Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 9 of 9

Full-Text Articles in Physical Sciences and Mathematics

Isotropic Loop Quantum Cosmology With Matter. Ii. The Lorentzian Constraint, F. Hinterleitner, Seth Major Dec 2003

Isotropic Loop Quantum Cosmology With Matter. Ii. The Lorentzian Constraint, F. Hinterleitner, Seth Major

Articles

The Lorentzian Hamiltonian constraint is solved for isotropic loop quantum cosmology coupled to a massless scalar field. As in the Euclidean case, the discreteness of quantum geometry removes the classical singularity from the quantum Friedmann models. In spite of the absence of the classical singularity, a modified DeWitt initial condition is incompatible with a late-time smooth behavior. Further, the smooth behavior is recovered only for positive or negatives times but not both. An important feature, which is shared with the Euclidean case, is a minimal initial energy of the order of the Planck energy required for the system to evolve …


Ecotoxicological Research At Dit, Maria Davoren, Colm O'Dowd, Sharon Ni Shuilleabhain Nov 2003

Ecotoxicological Research At Dit, Maria Davoren, Colm O'Dowd, Sharon Ni Shuilleabhain

Articles

The term ecotoxicology first defined by Rene Truhart in 1969, essentially describes the study of the harmful effects of chemicals upon ecosystems.


Transition Probabilities In Kr Ii And Kr Iii Spectra, Stevan Djenize, Vladimir Milosavljevic, Milan S. Dimitrijevic Sep 2003

Transition Probabilities In Kr Ii And Kr Iii Spectra, Stevan Djenize, Vladimir Milosavljevic, Milan S. Dimitrijevic

Articles

On the basis of the relative line intensity ratio (RLIR) method, transition probability values of the spontaneous emission (Einstein's A values) of 14 transitions in the singly (Kr II) and 7 transitions in doubly (Kr III) ionized krypton spectra have been obtained relatively to the reference A values related to the 435.548 nm Kr II and 324.569 nm Kr III, the most intensive transitions in the Kr II and Kr III spectra. Our Kr III transition probability values are the first data obtained experimentally using the RLIR method. A linear, low–pressure, pulsed arc operated in krypton discharge was used as …


Astrophysical Plasma Diagnostics Through Analysis Of Ar Iine Shape Characteristics, Vladimir Milosavljevic, Stevan Djenize Jul 2003

Astrophysical Plasma Diagnostics Through Analysis Of Ar Iine Shape Characteristics, Vladimir Milosavljevic, Stevan Djenize

Articles

On the basis of five accurately recorded neutral argon ( ) line shapes (in the 4s-5p transition) we have recovered the basic plasma parameters i.e. electron temperature ( T) and electron density ( N) using our new line deconvolution procedure in the case of three different plasmas created in a linear, low-pressure, pulsed arc discharge. The mentioned plasma parameters have also been measured using independent experimental diagnostic techniques. An excellent agreement has been found among the two sets of obtained parameters. This recommends our deconvolution procedure for plasma diagnostic purposes, especially in astrophysics where direct measurements of the …


Experimental And Calculated Stark Widths Within The Kr I Spectrum, Vladimir Milosavljevic, Stevan Djenize, Milan S. Dimitrijevic Jul 2003

Experimental And Calculated Stark Widths Within The Kr I Spectrum, Vladimir Milosavljevic, Stevan Djenize, Milan S. Dimitrijevic

Articles

On the basis of the precisely recorded 20 neutral krypton (Kr I) line shapes (in the 5s−5p and 5s−6p transitions), we have obtained the basic plasma parameters, i.e., electron temperature (T) and electron density (N) using our line deconvolution procedure in a plasma created in a linear, low-pressure, pulsed arc discharge operated in krypton. The mentioned plasma parameters have also been measured using independent experimental diagnostics techniques. Agreement has been found among the two sets of the obtained parameters. This recommends our deconvolution procedure for plasma diagnostical purposes, especially in astrophysics where direct measurements of the …


Reply To "Comment On ‘Atomic Spectral Line Free-Parameter Deconvolution Procedure’”, Vladimir Milosavljevic, Goran Poparic May 2003

Reply To "Comment On ‘Atomic Spectral Line Free-Parameter Deconvolution Procedure’”, Vladimir Milosavljevic, Goran Poparic

Articles

We do not agree with the authors of the preceding Comment [X. Nikolic, X. Ojurovic, and X. Mijatovic, Phys. Rev. E, 67, 058401, 2003]. Our numerical procedure for the deconvolution of the theoretical asymmetric convolution integral of a Gaussian and a plasma broadened spectral line profile jA,R(λ) for spectral lines enables the determination of all broadening parameters. All broadening parameters can be determined directly from the recorded line profile of a single line, with minimal assumptions or prior knowledge. Additional experimental diagnostics are not required.


The He I 706.52 Nm Line Shape Characteristics In The Plasma Diagnostics, Vladimir Milosavljevic, Stevan Djenize Apr 2003

The He I 706.52 Nm Line Shape Characteristics In The Plasma Diagnostics, Vladimir Milosavljevic, Stevan Djenize

Articles

On the basis of the precisely recorded 706.52 nm He I line shape we have obtained the basic plasma parameters i.e. electron temperature (T) and electron density (N) using our new line deconvolution procedure in the case of five various plasmas created in a linear, low–pressure, pulsed arc discharge. Plasma parameters have been also measured using independent experimental diagnostical techniques. Excellent agreement was found among the two sets of the obtained parameters. This enables our deconvolution procedure to recommendation for plasma diagnostical purposes, especially in astrophysics where direct measurements of the plasma parameters (T and …


Assessment Of The Acoustic Properties Of Common Tissue-Mimicking Test Phantoms, Jacinta Browne, K. Ramnarine, A. Watson, P. Hoskins Jan 2003

Assessment Of The Acoustic Properties Of Common Tissue-Mimicking Test Phantoms, Jacinta Browne, K. Ramnarine, A. Watson, P. Hoskins

Articles

Ultrasound (US) test phantoms incorporating tissue-mimicking materials (TMMs) play an important role in the quality control (QC) and performance testing of US equipment. Three commercially available TMMs (ZerdineTM from CIRS Inc.; condensed-milk-based gel from Gammex RMI; urethane-rubber-based from ATS Labs) and a noncommercial agar-based TMM, were investigated. Acoustic properties were measured over the frequency range 2.25 to 15 MHz at a range of ambient temperatures (10 to 35°C). The acoustic velocity of the TMMs remained relatively constant with increasing frequency. Only the agar-based TMM had a linear increase of attenuation with frequency, with the other materials exhibiting nonlinear responses to …


Characterization Of The Interaction Of Gamma Cyclodextrin With Single-Walled Carbon Nanotubes, Gordon Chambers, Clodagh Carroll, Garrett Farrell, Alan Dalton, Mary Mcnamara, Marc In Het Panhuis, Hugh Byrne Jan 2003

Characterization Of The Interaction Of Gamma Cyclodextrin With Single-Walled Carbon Nanotubes, Gordon Chambers, Clodagh Carroll, Garrett Farrell, Alan Dalton, Mary Mcnamara, Marc In Het Panhuis, Hugh Byrne

Articles

In this study a number of composite-like samples of ç-cyclodextrin and HiPco carbon nanotubes were prepared. The first sample was prepared by a simple grinding procedure, which has been reported to cut HiPco carbon nanotubes. The other samples were obtained via a refluxing procedure analogous to similar studies on other fullerenes and ç-cyclodextrin. The samples were analyzed using absorption and Raman spectroscopy, and differential scanning calorimetry. The results presented show clear evidence of an intermolecular interaction between ç-cyclodextrin and single-walled carbon nanotubes.