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Search Results: 1 - 10 of 118547 matches for " Kin T "
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Analytical study of the plasmonic modes of metal nanoparticle circular array
Kin Hung Fung,C. T. Chan
Physics , 2007, DOI: 10.1103/PhysRevB.77.205423
Abstract: We analyze the plasmonic modes of a metal nanoparticle circular array. Closed form solutions to the eigenmode problem are given. For each polarization, the plasmonic mode with the highest quality is found to be an antiphase mode. We found that the significant suppression in radiative loss can be understood as the cancellation of the dipolar radiation term in the radiative linewidth. The remaining finite radiative linewidth decreases exponentially as the number of particle increases.
Plasmonic modes in periodic metal nanoparticle chains: A direct dynamic eigenmode analysis
Kin Hung Fung,C. T. Chan
Physics , 2006, DOI: 10.1364/OL.32.000973
Abstract: We demonstrate an efficient eigen-decomposition method for analyzing the guided modes in metal nanoparticle chains. The proposed method has the advantage of showing the dispersion relation and mode quality simultaneously. It can also separate the material and geometrical properties, so its efficiency does not depend on the complexity of the material polarizability. The method is applied to analyze the guided modes of a single and a pair of metal chains. The more accurate dynamic dipole polarizability typically gives a red-shift compared with the results obtained with the broadly used quasistatic dipole polarizability with radiation correction.
Optical response of metal nanoparticle chains
Kin Hung Fung,C. T. Chan
Physics , 2006, DOI: 10.1016/j.optcom.2007.10.019
Abstract: We study the optical responses of metal nanoparticle chains. Multiple scattering calculations are used to study the extinction cross sections of silver nanosphere chains of finite length embedded in a glass matrix. The transmission and reflection coefficients of periodic 2D arrays of silver nanospheres are also calculated to understand the interaction between nanoparticle chains. The results are in agreement with recent experiments. The splitting of plasmon-resonance modes for different polarizations of the incident light are explored. Results on the effect of disorder are also presented.
Evaluation of Cytotoxicity and Genotoxicity of Inula viscosa Leaf Extracts with Allium Test
Tülay A kin elik, zlem Sultan Aslantürk
Journal of Biomedicine and Biotechnology , 2010, DOI: 10.1155/2010/189252
Abstract: I. viscosa has been used for years in folk medicine for its anti-inflammatory, antipyretic, antiseptic, and paper antiphlogistic activities. In this study, cytotoxic and genotoxic effects of I. viscosa leaf extracts on the root meristem cells of Allium cepa have been examined. Onion bulbs were exposed to 2.5 mg/ml, 5 mg/ml, and 10 mg/ml concentrations of the extracts for macroscopic and microscopic analysis. Tap water has been used as a negative control and Ethyl methanesulfonate (EMS) (2?10?2 M) has been used as a positive control. The test concentrations have been determined according to doses which are recommended for use in alternative medicine. There has been statistically significant (<.05) inhibition of root growth depending on concentration by the extracts when compared with the control groups. All the tested extracts have been observed to have cytotoxic effects on cell division in A. cepa. I. viscosa leaf extract induces the total number of chromosomal aberrations and micronuclei (MNC) formations in A. cepa root tip cells significantly when compared with control groups. Also, this paper shows for the first time the induction of cell death, ghost cells, cells with membrane damage, and binucleated cells by extract treatment. These results suggest the cytotoxic and genotoxic effects of the I. viscosa leaf extracts on A. cepa.
Efficacy of Bath PUVA Treatment in Palmoplantar Psoriasis
Dilek Se?kin,Züleyha Yaz?c?,Tülin Ergun
Turkderm , 2009,
Abstract: Background and Design: Although PUVA is widely used in the treatment of psoriasis, data on the efficacy of local PUVA in palmoplantar psoriasis is limited. The aim of current study is to evaluate the efficacy of local bath PUVA alone or in combination with systemic retinoid for treatment of palmoplantar psoriasis.Material and Method: The efficacy of bath PUVA was evaluated retrospectively in 18 patients with palmoplantar psoriasis. Treatment was performed 3 times weekly. Hands and feet were exposed to UVA immediately after a 15-minutes bath in 2 litres of tap water containing 10 mg/litre 8-methoxypsoralen. PUVA was used alone or in combination with acitretin in severe and resistant patients. Acitretin was either given from the beginning or was added to ongoing phototherapy. Bath PUVA was continued till complete or maximum improvement was achieved. Results: Of 18 patients, 7 received bath PUVA treatment alone whereas 11 used acitretin additionally. Six patients used acitretin and bath PUVA together from the beginning whereas in 5 patients who responded insufficiently to PUVA alone, acitretin was added to treatment later. Mean acitretin dose was 25 mg/day. Acitretin was added to ongoing phototherapy after a mean of 20 treatment sessions. Sixteen patients completed the treatment and 12 of them (75%) showed moderate to significant improvement. Mean number of treatments was 32 (8-69), mean cumulative UVA dose was 155.4 J/cm2 (22-373.5), maximum UVA dose per session was 6.6 J/cm2 (3-8). Mild to moderate erythema was observed in 2 patients (13%). No patient discontinued treatment due to side effects. Conclusion: Bath PUVA is an effective and safe treatment modality in palmoplantar psoriasis.
Islet Isolation and Transplantation from an Annular Pancreas: A Case Report
Kin T,Shapiro J,Ryan EA,Lakey JRT
JOP Journal of the Pancreas , 2005,
Abstract: CONTEXT: Annular pancreas is an uncommon congenital anomaly formed by a thin band of normal pancreatic tissue encircling the duodenum. CASE REPORT: We report the first case of an islet isolation and transplantation from an annular pancreas. The pancreas together with duodenum was procured from a 32-year-old previously healthy man after diagnosis of brain death. The pancreas including the annular portion was distended well after intraductal collagenase perfusion. A total of 276,064 islet equivalent was recovered and transplanted into a type 1 diabetic patient. CONCLUSIONS: Bearing in mind the shortage of donors, patients with this anomalous condition should not be excluded as potential organ donors.
Collective plasmonic modes of metal nano-particles in two-dimensional periodic regular arrays
Yu-Rong Zhen,Kin Hung Fung,C. T. Chan
Physics , 2008, DOI: 10.1103/PhysRevB.78.035419
Abstract: We investigate the collective plasmonic modes of metal nano-particles in periodic two-dimensional (2D) arrays within a point-dipole description. As an open system, the full-dynamic dispersion relations of the 2D arrays are obtained through an efficient method which gives an effective polarizability describing the collective response of a system. Both the dispersion relations and mode qualities are simultaneously related to the imaginary part of the effective polarizability, which has contributions from the single-particle response as well as the inter-particle coupling. The transversal long-range dipolar interaction is dominated by a wave term together with a purely geometrical constant representing the static geometrical contribution to resonant frequencies. As concrete examples, we considered small Ag spheres arranged in a square lattice. We find that inside the light-cone, the transverse quasi-mode has a reasonably high mode quality while the two in-plane modes show significant radiation damping. Near the light-line, we observe strong coupling with free photons for the bands of the transverse mode and the transversal in-plane mode, and the longitudinal in-plane mode exhibits a negative group-velocity inside the light-cone. Vanishing group velocities in the light-cone for all the quasi-modes are found to be intrinsic properties of the 2D metal nano-sphere dense arrays.
Negative group velocity in layer-by-layer chiral photonic crystals
Kin Hung Fung,Jeffrey Chi Wai Lee,C. T. Chan
Physics , 2008,
Abstract: We study the group velocity of light in layer-by-layer chiral photonic crystals composed of dielectrics and metals. Through studying the band structures with an extended-zone scheme that is given by a Fourier analysis, we show the existence of negative group velocity in the proposed chiral structures. The physical mechanism is interpreted with the help of a simplified model that has an analytical solution. The iso-frequency contours of the photonic band structure suggest that the negative group velocity can lead to either positive or negative refraction, depending on the orientation of the medium interface. We propose a feasible realization of such kind of photonic crystals. Computational results on the proposed realization are consistent with that of the simplified models.
Complex band structure and plasmon lattice Green's function of a periodic metal-nanoparticle chain
Kin Hung Fung,Ross Chin Hang Tang,C. T. Chan
Physics , 2009, DOI: 10.1364/OL.36.002206
Abstract: When the surface plasmon resonance in a metal-nanoparticle chain is excited at one point, the response signal will generally decay down the chain due to absorption and radiation losses. The decay length is a key parameter in such plasmonic systems. By studying the plasmon lattice Green's function, we found that the decay length is generally governed by two exponential decay constants with phase factors corresponding to guided Bloch modes and one power-law decay with a phase factor corresponding to that of free space photons. The results show a high level of similarity between the absorptive and radiative decay channels. By analyzing the poles (and the corresponding residues) of the Green's function in a transformed complex reciprocal space, the dominant decay channel of the real-space Green's function is understood.
Possible Topological Superconducting Phases of MoS$_{2}$
Noah F. Q. Yuan,Kin Fai Mak,K. T. Law
Physics , 2014, DOI: 10.1103/PhysRevLett.113.097001
Abstract: Molybdenum disulphide (MoS$_2$) has attracted much interest in recent years due to its potential applications in a new generation of electronic devices. Recently, it was shown that thin films of MoS$_2$ can become superconducting with a highest $T_{c}$ of 10K when the material is heavily gated to the conducting regime. In this work, using the group theoretical approach, we determine the possible pairing symmetries of heavily gated MoS$_2$. Depending on the electron-electron interactions, the material can support an exotic spin-singlet $p +ip $-wave-like, an exotic spin-triplet s-wave-like and an conventional spin-triplet $p$-wave pairing phases. Importantly, the exotic spin-singlet $p+ip$-wave phase is a topological superconducting phase which breaks time-reversal symmetry spontaneously and possesses chiral Majorana edge states.
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