in this paper some upper and lower bounds for the greatest eigenvalues of the pi and vertex pimatrices of a graph g are obtained. those graphs for which these bounds are best possible arecharacterized.

background: fractures of distal radius are one of the most common fractures seen by physicians and account for 20% of all fractures seen in the emergency room. various factors contribute in secondary displacement of fracture fragments after anatomic or near anatomic close reduction and cast immobilization in distal radius fractures. this study was designed to examine the correlation between rad...

the degree set of a graph is the set of its degrees. kapoor et al. [degree sets for graphs, fund. math. 95 (1977) 189-194] proved that for every set of positive integers, there exists a graph of diameter at most two and radius one with that degree set. furthermore, the minimum order of such a graph is determined. a graph is 2-self- centered if its radius and diameter are two. in this paper for ...

background: pulse wave velocity (pwv) is widely used for estimating the stiffness of an artery. v arious invasive and non-invasive methods have been developed to determine pwv over the years. in the present research , the non-invasive estimation of the pwv of large arteries was used as an index for arterial stiffness. methods: a dynamic model based on the navier-stokes equations coupled to elas...

materials and methods: one hundred and thirty five mesial root canals of mandibular first and second molar teeth were selected. access cavities were prepared. after inserting a k-file size #10 into each canal, radiographs were taken. canal curvature was determined by measuring the schneider angle, canal access angle, as well as the canal radius, length, height and curvature starting distance on...

potassium channels allow potassium flux and are essential for the generation of electric current acrossexcitable membranes. potassium channels are also the targets of various intracellular controlmechanisms; such that the suboptimal regulation of channel function might be related to pathologicalconditions. realistic studies of ion current in biologic channels present a major challenge for compu...

In the Manning equation the hydraulic radius can be defined as the cross-section dimension of the shape. In pipe flow the bed shear stress is assumed to be uniformly distributed along the wetted perimeter which cannot be true in open channel flow. Hence, three approximation of the true boundary shear-stress distribution are examined and more practical conveyance depth or resistance radius formu...