A feedback fluid queue with two congestion control thresholds

Feedback fluid queues play an important role in modeling congestion control mechanisms for packet networks. In this paper we present and analyze a fluid queue with a feedback-based traffic rate adaptation scheme which uses two thresholds. The higher threshold B ₁ is used to signal the beginning of congestion while the lower threshold B ₂ signals the end of congestion. These two parameters together allow to make the trade-off between maximizing throughput performance and minimizing delay. The difference between the two thresholds helps to control the amount of feedback signals sent to the traffic source. In our model the input source can behave like either of two Markov fluid processes. The first applies as long as the upper threshold B ₁ has not been hit from below. As soon as that happens, the traffic source adapts and switches to the second process, until B ₂ (smaller than B ₁) is hit from above. We analyze the model by setting up the Kolmogorov forward equations, then solving the corresponding balance equations using a spectral expansion, and finally identifying sufficient constraints to solve for the unknowns in the solution. In particular, our analysis yields expressions for the stationary distribution of the buffer occupancy, the buffer delay distribution, and the throughput.     

EPR spectrum of gadolinium in hydrated praseodymium sulphate

The electron paramagnetic resonance of Gd³⁺ in single crystal of Pr₂(SO₄)₃.8H₂O is studied at room temperature. Two magnetic complexes exhibiting orthorhombic or lower symmetry are found and the results have been fitted to a suitable spin Hamiltonian. The exact solution of Hamiltonian matrix is carried out and 10 “best fit” parameters are obtained using iterative optimization technique. The zero field splittings of Gd³⁺: Pr₂(SO₄)₃.8H₂O have been computed. Few forbidden transitions are observed and explained using numerical solution of the Hamiltonian matrix.     

Differential inhibition of postnatal brain,spinal cord and body growth by a growth hormone antagonist

Background  

Growth hormone (GH) plays an incompletely understood role in the development of the central nervous system (CNS). In this study, we use transgenic mice expressing a growth hormone antagonist (GHA) to explore the role of GH in regulating postnatal brain, spinal cord and body growth into adulthood. The GHA transgene encodes a protein that inhibits the binding of GH to its receptor, specifically antagonizing the trophic effects of endogenous GH.     

Polymerization of α-Methylstyrene in p-Dioxane with Potassium as Initiator. III. Gel-Permeation Chromatographic Analyses of Polymers

Gel-permeation chromatographic studies on poly-α-methyl-styrene initiated with potassium and potassium-naphthalene in p-dioxane as solvent and polymerized at 5, 15, 25, and 40°C, have been carried out. Bimodal and trimodal distributions are observed in these polymers. It has been shown that these multimodal distributions do not arise because of the monofunctional and bifunctional living ends produced by the reaction of solvent dioxane with the living polymer. These, on the other hand, may be related to the presence of different ion-pairs which contribute to the reaction but to different extents. Contrary to the belief that only contact ion-pairs are responsible for propagation in p-dioxane because of its low dielectric constant, the presence of solvent-separated ion-pairs yielding reversible propagation has been speculated. The different components (D + A), B, and C, similar to the ones present in the a-methyl-styrene-potassium tetrahydrofuran system, have been found in the present study also and are attributed to the dead and a dormant polymer, solvent-separated ion-pair polymer, and that due to a contact pair, respectively. The extent of the formation of component (D + A) has been linked directly to the concentration of living ends. In reactions where naphthalene was used along with potassium for initiation purposes, a unique component yielding reversible propagation was observed. This has been attributed to the presence of polymer due to potassium-naphthalene complex which is different in character to a contact ion-pair but may resemble a solvent-separated ion-pair.     

Bose-Einstein correlations for pions produced inp p collisions at 360 GeV/c

Zeitschrift für Physik C Particles and Fields - Correlations among identically charged pions were measured for pions produced inp p collisions at 360 GeV/c using the EHS spectrometer. The...     

Overtone spectroscopy of some benzaldehyde derivatives

Overtone spectrum of o, m and p-nitrobenzaldehydes and p-chlorobenzaldehyde has been studied in 2000–12000 cm⁻¹ region. Vibrational frequencies and anharmonicity constants for aryl as well as alkyl CH stretch vibrations have been determined. We have also determined the internuclear distances for the aryl CH bond in the different molecules. The small variation observed in these distances is an indication of the substitution effect. It is observed that in the case of p-disubstituted benzens, the shift in aryl CH bond is proportional to sum of the Hammet σ of the substituents. However in the case of o-disubstituted benzenes it is only 80% of the para-substituted shift.