Anisotropic assembly of conjugated polymer nanocrystallites for enhanced charge transport

The anisotropic assembly of P3HT nanocrystallites into longer nanofibrillar structures was demonstrated via sequential UV irradiation after ultrasonication to the pristine polymer solutions. The morphology of resultant films was studied by atomic force microscopy (AFM), and quantitative analysis of intra- and intermolecular ordering of polymer chains was performed by means of static absorption spectroscopy and quantitative modeling. Consequently, the approach to treat the precursor solution enhanced intra- and intermolecular ordering and reduced the incidence of grain boundaries within P3HT films, which contributed to the excellent charge carrier transport characteristics of the corresponding films (μ ≈ 12.0 × 10(-2) cm(2) V(-1) s(-1) for 96% RR P3HT).

Differentiation of solid-type serous cystic neoplasm from neuroendocrine tumour in the pancreas: value of abdominal MRI with diffusion-weighted imaging in comparison with MDCT

AIM

To evaluate the value of abdominal MRI with diffusion-weighted (DW) imaging for differentiation of solid-type serous cystic neoplasm (SCN) from neuroendocrine tumour (NET) in the pancreas compared with that of CT.

MATERIALS AND METHODS

Ten solid-type SCNs and 15 NETs were included in the study. Qualitative and quantitative analyses were performed, and two observers independently reviewed CT and MRI images for diagnosis of solid-type SCNs. Fisher's exact test and Mann-Whitney U-test, diagnostic performance [receiver operating characteristic (ROC) curve analysis] were evaluated.

RESULTS

SCNs showed more frequently hypo-attenuation on unenhanced CT images and marked hyperintensity on T2-weighted images compared with NETs (p < 0.01). The density of the tumour on unenhanced CT images and the apparent diffusion coefficient (ADC) value of the tumour were significantly different between SCNs (mean 18.5 HU; mean 2.45 × 10(-3) mm(2)/s) and NETs (mean 39.2 HU; mean 1.51 × 10(-3) mm(2)/s; p < 0.001). In the differentiation of SCNs from NETs, diagnostic performance of MRI with DW images was significantly higher than that of CT imaging (p < 0.01).

CONCLUSION

Abdominal DW-MRI shows a higher diagnostic accuracy than abdominal CT imaging in the differentiation of solid-type SCNs from NETs.

Mapping the nonlinear dynamics of a laser diode via its terminal voltage

We show that the bifurcations between dynamical states originating in the nonlinear dynamics of an external-cavity semiconductor laser at constant current can be detected by its terminal voltage V. We experimentally vary the intensity fed back into the gain medium by the external cavity and show that the dc component V(dc) of V tracks the optical intensity-based bifurcation diagram. It is shown using computational results based upon the Lang-Kobayashi model that whereas optical intensity accesses the dynamical-state variable |E|, V is related to population-inversion carrier density N. The change in feedback strength affects N and thereby the quasi-Fermi energy level difference at the p-i-n junction band-gap of the gain medium. The change in the quasi-Fermi energy-level thereby changes the terminal voltage V. Thus V is shown to provide information on the change in the dynamical-state variable N, which complements the more conventionally probed optical intensity.

Upper abdominal gadoxetic acid-enhanced and diffusion-weighted MRI for the detection of gastric cancer: Comparison with two-dimensional multidetector row CT

AIM

To evaluate the diagnostic performance of abdominal magnetic resonance imaging (MRI) for the detection of gastric cancer in comparison with that of two-dimensional (2D) multidetector row computed tomography (CT).

MATERIALS AND METHODS

The study included 189 patients with 170 surgically confirmed gastric cancers and 19 patients without gastric cancer, all of whom underwent gadoxetic acid-enhanced MRI with diffusion-weighted (DW) imaging, and multidetector contrast-enhanced abdominal CT imaging. Two observers independently analysed three sets of images (CT set, conventional MRI set, and combined conventional and DW MRI set). A five-point scale for likelihood of gastric cancer was used. Diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were evaluated. Quantitative [apparent diffusion coefficient (ADC) analyses with Mann-Whitney U-test were conducted for gastric cancers and the nearby normal gastric wall.

RESULTS

The diagnostic accuracy and sensitivity for detection of gastric cancer were significantly higher on combined conventional and DW MRI set (77.8-78.3%; 75.3-75.9%) than the CT imaging set (67.7-71.4%; 64.1-68.2%) or the conventional MRI set (72-73%; 68.8-70%; p < 0.01). In particular, for gastric cancers with pT2 and pT3, the combined conventional and DW MRI set (91.6-92.6%) yielded significantly higher sensitivity for detection of gastric cancer than did the CT imaging set (76.8-81.1%) by both observers (p < 0.01). The mean ADC of gastric cancer lesions (1 ± 0.23 × 10(-3) mm(2)/s) differed significantly from that of normal gastric wall (1.77 ± 0.25 × 10(-3) mm(2)/s; p < 0.01).

CONCLUSION

Abdominal MRI with DW imaging was more sensitive for the detection of gastric cancer than 2D-multidetector row CT or conventional MRI alone.