From z>6 to z~2: Unearthing Galaxies at the Edge of the Dark Ages

Galaxies undergoing formation and evolution can now be observed over a time baseline of some 12 Gyr. An inherent difficulty with high-redshift observations is that the objects are very faint and the best resolution (HST) is only ~0.5 kpc. Such studies thereby combine in a highly synergistic way with the great detail that can be obtained for nearby galaxies. 3 new developments are highlighted. First is the derivation of stellar masses for galaxies from SEDs using HST and now Spitzer data, and dynamical masses from both sub-mm observations of CO lines and near-IR observations of optical lines like Halpha. A major step has been taken with evidence that points to the z~2-3 LBGs having masses that are a few x 10^10 Msolar. Second is the discovery of a population of evolved red galaxies at z~2-3 which appear to be the progenitors of the more massive early-type galaxies of today, with dynamical masses around a few x 10^11 Msolar. Third are the remarkable advances that have occurred in characterizing dropout galaxies to z~6 and beyond, < 1 Gyr from recombination. The HST ACS has played a key role here, with the dropout technique being applied to i & z images in several deep ACS fields, yielding large samples of these objects. This has allowed a detailed determination of their properties and meaningful comparisons against lower-z samples. The use of cloning techniques has overcome many of the strong selection biases affecting the study of these objects. A clear trend of size with redshift has been identified, and its impact on the luminosity density and SFR estimated. There is a significant though modest decrease in the SFR from z~2.5 to z~6. The latest data also allow for the first robust determination of the LF at z~6. Finally, the latest UDF ACS and NICMOS data has resulted in the detection of some galaxies at z~7-8.Comment: 18 pages, 8 figures. To appear in Penetrating Bars through Masks of Cosmic Dust: The Hubble Tuning Fork Strikes a New Note, eds. D. Block, K. Freeman, R. Groess, I. Puerari, & E.K. Block (Dordrecht: Kluwer), in pres

Controlled interfacial assembly of 2D curved colloidal crystals and jammed shells

Assembly of colloidal particles on fluid interfaces is a promising technique for synthesizing two-dimensional micro-crystalline materials useful in fields as diverse as biomedicine1, materials science2, mineral flotation3 and food processing4. Current approaches rely on bulk emulsification methods, require further chemical and thermal treatments, and are restrictive with respect to the materials employed5-9. The development of methods that exploit the great potential of interfacial assembly for producing tailored materials have been hampered by the lack of understanding of the assembly process. Here we report a microfluidic method that allows direct visualization and understanding of the dynamics of colloidal crystal growth on curved interfaces. The crystals are periodically ejected to form stable jammed shells, which we refer to as colloidal armour. We propose that the energetic barriers to interfacial crystal growth and organization can be overcome by targeted delivery of colloidal particles through hydrodynamic flows. Our method allows an unprecedented degree of control over armour composition, size and stability.Comment: 18 pages, 5 figure

Human Computation and Convergence

Humans are the most effective integrators and producers of information, directly and through the use of information-processing inventions. As these inventions become increasingly sophisticated, the substantive role of humans in processing information will tend toward capabilities that derive from our most complex cognitive processes, e.g., abstraction, creativity, and applied world knowledge. Through the advancement of human computation - methods that leverage the respective strengths of humans and machines in distributed information-processing systems - formerly discrete processes will combine synergistically into increasingly integrated and complex information processing systems. These new, collective systems will exhibit an unprecedented degree of predictive accuracy in modeling physical and techno-social processes, and may ultimately coalesce into a single unified predictive organism, with the capacity to address societies most wicked problems and achieve planetary homeostasis.Comment: Pre-publication draft of chapter. 24 pages, 3 figures; added references to page 1 and 3, and corrected typ

The Complete Star Formation History of the Universe

The determination of the star-formation history of the Universe is a key goal of modern cosmology, as it is crucial to our understanding of how structure in the Universe forms and evolves. A picture has built up over recent years, piece-by-piece, by observing young stars in distant galaxies at different times in the past. These studies indicated that the stellar birthrate peaked some 8 billion years ago, and then declined by a factor of around ten to its present value. Here we report on a new study which obtains the complete star formation history by analysing the fossil record of the stellar populations of 96545 nearby galaxies. Broadly, our results support those derived from high-redshift galaxies elsewhere in the Universe. We find, however, that the peak of star formation was more recent - around 5 billion years ago. Our study also shows that the bigger the stellar mass of the galaxy, the earlier the stars were formed. This striking result indicates a very different formation history for high- and low-mass formation.Comment: Accepted by Nature. Press embargo until publishe

We are all one together : peer educators\u27 views about falls prevention education for community-dwelling older adults - a qualitative study

Background: Falls are common in older people. Despite strong evidence for effective falls prevention strategies, there appears to be limited translation of these strategies from research to clinical practice. Use of peers in delivering falls prevention education messages has been proposed to improve uptake of falls prevention strategies and facilitate translation to practice. Volunteer peer educators often deliver educational presentations on falls prevention to community-dwelling older adults. However, research evaluating the effectiveness of peer-led education approaches in falls prevention has been limited and no known study has evaluated such a program from the perspective of peer educators involved in delivering the message. The purpose of this study was to explore peer educators’ perspective about their role in delivering peer-led falls prevention education for community-dwelling older adults. Methods: A two-stage qualitative inductive constant comparative design was used.In stage one (core component) focus group interviews involving a total of eleven participants were conducted. During stage two (supplementary component) semi-structured interviews with two participants were conducted. Data were analysed thematically by two researchers independently. Key themes were identified and findings were displayed in a conceptual framework. Results: Peer educators were motivated to deliver educational presentations and importantly, to reach an optimal peer connection with their audience. Key themes identified included both personal and organisational factors that impact on educators’ capacity to facilitate their peers’ engagement with the message. Personal factors that facilitated message delivery and engagement included peer-to-peer connection and perceived credibility, while barriers included a reluctance to accept the message that they were at risk of falling by some members in the audience. Organisational factors, including ongoing training for peer educators and formative feedback following presentations, were perceived as essential because they affect successful message delivery. Conclusions: Peer educators have the potential to effectively deliver falls prevention education to older adults and influence acceptance of the message as they possess the peer-to-peer connection that facilitates optimal engagement. There is a need to consider incorporating learnings from this research into a formal large scale evaluation of the effectiveness of the peer education approach in reducing falls in older adults

Obesity and pre-hypertension in family medicine: Implications for quality improvement

<p>Abstract</p> <p>Background.</p> <p>Prevention of pre-hypertension is an important goal for primary care patients. Obesity is a risk factor for hypertension, but has not been addressed for pre-hypertension in primary care populations. The objective of this study was to assess the degree to which obesity independently is associated with risk for pre-hypertension in family medicine patients.</p> <p>Methods.</p> <p>This study was a retrospective analysis of information abstracted from medical records of 707 adult patients. Multivariable logistic regression was used to test the relationship between body mass index (BMI) and pre-hypertension, after adjustment for comorbidity and demographic characteristics. Pre-hypertension was defined as systolic pressure between 120 and 139 mm Hg or diastolic pressure between 80 and 89 mm Hg.</p> <p>Results.</p> <p>In our sample, 42.9% of patients were pre-hypertensive. Logistic regression analysis revealed that, in comparison to patients with normal body mass, patients with BMI > 35 had higher adjusted odds of being pre-hypertensive (OR = 4.5, CI 2.55–8.11, p < .01). BMI between 30 and 35 also was significant (OR = 2.7, CI 1.61–4.63, p < 0.01) as was overweight (OR = 1.8, CI 1.14–2.92, p = 0.01).</p> <p>Conclusion.</p> <p>In our sample of family medicine patients, elevated BMI is a risk factor for pre-hypertension, especially BMI > 35. This relationship appears to be independent of age, gender, marital status and comorbidity. Weight loss intervention for obese patients, including patient education or referral to weight loss programs, might be effective for prevention of pre-hypertension and thus should be considered as a potential quality indicator.</p

Rapid Evolution in the Most Luminous Galaxies During the First 900 Million Years

The first 900 million years (Myr) to redshift z~6 (the first seven per cent of the age of the Universe) remains largely unexplored for the formation of galaxies. Large samples of galaxies have been found at z~6, but detections at earlier times are uncertain and unreliable. It is not at all clear how galaxies built up from the first stars when the Universe was ~300 Myr old (z~12-15) to z~6, just 600 Myr later. Here we report the results of a search for galaxies at z~7-8, about 700 Myr after the Big Bang, using the deepest near-infrared and optical images ever taken. Under conservative selection criteria we find only one candidate galaxy at z~7-8, where ten would be expected if there were no evolution in the galaxy population between z~7-8 and z~6. Using less conservative criteria, there are four candidates, where 17 would be expected with no evolution. This demonstrates that very luminous galaxies are quite rare 700 Myr after the Big Bang. The simplest explanation is that the Universe is just too young to have built up many luminous galaxies at z~7-8 by the hierarchical merging of small galaxies.Comment: Accepted for publication in Nature, 20 pages, 5 figures, 2 tables (includes Supplementary Information), replaced to match version in pres

Exploration of the rotational power consumption of a rigid flapping wing

Accepted versio

Baseline values from the electrocardiograms of children and adolescents with ADHD

<p>Abstract</p> <p>Background</p> <p>An important issue in pediatric pharmacology is the determination of whether medications affect cardiac rhythm parameters, in particular the QT interval, which is a surrogate marker for the risk of adverse cardiac events and sudden death. To evaluate changes while on medication, it is useful to have a comparison of age appropriate values while off medication. The present meta-analysis provides baseline ECG values (i.e., off medication) from approximately 6000 children and adolescents with attention-deficit/hyperactivity disorder (ADHD).</p> <p>Methods</p> <p>Subjects were aged 6–18 years and participated in global trials within the atomoxetine registration program. Patients were administered a 12-lead ECG at study screening and cardiac rhythm parameters were recorded. Baseline QT intervals were corrected for heart rate using 3 different methods: Bazett's, Fridericia's, and a population data-derived formula.</p> <p>Results</p> <p>ECG data were obtained from 5289 North American and 641 non-North American children and adolescents. Means and percentiles are presented for each ECG measure and QTc interval based on pubertal status as defined by age and sex. Prior treatment history with stimulants and racial origin (Caucasian) were each associated with significantly longer mean QTc values.</p> <p>Conclusion</p> <p>Baseline ECG and QTc data from almost 6000 children and adolescents presenting with ADHD are provided to contribute to the knowledge base regarding mean values for pediatric cardiac parameters. Consistent with other studies of QT interval in children and adolescents, Bazett correction formula appears to overestimate the prevalence of prolonged QTc in the pediatric population.</p