Who is in the transition gap? Transition from CAMHS to AMHS in the Republic of Ireland
Get PDFObjective: The ITRACK study explored the process and predictors of transition between Child and Adolescent Mental Health Services (CAMHS) and Adult Mental Health Services (AMHS) in the Republic of Ireland. Method: Following ethical approval, clinicians in each of Ireland's four Health Service Executive (HSE) areas were contacted, informed about the study and invited to participate. Clinicians identified all cases who had reached the transition boundary (i.e. upper age limit for that CAMHS team ) between January and December 2010. Data were collected on clinical and socio-demographic details and factors that informed the decision to refer or not refer to AMHS and case notes were scrutinised to ascertain the extent of information exchanged between services during transition
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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