bluuebunny/crossref_metadata_2025 huggingface dataset:
PHYSICS OF SEMICONDUCTOR VERTICAL-CAVITY SURFACE-EMITTING LASERS
Authors: JIN R. , KHITROVA G. , BOGGAVARAPU D. , GIBBS H. M. , KOCH S. W. , TOBIN M. S. , LEAVITT R. P.
Published: November 2004

We describe recent progress in the physics of light-matter interactions in vertical-cavity surface-emitting-laser (VCSEL) structures. Enhanced spontaneous emission indicates strong medium-cavity coupling. The linewidth broadening factor is more accurately determined in VCSELs, supporting many-body theory of semiconductor nonlinearities. Threshold behavior of VCSELs and microlasers is investigated by photon-correlation experiment and quantum laser theory with emphasis on the importance of second-order coherence properties. External optical injection into a VCSEL cavity leads to injection locking, instabilities, acceleration of coherent energy transfer and sideband lasing, most of which are modeled successfully by recently-developed first-principles semiconductor laser theory.
TERAHERTZ OPTICAL RECTIFICATION
Authors: JIN Y. H. , ZHANG X.-C.
Published: November 2004

We present experimental measurements of Terahertz optical rectification in electro-optic crystals. The measured data was compared with a simple theoretical analysis (anharmonic oscillator model). We also measured Terahertz-bandwidth subpicosecond electromagnetic radiation via nearly-degenerate difference-frequency generation in electrooptic materials. The variation in Terahertz emission with crystal orientation demonstrated that the generation of Terahertz radiation via optical rectification involves a bulk second-order nonlinear process. We studied Terahertz optical rectification from zincblende crystals as the incident photon energy was tuned across the semiconductor optical absorption band-edge (resonant excitation). We also present the measurement of temperature-dependent Terahertz optical rectification. A comparison between the two second-order nonlinear processes, sum-frequency generation (second-harmonic generation) and different-frequency generation (optical rectification) is presented.
IMPORTANCE OF ELECTRON–ELECTRON INTERACTION FOR HARMONIC GENERATION
Authors: LAPPAS D. G. , GROBE R. , EBERLY J. H.
Published: November 2004

We compute the spectrum of the high-order harmonic radiation that is emitted during the interaction of a short laser pulse with a one-dimensional two-electron system. The flexibility of our numerical approach allows us to determine the relative importance of the e–e interaction for the scattered light by coupling only one of the two electrons to the field. The harmonic emission from each electron can then be determined. The e–e interaction appears to be at least as important as the coupling of one electron to the laser field. The coupling of both electrons to the field enhances the nonlinear response of the system.
INCOHERENT INTERFERENCE CONTROL OF PHOTODISSOCIATION IN THE STRONG FIELD DOMAIN
Authors: CHEN Z. , SHAPIRO M. , BRUMER P.
Published: November 2004

Control over channel specific line shapes and branching ratios in photodissociation is achievable by irradiating a molecule with two intense CW lasers whose relative phase need not be well defined. Control results from quantum interference between nonlinear pathways induced by the intense fields, within which the relative laser phase cancels. The interference, and hence the product yields, can be manipulated by changing the relative frequencies and intensities of the two lasers. In this paper, this theory of high field control is described, and computations on the photodissociation of Na 2 are discussed. Control over product yields is shown to be extensive, even with inclusion of rotational states. For example, the branching ratio between the Na (3s) + Na (3p) and Na (3s) + Na (4s) products can change by as much as a factor of ten as the frequencies are tuned.
NONPERTURBATIVE TIME-DEPENDENT THEORY OF TWO-ELECTRON ATOMS IN STRONG LASER FIELDS
Authors: ZHANG JIAN , LAMBROPOULOS P.
Published: November 2004

This work deals with the fundamental problem of the behavior of the two-electron atom under intense laser fields. We present a broad scope of calculations and results and, we believe, the first ATI spectrum, in He and Mg atom, beyond the single active electron model in a fully time-dependent nonperturbative calculation. For He, we perform calculations both on a two-electron basis with configuration interaction where both electrons are allowed to be excited, and on a frozen core basis. The comparison is a direct measure of the effect of correlation under strong fields. The results for Mg shows that the method also opens a way to the study of atoms with much stronger electron correlation in intense laser fields.
PONDEROMOTIVE SCATTERING AT RELATIVISTIC LASER INTENSITIES
Authors: GORESLAVSKY S. P. , NAROZHNY N. B.
Published: November 2004

We present a summary on the exact solutions to the classical relativistic equations of motion in the field of a plane electromagnetic wave and describe a modification of the averaging procedure, which yields equations governing the average electron motion in the field of a focused laser pulse when an electron oscillates at relativistic velocity. Applications to the barrier suppression ionization and Thompson radiation are briefly discussed.
NONLINEAR DIRECTIONAL COUPLERS IN AlGaAs
Authors: AITCHISON J. S. , VILLENEUVE A. , STEGEMAN G. I.
Published: November 2004

In this paper we review the progress made in implementing nonlinear directional couplers as potential all-optical switching devices. We will discuss the operation of the coupler and its application as an all-optical multiplexing, demultiplexing element and consider the possibility of integrating more than one nonlinear switching element. The limitation of dispersion and nonlinear absorption will also be addressed.
WAVEGUIDING EFFECT IN A CELL WITH A LIQUID CRYSTALLINE CORE
Authors: REYES J. A. , RODRÍGUEZ R. F.
Published: November 2004

We present a model for the propagation of an optical field in a nematic planar cell where hydrodynamic flows are neglected. We show that the distortion induced by the field produces an index-gradient which produces a waveguide effect that concentrates the electromagnetic field and its energy density in the central part of the cell. This is shown by first performing a perturbative analysis of the reorientational dynamics and the coupled dynamics of the electromagnetic field in powers of the dielectric anisotropy of the nematic. Up to the first order, we calculate analytically the normal modes of the field, its dispersion relation and the electromagnetic energy density spatial distribution within the cell. The existence of this effect is also shown in a non-perturbative way by calculating the ray trajectories from the eikonal equation for a low intensity beam in the optical limit. We show that the trajectories indeed bend towards the middle part of the cell.
Glomerular and tubular damage in normotensive and hypertensive rats
Authors: Ofstad Jarle , Iversen Bjarne M.
Published: November 2004

Tubular cell damage is an important mediator of interstitial fibrosis in chronic renal diseases. Glomerular and tubular damage in genetic hypertension was therefore studied. Tubular and glomerular damage was investigated in 10-, 40-, and 70-wk-old spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) and compared with glomerular capillary pressure (PGC) and glomerulosclerosis in superficial (OC) and juxtamedullary (JMC). Tubular vimentin was used as criterion of tubular damage. Variation in tubular diameter was measured during change in perfusion pressure, and ureter ligation was used to demonstrate the relationship between tubular pressure and appearance of vimentin-positive cells. Tubular and glomerular damage was most pronounced in JMC and greater in SHR than in WKY. It was absent in 10-wk-old WKY and significantly higher in JMC of SHR compared with WKY at 70 wk of age. Numbers of vimentin-positive segments were 18 ± 9 vs. 38 ± 7% in JMC of 70-wk-old WKY and SHR ( P < 0.02), and glomerulosclerosis was seen in 8 ± 3 vs. 19 ± 5% of glomeruli in JMC of 70-wk-old WKY and SHR, respectively ( P < 0.01). PGCwas 45 ± 3 mmHg in JMC of WKY and 57 ± 3 mmHg in JMC of 70-wk-old SHR ( P < 0.001). Tubular diameter variation was greatest in SHR ( P < 0.05) during pressure variation. Proteinuria was present only in 40- and 70-wk-old SHR and did not correlate with tissue damage. Tubular and glomerular damage in both strains develops in parallel and may be caused by a common mechanism, which may be glomerular capillary and tubular wall stretch during acute blood pressure variation which is greatest in JMC in SHR.
Serial analysis of gene expression during elongation of the peri-implantation porcine trophectoderm (conceptus)
Authors: Blomberg Le Ann , Long Ezhou L. , Sonstegard Tad S. , Van Tassell Curtis P. , Dobrinsky John R. , Zuelke Kurt A.
Published: November 2004

Conceptus loss during the preimplantation and early postimplantation period hinders the efficiency of swine reproduction. Significant conceptus loss occurs during trophectoderm elongation between gestational day 11 ( D11) and day 12 ( D12). Elongation of the porcine conceptus is a key stage of development during which maternal recognition of pregnancy, initial placental development, and preparation for implantation occurs. The objective of this study was to establish comparative transcriptome profiles of D11 ovoid and D12 filamentous conceptuses and thereby identify temporally regulated genes essential for developmental progression during conceptus elongation. Serial analysis of gene expression (SAGE) libraries were constructed from in vivo derived ovoid and filamentous swine conceptuses to yield a total of 42,389 tags (ovoid) and 42,391 tags (filamentous) representing 14,464 and 13,098 putative unique transcripts, respectively. Statistical analysis of tag frequencies revealed the differential expression of 431 tags between libraries ( P < 0.05). Nucleotide sequence alignment searches on public databases provided SAGE tag annotation and gene ontology assignments. Comparisons between the SAGE profiles of ovoid and filamentous conceptuses revealed increased expression of key genes in the steroidogenesis [cytochrome P-450scc ( CYP11A1), aromatase ( CYP19A), and steroidogenic acute regulatory protein ( STAR)] and oxidative stress response pathways [microsomal glutathione S-transferase 1 ( MGST1) and copper-zinc superoxide dismutase ( SOD1)]. Differential expression of these genes in the steroidogenic and oxidative stress response pathways was confirmed by real-time PCR. These results validate the utility of SAGE in the pig and establish an initial model linking gene expression profiles at the pathway level with phenotypic progression from ovoid to filamentous stages of conceptus development.
The Corfu δβ thalassemia deletion disrupts γ-globin gene silencing and reveals post-transcriptional regulation of HbF expression
Authors: Chakalova Lyubomira , Osborne Cameron S. , Dai Yan-Feng , Goyenechea Beatriz , Metaxotou-Mavromati Anna , Kattamis Antonios , Kattamis Christos , Fraser Peter
Published: November 2004

The 7.2 kilobase (kb) Corfu δβ thalassemia mutation is the smallest known deletion encompassing a region upstream of the human δ gene that has been suggested to account for the vastly different phenotypes in hereditary persistence of fetal hemoglobin (HPFH) versus β thalassemia. Fetal hemoglobin (HbF) expression in Corfu heterozygotes and homozygotes is paradoxically dissimilar, suggesting conflicting theories as to the function of the region on globin gene regulation. Here, we measure γ- and β-globin gene transcription, steady-state mRNA, and hemoglobin expression levels in primary erythroid cells cultured from several patients with Corfu δβ thalassemia. We show through RNA fluorescence in situ hybridization that the Corfu deletion results in high-level transcription of the fetal γ genes in cis with a concomitant reduction in transcription of the downstream β gene. Surprisingly, we find that elevated γ gene transcription does not always result in a corresponding accumulation of γ mRNA or fetal hemoglobin, indicating a post-transcriptional regulation of γ gene expression. The data suggest that efficient γ mRNA accumulation and HbF expression are blocked until β mRNA levels fall below a critical threshold. These results explain the Corfu paradox and show that the deleted region harbors a critical element that functions in the developmentally regulated transcription of the β-globin genes.
Genotypic inhibitory killer immunoglobulin-like receptor ligand incompatibility enhances the long-term antileukemic effect of unmodified allogeneic hematopoietic stem cell transplantation in patients with myeloid leukemias
Authors: Beelen Dietrich W. , Ottinger Hellmut D. , Ferencik Stanislav , Elmaagacli Ahmet H. , Peceny Rudolf , Trenschel Rudolf , Grosse-Wilde Hans
Published: November 2004

It remains controversial whether alloreactive donor-derived natural killer (NK) cells display graft-versus-leukemia reactions after unmodified allogeneic hematopoietic stem cell transplantation (HSCT). The present study evaluated the role of inhibitory killer immunoglobulin–like receptor (KIR) ligand incompatibility using a well-defined and uniform setting of unmodified allogeneic HSCT in 374 patients with myeloid leukemias. The most striking finding was a significant heterogeneity in the 5-year estimates of hematologic leukemic relapse after human leukocyte antigen (HLA)–identical (n = 237; 22%), HLA class I–disparate (n = 89; 18%), and KIR ligand–incompatible transplantations (n = 48; 5%) (P < .04). Multivariate analysis confirmed that the relative relapse risk (RR) was influenced by HLA class I disparity alone (RR 0.49), but was lowest after HLA class I–disparate, KIR ligand–incompatible transplantations (RR 0.24) (P < .008). The primary graft failure rates, however, increased from 0.4% after HLA class I–identical to 2.3% after HLA class I–disparate, and to 6.3% after KIR ligand–incompatible transplantations, respectively (P < .02). Unlike some other reports, no beneficial effect of KIR ligand incompatibility on other major endpoints of allogeneic HSCT (transplantation-related mortality, and overall and event-free survival) was detectable in the present study. In conclusion, unmodified allogeneic HSCT from KIR ligand–incompatible donors provides a superior long-term antileukemic efficacy in patients with myeloid malignancies.
Selective inhibition of c-Myb DNA-binding by RNA polymers
Authors: Nordgård Oddmund , Andersen Tor Ø , Gabrielsen Odd S
Published: November 2004

Background

The transcription factor c-Myb is expressed in hematopoietic progenitor cells and other rapidly proliferating tissues, regulating genes important for proliferation, differentiation and survival. The DNA-binding domain (DBD) of c-Myb contains three tandemly arranged imperfect repeats, designated Myb domain R1, R2 and R3. The three-dimensional structure of the DBD shows that only the second and third Myb domains are directly involved in sequence-specific DNA-binding, while the R1 repeat does not contact DNA and only marginally affects DNA-binding properties. No structural information is available on the N-terminal 30 residues. Since deletion of the N-terminal region including R1 plays an important role in oncogenic activation of c-Myb, we asked whether this region confers properties beyond DNA-binding to the neighbouring c-Myb DBD.

Results

Analysis of a putative RNA-binding function of c-Myb DBD revealed that poly(G) preferentially inhibited c-Myb DNA-binding. A strong sequence-selectivity was observed when different RNA polymers were compared. Most interesting, the poly(G) sensitivity was significantly larger for a protein containing the N-terminus and the R1-repeat than for the minimal DNA-binding domain.

Conclusion

Preferential inhibition of c-Myb DNA binding by poly(G) RNA suggests that c-Myb is able to interact with RNA in a sequence-selective manner. While R2 and R3, but not R1, are necessary for DNA-binding, R1 seems to have a distinct role in enhancing the RNA-sensitivity of c-Myb.
Computation of elementary modes: a unifying framework and the new binary approach
Authors: Gagneur Julien , Klamt Steffen
Published: November 2004

Background

Metabolic pathway analysis has been recognized as a central approach to the structural analysis of metabolic networks. The concept of elementary (flux) modes provides a rigorous formalism to describe and assess pathways and has proven to be valuable for many applications. However, computing elementary modes is a hard computational task. In recent years we assisted in a multiplication of algorithms dedicated to it. We require a summarizing point of view and a continued improvement of the current methods.

Results

We show that computing the set of elementary modes is equivalent to computing the set of extreme rays of a convex cone. This standard mathematical representation provides a unified framework that encompasses the most prominent algorithmic methods that compute elementary modes and allows a clear comparison between them. Taking lessons from this benchmark, we here introduce a new method, the binary approach, which computes the elementary modes as binary patterns of participating reactions from which the respective stoichiometric coefficients can be computed in a post-processing step. We implemented the binary approach in FluxAnalyzer 5.1, a software that is free for academics. The binary approach decreases the memory demand up to 96% without loss of speed giving the most efficient method available for computing elementary modes to date.

Conclusions

The equivalence between elementary modes and extreme ray computations offers opportunities for employing tools from polyhedral computation for metabolic pathway analysis. The new binary approach introduced herein was derived from this general theoretical framework and facilitates the computation of elementary modes in considerably larger networks.
Characterization of a novel ATR-dependent, Chk1-independent, intra-S-phase checkpoint that suppresses initiation of replication inXenopus
Authors: Luciani M. Gloria , Oehlmann Maren , Blow J. Julian
Published: November 2004

In most eukaryotes, replication origins fire asynchronously throughout S-phase according to a precise timing programme. When replication fork progression is inhibited, an intra-S-phase checkpoint is activated that blocks further origin firing and stabilizes existing replication forks to prevent them undergoing irreversible collapse. We show that chromatin incubated in Xenopus egg extracts displays a replication-timing programme in which firing of new replication origins during S phase depends on the continued activity of S-phase-inducing cyclin-dependent kinases. We also show that low concentrations of the DNA-polymerase inhibitor aphidicolin, which only slightly slows replication-fork progression, strongly suppress further initiation events. This intra-S-phase checkpoint can be overcome by caffeine, an inhibitor of the ATM/ATR checkpoint kinases, or by neutralizing antibodies to ATR. However, depletion or inhibition of Chk1 did not abolish the checkpoint. We could detect no significant effect on fork stability when this intra-S-phase checkpoint was inhibited. Interestingly, although caffeine could prevent the checkpoint from being activated, it could not rescue replication if added after the timing programme would normally have been executed. This suggests that special mechanisms might be necessary to reverse the effects of the intra-S-phase checkpoint once it has acted on particular origins.
A Mutant Ataxin-3 Putative-Cleavage Fragment in Brains of Machado-Joseph Disease Patients and Transgenic Mice Is Cytotoxic above a Critical Concentration
Authors: Goti Daniel , Katzen Scott M. , Mez Jesse , Kurtis Noam , Kiluk Jennifer , Ben-Haïem Lea , Jenkins Nancy A. , Copeland Neal G. , Kakizuka Akira , Sharp Alan H. , Ross Christopher A. , Mouton Peter R. , Colomer Veronica
Published: November 2004

Machado-Joseph disease (MJD) is an inherited neurodegenerative disorder caused by ataxin-3 with a polyglutamine expansion. It is proposed that a toxic cleavage fragment of mutant ataxin-3 alternatively spliced isoform mjd1a triggers neurodegeneration, although this fragment has not yet been detected in the brains of MJD patients or in animal models. We have now generated transgenic mice expressing human mutant (Q71) or normal (Q20) ataxin-3 mjd1a under the control of the mouse prion promoter. Q71 transgenic mice expressing mutant ataxin-3 mjd1a above a critical level developed a phenotype similar to MJD including progressive postural instability, gait and limb ataxia, weight loss, premature death, neuronal intranuclear inclusions, and decreased tyrosine hydroxylase-positive neurons in the substantia nigra (determined by unbiased stereology). Q20 transgenic mice had normal behavior and pathology. Brains from sick Q71 transgenic mice contained an abundant mutant ataxin-3 mjd1a putative-cleavage fragment (Fragment), which was scarce in normal Q71 transgenic mice. Reactivity of the Fragment with a panel of antibodies and comigration with truncations of mutant ataxin-3 revealed that it contained residues C terminal to amino acid 221 to include the polyglutamine expansion. A similar portion of mutant ataxin-3 mjd1a expressed in transfected neuroblastoma cells was toxic above a critical concentration. The Fragment was more abundant in two affected brain regions of MJD patients. Thus, we have developed a murine model for mutant ataxin-3 mjd1a toxicity and identified a putative-cleavage fragment of the disease protein in the brains of these transgenic mice and MJD patients that is cytotoxic above a critical concentration.
Extracellular Signal-Regulated Kinase 1/2 Signaling Pathway in Solitary Nucleus Mediates Cholecystokinin-Induced Suppression of Food Intake in Rats
Authors: Sutton Gregory M. , Patterson Laurel M. , Berthoud Hans-Rudolf
Published: November 2004

Increased food intake is a major factor in the development of obesity, and the control of meal size is a valid approach to reduce food intake in humans. Meal termination, or satiety, is thought to be organized within the caudal brainstem where direct signals from the food handling alimentary canal and long-term signals from the forebrain converge in the solitary nucleus. Cholecystokinin (CCK) released from the gut after ingestion of food has been strongly implicated in nucleus tractus solitarius (NTS)-mediated satiation, but the exact cellular and intracellular signaling events are not understood. Using Western blotting and immunohistochemistry with phosphospecific antibodies, we demonstrate here that peripheral administration of CCK in rats leads to rapid activation of the extracellular signal-regulated kinase (ERK) signaling cascade in NTS neurons and that blockade of ERK signaling with microinfusion of a selective mitogen-activated ERK kinase inhibitor into the fourth ventricle attenuates the capacity of CCK to suppress food intake. In addition, we show that CCK-induced activation of ERK results in phosphorylation of the voltage-dependent potassium channel Kv4.2 and the nuclear transcription factor CREB (cAMP response element-binding protein). The results demonstrate that ERK signaling is necessary for exogenous CCK to suppress food intake in deprived rats and suggest that this pathway may also be involved in natural satiation and the period of satiety between meals through coupling of ERK activation to both cytosolic and nuclear effector mechanisms that have the potential to confer acute and long-term changes in neuronal functioning.
Role of Neurokinin 3 Receptors in Supraoptic Vasopressin and Oxytocin Neurons
Authors: Howe Heather E. , Somponpun Suwit J. , Sladek Celia D.
Published: November 2004

Neurokinin 3 receptors (NK3-Rs) are expressed in the supraoptic nucleus (SON), and SON is innervated by substance P (SP)-expressing A1 neurons in the medulla. Because SP stimulates vasopressin (VP) and oxytocin release from explants of the hypothalamo-neurohypophyseal system (HNS), two hypotheses were tested: (1) SP-stimulated VP release is mediated by NK3-Rs, and (2) stimulation of the A1 pathway by hypotension activates SON NK3-Rs. Senktide, an NK3-R agonist, stimulated VP release from HNS explants, but neither a neurokinin 1 receptor antagonist [L732,138 (N-acetyl-L-tryptophan 3,5-bis(tri-fluoromethyl)benzyl ester)] nor two NK3-R antagonists (SB222200andSB235375) prevented SP-stimulated VP release. Because the affinity of these antagonists for rat NK-Rs may limit their efficacy, NK3-R internalization was used to assess the ability of SP to activate SON NK3-Rs. Senktide, SP, or vehicle was microinjected above SON. The brain was perfused 5 min after injection and stained for NK3-R immunoreactivity. Using confocal microscopy, the number of NK3-R-immunoreactive (-IR) endosomes was counted in a 5.62μ region of cytoplasm in SON neurons. Senktide, but not SP or vehicle, significantly increased the number of NK3-R-IR endosomes in the cytoplasm. When hypotension was induced with hydralazine, NK3-R internalization was observed within 5 min (p< 0.005). A decrease in cytoplasmic NK3-R immunoreactivity was observed within 15 min of hypotension. Unexpectedly, both senktide and hypotension resulted in translocation of NK3-R-IR immunoreactivity to the nucleus. Thus, although these studies do not identify SP as the NK3-R ligand, they do provide evidence for hypotension-induced release of an endogenous tachykinin in SON and evidence suggesting a role for NK3-Rs in transcription regulation.
Assessing the Cultural Appropriateness of the Finding Meaning Through Caregiving Scale for Korean Caregivers
Authors: Lee Eunice E. , Farran Carol J. , Tripp-Reimer Toni , Sadler Georgia Robins
Published: November 2004

Before psychometric instruments can be used for populations other than those for whom they were originally developed, validation of cultural appropriateness is essential. This article describes the assessment of the cultural appropriateness of the Finding Meaning Through Caregiving Scale (FMTCS) with Korean female family caregivers. The FMTCS measures finding meaning among caregivers from an existential perspective and has three subscales: Loss/Powerlessness, Provisional Meaning, and Ultimate Meaning. The instrument’s cultural appropriateness was examined through semistructured interviews with ten Korean-born female family caregivers, five caregivers living in Korea, and five living in the United States. The interview data are reported according to the three dimensions described by Flaherty and colleagues (1988): content, semantic, and conceptual equivalence. Although the majority of items of the FMTCS appeared applicable to Korean caregivers, items on the Loss/Powerlessness and Provisional Meaning subscales asking caregivers about feelings related to missing their past relationships or communications appeared inappropriate for many Korean daughters-in-law. Of equal importance, a unique source of meaning among Korean caregivers that is not assessed in the FMTCS is an interpersonal context, including the importance caregivers place on teaching children and feeling proud of one’s caregiving accomplishments in the eyes of other relatives. The addition of new items that address the interpersonal context is warranted to improve the instrument’s cultural appropriateness for Korean caregivers.
Comparison of Blood Pressure Measurement Consistency Using Tonometric and Automated Oscillometric Instruments
Authors: Yucha Carolyn B. , Yang Mark C. K. , Tsai Pei-Shan , Calderon Kristine S.
Published: November 2004

To effectively evaluate treatments for hypertension, researchers and clinicians must be able to measure blood pressure (BP) in a valid and reliable way. The purpose of this study is to compare measurements made in the clinic using beat-to-beat radial BP tonometry, measurements made during 24 hours using an ambulatory BP monitor, and measurements made in the clinic using an automated oscillometric BP monitor. Fifty-seven adults with primary hypertension participated in this study, which used a repeated measures descriptive design. Clinic and ABPM daytime averages were compatible for both SBP and DBP. In contrast, clinic SBP was 7.56 mmHg higher than the beat-to-beat SBP; clinic DBP was 9.83 mmHg higher than the beat-to-beat DBP. These data suggest that automated clinic measurements may be used in place of daytime ambulatory BP measurements. We also estimate sample sizes for future studies based on characteristics of clinic BP.
Using free bed surface fluctuations in a 3‐D fluidized bed for dynamic characterization
Authors: Villa Briongos Javier , Guardiola Soler Jesús
Published: November 2004

The use of free surface fluctuations in three‐dimensional (3‐D) fluidized bed dynamic characterization is addressed. This technique provides a noninvasive global measure of the quality of fluidization by measuring at one position in the bed. The well‐known effect of particle size on fluidized bed hydrodynamics was explored using a 3D fluidized bed operated with four different particle groups. The analytical methods used were mutual information functions, frequency, and state space analysis of time series collected from bed surface fluctuations. Turbulent, multiple, and noninteracting bubble flow patterns, occurring during bubble regimes, have been characterized. Kolmogorov entropy for the reconstructed attractor is very sensitive to the transition between fluidization regimes. Moreover, correlation dimension estimates ranging between 3 < D2 < 5 indicate apparent low‐dimensional dynamics. Additionally for larger particle groups, D2 reaches a value close to 3, indicating slow bubbling controlled by large bubbles before the transition between different bubble flow patterns takes place. Finally, particle size has been found to have strong influence on signal persistence. © 2004 American Institute of Chemical Engineers AIChE J, 50: 3060–3067, 2004
Reachability of particle size distribution in semibatch emulsion polymerization
Authors: Wang Yang , Doyle Francis J.
Published: November 2004

Reachability analysis is critical in the determination of achievable end‐point products for complex process systems. In emulsion polymerization, an economically important method of producing various products, particle size distribution (PSD) is an important property of the latex produced. However, the population balance modeling framework does not yield direct solutions to reachability analysis for the resulting nonlinear distributed systems. In this article, a programming‐based approach is introduced for the reachability analysis of the final PSD for general particulate systems described by population balance models. In the application to a semibatch styrene homopolymerization system, the reachable region is defined for both the nominal and perturbed cases, with final PSDs characterized as multi‐Gaussian distributions. Sensitivity studies reveal the limiting factors in determining the achievable final products, and quantitative criteria are developed. The evolution of the reachable region in the case of midcourse correction reveals the difficulties encountered during in‐batch control, and shows the best control performance achievable given the limited on‐line measurements. © 2004 American Institute of Chemical Engineers AIChE J, 50: 3049–3059, 2004
Nonlinear acoustics in pant hoots of common chimpanzees (Pan troglodytes): Frequency jumps, subharmonics, biphonation, and deterministic chaos
Authors: Riede Tobias , Owren Michael J. , Arcadi Adam Clark
Published: November 2004

The pant hoot calls produced by common chimpanzees (Pan troglodytes) are multi‐call vocalizations that have figured prominently in investigations of acoustic communication in this species. Although pant hoots are predominantly harmonically structured, they can exhibit an acoustic complexity that has recently been linked to nonlinearity in the vocal‐fold dynamics underlying typical mammalian sound production. We examined the occurrence of these sorts of nonlinear phenomena in pant hoot vocalizations, contrasting quieter and lower‐pitched “introduction” components with loud and high‐pitched “climax” calls in the same bouts. Spectrographic evidence revealed four kinds of nonlinear phenomena, including discrete frequency jumps, subharmonics, biphonation, and deterministic chaos. While these events were virtually never observed during the introduction, they occurred in more than half of the climax calls. Biphonation was by far the most common phenomenon, followed by subharmonics, chaos, and frequency jumps. Individual callers varied in the degree to which their climax calls exhibited nonlinear phenomena, but were consistent in showing more biphonation than other forms. These outcomes show that nonlinear phenomena are routinely present in chimpanzee pant hoots, and help lay the foundation for investigating the function of such events. Am. J. Primatol. 64:277–291, 2004. © 2004 Wiley‐Liss, Inc.
Characterizing gastrointestinal transit time in four lemur species using barium‐impregnated polyethylene spheres (BIPS)
Authors: Campbell J.L. , Williams C.V. , Eisemann J.H.
Published: November 2004

Differences in dietary profiles and gastrointestinal (GI) morphologies observed across lemur species suggest that there may be variation in patterns of digesta flow through the GI tract related to the method of digesta processing. Using radio‐opaque barium‐impregnated polyethylene spheres (BIPS), we characterized such patterns in four lemur species:Varecia variegata(VV),Eulemur fulvus(EF),Propithecus verreauxi(PV), andHapalemur griseus(HG) (n=2 per species). After an initial radiograph was taken under light sedation, the animals were fed the BIPS together with a small meal. A combination of 30 small (1.5 mm) and 10 large (5 mm) BIPS was administered. Radiographs were then taken on a species‐dependent basis up to 48 hr post‐dosage. For small BIPS, the gastric transit time (GTT; time of first exit of BIPS from stomach) was 0.25–2 hr for VV, EF, and HG, and approximately 10 hr for PV. The oro‐rectal transit time (ORTT; time of first appearance in the rectum) was <2 hr for VV and EF, and 24.0 hr for PV and HG. The intestinal transit time (ITT, measured as ORTT – GTT) was <1.5 hr for VV and EF, and approximately 14 hr and 22 hr for PV and HG, respectively. These data suggest that the GTT of digesta as measured with BIPS was rapid for VV, EF, and HG. For VV and EF, the ORTT and ITT were also rapid, while for HG they were much slower. PV was characterized by delayed GTT, and a more rapid ITT compared to HG. Thus, patterns of flow for PV and HG, despite similar ORTT, differed in that HG emptied BIPS more rapidly and ITT was slower. The flow of BIPS did not differ for VV and EF. These data reveal new information in addition to the total tract transit time, and complement existing knowledge regarding anatomy and diet. Am. J. Primatol. 64:309–321, 2004. © 2004 Wiley‐Liss, Inc.
Integrierte Hybridsysteme aus Nanopartikeln und Biomolekülen: Synthese, Eigenschaften und Anwendungen
Authors: Katz Eugenii , Willner Itamar
Published: November 2004

Metall‐ oder Halbleiter‐Nanopartikel und Nanostäbchen haben ähnliche Dimensionen wie Proteine (Enzyme, Antigene, Antikörper) oder DNA. Die Integration von Nanopartikeln (mit ihren besonderen elektronischen, photonischen und katalytischen Eigenschaften) mit Biomaterialien (mit ihren einzigartigen Erkennungsmechanismen sowie katalytischen und inhibierenden Fähigkeiten) ergibt hybride Nanobiomaterialien mit synergistischen Eigenschaften und Funktionen. Dieser Aufsatz beschreibt die aktuellsten Entwicklungen bei der Synthese von Hybridsystemen aus Biomolekülen und Nanopartikeln oder Nanostäbchen und deren Anwendung zum Aufbau von geordneten 2D‐ und 3D‐Strukturen in Lösung und auf Oberflächen. Schwerpunkte sind der Einsatz von Biomolekül‐Nanopartikel‐Konjugaten für die Bioanalytik sowie zur Herstellung bioelektronischer Funktionseinheiten und Nanoleiterbahnen aus Metall, Halbleitern oder magnetischen Materialien.
DNA Codes for Nanoscience
Authors: Samorì Bruno , Zuccheri Giampaolo
Published: November 2004

The nanometer scale is a special place where all sciences meet and develop a particularly strong interdisciplinarity. While biology is a source of inspiration for nanoscientists, chemistry has a central role in turning inspirations and methods from biological systems to nanotechnological use. DNA is the biological molecule by which nanoscience and nanotechnology is mostly fascinated. Nature uses DNA not only as a repository of the genetic information, but also as a controller of the expression of the genes it contains. Thus, there are codes embedded in the DNA sequence that serve to control recognition processes on the atomic scale, such as the base pairing, and others that control processes taking place on the nanoscale. From the chemical point of view, DNA is the supramolecular building block with the highest informational content. Nanoscience has therefore the opportunity of using DNA molecules to increase the level of complexity and efficiency in self‐assembling and self‐directing processes.
Oxorhenium Complexes as Aldehyde‐Olefination Catalysts
Authors: Santos Ana M. , Pedro Filipe M. , Yogalekar Ameya A. , Lucas Isabel S. , Romão Carlos C. , Kühn Fritz E.
Published: November 2004

Several oxorhenium compounds in the formal oxidation states V and VII are examined as catalysts for the aldehyde‐olefination starting from diazo compounds, phosphines, and aldehydes. Of these, [ReMeO2(η2‐alkyne)] complexes provide the simplest catalysts to study, although [ReOCl3(PPh3)2] still remains the most efficient rhenium catalyst for aldehyde‐olefination described to date. Prior to the reaction with the Re catalysts the phosphine and the diazo compound react to form a phosphazine. No catalytic reaction occurs in cases where no phosphazine formation is observed. The first step of the catalytic cycle involves the formation of a carbene intermediate by the reaction of phosphazine and catalyst under extrusion of phosphine oxide and dinitrogen. In a second step the carbene reacts with aldehyde under olefin formation and catalyst regeneration. Excess of alkyne as well as the presence of ketones slows down the catalytic reaction. The olefination of 4‐nitrobenzaldehyde with diazomalonate is possible with these Re catalysts. In contrast, this reaction does not take place either in the classical Wittig fashion from Ph3PC(CO2Et)2 and aldehyde or by use of all other catalysts for aldehyde olefination reactions reported to date. Catalytic ylide formation from diazo compounds seems therefore not to be the only pathway through which catalytic aldehyde‐olefination reactions can proceed.
On the Role of PIII Ligands in the Conjugate Addition of Diorganozinc Derivatives to Enones
Authors: Pfretzschner Tatjana , Kleemann Lutz , Janza Birgit , Harms Klaus , Schrader Thomas
Published: November 2004

A mechanistic study on the conjugate addition of diethylzinc to cyclohexenone catalyzed by various chiral PIII ligands, provides new insights into its mechanism. Complete in situ conversion of the catalytic amount of Cu(OTf)2 into CuI species by excess ZnEt2 is demonstrated by EPR spectroscopy. Experimental evidence is presented in favor of a critical ternary 1:1:1 complex between enone, Et2Zn and catalyst, supporting a rate‐limiting reductive elimination or carbocupration from a preformed mixed Cu/Zn cluster carrying one‐ or two‐ligand molecules. A crystal structure has been obtained for a CuI⋅L2 complex, which shows catalytic turnover on addition of reagent and substrate. NMR spectroscopic analyses and VT experiments reveal that steric hindrance may prevent complexation of a second ligand molecule on the CuI cation, leading to extremely fast precatalysts based on CuX⋅L species.
Selection of a Pentameric Host in the Host–Guest Complexes {[{[P(μ‐NtBu)]2(μ‐NH)}5]⋅I}−[Li(thf)4]+ and [{[P(μ‐NtBu)]2(μ‐NH)}5]⋅HBr⋅THF
Authors: García Felipe , Goodman Jonathan M. , Kowenicki Richard A. , Kuzu Istemi , McPartlin Mary , Silva María A. , Riera Lucía , Woods Anthony D. , Wright Dominic S.
Published: November 2004

The structures of the host–guest complexes {[{[P(μ‐NtBu)]2(μ‐NH)}5]I}−⋅[Li(thf)4]+ [2⋅I{Li(thf)4}] and [{[P(μ‐NtBu)]2(μ‐NH)}5]⋅HBr⋅THF (2⋅HBr⋅THF) show that increased distortion of the framework of the pentameric macrocycle [{[P(μ‐NtBu)]2(μ‐NH)}5] (2) occurs with the larger halide ions. Theoretical studies show that the thermodynamic stabilities of the model host–guest anions [2⋅X]− (X=Cl, Br, I) are in the order Cl−≈Br−>I−, that is, the reverse of the templating trend observed experimentally. These studies support the view that the selection of the pentamer 2 over the tetramer [{[P(μ‐NtBu)]2(μ‐NH)}4] (1) is kinetically controlled, a conclusion which is also consistent with the previous observation that the frameworks of 1 and 2 are not in dynamic equilibrium with each other.
Microwave‐Assisted Synthesis of Metallic Nanostructures in Solution
Authors: Tsuji Masaharu , Hashimoto Masayuki , Nishizawa Yuki , Kubokawa Masatoshi , Tsuji Takeshi
Published: November 2004

Microwave (MW) rapid heating has received considerable attention as a new promising method for the one‐pot synthesis of metallic nanostructures in solutions. In this concept, advantageous application of this method has been demonstrated by using some typical examples for the preparation of Ag, Au, Pt, and AuPd nanostructures. Not only spherical nanoparticles, but also single crystalline polygonal plates, sheets, rods, wires, tubes, and dendrites were prepared within a few minutes under MW heating. Morphologies and sizes of nanostructures could be controlled by changing various experimental parameters, such as the concentration of metallic salt and surfactant polymer, the chain length of the surfactant polymer, the solvent, and the reaction temperature. In general, nanostructures with smaller sizes, narrower size distributions, and a higher degree of crystallization were obtained under MW heating than those in conventional oil‐bath heating. The origin of these characteristic features under MW irradiation is discussed in terms of thermal and non‐thermal effects under MW irradiation.
Isotope Exchange in Ionised CO2/CO Mixtures: The Role of Asymmetrical C2O3+ Ions
Authors: de Petris Giulia , Cartoni Antonella , Rosi Marzio , Troiani Anna , Angelini Giancarlo , Ursini Ornella
Published: November 2004

A hitherto unknown, atmospherically relevant, isotope‐exchange reaction was studied in ionised gaseous mixtures containing carbon dioxide and monoxide. The mechanism of the O exchange, proceeding over a double‐minimum potential‐energy surface, was positively established by mass spectrometric and theoretical methods that also allowed the identification and characterisation of the C2O3+ intermediate. The increase of internal energy displaces the observed reactivity towards an endothermic reaction path that involves only CO2 and represents an indirect route to the dissociation of carbon dioxide.
Molybdenum Phosphide as an o‐Propylaniline Hydrodenitrogenation Catalyst: A First Principles Study
Authors: Milman Victor , Winkler Björn , Gomperts Roberto
Published: November 2004

MoP has been shown experimentally to be an active catalyst in the hydrodenitrogenation of o‐propylaniline. We investigate the structure and the energetics of the o‐propylaniline adsorption on the Mo‐terminated MoP(001) surface. Detailed information on the structure of the free MoP(001) surface and on the structure and adsorption energy of o‐propylaniline on MoP(001) is obtained by using density functional theory. The transition state, reaction path, and the energy barrier are reported for one of the branches of the HDN reaction network that leads to the formation of propylbenzene by hydrogenolysis of the CN bond.
Edge‐Bridging and Face‐Capping Coordination of Alkenyl Ligands in Triruthenium Carbonyl Cluster Complexes Derived from Hydrazines: Synthetic, Structural, Theoretical, and Kinetic Studies
Authors: Cabeza Javier A. , del Río Ignacio , Fernández‐Colinas José M. , García‐Granda Santiago , Martínez‐Méndez Lorena , Pérez‐Carreño Enrique
Published: November 2004

The reactions of the triruthenium cluster complex [Ru3(μ‐H)(μ3‐η2‐HNNMe2)(CO)9] (1; H2NNMe2=1,1‐dimethylhydrazine) with alkynes (PhCCPh, HCCH, MeO2CCCCO2Me, PhCCH, MeO2CCCH, HOMe2CCCH, 2‐pyCCH) give trinuclear complexes containing edge‐bridging and/or face‐capping alkenyl ligands. Whereas the edge‐bridged products are closed triangular species (three RuRu bonds), the face‐capped products are open derivatives (two RuRu bonds). For terminal alkynes, products containing gem (RCCH2) and/or trans (RHCCH) alkenyl ligands have been identified in both edge‐bridging and face‐capping positions, except for the complex [Ru3(μ3‐η2‐HNNMe2)(μ3‐η3‐HCCH‐2‐py)(μ‐CO)(CO)7], which has the two alkenyl H atoms in a cis arrangement. Under comparable reaction conditions (1:1 molar ratio, THF at reflux, time required for the consumption of complex 1), some reactions give a single product, but most give mixtures of isomers (not all the possible ones), which were separated. To determine the effect of the hydrazido ligand, the reactions of [Ru3(μ‐H)(μ3‐η2‐MeNNHMe)(CO)9] (2; HMeNNHMe=1,2‐dimethylhydrazine) with PhCCPh, PhCCH, and HCCH were also studied. For edge‐bridged alkenyl complexes, the RuRu edge that is spanned by the alkenyl ligand depends on the position of the methyl groups on the hydrazido ligand. For face‐capped alkenyl complexes, the relative orientation of the hydrazido and alkenyl ligands also depends on the position of the methyl groups on the hydrazido ligand. A kinetic analysis of the reaction of 1 with PhCCPh revealed that the reaction follows an associative mechanism, which implies that incorporation of the alkyne in the cluster is rate‐limiting and precedes the release of a CO ligand. X‐ray diffraction, IR and NMR spectroscopy, and calculations of minimum‐energy structures by DFT methods were used to characterize the products. A comparison of the absolute energies of isomeric compounds (obtained by DFT calculations) helped rationalize the experimental results.
Preparation and Redox Properties of N,N,N‐1,3,5‐Trialkylated Flavin Derivatives and Their Activity as Redox Catalysts
Authors: Lindén Auri A. , Hermanns Nina , Ott Sascha , Krüger Lars , Bäckvall Jan‐E.
Published: November 2004

Eight different flavin derivatives have been synthesized and the electronic effects of substituents in various positions on the flavin redox chemistry were investigated. The redox potentials of the flavins, determined by cyclic voltammetry, correlated with their efficiency as catalysts in the H2O2 oxidation of methyl p‐tolyl sulfide. Introduction of electron‐withdrawing groups increased the stability of the reduced catalyst precursor.
Novel Formulations of Vitamins and Insulin by Nanoengineering of Polyelectrolyte Multilayers around Microcrystals
Authors: Dai Zhifei , Heilig Anne , Zastrow Heidi , Donath Edwin , Möhwald Helmuth
Published: November 2004

Microcapsules loaded with vitamin K3 (VK3), biotin, or insulin were prepared by using a novel coating technology based on the layer‐by‐layer (LbL) deposition of oppositely charged polyelectrolytes onto microcrystal templates. This produced multilayered, polymeric shells of varying thickness around the crystalline cores. Dissolution of the core material (VK3 with ethanol, biotin with basic solution, and insulin with acidic solution), resulted in its release through the shells. Microelectrophoresis was employed to monitor the microcrystal coating process; confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM) were used to verify multilayer coating and the formation of hollow polymer shells following removal of the microcrystal templates. The release rates of both VK3 and insulin decreased as the wall thickness (the number of polyelectrolyte layers deposited onto the microcrystal cores), increased. The release time could be varied by a factor of more than ten, depending on the number of polyelectrolyte layers applied. Following the addition of 70 mass % ethanol, the solubility of VK3 increased by as much as 170‐fold, resulting in an increased rate of VK3 release. By selecting appropriate polymer materials for the shells, and by controlling the number of polyelectrolyte layers applied, shells of various thickness, stiffness, aqueous solubility, dispersibility, biocompatibility, and permeability can be constructed.