bluuebunny/crossref_metadata_2025 huggingface dataset:
Cryogen spray cooling in laser dermatology: Effects of ambient humidity and frost formation
Authors: Majaron Boris , Kimel Sol , Verkruysse Wim , Aguilar Guillermo , Pope Karl , Svaasand Lars O. , Lavernia Enrique J. , Nelson J. Stuart
Published: October 2004

Background and Objective

Dynamics of cryogen spray deposition, water condensation and frost formation is studied in relationship to cooling rate and efficiency of cryogen spray cooling (CSC) in combination with laser dermatologic surgery.

Study Design/Materials and Methods

A high‐speed video camera was used to image the surface of human skin during and after CSC using a commercial device. The influence of ambient humidity on heat extraction dynamics was measured in an atmosphere‐controlled chamber using an epoxy block with embedded thermocouples.

Results

A layer of liquid cryogen may remain on the skin after the spurt termination and prolong the cooling time well beyond that selected by the user. A layer of frost starts forming only after the liquid cryogen retracts. Condensation of ambient water vapor and subsequent frost formation deposit latent heat to the target site and may significantly impair the CSC cooling rate.

Conclusions

Frost formation following CSC does not usually affect laser dosage delivered for therapy of subsurface targets. Moreover, frost formation may reduce the risk of cryo‐injury associated with prolonged cooling. The epidermal protection during CSC assisted laser dermatologic surgery can be further improved by eliminating the adverse influence of ambient humidity. Lasers Surg. Med. 39:469–476, 2001. © 2001 Wiley‐Liss, Inc.
Ti‐O – Ein Stoffsystem mit erscheinungsreichen tribologischen Eigenschaften
Authors: Woydt M.
Published: October 2004

Das ungeschmierte tribologische Verhalten von verschiedenen Stoichiometrien und mit unterschiedlichen Verfahren hergestellten Schichten und Werkstoffen im System Ti‐O wird vorgestellt. Der Phasenreichtum geht einher mit dem gleichen Erscheinungsreichtum im tribologischen Verhalten. Obwohl aus den Stoffeigenschaften kaum erkennbar, offenbart das System Ti‐O eine phasenweise herausragende Verschleißbeständigkeit, allerdings wurden Reibungszahlen von 0,2 kaum unterschritten.
Differential expression of cytokines in rat osteosarcoma and malignant fibrous histiocytoma cell lines induced by 4‐(hydroxyamino)quinoline‐1‐oxide
Authors: Honoki Kanya , Tsujiuchi Toshifumi , Sasaki Yasutaka , Tsutsumi Masahiro , Morishita Toru , Kido Akira , Miyauchi Yoshizumi , Mii Yoshio , Takakura Yoshinori , Konishi Yoichi
Published: October 2004

Cytokines are considered to play an important role in tumor pathogenesis and progression, and recent studies have demonstrated that a variety of forms, including interleukins (ILs) and transforming growth factor‐βs (TGF‐βs), may regulate tumors. In the present study, the expression of TGF‐β isoforms and ILs was investigated in cell lines from a rat osteosarcoma and a malignant fibrous histiocytoma (MFH), both established from transplantable tumors induced by 4‐(hydroxyamino) quinoline 1‐oxide (4‐HAQO) in syngeneic F344 male rats. The results of a multiprobe RNase protection assay showed TGF‐β1 expression to be remarkably elevated, with no TGF‐β2 and β3 detectable in MFH cells, while TGF‐β1 and ‐β2 were found to be moderately and TGF‐β3 weakly expressed in osteosarcoma lines. All cell lines of osteosarcomas and MFHs expressed macrophage migration inhibitory factor at similar levels. In contrast to the lack of ILs in the MFH cells, moderate IL‐6 and very weak IL‐1β expression was detected in the osteosarcoma cells. These results suggest that variation in expression pattern of these cytokines in osteosarcomas and MFHs might be involved in differences in histological appearance and biological behavior, including metastatic ability, between these two mesenchyme‐derived tumor types. © 2002 Wiley‐Liss, Inc.
Tlag2, an N‐methyl‐N‐nitrosourea susceptibility locus, maps to mouse chromosome 4
Authors: Angel Joe M. , Richie Ellen R.
Published: October 2004

Susceptibility to N‐methyl‐N‐nitrosourea (MNU)–induced lymphomas is a multigenic trait. We previously mapped a resistance locus (Tlag1) to mouse chromosome 7 in genetic crosses of sensitive AKR with resistant C57L mice. Analysis of the MNU sensitivity of AKXL recombinant inbred strains that are homozygous for the AKR allele of Tlag1 suggested that at least two additional tumor susceptibility loci segregate in these crosses. A second susceptibility locus (Tlag2) now has been mapped to chromosome 4. Only those mice that inherited the susceptibility alleles at both Tlag1 and Tlag2 were sensitive to MNU induction of thymic lymphomas, suggesting that these two loci interact. Chromosome 4 has been associated with susceptibility to hematopoietic tumor development in several mouse models, suggesting that one or more genes mapping to this chromosome are important in lymphomagenesis in general. © 2002 Wiley‐Liss, Inc.
Bimanual coordination deficits with Parkinson's disease: The influence of movement speed and external cueing
Authors: Almeida Quincy J. , Wishart Laurie R. , Lee Timothy D.
Published: October 2004

Continuous coordinated movement of the upper limbs performed at different movement frequencies, and with different external timing conditions, was examined in individuals with Parkinson's disease (PD) and healthy, age‐ and gender‐matched controls. Participants performed symmetric in‐phase movements toward and away from the midline of the body, and isodirectional anti‐phase movements at one of three metronome speeds (0.75, 1.25, and 1.75 Hz), and in two different auditory cueing conditions (cue present, cue absent). Measures of relative phase accuracy (absolute mean error) and stability (standard deviation) revealed that individuals with PD performed in‐phase movements as well as the controls, while anti‐phase movements were performed with greater mean error and variability. The adverse effects of PD on the anti‐phase task were also reflected by freezing (8.1% of anti‐phase trials) and hypometric deficits (5.1% of anti‐phase trials) during movement. None of these PD‐related impairments occurred during in‐phase trials. The overall accuracy or stability of movement coordination was not improved with the presence of external pacing cues, suggesting that although execution impairments of individuals with PD may be dramatically influenced by attention, external cueing does not necessarily improve movement performance. © 2002 Movement Disorder Society.
On the simultaneous modeling of array mutual coupling and array–platform interactions
Authors: Su Tao , Ling Hao
Published: October 2004

The active element patterns of antenna arrays are strongly affected by the interaction between the elements and the mounting platform. In this article a combined model is proposed to model the array response, including both mutual coupling and the platform effect. The mutual coupling is described by a coupling matrix, and the platform scattering is represented with the use of the point‐scatterer model. An algorithm based on the matching pursuit concept is proposed to determine the model coefficients. Numerical results show that the active element patterns are well described by the model. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 167–171, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10266
Dispersion compensation in directly modulated transmission system with the use of the half‐split‐band technique and chirped fiber grating
Authors: Lu Hai‐Han
Published: October 2004

This study proposes and demonstrates, for the first time, a directly modulated NTSC AM‐VSB erbium‐doped fiber amplifier (EDFA) ‐repeated system in the 1550‐nm region that uses a directly modulated transmitter, a push–pull preamplifier, a half‐split band, wavelength‐division‐multiplexing (WDM) techniques, chirped fiber grating (CFG) as a fiber‐dispersion compensation device. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 214–218, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10279
Fractal multiband antennas based on lotus‐pod patterns
Authors: Liu Ji‐Chyun , Liu Yi‐Je , Chang Dau‐Chyrh , Chang Chung‐Chi , Cheng Ching
Published: October 2004

A novel microstrip antenna constructed with a lotus‐pod pattern is presented in this Letter. It exhibits a frequency‐independent antenna after a self‐similar design. In practice, the multiband spectrum depends on the iteration of the fractal pattern. Both outward and inward iteration approaches are introduced. Experimental results with multiband spectrums and radiation patterns are presented and discussed. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 223–228, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10282
Fabrication and measurement of an arrow‐shaped microstrip patch antenna in the 5‐GHz band
Authors: Ju Jeong‐Min , Yoon Joong‐Han , Ko Sung‐Won , Kang Moon‐Gyu , Kwak Kyung‐Sup
Published: October 2004

In this paper, an arrow‐shaped microstrip patch antenna is designed, fabricated, and measured for a 5‐GHz band wireless local area network (WLAN) application. The geometry of our proposed antenna is suitable for the wideband antenna in the 5‐GHz band. To obtain sufficient bandwidth in the operating band, a foam layer is inserted between the ground plane and the substrate. A coaxial probe source is used. The measured results for the bandwidth and radiation patterns are obtained, with the result of the fabricated antenna (4.79–5.94 GHz) satisfying the conditions of the VSWR < 2.0 in the 5‐GHz band (5.15–5.35 GHz, 5.470–5.725 GHz, 5.725–5.825 Ghz, 5.725–5.925 GHz), and a gain of 5.02–7.25 dBi and a broad radiation pattern are achieved. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 503–505, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20516
DOSY of sample‐limited mixtures: comparison of cold, nano and conventional probes
Authors: Bradley Scott A. , Paschal Jonathan , Kulanthaivel Palaniappan
Published: October 2004

The DOSY analysis of dilute mixtures can be a challenge because a high signal‐to‐noise ratio is required for the best DOSY results. The sensitivity increase gained from new probe technologies (e.g. cold and nano probes) could enable one to acquire good DOSY spectra on sample amounts too low for conventional probes. In this article, we investigated the performance of cold and nano probes for qualitative DOSY analysis of concentrated and sample‐limited mixtures, and compared the results with those of the conventional probe. We first measured the fluid flow for each probe. All three probes exhibited only relatively small levels of flow; consequently, a double‐stimulated echo pulse sequence was not employed in the subsequent DOSY experiments. This decision was based on three facts: (1) flow‐induced phase distortions were not observed, (2) our intentions are only to perform qualitative mixture analysis, and (3) discarding 50% of the already limited signal cannot be afforded. Although the cold and nano probes produced DOSY results for the concentrated mixture that were inferior to the conventional probe, the increase in the signal‐to‐noise ratio observed with these probes proved to be advantageous for the dilute three‐component mixture. Furthermore, the cold probe showed slightly superior performance over the nano probe; thus, we conclude that among the probes examined the cold probe is best suited for qualitative DOSY analysis of sample‐limited mixtures. Copyright © 2004 John Wiley & Sons, Ltd.
Keratins: Unraveling the coordinated construction of scaffolds in spermatogenic cells
Authors: Kierszenbaum Abraham L.
Published: October 2004

Recent work shows that two groups of keratins are expressed during mammalian spermatogenesis. One group, belonging to the classic epidermis‐type keratins, is present in spermatogonia, spermatocytes, and spermatids. A member of this group, Sak57, a keratin 5 homologue, has been shown to co‐align with microtubules and provide a scaffolding shell while also strengthening intercellular cytoplasmic bridges conjoining members of spermatogonial and spermatocyte cohorts. The other, keratin 9, is a component of the perinuclear ring of the manchette, a microtubular structure developed during the elongation and condensation of the spermatid nucleus. The second group, the outer dense fiber (Odf) proteins, is expressed preferentially during mammalian spermiogenesis. The family of Odf proteins—Odf1, Odf2, and Odf3—includes an expanding group of proteins co‐assembled along the axoneme during the development of the sperm tail. Investigations on the assembly of epidermis‐type and Odf sperm tail‐targeted keratins are now focused on a group of chaperone‐like Odf‐binding molecules, designated Spags. Spags appear to drive Odfs to a precise destination. A daunting task is to determine how members of the family of keratins get the signal to produce linear scaffolds in specific spermatogenic cell populations and transport keratins to microtubule‐containing structures such as the manchette and axoneme. Mol. Reprod. Dev. 61: 1–2, 2002. © 2002 Wiley‐Liss, Inc.
Secondary amyloidosis as a life‐ending event in multifocal motor neuropathy
Authors: Beydoun Said R. , Rison Richard A. , Commins Deborah
Published: October 2004

Multifocal motor neuropathy (MMN) is a disorder of peripheral nerve often associated with a high monosialoganglioside (GM1) antibody and multifocal conduction block. It has a chronic, indolent course with involvement of predominantly peripheral motor nerves, usually in an asymmetric fashion. There have been few reported cases of progression to frank quadriplegia. Secondary amyloidosis refers to the deposition of amyloid in various tissues due to an underlying chronic inflammatory state. We report the first case, to our knowledge, of a patient with MMN associated with high titer of GM1 antibody who developed acute paraplegia with both cranial nerve and worsening sensory involvement associated with multiorgan compromise due to a secondary amyloidosis involving the myocardium. © 2001 John Wiley & Sons, Inc. 24: 1396–1402, 2001
Continuous accumulation games on discrete locations
Authors: Kikuta Kensaku , Ruckle William H.
Published: October 2004

In an accumulation game, a HIDER attempts to accumulate a certain number of objects or a certain quantity of material before a certain time, and a SEEKER attempts to prevent this. In a continuous accumulation game the HIDER can pile material either at locations $1, 2, …, n, or over a region in space. The HIDER will win (payoff 1) it if accumulates N units of material before a given time, and the goal of the SEEKER will win (payoff 0) otherwise. We assume the HIDER can place continuous material such as fuel at discrete locations i = 1, 2, …, n, and the game is played in discrete time. At each time k > 0 the HIDER acquires h units of material and can distribute it among all of the locations. At the same time, k, the SEEKER can search a certain number s < n of the locations, and will confiscate (or destroy) all material found. After explicitly describing what we mean by a continuous accumulation game on discrete locations, we prove a theorem that gives a condition under which the HIDER can always win by using a uniform distribution at each stage of the game. When this condition does not hold, special cases and examples show that the resulting game becomes complicated even when played only for a single stage. We reduce the single stage game to an optimization problem, and also obtain some partial results on its solution. We also consider accumulation games where the locations are arranged in either a circle or in a line segment and the SEEKER must search a series of adjacent locations. © 2002 John Wiley & Sons, Inc. Naval Research Logistics, 49: 60–77, 2002; DOI 10.1002/nav.1048
Area efficient layouts of the Batcher sorting networks
Authors: Even Shimon
Published: October 2004

In the early 1980s, the grid area required by the sorting nets of Batcher for input vectors of length N was investigated by Thompson. He showed that the Ω(N2) area was necessary and sufficient, but the hidden constant factors, both for the lower and upper bounds, were not discussed. In this paper, a lower bound of (N − 1)2/2 is proven, for the area required by any sorting network. Upper bounds of 4N2 and 3N2 are shown for the bitonic sorter and the odd—even sorter, respectively. In the layouts, which are presented to establish these upper bounds, slanted lines are used and there are no knock‐knees. © 2001 John Wiley & Sons, Inc.
Solving the undirected multicommodity flow problem using a shortest path‐based pricing algorithm
Authors: McBride Richard D. , Mamer John W.
Published: October 2004

The undirected multicommodity flow problem is encountered in the solution to traffic‐scheduling problems related to computer, communication, railroad, and other networks. We show how to formulate this problem as a piecewise linear optimization problem (with piecewise linear convex functions in both the objective and the constraints). We discuss how EMNET, a primal basis partitioning simplex algorithm, was modified so as to efficiently solve these problems using a pricing procedure that we call “shortest path pricing.” Extremely good solution times for some very large problems are presented. The solutions are not only obtained quickly, but also with a fraction of the number of pivots that are needed for the standard simplex method. © 2001 John Wiley & Sons, Inc.
Cortical radial glial cells in human fetuses: Depth‐correlated transformation into astrocytes
Authors: deAzevedo Leonardo C. , Fallet Cathérine , Moura‐Neto Vivaldo , Daumas‐Duport Cathérine , Hedin‐Pereira Cecilia , Lent Roberto
Published: October 2004

In the human brain, the transformation of radial glial cells (RGC) into astrocytes has been studied only rarely. In this work, we were interested in studying the morphologic aspects underlying this transformation during the fetal/perinatal period, particularly emphasizing the region‐specific glial fiber anatomy in the medial cortex. We have used carbocyanine dyes (DiI/DiA) to identify the RGC transitional forms and glial fiber morphology. Immunocytochemical markers such as vimentin and glial fibrillary acidic protein (GFAP) were also employed to label the radial cells of glial lineage and to reveal the early pattern of astrocyte distribution. Neuronal markers such as neuronal‐specific nuclear protein (NeuN) and microtubule‐associated protein (MAP‐2) were employed to discern whether or not these radial cells could, in fact, be neurons or neuronal precursors. The main findings concern the beginning of RGC transformation showing loss of the ventricular fixation in most cases, followed by transitional figures and the appearance of mature astrocytes. In addition, diverse fiber morphology related to depth within the cortical mantle was clearly demonstrated. We concluded that during the fetal/perinatal period the cerebral cortex is undergoing the final stages of radial neuronal migration, followed by involution of RGC ventricular processes and transformation into astrocytes. None of the transitional or other radial glia were positive for neuronal markers. Furthermore, the differential morphology of RGC fibers according to depth suggests that factors may act locally in the subplate and could have a role in the process of cortical RGC transformation and astrocyte localization. The early pattern of astrocyte distribution is bilaminar, sparing the cortical plate. Few astrocytes (GFAP+) in the upper band could be found with radial processes at anytime. This suggests that astrocytes in the marginal zone could be derived from different precursors than those that differentiate from RGCs during this period. © 2003 Wiley Periodicals, Inc. J Neurobiol 55: 288–298, 2003
Sex‐peptides bind to two molecularly different targets in Drosophila melanogaster females
Authors: Ding Zhaobing , Haussmann Irmgard , Ottiger Michael , Kubli Eric
Published: October 2004

Sex‐Peptide (SP) and the peptide DUP99B elicit two postmating responses in Drosophila melanogaster females: receptivity is reduced and oviposition is increased. Both are synthesized in the male genital tract and transferred into the female during copulation. To elucidate their function, we characterized the binding properties of SP and DUP99B in females. Cryostat sections of adult females were incubated with alkaline phosphatase (AP)‐tagged peptides. In virgin females, both peptides have specific target sites in the nervous system and in the genital tract. The binding pattern is almost identical for both peptides. Incubation of sections of mated females confirm that some of these target sites correspond to the in vivo targets of the two peptides. Neuronal binding is dependent on an intact C‐terminal sequence of SP, binding in the genital tract is less demanding in terms of amino acid sequence requirement. On affinity blots the AP–SP probe binds to membrane proteins extracted from abdomen and head plus thorax, respectively. The binding proteins in the nervous system and the genital tract differ in their molecular properties. Calculation of dissociation constants (Kd), and also determination of the minimal peptide concentrations necessary for binding, indicate that SP is the more important peptide inducing the postmating responses. Our results suggest that binding of SP in the nervous system is responsible for eliciting the postmating responses, whereas binding in the genital tract reflects the presence of a peptide transporter. © 2003 Wiley Periodicals, Inc. J Neurobiol 55: 372–384, 2003
Dendritic growth induced by BMP‐7 requires Smad1 and proteasome activity
Authors: Guo Xin , Lin Yin , Horbinski Craig , Drahushuk Karen M. , Kim In‐Jung , Kaplan Paul L. , Lein Pamela , Wang Tongwen , Higgins Dennis
Published: October 2004

Bone morphogenetic proteins (BMPs) induce dendritic growth in cultured sympathetic neurons; however, the signaling pathways that mediate this dendrite‐promoting activity have not been previously characterized. Here we report studies of the signaling events that regulate the growth of these afferent processes. We find that Smad1 is expressed in sympathetic neurons and that BMPs rapidly induce its phosphorylation and translocation from the cytoplasm to the nucleus. Furthermore, a dominant negative form of Smad1 inhibits BMP‐7‐induced dendritic growth, suggesting a requirement for Smad1 activation in this biological activity of BMP‐7. A physical interaction between Smad1 and components involved in the proteasome‐mediated degradation system was detected with a yeast two‐hybrid screen, thereby prompting an examination of the effects of proteasome inhibitors on dendritic growth. Lactacystin and ALLN (N‐acetyl‐Leu‐Leu‐norleucinal) selectively blocked BMP‐7‐induced dendritic growth without adversely affecting either cell viability or axonal growth. Moreover, studies of transfected P19 cells suggest that the proteasome inhibitors directly block the effects of Smad1 on the transcriptional activity of the Tlx‐2 promoter. These data indicate that BMP‐induced dendritic growth requires Smad1 activation and involves proteasome‐mediated degradation events. © 2001 John Wiley & Sons, Inc. J Neurobiol 48: 120–130, 2001
First prenatal diagnosis for Wolfram syndrome by molecular analysis of the WFS1 gene
Authors: Domènech Enric , Kruyer Helena , Gómez Carolina , Calvo Maria Teresa , Nunes Virginia
Published: October 2004

Wolfram syndrome (WS) is an autosomal recessive neurodegenerative disorder characterized by early onset diabetes mellitus and progressive optic atrophy in the first decade of life. Other clinical features such as diabetes insipidus, deafness, renal tract abnormalities or psychiatric illnesses are often present. The sequence of the Wolfram syndrome gene (WFS1) was described in 1998, and mutations in the gene have been reported in many populations.

To date, the function of the putative protein remains unknown.

Here we report prenatal diagnosis by analysing the WFS1 gene, in a foetus belonging to a family with a child diagnosed for Wolfram syndrome. The parents are carriers of the c.2206G > C (G736R) mutation. To our knowledge this is the first description of prenatal diagnosis for Wolfram syndrome, based on the molecular analysis of the WFS1 gene. Copyright © 2004 John Wiley & Sons, Ltd.
Symptoms and long‐term outcomes for children who have been sexually assaulted
Authors: Webster Raymond E.
Published: October 2004

Violent behaviors by and toward children have become an increasing concern within the American school system, with a good deal of energy devoted to developing profiles about which children are likely to exhibit these behaviors (Goldstein & Huff, 1993). Unfortunately, much less publicity has been devoted toward children who are sexually abused, despite the fact that over 300,000 children and adolescents are sexually abused annually in this country (National Center of Child Abuse and Neglect, 1996). As such, this figure reflects about a 600% increase in actual reported cases since 1980 (Burgdoff, 1980). These data suggest that a large number of school‐aged children are experiencing this kind of personal assault and professional educators are likely to encounter these children in the routine course of the educational process. This article provides a summary of the issues involved in the determination of sexual assault against a child and reviews the empirical literature describing the symptoms which may be manifested by a child who has been sexually abused. © 2001 John Wiley & Sons, Inc.
Use of stimulant medication for treatment of attention‐deficit/hyperactivity disorder: A survey of middle and high school students' attitudes
Authors: Moline Scott , Frankenberger William
Published: October 2004

Six hundred fifty‐one students (ages 11–18) completed a questionnaire that asked if they were taking stimulant medication for ADHD. Those who responded positively were then asked to answer a section of the questionnaire that asked them about their experiences and attitudes related to their treatment with the medication. If they responded that they were not diagnosed with ADHD and not receiving treatment with stimulant medication, they answered a section of the questionnaire that inquired about their perceptions of students who did take medication. Fifty students completed the taking‐medication portion of the questionnaire. Although the students reported that the medication helped them somewhat in the areas of behavior, social ability with friends, parents, and teachers, and attention, they reported that the medication did not help them in the area of academic achievement. The majority of the students reported some side effects from their medication. Thirty‐four percent of students taking ADHD medication reported being approached to sell or trade their medication, and 53% of students not taking ADHD medication reported that some students taking ADHD medication gave away or sold their medication. © 2001 John Wiley & Sons, Inc.
Influence of acidity on the reaction between [PdCl(dien)]+andL‐cysteine or glutathione in the presence of sodium dodecyl sulfate micelles
Authors: Vasić Vesna M. , Živanović Momir A. , Čakar Mira M. , Savić Jasmina Z. , Nedeljković Jovan M. , Bugarčić Živadin D.
Published: October 2004

The reaction mechanism and thermodynamic parameters of the complex formation between [PdCl(dien)]+and sulfur‐containing ligandsL‐cysteine and glutathione (GSH) were investigated in the presence of sodium dodecyl sulfate micelles in the pH range 0.5–3.5. The reaction rates were determined under pseudo‐first‐order conditions (ligand in excess) in the temperature range 276–299 K by using the stopped‐flow technique. A reaction mechanism was proposed that consisted of at least two parallel paths involving protonated and zwitterionic forms of thiols. The pH effects on reaction rate were interpreted in terms of the electrostatic interactions between the negatively charged micelle surface and different ionic forms of the ligand species. The calculation of pH‐dependent activation parameters (ΔH≠and ΔS≠) revealed the considerable catalytic effects on the rate of complexation. The entropy of activation is strongly negative in the presence and absence of micelles, which is compatible with an associative reaction mechanism. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis of photoreactive polyimide having indan structure
Authors: Tamai S. , Kamada J. , Ono T. , Kuroki T. , Goto K. , Yamaguchi A.
Published: October 2004

Polyimide containing an indan unit and alkyl moiety with a high molecular weight was prepared from 5,7‐diamino‐1,1,4,6‐tetramethylindan and 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride. This polyimide was amorphous and soluble in common organic solvents, such as tetrahydrofuran, chloroform, and cyclopentanone. Thermogravimetry of the polyimide showed good thermal stability, indicating that a 10% weight loss of the polyimide was observed at 500 °C in nitrogen. The glass‐transition temperature of the polyimide was not observed by DSC measurement between room temperature and 400 °C at a heating rate of 10 °C/min (Apparatus: DSC3100 MAC Science Co., Ltd.). Transparency of the polyimide at 365 nm was 80%. The polyimide acted as a photosensitive resist of negative type by UV radiation. The resist had a sensitivity of 31 mJ/cm2 and a contrast of 2.3 when it was developed with cyclopentanone at room temperature. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 423–428, 2002
Tetraalkylammonium salt as photoinitiator of vinyl polymerization in organic and aqueous media: A mechanistic and laser flash photolysis study
Authors: Gómez María L. , Palacios Rodrigo E. , Previtali Carlos M. , Montejano Hernán A. , Chesta Carlos A.
Published: October 2004

N‐Dimethyl‐N‐[2‐(N,N‐dimethylamino)ethyl]‐N‐(1‐methylnaphthyl)ammonium tetrafluoroborate (I) was synthesized with the aim of obtaining a versatile photoinitiator for vinyl polymerization in organic solvents and water. Salt I was able to trigger the polymerization of acrylamide, 2‐hydroxyethylmethacrylate and styrene even at very low concentrations of the salt (∼1.0 × 10−5 M). Using laser flash photolysis and fluorescence techniques and analyzing the photoproduct distribution, we were able to postulate a mechanism for the photodecomposition of the salt. With irradiation, I undergoes an intramolecular electron‐transfer reaction to form a radical ion pair (RIP). The RIP intermediate decomposes into free radicals. The RIP and the free radicals are active species for initiating the polymerization. Depending on the concentration of the vinyl monomers studied, the initiation mechanism of the polymerization reaction changes. At large monomer concentrations, the RIP state is postulated to trigger the reaction by generating the anion radical of the olefin substrate. At a low monomer concentration, the free radicals produced by the decomposition of I are believed to start the chain reaction. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 901–913, 2002; DOI 10.1002/pola.10166
Synthesis of amphiphilic particles in the presence of inert solvents and their application to lipase immobilization
Authors: Yasuda Masahiro , Kobayashi Miho , Watanabe Shinji , Ogino Hiroyasu , Ishimi Kosaku , Ishikawa Haruo
Published: October 2004

To develop monodisperse amphiphilic polymer particles on which a large amount of lipase could be immobilized, we performed seed polymerizations of glycidyl methacrylate and allyl methacrylate in the presence of nonpolar inert and polar inert solvents. The amphiphilic porous polymer particles, which had both hydrophilic guanidino groups and hydrophobic stearoyl groups, were synthesized in the presence of n‐decane and had a large amount of macropores with diameters of 50–1000 nm. The amount of lipase immobilized on the amphiphilic particles synthesized in the presence of n‐decane was 3.85 times that of the lipase immobilized on the amphiphilic particles synthesized in the absence of a solvent. The immobilized lipase prepared with the amphiphilic particles synthesized in the presence of n‐decane exhibited a high transesterification activity in n‐hexane and could be used repeatedly without a considerable activity loss. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 874–884, 2002; DOI 10.1002/pola.10178
Effects of humidity on environmental stress cracking behavior in poly(methyl methacrylate)
Authors: Ishiyama C. , Sakuma T. , Shimojo M. , Higo Y.
Published: October 2004

Environmental stress cracking (ESC) in poly(methyl methacrylate) under different humidity conditions has been investigated. Constant stress‐intensity factor (K) ring‐type specimens were prepared, and all specimens were equilibrated at five different humidity conditions for about two years. ESC tests were carried out under the same humidity as specimens had been stored. Acoustic emission (AE) signals during ESC tests were also measured to examine the crack‐growth behavior. The threshold K value (Kth) tended to increase with increasing humidity. At a relative humidity (RH) of 11%, crack growth occurred gradually until 40 ks under a K value of 0.70 MPam1/2, and then the crack‐growth rate began to increase and AE events were observed. A laser microscopic observation indicated that the crack extended by the coalescence between a main crack and a microcrack ahead of the main crack tip. AE signals generated are considered to be associated with the coalescence. At 98% RH, an incubation period where no crack growth was observed existed under a K value of 0.94 MPam1/2, but the crack began to grow suddenly after that incubation period. This suggests that the craze at the crack tip may become weaker with increasing loading time under high humidity. Although the crack‐growth rate at 98% RH was higher than that at 11% RH, no AE events were observed. This suggests that the crack extended stably in the craze at a crack tip, and sorbed water may make the craze growth easy. All the results suggest that two different ESC mechanisms are activated depending on sorbed water that are varied by humidity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 1–9, 2002
Correlation between crystallization kinetics and microdomain morphology in block copolymer blends exhibiting confined crystallization
Authors: Lee Wenchuan , Chen Hsin‐Lung , Lin Tsang‐Lang
Published: October 2004

The crystallization kinetics of poly(ethylene oxide) (PEO) blocks in poly(ethylene oxide)‐block‐poly(1,4‐butadiene) (PEO‐b‐PB)/poly(1,4‐butadiene) (PB) blends were previously found to display a one‐to‐one correlation with the microdomain morphology. The distinct correlation was postulated to stem from the homogeneous nucleation‐controlled crystallization in the cylindrical and spherical PEO microdomains, where there existed a direct proportionality between the nucleation rate and the individual domain volume. This criterion was valid for confined crystallization in which the crystallization was spatially restricted within the individual domains. However, it was possibly not applicable to PEO‐b‐PB/PB, in that the melt mesophase was strongly perturbed upon crystallization. Therefore, it may be speculated that the crystal growth front developed in a given microdomain could intrude into the nearby noncrystalline domains, yielding the condition of cooperative crystallization. To establish an unambiguous model system for verifying the existence of microdomain‐tailored kinetics in confined crystallization, we crosslinked amorphous PB blocks in PEO‐b‐PB/PB with a photoinitiated crosslinking reaction to effectively suppress the cooperative crystallization. Small‐angle X‐ray scattering revealed that, in contrast to the noncrosslinked systems, the pre‐existing domain morphology in the melt was retained upon crystallization. The crystallization kinetics in the crosslinked system also exhibited a parallel transition with the morphological transformation, thereby verifying the existence of microdomain‐tailored kinetics in the confined crystallization of block copolymers. Homogeneous nucleation‐controlled crystallizations in cylindrical and spherical morphologies were demonstrated in an isothermal crystallization study in which the corresponding crystallinity developments followed a simple exponential rule not prescribed by conventional spherulitic crystallization. Despite the effective confinement imposed by the crosslinked PB phase, crystallization in the lamellar phase still proceeded through a mechanism analogous to the spherulitic crystallization of homopolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 519–529, 2002; DOI 10.1002/polb.10121
Two‐dimensional Fourier transform infrared spectroscopy study of biosynthesized poly(hydroxybutyrate‐co‐hydroxyhexanoate) and poly(hydroxybutyrate‐ co‐hydroxyvalerate)
Authors: Tian Ge , Wu Qiong , Sun Suqin , Noda Isao , Chen Guo‐Qiang
Published: October 2004

Generalized two‐dimensional (2D) Fourier transform infrared correlation spectroscopy was used to investigate the effect of the comonomer compositions on the crystallization behavior of two types of biosynthesized random copolymers, poly(hydroxybutyrate‐co‐hydroxyhexanoate) and poly(hydroxybutyrate‐co‐hydroxyvalerate). The carbonyl absorption band around 1730 cm−1 was sensitive to the degree of crystallinity. 2D correlation analysis demonstrated that the 3‐hydroxyhexanoate units preferred to remain in the amorphous phase of the semicrystalline poly(hydroxybutyrate‐co‐hydroxyhexanoate) copolymer, resulting in decreases in the degree of crystallinity and the rate of the crystallization process. The poly(hydroxybutyrate‐co‐hydroxyvalerate) copolymer maintained a high degree of crystallinity when the 3‐hydroxyvalerate fraction was increased from 0 to 25 mol % because of isodimorphism. The crystalline and amorphous absorption bands for the carbonyl bond for this copolymer, therefore, changed simultaneously. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 649–656, 2002; DOI 10.1002/polb.10126
Hodgkin's disease and ataxia telangiectasia with pulmonary cavities
Authors: Yalçin Bilgehan , Kutluk M. Tezer , Sanal Özden , Akyüz Canan , Anadol Deniz , Çağlar Melda , Göçmen Ayhan , Büyükpamukçu Münevver
Published: October 2004

Ataxia telangiectasia (AT) homozygotes have an increased risk for development of Hodgkin's disease (HD). Parenchymal lung involvement is not uncommon in HD; however, cavitary pulmonary lesions are quite unusual. We report on 3 cases of AT with HD who had mediastinal disease and parenchymal pulmonary involvement with cavitation. Of 6 AT patients in our HD series, 3 developed pulmonary cavities. The patients displayed pulmonary infiltration, cavitation in the lung parenchyma, and mediastinal enlarged lymph nodes on both plain chest X‐rays and thoracic computed tomographies. No infectious etiologies were established for the pulmonary findings. Histopathological examination of open lung and mediastinal biopsies revealed HD, and all patients received multiagent chemotherapies. The outcome was fatal in all 3 patients.

Respiratory infections are the principle cause for morbidity and mortality in AT patients. Reports on cavitating pulmonary lesions in HD are quite rare. Furthermore, data regarding the patterns of pulmonary involvement in AT patients with or without HD are lacking. The increased incidence of malignancies in AT patients may relate to immunodeficiency and to the chromosomal alterations identified. Pediatr Pulmonol. 2002; 33:399–403. © 2002 Wiley‐Liss, Inc.
A Quantum Mechanical Molecular Dynamics Study of Binary Collisions of Pentaerythritol Tetranitrate (PETN): Its Correlation to Shock Sensitivity
Authors: Wu Christine J. , Ree Francis H. , Yoo Choong‐Shik
Published: October 2004

We have carried out semi‐empirical quantum mechanical molecular dynamics (MD) simulations involving collisions of two pentaerythritol tetranitrate (PETN) molecules at different molecular orientations and at several intermolecular separations. The common features of reactive scattering among all molecular orientations are (1) the dissociation mechanism of PETN remains unimolecular and (2) the dominant reaction channel is the breaking of an ONO2 bond. However, the probability of collision‐induced decomposition of PETN depends strongly on initial conditions, in agreement with the experimentally observed sensitivity of shock‐initiated detonation in bulk PETN along different crystalline orientations. In addition, the next most frequent reaction path shows a dependence on initial orientations.
A critical analysis of continuum electrostatics: The screened Coulomb potential–implicit solvent model and the study of the alanine dipeptide and discrimination of misfolded structures of proteins
Authors: Hassan Sergio A. , Mehler Ernest L.
Published: October 2004

An analysis of the screened Coulomb potential–implicit solvent model (SCP–ISM) is presented showing that general equations for both the electrostatic and solvation free energy can be derived in a continuum approach, using statistical averaging of the polarization field created by the solvent around the molecule. The derivation clearly shows how the concept of boundary, usually found in macroscopic approaches, is eliminated when the continuum model is obtained from a microscopic treatment using appropriate averaging techniques. The model is used to study the alanine dipeptide in aqueous solution, as well as the discrimination of native protein structures from misfolded conformations. For the alanine dipeptide the free energy surface in the ϕ–ψ space is calculated and compared with recently reported results of a detailed molecular dynamics simulation using an explicit representation of the solvent, and with other available data. The study showed that the results obtained using the SCP–ISM are comparable to those of the explicit water calculation and compares favorably to the FDPB approach. Both transition states and energy minima show a high correlation (r > 0.98) with the results obtained in the explicit water analysis. The study of the misfolded structures of proteins comprised the analysis of three standard decoy sets, namely, the EMBL, Park and Levitt, and Baker's CASP3 sets. In all cases the SCP–ISM discriminated well the native structures of the proteins, and the best‐predicted structures were always near‐native (cRMSD ∼2 Å). Proteins 2002;47:45–61. © 2002 Wiley‐Liss, Inc.
Flexibility in monomeric Cu,Zn superoxide dismutase detected by limited proteolysis and molecular dynamics simulation
Authors: Falconi M. , Parrilli L. , Battistoni A. , Desideri A.
Published: October 2004

Limited proteolysis by trypsin of monomeric Cu,Zn superoxide dismutase from Escherichia coli induces a specific cleavage of the polypeptide chain at the level of Lys60 located in the S–S subloop of loop 6,5 where, when compared to the eukaryotic enzyme, a seven‐residues insertion, completely exposed to the solvent, is observed. This result suggests that this subloop is disordered and flexible, thus enabling binding and adaptation to the active site of the proteolytic enzyme. Indeed, molecular dynamics simulation indicates that the S–S subloop undergoes high fluctuations and that its high flexibility coupled to an high solvent accessibility can explain the specific bond selection of the protease. As a matter of fact, of the possible 14 solvent accessible proteolytic sites only the Lys60 flexible site is cleaved. High flexibility and solvent exposure are confirmed by the short water residence time for the residues corresponding to the cleavage site evaluated by molecular dynamics simulation. These experiments demonstrate that molecular dynamics simulation and limited proteolysis are complementary and unambiguous tools to identify flexible sites in proteins. Proteins 2002;47:513–520. © 2002 Wiley‐Liss, Inc.
Computational studies on density function theory for the bimolecular metathesis reaction CH3+HCl⇔︁CH4+Cl
Authors: Zhou Zhengyu , Chen Guang , Zhou Xingmin , Fu Hui
Published: October 2004

Density function theory has been applied to alkyl radical reaction to get helpful data for its geometric parameters, energy, and vibrational frequency compared with results obtained by ab initio methods and experimental values. The geometry optimization of the transition state, the precursor complex and the successor complex were performed at the 6‐311G* basis set level. The transition state of the CH4Cl system of the reaction computed was in agreement with the prediction of Benson. From analysis of the vibration frequency and the net charge on the atom of the precursor complex, transition state, successor complex and the isolated state, the reaction mechanism was derived which we complicated with the bond‐rupture electron‐transfer theory. The atom H in molecule HCl attacks the atom C, forming a transition state via the precursor complex and the electron transfer happens in the precursor complex. The reaction rate of the electron transfer determines the rate of the whole reaction to a certain extent, and active energy, electronic coupling matrix element, and reorganization energy were obtained. © 2001 Wiley Periodicals, Inc. Int J Quantum Chem, 2001
High‐spin silicon fullerene Si60 and its oligomers
Authors: Sheka Elena F. , Nikitina Ekaterina A. , Zayets Valentin A. , Ginzburg Ilya Ya.
Published: October 2004

High‐spin states of the Si60 fullerene and its oligomers are considered semiempirically by using sequential and parallel implementations of the AM1 codes. The states are energetically favorable and nearly degenerated over triplet, quintet, and septet spins. All atoms of the Si60 fullerene are in sp3‐configuration, which is supported by atomic spin density in addition to electron density, the latter to be responsible for the formation of chemical bonds. Spotted distribution of spin density over atoms provides molecular magnetism of the molecule. A similar picture is disclosed for oligomers {Si60}n with n up to 8, which according to computational results should be magnetic with a fractal‐like distribution of spin density over atoms. Opposite the latter, composites Si60C60 and Si60H60 behave conventionally and are nonmagnetic. A way of the Si60 fullerene synthesizing is suggested via the above composite product as intermediates. The considered oligomers are proposed as a model of silicon nanofibers observed recently. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Reactivity of molecular oxygen on the surface of ionic crystals
Authors: Mikheikin I. D. , Vorontsova I. K. , Abronin I. A.
Published: October 2004

A possibility of multiplicity change for ground‐state molecular oxygen adsorbed on the surface of regular and doped broad‐gap ionic crystals was considered in the framework of cluster approximation by using SCF MO LCAO quantum chemical methods [semiempirical INDO approximation and ab initio calculation with the 6‐311G** basis set taking into account the correlation effects on the level of second‐order Meller–Plesset perturbation theory (MP2)]. The formation energetics of cyclic products of addition reactions of dioxygen in different multiplet states to furan and cis‐butadiene in the gas phase and on the surface of ionic crystals was considered. (These reactions are typical for the O2 singlet state in the gas phase.) It is shown that the presence of sites with high effective charge on the crystal surface can result in a situation not requiring, as in the gas phase, multiplicity change in the transition of a system from an initial to the final state, which can significantly affect the kinetic parameters of the reactions. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002