Extreme Comminution Research Articles

Capillary suction predictions in granular materials subjected to 1D compression and triaxial loading with emphasis on projectile penetration

The role of partial saturation in penetration resistance of projectiles in granular materials is not clear due to experimental constraints imposed by high cost and special considerations in equipment design. In this work, granular material near the tip and far-field of the projectile is numerically simulated based on 1D compression and triaxial stress paths, respectively, using the finite discrete element method. The crushing of grains in 1D compression simulations is implemented by pre-inserting cohesive interface elements in regular finite element mesh. The capillary suction is numerically predicted by extracting the deformed granular assembly microstructure at different loading steps as an input to the pore morphology method. The results demonstrate the development of high capillary suction in 1D compression loading due to the significant crushing of grains. The evolution of capillary suction is negligible during triaxial loading compared to the 1D compression loading. This suggests that future simulations related to projectile penetration in partially saturated granular materials should account for coupled hydromechanical effects near the tip whereas the far-field can be approximated as a dry material. Finally, the capillary suction corresponding to extreme comminution near the projectile tip is estimated from a 3D assembly of spherical grains with a mean grain size of 1 µm.

Bead milling disruption kinetics of microalgae: Process modeling, optimization and application to biomolecules recovery from Chlorella sorokiniana

Industrial development of microalgae biomass valorization relies on process optimization and controlled scale-up. Both need robust modeling: (i) for biomass production and (ii) for integrated processes in the downstream processing (DSP). Cell disruption and primary fractionation are key steps in DSP. In this study, a kinetic model, including microalgal cell size distribution, was developed for Chlorella sorokiniana disruption in continuous bead milling. Glass beads of 0.4 mm size at impeller tip velocity of 14 m.s−1 were used as optimal conditions for efficient cell disruption. These conditions allowed faster disruption of big cells than small ones. A modified expression of the Stress Number, including cell size effect, was then proposed and validated.Separation of starch, proteins and chlorophyll by mild centrifugation was studied as function of the disruption parameters. Low energy consumption conditions led to extreme comminution. An intermediate zone drew attention for allowing moderate energy consumption and efficient metabolites separation by centrifugation.

Plate Fixation of Talus Fractures: Where, When, and How?

Talus fractures are rare orthopedic injuries. Surgical fixation is challenging for treating surgeons. The clear majority of fractures require operative treatment. The indication and use of plates in fixation of talus fractures are reviewed. Specific applications including fractures of the lateral process, posterior fractures, extreme comminution, bone grafting, and spring plating to hold key segments are reviewed in this article.

Management of complex intertrochanteric fractures of the femur in elderly patients – dynamic hip screws or proximal femoral nails or arthroplasty

<p class="abstract"><strong>Background:</strong> Ideal management of intertrochanteric fractures in elderly individuals has been debated for several years. Due to difficulty in obtaining anatomical reduction, management of the complex intertrochanteric fractures in elderly patients is challenging and controversial<span lang="EN-IN">.</span></p><p class="abstract"><strong>Methods:</strong> In the present study prospective comparative evaluation has been done between dynamic hip screws<strong> (</strong>DHS), proximal femoral nail (PFN) and bipolar hemiarthroplasty for overall clinical outcome of patients with unstable intertrochanteric fractures. The total numbers of patients were 90 with each group consisted of 30 patients.<strong></strong></p><p class="abstract"><strong>Results:</strong> Complication rate and requirement of revision surgery was more in DHS group but this was not found to be statistically significant. Harris Hip Score & hence the functional outcome was found to be more in PFN group as compared to DHS which was statistically significant. Bipolar hemiarthroplasty provides early full wieght bearing leading to better HHS at 6 weeks evaluation but almost similar score to PFN in long term<span lang="EN-IN">. </span></p><p class="abstract"><strong>Conclusions:</strong> PFN is better choice of fixation if good bone quality present while extremely osteoporotic patients or extreme comminution at fracture site favours bipolar hemiarthroplasty in elderly patients<span lang="EN-IN">.</span></p>

Silica gel formation during fault slip: Evidence from the rock record

Dynamic reduction of fault strength is a key process during earthquake rupture. Many mechanisms for causing coseismic weakening have been proposed based on theory and laboratory experiments, including silica gel lubrication. However, few have been observed in nature. Here we report on the fi rst documented occurrence of a natural silica gel coating a fault surface. The Corona Heights fault slickenside in San Francisco, California, is covered by a shiny layer of translucent silica. Microstructures in this layer show fl ow banding, armored clasts, and extreme comminution compared to adjacent cataclasites. The layer is composed of ~100 nm to 1 µm grains of quartz, hydrous crystalline silica, and amorphous silica, with 10‐100 nm inclusions of Fe oxides and ellipsoidal silica colloids. Kinematic indicators and mixing with adjacent cataclasites suggest the shiny layer was fl uid during fault slip. The layer therefore represents a relict silica gel that formed during fault motion, and which could have resulted in frictional instability. These observations confi rm that the silica gels formed in rock friction experiments do occur in natural faults and therefore that silica gel formation can act as a dynamic weakening mechanism in faults at shallow crustal conditions.

Origin of the Mt Ashmore structural dome, west Bonaparte Basin, Timor Sea

New insights into the 3D structure, composition and origin of the Mt Ashmore dome, west Bonaparte Basin, Timor Sea, are enabled by reprocessed seismic-reflection data and by optical microscopic, X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive spectrometry (EDS) and transmission electron microscopy (TEM) analyses of drill cuttings. The structural dome, located below a major pre-Oligocene post-Late Eocene unconformity and above a ∼6 km-deep-seated basement high indicated by marked gravity and magnetic anomalies, displays chaotic deformation at its core and a centripetal kinematic deformation pattern. A study of drill cuttings of Lower Oligocene to Lower Jurassic sedimentary rocks intersected by the Mt Ashmore 1B petroleum-exploration well reveals microbrecciation and extreme comminution and flow-textured fluidisation of altered sedimentary material. The microbreccia is dominated by aggregates of poorly diffracting micrometre to tens of micrometres-scale to sub-millimetre particles, including relic subplanar fractured quartz grains, carbonate, barite, apatite and K-feldspar. A similar assemblage occurs in fragments in basal Oligocene sediments, probably derived from the eroded top section of the dome, which protrudes above the unconformity. SEM coupled with EDS show the micrometre to tens of micrometres-scale particles are characterised by very low totals and non-stoichiometric compositions, including particles dominated by Si, Al–Si, Si–Ca–Al, Si–Al–Ca, Si–Mg, Fe–Mg–Ca, Fe–Mg and carbonate. XRD analysis identifies a high proportion of amorphous poorly diffracting material. TEM indicates internally heterogeneous, fragmented and recrystallised structure of the amorphous grains, which accounts for the low totals in terms of the high-volatile and porous nature of the particles. Another factor for the low totals is the uneven thin-section surfaces which affect the totals. No volcanic material or evaporites were encountered in the drillcore, militating against interpretations of the structure in terms of magmatic intrusion or salt diapirism. Such models are also inconsistent with the strong gravity and magnetic anomalies, which signify a basement high below the dome. An interpretation of the dome in terms of a central rebound uplift of an impact structure can not be proven due to the lack of shock metamorphic effects such as planar deformation features, impact melt or coesite. However, an impact model is consistent with the chaotic structure of the domal core, centripetal sense of deformation, microbrecciation, comminution and fluidisation of the Triassic to Eocene rocks. In this respect, an analogy can be drawn between the Mt Ashmore structural dome and likely but unproven impact structures formed in volatile (H2O, CO2)-rich sediments where shock is attenuated by high volatile pressure, such as Upheaval Dome, Utah. In terms of an impact hypothesis the Mt Ashmore dome is contemporaneous with a Late Eocene impact cluster (Popigai: D = 100 km, 35.7 ± 0.2 Ma; Chesapeake Bay: D = 85 km, 35.3 ± 0.1 Ma).

Comminuted fractures of the olecranon. Management by bone graft from the iliac crest and multiple tension-band wiring.

Between 1993 and 1999, we treated ten patients with comminuted fractures of the olecranon by multiple tension-band wiring and a graft from the iliac crest. Their mean age was 35 years (19 to 56). The mean follow-up was for 28.5 months (15 to 46) and the mean time to union of the fractures was four months (3 to 7). No patient reported difficulties with activities of daily living or symptoms of instability of the elbow. The mean flexion was to 135 degrees (125 to 145) with a mean flexion contracture of 15 degrees (10 to 30). The mean pronation was 70 degrees (60 to 80) and mean supination 79 degrees (70 to 90). Only three patients had mild pain and loss of strength. Five patients had excellent and five good results with a mean Broberg and Morrey index score of 94.5 points (84 to 100). Our results compare favourably with those previously reported and the technique is thought to be a practical alternative to plate fixation in fractures with extreme comminution.

Comminuted fractures of the olecranon

Between 1993 and 1999, we treated ten patients with comminuted fractures of the olecranon by multiple tension-band wiring and a graft from the iliac crest. Their mean age was 35 years (19 to 56). The mean follow-up was for 28.5 months (15 to 46) and the mean time to union of the fractures was four months (3 to 7). No patient reported difficulties with activities of daily living or symptoms of instability of the elbow. The mean flexion was to 135° (125 to 145) with a mean flexion contracture of 15° (10 to 30). The mean pronation was 70° (60 to 80) and mean supination 79° (70 to 90). Only three patients had mild pain and loss of strength. Five patients had excellent and five good results with a mean Broberg and Morrey index score of 94.5 points (84 to 100). Our results compare favourably with those previously reported and the technique is thought to be a practical alternative to plate fixation in fractures with extreme comminution.

Localized shock- and friction-induced melting in response to hypervelocity impact

Abstract The distribution of shock veins, friction melts and cataclastic rocks in complex impact craters reflects the response of target lithologies to varying rates of strain. Within the Sudbury impact structure, thin (<2 mm), anastomosing veins, which can define shatter cone surfaces, permeate the target rocks in a c. 15 km wide zone around the Sudbury igneous complex (SIC). A similar relationship exists within the Vredefort impact structure, with the additional association of the high-pressure SiO 2 polymorphs coesite and stishovite. These S- (shock-dominant) type pseudotachylytes are comparable with shock veins developed in meteorites. Both are considered to form primarily by shock compression-decompression during the contact and compression stage of the collision process. Larger, thicker (up to 1 km wide) friction melt bodies constitute pseudotachylytes formed by the extreme comminution of fault walls during rebound and gravitational collapse of the transient cavity. They also appear to define the concentric fault systems of multi-ring impact basins. These E- (endogenic-) type pseudotachylytes form during the modification stage of the cratering process and post-date S-type pseudotachylytes. At Sudbury, they occur up to 80 km beyond the SIC. E-type pseudotachylytes are formed by the same mechanism as pseudotachylytes in non-impact-related fault systems: frictional melting of fault walls during seismogenic slip. Those in impact structures can be large because the extreme displacements (several kilometres) facilitated by superfaults generate massive volumes of friction melt.

Unstable Metacarpal and Phalangeal Fracture Treatment with Screws and Plates

Plate and screw fixation of the metacarpals and phalanges has limited indications but can provide crucial assistance to the reconstructive hand surgeon in the treatment of complex fractures. Screws are indicated for unstable, long oblique or spiral fractures of the metacarpals and phalanges, intraarticular fractures with articular surface involvement in excess of 25% with or without comminution, and intraarticular condylar, T-condylar, and Y-condylar fractures. Plates at the metacarpal level are indicated for segmental defects with substance loss, fractures with extreme comminution, and unstable short oblique or transverse diaphyseal fractures. Plate fixation of phalangeal fractures is seldom necessary but helpful in treating segmental defects or extreme comminution of diaphysis or metaphysis as well as intraarticular T- or Y-condylar fractures. Screw and plate fixation at the metacarpal levels, when appropriately applied, renders rigid osteosynthesis while inflicting little to no interference on the surrounding soft tissues. Screws can be applied with little to no soft tissue interference throughout the proximal phalanx and proximal and distal aspects of the middle phalanx. Plate fixation for middle phalangeal fractures is limited to salvage situations for preservation of skeletal length. The essentials for successful use of implants are a hand surgeon well versed in a variety of internal fixation techniques including the Association for the Study of Internal Fixation (ASIF) technique of screw and plate fixation, a meticulous respect for, and protection of, the soft tissues, and a facility for delivery of functional aftercare.

Particle Size and Concentration Adjustments of Tomato Products for Howard Mold Count

The present AOAC method for mold counts of tomato products (44.096) provides no inter-product standardization of concentration among juice, sauce, paste, puree, and catsup; no intra-product standardization of concentration for juice, sauce, and catsup; and no adjustment for degree of comminution. Use of the official method, therefore, could result in an artificially increased mold count for products which have undergone extreme comminution. A new method was developed to adjust all products to the same concentration and grind them to a uniform particle size, thereby ensuring comparable mold counts on products produced by different processes. Collaborative study results showed equal repeatability for both the official and the proposed methods and a lower coefficient of variation for the proposed method.

A reconstruction operation for comminuted fracture of the upper third of the ulna

bIow striking the posterior surface of the upper third of the forearm whiIe the eIbow is in the position of ffexion, the force being directed upward toward the shotrIder. The resuIting bone injury is an anterior disIocation of the radia1 head with marked comminution of the upper third of the uIna and wide separation of the fragments. The action of the triceps tendon puIIs the oIecranon process upward, the shaft and the cornminuted fragments being driven anteriorIy. Fixation of these fragments by an intrameduIIary peg is usuaIIy unsatisfactory because of the short oIecranon fragment and extreme comminution of the shaft. It is diffrcuIt to maintain adequate fixation by means of wire because of the tendency of the radia1 head to disIocate anteriorIy, carrying with it the shaft and the cornminuted fragments. Overcoming this tendency by acute ffexion often causes embarrassment of the circmation, as there FIG. 2. Schematic drawing showing Steinman Pin directed through olecranon.