bluuebunny/crossref_metadata_2025 huggingface dataset:
Micromechanical properties of demineralized dentin collagen with and without adhesive infiltration
Authors: Katz J. Lawrence , Spencer Paulette , Nomura Tsutomu , Wagh Ajay , Wang Yong
Published: June 2003

In a previous study, we reported the upper limit of Young's modulus of the unprotected protein at the dentin/adhesive interface to be 2 GPa. In this study, to obtain a more exact value of the moduli of the components at the d/a interface, we used demineralized dentin collagen with and without adhesive infiltration. The prepared samples were analyzed using micro‐Raman spectroscopy (μRS) and scanning acoustic microscopy (SAM). Using an Olympus UH3 SAM (Olympus Co., Tokyo), measurements were recorded with a 400 MHz burst mode lens (120° aperture angle; nominal lateral resolution, 2.5 μm). A series of calibration curves were prepared using the relationship between the ultrasonically measured elastic moduli of a set of known materials and their SAM response. Finally, both the bulk and bar wave elastic moduli were computed for a set of 13 materials, including polymers, ceramics, and metals. These provided the rationale for using extensional wave measurements of the elastic moduli as the basis for extrapolation of the 400 MHz SAM data to obtain Young's moduli for the samples: E = 1.76 ± 0.00 GPa for the collagen alone; E = 1.84 ± 0.65 GPa for the collagen infiltrated with adhesive; E = 3.4 ± 1.00 GPa for the adhesive infiltrate. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 120–128, 2003
Assembly and characterization of biofunctional neurotransmitter‐immobilized surfaces for interaction with postsynaptic membrane receptors
Authors: Saifuddin Uroosa , Vu Tania Q. , Rezac Miroslav , Qian Haohua , Pepperberg David R. , Desai Tejal A.
Published: June 2003

Herein, we report progress toward the development of bioactive surfaces based on γ‐aminobutyric acid (GABA), a major neurotransmitter in the nervous system. Whereas immobilization techniques have focused largely on antibodies, enzymes, and receptors, to our knowledge, this is the first report of a prototype neurotransmitter‐immobilized surface. Biosurfaces were assembled onto either mica or glass using passive adsorption of avidin and subsequent attachment of a derivatized form of GABA via a biotin–avidin affinity bond. Surface characterization of these prepared bimolecular surfaces was determined using atomic force microscopy in tapping mode. The data reveal that passive adsorption of avidin is uniformly dispersed and cluster densities can be controlled through the concentration of the avidin incubation solution. GABA tethered via biotin to these avidin surfaces displayed a unique surface topology; in addition, histograms of surface heights suggest two different types of molecular cluster populations. Functional assays were performed to test the biological activity of the synthesized GABA. Anti‐GABA antibody directed to these bimolecular surfaces result in morphological topologies and histograms that indicate antibody–antigen binding. However, nonspecific anti‐immunoglobulin G antibodies directed to these surfaces show low binding affinity. Taken together, the data support the idea that the synthesized surfaces are biofunctional. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 184–191, 2003
In vitrofatigue behavior of human dentin with implications for life prediction
Authors: Nalla R. K. , Imbeni V. , Kinney J. H. , Staninec M. , Marshall S. J. , Ritchie R. O.
Published: June 2003

Although human dentin is known to be susceptible to failure under repetitive cyclic fatigue loading, there are few reports in the literature that reliably quantify this phenomenon. This study seeks to address the paucity of fatigue data through a systematic investigation of the effects of prolonged cyclical loading on human dentin in an environment of ambient temperature Hank's balanced salt solution (HBSS) at cyclic frequencies of 2 and 20 Hz. The “stress‐life” (S/N) data thus obtained are discussed in the context of possible mechanisms of fatigue damage and failure in this material. In addition, stiffness loss data collectedin situduring theS/Ntests are used to deduce crack velocities and the thresholds for such cracking. These results are presented in a fracture mechanics context as plots of fatigue‐crack propagation rates (da/dN) as a function of the stress‐intensity range (ΔK). SuchS/Nandda/dN‐ΔKdata are discussed in light of the development of a framework for a fracture‐mechanics‐based methodology for the prediction of the fatigue life of teeth. It is concluded that the presence of small (on the order of 250 μm) incipient flaws in human teeth will not radically affect their useful life. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 10–20, 2003
Effect of alkaline treatment of pure titanium and its alloys on the bonding strength of dental veneering resins
Authors: Ban Seiji
Published: June 2003

Commercially pure titanium (cpTi), Ti6Al4V, an experimental β‐type titanium (Ti 53.4 wt%, Nb 29 wt %, Ta 13 wt %, and Zr 4.6 wt %), and 12%AuPdAg alloy plates were sandblasted, cleaned in water, and dried. cpTi plates were treated with nine alkaline treatments that differed in the type of alkali, alkaline concentration, soaking temperature, soaking time, and heating temperature. cpTi plates that were only sandblasted or sandblasted and oxidized at 600°C for 1 h in air were also prepared. Finally, the bonding strengths of 11 kinds of surface‐treated cpTi to resin were measured using a pull‐shear bonding method after immersion in physiologic saline solution at 37°C for 24 h. The bonds of the standard alkaline‐treated cpTi and two titanium alloys to resins were 1.5–1.9 times stronger than those of sandblasted specimens (p < 0.01), but no significant effects of the alkaline treatment were observed on the 12% AuPdAg alloy. The greatest bonding strengths were found for cpTi treated with NaOH and KOH and then heated at 600°C (p < 0.01). In conclusion, alkaline treatment is a simple, effective surface modification of titanium that improves bonding to veneering resin. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 138–145, 2003
Vascular responsiveness to dimethylaminoethyl methacrylate and its degradation products
Authors: Abebe Worku , Maddux William F. , Schuster George S. , Lewis Jill B.
Published: June 2003

The increasing use of acrylate‐based resins in dentistry has raised questions about the biocompatibility of these substances with oral tissues. The focus of the present investigation was to assess the responsiveness of blood vessels to the resin polymerization accelerating agent dimethylaminoethyl methacrylate (DMAEMA) and its degradation products dimethylethanolamine (DME) and methacrylic acid (MAA), using the rat aortic ring preparation as a tissue model. DMAEMA induced concentration‐dependent relaxation of norepinephrine (NE)‐contracted aortic rings with and without endothelium. N‐nitro‐L‐arginine methyl ester (L‐NAME) selectively inhibited the endothelium‐dependent relaxation induced by DMAEMA, suggesting the release of nitric oxide from the endothelium by DMAEMA. Both indomethacin and glybenclamide attenuated the vasorelaxation elicited by DMAEMA in the presence as well as in the absence of endothelium, providing evidence for the role of vasorelaxant prostanoid(s) and KATP channel activation in the responses observed. On the other hand, while MAA was without any apparent effect on the rat aorta, DMAEMA at high and DME at relatively low concentrations caused contraction of the tissues with and without endothelium in the absence of NE. The DME‐induced contraction was inhibited by indomethacin, suggesting the involvement of contractile arachidonic acid metabolite(s) in the action of DME. This observation was supported by the findings of increased thromboxane A2 (TXA2) production in aortic rings incubated with DME. Taken together, the data suggest that both DMAEMA and its degradation product, DME, are vasoactive, inducing vasorelaxation and contraction by various mechanisms that may involve the release of nitric oxide from the endothelium, the activation of smooth muscle KATP channels, and the generation of vasorelaxant prostanoid(s) and TXA2. These effects may play a role in tissue homeostasis and certain adverse conditions associated with the use of dental resin materials containing DMAEMA and/or DME. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 155–161, 2003
Interactions between surface‐bound actin and complement, platelets, and neutrophils
Authors: Wetterö Jonas , Askendal Agneta , Tengvall Pentti , Bengtsson Torbjörn
Published: June 2003

Actin exists as globular (G) monomers or polymeric filaments (F) in the cytoplasm of eukaryotic cells, mediating cell morphologic changes and motility. Large amounts of this protein may be released out to the extracellular compartment during tissue injury, but little is known about its role in biomaterial‐related inflammation. We immobilized actin to methylated glass, methylated and aminated silicon, and gold model surfaces and studied the subsequent blood serum deposition and complement activation, generation of reactive oxygen species (ROS), and adhesion and aggregation of neutrophils and platelets. Null ellipsometry showed that approximately one monolayer of G‐actin can be immobilized onto the model surfaces and that actin in buffer polymerized on top of this by the addition of K+ and Mg2+ ions to form a thicker layer of firmly bound F‐actin. After serum incubation, F‐actin bound low amounts of anti‐complement factor 1q (anti‐C1q). Cell responses upon contact with actin‐coated surfaces were analyzed by luminol‐amplified chemiluminescence, lumi‐aggregometry, and fluorescence microscopy. It was shown that surface‐triggered aggregation, spreading, and generation of ROS are down‐regulated and comparable to the response by adsorbed albumin. However, F‐actin on gold surfaces recruited platelets in a C1q‐dependent manner. We conclude that in vitro adsorbed actin is a weak complement, platelet, and neutrophil activator, but that F‐actin associates with both C1q and platelets. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 162–175, 2003
Biological assessment of the bone–screw interface after insertion of uncoated and hydroxyapatite‐coated pedicular screws in the osteopenic sheep
Authors: Fini M. , Giavaresi G. , Greggi T. , Martini L. , Aldini N. Nicoli , Parisini P. , Giardino R.
Published: June 2003

The sheep seems to be a promising model of osteoporosis and biomaterial osteointegration in osteopenic bone. The long‐term ovariectomized sheep model was used for the biological investigation of bone healing around uncoated and hydroxyapatite (HA)‐coated pedicle screws in osteopenic bone. Four sheep were ovariectomized and four sheep were sham‐operated. Twenty‐four months after surgery, the animals were implanted with uncoated and HA‐coated stainless steel screws in the lumbar vertebral pedicles. Four months later, bone‐to‐implant contact, bone ingrowth, and bone hardness were measured around screws. Uncoated stainless steel presented significantly (p < 0.0005) lower bone‐to‐implant contact in healthy and osteopenic bone compared with HA‐coated stainless steel. HA significantly improved bone ingrowth in healthy bone (p < 0.05) compared with uncoated stainless steel. Osteopenia significantly (p < 0.05) reduced the area of bone ingrowth around the screw threads for both types of implants. In the inner thread area, bone microhardness significantly increased (p < 0.05) in HA‐coated surface versus uncoated for healthy and osteopenic bone. HA coating significantly enhances bone‐to‐implant contact also in osteopenic bone in comparison with uncoated stainless steel surfaces. Bone ingrowth and mineralization are ameliorated by the osteoconductive HA coating. However, osteopenia seems to greatly influence bone ingrowth processes around the implanted screws regardless of the characteristics of the material surface. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 176–183, 2003
The effects of degree of crosslinking on the fatigue crack initiation and propagation resistance of orthopedic‐grade polyethylene
Authors: Baker D. A. , Bellare A. , Pruitt L.
Published: June 2003

Crosslinked ultrahigh molecular weight polyethylene (UHMWPE) has been recently approved by the Food and Drug Administration for use in orthopedic implants. The majority of commercially available UHMWPE orthopedic components are crosslinked using e‐beam or gamma radiation. The level of crosslinking is controlled with radiation dose and free radicals are eliminated through heat treatments to prevent long‐term degradation associated with chain scission or oxidation mechanisms. Laboratory studies have demonstrated a substantial improvement in the wear resistance of crosslinked UHMWPE. However, a concern about the resistance to fatigue damage remains in the clinical community, especially for tibial components that sustain high cyclic contact stresses. The objective of this study was to investigate both the initiation and propagation aspects of fatigue cracks in radiation crosslinked medical‐grade UHMWPE. This work evaluated three levels of radiation, which induced three crosslink densities, on the fatigue crack propagation and total fatigue life behavior. Both as‐received UHMWPE, as well as those that underwent an identical thermal history as the crosslinked UHMWPE were used as controls. Fractured crack propagation specimens were examined using scanning electron microscopy to elucidate fatigue fracture mechanisms. The results of this work indicated that a low crosslink density may optimize the fatigue resistance from both a crack initiation and propagation standpoint. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 66A: 146–154, 2003
Cyber terrorism: Hype or reality?
Authors: Parks Chad
Published: June 2003

The cyber terrorist threat has been dubbed many things, including Digital Pearl Harbor, Digital Armageddon,
and Digital Waterloo to name a few. Whatever you want to call it, the threat of cyber terrorism is real; it
does exist. © 2003 Canaudit, Inc.
XBRL: Don't lag behind the digital information revolution
Authors: Higgins Leslee N. , Harrell Horace W.
Published: June 2003

Does your company present information on the Internet? If you're not using XBRL—a special
standard for reporting financial information on the Internet—you could get left behind! Why not reap
the benefits of using this latest innovation? © 2003 Wiley Periodicals, Inc.
The computer: An essential fraud detection tool
Authors: Christensen Jo Ann , Byington J. Ralph
Published: June 2003

As white collar crime has mushroomed, the computer has become an essential tool for uncovering fraud. How can
auditors use it to turn the tables on fraudsters? © 2003 Wiley Periodicals, Inc.
Supercharge your marketing and CRM with advanced document integration
Authors: Pucher Max J.
Published: June 2003

Financial service companies and others are using the latest new software to convert mundane documents into
powerful tools for marketing, consumer relations, and more. How is it done? © 2003 Wiley
Periodicals, Inc.
Is your audit committee watching IT risks?
Authors: Hadden Linda B. , Hermanson Dana R.
Published: June 2003

Recent high‐profile accounting disasters have put audit committees on the hot seat. Some want audit
committees to lead the way in protecting against increased IT risks. But what is the committee's
role? And what do CEOs need to know about audit committee oversight of it? © 2003 Wiley
Periodicals, Inc.
PIMs: Is it time to give up your day planner?
Authors: Bean LuAnn , Barlow Judith , Hott David
Published: June 2003

Personal Information Managers (PIMs) have been around for awhile now. Maybe you are even ready to
give up your Day Planner and Post‐it Notes—and trust your computer or PDA to store all that vital
information. But can PIMs really do the job you need? Which one should you choose? Or are they
obsolete, as some critics suggest? The authors have some important insights and useful advice on getting
the most out of these often‐frustrating products. © 2003 Wiley Periodicals,
Inc.
The real cost of being hacked
Authors: Garg Ashish , Curtis Jeffrey , Halper Hilary
Published: June 2003

You've been hacked! But what will be the real cost to your company? A new Ernst & Young
study has some revealing news about the impact. © 2003 Wiley Periodicals, Inc.
Corporate governance: Big changes ahead
Authors: Goldberg Stephen R. , Danko Dori
Published: June 2003

Is there life after Enron? The answer is obviously yes. But the business world—and corporate
governance—will never be the same. And what will this brave new world look like? The authors explain
what you need to know, and how to stay out of trouble. © 2003 Wiley Periodicals, Inc.
Dear Mr. Chairman: An open letter to the SEC
Authors: Rouse Robert W.
Published: June 2003

Our SEC columnist has some strong views about the sweeping Sarbanes‐ Oxley Act. He is especially
skeptical of the Act's Code of Ethics. © 2003 Wiley Periodicals, Inc.
Investing in technology
Authors: Goldberg Stephen R. , Godwin Joseph H.
Published: June 2003

Keen, Jack M. and Bonnie Digrius. 2003. Making Technology Investment Profitable, ROI Roadmap to
Better Business Cases (New York: John Wiley and Sons).

Spencer, Robert H. and Randolph P. Johnston. 2003. Technology Best Practices (New York:
John Wiley and Sons).
Update: Key IT issues and trends
Authors: Edwards James B.
Published: June 2003

It seems that changes are rushing toward us at an accelerating rate. Most business analysts see a period of
uncertainty ahead. So what will be the key issues and trends for IT in the immediate future—and
beyond? © 2003 Wiley Periodicals, Inc.
Parameterization of charge model 3 for AM1, PM3, BLYP, and B3LYP
Authors: Thompson Jason D. , Cramer Christopher J. , Truhlar Donald G.
Published: June 2003

We have recently developed a new Class IV charge model for calculating partial atomic charges in molecules. The new model, called Charge Model 3 (CM3), was parameterized for calculations on molecules containing H, Li, C, N, O, F, Si, S, P, Cl, and Br by Hartree–Fock theory and by hybrid density functional theory (DFT) based on the modified Perdew–Wang density functional with several basis sets. In the present article we extend CM3 to semiempirical molecular orbital theory, in particular Austin Model 1 (AM1) and Parameterized Model 3 (PM3), and to the popular BLYP and B3LYP DFT and hybrid DFT methods, respectively. For the BLYP extension, we consider the 6‐31G(d) basis set, and for the B3LYP extension, we consider three basis sets: 6‐31G(d), 6‐31+G(d), and MIDI!6D. We begin with the previous CM3 strategy, which involves 34 parameters for 30 pairs of elements. We then refine the model to improve the charges in compounds that contain N and O. This modification, involving two new parameters, leads to improved dipole moments for amides, bifunctional H, C, N, O compounds, aldehydes, ketones, esters, and carboxylic acids; the improvement for compounds not containing N results from obtaining more physical parameters for carbonyl groups when the OCN conjugation of amides is addressed in the parameterization. In addition, for the PM3 method, we added an additional parameter to improve dipole moments of compounds that contain bonds between C and N. This additional parameter leads to improved accuracy in the dipole moments of aromatic nitrogen heterocycles with five‐membered rings. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1291–1304, 2003
On the kinematics of protein folding
Authors: Cahill Sean , Cahill Michael , Cahill Kevin
Published: June 2003

We offer simple solutions to three kinematic problems that occur in the folding of proteins. We show how to construct suitably local elementary Monte Carlo moves, how to close a loop, and how to fold a loop without breaking the bond that closes it. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1364–1370, 2003
New analytic approximation to the standard molecular volume definition and its application to generalized Born calculations
Authors: Lee Michael S. , Feig Michael , Salsbury Freddie R. , Brooks Charles L.
Published: June 2003

In a recent article (Lee, M. S.; Salsbury, F. R. Jr.; Brooks, C. L., III. J Chem Phys 2002, 116, 10606), we demonstrated that generalized Born (GB) theory provides a good approximation to Poisson electrostatic solvation energy calculations if one uses the same definitions of molecular volume for each. In this work, we present a new and improved analytic method for reproducing the Lee–Richards molecular volume, which is the most common volume definition for Poisson calculations. Overall, 1% errors are achieved for absolute solvation energies of a large set of proteins and relative solvation energies of protein conformations. We also introduce an accurate SASA approximation that uses the same machinery employed by our GB method and requires a small addition of computational cost. The combined methodology is shown to yield an efficient and accurate implicit solvent representation for simulations of biopolymers. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1348–1356, 2003
Implementation of the finite field perturbation method in the CRYSTAL program for calculating the dielectric constant of periodic systems
Authors: Darrigan Clovis , Rérat Michel , Mallia Giuseppe , Dovesi Roberto
Published: June 2003

The finite field approach has been implemented in the periodic ab initio CRYSTAL program and been used for calculating the dielectric constants of crystalline LiF and MgO (FCC structure) and BeO (wurtzite structure). To maintain the periodicity along the applied field direction, a “sawtooth” potential is used in conjunction with a supercell scheme. Supercells four to five times longer than the primitive cell in the direction of the applied field provide well‐converged results. The influence of the computational parameters is discussed. An alternative scheme has also been implemented, for inner check, that consists of applying a static electric field to a slab of increasing thickness in the direction orthogonal to the surface; the dielectric response at the center of the slab is shown to converge rapidly to the bulk value evaluated with the sawtooth field. The method is accurate and permits the determination of nonlinear corrections to the dielectric constant. When used in conjunction with the local density approximation (LDA) scheme, it provides for the dielectric constant of the three above‐mentioned compounds values close to those recently obtained with a time‐dependent density functional theory approach. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1305–1312, 2003
A simple approach for improving the hybrid MMVB force field: Application to the photoisomerization of s‐cis butadiene
Authors: Garavelli Marco , Ruggeri Fabrizio , Ogliaro Francois , Bearpark Michael J. , Bernardi Fernando , Olivucci Massimo , Robb Michael A.
Published: June 2003

MMVB is a QM/MM hybrid method, consisting of a molecular mechanics force field coupled to a valence bond Heisenberg Hamiltonian parametrized from ab initio CASSCF calculations on several prototype molecules. The Heisenberg Hamiltonian matrix elements Qij and Kij, whose expressions are partitioned here into a primary contribution and second‐order correction terms, are calculated analytically in MMVB. When the original MMVB force field fails to produce potential energy surfaces accurate enough for dynamics calculations, we show that significant improvements can be made by refitting the second‐order correction terms for the particular molecule(s) being studied. This “local” reparametrization is based on values of Kij extracted (using effective Hamiltonian techniques) from CASSCF calculations on the same molecule(s). The method is demonstrated for the photoisomerization of s‐cis butadiene, and we explain how the correction terms that enabled a successful MMVB dynamics study [Garavelli, M.; Bernardi, F.; Olivucci, M.; Bearpark, M. J.; Klein, S.; Robb, M. A. J Phys Chem A 2001, 105, 11496] were refitted. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1357–1363, 2003
Theoretical studies on the molecular dependence of bond dissociation after core excitations II: CH3CO(CH2)nCN, n = 0–3
Authors: Takahashi Osamu , Joyabu Masanori , Mitani Masaki , Saito Ko , Iwata Suehiro
Published: June 2003

Approximate theoretical normal and resonant Auger spectra for a series of methylcyano ketones were calculated. Compared with our previous procedure, a set of initial molecular orbitals (MOs) for Auger decay probability calculations of the normal Auger process was modified by changing from a set of ground state MOs to a set of core‐holed MOs. For the resonant Auger process, a set of MOs was also modified in the same manner. Furthermore, the bond dissociation factor, which we introduced in the previous article, was also calculated to estimate the bond strength after Auger decay. The site‐selectivity for a series of methylcyano ketones was qualitatively explained, but a significant state‐specificity was not observed. Molecular size dependence after Auger decay was also discussed. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1329–1335, 2003
An ab initio study of microsolvation of LiF in water: Structures and properties of LiF–Wn, n = 1–9 complexes
Authors: Upadhyay D. M. , Mishra P. C.
Published: June 2003

Geometries of clusters of water molecules (Wn) and those of the LiF–Wn (n = 1–9) complexes were optimized using the B3LYP/6‐31+G** method. Geometries of the complexes up to n = 7 were also optimized using the MP2/6‐31+G** approach. Only one structure of each of Wn, n = 1–5 was considered to generate the complexes with LiF while two structures, one of a cage type and the other of a prism type, were considered for n = 6–9. The LiF–W2 complex is found to be most stable among the various complexes. The LiF–W6 complex, where W6 is of a cage type, is predicted to be substantially less stable than that where W6 is of a prism type. Certain existing ambiguities regarding the most stable structures of the LiF–Wn (n = 1–3) complexes have been resolved. The LiF molecule seems to divide the Wn clusters in the LiF–Wn (n = 3–6) complexes into different fragments where at least one W2‐like fragment is present. In LiF–W6 (cage), there is one W2‐like fragment while in LiF–W6 (prism), there are three W2‐like fragments. The LiF bond length is substantially increased in going from the gas phase to the different complexes, this increase being most prominent in LiF–W6, where W6 is of the cage or prism type. The LiF molecule, however, does not acquire the ionic structure Li+F− in any of the complexes studied here. An appreciable amount of electronic charge is transferred from LiF to the water molecules involved in the different complexes. In this process, the Li atom gains electronic charge in some cases, while the F atom considered separately, as well as the Li and F atoms taken together, lose the same in most cases. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1336–1347, 2003
A theoretical ab initio study on the H2NO + O3 reaction
Authors: Peiró–García Julio , Ramírez–Ramírez Víctor M. , Nebot–Gil Ignacio
Published: June 2003

The deviation of the NH2 pseudo‐first‐order decay Arrhenius plots of the NH2 + O3 reaction at high ozone pressures measured by experimentalists, has been attributed to the regeneration of NH2 radicals due to the subsequent reactions of the products of this reaction with ozone. Although these products have not yet been characterized experimentally, the radical H2NO has been postulated, because it can regenerate NH2 radicals through the reactions: H2NO + O3 → NH2 + O2 and H2NO + O3 → HNO + OH + O2. With the purpose of providing a reasonable explanation from a theoretical point of view to the kinetic observed behaviour of the NH2 + O3 system, we have carried ab initio electronic structure calculations on both H2NO + O3 possible reactions. The results obtained in this article, however, predict that of both reactions proposed, only the H2NO + O3 → NH2 + O2 reaction would regenerate indeed NH2 radicals, explaining thus the deviation of the NH2 pseudo‐first‐order decay observed experimentally. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1321–1328, 2003
Isomers of C20: An energy profile II
Authors: Beran Kyle A.
Published: June 2003

Semi‐empirical calculations, at the PM3 level provided within the Winmopac v2.0 software package, are used to geometrically optimize and determine the absolute energies (heats of formation) of a variety of C20 isomers that are predicted to exist in and around the bowl and cage isomers. Using the optimized Cartesian coordinates for the bowl and the cage isomers, a saddle‐point calculation was performed. The output file generated, containing energy, distance, and geometry information, is then organized into a graphical format. The resulting graph, which plots the energy of the 20‐atom system as a function of the distance from the geometric midpoint, is a two‐dimensional energy profile. This profile illustrates an estimation of the contours on the potential energy surface, showing energy minima and maxima that are encountered as the bowl evolves into the cage structure, or vice‐versa. To expand the surface into three dimensions, geometry optimizations were performed on the sets of Cartesian coordinates that correspond to energy minima in the bowl‐cage profile. Based on these optimizations, eight additional isomers of C20 have been identified and are predicted to be energetically stable. These additional isomers were subsequently subjected to saddle‐point calculations in order to identify those isomers that lie adjacent to one another on the three‐dimensional surface. Two isomers that are adjacent to each other will exhibit an energy profile that progresses smoothly from the potential well of each isomer up to the saddle point separating them. Consequently, these adjacent pairs of isomers establish a step‐wise transformation between the bowl and the cage. This process, which extends out over the three‐dimensional surface, is predicted to require less energy than that of the direct, two‐dimensional transformation predicted in the bowl‐cage profile. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1287–1290, 2003
Design and training of a neural network for predicting the solvent accessibility of proteins
Authors: Ahmad Shandar , Gromiha M. Michael
Published: June 2003

A feed‐forward neural network has been developed to predict the solvent accessibility/accessible surface area (ASA) of proteins using improved design and training methods. Several network issues ranging from the coding of ASA states to the problem of local minima of learning curve, have been addressed. Successful new approaches to overcome these problems are presented. Set of trained network weights for each ASA threshold is provided. It has been established that the prediction accuracy results with neural network are better than other reported results of ASA prediction, despite a high test to training data ratio. © 2003 Wiley Periodicals, Inc. J Comput Chem 11: 1313–1320, 2003
Wing‐locking mechanisms in aquatic Heteroptera
Authors: Gorb Stanislav N. , Goodwyn P.J. Perez
Published: June 2003

This account provides a detailed morphological and ultrastructural study of wing‐locking mechanisms (LM) in some aquatic Heteroptera. Scanning and transmission electron microscopy were used to describe the functional significance of macro‐ and microstructures holding wings tightly against the body at rest and those involved in functional diptery in flight. There are two types of LM holding the forewings (hemelytra) at rest: 1) wing‐to‐wing LM, and 2) wing‐to‐body LM. The first type includes the brush‐to‐brush LM, the clavus–clavus clamp and the clavus–clavus locking ridge. The second type includes devices locking the hemelytra to the body: the subcostal border of the hemelytra to the lateral border of mesepimeron, the knob‐and‐socket locking mechanism of the hemelytra, and the clavus‐locking mechanism to the scutellum groove. The hindwing is locked by a pair of microtrichial fields situated on the hindwing‐articulated pad at the basal area of the hindwing and on the thoracic pad in the vicinity of the wing articulation. Morphological and ultrastructural data suggest that different LM are parts of one mechanism holding wings to the body at rest. An additional locking mechanism, connecting the hemelytra with the hindwing, is the only LM providing functional diptery in flight. J. Morphol. 257:127–146, 2003. © 2003 Wiley‐Liss, Inc.
Anatomy of the middle ear of the japanese crane Grus japonensis (gruidae: Aves)
Authors: Vorster Willie , Starck J. Matthias
Published: June 2003

Comparative anatomical studies of the avian middle ear provide structural data from which functional models can be derived. Subsequent phylogenetic analyses may reveal the phylogenetic history of taxon and the evolution of the functional model of the middle ear. We studied serial sections of a nestling of Grus japonensis. The microscopic anatomy of the middle ear (including skeletal parts, nerves, blood vessels, tendons, and tympanic recesses) was described with the help of a polystyrene plate reconstruction. These results were compared to those from skulls of adult cranes. Structural peculiarities of the crane middle ear are: 1) the ventral and anterior closure of the middle ear cavity by a dense plate of connective tissue, which ossifies during posthatching development; 2) the S‐shaped infracolumellar process of the columella, of which the distal end forms a horizontal bar, and abuts against the ventral wall of the middle ear cavity; and 3) the absence of an intracolumellar hinge between the stapes and extracolumella. The crane middle ear shows the plesiomorphic pattern of middle ear structures of neognathous birds. We propose a one‐lever‐arm functional model for the middle ear of the crane, similar to that of paleognathous birds. J. Morphol. 257:260–269, 2003. © 2003 Wiley‐Liss, Inc.
Hemocytes of the centipede Scutigera coleoptrata (Chilopoda, Notostigmophora) with notes on their interactions with the tracheae
Authors: Hilken Gero , Brockmann Claudia , Nevermann Lutz
Published: June 2003

The hemocytes of Scutigera coleoptrata were investigated by light and electron microscopy. Four types of hemocytes were identified: prohemocytes, plasmatocytes, granulocytes, and spherulocytes. Only granulocytes could be distinguished from the three other types by May‐Grünwald staining, as this is the only hemocyte type demonstrating an eosinophilic reaction. Shape and size give further indications for distinguishing the cell types. In addition, differentiation is possible on the basis of their ultrastructure. However, only a combination of all three methods (staining and light and electron microscopy) allows clear separation of the cell types. As transitional stages between the cell types occur in S. coleoptrata, it is likely that prohemocytes, plasmatocytes, and granulocytes are ontogenetic stages of a single cell lineage. Special cell components and their possible functions are described. Plasmatocytes exocytose tubular structures that probably play a role in coagulation processes. These tubular structures develop in the grana of plasmatocytes. Also, a special arrangement of microtubules and microfilaments was demonstrated. For the first time interactions between hemocytes and tracheae are documented within the Chilopoda. It is assumed that the hemocytes meet their oxygen requirements directly from the tracheae. Phylogenetic implications of the results are discussed. J. Morphol. 257:181–189, 2003. © 2003 Wiley‐Liss, Inc.
Ventral neurons in the anterior nerve cord of amphioxus larvae. I. An inventory of cell types and synaptic patterns
Authors: Lacalli T.C. , Kelly S.J.
Published: June 2003

Serial sections were used to map the ventrally positioned neurons of the anterior nerve cord of a 12.5‐day amphioxus larva from the infundibular region to the end of somite 2. Synaptic patterns reveal five categories of descending pathways, four of which are associated with the ventral compartment (VC) motoneurons responsible for escape swimming. 1) Pre‐, para‐, and postinfundibular (tegmental) neurons with large varicosities and mixed vesicle populations provide both synaptic and paracrine input to various components of the tegmental neuropile and primary motor center. Four categories of these neurons are distinguished on the basis of their vesicles. 2) Multiple anterior sensory pathways converge on the large paired neurons (LPNs) located near the junction of somites 1 and 2. LPN synaptic output is almost exclusively contralateral. This, together with the evidence for cross‐innervation between the third pair of LPNs, is consistent with the latter acting as locomotory pacemakers. 3) Axons from several classes of tegmental neurons converge in the paraxial region on each side of the cord where they form distinct tracts, the upper paraxial bundles. The right bundle is larger than the left, which suggests a role during early development when myotome contractions are biased to one side. 4) Fibers in the ventral tracts from ipsilateral projection neurons, sensory neurons, and additional ascending fibers synapse repeatedly with VC motoneurons. This may be how the overall level of excitation of the latter is controlled so as to modulate their response to pacemaker input. The fifth pathway consists of fibers involved in controlling the dorsal compartment (DC) motoneurons responsible for slow swimming, which are largely isolated from inputs to the VC locomotory system. The ventral neurons of the primary motor center form a more or less continuous file on either side of the floor plate, with certain cell types showing a tendency to cluster. There are, however, few obvious patterns of the kind expected if development were controlled by a rigid, lineage‐based mechanism. The evolutionary implications of the involvement of a midbrain‐level pacemaker in controlling larval swimming in amphioxus is discussed. J. Morphol. 257:190–211, 2003. © 2003 Wiley‐Liss, Inc.
Postembryonic development of the wing imaginal discs in the female wingless bagworm moth Eumeta variegata (Lepidoptera, Psychidae)
Authors: Niitsu Shuhei
Published: June 2003

The process of wing disc development and degeneration in the bagworm moth Eumeta variegata was investigated histologically. Morphological differences between two sexes first appear in the penultimate (eighth) larval instar. In the male, wing discs proliferate rapidly in the penultimate larval instar and continue proliferating; a conspicuous peripodial epithelium forms in the last (ninth) larval instar. The hemopoietic organs break down in this stage and disappear completely by the prepupal stage. In the female, in contrast, the wing discs remain as in the previous (seventh) instar, without proliferation of cells inside. No peripodial epithelium forms in the penultimate instar or later. Hemopoietic organs are still attached to the wing discs in the last larval instar and the entire wing discs transform into a plain, thick epidermis in the prepupal period. It is suggested that the hemopoietic organs may prevent the wing discs from developing in E. variegata. J. Morphol. 257:164–170, 2003. © 2003 Wiley‐Liss, Inc.
Male genital system and spermiogenesis of Nanorchestes amphibius (Acari: Endeostigmata: Nanorchestidae): Anatomy, histology, and evolutionary implications
Authors: Müller Gunnar
Published: June 2003

In the present article the anatomy and histology of the male genital system of an endeostigmatid mite are described for the first time. The Endeostigmata probably are a paraphyletic group supposed to include the most primitive actinotrichid mites. In Nanorchestes amphibius, the testis comprises a paired germinal region connected with an unpaired glandular region. In the germinal region, spermiogenesis takes place in cysts of a somatic cell containing germ cells representing the same developmental stage. In the lumen of the glandular region, the spermatozoa are stored together with secretions of the glandular epithelium. These secretions are probably involved in the formation of spermatophores. From the glandular region, spermatozoa and secretions are released into the vasa deferentia that histologically can be divided into three sections, beginning with a short paired region with strong circular muscles serving as a sphincter, continuing with a paired proximal zone, followed by a short unpaired distal section. The distal vas deferens leads into the chitinous, unpaired ductus ejaculatorius which is followed by the progenital chamber. The ductus ejaculatorius is composed of a proximal section and a proximal, central, and anterior chamber. It is accompanied by a complex system of muscles and sclerites probably involved in the formation and ejaculation of the spermatophore. A similar organization can also be found in Prostigmata, but not in Oribatida. Anterior to the progenital chamber is located a paired accessory gland that probably produces a lipid secretion. Spermiogenesis is characterized by disintegration of the nuclear envelope, condensation of chromatin, and extensive reduction of the amount of sperm cell cytoplasm. The mature aflagellate, U‐shaped spermatozoa are simple in structure and lack mitochondria and an acrosome complex. The results do not support the current view that Nanorchestidae are more closely related to Sarcoptiformes, i.e., Oribatida and Astigmata, than to Prostigmata. J. Morphol. 257:171–180, 2003. © 2003 Wiley‐Liss, Inc.
Developmental transformations in a normal series of embryos of the sea lamprey Petromyzon marinus (linnaeus)
Authors: Richardson Michael K. , Wright Glenda M.
Published: June 2003

Lamprey development is of interest to evolutionary biologists because it can inform our understanding of primitive vertebrate developmental patterns. In this study, we describe and illustrate some of the principle landmarks of organogenesis in the embryonic sea lamprey Petromyzon marinus L. at different chronological ages. We examined 63 fixed embryos spanning Piavis developmental stages 11–18+ (5–70 days postfertilization) by gross observation and histology. This period begins at late neurulation stages and ends with the formation of the larva (ammocoete). A significant difference with some previous accounts is that the anus develops not from a persistent blastopore, but by secondary canalization and proctodeum formation at the former site of the blastopore. Further, we show that the ciliated bands of the pharyngeal roof originate in the esophagus, distinguishing it from the intestine. We clarify the epithelialization of the gut, showing that the secondary gut cavity is progressively epithelialized from each end. We identify possible germ cells in the coelomic and cloacal walls. Balfour's “subnotochordal rod” is lacking in our specimens; we suggest that he may have misinterpreted the corpus adiposum. Our study is of potential value to the growing number of biologists interested in lamprey development and provides a character set that will be used : 1) in a phylogenetic study of vertebrate development, and 2) to prepare a staging series for the lamprey based on parsimony analysis. J. Morphol. 257:348–363, 2003. © 2003 Wiley‐Liss, Inc.
Morphological response of a bdelloid rotifer to desiccation
Authors: Ricci Claudia , Melone Giulio , Santo Nadia , Caprioli Manuela
Published: June 2003

We desiccated bdelloid rotifers (Macrotrachela quadricornifera), submitting the animals to four desiccation procedures (protocols A, B, C, D) that differed in the rate of water evaporation, in the time of desiccation, and in the substrates provided. We observed external morphological changes of the rotifer bodies during drying with scanning electron microscopy and, in parallel, assessed rates of recovery after a 7‐day period of dormancy. Two protocols produced disorganized morphologies of the anhydrobiotic animals, with no (A) or very poor (B) recovery. Protocols C and D gave rather high rates of recovery and dry rotifers appeared unaltered and well organized. The different protocols affected rotifer morphology during the 7‐day anhydrobiosis and rates of recovery after the 7‐day anhydrobiosis; high recovery rates corresponded to well‐organized morphologies of anhydrobiotic bdelloids, suggesting that a proper contraction of the body into a tun shape and probably a rigorous packing of internal structures are necessary for survival after anhydrobiosis. These features are affected by the time between water shortage and full desiccation, but also by the surrounding relative humidity and by the nature of the substrate. Possible adaptations of anhydrobiotic rotifers are discussed. J. Morphol. 257:246–253, 2003. © 2003 Wiley‐Liss, Inc.
Original molluscan radula: Comparisons among Aplacophora, Polyplacophora, Gastropoda, and the Cambrian fossil Wiwaxia corrugata
Authors: Scheltema Amélie H. , Kerth Klaus , Kuzirian Alan M.
Published: June 2003

As the original molluscan radula is not known from direct observation, we consider what the form of the original radula may have been from evidence provided by neomenioid Aplacophora (Solenogastres), Gastropoda, Polyplacophora, and the Cambrian fossil Wiwaxia corrugata (Matthews). Conclusions are based on direct observation of radula morphology and its accessory structures (salivary gland ducts, radular sac, anteroventral radular pocket) in 25 species and 16 genera of Aplacophora; radula morphogenesis in Aplacophora; earliest tooth formation in Gastropoda (14 species among Prosobranchia, Opisthobranchia, and Pulmonata); earliest tooth formation in four species of Polyplacophora; and the morphology of the feeding apparatus in W. corrugata. The existence of a true radula membrane and of membranoblasts and odontoblasts in neomenioids indicates that morphogenesis of the aplacophoran radula is homologous to that in other radulate Mollusca. We conclude from p
redness of salivary gland ducts, a divided radular sac, and a pair of anteroventral pockets that the plesiomorphic state in neomenioids is bipartite, formed of denticulate bars that are distichous (two teeth per row) on a partially divided or fused radula membrane with the largest denticles lateral, as occurs in the genus Helicoradomenia. The tooth morphology in Helicoradomenia is similar to the feeding apparatus in W. corrugata. We show that distichy also occurs during early development in several species of gastropods and polyplacophorans. Through the rejection of the null hypothesis that the earliest radula was unipartite and had no radula membrane, we conclude that the original molluscan radula was similar to the radula found in Helicoradomena species. J. Morphol. 257:219–245, 2003. © 2003 Wiley‐Liss, Inc.