Diagnosis of suspicious breast lesions using an empirical mathematical model for dynamic contrast-enhanced MRI

The purpose of this study was to test whether an empirical mathematical model (EMM) of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can distinguish between benign and malignant breast lesions. A modified clinical protocol was used to improve the sampling of contrast medium uptake and washout. T(1)-weighted DCE magnetic resonance images were acquired at 1.5 T for 22 patients before and after injection of Gd-DTPA. Contrast medium concentration as a function of time was calculated over a small region of interest containing the most rapidly enhancing pixels. Then the curves were fitted with the EMM, which accurately described contrast agent uptake and washout. Results demonstrate that benign lesions had uptake (P<2.0 x 10(-5)) and washout (P<.01) rates of contrast agent significantly slower than those of malignant lesions. In addition, secondary diagnostic parameters, such as time to peak of enhancement, enhancement slope at the peak and curvature at the peak of enhancement, were derived mathematically from the EMM and expressed in terms of primary parameters. These diagnostic parameters also effectively differentiated benign from malignant lesions (P<.03). Conventional analysis of contrast medium dynamics, using a subjective classification of contrast medium kinetics in lesions as "washout," "plateau" or "persistent" (sensitivity=83%, specificity=50% and diagnostic accuracy=72%), was less effective than the EMM (sensitivity=100%, specificity=83% and diagnostic accuracy=94%) for the separation of benign and malignant lesions. In summary, the present research suggests that the EMM is a promising alternative method for evaluating DCE-MRI data with improved diagnostic accuracy.     

Unequally spaced multiple mid-infrared wavelength generation using an engineered quasi-phase-matching device

We propose a novel quasi-phase-matched (QPM) device that can generate unequally spaced multiple wavelengths. Unequally spaced multiple QPM peaks can be obtained by employing the optimized phase modulation of a periodic domain structure. We fabricated a LiNbO3 waveguide device for 3.2-3.4 microm band difference frequency generation based on the design. Using the multiple mid-infrared outputs, we demonstrate the detection of multiple hydrocarbon gases, namely, methane, ethylene, and ethane.     

Digital volume gratings

An optical element constructed by stacking a set of binary-phase grating sheets can simulate the functions of optically recorded volume gratings. Our electromagnetic numerical study also shows that if one of the grating sheets is replaced by another one with different grating period, power spectrum of the diffracted wave changes completely with extra diffraction orders. This property will claim strong advantage in security document applications. Analysis of alignment error reveals interesting phenomena concerning to how misalignment affects diffraction efficiency.     

Thermally responsive wettability of self-assembled methylcellulose nanolayers

Thermo-responsive cellulosic nanolayers were prepared from methylcellulose (MC), which is known to have a unique lower critical solution temperature. Thiosemicarbazide (TSC) was selectively introduced into the MC reducing end groups, and the corresponding MC-TSC derivative was spontaneously chemisorbed on an Au substrate at 4 °C to give MC self-assembled monolayers (SAMs). Linear MC chains were stably fixed onto the Au substrate, yielding an MC-SAM of thickness ca. 15 nm with a root mean square value less than 1 nm. The MC-SAM surface exhibited thermally responsive wetting characteristics; the water contact angle was found to rise and fall around 70 °C, possibly due to the solid-state phase transition of the MC nanolayers resulting from the inherent gelation of MC molecules in water. Such wetting behavior was shown to be reversible following repeated heating and cooling. The MC-SAM immersed in salt solution revealed lower phase transition temperatures, and an increase in sodium chloride concentration ranging from 0.0 to 1.0 M brought about a dramatic decrease in the apparent phase transition temperature from ca. 70 to 30 °C. For the purposely designed MC nanolayers, such controllable wetting properties are expected to prompt growing interest in the applications of cellulosic biopolymer interfaces.     

Observation of phase transition of cesium manganese hexacyanoferrates by X-ray absorption spectroscopy

Cesium manganese hexacyanoferrates exhibit an interesting phenomenon of temperature-induced phase transition accompanied by a variation in the magnetic susceptibility. We observed the variation in the electronic state of Mn during the phase transition by using X-ray absorption spectroscopy. The results of the analyses showed that the content ratio of Fe^II-CN-Mn^III and Fe^III-CN-Mn^II systematically varied during the phase transition. However, the ratio of Fe^II-CN-Mn^II remained constant at almost all temperatures. These results suggest that the charge transfer between Fe and Mn ions in the Fe^III-CN-Mn^II or the Fe^II-CN-Mn^III bond produces the phase transition.     

Theoretical evaluation of the effective work functions for positive-ionic and electronic emissions from polycrystalline metal surfaces

Effective work functions (φ⁺ and φ^e) for positive-ionic and electronic emissions from polycrystalline metals of Nb, Mo, Ta, W and Ir are calculated according to our theoretical model by using those published data on both fractional surface area (F_i) and local work function (φ_i) of each metal surface composed of several patchy faces (1, 2, …, i). Comparison between the theoretical values thus obtained and those experimental data published to date yields the conclusions as follows. (1) With a slight error of less than ∼0.1 eV, the value of φ^e calculated with each of the metals is in fair or good agreement with that determined by experiment. (2) Such agreement is found also with φ⁺ for W. (3) In a typical case of W, where the degree of monocrystallization (δ_m) corresponding to the largest among the values of F_i is less than ∼0.5, the thermionic contrast (Δφ* ≡ φ⁺ − φ^e) is found again to be nearly equal to both theoretical and experimental values reported previously. (4) Each of the five metals shows that Δφ* at δ_m = 0.68-0.95 is smaller than Δφ* at δ_m < 0.5. (5) This result strongly supports our theoretical prediction that Δφ* decreases gradually to zero as δ_m increases beyond ∼0.5 up to ∼1. (6) Particularly, such a surface which has δ_m ≥ 0.96 exhibits Δφ* ≈ 0, apparently equivalent to the so-called “monocrystalline surface (δ_m = 1)”. These results lead to the conclusion that our theoretical model is valid for evaluating the effective work functions probably with a slight error of less than ∼0.1 eV, irrespective of both the surface species and the range of δ_m. In addition, our simple model makes it possible to analyze the mechanism of change in φ⁺ and φ^e according to the change in surface characters of both φ_i and F_i.     

Performance improvement of rubrene-based organic light emitting devices with a mixed single layer

We have investigated the performance of organic light-emitting devices (OLEDs) with a rubrene-doped mixed single layer by using 4,4′-bis[N-(1-napthyl)-N-phenyl- amion] biphenyl (α-NPD) as hole transport layer. Comparing to a conventional heterostructure OLED, equal luminance vs. current density characteristics were obtained. In addition, maximum power efficiency was threefold improved, and the achieved value was 5.90 lm/W by optimizing a mixing ratio of hole and electron transport materials. By evaluating the temperature dependence of the J – V characteristics for electron-injection dominated device, the electron injection from Al/LiF to mixed organic layer is attributed to Schottky thermal emission model. And the barrier height of the electron injection from Al/LiF into mixed single layer was obtained to be 0.62 eV, which is lower than Al/Alq₃ interface. Meanwhile, the mixed single-layer device exhibited superior operational durability at a half-luminance of 2,250 h under a constant current operation mode. The reliability was improved with a factor of two compared to the heterostructure device due to the improvement of stability in mixed organic molecules and removal of the heterojunction interface in the mixed single-layer device.     

Local chemical state change in Co–O resistance random access memory

Kelvin probe force microscopy (KFM) and conductive atomic force microscopy (C‐AFM) together with micro X‐ray photoelectron spectroscopy (XPS) were performed for the stacking structure comprising of the transition metal oxide Co–O and metal electrode, which exhibits large reproducible resistance switching. The application of the external voltage by the C‐AFM cantilever decreases the resistance of Co–O, which well accords with the non‐polar forming process observed in the Pt/Co–O/Pt trilayer, known as the candidate of resistance random access memory (ReRAM). Furthermore, the KFM and micro XPS experimentally revealed that the local reductive reaction of Co–O possibly nucleates the defect related energy levels which dominates the current conduction in the low resistance state. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Can a linearly polarized light beam polarize atomic spin?

Lax et al. [Phys. Rev. 11 (1975) 1365] discovered that a light beam in vacuum is not a transverse wave but does have a longitudinal field component. We investigate atomic and molecular electric dipole transitions induced by such a light beam, in particular, linearly polarized in a transverse plane. We derive the selection rules and the transition rates for various quantization axes using the paraxial approximation up to the first order of 1/kw, where k is the wave number and w is the transverse size of the light beam. The light beam is able to yield atomic spin polarization in the direction perpendicular to both the optical axis and the transverse electric field, and its magnitude is approximately 1/kw times that generated by a circularly polarized light wave with the similar intensity.     

Investigation of the relationship between the ionic conductivity and the local structures of singly and doubly doped ceria compounds using EXAFS measurement

The oxide ionic conductivity measurements of singly and doubly doped ceria compounds were carried out. Singly and doubly doped ceria used in this study were Ce_0.8Ln_0.2O_1.9 (Ln=Y, Sm, Nd, or La) and Ce_0.8La_0.1Y_0.1O_1.9, respectively. Lattice constants of these compounds were in proportion to the ionic radius of the dopant(s). The doubly doped ceria compound showed oxide ionic conductivity comparative to the average of that of each corresponding singly doped sample. This finding indicates that the conductivity is influenced by both dopants in the doubly doped compounds. The extended X-ray absorption fine structure (EXAFS) study showed that the coordination number of oxide ions at the nearest neighbor of cation was related to the ionic conductivity. It was found that the conductivity gave the highest value when oxygen vacancies were randomly distributed in the lattice. This indicates that the local structure seriously affects oxide ionic conduction in singly and doubly doped ceria compounds.