Macroscopic Fragments Research Articles

Dynamic behaviors and bolt-strengthening effect of sand-powder 3D printing rock analog under static and dynamic coupled loading

In deep mining, surrounding rock mass are subjected to high in-situ stress and dynamic loading, which leads to the difficulties in maintaining the roadway stability. Therefore, it is important to investigate the mechanical characteristics of rock bolts and their ability to enhance stability when exposed to static and dynamic coupled loading (SDCL). 3D printing technology can effectively address the challenges of preparing weak rock specimens and overcoming high variability. Consequently, the Split Hopkinson pressure bar (SHPB) is used to conduct SDCL testing on 3D printing specimens with varying bolted lengths. The similarity in mechanical performance between sand-powder 3D printed specimens and natural coal specimens has been validated. The rock dynamic characteristics with different bolted lengths under SDCL of specimens were explored. The macroscopic fragmentation and microscopic electron microscope scanning were used to reveal the dynamic failure characteristics of specimens. The study shows that static, dynamic and combined strength are positively correlated with bolted length. The dynamic strength is negatively correlated with the axial stress, and the combined strength initially increases and then subsequently decreases as the axial stress increases. The dynamic strength and the combined strength are positively correlated with the impact pressure. Efficient prevention of specimen fracture was achieved by increasing the length of the bolted connection. It can be found that at the meso-scale, when the specimen is only under the static loads, the cross-section particles are fractured along particle bonding, and under the SDCL, there are fractured along particle bonding and fractured through particle. The conclusions obtained can offer a foundation for conducting dynamic rock mechanics experiments using sand-powder 3D printed specimens and for controlling the surrounding rock in dynamic pressure roadways.

Dynamic mechanical response and fracture mechanism of granite with structural plane containing planar and circular filling simultaneously: The influence of extension length

Weakly filled structural planes are an important influence on the stability control of engineering rock mass. Weak fillings with different geometrical characteristics are randomly distributed in the natural rock mass. To investigate the dynamic mechanical response and fracture mechanism of granite containing both planar and circular weak filling, the Split Hopkinson Pressure Bar (SHPB) experimental system was used to conduct the dynamic impact test. In this paper, the dynamic mechanical properties, the fracture process, the energy evolution and the micro-morphological characteristics of the fragments are mainly analyzed. The results show that: (1) the dynamic uniaxial compressive strength (DUCS), peak strain, and deformation modulus are synergistically affected by the extension length (L) of planar filling and strain rate. The presence of planar weak filling leads to a decrease in strain rate dependence while weakening the specimens' DUCS, and improves the overall synergistic deformation capacity of the specimen. (2) Strain rate and L jointly affect the energy distribution and evolution characteristics of the specimen; L has an enhancement effect on the distribution of reflected energy and a weakening effect on the distribution of transmitted energy. The effect of L on the dissipation of energy is transformed by the strain rate. The strain rate and L are the dominant factors in the variability of stress waveform conversion. (3) At a low strain rate, L has a positive effect on the intensification of the degree of fragmentation, however, at a high strain rate, the effect is characterised by a shift between positive and negative. The degree of fragmentation has a strain rate effect. As L increases, L has a “negative effect” on the “strain rate effect” that affects the degree of fragmentation. (4) The degree of fragmentation of macroscopic fragments is closely related to the energy dissipation density, the relationship between the two appears as a logarithmic function change. The presence of weak filling does not significantly change the microscopic morphology of granite fragments. The loose and porous microstructure of gypsum is the main reason for the altered propagation characteristics of the stress waves.

Computation of a possible Tunguska’s strewn field

On June 30, 1908, at about 0h 14.5 m UTC, the Tunguska Event occurred, most likely caused by the fall of a small stony asteroid of about 50–80 m in diameter over the basin of the Tunguska River (Central Siberia). The first expedition was made by the geologist Leonid Kulik 19 years after the event, and macroscopic meteorites have never been found around epicenter. In this paper, we want to establish whether stony macroscopic fragments could have survived the TCB’s airburst (Tunguska Cosmic Body) and where they might have fallen. For this purpose, we have implemented a fall model to describe the mass ablation, pancake expansion, airburst and fragments’s dark flight. In our scenario, the fragments have a higher mean strength than the main body due to Weibull’s law. The results, for a TCB with a kinetic energy of 15 Mt, atmospheric entry speed in the range of 11–20 km/s, trajectory inclination of 35° and average strength in the range of 3–70 MPa, tell us that for a macroscopic fragment with a mean strength between 14–85 MPa would be possible to survive the high pressure and temperature airburst to reach the ground. The falling speed of the fragments is in the range of 0.8–0.5 km/s, which favored their burial in the permafrost. The range of mean strength values for the TCB’s macroscopic fragment appears physically plausible if we consider the fall of Carancas in 2007, with an estimated strength of 20–40 MPa. So our possible strewn field, computed for a typical fragment’s speed of 10±3 km/s, is located about 11 km North-West from the epicenter, with an area of about 140km2. Finally, Cheko Lake, which by some authors is considered an impact crater, falls about 3.5 km outside the strewn fields at 3 sigma level and it is unlikely that it could be a real impact crater: only if the TCB’s trajectory had an azimuth in the range 150∘–180∘ would be in the strewn field area, but this is not consistent with the most likely trajectory azimuth.

Physical Properties of the Young Asteroid Pair 2010 UM26 and 2010 RN221

The main belt asteroids 458271 (2010 UM26) and 2010 RN221 share almost identical orbital elements, and currently appear as comoving objects ∼30″ apart in the plane of the sky. They are products of the breakup of a parent object, or the splitting of a binary, with a separation age measured in decades rather than thousands or millions of years as for most other asteroid pairs. The nature of the precursor body and the details of the breakup and separation of the components are unknown. We obtained deep, high-resolution imaging using the Hubble Space Telescope to characterize the pair and to search for material in addition to the main components that might have been released upon breakup. The primary and secondary have absolute magnitudes H = 17.98 and 19.69, respectively, and effective diameters 760 and 350 m (assuming geometric albedo 0.20). The secondary/primary mass ratio is 0.1, assuming equal densities. Time-series photometry shows that the primary rotates with period ∼5.9 hr and has a small photometric range (0.15 mag), while the period of the secondary is undetermined (but ≳20 hr) and its lightcurve range is at least 1 mag. The primary rotation period and component mass ratio are consistent with a simple model for the breakup of a rotationally unstable precursor. However, unlike other observationally supported instances of asteroid breakup, neither macroscopic fragments nor unresolved material are found remaining in the vicinity of this asteroid pair. We suggest that the pair is a recently dissociated binary, itself formed earlier by rotational instability of 2010 UM26.

Breaking behavior and stress distribution of T12A hard steel core penetrating ceramic/aluminum alloy lightweight composite armor

The armor-piercing incendiary (API) round inflicts significant damage to light armor. This article conducts penetration experiments on lightweight ceramic composite armor using 12.7 mm API rounds. The Rosin-Rammer distribution model is used to analyze the macroscopic fragmentation characteristics of the core, and the SEM is used to analyze the fracture surface of the bullet core after fragmentation at the microscopic level. Numerical simulations are also used to verify and expand the material parameters. The experimental results show that as the penetration velocity increases, the average feature size of the core decreases, indicating an increase in the degree of fragmentation of the core. The fragments generated by the fragmentation can be almost completely restored. The main fracture form is the brittle crushing fracture of the head of the projectile, while the tail and body of the projectile are basically intact, and the fracture surface is mainly a 45° shear fracture and radial platform-like tensile fracture.At the microscopic level, SEM images show that the material fracture mainly occurs in the form of radial cleavage shear fracture and river patterned tensile-shear fracture. The numerical simulation results show that as the penetration velocity increases, the energy dissipation of the core continuously increases. The main energy dissipation process of the core during penetration occurs during the contact with the ceramic cone, accounting for 66.48 % of the total energy loss, while the mass of the core remains almost unchanged during the interaction with the aluminum alloy.In addition, the experiment is verifiedusing different working conditions at different angles, confirming that the "unequal tearing" of the aluminum alloy backing plate is caused by the inclination of the penetration angle. It was also found that the penetration efficiency and destructive capability of the API round are significantly reduced when there is an angled penetration.

Dynamic properties and fragmentation mechanism of cemented tailings backfill with various particle size distributions of aggregates

The stability of cemented tailings backfill (CTB) is susceptible to dynamic loading from excavation or blasting. In this study, we investigate the strain rate and particle size distribution of aggregate effects on mechanical properties and fragmentation mechanism of cemented tailings backfill, in which the gradations of aggregate particles satisfy the Talbot gradation theory. The characteristic stress–strain curves, dynamic peak compression strength (DPCS), energy variations, macroscopic fragmentation characteristics and microstructure characteristics of CTB with various strain rates and gradations of aggregate particles are investigated by split Hopkinson pressure bar (SHPB), scanning electron microscope (SEM), and fragment distribution of CTB after impact. The results show that strain rate has a linear increase on both DPCS and total input energy but a negative correlation on the average particle size of fragments λ. A decrease in the average particle size means an increase in the degree of damage. The relationship between the aggregate grade and the DPCS of the CTB is approximated as a quadratic function and the gradation Talbot index of 0.5 has the best DPCS, the least dissipated energy, the lowest degree of fragmentation and the densest microstructure, which means it has the best dynamic mechanical properties and resistance to fragmentation mechanism. These results can provide an essential reference for the design of the underground mining backfill.

Late Failure of a Polyethylene Unicompartmental Knee Insert -Retrieval Analysis Protocol and Results

This study reports the investigation of a degraded polyethylene insert retrieved after the catastrophic failure of a mobile bearing knee implant, occurred after a traumatic event and leading to a late revision. Understanding wear mechanisms of polyethylene components is important to improve the implants for joint replacement. This model of unicompartmental arthroplasty, due to its mobile, congruent insert and design, has the potential to attain low rates of wear, leading to an improved survival of the prosthesis over fixed-bearing knee implants. During the surgical technique, however, it is critical to avoid any source of impingement or incongruent articulation, as this are associated with increased rates of polyethylene wear and may contribute to the early necessity for revision surgery. The investigated insert presented a macroscopic fragmentation, surface and bulk defects and debris. Characterization of the retrieved polyethylene implant fragments was performed by macroscopic examination, by scanning electron microscopy and Fourier transform infrared spectroscopy. Due to a systematic retrieval analysis according to current standards, we can question that, in our case, third body wear is rarely pure bone or pure cement debris related but a combination of the two mentioned. The combination enhanced contribution of polyethylene debris in severe wear initiation and progression. Complete examination of the explants exhibiting breakage or severe wear may help in understanding pathogenic ways of failure in unicompartmental knee.

A 1900 Year Sediment Record Suggests Recent Establishment of Black Mangrove (Avicennia Germinans) Stands within a Salt Marsh in St. Augustine, Florida, USA

Salt marshes and mangroves are currently being affected by rising temperatures. Mangroves thrive below −29° N latitude in Florida, USA, and have a low tolerance for extreme cold events, whereas salt marshes dominate further north. One potential effect of climate change is a reduction in the frequency of extreme cold events, which may lead to mangrove expansion into salt marsh systems. Our research identified sediment proxy indicators of salt marsh and mangrove environments. These indicators were applied to soil cores from intertidal wetlands near the current northern limit of mangrove presence on the east coast of Florida, to determine if mangrove expansion into salt marsh environments has precedence in the deeper past. Our findings suggest that mangrove and salt marsh sediments can be distinguished using a combination of stable carbon isotope ratios of sedimentary organic matter and macroscopic plant fragments, and our results showed that a mangrove stand that we cored established only recently. This result is consistent with other work in the southeastern United States that suggests that mangroves established at the current boreal limit only recently after the end of the Little Ice Age, and that the current mangrove expansion may be fueled by anthropogenic climate change.

Microscopic and Macroscopic Fragmentation Characteristics under Hypervelocity Impact Based on MD and SPH Method.

This work investigates the difference in the fragmentation characteristics between the microscopic and macroscopic scales under hypervelocity impact, with the simulations of Molecular Dynamics (MD) and Smoothed Particle Hydrodynamics (SPH) method. Under low shock intensity, the model at microscopic scale exhibits good penetration resistance due to the constraint of strength and surface tension. The bullet is finally embedded into the target, rather than forming a typical debris cloud at macroscopic scale. Under high shock intensity, the occurrence of unloading melting of the sample reduces the strength of the material. The material at the microscopic scale has also been completely penetrated. However, the width of the ejecta veil and external bubble of the debris cloud are narrower. In addition, the residual velocity of bullet, crater diameter and expansion angle of the debris cloud at microscopic scale are all smaller than those at macroscopic scale, especially for low-velocity conditions. The difference can be as much as two times. These characteristics indicate that the degree of conversion of kinetic energy to internal energy at the microscopic scale is much higher than that of the macroscopic results. Furthermore, the MD simulation method can further provide details of the physical characteristics at the micro-scale. As the shock intensity increases, the local melting phenomenon becomes more pronounced, accompanied by a decrease in dislocation atoms and a corresponding increase in disordered atoms. In addition, the fraction of disordered atoms is found to increase exponentially with the increasing incident kinetic energy.

Effects of dynamic strain rate on the energy dissipation and fragment characteristics of cross-fissured rocks

Internal initiation and propagation of micro cracks in rock materials might result in macroscopic fragmentation and energy dissipation under dynamic strain rate. Understanding the internal mechanism of rock failure and energy consumption is significant in assessing the stability of engineering rock mass under dynamic disturbance. This study experimentally investigated the energy dissipation and fragment distribution of rock specimens containing symmetrical and asymmetrical cross fissures under static and dynamic loadings. Our results reveal that the dynamic strength of rock specimens evidently increases with increasing strain rate, while the dynamic elastic modulus does not depend on the loading rate. For a given dynamic strain rate, the rock specimens containing asymmetrical cross fissures (one of the fissures had a relatively large dip angle) had higher dynamic strengths than those containing symmetrical cross fissures. During loading process, tensile cracks and shear cracks significantly affect the failure patterns of cross-fissured rock specimens under static and dynamic loadings, respectively. All the cross-fissured specimens show similar “X” shaped shear failure mode regardless of fissure configuration subjected to dynamic strain rate. The cross-fissured rock specimens with higher strain rates feature smaller location parameter and scale parameter of the fragment size distribution by GEV fitting. The fractal dimension of cross-fissured specimens show an evident loading rate dependence, and the size distribution of the fragments in asymmetrically cross-fissured specimens under dynamic loading is most homogeneous. The dissipated energy density of all the rock specimens obviously increase as the dynamic strain rate increases, while the energy utilization efficiency is less affected by the strain rate.

Experiments on the microscopic damage of coal induced by pure water jets and abrasive water jets

Microscopic damage and macroscopic fragmentation are induced in rocks when they are impacted by water jets. A combination of macroscopic and microscopic methods was developed into an effective way of revealing the mechanism underlying rock breaking. Based on Computed Tomography (CT) and digital image processing, this paper proposes a quantitative approach to study the microscopic damage induced by water jets on coal. 3D reconstructions of induced damage filed were established by segmenting the greyscale slices. Relying on the established 3D reconstructions, the distributions of the induced damage in the horizontal and vertical directions were discussed. The results show that the distribution range of microscopic damage induced by pure water jets was significantly larger than that induced by abrasive jets due to different erosion mechanisms. Furthermore, the damage induced by both pure water jets and abrasive jets decreased as the punching depth increased, which resulted from the energy consumption caused by the resistance of the mixture composed of the initial arrival liquid and the coal debris.

Macroscopic Magnetic Anisotropy Induced by the Combined Control of Size, Shape and Organization of NiFe Prussian Blue Analog Nanoparticles in an Ordered Mesoporous Silica Monolith

AbstractIntegration of coordination polymers and metal–organic frameworks into real applications requires a processing step at the nanoscale. However, their synthesis in the form of nanoparticles with controlled size, shape and organization remains a challenge faced by diverse scientific communities. Ordered mesoporous silica monolith with 2D‐hexagonal structure of the mesopores is used to form ferromagnetic NiFe Prussian blue analog (PBA) nanoparticles with anisotropic shape. The PBA nanowires formed within the nanochannels of the monolith are made of single chains of nanocrystals. Furthermore, when using an ordered mesoporous silica monolith instead of the more frequently used mesoporous powders a parallel organization of the pores is achieved over whole macroscopic fragments of the monolith. A 1×1×1 mm3 fragment of monolith exhibits a remarkably strong anisotropy in its magnetic properties, arising from unprecedented magnetic dipolar interaction along the chains of coordination nanocrystals, which is spread to the macroscopic scale thanks to the long‐range organization of the pores. As various confined chemistries can be developed within the ordered porosity of such monolith, this tool opens up new opportunities for the development of original nanostructured materials exhibiting anisotropy in their properties at the macroscopic scale.

The geological cycle of plastics and their use as a stratigraphic indicator of the Anthropocene

The rise of plastics since the mid-20th century, both as a material element of modern life and as a growing environmental pollutant, has been widely described. Their distribution in both the terrestrial and marine realms suggests that they are a key geological indicator of the Anthropocene, as a distinctive stratal component. Most immediately evident in terrestrial deposits, they are clearly becoming widespread in marine sedimentary deposits in both shallow- and deep-water settings. They are abundant and widespread as macroscopic fragments and virtually ubiquitous as microplastic particles; these are dispersed by both physical and biological processes, not least via the food chain and the ‘faecal express’ route from surface to sea floor. Plastics are already widely dispersed in sedimentary deposits, and their amount seems likely to grow several-fold over the next few decades. They will continue to be input into the sedimentary cycle over coming millennia as temporary stores – landfill sites – are eroded. Plastics already enable fine time resolution within Anthropocene deposits via the development of their different types and via the artefacts (‘technofossils’) they are moulded into, and many of these may have long-term preservation potential when buried in strata.

Tarkwaian Deposits of the Birimian Belt of Houndé: Petrological, Structural and Geochemical Study (Burkina-Faso, West Africa)

The Tarkwaian deposits of the Birimian belt of Hounde are located in the Baoule-Mossi Paleoproterozoic area of the West African Craton. The sedimentary units consist of sandstone heterometric pelitic feldspthic sandstone with locally interbedded breccias, puddings and polygenic conglomerates. Lithic pebbles and macroscopic fragments that are similar to vein type originated quart castings and andesitic-dacitic projections, felsic sub-volcanic rocks evolving from microdioritic to microgranite composition are detected in terrigenous sediments. The volcanic packages form a linear strip composed of basic to intermediate rocks and andesitic to dacitic volcaniclastites. The contacts between these units are not clearly exposed but the different facies between the polygenic conglomerates and sandstones show discordant tectonic contacts with the Tarkwaian and the Birimian. The geochemical nature of these Tarkwaian formations is strongly influenced by the relative decline of the dominant quartz of feldspars and phyllites. The improperly classified and immature feldspathic sandstones show context affinities of island arc probably dictated by Birimian lithic products. Sedimentologically, the cross-bedded stratification and the predominance of sandstone terrigenous lands indicate a deposition in a fluvio-deltaic hydrodynamic setting along intermontane Birimian rift. The similarities between these Tarkwaian formations and the typical Tarkwaian of the Tarkwa basin in Ghana are probably limited to petrographic and not stratigraphic aspects, which lead to likening them to flyscho?d or molassic tardi Birimian deposits.

Analysis of the time course of degradation for fully biobased nonwoven agricultural mulches in compost-enriched soil

The time course of degradation for biodegradable and fully biobased plastic agricultural mulches prepared from polylactic acid (PLA) and PLA–polyhydroxyalkanoate (PHA) blends using meltblown (MB) nonwovens processing technology in compost-enriched soil during a 45 week burial duration was investigated under controlled conditions in a greenhouse to better understand the underlying mechanism for degradation. Mulches underwent an initial 4 week period during which the tensile strength decreased by ≥ 60%. For MB-PLA, between weeks 4 and 12, the crystallinity increased and the molecular weight slightly increased. After 12 weeks, the molecular weight decreased linearly. At 28 weeks, the crystallinity increased significantly, corresponding to an observed increase of macroscopic fragmentation. For MB-PLA+PHA, the mass fraction of PHA decreased significantly (by 11.6%) during the first 4 weeks; subsequently; the PHA fraction decreased linearly. Between 17 and 22 weeks, a large increase of crystallinity for the PLA component and a decrease of molecular weight occurred. After 22 weeks, the molecular weight and crystallinity of PLA increased nearly linearly. These results suggest that during the first 4–12 weeks, microorganisms begin to utilize the more readily available components of the mulches as carbon sources: amorphous PLA regions and PHA for MB-PLA and PLA+PHA, respectively, and that microbial activity is greater and occurs more strongly for PHA. After the initial induction period, depolymerization occurs slowly and steadily for both MB plastic mulches.

Stability of spherically trapped three-dimensional Bose-Einstein condensates against macroscopic fragmentation

We consider spherically trapped Bose gases in three dimensions with contact interactions and investigate whether the Bose-Einstein condensate at zero temperature is stable against macroscopic fragmentation into a small number of mutually incoherent pieces. Our results are expressed in terms of a dimensionless interaction measure proportional to the Thomas-Fermi parameter. It is shown that while three-dimensional condensates are inherently much more stable against macroscopic fragmentation than their quasi-one- and quasi-two-dimensional counterparts, they fragment at a sufficiently large value of the dimensionless interaction measure, which we determine both fully numerically and semianalytically from a continuum limit of large particle numbers.

Assessing carnivore diet by faecal samples and stomach contents: a case study with Alpine red foxes

Abstract Research on the feeding habits of mammalian carnivores relies mainly on the analysis of stomach contents and faecal samples, but the outcomes of these two methods have only been compared in a few studies, with contrasting conclusions. In an Alpine area of NW Italy, we analysed both fox faeces collected along standardised transects, and the stomach contents of road-killed individuals. Faecal analysis involved the identification of macroscopic fragments, the identification of earthworm chaetae, and the assessment of relative volumes using Kruuk and Parish’s technique. Use of both methods indicated that the diet of the red fox included mainly fruit and mammals, but quantitative differences emerged. Garbage, birds, and cultivated fruit were overrepresented in the stomach contents, while earthworms, mammals, and wild fruit prevailed in the faecal samples. Logistic Regression Analysis suggested that the method of analysis was the main factor in determining the occurrence of food items in fox diet. Nonetheless, evidence suggests that road-killed foxes may include a disproportionately high percentage of synanthropic individuals and therefore be biased towards anthropogenic food. Results suggest that by using Kruuk and Parish’s technique, the main limitation of faecal analysis, i.e. the inaccurate estimation of the relative volume of each food item, can be overcome.

The impact and recovery of asteroid 2008 TC3

In the absence of a firm link between individual meteorites and their asteroidal parent bodies, asteroids are typically characterized only by their light reflection properties, and grouped accordingly into classes. On 6 October 2008, a small asteroid was discovered with a flat reflectance spectrum in the 554-995 nm wavelength range, and designated 2008 TC(3) (refs 4-6). It subsequently hit the Earth. Because it exploded at 37 km altitude, no macroscopic fragments were expected to survive. Here we report that a dedicated search along the approach trajectory recovered 47 meteorites, fragments of a single body named Almahata Sitta, with a total mass of 3.95 kg. Analysis of one of these meteorites shows it to be an achondrite, a polymict ureilite, anomalous in its class: ultra-fine-grained and porous, with large carbonaceous grains. The combined asteroid and meteorite reflectance spectra identify the asteroid as F class, now firmly linked to dark carbon-rich anomalous ureilites, a material so fragile it was not previously represented in meteorite collections.

Marrow emboli in acute chest syndrome: artifact or etiology?

A black man with HbSC sickle cell disease (SCD) complained of severe unrelenting chest, back, and abdominal pains for 1 hour. He had experienced several sickle cell crises in the past 2 years. Initial vital signs were BP 150/100, HR 90/ min, and RR unlabored, 30/min. He was diaphoretic, but otherwise his physical examination was unremarkable. Admitting lab values wereWBCs 9.2 x 10 9 per L, PLTs 140 x 10 9 per L, Hb 9.9 g per dL, and Hct 28.4 percent. He was given morphine. Within 24 hours after admission, his WBCs had increased to 23.1 × 10 9 per L with 17 percent bands; Hb decreased to 6.8 g per dL, Hct to 19.4 percent, and PLTs to 72 x 10 9 per L; and his peripheral blood smear contained 39 nucleated RBCs per HPF. Two units of RBCs were subsequently transfused because of his increasing anemia. His blood pH decreased to 6.9 from 7.38 within 4 hours of death while being ventilated with O 2 . He died in respiratory failure 30 hours after admission. Antibody testing for parvovirus B19 was not completed until after death, but the test was positive for the presence of both IgM and IgG antibodies to the virus. A clinical hospital autopsy was performed at the local hospital. At autopsy each lung weighed 1000 g and contained large, 4- to 10-mm macroscopic fragments of necrotic marrow, nearly obstructing several pulmonary arterial branches (Fig. A, macroimage of HE Fig. B, 4x photomicrograph of marrow embolus; Fig. C, 20x photomicrograph of megakaryocyte in necrotic marrow fragment) as well as paravertebral venous plexus vessels. Multiple large areas of necrosis were present within vertebral thoracic and lumbar medullary marrow spaces. This case was evaluated on referral of the medical record and autopsy slides. Acute chest syndrome (ACS), commonly developing in patients with HbSS and occasionally in patients with HbSC, is the leading cause of death and hospitalization in patients with SCD. Although the etiology of ACS remains unclear, pulmonary fat embolism, including microscopically sized marrow emboli, have been found. Autopsy pathologists frequently regard microscopic marrow and fat emboli to be the result of vigorous cardiopulmonary resuscitation, and consequently the finding of such emboli in a patient with ACS may be inadvertently dismissed as an incidental non-pathologic finding. ACS is associated with the triad of SCD, parvovirus infection, and marrow fat embolism. The origin of pulmonary and systemic fat emboli found in ACS, and appropriate diagnostic tests for that fat, remains speculative. Large, macroscopic necrotic emboli arising from the patient's vertebral marrow, presumably caused by vascular occlusion within his hyperplastic marrow by sickled RBCs, played a significant role in the development of ACS and his subsequent respiratory demise. In patients with SCD and parvovirus infections, sudden death from ACS can be caused by obstruction of pulmonary vessels with large macroscopic fragments of marrow, which are not artifacts of vigorous cardiopulmonary resuscitation.

Pathway from Condensation via Fragmentation to Fermionization of Cold Bosonic Systems

For small scattering lengths, cold bosonic atoms form a condensate the density profile of which is smooth. With increasing scattering length, the density gradually acquires more and more oscillations. Finally, the number of oscillations equals the number of bosons and the system becomes fermionized. On this pathway from condensation to fermionization intriguing phenomena occur, depending on the shape of the trap. These include macroscopic fragmentation and coexistence of condensed and fermionized parts that are separated in space.