Size Reduction Pattern Research Articles

Variation of Burkholderia cenocepacia cell wall morphology and mechanical properties during cystic fibrosis lung infection, assessed by atomic force microscopy

The influence that Burkholderia cenocepacia adaptive evolution during long-term infection in cystic fibrosis (CF) patients has on cell wall morphology and mechanical properties is poorly understood despite their crucial role in cell physiology, persistent infection and pathogenesis. Cell wall morphology and physical properties of three B. cenocepacia isolates collected from a CF patient over a period of 3.5 years were compared using atomic force microscopy (AFM). These serial clonal variants include the first isolate retrieved from the patient and two late isolates obtained after three years of infection and before the patient’s death with cepacia syndrome. A consistent and progressive decrease of cell height and a cell shape evolution during infection, from the typical rods to morphology closer to cocci, were observed. The images of cells grown in biofilms showed an identical cell size reduction pattern. Additionally, the apparent elasticity modulus significantly decreases from the early isolate to the last clonal variant retrieved from the patient but the intermediary highly antibiotic resistant clonal isolate showed the highest elasticity values. Concerning the adhesion of bacteria surface to the AFM tip, the first isolate was found to adhere better than the late isolates whose lipopolysaccharide (LPS) structure loss the O-antigen (OAg) during CF infection. The OAg is known to influence Gram-negative bacteria adhesion and be an important factor in B. cenocepacia adaptation to chronic infection. Results reinforce the concept of the occurrence of phenotypic heterogeneity and adaptive evolution, also at the level of cell size, form, envelope topography and physical properties during long-term infection.

Physically based model of downstream fining in bedrock streams with lateral input

Bed load particles in bedrock streams receiving lateral input from hillslopes may or may not show a clear, monotonic pattern of size reduction in the downstream direction. Both abrasion and selective sorting may play important roles in generating downstream fining. The objective of this study is to develop a physically based model of downstream fining in bedrock streams with lateral input based on both processes. A surface‐based gravel transport relation for the size mixture is employed to account for the effect of selective sorting (differential transport). While the model produces silt and sand by abrasion, it is also assumed to loosely capture particle fracturing via a lumped abrasion coefficient embodied in Sternberg's law. The model is here tested against field data from Vieux Habitants River in Guadeloupe Island, which is located in the Caribbean Sea. The river shows clear downstream fining, and this pattern is captured reasonably well by the model. The model results indicate that abrasion (including fracturing) is solely responsible for the downstream fining pattern for most of the study reach of the Vieux Habitants River. Sensitivity analysis of the model has also been performed. The model results suggest that, in general, selective sorting by differential transport can play a role in downstream fining only in cases of streams with relatively fine gravel sizes and lower slopes. The results also indicate that abrasion (including fracturing) and selective sorting can be equally important for downstream fining in bedrock rivers. The results also suggest that future work should explicitly consider fracturing (comminution) separately from abrasion (wear) rather than lumping them in a Sternberg‐type coefficient.

Assessment of Polymer/Bioactive Glass-Composite Microporous Spheres for Tissue Regeneration Applications

Conformable scaffold materials capable of rapid vascularization and tissue infiltration would be of value in the therapy of inaccessible wounds. Microporous spheres of poly(D,L-lactide-co-glycolide) (PLGA) containing bioactive glass (BG) were prepared using a thermally induced phase separation (TIPS) technique, and the bioactivity, in vitro degradation, and tissue integration of the microporous spheres were assessed. Microporous spheres containing 10% (w/w) BG stimulated a significant increase in vascular endothelial growth factor secretion from myofibroblasts consistently over a 10-day period (p < 0.01) compared with the neat PLGA microporous spheres. The microporous spheres degraded steadily in vitro over a 16-week period, with the neat PLGA microporous spheres retaining 82% of their original weight and microporous spheres containing 10% (w/w) BG retaining 77%. Both types of microporous spheres followed a similar pattern of size reduction throughout the degradation study, resulting in a 23% and 20% reduction after 16 weeks for the neat PLGA microporous spheres and PLGA microporous spheres containing 10% (w/w) BG, respectively (p < 0.01). After in vivo implantation into a subcutaneous wound model, the TIPS microporous spheres became rapidly integrated (interspherically and intraspherically) with host tissue, including vascularization of voids inside the microporous sphere. The unique properties of TIPS microporous spheres make them ideally suited for regenerative medicine applications where tissue augmentation is required.

Size variation of conodont elements of the Hindeodus–Isarcicella clade during the Permian–Triassic transition in South China and its implication for mass extinction

Based on the analysis of thousands of conodont specimens from the Permian –Triassic (P–T) transition at Meishan (the GSSP of P–T Boundary) and Shangsi sections in South China, this study investigates the size variation of Hindeodus and Isarcicella P1 elements during the mass extinction interval. The results demonstrate that Hindeodus– Isarcicella underwent 4 episodes of distinct size reduction during the P–T transition at the Meishan Section and 2 episodes of size reduction in the earliest Triassic at Shangsi. The size reductions at Meishan took place at the junctions of beds 24d/24e, 25/26, 27b/27c and 28/29, and at the junctions of beds 28/29c and 30d/31a at Shangsi. The two earliest Triassic size reduction episodes were correlative between the two sections. These changes coincide with some important geological events such as eustatic sea-level changes, anoxic events, carbon isotope oscillations, miniaturization of brachiopods and microbial changes. Through detailed investigation of the palaeoenvironment and the palaeoecology of Hindeodus– Isarcicella, the authors propose that the main causes of the size reduction was a sharp decline of food availability because of the mass extinction and the anoxic event during the P/T transition. The pattern of size reduction supports suggestions that the end-Permian mass extinction was multi-episodal, consisting of 3 extinction events rather than a single catastrophic event.

The evolution of a mineral liberation model by the repetition of a simple random breakage pattern

Mineral liberation models of multi-mineral particulate materials are described by functions of continuous or discrete random variables such as the size and the grade of their particles. In the present work that describes a binary system both size and grade are treated as discrete variables and particles are classified into size and grade classes accordingly. Initially the present work develops a model to predict the distribution of particles of the same size class into the different grade classes. This distribution gives the liberation status of each size class and if combined with the size distribution of the particulate material it produces the total liberation spectrum. Initially the process defines an equivalent size, below which liberation begins, called “critical liberation size”. It then describes a sequential size reduction pattern used only in order to relate the size class of the child particles to the probability of falling into any available grade class. This process defines the liberation model. The size reduction pattern accepted dictates by itself the size ratio of the equivalent size classes used. However this pattern is not used for the prediction of the volume-size (or mass-size) distribution of the final particulate material. It is believed that any size reduction model using selection and breakage functions independent of the particle grade in combination with the proposed liberation model can be used to predict the total liberation spectrum of the final product.

Effect of wheat bran ball-milling on fragmentation and marker extractability of the aleurone layer

Bran (branml) obtained by roller milling of soft (Scipion) and hard (Baroudeur) wheat cultivars was further ball-milled for increasing times and the observed particle size distribution expressed as a dispersion index. Bran (branhi) and aleurone layers were also hand-isolated from the same grains and the pattern of size reduction during ball-milling were compared with branml. Branml and branhi were found to fracture more rapidly than isolated aleurone layers due to the presence of the highly friable pericarp and the possible mechanical constraints due to tissues surrounding the aleurone layer. Previously identified markers of the aleurone layer cell contents (phytates) and cell walls (p-coumaric acid) were used to determine their water extractabilities from ball-milled samples and the state and degree of dissociation of the aleurone layer, either as an isolated tissue or within branml and branhi. The results suggest that ball-milling rapidly induces fractures in walls of cells in the aleurone layer. The partial opening of the cells in the aleurone layer allowed extraction of most (≈70%) of the water-extractable phytates, even though their mean particle size was much larger than the dimensions of the cells. A further increase in extractability of phytates was observed when the particle size was reduced below the aleurone cell dimensions. Although much less soluble, p-coumaric acid followed a similar trend to phytates. The different behaviour of branml and branhi was consistent with a weakening effect of the tissues in the former, probably due to the previous milling process. The bran and aleurone layers from both wheat varieties exhibited a similar behaviour.

CT evaluation of hepatic injury following proton beam irradiation: appearance, enhancement, and 3D size reduction pattern.

The purpose of this study was to investigate the long-term imaging appearances of hepatic injury following proton beam irradiation. The time-attenuation curves, time of appearance and recovery, and 3D size reduction pattern are described in patients of different ages and genders with different irradiation doses, irradiated portals, and Child groups. Forty-six patients with hepatocellular carcinoma underwent 50 to 84 Gy proton beam irradiation in periods of 14-52 days. CT including noncontrast and dynamic study was performed every 3 months starting 3 weeks after the end of irradiation. The 3D volume measurement of areas of radiation-induced hepatic injury was performed through incremental dynamic CT images in every follow-up study. CT follow-up study of the patients was done for 12-76 months. Radiation-induced hepatic injury was observed as low attenuation areas on noncontrast CT and enhanced areas on dynamic study in the regions corresponding to the irradiation portals. Of our cases, 67.5% showed the appearance of radiation hepatitis in 3-4 weeks and 95.3% in 3-4 months after the end of irradiation. In both periods, there was a significant delay in the female patients. The time-attenuation curve showed an early and prolonged enhancement of the irradiated regions. The volume reduction pattern of the injured areas was found to be longstanding, exponential, and directed from periphery to the center. Early appearance of radiation-induced hepatic injury was found only to be gender dependent, with a tendency to occur with higher irradiated doses; no other parameters affected this phenomenon in our cases. Disappearance of the injured areas, if present, takes a long time (at least 42 months).

Symmetrical reduction of M3 and hypoconulid loss in M. mulatta

AbstractAn adult male rhesus macaque from Morgan Island was found to have reduced third upper molars and to have lost the hypoconulid on the lower third molar. The pattern of reduction was symmetrical, with hypocone, metacone, and eleven of thirteen upper cheek tooth measurements markedly diminished in size. Mandibular cheek teeth were less affected. The pattern of size reduction yields a specimen whose individual teeth resemble in size those of Cercopithecus aethiops in particular and the Cercopithecini in general in its ‘derived’ features of M3 reduction, hypoconulid loss, and reduced cheek tooth size.