Influence of melt stability on the crystallization of bis(4-aminophenoxy)benzene-oxydiphthalic anhydride based polyimides

Novel high performance semicrystalline polyimides, based on controlled molecular weight phthalic anhydride (PA) endcapped 1,4-bis(4-aminophenoxy)benzene (TPEQ diamine) and oxydiphthalic dianhydride (ODPA), were synthesized. They exhibited excellent thermal stability in nitrogen and air atmospheres as determined by thermogravimetric analysis (TGA). The glass transition temperatures (T_g) for these polymers ranged from 225°C for the 10,000 M_n (10K) polymer, to 238°C for the 30,000 (30K) M_n material. The observed melting temperatures for all the polymers were ∼420°C. The crystallization behavior of these polymers showed a strong molecular weight dependence, as illustrated by the observation that the 10K and 12.5K polymers crystallized with relative ease, whereas the 15K, 20K, and 30K polymers showed little or no ability to undergo thermal recrystallization. The thermal stability of these polymers above T_m was investigated by studying the effect of time and temperature in the melt on the cold crystallization and melting of these polymers. Increased time and temperature in the melt resulted in lower crystallinity because of melt state degradation, such as crosslinking and branching, as evidenced by an increase in melt viscosity, which was more prominent for the higher molecular weight polymers.     

Tridimensional mapping: guided modification of the sinus node

Radiofrequency (RF) catheter modification of the sinus node appears to be a promising therapeutic modality for the treatment of inappropriate sinus tachycardia. Modification, as opposed to total obliteration, of the atrial pacemaker requires precise localization of the sinus node. This has been successfully achieved with a multicatheter approach guided by intracardiac echocardiography. This article describes the first clinical use of a tridimensional nonfluoroscopic mapping system to guide successful RF modification of the sinus node in two cases of inappropriate sinus tachycardia. This system simplifies the current approach and greatly reduces the fluoroscopy time.     

Ablation of right and left ectopic atrial tachycardias using a three-dimensional nonfluoroscopic mapping system

We report our experience with mapping and ablation of right and left atrial tachycardia using a 3-dimensional nonfluoroscopic mapping system. Twenty-nine ectopic atrial tachycardias were successfully ablated. This novel mapping system has the potential to increase a successful cure of this arrhythmia by catheter ablation.     

Scaling issues and Ge profile optimization in advanced UHV/CVD SiGeHBT's

The SiGe heterostructure device simulation tool SCORPIO is used to investigate profile optimization in SiGe HBT's for high-performance analog circuit applications. After calibrating SCORPIO to measured data, the effects of germanium profile shape on current gain, cut-off frequency, Early voltage and maximum oscillation frequency are compared over the temperature range of 200-360 K. The impact of aggressive base profile scaling on device performance is also investigated as a function of SiGe film stability     

The Perils and Promises of Self-Disclosure on Social Media

In addition to their professional social media accounts, individuals are increasingly using their personal profiles and casual posts to communicate their identities to work colleagues. They do this in order to ‘stand out from the crowd’ and to signal attributes that are difficult to showcase explicitly in a work setting. Existing studies have tended to treat personal posts viewed in a professional context as a problem, since they can threaten impression management efforts. These accounts focus on the attempts of individuals to separate their life domains on social media. In contrast, we present the narratives of professional IT workers in India who intentionally disrupt the boundaries between personal and professional profiles in order to get noticed by their employers. Drawing on the dramaturgical vocabulary of Goffman (1959) we shed light on how individuals cope with increased levels of self-disclosure on social media. We argue that their self-presentations can be likened to post-modern performances in which the traditional boundaries between actor and audience are intentionally unsettled. These casual posts communicate additional personal traits that are not otherwise included in professional presentations. Since there are no strict boundaries between formal front-stage and relaxed back-stage regions in these types of performance, a liminal mental state is often used, which enables a better assessment of the type of information to present on social media.     

The latent structure of dietary restraint, body dissatisfaction, and drive for thinness: A series of taxometric analyses.

Although the latent structure of various eating disorders has been explored in previous studies, no published studies have examined the latent structure of theoretically relevant variables that have been shown to cut across eating disorder diagnoses. The current study examined 3 such variables (dietary restraint, body dissatisfaction, and drive for thinness) among undergraduate women using the taxometric method. The 5 items from the Eating Disorders Examination Questionnaire's Dietary Restraint subscale were used as dietary restraint indicators, whereas items from the Eating Disorders Inventory Body Dissatisfaction and Drive for Thinness subscales were used as indicators of body dissatisfaction and drive for thinness, respectively. As hypothesized, MAXCOV (maximum covariance) and MAMBAC (mean above minus below a cut) analyses suggested that all 3 variables are dimensional; therefore, individuals with high levels of reported dietary restraint, body dissatisfaction, and drive for thinness appear to differ in degree, but not in kind, from those with lower levels. Implications for prevention, assessment, classification, and treatment are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

A new class of floating-point data formats with applications to 16-bit digital-signal processing systems [Accepted from Open Call]

Sixteen-bit, programmable, digital-signal processors suffer from inadequate dynamic range and noise performance due in part to the use of standard data formats with few bits available for numeric precision. A solution to this problem is developed that involves the use of irregular data formats. A new class of irregular floating-point formats is developed. A specific format is derived from this class that provides greater dynamic range and improved noise performance for 16-bit DSP applications. An experiment with one of the new formats is conducted and analyzed, and improved performance is verified. The importance of our work and its potential applications are discussed.     

Organizational citizenship behavior and performance evaluations: Exploring the impact of task interdependence.

The influence of task interdependence on the importance attributed to organizational citizenship behavior (OCB) in evaluations of employee performance was investigated in 3 studies. In Study 1,238 undergraduates were exposed to a task interdependence manipulation and a unit-level performance manipulation and provided citizenship ratings. In Study 2,148 master of business administration students were exposed to a task interdependence manipulation and then rated the importance of OCB in their evaluations of employee performance. In Study 3,130 managers rated the task interdependence in their unit of principal responsibility and the importance of OCB in their overall evaluations of employee performance. The results suggest task interdependence may affect the importance attributed to OCB by evaluators. Implications of these results are explored. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chemical Lesion of the Bed Nucleus of the Stria Terminalis Blocks the Behavioral Consequences of Uncontrollable Stress.

Uncontrollable or inescapable shock (IS) produces behavioral changes that are characterized by a sensitized fear system and a deficit in fight-flight responding. These behavioral changes have been argued to represent an anxiety-like state produced by the uncontrollability of the stressor. The bed nucleus of the stria tenninalis (BNST) has been implicated in the mediation of long-duration responses to unpredictable stressors, which have also been argued to represent anxiety. In the present study, the effects of BNST chemical lesion on the IS-induced sensitization of freezing to an environment previously paired with shock and the IS-induced impairment of escape responding were investigated. BNST chemical lesion blocked the potentiation of freezing and the increases in escape latency that normally follow IS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)