Origin and development of neuropil glia of the Drosophila larval and adult brain: Two distinct glial populations derived from separate progenitors

Glia comprise a conspicuous population of non-neuronal cells in vertebrate and invertebrate nervous systems. Drosophila serves as a favorable model to elucidate basic principles of glial biology in vivo. The Drosophila neuropil glia (NPG), subdivided into astrocyte-like (ALG) and ensheathing glia (EG), extend reticular processes which associate with synapses and sheath-like processes which surround neuropil compartments, respectively. In this paper we characterize the development of NPG throughout fly brain development. We find that differentiated neuropil glia of the larval brain originate as a cluster of precursors derived from embryonic progenitors located in the basal brain. These precursors undergo a characteristic migration to spread over the neuropil surface while specifying/differentiating into primary ALG and EG. Embryonically-derived primary NPG are large cells which are few in number, and occupy relatively stereotyped positions around the larval neuropil surface. During metamorphosis, primary NPG undergo cell death. Neuropil glia of the adult (secondary NPG) are derived from type II lineages during the postembryonic phase of neurogliogenesis. These secondary NPG are much smaller in size but greater in number than primary NPG. Lineage tracing reveals that both NPG subtypes derive from intermediate neural progenitors of multipotent type II lineages. Taken together, this study reveals previously uncharacterized dynamics of NPG development and provides a framework for future studies utilizing Drosophila glia as a model

Distribution of Endothelin Receptor Subtypes in the Rat Kidney Renal and Haemodynamic Effects of the Mixed (A/B) Endothelin Receptor Antagonist Bosentan

Peer Reviewe

Tetrode Based Technology Demonstrator at 352 MHz, 400 kWp for ESS Spoke Linac

The European Spallation Source (ESS) will be the world's most powerful spallation neutron source when it comes in operation at the end of this decade. The ESS linac will accelerate 50mA of protons to 2 GeV in 2.86 ms long pulses at a repetition rate of 14 Hz on a tungsten target for neutron spallation. The linac contains 26 superconducting spoke cavities, which are being developed by IPN Orsay, France, and which accelerate the protons from 90 to 220 MeV. The FREIA laboratory at Uppsala University (Sweden) has developed the required RF power sources, procured the RF distribution and will test the cavities at nominal power. As no suitable amplifier was available at the ESS specifications (352MHz, 400kWp / 20kWavg, pulse width = 3.5 ms, pulse repetition frequency = 14 Hz), various technologies were compared and tetrode technology was selected for the first technology demonstrator RF power station at FREIA. We discuss the design of the technology demonstrator and present the first test results

Selection of RF Power Source and Distribution Scheme at 352 MHz for Spoke Cavities at ESS and FREIA

The report describes selection of RF power source and distribution scheme for spoke cavities at ESS and FREIA.  The European Spallation Source (ESS) is the world’s most powerful neutron source, which contain 36 superconducting spoke cavities at 352MHz and provide power of 0.5MW to the beam. The baseline for the RF system is a point-to-point generation and distribution  from a single source to a single accelerating cavity.The RF system that has to generate this power and distribute it to the accelerating cavities, is a main resource driver for linear accelerators in form of investment, operation and maintenance. Therefore the technical alternatives are compared to minimize capital and running cost of the accelerator, without compromising its reliability. At 352 MHz and 350 kW RF power output, tetrode amplifiers are selected because of their advantages of being cheap, reliable, simple and efficient as compared to the other RF power amplifiers. The tetrodes, due to their low gain, need a pre-driver. The solid state amplifier technology is selected as a pre-driver due to its simplicity, reliability and efficiency. Half height aluminum WR2300 wave guides shall be used for RF distribution. This solution makes it possible to discard the circulator from the RF distribution chain, thus improving system efficiency

Selection of RF Power Source and Distribution Scheme at 352 MHz for Spoke Cavities at ESS and FREIA

The report describes selection of RF power source and distribution scheme for spoke cavities at ESS and FREIA.  The European Spallation Source (ESS) is the world’s most powerful neutron source, which contain 36 superconducting spoke cavities at 352MHz and provide power of 0.5MW to the beam. The baseline for the RF system is a point-to-point generation and distribution  from a single source to a single accelerating cavity.The RF system that has to generate this power and distribute it to the accelerating cavities, is a main resource driver for linear accelerators in form of investment, operation and maintenance. Therefore the technical alternatives are compared to minimize capital and running cost of the accelerator, without compromising its reliability. At 352 MHz and 350 kW RF power output, tetrode amplifiers are selected because of their advantages of being cheap, reliable, simple and efficient as compared to the other RF power amplifiers. The tetrodes, due to their low gain, need a pre-driver. The solid state amplifier technology is selected as a pre-driver due to its simplicity, reliability and efficiency. Half height aluminum WR2300 wave guides shall be used for RF distribution. This solution makes it possible to discard the circulator from the RF distribution chain, thus improving system efficiency

Power Supplies for Tetrode High Power Amplfiers at FREIA : ESS TDR Contribution

This paper select the topology of the power supplies to the RF power amplifier to one spoke cavity to be tested at FREIA Uppsala University.The power supplies are thought to fulfill the requirements of ESS in Lund. The amplifiers pulsed operation will have a strong impact of the choice of topology. The RF amplifier will have two tetrodes in the final stage. The anode power supply is studied for different topologies and number of anodes to supply. Storing the energy for pulse current to the anodes at high voltage or at low voltage is considered. The short circuit protection can be with a crowbar or a series switch. The series switch is selected for reasons of short interrupts in case of temporary short circuits. The grid and filament supplies are thought to be standard of the shelf power supplies. Cost estimate and comments on maintenance in the end of the paper

Power Supplies for Tetrode High Power Amplfiers at FREIA : ESS TDR Contribution

This paper select the topology of the power supplies to the RF power amplifier to one spoke cavity to be tested at FREIA Uppsala University.The power supplies are thought to fulfill the requirements of ESS in Lund. The amplifiers pulsed operation will have a strong impact of the choice of topology. The RF amplifier will have two tetrodes in the final stage. The anode power supply is studied for different topologies and number of anodes to supply. Storing the energy for pulse current to the anodes at high voltage or at low voltage is considered. The short circuit protection can be with a crowbar or a series switch. The series switch is selected for reasons of short interrupts in case of temporary short circuits. The grid and filament supplies are thought to be standard of the shelf power supplies. Cost estimate and comments on maintenance in the end of the paper

Proposal for Design and Test of a 352 MHz Spoke RF Source

More than a dozen of spoke resonators prototypes (SSR, DSR, TSR) have been constructed and tested worldwide. None have accelerated beam until now and the ESS LINAC will be the first accelerator to operate with spoke cavities. Experience with other types of superconducting cavities indicates that high-power test is vital for reliable operation of the cavity in an accelerator. Although characteristics of a bare cavity can be obtained in a low-power test some important features of a `dressed' cavity like the electroacoustic stability and tuning system can be studied only in a high-power test stand. The ESS LINAC is a pulsed machine and the Lorentz detuning originating from the electromagnetic pressure on the cavity walls is expected to be strong. The Lorentz force along with the cavity sensitivity to mechanical excitations at some resonant frequencies may lead to self-sustained mechanical vibrations which make cavity operation dicult. Practical experience shows that increasing the boundary stiness will decrease the static Lorentz force detuning but not necessarily the dynamic one. Therefore, the FREIA group at Uppsala University is building a high-power test stand able to study performance of the ESS spoke cavity at high power. The RF test stand will be able to drive the cavity not only in the self-excitation mode but also with closed RF loop and fixed frequency. The later technique will be used to reproduce the shape of the cavity voltage pulse as it is expected to be in the cavity operating in the ESS LINAC such that the cavity tuning compensation system will be tested under realistic conditions.FREI