Hearing and Sj?gren's syndrome

Immune sensorineural hearing loss is manifested in several systemic immune diseases. Although hearing loss has been previously documented in patients with Sj?gren's syndrome (SS), the effect of SS on hearing is unclear. This prospective study was designed to assess the presence of hearing loss in 14 patients with SS and, if sensorineural hearing loss was present, to determine if the hearing loss was immune-mediated. Patients were evaluated with basic audiologic tests as well as for cellular immune inner ear reactivity as measured by the lymphocyte transformation test (LTT). Three patients had evidence of sensorineural hearing loss. Two patients had a positive LTT without evidence of sensorineural hearing loss. This preliminary study suggests that SS may not directly cause sensorineural hearing loss, immuno-mediated or otherwise.     

Integrated electronic transport and thermometry at milliKelvin temperatures and in strong magnetic fields

We fabricated a He-3 immersion cell for transport measurements of semiconductor nanostructures at ultra low temperatures and in strong magnetic fields. We have a new scheme of field-independent thermometry based on quartz tuning fork Helium-3 viscometry which monitors the local temperature of the sample's environment in real time. The operation and measurement circuitry of the quartz viscometer is described in detail. We provide evidence that the temperature of two-dimensional electron gas confined to a GaAs quantum well follows the temperature of the quartz viscometer down to 4 mK.     

Determination of attenuation-velocity products in a layered homogeneous medium

Attenuation imaging has the promise to become a measurement technique for ultrasound imaging systems more sophisticated than those we currently possess; however, the difficulties in using the presently available methods tend to limit this potential for the non-specialist. In our recent work, we have investigated the attenuation imaging problem, and have had some success with an alternative technique, namely, attenuation-velocity product imaging. In certain cases this can be an acceptable substitute for purely attenuation imaging, particularly for the soft tissues encountered in some diagnostic medical situations where the acoustic velocities of the various layers are all of approximately the same value. This article discusses our technique in detail, beginning with fundamental considerations. We make no unreasonable assumptions about the object under study, and yet are able to show the uniqueness of the solution and also deal effectively with the problem of multiple reflections. The data encountered in this experimental configuration have several intriguing properties, which allow us to draw some conclusions about acoustic imaging in general.     

Brainstem dysfunction in the infant apnea syndrome

Thirty-six infants identified as infant apnea syndrome (IAS) and 25 controls with a comparable age distribution were evaluated with Brainstem Auditory Evoked Potential (BAEP) testing. There was a significant predilection for leftsided BAEP abnormalities in IAS patients. Fifteen IAS patients had bilateral abnormalities, and of the 21 IAS patients with unilateral abnormalities, 17 had abnormalities on the left side (p less than 0.01 by McNemar's test). Significant differences (p less than 0.05 by analysis of covariance adjusting for age) between normal controls and IAS infants were found for peak latencies I, III, and V, and amplitude III. Linear regression analyses of the above parameters versus age in months for normal controls were constructed with 68% and 95% prediction interval bands to permit analysis of individual data points. Data points from the IAS infants with bilateral BAEP abnormalities have been plotted on these linear regression curves. No single measurement of latency or amplitude is abnormal in the majority of IAS infants, but many of the individual points fall outside of the 95% prediction curve.     

Automatic load-frequency control of the united power system of Siberia

A centralized system for automatic load-frequency control (ALFC) has been developed by the Siberian Division of the Central Computing Center of the Power Industry and realized on the basis of a commercial OMRON controller that performs all control functions. The algorithmic and software support of ALFC performs several new functions, i.e., helps to produce control actions on regulating stations with allowance for the specified daily output, perform second-after-second (cumulative sum) accounting for the power produced by a power station due to participation in the control, initiate combined regulation of power flow and frequency (APFR), ensure maintenance of a 1-sec archive with a depth of over 30 days for any telemetry (TM) used in the ALFC, etc. The software has been developed with the help of special language based on the IEC 1131-3 standard.Translated from Élektricheskie Stantsii, No. 11, November 2004, pp. 17 – 20.     

Free convection of a heat generating fluid in a hemispherical closed volume

From a theoretical analysis and results of previous studies, a model of the free convection of a heat-generating fluid in a hemispherical closed volume with a completely isothermal boundary is developed. By applying analytical estimates, we establish that at values of modified Rayleigh numbers Ra₁ > 10¹³, the flow in the entire volume is turbulent, which substantially simplifies the problem. Integrated relations for heat emission through the upper and lower parts of the boundary of the hemispherical capacity are obtained as a result. Results of numerical calculations have shown that the majority of heat is removed through the spherical surface downwards. The ratio of the heat flux through the upper horizontal boundary to heat flux through the lower boundary decreases from 0.5 to 0.3 in the range of modified Rayleigh numbers Ra_I from 10⁹ to 10¹⁷.     

A New Type of Carbon Resistance Thermometer with Excellent Thermal Contact at Millikelvin Temperatures

Using a new brand of commercially available carbon resistor we built a cryogenic thermometer with an extremely good thermal contact to its thermal environment. Because of its superior thermal contact the thermometer is insensitive to low levels of spurious radio frequency heating. We calibrated our thermometer down to 5 mK using a quartz tuning fork He-3 viscometer and measured its thermal resistance and thermal response time.     

Gold‐ and Silver‐Coated Barium Titanate Nanocomposites as Probes for Two‐Photon Multimodal Microspectroscopy

Improved multiphoton‐excited imaging and microspectroscopy require nanoprobes that can give different nonlinear optical signals. Here, composite nanostructures with a barium titanate core and a plasmonic moiety at their surface are synthesized and characterized. It is found that the core provides a high second‐order nonlinear susceptibility for sensitive second harmonic generation (SHG) imaging in living cells. As a second function in the two‐photon regime, the plasmonic part yields high local fields for resonant and nonresonant surface enhanced hyper Raman scattering (SEHRS). SEHRS complements the one‐photon surface enhanced Raman scattering (SERS) spectra that are also enhanced by the plasmonic shells. Barium titanate silver core–shell (Ag@BaTiO₃) composites are specifically suited for SEHRS and SHG excited at 1064 nm, while gold at barium titanate (Au@BaTiO₃) nanoparticles can be useful in a combination of SHG and SERS at lower wavelengths, here at 785 nm and 850 nm. The theoretical models show that the optical properties of the BaTiO₃ dielectric core depend on probing frequency, shape, size, and plasmonic properties of the surrounding gold nanoparticles so that they can be optimized for a particular type of experiment. These versatile, tunable probes give new opportunities for combined multiphoton probing of morphological structure and chemical properties of biosystems.     

Preparation and characterization of cross‐linked polymeric nanoparticles for enhanced oil recovery applications

Chemically cross‐linked nanoparticles from dilute aqueous alkali solutions of hydroxyethylcellulose (HEC) in the presence of a cross‐linker agent (divinyl sulfone, DVS) were prepared from a reaction mixture, which was exposed to different stirring speeds during the cross‐linking process. At various stages during the cross‐linking procedure, the reaction was terminated and the species were characterized by means of turbidimetry, asymmetric flow field‐flow fractionation (AFFFF), dynamic light scattering (DLS), and rheo‐small‐angle light scattering (rheo‐SALS) methods. During the cross‐linking of a dilute polymer solution, the competition between intrapolymer and interpolymer is a prominent feature. The DLS results show that at early times in the cross‐linking process, intrachain cross‐linking with contraction of the complexes is promoted by high stirring speeds; at later times the growth of aggregates is inhibited by high stirring speeds. The results from the rheo‐SALS measurements disclosed that at early times during the cross‐linker reaction, the complexes are fragile against shear forces if the reaction mixture had been subjected to low stirring speeds. At a later state of cross‐linking, more cross‐links lead to better stability of the species, even for solutions that have been exposed to low stirring speeds during the cross‐linking process. This study shows that the sizes of the particles can be tuned by exposing the solutions to different stirring speeds during the cross‐linker reaction and to terminate the reaction at desired reaction times. The strategy discussed in this work for the preparation of particles of various sizes is of special interest in connection with enhanced oil recovery applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009