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The Case for an Accelerating Universe from
The Case for an Accelerating Universe from

... features. Although formal statistics are not currently available, we are aware that the SCP candidates have yielded a greater fraction of SNe Ia than the HZT candidates, a signiÐcant number of which turn out to be SNe II. Taken together, about half of the two teamsÏ candidates are revealed to be SNe ...
Decoding Galaxy Evolution with Gas
Decoding Galaxy Evolution with Gas

... guidance that made this dissertation possible. His excellent grasp of the larger picture continually forced me to understand our results in a broader context. His questions cut straight to the heart of the matter and would evoke sheer terror if asked by anyone who does not possess David’s constantly ...
- Mineralogical Society of America
- Mineralogical Society of America

... The advent of multi-collector inductively coupled plasma mass spectrometers (MC-ICPMS), as well as improvements to thermal ionization mass spectrometers (TIMS) in the 1990s has enabled very high precision measurement of isotope ratios for a variety of elements. These mass spectrometers can efficient ...
REVIEW Early star-forming galaxies and the reionization of the Universe
REVIEW Early star-forming galaxies and the reionization of the Universe

... galaxies. Second, fQ and fesc must be observationally estimated by determining the relative effects of stars, dust and nebular emission on the rest-frame ultraviolet region of high-redshift galaxy spectral energy distributions or by direct observations in the Lyman continuum at lower redshift. To re ...
Inflationary Cosmology
Inflationary Cosmology

... see also [11]. In this theory, inflation may begin either in the false vacuum, or in an unstable state at the top of the effective potential. Then the inflaton field φ slowly rolls down to the minimum of its effective potential. The motion of the field away from the false vacuum is of crucial import ...
Determination of the Charon/Pluto Mass Ratio from Center-of
Determination of the Charon/Pluto Mass Ratio from Center-of

... and Charon has made resolved observations of Pluto and Charon difficult: most groundbased images show only a blended image. Millis et al. (1989) attempted to make a determination of the mass ratio using blended images of Pluto–Charon taken with a 1.55-m groundbased telescope in support of the 1988 J ...
evidence for radiogenic sulfur-32 in type ab presolar
evidence for radiogenic sulfur-32 in type ab presolar

... et al. 1999). These stars experience a very-late thermal pulse (VLTP) where convective-reactive nucleosynthesis occurs and unprocessed, H-rich material is convectively mixed into the Heburning zone (Herwig et al. 2011). For the outer He intershell, which extends almost up to the stellar surface, Her ...
APS Neutrino Study
APS Neutrino Study

... neutrinoless double beta experiments. If neutrino mass is discovered by cosmological observations, it will confirm our assumption that the relativistic particle background required by BBN and the CMB is indeed composed of neutrinos. Leptogenesis models connect neutrinos to the unexplained matter dom ...
The HNC/HCN Ratio in Star-Forming Regions The Harvard
The HNC/HCN Ratio in Star-Forming Regions The Harvard

... mechanism was found to be the dissociative recombination of HCNH+ , forming both HNC and HCN in a 1:1 ratio. This branching ratio has been verified experimentally by Mendes et al. (2012). The same model predicted that the temperature dependence of the HNC/HCN ratio is regulated by the destruction ef ...
Observational motivation for Dark Matter
Observational motivation for Dark Matter

... Transfer from Thomson cross section to neutral Hydrogen makes the universe transparent to photons (but not to electrons!) Requires a full solution of the ionization and ...
Lithium abundances in nearby FGK dwarf and subgiant stars
Lithium abundances in nearby FGK dwarf and subgiant stars

... high resolution spectroscopic study of nearby stars from about 500 to 800 objects (Ramı́rez, Allende Prieto, & Lambert, in preparation, hereafter RAL). Their data are being used to study oxygen abundances in local stellar populations, but their spectra cover the 6708 Å region, which contains the li ...
Early Star-Forming Galaxies and the Reionisation of the Universe
Early Star-Forming Galaxies and the Reionisation of the Universe

... slopes with β < -2.5 have been claimed42,44. As the youngest starburst galaxies in the local Universe show UV spectra with β > -2.558,59, and extreme slopes (β < -3) may indicate Population III stars60,61, the steep values derived from the new Hubble data are intriguing. The UV slope measurements be ...
Follow-up observations of extremely metal
Follow-up observations of extremely metal

... to enlarge this sample. We present the first results of an effort to identify new extremely metal-poor stars in the Milky Way halo. Methods. Our targets have been selected from low-resolution spectra obtained as part of the Sloan Digital Sky Survey, and followedup with medium resolution spectroscopy ...
Circumstellar molecular composition of the oxygen
Circumstellar molecular composition of the oxygen

... 1965 by Neugebauer et al. (1965). It is an extremely red Miratype variable with spectral type ranging from M8.1 to M11.2 and a period around 470 days (Wing & Lockwood 1973). From dust shell motions detected at 11 μm with the ISI interferometer, Hale et al. (1997) deduced a distance of 265 pc. This a ...
Europium, Samarium, and Neodymium Isotopic Fractions in Metal
Europium, Samarium, and Neodymium Isotopic Fractions in Metal

... 4, respectively. We summarize the available atomic data for each species in § 3. Our measurements of the elemental abundances and isotopic fractions are presented in § 5 and § 6. In § 7 we discuss the implications of our measurements in the context of using isotopic fractions of multiple species to ...
The evolution and explosion of massive stars
The evolution and explosion of massive stars

... Like all true stars, massive stars are gravitationally confined thermonuclear reactors whose composition evolves as energy is lost to radiation and neutrinos. Unlike lower-mass stars ( M ⱗ8M 䉺 ) , however, no point is ever reached at which a massive star can be fully supported by electron degeneracy ...
Fundamentals in Nuclear Physics
Fundamentals in Nuclear Physics

... accelerators of Berkeley, Caen, Darmstadt and Dubna continue to produce new nuclei whose characteristics challenge models of nuclear structure. It has major technological applications, most notably in medicine and in energy production where a knowledge of some nuclear physics is essential for partic ...
Number Theory and the Periodicity of Matter
Number Theory and the Periodicity of Matter

... on the basis of Balmer’s formula, managed to construct the first convincing model of the atom and introduced the quantum theory into atomic physics. The quantum mechanics that developed from Bohr’s model managed to extend the Balmer formula into a complete description of atomic structure on the basis ...
the reality of the wolf 630 moving group - TigerPrints
the reality of the wolf 630 moving group - TigerPrints

... and chemical evolution of the Galactic disk. To this end, one of the principle approaches for probing the disk has been to study the so-called galactic (or open) clusters, broadly defined as gravitionally bound groups of hundreds to thousands of stars in the galactic disk. Clusters are valuable astr ...
Cosmology Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015
Cosmology Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015

... matter organizing the universe… occurred at about 100s. The actual galaxies appeared much later. “A fraction of a second and the elements were made” Inaccurate. H & He (a little Li) very quickly at few second. Everything else as massive stars fused elements up to iron in their core and then went ...
Here - NASA/IPAC Extragalactic Database
Here - NASA/IPAC Extragalactic Database

... higher Mneb or Q(H0 ). The number fractions of He and heavy elements (C, N, O. . . )† in real nebulae are about 10% and 0.1% respectively. Helium, although ten times less abundant than hydrogen, is the dominant source of absorption of photons at energies above 24.4 eV. For order of magnitudes estima ...
The Animate and the Inanimate
The Animate and the Inanimate

... unavailable or reserve energy of matter; only Lord Kelvin, instead of deriving this from the ordinary physical laws, immediately concluded that some mysterious vital force must be in operation. Under my theory, this reversal an be explained on the pure basis of the theory of probability. ...
The Animate and the Inanimate
The Animate and the Inanimate

... differences will be equalised, and energy of a still higher level or to a greater amount must become dissipated in order to re-create these difference of concentration. Of the various varieties of energy, all kinds tend to turn into heat, which is the least concentrated form of energy; and, even tho ...
PDF File
PDF File

... in that work. For line broadening by electron collisions, the approximations according to Griem (1968) (ions) and Cowley (1971) (neutrals) were applied. For the Si I and Si II lines used here, radiation damping is small compared to collisional broadening, and the classical approximation for γrad is ...
Chemical composition of B-type supergiants in the OB8, OB10
Chemical composition of B-type supergiants in the OB8, OB10

... the blue arm of the spectrograph – signal-to-noise ratios in the reduced spectra were always in excess of 200 for these bright comparison stars. The CCD frames were reduced to wavelength calibrated spectra using the IRAF reduction system1 . Standard procedures were used to bias correct and flat fiel ...
1 2 3 4 5 ... 44 >

Big Bang nucleosynthesis

In physical cosmology, Big Bang nucleosynthesis (abbreviated BBN, also known as primordial nucleosynthesis) refers to the production of nuclei other than those of the lightest isotope of hydrogen (hydrogen-1, 1H, having a single proton as a nucleus) during the early phases of the universe. Primordial nucleosynthesis is believed by most cosmologists to have taken place from 10 seconds to 20 minutes after the Big Bang, and is calculated to be responsible for the formation of most of the universe's helium as the isotope helium-4 (4He), along with small amounts of the hydrogen isotope deuterium (2H or D), the helium isotope helium-3 (3He), and a very small amount of the lithium isotope lithium-7 (7Li). In addition to these stable nuclei, two unstable or radioactive isotopes were also produced: the heavy hydrogen isotope tritium (3H or T); and the beryllium isotope beryllium-7 (7Be); but these unstable isotopes later decayed into 3He and 7Li, as above.Essentially all of the elements that are heavier than lithium and beryllium were created much later, by stellar nucleosynthesis in evolving and exploding stars.
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