Search

The International Commission on Radiological Protection (ICRP) has stated that its recommendations will be reviewed at least every 10-15 years. It is now some 13 years since the main commission released, for comment, a draft of what was to become the 1990 Recommendations of the ICRP. These have become the basis for international basic safety standards and have been adopted in almost all countries that have radiological protection legislation. Therefore, the ICRP has been stimulating discussion, during the last three years, on the best way of expressing protection philosophy for the next publication of its recommendations, which it hopes will he by 2005. It is now beginning to prepare a draft of these recommendations, with a view to distributing an early version for comment, even though the background work is incomplete.

There has been a hundred-year history of the uses of radiation in medicine and industry. Throughout that time there has also been advice on the need to protect people from the hazards associated with exposure. This paper traces the evolution of protection standards through the differing phases that are identified. These phases reflect changes both in scientific understanding of the biological effects of exposure and of the social and ethical standards to be applied. An analysis is then given of the reasons why the challenges to the International Commission on Radiological Protection (ICRP), especially about the linear non-threshold response model, have arisen. As a result of considering the issues, the Main Commission of ICRP is now consulting on a revised simpler approach which is based on an individual-oriented philosophy and represents a potential shift by the Commission from the past emphasis on societal-oriented criteria. These proposals have been promulgated through the International Radiation Protection Association (IRPA) and an open literature publication was published in the Journal of Radiological Protection in June 1999. On the basis of comments received and the observations presented at the IRPA 10 Conference, the Commission will begin to develop the outline of the next recommendations.

A technique is presented for the measurement and decomposition into component propagation modes of the time varying narrow bandwidth (10 kHz) transfer function of an HF sky wave frequency modulated continuous wave (FMCW) transmission at 15.085 MHz. One event on a 5244-km transmission path which exhibited nonselective fading within the 10-kHz bandwidth is analyzed and found to exhibit severe phase distortion due to multipath. A component transfer function for an individual propagation mode is also obtained by two-dimensional filtering of the signal in the Doppler frequency-time delay domain, resulting in a significant reduction in phase distortion. The filtering technique can be used on FMCW transmissions with a repetitive waveform for the time varying identification and measurement of component multipath modes with unresolvable group time delay differences.

The International Commission on Radiological Protection (ICRP) has published new Recommendations in ICRP Publication 60. These 1990 Recommendations provide a System of Radiological Protection that takes account of the most recent information on the effects on health of exposure to ionising radiation and trends in the setting of safety standards. Within the European Community the Recommendations of the ICRP are implemented through a Euratom Directive which is binding on member states, a draft of which has been accepted by the Article 31 Group and must eventually be ratified by the Council of Ministers. It is expected that the new directive will broadly endorse the principles of protection given in the 1990 Recommendations together with the dose limits for both workers and members of the public. There are likely to be some modifications to the 1990 Recommendations that are mainly related to their practical application. As it will be some time before the directive is incorporated into national regulations, a number of member states have taken independent initiatives. The development of dose constraints for occupational, medical and public exposure is being seen by national organisations in many countries as a significant new approach to improving standards of radiation protection.

Multiple scattering theory is applied to investigate the filter shape and bandwidth of the Christiansen filter which consists of a suspension of particles in a liquid such that the refractive index vs wavelength curves of the particles and the liquid intersect at a particular wavelength. It is shown that the filter shape is approximately gaussian, and that the fractional bandwidth depends inversely on the rate of change with wavelength of the difference in refractive index of the particles and the liquid and inversely on the square root of the product of the particle concentration, the average particle radius, and the length of the Christiansen cell. Initial agreement with reported experiments is encouraging.

We have applied a Raman spectroscopic approach to the analysis of aviation fuel mixtures. The fuel mixtures chosen are fuels blended to military specification, namely, JP-4, JP-5, JP-7, and JP-8. We expect that the Raman spectral bands from such fuel mixtures may serve to provide a clear and reproducible standard for the determination of fuel properties, suitable for the evaluation of both commercial and military aviation fuel products.

The application of Raman spectroscopy to the determination of the aromatic content of gasolines and aviation fuels is reported. Since aromatic components have very high Raman cross-sections owing to large polarizability changes under laser excitation, bands from these components will dominate specific Raman spectral regions. It is expected, therefore, that Raman scattering will be a particularly useful approach to broadly characterizing the fuel hydrocarbon makeup for aromatic content and the properties of fuels which are influenced by aromatic content.

In this report, the Commission recommends approaches to national authorities for their definition of the scope of radiological protection control measures through regulations, by using its principles of justification and optimisation. The report provides advice for deciding the radiation exposure situations that should be covered by the relevant regulations because their regulatory control can be justified, and, conversely, those that may be considered for exclusion from the regulations because their regulatory control is deemed to be unamenable and unjustified. It also provides advice on the situations resulting from regulated circumstances but which may be considered by regulators for exemption from complying with specific requirements because the application of these requirements is unwarranted and exemption is the optimum option. Thus, the report describes exclusion criteria for defining the scope of radiological protection regulations, exemption criteria for planned exposure situations, and the application of these concepts in emergency exposure situations and in existing exposure situations. The report also addresses specific exposure situations such as exposure to low-energy or low-intensity adventitious radiation, cosmic radiation, naturally occurring radioactive materials, radon, commodities, and low-level radioactive waste. The quantitative criteria in the report are intended only as generic suggestions to regulators for defining the regulatory scope, in the understanding that the definitive boundaries for establishing the situations that can be or need to be regulated will depend on national approaches.

AMP deaminase (AMPD) is a central enzyme in eucaryotic energy metabolism, and tissue-specific as well as stage-specific isoforms are found in many vertebrates. This study demonstrates the AMPD1 gene product in rat is alternatively spliced. The second exon, a 12-base miniexon, was found to be excluded or included in a tissue-specific and stage-specific pattern. This example of cassette splicing utilizes a unique pathway through an RNA intermediate that generates an alternative 5' splice donor site at the point where exon 2 is ligated to exon 1. In the analogous intermediate of human AMPD1, the potential 5' splice donor site created at the boundary of exon 1 and exon 2 was a poor substrate for splicing because of differences in exon 2 sequences, and human AMPD1 was not alternatively spliced. These results demonstrate that in some cases alternative splicing may proceed through an RNA intermediate that generates an alternative splice donor site not present in the primary transcript. Discrimination between alternative 5' splice donor sites in the RNA intermediate of AMPD1 is apparently controlled by tissue-specific and stage-specific signals.

AMP deaminase is an ubiquitous enzyme in eukaryotic cells, and tissue-specific isoforms are produced in mammals by differential expression of the two genes which encode this enzyme activity as well as by alternative splicing of the primary transcript of one of these genes. Deficiency of this enzyme activity is one of the most common causes of metabolic myopathy in man. To provide a framework for understanding the molecular basis of this inherited disorder and the mechanisms responsible for regulating the expression of this enzyme activity, both the human and rat muscle-specific genes for AMP deaminase have been cloned and partially sequenced. Comparison of the two genes shows a high degree of conservation of sequence and structural organization. The two genes share the following characteristics: 1) both are approximately 20 kilobases in size, have identical exon/intron boundaries, and exhibit similar intron/exon structural organization; 2) the transcription start site is located at the same position in both genes, and comparison of 5'-flanking sequences reveals four highly conserved domains that together contain the information necessary for muscle-specific expression of a receptor cDNA; 3) coding sequences are 88% identical and the 5'-untranslated regions are 67% identical; 4) both genes have extremely short 3'-untranslated regions (13-17 nucleotides); 5) highly conserved intervening sequences of several hundred nucleotides surround most exon/intron boundaries. In situ hybridization and analysis of human-mouse somatic cell hybrids have localized the human gene (designated AMPD1) to chromosome 1 in the region p13-p21. The implications of these structural properties for identifying functional domains in the AMP deaminase peptide, regulation of expression of this gene, and inheritance of AMP deaminase deficiency are discussed.

ICRP published a draft version of its recommendations for radiological protection in February and organised two international seminars in April in Paris and Luxembourg to present the concepts, biological bases, and practical application. Within the UK, the NRPB is consulting widely on the draft proposals. Comments received by ICRP will be discussed at Main commission meetings in June 1990; at a meeting of the Task Group drafting the recommendations in September 1990; and, if necessary, at a Main Commission further meeting in November 1990. The final test is expected to be published in the first quarter of 1991. The recommendations consist of a main text, supported by three major appendices covering quantities and units; biological effects of ionising radiation; and criteria for judging the significance of the effects of radiation.

We report the development and use of equipment which images groundwater distribution and the water flow pathways in aquifers. Aquifer permeability profiles and maps are obtained from electrokinetic signals using algorithms based upon theoretical and laboratory studies (Chandler, 1971, Nourbehecht 1963).

The current views of the International Commission on Radiological Protection on exposure to natural radiation are presented in the new recommendations (ICRP Publication 60) where the concepts of practice and intervention are both used to establish mechanisms of control. The history of the present recommendations is reviewed, and the latest guidance on the control of 222Rn at home and at work (ICRP Publication 65) is outlined. The new model of the respiratory tract, which has been adopted by ICRP, is discussed in the context of its predictions of the doses from radon and from particulate natural radionuclides. Consideration is given finally to criteria for the restoration of sites previously contaminated by natural radionuclides.

Myoadenylate deaminase (mAMPD) deficiency is a clinically heterogeneous metabolic myopathy consisting of primary (inherited) and secondary (acquired) forms based on a variety of clinical and laboratory findings. To provide a basis for delineating the underlying molecular defects in mAMPD deficiency, and as a means to test the proposal for multiple forms of the resulting disease, Northern blot analyses were performed with RNA isolated from individual patients with classified primary and secondary deficiency utilizing human mAMPD cDNA probes isolated from adult skeletal muscle libraries. Analysis of nine patients with primary mAMPD deficiency indicates normal abundance of mAMPD transcript. No immunoreactive mAMPD polypeptide is detected in Western blot analyses of skeletal muscle extracts prepared from these patients. Specificity to mAMPD is demonstrated by normal creatine kinase (CK) activities and M-creatine kinase (M-CK) transcript abundance. Similar analyses of four individuals with secondary mAMPD deficiency reveal heterogeneity in this subgroup of patients. Whereas two of these patients exhibit normal mAMPD transcript abundance, two others associated with inflammatory myopathy display reductions in mAMPD and M-CK transcript abundance. Examination of tissue sections derived from the same biopsies utilized in the isolation of RNA demonstrates the integrity of the skeletal muscle in those patients with associated inflammatory myopathy. Combined, these data support the proposal for multiple forms of mAMPD deficiency, and indicate that the primary condition is most commonly characterized by specific point mutations or small deletions/rearrangements in the ampd 1 gene, whereas some patients with secondary mAMPD deficiency display more generalized aberrations in gene expression.

Time resolved emission spectra of myocardium irradiated with 193‐ and 308‐nm excimer laser radiation were recorded as a function of laser fluence. The laser fluence impinging on the sample varied from 0.48 to 2.0 J/cm2. It was found that the recorded emission spectra depend greatly on the incident laser fluence and time delay. At a laser fluence of 2.0 J/cm2 and short delay, the emission spectra are dominated by nitrogen ion emission lines. At longer delays and lower laser fluences C2 and CN radical emission spectra are recorded. The sequence in which the emission from these species is seen, as a function of laser fluence and time delay, suggests that at high fluence a plasma is formed in the plume above the ablation site and that excited‐state nitrogen species may play an important role in the generation of radical fragments commonly seen in the laser induced plasma emission of organic materials. It is not clear to what extent these fragments may be generated as direct ablation products.

The reflection that occurs when a beam, rather than a plane wave, is incident normally on a quarter-wavelength matching layer can be of vital importance in semiconductor laser design. An analysis in three dimensions is given for the general case of a field of arbitrary form and polarization incident on the matching layer. The field is represented as an angular spectrum of plane waves, each component plane wave being modified by the appropriate Fresnel reflection coefficient to give the field reflected back onto the diode structure. Brown's antenna reciprocity theorem is used to determine the amplitude of the corresponding mode traveling back down the diode.

A theoretical formula is derived for the joint statistics of cross-polarization discrimination (XPD) and rain attenuation for a microwave link. This formula is then applied to the prediction of the distribution of XPD conditional on the copolar rain attenuation and also to the prediction of the distribution of XPD during a rain fade. Application is also made to the estimation of outage time of a dual-polarization communication system. Theoretical results are compared with experimental data from the eastern USA and southern England, and the agreement has been found to be quite good.

A method is presented for predicting the long-term statistics for rain depolarization in the case of spatially nonuniform rain, based on previous calculations for the uniform case. These calculations apply to any type of linear polarization. Assuming a lognormal form for the point rain rate statistics and using the idea of space-averaged rain rate, an approximate normal form is deduced for the probability density function of the cross-polarization isolation (XPI) or discrimination (XPD) in decibels. The parameters of this normal density are shown to be dependent on the parameters of the radio link and the rain rate distributions. These include the probabilities of rainfall along that particular path, the median and standard deviation of the point rainfall rate, the spatial correlation coefficient of the rainfall rate, radio frequency, path length, and type of polarization.

The beam propagation method, based on the parabolic approximation to the wave equation, is used in conjunction with Papoulis' redefinition for optical fields of Woodward's ambiguity function. A simple derivation is given of Tatarskii's formula for the lateral coherence function, and hence the mean intensity profile, of a laser beam propagating through a turbulent atmosphere. Statistics of the received signal and the effects of spatial nonstationarity of the turbulence can also be deduced using this technique, as can the effects of very large-scale variations in refractive index and receiver directivity.

This paper presents the results of a field expedition mounted in late September/early October 1979 to investigate the structure and origin of the “morning glory” of the Gulf of Carpentaria in northern Australia. The morning glory is a line wind squall, accompanied by a pressure jump, and often by a long roll-cloud or series of such clouds. It frequently occurs in the early morning, especially in October, in the Gulf area. A light aircraft, fitted with a temperature and humidity probe, was flown in two glories to determine their thermodynamic structure, and wind fields wore obtained principally by tracking pilot balloons using the double theodolite method. Data also were obtained from a network of surface stations, recording wind velocity and pressure, installed at locations across Cape York Peninsula, which is believed to be the area of genesis. The morning glory is identified as an internal undular bore propagating on the nocturnal and/or maritime inversion. Its origin appears to lie frequently ...

An electromagnetic or acoustic beam incident on a randomly rough boundary is modelled as a random phase screen. The particular case of a gaussian beam incident on a screen whose phase is a gaussian process is considered in detail. The technique, which uses Papoulis' extension of Woodward's ambiguity function for random fields, is finally applied to arbitrary transmitting and receiving antennas (or transducers) coupled through a phase screen whose statistics are arbitary but stationary

A new empirical assessment of the functions A and B of Rossby-number similarity theory is made based on the Wangara data. Variations of these functions with stability, baroclinicity and time of day are discussed. It is found that B is dependent on stability in agreement with older data but contradicting the prediction of Csanady (1972). Coefficients expressing the variation of A and B with the two components of baroclinicity have been derived from the data, and these are claimed to be correct in regard to sign and approximately in regard to magnitude. Longer period time changes, represented by the diurnal cycle, are shown to result in systematic differences in A and B between the case of increasing stability and that of decreasing stability, for the same value of the stability parameter. The first attempt, to our knowledge, to present the actual functional form of the wind departure components (based on field data) is made. As the surface layer is approached in near-neutral conditions, the departure component in the direction of the surface wind assumes the expected logarithmic form.

In ten rabbit ears the central auricular artery was percutaneously catheterized and subjected to doses of laser energy transmitted through a flexible optical fiber within the artery. Arterial occlusion was not produced in the initial three ears using energy levels less than 600 mW. Higher levels of laser energy, in the range of 800-1000 mW, caused arterial coagulation in six of the remaining seven rabbit ears. Serial observations by transillumination of the ears, postmortem angiography, and histologic examination demonstrated complete arterial ablation. The experiments showed that segmental arterial ablation is feasible using an intra-arterial optical fiber to direct laser energy to a specific arterial target. Technical refinements and potential therapeutic application are discussed.

Observations show that the angle between surface wind and isobar increases equatorward in low latitudes while the ratio of surface to geostrophic wind speed decreases. With the use of Southern Hemisphere winter fields of surface pressure and temperature over the oceans, and Rossby number similarity theory (including the effects of baroclinicity) in several different forms, the expected latitudinal variation of the angle and ratio has been computed. A check has also been made of mean ATEX and BOMEX data. It appear that the variations with latitude are probably mainly due to baroclinicity. With this factor taken into account, similarity theory fairly adequately explains the observations.

The present series of experiments used gas chromatography to identify vapor-phase photoproducts liberated during excimer laser irradiation of cardiovascular tissues in air and blood. In air, laser beams produced from ArF (193 nm) and XeF (351 nm) excimer laser gas mixtures were delivered to samples of myocardium and atherosclerotic coronary arterial segments through the wall of a quartz cell, using 8-40 mJ/pulse. In blood, 351 nm were delivered via an optical fiber, using 14 mJ/pulse. When the experiments were performed using an air-tissue interface, the dominant photoproducts identified in order of elution from the gas chromatographic column were methane, acetylene, ethylene, ethane, propyne, allene, propylene, propane, and butene. When a fiberoptic was used to accomplish 351-nm excimer laser tissue ablation in a blood field, a similar gas chromatographic spectral distribution was observed. These vapor-phase photoproducts are indistinguishable from those observed following continuous wave laser irradiation or flame torching of cardiovascular tissues. Thus, despite the fact that excimer laser ablation of cardiovascular tissues is characterized by the absence of signs of thermal injury, the results of these experiments suggest that the predominant mechanism of excimer ablation is, like continuous-wave laser irradiation, a thermal process.

Solitary waves are of intense interest in the physical and mathematical sciences1. These nonlinear waves often seem to have a primary role in the asymptotic description of propagating disturbances in inland lakes and coastal waters2–4, in the thermocline of the open sea5 and in the lower atmosphere6,7. We present here new acoustic sounder observations of complex tropospheric solitary-wave disturbances at Tennant Creek in the arid interior of Australia (Fig. 1), a description and interpretation of a new type of visible wave phenomena over northern Australia which appear as thin propagating cumulus cloud lines, and a discussion of observations at Burketown on the Gulf of Carpentaria of a new class of low-altitude propagating solitary-wave roll clouds which originate to the south. These observations, when correlated with observations at Tennant Creek, indicate that solitary-wave-generating disturbances in the form of internal bores8,9 propagate over large distances.

The angular plane wave spectrum and Brown's antenna coupling formula are used to calculate the signal reflected from an anti-reflection coating on a diode laser amplifier. It is shown that the amplitude of the reflected signal is proportional to the angular spread of the loser radiation.

The Group of Experts responsible for advising the Commission of the European Communities on Radiation Protection Standards under Article 31 of the Euratom Treaty have recently published guidance on Emergency Reference Levels of dose. This paper summarises that radiological protection guidance which is to be used when considering the introduction of measures to protect the public in the event of accidental releases of radionuclides.

A general circulation model is modified successively by adding five new features in the lower boundary layer; namely, (i) a different roughness parameter over land and sea, (ii) a Monin-Obukhov type treatment of the turbulent transfer process in the constant-flux layer, (iii) a Richardson number dependent parameterization for Ekman layer process, (iv) a diurnal variation of insolation, and (v) heat conduction into the soil. To assess the effect of each, the experiments are repeated by gradually increasing the complexity of the model. The circulation model has relatively low horizontal grid resolution and 9 vertical levels, and it is applied to a winter case for 14 day predictions. The results indicate that the sophistication of the boundary layer physics does not produce a particularly large effect on the synoptic scale prediction until about 7 days. Its effect may become large after 10 days. One noteworthy result is that the effect of the diurnal variation of insolation is not great for the free atmosphere but an influence is effectively transferred in the vertical, if the Richardson number dependent parameterization for the Ekman layer process is incorporated. The entire study is a preliminary test, the purpose of which is to determine the relative magnitude of each effect. A detailed comparison with observed data was not attempted.

A method is described for deriving acoustic-gravity wave velocity in the presence of wind shear. It is used to calculate numerical weighting factors for a few special cases of two and three layer model atmospheres. These show that the wind velocity in a cold layer between two warm layers has a predominant positive influence on group velocity, and the wind at higher levels a negative influence, while phase velocity is quite differently affected. The theory is illustrated by world-wide data relating to the Russian megaton explosion of 30 October 1961, and a study of global winds at the time. It was found possible to account for world-wide variations in wave propagation rate largely by a simple regression on the sine of the explosion longitude, which made possible estimates of effective wind over various ray path lengths. This was found, on the global scale, to be the mean of the wind in the 9–16 km layer, that is, approximately the mean wind in the “sound channel”. Negative weightings at higher levels predicted by the model appear to be incorrect, and due to its inadequacy. The data strongly suggest that the “level of effective mean wind” is approximately that of the tropopause in middle latitudes.DOI: 10.1111/j.2153-3490.1963.tb01389.x

The generation of widespread pressure oscillations in southern Australia on 26–27 January 1960 is examined in some detail, by means of available barograms, and spectral analysis of a Melbourne Dines microbarogram. Photographs of mamma cloud taken at Adelaide give some insight into the processes at work producing both cloud form and oscillations. It is concluded that the oscillations were due to wave motions on an interface with large density contrast, at about 1,500 m altitude, and that these motions propagated approximately in the direction of vertical shear, with the velocity of the wind at about 2·5 km. Their phase and group velocities were similar, and their wavelengths in the range 10–70 km. These waves appear to have been transmitted over great distances without marked attenuation. An estimate of the energy of oscillation was compared with that which could be imparted to a horizontal interface with strong shear by the passage of downdraughts through it, and the conclusion is reached that the combination of downdraughts and shear could have provided the energy. On the other hand, there is good evidence that the waves were unstable, and could therefore have drawn their energy from that of the mean motion. Examination of other occasions on which marked pressure oscillations occurred suggested that fallout and strong shear were both necessary conditions.

Data from a recent experiment indicate that the height scale for wind in the planetary boundary layer is u*/F, where u*/F is the friction velocity and f the Coriolis parameter, rather than zi, the height of the convection-limiting inversion, or |L| the Obukhov length. None of the scales u*/f, zi, |L| appears to be appropriate for temperature except in slight-to-moderate stability where again u*/f appears to be the most suitable. The data do not support either Businger's expression which gives the depth of the idealized thermal boundary layer, depending on surface heat flux and rate of temperature change, or Tennekes' expression for bulk temperature difference across the boundary layer in free convection, based on the ratio of −L to the roughness length z0.

Serial pilot balloon flights, radiosonde and aircraft data in the vicinity of dry cold fronts and seabreeze fronts in summertime have made possible a clearer view of the meso-scale structure of such phenomena. In the velocity field, closed circulations and wave motions appear to be the rule, but the density variations associated with these features are inadequately known. Strong vertical currents frequently accompany the leading edges of these fronts. A tendency for increasing development of the vertical circulation with distance from the coast was found in the case of seabreeze fronts moving inland, strong circulations being found up to 135 mi from the coast. Cross-isentrope flow in the sections is deduced to indicate the effects of turbulent transfers, as well as frontal deformation. Frictional rather than geostrophic constraint is indicated for many fronts, especially those of the seabreeze variety. Strong circulations about the leading edge of the front are probably promoted by coastal effect...

n/a

Winds and temperatures in the boundary layer measured during two Australian expeditions are analysed according to the similarity scheme, with the use of four stability classifications. Under conditions of deep convection there is a minimum potential temperature and a maximum velocity component in the direction of the surface wind, at a height of about 0.12 u*/f. In the very stable cases, the temperature gradient follows rather closely a z−2 law for a considerable height range from 0.08 u*/f upwards. An expression closely fitting the mean data in stable conditions is suggested for the vertical temperature structure at all levels in the boundary layer. Wind data processed in this way show, for all four stability classes, a rudimentary Ekman spiral. With deep convection the spiral is found to be reversed in sense, but the flow in the convecting layer is down the gradient of pressure. If the convective limit lies broadly within the Ekman layer, a spiral of the expected sense is found. The upper limit of the Ekman layer (as defined by the ‘spiral’) is found to lie at a height of 0.17 to 0.24 (increasing with stability) in units of u*/f. Stress and heat-flux are apparently considerable above this level, with sub-geostrophic wind, when deep convection is occurring. Approximations to the universal distributions of stress, eddy coefficients, mixing length and rate of degradation of mean flow kinetic energy are computed for the various stabilities. The mixing length in unstable conditions increases almost as height up to a level of about 0.08 u*/f, and then decreases, but in general appears not to vanish in stable layers above the boundary layer. In the unstable boundary layer with deep convection, the eddy transfer coefficient for heat exceeds that for momentum up to 0.12 u*/f, where it becomes infinite, and is negative at higher levels. In stable conditions the transfer coefficients for a small sample of soundings were estimated to be closely similar. The universal functions of stability, A, B and C, which enable one to compute free atmosphere wind vector and temperature, given surface conditions, have been evaluated with moderate success, although B, which essentially describes the change of wind direction with height, exhibits excessive variability. A method is suggested for computing horizontal advection in the boundary layer when this is to be ‘parameterized’ in mathematical models. The drag coefficient, in terms of free atmosphere wind, has almost a 50-fold range, due to stability variation only. Most of the variation occurs relatively close to neutral, so warning against too ready an assumption of neutrality in practical applications. It is suggested that, for modelling purposes, it is preferable to adopt boundary layer formulations which are not too sensitive to departures from ideal conditions, and eddy coefficients, perhaps based on mixing lengths, may well provide the best approach currently available.

“Morning glory” is a local name given to a frequently occurring, near-dawn squall, accompanied by long, low, narrow cloud bands, on the south coast of the Gulf of Carpentaria. A series of simple computation experiments lends strong support to the suggestion that the phenomenon arises through katabatic drainage from the highlands to the east; a shallow layer of cold air tends to accumulate at the foot of the hills and to form a hydraulic jump, which propagates westward. The computed phase of the jump in regard to time of day and geographical location agrees well with that of the morning glory, while other features show reasonable correspondence. It is concluded on the basis of these experiments that the formation of such hydraulic jumps should be favored by slack pressure gradients, cloudless skies, a shallow inversion, steeper slopes, low latitudes, a low drag coefficient, and topographic funnelling. Since such conditions should not be uncommon in low latitudes, jump-like phenomena associated wit...

Boundary layer data from the Wangara expedition show that, at a point in the mean winter west wind belt (but near its equatorward limit), eddies on the synoptic scale (periods greater than a day) transferred westerly momentum upward. Except in the lowest 500 m, this upward tranfer predominated over downward fluxes due to micro-scale (periods less than 2 hours) and meso-scale (2 - 24 hours) eddies, the latter transfers being very small. The effect of ageostrophic motions, due to accelerations, on this transfer was negligibly small. A characteristic circulation, relative to synoptic systems, in a vertical zonal plane, performing the vertical transfer of westerly momentum, has been deduced. The eddy flux of angular momentum, in the middle latitude boundary layer between 500 and 1,700 m appears to be directed up the angular momentum gradient, both horizontally and vertically, and, at all levels, down the horizontal gradient of angular velocity. An argument is presented to show that the intensity of circulation in the Ferrel cell may be greater than is usually estimated, the maximum absolute value of the stream function (except for the Northern Hemisphere in summer), being normally at least about 30 × 1012 g s−1.

Temporal spectra and cross-spectra of the three turbulent wind components for meso-synoptic scales at 250 m vertical intervals in the planetary boundary layer are presented. The data were derived from hourly simultaneous balloon ascents from a 5-point grid at Hay, New South Wales, Australia (lat. 34 ½S), during the Wangara expedition. The spectra indicate a meso-scale gap for u (eastward component of wind) and v (northward component). The computed w-spectra suggest that no marked gap is present. For periods less than 1 day the u- and v-spectra, with a correction applied for high frequency noise, fall off approximately as n−2·6, where n is the frequency, and this result appears to be invariant with height within and just above the planetary boundary layer. The corrected w-spectra exhibit n−1 dependency in this frequency range. The uv, uw, and vw cospectra also show only small contributions on the meso-scale (periods less than a day) compared to the synoptic scale, indicating that meso-scale motions may not have to be explicitly modelled in atmospheric general circulation models. An inertial peak is found for u and v but the w-spectra show a diurnal peak. The phase angles showed that u and v were in approximate quadrature at the inertial frequency, demonstrating the existence of the inertial cycle. Tests for horizontally two-dimensional isotropy indicated that the turbulence did not obey this simplification.

n/a

The statistical characteristics of the fields and signals in the reception of radio frequencies by a moving vehicle are deduced from a scattering propagation model. The model assumes that the field incident on the receiver antenna is composed of randomly phased azimuthal plane waves of arbitrary azimuth angles. Amplitude and phase distributions and spatial correlations of fields and signals are deduced, and a simple direct relationship is established between the signal amplitude spectrum and the product of the incident plane waves' angular distribution and the azimuthal antenna gain. The coherence of two mobile-radio signals of different frequencies is shown to depend on the statistical distribution of the relative time delays in the arrival of the component waves, and the coherent bandwidth is shown to be the inverse of the spread in time delays. Wherever possible theoretical predictions are compared with the experimental results. There is sufficient agreement to indicate the validity of the approach. Agreement improves if allowance is made for the nonstationary character of mobile-radio signals.

The plume of radioactive material from the Chernobyl reactor accident passed over the United Kingdom and will increase the radiation dose to the population in the coming year. The increase above the normal annual dose from natural radiation, averaged over persons of all ages, will be about 15% in the north and 1% in the south of the country. Averaged over all ages and areas, the increase will be about 4%. This excess dose will decrease substantially in subsequent years.

RECENT results1–3 on the amino-acid content of marine sediments have related to basin deposits; the diagenetic alteration of these may not be strictly comparable with analogous changes in shelf sediments.