Subsurface fracturing of sedimentary stones caused by bullet impacts.

The immovable nature of built heritage means that it is particularly vulnerable during times of armed conflict. Although impacts from small arms and shrapnel leave relatively inconspicuous impact scars, they elevate the risk of future stone deterioration. This study investigates the subsurface damage caused by bullet impacts, which is not apparent from surface inspection, in order to better understand the geometry and mechanics of this form of conflict damage to heritage. Controlled firearm experiments were conducted to simulate conflict damage to sandstone and limestone buildings. The bullet impacts created conical fractures or zones of increased fracture intensity below the impact, radial fractures, and spallation, in addition to a crater. Dynamic fracture distinguishes the formation of these features from quasi static cone crack experiments, while the lack of a shockwave differentiates these bullet impacts from hypervelocity experiments. Damage was created by momentum transfer from the bullet, so that differences in target properties had large effects on the nature of the damage. The crater in the limestone target was almost an order of magnitude deeper than the sandstone crater, and large open fractures formed in the limestone below the crater floor, compared with zones of increased fracture intensity in the sandstone target. Microstructural analysis of subsurface damage showed that fracture intensity decreased with increasing distance from the impact centre, suggesting that regions proximal to the impact are at increased risk of future deterioration. Conical subsurface fractures dipping away from the impact beneath multiple impact craters could link up, creating a continuous fracture network. By providing pathways for moisture and other weathering agents, fractures enlarge the region at increased risk of deterioration. Their lack of surface expression makes understanding their formation a vital part of future surveying and post conflict assessments.

Bullet impacts in building stone excavate approximately conical craters, with dimensions that are controlled by target material.

Bullet impacts are a ubiquitous form of damage to the built environment resulting from armed conflicts. Bullet impacts into stone buildings result in surficial cratering, fracturing, and changes to material properties, such as permeability and surface hardness. Controlled experiments into two different sedimentary stones were conducted to characterise surface damage and to investigate the relationship between the impact energy (a function of engagement distance) and crater volumes. Simplified geometries of crater volume using only depth and diameter measurements showed that the volume of a simple cone provides the best approximation (within 5%) to crater volume measured from photogrammetry models. This result suggests a quick and efficient method of estimating crater volumes during field assessments of damage. Impact energy has little consistent effect on crater volume over the engagement distances studied (100-400 m), but different target materials result in an order of magnitude variation in measured crater volumes. Bullet impacts in the experiments are similar in appearance to damage caused by hypervelocity experiments, but crater excavation is driven by momentum transfer to the target rather than a hemispherical shock wave. Therefore in contrast to predictions of impact scaling relationships for hypervelocity experiments, target material plays the dominant role in controlling damage, not projectile energy.

Surface damage from perpendicular and oblique bullet impacts in stone.

Controlled experiments were conducted to investigate the surface damage caused by perpendicular and oblique impacts of bullets into sandstone and limestone targets. Individual bullets fired in conditions simulating modern rifles at typical combat distances excavated craters with diameters from 22 to 74 mm and depths from 3 to 24 mm. Limestone target craters were up to twice as large and deep as those in sandstone. These craters have a complex shape consisting of a central excavation surrounded by a shallow dish, compared to the simple bowl shape of most sandstone impacts. Radial fractures extending to the edge of the target block were common in limestone targets. Impacts at an angle of 45° to the surface in both rock types result in asymmetric craters. Two common types of intermediate cartridge (ammunition) were compared: the steel-tipped 5.56 × 45 mm NATO projectile generally produced larger and deeper craters than the 7.62 × 39 mm projectile that is commonly fired from AK-47 rifles, despite having approximately half the mass of the latter. These results characterize the sort of damage that can be expected at many sites of cultural significance involved in contemporary conflict zones, and have important implications for their conservation: for example building stone with low tensile strength is likely to sustain more damage and be at risk of greater deterioration.

Normograma de flujometría en pacientes sin sintomatología urinaria / Normograma of flujometría in patients without urinary sintomatología

Se realizó un estudio descriptivo sobre los hallazgos de la flujometría en pacientes sin sintomatología urinaria que acuden a consulta urológica preventiva. Se recolectó una base de datos de 1680 pacientes, de los cuales 586 se sometieron a flujometría. Selecccionando apenas 200 que cumplieron los criterios de inclusión, éstos fueron sometidos a valoración clínica, estudio ecográfico y flujometría, con lo cual se trazó el normograma del Instituto Médico de Urología. Los pacientes fueron de sexo masculino con un rango de edad de 40 a 80 años. El promedio de edad encontrado en el estudio es de 55 años, con una media de 59 años. El promedio de flujo máximo de la serie fue de 16.02 ml/seg, lo que se ecuentra dentro de los valores aceptados internacionalmente...