Neutrino Tomography – Learning About The Earth’s Interior Using The Propagation Of Neutrinos

Because the propagation of neutrinos is affected by the presence of Earth matter, it opens new possibilities to probe the Earth’s interior. Different approaches range from techniques based upon the interaction of high energy (above TeV) neutrinos with Earth matter, to methods using the MSW effect on the oscillations of low energy (MeV to GeV) neutrinos. In principle, neutrinos from many different sources (sun, atmosphere, supernovae, beams etc.) can be used. In this talk, we summarize and compare different approaches with an emphasis on more recent developments. In addition, we point out other geophysical aspects relevant for neutrino oscillations.     

环境植物样品中铜铅锌铁锰的测定

将环境植物样品在４００─５００℃灰化，用硝酸、氢氟酸和高氯酸分解，用盐酸（１＋１）提取，控制２％─３％的盐酸介质，用火焰原子吸收分光光度法测定环境植物样品中的微量铜、铅、锌、铁、锰。该方法简单、快速、可靠。对环境植物标准样品的测定结果理想。     

Further constraints on variation of the fine-structure constant from alkali-doublet QSO absorption lines

Comparison of quasar (QSO) absorption-line spectra with laboratory spectra provides a precise probe for variability of the fine-structure constant, α , over cosmological time-scales. We constrain variation in α in 21 Keck/HIRES Si  iv absorption systems using the alkali-doublet (AD) method in which changes in α are related to changes in the doublet spacing. The precision obtained with the AD method has been increased by a factor of 3:     . We also analyse potential systematic errors in this result. Finally, we compare the AD method with the many-multiplet method, which has achieved an order of magnitude greater precision, and we discuss the future of the AD method.     

Cosmological variations in the space-time distribution of absorption systems in quasar spectra

Based on the catalog of Junkkarinen et al. (1991), we analyze the space-time distribution of absorption systems in quasar spectra at cosmological redshifts z=0–3.7. The z distribution of absorbing matter is shown to have a pattern of alternating maxima (peaks) and minima (dips). Within statistical uncertainty, the positions of such peaks and dips do not depend on the direction of observation. We have found a periodicity in the distribution of absorption systems in the functions ln(1+z) and (1+z)^?1/2. We show that the derived sequence of maxima and minima in the space-time distribution of absorbing matter is not a manifestation of the spatial large-scale structure alone, but it is more likely temporal in nature. The most probable source of the putative structure could be an alternation (in the course of cosmological evolution) of pronounced and depressed epochs with a characteristic time interval of 520±160 Myr, depending on the cosmological model chosen.     

Chemical evolution of the high redshift galaxies

We have tried to determine the rate of chemical evolution of high redshift galaxies from the observed redshift distribution of the heavy element absorption systems in the spectra of QSOs, taking into account the evolution in the intensity of the metagalactic UV ionizing radiation background, the radius and/or the co-moving number density of, and the fraction of mass in the form of gas in, the absorbers. The data for both the Lyman limit systems and the C IV systems have been fitted simultaneously. It seems that the abundance of carbon has possibly increased by about a factor of 5 to 20 from the cosmic time corresponding to the redshift ≃ 4 to 2. The data also suggest that either the radius or the co-moving number density of the galaxies increased with redshift up to z = 2.0 and decreased slowly thereafter. The total mass of the halo gas was higher in the past, almost equal to the entire mass of the galaxy at z = 4. The hydrogen column density distribution for Lyman limit systems predicted by the model is in agreement with the observed distribution.     

The chemical evolution of the Universe – I. High column density absorbers

We construct a simple, robust model of the chemical evolution of galaxies from high to low redshift, and apply it to published observations of damped Lyman α quasar absorption line systems (DLAs). The elementary model assumes quiescent star formation and isolated galaxies (no interactions, mergers or gas flows). We consider the influence of dust and chemical gradients in the galaxies, and hence explore the selection effects in quasar surveys. We fit individual DLA systems to predict some observable properties of the absorbing galaxies, and also indicate the expected redshift behaviour of chemical element ratios involving nucleosynthetic time delays.
Despite its simplicity, our 'monolithic collapse' model gives a good account of the distribution and evolution of the metallicity and column density of DLAs, and of the evolution of the global star formation rate and gas density below redshifts z ∼3. However, from the comparison of DLA observations with our model, it is clear that star formation rates at higher redshifts ( z >3) are enhanced. Galaxy interactions and mergers, and gas flows very probably play a major role.     

Variable 21-cm absorption at z=0.3127

We report multi-epoch Giant Metrewave Radio Telescope (GMRT) H  i observations of the z  = 0.3127 damped absorber towards the quasar PKS 1127−145, which reveal variability in both the absorption profile and the flux of the background source, over a time-scale of a few days.
The observed variations cannot be explained by simple interstellar scintillation (ISS) models where there are only one or two scintillating components and all of the ISS occurs in the Galaxy. More complicated models, where either there are more scintillating components or some of the ISS occurs in the interstellar medium of the z =0.3127 absorber, may be acceptable. However, the variability can probably be best explained in models incorporating motion (on sub-VLBI scales) of a component of the background continuum source, with or without some ISS.
All models producing the variable 21-cm absorption profile require small-scale variations in the 21-cm optical depth of the absorber. The length-scale for the opacity variations is ∼0.1 pc in pure superluminal motion models, and ∼10 pc in pure ISS models. Models involving subluminal motion, combined with scintillation of the moving component, require opacity variations on far smaller scales of ∼ 10–100 au .