This paper introduces a new robust method for the removal of background tissue fluorescence from Raman spectra. Raman spectra consist of noise, fluorescence and Raman scattering. In order to extract the Raman scattering, both noise and background fluorescence must be removed, ideally without human intervention and preserving the original data. We describe the rationale behind our robust background subtraction method, determine the parameters of the method and validate it using a Raman phantom against other methods currently used. We also statistically compare the methods using the residual mean square (RMS) with a fluorescence-to-signal (F/S) ratio ranging from 0.1 to 1000. The method, 'adaptive minmax', chooses the subtraction method based on the F/S ratio. It uses multiple fits of different orders to maximize each polynomial fit. The results show that the adaptive minmax method was significantly better than any single polynomial fit across all F/S ratios. This method can be implemented as part of a modular automated real-time diagnostic in vivo Raman system.

Raman spectroscopy shows potential in differentiating tumors from normal tissue. We used Raman spectroscopy with near‐infrared light excitation to study normal breast tissue and tumors from 11 mice injected with a cancer cell line. Spectra were collected from 17 tumors, 18 samples of adjacent breast tissue and lymph nodes, and 17 tissue samples from the contralateral breast and its adjacent lymph nodes. Discriminant function analysis was used for classification with principal component analysis scores as input data. Tissues were examined by light microscopy following formalin fixation and hematoxylin and eosin staining. Discriminant function analysis and histology agreed on the diagnosis of all contralateral normal, tumor, and mastitis samples, except one tumor which was found to be more similar to normal tissue. Normal tissue adjacent to each tumor was examined as a separate data group called tumor bed. Scattered morphologically suspicious atypical cells not definite for tumor were present in the tumor bed samples. Classification of tumor bed tissue showed that some tumor bed tissues are diagnostically different from normal, tumor, and mastitis tissue. This may reflect malignant molecular alterations prior to morphologic changes, as expected in preneoplastic processes. Raman spectroscopy not only distinguishes tumor from normal breast tissue, but also detects early neoplastic changes prior to definite morphologic alteration. © 2007 Wiley Periodicals, Inc. Biopolymers 89: 235–241, 2008. This article was originally published online as an accepted preprint. The “Published Online”date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

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A binary mixture of hard spheres is investigated within mode-coupling theory under conditions that ensure that the large particles form an amorphous solid. The localization length of small spheres grows continuously with decreasing diameter ratio S, diverging at a critical value £ c -0.15. Close to the localization-delocalization transition both the Lamb-Mossbauer and the Debye-Waller factors of the small particles show striking deviations from their commonly assumed wave-number dependence. Implications for quasielastic neutron scattering on hydrogen in (amorphous) metals are discussed.PACS numbers: 64.60. Cn, 61.40.+b In this Letter we apply the recent mode-coupling theory of the liquid-glass transition 1 to a binary mixture of hard spheres with the aim of studying the localization-delocalization transition of a system of interacting small particles in a glassy matrix executing thermal vibrations. Having in mind the description of dynamical properties of systems such as high loads of hydrogen in metals 2 or liquids in porous media, 3 it is obvious that our model overcomes several limitations inherent in the Lorentz-gas model studied extensively in the past. 4,5 For the numerical evaluation we choose numbers N\=N 2 of hard spheres with diameter ratio S = CJ\/(q,t) ss , of partial-density relaxation functions defined with variables N s (q)/^/S^(q) normalized by partial structure factors. These two quantities coincide in an harmonic solid and they show merely quantitative differences in a glass 1 as a result of anharmonicities. They will, however, differ from each other qualitatively in an assembly of small particles in a glassy matrix. For /-• °°, the generalized oscillator equation of motion for <& s (q,t) with relaxation kernel K s {q,t) reduces to the exact equation 7 q 2 fs(q) + K s (q,)[f s (q)-\]=0.(3)Applying a mode-coupling approximation to the friction kernel we find (s = 1,2; s '^s) KAq^)=(\/V)^k(k'q/q) 2 f s (\q-k\){c ss (k) 2 f(k) ss S ss (k) + 2c 5 ,Uk^)/U)^[S^ (4)The direct correlation functions c ss Xk) entering Eq. (4) represent the only external input required. We use results of the Percus-Yevick approximation 8 known to be reliable for hard spheres and available in analytical form for all values of the system parameters 77, 5, and c =N\/(N\ + N 2 ). Figure 1(a) shows representative examples of the partial static structure factors S ss .(q)-V-c(q)]->.

We report the structural and optical properties of xSnO2–yFe2O3 nanocrystalline composite thin films. SnO2 and Fe2O3 exhibit strong phase separation instability and their particle size and crystallinity are tunable by changing their composition and annealing temperature. The bandgap for these composites continuously increases from 2.3 to 3.89 eV. We discuss the increasing bandgap values in terms of the quantum confinement effect manifested by the decreasing size of Fe2O3 crystallites. The method provides a generic approach for the tuning of the bandgap in nanocomposite systems.

Rate of heat generated by magnetic nanoparticles in a ferrofluid is affected by their magnetic properties, temperature, and viscosity of the carrier liquid. We have investigated temperature dependent magnetic hyperthermia in ferrofluids, consisting of dextran coated superparamagnetic Fe 3 O 4 nanoparticles, subjected to external magnetic fields of various frequencies (188-375 kHz) and amplitudes (140-235 Oe). Transmission electron microscopy measurements show that the nanoparticles are polydispersed with a mean diameter of 13.8 6 3.1 nm. The fitting of experimental dc magnetization data to a standard Langevin function incorporating particle size distribution yields a mean diameter of 10.6 6 1.2 nm, and a reduced saturation magnetization ($65 emu/g) compared to the bulk value of Fe 3 O 4 ($95 emu/g). This is due to the presence of a finite surface layer ($1 nm thickness) of non-aligned spins surrounding the ferromagnetically aligned Fe 3 O 4 core. We found the specific absorption rate, measured as power absorbed per gram of iron oxide nanoparticles, decreases monotonically with increasing temperature for all values of magnetic field and frequency. Using the size distribution of magnetic nanoparticles estimated from the magnetization measurements, we have fitted the specific absorption rate versus temperature data using a linear response theory and relaxation dissipation mechanisms to determine the value of magnetic anisotropy constant (28 6 2 kJ/m 3) of Fe 3 O 4 nanoparticles. V

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