Wavelength division (de)multiplexing based on dispersive self-imaging.

We proposed and experimentally demonstrated wavelength division (de)multiplexers (WDMs) utilizing the wavelength dispersive nature of self-imaging multimode interferometers. Proof-of-principle devices fabricated on the silicon-on-insulator platform operated as 4-channel WDMs with a free spectral range of >90 nm, an averaging cross talk of <-20 dB for a 1 nm band, and an insertion loss of <2.0 dB. The potential for higher channel counts and smaller channel wavelength spacing was also predicted. This type of WDM is easy to design and fabricate. The underlying concept is applicable to all planar waveguide platforms.

Quasi-Gaussian output from dual case I waveguide resonators with mirrors of step-index reflectivity profiles.

There are three recognized low-loss configurations for waveguide laser resonators in which the waveguide is either closed at each end by a plane mirror (dual case I design) or one of the plane mirrors is replaced by a curved mirror at some distance from the guide exit. Some time ago, a variant of the latter design was proposed by exploiting the self-imaging properties of multimode waveguides. The resonator was predicted to produce a TEM(00)-like output with very low round-trip loss and excellent mode discrimination even though the curved mirror was placed much nearer to the guide exit (making the resonator more compact) than was conventional for achieving those results. In the present work, we show that the desirable features of the above design can be achieved even in a dual case I configuration by using end mirrors with suitable reflectivity profiles. Since there is no free space region between the waveguide and the mirrors, the resonator will have the additional advantages of being compact and portable. Furthermore, the absence of curved mirrors will also facilitate its realization in semiconductor integrated optics technology.

Theory of 1- N-way phase-locked resonators.

A 1-N-way resonator based on beam splitting and beam combining effects in rectangular cross-sectional multimode waveguides was recently proposed. Such a resonator structure offers a valuable way in which N low-power laser elements may be combined in a coherent fashion. We examine the case of passive 1-N-way resonators. We develop a theory of these 1-N-way structures to show that there is only one possible mode of these resonators. The theory is used to give a scaling law for the design tolerances of the beam splitting and beam combining region of the resonator.

Theory of 1-N-way phase-locked resonators with perturbations in the array elements.

The recently proposed 1-N-way resonator based on beam splitting and beam combining effects in rectangular cross-sectional multimode waveguides offers a valuable way in which N low-power laser elements can be combined in a coherent fashion. We develop a theory of such resonators in the presence of perturbations in the N-element array. We demonstrate that despite the presence of perturbations there is only one possible mode of the resonator. The theory is used to provide an understanding of the effects of a number of possible perturbations that could arise as a result of manufacturing processes and operational effects. The results give scaling laws for the design tolerances on array element mirror tilt, array element optical path length control, and the effects of array element malfunction and their need for gain balance.

Diagnostic accuracy of 99mTc-sestamibi breast imaging: multicenter trial results.

UNLABELLED: Although mammography is well established as a first-line tool for breast cancer screening and detection, efforts to develop complementary procedures continue. Observation of 99mTc-sestamibi tumor uptake provided the impetus for its evaluation as an adjunctive technique. This trial's objectives were to determine in a multicenter trial the diagnostic accuracy of 99mTc-sestamibi in women with suspected breast cancer and to investigate factors influencing diagnostic accuracy. METHODS: Our multicenter trial enrolled 673 women (387 with nonpalpable abnormalities; 286 with palpable abnormalities) scheduled for excisional biopsy or mastectomy. Blinded and unblinded interpretations of scintigraphic images were compared with core laboratory established histopathologic diagnoses to define the diagnostic accuracy of 99mTc-sestamibi breast imaging. RESULTS: Blinded readers' diagnostic accuracy was 78%-81%. Inter-reader agreement was excellent, ranging from 95% to 100% (kappa = 0.82-0.99). Overall institutional sensitivity and specificity for 99mTc-sestamibi breast imaging were 75.4% and 82.7%, respectively. In this population with a 40.1% disease prevalence, the positive predictive value was 74.5% and the negative predictive value was 83.4%. The negative predictive value was 94% in patients with a 40% or lower mammographic likelihood of breast cancer. Sensitivity was higher for palpable abnormalities; specificity was higher for nonpalpable abnormalities. Sensitivity was decreased for tumors <1 cm in largest dimension but appeared not to be affected by patient's age. CONCLUSION: As an adjunct to current procedures, 99mTc-sestamibi breast imaging may contribute to patient management decisions in selected populations, including women with dense breasts, mammographically indeterminate lesions >1 cm, and palpable abnormalities.

Comparison of Talbot and 1-to- N-way phase-locked array resonators.

Phased-array resonators provide an important basis for achieving high output powers from arrays of low-power elements. We have recently proposed a novel form of 1-to-N-way phased-array resonator based on the beam splitting and regeneration characteristics of rectangular sectioned multimode waveguides. We compare its performance with that of the widely used, yet problematic, Talbot resonator. Our design is found to have significant advantages over the Talbot resonator in terms of improved modal stability, unique photon-mixing characteristics, and near- and far-field outputs of quasi-Gaussian form.

Weakness in mouse masticatory muscles by repetitive contractions with forced lengthening.

The etiology of myofascial tenderness and pain of masticatory muscles in humans is difficult to understand. Parafunctional oral habits such as tooth grinding or vigorous chewing are thought to be factors. The objective of this study was to determine if masticatory muscles are susceptible to weakness and injury induced by repetitive, dynamic, forced-lengthening contractions. Results would support the hypothesis that contraction-induced injuries could occur in hyperactive masticatory muscles of humans in response to parafunctional oral habits. Mice were anesthetized and randomly assigned to three groups: non-treated controls, treated by repetitive passive jaw opening, or treated by repetitive isometric tetanic contractions with lengthening by jaw opening. In each treatment group, masticatory muscle injury was evaluated by contractile tension, plasma creatine kinase, and muscle glycogen. Contractile tension was determined at different stimulation frequencies and was significantly decreased 5 min, 4 h, and 72 h after repetitive contraction/lengthening. Plasma creatine kinase was significantly elevated at 4 but not at 72 h post-treatment in mice subjected to repetitive contraction/lengthening. Masticatory muscle glycogen was not significantly different in any groups at 4 or 72 h post-treatment. These results indicate that contraction injuries can be induced in masticatory muscle of mice by forced lengthening contractions which simulate eccentric contractions.

Effects of curved mirrors in waveguide resonators.

Waveguide gas lasers (CO(2) ones especially) continue to be widely used. We have previously studied simple resonator designs with plane mirrors close to each end of the waveguide. Here we examine theoretical predictions concerning hybrid waveguide/free-space resonators with square-bore guides and curved mirrors. We show how resonator mode losses vary as functions of guide length and width, guide-to-mirror distance, mirror radius of curvature, and mirror tilt. We have tested a 7-W cw rf-excited CO(2) laser with unusually good near-TEM(00) transverse-mode quality; it is one of many promising resonator geometries not covered by earlier published research. The common case 3 reflector, sometimes viewed as guaranteeing near-TEM(00) mode performance, is shown to be alarmingly sensitive to small misalignments for certain guide geometries.

Effect of the acyl-CoA:cholesterol acyltransferase inhibitor DuP 128 on cholesterol absorption and serum cholesterol in humans.

Intestinal cholesterol esterification by the enzyme acyl-CoA:cholesterol acyltransferase (ACAT) is a presumed prerequisite for cholesterol absorption. We evaluated the effect of a potent, poorly absorbed ACAT inhibitor (DuP 128: N'-(2,4-difluorophenyl)-N-[5-(4,5-diphenyl-1H-imidazol-2-ylthio)pe ntyl]- N-heptylurea) on cholesterol absorption in a randomized trial. Thirty subjects received DuP 128 for 7 weeks, 10 each at 900 mg per day, 1800 mg per day, and 3600 mg per day; six subjects received placebo; and nine subjects received 1 gm neomycin twice a day. Cholesterol absorption determinations used a continuous dual isotope 14C-cholesterol and 3H-beta sitosterol method. DuP 128 (pooled doses) induced at 14.4% +/- 11.4% reduction in cholesterol absorption (p < 0.05 versus placebo): 17.6% +/- 8.4% at 900 mg, 9.1% +/- 11.4% at 1800 mg, and 17.1% +/- 12.9% at 3600 mg. Neomycin induced a 26.4% +/- 10.7% reduction (p < 0.01). After 6 weeks, neomycin reduced serum total and low-density lipoprotein cholesterol by 22.4% +/- 9.2% and 24.0% +/- 11.6%, respectively (p < 0.01 versus placebo). DuP 128 induced reductions of 3.9% +/- 11% (difference not significant) and 4.95% +/- 14.3% (p = 0.05). ACAT inhibitors limit cholesterol absorption in humans; however, the magnitude of the effect, as exemplified by DuP 128, is small.

Quality of general practitioner referrals to outpatient departments: assessment by specialists and a general practitioner.

Thirty eight specialists in one district health authority were asked to take part in a questionnaire survey to assess the appropriateness of referral and the quality of the referral letter for 20 consecutive new patients each. A total of 705 new patient referrals to 13 specialties were included in the study. Twelve of the 38 specialists were randomly selected and their 234 new patient referral letters were independently assessed by a general practitioner for the appropriateness of the referral decision. The study revealed errors and omissions in between 5% and 28% of referral letters according to the category of information. Thirteen per cent of the new patient referrals were assessed by specialists to be inappropriate and 4% of patients had been referred to an inappropriate specialty. Significantly more of the referrals to medical specialties were inappropriate (20%) than to surgical specialties (9%) (P < 0.01). There were more than three times the number of errors and omissions in the referral letters of referrals assessed as inappropriate than in the referral letters of referrals assessed as appropriate (P < 0.01). The referral letters of referrals assessed as inappropriate were more than nine times as likely to omit the reasons for or objectives of the referral compared with letters for those referrals assessed as appropriate (P < 0.01). There was a good overall agreement between the specialists and general practitioner in their assessment of the appropriateness of the clinical referrals (kappa = 0.614, P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of field regeneration on the TEM(00) transmission characteristics of a circular-section waveguide.

The transmission of a 10.6-microm TEM(00) beam through a hollow circular-cross-section waveguide is modeled in terms of the excitation and propagation of the two lowest-order circularly symmetric EH(1n) modes. At points along the guide axis where the are in phase the TEM(00) input field is shown to be regenerated, but midway between these points, transverse-mode profiles that have a doughnut shape are produced. It is proposed that these dramatic field variations should cause variations in the effective attenuation coefficient along the length of the waveguide. The first direct experimental measurements to our knowledge of the guide-length-dependent attenuation characteristics of a 1.0-mm-bore hollow silica waveguide support this hypothesis by revealing a strong periodic component in addition to the anticipated exponential decay.

Effects of curved mirror misalignment in a folded waveguide.

We have previously discussed the transmission and coupling losses of a Gaussian beam in a folded waveguide structure made of two hollow square waveguides placed symmetrically above a spherical mirror with a nonzero on-axis angle between. Here we investigate the additional loss due to the misalignment of the mirror (axial displacement and/or angular tilt). The theoretical results are in good agreement with experiment and provide alignment tolerances for folded waveguide design.

Transmission and coupling losses in a folded waveguide.

This paper discusses the transmission and coupling losses of hollow dielectric waveguide modes in a folded waveguide structure. The folded structure consists of two square-bore waveguides placed symmetrically above a spherical mirror with a nonzero on-axis angle between them. The presence of the fold renders the structure astigmatic. However, for moderate fold angles (10-20 degrees ), the effect of the fold is negligible.

The symptomatic and objective effects of nifedipine in combination with beta-blocker therapy in severe angina pectoris.

Nine patients with severe coronary artery disease and disabling angina receiving either regular metoprolol or oxprenolol, together with glyceryl trinitrate tablets as required for chest pain, were studied. Nifedipine 10 mg three times per day was compared to placebo in a double blind randomized control trial, using patient diary cards and exercise tests. The number of recorded episodes of angina during the placebo period of 15.0 +/- 2.1 (mean +/- s.e.m.) per patient per week was significantly reduced to 11.2 +/- 2.5 during the nifedipine period (P less than 0.05). Similarly, the recorded number of glyceryl trinitrate tablets consumed during the placebo period of 12.6 +/- 2.1 was significantly reduced to 9.1 +/- 2.0 tablets per patient per week during the nifedipine period (P less than 0.05). There was a statistically significant increase in both the duration of exercise to onset of chest pain (from 241 +/- 16.3 seconds on placebo to 306 +/- 38.4 seconds on nifedipine (P less than 0.05)) and the total work performed to the onset of chest pain during the nifedipine period compared to the control and placebo periods (P less than 0.05). There was a significant increase (P less than 0.05) in exercise time before the onset of appreciable ST depression (greater than 1 mm) on exercise testing during the nifedipine period (66.2 +/- 4.2 sec) compared to the control period (51.2 +/- 3.0 sec) and placebo periods (58.7 +/- 3.5 sec). Although nifedipine was generally well tolerated, one patient experienced a severe episode of angina whilst taking the drug, which required admission to hospital.

Alcohol-induced Cushingoid syndrome.

Although it has been known for some time that alcohol affects the hypothalamic-pituitary-adrenal axis, the clinical significance of this disturbance has only recently become recognised. Over the last 5 years, 27 cases of an apparent Cushing's syndrome have been documented, usually resolving within weeks of alcohol withdrawal. Differentiation from the true Cushing's syndrome can be difficult before resolution, which may be prolonged for several months, but an insulin stress test can be useful in their distinction. The syndrome is invariably pituitary dependent but may not be a specific drug effect of ethanol but rather a consequence of the chronic stress of alcoholism.

Variation in response to cytotoxicity of cigarette smoke.

The cytotoxic effect of cigarette smoke condensate on human polymorphs was investigated in vitro by the method of vital dye exclusion. Exposure to 1/800 of the smoke from one high-tar cigarette killed a detectable proportion of a population of 10(6) cells. The response among the cells from 40 healthy people varied widely, the percentage of dead cells ranging from 3% to 66% and from 17% to 87% at exposure levels of 125 micrograms and 250 micrograms cigarette smoke condensate respectively. Differences in individuals' responses were reproducible and unrelated to age or sex or smoking habit. The cells from 10 patients with irreversible obstructive airways disease and probable emphysema were significantly more sensitive than those from 10 patients with no respiratory disability matched for age and smoking habits. Genetically influenced variation in cellular response to cytotoxicity may be an important determinant of the risk of developing emphysema among smokers.