34 research outputs found
Field on Poincare group and quantum description of orientable objects
We propose an approach to the quantum-mechanical description of relativistic
orientable objects. It generalizes Wigner's ideas concerning the treatment of
nonrelativistic orientable objects (in particular, a nonrelativistic rotator)
with the help of two reference frames (space-fixed and body-fixed). A technical
realization of this generalization (for instance, in 3+1 dimensions) amounts to
introducing wave functions that depend on elements of the Poincare group . A
complete set of transformations that test the symmetries of an orientable
object and of the embedding space belongs to the group . All
such transformations can be studied by considering a generalized regular
representation of in the space of scalar functions on the group, ,
that depend on the Minkowski space points as well as on the
orientation variables given by the elements of a matrix .
In particular, the field is a generating function of usual spin-tensor
multicomponent fields. In the theory under consideration, there are four
different types of spinors, and an orientable object is characterized by ten
quantum numbers. We study the corresponding relativistic wave equations and
their symmetry properties.Comment: 46 page
Superconducting properties of RuSr2GdCu2O8 studied by SQUID magnetometry
For polycrystalline RuSr2GdCu2O8 (Ru-1212), distinct peaks have been reported
in d.c. magnetization in the superconducting state of the sample. Sr2GdRuO6
(Sr-2116), the precursor for the preparation of Ru-1212, shows similar peaks in
the same temperature regime. Based on measurements performed on both bulk and
powdered samples of Ru-1212 and Sr-2116, we exclude the possibility, that the
observed behavior of the magnetization of Ru-1212 is due to Sr-2116 impurities.
The effect is related to the superconductivity of Ru-1212, but it is not an
intrinsic property of this compound. We provide evidence that the observation
of magnetization peaks in the superconducting state of Ru-1212 is due to flux
motion generated by the movement of the sample in an inhomogeneous field,
during the measurement in the SQUID magnetometer. We propose several tests,
that help to decide, whether the features observed in a SQUID magnetization
measurement of Ru-1212 represent a property of the compound or not.Comment: 22 pages, 9 figure
Membrane reactors for bioethanol production and processing
Dwindling supplies of fossil fuel along with detrimental release of greenhouse gases have led to the quest for renewable sources of fuel such as bioethanol from cellulosic materials. Conversion of biomass to bioethanol involves a set of âbiotransformationâ and ârecovery/concentrationâ processes. With the help of membrane technology, several process steps that were conventionally separate can be integrated and the production of bioethanol simplified. In addition to efficient recovery of bioethanol, this can facilitate removal of inhibitory side products from the fermentation broth and recovery of the inhibitory but valuable side products. This chapter provides a critical review of the application of membrane technology in various steps of bioethanol production. The challenges to widespread deployment of full-scale bioethanol facilities equipped with membranes have also been outlined
Experimental Investigation on the Static and Impact Behaviors of Basalt Fiber-Reinforced Concrete
Surveillance of viral contamination of invasive medical instruments in dentistry
Objective: To investigate the viral contamination of invasive medical instruments in dentistry and to provide health administrative institutions with surveillance data. Methods: Sterilized samples were randomly collected from the department of dentistry to detect HBV-DNA, HCV-RNA, HIV-RNA and HBsAg. Results: Of the invasive medical instruments that were sterilized with 2% glutaraldehyde, one of the samples was positive for HBV-DNA, and another sample was positive for HBsAg. Conclusion: Though massive virus contamination of invasive medical instruments in dentistry has been reduced to a low level, the occurrence of contamination still remains