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Skeletal muscle responds to endurance exercise via increased transcription of metabolic and stress-related genes ultimately to yield increased steady-state levels of specific proteins. These changes in transcriptional activity are highly dependent on the mode, duration, intensity and frequency of the contractile stimulus. One of the major challenges for exercise physiologists over the coming decades is to identify the exercise ‘signal(s)’ that are responsible for initiating the adaptive response and the precise signal transduction pathways which mediate the adaptive processes. In this regard, it is now becoming apparent that cellular energy status may have an important role to play in this process. For example, many stress-and metabolic-related genes are enhanced when the exercise is commenced under reduced pre-exercise muscle glycogen levels and attenuated when glucose is ingested during exercise. Taken together, such findings suggest that training under conditions of reduced carbohydrate availability from both endogenous and exogenous sources may provide an enhanced stimulus for inducing beneficial adaptations of skeletal muscle. This hypothesis is in marked contrast to the widely held belief that intense training periods should be supported by a high carbohydrate diet in order to maintain training intensity and replenish energy stores for future training sessions. This paper will outline the current thinking regarding the potential for carbohydrate availability to modulate the adaptations typically observed following periods of endurance training. Relevant data from the literature and our own laboratory is presented with a view to providing some potential advantages and disadvantages of training with reduced carbohydrate availability for both athletes and coaches., Trening izdržljivosti opći je naziv za bilo koju ponavljanu fizičku aktivnost kojoj je cilj usavršavanje sposobnosti organizma da zadrži intenzitet rad tijekom dužeg perioda. Dugotrajne vježbe dovest će do mnogobrojnih promjena koje poboljšavaju dopremanje i iskoristivost kisika te na taj način dolazi do povećanja potencijala aerobnog metabolizma i poboljšanja izvedbe u aerobnim uvjetima rada. Navedene promjene uključuju izmjene u strukturi i funkciji srčano-žilnog, dišnog i mišićno-skeletnog sustava. Skeletni mišići odgovaraju na vježbe izdržljivosti povećanjem transkripcije metaboličkih gena i gena povezanih sa stresom da bi, naposljetku, izazvali povećano stabilno stanje specifičnih proteina. Ti adaptacijski odgovori dovode do poboljšanja stanične funkcijei koja služi za održavanje ravnoteže između energetskih zahtjeva na sustav i kapaciteta koji zadovoljavaju te potrebe te na taj način dovode do poboljšanja u sportskoj izvedbi. Način prehrane je moćan modulator adaptacije skeletnih mišića, izazvane vježbama izdržljivosti. Nekoliko istraživanja pokazalo je da smanjena uporaba ugljikohidrata može pojačano potaknuti adaptacije skeletnog mišića izazvane vježbanjem. Ti rezultati upućuju na na to kako je dostupnost substrata i njihovo korištenje iz endogenih i egzogenih izvora, osobito onih povezanih s ugljikohidratima, vrlo važan faktor utjecaja na adaptacijske reakcije skeletnog mišića na vježbanje. Takvi podaci sugeriraju da pažljivo raspoređeni periodi treninga u uvjetima niskog unosa ugljikohidrata mogu biti korisni za poticanje adaptacija skeletnog mišića te poboljšanje kasnije izvedbe. Posljednji podaci iz našeg laboratorija ispitali su utjecaj šestotjednog visokointenzivnog intervalnog programa treninga, koji se provodio u uvjetima niske koncentracije mišićnog glikogena, s egzogenom suplementacijom ugljikohidratima i bez nje, na adaptaciju skeletnog mišićja čovjeka i izvedbu vježbi. Uzorci mišićne biopsije, koja se provodila nakon treninga, otkrila je znatnije

177 p. 25 cm., United States and Its Territories, 1898-1930: The Age of Imperialism, (dlps) AFJ0455.0001.001, (lccallno) DS 518.8 .C3, http://quod.lib.umich.edu/t/text/accesspolicy.html

1 p. L., 36 p. 22 cm., United States and Its Territories, 1898-1930: The Age of Imperialism, (dlps) ABK5557.0001.001, (lccallno) E179 .C16, http://quod.lib.umich.edu/t/text/accesspolicy.html

177 p. 25 cm., United States and Its Territories, 1898-1930: The Age of Imperialism, (dlps) AFJ0455.0001.001, (lccallno) DS 518.8 .C3, http://quod.lib.umich.edu/t/text/accesspolicy.html

1 p. L., 36 p. 22 cm., United States and Its Territories, 1898-1930: The Age of Imperialism, (dlps) ABK5557.0001.001, (lccallno) E179 .C16, http://quod.lib.umich.edu/t/text/accesspolicy.html

The Interlake area of Manitoba contains a great variety of physical and cultural phenomena of interest to historical geographers. The area was occupied only gradually, with most white settlement taking place between 1872 and 1920. During this period, settlers from almost every country in Europe (and some from elsewhere) entered the Interlake and soon far outnumbered the Metis and Indians already there. Though there was much mixing of ethnic groups, there were also a number of distinct ethnic settlements. Settlement took place in a great variety of natural environments. Soils ranged from deep, fertile, stone-free lacustrine soils to extremely thin, high-lime soils with bedrock less than six inches from the surface. The natural vegetation ranged from prairie grassland through scattered aspen groves to heavy spruce forests interspersed with tamarack and sedge swamps. The presence of lakes and rivers added another element of variety to the physical environment. With such a varied physical and cultural background, it is not surprising that there was also much variety in the type and intensity of economic activities and in the growth of transportation systems and service centers. The Interlake contained many examples of pioneer development that were illustrative of such development in the Canadian West as a whole.

The Interlake area of Manitoba contains a great variety of physical and cultural phenomena of interest to historical geographers. The area was occupied only gradually, with most white settlement taking place between 1872 and 1920. During this period, settlers from almost every country in Europe (and some from elsewhere) entered the Interlake and soon far outnumbered the Metis and Indians already there. Though there was much mixing of ethnic groups, there were also a number of distinct ethnic settlements. Settlement took place in a great variety of natural environments. Soils ranged from deep, fertile, stone-free lacustrine soils to extremely thin, high-lime soils with bedrock less than six inches from the surface. The natural vegetation ranged from prairie grassland through scattered aspen groves to heavy spruce forests interspersed with tamarack and sedge swamps. The presence of lakes and rivers added another element of variety to the physical environment. With such a varied physical and cultural background, it is not surprising that there was also much variety in the type and intensity of economic activities and in the growth of transportation systems and service centers. The Interlake contained many examples of pioneer development that were illustrative of such development in the Canadian West as a whole.

The Interlake area of Manitoba contains a great variety of physical and cultural phenomena of interest to historical geographers. The area was occupied only gradually, with most white settlement taking place between 1872 and 1920. During this period, settlers from almost every country in Europe (and some from elsewhere) entered the Interlake and soon far outnumbered the Metis and Indians already there. Though there was much mixing of ethnic groups, there were also a number of distinct ethnic settlements. Settlement took place in a great variety of natural environments. Soils ranged from deep, fertile, stone-free lacustrine soils to extremely thin, high-lime soils with bedrock less than six inches from the surface. The natural vegetation ranged from prairie grassland through scattered aspen groves to heavy spruce forests interspersed with tamarack and sedge swamps. The presence of lakes and rivers added another element of variety to the physical environment. With such a varied physical and cultural background, it is not surprising that there was also much variety in the type and intensity of economic activities and in the growth of transportation systems and service centers. The Interlake contained many examples of pioneer development that were illustrative of such development in the Canadian West as a whole.

The Interlake area of Manitoba contains a great variety of physical and cultural phenomena of interest to historical geographers. The area was occupied only gradually, with most white settlement taking place between 1872 and 1920. During this period, settlers from almost every country in Europe (and some from elsewhere) entered the Interlake and soon far outnumbered the Metis and Indians already there. Though there was much mixing of ethnic groups, there were also a number of distinct ethnic settlements. Settlement took place in a great variety of natural environments. Soils ranged from deep, fertile, stone-free lacustrine soils to extremely thin, high-lime soils with bedrock less than six inches from the surface. The natural vegetation ranged from prairie grassland through scattered aspen groves to heavy spruce forests interspersed with tamarack and sedge swamps. The presence of lakes and rivers added another element of variety to the physical environment. With such a varied physical and cultural background, it is not surprising that there was also much variety in the type and intensity of economic activities and in the growth of transportation systems and service centers. The Interlake contained many examples of pioneer development that were illustrative of such development in the Canadian West as a whole.

Thesis (M.S.)--University of Rochester. College of Engineering and Applied Science. Institute of Optics, 1984. This thesis was digitized by the Institute of Optics in 2014 and was determined to have lapsed into the public domain. If you are the author and have questions about the digitization of your work, please contact Kari Brick, Graduate Program Coordinator for the Institute of Optics, at kbrick@ur.rochester.edu. Other contact information for the Institute is available at http://www.optics.rochester.edu, Near-field amplitude and phase distributions from a high-peak-power, frequency converted Nd:glass laser (λ = 35lnm) have been holographically recorded on silver-halide emulsions. Conventionally, the absence of a suitable reference beam forces one to use some type of shearing interferometry to obtain phasefront information, while the near-field and far-field distributions are recorded as intensity profiles. In this study, a spatially filtered, locally generated reference beam was created to holographically store the complex amplitude distribution of the pulsed laser beam, while reconstruction of the original wavefront was achieved with a continuous-wave laser. Reconstructed near-field and quasi-far-field intensity distributions closely resembled those obtained from conventional techniques, and accurate phasefront reconstruction was achieved. Furthermore, several two-beam interferometric techniques, not practicable with a high-peak-power laser, have been successfully implemented on a continuous-wave reconstruction of the pulsed laser beam.

Thesis (M.S.)--University of Rochester. College of Engineering and Applied Science. Institute of Optics, 1978. This thesis was digitized by the Institute of Optics in 2014 and was determined to have lapsed into the public domain. If you are the author and have questions about the digitization of your work, please contact Kari Brick, Graduate Program Coordinator for the Institute of Optics, at kbrick@ur.rochester.edu. Other contact information for the Institute is available at http://www.optics.rochester.edu, A plasma was produced by focussing a pulse from a Nd:glass laser onto a solid aluminum target. The plasma was photographed along a direction perpendicular to the laser axis utilizing the light at the second harmonic of the laser frequency which is generated at the critical surface. This photograph was compared with a far field photograph that showed the intensity distribution of the laser focal spot. The comparison showed that structures which appeared in the focal intensity distribution also appeared in the distribution of the emitted second harmonic light. It was concluded that the laser intensity profile did not undergo any major modifications due to propagation through the underdense plasma to the critical surface at intensities up to 10¹⁴ watts/cm². Also, the second harmonic photograph could be used as a diagnostic of the laser focal distribution.

Thesis (Ph. D.)--University of Rochester. College of Engineering and Applied Science. Institute of Optics, 1981. This thesis was digitized by the Institute of Optics in 2014 and was determined to have lapsed into the public domain. If you are the author and have questions about the digitization of your work, please contact Kari Brick, Graduate Program Coordinator for the Institute of Optics, at kbrick@ur.rochester.edu. Other contact information for the Institute is available at http://www.optics.rochester.edu, Zone plate coded imaging (ZPCI) is a useful technique for imaging x-ray and particle emissions from laser-produced plasmas. Though past studies have developed a theory of ZPCI system parameters (e.g. resolution), image degradation has not been thoroughly explored, and optimization has not been studied. This thesis is the first treatment of image evaluation and optimization in ZPCI. Both theoretical and experimental studies are performed. The theoretical construct begins with a simple categorization scheme for optical coded imaging systems. Equating ZPCI with a multiple exposure holographic process permits easy analysis of the reconstruction step. Image degradation is classified as either deterministic (artifacts) or random (noise). Nonlinear ZPCI is treated for both absorption and phase reconstructions. The high diffraction efficiency and resolution of phase reconstructions can be offset by deterministic image degradation due to intermodulation effects. Ideally, it is possible to compensate for intermodulation, but practical phenomena (such as Fresnel diffraction in the recording step) tend to deter this. The grain noise treatments of previous workers are extended to account for reconstruction mask density effects and object spatial frequency content. Noise is coupled to the image field and peaks at low frequencies. Shot noise is treated briefly and compared with grain noise. The experiments performed are the first image evaluations in the x-ray region. Linear ZPCI is shown to have better image fidelity than nonlinear ZPCI. The variation of artifacts with image size is also demonstrated. Qualitative studies of grain noise verify that phase reconstructions have higher SNR than absorption reconstructions. The variation of SNR with object size is also shown. Optimization is a compromise between SNR, resolution, and nonlinearity; the images with highest SNR tend to suffer the most deterministic degradation. Measurable fi

Thesis (Ph.D.)--University of Rochester. Institute of Optics, 1988., We examine theoretically and experimentally the properties of three-dimensional microscope images. This evaluation includes quantitative comparison of numerical models and experimentally determined images of well-defined two- and three- dimensional test targets. We derive theory for numerical calculations and image analysis from the theory of partial coherence. We perform experiments with a well-corrected microscope, equipped for electronic recording and digitization of images and for the precise control of illumination coherence. Test objects include two- and three-dimensional bar and slit targets, which we fabricate by microlithography. The purpose of this investigation is twofold. First, we evaluate the agreement between the performance of an optical microscope and theoretical models. Prior to this investigation, quantitative agreement of theory and experiments in conventional microscopy had been demonstrated in only select cases. In this thesis, we demonstrate for the first time that object to image relations from coherence theory describe accurately three-dimensional imaging of a wide class of weakly scattering objects, including phase objects. We show that departures of theory from experiment occur when experimental conditions violate particular assumptions in the theoretical model. In particular, we vary the object transmittance properties to demonstrate the limited application of transmission functions and weak scattering approximations in modeling the objects. Also, we evaluate effects of alignment, aberrations, high numerical aperture, and stray light for a range of coherence conditions. Second, we analyze the consequences of inaccuracy in the modeling of microscope imaging for quantitative image analysis, including object reconstructions. We demonstrate that the intensity modulation in images recorded as optical sections from a two- or three-dimensional object provides unambiguous information about the object transmittance properties for

Thesis (Ph.D.)--University of Rochester. Institute of Optics, 1974., We present a study of the structure of various types of high-order transverse modes observed in a spherical mirror cavity containing Brewster windows with slight cylindrical power. From Weinstein's theory of modes in an ellipsoidal cavity we recognize two types of modes in our observation. These modes we referred to in the theory as the A- and B-type modes, respectively. Based on this theory we have derived a set of expressions to describe the geometry of both the A- and B-type modes, in terms of cavity parameters, cavity astigmatism, wavelength and mode order number. Among those parameters, the cavity astigmatism and the mode order number are most important in determining the shape of the mode patterns. The deviation of the mode patterns from the familiar Hermite-Gaussian or Laguerre-Gaussian distributions is very pronounced for cavity astigmatism of less than about 100 micrometers and mode order numbers larger than about 50. A 10mm bore Argon ion laser was constructed to verify the theory. The laser geometry allowed the order number of oscillating modes to exceed 70 and allowed the astigmatism to vary in the range of a few micrometers to a few millimeters. The experiments consisted of a systematic recording of mode patterns for various cavity geometries and characterizing the recorded patterns in terms of the geometrical parameters in the theory. We also discuss applications of the relationships between the shape of mode patterns and cavity geometry to specific laser systems used in active imaging and active beam scanning.

Thesis (Ph.D.)--University of Rochester. College of Engineering and Applied Science. Institute of Optics, 1972., In this thesis we develop a "Lamb-type" theory for a two-mode, standing wave, homogeneously broadened laser. The theory differs from Lamb's in that the coupled equations of motion for the atomic system are solved with a matrix perturbation theory that converges best for large, nearly equal mode amplitudes rather than with a perturbation theory that is a power series in the field which converges poorly for large mode amplitudes. The theory has an exact matrix solution when certain symmetries in mode amplitude and mode detuning occur. Asymmetries in these parameters may then be treated by a perturbation theory that converges best when the mode amplitudes are large and nearly equal. The theory makes it possible to solve for the macroscopic polarization at certain cavity positions, and it is found that the polarization consists of an infinite number of harmonic sidebands spaced at multiples of the mode difference frequency from atomic resonance. The projection of the first order polarization onto the two spatial modes gives the first order driving functions for the mode amplitude equations. Two investigations are made: 1) we expand the driving functions in powers of the mode amplitudes to compare with Lamb theory, and 2) we program the mode amplitude equations on a digital computer without expanding in a power series in mode amplitudes to plot out the evolution of the amplitudes for strong fields. The computer shows that even for strong fields, the stronger mode quenches the weaker mode in a time dependent on the laser parameters. Although the theory has been developed for use with longitudinal modes, it may also be used for transverse modes. While the losses of the various longitudinal modes are approximately equal, higher order transverse modes arc known to have higher losses than lower order transverse modes. When the losses of the various modes are taken to be unequal, the matrix theory is expected to give different results than i

Thesis (Ph. D.)--University of Rochester. College of Engineering and Applied Science. Institute of Optics, 1983. This thesis was digitized by the Institute of Optics in 2014 and was determined to have lapsed into the public domain. If you are the author and have questions about the digitization of your work, please contact Kari Brick, Graduate Program Coordinator for the Institute of Optics, at kbrick@ur.rochester.edu. Other contact information for the Institute is available at http://www.optics.rochester.edu, In recent years much progress has been reported in the fabrication of multilayer reflectors for x-ray and XUV radiation (1Å - 600Å). The characteristic optical properties of materials at these wavelengths (dielectric constants are complex and approach unity), allow one to obtain solutions to Maxwell's equations for a quasi-periodic reflector whose layers contain arbitrary index gradients. This solution can be formulated as a difference equation that propagates the amplitude reflectance across each layer pair. The difference equation resembles the Airy summation for single layers, but has a simpler Ricatti form. From the difference equation one can derive design criteria for maximization of multilayer reflectivity. These criteria provide guidance in the selection of appropriate multilayer materials, and have been used to derive approximate scaling laws for multilayer reflecting properties. The difference equation forms the basis for a non-perturbative analysis of multilayer reflectivity in the presence of random thickness errors (including the residual loss in reflectivity that remains when reflectance monitoring is used to compensate for thickness errors during multilayer fabrication). Under certain circumstances, the difference equation can be used to analyze the effect of interfacial roughness on multilayer reflectivity. Accurate closed-form solutions to such stochastic problems can be found by neglecting higher order powers in the incoherent camponent of multilayer reflectivity. The reflecting properties of x-ray multilayers may contain qualitative signatures that correspond to these different kinds of structural defects. Our theoretical results indicate that significant constraints on efficiency and field of view are involved in using multilayers to extend optical technology to the x-ray regime. Examples discussed include microscopes operating at short x-ray wavelengths (1Å - 2Å), where multilayers can

Thesis (Ph.D.)--University of Rochester. College of Engineering and Applied Science. Institute of Optics, 1979. This thesis was digitized by the Institute of Optics in 2014 and was determined to have lapsed into the public domain. If you are the author and have questions about the digitization of your work, please contact Kari Brick, Graduate Program Coordinator for the Institute of Optics, at kbrick@ur.rochester.edu. Other contact information for the Institute is available at http://www.optics.rochester.edu, Amplified spontaneous emission (ASE) is stimulated emission initiated by the fluorescence in a laser amplifier in the absence of optical feedback. A measurement of the angular distribution of ASE is shown to be a practical, sensitive, and unambiguous single-shot diagnostic of gain in laser amplifier experiments. The technique is more sensitive than spectral line narrowing observations in situations in which the measurements are spatially integrated. Other direct measurement techniques, such as pulse injection or gain-length variation, are often impractical because of the lack of reproducibility of the (pulsed) experimental conditions. A two-dimensional geometric model is presented that predicts the angular distribution of ASE from a rectangular amplifier with uniform fluorescence and gain. The radiation transport equation including gain is integrated over the amplifier to determine the total radiant intensity emitted into a given direction. Angular distribution curves are presented in terms of the amplifier length to width ratio and the gain-length product. The FWHM beam divergence is shown to be inversely proportional to the amplifier aspect ratio and to increase with decreasing gain-length product. Near threshold the beam divergence is several times larger than the inverse aspect ratio. Calculations for integrated measurements in which the gain coefficient and fluorescence rate are linear functions of a parameter (time, wavelength, space) show that an average gain coefficient may be used in the uniform gain model to good approximation at small gain-length products. A reasonable threshold for the determination of gain from directional ASE measurements is found to occur for an average gain-length product of unity. A transverse laser-pumped dye amplifier experiment is described which was designed to measure the ASE angular distribution from an optically freestanding amplifier with a non-uniform transverse gain profile. Measurements of the distribu

Thesis (Ph.D.)--University of Rochester. College of Engineering and Applied Science. Institute of Optics, 1977. This thesis was digitized by the Institute of Optics in 2014 and was determined to have lapsed into the public domain. If you are the author and have questions about the digitization of your work, please contact Kari Brick, Graduate Program Coordinator for the Institute of Optics, at kbrick@ur.rochester.edu. Other contact information for the Institute is available at http://www.optics.rochester.edu, The primary emphasis of this thesis involves an investigation of techniques for the control and modulation of x-ray radiation through acoustic perturbation of solids. The use of x-ray diffraction and x-ray optical techniques for the study of acoustic fields and atomic motion was also investigated. Analysis of the basic properties of x-ray propagation.in solids reveals that practical methods for x-ray control or modulation must involve changes in the spatial configuration of x-ray scatterers. Numerical methods for the study of x-ray propagation in acoustically perturbed crystals are formulated. In developing these methods special emphasis has been placed on Borrmann transmission in thick crystals. Modulation and shuttering (on a micro-second timescale) of x-rays are experimentally demonstrated. A quantitative investigation of the basic interactions used to produce modulation and shuttering is presented. Agreement between the experimental observations and the theoretical predictions is within experimental error. An analytical investigation of the basic potential and limitations of x-ray modulation shuttering and control devices is presented. Basic design criteria for x-ray modulation devices is formulated and applied to practical configurations.

Thesis (Ph.D.)--University of Rochester. College of Engineering and Applied Science. Institute of Optics, 1978. This thesis was digitized by the Institute of Optics in 2014 and was determined to have lapsed into the public domain. If you are the author and have questions about the digitization of your work, please contact Kari Brick, Graduate Program Coordinator for the Institute of Optics, at kbrick@ur.rochester.edu. Other contact information for the Institute is available at http://www.optics.rochester.edu, An enormous amount of theoretical and experimental work has gone into understanding the complex inter-molecular energy transfer processes of aromatic molecules in condensed phase environments. This contrasts sharply with the very limited attention received by these same processes in the gas phase. The absence of a background medium, and much faster diffusion of a dilute gas may be expected to result in qualitatively new features. In this work, the assumptions and corresponding limitations of the highly successful, condensed phase, electronic energy transfer theorv of Forster and Dexter are discussed. With these limitations in mind, a simple extension of this theory is made into the gas phase. It is concluded that the extended theory is applicable to almost all gas phase, electronic energy transfer in systems involving aromatic hydrocarbons. A primary result of this theory is that dipole-dipole, and higher order, long range energy transfer should be much more difficult to observe in aromatic vapors than they are in the corresponding condensed phase systems. It is shown that short range, exchange transfer will generally obscure the long range effects. In an effort to observe long range transfer in a gas phase aromatic system, a series of Stern-Volmer measurements of the absolute rates of energy transfer from the cadmium 5³P₁ state to POPOP vapor were performed. New techniques were used for the elimination of some of the most troublesome systematic errors of the Stern-Volmer methods and dependable values were found for the rates. The bimolcular rate constant for the total rate of cadmium state deactivation by POPOP was found to be 5.9 x 10⁻¹⁰ cm³/sec, or approximately the gas kinetic rate. This is consistent with the predicted rate of exchange transfer to the POPOP triplet state. The specific rate of energy transfer from the cadmium state to the POPOP excited singlet was also measured. A rate constant of 4.2 x 10⁻¹¹ cm³/sec was found. This

Thesis (Ph.D.)--University of Rochester. College of Engineering and Applied Science. Institute of Optics, 1972., A theoretical and experimental study of the output beams from large-bore Argon-Ion lasers was conducted. The objective of the study was to induce transverse mode-locking in a large-bore laser and to establish the suitability of this mode of operation for producing a high resolution scanning beam. An intra-cavity electro-optic beam deflector was used to induce transverse mode-locking. In spite of strong mode competition inherent in the Argon-Ion laser, a single set (i.e., all having the same longitudinal mode number) of transverse modes fully saturated the gain profile under these conditions. A scanning beam resulted from locking the transverse modes of the laser. The resolution of the beam was considerably lower than predicted for this kind of operation. This discrepancy appears to be caused by the poor (measured) optical quality of the intra-cavity modulator. The design of an appropriate optical cavity for use in this application was considered, and an analysis of the coupling of transverse modes by an intra-cavity beam deflector was made. An approximate method for predicting the highest-order transverse mode which will oscillate in a given optical cavity was derived, and suitable parameters for describing a transverse mode-locked laser beam were established. Experiments were performed with both quartz and beryllium oxide discharge tubes using r.f. helical-field excitation. A novel one centimeter diameter beryllium oxide discharge tube was designed and constructed for the study. Single high order transverse modes oscillated near threshold and the structure was in agreement with theoretical predictions. Oscillation in re-entrant cavity configurations was studied, and gave a measure of the effects of astigmatism introduced by the intra-cavity Brewster windows.