At mid-latitudes, HF communications are disrupted by solar radio bursts, by X-rays from solar flares ( which enhance and disturb the ionospheric D-layer ) and by TEC enhancements and irregularities during major geomagnetic storms which are infrequent.

At the equator this delay between fixes was several hours ; at mid-latitudes the delay decreased to an hour or two.

At a given wind speed, e. g. 8 m / s, and so at a given rate of the turbulence production, a PBL in wintertime Arctic could be as shallow as 50 m, a nocturnal PBL in mid-latitudes could be typically 300 m in thickness, and a tropical PBL in the trade-wind zone could grow to its full theoretical depth of 2000 m.

At various times in the more than 100 years that have elapsed since the song was written, particularly during the John F. Kennedy administration, there have been efforts to give " America the Beautiful " legal status either as a national hymn, or as a national anthem equal to, or in place of, " The Star-Spangled Banner ", but so far this has not succeeded.

At the 2 November 2004 election Eni F. H. Faleomavaega of the Democratic Party ( United States ) defeated the Republican candidate and was re-elected.

At Montgomery, in the central region, the average annual temperature is 66 ° F ( 19 ° C ), with a winter average of 49 ° F ( 9 ° C ), and a summer average of 81 ° F ( 27 ° C ).

At extremely rare intervals the thermometer has fallen below zero (- 18 ° C ), as was the case in the remarkable cold wave of the 12th-13 February 1899, when an absolute minimum of-17 ° F (- 29 ° C ) was registered at Valley Head.

At both Choate and Harvard, Lerner was a classmate of John F. Kennedy ; at Choate they had worked together on the yearbook staff.

At Yale, Whorf joined the circle of Sapir's students that included such luminary linguists as Morris Swadesh, Mary Haas, Harry Hoijer, G. L. Trager and Charles F. Voegelin.

At the same time the influx of federal funding also gave rise to demands for accountability and the behavioral objectives approach of Robert F. Mager and others foreshadowed the No Child Left Behind Act passed in 2002.

At 20 ° C ( 68 ° F ) the speed of sound in air is 343 m / s ( 1129 ft / s ).

Therefore whenever ( G ) appears before another representative lowercase letter ( subject ), the statement would read, " It is always Going to be the case ..." and whenever ( F ) appears before another subject, the statement would read, " At sometime in the Future it will be the case ...." Whenever ( H ) appears before another subject, the statement would read, " It Has always been the case ..." and whenever ( P ) appears before another subject, the statement would read, " At sometime in the Past it has been the case ...."

The halogens or halogen elements are a series of nonmetal elements from group 17 of the periodic table ( formerly: VII, VIIA ), comprising fluorine ( F ), chlorine ( Cl ), bromine ( Br ), iodine ( I ), and astatine ( At ).

At night the F layer is the only layer of significant ionization present, while the ionization in the E and D layers is extremely low.

At the toilet, the second most important star of the show, Harry, is feeling ill and asks himself what is happening to his body when he hears a voice from the toilet asking him if he does not feel well: It is the paparazzi F. W.

At least in the case of the fusobacterium P. modestum it drives the counter-rotation of subunits a and c of the F < sub > 0 </ sub > motor of ATP synthase.

At the beginning of 1961, it fell to Richard Nixon to preside over this process, which officially announced the election of his 1960 opponent, John F. Kennedy.

* July 31 – At Idlewild Field in New York, New York International Airport ( later renamed John F. Kennedy International Airport ) is dedicated.

At Mio in northern Michigan, it soars to 113 ° F ( 45 ° C ).

At the low end, the part of Sarastro, premiered by Franz Xaver Gerl, includes a conspicuous F in a few locations.

At the final meeting, F. M. Campbell, the first FA treasurer and the Blackheath representative, withdrew his club from the FA over the removal of two draft rules at the previous meeting, the first which allowed for the running with the ball in hand and the second, obstructing such a run by hacking ( kicking an opponent in the shins ), tripping and holding.

At Addyston Pipe and Steel Company v. United States, 85 F. 2d 1, affirmed, 175 U. S. 175 U. S. 211 ;

At the beginning of Margaret Mitchell's novel Gone with the Wind, first published in 1936, the fictional character Rhett Butler warns a group of upper-class secessionists of the folly of war with the North in terms very reminiscent of those Sherman directed to David F. Boyd before leaving Louisiana.

At night, temperatures are generally 30 to 40 ° F ( 17 to 22 ° C ) lower than the daytime highs, and high winds are common day or night.

At present, techniques to establish the realization of an ampere have a relative uncertainty of approximately a few parts in 10 < sup > 7 </ sup >, and involve realizations of the watt, the ohm and the volt.

Evidence for ( or against ) the existence of diatomic astatine ( At < sub > 2 </ sub >) is sparse and inconclusive.

Some sources state that At < sub > 2 </ sub > does not exist, or at least has never been observed, while other sources assert or imply its existence.

At ambient conditions, berkelium assumes its most stable α form which has a hexagonal symmetry, space group P6 < sub > 3 </ sub >/ mmc, lattice parameters of 341 pm and 1107 pm.

At about 10 < sup >− 6 </ sup > seconds, quarks and gluons combined to form baryons such as protons and neutrons.

At standard temperature and pressure, two chlorine atoms form the diatomic molecule Cl < sub > 2 </ sub >.

At least three isotopes – < sup > 110 </ sup > Cd, < sup > 111 </ sup > Cd, and < sup > 112 </ sup > Cd – are stable.

At the present time, approximately one third < ref > of human generated emissions are estimated to be entering the ocean.

At room temperature, the average speed of these random motions is 10 < sup > 6 </ sup > metres per second.

At each position s, unit vector u < sub > n </ sub > points along the outward normal to the curve and unit vector u < sub > t </ sub > is tangential to the path.

At the time of launch, the DSN had a small number of K < sub > a </ sub > receivers installed on an experimental basis ; K < sub > a </ sub > operations and missions are increasing.

At one particular angle for a given n < sub > 1 </ sub > and n < sub > 2 </ sub >, the value of R < sub > p </ sub > goes to zero and a p-polarised incident ray is purely refracted.

At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, highly combustible diatomic gas with the molecular formula H < sub > 2 </ sub >.

At the beginning of One-Dimensional Man Marcuse writes, “ The people recognize themselves in their commodities ; they find their soul in their automobile, hi-fi set, split-level home, kitchen equipment ,”< ref > Harold Marcuse < http :// www. marcuse. org / herbert / quotes / QuotRedThread. html # Capitalism ></ ref > meaning that under capitalism ( in consumer society ) humans become extensions of the commodities that they buy, thus making commodities extensions of people's minds and bodies.

At this time the work of Cavalieri with his method of indivisibles, and work by Fermat, began to lay the foundations of modern calculus, with Cavalieri computing the integrals of x < sup > n </ sup > up to degree in Cavalieri's quadrature formula.

At Earth's orbit its typical density is 6 ions / cm < SUP > 3 </ SUP > ( variable, as is the velocity ), and it contains a variable interplanetary magnetic field ( IMF ) of ( typically ) 2 – 5 nT.

At the confluence, the Ohio is even bigger than the Mississippi ( Ohio at Cairo: 281, 500 cu ft / s ( 7, 960 m < sup > 3 </ sup >/ s ); Mississippi at Thebes: 208, 200 cu ft / s ( 5, 897 m < sup > 3 </ sup >/ s )) and, thus, is hydrologically the main stream of the whole river system, including the Allegheny River further upstream.