Pilot-aided modulation for narrow-band satellite communications

This paper discusses a number of tone-aided modulation techniques which have been studied as part of the Mobile Satellite Experiment (MSAT-X) Program. In all instances tone(s) are inserted into data-free portions of the transmit spectrum and used by the receiver to sense the amplitude and frequency/phase distortions introduced by the channel. The receiver then uses this information in a feedforward manner to lessen the effect of the distortions on the data detection performance. Particular techniques discussed are the Tone Calibration Technique (TCT), the Dual Tone Calibrated Technique (DTCT), Transparent Tone-In-Band (TTIB), and Dual-Tone Single Sideband (DTSSB)

Modulation and coding technology for deep space and satellite applications

Modulation and coding research and development at the Jet Propulsion Laboratory (JPL) currently emphasize Deep Space Communications Systems and advanced near earth Commercial Satellite Communications Systems. The Deep Space Communication channel is extremely signal to noise ratio limited and has long transmission delay. The near earth satellite channel is bandwidth limited with fading and multipath. Recent code search efforts at JPL have found a long constraint, low rate convolutional code (15, 1/6) which, when concatenated with a ten bit Reed-Solomon (RS) code, provides a 2.1 dB gain over that of the Voyager spacecraft - the current standard. The new code is only 2 dB from the theoretical Shannon limit. A flight qualified version of the (15, 1/6) convolutional encoder was implemented on the Galileo Spacecraft to be launched later this year. An L-band mobile link, use of the Ka-band for personal communications, and the development of subsystem technology for the interconnection of satellite resources by using high rate optical inter-satellite links are noted

A study examining social skills ratings in a special education classroom

The purpose of this study was to examine the degree of relationship between students\u27 self-ratings scores and their teacher\u27s and teacher assistant\u27s scores. Ten students classified ED were chosen, along with a social comparison group of ten regular education students. A correlational matrix was computed to measure the degree of association between students\u27 self-ratings and their teachers\u27 ratings of them. The same was done for the regular education sample. Two t-tests for independent samples were used to (1) measure any differences between the ratings of the special education teacher and the regular education teacher, and (2) measure any differences between the self ratings of the students with EBD and the regular education students. Results showed significant correlations between the special education teacher\u27s and the teacher assistant\u27s ratings of the students with EBD in the areas of Classroom Survival Skills and Dealing with Feelings. A significant correlation was shown to exist between the regular education teacher\u27s ratings and students\u27 self-ratings in the area of Dealing with Stress only. A t-test for independent samples showed that students with EBD were rated lower than their regular education peers in all social skill areas. No significant differences were found between the self-rating scores of the student samples

Perceptions Of Empowered Teacher Leaders

Teacher Leadership movements over the last 30 years have attempted to create leadership opportunities within and across an organization. The purpose of this mixed method case study was to evaluate the impact of a district’s teacher leadership opportunities to reduce teacher isolation and increase teacher collaboration. This study illustrated how effective teacher leadership initiatives should take Piaget’s idea (1971) of discovery learning and combine it with the concept that teaching and learning are more powerful when they involve social interaction (Bandura, 1987). A literature review revealed a gap in understanding what systems and structures made collaboration more successful for teacher leaders. The design of these structures should move away from punitive accountability to developing new capacities that promote the improvement of the group (DuFour & Fullan, 2013). The study employed an interpretive qualitative research design (Creswell, 2015). The research process documented how the roles and supports from district leaders impacted teacher capacity and the collaborative culture of the organization. The perceptions of the teacher leaders who participated in the teacher leadership academy were that the experience had influenced the way they teach. Additionally, the use of teacher leadership as an improvement strategy helped reduce teacher isolation and improve collaboration among colleagues. It was found that effective collaboration should exist in smaller settings and have a common area of focus to increase the ability of teachers to take risks and to embrace innovative teaching practices. An important finding was the need for leaders to understand organizational culture and possible misunderstandings that arise when teacher leaders are viewed as formal leaders by colleagues. This case study added to the body of knowledge about the importance of processes and structures in supporting teacher leadership development

Stacking-induced fluorescence increase reveals allosteric interactions through DNA

From gene expression to nanotechnology, understanding and controlling DNA requires a detailed knowledge of its higher order structure and dynamics. Here we take advantage of the environment-sensitive photoisomerization of cyanine dyes to probe local and global changes in DNA structure. We report that a covalently attached Cy3 dye undergoes strong enhancement of fluorescence intensity and lifetime when stacked in a nick, gap or overhang region in duplex DNA. This is used to probe hybridization dynamics of a DNA hairpin down to the single-molecule level. We also show that varying the position of a single abasic site up to 20 base pairs away modulates the dye–DNA interaction, indicative of through-backbone allosteric interactions. The phenomenon of stacking-induced fluorescence increase (SIFI) should find widespread use in the study of the structure, dynamics and reactivity of nucleic acids

Kinematic, kinetic and electromyographic response to customized foot orthoses in patients with tibialis posterior tenosynovitis, pes plano valgus and rheumatoid arthritis

Objective. To describe the effect of customized foot orthoses (FOs) on the kinematic, kinetic and EMG features in patients with RA, tibialis posterior (TP) tenosynovitis and associated pes plano valgus.<p></p> Methods. Patients with RA and US-confirmed tenosynovitis of TP underwent gait analysis, including three-dimensional (3D) kinematics, kinetics, intramuscular EMG of TP and surface EMG of tibialis anterior, peroneus longus, soleus and medial gastrocnemius. Findings were compared between barefoot and shod with customized FO conditions.<p></p> Results. Ten patients with RA with a median (range) disease duration of 3 (1–18) years were recruited. Moderate levels of foot pain and foot-related impairment and disability were present with moderately active disease states. Altered timing of the soleus (P = 0.05) and medial gastrocnemius (P = 0.02) and increased magnitude of tibialis anterior (P = 0.03) were noted when barefoot was compared with shod with FO. Trends were noted for reduced TP activity in the contact period (P = 0.09), but this did not achieve statistical significance. Differences in foot motion characteristics were recorded for peak rearfoot eversion (P = 0.01), peak rearfoot plantarflexion (P < 0.001) and peak forefoot abduction (P = 0.02) in the shod with FOs compared with barefoot conditions. No differences in kinetic variables were recorded.<p></p> Conclusion. This study has demonstrated, for the first time, alterations in muscle activation profiles and foot motion characteristics in patients with RA, pes plano valgus and US-confirmed TP tenosynovitis in response to customized FOs. Complex adaptations were evident in this cohort and further work is required to determine whether these functional alterations lead to improvements in patient symptoms.<p></p&gt

The Detectability of AGN Cavities in Cooling-Flow Clusters

Chandra X-ray Observatory has revealed X-ray cavities in many nearby cooling flow clusters. The cavities trace feedback from the central active galactic nulceus (AGN) on the intracluster medium (ICM), an important ingredient in stabilizing cooling flows and in the process of galaxy formation and evolution. But, the prevalence and duty cycle of such AGN outbursts is not well understood. To this end, we study how the cooling is balanced by the cavity heating for a complete sample of clusters (the Brightest 55 clusters of galaxies, hereafter B55). In the B55, we found 33 cooling flow clusters, 20 of which have detected X-ray bubbles in their ICM. Among the remaining 13, all except Ophiuchus could have significant cavity power yet remain undetected in existing images. This implies that the duty cycle of AGN outbursts with significant heating potential in cooling flow clusters is at least 60 % and could approach 100 %, but deeper data is required to constrain this further.Comment: 4 pages, 2 figures; to appear in the proceedings of "The Monsters' Fiery Breath", Madison, Wisconsin 1-5 June 2009, Eds. Sebastian Heinz & Eric Wilcots; added annotation to the figur