Moisture-triggered physically transient electronics

Physically transient electronics, a form of electronics that can physically disappear in a controllable manner, is very promising for emerging applications. Most of the transient processes reported so far only occur in aqueous solutions or biofluids, offering limited control over the triggering and degradation processes. We report novel moisture-triggered physically transient electronics, which exempt the needs of resorption solutions and can completely disappear within well-controlled time frames. The triggered transient process starts with the hydrolysis of the polyanhydride substrate in the presence of trace amounts of moisture in the air, a process that can generate products of corrosive organic acids to digest various inorganic electronic materials and components. Polyanhydride is the only example of polymer that undergoes surface erosion, a distinct feature that enables stable operation of the functional devices over a predefined time frame. Clear advantages of this novel triggered transience mode include that the lifetime of the devices can be precisely controlled by varying the moisture levels and changing the composition of the polymer substrate. The transience time scale can be tuned from days to weeks. Various transient devices, ranging from passive electronics (such as antenna, resistor, and capacitor) to active electronics ( such as transistor, diodes, optoelectronics, and memories), and an integrated system as a platform demonstration have been developed to illustrate the concept and verify the feasibility of this design strategy

Knowledge, attitude and perception on radiation imaging among children's caregivers in the pediatric dental clinic

OBJECTIVE: Nuclear medicine provides important clinical information for diagnostic and therapeutic purposes. Use of medical imaging has gradually increased in the United States and this has raised health concerns about the potential future risks associated with radiation exposure in children. While studies have evaluated the adverse effects of imaging procedures, there is insufficient evidence about communicating radiation risks. The overall purpose of this paper is to review radiation risks in pediatric imaging using published evidence by the World Health Organization and to evaluate the knowledge and attitude of caregivers towards radiation risks in pediatric imaging. Specifically, we aim to determine whether an educational brochure improves parental knowledge of radiation and/or changes in attitude and perception to allow their children to undergo dental radiographs. METHODS: A prospective sample survey was performed of caregivers who presented with their child to the Boston University Pediatric Oral Healthcare Center. Parents or legal guardians (18 years or older) who accompanied a child were eligible for inclusion and approached for enrollment. Pre- and post-survey questionnaires were used to evaluate parents’ or guardians’ level of knowledge and attitude about the risks and benefits of dental radiographs. Parents were also asked their comfort level to allow their child to undergo dental radiographs. After completing the pre-survey questionnaire, parents were asked to read the English-language informational handout. Statistical analysis was performed through Microsoft Excel 2013. Descriptive analysis was conducted to summarize the survey responses. RESULTS: Among 30 parents who were surveyed, a small proportion (30%) of parents were very comfortable with dentist using dental radiographs on their child, versus 57% after reading the handout. Results showed that the informational handout improved the parental knowledge of risks and benefits of ionizing radiation. Most parents indicated that the handout was helpful and they reported increased level of comfort and willingness in their children receiving radiation imaging during dental treatment procedures. DISCUSSION: Educating parents or caregivers through an informational handout is a helpful resource in improving their knowledge and in relieving their concerns. Informing parents about the risks of ionizing radiation does not change parental willingness for their children to undergo dental radiographs

Origin of Extended Star Clusters

We have discovered new extended star clusters (ESCs) in a nearby dIrr galaxy NGC 6822. These clusters are the nearest sample of ESCs available to date. The key characteristic of ESCs is their large size compared to typical globular clusters even though the two cluster populations are rather similar in terms of other parameters, i.e., color and luminosity. Several scenarios have been suggested to explain the formation of ESCs. However, the currently known ESCs may be a mixture of populations with heterogeneous formation histories. Future observational and theoretical studies are expected to better constrain the origins of ESCs as well as to increase their sample size.Comment: 3 pages, 1 figure, conference proceeding (with updated references) for 'Stellar Clusters & Associations: A RIA Workshop on Gaia' held in Granada, Spain, May 23 - 27, 2011; 2011 Stellar Clusters and Associations, Conference..357

Conserved cosmological structures in the one-loop superstring effective action

A generic form of low-energy effective action of superstring theories with one-loop quantum correction is well known. Based on this action we derive the complete perturbation equations and general analytic solutions in the cosmological spacetime. Using the solutions we identify conserved quantities characterizing the perturbations: the amplitude of gravitational wave and the perturbed three-space curvature in the uniform-field gauge both in the large-scale limit, and the angular-momentum of rotational perturbation are conserved independently of changing gravity sector. Implications for calculating perturbation spectra generated in the inflation era based on the string action are presented.Comment: 5 pages, no figure, To appear in Phys. Rev.

Generalized slow-roll inflation

The slow-roll approximation to inflation is ultimately justified by the presence of inflationary attractors for the orbits of the solutions of the dynamical equations in phase space. There are many indications that the inflaton field couples nonminimally to the spacetime curvature: the existence of attractor points for inflation with nonminimal coupling is demonstrated, subject to a condition on the inflaton potential and the value of the coupling constant.Comment: 14 pages, LaTeX, some typos correcte