bluuebunny/crossref_metadata_2025 huggingface dataset:
Triazene derivatives of (1,x-)diazacycloalkanes. Part VI. 3-({5,5-Dimethyl-3-[2-aryl-1-diazenyl]-1-imidazolidinyl}methyl)-4,4-dimethyl-1-[2-aryl-1-diazenyl]imidazolidines — Synthesis, characterization, and X-ray crystal structure
Authors: Vaughan Keith , Moser Shasta Lee , Tingley Reid , Peori M Brad , Bertolasi Valerio
Published: December 2006

Reaction of a series of diazonium salts with a mixture of formaldehyde and 1,2-diamino-2-methylpropane affords the 3-({5,5-dimethyl-3-[2-aryl-1-diazenyl]-1-imidazolidinyl}methyl)-4,4-dimethyl-1-[2-aryl-1-diazenyl]imidazolidines (1a–1f) in excellent yield. The products have been characterized by IR and NMR spectroscopic analysis, elemental analysis, and X-ray crystallography. The X-ray crystal structure of the p-methoxycarbonyl derivative (1c) establishes without question the connectivity of these novel molecules, which can be described as linear bicyclic oligomers with two imidazolidinyl groups linked together by a one-carbon spacer. This is indeed a rare molecular building block. The molecular structure is corroborated by 1H and 13C NMR data, which correlates with the previously published data of compounds of types 5 and 6 derived from 1,3-propanediamine. The triazene moieties in the crystal of 1c display significant π conjugation, which gives the N—N bond a significant degree of double-bond character. This in turn causes restricted rotation around the N—N bond, which leads to considerable broadening of signals in both the 1H and 13C NMR spectra. The molecular ion of the p-cyanophenyl derivative (1b) was observed using electrospray mass spectrometry (ES + Na). The mechanism of formation of molecules of type 1 is proposed to involve diazonium ion trapping of the previously unreported bisimidazolidinyl methane (13).Key words: triazene, bistriazene, imidazolidine, synthesis, X-ray crystallography, NMR spectroscopy.
Effect of crown ether ring size on binding and fluorescence response to saxitoxin in anthracylmethyl monoazacrown ether chemosensors
Authors: Mao Hua , Thorne John B , Pharr Jennifer S , Gawley Robert E
Published: December 2006

Convenient macrocyclization synthetic routes for the preparation of different-sized monoaza anthracylmethyl crown ether chemosensors (15-crown-5, 18-crown-6, 21-crown-7, 24-crown-8, and 27-crown-9) are described. Evaluation of these crowns as chemosensors for saxitoxin revealed that the larger crowns have moderately higher binding constants, with the 27-crown-9 chemosensor having the largest binding constant (2.29 × 105 (mol/L)–1). Fluorescence enhancements of 100% were observed at saxitoxin concentrations of 5 µmol/L, which is close to the detection limit in mouse bioassay.Key words: anthracene, crown ethers, saxitoxin, paralytic shellfish poison (PSP), binding constants; chemosensors.
A chiral auxiliary cleavable by ring-closing alkene metathesis — Efficient synthesis of chiral nonracemic cycloalkenes
Authors: Boisvert Luc , Beaumier Francis , Spino Claude
Published: December 2006

p-Menthane-3-carboxaldehyde is a readily available chiral auxiliary used to prepare cycloalkenes and heterocycles bearing a chiral tertiary or quaternary carbon of high enantiomeric purity. The auxiliary is available in both enantiomeric forms and is inexpensive and recyclable. It is cleaved by a ring-closing alkene metathesis reaction directly yielding the cycloalkene.Key words: chiral auxiliary, cleavage reaction, cyclization, ring-closing alkene metathesis, enantioenriched cycloalkenes.
A theoretical and experimental investigation of some unusual intermolecular hydrogen-bond IR bands — Appearances can be deceptive
Authors: Litwinienko Grzegorz , DiLabio Gino A , Ingold K U
Published: December 2006

The IR spectra of the O-H stretch for hydrogen bonds (HBs) arising from complex formation between the HB donor (HBD), 4-fluorophenol, and the HB acceptors, peroxides and ethers, frequently show asymmetry that appears to arise from two incompletely resolved bands from two different complexes, but the O-H HB bands with the HBD methanol are symmetric (M. Berthelot, F. Bessau, and C. Laurence. Eur. J. Org. Chem. 925 (1998)). The present studies show that this difference in O-H HB band shapes also is true for other phenols and alcohols. However with ethylene oxide, 4-fluorophenol gives an almost symmetric O-H HB band with a very broad maximum, while alcohols give symmetric O-H HB bands with well-defined maxima. It is shown by experiment that the unusual O-H HB band shapes for the phenols are not due to Fermi resonance and are unrelated to the enthalpies of HB complex formation. Theoretical exploration of the potential energy (PE) surfaces for complexes of 4-fluorophenol and methanol with tert-butyl methyl ether and ethylene oxide reveals that O-H HB band asymmetry or broadness cannot be ascribed to the presence of two different HB complexes. For this ether, the PE surfaces for rotation about the HB and for up-and-down motion of the HBD with respect to the COC plane of the ether are relatively symmetric for methanol, but are strongly asymmetric for 4-fluorophenol, hence the differences in the O-H HB band shapes. The PE surfaces for the epoxide are effectively symmetric, but the PE for rotation about the HB has a single broad minimum for methanol, whereas with 4-fluorophenol there are two minima owing to attractive interactions between the phenyl group and the CH2 groups of the epoxide. The previously unknown β2H values for ethylene oxide and tetramethylethylene oxide are 0.36 and 0.58, respectively.Key words: asymmetric IR O-H bands, asymmetric potential energy surfaces, hydrogen-bonded complexes, hydrogen bond enthalpy, O-H frequency shift.
Design and synthesis of selenonium and sulfonium ions related to the naturally occurring glucosidase inhibitor salacinol
Authors: Liu Hui , Pinto B Mario
Published: December 2006

Four series of analogues of the naturally occurring glucosidase inhibitor salacinol were synthesized for structure–activity studies with different glycosidase enzymes. The target zwitterionic compounds were synthesized by means of nucleophilic attack at the least-hindered carbon atom of the 1,3-cyclic sulfates derived from D-glucose and D-mannose by the isopropylidene-protected 1,4-anhydro-4-thio- and seleno-D-allitols and the 4-thio- and seleno-L-allitols. Deprotection of the coupled products afforded the novel sulfonium and selenonium ions containing polyhy droxylated acyclic chains of four and six carbons, with different stereochemistry at the stereogenic centers and with 1,4-anhydro-4-seleno or 4-thio-D- or L- alditol heterocyclic rings. The compounds showed no significant activity against recombinant human maltase glucoamylase (MGA), a critical intestinal glucosidase involved in the processing of oligosaccharides of glucose into glucose itself.Key words: glycosidase inhibitors, zwitterionic, selenonium salts, sulfonium salts, cyclic sulfates, L-ascorbic acid, D-gulonic-γ-lactone.
Polycyclic oxonium ylides — Use of cyclic acetals as convenient scaffolds in the construction of fused bicyclic compounds containing a medium ring
Authors: Murphy Graham K , Marmsäter Fredrik P , West F G
Published: December 2006

Cyclic mixed acetals with pendant diazoketone side chains undergo efficient rearrangement to ether-bridged cyclooctanoid and cycloheptanoid systems upon treatment with Cu(hfacac)2. Stevens [1,2]-shift of an oxonium ylide furnishes the major product, in some cases accompanied by minor amounts of a product resulting from [1,2]-shift of a sulfonium ylide. These results demonstrate that hetero-substituted carbons are suitable migrating groups for the Stevens [1,2]-shift of oxonium ylides. In cases employing a mixed thioacetal, the resulting sulfide served as a trigger for cleavage of the bridging ether through one of two complementary strategies. In the hydrazulene series, the desired bicyclo[5.3.0]heptene was accompanied by the product of novel transannular SN2′ attack on the resulting allylic ketal.Key words: [1,2]-shift, diazo, medium-sized ring, oxonium ylide, ring expansion.
Deprotonation of β,β-disubstituted α,β-unsaturated amides - Mechanism and stereochemical consequences
Authors: Green James R , Majewski Marek , Snieckus Victor
Published: December 2006

A detailed study of the lithium dialkylamide induced deprotonation of β,β-disubstituted α,β-unsaturated amides is presented. The preferential γ-Z-deprotonation and stereochemical outcome of substituents on the γ-Z carbon atom are rationalized in terms of a cyclic eight-membered transition state, which is supported by DFT calculations. Analogous deprotonations on cyclohexylidenecarboxamides reveal a delicate balance of the preference for the eight-membered cyclic transition state with the effects of existing substituents on the ring and the intervention of a twist-boat transition state.Key words: dienolate, amide, deprotonation mechanism, transition state, enolization, regioselectivity, stereoselectivity.
In situ nitrosonium ion generation — α-Oximinylation of enol ethers from steroidal spiroketals: Introduction of C23 (R)-OH in cephalostatin intermediates
Authors: Lee Seongmin , Fuchs Philip L
Published: December 2006

Nitrosonium ion generated in situ from the reaction of t-BuNO2 and BF3·Et2 is an effective oximinylating agent for enol ethers derived from steroidal spiroketals. The scope and limitations of this method has been studied. The difficult reduction of C23 ketone to C23 (R)-alcohol has now been selectively achieved via L-Selectride® reduction. Application to cephalostatin intermediates is discussed.Key words: oximinylation, nitrosonium ion, steroid spiroketal, cephalostatins.
Hydrogen-bonded networks in crystals built from bis(biguanides) and their salts
Authors: Lebel Olivier , Maris Thierry , Wuest James D
Published: December 2006

Biguanide groups and biguanidinium cations incorporate multiple sites that can donate or accept hydrogen bonds. To assess their ability to associate and to direct the formation of extended hydrogen-bonded networks, we examined the structure of crystals of four compounds in which two neutral biguanide groups or the corresponding cations are attached to the 1,4- and 1,3-positions of phenylene spacers. As expected, all four structures incorporate extensive networks of hydrogen bonds and reveal other reliable features. In particular, (1) neutral biguanide groups favor a roughly planar conformation with an intramolecular hydrogen bond, and they associate as hydrogen-bonded pairs, (2) despite coulombic repulsion, biguanidinium cations can also associate as hydrogen-bonded pairs, and (3) the 1,3-phenylenebis(biguanidinium) dication favors a pincerlike conformation that allows chelation of suitable counterions. However, the precise patterns of hydrogen bonding in the structures vary substantially, limiting the usefulness of biguanide and biguanidinium as groups for directing supramolecular assembly.Key words: bis(biguanide), bis(biguanidinium), structure, hydrogen-bonded network, noncovalent interaction, supramolecular chemistry, crystal engineering.
Hydrosilylation of ketones catalyzed by C2-symmetric proline-derived complexes
Authors: Gan Li , Brook Michael A
Published: December 2006

Extracoordinate chiral hydrosilanes were generated in situ from triethoxysilane and a C2-symmetric ligand derived from bisproline 7. In the presence of a catalytic amount of ligand 7, prochiral ketones were reduced in moderate yield with moderate enantioselectivity (up to 64% ee). Alternatively, TiF4 complexes of 7 were used to provide higher enantioselectivity and with improved yields. The copper complex of ligand 7 and 29Si NMR data provide some guidance as to the key factors responsible for the observed reactivity at the silicon and at the ligand centre.Key words: extracoordinate chiral silane, C2-symmetry, enantioselectivity, Lewis acid titanium catalysis.
Preparation of enantiopure long chain threo-2-amino-3-hydroxyesters via chiral morpholinone-derived azomethine ylids
Authors: Brome Victoria A , Harwood Laurence M , Osborn Helen MI
Published: December 2006

The synthetic approach to threo-2-amino-3-hydroxyesters possessing long alkyl chains outlined herein centres on the generation of chiral azomethine ylids by reaction of (5R)-5-phenyl-morpholin-2-one, (R)-(1), with long chain aldehydes. In the presence of a second equivalent of aldehyde, the azomethine ylid can be trapped to afford a cycloadduct with three new stereodefined centres. Degradation of the cycloadduct allows entry to β-substituted-α-amino acid derivatives, which have potential as building blocks for sphingosine synthesis.Key words: sphingosine, morpholinone, chiral azomethine ylid, dipolar cycloaddition.
Intramolecular [4 + 3] cycloadditions – Stereochemical issues in the cycloaddition reactions of cyclopentenyl cations – A synthesis of (+)-dactylol
Authors: Harmata Michael , Rashatasakhon Paitoon , Barnes Charles L
Published: December 2006

Five cyclopentanones were prepared for the purpose of examining the effects of stereogenic centers on the course of the intramolecular [4 + 3] cycloaddition reactions of cyclopentenyl cations. One substrate reacted with very high levels of diastereoselectivity and was converted to (+)-dactylol. The cyclopentenone without stereogenic centers on the tether or the five-membered ring gave two cycloadducts, the endo isomer being only slightly favored over the exo. Other substrates reacted with generally good to poor stereoselectivity. An epimer of the substrate leading to (+)-dactylol afforded all possible isomers of the cycloadduct with relatively poor stereoselectivity.Key words: cycloaddition, total synthesis, dactylol.
Triazene derivatives of (1,x)-diazacycloalkanes. Part VII. Synthesis of a series of 1-aryl-2-[3-(3-[2-aryl-1-diazenyl]-1,3-diazepan-1-ylmethyl)-1,3-diazepan-1-yl]-1-diazenes from the reaction of diazonium salts with mixtures of formaldehyde and 1,4-diaminobutane
Authors: Tingley Reid , Vaughan Keith
Published: December 2006

A new series of bistriazenes, the 1-aryl-2-[3-(3-[2-aryl-1-diazenyl]-1,3-diazepan-1-ylmethyl)-1,3-diazepan-1-yl]-1-diazenes (8), has been synthesized from the reaction of diazonium salts with a mixture of 1,4-diaminobutane and formaldehyde. All new compounds of series 8 have been characterized by IR and NMR spectroscopy, and the elemental composition of selected examples has been verified by elemental analysis. The connectivity of the series has been unequivocally determined by X-ray crystallography. The new bistriazenes are important because the structure contains the novel saturated heterocycle, 1,3-diazepane. The general conclusion of this study is that alkanediamines with three or four carbon atoms in the spacer link between the nitrogen atoms give rise to the linear bicyclic molecules of type 2, in contrast to the case of ethylenediamine (two carbon atoms in spacer link), which affords molecules of type 3, which exemplify the cage structure of type 1.Key words: diazonium salt, triazene, bistriazene, diazepane, formaldehyde, nuclear magnetic resonance.
A highly efficient carbon–sulfur bond formation reaction via microwave-assisted nucleophilic substitution of thiols to polychloroalkanes without a transition-metal catalyst
Authors: Cao Yi-Ju , Lai Yuan-Yuan , Cao Hong , Xing Xiao-Ning , Wang Xiang , Xiao Wen-Jing
Published: December 2006

An efficient carbon–sulfur bond formation reaction has been developed under microwave irradiation. This reaction affords a novel and rapid synthesis of thioacetals and sulfides under mild conditions. This method is particularly noteworthy given its experimental simplicity and high generality, and no transition-metal catalysts were needed under our conditions.Key words: microwave, sulfide, thiol, nucleophilic substitution.
Interaction of dimethyltin(IV)dichloride with 5′-AMP and 5′-GMP
Authors: Gharib Farrokh , Farzad Elnaz , Amini Mostafa Mohammadpour
Published: December 2006

The formation constants of the species formed in the systems H+ + dimethyltin(IV) + 5′-AMP and 5′-GMP, H+ + 5′-AMP, and H+ + 5′-GMP have been determined in aqueous solution in the pH range of 1.5–9 at constant temperature (25 °C) and constant ionic strength (0.1 mol dm–3, NaClO4) using spectrophotometric and potentiometric techniques. 1H and 31P NMR investigations in aqueous solution confirmed the species formation and led us to propose their structures. The precipitated complexes of AMP and GMP by Me2Sn(IV)2+ at low pH values were characterized by elemental analysis and FTIR spectroscopy, which ruled out purine moiety (N-1 and N-7) coordination and a bidentated coordination of the phosphate group is concluded in both cases.Key words: dimethyltin(IV)dichloride, guanosine 5′-monophosphate, adenosine 5′-monophosphate, stability and protonation constants.
Reactivity of mesoporous palladium yttria-stablilized zirconia for solution phase reactions
Authors: Poulin Carl , Brown Matthew A , Wasslen Yamile A , Grgicak Catherine M , Fagnou Keith , Giorgi Javier B
Published: December 2006

A reduced mesoporous 5% Pd-YSZ precatalyst was observed to be very active for the Heck reaction providing up to 770,000 TON. Three-phase tests have experimentally confirmed that a leached homogeneous species is responsible for the activity. Residual Pd concentration in solution is minimal (<0.10 ppm) and therefore this material has potential applications because it can be easily removed by filtration. This paper describes the synthesis, structural characterization, and catalytic activity of the mesoporous Pd-YSZ material. The material was prepared using an amphiphillic surfactant templating method resulting in a homogeneous dispersion of Pd in an ordered mesoporous structure. Material properties were fully characterized using X-ray diffraction, surface area analysis, and electron microscopy.Key words: mesoporous catalysts, palladium, yttria-stabilized zirconia, Heck reaction, Pd-YSZ.
Montreal Medal Award Lecture — Coordination chemistry of molecular bowls: Ligands and their complexes derived from resorcinarenes
Authors: Puddephatt Richard J
Published: December 2006

A review is given of the design, synthesis, structures, and properties of octadentate or tetradentate ligands and their coordination compounds, based on the bowl-like resorcinarene skeleton.Key words: resorcinarene, coordination, phosphine, thiophosphinate, polymer.
Phenolic compounds from Mammea siamensis seeds
Authors: Laphookhieo Surat , Maneerat Wisanu , Kiattansakul Rattana
Published: December 2006

The investigation of dichloromethane and acetone extracts of the seeds of Mammea siamensis led to the isolation of a novel phenolic compound, siamensone A (1), together with three known compounds, suragin B (2), mammea E/BB (3), and δ-tocotrienol (4). The structures of the isolates were characterized by spectroscopic methods, and all compounds were reported for the first time as metabolites of M. siamensis.Key words: Mammea siamensis, siamensone, coumarins.
Efficient RuIII-catalyzed condensation of indoles and aldehydes or ketones
Authors: Tabatabaeian Khalil , Mamaghani Manouchehr , Mahmoodi Nosratollah , Khorshidi Alireza
Published: December 2006

Synthesis of bis(indolyl)methanes through condensation of indoles and various aldehydes or ketones, using RuIII as catalyst, is reported. It was found that the catalytic system involving RuIII affords the products smoothly under very mild conditions in good to high yields.Key words: aldehydes, ketones, bis(indolyl)methanes, indoles, ruthenium.
Principal component analysis of solvent effects on equilibria and kinetics — A hemisphere model
Authors: Stairs Robert A , Buncel Erwin
Published: December 2006

Principal Component Analysis (PCA) was applied to 17 selected properties relating to the properties of solvents and their effect on solute spectra and equilibria and rates of reactions in solution. The analysis showed affinities and contrasts among the parameters. Using the first three principal components (PC's) as unit vectors in the Cartesian directions, the properties were represented as vectors in this space with their directions being represented as points on the unit hemisphere; their magnitudes are lost in the process of correlation. Properties that fell into recognizable groups included the following: (i) those purporting to measure acidity (A) (α, AN, SA, and Aj), closely associated with ETN, Z, S, and A(14N), which are usually considered to be measures of polarity; (ii) properties supposed to measure basicity (B) (β, SB, and DN); (iii) polarity group (P), including pure (di-)polarity properties (βµ1/2 and Qv) and those measuring some combinations of polarity and polarizability (π*, πazo, SPP, and –χR). The space spanned by the three PCs of the properties provided a frame in which solvent effects on equilibria and on rates of reactions could be represented. Eight equilibria, represented by log10(K) measured in different solvents, and 10 reaction rates, similarly represented by log10(k), were correlated with the three PCs of the solvent properties. This enabled plotting of their directions in the hemisphere to show which groups of properties were most strongly correlated with the rate of each reaction. A separate plot showed the magnitudes and sense of the effects. These finding are considered in the light of the mechanisms proposed for the reactions.Key words: Chemometrics, Principal Component Analysis, solvent effects on equilibria and rates.
Expanding the scope of the Newman–Kwart rearrangement — A computational assessment
Authors: Jacobsen Heiko , Donahue James P
Published: December 2006

The Newman–Kwart rearrangement (NKR) has been studied for a variety of thioncarbamates using density functional (B3LYP) and ab initio (MP2) methodologies. The results confirm and support the generally accepted mechanism that the NKR proceeds through a four-membered cyclic transition state. The presence of a π system connected via an oxygen linkage to a thiocarbonyl functionality is identified as a crucial structural element for the NKR. The calculations further suggest that the NKR might also be feasible for thioncarbamates derived from π system containing groups other than phenols such as ethenol, ethenediol, and butadienol. The NKR is compared with the Schönberg rearrangements of thioncarbonates.Key words: density functional calculations, localized orbital locator, oxygen–sulfur transposition, thiols.
COMPOSITIONAL VERIFICATION FOR WORKFLOW NETS
Authors: JIAO LI , CHEUNG TO-YAT
Published: December 2006

A workflow is the automation of business processes that describe activities in a business context. Petri nets have been widely used as a workflow modeling technique. Workflow nets (WF-nets), introduced by van der Aalst [LNCS1248 (1997) 407–426], are a class of Petri nets tailored towards workflow analysis. Soundness is used as the least correctness criterion for WF-nets in order to ensure that a process can terminate properly. This paper extends WF-nets by considering resources and allowing for multi-cases in a process. For the extended model, the relationship between soundness and standard behavior properties of Petri nets is investigated. A compositional method to construct and verify sound WF-nets is introduced.
PERFORMANCE MODELS FOR STUDYING AND ANALYZING REAL-TIME MULTIMEDIA SYSTEMS
Authors: KORIEM SAMIR M.
Published: December 2006

As real-time systems continue to grow, performance evaluation plays a critical role in the design of these systems since the computation time, the service time, and the responsive actions must satisfy the time constraints. One of these systems is the real-time distributed multimedia-on-demand (MOD) service system. The MOD system usually fails when it misses a task deadline. The main units of the MOD system usually communicate with each other and work concurrently under timing constraints. The MOD system is designed to store, retrieve, schedule, synchronize and communicate objects comprising of mixed data types including images, text, video and audio, in real-time. In the MOD system, such data types represent the main concept of movie files. Modeling of such concurrency, communication, timing, and multimedia service (e.g., store, retrieve) is essential for evaluating the real-time MOD system. To illustrate how to model and analyze the important multimedia aspects of the MOD system, we use the Real-net (R-net) modeling technique. We choose R-net as an extension of Time Petri Net due to its ability to specify hard real-time process interaction, represent the synchronization of multimedia entities, describe concurrent multimedia activities, and illustrate the inter-process timing relationships as required for multimedia presentation. Based on modular techniques, we build three R-net performance models for describing the dynamic behavior of the MOD service system. The first model adopts the Earliest Deadline First (EDF) disk scheduling algorithm. The other models adopt the Scan-EDF algorithm. These algorithms help us to illustrate how the real-time user requests can be satisfied within the specified deadline times. Since R-nets are amenable to analysis including Markov process modeling, the interesting performance measures of the MOD service system such as the quality of service, the request response time, the disk scheduling algorithm time, and the actual retrieval time can be easily computed. In the performance analysis of the MOD models, we use our R-NET package.
ON USING LINEAR PERIODICALLY RESETTING FILTER IN CURRENT CONTROL LOOP FOR ACTIVE POWER FILTER
Authors: ZHOU LIDAN , KHAN MUHAMMAD MANSOOR , JI FEIFENG , YAO GANG , XIE DA , CHEN CHEN , SHU JOAN
Published: December 2006

Among linear control techniques, deadbeat control has been widely accepted as a feasible current control technique as far as the digital signal processor (DSP) implementation of active power filter (APF) is concerned. This control technique uses high gain on the error measured at one sample, to control the error ideally to zero by the next sample. The high gain makes the control very sensitive to any error or noise in the measurements, which is always there in electrical systems. Especially, the periodic noise in parallel implementation of an inverter or APF demands a higher order filter at the current transducer output, which affects the dynamic response of the system. Recently, few papers have reported the results about the use of linear periodically resetting integrators (LPRI) as filter in some electronic applications. This paper is an attempt to generalize the idea of LPRI and here we introduce the notion of linear periodically resetting filter (LPRF). The frequency characteristics of an LPRF are analyzed. Possible application of these filters in current control is studied. It is shown that these filters can be adopted to improve the performances of a current loop in APF.
CRITICAL ANALYSIS OF A COMBINED HUFFMAN AND CONVOLUTIONAL CODING SCHEME
Authors: SOYJAUDAH K. M. S. , FOWDUR T. P.
Published: December 2006

In this paper, a critical analysis of the joint source channel coding scheme proposed by Honary et al.1 is given. We show mathematically that although the algorithm leads to a reduction in the overall number of decoding states it increases both the time and space complexity of the decoding process. Moreover, the hardware complexity of the proposed scheme is also analyzed and it is observed that the joint decoding algorithm is in the first place extremely complex to implement and secondly, it significantly increases the number of components required, thereby increasing the power consumption. A mathematical proof that the joint decoding scheme has the same error performance as a separate scheme is also given. Finally, the simulation results show that the joint decoding scheme takes a significantly greater time to decode than a separate scheme, for the same error performance.
EXPANDED LORENZ SYSTEMS AND CHAOTIC SECURE COMMUNICATION SYSTEMS DESIGN
Authors: ACHO LEONARDO
Published: December 2006

Using Lyapunov theory, the Lorenz chaotic system was partitioned in two parts, where one of them is globally asymptotically stable. This partition facilitated the state–space expansion of the Lorenz system from three to four-order. This new four-order Lorenz system, one of its states is synchronized with other. This expansion allows us to design a secure communication system where the dynamic of the receiver is just one-order. The proposed secure communication system uses two-lines of transmission. Simulation results are included to demonstrate the performance of this secure communication system based on this new four-order Lorenz system.
A BiCMOS 120 mW 11 GHz TRANSIMPEDANCE AMPLIFIER DEDICATED FOR HIGH-SPEED PHOTORECEIVERS
Authors: BOYOGUÉNO ANDRÉ , SAWAN MOHAMAD , SLAMANI MUSTAPHA
Published: December 2006

We present a new low-noise, low-power SiGe transimpedance amplifier (TIA) by combining an automatic DC photo-current cancellation, an on-chip DC offset compensation circuit and a single-ended to differential conversion scheme. The conversion method is based of the replica biasing technique in order to provide balanced output signals to the subsequent stages. The chip was fabricated in a 0.18 μm SiGe BiCMOS technology. Experimental results show excellent performances such as 11 GHz bandwidth, 75-dBΩ transimpedance, -19.2 dBm sensitivity measured at 10 Gb/s at a Bit Error Rate (BER) of 10-12, [Formula: see text] input referred noise, and 9.5 ps peak-to-peak jitter which are the best overall performances reported in its category. The photoreceiver chip is expected to dissipate only 120 mW from a single 3.3 V power supply.
LOW POWER ENERGY RECOVERY COMPLEMENTARY PASS-TRANSISTOR LOGIC
Authors: CHANG ROBERT C. , HUNG PO-CHUNG , LIN HSIN-LEI
Published: December 2006

A proposed adiabatic logic called Energy Recovery Complementary Pass-transistor Logic (ERCPL) is presented in this paper. It operates with a two-phase nonoverlapping power-clock supply. It uses bootstrapping to achieve efficient power saving and eliminates any nonadiabatic losses on the charge-steering devices. A scheme is used to recover part of the energy trapped in the bootstrapping nodes. We compare the energy dissipation between ERCPL and other logic circuits by simulation. Simulation results show that a pipelined ERCPL carry look-ahead adder can achieve a power reduction of 80% over the conventional CMOS case. Operation of an 8-bit ERCPL CLA fabricated using the TSMC 0.35 μm 1P4M CMOS technology has been experimentally verified.
DESIGN OF DECOUPLING ACTIVE NOISE CONTROL SYSTEMS
Authors: TARINGOO F. , POSHTAN J. , NASIRI A. , KAHAE M. H.
Published: December 2006

In this paper a simple method for multi-channel Active Noise Control (ANC) is introduced. The proposed structure is a combination of an adaptive FIR filter, based on the FXLMS algorithm, and the ALIGN algorithm resulting in a decoupled matrix for secondary path transfer function.

This structure thus converts a multi-channel ANC system to decoupled systems which results in the reduction in computational load without affecting the convergence behavior of the FXLMS system.
Microinjection of exogenous somatostatin in the dorsal vagal complex inhibits pancreatic secretion via somatostatin receptor-2 in rats
Authors: Liao Zhuan , Li Zhao-Shen , Lu Yan , Wang Wei-Zhong
Published: December 2006

Previous studies have suggested that somatostatin inhibits pancreatic secretion at a central vagal site, and the dorsal vagal complex (DVC) is involved in central feedback inhibition of the exocrine pancreas. The aim of this study was to investigate the effect of exogenous somatostatin in the DVC on pancreatic secretion and the somatostatin receptor subtype(s) responsible for the effect. The effects of somatostatin microinjected into the DVC on pancreatic secretion stimulated by cholecystokinin octapeptide (CCK-8) or 2-deoxy-d-glucose (2-DG) were examined in anesthetized rats. To investigate the somatostatin inhibitory action site, a somatostatin receptor antagonist [SRA; cyclo(7-aminoheptanoyl-Phe-d-Trp-Lys-Thr)] was microinjected into the DVC before intravenous infusion of somatostatin and CCK-8/2-DG. The effects of injection of a somatostatin receptor-2 agonist (seglitide) and combined injection of somatostatin and a somatostatin receptor-2 antagonist (CYN 154806) in the DVC on the pancreatic secretion were also investigated. Somatostatin injected into the DVC significantly inhibited pancreatic secretion evoked by CCK-8 or 2-DG in a dose-dependent manner. SRA injected into the DVC completely reversed the inhibitory effect of intravenous administration of somatostatin. Seglitide injected into the DVC also inhibited CCK-8/2-DG-induced pancreatic protein secretion. However, combined injection of somatostatin and CYN 154806 did not affect the CCK-8/2-DG-induced pancreatic secretion. Somatostatin in the DVC inhibits pancreatic secretion via somatostatin receptor-2, and the DVC is the action site of somatostatin for its inhibitory effect.
The extracellular calcium-sensing receptor reciprocally regulates the secretion of BMP-2 and the BMP antagonist Noggin in colonic myofibroblasts
Authors: Peiris Dinithi , Pacheco Ivan , Spencer Craig , MacLeod R. John
Published: December 2006

To understand whether postprandial extracellular Ca2+(Cao2+) changes were related to intestinal epithelial homeostasis, we performed array analysis on extracellular calcium-sensing receptor (CaSR)-expressing colonic myofibroblasts (18Co cells) and observed increases in bone morphogenetic protein (BMP)-2 transcripts. The present experiments demonstrated that regulated secretion of BMP-2 occurs in response to CaSR activation of these cells and revealed a new property of BMP-2 on the intestinal barrier. Activation by Cao2+, spermine, GdCl3, or neomycin sulfate of 18Co cells or primary isolates of myofibroblasts from the normal human colon stimulated both the synthesis (RT-PCR) and secretion (ELISA) of BMP-2. Transient transfection with short interfering RNA against CaSR completely inhibited BMP-2 secretion. Transient transfection with dominant negative CaSR (R185Q) increased the EC50of Cao2+(5.7 vs. 2.3 mM). Upregulation of BMP-2 transcript and secretion occurring within 3 h of CaSR activation was prevented by actinomycin D. CaSR-mediated BMP-2 synthesis and secretion required phosphatidylinositol 3-kinase activation (as assessed by phospho-Akt generation). Exogenous BMP-2 and conditioned medium from CaSR-stimulated 18Co cells accelerated restitution in wounded postconfluent Caco-2 cells. Exogenous BMP-2 and conditioned medium from CaSR-stimulated 18Co cells increased the transepithelial resistance of low- and high-resistance T-84 epithelial monolayers. CaSR stimulation of T-84 epithelia and colonic myofibroblasts downregulated the BMP family antagonist Noggin, as assessed by RT-PCR and Western blot analysis. Together, our data suggest that the CaSR mediates the effective concentration of BMP-2 in the intestine, which leads to enhanced repair and barrier development.
Flagellin-induced tolerance of the Toll-like receptor 5 signaling pathway in polarized intestinal epithelial cells
Authors: Sun Jun , Fegan Pamela E. , Desai Anjali S. , Madara James L. , Hobert Michael E.
Published: December 2006

Salmonella typhimurium is a gram-negative enteric pathogen that invades the mucosal epithelium and is associated with diarrheal illness in humans. Flagellin from S. typhimurium and other gram-negative bacteria has been shown to be the predominant proinflammatory mediator through activation of the basolateral Toll-like receptor 5 (TLR5). Recent evidence has shown that prior exposure can render immune cells tolerant to subsequent challenges by TLR ligands. Accordingly, we examined whether prior exposure to purified flagellin would render human intestinal epithelial cells insensitive to future contact. We found that flagellin-induced tolerance is common to polarized epithelial cells and prevents further activation of proinflammatory signaling cascades by both purified flagellin and Salmonella bacteria but does not affect TNF-α stimulation of the same pathways. Flagellin tolerance is a rapid process that does not require protein synthesis, and that occurs within 1 to 2 h of flagellin exposure. Prolonged flagellin exposure blocks activation of the NF-κB, MAPK, and phosphoinositol 3-kinase signaling pathways and results in the internalization of a fraction of the basolateral TLR5 without affecting the polarity or total expression of TLR5. After removal of flagellin, cells require more than 24 h to fully recover their ability to mount a normal proinflammatory response. We have found that activation of phosphoinositol 3-kinase and Akt by flagellin has a small damping effect in the early stages of flagellin signaling but is not responsible for tolerance. Our study indicates that inhibition of TLR5-associated IL-1 receptor-associated kinase-4 activity occurs during the development of flagellin tolerance and is likely to be the cause of tolerance.
Loss of exocrine pancreatic stimulation during parenteral feeding suppresses digestive enzyme expression and induces Hsp70 expression
Authors: Baumler Megan D. , Nelson David W. , Ney Denise M. , Groblewski Guy E.
Published: December 2006

Luminal nutrients are essential for the growth and maintenance of digestive tissue including the pancreas and small intestinal mucosa. Long-term loss of luminal nutrients such as during animal hibernation has been shown to result in mucosal atrophy and a corresponding stress response characterized by the induction of heat shock protein (Hsp)70 expression. This study was conducted to determine if the loss of luminal nutrients during total parenteral nutrition (TPN) would result in atrophy of the exocrine pancreas and small intestinal mucosa as well as an induction of Hsp70 expression in rats. In experiment 1, the treatment groups included an orally fed control, a saline-infused surgical control, or TPN treatment for 7 days. In experiment 2, the treatment groups included an orally fed control and TPN alone or coinfused with varying doses of glucagon-like peptide (GLP)-2, a mucosal proliferation agent, for 7 days. In experiment 1, TPN resulted in a 40% reduction in pancreatic mass that was associated with a dramatic reduction in digestive enzyme expression, enhanced apoptosis, and a 200% increase in Hsp70 expression. Conversely, heat shock cognate 70, Hsp27, and Hsp60 expression was not changed in the pancreas. In experiment 2, TPN resulted in a 30% reduction in jejunal mucosa mass and a similar induction of Hsp70 expression. The inclusion of GLP-2 during TPN attenuated jejunal mucosal atrophy and inhibited Hsp70 expression, suggesting that Hsp70 induction is sensitive to cell growth. These data indicate that pancreatic and intestinal mucosal atrophy caused by a loss of luminal nutrient stimulation is accompanied by a compensatory response involving Hsp70.
Labeling of skeletal myoblasts with a novel oxygen-sensing spin probe for noninvasive monitoring of in situ oxygenation and cell therapy in heart
Authors: Wisel Sheik , Chacko Simi M. , Kuppusamy M. Lakshmi , Pandian Ramasamy P. , Khan Mahmood , Kutala Vijay Kumar , Burry Richard W. , Sun Benjamin , Kwiatkowski Pawel , Kuppusamy Periannan
Published: December 2006

We report the labeling (internalization) of skeletal myoblasts (SMs) with a novel class of oxygen-sensing paramagnetic spin probe for noninvasive tracking and in situ monitoring of oxygenation in stem cell therapy using electron paramagnetic resonance (EPR) spectroscopy. SM cells were isolated from thigh muscle biopsies of mice and propagated in culture. Labeling of SM cells with the probe was achieved by coincubating the cells with submicron-sized (270 ± 120 nm) particulates of the probe in culture for 48 h. The labeling had no significant effect on the viability or proliferation of the cells. The SM cells labeled with the probe were transplanted in the infarcted region of mouse hearts. The engraftment of the transplanted cells in the infarct region was verified by using MY-32 staining for skeletal myocytes. The in situ Po2 in the heart was determined noninvasively and repeatedly for 4 wk after transplantation. The results showed significant enhancement of myocardial oxygenation at the site of cell transplant compared with untreated control. In conclusion, labeling of SM cells with the oxygen-sensing spin probe offers a unique opportunity for the noninvasive monitoring of transplanted cells as well as in situ tissue Po2 in infarcted mouse hearts.
Resistance artery remodeling in deoxycorticosterone acetate-salt hypertension is dependent on vascular inflammation: evidence from m-CSF-deficient mice
Authors: Ko Eun A. , Amiri Farhad , Pandey Nihar R. , Javeshghani Danesh , Leibovitz Eyal , Touyz Rhian M. , Schiffrin Ernesto L.
Published: December 2006

Deoxycorticosterone acetate (DOCA)-salt hypertension has an important endothelin-1 (ET-1)-dependent component. ET-1-induced vascular damage may be mediated in part by oxidative stress and vascular inflammation. Homozygous osteopetrotic ( Op/Op) mice, deficient in macrophage colony-stimulating factor (m-CSF), exhibit reduced inflammation. We investigated in osteopetrotic ( Op/Op) mice the effects of DOCA-salt hypertension on vascular structure, function, and oxidative stress, the latter as manifested by reduced nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidase activity. Mice were implanted with DOCA (200 mg/mouse, under 5% isofluorane anesthesia) and given saline for 14 days. Systolic blood pressure (mmHg) was significantly increased (146 ± 2 and 138 ± 1; P < 0.001 vs. basal 115 ± 3 and 115 ± 3, respectively) by DOCA-salt in wild-type (+/+) and heterozygous ( Op/+) mice, but not in Op/Op mice (130 ± 1 vs. basal 125 ± 3). Norepinephrine contractile response was significantly enhanced, while acetylcholine endothelium-dependent vasodilation was significantly impaired in DOCA-salt-treated +/+ and Op/+ mice compared with control mice. No changes in norepinephrine-induced contraction and acetylcholine-induced relaxation were observed in DOCA-salt Op/Op mice. DOCA-salt +/+ and Op/+ mice had significantly increased mesenteric resistance artery media-to-lumen ratio and media cross-sectional area, neither of which were altered in Op/Op mice. Basal vascular superoxide production and NAD(P)H oxidase activity, vascular cell adhesion molecule-1 expression, and macrophage infiltration were significantly increased only in DOCA-salt +/+ mice. Thus m-CSF-deficient mice developed less endothelial dysfunction, vascular remodeling, and oxidative stress induced by DOCA-salt than +/+ and Op/+ mice, suggesting that inflammation may play a role in DOCA-salt hypertension, a model that results in part from effects of ET-1, which has proinflammatory actions.
Overexpression of human bone morphogenetic protein receptor 2 does not ameliorate monocrotaline pulmonary arterial hypertension
Authors: McMurtry M. Sean , Moudgil Rohit , Hashimoto Kyoko , Bonnet Sandra , Michelakis Evangelos D. , Archer Stephen L.
Published: December 2006

Pulmonary arterial hypertension (PAH) is associated with mutations of bone morphogenetic protein receptor 2 (BMPR2), and BMPR2 expression decreases with the development of experimental PAH. Decreased BMPR2 expression and impaired intracellular BMP signaling in pulmonary artery (PA) smooth muscle cells (PASMC) suppresses apoptosis and promotes proliferation, thereby contributing to the pathogenesis of PAH. We hypothesized that overexpression of BMPR2 in resistance PAs would ameliorate established monocrotaline PAH. Human BMPR2 was inserted into a serotype 5 adenovirus with a green fluorescent protein (GFP) reporter. Dose-dependent transgene expression was confirmed in PASMC using fluorescence microscopy, quantitative RT-PCR, and immunoblots. PAH was induced by injecting Sprague-Dawley rats with monocrotaline (60 mg/kg ip) or saline. On day 14, post-monocrotaline (MCT) rats received 5 × 109 plaque-forming units of either Ad-human BMPR2 (Ad-hBMPR2) or Ad-GFP. Transgene expression was confirmed by fluorescence microscopy, quantitative RT-PCR of whole lung samples, and laser-capture microdissected resistance PAs. Invasive hemodynamic and echocardiographic end points of pulmonary hypertension were assessed on day 24. Endogenous BMPR2 mRNA levels were greatest in resistance PAs, and expression declined with MCT PAH. Despite robust hBMPR2 expression in all lung lobes and within resistance PAs of treated rats, hBMPR2 did not lower mean PA pressure, pulmonary vascular resistance index, right ventricular hypertrophy, or remodeling of resistance PAs. Nebulized intratracheal adenoviral gene therapy with hBMPR2 reliably distributed hBMPR2 to resistance PAs but did not ameliorate PAH. Depressed BMPR2 expression may be a marker of PAH but is not central to the pathogenesis of this model of PAH.
Serotonergic mechanisms of the lateral parabrachial nucleus in renal and hormonal responses to isotonic blood volume expansion
Authors: Margatho Lisandra Oliveira , Giusti-Paiva Alexandre , Menani Jose Vanderlei , Elias Lucila Leico Kagohara , Vivas Laura M. , Antunes-Rodrigues Jose
Published: December 2006

This study investigated the involvement of serotonergic mechanisms of the lateral parabrachial nucleus (LPBN) in the control of sodium (Na+) excretion, potassium (K+) excretion, and urinary volume in unanesthetized rats subjected to acute isotonic blood volume expansion (0.15 M NaCl, 2 ml/100 g of body wt over 1 min) or control rats. Plasma oxytocin (OT), vasopressin (VP), and atrial natriuretic peptide (ANP) levels were also determined in the same protocol. Male Wistar rats with stainless steel cannulas implanted bilaterally into the LPBN were used. In rats treated with vehicle in the LPBN, blood volume expansion increased urinary volume, Na+ and K+ excretion, and also plasma ANP and OT. Bilateral injections of serotonergic receptor antagonist methysergide (1 or 4 μg/200 ηl) into the LPBN reduced the effects of blood volume expansion on increased Na+ and K+ excretion and urinary volume, while LPBN injections of serotonergic 5-HT2a/HT2c receptor agonist, 2.5-dimetoxi-4-iodoamphetamine hydrobromide (DOI; 1 or 5 μg/200 ηl) enhanced the effects of blood volume expansion on Na+ and K+ excretion and urinary volume. Methysergide (4 μg) into the LPBN decreased the effects of blood volume expansion on plasma ANP and OT, while DOI (5 μg) increased them. The present results suggest the involvement of LPBN serotonergic mechanisms in the regulation of urinary sodium, potassium and water excretion, and hormonal responses to acute isotonic blood volume expansion.
Disruption of adenosinergic modulation of ventilation at rest and during hypercapnia by neonatal caffeine in young rats: role of adenosine A1and A2Areceptors
Authors: Montandon Gaspard , Kinkead Richard , Bairam Aida
Published: December 2006

Caffeine is commonly used to treat respiratory instabilities related to prematurity. However, the role of adenosinergic modulation and the potential long-term effects of neonatal caffeine treatment (NCT) on respiratory control are poorly understood. To address these shortcomings, we tested the following hypotheses: 1) adenosine A1- and A2A-receptor antagonists modulate respiratory activity at rest and during hypercapnia; 2) NCT has long-term consequences on adenosinergic modulation of respiratory control. Rat pups received by gavage either caffeine (15 mg/kg) or water (control) once a day from postnatal days 3 to 12. At day 20, rats received intraperitoneal injection with vehicle, DPCPX (A1antagonist, 4 mg/kg), or ZM-241385 (A2Aantagonist, 1 mg/kg) before plethysmographic measurements of resting ventilation, hypercapnic ventilatory response (5% CO2), and occurrence of apneas in freely behaving rats. In controls, data show that A2A, but not A1, antagonist decreased resting ventilation by 31% ( P = 0.003). A1antagonist increased the hypercapnic response by 60% ( P < 0.001), whereas A2Aantagonist increased the hypercapnic response by 42% ( P = 0.033). In NCT rats, A1antagonist increased resting ventilation by 27% ( P = 0.02), but the increase of the hypercapnic response was blunted compared with controls. A1antagonist enhanced the occurrence of spontaneous apneas in NCT rats only ( P = 0.005). Finally, A2Aantagonist injected in NCT rats had no effect on ventilation. These data show that hypercapnia activates adenosinergic pathways, which attenuate responsiveness (and/or sensitivity) to CO2via A1receptors. NCT elicits developmental plasticity of adenosinergic modulation, since neonatal caffeine persistently decreases ventilatory sensitivity to adenosine blockers.