We deal with a two-queue model with mixed exhaustive and gated-type K-limited services. This model can achieve various degrees of priority in each queue by varying the value of K. Analyzing the model by using the delay cycle technique, we obtain the Laplace-Stieltjes transforms of the waiting time distributions for both cases with zero and non-zero walking times.

We design and analyze multigrid methods for the saddle point problems resulting from Raviart-Thomas-Nédélec mixed finite element methods (of order at least 1) for the Darcy system in porous media flow. Uniform convergence of the W -cycle algorithm in a nonstandard energy norm is established. Extensions to general second order elliptic problems are also addressed.

In this paper we consider multigrid methods for the parameter dependent problem of nearly incompressible materials. We construct and analyze multilevel-projection algorithms, which can be applied to the mixed as well as to the equivalent, non-conforming nite element scheme in primal variables. For proper norms, we prove that the smoothing property and the approximation property hold with consta...

Homocysteine is a sulphur-containing amino acid, which structurally is closely related to the essential amino acids methionine and cysteine. The cellular methylation cycle performs the metabolism of methionine and since homocysteine is an intermediate within this cycle, the body in this way is provided with all organic homocysteine. The term homocysteine is used to define the combined pool of h...

Synchronized cells of the cellular slime mould Dictyostelium discoideum were prepared by mitotic wash-off. Cell counts and DNA synthesis measurements indicated a high degree of synchrony. Cells from each phase of the cell cycle were fluorescently labelled and mixed with unlabelled asynchronous cells. Cells that were in S-phase and very early G2 at the onset of starvation demonstrated a strong t...

The various methods of treatment to mercury toxicity in the human body have been studied and investigated with somewhat mixed conclusions. This paper discusses the various types of mercury, the cycle of mercury in the environment, human exposure to mercury and treatment, and methods of reducing mercury pollution and its effect in the human population in the U.S.

Archaea play an important role in nitrification and are, thus, inextricably linked to the global carbon and nitrogen cycles. Since the initial discovery of an ammonia monooxygenase α-subunit (amoA) gene associated with an archaeal metagenomic fragment, archaeal amoA sequences have been detected in a wide variety of nitrifying environments. Recent sequencing efforts have revealed extensive diver...

Methanotrophs, cells that consume methane (CH(4)) as their sole source of carbon and energy, play key roles in the global carbon cycle, including controlling anthropogenic and natural emissions of CH(4), the second-most important greenhouse gas after carbon dioxide. These cells have also been widely used for bioremediation of chlorinated solvents, and help sustain diverse microbial communities ...

Nitrification plays a central role in the nitrogen cycle by determining the oxidation state of nitrogen and its subsequent bioavailability and cycling. However, relatively little is known about the underlying ecology of the microbial communities that carry out nitrification in freshwater ecosystems--and particularly within high-altitude oligotrophic lakes, where nitrogen is frequently a limitin...

In this work we study mixed mode oscillations in a model of secretion of GnRH (Gonadotropin Releasing Hormone). The model is a phantom burster consisting of two feedforward coupled FitzHughNagumo systems, with three time scales. The forcing system (Regulator) evolves on the slowest scale and acts by moving the slow null-cline of the forced system (Secretor). There are three modes of dynamics: p...