bluuebunny/crossref_metadata_2025 huggingface dataset:
System Design and Modeling of a Thermally Activated Reconfigurable Wing
Authors: Beblo Richard , Robertson Darrel , Joo James , Smyers Brian , Reich Gregory
Published: April 2011

Reconfigurable structures such as morphing aircraft generally require an on board energy source to function. Frictional heating during the high speed deployment of a blunt nosed low speed reconnaissance air vehicle can provide a large amount of thermal energy during a short period of time. This thermal energy can be collected, transferred, and utilized to reconfigure the deployable aircraft. Direct utilization of thermal energy has the ability to significantly decrease or eliminate the losses associated with converting thermal energy to other forms, such as electric. The following work attempts to describe possible system designs and components that can be utilized to transfer the thermal energy harvested at the nose of the aircraft during deployment to internal components for direct thermal actuation of a reconfigurable wing structure. A model of a loop heat pipe is presented and used to predict the time dependant transfer of energy. Previously reported thermal profiles of the nose of the aircraft calculated based on trajectory and mechanical analysis of the actuation mechanism are reviewed and combined with the model of the thermal transport system providing a system level feasibility investigation and design tool. The efficiency, implementation, benefits, and limitations of the direct use thermal system are discussed and compared with currently utilized systems.
The Low Frequency Characteristics of Dielectric Elastomer Acoustic Actuators
Authors: Moustgaard Allan J. , Jones Richard W. , Lassen Benny , Sarban Rahimullah
Published: April 2011

This contribution examines the low frequency acoustic characteristics of dielectric elastomer (DE) acoustic actuators. Both flat panel and tubular actuator geometries are investigated experimentally and compared in terms of sound level and total harmonic distortion (THD) for the frequency range of interest, 20–200 Hz. A number of operating factors are examined to determine their influence on the performance of the actuators. These include the use of a D.C. voltage bias signal as part of the applied voltage, pre-straining of the actuator and the use of a variety of mechanical bias’s on the flat panel acoustic actuator. The results provide insight into the appropriateness of the actuators for possible use as a low frequency loudspeaker for either music generation or noise cancelation purposes.
Nonlinear Aeroelastic Study of Bending Divergence
Authors: Thwapiah Ghalib Y. , Campanile L. Flavio
Published: April 2011

In the beginning of the history of aviation, aeroelastic static instabilities were a problem in operating monoplane aircraft. After being discovered, they have been systematically avoided by design, since they would have led to large deformations and structural failure. A new research trend (active aeroelasticity) reverts this approach and utilizes — instead of avoiding — static instabilities to realize wing morphing. Another modern research trend are compliant systems (i.e. structures designed to achieve large deformations within its elastic range). Joining those two trends lead to a novel class of airfoil structures (compliant, active aeroelastic wings) enables operating at and beyond aeroelastic instabilities. Such structures need a new modeling approach, which includes nonlinearities of structural and aerodynamic kind. In this paper, a non linear analysis of aeroelastic bending divergence (a phenomenon which concerns forward-swept wings) is presented, initially based on so-called low-fidelity models. Such models are to some extent inaccurate, but allow a good insight into the physical behavior of the phenomenon. Experimental tests of a compliant airfoil will then be presented, performed to investigate the trans-critical and post-critical response of the airfoil model and to validate the low fidelity models. At the end, high-fidelity modeling is approached, which makes use of computational numerical simulations methods (FEM, CFD, FSI). Selected results will be presented, which allow to predict the system response more accurately and to reproduce the wind tunnel test results more closely.
Fluidic Composite Tunable Vibration Isolators
Authors: Scarborough Lloyd H. , Rahn Christopher D. , Smith Edward C.
Published: April 2011

Coupling a Fluidic Flexible Matrix Composite (F2MC) to an air-pressurized fluid port produces a fundamentally new class of tunable vibration isolator. This device provides significant vibration reduction at an isolation frequency that can be tuned over a broad frequency range. The material properties and geometry of the F2MC element, as well as the port inertance, determine the isolation frequency. A unique feature of this device is that the port inertance depends on pressure so the isolation frequency can be adjusted by changing the air pressure. For constant port inertance, the isolation frequency is largely independent of the isolated mass so the device is robust to changes in load. A nonlinear model is developed to predict isolator length and port inertance. The model is linearized and the frequency response calculated. Experiments agree with theory, demonstrating a tunable isolation range from 9 Hz to 36 Hz and minimum transmitted force reductions of 90% at the isolation frequency.
Feasibility of Using Piezoelectric Probes to Measure Viscosity in Newtonian Fluids
Authors: Waxman Rachel , Erturun Ugur , Mossi Karla
Published: April 2011

Viscosity plays an important role in modeling fluid flow in different systems. In Newtonian fluids, viscosity is a constant, measureable property. Currently, viscosity is measured using viscometers that use an array of different techniques depending on the application. In this study, pre-stressed lead zirconate titanate (PZT) composites were used as probes to monitor changes in viscosity. The probes are used as an actuator-sensor pair: a voltage of 1Vrms will be applied to one probe, the actuator; the second probe, the sensor, receives a vibration wave and turns it into an output voltage. Measurements of gain and phase at different input signal frequencies are analyzed. The fluid-medium where the probes are tested consists of different glycerin-deionized water solutions. Results indicate that the frequency of peak phase shift can be correlated to fluid viscosity. This correlation is exponential with viscosity, with an R2 of 0.99. Results included viscosity values in the range of 0.8cP to 612cP. Possible applications for this type of sensor are numerous, and are both non-time-dependent (simple viscosity measurements of fluids), and time-dependent.
Multiphysics Modelling and Design of Shape Memory Alloy Wave Springs as Linear Actuators
Authors: Spaggiari Andrea , Dragoni Eugenio
Published: April 2011

This paper explores the merits of shape memory wave springs as powering elements of solid state actuators. Advantages and disadvantages of the wave construction in comparison to the traditional helical shape are presented and discussed by means of dimensionless functions. The main assets of the wave springs are the higher electrical resistance (leading to simpler electrical drives) and the lower cooling time (leading to enhanced working frequency). The wave geometry is also superior in purely mechanical terms to the helical counterpart when axial space is at a premium. A step-by-step design procedure is proposed, leading to the optimal wave spring meeting the multiphysics design specifications and constraints. A case study is finally reported, showing the application of shape memory wave springs to the design of a telescopic linear actuator.
Pareto Optimization Based Tradeoff Between the Controllable Damping Force and the Relative Displacement Sensing of a Self-Sensing Magnetorheological Damper
Authors: Wang Dai-Hua , Bai Xian-Xu
Published: April 2011

The theoretical analysis and the prototype testing of the integrated relative displacement self-sensing magnetorheological damper (IRDSMRD) indicate that the controllable damping performance and the relative displacement sensing performance influence each other. For the IRDSMRD with a constrained volume, in order to make the best compromise between the damping force and the IRDS performance (the linearity), a Pareto optimization principle based method, which optimizes the key structural parameters taking the linearity of the IRDS and the controllable damping performance of the IRDSMRD as the objective functions, is proposed and realized. The mathematical models that relate the linearity of the IRDS and the controllable damping performance of the developed IRDSMRD to the magnetomotive force and the key structural parameters are established by modeling and analyzing the magnetic circuit of the IRDSMRD. The key structure in the primary flux path of the IRDSMRD is analyzed and optimized using the finite element method with the software package Maxwell 2D. On these bases, the Pareto optimal curve, i.e. the Pareto front, representing the balance of the controllable damping and the linearity of the IRDS of the IRDSMRD is obtained by considering that the maximum input magnetomotive force is constant. The IRDSMRD with the optimized structural geometry is tested on the experimental setup based on the MTS 849 shock absorber test system and the real time simulation system. According to the research results, every point on the Pareto front is an optimal solution of the damping force and the linearity of the IRDS of the IRDSMRD. The optimal damping force of the IRDSMRD with a certain linearity of the IRDS can be determined on the Pareto front, and vice versa, for a specific application. The feasibility of the Pareto optimization principle based method is validated by the experimental results and the research results have a universal significance for making the tradeoff between the sensing performance and the actuation performance of the self-sensing actuators based on smart materials.
Active Twist Rotor for Wind Tunnel Investigations
Authors: Riemenschneider Johannes , Opitz Steffen , Schulz Martin , Plaßmeier Volker
Published: April 2011

This paper describes the design and manufacturing of active twist rotor blades for the use as secundary control of a helicopter main rotor. These blades have been developed at the DLR in Braunschweig, Germany over the last years. Special features of the blade are the capability to twist individual sections of the blade. It is planned to equip the blade so that the following test methods can be applied: strain gauges and SPR for deformations, optical measurements as a reference of the blade tip twist and pressure sensors in certain sections. I order to reduce the complexity of the blade/rotor shaft interface, blade integrated amplifiers for the strain gauge bridges have been developed and teste. Right now a set of six instrumented blades is being built, in order to test a four bladed rotor in a wind tunnel in 2012.
Structural Health Monitoring as an Enabler for Responsive Satellites: An Update
Authors: Doyle Derek , Reynolds Whitney , Arritt Brandon
Published: April 2011

The Air Force Research Laboratory/Space Vehicles Directorate (AFRL/RVSV) is developing Structural Health Monitoring (SHM) technologies in support of the Responsive Space (RS) initiative with plans for future capabilities on orbit to assist in overall awareness. Such technologies will significantly reduce the amount of time and effort required to assess a satellite’s structural surety without increasing system level risk associated with changed testing. Furthermore, successful implementation of multifunctional sensor capabilities may lead to savings in size, weight, and power (SWAP) allowing more options for technical performance. Although SHM development efforts abound, RS drives unique requirements on the development of these SHM systems; the biggest difference being that deviation from maintenance requires a technology driver. This paper describes several potential niches for SHM technology development efforts by AFRL, aimed at solving those technical issues unique to responsive space, as well as how an ideal SHM system could be implemented within various other processes including the potential for on-orbit performance.
Numerical Prediction of Effective Transformation Properties of Hybrid SMA-Ceramic Composites
Authors: Lester Brian , Chemisky Yves , Lagoudas Dimitris
Published: April 2011

Metal-ceramic composites are being increasingly explored in an effort to find new materials for use in extreme environments. Via functional grading of of the volume fraction of the constituant phases and other techniques, the material can be optimized to incorporate the mechanical properties of the metal phase with the thermal properties of the ceramic phase. To get further benefit of the metal phase, a new area being investigated is the incorporation of Shape Memory Alloys (SMAs). In order to predict the phase transformation features of an SMA embedded in a stiff ceramic matrix, a micromechanical approach is developed to find the effective phase diagram of the ceramic-SMA composite. From this analysis, other composite characteristics such as stress in each phase and the evolution of tranformation strain in the SMA can be determined in order to improve the design of such new composite materials.
Position and Force Control of an SMA Spring Based Differential Actuator
Authors: Hadi Alireza , Elahinia Mohammad , Yousefi-Koma Aghil , Moghadam Majid M. , Chapman Cory
Published: April 2011

Actuators as a major component of all mechanical systems require improving in size, power, noise and simplicity. In most presented actuators, there is no such feature of suitable positioning of load, variable stiffness/force and active shock damping simultaneously. Shape Memory Alloys (SMAs) can be a suitable choice for providing the above capabilities in the systems. Especially the spring type SMAs are less utilized in the developed SMA based systems. SMA springs in comparison to SMA wires may provide much more deflection although less force is produced through them. This property may tend to a more flexibility in the developed mechanisms. Additionally the actuator capability in controlling position and force is not presented in the works. In this paper, an actuator with one DOF utilizing SMA springs with the above features is considered. The actuator mechanism is based on the antagonistic application of SMA springs that provide faster actuation response and controllable stiffness. It is shown that such an actuator demonstrates a good positioning accuracy in addition to a higher level force and stiffness control capability. As a result, the mechanical systems with such actuator behave more flexible with less bodily damage while encountering environment.
Compact and Lightweight Hydraulic Actuation System for High Performance Millimeter Scale Robotic Applications: Modeling and Experiments
Authors: Solano Belen , Laloy Jean , Rotinat-Libersa Christine
Published: April 2011

In this work the design, modeling and testing of a compact and lightweight hydraulic actuation system is presented. Compared to similar compact actuators found in the literature, our system increases considerably the energy density while maintaining an equivalent force-to-volume ratio. An analytical model that is able to accurately predict the quasi-static behavior of the actuator has been developed and experimentally validated. Existing models in the literature are able to predict only one performance parameter at a time — either the force or the contraction — from the imposed pressure and the exteroceptive measurement of the other performance parameter. Contrary to those models, and also due to the design of our actuator, our analytical model predicts simultaneously both the force and the contraction by using the knowledge of two proprioceptive parameters of the fluid circuit (imposed volume and measurement of the pressure). The latter is particularly interesting, as it enables to precisely estimate the muscle behavior, only through the known parameters located at the fluid-transfer system, and not directly in the muscle, which is of crucial importance to simplify instrumentation and compactness of the actuation system. Three in-house fabricated muscles, with diameters down to 1.5 mm, have been tested with internal pressures up to 1.7 MPa. The experimental results showed in all cases a very good agreement with the predicted performances, thus validating the analytical model developed.
Investigation of Incident Lamb Wave Parameters on Detection of Composite Delamination
Authors: Jha Ratneshwar , Kim Inho , Widana-Gamage Dulip
Published: April 2011

A preliminary investigation of excitation signal parameters on the detection of delamination in composite plates is presented. Composite plates typical of aerospace applications are used and excitation is provided through integrated PZT actuator. A scanning laser vibrometer is used for recording structural responses. Experimental results at three frequencies (15, 18, and 20 kHz) and two pulse widths (3.5 and 5.5 cycles) show the significant effects of incident Lamb waves on damage signature. Numerical studies using a commercial finite element code (ABAQUS) show good correlation with experimental results with appropriate level of structural damping.
FEA of Fuel Sensors: Effect of Dynamics and Temperature on Solder Joints
Authors: Delaire J.-P. Gilles , Ivens Kirk M.
Published: April 2011

Purpose –To establish printed circuit board (PCB) solder fracture risk with and without a potting compound present. Design/methodology/approach – Non-linear material properties were established for FEA of interacting sensor components in two sensor configurations under thermal and dynamic loading. Findings – Solder joints showed a clear tendency to be the most-likely-to-fail part of the sensor under the given design conditions in both load cases both with and without potting. Originality/value – Calculations indicate the specific contribution that potting had to stress under each type of load and the relative risk of failure for the sensor components based on component tensile strength.
Domain Evolution of Herringbone Structures in Ferroelectric Single Crystals
Authors: Tsou N. T. , Huber J. E.
Published: April 2011

The microstructure of a ferroelectric single crystal is significantly affected by applied loads. Domains evolve through equilibrium states, following a route that minimizes the overall energy. The herringbone pattern is one of the most widely observed domain structures in ferroelectric crystals. In this work, the evolution of four types of herringbone pattern in the tetragonal crystal system is studied by using a variational method. These four herringbone patterns are periodic rank-2 laminates which satisfy compatibility across every domain wall. The unit cell of periodic structure dictates a set of domain walls whose positions may vary while maintaining the same topology. The model allows for a crystal with one type of herringbone domain pattern to switch to another pattern through “pivot states”. In this study, a domain evolution map showing all paths between the four types of rank-2 herringbone pattern and their pivot states is developed. Hysteresis loops such as those observed in ferroelectric single crystals subjected to variety of loads are reproduced.
Proper Othrogonal Decomposition of Collocated Signals for Detection of Damage in an Aircraft Propeller
Authors: Georgiou Ioannis
Published: April 2011

The powerful data-driven analysis furnished by the Proper Orthogonal Decomposition Transform (POD) reveals that ensembles of collocated acceleration signals associated with a sequence of point impulses applied over a backbone curve of a propeller are underlined by a high degree of spatiotemporal coherence, a fact reflecting Maxwell’s reciprocity principle. Thus collocated signals seem to furnish a true spatiotemporal sample of transient response to a point impulse of complex structures such as propellers. In view of this fact, three sensors are placed on an installed propeller to collect collocated signals at the blades and hub for damage detection. Preliminary results indicate that abnormality indicators present in the dominant POD mode of the ensembles of collocated signals are related directly to the presence of damage at the tip of a propeller blade.
Performance Metrics for Structural Composite Capacitiors
Authors: O’Brien Daniel J. , Baechle Daniel M. , Wetzel Eric D.
Published: April 2011

In previous efforts, structural composite capacitors were developed using off-the-shelf starting materials and conventional composites processing techniques [1]. Assuming a stiffness-driven design we showed that while these devices may not perform individual structural or energy storage functions as well as their conventional monofunctional counterparts, on a system level they perform these functions efficiently enough to save mass. In this work we examine the efficacy of these structural capacitors in saving mass for a strength-based design. We also consider the multifunctional performance assuming a stiffness-driven design in which the goal is to save overall system volume. Experiments and analysis show that the best-performing structural capacitors simultaneously reduce overall system mass and volume.
Writing for Non-scientists about Physics1
Authors: Hobson Art
Published: April 2011

Physicists should communicate their knowledge to the general public because, as the American Association for the Advancement of Science puts it, “without a scientifically literate population, the outlook for a better world is not promising.” This article discusses what I've learned about writing for non-scientists from working on my physics textbook for non-science college students,2 as well as from my hometown newspaper column and other writings.3 Lessons learned include tips for writing effective prose, do's and dont's when writing for non-scientists, choice of subject matter, being relevant to the needs of non-scientists, unifying one's book by using general themes, and the process of organizing and writing a textbook. Many of these lessons should be helpful in all scientific writing regardless of the target audience.
Studying Hooke's Law by Using a Pogo Stick
Authors: Silva Nicolás
Published: April 2011

Perhaps the pogo stick was little Robert Hooke's favorite childhood toy, consisting of a stiff spring inserted in a tube fixed at the upper end and connected to a moveable rod at the other. Hand grips and a foot rest are connected to the tube. The idea is to jump on it taking advantage of the force provided by the spring when it is compressed. Figure 1 shows a schematic of a pogo stick.
Adding Value to Force Diagrams: Representing Relative Force Magnitudes
Authors: Wendel Paul
Published: April 2011

Nearly all physics instructors recognize the instructional value of force diagrams, and this journal has published several collections of exercises to improve student skill in this area.1–4 Yet some instructors worry that too few students perceive the conceptual and problem-solving utility of force diagrams,4–6 and over recent years a rich variety of approaches has been proposed to add value to force diagrams. Suggestions include strategies for identifying candidate forces,6,7 emphasizing the distinction between “contact” and “noncontact” forces,5,8 and the use of computer-based tutorials.9,10 Instructors have suggested a variety of conventions for constructing force diagrams, including approaches to arrow placement and orientation2,11–13 and proposed notations for locating forces or marking action-reaction force pairs.8,11,14,15
Apparatus for demonstrating longitudinal wave pulses
Authors: Trikosko Walter L. , Callaway Thomas O.
Published: April 2011

For live classroom demonstrations there are a number of devices that have been used to simulate waves. Some are based upon a design produced by E. S. Ritchie & Sons1 and consist of rods and cams that are activated by turning a crank.2,3 These devices show what transverse and longitudinal waves look like, but they do not allow for the free manipulation of wave parameters and observations of the changes that take place. A simple device can be constructed using elastic bands and straws4 to demonstrate properties of transverse waves.
Finishing Well
Authors: Riendeau Diane
Published: April 2011

As we finish this publishing cycle, I'd like to thank all the readers who sent in video clips. If you have a YouTube clip that you use in class, please send the link and a brief description to driendeau@dist113.org.
Rattleback bet
Authors: Dail Steve
Published: April 2011

A neat twist to the “rattleback”1 or “celt” demonstration was revealed to me after a “bet” with one of my AP® Physics students.2 I asked the class to try to explain what is responsible for the spinning piece of plastic to suddenly reverse its direction of spin. Some thought about air friction, others discussed the offset center of gravity. There are many online sources with detailed explanations, as well as in TPT,3 so I will not try to explain it here, but I felt that friction between the rattleback and the table definitely played a major role in the explanation. My student disagreed. The next day my student showed up to class with a small container of Vaseline and declared, “We will settle this right now. Let's grease up a lab table and spin the rattleback and see what happens.” (I wish all my students were this curious!) First, we spun the rattleback several times on a clean table to see the interesting spin reversal. Then after applying a thin layer of Vaseline to the table, we spun the rattleback. Try it yourself (or email me) to see who won the bet!
Rapid Spread of a Bacterial Symbiont in an Invasive Whitefly Is Driven by Fitness Benefits and Female Bias
Authors: Himler Anna G. , Adachi-Hagimori Tetsuya , Bergen Jacqueline E. , Kozuch Amaranta , Kelly Suzanne E. , Tabashnik Bruce E. , Chiel Elad , Duckworth Victoria E. , Dennehy Timothy J. , Zchori-Fein Einat , Hunter Martha S.
Published: April 2011

A
Rickettsia
bacterium promotes its own geographical spread by manipulating its insect host’s sex ratio and fecundity.
Comment on “Calcareous Nannoplankton Response to Surface-Water Acidification Around Oceanic Anoxic Event 1a”
Authors: Gibbs Samantha J. , Robinson Stuart A. , Bown Paul R. , Jones Tom Dunkley , Henderiks Jorijntje
Published: April 2011

Erba
et al
. (Reports, 23 July 2010, p. 428) attributed calcareous nannofossil morphology and assemblage changes across Cretaceous Oceanic Anoxic Event 1a to the effects of surface ocean acidification. We argue that the quality of carbonate preservation in these sequences, the unsupported assumptions of the biotic response to acidity, and the absence of independent proxy estimates for ocean pH or atmospheric
p
CO
2
render this conclusion questionable.
Response to Comment on “Calcareous Nannoplankton Response to Surface-Water Acidification Around Oceanic Anoxic Event 1a”
Authors: Erba Elisabetta , Bottini Cinzia , Weissert Helmut J. , Keller Christina E.
Published: April 2011

Gibbs
et al
. question our reconstruction of surface- and deepwater acidification around Oceanic Anoxic Event 1a. We answer their criticisms to better substantiate our arguments and original conclusions. Contrary to their suggestion, preservation cannot explain the nannofossil changes we documented, which trace perturbations in the photic zone, including a substantial increase in partial pressure of CO
2
(
p
CO
2
) and an inferred decreased pH as derived from geochemical proxies.
Mekong Hydropower Development
Authors: Grumbine R. Edward , Xu Jianchu
Published: April 2011

Pending decisions may unleash lower Mekong dam construction, despite management challenges and troubling environmental and social impacts.
Venus’s Southern Polar Vortex Reveals Precessing Circulation
Authors: Luz D. , Berry D. L. , Piccioni G. , Drossart P. , Politi R. , Wilson C. F. , Erard S. , Nuccilli F.
Published: April 2011

Observations with the Venus Express Orbiter reveal complex polar atmospheric dynamics.
Orbital-Independent Superconducting Gaps in Iron Pnictides
Authors: Shimojima T. , Sakaguchi F. , Ishizaka K. , Ishida Y. , Kiss T. , Okawa M. , Togashi T. , Chen C.-T. , Watanabe S. , Arita M. , Shimada K. , Namatame H. , Taniguchi M. , Ohgushi K. , Kasahara S. , Terashima T. , Shibauchi T. , Matsuda Y. , Chainani A. , Shin S.
Published: April 2011

Bulk photoemission studies of iron pnictides suggest a role for orbital fluctuations in creating the superconducting state.
13
C NMR Guides Rational Design of Nanocatalysts via Chemisorption Evaluation in Liquid Phase
Authors: Tedsree Karaked , Chan Chun Wong Aaron , Jones Simon , Cuan Qian , Li Wei-Kun , Gong Xue-Qing , Tsang Shik Chi Edman
Published: April 2011

Nuclear magnetic resonance spectroscopy can reveal the strength of substrate interactions with heterogeneous catalysts.
Shooting for the Stars
Authors: Montgomery M. H.
Published: April 2011

Observations with the Kepler space telescope are revealing details of the internal structure of distant stars.
A Séance for Science
Radioactive
Marie and Pierre Curie: A Tale of Love and Fallout

by Lauren Redniss

HarperCollins, New York, 2010. 208 pp. $29.99. ISBN 9780061351327.
Authors: Shell Hanna Rose
Published: April 2011

Art by Redniss serves as a matrix for presenting episodes from the life and research of Marie Curie and interjections about radiation, its effects, and its uses.
A Call to Reorient Healthcare
Next Medicine
The Science and Civics of Health

by Walter M. Bortz II

Oxford University Press, Oxford, 2011. 265 pp. $34.95, £22.50. ISBN 9780195369687.
Authors: Krall Ronald L.
Published: April 2011

After diagnosing the problems afflicting healthcare in the United States, Bortz prescribes a remedy.
First Detection of Ozone Hole Recovery Claimed
Authors: Kerr Richard A.
Published: April 2011

Researchers have long projected that they will not glimpse the first signs that the Antarctic ozone hole is healing until well past 2020. But for the first time, a group of researchers claims they can already see the ozone hole slowly recovering.
Daring Experiment in Higher Education Opens Its Doors
Authors: Stone Richard
Published: April 2011

Last month saw the launch of the South University of Science and Technology of China, a bold challenge to the country's education system that enrolls high-flying students nominated not only for their grades but also for their creativity and passion for learning.
NSF Hits Ceiling on Graduate Fellowships
Authors: Mervis Jeffrey
Published: April 2011

The president's 2012 budget request suspends plans to triple the number of graduate research fellowships at the National Science Foundation.
Snapshots From the Meeting
Authors: Cho Adrian
Published: April 2011

Snapshots from the American Physical Society meeting include lowering the energy of a vibrating widget enough to achieve the least motion allowed by quantum mechanics—the so-called ground state of motion—and a network model that demonstrates that if 10% of the members of a group hold an unshakable conviction, their view will eventually win out.
Projecting prevalence by stage of care for prostate cancer and estimating future health service needs: protocol for a modelling study
Authors: Yu Xue Q , Smith David P , Clements Mark S , Patel Manish I , McHugh Bill , O'Connell Dianne L
Published: April 2011

Introduction

Current strategies for the management of prostate cancer are inadequate in Australia. We will, in this study, estimate current service needs and project the future needs for prostate cancer patients in Australia.

Methods and analysis

First, we will project the future prevalence of prostate cancer for 2010–2018 using data for 1972–2008 from the New South Wales (NSW) Central Cancer Registry. These projections, based on modelled incidence and survival estimates, will be estimated using PIAMOD (Prevalence, Incidence, Analysis MODel) software. Then the total prevalence will be decomposed into five stages of care: initial care, continued monitoring, recurrence, last year of life and long-term survivor. Finally, data from the NSW Prostate Cancer Care and Outcomes Study, including data on patterns of treatment and associated quality of life, will be used to estimate the type and amount of services that will be needed by prostate cancer patients in each stage of care. In addition, Central Cancer Registry episode data will be used to estimate transition rates from localised or locally advanced prostate cancer to metastatic disease. Medicare and Pharmaceutical Benefits data, linked with Prostate Cancer Care and Outcomes Study data, will be used to complement the Cancer Registry episode data. The methods developed will be applied Australia-wide to obtain national estimates of the future prevalence of prostate cancer for different stages of clinical care.

Ethics and dissemination

This study was approved by the NSW Population and Health Services Research Ethics Committee. Results of the study will be disseminated widely to different interest groups and organisations through a report, conference presentations and peer-reviewed articles.
Genetic control and identification of QTLs associated with visual quality traits of field pea (Pisum sativum L.)
Authors: Ubayasena Lasantha , Bett Kirstin , Tar’an Bunyamin , Warkentin Thomas
Published: April 2011

Visual quality of field pea (Pisum sativum L.) is one of the most important determinants of the market value of the harvested crop. Seed coat color, seed shape, and seed dimpling are the major components of visual seed quality of field pea and are considered as important breeding objectives. The objectives of this research were to study the genetics and to identify quantitative trait loci (QTLs) associated with seed coat color, seed shape, and seed dimpling of green and yellow field peas. Two recombinant inbred line populations (RILs) consisting of 120 and 90 lines of F5-derived F7 (F5:7) yellow pea (P. sativum ‘Alfetta’ × P. sativum ‘CDC Bronco’) and green pea (P. sativum ‘Orb’ × P. sativum ‘CDC Striker’), respectively, were evaluated over two years at two locations in Saskatchewan, Canada. Quantitative inheritance with polygenic control and transgressive segregation were observed for all visual quality traits studied. All 90 RILs of the green pea population and 92 selected RILs from the yellow pea population were screened using AFLP and SSR markers and two linkage maps were developed. Nine QTLs controlling yellow seed lightness, 3 for yellow seed greenness, 15 for seed shape, and 9 for seed dimpling were detected. Among them, five QTLs located on LG II, LG IV, and LG VII were consistent in at least two environments. The QTLs and their associated markers will be useful tools to assist pea breeding programs attempting to pyramid positive alleles for the traits.
Deicing salt scaling resistance of concrete incorporating fly ash and (or) silica fume: laboratory and field sidewalk test data
Authors: Bouzoubaâ N. , Bilodeau A. , Fournier B. , Hooton R.D. , Gagné R. , Jolin M.
Published: April 2011

Sidewalk sections were cast in fall 2002 with three concrete mixtures that consisted of a control concrete, a concrete mixture incorporating 25% fly ash, and a concrete mixture made with a ternary blended cement (fly ash and silica fume). The curing practices consisted of using curing compound and wet burlap. For each of the sidewalk sections, laboratory specimens were cast on site using the concrete from the same batch. Large slabs (1.2 m × 0.9 m) were also cast from which specimens could be cored and tested in the laboratory for compressive strength and deicing salt scaling resistance following the ASTM and the BNQ test procedures. The results were compared to the performance of the sidewalk sections after six winters of outdoor exposure. A similar study was completed on sidewalk sections cast in spring 2002; the objective of the present study being to confirm the results of the previous investigation, and to determine the effect of the time of casting on the scaling resistance of the concrete i.e., performance of sidewalks cast in spring versus that of sidewalks cast in fall. The field evaluation showed that all the concretes cast in fall scaled relatively more than those placed in spring. Both laboratory results and field evaluations have shown that the use of a curing compound increases the scaling resistance of all the concretes investigated. The results also confirmed the adequateness of the BNQ procedure to better evaluate the deicing salt scaling resistance of concrete made with supplementary cementing materials; however, monitoring the sidewalk sections for a longer period of time is still required to confirm the above observations.
The effectiveness of slow sand filters to treat Canadian rural prairie water
Authors: Gottinger Ann M. , McMartin Dena W. , Price Doug , Hanson Bruce
Published: April 2011

The following manuscript provides a technical review of slow sand filters (SSFs) as well as two case studies from the province of Saskatchewan, Canada in which an optimized technology has been successfully designed and implemented to produce high quality potable water for very small populations. Renewed interest in SSF systems for small communities has resulted in enhanced plant and filter design, improved operating procedures for increased efficiency and expanded range of acceptable raw water quality input and an overall low maintenance system design. Despite some limitations to the use of SSFs, recent design modifications and improvements for operation and maintenance of SSFs have expanded their application to a broader range of contaminants under highly variable environmental and operating conditions. The flexible and modular design options inherent to SSF systems, along with the modifications in expanded application, make SSFs highly attractive for potable water treatment in rural and remote regions. The SSFs designed and tested in Saskatchewan are modular polyethylene systems that include pre- and posttreatment processes such as ozone oxidation, roughing, and biological activated carbon (BAC) filters to provide significant reductions in turbidity, heavy metals, colour, and organics.
The influence of forest certification on environmental performance: an analysis of certified companies in the province of Quebec (Canada)
Authors: Roberge Amélie , Bouthillier Luc , Boiral Olivier
Published: April 2011

Forest certification is becoming increasingly important in modern forestry. The number of companies that use certification as a marketing tool increases every year. Despite this growing popularity, the influence of certification on the environmental performance of certified companies is still unclear. Thus, the objective of this study was to investigate the relationship between the environmental performance of companies and their participation in a forest certification process. A qualitative approach was used to establish this relationship. Analysis shows that it is difficult to clearly define improvement in environmental performance. Nevertheless, participants in this study believe that becoming certified had a positive influence on their company. Results also show that changes brought by certification vary by standard. It was also shown that forest certification can provide credibility and competiveness to certified companies.
Connectivity among populations of pygmy whitefish (Prosopium coulterii) in northwestern North America inferred from microsatellite DNA analyses
Authors: Taylor E.B. , Gow J.L. , Witt J. , Zemlak R.
Published: April 2011

We studied microsatellite DNA variation in 15 populations of northwestern North American pygmy whitefish ( Prosopium coulterii (Eigenmann and Eigenmann, 1892)), an enigmatic freshwater fish thought to be highly fragmented by residency in deep, cold postglacial lakes. Population subdivision (θ) across 10 loci was 0.12 (P < 0.001) across samples, but one western Alaskan population was more divergent than all others (θ = 0.31–0.41, P < 0.001). Within the Williston Reservoir watershed (WRW), θ averaged 0.08 (P < 0.001) and was positively associated with both the geographic distance between localities (r2= 0.36, P < 0.001) and the number of branch points interconnecting them (r2= 0.33, P < 0.001). Differentiation among populations was modeled as the sum of the genetic distances for the stream sections interconnecting them (r2= 0.74). Differences among subwatersheds with the WRW accounted for 5.1% of the total variation in allele frequencies (P < 0.001). Assignment tests suggested limited movement among lakes, with most inferred dispersal between adjacent watersheds. Coalescent analysis strongly supported a gene flow–drift equilibrium model of population structure over a drift-only model. Effective management of diversity in pygmy whitefish requires the maintenance of stream networks that interconnect lakes within a watershed.
Diet–tissue discrimination factors of carbon and nitrogen stable isotopes in blood of Snowy Owl (Bubo scandiacus)
Authors: Therrien J.-F. , Fitzgerald G. , Gauthier G. , Bêty J.
Published: April 2011

Analysis of carbon (13C/12C) and nitrogen (15N/14N) stable isotope ratios (hereafter δ13C and δ15N, respectively) in animal tissues is a powerful tool in food-web studies. However, isotopic ratios of prey are not transmitted directly to a consumer, as a diet–tissue discrimination factor (denoted Δ) occurs between sources and consumer’s tissues. An accurate assessment of the diet of a consumer with stable isotopes thus requires that the Δ13C and Δ15N of the studied species are known. Our aim was to establish Δ13C and Δ15N values in the Snowy Owl ( Bubo scandiacus (L., 1758)). Moreover, we assessed the potential effect of ethanol preservation of blood samples on δ13C and δ15N values. We kept four captive adult Snowy Owls on a pure diet of mice for ≥6 weeks. We then collected mouse muscle and blood samples from the owls and analyzed their δ13C and δ15N values. Δ13C and Δ15N values (mean ± SE) for owl blood were +0.3‰ ± 0.2‰ and +1.9‰ ± 0.1‰, respectively. These values are the first discrimination factors ever reported in Strigiformes and are lower, for Δ15N, than those obtained in terrestrial carnivores and other bird species, including falcons. Preservation in ethanol did not significantly affect δ13C and δ15N values.
A MODEL FOR THE LONG-TERM OPTIMAL CAPACITY LEVEL OF AN INVESTMENT PROJECT
Authors: LØKKA ARNE , ZERVOS MIHAIL
Published: April 2011

We consider an investment project that produces a single commodity. The project's operation yields payoff at a rate that depends on the project's installed capacity level and on an underlying economic indicator such as the output commodity's price or demand, which we model by an ergodic, one-dimensional Itô diffusion. The project's capacity level can be increased dynamically over time. The objective is to determine a capacity expansion strategy that maximizes the ergodic or long-term average payoff resulting from the project's management. We prove that it is optimal to increase the project's capacity level to a certain value and then take no further actions. The optimal capacity level depends on both the long-term average and the volatility of the underlying diffusion.
A NON-HOMOGENEOUS SEMI-MARKOV REWARD MODEL FOR THE CREDIT SPREAD COMPUTATION
Authors: D'AMICO GUGLIELMO , JANSSEN JACQUES , MANCA RAIMONDO
Published: April 2011

In this paper, we present a model to describe the evolution of the yield spread by considering the rating evaluation as the determinant of credit spreads. The underlying rating migration process is assumed to be a non-homogeneous discrete time semi-Markov process. We calculate the total sum of mean basis points paid within any given time interval. From this information we show how it is possible to extract the time evolution of expected interest rates and discount factors.
STATIC HEDGING OF DEFAULTABLE CONTINGENT CLAIMS: A SIMPLE HEDGING SCHEME ACROSS EQUITY AND CREDIT MARKETS
Authors: OHSAKI SHUICHI , YAMAZAKI AKIRA
Published: April 2011

This paper proposes a simple scheme for static hedging of defaultable contingent claims. It generalizes the techniques developed by Carr and Chou (1997), Carr and Madan (1998), and Takahashi and Yamazaki (2009a) to credit-equity models. Our scheme provides a hedging strategy across credit and equity markets, where suitable defaultable contingent claims are accurately replicated by a feasible number of plain vanilla equity options. Another point is that shorter maturity options are available to hedge longer maturity defaultable contingent claims. Through numerical examples, it is shown that the scheme is applicable to both structural and intensity-based models.
CHANGES OF RIPPLE MORPHOLOGY OF CLEAVED Si SURFACE BY LOW-ENERGY Ar+ ION BEAM SPUTTERING
Authors: PAHLOVY S. A. , MAHMUD S. F. , YANAGIMOTO K. , MIYAMOTO I.
Published: April 2011

We have investigated the changes of ripple morphology of an atomically flat cleaved Si surface due to Ar+ ion bombardment. The cleaved atomically flat and smooth plane of Si wafer was obtained by cutting vertically against the orientation flat of a Si (100) wafer. Then, the cleaved surface was bombarded by 1 keV Ar+ ion beam at ion incidence angle of 0°, 50°, 60°, 70°, and 80°. The ripples structure were depends on ion dose and angle formed on atomically flat surface at ion incidence angle of 50°, 60°, 70°, and 80°. Ripples were unclear and small at ion doses of 1.0 × 1018 ions/cm2 but pronounced at ion dose of 8.0 × 1018 ions/cm2. The wave lengths of ripples were measured and the maximum wave length is 425 nm at ion incidence angle of 70° and ion dose of 8.0 × 1018 ions/cm2. Results show that the wave length of ripple depends on ion doses and angle of ion incidence. It was also observed that the wave vector of ripple changes with changing the angle of ion incidence. This research is concluded by discussing the wave vector changing mechanism with the help of BH model.
SYNTHESIS OF PbS NANOCRYSTAL/FUNCTIONALIZED CONDUCTING POLYMERS FOR PLASTIC SOLAR CELLS
Authors: ZHOU M. , WANG B. , JIANG X. , ZAKHIDOV A. A. , FERRARIS J. P. , AZUNSKIS D. , HANLEY L.
Published: April 2011

Lead-based nanocrystals (NCs) are promising materials for high-efficiency solar cells since they are able to generate multiexcitons with high efficiency. One complication of utilizing these NCs is the insulating ligands capping their surfaces. In this paper, we have successfully developed and characterized a phosphonate-functionalized poly-3-hexylthiophene (POP3HT-50) and used it in the direct synthesis of PbS NCs within the polymeric host matrix without extraneous ligands. Devices made of POP3HT-50/PbS nanocomposites show an order of magnitude improvement in η when compared to that reported for a P3HT/ PbS device (η = 0.011% versus 0.001%). The improved performance is consistent with better electronic contact between PbS NCs and POP3HT-50.
IMPACT OF CULLING STRAY DOGS AND VACCINATION ON THE CONTROL OF HUMAN RABIES: A MATHEMATICAL MODELING APPROACH
Authors: BHUNU C. P.
Published: April 2011

Human rabies cases are not declining in Africa and Asia even though possible interventions are available. A mathematical model for the transmission dynamics of rabies is presented and analyzed in the presence of intervention strategies (culling, dog vaccinations, pre- and post-exposure vaccinations for humans). The reproduction number is computed and rigorously analyzed. Analytical results suggest that the key to rabies control lies in good animal control and seeking medical advice early, once exposed to a dog bite. Numerical simulations support analytical results obtained. We conclude that the post-exposure prophylaxis might be the best possible way to control rabies in developing nations if it can be made easily accessible to those in need. However, due to costs of vaccines which are beyond the reach of many people in developing nations, it may be best to come up with better animal control strategies to control the spread of rabies.