Adaptive thrust vector control during on-orbit servicing

On-orbit servicing missions often include a final propulsive phase where a spacecraft pushes the other one towards a different orbit. Specifically this is the case of the debris grasping mission where the chaser, after capturing the target by means of robotic arms, has to perform a de-orbit operation. The large thrust involved needs a perfect alignment with respect to the center of mass or the system composed by chaser and target, in order to avoid attitude changes. Such accurate alignment is quite difficult to achieve especially when the characteristics of the target are not perfectly known. A procedure is proposed in this paper, allowing a complete estimation of the center of mass position and of the moments of inertia of the system, starting from the data obtained by the gyros mounted on board of the spacecraft. The output is used to design a maneuver for correcting the target and chaser relative position by moving the robotic arms. Numerical simulations show the proficiency and the applicability of the estimation algorithm and of re-alignment maneuver to a selected mission scenario

Anosognosia and self-correction of naming errors in aphasia

Background: There has been comparatively little research into anosognosia for aphasia (a lack of awareness of acquired language deficits). Direct assessments of metacognitive awareness tend to rely on high levels of verbal competence and are difficult for people with aphasia to complete. Therefore indirect measures of awareness have been considered, notably the person’s self-correction of his or her naming errors. Different mechanisms for self-correction based in comprehension or production skills have been proposed. In addition, in other areas of cognition, the relationships between direct and indirect measures and underlying forms of awareness have not been clearly established. Aims: The aims of this study were: a) to investigate the relationship between a direct and an indirect measure of awareness of aphasia, b) to examine the role of executive functioning in performance on both assessment types, and c) to examine the relationship between these measures and underlying language comprehension and production skills. Methods & Procedures: Forty-eight people with aphasia participated, drawn from rehabilitation hospital caseloads. Participants were assessed on a language battery, a non-verbal test of executive function, a direct measure of awareness (ratings of difficulties), and had self-correction behaviour examined in a 40-item naming test. Outcomes & Results: There was a trend relationship between performance on the direct and indirect measures. Both related to overall severity of language impairment, with more severely impaired people being less aware of their difficulties. The two measures, however, dissociated with respect to single-word production and comprehension scores: the direct measure related to production and not comprehension, while the indirect measure related to comprehension and not production. Executive functioning related only to the direct measure of metacognitive awareness. Within production scores, the rate of correction success rather than pre-correction naming rate was associated with metacognitive awareness. Conclusions: This study revealed different underlying bases, in language processes and executive function, for two measures of anosognosia for aphasia. When used to assess awareness of deficits, direct and indirect methods should not be regarded as equivalent

Deese-roediger-McDermott paradigm: Effect of previous recall and type of memory task

Pretendeu-se averiguar se a activação dos itens críticos no paradigma de Deese-Roediger-McDermott também ocorreria numa tarefa de completamento. Para analisar a contaminação explícita explorámos a existência de resultados dissociados em função da manipulação do nível de processamento. Na tarefa de completamento, a primação semântica foi estatisticamente superior à primação directa. A ausência do efeito do nível de processamento demonstra que o teste foi de memória implícita. Também avaliámos o impacto de uma tarefa de evocação numa tarefa de memória posterior. Verificámos que a evocação prévia anulou o efeito do nível de processamento na tarefa de reconhecimento. Na tarefa de completamento de inícios de palavras, o incremento de inícios de palavras completados com associados só foi expressivo quando as palavras foram codificadas superficialmente.This study aimed to verifj whether lhe activation ofcritical items in the Deese-Roediger-McDermott paradigm ofproducing false memories could also occur in the word stem completion task. The finding that lhe levei ofprocessing did not seem to have any effect on the word stem completion task supported lhe conclusion that the stem completion task was in fact an irnplicit memory test. The impact of a previous recali in a followng memory task was also evaluated. The results indicated that lhe previous recall inhibited the effect ofthe processing levei in lhe recognition task. In the word stem completion task lhe increase ofstems completed with associates was only relevam when words were encoded superficialiy.(undefined

Produção de memórias falsas com listas de associados : análise do efeito do nível de processamento e da natureza da prova de memória

As memórias falsas têm sido amplamente estudadas com base num procedimento experimental designado paradigma DRM (Deese/Roediger/McDermott). Esse paradigma promove a criação de ilusões de memória a partir da apresentação de listas de palavras associadas a um item que não consta da lista. Uma das linhas de investigação com o paradigma DRM visa identificar o momento da criação das falsas memórias e explicar os mecanismos que estão na sua origem. Neste artigo, pretendemos fazer uma revisão da investigação sobre o efeito do nível de processamento e da natureza da tarefa de memória na facilitação ou inibição da produção de memórias falsas com listas de associados semânticos.False memories have been widely studied using an experimental procedure called DRM paradigm (Deese/Roediger/McDermott). This paradigm produces memory illusions due to the presentation of lists of words associated to a critical nonpresented word. One line of research on this topic aims at identifying the moment when the false memories are created and the explanation of the mechanisms underling false memories. In this paper we present a review about the effect of level-of-processing and the nature of memory task for the boost or inhibition of false memories created by means of lists of semantic associates.Le paradigme DRM (Deese/Roediger/McDermott) est un des plus connus et plus robustes parmi les études des faux mémoires dans le contexte du laboratoire. Ce paradigme permet la création d illusions de mémoire à partir des mots sémantiquement associés à un item qui n a pas été présenté. Au milieu des investigations basées sur le paradigme DRM il y a des études dont l objectif est d identifier e d´expliquer les mécanismes qui sont à l origine de la production des faux mémoires. Plus spécifiquement, on a pour but de faire une révision de la recherche sur l effet du niveau de codification et de la nature des tâches de mémoire sur la facilitation ou l´inhibition de la production de faux mémoires à partir des mots sémantiquement associés.Los falsos recuerdos han sido muy estudiados mediante la aplicación del paradigma DRM (Deese/Roediger/McDermott). El paradigma permite producir ilusiones de memoria tras la presentación de listas de palabras asociadas a una palabra que no se incluye en la lista. Una de las líneas de investigación que utilizan el paradigma DRM busca identificar el preciso momento de la creación de falsos recuerdos y explicar los mecanismos que originan ese efecto. El objetivo de este artículo es hacer una revisión de la investigación sobre el efecto de los niveles de procesamiento y la naturaleza de la tarea de memoria en la facilitación y inhibición de la producción de falsos recuerdos con listas de asociados semánticos.Fundação para a Ciência e a Tecnologia (FCT)Centro de Investigação em Psicologia da Universidade do Minho (CIPsi

Cross-domain interference costs during concurrent verbal and spatial serial memory tasks are asymmetric

Some evidence suggests that memory for serial order is domain-general. Evidence also points to asymmetries in interference between verbal and visual-spatial tasks. We confirm that concurrently remembering verbal and spatial serial lists provokes substantial interference compared with remembering a single list, but we further investigate the impact of this interference throughout the serial position curve, where asymmetries are indeed apparent. A concurrent verbal order memory task affects spatial memory performance throughout the serial positions of the list, but performing a spatial order task affects memory for the verbal serial list only for early list items; in the verbal task only, the final items are unaffected by a concurrent task. Adding suffixes eliminates this asymmetry, resulting in impairment throughout the list for both tasks. These results suggest that domain-general working memory resources may be supplemented with resources specific to the verbal domain, but perhaps not with equivalent spatial resources

The WOMAN Trial (World Maternal Antifibrinolytic Trial): tranexamic acid for the treatment of postpartum haemorrhage: an international randomised, double blind placebo controlled trial

<p>Abstract</p> <p>Background</p> <p>Each year, worldwide about 530,000 women die from causes related to pregnancy and childbirth. Of the deaths 99% are in low and middle income countries. Obstetric haemorrhage is the leading cause of maternal mortality, most occurring in the postpartum period. Systemic antifibrinolytic agents are widely used in surgery to prevent clot breakdown (fibrinolysis) in order to reduce surgical blood loss. At present there is little reliable evidence from randomised trials on the effectiveness of tranexamic acid in the treatment of postpartum haemorrhage.</p> <p>Methods</p> <p>The Trial aims to determine the effect of early administration of tranexamic acid on mortality, hysterectomy and other morbidities (surgical interventions, blood transfusion, risk of non-fatal vascular events) in women with clinically diagnosed postpartum haemorrhage. The use of health services and safety, especially thromboembolic effect, on breastfed babies will also be assessed. The trial will be a large, pragmatic, randomised, double blind, placebo controlled trial among 15,000 women with a clinical diagnosis of postpartum haemorrhage. All legally adult women with clinically diagnosed postpartum haemorrhage following vaginal delivery of a baby or caesarean section will potentially be eligible. The fundamental eligibility criterion is the responsible clinician's 'uncertainty' as to whether or not to use an antifibrinolytic agent in a particular woman with postpartum haemorrhage. Treatment will entail a dose of tranexamic acid (1 gram by intravenous injection) or placebo (sodium chloride 0.9%) will be given as soon as possible after randomisation. A second dose may be given if after 30 minutes bleeding continues, or if it stops and restarts within 24 hours after the first dose.</p> <p>The main analyses will be on an 'intention to treat' basis, irrespective of whether the allocated treatment was received or not. Subgroup analyses for the primary outcome will be based on type of delivery; administration or not of prophylactic uterotonics; and on whether the clinical decision to consider trial entry was based primarily on estimated blood loss alone or on haemodynamic instability. A study with 15,000 women will have over 90% power to detect a 25% reduction from 4% to 3% in the primary endpoint of mortality or hysterectomy.</p> <p>Trial registration</p> <p>Current Controlled Trials: ISRCTN76912190 and Clinicaltrials.gov ID: NCT00872469</p

Sleep Loss Produces False Memories

People sometimes claim with high confidence to remember events that in fact never happened, typically due to strong semantic associations with actually encoded events. Sleep is known to provide optimal neurobiological conditions for consolidation of memories for long-term storage, whereas sleep deprivation acutely impairs retrieval of stored memories. Here, focusing on the role of sleep-related memory processes, we tested whether false memories can be created (a) as enduring memory representations due to a consolidation-associated reorganization of new memory representations during post-learning sleep and/or (b) as an acute retrieval-related phenomenon induced by sleep deprivation at memory testing. According to the Deese, Roediger, McDermott (DRM) false memory paradigm, subjects learned lists of semantically associated words (e.g., “night”, “dark”, “coal”,…), lacking the strongest common associate or theme word (here: “black”). Subjects either slept or stayed awake immediately after learning, and they were either sleep deprived or not at recognition testing 9, 33, or 44 hours after learning. Sleep deprivation at retrieval, but not sleep following learning, critically enhanced false memories of theme words. This effect was abolished by caffeine administration prior to retrieval, indicating that adenosinergic mechanisms can contribute to the generation of false memories associated with sleep loss