Search

The rapid changes occurring in the polar regions require an improved understanding of the processes that are driving these changes. At the same time, increased human activities such as marine navigation, resource exploitation, aviation, commercial fishing, and tourism require reliable and relevant weather information. One of the primary goals of the World Meteorological Organization's Year of Polar Prediction (YOPP) project is to improve the accuracy of numerical weather prediction (NWP) at high latitudes. During YOPP, two Canadian "supersites" were commissioned and equipped with new ground-based instruments for enhanced meteorological and system process observations. Additional pre-existing supersites in Canada, the United States, Norway, Finland, and Russia also provided data from ongoing long-term observing programs. These supersites collected a wealth of observations that are well suited to address YOPP objectives. In order to increase data useability and station interoperability, novel Merged Observatory Data Files (MODFs) were created for the seven supersites over two Special Observing Periods (February to March 2018 and July to September 2018). All observations collected at the supersites were compiled into this standardized NetCDF MODF format, simplifying the process of conducting pan-Arctic NWP verification and process evaluation studies. This paper describes the seven Arctic YOPP supersites, their instrumentation, data collection and processing methods, the novel MODF format, and examples of the observations contained therein. MODFs comprise the observational contribution to the model intercomparison effort, termed YOPP site Model Intercomparison Project (YOPPsiteMIP). All YOPPsiteMIP MODFs are publicly accessible via the YOPP Data Portal (Whitehorse: 10.21343/a33e-j150, Huang et al., 2023a; Iqaluit: 10.21343/yrnf-ck57, Huang et al., 2023b; Sodankylä: 10.21343/m16p-pq17, O'Connor, 2023; Utqiaġvik: 10.21343/a2dx-nq55, Akish and Morris, 2023c; Tiksi: 10.21343/5bwn-w881, Akish and Morris, 2023b; Ny-Ålesund: 10.21343/y89m-6393, Holt, 2023; and Eureka: 10.21343/r85j-tc61, Akish and Morris, 2023a), which is hosted by MET Norway, with corresponding output from NWP models. [ABSTRACT FROM AUTHOR]

Amyotrophic lateral sclerosis (ALS) is characterized by upper and lower motor neuron dysfunction and loss, rapidly progressive muscle weakness, wasting and death (1-3). Many factors, including mitochondrial dysfunction, may contribute to ALS pathogenesis (4-9). Riluzole, which has shown only modest benefits in a measure of survival time without demonstrated effects on muscle strength or function, is the only approved treatment for ALS (10,11). We tested the putative mitochondrial modulator dexpramipexole (KNS-760704; (6R)-4,5,6,7- tetrahydro-N6-propyl-2,6-benzothiazole-diamine) (12-14) in subjects with ALS in a two-part, double-blind safety and tolerability study, with a preliminary assessment of its effects on functional decline and mortality. In part 1, the effects of dexpramipexole (50, 150 or 300 mg [d.sup.-1]) versus placebo were assessed over 12 weeks. In part 2, after a 4-week, single-blind placebo washout, continuing subjects were re-randomized to dexpramipexole at 50 mg [d.sup.-1] or 300 mg [d.sup.-1] as double-blind active treatment for 24 weeks. Dexpramipexole was safe and well tolerated. Trends showing a dose-dependent attenuation of the slope of decline of the ALS Functional Rating Scale-Revised (ALSFRS-R) in part 1 and a statistically significant (P = 0.046) difference between groups in a joint rank test of change from baseline in ALSFRS-R and mortality in part 2 strongly support further testing of dexpramipexole in ALS., ALS clinical investigators have employed various approaches to increase the efficiency of phase 2 studies, including futility designs and dose-selection studies (15-21). Our phase 2 study used a unique study [...]

The hydroxyl radical OH oxidizes many trace gases in the atmosphere. It initiates and then participates in chemical reactions that lead to such phenomena as photochemical smog, acid rain, and stratospheric ozone depletion. Because OH is so reactive, its volume mixing ratio is less than 1 part per trillion volume (pptv) throughout the troposphere. Its close chemical cousin, the hydroperoxyl radical H[O.sub.2], participates in many reactions as well. The authors have developed an instrument capable of measuring OH and H[O.sub.2] by laser-induced fluorescence in a detection chamber at low pressure. This prototype instrument is able to detect about 1.4 x [10.sup.5] molecules [cm.sup.-3] (0.005 pptv) of OH at the ground in a signal integration time of 30 s with negligible interferences. The absolute uncertainty is a factor of 1.5. This instrument is now being adapted to aircraft use for measurements throughout the troposphere.

Convection and magnetic field generation in the Earth and planetary interiors are driven by both thermal and compositional gradients. In this work numerical simulations of finite-amplitude double-diffusive convection and dynamo action in rapidly rotating spherical shells full of incompressible two-component electrically-conducting fluid are reported. Four distinct regimes of rotating double-diffusive convection identified in a recent linear analysis (Silva, Mather and Simitev, Geophys. Astrophys. Fluid Dyn. 2019, 113, 377) are found to persist significantly beyond the onset of instability while their regime transitions remain abrupt. In the semi-convecting and the fingering regimes characteristic flow velocities are small compared to those in the thermally- and compositionally-dominated overturning regimes, while zonal flows remain weak in all regimes apart from the thermally-dominated one. Compositionally-dominated overturning convection exhibits significantly narrower azimuthal structures compared to all other regimes while differential rotation becomes the dominant flow component in the thermally-dominated case as driving is increased. Dynamo action occurs in all regimes apart from the regime of fingering convection. While dynamos persist in the semi-convective regime they are very much impaired by small flow intensities and very weak differential rotation in this regime which makes poloidal to toroidal field conversion problematic. The dynamos in the thermally-dominated regime include oscillating dipolar, quadrupolar and multipolar cases similar to the ones known from earlier parameter studies. Dynamos in the compositionally-dominated regime exhibit subdued temporal variation and remain predominantly dipolar due to weak zonal flow in this regime. These results significantly enhance our understanding of the primary drivers of planetary core flows and magnetic fields. [ABSTRACT FROM AUTHOR]