La paletina: un pinzell pla i prim

Treball de recerca realitzat per una alumna d'ensenyament secundari i guardonat amb un Premi CIRIT per fomentar l'esperit científic del Jovent l'any 2009. L’origen de l’autora és la Sénia, un poble d'uns 6000 habitants de la província de Tarragona, on, tot i el predomini actual de la fabricació de mobles, les primeres mostres d'industrialització foren el paper i els pinzells. L’arrelament de la indústria pinzellera de la seva família, ha estat el motiu que l’ha portat a desenvolupar aquest treball sobre la paletina, un tipus de pinzell. L'objectiu del treball ha estat dissenyar un model de paletina, a partir de proves pràctiques i d'estudis estadístics sobre quins són els components més adients. En primer lloc, es fa una descripció detallada dels components de la paletina. A continuació, s’estudia el seu procés de fabricació, primer des del punt de vista manual i després d'acord amb els procediments moderns. Finalment, a partir d'un experiment i amb el corresponent estudi estadístic, s’arriba a una nova proposta de paletina amb unes condicions òptimes de qualitat i rendiment. A més també es descriu el procés de fabricació de la paletina que es duia a terme uns cinquanta anys enrere i es pot valorar, així, tant el mèrit del procés en aquella època com també l'evolució tecnològica que s'ha dut a terme fins al moment.

Statistical properties of subgroups of free groups

The usual way to investigate the statistical properties of finitely generated subgroups of free groups, and of finite presentations of groups, is based on the so-called word-based distribution: subgroups are generated (finite presentations are determined) by randomly chosen k-tuples of reduced words, whose maximal length is allowed to tend to infinity. In this paper we adopt a different, though equally natural point of view: we investigate the statistical properties of the same objects, but with respect to the so-called graph-based distribution, recently introduced by Bassino, Nicaud and Weil. Here, subgroups (and finite presentations) are determined by randomly chosen Stallings graphs whose number of vertices tends to infinity. Our results show that these two distributions behave quite differently from each other, shedding a new light on which properties of finitely generated subgroups can be considered frequent or rare. For example, we show that malnormal subgroups of a free group are negligible in the raph-based distribution, while they are exponentially generic in the word-based distribution. Quite surprisingly, a random finite presentation generically presents the trivial group in this new distribution, while in the classical one it is known to generically present an infinite hyperbolic group.

Chemical profiling of different hashish seizures by gas chromatography-mass spectrometry and statistical methodology: a case report

Limited information is available regarding the methodology required to characterize hashish seizures for assessing the presence or the absence of a chemical link between two seizures. This casework report presents the methodology applied for assessing that two different police seizures were coming from the same block before this latter one was split. The chemical signature was extracted using GC-MS analysis and the implemented methodology consists in a study of intra- and inter-variability distributions based on the measurement of the chemical profiles similarity using a number of hashish seizures and the calculation of the Pearson correlation coefficient. Different statistical scenarios (i.e., a combination of data pretreatment techniques and selection of target compounds) were tested to find the most discriminating one. Seven compounds showing high discrimination capabilities were selected on which a specific statistical data pretreatment was applied. Based on the results, the statistical model built for comparing the hashish seizures leads to low error rates. Therefore, the implemented methodology is suitable for the chemical profiling of hashish seizures.

Standardization of serological tests for detecting anti-Trypanosoma cruzi antibodies in dogs

This paper reports on the standardization of four serological reactions currently used in human serodiagnosis for the detection of anti-Trypanosoma cruzi antibodies in naturally and experimentally infected dogs. Indirect immunofluorescence test (IFAT) and hemagglutination test (IHAT) were standardized, and complement fixation test (CFT) and direct agglutination test (DAT) were used for diagnostic confirmation. Four hundred and eighty one mongrel dogs that were studied by xenodiagnosis were used: (1) parasitemic dogs of two localities of endemic area (EA) of Santiago del Estero province in Argentina (n = 134); (2) non-parasitemic dogs of the same area (n = 285); (3) dogs experimentally infected with T. cruzi in the patent period (n = 6); (4) non-infected dogs (n = 56) which were born in the city of Buenos Aires (BA), one non-EA for Chagas' disease. For IFAT, parasitemic dogs EA showed 95% of reactive sera. Non parasitemic dogs EA showed 77% of non reactive sera. None sera from BA were reactive for dilutions higher than four. For IHAT, 84% of sera of parasitemic dogs EA showed serological reactivity and among non parasitemic dogs BA, 61% were non reactive, while the remainder showed at most titres of 1/16. The cut-off titres for IFAT and IHAT were 1/16 and 1/32 respectively, and for CFT and DAT 1/1 and 1/128 respectively. Sensitivity for IFAT, IHAT, CF and DAT were 95%, 84%, 97% and 95% respectively.

Tests de dépistage de drogues dans les écoles et les entreprises

Problématiques sur le plan éthique, mais aussi sur le plan juridique, les tests de dépistage des substances psychoactives en milieu scolaire et en milieu professionnel renvoient d'abord et avant tout à un examen d'aptitude. Celui-ci est du ressort de l'intervenant médical, sous couvert des garanties d'adéquation, de pertinence et de proportionnalité des moyens d'évaluation mis en oeuvre, ainsi que des règles relatives au consentement et à la confidentialité.

DNA evidence, probabilistic evaluation and collaborative tests.

Forensic scientists working in 12 state or private laboratories participated in collaborative tests to improve the reliability of the presentation of DNA data at trial. These tests were motivated in response to the growing criticism of the power of DNA evidence. The experts' conclusions in the tests are presented and discussed in the context of the Bayesian approach to interpretation. The use of a Bayesian approach and subjective probabilities in trace evaluation permits, in an easy and intuitive manner, the integration into the decision procedure of any revision of the measure of uncertainty in the light of new information. Such an integration is especially useful with forensic evidence. Furthermore, we believe that this probabilistic model is a useful tool (a) to assist scientists in the assessment of the value of scientific evidence, (b) to help jurists in the interpretation of judicial facts and (c) to clarify the respective roles of scientists and of members of the court. Respondents to the survey were reluctant to apply this methodology in the assessment of DNA evidence.

As the world turns: short-term human spatial memory in egocentric and allocentric coordinates

We aimed to determine whether human subjects' reliance on different sources of spatial information encoded in different frames of reference (i.e., egocentric versus allocentric) affects their performance, decision time and memory capacity in a short-term spatial memory task performed in the real world. Subjects were asked to play the Memory game (a.k.a. the Concentration game) without an opponent, in four different conditions that controlled for the subjects' reliance on egocentric and/or allocentric frames of reference for the elaboration of a spatial representation of the image locations enabling maximal efficiency. We report experimental data from young adult men and women, and describe a mathematical model to estimate human short-term spatial memory capacity. We found that short-term spatial memory capacity was greatest when an egocentric spatial frame of reference enabled subjects to encode and remember the image locations. However, when egocentric information was not reliable, short-term spatial memory capacity was greater and decision time shorter when an allocentric representation of the image locations with respect to distant objects in the surrounding environment was available, as compared to when only a spatial representation encoding the relationships between the individual images, independent of the surrounding environment, was available. Our findings thus further demonstrate that changes in viewpoint produced by the movement of images placed in front of a stationary subject is not equivalent to the movement of the subject around stationary images. We discuss possible limitations of classical neuropsychological and virtual reality experiments of spatial memory, which typically restrict the sensory information normally available to human subjects in the real world.

Creació d’un programari per a l’avaluació de la qualitat dels resultats analítics generats al laboratori

La validació de mètodes és un dels pilars fonamentals de l’assegurament de la qualitat en els laboratoris d’anàlisi, tal i com queda reflectit en la norma ISO/IEC 17025. És, per tant, un aspecte que cal abordar en els plans d’estudis dels presents i dels futurs graus en Química. Existeix molta bibliografia relativa a la validació de mètodes, però molt sovint aquesta s’utilitza poc, degut a la dificultat manifesta de processar tota la informació disponible i aplicar-la al laboratori i als problemes concrets. Una altra de les limitacions en aquest camps és la manca de programaris adaptats a les necessitats del laboratori. Moltes de les rutines estadístiques que es fan servir en la validació de mètodes són adaptacions fetes amb Microsoft Excel o venen incorporades en paquets estadístics gegants, amb un alt grau de complexitat. És per aquest motiu que l’objectiu del projecte ha estat generar un programari per la validació de mètodes i l’assegurament de la qualitat dels resultats analítics, que incorporés únicament les rutines necessàries. Específicament, el programari incorpora les funcions estadístiques necessàries per a verificar l’exactitud i avaluar la precisió d’un mètode analític. El llenguatge de programació triat ha estat el Java en la seva versió 6. La part de creació del programari ha constat de les següents etapes: recollida de requisits, anàlisi dels requisits, disseny del programari en mòduls, programació d les funcions del programa i de la interfície gràfica, creació de tests d’integració i prova amb usuaris reals, i, finalment, la posada en funcionament del programari (creació de l’instal·lador i distribució del programari).

Direct Determination of mechanical properties in shallow formations by (ultra) sonic methods

For several decades mechanical properties of shallow formations (soil) obtained by sonic to ultrasonic wave testing were reported to be greater than those based on mechanical tests. The present article relying on a statistical analysis of more than 300 tests shows that elastic moduli of the soil can indeed be obtained from (ultra)sonic tests and that they are identical to those resulting from mechanical tests.

Encoding dysfunctions in a dynamic-static paradigm for visuospatial working memory in first-episode psychosis patients: a 2-year follow-up study.

Aim: To investigate static and dynamic visuospatial working memory (VSWM) processes in first-episode psychosis (FEP) patients and explore the validity of such measures as specific trait markers of schizophrenia. Methods: Twenty FEP patients and 20 age-, sex-, laterality- and education-matched controls carried out a dynamic and static VSWM paradigm. At 2-year follow up 13 patients met Diagnostic and Statistical Manual (of Mental Health Disorders) - Fourth Edition (DSM-IV) criteria for schizophrenia, 1 for bipolar disorder, 1 for brief psychotic episode and 5 for schizotypal personality disorder. Results: Compared with controls, the 20 FEP patients showed severe impairment in the dynamic VSWM condition but much less impairment in the static condition. No specific bias in stimulus selection was detected in the two tasks. Two-year follow-up evaluations suggested poorer baseline scores on the dynamic task clearly differentiated the 13 FEP patients who developed schizophrenia from the seven who did not. Conclusions: Results suggest deficits in VSWM in FEP patients. Specific exploratory analyses further suggest that deficit in monitoring-manipulation VSWM processes, especially involved in our dynamic VSWM task, can be a reliable marker of schizophrenia.

Emotional behavior in acute stroke: the Lausanne emotion in stroke study.

OBJECTIVE: To study emotional behaviors in an acute stroke population. BACKGROUND: Alterations in emotional behavior after stroke have been recently recognized, but little attention has been paid to these changes in the very acute phase of stroke. METHODS: Adult patients presenting with acute stroke were prospectively recruited and studied. We validated the Emotional Behavior Index (EBI), a 38-item scale designed to evaluate behavioral aspects of sadness, aggressiveness, disinhibition, adaptation, passivity, indifference, and denial. Clinical, historical, and imaging (computed tomography/magnetic resonance imaging) data were obtained on each subject through our Stroke Registry. Statistical analysis was performed with both univariate and multivariate tests. RESULTS: Of the 254 patients, 40% showed sadness, 49% passivity, 17% aggressiveness, 53% indifference, 76% disinhibition, 18% lack of adaptation, and 44% denial reactions. Several significant correlations were identified. Sadness was correlated with a personal history of alcohol abuse (r = P < 0.037), female gender (r = P < 0.028), and hemorrhagic nature of the stroke (r = P < 0.063). Aggressiveness was correlated with a personal history of depression (r = P < 0.046) and hemorrhage (r = P < 0.06). Denial was correlated with male gender (r = P < 0.035) and hemorrhagic lesions (r = P < 0.05). Emotional behavior did not correlate with either neurologic impairment or lesion localization, but there was an association between hemorrhage and aggressive behavior (P < 0.001), lack of adaptation (r = P < 0.015), indifference (r = P < 0.018), and denial (r = P < 0.045). CONCLUSIONS: Systematic observations of acute emotional behaviors after stroke suggest that emotional alterations are independent of mood and physical status and should be considered as a separate consequence of stroke.