Greater Degree Of Branching Research Articles

Pore Scale Numerical Modelling of Geological Carbon Storage Through Mineral Trapping Using True Pore Geometries

Mineral trapping (MT)is the most secure method of sequestering carbon for geologically significant periods of time. The processes behind MT fundamentally occur at the pore scale, therefore understanding which factors control MT at this scale is crucial. We present a finite elements advection–diffusion–reaction numerical model which uses true pore geometry model domains generated from upmuCT imaging. Using this model, we investigate the impact of pore geometry features such as branching, tortuosity and throat radii on the distribution and occurrence of carbonate precipitation in different pore networks over 2000 year simulated periods. We find evidence that a greater tortuosity, greater degree of branching of a pore network and narrower pore throats are detrimental to MT and contribute to the risk of clogging and reduction of connected porosity. We suggest that a tortuosity of less than 2 is critical in promoting greater precipitation per unit volume and should be considered alongside porosity and permeability when assessing reservoirs for geological carbon storage (GCS). We also show that the dominant influence on precipitated mass is the Damköhler number, or reaction rate, rather than the availability of reactive minerals, suggesting that this should be the focus when engineering effective subsurface carbon storage reservoirs for long term security.Article HighlightsThe rate of reaction has a stronger influence on mineral precipitation than the amount of available reactant.In a fully connected pore network preferential flow pathways still form which results in uneven precipitate distribution.A pore network tortuosity of <2 is recommended to facilitate greater carbon mineralisation.

Shading may alter the colonization pattern and dominance between two invasive submerged aquatic plant species

Egeria densa and Elodea canadensis are two common invasive submerged macrophytes in streams and rivers worldwide. We conducted a six-week growth experiment with monocultures of E. densa and E. canadensis and mixed communities of the two species under five different shade levels (35%, 63%, 79%, 90% and 95%). Our aim was to test the effect of shade and competition on colonization of vegetative propagules of these species in flowing waters. We found that biomass accrual in both species was greatly reduced at high shade (≥ 79%) and that E. densa individuals accrued more biomass than E. canadensis individuals at all shade levels. At the least shade level (35%), interspecific competition with E. densa stimulated biomass accrual of E. canadensis individuals, compared to those within an E. canadensis monoculture. At higher shade (≥ 63%), this facilitation response disappeared, although E. canadensis plants continued to have longer stem length and a greater degree of branching than E. densa plants at ≤ 79% shade. At the highest shade level, competition with E. canadensis reduced biomass accrual of E. densa. Hence, shade influenced the competitive interactions between these two species. At low shade, the competitiveness of E. canadensis was enhanced, but in the field E. densa appears to be the dominant species in streams, especially those with higher levels of shade and less frequent disturbance by flushing flow events.

EXTH-69. NANOTHERAPEUTICS FOR NEUROSURGICALLY-APPLIED DRUG DELIVERY

Abstract Despite multimodal treatment, the median survival of Glioblastoma multiforme (GBM) patients remains less than 15 months, in considerable part due to diffusely infiltrative disease. Better treatment methods are necessary to eradicate residual tumour burden remaining beyond the resection cavity boundary. It is hypothesised that incorporating drug-loaded polymer pro-drug nanoparticles into a biodegradable microparticulate paste will lead to efficacious local delivery. We report the formulation of numerous self-assembling cytocompatible nanoparticles, based on different linear and branched polymeric architectures, amenable for localised intra-cavity delivery post-surgery. The polymers were synthesised by ring-opening polymerisation with organic catalysts, leading to controlled reaction kinetics and greater potential biomedical applicability. A simple nanoprecipitation technique was employed to gain nanoparticles with the size range of 60–130 nm, depending on the initial monomer ratios and polymeric architectures. Successful biocompatibility studies of the self-assembling nanoparticles have been carried out in vitro on the U87 glioma cell line. We demonstrated that copolymerisation of a monomer with functional capability enabled the successful conjugation of doxorubicin to the polymer chain. We will discuss strategies to incorporate pH-sensitive linkers to the polymeric backbone, which would allow controlled drug release in acidic microenvironments. Based on an increasing understanding of GBM intra-tumour heterogeneity, the capability to deliver multiple therapeutic moieties from single formulations is clinically-relevant. Thus, we hypothesised that polymers with a greater degree of branching over traditional linear structures would lead to greater drug loading, and successfully tested this hypothesis through the encapsulation of olaparib. Future work will assess the efficacy of the polymer pro-drug nanoparticles against both commercial and primary cell lines, and safety/efficacy of intra-cavity delivery using orthotopic syngeneic allografts, thus giving a more therapeutically-relevant insight into the activity of the formulations. This is the first study incorporating polymer pro-drugs of this type into an existing localised micro-scale delivery system for GBM therapies.

Nanotherapeutics for neurosurgically-applied drug delivery

Abstract Despite multimodal treatment, the median survival of Glioblastoma multiforme (GBM) remains less than 15 months, in considerable part due to diffusely infiltrative disease. Better treatment methods are necessary to eradicate residual tumour burden remaining beyond the resection cavity boundary. Based on an increasing understanding of GBM intra-tumour heterogeneity, the capability to deliver multiple therapeutic moieties from single formulations is clinically-relevant. It is hypothesised that incorporating drug-loaded polymer pro-drugs, which are capable of transcytotic ‘hopping’, into a biodegradable microparticulate paste will lead to efficacious local delivery. Here we report the formulation of numerous self-assembling cytocompatible nanoparticles, based on different linear and branched polymeric architectures. The polymers were synthesised by ring opening polymerisation with organic catalysts, leading to controlled reaction kinetics and greater potential biomedical applicability. We demonstrated that copolymerisation of a monomer with functional capability enabled the successful conjugation of doxorubicin to the polymer chain. We hypothesised that polymers with a greater degree of branching over traditional linear structures would lead to greater drug loading, and successfully tested this hypothesis through the encapsulation of olaparib. We will discuss strategies to incorporate: i) pH-sensitive linkers to the polymeric backbone, which would allow controlled drug release in acidic microenvironments; ii) multiple combined chemotherapeutics, including doxorubicin and olaparib. Future work will assess the efficacy of the polymer pro-drugs against primary GBM lines derived from the invasive margin and safety/efficacy using orthotopic syngeneic allografts. This is the first study incorporating polymer pro-drugs of this type into an existing localised micro-scale delivery system for GBM therapies.

Trapping of Organophosphorus Chemical Nerve Agents in Water with Amino Acid Functionalized Baskets

We prepared eleven amino-acid functionalized baskets and used (1) H NMR spectroscopy to quantify their affinity for entrapping dimethyl methylphosphonate (DMMP, 118 Å(3) ) in aqueous phosphate buffer at pH=7.0±0.1; note that DMMP guest is akin in size to chemical nerve agent sarin (132 Å(3) ). The binding interaction (Ka ) was found to vary with the size of substituent groups at the basket's rim. In particular, the degree of branching at the first carbon of each substituent had the greatest effect on the host-guest interaction, as described with the Verloop's B1 steric parameter. The branching at the remote carbons, however, did not perturb the encapsulation, which is important for guiding the design of more effective hosts and catalysts in future.

Characterization of Water- and Alkali-Soluble Hemicellulosic Polymers from Sugarcane Bagasse

Four hemicellulosic preparations were extracted using hot water at 70° and 80°C from dewaxed sugarcane bagasse and 10% KOH and 10% NaOH from the corresponding delignified bagasse. Their chemical and physical characteristics were determined using GC, HPLC, GPC, and FT-IR and 1H and 13C NMR spectroscopy. The results showed that two water-soluble hemicellulosic fractions consisted of arabinoxylans and pectic polysaccharides as shown by their sugar composition of xylose (51.7–53.5%), galactose (22.1%), arabinose (11.6–12.3%), glucose (7.0–8.2%), mannose (5.1–5.6%), uronic acids (4.5–6.2%), and rhamnose (0.9–1.0%), while the two alkali-extractable hemicellulosic preparations were dominated by arabinoxylans in which xylose (82.2–82.5%) and arabinose (9.7–11.3%) were the major sugar components. These differences in the structure of arabinoxylans between water and alkali extracts indicated that water-soluble arabinoxylans had significantly lower xylose-to-arabinose ratios (4.3–4.5) than those extracted with alkali (7.3–8.5), implying a greater degree of branching in the water-soluble fractions. In addition, the studies showed that the two water-soluble hemicellulosic fractions were more acidic and had a much lower molecular weight (Mw, 8,080–8,560 g mol−1) than the two alkali-extractable hemicellulosic preparations (Mw, 50,700–53,180 g mol−1). Furthermore, it was found that the two water-soluble polymer fractions contained noticeable amounts of lignin (7.8–8.9%), whereas the two alkali-extractable polymer preparations were relatively free of bound lignin (1.1%).

Computational Analysis of Tumor Angiogenesis Patterns Using a Two-dimensional Model

Tumor angiogenesis was simulated using a two-dimensional computational model. The equation that governed angiogenesis comprised a tumor angiogenesis factor (TAF) conservation equation in time and space, which was solved numerically using the Galerkin finite element method. The time derivative in the equation was approximated by a forward Euler scheme. A stochastic process model was used to simulate vessel formation and vessel elongation towards a paracrine site, i.e., tumor-secreted basic fibroblast growth factor (bFGF). In this study, we assumed a two-dimensional model that represented a thin (1.0 mm) slice of the tumor. The growth of the tumor over time was modeled according to the dynamic value of bFGF secreted within the tumor. The data used for the model were based on a previously reported model of a brain tumor in which four distinct stages (multicellular spherical, first detectable lesion, diagnosis, and death of the virtual patient) were modeled. In our study, computation was not continued beyond the 'diagnosis' time point to avoid the computational complexity of analyzing numerous vascular branches. The numerical solutions revealed that no bFGF remained within the region in which vessels developed, owing to the uptake of bFGF by endothelial cells. Consequently, a sharp declining gradient of bFGF existed near the surface of the tumor. The vascular architecture developed numerous branches close to the tumor surface (the brush-border effect). Asymmetrical tumor growth was associated with a greater degree of branching at the tumor surface.

Linking fine root traits to maximum potential growth rate among 11 mature temperate tree species

Summary There is limited understanding of patterns of variation that exist among root traits of different species, especially under field conditions. We contrasted 11 fast‐ and slow‐growing species paired within five evolutionary lineages to investigate whether root traits associated with soil resource acquisition were related to species’ potential growth rate. Measurements of root morphology, architecture, nitrogen and phenolic concentration, respiration and phosphorus uptake were taken on fine, non‐woody roots sampled from forest stands in central Pennsylvania, USA. Across all five contrasts, roots of fast‐growing species generally had higher specific root length, smaller diameters, greater degree of branching, and lower phenolic concentrations than those of slow‐growing species. This suggests differences in potential soil exploration and root defences among species differing in potential growth rate. There were no significant differences between fast‐ and slow‐growing species in root tissue density, respiration or P uptake. Lack of root physiological differences between species differing in growth rate contrasted with previous research on chamber‐grown seedlings. These results imply that, while roots of fast‐growing species may be constructed for more rapid soil exploration and shorter life span than those of slow‐growing species, root physiology is either more closely tied to overall plant physiology, which is more similar among mature trees, or masked by variation in soil microsites, root age or interactions with mycorrhizal fungi.

The effects of aqueous chemical environments on crack and hydraulic fracture propagation and morphologies

The role of surface active aqueous environments in chemomechanical weakening of geologic materials is examined in light of the results of hydraulic fracture tests in sandstone, calorimetric studies, and crack propagation tests in synthetic quartz. In hydraulic fracture tests mploying Crab Orchard Sandstone it was found that the effective hydraulic fracture pressure was reduced, over that attained with distilled water, when 5×10−4 M aqueous solutions of dodecyl trimethyl ammonium bromide (DTAB) were used as the hydraulic fracture medium. The degree of branching of the fractures was also increased in the presence of the DTAB solution. Previously reported crack propagation stress values in quartz exposed to distilled water and various DTAB solutions displayed the same trend. When examined in this study, the cracks propagated in the presence of DTAB solutions also displayed a greater degree of branching than those propagated in the presence of distilled water or the ambient atmosphere. These results and results from calorimetric measurements of the heats of adsorption and desorption from quartz of distilled water and DTAB are synthesized in a model relating the weakening and morphological effects to a reduction in the surface free energy of quartz due to adsorption of species from the chemical environment onto the surfaces of the quartz and sandstone.

Formation and structure of extracellular glucans produced by Claviceps species.

SUMMARY: Submerged cultures of Claviceps fusiformis (Loveless) became progressively viscous during the incubation because of the production of an extracellular polysaccharide. The polysaccharide was shown to be a branched glucan with a β1 → 3 linked main chain having single glucopyranosyl units at intervals along it in the β1 → 6 configuration. For most of the media investigated growth at 27° and between pH 5 and 6 was accompanied by glucan production, which ceased when growth was arrested by lack of nutrient. The glucan was re-metabolized by the fungus only to a limited extent as the culture aged; the degree of branching varied during the culture period. The unit amount of glucan synthesized was not affected by numerous successive subculturings over a period of several months, but the product from the later cultures had a greater degree of branching. Branched glucans of similar structure to the above were also detected in low concentration in the natural sclerotia. The presence of β1 → 3 linked glucans in the cell walls of this and other fungal strains examined was also indicated.

Factors Influencing the Agglutinability of Red Cells

SummaryOx red blood cells of the so called ‘inagglutinable’ class have the same electrokinetic charge as those of the ‘agglutinable’ class when examined either before or after treatment with neuraminidase or pronase. However, a greater amount of sialic acid is released from the ‘inagglutinable’ cells after such treatments. These findings support the hypothesis that inagglutinability arises from the extensiveness of mucoid layer of the cell membrane, the ‘inagglutinable’ cells having longer mucopeptide chains of variable lengths or a greater degree of branching.

Studies on the Root Development of Sugar Beet : I. Effects of fertilizers upon the root habits of young plants

The author investigated the effects of fertilizers (N as sulphatate of ammonia, P as superphosphate and K as potassium chloride) upon the root habits of young plants (sown Oct. 1., about 3.5∼4 months old) of sugar beet grown in root boxes. Each of the rot boxes was divided into 3 equal sections vertically by vinyl nets, and one beet was grown in this central section. The method of application of the fertilizers in each box was classified as follows: [table] Thus, the total amount of 3 elements was applied equally per box. The washed young roots were gotten separately from each section of the box, which divided by nets, and spreaded them on the glass plate in uniform density as shown Fig. 4. As the results, first of all, the rots of suger beet grown in the box A, as compared with those in the box B, developed much more abundantly and branched more profusely. Among the boxes of C, D and E, the rots grown in soil section applied N or NP or NK branched much more profusely than those in soils applied P or K only or both of them. From these results, it was shown that when roots came in contact with the soil applied N fertilizer, the greater degree of branching were always induced, and in sections applied no fertilizers, root-branchs were limited extremely. But in this experiment, among the developments of root branchs in the soil sections applied P or K only or both of them, no remarkable differences were recognized. The investions of the further advanced rot systems should be affected by similar manner of application of fertilizers are remained in future.

The nature of some of the linkages in deoxypentose nucleic acids

AbstractKnowledge of the linkages in deoxyribonucleic acids is reviewed and extended. Chromatographic analyses and electrometric titrations on deoxyribonucleic acids isolated from various sources indicate a greater degree of branching than has been previously assumed. Available evidence on the nature of hydrogen bonding in these nucleic acids is surveyed. Evidence for the possible existence of a highly labile glycosidic linkage is presented. The action of dilute alkali under mild conditions on deoxyribonucleic acids, as described by Euler &amp; Fono (1948), is reinterpreted.