1,505 research outputs found
International Year of Planet Earth 1. Non-Renewable Resources, Sustainable Development, and Human Evolution — Short Story or Opening Chapter?
Humanity is beginning to grapple with the idea that the Earth is quite a small place when shared by over 6 billion people, and that the physical impact of this number of people on the planet is no longer negligible. In particular, our exponentially increasing use of energy is creating problems both in terms of supply and impact on the environment. Sustainable development has become the buzz word for solving the world’s social, environmental, and ecological problems, but our understanding of what is required for true sustainability is inadequate, and does not recognize the practical limitations we face. We continue to use non-renewable resources, especially fossil fuels, as though there was an unlimited supply, with no consequence to their unbridled consumption. The slow realization by scientists and policy-makers that neither of these things is true has not manifested itself yet in any effective policy formulation on a global scale, and on a local (national, state, or provincial) scale it is largely business as usual. The writer suggests that this is because the human mind has not yet evolved to respond effectively to its relatively novel capacity for reflection on the past and contemplation of the future. We are still stuck with a psyche that is geared to look after only our own interests and those of our immediate family or social group. Our outlook urgently needs to be expanded to embrace the expedient of planning for a secure future for our species as a whole. If we wait for the natural course of evolution to effect this change, we may be too late; but if we positively engage the other human trait of willpower, then perhaps great things are possible. Geoscientists are uniquely equipped with knowledge about the history of our planet and the evolution of the species that have lived on it to inform this debate — we should not keep this knowledge to ourselves, but boldly enter the discussion.
SOMMAIRE
L'humanité commence à se faire à l'idée que la Terre est un endroit bien petit pour une population de plus de 6 milliards de personnes, et que l'impact physique d'un si grand nombre de personnes n'est plus négligeable. En particulier, notre utilisation en croissance exponentielle de l'énergie crée à la fois des problèmes d'approvisionnement et d'impact sur notre milieu de vie. Le développement durable est devenu l'expression à la mode évoquant la solution aux problèmes sociaux, environnementaux et écologiques de notre monde, mais notre compréhension est insuffisante quant aux mesures à mettre en œuvre pour vraiment assurer la durabilité, et nous ne réalisons pas encore les limites pratiques auxquelles nous faisons face. Nous continuons d'utiliser les ressources non-renouvelables, particulièrement les énergies fossiles, comme si elles étaient inépuisables et sans égard aux conséquences d'une consommation effrénée. La lente prise de conscience de ces limites et de leurs conséquences par les scientifiques et les législateurs ne s'est pas encore matérialisée en termes de législation efficace à l'échelle planétaire, et à l'échelle locale (nationale, de l'état ou provinciale), on continue comme si rien n'était. L'auteur suggère qu'il en est ainsi parce que la mentalité humaine n'est pas suffisamment évoluée et n'est pas encore en mesure de profiter efficacement de moyens nouveaux lui permettant de réfléchir et de tirer parti du passé et de se projeter dans l'avenir. Nous ne disposons encore que d'une psyché qui nous pousse à ne tenir compte que de nos intérêts propres ainsi qu'à ceux de nos proches immédiats et de nos groupes sociaux. De toute urgence, nous devons ouvrir notre perspective afin qu'elle embrasse les mesures de planification permettant d'assurer la survie de l'espèce dans l'avenir. Si nous attendons que l'évolution naturelle nous y amène, il pourrait bien être trop tard; en contrepartie, si nous misons sur cet autre trait humain qu'est la volonté, de grandes choses sont peut-être possibles. De par leurs connaissances de l'histoire de notre planète et de l'évolution des espèces, les géoscientifiques peuvent éclairer ce débat - nous ne devons plus garder ces connaissances pour nous seuls, mais intervenir de manière décisive dans le débat
Platinum-Group Element Geochemistry of the Escondida Igneous Suites, Northern Chile: Implications for Ore Formation
Platinum-group element (PGE) geochemistry may be used to constrain the timing of sulfide saturation in magmas, which influences the Cu and Au fertility of evolving magmatic systems. We report new geochronological and geochemical data, with emphasis on PGE geochemistry, for a suite of regional porphyritic hornblende–diorite intrusions and ore-bearing porphyries from the super-giant Escondida and smaller Zaldivar Cu deposits of Northern Chile. The regional dioritic intrusions have zircon U–Pb ages between 39·6 to 37·1 Ma, which overlap with the ages of the ore-bearing Escondida and Zaldivar porphyries (38·1 to 35·0 Ma). Whole-rock major and trace element, and Sr–Nd–Pb and zircon O–Hf isotope geochemistry indicate that the regional diorites and ore-bearing porphyries are co-magmatic and originated from the same mantle-derived magma by fractional crystallization, with minor contamination by Paleozoic crust (∼10%). The low concentrations of PGE in the regional diorites show that they reached sulfide saturation before the MgO content of the melt fell to 4·7 wt %, the MgO content of the most primitive sample analysed. The fraction of sulfide melt which separated from the melts that formed the regional diorites is estimated to be ∼0·12 wt %; this resulted in the partitioning of highly chalcophile elements (Au and PGE) into a sulfide phase that was retained in cumulus rocks at depth. However, the fraction of sulfide melt was too low to have a significant effect on the Cu content of the fractionating melt. As a consequence, when the evolving melt eventually reached volatile saturation, it contained enough Cu (40 ± 10 ppm) to form a super-giant Cu deposit. In contrast, Au was largely stripped from the melt by sulfide precipitation, with the result that the mineralization at Escondida is Cu dominant, with only minor Au. The Zaldivar deposit, on the other hand, contains even less Au, which is attributed to a longer fractionation interval between sulfide and volatile saturation. This study provides evidence to support previously proposed models which suggest that the timing of sulfide saturation, the amount of sulfide melt produced, the water content and oxidation state of the melt, and the magma volume are critical factors in determining the potential to form a porphyry Cu deposit. Plots of Pd/MgO against Y can be used as empirical indicators of magma fertility for porphyry mineralization, and to discriminate between Cu–Au and Cu-dominated systems, but cannot predict the size of the deposit. The super-giant status of the Escondida deposit is attributed to it being underlain by a large batholith with a calculated minimum mass of 1012 tonnes (∼400 km3).This work was supported by the Australian Research
Council [DP170103140]
Expression and Site-Directed Mutagenesis of Type III Polyketide Synthases
Natural products are a well-established source of drugs, and evolution has yielded polyketides such as leinamycin and iso-migrastatin that have demonstrated anti-tumor activity. Polyketides are large metabolites with a high degree of chemical variability and are commonly produced by soil bacteria. Polyketide synthases (PKS) exist as three different archetypes, and the reaction mechanisms of ketosynthases from all archetypes is not understood. Type III PKSs exist as an independently functioning ketosynthase (KS), which primarily use coenzyme A (CoA), with some exceptions, for the biosynthesis of polyketides. We elected to focus our studies on ketosynthases, because they are responsible for forming the carbon-carbon bonds seen in polyketides. To study these Type III PKS KS, we expressed Streptomyces coelicolor germicidin synthase (Gcs) and tetrahydroxynaphthlene synthase (THNS) in E. coli and mutant versions where the catalytic active cysteine was changed to a serine or glutamine. In previous studies, serine slowed the overall progress of the reaction, and glutamine abolished carbon-carbon bond formation but promoted malonyl-CoA decarboxylation. We verified our mutations using a third party organization’s fluorescent sequencing by dye termination services, as well as confirmed that an acceptable level of expression of our protein is occurring in our BL21 cell lines using SDS-PAGE and Fast Protein Liquid Chromatography (FPLC). Now that we have successfully expressed and mutated our protein, we can move forward and use substrate mimics in conjunction with our mutants to further understand the catalytic mechanism of ketosynthases
Determination of overlap in lidar systems
The overlap profile, also known as crossover function or geometric form factor, is often a source of uncertainty for lidar measurements. This paper describes a method for measuring the overlap by presenting the lidar with a virtual cloud through the use of an imaging system. Results show good agreement with horizontal hard target lidar measurements and with geometric overlap calculated for the ideal aberration-free case
New laser technology to determine present weather parameters
Present weather sensors are becoming increasingly important as a means to
augment networks of automated weather stations and extend the capability
of manned observations. The classification of hydrometeors is one of the
principal tasks that is addressed by present weather sensors. In this paper,
we discuss a new laser-based technology for this purpose. The system
improves upon current precipitation monitors by using a derivative of phase
Doppler anemometry techniques to accurately determine particle speed and
size. The instrument is also capable of distinguishing between liquid
droplets and solid polycrystalline hydrometeors and can be used to estimate
visibility. The incorporation of this technology into a meteorological station
with other sensors, such as temperature and relative humidity probes, leads
to the accurate classification of particle type. The example data shown are
taken from tests in Leicestershire, England and Utah, USA and show the
differences between solid and liquid precipitation events
The SDSS-III Baryon Oscillation Spectroscopic Survey: Quasar Target Selection for Data Release Nine
The SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), a five-year
spectroscopic survey of 10,000 deg^2, achieved first light in late 2009. One of
the key goals of BOSS is to measure the signature of baryon acoustic
oscillations in the distribution of Ly-alpha absorption from the spectra of a
sample of ~150,000 z>2.2 quasars. Along with measuring the angular diameter
distance at z\approx2.5, BOSS will provide the first direct measurement of the
expansion rate of the Universe at z > 2. One of the biggest challenges in
achieving this goal is an efficient target selection algorithm for quasars over
2.2 < z < 3.5, where their colors overlap those of stars. During the first year
of the BOSS survey, quasar target selection methods were developed and tested
to meet the requirement of delivering at least 15 quasars deg^-2 in this
redshift range, out of 40 targets deg^-2. To achieve these surface densities,
the magnitude limit of the quasar targets was set at g <= 22.0 or r<=21.85.
While detection of the BAO signature in the Ly-alpha absorption in quasar
spectra does not require a uniform target selection, many other astrophysical
studies do. We therefore defined a uniformly-selected subsample of 20 targets
deg^-2, for which the selection efficiency is just over 50%. This "CORE"
subsample will be fixed for Years Two through Five of the survey. In this paper
we describe the evolution and implementation of the BOSS quasar target
selection algorithms during the first two years of BOSS operations. We analyze
the spectra obtained during the first year. 11,263 new z>2.2 quasars were
spectroscopically confirmed by BOSS. Our current algorithms select an average
of 15 z > 2.2 quasars deg^-2 from 40 targets deg^-2 using single-epoch SDSS
imaging. Multi-epoch optical data and data at other wavelengths can further
improve the efficiency and completeness of BOSS quasar target selection.
[Abridged]Comment: 33 pages, 26 figures, 12 tables and a whole bunch of quasars.
Submitted to Ap
The institutional shaping of management: in the tracks of English individualism
Globalisation raises important questions about the shaping of economic action by cultural factors. This article explores the formation of what is seen by some as a prime influence on the formation of British management: individualism. Drawing on a range of historical sources, it argues for a comparative approach. In this case, the primary comparison drawn is between England and Scotland. The contention is that there is a systemic approach to authority in Scotland that can be contrasted to a personal approach in England. An examination of the careers of a number of Scottish pioneers of management suggests the roots of this systemic approach in practices of church governance. Ultimately this systemic approach was to take a secondary role to the personal approach engendered by institutions like the universities of Oxford and Cambridge, but it found more success in the different institutional context of the USA. The complexities of dealing with historical evidence are stressed, as is the value of taking a comparative approach. In this case this indicates a need to take religious practice as seriously as religious belief as a source of transferable practice. The article suggests that management should not be seen as a simple response to economic imperatives, but as shaped by the social and cultural context from which it emerges
Magmatic evolution and porphyry–epithermal mineralization in the Taftan volcanic complex, southeastern Iran
The Taftan volcanic complex is located above the Makran subduction zone in Sistan and
Baluchestan province, southeastern Iran. The earliest volcanic activity at Taftan started in the
late Miocene (~8 Ma) with eruption of andesitic to dacitic lava onto a Cretaceous to Eocene
volcanic and sedimentary paleosurface ~20 km to the northwest of the current volcanic
edifice. Later Plio-Pleistocene volcanism consisted of voluminous andesitic and dacitic lavas
and pyroclastic flows (~3.1 to 0.4 Ma). Taftan, and the neighbouring Bazman volcano, are
the southeasternmost and youngest manifestations of arc-related volcanism in Iran, which
began with the Eocene–Miocene Urumieh-Dokhtar Magmatic Arc (UDMA) in northwest and
central Iran, and extends into western Pakistan (Chagai Arc).
Major porphyry Cu±Mo±Au deposits are associated with Miocene to Pliocene intrusive
rocks in the Kerman section of the Eocene–Neogene Urumieh-Dokhtar Magmatic Arc in
southeastern Iran (e.g., Sar Cheshmeh, Meiduk), and at Reko Diq and Saindak in the Late
Cretaceous–Quaternary Chagai Arc in western Pakistan. In a gap of ~300 km between these
two belts, several porphyry and epithermal prospects are exposed in the Miocene–Pliocene
sections of the Taftan volcanic complex, including the Kharestan (6.10 ± 0.80 Ma) and
Bidester porphyry-epithermal Cu-Au deposits (~4.3 Ma), and the Siah Jangal epithermal Au
deposit (late Miocene). In addition, several argillic to advanced argillic and fumarolic
alteration zones occur in Plio-Pleistocene volcanic rocks around the current volcanic edifice.
These deposits have received limited exploration. Electron microprobe analyses of amphibole (magnesio-hastingsite) phenocrysts and
magnetite–ilmenite mineral pairs from the Taftan and Bazman volcanic rocks indicate a
change of crystallization temperature and magmatic oxidation state from ~1000°C and
FMQ ≈ +1 in andesitic rocks, to ~900°C and FMQ ≈ +2 in dacitic rocks. Magmatic water
content was >4 wt.%, as indicated by the ubiquitous presence of amphibole phenocrysts.
Major and trace element compositions of the Taftan and Bazman volcanic rocks show
calc-alkaline to high-K calc-alkaline affinity, with relative depletions of Nb, Ta, and Ti and
enrichments of large-ion lithophile elements (LILE), Th, and U on normalized diagrams.
These trace element patterns, including listric-shaped normalized rare earth element profiles
and relatively high Sr/Y and La/Yb ratios, are similar to those of fertile Miocene igneous
rocks from the Kerman Belt and Chagai Arc, and suggest that the Taftan suite in particular
should be prospective for porphyry Cu ore formation. Regionally, there is no clear geochemical difference between the Neogene Kerman Belt
rocks, which are thought to post-date the onset of collision between the Afro-Arabian and
Eurasian plates (late Oligocene to earliest Miocene), and the subduction-related Bazman–
Taftan and Chagai Belt magmas. The porphyry deposits formed in these distinct settings are
also virtually indistinguishable. This suggests that most of the processes affecting the
geochemistry and metallogeny of the magmas in both settings take place in the lithosphere,
albeit that the ultimate source of the magmas is in the supra-subduction zone asthenospheric
mantle wedge. In collisional environments, subduction-related material previously
crystallized in the deep lithosphere is simply being remobilized
Intercomparison and Evaluation of Satellite Peroxyacetyl Nitrate Observations in the Upper Troposphere-Lower Stratosphere
Peroxyacetyl nitrate (PAN) is an important chemical species in the troposphere as it aids the long-range transport of NOx and subsequent formation of O3 in relatively clean remote regions. Over the past few decades observations from aircraft campaigns and surface sites have been used to better understand the regional distribution of PAN. However, recent measurements made by satellites allow for a global assessment of PAN in the upper troposphere-lower stratosphere (UTLS). In this study, we investigate global PAN distributions from two independent retrieval methodologies, based on measurements from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument, on board Envisat from the Institute of Meteorology and Climate Research (IMK), Karlsruhe Institute of Technology, and the Department of Physics and Astronomy, University of Leicester (UoL). Retrieving PAN from MIPAS is challenging due to the weak signal in the measurements and contamination from other species. Therefore, we compare the two MIPAS datasets with observations from the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS), in situ aircraft data and the 3-D chemical transport model TOMCAT. MIPAS shows peak UTLS PAN concentrations over the biomass burning regions (e.g. ranging from 150 to \u3e 200 pptv at 150 hPa) and during the summertime Asian monsoon as enhanced convection aids the vertical transport of PAN from the lower atmosphere. At 150 hPa, we find significant differences between the two MIPAS datasets in the tropics, where IMK PAN concentrations are larger by 50-100 pptv. Comparisons between MIPAS and ACE-FTS show better agreement with the UoL MIPAS PAN concentrations at 200 hPa, but with mixed results above this altitude. TOMCAT generally captures the magnitude and structure of climatological aircraft PAN profiles within the observational variability allowing it to be used to investigate the MIPAS PAN differences. TOMCAT-MIPAS comparisons show that the model is both positively (UoL) and negatively (IMK) biased against the satellite products. These results indicate that satellite PAN observations are able to detect realistic spatial variations in PAN in the UTLS, but further work is needed to resolve differences in existing retrievals to allow quantitative use of the products. © Author(s) 2016
From the Heart of The Ghoul: C and N Abundances in the Corona of Algol B
Chandra Low Energy Transmission Grating Spectrograph observations of Algol
have been used to determine the abundances of C and N in the secondary star for
the first time. The analysis was performed relative to similar observations of
an adopted "standard" star HR 1099. It is demonstrated that HR 1099 and Algol
are coronal twins in many respects and that their X-ray spectra are very
similar in nearly all details, except for the observed strengths of C and N
lines. The H-like transitions of C and N in the coronae of Algol and HR 1099
demonstrate that the surface abundances of Algol B have been strongly modified
by CN-processing, as shown earlier by Schmitt & Ness (2002). It is found that N
is enhanced in Algol B by a factor of 3 compared to HR 1099. No C lines are
detected in the Algol spectrum, indicating a C depletion relative to HR 1099 by
a factor of 10 or more. These C and N abundances indicate that Algol B must
have lost at least half of its initial mass, and are consistent with
predictions of evolutionary models that include non-conservative mass transfer
and angular momentum loss through magnetic activity. Little or no dredge-up of
material subjected to CN-processing has occurred on the subgiant component of
HR 1099. It is concluded that Fe is very likely depleted in the coronae of both
Algol and HR 1099 relative to their photospheres by 0.5 dex, and C, N and O by
0.3 dex. Instead, Ne is enhanced by up to 0.5 dex.Comment: 17 pages, 4 figures, ApJ accepte
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