128 research outputs found
Statistical Properties of Cross-Correlation in the Korean Stock Market
We investigate the statistical properties of the correlation matrix between
individual stocks traded in the Korean stock market using the random matrix
theory (RMT) and observe how these affect the portfolio weights in the
Markowitz portfolio theory. We find that the distribution of the correlation
matrix is positively skewed and changes over time. We find that the eigenvalue
distribution of original correlation matrix deviates from the eigenvalues
predicted by the RMT, and the largest eigenvalue is 52 times larger than the
maximum value among the eigenvalues predicted by the RMT. The
coefficient, which reflect the largest eigenvalue property, is 0.8, while one
of the eigenvalues in the RMT is approximately zero. Notably, we show that the
entropy function with the portfolio risk for the original
and filtered correlation matrices are consistent with a power-law function,
, with the exponent and
those for Asian currency crisis decreases significantly
A Unified Algebraic Approach to Few and Many-Body Correlated Systems
The present article is an extended version of the paper {\it Phys. Rev.} {\bf
B 59}, R2490 (1999), where, we have established the equivalence of the
Calogero-Sutherland model to decoupled oscillators. Here, we first employ the
same approach for finding the eigenstates of a large class of Hamiltonians,
dealing with correlated systems. A number of few and many-body interacting
models are studied and the relationship between their respective Hilbert
spaces, with that of oscillators, is found. This connection is then used to
obtain the spectrum generating algebras for these systems and make an algebraic
statement about correlated systems. The procedure to generate new solvable
interacting models is outlined. We then point out the inadequacies of the
present technique and make use of a novel method for solving linear
differential equations to diagonalize the Sutherland model and establish a
precise connection between this correlated system's wave functions, with those
of the free particles on a circle. In the process, we obtain a new expression
for the Jack polynomials. In two dimensions, we analyze the Hamiltonian having
Laughlin wave function as the ground-state and point out the natural emergence
of the underlying linear symmetry in this approach.Comment: 18 pages, Revtex format, To appear in Physical Review
Generalized Relativistic Meson Wave Function
We study the most general, relativistic, constituent meson
wave function within a new covariant framework. We find that by including a
tensor wave function component, a pure valence quark model is now capable of
reproducing not only all static pion data (, )
but also the distribution amplitude, form factor , and structure
functions. Further, our generalized spin wave function provides a much better
detailed description of meson properties than models using a simple
relativistic extension of the nonrelativistic wave function.Comment: 17 pages, REXTeX 3.0 file, (uuencoded postscript files of 8 figures
appended
Survival probability of mutually killing Brownian motions and the O'Connell process
Recently O'Connell introduced an interacting diffusive particle system in
order to study a directed polymer model in 1+1 dimensions. The infinitesimal
generator of the process is a harmonic transform of the quantum Toda-lattice
Hamiltonian by the Whittaker function. As a physical interpretation of this
construction, we show that the O'Connell process without drift is realized as a
system of mutually killing Brownian motions conditioned that all particles
survive forever. When the characteristic length of interaction killing other
particles goes to zero, the process is reduced to the noncolliding Brownian
motion (the Dyson model).Comment: v2: AMS-LaTeX, 20 pages, 2 figures, minor corrections made for
publication in J. Stat. Phy
A natural product compound inhibits coronaviral replication in vitro by binding to the conserved Nsp9 SARS-CoV-2 protein
The Nsp9 replicase is a conserved coronaviral protein that acts as an essential accessory component of the multi-subunit viral replication/transcription complex. Nsp9 is the predominant substrate for the essential nucleotidylation activity of Nsp12. Compounds specifically interfering with this viral activity would facilitate its study. Using a native mass-spectrometry-based approach to screen a natural product library for Nsp9 binders, we identified an ent-kaurane natural product, oridonin, capable of binding to purified SARS-CoV-2 Nsp9 with micromolar affinities. By determining the crystal structure of the Nsp9-oridonin complex, we showed that oridonin binds through a conserved site near Nsp9’s C-terminal GxxxG-helix. In enzymatic assays, oridonin’s binding to Nsp9 reduces its potential to act as substrate for Nsp12’s Nidovirus RdRp-Associated Nucleotidyl transferase (NiRAN) domain. We also showed using in vitro cellular assays oridonin, while cytotoxic at higher doses has broad antiviral activity, reducing viral titer following infection with either SARS-CoV-2 or, to a lesser extent, MERS-CoV. Accordingly, these preliminary findings suggest that the oridonin molecular scaffold may have the potential to be developed into an antiviral compound to inhibit the function of Nsp9 during coronaviral replication
Representational predicaments at three Hong Kong sites
Representational predicaments arise when a job incumbent believes that attributions and images assumed by dominant authorities unfavourably ignore, or disproportionately and unfavourably emphasize, aspects of the incumbent\u27s own work and social identity. This is likely to happen when the incumbent does not have a close relationship with a dominant authority, and when power asymmetries give the former relatively little control over which aspects of their work and social identity are made visible or invisible to the latter. We draw on critical incident interviews from three organizations to illustrate a typology of six types of representational predicament: invasive spotlighting, idiosyncratic spotlighting, embedded background work, paradoxical social visibility, standardization of work processes, and standardization of work outputs. We analyse responses to representational predicaments according to whether they entailed exit, voice, loyalty, or neglect. Incumbents tended to respond with loyalty if they felt able and willing to accommodate their work behaviour and/or social identity to the dominant representations, and if there were sufficient compensatory factors, such as intrinsic rewards from the work or solidarity with colleagues. Exit or neglect appeared to reflect the belief that it was impossible to accommodate. Power asymmetries appeared to deter voice. Individual employees with a close and cordial working relationship with a member of a dominant authority group, or who were relationally networked to one, appeared not to experience representational predicaments
Four-gene Pan-African Blood Signature Predicts Progression to Tuberculosis.
Contacts of tuberculosis (TB) patients constitute an important target population for preventative measures as they are at high risk of infection with Mycobacterium tuberculosis and progression to disease.
We investigated biosignatures with predictive ability for incident tuberculosis.
In a case-control study nested within the Grand Challenges 6-74 longitudinal HIV-negative African cohort of exposed household contacts, we employed RNA sequencing, polymerase chain reaction (PCR) and the Pair Ratio algorithm in a training/test set approach. Overall, 79 progressors, who developed tuberculosis between 3 and 24 months following exposure, and 328 matched non-progressors, who remained healthy during 24 months of follow-up, were investigated.
A four-transcript signature (RISK4), derived from samples in a South African and Gambian training set, predicted progression up to two years before onset of disease in blinded test set samples from South Africa, The Gambia and Ethiopia with little population-associated variability and also validated on an external cohort of South African adolescents with latent Mycobacterium tuberculosis infection. By contrast, published diagnostic or prognostic tuberculosis signatures predicted on samples from some but not all 3 countries, indicating site-specific variability. Post-hoc meta-analysis identified a single gene pair, C1QC/TRAV27, that would consistently predict TB progression in household contacts from multiple African sites but not in infected adolescents without known recent exposure events.
Collectively, we developed a simple whole blood-based PCR test to predict tuberculosis in household contacts from diverse African populations, with potential for implementation in national TB contact investigation programs
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