Calculation of a Hyperbolic Corrugated Horn Converting the TEM<Subscript>00</Subscript> Mode to the HE<Subscript>11</Subscript> Mode

Corrugated waveguide transmission lines are in use to transmit high power mm-wave radiation from gyrotrons to the plasma for electron cyclotron plasma heating in tokamaks such as ITER. The coupling efficiency of the gyrotron output radiation formed as a quasi-Gaussian beam to the waveguide mode is a critical issue. A hyperbolic corrugated horn serves as a converter of the TEM₀₀ Gaussian mode to the HE₁₁ mode of a corrugated waveguide. We report the design of a hyperbolic horn for application in the ITER transmission line at 170 GHz. The theoretical conversion efficiency of the horn is higher than 0.995.     

Experimental Determination of Correlations Between Spontaneously Formed Vortices in a Superconductor

We have imaged spontaneously created arrays of vortices (magnetic flux quanta), generated in a superconducting film quenched through its transition temperature at rates around 10⁹ K/s. From these images, we calculated the positional correlation functions for two vortices and for 3 vortices. We compared our results with simulations of the time dependent Ginzburg Landau equation in 2D. The results are consistent with the Kibble-Zurek scenario of spontaneous vortex creation. Effects due to fluctuations of the gauge field on the correlation functions are below our experimental resolution.     

Bottom-up photonic crystal lasers

The directed growth of III-V nanopillars is used to demonstrate bottom-up photonic crystal lasers. Simultaneous formation of both the photonic band gap and active gain region is achieved via catalyst-free selective-area metal-organic chemical vapor deposition on masked GaAs substrates. The nanopillars implement a GaAs/InGaAs/GaAs axial double heterostructure for accurate, arbitrary placement of gain within the cavity and lateral InGaP shells to reduce surface recombination. The lasers operate single-mode at room temperature with low threshold peak power density of ～625 W/cm2. Cavity resonance and lasing wavelength is lithographically defined by controlling pillar pitch and diameter to vary from 960 to 989 nm. We envision this bottom-up approach to pillar-based devices as a new platform for photonic systems integration.     

Self-assembling RNA nanorings based on RNAI/II inverse kissing complexes

RNA is an attractive biopolymer for nanodesign of self-assembling particles for nanobiotechnology and synthetic biology. Here, we experimentally characterize by biochemical and biophysical methods the formation of thermostable and ribonuclease resistant RNA nanorings previously proposed by computational design. High yields of fully programmable nanorings were produced based on several RNAI/IIi kissing complex variants selected for their ability to promote polygon self-assembly. This self-assembly strategy relying on the particular geometry of bended kissing complexes has potential for developing short interfering RNA delivery agents.     

Leaching assessments of hazardous materials in cellular telephones

Protocols for assessing the risks of discarded electronic products (e-waste) vary across jurisdictions, complicating the tasks of manufacturers and regulators. We compared the Federal Toxicity Characteristic Leaching Procedure (TCLP), California's Waste Extraction Test (WET), and the Total Threshold Limit Concentration (TTLC) on 34 phones to evaluate the consistency of hazardous waste classification. Our sample exceeded TCLP criteria only for lead (average 87.4 mg L(-1); range = 38.2-147.0 mg L(-1); regulatory limit = 5.0 mg L(-1), but failed TTLC for five metals: copper (average 203 g kg(-1); range = 186-224 g kg(-1); limit = 2.50 g kg(-1), nickel (9.25 g kg(-1); range = 6.34-11.20 g kg(-1); limit = 2.00 g kg(-1)), lead (10.14 g kg(-1); range = 8.2211.60 g kg(-1); limit = 1.00 g kg-1), antimony (1.02 g kg(-1); range = 0.86-1.29 g kg(-1); limit = 0.50 g kg(-1)), and zinc (11.01 g kg(-1); range = 8.82-12.80 g kg(-1); limit = 5.00 g kg(-1). Thresholds were not exceeded for WET. We detected several organic compounds, but at concentrations below standards. Brominated flame retardants were absent. These results improve existing environmental databases for e-waste and highlight the need to review regulatory testing for hazardous waste.     

Shape from shading using the facet model

In this paper, the facet model is used in the recovery of surface orientation from single and multiple images. Two methods for determining surface orientation from image shading are presented. The first method works in the single image domain and is formulated as a non-linear optimization problem. Since three-dimensional scene information available in a single image is usually ambiguous, the optimization procedure can result in multiple solutions. The possibility of adding boundary constraints to the optimization process is also investigated. In the second method, additional images are obtained from the same viewing position, but with changing illumination direction. With these additional images, local surface orientation is determined uniquely by a linear optimization procedure. Experimental results of the shape-from-shading methods are also described.     

The relationship between size and maturation in vitro in the unstimulated human oocyte

OBJECTIVE: To determine if the size of human oocytes at collection from unstimulated ovaries is related to their ability to resume meiosis and undergo maturation in vitro. DESIGN: A comparative study of oocyte diameter at collection. SETTING: Department of Obstetrics and Gynecology, Northwestern University Medical School. PATIENTS: Women age 25 to 39 years of age undergoing gynecological procedures yielding oophorectomy specimens. INTERVENTION: Oocytes obtained from ovarian tissue were cultured in Ham's F-10 and fetal bovine serum for 72 hours and observed two times per day. MAIN OUTCOME MEASURE: The oocytes ability to resume meiosis and complete maturation based on their diameter at collection. RESULTS: Chi-squared analysis revealed a significant difference in oocytes measuring 86 to 105 microns versus those measuring 106 to 125 microns. CONCLUSION: The unstimulated human oocyte appears to have a size-dependent ability to resume meiosis and complete maturation.     

Endogenous estrogens and risk of breast cancer by estrogen receptor status: a prospective study in postmenopausal women

A positive association between postmenopausal serum levels of total estradiol, percentage of free estradiol, and percentage of estradiol not bound to sex hormone-binding globulin (SHBG) and breast cancer risk was recently reported by the New York University Women's Health Study (P. Toniolo et al., J. Natl. Cancer Inst., 87: 190-197, 1995). Data from this prospective study are used to assess whether the observed associations differ according to estrogen receptor (ER) status of the tumor. Between 1985 and 1991, 7063 postmenopausal women donated blood and completed questionnaires at a large breast cancer screening clinic in New York City. Before 1991, 130 cases of first primary breast cancer were identified by active follow-up of the cohort. For each case, two controls were selected, matching the case on age at first blood donation and length of storage of specimens. Biochemical analyses were performed on sera that had been stored at -80 degrees since sampling. ER information was abstracted from pathology reports. Separate statistical analyses were conducted of ER-positive, ER-negative, and ER-unknown groups (53, 23, and 54 matched sets, respectively). In each of the 3 groups, the mean estradiol and the mean percentage of free estradiol were greater (21-28% and 6-7%, respectively) in cases than in controls. Conversely, the mean percentage of estradiol bound to SHBG was 9-12% lower in cases than in controls. The logistic regression coefficients measuring the strength of the association between estradiol and its free and SHBG-bound fractions and breast cancer risk were similar in the ER-positive, ER-negative, and ER-unknown groups. These data suggest that in postmenopausal women, the association of endogenous estrogens with breast cancer risk is independent of the ER status of the tumor. This result is more compatible with the hypothesis of a progression from ER-positive to ER negative tumors than with the hypothesis that ER status identifies two distinct types of breast cancer.