Pioneer Venus polarimetry and haze optical thickness

The Pioneer Venus mission provided us with high-resolution measurements at four wavelengths of the linear polarization of sunlight reflected by the Venus atmosphere. These measurements span the complete phase angle range and cover a period of more than a decade. A first analysis of these data by Kawabata et al. confirmed earlier suggestions of a haze layer above and partially mixed with the cloud layer. They found that the haze exhibits large spatial and temporal variations. The haze optical thickness at a wavelength of 365 nm was about 0.06 at low latitudes, but approximately 0.8 at latitudes from 55 deg poleward. Differences between morning and evening terminator have also been reported by the same authors. Using an existing cloud/haze model of Venus, we study the relationship between the haze optical thickness and the degree of linear polarization. Variations over the visible disk and phase angle dependence are investigated. For that purpose, exact multiple scattering computations are compared with Pioneer Venus measurements. To get an impression of the variations over the visible disk, we have first studied scans of the polarization parallel to the intensity equator. After investigating a small subset of the available data we have the following results. Adopting the haze particle characteristics given by Kawabata et al., we find a thickening of the haze at increasing latitudes. Further, we see a difference in haze optical thickness between the northern and southern hemispheres that is of the same order of magnitude as the longitudinal variation of haze thickness along a scan line. These effects are most pronounced at a wavelength of 935 nm. We must emphasize the tentative nature of the results, because there is still an enormous amount of data to be analyzed. We intend to combine further polarimetric research of Venus with constraints on the haze parameters imposed by physical and chemical processes in the atmosphere

Interactive exploration and modeling of large data sets: a case study with Venus light scattering data

We present a system where visualization and the control of the simulation are integrated to facilitate interactive exploration and modeling of large data sets. The system was developed to estimate properties of the atmosphere of Venus from comparison between measured and simulated data. Reuse of results, distributed computing, and multiple views on the data were the major ingredients to create an effective environment

Photometric Light Curves and Polarization of Close-in Extrasolar Giant Planets

The close-in extrasolar giant planets [CEGPs], \ltorder 0.05 AU from their parent stars, may have a large component of optically reflected light. We present theoretical optical photometric light curves and polarization curves for the CEGP systems, from reflected planetary light. Different particle sizes of three condensates are considered. In the most reflective case, the variability is $\approx 100$ micromagnitudes, which will be easily detectable by the upcoming satellite missions MOST, COROT, and MONS, and possibly from the ground in the near future. The least reflective case is caused by small, highly absorbing grains such as solid Fe, with variation of much less than one micromagnitude. Polarization for all cases is lower than current detectability limits. We also discuss the temperature-pressure profiles and resulting emergent spectra of the CEGP atmospheres. We discuss the observational results of Tau Boo b by Cameron et al. (1999) and Charbonneau et al. (1999) in context of our model results. The predictions - the shape and magnitude of the light curves and polarization curves - are highly dependent on the size and type of condensates present in the planetary atmosphere.Comment: 33 pages, accepted by Ap

Prevalence of painful temporomandibular disorders, awake bruxism and sleep bruxism among patients with severe post‐traumatic stress disorder

Background: Post‐traumatic stress disorder (PTSD) is associated with painful temporomandibular disorder (TMD) and may be part of the aetiology of awake bruxism (AB) and sleep bruxism (SB). Investigating the associations between PTSD symptoms on the one hand, and painful TMD, AB and SB on the other, can help tailoring treatment to the needs of this patient group. Objectives: The aim of this study was to investigate the associations between PTSD symptoms and painful TMD, AB and SB among patients with PTSD, focusing on prevalence, symptom severity and the influence of trauma history on the presence of painful TMD, AB and SB. Methods: Individuals (N = 673) attending a specialised PTSD clinic were assessed (pre‐treatment) for painful TMD (TMD pain screener), AB and SB (Oral Behaviours Checklist), PTSD symptoms (Clinician‐Administered PTSD Scale) and type of traumatic events (Life Events Checklist). Results: Painful TMD, AB and SB were more prevalent among patients with PTSD (28.4%, 48.3% and 40.1%, respectively) than in the general population (8.0%, 31.0% and 15.3%, respectively; all p's < .001). PTSD symptom severity was found to be significantly, but poorly, associated with the severity of painful TMD (r s = .126, p = .001), AB (r s = .155, p < .001) and SB (r s = .084, p = .029). Patients who had been exposed to sexual assault were more likely to report AB than patients who had not. Similarly, exposure to physical violence was associated with increased odds for SB. Conclusion: Patients with severe PTSD are more likely to experience painful TMD, AB or SB, whereas type of traumatic event can be of influence. These findings can contribute to selecting appropriate treatment modalities when treating patients with painful TMD, AB and SB

Novel model-based dosing guidelines for gentamicin and tobramycin in preterm and term neonates

Objectives In the heterogeneous group of preterm and term neonates, gentamicin and tobramycin are mainly dosed according to empirical guidelines, after which therapeutic drug monitoring and subsequent dose adaptation are applied. In view of the variety of neonatal guidelines available, the purpose of this study was to evaluate target concentration attainment of these guidelines, and to propose a new model-based dosing guideline for these drugs in neonates. Methods Demographic characteristics of 1854 neonates (birth weight 390-5200 g, post-natal age 0-27 days) were extracted from earlier studies and sampled to obtain a test dataset of 5000 virtual patients. Monte Carlo simulations on the basis of validated models were undertaken to evaluate the attainment of target peak (5-12 mg/L) and trough (<0.5 mg/L) concentrations, and cumulative AUC, with the existing and proposed guidelines. Results Across the entire neonatal age and weight range, the Dutch National Formulary for Children, the British National Formulary for Children, Neofax and the Red Book resulted in adequate peak but elevated trough concentrations (63%-90% above target). The proposed dosing guideline (4.5 mg/kg gentamicin or 5.5 mg/kg tobramycin) with a dosing interval based on birth weight and post-natal age leads to adequate peak concentrations with only 33%-38% of the trough concentrations above target, and a constant AUC across weight and post-natal age. Conclusions The proposed neonatal dosing guideline for gentamicin and tobramycin results in improved attainment of target concentrations and should be prospectively evaluated in clinical studies to evaluate the efficacy and safety of this treatmen

Dose-linearity of the pharmacokinetics of an intravenous [C-14]midazolam microdose in children

Aims Drug disposition in children may vary from adults due to age-related variation in drug metabolism. Microdose studies present an innovation to study pharmacokinetics (PK) in paediatrics; however, they should be used only when the PK is dose linear. We aimed to assess dose linearity of a [C-14]midazolam microdose, by comparing the PK of an intravenous (IV) microtracer (a microdose given simultaneously with a therapeutic midazolam dose), with the PK of a single isolated microdose. Methods Preterm to 2-year-old infants admitted to the intensive care unit received [C-14]midazolam IV as a microtracer or microdose, followed by dense blood sampling up to 36 hours. Plasma concentrations of [C-14]midazolam and [C-14]1-hydroxy-midazolam were determined by accelerator mass spectrometry. Noncompartmental PK analysis was performed and a population PK model was developed. Results Of 15 infants (median gestational age 39.4 [range 23.9-41.4] weeks, postnatal age 11.4 [0.6-49.1] weeks), 6 received a microtracer and 9 a microdose of [C-14]midazolam (111 Bq kg(-1); 37.6 ng kg(-1)). In a 2-compartment PK model, bodyweight was the most significant covariate for volume of distribution. There was no statistically significant difference in any PK parameter between the microdose and microtracer, nor in the area under curve ratio [C-14]1-OH-midazolam/[C-14]midazolam, showing the PK of midazolam to be linear within the range of the therapeutic and microdoses. Conclusion Our data support the dose linearity of the PK of an IV [C-14]midazolam microdose in children. Hence, a [C-14]midazolam microdosing approach may be used as an alternative to a therapeutic dose of midazolam to study developmental changes in hepatic CYP3A activity in young children

Dose-linearity of the pharmacokinetics of an intravenous [C-14]midazolam microdose in children

Aims Drug disposition in children may vary from adults due to age-related variation in drug metabolism. Microdose studies present an innovation to study pharmacokinetics (PK) in paediatrics; however, they should be used only when the PK is dose linear. We aimed to assess dose linearity of a [C-14]midazolam microdose, by comparing the PK of an intravenous (IV) microtracer (a microdose given simultaneously with a therapeutic midazolam dose), with the PK of a single isolated microdose. Methods Preterm to 2-year-old infants admitted to the intensive care unit received [C-14]midazolam IV as a microtracer or microdose, followed by dense blood sampling up to 36 hours. Plasma concentrations of [C-14]midazolam and [C-14]1-hydroxy-midazolam were determined by accelerator mass spectrometry. Noncompartmental PK analysis was performed and a population PK model was developed. Results Of 15 infants (median gestational age 39.4 [range 23.9-41.4] weeks, postnatal age 11.4 [0.6-49.1] weeks), 6 received a microtracer and 9 a microdose of [C-14]midazolam (111 Bq kg(-1); 37.6 ng kg(-1)). In a 2-compartment PK model, bodyweight was the most significant covariate for volume of distribution. There was no statistically significant difference in any PK parameter between the microdose and microtracer, nor in the area under curve ratio [C-14]1-OH-midazolam/[C-14]midazolam, showing the PK of midazolam to be linear within the range of the therapeutic and microdoses. Conclusion Our data support the dose linearity of the PK of an IV [C-14]midazolam microdose in children. Hence, a [C-14]midazolam microdosing approach may be used as an alternative to a therapeutic dose of midazolam to study developmental changes in hepatic CYP3A activity in young children