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Introduction: Based on recent data, the indication for transcatheter aortic valve implantation (TAVI) is expanding to individuals at lower surgical risk, who are generally younger than subjects historically treated for severe aortic stenosis. Indeed, younger patients have traditionally been under-represented in current TAVI literature. The aim of the present study is to report about clinical features, procedural outcomes and mid-term outcomes of patients younger than 70 who underwent TAVI in a single high-volume center. Materials and methods: Consecutive patients younger than 70 years of age who underwent TAVI for severe, symptomatic aortic stenosis between 2007 and 2019 at a single, tertiary referral center have been included in this retrospective study. Procedural and mid-term outcomes were analyzed, comparing 1st generation with 2nd generation devices. Results: Between 2007 and 2019, 1740 TAVI procedures were performed in our center. Among these, one hundred twenty-nine (7.4%) patients were younger than 70 years at the time of the intervention and were included in the present analysis. Fifty-eight patients (45%) were implanted with a 1st generation prosthesis while seventy-one patients (55%) were implanted with a 2nd generation device. Reasons which lead to a transcatheter approach in this population were: previous CABG (27.9%); porcelain aorta (24%); severe left ventricular systolic dysfunction (21.7%); prior chest radiation (19.4%); severe lung disease (8.5%); hemodynamic instability (7.0%); advanced liver disease (4.6%) and active cancer (3.9%). Overall device success rate was 89%, with no differences among 1st and 2nd generation devices. Threeyears all-cause mortality was 34%, with no difference among the two groups. Low incidence of aortic-valve re-intervention was observed at mid-term follow-up (late valve re-intervention = 2.3%). Conclusions: TAVI in young patient with appropriate indication for intervention is a safe procedure, associated with low rate of

Background: Several studies have compared surface electrocardiographic changes following different self-expandable (SE) (Evolut (Medtronic, USA); Acurate (Boston Scientific, USA); Portico (Abbott, USA); and Allegra (NVT, Germany)) and balloon-expandable (BE) Sapien-3 (Edwards Lifesciences, USA) transcatheter heart valves. We aimed to compare these prosthesis with the novel Myval BE prosthesis (Meril Life, India). Methods: Academic European registry of consecutive patients with severe aortic stenosis who received any of the 6 aforementioned valves. Baseline, post-procedural, and discharge 12‐leads electrocardiograms (ECG) were centrally analyzed and compared. Results: A total of 1131 patients were included: 135 Myval (11.9%), 290 Sapien-3 (25.6%), 298 Evolut (26.3%), 180 Acurate (15.9%), 125 Portico (11.1%), and 103 Allegra (9.1%). There were no baseline differences in intraventricular conduction disturbances rate. Compared to the novel BE Myval, there were similar procedural and in-hospital outcomes. Similar rates of early new permanent pacemaker implant (PPI) were observed amongst Myval (7.4%), Sapien-3 (13.4%), and Acurate (9.1%), but Evolut, Portico, and Allegra presented significantly higher rates (18.5%, p = 0.003; 29.5% p < 0.001 and 22%, p = 0.001, respectively). Central analysis of ECGs, unraveled significant prolongation of the PR segment with Evolut, Portico and Allegra whereas Evolut, Acurate, and Portico showed significant QRS widening compared to Myval. However, at discharge no differences in PR segment duration were observed while, Evolut, and Portico– but not Acurate, Allegra or Sapien-3 – still presented significant widening of QRS segment compared to Myval. Conclusions: After blinded central ECG analysis, the novel Myval balloon-expandable prosthesis was associated with a low rate of early conduction disturbances.

Objectives: We aimed to describe hemodynamic performance and clinical outcomes at 30-day follow-up of the balloon-expandable (BE) Myval transcatheter heart valve (THV) in low-risk patients. Background: The results of the next-generation BE Myval THV in low-risk aortic stenosis (AS) patients are still unknown. Methods: Retrospective registry performed in nine European centers including patients with low predicted operative mortality risk according to Society of thoracic surgeons (STS) and European system for cardiac operative risk evaluation (EuroSCORE-II) scores. Results: Between September 2019 and February 2021, a total of 100 patients (51% males, mean age 80 ± 6.5 years) were included. Mean STS score and EuroSCORE-II were 2.4 ± 0.8% and 2.2 ± 0.7%, respectively. Intermediate sizes were used in 39% (21.5 mm: 8%, 24.5 mm: 15%, 27.5 mm: 15%). There were no cases of valve embolization, coronary artery occlusion, annulus rupture, or procedural death. A definitive pacemaker implantation was needed in eight patients (8%). At 30-day follow-up aortic valve area (0.7 ± 0.2 vs. 2.1 ± 0.6 cm2) and mean aortic valve gradient (43.4 ± 11.1 vs. 9.0 ± 3.7 mmHg) improved significantly (p < 0.001). Moderate aortic regurgitation occurred in 4%. Endpoints of early safety and clinical efficacy were 3 and 1%, respectively. Conclusions: Hemodynamic performance and 30-day clinical outcomes of the BE Myval THV in low-risk AS patients were favorable. Longer-term follow-up is warranted.

Objective: To evaluate the role of the microaxial percutaneous mechanical circulatory support device (Impella® pump) implantation pre-percutaneous coronary intervention (PCI) versus during/after PCI in cardiogenic shock (CS) and high-risk PCI populations. Background: A better understanding of the safety and effectiveness of the Impella and the role of timing of this support initiation in specific clinical settings is of utmost clinical relevance. Methods: A total of 365 patients treated with Impella 2.5/CP in the 17 centers of the IMP-IT Registry were included. Through propensity-score weighting (PSW) analysis, 1-year clinical outcomes were assessed separately in CS and HR-PCI patients, stratified by timing of Impella support. Results: Pre-procedural insertion was associated with an improvement in 1-year survival in patients with CS due to acute myocardial infarction (AMI) treated with PCI (p =.04 before PSW, p =.009 after PSW) and HR-PCI (p <.01 both before and after PSW). Among patients undergoing HR-PCI, early Impella support was also associated with a lower rate of the composite of mortality, re-hospitalization for heart failure, and need for left-ventricular assist device/heart transplantation at 1-year (p =.04 before PSW, p =.01 after PSW). Furthermore, Impella use during/after PCI was associated with an increased in-hospital life-threatening and severe bleeding among patients with AMI-CS receiving PCI (7 vs. 16%, p =.1) and HR-PCI (1 vs. 9%, p =.02). Conclusions: Our findings suggested a survival benefit and reduced rates of major bleeding when a pre-PCI Impella implantation instead of during-after procedure was used in the setting of HR-PCI and AMI-CS.

Aims: The aim of this study was to investigate nationwide trends and clinical outcomes of the Impella device for cardiogenic shock (CS) and high-risk percutaneous coronary intervention (HR-PCI). Methods and results: The IMP-IT study was a multicentre observational national registry which enrolled all patients treated with Impella 2.5, Impella CP, Impella 5.0 and Impella RP, both for CS and HR-PCI indications, across 17 Italian centres from 2004 to June 2018. A total of 406 patients were included: 229 had CS (56.4%) and 177 underwent HR-PCI (43.6%). The use of Impella increased significantly during the study period (average annual percent change 39.8%, 95% confidence interval: 30.4 to 49.9; p<0.0001) for both indications. The Impella 2.5 was the most commonly used device (N=242; 59.6%). Rates of in-hospital and one-year all-cause death in patients with CS were 46.9% and 57.0%, respectively; 18.5% underwent left ventricular assist device implantation or heart transplant at one year. Rates of in-hospital and one-year allcause death in patients who underwent HR-PCI were 5.7% and 15.6%, respectively. Rates of device-related complications were 37.1% and 10.7% in the setting of CS and HR-PCI, respectively. Conclusions: Use of the Impella for CS and HR-PCI is increasing substantially in Italy, despite relatively high rates of device-related complications.

Objectives: The aim of this study was to investigate the safety and efficacy of coronary protection by preventive coronary wiring and stenting across the coronary ostia in patients at high risk for coronary obstruction after transcatheter aortic valve replacement (TAVR). Background: Coronary obstruction following TAVR is a life-threatening complication with high procedural and short-term mortality. Methods: Data were collected retrospectively from a multicenter international registry between April 2011 and February 2019. Results: Among 236 patients undergoing coronary protection with preventive coronary wiring, 143 had eventually stents implanted across the coronary ostia after valve deployment. At 3-year follow-up, rates of cardiac death were 7.8% in patients receiving stents and 15.7% in those not receiving stents (adjusted hazard ratio: 0.42; 95% confidence interval: 0.14 to 1.28; p = 0.13). There were 2 definite stent thromboses (0.9%) in patients receiving stents, both occurring after TAVR in “valve-in-valve” procedures. In patients not receiving stents, there were 4 delayed coronary occlusions (DCOs) (4.3%), occurring from 5 min to 6 h after wire removal. Three cases occurred in valve-in-valve procedures and 1 in a native aortic valve procedure. Distance between the virtual transcatheter valve and the protected coronary ostia <4 mm was present in 75.0% of patients with DCO compared with 30.4% of patients without DCO (p = 0.19). Conclusions: In patients undergoing TAVR at high risk for coronary obstruction, preventive stent implantation across the coronary ostia is associated with good mid-term survival rates and low rates of stent thrombosis. Patients undergoing coronary protection with wire only have a considerable risk for DCO.

Understanding and describing past or present societies is a complex task, as it involves a multi-faceted analysis of the norms, interactions, and evolutions that characterize them. This serves as the motivation for developing a tool, named Herodotus, aiming at supporting domain experts, such as historians or archaeologists, in the reasoning tasks over complex interactions characterizing a society in order to explain why some event took place and, possibly, to predict what could happen when some factors change. An important part of Herodotus is the text mining module that is responsible for the extraction of knowledge from written sources, such as books and scientific papers. Machines cannot always help users in dealing with natural language, because of the variety, ambiguity and non-rigidity that language shows in its use; they can only try to process information in a meaningful way for users. Information Extraction (IE) is the technology that pulls specific information from large volumes of unstructured texts and stores this information in structured forms. Users can then consult, compose, and analyze them. Domain-based IE should focus on an analysis of a specific state of affairs and, in this way, it can obtain more precise and detailed results. This helps domain experts to deal with the complexity of their everyday objects and environments. This chapter is centered on the Interactive Summary Extractor tool, whose scope is to organize, in a partially automated but substantially interactive way, text summaries for archaeological and historical documental sources. The texts so analyzed will help domain experts to collect data, viewing a synthesized version of it, compose such summaries in units of sense for the particular archaeological study or research that is in place, and so on. Summaries can then be modified, stored, retrieved and managed for later elaboration.

One of the most challenging problem in architecture is the automated construction of 3D (and 4D) digital models of cultural objects with the aim of implementing open data repositories, scientifically authenticated and responding to well accepted standards of validation, evaluation, preservation, publication, updating and dissemination. The realization of such an ambitious objective requires the adoption of special technological instruments. In this paper we plan to use portable devices (i.e. smartphones, tablets or PDAs eventually extended to wearable ones), extended with a small plug-in, for automatically extracting 3D models of single objects and building-scale mapping of the surrounding environment. At the same time, the device will provide the capability of inserting notes and observations. Where the instrument cannot be directly applied, for example for exploring the top of a complex building, we consider mounting our device, or using equivalent existing equipment, on a drone, in a modular approach for obtaining data de-facto interchangeable. The approach based on the expansion packs has the advantage of anticipating (or even promoting) future extensions of new mobile devices, when the spectrum of possible applications justify the corresponding increased costs. In order to experiment and verify this approach we plan to test it in two specific scenarios of the cultural heritage domain in which such devices seem particularly promising: Strada Nuova in Genoa and Palazzo Ducale in Urbino, both located in Italy.

Il contributo illustra la nuova disciplina della tutela cautelare nel processo tributario, a seguito delle innovazioni introdotte dal D. Lgs. 24 settembre 2015, n. 156

Lo scritto distingue, con riguardo all'imposta di registro, tra negozio elusivo e negozio riqualificato applicando l'art. 20 del Testo unico dell'imposta di registro

We propose an intelligent sensor system based on a new sensing methodology, relying also on 3D map reconstruction techniques, for computing with high precision, in real-time and without human intervention the parameters needed for stream-flow computation: water levels, morphology of the streams of all potentially flooded areas by each controlled stream. The collected data will be continuously transmitted, through a communication infrastructure, to software agents designed to compute the stream-flow and to quantify the spatial distribution of flood risk for each controlled watershed. The computed risks, together with other data coming from other sources (barometric sensors, camera operators of public organizations, emergency agencies, private citizens), will be analyzed by a diagnostic decision system implementing a risk-alert scheduling strategy. This system will be able to diagnose the health state of the controlled environment and to define specialized alarm levels for each potentially interested area that will be used to alert all citizens (ubiquity) locally present (alerting locality).© 2014 Published by Elsevier B.V. Open access under CC BY-NC-ND license

We propose an intelligent sensor system based on a new sensing methodology, relying also on 3D map reconstruction techniques, for computing with high precision, in real-time and without human intervention the parameters needed for stream-flow computation: water levels, morphology of the streams of all potentially flooded areas by each controlled stream. The collected data will be continuously transmitted, through a communication infrastructure, to software agents designed to compute the stream-flow and to quantify the spatial distribution of flood risk for each controlled watershed. The computed risks, together with other data coming from other sources (barometric sensors, camera operators of public organizations, emergency agencies, private citizens), will be analyzed by a diagnostic decision system implementing a risk-alert scheduling strategy. This system will be able to diagnose the health state of the controlled environment and to define specialized alarm levels for each potentially interested area that will be used to alert all citizens (ubiquity) locally present (alerting locality).© 2014 Published by Elsevier B.V. Open access under CC BY-NC-ND license

Nanoparticulate metal-insulator-metal ensemble chemiresistors in which the Au nanoclusters are functionalized with mercaptohexanoic acid are investigated as sensors of amines, and especially of triethylamine to which they are found to be extraordinarily sensitive with a minimum detectable level of less than 500 ppt. The dependences of the response on dose, time, and temperature are studied in detail. Modeling indicates that the entire data set is well explained by the interaction of partitioning and diffusion processes, both of which are temperature dependent., Published in Sensors and Actuators B: Chemical, v177 p936-946, 2013.

Het Nieuwe Werken is al sinds begin jaren negent ig in opkomst en raakt steeds meer ingeburgerd, zowel bij private als bij publieke organisaties. Dit artikel gaat in op de belangrijkste kenmerken en drijfveren, ervaringen van gebruikers, vereiste gebouweigenschappen en instrumenten ter ondersteuning van de besluitvorming., Real Estate & Housing

Het Nieuwe Werken is al sinds begin jaren negent ig in opkomst en raakt steeds meer ingeburgerd, zowel bij private als bij publieke organisaties. Dit artikel gaat in op de belangrijkste kenmerken en drijfveren, ervaringen van gebruikers, vereiste gebouweigenschappen en instrumenten ter ondersteuning van de besluitvorming., Real Estate & Housing

A fully coupled multi-dimensional continuum model of the thermoelectromechanics of GaN HEMTs is presented and discussed. The governing equations are those of linear thermoelectroelasticity, diffusion-drift transport theory, and heat conduction, with full coupling assumed, i.e., all mechanical, electrical, and thermal variables are solved for simultaneously. Apart from the known strains induced by epitaxy, plane-strain conditions are assumed, so that two-dimensional simulation suffices. Important aspects of the model are that it incorporates actual device geometries and that it captures field/ stress concentrations that often occur near material discontinuities and especially at corners. The latter are shown to be especially important with regards to understanding the mechanisms of both electrical and mechanical degradation in GaN HEMTs. Various possible contributors to degradation are discussed, including electron injection, the inverse piezoelectric effect, thermal stress, SiN intrinsic stress, and device geometry. The possibilities of crack propagation and fracture of the AlGaN are also analyzed., Published in the Journal of Applied Physics, v111 article ID 074504, 5 Apr 2012.

The Indiana MAS project, funded by the Italian Ministry of Education, University and Research "Futuro in Ricerca 2010" program, aims at providing a framework for the digital protection and conservation of rock art natural and cultural heritage sites, by storing, organizing and presenting information about them in such a way to encourage scientific research and to raise the interest and sensibility towards them from the common people. The project involves two research units, namely Genova (Dipartimento di Informatica, Bioingegneria, Robotica e Ingegneria dei Sistemi) and Salerno (Dipartimento di Matematica e Informatica), for a period of 36 months, starting from march 8th, 2012. The technologies adopted in the project range from agents to ontologies, as requested by the complex nature of the platform, where each module is devoted to a specific task: sketch and symbol recognition, semantic interpretation of complex visual scenes, multi-language text understanding, storing, classification and indexing of multimedia and heterogeneous digital objects. All of them should cooperate and coordinate in order to enable higher level components to reason on them and to detect relationships among different digital objects, hence providing new hypothesis based on such relationships.

Density-gradient theory provides a macroscopic approach to modeling quantum transport that is particularly well adapted to semiconductor device analysis and engineering. After some introductory observations, the basis of the theory in macroscopic and microscopic physics is summarized, and its scattering-dominated and scatteringfree versions are introduced. Remarks are also given about the underlying mathematics and numerics. A variety of applications of the theory to both quantum confinement and quantum tunneling situations are then reviewed. In doing so particular emphasis is put on understanding the range of validity of the theory and on its unexpected power as a phenomenology. The article closes with a few comments about the future., Published in Journal of Computational Electron, v10 p65-97, 2011.

Numerical device modeling is used to study p-channel FETs with InSb, GaSb and InGaSb channels. To be as realistic as possible, the basic parameters are chosen to be those measured experimentally in state-of-the- art high-mobility materials, and where possible, predictions are compared against published data. Confinement effects are captured in the simulations using the density-gradient description of quantum transport. The emphasis is on projecting scaling properties and ultimate performance, with key issues being short-channel effects, the importance of source-drain leakage current, power considerations and p+-cap design. Although important, issues related to gate leakage current and gate stack design are not well addressed by modeling, and so are not considered in detail. With III-V complementary circuits and high-speed, low-power applications in mind, the general conclusion is that among the antimonide- based pFETs, InGaSb devices provide the best balance of speed and power dissipation., Published in Solid-State Electronics, v54 p1349-1358, 2010.

Antimonide-based p+N junctions have been grown by molecular beam epitaxy and processed into diodes. The diodes have good rectification with ideality factors near 1, and high saturation current densities of 2.510 x 10(exp 2) A/cm2. S-parameter measurements to 50 GHz indicate a 1 Omega series resistance and a capacitance of 1.2 fF/micro-m2 for a 5 micro-meter diameter mesa diode. A cutoff frequency of 6.5 THz is estimated from the RC product. The high saturation current indicates that this diode will reach forward bias currents at substantially lower voltages than GaAs Schottky diodes. These properties suggest using the diode as a terahertz mixer., Published in Applied Physics Letters, v92 n243502 p1-3, 2008. Naval Research Laboratory (NRL) Release No. 08-1226-0814. Sponsored in part by the Defense Advanced Research Projects Agency (DARPA).

Motivated by the technological possibilities of electronics and sensors based on gold nanoparticles (Au NPs), we investigate the selective assembly of such NPs on electrodes via DNA hybridization. Protocols are demonstrated for maximizing selectivity and coverage using 15mers as the active binding agents. Detailed studies of the dependences on time, ionic strength, and temperature are used to understand the underlying mechanisms and their limits. Under optimized conditions, coverage of Au NPs on Au electrodes patterned on silicon dioxide (SiO2) substrates was found to be~25-35%. In all cases, Au NPs functionalized with non-complementary DNA show no attachment and essentially no nonspecific adsorption is observed by any Au NPs on the SiO2 surfaces of the patterned substrates. DNA-guided assembly of multilayers of NPs was also demonstrated and, as expected, found to further increase the coverage, with three deposition cycles resulting in a surface coverage of approximately 60%., Published in Langmuir, v24 p10245-10252, 2008.

Low-power electronics is essential for a number of military and commercial applications. Previous work at NRL has demonstrated high-performance, low-power, antimonide-based compound semiconductor transistors. In these devices, InAs is used as an electron channel with mobilities as high as 30,000 cm2/V-s at room temperature. This work has been transitioned to industry for analog applications, resulting in X-band and W-band low-noise amplifiers with record low power consumption (a factor of 3 and 10 lower than InP- and GaAs-based amplifiers, respectively). For digital and mixed-signal applications, power consumption can be minimized by designing circuits with complementary n(electron)- and p(hole)-channel transistors. These circuits consume negligible power except when being switched. Military applications for this technology are expected to include high-speed analog-to-digital conversion for high-performance radar and miniature air vehicles (MAVs), autonomous sensing, and application-specific integrated circuits (ASICs)., Published in NRL Review 2008, p175-177, 2008.

Antimonide-based p-channel HFETs with a 0.25 micro m gate length have been fabricated with an InAlSb/AlGaSb barrier and a strained In(sub 0.41)Ga(sub 0.59)Sb quantum well channel. The modulation-doped material exhibits a Hall mobility of 1020 cm(expn 2)/V s and a sheet density of 1.6 x 10(expn 12) cm(expn -2). The devices have a maximum DC transconductance of 133 mS/mm and an f(sub T) and f(sub max) of 15 and 27 GHz, respectively. These values are the highest reported to date for this material system., Published in Electronics Letters, v43 n15, 19 Jul 2007.

Surface-enhanced Raman spectroscopy (SERS) was performed on Ga2O3 /Ag and ZnO/Ag nanowires, which were arranged in either a crossover or noncrossing geometry. Results indicate a high SERS sensitivity (near 0.2 pg) for nanowires arranged in a crossing geometry. It is suggested that this is due to the dielectric core/metal shell structure, as well as to the nanowire crossings, which are regions of very high electric fields. Finite element simulations of the electric field near two crossed wires confirm an enhanced plasmon resonance in the vicinity of the crossing, which extends spatially in the crossings and around the nanowires., Published in Applied Physics Letters, v90 p093105-1/093105-3, 2007.

In this paper we propose an algorithm for automatic transformation of a graph into a 3D Virtual World and its Euclidean map, using the rectangular dualization technique. The nodes of the initial graph are transformed into rooms, the connecting arcs between nodes determine which rooms have to be placed next to each other and define the positions of the doors connecting those rooms. The proposed algorithm is general enough to be used for automatic generation of 3D Virtual Worlds representation of any planar graph, however, our research is particulary focused on the automatic generation of 3D Electronic Institutions from the Performative Structure graph. Copyright © 2007, Australian Computer Society, Inc.

In this paper we propose an algorithm for automatic transformation of a graph into a 3D Virtual World and its Euclidean map, using the rectangular dualization technique. The nodes of the initial graph are transformed into rooms, the connecting arcs between nodes determine which rooms have to be placed next to each other and define the positions of the doors connecting those rooms. The proposed algorithm is general enough to be used for automatic generation of 3D Virtual Worlds representation of any planar graph, however, our research is particulary focused on the automatic generation of 3D Electronic Institutions from the Performative Structure graph. Copyright © 2007, Australian Computer Society, Inc.

Solid source molecular beam epitaxy has been used to grow random alloy quaternary InAlAsSb and ternary InGaSb alloys with a 6.2 lattice constant for use in electronic devices such as p-n junctions and heterojunction bipolar transistors (HBTs). Several p-n hetrojunctions composed of p-type InGaSb and one of several different n-type InAlAsSb alloys have been fabricated and show good rectification with ideality factors near one. In addition, several of these alloys have been used to make an n-p-n HBT that has demonstrated a dc current gain of 25., Published in Journal of Vacuum Science Technology B, v24 n3 p1622-1625, May-June 2006.

An npn double heterojunction bipolar transistor has been made using In0.27Ga0.73Sb for the base and two different InxAl1-xAsySb1-y alloys for the emitter and collector. It has a common emitter current gain of 25. The emitter-base voltages required for a given collector current are smaller than those of InP-based HBTs., Published in Electronics Letters, v41 n6, 17 March 2005.

We report the development of high-mobility carbon-nanotube thin-film transistors fabricated on a polymeric substrate. The active semiconducting channel in the devices is composed of a random two-dimensional network of single-walled carbon nanotubes (SWNTs). The devices exhibit a field-effect mobility of 150 cm2 /Vs and a normalized transconductance of 0.5 mS/mm. The ratio of on-current (I(on)) to off-current (I(off)) is 100 and is limited by metallic SWNTs in the network. With electronic purification of the SWNTs and improved gate capacitance we project that the transconductance can be increased to 10 100 mS/mm with a significantly higher value of I(on)/ I(off), thus approaching crystalline semiconductor-like performance on polymeric substrates., Published in Applied Physics Letters, v86 p033105-1/033105-3, 2005.

Analytical and numerical results concerning thermal and mechanical effects in operating metal field emitter structures (tips, gates and anodes) are summarized. For the most part, it is found that such effects are too small to constitute a reliability threat unless the geometries (via their effect on heat sinking) or the operating frequencies (via their ac heating contribution) are extreme. For ideal structures of conventional (SRI-like) geometry under normal operating conditions the only two thermomechanical effects with the potential for triggering failure are; (1) anode heating due to electron impact and (2) Maxwell stress on the field emitter tip.

A macroscopic description of electron transport in semiconductors has recently been developed (M. G. Ancona and H. F. Tiersten, Phys. Rev. B35-II, 7959 (1987)) in which the equation of state of the electron gas was generalized to permit a dependence on the gradient of the gas density. This generalization leads to a macroscopic theory - density-gradient theory - which is often expressible as a generalized diffusion-drift description and which is capable of describing quantum transport phenomena associated with carrier confinement and tunneling. The original paper contained a derivation of this description from well known principles of classical field theory but only in a very condensed form. It is the purpose of the present report to supplement the earlier paper by giving the detailed derivations. As in the original paper two methods of derivation are presented: One is a variational approach which follows the work of Toupin while the other uses a balance law approach pioneered by Green and Rivlin. Keywords: Electron transport, Semiconductors., Prepared in collaboration with Rensselaer Polytechnic Inst., Troy, NY. Dept. of Mechanical Engineering.

A fully macroscopic description of semiconductors is presented which includes the boundary conditions at the surface of the semiconductor that are required for consistency with the usual diffusion-drift current equations. As in all field theories, e.g., electromagnetism, both the boundary conditions and the differential equations are obtained from the same governing integral forms. The new boundary conditions relate the jump discontinuities in the chemical potentials across the interface to the forces exerted by the lattice on the charge carries which prevent the carriers form leaving the solid. The expressions for the forces in the static case are found and the values of the material surface coefficients appearing therein are obtained from quasistatic MOS C-V measurements for some particular Si-Si02 interfaces. (Author)