Solution structure of the sodium channel antagonist conotoxin GS: A new molecular caliper for probing sodium channel geometry

Background: The venoms of Conus snails contain small, disulfide-rich inhibitors of voltage-dependent sodium channels. Conotoxin GS is a 34-residue polypeptide isolated from Conus geographus that interacts with the extracellular entrance of skeletal muscle sodium channels to prevent sodium ion conduction. Although conotoxin GS binds competitively with mu conotoxin GIIIA to the sodium channel surface, the two toxin types have little sequence identity with one another, and conotoxin GS has a four-loop structural framework rather than the characteristic three-loop mu-conotoxin framework. The structural study of conotoxin GS will form the basis for establishing a structure-activity relationship and understanding its interaction with the pore region of sodium channels. Results: The three-dimensional structure of conotoxin GS was determined using two-dimensional NMR spectroscopy. The protein exhibits a compact fold incorporating a beta hairpin and several turns. An unusual feature of conotoxin GS is the exceptionally high proportion (100%) of cis-imide bond geometry for the three proline or hydroxyproline residues. The structure of conotoxin GS bears little resemblance to the three-loop mu conotoxins, consistent with the low sequence identity between the two toxin types and their different structural framework. However, the tertiary structure and cystine-knot motif formed by the three disulfide bonds is similar to that present in several other polypeptide ion channel inhibitors. Conclusions: This is the first three-dimensional structure of a 'four-loop' sodium channel inhibitor, and it represents a valuable new structural probe for the pore region of voltage-dependent sodium channels. The distribution of amino acid sidechains in the structure creates several polar and charged patches, and comparison with the mu conotoxins provides a basis for determining the binding surface of the conotoxin GS polypeptide.

Phronesis and Energeia : a reading of Heidegger's early appropriation of Aristotelian Phronesis (1922-24) in the light of Energeia

L’objectif de cette thèse est d’élucider l’intention, la pertinence et la cohérence de l’appropriation par Heidegger des concepts principaux de la philosophie pratique aristotélicienne dans ses premiers cours. Notre analyse portera principalement sur les notions clefs d’energeia et de phronēsis. La première section de la thèse est préparatoire : elle est consacrée à une analyse étroite des textes pertinents de l’Éthique à Nicomaque, mais aussi de la Métaphysique, en discussion avec d’autres commentateurs modernes. Cette analyse jette les fondations philologiques nécessaires en vue d’aborder les audacieuses interprétations de Heidegger sur une base plus ferme. La deuxième et principale section consiste en une discussion de l’appropriation ontologique de l’Éthique à Nicomaque que Heidegger entreprend de 1922 à 1924, à partir des textes publiés jusqu’à ce jour et en portant une attention spéciale à Métaphysique IX. Le résultat principal de la première section est un aperçu du caractère central de l’energeia pour le projet d’Aristote dans l’Éthique à Nicomaque et, plus spécifiquement, pour sa compréhension de la praxis, qui dans son sens original s’avère être un mode d’être des êtres humains. Notre analyse reconnaît trois traits essentiels de l’energeia et de la praxis, deux desquels provenant de l’élucidation aristotélicienne de l’energeia dans Métaphysique IX 6, à savoir son immédiateté et sa continuité : energeia exprime l’être comme un « accomplissement immédiat mais inachevé ». L’irréductibilité, troisième trait de l’energeia et de la praxis, résulte pour sa part de l’application de la structure de l’energeia à la caractérisation de la praxis dans l’Éthique à Nicomaque, et du contraste de la praxis avec la poiēsis et la theōria. Ces trois caractéristiques impliquent que la vérité pratique ― la vérité de la praxis, ce qui est l’ « objet » de la phronēsis ― ne peut être à proprement parler possédée et ainsi transmise : plus qu’un savoir, elle se révèle surtout comme quelque chose que nous sommes. C’est ce caractère unique de la vérité pratique qui a attiré Heidegger vers Aristote au début des années 1920. La deuxième section, consacrée aux textes de Heidegger, commence par la reconstruction de quelques-uns des pas qui l’ont conduit jusqu’à Aristote pour le développement de son propre projet philosophique, pour sa part caractérisé par une profonde, bien qu’énigmatique combinaison d’ontologie et de phénoménologie. La légitimité et la faisabilité de l’appropriation clairement ontologique de l’Éthique à Nicomaque par Heidegger est aussi traitée, sur la base des résultats de la première section. L’analyse de ces textes met en lumière la pénétrante opposition établie par Heidegger entre la phronēsis et l’energeia dans son programmatique Natorp Bericht en 1922, une perspective qui diverge fortement des résultats de notre lecture philologique d’Aristote dans la première section. Cette opposition est maintenue dans nos deux sources principales ― le cours du semestre d’hiver 1924-25 Platon: Sophistes, et le cours du semestre d’été 1924 Grundbegriffe der aristotelischen Philosophie. Le commentaire que Heidegger fait du texte d’Aristote est suivi de près dans cette section: des concepts tels que energeia, entelecheia, telos, physis ou hexis ― qui trouvent leur caractérisation ontologique dans la Métaphysique ou la Physique ― doivent être examinés afin de suivre l’argument de Heidegger et d’en évaluer la solidité. L’hypothèse de Heidegger depuis 1922 ― à savoir que l’ontologie aristotélicienne n’est pas à la hauteur des aperçus de ses plus pénétrantes descriptions phénoménologiques ― résulte en un conflit opposant phronēsis et sophia qui divise l’être en deux sphères irréconciliables qui auraient pour effet selon Heidegger de plonger les efforts ontologiques aristotéliciens dans une impasse. Or, cette conclusion de Heidegger est construite à partir d’une interprétation particulière de l’energeia qui laisse de côté d’une manière décisive son aspect performatif, pourtant l’un des traits essentiels de l’energeia telle qu’Aristote l’a conçue. Le fait que dans les années 1930 Heidegger ait lui-même retrouvé cet aspect de l’energeia nous fournit des raisons plus fortes de mettre en doute le supposé conflit entre ontologie et phénoménologie chez Aristote, ce qui peut aboutir à une nouvelle formulation du projet heideggérien.

Ética hacker y propiedad intelectual: una nueva perspectiva para abordar la normatividad sobre derechos de autor en el espacio digital

En el presente texto se busca mostrar las capacidades explicativas que puede tener la conjunción entre las perspectivas de la ética hacker y la defensa de la propiedad intelectual para dar cuenta de las reacciones generalizadas de rechazo ante las normatividades de derechos de autor en el espacio digital. Así, se lleva a cabo un resumen de los principios de cada una de estas perspectivas dando cuenta de sus capacidades explicativas y características teóricas para, posteriormente, aplicarlas a la realidad empresarial, laboral y de opinión en el marco social contemporáneo. Cómo conclusión de este trabajo se logra observar que a pesar de que en principio ambas perspectivas podrían parecer contradictorias, existen aspectos comunes que permiten vislumbrar como un trabajo en conjunto permitiría generar normatividades que se acoplen a las realidades contemporáneas.

Interval training at 95% and 100% of the velocity at VO2 max: effects on aerobic physiological indexes and running performance

The objective of this study was to analyze the effect of two different high-intensity interval training (HIT) programs on selected aerobic physiological indices and 1500 and 5000 m running performance in well-trained runners. The following tests were completed (n = 17): (i) incremental treadmill test to determine maximal oxygen uptake (VO2max), running velocity associated with VO2 max (VVO2max), and the velocity corresponding to 3.5 mmol/L of blood lactate concentration (vOBLA); (ii) submaximal constant-intensity test to determine running economy (RE); and (iii) 1500 and 5000 m time trials on a 400 m track. Runners were then randomized into 95% vVO(2max) or 100% vVO(2max) groups, and undertook a 4 week training program consisting of 2 HIT sessions (performed at 95% or 100% vVO(2max), respectively) and 4 submaximal run sessions per week. Runners were retested on all parameters at the completion of the training program. The VO2 max values were not different after training for both groups. There was a significant increase in post-training vVO(2 max), RE, and 1500 in running performance in the 100% vVO(2 max) group. The vOBLA and 5000 m running performance were significantly higher after the training period for both groups. We conclude that vOBLA and 5000 m running performance can be significantly improved in well-trained runners using a 4 week training program consisting of 2 HIT sessions (performed at 95% or 100% vVO(2max)) and 4 submaximal run sessions per week. However, the improvement in vVO(2 max), RE, and 1500 in running performance seems to be dependent on the HIT program at 100% vVO(2 max).

Amitriptyline prolongs the antihyperalgesic effect of 2- or 100-Hz electro-acupuncture in a rat model of post-incision pain

The mechanisms through which electro-acupuncture (EA) and tricyclic antidepressants produce analgesia seem to be complementary: EA inhibits the transmission of noxious messages by activating supraspinal serotonergic and noradrenergic neurons that project to the spinal cord, whereas tricyclic antidepressants affect pain transmission by inhibiting the reuptake of norepinephrine and serotonin at the spinal level. This study utilized the tail-flick test and a model of post-incision pain to compare the antihyperalgesic effects of EA at frequencies of 2 or 100 Hz in rats treated with intraperitoneal or intrathecal amitriptyline (a tricyclic antidepressant). A gradual increase in the tail-flick latency (TFL) occurred during a 20-min period of EA. A strong and long-lasting reduction in post-incision hyperalgesia was observed after stimulation; the effect after 2 Hz lasting longer than after 100-Hz EA. Intraperitoneal or intrathecal amitriptyline potentiated the increase in TFL in the early moments of 2- or 100-Hz EA, and the intensity of the antihyperalgesic effect of 100-Hz EA in both the incised and non-incised paw. In contrast, it did not significantly change the intensity of the antihyperalgesic effect of 2-Hz EA. The EA-induced antihyperalgesic effects lasted longer after intraperitoneal or intrathecal amitriptyline than after saline, with this effect of amitriptyline being more evident after 100-than after 2-Hz EA. The synergetic effect of amitriptyline and EA against post-incision pain shown here may therefore represent an alternative for prolonging the efficacy of EA in the management of post-surgical clinical pain.

Diffusion-weighted MR imaging of the placenta in fetuses with placental insufficiency

PURPOSE: To evaluate diffusion-weighted magnetic resonance (MR) imaging of the human placenta in fetuses with and fetuses without intrauterine growth restriction (IUGR) who were suspected of having placental insufficiency. MATERIALS AND METHODS: The study was approved by the local ethics committee, and written informed consent was obtained. The authors retrospectively evaluated 1.5-T fetal MR images from 102 singleton pregnancies (mean gestation ± standard deviation, 29 weeks ± 5; range, 21-41 weeks). Morphologic and diffusion-weighted MR imaging were performed. A region of interest analysis of the apparent diffusion coefficient (ADC) of the placenta was independently performed by two observers who were blinded to clinical data and outcome. Placental insufficiency was diagnosed if flattening of the growth curve was detected at obstetric ultrasonography (US), if the birth weight was in the 10th percentile or less, or if fetal weight estimated with US was below the 10th percentile. Abnormal findings at Doppler US of the umbilical artery and histopathologic examination of specimens from the placenta were recorded. The ADCs in fetuses with placental insufficiency were compared with those in fetuses of the same gestational age without placental insufficiency and tested for normal distribution. The t tests and Pearson correlation coefficients were used to compare these results at 5% levels of significance. RESULTS: Thirty-three of the 102 pregnancies were ultimately categorized as having an insufficient placenta. MR imaging depicted morphologic changes (eg, infarction or bleeding) in 27 fetuses. Placental dysfunction was suspected in 33 fetuses at diffusion-weighted imaging (mean ADC, 146.4 sec/mm(2) ± 10.63 for fetuses with placental insufficiency vs 177.1 sec/mm(2) ± 18.90 for fetuses without placental insufficiency; P < .01, with one false-positive case). The use of diffusion-weighted imaging in addition to US increased sensitivity for the detection of placental insufficiency from 73% to 100%, increased accuracy from 91% to 99%, and preserved specificity at 99%. CONCLUSION: Placental dysfunction associated with growth restriction is associated with restricted diffusion and reduced ADC. A decreased ADC used as an early marker of placental damage might be indicative of pregnancy complications such as IUGR.

The Art of Aidagara: Ethics, Aesthetics, and the Quest for an Ontology of Social Existence in Watsuji Tetsurō’s Rinrigaku

This paper provides an analysis of the key term aidagara (“betweenness”) in the philosophical ethics of Watsuji Tetsurō (1889-1960), in response to and in light of the recent movement in Japanese Buddhist studies known as “Critical Buddhism.” The Critical Buddhist call for a turn away from “topical” or intuitionist thinking and towards (properly Buddhist) “critical” thinking, while problematic in its bipolarity, raises the important issue of the place of “reason” versus “intuition” in Japanese Buddhist ethics. In this paper, a comparison of Watsuji’s “ontological quest” with that of Martin Heidegger (1889-1976), Watsuji’s primary Western source and foil, is followed by an evaluation of a corresponding search for an “ontology of social existence” undertaken by Tanabe Hajime (1885-1962). Ultimately, the philosophico-religious writings of Watsuji Tetsurō allow for the “return” of aesthesis as a modality of social being that is truly dimensionalized, and thus falls prey neither to the verticality of topicalism nor the limiting objectivity of criticalism.

The Effects Of Farnesyltransferase Inhibitor Abt-100 On Murine Helper T-Cell Differentiation And Cytokine Secretion

Farnesyltransferase Inhibitors (FTIs) are a class of drugs known to prevent the farnesylation and subsequent membrane attachment of a number of intracellular proteins. In various studies, the administration of FTIs has been found to play a role in the activation and development of T-cells in the immune system. FTIs have also been found to act as immunomodulators in delaying MHC-II mismatched skin allografts in mice. This study focuses on the effect of the FTI, ABT-100, on the differentiation and cytokine secretion of Th1 and Th2 helper T-cells in BALB/C mice to better understand which immune responses are targeted by FTIs. Splenocytes were isolated from BALB/C mice, skewed towards either a Th1 or a Th2 phenotype with the addition of cytokines, and treated with various concentrations of ABT-100. Splenocytes were also isolated and immediately cultured in the presence of ABT-100 to observe differentiation trends of helper T-cells. Cytokine production was measured using intracytoplasmic flow cytometry analysis. I found that ABT-100 treatment does not block Th1 or Th2 cell differentiation. Instead, ABT-100 treatment appears to affect cytokine production from effector T-cells. I found that ABT-100 causes a decrease in IFN-¿ production in mature Th1 cells yet does not affect IL-4 production in mature Th2 cells. This decrease in cytokine production as a result of ABT-100 treatments provides a potential mechanism for how ABT-100 works to delay MHC-II mismatched allograft rejection.

[Fixed-combination of losartan/hydrochlorothiazide 100 mg/25 mg. Tolerability and efficacy on blood pressure measured in the practice and for 24 hours]

BACKGROUND: A high proportion of patients with essential hypertension need a combination therapy to reach the therapeutic goal. In the present study, the tolerability and efficacy of a fixed, once daily combination of the AT1 blocker Losartan (100 mg) and the diuretic hydrochlorothiazide (HCTZ) (25 mg) for patients in the real-life situation was investigated. Special consideration was given to the results of ambulatory 24-hourblood pressure (ABP) measurements. METHODS: The open label, prospective non-interventional surveillance study took place from October 2005 to June 2006. A total of 1139 patients over 18 years in age were included whose blood pressures could not be adequately treated with HCTZ alone and for whom an individual dose titration for Losartan and HCTZ had already been performed. RESULTS: The average age (+/- standard deviation) of the patients was 61.2 +/- 11.6 years; 55.8% were men. Comorbidities were common. Specifically, left ventricular hypertrophy was present in 3.1% of the patients, coronary heart disease in 30.1%, chronic heart failure in 11.8% and status post myocardial infarction in 10.5%, respectively. In addition to the Losartan/HCTZ treatment, 61.0% of the patients received a second antihypertensive medicine. After an average treatment duration of 50.4 +/- 17.2 days, the base line systolic blood pressure of 160.8 +/- 16.3 mmHg decreased by 24.0 +/- 17.0 mmHg (-14.4%) and the diastolic blood pressure of 94.4 +/- 9.9 mmHg decreased by 11.8 +/- 10.2 mmHg (-11.8%). For the ABP measurements, the overall average systolic and diastolic blood pressures fell by 16.9 +/- 14.2 mmHg and 8.8 +/-10.3 mmHg, the day average by 17.3 +/- 14.8 mmHg and 9.0 +/- 10.2 mmHg and the night average by 15.1 +/- 17.6 mmHg and 7.8 +/- 11.7 mmHg, respectively. In twelve of the 1139 patients (1.1%), a total of 15 adverse events occurred. A causal connection with the medication was suspected in only in one case (one patient with three). CONCLUSION: The combination of Losartan/HCTZ 100/25 mg, as the exclusive therapy or in addition to other antihypertensive medicines, was for patients, many of whom who had comorbidities, in the real-life situation well tolerated and effective. The efficacy was demonstrated also during the night through ABP.

In situ control of Si(100) and Ge(100) surface preparation for the heteroepitaxy of III-V solar cell architectures

Si(100) and Ge(100) substrates essential for subsequent III-V integration were studied in the hydrogen ambient of a metalorganic vapor phase epitaxy reactor. Reflectance anisotropy spectroscopy (RAS) enabled us to distinguish characteristic configurations of vicinal Si(100) in situ: covered with oxide, cleaned by thermal removing in H2, and terminated with monohydrides when cooling in H2 ambient. RAS measurements during cooling in H2 ambient after the oxide removal process revealed a transition from the clean to the monohydride terminated Si(100) surface dependent on process temperature. For vicinal Ge(100) we observed a characteristic RA spectrum after annealing and cooling in H2 ambient. According to results from X-ray photo electron spectroscopy and Fourier-transform infrared spectroscopy the spectrum corresponds to the monohydride terminated Ge(100) surface.

Business ethics: a way to identify fraud from the basics

When we look to perform a work for developing a framework to create a business and take it correctly, there are always some persons looking as a challenge those bases and finding a mistake. The way to work in these situations is not a matter of law, is a matter of devoting time to identify these situations. It is always said that the evil goes a step ahead. The business ethics have been altered for quite time by some would-be entrepreneurs. These people have learned to play with business ethics to show your business as prosperous as something that is sought to highlight and adulterate their results quickly. Once the company reaches an international dimension, many companies take on global responsibility and, in these cases where you can see if the objective has been to obtain a rapid capital increase or growth is in line with its proportions. A business ethics is based on establishing a strong base so that interest is encouraged from an early time. Good staff, organizational level should be achieved and not only at the company but, out of the company too. Thus, you can create a secure base to convince potential investors and employees about the business. There are no freeways in business ethics and all fast track can be or a genius or leads to failure. We must find where these jumps are occurring, such errors or corrections to business ethics and their rules. Thus we can differentiate a company or an entrepreneur who is working correctly from the cloaking. Starting from the basics of business ethics and studying the different levels from the personal to the prospect that the company shows in the world. Lets see where these changes are occurring and how we can fight against them and anticipate the market to possible cases of fraud or strange movements seeking to attract the unwary

Naturaleza, ética, y arquitectura: Autenticidad y criterios éticos que integran el desarrollo de una arquitectura más sostenible = Nature, ethics and architecture: Authenticity and ethics criteria that integrate the development of a more sustainable architecture

La ecología no solamente ha puesto de manifiesto problemas ambientales, sino que ha confirmado la necesidad de una nueva armonía entre los propios seres humanos y de éstos con la naturaleza y con todos los seres que la habitan. Es necesario un nuevo contrato que determine nuestras relaciones con la Naturaleza (Serrs1), y una nueva Ética para nuestras vidas (Guattari2). La ética medioambiental nos ha dado una visión universal y supra-generacional de la gestión de la naturaleza y como consecuencia, una nueva forma de construir nuestra ‘segunda’ Naturaleza, que es la arquitectura. ¿Qué es lo esencial que esta nueva ética exige para la arquitectura? Este es un momento crucial para reconsiderar los objetivos de la arquitectura, porque lo ‘eco’ está produciendo grandes cambios. ¿Implica esta era post-ecológica una particular ética, es decir, referida a sus fines y medios? ¿Porqué, para qué, para quién, cómo debemos hacer la arquitectura de nuestro tiempo? Es momento de afrontar críticamente el discurso de la eco-arquitectura, e incluso de repensar los propios límites de la arquitectura. El desarrollo actual del conocimiento medioambiental es esencialmente técnico y utilitario, pero ¿es el reto solamente técnico?¿Es suficiente la suma de lo medioambiental-social-económico-cultural para definirla? ¿Hay claves que nos puedan dar la dimensión ética de esta aproximación técnica-empírica? ¿Sabemos lo que estamos haciendo cuando aplicamos este conocimiento? Y, sobre todo, ¿cuál es el sentido de lo que estamos haciendo? La tesis que se propone puede resumirse: De acuerdo con el actual conocimiento que tenemos de la Naturaleza, la Arquitectura de nuestro tiempo deber reconsiderar sus fines y medios, puesto que la ética medioambiental está definiendo nuevos objetivos. Para fundamentar y profundizar en esta afirmación la tesis analiza cómo son hoy día las relaciones entre Ética-Naturaleza-Arquitectura (Fig.1), lo que facilitará las claves de cuáles son los criterios éticos (en cuanto a fines y medios) que deben definir la arquitectura del tiempo de la ecología. ABSTRACT Ecology shows us not only environmental problems; it shows that we need a new balance and harmony between individuals, beings, communities and Nature. We need a new contract with Nature according to Serres576, and a new Ethics for our lives according to Guattari577. Environmental ethics have given us a universal and supra-generational vision of the management of our Nature and, as a consequence, a new way to construct our ‘second’ nature, which is architecture. What is essential for this new architecture that the new ethics demand? This is a critical moment to reconsider the object of architecture, because the ‘eco’ is making significant changes in it. Are there any specifically ethical concerns (ends and means) in the post-ecological era? Why, for what, for whom, how should we make architecture in our times? This is the time to approach the eco-architectural discourse critically and to question the current boundaries of architecture itself: Where is eco-architecture going? The current development of environmental knowledge is essentially technical and utilitarian, but it is its technical aspect the only challenge? Is the sum of environmental-social-economic aspects enough to define it? Are there any clues which can give an ethical sense to this technical-empirical approach? Do we know what we are doing when we apply this knowledge? And overall, what is the meaning of what we are doing? Exploring this subject, this thesis makes a statement: In accordance with the actual knowledge of Nature, Architecture of our time must reconsider its ends and means, since the environmental ethics is defining new objectives. To support that, the thesis analyzes what the relationships between Ethics –Nature- Architecture (Fig. 53) are like nowadays, this will provide the clues of which ethical criteria (ends and means) must architecture of an ecological era define.

Contribution to the analysis and design of reflectarray antennas for reconfigurable beam applications at frequencies above 100 GHz using liquid crystal technology

El trabajo contenido en esta tesis doctoral está encuadrado en el desarrollo de antenas reconfigurables electrónicamente capaces de proporcionar prestaciones competitivas a las aplicaciones cada vez más comunes que operan a frecuencias superiores a 60 GHz. En concreto, esta tesis se centra en el estudio, diseño, e implementación de las antenas reflectarray, a las que se introduce la tecnología de cristal líquido como elemento característico con el que se consigue reconfigurabilidad de haz de forma electrónica. Desde un punto de vista muy general, se puede describir un cristal líquido como un material cuya permitividad eléctrica es variable y controlada por una excitación externa, que generalmente suele corresponderse con un campo eléctrico quasi-estático (AC). Las antenas reflectarray de cristal líquido se han escogido como objeto de estudio por varias razones. La primera de ellas tiene que ver con las ventajas que los reflectarrays, y en especial aquellos realizados en configuración planar, proporcionan con respecto a otras antenas de alta ganancia como los reflectores o los “phased-arrays”. En los reflectarrays, la alimentación a través de una fuente primaria común (característica de reflectores) y el elevado número de grados de libertad de las celdas que los componen (característica de arrays) hacen que estas antenas puedan proporcionar prestaciones eléctricas iguales o mejores que las anteriores, a un coste más reducido y con estructuras de antena más compactas. La segunda razón radica en la flexibilidad que ofrece el cristal líquido a ser confinado y polarizado en recintos de geometría variada, como consecuencia de su fluidez (propiedad de los líquidos). Por ello, la tecnología de cristal líquido permite que el propio elemento reconfigurable en las celdas de reflectarray se adapte a la configuración planar de manera que en sí mismo, el cristal líquido sea una o varias de las capas características de esta configuración. Esto simplifica de forma drástica la estructura y la fabricación de este tipo de antenas, incluso si se comparan con reflectarrays reconfigurables basados en otras tecnologías como diodos, MEMS, etc. Por tanto, su coste y desarrollo es muy reducido, lo que hace que se puedan fabricar reflectarrays reconfigurables eléctricamente grandes, a bajo coste, y en producción elevada. Un ejemplo claro de una estructura similar, y que ha tenido éxito comercial, son las pantallas de cristal líquido. La tercera razón reside en el hecho de que el cristal líquido es, hasta la fecha, de las pocas tecnologías capaces de ofrecer reconfigurabilidad del haz a frecuencias superiores a 60 GHz. De hecho, el cristal líquido permite reconfigurabilidad en un amplio margen de frecuencias, que va desde DC a frecuencias del espectro visible, incluyendo las microondas y los THz. Otras tecnologías, como los materiales ferroeléctricos, el grafeno o la tecnología CMOS “on chip” permiten también conmutar el haz en estas frecuencias. Sin embargo, la tecnología CMOS tiene un elevado coste y actualmente está limitada a frecuencias inferiores a 150 GHz, y aunque los materiales ferroeléctricos o el grafeno puedan conmutar a frecuencias más altas y en un rango más amplio, tienen serias dificultades que los hacen aún inmaduros. En el caso de los materiales ferroeléctricos, los elevados voltajes para conmutar el material los hacen poco atractivos, mientras que en el caso del grafeno, su modelado aún está en discusión, y todavía no se han arrojado resultados experimentales que validen su idoneidad. Estas tres razones hacen que los reflectarrays basados en cristal líquido sean atractivos para multitud de aplicaciones de haz reconfigurable a frecuencias superiores a 60 GHz. Aplicaciones como radar de escaneo de imágenes de alta resolución, espectroscopia molecular, radiómetros para observación atmosférica, o comunicaciones inalámbricas de alta frecuencia (WiGig) son algunas de ellas. La tesis está estructurada en tres partes. En la primera de ellas se describen las características más comunes de los cristales líquidos, centrándonos en detalle en aquellas propiedades ofrecidas por este material en fase nemática. En concreto, se estudiará la anisotropía dieléctrica (Ae) de los cristales líquidos uniaxiales, que son los que se emplean en esta tesis, definida como la diferencia entre la permitividad paralela (£//) y la perpendicular (e±): Ae = e,, - e±. También se estudiará la variación de este parámetro (Ae) con la frecuencia, y el modelado electromagnético macroscópico más general que, extraído a partir de aquella, permite describir el cristal líquido para cada tensión de polarización en celdas de geometría planar. Este modelo es de suma importancia para garantizar precisión en el desfasaje proporcionado por las diferentes celdas reconfigurables para reflectarrays que se describirán en la siguiente parte de la tesis. La segunda parte de la tesis se centra en el diseño de celdas reflectarray resonantes basadas en cristal líquido. La razón por la que se escogen estos tipos de celdas reside en el hecho de que son las únicas capaces de proporcionar rangos de fase elevados ante la reducida anisotropía dieléctrica que ofrecen los cristales líquidos. El objetivo de esta parte trata, por tanto, de obtener estructuras de celdas reflectarray que sean capaces de proporcionar buenas prestaciones eléctricas a nivel de antena, mejorando sustancialmente las prestaciones de las celdas reportadas en el estado del arte, así como de desarrollar una herramienta de diseño general para aquellas. Para ello, se estudian las prestaciones eléctricas de diferentes tipos de elementos resonantes de cristal líquido que van, desde el más sencillo, que ha limitado el estado de la técnica hasta el desarrollo de esta tesis y que está formado por un sólo resonador, a elementos que constan de varios resonadores (multi-resonantes) y que pueden ser monocapa o multicapa. En un primer paso, el procedimiento de diseño de estas estructuras hace uso de un modelo convencional de cristal líquido que ha venido siendo usado en el estado del arte para este tipo de celdas, y que considera el cristal líquido como un material homogéneo e isótropo cuya permitividad varía entre (e/7) y (e±). Sin embargo, en esta parte de la tesis se demuestra que dicho modelado no es suficiente para describir de forma genérica el comportamiento del cristal líquido en las celdas tipo reflectarray. En la tesis se proponen procedimientos más exactos para el análisis y diseño basados en un modelo más general que define el cristal líquido como un material anisótropo e inhomogeneo en tres dimensiones, y se ha implementado una técnica que permite optimizar celdas multi-resonantes de forma eficiente para conseguir elevadas prestaciones en cuanto a ancho de banda, rango de fase, pérdidas, o sensibilidad al ángulo de incidencia. Los errores cometidos en el uso del modelado convencional a nivel de celda (amplitud y fase) se han analizado para varias geometrías, usando medidas de varios prototipos de antena que usan un cristal líquido real a frecuencias superiores a 100 GHz. Las medidas se han realizado en entorno periódico mediante un banco cuasi-óptico, que ha sido diseñado especialmente para este fin. Uno de estos prototipos se ha optimizado a 100 GHz para conseguir un ancho de banda relativamente elevado (10%), pérdidas reducidas, un rango de fase mayor de 360º, baja sensibilidad al ángulo de incidencia, y baja influencia de la inhomogeneidad transversal del cristal líquido en la celda. Estas prestaciones a nivel de celda superan de forma clara aquellas conseguidas por otros elementos que se han reportado en la literatura, de manera que dicho prototipo se ha usado en la última parte de la tesis para realizar diversas antenas de barrido. Finalmente, en esta parte se presenta una estrategia de caracterización de la anisotropía macroscópica a partir de medidas de los elementos de reflectarray diseñados en banco cuasi-óptico, obteniendo resultados tanto en las frecuencias de interés en RF como en AC, y comparándolas con aquellas obtenidas mediante otros métodos. La tercera parte de la tesis consiste en el estudio, diseño, fabricación y medida de antenas reconfigurables basadas en cristal líquido en configuraciones complejas. En reflectarrays pasivos, el procedimiento de diseño de la antena se limita únicamente al ajuste en cada celda de la antena de las dimensiones de las metalizaciones que se emplean para el control de fase, mediante procesos de optimización bien conocidos. Sin embargo, en el caso de reflectarrays reconfigurables basados en cristal líquido, resulta necesario un paso adicional, que consiste en calcular de forma adecuada las tensiones de control en cada celda del reflectarray para configurar la fase requerida en cada una de ellas, así como diseñar la estructura y los circuitos de control que permitan direccionar a cada elemento su tensión correspondiente. La síntesis de tensiones es por tanto igual o más importante que el diseño de la geometría de las celdas, puesto que éstas son las que están directamente relacionadas con la fase. En el estado del arte, existen varias estrategias de síntesis de tensiones que se basan en la caracterización experimental de la curva de fase respecto al voltaje. Sin embargo, esta caracterización sólo puede hacerse a un solo ángulo de incidencia y para unas determinadas dimensiones de celda, lo que produce que las tensiones sintetizadas sean diferentes de las adecuadas, y en definitiva que se alcancen errores de fase mayores de 70º. De esta forma, hasta la fecha, las prestaciones a nivel de antena que se han conseguido son reducidas en cuanto a ancho de banda, rango de escaneo o nivel de lóbulos secundarios. En esta última parte de la tesis, se introduce una nueva estrategia de síntesis de tensiones que es capaz de predecir mediante simulaciones, y con alta precisión, las tensiones que deben introducirse en cada celda teniendo en cuenta su ángulo de incidencia, sus dimensiones, la frecuencia, así como la señal de polarización definida por su frecuencia y forma de onda AC. Esta estrategia se basa en modelar cada uno de los estados de permitividad del cristal líquido como un sustrato anisótropo con inhomogeneidad longitudinal (1D), o en ciertos casos, como un tensor equivalente homogéneo. La precisión de ambos modelos electromagnéticos también se discute. Con el objetivo de obtener una herramienta eficiente de cálculo de tensiones, también se ha escrito e implementado una herramienta de análisis basada en el Método de los Momentos en el Dominio Espectral (SD-MoM) para sustratos estratificados anisótropos, que se usa en cada iteración del procedimiento de síntesis para analizar cada una de las celdas de la antena. La síntesis de tensiones se ha diseñado además para reducir al máximo el efecto del rizado de amplitud en el diagrama de radiación, que es característico en los reflectarrays que están formados por celdas con pérdidas elevadas, lo que en sí, supone un avance adicional para la obtención de mejores prestaciones de antena. Para el cálculo de los diagramas de radiación empleados en el procedimiento de síntesis, se asume un análisis elemento a elemento considerando periodicidad local, y se propone el uso de un método capaz de modelar el campo incidente de forma que se elimine la limitación de la periodicidad local en la excitación. Una vez definida la estrategia adecuada de cálculo de las tensiones a aplicar al cristal líquido en cada celda, la estructura de direccionamiento de las mismas en la antena, y diseñados los circuitos de control, se diseñan, fabrican y miden dos prototipos diferentes de antena de barrido electrónico a 100 GHz usando las celdas anteriormente presentadas. El primero de estos prototipos es un reflectarray en configuración “single offset” con capacidad de escaneo en un plano (elevación o azimut). Aunque previamente se realizan diseños de antenas de barrido en 2D a varias frecuencias en el rango de milimétricas y sub-milimétricas, y se proponen ciertas estrategias de direccionamiento que permiten conseguir este objetivo, se desarrolla el prototipo con direccionamiento en una dimensión con el fin de reducir el número de controles y posibles errores de fabricación, y así también validar la herramienta de diseño. Para un tamaño medio de apertura (con un numero de filas y columnas entre 30 y 50 elementos, lo que significa un reflectarray con un número de elementos superior a 900), la configuración “single offset” proporciona rangos de escaneo elevados, y ganancias que pueden oscilar entre los 20 y 30 dBi. En concreto, el prototipo medido proporciona un haz de barrido en un rango angular de 55º, en el que el nivel de lóbulos secundarios (SLL) permanece mejor de -13 dB en un ancho de banda de un 8%. La ganancia máxima es de 19.4 dBi. Estas prestaciones superan de forma clara aquellas conseguidas por otros autores. El segundo prototipo se corresponde con una antena de doble reflector que usa el reflectarray de cristal líquido como sub-reflector para escanear el haz en un plano (elevación o azimut). El objetivo básico de esta geometría es obtener mayores ganancias que en el reflectarray “single offset” con una estructura más compacta, aunque a expensas de reducir el rango de barrido. En concreto, se obtiene una ganancia máxima de 35 dBi, y un rango de barrido de 12º. Los procedimientos de síntesis de tensiones y de diseño de las estructuras de las celdas forman, en su conjunto, una herramienta completa de diseño precisa y eficiente de antenas reflectarray reconfigurables basados en cristales líquidos. Dicha herramienta se ha validado mediante el diseño, la fabricación y la medida de los prototipos anteriormente citados a 100 GHz, que consiguen algo nunca alcanzado anteriormente en la investigación de este tipo de antenas: unas prestaciones competitivas y una predicción excelente de los resultados. El procedimiento es general, y por tanto se puede usar a cualquier frecuencia en la que el cristal líquido ofrezca anisotropía dieléctrica, incluidos los THz. Los prototipos desarrollados en esta tesis doctoral suponen también unas de las primeras antenas de barrido real a frecuencias superiores a 100 GHz. En concreto, la antena de doble reflector para escaneo de haz es la primera antena reconfigurable electrónicamente a frecuencias superiores a 60 GHz que superan los 25 dBi de ganancia, siendo a su vez la primera antena de doble reflector que contiene un reflectarray reconfigurable como sub-reflector. Finalmente, se proponen ciertas mejoras que aún deben se deben realizar para hacer que estas antenas puedan ser un producto completamente desarrollado y competitivo en el mercado. ABSTRACT The work presented in this thesis is focused on the development of electronically reconfigurable antennas that are able to provide competitive electrical performance to the increasingly common applications operating at frequencies above 60 GHz. Specifically, this thesis presents the study, design, and implementation of reflectarray antennas, which incorporate liquid crystal (LC) materials to scan or reconfigure the beam electronically. From a general point of view, a liquid crystal can be defined as a material whose dielectric permittivity is variable and can be controlled with an external excitation, which usually corresponds with a quasi-static electric field (AC). By changing the dielectric permittivity at each cell that makes up the reflectarray, the phase shift on the aperture is controlled, so that a prescribed radiation pattern can be configured. Liquid Crystal-based reflectarrays have been chosen for several reasons. The first has to do with the advantages provided by the reflectarray antenna with respect to other high gain antennas, such as reflectors or phased arrays. The RF feeding in reflectarrays is achieved by using a common primary source (as in reflectors). This arrangement and the large number of degrees of freedom provided by the cells that make up the reflectarray (as in arrays), allow these antennas to provide a similar or even better electrical performance than other low profile antennas (reflectors and arrays), but assuming a more reduced cost and compactness. The second reason is the flexibility of the liquid crystal to be confined in an arbitrary geometry due to its fluidity (property of liquids). Therefore, the liquid crystal is able to adapt to a planar geometry so that it is one or more of the typical layers of this configuration. This simplifies drastically both the structure and manufacture of this type of antenna, even when compared with reconfigurable reflectarrays based on other technologies, such as diodes MEMS, etc. Therefore, the cost of developing this type of antenna is very small, which means that electrically large reconfigurable reflectarrays could be manufactured assuming low cost and greater productions. A paradigmatic example of a similar structure is the liquid crystal panel, which has already been commercialized successfully. The third reason lies in the fact that, at present, the liquid crystal is one of the few technologies capable of providing switching capabilities at frequencies above 60 GHz. In fact, the liquid crystal allows its permittivity to be switched in a wide range of frequencies, which are from DC to the visible spectrum, including microwaves and THz. Other technologies, such as ferroelectric materials, graphene or CMOS "on chip" technology also allow the beam to be switched at these frequencies. However, CMOS technology is expensive and is currently limited to frequencies below 150 GHz, and although ferroelectric materials or graphene can switch at higher frequencies and in a wider range, they have serious difficulties that make them immature. Ferroelectric materials involve the use of very high voltages to switch the material, making them unattractive, whereas the electromagnetic modelling of the graphene is still under discussion, so that the experimental results of devices based on this latter technology have not been reported yet. These three reasons make LC-based reflectarrays attractive for many applications that involve the use of electronically reconfigurable beams at frequencies beyond 60 GHz. Applications such as high resolution imaging radars, molecular spectroscopy, radiometers for atmospheric observation, or high frequency wireless communications (WiGig) are just some of them. This thesis is divided into three parts. In the first part, the most common properties of the liquid crystal materials are described, especially those exhibited in the nematic phase. The study is focused on the dielectric anisotropy (Ac) of uniaxial liquid crystals, which is defined as the difference between the parallel (e/7) and perpendicular (e±) permittivities: Ae = e,, - e±. This parameter allows the permittivity of a LC confined in an arbitrary volume at a certain biasing voltage to be described by solving a variational problem that involves both the electrostatic and elastic energies. Thus, the frequency dependence of (Ae) is also described and characterised. Note that an appropriate LC modelling is quite important to ensure enough accuracy in the phase shift provided by each cell that makes up the reflectarray, and therefore to achieve a good electrical performance at the antenna level. The second part of the thesis is focused on the design of resonant reflectarray cells based on liquid crystal. The reason why resonant cells have been chosen lies in the fact that they are able to provide enough phase range using the values of the dielectric anisotropy of the liquid crystals, which are typically small. Thus, the aim of this part is to investigate several reflectarray cell architectures capable of providing good electrical performance at the antenna level, which significantly improve the electrical performance of the cells reported in the literature. Similarly, another of the objectives is to develop a general tool to design these cells. To fulfill these objectives, the electrical yields of different types of resonant reflectarray elements are investigated, beginning from the simplest, which is made up of a single resonator and limits the state of the art. To overcome the electrical limitations of the single resonant cell, several elements consisting of multiple resonators are considered, which can be single-layer or multilayer. In a first step, the design procedure of these structures makes use of a conventional electromagnetic model which has been used in the literature, which considers that the liquid crystal behaves as homogeneous and isotropic materials whose permittivity varies between (e/7) y (e±). However, in this part of the thesis it is shown that the conventional modelling is not enough to describe the physical behaviour of the liquid crystal in reflectarray cells accurately. Therefore, a more accurate analysis and design procedure based on a more general model is proposed and developed, which defines the liquid crystal as an anisotropic three-dimensional inhomogeneous material. The design procedure is able to optimize multi-resonant cells efficiently to achieve good electrical performance in terms of bandwidth, phase range, losses, or sensitivity to the angle of incidence. The errors made when the conventional modelling (amplitude and phase) is considered have been also analysed for various cell geometries, by using measured results from several antenna prototypes made up of real liquid crystals at frequencies above 100 GHz. The measurements have been performed in a periodic environment using a quasi-optical bench, which has been designed especially for this purpose. One of these prototypes has been optimized to achieve a relatively large bandwidth (10%) at 100 GHz, low losses, a phase range of more than 360º, a low sensitivity to angle of incidence, and a low influence of the transversal inhomogeneity of the liquid crystal in the cell. The electrical yields of this prototype at the cell level improve those achieved by other elements reported in the literature, so that this prototype has been used in the last part of the thesis to perform several complete antennas for beam scanning applications. Finally, in this second part of the thesis, a novel strategy to characterise the macroscopic anisotropy using reflectarray cells is presented. The results in both RF and AC frequencies are compared with those obtained by other methods. The third part of the thesis consists on the study, design, manufacture and testing of LCbased reflectarray antennas in complex configurations. Note that the design procedure of a passive reflectarray antenna just consists on finding out the dimensions of the metallisations of each cell (which are used for phase control), using well-known optimization processes. However, in the case of reconfigurable reflectarrays based on liquid crystals, an additional step must be taken into account, which consists of accurately calculating the control voltages to be applied to each cell to configure the required phase-shift distribution on the surface of the antenna. Similarly, the structure to address the voltages at each cell and the control circuitry must be also considered. Therefore, the voltage synthesis is even more important than the design of the cell geometries (dimensions), since the voltages are directly related to the phase-shift. Several voltage synthesis procedures have been proposed in the state of the art, which are based on the experimental characterization of the phase/voltage curve. However, this characterization can be only carried out at a single angle of incidence and at certain cell dimensions, so that the synthesized voltages are different from those needed, thus giving rise to phase errors of more than 70°. Thus, the electrical yields of the LCreflectarrays reported in the literature are limited in terms of bandwidth, scanning range or side lobes level. In this last part of the thesis, a new voltage synthesis procedure has been defined and developed, which allows the required voltage to be calculated at each cell using simulations that take into account the particular dimensions of the cells, their angles of incidence, the frequency, and the AC biasing signal (frequency and waveform). The strategy is based on the modelling of each one of the permittivity states of the liquid crystal as an anisotropic substrate with longitudinal inhomogeneity (1D), or in certain cases, as an equivalent homogeneous tensor. The accuracy of both electromagnetic models is also discussed. The phase errors made by using the proposed voltage synthesis are better than 7º. In order to obtain an efficient tool to analyse and design the reflectarray, an electromagnetic analysis tool based on the Method of Moments in the spectral domain (SD-MoM) has also written and developed for anisotropic stratified media, which is used at each iteration of the voltage synthesis procedure. The voltage synthesis is also designed to minimize the effect of amplitude ripple on the radiation pattern, which is typical of reflectarrays made up of cells exhibiting high losses and represents a further advance in achieving a better antenna performance. To calculate the radiation patterns used in the synthesis procedure, an element-by-element analysis is assumed, which considers the local periodicity approach. Under this consideration, the use of a novel method is proposed, which avoids the limitation that the local periodicity imposes on the excitation. Once the appropriate strategy to calculate the voltages to be applied at each cell is developed, and once it is designed and manufactured both the structure to address the voltages to the antenna and the control circuits, two complete LC-based reflectarray antennas that operate at 100 GHz have been designed, manufactured and tested using the previously presented cells. The first prototype consists of a single offset reflectarray with beam scanning capabilities on one plane (elevation and azimuth). Although several LC-reflectarray antennas that provide 2-D scanning capabilities are also designed, and certain strategies to achieve the 2-D addressing of the voltage are proposed, the manufactured prototype addresses the voltages in one dimension in order to reduce the number of controls and manufacturing errors, and thereby validating the design tool. For an average aperture size (with a number of rows and columns of between 30 and 50 elements, which means a reflectarray with more than 900 cells), the single offset configuration provides an antenna gain of between 20 and 30 dBi and a large scanning range. The prototype tested at 100 GHz exhibits an electronically scanned beam in an angular range of 55º and 8% of bandwidth, in which the side lobe level (SLL) remains better than -13 dB. The maximum gain is 19.4 dBi. The electrical performance of the antenna is clearly an improvement on those achieved by other authors in the state of the art. The second prototype corresponds to a dual reflector antenna with a liquid crystal-based reflectarray used as a sub-reflector for beam scanning in one plane (azimuth or elevation). The main objective is to obtain a higher gain than that provided by the single offset configuration, but using a more compact architecture. In this case, a maximum gain of 35 dBi is achieved, although at the expense of reducing the scanning range to 12°, which is inherent in this type of structure. As a general statement, the voltage synthesis and the design procedure of the cells, jointly make up a complete, accurate and efficient design tool of reconfigurable reflectarray antennas based on liquid crystals. The tool has been validated by testing the previously mentioned prototypes at 100 GHz, which achieve something never reached before for this type of antenna: a competitive electrical performance, and an excellent prediction of the results. The design procedure is general and therefore can be used at any frequency for which the liquid crystal exhibits dielectric anisotropy. The two prototypes designed, manufactured and tested in this thesis are also some of the first antennas that currently operate at frequencies above 100 GHz. In fact, the dual reflector antenna is the first electronically scanned dual reflector antenna at frequencies above 60 GHz (the operation frequency is 100 GHz) with a gain greater than 25 dBi, being in turn the first dual-reflector antenna with a real reconfigurable sub-reflectarray. Finally, some improvements that should be still investigated to make these antennas commercially competitive are proposed.

Levinasian ethics and the representation of the other in international and cross-cultural management

In this paper, we seek to further the discussion, problematization and critique of west/east identity relations in ICM studies by considering the ethics of the relationship – an issue never far beneath the surface in discussions of Orientalism. In particular we seek to both examine and question the ethics of representation in relation to a critique of what has come to be known as international and cross-cultural management (ICM). To pursue such a discussion, we draw specifically on the ethical elaborations of Emmanuel Levinas as well as his chief interlocutors Jacques Derrida and Zygmunt Bauman. The value of this discussion, we propose, is that Levinas offers a philosophy that holds as its central concept the relationship between the self and Other as the primary ethical and pre-ontological relation. Levinas’ philosophy provides a means of extending the post-colonial critique of ICM, and ICM provides a context in which the Levinasian ethics can be brought to bear on a significant issue on contemporary business and management.

Professional Ethics and Welfare Reform: The Importance of Ethical Competence

This paper explores the professional ethics of welfare reform providers and its influence in the achievement of welfare reform goals. Four themes address the professional ethics and ethical competence of welfare reform providers.