Positron annihilation lifetime study of vapor sorption in polypropylene and polytetrafluoroethylene

Positron annihilation lifetime (PAL) spectra were measured for two different kinds of polymers: polypropylene (PP) and polytetrafluoroethylene (PTFE), during sorption of vapors of the following molecules: n-hexane, cyclohexane, benzene, methyl methacrylate, acrylic acid, and water. The behavior of ortho-positronium (o-Ps) annihilation parameters: lifetime, τ₃, and intensity, I₃, can be explained by considering different sorption mechanisms in rubbery and glassy polymers. The mean size of the intermolecular-space holes and the relative free-volume fraction of PP and PTFE were estimated before and during the sorption process from the o-Ps parameters obtained. Sorption of n-hexane, cyclohexane, and benzene in both polymers affect the o-Ps component in a systematic way, for PP τ₃ and I₃ tend to decrease, while in PTFE, τ₃ stay almost constant and I₃ diminishes. These effects are interpreted in relation to the different states of the polymers studied: rubbery for PP and glassy for PTFE. In case of methyl methacrylate molecules, the behavior of o-Ps parameters was more complicated. For acrylic acid and water, their associated polarity provokes a diminution in I₃, which is explained from the viewpoint of the spur model of positronium formation. Large changes in the mean size and the fraction of free volume, as well as their constant behavior in some cases, were interpreted to be due to positive or negative interactions, respectively, between vapor molecules and PP and PTFE, which could be correlated with the solvent-interaction parameters calculated. © 1995 John Wiley & Sons, Inc.     

Treatment outcome with radiation therapy after breast augmentation or reconstruction in patients with primary breast carcinoma

BACKGROUND: Analyses were performed to determine local control and cosmetic outcome of breast carcinoma patients with prosthetically augmented or reconstructed breasts who had received radiation therapy (RT). METHODS: Twenty-one newly diagnosed breast carcinoma patients with prosthetically augmented or reconstructed breasts were treated with external beam RT. All patients received whole breast RT (median dose, 50.4 gray [Gy]) and 19 were boosted to a median dose of 60.4 Gy. A median dose of 50.4 Gy was delivered to the regional lymph nodes in 12 patients. Tissue equivalent bolus material was used in six patients. Seventeen patients received adjuvant systemic therapy. Cosmetic results were evaluated at 3-6-month intervals. RESULTS: With a median follow-up of 32 months, good/excellent cosmetic results were observed in 71% of patients (100% in those with augmented breasts and 54% in those with reconstructed breasts). Four patients (19%) with fair/poor cosmetic outcomes required implant removal and/or revision. Multiple clinical and treatment-related factors were analyzed for their impact on cosmetic outcome. A worsened cosmetic result was observed with increasing stage (P = 0.076), breast reconstruction (vs. augmentation) (P = 0.030), and bolus application (P = 0.016). All patients with fair/poor cosmetic outcomes had time intervals from implant insertion to RT ranging from 53-213 days. Two patients developed an isolated local recurrence within the augmented breast. CONCLUSIONS: Patients with prosthetically augmented breasts can undergo RT and expect good/excellent cosmetic results. Patients with reconstructed breasts are at a significantly greater risk for cosmetic failure. This risk may be related to the higher percentage of patients with advanced disease, those who received bolus application, and those who received earlier delivery of RT (after the cosmetic procedure) in reconstructed breasts.     

Levels of sophistication of information management systems and their upgrading

The organizational Information Management System is identified, analyzed and evaluated. In order to identify it, the objectives and functional components of such a system are described; then, the different levels of sophistication of the alternatives implementing each one of the system components are presented. A proposed “upgrading approach” is applied to analyze the information management activities within the organization.     

A multiple access scheme for multimedia traffic in wireless ATM

This paper proposes a multiple access scheme for the forthcoming wireless ATM (Asynchronous Transfer Mode) system. Such ATM compatible wireless systems are motivated by the rapidly increasing demand for wireless extensions to broadband networks, which are expected to support mixed broadband services including Constant Bit Rate (CBR), Variable Bit Rate (VBR), and Available Bit Rate (ABR) traffic. Since these different traffics have very different performance requirements, the multiple access scheme design is very challenging. In this paper, we propose a multiple access scheme called Dynamic Time Division Multiple Access with Piggybacked Reservation (DTDMA/PR), attempting to achieve higher statistical multiplexing efficiency in the mixed VBR/CBR/ABR traffic scenario. The basic idea is to exploit two levels of reservation. The first level deals with the isochronous nature of CBR and VBR traffic and the bursty nature of ABR traffic by using the ALOHA reservation procedure. The second level exploits the piggybacked reservation approach to cope with the dynamic feature of VBR traffic in order to increase the multiplexing efficiency. An analytical model is also developed in this paper and verified by simulation. Numerical examples are given to gain some insight into the protocol itself.     

Zero base budgeting for human service agencies

This paper describes the development of a zero base budgeting process as part of an integral planning-budgeting-control system relating client needs with service programs. Particular attention is focused on designing, gaining acceptance for and implementing a new budgeting system for the human services agencies of a rural county government. The relationship of the zero base budgeting process to the client case management and evaluation system are explored. Problems encountered in implementing the system and an evaluation of the results are discussed.     

Relationship between age and risk taking among managers.

Administered a short version of N. Kogan and M. Wallach's (see pa, vol. 39:6826) choice-dilemma test to 1,484 managers from over 200 companies. Results show a significant negative relationship between age and both risk taking and the value placed upon risk. The relationships were small in size when individual scores were correlated with age, but increased markedly when mean scores were used. Furthermore, the relationships were relatively stable across items and across companies. Developmental and sociocultural mechanisms that might underlie these findings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acoustic communication is better than none

The transmission of electromagnetic energy through seawater is so heavily attenuated that it is necessary to turn to acoustic energy to transmit information over any appreciable range of ocean. In the sea, the absorption of acoustic energy is several orders of magnitude less than that of electromagnetic waves. Still, this absorption constitutes a limitation on the bandwidth of the communication link. In addition, the upper and lower boundaries of the ocean, and the multipaths caused by them, distort the communication path and further reduce the usable bandwidth.     

The antisteroid action on the pineal gland

The study presents the data gathered along the years on the antisteroid action of the pineal gland. Thus, it was demonstrated that administration of pineal polypeptides to the rabbit lowers the urinary 17-KS both of testicular and adrenal origin. Conversely, pinealectomy caused an increase in the level of these steroid hormones. The same pineal material induced a marked decrease both in the serum and testicular testosterone and in the plasma and adrenal corticosterone in the rat. At the same time administration of pineal polypeptides lowered the cholesterol in the serum, bile, liver, testis and adrenal. Melatonin had no effect on these biochemical indices, which demonstrates that the effects obtained with pineal polypeptides are not mediated by melatonin.     

Gypsy moth mating disruption: Dosage effects

Small (1-hectare) plots in a dense gypsy moth (Lymantria dispar) infestation were treated with 5, 50, or 500 g racemic disparlure, and effects on male trap catch and mating behavior were studied. Capture of males in traps baited with 1, 10, 100, or 1000 g (+)-disparlure declined as disruptant dosages increased. Traps with high levels of attractant caught moths when capture in those with lower baitings was dramatically reduced. While all disruptant dosages reduced trap catch, it was reducd at least 95% at all attractant levels at the 500-g disruptant application rate. Visual estimates indicated that male moth density was similar in treated and control plots; female mating success was reduced 6.5, 34.5, and 84% in plots with 5, 50, and 500 g/ hectare disruptant, respectively. The duration of precopulatory and copulatory periods was similar for all females that were observed mating, regardless of disruptant treatment. It is proposed that reduced trap catch and female mating success are due to effects of atmospheric synthetic disparlure (disruptant) camouflaging natural attractant point sources.Lepidoptera: Lymantriidae.     

Ligands and receptors mediating signal transduction in sea urchin spermatozoa

Sea urchins have long been a model system for the study of fertilization. Much has been learned about how sea urchin sperm locate and fertilize the egg. Sperm and eggs are spawned simultaneously into the surrounding seawater. Sperm signaling pathways lead to downstream events that ensure fertilization. Upon spawning, sperm must acquire motility and then they must swim towards or respond to the egg in some way. Finally, they must undergo a terminal exocytotic event known as the acrosome reaction that allows the sperm to bind to the vitelline layer of the egg and then to fuse with the egg plasma membrane. Motility is stimulated by exposure to seawater, while later events are orchestrated by factors from the egg. The sperm signaling pathways are exquisitely tuned to bring the sperm to the egg, bind, and fuse the two cells as quickly as possible.