bluuebunny/crossref_metadata_2025 huggingface dataset:
Expression of Interleukin (IL)-18 and Functional IL-18 Receptor on Human Vascular Endothelial Cells, Smooth Muscle Cells, and Macrophages
Authors: Gerdes Norbert , Sukhova Galina K. , Libby Peter , Reynolds Rebecca S. , Young James L. , Schönbeck Uwe
Published: July 2002

Although considerable evidence implicates the cytokine interferon (IFN)-γ in atherogenesis, the proximal inducers and the range of sources of its expression remain unknown. This study tested the hypothesis that interleukin (IL)-18 regulates IFN-γ expression during atherogenesis. Indeed, human atheroma in situ expressed IL-18 and elevated levels of its receptor subunits, IL-18Rα/β, compared with nondiseased arterial tissue. IL-18 occurred predominantly as the mature, 18-kD form and colocalized with mononuclear phagocytes (MØ), while endothelial cells (ECs), smooth muscle cells (SMCs), and MØ all expressed IL-18Rα/β. Correspondingly in vitro, only MØ expressed IL-18, while all three cell types displayed the IL-18Rα/β complex constitutively, exhibiting enhanced expression upon stimulation with LPS, IL-1β, or tumor necrosis factor (TNF)-α. IL-18 signaling evoked effectors involved in atherogenesis, e.g., cytokines (IL-6), chemokines (IL-8), intracellular adhesion molecules (ICAM)-1, and matrix metalloproteinases (MMP-1/-9/-13), demonstrating functionality of the receptor on ECs, SMCs, and MØ. Finally, IL-18, particularly in combination with IL-12, induced the expression of IFN-γ in cultured MØ and, surprisingly, in SMCs (but not in ECs). The expression of functional IL-18 and IL-18 receptor on human atheroma-associated ECs, SMCs, and MØ, and its unexpected ability to induce IFN-γ expression in SMCs, suggests a novel paracrine proinflammatory pathway operating during atherogenesis.
The piecewise polynomial collocation method for nonlinear weakly singular Volterra equations
Authors: Brunner Hermann , Pedas Arvet , Vainikko Gennadi
Published: July 2002

Second-kind Volterra integral equations with weakly singular kernels typically have solutions which are nonsmooth near the initial point of the interval of integration. Using an adaptation of the analysis originally developed for nonlinear weakly singular Fredholm integral equations, we present a complete discussion of the optimal (global and local) order of convergence of piecewise polynomial collocation methods on graded grids for nonlinear Volterra integral equations with algebraic or logarithmic singularities in their kernels.
Geometric invariant theory and flips
Authors: Thaddeus Michael
Published: July 2002

We study the dependence of geometric invariant theory quotients on the choice of a linearization. We show that, in good cases, two such quotients are related by a flip in the sense of Mori, and explain the relationship with the minimal model program. Moreover, we express the flip as the blow-up and blow-down of specific ideal sheaves, leading, under certain hypotheses, to a quite explicit description of the flip. We apply these ideas to various familiar moduli problems, recovering results of Kirwan, Boden-Hu, Bertram-Daskalopoulos-Wentworth, and the author. Along the way we display a chamber structure, following Duistermaat-Heckman, on the space of all linearizations. We also give a new, easy proof of the Bialynicki-Birula decomposition theorem.
Identification of sequence-dependent DNA features correlating to activity of DNA sites interacting with proteins.
Authors: Ponomarenko M P , Ponomarenko J V , Frolov A S , Podkolodny N L , Savinkova L K , Kolchanov N A , Overton G C
Published: July 2002

MOTIVATION: The commonly accepted statistical mechanical theory is now multiply confirmed by using the weight matrix methods successfully recognizing DNA sites binding regulatory proteins in prokaryotes. Nevertheless, the recent evaluation of weight matrix methods application for transcription factor binding site recognition in eukaryotes has unexpectedly revealed that the matrix scores correlate better to each other than to the activity of DNA sites interacting with proteins. This observation points out that molecular mechanisms of DNA/protein recognition are more complicated in eukaryotes than in prokaryotes. As the extra events in eukaryotes, the following processes may be considered: (i) competition between the proteins and nucleosome core particle for DNA sites binding these proteins and (ii) interaction between two synergetic/antagonist proteins recognizing a composed element compiled from two DNA sites binding these proteins. That is why identification of the sequence-dependent DNA features correlating with affinity magnitudes of DNA sites interacting with a protein can pinpoint the molecular event limiting this protein/DNA recognition machinery. RESULTS: An approach for predicting site activity based on its primary nucleotide sequence has been developed. The approach is realized in the computer system ACTIVITY, containing the databases on site activity and on conformational and physicochemical DNA/RNA parameters. By using the system ACTIVITY, an analysis of some sites was provided and the methods for predicting site activity were constructed. The methods developed are in good agreement with the experimental data. AVAILABILITY: The database ACTIVITY is available at http://wwwmgs.bionet.nsc.ru/systems/Activity/ and the mirror site, http://www.cbil.upenn.edu/mgs/systems/acti vity/.
Strategies for the development of a peptide computer
Authors: Hug Hubert , Schuler Rainer
Published: July 2002

Motivation: We devise a computational model using protein–protein interactions.

Results: Peptide–antibody interactions can be used to perform a large number of small logical operations in parallel. We show for example how a sequence of operations can be used to compare the number of occurrences of an element in two sets and how to estimate the number of occurrences of an element in a set. Similar to DNA-computing, these techniques could in principle be extended to solve instances of NP-complete problems. We give as an example a procedure to solve examples of the satisfiability problem.

Contact: hubert.hug@medizin.uni-ulm.de; schuler@informatik.uni-ulm.de

* To whom correspondence should be addressed.
Protein unfolding by mitochondria
Authors: Matouschek Andreas , Pfanner Nikolaus , Voos Wolfgang
Published: July 2002

Protein unfolding is a key step in the import of some proteins into mitochondria and chloroplasts and in the degradation of regulatory proteins by ATP‐dependent proteases. In contrast to protein folding, the reverse process has remained largely uninvestigated until now. This review discusses recent discoveries on the mechanism of protein unfolding during translocation into mitochondria. The mitochondria can actively unfold preproteins by unraveling them from the N‐terminus. The central component of the mitochondrial import motor, the matrix heat shock protein 70, functions by both pulling and holding the preproteins.
The Drosophila Toll‐9 activates a constitutive antimicrobial defense
Authors: Ooi James Y , Yagi Yoshimasa , Hu Xiaodi , Ip Y Tony
Published: July 2002

The Toll family of transmembrane proteins participates in signaling infection during the innate immune response. We analyzed the nine Drosophila Toll proteins and found that wild‐type Toll‐9 behaves similar to gain‐of‐function Toll‐1. Toll‐9 activates strongly the expression of drosomycin, and utilizes similar signaling components to Toll‐1 in activating the antifungal gene. The predicted protein sequence of Toll‐9 contains a tyrosine residue in place of a conserved cysteine, and this residue switch is critical for the high activity of Toll‐9. The Toll‐9 gene is expressed in adult and larval stages prior to microbial challenge, and the expression correlates with the high constitutive level of drosomycin mRNA in the animals. The results suggest that Toll‐9 is a constitutively active protein, and implies its novel function in protecting the host by maintaining a substantial level of antimicrobial gene products to ward off the continuous challenge of microorganisms.
MyRIP, a novel Rab effector, enables myosin VIIa recruitment to retinal melanosomes
Authors: El‐Amraoui Aziz , Schonn Jean‐Sébastien , Küssel‐Andermann Polonca , Blanchard Stéphane , Desnos Claire , Henry Jean‐Pierre , Wolfrum Uwe , Darchen François , Petit Christine
Published: July 2002

Defects of the myosin VIIa motor protein cause deafness and retinal anomalies in humans and mice. We report on the identification of a novel myosin‐VIIa‐interacting protein that we have named MyRIP (myosin‐VIIa‐ and Rab‐interacting protein), since it also binds to Rab27A in a GTP‐dependent manner. In the retinal pigment epithelium cells, MyRIP, myosin VIIa and Rab27A are associated with melanosomes. In transfected PC12 cells, overexpression of MyRIP was shown to interfere with the myosin VIIa tail localization. We propose that a molecular complex composed of Rab27A, MyRIP and myosin VIIa bridges retinal melanosomes to the actin cytoskeleton and thereby mediates the local trafficking of these organelles. The defect of this molecular complex is likely to account for the perinuclear mislocalization of the melanosomes observed in the retinal pigment epithelium cells of myosinVIIa‐defective mice.
APC/Fizzy‐Related targets Aurora‐A kinase for proteolysis
Authors: Castro Anna , Arlot‐Bonnemains Yannick , Vigneron Suzanne , Labbé Jean‐Claude , Prigent Claude , Lorca Thierry
Published: July 2002

Aurora‐A kinase is a mitotic spindle‐pole‐associated protein that has been implicated in duplication and separation of centrosomes and in spindle assembly. The proper timing and amplitude of Aurora‐A expression seems to be important, as elevated levels of this protein have been associated with centrosome abnormalities and aneuploidy in mammalian cells. We show that Aurora‐A increases at the G2–M transistion and disappears completely at G1 in XL2 cells. Using Xenopus oocyte extracts, we demonstrate that degradation of Aurora‐A is mediated by the anaphase‐promoting complex (APC) and is regulated by Fizzy‐Related but not by Fizzy. Degradation of Aurora‐A depends on a D‐Box, but not on its KEN‐Box motif, as mutation of its C‐terminal D‐Box sequence induces stabilization of the protein. Accordingly, addition into the extracts of a cyclin B‐type D‐Box‐motif‐containing peptide completely suppresses its degradation. Furthermore, APC/Fizzy‐Related ubiquitylates the wild type but not a D‐Box mutant form of Aurora‐A in vitro. Consistent with these data, ectopic expression of Fizzy‐Related in Xenopus oocytes induces complete degradation of endogenous Aurora‐A. Aurora‐A is thus the first protein, at least in our assay system, that undergoes a D‐Box‐dependent degradation mediated by APC/Fizzy‐Related but not by APC/Fizzy.
A comparative study of the in-vitro activity of levofloxacin against Streptococcus pneumoniae
Authors: Reinert R. R. , Lütticken R. , Lemperle M. , Bryskier A.
Published: July 2002

In this study, the in-vitroactivity of levofloxacin against Streptococcus pneumoniae was compared with the activities of a range of other antibiotics. In total, 320 penicillin-susceptible and 30 penicillin-intermediate clinical isolates of S. pneumoniae were collected in Germany between 1992 and 1994 from patients with bacteraemic pneumonia. MICs were determined using the agar dilution methodology recommended by the NCCLS and the results with levofloxacin compared with those with ofloxacin, d -ofloxacin, ciprofloxacin, amoxycillin, cefpodoxime, cefixime, cefuroxime, faropenem, erythromycin and tetracycline. Levofloxacin (MIC 50 1 mg/L) was approximately twice as active against the isolates as ofloxacin (MIC 50 2 mg/L). d -ofloxacin (MIC 90 32 mg/L) showed no activity, while β-lactam antibiotics showed elevated MIC 90 values against penicillin-intermediate strains (amoxycillin, 1 mg/L; cefpodoxime, 2 mg/L; cefixime, 32 mg/L; cefuroxime, 8 mg/L) in comparison with the MIC 90 obtained with penicillin-susceptible strains (amoxycillin, 0.015 mg/L; cefpodoxime, 0.03 mg/L; cefixime, 0.5 mg/L; cefuroxime, 0.03 mg/L). Faropenem showed good activity against pneumococcal isolates (penicillin-susceptible strains, MIC 90 0.016 mg/L; penicillin-intermediate strains, MIC 90 0.25 mg/L). Erythromycin (MIC 90 8 mg/L) and tetracycline (MIC 90 64 mg/L) were also less active against penicillin-intermediate pneumococcal isolates. In conclusion, levofloxacin and faropenem may be useful in the treatment of pneumococcal infections caused by organisms with decreased susceptibility to penicillin.
CD44 anchors the assembly of matrilysin/MMP-7 with heparin-binding epidermal growth factor precursor and ErbB4 and regulates female reproductive organ remodeling
Authors: Yu Wei-Hsuan , Woessner J. Frederick , McNeish John D. , Stamenkovic Ivan
Published: July 2002

CD44 is a facultative proteoglycan implicated in cell adhesion and trafficking, as well as in tumor survival and progression. We demonstrate here that CD44 heparan sulfate proteoglycan (CD44HSPG) recruits proteolytically active matrix metalloproteinase 7 (matrilysin, MMP-7) and heparin-binding epidermal growth factor precursor (pro-HB-EGF) to form a complex on the surface of tumor cell lines, postpartum uterine and lactating mammary gland epithelium, and uterine smooth muscle. The HB-EGF precursor within this complex is processed by MMP-7, and the resulting mature HB-EGF engages and activates its receptor, ErbB4, leading to, among other events, cell survival. In CD44−/− mice, postpartum uterine involution is accelerated and maintenance of lactation is impaired. In both uterine and mammary epithelia of these mice, MMP-7 localization is altered and pro-HB-EGF processing as well as ErbB4 activation are decreased. Our observations provide a mechanism for the assembly and function of a cell surface complex composed of CD44HSPG, MMP 7, HB-EGF, and ErbB4 that may play an important role in the regulation of physiological tissue remodeling.
Calcineurin-dependent regulation of Crz1p nuclear export requires Msn5p and a conserved calcineurin docking site
Authors: Boustany Leila M. , Cyert Martha S.
Published: July 2002

Calcineurin, a conserved Ca2+/calmodulin-regulated protein phosphatase, plays a crucial role in Ca2+ signaling in a wide variety of cell types. In Saccharomyces cerevisiae, calcineurin positively regulates transcription in response to stress by dephosphorylating the transcription factor Crz1p/Tcn1p. Dephosphorylation promotes Crz1p nuclear localization in part by increasing the efficiency of its nuclear import. In this work, we show that calcineurin-dependent dephosphorylation of Crz1p also down-regulates its nuclear export. Using a genetic approach, we identify Msn5p as the exportin for Crz1p. In addition, we define the Crz1p nuclear export signal (NES) and show that it interacts with Msn5p in a phosphorylation-dependent manner. This indicates that calcineurin regulates Crz1p nuclear export by dephosphorylating and inactivating its NES. Finally, we define a motif in Crz1p, PIISIQ, similar to the PxIxIT docking site for calcineurin on the mammalian transcription factor NFAT, that mediates the in vivo interaction between calcineurin and Crz1p and is required for calcineurin-dependent regulation of Crz1p nuclear export and activity. Therefore, in yeast as in mammals, a docking site is required to target calcineurin to its substrate such that it can dephosphorylate it efficiently.
Rescue of neural tube defects in Pax-3-deficient embryos by p53 loss of function: implications for Pax-3- dependent development and tumorigenesis
Authors: Pani Lydie , Horal Melissa , Loeken Mary R.
Published: July 2002

Pax-3 is a transcription factor that is expressed in the neural tube, neural crest, and dermomyotome. We previously showed that apoptosis is associated with neural tube defects (NTDs) in Pax-3-deficient Splotch (Sp/Sp) embryos. Here we show that p53 deficiency, caused by germ-line mutation or by pifithrin-α, an inhibitor of p53-dependent apoptosis, rescues not only apoptosis, but also NTDs, in Sp/Sp embryos. Pax-3 deficiency had no effect on p53 mRNA, but increased p53 protein levels. These results suggest that Pax-3 regulates neural tube closure by inhibiting p53-dependent apoptosis, rather than by inducing neural tube-specific gene expression.
Structural studies of the pigeon cytosolic NADP+‐dependent malic enzyme
Authors: Yang Zhiru , Zhang Hailong , Hung Hui‐Chi , Kuo Chen‐Chin , Tsai Li‐Chu , Yuan Hanna S. , Chou Wei‐Yuan , Chang Gu‐Gang , Tong Liang
Published: July 2002

Malic enzymes are widely distributed in nature, and have important biological functions. They catalyze the oxidative decarboxylation of malate to produce pyruvate and CO2 in the presence of divalent cations (Mg2+, Mn2+). Most malic enzymes have a clear selectivity for the dinucleotide cofactor, being able to use either NAD+ or NADP+, but not both. Structural studies of the human mitochondrial NAD+‐dependent malic enzyme established that malic enzymes belong to a new class of oxidative decarboxylases. Here we report the crystal structure of the pigeon cytosolic NADP+‐dependent malic enzyme, in a closed form, in a quaternary complex with NADP+, Mn2+, and oxalate. This represents the first structural information on an NADP+‐dependent malic enzyme. Despite the sequence conservation, there are large differences in several regions of the pigeon enzyme structure compared to the human enzyme. One region of such differences is at the binding site for the 2′‐phosphate group of the NADP+ cofactor, which helps define the cofactor selectivity of the enzymes. Specifically, the structural information suggests Lys362 may have an important role in the NADP+ selectivity of the pigeon enzyme, confirming our earlier kinetic observations on the K362A mutant. Our structural studies also revealed differences in the organization of the tetramer between the pigeon and the human enzymes, although the pigeon enzyme still obeys 222 symmetry.
Validation of reconstructed bremsstrahlung spectra between 6 MV and 25 MV from measured transmission data
Authors: Francois P. , Coste F. , Bonnet J. , Caselles O.
Published: July 2002

We have previously investigated a method of high‐energy x‐ray spectral reconstruction from transmission data by direct resolution of a matrix system. This technique uses the spectral vectorial algebra formalism. The resolution has previously been tested on a 12 MV photon beam. To extend and to test the validity of the results to the entire radiotherapy energy range, we have performed the method on photon beams with nominal energies of 6, 12, 15, and 25 MV. The influence on the 6 MV spectrum of a 60° built‐in wedge has also been investigated to test the sensitivity of the method and the results are reported. To validate our reconstructed spectra, dosimetric quantities such as tissue phantom ratios (TPR), water‐to‐air stopping power ratios and quality indexes have been calculated. The results show good agreement between the measured and calculated data. Mean mass energy absorption coefficient ratios for different materials have also been computed and compared to data published recently and the results are very close (within ±0.5%). Primary depth dose functions in water have also been computed to deduce primary dose attenuation coefficients.
X‐ray spectra estimation using attenuation measurements from 25 kVp to 18 MV
Authors: Waggener Robert G. , Blough Melissa M. , Terry James A. , Chen Di , Lee Nina E. , Zhang Sean , McDavid William D.
Published: July 2002

Attenuation measurements for primary x‐ray spectra from 25 kVp to 18 MV were made using aluminum filters for all energies except for orthovoltage where copper filters were used. An iterative perturbation method, which utilized these measurements, was employed to derive the apparent x‐ray spectrum. An initial spectrum or pre‐spectrum was used to start the process. Each energy value of the pre‐spectrum was perturbed positively and negatively, and an attenuation curve was calculated using the perturbed values. The value of x‐rays in the given energy bin was chosen to minimize the difference between the measured and calculated transmission curves. The goal was to derive the minimum difference between the measured transmission curve and the calculated transmission curve using the derived x‐ray spectrum. The method was found to yield useful information concerning the lower photon energy and the actual operating potential versus the nominal potential. Mammographic, diagnostic, orthovoltage, and megavoltage x‐ray spectra up to 18 MV nominal were derived using this method. The method was validated using attenuation curves from published literature. The method was also validated using attenuation curves calculated from published spectra. The attenuation curves were then used to derive the x‐ray spectra.
Field just outside a long solenoid
Authors: Farley Jason , Price Richard H.
Published: July 2002

Simple lessons about static magnetic fields are often taught with the model of an “infinite” solenoid, outside of which the fields vanish. Just outside a very long but finite solenoid of length L, the field must be a decreasing function of L. We show that this external field is approximately uniform and decreases as L−2. Furthermore, we show that the study of this external field provides interesting and surprisingly simple illustrations of techniques for analyzing magnetic fields.
Development of energy concepts in introductory physics courses
Authors: Arons Arnold B.
Published: July 2002

The work-energy theorem, derived from Newton’s second law, applies to the displacement of a particle or the center of mass of an extended body treated as a particle. Because work, as a quantity of energy transferred in accordance with the First Law of Thermodynamics, cannot be calculated in general as an applied force times the displacement of center of mass, the work-energy theorem is not a valid statement about energy transformations when work is done against a frictional force or actions on or by deformable bodies. To use work in conservation of energy calculations, work must be calculated as the sum of the products of forces and their corresponding displacements at locations where the forces are applied at the periphery of the system under consideration. Failure to make this conceptual distinction results in various errors and misleading statements widely prevalent in textbooks, thus reinforcing confusion about energy transformations associated with the action in everyday experience of zero-work forces such as those present in walking, running, jumping, or accelerating a car. Without a thermodynamically valid definition of work, it is also impossible to give a correct description of the connection between mechanical and thermal energy changes and of dissipative effects. The situation can be simply corrected and student understanding of the energy concepts greatly enhanced by introducing and using the concept of internal energy, that is, articulating the First Law of Thermodynamics in a simple, phenomenological form without unnecessary mathematical encumbrances.
Acoustic monopoles, dipoles, and quadrupoles: An experiment revisited
Authors: Russell Daniel A. , Titlow Joseph P. , Bemmen Ya-Juan
Published: July 2002

A simple and inexpensive demonstration of acoustic monopole, dipole, and quadrupole sources utilizes four 4-in. boxed loudspeakers and a homemade switch box. The switch box allows the speakers to be driven in any combination of phase relationships. Placing the speakers on a rotating stool allows students to measure directivity patterns for monopole, dipole, and quadrupole speaker combinations. Stacking the speakers in a square, all facing the same direction, allows students to aurally compare the frequency and amplitude dependence of sound radiation from monopoles, dipoles, and quadrupoles.
A new method for true and spurious eigensolutions of arbitrary cavities using the combined Helmholtz exterior integral equation formulation method
Authors: Chen I. L. , Chen J. T. , Kuo S. R. , Liang M. T.
Published: July 2002

Integral equation methods have been widely used to solve interior eigenproblems and exterior acoustic problems (radiation and scattering). It was recently found that the real-part boundary element method (BEM) for the interior problem results in spurious eigensolutions if the singular (UT) or the hypersingular (LM) equation is used alone. The real-part BEM results in spurious solutions for interior problems in a similar way that the singular integral equation (UT method) results in fictitious solutions for the exterior problem. To solve this problem, a Combined Helmholtz Exterior integral Equation Formulation method (CHEEF) is proposed. Based on the CHEEF method, the spurious solutions can be filtered out if additional constraints from the exterior points are chosen carefully. Finally, two examples for the eigensolutions of circular and rectangular cavities are considered. The optimum numbers and proper positions for selecting the points in the exterior domain are analytically studied. Also, numerical experiments were designed to verify the analytical results. It is worth pointing out that the nodal line of radiation mode of a circle can be rotated due to symmetry, while the nodal line of the rectangular is on a fixed position.
The contribution of two ears to the perception of vertical angle in sagittal planes
Authors: Morimoto Masayuki
Published: July 2002

Because the input signals to the left and right ears are not identical, it is important to clarify the role of these signals in the perception of the vertical angle of a sound source at any position in the upper hemisphere. To obtain basic findings on upper hemisphere localization, this paper investigates the contribution of each pinna to the perception of vertical angle. Tests measured localization of the vertical angle in five planes parallel to the median plane. In the localization tests, the pinna cavities of one or both ears were occluded. Results showed that pinna cavities of both the near and far ears play a role in determining the perceived vertical angle of a sound source in any plane, including the median plane. As a sound source shifts laterally away from the median plane, the contribution of the near ear increases and, conversely, that of the far ear decreases. For saggital planes at azimuths greater than 60° from midline, the far ear no longer contributes measurably to the determination of vertical angle.
Experimental study of vibrational behavior of laminated annular disks
Authors: Wang Huan
Published: July 2002

The purpose of this paper is to present an experimental study of the vibrational behavior of laminated annular disks, and effects of laminations on the vibrations of the disks. The vibrations of a series of solid annular disks were calculated using the finite-element method in order to provide a basis for comparison with experimental data. An extensive range of experiments was performed on both a series of solid disks and a series of laminated disks under a range of normal clamping pressures. Based on the calculated and experimental results, it was found that the vibrational behavior of the laminated disks was dominated by that of the individual disk, of which the laminated disks were composed. Laminations had great effects on the vibrational behavior of the laminated disks and the effects depended upon the mode type, the clamping pressure, and the number of disk assembly. Laminations increased damping and reduced the amplitude of frequency response function for both the transverse modes and in-plane modes of disks. The resonant frequency of transverse modes shifted higher because of the effects of laminations. For the in-plane vibrational modes, the effects on the resonant frequency could be neglected and the resonant frequency could be considered to be a constant.
Active, wideband detection and localization in an uncertain multipath environment
Authors: Wazenski M. , Alexandrou D.
Published: July 2002

Active, wideband detection and localization of targets in a dense multipath environment is approached via optimal detection and estimation theory in conjunction with a received signal model described by weighted, delayed, and phase-shifted replicas of the transmitted signal. These multipath signal parameters are known to vary with acoustic medium properties including sound-speed profile, bottom composition and topography, and sea surface state. The optimum receiver is a time domain processor based on the statistical properties of the multipath parameters. An acoustic propagation model drives the optimum receiver by mapping acoustic medium parameters to multipath signal parameters through Monte Carlo simulation. The generic sonar model (GSM) software package provides the required simulation environment. Illustrative detection and localization examples are presented in the form of receiver operator characteristics (ROC) and localization ROCs, respectively. Results demonstrate significant improvement in detection and localization over standard matched filtering, even with uncertainty of the physical environment and random effects of boundary scattering.
Optical pulse width measurements of sonoluminescence in cavitation-bubble fields
Authors: Matula Thomas J. , Roy Ronald A. , Mourad Pierre D.
Published: July 2002

Optical pulse width measurements of sonoluminescence from cavitation-bubble fields have been obtained for two well-defined cavitation zones in an aqueous solution of Glycerin using a fast (650 ps rise-time) PMT and a fast (10 GS/S) digitizer. One zone corresponds to cavitation produced from an ultrasonic homogenizer. A lens was used to focus on a particular region of “streaming” sonoluminescence. A second, more localized cavitation zone was produced using a 2-in-diam PZT driving crystal in a rectangular fluid-filled container. Single-bubble sonoluminescence was used to characterize the response of the PMT to low-level light input. The measured rise-time and pulse width for sonoluminescence from cavitation fields is indicative of the response of the PMT and suggests that the pulse width of cavitation-field sonoluminescence is much less than 1.1 ns.
The natural frequency of oscillation of gas bubbles in tubes
Authors: Og̃uz H. N. , Prosperetti A.
Published: July 2002

A numerical study is presented of the natural frequency of the volume oscillations of gas bubbles in a liquid contained in a finite-length tube, when the bubble is not small with respect to the tube diameter. Tubes rigidly terminated at one end, or open at both ends, are considered. The open ends may be open to the atmosphere or in contact with a large mass of liquid. The numerical results are compared with a simple approximation in which the bubble consists of a cylindrical mass of gas filling up the cross section of the tube. It is found that this approximation is very good except when the bubble radius is much smaller than that of the tube. An alternative approximate solution is developed for this case. The viscous energy dissipation in the tube is also estimated and found generally small compared with the thermal damping of the bubble. This work is motivated by the possibility of using gas bubbles as actuators in fluid-handling microdevices.
The potential of transskull ultrasound therapy and surgery using the maximum available skull surface area
Authors: Sun Jie , Hynynen Kullervo
Published: July 2002

Based on previous studies, the transskull ultrasound field is re-examined by utilizing the maximum available skull surface area. The source is assumed to be in direct contact with the skull outer surface, and phase correction is adopted to obtain a sharp focus at a desired location. A digitized skull profile was obtained from Magnetic Resonance (MR) scan images of a volunteer. Two driving frequencies (0.5 and 1.0 MHz) within the appropriate frequency range for transskull ultrasound therapy and surgery are investigated. With no phase correction, there is no apparent transskull focus. With phase correction, a sharp transskull focus is obtained at the desired location. Both pressure and specific absorption rate (SAR) gains (ratios of pressure amplitude and SAR at the focal point compared to those on the outer skull surface) are examined, and it is shown that the skull heating problem can be overcome by utilizing the maximum available skull surface area. By specifying the phase correction for different locations, the focus can be successfully moved inside the deep brain volume without significantly compromising the pressure and SAR gains; however, the sidelobes may be of concern at superficial sites.
Exact solutions for the problem of source location from measured time differences of arrival
Authors: Duraiswami Ramani , Zotkin Dmitry , Davis Larry
Published: July 2002

Source location using the difference in time of arrival of a signal (TDOA) at an array of receivers is used in many fields including speaker location. Using three TDOA values from four noncollinear receivers one can, in principle, solve for the unknown source coordinates in terms of the receiver locations. However, the equations are nonlinear, and in practice signals are contaminated by noise. Practical systems often use multiple receivers for accuracy and robustness, and improved S/N, and solutions must be obtained via minimization. A new family of exact solutions, for the case of four receivers located in a plane, is presented. These solutions can be evaluated using a small number of arithmetic operations. The performance of these solutions for several practical situations is examined via simulation, and possible geometries of receiver locations suggested. For the case where multiple receivers (>4) are used, a new formulation is presented, that incorporates the present solutions, imposes additional constraints on source location, and enables use of a constrained L1 optimization procedure to achieve a robust estimate of the source location. The present estimator is compared with ones from the literature, and found to be robust and accurate, and more efficient. [Work partially supported by DARPA.]
Falling Sphere Viscometry. II. End Effects in Short Tubes
Authors: Sutterby J. Lloyd
Published: July 2002

Stokes' law for determining viscosity from sphere fall velocity applies in the absence of wall, inertial, and end effects. One objective of this investigation was to establish a criterion for choosing a tube long enough to avoid end effects. The resulting criterion is as follows. For L/D=2 and d/D<0.125 there are no observable end effects throughout the middle third of the fall tube, even for Re as large as 2. Another objective was to establish a correlation of simultaneous wall and end corrections to Stokes' law in the absence of inertial effects, for application in short tube viscometry. The desired correlation is presented in Figure 3 and Table I.
Steady shear alignment of block copolymers near the isotropic–lamellar transition
Authors: Fredrickson Glenn H.
Published: July 2002

A theory is presented to describe the orientational dynamics of block copolymer lamellar phases subjected to steady shear flow. By modifying an earlier theory by Cates and Milner to incorporate different viscosities of the pure block components, as well as restoring some neglected couplings between the mean composition pattern and composition fluctuations about the mean, it is demonstrated that the qualitative features of experimental observations on sheared poly(ethylene–propylene)–poly(ethylethylene) diblock copolymer melts can be reproduced. The theory may also be applicable to certain lyotropic lamellar phases assembled from nonpolymeric surfactants.
New technique allowing the quantification of diffusion at polymer/polymer interfaces using rheological analysis: Theoretical and experimental results
Authors: Qiu Hua , Bousmina M.
Published: July 2002

A new technique allowing the quantification of diffusion at polymer/polymer interfaces and also measurement of the self-diffusion coefficient of polymer melts using rheological tools has been developed. The technique consists of measuring the dynamic moduli as a function of time for a multilayer sandwich-like assembly at temperature slightly above Tg. The technique was tested on a polystyrene/polystyrene (PS/PS) system sheared in oscillatory mode under small amplitudes of deformation for different times of welding. The experimental results showed that the dynamic complex shear modulus increased with the elapsed time of welding. The increase was attributed to the diffusion of polymer chains at the superimposed interface layers. Based on the reptation theory, an analytical expression for the self-diffusion coefficient as a function of polymer rheological material functions was derived. Graessley’s expression [] for the bulk self-diffusion coefficient is recovered as a special case. The obtained self-diffusion coefficient for polystyrene was found to be in good agreement with the literature data reporting the self-diffusion coefficient of PS measured by classical techniques.
Atomic Layer Deposition of CoxOy Films: Oxidants versus Composition
Authors: Wan Zhixin , Zhang Teng Fei , Zeng Zhihao , Xi Bin
Published: April 2022

Cobalt oxides (CoxOy) have shown great potential for applications in catalysts, sensors, and energy storage fields, and their performance remarkably depends on their oxidation states. Herein, CoxOy films with precisely controlled composition are first introduced by atomic layer deposition (ALD) using bis(N,N0‐di‐iso‐propylacetamidinato)cobalt(II) (Co(iPr2‐Me‐AMD)2) as Co precursor and H2O/O3 as oxidants. The results show that the ALD processes using both oxidants exhibit typical self‐limiting characteristic, where cubic‐CoO films, with growth rate of 0.045 nm per cycle, are obtained at 150–200 °C using H2O oxidant, while cubic‐Co3O4 films, with growth rate of 0.05 nm per cycle, can be deposited at 200–225 °C using O3 oxidant. Both CoO and Co3O4 films show dense, smooth microstructure, and good crystallinity with typical columnar crystal feature, where the Co3O4 film shows smaller columnar size because the O3 promotes rapid nucleation with relatively higher density of nucleation sites. The thermodynamic growth mechanism of ALD process is established via density functional theory calculations, which demonstrates that the exothermic reaction path of O3 is more energetically than that of H2O. Both films possess relatively low resistivity of ≈10−1 Ω cm−1 with p‐type semiconductor behavior, which shows promising application potentials of these films.
Printed Chalcogenide/Metal Heterostructured Photodetectors for Flexible Near‐Infrared Sensing
Authors: Wang Jianyang , Pan Qi , Xie Hongfei , Ma Ying , Su Meng , Chen Binda , Wang Huadong , Xue Tangyue , Zhang Zeying , Chi Jimei , Li Siyi , Song Yanlin
Published: April 2022

Near‐infrared (NIR) photodetectors can be fabricated for various applications, such as imaging, military tracking, and medical diagnosis. However, achieving miniaturization and high responsivity for NIR photodetector arrays is still a challenge. In this study, a high‐density NIR photodetector array with a micro/nano chalcogenide and silver nanoparticle heterostructure is achieved using a low‐cost printing strategy. The Ag/Ge2Sb2Te5(GST)/Ag heterostructure is fabricated using a template‐assisted sequential printing strategy. At an absorption wavelength of λ = 980 nm, the NIR photodetector has a high light responsivity of 6.7 × 104 A W−1 owing to the high crystallinity of the GST microwire and refined GST/Ag heterointerface during the printing process. In addition, the sensing pixel interval can be reduced to 25 µm, corresponding to the highest resolution of NIR photodetectors achieved thus far (resolution: 1.0 × 103 dpi). In addition, the NIR photodetector printed on soft substrates exhibits flexibility. Thus, a simple and effective strategy for the fabrication of NIR photodetectors is demonstrated, and precise flexible infrared sensing is achieved.
Theoretical Study on Thermoelectric Performance of N‐Type Mg3(Sb,Bi)2 Single Crystal for Cooling or Power Generation
Authors: Li Juan , Zhang Shuai , Zheng Shuqi , Han Kai , Sun Bing , Bi Zuozhang , Wang Xinle
Published: April 2022

Mg3Sb2‐based Zintl compounds have been paid much attention in recent years because of their high peak figure of merit (zT), however, there is room for the improvement of the average zT. In this work, the thermoelectric performance of Mg3(Sb,Bi)2 single crystal by using density functional theory is investigated. The optimal carrier concentration (n) of Mg3SbBi is 2 × 1019 to 3 × 1020 cm–3 at 100−700 K. At the n of 3 × 1019 cm–3, it can exhibit a high average zT of ≈1.27 at cold‐side temperature (Tc) of 300 K and hot‐side temperature (Th) of 700 K, and the electrical transport performance can be further improved by increasing the n. When the optimal n is reached, the maximum average zT of Mg3SbBi at Tc of 100 K and Th of 300 K can be up to 0.54, which is comparable to that of state‐of‐the‐art Bi2(Te,Se)3. Because the decreasing trend of the optimal n with temperature, the maximum low‐temperature thermoelectric performance is easier to be achieved by less extrinsic doping. This work reveals the great potential of Mg3(Sb,Bi)2 single crystal for thermoelectric cooling or power generation, which is expected to provide useful guidance for thermoelectric devices.
Artificial Olfactory Neuron for an In‐Sensor Neuromorphic Nose
Authors: Han Joon‐Kyu , Kang Mingu , Jeong Jaeseok , Cho Incheol , Yu Ji‐Man , Yoon Kuk‐Jin , Park Inkyu , Choi Yang‐Kyu
Published: April 2022

A neuromorphic module of an electronic nose (E‐nose) is demonstrated by hybridizing a chemoresistive gas sensor made of a semiconductor metal oxide (SMO) and a single transistor neuron (1T‐neuron) made of a metal‐oxide‐semiconductor field‐effect transistor (MOSFET). By mimicking a biological olfactory neuron, it simultaneously detects a gas and encoded spike signals for in‐sensor neuromorphic functioning. It identifies an odor source by analyzing the complicated mixed signals using a spiking neural network (SNN). The proposed E‐nose does not require conversion circuits, which are essential for processing the sensory signals between the sensor array and processors in the conventional bulky E‐nose. In addition, they do not have to include a central processing unit (CPU) and memory, which are required for von Neumann computing. The spike transmission of the biological olfactory system, which is known to be the main factor for reducing power consumption, is realized with the SNN for power savings compared to the conventional E‐nose with a deep neural network (DNN). Therefore, the proposed neuromorphic E‐nose is promising for application to Internet of Things (IoT), which demands a highly scalable and energy‐efficient system. As a practical example, it is employed as an electronic sommelier by classifying different types of wines.
RETRACTED: Research on the mechanism and efficiency of agricultural products logistics transportation based on big data
Authors: Liu Huiyi
Published: April 2022

In order to improve the efficiency of agricultural product logistics transportation, based on big data technology, this paper starts from the factors that affect the efficiency of agricultural product logistics and combines big data technology to conduct the research on the mechanism and efficiency of agricultural products logistics transportation. Moreover, this paper analyzes how to improve the efficiency of agricultural product logistics by studying the dynamic relationship between influencing factors and the efficiency of agricultural product logistics. At the same time, this paper takes the efficiency evaluation of agricultural product logistics transportation network as the research object to improve the agricultural product data analysis algorithm, and constructs the system model from the perspective of the supply chain. In addition, this paper constructs system function modules according to the actual needs of agricultural product logistics transportation, and analyzes agricultural product transportation logistics by factor analysis. Finally, this paper verifies the effect of the model proposed in this paper through experimental research. From the test results, it can be seen that the model proposed in this paper basically meets the actual needs.
Morphological differences between putative Paleolithic dogs and wolves: A commentary to Janssens et al. (2021)
Authors: Galeta Patrik , Lázničková‐Galetová Martina , Sablin Mikhail , Germonpré Mietje
Published: April 2022

Janssens et al. (2021, doi: 10.1002/ar.24624) recently commented on our article (Galeta et al., 2021, doi: 10.1002/ar.24500) regarding the morphological differences between putative Paleolithic dog and Pleistocene wolf crania. The authors argued that these differences reflect the normal population variation of wolves, that some of the cranial measurements used do not reflect morphological changes during domestication, and that our canid dataset was small because we inexplicably omitted several specimens we analyzed in our previous publications. In this commentary, we briefly address the issue of within and between morpho‐population variability. The results based on our canid sample suggest that the magnitude of morphological differences between distinct morpho‐populations (i.e., recent northern dogs and wolves) is at least twice as large as that observed within morpho‐populations (between two groups of recent northern wolves segregated by cluster analysis). The morphological differences between putative Paleolithic dogs and Pleistocene wolves are relatively large, which may indicate that they did not likely represent a single Late Pleistocene morpho‐population. Finally, we clarified the rationale behind the composition of our 2021 dataset to show that we did not adjust the list of the analyzed specimens. Although the sample size was small, the randomization analysis published in 2021 confirmed that the unbalanced composition of the reference sample did not affect the reliability of the morphological segregation of putative Paleolithic dogs and Pleistocene wolves.
Synthesis of Novel Glycolipid Mimetics of Heparan Sulfate and Their Application in Colorectal Cancer Treatment in a Mouse Model
Authors: Spijkers‐Shaw Sam , Campbell Katrin , Shields Nicholas J. , Miller John H. , Rendle Phillip M. , Jiao Wanting , Young Sarah L. , Zubkova Olga V.
Published: April 2022

Heparan sulfate (HS) is a highly sulfated natural carbohydrate that plays crucial roles in cancer, inflammation, and angiogenesis. Heparanase (HPSE) is the sole HS degrading endoglycosidase that cleaves HS at structure‐dependent sites along the polysaccharide chain. Overexpression of HPSE by cancer cells correlates with increased tumor size and enhanced metastasis. Previously we have shown that a tetramer HS mimetic is a potent HPSE inhibitor displaying remarkable anticancer activity in vivo. Building on that work, we report the synthesis and testing of a novel library of single entity trimer glycolipid mimetics that effectively inhibit HPSE at low nanomolar concentrations. A lipophilic arm was introduced to assess whether an improvement of pharmacokinetics and plasma residence time would offset the reduction in charge and multivalency. Preclinical tests in a mouse syngeneic model showed effective tumor growth inhibition by the tetramer but not the trimer glycomimetic.