Scintillation observations at Ancon and Jicamarca Observatories

Satellite scintillation and diffraction pattern scale size distribution from ionospheric irregularitie

Observations of meteor-head echoes using the Jicamarca 50 MHz radar in interferometer mode

International audienceWe present results of recent observations of meteor-head echoes obtained with the high-power large-aperture Jicamarca 50 MHz radar (11.95° S, 76.87° W) in an interferometric mode. The large power-aperture of the system allows us to record more than 3000 meteors per hour in the small volume subtended by the 1° antenna beam, albeit when the cluttering equatorial electrojet (EEJ) echoes are not present or are very weak. The interferometry arrangement allows the determination of the radiant (trajectory) and speed of each meteor. It is found that the radiant distribution of all detected meteors is concentrated in relative small angles centered around the Earth's Apex as it transients over the Jicamarca sky, i.e. around the corresponding Earth heading for the particular observational day and time, for all seasons observed so far. The dispersion around the Apex is ~18° in a direction transverse to the Ecliptic plane and only 8.5° in heliocentric longitude in the Ecliptic plane both in the Earth inertial frame of reference. No appreciable interannual variability has been observed. Moreover, no population related to the optical (larger meteors) Leonid showers of 1998?2002 is found, in agreement with other large power-aperture radar observations. A novel cross-correlation detection technique (adaptive match-filtering) is used in combination with a 13 baud Barker phase-code. The technique allows us to get good range resolution (0.75 km) without any sensitivity deterioration for the same average power, compared to the non-coded long pulse scheme used at other radars. The matching Doppler shift provides an estimation of the velocity within a pulse with the same accuracy as if a non-coded pulse of the same length had been used. The velocity distribution of the meteors is centered around 60 km s?1 corresponding to velocities slightly under the solar escape velocity (72 km s?1). Less than 8% of the velocities correspond to interstellar speeds. Higher relative velocity accuracy is obtained by cross-correlating the echoes from pulse-to-pulse, albeit with an ambiguous velocity displacement which cannot be resolved with the current observing technique. This higher relative accuracy allows the precise measurement of the deceleration of the meteors as they enter the atmosphere. In addition, an independent radial velocity is determined from the derivative of the instantaneous position. Other statistical distributions of interest are also presented

Who comes back with what: a retrospective database study on reasons for emergency readmission to hospital in children and young people in England

OBJECTIVE: To determine the proportion of children and young people (CYP) in England who are readmitted for the same condition. DESIGN: Retrospective cohort study. SETTING: National administrative hospital data (Hospital Episode Statistics). PARTICIPANTS: CYP (0-year-olds to 24-year-olds) discharged after an emergency admission to the National Health Service in England in 2009/2010. MAIN OUTCOME MEASURES: Coded primary diagnosis classified in six broad groups indicating reason for admission (infection, chronic condition, injury, perinatal related or pregnancy related, sign or symptom or other). We grouped readmissions as ≤30 days or between 31 days and 2 years after the index discharge. We used multivariable logistic regression to determine factors at the index admission that were predictive of readmission within 30 days. RESULTS: 9% of CYP were readmitted within 30 days. Half of the 30-day readmissions and 40% of the recurrent admissions between 30 days and 2 years had the same primary diagnosis group as the original admission. These proportions were consistent across age, sex and diagnostic groups, except for infants and young women with pregnancy-related problems (15-24 years) who were more likely to be readmitted for the same primary diagnostic group. CYP with underlying chronic conditions were readmitted within 30 days twice as often (OR: 1.93, 95% CI 1.89 to 1.99) compared with CYP without chronic conditions. CONCLUSIONS: Financial penalties for readmission are expected to incentivise more effective care of the original problem, thereby avoiding readmission. Our findings, that half of children come back with different problems, do not support this presumption

Responses to concerns about child maltreatment: a qualitative study of GPs in England

To provide a rich description of current responses to concerns related to child maltreatment among a sample of English general practitioners (GPs)

Statistical characteristics of low-latitude ionospheric field-aligned irregularities obtained with the Piura VHF radar

International audienceWe present a summary of the statistical characteristics of echoes from ionospheric (E- and F-region) field-aligned irregularities obtained with the Piura VHF radar. This radar is located at ~ 7.0° dip latitude, just outside the equatorial electrojet (EEJ) region. Our results are based on (1) intermittent observations made between 1991 and 1999 just few days a year, and (2) continuous observations made between January 2000 and June 2001. During most of the intermittent observations, simultaneous measurements of EEJ and equatorial spread F (ESF) irregularities were performed with the Jicamarca VHF radar. From the continuous measurements, we have obtained the diurnal and seasonal characteristics of a variety of parameters (percentage of occurrence, signal-to-noise ratio and/or Doppler velocities) from the lower and upper E-region irregularities and also from F-region irregularities over Piura. For example, we have found that (1) the E-region echoes are stronger and occur more frequently during local summer (i.e. between December and March); (2) between May and June, the E-region echoes are weaker and occur less frequently; moreover, during these months, a semidiurnal wave with large amplitudes is observed in the meridional wind (> 100 ms- 1); (3) there is vertical wavelength of about 20 km in the Doppler velocity, particularly after midnight; (4) the lower (upper) E-region Doppler velocities are influenced mainly by meridional winds (equatorial F-region vertical drifts). In addition, we have observed that the seasonal and daily occurrences of Piura F-region irregularities are similar to the occurrence of topside ESF irregularities over Jicamarca. The likelihood of occurrence of F-region irregularities over Piura and, therefore, topside ESF over Jicamarca is greater when there are no E-region irregularities over Piura. On the other hand, there is more probability of observing bottomtype/bottomside ESF irregularities over Jicamarca when E-region irregularities are observed over Piura

SNP-induced Dilation Following a Short-term Intraluminal Pressure Increase in Aged Skeletal Muscle Feed Arteries

A decline in peripheral vascular function occurs with age and is associated with an increased risk for cardiovascular disease. Moderate, aerobic exercise has been documented to improve or reverse the age-related decline in vascular function. The signal(s) associated with exercise responsible for the improvement in vascular function is not known; however, increased intraluminal pressure that occurs during a bout of exercise has been proposed to play an integral role. Previously, we reported that exposure to a short-term increase in intraluminal pressure improves endothelium-dependent vasodilator responses in aged arteries. The purpose of this study was to determine whether pressure treatment enhances endothelium-independent vasodilator responses. We hypothesized that a short-term (1 h) increase in intraluminal pressure, to mimic the intraluminal pressure believed to be present during a 1 h bout of exercise, would not improve endothelium-independent vasodilator responses. Soleus muscle feed arteries from young (4 month) and old (24 month) Fischer 344 rats were isolated, cannulated, and pressurized at 90 (P90) or 130 (P130) cmH20 for 1 h. Following the 1 h pressure treatment, intraluminal pressure was lowered to 90 cmH20 for all vessels and SNP-induced vasodilation was assessed immediately or following a 2 h recovery period. SNP-induced dilation was significantly blunted in old P90 SFA when compared to young P90 SFA. Pre-treatment with increased intraluminal pressure for 1 h improved SNP-induced vasodilator responses and abolished the age group difference between the old and young SFA. Maximal dilation to SNP was greater in the young P130 compared to the young P90 SFA. The effects of the 1 h increased intraluminal pressure treatment were no longer present following a 2 h recovery period. Collectively, these results indicate that treatment of aged arteries with a short-term increase in intraluminal pressure to mimic pressure during a bout of exercise improves endothelium-independent dilation in aged arteries. In addition, these results suggest that a short-term increase in intraluminal pressure, associated with a single bout of exercise, is one signal contributing to the beneficial effect of exercise on vasodilator responses in aged arteries

Six-months follow-up of a cluster randomized trial of school-based smoking prevention education programs in Aceh, Indonesia

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Aging Impairs ACh-induced Dilation in Skeletal Muscle Feed Arteries: Role of Akt-dependent Phosphorylation of eNOS.

Aging impairs ACh-induced dilation in skeletal muscle feed arteries: role of Akt-dependent phosphorylation of eNOS. Meredith J. Luttrell1, John W. Seawright1, Daniel W. Trott1 and Christopher R. Woodman1,2 1. Dept. of Health and Kinesiology Texas A&M University, College Station, TX 77843 2. Dept of Veterinary Physiology and Pharmacology Texas A&M University, College Station, TX 77843 We tested the hypothesis that impaired nitric oxide (NO)-mediated, endothelium-dependent dilation in aged soleus muscle feed arteries (SFA) is due to an age-related decrement in PI3-kinase(PI3K)/protein kinase B (Akt)-dependent phosphorylation of endothelial NO synthase (eNOS) on serine residue 1177 (p-eNOSser1177). SFA from young (4 mo) and old (24 mo) Fischer 344 rats were cannulated for examination of endothelium-dependent vasodilator responses to acetylcholine (ACh). To determine the mechanism by which aging affected vasodilation to ACh, vasodilator responses were assessed in the absence and presence of Nw-nitro-L-arginine (L-NNA, to inhibit NOS), LY-294002 (to inhibit PI3K), or 1L6-hydroxymethyl-chiro-inositol-2-(R)-2-O-methyl-3-O-octadecyl-sn-glycerocarbonate (AktI, to inhibit Akt). Results indicate that ACh-induced vasodilation was significantly blunted in old SFA, whereas dilation to sodium nitroprusside (a NO donor) was not compromised. The age-group difference in ACh-induced dilation was abolished in the presence of L-NNA, LY-294002, or AktI. In a separate set of experiments, ACh-induced vasodilation was assessed in SFA from young and old rats. SFA were subsequently removed from the pipettes, snap frozen, and immunoblot analysis was used to assess p-AktSer473, p-eNOSser1177, total Akt and total eNOS protein content. ACh-induced vasodilation was blunted in old SFA; however, the p-AktSer473/Akt and p-eNOSser1177/eNOS ratios were similar in young and old SFA. Collectively, these results indicate that NO-mediated dilation is impaired in old SFA; however, the decrement in endothelial function is not due to reduced PI3K/Akt-dependent phosphorylation of eNOS on serine residue 1177

Naturally enhanced ion-line spectra around the equatorial 150-km region

For many years strong radar echoes coming from 140–170 km altitudes at low latitudes have been associated to the existence of field-aligned irregularities (FAIs) (the so called 150-km echoes). In this work, we present frequency spectra as well as angular distribution of 150-km echoes. When the 150-km region is observed with beams perpendicular to the magnetic field (<B>B</B>) the observed radar spectra are very narrow with spectral widths between 3–12 m/s. On the other hand, when few-degrees off-perpendicular beams are used, the radar spectra are wide with spectral widths comparable to those expected from ion-acoustic waves at these altitudes (>1000 m/s). Moreover the off-perpendicular spectral width increases with increasing altitude. The strength of the received echoes is one to two orders of magnitude stronger than the expected level of waves in thermal equilibrium at these altitudes. Such enhancement is not due to an increase in electron density. Except for the enhancement in power, the spectra characteristics of off-perpendicular and perpendicular echoes are in reasonable agreement with expected incoherent scatter spectra at these angles and altitudes. 150-km echoes are usually observed in narrow layers (2 to 5). Bistatic common volume observations as well as observations made few kilometers apart show that, for most of the layers, there is very high correlation on power fluctuations without a noticeable time separation between simultaneous echoes observed with Off-perpendicular and Perpendicular beams. However, in one of the central layers, the echoes are the strongest in the perpendicular beam and absent or very weak in the off-perpendicular beams, suggesting that they are generated by a plasma instability. Our results indicate that most echoes around 150-km region are not as aspect sensitive as originally thought, and they come from waves that have been enhanced above waves in thermal equilibrium