857 research outputs found
Tentative detection of ethylene glycol toward W51/e2 and G34.3+0.2
How complex organic - and potentially prebiotic - molecules are formed in
regions of low- and high-mass star-formation remains a central question in
astrochemistry. In particular, with just a few sources studied in detail, it is
unclear what role environment plays in complex molecule formation. In this
light, a comparison of relative abundances of related species between sources
might be useful to explain observed differences. We seek to measure the
relative abundance between three important complex organic molecules, ethylene
glycol ((CHOH)), glycolaldehyde (CHOHCHO) and methyl formate
(HCOOCH), toward high-mass protostars and thereby provide additional
constraints on their formation pathways. We use IRAM 30-m single dish
observations of the three species toward two high-mass star-forming regions -
W51/e2 and G34.3+0.2 - and report a tentative detection of (CH2OH)2 toward both
sources. Assuming that (CHOH), CHOHCHO and HCOOCH spatially
coexist, relative abundance ratios, HCOOCH/(CHOH), of 31 and 35 are
derived for G34.3+0.2 and W51/e2, respectively. CHOHCHO is not detected,
but the data provide lower limits to the HCOOCH/CHOHCHO abundance
ratios of 193 for G34.3+0.2 and 550 for W51/e2. A comparison of these
results to measurements from various sources in the literature indicates that
the source luminosities may be correlated with the HCOOCH/(CHOH)
and HCOOCH/CHOHCHO ratios. This apparent correlation may be a
consequence of the relative timescales each source spend at different
temperatures-ranges in their evolution. Furthermore, we obtain lower limits to
the ratio of (CHOH)/CH2OHCHO for G34.3+0.2 (6) and W51/e2
(16). This result confirms that a high (CHOH)/CHOHCHO
abundance ratio is not a specific property of comets, as previously speculated.Comment: Accepted for publication by A&
GPsâ strategies in exploring the preschool childâs wellbeing in the paediatric consultation
Background:
Although General Practitioners (GPs) are uniquely placed to identify children with emotional, social, and behavioural problems, they succeed in identifying only a small number of them. The aim of this article is to explore the strategies, methods, and tools employed by GPs in the assessment of the preschool childâs emotional, mental, social, and behavioural health. We look at how GPs address parental care of the child in general and in situations where GPs have a particular awareness of the child.
Method:
Twenty-eight Danish GPs were purposively selected to take part in a qualitative study which combined focus-group discussions, observation of child consultations, and individual interviews with GPs.
Results:
Analysis of the data suggests that GPs have developed a set of methods, and strategies to assess the preschool child and parental care of the child. They look beyond paying narrow attention to the physical health of the child and they have expanded their practice to include the relations and interactions in the consultation room. The physical examination of the child continues to play a central role in doctor-child communication.
Conclusion:
The participating GPsâ strategies helped them to assess the wellbeing of the preschool child but they often find it difficult to share their impressions with parents
Unbiased sampling of globular lattice proteins in three dimensions
We present a Monte Carlo method that allows efficient and unbiased sampling
of Hamiltonian walks on a cubic lattice. Such walks are self-avoiding and visit
each lattice site exactly once. They are often used as simple models of
globular proteins, upon adding suitable local interactions. Our algorithm can
easily be equipped with such interactions, but we study here mainly the
flexible homopolymer case where each conformation is generated with uniform
probability. We argue that the algorithm is ergodic and has dynamical exponent
z=0. We then use it to study polymers of size up to 64^3 = 262144 monomers.
Results are presented for the effective interaction between end points, and the
interaction with the boundaries of the system
StratĂ©gies dâadaptation Ă la rĂ©duction des services Ă©cosystĂ©miques : cas des potentialitĂ©s de substitution de trois espĂšces forestiĂšres dans le Sud-Ouest du Burkina Faso
Les consĂ©quences de la perte de biodiversitĂ© sont entre autres la baisse des services Ă©cosystĂ©miques, avec des incidences graves sur la santĂ© des populations, leur alimentation, voire leur habitat. Dans ce contexte, les populations locales ont tendance Ă adopter des stratĂ©gies dâadaptation quâil importe dâidentifier et dâen analyser la durabilitĂ©. Lâobjectif de cette lâĂ©tude Ă©tait de dĂ©terminer les substituts de trois plantes (Crateva adansonii D.C., Sarcocephalus latifolius (Smith) Buce et Burkea africana Hook.) Ă haute valeur sociale et culturelle dans le Sud-Ouest du Burkina Faso. Il sâagit de fournir des informations Ă mĂȘme dâorienter les mesures de conservation et dâanticipation des effets de la dĂ©forestation. Une enquĂȘte a Ă©tĂ© conduite auprĂšs de 253 personnes de neuf localitĂ©s appartenant Ă trois groupes ethniques. Les rĂ©sultats ont montrĂ© que les populations ont identifiĂ© seize substituts pour C. adansonii, vingt-deux pour S. latifoliius et seize pour B. africana. La plupart des substituts sont des espĂšces locales ou exotiques, et trĂšs peu de produits manufacturĂ©s. Il est donc possible, plutĂŽt que dâinterdire sans proposition de rechange Ă lâexploitation des espĂšces menacĂ©es, dâinverser la tendance en accompagnant les populations Ă utiliser les diverses potentialitĂ©s de substitution des espĂšces. Ceci est un axe de conservation efficace des ressources vĂ©gĂ©tales.Mots clĂ©s : Crateva adansonii D.C, Sarcocephalus latifoliius (Smith) Buce, Burkea africana Hook.,biodiversitĂ©, conservatio
Exact enumeration of Hamiltonian circuits, walks, and chains in two and three dimensions
We present an algorithm for enumerating exactly the number of Hamiltonian
chains on regular lattices in low dimensions. By definition, these are sets of
k disjoint paths whose union visits each lattice vertex exactly once. The
well-known Hamiltonian circuits and walks appear as the special cases k=0 and
k=1 respectively. In two dimensions, we enumerate chains on L x L square
lattices up to L=12, walks up to L=17, and circuits up to L=20. Some results
for three dimensions are also given. Using our data we extract several
quantities of physical interest
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