17,825 research outputs found
Randomness Extraction in AC0 and with Small Locality
Randomness extractors, which extract high quality (almost-uniform) random
bits from biased random sources, are important objects both in theory and in
practice. While there have been significant progress in obtaining near optimal
constructions of randomness extractors in various settings, the computational
complexity of randomness extractors is still much less studied. In particular,
it is not clear whether randomness extractors with good parameters can be
computed in several interesting complexity classes that are much weaker than P.
In this paper we study randomness extractors in the following two models of
computation: (1) constant-depth circuits (AC0), and (2) the local computation
model. Previous work in these models, such as [Vio05a], [GVW15] and [BG13],
only achieve constructions with weak parameters. In this work we give explicit
constructions of randomness extractors with much better parameters. As an
application, we use our AC0 extractors to study pseudorandom generators in AC0,
and show that we can construct both cryptographic pseudorandom generators
(under reasonable computational assumptions) and unconditional pseudorandom
generators for space bounded computation with very good parameters.
Our constructions combine several previous techniques in randomness
extractors, as well as introduce new techniques to reduce or preserve the
complexity of extractors, which may be of independent interest. These include
(1) a general way to reduce the error of strong seeded extractors while
preserving the AC0 property and small locality, and (2) a seeded randomness
condenser with small locality.Comment: 62 page
A study of allosteric binding behaviour of a 1,3-alternate thiacalix[4]arene-based receptor using fluorescence signal
A novel heteroditopic thiacalix[4]arene receptor L possessing 1,3-alternate conformation, which contains two pyrene moieties attached to the lower rim via urea linkages together with a crown ether moiety appended at the opposite side of the thiacalix[4]arene cavity, has been synthesized. The complexation behaviour of receptor L was studied by means of fluorescence spectra and ¹H NMR titration experiments in the presence of K⁺ ions and a variety of other anions. The results suggested that receptor L can complex efficiently via the urea cavity or the crown ether moiety, and a positive/negative allosteric effect operating in receptor L was observed
Lost and Found : The Development of Identity Among Chinese Immigrants to Sweden
Although previous researches have covered various kinds of identity studies, the identity issues particularly among the Chinese immigrants to Sweden remain poorly understood. Therefore, this thesis contributes to the vast amount of research by focusing on how and why the Chinese immigrants’ identities have developed after immigration. Based on nationalism and national identity theories in modern Chinese history, four assumptions are brought up to test their identity development patterns. By using narrative analysis, the Chinese immigrants are grouped into four categories and this study aims to find out whether the four categories correspond to the four assumptions. The results suggest that while some of the identity development patterns fit into some assumptions, others remain under defined or they represent new phenomena that are open for future research
Bernstein Theorems for Space-like Graphs with Parallel Mean Curvature and Controlled Growth
In this paper, we obtain an Ecker-Huisken type result for entire graphs with
parallel mean curvature.Comment: 12 page
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