Polymer-directed inhibition of reversible to irreversible attachment prevents Pseudomonas aeruginosa biofilm formation

Non-toxic, biocompatible materials that inhibit bacterial biofilm formation on implanted medical devices and so prevent infection are urgently required. Weakly amphiphilic acrylate polymers with rigid hydrocarbon pendant groups resist bacterial biofilm formation in vitro and in vivo but the biological mechanism involved is not known. By comparing biofilm formation on polymers with the same acrylate backbone but with different pendant groups, we show that poly(ethylene glycol dicyclopentenyl ether acrylate; pEGdPEA) but not neopentyl glycol propoxylate diacrylate (pNGPDA) inhibited the transition from reversible to irreversible attachment. By using single-cell tracking algorithms and controlled flow microscopy we observed that fewer Pseudomonas aeruginosa PAO1 cells accumulated on pEGdPEA compared with pNGPDA. Bacteria reaching the pEGdPEA surface exhibited shorter residence times and greater asymmetric division with more cells departing from the surface post-cell division, characteristic of reversible attachment. Migrating cells on pEGdPEA deposited fewer exopolysaccharide trails and were unable top adhere strongly. Discrimination between the polymers required type IV pili and flagella. On pEGdPEA, the lack of accumulation of cyclic diguanylate or expression of sadB were consistent with the failure to transit from reversible to irreversible attachment. Constitutive expression of sadB increased surface adhesion sufficient to enable P. aeruginosa to form biofilms in a Mot flagellar stator dependent manner. These findings were extendable to other biofilm resistant acrylates highlighting their unique ability to inhibit reversible to irreversible attachment as a mechanism for preventing biofilm-associated infections.

Numerical Demonstration of an Unconventional EGS Arrangement

A new EGS arrangement, Robust EGS (REGS), is studied for its potential benefits for wide-spread applications for clean, carbon-free, electrical energy generation. Numerical simulations are carried out to prove the key benefit of REGS in a simple, but effective, geologic heat exchanger arrangement with large, stabilized fracture aperture and controlled flow zones. The numerical model results show the estimated potential energy capacity and the converted value to electrical energy generation over a 30-year operation time period for two simple REGS arrangements. The results may assist EGS investors and drilling companies in deciding whether the investment and operation can be made profitable for the wide-scale application of REGS for green energy generation.

Pain Experienced during Various Dental Procedures: Clinical Trial Comparing the Use of Traditional Syringes with the Controlled-Flow Delivery Dentapen® Technique

Background and Objectives: Currently, one of the most discouraging aspects for many patients undergoing dental procedures is the administration of anaesthesia. Consequently, there is a constant search for new techniques to avoid the invasive and painful nature of the injection. A new motorised syringe system (Dentapen®) has recently been developed, standing out for its convenience and ease of use. Material and Methods: Randomised, controlled, single-blind, and single-centre study including 178 voluntary adult participants aged between 18 and 90 years. Individuals were randomly assigned using a randomised table. Patients were asked to rate the level of pain experienced during the injections, using a 10-point visual analogue scale (VAS). The following data were recorded: pain index, heart rate, blood pressure, and saturation, both before and after anaesthesia. Results: Of the total 178 participants, 87 participants (48.9%) were men and 91 (51.1%) were women. The first variable to be assessed was the pain experienced by patients when anaesthetised with a syringe, obtaining a mean value of 2.63 ± 1.86 on the VAS with the conventional syringe and 1.06 ± 1.28 with the Dentapen® syringe, showing statistically significant differences (p-value < 0.01). When stratifying, based on the procedure that was undertaken, differences were also significant for all treatments (p-value < 0.01) except for endodontics, where differences were likely to be significant (p-value = 0.02). Conclusions: In conclusion, from a clinical standpoint, the Dentapen® syringe is a valid alternative to traditional infiltration syringes, causing minimum pain with the injection.

Performance Mechanism of Hydrogel for Enhanced Oil Recovery: A Numerical Simulation Study Based on the Phase-Field Approach

Hydrogels are increasingly applied in oil recovery processes. This leads to more controlled flow of fluids in porous media. In this process, hydrogel is injected to the reservoir to block the high permeability areas. The trapped oil in low permeability regions, is then swept by water flooding. pH-sensitive hydrogel microspheres were synthesized in another work of the authors, which effectively increased the oil recovery factor in experimental studies. In this communication, phase-field approach was used to simulate this process and to obtain the tuning parameters of the model including thickness of the contact surface(є), phase transform parameter(M0), excess free energy(\(\wedge\)), and interfacial tension. Diffusion of hydrogels was studied by Cahn–Hilliard conservative approach and the breakage, deformation, and plugging mechanisms were analyzed, based on pressure drop variations in micromodel. Moreover, Effective parameters on oil recovery factor were analyzed. Results indicated a good agreement between experimental and modeling studies of oil recovery factor in water and hydrogel flooding with absolute errors of 2.29% and 4.06%, respectively. The recovery factor was calculated using a statistical method which was in good agreement with the modeling results. The tuned parameters of the model were reported as, є= 111.7µm, M0= 5*10-13m3/s, \(\wedge\)=-0.0003 J/m3, and δ = 2×10-5 Pa.s.

Physical Property Characterization of the Waipapa Greywacke: An Important Geothermal Reservoir Basement Rock in New Zealand

Greywacke basement rocks in New Zealand host conventional geothermal reservoirs and may supply important hotter and deeper geothermal energy resources in the future. This work combines petrological analyses and physical property measurements of Waipapa greywacke, a basement unit hosting New Zealand geothermal reservoirs, in order to understand better how structurally controlled flow networks develop and channel geothermal fluids within it. Results show intact Waipapa greywacke has high tensile and triaxial compressive strengths, and low intrinsic permeability (~10-21 m2). Permeability of intact Waipapa greywacke does not increase significantly during triaxial loading to failure and is accompanied by minimal changes ultrasonic wave velocities. These data taken together suggest that microcrack development during brittle deformation is very limited. Upon failure, the permeability increases by two orders of magnitude and shows similar permeability to tests performed on synthetic, single, mode I fractures in intact Waipapa greywacke. Permeability persists in Waipapa greywacke fractures under confining pressures of at least 150 MPa. It is concluded that Waipapa greywacke rocks will not allow fluid flow through the matrix of the rock and that substantial geothermal fluid flow will only occur through macrofracture networks.

Quantitative analysis of Cenozoic faults and fractures and their impact on groundwater flow in the bedrock aquifers of Ireland

Faults and fractures are a critical store and pathway for groundwater in Ireland’s limestone bedrock aquifers either directly as conductive structures or indirectly as the locus for the development of karst conduits. From the quantitative analysis of post-Devonian faults and fractures in a range of lithological sequences, this report describes the principal characteristics of Cenozoic strike-slip faults and joints, the youngest and the most intrinsically conductive fractures within Irish bedrock. Analysis of these structures in more than 120 outcrop, quarry, mine and cave locations in a range of bedrock types, provides a basis for: (1) definition of quantitative models for their depth dependency, lithological control, scaling systematics and links to preexisting structure, (2) conceptualisation of their impact on groundwater behaviour, and (3) estimation of groundwater flow parameters. The quantitative models provide constraints on fracture-controlled flow connectivity. Commonly observed decreases in sustainable flows and water strike interceptions with depth are attributed to increasing confinement and decreasing fracture connectivity and dissolution. Faults and joints have quite different end member geometries, with faults having strongly heterogeneous scale-independent properties and joints more often showing scale-dependent stratabound properties. The highest and most sustainable groundwater flows are usually associated with the complexity of structure of Cenozoic faults and of preexisting Carboniferous structures (on which conductive fracturing localises), enhanced by karstification and strongly jointed limestone bedrock particularly in the near-surface. Increased groundwater flow is promoted within bedded, rather than massive (i.e. unbedded), limestone sequences, characterised by bedding-parallel fractures and karst connecting otherwise subvertical fractures and subvertical wells.

On a free boundary problem for a Maxwell fluid

In this paper we consider a hyperbolic free boundary problem describing a pressure-controlled flow of a Bingham-like fluid in a channel. The free boundary is the surface that separates the inner core (where the velocity is uniform) from the outer layer, where the fluid behaves like the upper convective Maxwell fluid. First, the problem is reduced to an equivalent system of equations of the first order, which allows us to study the behavior of the free boundary in the considered time interval and establish the global solvability of the problem