The pre-ZAMS nature of Mol160/IRAS23385+6053 confirmed by Spitzer

Determining the timeline for the formation of massive YSOs requires the identification and characterisation of all the phases that a massive forming YSO undergoes. It is of particular interest to verify the observability of the phase in which the object is rapidly accreting while not yet igniting the fusion of hydrogen that marks the arrival on the ZAMS. One of the candidate prototypical objects for this phase is Mol160/IRAS23385+6053, which previous studies suggest it could be in a pre-Hot Core stage. We further investigate this issue by means of Spitzer imaging and spectroscopy in the 5-70 micron range. The dense core of Mol160/IRAS23385+6053, which up to now had only been detected at submm and mm wavelenghts has been revealed for the first time at 24 and 70 micron by Spitzer. The complete 24 micron -3.4 mm continuum cannot be fitted with a standard model of a Zero-Age Main-Sequence (ZAMS) star embedded in an envelope. A simple greybody fit yields a mass of 220 solar masses. The luminosity is slightly in excess of 3000 solar luminosities, which is a factor of 5 less than previous estimates when only IRAS fluxes were available between 20 and 100 micron. The source is under-luminous by the same factor with respect to UCHII regions or Hot-Cores of similar circumstellar mass, and simple models show that this is compatible with an earlier evolutionary stage. Spectroscopy between 5 and 40 microns revelas typical PDR/PIR conditions, where the required UV illumination may be provided by other sources revealed at 24 microns in the same region, and which can be plausibly modeled as moderately embedded intermediate-mass ZAMS stars. Our results strengthen the suggestion that the central core in Mol160/IRAS23385+6053 is a massive YSO actively accreting from its circumstellar envelope and which did not yet begin hydrogen fusion.Comment: Accepted by A&

Factors influencing take-up of free school meals in primary- and secondary-school children in England.

OBJECTIVE: The present study sought to explore the factors that influence registration for free school meals and the subsequent take-up following registration in England. DESIGN: The research design consisted of two phases, a qualitative research phase followed by an intervention phase. Findings are presented from the qualitative research phase, which comprised interviews with head teachers, school administrators, parents and focus groups with pupils. SETTING: The study took place in four primary schools and four secondary schools in Leeds, UK. SUBJECTS: Participants included head teachers, school administrators, parents and pupils. RESULTS: Findings suggested that parents felt the registration process to be relatively straightforward although many secondary schools were not proactive in promoting free school meals. Quality and choice of food were regarded by both pupils and parents as significant in determining school meal choices, with stigma being less of an issue than originally anticipated. CONCLUSIONS: Schools should develop proactive approaches to promoting free school meals and attention should be given not only to the quality and availability of food, but also to the social, cultural and environmental aspects of dining. Processes to maintain pupils' anonymity should be considered to allay parents' fear of stigma

Interventions to increase free school meal take-up

Purpose: The purpose of this paper is to design and implement interventions to increase free school meal (FSM) uptake in pilot schools. This paper describes the interventions, reports on acceptability (as perceived by school working parties) and explores the process of implementing change. Design/methodology/approach: The research consisted of two phases, an exploratory phase followed by an intervention phase. Findings from the latter are presented. Ten pilot schools (five primary and five secondary) in Leeds, England were recruited. Each established a working party, examined current claiming processes and implemented individualised action plans. This paper draws on the final action plans and interviews/focus groups with working parties. Findings: Interventions to improve FSM claiming process, minimise discrimination and maximise awareness were designed. The majority were implemented successfully, the exception being amending anti-bullying policies. Creative ways of delivering interventions were demonstrated. The process of change was effective, critical factors being having individualised action plans that allowed flexibility in implementation, reflecting on current claiming processes, and setting up working parties. Practical implications: Ways of working with schools to increase FSM uptake and more generally improve nutritional policies are suggested. Amending claiming systems in schools is recommended as is greater pupil and parent involvement in nutrition policies. Originality/value: An estimated 300,000 UK children do not take FSMs they are entitled to – with many schools unaware of the issue. This study worked with schools to discover how to address this issue and evaluated the perceived acceptability and feasibility of the approach

IRAS 23385+6053: a candidate protostellar massive object

We present the results of a multi-line and continuum study towards the source IRAS 23385+6053,performed with the IRAM-30m telescope, the Plateau de Bure Interferometer, the Very Large Array Interferometer and the James Clerk Maxwell Telescope. The new results confirm our earlier findings, namely that IRAS 23385+6053 is a good candidate high-mass protostellar object, precursor of an ultracompact H$_{II}$ region. The source is roughly composed of two regions: a molecular core $\sim0.03\div0.04$ pc in size, with a temperature of $\sim40$ K and an H$_{2}$ volume density of the order of 10$^{7}$ cm$^{-3}$, and an extended halo of diameter $\leq$0.4 pc, with an average kinetic temperature of $\sim 15$ K and H$_{2}$ volume density of the order of 10$^{5}$ cm$^{-3}$. The core temperature is much smaller than what is typically found in molecular cores of the same diameter surrounding massive ZAMS stars. We deduce that the core luminosity is between 150 and $1.6\times10^{4}L_{\odot}$, and we believe that the upper limit is near the ``true'' source luminosity. Moreover, by comparing the H$_{2}$ volume density obtained at different radii from the IRAS source, we find that the halo has a density profile of the type $n_{\rm H_{2}}\propto r^{-2.3}$. This suggests that the source is gravitationally unstable. Finally, we demonstrate that the temperature at the core surface is consistent with a core luminosity of $10^3 L_{\odot}$ and conclude that we might be observing a protostar still accreting material from its parental cloud, whose mass at present is $\sim 6 M_{\odot}$.Comment: 18 pages, 20 figure

G-quartet biomolecular nanowires

We present a first-principle investigation of quadruple helix nanowires, consisting of stacked planar hydrogen-bonded guanine tetramers. Our results show that long wires form and are stable in potassium-rich conditions. We present their electronic bandstructure and discuss the interpretation in terms of effective wide-bandgap semiconductors. The microscopic structural and electronic properties of the guanine quadruple helices make them suitable candidates for molecular nanoelectronics.Comment: 7 pages, 3 figures, to be published in Applied Physics Letters (2002

Class I and Class II methanol masers in high-mass star forming regions

Among the tracers of the earliest phases in the massive star formation process, methanol masers have gained increasing importance. The phenomenological distinction between Class I and II methanol masers is based on their spatial association with objects such as jets, cores, and ultracompact HII regions, but is also believed to correspond to different pumping mechanisms: radiation for Class II masers, collisions for Class I masers. In this work, we have surveyed a large sample of massive star forming regions - 296 objects divided into two groups named 'High' and 'Low' according to their [25-12] and [60-12] IRAS colours - in Class I and II methanol masers. Previous studies indicate that the High sources are likely more evolved. Therefore, the sample can be used to assess the existence of a sequence for the occurrence of Class I and II methanol masers during the evolution of a massive star forming region. We observed the 6 GHz (Class II) CH3OH maser with the Effelsberg 100-m telescope, and the 44 GHz and 95 GHz (Class I) CH3OH masers with the Nobeyama 45-m telescope. We have detected: 55 sources in the Class II line (12 new detections); 27 sources in the 44 GHz Class I line (17 new detections); 11 sources in the 95 GHz Class I line (all except one are new detections). Our statistical analysis shows that the ratio between the detection rates of Class II and Class I methanol masers is basically the same in High and Low sources. Therefore, both masers are equally associated with each evolutionary phase. In contrast, all maser species have about 3 times higher detection rates in High than in Low sources. This might indicate that the phenomena that originate all masers become progressively more active with time, during the earliest evolutionary phases of a high-mass star forming region.Comment: 30 pages including Appendices, 11 figures, accepted for publication in Astronomy & Astrophysic

Search for massive protostellar candidates in the southern hemisphere: I. Association with dense gas

(Abridged) We have observed CS and C17O lines, and 1.2 mm cont. emission towards a sample of 130 high-mass protostellar candidates with DEC<-30 deg. This is the first step of the southern extension of a project started more than a decade ago aimed at the identification of massive protostellar candidates. We selected from the IRAS PSC 429 sources which potentially are compact molecular clouds. The sample is divided into two groups: the 298 sources with [25-12]>0.57 and [60-12]>1.30 we call 'High' sources, the remaining 131 we call 'Low' sources. In this paper, we check the association with dense gas and dust in 130 'Low' sources. We find a detection rate of ca. 85% in CS, demonstrating a tight association with dense molecular clumps. Among the sources detected in CS, ca. 76% have also been detected in C17O and ca. 93% in the 1.2 mm cont. Mm-cont. maps show the presence of clumps with diameters 0.2-2 pc and masses from a few Msun to 10^5 Msun; H2 volume densities lie between ca. 10^{4.5} and 10^{5.5} cm^{-3}. The L(bol) are 10^3-10^6 Lsun, consistent with embedded high-mass objects. Based on our results and those found in the literature for other samples, we conclude that our sources are massive objects probably in a stage prior to the formation of an HII region. We propose a scenario in which 'High' and 'Low' sources are both made of a massive clump hosting a high-mass protostellar candidate and a nearby stellar cluster. The difference might be due to the fact that the IRAS 12mu flux, the best discriminant between the two groups, is dominated by the emission from the cluster in 'Lows' and from the massive protostellar object in 'Highs'.Comment: Accepted for publication in Astron. & Astroph.; 34 pages (incl. 14 figures and 8 tables

A simple model for NN correlations in quasielastic lepton-nucleus scattering

We present a covariant extension of the relativistic Fermi gas model which incorporates correlation effects in nuclei. Within this model, inspired by the BCS descriptions of systems of fermions, we obtain the nuclear spectral function and from it the superscaling function for use in treating high-energy quasielastic electroweak processes. Interestingly, this model has the capability to yield the asymmetric tail seen in the experimental scaling function.Comment: 11 pages, 6 figures, Proceedings of the Twenty Seventh International Workshop on Nuclear Theory, June 23 - 28, 2008, Rila mountains, Bulgari

Excitons in carbon nanotubes: an ab initio symmetry-based approach

The optical absorption spectrum of the carbon (4,2) nanotube is computed using an ab-initio many-body approach which takes into account excitonic effects. We develop a new method involving a local basis set which is symmetric with respect to the screw symmetry of the tube. Such a method has the advantages of scaling faster than plane-wave methods and allowing for a precise determination of the symmetry character of the single particle states, two-particle excitations, and selection rules. The binding energy of the lowest, optically active states is approximately 0.8 eV. The corresponding exciton wavefunctions are delocalized along the circumference of the tube and localized in the direction of the tube axis.Comment: 4 pages, 1 LaTex file + 4 eps figure