bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Side-View Mirror Flow-Induced Vibration Phenomena
Authors: Tomac Mehmet N. , Yugulis Kevin , Gregory James W.
Published: March 2011

The primary objective of this research is to develop an understanding of the flow mechanisms which induce side-view mirror vibrations. The unsteady nature of the flow over side-view mirrors causes unsteady aerodynamic load distributions and flow-induced vibrations on the mirror assembly. These vibrations generate blurred rear-view images and higher noise levels, affecting the safety and comfort of the passengers. Geometrical design features of side-view mirrors exacerbate the flow-induced vibration levels of the mirror assembly significantly. This work quantifies the impact of these design features on the vibration amplitude; develops a methodology for testing mirror vibrations in a small, low-speed wind tunnel using only the mirror of interest; and delves into the interactions between the bluff body mirror geometry and its wake. Two similar side-view mirror designs, a baseline design and a turn-signal design, were investigated. The baseline mirror has a sharp-edged corner near the trailing edge, while the turn-signal design has an edge with an increased radius of curvature for the tip profile. A laser-based vibration measurement technique was developed and used to quantify vibration levels. Flow visualization, Particle Image Velocimetry (PIV), Constant Temperature Anemometry (CTA), and Surface Stress Sensitive Film (S3F) techniques were used to understand the separation characteristics over the mirrors since the time-dependent changes in separation location directly affect the unsteady loading on the mirror. The flow over the turn signal mirror with larger tip radius has larger excursions in the separation location, a wider wake, increased unsteadiness, and higher vibration levels. Results at the high Reynolds numbers for these test conditions indicate the absence of a discrete vortex shedding frequency. However, vortical structures in the wake are correlated with unsteady movement of the separation location.
Study on Modeling Method of Vortex Shedding Synchronization in Heat Exchanger Tube Bundles
Authors: Nishida Eiichi , Hamakawa Hiromitsu , Arshad Azim
Published: March 2011

Acoustic resonance may occur in heat exchangers such as gas heaters or boilers which contain tube bundles. The purpose of this study is to develop modeling method of vortex shedding synchronization because this is the most essential part of critical flow velocity prediction. Here, acoustic resonance level dependence of spatial correlation of vortex shedding is expressed by coherence function between wake-oscillator behaviors in any two locations in the cavity. The feedback effect in synchronization of vortex shedding is represented by resonant level dependence of the wake-oscillator phase fluctuation range. This method gives the result that when resonance level increases, synchronization level in the tube bundles also increases, which seems to be a reasonable conclusion. Experimental method to identify the undefined parameters in the proposed method is also mentioned.
Fluid-Structure Interaction Exciting Mechanisms of Flexible Structures in Uniform Flows
Authors: Gomes Jorge Pereira , Lienhart Hermann
Published: March 2011

The oscillation of a structure immersed on a flow can become self-excited as a result of different fluid-structure interaction mechanisms. To identify the self-exciting mechanisms and to understand the influence of the physical parameters on the different exciting processes, the two-dimensional free swivelling movement of flexible structure models were investigated in both laminar and turbulent uniform flows. The coupled fluid and structure movement was characterized using a particle image velocimetry (PIV) system complemented by a time-phase detector to obtain accurate time-phase resolved measurements of the flow velocity field and structure deformation. The experimental tests proved that the self-exciting mechanisms are strongly dependent on the approaching flow velocity. For the velocity range tested, a sequence of clearly defined movement-induced excitation (MIE) and instability-induced excitation (IIE) of the model was observed on increasing the velocity of the incoming flow. In this contribution, the results for one specific structure configuration are presented.
Internal Turbulent Flow Induced Pipe Vibrations With and Without Baffle Plates
Authors: Thompson Andrew S. , Maynes Daniel , Blotter Jonathan D.
Published: March 2011

The induced vibration in pipes due to turbulent flow through them is important in many industries and applications. This paper presents the results of an experimental investigation that characterizes pipe wall vibration caused by turbulent internal flow. Experiments were conducted using a water flow loop to characterize how the pipe wall vibration depends on the average flow speed, the pipe diameter, and the pipe thickness for fully-developed turbulent pipe flow. Experiments were also conducted to characterize the influence on the pipe response of turbulence generation due to the flow passing through baffle plates with various hole sizes and constant through area. All experiments were conducted using PVC pipe with diameters ranging from 51 mm to 102 mm and diameter to thickness ratios ranging from 8.9 to 16.9. Average flow speeds for the experiments ranged from 3 to 11.5 m/s and the baffle plates employed exhibited hole sizes ranging from 1.6 to 25 mm. Accelerometers mounted on the pipe walls were used to characterize the pipe vibrations. The results show that for fully developed turbulent flow the rms of the pipe wall acceleration scales nominally as the square of the average fluid speed and increases with decreasing pipe wall thickness. Based on the data, a non-dimensional parameter describing the pipe wall acceleration for the fully-developed turbulent flow scenario is proposed and its dependence on relevant independent nondimensional parameters is presented. Lastly, when turbulence was induced using baffle plates the localized turbulence intensity was greatly increased. For the largest holed baffle plates, cavitation was observed to occur, significantly increasing the rms pipe wall acceleration. As baffle plate hole size decreased, vibration levels were observed to approach levels that were measured when no baffle plate was employed. For all baffle plate experiments the magnitude of the vibration was observed to decrease with increasing downstream distance from the turbulence source, approaching the baseline no baffle plate case.
Vav1-Mediated Scaffolding Interactions Stabilize SLP-76 Microclusters and Contribute to Antigen-Dependent T Cell Responses
Authors: Sylvain Nicholas R. , Nguyen Ken , Bunnell Stephen C.
Published: March 2011

Scaffolding functions of Vav1 contribute to SLP-76 clustering and signaling downstream of the T cell receptor.
Eliminating Unnecessary Repair Machinery?
Authors: Adler Elizabeth M.
Published: March 2011

Acetylation coordinates the DNA double-strand break processing with autophagy.
FATtening Up Against Neurodegeneration
Authors: Wong Wei
Published: March 2011

A neurodegenerative disorder could be caused by decreased signaling through the Hippo pathway.
Break It Down, Sweep It Out
Authors: Hines Pamela J.
Published: March 2011

Natural-product effectors of disease resistance in
Arabidopsis
reveal complementary disabling mechanisms in the pathogen.
Proteomic Signature of Fatty Acid Biosynthesis Inhibition Available for In Vivo Mechanism-of-Action Studies
Authors: Wenzel Michaela , Patra Malay , Albrecht Dirk , Chen David Y.-K. , Nicolaou K. C. , Metzler-Nolte Nils , Bandow Julia E.
Published: March 2011

Fatty acid biosynthesis is a promising novel antibiotic target. Two inhibitors of fatty acid biosynthesis, platencin and platensimycin, were recently discovered and their molecular targets identified. Numerous structure-activity relationship studies for both platencin and platensimycin are currently being undertaken. We established a proteomic signature for fatty acid biosynthesis inhibition in
Bacillus subtilis
using platencin, platensimycin, cerulenin, and triclosan. The induced proteins, FabHA, FabHB, FabF, FabI, PlsX, and PanB, are enzymes involved in fatty acid biosynthesis and thus linked directly to the target pathway. The proteomic signature can now be used to assess the
in vivo
mechanisms of action of compounds derived from structure-activity relationship programs, as demonstrated for the platensimycin-inspired chromium bioorganometallic PM47. It will further serve as a reference signature for structurally novel natural and synthetic antimicrobial compounds with unknown mechanisms of action. In summary, we described a proteomic signature in
B. subtilis
consisting of six upregulated proteins that is diagnostic of fatty acid biosynthesis inhibition and thus can be applied to advance antibacterial drug discovery programs.
Improved Detection of Candida sp.
fks
Hot Spot Mutants by Using the Method of the CLSI M27-A3 Document with the Addition of Bovine Serum Albumin
Authors: Garcia-Effron Guillermo , Park Steven , Perlin David S.
Published: March 2011

Echinocandins are highly bound to serum proteins, altering their antifungal properties. The addition of 50% human serum to the MIC assay improves the identification of echinocandin-resistant
Candida
spp. harboring
fks
hot spot mutations. However, this modification cannot readily be applied to the method of the CLSI M27-A3 document due to safety and standardization difficulties. The aim of this study was to evaluate commercial bovine serum albumin (BSA) as a safe and standardized alternative to human serum. A collection of 28 echinocandin-susceptible strains, 10
Candida parapsilosis
sensu lato strains (with naturally reduced echinocandin susceptibility), and 40
FKS
hot spot mutants was used in this work. When RPMI 1640 was used for susceptibility testing, wild-type strains and
fks
mutants showed MIC range overlaps (−2, −1, and −3 2-fold-dilution steps separated these populations for anidulafungin, caspofungin, and micafungin, respectively). On the other hand, the addition of BSA to RPMI 1640 differentially increased echinocandin MIC values for these groups of strains, allowing better separation between populations, with no MIC range overlaps for any of the echinocandin drugs tested. Moreover, the use of RPMI-BSA reduced the number of
fks
hot spot mutant isolates for which MIC values were less than or equal to the upper limit for the wild type (very major errors) from 9, 2, and 7 with RPMI alone to 3, 0, and 3 for anidulafungin, caspofungin, and micafungin, respectively. When RPMI-BSA was used to study the susceptibility of
C. parapsilosis
sensu lato species to echinocandins, the strains behaved as anidulafungin- and micafungin-resistant isolates (MIC, ≥8 μg/ml). These data support the need for a revision of the CLSI protocol for
in vitro
testing of echinocandin susceptibility in order to identify all or most of the
fks
hot spot mutants. Also, caspofungin could be used as a surrogate marker of reduced susceptibility to echinocandins.
Effect of Cytokine Interplay on Macrophage Polarization during Chronic Pulmonary Infection with Cryptococcus neoformans
Authors: Arora Shikha , Olszewski Michal A. , Tsang Tiffany M. , McDonald Roderick A. , Toews Galen B. , Huffnagle Gary B.
Published: March 2011

The immune response toCryptococcus neoformansfollowing pulmonary infection of C57BL/6 wild-type (WT) mice results in the development of persistent infection with characteristics of allergic bronchopulmonary mycosis (ABPM). To further clarify the role of Th1/Th2 polarizing cytokines in this model, we performed kinetic analysis of cytokine responses and compared cytokine profiles, pathologies, and macrophage (Mac) polarization status inC. neoformans-infected WT, interleukin-4-deficient (IL-4−/−), and gamma interferon-deficient (IFN-γ−/−) C57BL/6 mice. Results show that cytokine expression in the infected WT mice is not permanently Th2 biased but changes dynamically over time. Using multiple Mac activation markers, we further demonstrate that IL-4 and IFN-γ regulate the polarization state of Macs in this model. A higher IL-4/IFN-γ ratio leads to the development of alternatively activated Macs (aaMacs), whereas a higher IFN-γ/IL-4 ratio leads to the generation of classically activated Macs (caMacs). WT mice that coexpress IL-4 and IFN-γ during fungal infection concurrently display both types of Mac polarization markers. Concurrent stimulation of Macs with IFN-γ and IL-4 results in an upregulation of both sets of markers within the same cells, i.e., formation of an intermediate aaMac/caMac phenotype. These cells express both inducible nitric oxide synthase (important for clearance) and arginase (associated with chronic/progressive infection). Together, our data demonstrate that the interplay between Th1 and Th2 cytokines supports chronic infection, chronic inflammation, and the development of ABPM pathology inC. neoformans-infected lungs. This cytokine interplay modulates Mac differentiation, including generation of an intermediate caMac/aaMac phenotype, which in turn may support chronic “steady-state” fungal infection and the resultant ABPM pathology.
Malaria Immunoepidemiology in Low Transmission: Correlation of Infecting Genotype and Immune Response to Domains of Plasmodium falciparum Merozoite Surface Protein 3
Authors: Jordan Stephen J. , Oliveira Ana L. , Hernandez Jean N. , Oster Robert A. , Chattopadhyay Debasish , Branch OraLee H. , Rayner Julian C.
Published: March 2011

Malaria caused by
Plasmodium falciparum
is a major cause of global infant mortality, and no effective vaccine currently exists. Multiple potential vaccine targets have been identified, and immunoepidemiology studies have played a major part in assessing those candidates. When such studies are carried out in high-transmission settings, individuals are often superinfected with complex mixtures of genetically distinct
P. falciparum
types, making it impossible to directly correlate the genotype of the infecting antigen with the antibody response. In contrast, in regions of low transmission
P. falciparum
infections are often genetically simple, and direct comparison of infecting genotype and antigen-specific immune responses is possible. As a test of the utility of this approach, responses against several domains and allelic variants of the vaccine candidate
P. falciparum
merozoite surface protein 3 (PfMSP3) were tested in serum samples collected near Iquitos, Peru. Antibodies recognizing both the conserved C-terminal and the more variable N-terminal domain were identified, but anti-N-terminal responses were more prevalent, of higher titers, and primarily of cytophilic subclasses. Comparing antibody responses to different PfMSP3 variants with the
PfMSP3
genotype present at the time of infection showed that anti-N-terminal responses were largely allele class specific, but there was some evidence for responses that cross-reacted across allele classes. Evidence for cross-reactive responses was much stronger when variants within one allele class were tested, which has implications for the rational development of genotype-transcending PfMSP3-based vaccines.
Apparatus for measuring the potential of zero charge and for automatic recording the charge density and differential capacitance curves of mercury electrodes by the vibrating interface method
Authors: Figaszewski Zbigniew , Koczorowski Zbigniew
Published: March 2011

The set comprises a glass vessel, an automatic voltage stabilizer, a system for analyzing and recording the output short-circuit current, an added signal system making it possible to record charge density curves (taking into account the sign), an optical system, and a system for stimulating the interface vibrations in the capillary. Typical experimental results for 0.1 M aqueous NaCl and 0.1M-KPF6 in acetone are given.
Influence of high pressure on texture of carbonaceous substances
Authors: Medek Jiří , Mohyla Ivan
Published: March 2011

The texture changes of carbonaceous substances caused by high pressure (1 500 Mpa) have been studied by sorption of N2 (at 78 K) and CO2 (at 298 K) and by electron microscopy. The surface increase of cokes is observed in the region of micropores as well as meso- and macropores, whereas that of semicoke is only limited to the region of meso- and macropores. No effect is observed with formed coke and charcoal. Microscopically it has been found that cokes form a layer texture, whereas semicokes show a disconnection of microbreccia character. The surface area increase is ascribed to formation of new surfaces produced by shift and/or deformation of lamellar structures.
Identification of low-boiling fraction of pyrolysis oil
Authors: Novrocík Jan , Novrocíková Marta
Published: March 2011

Composition of the low-boiling fraction of the pyrolysis oil obtained from continuous rectification has been determined by combination of capillary gas-liquid chromatography with other identification methods (catalytic hydrogenation, polymerization). In this way components have been identified which form overall 86.0 per cent (m/m) of the low-boiling fraction. The said pyrolysis oil fraction has been found to contain almost 50 per cent (m/m) of unsaturated components able of polymerization, especially methylindenes, methyl-, ethyl- and dimethylvinylbenzenes, divinylbenzenes and 1,2-dihydronaphthalene. Elution behaviour of all the identified isomeric methylindenes, divinylbenzenes and 1,2-dihydronaphthalene has been evaluated by determination of parameters of the equation Ist.phase (2) = k . Ist.phase(1) + q. The Kovats elution indices of all the identified aromatic hydrocarbons have been determined with the use of a glass capillary column wetted with Carbowax 20M at 80 °C.
Reaction of substituted γ-crotonolactones under the conditions of the Michael addition
Authors: Janda Miroslav , Körblová Eva , Stibor Ivan
Published: March 2011

Under the conditions of the Michael addition γ-lactone of ethyl 4-hydroxy-6-oxo-2-octenedioate (II) isomerizes to γ-lactone of ethyl 4-hydroxy-6-oxo-4-octenedioate (VIII). The addition of an excess of ethyl acetate anion to γ-lactone of ethyl 4-hydroxy-2-hexenedioate (I) affords γ-lactone of ethyl 3-ethoxycarbonylmethyl-4-hydroxy-6-oxo-octanedioate (XI). The dimers IX and X are formed during the usual performance of the same addition. The mechanism of isomerization of II and the factors affecting the addition of the ethyl acetate anion are discussed.
Fluorinated tricyclic neuroleptics with prolonged action: 3-Fluoro-10-[4-(2-hydroxyethyl)piperazino]-10,11-dihydrodibenzo[b,f]thiepins with less common substituents in position 8
Authors: Šindelář Karel , Metyšová Jiřina , Holubek Jiří , Svátek Emil , Ryska Miroslav , Protiva Miroslav
Published: March 2011

Cyclization of [4-fluoro-2-(4-nitrophenylthio)phenyl]acetic acid resulted in 3-fluoro-8-nitrodibenzo[b,f]thiepin-10(11H)-one (IIa) which was transformed via the intermediates IVa and Va to the compound Ia. Its reduction gave the amino alcohol Ib. 8-Amino-3-fluorodibenzo[b,f]thiepin-10(11H)-one (IIb) was diazotized and the diazonium salt was converted by treatment with sulfur dioxide and cuprous chloride, followed by dimethylamine, to the N,N-dimethylsulfonamide IIc. Its processing via the intermediates IVc and Vc afforded Ic. Reduction of the amino ketone IIb gave the amino alcohol IVb which was transformed by the Beech method to the hydroxy ketone IVd. Id was obtained via the chloro derivative Vd. A reaction of 3-fluoro-8-iodo-10,11-dihydrodibenzo[b,f]thiepin-10-ol with cuprous cyanide in dimethylformamide led to the cyano alcohol IVe which was used for concluding the synthesis of Ie. Compounds Ia - Id are neuroleptics with central depressant and cataleptic activity; the sedative effects reveal protraction in all cases. In the test of catalepsy the least active compound Ib shows, however, a clear prolongation of this effect. Compound Ia is the most active one in the test of antiapomorphine activity but its effects are not protracted.
Isomers of bis(S)-lysinato-O,N,N)cobalt(III) cation: Preparation and properties
Authors: Hájek Bohumil , Sýkorová Dagmar , Jursík František
Published: March 2011

In the complex cation of the compound [Co((S)-Lys)2]NO3 (S)-lysine is coordinated as a tridentate ligand, giving rise to ΛΔΔΔ-cis, cis, trans and cis, trans,cis isomers. Yields of both isomers are higher in dimethyl sulfoxide than in water. Their structure was derived from 1H NMR, CD and electronic absorption spectra.
Synthesis of triphenylphosphine oxide by oxidation of triphenylphosphine by oxygen under the catalytic effect of iron compounds
Authors: Ondrejkovičová Iveta , Vančová Vlasta , Ondrejovič Gregor
Published: March 2011

Triphenylphosphine oxide, OP(C6H5)3, can be conveniently prepared by oxidation of triphenylphosphine, P(C6H5)3, by oxygen under the catalytic effect of iron compounds such as FeX3 FeX3[OP(C6H5)3]2, (X = Cl, Br, NCS), or FeCl3[P(C6H5)32]. The highest catalytic effect was observed in the case of the complexes containing the bromo or thiocyanato ligands. The oxidation in acetonitrile solution is quantitative and selective at 30 - 70 °C and atmospheric pressure of oxygen gas.
Study of photolysis of 1,3-bis(4-nitrophenyl)-1-butene in acetonitrile and 2-propanol
Authors: Čík Gabriel , Lapčík Ľubomír , Blažej Anton , Šurina Igor
Published: March 2011

Photolysis of 1,3-bis(4-nitrophenyl)-1-butene (I) in acetonitrile and 2-propanol by polychromatic radiation of a mercury lamp was studied. The photolysis kinetics was followed by UV spectra and the reaction products were analysed by IR and mass spectroscopy and by gas-liquid chromatography. The reaction mechanism in markedly affected by the presence of oxygen. Photolysis of I in acetonitrile gives mainly 4-nitrobenzaldehyde, n-heptane and toluene, in 2-propanol the principal products are stereoisomeric 1,3-diphenyl-1-butenes.
Test of simple fluid theories
Authors: Labík Stanislav , Malijevský Anatol
Published: March 2011

The compressibility factors and configuration energies of the Lennard-Jones pair-additive fluid were calculated in terms of the PY, HNC, HTA, ORPA, and EXP approximations, the Lado method and the method by Madden and Fitts. The results were compared with Monte Carlo data. In the gaseous region, the EXP approximation, the Lado method and the method by Madden and Fitts are substantially better than the remaining approaches. The last-mentioned method is the most successful.
PCILO study of non-bonding interactions
Authors: Remko Milan , Frecer Vladimír
Published: March 2011

The PCILO method has been used for study of non-bonding interactions in the systems water-water and water-ethylene. The PCILO method is unable to account correctly for the intermolecular non-bonding interactions of the types lone electron pair - lone electron pair and lone electron pair-π bond. The potential energy curves, which should be strongly repulsive, are predicted as being attractive. The results obtained are discussed from the point of view of energy partitioning in terms of PCILO theory.
Electrochemical reduction of 2,2'-dinitrodiphenylmethane and 2,2'-dinitrobenzophenone at mercury electrodes
Authors: Voigtländer Rolf , Hlavatý Jaromír , Volke Jiří , Bakos Viktor
Published: March 2011

The last two compounds in a 5-membered series of aromatic dinitro compounds are reduced in a completely different manner at mercury electrodes. 2,2'-Dinitrodiphenylmethane (I) - in which a conjugation of both symmetrical moieties is ruled out - is electrolytically reduced in an eight-electron step to a bishydroxylamine this being most stable between pH 4.5 and 5.0. In processing the catholyte increase in concentration of this product leads to its intermolecular disproportionation, resulting in the formation of dibenzo[b, e]-1,2-diazepine 5-oxide (IV) and 2,2'-diaminodiphenylmethane (III). 2,2'-Dinitrobenzophenone (II) reduces at more positive potentials. Its preparative electrolysis in acetonitrile (with 0.1M-N(n-C4H9)4PF6 as supporting electrolyte) the application of which was made necessary by the low solubility of II in ethanol, proceeding in an anomalous way. In the most positive cathodic wave a radical anion results, the following cathodic wave corresponds to a 6-electron reduction of the one nitro group to an amino group while the other nitro group splits off as the anion NO-2 (this later giving an anodic wave). Its formation has been proved by standard addition in polarography and by a qualitative analytical test. The product which results through this electrode process and a follow-up chemical reaction is acridone. This in turn, reduces in the third, most negative 4-electron wave to dihydroacridine. The comparison of all substances studied in this series reveals that their reducibility decreases with respect to the link X, viz. in the sequence CO > O > S and CH2 > NH. The electrolytical reduction on mercury cathodes occurs in a similar manner with analogues where X = O, S or CH2. Here, the main intermediate is the bis-hydroxylamine the stability of which predetermines the structure of final products. The other group comprises the substances with X = CO and NH. Here the main intermediate is the 2-nitro-2'-amino-diphenyl-X which is formed in a 6-electron process taking place at one of the nitro groups. The follow-up cyclization reaction leading to seven-membered heterocyclic rings located between two benzene nuclei only occurs with analogues of the type X = CH2, O and S. A partial reduction of dinitro compounds of this series has been observed with the analogue containing the NH link although that with X = CO has generally good preconditions for this mechanism.
Oxidative elimination of tert-butyl group from α position of quarternary pyridinium salts
Authors: Nesvadba Petr , Kuthan Josef
Published: March 2011

Ferricyanide oxidation of 1-methyl-2-tert-butyl-4,6-diphenylpyridinium tetrafluoroborate (I) and its 2,6-ditert-butyl analogue (II) is accompanied by elimination of the 2-substituent with formation of the corresponding 2-pyridones VII and VIII, respectively. On the contrary, oxidation of quarternary salt III with tert-butyl group at 4 position gives a complex reaction mixture from which a small amount of pyrrole derivative IX only could be isolated.
Modification of tyrosine residues of tomato pectin esterase
Authors: Markovič Oskar
Published: March 2011

Selective acetylation of tyrosine residues in tomato pectin esterase with an 80 molar excess of n-acetylimidazole reduced the activity of the enzyme to 50%. Deacetylation with hydroxylamine restored the original activity of the enzyme. The difference in absorptivities at 278 nm showed that 2 tyrosine residues of the enzyme had been acetylated. Spectrophotometric pH-titration of native pectin esterase revealed that 2 of the 12 tyrosine residues in the enzyme molecule were ionized at pH 9.3-9.5, and the remaining 10 residues at pH > 10.5. Acetylation of the pectin esterase with acetanhydride resulted in an irreversible inhibition of the enzyme. Nitration of the enzyme with tetranitromethane also suggested a role of the tyrosine residues in the catalytic function of the enzyme. However, 10 min after the start of the nitration precipitation set in.
A specific enzyme electrode for spermine and spermidine
Authors: Macholán Lumír , Jílková Dagmar
Published: March 2011

A sensor method has been worked out for the determination of spermine and spermidine in concentrations 0.02-0.5 mmol l-1. The method is based on amperometric measurement of the consumption of oxygen and the formation of hydrogen peroxide in a reaction catalyzed by crosslinked polyamine oxidase from maize. One determination takes 1 to 2 min, with phosphate at least 8 months. The optimum conditions for the analysis are described and the applicability of the sensor to urine samples is dealt with.
Selective photochemical reduction of carbon-chlorine bond in fluoropropanoates and its quantum yields
Authors: Paleta Oldřich , Ježek Rudolf , Dědek Václav
Published: March 2011

Ultraviolet light initiated reduction of methyl 2,2,3-trichlorodifluoropropanoate (I), methyl 2,3-dichlorotrifluoropropanoate (II) and methyl 2-chlorotetrafluoropropanoate (III) in 2-propanol afforded methyl 2,3-dichloro-3,3-difluoropropanoate (IV), methyl 3-chloro-2,3,3-trifluoropropanoate (V) and methyl 2,3,3,3-tetrafluoropropanoate (VI) in the respective yields 81%, 86% and 75%. Maximum quantum yields, φmax, of the reduction at 254 nm for the ester IV, V and VI are 225, 240 and 270, respectively, indicating thus a chain reduction mechanism.
Preparation of 2'(3')-O-phosphonylmethyl derivatives of ribonucleosides
Authors: Rosenberg Ivan , Holý Antonín
Published: March 2011

Reaction of 5'-O-tritylribonucleosides I with dimethyl p-toluenesulfonyloxymethanephosphonate (III) followed by hydrolysis afforded 2'(3')-O-phosphonylmethyluridine (IIa), -cytidine (IIb) and -adenosine (IIc). With 2',5'-di-O-trityluridine (IX), this procedure led to the 3'-isomer of IIa, with 3',5'-di-O-trityluridine (X) to the 2'-isomer. 5'-O-Trityluridine (Ia) and -cytidine (Ib) were converted by reaction with iodomethanephosphonic acid and N,N'-dicyclohexylcarbodiimide into the 2'(3')-O-iodomethanephosphonyl derivatives IVa, b which on reaction with sodium hydride and subsequent hydrolysis gave the compounds IIa and IIb. Reaction of compound I or 5'-O-benzoyluridine (VIII) with chloromethanephosphonyl dichloride (V) and removal of the protecting groups afforded 2'(3')-O-chloromethanephosphonylribonucleosides VI which on reaction with sodium hydride, or better with aqueous alkali, gave 2'(3')-O-phosphonylmethyl derivatives of uridine (IIa), cytidine (IIb), adenosine (IIc) and guanosine (IId). 2',3'-O-Isopropylideneribonucleosides XI reacted with the compound V to give, after hydrolysis, 5'-O-chloromethanephosphonyluridine (XIIa) and cytidine (XIIb). These compounds were not affected by an alkali metal hydride or hydroxide.
Adsorption of noble gases on the carbon adsorbents supersorbon HS and Jado
Authors: Wilhelmová Ludmila , Cejnar František
Published: March 2011

The isotherms, isosters and heats of adsorption of argon, krypton and xenon were measured on the active carbon Supersorbon HS and the carbon adsorbent Jado LD 1191 - in a temperature range 298-473 K, using gas chromatography. Differences were observed in the adsorption behaviour of both types of adsorbents - which showed especially on the nonlinearity of adsorption isosters of all gases studied with the Jado LD 1191 adsorbent. It was found that both types of adsorbents possess good adsorption properties, which can be - for Supersorb HS - utilized in the beds of the delaying lines of radioactive noble gases. The practical application of the Jado LD 1191 adsorbent for the same purposes is limited by the presence of inactive teflon support in the structure of this adsorbent.
Determination of specific interfacial areas in swirled two-phase flow
Authors: Winkler Kurt , Kaštánek František , Kratochvíl Jan
Published: March 2011

Specific gas-liquid interfacial area in flow tubes 70 mm in diameter of the length 725 and 1 450 mm resp. containing various swirl bodies were measured for concurrent upward flow in the ranges of average gas (air) velocities 11 to 35 ms-1 and liquid flow rates 13 to 80 m3 m-2 h-1 using the method of CO2 absorption into NaOH solutions. Two different flow regimes were observed: slug flow swirled annular-mist flow. In the latter case the determination was carried out separately for the film and spray flow components, respectively. The obtained specific areas range between 500 to 20 000 m3 m-2. Correlation parameters are energy dissipation criteria, related to the geometrical reactor volume and to the static liquid volume in the reactor.
Hydrogenolytic opening of 4,4-dimethyl-4a,5-epoxy-a-homocholestane derivatives and mass spectra of some reaction products
Authors: Velgová Helena , Trka Antonín
Published: March 2011

The hydrogenolytic opening of the epoxide ring of all four stereoisomeric 3-acetoxy-4,4-dimethyl-4a,5-epoxy-A-homocholestanes was investigated. The reaction proceeds at the more substituted carbon atom C(5), giving rise to 4a-hydroxy-5,6-unsaturated derivatives. The hydrogenation of the 5,6-double bond of these allylic alcohols affords 4,4-dimethyl-A-homo-5β-cholestane derivatives. The mass spectra of 3,4a-diketones XI and XVII and 4a-ketones XVI and XXVIII to XXX were also studied. In the case of the saturated diketone XVII it was observed that the most abundant metastable peak corresponds to a two-step fragmentation process. The decomposition of the molecular ion of the unsaturated diketone XI is associated with ring A expansion. The mass spectra of 3-acetoxy ketones XVI and XXVIII are characterized by an elimination of a C4H8 molecule from the contracted ring A of the ion [M-CH3COOH]+. The unexpected elimination of the species C6H11, C6H12, and C6H13 from the ring A of the molecular ions of 3-hydroxy ketones XXIX and XXX is shown to be preceded by hydroxyl migration and ring A rearrangement.
Basicity of 1,4-tetracenequinone and its electronic spectra in the protonated states
Authors: Nepraš Miloš , Kratochvíl Václav , Štěpán Václav , Titz Miloš , Gaš Bohuslav
Published: March 2011

Basicity of 1,4-tetracenequinone to the first and the second protonation degrees has been studied spectrophotometrically. Electronic spectra of mono- and diprotonated 1,4-tetracenequinone have been interpreted on the basis of the PPP method in the approximation of invariable βc and γ integrals.
MO study of molecular and electronic structure of 2,2-dimethyl-2H-pyran and its acyclic valence isomers
Authors: Böhm Stanislav , Kuthan Josef
Published: March 2011

CNDO/2, MNDO, STO-3G, and 4-31 G MO calculations of I to IIId molecules have been carried out. The effect of the presence of two methyl groups in the studied systems on their molecular and electronic structure and on valence isomerism (A) is discussed.
Phenylsulfonyl derivatives of chalcones derived from 5-nitrofuran
Authors: Jurášek Adolf , Polakovičová Dana , Kováč Jaroslav
Published: March 2011

1-(5-Nitro-2-furoyl)-1-phenylsulfonyl-2-(4-X-phenyl)ethylenes II were synthesized by condensation of phenyl-2-(5-nitro-2-furyl)-2-oxoethyl sulfone (I) with 4-substituted benzaldehydes (X = H, CH3, CH3O, N(CH3)2, F, Cl, NO2, CN) in tetrahydrofuran or dioxane under catalysis of titanium-IV chloride and pyridine. As evidenced by spectral data (1H NMR, IR, UV) the stereospecific condensation afforded exclusively Z isomers of ethylenes II; these exist in an 0,0-trans, s-cis conformation.
Molecular complexes of iodine with cyclic polyethers in chloroform: Kinetics of formation
Authors: Muchová Jana , Holba Vladislav
Published: March 2011

Absorbance changes of solutions of iodine and 15-crown-5, 18-crown-6 and dibenzo-18-crown-6 in chloroform were studied. Absorption maxima due to the triiodide anion were observed. The obtained rate constants and their temperature dependence indicate formation of molecular complexes (cyclic polyether...I2) and (cyclic polyether...I(+)) I(-).
Potential anticonvulsants: Substituted N-benzylidene derivatives of 10-(4-aminopiperazino)-10,11-dihydrodibenzo[b,f]thiepins
Authors: Bártl Václav , Holubek Jiří , Svátek Emil , Bartošová Marie , Protiva Miroslav
Published: March 2011

Reactions of 10-(4-aminopiperazino)-10,11-dihydrodibenzo[b,f]thiepins XIVa-XIVd with benzaldehyde, 3,4-dimethoxybenzaldehyde, 4-dimethylaminobenzaldehyde, salicylaldehyde, 3-ethoxy-4-hydroxybenzaldehyde, 2-(2-dimethylaminoethoxy)benzaldehyde, 3-(2-dimethylaminoethoxy)benzaldehyde and 3-ethoxy-4-(2-dimethylaminoethoxy)benzaldehyde afforded a series of 19 hydrazones IIIa-Xc. Some of them showed the expected anticonvulsant effect but only towards pentetrazole; antagonism of maximal electroshock seizures was not observed. In general, the products have a character of tranquillizers: in higher does they produce central depression, potentiate the thiopental sleeping time, have hypothermic action; in single cases antiamphetamine, antireserpine, antihistamine and cataleptic effects were observed. The water-soluble salts of the basic hydrazones VIIIa, VIIIc, IXc and Xc, administered parenterally, showed a rather high acute toxicity and revealed also adrenolytic and hypotensive activity.
On the problem of empirical characteristics of a medium and their mutual relations
Authors: Bekárek Vojtěch , Stolařová Marie
Published: March 2011

New parameters of polarity, acidity, and basicity of a medium, which are more suitable to characterize nonspectral solvent effects, were derived by dividing the Taft-Kamlet solvent parameters π*, α, and β by a function of the refractive index n, f(n) = (n2 - 1)/(2n2 + 1). The new parameters were used in evaluating the effect of the medium on reaction rates, equilibria, solubilities, hyperfine splitting constants in EPR spectra, fluorescence life time, free energy of dissolution of ions and ion pairs, and on the Snyder solvent factors of the elution strength in chromatography.
Adsorption of deoxyribonucleic acid at mercury electrodes from alkaline solutions of higher ionic strength
Authors: Brabec Viktor , Glezers Viktor , Kadysh Valentina
Published: March 2011

Adsorption of double-stranded, thermally denatured DNAs and degradation products of DNA at mercury electrodes from alkaline solutions of higher ionic strength (0.5) has been studied with the aid of phase-sensitive alternating current (AC) and linear sweep voltammetry at the H.M.D.E. and phase-selective AC polarography (at the D.M.E.). It was found that the addition of DNA to the supporting electrolyte lowered the out-of-phase component of AC around the potential of zero charge. At potentials more negative than ca. - 1.0 V nucleic acids yielded nonfaradaic peaks on voltammetric or polarographic curves. The model of adsorption of DNA at the mercury electrode from alkaline solution of higher ionic strength that fits best with the experimental data to date is proposed.
cw CO2 laser-induced halogen exchange reaction between hexafluorobenzene and boron trichloride
Authors: Engst Pavel , Horák Milan , Pola Josef
Published: March 2011

The halogen exchange reaction between hexafluorobenzene (HFB) and boron trichloride, BCl3 initiated by a continuous-wave CO2 laser primarily affords chloropentafluorobenzene, C6F5Cl and dichlorofluoroborane, BCl2F. For the reaction initiation a number of rotational-vibrational lines of the vibrational 00°1→10°0 transition was used. With wavenumber radiation 977.21 cm-1 a faster V-V energy transfer between HFB and BCl3 molecules may occur. For this case the rate of the exchange reaction was observed to be by an order of magnitude higher compared to the reaction initiated by the laser radiation at 949.48 cm-1 and carried out under the identical absorption conditions.
Use of current-less potential-time curves for the determination of rate constants of other than redox reactions
Authors: Tockstein Antonín , Dlask Vladimír
Published: March 2011

The use of current-less potential-time curves for kinetic measurements and determination of rate constants is demonstrated on five different reaction types, viz., nitration, copulation, diazotation, addition of bromine to a double bond and hydrolysis.
Syntheses of some ω-(1,2,3,6-tetrahydro-1-pyridyl)-1-alkanols
Authors: Šilhánková Alexandra , Lávička Jiří , Kafka Stanislav , Ferles Miloslav
Published: March 2011

Quaternary salts of pyridine and 4-methylpyridine with ethyl esters of ω-bromoalkanoic acids, IIa-IIe, were converted into esters IIIa-IIIe by the action of sodium borohydride. These were further reduced by lithium aluminium hydride to alcohols Ia-Ie. 4-(1,2,3,6-Tetrahydro-1-pyridyl)-butanol (Ic) was also obtained from 1-(3-ethoxycarbonylpropyl)pyridinium bromide(IIc) by the action of LiAlH4. The ethyl ester IIIa was converted into amide IV.
Hydrolytic stability and pesticidal activity of N'-methyl- and N'-arylcarbamates of 3-(N,N-diethylamino)phenol
Authors: Čegan Alexandr , Večeřa Miroslav
Published: March 2011

Twelve carbamates based on 3-(N,N-diethylamino)phenol have been prepared, and their hydrolysis rate in aqueous media of pH 7-12.5, their inhibition of butyrylcholin esterase and acetylcholin esterase and herbicidal activity have been studied. The hydrolysis of the compounds studied in the mentioned media proceeds by the ElcB mechanism, the value of reaction constant at 25 °C is ρ = 1.12 ± 0.08. The hydrolysis rate in the pH region 7-8.5 is affected by protonation of the 3-N,N-diethylamino group. The compounds I-XII inhibit butyrylcholin esterase (pI50 value 5.1-6.5). Acetylcholin esterase is inhibited most efficiently by the carbamates XII (pI50 = 8.3), XI (pI50 = 6.25) and VII (pI50 = 5.07). Herbicidal effects are small, the effective dose being above 5 kg/ha.
α-(4-Tolyl)dopamine, derivatives and analogues; Synthesis and pharmacological screening
Authors: Valenta Vladimír , Holubek Jiří , Svátek Emil , Dlabač Antonín , Bartošová Marie , Protiva Miroslav
Published: March 2011

The ketone XIII, obtained by Friedel-Crafts reaction of toluene with homoveratroyl chloride, was converted by the Leuckart reaction to the formamido derivative IXb which was used as the starting product for the synthesis of amines IIIb-Vb. Reduction of the ketone XIII gave the alcohol XVI which was treated with hydrogen chloride and afforded the chloro compound XVII. Its substitution reactions with 1-methylpiperazine, 1-(2-hydroxyethyl)piperazine and 1-phenylpiperazine resulted in the piperazines VIb-VIIIb. Acylations of the amine IIIb with acetic anhydride and homoveratroyl chloride gave the amides Xb and XIb which, together with the formamide IXb, were subjected to the Bischler-Napieralski reaction. 3,4-Dihydroisoquinolines XXII-XXIV were obtained and reduced to the 1,2,3,4-tetrahydroisoquinolines XXVb-XXVIIb. Treatment of XXVIIb with formaldehyde afforded the berbine derivative XXVIII. Demethylation of the amine IIIb with hydrobromic acid resulted in the title compound IIIa. Similar demethylations of the dimethoxyamines IVb-VIIIb, XXVb and XXVIb led to the dihydroxyamines IVa-VIIIa, XXVa and XXVIa which are dopamine derivatives. Reaction of Va with benzoyl chloride gave the dibenzoate XXX. The CNS activities of the compounds prepared are of a low degree. Several of them (IIIa-VIa, IIIb-Vb, XXVb) show in higher doses signs of central stimulant action but only for compound IVa an antireserpine effect was proven. The expected anticataleptic activity was found only in a low degree with compound VIIIa; on the contrary, compounds IIIa and XXVa are procataleptogenic. Some compounds (IIIa, IXb, XXVIa, XXVIII) potentiated thiopental. In single cases local anaesthetic, spasmolytic, hypotensive, hypertensive, hypoglycaemic, diuretic and antiarrhythmic effects were observed.
Aristolochic acids in Aristolochia chilensis and the Aristolochia-FEEDER Battus Archidamas (Lepidoptera)
Authors: Urzúa Alejandro , Salgado Guillermo , Cassels Bruce K. , Eckhardt Gert
Published: March 2011

The larval stages of Battus archidamas, the only Papilionoid butterfly living in Chile, feed on the aerial parts of Aristolochia chilensis. The food material contains aristolochic acids, and so do the insects, which retain these compounds after metamorphosis. The compositions of the acid fractions of plant and herbivore extracts are different, however, indicating selective uptake and/or metabolic transformation by the insect. Aristolochic acids I (I) and Ia (II) are major components of the leaves and tender stems of A. chilensis, while aristolochic acids I (I) and (probably) IVa (III) appear to be the main acid components of B. archidamas imagines. The selective sequestration of aristolochic acids by B. archidamas and other Aristolochia-feeders is discussed.
A new algorithm of solving the Lado perturbation method
Authors: Labík Stanislav , Malijevský Anatol
Published: March 2011

A new numerical procedure was proposed for solving the Lado perturbation method which speeds up the computations several times. The procedure was tested by computing the thermodynamic properties of a Lennard-Jones pair-additive fluid.
Hydrolysis of ethylenediphosphinetetraacetate anions
Authors: Podlahová Jana , Podlaha Jaroslav
Published: March 2011

The anions of ethylenediphosphinetetraacetic acid are hydrolyzed in aqueous solutions at 80 °C in the two following reactions: ((OOCCH2)2PCH2CH2P(CH2COO)2)4- → (OOCCH2(O)HPCH2CH2PH(O)CH2COO)2- → (O(O)HPCH2CH2PH(O)O)2-. Both reactions are acid and base catalyzed so that, at pH < 12, the first reaction is much faster than the second. The reaction course was studied by 1H NMR spectroscopy and by isolation and characterization of the products. The effect of both reactions on the stability of solutions of ethylenediphosphinetetraacetic acid and their salts is negligible at laboratory temperature.
Convective diffusion to a slowly rotating spherical electrode; Basic model for Re → O, Pe → ∞
Authors: Wein Ondřej
Published: March 2011

Theory has been formulated of a convective rotating spherical electrode in the creeping flow regime (Re → 0). The currently available boundary layer solution for Pe → ∞ has been confronted with an improved similarity description applicable in the whole range of the Peclet number.
Pulsatile pipe flow pseudoplastic materials; The flow enhancement for Re ≪ 1
Authors: Wein Ondřej
Published: March 2011

Solution of the title problem for the power-law model of viscosity function is constructed by the method of small parameter in the region of small Reynolds numbers. The main result of the paper is a quantitative estimation of the values of Re, when the influence of inertia on flow enhancement may be quite neglected.
Structure of „carbonyl cyanide phenylhydrazones" as evidenced by multinuclear NMR
Authors: Liptaj Tibor , Šturdík Ernest , Sulo Pavol
Published: March 2011

The structure of „carbonyl cyanide phenylhydrazones" has so far not been settled. The substances possess, according to a multinuclear NMR measurements, a phenylhydrazone grouping. This finding enabled us to propose the denomination phenylhydrazonopropanedinitriles for these compounds.
Isothermal and isobaric vapour-liquid equilibrium data in the tetrachloromethane-tert-butyl alcohol system
Authors: Linek Jan , Bernatová Svatoslava
Published: March 2011

Isothermal vapour-liquid equilibrium data at 55, 63 and 70 °C and isobaric ones at 101.3 kPa were measured in the tetrachloromethane-tert-butyl alcohol system. A modified circulation still of the Gillespie type was used for the measurements. Under the conditions of measurement, the system exhibits positive deviations from Raoult's law and minimum boiling-point azeotropes. The experimental data were fitted to a number of correlation equations, the most suitable being the Wilson equation.
Redox chain addition of chloroform to 1-alkenes catalysed by copper complexes
Authors: Hájek Milan , Šilhavý Přemysl
Published: March 2011

The addition of chloroform to alkenes to give 1 : 1 adducts has been studied at 60-160 °C. In the addition to styrene taken as a model reaction, copper complexes formed from metallic copper or cuprous oxide and 1,10-phenanthroline showed highest catalytic activity and selectivity even under mild conditions and gave 1,1,3-trichloro-3-phenylpropane in up to 95% yields. Aliphatic alkenes and vinyl monomers were less reactive than styrene. The mechanism proposed for redox chain additions of chloroform involves chain transfer via copper complexes.
Oxytocin and vasopressin analogues capable of competition with vasopressin binding to rat liver membranes
Authors: Barth Tomislav , Cantau Bernard , Butlen Daniel , Guillon Gilles , Jard Serge , Lebl Michal , Jošt Karel
Published: March 2011

A number of vasopressin and oxytocin analogues modified in positions 1, 2, 4, 6 and 9 of the peptide chain were tested regarding their affinity to the rat liver membrane receptor. The affinities were estimated from the ability of the analogues to compete with the binding of tritiated vasopressin to rat liver membranes. In the series of vasopressin agonists, the degree of competition was in good agreement with the corresponding pressor activities. In the case of inhibitors of vasopressin pressor action, binding to the membrane system was also observed.