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Dear Mr. President
A letter expressing warm regards on the eve of the ambassador's departure
Measuring molecular abundances in comet C/2014 Q2 (Lovejoy) using the APEX telescope
Comet composition provides critical information on the chemical and physical
processes that took place during the formation of the Solar system. We report
here on millimetre spectroscopic observations of the long-period bright comet
C/2014 Q2 (Lovejoy) using the Atacama Pathfinder Experiment (APEX) band 1
receiver between 2015 January UT 16.948 to 18.120, when the comet was at
heliocentric distance of 1.30 AU and geocentric distance of 0.53 AU. Bright
comets allow for sensitive observations of gaseous volatiles that sublimate in
their coma. These observations allowed us to detect HCN, CH3OH (multiple
transitions), H2CO and CO, and to measure precise molecular production rates.
Additionally, sensitive upper limits were derived on the complex molecules
acetaldehyde (CH3CHO) and formamide (NH2CHO) based on the average of the
strongest lines in the targeted spectral range to improve the signal-to-noise
ratio. Gas production rates are derived using a non-LTE molecular excitation
calculation involving collisions with H2O and radiative pumping that becomes
important in the outer coma due to solar radiation. We find a depletion of CO
in C/2014 Q2 (Lovejoy) with a production rate relative to water of 2 per cent,
and relatively low abundances of Q(HCN)/Q(H2O), 0.1 per cent, and
Q(H2CO)/Q(H2O), 0.2 per cent. In contrast the CH3OH relative abundance
Q(CH3OH)/Q(H2O), 2.2 per cent, is close to the mean value observed in other
comets. The measured production rates are consistent with values derived for
this object from other facilities at similar wavelengths taking into account
the difference in the fields of view. Based on the observed mixing ratios of
organic molecules in four bright comets including C/2014 Q2, we find some
support for atom addition reactions on cold dust being the origin of some of
the molecules.Comment: 10 pages, 7 figures, to be published in MNRA
Ochre use at Olieboomspoort, South Africa: insights into specular hematite use and collection during the Middle Stone Age
Recent excavations at Olieboomspoort (OBP) in the Waterberg Mountains of South Africa confirmed previous research at the site that highlighted an abundance of ochre in the Middle Stone Age (MSA) deposits. Here, we report on the results of an analysis of the ochre from the MSA deposits excavated in 2018-2019. Fossilised equid teeth from these deposits were recently dated to approximately 150 ka, an early date for such a sizeable ochre assemblage in southern Africa. Calcium carbonate concretions were removed from ochre pieces using hydrochloric acid. Macro- and microscopic analyses were undertaken to identify raw material types and to investigate utilisation strategies. There are 438 pieces in the assemblage and only 14 of them show definite use-traces. The predominant raw material is a micaceous, hard specular hematite, which is rare at MSA sites elsewhere in southern Africa. A preliminary investigation into the geological nature of the ochreous materials in the archaeological sample and those available in the area was performed using semi-quantitative portable X-ray fluorescence (pXRF), XRF, and inductively coupled plasma mass spectrometry (ICP-MS). Together with site formation processes, we suggest possible, primarily local sources of the ochre found in the deposits. The data do not support previous suggestions that OBP was used as an ochre caching site that may have formed part of an exchange network during the MSA. Instead, the local abundance of nodules of specular hematite within the Waterberg sandstone, the limited number of used pieces in the assemblage, and the stratigraphic context indicate a more natural, less anthropogenic explanation for the abundance of ochre at the site.European Social Fund (ESF) RYC2020-029506-Iinfo:eu-repo/semantics/publishedVersio
O crescimento populacional do rebanho bovino brasileiro.
A população do rebanho bovino mundial tende a se estabilizar ou mesmo reduzir, enquanto que no Brasil, o crescimento tem sido positivo nos últimos anos. Considerando-se o número efetivo de animais e a taxa de abate do rebanho brasileiro no período de 1983 a 2000, o objetivo do trabalho foi estimar o crescimento dessa população, por meio do modelo não-linear de Richards. O ajuste foi feito utilizando-se a técnica de verossimilhança profile em cadeias de Markov, por meio de programas desenvolvidos em MATLAB. Como o modelo se mostrou adequado para descrever o crescimento da população de bovinos brasileira, foram utilizados dois parâmetros; tamanho inicial e taxa de crescimento da população, para estimar dois indicadores da população de bovinos brasileira: a) probabilidade de se atingir 200 milhões de animais até o ano de 2015; b) tempo para atingir este tamanho populacional com taxa de abate variável. As estimativas de máxima verossimilhança do modelo proporcionaram os seguintes resultados para estes dois indicadores: a) o rebanho brasileiro atinge 200 milhões de animais no ano de 2015 com taxa de abate de aproximadamente 17%; b) o rebanho atinge este tamanho no intervalo 11 anos com taxa de abate de 16%, até 20 anos com taxa de abate de 18%
An upper limit for the water outgassing rate of the main-belt comet 176P/LINEAR observed with Herschel/HIFI
176P/LINEAR is a member of the new cometary class known as main-belt comets
(MBCs). It displayed cometary activity shortly during its 2005 perihelion
passage that may be driven by the sublimation of sub-surface ices. We have
therefore searched for emission of the H2O 110-101 ground state rotational line
at 557 GHz toward 176P/LINEAR with the Heterodyne Instrument for the Far
Infrared (HIFI) on board the Herschel Space Observatory on UT 8.78 August 2011,
about 40 days after its most recent perihelion passage, when the object was at
a heliocentric distance of 2.58 AU. No H2O line emission was detected in our
observations, from which we derive sensitive 3-sigma upper limits for the water
production rate and column density of < 4e25 molec/s and of < 3e10 cm^{-2},
respectively. From the peak brightness measured during the object's active
period in 2005, this upper limit is lower than predicted by the relation
between production rates and visual magnitudes observed for a sample of comets
by Jorda et al. (2008) at this heliocentric distance. Thus, 176P/LINEAR was
likely less active at the time of our observation than during its previous
perihelion passage. The retrieved upper limit is lower than most values derived
for the H2O production rate from the spectroscopic search for CN emission in
MBCs.Comment: 5 pages, 2 figures. Minor changes to match published versio
Affine Wa(A4), Quaternions, and Decagonal Quasicrystals
We introduce a technique of projection onto the Coxeter plane of an arbitrary
higher dimensional lattice described by the affine Coxeter group. The Coxeter
plane is determined by the simple roots of the Coxeter graph I2 (h) where h is
the Coxeter number of the Coxeter group W(G) which embeds the dihedral group Dh
of order 2h as a maximal subgroup. As a simple application we demonstrate
projections of the root and weight lattices of A4 onto the Coxeter plane using
the strip (canonical) projection method. We show that the crystal spaces of the
affine Wa(A4) can be decomposed into two orthogonal spaces whose point groups
is the dihedral group D5 which acts in both spaces faithfully. The strip
projections of the root and weight lattices can be taken as models for the
decagonal quasicrystals. The paper also revises the quaternionic descriptions
of the root and weight lattices, described by the affine Coxeter group Wa(A3),
which correspond to the face centered cubic (fcc) lattice and body centered
cubic (bcc) lattice respectively. Extensions of these lattices to higher
dimensions lead to the root and weight lattices of the group Wa(An), n>=4 . We
also note that the projection of the Voronoi cell of the root lattice of Wa(A4)
describes a framework of nested decagram growing with the power of the golden
ratio recently discovered in the Islamic arts.Comment: 26 pages, 17 figure
Searches for HCl and HF in comets 103P/Hartley 2 and C/2009 P1 (Garradd) with the Herschel space observatory
HCl and HF are expected to be the main reservoirs of fluorine and chlorine
wherever hydrogen is predominantly molecular. They are found to be strongly
depleted in dense molecular clouds, suggesting freeze-out onto grains in such
cold environments. We can then expect that HCl and HF were also the major
carriers of Cl and F in the gas and icy phases of the outer solar nebula, and
were incorporated into comets. We aimed to measure the HCl and HF abundances in
cometary ices as they can provide insights on the halogen chemistry in the
early solar nebula. We searched for the J(1-0) lines of HCl and HF at 626 and
1232 GHz, respectively, using the HIFI instrument on board the Herschel Space
Observatory. HCl was searched for in comets 103P/Hartley 2 and C/2009 P1
(Garradd), whereas observations of HF were conducted in comet C/2009 P1. In
addition, observations of HO and HO lines were performed in C/2009
P1 to measure the HO production rate. Three lines of CHOH were
serendipitously observed in the HCl receiver setting. HCl is not detected,
whereas a marginal (3.6-) detection of HF is obtained. The upper limits
for the HCl abundance relative to water are 0.011% and 0.022%, for 103P and
C/2009 P1, respectively, showing that HCl is depleted with respect to the solar
Cl/O abundance by a factor more than 6 in 103P, where the error is
related to the uncertainty in the chlorine solar abundance. The marginal HF
detection obtained in C/2009 P1 corresponds to an HF abundance relative to
water of (1.80.5) 10, which is approximately consistent
with a solar photospheric F/O abundance. The observed depletion of HCl suggests
that HCl was not the main reservoir of chlorine in the regions of the solar
nebula where these comets formed. HF was possibly the main fluorine compound in
the gas phase of the outer solar nebula.Comment: Accepted for publication in Astronomy & Astrophysic
Ammonia and other parent molecules in comet 10P/Tempel 2 from Herschel/HIFI and ground-based radio observations
The Jupiter-family comet 10P/Tempel 2 was observed during its 2010 return
with the Herschel Space Observatory. We present here the observation of the (J,
K) = (1, 0)-(0, 0) transition of ammonia at 572 GHz in this comet with the
Heterodyne Instrument for the Far Infrared (HIFI) of Herschel. We also report
on radio observations of other molecules (HCN, CH3OH, H2S and CS) obtained
during the 1999 return of the comet with the CSO telescope and the JCMT, and
during its 2010 return with the IRAM 30-m telescope. Molecular abundances
relative to water are 0.09%, 1.8%, 0.4%, and 0.08% for HCN, CH3OH, H2S, and CS,
respectively. An abundance of 0.5% for NH3 is obtained, which is similar to the
values measured in other comets. The hyperfine structure of the ammonia line is
resolved for the first time in an astronomical source. Strong anisotropy in the
outgassing is present in all observations from 1999 to 2010 and is modelled to
derive the production rates.Comment: 6 pages and 8 figures. Accepted for publication in Astronomy &
Astrophysic
Avaliação de cultivares de coqueiro anão na microrregião do Baixo Parnaíba Piauiense: características de desenvolvimento vegetativo.
O coqueiro (Cocos nucifera L.), cuja origem mais provável é o Sudeste Asiático, foi introduzido no Brasil em l553, procedente da ilha de Cabo Verde, sendo no Nordeste onde a espécie encontrou melhor adaptação. O coqueiro gigante, cuja aptidão é a indústria de polpa, foi a primeira variedade a ser introduzida. O coqueiro anão, com aptidão para água ou coco verde, foi introduzido somente em 1925 (Siqueira et al. 1998). A região Nordeste é onde está concentrada a maior produção de coco do País. Em 1999, com uma produção de 907, 511 milhões de frutos essa região respondeu por 79% da produção nacional de coco. O Estado da Bahia é o principal produtor, com uma área colhida de 71.626 ha e produção de 426,613 milhões de frutos, seguido dos Estados do Ceará, com área colhida de 35.647 ha e produção de 180,886 milhões de frutos, e do Pará com área colhida de 15.819 ha e produção de 142,725 milhões de frutos (Agrianual, 2001)
Threading holder based on axial metal cylinder pins to reduce tap risk during reversion instant
Internal thread profiles are used widely in manufacturing processes with the aim of assembling/disassembling different components during maintenance activities from the aeronautics sector until common industrial parts. The threading process is one of the last operations carried out to obtain those components, and consequently, it is an operation of high added value. Threading is a complex operation that must carefully synchronize the rotation with the feed movements to avoid tool breakage during the instant of tapping reversion stage. In order to avoid this risk, several toolholders were developed present in the literature but deficiencies in terms of stability and productivity. Therefore, in this work, a new toolholder is proposed in which the common springs used to mitigate the lack of perfect synchronization between rotation and feed movements are replaced by elastic metal pins achieving a torsional compliance toolholder. The results show that the use of the proposed toolholder implies not only a productivity increase but also a surface integrity improvement as well as a stress reduction that the cutting tap is subjected and thus, achieving a substantial improvement in the current tapping processes. In particular, the use of the proposed toolholder implied a 75% reduction of the maximum stress achieved in the reversal instant, improving 20% tool life with an increase of 30% cutting speed. Therefore, the use of the proposed toolholder implies a substantial improvement in the current tapping processes
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