Fiber-integrated frequency-doubling of a picosecond Raman laser to 560 nm.

We report the development of a fiber-integrated picosecond source at 560 nm by second harmonic generation of a Raman fiber laser. A picosecond ytterbium master oscillator power fiber amplifier is used to pulse-pump a Raman amplifier, which is seeded by a continuous wave distributed feedback laser diode operating at 1120 nm. The pulse train generated at 1120 nm is frequency-doubled in a fiber-coupled periodically-poled lithium niobate crystal module, producing 450 mW of average power at 560 nm with a pulse duration of 150 ps at a repetition rate of 47.5 MHz. The near diffraction-limited (M(2) = 1.02) collimated output beam is ideal for super-resolution microscopy applications.

Fiber-integrated 780 nm source for visible parametric generation.

We report the development of a fully fiber-integrated pulsed master oscillator power fibre amplifier (MOPFA) source at 780 nm, producing 3.5 W of average power with 410 ps pulses at a repetition rate of 50 MHz. The source consists of an intensity modulated 1560 nm laser diode amplified in an erbium fiber amplifier chain, followed by a fiber coupled periodically poled lithium niobate crystal module for frequency doubling. The source is then used for generating visible light through four-wave mixing in a length of highly nonlinear photonic crystal fiber: 105 mW at 668 nm and 95 mW at 662 nm are obtained, with pump to anti-Stokes conversion slope efficiencies exceeding 6% in both cases.

Females without reflux symptoms or gastroesophageal reflux disease have less distal esophageal acid exposure than males without reflux symptoms or gastroesophageal reflux disease.

Ambulatory 24-hour esophageal pH monitoring is the gold standard examination to assess esophageal acid exposure. Gender-related variation is a well-recognized physiologic phenomenon in health and disease. To date, limited gender-specific 24-hour esophageal pH monitoring data are available. The aim of this study was to obtain values of esophageal pH monitoring in males and females without reflux symptoms or gastroesophageal reflux disease (GERD) to determine if gender variation exists in esophageal acid exposure among individuals without these factors. Twenty-four-hour dual esophageal pH monitoring was performed in male and female volunteers without reflux symptoms or GERD. Values for total number of reflux episodes, episodes longer than 5 minutes, total reflux time in minutes, % time with pH below 4, and longest reflux episode in the proximal/distal esophagus were obtained and recorded for both groups. The distal channel was placed 5 cm and proximal channel 15 cm above the manometrically determined lower esophageal sphincter. Means were compared using an independent sample t-test. Sixty-seven males and 69 females were enrolled. All subjects completed esophageal 24-hour pH monitoring without difficulty. There was no age or body mass difference between groups. Females had significantly fewer reflux episodes at both esophageal measuring sites and, significantly less total reflux time and % time with pH below 4 in the distal esophagus than males. All other parameters were similar. Significant gender-related differences exist in esophageal acid exposure, especially in the distal esophagus in individuals without reflux symptoms or GERD. These differences underscore the need for gender-specific reference values for 24-hour pH monitoring, allowing for an accurate evaluation of esophageal acid exposure in symptomatic patients.

Reflux episodes are similar in healthy African Americans and non-Hispanic whites.

Ambulatory esophageal pH monitoring is the current gold standard diagnostic exam for gastroesphageal reflux disease. Presently, no data are available for normal 24-hour esophageal pH monitoring among any US ethnic group. The aim of the present study was to obtain normal values of 24-hour esophageal pH monitoring in healthy adult African American (AA) volunteers and compare these with values obtained in healthy non-Hispanic white (nHw) volunteers to determine if ethnic variation exists in 24-hour esophageal pH testing. Twenty-four-hour dual esophageal pH monitoring was performed in healthy AA and nHw. Values for total number of reflux episodes, episodes longer than 5 min, total reflux time in minutes, and longest reflux episode in the proximal and distal esophagus were obtained for both ethnic groups. Differences between groups were considered significant if P < 0.05. Eighty subjects volunteered for the study and completed 24-hour pH testing. Forty-one were AAs and 39 were nHws, with males making up 49% of each group. The AAs were older and had higher body mass index than the nHws. No difference was observed between the AA and the nHw subjects for any measured pH parameter in either the proximal or distal esophagus. There is no difference in values obtained during esophageal pH monitoring in healthy African Americans and non-Hispanic whites. This indicates that the currently accepted normal values of ambulatory esophageal pH monitoring are readily applicable to African Americans and can be used without compromising diagnostic accuracy in this ethnic group.

Long base line interferometry: a new technique.

The technique of using magnetic-tape recorders and atomic frequency standards to operate two widely separated radio telescopes as a phase-coherent interferometer when the stations have no radio-frequency connecting link has been successfully tested at the National Research Council of Canada's Algonquin Radio Observatory.

Ethnic variation in lower oesophageal sphincter pressure and length.

BACKGROUND: Oesophageal manometry (OM) is used to diagnose oesophageal motor disorders. Normal values of OM among United States ethnic groups are only available for Hispanic Americans (HA). AIM: To obtain normal values of OM in adult African American (AA) volunteers, compare these with those obtained in HA and non-Hispanic white (nHw) volunteers to determine if ethnic variation in normal oesophageal motor function exists. METHODS: Healthy AA, HA and nHw were recruited from the Jacksonville metropolitan area. Ethnicity was self-reported. Exclusion criteria were symptoms suggestive of oesophageal disease, medication use or concurrent illness affecting OM. All underwent OM using a solid-state system with wet swallows. Resting lower oesophageal sphincter (LOS) pressure and LOS length were measured at mid-expiration, while per cent peristaltic contractions, distal oesophageal contraction velocity, amplitude and duration were measured after 5 cc water swallows. RESULTS: Fifty-six AA, 20 HA and 48 nHw were enrolled. All completed OM. AA had significantly higher resting LOS pressure, LOS length and distal oesophageal contraction duration than nHw (P < 0.05). CONCLUSIONS: Significant ethnic exist in OM findings between AA and nHw. These underscore the need for ethnic specific reference values for OM to allow for correct diagnosis of oesophageal motor disorders in AA.