157 research outputs found
Kinetics of the [4+2] cycloaddition of cyclopentadiene with (E)-2-aryl-1-cyano-1-nitroethenes
A reexamination of the molecular mechanism of the DielsâAlder reaction between tetrafluoroethene and cyclopentadiene
Impact of European Integration on the Functioning of the Insurance Market in Poland
The transformation process, that has begun 20 years ago, generated significant changes in the structure and organization of Polish economy. It stimulated development of particular market's segments, especially of the insurance sector. Poland's accession to the European Union required conformity to Its regulations, fulfillment of several conditions connected with the membership in the European Community. The purpose of this article is to present the main consequences of Poland's integration with EU in the field of insurance market. Joining the common market was an important challenge for this sector in our country.Rok 1990 stanowiĆ poczÄ
tek procesu transformacji systemu spoĆeczno - gospodarczego i ustrojowego. Ostatnie 20 lat to okres intensywnych przemian o charakterze strukturalnym i organizacyjnym, w wyniku ktĂłrych uksztaĆtowaĆy siÄ warunki rozwoju poszczegĂłlnych segmentĂłw systemu finansowego paĆstwa, zwĆaszcza sektora ubezpieczeĆ. PrzystÄ
pienie Polski do Unii Europejskiej wymagaĆo wprowadzenia szeregu zmian, dostosowujÄ
cych polski porzÄ
dek prawny do uregulowaĆ wspĂłlnotowych regulujÄ
cych funkcjonowanie rynku ubezpieczeĆ. Celem artykuĆu jest zaprezentowanie szans i zagroĆŒeĆ, jakie wynikajÄ
dla tego segmentu gospodarki z przystÄ
pienia Polski do UE. NiewÄ
tpliwie proces integracji stanowiĆ powaĆŒne wyzwanie dla polskiego rynku ubezpieczeĆ
An experimental and theoretical study of the hetero DielsâAlder reactions between (E)-2-aryl-1-cyano-1-nitroethenes and ethyl vinyl ether: one-step or zwitterionic, two-step mechanism?
2-Unsubstituted Imidazole N-Oxides as Novel Precursors of Chiral 3-Alkoxyimidazol-2-ylidenes Derived from trans-1,2-Diaminocyclohexane and Other Chiral Amino Compounds
âDesymmetrizationâ of trans-1,2-diaminocyclohexane by treatment with α,Ï-dihalogenated alkylation reagents leads to mono-NH2 derivatives (âprimary-tertiary diaminesâ). Upon reaction with formaldehyde, these products formed monomeric formaldimines. Subsequently, reactions of the formaldimines with α-hydroxyiminoketones led to the corresponding 2-unsubstituted imidazole N-oxide derivatives, which were used here as new substrates for the in situ generation of chiral imidazol-2-ylidenes. Upon O-selective benzylation, new chiral imidazolium salts were obtained, which were deprotonated by treatment with triethylamine in the presence of elemental sulfur. Under these conditions, the intermediate imidazol-2-ylidenes were trapped by elemental sulfur, yielding the corresponding chiral non-enolizable imidazole-2-thiones in good yields. Analogous reaction sequences, starting with imidazole N-oxides derived from enantiopure primary amines, amino alcohols, and amino acids, leading to the corresponding 3-alkoxyimidazole-2-thiones were also studied
The life cycle impact for platinum group metals and lithium to 2070 via surplus cost potential
© 2017 The Author(s)Purpose: A surplus cost potential (SCP) indicator has been developed as a measure of resource scarcity in the life cycle impact assessment (LCIA) context. To date, quality SCP estimates for other minerals than fossils are either not yet available or suffer methodological and data limitations. This paper overcomes these limitations and demonstrate how SCP estimates for metals can be calculated without the utilisation of ore grade function and by collecting primary economic and geological data. Methods: Data were collected in line with the geographical distribution, mine type, deposit type and production volumes and total production costs in order to construct cost-cumulative availability curves for platinum group metals (PGMs) and lithium. These curves capture the total amount of known mineral resources that can be recovered profitably at various prices from different types of mineral deposits under current conditions (this is, current technology, prevailing labour and other input prices). They served as a basis for modelling the marginal cost increase, a necessary parameter for estimating the SCP indicator. Surplus costs were calculated for different scenario projections for future mineral production considering future market dynamics, recyclability rates, demand-side technological developments and economic growth and by applying declining social discount rate. Results and discussion: Surplus costs were calculated for three mineral production scenarios, ranging from (US$2014/kg) 6545â8354 for platinum, 3583â4573 for palladium, 8281â10,569 for rhodium, 513â655 for ruthenium, 3201â4086 for iridium and 1.70â5.80 for lithium. Compared with the current production costs, the results indicate that problematic price increases of lithium are unlikely if the latest technological trends in the automotive sector will continue up to 2070. Surplus costs for PGMs are approximately one-third of the current production costs in all scenarios; hence, a threat of their price increases by 2070 will largely depend on the discovery of new deposits and the ability of new technologies to push these costs down over time. This also applies to lithium if the increasing electrification of road transport will continue up to 2070. Conclusions: This study provides useful insight into the availability of PGMs and lithium up to 2070. It proves that if time and resources permit, reliable surplus cost estimates can be calculated, at least in the short-run, based on the construction of oneâs own curves with the level of quality comparable to expert-driven consulting services. Modelling and incorporating unknown deposits and potential future mineral production costs into these curves is the subject of future work
Regioisomeric and substituent effects upon the outcome of the reaction of 1-borodienes with nitrosoarene compounds
A study of the reactivity of 1-borodienes with nitrosoarene compounds has been carried out showing an outcome that differs according to the hybridization state of the boron moiety. Using an sp2 boron substituent, a one-pot hetero-DielsâAlder/ring contraction cascade occurred to afford N-arylpyrroles with low to good yields depending on the electronic properties of the substituents on the borodiene, whereas an sp3 boron substituent led to the formation of stable boro-oxazines with high regioselectivity in most of the cases, in moderate to good yields. 1H and 11B NMR studies on two boro-oxazine regioisomers showed that selective deprotection can be performed. Formation of either the pyrrole or the furan derivative is pH- and regioisomer-structure-dependent. The results obtained, together with previous B3LYP calculations, support mechanistic proposals which suggest that pyrrole, or furan, formation proceeds via oxazine formation, followed by a boryl rearrangement and an intramolecular additionâelimination sequence
Magnetic Resonance Microscopy for Assessment of Morphological Changes in Hydrating Hydroxypropylmethyl Cellulose Matrix Tablets In Situ
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