A reduction approach for determining generalized simple waves

A reduction approach is developed in order to construct generalized simple wave solutions to quasilinear nonhomogenous hyperbolic systems of first order PDEs. The solutions sought must possess a special ansatz which permits time-evolution of the profile of a simple wave due to a source-like term. These solutions involve a free function which can be used to fit classes of initial or boundary value problems. By means of the proposed approach two governing models of interest in a variety of applications are investigated. Model constitutive laws consistent with the full reduction process are obtained and the occurence of singularities at a finite time for the resulting solutions is analysed. Furthermore a comparison is made between the results obtained within the present theoretical framework and the standard simple wave solutions of the corresponding homogeneous (source free) governing models.      

Dip and wait: a facile route to nanostructured porphyrin films for QCM functionalization

A facile and straightforward way to deposit nanostructured porphyrin films onto quartz surfaces is presented. The particular peripheral functionalization on the macrocycle is exploited to drive the formation of aggregates in solution, which then spontaneously deposit as ordered solid layers. Film deposition is then achieved by simple dipping the quartz slide into a solution containing porphyrin aggregates and waiting the formation of the related thin films. QCMs covered with different metalloporphyrin derivatives have been exposed to some model VOCs, showing in general good performances especially in all the cases where film morphology is fundamental for sensing interactions.     

Absolute measurement of the S(0) and S(1) lines in the electric quadrupole fundamental band of D(2) around 3μm

The electric quadrupole fundamental (v=1←0) band of molecular deuterium around 3?μm is accessed by cavity ring-down spectroscopy using a difference-frequency-generation source linked to the Cs-clock primary standard via an optical frequency comb synthesizer. An absolute determination of the line position and strength is reported for the first two transitions (J=2←0 and J=3←1) of the S branch. An accuracy of 6×10(-8) is achieved for the line-center frequencies, which improves by a factor 20 previous experimental results [A. R. W. McKellar and T. Oka, Can. J. Phys. 56, 1315 (1978)]. The line strength values, measured with 1% accuracy, are used to retrieve the quadrupole moment matrix elements which are found in good agreement with previous theoretical calculations [A. Birnbaum and J. D. Poll, J. Atmos. Sci. 26, 943 (1969); J. L. Hunt, J. D. Poll, and L. Wolniewicz, Can. J. Phys. 62, 1719 (1984)].     

Beyond laparoscopy: 3-T magnetic resonance imaging in the evaluation of posterior cul-de-sac obliteration

Objectives

Endometriosis is the ectopic localization of endometrial glands. Symptoms include a wide variety of chronic pelvic pain. Ovarian endometriosis represents the most frequent site of implantation followed by the Douglas pouch which is undepicted unless peritoneal fluid is present. Pelvic exams may be reported as normal in 40% of evaluations, although multiple nodularities are located in this region. Nowadays, laparoscopy represents the standard technique for endometriosis evaluation. However, magnetic resonance imaging (MRI) remains the best noninvasive technique for the evaluation of pelvic lesions. According to the importance of a precise preoperative diagnosis of deep infiltrative endometriosis involving the Douglas pouch, we evaluated feasibility of a 3-T system in the evaluation of this particular region.

Methods

We enrolled 19 women coming with either ultrasound or anamnestic suspicion of endometriosis. Pelvic MRI examination was performed on the 3-T system. We applied a standard exam protocol including pulse sequences [single-shot fast spin echo (FSE)] and high-resolution T2W and T1W FSE sequences with and without FS.

Results

MRI diagnosed posterior cul-de-sac obliteration in 15/19 patients. MRI findings were compared with laparoscopy, thus obtaining the following statistical values: mean sensitivity, specificity, positive predictive value and negative predictive value, respectively, of 93%, 75%, 93% and 75%. Moreover, we calculated an interobserver agreement k value of 0.72 with a substantial degree of agreement between two radiologists of a sensitivity value of 93% and specificity value of 75%.

Conclusions

Precise preoperative mapping of posterior cul-de-sac region is essential for a preoperative planning. In our work, the 3-T MRI was shown to be excellent in the evaluation of posterior cul-de-sac obliteration associated to an optimal evaluation of the uterosacral ligaments due to the higher contrast spatial resolution.     

Differential Constraints and Exact Solution to Riemann Problems for a Traffic Flow Model

In view of solving in a closed form initial and/or boundary value problems of interest in nonlinear hyperbolic and dissipative wave processes it is considered a reduction approach based upon appending differential constraints to quasilinear nonhomogeneous hyperbolic systems of first order PDEs. In this context a governing model of traffic flow is analyzed thoroughly and a classification of possible constraints along with sets of consistent response functions involved therein is worked out whereupon the classes of corresponding exact solutions are determined. To some extent these solutions generalize the classical simple wave solutions and may also incorporate dissipative effects. Furthermore, in order to solve a Riemann Problem, an exact rarefaction wave-like solution is built. Finally an application of the results to the so-called ??green traffic light problem?? is also illustrated.     

Frequency metrology of helium around 1083 nm and determination of the nuclear charge radius

We measure the absolute frequency of seven out of the nine allowed transitions between the 2 (3)S and 2 (3)P hyperfine manifolds in a metastable (3)He beam by using an optical frequency comb synthesizer-assisted spectrometer. The relative uncertainty of our measurements ranges from 1×10(-11) to 5×10(-12), which is, to our knowledge, the most precise result for any optical ^{3}He transition to date. The resulting 2 (3)P-2 (3)S centroid frequency is 276,702,827,204.8(2.4) kHz. Comparing this value with the known result for the (4)He centroid and performing ab initio QED calculations of the (4)He-(3)He isotope shift, we extract the difference of the squared nuclear charge radii δr(2) of (3)He and (4)He. Our result for δr(2)=1.074(3) fm(2) disagrees by about 4σ with the recent determination [R. van Rooij et al., Science 333, 196 (2011)].     

Electronic tongue based on an array of metallic potentiometric sensors

An electronic tongue system based on the array of six metallic potentiometric sensors (metallic wires) was developed and utilized for discrimination of foodstuffs: several types of vinegar and fruit juices. Copper, tin, iron, aluminum, brass and stainless steel wires were included in the array and supplemented by pH glass electrode. The response of potentiometric metallic sensors towards various organic acids has been studied and possible sensitivity mechanisms were discussed. Overall potential changes of metallic sensors were exanimate as complex mixed signals influenced by several components presenting in analyte employing chemometric approach. The multisensor array of such a type can be useful for several applications since of simplicity in handling, low cost of sensors and easy measure procedure.     

Spatial mode control of radiation generated by frequency difference in periodically poled crystals

We demonstrate the possibility to control the spatial mode of a narrow-linewidth, continuous-wave, infrared radiation beam generated by difference frequency in a periodically poled crystal. This can be achieved by acting directly on a few experimental parameters. We show that hollow beams can be generated. A numerical routine has been developed and results agree with experimental observations, without requiring any free parameters. The relevance of these results for high-resolution spectroscopy and atom manipulation is discussed.     

On the possible use of optical fiber Bragg gratings as strain sensors for geodynamical monitoring

Optical fiber sensors can be used to measure many different parameters including strain, temperature, pressure, displacement, electrical field, refractive index, rotation, position and vibrations. Among a variety of fiber sensors, fiber Bragg gratings (FBG) have numerous advantages over other optical fiber sensors. One of the major advantages of this type of sensors is attributed to wavelength-encoded information given by the Bragg grating. Since the wavelength is an absolute parameter, signal from FBG may be processed such that its information remains immune to power fluctuations along the optical path. This inherent characteristic makes the FBG sensors very attractive for application in harsh environments, “smart structures” and on-site measurements.This paper reviews the achievements about the FBG as a strain and temperature sensor and describes the potential applications of FBG sensors for applications in the field of geophysics and its expected development in the near future. The applications could include: rock deformation, fiber-optic geophone, optical based seismograph, vertical seismic profiling and structural monitoring of civil structures. Different techniques to detect strains and various applications will be reviewed and discussed. The problem of temperature–strain cross sensitivity, that is particularly difficult to eliminate, is addressed and approaches to overcome it are discussed.