Towards urban drainage sediment accumulation monitoring using temperature sensors

[Abstract:] Sewer sediments are among the main concerns related to urban drainage system management as they represent the largest contribution of suspended solid loads during rainfall events due to their resuspension. This study presents a novel methodology to detect and assess bed deposits in urban drainage systems based on temperature monitoring by using well-known thermodynamics and sediment properties. To illustrate the heat transfer processes in a liquid–sediment system and their relation to accumulation, a lab-scale experimental campaign was performed using sewer sediments and simulating water temperature gradients in sewers. Wastewater temperatures showed a marked daily pattern, while the presence of sediment dampened dynamics. Sediment thickness could therefore be estimated from the time evolution of the temperature differences measured between the bottom of the sediment bed and the water phase. Likewise, experimental data were used to calibrate a 1D heat transfer model, from which several sediment accumulation scenarios were simulated by using real wastewater temperature series. Thus, the influence of sediment properties on accumulation processes was assessed, and the range of potentially measurable sediments within an optimal range of [5–20] cm was identified. As a conclusion, temperature measurements and heat transfer model analysis can be used to approximate and monitor the sediments deposited in urban drainage systems. Future studies will extend the method to spatially-resolved sediment monitoring and active temperature sensing to improve sediment accumulation monitoring capabilities.The work developed by Manuel Regueiro-Picallo is funded within the postdoctoral fellowship programme from the Xunta de Galicia (Consellería de Cultura, Educación e Universidade). This work was partially founded by the EU under the Horizon 2020 program within a contract for Integrating Activities for Starting Communities (Co-UDlabs project. GA No.101008626). Finally, the authors would like to thank Raúl Pernas for his collaboration during part of the experimental campaign

Understanding stability trends along the lanthanide series

[Abstract] The stability trends across the lanthanide series of complexes with the polyaminocarboxylate ligands TETA4− (H4TETA=2,2′,2′′,2′′′‐(1,4,8,11 tetraazacyclotetradecane‐1,4,8,11‐tetrayl)tetraacetic acid), BCAED4− (H4BCAED=2,2′,2′′,2′′′ {[(1,4‐diazepane‐1,4‐diyl)bis(ethane‐2,1‐diyl)]bis(azanetriyl)}tetraacetic acid), and BP18C62− (H2BP18C6=6,6′‐[(1,4,10,13‐tetraoxa‐7,16‐diazacyclooctadecane‐7,16 diyl)bis(methylene)]dipicolinic acid) were investigated using DFT calculations. Geometry optimizations performed at the TPSSh/6‐31G(d,p) level, and using a 46+4fn ECP for lanthanides, provide bond lengths of the metal coordination environments in good agreement with the experimental values observed in the X‐ray structures. The contractions of the Ln3+ coordination spheres follow quadratic trends, as observed previously for different isostructural series of complexes. We show here that the parameters obtained from the quantitative analysis of these data can be used to rationalize the observed stability trends across the 4f period. The stability trends along the lanthanide series were also evaluated by calculating the free energy for the reaction [La(L)]n+/−(sol)+Ln3+(sol)→[Ln(L)]n+/ (sol)+La3+(sol). A parameterization of the Ln3+ radii was performed by minimizing the differences between experimental and calculated standard hydration free energies. The calculated stability trends are in good agreement with the experimental stability constants, which increase markedly across the series for BCAED4−complexes, increase smoothly for the TETA4− analogues, and decrease in the case of BP18C62− complexes. The resulting stability trend is the result of a subtle balance between the increased binding energies of the ligand across the lanthanide series, which contribute to an increasing complex stability, and the increase in the absolute values of hydration energies along the 4f period.Xunta de Galicia; CN2012/01

Magnetic anisotropies in rhombic lanthanide(III) complexes do not conform to Bleaney’s theory

[Abstract] We report a complete set of magnetic susceptibilities of lanthanide complexes with a macrocyclic ligand based on a 3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane platform containing four hydroxyethyl pendant arms (L1). The [LnL1]3+ complexes are isostructural along the lanthanide series from Ce3+ to Yb3+, with the only structural change observed along the series being the monotonous shortening of the Ln–donor distances due to lanthanide contraction. The 1H NMR spectra point to a D2 symmetry of the [LnL1]3+ complexes in aqueous solution, which provides a unique opportunity for analysis of the rhombic magnetic anisotropies with an unequivocal location of the magnetic axes. The contact contributions for the observed paramagnetic shifts have been estimated with density functional theory calculations on the [GdL1]3+ complex. Subsequently, the pseudocontact shifts could be factored out, thereby giving access to the axial and rhombic contributions of the magnetic susceptibility tensor. Our results show that the calculated magnetic anisotropies do not follow the trends predicted by Bleaney’s theory, particularly in the case of Ho3+ and Er3+ complexes.Ministerio de Economía y Competitividad; CTQ2013-43243-PMinisterio de Ciencia e Innovación; CTQ2011-2448

Developing the family of picolinate ligands for Mn2+ complexation

[Abstract] We have reported here a series of ligands containing pentadentate 6,6′-(azanediylbis(methylene))dipicolinic acid units that differ in the substituent present at the amine nitrogen atom (acetate: H3DPAAA; phenyl: H2DPAPhA; dodecyl: H2DPAC12A; 4-hexylphenyl: H2DPAC6PhA). The protonation constants of the hexadentate DPAAA3− and pentadentate DPAPhA2−ligands and the stability constants of their Mn2+ complexes were determined using pH-potentiometry (25 °C, 0.15 M NaCl). The mono-hydrated [Mn(DPAAA)]− complex (logKMnL = 13.19(5)) was found to be considerably more stable than the bis-hydrated [Mn(DPAPhA)] analogue (logKMnL = 9.55(1)). A detailed 1H and 17O NMR relaxometric study was carried out to determine the parameters that govern the proton relaxivities of these complexes. The [Mn(DPAC12A)] complex, which contains a dodecyl lipophilic chain, forms micelles in solution characterized by a critical micellar concentration (cmc) of 96(9) μM. The lipophilic [Mn(DPAC6PhA)] and [Mn(DPAC12A)] derivatives form rather strong adducts with Human Serum Albumin (HSA) with association constants of 7.1 ± 0.1 × 103 and 1.3 ± 0.4 × 105 M−1, respectively. The X-ray structure of the complex {K(H2O)4}{[Mn(DPAAA)(H2O)]}2 shows that the Mn2+ ion in [Mn(DPAAA)]− is coordinated to the six donor atoms of the ligand, a coordinated water molecule completing the pentagonal bipyramidal coordination environment.Ministerio de Economía y Competitividad; CTQ2015-71211-REDTMinisterio de Economía y Competitividad; CTQ2016-76756-

Water exchange rates and mechanisms in tetrahedral [Be(H2O)4]2+ and [Li(H2O)4]+ complexes using DFT methods and cluster‐continuum models

[Abstract] The water exchange reactions in aquated Li+ and Be2+ ions were investigated with density functional theory calculations performed using the [Li(H2O)4]+·14H2O and [Be(H2O)4]2+·8H2O systems and a cluster‐continuum approach. A range of commonly used functionals predict water exchange rates several orders of magnitude lower than the experimental ones. This effect is attributed to the overstabilization of coordination number four by these functionals with respect to the five‐coordinated transition states responsible for the associative (A) or associative interchange (Ia) water exchange mechanisms. However, the M06 and M062X functionals provide results in good agreement with the experimental data: M062X/TZVP calculations yield a concerted Iamechanism for the water exchange in [Be(H2O)4]2+·8H2O that gives an average residence time of water molecules in the first coordination sphere of 260 μs. For [Li(H2O)4]+·14H2O the water exchange reaction is predicted to follow an A mechanism with a residence time of inner‐sphere water molecules of 25 ps.Ministerio de Economía y Competitividad; CTQ2013‐43243‐PMinisterio de Economía y Competitividad; CTQ2015‐71211‐RED

Density functional dependence of molecular geometries in lanthanide(III) complexes relevant to bioanalytical and biomedical applications

[Abstract] A set of 15 lanthanide-containing model systems was used to evaluate the performance of 15 commonly available density functionals (SVWN, SPL, BLYP, G96LYP, mPWLYP, B3LYP, BH&HLYP, B3PW91, BB95, mPWB95, TPSS, TPSSh, M06, CAM-B3LYP and wB97XD) in geometry determination, benchmarked against MP2 calculations. The best agreement between DFT optimized geometries and those obtained from MP2 calculations is provided by meta-GGA and hybrid meta-GGA functionals. The use of hybrid-GGA functionals such as BH&HLYP and B3PW91 also provide reasonably good results, while B3LYP provides an important overestimation of the metal–ligand bonds. The performance of different basis sets to describe the ligand(s) atoms, as well as the use of large-core (LC) RECPs and small-core (SC) RECPs, has been also assessed. Our calculations show that SCRECP calculations provide somewhat shorter GdIII–donor distances than the LCRECP approach, the average contraction of bond distances for the systems investigated amounting to 0.033 Å. However, geometry optimizations with the SCRECP (in combination with the mPWB95 functional and the 6-31G(d) basis set for the ligand atoms) take about 15 times longer than the LC counterparts, and about four times longer than MP2/LCRECP/6-31G(d) calculations. The 6-31G(d), 6-311G(d), 6-311G(d,p) or cc-pVDZ basis sets, in combination with LCRECPs, appear to offer an adequate balance between accuracy and computational cost for the description of molecular geometries of LnIII complexes. Electronic energies calculated with the the cc-pVxZ family (x = D-6) indicate a relative fast convergence to the complete basis set (CBS) limit with basis set size. The inclusion of bulk solvent effects (IEFPCM) was shown to provoke an important impact on the calculated geometries, particularly on the metal–nitrogen distances. Calculations performed on lanthanide complexes relevant for practical applications confirmed the important effect of the solvent on the calculated geometries.Ministerio de Educación y Ciencia; CTQ2009-10721Xunta de Galicia; IN845B-2010/06

Applications of density functional theory (DFT) to investigate the structural, spectroscopic and magnetic properties of lanthanide(III) complexes

[Abstract] Density functional theory (DFT) has become a general tool to investigate the structure and properties of complicated inorganic molecules, such as lanthanide(III) coordination compounds, due to the high accuracy that can be achieved at relatively low computational cost. Herein, we present an overview of different successful applications of DFT to investigate the structure, dynamics, vibrational spectra, NMR chemical shifts, hyperfine interactions, excited states, and magnetic properties of lanthanide(III) complexes. We devote particular attention to our own work on the conformational analysis of LnIII-polyaminocarboxylate complexes. Besides, a short discussion on the different approaches used to investigate lanthanide(III) complexes, i. e. all-electron relativistic calculations and the use of relativistic effective core potentials (RECPs), is also presented. The issue of whether the 4f electrons of the lanthanides are involved in chemical bonding or not is also shortly discussed.Ministerio de Educación y Ciencia; CTQ2009-10721Xunta de Galicia; IN845B-2010/06

Hakai reduces cell-substratum adhesion and increases epithelial cell invasion

BACKGROUND: The dynamic regulation of cell-cell adhesions is crucial for developmental processes, including tissue formation, differentiation and motility. Adherens junctions are important components of the junctional complex between cells and are necessary for maintaining cell homeostasis and normal tissue architecture. E-cadherin is the prototype and best-characterized protein member of adherens junctions in mammalian epithelial cells. Regarded as a tumour suppressor, E-cadherin loss is associated with poor prognosis in carcinoma. The E3 ubiquitin-ligase Hakai was the first reported posttranslational regulator of the E-cadherin complex. Hakai specifically targetted E-cadherin for internalization and degradation and thereby lowered epithelial cell-cell contact. Hakai was also implicated in controlling proliferation, and promoted cancer-related gene expression by increasing the binding of RNA-binding protein PSF to RNAs encoding oncogenic proteins. We sought to investigate the possible implication of Hakai in cell-substratum adhesions and invasion in epithelial cells. METHODS: Parental MDCK cells and MDCK cells stably overexpressing Hakai were used to analyse cell-substratum adhesion and invasion capabilities. Western blot and immunofluoresecence analyses were performed to assess the roles of Paxillin, FAK and Vinculin in cell-substratum adhesion. The role of the proteasome in controlling cell-substratum adhesion was studied using two proteasome inhibitors, lactacystin and MG132. To study the molecular mechanisms controlling Paxillin expression, MDCK cells expressing E-cadherin shRNA in a tetracycline-inducible manner was employed. RESULTS: Here, we present evidence that implicate Hakai in reducing cell-substratum adhesion and increasing epithelial cell invasion, two hallmark features of cancer progression and metastasis. Paxillin, an important protein component of the cell-matrix adhesion, was completely absent from focal adhesions and focal contacts in Hakai-overexpressing MDCK cells. The expression of Paxillin was found to be regulated by a proteasome-independent mechanism, possibly due to the decreased abundance of E-cadherin. CONCLUSIONS: Taken together, these results suggest that Hakai may be involved in two hallmark aspects of tumour progression, the lowering cell-substratum adhesion and the enhancement of cell invasion

High relaxivity Mn2+-based MRI contrast agents

[Abstract] Stable Mn2+ mono- and binuclear complexes containing pentadentate 6,6′-((methylazanediyl)bis(methylene)) dipicolinic acid coordinating units give remarkably high relaxivities due to the presence of two inner-sphere water molecules. The mononuclear derivative binds human serum albumin (HSA) with an association constant of 3372 M−1, which results in the replacement of the coordinated water molecules by donor atoms of protein residues. The dinuclear analogue also binds HSA while leaving one of the Mn2+ centres exposed to the solvent with two coordinated water molecules. Thus, this complex shows remarkably high relaxivities upon protein binding (39.0 mM−1 s−1 per Mn, at 20 MHz and 37 °C).Galicia. Consellería de Cultura, Educación e Ordenación Universitaria; EM 2012/088Galicia. Consellería de Cultura, Educación e Ordenación Universitaria; CN 2012/01

Definition of an intramolecular Eu‐to‐Eu energy transfer within a discrete [Eu2L] complex in solution

[Abstract] Ligand L, based on two do3a moieties linked by the methylene groups of 6,6′‐dimethyl‐2,2′‐bipyridine, was synthesized and characterized. The addition of Ln salts to an aqueous solution of L (0.01 M Tris‐HCl, pH 7.4) led to the successive formation of [LnL] and [Ln2L] complexes, as evidenced by UV/Vis and fluorescence titration experiments. Homodinuclear [Ln2L] complexes (Ln=Eu, Gd, Tb, Yb, and Lu) were prepared and characterized. The 1H and 13C NMR spectra of the Lu and Yb complexes in D2O solution (pD=7.0) showed C1 symmetry of these species in solution, pointing to two different chemical environments for the two lanthanide cations. The analysis of the chemical shifts of the Yb complex indicated that the two coordination sites present square antiprismatic (SAP) coordination environments around the metal ions. The spectroscopic properties of the [Tb2L] complex upon ligand excitation revealed conventional behavior with τH2O=2.05(1) ms and ϕH2O=51 %, except for the calculation of the hydration number obtained from the luminescent lifetimes in H2O and D2O, which pointed to a non‐integer value of 0.6 water molecules per TbIII ion. In contrast, the Eu complex revealed surprising features such as: 1) the presence of two and up to five components in the 5D0→7F0 and 5D0→7F1 emission bands, respectively; 2) marked differences between the normalized spectra obtained in H2O and D2O solutions; and 3) unconventional temporal evolution of the luminescence intensity at certain wavelengths, the intensity profile first displaying a rising step before the occurrence of the expected decay. Additional spectroscopic experiments performed on [Gd2−xEuxL] complexes (x=0.1 and 1.9) confirmed the presence of two distinct Eu sites with hydration numbers of 0 (site I) and 2 (site II), and showed that the unconventional temporal evolution of the emission intensity is the result of an unprecedented intramolecular Eu‐to‐Eu energy-transfer process. A mathematical model was developed to interpret the experimental data, leading to energy‐transfer rates of 0.98 ms−1 for the transfer from the site with q=0 to that with q=2 and vice versa. Hartree–Fock (HF) and density functional theory (DFT) calculations performed at the B3LYP level were used to investigate the conformation of the complex in solution, and to estimate the intermetallic distance, which provided Förster radii (R0) values of 8.1 Å for the energy transfer from site I to site II, and 6.8 Å for the reverse energy transfer. These results represent the first evidence of an intramolecular energy‐transfer equilibrium between two identical lanthanide cations within a discrete molecular complex in solution.Ministerio de Educación y Ciencia; CTQ2009–10721Xunta de Galicia; IN845B‐2010/06