The authors assess the ability of the Hodrick-Prescott filter (HP) and the band-pass filter proposed by BAXTER and KING (BK) to extract the business-cycle component of macroeconomic time series by using two different definitions of the business-cycle component. First, they define that component to be fluctuations lasting no fewer than 6 and no more than 32 quarters; this is the definition of business-cycle frequencies used by BAXTER and KING. Second, they define the business-cycle component on the basis of a decomposition of the series into permanent and transitory components. The conclusions are the same in both cases. The filters perform adequately when the spectrum of the original series has a peak at business-cycle frequencies. When the spectrum is dominated by low frequencies, the filters provide a distorted business cycle. These findings suggest that the use of the HP and BK filters with series having the typical Granger shape is highly problematic. JEL classification: E32. The views expressed in this study are those of the authors and do not necessarily represent those of the Bank of Canada.
An exploration of the characteristics of the nitrifying bacterial community, and more specifically the genus Nitrobacter, colonizing biological filters, was carried out using an immunofluorescence (IF) procedure and the polymerase chain reaction (PCR) together with the most probable number (MPN) technique. The biofilters were made of activated carbon (AC) or peat as the packing material, through which ammonia or industrial gaseous effluents were introduced. Serological diversity amongst Nitrobacter was investigated by the IF procedure. The PCR method was rapid, efficient, and allowed the detection and enumeration of Nitrobacter species in different biological filters on the laboratory and industrial scale. An evaluation of species distribution in this genus was also made in the column. Although the results were promising, it will be necessary to limit DNA and cell losses if the PCR method is to be used for the enumeration of the Nitrobacter population.
Les troubles d’apprentissage de la lecture sont encore trop méconnus et incompris d’un bon nombre de professionnels qui oeuvrent auprès de ces enfants qui tentent de surmonter l’insurmontable, soit apprendre à lire. Cet article propose une recension de la documentation scientifique récente sur la dyslexie. Il vise précisément à informer les professionnels des milieux scolaires et de la santé des modèles théoriques de ce trouble d’apprentissage et des déficits cognitifs à observer pour mieux le dépister et l’évaluer en vue d’une rééducation spécialisée. En raison des comportements de distraction et d’inattention qu’elle peut engendrer, la dyslexie peut semer la confusion et être perçue à tort comme le reflet d’un trouble déficitaire de l’attention. Cet article tente aussi de départager les caractéristiques de chacun de ces troubles. En conclusion, les auteurs soulignent l’importance d’un dépistage précoce des difficultés d’acquisition de la lecture afin d’offrir le plus tôt possible aux enfants qui en souffrent, les interventions dont ils ont besoin pour assurer leur réussite scolaire.
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