Editorial: Essential Biomolecules Caught in the Food Web?

Peer Reviewe

Determining the Novel Pathogen Neodothiora populina as the Causal Agent of the Aspen Running Canker Disease in Alaska

Neodothiora populina Crous, G.C. Adams & Winton was determined to be a new pathogen of trembling aspen (Populus tremuloides) growing in Alaska, based on completion of Koch’s Postulates in replicated forest and growth chamber inoculation trials. The pathogen is responsible for severe damage and widespread rapid mortality of sapling to mature aspen (≥ 80 years) in the boreal forests of interior Alaska, due to large diffuse annual (1–2 years) cankers. Isolation of the pathogen was challenging, and identification based on cultural characters was difficult. Fruiting bodies were not found on wild diseased trees, but erumpent pycnidia were found in bark overlying cankers on several stems inoculated with pure cultures

Widespread Mortality of Trembling Aspen (Populus tremuloides) Throughout Interior Alaskan Boreal Forests Resulting from a Novel Canker Disease

Over the past several decades, growth declines and mortality of trembling aspen throughout western Canada and the United States have been linked to drought, often interacting with outbreaks of insects and fungal pathogens, resulting in a “sudden aspen decline” throughout much of aspen’s range. In 2015, we noticed an aggressive fungal canker causing widespread mortality of aspen throughout interior Alaska and initiated a study to quantify potential drivers for the incidence, virulence, and distribution of the disease. Stand-level infection rates among 88 study sites distributed across 6 Alaska ecoregions ranged from \u3c 1 to 69%, with the proportion of trees with canker that were dead averaging 70% across all sites. The disease is most prevalent north of the Alaska Range within the Tanana Kuskokwim ecoregion. Modeling canker probability as a function of ecoregion, stand structure, landscape position, and climate revealed that smaller-diameter trees in older stands with greater aspen basal area have the highest canker incidence and mortality, while younger trees in younger stands appear virtually immune to the disease. Sites with higher summer vapor pressure deficits had significantly higher levels of canker infection and mortality. We believe the combined effects of this novel fungal canker pathogen, drought, and the persistent aspen leaf miner outbreak are triggering feedbacks between carbon starvation and hydraulic failure that are ultimately driving widespread mortality. Warmer early-season temperatures and prolonged late summer drought are leading to larger and more severe wildfires throughout interior Alaska that are favoring a shift from black spruce to forests dominated by Alaska paper birch and aspen. Widespread aspen mortality fostered by this rapidly spreading pathogen has significant implications for successional dynamics, ecosystem function, and feedbacks to disturbance regimes, particularly on sites too dry for Alaska paper birch

Stand up Paddle Surfing-An Aerobic Workout and Balance Training

AbstractOriginating from an ancient Hawaiian tradition Stand Up Paddle Surfing (SUP) is a growing pastime and sports activity in which a person stands upright on a surfboard and propels it using a single paddle. During paddling the board constantly is in an unstable condition forcing paddlers to focus on keeping balance and simultaneously propelling the board by paddling. Therefore it is expected that SUP can be a high impact aerobic workout and balance training. A total of 68 subjects performed on-water and SUP ergometer trials, during ergometer trials heart rate (HR) was permanently measured and balance was assessed before and after all trials (ergometer and on-water) using a single leg hop test on a Win Pod electronic baropedometric platform. Results of the balance tests - though for a relatively small number of participants - showed that after ergometer trials a significant improvement in stability occurred whereas it was only significant for the right foot's anteroposterior movement after on-water trials. The result of the exercise-test illustrated that the HR of beginners stays in the aerobic zone which makes SUP suitable for endurance training

Overview of KIT activities on high power, high frequency gyrotron development and the role of the new FULGOR teststand at KIT

For a future DEMOnstration fusion power plant two challenging trends with respect to gyrotron features are recognized: (a) the operating frequency will be above 200 GHz and (b) the requested total efficiency of the gyrotron should be as high as possible. ECRH systems for future plants (DEMO) or Fusion Power Plants (FPP) will most probably require multi-megawatt and continuous wave gyrotrons which are able to oscillate at a frequency significantly above 200 GHz. The coaxial cavity technology which is under investigation and development at KIT since several years, seems to have the optimum properties to fulfill the requirements towards sub-THz operation in the MW output power regime. To benefit from these advantages and to profit from the existing experience on this technology the modular 2 MW 170 GHz gyrotron has been taken as a starting point for a 170/204/238 GHz multi-frequency gyrotron design study. Recent activities for improvement of the performance of this gyrotron and preparations for long pulse operation will be shown. In a first step we aim at ~ 100 ms operation, in a second step, with the tube being equipped with an improved cooling system, 1 s operation is envisaged. KIT is currently constructing a new gyrotron teststand, FULGOR, having specific features, such as: 10 MW electrical input power in CW, magnetic field up to 10.5 T with 261 mm warm bore hole of the SCM and several voltage taps from the high-voltage DC power supply. The CW HV Power supply (120 kV, 130 A) has already been delivered and accepted, a dry superconducting magnet will be delivered in 2019. For the first time it will be possible with FULGOR to test Multistage Depressed Collector (MDC) gyrotrons which are supposed to increase the overall efficiency from 50 % (state of the art) to 60 % or even higher. There are two concepts for gyrotron MDC: a axisymmetric concept, which relies on the demagnetization combined with non-adiabatic magnetic transitions and a concept based on E×B drifts to sort electrons. First considerations of a proof-of-principle design for the ExB drift concept will be shown

Theoretical Study on the Operation of the EU/KIT TE34,19-Mode Coaxial-Cavity Gyrotron at 170/204/238 GHz

The 170 GHz 2 MW TE34,19-mode coaxial-cavity modular short-pulse pre-prototype gyrotron at KIT was recently modified in order to verify the multi-megawatt coaxial-cavity technology at longer pulses. In parallel, theoretical investigations on a possibility to operate the 170 GHz TE34,19-mode coaxial-cavity prototype at multiple frequencies up to 238 GHz have been started, with a goal to find a configuration at which the tube could operate in the KIT FULGOR gyrotron test facility using the new 10.5 T SC magnet. This paper indicates which adjustments have to be made and show the feasibility of the multi-frequency operation. Small modifications at the gyrotron cavity will support an RF output power of more than 2 MW at 170/204 GHz. Furthermore, a new gyrotron launcher has been designed capable of producing a Gaussian microwave beam with a Gaussian mode content of more than 96% at these frequencies

Triode magnetron injection gun for the KIT 2 MW 170 GHz coaxial cavity gyrotron

Considering the recent understanding of the physics of electron trapping mechanisms taking place in the magnetron injection gun (MIG) region of gyrotrons and the sensitivity of the emitter ring manufacturing tolerances on the electron beam quality, a MIG has been designed and manufactured for the 2 MW, 170 GHz coaxial cavity gyrotron developed at Karlsruhe Institute of Technology. The new MIG has the following novelties: (i) the design satisfies the criteria for the suppression of the electron trapping mechanisms, (ii) a new type of emitter ring is used for the suppression of the influence of the manufacturing tolerances and misalignments on the quality of the generated electron beam, and (iii) the design was optimized to generate a good beam quality in a wide variety of magnetic field profiles to increase the flexibility. An additional important feature of the new triode MIG design is the possibility to operate with only two power supplies by using a special start-up scenario. The first experimental results of the coaxial cavity gyrotron with the new MIG are presented