Search results for "cycles"
showing 10 items of 306 documents
Deficiencies in reporting results of lesbians and gays after donor intrauterine insemination and assisted reproductive technology treatments: a revie…
2015
At a time when increasing numbers of lesbians and gays consider parenthood using reproductive assistance in infertility centers, the present review aims to summarize the results obtained so far by lesbians after intrauterine insemination (IUI) and in-vitro fertilization (IVF) using donor spermatozoa (D-IUI and D-IVF, respectively) and gays entering into gestational-surrogacy programs. Data show that gays display normal semen parameters and lesbians exhibit no specific causes of female infertility except perhaps for polycystic ovary syndrome (PCOS) and some PCOS-related factors. Pair-bonded lesbians entering into D-IUI programs, tend to have higher pregnancy and delivery percentages followin…
Global factors, uncertainty, weather conditions and energy prices: On the drivers of the duration of commodity price cycle phases
2020
We investigate the role of global factors in explaining the length of commodity price cycle phases, using a continuous-time Weibull duration model and data for a panel of 33 countries over the period 1980Q1-2015Q4. We find evidence of increasing (constant) positive duration dependence for commodity price booms and busts (normal time spells). Global macroeconomic conditions - in particular, inflation, economic policy uncertainty and monetary policy actions - significantly affect the duration of all commodity price cycle phases. Global environmental conditions also impact the duration of commodity price booms, with a rise in average temperature (rainfall) increasing (reducing) their length. A…
Inflation dynamics in a model with firm entry and (some) heterogeneity
2014
We analyse the incidence of endogenous entry and firm TFP-heterogeneity on the response of aggregate inflation to exogenous shocks. We build up an otherwise standard DSGE model in which the number of firms is endogenously determined and firms differ in their steady state level of productivity. This splits the industry structure into firms of different sizes. Calibrating the different transition rates, across firm sizes and out of the market we reproduce the main features of the distribution of firms in Spain. We then compare the inflation response to technology, interest rate and entry cost shocks, among others. We find that structures in which large (more productive) firms predominate tend…
A Long Term View on the Short Term Co-movement of Output and Prices in a Small Open Economy
2012
- One assumption behind inflation targeting as objective for monetary policy is that inflation rates in the short run to some extent reflect output cycles. The present paper investigates the historical co-movements of output and prices for a small open raw material based economy, in this case Norway 1830 – 2006. Looking at contemporaneous movements we find more often negative correlations between the two variables than positive. The correlations do not give any evidence of causality. However, they may indicate that supply side shocks, often caused by the foreign sector, were more important for historical output cycles in Norway than assumed hitherto
Straightforward One-Pot Synthesis of New 4-Phenyl-1,2,5,6-tetraazafluoranthen-3(2H)-one Derivatives: X-ray Single Crystal Structure and Hirshfeld Ana…
2022
A straightforward one-pot route for the synthesis of a new 4-phenyl-1,2,5,6-tetraazafluoranthen-3(2H)-one is reported form the direct hydrazinolysis of triketo ester and hydrazine hydrate in ethanol. 4-Phenyl-1,2,5,6-tetraazafluoranthen-3(2H)-one was subjected to aza-Michael addition and N-alkylation on reaction with a set of alkylating agents in the presence of K2CO3. Hydrazinolysis of 4-phenyl-1,2,5,6-tetraazafluoranthen-3(2H)-one ester to hydrazide and conversion of hydrazide to thiosemicarbazide were successful. X-Ray single crystals analysis and 1H, 13C NMR were used for unambiguous structure confirmation. The O…H, N…H, C…N and C…C in 2, and the N…H, …
FDA-Approved Fluorinated Heterocyclic Drugs from 2016 to 2022
2023
The inclusion of fluorine atoms or heterocyclic moiety into drug structures represents a recurrent motif in medicinal chemistry. The combination of these two features is constantly appearing in new molecular entities with various biological activities. This is demonstrated by the increasing number of newly synthesized fluorinated heterocyclic compounds among the Food and Drug Administration FDA-approved drugs. In this review, the biological activity, as well as the synthetic aspects, of 33 recently FDA-approved fluorinated heterocyclic drugs from 2016 to 2022 are highlighted.
Non-oxidative dehydroaromatization of methane:an effective reaction regeneration cyclic operation for catalyst life extension
2015
[EN] Non-oxidative methane aromatization is an attractive direct route for producing higher hydrocarbons. It is highly selective to benzene despite the low conversion due to thermodynamic limitations, and Mo/H-ZSM-5, the first catalyst proposed for this reaction, is still considered as one of the most adequate. The major problem of this process is the severe catalyst deactivation due to the rapid build-up of carbonaceous deposits on the catalysts. Here we present an effective regeneration procedure that extends the life of Mo/zeolite based catalysts by combining reaction periods of 1.5 h with 0.5 h regeneration steps in a continuous cyclic mode and methane activation after each regeneration…
The International Business Cycle in a Changing World: Volatility and the Propagation of Shocks
2003
This paper examines the changing relationships between the G-7 countries through VAR models for the quarterly growth rates, estimated both over sub-periods and using a rolling data window. Six trivariate models are estimated, all of which include the US and a European (E15) aggregate. In relative terms, the conditional volatility of E15 growth has declined more since 1980 than the well-documented decline for the US. The propagation of shocks has also changed, with the volatility and propagation effects separated by applying shocks of pre-1980 magnitude to VARs estimated over various periods. Rolling estimation reveals that E15 has a steadily increasing impact on the US economy over time, wh…
Radical addition to iminium ions and cationic heterocycles
2014
Carbon-centered radicals represent highly useful reactive intermediates in organic synthesis. Their nucleophilic character is reflected by fast additions to electron deficient C=X double bonds as present in iminium ions or cationic heterocycles. This review covers diverse reactions of preformed or in situ-generated cationic substrates with various types of C-radicals, including alkyl, alkoxyalkyl, trifluoromethyl, aryl, acyl, carbamoyl, and alkoxycarbonyl species. Despite its high reactivity, the strong interaction of the radical’s SOMO with the LUMO of the cation frequently results in a high regioselectivity. Intra- and intermolecular processes such as the Minisci reaction, the Porta react…
A Domino Ring‐Closure Followed by Retro‐Diels–Alder Reaction for the Preparation of Pyrimido[2,1‐ a ]isoindole Enantiomers
2016
A simple method was developed to prepare pyrimido[2,1-a]isoindole derivatives by using di-endo- and di-exo-ethyl 3-aminobicyclo[2.2.1]hept-5-ene-2-carboxylate enantiomers as chiral sources. The method is based on a domino ring-closure reaction of norbornene 2-aminohydroxamic acid followed by microwave-induced retro-Diels–Alder reaction. In the case of enantiomeric starting substances, the chirality is transferred from norbornene derivatives to pyrimido[2,1-a]isoindoles. The configurations of the synthesized compounds were determined by 1D and 2D NMR spectroscopy [based on 2D NOE cross-peaks and 3JH,H coupling constants] and X-ray crystallography.