Level Of Scaling Research Articles

Association between dental scaling and metabolic syndrome and lifestyle.

Periodontal disease is a risk factor for diabetes and metabolic syndrome, and non-surgical periodontal treatment has been shown to help maintain stable blood sugar in diabetic patients. Determining the level of preventive scaling in patients with metabolic syndrome will help manage the disease. The purpose of this study was to investigate the extent to which people with metabolic syndrome or bad lifestyle performed scaling and the association between preventive scaling and metabolic syndrome or lifestyle in a large population. This study was conducted on adults aged 20 years or older from January 2014 to December 2017 in the National Health Insurance System (NHIS) database. Among 558,067 people who underwent health checkups, 555,929 people were included. A total of 543,791 people were investigated for preventive scaling. Metabolic syndrome components were abdominal obesity, lower high density lipoprotein cholesterol (HDL)-C, high triglycerides, high blood pressure and hyperglycemia. Unhealthy lifestyle score was calculated by assigning 1 point each for current smokers, drinkers, and no performing regular exercise. When multiple logistic regression analysis was performed after adjusting for age, sex, income, body mass index (BMI), smoking, drinking and regular exercise, the Odds ratios (OR) and 95% confidence intervals (CI) of the group with 5 metabolic syndrome components were 0.741 (0.710, 0.773) (p<0.0001). After adjustment for age, sex, income, BMI, smoking, drinking, regular exercise, diabetes, hypertension and dyslipidemia, the OR (95% CI) of the group with unhealthy lifestyle score = 3 was 0.612 (0.586, 0.640) (p<0.0001). The more metabolic syndrome components, and the higher unhealthy lifestyle score, the less scaling was performed.

Investigation on the heat transfer and charge/discharge performance of phase change material capsule emulsion based on nanoparticles enhanced thermal conductivity

Both internal encapsulation and external added nanoparticles have been employed in this study to enhance thermal conductivity and explore the corresponding heat transfer characteristics. Specifically, the correlation between thermal conductivity and capsule, nanoparticle content, as well as the enhanced heat transfer/thermal energy storage performance facilitated by internal encapsulation are demonstrated through numerical and experimental study. Furthermore, it compares key parameters like heat transfer and pressure drop, providing quantifiable evidence that the addition of nanoparticles, whether internally or externally, leads to an increase of thermal conductivity by 6.63 %/2.75 % (5 wt%) and 5.92 %/4.26 % (10 wt%), respectively. Internal encapsulation was observed to yield a more substantial enhancement in heat transfer. Moreover, higher capsule concentrations tend to induce an inverted concentration profile near the heat exchange wall, particularly at higher flow rates. Furthermore, encapsulating nanoparticles within these capsules enhances heat transfer performance, with the level of enhancement scaling with the nanoparticle quantity. Increasing the flow rate of emulsion from 0.4 m·s−1 to 0.6 m·s−1 in a horizontal tube resulted in a 26.67 % increase in heat transfer and a 41.55 % increase in pressure drop. As a result of the disturbed heating, thermal fluctuations of external addition showed more pronounced thermal fluctuations due to disrupted heating, while a internal encapsulation exhibited a more stable temperature distribution and superior heat storage performance.

A chip-scale polarization-spatial-momentum quantum SWAP gate in silicon nanophotonics

Recent progress in quantum computing and networking has enabled high-performance, large-scale quantum processors by connecting different quantum modules. Optical quantum systems show advantages in both computing and communications, and integrated quantum photonics further increases the level of scaling and complexity. Here we demonstrate an efficient SWAP gate that deterministically swaps a photon’s polarization qubit with its spatial-momentum qubit on a nanofabricated two-level silicon photonics chip containing three cascaded gates. The on-chip SWAP gate is comprehensively characterized by tomographic measurements with high fidelity for both single-qubit and two-qubit operation. The coherence preservation of the SWAP gate process is verified by single-photon and two-photon quantum interference. The coherent reversible conversion of our SWAP gate facilitates examinations of a quantum interconnect between two chip-scale photonic subsystems with different degrees of freedom, now demonstrated by distributing four Bell states between the two chips. We also elucidate the source of decoherence in the SWAP operation in pursuit of near-unity fidelity. Our deterministic SWAP gate in the silicon platform provides a pathway towards integrated quantum information processing for interconnected modular systems. A deterministic single-photon two-qubit SWAP gate between polarization and spatial-momentum is demonstrated on a silicon chip. A two-qubit swapping process fidelity of 94.9% is obtained. The coherence preservation of the SWAP gate process is verified by two-photon interference.

Prioritization of pig farm biosecurity for control of Salmonella and hepatitis E virus infections: results of a European expert opinion elicitation

BackgroundIn the literature, there is absent or weak evidence on the effectiveness of biosecurity measures to the control of Salmonella spp. and hepatitis E virus (HEV) on pig farms. Therefore, the present study aimed to collect, weigh, and compare opinions from experts on the relevance of several biosecurity measures. An online questionnaire was submitted to selected experts, from multiple European countries, knowledgeable on either HEV or Salmonella spp., in either indoor or outdoor pig farming systems (settings). The experts ranked the relevance of eight biosecurity categories with regards to effectiveness in reducing the two pathogens separately, by assigning a score from a total of 80, and within each biosecurity category they scored the relevance of specific biosecurity measures (scale 1–5). Agreement among experts was analysed across pathogens and across settings.ResultsAfter filtering for completeness and expertise, 46 responses were analysed, with 52% of the experts identified as researchers/scientists, whereas the remaining 48% consisted of non-researchers, veterinary practitioners and advisors, governmental staff, and consultant/industrial experts. The experts self-declared their level of knowledge but neither Multidimensional Scaling nor k-means cluster analyses produced evidence of an association between expertise and the biosecurity answers, and so all experts’ responses were analysed together without weighting or adaptation. Overall, the top-ranked biosecurity categories were pig mixing; cleaning and disinfection; feed, water and bedding; and purchase of pigs or semen, while the lowest ranked categories were transport, equipment, animals (other than pigs and including wildlife) and humans. Cleaning and disinfection was ranked highest for both pathogens in the indoor setting, whereas pig mixing was highest for outdoor settings. Several (94/222, 42.3%) measures across all four settings were considered highly relevant. Measures with high disagreement between the respondents were uncommon (21/222, 9.6%), but more frequent for HEV compared to Salmonella spp.ConclusionsThe implementation of measures from multiple biosecurity categories was considered important to control Salmonella spp. and HEV on farms, and pig mixing activities, as well as cleaning and disinfection practices, were perceived as consistently more important than others. Similarities and differences in the prioritised biosecurity measures were identified between indoor and outdoor systems and pathogens. The study identified the need for further research especially for control of HEV and for biosecurity in outdoor farming.

Occupational hazards among dental hygienists: Risk level assessment of scaling work.

This study aimed to classify occupational hazards of ultrasonic scaling by factor and to identify the distribution of occupational risk levels of the study participants according to occupational hazards. In addition, the relationship between the general characteristics of dental hygienists and the occupational risk level of scaling was investigated. This study was conducted on 237 dental hygienists. Exposure frequency and the degree of work loss were investigated on a five-point scale for each of the 15 occupational hazards of scaling. Among occupational hazards, the proportion of high-risk individuals for biological hazards (32.9%) was the highest. Dental clinics (33.6%) were found to have a higher proportion of high-risk individuals than dental hospitals (16.5%) (p < 0.05). The proportion of high-risk individuals was higher in the absence of an infection control coordinator (33.9%) (p < 0.05) and infection control education in the preceding 2 years (28.6%) (p < 0.05). To create a safe dental work environment, appropriate measures according to the risk level and measurement of occupational risk should be discussed.

Spike-Timing-Dependent Plasticity With Activation-Dependent Scaling for Receptive Fields Development.

Spike-timing-dependent plasticity (STDP) is one of the most popular and deeply biologically motivated forms of unsupervised Hebbian-type learning. In this article, we propose a variant of STDP extended by an additional activation-dependent scale factor. The consequent learning rule is an efficient algorithm, which is simple to implement and applicable to spiking neural networks (SNNs). It is demonstrated that the proposed plasticity mechanism combined with competitive learning can serve as an effective mechanism for the unsupervised development of receptive fields (RFs). Furthermore, the relationship between synaptic scaling and lateral inhibition is explored in the context of the successful development of RFs. Specifically, we demonstrate that maintaining a high level of synaptic scaling followed by its rapid increase is crucial for the development of neuronal mechanisms of selectivity. The strength of the proposed solution is assessed in classification tasks performed on the Modified National Institute of Standards and Technology (MNIST) data set with an accuracy level of 94.65% (a single network) and 95.17% (a network committee)-comparable to the state-of-the-art results of single-layer SNN architectures trained in an unsupervised manner. Furthermore, the training process leads to sparse data representation and the developed RFs have the potential to serve as local feature detectors in multilayered spiking networks. We also prove theoretically that when applied to linear Poisson neurons, our rule conserves total synaptic strength, guaranteeing the convergence of the learning process.

NUGGET AYAM DAN HALILING UNTUK MENCEGAH ANEMIA PADA BALITA: UJI KADAR PROTEIN, ZAT BESI, DAN TINGKAT KESUKAAN

Toddlers are a group that is prone to anemia. One of the efforts to prevent anemia in a toddler is by fulfilling nutrients such as protein and iron. Chicken and haliling are high protein and iron foods that can be used to prevent anemia in toddlers. This study aims to determine the level of protein, iron and hedonic scaling (color, aroma, texture, and taste) of chicken nuggets and haliling as a snack for a toddler to prevent anemia. The method used in this study was a pure experimental design with a completely randomized design (CRD) with 4 treatments and 3 replications with the proportions of chicken and haliling P0 (100%:0%), P1 (90%:10%), P2 (80%:20%), P3 (70%:30%). The research panelists consisted of 25 untrained panelists. Analysis of protein content using the Kjeldahl method and iron using the visible spectrophotometric method, analysis of protein content data using Kruskal Wallis, iron using One Way Anova and hedonic scaling using Friedman. The results showed that there was an effect of the proportion of chicken and haliling on protein content (p=0.016), iron (p=0.001), color hedonic scaling (p=0.004), aroma (p=0.001), texture (p=0.001) and taste (p=0.001) on nuggets. The highest protein content at P3 was 11.27 g/100 g, the highest iron content at P3 was 2.2 mg/100 g, and the hedonic scaling for nuggets containing the proportions of chicken and halilings for color, aroma, texture, and taste was highest at P1 with an average of 3.2, 2.95, 3.25 and 2.85

Метод оптимізації інформаційних моделей масштабованих у просторі аналітичних веб-систем за критерієм повноти їхньої топологічної спостережуваності

The article considers the issue of optimization of information models of space-scaled analytical web systems by the criterion of completeness of their topological observability. The previously created, with the participation of some co-authors, information technology analysis and optimization of topological observability of multilinked geographic information systems, i.e. — optimization of the system model in the form of a dichromatic graph, which allows arbitrary input variables to obtain values of state variables or current system parameters. information about the current state to synthesize the law of its management. In such a bichromatic graph, some vertices are variable and others are dependencies between them. This technology introduces the criterion of observability, which can take values from 0 to 1 and compare different models according to the level of their observability and optimize them by choosing the most observable option. This paper proposes how such a model formalization and this technology can be extended to the formalization of space-scaled analytical web systems. Then a new method of optimizing information models of such systems by the criterion of completeness of their topological observability was proposed, which allows to analyze the completeness of this observability both at each level of scaling in space where analytical operations are planned in the projected web system and for the whole systems in general. It is proposed to optimize the model by introducing additional vertices-variables and vertices-dependencies between different levels. That is, in the absence of data or dependencies at one level of the system, they can sometimes be obtained from data or dependencies at another level, and vice versa, which will increase the observability of the system as a whole. The method allows both to analyze the level of topological observability and to analyze it after optimization. As a result of such analysis, it is possible to impose software constraints on the functionality of the web system to avoid queries or dependencies that are not provided with data or dependencies from which they could be obtained due to incomplete topological observability of individual (or all) levels. The paper demonstrates the work of the method on the example of developing an automated web system for calculating and forecasting the water balance of the Dniester basin. The application of the developed approach at the design stage of this system ensured the avoidance of queries or dependencies not provided with data. The system was developed and successfully implemented. The developed method of optimizing information models of space-scaled analytical web systems by the criterion of completeness of their topological observability can be used in the analysis and design of systems that reflect environmental or infrastructure data distributed in space and have several levels of detail. These can be cadastral systems, environmental monitoring systems, etc.

Scaling of the AIS and Somatodendritic Compartments in α S RGCs.

The anatomical properties of the axon initial segment (AIS) are tailored in certain types of CNS neurons to help optimize different aspects of neuronal function. Here, we questioned whether the AISs of retinal ganglion cells (RGC) were similarly customized, and if so, whether they supported specific RGC functions. To explore this, we measured the AIS properties in alpha sustained RGCs (α S RGCs) of mouse; α S RGCs sizes vary systematically along the nasal temporal axis of the retina, making these cells an attractive population with which to study potential correlations between AIS properties and cell size. Measurements of AIS length as well as distance from the soma revealed that both were scaled to cell size, i.e., cells with large dendritic fields had long AISs that were relatively far from the soma. Within the AIS, the percentage of Nav1.6 voltage-gated sodium channels remained highly consistent, regardless of cell size or other AIS properties. Although ON RGCs were slightly larger than OFF cells at any given location of the retina, the level of scaling and relative distribution of voltage-gated sodium channels were highly similar. Computational modeling revealed that AIS scaling influenced spiking thresholds, spike rate as well as the kinetics of individual action potentials, Interestingly, the effect of individual features of the AIS varied for different neuronal functions, e.g., AIS length had a larger effect on the efficacy by which the AIS initiated spike triggered the somatic spike than it did on repetitive spiking. The polarity of the effect varied for different properties, i.e., increases to soma size increased spike threshold while increases to AIS length decreased threshold. Thus, variations in the relative level of scaling for individual components could fine tune threshold or other neuronal functions. Light responses were highly consistent across the full range of cell sizes suggesting that scaling may post-synaptically shape response stability, e.g., in addition to several well-known pre-synaptic contributors.

Accelerating magnetic induction tomography‐based imaging through heterogeneous parallel computing

SummaryMagnetic Induction Tomography (MIT) is a non‐invasive imaging technique, which has applications in both industrial and clinical settings. In essence, it is capable of reconstructing the electromagnetic parameters of an object from measurements made on its surface. With the exploitation of parallelism, it is possible to achieve high quality inexpensive MIT images for biomedical applications on clinically relevant time scales. In this paper we investigate the performance of different parallel implementations of the forward eddy current problem, which is the main computational component of the inverse problem through which measured voltages are converted into images. We show that a heterogeneous parallel method that exploits multiple CPUs and GPUs can provide a high level of parallel scaling, leading to considerably improved runtimes. We also show how multiple GPUs can be used in conjunction with deal.II, a widely‐used open source finite element library.

Influence of natural gas production chemicals on scale production in MEG regeneration systems

Monoethylene glycol (MEG), a common hydrate inhibitor in natural gas transportation pipelines is usually regenerated and reused to minimize operating costs. In this study, three corrosion inhibitors and a scale inhibitor were investigated to understand how production chemicals contribute to scaling (salt loading) at pretreatment and reclamation sections of the regeneration process. The first set of study involved the use of ScaleSoftPitzer software to investigate the possibility of salt deposition at the pretreatment stage. Experiments were then conducted at pretreatment stage for inhibitor doses of 250ppm and 1000ppm. The same sets of experiments were repeated by adding equal concentration of scale inhibitor with each corrosion inhibitor. In the second part of the study, rich MEG recovered from the pretreatment stage was regenerated by reconcentration and vacuum distillation techniques. The solids formed in the liquor were filtered, dried and weighed and the experiments performed at the pretreatment stage repeated. The results showed that level of scaling in the pretreatment stage was well predicted by the software. The experimental results were also consistent with the software predictions. Corrosion inhibitors produced salts that add up to the scaling problems while the scale inhibitor showed more adverse scaling effects comparatively. This is attributed to reduced hydration ability of scale inhibitors compared to corrosion inhibitors that contained smaller functional groups and large alkyl groups. Benzyl dimethyl hexadecylammonium chloride (B.D.H.C) showed higher scale formation ability compared to the other two corrosion inhibitors due to its polarity that influences its affinity for water. Alkalinity was another factor affecting scale formation; the higher the alkalinity, the higher the scale formation. Furthermore, the reclamation stage was found to be highly prone to corrosion and other impacts due to high total dissolved solids (TDS). Besides, a combination of corrosion and scale inhibitors in MEG regeneration system resulted in higher scaling effects compared to the effect of individual inhibitor due to the synergistic interaction between the two inhibitors. The findings of this study show significant implications in large scale continuous operation where salts dissolved in MEG could precipitate to cause scaling, corrosion and gunking amongst others. Escaping less soluble divalent ions are also capable of salting out downstream to cause the same problems within the pipeline and refinery. All these will adversely influence the process safety and the environment.

Flexible integrated circuits and multifunctional electronics based on single atomic layers of MoS2 and graphene

Two-dimensional materials, such as graphene and its analogues, have been investigated by numerous researchers for high performance flexible and conformal electronic systems, because they offer the ultimate level of thickness scaling, atomically smooth surfaces and high crystalline quality. Here, we use layer-by-layer transfer of large area molybdenum disulphide (MoS2) and graphene grown by chemical vapor deposition (CVD) to demonstrate electronics on flexible polyimide (PI) substrates. On the same PI substrate, we are able to simultaneously fabricate MoS2 based logic, non-volatile memory cells with graphene floating gates, photo-detectors and MoS2 transistors with tunable source and drain contacts. We are also able to demonstrate that these flexible heterostructure devices have very high electronic performance, comparable to four point measurements taken on SiO2 substrates, with on/off ratios >107 and field effect mobilities as high as 16.4 cm2 V−1 s−1. Additionally, the heterojunctions show high optoelectronic sensitivity and were operated as photodetectors with responsivities over 30 A W−1. Through local gating of the individual graphene/MoS2 contacts, we are able to tune the contact resistance over the range of 322–1210 Ω mm for each contact, by modulating the graphene work function. This leads to devices with tunable and multifunctional performance that can be implemented in a conformable platform.

Continuous wireless pressure monitoring and mapping with ultra-small passive sensors for health monitoring and critical care.

Continuous monitoring of internal physiological parameters is essential for critical care patients, but currently can only be practically achieved via tethered solutions. Here we report a wireless, real-time pressure monitoring system with passive, flexible, millimetre-scale sensors, scaled down to unprecedented dimensions of 1 × 1 × 0.1 cubic millimeters. This level of dimensional scaling is enabled by novel sensor design and detection schemes, which overcome the operating frequency limits of traditional strategies and exhibit insensitivity to lossy tissue environments. We demonstrate the use of this system to capture human pulse waveforms wirelessly in real time as well as to monitor in vivo intracranial pressure continuously in proof-of-concept mice studies using sensors down to 2.5 × 2.5 × 0.1 cubic millimeters. We further introduce printable wireless sensor arrays and show their use in real-time spatial pressure mapping. Looking forward, this technology has broader applications in continuous wireless monitoring of multiple physiological parameters for biomedical research and patient care.

Full 3D surface reconstruction of partial scan data with noise and different levels of scale

We propose an algorithm to align partial surfaces. The algorithm does not assume specific initial positions and the same level of scaling for source and target models. The corresponding points between models are computed by detecting the scale-space extrema of the geometric invariant of the models in 2D parametric domain induced by conformal parameterization. We also propose squared distance function (SDF) to describe the invariant geometric values of a model. SDF represents the rich local shape of a surface and shows relatively robust results for a noisy model. These characteristics of SDF improve the matching result in the parametric domain for they are helpful to detect the extrema of the geometric invariant of the local shape. The proposed method computes faster the corresponding points between models and finds a greater number of corresponding points than existing methods do. Experimental results show that our proposed algorithm can successfully handle 3D scan models that have less overlap between them than that required for the existing methods.

Low-frequency scaling applied to stochastic finite-fault modeling

Stochastic finite-fault modeling is an important tool for simulating moderate to large earthquakes. It has proven to be useful in applications that require a reliable estimation of ground motions, mostly in the spectral frequency range of 1 to 10 Hz, which is the range of most interest to engineers. However, since there can be little resemblance between the low-frequency spectra of large and small earthquakes, this portion can be difficult to simulate using stochastic finite-fault techniques. This paper introduces two different methods to scale low-frequency spectra for stochastic finite-fault modeling. One method multiplies the subfault source spectrum by an empirical function. This function has three parameters to scale the low-frequency spectra: the level of scaling and the start and end frequencies of the taper. This empirical function adjusts the earthquake spectra only between the desired frequencies, conserving seismic moment in the simulated spectra. The other method is an empirical low-frequency coefficient that is added to the subfault corner frequency. This new parameter changes the ratio between high and low frequencies. For each simulation, the entire earthquake spectra is adjusted, which may result in the seismic moment not being conserved for a simulated earthquake. These low-frequency scaling methods were used to reproduce recorded earthquake spectra from several earthquakes recorded in the Pacific Earthquake Engineering Research Center (PEER) Next Generation Attenuation Models (NGA) database. There were two methods of determining the stochastic parameters of best fit for each earthquake: a general residual analysis and an earthquake-specific residual analysis. Both methods resulted in comparable values for stress drop and the low-frequency scaling parameters; however, the earthquake-specific residual analysis obtained a more accurate distribution of the averaged residuals.

Mitigating the effect of optical back-scatter in multispectral underwater imaging

Multispectral imaging is a very useful technique for extracting information from the underwater world. However, optical back-scatter changes the intensity value in each spectral band and this distorts the estimated spectrum. In this work, a filter is used to detect the level of optical back-scatter in each spectral band from a set of multispectral images. Extraction of underwater object spectra can be done by subtracting the estimated level of optical back-scatter and scaling the remainder in each spectral band from the captured image in the corresponding band. An experiment has been designed to show the performance of the proposed filter for correcting the set of multispectral underwater images and recovering the pixel spectra. The multispectral images are captured by a B/W CCD digital camera with a fast tunable liquid-crystal filter in 33 narrow spectral bands in clear and different levels of turbid water. Reference estimates for the optical back-scatter spectra are found by comparing a clear and a degraded set of multispectral images. The accuracy and consistency of the proposed method, the extended Oakley–Bu cost function, is examined by comparing the estimated values with the reference level of an optical back-scatter spectrum. The same comparison is made for the simple estimation approach. The results show that the simple method is not reliable and fail to estimate the level of optical back-scatter spectrum accurately. The results from processing experimental images in turbid water show that the effect of optical back-scatter can be mitigated in the image of each spectral band and, as a result, the spectra of the object can be recovered. However, for a very high level of turbid water the recovery is limited because of the effect of extinction.

A numerical study of the 2-flavour Schwinger model with dynamical overlap hypercube fermions

We present numerical results for the 2-flavour Schwinger model with dynamical chiral lattice fermions. We insert an approximately chiral hypercube Dirac operator into the overlap formula to construct the overlap hypercube operator. This is an exact solution to the Ginsparg-Wilson relation, with an excellent level of locality and scaling. Due to its similarity with the hypercubic kernel, a low polynomial in this kernel provides a numerically efficient Hybrid Monte Carlo force. We measure the microscopic Dirac spectrum and discuss the corresponding scale-invariant parameter, which takes a surprising form. This is an interesting case, since Random Matrix Theory is unexplored for this setting, where the chiral condensate {\Sigma} vanishes in the chiral limit. We also measure {\Sigma} and the "pion" mass, in distinct topological sectors. In this context we discuss and probe the topological summation of observables by various methods, as well as the evaluation of the topological susceptibility. The feasibility of this summation is essential for the prospects of dynamical overlap fermions in QCD.

A Comparison of Psychometric Properties and Normality in 4-, 5-, 6-, and 11-Point Likert Scales

ABSTRACT The Likert scale is very popular, but the question as to the number of scale points is still controversial. This article studies the differences among 4-, 5-, 6-, and 11-point Likert scales with a sample of 1,217 students in Macau, using the Rosenberg Self-Esteem Scale as the measuring instrument. There is no major difference in internal structure in terms of means, standard deviations, item–item correlations, item–total correlations, Cronbach's alpha, or factor loadings. Findings indicate that having more scale points seems to reduce skewness, and the 11-point scale, ranging from 0 to 10, has the smallest kurtosis and is closest to normal. Only the 6- and 11-point scales follow normal distributions from Kolmogorov–Smirnov and Shapiro–Wilk statistics. Results on predictive validity are inconclusive. This article discusses future applications and suggests the use of an 11-point scale as it increases sensitivity and is closer to interval level of scaling and normality. Recommendations for social workers and teachers are made to better assist when using self-reported measurement scales.

Quantum Monte Carlo Simulation of Nanoscale MgH2 Cluster Thermodynamics

We calculated the desorption energy of MgH(2) clusters using the highly accurate quantum Monte Carlo (QMC) approach, which can provide desorption energies with chemical accuracy (within approximately 1 kcal/mol) and therefore provides a valuable benchmark for such hydrogen-storage simulations. Compared with these QMC results, the most widely used density functional theory (DFT) computations (including a wide range of exchange-correlation functionals) cannot reach a consistent and suitable level of accuracy across the thermodynamically tunable range for MgH(2) clusters. Furthermore, our QMC calculations show that the DFT error depends substantially on cluster size. These results suggest that in simulating metal-hydride systems it is very important to apply accurate methods that go beyond traditional mean-field approaches as a benchmark of their performance for a given material, and QMC is an appealing method to provide such a benchmark due to its high level of accuracy and favorable scaling (N(3)) with the number of electrons.

Membrane autopsy to investigate CaCO3 scale formation in pilot‐scale, submerged membrane bioreactor treating calcium‐rich wastewater

AbstractBACKGROUND: Membrane scaling is an area of research interest because it can deteriorate membrane performance. The extent to which membrane scaling is produced varies depending upon the concentration of scale‐forming species such as calcium on the membrane surface. Bench‐scale tests have been conducted to better understand membrane scaling in submerged membrane reactors (MBR). However, relatively few studies of membrane scaling in pilot‐scale, submerged MBR have been reported. The objective of this study was to perform membrane autopsy work to analyze membrane scaling in a submerged MBR treating calcium‐rich wastewater.RESULTS: Membrane autopsy work provided evidence that deposition of calcium carbonate (CaCO3) scale occurred on the membrane surface at the completion of pilot‐scale, submerged MBR operation. The CaCO3 scaling resulted in significant external fouling on the surface of the membrane. The membrane scaling increased the rejection of calcium with MF membranes. However, the level of CaCO3 scaling as internal fouling (in the pores) was almost negligible. This autopsy work also showed that aeration did not play a major role in controlling CaCO3 scaling at the membrane surface in a submerged MBR. Chemical cleaning using citric acid solution efficiently removed CaCO3 scale from the membrane. Combining citric acid with sodium hypochlorite pretreatment provided synergistic effects, further reducing CaCO3 scale formation.CONCLUSION: The carbonate salt of calcium leads to precipitation resulting in surface fouling of membranes, and this cannot be removed physically by aeration in a submerged MBR treating calcium‐rich wastewater. It is necessary to combine properly‐selected cleaning strategies with submerged MBR treating wastewater containing a high potential for inorganic chemical precipitates. Copyright © 2009 Society of Chemical Industry