Impact of setup errors on the robustness of linac-based single-isocenter coplanar and non-coplanar VMAT plans for multiple brain metastases.

PURPOSE: Patient setup errors have been a primary concern impacting the dose delivery accuracy in radiation therapy. A robust treatment plan might mitigate the effects of patient setup errors. In this reported study, we aimed to evaluate the impact of translational and rotational errors on the robustness of linac-based, single-isocenter, coplanar, and non-coplanar volumetric modulated arc therapy treatment plans for multiple brain metastases. METHODS: Fifteen patients were retrospectively selected for this study with a combined total of 49 gross tumor volumes (GTVs). Single-isocenter coplanar and non-coplanar plans were generated first with a prescribed dose of 40 Gy in 5 fractions or 42 Gy in 7 fractions to cover 95% of planning target volume (PTV). Next, four setup errors (+1  and +2 mm translation, and +1° and +2° rotation) were applied individually to generate modified plans. Different plan quality evaluation metrics were compared between coplanar and non-coplanar plans. 3D gamma analysis (3%/2 mm) was performed to compare the modified plans (+2 mm and +2° only) and the original plans. Paired t-test was conducted for statistical analysis. RESULTS: After applying setup errors, variations of all plan evaluation metrics were similar (p > 0.05). The worst case for V100% to GTV was 92.07% ± 6.13% in the case of +2 mm translational error. 3D gamma pass rates were > 90% for both coplanar (+2 mm and +2°) and the +2 mm non-coplanar groups but was 87.40% ± 6.89% for the +2° non-coplanar group. CONCLUSION: Translational errors have a greater impact on PTV and GTV dose coverage for both planning methods. Rotational errors have a greater negative impact on gamma pass rates of non-coplanar plans. Plan evaluation metrics after applying setup errors showed that both coplanar and non-coplanar plans were robust and clinically acceptable.

The Distribution of Regulation in Aged and Dementia Care: A Continuum Approach.

The regulation of care services has become the principal means by which the state influences provision. In this article we examine the regulation of dementia care within organizations to show how some care activities attract more regulation than others. While often perceived to be overwhelming, regulation is in fact unevenly distributed at the system, organization and, in particular, the care practice levels. In practice, some areas of care are heavily regulated, while others are less so. Drawing on research interviews with staff (N = 60) at three levels of care provider organizations-senior managers, facility managers, and direct care workers-a continuum of regulation, with regulations collecting around some care activities and not others, is developed. This is used to plot how different care activities are affected by regulation. Understanding how regulations collect around some activities and not others shows where flexibility and innovation in care are possible. This has implications for the discretion care workers can exercise in daily care, effective organizational strategies for managing care and regulation, and regulatory policy. Current debates around regulation should shift from notions of good/bad and more/less regulation to an analysis of how regulation creates areas that are closely controlled and those that allow practice innovation.

Analytical Model for Diffusive Evaporation of Sessile Droplets Coupled with Interfacial Cooling Effect.

Current analytical models for sessile droplet evaporation do not consider the nonuniform temperature field within the droplet and can overpredict the evaporation by 20%. This deviation can be attributed to a significant temperature drop due to the release of the latent heat of evaporation along the air-liquid interface. We report, for the first time, an analytical solution of the sessile droplet evaporation coupled with this interfacial cooling effect. The two-way coupling model of the quasi-steady thermal diffusion within the droplet and the quasi-steady diffusion-controlled droplet evaporation is conveniently solved in the toroidal coordinate system by applying the method of separation of variables. Our new analytical model for the coupled vapor concentration and temperature fields is in the closed form and is applicable for a full range of spherical-cap shape droplets of different contact angles and types of fluids. Our analytical results are uniquely quantified by a dimensionless evaporative cooling number Eo whose magnitude is determined only by the thermophysical properties of the liquid and the atmosphere. Accordingly, the larger the magnitude of Eo, the more significant the effect of the evaporative cooling, which results in stronger suppression on the evaporation rate. The classical isothermal model is recovered if the temperature gradient along the air-liquid interface is negligible ( Eo = 0). For substrates with very high thermal conductivities (isothermal substrates), our analytical model predicts a reversal of temperature gradient along the droplet-free surface at a contact angle of 119°. Our findings pose interesting challenges but also guidance for experimental investigations.

Adsorption of Catalytic Nanoparticles onto Polymer Substrates for Controlled Deposition of Microcapsule Metal Shells.

Efficient encapsulation of small chemical molecules and their controlled targeted delivery provides a very important challenge to be overcome for a wide range of industrial applications. Typically rapid diffusion of these actives across capsule walls has so far prevented the development of a versatile widely applicable solution. In an earlier publication, we have shown that thin metal shells are able to permanently retain small molecules. The critical step in the microcapsule synthesis is the formation of a strongly adsorbed, dense monolayer of catalytic nanoparticles on the surface as this affects the secondary metal film quality. Control over Pt-nanoparticle adsorption density and a clear understanding of Pt-nanoparticle adsorption kinetics is therefore paramount. Maximising the density of heterogeneous catalysts on surfaces is generally of interest to a broad range of applications. In this work, transmission electron microscopy (TEM) and quartz crystal microbalance (QCM) are used to demonstrate that the concentration of nanoparticle polymer stabilizer used during particle synthesis and nanoparticle suspension concentration can be used to control nanoparticle surface adsorption density. We demonstrate that excess polymer, which is often used in nanoparticle synthesis but rarely discussed as an important parameter in the literature, can compete with and thus drastically affect the adsorption of the Pt-nanoparticles.

Social aspects of dementia and dementia practice.

Social aspects of dementia are becoming increasingly important as part of a wider shift in emphasis from cure to care. This is partly because approaches based on finding a cure have proved far more difficult and complex than originally imagined (WHO, 2016). New evidence on the effectiveness of public health measures, that while incidence is growing as the proportion of older people in society increases its prevalence amongst older adults is actually falling, has also lead to increased interest in social dimensions of prevention, lifestyle change, and practical intervention in community settings (Prince et al., 2016; Kivipelto et al., 2017). This, in turn, has led to a rediscovery of the role of supports to people living with dementia in their daily lives, the needs of informal carers, and professional activities that can maintain the social engagement of each party (Winblad et al., 2016). The expansion of practice around person-centered care, beyond traditional institutional settings, has also contributed to a socialized view of how interactions in dementia care are thought about (Bartlett et al., 2017), as has an increased awareness of the effects of the social construction of dementia in the public mind (Biggs, 2018). Most recently, people living with dementia, and particularly with respect to younger onset dementia, have begun to find a voice and to make connections to the wider disability movement (Dementia Alliance International, 2017). Each of these developments, in their different ways, have led to a re-emphasis on psycho-social elements of dementia, its experience, and how that might translate into clinical practice and service delivery.

Differences in priority by age group and perspective: implications for public health education and campaigning in relation to dementia.

ABSTRACTObjectives:A shift toward public health responses to dementia, raises questions about the most appropriate approaches to specific population groups. We examined perspective and age as elements in effective campaigning. Implications from the standpoint of the recipient are drawn for public health education and practice. DESIGN: In-depth semi-structured face-to-face and telephone interview with self-selected participants recruited via adverts, contact with provider organizations and cards placed in retail and service settings. Questions focused on attitudes to dementia and expectations of public campaigning and education. SETTING: Community-dwelling adults were interviewed across five Australian states. PARTICIPANTS: A total of 111 people from 5 target groups: people with dementia (n = 19), carers (n = 28), care work and service professionals from healthcare (n = 21), social work (n = 23) and commercial service professions (n = 20) involving people in younger adulthood (n = 13), early midlife (n = 23), later midlife (n = 54), and older age (n = 21). MEASUREMENTS: All interviews were transcribed and analyzed thematically by three researchers, reaching consensus before coding and further analysis in NVivo. Narrative analysis of transcripts included 330 topics relating to 6 main areas of focus. RESULTS: Attitudes and views on effective future campaigning reflected a desire for greater social inclusion, but did not focus on prevention and health services. Professionals focused on increasing interpersonal skills, people with dementia on normalization, and carers on awareness-raising. CONCLUSIONS: Public health campaigning and education in relation to dementia, could benefit from closer consideration of perspective and age of recipient in intervention design. Interpersonal skills and social inclusion were identified as key issues.

Foaming Behavior of Polymer-Coated Colloids: The Need for Thick Liquid Films.

The current study examined the foaming behavior of poly(vinylpyrrolidone) (PVP)-silica composite nanoparticles. Individually, the two components, PVP and silica nanoparticles, exhibited very little potential to partition at the air-water interface, and as such, stable foams could not be generated. In contrast, combining the two components to form silica-PVP core-shell nanocomposites led to good "foamability" and long-term foam stability. Addition of an electrolyte (Na2SO4) was shown to have a marked effect on the foam stability. By varying the concentration of electrolyte between 0 and 0.55 M, three regions of foam stability were observed: rapid foam collapse at low electrolyte concentrations, delayed foam collapse at intermediate concentrations, and long-term stability (∼10 days) at the highest electrolyte concentration. The observed transitions in foam stability were better understood by studying the microstructure and physical and mechanical properties of the particle-laden interface. For rapidly collapsing foams the nanocomposite particles were weakly retained at the air-water interface. The interfaces in this case were characterized as being "liquid-like" and the foams collapsed within 100 min. At an intermediate electrolyte concentration (0.1 M), delayed foam collapse over ∼16 h was observed. The particle-laden interface was shown to be pseudo-solid-like as measured under shear and compression. The increased interfacial rigidity was attributed to adhesion between interpenetrating polymer layers. For the most stable foam (prepared in 0.55 M Na2SO4), the ratio of the viscoelastic moduli, G'/G″, was found to be equal to ∼3, confirming a strongly elastic interfacial layer. Using optical microscopy, enhanced foam stability was assessed and attributed to a change in the mechanism of foam collapse. Bubble-bubble coalescence was found to be significantly retarded by the aggregation of nanocomposite particles, with the long-term destabilization being recognized to result from bubble coarsening. For rapidly destabilizing foams, the contribution from bubble-bubble coalescence was shown to be more significant.

Measurements of Submicron Particle Adsorption and Particle Film Elasticity at Oil-Water Interfaces.

The influence of particle adsorption on liquid/liquid interfacial tension is not well understood, and much previous research has suggested conflicting behaviors. In this paper we investigate the surface activity and adsorption kinetics of charge stabilized and pH-responsive polymer stabilized colloids at oil/water interfaces using two tensiometry techniques: (i) pendant drop and (ii) microtensiometer. We found, using both techniques, that charge stabilized particles had little or no influence on the (dynamic) interfacial tension, although dense silica particles affected the "apparent" measured tension in the pendent drop, due to gravity driven elongation of the droplet profile. Nevertheless, this apparent change additionally allowed the study of adsorption kinetics, which was related qualitatively between particle systems by estimated diffusion coefficients. Significant and real interfacial tension responses were measured using ∼53 nm core-shell latex particles with a pH-responsive polymer stabilizer of poly(methyl methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate) (pMMA-b-pDMAEMA) diblock copolymer. At pH 2, where the polymer is strongly charged, behavior was similar to that of the bare charge-stabilized particles, showing little change in the interfacial tension. At pH 10, where the polymer is discharged and poorly soluble in water, a significant decrease in the measured interfacial tension commensurate with strong adsorption at the oil-water interface was seen, which was similar in magnitude to the surface activity of the free polymer. These results were both confirmed through droplet profile and microtensiometry experiments. Dilational elasticity measurements were also performed by oscillation of the droplet; again, changes in interfacial tension with droplet oscillation were only seen with the responsive particles at pH 10. Frequency sweeps were performed to ascertain the dilational elasticity modulus, with measured values being significantly higher than previously reported for nanoparticle and surfactant systems, and similar in magnitude to protein stabilized droplets.

Manufacture of poly(methyl methacrylate) microspheres using membrane emulsification.

Accurate control of particle size at relatively narrow polydispersity remains a key challenge in the production of synthetic polymer particles at scale. A cross-flow membrane emulsification (XME) technique was used here in the preparation of poly(methyl methacrylate) microspheres at a 1-10 l h(-1) scale, to demonstrate its application for such a manufacturing challenge. XME technology has previously been shown to provide good control over emulsion droplet sizes with careful choice of the operating conditions. We demonstrate here that, for an appropriate formulation, equivalent control can be gained for a precursor emulsion in a batch suspension polymerization process. We report here the influence of key parameters on the emulsification process; we also demonstrate the close correlation in size between the precursor emulsion and the final polymer particles. Two types of polymer particle were produced in this work: a solid microsphere and an oil-filled matrix microcapsule.This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'.

Poly(dimethylsiloxane)-stabilized polymer particles from radical dispersion polymerization in nonpolar solvent:influence of stabilizer properties and monomer type [corrected].

Particles used in electrophoretic display applications (EPD) must possess a number of specific properties ranging from stability in a nonaqueous solvent, high reflectivity, low polydispersity, and high charge density to name but a few. The manufacture of such particles is best carried out in the solvent of choice for the EPD. This opens up new interests in the study of nonaqueous dispersion polymerization methods, which deliver polymer particles suspended in low dielectric constant solvents. We explore in this article the use of a poly(dimethylsiloxane) macromonomer for the stabilization of poly(methyl methacrylate) polymer particles in dodecane, a typical solvent of choice for EPDs. The use of this stabilizer is significant for this method as it is directly soluble in the reaction medium as opposed to traditionally used poly(12-hydroxystearic acid)-based stabilizers. Additionally, the present study serves as a baseline for subsequent work, where nonaqueous dispersion polymerization will be used to create polymer particles encapsulating liquid droplets and solid pigment particles. In this article, the influence of the macromonomer molecular weight and concentration on the properties of the synthesized particles is studied. In addition, we investigate the possibility of synthesizing polymer particles from other monomers both as a comonomer for methyl methacrylate and as the only monomer in the process. The influence of macromonomer concentration is also studied throughout all experiments.

Measuring particle concentration in multiphase pipe flow using acoustic backscatter: generalization of the dual-frequency inversion method.

A technique that is an extension of an earlier approach for marine sediments is presented for determining the acoustic attenuation and backscattering coefficients of suspensions of particles of arbitrary materials of general engineering interest. It is necessary to know these coefficients (published values of which exist for quartz sand only) in order to implement an ultrasonic dual-frequency inversion method, in which the backscattered signals received by transducers operating at two frequencies in the megahertz range are used to determine the concentration profile in suspensions of solid particles in a carrier fluid. To demonstrate the application of this dual-frequency method to engineering flows, particle concentration profiles are calculated in turbulent, horizontal pipe flow. The observed trends in the measured attenuation and backscatter coefficients, which are compared to estimates based on the available quartz sand data, and the resulting concentration profiles, demonstrate that this method has potential for measuring the settling and segregation behavior of real suspensions and slurries in a range of applications, such as the nuclear and minerals processing industries, and is able to distinguish between homogeneous, heterogeneous, and bed-forming flow regimes.

Competing frameworks in planning for the aged in the growth corridors of Melbourne.

The Ageing in the Growth Corridors Project was initiated as a partnership between the University of Melbourne and the Department of Health in the Northwest Metropolitan Region of Melbourne, Australia. It involved a research team working with six project officers appointed to stimulate development in relation to an aging population in the sprawling outer metropolitan growth corridors. This article identifies the key lessons learned in terms of project implementation relating to attitudinal and structural barriers to the development of an age-friendly environment in areas of rapid urban growth. The findings illustrate some of the dilemmas raised by competing program conceptions, a dynamic and changing federal/state policy context, and local resource and strategic management constraints. The partnership with the university, nevertheless, provided a point of stability and continuity for the project officers in implementing their mandate.

Elder mistreatment, ageism, and human rights.

BACKGROUND: Elder mistreatment, social ageism, and human rights are increasingly powerful discourses in positioning older people in society, yet the relationship between them has rarely been subjected to critical investigation. This perceived relationship will have implications for how mistreatment is understood and responded to. METHOD: Critical gerontological approach based on narrative and textual analysis. RESULTS: Reports of public attitudes toward mistreatment suggest that it is thought to be more common than scientific evidence would suggest; however, reporting is much lower than prevalence. While the discourse over mistreatment has tended to focus on interpersonal relationships, ageism has emphasized social attitudes, and human rights have concentrated on relations between the state and the individual. CONCLUSIONS: In this paper, a series of models have been examined which mark a tendency to restrict and then attempt to reintegrate individual, interpersonal, and social levels of analysis. It is concluded that a focus on the processes of transaction across boundaries rather than contents would facilitate both integrative modeling and deeper understanding of the qualities of abusive situations.

Interactional perspectives on the mistreatment of older and vulnerable people in long-term care settings.

This article draws on a study aimed at developing theoretical and methodological understanding of the abuse and neglect (mistreatment) of older people in long-term care settings such as care homes and hospitals. It presents an interactionist account of mistreatment of older people in such establishments. Starting with an outline of definitional issues surrounding the topic, the allied concept of dignity is also briefly explored, and one important model described; we present dignity as the converse of mistreatment. The article argues for the potential of a positioning theory analysis of mistreatment. Positioning theory proposes that interactions are based on taking of 'positions', clusters of rights and duties to act in certain ways and impose particular meanings, which enable or prohibit access to certain storylines. It is argued that 'malignant' positioning can contribute to the creation of a climate that allows mistreatment to take place, or fails to prohibit its development. Mistreatment of people with dementia is used as an illustration, and it is argued that this is potentially generated by negative feedback loops of behaviour patterns, interpretations and malignant positioning by staff or family carers and subsequent response to these interpretations by the person with dementia. Positioning theory also allows for an explanation of the importance and impact of organizational cultures and social factors such as ageism. Individual staff members take positions, use meanings and develop storylines imbued with such factors. This understanding therefore overcomes some of the potential confusions created by concepts such as organizational or institutional abuse, removing the need to ascribe intentions and personal responsibility to such constructs. The article concludes with some suggestions for further research to develop an understanding of the kinds of cultures that allow mistreatment and consequently to inform the development of protective measures.

Behavior of pH-sensitive core shell particles at the air-water interface.

In this article, the adsorption of latex core-responsive polymer-shell nanoparticles at the air-water interface is investigated using a Langmuir trough. Phase transition isotherms are used to explore their responsive behavior at the interface as a function of changes in the pH of the subphase. By adjusting the pH of the water prior to particle deposition, we probe the effect of the stabilizing polymer wetting by the water subphase on the stability of these particles at the air-water interface. In addition, by initially compressing a stable film of adsorbed particles and then subsequently changing the pH of the subphase we study desorption of these particles into the water phase.

Deposition of non-porous calcium phosphate shells onto liquid filled microcapsules.

The efficient encapsulation of small molecule active ingredients has been a challenge for many decades across many commercial applications. Recently, successful attempts to address this issue have included deposition of thin metal shells onto liquid filled polymer microcapsules or emulsion droplets to provide an impermeable barrier to diffusion. In this work we have developed a novel method to protect small molecule active ingredients by deposition of thin mineral shells. Platinum nanoparticles are used to catalyse and direct growth of a calcium phosphate shell onto liquid filled polymer microcapsules under various reaction conditions. Findings indicate that a non-porous protective shell is formed on the majority of the microcapsule population, with small concentrations of the core material being released only from those microcapsules with defects, over a 7 days period, when conducting forced release studies into a solvent for the core oil. The resulting microcapsules show no significant cell toxicity when exposed to HEK 293 cells for 72 h.

Controlling adsorption density of polymer-stabilised metal nanoparticles at the oil-water interface.

Emulsion droplets offer an alternative to solid supports as templates for the deposition of metallic nanoparticles. An emulsion interface provides the opportunity to exploit both sides of the nanoparticles and to utilise the liquid core as a microreactor in addition to forming a scaffold for encapsulation. However, despite the extensive literature studying a very broad range of factors influencing the characteristics of particle-stabilised (Pickering) emulsions, most reports focus on particles of diameters >100 nm and a very small proportions consider particles of diameters <10 nm. For catalytic purposes of course, the latter species are of utmost interest. Here, we report the synthesis of poly(vinyl pyrrolidone) (PVP) stabilised platinum nanoparticles, where the platinum core ranges between 3 and 5 nm in diameter and their subsequent use as emulsifiers for the oil-water interface where they form a densely packed layer. The nanoparticle density at the interface is quantified by both measuring the remaining concentration of nanoparticles in the aqueous phase after adsorption and also directly at the oil-water interface via cryo-TEM. The effect of electrolyte concentration and of addition of excess PVP in the bulk aqueous nanoparticle dispersion prior to emulsification on the resulting nanoparticle density at the oil-water interface is also determined.

Adsorption of phytosterol ethoxylates on silica in an aprotic room-temperature ionic liquid.

The adsorption of a nonionic surfactant at a silica/room-temperature ionic liquid interface has been characterized on the basis of analytical data obtained through a combination of surface force measurements, in situ soft-contact atomic force microscope (AFM) images, and quartz crystal microbalance with dissipation monitoring (QCM-D) data. The surfactant employed in this study is a kind of phytosterol ethoxylate (BPS-20), and the ionic liquid selected here is aprotic 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (EmimTFSI). This ionic liquid spontaneously forms solvation layers on silica, being composed of an Emim(+) cation layer and EmimTFSI ion pair layers. The addition of BPS-20 disrupts these solvation layers and suggests a surfactant layer adsorbed at the interface. This is the first report demonstrating the adsorption of nonionic surfactants at the solid/aprotic ionic liquid interface.

Influence of a latent period in QALY analysis: pilot study of intrathecal drug delivery systems for chronic non-malignant pain.

Cost effectiveness of a treatment is an important factor in decision making in the United Kingdom. Preceding most interventional health care treatments there is a waiting period between decision and procedure where health care costs may be lessened. Intrathecal drug delivery systems (IDDS) are a recognised pain management therapy for chronic non-malignant pain. To our knowledge, the period of time between being placed on a waiting list for IDDS and the implant (latent period) has not been taken into consideration for cost effectiveness analysis. A retrospective longitudinal analysis of all pain related costs for a period no less than 4 years was undertaken by assessment of medical records of 12 consecutive patients implanted with IDDS for chronic non-malignant pain. The total cost of patient care for 2 years before latent, the latent period itself and 2 years after the implant of an IDDS was computed, according to the National Health Service tariff. An EQ-5D questionnaire was filled by all participants before and after IDDS implant. Total costs were converted to cost per day for comparison with latent period. The average duration of the latent period was 263 ± 176 days (range 3-489). The cost of conventional treatments during the pre-implant phase excluding the latent period was significantly higher (M = £ 5,005.86, SE = £ 918.56) compared with the costs of the same phase including the latent period (M = £ 4,086.35, SE = £ 959.09, t(11) = 2.23, p = 0.05, r = 0.56). The cost per day changed significantly over the different periods (χ(2)(2) = 24.00, p < 0.05). The variability and significantly lower costs of the latent period may influence cost effectiveness evaluations and consequently decision making, if not considered. Further studies analysing the influence of a latent period on the cost effectiveness of other treatments are warranted.