H-alpha Activity of Old M Dwarfs: Stellar Cycles and Mean Activity Levels For 93 Low-Mass Stars in the Solar Neighborhood

Through the McDonald Observatory M Dwarf Planet Search, we have acquired nearly 3,000 high-resolution spectra of 93 late-type (K5-M5) stars over more than a decade using HET/HRS. This sample provides a unique opportunity to investigate the occurrence of long-term stellar activity cycles for low-mass stars. In this paper, we examine the stellar activity of our targets as reflected in the H-alpha feature. We have identified periodic signals for 6 stars, with periods ranging from days to more than 10 years, and find long-term trends for 7 others. Stellar cycles with P > 1 year are present for at least 5% of our targets. Additionally, we present an analysis of the time-averaged activity levels of our sample, and search for correlations with other stellar properties. In particular, we find that more massive, earlier type (M0-M2) stars tend to be more active than later type dwarfs. Furthermore, high-metallicity stars tend to be more active at a given stellar mass. We also evaluate H-alpha variability as a tracer of activity-induced radial velocity (RV) variation. For the M dwarf GJ 1170, H-alpha variation reveals stellar activity patterns matching those seen in the RVs, mimicking the signal of a giant planet, and we find evidence that the previously identified stellar activity cycle of GJ 581 may be responsible for the recently retracted planet f (Vogt et al. 2012) in that system. In general, though, we find that H-alpha is not frequently correlated with RV at the precision (typically 6-7 m/s) of our measurements.Comment: Submitted to ApJ. Reflects comments from a positive refere

What determines cognitive estimation ability? Changing contributions of semantic and executive domains as a function of age

The Cognitive Estimation Test (CET) is commonly used in neuropsychological assessment. It is typically assumed to load on executive functions, although research has shown that CET performance also depends on access to semantic knowledge. It is unknown whether these contributions vary with age. It is important to examine this question as these abilities have divergent life course trajectories: executive functions tend to decline as people age but semantic knowledge continues to accrue. In addition, previous research has not examined potential contributions to CET performance from semantic control abilities, that is cognitive control processes involved specifically in the retrieval and use of semantic information. To address these questions, we investigated cognitive predictors of CET performance in healthy young and older adults. We found that better executive function was associated with more accurate estimation in both age groups. However, the effect of semantic knowledge on CET performance was significantly larger in older people, having no predictive power in the younger group. The ability to detect weak semantic associations, which is thought to index controlled search and retrieval of semantic information, also had divergent effects on CET performance in the two age groups. Our results provide empirical support for the idea that older people are more reliant on semantic knowledge when estimating quantities, which may explain why age‐related decline in CET scores is not typically found. We conclude that deficits on the CET may be indicative either of semantic or executive impairments, particularly in older age groups

“Putting on a Happy Face,” “Getting Back to Work,” and “Letting It Go”: Traditional and Restorative Justice Understandings of Emotions at Work

Coping with the emotional consequences of hurtful situations in the workplace can be problematic for organizational members. Traditional approaches depending on rationality and professionalism come with expectations that employees suppress or minimize emotion by focusing on their work and maintaining composure. However, an alternative approach to justice – restorative justice – is gaining notice in organizational scholarship and appears to offer a different approach to managing painful situations and their associated emotions. This study examines how the experience and management of emotion following hurtful events are connected with traditional and restorative principles in a workplace setting. The results of the study offer insight into the consequences of restorative justice in organizational life.Citation: Paul, G. D. & Riforgiate, S. E. (2015). “Putting on a happy face,” “getting back to work,” and “letting it go”: Traditional and restorative justice understandings of emotions at work. Electronic Journal of Communication, 25 (3 & 4)

Emerging Neurotechnologies for Lie Detection and the Fifth Amendment

The article examines the legal implications and advantages of emerging Neurotechnological Lie Detection (NTLD). The self-incrimination clause of the Fifth Amendment to the U.S. Constitution was taken into account, including its scope over NTLD. Key information about the reliability and privacy issues of NTLD is further presented

On the temperature structure of the Galactic Centre cloud G0.253+0.016

We present a series of smoothed particle hydrodynamical models of G0.253+0.016 (also known as 'The Brick'), a very dense molecular cloud that lies close to the Galactic Centre. We explore how its gas and dust temperatures react as we vary the strength of both the interstellar radiation field (ISRF) and the cosmic ray ionisation rate (CRIR). As the physical extent of G0.253+0.016 along our line-of-sight is unknown, we consider two possibilities: one in which the longest axis is that measured in the plane of the sky (9.4 pc in length), and one in which it is along the line of sight, in which case we take it to be 17 pc. To recover the observed gas and dust temperatures, we find find that the ISRF must be around 1000 times the solar neighbourhood value, and the CRIR must be roughly 1E-14 /s, regardless of the geometries studied. For such high values of the CRIR, we find that cooling in the cloud's interior is dominated by neutral oxygen, in contrast to standard molecular clouds, which at the same densities are mainly cooled via CO. Our results suggest that the conditions near G0.253+0.016 are more extreme than those generally accepted for the inner 500 pc of the galaxy.Comment: 6 pages, 4 figures, 1 table, accepted for publication in ApJ Letter

Herschel Observations and Updated Spectral Energy Distributions of Five Sunlike Stars with Debris Disks

Observations from the Herschel Space Observatory have more than doubled the number of wide debris disks orbiting Sunlike stars to include over 30 systems with R > 100 AU. Here we present new Herschel PACS and re-analyzed Spitzer MIPS photometry of five Sunlike stars with wide debris disks, from Kuiper belt size to R > 150 AU. The disk surrounding HD 105211 is well resolved, with an angular extent of >14" along the major axis, and the disks of HD 33636, HD 50554, and HD 52265 are extended beyond the PACS PSF size (50% of energy enclosed within radius 4.23"). HD 105211 also has a 24-micron infrared excess that was previously overlooked because of a poorly constrained photospheric model. Archival Spitzer IRS observations indicate that the disks have small grains of minimum radius ~3 microns, though the minimum grain gradius is larger than the radiation pressure blowout size in all systems. If modeled as single-temperature blackbodies, the disk temperatures would all be <60 K. Our radiative transfer models predict actual disk radii approximately twice the radius of model blackbody disks. We find that the Herschel photometry traces dust near the source population of planetesimals. The disk luminosities are in the range 0.00002 <= L/L* <= 0.0002, consistent with collisions in icy planetesimal belts stirred by Pluto-size dwarf planets.Comment: Accepted for publication in ApJ. 18 pages, including 10 figures and 3 table

Contrast agents for molecular photoacoustic imaging.

Photoacoustic imaging (PAI) is an emerging tool that bridges the traditional depth limits of ballistic optical imaging and the resolution limits of diffuse optical imaging. Using the acoustic waves generated in response to the absorption of pulsed laser light, it provides noninvasive images of absorbed optical energy density at depths of several centimeters with a resolution of ∼100 μm. This versatile and scalable imaging modality has now shown potential for molecular imaging, which enables visualization of biological processes with systemically introduced contrast agents. Understanding the relative merits of the vast range of contrast agents available, from small-molecule dyes to gold and carbon nanostructures to liposome encapsulations, is a considerable challenge. Here we critically review the physical, chemical and biochemical characteristics of the existing photoacoustic contrast agents, highlighting key applications and present challenges for molecular PAI.This work was supported by CRUK (Career Establishment Award no. C47594/A16267 to J.W. and S.E.B., Core Funding C14303/A17197 to J.W. and S.E.B.), the European Commission (CIG FP7-PEOPLE- 2013-CIG-630729 to J.W. and S.E.B.), the EPSRC-CRUK Cancer Imaging Centre in Cambridge and Manchester (C197/A16465 to J.W. and S.E.B.), King’s College London and University College London Comprehensive Cancer Imaging Centre Cancer Research UK & Engineering and Physical Sciences Research Council, in association with the Medical Research Council and the Department of Health, UK (P.B.), and the European Union (project FAMOS FP7 ICT, contract 317744 to P.B.).This is the author accepted manuscript. The final version is available from Nature Publishing Group via http://dx.doi.org/10.1038/nmeth.392

Which Investments Improve Student Performance? The Impact of Extracurricular Activities, Paid Classes, and At-Home Internet Use on Student Performance in Secondary School

The importance of education is acknowledged by modern society. As more and more people are willing to invest in education to improve students’ performance, the question of which areas of investment contribute most strongly to better academic performance arises. Parents can choose to involve their children in extracurricular activities, or they can choose to pay for additional classes outside of regular schooling. In addition, the use of technology, or, more specifically, access to the Internet at home, is becoming more and more common, and its influence on student performance is a popular topic of study. In this paper, we use two experiments to uncover the factors that influence students’ performance in Math and Portuguese Language and to support strategies for investment in education

Photovoltaic Performance of Ultrasmall PbSe Quantum Dots

We investigated the effect of PbSe quantum dot size on the performance of Schottky solar cells made in an ITO/PEDOT/PbSe/aluminum structure, varying the PbSe nanoparticle diameter from 1 to 3 nm. In this highly confined regime, we find that the larger particle bandgap can lead to higher open-circuit voltages (~0.6 V), and thus an increase in overall efficiency compared to previously reported devices of this structure. To carry out this study, we modified existing synthesis methods to obtain ultrasmall PbSe nanocrystals with diameters as small as 1 nm, where the nanocrystal size is controlled by adjusting the growth temperature. As expected, we find that photocurrent decreases with size due to reduced absorption and increased recombination, but we also find that the open-circuit voltage begins to decrease for particles with diameters smaller than 2 nm, most likely due to reduced collection efficiency. Owing to this effect, we find peak performance for devices made with PbSe dots with a first exciton energy of ~1.6 eV (2.3 nm diameter), with a typical efficiency of 3.5%, and a champion device efficiency of 4.57%. Comparing the external quantum efficiency of our devices to an optical model reveals that the photocurrent is also strongly affected by the coherent interference in the thin film due to Fabry-Pérot cavity modes within the PbSe layer. Our results demonstrate that even in this simple device architecture, fine-tuning of the nanoparticle size can lead to substantial improvements in efficiency