Effects of surface chemical structure on the mechanical properties of Si(1-x)Ge(x) nanowires.

The Young's modulus and fracture strength of Si(1-x)Ge(x) nanowires (NWs) as a function of Ge concentration were measured from tensile stress measurements. The Young's modulus of the NWs decreased linearly with increasing Ge content. No evidence was found for a linear relationship between the fracture strength of the NWs and Ge content, which is closely related to the quantity of interstitial Ge atoms contained in the wire. However, by removing some of the interstitial Ge atoms through rapid thermal annealing, a linear relationship could be produced. The discrepancy in the reported strength of Si and Ge NWs between calculated and experimented results could be related to SiO(2-x)/Si interfacial defects that are found in Si(1-x)Ge(x) NWs. It was also possible to significantly decrease the number of interfacial defects in the NWs by incorporating a surface passivated Al2O3 layer, which resulted in a substantial increase in fracture strength.

Propagation of self-collimated ultrashort pulses in a hybrid photonic crystal.

We report the propagation of self-collimated ultrashort Gaussian pulses in a hybrid photonic crystal structure, in which broadband super-collimation was proposed recently. To choose their center frequencies, we compute group velocity dispersion and third-order dispersion as a function of frequency. Using the finite-difference time-domain method, we simulate the propagation of the pulses at two frequencies, one for zero group-velocity-dispersion and the other for optimized super-collimation. It is shown that the pulses nearly retain their transverse and longitudinal shapes during propagation over a long distance, and that third-order dispersion affects the pulse shape at zero group-velocity-dispersion frequency.

Change in the interfacial reaction of Hf-silicate film as a function of thickness and stoichiometry.

Medium energy ion scattering and high-resolution transmission electron microscopy are used to investigate the depth of the interfacial reaction of Hf-silicate film. The interfacial reaction is critically affected by the film thickness and the mole fraction of HfO(2) in silicate film. The interfacial compressive strain generated at the surface of the Si substrate is dependent on the film thickness during the postannealing process in film with a thickness of approximately 4 nm. Finally, the phase separation phenomenon demonstrates critically different behaviors at different film thicknesses and stoichiometries because the diffusion of Si from interface to surface is dependent on these factors. Moreover, the oxidation by oxygen impurity in the inert ambient causes SiO(2) top formation.

Deep tracheal laceration after balloon dilation for benign tracheobronchial stenosis: case reports of two patients.

We report two cases of deep tracheal laceration in female patients after balloon dilation for benign tracheobronchial stenosis. Immediate post-procedure bronchoscopy and CT including 3D reconstructions showed deep lacerations in the posterior tracheal wall. Clinically, the patients' dyspnoea subsided and there has been no recurrence during follow-up after balloon dilation. On the follow-up 3D-reconstructed CT scans obtained 2 months and 8 months following balloon dilation, respectively, the lacerations had healed completely and there was considerable improvement in lumen size.

Acute myelofibrosis in progressive systemic sclerosis. Report of a case developing during long term chlorambucil therapy and discussion of pathogenetic factors.

A case of acute myelofibrosis occurring in the course of long-term chlorambucil therapy for cardiac manifestations of progressive systemic sclerosis (PSS) is reported. Although hematologic malignancies have been known to develop consequent to long-term use of alkylating agents, and bone marrow suppression is well known, acute myelofibrosis has not, to our knowledge, been reported as a complication of this therapy, nor has any specific myeloproliferative syndrome been described consequent to such therapy in a patient with PSS. As abnormal fibroblastic proliferation is central to both PSS and myelofibrosis, it may be speculated that the patient with scleroderma may be predisposed to this particular expression of hematologic dyscrasia. The roles of fibroblastic proliferation, and immunologic and vascular factors in these two illnesses are currently poorly understood.

Programmed changes of cell cycle regulators by serum deprivation regardless of skeletal myocyte differentiation.

Permanent withdrawal of skeletal myoblasts from the cell cycle precedes differentiation. We examined the changes of protein levels of cell cycle regulators and the activities of CDKs in differentiating (by serum deprivation) or in differentiation-inhibited (by serum deprivation + TGF-beta1 treated) C2C12 skeletal myocytes. Regardless of differentiation, protein levels of most cyclins declined over time while this effect was delayed slightly by TGF-beta1 for cyclins D1 and F. Although the protein levels of CDKs gradually decreased over time, the activities of CDK2 and cdc2 decreased dramatically between 0 and 12 h after serum deprivation in both groups. Decreased CDK2 and cdc2 activities were temporally related to decreased DNA synthesis. While the p27KIP1 protein increased in both groups, the p21CIP1 protein increased only in differentiating cells. In vivo, protein expressions of cyclins, CDKs, and p21CIP1 were high in fetal, but almost undetectable in adult skeletal muscle. In contrast, the levels of p27KIP1 protein in skeletal muscle were high throughout development. Thus, changes of cell cycle regulators in differentiating C2C12 myocytes paralleled those during skeletal muscle development of mice. These results suggest that the rapid reduction of DNA synthesis and activities of CDKs slow reduction of protein levels of cyclins and CDKs, and that the increase of p27KIP1 are programmed mechanisms upon mitogen deprivation regardless of differentiation in skeletal myocytes.

Acinar cell carcinoma of the pancreas. Ultrasonography and computed tomography findings.

The radiologic findings in two cases of acinar cell carcinoma of the pancreas are described. Sonographic findings were a midrange echogenic mass with heterogeneity, containing some small- and medium-sized low echogenic areas suggesting necrosis. Ultrasonic through-transmission was good. Computed tomography findings were a well-defined, hypodense, large mass having an enhancing, thin capsule. There were multiple small- and medium-sized irregular low-density areas suggesting necrosis. Small punctate calcific foci were present in one case. With these characteristics, acinar cell carcinoma can be distinguished from the locally invasive common adenocarcinoma of the pancreas, but the differentiation from some other less common pancreatic tumors remains difficult.

Complete eversion and prolapse of bladder concurrent with primary adenocarcinoma.

Complete eversion and prolapse of the urinary bladder is extremely rare. To the best of our knowledge, the imaging findings of complete bladder eversion have not been documented in the literature. Here, we report a case of complete eversion and prolapse of the urinary bladder demonstrated on MRI. Concurrent primary adenocarcinoma was found in the thickened wall of the everted urinary bladder.

Numerical analysis of readout-signal cross talk in magneto-optical land and groove recording.

The effects of recorded marks, groove geometry, and aberrations on readout-signal cross talk are numerically analyzed in magneto-optical land and groove recording, with an application of scalar diffraction theory. Three simple patterns of recorded marks are considered, and each of them consists of three tracks that respectively have three marks of a single frequency. Cross talk as a function of groove depth is calculated at the edges, as well as at the center, of a mark in the center track for each frequency. The groove-depth ranges over which cross talk is less than -30 dB are obtained for each pattern.

Experimental reconstruction of the spatial density distribution of a nonreacting flow with a small number of absorption measurements.

The finite-domain direct inversion method, which was developed for use with sparse data sets, assumes smooth distributions, uses a priori information, and is well suited to the study of fluid mechanical and combustion phenomena. We successfully applied the inversion method, together with shifting functions that improve the reconstruction of distributions with nonzero values at the boundaries of their domain, to a real experimental situation and reconstructed the density distribution of methane in a nonuniform, nonreacting flow of methane and argon from projections measured optically. A point-by-point probe measurement of the methane concentration through the use of a hydrocarbon analyzer was performed to confirm the quality of the reconstruction of the optical measurement data with the inversion method.

Posterior hepatodiaphragmatic interposition of the colon: ultrasonographic and computed tomographic appearance.

High posterior hepatodiaphragmatic interposition of the colon is an unusual normal variant that may mimic posterior hepatic lesions, posterior retroperitoneal masses, or a disrupted right diaphragm on sonography. The correct diagnosis of this entity may be suggested on plain abdominal films, and is made easily with computed tomography.

Radiological findings of human fascioliasis.

Fasciola hepatica is a trematode of herbivorous mammals. Humans are accidentally infected by the ingestion of water or raw aquatic vegetables contaminated with the metacercaria. Radiological findings of six patients with fascioliasis (five hepatic fascioliasis, one biliary fascioliasis) were analyzed. The diagnosis was based on serological testing and/or histopathologic findings of eosinophilic abscess in five patients and identification of the adult worm in one patient. The characteristic radiological features of hepatic fascioliasis were (1) cluster of microabscesses arranged in tract-like fashion (burrow tract), (2) subcapsular location of the hepatic lesions, and (3) very slow evolution of the lesion on follow-up examinations. In biliary fascioliasis, there were multiple conglomerated filling defects in the common bile duct. The authors believe that the demonstration of these features, together with peripheral eosinophilia or eosinophilic aspirate from the hepatic lesion, is very helpful in making the correct diagnosis.

Preoperative evaluation of gastric cancer: value of spiral CT during gastric arteriography (CTGA).

BACKGROUND: To evaluate the utility of dual-phase spiral computed tomography during gastric arteriography (CTGA) in the preoperative staging of gastric cancers. METHODS: We performed CTGA in 21 patients with pathologically proven gastric cancers. CTGA findings were prospectively analyzed and correlated with surgical and pathologic findings. Dual-phase scans were performed at 10 s (early) and 60-100 s (delayed) after injection of 120 mL of contrast medium at an injection rate of 6 mL/s through a preset 5-Fr catheter positioned in the celiac trunk. Spiral CT scans were assessed for enhancing pattern of the normal gastric wall, tumor detectability, and accuracy of tumor staging. RESULTS: Normal gastric mucosa was clearly visible as two or three layers in all patients on early-phase scans and in eight patients on delayed-phase scans. The primary tumors were correctly detected with CTGA in seven (88%) of the eight early gastric cancers and in all 13 (100%) advanced gastric cancers. The accuracy of CTGA for T staging was 50% and 77% in early and advanced gastric cancers, respectively. The overall accuracy for tumor detection and T staging was 95% and 67%, respectively. The accuracy of CTGA for the degree of serosal invasion and regional lymph node metastasis was 77% and 76%, respectively. CONCLUSION: The CTGA technique improved tumor detection rate and accuracy of tumor staging, especially in early gastric cancer, and may be very useful in the preoperative staging of gastric cancer.

Hepatocellular carcinoma in extrahepatic bile ducts.

An elongated solid lesion observed on ultrasonography and CT in the biliary tree causing a smooth filling defect on cholangiography was observed in 2 patients. No tumor was observed in the liver parenchyma either on radiography or at operation. Histopathology showed hepatocellular carcinoma. After removal of the intraductal tumors, recurrence was observed in 2 and 6 months, respectively.

Calcified gastric carcinoma: CT findings.

The computed tomographic (CT) findings of 13 cases of calcified gastric carcinoma were analyzed retrospectively. Eleven cases were confirmed as a mucinous adenocarcinoma by surgery (three cases), or endoscopic biopsy (eight cases). Two cases were diagnosed as adenocarcinoma by endoscopic biopsy. In all cases the calcifications were of the punctate or miliary shape and the size varied from 1-3 mm in diameter. The calcifications were located in the thickened gastric wall in all cases, and were seen in metastatic lesions such as lymph nodes and the liver in two cases. In 10 cases, some tumor portions showed lower attenuation number than that of the muscle on CT scans, and corresponded to mucin pool in tumor portions histologically. Twelve cases were in inoperable advanced stage.

Saline-filled appendiceal ultrasonography in clinically equivocal acute appendicitis.

BACKGROUND: To establish the value of saline-filled appendiceal ultrasonography in the the diagnosis of clinically equivocal acute appendicitis. METHODS: Saline-filled ultrasonography was performed in 43 patients with an equivocal clinical diagnosis of acute appendicitis. RESULTS: Sonography diagnosed 31 of 32 patients without acute appendicitis (97%). A normal appendix was visualized in 15 patients (47%), and we identified a normal appendix in 15 of 22 patients (68%) in whom the colon was cleansed with Golytely(R). Sonography diagnosed 10 of 11 patients with acute appendicitis (91%). In three of 10 patients, the findings corresponded to sonographic pitfalls. CONCLUSION: Saline-filled appendiceal ultrasonography enables the detection of a normal appendix and may overcome sonographic pitfalls in acute appendicitis.

Hepatic arterioportal shunts not directly related to hepatocellular carcinoma: findings on CT during hepatic arteriography, CT arterial portography and dual phase spiral CT.

AIM: To evaluate findings of arterioportal shunts not directly related to hepatocellular carcinoma (HCC) which were seen within third-order portal branches on computed tomography (CT) during hepatic arteriography (CTHA), arterial portography (CTAP), and dual phase spiral CT. MATERIALS AND METHODS: At CTHA in 112 patients, we examined third-order portal vein branches to find arterioportal shunts not directly related to HCC. Six cases were found. We evaluated the findings of these shunts on CTHA and investigated whether CTAP (n = 6) and dual phase spiral CT (n = 5) showed perfusion defects in the corresponding areas on arterioportal shunts. RESULTS: Five of six cases showed abrupt visualization of portal branches without visualization of the proximal portion of CTHA. Five of six cases showed no perfusion defect on CTAP and no hyperattenuating area on CTHA. Four of five cases showed no hyperattenuating area on hepatic arterial phase spiral CT. CONCLUSION: Arterioportal shunts not directly related to HCC and occuring within third-order portal branches mainly showed abrupt visualization of portal branches on CTHA. These occurred frequently without perfusion defects on CTAP and without a hyperattenuating area on CTHA and hepatic arterial phase spiral CT.Park, C. M. (2000). Clinical Radiology55, 465-470.

High-resolution CT appearance of miliary tuberculosis.

OBJECTIVE: The purpose of this study was to define the range of abnormalities and to assess the contribution of high-resolution CT (HRCT) in the evaluation of miliary tuberculosis involving the lung parenchyma. MATERIALS AND METHODS: The authors retrospectively reviewed HRCT scans of 11 patients with microbiologically or clinically proved miliary tuberculosis. RESULTS: In 10 patients, the most characteristic HRCT finding of miliary tuberculosis was the presence of small nodules uniformly distributed throughout both lungs. The profusion of nodules was numerous in all 10 patients. High-resolution CT scans showed both sharply and poorly defined, small nodules varying in sizes from 1 to 2 mm (n = 6), 1 to 3 mm (n = 2), and 1 to 4 mm (n = 2) in diameter. These nodules had a diffuse random distribution in the secondary lobule in all 10 patients. In 1 of the 10 patients with small nodules on HRCT, chest radiography had shown no evidence of miliary nodules in the lung. In addition to nodules, HRCT showed diffuse or localized reticular opacities superimposed on nodules in five patients, especially in the lower lung zones. In 1 of all 11 patients, ground-glass attenuation was the predominant abnormality seen on HRCT. CONCLUSION: We believe that in the appropriate clinical situation, miliary tuberculosis may be suggested on HRCT. Moreover, in cases with no evidence of miliary nodules on the chest radiograph, HRCT scan may depict miliary nodules in the lung parenchyma.

Intra-articular ganglion cysts of the knee: clinical and MR imaging features.

The purpose of this study was to present clinical and MR imaging features of intra-articular ganglion cysts of the knee. Retrospective review of 1685 consecutive medical records and MR examinations of the knee performed at three imaging centers allowed identification of 20 patients (13 men and 7 women; mean age 35 years), in whom evidence of intra-articular ganglion cyst was seen. Of the 20 ganglion cysts, 5 were found in the infrapatellar fat pad, 10 arose from the posterior cruciate ligament, and 5 from the anterior cruciate ligament. Three of five patients with ganglion cyst in the infrapatellar fat pad had a palpable mass. In 7 of 15 patients with ganglion cyst in the intercondylar notch, exacerbation of pain occurred in a squatting position. On four MR arthrographies, ganglion cysts were an intra-articular round, lobulated, low signal intensity lesion. Five cases of fat-suppressed contrast-enhanced T1-weighted SE images demonstrated peripheral thin rim enhancement. The clinical presentation of intra-articular ganglion cyst is varied according to its intra-articular location. The MR appearance of intra-articular ganglion cyst is characteristic and usually associated with the cruciate ligament or the infrapatellar fat pad. Magnetic resonance arthrography has no definite advantage over conventional MR in the evaluation of the lesion. For intra-articular ganglion cyst in the infrapatellar fat pad, fat-suppressed contrast-enhanced MR imaging could be useful, because a thin, rim-enhancing feature of intra-articular ganglion cyst allows it to be distinguished from synovial hemangioma and synovial sarcoma.