377 research outputs found
The Fundamental Commutator For Massless Particles
It is discussed that the usual Heisenberg commutation relation (CR) is not a
proper relation for massless particles and then an alternative is obtained. The
canonical quantization of the free electromagnetic(EM)fields based on the field
theoretical generalization of this alternative is carried out. Without imposing
the normal ordering condition,the vacuum energy is automatically zero.This can
be considered as a solution to the EM fields vacuum catastrophe and a step
toward managing the cosmologial constant problem at least for the EM fields
contribution to the state of vacuum.Comment: 12 pages,no figures,To appear in Mod.Phys.Ltt.
Cosmological constant influence on cosmic string spacetime
We investigate the line element of spacetime around a linear cosmic string in
the presence of a cosmological constant. We obtain the metric and argue that it
should be discarded because of asymptotic considerations. Then a time dependent
and consistent form of the metric is obtained and its properties are discussed.Comment: 3 page
The Cytotoxic Effect of 2-Deoxy-D-Glucose Combination with 5-Fluorourasil and NO-Aspirin on Mammary Adenocacinoma Cell Line
2-deoxy-D-glucose (2DG) and NO-Aspirin (NO-ASA) are new anticancer agents that are under intense clinical investigation for their remarkable cytotoxic activity. Combining 2DG, which targets glucose metabolism, with other agents mainly the DNA- and the mitochondrial-damaging agents represent a promising chemotherapeutic strategy. In this study, we investigated the cytotoxic effects of 2DG, 5-fluorourasil (5FU), and NO-ASA on AMN3 breast cancer model, in addition to the cytotoxic effects of 2DG combination with 5FU and NO-ASA on the same cells. The cytotoxic activity of 2DG, 5FU, and NO-ASA was measured by using the MTT assay at 24, 48, and 72 hr. Then 2DG was combined with 5FU and NO-ASA in a constant concentration ratio based on their corresponding IC50s and the inhibition of cell growth was measured by MTT assay at 72hr. Median effect analysis was conducted to determine the cytotoxic activity of the combinations. 2DG, 5FU, and NO-ASA were found to exert a significant dose- and time-dependant growth inhibition on AMN3 cells. The mean combination index values reveal an additive effect for both combinations. This study demonstrated that 2DG and NO-ASA are capable of inhibiting the breast tumor growth effectively. It also shows that 2DG/5FU and 2DG/NO-ASA combinations result in mean additive effects with good dose reduction index values that have the advantages of reducing the toxicity, adverse effects, and the drug resistance in cancer patients. Key words: 2-deoxy-D-glucose (2DG), NO-Aspirin (NO-ASA), 5-fluorourasil (5FU), Glucose metabolism, Median effect analysis, Breast cance
Vertically Self-Gravitating ADAFs in the Presence of Toroidal Magnetic Field
Force due to the self-gravity of the disc in the vertical direction is
considered to study its possible effects on the structure of a magnetized
advection-dominated accretion disc. We present steady-sate self similar
solutions for the dynamical structure of such a type of the accretion flows.
Our solutions imply reduced thickness of the disc because of the self-gravity.
It also imply that the thickness of the disc will increase by adding the
magnetic field strength.Comment: Accepted for publication in Astrophysics and Space Science
Electrolyte gate dependent high-frequency measurement of graphene field-effect transistor for sensing applications
We performed radiofrequency (RF) reflectometry measurements at 2.4 GHz on
electrolyte-gated graphene field-effect transistors (GFETs) utilizing a tunable
stub-matching circuit for impedance matching. We demonstrate that the gate
voltage dependent RF resistivity of graphene can be deduced even in the
presence of the electrolyte which is in direct contact with the graphene layer.
The RF resistivity is found to be consistent with its DC counterpart in the
full gate voltage range. Furthermore, in order to access the potential of
high-frequency sensing for applications, we demonstrate time-dependent gating
in solution with nanosecond time resolution.Comment: 14 pages, 4 figure
Energy-momentum Distribution in Static and Non-static Cosmic String Space-times
We elaborate the problem of energy-momentum in general relativity by
energy-momentum prescriptions theory. In this regard, we calculate
M\oller,Landau-Lifshitz, Papapetrou, Einstein, Bergman, Tolman, and Weinberg's
energy-momentum complexes in static and nonstatic cosmic string space-times. We
obtain strong coincidences between the results. These coincidences can be
considered as an extension of Virbhadra's viewpoint that different
energy-momentum prescriptions may provide some basis to define a unique
quantity. In addition, our results disagree with Lessner's belief about
M\oller's prescription and support the Virbhadra's conclusion about the power
of Einstein's prescription.Comment: LaTeX, 5 page: added reference
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