Whispering gallery resonators with broken axial symmetry: Theory and experiment.

Axial symmetry is the cornerstone for theory and applications of high-Q optical whispering gallery resonators (WGRs). Nevertheless, research on birefringent crystalline material persistently pushes towards breaking this symmetry. We show theoretically and experimentally that the effect of broken axial symmetry, caused by optical anisotropy, is modest for the resonant frequencies and Q-factors of the WGR modes. Thus, the most important equatorial whispering gallery modes can be quantitatively described and experimentally identified. At the same time, the effect of broken axial symmetry on the light field distribution of the whispering gallery modes is typically very strong. This qualitatively modifies the phase-matching for the χ(2) nonlinear processes and enables broad-band second harmonic generation and optical parametric oscillation. The effect of weak geometric ellipticity in nominally symmetric WGRs is also considered. Altogether our findings pave the way for an extensive use of numerous birefringent (uniaxial and biaxial) crystals with broad transparency window and large χ(2) coefficients in nonlinear optics with WGRs.

Quantum light from a whispering-gallery-mode disk resonator.

Optical parametric down-conversion has proven to be a valuable source of nonclassical light. The process is inherently able to produce twin-beam correlations along with individual intensity squeezing of either parametric beam, when pumped far above threshold. Here, we present for the first time the direct observation of intensity squeezing of -1.2 dB of each of the individual parametric beams in parametric down-conversion by use of a high quality whispering-gallery-mode disk resonator. In addition, we observed twin-beam quantum correlations of -2.7 dB with this cavity. Such resonators feature strong optical confinement and offer tunable coupling to an external optical field. This work exemplifies the potential of crystalline whispering-gallery-mode resonators for the generation of quantum light. The simplicity of this device makes the application of quantum light in various fields highly feasible.

Localized edge vibrations and edge reconstruction by joule heating in graphene nanostructures.

Control of the edge topology of graphene nanostructures is critical to graphene-based electronics. A means of producing atomically smooth zigzag edges using electronic current has recently been demonstrated in experiments [Jia, Science 323, 1701 (2009)10.1126/science.1166862]. We develop a microscopic theory for current-induced edge reconstruction using density functional theory. Our calculations provide evidence for localized vibrations at edge interfaces involving unpassivated armchair edges. We demonstrate that these vibrations couple to the current, estimate their excitation by Joule heating, and argue that they are the likely cause of the reconstructions observed in the experiments.

Low-threshold optical parametric oscillations in a whispering gallery mode resonator.

In whispering gallery mode (WGM) resonator light is guided by continuous total internal reflection along a curved surface. Fabricating such resonators from an optically nonlinear material one takes advantage of their exceptionally high quality factors and small mode volumes to achieve extremely efficient optical frequency conversion. Our analysis of the phase-matching conditions for optical parametric down-conversion (PDC) in a spherical WGM resonator shows their direct relation to the sum rules for photons' angular momenta and predicts a very low parametric oscillation threshold. We realized such an optical parametric oscillator (OPO) based on naturally phase-matched PDC in lithium niobate. We demonstrated a single-mode, strongly nondegenerate OPO with a threshold of 6.7 µW and linewidth under 10 MHz. This work demonstrates the remarkable capabilities of WGM-based OPOs.

Naturally phase-matched second-harmonic generation in a whispering-gallery-mode resonator.

We demonstrate for the first time natural phase matching for optical frequency doubling in a high-Q whispering-gallery-mode resonator made of lithium niobate. A conversion efficiency of 9% is achieved at 30 microW in-coupled continuous wave pump power. The observed saturation pump power of 3.2 mW is almost 2 orders of magnitude lower than the state-of-the-art value. This suggests an application of our frequency doubler as a source of nonclassical light requiring only a low-power pump, which easily can be quantum noise limited. Our theoretical analysis of the three-wave mixing in a whispering-gallery-mode resonator provides the relative conversion efficiencies for frequency doubling in various modes.

High accuracy of external ventricular drainage placement using anatomical landmarks.

BACKGROUND: The conventional approach for external ventricular drainage (EVD) application is the freehand method. Technical devices can improve the accuracy of placement, but they have not yet replaced anatomical landmarks owing to the cost and effort that they entail. There is disagreement as to whether freehand EVD application is safe enough to be accepted as a standard technique. Many authors have investigated the final catheter position in retrospect. They describe variable rates of malpositioning. However, few studies have assessed in how far cranial surface anatomy has really been respected during burr-hole drilling and catheter insertion. The aim of this study was to investigate parameters that might play a part in determining the final intracranial catheter position. METHODS: In all, 100 pre- and postprocedural thin-layer computed-tomography (CT) scans of EVD patients were analysed with the help of JiveX® and OsiriX Lite® software. A series of anatomical and catheter-related parameters, including inter alia intraventricular blood, midline shift, burr-hole location and catheter entrance angle, were correlated with the final catheter position. RESULTS: A majority of EVDs show an optimal or nearly optimal position. Only the deviation of catheter entrance angle has a significant influence on catheter malpositioning. The burr-hole location can vary within an area of several centimetres around the coronary suture. CONCLUSIONS: The freehand application of EVD is safe as long as the intracranial anatomy is not disfigured to a large extent, the surface measurements are carried out precisely and the puncturing is done perpendicularly to the skull.

Fusion pore expansion is a slow, discontinuous, and Ca2+-dependent process regulating secretion from alveolar type II cells.

In alveolar type II cells, the release of surfactant is considerably delayed after the formation of exocytotic fusion pores, suggesting that content dispersal may be limited by fusion pore diameter and subject to regulation at a postfusion level. To address this issue, we used confocal FRAP and N-(3-triethylammoniumpropyl)-4-(4-[dibutylamino]styryl) pyridinium dibromide (FM 1-43), a dye yielding intense localized fluorescence of surfactant when entering the vesicle lumen through the fusion pore (Haller, T., J. Ortmayr, F. Friedrich, H. Volkl, and P. Dietl. 1998. Proc. Natl. Acad. Sci. USA. 95:1579-1584). Thus, we have been able to monitor the dynamics of individual fusion pores up to hours in intact cells, and to calculate pore diameters using a diffusion model derived from Fick's law. After formation, fusion pores were arrested in a state impeding the release of vesicle contents, and expanded at irregular times thereafter. The expansion rate of initial pores and the probability of late expansions were increased by elevation of the cytoplasmic Ca2+ concentration. Consistently, content release correlated with the occurrence of Ca2+ oscillations in ATP-treated cells, and expanded fusion pores were detectable by EM. This study supports a new concept in exocytosis, implicating fusion pores in the regulation of content release for extended periods after initial formation.

Density functional theory based screening of ternary alkali-transition metal borohydrides: a computational material design project.

We present a computational screening study of ternary metal borohydrides for reversible hydrogen storage based on density functional theory. We investigate the stability and decomposition of alloys containing 1 alkali metal atom, Li, Na, or K (M(1)); and 1 alkali, alkaline earth or 3d/4d transition metal atom (M(2)) plus two to five (BH(4))(-) groups, i.e., M(1)M(2)(BH(4))(2-5), using a number of model structures with trigonal, tetrahedral, octahedral, and free coordination of the metal borohydride complexes. Of the over 700 investigated structures, about 20 were predicted to form potentially stable alloys with promising decomposition energies. The M(1)(Al/Mn/Fe)(BH(4))(4), (Li/Na)Zn(BH(4))(3), and (Na/K)(Ni/Co)(BH(4))(3) alloys are found to be the most promising, followed by selected M(1)(Nb/Rh)(BH(4))(4) alloys.

Oligonucleotide microarray identification of Bacillus anthracis strains using support vector machines.

The capability of a custom microarray to discriminate between closely related DNA samples is demonstrated using a set of Bacillus anthracis strains. The microarray was developed as a universal fingerprint device consisting of 390 genome-independent 9mer probes. The genomes of B. anthracis strains are monomorphic and therefore, typically difficult to distinguish using conventional molecular biology tools or microarray data clustering techniques. Using support vector machines (SVMs) as a supervised learning technique, we show that a low-density fingerprint microarray contains enough information to discriminate between B. anthracis strains with 90% sensitivity using a reference library constructed from six replicate arrays and three replicates for new isolates.

Sustained local delivery of dexamethasone by a novel intravascular eluting stent to prevent restenosis in the porcine coronary injury model.

OBJECTIVES: This study sought to assess the feasibility, safety and efficacy of sustained intracoronary delivery of dexamethasone by a novel polymer-coated eluting stent. BACKGROUND: Development of techniques to provide sustained local drug delivery has focused on polymers as matrices for drug incorporation and elution. METHODS: A tantalum wire stent was coated with dexamethasone (0.8 mg) suspended in a matrix of either low (approximately 80 kD) or high (approximately 321 kD) molecular weight poly-L-lactic acid (PLLA [0.4 mg]). Uncoated stents, stents coated with PLLA or stents coated with dexamethasone in PLLA were overexpanded by 30% to the normal vessel diameter in the coronary arteries of juvenile farm pigs. Animals were euthanized 28 days later, and neointimal thicknesses were measured. Additional pigs underwent placement of stents coated with high molecular weight PLLA-dexamethasone for assessment of arterial tissue and serum concentrations of dexamethasone at 1 h and 1, 2, 10 and 28 days after stent implantation. RESULTS: In vitro dexamethasone release occurred over the first 6 days. Stents coated with low molecular weight PLLA produced an intense inflammatory neointimal response. Stents utilizing the high molecular weight PLLA were well tolerated within the coronary vessel during the 28-day experiment. However, dexamethasone did not decrease neointimal hyperplasia. Dexamethasone concentrations in the arterial tissue were approximately 300,000-fold higher than those in the serum 24 h after stent implantation, remaining approximately 3,000-fold higher at 28 days. CONCLUSIONS: The eluting stent utilizing high molecular weight PLLA appeared to be a well tolerated and effective means of providing sustained, site-specific drug delivery to the porcine coronary artery wall for at least 28 days.

The pharmacokinetics of etodolac in serum and synovial fluid of patients with arthritis.

The pharmacokinetics of etodolac have been evaluated in five patients with arthritis given 200 mg etodolac, twice daily, at 12-hour intervals, for 7 days. Albumin and total protein concentrations were markedly lower in synovial fluid than in serum, and etodolac free fraction was significantly higher. Etodolac readily penetrated into the synovial fluid, and in the postdistributive phase the concentration of free etodolac (i.e., the drug responsible for pharmacologic activity) remained higher than that in serum at all times. No differences in the half-life of etodolac elimination were noted.

Characterization of the human gene coding for the swelling-dependent chloride channel ICln at position 11q13.5-14.1 (CLNS1A) and further characterization of the chromosome 6 (CLNS1B) localization.

Expression cloning revealed a chloride channel (ICln) that we found to be fundamental for the regulatory volume decrease in a variety of cells. The chromosomal localization of the human ICln-gene showed two loci, one at chromosome 11 in position q13.5-q14.1, termed CLNS1A, and a second one at chromosome 6 at position p12.1-q13, termed CLNS1B. In this study, we offer a detailed characterization of the CLNS1A gene and provide the exact position (6p12) and sequence data of CLNS1B, an intronless gene 91.3% homologous to the coding region of CLNS1A.

Impact of enoxaparin low molecular weight heparin in patients with Q-wave myocardial infarction.

A subgroup meta-analysis from the Efficacy and Safety of Subcutaneous Enoxaparin in Non-Q-Wave Coronary Events (ESSENCE) and the Thrombolysis in Myocardial Infarction (TIMI) 11B studies has shown that enoxaparin is superior to unfractionated heparin in reducing the composite end points of death, myocardial infarction, and emergency revascularization in patients with Q-wave myocardial infarction. The beneficial treatment effect was significant at 43 days.

The gastric H,K-ATPase blocker lansoprazole is an inhibitor of chloride channels.

1. It was postulated that swelling dependent chloride channels are involved in the proton secretion of parietal cells. Since omeprazole, lansoprazole and its acid activated sulphenamide form AG2000 are structurally related to phenol derivatives known to block swelling dependent chloride channels, we set out to test, whether these substances--which are known to block the H,K-ATPase--could also lead to an inhibition of swelling-dependent chloride channels. Swelling-dependent chloride channels--characterized in many different cell types--show highly conserved biophysical and pharmacological features, therefore we investigated the effect of omeprazole, lansoprazole and its acid activated sulphenamide form AG2000 on swelling-dependent chloride channels elicited in fibroblasts, after the reduction of the extracellular osmolarity. 2. Omeprazole, lansoprazole and its acid activated sulphenamide form AG2000 are able to block swelling-dependent chloride channels (IClswell). 3. Lansoprazole and its protonated metabolite AG2000 act on at least two different sites of the IClswell protein: on an extracellular site which seems to be in a functional proximity to the nucleotide binding site, and on an intracellular site which allows the formation of disulfide-bridges. 4. The inhibition of the proton pump and the simultaneous blocking of chloride channels by omeprazole, lansoprazole and its acid activated sulphenamide form AG2000, as described here could be an effective mode to restrict proton secretion in parietal cells.

Increased incidence of positive tests for estrogen binding in mammary carcinoma specimens transported in liquid nitrogen.

Use of a liquid nitrogen container for convenient transport of frozen mammary carcinoma tissue for hormone-receptor assays is described. The container can be used in dry or wet mode and is appropriate for all types of transport, including air. Experience shows a significantly higher incidence of positive tests on specimens transported by this means than on specimens transported in dry ice.

Placebo-controlled, double-blind study of the efficacy and safety of triamcinolone acetonide aerosol nasal inhaler in pediatric patients with seasonal allergic rhinitis.

Triamcinolone acetonide (TAA) aerosol nasal inhaler has been shown to effectively relieve the symptoms of seasonal allergic rhinitis in adults and adolescents. We conducted a study to evaluate the efficacy and safety of once-daily administration of TAA aerosol nasal inhaler in pediatric patients aged 6 to 11 years with grass seasonal allergic rhinitis. This multicenter, randomized, double-blind, placebo-controlled, parallel-group study enrolled 116 children who were treated with either TAA aerosol nasal inhaler (220 micrograms/d) or placebo once daily for 2 weeks. Patients evaluated the severity of rhinitis symptoms (nasal stuffiness, discharge, sneezing, and itching) daily according to a four-point scale (0 = absent, 1 = mild, 2 = moderate, and 3 = severe). Patients' and physicians' global evaluations of overall treatment efficacy were assessed at the end of the 2-week treatment period. Patients treated with TAA aerosol nasal inhaler had significantly greater reductions in all nasal symptom scores overall and in virtually all symptoms at the end of week 1 and week 2 compared with those in the placebo group. Both patients' and physicians' global evaluations of efficacy favored TAA aerosol nasal inhaler over placebo. This study demonstrated that once-daily administration of 220 micrograms of TAA aerosol nasal inhaler was well tolerated and effectively reduced the symptoms of seasonal allergic rhinitis in pediatric patients.

Assessing vulnerability to suicide.

Three hundred members of the American Association of Suicidology (30% of those who apparently received the questionnaire) participated in a survey in which case histories of two men who had committed suicide and two who had not were presented. Respondents assessed the vulnerability to suicide of each man, recorded their levels of confidence in their assessments, and provided information about themselves. The two men who killed themselves were rated as less vulnerable to suicide than the other two men, and as less vulnerable than one would expect by chance. Respondent characteristics that predicted to accuracy in assessing vulnerability were gender and level of involvement in research. The findings are discussed in terms of the limitations of theoretical models as well as characteristics of the respondents and nature of the study design.

Anabolic steroids as a countermeasure against bone demineralization during space flight.

A progressive loss of bone mass is consistently reported in humans exposed to weightlessness during space flight. The mechanism of this metabolic alteration is unknown but may be due in part to the effects of disuse osteoporosis along with the influence of elevated corticosteroid levels. With a goal toward mankind's permanent presence in space, effective countermeasures against bone demineralization will be required. Synthetic anabolic steroids have been shown to prevent bone loss in ground-based immobilization studies and in excess corticosteroid states. These agents may offer a means of slowing or preventing bone loss thus facilitating long term space habitation.