Using Narrow Band Photometry to Detect Young Brown Dwarfs in IC348

We report the discovery of a population of young brown dwarf candidates in the open star cluster IC348 and the development of a new spectroscopic classification technique using narrow band photometry. Observations were made using FLITECAM, the First Light Camera for SOFIA, at the 3-m Shane Telescope at Lick Observatory. FLITECAM is a new 1-5 micron camera with an 8 arcmin field of view. Custom narrow band filters were developed to detect absorption features of water vapor (at 1.495 microns) and methane (at 1.66 microns) characteristic of brown dwarfs. These filters enable spectral classification of stars and brown dwarfs without spectroscopy. FLITECAM's narrow and broadband photometry was verified by examining the color-color and color-magnitude characteristics of stars whose spectral type and reddening was known from previous surveys. Using our narrow band filter photometry method, it was possible to identify an object measured with a signal-to-noise ratio of 20 or better to within +/-3 spectral class subtypes for late-type stars. With this technique, very deep images of the central region of IC348 (H ~ 20.0) have identified 18 sources as possible L or T dwarf candidates. Out of these 18, we expect that between 3 - 6 of these objects are statistically likely to be background stars, with the remainder being true low-mass members of the cluster. If confirmed as cluster members then these are very low-mass objects (~5 Mjupiter). We also describe how two additional narrow band filters can improve the contrast between M, L, and T dwarfs as well as provide a means to determine the reddening of an individual object.Comment: 43 pages, 17 figures. Accepted for publication in the Astrophysical Journal 27 June 200

Fuel conservative guidance concept for shipboard landing of powered-life aircraft

A simulation study was undertaken to investigate the application of energy conservative guidance (ECG) software, developed at NASA Ames Research Center, to improve the time and fuel efficiency of powered lift airplanes operating from aircraft carriers at sea. When a flightpath is indicated by a set of initial conditions for the aircraft and a set of positional waypoints with associated airspeeds, the ECG software synthesizes the necessary guidance commands to optimize fuel and time along the specified path. A major feature of the ECG system is the ability to synthesize a trajectory that will allow the aircraft to capture the specified path at any waypoint with the desired heading and airspeed from an arbitrary set of initial conditions. Five paths were identified and studied. These paths demonstrate the ECG system's ability to save flight time and fuel by more efficiently managing the aircraft's capabilities. Results of this simulation study show that when restrictions on the approach flightpath imposed for manual operation are removed completely, fuel consumption during the approach was reduced by as much as 49% (610 lb fuel) and the time required to fly the flightpath was reduced by as much as 41% (5 min). Savings due to ECG were produced by: (1) shortening the total flight time; (2) keeping the airspeed high as long as possible to minimize time spent flying in a regime in which more engine thrust is required for lift to aid the aerodynamic lift; (3) minimizing time spent flying at constant altitude at slow airspeeds; and (4) synthesizing a path from any location for a direct approach to landing without entering a holding pattern or other fixed approach path

What drives me there? The interplay of socio-psychological gratification and consumer values in social media brand engagement

The social behavioral perspective is under-researched in the extant literature. This hinders the holistic understanding of social media brand engagement. This study examines the interplay of socio-psychological gratification variables (perceived homophily, perceived critical mass, and self-status seeking) and consumer values (personal, interpersonal, and fun) on consumer participation in social media brand engagement. The conceptual model in this study is situated on the principles of Uses and Gratifications, Critical Mass, Homophily, and Values theories. Based on an online survey of 713 Facebook users, we examine the model using structural equation modeling (with Amos 23.0). The analysis disclosed insights on the interplay of motivational factors that underlie social media brand engagement. Our findings suggest that socio-psychological gratification variables (perceived homophily, perceived critical mass, and self-status seeking) drive consumers’ engagement with brand pages and brand communities on social media. This relationship is strengthened by the consumer values. These insights serve as an important basis for researchers and practitioners to understand social media brand engagement and its outcomes

The Effects of Shoe Design on Lower Limb Running Kinematics

The preference of running as a form of exercise exposes more recreational athletes to the risk of injury. Stress fractures occur for 0.7-20% of all running injuries (Wilder & Sethi, 2004) and 24-50% of stress fractures occur in the tibia (Aweid, Aweid, Talibi, & Porter, 2013). Stress fractures have been associated with high vertical impact peaks while running (Willy & Davis, 2013) so methods such as barefoot running and minimalist shoes aim to reduce these impact peaks by enforcing a more forefoot running pattern. Shoes with a lower drop height have been shown to induce a more forefoot running pattern without the discomfort of running barefoot or in non-cushioned minimalist shoes (Horvais & Samozino, 2012). The purpose of this study was to compare ankle joint kinematics, dorsiflexor muscle activity, and tibial axial acceleration while wearing low and high heel-drop shoes. Six female participants (19.8(1.0) years, 163.0(3.8) cm, and 60.4(5.5) kg) who ran a minimum of 10 miles per week provided informed consent prior to testing. Participants were equipped with a 16g BioNomadix tri-axial accelerometer attached to the tibia, a Bi-axial electrogoniometer attached at the ankle, two Ag-AgCl surface electrodes attached to the tibialis anterior with adhesive discs, one reference electrode placed on the anteromedial aspect of the tibia (not above a muscle), and a heart rate monitor. Participants completed two data running trials at a target effort of 65-70% of the heart rate reserve. Trials were performed in different shoes (drop heights 4mm(S1) and 11.7mm(S2)) with a minimum 10-minute rest between trials. Paired t-tests were used to compare conditions for each variable. Mean ankle angles at ground contact (S1=100.9(3.8)°, S2=102.6(3.0)°) were not significantly different (t(5)=-1.465, p=0.203) and had a small effect size (Cohen d=0.598). Mean peak tibial accelerations (S1=5.22(2.51g), S2=5.90(2.90)g) were not significantly different (t(5)=-1.238, p=0.271) and had a small effect size (Cohen d=0.505). The mean percentages of maximal EMG for the tibialis anterior (S1=66.2(45.7)%, S2=55.6(38.5)%) were not significant (t(5)=1.380, p=0.226) and had a small effect size (Cohen d=0.563). Though differences were observed between shoe conditions for each participant, the shoe drop height did not significantly affect the measured variables and cannot be assumed to be responsible for these observed differences

K-Band Spectroscopy of an Obscured Massive Stellar Cluster in the Antennae Galaxies (NGC 4038/4039) with NIRSPEC

We present infrared spectroscopy of the Antennae Galaxies (NGC 4038/4039) with NIRSPEC at the W. M. Keck Observatory. We imaged the star clusters in the vicinity of the southern nucleus (NGC 4039) in 0.39" seeing in K-band using NIRSPEC's slit-viewing camera. The brightest star cluster revealed in the near-IR (M_K(0) = -17.9) is insignificant optically, but coincident with the highest surface brightness peak in the mid-IR (12-18 um) ISO image presented by Mirabel et al (1998). We obtained high signal-to-noise 2.03-2.45 um spectra of the nucleus and the obscured star cluster at R = 1900. The cluster is very young (age ~ 4 Myr), massive (M ~ 16E6 M_sun), and compact (density ~ 115 M_sun pc^(-3) within a 32 pc half-light radius), assuming a Salpeter IMF (0.1-100 M_sun). Its hot stars have a radiation field characterized by T_eff ~ 39,000 K, and they ionize a compact HII region with n_e ~ 10^4 cm^(-3). The stars are deeply embedded in gas and dust (A_V = 9-10 mag), and their strong FUV field powers a clumpy photodissociation region with densities n_H > 10^5 cm^(-3) on scales of ~ 200 pc, radiating L{H_2 1-0 S(1)}= 9600 L_sun.Comment: 4 pages, 4 embedded figures, uses emulateapj.sty. To appear in ApJL. Also available at http://astro.berkeley.edu/~agilber