Dynamic viscosities of mixtures of n-butyraldehyde and isobutyraldehyde over wide ranges in the state parameters

Dynamic-viscosity measurements are reported for liquid mixtures in the system formed by n-butyraldehyde and isobutyraldehyde.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 2, pp. 321–322, February, 1985.     

Indoor body-area channel model for narrowband communications

Using wireless sensors placed on a person to continuously monitor health information is a promising new application. At the same time, new low-power wireless standards such as Bluetooth and Zigbee have been proposed for short range, low data-rate communication matching the requirements of these bio-medical applications. However, there are currently few measurements or models describing propagation around the body. To address this problem, electromagnetic waves near the torso are measured and a statistical model is derived for communication in the 915 MHz and 2.45 GHz industrial, scientific and medical bands associated with Zigbee and Bluetooth. Measurement setup and statistical analysis are described.     

Finite element analysis of helicoidal waveguides

The purpose of the paper is to propose an efficient method to compute propagation modes in helicoidal waveguides. An helicoidal system of co-ordinates is introduced to define the structure and to set up the problem. These co-ordinates, albeit non-orthogonal, preserve the translational invariance in a way that allows a two-dimensional finite element model similar to that of classical straight waveguides     

Pesticide monitoring programme of the Ministry of Health of Brazil

The structure of the recently introduced Brazilian government programme for monitoring pesticide residues in six major agricultural products is described. Residues found from the analysis of samples of tomatoes and strawberries are discussed in detail. The much greater frequency of detection of pesticide residues, many of which are not approved for use in Brazil, in produce being sold on the domestic market, as opposed to that produced for export, is of major concern. It is perceived that this new monitoring programme will become permanent and be used to underpin enforcement actions that will need to be taken to reduce the numbers of incidents of illegal residues occurring, particularly in fresh fruits and vegetables.     

Oscillations of the Electric-Dipole Echo in Glasses in a Magnetic Field

Using a simple diagram technique we derive the electric-dipole echo amplitude from two-level systems with a quadrupole nuclear moment in glasses in an external magnetic field. We show, that due to the quadrupole moment interaction of a tunneling particle with a gradient of an internal electric field, the echo amplitude experiences oscillations in rather weak magnetic fields. With an increase of the magnetic field, when the Zeeman energy becomes larger than the quadrupole energy splitting, the average echo amplitude increases and saturates (for high magnetic fields) at some level which is above the average level of echo oscillations for small magnetic fields. PACS numbers: 77.22.Ch, 61.43.Fs, 76.60.Gv, 76.60.Lz     

Temperature and Frequency Dependence of the Ultrasound Velocity in Neutron-Irradiated Quartz Crystals Above 5 K

Neutron-irradiated quartz crystal is one of the interesting materials for the study of the glassy dynamics. The temperature and frequency dependence of the sound velocity in amorphous materials at temperatures above the low-temperature maximum is not well understood. In this paper we present the results of our measurements of the variation of the ultrasound velocity (270 – 650 MHz) in neutron-irradiated quartz crystals with different irradiation doses in temperature range 5 - 35 K. We have found that the temperature dependence of the ultrasound velocity is linear in the sample with a dose < 10 ¹⁹ n/cm² and is sublinear in samples with a dose > 10 ¹⁹ n/cm² . We discuss our results in the framework of the different theoretical approaches. PACS numbers: 61.43. j, 62.65.+k, 63.     

Influence of the shape of fiber cross section on fabric surface characteristics

Fiber cross sections for use in textiles and composites are becoming more and more complex. Shape impacts fiber or filaments properties and therefore the yarn and fabric characteristics. This paper presents the influence of the fiber cross section on the fabric surface characteristics. The material used was polyester staple fibers, of four different shapes: round, scalloped oval, cruciform and hexachannel. All fibers had the same cut length with different fineness. Yarns obtained from these fibers had nominally the same yarn count, torsion value and structure. Plain jersey fabrics were knitted from each of the yarns under identical conditions and then relaxed prior to testing. Friction behavior was evaluated and a roughness-friction criterion developed. An indirect measurement of the real area of contact was obtained in order to provide roughness and friction properties. The influence of fiber cross section on yarn bending rigidity and on the state of the knitted fabric surface was characterized.