Prevalence of rectocele in young nulliparous women

Background: It is generally assumed that fascial defects in the rectovaginal septum are the result of childbirth. However, rectoceles do occur in women who have never delivered vaginally. Aims: To determine the incidence of rectocele in a cohort of asymptomatic, young nulliparous women. Methods: Observational cohort study on 178 nulliparous caucasian women (aged 18-24) recruited for a twin study of pelvic floor dysfunction. All women were interviewed and examined by translabial ultrasound, supine and after voiding. In 52 women, 3D imaging was obtained and 171 datasets were complete and available for analysis. Ultrasound findings were reviewed for rectovaginal septal integrity by an assessor blinded against interview and demographic data for rectovaginal septal integrity. Results: A discontinuity of the anterior rectal wall with extrusion of rectal mucosa or contents (depth of ! 10 mm) was observed in 21/171 (12%). The depth of this herniation ranged from 10 to 25 mm and was filled with stool (n = 10) or rectal mucosa (n = 11). Defects were associated with a higher BMI (P = 0.049), with the complaint of constipation (P = 0.049) and non-significantly with straining at stool (P = 0.09). Descent of the ampulla to beyond the level of the symphysis pubis without fascial defect, that is, significant perineal relaxation, was observed in 23/171 (13%). Conclusions: Twelve percent of 171 young nulligravid caucasian women showed a defect of the rectovaginal septum. Associations were observed with higher body mass index and a history of constipation. It is hypothesised that in some women defects of the rectovaginal septum and perineal hypermobility may be congenital in nature.

The abundance of short proteins in the mammalian proteome

Short proteins play key roles in cell signalling and other processes, but their abundance in the mammalian proteome is unknown. Current catalogues of mammalian proteins exhibit an artefactual discontinuity at a length of 100 aa, so that protein abundance peaks just above this length and falls off sharply below it. To clarify the abundance of short proteins, we identify proteins in the FANTOM collection of mouse cDNAs by analysing synonymous and nonsynonymous substitutions with the computer program CRITICA. This analysis confirms that there is no real discontinuity at length 100. Roughly 10% of mouse proteins are shorter than 100 aa, although the majority of these are variants of proteins longer than 100 aa. We identify many novel short proteins, including a dark matter'' subset containing ones that lack detectable homology to other known proteins. Translation assays confirm that some of these novel proteins can be translated and localised to the secretory pathway.

The lattice solid model to simulate the physics of rocks and earthquakes: Incorporation of friction

The particle-based lattice solid model developed to study the physics of rocks and the nonlinear dynamics of earthquakes is refined by incorporating intrinsic friction between particles. The model provides a means for studying the causes of seismic wave attenuation, as well as frictional heat generation, fault zone evolution, and localisation phenomena. A modified velocity-Verlat scheme that allows friction to be precisely modelled is developed. This is a difficult computational problem given that a discontinuity must be accurately simulated by the numerical approach (i.e., the transition from static to dynamical frictional behaviour). This is achieved using a half time step integration scheme. At each half time step, a nonlinear system is solved to compute the static frictional forces and states of touching particle-pairs. Improved efficiency is achieved by adaptively adjusting the time step increment, depending on the particle velocities in the system. The total energy is calculated and verified to remain constant to a high precision during simulations. Numerical experiments show that the model can be applied to the study of earthquake dynamics, the stick-slip instability, heat generation, and fault zone evolution. Such experiments may lead to a conclusive resolution of the heat flow paradox and improved understanding of earthquake precursory phenomena and dynamics. (C) 1999 Academic Press.

Cracks of higher modes in Cosserat continua

Rotational degrees of freedom in Cosserat continua give rise to higher fracture modes. Three new fracture modes correspond to the cracks that are surfaces of discontinuities in the corresponding components of independent Cosserat rotations. We develop a generalisation of J- integral that includes these additional degrees of freedom. The obtained path-independent integrals are used to develop a criterion of crack propagation for a special type of failure in layered materials with sliding layers. This fracture propagates as a progressive bending failure of layers – a “bending crack that is, a crack that can be represented as a distribution of discontinuities in the layer bending. This situation is analysed using a 2D Cosserat continuum model. Semi-infinite bending crack normal to layering is considered. The moment stress concentrates along the line that is a continuation of the crack and has a singularity of the power − 1/4. A model of process zone is proposed for the case when the breakage of layers in the process of bending crack propagation is caused by a crack (microcrack in our description) growing across the layer adjacent to the crack tip. This growth is unstable (in the moment-controlled loading), which results in a typical descending branch of moment stress – rotation discontinuity relationship and hence in emergence of a Barenblatt-type process zone at the tip of the bending crack.