A critical analysis of clustering phenomenon in Al2O3 nanofluids

Journal of Thermal Analysis and Calorimetry - In the present work, an investigation on the relationship between clustering phenomenon and thermal conductivity of nanofluids is presented....     

Enantioselective gold-catalyzed synthesis of polycyclic indolines

The synthesis of architecturally complex polycyclic fused indolines is achieved in a chemo-, regio-, and stereodefined manner, via an enantioselective gold-catalyzed cascade hydroindolination/iminium trapping synthetic sequence. Highly functionalized tetracyclic fused furoindolines (2) and dihydropyranylindolines (4) are synthesized in moderate to good yields and enantiomeric excesses of up to 87%.     

Toxic elements content in PM<Subscript>10</Subscript> samples from a coastal area of the Northern Adriatic Sea

PM₁₀ samples were collected during winter and summer seasons at two different sites in the area of Trieste (Italy). The content of As, Cd, Cr, Mn, Ni, Pb and V in the PM₁₀ samples was determined by inductively coupled plasma-mass spectrometry, with the purpose of evaluating the relevance of PM₁₀ inhalation as a route of human exposure to these elements. The results showed that the ambient air concentration of the aforementioned elements were below the limits or target values for both sites and season. Site and season-specific correlation analysis was conducted for the identification of metals with similar origin: very good correlation for the couple Ni-V was found in both sites and seasons, showing the influence of combustion of heavy oils in PM₁₀ composition. The inter-site and seasonal variability of both PM₁₀ and metal concentrations were examined. A stronger impact by the vehicular traffic on the PM₁₀ and metal concentrations was found for the urban site in both seasons. Because of the great importance of the “Bora” wind on the local climate, variability of PM₁₀ and toxic elements concentration with wind were analysed, allowing determination of the effect of wind on dilution of the pollutants for the urban site during both seasons.      

A min-cut approach to functional regionalization,with a case study of the Italian local labour market areas

In several economical, statistical and geographical applications, a territory must be subdivided into functional regions. Such regions are not fixed and politically delimited, but should be identified by analyzing the interactions among all its constituent localities. This is a very delicate and important task, that often turns out to be computationally difficult. In this work we propose an innovative approach to this problem based on the solution of minimum cut problems over an undirected graph called here transitions graph. The proposed procedure guarantees that the obtained regions satisfy all the statistical conditions required when considering this type of problems. Results on real-world instances show the effectiveness of the proposed approach.     

Balancing of agricultural census data by using discrete optimization

In the case of large-scale surveys, such as a Census, data may contain errors or missing values. An automatic error correction procedure is therefore needed. We focus on the problem of restoring the consistency of agricultural data concerning cultivation areas and number of livestock, and we propose here an approach to this balancing problem based on optimization. Possible alternative models, either linear, quadratic or mixed integer, are presented. The mixed integer linear one has been preferred and used for the treatment of possibly unbalanced data records. Results on real-world Agricultural Census data show the effectiveness of the proposed approach.     

Tuning the Fluorescence Through Reorientation of the Axle in Calix[6]arene-Based Pseudorotaxanes

This work describes a calix[6]arene-based wheel that binds, in non-polar media, a stilbazolium salt to yield a mixture of pseudorotaxane orientational isomers. The isomer's abundance ratio evolves with time and can be reversibly tuned by adjusting the temperature. The spectroscopic properties, and notably the emission spectrum, of the bound guest depend on its orientation inside the non-palindromic wheel, suggesting such a system as a switch with spectroscopic readout.     

Giant Enhancement of Second Harmonic Generation Accompanied by the Structural Transformation of 7‐Fold to 8‐Fold Interpenetrated Metal–Organic Frameworks (MOFs)

Interpenetration in metal–organic frameworks (MOFs) is an intriguing phenomenon with significant impacts on their properties, and functional applications. Herein, we show that a 7‐fold interpenetrated MOF ( 1 ) is transformed into an 8‐fold interpenetrated MOF by the loss of DMF in a single‐crystal‐to‐single‐crystal manner. This is accompanied by a giant enhancement of the second harmonic generation (SHG ca. 125 times) and two‐photon photoluminescence (ca. 14 times). The strengthened π–π interaction between the individual diamondoid networks and intensified oscillator strength of the molecules aid the augment of dipole moments and boost the nonlinear optical conversion efficiency. Large positive and negative thermal expansions of 1 occur at 30–150 °C before the loss of DMF. These results offer an avenue to manipulate the NLO properties of MOFs using interpenetration and provide access to tunable single‐crystal NLO devices.     

Synthesis,Crystal Structures,and Properties of Mn(NCS)2 Coordination Compounds with 4-Picoline as Coligand and Crystal Structure of Mn(NCS)2

Reaction of Mn(NCS)₂ with 4-picoline (4-methylpyridine) leads to the formation of [Mn(NCS)₂(4-picoline)₄] · 0.67 · 4-picoline · 0.33 · H₂O ( 1 - Mn ) reported in literature, Mn(NCS)₂(4-picoline)₂(H₂O)₂ ( 2-Mn/H₂O ), and of [Mn(NCS)₂(4-picoline)₂]_n ( 2-Mn/I ). 1-Mn and 2-Mn/H₂O consist of discrete complexes, in which the metal cations are octahedrally coordinated, whereas in 2-Mn/I the metal cations are linked by pairs of μ-1,3-bridging thiocyanate anions into corrugated chains. Measurements using thermogravimetry and differential scanning calorimetry as well as temperature dependent X-ray powder diffraction on 1-Mn and 2-Mn/H₂O reveal that upon heating both compounds transform into [Mn(NCS)₂(4-picoline)]_n ( 3-Mn ) via 2-Mn/I as intermediate. 3-Mn shows a very rare chain topology in which the metal cations are linked by μ-1,3,3 (N,S,S) coordinating anionic ligands which was never observed before with Mn^II. From these investigations there is no hint that a further modification of 2-Mn can be prepared as recently observed for [M(NCS)₂(4-picoline)₂]_n (M = Fe, Cd) and such a form is also not available if the metastable forms of the Fe^II or Cd^II compounds were used as template during thermal decomposition. Magnetic investigations on 2-Mn/H₂O show only paramagnetic behavior, whereas for 2-Mn/I antiferromagnetic ordering is observed. Finally, the crystal structure of Mn(NCS)₂ was determined from XRPD data, which shows that it is strongly related to that of 3-Mn .     

Hydrodynamic cavitation: from theory towards a new experimental approach

Hydrodynamic cavitation is analysed by a global thermodynamics principle following an approach based on the maximum irreversible entropy variation that has already given promising results for open systems and has been successfully applied in specific engineering problems. In this paper we present a new phenomenological method to evaluate the conditions inducing cavitation. We think this method could be useful in the design of turbo-machineries and related technologies: it represents both an original physical approach to cavitation and an economical saving in planning because the theoretical analysis could allow engineers to reduce the experimental tests and the costs of the design process.