The efforts and accomplishments fall into three main categories: absolute thermometry based upon the velocity of sound in helium gas, secondary thermometry involving principally studies of the behavior of germanium resistors, and helium-4 vapor-pressure measurements ( see p. 144 ).

However, the surface temperature gradient can produce erroneous vapor-pressure measurements for the bulk liquid helium unless precautions are taken to isolate the tube ( which passes through the surface to the vapor pressure bulb ) from the liquid helium surface.

Carbon resistors and impurity-doped germanium resistors have been investigated for use as precision secondary thermometers in the liquid helium temperature region.

These include helium vapor pressure thermometers, helium gas thermometers, standard platinum resistance thermometers ( known as SPRTs, PRTs or Platium RTDs ) and monochromatic radiation thermometers.

Several germanium resistors have been thermally cycled from 300 to 4.2 Af and their resistances have been found to be reproducible within 1/3 millidegree when temperatures were derived from a vapor pressure thermometer whose tubing is jacketed through most of the liquid helium.

Surface temperature gradients have been found to exist in liquid helium baths contained in 15- and 25-liter metallic storage dewars.

The chemical elements are thought to have been produced by various cosmic processes, including hydrogen, helium ( and smaller amounts of lithium, beryllium and boron ) created during the Big Bang and cosmic-ray spallation.

Nearby galaxies that have evolved along similar lines have a corresponding enrichment of elements heavier than hydrogen and helium.

This is a logical dividing line, since the normal boiling points of the so-called permanent gases ( such as helium, hydrogen, neon, nitrogen, oxygen, and normal air ) lie below − 180 ° C while the Freon refrigerants, hydrogen sulfide, and other common refrigerants have boiling points above − 180 ° C.

* Halo stars are typically much older and have much lower metallicities ( that is to say, they are almost exclusively composed of hydrogen and helium ) than disk stars.

These were composed almost entirely of hydrogen and helium, and may have been massive.

Most helium in the universe is helium-4, and is believed to have been formed during the Big Bang.

He tried to solidify it by further reducing the temperature but failed because helium does not have a triple point temperature at which the solid, liquid, and gas phases are at equilibrium.

Such computational chemistry methods have been used to create a quantum mechanical picture of helium electron binding which is accurate to within < 2 % of the correct value, in a few computational steps.

All heavier elements ( including those necessary for rocky planets like the Earth, and for carbon-based or other life ) have thus been created since the Big Bang in stars which were hot enough to fuse helium itself.

Since then, four other novae explosions have been proposed as helium novae.

Apart from helium and probably neon, all gases that can be breathed have a narcotic effect.

The Big Bang hypothesis, by contrast, predicts that the CBR should have the same energy density as the binding energy density of the primordial helium, which is much greater than the binding energy density of the non-primordial elements ; so it gives almost the same result.

Red giants all have inert cores with hydrogen-burning shells: concentric layers atop the core that are still fusing hydrogen into helium.

Also, some helium white dwarfs appear to have been formed by mass loss in binary systems.

In another much-publicized case, issues have been raised about the underlying motives that led to the balloon boy hoax, in which six-year-old Falcon Heene was reportedly coerced by his father to stage for a frantic, live-on-TV chase for an out-of-control helium balloon, in which he was suspected to be.

Primordial nucleosynthesis is believed by many scientists to have taken place just a few moments after the Big Bang and is believed to be responsible for the formation of a heavier isotope of hydrogen known as deuterium ( H-2 or D ), the helium isotopes He-3 and He-4, and the lithium isotopes Li-6 and Li-7.

Free neutrons and protons are less stable than helium nuclei, and the protons and neutrons have a strong tendency to form helium-4.

Cosmic rays are enriched in lithium, beryllium, and boron with regard to the relative abundance of these elements in the universe compared to hydrogen and helium, and thus are thought to have a primary role in the synthesis of these three elements through the process of " cosmic ray nucleosynthesis ".

An acoustical interferometer has been constructed and used, with helium gas as the thermometric fluid, to measure temperatures near 4.2 and 2.1 Af.

A hydrostatic head correction has been neither necessary nor applicable in the determination of vapor pressures or temperatures for the bulk liquid helium.

It has also been observed, in helium 2, that large discrepancies can exist between surface vapor pressures and those pressures measured by a vapor pressure thermometer.

This has been attributed to helium film flow in the vapor pressure thermometer.

In supernova explosions, calcium is formed from the reaction of carbon with various numbers of alpha particles ( helium nuclei ), until the most common calcium isotope ( containing 10 helium nuclei ) has been synthesized.

This property has been experimentally verified by showing that the charge of one helium nucleus ( two protons and two neutrons bound together in a nucleus and moving around at high speeds ) is the same as two deuterium nuclei ( one proton and one neutron bound together, but moving much more slowly than they would if they were in a helium nucleus ).

A total of 5, 700 m < sup > 3 </ sup > ( 200, 000 cubic feet ) of 92 % helium was produced in the program even though less than a cubic meter of the gas had previously been obtained.

Helium-4 nuclear binding per nucleon is stronger than in any of these elements ( see nucleogenesis and binding energy ) and thus no energetic drive was available, once helium had been formed, to make elements 3, 4 and 5.

This helium is not only liquid, but has been cooled to the point of superfluidity.

In 1909, Hans Geiger and Ernest Marsden, under the direction of physicist Ernest Rutherford, bombarded a sheet of gold foil with alpha rays — by then known to be positively charged helium atoms — and discovered that a small percentage of these particles were deflected through much larger angles than was predicted using Thomson's proposal.

which defines the Abbe number with respect to the yellow Fraunhofer d ( or D < sub > 3 </ sub >) helium line at 587. 5618 nm wavelength.

Astronomers term " metals " those elements with higher atomic numbers than helium.

The first element produced was hydrogen, along with traces of helium and lithium.

A few minutes into the expansion, when the temperature was about a billion ( one thousand million ; 10 < sup > 9 </ sup >; SI prefix giga -) kelvin and the density was about that of air, neutrons combined with protons to form the Universe's deuterium and helium nuclei in a process called Big Bang nucleosynthesis.

Kamerlingh Onnes and Johannes van der Waals with the helium " liquefactor " in Leiden ( 1908 )

Beginning with carbon, elements are produced in stars by buildup from alpha particles ( helium nuclei ), resulting in an alternatingly-larger abundance of elements with even atomic numbers ( these are also more stable ).

In 1950, Glenn T. Seaborg, Albert Ghiorso, and Stanley G. Thompson bombarded < sup > 241 </ sup > Am with helium ions, which produced atoms with an atomic number of 97 and which closely resembled the neighboring lanthanide terbium.

Neutrons and other particles heavier than protons, as well as helium and other atoms with more than one proton, are so rare that their total mass in the visible universe is much less than the total mass of protons in hydrogen atoms.

In FIM, a sharp (< 50 nm tip radius ) metal tip is produced and placed in an ultra high vacuum chamber, which is backfilled with an imaging gas such as helium or neon.

In 1903, with Sir William Ramsay at University College London, Soddy verified that the decay of radium produced alpha particles composed of positively charged nuclei of helium.

A gas giant is a massive planet with a thick atmosphere of hydrogen and helium.

Jupiter and Saturn consist mostly of hydrogen and helium, with heavier elements making up between 3 and 13 percent of the mass.

The radiation sensing element is an inert gas-filled Geiger-Muller tube ( usually containing helium, neon or argon with halogens added ) which briefly conducts electrical charge when a particle or photon of radiation makes the gas conductive by ionisation.

This is due to the very high nuclear binding energy ( per nucleon ) of helium-4 with respect to the next three elements after helium.

As with any gas with differing density from air, inhaling a small volume of helium temporarily changes the timbre and quality of the human voice.

This radiogenic helium is trapped with natural gas in concentrations up to 7 % by volume, from which it is extracted commercially by a low-temperature separation process called fractional distillation.