Hole Sign Research Articles

"Hole sign" of the gallbladder.

"Hole sign" of the gallbladder.

Crystal growth and transport properties of CuAlO2 single crystal

The transport properties of the delafossite CuAlO2 single crystal, grown by the flux method, are confined in ∞[AlO2] layers extending in the (001) plans. The dielectric properties are measured up to 490 K in the frequency range (102–105 Hz). The small variation of the dielectric loss tan(δ) is attributed to the wide space charge region. The linear plot log (conductivity) vs. 1000/T follows an Arrhenius type law and the results are discussed in terms of electron hopping among localized states. The activation energy (0.18 eV) gives an effective mass of 16m0 indicating that the levels in the vicinity of the Fermi level are strongly localized. Hence, the increase of the conductivity (σ) results from a thermal activation of the mobility (μ300 K = 1.2 × 10−5 cm−2 V−1 s−1). The sign of hole like small polarons is that of p type carriers originating from oxygen intercalation. The thermopower is little temperature dependent and characteristic of non degenerate conductivity with a low holes concentration and a large concentration of surface states within the gap region.

Gallbladder perforation: the hole sign

We report a case of gallbladder perforation (GBP) in a patient with right upper quadrant pain and a positive Murphy's sign, a previous history of cholelithiasis and co-morbidities. We compare the diagnosis of GBP using the ‘hole-sign’ on ultrasound with the literature for contrast-enhanced ultrasound, computed tomography and magnetic resonance imaging.

Intrahepatic rupture of empyema gallbladder

A 70-year-old woman presented with right upper quadrant pain and fever since 1 month, with exacerbation of symptoms since 1 week. Clinically, she had tenderness in the right hypochondrium; laboratory parameters showed elevated AST, ALT and alkaline phosphatase values. Ultrasonogram abdomen showed a large abscess in liver with suspicious communication with gallbladder. CT scan of abdomen showed a large irregular thick-walled cystic lesion in segments 5 and 8 of liver suggestive of a liver abscess. This cavity communicated with a thick-walled edematous gallbladder, that contained few calculi (Fig. 1). A diagnosis of empyema gallbladder with intrahepatic rupture and abscess formation in the liver was made. Ultrasound-guided percutaneous drainage of the abscess was done with a plan for elective laparoscopic cholecystectomy. Perforation of the gallbladder is a rare complication that occurs in 2 % to 11 % of acute cholecystitis; delay in diagnoses is a major cause of morbidity and mortality [1]. Niemeier classified gallbladder perforations into 3 types: type I—acute, manifests with generalized peritonitis; type II—subacute, which denotes localization of fluid at the site of perforation with formation of a pericholecystic abscess; and type III—chronic, in which internal or external fistula occur [2]. Our patient had Type II perforation. CT scan is more sensitive than ultrasonogram for the diagnosis of perforation [2], Visualization of the perforation “hole sign”, the demonstration of communication between the abscess and the gallbladder and points towards the diagnosis [3]. References

Negatively charged excitons in semimagnetic CdSe/ZnSe/ZnMnSe quantum dots

Low-temperature (T = 1.6 K) photoluminescence (PL) of individual CdSe/ZnSe/ZnMnSe quantum dots (QDs) with different magnitudes of the sp-d exchange interaction between the magnetic impurity ions and charge carriers has been studied in a magnetic field up to 12 T applied in the Faraday and Voigt geometry. The magnitude of the interaction was controlled by changing the fraction (ηe, h) of the squared wave function of charge carriers in the semimagnetic barrier by means of variation of the nonmagnetic (ZnSe) layer thickness. It is established that the sp-d exchange interaction leads to a change in the sign of the effective hole g factor even for ηe, h ∼ 5%, while further increase in the interaction magnitude is accompanied by a rapid growth in the magnitude of spin splitting for both electrons and holes. The quantum yield of PL exhibits a significant decrease due to nonradiative Auger recombination with the excitation of Mn ions only for ηe, h ∼ 12%, while the rate of the holes spin relaxation starts growing only for still higher ηe, h values. In a strong magnetic field perpendicular to the sample plane, the alignment of Mn spins leads to suppression of the Auger recombination only in the excited spin state. For a small rate of the hole spin relaxation, this leads to a rather unusual result: the emission from an excited trion state predominates in strong magnetic fields.

Performance Improvement of DPLL's in Non-Gaussian Noise Using Robust Estimators

This paper deals with the analysis of DPLL's operating in the presence of non-Gaussian noise. The loop model developed here allows for multiple input samples each loop sampling period, complex processing of the input sample set, and various noise distributions. In particular, six different robust estimators are used as processors of the input: these are the trimmed mean estimator, a one-step Huber M -type estimator, a new M -type estimator, and three versions of a zero-memory nonlinear (ZNL) estimator: hole punch, limiter, and sign detector. The tracking performance of a second-order DPLL is simulated and analyzed for five different types of noise: Gaussian, contaminated Gaussian, Laplace, Middleton Class A , and generalized exponential. Comparisons are made for signal-to-noise ratios ranging from 0 to - 10 dB. It is found that the ZNL estimators provide performance superior to that of the other robust estimators, especially for noise densities that are heavy tailed.