bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystal structures of a psychrophilic metalloprotease reveal new insights into catalysis by cold‐adapted proteases
Authors: Aghajari Nushin , Van Petegem Filip , Villeret Vincent , Chessa Jean‐Pierre , Gerday Charles , Haser Richard , Van Beeumen Jozef 
Published: February 2003

AbstractEnzymes from psychrophilic organisms differ from their mesophilic counterparts in having a lower thermostability and a higher specific activity at low and moderate temperatures. It is in general accepted that psychrophilic enzymes are more flexible to allow easy accommodation and transformation of the substrates at low energy costs. Here, we report the structures of two crystal forms of the alkaline protease from an Antarctic Pseudomonas species (PAP), solved to 2.1‐ and 1.96‐Å resolution, respectively. Comparative studies of PAP structures with mesophilic counterparts show that the overall structures are similar but that the conformation of the substrate‐free active site in PAP resembles that of the substrate‐bound region of the mesophilic homolog, with both an active‐site tyrosine and a substrate‐binding loop displaying a conformation as in the substrate‐bound form of the mesophilic proteases. Further, a region in the catalytic domain of PAP undergoes a conformational change with a loop movement as large as 13 Å, induced by the binding of an extra calcium ion. Finally, the active site is more accessible due to deletions occurring in surrounding loop regions. Proteins 2003;50:636–647. © 2003 Wiley‐Liss, Inc.
About the sharpness of the stability estimates in the Kreiss matrix theorem
Authors: Spijker M. , Tracogna S. , Welfert B. 
Published: February 2003

One of the conditions in the Kreiss matrix theorem involves the resolvent of the matrices

A
A

under consideration. This so-called resolvent condition is known to imply, for all

n
≥
1

n\ge 1

, the upper bounds

‖

A
n

‖
≤
e
K
(
N
+
1
)

\|A^n\|\le eK(N+1)

and

‖

A
n

‖
≤
e
K
(
n
+
1
)

\|A^n\|\le eK(n+1)

. Here

‖
⋅
‖

\|\cdot \|

is the spectral norm,

K
K

is the constant occurring in the resolvent condition, and the order of

A
A

is equal to

N
+
1
≥
1

N+1\ge 1

. It is a long-standing problem whether these upper bounds can be sharpened, for all fixed

K
>
1

K>1

, to bounds in which the right-hand members grow much slower than linearly with

N
+
1

N+1

and with

n
+
1

n+1

, respectively. In this paper it is shown that such a sharpening is impossible. The following result is proved: for each

ϵ
>
0

\epsilon >0

, there are fixed values

C
>
0
,
K
>
1

C>0, K>1

and a sequence of

(
N
+
1
)
×
(
N
+
1
)

(N+1)\times (N+1)

matrices

A
N

A_N

, satisfying the resolvent condition, such that

‖
(

A
N

)
n

‖
≥
C
(
N
+
1

)

1
−
ϵ

\|(A_N)^n\|\ge C(N+ 1)^{1-\epsilon }

=
C
(
n
+
1

)

1
−
ϵ

=C(n+1)^{1-\epsilon }

for

N
=
n
=
1
,
2
,
3
,
…

N=n=1,2,3,\ldots

. The result proved in this paper is also relevant to matrices

A
A

whose

ϵ
\epsilon

-pseudospectra lie at a distance not exceeding

K
ϵ

K\epsilon

from the unit disk for all

ϵ
>
0

\epsilon >0

.
Ab initio Study of the Li-CO van der Waals Complex
Authors: Lukeš Vladimír , Laurinc Viliam , Ilčin Michal , Biskupič Stanislav 
Published: February 2003

The adiabatic potential energy surface (PES) of the Li-CO complex in the van der Waals region, described by Jacobi coordinates (r = 1.15 Å, R, Θ), was investigated using the supermolecular coupled-clusters CCSD(T) method. Our calculations indicate minima for bent arrangements. The first minimum was found on the carbon side of CO molecule at R = 5.27 Å (Θ = 50.7°) with a well depth of De = -167.2 μEh. The second minimum is indicated at R = 5.35 Å (Θ = 148.7°) with a well depth of De = -121.9 μEh. The saddle point is localised at θ = 111.5° and R = 5.35 Å. The physical origin of the weak interaction studied was analysed by the intermolecular perturbation theory based on the single determinant UHF wave function. The separation of the interaction energies shows that the locations of the predicted stable bent structures are primarily determined by the anisotropy of the repulsive Heitler-London exchange penetration and attractive dispersion and induction energy components.
Analyzing the effectiveness of receiver arrays for multicomponent seismic exploration
Authors: Hoffe Brian H. , Margrave Gary F. , Stewart Robert R. , Foltinek Darren S. , Bland Henry C. , Manning Peter M. 
Published: February 2003

This paper uses an experimental seismic line recorded with three‐component (3C) receivers to develop a case history demonstrating very little benefit from receiver arrays as compared to point receivers. Two common array designs are tested; they are detrimental to the P‐S wavefield and provide little additional benefit for P‐P data. The seismic data are a 3C 2‐D line recorded at closely spaced (2 m) point receivers over the Blackfoot oil field, Alberta. The 3C receiver arrays are constructed by summing five (one group interval) and ten (two group intervals) point receivers. The shorter array emphasizes signal preservation while the longer array places priority on noise rejection. The effectiveness of the arrays versus the single geophones is compared in both the t−x and f−k domains of common source gathers. The quality of poststack data is also compared by analyzing the f−x spectra for signal bandwidth on both the vertical receiver component (P‐P) and radial receiver component (P‐S) structure stacks produced using these two array design philosophies. The prestack analysis shows that the two arrays effectively suppress coherent noise on both the vertical and radial geophone data and perform reasonably as spatial antialias filters. The poststack analysis reveals that, for both the P‐P and P‐S data, neither of the two arrays significantly improves the quality of the final seismic image over that obtained from point receiver data. For the P‐P data there are subtle differences between the final stacked sections, while for the P‐S data there is a significant deterioration in image quality from the application of the arrays. This P‐S image deterioration is attributed to significant variation of shear‐wave statics across the array. For this specific survey area and acquisition parameters, 3C receiver arrays are unnecessary for P‐P data and are detrimental to P‐S data.
The joint nonhyperbolic moveout inversion of PP and PS data in VTI media
Authors: Grechka Vladimir , Tsvankin Ilya 
Published: February 2003

Nonhyperbolic moveout of P‐waves in horizontally layered transversely isotropic media with a vertical symmetry axis (VTI) can be used to estimate the anellipticity coefficient η in addition to the NMO velocity Vnmo,P. Those two parameters are sufficient for time processing of P‐wave data (despite a certain instability in the inversion for η), but they do not constrain the vertical velocity VP0and the depth scale of the model. It has been suggested in the literature that this ambiguity in the depth‐domain velocity analysis for layer‐cake VTI media can be resolved by combining long‐spread reflection traveltimes of P‐waves and mode‐converted PSV‐waves.Here, we show that reflection traveltimes of horizontal PSV events help to determine the ratio of the P‐ and S‐wave vertical velocities and the NMO velocity of SV‐waves, and they give a more accurate estimate of η. However, nonhyperbolic moveout of PSV‐waves turns out to be mostly controlled by wide‐angle P‐wave traveltimes and does not provide independent information for the inversion. As a result, even for a single‐layer model and uncommonly large offsets, traveltimes of P‐ and PSV‐waves cannot be inverted for the vertical velocity and anisotropic parameters ε and δ. To reconstruct the horizontally layered VTI model from surface data, it is necessary to combine long‐spread traveltimes of pure P and SV reflections.
Influence of Several Process Parameters on Sourdough Fermentation
Authors: Wick M. , Stolz P. , Böcker G. , Lebeault J.‐M. 
Published: February 2003

AbstractThe influence of several process parameters (starter, sourdough refreshment, dough yield, ingredients) on sourdough fermentation was investigated. This was realised by online measurement of both pH and gas pressure in sourdough in a closed air‐tight reactor. Firstly, the effect of sourdough refreshment on both gas pressure and acidification was evaluated and shown to be accompanied by an increase in both acidification and gas pressure evolution rates. Secondly, two commercial starters (BRS and BIO) differing in their microflora were compared as regards to their gassing power and acidifying properties. BRS exhibited faster acidification but less gassing power. Moreover, the variation of sourdough yield for BRS starter induced a different evolution of the acidification profile. Sourdough fermentation varied also depending on the presence of NaCl. 2% of NaCl induced a lower gassing power in sourdough by inhibiting the yeasts.
Production of Industrial Enzymes (Amylase, Carboxymethylcellulase and Protease) by Bacteria Isolated from Marine Sedentary Organisms
Authors: Mohapatra B. R. , Bapuji M. , Sree A. 
Published: February 2003

AbstractThe abilities of bacteria isolated from eight marine sedentary organisms, six marine sponges (Spirastrella sp., Phyllospongia sp., Ircinia sp., Aaptos sp., Azorica sp. and Axinella sp.), one soft coral (Lobophytum sp.) and one alga (Sargassum sp.) to produce industrial enzymes (amylase, carboxymethylcellulase and protease) were examined. The mean total viable counts of the bacterial isolates ranged from 8.7 × 104 to 8.4 × 105 cfu/g wet weight of the organism. All eight organisms harboured amylase (0.05–0.5 IU/ml), carboxymethylcellulase (0.05–0.5 IU/ml) and protease (0.1–0.5 IU/ml) producing bacteria. Of 56 bacterial strains tested, as many as 60 to 83% of the strains produced at least one of the three enzymes, and 47% of strains were able to produce all three enzymes. High activities (> 0.5 IU/ml) of the three enzymes were recorded in bacterial strains belonging to the genera Alcaligenes and Bacillus. From the results of this study, it appears that bacteria associated with marine sedentary organisms are the novel source of industrial enzymes for possible commercial applications and may play an important role in enzyme‐catalysed organic matter cycling in marine environments.
Citric Acid Fermentation and the Effects of Temperature
Authors: Selahzadeh R. M. , Roehr M. 
Published: February 2003

AbstractThe temperature of the fermentation media heavily affects yields as well as rates of citric acid fermentations. At 26–28 °C, more than 40% of the available carbohydrate raw material is wasted, apparently through the respiratory activity of the fungus. At 30–32 °C, these losses are decreased to about 10%. The results thus emphasise the economic importance of adequate temperature control in industrial citric acid fermentation.
Electron Transport in a Methanofullerene
Authors: Mihailetchi V.D. , van Duren J.K.J. , Blom P.W.M. , Hummelen J.C. , Janssen R.A.J. , Kroon J.M. , Rispens M.T. , Verhees W.J.H. , Wienk M.M. 
Published: February 2003

AbstractThe current–voltage characteristics of methanofullerene [6,6]‐phenyl C61‐butyric acid methyl ester (PCBM)‐based devices are investigated as a function of temperature. The occurrence of space–charge limited current enables a direct determination of the electron mobility. At room temperature, an electron mobility of μe = 2 × 10–7 m2 V–1 s–1 has been obtained. This electron mobility is more than three orders of magnitude larger than the hole mobility of donor‐type conjugated polymer poly(2‐methoxy‐5‐(3′,7′‐dimethyloctyloxy)‐p‐phenylene vinylene) (OC1C10‐PPV). As a result, the dark current in PCBM/OC1C10‐PPV based devices is completely dominated by electrons. The observed field and temperature‐dependence of the electron mobility of PCBM can be described with a Gaussian disorder model. This provides information about the energetic disorder and average transport‐site separation in PCBM.
Self‐Assembly and Characterization of Mesostructured Silica Films with a 3D Arrangement of Isolated Spherical Mesopores
Authors: Yu K. , Smarsly B. , Brinker C.J. 
Published: February 2003

AbstractWe report the self‐assembly and characterization of mesoporous silica thin films with a 3D ordered arrangement of isolated spherical pores. The preparation method was based on solvent‐evaporation induced self‐assembly (EISA), with MTES (CH3–Si(OCH2CH3)3) as the silica precursor and a polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) diblock copolymer as the structure‐directing agent. The synthetic approach was designed to suppress the siloxane condensation rate of the siloxane network, allowing co‐self‐assembly of the silica and the amphiphile, followed by retraction of the PEO chains from the silica matrix and matrix consolidation, to occur unimpeded. The calcined films retained the methyl ligands and exhibited no measurable microporosity, thereby indicating that the 3D‐ordered spherical mesopores are not interconnected. A solvent‐mediated formation mechanism is proposed for the absence of microporosity. Due to their closed porosity and hydrophobicity, the MTES‐based films and MTES‐TEOS (Si(OCH2CH3)4)‐based hybrid films we describe should be promising for applications such as low‐k dielectrics.
Raman Anisotropy Measurements: An Effective Probe of Molecular Orientation in Conjugated Polymer Thin Films
Authors: Liem H.‐M. , Etchegoin P. , Whitehead K.S. , Bradley D.D.C. 
Published: February 2003

AbstractUnderstanding the molecular alignment of conjugated polymers within thin‐film samples is essential for a complete picture of their optical and transport properties, and hence for the continued development of optoelectronic device applications. We report here on the efficacy of Raman anisotropy measurements as a probe of molecular orientation, presenting results for aligned polyfluorene nematic glass films. Comparison is made with the results of optical dichroism measurements performed on the same samples. We show that in many cases molecular orientation can be more directly characterized by Raman anisotropy, and that it can have a greater sensitivity to the degree of molecular orientation than conventional optical dichroism. The fact that the Raman measurements can be readily performed on the same thin films (∼ 100 nm thickness) that are required for optical dichroism means that there is no ambiguity in a direct comparison of results. This situation differs from that for standard X‐ray diffraction measurements (these require film thicknesses of several μm) and electron diffraction or electron energy loss spectroscopy measurements (these require film thicknesses of 10 nm or less). The Raman data allow the angle (relative to the chain axis) for the optical dipole transition moment to be deduced from the dichroic ratio, and confirm the role that its off‐axis component plays in limiting this ratio. The added fact that Raman anisotropy data can be collected in situ, in reflection geometry for standard device structures, and with microscopic resolution and chemical specificity makes the technique even more attractive as a non‐invasive device probe.
Effects of Postproduction Treatment on Plastic Solar Cells
Authors: Padinger F. , Rittberger R.S. , Sariciftci N.S. 
Published: February 2003

AbstractEfficiencies of organic solar cells based on an interpenetrating network of a conjugated polymer and a fullerene as donor and acceptor materials still need to be improved for commercial use. We have developed a postproduction treatment that improves the performance of solar cells based on poly(3‐hexylthiophene) (P3HT) and [6,6]‐phenyl C61‐butyric acid methyl ester (PCBM) by means of a tempering cycle at elevated temperatures in which an external voltage is simultaneously applied, resulting in a significant increase of the short‐circuit current. Using this postproduction treatment, an enhancement of the short‐circuit current density, Isc, to 8.5 mA cm–2 under illumination with white light at an illumination intensity of 800 W m–2 and an increase in external quantum efficiency (IPCE, incident photon to collected electron efficiency) to 70 % are demonstrated.
Preparation and Properties of Resorcinol–Formaldehyde Organic and Carbon Gels
Authors: Al‐Muhtaseb S.A. , Ritter J.A. 
Published: February 2003

AbstractA brief overview on the preparation and properties of resorcinol–formaldehyde organic and carbon gels reveals very interesting features about their structural and performance characteristics. The resulting nanostructure was very sensitive to the various synthesis and processing conditions. This leads to a remarkable potential for designing and tailoring these materials to fit specific applications. Based on step‐by‐step comparisons of the published studies, approximate generalizations on the specific roles the synthesis and processing conditions play on the final properties are provided. Overall, resorcinol–formaldehyde organic gels undergo two main stages during synthesis. The first stage is associated with the preparation of the sol mixture, and the subsequent gelation and curing of the gel. The second stage is associated with the drying of the wet gel. The most important factors that affect the properties of the organic gel during the first stage are the catalyst concentration, the initial gel pH, and the concentration of the solids in the sol. The most important factors that affect the properties of the organic gel during the second stage are the drying procedure (e.g., super‐ or subcritical drying), and the difference between the surface tensions of the solvent before and after drying. The corresponding resorcinol–formaldehyde carbon gels are produced from the organic gels during a third stage, which is associated with carbonization or activation. Depending on the conditions, carbonization and activation both impact the structural and performance characteristics significantly.
Protein‐Mikroarray‐Technologie – Prinzipien und neuere Entwicklungen
Authors: Wilson David S. , Nock Steffen 
Published: February 2003

AbstractDie Sequenzierung des menschlichen Genoms, die Entwicklung von DNA‐Chips und die Bioinformatikprogramme ermöglichen, ganzheitliche Blicke auf biologische Systeme zu werfen und die natürlich vorkommenden genetischen Variationen zu untersuchen. Antikörper‐Mikroarrays können die Konzentration vieler Proteine gleichzeitig und schnell messen. Mikroarrays genetisch kodierter Proteine ermöglichen Wissenschaftlern, das gesamte Genom nach Proteinen zu durchsuchen, die mit bestimmten Faktoren interagieren, bestimmte Reaktionen katalysieren oder als Substrate für Protein‐modifizierende Enzyme sowie als Zielproteine bei einer Autoimmunreaktion dienen. Die neuartigen Protein‐Mikroarray‐Verfahren werden die Entdeckung und Entwicklung von Wirkstoffen sowie diagnostischen Biomarkern stark beschleunigen.
Removal of heavy metal ions using the chelating polymers derived by the condensation of poly(3‐hydroxy‐4‐acetylphenyl methacrylate) with different diamines
Authors: Reddy K. Hussain , Reddy A. Ravikumar 
Published: February 2003

AbstractA series of methacrylate‐based chelating polymers was synthesized by the reaction of 3‐hydroxy‐4‐acetylphenyl methacrylate with amines (e.g., ethylenediamine, propylenediamine, and phenylenediamine) in tetrahydrofuran. The chelating polymers were characterized by infrared (IR) and carbon‐13 nuclear magnetic resonance (13C–NMR) spectroscopic techniques. The thermal stabilities of these polymers were investigated by thermogravimetric (TG) and differential thermal analyses (DTA). Heavy metal ions [viz., Pb(II), Hg(II), Cd(II), and Cr(VI)] were removed with these chelating polymers, and metal ion uptake efficiency, reusability of the resins, and effects of pH and time on the metal removal were also studied. The chelating polymers possess appreciable selectivity for Pb(II) and Hg(II) compared with Cd(II) and Cr(VI). The chelating ability of the polymers towards the heavy metal ions is a sensitive function of the nature of the substituent on the nitrogen atom. The amount of metal uptake by the chelating polymer was determined by atomic absorption spectrophotometry (AAS). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 414–421, 2003
Preparation of composite particles made from solid powders and wasted plastics by semichemical recycle method
Authors: Taguchi Yoshinari , Tanaka Masto 
Published: February 2003

AbstractComposite particles composed of solid powders and polymer were prepared by semichemical recycle of wasted plastics. Waste expanded polystyrene was used as raw materials of polymer matrix of composite particles. Both magnetite and silicon carbide powders were used as solid powders to give thermal and electric conductivity and magnetization, respectively. In the experiment, the oil‐phase dissolving expanded polystyrene was dispersed in fine droplets into the continuous water phase. Two kinds of powders were added at the same time or separately in the O/W dispersion. Composite particles were found to have the structure that polymer particle was covered with two kinds of solid powders. The mean diameter of composite particles and the content of each solid powder were strongly affected by the addition time when silicon carbide powder was added into the dispersion. Furthermore, it was found that the gradient adhesion layer due to two solid powders was able to be formed on the surface of polymer particle. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 483–488, 2003
Quality of well‐being in older people with osteoarthritis
Authors: Groessl Erik J. , Kaplan Robert M. , Cronan Terry A. 
Published: February 2003

AbstractObjectiveTo examine the sensitivity of the Quality of Well‐Being Scale (QWB) as a measure of health‐related quality of life (HRQOL) in people with osteoarthritis (OA).MethodsThe QWB was administered, along with the Arthritis Impact Measurement Scale (AIMS) and other health measures. Health care utilization data were also obtained.ResultsPeople with OA had a mean QWB score of 0.643. The QWB scores were significantly correlated with total AIMS scores, self‐rated health status, health care costs, depression scores, and most AIMS subscales. In addition, changes in QWB scores after 1 year were significantly correlated with changes in total AIMS scores and some AIMS subscales.ConclusionThe QWB appears to be a useful and sensitive generic, utility‐based measure of HRQOL in people with OA.
Assessment of the molecular dynamics structure of DNA in solution based on calculated and observed NMR NOESY volumes and dihedral angles from scalar coupling constants
Authors: Arthanari Haribabu , McConnell Kevin J. , Beger Richard , Young Matthew A. , Beveridge D. L. , Bolton Philip H. 
Published: February 2003

AbstractTo assess the accuracy of the molecular dynamics (MD) models of nucleic acids, a detailed comparison between MD‐calculated and NMR‐observed indices of the dynamical structure of DNA in solution has been carried out. The specific focus of our comparison is the oligonucleotide duplex, d(CGCGAATTCGCG)2, for which considerable structural data have been obtained from crystallography and NMR spectroscopy. An MD model for the structure of d(CGCGAATTCGCG)2 in solution, based on the AMBER force field, has been extended with a 14 ns trajectory. New NMR data for this sequence have been obtained in order to allow a detailed and critical comparison between the calculated and observed parameters. Observable two‐dimensional (2D) nuclear Overhauser effect spectroscopy (NOESY) volumes and scalar coupling constants were back‐calculated from the MD trajectory and compared with the corresponding NMR data. The comparison of these results indicate that the MD model is in generally good agreement with the NMR data, and shows closer accord with experiment than back‐calculations based on the crystal structure of d(CGCGAATTCGCG)2 or the canonical A or B forms of the sequence. The NMR parameters are not particularly sensitive to the known deficiency in the AMBER MD model, which is a tendency toward undertwisting of the double helix when the parm.94 force field is used. The MD results are also compared with a new determination of the solution structure of d(CGCGAATTCGCG)2 using NMR dipolar coupling data. © 2002 Wiley Periodicals, Inc. Biopolymers 68: 3–15, 2003