Eastern Longitude Research Articles

Some characteristics of the seismicity of the Tyrrhenian Sea Region

In the first p a r t of the paper the seismic strain release of the T y r r h e n i a n Sea Region (including Italy), as the function of time, is examined on the basis of t h e d a t a of the e a r t h q u a k e s t h a t took place f r om 1901.01.01 to 1970.12.31, between the northern l a t i t u d e s of 34° and 44° and between the eastern longitudes of 8° and 18.5°, respectively. All registered shocks with a R i c h t e r - m a g n i t u d e of 5.5 or over it were considered, i n d e p e n d e n t l y f r om t h e focal d e p t h . Three periods were recognized in the a c t i v i t y ; t h e lengths of which are not t h e same, however. I n the second p a r t the elastic strain release in accordance with the focal d e p t h of t h e same e a r t h q u a k e s is t r e a t e d briefly. It was found t h at t h e t o t a l strain-release had a maximum value in t h e depth between 0 and 74 kms and there was a minimum between the depth of 300 and 524 kins with an interval between 375 and 449 kms within which no earthquakes occurred at all. The general p a t t e r n of the d i s t r i b u t i o n of seismicity as t h e f u n c t i o n of hypocentral d e p t h reminds to the well-known picture, one can experience in other regions where i n t e r m e d i a t e and deep shocks occur. This s t a t e m e n t is consistent w i t h t h e idea, according to which t h e seismicity of t h e Tyrrhenian Sea Region can be discussed and explained in t h e light of t h e theory of new global tectonics. F i n a l l y , in the t h i r d p a r t of the study, the authors have s t a t e d t h at in some cases multiple events occurred b e n e a t h t h e Tyrrhenian Sea Region. Such multiple seismic events were detected in the case of other areas, such as the Fiji-Tonga-Kermadec Region, the seismic belt of South America etc., — but, according to the knowledge of t h e authors, this is t h e first occasion when multiple seismic events are demonstrated in the Tyrrhenian Sea Region.

Intraocular Pressure and Related Systemic and Ocular Biometric Factors in a Population-Based Study in Japan: The Kumejima Study

To examine the distribution of intraocular pressure (IOP) and its related systemic and ocular biometric factors in a population-based study in a southwestern island of Japan. Cross-sectional, population-based study. All residents of Kumejima Island, Japan, located in southwestern Japan (eastern longitude, 126 degrees 48 minutes and northern latitude 26 degrees 20 minutes), 40 years of age and older were asked to undergo a comprehensive questionnaire and ocular examination, including measurement of IOP with Goldmann applanation tonometry. Of the 4632 eligible residents, 3762 (81.2%) underwent the examination. In 2838 non-glaucomatous subjects from whom reliable measurements of IOP were obtained, the mean IOPs +/- standard deviation in all, men, and women were 15.1 +/- 3.1 mm Hg (n = 2838), 15.2 +/- 3.1 mm Hg (n = 1450), and 15.1 +/- 3.0 mm Hg (n = 1388), respectively, with no significant intersex difference (P = .63). Multivariate regression analysis demonstrated that higher IOP was significantly correlated with younger age (P < .001), higher body mass index (P < .001), higher systolic blood pressure (P < .001), history of diabetes mellitus (P = .001), thicker central corneal thickness (P < .001), steeper corneal curvature (P < .001), and longer axial length (P < .018), but not with anterior chamber depth and the Shaffer angle width grade. Younger age, higher body mass index, higher systolic blood pressure, diabetes, thicker central corneal thickness, and steeper corneal curvature were significantly correlated with higher IOP. The present results confirm that IOP is associated with systemic and ocular biometric factors and may define specific subgroups most likely to have an elevated IOP.

Estimating Error in Using Ambient PM2.5 Concentrations as Proxies for Personal Exposures: A Review

Several methods have been used to account for measurement error inherent in using ambient concentration of particulate matter < 2.5 microm/m(3) (PM(2.5)) as a proxy for personal exposure. Such methods commonly rely on the estimated correlation between ambient and personal PM(2.5) concentrations (r). However, studies of r have not been systematically and quantitatively assessed for publication bias or heterogeneity. We searched 7 electronic reference databases for studies of the within-participant correlation between ambient and personal PM(2.5). We identified 567 candidate studies, 18 (3%) of which met inclusion criteria and were abstracted. The studies were published between 1999 and 2008, representing 619 nonsmoking participants aged 6-93 years in 17 European and North American cities. Correlation coefficients (median 0.54; range 0.09-0.83) were based on a median of 8 ambient-personal PM(2.5) pairs per participant (range 5-20) collected over 27-547 days. Overall, there was little evidence for publication bias (funnel plot symmetry tests: Begg's log-rank test, P 0.9; Egger's regression asymmetry test, P 0.2). However, strong evidence for heterogeneity was noted (Cochran's Q test for heterogeneity, P = 0.001). European locales, eastern longitudes in North America, higher ambient PM(2.5) concentrations, higher relative humidity, and lower between-participant variation in r were associated with increased r. Characteristics of participants, studies, and the environments in which they are conducted may affect the accuracy of ambient PM2.5 as a proxy for personal exposure.

Regional variation in infant hypoallergenic formula prescriptions in Australia

There is little information on the regional distribution of food allergy in Australia. We examined the influence of latitude (a marker of sunlight/vitamin D status) on food allergy, as measured by 2007 infant hypoallergenic formula (IHF) prescription rates in children ages 0-2 yrs. Data were compiled from the 52 statistical divisions in mainland Australia plus the island of Tasmania (n=53 observations). Data from the Australian Department of Health and Aging and the Australian Bureau of Statistics were analysed by statistical division. There was significant regional variability in hypoallergenic formula prescription rates (per 100,000 population/yr), with the highest rates in southern Australia (14,406) and the lowest in the north (721), compared with a national average of 4099. Geographical factors (decreasing latitude and increasing longitude) were associated with a higher rate of IHF prescriptions, such that rates were higher in southern vs. northern regions, and in eastern compared with western regions. Controlling for longitude, physician density and markers of socioeconomic status, southern latitudes were associated with higher hypoallergenic formulae prescription rates [beta, -147.98; 95% confidence interval (CI)=-281.83 to -14.14; p=0.03]. Controlling for latitude, physician density and markers of socioeconomic status, eastern longitudes were also associated with higher hypoallergenic formulae prescription rates (beta, 89.69; 95% CI=2.90-176.49; p=0.04). Among young children, hypoallergenic formula prescription rates are more common in the southern and eastern regions of Australia. These data provide support for a possible role of sun exposure/vitamin D status (amongst other potential factors) in the pathogenesis of food allergy.

Mercury’s magnetospheric magnetic field after the first two MESSENGER flybys

The “paraboloid” model of Mercury’s magnetospheric magnetic field is used to determine the best-fit magnetospheric current system and internal dipole parameters from magnetic field measurements taken during the first and second MESSENGER flybys of Mercury on 14 January and 6 October 2008. Together with magnetic field measurements taken during the Mariner 10 flybys on 29 March 1974 and 16 March 1975, there exist three low-latitude traversals separated in longitude and one high-latitude encounter. From our model formulation and fitting procedure a Mercury dipole moment of 196 nT · R M 3 (where R M is Mercury’s radius) was determined. The dipole is offset from Mercury’s center by 405 km in the northward direction. The dipole inclination to Mercury’s rotation axis is relatively small, ∼4°, with an eastern longitude of 193° for the dipole northern pole. Our model is based on the a priori assumption that the dipole position and the moment orientation and strength do not change in time. The root mean square (rms) deviation between the Mariner 10 and MESSENGER magnetic field measurements and the predictions of our model for all four flybys is 10.7 nT. For each magnetic field component the rms residual is ∼6 nT or about 1.5% of the maximum measured magnetic field, ∼400 nT. This level of agreement is possible only because the magnetospheric current system parameters have been determined separately for each flyby. The magnetospheric stand-off distance, the distance from the planet’s center to the inner edge of the tail current sheet, the tail lobe magnetic flux, and the displacement of the tail current sheet relative to the Mercury solar-magnetospheric equatorial plane have been determined independently for each flyby. The magnetic flux in the tail lobes varied from 3.8 to 5.9 MWb; the subsolar magnetopause stand-off distance from 1.28 to 1.43 R M ; and the distance to the inner edge of the current sheet from 1.23 to 1.32 R M . The differences in the current systems between the first and second MESSENGER flybys are attributed to the effects of strong magnetic reconnection driven by southward interplanetary magnetic field during the latter flyby.

Peculiarities of the tectonic and magma evolution of the southwestern Indian middle-ocean crust within the range of 51°–67° eastern longitude

The comparative estimation of the parameters of the lithosphere of the Mid-Ocean Southwestern Indian range in the areas westwards and eastwards of the Atlantis II transform fault zone shows that, within this zone, an alteration in the basalt composition occurred. Eastwards of this zone, a decrease of the anomaly of the magnetic field occurred and increased average depths of the axial part (4.7 km) and thinning (up to 4–5 km) of the ocean crust with increased rates of seismic waves in the upper mantle were observed. This, first of all, indicates an anomalously cold mantle below the oceanic crust. The changes that occurred in the location of the Euler pole within the last millions of years resulted in slanting spreading in the area of the investigation with rates of opening lower than 1.8 cm/year probably accompanied by the phenomena of transtension in the active parts of the transform faults. The interaction between the Landly and Somali lithosphere plates occurred along the diffusion boundary and was accompanied by problems with tracing the chrones between the neighboring profiles of geomagnetic observations. Consequently, the more detailed investigation of the configuration of the diffusion boundary will contribute to the more accurate reconstruction of the paleogeodynamics of the central part of the Indian Ocean.

Estimating Error in Using Residential Outdoor PM 2.5 Concentrations as Proxies for Personal Exposures: A Meta-analysis

BackgroundStudies examining the health effects of particulate matter ≤ 2.5 μm in aerodynamic diameter (PM2.5) commonly use ambient PM2.5 concentrations measured at distal monitoring sites as proxies for personal exposure and assume spatial homogeneity of ambient PM2.5. An alternative proxy—the residential outdoor PM2.5 concentration measured adjacent to participant homes—has few advantages under this assumption.ObjectivesWe systematically reviewed the correlation between residential outdoor PM2.5 and personal PM2.5 (r̄j) as a means of comparing the magnitude and sources of measurement error associated with their use as exposure surrogates.MethodsWe searched seven electronic reference databases for studies of the within-participant residential outdoor-personal PM2.5 correlation.ResultsThe search identified 567 candidate studies, nine of which were abstracted in duplicate, that were published between 1996 and 2008. They represented 329 nonsmoking participants 6–93 years of age in eight U.S. cities, among whom r̄j was estimated (median, 0.53; range, 0.25–0.79) based on a median of seven residential outdoor-personal PM2.5 pairs per participant. We found modest evidence of publication bias (symmetric funnel plot; pBegg = 0.4; pEgger = 0.2); however, we identified evidence of heterogeneity (Cochran’s Q-test p = 0.05). Of the 20 characteristics examined, earlier study midpoints, eastern longitudes, older mean age, higher outdoor temperatures, and lower personal-residential outdoor PM2.5 differences were associated with increased within-participant residential outdoor-personal PM2.5 correlations.ConclusionsThese findings were similar to those from a contemporaneous meta-analysis that examined ambient-personal PM2.5 correlations (r̄j = median, 0.54; range, 0.09–0.83). Collectively, the meta-analyses suggest that residential outdoor-personal and ambient-personal PM2.5 correlations merit greater consideration when evaluating the potential for bias in studies of PM2.5-mediated health effects.

The quasigeoid modelling in New Zealand using the boundary element method

We compile a quasigeoid model at the study area of New Zealand using theboundary element method (BEM). The direct BEM formulation for the Laplace equationis applied to obtain a numerical solution to the linearized fixed gravimetric boundaryvalueproblem in points at the Earth’s surface. The numerical scheme uses the collocationmethod with linear basis functions. It involves a discretisation of the Earth’s surfacewhich is considered as a fixed boundary. The surface gravity disturbances represent theoblique derivative boundary condition. The geocentric positions of the collocation pointsare determined combining the digital elevation data and the a priori quasigeoid model(onshore) and the mean sea surface topography (offshore). In our numerical realization,we use the global elevation data from SRTM30PLUS V5.0, the detailed DTM of NewZealand, the EGM2008 quasigeoid heights, and the mean sea surface topography fromthe DNSC08 marine database. The gravity disturbances are computed using two heterogeneousgravity data sets: the altimetry-derived gravity anomalies from the DNSC08gravity database (offshore) and the observed ground gravity anomalies from the GNSScience gravity database (onshore). The transformation of gravity anomalies to gravitydisturbances is realized using the quasigeoid heights calculated from the EGM2008 globalgeopotential model. The new experimental quasigeoid model NZQM2010 is compiled atthe study area of New Zealand bounded by the parallels of 34 and 47.5 arc-deg southernlatitude and the meridians of 166 and 179 arc-deg eastern longitude. The least-squaresanalysis is applied to combine the gravimetric solution with GPS-levelling data using a7-parameter model. NZQM2010 is validated using GPS-levelling data and compared withthe existing regional and global quasigeoid models NZGeoid2009 and EGM2008.&nbsp

Out of the North Sea: the Zeeland Ridges Neandertal

In 2001, a portion of human frontal bone was discovered in sediments extracted from the bottom of the North Sea, 15 km off the coast of the Netherlands. The extraction zone is located in the so-called Zeeland Ridges area located at 51°40′ northern latitude and 3°20′ eastern longitude. The specimen was dredged up from sediments containing Late Pleistocene faunal remains and Middle Palaeolithic artefacts, including well-finished small handaxes and Levallois flakes. The details of the supraorbital morphology, as well as the quantitative assessment of the shape of the external surface of the squama using traditional and 3D geometric morphometrics, unambiguously assign the Zeeland Ridges frontal bone to Homo neanderthalensis. Carbon and nitrogen isotopic analysis indicate that the Zeeland Ridges hominin, like other Neandertals, was highly carnivorous and does not show evidence for the consumption of aquatic foods. A lesion on the outer table and diploic layer of the bone in the area of the supratoral sulcus can be interpreted as the result of an intradiploic epidermoid cyst, a type of neoplasm diagnosed for the first time in Neandertal remains. So far, the Zeeland Ridges Neandertal is the first Pleistocene fossil hominin found under seawater and the first recorded in the Netherlands.

Prevalence and Risk Factors of Pterygium in a Southwestern Island of Japan: The Kumejima Study

To determine the prevalence and risk factors for pterygium in a Japanese population aged 40 years or older on Kumejima Island, Japan. Cross-sectional, population-based study. All residents of Kumejima Island, Japan, located in Southwestern Japan (Eastern longitude 126 degrees, 48 feet and Northern latitude 26 degrees, 20 feet), aged 40 years and older were asked to undergo a comprehensive questionnaire and ocular examination. Of the 4,632 residents, 3,762 (81.2%) underwent the examination. The presence of pterygium could not be determined in 15 subjects. Of the 3,747 eligible subjects, 1,154 (30.8%; 95% confidence interval [CI], 29.3% to 32.3%) had pterygium in at least 1 eye and 491 subjects (13.1%; 95% CI, 12.1% to 14.3%) had pterygium in both eyes. In the logistic regression analysis, older age (P < .001), male gender (P = .024), hyperopic refraction (P = .001), lower intraocular pressure (P = .002), and outdoor job experience (P < .001) were independently associated with a higher risk of pterygium. The prevalence of pterygium is 30.8% among adult Japanese aged 40 years and older in Kumejima. Older age, male gender, hyperopic refraction, lower intraocular pressure, and outdoor job history were independently associated with a higher risk of pterygium.

Enzootic Angiostrongyliasis in Shenzhen, China

To the Editor: Angiostrongylus cantonensis is a zoonotic parasite that causes eosinophilic meningitis in humans after they ingest infective larvae in freshwater and terrestrial snails and slugs, paratenic hosts (such as freshwater fish, shrimps, frogs, and crabs), or contaminated vegetables. With the increase of income and living standards, and the pursuit of exotic and delicate foods, populations around the world have seen angiostrongyliasis become an important foodborne parasitic zoonosis (1–9). Shenzhen municipality is situated in the most southern part of mainland People’s Republic of China between the northern latitudes of 22°27′ to 22°52′ and eastern longitudes of 113°46′ to 114°37′; it shares a border with the Hong Kong Special Administrative Region, China, in the south. The climate is subtropical, with an average annual temperature of 23.7°C. The city is 1,952.84 km2 and has a population of 10 million. Since 2006, thirty-two sporadic cases of human eosinophilic meningitis caused by consumption of undercooked aquacultured snails have been documented in Shenzhen (Shenzhen Center for Disease Control and Prevention, unpub. data). To identify the source of these infections and assess the risk for an outbreak of eosinophilic meningitis, we conducted a survey to investigate whether A. cantonensis occurs in wild rats and snails in Shenzhen. To examine A. cantonensis infection in intermediate host snails, 302 terrestrial snails (Achatina fulica) were collected from 10 investigation sites across Shenzhen, and 314 freshwater snails (Pomacea canaliculata)were sampled from 6 investigation sites. We examined the snails for A. cantonensis larvae by using pepsin digestion standardized procedures (3). To survey the prevalence of adult A. cantonensis in definitive host rats, we collected 187 Rattus norvegicus rats and 121 R. flavipectus rats collected from 4 sites where positive snails positive for A. cantonensis were found. These rats were examined for the presence of adult A. cantonensis in their cardiopulmonary systems. A. cantonensis larvae were found in 96 (15.6%) of 616 examined snails. Of these, P. canaliculata had an average infection rate of 20.7% (65/314), significantly higher (p<0.01) than that of A. fulica (10.3%, 31/302), an indication that P. canaliculata may be the principal intermediate host for A. cantonensis in Shenzhen. A. cantonensis adults were recovered from the cardiopulmonary systems of 37 (12%) of 308 examined rats. Infection rate for R. norvegicus rats was 16.6% (31/187), significantly higher (p<0.01) than that for R. flavipectus (4.9%, 6/121), an indication that R. norvegicus may be the principal definitive host for A. cantonensis in Shenzhen, possibly due to the rat’s preference for eating snails. Infection rates were higher for female rats (25.6% for R. norvegicus and 7.8% for R. flavipectus) than for male rats (8.9% for R. norvegicus, 2.9% for R. flavipectus), possibly because female rats eat more snails to supply proteins for reproduction. This report of enzootic A. cantonensis infection in wild rats and snails in Shenzhen demonstrates the existence of natural origins of infection with A. cantonensis for humans in this city. Persons in Shenzhen eat raw or undercooked freshwater and terrestrial snails and slugs. This practice provides opportunities for infection with A. cantonensis, particularly given that P. canaliculata has been aquacultured intensively for human consumption. The prevalence of A. cantonensis in wild rats and snails in Shenzhen poses substantial risk for future outbreaks of human eosinophilic meningitis. Moreover, public health officials, epidemiologists, researchers, clinical technicians, medical practitioners, parasitologists, and veterinarians, as well as the general public, should be aware of such risks, and integrated strategies should be taken to reduce or eliminate such risks.

Abnormal evening vertical plasma drift and effects on ESF and EIA over Brazil‐South Atlantic sector during the 30 October 2003 superstorm

Equatorial F region vertical plasma drifts, spread F and anomaly responses, in the south American longitude sector during the superstorm of 30 October 2003, are analyzed using data from an array of instruments consisting of Digisondes, a VHF radar, GPS TEC and scintillation receivers in Brazil, and a Digisonde and a magnetometer in Jicamarca, Peru. Prompt penetrating eastward electric field of abnormally large intensity drove the F layer plasma up at a velocity ∼1200 ms−1 during post dusk hours in the eastern sector over Brazil. The equatorial anomaly was intensified and expanded poleward while the development of spread F/plasma bubble irregularities and GPS signal scintillations were weaker than their quiet time intensity. Significantly weaker F region response over Jicamarca presented a striking difference in the intensity of prompt penetration electric field between Peru and eastern longitudes of Brazil. The enhanced post dusk sector vertical drift over Brazil is attributed to electro‐dynamics effects arising energetic particle precipitation in the South Atlantic Magnetic Anomaly (SAMA). These extraordinary results and their longitudinal differences are presented and discussed in this paper.

Crown and tree allometry of open-grown ash (Fraxinus excelsior L.) and sycamore (Acer pseudoplatanus L.)

The aim of this study was to set up allometric models on the development of open-grown trees (OGT) of ash (Fraxinus excelsior L.) and sycamore (Acer pseudoplatanus L.). Sampling was carried out during a study on valuable broadleaves in Europe and covers a geographical location from 0° to 9° eastern longitude and 47° to 51° northern latitude in Western Europe. We set up models describing (I) crown allometry, taking into account possible effects of (II) site-specific differences and (III) species effects. In addition, simulations were used calculating the potential width of the knotty core inside the stem for self-pruned OGTs. The models also procured insight into space occupation of OGTs. This investigation on crown and tree allometry for a broad range of tree size complements dynamic models on growth of broadleaved trees only monitored at young ages and for a small number of years. It quantifies the relationship between tree height, stem diameter, height-stem diameter ratio, height to crown base, and descriptors of crown form. Only for the models on the crown width/length ratio (WL ratio) and on the crown ratio were there no significant allometric differences between the two species. For none of the models were site effects found to be significant. Self-pruning of ash and sycamore OGTs was slow and the simulated knottiness of the trunk was considerable. Therefore artificial pruning is necessary for a long clear bole, although both species are known for fast self-pruning. In addition, comparison of crown allometric models for forest trees and open-grown ash and sycamore trees underlined the need for specific models in agroforestry based on OGT. Specifically, when tree diameter being equal, OGTs have larger crowns compared to trees from closed forests. During tree development crown form changes uniformly with no significant species-related difference: The vertical crown expansion of young ash and sycamore overweighs the lateral expansion. As trees mature, the crown WL ratio increases leading to crown width values almost equal to crown length. Thus in their early stages of development ash and sycamore OGTs invest more in the vertical space occupation and only at later stages in horizontal expansion.

Climatologies of nighttime upper thermospheric winds measured by ground‐based Fabry‐Perot interferometers during geomagnetically quiet conditions: 2. High‐latitude circulation and interplanetary magnetic field dependence

We analyze upper thermospheric (∼250 km) nighttime horizontal neutral wind patterns, during geomagnetically quiet (Kp &lt; 3) conditions, over the following locations: South Pole (90°S), Halley (76°S, 27°W), Millstone Hill (43°N, 72°W), Søndre Strømfjord (67°N, 51°W), and Thule (77°N, 68°W). We examine the wind patterns as a function of magnetic local time and latitude, solar cycle, day of year, and the dawn‐dusk and north‐south components of the interplanetary magnetic field (IMF By and Bz). In magnetic coordinates, the quiet time high‐latitude wind patterns are dominated by antisunward flow over the polar cap, with wind speeds that generally increase with increasing solar extreme ultraviolet (EUV) irradiation. The winds are generally stronger during equinox than during winter, particularly over the South Pole in the direction of eastern longitudes. IMF By exerts a strong influence on the wind patterns, particularly in the midnight sector. During winter, By positive winds around midnight in the northern (southern) hemisphere are directed more toward the dusk (dawn) sector, compared to corresponding By negative winds; this behavior is consistent with the By‐dependence of statistical ionospheric convection patterns. The strength of the wind response to By tends to increase with increasing solar EUV irradiation, roughly in proportion to the increased wind speeds. Quiet time By effects are detectable at latitudes as low as that of Millstone Hill (magnetic latitude 53°N). Quiet time Bz effects are negligible except over the magnetic polar cap station of Thule.

Environmental, spatial, temporal and operational effects on swordfish ( Xiphias gladius) catch rates of eastern Mediterranean Sea longline fisheries

Generalized additive models (GAMs) were applied to examine the relative influence of environmental, spatial, temporal and operational factors on swordfish catch rates in the Greek swordfish longline fishery between 1998 and 2004. GAM analysis accounted for 47% of the variance in nominal catch per unit effort (CPUE) expressed in number of fish per 1000 hooks. Stepwise GAM building revealed the relative importance of eight variables ranked by decreasing magnitude: Fishing gear type, Month, Year, Sea surface temperature, Longitude, Latitude, Lunar index and Bottom depth. Longlines having deeper, thicker and more resilient branch lines with illuminated fish attractants yielded significantly higher swordfish catches. CPUE peaked during the last quarter of the fishing season, at sea surface temperatures 16–18 °C and over 26 °C, when the Lunar disc illumination was high and at greater depths. Elevated relative abundance was observed in southern and eastern longitudes, corresponding to the Levantine region. A moderate decline in swordfish abundance was detected from 1998 to 2003 followed by a sharp rise in 2004, while average individual swordfish weight decreased from 30 kg in 1998 to 23 kg in 2004.

The Effect of Physiographic Region and Geographic Locale on Predicting the Dominant Height and Basal Area of Loblolly Pine Plantations

Abstract Analysis of loblolly pine plantation permanent plot data established across the southeastern United States indicates that differences in dominant height and stand basal area may be related to geographic locale as well as physiographic region. In general, holding other factors constant,plantations at southern latitudes and eastern longitudes have less basal area than plantations at northern latitudes and western longitudes. Plantations at southern latitudes and eastern longitudes in the Atlantic Coastal Plain are generally taller than elsewhere in the Atlantic Coastal Plain.These trends were consistent for a younger population of intensively managed plantations, as well as for an older population of nonintensively managed plantations. Regression equations were developed to test the significance of geographic location on the prediction of basal area and dominantheight. Even in the presence of stand variables that are highly correlated with basal area and dominant height, latitude and longitude were highly significant predictors. Including them as predictor variables increased considerably the precision of the regression equations. South. J. Appl.For. 30(3):142–146.

Geomagnetic field behavior during the Iceland Basin and Laschamp geomagnetic excursions: A simple transitional field geometry?

We present four new records of the Iceland Basin Excursion (IBE) and five new records of the Laschamp Excursion (LE) obtained from rapidly deposited marine sediments in the North Atlantic Ocean, the Nordic Seas, the Gulf of Mexico, the South China Sea, and the southern Indian Ocean. Marked minima in relative paleointensity correspond with the paleomagnetic directional changes associated with all of the excursion records. The virtual geomagnetic pole (VGP) paths of the four IBE records are all similar. The VGPs move southward over Europe and Africa, reaching the southern hemisphere (three reach Antarctica), and then move to more eastern longitudes before returning northward over Australia and east Asia, describing a large counterclockwise loop. The same VGP pattern is observed in other published records. The VGP paths observed for the LE are similar to those of the IBE; however, they loop clockwise instead of counterclockwise. Despite the different sense of looping, the marked similarity among the paths for the two excursions suggests that a similar, relatively simple geometry dominated the transitional field during both the IBE and the LE. Similar dynamo mechanisms must therefore have been active in the Earth's core for both excursions. The duration of the excursions is estimated at &lt;2,000 years, which supports the suggestion that a difference exists between the mechanisms for excursions and reversals. However, the coincidence of the longitudinal bands for VGPs associated with excursions compared to some reversal paths could also indicate an inherent link between the mechanisms for reversals and excursions.

Distinguishing the distributions of two cryptic frogs (Anura: Discoglossidae) using molecular data and environmental modeling

Currently, the identification of two cryptic Iberian amphibians, Discoglossus galganoi Capula, Nascetti, Lanza, Bullini and Crespo, 1985 and Discoglossus jeanneae Busack, 1986, relies on molecular characterization. To provide a means to discern the distributions of these species, we used 385-base-pair sequences of the cytochrome b gene to identify 54 Spanish populations of Discoglossus. These data and a series of environmental variables were used to build up a logistic regression model capable of probabilistically designating a specimen of Discoglossus found in any Universal Transverse Mercator (UTM) grid cell of 10 km × 10 km to one of the two species. Western longitudes, wide river basins, and semipermeable (mainly siliceous) and sandstone substrates favored the presence of D. galganoi, while eastern longitudes, mountainous areas, severe floodings, and impermeable (mainly clay) or basic (limestone and gypsum) substrates favored D. jeanneae. Fifteen percent of the UTM cells were predicted to be shared by both species, whereas 51% were clearly in favor of D. galganoi and 34% were in favor of D. jeanneae, considering odds of 4:1. These results suggest that these two species have parapatric distributions and allow for preliminary identification of potential secondary contact areas. The method applied here can be generalized and used for other geographic problems posed by cryptic species.

Seasonal-longitudinal variability of equatorial plasma bubbles

Abstract. We compare seasonal and longitudinal distributions of more than 8300 equatorial plasma bubbles (EPBs) observed during a full solar cycle from 1989-2000 with predictions of two simple models. Both models are based on considerations of parameters that influence the linear growth rate, γRT, of the generalized Rayleigh-Taylor instability in the context of finite windows of opportunity available during the prereversal enhancement near sunset. These parameters are the strength of the equatorial magnetic field, Beq, and the angle, α, it makes with the dusk terminator line. The independence of α and Beq from the solar cycle phase justifies our comparisons. We have sorted data acquired during more than 75000 equatorial evening-sector passes of polar-orbiting Defense Meteorological Satellite Program (DMSP) satellites into 24 longitude and 12 one-month bins, each containing ~250 samples. We show that: (1) in 44 out of 48 month-longitude bins EPB rates are largest within 30 days of when α=0°; (2) unpredicted phase shifts and asymmetries appear in occurrence rates at the two times per year when α≈0°; (3) While EPB occurrence rates vary inversely with Beq, the relationships are very different in regions where Beq is increasing and decreasing with longitude. Results (2) and (3) indicate that systematic forces not considered by the two models can become important. Damping by interhemispheric winds appears to be responsible for phase shifts in maximum rates of EPB occurrence from days when α=0°. Low EPB occurrence rates found at eastern Pacific longitudes suggest that radiation belt electrons in the drift loss cone reduce γRT by enhancing E-layer Pedersen conductances. Finally, we analyze an EPB event observed during a magnetic storm at a time and place where α≈-27°, to illustrate how electric-field penetration from high latitudes can overwhelm the damping effects of weak gradients in Pedersen conductance near dusk.

A latitudinal network of GPS receivers dedicated to studies of equatorial spread F

Five GPS receivers have been deployed near the 74°W longitude meridian to measure the variability of total electron content (TEC) latitudinal profiles and to study the relation of this variability with the onset and evolution of spread F plasma structures. These five GPS receivers, together with two others that form part of the International GPS Service (IGS) network, three more that belong to the South Andes Project network, and an additional receiver located at Ancon, Peru, provide TEC values between 8°N and 40°S geographic latitude. In addition, all five GPS receivers managed by Boston College give the amplitude scintillation on a near‐real time basis. This fact allows us to know the maximum latitude to which the irregularities extend and to infer the maximum altitude of the plasma bubbles. We have calculated TEC latitudinal profiles using the TEC values obtained by all the receivers between 1998 and 2001. We found that during the equinoxes, UHF scintillations occur when the ratio of the crest to the trough of the anomaly is 2 or larger. During the December solstice the crest is not very pronounced, but a sharp decrease of TEC at the magnetic equator precedes the onset of 1‐km scale irregularities. We have also examined a longitudinal variability of scintillations by partitioning the sky in two sectors separated at the 74°W meridian. We consistently observe a greater number of GPS scintillation events at the eastern longitudes over the Amazon rain forest. This intriguing finding could well be explained by a larger population of gravity waves at longitudes east of the Andes.