42,312 research outputs found
Gauge Coupling Unification in E6 F-Theory GUTs with Matter and Bulk Exotics from Flux Breaking
We consider gauge coupling unification in E6 F-Theory Grand Unified Theories
(GUTs) where E6 is broken to the Standard Model (SM) gauge group using fluxes.
In such models there are two types of exotics that can affect gauge coupling
unification, namely matter exotics from the matter curves in the 27 dimensional
representation of E6 and the bulk exotics from the adjoint 78 dimensional
representation of E6. We explore the conditions required for either the
complete or partial removal of bulk exotics from the low energy spectrum. In
the latter case we shall show that (miraculously) gauge coupling unification
may be possible even if there are bulk exotics at the TeV scale. Indeed in some
cases it is necessary for bulk exotics to survive to the TeV scale in order to
cancel the effects coming from other TeV scale matter exotics which would by
themselves spoil gauge coupling unification. The combination of matter and bulk
exotics in these cases can lead to precise gauge coupling unification which
would not be possible with either type of exotics considered by themselves. The
combination of matter and bulk exotics at the TeV scale represents a unique and
striking signature of E6 F-theory GUTs that can be tested at the LHC.Comment: 21 pages, 5 figure
Seasonal Shoot-Feeding by \u3ci\u3eTomicus Piniperda\u3c/i\u3e (Coleoptera: Scolytidae) in Michigan
Seasonal shoot-feeding by Tomicus piniperda (L.) was monitored at 2┬н week intervals on 15 Scotch pine, Pinus sylvestris L., trees from 8 April through 16 November 1994 in southern Michigan. All shoots that showed evidence of T. piniperda attack were removed every two weeks. In 1994, initial spring flight of T. piniperda began on 22 March. At least two live T. piniperda adults were found on the 15 trees on each sampling date from 8 April through 1 November 1994. In addition, at least one freshly attacked, beetle- free shoot was found on each sampling date except for 1 November. The greatest numbers of newly attacked shoots, with or without adults present, were found from mid-June through mid-August. All adults found in April and May were likely parent adults, while those from June onward were primarily brood adults. Therefore, at all times of the year, live T. piniperda adults can be found on live pine trees, either feeding in the shoots or overwintering at the base of the trunk. Implications of these findings are provided in light of the US federal quarantine on T. piniperda
X-ray spectrum of the high polarization quasar PKS 1510-089
We present results on the X-ray spectra of the radio-loud, high-polarization
quasar, PKS 1510-089, based on new data obtained using ASCA, and from archival
ROSAT data. The X-ray spectrum obtained by ASCA is unusually hard, with the
photon index=1.30+-0.06, while the (non-simultaneous) ROSAT data indicate a
steeper spectrum (1.9+-0.3). The X-ray flux at 1 keV is within 10% during both
observations. A break in the underlying continuum at about 0.7 keV is
suggested. Flat X-ray spectra seem to be the characteristic of high
polarization quasars, and their spectra also appear to be harder than that of
the other radio-loud but low-polarization quasars. The multiwavelength spectrum
of PKS 1510-089 is similar to many other gamma-ray blazars, suggesting the
emission is dominated by that from a relativistic jet. A big blue-bump is also
seen in its multiwavelength spectrum, suggesting the presence of a strong
thermal component as well.Comment: 19 pages (Latex + 5 ps figures), Accpeted for publication in the
Astrophysical Journal, December 20, 199
IRAS observations of AGN candidates at low flux levels
IRAS additional observations were used to obtain a sample of point sources at much fainter flux levels than hitherto available through the IRAS Point Source Catalogue. This sample is being used to compile an incomplete but representative catalogue of faint IRAS candidate Active Galactic Nuclei (AGNs) and to study the evolution of the infrared bright galaxies. Ground based follow up observations (optical spectroscopy) are mainly hampered by identification confusion
Identification of eggs and larvae
History of identification of fish eggs and larvae;
Towards the end of the 19th century Marine Biologists,
Holt and Scott (1898) Mintosh and Masterman (1897).,
Cunningham (1897) and E hrenbaum (1905-1909) succeeded
in describing the eggs and larvae of a large number of
marine teleostean fishes in European waters. The Danish
scientists, Schmidt (1904-1918) and Petersen (1892-1919)
described several postlarval stages of demersal fishes,
These efforts were supplemented by Claric (1920), Ford
(1920-1931) and Lebour (1919-1927) at Plymouth. The
prolific contributions of Japanese workers as well as
those from USSR and Germany have not been freely accessible
to Indian workers either due to language problems or for
other reasons
Diseases and their control in aquaculture system
The importance of aquaculture to the population of India
is well known. There is considerable scope for improving the fish
protein resources by resorting to intensive and scientific
methods of aquaculture. Aquaculture helps to augment
production and provides gainful employment to people. In this
system, fish is stocked in culture farms at a high density and
given artificial feeds. Unnaturally high population favours the
spread of diseases. Disease is one of the most serious problems
in aquaculture. The frequency and severity of disease outbreaks
have increased with the intensification of aquaculture
An overview of diseases in mariculture - Winter school on recent advances in diagnosis and management of diseases in mariculture, 7th to 27th November 2002, Course Manual
The importance of aquaculture in the agricultural development of India is well
known. The protein intake of our population is well below the required amount. The
continued population growth in south East Asian countries depletes the available source
of animal protein. Fish provide a cheap source of animal protein. Fish production in many
parts of the world is stagnant because the major source of fish production comes from
open waters. There is no way to improve these sources
Histological examination of tissues of experimental fish
Nutrition and pathology are related disciplines.
Gounelle (1961) observed that "Every disease has a nutritional
aspect. Pathology is concerned with specific disease
process and resultant tissue changes in the individual what
ever its systemic position. The study of disease process
involves at a greater extent the histological examination of
various organs and tissues. The histological examination of
tissue in a nutritional experiment provide an opportunity to
observe the resultant changes occurring at cellular level.
Many times a particular treatment may not produce any
physiological or reproductive effect immediately; however
histological examination may reveal considerable changes.
It is also important before advocating any feed or a
combination of feed for field use we have to ascertain
whether the said combination contain any type of toxic factor
This can be settled only by conducting an experiment in which
histopathological examination forms the major component
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