From Gd2O3suspension to nanocomposite: Synthesis, properties and radiation protection

This study provides details for the design, preparation of an environmentally friendly, clinically safe and lightweight radiation protective shield made ofGd2O3/epoxy nanocomposite (Gd-nanocomposite) which is proposed as an alternative to traditional toxic lead (Pb)-based aprons for diagnostic X-ray protection. In theory, this particulate nanocomposite can possess significant features of both inorganic particles and organic polymeric matrices. However, in practice, its performance does not simply depend on the sum of the individual contributions of characteristics of the constituent phases but on the interaction of their inner interfaces and the homogeneous dispersion of inorganic particles in the polymer matrix. The miniaturization of inorganic particles to nanoscale before mixing with an organic matrix has been considered as an effective way to improve the interface of the dispersion phase. Unfortunately, homogeneous dispersion has still not yet been achieved in this type of material due to the coalescence of nanoparticles resulting from the large surface area of nanoparticles and their chemical incompatibility with the matrix. The effect of inter-particle forces arising from adsorbed typical cationic and anionic surfactants on the morphology of the ball milled gadolinium oxide (Gd2O3) is investigated to attain the optimal conditions for interface improvement between Gd2O3 particles and an epoxy matrix. The experimental outcomes are interpreted in terms of the stabilization and interaction mechanisms of the fine washed Gd2O3 particles (size diameter \u3c1μm) in an aqueous medium under the variation of the surface forces arising from adsorbed surfactants. The point of zero charge or isoelectric point (IEP) of ball milled Gd2O3 particles suspension is at pH 11. In the presence of adsorbed anionic SDS (Sodium dodecyl sulphate), the particles are refined together with numerous 2D nanowire or nano-rod particles at pH ~ 8. In contrast, the coarser particles are found when cationic CTAB (Cetyl trimethylammonium bromide) is used to modify the Gd2O3 surface. This is invoked from organic shell formed by the high adsorbability of negatively charged heads of SDS into the bare positive charge density of the particle. This capping agent acts as (i) a steric barrier preventing the agglomeration or rewelding of the powder during nanoparticle preparation and (ii) an intermediate adhesive that enhances the miscibility of the particle and liquid matrix, thereby improving the particle dispersion in the organic matrix. VI Based on the above outcomes, an optimal geometric design of a non-lead based X-ray protective material with lightweight per volume unit is prepared. A plateau with 28-30% increments in the value of fracture toughness (KIC (Mpa.m1/2)) is observed with a specific addition of 0.08 to 0.1 volume fraction (ϕs) of SDS-encapsulated Gd2O3 particles in pure epoxy. The same quantity of particles also optimally raises the critical strain energy release rate (GIC (J.m-2)) and Young’s modulus (E (MPa)) of epoxy by approximately 22-24% and 18-25% respectively. A 16 mm thick sheet of fabricated filled composite at ϕs of 0.08 and 0.1 can shield greater than 95% (0.5 mm Pb-equivalence) and 99% (1 mm Pb-equivalence) respectively of a primary X-ray beam in the range of 60-120kVp. At the same X-ray attenuation (99% attenuation), the specimen is 7, 8.5, and 16 times lighter than wood, glass, and concrete respectively. At 0.5 mm Pb-equivalence, the composite also has 4.5-19.4% less weight per unit area than current commercial non-lead products

TARGET: Rapid Capture of Process Knowledge

TARGET (Task Analysis/Rule Generation Tool) represents a new breed of tool that blends graphical process flow modeling capabilities with the function of a top-down reporting facility. Since NASA personnel frequently perform tasks that are primarily procedural in nature, TARGET models mission or task procedures and generates hierarchical reports as part of the process capture and analysis effort. Historically, capturing knowledge has proven to be one of the greatest barriers to the development of intelligent systems. Current practice generally requires lengthy interactions between the expert whose knowledge is to be captured and the knowledge engineer whose responsibility is to acquire and represent the expert's knowledge in a useful form. Although much research has been devoted to the development of methodologies and computer software to aid in the capture and representation of some types of knowledge, procedural knowledge has received relatively little attention. In essence, TARGET is one of the first tools of its kind, commercial or institutional, that is designed to support this type of knowledge capture undertaking. This paper will describe the design and development of TARGET for the acquisition and representation of procedural knowledge. The strategies employed by TARGET to support use by knowledge engineers, subject matter experts, programmers and managers will be discussed. This discussion includes the method by which the tool employs its graphical user interface to generate a task hierarchy report. Next, the approach to generate production rules for incorporation in and development of a CLIPS based expert system will be elaborated. TARGET also permits experts to visually describe procedural tasks as a common medium for knowledge refinement by the expert community and knowledge engineer making knowledge consensus possible. The paper briefly touches on the verification and validation issues facing the CLIPS rule generation aspects of TARGET. A description of efforts to support TARGET's interoperability issues on PCs, Macintoshes and UNIX workstations concludes the paper

Draft Genome Sequence of an Enterococcus faecalis ATCC 19433 Siphovirus Isolated from Raw Domestic Sewage.

We previously isolated and characterized an Enterococcus faecalis ATCC 19433 siphovirus from raw domestic sewage as a viral indicator of human fecal pollution. Here, we report the draft genome sequence of this bacteriophage

System and method for transferring telemetry data between a ground station and a control center

Disclosed herein are systems, computer-implemented methods, and tangible computer-readable media for coordinating communications between a ground station, a control center, and a spacecraft. The method receives a call to a simple, unified application programmer interface implementing communications protocols related to outer space, when instruction relates to receiving a command at the control center for the ground station generate an abstract message by agreeing upon a format for each type of abstract message with the ground station and using a set of message definitions to configure the command in the agreed upon format, encode the abstract message to generate an encoded message, and transfer the encoded message to the ground station, and perform similar actions when the instruction relates to receiving a second command as a second encoded message at the ground station from the control center and when the determined instruction type relates to transmitting information to the control center

Pandemic and public health controls: toward an equitable compensation system

There is increasing global concern about the potential impact of pandemic infections, including influenza, SARS and bioterrorist attacks involving infectious diseases. Many countries have prepared plans for responding to a major pandemic. In Australia, the Federal and State pandemic plans include measures such as contact tracing, ensuring availability of antimicrobials, quarantine and social distancing. Many of these measures would involve severe restrictions on individual citizens and small businesses. Issues of compensation for cooperation and compliance with pandemic plans need to be addressed in policy discussion. The instrumental benefits of compensation in the event of a pandemic have not been sufficiently recognised. Greater attention paid now to mechanisms to compensate individual and business costs associated with compliance would increase trust in government pandemic plans, encourage compliance and reduce the health and economic impact of a pandemic

Agents in adversarial domains - modelling environments in parallel

We present a model of an environment to evaluate the behavior of an agent trying to hide from a pursuer is presented. The model computes the direction and the amount of protection provided by the environment. The computational complexity of this problem is improved by using a parallel implementation of this algorithm.<br /

Dynamic Interchanging Native States of Lymphotactin Examined by SNAPP-MS

The human chemokine lymphotactin (Ltn) is a remarkable protein that interconverts between two unrelated native state structures in the condensed phase. It is possible to shift the equilibrium toward either conformation with selected sequence substitutions. Previous results have shown that a disulfide-stabilized variant preferentially adopts the canonical chemokine fold (Ltn10), while a single amino acid change (W55D) favors the novel Ltn40 dimeric structure. Selective noncovalent adduct protein probing (SNAPP) is a recently developed method for examining solution phase protein structure. Herein, it is demonstrated that SNAPP can easily recognize and distinguish between the Ltn10 and Ltn40 states of lymphotactin in aqueous solution. The effects of organic denaturants, acid, and disulfide bond reduction and blocking were also examined using SNAPP for the CC3, W55D, and wild type proteins. Only disulfide reduction was shown to significantly perturb the protein, and resulted in considerably decreased adduct formation consistent with loss of tertiary/secondary structure. Cold denaturation experiments demonstrated that wild-type Ltn is the most temperature sensitive of the three proteins. Examination of the higher charge states in all experiments, which are presumed to represent transition state structures between Ltn-10 and Ltn-40, reveals increased 18C6 attachment relative to the more folded structures. This observation is consistent with increased competitive intramolecular hydrogen bonding, which may guide the transition. Experiments examining the gas phase structures revealed that all three proteins can be structurally distinguished in the gas phase. In addition, the gas phase experiments enabled identification of preferred adduct binding sites

Current situation analysis of the government invested project management

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