761 research outputs found
Nonlocal Matrix Generalizations of N=2 Super Virasoro Algebra
We study the generalization of second Gelfand-Dickey bracket to the
superdifferential operators with matrix-valued coefficients. The associated
Miura transformation is derived. Using this bracket we work out a nonlocal and
nonlinear N=2 superalgebra which contains the N=2 super Virasoro algebra as a
subalgebra. The bosonic limit of this algebra is considered. We show that when
the spin-1 fields in this bosonic algebra are set to zero the resulting Dirac
bracket gives precisely the recently derived algebra.Comment: 14 pages (Plain TeX), NHCU-HEP-94-2
Gelfand-Dikii Brackets for Nonstandard Lax Equations
We generalize the construction of Gelfand-Dikii brackets to the case of
nonstandard Lax equations. We also discuss the possible origin of Kac-Moody
algebras present in such systems.Comment: 11 pages, Preprint no. UR1347, ER40685-79
Classical Extended Conformal Algebras Associated with Constrained KP Hierarchy
We examine the conformal property of the second Hamiltonian structure of
constrained KP hierarchy derived by Oevel and Strampp. We find that it
naturallygives a family of nonlocal extended conformal algebras. We give two
examples of such algebras and find that they are similar to Bilal's V algebra.
By taking a gauge transformation one can map the constrained KP hierarchy to
Kuperschmidt's nonstandard Lax hierarchy. We consider the second Hamiltonian
structure in this representation. We show that after mapping the Lax operator
to a pure differential operator the second structure becomes the sum of the
second and the third Gelfand-Dickey brackets defined by this differential
operator. We show that this Hamiltonian structure defines the W-U(1)-Kac-Moody
algebra by working out its conformally covariant form.Comment: NHCU-HEP-94-28, 19 pages (Plain TeX
Matrix Formulation of Hamiltonian Structures of Constrained KP Hierarchy
We give a matrix formulation of the Hamiltonian structures of constrained KP
hierarchy. First, we derive from the matrix formulation the Hamiltonian
structure of the one-constraint KP hierarchy, which was originally obtained by
Oevel and Strampp. We then generalize the derivation to the multi-constraint
case and show that the resulting bracket is actually the second Gelfand-Dickey
bracket associated with the corresponding Lax operator. The matrix formulation
of the Hamiltonian structure of the one-constraint KP hierarchy in the form
introduced in the study of matrix model is also discussedComment: 19 pages, Revtex, no figures. Minor changes, reference correcte
A LITERATURE REVIEW OF SUSTAINABLE TOURISM (1990-2016): DEVELOPMENT TRAJECTORY AND FRAMEWORK
Purpose of the studyāTourism is one of the largest and fastest growing industries in the world. Just like an enterprise today, sustainability is the long-term objective pursued by tourism industry. However, little effort has been made to systematically provide sufficient information to academicians and practitioners who have great research interests in sustainable tourism. Therefore, this paper aims to figure out the knowledge mapping of sustainable tourism and to indicate its research hot spots and trends for future research.
MethodologyāThis paper surveys the development trajectory of sustainable tourism using a literature review and classification of articles retrieved from 5 online databases with solo keyword āsustainable tourismā from 1900 to 2016.
Main findingsāBased on the scope of 641 articles, this study reveals that the number of publication on sustainable tourism has significantly increased since 2006. In addition, these articles are scattered across 125 journals and mostly published in 23 academic journals. The majority of targeted countries/regions for sustainable tourism focus on Asia, Europe and America.
LimitationāRestricted to limited knowledge, we make a brief literature survey on sustainable tourism from 1990-2016 to explore how sustainable tourism and its applications have developed in this period.
Originality/valueāIn fact, sustainable tourism is a belief and an overall concept in every tourism activities. Though this research has done lots, it still has rooms to make more complete. Finally, we present a conceptual framework integrating 13 classifications criteria derived from our analysis with 3247 keywords. Most interestingly, we further present a conceptual framework with a visual effect to operationalize the coverage of sustainable tourism. Based on our analysis, any researcher can easily find the popular and right journal to get into it, if he/she is in need, he/she also can roughly know its applications so far and completely get a whole picture of sustainable tourism quickly
Development of Taiwan’s strategies for regulating nanotechnology-based pharmaceuticals harmonized with international considerations
Single-crystalline Ī“-Ni2Si nanowires with excellent physical properties
[[abstract]]In this article, we report the synthesis of single-crystalline nickel silicide nanowires (NWs) via chemical vapor deposition method using NiCl2Ā·6H2O as a single-source precursor. Various morphologies of Ī“-Ni2Si NWs were successfully acquired by controlling the growth conditions. The growth mechanism of the Ī“-Ni2Si NWs was thoroughly discussed and identified with microscopy studies. Field emission measurements show a low turn-on field (4.12 V/Ī¼m), and magnetic property measurements show a classic ferromagnetic characteristic, which demonstrates promising potential applications for field emitters, magnetic storage, and biological cell separation.[[notice]]č£ę£å®ē¢[[incitationindex]]SCI[[booktype]]é»åē[[booktype]]ē“
Bioactive Eunicellin-Based Diterpenoids from the Soft Coral Cladiella krempfi
Four new eunicellin-based diterpenoids, krempfielins AāD (1ā4), along with two known compounds (5 and 6) have been isolated from a soft coral Cladiella krempfi. The structures of the new metabolites were elucidated by extensive spectroscopic analysis and by comparison with spectroscopic data of related known compounds. Compounds 5 and 6 were shown to exhibit cytotoxicity against a limited panel of cancer cell lines. Furthermore, compounds 2, 3, 5 and 6 were shown to exert significant in vitro anti-inflammatory activity against LPS-stimulated RAW264.7 macrophage cells
A lack of association between genetic polymorphisms in beta-defensins and susceptibility of psoriasis in Taiwanese: A caseācontrol study
AbstractBackgroundGenetic predisposition of the inflammatory-host response may affect the development of psoriasis. Previous studies have shown that copy number variations (CNVs) of Ī²-defensin genes (DEFB) are associated with the susceptibility of psoriasis in Caucasian populations.ObjectivesThis study aimed to assess the role of the CNVs of the DEFB4 gene and functional variants in the DEFB1 gene in Taiwanese patients with psoriasis.MethodsIn total, 196 patients with psoriasis and 196 control individuals were analyzed for the presence of the DEFB4 CNVs using the paralogue ratio test, and also for the DEFB1 polymorphisms rs11362, rs1800972, and rs1799946, using a polymerase chain reaction.ResultsNone of the polymorphisms were found to be associated with psoriasis. The distribution of DEFB4 genomic CNVs did not significantly differ between the control group and psoriasis group. The frequencies of patients who carried a greater than the median (ā„ 5) number of copies did not significantly differ in patients with psoriasis and controls. The multivariate analysis similarly revealed that the DEFB4 CNVs were not associated with psoriasis (odds ratioĀ =Ā 1.03, 95% confidence intervalĀ =Ā 0.89ā1.19, pĀ =Ā 0.720). No significant difference was detected in the genotype and allele distribution for any of the individual DEFB1 polymorphisms between the cases and the controls. Finally, the overall haplotype frequency profiles derived from the three polymorphisms did not significantly differ between the cases and the controls.ConclusionOur results do not suggest that these genetic variants of the Ī²-defensin genes contribute to the genetic background of psoriasis in Taiwanese patients
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