Pluto's Interaction With Energetic Heliospheric Ions.

Pluto energies of a few kiloelectron volts and suprathermal ions with tens of kiloelectron volts and above. We measure this population using the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument on board the New Horizons spacecraft that flew by Pluto in 2015. Even though the measured ions have gyroradii larger than the size of Pluto and the cross section of its magnetosphere, we find that the boundary of the magnetosphere is depleting the energetic ion intensities by about an order of magnitude close to Pluto. The intensity is increasing exponentially with distance to Pluto and reaches nominal levels of the interplanetary medium at about 190R P distance. Inside the wake of Pluto, we observe oscillations of the ion intensities with a periodicity of about 0.2 hr. We show that these can be quantitatively explained by the electric field of an ultralow-frequency wave and discuss possible physical drivers for such a field. We find no evidence for the presence of plutogenic ions in the considered energy range.

Anxiety and quality of life in phobic dental patients.

Little is known about the anxiety patients experience before attending for dental treatment. The aim of this study was to determine, in dentally phobic patients, the temporal relationship of pre-operative anxiety levels, and the disruption to daily life caused by this. Twenty-four phobic and 19 comparison (non-phobic) dental patients were recruited. Four validated questionnaires were used to assess anxiety and quality of life, which each patient completed for 5 days prior to, and on the day of, treatment. Those in the experimental group were found to have significantly greater levels of dental and general anxiety, and a significantly lower quality of life compared with those in the comparison group. Significant temporal relationships were found with all of the questionnaires. Dental and general anxiety scores were significantly correlated with quality-of-life measures. This study suggests that phobic dental patients are experiencing significant increased anxiety, and significant negative quality-of-life effects, in this period.

Medical management of parapneumonic pleural disease.

Considerable heterogeneity exists in the management of parapneumonic pleural disease. A randomized controlled trial (RCT) demonstrated the effectiveness of small-catheter drainage with fibrinolysis, but surgical devotees suggest this may only be applicable to "early" cases. We examined evidence-based medical management in "all-comers." We performed a retrospective database analysis of the management of all children with complex pleural effusion admitted to the John Radcliffe Hospital over the 7-year period 1996-2003. One hundred and ten children were admitted. Ten were excluded as they were part of a multicenter RCT and had received intrapleural saline instead of urokinase. Of the remaining 100, 51 were female and 49 male. Median age on admission was 5.8 years (range, 0.3-16.5). Symptoms preadmission averaged 11 days, with December the most common month for presentation. Ninety-six underwent chest ultrasound, confirming an effusion in all, described as loculated/septated (68) or echogenic (11). In 17 cases, no specific comment was made regarding the nature of the fluid seen on ultrasound. Ninety-five had subsequent chest tube drainage and then received intrapleural fibrinolysis with urokinase. An etiological organism was identified in 21 cases (21%) (Streptococcus pneumoniae in 10, group A Streptococcus in 5, Staphylococcus aureus in 4, Haemophilus influenzae in 1, and coliform in 1). In a further 9 cases (9%), Gram-positive organisms were seen on pleural fluid microscopy, but did not grow on culture. Two (2%) required surgery due to the persistence of symptoms and an inadequate response to medical management. Median duration of admission was 7 days (range, 2-21 days); median duration of stay from intervention was 5 days (range, 2-19 days). At median follow-up of 8 weeks (range, 3-20 weeks), all children were symptom-free, with minimal pleural thickening on chest X-ray. In conclusion, antibiotic therapy with chest drain insertion and intrapleural urokinase is effective in treating complex parapneumonic effusion and is associated with a good long-term outcome.

Ventriculoperitoneal shunt block: what are the best predictive clinical indicators?

AIMS: To evaluate the predictive value of symptoms, signs, and radiographic findings accompanying presumed ventriculoperitoneal (VP) shunt malfunction, by comparing presentation with operative findings and subsequent clinical course. METHODS: Prospective study of all 53 patient referrals to a paediatric neurosurgical centre between April and November 1999 with a diagnosis of presumed shunt malfunction. Referral pattern, presenting symptoms and signs, results of computed tomography (CT) scanning, operative findings, and clinical outcome were recorded. Two patient groups were defined, one with proven shunt block, the other with presumed normal shunt function. Symptomatology, CT scan findings, and the subsequent clinical course for each group were then compared. RESULTS: Common presenting features were headache, drowsiness, and vomiting. CT scans were performed in all patients. Thirty seven had operatively proven shunt malfunction, of whom 34 had shunt block and three shunt infection; 84% with shunt block had increased ventricle size when compared with previous imaging. For the two patient groups (with and without shunt block), odds ratios with 95% confidence intervals on their presenting symptoms were headache 1.5 (0.27 to 10.9), vomiting 0.9 (0.25 to 3.65), drowsiness 10 (0.69 to 10.7), and fever 0.19 (0.03 to 6.95). Every patient with ventricular enlargement greater than their known baseline had a proven blocked shunt. CONCLUSIONS: Drowsiness is by far the best clinical predictor of VP shunt block. Headache and vomiting were less predictive of acute shunt block in this study. Wherever possible CT scan findings should be interpreted in the context of previous imaging. We would caution that not all cases of proven shunt blockage present with an increase in ventricle size.

High-power cladding-pumped Tm-doped silica fiber laser with wavelength tuning from 1860 to 2090 nm.

A high-power double-clad Tm-doped silica fiber laser, pumped by two beam-shaped and polarization-coupled diode bars at 787 nm, was wavelength tuned by use of an external cavity containing a diffraction grating. The Tm fiber laser produced a maximum output power of 7 W at 1940 nm for 40 W of incident diode power and was tuned over a wavelength range of 230 nm from 1860 to 2090 nm, with >5-W output power over the range 1870-2040 nm. The prospects for further improvement in performance and extension of the tuning range are discussed.

125-mJ diode-pumped injection-seeded Ho:Tm:YLF laser.

We describe a diode-pumped, room-temperature Ho:Tm:YLF power oscillator with an optical-to-optical efficiency of 0.03. A Q -switched output energy of as much as 125 mJ at 6 Hz with a pulse width of 170 ns was obtained. Single-frequency, nearly transform-limited operation of the laser was achieved by injection seeding. Laser performance as a function of laser rod temperature and pump intensity was also investigated. The high power and high beam quality of this laser make it well suited for use as a coherent wind lidar transmitter on a space platform.

Flash-lamp-pumped Ho:Tm:Cr:YAG and Ho:Tm:Er:YLF lasers: experimental results of a single, long pulse length comparison.

Flash-lamp-pumped, room-temperature Ho:Tm:Cr:YAG and Ho:Tm:Er:YLF are compared for single but long pulse operation, with pulse lengths of approximately 1.0 mus. Under similar operating conditions in normal-mode operation, a slope efficiency of 0.0331 was observed for Ho:Tm:Er:YLF compared with 0.0047 for Ho:Tm:Cr:YAG. For Q-switched operation, Ho:Tm:Er:YLF yielded a slope efficiency of 0.0075. In comparison, a slope efficiency of 0.0012 was obtained for Ho:Tm:Cr:YAG. Two methods of producing long pulse lengths are compared: pulse selection of normal-mode relaxation oscillations and Q-switching in a long resonator. Theoretical models developed in a companion paper for normal-mode relaxation oscillations and Q-switching in quasi-four-level solid-state lasers are in agreement with the experimental results.

Flash-lamp-pumped Ho:Tm:Cr:YAG and Ho:Tm:Er:YLF lasers: modeling of a single, long pulse length comparison.

Two methods of producing the long pulse lengths that promote efficient extraction of energy from low-gain, quasi-four-level lasers are analyzed. A long pulse length output can mitigate laser-induced damage effects and can be generated in quasi-four-level lasers by two disparate methods. One method utilizes Q-switching techniques in resonators designed to extend the pulse length and another utilizes the first pulse in a relaxation oscillation pulse train. Models for quasi-four-level lasers are derived here taking into account the nonnegligible thermal population of the lower laser level. Closed-form expressions are derived for both modes of operation of quasi-four-level laser systems so the parametric dependencies of both forms of operation become obvious, allowing facile comparison. In addition, a combined absorption and quantum efficiency, germane for flash-lamp pumping, is calculated for both Cr and Er sensitizers. Although the former has the advantage of broad absorption bands, the latter has the advantage of a quantum efficiency approaching 3.

Room-temperature lasing of end-pumped Ho:Lu(3)Al(5)O(12).

Room-temperature lasing at 2.1-microm has been demonstrated in Ho:Lu(3)Al(5)O(12) with a slope efficiency of 82% and a threshold energy of 4.4 mJ. A maximum absorbed energy of 17 mJ yielded 10 mJ of laser output energy. To simulate diode-pumping experiments, a tunable Co:MgF(2) laser operating at 1.878 microm was used to achieve lasing on (5)I(7) ? (5)I(8) transitions.

Diode-pumped long-pulse-length Ho:Tm:YLiF(4) laser at 10 Hz.

An optical efficiency of 0.052 under normal mode operation for diode-pumped Ho:Tm:YLiF(4) at a pulse repetition frequency of 10 Hz has been achieved. Laser output energy of 30 mJ in single Q-switched pulses with 600-ns pulse length were obtained for an input energy of 3 J. A diffusion-bonded birefringent laser rod consisting of Ho:Tm-doped and undoped pieces of YLF was utilized for 10-Hz operation.

Diode-pumped, room-temperature Tm:LuAG laser.

A diode-pumped, room-temperature Tm:LuAG laser demonstrated a total optical-to-optical efficiency of 0.073 and an optical-to-optical differential efficiency as high as 0.236. Laser performance and operating wavelength were investigated as a function of the Tm concentration. The highest laser output energy was achieved with a Tm concentration of 0.04 and at a wavelength of 2.0238 µm.

Spectroscopic and lasing properties of Ho:Tm:LuAG.

Ho:Tm:LuAG has been grown, examined spectroscopically, and lased at 2.1 microm. Ho:Tm:LuAG was selected for this experimental investigation when quantum-mechanical modeling predicted that it would be a good laser material for Ho laser operation on one of the (5)I(7) to (5)I(8) transitions. Lasing was achieved at 2.100 microm, one of the three wavelengths predicted to be most probable for laser action.

Investigation of 2.1-microm lasing properties of Ho:Tm:Cr:YAG crystals under flash-lamp pumping at various operating conditions.

Flash-lamp-pumped normal-mode and Q-switched 2.1-microm laser operations of Ho:Tm:Cr:YAG crystals have been evaluated under a wide variety of experimental conditions in order to determine an optimum lasing condition and to characterize the laser outputs. Q-switched laser-output energies equal to or in some cases more than the normal-mode laser energies were obtained in the form of a strong single spike by optimizing the opening time of a lithium niobate Q switch. The increase of the normal-mode laser slope efficiency was observed with the increase of the Tm concentration from 2.5 to 4.5 at. % at operating temperatures from 120 K to near room temperature. Laser transitions were observed only at 2.098 and 2.091 microm under various conditions. The 2.091-microm laser transition appeared to be dominant at high-temperature operations with low-reflective-output couplers and to have an energy-level assignment from 5313 cm(-1) to 534 cm(-1) or (and) from 5313 cm(-1) to 536 cm(-1).

Performance of Ho:YAG as a function of temperature.

The performance of two multiply doped Ho:YAG lasers has been characterized as a function of the laser rod temperature. From the experimental results, the dependence of the slope efficiency and threshold on temperature has been extracted. Threshold can be correlated with the occupation of the lower laser level. Implications on the optimum operating temperature are discussed.

Blackbody absorption efficiencies for six lamp pumped Nd laser materials.

Utilizing high resolution spectra, the absorption efficiency for six Nd laser materials was calculated as functions of the effective blackbody temperature of the lamp and laser crystal size. The six materials were Nd:YAG, Nd:YLF, Nd:Q-98 Glass, Nd:YVO(4), Nd:BEL, and Nd:Cr:GSGG. Under the guidelines of this study, Nd:Cr:GSGG's absorption efficiency is twice the absorption efficiency of any of the other laser materials.

Parametric amplification in AgGaSe(2).

AgGaSe(2) has been grown, annealed, and characterized for the mid-IR. Characterization includes measurement of the average power-limiting factors including absorption and the variation of the refractive indices with temperature. Using specially annealed crystals 20 mm long and a Ho:YAG pump, parametric amplification at 3.39 microm has achieved a gain of 2.9 with a peak power input of only 8 MW/cm(2).