Fracture mechanics model of stone comminution in ESWL and implications for tissue damage

Focused shock waves administered during extracorporeal shock-wave lithotripsy (ESWL) cause stone fragmentation. The process of stone fragmentation is described in terms of a dynamic fracture process. As is characteristic of all brittle materials, fragmentation requires nucleation, growth and coalescence of flaws, caused by a tensile or shear stress. The mechanisms, operative in the stone, inducing these stresses have been identified as spall and compression-induced tensile microcracks, nucleating at pre-existing flaws. These mechanisms are driven by the lithotripter-generated shock wave and possibly also by cavitation effects in the surrounding fluid. In this paper, the spall mechanism has been analysed, using a cohesive-zone model for the material. The influence of shock wave parameters, and physical properties of stone, on stone comminution is described. The analysis suggests a potential means to exploit the difference between the stone and tissue physical properties, so as to make stone comminution more effective, without increasing tissue damage

Damage index for stone monuments

Precise diagnosis is required for characterisation, interpretation, rating and prediction of the weathering damages at stone monuments and is vital for remedy of stone damages and sustainable monument preservation. Quantitative rating of damages represents an important scientific contribution to reliable damage diagnosis at stone monuments. Damage indices are introduced as new tool for scientific quantification and rating of stone damages. Application of damage indices improves stone damage diagnosis and is very suitable for evaluation and certification of preservation measures and for long-term survey and maintenance of stone monuments. Importance and use of damage indices are presented for monuments in Germany, Malta, Jordan, Egypt and Brazil.peer-reviewe

The hybrid of floating stone column by numerical and physical evaluation

Rapid population growth amplifying demand for accommodation and infrastructure has resulted in soft ground being increasingly used in construction. Problems related to soft ground can be remedied by adopting a ground improvement technique. The stone column is one of the most effective and feasible techniques for soft clay soil improvement. Stone columns increase bearing capacity and reduce the settlement of soil. However, soft ground of more than 40 meters depth makes stone column treatment costlier. The design of floating stone columns within soft ground is sometimes needs to adopt. However, this method is not popular compared to the end bearing stone columns due to low mobilised shear resistance and resulted in higher occurrence of punching failure. This research is aimed for addressing the shortcoming floating stone columns with proposing the hybrid dimension floating stone columns. The hybrid stone column size able to increase the mobilised shear resistance, decrease punching failure, and reduce the volume of aggregates. In the present work, finite element analysis was performed using the program PLAXIS 2D. An elastic-perfectly plastic constitutive soil model relation based on the Mohr-Coulomb criterion was utilized to predict the behaviour of soft clay strengthen by stone column. Response Surface Methodology (RSM) was used to optimize the hybrid stone column size with the Design-Expert 6.0.4 software. The laboratory physical model tests were performed based on the sizes of optimum hybrid stone column size proposed by RSM. The results revealed that the optimal parameter of the uniform diameter of 44 mm with a length of 100 mm increases its load bearing capacity of 3260.7 N and the lowest settlement was recorded at a diameter of 24.2 mm with a length of 400 mm to achieve 25.8 mm of settlement. Moreover, the hybrid column size i.e. the first stone column diameter of 43 mm and second diameter of 21.2 mm with the same lengths of 200 mm each diameter able to achieve load-bearing capacity of 3350.9 N and settlement of 24.5 mm. Thus, by comparing with the uniform diameter stone column of 44 mm and length of 400 mm, the hybrid column able to increase the load bearing capacity by 3% and decrease the settlement by 5%. In addition, a good agreement was obtained between the numerical and physical models with variation 25%. In addition, the hybrid stone column size is able to reduce the volume of aggregates up to 40%

Maltese stone

The rich history of Malta testifies that over the centuries, or rather millennia, it has played an important strategic role as a defensible point in the middle of the Mediterranean. The remains of the Ggantija Temples can be seen today on the island of Gozo, which have a specific place in the development of the earliest sacral architecture. The underground temples and tombs hold a special place. The next important period is the Renaissance. Valletta is one of the most important Renaissance towns, which, according to tradition, was planned in a mere six days. This period was followed by the Baroque. A well-known name from that time is Count Giovanni Battista Vertova, who was a mathematician and military engineer. Contemporary architecture provides the last framework. Here it is worth mentioning as a curiosity the production of modular stone in quarries in a way that is characteristic only for this area. In addition to new buildings, vernacular architecture must also be mentioned, to which belong girnas or shelters, hides for bird hunters, beehives in walls, wells etc.peer-reviewe

The Soft Side of Stone: Notes for a Phenomenology of Stone

Stone represents the firmness and intransigence of the world within which we live and act. But beyond the perception and appropriations of stone, diverse meanings lie hidden between the hardness of stone and its uses. At the same time meaning must be grounded in the stabilizing presence of a common world. Yet if all that can be said is not about stone simpliciter but only an aesthetics of its perception, uses, and meanings, have we not gained the whole world but lost its reality? The underlying issue is therefore not aesthetic but ontological

Archeometric Investigation of the Stone Tools of the Vatya Culture (Pest County, Hungary)

With the analysis of the middle Bronze Age (2000–1350 BC) Vatya culture findings in Pest county (Central Hungary) comprising of more than 400 polished stone tools and instrument tools this is the first archaeometric study with such scale in Hungary. In order to characterize petrographically the raw-material of the stone tools macroscopic and microscopic stone analyses were made together with mineralogical and geochemical analyses. In the course of the work a new digital database the Archaeometric Stone Tool Database was established. Based on the results, the material of the instrument stones is mainly sandstone and quartzite that were easy to collect from their source areas. Local volcanics, mostly amphibole containing andesite variations dominated among the material of the polished stone tools. Ophiolites (metamorphic basic rocks, serpentinized basic and ultrabasic rocks) were the raw-material of stone axes that indicate either more distant travels for raw-material or exchange import

Treatment of renal stones by extracorporeal shockwave lithotripsy - An update

Aim: Despite the extensive experience with minimal invasive stone therapy, there are still different views on the ideal management of renal stones. Materials and Methods: Analysis of the literature includes more than 14,000 patients. We have compared these data with long-term results of two major stone centers in Germany. The results have been compared concerning the anatomical kidney situation, stone size, stone localization and observation time. Results: According to the importance of residual fragments following extracorporeal shock wave lithotripsy (ESWL), we have to distinguish between clinically insignificant residual fragments and clinically significant residual fragments (CIRF). 24 months following ESWL stone passage occurs as a continous process, and if there are no clinical symptoms, any endoscopic procedure should be considered as overtreatment. According to these results, stone-free rates of patients increase in longer follow-up periods. Newer ESWL technology has increased the percentage of CIRF. Conclusion: We consider ESWL in most patients with renal calculi as first-line treatment, except in patients with renal calculi bigger than 30 mm in diameter. Copyright (C) 2001 S. Karger AG, Basel

The physics of stone skipping

The motion of a stone skimming over a water surface is considered. A simplified description of the collisional process of the stone with water is proposed. The maximum number of bounces is estimated by considering both the slowing down of the stone and its angular stability. The conditions for a successful throw are discussed.Comment: 7 pages, 5 figures (to appear in American Journal of Physics