Maximizing optical production of metastable xenon.

The wide range of applications using metastable noble gas atoms has led to a number of different approaches for producing large metastable state densities. Here we investigate a recently proposed hybrid approach that combines RF discharge techniques with optical pumping from an auxiliary state in xenon. We study the effect of xenon pressure on establishing initial population in both the auxiliary state and metastable state via the RF discharge, and the role of the optical pumping beam power in transferring population between the states. We find experimental conditions that maximize the effects, and provide a robust platform for producing relatively large long-term metastable state densities.

Transmission characteristics of optical nanofibers in metastable xenon.

We study the transmission characteristics of subwavelength diameter silica optical nanofibers (ONFs) surrounded with xenon plasma produced by low-pressure inductive RF discharge. In contrast with related experiments using rubidium vapor, we find essentially no degradation of optical transmission through the ONFs as a function of time. We also observe a pronounced ONF transmission modulation effect that depends on the conditions of the xenon plasma.

Comprehensive Review of Cranial Chordomas Using National Databases in the USA.

AIMS: The management of cranial chordomas is controversial. We provide a comprehensive review of the evolving patterns of care of cranial chordomas in the USA. MATERIALS AND METHODS: We analysed the National Cancer Database (NCDB) and the Surveillance, Epidemiology, and End Results (SEER) database between 2004 and 2014 for clinical characteristics and long-term survival, and the National Surgical Quality Improvement Program (NSQIP) dataset between 2005 and 2016 for perioperative characteristics and surgical morbidity. RESULTS: In total, 936 patients were identified from the NCDB, 405 patients from SEER and 64 patients from the NSQIP. Most patients were men (56.2, 54.8 and 57.8% in NCDB, SEER and NSQIP, respectively) and White (80.9 and 83.2% in NCDB and SEER, respectively). Surgery was the preferred treatment modality (87.3% in NCDB and 86.2% in SEER). Surgery was carried out alone (41.8% in NCDB and 40.7% in SEER) or in combination with radiation (42.1% in NCDB and 45.4% in SEER). Proton therapy was the most common type of radiation (32.2% in NCDB), particularly after 2011. The median operative time, median hospital length and postoperative morbidity were significantly higher in chordoma patients compared with patients who underwent other skull-base procedures. The 5-year survival rate was 79.8% in NCDB and 76.9% in SEER. There was a trend towards longer survival in patients receiving surgery and radiation, which has been increasingly used since 2004. Patients younger than 60 years had a decreased risk of mortality. CONCLUSIONS: Our analysis reflects patterns of care in the USA. The use of surgery and radiation is increasing, with a trend towards longer survival. Surgery is complicated with long operative time, hospital stay and a higher rate of complications.

Optically enhanced production of metastable xenon.

Metastable states of noble gas atoms are typically produced by electrical discharge techniques or "all-optical" excitation methods. Here we combine electrical discharges with optical pumping to demonstrate "optically enhanced" production of metastable xenon (Xe*). We experimentally measure large increases in Xe* density with relatively small optical control field powers. This technique may have applications in systems where large metastable state densities are desirable.

Nanofiber-segment ring resonator.

We describe a fiber ring resonator comprised of a relatively long loop of standard single-mode fiber with a short nanofiber segment. The evanescent mode of the nanofiber segment allows the cavity-enhanced field to interact with atoms in close proximity to the nanofiber surface. We report on an experiment using a warm atomic vapor and low-finesse cavity, and briefly discuss the potential for reaching the strong coupling regime of cavity QED by using trapped atoms and a high-finesse cavity of this kind.

Saturated absorption at nanowatt power levels using metastable xenon in a high-finesse optical cavity.

Strong saturated absorption at nanowatt power levels has been demonstrated using metastable xenon in a high finesse optical cavity. The use of metastable xenon allows a high quality factor of Q = 2 × 10(8) to be achieved at relatively high atomic densities without any contamination or damage to the optical surfaces, which is often a problem when using high-density rubidium or other alkali atoms. This technique provides a relatively straightforward way to produce nonlinearities at the single-photon level with possible applications in quantum communications and computing.

Observation of two-photon absorption at low power levels using tapered optical fibers in rubidium vapor.

Nonlinear optical effects can be enhanced in tapered optical fibers with diameters less than the wavelength of the propagating light. Here we report on the observation of two-photon absorption using tapered fibers in rubidium vapor at power levels of less than 150 nW. Transit-time broadening produces two-photon absorption spectra with sharp peaks that are very different from conventional line shapes.

Violation of Bell's inequality with photons from independent sources.

We report a violation of Bell's inequality using one photon from a parametric down-conversion source and a second photon from an attenuated laser beam. The two photons were entangled at a beam splitter using the postselection technique of Shih and Alley [Phys. Rev. Lett. 61, 2921 (1988)]]. A quantum interference pattern with a visibility of 91% was obtained using the photons from these independent sources, as compared with a visibility of 99.4% using two photons from a central parametric down-conversion source.

Strategy for the treatment of noncompliant hypertensive hemodialysis patients.

Hypertensive hemodialysis patients noncompliant for their medications do not benefit from pharmacologic advances in the treatment of high blood pressure, and increase their already high risk of cardiovascular complications. The medical staff often becomes frustrated by severe hypertension in those who refuse to take medicines at home, drink excessive fluids, miss multiple dialysis sessions and sign-off dialysis early. In addition to addressing the psychosocial, financial, educational and substance abuse problems which contribute to noncompliance, we have developed a medication strategy to serve as an at least interim means of lowering blood pressure. Antihypertensive agents which have long half-lives in renal failure (lisinopril) and/or are intrinsically long acting (transdermal clonidine and amlodipine) were administered on dialysis days by the unit personnel to those patients who did not or would not take that or any dose on their own. The lisinopril and amlodipine were assured to have been taken on at least the dialysis days (thrice weekly), and the clonidine patch replaced weekly. Sixteen patients were thus treated when they failed to reliably self-administer medications. They had a significant decline in the predialysis systolic pressure of 15 mm Hg (175 +/- 6 to 160 +/- 5 mm Hg), diastolic of 12 mm Hg (103 +/- 3 to 91 +/- 3 mm Hg), and mean pressure of 13 mm Hg (127 +/- 4 to 114 +/- 4 mm Hg). There was an improvement in post-dialysis bood pressures, with the mean pressure declining 13 mm Hg from 110 +/- 4 to 97 +/- 4 mm Hg. Many individuals had erratic blood pressure control, having intermittently missed dialysis and hence unit-administered medicine, as well as continued fluid or drug abuse. The patients had uniformly excellent acceptance of this regimen, even spontaneously requesting it, and had no appreciable adverse effects. In summary while noncompliance is being addressed by the entire medical team, dialysis unit administration of long-acting medicines helps many hypertensive dialysis patients who would otherwise be at increased risk for severe cardiovascular complications.

High-fidelity quantum logic operations using linear optical elements.

Knill, Laflamme, and Milburn [Nature (London) 409, 46 ((2001))]] have shown that quantum logic operations can be performed using linear optical elements and additional ancilla photons. Their approach is probabilistic in the sense that the logic devices fail to produce an output with a failure rate that scales as 1/n, where n is the number of ancilla. Here we present an alternative approach in which the logic devices always produce an output with an intrinsic error rate that scales as 1/n(2), which may have several advantages in quantum computing applications.

Demonstration of nondeterministic quantum logic operations using linear optical elements.

Knill, Laflamme, and Milburn [Nature (London) 409, 46 (2001)] recently showed that nondeterministic quantum logic operations could be performed using linear optical elements, additional photons (ancilla), and postselection based on the output of single-photon detectors. Here we report the experimental demonstration of two logic devices of this kind, a destructive controlled-NOT (CNOT) gate and a quantum parity check. These two devices can be combined with a pair of entangled photons to implement a conventional (nondestructive) CNOT that succeeds with a probability of 1/4.

Functional role of alpha-calcitonin gene-related peptide in the regulation of the cardiovascular system.

It remains unknown whether the extent of vasoactive response to exogenous calcitonin gene-related peptide (CGRP) varies among different regional vascular beds. It is also unclear whether endogenous CGRP plays a functional role in regulating basal vascular activity. To address these two issues, experiments were conducted in 27 anesthetized rats instrumented with a carotid flow probe and catheters in a jugular vein, left ventricle (LV), and femoral artery, and in 6 conscious dogs, chronically instrumented with LV pressure gauge, aortic and atrial catheters, and ascending aortic, coronary, carotid, and renal flow probes. In both species, administration of human alpha-CGRP (0.1-0.5 microg/kg, i.v.) induced a dose-dependent peripheral vasodilation that was completely abolished by pretreatment with alpha-CGRP[8-37] (30 microg/kg/min, i.v.), a competitive antagonist of CGRP receptors. Regional blood flow measured by the radioactive microsphere technique in rats showed that the alpha-CGRP (0.3 microg/kg, i.v.)-induced increase in blood flow was greater (p < 0.05) in the heart (+53 +/- 16%) than in the brain (+14 +/- 6%). In the presence of beta-adrenergic receptor blockade with propranolol, however, the increases in blood flow in these two vascular beds were identical. In conscious dogs, alpha-CGRP (0.3 microg/kg, i.v.) produced similar increases in coronary (+24 +/- 6%), carotid (+26 +/- 3%), and renal (+26 +/- 6%) blood flow, which were different from the patterns induced by other vasodilators; at an equivalent level of reduction in mean arterial pressure and total peripheral resistance, alpha-CGRP increased coronary and carotid blood flow significantly less (p < 0.05) than adenosine or nitroprusside. Unlike alpha-CGRP, adenosine and nitroprusside, as expected, induced pronounced differential blood flow changes in these vascular beds. Neither systemic hemodynamics nor regional blood flow distribution was altered by the administration of a pharmacological blocking dose of alpha-CGRP[8-37] in the two species. Thus, we conclude that endogenous alpha-CGRP does not play an important role in cardiovascular regulation under normal, resting conditions, although exogenous alpha-CGRP induces a marked, comparable vasorelaxation in different regional vascular beds.

Patient education: designing a state-of-the-art consumer health information library.

Many patients believe that the education they receive about their health and their illnesses is inadequate or lacking. Nurse executives are in a key position to influence their patients' abilities to become more informed and to take greater responsibility for their healthcare decisions. In the article, the authors discuss Massachusetts General Hospital's state-of-the-art consumer health information library, including how the project was planned, organized, and implemented.

Simultaneous detection of Mycobacterium leprae and its susceptibility to dapsone using DNA heteroduplex analysis.

Currently recommended control measures for treating leprosy with multidrug therapy should control the spread of drug-resistant strains; however, dapsone (DDS) resistance continues to be reported. Comprehensive estimates of drug-resistant leprosy are difficult to obtain due to the cumbersome nature of the conventional drug susceptibility testing method using mouse footpad inoculation, which requires at least 6 months to obtain results. Recently, it has been determined that DDS-resistant strains contain missense mutations in codon 53 or 55 of the folP1 gene of Mycobacterium leprae, and definitive evidence linking these mutations with DDS resistance in M. leprae has been obtained. Based on these mutations, a heteroduplex DDS M. leprae (HD-DDS-ML) assay was developed for the simultaneous detection of M. leprae and of its susceptibility to DDS. The assay relies on the PCR amplification of an M. leprae-specific 231-bp fragment of folP1 containing codons 53 and 55. The PCR products are allowed to anneal to a universal heteroduplex generator, and the separation of the resultant DNA duplexes is accomplished by polyacrylamide gel electrophoresis. M. leprae was detected in crude cell lysates of skin biopsy specimen homogenates from eight leprosy patients and from M. leprae-infected mouse or armadillo tissues infected with 14 separate strains using the HD-DDS-ML assay. The assay was specific for M. leprae in a comparison with results obtained from 14 species of mycobacteria other than M. leprae and four bacterial species known to colonize human skin. The HD-DDS-ML assay detected as few as 100 M. leprae organisms present in homogenates of human skin and demonstrated a 93% correlation with DDS susceptibility as determined by both DNA sequencing of folP1 and mouse footpad susceptibility testing. The HD-DDS-ML assay provides a new tool for the simultaneous detection of M. leprae and of its susceptibility to DDS from a single specimen. The assay should prove useful for drug resistance surveillance in leprosy control programs when combined with similar molecular tests developed for other drug resistance markers.

Headspace gas chromatographic method for the measurement of difluoroethane in blood.

OBJECTIVES: To develop a gas chromatographic assay for the analysis of difluoroethane, a volatile substance, in blood and to determine assay characteristics including linearity, limit of quantitation, precision, and specificity. SETTING: Referral toxicology laboratory RESULTS: Difluoroethane, a colorless, odorless, highly flammable gas used as a refrigerant blend component and aerosol propellant, may be abused via inhalation. A headspace gas chromatographic procedure for the identification and quantitation of difluoroethane in blood is presented. A methanolic stock standard prepared from pure gaseous difluoroethane was used to prepare whole blood calibrators. Quantitation of difluoroethane was performed using a six-point calibration curve and an internal standard of 1-propanol. The assay is linear from 0 to 115 mg/L including a low calibrator at 4 mg/L, the limit of quantitation. Within-run coefficients of variation at mean concentrations of 13.8 mg/L and 38.5 mg/L were 5.8% and 6.8% respectively. Between-run coefficients of variation at mean concentrations of 15.9 mg/L and 45.7 mg/L were 13.4% and 9.8% respectively. Several volatile substances were tested as potential interfering compounds with propane having a retention time identical to that of difluoroethane. CONCLUSIONS: This method requires minimal sample preparation, is rapid and reproducible, can be modified for the quantitation of other volatiles, and could be automated using an automatic sampler/injector system.

Cranial vault expansion: a comparison of magnetic coupled distraction to traditional surgical repositioning.

We compared the effectiveness of transcutaneously activated magnetic distraction of an osteotomized cranial bone flap to surgical repositioning of the flap with immediate, rigid internal fixation. Thirty immature rabbits were studied. All 30 rabbits underwent complete circumferential osteotomies of both parietal bones and postoperatively all were fitted with head frames. The rabbits were divided into 4 groups. The experimental magnetic distraction group consisted of 10 animals (group 1). In these rabbits magnets were secured to both parietal bones and magnets of opposite polarity were placed in the headframes. Each morning, the magnets in the head-frames were moved 0.25 mm farther away from the skull; this continued for 20 days for a total setback of 5 mm. Five animals served as the magnetic distraction controls; in these animals magnets were placed on the parietal bones but none were attached to the headframes (group 2). The experimental surgical repositioning group consisted of 10 rabbits (group 3). In each the parietal bones were elevated and fixed 5 mm above the rest of the skull using vitallium mesh and screws. Five rabbits made up the surgical respositioning control group (group 4). In these animals, parietal osteotomies were performed but the bones were secured to the skull in their original positions using hardware identical to that used in the experimental group. Six weeks later all of the animals were sacrificed. Two significant differences were identified between the experimental groups: (1) the cranial contours of the animals in the magnetic distraction group were rounded while those of the surgically repositioned group were acutely angled; (2) the osteotomies in rabbits in the magnetic distraction group were essentially completely ossified while in rabbits in the surgically repositioned group there were obvious gaps at the osteotomy sites that were filled with fibrous tissue. These conclusions support the potential utility of magnetically activated distraction as an alternative to current methods of cranial vault remodeling.

Stroke associated with marijuana abuse.

We present the case of a 15-year-old with a cerebellar infarct that involved multiple arterial territories. It was temporally related to, and probably caused by, heavy marijuana use. While the mechanism of marijuana-associated stroke is unclear, the drug is known to cause hypotension and to impair peripheral vasomotor reflexes. We suspect that the child had diminished cerebral autoregulatory capacity and developed the stroke during a period of hypotension.

Exophytic juvenile pilocytic astrocytomas of the posterior fossa.

In children, posterior fossa juvenile pilocytic astrocytomas are common tumors. Radiologically, primarily extra-axial brainstem pilocytic astrocytomas are uncommon and extra-axial cerebellar pilocytic tumors are exceptional. We report two cases of such exophytic tumors, contrasting their presentation, imaging appearance, and prognosis. We also report the radiographic features of posterior fossa juvenile pilocytic astrocytomas from a 5-year review of our institutional experience.

Death due to inhalation of ethyl chloride.

A 30-year-old white male was found dead in a locked apartment with a rag held loosely in his mouth. Four cans (3 empty, 1 partially empty) containing ethyl chloride and labeled as VCR head cleaner were found next to the body. Phenylpropanolamine and low therapeutic levels of diazepam (64 microg/L) and nordiazepam (126 microg/L) were detected during toxicological analysis. An unidentified peak was observed when performing ethanol analysis by headspace gas chromatography. The peak was identified as ethyl chloride and the concentrations in the blood, urine, vitreous, brain, and lungs of the deceased were 423 mg/L, 35 mg/L, 12 mg/L, 858 mg/kg, and 86 mg/kg, respectively. The results were compared with previously reported levels of ethyl chloride in blood and vitreous and, based on a literature search, we believe that this is the first report of ethyl chloride levels in tissue.