4,985 research outputs found
The application of GAC sandwich slow sand filtration to remove pharmaceutical and personal care products
Lab-scale GAC sandwich slow sand filters with different GAC layer depths were evaluated for the first time to remove selected pharmaceutical and personal care products (PPCPs) (namely DEET, paracetamol, caffeine and triclosan, 25 μg/L). Coarse sand (effective grain size of 0.6 mm) was used instead of conventional fine sand. In addition to single sand and GAC filters, GAC sandwich filters were assessed at three filtration rates (i.e. 5 cm/h, 10 cm/h and 20 cm/h) to compare removals. Sandwich filter with 20 cm GAC achieved the best average PPCP removal (98.2%) at 10 cm/h rate. No significant difference of average PPCP removal was found between 10 and 20 cm/h filtration rates for the three GAC sandwich filters (p > 0.05). Among the selected PPCPs, DEET, the recalcitrant compound, was most effectively removed by the GAC sandwich filters. Combining the GAC layers with the slow sand filters significantly enhanced the removal of the target PPCP compounds (p 0.05). Results of this lab-scale investigation show that GAC sandwich slow sand filter is potentially an effective process for removing PPCPs from tertiary wastewater
Optimization of total trihalomethanes' (TTHMs) and their precursors' removal by granulated activated carbon (GAC) and sand dual media by response surface methodology (RSM)
A response surface methodology (RSM) applying central composite design with rotatable full factorial (14 non-center and six center points) was used to discern the effect of granular activated carbon (GAC), sand and pH on total trihalomethanes (TTHMs) and humic acid (HA) removal from drinking water. Results showed efficient TTHMs and HA removal by GAC while a sand column showed little effect for TTHMs but was significant for total organic carbon (TOC) removal. With GAC and a sand column of 4 cm, a pH increase from 6 to 8 caused an increase in TTHM removal from 79.8 to 83.6% while a decrease in HA removal from 26.6 to 6.6% was observed. An increase in GAC column depth from 10 to 20 cm caused a slight increase in TTHM removal from 99.4 to 99.7%, while TOC removal was increased from an average of 38.85% to 57.4% removal. The developed quadratic model for TTHM removal (p = 0.048) and linear model for TOC removal (p = 0.039) were significant. GAC column depth (p < 0.0117) and column depth2 (p < 0.039) were the most significant factors. A 98% TTHMs, 30%TOC and 51% residual chlorine removal were optimized at 9 cm GAC and 4 cm sand column depth at pH 8 with desirability factor (D) 0.64
Central composite rotatable design for optimization of trihalomethane extraction and detection through gas chromatography: a case study
Central composite rotatable design (CCRD) was employed to optimize initial temperature (ºC), ramp function (ºC/min) and salt addition for trihalomethane extraction/quantification from the drinking water distribution network in Ratta Amral, Rawalpindi., Pakistan. Drinking water samples were collected from the treatment plant, overhead reservoir and consumer’s taps. The USEPA method for trihalomethane detection 551.1 via gas chromatography was applied using liquid–liquid extraction. The experiments with input variables for sample preparation and operational conditions were performed in a randomized order as per design of experiment by central composite rotatable design and responses were evaluated for model development. A significant (p = 0.005) two-factor interaction model was optimized. Initial temperature was observed to be insignificant (p = 0.64), while ramp function (p = 0.0043) and salt addition (p = 0.04) were significant. Product of salt addition and ramp was significant (p = 0.004), while product of initial temperature and salt addition was insignificant (p = 0.008). With a desirability function of 0.97, an initial temperature of 50 ºC, 6 ºC rise/min to 180 ºC and 0.5 g salt were optimized. It was found that development and optimization of the analytical methods for rapid trihalomethane detection would improve optimization of the current treatment practices in the country
Concurrent Segmentation and Localization for Tracking of Surgical Instruments
Real-time instrument tracking is a crucial requirement for various
computer-assisted interventions. In order to overcome problems such as specular
reflections and motion blur, we propose a novel method that takes advantage of
the interdependency between localization and segmentation of the surgical tool.
In particular, we reformulate the 2D instrument pose estimation as heatmap
regression and thereby enable a concurrent, robust and near real-time
regression of both tasks via deep learning. As demonstrated by our experimental
results, this modeling leads to a significantly improved performance than
directly regressing the tool position and allows our method to outperform the
state of the art on a Retinal Microsurgery benchmark and the MICCAI EndoVis
Challenge 2015.Comment: I. Laina and N. Rieke contributed equally to this work. Accepted to
MICCAI 201
Fenton pre-oxidation of natural organic matter in drinking water treatment through the application of iron nails
This study investigated for the first time the efficiency of an advanced oxidation process (AOP) zero valent iron/hydrogen peroxide (ZVI/H2O2) employing iron nails for the removal of Natural Organic Matter (NOM) from natural water of Regent's Park lake, London, UK. The low cost of nails and their easy separation from the water after the treatment make this AOP attractive for water utilities in low- and middle-income countries. The process was investigated as a pre-oxidation step for drinking water treatment. Results showed that UV254 removal in the natural water was lower than that of simulated water containing commercial humic acid (HA), indicating a matrix effect. Statistical analysis confirmed the maximum removal of dissolved organic carbon (DOC) in natural water depends on the initial pH (best at 4.5) and H2O2 dosage (best at 100% excess of stoichiometric dosage). DOC and UV254 removals under this operational condition were 51% and 89%, respectively. Molecular weight (MW) and specific UV absorbance (SUVA254) were significantly reduced to 74% and 78%, respectively. Formation of chloroform THM in natural water sample after the ZVI/H2O2 process (initial pH 4.5) was below the limit for drinking water, and 48% less than the THM formation in the same water not subjected to pre-oxidation. Characterization of oxidation products on the iron-nail-ZVI surface after the ZVI/H2O2 treatment by SEM, XRD, and XPS identified the formation of magnetite and lepidocrocite. Results suggest that the investigated ZVI/H2O2 process to be a promising technology for removing NOM and reducing THM formation during drinking water treatment
Structural and Functional Brain Remodeling during Pregnancy with Diffusion Tensor MRI and Resting-State Functional MRI
Although pregnancy-induced hormonal changes have been shown to alter the brain at the neuronal level, the exact effects of pregnancy on brain at the tissue level remain unclear. In this study, diffusion tensor imaging (DTI) and resting-state functional MRI (rsfMRI) were employed to investigate and document the effects of pregnancy on the structure and function of the brain tissues. Fifteen Sprague-Dawley female rats were longitudinally studied at three days before mating (baseline) and seventeen days after mating (G17). G17 is equivalent to the early stage of the third trimester in humans. Seven age-matched nulliparous female rats served as non-pregnant controls and were scanned at the same time-points. For DTI, diffusivity was found to generally increase in the whole brain during pregnancy, indicating structural changes at microscopic levels that facilitated water molecular movement. Regionally, mean diffusivity increased more pronouncedly in the dorsal hippocampus while fractional anisotropy in the dorsal dentate gyrus increased significantly during pregnancy. For rsfMRI, bilateral functional connectivity in the hippocampus increased significantly during pregnancy. Moreover, fractional anisotropy increase in the dentate gyrus appeared to correlate with the bilateral functional connectivity increase in the hippocampus. These findings revealed tissue structural modifications in the whole brain during pregnancy, and that the hippocampus was structurally and functionally remodeled in a more marked manner.published_or_final_versio
Prioritizing genes responsible for host resistance to influenza using network approaches
published_or_final_versio
Probing Lepton Flavor Violation Signal Induced by R-violating Minimal Supersymmetric Standard Model at a Linear Collider
The lepton-flavor violation (LFV) effect at an linear collider (LC),
in the frame of R-parity violating minimal supersymmetric standard model is
studied. We take the R-parity violating processes
as signal, and define the summation of the two processes as ``experiment''
observable. We find that the cross-section summation can reach
in the parameter space without sneutrino resonance
effect(). The summation treatment manifests
uniform differential distribution on , where denotes the
polar angles of both outgoing respectively to incoming electron beam
in two signal processes. The uniform feature together with collinearity
would help to reduce the SM background dramatically. Consequently we conclude
that at a LC with annual luminosity, it's either
possible to detect the distinctive R-violating LFV signal, or exclude
sneutrino to at 95% CL in the machine's biennial
runtime interval.Comment: 14 pages, 9 figure
"Centralized or Decentralized?": Concerns and Value Judgments of Stakeholders in the Non-Fungible Tokens (NFTs) Market
Non-fungible tokens (NFTs) are decentralized digital tokens to represent the
unique ownership of items. Recently, NFTs have been gaining popularity and at
the same time bringing up issues, such as scams, racism, and sexism.
Decentralization, a key attribute of NFT, contributes to some of the issues
that are easier to regulate under centralized schemes, which are intentionally
left out of the NFT marketplace. In this work, we delved into this
centralization-decentralization dilemma in the NFT space through mixed
quantitative and qualitative methods. Centralization-decentralization dilemma
is the dilemma caused by the conflict between the slogan of decentralization
and the interests of stakeholders. We first analyzed over 30,000 NFT-related
tweets to obtain a high-level understanding of stakeholders' concerns in the
NFT space. We then interviewed 15 NFT stakeholders (both creators and
collectors) to obtain their in-depth insights into these concerns and potential
solutions. Our findings identify concerning issues among users: financial
scams, counterfeit NFTs, hacking, and unethical NFTs. We further reflected on
the centralization-decentralization dilemma drawing upon the perspectives of
the stakeholders in the interviews. Finally, we gave some inferences to solve
the centralization-decentralization dilemma in the NFT market and thought about
the future of NFT and decentralization.Comment: Accepted by CSCW 202
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