bluuebunny/crossref_metadata_2025_split huggingface dataset:
Equitable list‐coloring for graphs of maximum degree 3
Authors: Pelsmajer Michael J. 
Published: May 2004

AbstractGiven lists of available colors assigned to the vertices of a graph G, a list coloring is a proper coloring of G such that the color on each vertex is chosen from its list. If the lists all have size k, then a list coloring is equitable if each color appears on at most ⌈|V(G)|/k⌉ vertices. A graph is equitably k‐choosable if such a coloring exists whenever the lists all have size k. Kostochka, Pelsmajer, and West introduced this notion and conjectured that G is equitably k‐choosable for k > Δ (G). We prove this for Δ(G) = 3. We also show that every graph G is equitably k‐choosable for k ≥ Δ(G)(Δ(G)−1)/2 + 2. © 2004 Wiley Periodicals, Inc. J Graph Theory 47: 1–8, 2004
Algorithms for minimum‐cost paths in time‐dependent networks with waiting policies
Authors: Dean Brian C. 
Published: May 2004

AbstractWe study the problem of computing minimum‐cost paths through a time‐varying network, in which the travel time and travel cost of each arc are known functions of one's departure time along the arc. For some problem instances, the ability to wait at nodes may allow for less costly paths through the network. When waiting is allowed, it is constrained by a (potentially time‐varying) waiting policy that describes the length of time one may wait and the cost of waiting at every node. In discrete time, time‐dependent shortest path problems with waiting constraints can be optimally solved by straightforward dynamic programming algorithms; however, for some waiting policies these algorithms can be computationally impractical. In this article, we survey several broad classes of waiting policies and show how techniques for speeding up dynamic programming can be effectively applied to obtain practical algorithms for these different problem variants. © 2004 Wiley Periodicals, Inc. NETWORKS, Vol. 44(1), 41–46 2004
Intramedullary spinal cord astrocytomas in children
Authors: Townsend Nicole , Handler Michael , Fleitz Julie , Foreman Nicholas 
Published: May 2004

AbstractBackgroundIntramedullary spinal cord astrocytomas are uncommon tumors in childhood. There is little information on therapy and outcome of astrocytomas in this location.ProcedureA retrospective review was performed for the 10 children who were treated between 1996 and 2003 for spinal cord astrocytomas in our institution. Only one had metastatic disease. All ten patients underwent surgical resection, nine partial and one total. Eight had low‐grade tumors, and two high‐grade tumors. Two had surgery only, four had chemotherapy only, two had radiation only, and two had both radiation and chemotherapy.ResultsProgression free survival was 58% and survival was 68% at 4 years. Four patients had disease progression, of which three died. Both children with high‐grade astrocytomas died. Two of eight of the children with low‐grade astrocytomas of the cord recurred, one having received radiation as initial therapy and the other chemotherapy. The child, who relapsed after radiation, had a spastic quadriplegia from radiation myelitis and no salvage therapy was attempted. The four patients, all with low‐grade astrocytomas, who treated with chemotherapy alone, received carboplatin and vincristine. Of these four, three are in continuous remission and one relapsed, but was salvaged with radiation.ConclusionsChemotherapy and radiation did not benefit those with high‐grade astrocytomas of the spinal cord. Good outcomes can be achieved by conservative surgery for low‐grade astrocytomas of the cord when adjuvant therapy is given. Carboplatin and vincristine appeared to be effective, safe therapy for those with low‐grade astrocytomas of the cord. © 2004 Wiley‐Liss, Inc.
Pineal gland abnormalities in Langerhans cell histiocytosis
Authors: Grois N. , Prosch H. , Waldhauser F. , Minkov M. , Strasser G. , Steiner M. , Unger E. , Prayer D. 
Published: May 2004

AbstractBackgroundThe most common types of central nervous system (CNS) disease in Langerhans cell histiocytosis (LCH) comprise involvement of the hypothalamic‐pituitary region (HPR) and neurodegenerative changes in the cerebellum, basal ganglia or pons. In the review process of magnetic resonance images (MRI) from 129 LCH patients a high frequency of cysts within or large pineal glands was noted by chance.ProcedureTo prove whether this observation was specific for LCH or not, we compared MRI findings of the HPR in LCH patients with a control group of 55 non‐LCH patients with the same age and sex distribution.ResultsIn LCH patients, the pineal gland was significantly larger and also the number of pineal cysts was significantly higher as compared to the control group. No difference was found regarding the size or frequency of cystic changes between patients who had received chemotherapy prior to the MRI and untreated patients. In the LCH patients, we further found a significant correlation of pineal gland enlargement with involvement of the HPR, but not with neurodegenerative changes. Analysis of melatonin (the principal hormone of the pineal gland) levels in 24 hr urine in 14 LCH patients did not reveal a melatonin deficiency or overproduction in the LCH group as compared to 6 normal controls.ConclusionsThe pineal gland is another site of possible CNS involvement in LCH. LCH CNS patients did not show an overt disturbance in melatonin levels. The role of the pineal gland in CNS LCH remains to be defined. © 2004 Wiley‐Liss, Inc.
Role of nucleophilic solvation and the mechanism of covalent bond heterolysis
Authors: Dvorko Genrih F. , Ponomareva Engelsine A. , Ponomarev Mykola E. 
Published: May 2004

AbstractBased on data obtained mainly by the verdazyl method, the effects of a solvent on the rates of the heterolyses of 20 substrates (t‐BuCl, t‐BuBr, t‐BuI, 1‐AdBr, 1‐AdI, 1‐AdOTs, 1‐AdOPic, 1‐chloro‐1‐methylcyclopentane, 1‐bromo‐1‐methylcyclopentane, 1‐chloro‐1‐methylcyclohexane, 1‐bromo‐1‐methylcyclohexane, 2‐bromo‐2‐methyladamantane, p‐methoxyneophyl tosylate, 2‐chloro‐2‐phenylpropane, p‐methoxybenzotrichloride, Ph2CCl2, 7α‐bromocholesterol benzoate, 1‐chloro‐1‐phenylethane, Ph2CHBr, 3‐bromocyclohexene) were analyzed in a wide set of protic and aprotic solvents. The heterolysis rate of tertiary substrates decreases with increase in solvent nucleophilicity, but for secondary substrates it does not depend on solvent nucleophilicity. The negative effect of nucleopilic solvation is caused by the solvation of a contact ion pair, which appears before the limiting step. The lack of nucleophilic solvent assistance indicates that a solvent‐separated ion pair of substrates appears after the limiting step. The limiting step involves the interaction of a contact ion pair with a solvent cavity, resulting in the formation of a cavity‐separated ion pair of substrates. Copyright © 2004 John Wiley & Sons, Ltd.
Kinetics of oxidation of acidic amino acids and their monoamides by N‐chloroarylsulphonamides in aqueous acidic medium
Authors: Gowda B. Thimme , Shetty Mahesha 
Published: May 2004

AbstractTwelve sodium salts of N‐chloroarylsulphonamides were employed as oxidants for studying the kinetics of oxidation of two acidic amino acids (aspartic and glutamic acid) and their monoamides (aspargine and glutamine) in aqueous acidic medium under various conditions, to see how the oxidative strength of these reagents vary with substitution. The sodium salts of N‐chloroarylsulphonamides employed are of the general formulae i‐X‐C6H4SO2NaNCl·xH2O (where i‐X = 4‐C2H5, 4‐F, 4‐Cl or 4‐Br) and i‐X‐j‐Y‐C6H3SO2NaNCl·xH2O [where i‐X‐j‐Y = 2,3‐(CH3)2, 2,4‐(CH3)2, 2,5‐(CH3)2, 2‐CH3‐4‐Cl, 2,4‐Cl2 and 3,4‐Cl2]. The reactions show second‐order kinetics in [oxidant], fractional order in [amino acid] and an inverse dependence on [H+]. Addition of the reduced product of the oxidants or variation in ionic strength of the medium has no significant effect on the rates of oxidations. Mechanisms in conformity with the observed kinetics are discussed. The effective oxidizing species of the oxidants is Cl+ in different forms. The oxidizing strengths of N‐chloroarylsulphonamides depend on the ease with which Cl+ is released from them. The study reveals that the introduction of electron‐withdrawing groups such as halides to the benzene ring eases the release of Cl+ from the reagent and hence increases the oxidizing strengths of the N‐chloroarylsulphonamides. The effect of substituents on Ea of the reactions was analysed by optimising Ea with reference to log A, and log A with reference to Ea of the parent oxidant. Copyright © 2004 John Wiley & Sons, Ltd.
Reactions of carbocations with water and azide ion: calculation of rate constants from equilibrium constants and distortion energies using No Barrier Theory
Authors: Guthrie J. Peter , Pitchko Vladimir 
Published: May 2004

AbstractRate constants for the reaction of water or azide ion with various substituted benzylic carbocations can be calculated from the equilibrium constants for cation formation and distortion energies by means of the No Barrier Theory. Rate constants for the water reactions span 10 orders of magnitude. Most but not all of the azide reactions are diffusion controlled. The rate constants, and in particular those less than diffusion controlled, were successfully calculated. The set of equilibrium constants available from the literature was supplemented using alkyl chloride hydrolysis equilibrium constants and relative cation formation equilibrium constants derived from DFT/continuum calculations. The model used for these reactions allows for the entropic cost of bringing solutes together, the desolvational cost of losing hydrogen bonding solvation by water and the cost of moving the aryl ring through the solvent as the central atom changes from sp2 to sp3 hybridization and from planar to pyramidal geometry. Copyright © 2004 John Wiley & Sons, Ltd.
Mononuclear Co(III)‐complex promoted phosphate diester hydrolysis: dependence of reactivity on the leaving group
Authors: Padovani Michela , Williams Nicholas H. , Wyman Paul 
Published: May 2004

AbstractThe TrpnCo(III)(OH)(OH2)‐promoted hydrolysis of a range of methyl aryl phosphate diesters was investigated at 37°C and I = 0.1 M (NaClO4). The pH–rate profile confirms that the aqua‐hydroxy form of the complex is the only kinetically significant ionic form. At pH 6.9, all the reactions are first order in both diester and Co(III) complex. Plotting the second‐order rate constant for Co(III) complex‐promoted hydrolysis against the pKa of the leaving aryloxy group revealed a bent LFER indicating a change in rate‐limiting step. This is discussed in terms of either a change from rate‐limiting hydrolysis to rate‐limiting binding or the presence of a phosphorane intermediate. Copyright © 2004 John Wiley & Sons, Ltd.
A zinc(II) complex‐conjugated polymer for selective recognition and separation of phosphates
Authors: Aoki Shin , Jikiba Akiko , Takeda Kei , Kimura Eiichi 
Published: May 2004

AbstractA new polymer, Zn2+–cyclen complex‐conjugated polymer 4 (cyclen = 1,4,7,10‐tetraazacyclododecane), was synthesized by copolymerization of a Zn2+–(4‐vinyl)benzylcyclen complex (3, ZnL2) with ethylene glycol dimethacrylate (EGDMA). The contents of the zinc(II) ions in Zn2+–cyclen polymer 4 were determined as 36–42 μmol g−1, utilizing a Zn2+‐selective fluorophore, dansylamidoethylcyclen 10 (L3). It was found that 31% of deoxyadenosine 5′‐monophosphate (5′‐dAMP) (50 μM) is adsorbed on 4 (corresponding to 50 μM) in 20 mM HEPES (pH 7.0) with I = 0.1 (NaNO3) at 25°C. The apparent complexation constants for the 1:1 complex of ZnL2 on 4 with 5′‐dAMP and 4‐NPP, logKapp(ZnL–S2−) (S2− denotes a phosphomonoester dianion), at pH 7.0 and 25°C were determined as 4.1±0.1, which was larger than that (3.5) for the 1:1 complex of 3 (ZnL2) with 5′‐dAMP in homogeneous aqueous solution at pH 7.0 and 25°C. Deoxyadenosine (dA) and adenosine 3′,5′‐cyclic‐monophosphate (3′,5′‐cAMP), a cyclic phosphodiester monoanion, were negligibly adsorbed on Zn2+–cyclen polymer 4, implying that 4 interacts selectively with phosphomonoester dianions. For reference, Zn2+‐free polymer 8 (prepared from 4) and control polymer 9 (prepared by copolymerization of styrene with EGDMA) hardly adsorbed 5′‐dAMP, dA and 3′,5′‐cAMP. High‐performance liquid chromatography (HPLC) of mononucleotides such as 5′‐dAMP, cytidine 5′‐monophosphate (5′‐CMP), guanosine 5′‐monophosphate (5′‐GMP), and thymidine 5′‐monophosphate (5′‐dTMP) was achieved using 4 as a stationary phase and continuous gradient elution with 10:90 MeOH–1 mM HEPES (pH 7.0) and 10:90 MeOH–1 mM HEPES+10 mM (NH4)2HPO4 (pH 7.0). As expected, the retention times of mononucleotides were larger than those of the corresponding nucleosides, owing to the Zn2+‐phosphate interactions. These results indicated that Zn2+–cyclen‐conjugated polymer 4 affords a strong methodology to detect and separate biologically important phosphates. Copyright © 2004 John Wiley & Sons, Ltd.
Investigation of the sulfuryl transfer step from substrate to enzyme by arylsulfatases
Authors: Gibby Stuart G. , Younker Jarod M. , Hengge Alvan C. 
Published: May 2004

AbstractThe reactions of the arylsulfatase A (ASA) from Helix pomatia and that from Aerobacter aerogenes with p‐nitrophenyl sulfate were examined by determination of the pH dependence of Vmax/Km and by measurement of kinetic isotope effects. Both enzymes exhibit bell‐shaped pH–rate dependences for Vmax/Km. The ASA from Helix pomatia exhibits a more acidic pH optimum (pH 4–5) than the ASA from Aerobacter aerogenes (pH ∼7). The sulfuryl transfer from substrate to enzyme is general acid‐assisted in both enzymes, but isotope effects indicate differences in the synchronicity of protonation with SO bond fission. In the reaction of the Helix pomatia enzyme, protonation is synchronous with bond fission and the leaving group is fully neutralized in the transition state. In the reaction catalyzed by the Aerobacter aerogenes ASA, protonation of the leaving group lags behind bond fission and the leaving group bears a partial negative charge in the transition state. Copyright © 2004 John Wiley & Sons, Ltd.
Rate and equilibrium constants for hydrolysis and isomerization of (E)‐ and (Z)‐p‐methoxybenzaldehyde oximes
Authors: O'Ferrall Rory A. More , O'Brien Deirdre 
Published: May 2004

AbstractThe interconversion and hydrolysis of (E)‐ and (Z)‐oximes of p‐methoxybenzaldehyde in aqueous solutions of perchloric acid have been studied in the acid concentration range from pH 3 to 11 M. Kinetic measurements confirm that isomerization and hydrolysis proceed through a common tetrahedral intermediate T0. At low acid concentrations, attack of water on the protonated oxime is rate‐determining in the hydrolysis reaction and no separate isomerization is observable. However, as the acid concentration increases the attack of water becomes faster than loss hydroxylamine from T0 and E to Z isomerization is observable as a faster reaction in competition with hydrolysis. From kinetic and equilibrium measurements a comprehensive set of rate and equilibrium constants for protonation, hydrolysis and hydration of (E)‐ and (Z)‐oximes is derived. For the neutral oximes KT = [E]/[Z] = 8 and for the protonated oximes pKa = −0.55 and 0.80 for the E and Z isomers, respectively. By combining these values with measurements of oxime formation from p‐methoxybenzaldehyde and hydroxylamine, including Kadd = [T0]/[aldehyde][NH2OH] = [T0]/[oxime] = 1.8, values of pKR = −3.65 and −5.90 and K = 6.3 × 10−5 and 7.9 ×  10−6 for (E)‐ and (Z)‐oximes may also be derived. The values of pKa, pKR and K for the oximes are compared with corresponding values for p‐methoxybenzaldehyde and its hydrate (≡ T0). Copyright © 2004 John Wiley & Sons, Ltd.
Novel aromatic polyamides bearing pendent diphenylamino or carbazolyl groups
Authors: Hsiao Sheng‐Huei , Chen Chien‐Wei , Liou Guey‐Sheng 
Published: May 2004

AbstractTwo new diamines, 2,4‐diaminotriphenylamine (3) and N‐(2,4‐diaminophenyl)carbazole (4), were synthesized via the cesium fluoride‐mediated aromatic substitution reactions of 1‐fluoro‐2,4‐dinitrobenzene with diphenylamine and carbazole, followed by palladium‐catalyzed hydrazine reduction. Amorphous and soluble aramids having pendent diphenylamino and carbazolyl groups were prepared by the phosphorylation polycondensation of aromatic dicarboxylic acids with diamines 3 and 4, respectively. The aramids derived from diamine 3 had sufficiently high molecular weights to permit the casting of flexible and tough films. They exhibited excellent mechanical properties and moderately high softening temperatures in the 221–298 °C range. However, the reactions of diamine 4 with aromatic diacids gave relatively lower molecular weights products that could not afford flexible films. For a comparative purpose, the parent aramids derived from m‐phenylenediamine and aromatic diacids were also prepared and characterized. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3302–3313, 2004
Structure of a poly(2,5‐benzimidazole)/phosphoric acid complex
Authors: Cho Jaedong , Blackwell John , Chvalun Sergei N. , Litt Morton , Wang Yuan 
Published: May 2004

AbstractAs‐cast films of poly(2,5‐benzimidazole) exhibit uniplanar orientation in which the planes of the aromatic rings lie parallel to the film surface. Upon doping with phosphoric acid, the original crystalline order is lost, but the doped film can be stretched to produce films with uniaxial orientation. After thermal annealing at 540 °C, nine Bragg reflections are resolved in the fiber diagram, and these are indexed by an orthorhombic unit cell with the dimensions a = 18.1 Å, b = 3.5 Å, and c = 11.4 Å, containing four monomer units of two chains. The absence of odd‐order 00l reflections points to a 21 chain conformation, which is probably planar so that the aromatic units can be stacked along the b axis. The water and phosphoric acid contents of the crystalline structure cannot be determined exactly because of the presence of extensive amorphous regions that probably have different solvation. The best agreement between the observed and calculated intensities is for an idealized structure containing two phosphoric acids and two water molecules per unit cell. However, the phosphoric acid is probably present mainly in the form of pyrophosphoric acid and its higher oligomers. In addition, the X‐ray data are consistent with a more disordered structure containing chains with random (up and down) polarity and a lack of c‐axis registry. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2576–2585, 2004
The Flow Patterns and Wall Stresses in a Louvered‐Wall Moving Granular Filter Bed of Quartz Sand
Authors: Chou Chuen‐Shii , Chen Huang‐Hsiang 
Published: May 2004

AbstractThe flow patterns and wall stresses in a two‐dimensional louvered moving granular filter bed of quartz sand were investigated. The flow pattern histories of granular solids in the filter bed were recorded using a digital camcorder and a pressure gauge for simultaneously measuring the normal stresses as well as shear stresses of the granular solids. The static wall stress distributions produced by the granular solids were measured, and agreed with a theoretical prediction formed using the differential slice and Runge‐Kutta (order four) methods. The variations in the dynamic wall stresses with time in a moving granular filter bed were obtained and the effect of the louver angle upon the flow patterns and wall stresses was also investigated. Employing the results obtained by stress measurements and image processing, the wall pressure pulsation phenomena in a moving granular filter bed may be further understood. The results reported here provide fundamental information for the design of moving granular filter beds to act as high‐temperature flue gas cleanup filters.
A combined imaging, microthermal and spectroscopic study of a multilayer packaging system
Authors: Woodward I. , Ebbens S. , Zhang J. , Luk S. , Patel N. , Roberts C.J. 
Published: May 2004

AbstractThe effectiveness of a packaging solution for the pharmaceutical and food industry is dependent on the integrity of the constituent layers and the interfaces formed between them. The deconvolution and analysis of the many intimate layers found in packaging is analytically challenging, requiring techniques capable of identifying sub‐micron regions. Here we have characterized the chemical and physical nature of the layers in a multilayer packaging system along with the interfaces, using a combination of high‐resolution atomic force microscopy (AFM), microthermal analysis using scanning thermal microscopy (SThM), and Fourier transform infrared (FT‐IR) spectroscopy. In particular, localized thermal analysis is shown to reveal the thermal transitions of the individual layers, but it was found that care must be exercised when melting through one layer to the next, as this can result in overestimates of melting temperatures of the underlying layer due to excess power loss from the SThM probe to the already molten top layer surrounding the probe. Copyright © 2004 John Wiley & Sons, Ltd.
The effect of high‐pressure food processing on the sorption behaviour of selected packaging materials
Authors: Caner C. , Hernandez R.J. , Pascall M. , Balasubramaniam V.M. , Harte B.R. 
Published: May 2004

AbstractThe sorption behaviour and flavour‐scalping potential of selected packaging films in contact with food simulant liquids (FSLs) (ethanol and acetic acid solutions) were evaluated after high‐pressure processing (HPP). The films used were monolayer polypropylene (PP), a multilayer (polyethylene/nylon/ethylene vinyl alcohol/polyethylene: PE/nylon/EVOH/PE), film and a metallized (polyethylene terephthalate/ethylene–vinyl acetate/linear low‐density polyethylene: metallized PET/EVA/LLDPE) material. D‐limonene was used as the sorbate and was added to each of the FSLs. After HPP treatment at 800 MPa, 10 min, 60°C, the amount of D‐limonene sorbed by the packaging materials and the amount remaining in the FSL was measured. Untreated controls (1 atm, 60°C and 40°C) were also prepared. Extraction of the D‐limonene from the films was performed using a purge/trap method. D‐limonene was quantified in both the films and the FSL, using gas chromatography (GC). The results showed that D‐limonene concentration, in both the films and the food simulants, was not significantly affected by HPP, except for the metallized PET/EVA/LLDPE. Significant differences in D‐limonene sorption were found in comparison with the control pouches. The results also showed that changes in temperature significantly affected the sorption behaviour of all films. Copyright © 2004 John Wiley & Sons, Ltd.
Stress recovery during an ocean boat race
Authors: Gunnarsson Lars‐Gunnar , Bäck Hans , Jones Ian , Olsson Tommy 
Published: May 2004

AbstractThe aim was to study the effects of intense and sustained stress associated with a several months long endurance test with special emphasis on the biology of recovery. Biological stress markers of ‘catabolism’ (cortisol in saliva and HbA1c in blood) and ‘anabolism’ (testosterone in saliva) were followed in crewmembers during a 9‐month around the world sailing race. During sustained mental stress the diurnal cortisol curve was flattened, HbA1c was at the upper part of the normal range and testosterone levels were low. In the latter part of the race the crew mastered the situation and the stress markers were normalized. Our longitudinal approach disclosed a striking shift in the profile of stress markers from a ‘catabolic’ to an ‘anabolic’ state, corresponding to a decline of mental stress. Copyright © 2004 John Wiley & Sons, Ltd.
Update on transcervical sterilization
Authors: Neuwirth R.S. 
Published: May 2004

AbstractTranscervical sterilization techniques as of 1980 are reviewed. A personal and literature search is reported on developments between 1980 and 1992. The potential of endometrial ablation for a transcervical method of fertility control is explored. An appraisal of the more promising methods for future study is made, including silastic tubal plugs, quinacrine, Femcept delivery of an iodine mixture and endometrial ablation.