Demolished concretes recycling by the use of pneumatic jigs.

Large quantities of construction and demolition waste is generated annually around the world. Part of this material is processed in recycling plants. After removing metals, fines and lights, the construction and demolition waste is crushed and sized and can be used as aggregates for low resistance concrete, for road sub-base, city landfill and other low value-added applications. For their use as coarse aggregate in structural concretes, construction and demolition waste must exhibit high densities and regularity of the material. This material usually is presented in demolished concretes. About 20% of the particles from demolished concretes can be used as coarse aggregates substituting part of natural aggregates in structural concretes. This article presents studies of demolished concretes recycling by the use of a pneumatic jig. All jigging tests were carried out with three different concretes produced in three strength classes: C16/20, ordinary concrete; C50/60, high strength concrete; and C70/85, very high strength concrete. Based on density distribution of the three concretes, there are reasonable masses with densities over 2.7 g cm-3, particle density considered appropriate to the used as coarse aggregate for structural concretes. The concretes present different mass recoveries of the denser particles (different liberation). Coarse aggregates can be recovered with reasonable masses by the use of air jigs: About 65% for high strength concretes and about 75% for the low strength concrete. The jigging concentration efficiency depends on the concrete liberation, density and size distribution.

Ab initio quantum-chemical computations of the electronic states in HgBr2 and IBr: Molecules of interest on the Earth's atmosphere.

The electronic states of atmospheric relevant molecules IBr and HgBr2 are reported, within the UV-Vis spectrum range (170nm≤λphoton≤600 nm) by means of the complete-active-space self-consistent field/multi-state complete-active-space second-order perturbation theory/spin-orbit restricted-active-space state-interaction (CASSCF/MS-CASPT2/SO-RASSI) quantum-chemical approach and atomic-natural-orbital relativistic-correlation-consistent (ANO-RCC) basis sets. Several analyses of the methodology were carried out in order to reach converged results and therefore to establish a highly accurate level of theory. Good agreement is found with the experimental data with errors not higher than around 0.1 eV. The presented analyses shall allow upcoming studies aimed to accurately determine the absorption cross sections of interhalogen molecules and compounds with Hg that are relevant to better comprehend the photochemical processes taking place in the atmosphere.

A GIS-based approach: Influence of the ventilation layout to the environmental conditions in an underground mine.

Gases such as CO, CO2 or NOx are constantly generated by the equipment in any underground mine and the ventilation layout can play an important role in keeping low concentrations in the working faces. Hence, a method able to control the workplace environment is crucial. This paper proposes a geographical information system (GIS) for such goal. The system created provides the necessary tools to manage and analyse an underground environment, connecting pollutants and temperatures with the ventilation characteristics over time. Data concerning the ventilation system, in a case study, has been taken every month since 2009 and integrated into the management system, which has quantified the gasses concentration throughout the mine due to the characteristics and evolution of the ventilation layout. Three different zones concerning CO, CO2, NOx and effective temperature have been found as well as some variations among workplaces within the same zone that suggest local airflow recirculations. The system proposed could be a useful tool to improve the workplace conditions and efficiency levels.

Acidities of closo-1-COOH-1,7-C2B10H11 and amino acids based on icosahedral carbaboranes.

Carborane clusters are not found in Nature and are exclusively man-made. In this work we study, both experimentally and computationally, the gas-phase acidity (measured GA = 1325 kJ·mol(-1), computed GA = 1321 kJ·mol(-1)) and liquid-phase acidity (measured pKa = 2.00, computed pKa = 1.88) of the carborane acid closo-1-COOH-1,7-C2B10H11. The experimental gas-phase acidity was determined with electrospray tandem mass spectrometry (ESI/MS), by using the extended Cooks kinetic method (EKM). Given the similar spatial requirements of the title icosahedral cage and benzene and the known importance of aminoacids as a whole, such a study is extended, within an acid-base context, to corresponding ortho, meta, and para amino acids derived from icosahedral carborane cages, 1-COOH-n-NH2-1, n-R with {R = C2B10H10, n = 2, 7, 12}, and from benzene {R = C6H4, n = 2, 3, 4}. A remarkable difference is found between the proportion of neutral versus zwitterion structures in water for glycine and the carborane derived amino acids.

Tuning the photophysical properties of anti-B18H22: efficient intersystem crossing between excited singlet and triplet states in new 4,4'-(HS)2-anti-B18H20.

The tuning of the photophysical properties of the highly fluorescent boron hydride cluster anti-B18H22 (1), by straightforward chemical substitution to produce 4,4'-(HS)2-anti-B18H20 (2), facilitates intersystem crossing from excited singlet states to a triplet manifold. This subsequently enhances O2((1)Δg) singlet oxygen production from a quantum yield of ΦΔ âˆ¼ 0.008 in 1 to 0.59 in 2. This paper describes the synthesis and full structural characterization of the new compound 4,4'-(HS)2-anti-B18H20 (2) and uses UV-vis spectroscopy coupled with density functional theory (DFT) and ab initio computational studies to delineate and explain its photophysical properties.

15-Year Post-Market Clinical Follow-up Study of 1,828 Ceramic (Zirconia) Implants in Humans.

Purpose: To evaluate the 15-year survival rate of zirconia (Y-TZP) implants with a roughened acid-etched surface in a retrospective post-market clinical follow-up (PMCF) study. Materials and Methods: One-piece ceramic implants (CeraRoot) with a roughened acid-etched surface (ICE) were used. Six different implant shapes/sizes were used in this study. Either a standard or flapless surgical approach was used for implant placement. Simultaneous bone augmentation or sinus elevation was performed when bone height or width was deficient. Definitive zirconia restorations were placed after 2 months or later if the Periotest value was > -3. The implants were followed up for up to 15 years. Results: A total of 1,828 implants were placed in 771 patients with a mean age of 51.18 years. The overall implant survival rate after 15 years of follow-up was 98.69%. Conclusion: From this long-term investigation, it can be concluded that CeraRoot ceramic implants showed a 15-year long-term clinical performance with a survival rate of 98.69% under the described protocol, without significant differences between the six implant shapes/sizes.

Distinct photophysics of the isomers of B18H22 explained.

The photophysics of the two isomers of octadecaborane(22), anti- and syn-B(18)H(22), have been studied by UV-vis spectroscopic techniques and theoretical computational methods. In air-saturated hexane, anti-B(18)H(22) shows fluorescence with a high quantum yield, Φ(F) = 0.97, and singlet oxygen O(2)((1)Δ(g)) production (Φ(Δ) ∼ 0.008). Conversely, isomer syn-B(18)H(22) shows no measurable fluorescence, instead displaying much faster, picosecond nonradiative decay of excited singlet states. Computed potential energy hypersurfaces (PEHs) for both isomers rationalize these data, pointing to a deep S(1) minimum for anti-B(18)H(22) and a conical intersection (CI) between its S(0) and S(1) states that lies 0.51 eV higher in energy. Such an energy barrier to nonradiative relaxation is not present in the PEH of syn-B(18)H(22), and the system therefore has sufficient initial energy on excitation to reach the (S(0)/S(1)) CI and to then decay to the ground state without fluorescence. The computational analysis of the geometries at stationary points along the PEH of both isomers shows that the determining factor for the dissimilar photophysics of anti- and syn-B(18)H(22) may be due to the significant differences in the geometrical rearrangements at their respective conical intersections. Thus, the syn isomer shows one very large, B-B elongation of 1.2 Å from 1.8 Å in the ground state to 3.0 Å at the CI, whereas the anti isomer shows smaller elongations (below 1 Å) in several B-B connectivities at its (S(0)/S(1))(CI). The absorbed energy in S(1) for the anti-B(18)H(22) is therefore redistributed vibrationally into several regions of the molecule rather than almost completely into a single vibrational mode as in the case for the syn isomer. The consequent prolonged S(1) lifetime for the anti isomer allows for relaxation via fluorescence.

A distance-dependent parameterization of the extended Hubbard model for conjugated and aromatic hydrocarbons derived from stretched ethene.

The Hubbard model, which is widely used in physics but is mostly unfamiliar to chemists, provides an attractive yet simple model for chemistry beyond the self consistent field molecular orbital approximation. The Hubbard model adds an effective electron-electron repulsion when two electrons occupy the same atomic orbital to the familiar Hückel Hamiltonian. Thus it breaks the degeneracy between excited singlet and triplet states and allows an explicit treatment of electron correlation. We show how to evaluate the parameters of the model from high-level ab initio calculations on two-atom fragments and then to transfer the parameters to large molecules and polymers where accurate ab initio calculations are difficult or impossible. The recently developed MS-RASPT2 method is used to generate accurate potential energy curves for ethene as a function of carbon-carbon bond length, which are used to parameterize the model for conjugated hydrocarbons. Test applications to several conjugated/aromatic molecules show that even though the model is very simple, it is capable of reasonably accurate predictions for bond lengths, and predicts molecular excitation energies in reasonable agreement with those from the MS-RASPT2 method.

Solution and computed structure of O-lithium N,N-diisopropyl-P,P-diphenylphosphinic amide. Unprecedented Li-O-Li-O self-assembly of an aryllithium.

The structural characterization of an ortho-lithiated diphenylphosphinic amide is described for the first time. Multinuclear magnetic resonance ((1)H, (7)Li, (13)C, (31)P) studies as a function of temperature and concentration employing 1D and 2D methods showed that the anion exists as a mixture of one monomer and two diastereomeric dimers. In the dimers the chiral monomer units are assembled in a like and unlike manner through oxygen-lithium bonds, leading to fluxional ladder structures. This self-assembling mode leads to the formation of Li(2)O(2) four-membered rings, a structural motif unprecedented in aryllithium compounds. DFT computations of representative model compounds of ortho-lithiated phosphinic amide monomer and Li(2)C(2) and Li(2)O(2) dimers with different degrees of solvation by THF molecules showed that Li(2)O(2) dimers are thermodynamically favored with respect to the alternative Li(2)C(2) structures by 4.3 kcal mol(-1) in solvent-free species and by 2.3 kcal mol(-1) when each lithium atom is coordinated to one THF molecule. Topological analysis of the electron density distribution revealed that the Li(2)O(2) four-membered ring is characterized by four carbon-lithium bond paths and one oxygen-oxygen bond path. The latter divides the Li-O-Li-O ring into two Li-O-Li three-sided rings, giving rise to two ring critical points. On the contrary, the bond path network in the Li(2)C(2) core includes a catastrophe point, suggesting that this molecular system can be envisaged as an intermediate in the formation of Li(2)O(2) dimers. The computed (13)C chemical shifts of the C-Li carbons support the existence of monomeric and dimeric species containing only one C-Li bond and are consistent with the existence of tricoordinated lithium atoms in all species in solution.

Can (pi)6 + (pi)4 = 10? Exploring cycloaddition routes to highly unsaturated 10-membered rings.

This paper uses DFT and G3(MP2) calculations to examine whether unbridged 10-membered rings can be made by (pi)6 + (pi)4 cycloadditions to (Z)- and (E)-hexatrienes, hexa-1,5-dien-3-ynes, (Z)-hexa-1,3-dien-5-ynes, hexa-1,2,3,5-tetraenes, and (Z)-hexa-3-ene-1,5-diynes. Cycloadditions to four 4pi reactants, buta-1,3-diene, butenyne, butatriene, and butadiyne, are explored. Thirty different basic cycloadditions are identified, and all are shown to be exothermic according to G3(MP2) calculations; strain energies in the products are comparable with that of cyclodecane itself, despite the presence of trans-alkene, alkyne, allene, cumulene, and s-trans diene moieties. The major obstacles to the isolation of 6 + 4 cycloaddition products are competing (pi)4 + (pi)2 cycloadditions and, especially, rapid Cope rearrangement of the products, but, in many cases, the judicious introduction of substituents can overcome these problems so that practical syntheses should be possible. Reactions between (E)-hexa-1,3,5-triene and s-trans-buta-1,3-diene are shown to have substantially lower activation energies than those involving (Z)-hexa-1,3,5-triene reacting with either s-cis- or s-trans-buta-1,3-diene. Conformationally locked derivatives of s-cis,s-cis (E)-hexa-1,3,5-trienes can lead to derivatives of (Z,Z,E)-cyclodeca-1,3,7-triene that are stable to Cope rearrangement, and reactions should proceed at close to ambient temperatures with suitable activating groups. We predict that it should be possible to prepare suitably substituted derivatives of at least 11 more highly unsaturated ring systems: (5Z,7Z)-cyclodeca-1,2,5,7-tetraene, (1Z,3Z)-cyclodeca-1,3-dien-7-yne, (2Z,7E)-cyclodeca-1,2,3,7-tetraene, (Z)-cyclodeca-1,2,3-trien-7-yne, (4Z,8E)-cyclodeca-1,2,4,8-tetraene, (Z)-cyclodeca-1,2,4,5,7-pentaene, (Z)-cyclodeca-1,2,4-trien-8-yne, (1Z,7E)-cyclodeca-1,7-dien-3-yne, (R,S,E)-cyclodeca-1,2,4,5,8-pentaene, cyclodeca-1,2,4,5,8,9-hexaene, and (R,S)-cyclodeca-1,2,4,5-tetraen-8-yne. In three other cases, we predict that cycloaddition will be followed by unusual and intriguing rearrangements. Cycloadditions can be accelerated by the presence of electron-withdrawing groups in either the 6pi or 4pi reactants. Transannular cyclizations of some products may lead to interesting stereocontrolled routes to 6,6- and/or 5,7-bicyclic structures.

On the electronic structure and stability of icosahedral r-X2Z10H12 and Z12H(12)(2-) clusters; r = {ortho, meta, para}, X = {C, Si}, Z = {B, Al}.

We report on the electronic structure of the 12-vertex icosahedral clusters r-X(2)Z(10)H(12) and Z(12)H(12)(2-), where X = {C, Si} and Z = {B, Al}. The least stable cluster--with the lowest HOMO-LUMO gap (E(g))--corresponds to the ortho-X(2)Z(10)H(12) isomers for all values of X = {C, Si} and Z = {B, Al}. The well-known energetic order E(para) < E(meta) < E(ortho) for r-carboranes is also valid for all compounds except r-C(2)Al(10)H(12). Substitution of two atoms of carbon or silicon into the icosahedral cage B(12)H(12)(2-) enhances considerably the stability of the system as analyzed from E(g) gaps, as opposite to Al(12)H(12)(2-), where similar gaps are found upon double carbon or silicon substitution regardless of the positions in the cage. In order to highlight similarities and differences in the title clusters, topological analysis of the electron density was performed, together with analysis of the deviation from polyhedron icosahedral form with (i) volumes, skewness and kurtosis calculations; and (ii) continuous shape measures.

Five-year success rate of 831 consecutively placed Zirconia dental implants in humans: a comparison of three different rough surfaces.

PURPOSE: The aim of this study was to evaluate the 5-year success rate of zirconia (ZrO2) implants with three different kinds of surfaces. MATERIALS AND METHODS: One-piece zirconia dental implants (CeraRoot) with three different roughened surfaces were designed and manufactured for this study: coated, uncoated, and acid-etched. Five different implant designs were manufactured. Standard or flapless surgical procedures were used for implant placement. Simultaneous bone augmentation or sinus elevation was performed when bone height or width was insufficient. Definitive all-ceramic restorations were placed 4 months after implant placement (8 months or more for implants when bone augmentation or sinus elevation was performed). The implants were followed up to 5 years (mean, 3.40 +/- 0.21). RESULTS: In all, 831 implants were placed in 378 patients with a mean age of 48 years. The overall implant success rate after 5 years of follow-up was 95% (92.77% for uncoated implants, 93.57% for coated implants, and 97.60% for acid-etched implants). The success rate of the acid-etched surface group was significantly better than that of the other two. CONCLUSION: From this midterm investigation, it can be concluded that zirconia dental implants with roughened surfaces might be a viable alternative for tooth replacement. Further follow-up is needed to evaluate the long-term success rates of the implant surfaces studied.

Ovoid zirconia implants: anatomic design for premolar replacement.

Traditionally, missing and hopeless teeth have been replaced by threaded cylindric implants. Implant manufacturers have tried to design implants that more closely resemble tooth anatomy, but the neck and abutment connection areas have not changed much in the past 30 years. Some companies have produced titanium implants with scalloped contours, but the clinical application of this remains uncertain. The combination of anatomically oriented implant designs, newer biomaterials such as zirconia ceramics, and modified surfaces has resulted in dental implants that can be specially designed for the replacement of individual teeth in both arches. Ovoid zirconia implants have been specially developed and produced to replace missing or hopeless premolars. This article discusses the treatment of a patient with an ovoid zirconia implant (CeraRoot Type 14) to replace a premolar.

One-year follow-up of first consecutive 100 zirconia dental implants in humans: a comparison of 2 different rough surfaces.

PURPOSE: The aim of this study was to evaluate the success rate of 100 consecutive zirconia dental implants with 2 different rough surfaces after 1 year of follow-up. MATERIALS AND METHODS: One-piece zirconia dental implants (CeraRoot, Barcelona, Spain) with 1 of 2 different roughened surfaces were designed and manufactured for this study. Five different implant designs were manufactured. Standard or flapless surgical procedures were used for implant placement. Simultaneous bone augmentation or sinus elevation were performed in the cases where bone height or width was insufficient. Implants in the anterior region (canine to canine) were immediately restored with provisional prostheses. Implants placed using less than 35 N torque were splinted with composite resin using an etched and bonded approach to the neighboring teeth or implants to minimize implant mobility and failure. Definitive all-ceramic restorations were placed 4 months after implant placement (8 months for implants where bone augmentation or sinus elevation was performed). RESULTS: The study included 36 patients with a mean age of 50 years. The overall implant success rate after 1 year of follow-up was 98% in both the coated and noncoated groups. CONCLUSIONS: From the preliminary results of this investigation, it can be concluded that zirconia dental implants with roughened surfaces might be a viable alternative for tooth replacement. Further follow-up is needed to evaluate the long-term success rates of the implant surfaces studied.

Ab initio predictions of ferroelectric ternary fluorides with the LiNbO3 structure.

First-principles periodic density-functional theory calculations suggest ternary fluorides LiMgF3, NaCaF3 and LiNiF3 should adopt the ferroelectric LiNbO3 structure at low temperatures; LiMgF3 and LiNiF3 are predicted to have negative enthalpies of formation from the binary fluorides.

All-on-three delayed implant loading concept for the completely edentulous maxilla and mandible: a retrospective 5-year follow-up study.

PURPOSE: Full-arch implant rehabilitation with four implants has become an accepted modality of treatment for fixed restorations in totally edentulous mandibles or maxillas; however, there is little scientific evidence on the outcome for the same treatment with three implants. The purpose of this study was to evaluate a protocol for three implants (all-on-three) supporting a delayed loaded fixed prosthesis in the completely edentulous maxilla, mandible, or both. MATERIALS AND METHODS: This retrospective clinical study included 17 patients with 72 implants to restore 24 fully edentulous arches. The implants were loaded 4 months after surgery with fixed zirconia prostheses. A 5-year follow-up was performed. RESULTS: No implants were lost, giving a 100% success rate. The marginal bone loss was, on average, 0.53 mm (SD, 0.32 mm) for the internal connection implants and 0.84 mm (SD, 0.62 mm) for the external connection implants. CONCLUSIONS: Within the limits of this small group clinical study, the high survival rate of the all-on-three protocol with delayed loading may be a viable concept.

Electronic structure and geometries of o-carborane derived cyclic structures [{µ-1,2-(C2B10H10)(n)M(n)}Ag(m)]z-, M = {Au, Hg}, n = {3, 4}, m = {0, 1, 2}, z = {n-m, -m}.

To date, crystal structures of the cyclic mercury complexes [µ-1,2-(C(2)B(10)H(10))(n)Hg(n)], with n = {3, 4}, have been found. However, the same structures substituting Hg by Au, which implies a charge z = {-3, -4} for n = {3, 4} respectively, have not been found. In this work, we present geometrical and electronic structure properties of the title structures [µ-1,2-(C(2)B(10)H(10))(n)M(n)](z-), M = {Au, Hg}, n = {3, 4}, z = {n, 0}, and study the stability of structures with one and two added Ag(+) ions.

Removal of cadmium, copper, nickel, cobalt and mercury from water by Apatite II™: column experiments.

Apatite II™, a biogenic hydroxyapatite, was evaluated as a reactive material for heavy metal (Cd, Cu, Co, Ni and Hg) removal in passive treatments. Apatite II™ reacts with acid water by releasing phosphates that increase the pH up to 6.5-7.5, complexing and inducing metals to precipitate as metal phosphates. The evolution of the solution concentration of calcium, phosphate and metals together with SEM-EDS and XRD examinations were used to identify the retention mechanisms. SEM observation shows low-crystalline precipitate layers composed of P, O and M. Only in the case of Hg and Co were small amounts of crystalline phases detected. Solubility data values were used to predict the measured column experiment values and to support the removal process based on the dissolution of hydroxyapatite, the formation of metal-phosphate species in solution and the precipitation of metal phosphate. Cd(5)(PO(4))(3)OH(s), Cu(2)(PO(4))OH(s), Ni(3)(PO(4))(2)(s), Co(3)(PO(4))(2)8H(2)O(s) and Hg(3)(PO(4))(2)(s) are proposed as the possible mineral phases responsible for the removal processes. The results of the column experiments show that Apatite II™ is a suitable filling for permeable reactive barriers.

Full-mouth oral rehabilitation in a titanium allergy patient using zirconium oxide dental implants and zirconium oxide restorations. A case report from an ongoing clinical study.

This case report describes the full-mouth oral rehabilitation of a titanium allergic patient. The patient was a young female with amelogenesis imperfecta who had generalized massive tooth destruction. All teeth in the mouth were extracted and 15 CeraRoot acid-etched (ICE surface) implants were placed (seven implants in the maxilla and eight implants in the mandible). No immediate temporaries were placed. Temporaries were placed 3 months after surgery, and left in function for 2 months. The case was finally restored with zirconium oxide bridges and ceramic veneering (three bridges in the maxilla and another three in the mandible). The 3-year follow-up showed good stability of soft tissues and bone level. Zirconium oxide implants and restorations might be an alternative for the oral rehabilitation of titanium allergic patients.

The use of Apatite II™ to remove divalent metal ions zinc(II), lead(II), manganese(II) and iron(II) from water in passive treatment systems: column experiments.

The conventional passive treatments for remediation of acid mine drainage using calcite are not totally efficient in the removal of certain heavy metal ions. Although pH increases to 6-7 and promotes the precipitation of trivalent and some divalent metals as hydroxides and carbonates, the remaining concentrations of some divalent metals ions do not fulfill the environmental regulations. In this study, Apatite II™, a biogenic hydroxyapatite, is used as an alternative reactive material to remove Zn(II), Pb(II), Mn(II) and Fe(II). Apatite II™ reacted with acid water releasing phosphate and increasing pH up to 6.5-7, inducing metals to precipitate mainly as metal-phosphates: zinc precipitated as hopeite, Zn(3)(PO(4))(2)·4H(2)O, lead as pyromorfite, Pb(5)(PO(4))(3)OH, manganese as metaswitzerite, Mn(3)(PO(4))(2)·4H(2)O and iron as vivianite, Fe(3)(PO(4))(2)·8H(2)O. Thus, metal concentrations from 30 to 75 mg L(-1) in the inflowing water were depleted to values below 0.10 mg L(-1). Apatite II™ dissolution is sufficiently fast to treat flows as high as 50 m/a. For reactive grain size of 0.5-3mm, the treatment system ends due to coating of the grains by precipitates, especially when iron and manganese are present in the solution.