Methods: A cohesive fracture model is adopted together with a discrete crack and without predetermined fracture path. The fracture is filled with interface elements which in the 2D case are quadrangular and triangular elements and in the 3D case are either tetrahedral or wedge elements. The Rankine criterion is used for fracture nucleation and advancement. In a 2D setting the fracture follows d...

To examine the freeze-fracture appearance of membrane alterations accompanying the preparation of sperm membranes for fusions-the first preparatory stage occurring before physiological release of the acrosomal content, the second afterward-we induced the acrosome reaction in capacitated guinea pig spermatozoa by adding calcium to the mixture. The most common features observed before fusion of t...

[1] A mechanistic model is presented to describe closure of a fracture mediated by pressure solution; closure controls permeability reduction and incorporates the serial processes of dissolution at contacting asperities, interfacial diffusion, and precipitation at the free face of fractures. These processes progress over a representative contacting asperity and define compaction at the macrosco...

Low resistance junctions between axons of crayfish ganglia are studied by freeze-fracture and negative staining . In freeze-fracture, fracture planes that go through a junctional membrane expose two faces, both internal, called face A and face B . Face A belongs to the internal membrane leaflet and faces the gap . Face B belongs to the external membrane leaflet and faces the axoplasm. Face A di...

The intercellular junctions of the anterior ciliary and iridial epithelia of the inflamed rabbit eye were examined by use of an ultrastructural tracer, conventional electron microscopy, and the freeze-fracture technique. In normal control eyes, intravascularly injected horseradish peroxidase was prevented from entering the posterior chamber by the zonulae occludentes of the nonpigmented ciliary...

The mechanical response and fracture of metal sandwich panels subjected to multiple impulsive pressure loads (shocks) were investigated for panels with honeycomb and folded plate core constructions. The structural performance of panels with specific core configurations under multiple impulsive pressure loads is quantified by the maximum transverse deflection of the face sheets and the core crus...

BACKGROUND Fractures of mid-face were first described by Le Fort and are classified into three categories - Le Fort I, Le Fort II and Le Fort III. The pterygoid processes of the sphenoid bone are fractured in all the three categories of Le Fort fractures as the sphenoid bone connects the cranium vault to the facial bones. Fractures of the pterygoid processes without associated Le Fort fractures...

A rare case of fracture of the coronoid and the pterygoid process caused by firearms is described. A 28-year-old male was hit by a bullet in the face, resulting in restricted mouth opening, difficulty in chewing and pain when opening the mouth. Clinical examination revealed a perforating wound in the right parotid region and a similar wound on the left side of the same region. A CT scan showed ...

The experimentally determined marked rise of the stress intensity factor required to initiate crack propagation in brittle solids under variably high loading rates, is analyzed. This problem of fracture initiation at the tip of a crack is considered in terms of activating a flaw at some distance away from the tip. By using a semi-infinite crack in an unbounded two-dimensional solid subjected to...