SETI science working group report

This report covers the initial activities and deliberations of a continuing working group asked to assist the SETI Program Office at NASA. Seven chapters present the group's consensus on objectives, strategies, and plans for instrumental R&D and for a microwave search for extraterrestrial in intelligence (SETI) projected for the end of this decade. Thirteen appendixes reflect the views of their individual authors. Included are discussions of the 8-million-channel spectrum analyzer architecture and the proof-of-concept device under development; signal detection, recognition, and identification on-line in the presence of noise and radio interference; the 1-10 GHz sky survey and the 1-3 GHz targeted search envisaged; and the mutual interests of SETI and radio astronomy. The report ends with a selective, annotated SETI reading list of pro and contra SETI publications

Analysis of the Interlimb similarity of motor patterns for improving stroke assessment and neurorehabilitation

Stroke is the leading cause of adult disability, with upper limb hemiparesis being one of the most common consequences. Regaining voluntary arm movement is one of the major goals of rehabilitation. However, even with intensive rehabilitation, approximately 30% of patients remain permanently disabled and only 5 to 20% of them recover full independence. Hence, there is an increasing interest in incorporating the latest advances in neuroscience, medicine and engineering to improve the efficacy of conventional therapies. In the last years, a variety of promising targets have been identified to improve rehabilitation. However, there is no consensus on which measure should be applied as a gold standard to study functional recovery. This fact dramatically hinders the development of new interventions since it turns difficult to compare different clinical trials and draw consistent conclusions about therapeutic efficiency. In addition, available scales are subjective, qualitative and often lead to incongruent outcomes. Indeed, there is increasing suspicion that the lack of optimal assessment measures hampers the detection of benefits of new therapies. Moreover, existing scales totally ignore the neuromuscular state of the patient masking the ongoing recovery processes. In consequence, making appropriate clinical decisions in such environment is almost impossible. In light of all these facts, the need for new objective biomarkers to develop effective therapies is undeniable. To give response to these demands we have organized this thesis into two main branches. On the one hand, we have developed an innovative physiological scale that reveals the neuromuscular state of the patient and is able to discriminate between motor impairment levels. The innovation here resides in the concept of interlimb similarity (ILS). Based on the latest findings about the modular organization of the motor system and taking into account that stroke provokes unilateral motor damage, we propose comparing the control structure of the unaffected arm with the control structure of the paretic arm to quantify motor impairment. We have defined the control structure as the set of muscle synergies and activation coefficients needed to complete a task. The advantage of this approach is not only its capacity to provide neuromuscular information about the patient, but also that the ILS is personalized to each patient and can purposely guide rehabilitation based on the patient¿s own physiological patterns. This supposes a huge advance taking into account the heterogeneity of stroke pathogenesis. On other hand, we have characterized the therapeutic potential of Visual Feedback (VF) as a tool to purposely induce neuroplastic changes. We have chosen VF among the various interventions proven to improve motor performance, because VF is a cheap strategy that can be implemented in almost any rehabilitation center. We demonstrate that VF is able to modulate the human control structure. In healthy subjects, it seems that VF makes accessible the refined dominant motor programs for the nondominant hemisphere giving rise to an increased interlimb similarity of the control structure. Interestingly, in stroke patients VF is able to manipulate the ILS of upper-limb kinematics in favor of finer motor control but a single training session seems not to be enough to fix those changes in the neuromuscular system of a damaged brain. Overall, these findings offer a new promising framework to develop and assess an effective intervention to guide the restoration of the original neuromuscular patterns and avoid unwanted maladaptive neuroplasticity. In conclusion, this thesis seeks moving forward in the understanding of human motor recovery processes and their relationship with neuroplasticity. In this sense, it provides important advances in the design of a new biomarker of motor impairment and tests the power of VF to modulate the neuromuscular control of patients with stroke.L'ictus és la principal causa de discapacitat en adults, essent l'hemiparèsia del membre superior una de les conseqüències més comunes. Els programes de rehabilitació tenen com a objectiu fonamental restituir la mobilitat del braç afectat. No obstant això, es calcula que només entre el 5 i el 20% dels pacients aconsegueixen recuperar la seva independència mentre que el 30% queden incapacitats permanentment. En front d'aquest escenari es fa necessari incorporar els últims avenços de la neurociència, la medicina i l'enginyeria en aquesta àrea. En els darrers anys s'han identificat diversos aspectes clau per intentar millorar la rehabilitació. El problema, però, és que no hi ha consens per definir una mesura com a "gold estàndard" per avaluar la recuperació funcional, motiu pel qual, el desenvolupament de noves teràpies queda profundament afectat, ja que esdevé impossible poder comparar diferents assajos clínics i extreure conclusions consistents sobre la seva eficiència terapèutica. A més, les diverses mesures que s'utilitzen són subjectives, qualitatives i sovint donen resultats incongruents. De fet, se sospita que la manca de mesures d'avaluació òptimes dificulta la detecció dels beneficis de noves teràpies. A tot això se li ha d'afegir que les mesures actuals no consideren l'estat neuromuscular del pacient, emmascarant els processos reparadors subjacents. Així doncs, prendre les decisions clíniques adequades sota aquestes condicions esdevé pràcticament impossible. En aquestes circumstàncies, no es pot ignorar el requeriment de nous biomarcadors que proporcionin dades objectives per catalitzar el disseny de teràpies efectives. Per donar resposta a aquesta situació, la tesi s'ha estructurat en dues parts. Per una banda, s'ha desenvolupat una innovadora escala fisiològica que revela l'estat neuromuscular del pacient i és capaç de discriminar entre diferents nivells d'incapacitat motora. La innovació rau en el concepte de similitud entre membres (ILS, en anglès). Així, basant-nos en els darrers descobriments sobre l'organització modular del sistema motor, i en el fet que l'ictus provoca dany unilateral, proposem comparar l'estructura de control del braç no-afectat amb l'estructura de control del braç parètic per quantificar la incapacitat motora. L'estructura de control l'hem definida com el conjunt de sinergies musculars i coeficients d'activació que es necessiten per a dur a terme una tasca. L'avantatge d'aquesta proposta és doble, ja que proporciona informació sobre l'estat neuromuscular del pacient i en ser personalitzable, pot guiar la rehabilitació d'acord amb els patrons fisiològics propis de cada pacient. Això suposa un enorme avenç en aquesta àrea, donada la immensa heterogeneïtat de la patogènesi d'aquest trastorn. D'altra banda, s'ha caracteritzat el potencial terapèutic del feedback visual (VF) per induir canvis neuroplàstics. Aquesta és una eina molt interessant perquè a més de millorar el control motor, és assequible per gairebé qualsevol centre de rehabilitació. S'ha demostrat que el VF és capaç de modular l'estructura de control. Concretament, el VF sembla transferir els programes motors de l'hemisferi dominant al costat no dominant augmentant així el ILS dels subjectes sans. En pacients amb ictus, el VF és capaç d'augmentar el ILS cinemàtic afavorint patrons de control més fins. En conclusió, l'objectiu d'aquesta tesi és aprofundir en la comprensió dels processos de recuperació motora i la seva relació amb la neuroplasticitat. La tesi ofereix un nou i prometedor marc per desenvolupar i avaluar procediments efectius per guiar la restauració dels patrons neuromusculars originals i evitar que el cervell pateixi canvis neuroplàstics indesitjables. Així, la tesi proporciona avanços importants en el disseny d'un biomarcador per quantificar la incapacitat motora i avaluar el potencial del VF per modular el control neuromuscular de pacients amb ictus

Optical Fiber Interferometric Sensors

The contributions presented in this book series portray the advances of the research in the field of interferometric photonic technology and its novel applications. The wide scope explored by the range of different contributions intends to provide a synopsis of the current research trends and the state of the art in this field, covering recent technological improvements, new production methodologies and emerging applications, for researchers coming from different fields of science and industry. The manuscripts published in the Special issue, and re-printed in this book series, report on topics that range from interferometric sensors for thickness and dynamic displacement measurement, up to pulse wave and spirometry applications

Low-Complexity Rotators for the FFT Using Base-3 Signed Stages

Rotations by angles that are fractions of the unit circle find applications in e.g. fast Fourier transform (FFT) architectures. In this work we propose a new rotator that consists of a series of stages. Each stage calculates a micro-rotation by an angle corresponding to a power-of-three fractional parts. Using a continuous powers-of-three range, it is possible to carry out all rotations required. In addition, the proposed rotators are compared to previous approaches, based of shift-and-add algorithms, showing improvements in accuracy and number of adders.Paper for special session.</p

LASER Tech Briefs, Fall 1994

Topics in this issue of LASER Tech briefs include: Electronic Components and Circuits. Electronic Systems, Physical Sciences, Materials, Computer Programs, Fabrication Technology, Mathematics and Information Sciences, and Life Science