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A broad set of data on poly-allyl diglycol carbonate (PADC) exposure to various environmental conditions has been collected for a period of 1 year in order to study the aging effect on the sensitivity to radon detection. Aging is a phenomenon that occurs during long PADC storage resulting in a loss of sensitivity and/or creation of false tracks. Conditions under investigation were storages under pure nitrogen or air atmospheres, in water solutions of different pHs, in a range of temperatures, humidity and exposure to UV, gamma and neutron radiations. It was found that PADC strongly responds to some external conditions through physical changes in the polymer material; for example, etching of UV exposed detectors led to 10% loss of their thickness and the removal of the tracks layer. Performance of detectors was compared with a control that was the sensitivity of detectors from the same sheet at the time of primary calibration – within 1 month of each sheet being manufactured. Substantial difference in performance was found between storage under pure, dry nitrogen and in the presence of water. The former preserves PADC radon detection properties for the period of one year without noticeable change. The latter, on the other hand significantly reduces its performance even after 3 months’ storage. It was also established that storage under low temperature is not a suitable means to preserve PADC sensitivity to radon detection due to significant loss in the detector sensitivity.

This study reports the results from continuous measurement of indoor and outdoor radon concentrations in the area surrounding an unconventional shale gas exploration site in North Yorkshire, England, prior to the commencement of hydraulic fracturing. Public Health England has monitored the baseline radon levels in homes and in outdoor air in the Vale of Pickering since 2015. The statistical analysis presented here includes three full years (November 2015‐ –December 2018) of indoor and four and half years (October 2015 – April 2019) of outdoor radon measurements. Stratified sampling was used to select 171 dwellings in four areas, with two different radon potential. Statistical analysis confirms that homes in Kirby Misperton and Little Barugh and those in Yedingham are situated in areas with low radon potential, as was predicted by the UK radon potential map. On the other hand, both Pickering and Malton are confirmed as radon Affected Areas. Radon was measured continuously in the outdoor air using a newly developed outdoor kit containing passive radon detectors. The monitoring points were set up at 36 locations in the same local areas as those selected for the indoor monitoring. The results from statistical analysis show that outdoor radon had a different seasonality pattern to indoor radon. The monitoring of outdoor radon levels over the four and half years indicates a year-to-year variation in outdoor radon concentrations with levels fluctuating between 3 and 9 Bq m−3. There was a very good agreement between long-term average radon concentrations measured using passive detectors and using an active AlphaGUARD monitor.

Summary: Over 18 months long measurements of outdoor radon in three areas (a total of 69 locations) in England were conducted between years 2015 and 2017 using PADC based passive nuclear track detectors. Special measurement equipment and protocols to counteract unfavourable weather conditions have been designed, developed and optimised for the low level radon concentration. Keywords: Outdoor radon, PADC, Baseline monitoring

The Vale of Pickering in Yorkshire, England has been identified as a potential area for shale gas extraction. Public Health England joined a collaboration led by the British Geological Survey for environmental baseline monitoring near the potential shale gas extraction site following a grant award from UK Government Department for Business, Energy and Industrial Strategy. The analysis of results for the first 6 months of indoor monitoring indicated that the results followed a log-normal distribution. The numbers of homes found to be at or above the Action Level followed the numbers predicted by the radon potential maps. The results from the measurements of outdoor air in this study indicated that the radon concentrations are slightly higher than previously measured but close to the detection limit of the technique.

Chitosan degradation in 0.1 M acetic acid solution by microwave radiation alone (without any additives and initiators) is reported. At the condition of reduced thermal effects of microwave heating degradation manifested most of typical features associated with mechanical (and or mechanochemical) degradations induced by shear forces, in this particular case oscillating molecules. At the absorbed energy dose of 9 MJ kg−1 chitosan in 1% w/v solution degrades within 20 min to the weight average molecular weight of 30 kDa. Comparative evaluation of degradation yield of chain scission (Gs) with other high energy radiations such as ultraviolet- and gamma radiation showed microwave to be the least efficient, but considering the environmental impact and low running costs it presents a viable alternative to obtain targeted molecular weights of charged polysaccharides.

A new modified silicone was obtained by the physical entrapment of a hydrophobic lipid, isopropyl myristate (IPM), to improve the encapsulation properties and corrosion resistance of medical electronic implants. Differences between the water transport for films in contact with water vapor versus those in contact with liquid water were identified; they showed increased permeability to water vapor, which was possibly the result of differences in the water organization at the hydrophobic film interface. Improvements, including enhanced scratch resistance and adhesion, in the mechanical properties of the modified material was also achieved. The incorporation of IPM further resulted in a significant improvement in the cell biocompatibility compared with the unmodified polymer; this suggested that the IPM combination could be a viable basis for implant device packaging. ?? 2010 Wiley Periodicals, Inc.

Medical polyurethanes have shown good bio-stability and mechanical properties and have been used as coating for implantable medical devices. However, despite their excellent properties, they are relatively permeable to liquid water and water vapour which is a drawback for electronic implant encapsulation. In this study polyether polyurethanes with different soft segment molecular weights were modified by incorporating isopropyl myristate (IPM), as a hydrophobic modifying agent, and the effect of IPM on water resistant and biocompatibility of membranes were investigated. IPM changed the surface properties of the polyurethane film and reduced its surface energy. Polyurethane films were found to be stable with IPM concentrations of 1–5 wt% based upon their chemistry; however it leached out in BSA at higher concentrations. Though, low concentrations of IPM reduced both liquid water and water vapour permeability; at higher IPM content liquid permeability did not improved significantly. In general, the polyurethane materials showed much lower water permeability compared with currently used silicone packaging material for electronic implants. In addition, cytotoxicity assessment of IPM containing polyurethanes showed no evidence of cytotoxcity up to 5 wt% IPM.

A new, nickel-coated graphite resistance-change-based method for gel-point determination for epoxy-based thermoset resins is presented and compared with {DSC} and rheological methods. Gelation times determined by this new method are in very good agreement with conventional techniques; this new method is potentially simpler and less time consuming than existing ones. ?? 2010 {WILEY-VCH} Verlag {GmbH} \& Co. {KGaA}, Weinheim.

Polymeric membranes have been used as interfaces between implantable devices and biological tissues to operate as a protective barrier from water exchanging and to enhance biocompatibility. Polyurethanes have been used as biocompatible membranes for decades. In this study, copolymers of polyether urethane (PEU) with polydimethylsiloxane (PDMS) were synthesised with the goal of creating materials with low water permeability and high elasticity. PDMS was incorporated into polymer backbone as a part of the soft segment during polyurethane synthesis and physical properties as well as water permeability of resulting copolymer were studied in regard to PDMS content. Increase in PDMS content led to increase of microphase separation of the copolymer and corresponding increase in elastic modulus. Surface energy of the polymer was decreased by incorporating PDMS compared to unmodified PEU. PDMS in copolymer formed a hydrophobic surface which caused reduction in water permeability and water uptake of the membranes. Thus, PDMS containing polyurethane with its potent water resistant properties demonstrated a great promise for use as an implantable encapsulation material.

Current state-of-the-art implantable micron feature electronic devices are capable of monitoring and stimulating functions in vivo. Within an EU Framework VI project a further step was taken in developing key microsystem technologies and communication methods that could bring intelligence directly to the human interface, in the form of reactive medical implants and ambulatory measurement systems. Information from these devices is planned to be transmitted out into the wider environment for remote processing. However, the packaging of such state-of-the-art devices to enhance tissue biocompatibility, and to protect conducting elements from in vivo corrosion during extended use, along with protecting the body from toxins leaching from implant components, remains a concern. Candidate polymeric barriers as hydration resistant and solute impermeable interfaces to mitigate such major problems of chronic implantation were investigated. Materials studied included silicone rubber, PVC, polyurethane, and diamond-like carbon (DLC). Polymer permeability to water solutes was marginally improved through incorporation of lipid into these structures. Surface biocompatibility was assessed on the basis of protein film deposition in vitro and by cell viability studies in tissue culture. Short-term toxicity was not observed for any of the tested materials, though there were substantial differences in hydration. Additionally, polypyrrole over active electrodes shows feasibility for controlled tissue interfacing whilst retaining electrical conductivity.

Degradation of a commercially available collagen-glycosaminoglycan dermal equivalent matrix was studied using electrochemical techniques. Degradation was accelerated by exposure to gamma radiation followed by storage at elevated temperatures or exposure to enzymes. The time-dependent diffusion of a small, electrochemically active, molecular probe, potassium ferrocyanide, through the matrix was monitored via changes in the oxidation peak currents of cyclic voltammograms. These measurements were made using a two-compartment diffusion chamber with the sample positioned well away from the working electrodes and a single-compartment electrode cell where the matrix was in direct contact with the working electrode. The relative merits of these two approaches are considered. Regardless of the approach chosen, amperometry appears well suited to monitoring progressive diffusivity changes through mechanically weak porous structures subject to different solution environments.

This paper presents the adsorption of humic acid from aqueous solution onto crosslinked chitosan derivative (carboxymethylchitosan), formed by additionless irradiation technique. The surface charge and swelling properties of crosslinked samples were investigated. The adsorption of humic acid onto crosslinked carboxymethylchitosan was carried out by the batch method at room temperature, and it was found to be strongly pH-dependent. Maximum amount of humic acid was adsorbed under acidic conditions at the optimum pH value of 3.5. Adsorption kinetic studies indicated the adsorption process was transport-limited at the same pH. The adsorption isotherm analysis data under various initial humic acid concentrations confirms that experimental data fitted well into the Langmuir equation. X-ray photoelectron spectroscopy (XPS) revealed that the amino groups of carboxymethylated chitosan were protonated, suggesting the formation of organic complex between the protonated amino groups and humic acid. From these preliminary evaluations, it was concluded that crosslinked carboxymethylated chitosan derivatives have a great potential in water treatment for the removal of humic acid and other polarized or electrically charged species.

This article deals with the determination of the adsorption properties of metal ions and humic acid in water on crosslinked chitosan derivatives (carboxymethylchitosan) which were formed using the irradiation technique without any additives. The solubility test of these crosslinked materials were investigated in acidic, alkaline media, distilled water, and certain organic solvents. Scanning electron microscopic (SEM) images showed that the crosslinked chitosan derivatives possessed a porous morphological structure. Charged characteristic analyses demonstrated typically pH-dependent properties of the crosslinked materials. The adsorption studies were carried out by the batch method at room temperature. Adsorption of heavy metal ions (such as Cu2+, Cd2+) and humic acid onto crosslinked samples was found to be strongly pH-dependent. Adsorption kinetic studies indicated the rapid removal of metal ions, and humic acid from the aqueous solutions. Moreover, isothermal adsorption data revealed that Cu2+, Cd2+, and humic acid were removed by these crosslinked materials with high efficiency. Adsorption isothermal data were interpreted well by the Langmuir equation. These crosslinked carboxymethylated chitosan derivatives indicate favorable adsorption of metal ions and humic acid. ?? 2007 Shanghai Institute of Applied Physics.

Adsorption of palladium and platinum ions at the trace amounts onto radiation crosslinked carboxymethylchitin (CMCht) and carboxymethylchitosan (CMChts) has been investigated. Maximum adsorption capacities for palladium were 2.679 and 1.053 mg/g dry gel, whereas for platinum they were 2.513 and 1.155 mg/dry gel for CMCht and CMChts, respectively. Retention capacity values for palladium were 0.45 and 0.06; for platinum 0.25 and 0.11 mEquiv./g for CMCht and CMChts, correspondingly. It has been shown that adsorption of Pd and Pt ions onto both hydrogels were dependent on the chloric and nitric ions concentration. Desorption experiments in HCl and HNO3 solutions proved that adsorption is governed by chelating mechanism rather than ion-exchange one. SEM-EDX spectroscopy showed that palladium and platinum ions were homogeneously distributed in all sections of hydrogel matrix. DSC experiments demonstrated decreasing in the decomposition temperature of polymers after inclusion of palladium and platinum ions, suggesting that metals are causing lowering of stability in polymer structural integrity. ?? 2007 Wiley Periodicals, Inc.

Three degradation methods: ultrasonic, ultraviolet and gamma irradiation were applied to sodium alginate and chitosan in aqueous solutions. The changes in molecular weight were monitored by GPC measurements. It has been found that from the energetic point of view the most effective method for both polymers is gamma radiation method with a yield of scission G s = 0.55 × 1 0 - 7 mol / J for 1% alginate and G s = 3.53 × 1 0 - 7 mol / J for 1% chitosan. However, considering the reaction time, the ultraviolet method is the most effective, with reaction rate constant k = 0.52 h - 1 for alginate and 1.6 h−1 for chitosan. Based on FTIR spectra, taken before and after degradation it was revealed, that degradation undergoes by the breakage of the glycosidic bonds of polymers. UV spectroscopy showed absorption peak at 265 nm for alginate, and two peaks at the range of 250–280 nm for chitosan. UV spectroscopy for ultrasonic is not revealed and any peak suggesting ultrasonic degradation undergoes different mechanism than ultraviolet and gamma degradations, probably mechanical one.

Radiation cross-linking of CM-chitin and CM-chitosan has been investigated. Such parameters of radiation cross-linking as gelation doses, cross-linking and degradation radiation yields and ratios of scission to cross-linking has been determined for both polymers. The absorption ability of various metal ions into EB-radiation cross-linked carboxymethylchitin and carboxymethylchitosan has been investigated. The highest adsorption of scandium and gold has been obtained for carboxymethylchitin (CMCht) and carboxymethylchitosan (CMChts), respectively. Kinetic studies showed that adsorption of most of the metal ions occur in a relatively short period of time (2 h). Detail investigation of adsorption of gold ions has been carried out for both hydrogels. The maximum uptake of Au cations, based on Langmuir equation was determined to be 37.59 for CM-chitosan and 11.86 for CM-chitin. Both hydrogels indicate favorable adsorption of gold cations.

Implantable micro-electromechanical systems (MEMS) offer a valuable means of sensing and actuation within the body at unprecedented levels of miniaturisation and internal functional complexity. However, function can be compromised by moisture uptake and adverse interactions within the body. Consequently, packaging materials serve as barrier phases for controlling exchange of solutes and furnishing biocompatible surfaces for MEMS devices. This chapter covers a range of coatings used to protect MEMS devices in the body. Surface modification and bioactive agent release are described as strategies for enhancing biocompatibility and reducing surface fouling. The full range of mechanical, permeability and chemical features of packaging materials are involved in the extended survival of MEMS implants and are described for contemporary packaging materials.

Polyurethane films have potential applications in medicine, especially for packaging implantable medical devices. Although polyether-urethanes have superior mechanical properties and are biocompatible, achieving water resistance is still a challenge. Polyether based polyurethanes with two different molecular weights (PTMO1000, PTMO2000) were prepared from 4,4’-diphenylmethane diisocyanate and poly(tetra-methylene oxide). Polymer films were introduced using different concentrations (0.5-10 wt %) of isopropyl myristate lipid (IPM) as a non-toxic modifying agent. The physical and mechanical properties of these polymers were characterised using physical and spectroscopy techniques (FTIR, Raman, DSC, DMA, tensile testing). Water contact angle and water uptake of the membranes as a function of IPM concentration was also determined accordingly. The FTIR and Raman data indicate that IPM is dispersed in polyurethane at ≤ 2wt% and thermal analysis confirmed this miscibility to be dependent on soft segment length. Modified polymers showed increased tensile strength and failure strain as well as reduced water uptake by up to 24% at 1-2 wt% IPM.

In the framework of the EU-supported research project Healthy Aims, we developed a range of novel electrode arrays and related technologies for use in hearing prosthesis. This paper summarizes our ongoing research activities on alternative electrode manufacturing routes, functional electrode interfaces and smart intra-cochlear and intra- modiolus electrode arrays.

Polyurethanes have been widely used in medicine for coating and packaging implantable and other medical devices. Polyether-urethanes, in particular, have superior mechanical properties and are biocompatible, but in common with other medical materials they are susceptible to microbial film formation. In this study, polyether-urethane was end-capped with silver lactate and silver sulfadiazine functional groups to produce a bacterially resistant polymer without sacrificing the useful mechanical properties of the polyether-polyurethane. The silver ions were covalently incorporated into the polymer during chain extension of the prepolymer. The functionalized polymers were structurally characterized by light scattering, electron microscopy, NMR, FTIR and Raman spectroscopy. Mechanical properties, hydrophilicity, in vitro stability and antibacterial action of polymers were also investigated. Results indicate that both silver salts were successfully incorporated into the polymer structure without significant effect on mechanical properties, whilst conferring acceptable bacterial resistance.