Modeling and experimentation of bone drilling forces

Prediction and control of bone drilling forces are critical to the success of many orthopaedic operations. Uncontrolled and large forces can cause drill-bit breakage, drill breakthrough, excessive heat generation, and mechanical damage to the bone. This paper presents a mechanistic model for prediction of thrust forces and torques experienced during bone drilling. The model incorporates the radially varying drill-bit geometry and cutting conditions analytically, while capturing the material and friction properties empirically through a specific energy formulation. The forces from the chisel edge are modeled by considering the indentation process that occurs in the vicinity of the drill-bit axis. A procedure is outlined to calibrate the specific energies, where only a small number of calibration experiments are required for a wide range of drilling conditions and drill-bit geometry. The calibration parameters for the cortical portions of bovine tibia are identified through drilling tests. Subsequently, a series of validation tests are conducted under different feed rates and spindle speeds. The thrust forces and torques were observed to vary considerably between bones from different animals. The forces from the model were seen to match well with those from the experimentation within the inherent variations from the bone characteristics. The model can be used to select favorable drilling conditions, to assist in robotic surgeries, and to design optimal orthopaedic drill bits.     

The approximate entropy of the electromyographic signals of tremor correlates with the osmotic fragility of human erythrocytes

Background  

The main problem of tremor is the damage caused to the quality of the life of patients, especially those at more advanced ages. There is not a consensus yet about the origins of this disorder, but it can be examined in the correlations between the biological signs of aging and the tremor characteristics.     

Heat-shock responsive genes identified and validated in Atlantic cod (Gadus morhua) liver, head kidney and skeletal muscle using genomic techniques

Background

The Mongolian gerbils are a good model to mimic the Helicobacter pylori -associated pathogenesis of the human stomach. In the current study the gerbil-adapted strain B8 was completely sequenced, annotated and compared to previous genomes, including the 73 supercontigs of the parental strain B128.

Results

The complete genome of H. pylori B8 was manually curated gene by gene, to assign as much function as possible. It consists of a circular chromosome of 1,673,997 bp and of a small plasmid of 6,032 bp carrying nine putative genes. The chromosome contains 1,711 coding sequences, 293 of which are strain-specific, coding mainly for hypothetical proteins, and a large plasticity zone containing a putative type-IV-secretion system and coding sequences with unknown function. The cag -pathogenicity island is rearranged such that the cag A-gene is located 13,730 bp downstream of the inverted gene cluster cag B- cag 1. Directly adjacent to the cag A-gene, there are four hypothetical genes and one variable gene with a different codon usage compared to the rest of the H. pylori B8-genome. This indicates that these coding sequences might be acquired via horizontal gene transfer. The genome comparison of strain B8 to its parental strain B128 delivers 425 unique B8-proteins. Due to the fact that strain B128 was not fully sequenced and only automatically annotated, only 12 of these proteins are definitive singletons that might have been acquired during the gerbil-adaptation process of strain B128.

Conclusion

Our sequence data and its analysis provide new insight into the high genetic diversity of H. pylori -strains. We have shown that the gerbil-adapted strain B8 has the potential to build, possibly by a high rate of mutation and recombination, a dynamic pool of genetic variants (e.g. fragmented genes and repetitive regions) required for the adaptation-processes. We hypothesize that these variants are essential for the colonization and persistence of strain B8 in the gerbil stomach during inflammation.