This paper describes two experiments in the domain of Cross Language Information Retrieval. Our basic approach is to translate queries word by word using machine readable dictionaries. The rst... Show moreThis paper describes two experiments in the domain of Cross Language Information Retrieval. Our basic approach is to translate queries word by word using machine readable dictionaries. The rst experiment compared different strategies to deal with word sense ambiguity: i) keeping all translations and integrate translation probabilitiesin the model, ii) a single translation is selected on the basis of the number of occurrences in the dictionary iii) word by word translation after word sense disambiguation in the source language. In a second experiment we constructed parallel corpora from web documents in order to construct bilingual dictionaries or improve translation probability estimates. We conclude that our best dictionary based CLIR approach is based on keeping all possible translations, not by simple substitution of a query term by its translations but by creating a structured query and including reverse translation probabilitiesin the retrieval model. Show less
This thesis describes several patterns of phonetic variation in Sign Language of the Netherlands. While lexical variation between different regions has been found in the Netherlands, little is... Show moreThis thesis describes several patterns of phonetic variation in Sign Language of the Netherlands. While lexical variation between different regions has been found in the Netherlands, little is known about phonetic or phonological variation. Phonetic variation in the realization of some of the traditional handshape and orientation features is analyzed in detail. Furthermore, data were elicited from different registers: short-distance signing (__whispering__) was compared to long-distance signing (__shouting__). Results show that differences between registers lead not only to variation in movement size, but also to changes in the traditional phonological categories. In enlarged realizations, as in shouting, handshape and orientation changes may be enhanced by a location change; in reduced forms, as in whispering, location changes may be realized as changes in orientation or handshape. While the distinction between the three parameters handshape, orientation and location remains valid, it is argued that their definition needs to be stated in global perceptual targets rather than in detailed articulatory terms in a comprehensive analysis of the various differences between registers. The data thus provide evidence for a strict separation of perceptual and articulatory characterizations of signs. The lexical specification contains only perceptual targets. The variation is thus not generated by a phonological process, but is a matter of phonetic implementation. Show less
The transfer of electrons between proteins is an essential step in biological energy production. Two protein redox partners are often artificially crosslinked to investigate the poorly understood... Show moreThe transfer of electrons between proteins is an essential step in biological energy production. Two protein redox partners are often artificially crosslinked to investigate the poorly understood mechanism by which they interact. To better understand the effect of crosslinking on electron transfer rates, we have constructed dimers of azurin by crosslinking the monomers. The measured electron exchange rates, combined with crystal structures of the dimers, demonstrate that the length of the linker can have a dramatic effect on the structure of the dimer and the electron transfer rate. The presence of ordered water molecules in the protein protein interface may considerably influence the electronic coupling between redox centers. Show less
L-type Ca(2+) channels are an important means by which a cell regulates the Ca(2+) influx into the cytosol on electrical stimulation. Their structure and dynamics in the plasma membrane, including... Show moreL-type Ca(2+) channels are an important means by which a cell regulates the Ca(2+) influx into the cytosol on electrical stimulation. Their structure and dynamics in the plasma membrane, including their molecular mobility and aggregation, is of key interest for the in-depth understanding of their function. Construction of a fluorescent variant by fusion of the yellow-fluorescent protein to the ion channel and expression in a human cell line allowed us to address its dynamic embedding in the membrane at the level of individual channels in vivo. We report on the observation of individual fluorescence-labeled human cardiac L-type Ca(2+) channels using wide-field fluorescence microscopy in living cells. Our fluorescence and electrophysiological data indicate that L-type Ca(2+) channels tend to form larger aggregates which are mobile in the plasma membrane. Show less
There is no agreement, in the chick, about the number of the endocardial cushions within the outflow tract or their pattern of fusion. Also, little is known of their relative contributions to the... Show moreThere is no agreement, in the chick, about the number of the endocardial cushions within the outflow tract or their pattern of fusion. Also, little is known of their relative contributions to the formation of the arterial valves, the subpulmonary infundibulum, and the arterial valvar sinuses. As the chick heart is an important model for studying septation of the outflow tract, our objective was to clarify these issues. Normal septation of the outflow tract was studied in a series of 60 staged chick hearts, by using stained whole-mount preparations, serial sections, and scanning electron microscopy. A further six hearts were examined subsequent to hatching. At stage 21, two pairs of endocardial cushions were seen within the developing outflow tract. One pair was positioned proximally, with the other pair located distally. By stage 25, a third distal cushion had developed. This finding was before the appearance of two further, intercalated, endocardial cushions, also distally positioned, which were first seen at stage 29. In the arterial segment, the aortic and pulmonary channels were separated by the structure known as the aortopulmonary septum. The dorsal limb of this septum penetrated the distal dorsal cushion, whereas the ventral limb grew between the remaining two distal cushions, both of which were positioned ventrally. The three distal endocardial cushions, and the two intercalated endocardial cushions, contributed to the formation of the leaflets and sinuses of the arterial roots. The two proximal cushions gave rise to a transient septum, which later became transformed into the muscular component of the subpulmonary infundibulum. Concomitant with these changes, an extracardiac tissue plane was formed which separated this newly formed structure from the sinuses of the aortic root. Our study confirms that three endocardial cushions are positioned distally, and two proximally, within the developing outflow tract of the chick. The pattern of the distal cushions, and the position of the ventral limb of the aortopulmonary septum, differs significantly from that seen in mammals. Anat Rec 264:273-283, 2001. (C) 2001 Wiley-Liss, Inc. Show less
