We consider a dynamical approach to the cosmological constant. There is a scalar field with a potential whose minimum occurs at a generic, but negative, value for the vacuum energy, and it has a non-standard kinetic term whose coefficient diverges at zero curvature as well as the standard kinetic term. Because of the divergent coefficient of the kinetic term, the lowest energy state is never ac...

mathematical modeling and simulation of microbial polyhydroxybutyrate (phb) production process is beneficial for optimization, design, and control purposes. in this study a batch model developed by mulchandani et al., [1] was used to simulate the process in matlab environment. it was revealed that the kinetic model parameters were estimated off the optimal or at a local optimal point. therefore...

Gibson scaling and related properties of flame-surface geometry in turbulent premixed combustion are demonstrated using a novel computational model, Deterministic Turbulent Mixing (DTM). In DTM, turbulent advection is represented by a sequence of maps applied to the computational domain. The structure of the mapping sequence incorporates pertinent scaling properties of the turbulent cascade. He...

[1] Both local and large‐scale processes affect the Amazon hydrologic cycle. We investigate the impact of deep soils on the atmosphere through local feedbacks. The Simple Biosphere model, version 3 (SiB3), is coupled to a single column model. Historically, land surface schemes parameterize soil moisture stress based on shallow soils and incorrectly capture seasonal cycles in the Amazon. Followi...

in this study, the effect of the secondary structure of the protein on the acid strength of three structures of random (r), alpha helix (α) and beta sheet (b) were investigated theoretically. these structures are related to the cationic amino acids of histidine and lysine in the polypeptide chain of eight-glycine residue. computational methods at the hf, b3lyp, x3lyp and m05-2x levels in the ga...

a mathematical model for commercial naphtha catalytic reformer of tehran refinery was developed. this model includes three sequencing fixed beds of pt/al2o3 catalyst at the steady state condition using detailed kinetic scheme involving 26 pseudo-components connected by a network of 47 reactions, in the range of c6 to c9 hydrocarbons. the reaction network consisted dehydrogenation, hydrogenation...

Modeling and simulation of Polyhydroxybutyrate (PHB) production by Protomonas extorquens in fed-batch culture were conducted in this research. The fed-batch model, developed for this process, employed a kinetic model proposed by other researchers. Several kinetic models were investigated to choose the best model. The criterion for this selection was goodness of fit (δ2). Haldane kinetic model w...

the removal of uranium and any other heavy metals from wastewater might be achieved via several chemical or physical treatment techniques. biosorption process has been considered as a potential alternative way to remove contaminants from industrial effluents. moreover the surface of biosorbent was characterized by sem. the biosorption characteristics of uranium (vi) on pretreated a. niger were ...