Degrees North Latitude Research Articles

The Shuttle Radar Topography Mission (SRTM): a breakthrough in remote sensing of topography

The Shuttle Radar Topography Mission (SRTM), flown on the Space Shuttle Endeavour on Flight STS-99 and launched on 11 February 2000, will produce digital elevation data of the Earth's land mass between 60 degrees north latitude and 54 degrees south latitude. This data will be at least one order of magnitude more precise in the elevation resolution, and will have postings of 30 m, representing an order of magnitude increase in the density of the postings over currently available data.

War and record keeping practices in Eritrea

Eritrea is a tropical country which stretches from 12 to 18 degrees north latitude and 36 to 43 degrees east longitude. It is located in North East Africa - sometimes called the Horn of Africa - west of the Red Sea. Eritrea, with an area of 124,320 square kilometres, has about 1000 kilometres of coastline and over 350 islands in the Red Sea. Its neighbours are Sudan in the west and north-west, Ethiopia in the south and Djibouti in the east. Yemen and Saudi Arabia, across the Red Sea in the east, are also its neighbours.The population of Eritrea is about 4 million. There are nine nationalities, Afar, Baza, Bilen, Hidareb, Kunama, Rashaida, Saho, Tigre, and Tigrigna, each with its own language. According to their racial origin the people are divided into three main groups; Nilotic, Hemetic and Semitic.

Tectonic evolution of early precambrian south indian shield (rocks) using remotely sensed data

The interpretation of satellite imagery of part of South India falling South of 15 degree North latitude shows that the regional anticlines, synclines, domes and basins of the Precambrian group of metamorphites are aligned in three major hill ranges/domains such as Chitra-durga domain in the north, the Mangalore-Ootacamund-Bangalore domain in the centre and the Cochin-Cape Comorin-Madurai-Chittoor domain in the south. These hills are crescent shaped with their axes of elongation oriented in NNW-SSE direction. The lineaments with ENE-WSW, NE-SW/WNW-ESE and NNW-SSE azimuthal frequencies respectively exhibit extensional, shear and release geometries. Such deformational fabric shows that the tectonic evolution of South India was controlled by two major compressive forces, the first one aligned in N-S direction and the second in ENE-WSW direction.

Estimates of gene flow among Anopheles maculatus populations in Thailand using microsatellite analysis.

We report an analysis of seven microsatellite loci in eight populations of Anopheles maculatus mosquitoes dispersed over a distance of approximately 1,100 km in Thailand. A wide spectrum of genetic variability, with mean heterozygosities ranging from 0.738 to 0.847 were found. Based on microsatellite analysis, geographic populations of An. maculatus can be grouped into two clusters; one includes upper and lower northern populations that extend from approximately 11 degrees to 16 degrees north latitude, and the other (southern populations) extends south from about 7 degrees to 6 degrees north latitude. Wright's F(ST) and Slatkins's R(ST) for all seven microsatellite loci indicated low estimates of differentiation among all populations (mean values of F(ST) and R(ST) = 0.0406 and 0.051, respectively, corresponding to the Nm values of 5.91 and 4.65, respectively), and suggested that gene flow occurs among populations. However, there is some restriction of gene flow between the northern and southern populations. Geographic barriers could be limiting factors for greater gene flow between populations.

SIMULATING THE EFFECT OF CONDENSATION TYPE ON GREENHOUSE SHORTWAVE RADIATION TRANSMISSION AND UTILIZATION

To investigate the effect of condensation type (filmwise or dropwise) on the shortwave radiation transmission and utilization in greenhouses, the Gembloux Dynamic Greenhouse Climate Model (G.D.G.C.M.) was modified by introducing two series of solar radiation transmittance values: one that is used when the cover is dry, the other when the cover is wetted by condensation. Simulations were carried out for the whole Belgian typical reference year, assuming that a tomato crop was grown from 1 December to 30 November in an infinitely large polyethylene covered greenhouse at 51 degrees North latitude. The solar radiation transmission was simulated for some idealized cases: condensation which does not affect the transmittance (reference state), filmwise condensation, and condensation as cap shaped drops with contact angles of 30, 60, and 90 degrees. The assumption of complete covering of the wet part of the roof by condensation implies that the simulation results should be considered limit values between which the real results are situated. The simulations pointed out that the solar radiation flux density inside the greenhouse with film condensation was 1% (summer) to 3% (winter) higher than for the reference state. For condensation as hemispherical drops, however, a decrease of 10% (summer) to 20% (winter) with respect to the reference state was found. The lower incoming shortwave radiation flux density in the greenhouse covered with hemispherical drops resulted in a decrease of the yearly vegetation transpiration flux density of about 9%, while the greenhouse heating requirements increased by about 3%. For the greenhouse covered with a condensation film, it was found that the slightly higher amount of solar radiation entering the greenhouse had hardly any influence on the yearly heating requirements and on the vegetation temperature and transpiration.

Relating Degree–Day Accmuulations to Calendar Dates: Alfalfa Weevil (Coleoptera: Curculionidae) Egg Hatch in the North Central United States

We present a technique for determining dates of alfalfa weevil, Hypera postica (Gyllenhal), egg eclosion by correlating degree-day accumulations with calendar dates. This technique uses historical climate data from various locations to calculate the median date a degree-day accumulation has been reached. ClimProb 3.1, a computer software program and weather database, was used to assess these correlations. We used 165 locations in 12 midwestern states for the analysis. Sixty years (1931-1990) of continuous daily climate data (maximum temperature, minimum temperature, and liquid precipitation) were used for each location. We began degree-day accumulations on 1 January of each year and used a minimum developmental threshold of 8.9°C (48°F). Degree-day accumulations were determined using a sine-wave method. The relationship between the date when the accumulated degree-days reached a threshold and the location (expressed as degrees north latitude) was quadratic from 36° N to 48° N. The technique gives approximate dates when egg hatch is likely to occur throughout the north central United States, and these dates can be used to augment existing decision criteria for initiating sampling programs for alfalfa weevil. This technique can be used for other pest management programs that depend on estimating pest development.

Clinal variation at aspartate aminotransferase‐2 in spotted seatrout, Cynoscion nebulosus (Cuvier), inhabiting the north‐western Gulf of Mexico

SummaryClinal variation was observed at the aspartate aminotransferase‐2 (AAT‐2) locus in the marine fish Cynoscion nebulosus (Cuvier) inhabiting the bays and estuaries of the Texas and northern Mexico Gulf coasts. Frequency of the AAT‐2(80) allele increased from 0.9% at Sabine Lake, Texas to 17.1% at Rio Soto La Marina, Mexico. A statistically significant correlation existed in the frequency of this allele with degrees north latitude and west longitude. This information, if properly incorporated into a comprehensive enhancement programme, could facilitate supplemental stocking success.

Well-Log Seismic Sequence Stratigraphy of Aruba and its Application to the Hydrocarbon Exploration in the Caribbean Area

Several wells have recently been drilled in offshore Aruba approximately 12 degrees NOrth Latitude and 70 degrees West Longitude, just north of the Westernpart of Venezuela, South Central Caribbean. One of the wells, the Oxy Chuchubi No. 1 well penetrated a largely carbonate section that ranged in age from early Pliocene to early Oligocene to late Eocene at its total depth of 9,210 feet. High resolution biostratigraphy of benthic and planktonic foraminifers and calcareous nannofossils provided the abundance and diversity histograms necessary to recognized a series of maximum flooding surface condensed sections (MSF). Fourteen maximum flooding surfaces within the MFS condensed sections were identified on the well log and dated using the planktonic foraminifers and calcareous nannofossils. These maximum flooding surfaces range in age from 4.0 Ma or possibly 36.5 Ma. The paleobathymetry varies from middle to outer neritic in the upper portion of the well to lower bathyal to abyssal in the lower portion of the well. Fourteen third order sequences and their systems tracts were identified and annotated on a well log. These sequences were correlated with the Global Cycle Chart of Hag, 1987. The sequence stratigraphy provides a means of chronostratigraphic correlation to Venezuela and provides amore » direct tie to the geological history and hydrocarbon potential of the area.« less

Population Structure of Spotted Seatrout Inhabiting the Texas Gulf Coast: An Allozymic Perspective

Abstract Spotted seatrout Cynoscion nebulosus (N = 674) from 12 geographic populations along the Texas and northern Mexico Gulf coasts were surveyed to determine population structure as indicated by the distribution of electrophoretically detectable allelic variants. The percentage of polymorphic loci among 44 putative gene loci averaged 15.5% and ranged from 13.6 to 15.9%. The percentage of heterozygous loci per individual (H) for all loci averaged 1.6% and ranged from 1.2% in East Matagorda Bay to 2.3% in Rio Soto La Marina. A cline existed in the frequency of the sAAT-2*80 allele (for aspartate aminotransferase) (0.9–17.1%) and in average individual heterozygosity with respect to degrees north latitude and west longitude, Heterogeneity tests indicated allele counts at the sAAT-2 * locus were distributed heterogeneously among the 12 localities. Subpopulation differentiation was low (F ST = 0.012), and quantitative (Nem) and qualitative estimators suggested high gene flow throughout this study area. The ...

Growth and survival of spontaneous provenance hybrids of Pinus sylvestris

Survival and growth were assessed for 17 provenance hybrids and three natural populations of Pinus sylvestris (L.) planted in three field trials in central and northern Sweden. Restricted to the high mortality site the 18‐year hybrid survival percentage increased by three units per degree north latitude and one percent per 100 m higher altitude of the mother. The hybrid height was less influenced by the geographical origin than hybrid survival. For both traits the natural populations were better than or equal to hybrids with the same geographical mean origin. The variance component of the mother was mostly 2–3 times larger than the provenance component. The effect of the grandmother was nonsignificant for both traits.

Growth of Greenland Ice Sheet: Measurement

Measurements of ice-sheet elevation change by satellite altimetry show that the Greenland surface elevation south of 72 degrees north latitude is increasing. The vertical velocity of the surface is 0.20 +/- 0.06 meters per year from measured changes in surface elevations at 5906 intersections between Geosat paths in 1985 and Seasat in 1978, and 0.28 +/- 0.02 meters per year from 256,694 intersections of Geosat paths during a 548-day period of 1985 to 1986.

Infrared Speckle Observations of Io: An Eruption in the Loki Region

Speckle observations of Jupiter's satellite Io at a wavelength of 5 micrometers during July 1984 resolved the disk and showed emission from a hot spot in the Loki region. The hot spot contributed a flux approximately equal to 60 percent of that from the disk. Images reconstructed by means of the Knox-Thompson algorithm showed the spot moving across the disk as the satellite rotated. It was located at 301 degrees +/- 6 degrees west longitude, 10 degrees +/- 6 degrees north latitude, and had a radiance of (2.96 +/- 0.54) x 10(22) ergs sec(-1) cm(-1) sr(-1)/A where A is the area of the spot. For an assumed temperature of 400 K, the area of the source would be 11,400 square kilometers. An active "lava lake" similar to that seen by Voyager may be the source of the infrared emission.

An inexpensive microprocessor‐based lighting control for simulating natural photoenvironments in the laboratory

Abstract A lighting control system interfaced with the inexpensive VIC‐20 microcomputer is described which can automatically vary light intensity and photoperiod in the laboratory to simulate natural intensity curves throughout the day, and daylengths throughout the changing seasons. Adjustments to compensate for differing latitudes and habitat types are easily accomplished through modifications of the controlling software. The system enables the study of effects of crepuscular lighting and circannual periodicities of physiology and behavior which were previously infeasible. Circuit diagrams, details of construction for simultaneous control of three sets of lights, and a menu‐driven BASIC program for accurately simulating the annual light cycle for any point between the equator and 60 degrees north latitude are presented. The importance of photoenvironment in laboratory studies of physiology and behavior is discussed.

Ocean Margin Drilling Project Data Synthesis off Eastern North America: 28 to 36 Degrees North Latitude: ABSTRACT

An atlas of geological and geophysical maps has been compiled for the east coast of the North American continent covering an area from well onshore to the ocean crust, and from 28 to 36°N as part of the Ocean Margin Drilling Project. Included in the atlas are maps of the depth to continental and oceanic basement, depth to the top of Lower and Middle Jurassic (reflectors JM/J2 and JS/J2), to the top of Jurassic (reflectors J/J1), to the top of Neocomian (reflector Beta), to the top of Cretaceous (reflector A*), to the top of Paleogene (reflector Au), and to the top of lower Miocene (reflector X). Isopach maps between these reflectors and between them and the seafloor are also included. Contours are two-way travel time with a contour interval of 0.25 to 1 sec. The atlas also contains a tectonic map of basement, a pre-Quaternary geologic map, and lithofacies maps for six time slices. There are geophysical maps of magnetic and gravity anomalies and compressional wave velocities in sediments and basement. End_of_Article - Last_Page 481------------

Photometric Observations of Jupiter at 2400 Angstroms

The photopolarimeter instrument on Voyager 2 was used to obtain a map of Jupiter at an effective wavelength of 2400 angstroms. Analysis of a typical north-south swath used to make this map shows strong absorption at high latitudes by a molecular or particulate constituent in the Jovian atmosphere. At 65 degrees north latitude, the absorbing constituent extends to altitudes above the 50-millibar pressure level.

Thermal Contrast in the Atmosphere of Venus: Initial Appraisal from Pioneer Venus Probe Data

The altitude profiles of temperature and pressure measured during the descent of the four Pioneer Venus probes show small contrast below the clouds but significant differences within the clouds at altitudes from 45 to 61 kilometers. At 60 kilometers, the probe which entered at 59.3 degrees north latitude sensed temperatures 25 K below those of the lower latitude probes, and a sizable difference persisted down to and slightly below the cloud base. It also sensed pressure below those of the other probes by as much as 49 millibars at a mean pressure of 200 millibars. The measured pressure differences are consistent with cyclostrophic balance of zonal winds ranging from 130 +/- 20 meters per second at 60 kilometers to 60 +/- 17 meters per second at 40 kilometers, with evidence in addition of a nonaxisymmetric component of the winds. The clouds were found to be 10 to 20 K warmer than the extended profiles of the lower atmosphere, and the middle cloud is convectively unstable. Both phenomena are attributed to the absorption of thermal radiation from below. Above the clouds, in the lower stratosphere, the lapse rate decreases abruptly to 3.5 K per kilometer, and a superimposed wave is evident. At 100 kilometers, the temperature is minimum, with a mean value of about 170 K.

Expanding The Boundaries of Geography

Hamilton is a picture-postcard village at the orthern end f the Chenango Valley in upstate New York. In an atlas you will find it at about 75 degrees west longitude and close to 43 degrees north latitude. It is 1,126 feet above sea level and its annual precipitation averages 34 inches. It has cold winters and warm to cool summers. Its prevailing winds are from the west and northwest. Its growing season is five to five and a half months. Its 1975 census showed 2,500 villagers and 2,516 Colgate University students. It is 182 years old. Eugene L. Ziegler, age 37, lives in Hamilton and seems to know just about everybody there. Driving around the village in his battered station wagon, he is forever taking one hand off the wheel to wave to a friend or acquaintance. But although Ziegler is a Colgate geographer (PhD, Penn State), he might flunk a geography quiz based on the data cited above. He has basic concepts in his head. He will tell you, for example, that Hamilton is located in a watershed divide, and that if three glasses of water were spilled at three different points in and

Geography in multiple sclerosis.

Both mortality and morbidity data indicate quite clearly that multiple sclerosis is a geographically-related disease, and thus MS can be thought of as an acquired environmental (exogenous) illness. High frequency parts of the world for MS are Europe between 65 degrees and 45 degrees north latitude, northern United States and southern Canada, New Zealand, and southern Australia. These regions are bounded by medium frequency MS regions: in Europe to the north, east, and south; in America for southern U.S.; and the remainder of Australia. Latin America, Asia and Africa are essentially of low frequency from present data. Latitude is not a sufficient criterion: at 40 degrees north latitude, MS is high in America, medium in Europe, and low in Asia. All high and medium risk areas therefore are in Europe or European colonies; thus MS is the white man's burden spread from western Europe. Within the U.S., MS is less common among Negroes, Japanese, and possibly Amerindians than in whites regardless of geography. Migration studies among risk areas indicate that migrants keep much of the risk of their birthplace, but also that overall the risk is decreased by high-to-low migration, and probably increased by low-to-high. For the former, it seems that adolescence is the age critical for retention of birthplace risk. Some preliminary data on a possible epidemic of MS are also presented. All the epidemiologic information would be most easily explained if MS were an infectious (viral) illness with prolonged latency. The proof of this though must come from the laboratory.

Environmental Determinants of Island Species Number in the British Isles: A Reconsideration

It is well known statistically that outlying values of independent variables contribute disproportionately to the fitting of a regression line. A previous examination of the environmental determinants of numbers of plant species in the British Isles includes one such outlier, Britain itself. Analyses identical to those previously performed are reported here, excluding Britain. Without the outlier, the prior conclusion that environmental heterogeneity contributes to floristic richness is unsupported. Introduction and methods Johnson & Simberloff (1974) used the technique of mixed multiple regression analysis to examine the relative importance of certain environmental variables in the determination of numbers of species of plants (S) present on the British Isles. This technique, first introduced for the analysis of species richness patterns on islands by Hamilton et al. (1963), employs variables in both transformed and untransformed modes. Johnson & Simberloff's (1974) results singled out number of soil types (ST) as the best predictor of S. Area (A), degrees North latitude (L), and distance from Britain (Di) entered their multiple regressions after ST was included in the model (Johnson & Simberloff, 1974, Tables 3 and 4). Although S, ST, and A were all highly intercorrelated, the authors inferred from their regressions that ST was the more proximal cause of the observed distribution of species on the islands since it was a better predictor of S than was A. Johnson & Simberloff (1974) considered ST to be a measure of environmental heterogeneity, and interpreted its higher simple correlation with S as demonstrating the importance of environmental heterogeneity in the determination of S. We note that one of the islands they considered, Britain, is greater in area than Lewis, the next largest, by more than two orders of magnitude (Johnson & Simberloff, 1974, Table 1), and is more than four standard deviations from the mean of the distribution of island areas (log X= 179; s.d.=088; N= 41) calculated with Britain removed. Britain is thus an outlying value of the independent variable A, and is disproportionately weighted in regression analyses. It is not clear whether Britain, the outlier, is a sample from the same population as the other islands, a necessary assumption in linear regression analysis. To determine this, we proceeded as recommended by Kruskal (1960), to reanalyse the data with Britain removed. If Britain is indeed drawn from the same population as the other islands, its removal should not significantly alter Johnson & Simberloff's (1974) findings. Conversely, if their results are markedly changed by the removal of Britain, then conclusions based upon these data are

Viking: Mars Atmospheric Water Vapor Mapping Experiment—Preliminary Report of Results

Observations made from the Viking I orbiter show very little water vapor in the Mars atmosphere in the southern hemisphere (0 to 3 precipitable micrometers) with a gradual increase across the equator to northern latitudes. Maximum amounts between 20 and 30 micrometers have been observed in the short period covered by the observations to date. The season, northern midsummer, corresponds to the beginning of the water vapor cycle in that hemisphere. A strong repetitive diurnal cycling between the solid and vapor phases is observed at a site to the east of the Tharsis Ridge at 10 degrees north latitude; the vapor lies close to the martian surface and is most probably in saturation equilibrium with a surface haze or fog throughout much of the day.