1,721,061 research outputs found
A safe and mild synthesis of organic carbonates from alkyl halides and tetrabutylammonium alkyl carbonates
No full textA safe and mild procedure for the synthesis of
mixed organic carbonates is described. Reaction of com-
mercially available tetrabutylammonium methoxide and
ethoxide with carbon dioxide yields the corresponding meth-
yl and ethyl tetrabutylammonium carbonates (TBAMC and
TBAEC). The reactions of these new compounds with several
different alkyl halides give methyl and ethyl carbonates in
high yields. The use of classic toxic and harmful chemicals
such as phosgene and carbon monoxide is avoided
A Tranformed Eulerian Model for the Possible Effects of the El Chich'on Eruption on the Stratospheric Circulation
No full text
Epilepsy in tuberous sclerosis complex.
No full textTuberous Sclerosis Complex (TSC) is a multisystem genetic disorder characterized by hamartomatous lesions involving skin, brain, kidneys, eyes and heart. Because of the wide variability of clinical expression and severity of TSC and the absence of a reliable molecular marker of the disease, diagnosis can be difficult in patients with only subtle manifestations. Genetic linkage studies indicate that about half of cases are due to TSC1, the gene on chromosome 9q34, and half are due to TSC2, the gene on chromosome 16p13. Clinical phenotypes associated with TSC1 vs TSC2 disease appear similar. Pathologically, TSC is a disorder of cell migration, proliferation and differentiation. Cell lineage and cell migration disorders in the developing cortex of TSC patients might produce very different neurological phenotypes. Cortical tubers constitute the hallmark of the disease and are pathognomonic of cerebral TSC. Epilepsy is the most common neurologic feature in TSC, occurring in 92% of patients. Seizures often begin in the first year of life and are frequently severe and intractable. The treatment of seizures has recently benefited from the advent of the new antiepileptic drugs (AEDs). However, current data suggest that despite the use of the new AEDs at the moment will still need a better treatment for at least 20 to 25% of TSC patients. Selected drug-resistant patients with TSC could be considered for surgical treatment. Clear localization of the most active epileptogenic focus and the zone of the cortical abnormality may lead to tuberectomy and improved seizure control in selective drug-resistant patients. The finding of multiple areas of cerebral involvement should not automatically preclude epilepsy surgery in a child with intractable seizures and a well-defined seizure origin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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