Low Cost Dewatering of Waste Slurries

The U.S. Bureau of Mines has developed a technique for dewatering mineral waste slurries which utilizes polymer and a static screen. A variety of waste slurries from placer gold mines and crushed stone operations have been successfully treated using the system. Depending on the waste, a number of polymers have been used successfully with polymer costs ranging from $0.05 to$0.15 per 1,000 gal treated. The dewatering is accomplished using screens made from either ordinary window screen or wedge wire. The screens used are 8 ft wide and 8 ft long. The capacity of the screens varies from 3 to 7 gpm/sq. ft. The water produced is acceptable for recycling to the plant or for discharge to the environment. For example, a fine grain dolomite waste slurry produced from a crushed stone operation was dewatered from a nominal 2.5 pct solids to greater than 50 pct solids using $0.10 to$0.15 worth of polymer per 1,000 gal of slurry. The resulting waste water had a turbidity of less than 50 NTU and could be discharged or recycled. The paper describes field tests conducted using the polymer-screen dewatering system

Polarization forces in water deduced from single molecule data

Intermolecular polarization interactions in water are determined using a minimal atomic multipole model constructed with distributed polarizabilities. Hydrogen bonding and other properties of water-water interactions are reproduced to fine detail by only three multipoles $\mu_H$, $\mu_O$, and $\theta_O$ and two polarizabilities $\alpha_O$ and $\alpha_H$, which characterize a single water molecule and are deduced from single molecule data.Comment: 4 revtex pages, 3 embedded color PS figure

Studying patterns of use of transport modes through data mining - Application to U.S. national household travel survey data set

Data collection activities related to travel require large amounts of financial and human resources to be conducted successfully. When available resources are scarce, the information hidden in these data sets needs to be exploited, both to increase their added value and to gain support among decision makers not to discontinue such efforts. This study assessed the use of a data mining technique, association analysis, to understand better the patterns of mode use from the 2009 U.S. National Household Travel Survey. Only variables related to self-reported levels of use of the different transportation means are considered, along with those useful to the socioeconomic characterization of the respondents. Association rules potentially showed a substitution effect between cars and public transportation, in economic terms but such an effect was not observed between public transportation and nonmotorized modes (e.g., bicycling and walking). This effect was a policy-relevant finding, because transit marketing should be targeted to car drivers rather than to bikers or walkers for real improvement in the environmental performance of any transportation system. Given the competitive advantage of private modes extensively discussed in the literature, modal diversion from car to transit is seldom observed in practice. However, after such a factor was controlled, the results suggest that modal diversion should mainly occur from cars to transit rather than from nonmotorized modes to transi

Hydrogen bonding in infinite hydrogen fluoride and hydrogen chloride chains

Hydrogen bonding in infinite HF and HCl bent (zigzag) chains is studied using the ab initio coupled-cluster singles and doubles (CCSD) correlation method. The correlation contribution to the binding energy is decomposed in terms of nonadditive many-body interactions between the monomers in the chains, the so-called energy increments. Van der Waals constants for the two-body dispersion interaction between distant monomers in the infinite chains are extracted from this decomposition. They allow a partitioning of the correlation contribution to the binding energy into short- and long-range terms. This finding affords a significant reduction in the computational effort of ab initio calculations for solids as only the short-range part requires a sophisticated treatment whereas the long-range part can be summed immediately to infinite distances.Comment: 9 pages, 4 figures, 3 tables, RevTeX4, corrected typo

Quasiparticle band structure of infinite hydrogen fluoride and hydrogen chloride chains

We study the quasiparticle band structure of isolated, infinite HF and HCl bent (zigzag) chains and examine the effect of the crystal field on the energy levels of the constituent monomers. The chains are one of the simplest but realistic models of the corresponding three-dimensional crystalline solids. To describe the isolated monomers and the chains, we set out from the Hartree-Fock approximation, harnessing the advanced Green's function methods "local molecular orbital algebraic diagrammatic construction" (ADC) scheme and "local crystal orbital ADC" (CO-ADC) in a strict second order approximation, ADC(2,2) and CO-ADC(2,2), respectively, to account for electron correlations. The configuration space of the periodic correlation calculations is found to converge rapidly only requiring nearest-neighbor contributions to be regarded. Although electron correlations cause a pronounced shift of the quasiparticle band structure of the chains with respect to the Hartree-Fock result, the bandwidth essentially remains unaltered in contrast to, e.g., covalently bound compounds.Comment: 11 pages, 6 figures, 6 tables, RevTeX4, corrected typoe

Interaction between Temozolomide and Water: Preferred Binding Sites

Computational methods are used to predict the most favorable site of temozolomide towards attack by a water molecule. The energetics of the various complexes are presented as well as their geometries, including perturbations of each subunit caused by the presence of the other. Molecular electrostatic potential and Natural Bond Orbital (NBO) data are used to understand the interactions which conclude the terminal amide group is the preferred attack site where water can act as simultaneous proton donor and acceptor. Other potential proton acceptor N atoms within the aromatic ring structure represent weaker binding sites. Some of the less strongly bound structures include a CH⋯O H-bond

Life events and travel behavior exploring the interrelationship using UK Household Longitudinal Study data

Recent research has indicated that changes in travel behavior are more likely at the time of major life events. However, much remains to be learned about the extent to which different life events trigger behavioral change and the conditions under which life events are more likely to trigger change. The UK Household Longitudinal Study (UKHLS) offers a previously unavailable opportunity to investigate this topic for a large, representative sample of the UK population. UKHLS data were also linked to local spatial data drawn from the census and other sources to elucidate the effect of the spatial context on changes to travel behavior in association with life events. Findings from an exploratory analysis of data from UKHLS Waves 1 and 2 are presented first Transition tables demonstrate a strong association between changes in car ownership and commute mode and the following life events: employment changes, residential relocation, retirement, the birth of children, and changes in household structure. The results of logit models that relate the probability of an increase and a decrease in the number of cars owned to the occurrence of life events and that control for individual and household characteristics and spatial context are then shown. These models show, for example, that moves to urban and rural areas have contrasting effects on travel behavior and that having a new child in itself is not a significant influence on car ownership in the short term

Comparison Between Hydrogen and Halogen Bonds in Complexes of 6-OX-Fulvene with Pnicogen and Chalcogen Electron Donors

Quantum chemical calculations are applied to complexes of 6‐OX‐fulvene (X=H, Cl, Br, I) with ZH3/H2Y (Z=N, P, As, Sb; Y=O, S, Se, Te) to study the competition between the hydrogen bond and the halogen bond. The H‐bond weakens as the base atom grows in size and the associated negative electrostatic potential on the Lewis base atom diminishes. The pattern for the halogen bonds is more complicated. In most cases, the halogen bond is stronger for the heavier halogen atom, and pnicogen electron donors are more strongly bound than chalcogen. Halogen bonds to chalcogen atoms strengthen in the order

The Magnitude and Mechanism of Charge Enhancement of CH∙∙O H-bonds

Quantum calculations find that neutral methylamines and thioethers form complexes, with N-methylacetamide (NMA) as proton acceptor, with binding energies of 2–5 kcal/mol. This interaction is magnified by a factor of 4–9, bringing the binding energy up to as much as 20 kcal/mol, when a CH3+ group is added to the proton donor. Complexes prefer trifurcated arrangements, wherein three separate methyl groups donate a proton to the O acceptor. Binding energies lessen when the systems are immersed in solvents of increasing polarity, but the ionic complexes retain their favored status even in water. The binding energy is reduced when the methyl groups are replaced by longer alkyl chains. The proton acceptor prefers to associate with those CH groups that are as close as possible to the S/N center of the formal positive charge. A single linear CH··O hydrogen bond (H-bond) is less favorable than is trifurcation with three separate methyl groups. A trifurcated arrangement with three H atoms of the same methyl group is even less favorable. Various means of analysis, including NBO, SAPT, NMR, and electron density shifts, all identify the +CH··O interaction as a true H-bond

Segmentation and Additive Approach: A Reliable Technique to Study Noncovalent Interactions of Large Molecules at the Surface of Single‐Wall Carbon Nanotubes

This investigation explores a new protocol, named Segmentation and Additive approach (SAA), to study exohedral noncovalent functionalization of single-walled carbon nanotubes (SWNTs) with large molecules, such as polymers, bio-molecules etc, by segmenting the entire system into smaller units to reduce computational cost. A key criterion of the segmentation process is the preservation of the molecular structure responsible for stabilization of the entire system in smaller segments. Noncovalent interaction of linoleic acid (LA, C18H32O2), a fatty acid, at the surface of a (10,0) zigzag nanotubeis considered for test purposes. Three smaller segmented models have been created from the full (10,0)-LA system and interaction energies were calculated for these models and compared with the full system at different levels of theory, namely ωB97XD, LDA. The success of this SAA is confirmed as the sum of the interaction energies is in very good agreement with the total interaction energy. Besides reducing computational cost, another merit of SAA is an estimation of the contributions from different sections of the large system to the total interaction energy which can be studied in-depth using a higher level of theory to estimate several properties of each segment. On the negative side, bulk properties, such as HOMO-LUMO gap, of the entire system cannot be estimated by adding results from segment models