The concept of an endurance limit for adhesive joints

The effect of cyclic stressing on the strength of single lap adhesive joints has been studied and a considerable reduction in strength observed when the maximum stress exceeds about 40% of the ultimate tensile strength, but whether or not a true endurance limit exists is not proven. Fallacies are shown in some of the techniques which have been proposed for studying the fatigue behaviour of adhesive joints.     

Construction experiences with SSC collider dipole magnets atFermilab

Full length and short model SSC (Superconducting Super Collider) 50 mm bore dipoles are being built and tested at Fermilab. The mechanical design of these magnets has been determined from experience with the construction of previous superconducting magnets. Construction experience includes coil fabrication, ground insulation, instrumentation, collaring, and yoke assembly. Fabrication techniques are explained, and construction problems and their solutions are reviewed. The relationship of short to long model construction is discussed     

Compact optical millimetre-wave source using a dual-modesemiconductor laser

The authors demonstrate the optical generation of extremely narrow linewidth millimetre-wave signals between 40 and 60 GHz using a single-chip semiconductor laser. A dual-mode long-cavity multisection DFB semiconductor laser is driven at a subharmonic of the free-running-mode beat signal frequency to produce phase-locked millimetre waves with a 3 dB linewidth of less than 10 Hz and a 3 dB locking range of ~500 MHz     

Modelling powder mixing in mass flow discharge: A kinematic approach

The dynamics of a powder flowing in a mass flow regime through a storage bin with a conical hopper, is a well studied problem. However, many challenges remain, including quantification of the mixing that occurs during discharge through the hopper. We have formulated a model based on the conservation of volume of the powder and a semi-empirical expression for velocity profile, (see [1], [2]), and used this to estimate mixing parameters. We have specifically considered the case of an inflow which is disposed in homogeneous horizontal layers as it enters the storage bin. When the powder, in successive layers, enters the hopper, it accelerates and its velocity along the longitudinal axis of the hopper is greater than at the walls. Portions of layers high in the hopper may overtake layers closer to the exit resulting in mixing of the layers. Using this model we are able to quantify the percentage of each layer in a given output volume and present results for typical hopper geometries.     

Inverse method for the detection of a foreign object using microwave measurements

A two-dimensional inverse computing method to detect an internal object using microwave measurements is presented. The modelling of the application system has been directed towards the eventual in vivo detection of breast tumours, in particular. This procedure will enable the non-destructive determination of the internal object size and location. The model procedure has been tested by using complex reflection coefficients measured in a microwave experimental application system. Measured data agree with the theoretical calculations.     

Maturation of rat dendritic cells during intrahepatic translocation evaluated using monoclonal antibodies and electron microscopy

Specific populations of hepatic sinusoidal cells were stained with monoclonal antibodies that recognize monocytes/macrophages (ED1), tissue macrophages (Kupffer cells) (ED2), MHC class II (Ia) antigen (MRC OX6), and dendritic cells/gamma,delta T-cells (MRC OX62) and analyzed by light and electron microscopy. The majority of ED1(+) and/or ED2(+) cells were localized to the hepatic parenchyma, whereas OX6(+) and/or OX62(+) cells were more densely distributed within Glisson's sheath than in the hepatic parenchyma. Double-immunoperoxidase staining of normal liver for ED1, ED2, and OX6 identified dendritic cells (DC) of two different phenotypes, ED1(+)ED2(-)OX6(+) and ED1(-)ED2(-)OX6(+). DC can be classified into three different types based on ultrastructural characteristics. The first type (type I) is characterized by one or more long cytoplasmic processes and a well-developed lysosomal system. The second type (type II) has an inconspicuous lysosomal system, abundant hyaloplasm, and characteristic short cytoplasmic processes. The third type (type I-II) has cytologic features intermediate between those of type I and type II DC. At the electron-microscopic level, these three cell types are found in the sinusoidal lumen, whereas the majority of type II DC are located in the space of Disse and Glisson's sheath. Furthermore, some OX6-labeled elongated DC appeared to traverse the lumen of sinusoids through endothelial pores to enter the space of Disse. One hour after intravenous injection of latex particles (0.81 micrometer in diameter), numerous latex-laden dendritic cells (ED1(+)OX6(+), type I and type I-II) were detected in the lumen of hepatic sinusoids, but not in the space of Disse or Glisson's sheath. These findings suggest that normal rat liver contains resident dendritic cells which downregulate phagocytic activity and mature into potent accessory cells during migration from the portal vein toward the central vein. These DC then traverse the sinusoidal lumen to the hepatic lymph system via the space of Disse.     

Transient complete left bundle branch block during epidural anesthesia with mepivacaine

A 65-year-old woman with ovarian tumor was scheduled for abdominal total hysterectomy and bilateral adnexectomy under epidural anesthesia. Preoperative examinations revealed no abnormalities including ECG. Twenty minites after the epidural injection of mepivacaine, widened QRS complexes, which were diagnosed as complete left bundle branch block (CLBBB) later, appeared on ECG. At that time, heart rate (HR) was 150.min-1. CLBBB disappeared when HR decreased to 110.min-1 following the administration of pindolol and verapamil. The operation was postponed. Exercise-treated ECG showed neither CLBBB nor ischemic change even when HR increased to 160.min-1. Two weeks later the operation was attempted again. CLBBB appeared again twenty minites after the epidural injection of mepivacaine. The CLBBB disappeared 5 minites after the induction of general anesthesia when HR decreased to 100.min-1. The operation was performed uneventfully. The effective refractory period (ERP) is shortened with the increase in HR, but the shortning of ERP varies in different part of the cardiac conduction system. In tachycardia, ERP of left bundle branch is longer than that of right one. Because the cardiac conduction system is depressed by local anesthetics, it is speculated that ERP of left bundle branch is elongated further by mepivacaine and CLBBB appeared in this case.     

Aerosol and Precipitation Chemistry at a Remote Himalayan Site in Nepal

As a part of a year long aerosol measurement program in the Nepal Himalayas, a series of 12 h samples of aerosol and event-based samples of precipitation were collected in postmonsoon, 1996; premonsoon, 1997; and monsoon, 1997. Results show that diurnal variations in the regional valley wind system are responsible for variations in the major ion (Na + , NH 4 + , K + , Mg 2+ , Ca 2+ , Cl - , NO 3 - , and SO 4 -2 ) concentrations in the aerosol. On time scales greater than a day, changes in atmospheric circulation and associated changes in the precipitation regime have an important effect on aerosol ion concentrations. Periods of high major ion concentration in the aerosol generally coincide with similar periods in precipitation chemistry, although a linear relationship between concentrations in these 2 media is not robust due to limited data. High scavenging ratio values are found for all species except SO 4 2- . Nitrate, Cl - , and NH 4 + are enriched in the precipitation compared to the aerosol, implying the presence of gaseous acidic species (HNO 3 and HCl) and gaseous NH 3 in the air. Ammonium was also enriched with respect to SO 4 2- in aerosol during a dry episode in the monsoon season. This may represent relatively local sources of NH 3 (from neighboring villages) and was not scavenged due to the lack of precipitation. Empirical orthogonal function (EOF) analysis clearly shows the presence of 2 dominant pollutant transport mechanisms for the premonsoon and monsoon seasons (i.e., valley wind system and monsoon circulation). Although physically different, these 2 transport mechanisms follow similar transport pathways and transport aerosol into the Himalayas from similar source regions. Further, EOF analysis suggests a southerly maritime signal in the aerosol during monsoon and a more distant westerly maritime signal during premonsoon. Our results support the potential for using glaciochemical records from the Himalayas to investigate variations in the strength of past monsoon circulation and westerly disturbances.