bluuebunny/crossref_metadata_2025 huggingface dataset:
Orbital Mechanics Fundamentals
Authors: Vallado David A.
Published: December 2010

Reviews basic statements of the equations of motion, including Kepler's and Newton's laws and the constants of orbital motion. Orbital elements are introduced and the two‐body problem is shown along with conic sections. These relations form the basis for astrodynamic applications and permit many useful studies to be accomplished. Perturbation theory and the major forces affecting satellite motion are discussed, along with the variability of those forces. Graphs are included to show the effect of perturbing forces on typical satellite orbits. The distinction is made between mean and osculating elements, fast and slow variables, and periodic forces. Discussion about the main problems in astrodynamics is included – orbit propagation and orbit estimation – along with definitions of analytical, numerical, and semianalytical propagation. The broad concept of orbit determination is introduced. Some relevant problems in astrodynamics are introduced noting the tie to propagation and orbit estimation. A summary concludes the remarks.
Mission Design and Trajectory Optimization
Authors: Ocampo Cesar A. , Byrnes Dennis V.
Published: December 2010

The fundamental concepts associated with designing spacecraft missions and optimizing trajectories with impulsive and/or finite thrust maneuvers are discussed. The description of ballistic motion for the central two‐body force field and a more realistic force field used in interplanetary mission design is presented. Basic orbital transfer maneuvers are discussed which form the basis for more complex transfers. The rocket equation is used to relate velocity impulses to propellent mass consumption and finite thrust maneuvers. The gravity assist maneuver is described to illustrate its use in the design of multi‐body trajectories. The state transition matrix and its applications to the trajectory design process is discussed. The trajectory design and optimization process is discussed in the context of solving nonlinear root finding or constrained optimization problems. A complex interplanetary trajectory problem is posed and solved to illustrate some of the concepts and ideas presented.
Missions to Dynamic Environments
Authors: Russell Ryan P.
Published: December 2010

From planets to planetary satellites to comets and asteroids, the solar system beyond the Earth's immediate environment is rich with potential targets for space science missions. The exploration of such exotic space destinations requires a deep understanding of their surrounding dynamic environments. In this chapter, a survey of the dominant perturbations in the dynamical environments of high priority targets is given in the context of the orbit mechanics and preliminary design techniques of past, present, and future missions. The chapter is organized around the three dominant non‐Keplerian perturbations and their respective roles in missions that target three general classes of celestial bodies. The dominant perturbations are non‐spherical gravity, third body gravity, and solar pressure radiation while the bodies are generally classified as planets, large planetary satellites, or small bodies consisting of comets, asteroids, and small planetary satellites. A main contribution is a mission design reference that quantifies the relative importance of these perturbations providing a quick calibration of the dynamic environments of potential target bodies. Mission classes and design techniques considered include low‐ and high‐altitude orbiters, grand tour trajectories, patched conics, gravity assisted flybys, Tisserand graphs, three‐body models, periodic orbits, orbit averaging, and stable/unstable manifold design.
Attitude Dynamics Fundamentals
Authors: Schaub Hanspeter
Published: December 2010

The rotational motion of a rigid body or system of rigid bodies is a fundamental field for the study of spacecraft pointing problems. This chapter presents the fundamental aspects of describing the orientation, angular momentum, energy and differential equations of motion of a rigid body. After discussing the rigid body kinematics, the inertia properties of a body about arbitrary reference points are developed. The angular momentum and energy of a rigid body are critical to discussing the equations of motion, as well as investigating the stability of torque‐free spin solutions. Next, passive methods of attitude stabilization are discussed. Here the spacecraft angular momentum, or external torques such as the gravity gradient torque, are used to stabilize the orientation. These fundamental kinematics and kinetics properties form the foundation for follow‐on chapters discussing more complex pointing scenarios including systems with multiple rigid bodies (reaction wheels, etc.), attitude estimation, as well active attitude pointing problems.
Sensors for Attitude Determination
Authors: Pittelkau Mark E.
Published: December 2010

The various types of attitude sensors and inertial sensors used on spacecraft are presented, including their principle of operation, how they are used, and what accuracy can be expected from the sensors. Attitude sensors include sun sensors, Earth horizon‐sensors, star trackers, and magnetometers. Intertial angular rate sensors include spinning mass gyros, dry‐tuned rotor units, hemispherical resonator gyros, ring‐laser gyros, interferometric fiber optic gyros, and angular displacement sensors.
Statistical Attitude Determination
Authors: Markley Francis Landis
Published: December 2010

Statistical attitude determination methods combine, in some optimal sense, the information included in a set of observations containing more than the minimum amount needed to determine a spacecraft's attitude uniquely. Single‐frame methods use observations made at a single point in time, a notable example being a set of unit vectors to stars imaged by a star tracker. The most widely employed single‐frame methods, such as the QUEST algorithm, satisfy an optimality criterion proposed by Wahba. Sequential methods, on the other hand, use spacecraft dynamics knowledge to combine the information from observations made over an extended period of time. Sequential methods generally provide more accurate attitude estimates than can be obtained by single‐frame methods, and are capable of providing estimates when insufficient information is available at a single time for single‐frame estimators to provide any solution at all. The most common sequential estimator is the extended Kalman filter, especially in the multiplicative form employing the quaternion representation of the attitude and a minimal three‐component representation of attitude errors.
Meteorology
Authors: Bedard Alfred. J.
Published: December 2010

This chapter reviews impacts on aircraft posed by a variety of atmospheric phenomena covering a large range of altitudes, scale sizes, and origins. Such weather hazards can be regional, long‐duration fields of turbulence or, on the other hand, concentrated, short‐duration microbursts. Accident statistics indicate the frequency and severities of encounters with various types of weather. A review of key weather features describes physical processes involved. Methods for prediction and warning discussed suggest hazard mitigation approaches and areas of need for further research.
Launch Environment
Authors: Aglietti Guglielmo S. , Richardson Guy , Quill Padraig.
Published: December 2010

The structural design of spacecraft is mainly driven by their necessity to survive the launch environment and, in mechanical terms, this consists of low frequency vibrations and steady accelerations, combined with random vibrations, acoustic loads, and shocks. The purpose of this chapter is therefore to describe sources and nature of the mechanical loading produced by the launch vehicle, and how these are translated into a “mechanical environment” that has to be withstood by the satellite. In particular, the typical requirements and specification imposed by the launch agencies are presented together with an overview of the test methods that are typically employed to insure compliance with these requirements.
Spacecraft End‐of‐Life Disposal
Authors: Ailor William
Published: December 2010

There is general recognition that space debris, non‐functioning human‐made objects in Earth orbit, will have long‐term effects on satellite operations. As a result, there are increasing calls for slowing the growth of the debris population by limiting debris released during normal satellite deployment and operations, minimizing on‐orbit explosions and breakups, preventing collisions of space objects, and disposing of space hardware at end‐of‐mission. This chapter discusses the latter option: disposing of hardware, both satellites and launch vehicle stages, at end of mission. Disposal options depend on the object's orbit: for example, objects in or passing through low earth orbits may be disposed by allowing orbits to naturally decay within a fixed time limit (hazards posed by debris surviving such reentries can eliminate this option), and objects in geosynchronous orbits should be moved to a disposal orbit several hundred kilometers above that region. This chapter describes the disposal options available for satellites and launch vehicle stages in each orbit regime. Related topics include: techniques for estimating the hazard posed by reentry of space hardware and designing space hardware to minimize reentry hazards, depletion of energy sources (passivation) prior to end‐of‐life to prevent on‐orbit explosions, and disposal techniques that may be available in the future, such as space tugs, electrodynamic and momentum exchange tethers, and drag‐enhancing devices to speed orbit decay.
Machining Aerospace Materials
Authors: Ridgway Keith , Turner Michael. S. , Sharman Adrian. R. C. , Hughes James , Chapman Tim , Durante Sergio
Published: December 2010

The aerospace industry is driving the use of advanced materials such as titanium and heat‐resistant nickel alloys and composites, and demand for large monolithic parts. The desirable properties of these materials also make them difficult to machine, presenting problems such as rapid tool wear and chatter. This chapter surveys the problems of machining these difficult‐to‐cut aerospace materials, with a focus on titanium alloys. Cutting theory is introduced, and common problems and their causes are explained. The mechanisms of tool wear and failure are examined. The chapter outlines machining strategies to avoid these problems, with consideration of a range of tool and cutting parameters.
Applied Aerodynamics and Propulsion Foundations – Fixed Wing Vehicles
Authors: van Tooren Michel , Rao Arvind G. , Obert Ed , van Buijtenen Jos
Published: December 2010

Aerodynamics and propulsion are probably the most important elements in aircraft design. While aerodynamics is mainly used to shape the aircraft such that it can fulfill all the mission requirements with minimum drag penalty, the aim of the propulsion system is to provide the required amount of thrust to the aircraft under all conditions. This chapter describes general considerations that are taken into account while designing the external shape of an aircraft and selecting the propulsion system for the aircraft. The basic physical phenomenal and the design variables and methods for aircraft design are described. The influence of the flight Mach number on the design variables has been explained. The various considerations involved in making the appropriate choice of the propulsion system are described, with more emphasis on gas turbine engines. The gas turbine system power and efficiencies have been mentioned. The various gas‐turbine‐based aircraft engine configurations have also been described.
Applied Aerodynamics and Propulsion Foundation Rotary Wing
Authors: van Holten Theo , Pavel Marilena D.
Published: December 2010

Rotary wing aerodynamics is a challenging subject because of the compound complexity of the flow passing through the rotor. The present chapter discusses the aerodynamics of hovering and forward flight. Basic theories such as actuator disc theory (momentum theory) and blade element theory are put into light. More detailed models for hover and forward flight including the prescribed wake models and free wake models are discussed qualitatively.
Fixed‐Wing Aircraft Performance
Authors: Ruijgrok Ger J.J. , Voskuijl Mark
Published: December 2010

This chapter deals with aircraft performance, that is, the capability of aircraft to execute certain maneuvers and to meet mission requirements. Aircraft performance is based on the study of the forces acting on an aircraft and the effects that these forces have on its flight path. The resulting motions are grouped into four main classes: (i) accelerated curved symmetric flight; (ii) steady straight symmetric flight; (iii) accelerated straight symmetric flight; and (iv) non‐symmetric flight. The basic forces are weight, thrust, and aerodynamic force (lift and drag). Additionally, in curved flight a centrifugal force appears. Presented are a few of the most important key performance measures of fixed‐wing aircraft together with approximate equations that have been used in aeronautics to assess such performance in the early design stage of an aircraft. Range and endurance expressions are derived and attention is given to the weight breakdown and payload‐range relationship for transport aircraft.
Performance of Rotary Wing Vehicles
Authors: Pavel Marilena D.
Published: December 2010

Rotary wing aircraft and especially helicopters are relatively slow machines that normally fly at altitudes below 3000 m. The continual advances in the fields of smart rotor design, lightweight structures and integrated flight management and avionics systems, alongside improvements of the fuselage aerodynamics and the advances recorded in engine efficiency have resulted in an incredible improvement of the performance of modern rotary wing configurations, compared with 20, 30, and 40 years ago. The present chapter reviews specific methods to calculate the helicopter performance and discusses key helicopter performance characteristics. The chapter includes issues related to both “classical performance” (i.e., how fast, how far, how high and with how much payload a rotorcraft can operate) and “environmental performance” (i.e., how easy and how comfortable it is to fly and maintain, how safe is the rotorcraft).
Materials, Structure, and Dynamics of Insect Wings as Bioinspiration forMAVs
Authors: Combes Stacey A.
Published: December 2010

Insect wings are complex, deformable structures that change shape dynamically during flight. Muscles are restricted to the wing base – thus, shape changes are largely passive, determined by the interaction between the wing's architecture and the aerodynamic and inertial forces associated with flapping flight. Because insect wing structure reflects numerous evolutionary trade‐offs and constraints, no single wing represents the “optimal” design for flight, but particular features may enhance certain aspects of flapping flight performance. Wings are primarily composed of tubular supporting veins and deformable membranes, with diverse material and structural properties. Venation pattern and planform shape vary widely, and wings display three‐dimensional corrugation, camber, and twist. Specialized features such as flexion lines, one‐way hinges, patches of rubber‐like protein, and inertial balancers contribute to patterns of wing deformation during flight. Spatial variation in mechanical properties and “smart” structures promote and control dynamic camber generation, transverse bending, and torsional waves. The effects of wing structure and dynamic shape changes on unsteady aerodynamic force production remain unknown, and their exploration requires the development of novel experimental tools.
MAV Guidance Inspired by Principles of Insect Vision
Authors: Srinivasan Mandyam V. , Thurrowgood Saul , Soccol Dean
Published: December 2010

The study of visually guided flight in insects is offering novel, computationally elegant solutions to challenges in machine vision and robot navigation. Insects are remarkably adept at seeing and perceiving the world and navigating in it, despite possessing a brain that weighs less than a milligram and carries fewer than 0.01% as many neurons as ours does. Although most insects lack stereo‐vision, they use a number of ingenious strategies for perceiving their world in three dimensions and navigating successfully in it. For example, distances to objects are gauged in terms of the apparent speeds of motion of the objects' images, rather than by using complex stereo mechanisms. Narrow gaps are negotiated by balancing the apparent speeds of the images in the two eyes. Flight speed is regulated by holding constant the average image velocity as seen by both eyes. Bees landing on a horizontal surface hold constant the image velocity of the surface as they approach it, thus automatically ensuring that flight speed is close to zero at touchdown. This chapter describes how some of the strategies described above are being used to design, implement, and test biologically inspired algorithms for the guidance of autonomous aerial vehicles.
Mechanics and Actuation for Flapping‐Wing Robotic Insects
Authors: Wood Robert J. , Whitney John P. , Finio Benjamin M.
Published: December 2010

Techniques for modeling, design, fabrication, and analysis of the mechanics and actuation for a flapping‐wing robotic insect are presented. Passive dynamics can be exploited to efficiently generate wing motions that closely resemble those of hovering insects. These microrobotic structures are enabled by high‐performance piezoelectric actuators and a novel method to produce layered composite flexure‐based articulated mechanisms. By careful design and fabrication, this Chapter concludes by demonstrating an insect‐inspired thoracic design that can asymmetrically modulate wing motions in order to generate controlled body torques.
Spacecraft Technologies: Satellite Reliability
Authors: Castet Jean‐Francois , Saleh Joseph H.
Published: December 2010

Reliability has long been recognized as a critical design attribute for space systems. Since physical access to these high‐value assets is difficult or impossible, maintenance cannot be relied upon to compensate for substandard reliability. It is therefore imperative to design high reliability into satellites. Statistical analysis of flight data, in particular of actual on‐orbit failure data, would provide particularly useful feedback to spacecraft designers. For example, such analysis can help guide satellite test and screening programs and provide an empirical basis for subsystem redundancy and reliability growth plans.

This chapter provides a nonparametric statistical analysis of satellite reliability. Parametric fits using a Weibull and mixture distributions are also provided and discussed. The relative contribution of each subsystem to the failure of satellites is quantified, and the “culprit” subsystems driving unreliability are identified.
Electromagnetic Hazard Vulnerability Verification
Authors: Wraight Anthony
Published: December 2010

The effects of electromagnetic (EM) hazards on aircraft have been understood since the early 1930s when early communication systems were affected by engine interference. Since then, the level of understanding of the issue has been developed significantly and, particularly with the introduction of fly‐by‐wire aircraft, the potential of significant aircraft failure as a result of EM hazards has increased. This chapter discusses the methods available for the assessment of aircraft vulnerability to EM hazards. Details are given on low‐ and high‐level techniques that provide an indication of the severity of the hazard with respect to the aircraft of interest and an indication of its vulnerability. This chapter also discusses the issues of applying these methods to large aircraft.
Product Lifecycle Engineering (
PLE
): An Application
Authors: Schrage Daniel P.
Published: December 2010

Product Lifecycle Engineering (PLE) is the application of Systems Design and Analysis (SDA) to the Systems Engineering (SE) activities during the various phases along a system/product lifecycle. SE is an interdisciplinary approach and means for enabling the realization and deployment of successful systems. Systems engineers deal with whole systems having many separate contributing components/parts. They rely on other engineers to design, analyze, and deliver the individual components/parts which together make up the whole system. The SE effort spans the whole system lifecycle. SE focuses on defining customer needs and required functionality early in the development cycle, documenting requirements, and then proceeding with design synthesis and system validation while considering the complete problem from cradle to grave. This chapter will address PLE during the critical transition from product development to production where necessary Integrated Design and Manufacturing (IDM) tradeoffs are made. The redesign of the wing of an F‐86 Strato Sabre Vintage Jet Fighter, as a case study example for IDM through Product Lifecycle Management (PLM), will be presented. A Georgia Tech Professional Education Certificate Program with a large aerospace company during 2008–2009 served as the basis for this case study example.
Computing Hardware Selection and Integration
Authors: Marshall Joseph R.
Published: December 2010

Today's modern aerospace systems utilize significant proportions of embedded computing hardware. The amount and complexity of this hardware and the embedded software that run on this hardware has increased significantly over the past decades in order to better sense the environments and control the aerospace systems to accomplish the missions the systems are developed to meet. This chapter explores the selection of computing hardware from architecture to integration. It documents how a computing hardware element is specified, how it is architected into multiple approaches, how one approach is selected as a baseline, how that baseline is designed, analyzed, prototyped, reviewed, and released to fabrication, and then brought up, integrated, and tested. The approach covers areas of concern from the smallest elements of computing hardware logic to systems of computing hardware, including any needed test equipment. The selection and integration of computing hardware documented in this chapter continues to increase in its importance and contribution to the success of today's and future aerospace missions.
Aircraft Fuel Systems
Authors: Langton Roy , Clark Chuck , Hewitt Martin , Richards Lonnie
Published: December 2010

Aircraft Fuel Systems covers all aspects of the subject from the refuel source to the delivery of fuel to the engine or engines for both commercial and military aircraft including:

The refuel/defuel process and associated fuel storage issues

All aspects of fuel handling, fuel transfer and fuel feed systems

Fuel measurement and management systems

Aerial refueling systems

Fuel properties and fuel system components

Design practices associated with the protection of fuel systems from electromagnetic, electrostatic and lighting strike hazards

Fuel tank inerting systems

In addition the book describes the design, development and certification process including program management, risk management and mitigation and the application of modern design support tools.

The penultimate chapter contains several real world examples of aircraft fuel systems and the book concludes with a discussion of new and future technologies.
Environmental Control Systems
Authors: Lawson Craig P.
Published: December 2010

An aircraft environmental control system is tasked with maintaining on‐board conditions suitable for equipment operation, and comfortable for vehicle occupants. This chapter covers systems in use today to provide environmental control on aircraft, with both open loop air cycle and closed loop vapor cycle systems described. The major environmental control system components and sub‐systems are then considered in more detail. This includes humidity and pressure control components and principles of operation, ozone conversion performance, filtration of recycled cabin air, cold air units (bootstrap machines) operation and design, and the use of heat exchangers. Oxygen provision systems are also considered in the form of liquid oxygen (LOX) systems and on‐board oxygen gas generation systems (OBOGGS). This chapter culminates by bring many of the aforementioned sub‐systems and components together to present and describe an environmental control system that is typical of that used on many aircraft presently in‐service.
Introduction and Overview
Authors: Seabridge Allan
Published: December 2010

The modern aircraft – the platform, the major systems and its crew – are designed as a tightly integrated system. In this context the vehicle systems have their own specific integration issues, but they cannot be designed without due regard to the rest of the aircraft systems. There are interactions between systems and there are inter‐dependencies that must be considered during the design of the total platform in order that its fitness for purpose can be demonstrated to the satisfaction of the customer or the certification authority.

There are sound reasons for achieving integrated systems or products. The end result is often smaller or lighter, cheaper to manufacture, and perceived by users as being “neater”, more compact, and more user friendly. However, this integration has the potential to lead to a lack of visibility of the behavior of the total system and a lack of understanding of the emergent properties that arise from integration of complex systems and a complex human–machine interface.

These systems can have a severe impact on the performance, testing, and qualification. In this chapter, a number of aspects of integration factors that affect the whole aircraft are examined to determine the potential threat to performance, safety, integrity, and qualification.
Modeling and Simulation
Authors: Diston Dominic J.
Published: December 2010

Modeling and Simulation (or M&S) encompasses a wide range of techniques for building representations of vehicles and systems and using them in order to predict/replicate behavior and performance. This chapter will provide a context for M&S and then summarize some of the mathematical modeling that is associated with air vehicles (covering principles of flight) and synthetic environment (covering the operational space within which vehicles are immersed). The brief discussion of vehicles will focus on the concepts of architecture, energy and force and will summarize the equations of motion. The synthetic environment will be limited to the essential aspects of a geospatial reference model (namely the shape and motion of the Earth), gravitation and atmosphere. Finally, there will be a brief discussion of simulation principles. The overall aim is to show the diversity of the subject matter as it is applied to real engineering.
Human Health Issues Caused by the Aircraft Environment
Authors: Seabridge Allan
Published: December 2010

This chapter considers the potential impact of the aircraft environment from the point of view of the systems engineer. The aircraft, as a system, is designed to be operated by humans and may carry people as occupants. The aircraft imposes upon its inhabitants various physical stimuli that may affect their physiology. The chapter is not intended to be diagnostic or definitive view; it cannot be because aircraft performance and legislation change periodically. The chapter does not include reference to damage to inhabitants as a result of accidents; it is concerned about those phenomena that are “normal” in the day‐to‐day operation of a complex mechanical machine. The chapter is intended as information for systems engineers to use as guidelines or the design of the aircraft as a system, and to ensure that the well‐being of aircrew, cabin crew, and passengers is taken into account to minimize the impact on their health and the aircraft is compliant with contemporary legislation.
Sensitivity Analysis
Authors: Kim Nam H.
Published: December 2010

Gradient‐based optimization algorithms require functions values and gradients of objective function and constraints. When an optimization problem has many design variables, calculating gradients is the most time‐consuming part in gradient‐based optimization algorithms. Since the gradient is the rate of change of a function with respect to change in design variables, the method of calculating gradients is often called sensitivity analysis. In this chapter, a brief overview of the most popular sensitivity analysis methods are presented: global finite difference method, discrete method, continuum method, and automatic differentiation method. The performance of each sensitivity analysis method is discussed in terms of accuracy, efficiency, and difficulty in implementation. The global finite difference method is the easiest to implement, but is expensive and its accuracy depends on the perturbation size. The discrete and continuum sensitivities are accurate and efficient, but they require a certain level of effort in implementation. The automatic differentiation method is accurate but requires a huge amount of initial effort in implementation. Several numerical examples are provided using analytical and numerical methods of calculating sensitivity information.
Living on the Moon
Authors: Thangavelu Madhu
Published: December 2010

Humans have long dreamt of exploring and settling the Moon. The visions of human space activity stemming from the first half of the 20th century culminated in the Apollo program landing two astronauts on the Moon in 1969, and until 1972, 12 astronauts had walked the Moon and performed scientific experiments. In the new millennium, several nations have begun precursory missions, orbiting a new generation of satellites and gleaning new information. Most recently, water has been discovered in the polar regions, setting the stage for lunar development and human settlement. This chapter provides a brief overview of past visions, present projects and technology developments, and some concepts and technologies for future permanent human settlements on our celestial neighbor.
Study of the Piezoelectric Power Generation of ZnO Nanowire Arrays Grown by Different Methods
Authors: Riaz Mohammed , Song Jinhui , Nur Omer , Wang Zhong Lin , Willander Magnus
Published: December 2010

The piezoelectric power generation from ZnO nanowire arrays grown on different substrates using different methods is investigated. ZnO nanowires were grown on n‐SiC and n‐Si substrates using both the high‐temperature vapor liquid solid (VLS) and the low‐temperature aqueous chemical growth (ACG) methods. A conductive atomic force microscope (AFM) is used in contact mode to deflect the ZnO nanowire arrays. No substrate effect was observed but the growth method, crystal quality, density, length, and diameter (aspect ratio) of the nanowires are found to affect the piezoelectric behavior. During the AFM scanning in contact mode without biasing voltage, the ZnO nanowire arrays grown by the VLS method produced higher and larger output voltage signal of 35 mV compared to those grown by the ACG method, which produce smaller output voltage signal of only 5 mV. The finite element (FE) method was used to investigate the output voltage for different aspect ratio of the ZnO nanowires. From the FE results it was found that the output voltage increases as the aspect ratio increases and starts to decreases above an aspect ratio of 80 for ZnO nanowires.
Fabrication of Multiscale Gradient Polymer Patterns by Direct Molding and Spatially Controlled Reflow
Authors: Chae Jae Joon , Lee Sung Hoon , Suh Kahp Y.
Published: December 2010

Size variations of pattern spacing as well as gradient control of the as‐formed polymeric pattern via a spatially controlled reflow process are presented. Micro‐ and nanopatterns of polymethyl methacrylate (PMMA) in the form of line‐and‐space strips are first generated by capillary force lithography (CFL), and the residual layers are removed by ashing process. Subsequently, the exposed PMMA strips underwent a controlled reflow process above the glass transition temperature (Tg) while heating single or both sides of the substrate either in parallel to the line pattern (parallel reflow) or perpendicular to the line pattern (perpendicular reflow). As a result of this controlled reflow, a linear or a parabolic profile of pattern spacing is achieved depending on the heating mode. Furthermore, multiscale gradient patterns are formed with the spacing ranging from 98 nm to 4.23 μm (a difference of two orders of magnitude) in a single patterned layer using the original micropattern of 16 μm width and 8 μm spacing. In order to explain reflow behaviors, a simple theoretical model relating the normalized pattern width to the polymer viscosity is derived based on a leveling kinetics of polymer melt. Also, gradient PMMA channels are fabricated and bonded to a glass substrate, which are used to flow a liquid inside the channels by capillarity‐driven flow.
Synthesis and Characterization of New Thieno[3,4‐c]pyrrole‐4,6‐dione Derivatives for Photovoltaic Applications
Authors: Najari Ahmed , Beaupré Serge , Berrouard Philippe , Zou Yingping , Pouliot Jean‐Rémi , Lepage‐Pérusse Charlotte , Leclerc Mario
Published: December 2010

A new class of low‐bandgap copolymers based on benzodithiophene (BDT) and thieno[3,4‐c]pyrrole‐4,6‐dione (TPD) units is reported. Chemical modifications of the conjugated backbone promote both high molecular weights and processability while allowing for tuning of the electronic properties. Copolymers with substituted thiophene spacers (alkyl chains facing the BDT unit) or unsubstituted thiophene spacers tend to have low power conversion efficiencies (PCE less than 1%) due to a bad morphology of the active layer, whereas copolymers with substituted thiophene spacers (alkyl chains facing TPD unit) show enhanced morphology and PCEs up to of 3.9%. Finally, BDT‐TPD copolymers without any thiophene spacers still show the best performances with power conversion efficiencies up to 5.2%.
Evaluation of Charge Mobility in Organic Materials: From Localized to Delocalized Descriptions at a First‐Principles Level
Authors: Shuai Zhigang , Wang Linjun , Li Qikai
Published: December 2010

The carrier mobility for carbon electronic materials is an important parameter for optoelectronics. We report here some recently developed theoretical tools to predict the mobility without any free parameters. Carrier scatterings with phonons and traps are the key factors in evaluating the mobility. We consider three major scattering regimes: i) where the molecular internal vibration severely induces charge self‐trapping and, thus, the hopping mechanism dominates; ii) where both intermolecular and intramolecular scatterings come to play roles, so the Holstein‐Peierls polaron model is applied; and, iii) where charge is well delocalized with coherence length comparable with acoustic phonon wavelength, so that a deformation potential approach is more appropriate. We develop computational methods at the first‐principles level for the three different cases that have extensive potential application in rationalizing material design.
Titanium/Palladium‐Mediated Regioselective Propargylation of Ketones using Propargylic Carbonates as Pronucleophiles
Authors: Millán Alba , de Cienfuegos Luis Álvarez , Martín‐Lasanta Ana , Campaña Araceli G. , Cuerva Juan M.
Published: December 2010

An efficient protocol for the synthesis of homopropargylic alcohols using propargylic carbonates as pronucleophiles is reported. The reaction is based on a combination of transition metal (palladium) and radical chemistry (titanium). The reaction takes place with an excellent regioselectivity and tolerates a great degree of substitution of the starting propargylic carbonate, thus being an interesting tool in the context of synthetic organic chemistry.
Lung diffusing capacity relates better to short‐term progression on HRCT abnormalities than spirometry in mild asbestosis
Authors: Nogueira Cristiano Rabelo , Nápolis Lara Maris , Bagatin Ericson , Terra‐Filho Mario , Müller Nestor L. , Silva C. Isabela S. , Rodrigues Reynaldo Tavares , Neder J. Alberto , Nery Luiz E.
Published: December 2010

Background

Pulmonary function tests (PFT), particularly spirometry and lung diffusing capacity for carbon monoxide (DLCO), have been considered useful methods for the detection of the progression of interstitial asbestos abnormalities as indicated by high‐resolution computed tomography (HRCT). However, it is currently unknown which of these two tests correlates best with anatomical changes over time.

Methods

In this study, we contrasted longitudinal changes (3–9 years follow‐up) in PFTs at rest and during exercise with interstitial abnormalities evaluated by HRCT in 63 ex‐workers with mild‐to‐moderate asbestosis.

Results

At baseline, patients presented with low‐grade asbestosis (Huuskonen classes I–II), and most PFT results were within the limits of normality. In the follow‐up, most subjects had normal spirometry, static lung volumes and arterial blood gases. In contrast, frequency of DLCO abnormalities almost doubled (P < 0.05). Twenty‐three (36.5%) subjects increased the interstitial marks on HRCT. These had significantly larger declines in DLCO compared to patients who remained stable (0.88 vs. 0.31 ml/min/mm Hg/year and 3.5 vs. 1.2%/year, respectively; P < 0.05). In contrast, no between‐group differences were found for the other functional tests, including spirometry (P > 0.05).

Conclusions

These data demonstrate that the functional consequences of progression of HRCT abnormalities in mild‐to‐moderate asbestosis are better reflected by decrements in DLCO than by spirometric changes. These results might have important practical implications for medico‐legal evaluation of this patient population. Am. J. Ind. Med. 54:185–193, 2011. © 2010 Wiley‐Liss, Inc.
“Sarcoid like” granulomatous pulmonary disease in World Trade Center disaster responders
Authors: Crowley Laura E. , Herbert Robin , Moline Jacqueline M. , Wallenstein Sylvan , Shukla Gauri , Schechter Clyde , Skloot Gwen S. , Udasin Iris , Luft Benjamin J. , Harrison Denise , Shapiro Moshe , Wong Karen , Sacks Henry S. , Landrigan Philip J. , Teirstein Alvin S.
Published: December 2010

Background

More than 20,000 responders have been examined through the World Trade Center (WTC) Medical Monitoring and Treatment Program since September 11, 2001. Studies on WTC firefighters have shown elevated rates of sarcoidosis. The main objective of this study was to report the incidence of “sarcoid like” granulomatous pulmonary disease in other WTC responders.

Methods

Cases of sarcoid like granulomatous pulmonary disease were identified by: patient self‐report, physician report and ICD‐9 codes. Each case was evaluated by three pulmonologists using the ACCESS criteria and only “definite” cases are reported.

Results

Thirty‐eight patients were classified as “definite” cases. Six‐year incidence was 192/100,000. The peak annual incidence of 54 per 100,000 person‐years occurred between 9/11/2003 and 9/11/2004. Incidence in black responders was nearly double that of white responders. Low FVC was the most common spirometric abnormality.

Conclusions

Sarcoid like granulomatous pulmonary disease is present among the WTC responders. While the incidence is lower than that reported among firefighters, it is higher than expected. Am. J. Ind. Med. 54:175–184, 2011. © 2010 Wiley‐Liss, Inc.
Synthesis and Anti‐Hepatitis B Virus Activity of a Novel Class of Thiazolylbenzimidazole Derivatives
Authors: Luo Yu , Yao Jia‐Ping , Yang Li , Feng Chun‐Lan , Tang Wei , Wang Gui‐Feng , Zuo Jian‐Pin , Lu Wei
Published: December 2010

Recently, heterocyclic benzimidazole derivatives have been investigated and validated as a promising class of antiviral agents. In this paper, a series of novel thiazolylbenzimidazole derivatives was synthesized and evaluated for their anti‐hepatitis B virus (HBV) activity and cytotoxicity on the HepG2.2.15 cell line. Afterwards, the preliminary structure–activity relationship (SAR) was discussed. Compound 8b, with IC50 = 1.1 µM and SI > 90.9, was the most promising compound and could be selected as a benchmark compound for further investigation.
Platinum Complexes with 5‐Methyl‐5(4‐pyridyl)hydantoin and Its 3‐Methyl Derivatives: Synthesis and Cytotoxic Activity – Quantitative Structure‐Activity Relationships
Authors: Bakalova Adriana , Varbanov Hristo , Buyukliev Rossen , Momekov Georgi , Ivanov Darvin , Doytchinova Irini
Published: December 2010

3,5‐Dimethyl‐5‐(4‐pyridyl)hydantoin (L) and its platinum(II) and platinum(IV) complexes with the general formula cis‐[PtL2X2] · n H2O and [PtL2Cl4], where XCl, I and n = 2‐4 were synthesized. A new Pt(IV) complex with 5‐methyl‐5‐(4‐pyridyl)hydantoin (L′) with the formula cis‐[Pt(L′)2Cl2(OH)2] · 5 H2O was also synthesized. The novel compounds were characterized by elemental analysis, IR, 1H‐, 13C‐, 195Pt‐NMR spectra and molar conductivity. The cytotoxic effects of these complexes were examined on three human tumor cell lines by MTT‐dye reduction assay. These four new Pt(II) and Pt(IV) complexes and a set of another twelve Pt(II), Pt(IV), and Pd(II) complexes previously synthesized and tested were compiled and a QSAR model was derived in order to direct the further rational synthesis.
Ibuprofen and Glutathione Conjugate as a Potential Therapeutic Agent for Treating Alzheimer's Disease
Authors: Pinnen Francesco , Sozio Piera , Cacciatore Ivana , Cornacchia Catia , Mollica Adriano , Iannitelli Antonio , D′Aurizio Eleonora , Cataldi Amelia , Zara Susi , Nasuti Cinzia , Di Stefano Antonio
Published: December 2010

Non‐steroidal anti‐inflammatory drugs (NSAIDs) and antioxidant therapy might protect against the development of Alzheimer's disease (AD). In the present work, we synthesized a molecular combination of glutathione (GSH) and ibuprofen (IBU) via an amide bond and investigated its potential for targeted delivery of the parent drugs to neurons, where cellular oxidative stress and inflammation are related to AD. Evaluation of its physicochemical and in‐vitro antioxidant properties indicated that compound 1 exhibits good stability toward human plasma enzymatic activity, and, like GSH, displays in‐vitro free radical scavenging activity in a time and concentration‐dependent manner. The new compound was also assessed by infusion in a rat model for Alzheimer's disease for its potential to antagonize the deleterious structural and cognitive effects of β‐amyloid(1‐40). In behavioral tests of long‐term spatial memory, animals treated with codrug 1 performed significantly better than those treated with β‐amyloid (Aβ) peptide. Histochemical findings confirmed the behavioral data, revealing that Aβ protein was less expressed in cerebral cortex treated with 1 than that treated with IBU. Taken together, the present findings suggest that conjugate 1 treatment may protect against the oxidative stress generated by reactive oxygen species (ROS) and the cognitive dysfunction induced by intracerebroventricular (i.c.v.) infusion of Aβ(1‐40) in rats, and thus that codrug 1 could prove useful as a tool for controlling AD induced cerebral amyloid deposits and behavioral deterioration.
Design, Synthesis and Structure–Activity Relationship of Functionalized Tetrahydro‐β‐carboline Derivatives as Novel PDE5 Inhibitors
Authors: Ahmed Nermin S. , Gary Bernard D. , Tinsley Hethar N. , Piazza Gary A. , Laufer Stefan , Abadi Ashraf H.
Published: December 2010

Starting from tadalafil as a template, a series of functionalized tetrahydro‐β‐carboline derivatives have been prepared and identified as novel potent and selective PDE5 inhibitors. Replacing the 3,4‐methylenedioxyphenyl at position 6 of tadalafil, together with elongation of the N2‐methyl substituent and manipulation of the stereochemical aspects of the two chiral carbons led to the identification of compound XXI, a highly potent PDE5 inhibitor (IC50 = 3 nM). Compound XXI was also highly selective for PDE5 versus PDE3B, PDE4B, and PDE11A, with a selectivity index of 52 and 235 towards PDE5 rather than PDE11 with both cAMP and cGMP as substrate, respectively.
Late‐Stage Diversification of Chiral N‐Heterocyclic‐Carbene Precatalysts for Enantioselective Homoenolate Additions
Authors: Zheng Pinguan , Gondo Chenaimwoyo A. , Bode Jeffrey W.
Published: December 2010

A library of chiral triazolium salts has been prepared by late‐state diversification of a triazolium amine salt. By utilizing a primary amine as a functional handle, a single triazolium salt can be transformed into a variety of chiral N‐heterocyclic carbene precatalysts. This approach makes the preparation of chiral N‐heterocyclic carbenes possible by a single‐step modification of a triazolium salt, rather than the usual need for multistep organic synthesis and challenging heterocycle formation for each member of a catalyst library. We have screened these catalysts for control of diastereo‐ and enantioselectivity in a γ‐lactam‐forming reaction between α,β‐unsaturated aldehydes and cyclic ketimines.
Synthesis of Chiral Biphenol‐Based Diphosphonite Ligands and Their Application in Palladium‐Catalyzed Intermolecular Asymmetric Allylic Amination Reactions
Authors: Shi Ce , Chien Chih‐Wei , Ojima Iwao
Published: December 2010

A library of new 2,2′‐bis(diphenylphosphinoyloxy)‐1,1′‐binaphthyl (binapo)‐type chiral diphosphonite ligands was designed and synthesized based on chiral 3,3′,5,5′,6,6′‐hexasubstituted biphenols. These bop ligands have exhibited excellent efficiency in a palladium‐catalyzed intermolecular allylic amination reaction, which provides a key intermediate for the total synthesis of Strychnos indole alkaloids with enantiopurities of up to 96 % ee.
Variants in several genomic regions associated with asperger disorder
Authors: Salyakina D. , Ma D.Q. , Jaworski J.M. , Konidari I. , Whitehead P.L. , Henson R. , Martinez D. , Robinson J.L. , Sacharow S. , Wright H.H. , Abramson R.K. , Gilbert J.R. , Cuccaro M.L. , Pericak‐Vance M.A.
Published: December 2010

Asperger disorder (ASP) is one of the autism spectrum disorders (ASD) and is differentiated from autism largely on the absence of clinically significant cognitive and language delays. Analysis of a homogenous subset of families with ASP may help to address the corresponding effect of genetic heterogeneity on identifying ASD genetic risk factors. To examine the hypothesis that common variation is important in ASD, we performed a genome‐wide association study (GWAS) in 124 ASP families in a discovery data set and 110 ASP families in a validation data set. We prioritized the top 100 association results from both cohorts by employing a ranking strategy. Novel regions on 5q21.1 (P = 9.7 × 10−7) and 15q22.1–q22.2 (P = 7.3 × 10−6) were our most significant findings in the combined data set. Three chromosomal regions showing association, 3p14.2 (P = 3.6 × 10−6), 3q25–26 (P = 6.0 × 10–5) and 3p23 (P = 3.3 × 10−4) overlapped linkage regions reported in Finnish ASP families, and eight association regions overlapped ASD linkage areas. Our findings suggest that ASP shares both ASD‐related genetic risk factors, as well as has genetic risk factors unique to the ASP phenotype.