A Coupled Bio-Chemo-Hydro-Mechanical Model for Bio-cementation in Porous Media

A key challenge involving microbial induced carbonate precipitation (MICP) is lack of rigorous yet practical theoretical models to predict the intricate biological-chemical-hydraulic-mechanical (BCHM) processes and the resulting bio-cement production. This paper presents a novel BCHM model based on multiphase, multispecies reactive transport approach in the framework of poroelasticity, aimed at achieving reasonable prediction of the produced bio-cement, and the enhanced geomechanical characteristics. The proposed model incorporates four key components: (i) coupling of hydro-mechanical stress/strain alterations with bio-chemical processes; (ii) stress/strain changes induced due to precipitation and growth of bio-cement within the porous matrix; (iii) spatiotemporal variability in hydraulic and stiffness characteristics of the treated medium; (iv) and velocity dependency of the attachment rate of bacteria. The fully-coupled BCHM model predicts key unknown parameters during treatment including: concentration of bacteria and chemical solutions, precipitated calcium carbonate, hydraulic properties of the solid skeleton, and in-situ pore pressures and strains. The model was able to reasonably predict bio-cementation from two different laboratory column experiments. The Kozeny–Carman permeability equation is found to underestimate permeability reductions due to bio-cementation, while the Verma–Pruess relation could be more accurate. A sensitivity analysis revealed bio-cement distribution to be particularly sensitive to the attachment rate of bacteria.

Influence of flow rate on the transport of nTiO2 and phosphate and its modeling

We studied Zeta potentials of nanoparticles titanium dioxides （nTiO2） in different concentration of NaNO3 and phosphate (P) solutions. In addition, the effect of flow rate on the transport of nTiO2 in P was investigated at pH＝6.5. Experimental results show that the Zeta potential of nTiO2 is compressed with the increasing ion concentration (IC) of NaNO3 at pH＝6.5. The negative charge increases with the augment of P. Therefore, the high P and low NaNO3 induce the stabilization of nTiO2 aggregates. The transport experiments suggest that the rapid flow rate is favorable for the transportability of nTiO2 and soluble phosphate. The breakthrough transport curves (BTCs) of nTiO2 in sand columns can be fitted well with two-site kinetic attachment model. The modeling results suggest that the values of first-order attachment rate coefficients (k2) and detachment rate coefficients (k2d) on site 2 and first-order attachment rate coefficients (k1) on site 1 are responsible to the attaching efficiency of nTiO2 on sands and their transportability.

Turkey Ovarian Tissue Transplantation: Effects of Surgical Technique on Graft Attachment and Immunological Status of the Grafts 6 Days Post-surgery

Background: Biobanked poultry ovaries can be revived via transplantation, into a recipient female, which upon maturity will produce donor-derived progeny. Previously, a large portion of these recipients also produced recipient-derived progeny, making them gonadal chimeras. These were potentially created when portions of the recipient’s ovary were inadvertently left behind. Completely removing the recipient ovary would solve this problem, however, leaving a portion of the recipient’s ovary may have inadvertently increased the transplant attachment rate by providing a damaged area for the transplant to attach too. To test this hypothesis in the turkey, we removed various portions (33% to 100%) of recipient ovarian tissue and determined the transplant attachment rate. Furthermore, the use of the abdominal air sac membrane as an additional anchoring point was tested. Finally, the immunological status of the grafts was evaluated by analyzing the presences of CD3 and MUM-1 (T and B cell markers), 6 days post-surgery.Results: The overall attachment rate of transplants was 91% (32/35), while the average size of the transplants was 4.2 ± 0.6 mm2. There was no difference (P > 0.05) in the attachment rates, or transplant size between groups with varying amounts of recipent tissue removed, or by using the abdominal air sac membrane as an anchor. However, all transplants were infiltrated by large numbers of T and B cells. This was shown by a high (P ≤ 0.001) percentage of CD3-positive immunostained cytoplasmic area (49.78 ± 3.90%) in transplants compared to remnant recipient tissue (0.30 ± 0.10%), as well as a high (P ≤ 0.001) percentage of MUM-1-positive immunostained nuclear area (9.85 ± 1.95%) in transplants over remnant recipient tissues (0.39 ± 0.12%).Conclusions: This study showed that neither the portion of the recipient ovary left behind nor the use of the abdominal air sac membrane affected the rate of attachment or the amount of donor tissue that attached. Thus, we recommend removing the entire recipient ovary to prevent gonadal chimeras. The high levels of lymphocytes within the grafts indicate possible tissue rejection, which could be overcome via immunosuppression with or without histocompatibility matching between donors and recipients.

Retinotomy and retinectomy for anterior inferior proliferative vitreoretinopathy: Can visual outcome be improved?

Purpose: To describe the treatment outcomes and prognostic factors of retinotomy/retinectomy for rhegmatogenous retinal detachment (RD) complicated anterior inferior proliferative vitreoretinopathy (PVR). Methods: Retrospective, nonrandomized, single-center case series. The outcomes of 126 cases of retinotomy/retinectomy for RD complicated by advanced (Grade C) anterior inferior PVR managed consistently by one surgeon during a 15-year period were evaluated. Results: Forty-two eyes (33%) had primary RDs and 84 (67%) had recurrent RDs. The extent of retinotomy/retinectomy varied: 90° in 21 eyes (17%), >90° to <180° in 49 eyes (39%), and ⩾180° to ⩽240° in 56 eyes (44%). The retinotomy/retinectomy location was peripheral in 58 eyes (46%) and equatorial in 68 eyes (54%). The mean follow-up period was 43 ± 42 months. The silicone oil (SO) was removed from 98% of the eyes. The single-operation success rate after the primary retinectomy was 87%, and the final attachment rate was 94%. Visual acuity improved from 20/630 to 20/160 ( p < 0.001). Vision ⩾20/200 was achieved in 101 eyes (80%). Good visual outcome was correlated positively with preoperative VA ( p = 0.02), previous vitrectomy with gas tamponade ( p = 0.007), and was negatively correlated with number of previous RD operations ( p = 0.01), larger extent of RD ( p = 0.02) and more extensive retinotomy/retinectomy ( p = 0.04). Conclusions: An appropriate and timely intervention, including vitrectomy alone, inferior relaxing retinotomy/retinectomy and standard SO tamponade provide satisfactory outcomes for RDs complicated by PVR. Lesser extension of grade C PVR at baseline, such as PVR limited to one quadrant should encourage vitreoretinal specialists to consider retinotomy/retinectomy at a milder clinical stage of PVR development.

In situ microbeam surface X-ray scattering reveals alternating step kinetics during crystal growth

The stacking sequence of hexagonal close-packed and related crystals typically results in steps on vicinal {0001} surfaces that have alternating A and B structures with different growth kinetics. However, because it is difficult to experimentally identify which step has the A or B structure, it has not been possible to determine which has faster adatom attachment kinetics. Here we show that in situ microbeam surface X-ray scattering can determine whether A or B steps have faster kinetics under specific growth conditions. We demonstrate this for organo-metallic vapor phase epitaxy of (0001) GaN. X-ray measurements performed during growth find that the average width of terraces above A steps increases with growth rate, indicating that attachment rate constants are higher for A steps, in contrast to most predictions. Our results have direct implications for understanding the atomic-scale mechanisms of GaN growth and can be applied to a wide variety of related crystals.

Dreissenids’ breaking loose: differential attachment as a possible driver of the dominance shift between two invasive mussel species

Ponto-Caspian dreissenids are notorious freshwater invaders. Recently, widespread observations show a dominance shift from the early invader, Dreissena polymorpha, to its successor, Dreissena bugensis. These observations likely reflect congeneric species differences in physiological and behavioural traits. Here, we assessed the mussel attachment strength, attachment rate, and the mode of byssal failure as trait differences that could potentially contribute to dominance shifts. The attachment traits were measured in field and laboratory experiments. Fouling plates were deployed in the Rhine-Meuse river delta and dreissenids were collected and acclimatised in 60 L non-aerated freshwater tanks. Attachment strength was positively correlated with shell size. The attachment strength of D. bugensis was significantly greater compared to slower growing D. polymorpha individuals of a dreissenid field assemblage. This corresponded to the superior byssal thread morphology of D. bugensis (i.e. higher number and two times wider byssal threads). Moreover, our results indicated that byssal threads of D. bugensis are stronger than those of D. polymorpha, as the latter ruptured more often. Additionally, D. bugensis had a significantly lower attachment rate than D. polymorpha. Having a greater attachment strength gives D. bugensis an advantage when it comes to withstanding currents and predators. On the other hand, not being attached allows an individual to actively move around. This would allow them to move away from fast changing unfavourable environmental conditions. These attachment traits indicate competitive benefits for D. bugensis over D. polymorpha, therefore possibly contributing to the dominance shifts.

Filtration by porous media: a microfluidics approach

&lt;p&gt;The transport of colloids in porous media is governed by deposition on solid surfaces and pore-scale flow variability. Classical approaches, like colloid filtration theory (CFT), do not capture behaviours observed experimentally, such as non-exponential steady state deposition profiles and heavy tailed BreakThrough Curves (BTC). In the framework of CFT, a key assumption is that the colloid attachment rate&amp;#160;&lt;span&gt;&lt;span&gt;&lt;span&gt;&lt;span&gt;&amp;#119896;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt; is constant and empirically estimated via a posteriori macroscopic data fitting. We design a novel experimental set-up based on time-lapse microscopy and continuous injection of fluorescent monodisperse colloids into a folded microfluidics device (1mt total length) designed with a controlled level of 2D spatial disorder. This set-up allows us to i) measure both BTC and deposition profile over several orders of magnitude and ii) to perform particle tracking and Lagrangian analysis of single colloid's trajectories. Based on this analysis, we propose a stochastic model that takes into account pore scale heterogeneities in terms of correlation length, velocity and attachment rate distribution, that captures the anomalous behaviour shown by the experimental data.&lt;/p&gt;

EFFECT OF AIR VELOCITY ON INHALATION DOSES DUE TO RADON AND THORON PROGENY IN A TEST CHAMBER

Inhalation doses due to radon and thoron are predominantly due to the inhalation of progeny of Radon and Thoron. The progeny/decay-products of radon and thoron are particulates unlike their parent gas and exhibit different physical properties like attachment to the aerosols and deposition on different surfaces. All these properties in turn depend on the environmental conditions such as air velocity, aerosol concentration, attachment rate, etc. The role of air velocity on deposition on surfaces decides the progeny particles left in the air for inhalation. Therefore, in the present work, we have studied the effect of air velocity on the inhalation dose due to radon and thoron progeny at the centre of a 0.5-m3 calibration chamber as well as on all surfaces. Hence, the studies were carried out at different air velocities, and inhalation doses were measured using deposition-based direct radon and thoron progeny sensors.

Analytical Results for the Three-Body Radiative Attachment Rate Coefficient, with Application to the Positive Antihydrogen Ion H+

To overcome the numerical difficulties inherent in the Maxwell–Boltzmann integral of the velocity-weighted cross section that gives the radiative attachment rate coefficient α R A for producing the negative hydrogen ion H − or its antimatter equivalent, the positive antihydrogen ion H ¯ + , we found the analytic form for this integral. This procedure is useful for temperatures below 700 K, the region for which the production of H ¯ + has potential use as an intermediate stage in the cooling of antihydrogen to ultra-cold (sub-mK) temperatures for spectroscopic studies and probing the gravitational interaction of the anti-atom. Our results, utilizing a 50-term explicitly correlated exponential wave function, confirm our prior numerical results.