פרסומים

In discrete models, such as spin chains, the entanglement between a pair of particles in a chain has been shown to vanish beyond a certain separation. In the continuum, a quantum field ⊘(x) at a point represents a single degree of freedom, thus at a region of finite size there are infinite separate degrees of freedom. We show that as a consequence, in contrast to discrete models, the ground state of a free, quantized and relativistic field exhibits entanglement between any pair of arbitrarily separated finite regions. We also provide a lower bound on the decay rate of the entanglement as a function of the separation length between the regions and briefly discuss the physical reasons behind this different behaviour of discrete and continuous systems.

Conventional wisdom would expect government to react to disaster or crisis in order to prevent recurrence. Atrophy of vigilance theory contends that disasters in hazardous systems necessarily lead to such corrective policy. Yet policy change theory recognizes that even disaster or crisis spurs policy change only when there is a conducive political climate. When is disaster or crisis insufficient to produce a political climate favoring change aimed at preventing recurrence? What is the durability of policy change in the long term? This article uses three Israeli and two parallel American case studies to further understanding of policy reactions to disaster and crisis in environments dominated by production results pressures. Patterns of reaction do not conform completely with either atrophy of vigilance or policy change theories.

BACKGROUND: Mast cells and eosinophils have an important role in allergic inflammation and probably also in chronic inflammatory diseases resulting in fibrosis, such as Crohn disease where fibrosis is present as strictures. The involvement of mast cells and eosinophils in Crohn disease fibrosis was investigated. METHODS: Biopsies from diseased foci were stained for mast cells, eosinophils, anti-collagen type IV and VIII, laminin and alpha-smooth muscle actin (alpha-SMA) (IHC). Fibroblasts outgrown from the biopsies and a normal fetal intestinal fibroblast line were cultured in the presence of the human mast cell line HMC-1, or of human peripheral blood eosinophil (MACS, purity > 98%) sonicates, or of selected mediators. Fibroblast proliferation (3H-thymidine), collagen synthesis ([3H]-proline) and collagen gel contraction were evaluated. RESULTS: Mast cells were present in all the biopsies and only faintly positive for extra cellular matrix (ECM) products. Pronounced eosinophilia was detected in only two cases. Mast cell sonicates increased both Crohn disease (alpha-SMA positive) and control fibroblast proliferation, decreased collagen production and increased collagen gel contraction. Eosinophil sonicates increased fibroblast proliferation, gel contraction and collagen production. TNF-alpha decreased collagen production. Histamine, tryptase and chymase had no influence. CONCLUSIONS: These in vitro data show that mast cells and eosinophils could be involved in modulating Crohn disease fibrosis by directly influencing intestinal fibroblast properties.

Caenorhabditis elegans mtf-1 encodes matefin, which has a predicted SUN domain, a coiled-coil region, an anti-erbB-2 IgG domain, and two hydrophobic regions. We show that matefin is a nuclear membrane protein that colocalizes in vivo with Ce-lamin, the single nuclear lamin protein in C. elegans, and binds Ce-lamin in vitro but does not require Ce-lamin for its localization. Matefin is detected in all embryonic cells until midembryogenesis and thereafter only in germ-line cells. Embryonic matefin is maternally deposited, and matefin is the first nuclear membrane protein known to have germ line-restricted expression. Animals homozygous for an mtf-1 deletion allele show that matefin is essential for germ line maturation and survival. However, matefin is also required for embryogenesis because mtf-1 (RNAi) embryos die around the approximately 300-cell stage with defects in nuclear structure, DNA content, and chromatin morphology. Down-regulating matefin in mes-3 animals only slightly enhances embryonic lethality, and elimination of UNC-84, the only other SUN-domain gene in C. elegans, has no affect on mtf-1 (RNAi) animals. Thus, mtf-1 mediates a previously uncharacterized pathway(s) required for embryogenesis as well as germ line proliferation or survival.

Pharmacokinetic textbooks state that the (apparent) volume of distribution based on drug concentration in plasma (V or Vbeta) is always greater than the volume of distribution (apparent) under steady state conditions (Vss), but do not provide a general model-independent mathematical proof. Wagner's mathematical comparison between Vbeta and Vss is based on microscopic rate constants of either specific models and is restricted solely to the two-compartment open body model. Nakashima and Benet utilizing a model-dependent approach showed a mathematical relationship between Vbeta and Vss for a multicompartment model, but again by using microscopic model constants. The limitation of these two above mentioned mathematical comparisons is the necessity of knowledge of the model's structure and its microscopic rate constants. The present article describes a new non-compartmental, model-independent, general mathematical proof for Vbeta to be always greater than Vss. This new method does not require any knowledge of microscopical rate constants and is based solely on an exponentially decreasing function, which is the common way to describe drug disposition following i.v. bolus.

Let Xn, ¦,X1 be i.i.d. random variables with distribution function F and finite expectation. A statistician, knowing F, observes the X values sequentially and is given two chances to choose X's using stopping rules. The statistician's goal is to select a value of X as large as possible. Let Vn2 equal the expectation of the larger of the two values chosen by the statistician when proceeding optimally. We obtain the asymptotic behavior of the sequence Vn2 for a large class of F's belonging to the domain of attraction (for the maximum) D(GII''$\pm$), where GII''$\pm$ (x) = exp(-x-''$\pm$)''(x > 0) with$\pm$ > 1. The results are compared with those for the asymptotic behavior of the classical one choice value sequence Vn1, as well as with the ""prophet value"" sequence E(maxXn, ¦,X1), and indicate that substantial improvement is obtained when given two chances to stop, rather than one.

The structural and energetic characteristics of the interaction between interfacially adsorbed (partially inserted) a-helical, amphipathic peptides and the lipid bilayer substrate are studied using a molecular level theory of lipid chain packing in membranes. The peptides are modeled as ‘‘amphipathic cylinders’’ characterized by a well-defined polar angle. Assuming two-dimensional nematic order of the adsorbed peptides, the membrane perturbation free energy is evaluated using a cell-like model; the peptide axes are parallel to the membrane plane. The elastic and interfacial contributions to the perturbation free energy of the ‘‘peptide-dressed’’ membrane are evaluated as a function of: the peptide penetration depth into the bilayer’s hydrophobic core, the membrane thickness, the polar angle, and the lipid/peptide ratio. The structural properties calculated include the shape and extent of the distorted (stretched and bent) lipid chains surrounding the adsorbed peptide, and their orientational (C-H) bond order parameter profiles. The changes in bond order parameters attendant upon peptide adsorption are in good agreement with magnetic resonance measurements. Also consistent with experiment, our model predicts that peptide adsorption results in membrane thinning. Our calculations reveal pronounced, membrane-mediated, attractive interactions between the adsorbed peptides, suggesting a possible mechanism for lateral aggregation of membrane-bound peptides. As a special case of interest, we have also investigated completely hydrophobic peptides, for which we find a strong energetic preference for the transmembrane (inserted) orientation over the horizontal (adsorbed) orientation.

This paper describes a continuously variable and independently addressable channelized dispersion compensator. The optical system is a free-space grating-based system used in a four-pass configuration to ensure flat passbands. The variable dispersion is produced by an array of thermally adaptable curvature micromechanical mirrors. A per-channel variable dispersion greater than +/-400 ps/nm has been demonstrated, with 58 GHz +/-0.4 dB flat passband on 85 GHz spacing. The group delay ripple is less than 7 ps and the penalty with 40 Gb/s CSRZ is 0.7 dB.

This paper describes a continuously variable and independently addressable channelized dispersion compensator. The optical system is a free-space grating-based system used in a four-pass configuration to ensure flat passbands. The variable dispersion is produced by an array of thermally adaptable curvature micromechanical mirrors. A per-channel variable dispersion greater than +/-400 ps/nm has been demonstrated, with 58 GHz +/-0.4 dB flat passband on 85 GHz spacing. The group delay ripple is less than 7 ps and the penalty with 40 Gb/s CSRZ is 0.7 dB.

N-methyl-tetramethylcyclopropanecarboxamide (MTMCD) is a new antiepileptic drug (AED) structurally related to valproic acid (VPA) that has a broad spectrum of anticonvulsant activity including models of therapy-resistant epilepsy. The purpose of this study was to identify in vivo metabolites of MTMCD that could contribute to its anticonvulsant efficacy. The metabolism of MTMCD was studied in mice, in human liver microsomes (HLM), and in recombinant human CYP isoforms with focus on formation of the hydroxylation product, N-hydroxymethyl-tetramethylcyclopropanecarboxamide (OH-MTMCD) and the N-demethylation product tetramethylcyclopropanecarboxamide (TMCD). The anticonvulsant activity of MTMCD's metabolites was evaluated in the maximal electroshock (MES), subcutaneous metrazole (s.c. Met), and in the 6Hz model in mice. In mice, OH-MTMCD was identified as a phase I metabolite of MTMCD and detected in plasma and brain after administration of MTMCD. In human liver microsomes MTMCD was biotransformed to OH-MTMCD but not to TMCD. Chemical inhibition studies suggested that MTMCD hydroxylation is mainly mediated by CYP 2A6 and CYP 2C19, which was confirmed using cDNA-expressed P450 isozymes. OH-MTMCD was a broad-spectrum anticonvulsant and possessed significant anticonvulsant activity in mouse models of partial and generalized seizures (ED50 values 75-220mg/kg), but was less potent than MTMCD. As OH-MTMCD was also present at lower concentrations than MTMCD in mouse brain, it is likely that MTMCD itself and not one of its metabolites is responsible for its activity in therapy-resistant epilepsy.

Solubilization and structural transformations in nonionic food microemulsions, characterized by large continuous isotropic region, contg. solubilized lutein, and lutein ester were studied. The prepns. are of oil-based concs. composed of solubilized lutein or lutein ester in reverse micelles constructed from hydrophilic surfactant, alc. and R(+)-limonene. The reverse micelles are dild. along a 60/40 surfactant/oil diln. line with aq. phase (contg. water and glycerol) up to the opposite corner of the diagram where o/w microemulsions are formed passing through a bicontinuous phase, without any visual phase sepn. The diln. goes through two structural transitions that were detd. in empty (ref.) and solubilized systems. The solubilization capacity of both free lutein (FL) and lutein ester (LE) is considerably higher (as expected) in the reverse micelles (no aq. phase), and in the W/O microemulsions than in the O/W microemulsions, but the highest solubilization was obtained within the bicontinuous phase. The solubilization was found to be affected by the lipophilicity of the surfactant and is also concn.-dependent throughout all the microemulsions structures, but the most pronounced surfactant effect was shown to be in the bicontinuous region. Structural transitions w/o → bicontinuous occurred at 30% aq. phase in empty (ref.) microemulsions as well as in microemulsions contg. solubilized free and esterified lutein (at the max. solubilization levels). However, the transitions bicontinuous → o/w occurred at higher aq. phase contents of 50 and 60% aq. phase for FL and LE, resp., in comparison to a transition at 40% for the empty microemulsion. As a result, the bicontinuous region in the presence of the guest mols. becomes much broader. The results indicate that in the reverse swollen micelles the guest mols., being practically lipophilic will be easily accommodated at the concaved water interfaces (in the w/o region), which will enable high solubilization capacities, and without significant modifications of the interface. It becomes also evident that at zero curvature interfaces (bicontinuous) and in convex interfaces (oil/water) the lutein ester (the more lipophilic mol.) penetrates into the interface and swells both the bicontinuous interface and the droplets, similarly to most guest mols. However, free lutein is poorly accommodated at the interface and interferes with the interfacial organization and modifies the flattened curvature, affecting the transformation from bicontinuous to o/w droplets. [on SciFinder(R)]

We achieved the soliton-based miniaturized integration of electro-optic devices in a photorefractive paraelectric bulk crystal, by driving self-trapping through an external bias field in a top-sided electrode geometry. The ensuing spatially resolved electric field manifests a localized voltage-dependent region in which a quasi-uniform field leads to screening-like self-trapped waves at considerably low voltages without sample miniaturization, along with their electro-optic beam manipulation. By replicating the electrode structure, our achievements constitute the basic building block that paves the way to digitally addressable volume photonic manipulator arrays. [ABSTRACT FROM AUTHOR]Copyright of Applied Physics Letters is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder’s express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Cationic lipid-DNA complexes, often referred to as lipoplexes, are formed spontaneously in aqueous solutions upon mixing DNA and liposomes composed of cationic and nonionic lipids. Understanding the mechanisms underlying lipoplex formation, structure and phase behavior is crucial for their further development and design as non-viral transfection vectors in gene therapy. From a physical point of view, lipoplexes are ordered, self-assembled, composite aggregates. Their preferred spatial geometry and phase behavior are governed by a delicate coupling between the electrostatic interactions which drive lipoplex formation and the elastic properties of the constituent lipid layers, both depending on the molecular nature and composition of the lipid mixture. In this review we outline some recent efforts to model the microscopic structure, energetic and phase behavior of cationic lipid-DNA mixtures, focusing on the two principal aggregation geometries: the lamellar (L-alpha(C)), or ‘‘sandwich’’ complexes, and the hexagonal (H-II(C)), or ‘‘honeycomb’’ complexes. We relate the structural and thermodynamic properties of these two ‘‘canonical’’ lipoplex morphologies to their appearance in phase diagrams of DNA-lipid mixtures, emphasizing the crucial role fulfilled by the molecular packing characteristics of the cationic and neutral lipids, as reflected in the curvature elastic properties of the mixed lipid layer.