Polymer-Capped Nanoparticle Transport in Granular Media Filtration: Deviation from the Colloidal Filtration Model

The single-collector removal efficiency based on the colloidal filtration model is widely used to quantify deposition of nanoparticles in porous media filtration. The validity of this theory for nanoparticles, especially at filtration rates used in water treatment, was evaluated. Granular media filtration experiments were performed under widely variant physical conditions. Chemical effects were minimized by selecting spherical branched polyethylenimine capped silver nanoparticles as a positively charged nanoparticle to avoid electrostatic repulsion with the negatively charged silica filter media. The model and experimental results agreed well for 50 and 100 nm particles, but 10 nm particles were removed to a lesser extent than the model predicted. An updated Derjaguin-Landau-Verwey-Overbeek calculation was performed for the interaction energy between polymer-capped nanoparticles and the collector surface, under constant potential, constant charge, and mixed assumptions. The effect of particle size on these calculations was dramatic, leading to far less attractive energy for the smallest particles in the mixed case, and even repulsion in the constant charge case. These revised calculations are the primary means to explain the unexpected data

Estimation of surface turbulent heat fluxes via variational assimilation of sequences of land surface temperatures from Geostationary Operational Environmental Satellites

Recently, a number of studies have focused on estimating surface turbulent heat fluxes via assimilation of sequences of land surface temperature (LST) observations into variational data assimilation (VDA) schemes. Using the full heat diffusion equation as a constraint, the surface energy balance equation can be solved via assimilation of sequences of LST within a VDA framework. However, the VDA methods have been tested only in limited field sites that span only a few climate and land use types. Hence, in this study, combined-source (CS) and dual-source (DS) VDA schemes are tested extensively over six FluxNet sites with different vegetation covers (grassland, cropland, and forest) and climate conditions. The CS model groups the soil and canopy together as a single source and does not consider their different contributions to the total turbulent heat fluxes, while the DS model considers them to be different sources. LST data retrieved from the Geostationary Operational Environmental Satellites are assimilated into these two VDA schemes. Sensible and latent heat flux estimates from the CS and DS models are compared with the corresponding measurements from flux tower stations. The results indicate that the performance of both models at dry, lightly vegetated sites is better than that at wet, densely vegetated sites. Additionally, the DS model outperforms the CS model at all sites, implying that the DS scheme is more reliable and can characterize the underlying physics of the problem better

Comprehensive understanding of nano-sized particle separation processes using nanoparticle tracking analysis

Understanding of nano-sized particle separation processes has been limited by difficulties of nanoparticle characterization. In this study, nanoparticle tracking analysis (NTA) was deployed to evaluate the absolute particle size distributions in laboratory scale flocculation and filtration experiments with silver nanoparticles. The results from NTA were consistent with standard theories of particle destabilization and transport. Direct observations of changes in absolute particle size distributions from NTA enhance both qualitative and quantitative understanding of particle separation processes of nano-sized particles

Evaluation of the Weak Constraint Data Assimilation Approach for Estimating Turbulent Heat Fluxes at Six Sites

A number of studies have estimated turbulent heat fluxes by assimilating sequences of land surface temperature (LST) observations into the strong constraint-variational data assimilation (SC-VDA) approaches. The SC-VDA approaches do not account for the structural model errors and uncertainties in the micrometeorological variables. In contrast to the SC-VDA approaches, the WC-VDA approach (the so-called weak constraint-VDA) accounts for the effects of structural and model errors by adding a model error term. In this study, the WC-VDA approach is tested at six study sites with different climatic and vegetative conditions. Its performance is also compared with that of SC-VDA at the six study sites. The results show that the WC-VDA produces 10.16% and 10.15% lower root mean square errors (RMSEs) for sensible and latent heat flux estimates compared with the SC-VDA approach. The model error term can capture errors in the turbulent heat flux estimates due to errors in LST and micrometeorological measurements, as well as structural model errors, and does not allow those errors to adversely affect the turbulent heat flux estimates. The findings also indicate that the estimated model error term varies reasonably well, so as to capture the misfit between predicted and observed net radiation in different hydrological and vegetative conditions. Finally, synthetically generated positive (negative) noises are added to the hydrological input variables (e.g., LST, air temperature, air humidity, incoming solar radiation, and wind speed) to examine whether the WC-VDA approach can capture those errors. It was found that the WC-VDA approach accounts for the errors in the input data and reduces their effect on the turbulent heat flux estimates

Mapping Regional Turbulent Heat Fluxes via Assimilation of MODIS Land Surface Temperature Data into an Ensemble Kalman Smoother Framework

Estimation of turbulent heat fluxes via variational data assimilation (VDA) approaches has been the subject of several studies. The VDA approaches need an adjoint model that is difficult to derive. In this study, remotely sensed land surface temperature (LST) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) are assimilated into the heat diffusion equation within an ensemble Kalman smoother (EnKS) approach to estimate turbulent heat fluxes. The EnKS approach is tested in the Heihe River Basin (HRB) in northwest China. The results show that the EnKS approach can estimate turbulent heat fluxes by assimilating low temporal resolution LST data from MODIS. The findings indicate that the EnKS approach performs fairly well in various hydrological and vegetative conditions. The estimated sensible (H) and latent (LE) heat fluxes are compared with the corresponding observations from large aperture scintillometer systems at three sites (namely, Arou, Daman, and Sidaoqiao) in the HRB. The turbulent heat flux estimates from EnKS agree reasonably well with the observations, and are comparable to those of the VDA approach. The EnKS approach also provides statistical information on the H and LE estimates. It is found that the uncertainties of H and LE estimates are higher over wet and/or densely vegetated areas (grassland and forest) compared to the dry and/or slightly vegetated areas (cropland, shrubland, and barren land)

Susceptibility of Anopheles Gambiae to Insecticides used for Malaria Vector Control in Rwanda

Background: The widespread emergence of resistance to pyrethroids is a major threat to the gains made in malaria control. To monitor the presence and possible emergence of resistance against a variety of insecticides used for malaria control in Rwanda, nationwide insecticide resistance surveys were conducted in 2011 and 2013. Methods: Larvae of Anopheles gambiae sensu lato mosquitoes were collected in 12 sentinel sites throughout Rwanda. These were reared to adults and analysed for knock-down and mortality using WHO insecticide test papers with standard diagnostic doses of the recommended insecticides. A sub-sample of tested specimens was analysed for the presence of knockdown resistance (kdr) mutations. Results: A total of 14,311 mosquitoes were tested and from a sample of 1406 specimens, 1165 (82.9%) were identified as Anopheles arabiensis and 241 (17.1%) as Anopheles gambiae sensu stricto. Mortality results indicated a significant increase in resistance to lambda-cyhalothrin from 2011 to 2013 in 83% of the sites, permethrin in 25% of the sites, deltamethrin in 25% of the sites and DDT in 50% of the sites. Mosquitoes from 83% of the sites showed full susceptibility to bendiocarb and 17% of sites were suspected to harbour resistance that requires further confirmation. No resistance was observed to fenitrothion in all study sites during the entire survey. The kdr genotype results in An. gambiae s.s. showed that 67 (50%) possessed susceptibility (SS) alleles, while 35 (26.1%) and 32 (23.9%) mosquitoes had heterozygous (RS) and homozygous (RR) alleles, respectively. Of the 591 An. arabiensis genotyped, 425 (71.9%) possessed homozygous (SS) alleles while 158 (26.7%) and 8 (1.4%) had heterozygous (RS) and homozygous (RR) alleles, respectively. Metabolic resistance involving oxidase enzymes was also detected using the synergist PBO. Conclusion: This is the first nationwide study of insecticide resistance in malaria vectors in Rwanda. It shows the gradual increase of insecticide resistance to pyrethroids (lambda-cyhalothrin, deltamethrin, permethrin) and organochlorines (DDT) and the large presence of target site insensitivity. The results demonstrate the need for Rwanda to expand monitoring for insecticide resistance including further metabolic resistance testing and implement an insecticide resistance management strategy to sustain the gains made in malaria control

Anatomy and Pathology/Oncology Retinal Thickness and Axial Length

PURPOSE. To examine the relationships between axial length and foveal and peripheral retinal thickness. METHODS. Using optical coherence tomography, foveal retinal thickness was measured in participants of the population-based Beijing Eye Study without optic nerve or macula diseases. Inner and outer nuclear layer thickness as surrogate for retinal thickness was assessed in the fundus periphery in human globes enucleated due to malignant uveal melanoma or painful glaucoma. RESULTS. The study included 1117 individuals with a mean age of 64.2 6 9.7 years (range: 50-93 years) and mean axial length of 23.4 6 1.04 mm (range: 20.29-28.68 mm). In multivariate analysis, thicker central foveal thickness was associated with male sex (P < 0.001; standardized regression coefficient beta: À0.13; nonstandardized regression coefficient B: À5.84; 95% confidence interval (CI): À8.56, À3.13); urban region of habitation (P ¼ 0.02; beta: 0.07; B: 3.56; 95% CI: 0.55, 6.57); thinner lens thickness (P ¼ 0.01; beta: À0.08; B: À5.11; 95% CI: À9.01, À1.21); thinner subfoveal choroidal thickness (P ¼ 0.04; beta: À0.07; B: À0.01; 95% CI: À0.03, À0.001); and longer axial length (P < 0.001; beta: 0.18; B: 3.79; 95% CI: 2.41, 5.17). In the same multivariate model, superior, inferior, and temporal foveal thickness was not significantly associated with axial length (P ¼ 0.26, P ¼ 0.19, P ¼ 0.08, respectively), while thicker nasal foveal thickness was associated with longer axial length (P ¼ 0.009; beta: 0.09; B: 1.50; 95% CI: 0.37, 2.62). In the histomorphometric part of the study including 32 eyes (sagittal diameter: 27.0 6 4.2 mm; range: 22-37 mm), mean thickness of the inner and outer nuclear layers at the equator and at the midpoint equator/posterior pole decreased with longer axial length (P ¼ 0.004; beta: À0.48; and P ¼ 0.02; beta: À0.44, respectively). CONCLUSIONS. Myopic axial globe elongation was associated with retinal thinning in the equatorial and pre-equatorial region, while foveal retinal thickness was mostly unaffected by axial length. It suggests that axial elongation takes place predominantly in the equatorial and pre-equatorial region of the eye

Antibody responses to the merozoite surface protein-1 complex in cerebral malaria patients in India

<p>Abstract</p> <p>Background</p> <p><it>Plasmodium falciparum </it>infection causes cerebral malaria (CM) in a subset of patients with anti-malarial treatment protecting only about 70% to 80% of patients. Why a subset of malaria patients develops CM complications, including neurological sequelae or death, is still not well understood. It is believed that host immune factors may modulate CM outcomes and there is substantial evidence that cellular immune factors, such as cytokines, play an important role in this process. In this study, the potential relationship between the antibody responses to the merozoite surface protein (MSP)-1 complex (which consists of four fragments namely: MSP-1₈₃, MSP-1₃₀, MSP-1₃₈and MSP-1₄₂), MSP-6₃₆and MSP-7₂₂and CM was investigated.</p> <p>Methods</p> <p>Peripheral blood antibody responses to recombinant antigens of the two major allelic forms of MSP-1 complex, MSP-6₃₆and MSP-7₂₂were compared between healthy subjects, mild malaria patients (MM) and CM patients residing in a malaria endemic region of central India. Total IgG and IgG subclass antibody responses were determined using ELISA method.</p> <p>Results</p> <p>The prevalence and levels of IgG and its subclasses in the plasma varied for each antigen. In general, the prevalence of total IgG, IgG1 and IgG3 was higher in the MM patients and lower in CM patients compared to healthy controls. Significantly lower levels of total IgG antibodies to the MSP-1_f38, IgG1 levels to MSP-1_d83, MSP-1₁₉and MSP-6₃₆and IgG3 levels to MSP-1_f42and MSP-7₂₂were observed in CM patients as compared to MM patients.</p> <p>Conclusion</p> <p>These results suggest that there may be some dysregulation in the generation of antibody responses to some MSP antigens in CM patients and it is worth investigating further whether perturbations of antibody responses in CM patients contribute to pathogenesis.</p

Plasma IP-10, apoptotic and angiogenic factors associated with fatal cerebral malaria in India

<p>Abstract</p> <p>Background</p> <p><it>Plasmodium falciparum </it>in a subset of patients can lead to cerebral malaria (CM), a major contributor to malaria-associated mortality. Despite treatment, CM mortality can be as high as 30%, while 10% of survivors of the disease may experience short- and long-term neurological complications. The pathogenesis of CM is mediated by alterations in cytokine and chemokine homeostasis, inflammation as well as vascular injury and repair processes although their roles are not fully understood. The hypothesis for this study is that CM-induced changes in inflammatory, apoptotic and angiogenic factors mediate severity of CM and that their identification will enable development of new prognostic markers and adjunctive therapies for preventing CM mortalities.</p> <p>Methods</p> <p>Plasma samples (133) were obtained from healthy controls (HC, 25), mild malaria (MM, 48), cerebral malaria survivors (CMS, 48), and cerebral malaria non-survivors (CMNS, 12) at admission to the hospital in Jabalpur, India. Plasma levels of 30 biomarkers ((IL-1β, IL-1ra, IL-2, IL-4, IL-5, IL-6, IL-8, IL-9, IL-10, IL-12 (p70), IL-13, IL-15, IL-17, Eotaxin, FGF basic protein, G-CSF, GM-CSF, IFN-γ, IP-10, MCP-1 (MCAF), MIP-1α, MIP-1β, RANTES, TNF-α, Fas-ligand (Fas-L), soluble Fas (sFas), soluble TNF receptor 1 (sTNF-R1) and soluble TNF receptor 2 (sTNFR-2), PDGF bb and VEGF)) were simultaneously measured in an initial subset of ten samples from each group. Only those biomarkers which showed significant differences in the pilot analysis were chosen for testing on all remaining samples. The results were then compared between the four groups to determine their role in CM severity.</p> <p>Results</p> <p>IP-10, sTNF-R2 and sFas were independently associated with increased risk of CM associated mortality. CMNS patients had a significantly lower level of the neuroprotective factor VEGF when compared to other groups (P < 0.0045). The ratios of VEGF to IP-10, sTNF-R2, and sFas distinguished CM survivors from non survivors (P < 0.0001).</p> <p>Conclusion</p> <p>The results suggest that plasma levels of IP-10, sTNF-R2 and sFas may be potential biomarkers of CM severity and mortality. VEGF was found to be protective against CM associated mortality and may be considered for adjunctive therapy to improve the treatment outcome in CM patients.</p