The odd log-logistic Topp–Leone G family of distributions: heteroscedastic regression models and applications

We introduce a new class of distributions and provide a comprehensive treatment of its mathematical properties. The maximum likelihood method is discussed to estimate the parameters of the new model by means of Monte-Carlo simulation study. The heteroscedastic regression models with long-term survival are introduced to model data sets with the non homogeneity of the error variances in the presence of cured individuals. The potentiality of the proposed models is illustrated by means of four real data sets.     

Mössbauer and XRD study of Al-Sn linished steel bimetal alloy

Aluminium alloy free CS1 type steel (0.06 wt% C, 0.45 wt% Mn) and samples of cold roll bonded steel bimetal alloys (MAS15 and MAS16) were fabricated and investigated by X-ray diffraction (XRD), ⁵⁷Fe conversion electron Mössbauer spectroscopy (CEMS) at room temperature. XRD has revealed only the existence of the alpha iron solid solution (steel) phase in the steel only sample, while identified steel and metallic Al and Sn constituent phases in the bimetallic alloys. ⁵⁷Fe Mössbauer spectroscopy revealed the presence of 4 % secondary iron-bearing phase attributed mainly to iron oxide/ oxyhydroxides (ferrihydrite) besides the steel matrix on the surface of the steel sample. A significant difference between the occurrences of the secondary phase of differently prepared bimetal alloys found in their ⁵⁷Fe CEM spectra allowed to identify the main phase of debris as different iron oxide/ oxyhydroxides.     

Characteristics and nature of the halogen-bonding interactions between CCl3F and ozone: a supermolecular and SAPT study

The strength and nature of the halogen-bond interactions in CCl₃F···O₃ complexes were examined by means of ab initio quantum-chemical calculations and symmetry-adapted perturbation theory (SAPT). Our calculations predict a trifurcated C–Cl···O interaction for the global minimum of CCl₃F···O₃ complex and several local minima, differing slightly in energy, separated by very low barriers. The calculations, which include a rigorous decomposition of the interaction energies, also indicate that the interaction of CCl₃F molecule with O₃ is characterised by contributions from both electrostatic and dispersion energies, with the contribution of the latter being dominant. The evaluated SAPT interaction energies for the CCl₃F···O₃ complexes are generally in good agreement with those obtained using the supermolecule CCSD(T) method, suggesting that SAPT is a proper method to study the intermolecular interactions in these complexes.     

An extension of weighted generalized cumulative past measure of information

Ricerche di Matematica - In this paper, we consider a shift-dependent measure of generalized cumulative entropy and its dynamic (past) version in the case where the weight is a general non-negative...     

Stereoselective synthesis of 3-azido-2,3-dideoxy-D-ribose derivatives and its utilization for the synthesis of anti-HIV nucleosides

Detail account of the synthesis of 3′-azido nucleosides utilizing 3-azido-2,3-dideoxy-D-ribose derivative 7 as the key intermediate was described. The key intermediate 7 was synthesized from D-mannitol in 8 steps in a preparative scale. The Michael reaction of the azide group with α,β-unsaturated-γ-butyrolactone 4 was affected by the steric bulkiness of the substituent at the 5-O position. A bulky t-butyldiphenylsilyl substitution at 5-O gave almost exclusively the α-azido adduct 5b , while unsubstitution at 5-O produced 1:1 mixture of α-and β-adducts. The ratio of α to β anomers in the condensation between azido acetate 7a and pyrimidine bases for the preparation of AZT and AZDU was greatly influenced by the solvent and the Lewis acid catalyst used. In the synthesis of 12 (AZDU, CS-87), the combination of dichloroethane and trimethylsilyl triflate gave an optimal result, while in the case of 14 (AZT), various conditions gave similar ratio of α,β anomers. The azido intermediate 7b was also utilized for the synthesis of several 3′-azido purine-like nucleosides 16–27 . The glycosylation was also affected by the Lewis acid catalyst. Boron trifluoride etherate gave the desired N₁-glycosylated compounds in which the α-anomer was major, but other catalysts such as trimethylsilyl triflate or stannic chloride produced N₂-glycosylated compounds as the major products. The newly synthesized purine-like compounds have been tested against HIV, however, none of them showed any significant activity.     

Negative dispersion mirrors for dispersion control in femtosecond lasers: chirped dielectric mirrors and multi-cavity Gires-Tournois interferometers

Chirped dielectric laser mirrors have been known for years as useful devices for broadband feedback and dispersion control in femtosecond pulse lasers. First we present a novel design technique referred to as frequency domain synthesis of chirped mirrors. These mirrors exhibit high reflectivity and nearly constant group delay over 150 THz supporting generation of sub-5-fs pulses in the visible. Afterwards, multi-cavity thin-film Gires-Tournois interferometers are introduced for the first time as an alternative approach to realize "negative dispersion mirrors". These novel dielectric high reflectors exhibit reflectivities R>99.97% and a negative group delay dispersion of ⫆ǃ fs² over a bandwidth of 56 THz. Dispersive properties originate from coupled resonances in multiple 5/2 cavities embedded in the layer structure. The general structure and performance of multi-cavity Gires-Tournois interferometers are compared to that of chirped dielectic mirrors and their distinct applications are discussed.     

Stereoselective amination of chiral benzylic ethers using chlorosulfonyl isocyanate: total synthesis of (+)-sertraline

The stereoselective amination of various chiral benzylic ethers using chlorosulfonyl isocyanate is developed, and the application of this method to the total synthesis of a potent antidepressant, (+)-sertraline, from readily available 1-naphthol is also described.     

First synthesis of 4'-selenonucleosides showing unusual Southern conformation

The first synthesis of 4'-selenonucleosides was achieved using a Pummerer-type condensation as a key step. All stereoelectronic effects shown in 4'-oxonucleosides were overwhelmed by the size of selenium and steric interactions, driving the conformation to the C2'-endo/ C3'-exo twist (Southern) conformation.     

Synthesis of novel apio carbocyclic nucleoside analogues as selective a(3) adenosine receptor agonists

On the basis of the biological activity of neplanocin A and apio-dideoxyadenosine (apio-ddA), novel apio-neplanocin A analogues 5a-d, combining the properties of two nucleosides, were stereoselectively synthesized. The apio moiety of the target nucleosides 5a-d was stereoselectively introduced by treating lactol 10 with 37% formaldehyde in the presence of potassium carbonate. The carbasugar moiety of neplanocin A was successively built by exposing diene 12 on a Grubbs catalyst in methylene chloride. The final nucleosides 5a-d were synthesized from the condensation of the glycosyl donor 14 with nucleic bases under the standard Mitsunobu conditions. Similarly, apio-aristeromycin 6 and (N)-apio-methanocarbaadenosine 7 were derived from the common intermediate 13 using catalytic hydrogenation and Simmons-Smith cyclopropanation as key steps. All of the final nucleosides 5a-d, 6, and 7 did not show significant inhibitory activity against S-adenosylhomocysteine hydrolase (SAH) up to 100 muM, maybe due to the absence of the secondary hydroxyl group at the C3'-position, which should be oxidized by cofactor-bound NAD(+). However, apio-neplanocin A (5a) showed potent and highly selective binding affinity (K(i) = 628 +/- 69 nM) at the A(3) adenosine receptor without any binding affinity at the A(1) and A(2A) adenosine receptors. In conclusion, we have first developed novel carbocyclic nucleosides with unnatural apio-carbasugars using stereoselective hydroxymethylation and RCM reaction and also discovered a new template of human A(3) adenosine receptor agonist, which play a great role in developing new A(3) adenosine receptor agonist as well as in identifying the binding site of the receptor.