Microorganisms such as fungi and bacteria cause many human diseases and therefore rapid and accurate identification of these substances is essential for effective treatment and prevention of further infections. In particular, contemporary microbial detection technique is limited by the low detection speed which usually extends over a couple of days. Here we demonstrate that metamaterials operating in the terahertz frequency range shows promising potential for use in fabricating the highly sensitive and selective microbial sensors that are capable of high-speed on-site detection of microorganisms in both ambient and aqueous environments. We were able to detect extremely small amounts of the microorganisms, because their sizes are on the same scale as the micro-gaps of the terahertz metamaterials. The resonant frequency shift of the metamaterials was investigated in terms of the number density and the dielectric constants of the microorganisms, which was successfully interpreted by the change in the effective dielectric constant of a gap area.

BACKGROUND AND PURPOSE:The traditional paradigm has regarded essential tremor (ET) as a benign disorder. However, recent clinical, neuroimaging, and neuropathologic studies suggest that ET may be a progressive neurologic disorder. Based on clinicopathologic findings that cerebellum and its outflow are the key structures in ET and degeneration of gray matter in cerebellum is followed by consequent wallerian degeneration of white matter (WM) fibers, the aim of the present study was to investigate changes in anisotropy in patients with ET.

ABSTRACT

We demonstrated sensitive detection of individual yeast cells and yeast films by using slot antenna arrays operating in the terahertz frequency range. Microorganisms located at the slot area cause a shift in the resonant frequency of the THz transmission. The shift was investigated as a function of the surface number density for a set of devices fabricated on different substrates. In particular, sensors fabricated on a substrate with relatively low permittivity demonstrate higher sensitivity. The frequency shift decreases with increasing slot antenna width for a fixed coverage of yeast film, indicating a field enhancement effect. Furthermore, the vertical range of the effective sensing volume has been studied by varying the thickness of the yeast film. The resonant frequency shift saturates at 3.5 μm for a slot width of 2 μm. In addition, the results of finite-difference time-domain simulations are in good agreement with our experimental data.

. Diagnostic accuracy and interobserver variability of pulsed arterial spin labeling for glioma grading. Acta Radiol 2008;49:450Á457.Background: Although pulsed arterial spin labeling (PASL) enables the reliable qualitative grading of brain tumors, its use in quantification for glioma grading may be hampered by the limited interobserver variability associated with low spatial resolution. Purpose: To assess the interobserver variability and diagnostic accuracy of the relative tumor perfusion signal intensity (rTPS) calculated using PASL in glioma grading. Material and Methods: Fifty-eight patients with 61 cerebral astrocytomas underwent conventional MR imaging and PASL. Receiver operating characteristic analyses were used to determine the optimum thresholds for tumor grading. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for identifying highgrade gliomas were also calculated. Cohen's k statistic was used to determine the levels of interobserver variability in the quantitative analysis of PASL. Results: The sensitivity, specificity, PPV, and NPV for determining a high-grade glioma with conventional MR imaging were 77.1, 73.1, 79.4, and 70.4%, respectively. A threshold value of 1.28 for rTPS provided a sensitivity, specificity, PPV, and NPV of 82.9, 96.2, 96.7, and 80.6%, respectively. There was a statistically significant difference in the rTPS between low-and high-grade astrocytomas (1.14 vs. 1.47, P B0.05). In the interobserver variability analysis, substantial agreement was obtained for the quantitative rTPS measurement from PASL (k 00.72). Conclusion: Quantitative perfusion measurement with PASL can improve the diagnostic accuracy of preoperative glioma grading, as compared to the application of conventional imaging alone. However, the interobserver variability for quantification is substantial.