Fringing in tubular permanent-magnet Machines: part II. Cogging force and its minimization

In Part I of the paper, analytical field solutions, which account for the fringing flux associated with the finite length of the ferromagnetic armature core in tubular permanent-magnet machines, are established. In Part II, the technique is applied to both slotless and slotted machines, and the results are verified by finite-element calculations. The analytical field solutions enable the resultant cogging force associated with the finite length of the armature to be determined as a function of the armature displacement, for both radially and Halbach magnetized stators. Thus, they not only provide an effective means for evaluating the influence of leading design parameters on the cogging force waveform, but also facilitate its minimization.     

High-speed modulation of vertical-cavity surface-emitting lasers

The IM (intensity modulation) and FM (frequency modulation) characteristics of vertical-cavity surface-emitting lasers are studied. The laser has high FM efficiency and broad IM bandwidth (near 8 GHz) at a very low bias (4.5 mA). Five Gb/s pseudorandom direct intensity modulation of this laser with open eyes is demonstrated.<>     

Aorto-esophageal fistula secondary to benign Barrett's ulcer: a rare cause of massive gastrointestinal hemorrhage

Aorto-intestinal fistula is a rare cause of massive upper gastrointestinal bleeding. The authors report on an 82-year-old man who had an aorto-esophageal fistula due to a benign Barrett's ulcer. The patient presented with a sentinel hemorrhage followed by fatal exsanguination despite vigorous attempts at resuscitation. Management of the entity requires awareness, appropriate radiologic and endoscopic investigation and early surgery. Even with appropriate management, the mortality remains high.     

Carbon Nanotube Docking Stations: A New Concept in Catalysis

The mobility of surface-bound metallic nanoparticles (NPs) on catalyst supports results in agglomeration leading to a subsequent decrease in effectiveness of the catalytic behavior of the metal NPs over time. We report here the synthesis and characterization of a carbon nanotube (CNT) catalyst support system enhanced with ‘docking stations’ along the exterior which limit the surface mobility of ultra small iron catalyst particles on CNT surfaces during Fisher–Tropsch synthesis.     

High rate low solids methane fermentation of sorghum, corn and cellulose

Sorghum, sorghum/alpha-cellulose mixture, and corn were anaerobically digested at 55°C at effluent solids contents of 8–12% total solids (TS), using trace nutrient supplementation. Volatile solids (VS) loading rates at much higher levels than conventional maxima were maintained without volatile fatty acid (VFA) accumulation. Semi-continuously fed digesters with organic loading rates (OLR) up to 12 gVS kg⁻¹ d⁻¹ produced methane at rates up to 3.3 L kg⁻¹d⁻¹. Continuous feeding of corn at an OLR of 18 gVS kg⁻¹ d⁻¹ resulted in a methane production rate of 5.4 L kg⁻¹d⁻¹. VS removal efficiencies at maximum OLRs were 60% (sorghum) and 67% (corn). At an OLR of 4 gVS kg⁻¹ d⁻¹ sorghum alone as a feedstock led to excess ammonia-N accumulation. Excess ammonia did not accumulate at sorghum loading rates of 8 and 12 gVS kg⁻¹ d⁻¹ nor with a sorghum/alpha-cellulose mix loaded at 8 gVS kg⁻¹ d⁻¹. Instantaneous gas production rates were directly related to feedstock cell soluble content, with peak instantaneous biogas production rates from corn (OLR of 8 gVS kg⁻¹ d⁻¹ approaching 25 L kg⁻¹ d⁻¹ following a three-day feeding.     

A new and rapid method for the electron microscopic examination of fats

A replica technique was developed to study the crystal structure of fats using the electron microscope. The fats were frozen prior to replicating, and it was shown that differing rates of freezing produce structural differences within the fat. The use of Teepol solutions permitted a degree of separation of the solid and liquid phases, and the differences between crystals of the solid phase were shown.     

CD5 B cells and B-cell malignancies

Evidence from both animal, and human, studies suggests that repeated administration of 3,4-methylenedioxymethamphetamine (MDMA: "ecstasy") produces lasting decreases in serotonergic activity. Serotonin is believed to play a modulatory role in a variety of psychological processes, including learning and memory. There are recent reports that polydrug users, who have used ecstasy recreationally, exhibit selective impairments in memory. However, these studies did not compare ecstasy users with polydrug users who had not taken ecstasy, leaving open the possibility that the memory deficits may be associated with a history of use of other illicit drugs. The present study used the Rivermead Behavioural Memory test to investigate immediate and delayed recall in: 25 polydrug-users who had taken more than 20 tablets of ecstasy (MDMA group), 22 participants (polydrug controls) who had never taken ecstasy, but, otherwise has personal characteristics (e.g. age, gender, education, height, weight), and illicit drug use histories, that were generally not significantly different from those of the MDMA group, and 19 participants who had not used illicit drugs but who also had similar personal characteristics (non-drug controls). Participants in the MDMA group recalled significantly fewer ideas (approximately 75% of the number of ideas recalled by participants in either of the other two groups), in both immediate and delayed recall conditions. The two illicit drug-using groups did differ in their estimated IQ scores and their duration of use of LSD, but only the latter proved to be a statistically significant covariate, and the difference in recall performance between the MDMA and polydrug controls groups remained statistically significant when this variable was treated as a covariate. The present findings provide the first evidence that deficits in memory performance in recreational ecstasy users are primarily associated with past exposure to ecstasy, rather than with the other legal and illicit drugs consumed by these individuals, and are consistent with reduced serotonergic modulation of mnemonic function as a result of long-term neurotoxic effects of MDMA in humans.