A sleeve and bulk method for fabrication of photonic structures with features on multiple length scales.

Traditional photonic structures such as photonic crystals utilize (a) large arrays of small features with the same size and pitch and (b) a small number of larger features such as diffraction outcouplers. In conventional nanofabrication, separate lithography and etch steps are used for small and large features in order to employ process parameters that lead to optimal pattern transfer and side-wall profiles for each feature-size category, thereby overcoming challenges associated with reactive ion etching lag. This approach cannot be scaled to more complex photonic structures such as those emerging from inverse design protocols. Those structures include features with a large range of sizes such that no distinction between small and large can be made. We develop a sleeve and bulk etch protocol that can be employed to simultaneously pattern features over a wide range of sizes while preserving the desired pattern transfer fidelity and sidewall profiles. This approach reduces the time required to develop a robust process flow, simplifies the fabrication of devices with wider ranges of feature sizes, and enables the fabrication of devices with increasingly complex structure.

Quantitative spectroscopic imaging with in situ measurements of tissue water T1, T2, and density.

The use of tissue water as a concentration standard in proton magnetic resonance spectroscopy ((1)H-MRS) of the brain requires that the water proton signal be adjusted for relaxation and partial volume effects. While single voxel (1)H-MRS studies have often included measurements of water proton T(1), T(2), and density based on additional (1)H-MRS acquisitions (e.g., at multiple echo or repetition times), this approach is not practical for (1)H-MRS imaging ((1)H-MRSI). In this report we demonstrate a method for using in situ measurements of water T(1), T(2), and density to calculate metabolite concentrations from (1)H-MRSI data. The relaxation and density data are coregistered with the (1)H-MRSI data and provide detailed information on the water signal appropriate to the individual subject and tissue region. We present data from both healthy subjects and a subject with brain lesions, underscoring the importance of water parameter measurements on a subject-by-subject and voxel-by-voxel basis.

Antibonding ground states in InAs quantum-dot molecules.

Coherent tunneling between two InAs quantum dots forms delocalized molecular states. Using magnetophotoluminescence spectroscopy we show that when holes tunnel through a thin barrier, the lowest energy molecular state has bonding orbital character. However, as the thickness of the barrier increases, the molecular ground state changes character from a bonding orbital to an antibonding orbital, confirming recent theoretical predictions. We explain how the spin-orbit interaction causes this counterintuitive reversal by using a four-band k.p model and atomistic calculations that account for strain.

Photoluminescence spectroscopy of the molecular biexciton in vertically stacked InAs-GaAs quantum dot pairs.

We present photoluminescence studies of the molecular neutral biexciton-exciton spectra of individual vertically stacked InAs/GaAs quantum dot pairs. We tune either the hole or the electron levels of the two dots into tunneling resonances. The spectra are described well within a few-level, few-particle molecular model. Their properties can be modified broadly by an electric field and by structural design, which makes them highly attractive for controlling nonlinear optical properties.

Electrically tunable g factors in quantum dot molecular spin states.

We present a magnetophotoluminescence study of individual vertically stacked InAs/GaAs quantum dot pairs separated by thin tunnel barriers. As an applied electric field tunes the relative energies of the two dots, we observe a strong resonant increase or decrease in the g factors of different spin states that have molecular wave functions distributed over both quantum dots. We propose a phenomenological model for the change in g factor based on resonant changes in the amplitude of the wave function in the barrier due to the formation of bonding and antibonding orbitals.

Optical signatures of coupled quantum dots.

An asymmetric pair of coupled InAs quantum dots is tuned into resonance by applying an electric field so that a single hole forms a coherent molecular wave function. The optical spectrum shows a rich pattern of level anticrossings and crossings that can be understood as a superposition of charge and spin configurations of the two dots. Coulomb interactions shift the molecular resonance of the optically excited state (charged exciton) with respect to the ground state (single charge), enabling light-induced coupling of the quantum dots. This result demonstrates the possibility of optically coupling quantum dots for application in quantum information processing.

Polarized fine structure in the photoluminescence excitation spectrum of a negatively charged quantum dot.

We report polarized photoluminescence excitation spectroscopy of the negative trion in single charge-tunable quantum dots. The spectrum exhibits a p-shell resonance with polarized fine structure arising from the direct excitation of the electron spin triplet states. The energy splitting arises from the axially symmetric electron-hole exchange interaction. The magnitude and sign of the polarization are understood from the spin character of the triplet states and a small amount of quantum dot asymmetry, which mixes the wave functions through asymmetric e-e and e-h exchange interactions.

Maintaining health insurance during a recession: likely COBRA eligibility.

Findings from The Commonwealth Fund 2001 Health Insurance Survey.

IL-5 up-regulates cysteinyl leukotriene 1 receptor expression in HL-60 cells differentiated into eosinophils.

The cysteinyl leukotrienes, leukotriene (LT) C(4), LTD(4), and LTE(4), are lipid mediators that have been implicated in the pathogenesis of several inflammatory processes, including asthma. The human LTD(4) receptor, CysLT(1)R, was recently cloned and characterized. We had previously shown that HL-60 cells differentiated toward the eosinophilic lineage (HL-60/eos) developed specific functional LTD(4) receptors. The present work was undertaken to study the potential modulation of CysLT(1)R expression in HL-60/eos by IL-5, an important regulator of eosinophil function. Here, we report that IL-5 rapidly up-regulates CysLT(1)R mRNA expression, with consequently enhanced CysLT(1)R protein expression and function in HL-60/eos. CysLT(1)R mRNA expression was augmented 2- to 15-fold following treatment with IL-5 (1-20 ng/ml). The effect was seen after 2 h, was maximal by 4 h, and maintained at 8 h. Although CysLT(1)R mRNA was constitutively expressed in undifferentiated HL-60 cells, its expression was not modulated by IL-5 in the absence of differentiation. Differentiated HL-60/eos cells pretreated with IL-5 (10 ng/ml) for 24 h showed enhanced CysLT(1)R expression on the cell surface, as assessed by flow cytometry using a polyclonal anti-CysLT(1)R Ab. They also showed enhanced responsiveness to LTD(4), but not to LTB(4) or platelet-activating factor, in terms of Ca(2+) mobilization, and augmented the chemotactic response to LTD(4). Our findings suggest a possible mechanism by which IL-5 can modulate eosinophil functions and particularly their responsiveness to LTD(4), and thus contribute to the pathogenesis of asthma and allergic diseases.

Early coronary angiogenesis in response to thyroxine: growth characteristics and upregulation of basic fibroblast growth factor.

Although a substantial coronary angiogenesis occurs after thyroid hormone treatment, its regulation and relationship to cardiac hypertrophy are not understood. This study was designed to determine (1) the onset of capillary proliferation, (2) the sites of capillary proliferation, and (3) whether basic fibroblast growth factor (bFGF) upregulation occurs in response to thyroxine administration. Male Sprague-Dawley rats were injected daily with L-thyroxine (T4, 0.2 mg/kg s.c.). Bromodeoxyuridine labeling of capillary endothelial cells increased during the first 24 hours of treatment and peaked after 2 days of treatment. Northern blot analysis revealed a slight increase in bFGF mRNA during this period, followed by a doubling of expression by 48 hours, at which time bFGF protein was also increased. In situ hybridization, used to localize bFGF mRNA, showed an increase in transcripts within 24 hours after T4. This enhancement was uniform in the epimyocardium and endomyocardium. Histochemical analysis (double staining for alkaline phosphatase and dipeptidyl peptidase) of frozen sections, used to discriminate capillary profiles as arteriolar and venular, respectively, showed that growth occurred in the latter, since the percentage of capillary profiles positive for dipeptidyl peptidase was higher than the control value after 4 days of T4 administration. These data indicate that in the thyroxine model of cardiac hypertrophy (1) capillary DNA synthesis occurs after a single injection of thyroxine, (2) capillary growth coincides with an upregulation in bFGF mRNA and increase in bFGF protein, and (3) proliferation occurs in the venular capillaries.

College students' attitudes toward finding a mate to escape depression: sex differences.

College student respondents (n = 128) were compared on their consideration of finding a mate or significant other as a strategy for a hypothetical teacher ("Terry") displaying symptoms of dysthymic disorder (DSM-IV criteria). The sex of "Terry" was manipulated by descriptive pronoun (he or she) only. Analysis indicated differences based on sex of Terry and sex of respondent. Respondents favored finding a mate for the hypothetical male more than the female. Men, more than women, supported finding a mate or significant other for the teacher.

Relationship of the extracellular matrix to coronary neovascularization during development.

The main goal of this study was to determine the temporal and spatial relationship of several components of the extracellular matrix (ECM) to coronary vascularization during prenatal and early postnatal development. Rat microvessels were visualized by immunolabeling for platelet endothelial cell adhesion molecule (PECAM-1), and by exposure to the lectin from Griffonia simplicifolia I. Coronary vasculogenesis, which first occurs in gestation day 13 (E13) hearts, was preceded by the deposition of fibronectin. The onset of laminin immunoreactivity in basement membranes coincided with tube formation and was followed by the appearance of collagen IV. Discontinuous collagen IV staining of basement membranes typified early tube formation but progressed to completely encircle capillaries. Sparse staining of collagen I and III was observed in prenatal hearts, but increased after birth. Staining for both molecules was limited mainly to the adventitia of vessels larger than capillaries, and as a component of septa and the epicardium. To determine the effects of loading conditions on key ECM molecules relating to neovascularization, avascular E12 rat hearts were grafted to the anterior eye chamber of adult hosts. In these hearts, which are hemodynamically unloaded, the appearance and distribution of ECM components were similar to hearts developing in utero. It was concluded that during heart development: (1) fibronectin may provide a primary scaffolding for the migration of primordial endothelial cells/angioblasts; (2) tube formation coincides with lamin deposition and is closely followed by the appearance of collagen IV; (3) collagens I and III are not related to tube formation in the prenatal heart; and (4) the relationship of the ECM to vessel formation is not notably altered in the absence of a ventricular load. Furthermore the early onset of PECAM-1 immunoreactivity suggests that it is a useful endothelial marker and may play a role in tube formation.

Increased sensitivity to rate-altering and discriminative stimulus effects of morphine following continuous exposure to naltrexone.

Two experiments evaluated whether termination of a continuous infusion of naltrexone altered sensitivity to the rate-suppressing or discriminative stimulus effects of morphine in rats. An 8-day infusion of saline or doses of 3, 10, or 18 mg/kg/day naltrexone did not alter rates of lever pressing maintained under fixed-ratio 30 schedules of food delivery. A dose of 10 mg/kg day naltrexone produced insurmountable antagonism of the rate-suppressing and analgesic effects of morphine. The ED50 of morphine for rate suppression decreased by 2-fold 1 day after termination of the 8-day infusion of 10 or 18 mg/kg/day naltrexone. The ED50 of morphine returned to initial values within 8 days. Termination of infusion of either saline or 3 mg/kg/day naltrexone did not alter the ED50 of morphine. Changes in morphine stimulus control were evaluated in rats trained to discriminate saline and 3.2 mg/kg morphine under fixed-ratio 15 schedules of food delivery. The ED50 of morphine for stimulus control or rate suppression decreased by 2-fold 1 day after termination of an 8-day infusion of 18 mg/kg/day naltrexone. The ED50 of morphine for rate suppression returned to initial values within 3 days; that for stimulus control, within 5 days. Thus, termination of exposure to high doses of naltrexone produced brief changes in sensitivity to the rate-altering and discriminative stimulus effects of morphine that parallel reported changes in sensitivity to the analgesic and lethal effects of morphine.

Tolerance to morphine stimulus control: role of morphine maintenance dose.

Experiments assessed the development of tolerance to morphine stimulus control during treatment with selected maintenance doses of morphine. Separate groups of rats were trained to discriminate saline and either 3.2 mg/kg or 5.6 mg/kg morphine under fixed-ratio schedules of food delivery. Dose-response functions for generalization of morphine stimulus control were determined before, during, and after repeated treatment with selected doses of morphine. Similar experiments were performed with repeated pentobarbital treatment in order to assess the pharmacological selectivity of tolerance. Repeated treatment with saline, 3.2 mg/kg morphine, or twice daily injections of 17.8 mg/kg pentobarbital produced no tolerance to morphine stimulus control. In contrast, treatment with daily injections of 10 mg/kg or twice daily injections of 10 or 17.8 mg/kg morphine produced a dose-dependent increase in the dose of morphine required for stimulus control. The magnitude of tolerance to morphine stimulus control varied directly with the maintenance dose of morphine and was slightly greater for a lower than a higher morphine training dose. Termination of repeated treatment was followed by a return to initial sensitivity, without additional training. Tolerance to morphine stimulus control was not necessarily accompanied by tolerance to its rate-suppressing effects.

Xerophthalmia and anterior-segment blindness among preschool-age children in El Salvador.

A countrywide prevalence survey of 9,508 children was conducted in El Salvador to determine the prevalence of anterior-segment abnormalities and magnitude of clinical vitamin A deficiency. Thirty-six children had corneal opacities, 56% of them secondary to trauma. Such traumatic corneal opacities were 19 times more frequent among urban than rural children, 57.6 vs. 3.1 per 1,000. Keratomalacia accounted for only 8% of all corneal opacities, and for one (and possibly two) of the five cases of bilateral anterior-segment blindness encountered. The prevalance of Bitot spots and vitamin-A-related corneal opacities was 5.3 and 3.2 per 10,000, respectively. There are an estimated 43 new surviving cases of vitamin-A-related corneal opacities in the country each year, one third of which result in bilateral blindness. Fifteen percent of all children examined had grossly purulent conjunctivitis.

IR studies on carrageenan of Ahnfeltia concinna, a marine red alga.

The principal polysaccharide of Ahnfeltia concinna gave IR absorptions at 1240, 930, 845-850, and 805 cm-1, all typical of a carrageenan. The polysaccharide was separated into soluble and insoluble fractions with potassium chloride.