Potential of magnetic resonance spectroscopy to detect metastasis in axillary lymph nodes in breast cancer

Focused pathological evaluation of axillary lymph nodes in breast cancer is gaining importance. Nuclear magnetic resonance (NMR) spectroscopy that assesses the whole of the specimen has the potential in evaluating micrometastases. The biochemical changes associated with breast cancer metastases in axillary nodes by in vitro NMR and its use in the detection of axillary metastases in a clinical setting in comparison with conventional histopathology is presented in this study. Eighty-eight lymph nodes obtained from 30 patients with breast cancer were investigated. Histopathology revealed metastases in 20 nodes from 11 patients, while in vitro NMR spectroscopy revealed metastases in 22 nodes. Out of these 22 nodes, 16 were the same, which showed metastases on histopathology, while 6 nodes have shown metastases only on in vitro magnetic resonance spectroscopy (MRS). These 6 nodes with suspicion of metastases on MRS were subjected to reevaluation with serial sectioning and immunohistochemistry, but no additional metastases were revealed. Forty metabolites could be identified from the MR spectrum of lymph nodes. The levels of the glycerophosphocholine-phosphocholine (GPC-PC), choline, lactate, alanine and uridine diphosphoglucose were elevated significantly in nodes with metastases. In addition, the intensity ratio of GPC-PC/threonine (Thr) was higher in nodes with metastases, and using this as marker, MRS detected the axillary metastases with a sensitivity, specificity and accuracy of 80%, 91% and 88%, respectively. Neoadjuvant chemotherapy (NACT) lowered the concentrations of GPC-PC and GPC-PC/Thr ratio. The accuracy of MRS in detecting metastases was 75% in patients who received NACT (n=9) as compared to 96% in those who did not (n=21). Our results demonstrate the potential of in vitro MRS in characterizing the metabolite profile of the axillary nodes with breast cancer metastases. It detected axillary metastases with reasonable accuracy and can be complementary to histopathological evaluation and immunohistochemistry.     

Evidence for a solid phase of dodecahedral C 20

Evidence is presented for the formation of a solid phase based on the smallest fullerene, C₂₀, in thin diamond-like carbon films deposited by ultraviolet laser ablation from diamond onto nickel substrates at room temperature in the presence of 10^-4 torr of cyclohexane or benzene. Laser desorption mass spectrometry from the films shows the presence of C₂₀, C₂₁ and C₂₂ species, while micro-Raman spectroscopy and electron diffraction from selected particles together with first principle density-functional calculations, indicate a cubic solid with dodecahedral C₂₀ cages as building blocks. Unlike solid C₆₀ and fully protonated C₂₀, which are bound by van der Waals forces, the proposed structure is stabilized by linking of the C₂₀ dodecahedra with bridging carbon atoms at interstitial tetrahedral sites to form a face-centered-cubic lattice with 22 carbon atoms per unit cell. Received 10 October 2002 / Received in final form 24 December 2002 Published online 6 March 2003 RID="a" ID="a"e-mail: zafar.iqbal@njit.edu     

Simple theoretical analysis of the thermoelectric power in quantum dot superlattices of non-parabolic heavily doped semiconductors with graded interfaces under strong magnetic field

We study theoretically the thermoelectric power in the presence of a large magnetic field (TPM) in heavily doped III–V, II–VI, PbTe/PbSnTe, strained layer and HgTe/CdTe quantum dot superlattices (QDSLs) with graded structures on the basis of newly formulated electron energy spectra and compare the same with that of the constituent materials. It has been found, taking heavily doped GaAs/Ga_1−xAl_xAs, CdS/CdTe, PbTe/PbSnTe, InAs/GaSb and HgTe/CdTe QDSLs as examples, that the TPM increases with increasing inverse electron concentration and film thickness, respectively, in different oscillatory manners and the nature of oscillations is totally band structure dependent. We have also suggested the experimental methods of determining the Einstein relation for the diffusivity–mobility ratio, the Debye screening length and the electronic contribution to the elastic constants for materials having arbitrary dispersion laws.     

Two-phase electrohydrodynamic simulations using a volume-of-fluid approach

A numerical methodology to simulate two-phase electrohydrodynamic flows under the volume-of-fluid paradigm is proposed. The electric force in such systems acts only at the interface and is zero elsewhere in the two fluids. Continuum surface force representations are derived for the electric field force in a system of dielectric–dielectric and conducting–conducting fluids. On the basis of analytical calculations for simple flow problems we propose a weighted harmonic mean interpolation scheme to smoothen the electric properties in the diffused transition region (interface). It is shown that a wrong choice of interpolation scheme (weighted arithmetic mean) may lead to a transition region thickness dependent electric field in the bulk. We simulate a set of problems with exact or approximate analytical solutions to validate the numerical model proposed. A coupled level set and volume-of-fluid (CLSVOF) algorithm has been used for simulations presented here.     

10 Gbps optical soliton transmission link using in-line SOA on standard SMF at 1.3 μm

In this paper, 10 Gbps optical soliton transmission link using in-line semiconductor optical amplifiers (SOAs) for already installed standard single mode fibers (SMF) at 1.3 μm wavelength has been reported. The pattern effect and the impact of chirp on pulse propagation after amplification have been investigated. The observations are based on modeling and simulation optical soliton transmission link. Optical soliton pulse transmission over distances of the order of several hundreds of kilometers has been shown with and without initial chirp.     

Quantized field-electron emission at 300 K in self-assembled arrays of silicon nanowires

Dense ensembles of silicon nanowires were prepared by metal-catalyzed chemical vapor deposition on silicon substrates. Some of these ensembles were doped with phosphorous during growth. The nanowires were characterized using scanning electron microscopy, X-ray diffraction, and mass spectroscopy. Field emission of electrons from these structures was studied at room temperatures in ultra-high vacuum. The measurements were carried out using a parallel-plate diode cell. At high-applied fields, the current–voltage characteristics deviate from the Fowler–Nordheim law and exhibit a step-wise increase in the current with the increasing voltage at 300 K. Possible mechanisms of the observed quantized field emission are discussed.     

Multilayer polymeric mode and polarization filters for integrated optics

We demonstrate theoretically as well as experimentally that a four-layer polymeric waveguide structure can be used to produce a mode and a polarization filter. Various optical properties such as refractive index, birefringence and propagation constant of polycarbonate, polystyrene and a commercially available photoresist (from Shipley) are presented. The thin film structures consisting of glass/polycarbonate/polystyrene/air are used for demonstrating polarization filter action and glass/photoresist/polystyrene/air structure for mode filter. Expressions for the electric field intensity spatial distribution for the structure are used to calculate the intensity profiles to support the observed behavior. The experimental values were in good agreement with the one obtained theoretically.     

ZnSe sintered films: Growth and characterization

The II-VI compound semiconductor, ZnSe having wide band gap between 2.58 and 2.82 eV is a promising material for use in photovoltaic devices, blue light emitting diodes and laser diodes. Several methods have been used to prepare ZnSe thin films. We have deposited ZnSe films on ultra-clean glass substrate by sintering technique. The optical, structural and electrical properties of ZnSe thin films have been examined. The optical band gap of these films is studied using reflection spectra in wavelength range 325-600 nm and structure of these films is studied using XRD. The DC conductivity of the films was measured in vacuum by two-probe technique.Sintering is a very simple and viable method compared to other intensive methods. The results of the present investigation will be useful in characterizing the material ZnSe for its applications in photovoltaics.     

Neural stem cells express melatonin receptors and neurotrophic factors: colocalization of the MT<Subscript>1</Subscript>receptor with neuronal and glial markers

Background  

In order to optimize the potential benefits of neural stem cell (NSC) transplantation for the treatment of neurodegenerative disorders, it is necessary to understand their biological characteristics. Although neurotrophin transduction strategies are promising, alternative approaches such as the modulation of intrinsic neurotrophin expression by NSCs, could also be beneficial. Therefore, utilizing the C17.2 neural stem cell line, we have examined the expression of selected neurotrophic factors under different in vitro conditions. In view of recent evidence suggesting a role for the pineal hormone melatonin in vertebrate development, it was also of interest to determine whether its G protein-coupled MT₁ and MT₂ receptors are expressed in NSCs.     

Complex impedance spectroscopy of Mn-doped zinc oxide nanorod films

The frequency-dependent properties of Mn-doped (3-5 at.%) aligned zinc oxide (Mn-ZnO) nanorods, synthesized by hybrid wet chemical route onto glass substrates, were investigated by bias-dependent impedance spectroscopy. No peak of Mn cluster/secondary phases was detected in the X-ray diffraction traces of the samples. XPS studies show the presence of oxygen vacancies in Mn-ZnO nanorods and Mn in Mn²⁺ and Mn⁴⁺ charge states. Although X-ray diffraction/X-ray photoelectron spectroscopy does not give any indication of the presence of metal clusters in the samples, bias-dependent impedance spectroscopy demonstrates significant sensitivity to the formation of Mn clusters in Mn-ZnO nanorods.