A New Measurement of the Stellar Mass Density at z~5: Implications for the Sources of Cosmic Reionization

We present a new measurement of the integrated stellar mass per comoving volume at redshift 5 determined via spectral energy fitting drawn from a sample of 214 photometrically-selected galaxies with z'<26.5 in the southern GOODS field. Following procedures introduced by Eyles et al. (2005), we estimate stellar masses for various sub-samples for which reliable and unconfused Spitzer IRAC detections are available. A spectroscopic sample of 14 of the most luminous sources with =4.92 provides a firm lower limit to the stellar mass density of 1e6 Msun/Mpc^3. Several galaxies in this sub-sample have masses of order 10^11 Msun implying significant earlier activity occurred in massive systems. We then consider a larger sample whose photometric redshifts in the publicly-available GOODS-MUSIC catalog lie in the range 4.4 <z 5.6. Before adopting the GOODS-MUSIC photometric redshifts, we check the accuracy of their photometry and explore the possibility of contamination by low-z galaxies and low-mass stars. After excising probable stellar contaminants and using the z'-J color to exclude any remaining foreground red galaxies, we conclude that 196 sources are likely to be at z~5. The implied mass density from the unconfused IRAC fraction of this sample, scaled to the total available, is 6e6 Msun/Mpc^3. We discuss the uncertainties as well as the likelihood that we have underestimated the true mass density. Including fainter and quiescent sources the total integrated density could be as high as 1e7 Msun/Mpc^3. Using the currently available (but highly uncertain) rate of decline in the star formationhistory over 5 <z< 10, a better fit is obtained for the assembled mass at z~5 if we admit significant dust extinction at early times or extend the luminosity function to very faint limits. [abridged]Comment: Accepted for Publication in ApJ, 39 page

A synoptic view of solar transient evolution in the inner heliosphere using the Heliospheric Imagers on STEREO

By exploiting data from the STEREO/heliospheric imagers (HI) we extend a well-established technique developed for coronal analysis by producing time-elongation plots that reveal the nature of solar transient activity over a far more extensive region of the heliosphere than previously possible from coronagraph images. Despite the simplicity of these plots, their power in demonstrating how the plethora of ascending coronal features observed near the Sun evolve as they move antisunward is obvious. The time-elongation profile of a transient tracked by HI can, moreover, be used to establish its angle out of the plane-of-the-sky; an illustration of such analysis reveals coronal mass ejection material that can be clearly observed propagating out to distances beyond 1AU. This work confirms the value of the time-elongation format in identifying/characterising transient activity in the inner heliosphere, whilst also validating the ability of HI to continuously monitor solar ejecta out to and beyond 1A

Developmentally vitamin D-deficient rats show enhanced prepulse inhibition after acute δ9-tetrahydrocannabinol

Developmental vitamin D (DVD) deficiency has been proposed as a risk factor for schizophrenia. DVD-deficient rats show selective cognitive deficits and novelty-induced hyperlocomotion and enhanced locomotor responses from acute treatment with psychomimetic drugs, such as amphetamine and MK-801. Here we aimed to examine the effect of a drug from a different class of psychomimetic/psychoactive compounds, Δ-tetrahydrocannabinol (THC), on tasks of relevance to the cognitive and positive symptoms of schizophrenia. The aim of this study was to investigate whether DVD deficiency modulates the behavioural effects of THC on tests of delay-dependent memory, sensorimotor gating and locomotion. Adult control and DVD-deficient rats were injected with THC (0, 0.3, 0.6, 1.25, 2.5 mg/kg) 15 min before a delay match to sample (DMTS) task using variable delays (0-24 s). A separate group of rats was injected with either 2.5 mg/kg THC or vehicle before tests of either prepulse inhibition (PPI) of the acoustic startle response or in the open field. Control and DVD-deficient rats showed a similar dose-dependent impairment in performance on the DMTS. The greatest impairment was observed at 2.5 mg/kg for all delays (0-24 s). DVD-deficient rats showed THC-induced enhancement of PPI, which was not observed in control rats. There was no effect of maternal diet on acoustic startle response or locomotor responses in the open field. This study reports the novel findings that DVD-deficient rats were more sensitive to the acute effects of THC on PPI. It appears that prenatal vitamin D deficiency has long-term effects on sensitivity to the behavioural effects of cannabinoids

"Equity and efficiency in health-care delivery: The distribution of health-care resources in Canada and its relationship to needs for care."

In this report we consider the case for using population-needs based approach to the planning and allocation of health-care resources in Ontario. In section 1 the needs-based approach is contrasted with systems of allocation used currently in Ontario. These existing systems tend to allocate resources on the basis of past levels of service utilization which, in turn, are determined largely by historical patterns of distribution of health-care providers and facilities. Under these systems, any existing inequities in access to care are perpetuated. In contrast, the needs-based approach relates resource allocations to characteristics of the population being served on the basis of health risks, morbidity and the need for health-care services. Consequently the link between current use of future allocation is severed and a population's current level of service utilization. The needs-based approach therefore provides a financial framework for directing (or targeting) resources to populations with greatest need and hence allocates the capacity for caring in a way which promotes the efficient and equitable use of limited health-care resources. In section two the literature on population-based measures of health status and the relationships between these measures and other socio-demographic and socioeconomic indicators is reviewed. Because health care is not provided as an end in itself, but as a means to producing improvements in health status or health-related quality of life, then the need for health care is not the same as the presence of morbidity. In the context of Canadian health policy, health care is needed only where there is an expectation that the utilization of such care would improve health status or health related quality of life. Accordingly measures of morbidity may not be valid indicators of relative health-care need. Several characteristics are identified as required in an indicator, or proxy measure, of health-care need. These range from statistical characteristics of validity (indicator value responds to changes in need), to practical issues of administrative feasibility, (data are already available and updated at regular and frequent intervals) and resistant to manipulation by interested parties (low ‘gameability). In section three both direct and indirect approaches to measuring relative health-care need are considered. Particular attention is paid the whether the measures are a valid indicator of need for care, the form of the relationship between the measure and health-care need (i.e. the relationship linear), and issues concerning the combination of different measures to produce a single indicator of need. Little attention has been paid to these issues in the literature and applications of the needs based approach. To date, the Standardized Mortality Ratio, as a measure of premature mortality,- appears to come closest to meeting the required characteristics, although its validity as an indicator of relative need requires replication using Canadian-based data and for services other than acute care. Section four outlines several issues concerning the implementation of a needs-based approach, covering technical issues (the availability and use of appropriate data, the identiication of appropriate planning populations and the management of patient flows (across population boundaries), organizational issues (providing the appropriate levels and quantities of skills to support the approach, the method and rate of implementation of needs-based planning from a use-based system), institutional issues (the impact of the adoption of a needs-based approach on the population, health- care providers, employers, the Ministry of Health and other Ministries) and contextual issues (the scope of the use of a needs-based approach in terms of services and populations to be covered, and the planned levels of resources to be allocated to health care in total, within which the needs-based approach might be used). Experiences from other jurisdictions are drawn upon to illustrate many of these issues. In section five several research questions are identified, the answers to which would enhance or support the application of a needs-based approach. In particular more attention should be paid to the identification and validation of more refined measures of relative health-care need at the population level. It is suggested that existing data sources might be used to address this issue. Similarly attention should be paid to the identification of the determinants of variations between populations in the cost of providing a given level of care and hence the resource requirements to meet health-care needs. Finally it is emphasized that the needs-based approach provides a framework for allocating resources (i.e. inputs) efficiently and equitably between populations. How these resources are used within the population requires further attention which compares the levels of resources used with the outputs (i.e. health status improvements) produced (i.e. performance appraisal). In other words, the needs-based approach alone is necessary but not sufficient to ensure the efficient and equitable use of health-care resources. It is emphasized that the needs-based approach is proposed here, not as an ideal system of resource management, but as a method of resource allocation within a jurisdiction which provides a framework (or geographical allocation) consistent with the fulfilment of the objectives of health-care policy in Ontario, and which represents a considerable improvement upon the current system in place.

The Role of the Dust in Primeval Galaxies: A Simple Physical Model for Lyman Break Galaxies and Lyman Alpha Emitters

We explore the onset of star formation in the early Universe, exploiting the observations of high-redshift Lyman-break galaxies (LBGs) and Lyman alpha emitters (LAEs), in the framework of the galaxy formation scenario elaborated by Granato et al. (2004) already successfully tested against the wealth of data on later evolutionary stages. Complementing the model with a simple, physically plausible, recipe for the evolution of dust attenuation in metal poor galaxies we reproduce the luminosity functions (LFs) of LBGs and of LAEs at different redshifts. This recipe yields a much faster increase with galactic age of attenuation in more massive galaxies, endowed with higher star formation rates. These objects have therefore shorter lifetimes in the LAE and LBG phases, and are more easily detected in the dusty submillimeter bright phase. The short UV bright lifetimes of massive objects strongly mitigate the effect of the fast increase of the massive halo density with decreasing redshift, thus accounting for the weaker evolution of the LBG LF, compared to that of the halo mass function, and the even weaker evolution between z~6 and z~3 of the LAE LF. LAEs are on the average expected to be younger, with lower stellar masses, and associated to less massive halos than LBGs. Finally, we show that the intergalactic medium can be completely reionized at redshift z~6-7 by massive stars shining in protogalactic spheroids with halo masses from a few 10^10 to a few 10^11 M_sun, showing up as faint LBGs with magnitude in the range -17<M_1350<-20, without resorting to any special stellar initial mass function.Comment: 13 pages, 8 figures, uses REVTeX 4 + emulateapj.cls and apjfonts.sty. Title changed and text revised following referee's comments. Accepted by Ap

Optical to mid-IR observations of Lyman-alpha galaxies at redshift 5 in the HUDF: a young and low mass population

High redshift galaxies selected on the basis of their strong Lyman-alpha emission tend to be young ages and small physical sizes. We show this by analyzing the spectral energy distribution (SED) of 9 Lyman-alpha emitting (LAE) galaxies at 4.0 < z < 5.7 n the Hubble Ultra Deep Field (HUDF). Rest-frame UV to optical 700A < lambda < 7500A luminosities, or upper limits, are used to constrain old stellar populations. We derive best fit, as well as maximally massive and maximally old, properties of all 9 objects. We show that these faint and distant objects are all very young, being most likely only a few millions years old, and not massive, the mass in stars being ~10^6-10^8 M_sun. Deep Spitzer Infrared Array Camera (IRAC) observations of these objects, even in cases where objects were not detected, were crucial in constraining the masses of these objects. The space density of these objects, ~1.25x10^-4 Mpc^-3 is comparable to previously reported space density of LAEs at moderate to high redshifts. These Lyman-alpha galaxies show modest star formation rates of ~8 M_sun yr^-1, which is nevertheless strong enough to have allowed these galaxies to assemble their stellar mass in less than a few x10^6 years. These sources appear to have small physical sizes, usually smaller than 1 Kpc, and are also rather concentrated. They are likely to be some of the least massive and youngest high redshift galaxies observed to date.Comment: 27 pages. Accepted. To appear in The Astrophysical Journa

First imaging of corotating interaction regions using the STEREO spacecraft

Plasma parcels are observed propagating from the Sun out to the large coronal heights monitored by the Heliospheric Imagers (HI) instruments onboard the NASA STEREO spacecraft during September 2007. The source region of these out-flowing parcels is found to corotate with the Sun and to be rooted near the western boundary of an equatorial coronal hole. These plasma enhancements evolve during their propagation through the HI cameras’ fields of view and only becoming fully developed in the outer camera field of view. We provide evidence that HI is observing the formation of a Corotating Interaction Region(CIR) where fast solar wind from the equatorial coronal hole is interacting with the slow solar wind of the streamer belt located on the western edge of that coronal hole. A dense plasma parcel is also observed near the footpoint of the observed CIR at a distance less than 0.1AU from the Sun where fast wind would have not had time to catch up slow wind. We suggest that this low-lying plasma enhancement is a plasma parcel which has been disconnected from a helmet streamer and subsequently becomes embedded inside the corotating interaction region

Development and Application of a Needs-based Methodology for Calculating a Capitation Rate for a Comprehensive Health Organization

In this study we develop a methodology for calculating a capitation rate for a Comprehensive Health Organization (CHO). We apply the methodology to the population served by the proposed Fort Frances CHO. The methods of calculating capitation rates used currently by the Ontario Ministry of Health to determine funding levels of Health Service Organizations (HSOs), as well as the methods proposed for calculating CHO capitation rates, are critically reviewed. Both approaches base the calculated capitation rates on the current, or past, levels of health-care utilization, which perpetuate any existing inequalities in access to health care in the province. The methodology developed in this study has the health-care needs of the study population, as distinct from the health-care use of patients, as its focus. We argue that this needs-based approach is consistent with the philosophy of the Canada Health Act (1984) and encompasses aspects of both efficiency and equity in the allocation of health-care resources. Studies on population characteristics which correlate with health status and risks to health are reviewed, as is the literature on population-based planning of health-care resources. The strengths and weaknesses of potential indicators of health-care needs are evaluated. A profile of the study population is constructed, using data from the national census and other sources, which is compared with a corresponding profile of the provincial population. Particular features of the study population are identified as factors giving rise to atypical levels of need for health care. On the basis of the literature review, the standardized mortality ratio (SMR) is used as the best available indicator of need for most programmes.