Design considerations for achieving MLS Category III requirements

The authors examine microwave landing system (MLS) ground equipment design considerations for achieving the requirements for Category III landing operations. Specifically addressed are accuracy, continuity of service, and integrity requirements. Accuracy near the touchdown region is achieved by providing adequate transmitter power, sufficiently small antenna beamwidth, low effective sidelobes (e.g. by introducing a degree of randomness in the dynamic sidelobes and by using a directive element pattern), and, in the azimuth antenna, by shaping the vertical pattern. High continuity of service is achieved by using a high-reliability design, through redundancy of critical elements, by providing an uninterruptible power supply, and by incorporating prealarm warnings. High integrity is achieved by providing an appropriate configuration of redundant monitors, a capability to verify monitor performance periodically, a high-reliability control circuit, and sufficiently independent implementation of transmitter, monitor, and control functions     

Duodenal ulcer patients exhibit a greater skin response to histamine

Smoking is responsible for the highest number of avoidable illnesses and deaths in Canada. Cigarette smoking declined considerably in the adult population between 1965 and 1986, but what has happened over the past decade? Quebec and Canadian public surveys were used to compare types of cigarette use in Quebec and Canada between 1985 and 1994, as well as to compare them by sex. In recent years, the prevalence of smoking has increased among Quebec men only. Differences between Quebec and Canada can be seen in the evolution of the quit rate and the prevalence of smokers. There does not appear to be any indication that differences in cigarette smoking between Quebec and Canada are being eradicated. In Quebec, the evolution of this habit differs according to sex, which indicates that certain factors affect men and women differently. The public survey data make it possible to follow trends in the medium and long term, whereas it is difficult to accurately track the evolution of cigarette smoking from one year to the next, given the small size of the samples in each region and the slow evolution of behaviour.     

Temporomandibular joint derangement after air bag deployment: report of two cases

BACKGROUND: The outcome of 60 renal transplantations in 53 patients with end-stage renal disease (ESRD) because of lupus nephritis was studied retrospectively and compared with 106 controls matched for age, sex, maximum panel-reactive antibody (PRA) level, and date of transplantation. METHODS: The patients received their transplants over a 260-month period (21.5 years) between October 1971 and August 1993. The population was predominantly women (90%), and the mean age at the time of the transplantation was 33.2 years (range: 21-54 years). Fifty-six transplants (93%) were from cadaveric donors, and 4 (7%) were from living-related donors; 46 patients (86%) had primary allografts, and 7 (14%) received a second allograft. The duration of disease before transplantation was 93.6+/-6.2 months, and the duration of dialysis before transplantation was 48+/-6 months. RESULTS: No patient had clinically active systemic lupus erythematosus (SLE) at the time of transplantation. The 1-year graft and patient survival rates were 83% and 98%, and the 5-year graft and patient survival rates were 69% and 96%. Actuarial graft and patient survival rates in SLE patients were not significantly different from those of the matched control group. Chronic rejection was the major risk factor for graft loss. Lupus nephritis recurred in the graft of one patient 3 months after transplantation, and there were extrarenal manifestations of SLE in four others. CONCLUSIONS: The present study confirms that patients with SLE can receive transplants with excellent graft and patient survival rates and a low rate of clinical recurrent lupus nephritis.     

Backbone cyclization of the C-terminal part of substance P. Part 1: The important role of the sulphur in position 11

Novel backbone-to-side chain and backbone-to-backbone cyclic analogues of substance P (SP) were prepared by solid-phase synthesis and screened for biological activity. An analogue containing a thioetherlactam ring between positions 9 and 11 showed an EC50 value of 20 nM toward the neurokinin 1 (NK-1) and was inactive toward the NK-2 and NK-3 receptors. On the other hand, in a multiple backbone cyclic peptide library of similar analogues, in which the sulphur was excluded from the ring, very low activity was detected. The activity was re-evaluated and was found to be even lower (EC50 = 0.11 mM) than the previously published data. These results indicate that the thioether moiety has a crucial role in receptor activation. The results also show tolerance of the NK-1 receptor, but not NK-2 or NK-3, to cyclization of the C-terminal portion of the SP6-11 hexapeptide.     

GMR multilayers and head design for ultrahigh density magneticrecording

This paper describes materials development, device modeling, and initial test results for a novel GMR reproduce head for ultrahigh density recoding (~ 10 Gbit/in²). It consists simply of a 20-bilayer GMR multilayer, self-stabilized by intrinsic antiferromagnetic interlayer coupling, and self-biased by sense current into a bipolar, field-gradient-sensing bias state. Analogous to a dual magnetoresistive (DMR) such a GMR-DMR head is capable of achieving very high linear resolution without shields. Tape-test results using evaporated NiFe/Cu and sputtered NiFeCo/Cu agree reasonably well with theoretical expectations. 1/f noise in these GMR multilayers will also be discussed     

Pinacol rearrangement of jojoba bis-epoxide

Jojoba bis-epoxide (1.6 mmol) undergoes pinacol rearrangement upon reaction with the iodide ion (60 mmol) under slightly acidic conditions, via an iodohydrin as an intermediate, to yield bis-ketojojoba in high yield (92%) after 25 h reflux in THF; no hydroxy derivatives were detected. Since the nucleophilic opening of the epoxide ring is statistically equal on both sides, the rearranged product may have the two carbonyl groups on either side of the original carbon atoms of the two epoxide rings, both completely opened. MS of the rearranged products reveals that the ring opening is approximately equal on both sides of the epoxide ring. Other nucleophiles, such as acetate and amine, open the ring sluggishly without rearrangement.     

Reducing IGBT losses in ZCS series resonant converters

The fundamental operational parameter that controls the losses in series resonant power converters was found to be the reflected DC voltage transfer ratio. Losses which are a function of the average current (such as conduction losses of insulated gate bipolar transistors and diodes) are independent of the switching frequency. Losses which are associated with the RMS current are a function of both the reflected DC voltage ratio and the switching frequency ratio. Universal and normalized graphs, derived in this paper, can be conveniently used to assess the expected RMS and average current conduction losses under any given operational conditions. The residual switching losses in zero-current-switching series resonant power converters operating in continuous current mode can be reduced by simple current snubbers placed in the commutation circuits. The experimental results of this paper confirm the theoretical predictions and demonstrate that the turn-on snubbers can reduce switching losses by about 1.5% at a switching frequency of 65 kHz     

Thermal stability of NiMn spin valve heads

The thermal stability of NiMn-based spin valves was studied both at the coupon level and in full read/write heads. In the coupons, the blocking temperature distribution showed no component below 150°C. As a result, the exchange field at elevated temperature was found to increase with time (because of improved chemical ordering of the NiMn layer), and irreversible losses in the ΔR/R response were observed only above 250°C (because of layer interdiffusion). If a 10% drop in ΔR/R amplitude is used as a criterion to calculate time to failure, the NiMn heads should have several hundred years of lifetime at 150°C operating temperature. Full read/write heads showed linear response with read-back amplitudes above 2 mV/μm at 6-mA operating current. In contrast to most other giant magnetoresistance heads, the output of the head remains the same after heating with a high bias current and degrades only with the shorting of the stripe. All these properties make NiMn superior to other antiferromagnets for spin valve head applications     

Retardation effect of jojoba chain length on the chemical reactivity of the liquid wax

Jojoba wax and its derivatives are slow-reacting compounds. To elucidate the reasons for this phenomenon, we reacted jojoba mono- and bis-epoxide and trans-jojoba bis-epoxide (C₃₈–C₄₄ long-chain esters), as well as side chain esters of three steroid skeleton mono-epoxide derivatives with NaI under acidic conditions to yield the corresponding iodohydrins, which then formed the respective bis-keto (or mono-ketone) derivatives. The kinetics, activation energies, and thermodynamic parameters of activation of nucleophilic epoxide opening and pinacol rearrangement were determined for all these compounds. The reaction rates of the jojoba derivatives were similar to those of two of the epoxides derived from the steroid skeleton compounds, and in the third case the steroid derivative reacted somewhat faster than all the rest. This pattern of rate retardation could stem either from folding of the long jojoba chain, resulting in steric hindrance around the reaction centers, or from repeated unproductive collisions along the long hydrocarbon chain of the jojoba wax (statistical effect). Our results appear to suggest that the multiple unsuccessful collisions were the dominant factor, although steric hindrance cannot be ruled out.