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This review gives a general overview of the organization of complex brain networks at the systems level, in particular in the cerebral cortex of the cat brain. We identify fundamental parameters of the structural organization of cortical networks, illustrate how these characteristics may arise during brain development and how they give rise to robustness of the cortical networks against damage. Moreover, we review potential implications of the structural organization of cortical networks for brain function. [ABSTRACT FROM AUTHOR]

Gravitatioanl Wave Astronomy progressively becomes this new window on the universe that we expected since tens of years. The technology has now reached a point where large instruments meet a level of sensitivity relevant for astrophysics. Depending on the sector of physics to be addressed, quired. Ground based antennas are already built in Europe, in Japan and in the USA and begin to deliver science data. The ESA/NASA space mission LISA in not yet definitively approved, but a number of teams endeavour to successfully pass the coming project reviews. We review the general principles of the optical detection of gravitation waves. [ABSTRACT FROM AUTHOR]

The Gravity Probe B Relativity Mission was successfully launched on April 20, 2004 from Vandenberg Air Force Base in California, a culmination of 40 years of collaborative development at Stanford University and NASA. The goal of the GP-B experiment is to perform precision tests of two independent predictions of general relativity, the geodetic effect and frame dragging. On-orbit cryogenic operations lasted 17.3 months, exceeding requirements. Analysis of the science data is now in progress with a planned announcement of results scheduled for December 2007. [ABSTRACT FROM AUTHOR]

A new eaa in fundamental physics began with the discovery of pulsars 1967, the discovery of the first binary pulsar in 1974 and the first millisecond pulsar in 1982. Ever since, pulsars have been used as precise cosmic clocks, taking us beyond the weak-field regime of the solar-system in the study of theories of gravity. Their contribution is crucial as no test can be considered to be complete without probing the strong-field realm of gravitational physics by finding and timing pulsars. This is particularly highlighted by the discovery of the first double pulsar system which was discovered by our team in 2003. The double pulsar is unique in that both neutron stars are detectable as radio pulsars. This, combined with significantly higher mean orbital velocities and accelerations when compared to other binary pulsars, suggested that the system would become the best available testbed for general relativity and alternative theories of gravity in the strong-field regime. Indeed, this has been achieved only three years after its discovery with four independent strong-field tests of GR, more than has been obtained for any other system. Use of the theory-independent mass ratio of the two stars makes these tests uniquely different from all preceding studies. Ourresults confirm the validity of GR at the 0.05% level, which is by far the best precision yet achieved for the strong-field regime. Remarkably, the transverse velocity of the systems center of mass is extremely small, a result which is important for future GR. tests and evolutinary studies. [ABSTRACT FROM AUTHOR]

Despite the impotant experimental success of General Relativity, there are several theoretical reasons indicating that gravitational phenomena may change radically from the predictions of Einstein's theory at very short distances. A main motivation comes from studies of unifying all fundamental forces in the framework of a consistent quantum theory, called string theory. This theory introduces a new physical constant, the string length, under which a new elementary structure shows up, changing drastically all physical laws of nature. In particular, lowering the string scale in the TeV region provides a theoretical framework for solving the so-called mass hierarchy problem: the apparent weakness of gravity can then be accounted by the existence of large internal dimensions, in the submillimeter tegion, and transverse to a braneworld where our obserbed universe is confined. I review the main properties of this scenario and its implications for new travitational phenomena that can be obserbed at both particle colliders, and in non-accelerator experiments searching for new short range forces at submillimeter distaces. I also discuss the warped metric case and possible localization of gravity in the presence of infinite size extra dimensions that cal modify Newton's law at cosmoligical distance scales. [ABSTRACT FROM AUTHOR]

After recalling the coceptual foundations and the vasic sturcture of general relativity, we review some of its main modern developments (apart from cosmology): ( i ) the post-Newtonian limit and weak-field tests in the solar system, (ii) strong gravitationl feelds and black holes, (iii) strong-field and radiative tests in binary pulsar observations, (iv) gravitational waves, (v) general relativity and quantum theory. [ABSTRACT FROM AUTHOR]

This is a report on our joint work with A. Chamseddine and M. Marcolli. This essay gives a short introduction to a potential application in physics of a new type of geometry based on spectral considerations which is convenient when dealing with non-commutative spaces, i.e., spaces in which the simplifying rule of commutativity is no longer applied to the coordinates. Starting from the phenomenological Lagrangian of gravity coupled with matter one infers, using the spectral action principle, that space-time admits a fine structure which is a subtle mixture of the usual 4-dimensional continuum with a finite discrete structure F. Under the (unrealistic) hypothesis that this structure remains valid (i.e., one does not have any "hyperfine" modification) until the unification scale, one obtains a number of predictions whose approximate validity is a basic test of the approach. [ABSTRACT FROM AUTHOR]

Heisenberg spin-1/2 chains are the archetype of quantum integrable one-dimensional models describing magnetic properties of a wide range of compounds (like the KCuF3 crystal), which can be probed experimentally through neutron scattering experiments, while being at the same time at the root of the invention of Bethe ansatz and Yang-Baxter structures that led in turn to quantum groups discovery. The aim of this contribution is to describe these algebraic ingredients and to show how to obtain from them (using combined analytical and numerical analysis) dynamical correlation functions of integrable Heisenberg spin-1/2 chains, the Fourier transform of which, the so-called dynamical structure factors, being directly measured in inelastic neutron scattering experiments. Our method is based on the algebraic Bethe ansatz and the resolution of the quantum inverse scattering problem. It leads to recent progress in the computation of integrable Heisenberg spin-1/2 chains correlation functions that we review here. [ABSTRACT FROM AUTHOR]

We review the connection between non-commutative gauge theory, matrix models and fluid mechanical systems. The non-commutative Chern-Simons description of the quantum Hall effect and bosonization of collective fermion states are used as specific examples. [ABSTRACT FROM AUTHOR]

A new version of scale analysis and renormalization theory has been found on the non-commutative Moyal space. It could be useful for physics beyond the standard model or for standard physics in strong external fields. The good news is that quantum field theory is better behaved on non-commutative than on ordinary space: indeed it has no Landau ghost. We review this rapidly growing subject. [ABSTRACT FROM AUTHOR]

Our aim is to introduce the ideas of non-commutative geometry through the example of the Quantum Hall Effect (QHE). We present a few concrete situations where the concepts of non-commutative geometry find physical applications. [ABSTRACT FROM AUTHOR]

The results of hydrodynamic simulations of the Virgo and Perseus clusters suggest that thermal conduction is not responsible for the observed temperature and density profiles. As a result it seems that thermal conduction occurs at a much lower level than the Spitzer value. Comparing cavity enthalpies to the radiative losses within the cooling radius for seven clusters suggests that some clusters are probably heated by sporadic, but extremely powerful, AGN outflows interspersed between more frequent but lower power outflows. [ABSTRACT FROM AUTHOR]

During the course of this conference, much evidence was presented that points to an intimate connection between the energetic outflows driven by AGN and the energy budget and quite possibly also the evolution of their gaseous environments. However, it is still not clear if and how the AGN activity is triggered by the cooling gas, how long the activity lasts for and how these effects give rise to the observed distribution of morphologies of the outflows. In this contribution we concentrate on the high radio luminosity end of the AGN population. While most of the heating of the environmental gas may be due to less luminous and energetic outflows [1], these more powerful objects have a very profound influence on their surroundings [2]. We will describe a simple model for powerful radio galaxies and radio-loud quasars that explains the dichotomy of their large-scale radio morphologies as well as their radio luminosity function. [ABSTRACT FROM AUTHOR]

Truly man is a marvelously vain, diverse, and undulating object. It is hard to found any constant and uniform judgment on him. Michel de Montaigne, Les Essais, Book I, Chapter 1: “By diverse means we arrive at the same end”; in The Complete Essays of Montaigne, Donald M. Frame transl., Stanford University Press (1958). [ABSTRACT FROM AUTHOR]

We review Einstein’s epistemological conceptions, and indicate their philosophical roots. The particular importance of the ideas of Hume, Kant, Mach, and Poincaré is highlighted. The specific characteristics of Einstein’s approach to physics are underlined. Lastly, we consider the practical application of Einstein’s methodological principles to the two theories of relativity, and to quantum theory. We emphasize a Kantian approach to quantum theory. [ABSTRACT FROM AUTHOR]

This is a previously unpublished manuscript of the lecture given by A. Einstein on November 2, 1910 before the Zürich Physical Society. The original document can be found in the bequest of Heinrich Zangger, at the Manuscripts Department of the Central Library of Zürich. Transcribed with the permission of the Central Library by W. Hunziker and A. Schultze (Institute for Theoretical Physics, ETH Zürich), kindly transmitted by N. Straumann (Institute for Theoretical Physics, University of Zürich-Irchel). The notes are by B. Duplantier (Department of Theoretical Physics, Saclay). [ABSTRACT FROM AUTHOR]

An extended experimental program to investigate the Gerasimov-Drell-Hearn (GDH) sum rule and related partial reaction cross sections on proton and neutron has been carried out by the GDH collaboration at the electron accelerators MAMI (Mainz) and ELSA (Bonn). The GDH sum rule connects the helicity-dependent photoabsorption cross section with the anomalous magnetic moment of the nucleon. The GDH collaboration has measured the total cross section of circularly polarised photons with longitudinally polarised protons at MAMI and ELSA to check this sum rule experimentally. In addition partial reaction channels like pion, double pion and eta production were determined. This provides new information on the helicity-dependent excitation spectrum of the nucleon. With the help of partial wave analyses it is possible to extract new, complementary information on the broad, overlapping resonances in this energy region. The double polarisation observable E measured in this experiment enhances the smaller multipoles via interference terms. The analysis of our data provides a new possibility to study the photon couplings to the nucleon resonances, especially above the Δ resonance where many properties of the observed states (e.g., coupling constants, branching ratios, helicity amplitudes) are only poorly known. In this paper we present several new results from our measurements on polarised proton and deuteron targets. [ABSTRACT FROM AUTHOR]

Experiments have been performed to explore the potential of the low emittance 855 MeV electron beam of the Mainz Microtron MAMI for imaging with coherent X-rays. Transition radiation from a micro-focused electron beam traversing a foil stack served as X-ray source with good transverse coherence. Refraction contrast radiographs of low absorbing materials, in particular polymer strings with diameters between 30 and 450 µm, were taken with a polychromatic transition radiation X-ray source with a spectral distribution in the energy range between 8 and about 40 keV. The electron beam spot size had standard deviation σh=(8.6 ± 0.1) µm in the horizontal and σv=(7.5 ± 0.1) µm in the vertical direction. X-ray films were used as detectors. The source-to-detector distance amounted to 11.4 m. The objects were placed in a distance of up to 6 m from the X-ray film. Holograms of strings were taken with a beam spot size σv=(0.50 ± 0.05) µm in vertical direction, and a monochromatic X-ray beam of 6 keV energy. A good longitudinal coherence has been obtained by the (111) reflection of a flat silicon single crystal in Bragg geometry. It has been demonstrated that a direct exposure CCD chip with a pixel size of 13 × 13 µm2 provides a highly effcient on-line detector. Contrast images can easily be generated with a complete elimination of all parasitic background. The on-line capability allows a minimization of the beam spot size by observing the smallest visible interference fringe spacings or the number of visible fringes. It has been demonstrated that X-ray films are also very useful detectors. The main advantage in comparison with the direct exposure CCD chip is the resolution. For the Structurix D3 (Agfa) X-ray film the standard deviation of the resolution was measured to be σf=(1.2 ± 0.4) µm, which is about a factor of 6 better than for the direct exposure CCD chip. With the small effective X-ray spot size in vertical direction of σv=(1.2±0.3) µm and a geometrical magnification of up to 7.4 high-quality holograms of tiny transparent strings were taken in which the holographic information is contained in up to 18 interference fringes. [ABSTRACT FROM AUTHOR]

The development over the last twenty years of the physics program and the experimental facilities at the Mainz Microtron MAMI will be reviewed. Ground-breaking contributions have been made to the development of experimental techniques and to our understanding of the structure of nucleons and nuclei. [ABSTRACT FROM AUTHOR]

Coherent radiation in the range from soft X-rays up to hard X-rays, produced by the low-emittance electron beam of MAMI, can be used for various applications. Novel types of interferometers have been developed for the measurement of the complex index of refraction of thin self-supporting foils. For the vacuum ultraviolet and soft X-ray region the interferometer consists of two collinear undulators, and a grating spectrometer. A foil placed between the undulators causes a phase shift and an attenuation of the oscillation amplitude. The complex index of refraction has been measured at the L2,3-absorption edges of nickel. A novel method is described for the measurement of the X-ray magnetic circular birefringence. For the hard X-ray region the interferometer consists of two foils at which the 855 MeV electron beam produces transition radiation. Distinct interference oscillations have been observed as a function of both, the photon emission angle and the distance between the foils. The refractive index decrement δ(ω) of a 2 µm thick nickel sample foil has been measured at X-ray energies around the K absorption edge at 8333 eV and at 9930 eV with an accuracy of better than 1.5 %. The line width of parametric X radiation (PXR) was measured in backward geometry with a Si single-crystal monochromator. Upper limits of the line width of 42meV, 50meV, and 44meV, have been determined for the (333), (444) and (555) reflections at photon energies of 5932 eV, 7909 eV, and 9887 eV, respectively. Small angle scattering of the electrons in the crystal leads to a stochastic frequency modulation of the exponentially damped wave train which results in the line broadening. To elucidate the quest if the production of PXR is a kinematical or a dynamical process the radiation from silicon single-crystal targets, emitted close to the electron direction, has been studied. The observed interference structures and the narrow-band radiation in forward direction shows that PXR is produced in a dynamical process. [ABSTRACT FROM AUTHOR]

A very successful experimental program with real photons has been achieved in 20 years of operation at the Mainz Microtron (MAMI) facility. The different detector setups, like DAPHNE, TAPS and the Crystal Ball are centered around the tagged photon facility the so-called Glasgow Tagger. From the rich spectrum of results only a few highlights will be discussed here, the proton polarizabilities, the pion polarizabilities, pion photoproduction close to the pion threshold and in the Δ(1232)-resonance region. [ABSTRACT FROM AUTHOR]

The Mainz Microtron MAMI is a cascade of three racetrack microtrons, delivering since 1991 a high-quality 855MeV, 100 µA cw-electron beam for nuclear, hadron and radiation physics experiments. An energy upgrade of this facility to 1.5 GeV by adding a Harmonic Double-Sided Microtron (HDSM) as a fourth stage is well underway and first beam is expected during the first half of 2006. A detailed description of the multiple recirculation scheme with normal conducting accelerator structures, the basis for the reliable operation of MAMI, is given and the historical development from MAMIA to MAMIB is described. The natural advancement to MAMIC by realizing a polytron of the next higher order, the HDSM, is covered in the last section and a first glimpse into the future of MAMI is given. [ABSTRACT FROM AUTHOR]

In 1953, it was decided to build a 500MeV electron synchrotron in Bonn. It came into operation 1958, being the first alternating gradient synchrotron in Europe. After five years of performing photoproduction experiments at this accelerator, a larger 2.5 GeV electron synchrotron was built and set into operation in 1967. Both synchrotrons were running for particle physics experiments, until from 1982 to 1987 a third accelerator, the electron stretcher ring ELSA, was constructed and set up in a separate ring tunnel below the physics institute. ELSA came into operation in 1987, using the pulsed 2.5 GeV synchrotron as pre-accelerator. ELSA serves either as storage ring producing synchrotron radiation, or as post-accelerator and pulse stretcher. Applying a slow extraction close to a third integer resonance, external electron beams with energies up to 3.5 GeV and high duty factors are delivered to hadron physics experiments. Various photo- and electroproduction experiments, utilising the experimental set-ups PHOENICS, ELAN, SAPHIR, GDH and Crystal Barrel have been carried out. During the late 90's, a pulsed GaAs source of polarised electrons was constructed and set up at the accelerator. ELSA was upgraded in order to accelerate polarised electrons, compensating for depolarising resonances by applying the methods of fast tune jumping and harmonic closed orbit correction. With the experimental investigation of the GDH sum rule, the first experiment requiring a polarised beam and a polarised target was successfully performed at the accelerator. In the near future, the stretcher ring will be further upgraded to increase polarisation and current of the external electron beams. In addition, the aspects of an increase of the maximum energy to 5 GeV using superconducting resonators will be investigated. [ABSTRACT FROM AUTHOR]

Over the last decade, a series of dedicated experiments to test heavy baryon chiral perturbation theory was performed at MAMI. Photo production of neutral pions close to threshold with unpolarized and polarized photon beam was performed to separate the multipole amplitudes at threshold. The extension of this experiments to a modest photon virtuality of Q2<0.1 GeV2/c2 was performed to extract additional longitudinal multipoles and to exploit the Q2 evolution predicted by theory. An out-of-plane measurement above π+ threshold with polarized electron beam gave access to the imaginary part of the s-wave amplitude. Finally, by coherent photo and electro production from the deuteron the neutron amplitude could be extracted. [ABSTRACT FROM AUTHOR]

Virtual Compton Scattering (VCS) off the proton is a recent field of investigation of the nucleon structure. VCS at threshold gives access to the Generalized Polarizabilities (GPs) of the proton. The qualities of both the beam and the high-resolution spectrometers available at the Mainz Microtron MAMI allowed us to perform at first such delicate experiments. This paper deals with different experiments dedicated to the GPs measurements. They are realized without and with polarization, below and just above pion threshold. [ABSTRACT FROM AUTHOR]

Parity-violating electron scattering has been a very useful tool for probing the structure of neutral currents and providing detailed information on electroweak form factors. A pioneering SLAC measurement in the mid-70s provided an important early test of the Standard Model. Modern electron accelerators provide high-intensity (> 100 µA), CW beams with polarizations as high as 85%. Experiments such as SAMPLE, A4, HAPPEX and G0 have exploited these capabilities and obtained new information on electroweak strange form factors in the Q2 range of 0.1-1.0 (GeV/c)2. That activity continues. Other experiments are designed to provide stringent tests of the Standard Model. E-158 at SLAC recently measured the weak charge of the electron. Qweak is a challenging new experiment at JLAB which is designed to measure the weak charge of the proton. This will probe for physics beyond the Standard Model corresponding to energy scales of more than 5TeV. [ABSTRACT FROM AUTHOR]

A measurement of the weak form factor of the proton allows a separation of the strangeness contribution to the electromagnetic form factors. The weak form factor is accessed experimentally by the measurement of a parity violating (PV) asymmetry in the scattering of polarized electrons on unpolarized protons. We performed such measurements with the setup of the A4-experiment at the MAMI accelerator facility in Mainz. The role of strangeness in low energy nonperturbative QCD is discussed. The A4-experiment is presented as well as the results on the strangeness form factors which have been measured at two Q2-values. The plans for backward angle measurements at the MAMI facility are presented. [ABSTRACT FROM AUTHOR]

Over the last decade accurate experiments at MAMI played an essential role to improve our understanding of the nucleon to Δ(1232) transition. Originally to a large extent motivated through intraquark hyperfine interactions anticipated in QCD-inspired quark models they showed that pionic degrees of freedom are essential. The meson cloud is mainly responsible for the observed quadrupole excitation strength and affects the magnetic dipole transition strength as well [ABSTRACT FROM AUTHOR]

Elastic form factors are of fundamental importance for the understanding of microscopic spatial structures. In case of the proton and the neutron, charge and magnetic form factors can be studied in elastic electron scattering. Techniques to accelerate polarised continuous electron beams, the availability of polarised targets as well as modern concepts and instrumentation for coincidence experiments and recoil polarimetry had an enormous impact on these measurements. The developments and experiments at the Mainz Microtron MAMI will be discussed in a general context. [ABSTRACT FROM AUTHOR]

It is reviewed how Compton scattering sum rules relate low-energy nucleon structure quantities to the nucleon excitation spectrum. In particular, the GDH sum rule and recently proposed extensions of it will be discussed. These extensions are sometimes more calculationally robust, which may be an advantage when estimating the chiral extrapolations of lattice QCD results, such as for anomalous magnetic moments. Subsequently, new developments in our description of the nucleon excitation spectrum will be discussed, in particular a recently developed chiral effective field theory framework for the Δ(1232)-resonance region. Within this framework, we discuss results on N and Δ masses, the γNΔ transition and the Δ magnetic dipole moment. [ABSTRACT FROM AUTHOR]

Chiral perturbation theory is the effective field theory of the strong interactions at low energies. We will give a short introduction to chiral perturbation theory for mesons and will discuss, as an example, the electromagnetic polarizabilities of the pion. These have recently been extracted from an experiment on radiative π+ photoproduction from the proton (γp → γ π+n) at the Mainz Microtron MAMI. Next we will turn to the one-baryon sector of chiral perturbation theory and will address the issue of a consistent power counting scheme. As examples of the heavy-baryon framework we will comment on the extraction of the axial radius from pion electroproduction and will discuss the generalized polarizabilities of the proton. Finally, we will discuss two recently proposed manifestly Lorentz-invariant renormalization schemes and illustrate their application in a calculation of the nucleon electromagnetic form factors. [ABSTRACT FROM AUTHOR]

Dispersion relations provide a powerful tool to analyse the electromagnetic form factors of the nucleon in both the space-like and the time-like regions with constraints from other experiments, unitarity, and perturbative QCD. We give a brief introduction into dispersion theory for nucleon form factors and present first results from our ongoing form factor analysis. We also calculate the two-pion continuum contribution to the isovector spectral functions drawing upon the new high statistics measurements of the pion form factor by the CMD-2, KLOE, and SND collaborations. [ABSTRACT FROM AUTHOR]

Experiments with polarized $$ ^3 \overrightarrow H e $$ at MAMI have already a long tradition. The A3 Collaboration started in 1993 with the aim to measure the electric form factor of the neutron. At this time MAMI was the second accelerator where experiments with $$ ^3 \overrightarrow H e $$ were possible. Some years before this pilot experiment the development of the apparatus to polarize 3He in Mainz started. There are two techniques which allow to polarize sufficient large quantities of 3He. Both techniques will be compared and the benefit of $$ ^3 \overrightarrow H e $$ for nuclear physics will be discussed. A review of the experiments done so far with $$ ^3 \overrightarrow H e $$ at MAMI will be given and the progress in the target development, the detector setup and the electron beam performance will be pointed out. [ABSTRACT FROM AUTHOR]

An overview over present achievements and future challenges in the field of few-nucleon systems is presented. Special emphasis is laid on the construction of a unified approach to hadronic and electro- magnetic reactions on few-nucleon systems, necessary for studying the borderline between quark-gluon and effective descriptions. [ABSTRACT FROM AUTHOR]

Few-body systems provide a testing ground for models of the NN interaction, reaction mechanisms and for models of nuclei. An overview of results of coincidence experiments on the deuteron, 3He and 4He obtained in the last 20 years at MAMI and at other facilities, covering a wide range of momentum and energy transfers, is presented. [ABSTRACT FROM AUTHOR]

The Continuous Electron Accelerator Facility, CEBAF, located at the Thomas Jefferson National Accelerator Facility, is devoted to the investigation of the electromagnetic structure of mesons, nucleons, and nuclei using high energy, high duty-cycle electron and photon beams. Selected experimental results of particular interest to the MAMI community are presented. [ABSTRACT FROM AUTHOR]

Precision experiments using the electromagnetic probe have recently produced important new data on fundamental properties of the nucleon, e.g. charge, magnetism, shape, polarizability, spin and sea quark structure. These experiments have been made possible by a new generation of high duty factor electron accelerators, advances in spin polarization technology (beams, targets and recoil polarimeters), and the development of unique, optimized detector systems. In this contribution, the role of multiple photon exchange in electron scattering from the proton and the role of sea quarks in nucleon structure are highlighted. [ABSTRACT FROM AUTHOR]

The large mechanical luminosity of the jets of GRS 1915+105 should give rise to luminous emission regions, similar to those observed in radio galaxies, where the jets interact with the gas surrounding the source. However, no radio synchrotron emission of the expected morphology has been found. Here we present the results of a study suggesting that radio bremsstrahlung from the compressed and heated ISM in front of the jets should be detectable, while the synchrotron lobes may be too faint. We identify these jet impact sites with two well-known IRAS regions. This identification suggests a distance of GRS 1915+105 of 6.5 ± 1.6 kpc, significantly closer than the usually assumed distance of 11-12 kpc.We discuss the implications of this reduced distance estimate. The non-detection of the synchrotron radio lobes implies a significant fraction of non-radiating particles, possibly protons, in the jets. The apparent motion of small-scale jet components is not superluminal, so if superluminal motion is required for an object to be termed a microquasar, GRS 1915+105 actually does not qualify. The mass of the black hole in the system is increased to 21±9 M⊙, while the mechanical luminosity of the jets is reduced to 14% of the Eddington luminosity. [ABSTRACT FROM AUTHOR]

A digital image intensified CCD camera with an electronically gated image intensifier was used to produce very short duration images of meteors. The observational system employed a 0.40 m F/4.5 Newtonian telescope to obtain high spatial resolution. A second intensified CCD camera was used to yield height information using parallax. At a typical meteor height one pixel (for the vertically oriented system) corresponded to about 1.1 m. A sampling of 59 mainly sporadic meteors was analyzed. There is clear variability from meteor to meteor, with many meteors (nearly 50%) showing only a small amount of wake, while some meteors (approximately 20%) have the off segments completely filled in. [ABSTRACT FROM AUTHOR]

We report results from two station, short-baseline (<100 m) high resolution measurements of faint meteors (limiting meteor magnitude +9) with the goal of measuring their optical trail widths. Meteors were observed using two 0.40 m Newtonian telescopes (field of view ∼0.4 degrees) equipped with image intensifiers. Both telescopes were vertically oriented in a fixed mount and pointed to the same field of view. One system used a gated image intensified camera allowing the transverse velocity component to be measured. The widest trail captured, out of a total of 34 common events measured by both optical systems, had a full-width to half-maximum of 1.37±0.71 m. The widest trail overall was captured by the gated system only, and was found to have a full-width of ∼10 m. The brightness variation across this trail was found to be best represented by a Lorentzian. Most trails were smaller than our resolution limit and hence we could only place upper limits on their optical width. These were generally less than 1 m after correction for instrumental effects. Four meteors were found to have heights near 65 km and very low transverse velocities. These may be indicative of a largely unreported high density asteroidal component at these faint meteor magnitudes. [ABSTRACT FROM AUTHOR]