Compact stellarators with modular coils

Compact stellarator designs with modular coils and only two or three field periods are now available; these designs have both good stability and quasiaxial symmetry providing adequate transport for a magnetic fusion reactor. If the bootstrap current assumes theoretically predicted values a three field period configuration is optimal, but if that net current turns out to be lower, a device with two periods and just 12 modular coils might be better. There are also attractive designs with quasihelical symmetry and four or five periods whose properties depend less on the bootstrap current. Good performance requires that there be a satisfactory magnetic well in the vacuum field, which is a property lacking in a stellarator-tokamak hybrid that has been proposed for a proof of principle experiment. In this paper, we present an analysis of stability for these configurations that is based on a mountain pass theorem asserting that, if two solutions of the problem of magnetohydrodynamic equilibrium can be found, then there has to be an unstable solution. We compare results of our theory of equilibrium, stability, and transport with recently announced measurements from the large LHD experiment in Japan.

Electrical microstimulation suggests two different forms of representation of head-centered space in the intraparietal sulcus of rhesus monkeys.

We examined the effects of eye position on saccades evoked by electrical stimulation of the intraparietal sulcus (IPS) of rhesus monkeys. Microstimulation evoked saccades from sites on the posterior bank, floor, and the medial bank of the IPS. The size and direction of the eye movements varied as a function of initial eye position before microstimulation. At many stimulation sites, eye position affected primarily the amplitude and not the direction of the evoked saccades. These "modified vector saccades" were characteristic of most stimulation-sensitive zones in the IPS, with the exception of a narrow strip located mainly on the floor of the sulcus. Stimulation in this "intercalated zone" evoked saccades that moved the eyes into a particular region in head-centered space, independent of the starting position of the eyes. This latter response is compatible with the stimulation site representing a goal zone in head-centered coordinates. On the other hand, the modified vector saccades observed outside the intercalated zone are indicative of a more distributed representation of head-centered space. A convergent projection from many modified vector sites onto each intercalated site may be a basis for a transition from a distributed to a more explicit representation of space in head-centered coordinates.

Very-long-baseline radio interferometry surveys of the compact structure in active galactic nuclei.

Very-long-baseline radio interferometry (VLBI) imaging surveys have been undertaken since the late 1970s. The sample sizes were initially limited to a few tens of objects but the snapshot technique has now allowed samples containing almost 200 sources to be studied. The overwhelming majority of powerful compact sources are asymmetric corejects of one form or another, most of which exhibit apparent superluminal motion. However 5-10% of powerful flat-spectrum sources are 100-parsec (pc)-scale compact symmetric objects; these appear to form a continuum with the 1-kpc-scale double-lobed compact steep-spectrum sources, which make up 15-20% of lower frequency samples. It is likely that these sub-galactic-size symmetric sources are the precursors to the large-scale classical double sources. There is a surprising peak around 90 degrees in the histogram of misalignments between the dominant source axes on parsec and kiloparsec scales; this seems to be associated with sources exhibiting a high degree of relativistic beaming. VLBI snapshot surveys have great cosmological potential via measurements of both proper motion and angular size vs. redshift as well as searches for gravitational "millilensing."

Morphology of high-luminosity compact radio sources.

High-dynamic range imaging and monitoring with very-long-baseline interferometry reveal a rich morphology of luminous flat-spectrum radio sources. One-sided core-jet structures abound, and superluminal motion is frequently measured. In a few cases, both distinct moving features and diffuse underlying jet emission can be detected. Superluminal motion seen in such sources is typically complex, on curved trajectories or ridge lines, and with variable component velocities, including stationary features. The curved trajectories seen can be modeled by helical motion within the underlying jet flow. The very-long-baseline interferometry properties of the superluminal features in the jet of 3C 345 and other similar sources can be explained by models invoking the emission from shocks, at least within the vicinity of the compact core. Inverse-Compton calculations, constrained by x-ray observations, yield realistic estimates for the physical conditions in the parsec-scale jet. There is evidence for a transition region in this source beyond which other factors (e.g., plasma interactions and nonsynchrotron radiation processes) may become prominent. Multifrequency and polarization imaging (especially at high frequencies) are emerging as critical tools in testing model predictions.

Electrical investigation of p-type 4H-SiC heavily doped by ion implantation

In the last decades, an increasing interest in the research field of wide bandgap semiconductors was observed, mostly due to the progressive approaching of silicon-based devices to their theoretical limits. 4H-SiC is an example among these, and is a mature compound for applications. The main advantages offered 4H-SiC in comparison with silicon are an higher breakdown field, an higher thermal conductivity, a higher operating temperature, very high hardness and melting point, biocompatibility, but also low switching losses in high frequencies applications and lower on-resistances in unipolar devices. Then, 4H-SiC power devices offer great performance improvement; moreover, they can work in hostile environments where silicon power devices cannot function. Ion implantation technology is a key process in the fabrication of almost all kinds of SiC devices, owing to the advantage of a spatially selective doping. This work is dedicated to the electrical investigation of several differently-processed 4H-SiC ion- implanted samples, mainly through Hall effect and space charge spectroscopy experiments. It was also developed the automatic control (Labview) of several experiments. In the work, the effectiveness of high temperature post-implant thermal treatments (up to 2000°C) were studied and compared considering: (i) different methods, (ii) different temperatures and (iii) different duration of the annealing process. Preliminary p + /n and Schottky junctions were also investigated as simple test devices. 1) Heavy doping by ion implantation of single off-axis 4H-SiC layers The electrical investigation is one of the most important characterization of ion-implanted samples, which must be submitted to mandatory post-implant thermal treatment in order to both (i) recover the lattice after ion bombardment, and (ii) address the implanted impurities into lattice sites so that they can effectively act as dopants. Electrical investigation can give fundamental information on the efficiency of the electrical impurity activation. To understand the results of the research it should be noted that: (a) To realize good ohmic contacts it is necessary to obtain spatially defined highly doped regions, which must have conductivity as low as possible. (b) It has been shown that the electrical activation efficiency and the electrical conductivity increase with the annealing temperature increasing. (c) To maximize the layer conductivity, temperatures around 1700°C are generally used and implantation density high till to 10 21 cm -3 . In this work, an original approach, different from (c), is explored by the using very high annealing temperature, around 2000°C, on samples of Al + -implant concentration of the order of 10 20 cm -3 . Several Al + -implanted 4H-SiC samples, resulting of p-type conductivity, were investigated, with a nominal density varying in the range of about 1-5∙10 20 cm -3 and subjected to two different high temperature thermal treatments. One annealing method uses a radiofrequency heated furnace till to 1950°C (Conventional Annealing, CA), the other exploits a microwave field, providing a fast heating rate up to 2000°C (Micro-Wave Annealing, MWA). In this contest, mainly ion implanted p-type samples were investigated, both off-axis and on-axis <0001> semi-insulating 4H-SiC. Concerning p-type off-axis samples, a high electrical activation of implanted Al (50-70%) and a compensation ratio below 10% were estimated. In the work, the main sample processing parameters have been varied, as the implant temperature, CA annealing duration, and heating/cooling rates, and the best values assessed. MWA method leads to higher hole density and lower mobility than CA in equivalent ion implanted layers, resulting in lower resistivity, probably related to the 50°C higher annealing temperature. An optimal duration of the CA treatment was estimated in about 12-13 minutes. A RT resistivity on the lowest reported in literature for this kind of samples, has been obtained. 2) Low resistivity data: variable range hopping Notwithstanding the heavy p-type doping levels, the carrier density remained less than the critical one required for a semiconductor to metal transition. However, the high carrier densities obtained was enough to trigger a low temperature impurity band (IB) conduction. In the heaviest doped samples, such a conduction mechanism persists till to RT, without significantly prejudice the mobility values. This feature can have an interesting technological fall, because it guarantee a nearly temperature- independent carrier density, it being not affected by freeze-out effects. The usual transport mechanism occurring in the IB conduction is the nearest neighbor hopping: such a regime is effectively consistent with the resistivity temperature behavior of the lowest doped samples. In the heavier doped samples, however, a trend of the resistivity data compatible with a variable range hopping (VRH) conduction has been pointed out, here highlighted for the first time in p-type 4H-SiC. Even more: in the heaviest doped samples, and in particular, in those annealed by MWA, the temperature dependence of the resistivity data is consistent with a reduced dimensionality (2D) of the VRH conduction. In these samples, TEM investigation pointed out faulted dislocation loops in the basal plane, whose average spacing along the c-axis is comparable with the optimal length of the hops in the VRH transport. This result suggested the assignment of such a peculiar behavior to a kind of spatial confinement into a plane of the carrier hops. 3) Test device the p + -n junction In the last part of the work, the electrical properties of 4H-SiC diodes were also studied. In this case, a heavy Al + ion implantation was realized on n-type epilayers, according to the technological process applied for final devices. Good rectification properties was shown from these preliminary devices in their current-voltage characteristics. Admittance spectroscopy and deep level transient spectroscopy measurements showed the presence of electrically active defects other than the dopants ones, induced in the active region of the diodes by ion implantation. A critical comparison with the literature of these defects was performed. Preliminary to such an investigation, it was assessed the experimental set up for the admittance spectroscopy and current-voltage investigation and the automatic control of these measurements.

A continuous model for quasinilpotent operators.

A classical result due to Foias and Pearcy establishes a discrete model for every quasinilpotent operator acting on a separable, infinite-dimensional complex Hilbert space HH . More precisely, given a quasinilpotent operator T on HH , there exists a compact quasinilpotent operator K in HH such that T is similar to a part of K⊕K⊕⋯⊕K⊕⋯K⊕K⊕⋯⊕K⊕⋯ acting on the direct sum of countably many copies of HH . We show that a continuous model for any quasinilpotent operator can be provided. The consequences of such a model will be discussed in the context of C0C0 -semigroups of quasinilpotent operators.

CANDELS: The progenitors of compact quiescent galaxies at z ~ 2

We combine high-resolution Hubble Space Telescope/WFC3 images with multi-wavelength photometry to track the evolution of structure and activity of massive (M_*> 10^10 M_☉) galaxies at redshifts z = 1.4-3 in two fields of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. We detect compact, star-forming galaxies (cSFGs) whose number densities, masses, sizes, and star formation rates (SFRs) qualify them as likely progenitors of compact, quiescent, massive galaxies (cQGs) at z = 1.5-3. At z≲2, cSFGs present SFR = 100-200 M_☉ yr^–1, yet their specific star formation rates (sSFR ~ 10^–9 yr^–1) are typically half that of other massive SFGs at the same epoch, and host X-ray luminous active galactic nuclei (AGNs) 30 times (~30%) more frequently. These properties suggest that cSFGs are formed by gas-rich processes (mergers or disk-instabilities) that induce a compact starburst and feed an AGN, which, in turn, quench the star formation on dynamical timescales (few 10^8 yr). The cSFGs are continuously being formed at z = 2-3 and fade to cQGs down to z ~ 1.5. After this epoch, cSFGs are rare, thereby truncating the formation of new cQGs. Meanwhile, down to z = 1, existing cQGs continue to enlarge to match local QGs in size, while less-gas-rich mergers and other secular mechanisms shepherd (larger) SFGs as later arrivals to the red sequence. In summary, we propose two evolutionary tracks of QG formation: an early (z≲2), formation path of rapidly quenched cSFGs fading into cQGs that later enlarge within the quiescent phase, and a late-arrival (z≳2) path in which larger SFGs form extended QGs without passing through a compact state.

The Study of the Public Space

Except for the "practical exercises" section, this work is registered under the following ISBN numbers: 978-84-15768-61-6 and 978-84-15768-62-3

Stability in Linear Optimization Under Perturbations of the Left-Hand Side Coefficients

This paper studies stability properties of linear optimization problems with finitely many variables and an arbitrary number of constraints, when only left hand side coefficients can be perturbed. The coefficients of the constraints are assumed to be continuous functions with respect to an index which ranges on certain compact Hausdorff topological space, and these properties are preserved by the admissible perturbations. More in detail, the paper analyzes the continuity properties of the feasible set, the optimal set and the optimal value, as well as the preservation of desirable properties (boundedness, uniqueness) of the feasible and of the optimal sets, under sufficiently small perturbations.

La humanització del monstre: Albert Sánchez Piñol vs. H. P. Lovecraft

Aquest article pretén bastir una comparativa entre la figura teratològica mostrada a l’obra A les muntanyes de la follia de Howard Phillips Lovecraft i La pell freda d’Albert Sánchez Piñol. Una comparativa que té per finalitat mostrar com Howard Phillips Lovecraft inicia una evolució en el gènere de por (basada en la introducció de la versemblança en les narracions d’aquest gènere a través d’un racionalisme que connecta amb exactitud tots els elements de la narració, tot introduint una realitat que contrasta amb allò sobrenatural i crea la por als ulls del lector) que és assumida per Sánchez Piñol en alguns aspectes i transgredida en altres. Així, aquest darrer autor traspassa la frontera infranquejable entre humans i monstres que planteja Lovecraft en humanitzar el monstre, tot atribuint-li qualitats físiques i psicològiques humanes. Una acció que ocasiona un sentiment d’empatia dels personatges humans envers els monstres que derivarà, en última instància, en un intent d’aproximació d’aquests al monstre. O, dit d’una altra manera, en una aproximació de l’ésser humà a l’obscuritat, espai que, lluny de ser perniciós per aquest, l’ajudarà a assolir un coneixement aprofundit de si mateix. Una característica del text de Sánchez Piñol que atorga a La pell freda (i a la major part de l’obra de l’autor) un important valor antropològic i sociològic que pot salvaguardar la narrativa de por de la tendència a desaparèixer que experimenta en una societat cada cop més marcada per l’escepticisme.

Una aproximación a los instrumentos económicos de las leyes del suelo del 2008 y 2015. ¿Hacia un cambio en el modelo de desarrollo en España?

Tras la aprobación del Real Decreto Legislativo 2/2008 –Ley del Suelo–, nos encontramos ante un modelo territorial y un modelo de desarrollo, que acaba con el arcaico patrón de ciudad dispersa, encontrándose, no obstante, ante las gravísimas consecuencias espaciales generadas por la denominada “burbuja inmobiliaria”, unida a una crisis de consecuencias insospechadas, en el ámbito de la denominada globalización económica, de la que nuestro país no ha logrado sustraerse con Leyes vacías de instrumentos económicos que se han transferido a las Comunidades Autónomas, nos hallamos ante una oportunidad perdida fruto de una no siempre bien calculada descentralización. De este modo, en el presente artículo nos aproximamos a la importancia que muestran los denominados “instrumentos económicos” en la normativa que recoge los pormenores relacionados con el “suelo”, en España, en la primera de nuestras Leyes, la de 1956, en la de 2008 y en el recién aprobado Texto Refundido de la Ley del Suelo y Rehabilitación Urbana –Real Decreto Legislativo 7/2015–, en el ámbito estatal. Para ello, tras definir y valorar los enfoques conceptuales relativos al “suelo” y sus tipologías, se concretan y estudian los instrumentos económicos que se recogen en la Ley del Suelo española y su relación con las nuevas formas de “hacer ciudad”.

Requalificação urbana e meio ambiente: a inserção da temática ambiental nas propostas de intervenção sobre centros antigos

O crescimento espraiado e periférico das cidades nos países dependentes, tal qual o Brasil, tem reproduzido um movimento de segregação socioespacial das classes de baixos rendimentos, as quais são relegadas a condições ambientais insalubres. Nos países centrais do capitalismo, sob formas distintas, se observa também desde os anos 1960 discussões com respeito à expansão urbana para áreas cada vez maiores, seja por fenômenos como o urban sprawl anglo-saxão, ou a urbanização difusa, dos países da Europa latina. Diante desse quadro, com a publicação do Livro Verde sobre o Ambiente Urbano, documento elaborado em 1990 pela Comissão das Comunidades Européias para fornecer subsídios à elaboração das políticas urbano-ambientais, tem se propagado a ideia de que a promoção de “cidades compactas” seria uma solução adequada para reverter o atual estágio de expansão urbana para novas áreas, aumentando as densidades demográficas em áreas infraestruturadas, sobretudo por meio da reabilitação de edificações e terrenos ociosos localizados nos centros tradicionais, os quais tem passado por processos de abandono, perda de população e deterioração física do patrimônio edificado. Tendo isso em vista, na presente comunicação temos por objetivo analisar como a temática ambiental tem se inserido no contexto das discussões sobre a requalificação de centros antigos com foco na promoção de habitações para as classes populares. Para tal realizamos revisão da literatura sobre o tema proposto bem como procuramos identificar os princípios que tem regido tais políticas com relação ao tema ambiental. A relevância do tema encontra-se na necessidade de buscar caminhos alternativos a política habitacional e urbana brasileira, a qual tem reproduzido um modelo predatório de reprodução do espaço urbano.

Use of space by domestic chicks housed in complex aviaries.

To improve the understanding of the development of locomotor capacity in layer hens, we measured how female laying hen chicks (n=120) of four different strains (LSL-lite, Hyline Brown, Dekalb White, Lohmann Brown; 3 groups of 10 chicks per line) utilized the ground, the air, elevated horizontal (platforms and perches) and inclined surfaces (ramps and ladders) in an aviary until 9 weeks of age. We used infra-red video recordings to perform all-occurrences sampling of locomotive behavioural and perching events that occurred on the ground—where bedding material, food and water were provided, in the air, and on elevated horizontal and inclined surfaces within weekly 30-min sampling periods. Chicks preferred level ground during the first week of life compared to weeks 5–9 (P<0.0001) and performed 52% of all behavioural events in this section. Elevated surface use began at 2 weeks of age and increased over time (P=0.003), where most behaviour was performed in S2 (45% of all events). Chicks preferred horizontal to inclined surfaces, which were used from weeks 2–5 with maximum use occurring during weeks 2 and 3. Lohmann LSL chicks used the space above the ground most frequently (P=0.05) and performed more aerial ascent/descent behaviour than other lines (P<0.0001). Overall activity levels declined with age (P<0.0001). In summary layer chicks almost exclusively locomoted on the ground but utilized elevated horizontal surfaces (perch, first platform) as early as 2 weeks. These results provide information for improving space use in rearing aviaries by introducing lower perches, platforms and ramps/ladders to accommodate age-dependent locomotor abilities.

Extension of funding and program assistance under the Compact of Free Association : hearing before the Committee on Energy and Natural Resources, United States Senate, One Hundred Seventh Congress, first session, to receive testimony on negotiations on extension of funding and program assistance under the Compact of Free Association, December 6, 2001.

Shipping list no.: 2002-0182-P.

Minimum wage state compact : report (to accompany S.J. Res. 148).

"May 13 (calendar day, June 21), 1935."