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.

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.

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.

De novo expression of the class-A macrophage scavenger receptor conferring resistance to apoptosis in differentiated human THP-1 monocytic cells.

The class-A macrophage scavenger receptor (MSR) is a trimeric multifunctional protein expressed selectively in differentiated monomyeloid phagocytes which mediates uptake of chemically modified lipoproteins and bacterial products. This study investigated whether MSR plays a role in the regulation of apoptosis, a model of genetically programmed cell death. De novo expression of MSR occurred in human THP-1 monocytic cells differentiated with phorbol esters, which activated a nuclear transcription factor binding to the Ap1/ets-like domain of the MSR promoter. The phorbol ester-stimulated THP-1 cells also expressed increased levels of the pro-apoptotic gene products, caspase-3 and Fas ligand, but the cells exhibited no change in apoptosis. Global activation of GTP-binding proteins with fluoride anions triggered apoptosis of THP-1 cells in a time- and concentration-dependent manner, demonstrated by nuclear shrinkage and fragmentation and internucleosomal DNA fragmentation. However, the MSR-expressing THP-1 macrophage-like cells showed a significant reduction in apoptosis compared to undifferentiated control THP-1 cells, which produce MSR at undetectable levels. Fluoride stimulation also triggered apoptosis of human Jurkat T cells. Stimulation with phorbol ester made no difference in apoptosis between treated and untreated Jurkat cells. Finally, Chinese hamster ovary (CHO) cells overexpressing the class-A MSR type I by cDNA transfection showed markedly increased resistance to G-protein-coupled apoptosis. Thus, de novo expression of MSR associated with monocyte maturation into macrophages appears to confer the resistance of macrophages to apoptotic stimulation by G-protein activation.

Chronic NMDA receptor blockade or muscimol inhibition of cerebellar cortical neuronal activity alters the development of spinocerebellar afferent topography.

The requirement for cerebellar cortical neuronal activity in the development of spinocerebellar afferent topography was investigated in neonatal rats. In adult rats lower thoracic-upper lumbar spinocerebellar projections are localized to sharply circumscribed patches in the granule cell layer of the cerebellar anterior lobe. In transverse sections these patches appear as sagittally oriented stripes. This pattern develops postnatally as many spinal axons which initially project between the incipient stripes are eliminated thereby sharpening the stripe boundaries. We attempted to alter cerebellar cortical neuronal activity in neonatal animals to study the effects of these changes on the development of spinocerebellar stripes. In some experiments glutaminergic excitatory synaptic transmission was chronically blocked with the N-methyl-D-aspartate (NMDA) receptor antagonist 2-aminophosphovaleric acid (APV). In other experiments postsynaptic activity was directly inhibited by the gamma-aminobutyric acid agonist muscimol. Chronic exposure to APV or to muscimol did not affect the initial development of spinocerebellar projections; many spinal axons were present in the anterior lobe and arranged in incipient stripes. Both the APV and the muscimol appeared to prevent the elimination of interstripe projections; consequently the boundaries of the stripes remained poorly defined. These findings suggest that cerebellar cortical neuronal activity is a necessary requirement for the refinement of spinal afferent topography in the anterior lobe.

Endoscopic coagulation of the choroid plexus using the Nd:YAG laser: initial experience and proposal for management.

Although most patients with hydrocephalus are treated effectively with ventriculoperitoneal shunts, a small group fails to respond to diversion procedures. In some patients within this group, hydrocephalus may be caused in part by the overproduction of the cerebrospinal fluid (CSF). In other patients, previous shunt infections may limit the ability of the peritoneum to absorb fluid, and patient response to a ventriculoperitoneal shunt may be improved by reducing CSF production. We discuss a case of a 29-month-old hydrocephalic infant with a ventriculoperitoneal shunt who had ascites. Computed tomography showed bilateral symmetrical enlargement of the choroid plexus. Repeated cultures of the CSF and shunt tubing were sterile, and the daily production of the CSF exceeded 1000 ml. Therapy with acetazolamide decreased the CSF output temporarily, but it was discontinued after serious electrolyte abnormalities occurred. The endoscopic coagulation of the choroid plexus with a neodymium:YAG laser transmitted through a flexible quartz fiber decreased CSF production effectively. This procedure may be useful in a variety of clinical conditions associated with hydrocephalus or with other intraventricular lesions.

Effects of amount of helplessness training and internal-external locus of control on mood and performance.

Based on Wortman and Brehm's integration of reactance theory with Seligman's model of learned helplessness, an investigation was conducted to examine the effects of amount of helplessness training and internal--external locus of control on subsequent task performance and on self-ratings of mood. Subjects were divided into "internal" and "external" groups and were then given either high, low, or no helplessness training on a series of concept-formation problems. After completing a mood checklist, all subjects worked on an anagram task presented as a second experiment by a second experimenter. The results revealed that internals exhibited greater performance decrements and reported greater depression under high helplessness than did externals. In the low helplessness conditions, internals tended to perform better than control subjects, while externals tended to perform worse than control subjects; low helplessness subjects also reported the highest levels of hostility. The results are discussed within the context of Wortman and Brehm's integration of reactance and learned helplessness theories.

Organization of transient projections from the primary somatosensory cortex to the cerebellar nuclei in kittens.

The organization of transient projections from the primary somatosensory cortex (SI) to the cerebellar nuclei was studied in neonatal cats. Tritiated amino acids were injected into the face, forelimb, or hindlimb areas of SI in 4 to 6-day-old kittens. The animals were killed 3 to 6 days later and their brains processed for autoradiography. Labeled axons were found bilaterally in the cerebellar nuclei, but, although the distribution of label was similar on both sides, the label was always much denser on the side of the injection. Each area of SI demonstrated a characteristic pattern of projection to the cerebellar nuclei. Neurons in the hindlimb area projected to the rostral part of the anterior interpositus nucleus, the caudal part of the posterior interpositus nucleus, and the medial quadrant of the dentate nucleus. Fibers from the forelimb area were directed to the caudal part of the anterior interpositus and the rostral part of the posterior interpositus. Projections from the face area terminated principally in the caudal pole of the posterior interpositus. A small transitional area between the interpositus and fastigial nuclei was labeled with all injections. These data indicate that transient neocortical projections to the deep nuclei are organized and that the somatotopy of these projections is similar to that of other cerebellar nuclear connections.

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.

The risk of abdominal operations in children with ventriculoperitoneal shunts.

Ventriculoperitoneal (VP) shunts are the operations of choice for patients with hydrocephalus in most pediatric hospitals. Children with VP shunts frequently undergo abdominal operations unrelated to their shunts, which might lead to shunt infections or to malfunctions related to adhesions. Although prophylactic antibiotics are usually used in this setting, there are few data to support their use, or to assess other risks to the shunt from the abdominal procedures. Consequently, we reviewed the records of 37 children with VP shunts who underwent a total of 44 abdominal operations. In 8 cases, the genitourinary (GU) tract was opened (ureteral reimplantation, bladder augmentation, nephrectomy), whereas in 18 patients the gastrointestinal (GI) tract was opened (appendectomy, gastrostomy, small/large bowel resection). In 18 operations neither GI nor GU tract was opened (lysis of adhesions, herniorrhaphy, orchiopexy). Antibiotic coverage was highly variable: 9 received no antibiotics, 9 received antibiotics only postoperatively, 4 were given antibiotics only preoperatively, and in 22 cases antibiotics were given both preoperatively and postoperatively. One shunt that was involved in a periappendiceal abscess was exteriorized and later successfully replaced. In the remaining cases, no episodes of shunt infection or malfunction occurred in 1 to 10 years of follow-up. Likewise, no abdominal cerebrospinal fluid pseudocysts formed as a result of abdominal adhesions. These data demonstrate that children with VP shunts can safely undergo abdominal operations, even when the GI or GU systems are opened, with minimal risk of shunt infection or malfunction. Rigid protocols of prophylactic antibiotics cannot be supported by this series.

Early hypotension worsens neurological outcome in pediatric patients with moderately severe head trauma.

PURPOSE: The objective of this study was to determine the morbidity associated with hypotension in the resuscitative phase of pediatric head trauma. METHODS: A retrospective review (1990 to 1995) was performed at a level-1 pediatric trauma facility. Inclusion criteria included a Glasgow coma score (GCS) of 6 to 8 and absence of penetrating trauma or bleeding disorders. The GCS was assigned using a postresuscitation examination by a neurosurgeon. Hypotension was defined as a blood pressure reading of less than the fifth percentile for age that lasted longer than 5 minutes. Episodes were monitored from the onset of injury through the first 24 hours of hospitalization. Glasgow outcome scale (GOS) was assigned based on a 3-month follow-up evaluation. Analysis of variance (ANOVA) and contingency table analysis were performed on all groups, and a P value of less than .05 was taken to represent statistical significance. RESULTS: Seventy-two patients met inclusion criteria. They had a mean GCS of 7.2 and a mean age of 6 years; 97% survived. Early hypotension was associated with worse neurological outcome (GOS) and prolonged hospitalization. There was no significant correlation between GOS and age, gender, injury mechanism, associated injuries, or transport time. CONCLUSIONS: These data suggest that maintaining adequate blood pressure during the early resuscitation of pediatric blunt head trauma patients may improve neurological outcome.

Leuprolide acetate for inducing ovulation in women undergoing ovarian stimulation.

OBJECTIVE: To determine whether leuprolide acetate (LA), given subcutaneously at the time of follicular maturity in stimulated cycles, can result in ovulation and in vivo fertilization. STUDY DESIGN: Sixty-seven women underwent 91 cycles of ovarian stimulation (OS) and received a single subcutaneous injection of 1 mg of LA when follicular maturity was reached. Only clomiphene citrate (CC) was used for 15 cycles, CC/FSH for 66 cycles and human menopausal gonadotropin only for 10 cycles. Thirty-four cycles were in oligoovulatory women. Eighty-two cycles were combined with intra-uterine insemination. RESULTS: Viable pregnancies occurred in 21/91 cycles (23%). Forty-two women testing with home urinary luteinizing hormone (LH) kits noted a surge. Seventy-one or 71 cycles demonstrated a biphasic curve. Sixty-eight of 75 cycles demonstrated follicular collapse (91%). Six women had serum LH levels of 12 +/- 4, 136 +/- 22 and 17 +/- 3 mIU/mL before and 12 and 36 hours after LA, respectively. CONCLUSION: LA successfully induced ovulation, fertilization and luteinization in women receiving OS. The pituitary LH response to LA appeared to be normal in women having OS. The pregnancy rate was similar to that generally observed with human chorionic gonadotropin (hCG). A large, prospective, randomized study may be warranted to compare LA to hCG since the subcutaneous route of LA administration and potential for reduced hyperstimulation could be significant advantages, making OS more practical and safe.

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.

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.

Two traffic fatalities related to the use of difluoroethane.

The 18-year-old white male driver and 17-year-old white male passenger of an automobile were killed when their vehicle crossed the median of a 4-lane highway and collided with a minivan. A can of airbrush propellant was found in the automobile of the deceased. The only drug detected during initial toxicological analyses was 130 mg/L ethanol in the blood of the driver. When performing ethanol analysis by headspace gas chromatography, an unidentified peak was observed in the blood of both deceased. This peak was identified as difuoroethane (Freon 152), the propellant in the aerosol can found in the automobile. The concentrations of difluoroethane in the blood of the driver and passenger were 78 mg/L and 35 mg/L, respectively. Based on a literature search we believe that this is the first report of the quantitation of difluoroethane in biological samples.

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.