爱上海,上海龙凤419,上海419论坛 – Powered by Coral Miller!

Archives for: May 9, 2021

Giant Epiphyses in a Ross Seal

Posted on by

first_imgTHE Ross Seal (Ommatophoca rossi) is a relatively little-known animal and it was not until recently, when the British Museum (Natural History) received two frozen specimens from the British Antarctic Survey, that any detailed investigation of it could be attempted. Several curious characters have been noted in the first of these seals to be dissected, including a peculiarity of the flippers.last_img

Tagged: , , , , , , , , , , , , , , .

The BEAN experiment – An EISCAT study of ion temperature anisotropies

Posted on by

first_imgResults are presented from a novel EISCAT special programme, SP-UK-BEAN, intended for the direct measurement of the ion temperature anisotropy during ion frictional heating events in the high-latitude F-region. The experiment employs a geometry which provides three simultaneous estimates of the ion temperature in a single F-region observing volume at a range of aspect angles from 0° to 36°. In contrast to most previous EISCAT experiments to study ion temperature anisotropies, field-aligned observations are made using the Sodankylä radar, while the Kiruna radar measures at an aspect angle of the order of 30°. Anisotropic effects can thus be studied within a small common volume whose size and altitude range is limited by the radar beamwidth, rather than in volumes which overlap but cover different altitudes. The derivation of line-of-sight ion temperature is made more complex by the presence of an unknown percentage of atomic and molecular ions at the observing altitude and the possibility of non-Maxwellian distortion of the ion thermal velocity distribution. The first problem has been partly accounted for by insisting that a constant value of electron temperature be maintained. This enables an estimate of the ion composition to be made, and facilitates the derivation of more realistic line-of-sight ion temperatures and temperature anisotropies. The latter problem has been addressed by assuming that the thermal velocity distribution remains bi-Maxwellian. The limitations of these approaches are discussed. The ion temperature anisotropies and temperature partition coefficients during two ion heating events give values intermediate between those expected for atomic and for molecular species. This result is consistent with an analysis which indicates that significant proportions of molecular ions (up to 50%) were present at the times of greatest heating.last_img read more

Tagged: , , , , , , , , , , , , , , .

Some comments on transient and steady-state reconnection at the dayside magnetopause

Posted on by

first_imgReconnection at the dayside magnetopause is the principal method by which energy is transferred from the solar wind into the magnetosphere-ionosphere system. There is still considerable uncertainty as to whether reconnection is transient or quasi-steady. Here we discuss some of the implications of assuming that reconnection occurring in regions where the magnetosheath flow is super-Alfvénic must be transient. We use a simple magnetospheric model to illustrate where on the magnetopause transient reconnection is most likely to occur, and show that the location of these regions is dependent critically upon the dipole tilt angle and the interplanetary magnetic field orientation. Although our idealised examples do not take into account temporal variations of the solar wind conditions, or the influence of the bow shock or magnetosheath, we believe that they demonstrate interesting features. For example, the results suggest that reconnection for northward IMF is almost always likely to be transient.last_img read more

Tagged: , , , , , , , , , , , , , , .

Minimal change in Antarctic Circumpolar Current flow speed between the last glacial and Holocene

Posted on by

first_imgThe Antarctic Circumpolar Current is key to the mixing and ventilation of the world’s oceans. This current flows from west to east between about 45° and 70°S connecting the Atlantic, Pacific and Indian oceans, and is driven by westerly winds and buoyancy forcing. High levels of productivity in the current regulate atmospheric CO2 concentrations. Reconstructions of the current during the last glacial period suggest that flow speeds were faster or similar to present, and it is uncertain whether the strength and position of the westerly winds changed. Here we reconstruct Antarctic Circumpolar Current bottom speeds through the constricting Drake Passage and Scotia Sea during the Last Glacial Maximum and Holocene based on the mean grain size of sortable silt from a suite of sediment cores. We find essentially no change in bottom flow speeds through the region, and, given that the momentum imparted by winds, and modulated by sea-ice cover, is balanced by the interaction of these flows with the seabed, this argues against substantial changes in wind stress. However, glacial flow speeds in the sea-ice zone south of 56°S were significantly slower than present, whereas flow in the north was faster, but not significantly so. We suggest that slower flow over the rough topography south of 56°S may have reduced diapycnal mixing in this region during the last glacial period, possibly reducing the diapycnal contribution to the Southern Ocean overturning circulation.last_img read more

Tagged: , , , , , , , , , , , , , , .

Factors controlling the last interglacial climate as simulated by LOVECLIM1.3

Posted on by

first_imgThe last interglacial (LIG), also identified to the Eemian in Europe, began at approximately 130 kyr BP and ended at about 115 kyr BP (before present). More and more proxy-based reconstructions of the LIG climate are becoming more available even though they remain sparse. The major climate forcings during the LIG are rather well known and therefore models can be tested against paleoclimatic data sets and then used to better understand the climate of the LIG. However, models are displaying a large range of responses, being sometimes contradictory between them or with the reconstructed data. Here we would like to investigate causes of these differences. We focus on a single climate model, LOVECLIM, and we perform transient simulations over the LIG, starting at 135 kyr BP and run until 115 kyr BP. With these simulations, we test the role of the surface boundary conditions (the time-evolution of the Northern Hemisphere (NH) ice sheets) on the simulated LIG climate and the importance of the parameter sets (internal to the model, such as the albedos of the ocean and sea ice), which affect the sensitivity of the model. The magnitude of the simulated climate variations through the LIG remains too low compared to reconstructions for climate variables such as surface air temperature. Moreover, in the North Atlantic, the large increase in summer sea surface temperature towards the peak of the interglacial occurs too early (at ∼128 kyr BP) compared to the reconstructions. This feature as well as the climate simulated during the optimum of the LIG, between 131 and 121 kyr BP, does not depend on changes in surface boundary conditions and parameter sets. The additional freshwater flux (FWF) from the melting NH ice sheets is responsible for a temporary abrupt weakening of the North Atlantic meridional overturning circulation, which causes a strong global cooling in annual mean. However, the changes in the configuration (extent and albedo) of the NH ice sheets during the LIG only slightly impact the simulated climate. Together, configuration of and FWF from the NH ice sheets greatly increase the magnitude of the temperature variations over continents as well as over the ocean at the beginning of the simulation and reduce the difference between the simulated climate and the reconstructions. Lastly, we show that the contribution from the parameter sets to the climate response is actually very modest.last_img read more

Tagged: , , , , , , , , , , , , , , .

The characteristics of the lower stratospheric gravity wave field above Halley (75°S, 26°W), Antarctica, from radiosonde observations

Posted on by

first_imgDaily radiosonde observations between 2003 and 2013 from Halley research station, Antarctica (75°S, 26°W) are used to determine climatologies of gravity wave properties in the lower stratosphere (between 15 km and 22 km altitude). Individual waves are extracted from the radiosonde profile using wavelet analysis and separated into upward and downward propagating waves. An increase in the percentage of downward propagating waves (~30% of the waves) is seen during the winter months. For the upward and downward propagating waves their horizontal and vertical wavelength, intrinsic frequency, energy density, pseudo-momentum flux and direction of propagation are determined. The upward propagating wave field is found to be dominated by waves with short vertical wavelength (~1 km) and low intrinsic frequency (ω~f). The downward propagating wave field is composed of a wider distribution of vertical wavelength waves and has a larger proportion of higher frequency waves present. The upward propagating waves show an increase in total energy density in autumn and spring, the larger increase occurs during spring (up to 1.7 J kg-1 in September). The downward propagating waves increase in total energy density occurs during wintertime (up to 0.7 J kg-1 in June). During winter the contributions of the upward and downward propagating waves to the total energy density and pseudo-momentum flux are almost equal. This paper details the first study of individual gravity wave properties combined into upward and downward propagating wave climatologies in the lower stratosphere above Halley.last_img read more

Tagged: , , , , , , , , , , , , , , .

BYU Men’s Golf Tied For 19th After Day 1 of NCAA Championships

Posted on by

first_img Brad James Written by Tags: BYU Men’s Golf/NCAA Championships/Northwestern/Patrick Fishburn/Ryan Lumsden May 25, 2018 /Sports News – Local BYU Men’s Golf Tied For 19th After Day 1 of NCAA Championships FacebookTwitterLinkedInEmailSTILLWATER, Okla.-Friday, as the NCAA Men’s golf championships commenced at Karsten Creek, hosted by Oklahoma State University, the Brigham Young men’s golf squad has a considerable distance to make up.The Cougars are tied for 19th with Kansas and North Florida thus far as the Cougars have a collective +5 thus far.Patrick Fishburn is the Cougars’ individual leader thus far with a -1 (8).The current leaders overall thus far in the championships are the Northwestern Wildcats who are at 280 as the Wildcats’ leader is Ryan Lumsden who shot a 67. The championship tournament resumes Saturday morning at 7:00 am MDT.last_img read more

Tagged: , , , , , , , , , , , , , , .

UVU Men’s Basketball Hosts Sam Houston State Saturday

Posted on by

first_img Brad James Tags: Cameron Delaney/Conner Toolson/Jake Toolson/Sam Houston State/Southland Conference/UVU Men’s Basketball FacebookTwitterLinkedInEmailOREM, Utah-Saturday, Utah Valley men’s basketball, currently tied for the 4th longest home-winning streak in the country with 19 games, hosts Sam Houston State Saturday.The 9-4 Wolverines will be meeting the Bearkats, who represent the Southland Conference, for only the second time in history.Utah Valley bested Sam Houston State 75-64 at Huntsville, Texas December 22, 2017.The Wolverines have won eight of their last nine games and rank 19th nationally with 490 total rebounds.Utah Valley is also 33rd in the nation in both defensive rebounds per game (28.92) and total assists (192).The Wolverines rank 37th nationally in made 3-point field goals (109) and are 50th in field goal percentage, at 48.2 percent.Jake Toolson remains the Wolverines’ leading scorer, averaging 15.7 points per game and is shooting 56.2 percent from the field. Conner Toolson is close behind, posting 14.3 points per contest. Conner Toolson is also shooting 48.1 percent behind the arc on the season.The Wolverines score 77.9 points per game and only give up 72.3 points per contest.The Bearkats come into Orem at 4-7 but have played lots of close games as they give up 70 points per game and score 69.9 points per contest.Sam Houston State is led by redshirt senior guard Cameron Delaney who posts 11.5 points and 4.3 rebounds per game. Written by December 21, 2018 /Sports News – Local UVU Men’s Basketball Hosts Sam Houston State Saturdaylast_img read more

Tagged: , , , , , , , , , , , , , , .

Utah Men’s Basketball Returns Home To Host Washington and Washington State

Posted on by

first_img FacebookTwitterLinkedInEmailSALT LAKE CITY-Thursday, Utah men’s basketball returns to the Huntsman Center to host Washington after splitting on an Arizona road trip last week to commence Pac-12 conference play. This will be followed by a Saturday home game against Washington State. Washington State is led by senior forward Robert Franks as he amasses 22.1 points and 7.9 rebounds per game. Sophomore guard Jaylen Nowell is the Huskies’ leading scorer, posting 17.3 points per game and 4.8 rebounds per contest. The Utes are 66-62 all-time in Pac-12 play in program history and are 9-3 against Washington in Pac-12 games and 10-2 against Washington State in league competition. The Utes are 11-7 in Pac-12 play the past two seasons. The Cougars are also bolstered by freshman forward CJ Elleby who nets 16.4 points and 7.7 rebounds per game. The Cougars score 81.1 points per game and surrenders 76.7 points per contest. Sophomore forward Donnie Tillman posts 11.6 points and 6.1 rebounds per game for the Utes in a complementary role. The Utes come into Thursday’s game at 7-7 and 1-1 in conference play, having downed Arizona State 96-86 and falling 84-81 to Arizona in overtime at Tucson, Ariz. Washington scores 72.1 points per game and surrenders 66.5 points per contest. January 8, 2019 /Sports News – Local Utah Men’s Basketball Returns Home To Host Washington and Washington State Senior forward Noah Dickerson nets 14.5 points and 6.6 rebounds per game as well to bolster the Huskies. Tags: Arizona/Arizona State/CJ Elleby/Donnie Tillman/Huntsman Center/Jaylen Nowell/Noah Dickerson/Robert Franks/Sedrick Barefield/Utah Men’s Basketball/Washington Huskies/Washington State Cougars Entering Thursday’s game against the Huskies, the Utes are scoring 75.6 points per game and surrendering 74.6 points per contest. Saturday, Utah faces a 7-7 Washington State squad that is 0-1 in Pac-12 play. The Huskies come into this game at 10-4 and 1-0 in conference play, having routed Washington State 85-67 January 5. Brad James Written by Senior guard Sedrick Barefield remains the Utes’ leading scorer as he nets 16.4 points per game.last_img read more

Tagged: , , , , , , , , , , , , , , .

Real Salt Lake, Chicago Fire play to 1-1 tie

Posted on by

first_img Tags: Chicago Fire/MLS/Real Salt Lake FacebookTwitterLinkedInEmailBRIDGEVIEW, Ill. (AP) — Albert Rusnak scored on a penalty kick in the 33rd minute to help Real Salt Lake tie the Chicago Fire 1-1 on Saturday night.The free kick was set up when Mohammed Adams was called for a hand ball in the penalty area. Rusnak has six goals this season.Chicago struck early when Aleksandar Katai scored in the fifth minute on a free kick. Katai came up empty at the 82nd when he fired a solid shot from the right that was just wide.Chicago (4-6-7) extended its home unbeaten streak to seven. Real Salt Lake (6-8-2) has been outscored 8-1 in its last three games. June 22, 2019 /Sports News – Local Real Salt Lake, Chicago Fire play to 1-1 tie Written by Associated Presslast_img read more

Tagged: , , , , , , , , , , , , , , .