1,102 research outputs found
Health activism and the logic of connective action. A case study of rare disease patient organisations
This exploratory work investigates the role of digital media in expanding health discourse practices in a way to transform traditional structures of agency in public health. By focusing on a sample of rare disease patient organisations as representative of contemporary health activism, this study investigates the role of digital communication in the development of (1) bottom-up sharing and co-production of health knowledge, (2) health public engagement dynamics and (3) health information pathways. Findings show that digital media affordances for patient organisations go beyond the provision of social support for patient communities; they ease one-way, two-way and crowdsourced processes of health knowledge sharing, exchange and co-production, provide personalised routes to health public engagement and bolster the emergence of varied pathways to health information where experiential knowledge and medical authority are equally valued. These forms of organisationally enabled connective action can help the surfacing of personal narratives that strengthen patient communities, the bottom-up production of health knowledge relevant to a wider public and the development of an informational and eventually cultural context that eases patients’ political action
Second-order and Fluctuation-induced First-order Phase Transitions with Functional Renormalization Group Equations
We investigate phase transitions in scalar field theories using the
functional renormalization group (RG) equation. We analyze a system with
U(2)xU(2) symmetry, in which there is a parameter that controls the
strength of the first-order phase transition driven by fluctuations. In the
limit of \lambda_2\to0\epsilon$-expansion results. We compare results from the expansion and from
the full numerical calculation and find that the fourth-order expansion is only
of qualitative use and that the sixth-order expansion improves the quantitative
agreement.Comment: 15 pages, 10 figures, major revision; discussions on O(N) models
reduced, a summary section added after Introduction, references added; to
appear in PR
Learning by observation: insights from Williams syndrome.
Observing another person performing a complex action accelerates the observer's acquisition of the same action and limits the time-consuming process of learning by trial and error. Observational learning makes an interesting and potentially important topic in the developmental domain, especially when disorders are considered. The implications of studies aimed at clarifying whether and how this form of learning is spared by pathology are manifold. We focused on a specific population with learning and intellectual disabilities, the individuals with Williams syndrome. The performance of twenty-eight individuals with Williams syndrome was compared with that of mental age- and gender-matched thirty-two typically developing children on tasks of learning of a visuo-motor sequence by observation or by trial and error. Regardless of the learning modality, acquiring the correct sequence involved three main phases: a detection phase, in which participants discovered the correct sequence and learned how to perform the task; an exercise phase, in which they reproduced the sequence until performance was error-free; an automatization phase, in which by repeating the error-free sequence they became accurate and speedy. Participants with Williams syndrome beneficiated of observational training (in which they observed an actor detecting the visuo-motor sequence) in the detection phase, while they performed worse than typically developing children in the exercise and automatization phases. Thus, by exploiting competencies learned by observation, individuals with Williams syndrome detected the visuo-motor sequence, putting into action the appropriate procedural strategies. Conversely, their impaired performances in the exercise phases appeared linked to impaired spatial working memory, while their deficits in automatization phases to deficits in processes increasing efficiency and speed of the response. Overall, observational experience was advantageous for acquiring competencies, since it primed subjects' interest in the actions to be performed and functioned as a catalyst for executed action
Corrections to scaling in multicomponent polymer solutions
We calculate the correction-to-scaling exponent that characterizes
the approach to the scaling limit in multicomponent polymer solutions. A direct
Monte Carlo determination of in a system of interacting
self-avoiding walks gives . A field-theory analysis based
on five- and six-loop perturbative series leads to . We
also verify the renormalization-group predictions for the scaling behavior
close to the ideal-mixing point.Comment: 21 page
Chiral symmetry restoration, eigenvalue density of Dirac operator and axial U(1) anomaly at finite temperature
We reconsider constraints on the eigenvalue density of the Dirac operator in
the chiral symmetric phase of 2 flavor QCD at finite temperature. To avoid
possible ultra-violet(UV) divergences, we work on a lattice, employing the
overlap Dirac operator, which ensures the exact "chiral" symmetry at finite
lattice spacings. Studying multi-point correlation functions in various
channels and taking their thermodynamical limit (and then taking the chiral
limit), we obtain stronger constraints than those found in the previous
studies: both the eigenvalue density at the origin and its first and second
derivatives vanish in the chiral limit of 2 flavor QCD. In addition we show
that the axial U(1) anomaly becomes invisible in susceptibilities of scalar and
pseudo scalar mesons, suggesting that the 2nd order chiral phase transition
with the O(4) scaling is not realized in 2 flavor QCD. Possible lattice
artifacts when non-chiral lattice Dirac operator is employed are briefly
discussed.Comment: 39 pages, 1 figure(2 eps files), a version published in PR
Zero-temperature behavior of the random-anisotropy model in the strong-anisotropy limit
We consider the random-anisotropy model on the square and on the cubic
lattice in the strong-anisotropy limit. We compute exact ground-state
configurations, and we use them to determine the stiffness exponent at zero
temperature; we find and respectively
in two and three dimensions. These results show that the low-temperature phase
of the model is the same as that of the usual Ising spin-glass model. We also
show that no magnetic order occurs in two dimensions, since the expectation
value of the magnetization is zero and spatial correlation functions decay
exponentially. In three dimensions our data strongly support the absence of
spontaneous magnetization in the infinite-volume limit
The critical exponents of the superfluid transition in He4
We improve the theoretical estimates of the critical exponents for the
three-dimensional XY universality class, which apply to the superfluid
transition in He4 along the lambda-line of its phase diagram. We obtain the
estimates alpha=-0.0151(3), nu=0.6717(1), eta=0.0381(2), gamma=1.3178(2),
beta=0.3486(1), and delta=4.780(1). Our results are obtained by finite-size
scaling analyses of high-statistics Monte Carlo simulations up to lattice size
L=128 and resummations of 22nd-order high-temperature expansions of two
improved models with suppressed leading scaling corrections. We note that our
result for the specific-heat exponent alpha disagrees with the most recent
experimental estimate alpha=-0.0127(3) at the superfluid transition of He4 in
microgravity environment.Comment: 45 pages, 16 fig
Influence of bicarbonate/carbonate removal on magnesium hydroxide slurry: A pilot study
Nowadays, the continuous increase in raw materials demand is leading research to seek alternative and unconventional sources, such as waste industrial brine or seawater.
Indeed, seawater and seawater brines (e.g. produced by seawater reverse osmosis (RO) desalination plant) can be exploited in order to recover fresh water but also to produce many other valuable minerals such as magnesium.
The importance of the magnesium recovery stands for its high risk of supply and significant economic importance for key sectors in the European economy. Thus, magnesium has been defined as one of thirty-four Critical Raw Materials (CRMs) by the European Commission.
In the framework of the Horizion 2020 European Project Water Mining, a novel and unconventional selective reactive crystallizer designed by ResourSEAs was tested for the recovery of magnesium in form of hydroxide by means of direct mixing with an alkaline solution (i.e. sodium hydroxide solution). This crystallizer is called Multiple Feed Plug Flow Reactor (MF-PFR). The MF-PFR was installed within an integrated demonstration plant aiming at the production of magnesium hydroxide, chemicals (such as sodium hydroxide and hydrochloric acid), fresh water, sodium sulfate, and sodium chloride, combining together (i) nanofiltration, (ii) MF-PFR, (iii) Eutetic Freez Crystallizer (EFC), (iv) Electro-dialysis with bipolar membrane, and (v) Multiple Effect Distillation (MED).
A wide experimental campaign has been carried out aiming at investigating how the settling rate and purity are influenced by operative conditions, such brine feed or recycle flow-rates, and by the nature of the feed brine itself (i.e. NF retentate or RO retentate).
The results obtained show that decreasing feed brine flow-rate is consistent with an increase in the settling rate, while conversely decreasing recycle flow rate leads to a clear decrease. This behavior was observed for both feed brine solutions. Moreover, also the influence of the presence of carbonate and bicarbonates in the feed stream on product settling rate and purity was investigated by applying an acidification pretreatment step. After this step, a purity increase from 94% up to 98/99% along with an increase in sedimentation rate (up to two times) was obtained. These outcomes were observed for both feed brine solutions
The critical behavior of 3D Ising glass models: universality and scaling corrections
We perform high-statistics Monte Carlo simulations of three three-dimensional
Ising spin-glass models: the +-J Ising model for two values of the disorder
parameter p, p=1/2 and p=0.7, and the bond-diluted +-J model for
bond-occupation probability p_b = 0.45. A finite-size scaling analysis of the
quartic cumulants at the critical point shows conclusively that these models
belong to the same universality class and allows us to estimate the
scaling-correction exponent omega related to the leading irrelevant operator,
omega=1.0(1). We also determine the critical exponents nu and eta. Taking into
account the scaling corrections, we obtain nu=2.53(8) and eta=-0.384(9).Comment: 9 pages, published versio
Energetic Valorisation of Saltworks Bitterns via Reverse Electrodialysis: A Laboratory Experimental Campaign
Concentrated bitterns discharged from saltworks have extremely high salinity, often up to 300 g/L, thus their direct disposal not only has a harmful effect on the environment, but also generates a depletion of a potential resource of renewable energy. Here, reverse electrodialysis (RED), an emerging electrochemical membrane process, is proposed to capture and convert the salinity gradient power (SGP) intrinsically conveyed by these bitterns also aiming at the reduction of concentrated salty water disposal. A laboratory-scale RED unit has been adopted to study the SGP potential of such brines, testing ion exchange membranes from different suppliers and under different operating conditions. Membranes supplied by Fujifilm, Fumatech, and Suez were tested, and the results were compared. The unit was fed with synthetic hypersaline solution mimicking the concentration of natural bitterns (5 mol/L of NaCl) on one side, and with variable concentration of NaCl dilute solutions (0.01–0.1 mol/L) on the other. The influence of several operating parameters has also been assessed, including solutions flowrate and temperature. Increasing feed solutions’ temperature and velocity has been found to lower the stack resistance, which enhances the output performance of the RED stack. The maximum obtained power density (corrected to account for the effect of electrodic compartments, which can be very relevant in five cell pairs laboratory stacks) reached around 10.5 W/m2cellpair, with FUJIFILM Type 10 membranes, temperature of 40 °C, and a fluid velocity of 3 cm s−1 (as empty channel, considering 270 μm thickness). Notably, the present study results confirm the large potential for SGP generation from hypersaline brines, thus providing useful guidance for the harvesting of SGP in seawater saltworks all around the world
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