bluuebunny/crossref_metadata_2025 huggingface dataset:
Tumor R2* is a prognostic indicator of acute radiotherapeutic response in rodent tumors
Authors: Rodrigues Loreta M. , Howe Franklyn A. , Griffiths John R. , Robinson Simon P.
Published: March 2004

Purpose

To test the prognostic potential of tumor R2* with respect to radiotherapeutic outcome. Blood oxygenation level dependent (BOLD) MRI images are sensitive to changes in deoxyhemoglobin concentration through the transverse MRI relaxation rate R2* of tissue water, hence the quantitative measurement of tumor R2* may be related to tissue oxygenation.

Methods and Materials

Tumor growth inhibition in response to radiation was established for both GH3 prolactinomas and RIF‐1 fibrosarcomas with animals breathing either air or carbogen during radiation. In a separate cohort, the baseline R2* and carbogen (95% O2, 5% CO2)‐induced ΔR2* of rat GH3 prolactinomas and murine RIF‐1 fibrosarcomas were quantified using multigradient echo (MGRE) MRI prior to radiotherapy, and correlated with subsequent tumor growth inhibition in response to ionizing radiation, while the animals breathed air.

Results

A radiation dose of 15 Gy caused pronounced growth delay in both tumor models and transient regression of the GH3 prolactinomas. When the animals breathed carbogen during radiation, the growth delay/regression was enhanced only in the GH3 prolactinomas. The GH3 prolactinomas, which exhibit a relatively fast baseline R2* and large ΔR2* in response to carbogen breathing prior to radiotherapy, showed a substantial reduction in normalized tumor volume to 66 ± 3% with air breathing and 36 ± 5% with carbogen seven days after 15 Gy irradiation. In contrast, the effect of 15 Gy on the RIF‐1 fibrosarcomas, which give a relatively slow baseline R2* and negligible ΔR2* response to carbogen prior to treatment, showed a much smaller growth inhibition (143 ± 3% with air, 133 ± 12% with carbogen).

Conclusion

Quantitation of tumor R2* and carbogen‐induced ΔR2* by MGRE MRI provides completely noninvasive prognostic indicators of a potential acute radiotherapeutic response. J. Magn. Reson. Imaging 2004;19:482–488. © 2004 Wiley‐Liss, Inc.
Time‐of‐flight quantitative measurements of blood flow in mouse hindlimbs
Authors: Wagner Shawn , Helisch Armin , Bachmann Georg , Schaper Wolfgang
Published: March 2004

Purpose

To evaluate the feasibility of using time‐of‐flight (TOF) imaging to directly measure hindlimb blood flow in a mouse model of peripheral vascular disease.

Materials and Methods

Four tubes were imaged simultaneously (diameters = 0.39 mm, 0.59 mm, and two at 1.46 mm) with a 1.0 mM copper sulfate solution for 19 flow velocities. In vivo measurements were performed in the hindlimbs of three mouse strains—C57BL/6 (N = 5), BALB/c (N = 5), and 129S2/Sv (N = 5)—three weeks after femoral artery ligation with a calibration standard.

Results

The flow phantom showed that the intensity was linear (r2 = 0.92) over the pertinent blood flow velocities in the mouse hindlimbs. Measurements of the blood flow in the distal hindlimbs in different strains of mice (combination of both the venous and arterial flows) were obtained 21 days after right‐sided femoral artery occlusion. The results showed that under similar conditions of anesthesia and temperature, SV129 mice on the nonligated side had the highest flows (0.50 ± 0.07 mL/minute), followed by C57BL/6 (0.28 ± 0.04 mL/minute) and BALB/c (0.23 ± 0.05 mL/minute), P < 0.02. The ligated side measurements (SV129, 0.31 ± 0.05 mL/minute (P = 0.02); C57BL/6, 0.21 ± 0.02 mL/minute (P = 0.13); and BALB/c, 0.12 ± 0.02 mL/minute (P= 0.06)) showed a trend in BALB/c and C57BL/6 and significant differences in SV129 for incomplete recovery three weeks after surgery, compared to the nonligated side.

Conclusion

Two‐dimensional TOF imaging permits quantitative in vivo measurements of hindlimb blood flow in a mouse model of peripheral vascular disease without the need of contrast injection, offering advantages of serial imaging not limited by tissue penetration. J. Magn. Reson. Imaging 2004;19:468–474. © 2004 Wiley‐Liss, Inc.
Screening of colonic tumors by air‐inflated magnetic resonance (MR) colonography
Authors: Lam Wynnie W.M. , Leung Wai K. , Wu Justin K.L. , So Nina M.C. , Sung Joseph J.Y.
Published: March 2004

Purpose

To assess the accuracy of air‐inflated magnetic resonance (MR) colonography for the detection of colonic lesions.

Materials and Methods

A total of 36 patients underwent both colonoscopy and air‐inflated MR colonography. Breath‐hold sequences (volumetric interpolated breath‐hold examination (VIBE) coronal, and half‐Fourier acquisition single‐shot turbo spin‐echo (HASTE) axial and coronal, both supine and prone) were performed with a 1.5T scanner. The detection of colonic lesions by MR colonography was then correlated with the findings from the colonoscopy performed on the same day.

Results

Two patients were unable to complete the MR colonography examination. Analysis was based on the results from 34 patients (17 males and 17 females, 38–70 years old, mean age = 54.9 years) who completed both examinations. MR colonography depicted two of two colonic tumors, one of one P4 (>2 cm) polyp, one of two P2 (0.5–1 cm) polyps, and two of 11 P1 (<0.5 cm) polyps. False‐positive MR colonography interpretations were noted for one P1 polyp and two P2 polyps. The overall sensitivity, positive predictive value, and accuracy of MR colonography were 38%, 67%, and 46.2%, respectively. For the detection of endoluminal lesions >5 mm, air‐inflated MR colonography yielded a sensitivity of 75%, specificity of 93.3%, accuracy of 91.2%, positive predictive value of 60%, and negative predictive value of 96.6%.

Conclusion

Air‐inflated MR colonography is a new technique that deserves further investigation. J. Magn. Reson. Imaging 2004;19:447–452. © 2004 Wiley‐Liss, Inc.
Real‐time high‐resolution MRI for the assessment of gastric motility: Pre‐ and postpharmacological stimuli
Authors: Ajaj Waleed , Lauenstein Thomas , Papanikolaou Nickolas , Holtmann Gerald , Goehde Susanne C. , Ruehm Stefan G. , Debatin Joerg F.
Published: March 2004

Purpose

To determine the practicality of MRI using a new real‐time sequence for the assessment of gastric motion, and quantify the effects of motility‐modifying substances.

Materials and Methods

Six healthy volunteers ingested 400 mL of a high‐calorie liquid nutrient. Two‐dimensional real‐time TrueFISP sequences were acquired for up to 30 minutes following the ingestion. The acquisition plane was chosen parallel to the axis of the gastric antrum. The examination was performed on three separate days with and without i.v. administration of 10 mg metoclopramide or 20 mg scopolamine. A motility index was calculated for each real‐time data set.

Results

Delineation of the gastric lumen proved easy and robust. The intravenous application of motility‐modifying agents resulted in significant changes in the motility index. The administration of metoclopramide resulted in an average increase of the index by a factor of 1.5, whereas the application of scopolamine led to a decrease of the index by a factor of 3.0.

Conclusion

TrueFISP MRI performed well in depicting the gastric lumen and assessing gastric motility. Furthermore, we were able to evaluate and quantify the effect of motility‐modifying agents. The noninvasive nature of MRI makes this imaging modality an attractive alternative to conventional invasive diagnostic tools for gastric motility disorders and monitoring of therapy. J. Magn. Reson. Imaging 2004;19:453–458. © 2004 Wiley‐Liss, Inc.
Tolerance of MRI vs. SPECT myocardial perfusion studies—A patient survey
Authors: Sparrow Patrick , Plein Sven , Jones Tim R. , Thorley Penelope J. , Hale Claire , Sivananthan Mohan U.
Published: March 2004

Purpose

To compare patients' perceived satisfaction and tolerance of magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT) myocardial perfusion imaging.

Materials and Methods

A questionnaire was sent retrospectively to 41 patients who had undergone both SPECT and MRI myocardial perfusion scans at our institution. The questionnaire assessed SPECT and MRI separately, and in a separate section compared the tests directly. The answers were scored and analyzed for statistical significance by the use of Wilcoxon signed‐ranks and χ2 tests.

Results

Thirty‐five completed questionnaires were returned. In a direct comparison, 12 patients (34%) preferred MRI overall, nine (26%) preferred SPECT, and 14 (40%) expressed no preference. The ratings for the overall comfort of the scans were similar, with a score of 5.8 for SPECT and 5.7 for MRI (on a scale of 1–10). More patients stated a preference for MRI on scan comfort, duration, and safety (no statistical significance), but it was less well rated than SPECT for space on the scanner (P = 0.008). Three patients (9%) stated that they would not have an MRI scan again, while two patients (6%) said they would not repeat a SPECT scan.

Conclusion

MRI myocardial perfusion imaging represents an acceptable alternative to SPECT with respect to patient tolerance and satisfaction. J. Magn. Reson. Imaging 2004;19:410–416. © 2004 Wiley‐Liss, Inc.
Characterization of peptides by liquid chromatography/electrospray ionization mass spectrometry using silver nitrate as a post‐column complexant
Authors: Cheguillaume Ghislain , Buchmann William , Desmazières Bernard , Tortajada Jeanine
Published: March 2004

Two model peptides, des‐Arg1‐bradykinin (DAB) and bradykinin (B), were cationized by Ag+ after their separation by reversed‐phase liquid chromatography (RPLC) prior to mass spectrometry (MS). Silver nitrate solution was used as a post‐column reagent. The RPLC and MS experimental conditions were optimized using flow injection in order to obtain sufficiently abundant silver adducts to permit MS/MS experiments. The use of water–methanol with 0.1% formic acid as mobile phase allowed a good chromatographic separation of the two peptides with a polymeric stationary phase and sufficiently abundant silver‐containing adducts, [M + Ag + H]2+ and [M + 2Ag]2+. The gas‐phase dissociation of [DAB + Ag + H]2+ and [DAB + 2Ag]2+ led to interpretable mass spectra during the on‐line cationization experiment. Most of the ions obtained by dissociating [DAB + Ag + H]2+ and [DAB + 2Ag]2+ species are silver‐containing ions but the ions produced depend on the parent. The ions coming from the dissociation of the doubly charged silver adducts [DAB + Ag + H]2+ or [DAB + 2Ag]2+ are of interest compared with those coming from the singly charged silver species or doubly charged protonated species. The fragmentation of the doubly charged silver adducts provides ions over the entire mass range. Although the presence of several prolines in des‐Arg1‐bradykinin prevents the formation of some expected ions, the observation of triplets [an−H + Ag]+, [bn−H + Ag]+ and [bn + OH + Ag]+ produced by the dissociation of on‐line Ag+‐cationized peptides could contribute to greater success of automatic sequencing of peptides. Copyright © 2004 John Wiley & Sons, Ltd.
Determination of fatty acid positions in native lipid A by positive and negative electrospray ionization mass spectrometry
Authors: Sforza Stefano , Silipo Alba , Molinaro Antonio , Marchelli Rosangela , Parrilli Michelangelo , Lanzetta Rosa
Published: March 2004

Lipid A is the endotoxic principle of the lipopolysaccharide fraction from Gram‐negative bacteria. It is involved in the elicitation of cytokine production that leads to massive inflammation and to septic shock as a lethal consequence. For this reason, the structural elucidation of lipopolysaccharides from toxic Gram‐negative bacteria is an important and complicated task, mainly owing to its natural heterogeneity. Here, a new methodology to infer the distribution of the primary and secondary acyl residues is described, based on electrospray ionization mass spectrometry (ESI‐MS) of intact lipid A under high cone voltage in order to achieve in‐source fragmentation. Under these conditions, acyl fragmentation is induced and a different regioselective cleavage of secondary fatty acids is observed in positive and negative ESI‐MS, allowing the rapid identification of the lipid A structure. Copyright © 2004 John Wiley & Sons, Ltd.
Comparison of sustained off‐resonance irradiation collisionally activated dissociation and multipole storage‐assisted dissociation for top‐down protein analysis
Authors: Keller Karin M. , Brodbelt Jennifer S. , Hettich Robert L. , Berkel Gary J. Van
Published: March 2004

Tandem mass spectrometric data acquired for small (8–18 kDa) intact proteins by sustained off‐resonance irradiation collisionally activated dissociation (SORI‐CAD) and multipole storage‐assisted dissociation (MSAD) were compared, and the results indicate that the two activation methods do not always provide the same fragmentation patterns. In MSAD experiments, the charge state distribution made available by the ionization conditions may dictate the range of fragment ions that can be generated. In addition, conditions of high space charge within the hexapole impair transmission and/or trapping of high m/z species, which can result in loss of important precursor and product ions. Finally, the non‐resonant nature of activation in MSAD can provide access to secondary dissociation processes that are not available by SORI. Because of these considerations, MSAD is less reliable than SORI for generating sequence tag data. However, it appears that MSAD samples ‘preferred’ cleavage processes (i.e. those occurring at D and P residues) just as well as SORI, which implies that MSAD data may be somewhat more compatible with search algorithms that utilize unprocessed fragment ion masses. Copyright © 2004 John Wiley & Sons, Ltd.
Identification of the hydrolysis products of AlCl3·6H2O by electrospray ionization mass spectrometry
Authors: Sarpola Arja , Hietapelto Vesa , Jalonen Jorma , Jokela Jukka , Laitinen Risto S.
Published: March 2004

The hydrolysis reactions of AlCl3 in 0.1 M aqueous solutions at pH 3.27–4.20 were monitored by electrospray ionization time‐of‐flight mass spectrometry (ESI‐ToF MS) as a function of time. The cationic and anionic ESI mass spectra of aluminum(III) solutions gave strong evidence of the presence of a variety of monomeric and polymeric complexes. Competition between the OH− and Cl− ligands within the same aluminum core was observed. The influence of the sample cone voltage on the product distribution was also explored. The optimum sample cone voltage for the cationic spectra was 70 V. For the anionic spectra no optimum sample cone voltage was found and the appearance of the anionic spectra was strongly dependent on the sample cone voltage within the whole range explored. Copyright © 2004 John Wiley & Sons, Ltd.
A novel class of chemically modified iodo‐containing resins: design, synthesis and application to mass spectrometry‐based proteome analysis
Authors: Zhang Li , Guo Yin‐Long , Liu Han‐Qing
Published: March 2004

A novel class of chemically modified iodo‐containing resins with isotope‐labeled tagging for mass spectrometry‐based proteome analysis is described. This iodo‐containing resin contains a thiol‐reactive group that is used to capture the cysteine (Cys)‐containing peptides from peptide mixtures, one ‘tag’ amino acid, and an aminomethyl polystyrene resin with Rink Amide Linker. The ‘tag’ amino acid is synthesized in both heavy and light isotope‐coded forms and therefore permits the direct relative quantification of peptides/proteins through mass spectrometric analysis. In the iodo‐containing resin strategy, the Cys‐containing peptides of two samples covalently captured by either light or heavy iodo‐containing resin were mixed and washed extensively under stringent conditions. Then the Cys‐containing peptides were retrieved by acid‐catalyzed elution. Finally, the eluted peptides were directly analyzed by micro liquid chromatography/mass spectrometry for identification and relative quantification. The iodo‐containing resins were synthesized by a simple but effective method. Their abilities to identify and quantify the Cys‐containing part in two samples were proved by the analysis of mixtures of amino acids, peptides and proteins. Copyright © 2004 John Wiley & Sons, Ltd.
Method of moments modelling of cylindrical microwave integrated circuits interconnections
Authors: Al Salameh M. S. , Olaimat A. M.
Published: March 2004

In this paper, a numerical technique suitable for characterizing a wide variety of interconnection configurations printed on cylindrical surfaces, is presented. The interconnection lines may have either finite or infinitesimal cross‐sections. To model cylindrical interfaces, suitable space‐domain integral equations are formulated to represent the potential on conductors and electric field at dielectric interfaces. The solution of the integral equations is then obtained numerically by applying the method of moments (MOM). The objective of this approach is to determine the capacitance matrix of cylindrical interconnection systems with different configurations. From the capacitance matrix, other quantities such as characteristic impedance, coupling coefficient and effective permittivity can be determined. The numerical technique described in this paper is implemented as a general computer program. Various circular cylindrical as well as elliptical cylindrical structures have been solved including microstrip lines and coplanar waveguide lines. The results obtained compare very well with other published data. Copyright © 2004 John Wiley & Sons, Ltd.
Input resistance is voltage dependent due to activation of Ih channels in rat CA1 pyramidal cells
Authors: Surges Rainer , Freiman Thomas M. , Feuerstein Thomas J.
Published: March 2004

The contribution of the hyperpolarization‐activated cation current (Ih) to input resistance (RN) and resting potential (RP) was investigated during whole‐cell patch‐clamp recordings in CA1 pyramidal cells of rat hippocampal slices. In current‐clamp mode, RN was determined at different membrane potentials. RN decreased with increasing hyperpolarization, from about 260 MΩ to 140 MΩ at potentials of about −60 mV and −110 mV, respectively. Both the potential of half‐maximal reduction of RN and the potential of half‐maximal Ih activation (determined in voltage‐clamp mode) were approximately −90 mV. The analysis of the voltage sag indicative of Ih activation revealed a preferential activity of Ih channels in a voltage range between −70 and −95 mV. ZD7288 (50 μM), a specific Ih blocker, led to a hyperpolarization by about 4.8 mV, increased RN by approximately 45% within a potential range between −65 and −80 mV, and abolished the voltage dependence of RN. Gabapentin (GBP, 100 μM), an Ih channel agonist, led to a depolarization by about 2.4 mV and reduced RN by about 20% within a potential range between −65 and −80 mV. In conclusion, our data show that RN is voltage dependent due to Ih channel activation and that Ih channels are preferentially active at voltages between −70 and −95 mV. Furthermore, we demonstrated that RN can be modulated by antiepileptic drugs such as GBP, which may partly explain its antiepileptic effect as due to decreasing the sensitivity to excitatory input. © 2004 Wiley‐Liss, Inc.
Mulching effects on phosphorus and sulfur concentrations in a Miamian soil in central Ohio, USA
Authors: Saroa G. S. , Lal R.
Published: March 2004

In addition to nitrogen (N), phosphorus (P) and sulfur (S) elements are also essential to conversion of biomass carbon into soil humus. Therefore, soil analyses were done on two long‐term mulching experiments initiated in 1989 and 1996 on a Crosby silt loam (Aeric Ochraqualf or Stagnic Luvisol) soil in central Ohio to assess P and S dynamics in soil for different rates of mulching. Mulch treatments were 0, 8 and 16 Mg ha−1 y−1 without any crop cultivation. Our objectives were to assess: (i) the effect of different mulch rates on P and S concentrations, and soil organic carbon sequestration; (ii) association of available and total P and S with different particle size fractions; and (iii) temporal changes in available and total P and total S concentrations within aggregate and particle size fractions with duration of mulching. Soil samples from 0 to 5 and 5 to 10 cm depths were obtained in November 2000. Mulch rate significantly increased Bray‐P in 0 to 5 and 5 to 10 cm depths but had no significant effect on total P after 4 years of mulching. Total P concentration in the 5 to 10 cm layer increased significantly with mulch application after 11 years, but the total S concentration was not affected. Total P in aggregates>2 mm size at 5 to 10 cm depth was significantly higher than whole soil after 11 years of mulching. More than 50 per cent of the total P was associated with clay fraction, and P concentration increased with duration of mulching. The enrichment factor for total P was in the order: clay>sand>silt. Total S concentration in aggregates increased with increase in aggregate size for both depths, and was in the order: clay>sand>silt. The clay fraction accounted for 48 per cent of total S after 4 years of mulching and 50 per cent after 11 years of mulching. The enrichment factor of S in clay and sand fractions increased with duration of mulching and with depth for clay, and decreased for sand. The C:P and C:S ratios decreased both with duration of mulching and particle size. Availability of P and S is essential for humification of carbon input in crop residue mulch. Copyright © 2004 John Wiley & Sons, Ltd.
Laying the groundwork: First steps in evaluating leadership development
Authors: Martineau Jennifer
Published: March 2004

Evaluating the impact of an organization's efforts to develop leaders is challenging. However, if the
evaluation is set up properly, it will not only improve development efforts, and thereby the quality of
leadership, but also contribute to the effectiveness of the organization.
Erosion Induced Controllable Release of Gliclazide Encapsulated Inside Degradable Polymeric Particles
Authors: Zhao Yue , Chen Wenna , Cai Qing , Wang Shenguo , Bo Jun , Wu Chi
Published: March 2004

Summary: The microphase inversion of water‐insoluble poly(L‐lactide), “poly[(L‐lactide)‐co‐glycolide] and polylactide‐block‐poly(ethylene oxide)‐block‐polylactide from THF to water can result in narrowly distributed stable particles. Gliclazide, a commercial drug, can be encapsulated inside during the process. The formation and degradation of such particles was studied by laser light scattering. In comparison with the corrosion of a bulk material, the degradation of each particle is so fast that we only detect the decrease of the particle number, not the corrosion of individual particles. Therefore, the degradation is a “one‐by‐one” random process, just like the chemical reaction of molecules in solution. The disappearing rate of the particle number is nearly independent of time, ideal for the controlled release of drugs encapsulated inside. The amount of encapsulated gliclazide depends on the copolymer's hydrophobicity (composition), while the releasing rate mainly is, directly related to the disappearing rate of the particles. The correlation between the fluorescence intensity and the degradation was used to study the kinetics of gliclazide releasing. The releasing pattern is controllable with a proper choice of the drug loading, copolymer composition, pH and temperature.

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Biosynthesis and Compositional Regulation of Poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyhexanoate)] in Recombinant Ralstonia eutropha Expressing Mutated Polyhydroxyalkanoate Synthase Genes
Authors: Tsuge Takeharu , Saito Yu , Kikkawa Yoshihiro , Hiraishi Tomohiro , Doi Yoshiharu
Published: March 2004

Summary: A new strategy for bacterial polyhydroxyalkanoate (PHA) production by recombinant Ralstonia eutropha PHB−4 harboring mutated PHA synthase genes (phaCAc) from Aeromona caviae was investigated. The strain harboring wild‐type phaCAc gene produced a PHA copolymer consisting of (R)‐3‐hydroxybutyrate and (R)‐3‐hydroxyhexanoate [P(3HB‐co‐3HHx)] with 3.5 mol‐% of 3HHx fraction from soybean oil. When the mutants of phaCAc gene were applied to this production system, 3HHx fraction in copolymers was varied in the range of 0–5.1 mol‐%. Thus, the regulation of PHA copolymer compositions has been achieved by the use of mutated PHA synthase genes.

Relationship between PHA synthase activity and 3HHx fraction in P(3HB‐co‐3HHx).

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Relationship between PHA synthase activity and 3HHx fraction in P(3HB‐co‐3HHx).
Ring‐Opening Polymerization of L‐Lactide and Preparation of Its Microsphere in Supercritical Fluids
Authors: Pack Ji Won , Kim Soo Hyun , Park Soo Young , Lee Youn‐Woo , Kim Young Ha
Published: March 2004

Summary: The ring‐opening polymerization of L‐lactide initiated by stannous octoate was carried out in supercritical chlorodifluoromethane (scR22) at various reaction conditions (time and temperature) and reactant concentrations (initiator, monomer, and solvent). The monomer conversion increased to ca. 70% on increasing the reaction time to 1 h. The molecular weight of the poly(L‐lactide) (PLLA) product also increased to ca. 160 000 g · mol−1 over the same period. Increasing reaction temperature from 90 to 130 °C resulted in increased monomer conversion and PLLA molecular weight. A series of polymerizations conducted at various 1‐dodecanol and stannous octoate concentrations suggested that stannous octoate does not act as an initiator by itself, and that the tin‐alkoxide formed from 1‐dodecanol and stannous octoate serves as the initiating species in scR22. While enhancements of the monomer conversion and PLLA molecular weight were observed with increasing monomer concentration, the chlorodifluoromethane concentration had the opposite on both. After the polymerization, PLLA microspheres were prepared in situ by using a continuous supercritical antisolvent process without residual organic solvent and monomer to yield highly purified microspheres for environmental and biomedical applications.

Relation between monomer conversion (○) and poly(L‐lactide) molecular weight (•).

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Relation between monomer conversion (○) and poly(L‐lactide) molecular weight (•).
Fermentative Production of Chemicals That Can Be Used for Polymer Synthesis
Authors: Lee Sang Y. , Hong Soon H. , Lee Seung H. , Park Si J.
Published: March 2004

Summary: The fermentative production of chemicals that can be used as monomers for the synthesis of polymers has become an important topic in biotechnology research because of the limited nature of petroleum and environmental issues. In particular, the fermentative production of metabolites such as dicarboxylic acids, amino acids, and diols, which are suitable as building blocks for subsequent polymerization, has attracted much attention. Various wild‐type and metabolically engineered microorganisms have been developed for the efficient production of these chemicals from renewable resources. In addition, the development of fermentation strategies to achieve the highest possible productivities has been another focus of research, considering that these monomers should be produced at costs low enough to compete with petroleum‐derived ones. In this paper, the metabolic pathways leading to the synthesis of such important monomers including succinic acid, lactic acid, fumaric acid, propan‐1,2‐diol, and propan‐1,3‐diol are reviewed. In addition, the metabolic engineering and fermentation strategies for their production are reviewed.

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Biodegradable Water Absorbent Synthesized from Bacterial Poly(amino acid)s
Authors: Kunioka Masao
Published: March 2004

Summary: Biodegradable hydrogels prepared by γ‐irradiation from microbial poly(amino acid)s have been studied. pH‐Sensitive hydrogels were prepared by the γ‐irradiation of poly(γ‐glutamic acid) (PGA) produced by Bacillus subtilis and poly(ε‐lysine) (PL) produced by Streptomyces albulus in aqueous solutions. When the γ‐irradiation dose was 19 kGy or more, and the concentration of PGA in water was 2 wt.‐% or more, transparent hydrogels could be produced. For the 19 kGy dose, the produced hydrogel was very weak, however, the specific water content (wt. of absorbed water/wt. of dry hydrogel) of this PGA hydrogel was approximately 3 500. The specific water content decreased to 200, increasing when the γ‐irradiation dose was over 100 kGy. Under acid conditions or upon the addition of electrolytes, the PGA hydrogels shrunk. The PGA hydrogel was pH‐sensitive and the change in the volume of the hydrogel depended on the pH value outside the hydrogel in the swelling medium. This PGA hydrogel was hydrodegradable and biodegradable. A new novel purifier reagent (coagulant), made from the PGA hydrogels, for contaminated turbid water has been found and developed by Japanese companies. A very small amount of this coagulant (only 2 ppm in turbid water) with poly(aluminum chloride) can be used for the purification of turbid water.

A PL aqueous solution also can change into a hydrogel by γ‐irradiation. The specific water content of the PL hyrdogel ranged from 20 to 160 depending on the preparation conditions. Under acid conditions, the PL hydrogel swelled because of the ionic repulsion of the protonated amino groups in the PL molecules. The rate of enzymatic degradation of the respective PL hydrogels by a neutral protease was much faster than the rate of simple hydrolytic degradation.

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Grafting of Polystyrene onto Poly(butyl acrylate) and Polystyrene Backbones Using Functionalized Methacrylates
Authors: Böhme Karsten , Peppers Michel , Schmidt‐Naake Gudrun
Published: March 2004

Summary: Grafting of terminal epoxide‐functionalized polystyrene onto poly[styrene‐co‐(2‐hydroxyethyl methacrylate)] or poly[(butyl acrylate)‐co‐(2‐hydroxyethyl methacrylate)] backbones was carried out by coupling reactions catalyzed by boron trifluoride. The functionalized backbones were prepared by free radical copolymerization of 2‐hydroxyethyl methacrylate (HEMA) with styrene or butyl acrylate. For the synthesis of terminal functionalized polymer chains a side reaction of the TEMPO‐mediated free radical polymerization of methacrylates could be used successfully to convert TEMPO‐terminated polymers into terminal epoxide‐functionalized polymers by the use of glycidyl methacrylate. The number of epoxide units attached to the backbone was directly related to the TEMPO concentration during the disproportionation reaction. Taking P(S‐co‐HEMA) as well as P(BuA‐co‐HEMA) backbones in coupling reactions with different epoxy‐functionalized polystyrenes in the presence of boron trifluoride, graft polymers with up to 7 and 37 side chains per backbone were produced.

Molecular weight distribution curves of a linking experiment between P(BuA‐co‐HEMA) backbones and epoxide‐functionalized polystyrene side chains.

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Molecular weight distribution curves of a linking experiment between P(BuA‐co‐HEMA) backbones and epoxide‐functionalized polystyrene side chains.
Stable Free Radical Polymerization Kinetics of Alkyl Acrylate Monomers Using in situ FTIR Spectroscopy: Influence of Hydroxyl‐Containing Monomers and Additives
Authors: Lizotte Jeremy R. , Long Timothy E.
Published: March 2004

Summary: The homopolymerization and copolymerization of various alkyl acrylate monomers was studied under stable free radical polymerization (SFRP) conditions using in situ FTIR spectroscopy to monitor polymerization kinetics. The IR absorbance corresponding to the CH deformation of the monomer (968 cm−1) was measured to determine monomer conversion in real‐time fashion. The monomer disappearance profiles were subsequently converted to pseudo‐first order kinetic plots. Altering the alkyl ester chain length and configuration did not reveal a significant trend in the resulting polymerization kinetics. However, addition of 2‐hydroxyethyl acrylate (HEA) to a polymerization of n‐butyl acrylate (nBA) substantially accelerated the rate of total monomer conversion, increasing the observed rate constant almost two times. 1H NMR spectroscopy also showed that the resulting HEA/nBA copolymers were enriched with the HEA monomer. Moreover, a similar but enhanced effect was also observed upon the addition of small amounts of dodecanol to an n‐butyl acrylate homopolymerization resulting in more than a doubling of the observed rate constant.

Resonance forms associated with the DEPN nitroxide and stabilization resulting from hydrogen bonding.

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Resonance forms associated with the DEPN nitroxide and stabilization resulting from hydrogen bonding.
On Alternative Thermal Methods for Discerning the Miscibility in Blends of Isotactic Polystyrene and Poly(cyclohexyl methacrylate) with Closely‐Spaced Glass Transitions
Authors: Chang Li‐Ling , Woo Ea‐Mor , Chiang Chih‐Pei
Published: March 2004

Summary: Thermal characterizations were performed to further discern the miscibility and qualitative interactions in blends of isotactic polystyrene (iPS) and poly(cyclohexyl methacrylate) (PCHMA). A method based on the enthalpy relaxation of the blends was used to overcome the difficulty or ambiguity in resolving closely‐spaced glass transitions of these two constituent polymers. Interactions between the blend components were further estimated by two additional methods: the blend's glass transition temperature (Tg) and the melting point depression. The blend's Tg method yielded a χ12 value ranging from −0.0016 (i.e., almost 0) to −1.98 (with the values depending on the amorphous PCHMA contents in the blends) in the temperature range of 95–110 °C, whereas the melting point depression led to χ12 = −0.039 at 240 °C. The interaction parameters obtained from these two methods are negative, confirming the miscibility with weak interactions. The results of these alternative thermal characterizations further clarified that the iPS/PCHMA blends, whose Tg's are too close to allow the use of conventional Tg criteria, are indeed completely miscible.

Specific heat increment (ΔCP) at Tg for the iPS/PCHMA blends.

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Specific heat increment (ΔCP) at Tg for the iPS/PCHMA blends.
What influences the relationship between customer satisfaction and repurchase intention? Investigating the effects of adjusted expectations and customer loyalty
Authors: Yi Youjae , La Suna
Published: March 2004

This study examines how loyalty influences the relationship between customer satisfaction (CS) and repurchase intention (RPI). Considering the effect of time, the study introduces adjusted expectations, which are expectations updated after consumption experience. The present study investigates the role of adjusted expectations in the CS–RPI link. With structural‐equation analysis, the proposed model was tested in the family‐restaurant setting. The results show that adjusted expectations can mediate the effect of CS on RPI. The results also indicate that processes underlying the CS–RPI link are different between low‐loyalty and high‐loyalty customers. Specifically, the transient route, which reflects the indirect path from CS to RPI via adjusted expectations, has a greater impact for nonloyals than for loyals. On the other hand, the chronic route, which represents the direct path from CS to RPI, has a greater impact for loyals than for nonloyals. CS is found to have no direct influence on RPI for low‐loyalty customers. © 2004 Wiley Periodicals, Inc.
Optical Probes for Monitoring Intercalation and Exfoliation in Melt‐Processed Polymer Nanocomposites
Authors: Maupin Paul H. , Gilman Jeffrey W. , Harris Richard H. , Bellayer Severine , Bur Anthony J. , Roth Steven C. , Murariu Marius , Morgan Alexander B. , Harris Joseph D.
Published: March 2004

Summary: Laser‐induced fluorescence spectroscopy of the optical probe Nile Blue A in polymer clay nanocomposites is described. Concentration quenching of the fluorescence dominates the probe behavior until the clay platelets are physically separated by polymer intercalation. Further separation into an exfoliated structure results in an intense increase in probe fluorescence. Preliminary results indicate the ability to discriminate between intercalated and exfoliated structures in nanocomposites formed by melt processing.

Polyamide 6 nanocomposites: Purple, 1 minute processing (left). Red, 7 minute processing (right).

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Polyamide 6 nanocomposites: Purple, 1 minute processing (left). Red, 7 minute processing (right).
Rodlike Cellulose Microcrystals: Structure, Properties, and Applications
Authors: de Souza Lima M. Miriam , Borsali Redouane
Published: March 2004

Summary: In this article we present some interesting properties of rodlike cellulose microcrystals (so‐called “whiskers”). These microcrystals can be obtained from different cellulose sources such as wood, cotton, or animal origin. When submitted to acid hydrolysis, the cellulose fibers yield stable aqueous suspensions because of the presence of negative charges on the surface of the microcrystallites during the hydrolysis process. The obtained microcrystals are rod‐shaped particles, the dimensions of which depend on the cellulose origin. For instance, the cotton whiskers have typical dimensions varying from 100 to 300 nm in length, L, and 8 to 10 nm in diameter, d, while those of the tunicate whiskers range from 100 nm to few micrometers in length and 10 to 20 nm in diameter. At very low concentrations, these whiskers are randomly suspended in water and form an isotropic phase. When the concentration reaches a critical value, the whiskers spontaneously display ordered phases showing interesting liquid crystal properties (nematic and chiral nematic). The chiral nematic orders can be retained after evaporation of the solvent (generally water), leaving iridescent films. The reflected color can be controlled by changing either the ionic strength or by applying an electric field. These colloidal particles have been investigated using several techniques including small‐angle neutron scattering (SANS), small angle X‐ray scattering, rheology, and more recently dynamic and static light scattering techniques (DLS and SLS) to highlight their static and dynamic behavior. Because of their geometry, important axis ratio (L/d), and high crystallinity, these rods have been also extensively used to process nanocomposites based on polymer matrices, to reinforce their mechanical properties. All these properties are discussed in this contribution.

Rodlike nanocrystals in aqueous suspension (left, Tunicate, 1 wt.‐%) and film (right), observed between cross‐polarizers.

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Rodlike nanocrystals in aqueous suspension (left, Tunicate, 1 wt.‐%) and film (right), observed between cross‐polarizers.
Glass Transition of Low‐Dimensional Polystyrene
Authors: Jiang Qing , Lang Xing You
Published: March 2004

Summary: A unified model is developed for the finite size‐effect on the glass‐transition temperature of polymers, Tg(D), where D denotes the diameter of particles or thickness of films. In terms of this model, Tg depends on both the size and interface conditions. The predicted results are consistent with the experimental evidence for polystyrene (PS) particles and films with different interface situations.

Tg(D) function of free‐standing PS films.

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Tg(D) function of free‐standing PS films.
Spontaneous Ring‐Opening Polymerization of Macrocyclic Aromatic Thioether Ketones under Transient High‐Temperature Conditions
Authors: Colquhoun Howard M. , Zolotukhin Mikhail G. , Zhu Zhixue , Hodge Philip , Williams David J.
Published: March 2004

Summary: Spontaneous ring‐opening polymerization of macrocyclic aromatic thioether ketones [1,4‐SC6H4COC6H4]n (n = 3 and 4), in which the thioether linkages are para to the ketone, occurs during rapid, transient heating to 480 °C, to afford a soluble, semi‐crystalline poly(thioether ketone) of high molar mass (ηinh > 1.0 dL · g−1). Corresponding macrocyclic ether ketones, and a macrocyclic thioether ether ketone in which the thioether linkage is para to the ether rather than to the ketone, show no evidence of polymerization under analogous conditions.

The uncatalysed ring‐opening polymerization of macrocycle 1, within the pores of an alumina microfiltration membrane, leads to formation of polymer 3 with the microstructure shown in the above scanning electron micrograph.

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The uncatalysed ring‐opening polymerization of macrocycle 1, within the pores of an alumina microfiltration membrane, leads to formation of polymer 3 with the microstructure shown in the above scanning electron micrograph.
Theoretical Consideration of the Grafting of Polymer Chains onto Fullerene C60
Authors: Kuchanov Semion , Pizik Ilya , Ivanov Viktor
Published: March 2004

Summary: For the first time, the kinetics and statistics of the formation of polymer stars by grafting linear macromolecules onto the fullerene C60 are considered. Two kinetic models are put forward providing an explanation for some important experimentally observed peculiarities of these macromolecular reactions. The comparison of the results found from the solution of the kinetic equations and those obtained by Monte Carlo simulations demonstrates their good agreement. Due to the minimal number of the parameters involved, the theoretical approach proposed is rather convenient for the treatment of experimental data.

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On hybrid quantum–classical transport models
Authors: Ben Abdallah Naoufel , Tang Shaoqiang
Published: March 2004

This paper contains a review on the coupling between classical models and quantum models for electron transport in semiconductors. Starting from the quantum analogue of the boundary value problem for the Vlasov equation, the coupling with the Boltzmann equation in the one‐dimensional stationary situation is reviewed for the stationary and time‐dependent problems. Then a numerical scheme based on the characteristics method is applied to the stationary hybrid model. Some mathematical properties of the scheme are proven and illustrated in some numerical experiments. Copyright © 2004 John Wiley & Sons, Ltd.
Magnetic relaxation dispersion of lithium ion in solutions of DNA
Authors: Victor Ken G. , Teng Ching‐Ling , Dinesen T. R. D. , Korb Jean‐Pierre , Bryant Robert G.
Published: March 2004

The magnetic field dependence of the nuclear spin–lattice relaxation rate constant defines the magnetic relaxation dispersion (MRD) and provides a direct characterization of the molecular dynamics that cause fluctuations in the magnetic couplings in the system and may also indicate the dimensional constraints on the motion. The counterion cloud surrounding a linear polyelectrolyte ion, such as DNA in solution, provides an interesting opportunity for ion confinement that helps in understanding the thermodynamics and the dynamics of the interactions between the polyion and other solutes. The MRD profiles of lithium ion and tetramethylammonium ion were recorded in dilute aqueous solutions of native calf thymus DNA, which provides a long, charged rod that reorients slowly. The 7Li ion relaxes through the nuclear electric quadrupole coupling and the proton–lithium dipole–dipole coupling; the protons of the tetramethylammonium ion relax by dipole–dipole coupling. MRD profiles of the 7Li+ ion are dominated by transient interactions with the DNA that yield a linear dependence of the spin–lattice relaxation rate constant on the logarithm of the Larmor frequency. This magnetic field dependence is consistent with diffusive ion motions that modulate two spatial coordinates that characterize the relaxation couplings in the vicinity of the polyion. Motions around the rod and fluctuations in the ion distance from the rod are consistent with these constraints for lithium. The magnetic field dependence of the tetramethylammonium ion proton relaxation rate constant is weak, but also approximately a linear function of the logarithm of the Larmor frequency, which implies that the field dependence is caused in part by local order in the DNA solution. Copyright © 2004 John Wiley & Sons, Ltd.
Modeling 1H exchange: An estimate of the error introduced in MRI by assuming the fast exchange limit in bolus tracking
Authors: Moran G.R. , Prato F.S.
Published: March 2004

A simulation is presented which calculates the MRI signal expected from a model tissue for a given pulse sequence after a bolus injection of a contrast agent. The calculation assumes two physiologic compartments only, the intravascular and extravascular spaces. The determination of the concentration of contrast in each compartment as a function of time and position has been outlined in a previous publication (Moran and Prato, Magn Reson Med 2001;45:42–45). These contrast agent concentrations are used here to determine the NMR relaxation times as a function of time and position within the tissue. Knowledge of this simulated tissue ‘map’ of relaxation times as a function of time provides the information required to determine whether the proton exchange rate is fast or slow on the NMR timescale. Since with a bolus injection the concentration of contrast and hence the relaxation time may vary with position along the capillary, some segments of the capillary are allowed to be in fast exchange with the extravascular space, while others may be in slow exchange. Using this information, and parameters specific to a given tissue, the MRI signal for a given pulse sequence is constructed which correctly accounts for differences in proton exchange across the length of the capillary. It is shown that extravascular contrast agents show less signal dependence on water exchange, and thus may be more appropriate for quantitative imaging when using fast exchange assumptions. It is also shown that nondistributed compartment models can incorrectly estimate the water exchange that is occurring at the capillary level if exchange‐minimizing pulse sequences are not used. Magn Reson Med 51:816–827, 2004. © 2004 Wiley‐Liss, Inc.
Designing acceptance sampling schemes for life testing with mixed censoring
Authors: Chen Jianwei , Chou Winlin , Wu Hulin , Zhou Haibo
Published: March 2004

Mixed censoring is useful extension of Type I and Type II censoring and combines some advantages of both types of censoring. This paper proposes a general Bayesian framework for designing a variable acceptance sampling scheme with mixed censoring. A general loss function which includes the sampling cost, the time‐consuming cost, the salvage value, and the decision loss is employed to determine the Bayes risk and the corresponding optimal sampling plan. An explicit expression of the Bayes risk is derived. The new model can easily be adapted to create life testing models for different distributions. Specifically, two commonly used distributions including the exponential distribution and the Weibull distribution are considered with a special decision loss function. We demonstrate that the proposed model is superior to models with Type I or Type II censoring. Numerical examples are reported to illustrate the effectiveness of the method proposed. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004
A sequential dynamic pricing model and its applications
Authors: Lin Kyle Y.
Published: March 2004

Consider a sequential dynamic pricing model where a seller sells a given stock to a random number of customers. Arriving one at a time, each customer will purchase one item if the product price is lower than her personal reservation price. The seller's objective is to post a potentially different price for each customer in order to maximize the expected total revenue. We formulate the seller's problem as a stochastic dynamic programming model, and develop an algorithm to compute the optimal policy. We then apply the results from this sequential dynamic pricing model to the case where customers arrive according to a continuous‐time point process. In particular, we derive tight bounds for the optimal expected revenue, and develop an asymptotically optimal heuristic policy. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004.