Note from the Series Editor. Foreword. Preface. Acknowledgments. Chapter 1: Introduction. 1.1 Electric Propulsion Background. 1.2 Electric Thruster Types. 1.3 Ion Thruster Geometry. 1.4 Hall Thruster Geometry. 1.5 Beam/Plume Characteristics. References. Chapter 2: Thruster Principles. 2.1 The Rocket Equation. 2.2 Force Transfer in Ion and Hall Thrusters. 2.3 Thrust. 2.4 Specific Impulse. 2.5 Thruster Efficiency. 2.6 Power Dissipation. 2.7 Neutral Densities and Ingestion in Electric Thrusters. References. Problems. Chapter 3: Basic Plasma Physics. 3.1 Introduction. 3.2 Maxwell's Equations. 3.3 Single Particle Motions. 3.4 particle Energies and Velocities. 3.5 Plasma as a Fluid. 3.6 Diffusion in Partially Ionized Gases. 3.7 Sheaths at the Boundaries of Plasmas. References. Problems. Chapter 4: Ion Thruster Plasma Generators. 4.1 Introduction. 4.2 Idealized Ion Thruster Plasma Generator. 4.3 DC Discharge Ion Thruster. 4.4 Kaufman Ion Thrusters. 4.5 rf Ion Thrusters. 4.6 Microwave Ion Thrusters. 4.7 2-D Computer Models of the Ion Thruster Discharge Chamber. References. Problems. Chapter 5: Ion Thruster Accelerator Grids. 5.1 Grid Configurations. 5.2 Ion Accelerator Basics. 5.3 Ion Optics. 5.4 Electron Backstreaming. 5.5 High-Voltage Considerations. 5.6 Ion Accelerator Grid Life. References. Problems. Chapter 6: Hollow Cathodes. 6.1 Introduction. 6.2 Cathode Configurations. 6.3 Thermionic Electron Emitter Characteristics. 6.4 Insert Region Plasma. 6.5 Orifice Region Plasma. 6.6 Hollow cathode Thermal Models. 6.7 Cathode Plume-Region Plasma. 6.8 Hollow Cathode Life. 6.9 Keeper Wear and Life. 6.10 Hollow Cathode Operation. References. Problems. Chapter 7: Hall Thrusters. 7.1 Introduction. 7.2 Thruster Operating Principles and Scaling. 7.3 Hall Thruster Performance Models. 7.4 Channel Physics and Numerical Modeling. 7.5 Hall Thruster Life. References. Problems. Chapter 8: Ion and Hall Thruster Plumes. 8.1 Introduction. 8.2 Plume Physics. 8.3 Plume Models. 8.4 Spacecraft Interactions. 8.5 Interactions with Payloads. References. Problems. Chapter 9: Flight Ion and Hall Thrusters. 9.1 Introduction. 9.2 Ion Thrusters. 9.3 Hall Thrusters. References. Appendices. A: Nomenclature. B: Gas Flow Unit Conversions and Cathode Pressure Estimates. C: Energy Loss by Electrons. D: Ionization and Excitation Cross Sections for Xenon. E: Ionization and Excitation Reaction Rates for Xenon in Maxwellian Plasmas. F: Electron Relaxation and Thermalization Times. G: Clausing Factor Monte Carlo Calculation. Index..

/pdf/fundamentals-of-electric-propulsion-ion-and-hall-thrusters-4zwus65dx4.pdf

Fundamentals of electric propulsion : ion and Hall thrusters

Electron transmission through molecules and molecular interfaces has been a subject of intensive research due to recent interest in electron-transfer phenomena underlying the operation of the scanning-tunneling microscope on one hand, and in the transmission properties of molecular bridges between conducting leads on the other. In these processes, the traditional molecular view of electron transfer between donor and acceptor species gives rise to a novel view of the molecule as a current-carrying conductor, and observables such as electron-transfer rates and yields are replaced by the conductivities, or more generally by current-voltage relationships, in molecular junctions. Such investigations of electrical junctions, in which single molecules or small molecular assemblies operate as conductors, constitute a major part of the active field of molecular electronics. In this article I review the current knowledge and understanding of this field, with particular emphasis on theoretical issues. Different approaches to computing the conduction properties of molecules and molecular assemblies are reviewed, and the relationships between them are discussed. Following a detailed discussion of static-junctions models, a review of our current understanding of the role played by inelastic processes, dephasing and thermal-relaxation effects is provided. The most important molecular environment for electron transfer and transmission is water, and our current theoretical understanding of electron transmission through water layers is reviewed. Finally, a brief discussion of overbarrier transmission, exemplified by photoemission through adsorbed molecular layers or low-energy electron transmission through such layers, is provided. Similarities and differences between the different systems studied are discussed.

http://atto.tau.ac.il/~nitzan/anrev-published.pdf

Electron transmission through molecules and molecular interfaces

A comparative study of protein adsorption on titanium oxide surfaces using in situ ellipsometry, optical waveguide lightmode spectroscopy, and quartz crystal microbalance/dissipation

Trapped ions are among the most promising systems for practical quantum computing (QC). The basic requirements for universal QC have all been demonstrated with ions, and quantum algorithms using few-ion-qubit systems have been implemented. We review the state of the field, covering the basics of how trapped ions are used for QC and their strengths and limitations as qubits. In addition, we discuss what is being done, and what may be required, to increase the scale of trapped ion quantum computers while mitigating decoherence and control errors. Finally, we explore the outlook for trapped-ion QC. In particular, we discuss near-term applications, considerations impacting the design of future systems of trapped ions, and experiments and demonstrations that may further inform these considerations.

Trapped-ion quantum computing: Progress and challenges

The connection between hydrogen-enhanced plasticity and the hydrogen-induced fracture mechanism and pathway is established through examination of the evolved microstructural state immediately beneath fracture surfaces including voids, “quasi-cleavage,” and intergranular surfaces. This leads to a new understanding of hydrogen embrittlement in which hydrogen-enhanced plasticity processes accelerate the evolution of the microstructure, which establishes not only local high concentrations of hydrogen but also a local stress state. Together, these factors establish the fracture mechanism and pathway.

/pdf/hydrogen-embrittlement-understood-22elkmqzna.pdf

Hydrogen Embrittlement Understood

A CO2-laser-based photoacoustic spectrometer was used to determine the temporal concentration profile of atmospheric ethene in Mexico City. Ethene measurements were conducted at the facilities of our institute, which is located in the north of the city and next to an avenue with heavy traffic density. Ambient air from outside our laboratory was continuously pumped into the spectrometer. This campaign was performed for 24 h a day, from November 24–30, 2001. The maximum ethene levels ranged between 26 and 81 ppbV. As expected, the lowest concentrations were monitored on weekends. These data were analyzed in combination with ozone and nitrogen oxides profiles, which were permanently monitored by an air-pollution-monitoring government network. Information on the seasonal variability of ethene was obtained by comparing the results of this campaign with data obtained in the winter of 2001. In general, the ethene concentration in November was about 30% higher than in February. On weekdays, the mean dose of human...

Atmospheric pollution profiles in Mexico City in two different seasons

This work proposes a feasible, reproducible, and low-cost modified method to manufacture chitosan, chitosan/IgG-protein-loaded, and trimethylated chitosan nanoparticles, using microfluidics combined with the microemulsion technique, which differs from the traditional batch process of chitosan-based nanoparticles. The synthesis process consists of generating microreactors of chitosan-based polymer in a poly-dimethylsiloxane ψ-shaped microfluidic device and then crosslinking with sodium tripolyphosphate outside the cell. Transmission electron microscopy demonstrates an improvement in size control and distribution of the solid-shape chitosan nanoparticles (~80 nm) compared to the batch synthesis. Regarding chitosan/IgG-protein-loaded nanoparticles, these presented a core-shell morphology having a diameter of close to 15 nm. Raman and X-ray photoelectron spectroscopies confirmed the ionic crosslinking between the amino groups of chitosan and the phosphate groups of sodium tripolyphosphate in the fabricated samples and the total encapsulation of IgG protein during the fabrication of chitosan/IgG-loaded nanoparticles. Then, an ionic crosslinking and nucleation-diffusion process of chitosan-sodium tripolyphosphate was carried out during the nanoparticle formation, with and without IgG protein loading. The use of N-trimethyl chloride chitosan nanoparticles in vitro on human-keratinocyte-derived cell line HaCaT did not show side effects independently of its concentration from 1 to 10 μg/mL. Therefore, the proposed materials could be used as potential carrier-delivery systems.

/pdf/chitosan-chitosan-igg-loaded-and-n-trimethyl-chitosan-q2jlbvo1.pdf

Chitosan, Chitosan/IgG-Loaded, and N-Trimethyl Chitosan Chloride Nanoparticles as Potential Adjuvant and Carrier-Delivery Systems

Bioinspired membranes as extracellular matrices are desired for skin regeneration. Herein, we fabricate four systems of fibrillar membranes composed of polycaprolactone (PCL), aminolyzed PCL, denatured collagen type I (C), and the blend of collagen hydrolysate types I and III (bC) or elastin (E), fabricated by the electrospinning process. The superficial features by SEM and optical profilometry, mechanical properties by puncture strength assays, and biological evaluation with a human keratinocyte cell line (HaCaT) for one day of aPCL6bCE (aPCL/collagen hydrolysate type I and III/Elastin), aPCL6CE (aPCL/denaturated Col I/elastin), aPCL6bC (aPCL/collagen hydrolysate type I and III), and PCL6bCE (PCL/collagen hydrolysate type I and III/Elastin) membranes are described. The aPCL6bCE and aPCL6CE fibers resulted in better structural properties for culturing cells, while aPCL6bC and PCL6bCE membranes have shown lower viability for keratinocytes, probably due to their different chemical surface and nanotopography. The roughness of these materials varied from 4.53 to 114.4 µm, depending on their diameter values. Puncture strength results were not significantly different within 2.25–2.66 MPa. Our results suggest that aPCL6bCE and aPCL6CE fibers have potential applications in skin tissue engineering, where the synergy among aminolyzed PCL and E seems to be a prerequisite to developing such activity.

Mechanical properties and Keratinocytes cellular evaluation of Polycaprolactone/Collagen/Elastin Electrospun Fiber Scaffolds

Cerium polymeric composites have novel applications in fuel cells, optical devices, gas sensors, catalysis, ultraviolet absorbers, hydrogen storage materials, and biomedicines. This study reports the fabrication of low-cost electrospun single and core-shell polyethylene oxide (PEO) doped with Cerium fibers fabricated in two moisture ambients. Scanning electron microscopy and atomic force microscopy revealed that obtaining the thinnest average fiber diameter requires 47-52 %RH and 2 % Cerium dopant. Using a PEO capping (shell fiber) allows the increment of Cerium in the inner matrix (core-fiber) to produce non-beading continuous fibers with 3.5% of the dopant. The undoped single or core-shell fibers presented a 52.7 to 54.2 % crystallinity, indecently of relative humidity used during the fabrication process. In contrast, the use of Cerium dopant up to 2% induces an increase in their crystallinity due to the formation of Ce-O species, enhancing their thermal properties, regardless of the moisture during manufacturing as was found with Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis.

/pdf/effect-of-ce3-on-the-morphology-composition-and-thermal-1d4sqy25.pdf

V. Altuzar

Papers

Atmospheric pollution profiles in Mexico City in two different seasons

Chitosan, Chitosan/IgG-Loaded, and N-Trimethyl Chitosan Chloride Nanoparticles as Potential Adjuvant and Carrier-Delivery Systems

Mechanical properties and Keratinocytes cellular evaluation of Polycaprolactone/Collagen/Elastin Electrospun Fiber Scaffolds

Effect of Ce3+ on the morphology, composition, and thermal properties of single and core-shell polyethylene oxide electrospun fibers