Energy-efficient vertical handover parameters, classification and solutions over wireless heterogeneous networks: a comprehensive survey

In the last few decades, the popularity of wireless networks has been growing dramatically for both home and business networking. Nowadays, smart mobile devices equipped with various wireless networking interfaces are used to access the Internet, communicate, socialize and handle short or long-term businesses. As these devices rely on their limited batteries, energy-efficiency has become one of the major issues in both academia and industry. Due to terminal mobility, the variety of radio access technologies and the necessity of connecting to the Internet anytime and anywhere, energy-efficient handover process within the wireless heterogeneous networks has sparked remarkable attention in recent years. In this context, this paper first addresses the impact of specific information (local, network-assisted, QoS-related, user preferences, etc.) received remotely or locally on the energy efficiency as well as the impact of vertical handover phases, and methods. It presents energy-centric state-of-the-art vertical handover approaches and their impact on energy efficiency. The paper also discusses the recommendations on possible energy gains at different stages of the vertical handover process

O-Silyl triflate-promoted addition of diethyl phosphite to chiral aldonitrones. A rapid access to complex alpha-amino phosphonates and their N-hydroxy derivatives

The addition reaction of diethyl phosphite to O-silylated N-benzyl nitrones derived from chiral alpha-alkoxy and N-Boc alpha-amino aldehydes has been studied as a stereoselective carbon-phosphorus bond forming process for the synthesis of polyhydroxylated alpha-amino and alpha,beta-diamino phosphonates. Key intermediates are the corresponding N-hydroxy alpha-amino phosphonates

A new simple route for the synthesis of (+/-)-2-azetidinones starting from beta-enamino ketoesters

beta-Enaminoketoesters, obtained through metal-catalysed reaction of methyl acetoacetate with alkyl cyanoformates have been conveniently transformed into beta-aminoesters by reduction of both the carbonyl group and the carbon-carbon double bond of the enaminoester moiety. These intermediates could be easily converted to (+/-)-2-azetidinones structurally related to thienamycin in good yield and high diastereoselectivity

A new simple route for the synthesis of (+/-)-2-azetidinones starting from beta-enaminoketoesters

beta-Enaminoketoesters, obtained by metal-catalyzed reaction between alkyl acetoacetates and alkyl cyanoformates, are useful starting materials for rapid access to beta-acetyl-dehydroaspartic acid derivatives which could be transformed into (+/-)-2-azetidinones bearing a 1-hydroxy-ethyl substituent through suitable reductive processes

Synthesis of 1-phathalimidoalkane phosphonate

Phosphonylation of RCHO with HP(O)​(OEt)​2 gave RCH(OH)​P(O)​(OEt)​2 which condensed with phthalimide to give 60-​71​% I [R = H, Me, Pr, Me(CH2)​5, Me(CH2)​6]​

A [3+2]-NITRILE OXIDE CYCLOADDITION APPROACH TO (-)-PYRENOPHORIN, AND ROSEFURAN

[3+2] Nitrile oxide cycloaddition chemistry has been conveniently applied as carbon-carbon bond forming reaction for the assemblage of the functionalized carbon atom fragments required for the synthesis of two simple but different targets such as (-)-pyrenophorin and rosefuran. In both cases, an intermediate 3,5-disubstituted isoxazoline ring system has been used as serviceable precursor of the salient structural feature of the targets

From (-)-quinic acid to 8-azabicyclo[3.2.1]octane framework: Preparation of an enantiopure tropan-6 alpha-ol

The carbon atom ring-insertion via pyrolysis of an alpha-diazo-beta-hydroxy ester intermediate, in turn obtained by reaction between ethyldiazoacetate and 3,4-O-isopropylidene-3(R),4(S)-dihydroxycyclohexanone, a chiron easily prepared through a five step sequence from D-(-)-quinic acid, was the key step for the construction of (3R,4S)-3,4-O-isopropylidene-cycloheptan-1-one. Its transformation into (1S,3R,4S)-1-azido-3,4-O-sulfonyl-cycloheptane set the stage for the preparation of optically pure (1S,5R,6R)-N-ethoxycarbonyl-6-hydroxy-8-azabicyclo[3.2.1]octane, as well as tropan-6-alpha-ol