Asymmetric photonic resonances in GaN slab waveguide for mid infrared selective filters.

We demonstrate a spectrally selective reflector that exploits asymmetric photonic resonances of a 1D photonic crystal. The proposed spectrally selective reflector has a very simple structure - essentially just a single high-index slab of GaN, properly perforated, and supported by a transparent sapphire substrate. With the proper 1D array design, nearly 100% reflection is achieved with a narrow spectral width between 10 cm⁻¹ - 18 cm⁻¹, while the background reflection remains low across the entire mid-IR range. The reflection peak can be tuned over a large wavelength span based on physical parameters. Resonant transmission dips in the experimentally measured spectra corroborate the device theory and simulation, exhibiting the narrowband low-background mid-IR reflection as predicted.

Axillary bud banks of two semiarid perennial grasses: occurrence, longevity, and contribution to population persistence.

The occurrence, longevity, and contribution of axillary bud banks to population maintenance were investigated in a late-seral perennial grass, Bouteloua curtipendula, and a mid-seral perennial grass, Hilaria belangeri, in a semiarid oak-juniper savanna. Axillary buds of both species were evaluated over a 2-year period in communities with contrasting histories of grazing by domestic herbivores. A double staining procedure utilizing triphenyl tetrazolium chloride and Evan's blue indicated that both viable and dormant axillary buds remained attached to the base of reproductive parental tillers for 18-24 months which exceeded parental tiller longevity by approximately 12 months. Bud longevity of the late-seral species, B. curtipendula, exceeded bud longevity of the mid-seral species, H. belangeri, by approximately 6 months. Younger buds located on the distal portion of the tiller base were 3.2 and 1.4 times more likely to grow out than older proximal buds of B. curtipendula and H. belangeri, respectively. The percentage of older proximal buds, which included comparable portions of viable and dormant buds, that grew out to produce tillers following mortality of parental tillers was 6.0% for B. curtipendula and 8.4% for H. belangeri. In spite of the occurrence of relative large axillary bud banks for both species, the magnitude of proximal bud growth did not appear sufficient to maintain viable tiller populations. We found no evidence to support the hypothesis of compensatory bud growth on an individual tiller basis for either species. Grazing history of the communities from which the buds were collected did not substantially affect the number, status, longevity, or outgrowth of axillary buds on an individual tiller basis for either species. However, long-term grazing by domestic herbivores influenced axillary bud availability by modifying population structure of these two species. Bud number per square meter for B. curtipendula was 25% lower in the long-term grazed compared to the long-term ungrazed community based on a reduction in both tiller number per plant and plant number per square meter. In contrast, bud number per square meter for H. belangeri was 190% greater in the long-term grazed than in the long-term ungrazed community based on a large increase in plant density per square meter. Minimal contributions of axillary bud banks to annual maintenance of tiller populations in this mid- and late-seral species underscores the ecological importance of consistent tiller recruitment from recently developed axillary buds. Consistent tiller recruitment in grasslands and savannas characterized by intensive grazing and periodic drought implies that (1) bud differentiation and maturation must be remarkably tolerant of adverse environmental conditions and/or (2) tiller recruitment may resume from buds that mature following the cessation of severe drought and/or grazing, rather than from mature buds that survive these disturbances. These scenarios warrant additional research emphasis given the critical importance of this demographic process to tiller replacement in species populations and the maintenance of relative species abundance in grasslands and savannas.

Pharmacoeconomic benefit of antibiotic step-down therapy: converting patients from intravenous ceftriaxone to oral cefpodoxime proxetil.

OBJECTIVE: To evaluate the economic benefit associated with the early conversion of therapy from intravenous ceftiaxone to the comparable oral third-generation cephalosporin, cefpodoxime proxetil. DESIGN: Open-label, unblind, nonrandomized clinical trial. SETTING: A 360-bed Veterans Affairs Medical Center. PATIENTS: Forty patients who began receiving intravenous ceftriaxone for either a community-acquired pneumonia or a complicated urinary tract infection. INTERVENTION: twenty patients were selected, based on clinical assessment, to be converted from intravenous ceftriaxone to oral cefpodoxime proxetil. Twenty other comparable patients who would have been appropriate for step-down therapy, did not receive pharmacy intervention and were used as a control group. MEASUREMENTS: Both groups were assessed and compared for length of ceftiaxone therapy, length of oral follow-up therapy (if any), length of hospitalization, results of culture and sensitivity testing, treatment success and readmissions, and cost of respective therapeutic regimens. RESULTS: In the cefpodoxime study group, the average time receiving intravenous and oral antibiotics was 9.1 days at a total cost of $3040.26 for the 20 patients. In the control group, the average time receiving intravenous and oral antibiotics was 11.9 days at a total cost of $3961.26. A savings of $46.05 per patient was achieved. Patients receiving step-down therapy averaged 1 fewer day of hospitalization. CONCLUSION: Pharmacist intervention and cefpodoxime step-down therapy were associated with decreased overall antibiotic costs in our intravenous-to-oral program.

The structure of the carapace and plastron of juvenile turtles, Chelonia mydas (the green turtle) and Caretta caretta (the loggerhead turtle).

Consistent with their primary function as a protective covering, the carapace and plastron are heavily keratinised. In both species, the carapace is heavily pigmented and during the development and translocation of basal cells from the germinal layer of the epidermis, pigment granules migrate towards the surface layers. The epidermis is generally 2-4 cells thick; however at the growing points it can attain 6 cell layers. The epidermis is much thicker over the plastron of the loggerhead turtle. The ultrastructure of the epidermal cells supports the observation that the keratin scales are of the hard variety and the microfolds which characterise the scutes covering the carapace are discussed in relation to the lowering of frictional drag in water.

1. Estrogen antagonists. Aromatase inhibitors, their pharmacology and application.

Aromatase inhibitors, 4-OHA, 4-acetoxy-A and ATD cause competitive inhibition and inactivation of aromatase in vitro. The latter property may account for sustained aromatase inhibition observed in vivo, even though 4-OHA is cleared rapidly from the circulation. Thus, all 3 compounds inhibit the prosestrus oestrogen surge in rats. Treatment with 4-OHA for one oestrus cycle is sufficient to block ovulation for at least 10 additional days. Although ovarian oestrogen production was reduced by long-term inhibitor treatment, gonadotrophins remained at basal levels, suggesting a direct effect of 4-OHA on gonadotrophins. Marked regression of DMBA-induced mammary tumours occurred in rats treated with aromatase inhibitors. The compounds were more effective alone against these tumours than when combined with the antioestrogen, tamoxifen. Sustained antitumour effects of 4-OHA were observed in rats treated twice daily (50 mg/kg/day) for 9 days and twice weekly thereafter for 20 weeks. Tumours regressed during the first 9 days and 18/19 tumours remained suppressed for 20 weeks. The results in animal models suggest that highly potent aromatase inhibitors may be useful for breast cancer treatment and for other oestrogen related clinical problems.

Effects of aromatase inhibitor 4-hydroxyandrostenedione and other compounds in the 7, 12-dimethylbenz(a)anthracene-induced breast carcinoma model.

Aromatase inhibitor, 4-hydroxyandrostene-3,17-dione (4-OHA), is a highly effective treatment in rats with 7,12-dimethylbenz(a) anthracene-induced hormone-dependent mammary tumors. Over 90% of tumors regress to less than one-half of their original size, and a high proportion regress completely. Treatment of rats with other inhibitors, 4-acetoxyandrostene-3,17-dione and 1,4,6-androstatriene-3,17-dione produce similar results. In comparison with other aromatase inhibitors, the compounds reduced ovarian estrogen secretion in the rat to the same extent as aminoglutethimide, whereas Teslac was without effect. The latter two compounds caused little and no regression of DMBA-induced mammary tumors, respectively. Our recent studies with 4-OHA, 4-acetoxyandrostene-3,17-dione, and 1,4,6-androstatriene-3,17-dione indicate that they interact with aromatase by a two-component mechanism, a rapid competitive inhibition, and a slower enzyme inactivation. Treatment of rats with 4-OHA also caused greater than 80% loss of ovarian aromatase activity in vivo and a reduction in ovarian estrogen secretion, which are maintained for at least 48 hr after injection. Although 4-OHA is cleared rapidly in vivo, the above results suggest that the compound has a sustained effect. Thus, when 7,12-dimethylbenz(a)anthracene-induced tumor-bearing rats were treated with 4-OHA injections on alternate weeks, tumor regression continued to occur during weeks without treatment. The overall regression was similar to that with continuous treatment. 4-OHA is also effective and similar to ovariectomy in rats with hormone-dependent metastatic mammary tumors produced by nitrosomethylurea. Our results indicate that mammary tumor regression induced by 4-OHA is mainly the result of the inhibition of aromatization, although other activities of the compound may also contribute.

Effect of an aromatase inhibitor, 1,4,6-androstatriene-3,17-dione, on 7,12-dimethylbenz[a]anthracene-induced mammary tumors in the rat and its mechanism of action in vivo.

In this study, 1,4,6-androstatriene-3,17-dione (ATD) was demonstrated to cause time-dependent loss of aromatase activity in rat ovarian microsomes in vitro. In vivo, an injection of ATD caused inhibition of ovarian aromatase and reduced estrogen secretion in pregnant mare's serum gonadotropin-primed rats for at least 24 hr after injection. In rats with 7,12-dimethylbenz[a]anthracene-induced, hormone-dependent, mammary tumors, marked regression occurred with ATD treatment. Although estrogen secretion was not reduced below the diestrus level of controls, the rats remained anestrus, indicating that the proestrus surge of estrogen was prevented. LH, FSH and prolactin levels were also basal and LH and FSH did not rise after ovariectomy. ATD had no detectable hormonal activity in bioassay. Consistent with this, the compound did not interact appreciably with either androgen or estrogen receptors, was not uterotrophic, and did not interfere with mammary tumor regression in ovariectomized rats. Thus, the major activities of the compound which cause mammary regression in the rat appear to be inhibition of estrogen synthesis, via aromatase and gonadotropin suppression.

Inactivation of aromatase in vitro by 4-hydroxy-4-androstene-3,17-dione and 4-acetoxy-4-androstene-3,17-dione and sustained effects in vivo.

4-Hydroxy-4-androstene-3,17-dione (4-OHA) and 4-acetoxy-4-androstene-3,17-dione (4-AcA), in addition to being competitive inhibitors of aromatase, cause time-dependent, irreversible, loss of enzyme activity in both human placental and rat ovarian microsomes. In vivo, treatment of rats with 4-OHA also causes loss of ovarian aromatase activity. To test whether this loss of activity could have in vivo significance, rats with hormone-dependent, mammary tumors were treated with 4-OHA on alternate weeks. Tumor regression continued to occur during the weeks without treatment. These findings suggest that inactivation of aromatase is important in the mechanism of action of the compounds in vivo.

Resonant torsional apparatus for contactless measurements of electrical conductivity and magnetic susceptibility of solids.

We have constructed a torsional resonance apparatus for contact-free measurements of the electrical conductivity of solids. Owing to its use of modulation spectroscopy, the technique achieves considerable enhancement of sensitivity compared to previous contactless methods. Conductivities in the range 10(-5) mho/cm to 10(-6) mho/cm can now be measured by the contactless technique. Measurements of magnetic susceptibility as low as 10(-12) can be made. This sensitivity allows for investigation of magnetic impurities as dilute as 1 part in 10(7). In samples which display both phenomena of electrical conductivity and magnetic susceptibility, the two effects can be sorted out via analysis of frequency and/or temperature dependence. The present apparatus has potential for considerable improvement.