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A quasi-polynomial-time algorithm is presented for sampling almost uniformly at random from the n-slice of the language L(G) generated by an arbitrary context-free grammar G. (The n-slice of a language L over an alphabet is the subset L\ n of words of length exactly n.) The time complexity of the algorithm is " ?2 (n jGj) O(log n) , where the parameter "(More)
We show that uniform families of ACC circuits of subexponential size cannot compute the permanent function. This also implies similar lower bounds for certain sets in PP. This is one of the very few examples of a lower bound in circuit complexity where the uniformity condition is essential; it is still unknown if there is any set in Ntime (2 n O(1)) that(More)
A preliminary version of this paper appeared as AG91a]. 1 SUMMARY As part of a study of almost-everywhere complex sets, we investigate sets that are immune to AC 0 ; that is, sets with no innnite subset in AC 0. We show that such sets exist in P PP and in DSPACE(log n log n). Our main result is an oracle construction indicating that any improvement in these(More)
1 SUMMARY As part of a study of almost-everywhere complex sets, we i n vestigate sets that are immune to AC 0 ; that is, sets with no innnite subset in AC 0. W e show that such sets exist in P PP and in DSPACElog n log n. Our main result is an oracle construction indicating that any improvement in these immunity results will represent a signiicant advance,(More)
The task of nursing people with severe and enduring mental illness can evoke stresses and anxieties for staff which are not consciously known about, but which, nevertheless, impinge upon the quality of care delivered. As a way of exploring this issue, the interactions between staff and between staff and residents in long-term residential care were observed.(More)
A new process impurity was detected during the HPLC analysis of Tizanidine hydrochloride (I) batches. The impurity (II) was isolated by preparative HPLC and characterized by NMR and Mass spectral analysis as 5-S-ethyl-N-(4,5-dihydro-1H-imidazol-2-yl)-2,1,3-benzothiadiazol-4-amine hydrochloride.
One of the important issues in both complexity theory and algorithm design is to understand whether randomness can be more powerful than determinism. In this dissertation, we explore some problems related to this issue and study how to reduce randomness in computation via explicit combinatorial constructions. One approach to achieving determinism from(More)
A quasi-polynomial-time algorithm is presented for sampling almost uniformly at random from the n-slice of the language L(G) generated by an arbitrary context-free grammar G. (The n-slice of a language L over an alphabet is the subset L\ n of words of length exactly n.) The time complexity of the algorithm is " ?2 (n jGj) O(log n) , where the parameter "(More)