The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory

The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments on ESA's far infrared and submillimetre observatory. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16x25 pixels, each, and two filled silicon bolometer arrays with 16x32 and 32x64 pixels, respectively, to perform integral-field spectroscopy and imaging photometry in the 60-210\mu\ m wavelength regime. In photometry mode, it simultaneously images two bands, 60-85\mu\ m or 85-125\mu\m and 125-210\mu\ m, over a field of view of ~1.75'x3.5', with close to Nyquist beam sampling in each band. In spectroscopy mode, it images a field of 47"x47", resolved into 5x5 pixels, with an instantaneous spectral coverage of ~1500km/s and a spectral resolution of ~175km/s. We summarise the design of the instrument, describe observing modes, calibration, and data analysis methods, and present our current assessment of the in-orbit performance of the instrument based on the Performance Verification tests. PACS is fully operational, and the achieved performance is close to or better than the pre-launch predictions

The fluency/nonfluency dichotomy in the spontaneous verbal output of children with acquired aphasia

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Spontaneous speech fluency in acquired childhood aphasia

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An analysis of spontaneous conversational speech fluency in children with acquired aphasia.

We report on an instrumental analysis of spontaneous conversational speech (SCS) fluency in acquired childhood aphasia (ACA). Tape-recorded SCS samples of 25 children with ACA (clinical judgment: 12 nonfluent and 13 fluent), and of 12 dysarthric and 12 nonaphasic and nondysarthric right hemisphere injured children were analysed in order to: (1) investigate whether a more refined analysis can objectively contribute to the differentiation of patients who were labelled as fluent or nonfluent on the basis of a clinical judgment: (2) verify whether an instrumental analysis of phonation duration does confirm the subjective estimation of verbal rate (i.e. the number of words produced in a unit of time) in groups of children with acquired neurogenic speech/language disorders frequently met in clinical practice. The results are: (1) phonation rate (i.e. the vocalization percentage) seems to represent an adequate variable to distinguish clinically diagnosed nonfluent aphasic children from speech/language impaired children belonging to other clinical groups of acquired neurogenic speech/language disorders; (2) the verbal rate is highly correlated to the phonation rate in all investigated groups except the dysarthric one. We suggest the instrumental method discussed here might contribute to the differential diagnosis between dysarthric and aphasic disturbances in the acute stage of the disease. Concerning the study of ACA, the main issue of the present investigation is that an objective fluency measurement has succeeded in identifying aphasic children who obviously do not fit in with the standard doctrine on ACA, which claims that ACA is invariably nonfluent irrespective of lesion location.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Recognizable spontaneous language characteristics in a young adult twelve years after she became aphasic as a child

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An analysis of spontaneous conversational speech fluency in children with acquired aphasia

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Clinical evaluation of conversational speech fluency in the acute phase of acquired childhood aphasia: does a fluency/nonfluency dichotomy exist?

Traditional neurologic tenets claim that the clinical picture of acquired childhood aphasia is nonfluent irrespective of lesion location. In the past 20 years, however, several case studies have shown that fluent aphasic patterns can be observed in children with acquired childhood aphasia. But the question remains open as to whether the pattern of their speech characteristics is similar to the one described in adult aphasics as studies addressing spontaneous speech fluency characteristics in larger series of children with acquired childhood aphasia are scarce. The objective of this study was to investigate whether an analysis of spontaneous speech fluency as has previously been performed in adult aphasics by other investigators would also yield two distinct groups of aphasic children and, if so, whether the distribution of the different speech characteristics in both groups would reflect the rank order found in adults, that is, whether nonfluent verbal output characteristics would predominate in one group and fluent features in the other. Audiotaped and videotaped recordings of 24 cooperative children with acute acquired childhood aphasia unselected for age, gender, etiology, and aphasia severity ratings were analyzed according to 10 different speech characteristics. A cluster analysis (two-means clustering) was performed to seek the existence of two distinct groups of aphasic children. Results were confirmed, and exact P values were computed with Mann-Whitney U-tests. A two-means clustering created two distinct classes. Mann-Whitney U-tests ranked the speech characteristics according to their discriminating power between clusters. Comparing this rank order with the one previously found in adults revealed a high correlation (Spearman's rank correlation: r = .915, P << .005), thus indicating that the clusters we found were highly similar to the adult clusters. Thus, the use of the speech variables proposed to evaluate adult aphasic spontaneous speech enabled us to demonstrate a fluent/nonfluent dichotomy in a childhood aphasic population as well. This study shows that the traditional views on the uniformity of the clinical picture of acquired childhood aphasia are obsolete. Our findings corroborate data issued from several case reports of fluent acquired childhood aphasia and from the few studies focusing on speech fluency in acquired childhood aphasia, which all point to the existence of an adultlike heterogeneity of childhood aphasic syndromes. Current clinical evidence no longer supports the hypotheses of equipotentiality and progressive lateralization but favors the notion that the anatomic substrate for language representation in the child is similar to that in adults, even in young subjects.Journal Articleinfo:eu-repo/semantics/publishe