Optimal subset-difference broadcast encryption with free riders

Cataloged from PDF version of article.Broadcast encryption (BE) deals with secure transmission of a message to a group of receivers such that only an authorized subset of receivers can decrypt the message. The transmission cost of a BE system can be reduced considerably if a limited number of free riders can be tolerated in the system. in this paper, we study the problem of how to optimally place a given number of free riders in a subset-difference (SD)-based BE system, which is currently the most efficient BE scheme in use and has also been incorporated in standards, and we propose a polynomial-time optimal placement algorithm and three more efficient heuristics for this problem. Simulation experiments show that SD-based BE schemes can benefit significantly from the proposed algorithms. (C) 2009 Elsevier Inc. All rights reserved

Effects of stress produced by adrenocorticotropin (ACTH) on lipid peroxidation and some antioxidants in vitamin C treated and nontreated chickens

The aim of this study was to examine the effects of vitamin C on malonaldehyde (MDA) and glutathione (GSH) concentrations, and superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity in chickens stressed by adrenocorticotropin (ACTH). Sixty Leghorn chickens (20 weeks old) were randomly allotted to a control and a vitamin C treated group. An isotonic sodium chloride solution was administrated intramuscularly for a period of five days to the control group at a dose of 2.5 mL per chicken per day, and the treatment group received a vitamin C solution (containing 250 mg vitamin C/2.5 mL) intramuscularly for five days. On the fifth day of the experiment the chickens in both groups received 50 IU ACTH intramuscularly. Three hours after ACTH application blood samples were collected to determine the concentrations of MDA and GSH, and activities of SOD and GSH-Px in the blood. The concentration of MDA in the control group increased compared to that in the vitamin C treated group. After the ACTH application the activity of SOD increased in both groups, thought significantly so in the vitamin C treated group. The GSH-Px activity did not differ significantly between the treatments after ACTH application. It was concluded that intramuscularly administrated vitamin C facilitated an adaptation against stress and decreased negative effects of stress in chickens. Keywords: ACTH, glutathione (GSH), Glutathione peroxidase (GSH-Px), Malonaldehyde (MDA), Superoxide dismutase (SOD), Vitamin C South African Journal of Animal Science Vol.33(3) 2003: 201-20

Assessment of material properties of gallium orthophosphate piezoelectric elements for development of phased array probes for continuous operation at 580 degrees C

In this paper, the thickness extension mode gallium orthophosphate single crystal elements were characterised using the impedance analyser. Impedance characteristics of piezoelectric elements were investigated at temperatures from 25°C up to 580°C at first and then at a constant temperature of 580°C for a period of 25 days. The resonant and anti-resonant frequencies extracted from the impedance characteristics, capacitance (measured at 1 kHz), density and dimensions of the gallium orthophosphate elements were used to calculate electromechanical, piezoelectric and elastic properties of these elements at high temperatures as a function of time. The tested gallium orthophosphate elements proved to possess very stable efficiency and sensing capability when subjected to high temperature. The results are very encouraging for proceeding with development of phased array probes using gallium orthophosphate, for inspection and condition monitoring of high temperature pipelines in power plants at a temperature up to 580°C

The Genetic Basis of Creativity and Ideational Fluency The Genetic Basis of Creativity and Ideational Fluency

Reuter, Roth, Holve, & Hennig (2006) described what they called the first candidate gene for creativity. This study replicated and extended their work for a more careful analysis of five candidate genes: Dopamine Transporter (DAT), Catechol-O-Methyltransferase (COMT), Dopamine Receptor D4 (DRD4), D2 Dopamine Receptor (DRD2), and Tryptophane Hydroxylase (TPH1). Participants were 147 college students who received a battery of tests of creative potential. Multivariate analyses of variance indicated that ideational fluency scores were significantly associated with several genes (DAT, COMT, DRD4, and TPH1). This was apparent in both verbal and figural fluency ideation scores, before and after controlling general intelligence. Yet fluency, alone, is not an adequate measure of creativity, and the index that is by far the most important part of creativity (i.e., originality) had a negligible relationship with the genes under investigation. Hence, in contrast to earlier research, the conclusion offered here is that there is a clear genetic basis for ideational fluency, but that fluency, alone, is not sufficient to predict or guarantee creative performance. Hence, at present, the genetic basis of creativity remains uncertain

Development of phased array probes to operate in time-of-flight diffraction configuration to continuously monitor defect growth in thermal power plants

A high temperature (HT) structural health monitoring system for pipes that utilises phased array (PA) probes in time-of-flight diffraction (TOFD) configuration to continuously monitor the defect growth over time is being developed, so that when the defect reaches a critical size the plant can be shut down and maintenance can take place before failure. The numerical models for PA/TOFD inspection technique in either symmetric or asymmetric pitch-catch configuration were developed using the CIVA simulation platform. The probe characteristics were selected and the ultrasonic beam profile was predicted for different points in the volume of interest i.e. the weld and the heat affected zone (HAZ). The probes positions and interspacing between the probes in emission and reception were also selected in order to achieve maximum inspection coverage. The PA probes use piezoelectric elements for generation and reception of ultrasound beam. Single crystal gallium orthophosphate (GaPO4) has been selected for impedance analysis as a candidate for application in the PA probes operating at HT. Impedance characteristics of GAPO4 elements were investigated up to 580°C and together with measured capacitance (at 1 kHz), density and dimensions of the GAPO4 elements used to calculate material properties of these elements at HT as a function of time. The calculated material properties were used to evaluate the developed PA on TOFD technique at HT using COMSOL simulation package. The simulated and experimental results are encouraging for proceeding with development of PA/TOFD probes using GaPO4, for inspection and condition monitoring of HT pipelines in power plants at temperatures up to 580°C.European Commission through the FP7 Programme (FP7-SME-2013-1) under the grant agreement no. 605267, iKnowHow Informatics, CeramTec, InnoTecUK, Brunel University, Enkon, Vermon, Tecnitest Ingenieros and INETEC

An ICT-Enabled Approach to Optimising the Reliability of Manual Ultrasonic Non-Destructive Testing

Manual Ultrasonic Testing (MUT) is the most cost effective NDT method for the in-situ inspection of aerospace structures, in particular composite structures. However, its defect detection reliability is low. Manual Ultrasonic Testing (MUT) reports may vary depending on the operator conducting the test. Its reliability is therefore greatly influenced by human factors. Nonetheless, MUT continues to play a key role in the NDT suite of techniques. Despite its simplicity, it often meets the required performance at a reduced cost. No mechanised system exists which is as dextrous as the human hand for moving a probe over complex shapes while also dynamically skewing the probe to achieve the maximum amplitude from a reflector. It is therefore worth looking at ways to improve the reliability of MUT

Development of low frequency high temperature ultrasonic transducers for in-service monitoring of pipework in power plants

In this paper, a low-frequency (20-100 kHz) long-range ultrasonic guided wave transducer for in-service structural health monitoring of high temperature pipework in power plants has been developed. The transducer is designed for continuous operation at a target temperature of 350 °C. This paper describes the methodology followed to develop and test the high temperature transducer. The method includes selection of the suitable piezoelectric material and characterisation of their high temperature properties for the desired thickness-shear mode of vibration to validate its performance at the target temperature. The assembly procedure established for manufacturing transducer is discussed. Ultrasonic performance of the developed transducer was examined and has demonstrated its application for in-service monitoring of pipework operating at the target temperature

High temperature gallium orthophosphate transducers for NDT and monitoring purposes in nuclear power plants

There is a need for ultrasonic transducers to operate at temperatures up to 580°C for NDT and monitoring purposes in nuclear power plants. One of the key aspects of designing such transducers using high temperature (HT) piezoelectric single crystal material gallium orthophosphate - GaPO4 has been studied: ultrasonic performance of this piezoelectric material at HT as a function of time. An experimental setup was used where two thickness extension mode GaPO4 plates operating at frequency of 2.17 MHz were bonded to a carbon steel block using HT silver adhesive and these were placed in an electric furnace. HT wiring led from the piezoelectric plates through an opening in the furnace outside to an ultrasonic testing device. The ultrasonic measurements show that GaPO4 works as a functional ultrasonic transducer generating and receiving ultrasound at the temperature of 580°C for 13 consecutive days when HT corrosion of carbon steel block occurred leading to failure of the experiment. From the aspect of HT operation of this piezoelectric material, the results are very encouraging for proceeding with development of ultrasonic transducers using GaPO4 for application in nuclear power plants

Impact of SARS-CoV-2 on training and mental well-being of surgical gynecological oncology trainees

Introduction: The SARS-CoV-2 global pandemic has caused a crisis disrupting health systems worldwide. While efforts are being made to determine the extent of the disruption, the impact on gynecological oncology trainees/training has not been explored. We conducted an international survey of the impact of SARS-CoV-2 on clinical practice, medical education, and mental well-being of surgical gynecological oncology trainees. Methods: In our cross-sectional study, a customized web-based survey was circulated to surgical gynecological oncology trainees from national/international organizations from May to November 2020. Validated questionnaires assessed mental well-being. The Wilcoxon rank-sum test and Fisher's exact test were used to analyse differences in means and proportions. Multiple linear regression was used to evaluate the effect of variables on psychological/mental well-being outcomes. Outcomes included clinical practice, medical education, anxiety and depression, distress, and mental well-being. Results: A total of 127 trainees from 34 countries responded. Of these, 52% (66/127) were from countries with national training programs (UK/USA/Netherlands/Canada/Australia) and 48% (61/127) from countries with no national training programs. Altogether, 28% (35/125) had suspected/confirmed COVID-19, 28% (35/125) experienced a fall in household income, 20% (18/90) were self-isolated from households, 45% (57/126) had to re-use personal protective equipment, and 22% (28/126) purchased their own. In total, 32.3% (41/127) of trainees (16.6% (11/66) from countries with a national training program vs 49.1% (30/61) from countries with no national training program, p=0.02) perceived they would require additional time to complete their training fellowship. The additional training time anticipated did not differ between trainees from countries with or without national training programs (p=0.11) or trainees at the beginning or end of their fellowship (p=0.12). Surgical exposure was reduced for 50% of trainees. Departmental teaching continued throughout the pandemic for 69% (87/126) of trainees, although at reduced frequency for 16.1% (14/87), and virtually for 88.5% (77/87). Trainees reporting adequate pastoral support (defined as allocation of a dedicated mentor/access to occupational health support services) had better mental well-being with lower levels of anxiety/depression (p=0.02) and distress (p<0.001). Trainees from countries with a national training program experienced higher levels of distress (p=0.01). Mean (SD) pre-pandemic mental well-being scores were significantly higher than post-pandemic scores (8.3 (1.6) vs 7 (1.8); p<0.01). Conclusion: SARS-CoV-2 has negatively impacted the surgical training, household income, and psychological/mental well-being of surgical gynecological oncology trainees. The overall clinical impact was worse for trainees in countries with no national training program than for those in countries with a national training program, although national training program trainees reported greater distress. COVID-19 sickness increased anxiety/depression. The recovery phase must focus on improving mental well-being and addressing lost training opportunities

Indiscriminate ingestion of entomopathogenic nematodes and their symbiotic bacteria by Aedes aegypti larvae: a novel strategy to control the vector of Chikungunya, dengue and yellow fever

Third and fourth instar larvae of Aedes aegypti actively ingested entomopathogenic nematodes (EPNs) and their symbiotic bacteria, resulting in larval mortality. All six EPN species evaluated in this study were pathogenic to Ae. aegypti but varied significantly in their virulence. Heterorhabditis bacteriophora and Steinernema carpocapsae were most virulent, H. megidis and S. kraussei showed the least virulence, whereas H. downesi and S. feltiae had intermediate virulence. Larval mortality was dose dependent for all EPN species. When using a dose of 100 infective juveniles (IJs) per larva, H. bacteriophora and S. carpocapsae caused 90%-100% mortality, whereas H. downesi and S. feltiae caused only 40%-60% mortality. Even when using 200 IJs/larva, H. megidis and S. kraussei caused a maximum of 30%-40% mortality. Some of the invasive EPNs were melanized, suggesting a strong humoral defense response by the Aedes larvae. The degree of melanization was quite variable; some EPNs were totally enveloped in a melanin sheath while others were partially coated with melanin. Melanization did not stop the EPN from multiplying and killing the Aedes larvae. IJs released from infected larvae would have the potential to infect healthy mosquito larvae. Also, both bacterial supernatant and bacterial cell suspension of Xenorhabdus nematophila caused >91% larval mortality after 48 h, whereas only the bacterial cell suspension of Photorhabdus laumondii was effective against the mosquito larvae. These data provides useful information on the potential use of EPNs and/or formulated bacterial cell suspensions in the control of the important urban and container-breeding mosquito, Ae. aegypti, and are a starting point for future simulated and actual field studies