Diffusion-weighted magnetic resonance imaging to evaluate microvascular density after transarterial embolization ablation in a rabbit VX2 liver tumor model

Objective

To evaluate the correlation between findings from diffusion weighted imaging (DWI) and microvascular density (MVD) measurements in VX2 liver tumors after transarterial embolization ablation (TEA).

Materials and Methods

Eighteen New Zealand white rabbits were used in this study. VX2 tumor cells were implanted in livers by percutaneous puncture under computed tomography (CT) guidance. Two weeks later, all rabbits underwent conventional magnetic resonance imaging (MRI) (T1 and T2 imaging), DWI, (b = 100, 600, and 1000 s/mm²) and TEA. MRI was performed again1 week after TEA. Liver tissue was then harvested and processed for hematoxylin and eosin (H&E) staining and immunohistochemical staining for CD31to determine MVD.

Results

VX2 liver tumors were successfully established in all 18 rabbits. Optimal contrast was achieved with a b value of 600 s/mm².The maximum pre-operative apparent diffusion coefficient (ADC)_difference value was 0.28 × 10^− 3 ± 0.10 × 10^− 3 mm²/s, and was significantly different (P < 0.001) from the maximum postoperative ADC_difference value of 0.47 × 10^− 3 ± 0.10 × 10^− 3 mm²/s. However, the mean ADC value for the entire tumor was not significantly correlated with MVD (r = 0.221, P = 0.379), nor was the ADC value for the regions of viable tumor (r = − 0.044, P = 0.862). However, the maximum postoperative ADC_difference value was positively correlated with MVD(r = 0.606, F = 12.247, P = 0.003).

Conclusion

DWI is effective to evaluate the therapeutic efficacy of TEA. The maximum ADC_difference offers a promising new method to noninvasively assess tumor angiogenesis.     

Measurements of optical parameters of phantom solution and bulk animal tissues in vitro at 650 nm

Optical parameters of bulk animal tissue in vitro, including absorption coefficient (μ_a), reduced scattering coefficient (μ′_s) or scattering coefficient (μ_s), total attenuation coefficient (μ_t), anisotropy factor (g) and refractive index (n) are measured at wavelength of 650 nm. Clinical Intralipid-10% is diluted in distilled water into different concentrations to use as tissue phantoms. Four types of animal tissues in vitro are studied. The relationships among the optical parameters are analyzed systemically. For animal tissues, μ_a, μ′_s or μ_s and n rely on muscle fiber orientations. μ_s and μ_t range from 10 to 20 mm⁻¹, μ_a from 10⁻² to 10⁻³ mm⁻¹ and g from 0.95 to 0.99.     

Study on contamination of projection optics surface for extreme ultraviolet lithography

Ru-capped Mo/Si multilayer mirrors were irradiated by EUV in a vacuum atmosphere with ethanol or decane gas, and their reflectivity changes by contamination were investigated by changing the amount of introduced gas. The reflectivity hardly decreased by EUV irradiation in the ethanol-introduced atmosphere. On the other hand, the reflectivity decreased by about 5% in the decane-introduced atmosphere at a decane pressure of P_Decane = 1.3 × 10⁻⁴ Pa, an EUV power of about 200 mW/mm², and an EUV dose of 150 J/mm². EUV irradiation to the Ru-capped multilayer mirrors was also performed in the presence of water vapor and decane. The surface oxidation by EUV irradiation with a water vapor pressure of PH₂O=1.3×10⁻⁵ Pa was controlled by the introduction of decane at a pressure of P_Decane = 7.0 × 10⁻⁷ to 1.3 × 10⁻⁶ Pa.     

Photocarrier transport in iron-doped potassium lithium tantalate niobate studied by time-of-flight measurement

The photocarrier mobility of Fe 0.03 wt%-doped potassium lithium tantalate niobate (K_0.95Li_0.05Ta_0.61Nb_0.39O₃) was investigated by time-of-flight (TOF) measurement. The longitudinal photocarrier response due to pulsed excitation leads to values of the drift mobility of μ_h = 1.45 × 10⁻² cm²/V s for holes, μ_e = 0.325 × 10⁻² cm²/V s for electrons, and a value for the range of holes (μτ)_h = 4.38 × 10⁻⁵ cm²/V at room temperature and at low field 3 KV/cm. The response time of holes and electrons (or the relaxation time) is determined to be 3.02 × 10⁻³ s and 3.74 × 10⁻³ s, respectively. The mobility of holes strongly depends on the field strength, and is observed to decrease with increasing bias field.     

Towards beyond 1 GHz NMR: Mechanism of the long-term drift of screening current-induced magnetic field in a Bi-2223 coil

The screening current-induced magnetic field in the (Bi,Pb)₂Sr₂Ca₂Cu₃O_x (Bi-2223) insert coil proposed for a beyond 1 GHz nuclear magnetic resonance (NMR) spectrometer may generate a long-term field drift, resulting in a loss of field-frequency lock operation and an inability to make high resolution NMR measurements. The measured screening current-induced magnetic field of a Bi-2223 double-pancake coil exhibits a hysteresis effect at 4.2 K that is reproduced by a numerical simulation based on a finite thickness rectangular superconductor bar model. The screening current-induced field at the coil center is of opposite polarity to that generated by the coil current, and thus the apparent field intensity shows a positive drift with time. On the contrary, the field at a coil end is of the same polarity as the coil field, and the apparent field intensity decreases with time. If we wait for ∼1000 h after coil excitation, the field drift rate approaches the field decay rate of the persistent current of 10⁻⁸ h⁻¹, suitable for a long-term NMR measurement in a beyond 1 GHz NMR spectrometer.     

Ethylene adsorption on the Pt-Cu bimetallic catalysts. Density functional theory cluster study

The adsorption of ethylene on Cu₁₂Pt₂ clusters has been studied within the density functional theory (DFT) approach to understand the high ethylene selectivity of Cu-rich Pt-Cu catalyst particles in the reaction of hydrogen-assisted 1,2-dichloroethane dechlorination. The structural parameters for Cu₁₂Pt₂ clusters with D_4h, D_2d, and C_3v symmetry have been calculated. The relative stability of the isomeric Cu₁₂Pt₂ clusters follows the order: C_3v > D_2d > D_4h. Each isomer has an active site for ethylene adsorption that consists of a single Pt atom surrounded by Cu atoms. The interaction of ethylene with the active site yields a π-C₂H₄ adsorption complex. The strongest π-C₂H₄ complex forms with the cluster of C_3v symmetry; the bonding energy, ΔE_π(C₂H₄), is −15.6 kcal mol⁻¹. The bonding energies for the π-C₂H₄ complex with Cu₁₄ and Pt₁₄ clusters are −6.5 and −18.8 kcal mol⁻¹, respectively.The addition of Pt to Cu modifies the valence spd-band of the cluster as compared to a Cu₁₄ cluster. The DOS near the Fermi level increases when C₂H₄ adsorbs on the Cu₁₂Pt₂ cluster. As well, the center of the d-band shifts toward lower binding energies. Ethylene adsorption also induces a number of states below the d-band. These states correspond to those of gas-phase C₂H₄.The vibrational frequencies of C₂H₄ adsorbed on the clusters of D_4h and C_3v symmetry have been calculated. The phonon vibrations occur below 250 cm⁻¹. The intense bands around 200 cm⁻¹ are attributed to stretching vibrations of the Pt-Cu bonds normal to the cluster surface. The stretching vibrations of the Pt-C bonds depend on the local structure of the active site: ν_s(Pt-C) = 268 cm⁻¹ and ν_as(Pt-C) = 357 cm⁻¹ for the cluster of the D_4h symmetry; ν_s(Pt-C) = 335 cm⁻¹ and ν_as(Pt-C) = 397 cm⁻¹ for the cluster of the C_3v symmetry. Bands in the range of 800-3100 cm⁻¹ are attributed to vibrations of the adsorbed C₂H₄ molecule. The signature frequencies of the π-C₂H₄ adsorption complex are the δ_s(CH₂) deformation vibration at ∼1200 cm⁻¹ and the ν(C-C) stretching vibration at ∼1500 cm⁻¹. These vibration are absent for di-σ-C₂H₄ adsorption complexes.     

Nucleation control for ZnO nanorods grown by catalyst-driven molecular beam epitaxy

We report a study of the annealing temperature and time on Ag catalyst size and density for subsequent growth of ZnO nanorods by catalyst-driven molecular beam epitaxy (MBE). Two different substrates (SiO₂ and SiN_X) for the Ag deposition were used and the thickness of the Ag held constant at 25 Å. Annealing between 600 and 800 °C produced Ag cluster sizes in the range 8-30 nm diameter on SiO₂ and 10-65 nm on SiN_X with a cluster density from 100 to 2500 mm⁻² for SiO₂ and 30 to 1900 mm⁻² for SiN_X. ZnO nanorods grown on these clusters show single-crystal, wurtzite-phase nature and strong band-edge photoluminescence at 380 nm. The nanorods can also be grown selectively on lithographically-patterned dielectric stripes with Ag clusters formed on top by e-beam evaporation and annealing.     

Effects of seed layer on the structure and property of zinc oxide thin films electrochemically deposited on ITO-coated glass

ZnO films with different morphologies were deposited on the ITO-coated glass substrate from zinc nitrate aqueous solution at 65 °C by a seed-layer assisted electrochemical deposition route. The seed layers were pre-deposited galvanostatically at different current densities (i_sl) ranging from −1.30 to −3.0 mA/cm², and the subsequent ZnO films had been done using the potentiostatic technique at the cathode potential of −1.0 V. Densities of nucleation centers in the seed layers varied with increasing the current density, and the ZnO films on them showed variable morphologies and optical properties. The uniform and compact nanocrystalline ZnO film with (0 0 2) preferential orientation was obtained on seed layer that was deposited under the current density (i_sl) of −1.68 mA/cm², which exhibited good optical performances.     

χ measurement and optical limiting studies of urea picrate

The molecular charge complex urea picrate (UP) was synthesized and its third order nonlinear optical properties have been investigated using a single beam Z-scan technique with nanosecond laser pulses at 532 nm. Open aperture data of the compound indicates two photon absorption at this wavelength. The nonlinear refractive index n₂, nonlinear absorption coefficient β, magnitude of effective third order susceptibility χ⁽³⁾, the second order hyperpolarizability γ_h and the coupling factor ρ have been estimated. The experimentally determined values of β, n₂, Re χ⁽³⁾ and Im χ⁽³⁾, γ_h and ρ of the compound UP are 2.146 cm/GW, −1.258×10⁻¹¹ esu, −1.347×10⁻¹³ esu, 0.377×10⁻¹³ esu, 0.69×10⁻³² esu and 0.28, respectively. The compound exhibits good optical limiting at 532 nm with the limiting threshold of 80 μJ/pulse. Our studies suggest that compound UP is a potential candidate for optical device applications such as optical limiters.     

Single crystal EPR and optical absorption study of Cr doped l-histidine hydrochloride monohydrate

EPR study of the Cr³⁺ ion doped l-histidine hydrochloride monohydrate single crystal is done at room temperature. Two magnetically inequivalent interstitial sites are observed. The hyperfine structure for Cr⁵³ isotope is also obtained. The zero field and spin Hamiltonian parameters are evaluated from the resonance lines obtained at different angular rotations and the parameters are: D=(300±2)×10⁻⁴ cm⁻¹, E=(96±2)×10⁻⁴ cm⁻¹, g_x=1.9108±0.0002, g_y=1.9791±0.0002, g_z=2.0389±0.0002, A_x=(252±2)×10⁻⁴ cm⁻¹, A_y=(254±2)×10⁻⁴ cm⁻¹, A_z=(304±2)×10⁻⁴ cm⁻¹ for site I and D=(300±2)×10⁻⁴ cm⁻¹, E=(96±2)×10⁻⁴ cm⁻¹, g_x=1.8543±0.0002, g_y=1.9897±0.0002, g_z=2.0793±0.0002, A_x=(251±2)×10⁻⁴ cm⁻¹, A_y=(257±2)×10⁻⁴ cm⁻¹, A_z=(309±2)×10⁻⁴ cm⁻¹ for site II, respectively. The optical absorption studies of single crystals are also carried out at room temperature in the wavelength range 195-925 nm. Using EPR and optical data, different bonding parameters are calculated and the nature of bonding in the crystal is discussed. The values of Racah parameters (B and C), crystal field parameter (Dq) and nephelauxetic parameters (h and k) are: B=636, C=3123, Dq=2039 cm⁻¹, h=1.46 and k=0.21, respectively.     

Molecular interactions in methylimidazolium tetrafluoroborate ionic liquid ([Mim][BF4]): Structures, binding energies, topological properties and NMR one- and two bonds spin-spin coupling constants

Molecular interactions in methylimidazolium tetrafluoroborate ionic liquid ([Mim⁺][BF₄⁻]) have been investigated using B3LYP, B3PW91 and MP2 methods with a wide range of basis sets. Binding energy, topological properties of electron density, charge transfer, nucleus-independent chemical shift (NICS) and NMR one- and two bonds spin-spin coupling constants were calculated. With five preferential binding sites in the vicinity of the Mim⁺ ring, five ion pairs (A-E) with three intermolecular hydrogen bonds were found on the potential energy surface. The most stable ion pairs are formed via N-H and C-H bonds of Mim⁺ and B-F bonds of BF₄⁻. Ion pairs have electronic binding energies (BEs) in the range of − 335.6 to − 402.9 kJ/mol at MP2/6-311++G(2d,2p) level and − 328.1 to − 383.6 kJ/mol at B3LYP/AUG-cc-pVTZ level. NBO analysis confirms that the charge transfer takes place from BF₄⁻ to Mim⁺. The NICS values reveal the aromaticity of imidazole ring. The results show a correlation between absolute value of ^1hJ(H?F) and electron density at H?F bond critical point.     

EPR and optical absorption study of Cr-doped ammonium oxalate monohydrate single crystals

The electron paramagnetic resonance (EPR) study of the Cr³⁺-doped ammonium oxalate monohydrate (AOM) single crystal is done at room temperature. Two magnetically inequivalent sites for chromium are observed. The hyperfine structure for Cr⁵³ isotope is also obtained. The spin Hamiltonian parameters are evaluated as: D=(309±2)×10⁻⁴ cm⁻¹, E=(103±2)×10⁻⁴ cm⁻¹, g=1.9820±0.0002, A=(161±2)×10⁻⁴ cm⁻¹ for site I and D=(309±2)×10⁻⁴ cm⁻¹, E=(103±2)×10⁻⁴ cm⁻¹, g=1.9791±0.0002, A=(160±2)×10⁻⁴ cm⁻¹ for site II, respectively. On the basis of EPR data the site symmetry of Cr³⁺ doped single crystal is discussed. The optical absorption spectra are recorded in 195-925 nm wavelength range at room temperature. The energy values of different orbital levels are determined. On the basis of EPR and optical data, the nature of bonding in the crystal is discussed. The values of different parameters are B=803, C=3531, D_q=2208 cm⁻¹, h=0.59 and k=0.21, where B and C are Racah parameters, D_q is crystal field parameter and h and k are nephelauxetic parameters, respectively.     

MRI quantification of diffusion and perfusion in bone marrow by intravoxel incoherent motion (IVIM) and non-negative least square (NNLS) analysis

Object

To assess the feasibility of measuring diffusion and perfusion fraction in vertebral bone marrow using the intravoxel incoherent motion (IVIM) approach and to compare two fitting methods, i.e., the non-negative least squares (NNLS) algorithm and the more commonly used Levenberg–Marquardt (LM) non-linear least squares algorithm, for the analysis of IVIM data.

Materials and Methods

MRI experiments were performed on fifteen healthy volunteers, with a diffusion-weighted echo-planar imaging (EPI) sequence at five different b-values (0, 50, 100, 200, 600 s/mm²), in combination with an STIR module to suppress the lipid signal. Diffusion signal decays in the first lumbar vertebra (L1) were fitted to a bi-exponential function using the LM algorithm and further analyzed with the NNLS algorithm to calculate the values of the apparent diffusion coefficient (ADC), pseudo-diffusion coefficient (D*) and perfusion fraction.

Results

The NNLS analysis revealed two diffusion components only in seven out of fifteen volunteers, with ADC = 0.60 ± 0.09 (10^− 3 mm²/s), D* = 28 ± 9 (10^− 3 mm²/s) and perfusion fraction = 14% ± 6%. The values obtained by the LM bi-exponential fit were: ADC = 0.45 ± 0.27 (10^− 3 mm²/s), D* = 63 ± 145 (10^− 3 mm²/s) and perfusion fraction = 27% ± 17%. Furthermore, the LM algorithm yielded values of perfusion fraction in cases where the decay was not bi-exponential, as assessed by NNLS analysis.

Conclusion

The IVIM approach allows for measuring diffusion and perfusion fraction in vertebral bone marrow; its reliability can be improved by using the NNLS, which identifies the diffusion decays that display a bi-exponential behavior.     

Study of the switching phenomena of TlGaS2 single crystals

Single crystals of TlGaS₂ were prepared by a special modified Bridgman technique and used to investigate the switching phenomena. The particular interest shown in switching studies of p-type TlGaS₂ compound is associated with the possibility of its uses as an effective switching and memory elements in electronic devices. The switching effect observed in such crystal shows a memory character. Using a crystal holder and cryostat we measured the switching phenomenon at different ambient conditions such as temperature, light illumination as well as sample thickness. Pronounced parameters for switching for sample of thickness 0.17 cm were determined from the experimental data such as threshold voltage V_th = 400 V, threshold current I_th = 37 μA, holding voltage V_h = 350 V, holding current I_h = 42.3 × 10⁻⁴ A, threshold power P_th = 1.48 × 10⁻² W, threshold field E_th = 196.429 V/cm as well as the ratio between the resistance in the off state R_OFF to the resistance in the conducting state R_ON as 130.253. The factors affecting these parameters have also been investigated.     

Molecular dynamics and phase transitions in paramagnetic [Mn(H2O)6][SiF6] investigated by H NMR

The temperature dependences of ²H NMR spectra and spin-lattice relaxation time T₁ have been measured for paramagnetic [Mn(H₂O)₆][SiF₆]. The obtained ²H NMR spectra were simulated by considering the quadrupole interaction and paramagnetic shift. The variation of the spectra measured in phase III was explained by the 180° flip of water molecules. The activation energy E_a and the jumping rate at infinite temperature k₀ for the 180° flip of H₂O were obtained as 35 kJ mol⁻¹ and 4×10¹⁴ s⁻¹, respectively. The spectral change in phases I and II was ascribed to the reorientation of [Mn(H₂O)₆]²⁺ around the C₃ axis where the E_a and k₀ values were estimated as 45 kJ mol⁻¹ and 1×10¹³ s⁻¹, respectively. From the almost temperature independent and short T₁ value, the correlation time for electron-spin flip-flops, τ_e, and the exchange coupling constant J were obtained as 3.0×10⁻¹⁰ s and 2.9×10⁻³ cm⁻¹, respectively. The II-III phase transition can be caused by the onset of the jumping motion of [Mn(H₂O)₆]²⁺ around the C₃ axis.     

Growth and spectroscopic characterization of Er: Sr3Y(BO3)3 crystal

This paper reports the growth and spectroscopic characterization of Er³⁺:Sr₃Y(BO₃)₃ crystal. Er³⁺:Sr₃Y(BO₃)₃ crystal with dimensions up to ∅20×35 mm³ has been grown by Czochralski method. The polarized spectroscopic properties of Er³⁺:Sr₃Y(BO₃)₃ crystal were investigated. Based on the Judd-Ofelt theory, the effective intensity parameters Ω_t were obtained: Ω₂=1.71×10⁻²⁰ cm², Ω₄=1.39×10⁻²⁰ cm², Ω₆=0.74×10⁻²⁰ cm² for π-polarization, and Ω₂=1.77×10⁻²⁰ cm², Ω₄=1.44×10⁻²⁰ cm², Ω₆=0.65×10⁻²⁰ cm² for σ-polarization. The emission cross-section σ_em was calculated to be 4.75×10⁻²¹ cm² for π-polarization at 1536 nm and 6.30×10⁻²¹ cm² for σ-polarization at 1537 nm. The investigated results showed that Er³⁺:Sr₃Y(BO₃)₃ crystal may be regarded as a potential laser host material for 1.55 μm IR solid-state lasers.     

Diffusion tensor parameters and principal eigenvector coherence: Relation to b-value intervals and field strength

Diffusion-weighted MRI images acquired at b-value greater than 1000 s mm^− 2 measure the diffusion of a restricted pool of water molecules. High b-value images are accompanied by a reduction in signal-to-noise ratio (SNR) due to the application of large diffusion gradients. By fitting the diffusion tensor model to data acquired at incremental b-value intervals, we determined the effect of SNR on tensor parameters in normal human brains, in vivo. In addition, we also investigated the impact of field strength on the diffusion tensor model. Data were acquired at 1.5 and 3 T, at b-values 0, 1000, 2000 and 3000 s mm^− 2 in twenty diffusion-sensitised directions. Fractional anisotropy (FA), mean diffusivity (MD) and principal eigenvector coherence (κ) were calculated from diffusion tensors fitted between datasets with b-values 0–1000, 0–2000, 0–3000, 1000–2000 and 2000–3000 s mm^− 2. Field strength and b-value effects on diffusion parameters were analysed in white and grey matter regions of interest. Decreases in FA, κ and MD were found with increasing b-value in white matter. Univariate analysis showed a significant increase in FA with increasing field strength in highly organised white matter. These results suggest there are significant differences in diffusion parameters at 1.5 and 3 T and that the optimal results, in terms of the highest values of FA in white matter, are obtained at 3 T with a maximum b = 1000 s mm^− 2.     

Structure and properties of DLC–MoS2 thin films synthesized by BTIBD method

Diamond-like carbon (DLC)–MoS₂ composite thin films were synthesized using a biased target ion beam deposition (BTIBD) technique in which MoS₂ was produced by sputtering a MoS₂ target using Ar ion beams while DLC was deposited by ion beam deposition with CH₄ gas as carbon source. The structure and properties of the synthesized films were characterized by X-ray diffraction, X-ray absorption near edge structure (XANES), Raman spectroscopy, nanoindentation, ball-on-disk testing, and corrosion testing. The effect of MoS₂ target bias voltage, ranging from −200 to −800 V, on the structure and properties of the DLC–MoS₂ films was further investigated. The results showed that the hardness decreases from 9.1 GPa to 7 GPa, the Young?s modulus decreases from 100 GPa to 78 GPa, the coefficient of friction (COF) increases from 0.02 to 0.17, and the specific wear rate coefficient (k) increases from 5×10⁻⁷ to 5×10⁻⁶ mm³ N⁻¹ m⁻¹, with increasing the biasing voltage from 200 V to 800 V. Also, the corrosion resistance of the DLC–MoS₂ films decreased with the raise of biasing voltage. Comparing with the pure DLC and pure MoS₂ films, the DLC–MoS₂ films deposited at low biasing voltages showed better tribological properties including lower COF and k in ambient air environment.     

Effect of microstructure on the conductivity of a NASICON-type lithium ion conductor

Sintering temperature is used to control the microstructure of Li_{1 + x + y}Al_xTi_2 − xSi_yP_3 − yO₁₂ (x = 0.3, y = 0.2), a NASICON-type glass-ceramic. Scanning Electron Microscope imaging, X-Ray Diffraction, and Electrochemical Impedance Spectroscopy are employed to show that increase in sintering temperature increases conductivity while generating secondary crystalline phases. Total conductivity is as high as 3.81 × 10⁻⁴ S cm⁻¹ for sintering temperatures above 1000 °C. Crystallization of dielectric phases places the optimal sintering temperature in the 900 °C to 1000 °C range. Thermal analysis of the glass precursor reveals the glass transition, and crystallization temperatures.