Daily rates of dentine formation in macaque tooth roots

When tetracycline antibiotics are administered either orally or by injection they bind at the forming mineral front of the dentine and become incorporated into teeth as a permanent label. In this study, oxytetracycline was used as a label in order to investigate the growth of root dentine in macaques. There are no good data available in the literature for daily rates of root dentine formation over a prolonged period of time in either humans or macaques. Records of ten doses of oxytetracycline administered orally at irregular intervals (but at the same time of day) over a period of 10 months to a young rhesus macaque monkey (Macaca mulatta) were used to calculate the rate of dentine formation in tooth roots. Rates of dentine formation in the first portion of third permanent molar root formation, and in the apical portion of permanent canine and premolar root formation, were consistently between 3 μm and 4 μm per day. There was no evidence in this study of a gradual decrease in daily dentine formation rate from the crown to the root, or along the length of a dentine tubule through the bulk of the dentine, as has been implied previously. With the exception of faster rates recorded in cusps or slower rates recorded at the very beginning or very end of primary dentine secretion in other studies, the results of the present study suggest a consistent rate of dentine formation in permanent macaque teeth. What data there are for human dentine formation rates suggests that it is likely this finding can be extended to human dentine as well.     

A longitudinal study of tooth growth in a single individual based on long- and short-period incremental markings in dentine and enamel

Ground sections of teeth from a single individual revealed approximately 30 fluorescent lines in the dentine resulting from successive courses of tetracycline antibiotics given over a period of approximately 12 years. In addition, many teeth showed long-period incremental markings in the dentine. Short-period daily cross-striations in the enamel were used to calculate the periodicity of the long-period incremental lines in both enamel and dentine. The incremental markings in the dentine were then used to calibrate the time of administration of each of the courses of tetracycline antibiotics. Enlarged micrographs of the teeth, constructed using fluorescence microscopy, were used to measure the increase in height of different teeth throughout the growth period on each occasion the tetracycline antibiotics were given. The times of initial mineralization of the teeth and the duration of crown formation were also determined for each tooth section. Line plots of tooth height against age were computed and used to calculate the rate of increase in tooth height during crown and root formation for one example of each tooth type. Initial rates of increase in height during enamel apposition and coronal dentine formation were fast, between 10 μm and 14 μm per day. During the latter phase of crown formation and during early root formation, tooth height increased at a slower rate of between 4 μm and 6 μm per day. Rates of increase in tooth height then rose to between 13 μm and 26 μm per day during the second half of root formation before falling off to a rate of approximately 4 μm per day during root completion (as the root apex formed). The times of initial crown mineralization and the total crown formation times estimated in this individual were all within the range known for modern humans but there was comparatively early mineralization of the third permanent molar. These findings are discussed in the context of other studies on human dental development.     

Measurements of mesospheric gravity wave momentum fluxes and mean flow accelerations at Adelaide,Australia

Forty-one days of measurements of the upward flux of zonal momentum associated with internal atmospheric gravity waves propagating in the upper mesosphere and lower thermosphere, made in thirteen 2–5 day periods, in each season, for the years 1981 and 1982 are presented, and the zonal mean flow acceleration is calculated for each period. For five periods of observation the upward fluxes of both zonal and meridional momentum are presented and for these, the total mean flow acceleration is calculated. When averaged over periods of 2–5 days, the magnitude of the upward flux of zonal momentum is typically less than about 3 m² s⁻¹, with the largest values tending to occur in the summer and winter months, suggesting a semi-annual variation with minima at the equinoxes, although large fluctuations in magnitude and sign are possible. About 70% of the upward flux of horizontal momentum appears to be due to motions with periods less than 1 h and their contribution to the mean flow acceleration is comparable. The zonal mean flow acceleration is often in the correct sense, and of sufficient magnitude, to decelerate the zonal wind component and to balance the Coriolis torque due to the mean meridional wind, when experimental uncertainties are taken into account. When averaged over periods of around 3 days, zonal mean flow accelerations with magnitudes of up to 190 m s⁻¹ day⁻¹ were calculated, but more typical values are between 50 and 80 m s⁻¹ day⁻¹. Magnitudes of the meridional and zonal mean flow accelerations were found to be similar, so that the total mean flow acceleration is not aligned with the zonal direction in general.     

Stable carbon and nitrogen isotope variations in tooth dentine serial sections from Wharram Percy

Here we report δ¹³C and δ¹⁵N measurements of serial sections of human deciduous and permanent tooth dentine from archaeological samples taken from the medieval village site of Wharram Percy, Yorkshire, UK. We found a pattern of enrichment, for both δ¹³C and δ¹⁵N, where the tooth crown was greater than the cervical part of the root, which in turn was greater than the apical portion of the root and the associated rib collagen values. This pattern reflects a decrease in the consumption of isotopically enriched breast milk and the introduction of less enriched weaning foods in the diet. The (mean±SD) difference between the deciduous second molar crowns and corresponding rib samples from the same individuals after 2 years of age was 1.2±0.4‰ for δ¹³C and 3.2±0.8‰ for δ¹⁵N. The δ¹⁵N values are as predicted, but as there were no C₄plants at Wharram Percy, this 1.2‰ enrichment in δ¹³C represents clear evidence of a carbon trophic level effect in collagen from breastfeeding infants. Carbon and nitrogen results also show that the infant diet among those who died in infancy did not differ from those who survived into childhood. This study demonstrates the promise of using dentine serial sections to study the temporal relationships of breastfeeding, weaning, and dietary patterns of single individuals.     

Parameterization of the radiative flux divergence in the 15 μm CO2 band in the 30–75 km layer

A parameterization of the cooling rate of the earth's middle atmosphere due to radiation transfer in the 15 μm CO₂ band is proposed. The parameterization has been performed for such an atmospheric layer with local thermodynamic equilibrium (below approximately 75 km), for which in the major part of the frequency interval occupied by the 15 μm band the approximation of non-overlapping lines (above about 30 km) is justified. The overlap of lines has only been taken account of for superposed strong Q-branches at the centre of the 15 μm band. The parameterization takes into account the peculiar features of radiation transfer:

• 1.(1) the height step increases with the growing distance from the level, for which cooling is calculated;
• 2.(2) the dependence of line intensity on temperature has partially been taken account of in an explicit form. The procedure proposed is multiparametric: 42 parameters are prescribed for calculating cooling at a given level. With an error less than 0.5 K day⁻¹ the procedure can be recommended for calculating radiative cooling in the case of any temperature profile undisturbed by small- and meso-scale motions and, in particular, for use in the modelling of the middle atmospheric circulation.

     

Do beats affect sun-weather correlations?

Kinget al. (1977) have presented evidence to suggest that variations in the height of the 500 mbar level may be solar induced. Using a superposed epoch analysis they show a high correlation between the 27.5 day variation (frequency 0.0364 day⁻¹) in the sunspot number and the tropospheric pressure using a ten year run of data. It is suggested here that using such an analysis, side bands in the isobaric height variations spaced equally either side of the 0.0364 day⁻¹ component may add to enhance the variation at 0.0364 day⁻¹. That such a situation may occur is confirmed by an analysis of isobaric height data at three Australian locations for the winter of 1973 which shows that the isobaric surfaces do not respond to the solar component, but that frequency components spaced equally either side of the solar components do occur.     

Shadow bands during the total solar eclipse of 11 July 1991

We recorded shadow bands just before and just after the total phase of the solar eclipse of 11 July 1991. The recordings were made using two broad band silicon photodiodes separated horizontally by 100 mm. They faced the zenith, near to where the eclipsed Sun lay as seen from our observing site close to San José del Cabo in Baja California. The irradiance fluctuations associated with the shadow bands were around 0.04 W m⁻² peak to peak on a background of 1–3 W m⁻². The cross-correlation function indicates that the shadow bands were moving at about 1.8 m s⁻¹ perpendicular to their extent. The power spectral density functions are in accord with the shadow band theory of Codona [(1986), Astron. Astrophys. 164, 415–427].     

Time evolution of the optical effects and aerosol characteristics of Mt. Pinatubo origin from ground-based observations

The time evolution of the perturbations in aerosol spectral optical depths associated with the Mt. Pinatubo volcanic eruption of June 1991 is investigated using a ground-based multiwavelength solar radiometer at the tropical station, Trivandrum. The spectral optical depths of the volcanic aerosols deduced from the radiometer data are inverted to retrieve the size distributions of the particles, from which the effective radius and columnar mass loading are estimated. Observations showed that during the initial phase (within one year after the eruption) the optical depths showed fluctuations with two peaks, one in November 1991 and another in February 1992 superposed over a very weak decreasing trend. During this period, the size distributions have been generally bimodal, with a secondary large particle mode occurring at ∼0.75 μm, and the columnar mass loading varied between about 170 and 110 mg m⁻². The optical depths and mass loading decreased with an e-folding time of about 15 months. The effective radius is found to increase from ∼0.35 μm in September 1991 to ∼0.60 μm in October 1992 and then remain rather steady, while the mass loading decreased to reach near-background levels (within error limits) by early 1993.     

Natural‐gradient tracer experiments in epikarst: a test study in the Acqua dei Faggi experimental site,southern Italy

Two natural‐gradient tracer experiments were carried out using borehole fluorometers in order to characterize the internal structure of epikarstic horizons and analyze subsurface flow within these high‐conductivity layers. The experiments were carried out in a test site in southern Italy where the epikarst is made up of an upper part with pervasive karstification and a lower part without pervasive karstification. Injection and observation boreholes were 6.9 m apart. An initial experiment demonstrated that wider (conduits) and narrower (fractures and bedding planes) openings coexist in a well‐connected network within the lower epikarst. The adjusted aperture of the opening network (105 μm) suggests that conduits are subordinately developed. The lower epikarstic horizon is hydraulically similar to granular porous media and Darcy’s law can be applied to describe groundwater flow. A small value of longitudinal dispersivity (0.13 m) shows that variations in the velocity field in the direction of flow are less significant than those typical of carbonate systems at the same experiment scale. A second experiment demonstrated that longitudinal dispersivity (2.42 m) in the upper epikarst is in agreement with findings in other carbonates at the same experiment scale. However, despite the higher dispersivity and more pervasive karstification, the mean tracer velocity (3.7 m day^?1) in the upper epikarst is slightly lower than the velocity in the lower epikarst (13.6 m day^?1).     

Mean winds at 60–90 km observed with the MU radar (35°N)

Mean winds at 60–90 km altitudes observed with the MU radar (35°N, 136°E) in 1985–1989 are presented in this paper. The zonal wind at 70 km became westward and eastward in summer and winter, respectively, with a maximum amplitude of 45 m s⁻¹ westward in early July and 80 m s⁻¹ eastward at the end of November. The meridional wind below 85 km was generally northward with the amplitudes less than 10 m s⁻¹. In September to November, the meridional wind at 75–80 km becomes as large as 20–30 m s⁻¹. Those zonal wind profiles below 90 km show good coincidence with the CIRA 1986 model, except for the latter half of winter, from January to March, when the observational result showed a much weaker eastward wind than the CIRA model. The height of the reversal of the summer wind from westward to eastward was determined as being 83–84 km, which is close to the CIRA 1986 model of 85 km. The difference between the previous meteor radar results at 35–40°N, which showed the reversal height below 80 km, could be due to interannual variations or the difference in wind measurement technique. In order to clarify that point, careful comparative observations would be necessary. These mean winds were compared with Adelaide MF radar observations, and showed good symmetry between the hemispheres, including the summer reversal height, except for the short period of eastward winds above Kyoto and the long period over Adelaide.     

Measurement of O2(a1Δg) emission in a total solar eclipse

The altitude distribution of the oxygen infrared atmospheric bands at 1.27 μm was measured during the total solar eclipse of 26 February 1979. The ozone concentration profile has been derived from these airglow measurements and indicates that at 85 km the concentration at totality was 7 × 1.7 cm⁻³, with no well defined upper layer. This reduced concentration, which is typical of summertime conditions, was probably due to perturbations in the mesospheric chemistry and transport induced by a winter warming event that was in progress at the time of the eclipse. At 60 km the ozone concentration, 2.7 × 10¹⁰ cm⁻³, was enhanced above that normally measured. This increase may also have been caused by the stratospheric warming event but the effects of a particle precipitation event, which was also in progress during the eclipse, may be important.     

Refilling process in the plasmasphere and its relation to magnetic activity

When geomagnetic activity is moderate, the geosynchronous orbit crosses the plasmasphere bulge region in which the variations of plasma density from day to day can therefore be detected by geosynchronous satellites. The plasma density was measured by the Relaxation Sounder onboard ESA's GEOS-2 satellite. Variations of plasma density reflect the combined effects of refilling of particles from the ionosphere and loss of plasma by convection. The saturation level of the electron density at the geo-synchronous orbit and the refilling rate under different conditions of geomagnetic activity have been obtained and are found to be 70.5 cm⁻³ and 7–25 cm⁻³ day⁻¹, respectively. In this paper the refilling morphology and the relationship between the refilling process and magnetic activity (Dst index) are analysed. The refilling rate or refilling time constant inferred from the data, either directly on fairly well-defined refilling events, or indirectly through a simple model, are found to compare reasonably well with the refilling time constant expected by theory. The observed correlation of refilling rate with Dst index is interpreted as resulting from the modification of the composition of the topside ionosphere occurring after intense storms.     

EXAMINING CHILDHOOD DIETS AT KAMINALJUYU,GUATEMALA, THROUGH STABLE ISOTOPIC ANALYSIS OF SEQUENTIAL ENAMEL MICROSAMPLES*

Stable carbon and oxygen isotope ratios of tooth enamel provide a means to examine nutritional changes during childhood. To date, such studies have used large enamel samples, often spanning the developmental period of the tooth. This paper reports the results of small samples drilled from first molars and premolars of human teeth from Kaminaljuyu, a Classic period city in highland Guatemala. Carbon isotopes show considerable increase between cuspal and cervical enamel for both teeth, indicating an increase in maize consumption during childhood. Oxygen isotope trends are more variable, and suggest some seasonal fluctuation. While the oxygen isotope data confirm the identification of foreign skeletons among the samples, they illustrate a need for caution when sampling teeth due to variable δ¹⁸O composition of enamel within a tooth.     

Osteometric scoring of adult residual rickets skeletal plasticity in two archaeological populations from southeastern England: Relationship to sunshine and calcium deficits and demographic stress

An osteometric scoring technique is developed for the quantification of rickets deformational effects persisting in the healed adult skeleton. Termed RR-15 scoring (for residual rickets estimate, based on 15 main diagnostic osteometric traits), the method is first validated for sunshine deficit, and is then tested in a comparison of three climatically distinct archaeological populations from southeastern England. Two well-dated cemetery series were sampled: the Saint Bride's Church columbarium collection (SBC) from London at the time of the Industrial Revolution, for which the sex, age, and calender year at death of each individual are known; and the early Anglo-Saxons from Abingdon, near Oxford (AAS). Estimates of insolation in the past were developed indirectly by reference to δ¹⁸O mass spectrometer analyses of dated layers of the Greenland ice sheet. In SBC and AAS, the RR-15 score varies primarily as a direct function of computed sunshine deficit, but is also incremented by deficits of bioavailable calcium in their reconstructed diets, and by demographic stress in AAS, the inferred result of a high birth rate. The amounts of interglobular dentine present in the permanent first and third molar crowns of SBC and AAS have been shown to correlate similarly with sunshine and calcium deficits. The relatively high RR-15 score obtained in a small sample of northwestern European neanderthals lends quantitative support to the bioenvironmental hypothesis that sunshine-deficit rickets accounts for much of their paranormal gross morphology.     

E-region nitric oxide concentrations inferred from the 26 February 1979 eclipse expedition

Nitric oxide (NO) concentrations have been determined from the analysis of positive ion composition data obtained by AFGL for eclipse and post-eclipse conditions near Red Lake, Canada. Values of about 3 × 10⁸ cm⁻³ for 105–110 km and about 3 × 107 cm⁻³ for 90 km have been established. A residual ion-pair production rate of about 50 cm⁻³ s⁻¹ is estimated for eclipse totality at 110 km. A factor of two uncertainty is thought to be appropriate for all deduced values. The calculated NO concentrations appear to be within the range of typical variations for this season (late winter) and latitude (51°N).     

Vertical neutral wind in the equatorial F-region deduced from electric field and ion density measurements

DC electric field and ion density measurements near density depletion regions (that is, equatorial plasma bubbles) are used to estimate the vertical neutral wind speed. The measured zonal electric field in a series of density depletions crossed by the San Marco D satellite at 01.47-01.52 UT on 25 October 1988, can be explained if a downward neutral wind of 15–30 m s⁻¹ exists. Simultaneously, the F-region plasma was moving downward at a speed of 30–50 m s⁻¹ These events appear in the local time sector of 23.002̄23.15 in which strong downward neutral winds may occur. Indeed, airglow measurements suggest that downward neutral velocities of 25–50 m s⁻¹ are possible at times near midnight in the equatorial F-region.     

HF produced ionospheric electron density irregularities diagnosed by UHF radio star scintillations

High frequency waves incident on an overdense ionosphere (i.e. HF < penetration frequency) are known to produce large-scale irregularities with scale sizes of several hundred meters in the F-region of the ionosphere. Three observations of radio star intensity fluctuations at UHF are reported for HF ionospheric modification experiments performed at the Arecibo Observatory. Two observations at 430 MHz and one observation at 1400 MHz indicate that the thin phase screen theory is a good approximation to the observed power spectra. However, the theory has to be extended to include antenna filtering. Such filtering is important for UHF radio star scintillations since the antenna usually has a narrow beam width. HF power densities of less than 37 μW m⁻² incident on the ionosphere produce electron density irregularities larger than 13% of the ambient density (at 260 km) having scale sizes of ~510 m perpendicular to the geomagnetic field. The irregularities form within 20–25 s after the HF power is turned on. From the observed power spectra driftvelocities of the irregularities can be estimated.     

Observational evidence of local turbulence production due to gravity wave saturation in the summer mesosphere

Five foil chaff and two falling sphere rockets flown during the MAC/SINE Campaign on 15 July 1987 at Andenes, Northern Norway (69°17′N). From these rocket measurements, turbulent energy dissipation rates, vertical wind shears and Richardson numbers as functions of height were derived in the range from 82 to 92km. Turbulent energy dissipation rates generally range from 1.4 × 10⁻⁵ to 2.0 × 10⁻²W/kg and are consistent with other experiments performed at the same latitude. Strong wind shears of the order of 50–90 m/s/km are observed at various heights. Good correspondence between turbulence intensity peaks, regions of strong wind shear and low Richardson number is found. Vertical wavenumber spectra of the five scalar winds measured by the foil chaff rockets indicate that there is an excellent agreement with the saturation hypothesis, suggesting that the turbulence intensity peaks measured in this salvo are linked directly to the saturation of gravity wave motions via dynamical instabilities.