991 resultados para BASEL III
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Na Europa Central, onde ocorreram as principais batalhas terrestres, chamou-se Guerra dos Sete Anos; na Inglaterra, que foi a principal vencedora, chamou-se A Grande Guerra do Império; Nos Estados Unidos e no Canadá, que passou a ser inglês ao final dos combates, chamou-se de Guerra Franco-Índia.
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Referência: Diccionario Bibliographico Portuguez / Innocencio Francisco da Silva, 1862. v. 7, p. 386.
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9 p.
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Bi-weekly phytoplankton samples were collected at 0, 10, and 20 m and enumerated by the Utermöhl sedimentation technique; 14C productivity measurements at 10 m, oblique zooplankton tows, and routine hydrographic observations were also made. Northerly winds induce upwelling during December-April, followed by a rainy season; a slight resurgence in upwelling may occur during July and/or August. Annual variations in upwelling intensity and rainfall occur. During upwelling, the upper 50 m, about 30 per cent of the total volume of the Gulf of Panama, is replaced with water 5 to 10 C colder than the more stratified, turbid and nutrient impoverished watermass present during the rainy season. The mean annual runoff accompanying an average annual precipitation of 2731 mm is estimated to equal a layer of fresh water 3.2 m thick. About 10 per cent of the phytoplankton phosphate and inorganic nitrogen requirements during the rainy season are accreted. (PDF contains 260 pages.)
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irakasgaia gainditu behar duten ikasleentzat, eta baita ere, gai batzuetan, gradu berriko Matematika I eta Matematika II irakasgaiko ikasleentzat.Ekonomian Lizentziaturako Matematika III irakasgaiko azken hamar urteetan jarri diren azterketak eta haien erantzunak aurkituko dituzue. Lehenengo zatian, egin gabeko azterketak daude, ordena kronologikoan, zaharrenetik berrienera, eta bigarren zatian, erantzunak daude, ordena kronologikoan ere baina gaika ere. Horrela, programaren gai bakoitzaren ariketa guztiak elkarrekin aurkituko dituzue, gaiz gai ikasi nahi izanez gero.
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Enpresen Administrazio eta Zuzendaritzako Lizentziaturako Matematika III irakasgaia gainditu behar duten ikasleentzat, eta baita ere, gai batzuetan, gradu berriko Matematika I eta Matematika II irakasgaiko ikasleentzat.Enpresen Administrazio eta Zuzendaritzako Lizentziaturako Matematika III irakasgaiko azken hamar urteetan jarri diren azterketak eta haien erantzunak aurkituko dituzue. Lehenengo zatian, egin gabeko azterketak daude, ordena kronologikoan, zaharrenetik berrienera, eta bigarren zatian, erantzunak daude, ordena kronologikoan ere baina gaika ere. Horrela, programaren gai bakoitzaren ariketa guztiak elkarrekin aurkituko dituzue, gaiz gai ikasi nahi izanez gero.
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Anais do Parlamento Brasileiro, 1878.
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Bihotz - errehabilitazioaren III. fasean alderdi ezberdinak hartu behar dira kontuan eta lan honek, alderdi ezberdin hauek azaldu nahi izan dit u: patologia ezberdinak azaltzea , jarduera fisikoaren orokortasunak eta entrena mendu metodo ezberdinak azaltzea eta azkenik, patologia zehatzen arabera kont uan hartu beharrekoak azaltzea Orain arte bihotz - errehabilitazioaren barruan entrenamendu aerobiko jarraia soilik landu den arren, lan honek entrenamendu aerobiko interbalikoaren onura adierazgarriak baieztatzen ditu: ahalmen aerobikoa hobetzea, VO 2pikoa hobetzea, ezker bentrikuluaren eiekzio frakzioa handitzea ... Gainera, entrenamendu aerobikoaz gain, indar entrenamenduak, arnasketa entrenamenduak eta malgutasun entrenamenduak ere onura adierazgarriak lortzen dituztela frogatu da, entrenamendu mota hauek entrenamendu aerobikoaren konplimentagarri izan behar direlarik.
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Esta es una colección de 10 vídeos tutoriales que pueden ser empleados como material educativo en los cursos de fonética básica en el ámbito universitario. Los vídeos 1-3 tratan aspectos relacionados con la grabación: el tipo de micrófonos que se emplean, las clases de espacios en las que se suelen llevar a cabo la captura de señales de audio y las grabadoras que se suelen emplear. El vídeo 4 explora técnicas de captura y observación de datos de flujo y presión en fonética aerodinámica. Los vídeos 5-10 presentan información sobre los principales usos que se le brindan al programa Praat (Boersma y Weenink, 2014) en los estudios actuales de fonética acústica, desde la clase de información sobre modos de articulación de las consonantes que se puede identificar en oscilogramas hasta la creación de señales sonoras sintetizadas por medio de unos procedimientos que tiene el programa para tal propósito, los cuales son susceptibles de ser empleados en experimentos de percepción auditiva.
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The material presented in this thesis concerns the growth and characterization of III-V semiconductor heterostructures. Studies of the interactions between bound states in coupled quantum wells and between well and barrier bound states in AlAs/GaAs heterostructures are presented. We also demonstrate the broad array of novel tunnel structures realizable in the InAs/GaSb/AlSb material system. Because of the unique broken-gap band alignment of InAs/GaSb these structures involve transport between the conduction- and valence-bands of adjacent layers. These devices possess a wide range of electrical properties and are fundamentally different from conventional AlAs/GaAs tunnel devices. We report on the fabrication of a novel tunnel transistor with the largest reported room temperature current gains. We also present time-resolved studies of the growth fronts of InAs/GainSb strained layer superlattices and investigations of surface anion exchange reactions.
Chapter 2 covers tunneling studies of conventional AlAs/GaAs RTD's. The results of two studies are presented: (i) A test of coherent vs. sequential tunneling in triple barrier heterostructures, (ii) An optical measurement of the effect of barrier X-point states on Γ-point well states. In the first it was found if two quantum wells are separated by a sufficiently thin barrier, then the eigenstates of the system extend coherently across both wells and the central barriers. For thicker barriers between the wells, the electrons become localized in the individual wells and transport is best described by the electrons hopping between the wells. In the second, it was found that Γ-point well states and X-point barrier states interact strongly. The barrier X-point states modify the energies of the well states and increase the escape rate for carriers in the quantum well.
The results of several experimental studies of a novel class of tunnel devices realized in the InAs/GaSb/AlSb material system are presented in Chapter 3. These interband tunnel structures involve transport between conduction- and valence-band states in adjacent material layers. These devices are compared and contrasted with the conventional AlAs/GaAs structures discussed in Chapter 2 and experimental results are presented for both resonant and nonresonant devices. These results are compared with theoretical simulations and necessary extensions to the theoretical models are discussed.
In chapter 4 experimental results from a novel tunnel transistor are reported. The measured current gains in this transistor exceed 100 at room temperature. This is the highest reported gain at room temperature for any tunnel transistor. The device is analyzed and the current conduction and gain mechanisms are discussed.
Chapters 5 and 6 are studies of the growth of structures involving layers with different anions. Chapter 5 covers the growth of InAs/GainSb superlattices for far infrared detectors and time resolved, in-situ studies of their growth fronts. It was found that the bandgap of superlattices with identical layer thicknesses and compositions varied by as much as 40 meV depending on how their internal interfaces are formed. The absorption lengths in superlattices with identical bandgaps but whose interfaces were formed in different ways varied by as much as a factor of two. First the superlattice is discussed including an explanation of the device and the complications involved in its growth. The experimental technique of reflection high energy electron diffraction (RHEED) is reviewed, and the results of RHEED studies of the growth of these complicated structures are presented. The development of a time resolved, in-situ characterization of the internal interfaces of these superlattices is described. Chapter 6 describes the result of a detailed study of some of the phenomena described in chapter 5. X-ray photoelectron spectroscopy (XPS) studies of anion exchange reactions on the growth fronts of these superlattices are reported. Concurrent RHEED studies of the same physical systems studied with XPS are presented. Using the RHEED and XPS results, a real-time, indirect measurement of surface exchange reactions was developed.
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The relentlessly increasing demand for network bandwidth, driven primarily by Internet-based services such as mobile computing, cloud storage and video-on-demand, calls for more efficient utilization of the available communication spectrum, as that afforded by the resurging DSP-powered coherent optical communications. Encoding information in the phase of the optical carrier, using multilevel phase modulationformats, and employing coherent detection at the receiver allows for enhanced spectral efficiency and thus enables increased network capacity. The distributed feedback semiconductor laser (DFB) has served as the near exclusive light source powering the fiber optic, long-haul network for over 30 years. The transition to coherent communication systems is pushing the DFB laser to the limits of its abilities. This is due to its limited temporal coherence that directly translates into the number of different phases that can be imparted to a single optical pulse and thus to the data capacity. Temporal coherence, most commonly quantified in the spectral linewidth Δν, is limited by phase noise, result of quantum-mandated spontaneous emission of photons due to random recombination of carriers in the active region of the laser.
In this work we develop a generically new type of semiconductor laser with the requisite coherence properties. We demonstrate electrically driven lasers characterized by a quantum noise-limited spectral linewidth as low as 18 kHz. This narrow linewidth is result of a fundamentally new laser design philosophy that separates the functions of photon generation and storage and is enabled by a hybrid Si/III-V integration platform. Photons generated in the active region of the III-V material are readily stored away in the low loss Si that hosts the bulk of the laser field, thereby enabling high-Q photon storage. The storage of a large number of coherent quanta acts as an optical flywheel, which by its inertia reduces the effect of the spontaneous emission-mandated phase perturbations on the laser field, while the enhanced photon lifetime effectively reduces the emission rate of incoherent quanta into the lasing mode. Narrow linewidths are obtained over a wavelength bandwidth spanning the entire optical communication C-band (1530-1575nm) at only a fraction of the input power required by conventional DFB lasers. The results presented in this thesis hold great promise for the large scale integration of lithographically tuned, high-coherence laser arrays for use in coherent communications, that will enable Tb/s-scale data capacities.
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Chapter I
Theories for organic donor-acceptor (DA) complexes in solution and in the solid state are reviewed, and compared with the available experimental data. As shown by McConnell et al. (Proc. Natl. Acad. Sci. U.S., 53, 46-50 (1965)), the DA crystals fall into two classes, the holoionic class with a fully or almost fully ionic ground state, and the nonionic class with little or no ionic character. If the total lattice binding energy 2ε1 (per DA pair) gained in ionizing a DA lattice exceeds the cost 2εo of ionizing each DA pair, ε1 + εo less than 0, then the lattice is holoionic. The charge-transfer (CT) band in crystals and in solution can be explained, following Mulliken, by a second-order mixing of states, or by any theory that makes the CT transition strongly allowed, and yet due to a small change in the ground state of the non-interacting components D and A (or D+ and A-). The magnetic properties of the DA crystals are discussed.
Chapter II
A computer program, EWALD, was written to calculate by the Ewald fast-convergence method the crystal Coulomb binding energy EC due to classical monopole-monopole interactions for crystals of any symmetry. The precision of EC values obtained is high: the uncertainties, estimated by the effect on EC of changing the Ewald convergence parameter η, ranged from ± 0.00002 eV to ± 0.01 eV in the worst case. The charge distribution for organic ions was idealized as fractional point charges localized at the crystallographic atomic positions: these charges were chosen from available theoretical and experimental estimates. The uncertainty in EC due to different charge distribution models is typically ± 0.1 eV (± 3%): thus, even the simple Hückel model can give decent results.
EC for Wurster's Blue Perchl orate is -4.1 eV/molecule: the crystal is stable under the binding provided by direct Coulomb interactions. EC for N-Methylphenazinium Tetracyanoquino- dimethanide is 0.1 eV: exchange Coulomb interactions, which cannot be estimated classically, must provide the necessary binding.
EWALD was also used to test the McConnell classification of DA crystals. For the holoionic (1:1)-(N,N,N',N'-Tetramethyl-para- phenylenediamine: 7,7,8,8-Tetracyanoquinodimethan) EC = -4.0 eV while 2εo = 4.65 eV: clearly, exchange forces must provide the balance. For the holoionic (1:1)-(N,N,N',N'-Tetramethyl-para- phenylenediamine:para-Chloranil) EC = -4.4 eV, while 2εo = 5.0 eV: again EC falls short of 2ε1. As a Gedankenexperiment, two nonionic crystals were assumed to be ionized: for (1:1)-(Hexamethyl- benzene:para-Chloranil) EC = -4.5 eV, 2εo = 6.6 eV; for (1:1)- (Napthalene:Tetracyanoethylene) EC = -4.3 eV, 2εo = 6.5 eV. Thus, exchange energies in these nonionic crystals must not exceed 1 eV.
Chapter III
A rapid-convergence quantum-mechanical formalism is derived to calculate the electronic energy of an arbitrary molecular (or molecular-ion) crystal: this provides estimates of crystal binding energies which include the exchange Coulomb inter- actions. Previously obtained LCAO-MO wavefunctions for the isolated molecule(s) ("unit cell spin-orbitals") provide the starting-point. Bloch's theorem is used to construct "crystal spin-orbitals". Overlap between the unit cell orbitals localized in different unit cells is neglected, or is eliminated by Löwdin orthogonalization. Then simple formulas for the total kinetic energy Q^(XT)_λ, nuclear attraction [λ/λ]XT, direct Coulomb [λλ/λ'λ']XT and exchange Coulomb [λλ'/λ'λ]XT integrals are obtained, and direct-space brute-force expansions in atomic wavefunctions are given. Fourier series are obtained for [λ/λ]XT, [λλ/λ'λ']XT, and [λλ/λ'λ]XT with the help of the convolution theorem; the Fourier coefficients require the evaluation of Silverstone's two-center Fourier transform integrals. If the short-range interactions are calculated by brute-force integrations in direct space, and the long-range effects are summed in Fourier space, then rapid convergence is possible for [λ/λ]XT, [λλ/λ'λ']XT and [λλ'/λ'λ]XT. This is achieved, as in the Ewald method, by modifying each atomic wavefunction by a "Gaussian convergence acceleration factor", and evaluating separately in direct and in Fourier space appropriate portions of [λ/λ]XT, etc., where some of the portions contain the Gaussian factor.
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Spontaneous emission into the lasing mode fundamentally limits laser linewidths. Reducing cavity losses provides two benefits to linewidth: (1) fewer excited carriers are needed to reach threshold, resulting in less phase-corrupting spontaneous emission into the laser mode, and (2) more photons are stored in the laser cavity, such that each individual spontaneous emission event disturbs the phase of the field less. Strong optical absorption in III-V materials causes high losses, preventing currently-available semiconductor lasers from achieving ultra-narrow linewidths. This absorption is a natural consequence of the compromise between efficient electrical and efficient optical performance in a semiconductor laser. Some of the III-V layers must be heavily doped in order to funnel excited carriers into the active region, which has the side effect of making the material strongly absorbing.
This thesis presents a new technique, called modal engineering, to remove modal energy from the lossy region and store it in an adjacent low-loss material, thereby reducing overall optical absorption. A quantum mechanical analysis of modal engineering shows that modal gain and spontaneous emission rate into the laser mode are both proportional to the normalized intensity of that mode at the active region. If optical absorption near the active region dominates the total losses of the laser cavity, shifting modal energy from the lossy region to the low-loss region will reduce modal gain, total loss, and the spontaneous emission rate into the mode by the same factor, so that linewidth decreases while the threshold inversion remains constant. The total spontaneous emission rate into all other modes is unchanged.
Modal engineering is demonstrated using the Si/III-V platform, in which light is generated in the III-V material and stored in the low-loss silicon material. The silicon is patterned as a high-Q resonator to minimize all sources of loss. Fabricated lasers employing modal engineering to concentrate light in silicon demonstrate linewidths at least 5 times smaller than lasers without modal engineering at the same pump level above threshold, while maintaining the same thresholds.