bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical Solution of a Creeping Flow Impinging on a Spherical Cap-Shaped Bubble on a Flat Solid Surface
Authors: Wei P. S. , Ho C. Y.
Published: May 2006

In this study, a general, analytical solution of a steady creeping or Stokes flow impinging on a stationary spherical cap-shaped bubble on a solid flat surface is provided. The phenomena usually take place in bubble∕pore formation in materials and manufacturing processing and MEMS, boiling heat transfer, and nucleation and growth of gas bubbles in tissues of animals and human, etc. In view of high capillary pressure and small liquid pressure, the shape of the bubble in a microscale can be considered as a spherical cap on a surface. In this model, shear stresses associated with the no-slip condition, interfacial mass transport such as condensation and evaporation are absent on the bubble surface. An analytical solution of the Stokes equations for zero Reynolds number flow in a toroidal coordinate system is found by decomposing the flow into a stagnation flow and a flow disturbed by the bubble and applying the separation-of-variables method. The stream function can be expressed in terms of a difference in Legendre functions of the first kind. The effects of impinging velocity and contact angle of the bubble on the flow pattern and pressure distribution are provided.
Lattice Boltzmann Simulations of CO2 Bubble Dynamics at the Anode of a μDMFC
Authors: Fei K. , Cheng C. H. , Hong C. W.
Published: May 2006

This paper presents the bubble transport phenomenon at the anode of a micro-direct methanol fuel cell (μDMFC) from a mesoscopic viewpoint. Carbon dioxide bubbles generated at the anode may block part of the catalyst/diffusion layer and also the flow channels that cause the μDMFC malfunction. Lattice-Boltzmann simulations were performed in this paper to simulate the two-phase flow in a microchannel with an orifice which emulates the bubble dynamics in a simplified porous diffusion layer and in the flow channel. A two-dimensional, nine-velocity model was established. The buoyancy force, the liquid-gas surface tension, and the fluid-solid wall interaction force were considered and they were treated as source terms in the momentum equation. Simulation results and parametric studies show that the pore size, the fluid stream flow rate, the bubble surface tension, and the hydrophilic effect between the fluid and the solid wall play the major roles in the bubble dynamics. Larger pore size, higher methanol stream flow rate, and greater hydrophilicity are preferred for bubble removal at the anode diffusion layer and also the flow channels of the μDMFC.
Permeability and Form Coefficient Measurement of Porous Inserts With Non-Darcy Model Using Non-Plug Flow Experiments
Authors: Wilson L. , Narasimhan Arunn , Venkateshan S. P.
Published: May 2006

Permeability (K) and form coefficient (C) are the characteristic hydraulic properties of any porous medium. They are determined simultaneously, for known fluid thermo-physical properties by using the Hazen-Dupuit-Darcy model (HDD) to curve-fit the longitudinal global pressure-drop versus average fluid speed data from an isothermal, steady flow, hydraulic experiment across a test section of the porous medium. The K and C thus measured are global parameters, i.e., valid for the entire porous medium and universal provided the flow throughout the porous medium is of plug flow nature. We report here experimental evidence on the influence of non-plug flow velocity profiles at the inlet, on the simultaneous determination of K and C of fissure- and rod bundle-type porous inserts. Although variation in K is minimal, as much as 12.1% variation in C is observed, when going from a fully developed velocity profile to a plug flow profile at the inlet.
Temporal subtraction in chest radiography: Automated assessment of registration accuracy
Authors: Armato Samuel G. , Doshi Devang J. , Engelmann Roger , Croteau Charles L. , MacMahon Heber
Published: May 2006

Radiologists routinely compare multiple chest radiographs acquired from the same patient over time to more completely understand changes in anatomy and pathology. While such comparisons are achieved conventionally through a side‐by‐side display of images, image registration techniques have been developed to combine information from two separate radiographic images through construction of a “temporal subtraction image.” Although temporal subtraction images provide a powerful mechanism for the enhanced visualization of subtle change, errors in the clinical evaluation of these images may arise from misregistration artifacts that can mimic or obscure pathologic change. We have developed a computerized method for the automated assessment of registration accuracy as demonstrated in temporal subtraction images created from radiographic chest image pairs. The registration accuracy of 150 temporal subtraction images constructed from the computed radiography images of 72 patients was rated manually using a five‐point scale ranging from “5‐excellent” to “1‐poor;” ratings of 3, 4, or 5 reflected clinically acceptable subtraction images, and ratings of 1 or 2 reflected clinically unacceptable images. Gray‐level histogram‐based features and texture measures are computed at multiple spatial scales within a “lung mask” region that encompasses both lungs in the temporal subtraction images. A subset of these features is merged through a linear discriminant classifier. With a leave‐one‐out‐by‐patient training/testing paradigm, the automated method attained an value of 0.92 in distinguishing between temporal subtraction images that demonstrated clinically acceptable and clinically unacceptable registration accuracy. A second linear discriminant classifier yielded an value of 0.82 based on a feature subset selected from an independent database of digitized film images. These methods are expected to advance the clinical utility of temporal subtraction images for chest radiography.
Clinical comparison of a novel breast DXA technique to mammographic density
Authors: Shepherd John A. , Herve Lionel , Landau Jessie , Fan Bo , Kerlikowske Karla , Cummings Steve R.
Published: May 2006

We compare mammography breast density to the measure of breast composition using a clinical dual energy absorptiometry (DXA) system calibrated to measure breast density. A DXA scanning protocol was developed to scan breasts isolated in the DXA scan field in either a prone pendulous or decubitus mediolateral position. A total of 17 participants were recruited among women undergoing clinical mammography examinations. Each participant had duplicate DXA scans and duplicate craniocaudal‐view mammograms of their right breast with repositioning between each scan and one DXA and one craniocaudal‐view mammogram of their left breast. The in vivo repeatability (RMS SD) of and on duplicate scans was found to be 1.2% for and 1.4% for when repeat measures were made on the same day. When repeat measures of the same breast were made more than 50 days apart, the repeatability decreased to 5.5%. Left and right breast measurements were highly correlated with both techniques at for and for . Moderate correlation was found between and measurements. However, after recalibrating the DXA system to mammography reference materials, negative percent fibroglandular values were measured for the most fatty breasts. Thus, our results are reproducible and accurate to common mammography tissue standards, but did not accurately reflect true percent fibroglandular levels and further development of phantom standards are necessary. We conclude that breast composition can be precisely evaluated and assessed with clinical DXA densitometers at a lower dose than with mammographic breast density methods.
Isolation and Sequencing of a Temperate Transducing Phage forPasteurella multocida
Authors: Campoy Susana , Aranda Jesús , Àlvarez Gerard , Barbé Jordi , Llagostera Montserrat
Published: May 2006

A temperate bacteriophage (F108) has been isolated through mitomycin C induction of aPasteurella multocidaserogroup A strain. F108 has a typical morphology of the familyMyoviridae, presenting a hexagonal head and a long contractile tail. F108 is able to infect allP. multocidaserogroup A strains tested but not those belonging to other serotypes. Bacteriophage F108, the firstP. multocidaphage sequenced so far, presents a 30,505-bp double-stranded DNA genome with cohesive ends (CTTCCTCCCCcossite). The F108 genome shows the highest homology with those ofHaemophilus influenzaeHP1 and HP2 phages. Furthermore, an F108 prophage attachment site in theP. multocidachromosome has been established to be inside a gene encoding tRNALeu. By using several chromosomal markers that are spread along theP. multocidachromosome, it has been demonstrated that F108 is able to perform generalized transduction. This fact, together with the absence of pathogenic genes in the F108 genome, makes this bacteriophage a valuable tool forP. multocidagenetic manipulation.
High-Pressure-Mediated Survival of
Clostridium botulinum
and
Bacillus amyloliquefaciens
Endospores at High Temperature
Authors: Margosch Dirk , Ehrmann Matthias A. , Buckow Roman , Heinz Volker , Vogel Rudi F. , Gänzle Michael G.
Published: May 2006

Endospores of proteolytic type B
Clostridium botulinum
TMW 2.357 and
Bacillus amyloliquefaciens
TMW 2.479 are currently described as the most high-pressure-resistant bacterial spores relevant to food intoxication and spoilage in combined pressure-temperature applications. The effects of combined pressure (0.1 to 1,400 MPa) and temperature (70 to 120°C) treatments were determined for these spores. A process employing isothermal holding times was established to distinguish pressure from temperature effects. An increase in pressure (600 to 1,400 MPa) and an increase in temperature (90 to 110°C) accelerated the inactivation of
C. botulinum
spores. However, incubation at 100°C, 110°C, or 120°C with ambient pressure resulted in faster spore reduction than treatment with 600 or 800 MPa at the same temperature. This pressure-mediated spore protection was also observed at 120°C and 800, 1,000, or 1,200 MPa with the more heat-tolerant
B. amyloliquefaciens
TMW 2.479 spores. Inactivation curves for both strains showed a pronounced pressure-dependent tailing, which indicates that a small fraction of the spore populations survives conditions of up to 120°C and 1.4 GPa in isothermal treatments. Because of this tailing and the fact that pressure-temperature combinations stabilizing bacterial endospores vary from strain to strain, food safety must be ensured in case-by-case studies demonstrating inactivation or nongrowth of
C. botulinum
with realistic contamination rates in the respective pressurized food and equipment.
Trends in Production of Extended-Spectrum β-Lactamases among Enterobacteria of Medical Interest: Report of the Second Italian Nationwide Survey
Authors: Luzzaro Francesco , Mezzatesta Marilina , Mugnaioli Claudia , Perilli Mariagrazia , Stefani Stefania , Amicosante Gianfranco , Rossolini Gian Maria , Toniolo Antonio
Published: May 2006

Results of a 2003 survey carried out in Italy to evaluate the prevalence of extended-spectrum β-lactamase (ESBL)-producing enterobacteria are presented. Eleven Italian Microbiology Laboratories investigated 9,076 consecutive nonreplicate isolates (inpatients, 6,850; outpatients, 2,226). ESBL screening was performed by MIC data analysis. Confirmation was obtained using the double-disk synergy test and the combination disk test based on CLSI methodology. ESBL determinants were investigated by colony blot hybridization and confirmed by sequencing. Results were compared to those of the 1999 Italian survey (8,015 isolates). The prevalence of ESBL producers was 7.4% among isolates from inpatients (in 1999, 6.3%) and 3.5% among outpatients (no data were available for 1999). Among hospitalized patients, the most prevalent ESBL-positive species was
Escherichia coli
(
Klebsiella pneumoniae
in 1999).
Proteus mirabilis
was the most prevalent ESBL-positive species among outpatients. In both groups, most ESBL-positive pathogens were obtained from urinary tract infections. TEM-type ESBLs were the most prevalent enzymes (45.4%). Non-TEM, non-SHV determinants emerged: CTX-M-type in
E. coli
and
K. pneumoniae
, and PER-type in
P. mirabilis
,
Providencia
spp., and
E. coli
. With the exception of 3/163
P. mirabilis
isolates and 1/44
Providencia stuartii
isolate (all of which were intermediate for imipenem), carbapenems were active against all ESBL-positive enterobacteria. Susceptibility to other drugs was as follows: 84.7% for amikacin, 84.4% for piperacillin-tazobactam, 48.0% for gentamicin, and 32.8% for ciprofloxacin. Carbapenems appear to be the drug of choice. Amikacin and β-lactam/β-lactamase inhibitor combinations represent an alternative in non-life-threatening infections. The appearance of ESBL-positive enterobacteria in the community makes it mandatory that family physicians learn how to treat these pathogens.
Molecular Diversity of Rabies Viruses Associated with Bats in Mexico and Other Countries of the Americas
Authors: Velasco-Villa Andrés , Orciari Lillian A. , Juárez-Islas Víctor , Gómez-Sierra Mauricio , Padilla-Medina Irma , Flisser Ana , Souza Valeria , Castillo Amanda , Franka Richard , Escalante-Mañe Maribel , Sauri-González Isaias , Rupprecht Charles E.
Published: May 2006

Bat rabies and its transmission to humans and other species in Mexico were investigated. Eighty-nine samples obtained from rabid livestock, cats, dogs, and humans in Mexico were studied by antigenic typing and partial sequence analysis. Samples were further compared with enzootic rabies associated with different species of bats in the Americas. Patterns of nucleotide variation allowed the definition of at least 20 monophyletic clusters associated with 9 or more different bat species. Several lineages associated with distinctive antigenic patterns were found in rabies viruses related to rabies in vampire bats in Mexico. Vampire bat rabies virus lineages associated with antigenic variant 3 are widely spread from Mexico to South America, suggesting these lineages as the most likely ancestors of vampire bat rabies and the ones that have been moved by vampire bat populations throughout the Americas. Rabies viruses related to
Lasiurus cinereus
,
Histiotus montanus
, and some other not yet identified species of the genus
Lasiurus
were found circulating in Mexico. Long-range dissemination patterns of rabies are not necessarily associated with migratory bat species, as in the case of rabies in
Desmodus rotundus
and
Histiotus montanus
. Human rabies was associated with vampire bat transmission in most cases, and in one case, rabies transmission from free-tailed bats was inferred. The occurrence of rabies spillover from bats to domestic animals was also demonstrated. Genetic typing of rabies viruses allowed us to distinguish trends of disease dissemination and to address, in a preliminary fashion, aspects of the complex evolution of rabies viruses in different host-reservoir species.
In Vitro Release by
Aspergillus fumigatus
of Galactofuranose Antigens, 1,3-β-
d
-Glucan, and DNA, Surrogate Markers Used for Diagnosis of Invasive Aspergillosis
Authors: Mennink-Kersten Monique A. S. H. , Ruegebrink Dorien , Wasei Nazhat , Melchers Willem J. G. , Verweij Paul E.
Published: May 2006

Aspergillus
markers are becoming increasingly important for the early diagnosis of invasive aspergillosis. The kinetics of release of these surrogate markers, however, is largely unknown. We investigated the release of β-(1-5)-galactofuranosyl (gal
f
) antigens (Platelia
Aspergillus
), 1,3-β-
d
-glucan (BG) (Fungitell), and DNA (PCR) in an in vitro model of
Aspergillus fumigatus
. The results showed that release is correlated to the growth phase of the fungus, which depends on available nutrients. Whereas gal
f
antigens and BG are released during logarithmic growth, DNA is released only after mycelium breakdown. During early logarithmic growth, gal
f
antigens seem to be released somewhat earlier than BG. Furthermore, gal
f
antigen concentrations of more than 120,000 times the serum cutoff value (0.5 ng/ml) can be measured, while BG concentrations reach a value only 978 times the serum cutoff value (60 pg/ml). During lytical growth, release of gal
f
antigens further increased to a maximum level, which depended on pH. After that, the concentration of gal
f
antigens stayed high (pH 7.4) or decreased to zero within 4 days (pH 5.0). In contrast to gal
f
antigens, BG concentration decreased after 1 day of growth. The decrease of gal
f
components seems to be due to the enzyme β-galactofuranosidase, which is able to destroy gal
f
epitopes and whose activity fluctuates in the culture filtrates in parallel with gal
f
antigen concentration. Fungal DNA seems to be released only due to autolysis caused by nutrient limitation. In conclusion, several factors clearly influence the release of surrogate markers in vitro. These same factors might also play a role at the infection site of
Aspergillus
disease in humans.
Comparison between the Hybrid Capture II Test and an SPF1/GP6+ PCR-Based Assay for Detection of Human Papillomavirus DNA in Cervical Swab Samples
Authors: Huang Shang-Lang , Chao Angel , Hsueh Swei , Chao Fang-Yu , Huang Chu-Chun , Yang Jung-Erh , Lin Ching-Yu , Yan Chiu-Cho , Chou Hung-Hsueh , Huang Kuan-Gen , Huang Huei-Jean , Wu Tzu-I , Tseng Mao-Jung , Qiu Jian-Tai , Lin Cheng-Tao , Chang Ting-Chang , Lai Chyong-Huey
Published: May 2006

We compared the efficacy of human papillomavirus (HPV) DNA detection between a PCR-based genechip (Easychip HPV Blot [hereafter referred to as HPV Blot]; King Car, Taiwan) method and Hybrid Capture II (HCII; Digene, Gaithersburg, MD) in women with previous normal (
n
= 146) or abnormal (≥atypical squamous cells of undetermined significance [ASCUS] [
n
= 208]) cytology. A total of 354 cervical swab samples were collected for HPV DNA assay by both HCII and SPF1/GP6+ PCR followed by HPV Blot tests. Colposcopy-directed biopsy was performed if clinically indicated. Of the 354 samples, HPV-positive rates by these two methods (HCII and HPV Blot) were 12.6% and 18.2% in 143 normal samples, 36.2% and 45.7% in 105 ASCUS samples, 57.4% and 57.4% in 94 low-grade squamous intraepithelial lesion samples, and 83.3% and 75.0% in 12 high-grade squamous intraepithelial lesion samples, respectively. The concordance of HPV Blot and HCII was 80.8% (286/354), and the agreement between the methods (κ value, 0.68) was substantial. Discrepancies were further investigated by at least one of the following three methods: direct sequencing, type-specific PCR, and HPV Blot genotyping of cervical biopsy tissue. In the 15 HCII-positive samples, HPV Blot detected only non-HCII HPV genotypes; results of further verification methods were consistent with the latter test in the 15 samples. Of the 20 samples with HCII-negative and HPV Blot-positive results, 18 were found to contain the 13 HCII high-risk genotypes by verification methods. In only 16.7% (3/18) of the HCII-positive but HPV Blot-negative samples, further studies detected the 13 HCII genotypes. We conclude that HPV Blot seemed comparable to HCII for detection of HPV DNA in cervical swab samples.
Novel Approach to Designing Primers for Identification and Distinction of the Human Pathogenic Fungi
Coccidioides immitis
and
Coccidioides posadasii
by PCR Amplification
Authors: Umeyama Takashi , Sano Ayako , Kamei Katsuhiko , Niimi Masakazu , Nishimura Kazuko , Uehara Yoshimasa
Published: May 2006

We developed a pair of primers that specifically identifies
Coccidioides
species, etiologic agents of the human fungal disease coccidioidomycosis. These primers could be used for distinguishing
Coccidioides immitis
and
Coccidioides posadasii
by simply comparing the amplicon sizes on an agarose gel.
Reactions of ethylene with rhodium(III) chloride. Part II. Catalyzed substitution at rhodium(III)
Authors: James B. R. , Kastner M. , Rempel G. L.
Published: May 2006

Ethylene has been found to catalyze at ambient temperatures the production of RhCl2(H2O)4+ species from freshly made solutions of RhCl3.3H2O in water. A mechanism involving trace amounts of chlororhodate(I) species is indicated.
Octacyanomolybdate(IV) ion, scavenger for hydroxyl radical
Authors: Sharma B. K.
Published: May 2006

not available
Concerning the so-called "isohydric point"
Authors: McBryde W. A. E.
Published: May 2006

Evaluation of the formation function [Formula: see text] for a system of monomeric and polymeric (condensed) acids in mutual equilibrium can account for the appearance of a network of formation curves with a crossover point at a fixed value of the coordinates [Formula: see text], pH. The value of [Formula: see text] at this isohydric point is equal to 1 − z/n, where n is the degree of condensation and z the basicity of the condensed acid. A third formation curve is unlikely to pass through the same isohydric coordinates, so that the system is very probably restricted to two predominant species in equilibrium. These conclusions confirm the work of Carpéni and collaborators, but appear to have been derived in a different way.
Metal ion initiated halogenation reactions of N-haloamines
Authors: Tanner Dennis D. , Mosher Melvyn W.
Published: May 2006

The metal ion catalyzed chlorination of hydrocarbon substrates by N-chloroamines and imides in acid media proceeds by a free radical chain mechanism. Reactions of four different N-chloro halogenating reagents with cuprous chloride, ferrous sulfate, and ferrous chloride initiators have been investigated. Contrary to the previously reported observations no experimental differences were observed in the halogenation reactions of individual N-halo compounds or with the different initiators. The chain carrying species in all cases was shown to be the chlorine atom and the radical chain process showed identical reactivity to that of photo-chlorination by molecular chlorine.
Etude de résonance magnétique nucléaire dans la série des pregnane et D-homopregnane
Authors: Jankowski Krzysztof , Berse Casimir
Published: May 2006

not available
Ultraviolet absorption maxima, both calculated and observed, for some α-benzoyl-trans-benzalacetones, ethyl α-benzoyl-trans-cinnamates, and some α-cyano-trans-benzalacetophenones
Authors: Currie D. J. , Holmes H. L.
Published: May 2006

The equation for the calculation of absorption maxima for conjugated heteroenoid compounds has been extended to include a number of α-benzoyl-trans-benzalacetones and ethyl α-benzoyl-trans-cinnamates and has been used to assign configuration to the α-cyano-trans-benzalacetophenones. The method for calculating the substituent constant, D, has been refined to give more accurate values.
Reaction of diphenylphosphine and 1,2-dichlorotetrafluorocyclobutene
Authors: Stockel Richard F.
Published: May 2006

Diphenylphosphine and 1,2-dichlorohexafluorocyclobutene react in a solvent medium of dimethyl formamide to give both the mono (3) and 1,2-disubstituted (2) derivatives as products. In contrast, these same reactants give entirely different products when the reaction is conducted in the absence of a solvent.Analytical and spectroscopic data are presented for the proposed structures.
Thiohydantoins. VII. Ionization and ultraviolet spectra of 4-thiohydantoins and 2,4-dithiohydantoins
Authors: Edward J. T. , Liu J. K.
Published: May 2006

The acid and base dissociation constants of 5,5-pentamethylene-4-thiohydantoin, 5,5-pentamethylene-2,4-dithiohydantoin, and their 1-methyl derivatives, have been determined by ultraviolet studies in basic and acid media. In aqueous sulfuric acid the 4-thiohydantoins are protonated on oxygen at the 2-position, so that the extent of protonation varies with the HA function of the acid solution, while the 2,4-dithiohydantoins are protonated on sulfur at the 2-position, so that the extent of their protonation varies with H0′′′. The importance of using acidity functions appropriate to the different types of compounds when comparing their basicities is emphasized.
Thiohydantoins. VIII. Structure of the reported 5-phenyl-2,4-dithiohydantoin and its benzylation products
Authors: Edward J. T. , Liu J. K.
Published: May 2006

The supposed 5-phenyl-2,4-dithiohydantoin (3) actually exists as its tautomer 5-mercapto-4-phenyl-4-imidazolin-2-thione (12). The reactions of the compound have been clarified by spectral studies of the products; in particular, mono- and dibenzylation have been shown to take place on sulfur and not (as reported) on nitrogen.
Effect of N-acylamino groups on the chemical shift of the ortho proton in biphenyls
Authors: Hess F. K. , Pook K. H.
Published: May 2006

The proton magnetic resonance spectra of several acylamino biphenyls were determined. Evidence was obtained that the proton adjacent to the acylamino group was shifted to lower field relative to the remaining ring protons.
Infrared spectra of the interactions of aniline and porous glass surfaces
Authors: Low M. J. D. , Rao V. V. Subba
Published: May 2006

Infrared spectra were recorded of aniline sorbed on highly dehydroxylated, deuterated, and on fluoridated porous glass as well as on pure and boria-impregnated silica. The results suggest that two types of weak interactions involving the surface SiOH and B—OH groups occurred; the nitrogen atom of the amine was hydrogen bonded to surface OH and there was an interaction between OH groups and the π system of the aromatic ring. Some aniline chemisorbed on surface boron via the nitrogen atom of the amine group. Some aniline chemisorbed dissociatively to form secondary amine structures bonded through the nitrogen to surface boron atoms and new B—OH groups formed. Surface boron impurity acted as an adsorption and dissociation center.
Conformation of the esters of steroid hydroxyl groups by infrared spectroscopy
Authors: Narayanan C. R. , Sarma M. R. , Srinivasan T. K. K. , Wadia M. S.
Published: May 2006

Infrared spectral studies show that the carbonyl group of the esters of steroid hydroxyl groups are stabilized near the adjacent alkyl hydrogen atoms; this energy of stabilization appears to be more than that of hydrogen bonding between the carbonyl and a nearby hydroxyl group.
Comments, Replies, and Summary
Authors: Lawrence G. M.
Published: May 2006

not available
Polychloro-alicyclic ketones. I. Polychloro-2-methylcyclohexenones, polychloro-3-methylcyclohexenones, and related polychlorocyclohexadienones
Authors: Morita Eiichi , Dietrich Martin W.
Published: May 2006

The structures of eighteen polychloro-alicyclic ketones prepared by the chlorination of chlorinated phenols, ortho and meta cresols, or the corresponding toluidines were determined by nuclear magnetic resonance, infrared, and ultraviolet spectroscopy. Stereochemistry and the sequence of the formation of these polychloro-alicyclic ketones are described.
Dimethyl sulfoxide as a solvent in the Williamson ether synthesis
Authors: Smith Russel G. , Vanterpool Alan , Kulak H. Jean
Published: May 2006

Using the conventional Williamson ether synthesis, n-butyl ether was prepared from sodium hydroxide, n-butyl alcohol, and n-butyl chloride using excess of the alcohol as solvent in 61% yield after 14 h reaction time. However, when the excess alcohol was replaced by dimethyl sulfoxide, the yield of ether rose to 95% with 9.5 h reaction time. Other primary alkyl chlorides exhibited similar behavior to n-butyl chloride, but secondary alkyl chlorides and primary alkyl bromides gave little etherification, elimination being the major reaction. Unreactive halides, such as vinyl chloride, phenyl bromide, and 2,4-dinitrobromobenzene, were not etherified in dimethyl sulfoxide. The reaction products obtained from aliphatic dichlorides depended upon the relative positions of the chlorine atoms. Secondary alcohols reacted to give ethers, but tertiary alcohols were very unreactive. Polyols generally gave high yields of ethers, the major product being that in which all but one of the hydroxyl groups became etherified. Under forcing conditions, however, completely etherified polyols could be obtained.
Structure and reactivity of the mono-oxime of 2,6-dimethoxy-1,4-benzoquinone
Authors: Bolker H. I. , Kung F. L.
Published: May 2006

Reaction of 2,6-dimethoxy-1,4-benzoquinone with hydroxylamine yielded 2,6-dimethoxy-4-oximino-2,5-cyclohexadienone-1 (3), as confirmed by spectroscopic analysis, and by independent synthesis from 5-nitro-1,2,3-trimethoxybenzene. Infrared and proton magnetic resonance spectra in solution showed no significant proportion of the tautomeric nitrosophenolic form of 3. When 3 was heated for 3 min at 90–95° in 1.0 N HCl in H218O, the N—OH group was stable, but the keto oxygen underwent complete exchange. Mass spectra of 3, its 18O- and deuterium-substituted derivatives indicated that a major process leading to fragmentation upon electron impact was loss of oxygen from N—OH to form the corresponding quinone imine.
Radiation induced bonding of hexamethyldisiloxane to silica
Authors: Chahal R. S. , Pierre L. E. St.
Published: May 2006

An infrared technique was used to study the interfacial interaction between silica and hexamethyldisiloxane systems in the absence and presence of a radiation field. In the absence of the radiation, physisorbed hexamethyldisiloxane and higher molecular weight silicone compounds could be completely removed from the silica surface. In the irradiated samples, however, relatively large amounts of hexamethyldisiloxane were found to be chemisorbed on the surface. The evidence presented supports a radiation-induced chemical bonding of the products of the radiolysis of hexamethyldisiloxane to a silica surface at coverages of less than a monolayer.
A synthesis in the series of aconitine and delphinine
Authors: Wiesner K. , Kao Wen-ling , Šantroch J.
Published: May 2006

The synthesis of compound 3 is described. This synthesis represents the solution of most of the problems which will be encountered in the approach to the delphinine and aconitine aromatization products 1 and 2. The synthetic compound 3 incorporates the complete skeleton and functionality of 1 and 2 except the substitution of ring A.
Complexes of palladium(II) with cis- and trans-1,2-bis(dimethylarsino)ethylene
Authors: Erskine G. J.
Published: May 2006

Palladium(II) complexes of cis- and trans-1,2-bis(dimethylarsino)ethylene, 1 and 2, respectively, in the metal: ligand ratios 1:1 and 1:2 are described. Their structures are discussed in terms of nuclear magnetic resonance, infrared, conductivity, and analytical data, and by comparison with the corresponding platinum(II) complexes (1). The cis-isomer, cis-ED, is a strong chelating ligand and forms the complexes Pd(cis-ED)X2, 9 (X = Cl−, Br−), and Pd(cis-ED)2X2•3H2O, 8 (X = Cl−, Br−, ClO4−, PF6−). The trans-isomer, trans-ED is a bridging ligand and forms the dimeric complexes, [Pd(trans-ED)X2]2, 10 (X = Cl−, Br−), and Pd2(trans-ED)4X4•3H2O, 7 (X = Cl−, Br−, ClO4−, PF6−). All these complexes contain 4-coordinate, square planar palladium(II). The anhydrous form of 7 (X = Cl−) shows evidence for a Pd—Cl bond, suggesting 5-coordination in the solid state. Room temperature irradiation (with ultraviolet light) of 7 (X = Cl−), in non-aqueous solvents, causes isomerization of the ligand and the formation of complex 8 (X = Cl−). No change occurs under these conditions in aqueous solutions. Contrary to the original suggestion for the corresponding platinum(II) derivative, 10 (M = Pt(II), ref. 1) far infrared evidence supports a cis-configuration about the metal ion rather than the trans-configuration, 6.
Carbonyl stretching frequencies and force constants in cyclopentadienylmolybdenum tricarbonyl derivatives
Authors: King R. B. , Houk L. W.
Published: May 2006

The infrared spectra of compounds of the type RM(CO)3C5H5 (M = Mo or W; R = (CH3)3Sn, σ-alkyl groups, halides, etc.) exhibit the expected three v(CO) frequencies (2A′ + A″). The relative positions of the A″ and the lower A′ frequencies interchange upon variation of the electronegativity of the R group. Values for the Cotton–Kraihanzel stretching force constants k1 and k2 have been calculated from these v(CO) frequencies assuming the ratio kd/ks = 2 for the interaction force constants. From these force constants the σ and π parameters of Graham were calculated. The σ and π parameters were found to be very similar for analogous RM(CO)3C5H5 and RMn(CO)5 compounds.
Ring enlargement through acyloin condensation of cycloalkane-1,2-dicarboxylic esters
Authors: Mori T. , Nakahara T. , Nozaki H.
Published: May 2006

Cycloalkane-1,2-dicarboxylic esters of 11-, 12-, and 13-membered rings were prepared from cyclododecanone. Acyloin condensation of these esters in the presence of trimethylchlorosilane followed by acidic hydrolysis afforded 13-, 14-, and 15-membered cycloalkane-1,2-diones in 71–74% yields. The diketones were reduced by treatment with triethyl phosphite and alkali hydroxide into corresponding acyloins.
Stability of fused rings in metal chelates. VI. Structures and stability constants of the copper(II) chelates of dipeptides containing glycine and/or β-alanine
Authors: Yamauchi Osamu , Hirano Yumi , Nakao Yasuo , Nakahara Akitsugu
Published: May 2006

The reactions of the dipeptides containing glycine and/or β-alanine with an equimolar amount of copper(II) nitrate in acid solution were investigated potentiometrically, and the stability constants for the copper(II) chelates formed in acid solution were determined at 25 °C by the method of Datta and Rabin. The chelates with the composition [Cu.peptide(OH2)] were isolated in the pure state. The dipeptides exhibited analogous reactivities, and the stability constants, log K1, for the charged chelates, CuHL+, were found to be between 5.5–5.7. Comparison of the values for glycylglycine and β-alanyl-glycine with those for glycine and β-alanine suggests that these dipeptides act as terdentate ligands forming fused-ring chelates, where the coordinating sites are probably the amino nitrogen, amide nitrogen, and carboxyl oxygen, although the complexing ability of the amide NH group may be weak. The constants, Kc, for the dissociation of the amide hydrogen from the charged chelates to form the deprotonated chelates, CuL, with the rigid 5-5-, 5-6-, or 6-6-membered ring system decrease in the order glycylglycine > β-alanylglycine > glycyl-β-alanine > β-alanyl-β-alanine. The log K1Kc values indicate that the tendency of forming the deprotonated chelates also decreases in this order.
Derivatives of 2,3-benzo-1-azabicyclo[2•2•1]hept-2-ene
Authors: McLean Stewart , Fallas A. L. , Trotz U. O. , Reynolds W. F.
Published: May 2006

2,3-Benzo-1-azabicyclo[2•2•1]hept-2-ene derivatives have been prepared by the introduction of a two-carbon bridge between positions-1 and -3 of the indole ring in 2,3-dimethylindole and tetrahydrocarbazole. In the former case both C-7 epimers were isolated and identified, and their nuclear magnetic resonance spectra were analyzed in detail. In the tetrahydrocarbazole series only one product was obtained and some ambiguity remains concerning the stereochemistry of this material. The physical properties of these compounds are of interest because the lone pair electrons on nitrogen are not able to overlap with the aromatic π system; the chemical properties are characterized by a facile cleavage of the tertiary amine under acylating conditions.
Dehydrobromination of methyl 11α-bromo-12-oxopodocarpan-19-oate
Authors: Bell R. A. , Gravestock M. B.
Published: May 2006

The configuration and stereochemistry of methyl 11α-bromo-12-oxopodocarpan-19-oate 1 have been determined by application of the nuclear Overhauser effect. The dehydrobromination of 1 with dimethylacetamide–calcium carbonate results in a predominant 1,4-elimination process which for short reaction periods yields the non-conjugated ketone 8 and for long reaction periods yields the conjugated ketone 2. The 1,2-elimination of hydrogen bromide is a minor process and takes place to the extent of 20–22%. The ketone 8 has been oxidatively cleaved to the keto-acid 11, a valuable intermediate for the synthesis of bicyclic diterpenoids.
Absorption of β particles from tritium and rhenium 187 in helium and aluminum
Authors: Naldrett S. N.
Published: May 2006

The absorption of the β particles from tritium and from 187Re was found to obey an exponential law for a range of about 6 or 7 times the half-thicknesses. In helium the half-thicknesses of tritium and of 187Re are found to be 0.0460 ± 0.0007 and 0.0393 ± 0.0012 mg/cm2; in aluminum they are 0.0367 ± 0.0009 and 0.0336 ± 0.0013 mg/cm2, respectively.
Studies on metal hydroxy compounds. IX. Kinetics of thermal decomposition of twelve copper halide derivatives
Authors: Ramamurthy P. , Secco E. A.
Published: May 2006

The kinetics of the thermal decomposition of 12 halide (F, Cl, Br, I) derivatives of copper hydroxide are reported. The kinetic results and their interpretation in terms of activated complex theory are compared with the results and interpretation of the thermal decomposition of zinc and cadmium hydroxyhalides.
Substitutions électrophiles en série naphtalènique. VI. Sur le diméthoxy-2,6 naphtalène
Authors: Richer Jean-Claude , Rossi Armand
Published: May 2006

not available
4,6-O-Benzylidene-3-deoxy-3-C-(iodomethyl)-D-allal: precursor of a cyclopropylcarbinyl-oxo-carbonium ion
Authors: Fraser-Reid Bert , Radatus Bruno
Published: May 2006

Treatment of methyl 4,6-O-benzylidene-α-D-erythro-hex-2-enopyranoside (5) with the Simmons–Smith reagents gives 85% of the expected cyclopropane adduct 6 and about 10% of a second product 4. When the cyclopropane derivative 6 is allowed to react further with the Simmons–Smith reagents, it is 40% converted to 4. The structure of compound 4 is established to be 4,6-O-benzylidene-3-deoxy-3-C-(iodomethyl)-D-allal (4,6-O-benzylidene-1,2,3-trideoxy-3-C-iodomethyl-D-ribo-hex-1-enopyranose), and the unusually high solvolytic reactivity observed for it, as well as its formation from 6, are rationalized as proceeding through the cyclopropylcarbinyl-oxo-carbonium ion3.
The photolyses of acetyl and ethyl isocyanates in the vapor phase: new examples of Type II photodissociation
Authors: Friswell N. J. , Back R. A.
Published: May 2006

The photolyses of acetyl and ethyl isocyanate vapors have been studied at 25 °C, at pressures between about 2 and 30 Torr, using either monochromatic 2288 Å radiation or light from a medium-pressure mercury arc equipped with a Vycor filter. Molecular photodissociations were of major importance with both compounds, with formation of HNCO + CH2CO and HNCO + C2H4 accounting for about 70 and 60% of the decomposition of the acetyl and ethyl esters, respectively. It is suggested that these products were formed through a 6-membered ring transition state analogous to that involved in the Norrish Type II process observed in other carbonyl compounds.Minor free-radical processes also occurred with both isocyanates, with evidence for photodissociation of both R—NCO and RN—CO bonds. There was also apparently some collisional deactivation of excited precursors of both the molecular and free-radical photodissociations.Vapor pressure data for the 2 isocyanates, and molar extinction coefficients between about 2200 and 3000 Å, are also reported.
Isomers of bis(trifluoromethyl)phosphinomethylhydrazine, (CF3)2PNHNHMe and (CF3)2PN(Me)NH2
Authors: Peterson L. K. , Wilson G. L.
Published: May 2006

The synthesis of isomers of bis(trifluoromethyl)phosphinomethylhydrazine, (CF3)2PNHNHMe, 1, and (CF3)2PN(Me)NH2, 2, and their characterization by infrared, nuclear magnetic resonance, and mass spectra, and by vapor phase molecular weight measurements are described. The significance of the formation of both isomers is discussed in terms of steric and electronic effects.
Etude du comportement thermique de l'alcool diméthyl allylique
Authors: Roux Claude , Katzanevas Françoise
Published: May 2006

not available
Effect of an external heavy atom on the photochemistry of monofluorobenzene vapor
Authors: Cook A. , Semeluk G. P. , Unger I.
Published: May 2006

Spectrofluorometric techniques have been used to study the effect of added xenon on the singlet and triplet yields of monofluorobenzene vapor excited by 2670, 2520, and 2470 Å radiation. For each wavelength examined, the fluorescent yield was found to decrease with increasing xenon pressure and plots of 1/Фp vs.Pxe are linear. The sensitized emission of biacetyl technique was used to determine triplet yields. The effect of xenon on the emission yield of biacetyl excited directly at 4358 Å was also examined and it was found that xenon reduced the phosphorescent yield of biacetyl. Plots of 1/Φp vs. Pxe were found to be linear, for all cases of sensitized as well as directly excited emission. At 2470 Å both the fluorescence yield and the triplet yield initially increase with increasing Xe pressure, but when the Xe pressure exceeds about 30 Torr the behavior at this wavelength is the same as it is at the other two wavelengths.The data suggest that xenon enhances intersystem crossover in both monofluorobenzene (FB) and biacetyl (BiA). The important process in the former is 1FB + Xe → 3FB + Xe, while in the latter is 3BiA + Xe → BiA + Xe. A mechanism consistent with the experimental observation is presented.
Perchlorate catalysis of the methanolysis of triphenylmethyl chloride in benzene solution and its relation to special salt effects in solvolysis reactions
Authors: Leffek K. T.
Published: May 2006

The kinetic form of the suppression of the perchlorate catalysis of the methanolysis of triphenylmethyl chloride in benzene solvent by tetra-n-butylammonium chloride has been investigated. This is consistent with a catalysis brought about by a simple perchlorate ion, suppressed by a competition between such ions and alkylammonium chloride ion-pairs for the alkyl halide ion-pair.The results are discussed in relation to the qualitatively similar special salt effects observed in acetolysis reactions by Winstein and co-workers, with particular reference to the necessity of the concept of intimate and solvent-separated ion-pairs in the interpretation of these effects.
Theory of molecular size distribution In multichain polymers
Authors: Whiteway S. G. , Smith I. B. , Masson C. R.
Published: May 2006

Expressions are derived for the most probable distribution of molecular sizes in multi-chain polymers formed by the self-condensation of the monomer A—R—Xf − 1, where A and X are functional groups and X may be either A or B. It is assumed that all functional groups of the same kind are chemically equivalent and that intramolecular condensation may be neglected. For the case A—R—Bf − 1 the results are identical with those of Flory, although it is shown that this is fortuitous and due to a cancellation of two errors in Flory's method. For the case R—Af the results differ significantly from expressions derived by Flory and sources of error in previous work are discussed. In theory, the mole and weight fractions of individual x-mers vary continuously with the extent of reaction α over the entire range up to αmax = 2/f. The ratio of the weight average to the number average degree of polymerization is finite for all values of α below αmax. The critical point for the formation of infinitely large (wall-to-wall) molecules occurs, not at α = 1/(f − 1) as predicted by Flory, but at α = 2/f. The prediction of actual gel points is discussed in terms of the largest molecule which can have a physically meaningful existence at any fixed value of α.
New method for the synthesis of 6-amino-6-deoxy-α-D-glucopyranosides
Authors: Nagabhushan T. L.
Published: May 2006

A general method for the synthesis of 6-amino-6-deoxy-α-D-glucopyranosides from 3,4-di-O-acetyl-1,2-dideoxy-6-O-p-tolylsulfonyl-D-arabino-hex-1-enopyranose (3,4-di-O-acetyl-6-O-p-tolylsulfonyl-D-glucal) is described. The key steps in the synthesis are addition of nitrosyl chloride to the above glycal, condensation of the resulting nitroso–chloro adduct with alcohols or phenols to provide α-glycosides of 3,4-di-O-acetyl-2-oximino-6-O-p-tolylsulfonyl-D-arabino-hexopyranose, and conversion of the α-oximino-glycosides to α-glucoside derivatives. Propyl, isopropyl, phenyl, and L-menthyl 2,3,4-tri-O-acetyl-6-O-p-tolylsulfonyl-α-D-glucopyranosides are thus prepared and the last compound is converted to L-menthyl 6-amino-6-deoxy-α-D-glucopyranoside.
Electron paramagnetic resonance spectroscopic study of radicals derived from glycine, dl-α-alanine, and β-alanine in aqueous solution
Authors: Smith P. , Fox W. M. , McGinty D. J. , Stevens R. D.
Published: May 2006

The substrates glycine, dl-α-alanine, and β-alanine have been examined in turn within an aqueous continuous-flow system using the titanous chloride – hydrogen peroxide radical-generating method. The temperature was 25 ± 2 °C and the pH of the reaction mixture was varied within the range of values ca. 2 to ca. 5 by addition of sulfuric acid. The electron paramagnetic resonance spectra of the following transient radicals were observed: from glycine, •CH(NH2)COOH; from dl-α-alanine, CH3Ċ(NH2)COOH and •CH2CH(NH3+)COOH; and from β-alanine, CH2(NH3+)ĊHCOOH. The structure of the radical from glycine has been established as •CH(NH2)COOH, not •CH(NH3+)COO−; in clarification of conflicting analyses by earlier workers, who employed reaction conditions similar to those of this present study but who did not obtain spectra as well resolved as those reported here. One group of these earlier workers claimed that glycine gave the radicals •CH(NH3+)COO− and •CH2COO− and the other group postulated correctly that the radical formed was •CH(NH2)COOH. The structural assignment •CH(NH2)COOH is confirmed by the observation in the present investigation of a similarly-structured radical, CH3Ċ(NH2)COOH, from dl-α-alanine. This latter radical was not found by the earlier workers. An additional, small, previously unreported proton hyperfine coupling has been observed in the spectrum from •CH(NH2)COOH when no sulfuric acid is added to the reaction mixture, i.e. pH ca. 4. It has been assigned to the carboxyl-group proton in the above radical. This appears to be the first time such an assignment has been made, and hence, arguments have been cited for its justification. The coupling-constant data obtained for the •CH(NH2)COOH radical are markedly different from those for the radicals •CH(NH3+)COC− and •CH(NH2)COO− reported by other investigators to be formed from glycine under reaction conditions clearly unlike those employed in this present study, even though all three formulas differ only with respect to protonation. These differences are discussed.
Variation of the nuclear Overhauser effect in dimethylformamide with temperature
Authors: Saunders J. K. , Bell R. A.
Published: May 2006

The nuclear Overhauser effects at the formyl proton of dimethylformamide have been measured at and above room temperature. At 90° separate irradiation of the high field and low field methyl signals results in equal nuclear Overhauser effects from both methyls.
Deuterium and hydrogen sulfides: vapor pressures, molar volumes, and thermodynamic properties
Authors: Clarke E. C. W. , Glew D. N.
Published: May 2006

An apparatus is described in which deuterium and hydrogen sulfides have been prepared by the hydrolysis of aluminum sulfide. Liquid densities have been determined at −79 °C and give the molar volumes 34.811 ± 0.003 cm3 for deuterium sulfide and 34.711 ± 0.003 for hydrogen sulfide. Vapor pressures of deuterium and hydrogen sulfides have been determined at −78 °C in a quartz–metal apparatus, and in the range −30 to +30 °C in a stainless steel apparatus. Equations are derived for the deuterium and hydrogen sulfide vapor pressures and for their ratio. An isotopic vapor pressure cross-over point is found at −48 °C, above which deuterium sulfide is more volatile than hydrogen sulfide. Gas and liquid molar volumes and enthalpy changes are evaluated for liquid vaporization at saturation. The deuterium and hydrogen sulfide vaporization standard thermodynamic function changes and their errors, together with the isotopic differences for these functions and their errors, are tabulated between −80 and +50°C.
Reaction of trialkylboranes with diazoacetaldehyde. A new synthesis of aldehydes
Authors: Hooz John , Morrison Geoffrey F.
Published: May 2006

A new aldehyde synthesis has been developed, based on the reaction of organoboranes with diazoacetaldehyde.