Sub-Poissonian Shot Noise In A Diffusive Conductor

A review is given of the shot-noise properties of metallic, diffusive conductors. The shot noise is one third of the Poisson noise, due to the bimodal distribution of transmission eigenvalues. The same result can be obtained from a semiclassical calculation. Starting from Oseledec's theorem it is shown that the bimodal distribution is required by Ohm's law.Comment: 9 pages, LaTeX, including 2 figure

Doubled Shot Noise In Disordered Normal-Metal-Superconductor Junctions

The low-frequency shot-noise power of a normal-metal-superconductor junction is studied for arbitrary normal region. Through a scattering approach, a formula is derived which expresses the shot-noise power in terms of the transmission eigenvalues of the normal region. The noise power divided by the current is enhanced by a factor two with respect to its normal-state value, due to Cooper-pair transport in the superconductor. For a disordered normal region, it is still smaller than the Poisson noise, as a consequence of noiseless open scattering channels.Comment: 4 pages, RevTeX v3.0, including 1 figure, Submitted to Physical Review

Immunity in barren and enriched housed pigs differing in baseline cortisol concentration

It was shown recently that barren housed pigs (small pens, no substrate) have a blunted circadian rhythm of salivary cortisol as compared to enriched housed pigs (large pens with daily fresh bedding). In the light period, enriched housed pigs showed significantly higher concentrations of cortisol in saliva than barren housed pigs, whereas in the dark period, cortisol concentrations were low in both enriched and barren housed pigs. In the present study, the immunological consequences of the difference in baseline salivary cortisol concentration in the light period were evaluated. It appeared that leukocyte and lymphocyte distributions, and in vitro lymphocyte proliferation following ConcanavalineA (ConA) stimulation in the assay using purified lymphocytes were not affected. However, barren and enriched housed pigs did show a different proliferation response to ConA in the whole blood assay. At day 2 of culture, proliferation was higher in barren housed pigs than in enriched housed pigs, whereas at day 4 of culture, proliferation was higher in enriched housed pigs than in barren housed pigs. Lymphocyte proliferation at day 2 of culture in the whole blood assay correlated negatively with plasma cortisol levels, which might thus explain the higher proliferation in barren housed pigs at day 2 of culture. The in vivo humoral and cellular (delayed type hypersensitivity, DTH) immune response to KLH was not affected by housing conditions. We conclude that, although baseline salivary cortisol concentrations differ between enriched and barren housed pigs, immune function appears to be relatively unaffected.

A Look At Three Different Scenarios for Bulge Formation

In this paper, we present three qualitatively different scenarios for bulge formation: a secular evolution model in which bulges form after disks and undergo several central starbursts, a primordial collapse model in which bulges and disks form simultaneously, and an early bulge formation model in which bulges form prior to disks. We normalize our models to the local z=0 observations of de Jong & van der Kruit (1994) and Peletier & Balcells (1996) and make comparisons with high redshift observations. We consider model predictions relating directly to bulge-to-disk properties. As expected, smaller bulge-to-disk ratios and bluer bulge colors are predicted by the secular evolution model at all redshifts, although uncertainties in the data are currently too large to differentiate strongly between the models.Comment: 19 pages, 6 figures, accepted for publication in the Astrophysical Journa

THE EFFECTS OF INTERNAL AND EXTERNAL FOCUS ATTENTION ON THE STANDING LONG JUMP AMONG HIGH SCHOOL FEMALE ATHLETES

Coaches and trainers often use verbal cues to help players improve their sport performance and training quality. The type of verbal instructions implemented by a coach may influence how players execute certain tasks. External and internal focus attention are verbal ques that may help athletes improve performance in various tasks such as running and jumping. Purpose: This study attempted to determine if implementing external focus attention ques (EFAQ) improved standing long jump (SLJ) performance when compared to implementing internal focus attention ques (IFAQ). Methods: Female (n=14) high school soccer players completed three testing sessions where three trials of the SLJ were collected (3 sessions with 3 trials each). Prior to each testing session a dynamic warmup was implemented to prepare the participants for the subsequent SLJ trials. During the initial test session, the coach/investigator provided no attention ques (NQ) prior to the SLJ trials. During the other two testing sessions the coach provided either an EFAQ or IFAQ prior to the SLJ trials. Second and third testing session were carried out in a randomized repeated measures fashion. The testing sessions occurred on three different days at the beginning of the week over three weeks. The best SLJ score from each testing session was used for statistical analysis. A paired t-test was used to compare the SLJ scores between the sessions. Gain scores and effect size (EF) differences between the NQ SLJ scores and the EFAQ and IFAQ conditions were also calculated. Results: The best SLJ scores for the test conditions were as follows: NQ=174.0±17.4, IFAQ=169.1±20.7 and EFAQ=178.2±16.4 (cms). The EFAQ SLJ scores were significantly greater than both the IFAQ and NQ SLJ scores (p<0.05). The IFAQ SLJ scores were significantly less than the NQ SLJ scores (p<0.05). The ES difference and gain score between the EFAQ and NQ were: 0.24 SD and 4.2±7.3 cms. The ES difference and gain score between the IFAQ and NQ were: -0.28 SD and -4.9±10.0 cms. Conclusion: Within the parameters of this study, EFAQ improves SLJ scores when compared to either NQ or IFAQ scenarios. Further, IFAQ appears to degrade SLJ performance when compared to a NQ scenario.  Article visualizations

Bariatric surgery in young adults:A multicenter study into weight loss, dietary adherence, and quality of life

Background: Numerous studies have demonstrated that bariatric surgery is an effective intervention for morbid obesity, but study samples are characterized by an underrepresentation of young adult patients.Objectives: The aim of this study was to evaluate weight loss, dietary adherence, and quality of life (QoL) in a multicenter, young adult sample, in the first 6 years after bariatric surgery.Setting: Four general hospitals in the Netherlands.Methods: A total of 184 young adult patients who underwent bariatric surgery between 6 and 74 months previously at the age of 18 to 24 years were included, interviewed by phone, and sent questionnaires assessing postoperative weight, QoL, and lifestyle behaviors including dietary adherence. Complete data were available for those 96 patients who returned the questionnaires.Results: Mean percent weight loss was 30.2 (SD 10.7) for laparoscopic sleeve gastrectomy and 35.6 (SD 6.9) for laparoscopic Roux-en-Y gastric bypass. Adherence to postoperative dietary recommendations declined over the years (r = .25, P = .02) and explained 8.3% of the variance in weight loss (r = .29, P = .005). QoL scores lagged behind national norms for young adults and were largely unrelated to weight loss. A quarter of patients (25%) turned out to be not in education, employment, or training and 38% had used mental healthcare services since surgery, which occurred independent of weight loss and concurred with poorer QoL.Conclusion: Young adult patients achieve weight loss comparable to adult patients after bariatric surgery. However, postoperative adherence to behavioral recommendations and psychosocial functioning clearly demonstrate room for improvement and require adjunctive interventions.</p

Models of Disk Evolution: Confrontation with Observations

We present simple models for disk evolution based on two different approaches: a forward approach based on predictions generic to hierarchical models for structure formation (e.g., Mo, Mao, & White 1998) and a backwards approach based on detailed modeling of the Milky Way galaxy (e.g., Bouwens, Cayon, & Silk 1997). We normalize these models to local observations and predict high-redshift luminosities, sizes, circular velocities, and surface brightnesses. Both approaches yield somewhat similar predictions for size, surface brightness, and luminosity evolution though they clearly differ in the amount of number evolution. These predictions seem to be broadly consistent with the high-redshift observations of Simard et al. (1999), suggesting that the B-band surface brightness of disks has indeed evolved by ~1.5 mag from z~0 to z~1 similar to the models and is not an artifact of selection effects as previously claimed. We also find a lack of low surface brightness galaxies in several high redshift samples relative to model predictions based on local samples (de Jong & van der Kruit 1994; Mathewson, Ford, & Buchhorn 1992).Comment: 34 pages, 9 figures, accepted to Ap

Structure of Disk Dominated Galaxies I. Bulge/Disk Parameters, Simulations, and Secular Evolution

(Abridged) A robust analysis of galaxy structural parameters, based on the modeling of bulge and disk brightnesses in the BVRH bandpasses, is presented for 121 face-on and moderately inclined late-type spirals. Each surface brightness (SB) profile is decomposed into a sum of a generalized Sersic bulge and an exponential disk. The reliability and limitations of our bulge-to-disk (B/D) decompositions are tested with extensive simulations of galaxy brightness profiles (1D) and images (2D). Galaxy types are divided into 3 classes according to their SB profile shapes; Freeman Type-I and Type-II, and a third ``Transition'' class for galaxies whose profiles change from Type-II in the optical to Type-I in the infrared. We discuss possible interpretations of Freeman Type-II profiles. The Sersic bulge shape parameter for nearby Type-I late-type spirals shows a range between n=0.1-2 but, on average, the underlying surface density profile for the bulge and disk of these galaxies is adequately described by a double-exponential distribution. We confirm a coupling between the bulge and disk with a scale length ratio r_e/h=0.22+/-0.09, or h_bulge/h_disk=0.13+/-0.06 for late-type spirals, in agreement with recent N-body simulations of disk formation and models of secular evolution. This ratio increases from ~0.20 for late-type spirals to ~0.24 for earlier types. The similar scaling relations for early and late-type spirals suggest comparable formation and/or evolution scenarios for disk galaxies of all Hubble types.Comment: 78 pages with 23 embedded color figures + tables of galaxy structural parameters. Accepted for publication in the Astrophysical Journal. The interested reader is strongly encouraged to ignore some of the low res figures within; instead, download the high resolution version from http://www.astro.ubc.ca/people/courteau/public/macarthur02_disks.ps.g

Gasification of woody biomass in a novel indirectly heated bubbling fluidized bed steam reformer

Within this work, a novel 50 kWth indirectly heated bubbling fluidized bed steam reformer (IHBFBSR) is presented, along with its commissioning experiments. In the IHBFBSR, heat is provided through two radiant tube natural gas burners in the bed and the freeboard area. The aim of this innovative design is sufficient heat provision for biomass steam reforming and cracking reactions and heat loss reduction, thus allowing the possibility of scaling-up to an industrial level. Experiments were performed with two woody biomass feedstocks and two bed material particle sizes under different operating conditions (steam to biomass ratio, lambda, temperature), in order to identify the setup's main characteristics. Product gas composition and quality, as well as the cold gas efficiency of the IHBFBSR were in reasonable agreement to similar systems, however carbon conversion prediction needs further improvement. H2 production and tar removal are favoured by small bed material particle sizes as well as by char accumulation in the bed area. Furthermore, air injection above the bed led to improved H2/CO ratios and lower tar yields compared to when air is used as a fluidization agent. Overall, it was shown that the IHBFBSR technology constitutes a promising development in the field of biomass allothermal gasification.Large Scale Energy Storag

On Star Formation and the Non-Existence of Dark Galaxies

We investigate whether a baryonic dark galaxy or `galaxy without stars' could persist indefinitely in the local universe, while remaining stable against star formation. To this end, a simple model has been constructed to determine the equilibrium distribution and composition of a gaseous protogalactic disk. Specifically, we determine the amount of gas that will transit to a Toomre unstable cold phase via the H2 cooling channel in the presence of a UV--X-ray cosmic background radiation field. All but one of the models are predicted to become unstable to star formation. Moreover, we find that all our model objects would be detectable via HI line emission, even in the case that star formation is potentially avoided. These results are consistent with the non-detection of isolated extragalactic HI clouds with no optical counterpart (galaxies without stars) by HIPASS. Additionally, where star formation is predicted to occur, we determine the minimum interstellar radiation field required to restore gravothermal stability, which we then relate to a minimum global star formation rate. This leads to the prediction of a previously undocumented relation between HI mass and star formation rate that is observed for a wide variety of dwarf galaxies in the HI mass range 10^8--10^10 M_sun. The existence of such a relation strongly supports the notion that the well observed population of dwarf galaxies represent the minimum rates of self-regulating star formation in the universe. (Barely abridged)Comment: 19 pages, 8 figures, TeX using emulateapj.cls, v2 accepted for publication in ApJ (16/8/5) with one figure deleted and a number of minor clarifying revision