A functional central limit theorem for a Markov-modulated infinite-server queue

We consider a model in which the production of new molecules in a chemical reaction network occurs in a seemingly stochastic fashion, and can be modeled as a Poisson process with a varying arrival rate: the rate is $\lambda_i$ when an external Markov process $J(\cdot)$ is in state $i$. It is assumed that molecules decay after an exponential time with mean $\mu^{-1}$. The goal of this work is to analyze the distributional properties of the number of molecules in the system, under a specific time-scaling. In this scaling, the background process is sped up by a factor $N^{\alpha}$, for some $\alpha>0$, whereas the arrival rates become $N\lambda_i$, for $N$ large. The main result of this paper is a functional central limit theorem ({\sc f-clt}) for the number of molecules, in that the number of molecules, after centering and scaling, converges to an Ornstein-Uhlenbeck process. An interesting dichotomy is observed: (i)~if $\alpha>1$ the background process jumps faster than the arrival process, and consequently the arrival process behaves essentially as a (homogeneous) Poisson process, so that the scaling in the {\sc f-clt} is the usual $\sqrt{N}$, whereas (ii)~for $\alpha\leq1$ the background process is relatively slow, and the scaling in the {\sc f-clt} is $N^{1-\alpha/2}.$ In the latter regime, the parameters of the limiting Ornstein-Uhlenbeck process contain the deviation matrix associated with the background process $J(\cdot)$

The impact of increasing urban surface albedo on outdoor summer thermal comfort within a university campus

The impact of increasing urban surface albedo on outdoor thermal comfort was studied in two phases: Firstly, the thermal conditions of three locations with different ground surface materials were compared. The study used CFD modelling followed by a measurement campaign to validate the control simulation. It was observed that the physiological equivalent temperature (PET as the outdoor thermal comfort index) in the campus park (covered with grass) was 11.0 °C lower than the parking lot (paved with concrete) at 16:00 CET. As the next step, the albedo of the roofs and walls were increased from 0.2 (control) to 0.3, 0.4, 0.5 and 0.6. It was found that increasing the albedo made the open space of the courtyard uncomfortable due to the higher reflectivity of high-albedo materials. An increase of every 0.1 albedo of the surfaces led to 1.2 °C higher mean radiant temperature, and consequently, 0.8 °C higher PET. The study also showed that the increase of albedo radiated more sun to the ground surface. This increased average ground surface sensible heat flux (6.7 W/m2) and surface temperature (0.4 °C) during the day. This finding shows that the position and orientation of high albedo materials can significantly affect pedestrians' thermal comfort in urban open spaces

Potential of macrophytes for removing atrazine from aqueous solution

The potential of three macrophytes, Azolla caroliniana, Salvinia minima, and Lemna gibba was assessed in this study to select plants for use in environmental remediation contaminated with atrazine. Experiments were carried out in a greenhouse over six days in pots containing Hoagland 0.25 strength nutritive solution at the following atrazine concentrations: 0; 0.01; 0.1; 1.0; 10.0 mg L-1. Decrease in biomass accumulation was observed in the three macrophytes, as well as toxic effects evidenced by the symptomatology developed by the plants which caused their deaths. The chlorosis and necrosis allowed to observe in the plants the high sensitivity of the three species to the herbicide. Plants presented low potential for removal of atrazine in solution when exposed to low concentrations of the herbicide. However, at the 10.0 mg L-1 atrazine concentration, L. gibba and A. caroliniana showed potential to remove the herbicide from the solution (0.016 and 0.018 mg atrazine per fresh mass gram, respectively). This fact likely resulted from the processes of atrazine adsorption by the dead material. The percentage of atrazine removed from the solution by the plants decreased when the plants were exposed to high concentrations of the pollutant. Azolla caroliniana, S. minima, and L. gibba were not effective in removing the herbicide from solution. The use of these species to remedy aquatic environments was shown to be limited.Avaliou-se, neste estudo, o potencial de três macrófitas - Azolla caroliniana, Salvinia minima e Lemna gibba - com vistas à seleção de plantas para remediação de ambientes contaminados por atrazine. Foram realizados experimentos em casa de vegetação durante seis dias, em vasos contendo solução nutritiva Hoagland (0,25 de força iônica), nas seguintes concentrações de atrazine: 0; 0,01; 0,1; 1,0; e 10,0 mg L-1. A redução da biomassa acumulada pelas macrófitas foi observada, bem como os efeitos de toxidez evidenciados pela sintomatologia desenvolvida nas plantas, os quais causaram sua morte. Clorose e necrose observadas nas plantas mostraram a alta sensibilidade das três espécies ao herbicida. As plantas demonstraram baixo potencial para remoção de atrazine, quando expostas ao herbicida em baixas doses. Entretanto, na concentração de 10,0 mg L-1 de atrazine, L. gibba e A. caroliniana mostraram potencial para remover o herbicida da solução (0,016 e 0,018 mg de atrazine por grama de massa fresca, respectivamente). Esse fato provavelmente resultou do processo de adsorção de atrazine pela matéria morta. A porcentagem de atrazine removida da solução pelas plantas diminuiu quando estas foram expostas a altas concentrações do poluente. Azolla caroliniana, S. minima e L. gibba não foram eficazes na remoção do herbicida na solução. A utilização dessas espécies para sanar ambientes aquáticos mostrou-se limitada

Pollutant Transport in Geomedia Using X-ray Computed Tomography

AbstractComputed tomography (CT) measurement systems have been introduced as a method to measure fluid transport at the macropore-scale to estimate transport parameters. The objective of this study was to use x-ray CT methods to measure transport of iodophenol solution in geomedia columns and estimate spatial distributions of chemical retardation. An initial CT-measured breakthrough curve experiment was conducted with potassium iodide to spatially estimate pore-water velocity and dispersivity in the geomedia core, with a subsequent transport experiment with iodophenol to estimate the spatial distribution of chemical retardation. A geomedia core was removed from the surface horizon of Sarpy loamy sand (Typic Udispamment). Spatial distributions followed a fractal pattern with dimension values similar among pore-water velocity, dispersivity and retardation coefficient parameters. The retardation coefficient estimated using CT methods was similar compared to the dynamic fluid experiment indicating this new method may be appropriate for pollutant transport analysis. This study illustrates that the CT method is useful for evaluating solute transport on a macropore-scale for porous materials

Treatment-emergent adverse events after infusion of adherent stem cells: the MiSOT-I score for solid organ transplantation

BACKGROUND: Cellular therapy after organ transplantation is emerging as an intriguing strategy to achieve dose reduction of classical immunosuppressive pharmacotherapy. Here, we introduce a new scoring system to assess treatment-emergent adverse events (TEAEs) of adherent stem cell therapies in the clinical setting of allogeneic liver transplantation (for example, the MiSOT-I trial Eudract CT: 2009-017795-25). METHODS: The score consists of three independent modalities (set of parameters) that focus on clinically relevant events early after intravenous or intraportal stem cell infusion: pulmonary toxicity, intraportal-infusional toxicity and systemic toxicity. For each modality, values between 0 (no TEAE) and 3 (severe TEAE) were defined. The score was validated retrospectively on a cohort of n=187 recipients of liver allografts not receiving investigational cell therapy between July 2004 and December 2010. These patients represent a control population for further trials. Score values were calculated for days 1, 4, and 10 after liver transplantation. RESULTS: Grade 3 events were most commonly related to the pulmonary system (3.5% of study cohort on day 4). Almost no systemic-related TEAEs were observed during the study period. The relative frequency of grade 3 events never exceeded 5% over all modalities and time points. A subgroup analysis for grade 3 patients provided no descriptors associated with severe TEAEs. CONCLUSION: The MiSOT-I score provides an assessment tool to score specific adverse events that may occur after adherent stem cell therapy in the clinical setting of organ transplantation and is thus a helpful tool to conduct a safety study

The effects of customisation on player experiences and motivation in a virtual reality game

There is a high demand for physical rehabilitation therapies: More than 475,000 Australian citizens are living with the effects of stroke and are engaged in physical therapies. Developing effective physical rehabilitation programs for these individuals is important both for their health outcomes and for the medical field. Virtual Reality (VR) technologies provide opportunities for improvements in this area. One of the opportunities is to create motivational rehabilitation processes for patients' persistence with their therapies. Using the theoretical framework of Self Determination Theory, this paper reports results from an experimental study (N=60) that tested a motivational design principle (i.e., functional and aesthetic customisation) on participants' player experiences in a VR game. The VR game has simple mechanics that share similarities with a type of upper body rehabilitation exercise; which has been validated as effective for the optimal restoration of scapular muscle imbalances. Findings from the study showed that customisation has a positive effect on players' experiences of autonomy need satisfaction and enjoyment in the VR game setting. These findings have implications that aid designers when designing motivational VR physical rehabilitation applications

Autonomic nervous system involvement in the giant axonal neuropathy (GAN) KO mouse: implications for human disease

PURPOSE: Giant axonal neuropathy (GAN) is an inherited severe sensorimotor neuropathy. The aim of this research was to investigate the neuropathologic features and clinical autonomic nervous system (ANS) phenotype in two GAN knockout (KO) mouse models. Little is known about ANS involvement in GAN in humans, but autonomic signs and symptoms are commonly reported in early childhood. METHODS: Routine histology and immunohistochemistry was performed on GAN KO mouse specimens taken at various ages. Enteric dysfunction was assessed by quantifying the frequency, weight, and water content of defecation in GAN KO mice. RESULTS: Histological examination of the enteric, parasympathetic and sympathetic ANS of GAN KO mice revealed pronounced and widespread neuronal perikaryal intermediate filament inclusions. These neuronal inclusions served as an easily identifiable, early marker of GAN in young GAN KO mice. Functional studies identified an age-dependent alteration in fecal weight and defecation frequency in GAN KO mice. CONCLUSIONS: For the first time in the GAN KO mouse model, we described the early, pronounced and widespread neuropathologic features involving the ANS. In addition, we provided evidence for a clinical autonomic phenotype in GAN KO mice, reflected in abnormal gastrointestinal function. These findings in GAN KO mice suggest that consideration should be given to ANS involvement in human GAN, especially when considering treatments and patient care