Search

Field biology is an area of research that involves working directly with living organisms in situ through a practice known as “fieldwork.” Conducting fieldwork often requires complex logistical planning within multiregional or multinational teams, interacting with local communities at field sites, and collaborative research led by one or a few of the core team members. However, existing power imbalances stemming from geopolitical history, discrimination, and professional position, among other factors, perpetuate inequities when conducting these research endeavors. After reflecting on our own research programs, we propose four general principles to guide equitable, inclusive, ethical, and safe practices in field biology: be collaborative, be respectful, be legal, and be safe. Although many biologists already structure their field programs around these principles or similar values, executing equitable research practices can prove challenging and requires careful consideration, especially by those in positions with relatively greater privilege. Based on experiences and input from a diverse group of global collaborators, we provide suggestions for action-oriented approaches to make field biology more equitable, with particular attention to how those with greater privilege can contribute. While we acknowledge that not all suggestions will be applicable to every institution or program, we hope that they will generate discussions and provide a baseline for training in proactive, equitable fieldwork practices.

The Flint Hills represent the largest tract of tallgrass prairie in North America and is located near the western edge of the native range of the Virginia opossum (Didelphis virginiana). This region is undergoing rapid landscape changes (e.g., urbanization, agriculture, woody encroachment) that are negatively affecting mammal communities. Although previous research has revealed northward distributional expansions of Virginia opossums facilitated by urban development, no studies have assessed how landscape change affects distribution patterns along the western edge of their geographic range. During 2016–2018, we monitored site (n = 74) occupancy along urban–rural transects in the Flint Hills to assess the influence of landscape change (i.e., urban, grassland, agriculture, woody encroachment) and water availability on the distribution of Virginia opossums. Sites surrounded by urban land cover had greater initial occupancy probabilities and lower extinction rates. Sites closer to permanent water sources experienced greater colonization rates and lower extinction rates. In addition, site extinction rates were lower in areas surrounded by woody encroachment. Our results concur with other studies suggesting that growing urban areas may expand opossum distributions along the edges of their geographic range. Our study also suggests that woody encroachment into tallgrass prairies may provide an alternative pathway for future distributional expansions. Future research must consider the potential for landscape change, along with dynamic water availability, in models predicting the distribution of Virginia opossums.

Species delimitation requires a broad assessment of population-level variation using multiple lines of evidence, a process known as integrative taxonomy. More specifically, studies of species limits must address underlying questions of what limits the distribution of populations, how traits vary in association with different environments, and whether the observed trait differences may lead to speciation through reproductive isolation. While genomic data have revolutionized the process of delimiting species, such data should be analyzed along with phenotypic, behavioral, and ecological traits that shape individuals across geographic and environmental space. The integration of multiple traits promotes taxonomic stability and should be a major guiding principle for species delimitation. Equally important, however, is thorough geographic sampling to adequately represent population-level variation—both in allopatry and across putative contact zones. We discuss the importance of both of these factors in the context of species concepts and traits and present different examples from birds that illustrate criteria for species delimitation. In addition, we review a decade of proposals for species-level taxonomic revisions considered by the American Ornithological Society’s North American Classification Committee, and summarize the basis for decisions on whether to split or lump species. Finally, we present recommendations and discuss challenges (specifically permits, time, and funding) for species delimitation studies. This is an exciting time to be studying species delimitation in birds: many species-level questions remain, and methodological advances along with increased access to data enable new approaches to studying age-old problems in avian taxonomy.

We review past research on the propagation of electromagnetic pulse signals over the surface of the earth with emphasis on analytical methods to predict waveforms. The best example is the electromagnetic field radiated from a lightning stroke that can be observed at global distances or very close in if one has sufficient motivation. In any case, the propagation channel will distort the signal wave shape because of the strong frequency dependence of the attenuation factors and the phase velocities of the modes. We begin with a flat earth model that has the virtue of simplicity particularly when displacement currents in the earth are relatively small compared with the conduction currents. Here we see that the rise time of the ideally radiated step function signal is of the order of a few microseconds at a range of 50 km over average land paths. Such a prediction is in accord with published experimental data. At greater ranges, earth curvature comes into play and we show here how various analytical and numerical methods can be used in overlapping time regions which serves as a good consistency check. Other complicated effects such as mixed land-sea paths and ionospheric influences are also reviewed.

This workwas supported by UC Berkeley Summer Undergradu-ate Research Fellowships to MAP and ML, UC Berke-ley Biology Fellows Program Awards to DRW and MAP,the Museum of Vertebrate Zoology UndergraduateBiodiversity Award, and the NSF DEB 0640859 to CM.

Dogs are relevant to biomedical research in connection both to veterinary medicine for their role as pets and to basic investigations for their use as animal models in pathology, pharmacology and toxicology studies. Proteomic analysis of biological fluids is less advanced for dogs than for other animal species but a wealth of information has already been gathered, which we summarize in this review. As a remarkable feature, we also assemble here for due reference a number of 2-DE serum/plasma or urine patterns in health and disease; some of them correspond to unpublished data from the University of Veterinary Medicine Vienna.

Smooth muscle cells (SMC) contribute to the development and stability of atherosclerotic lesions. The molecular mechanisms that mediate their properties are incompletely defined. We employed proteomics and in vitro functional assays to identify the unique characteristics of intimal SMC isolated from human carotid endarterectomy specimens and medial SMC from thoracic aortas and carotids. We verified our findings in the Tampere Vascular Study. Human atheroma-derived SMC exhibit decreased expression of mitochondrial proteins ATP Synthase subunit-beta and Aldehyde dehydrogenase 2, and decreased mitochondrial activity when compared to control SMC. Moreover, a comparison between plaque-derived SMC isolated from patients with or without recent acute cerebrovascular symptoms uncovered an increase in Annexin A1, an endogenous anti-inflammatory protein, in the asymptomatic group. The deletion of Annexin A1 or the blockade of its signaling in SMC resulted in increased cytokine production at baseline and after stimulation with the pro-inflammatory cytokine Tumor Necrosis Factor α. In summary, our proteomics and biochemical analysis revealed mitochondrial damage in human plaque-derived SMC as well as a role of Annexin A1 in reducing the production of pro-inflammatory mediators in SMC.

Objective To investigate whether cartilage injury activates protein tyrosine kinases distinct from fibroblast growth factor (FGF)–related signaling, and whether they contribute to injury-induced gene responses. Methods Phosphokinases and protein tyrosine phosphorylation were assayed by Western blotting of cartilage lysates. Immunoprecipitation and Western blotting with 4G10 antibody and immunoprecipitation kinase assay were carried out. Tyrosine-phosphorylated proteins on silver-stained gels of injured cartilage lysates were identified by mass spectrometry. Messenger RNA induction in cartilage explants was assessed by quantitative reverse transcriptase–polymerase chain reaction. Results Protein tyrosine phosphorylation occurred within seconds of injury to the surface of intact articular cartilage, as did activation of MAPKs and IKK. Activation did not reoccur upon reinjury of cultured explants. The prominent tyrosine-phosphorylated proteins focal adhesion kinase, paxillin, and cortactin were identified as substrates of Src family kinases. The Src family kinase inhibitor PP2 blocked injury-induced tyrosine phosphorylation. It did not prevent activation of the MAPKs and IKK but differentially inhibited 8 of 10 inflammatory response genes that were induced by injury. In contrast, FGF signaling blockade with PD173074 reduced all MAPK and IKK activation by ~50% and inhibited a different subset of genes but had no effect on Src-like signaling. Conclusion Injury to the surface of intact articular cartilage activates Src-like kinases as well as MAPKs and IKK (implying NF-κB activation). FGF-2 contributes to MAPK/IKK activation but not to Src-like signaling, suggesting that the latter is a parallel pathway that also regulates the injury-induced inflammatory gene response.

Background Androgen-dependent proteins (lipocalins) circulate in blood of male rats and mice and, being small (~ 18 kDa), pass freely into glomerular filtrate. Some are salvaged in proximal nephrons but some escape in urine. Several organic molecules can bind to these proteins causing, where salvage occurs, nephropathy including malignancy in renal cortex. In urine, both free lipocalins and ligands contribute to an increasingly-recognised vital biological role in social communication between adults, especially in the dark where reliance is on smell and taste. Crystal structure of the first-characterised lipocalin of male rats, α2u-globulin, has been determined and peptide sequences for others are available, but no study of occurrence during early puberty has been made. We have followed temporal occurrence in urine of juveniles (n = 3) for non-invasive pilot study by high resolution gradient mini-gel electrophoresis, tryptic digest of excised protein bands, and LC-MS/MS of digest to identify peptide fragments and assign to specific lipocalins. Study objective refers directly to external availability for social communication but also indirectly to indicate kinetics of circulating lipocalins to which some xenobiotics may bind and constitute determinants of renal disease. Results Mini-gels revealed greater lipocalin complexity than hitherto recognised, possibly reflecting post-translational modifications. Earliest patterns comprised rat urinary protein 1, already evident in Sprague-Dawley and Wistar strains at 36 and 52 days, respectively. By 44 and 57 days major rat protein (α2u-globulin) occurred as the progressively more dominant protein, though as two forms with different electrophoretic mobility, characterised by seven peptide sequences. No significant change in urinary testosterone had occurred in Wistars when major rat protein became evident, but testosterone surged by 107 days concomitant with the marked abundance of excreted lipocalins. Conclusions Qualitative temporal changes in the composition of excreted lipocalins early in puberty, and apparent increase in major urinary protein as two resolvable forms, should catalyse systematic non-invasive study of urinary lipocalin and testosterone dynamics from early age, to illuminate this aspect of laboratory rodent social physiology. It could also define the potential temporal onset of nephrotoxic ligand risk, applicable to young animals used as toxicological models.

Collapsin response mediator protein 2 (CRMP-2) is known as a regulator of neuronal polarity and differentiation through microtubule assembly and trafficking. Here, we show that CRMP-2 is ubiquitously expressed and a splice variant (CRMP-2L), which is expressed mainly in epithelial cells among nonneuronal cells, regulates myosin II-mediated cellular functions, including cell migration. While the CRMP-2 short form (CRMP-2S) is recognized as a substrate of the Rho-GTP downstream kinase ROCK in neuronal cells, a CRMP-2 complex containing 2L not only bound the catalytic domain of ROCK II through two binding domains but also trapped and inhibited the kinase. CRMP-2L protein levels profoundly affected haptotactic migration and the actin-myosin cytoskeleton of carcinoma cells as well as nontransformed epithelial cell migration in a ROCK activity-dependent manner. Moreover, the ectopic expression of CRMP-2L but not -2S inhibited fibronectin matrix assembly in fibroblasts. Underlying these responses, CRMP-2L regulated the kinase activity of ROCK II but not ROCK I, independent of GTP-RhoA levels. This study provides a new insight into CRMP-2 as a controller of myosin II-mediated cellular functions through the inhibition of ROCK II in nonneuronal cells.

An audience response system (ARS) has become popular among educators in medicine and the health professions because of the system's ability to engage listeners during a lecture presentation. No one has described the usefulness of ARS technology during planned nonlecture peer teaching sessions in gross anatomy instruction for health professionals. The unique feature of each peer teaching session was a nongraded 12–15 item ARS quiz assembled by six second-year doctor of physical therapy (DPT) students and purposely placed at the beginning of the review session for those first-year DPT students in attendance. This study used a ten-item questionnaire and a five-point Likert scale in addition to three open ended questions to survey perceptions of both first-year and second-year DPT students about the usefulness of ARS technology implemented during weekly interactive peer teaching sessions during a semester course in Anatomy for Physical Therapists. First-year students overwhelmingly acknowledged the ARS system permitted each student to self-assess his/her preparedness for a quiz or examination and compare his/her performance with that of classmates. Peer teachers recognized an ARS quiz provided them an opportunity to: (1) estimate first-year students' level of understanding of anatomical concepts; and (2) effectively prepare first-year students for their weekly quizzes and future examinations. On the basis of the mutual benefits derived by both students/tutees and teachers/tutors, physical therapist educators may wish to consider using ARS technology to enhance teaching methods for a class in gross human anatomy. Anat Sci Educ 2: 286–293, 2009. © 2009 American Association of Anatomists.

Pipeline structures are susceptible to cracks, corrosion, and other ageing defects. If left undetected, these forms of damage can lead to the failure of the pipeline system, which may have catastrophic consequences. Most current forms of health monitoring for pipeline systems involve non-destructive evaluation (NDE) techniques. These techniques require sophisticated instruments and direct access to the structure, which is not always possible for civil pipeline applications. This research proposes the use of macro-fibre composite (MFC) transducers for real-time structural health monitoring in pipeline systems. In particular, we propose the coupled implementation of impedance-based and Lamb wave-based methods that are simultaneously used to accurately determine the health of a pipeline network. The self-sensing impedance methods are used to detect structural damage occurring at pipeline connection joints, while the Lamb wave propagation measurements identify cracks and corrosion along the surface and through the wall thickness of the pipe structure. Both methods utilize the same MFC active sensors, which are flexible, durable, relatively inexpensive, and can be permanently bonded to the surface of a pipe during installation. Therefore, measurements for damage identification can be performed at any time, even while the system is in operation. Based on the success of this study, guidelines are outlined for the full-scale development of a low-cost, active-sensing-based SHM system suitable for pipeline applications. Published in 2007 by John Wiley & Sons, Ltd.

Hypoxia-induced changes of rat skeletal muscle were investigated by two-dimensional difference in-gel electrophoresis (2D-DIGE) and mass spectrometry. The results indicated that proteins involved in the TCA cycle, ATP production, and electron transport are down-regulated, whereas glycolytic enzymes and deaminases involved in ATP and AMP production were up-regulated. Up-regulation of the hypoxia markers hypoxia inducible factor 1 (HIF-1α) and pyruvate dehydrogenase kinase 1 (PDK1) was also observed, suggesting that in vivo adaptation to hypoxia requires an active metabolic switch. The kinase protein, mammalian target of rapamycin (mTOR), which has been implicated in the regulation of protein synthesis in hypoxia, appears unchanged, suggesting that its activity, in this system, is not controlled by oxygen partial pressure. Keywords: skeletal muscle • hypoxia • 2D-DIGE • mass spectrometry

In this study, frequency response functions (FRF) measured by piezoelectric Macro-Fiber Composite (MFC) actuators/sensors are used to detect subsurface delamination in a composite plate. The plate is impacted to seed damage in the form of ply delamination. Then, the MFCbased active-sensing system exerts an excitation into the plate, and measures the subsequent responses. Traditional piezoceramic materials are also mounted in comparable locations on the plate to compare their performances. FRF and damage indicator features are derived from the measured signals and used to assess the condition of the plate. Validation of the delamination is completed using an ultrasonic C-scan method. The effective area of observed damage is well correlated to the damage indicator feature.

Recent works by Nichols et al. (Nichols, J.M., Todd, M.D., Seaver, M. and Virgin, L.N. (2003). Use of chaotic excitation and attractor property analysis in structural health monitoring. Phys Rev E, 67(016209)) and Pecora et al. (Todd, M.D., Nichols, J.M., Pecora, L.M. and Virgin, L.N. (2001). Vibration-based damage assessment utilizing state-space geometry changes: Local attractor variance ratio. Smart Materials and Structures, 10, 1000-1008.) have shown that steady-state dynamic analysis of structural health exhibits advantages over transient vibrational analysis. A geometric representation of system dynamics can be used to extract information about a structure’s response to sustained excitation. Analysis of various features of the geometric representation can be used to describe the degree to which the dynamics have been altered by damage. Here, the feature we employ is the ‘‘continuity test,’’ a statistical test first described by Pecora et al. (Pecora, L.M., Carroll, T.L. and Heagy, J.F. (1997). Statistics for continuity and differentiability: an application to attractor reconstruction from time-series. Fields Institute Communications, 11). This test measures the probability that a continuous function exists from one geometric object to another. In this implementation, we formulate a new null hypothesis which serves to make the test less sensitive to noise in the data than the original test. Using experimental data from an excited three-story aluminum frame structure with multiple sensors at the joints, we show that the continuity test can be used not only to detect, but also in some cases to localize damage to particular joints in the frame structure.

There exists a clear need to monitor the performance of civil structures over their operational lives. Current commercial monitoring systems suffer from various technological and economic limitations that prevent their widespread adoption. The wires used to route measurements from system sensors to the centralized data server represent one of the greatest limitations since they are physically vulnerable and expensive from an installation and maintenance standpoint. In lieu of cables, the introduction of low-cost wireless communications is proposed. The result is the design of a prototype wireless sensing unit that can serve as the fundamental building block of wireless modular monitoring systems (WiMMS). An additional feature of the wireless sensing unit is the incorporation of computational power in the form of state-of-art microcontrollers. The prototype unit is validated with a series of laboratory and field tests. The Alamosa Canyon Bridge is employed to serve as a full-scale benchmark structure to validate the performance of the wireless sensing unit in the field. A traditional cable-based monitoring system is installed in parallel with the wireless sensing units for performance comparison.

In this paper a signal processing technique is developed to detect delamination on composite structures. In particular, a wavelet-based signal processing technique is developed and combined with an active sensing system to produce a near-real-time, online monitoring system for composite structures. A layer of piezoelectric patches is used to generate an input signal with a specific wavelet waveform and to measure response signals. Then, the response signals are processed by a wavelet transform to extract damage-sensitive features from the original signals. The applicability of the proposed method to delamination identification has been demonstrated by experimental studies of a composite plate under varying temperature and boundary conditions.

This work explores the role of steady-state dynamic analysis in the vibration-based structural health monitoring field. While more traditional approaches focus on transient or stochastic vibration analysis, the method described here utilizes a geometric portrait of system dynamics to extract information about the steady-state response of the structure to sustained excitation. The approach utilizes the fundamental properties of chaotic signals to produce low-dimensional response data which are then analyzed for features which indicate the degree to which the dynamics have been altered by damage. A discussion of the fundamental issues involved in the approach is presented along with experimental evidence of the approach's ability to discriminate among several damage scenarios.

System integration of an online structural health monitoring module was accomplished by coupling commercially available microelectro-mechanical system sensors and a wireless telemetry unit with damage detection firmware. To showcase the capabilities of the integrated monitoring module, a bolted frame structure was constructed, and the preload in one of the bolted joints was controlled by a piezoelectric stack actuator to simulate gradual deterioration of a bolted connection. Two separate damage detection algorithms were used to classify a joint as damaged or undamaged. First, a statistical process control algorithm was used to monitor the correlation of vibration data from two accelerometers mounted across a joint. Changes in correlation were used to detect damage to the joint. For each joint, data were processed locally on a microprocessor integrated with the wireless module, and the diagnosis result was remotely transmitted to the base monitoring station. Second, a more sophisticated damage detection algorithm combining time series analysis and statistical hypothesis testing was employed using a conventional wired data acquisition system to classify a joint on the demonstration structure as damaged or undamaged.

The Operational Multiscale Environment model with Grid Adaptivity (OMEGA) is an atmospheric simulation system that links the latest methods in computational fluid dynamics and high-resolution gridding technologies with numerical weather prediction. In the fall of 1999, OMEGA was used for the first time to examine the structure and evolution of a hurricane (Floyd, 1999). The first simulation of Floyd was conducted in an operational forecast mode; additional simulations exploiting both the static as well as the dynamic grid adaptation options in OMEGA were performed later as part of a sensitivity‐capability study. While a horizontal grid resolution ranging from about 120 km down to about 40 km was employed in the operational run, resolutions down to about 15 km were used in the sensitivity study to explicitly model the structure of the inner core. All the simulations produced very similar storm tracks and reproduced the salient features of the observed storm such as the recurvature off the Florida coast with an average 48-h position error of 65 km. In addition, OMEGA predicted the landfall near Cape Fear, North Carolina, with an accuracy of less than 100 km up to 96 h in advance. It was found that a higher resolution in the eyewall region of the hurricane, provided by dynamic adaptation, was capable of generating better-organized cloud and flow fields and a well-defined eye with a central pressure lower than the environment by roughly 50 mb. Since that time, forecasts were performed for a number of other storms including Georges (1998) and six 2000 storms (Tropical Storms Beryl and Chris, Hurricanes Debby and Florence, Tropical Storm Helene, and Typhoon Xangsane). The OMEGA mean track error for all of these forecasts of 101, 140, and 298 km at 24, 48, and 72 h, respectively, represents a significant improvement over the National Hurricane Center (NHC) 1998 average of 156, 268, and 374 km, respectively. In a direct comparison with the GFDL model, OMEGA started with a considerably larger position error yet came within 5% of the GFDL 72-h track error. This paper details the simulations produced and documents the results, including a comparison of the OMEGA forecasts against satellite data, observed tracks, reported pressure lows and maximum wind speed, and the rainfall distribution over land.

The Operational Multiscale Environment Model with Grid Adaptivity (OMEGA) is a multiscale nonhydrostatic atmospheric simulation system based on an adaptive unstructured grid. The basic philosophy behind the OMEGA development has been the creation of an operational tool for real-time aerosol and gas hazard prediction. The model development has been guided by two basic design considerations in order to meet the operational requirements: 1) the application of an unstructured dynamically adaptive mesh numerical technique to atmospheric simulation, and 2) the use of embedded atmospheric dispersion algorithms. An important step in proving the utility and accuracy of OMEGA is the full-scale testing of the model using simulations of real-world atmospheric events and qualitative as well as quantitative comparisons of the model results with observations. The main objective of this paper is to provide a comprehensive evaluation of OMEGA against a major dispersion experiment in operational mode. Therefore, O...

A general Sommerfeld integral formulation is given for the electromagnetic (EM) fields of an oscillating vertical magnetic or electric dipole over an electrically inhomogeneous thin sheet. The electrical properties of the sheet are characterized by a conductance function that is an arbitrary function of spatial coordinates. When the conductance function has axial symmetry relative to the source dipole, the general solution form simplifies to a Fredholm integral equation of the third kind. The general solution is shown to reduce to the special case of an infinite sheet having uniform conductance. When the sheet conductance is either uniform or varies linearly, the field expressions show an algebraic dependence on the conductance. For a general inhomogeneous conductance distribution, the field dependence is not algebraic.

In 1977, Rosich and Wait (see Radio Science, vol.12, no.5, p.719-29, Sept./Oct. 1977) presented a general expression for a perturbation series solution to electromagnetic (EM) reflection from an imperfectly conducting periodic rough surface. This is the first known publication of such a general result. Although this expression was shown to be consistent with earlier published results, all questions concerning the convergence of the series were deferred. This paper takes a first step in addressing this oversight.

In this paper, we are interested in controlling the power dissipation within a homogeneous lossy cylinder of finite length when a field is applied to the surface of the cylinder. The fields are assumed to be independent of the azimuthal angle. To begin, a field which satisfies the required dissipation inside the cylinder is assumed on the axis of the lossy cylinder. An analytical evaluation of the continuous source on the surface of the cylinder can then be carried out. This is an inverse problem where the response is known and the source is to be determined. A realization of the continuous source (surface field) in terms of a discrete array is also given. Results are presented that show an excellent agreement between the actual continuous sources and the discrete array in producing the field on the axis of the lossy cylinder. In fact, a small number of slots (fifteen or less) produce accurate agreement for the required field on the axis of the cylinder. Bioelectromagnetics and hyperthermia treatment of cancer in cylindrical objects such as limbs and torsos is one potential application. Nondestructive testing of manufactured cylindrical products is another one where the energy is focused in a given region in the cylinder.

Red sprites were discovered by chance in 1989 when a low-light TV system was pointed above an active thunderstorm. Optically, they are observed as clusters of short-lived (∼50 ms) pinkish-red luminous events, sometimes stretching from ∼40 to ∼85 km altitude. Red sprites are associated with ionization in the Earth-ionosphere waveguide, which can persist for up to ∼100 s at higher altitudes. The structured ionization associated with red sprites has been observed through “VLF sprites,” perturbations of the phase and/or amplitude of subionospheric VLF transmissions, which can be used to study the electrical properties of the red sprite plasma. Previous theoretical studies have simplified the problem by assuming the red sprite associated ionizations were columns of infinite length, or inside a “flat-Earth” waveguide. In this paper we present an approach for examining the scattering of VLF transmissions by a finite-length column of ionization inside the Earth-ionosphere waveguide, including the effect of realistic curvature of the waveguide. These expressions are applied to the detection and study of red sprites by assuming that the associated ionization can be treated as a (cluster of) truncated columns in the Earthionosphere waveguide. An example calculation is presented, examining the farthest distance from the red sprite from which it might be detected as a VLF sprite.

Electromagnetic induction on a layered earth model is reexamined when the usually neglected magnetic permeability contrast is considered. It is shown that for a two-layered earth model, where the upper layer is permeable, the electromagnetic induction response is modified over the nonpermeable case. Universal plots of normalized induced fields due to an electrically small current loop are produced. Special attention is paid to the case when the upper earth layer consists of a superparamagnetic material. This formulation should be useful for interpreting airborne electromagnetic systems and in cases where superparamagnetic mineral content is present.

In an accompanying paper, Rodger et al. (1998) modelled a red sprite as a set of thin columns (‘spritelets’). By examining a semi-random distribution of coupled spritelets, they showed that the scattered field from a VLF radio transmitter has a complex amplitude pattern with deep minima, and sometimes produces backscattering with similar amplitudes to forward scatter. In this special issue, Wescott et al. (1998) have presented the positions of the columns in a sprite event determined by 3D triangulation. Using this distribution of columns and with specific reference to the radio physics observations during Sprites campaigns, we show that the conclusions arrived at using a semi-random distribution of columns holds for the experimentally determined distribution.

A relatively simple model of Red Sprites as a set of conducting columns reproduces the radio physics properties of VLF sprites. The columnar structure of optical sprites is represented by thin vertical conducting columns (or ‘Spritelets’) in free space, with dimensions taken from optical observations. The scattered field from a set of coupled Spritelets has a complex amplitude pattern which normally includes some deep minima reproducing the ‘perturbation shadows’ seen in some experimental events. It is not uncommon for the back scattered amplitudes to be similar to those for forward scatter in the theoretical model, as in experimental reports. As some sprite events appear to have closely spaced Spritelets, the results presented here indicate that there will be a high degree of electrical shielding. This is an application of the theory presented by Rodger et al. (1997a) .

Expressions are developed to characterise the scattering of VLF electromagnetic waves from a finite-length ionised column at some height in the Earth–ionosphere waveguide. This formulation has been examined to investigate the perturbations of VLF transmissions caused by scattering from red sprites (very large luminous phenomena observed over thunderstorms). The idea of a correction factor is advanced to move from a previous model using infinitely long columns to one with truncated columns (50–90 km altitude) inside the waveguide. Using a night-time ionosphere model a quantitative comparison is made between experimentally observed and modelled red sprite scattering characteristics. It is found that the conductivity of the sprite columns (spritelets) must be about 10 −4 S m −1 to generate the experimentally observed scattered fields. This suggests that the electron density of red sprites can be five orders of magnitude greater than the night-time ambient electron density at some heights.

Radio-wave transmission over the surface of the Earth is a subject of enquiry going back to the beginning of the century. In this review, an attempt is made to describe the ground-wave mechanism that is omni-present. We first call attention to the early analytical contributions of Zenneck and Sommerfeld, based on a flat-Earth model. The subsequent controversies, particularly with regard to the role of the Zenneck surface wave, are outlined. Further developments by other pioneers, such as van der Pol, Fock, Bremmer, Norton, and Millington, are reviewed, and an attempt is made to put these in a modern context. We also show that the trapped surface wave can be a significant contribution to the total ground-wave field, when the Earth boundary is sufficiently inductive. Mixed-path theory and confirming model tests by Ray King are described briefly, along with calculated propagation curves for twoand three-section paths. The bibliography includes references to related topics, such as tropospheric refraction and topographic influences.

Methods and media (defined and complex) are described which permit studies designed to determine the influence of single environmental factors on the survival and virulence of Campylobacter jejuni. The effect of growth rate on selected physiological traits (amino acid utilization, membrane lipid composition, motility, cell morphology) was studied in continuous culture. In both media, growth was at the expense of amino acid (serine, aspartate, glutamate and proline) catabolism. Slow growth in the complex medium shifted amino acid utilization from more (serine and aspartate) to less preferred substrates (glutamate, proline and possibly amino acids from the proteolysis of peptones). Low growth rates promoted the conversion of unsaturated 11-octadecenoic acid substituted phosphatidyl ethanolamines to corresponding 11-methylene substituted species, a feature correlated with stationary phase and exposure to environmental stress in other organisms. During continuous growth, cells lost motility although they still possessed flagella. Slow growth resulted in longer cells. Future studies will investigate the independent effects of nutrient stress and growth rate on the virulence and persistence of cells.

Solutions are given for the problem of scattering of plane waves from an arbitrary number of vertical columns that are thin in terms of the incident wavelength. The electric properties of the cylinders are taken as homogenous and isotropic but otherwise arbitrary, and the incident electric field vector is taken to be parallel to the axis of the cylinders. The scattering solution for individual columns is described, which is used to introduce that for multiple columns under the Born approximation. A more general approach is presented that leads to a solution which includes multiple scattering (coupling) between the cylinders. Comparison is made between this solution for a ring of cylindrical elements and one that treats the scattering from the ring as a whole. The theory described here is now being extended and applied to the scattering from vertical ionized columns known as “sprites”. These are associated with lightning discharges between the ionosphere and cloud tops.

Using an exact numerical solution, the transient response of a two-layer Earth model is obtained for an obliquely incident transverse magnetic (TM) plane wave. It is shown that the decomposition of the general case into ray contributions is an alternative approach that yields consistent results. Several examples are given to demonstrate the sensitivity of the results to the electrical properties of the subsurface region.

The compositions of the major glycolipids (GL-1) of five strains of Thermus aquaticus, the type strain of T. filiformis, T. oshimai SPS-11, and Thermnus sp. strain CG-2 were examined by gas chromatography, gas chromatography-mass spectroscopy, fast atom bombardment-mass spectroscopy, and chemical methods. The results showed that, with the exception of T. aquaticus 15004, the organisms each have a major glycolipid whose structure was established as diglycosyl-(N-acyl)glycosaminyl-glycosyl diacylglycerol. Glucosamine was present in GL-1 of T. oshimai SPS-11 and Thermus sp. strain CG-2, while galactosamine was present in the GL-1 of T. aquaticus and T. filiformis. The novel major glycolipid of T. aquaticus 15004 was identified as galactofuranosyl-(N-acetyl)galactosaminyl-(N-acyl)galactosaminyl-gluc - osyl diacylglycerol. The hydroxy fatty acids found in the T. aquaticus strains and in the type strain of T. filiformis were exclusively amide linked to the galactosamine of the major glycolipid. Ester-linked hydroxy fatty acids were not detected in the diacylglycerol moiety of GL-1 of these organisms. Hydroxy fatty acids were detected neither in the major glycolipid of T. oshimai SPS-11 and Thermnus sp. strain CG-2, in which glucosamine is present, nor in the major phospholipid of any of the strains examined.

We call attention here to the limitation of the “Q approximation” in characterizing the complex wave tilt W over a layered half‐space. Using an improved formulation the frequency dependence of W is shown to be a discriminator of the electrical characteristic of the subsurface. The height dependence of the observer is also illustrated.

In this paper the possibility of detecting a semi-insulating layer in a homogeneous half-space model of the earth is examined using VHF electromagnetic waves (30–300 MHz). The scheme is to employ an obliquely incident TM (transverse magnetic) plane wave. The corresponding TM reflection coefficient in the vicinity of the Brewster angle null is then considered for possible clues. It is shown that when the host medium is not excessively lossy, the TM reflection coefficient shows significant deviation from the homogeneous half-space case. The measurement and interpretation have possible relevance to the detection of liquid hazardous waste layers at depth.

A concise derivation is given for the downward continuation of the tangential fields on the surface to yield expressions for the fields at a specified depth. A homogeneous slab region is assumed for the analysis.

A previous analysis for a horizontal loop antenna is extended to deal with a horizontal wire antenna located over a layered half-space. As before, the exact solution so obtained is reduced to known special cases for the T.M.(transverse magnetic) and T.E. (transverse electric) radiated fields. These expressions are valid for zero or small heights above the air/ground interface. The application to a flat lying butterfly antenna, as a source, is also outlined.

The analysis deals with the formulation of a boundary value problem where the complex immitivity has a principal axis tilted to the interface between the regions. An example is a half-space model of the earth where the fine layering or striations are not parallel to the air interface. The objective is to obtain expressions for effective surface impedance when the source is an obliquely incident plane wave from the upper (air) region. The case treated in detail is when the magnetic field direction is parallel to the strike of the structure which is a purely 2D problem. The more difficult case is when the incidence is arbitrary which leads to coupled wave equations for the E and H fields parallel to the srike of the structure. We also deal with the simplification achieved when the conductivity of the structure is sufficiently high. The general layered case is also treated where the analogy with the layered isotropic media problem is exploited.