MRI findings of gastric metastases from breast carcinoma

We describe the MR appearance of breast cancer metastases to the stomach. The stomach wall was diffusely thickened with loss of the regular fold pattern best shown on the single shot T2-weighted images and enhanced with moderate mural enhancement on early and late post gadolinium images. The combination of gastric wall thickening and abnormal enhancement should suggest the diagnosis of diffuse mural metastases in a woman with a history of breast cancer.     

Common bile duct anteroposterior movement synchronized with inferior vena cava pulsation observed by cine magnetic resonance imaging

Purpose

To reveal the phenomenon of common bile duct (CBD) anteroposterior movement caused by inferior vena cava (IVC) pulsation depending on the cardiac cycle using cine magnetic resonance imaging.

Materials and Methods

A breath-hold trans-axial cine segmented true fast imaging with steady-state precession (trueFISP) sequence was prospectively performed on 11 healthy volunteers to observe CBD anteroposterior movement and IVC pulsation during the cardiac cycle. Changes in IVC anterior–posterior diameter and CBD location were compared using Pearson rank correlation analysis.

Results

Nine (81.8%) of 11 CBDs moved back and forth in synchronicity with IVC anterior wall motion depending on the cardiac cycle; the mean maximum and minimum IVC diameters were 16.2±2.7 and 12.9±3.1 mm, respectively. Two (18.2%) of 11 CBDs and IVC walls did not move; the mean unchanged IVC diameter was 5.3±2.1 mm. There were significant correlations between the mean change in IVC diameter and distance of CBD anteroposterior movement (2.7±2.1 and 1.8±1.4 mm, respectively, r=0.911, P<.05).

Conclusion

Many CBDs move back and forth in synchronicity with IVC pulsation depending on the cardiac cycle.     

Dynamic contrast-enhanced MR imaging of the liver: Parenchymal enhancement patterns

A retrospective study of 164 patients undergoing dynamic contrast-enhanced magnetic resonance (MR) imaging was performed to assess hepatic parenchymal enhancement patterns and to correlate these patterns with hepatic function and disease. Rapid T₁-weighted images were acquired before and after gadolinium administration. Hepatic enhancement patterns were analyzed blindly by two observers. Medical records were reviewed to document known liver pathology and liver function test results. A total of 72% of patients had homogeneous enhancement of the liver parenchyma; 28% had heterogeneous enhancement. Of the latter group, 61% of patients had enhancement conforming to segmental or lobar boundaries. Patients with heterogeneous enhancement patterns were more likely to have abnormal liver function test results and hepatic morphological abnormalities on their MR examinations than patients with homogeneous enhancement patterns. Heterogeneous hepatic enhancement on dynamic MR images is associated with a higher likelihood of liver disease and biochemical evidence of hepatic dysfunction than homogeneous enhancement.     

MRI of acute cholecystitis: Comparison with the normal gallbladder and other entities

Our purpose was to prospectively compare MRI findings with histopathologic findings in the evaluation of suspected acute cholecystitis. Fourteen patients with clinically suspected acute cholecystitis were entered into the study. MR sequences included T₁-weighted fat-suppression and breath-hold spoiled gradient echo (SGE) before and after intravenous gadolinium chelate administration. Percent contrast enhancement (%CE) of the gallbladder wall and gallbladder wall thickness (WT) were measured and liver enhancement patterns determined prospectively on MR images. Correlation was obtained with pathological findings at cholecytectomy in all patients. In a second phase of the study MR images on 10 additional subjects who underwent MR examination for reasons other than hepatobiliary disease were analyzed to determine normal values for %CE and gallbladder wall thickness. Mean %CE was 124.0% in patients with acute cholecystitis (10 patients), 58.0% in patients with chronic cholecystitis (2 patients), and 73.0% in patients with gallbladder malignancy (2 patients). Mean gallbladder WT was 6.1 mm in acute cholecystitis, 4.5 mm in chronic cholecystitis, and 6.0 mm in malignant disease. There was a significant difference in %CE between acute and chronic cholecystitis (p = 0.03); no other significant differences in %CE or WT were observed among the patients with gallbladder disease. Patients without biliary disease had %CE of 37.3% and WT of 2.9 mm, which were both significantly less (p < 0.001) than in patients with acute cholecystitis. Transient enhancement of pericholecystic hepatic parenchyma on immediate postgadolinium SGE images was seen in 7 of 10 patients with acute cholecystitis, and not observed in other patients. Patients with acute cholecystitis had increased %CE and WT on MR images that were significantly greater than normal and %CE that was significantly greater than in patients with chronic cholecystitis. Transient increased pericholecystic hepatic enhancement was observed in 70% of acute cholecystitis patients and in no other patient groups.     

Forced Convective Condensation of R134A Vapor Inside a Vertical Microfin Tube

In this study, condensation of pure refrigerant R134a vapor inside a vertical 18° helical microfin tube was experimentally investigated. Tests were performed at saturation pressure of 5.7–5.9 bar with mass fluxes of 20–100 kg/m²s and heat fluxes of 1.7–5.3 kW/m². The effects of mass flux and the temperature difference between the refrigerant and tube wall (ΔT) on the heat transfer performance were analyzed throughout experimental data. For experiments in which ΔT is more than 2.5°C, the average condensation Nusselt number showed a tendency to be independent from ΔT. Heat transfer enhancement ratio was found to be 1.59–1.71, which is always higher than the heat transfer area enhancement factor (1.55). Fins always act as a turbulence promoter in the given experimental data range. Finally, the most widely used heat transfer coefficient correlations for condensation inside microfin tubes were analyzed through the experimental data. Best fit was obtained with Yu and Koyama's correlation with an absolute mean deviation of 17% and Kedzierski and Goncalves's correlation with an absolute mean deviation of 19%.     

Experimental evidence of enhancement in the anticipation time by cascading

We have studied and verified experimentally the enhancement in the anticipation time by cascading Chua's circuits. The experiments have been carried out in a one dimensional array of Chua's circuits (2 to 8) coupled unidirectionally, such that each one acts as a master for the next one. By doing so, it has been observed that the anticipation time increases with an increase in the array size. Moreover, the numerical simulations of an array of eighty Chua's circuits verify the experimental observations.     

Wetting of Heterogeneous Surfaces at the Mesoscopic Scale

We consider the problem of wetting on a heterogeneous wall with mesoscopic defects: i.e., defects of order L ^ε , 0<ε<1, where L is some typical length-scale of the system. In this framework, we extend several former rigorous results which were shown for walls with microscopic defects.^{(10, 11)} Namely, using statistical techniques applied to a suitably defined semi-infinite Ising-model, we derive a generalization of Young's law for rough and heterogeneous surfaces, which is known as the generalized Cassie–Wenzel's equation. In the homogeneous case, we also show that for a particular geometry of the wall, the model can exhibit a surface phase transition between two regimes which are either governed by Wenzel's or by Cassie's law.     

基于蚯蚓背孔射流的仿生射流表面减阻性能研究

为了减小流体对固体壁面的阻力, 基于蚯蚓生物学特征, 对蚯蚓背孔射流特性进行分析, 建立仿蚯蚓背孔射流的仿生射流表面计算模型, 采用SST k-ω 湍流模型对仿生射流表面的减阻特性进行数值模拟, 同时对数值模拟结果进行实验验证, 并以此研究了仿蚯蚓背孔射流表面的减阻机理.结果表明, 在一定条件下, 仿蚯蚓背孔射流的仿生射流表面具有较好的减阻效果; 在同一射流方向角下, 随着射流速度的增加, 减阻率逐渐增大; 在同一射流速度下, 随着射流方向角的增加, 减阻率呈先减小后增大的变化趋势; 数值模拟与实验均在射流速度为1 m·s^-1、射流方向角为-30°时达到最大, 分别为8.69%, 7.86%; 射流表面改变了原有光滑壁面的边界层结构, 对壁面边界层进行了有效的控制, 减小了壁面的剪应力, 降低了壁面边界层的速度.     

Value of Gd-DTPA-enhanced MR imaging of the labyrinth in patients with sudden hearing loss

Recent reports describe labyrinthine enhancement on MRI as a highly specific sign of labyrinthine disease. This paper reports 44 patients with unilateral sensorineural hearing loss (SNHL) and laboratory evidence of cochlear damage investigated with Gd-enhanced MR imaging. Enhancement of the cochlea was observed in only one patient with a lesion at the fundus of the internal auditory canal (IAC) that extended into the cochlea after Gd-DTPA administration. In one more patient, MR imaging demonstrated large vestibular aqueducts as underlying cause for his hearing loss, but no enhancement of the labyrinth was observed. No abnormal signal intensity on precontrast MR scans nor pathologic enhancement of the membranous labyrinth were identified in the other 42 patients. Gd-enhanced MR imaging appears to be insensitive in demonstrating labyrinthine disease and normal examination findings in a patient with sudden SNHL cannot exclude damage at the cochlear level.     

MR findings of intestinal graft-versus-host disease

Graft-versus-host disease (GVHD) occurs as a complication of allogenic bone marrow transplantation (BMT). The disease is characterized by skin rash, jaundice, mucosal inflammation, and diarrhea. In this report, we describe magnetic resonance (MR) findings of intestinal GVHD, which is correlated with endoscopic biopsy. MR findings demonstrated generalized increased bowel wall thickness associated with substantial bowel wall enhancement with gadolinium chelate.     

Exact formula for the domain-width-dependence of the Bloch wall's magnetic moment in uniaxial ferromagnets

By applying the theory of periodic domain structures to a 180° Bloch wall in a uniaxial ferromagnet, an exact formula for the dependence of the wall's magnetic moment on the domain width is derived and numerically examined.     

Experimental study of the enhanced Raman scattering in the Sarid-type 4-layered attenuated total reflection configurations

We experimentally explored the enhanced Raman scattering in pyridine (C₅H₅N) due to the excitation of long range surface plasmons (LRSP's) guided by a symmetrically bounded silver slab in the Sarid-type ATR (attenuated total reflection) configuration. We have observed that, with decreasing the metallic thickness, the absolute enhancement of the Raman cross section increases while the width of the polar angular distribution of the signal decreases. This observed dependence of the enhanced Raman intensity on the thickness of the thin Ag slab and the collecting solid angle is well explained by assuming that the Raman scattering is mediated by LRSP's. The observed maximum enhancement factor is 4 × 10⁶ for the 140 Å silver slab which agrees well with the theoretically predicted value of 6 × 10⁶.     

Lithium ion beam impact on selenium nanowires

This study is structured on Li³⁺ ion irradiation effect on the different properties of selenium (Se) nanowires (NW's) (80 nm). Template technique was employed for the synthesis of Se nanowires. Exploration of the effect of 10 MeV Li³⁺ ions on Se NW's was done for structural and electrical analysis with the help of characterization tools. X-ray diffraction revealed the variation in peak intensity only, with no peak shifting. The grain size and texture coefficients of various planes were also found to vary. Current-Voltage characteristics (IVC) show an increment in the conductivity up to a fluence of 1×10¹² ions/cm² and a decrease at the next two fluences. The effects of irradiation are presented in this paper and possible reasons for the variation in properties are also discussed in this study.     

On the form of the imaginary part of the optical potential

The imaginary part of the optical potential is derived fromMigdal's theory of nuclear structure. It is shown that the strong enhancement of ImV(r) at the nuclear surface is mainly due to a suppression of the effective nucleon-nucleon force by collective effects in the nuclear interior.     

激光聚焦位置对半球腔约束等离子体光谱增强特性的影响

光谱信号增强是提高激光诱导击穿光谱技术分析性能的重要手段之一,对等离子体进行空间约束由于装置简单且约束效果好而常被采用,等离子体的特性会直接影响空间约束的效果,而等离子体的特性与实验系统中激光的聚焦情况密切相关,为研究激发光源的聚焦情况对半球形空腔约束等离子体光谱增强特性的影响,通过控制透镜到样品之间的距离(LTSD)来改变激光的聚焦位置,分别在无约束和有半球形空腔约束两种实验条件下,烧蚀合金钢产生等离子体,采集15个不同LTSD位置时等离子体的时间演变光谱,得到谱线强度和增强倍数随着LTSD和采集延时的二维空间分布图。研究结果发现：无约束情况下,谱线强度分别在LTSD为94和102 mm时出现峰值,在采集延时小于8 μs时,谱线强度的最大值在LTSD为94 mm的位置,采集延时大于8 μs后,谱线强度的最大值出现在LTSD为102 mm的位置;当用半球空腔约束等离子体,谱线强度先后在采集延时范围为4~10和12~15 μs出现第一次增强和第二次增强。谱线强度出现第二次增强的主要原因是被半球腔内壁反射的冲击波与等离子体相互作用后会继续向前传播,遇到另一侧的腔壁再次被反射,进而对等离子体产生二次压缩。分析增强倍数随LTSD和采集延时的二维变化关系发现,第一次增强的最大增强倍数随LTSD的变化没有明显规律,增强倍数在2~6之间波动;谱线第二次增强时的增强倍数相对较高,最大增强倍数随着LTSD变化呈现出先增大再减小,然后再小幅增加后降低的变化规律,在LTSD为96 mm时达到最大值,两条谱线的最大增强倍数约为6倍。分析出现最大增强倍数对应的延迟时间发现,第一次增强出现的最优延迟时间在6~9 μs之间变化,当LTSD在85~93 mm范围时,最优延迟时间保持不变,当LTSD在94~105 mm时,出现先降低再增大的变化规律;第二次增强出现的延迟时间主要在14~15 μs,随着LTSD的变化没有明显的变化规律。     

Magnetic resonance of the inferior vena cava.

MRI was performed in 54 patients with abnormalities of the inferior vena cava (IVC). These included 16 patients with extrinsic IVC compression, 32 patients with intrinsic IVC abnormalities, and 6 patients with IVC dilatation. All patients had spin-echo imaging, and 21 had MR angiography. While presaturated spin-echo images showed intrinsic lesions to advantage, collateral vessels were best appreciated with MR angiography. The IVC is well evaluated with MRI techniques.     

Current-voltage characteristics of SIS structures with localized states in the material of the barrier layer

Elastic resonant tunneling through a single localized state in an insulating layer (I-layer) situated in the constriction zone between two thick superconducting electrodes is investigated theoretically, and the current-voltage characteristic (IVC) of the structure is calculated. The accompanying analysis leads to the prediction that an appreciable current can flow through the structure, not at |eV|=2Δ (Δ is the modulus of the order parameter of the superconducting electrodes) as in the case of an ordinary SIS junction, but at |eV|⩾Δ, and also that the IVC can acquire segments of negative differential resistance in the case of tunneling through a single localized state. Averaging of the IVC over an ensemble of localized states distributed uniformly throughout the volume of the I-layer and with respect to the energy near the chemical potential min the limit Γ₀/Δ≫1 (Γ₀ is the half-width of the resonance line of the localized state) produces a smaller excess current than in a junction of the SNS type. It is shown that the IVC’s exhibit a transition from an excess current to a deficit current as Γ₀ decreases in the high-voltage range. Zh. éksp. Teor. Fiz. 114, 687–699 (August 1998)     

Effect of a Hydrogen-Bonding Layer on a Hollow Capsule's Permeability

Hollow capsules formed by layer-by-layer self-assembly polymers have been intensively studied for their potential applications in medicine and biotechnology. We have controlled such capsules’ permeability with a hydrogen-bonding layer. Scanning electron microscopy and Fourier transform infrared results showed the fabrication of multilayer polyelectrolyte films. Z-potential results were employed to record the deposition of the polyelectrolyte. The diffusion coefficients for 6-carboxyfluorescein (6-CF) and fluorescently labeled goat anti-human IgG-FITC molecules passing through the wall were calculated based on the fluorescence recovery after photobleaching experiment. The results show that 6-CF molecules can pass through the capsule wall more easily than IgG-FITC molecules. By decreasing the solution's pH, the capsule's permeability to macromolecular dyes or small molecular dyes can be controlled, i.e., the capsule's permeability can be tuned by the hydrogen-bonding interaction.     

特性异常的发光管的分析研究

介绍了二类不同结构的(表面和侧面发射型)红外发光二极管.研究和分析了它们在低频大电流脉冲注入下的Pp—Ip特性和直流注入下的光谱特性.结果表明:正常情况下,器件具有线性的Pp—Ip特性,直流注入下的发射光谱具有高斯分布形状,对于Burrus表面发射型器件,在0—3A的峰值脉冲电流注入下,部分器件具有的异常Pp—Ip特性:线性-亚线性-超线性区.在20—100mA的直流电流注入下,部分器件的发射光谱具有多峰状.