The interaction between the Moon and the solar wind

We study the interaction between the Moon and the solar wind using a three-dimensional hybrid plasma solver. The proton fluxes and electromagnetical fields are presented for typical solar wind conditions with different magnetic field directions. We find two different wake structures for an interplanetary magnetic field that is perpendicular to the solar wind flow, and for one that is parallell to the flow. The wake for intermediate magnetic field directions will be a mix of these two extreme conditions. Several features are consistent with a fluid interaction, e.g., the presence of a rarefaction cone, and an increased magnetic field in the wake. There are however several kinetic features of the interaction. We find kinks in the magnetic field at the wake boundary. There are also density and magnetic field variations in the far wake, maybe from an ion beam instability related to the wake refill. The results are compared to observations by the WIND spacecraft during a wake crossing. The model magnetic field and ion velocities are in agreement with the measurements. The density and the electron temperature in the central wake are not as well captured by the model, probably from the lack of electron physics in the hybrid model.Comment: Accepted for publication in Earth, Planets and Spac

“Suspension of the eyelid to the check ligament of the superior fornix in congenital blepharoptosis”

A new surgical procedure for the treatment of all types of congenital blepharoptosis is described: suspension of the eyelid to the check ligament of the superior fornix. This is a dynamic suspension technique by which the check ligament, which is an extension of Tenon's capsule and normally inserts into the superior conjunctival fornix, is brought forward and sutured to the tarsus, which raises the eyelid. This technique does not sacrifice or add any tissue and is simple to repeat if necessary. Sixty-two patients were operated on using the technique and followed up for a mean of 23 months (range 3 months to 9.6 years). In a group of patients not operated on before for ptosis, 50 eyelids were raised with 74% normalisation, 22% improvement, and one eyelid each that showed only slight change or overcorrection. In a group of patients with 27 eyelids operated on before using other techniques, 67% of the eyelids were normalised, 30% were improved, and only one eyelid showed no change. In conclusion, this new technique has proved to be quite successful in raising the level of the upper eyelid in congenital blepharoptosis, with results at least comparable to those of most other techniques. The advantages with the check ligament over other techniques are the minimal trauma of the surgery, its simplicity, and its repeatability

Mechanisms underlying mitochondrial function and biogenesis: Implications for type 2 diabetes mellitus and obesity

The ample supply of food, in conjunction with a sedentary lifestyle and certain genetic risk factors contribute to the rise in obesity, insulin resistance and type 2 diabetes mellitus. Reduced mitochondrial capacity for oxidative metabolism has been implicated as one possible cause of insulin resistance in several tissues; such as liver and skeletal muscle. The adipose-derived hormone leptin and the metabolic sensor 5’-AMP-activated protein kinase, are two key regulators that modulate intracellular fuel handling. The aim of this thesis is to investigate the effects of these metabolic signals on tissue-specific mitochondrial respiration and biogenesis. The aim of study I was to investigate the role of the AMPK γ3 subunit in determining mitochondrial function in glycolytic skeletal muscle. The AMPK signaling axis is a metabolic switch regulated by the intracellular energy charge. A single-nucleotide mutation (R225Q) in the AMPKγ3 subunit causes elevated basal enzyme activity. Transgenic expression in mice (Tg-AMPKγ3R225Q) increased expression of regulators and mediators of substrate oxidation, as well as components of mitochondrial dynamics and electron transport. In summary, this single nucleotide mutation is associated with mitochondrial biogenesis, concomitant with increased expression of transcription factors that regulate mitochondrial proteins. The focus of study II was to characterize tissue-specific mitochondrial function in permeabilized tissue from lean and leptin receptor-deficient obese db/db mice. Respiratory capacity in oxidative soleus muscle was similar between genotypes, except for decreased complex II function in db/db mice. Oxidative function in glycolytic EDL muscle was higher in db/db mice than in lean littermates; likely as a result of increased mitochondrial biogenesis. Maximal respiratory capacity in liver from db/db mice was blunted, concomitant with increased mitochondrial fission. In summary, mitochondrial respiratory performance is controlled by tissue-specific mechanisms and is not uniformly altered in obesity. The aim of study III was to determine tissue-specific mitochondrial respiration in obese leptin-deficient ob/ob mice, and lean littermates, following treatment with leptin or saline. Oxidative capacity in soleus muscle was unaffected in saline- and leptin-treated ob/ob mice, whereas maximal electron transport capacity was increased with obesity in EDL muscle. Regulation of transcription and mitochondrial fission in EDL was altered in saline-treated ob/ob mice, and only partially normalized with leptin repletion. In liver, maximal respiratory capacity and mediators of lipid oxidation were reduced with in saline- and leptin-treated ob/ob mice; while leptin treatment normalized indicators of mitochondrial stress. In conclusion, mitochondrial respiratory function is a dynamic process that is tightly regulated to meet the energy needs of the cell. Despite profound alterations in whole-body or intracellular energy sensing, mitochondrial adaptation can occur and respiratory adaptations are comparatively modest. This highlights the need to target several pathways of metabolic regulation to modulate mitochondrial function to improve systemic homeostasis

Stellar wind interaction and pick-up ion escape of the Kepler-11 "super-Earths"

We study the interactions between stellar wind and the extended hydrogen-dominated upper atmospheres of planets and the resulting escape of planetary pick-up ions from the 5 "super-Earths" in the compact Kepler-11 system and compare the escape rates with the efficiency of the thermal escape of neutral hydrogen atoms. Assuming the stellar wind of Kepler-11 is similar to the solar wind, we use a polytropic 1D hydrodynamic wind model to estimate the wind properties at the planetary orbits. We apply a Direct Simulation Monte Carlo Model to model the hydrogen coronae and the stellar wind plasma interaction around Kepler-11b-f within a realistic expected heating efficiency range of 15-40%. The same model is used to estimate the ion pick-up escape from the XUV heated and hydrodynamically extended upper atmospheres of Kepler-11b-f. From the interaction model we study the influence of possible magnetic moments, calculate the charge exchange and photoionization production rates of planetary ions and estimate the loss rates of pick-up H+ ions for all five planets. We compare the results between the five "super-Earths" and in a more general sense also with the thermal escape rates of the neutral planetary hydrogen atoms. Our results show that for all Kepler-11b-f exoplanets, a huge neutral hydrogen corona is formed around the planet. The non-symmetric form of the corona changes from planet to planet and is defined mostly by radiation pressure and gravitational effects. Non-thermal escape rates of pick-up ionized hydrogen atoms for Kepler-11 "super-Earths" vary between approximately 6.4e30 1/s and 4.1e31 1/s depending on the planet's orbital location and assumed heating efficiency. These values correspond to non-thermal mass loss rates of approximately 1.07e7 g/s and 6.8e7 g/s respectively, which is a few percent of the thermal escape rates.Comment: 8 pages, 3 figures, accepted to A&

Transit Ly-α\alpha signatures of terrestrial planets in the habitable zones of M dwarfs

We modeled the transit signatures in the Lya line of a putative Earth-sized planet orbiting in the HZ of the M dwarf GJ436. We estimated the transit depth in the Lya line for an exo-Earth with three types of atmospheres: a hydrogen-dominated atmosphere, a nitrogen-dominated atmosphere, and a nitrogen-dominated atmosphere with an amount of hydrogen equal to that of the Earth. We calculated the in-transit absorption they would produce in the Lya line. We applied it to the out-of-transit Lya observations of GJ 436 obtained by the HST and compared the calculated in-transit absorption with observational uncertainties to determine if it would be detectable. To validate the model, we also used our method to simulate the deep absorption signature observed during the transit of GJ 436b and showed that our model is capable of reproducing the observations. We used a DSMC code to model the planetary exospheres. The code includes several species and traces neutral particles and ions. At the lower boundary of the DSMC model we assumed an atmosphere density, temperature, and velocity obtained with a hydrodynamic model for the lower atmosphere. We showed that for a small rocky Earth-like planet orbiting in the HZ of GJ436 only the hydrogen-dominated atmosphere is marginally detectable with the STIS/HST. Neither a pure nitrogen atmosphere nor a nitrogen-dominated atmosphere with an Earth-like hydrogen concentration in the upper atmosphere are detectable. We also showed that the Lya observations of GJ436b can be reproduced reasonably well assuming a hydrogen-dominated atmosphere, both in the blue and red wings of the Lya line, which indicates that warm Neptune-like planets are a suitable target for Lya observations. Terrestrial planets can be observed in the Lya line if they orbit very nearby stars, or if several observational visits are available.Comment: 17 pages, 12 figures, accepted for publication in Astronomy & Astrophysic

The Jervell and Lange-Nielsen syndrome; atrial pacing combined with ß-blocker therapy, a favorable approach in young high-risk patients with long QT syndrome?

BackgroundPatients with Jervell and Lange-Nielsen syndrome (JLNS) exhibit severe phenotypes that are characterized by congenital deafness, very long QT intervals, and high risk of life-threatening arrhythmias. Current treatment strategies include high doses of beta-blocker medication, left cardiac sympathetic denervation, and ICD placement, which is challenging in young children.ObjectiveThe purpose of this study was to evaluate the safety and effect of pacing in addition to beta-blocker treatment in children with JLNS.MethodsAll genetically confirmed patients with JLNS born since 1999 in Norway were included in the study. Data on history of long QT syndrome–related symptoms, QT interval, and beta-blocker and pacemaker treatment were recorded.ResultsA total of 9 patients with QT intervals ranging from 510 to 660 ms were identified. Eight patients developed long QT syndrome–related symptoms, and 1 patient died before diagnosis. The survivors received beta-blocker medication. Seven patients also received a pacemaker; 1 had a ventricular lead and 6 had atrial leads. The patient with the ventricular lead died during follow-up. The 6 patients with atrial leads survived without events at a mean follow-up of 6.9 years after pacemaker implantation. Two patients received prophylactic upgrade to a 2-chamber ICD.ConclusionNo arrhythmic events occurred in 6 very young JLNS patients who received atrial pacing in combination with increased doses of beta-blockers during 7-year follow-up. If confirmed in additional patients, this treatment strategy may prevent life-threatening arrhythmias in this high-risk patient group and may act as a bridge to insertion of a 2-chamber ICD when left cardiac sympathetic denervation is not available