Formation of Fermi surfaces and the appearance of liquid phases in holographic theories with hyperscaling violation

We consider a holographic fermionic system in which the fermions are interacting with a U(1) gauge field in the presence of a dilaton field in a gravity bulk of a charged black hole with hyperscaling violation. Using both analytical and numerical methods, we investigate the properties of the infrared and ultaviolet Green's functions of the holographic fermionic system. Studying the spectral functions of the system, we find that as the hyperscaling violation exponent is varied, the fermionic system possesses Fermi, non-Fermi, marginal-Fermi and log-oscillating liquid phases. Various liquid phases of the fermionic system with hyperscaling violation are also generated with the variation of the fermionic mass. We also explore the properties of the flat band and the Fermi surface of the non-relativistic fermionic fixed point dual to the hyperscaling violation gravity.Comment: 19 pages, 8 figures; v2: minor clarifications, section VI added, references added; accepted for publication in JHE

Fermionic phase transition induced by the effective impurity in holography

We investigate the holographic fermionic phase transition induced by the effective impurity in holography, which is introduced by massless scalar fields in Einstein-Maxwell-massless scalar gravity. We obtain a phase diagram in $(\alpha, T)$ plane separating the Fermi liquid phase and the non-Fermi liquid phase.Comment: 17 pages, 9 figure

Antioxidant and Anti-proliferative Activities of Flavonoids from Bidens pilosa L var radiata Sch Bip

Purpose: To investigate the chemical composition of Bidens pilosa L. var. radiata. Sch Bip. (BP), as well as its antioxidant and anti-proliferative activities.Methods: The whole herb of BP was extracted with 95 % ethanol, which was then partitioned sequentially with petroleum ether, ethyl acetate and n-butyl alcohol to obtain petroleum ether, ethyl acetate (EE-BP), n-BuOH and water fractions. EE-BP was further isolated and purified by repeated column chromatography. The obtained compounds were identified by comparing 1H and 13C nuclear magnetic resonance (NMR) spectra with published data for the compounds. Flavonoids were evaluated for 1,1-diphenyl-2-picrylhydrazy (DPPH) and 2, 2 -azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) free radical scavenging activity by colorimetric methods, while their anti-proliferative effect against human colon cancer RKO cells was determined by 3-(4,5) dimethylthiahiazo (-z-y1)-3,5-diphenytetrazoliumromide (MTT) method.Results: A total of 6 compounds were isolated from BP, including flavonoids or flavonoid glycosides, among which were isoquercitrin (1), vitexin (2), astragalin (3), 5,6,7,4'-tetramethoxylflavone (4), 5,3',4'- trihydroxy-3,7-dimethoxylflavone (5) and quercetin (6). The results indicate that compound 6 was the most effective in both DPPH and ABTS free radical-scavenging assays, with half maximal inhibitory concentration (IC50) of 10.7 μmol/L and 17.5 μmol/L, respectively. Both compounds 4 and 5 exhibited significant growth inhibitory effect on RKO cells with IC50 of 39.08 μmol/L and 17.68 μmol/L, respectively (p < 0.01).Conclusion: BP contains a series of flavonoid compounds, possessing significant antioxidant activity and antiproliferative effect in RKO cells, thus suggesting that it is a potential health supplement and an easily available resource of natural antioxidants for use in colon cancer prevention.Keywords: Bidens pilosa, Flavonoid, Antioxidant, Anti-proliferation, Colon cance

Exposure of the Hidden Anti-Ferromagnetism in Paramagnetic CdSe:Mn Nanocrystals

We present theoretical and experimental investigations of the magnetism of paramagnetic semiconductor CdSe:Mn nanocrystals and propose an efficient approach to the exposure and analysis of the underlying anti-ferromagnetic interactions between magnetic ions therein. A key advance made here is the build-up of an analysis method with the exploitation of group theory technique that allows us to distinguish the anti-ferromagnetic interactions between aggregative Mn2+ ions from the overall pronounced paramagnetism of magnetic ion doped semiconductor nanocrystals. By using the method, we clearly reveal and identify the signatures of anti-ferromagnetism from the measured temperature dependent magnetisms, and furthermore determine the average number of Mn2+ ions and the fraction of aggregative ones in the measured CdSe:Mn nanocrystals.Comment: 26 pages, 5 figure