Strong Interaction Force Research Articles

Temporal variation of the fine structure constant and the strong interaction parameter in the 229Th transition

The very low energy ( 7.6 ± 0.5 eV ) of the long-lived isomer state in 229Th has inspired the idea that the transition between this isomer and the ground state might be used to measure the temporal variation of some fundamental physical constants with great enhanced sensitivity in laboratory. Physicists have used several models to test whether this significantly enhanced sensitivity does exist. However, incongruous conclusions were reached. Based on the formulae derived from Feynman–Hellmann theorem, we reexamine the physics involved in those argument by the relativistic mean field theory. The results show that the correlation between the nuclear strong interaction and Coulomb force is important and cannot be neglected. The sensitivity to variations of fine structure constant, nucleon mass and meson masses could be enhanced by several orders of magnitude in the 229Th transition.

Intramolecular Cation—π Interaction in Organic Synthesis.

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Intramolecular cation–π interaction in organic synthesis

Controlling molecular conformation is a significantly important issue in a wide variety of organic reactions because the ground state structure is significantly responsible for the transition one. As observed in enzymes and proteins, the cation-pi interaction plays a key role in the formation of the tertiary structure and the biochemical processes. Therefore, the cation-pi interaction would be a promising conformation-controlling tool not only in large molecules, but also in small molecules due to its stronger interaction force. This article describes the utility of the intramolecular cation-pi interaction in various organic syntheses with evidence for the existence of the cation-pi interactions.

Enhancement of poly(ethylene glycol) mucoadsorption by biomimetic end group functionalization

Poly(ethylene glycol) (PEG) is widely used in the pharmaceutical, biotechnology, and medical device industries. Although PEG is a biocompatible polymer that has enjoyed widespread use in drug delivery technology, it is not considered adhesive toward mucosal tissue. Here the authors describe a simple approach to enhancing mucoadsorption of PEG polymers through end group functionalization with the amino acid 3,4-dihydroxyphenyl-L-alanine (DOPA). Using a variety of surface analytical techniques, the authors show that a four-armed poly(ethylene glycol) polymer functionalized with a single DOPA residue at the terminus of each arm (PEG-(DOPA)(4)) adsorbed strongly to surface immobilized mucin. Successful mucoadsorption of PEG-(DOPA)(4) across several pH values ranging from 4.5 to 8.5 was demonstrated, and control experiments with unfunctionalized four-arm PEG demonstrated that mucoadsorption of PEG-(DOPA)(4) is due largely to the presence of DOPA end groups. This conclusion was confirmed with single molecule atomic force microscopy experiments that revealed a surprisingly strong interaction force of 371+/-93 pN between DOPA and adsorbed mucin. Direct comparisons with known mucoadhesive polymers revealed that PEG-(DOPA)(4) was equal to or more adsorptive to immobilized mucin than these existing mucoadhesive polymers. In addition to demonstrating significant enhancement of mucoadhesive properties of PEG by DOPA functionalization, this study also introduced a new simple approach for rapid screening of mucoadhesive polymers.

A dissipative discretization scheme for a nonlocal phase segregation model

AbstractI want to thank H. Gajewski for many years of fruitful collaboration and his continuous encouragement, K. Gärtner We are interested in finite volume discretization schemes and numerical solutions for a nonlocal phase segregation model, suitable for large times and interacting forces. Our main result is a scheme with definite discrete dissipation rate proportional to the square of the driving force for the evolution, i. e., the discrete antigradient of the chemical potential v. Steady states are characterized by constant v and satisfy a nonlocal stationary equation. A numerical bifurcation analysis of that stationary equation explains the observed global behavior of numerically computed trajectories of the evolution equation. For strong interaction forces the model shows steady states distinguished by small deformations of the 'mushy region' or 'interface states'. One essential open question in the discrete case is the global boundedness of v.

Atomic force microscopy study on specificity and non-specificity of interaction forces between Enterococcus faecalis cells with and without aggregation substance

Enterococcus faecalis is one of the leading causes of hospital-acquired infections, and indwelling medical devices are especially prone to infection. E. faecalis expressing aggregation substance (Agg) adheres to biomaterial surfaces by means of positive cooperativity, i.e. the ability of one adhering organism to stimulate adhesion of other organisms in its immediate vicinity. In this study, atomic force microscopy (AFM) was used to measure the specificity and non-specificity of interaction forces between E. faecalis cells with and without Agg. Bacteria were attached to a substratum surface and a tip-less cantilever. Two E. faecalis strains expressing different forms of Agg showed nearly twofold higher interaction forces between bacterial cells than a strain lacking Agg [adhesive force (F(adh)), -1.3 nN]. The strong interaction forces between the strains with Agg were reduced after adsorption of antibodies against Agg from -2.6 and -2.3 nN to -1.2 and -1.3 nN, respectively. This suggests that the non-specific interaction force between the enterococci amounts to approximately 1.2 nN, while the specific force component is only twofold stronger. Comparison of the results of the AFM interaction forces with the positive cooperativity after adhesion to a biomaterial in a parallel-plate flow chamber showed that in the absence of strong interaction forces between the cells, positive cooperativity was also absent. In conclusion, this is believed to be the first time that the influence of specific antibodies on interaction forces between E. faecalis cells has been demonstrated by AFM, thereby experimentally distinguishing between specific and non-specific force components.

Imaging atomically sharp crack tips in mica by contact mode AFM under ambient conditions

Using an Atomic Force Microscope (AFM) operated in contact mode under ambient conditions, we have tried to resolve atomically sharp cracks perpendicular to the basal plane of muscovite mica. However, although tip radius of probes of less than 10 nm allowed a lateral resolution of 0.7 nm and the tip-sample adhesive force has been minimized, our experimental results demonstrate that the molecular structure of crack tips can't still be resolved. Even worse, sometimes the tip-sample friction can disrupt the region around the crack tip. This thus leads to the conclusion that one will fail to resolve atomically sharp cracks under ambient conditions by contact AFM. The inability is due to low lateral resolution of contact AFM and strong tip-sample interaction force under ambient conditions. New techniques of scanning samples in liquids and UHV non-contact AFM both of which have true atomic resolution are strongly recommended for future studies.

Effect of poly-HEMA hydrophilic gel environment on the photo-physical behavior of rhodamine dyes

The absorption spectra of rhodamine B (RB) chloride, rhodamine 6G (R6G) tetrafluoroborate and rhodamine 6G chloride in poly-2-hydoxyethyl methacrylate hydrogel (PHEMA) matrix were studied using absorption spectroscopy in the visible region. The transport and aggregative properties of these ionic dyes in aqueous solution across the hydrophilic gel were also investigated. The similarities of absorption spectra of RB in aqueous solutions and in hydrogel host suggest that the hydrogel framework has a minor effect in their absorption spectra. In contrast, there is a relatively strong interaction or electrostatic forces between R6G dyes and the hydrogel matrix. The permeability of R6G chloride through hydrogel host is seen to be markedly higher than RB chloride and R6G tetrafluoroborate.

Adhesion and rupture of liposomes mediated by electrostatic interaction monitored by thickness shear mode resonators.

Adhesion and spreading of negatively charged unilamellar vesicles composed of POPG/POPC and DPPG/DPPC on positively charged self-assembly monolayers of 11-amino-1-undecanethiol were monitored by means of thickness shear mode (TSM) resonators with a fundamental frequency of 5 MHz. Changes of frequency and motional resistance upon vesicle adsorption were recorded as a function of surface charge density and lyotropic phase state of the lipids. From the readout of the TSM resonator, changes of the shape of the vesicles as well as the formation of supported lipid bilayers can be inferred in a quantitative manner. Increasing surface charge densities on the vesicles, which are tunable by the POPG content, led to decreasing frequency and resistance changes. At very high PG content, a lower limit of 3-12 Hz was found, indicative of the formation of planar bilayers due to vesicle rupture induced by the strong electrostatic interaction forces. Vesicles composed of DPPG/DPPC were less susceptible to deformation and rupture, a fact that can be attributed to the higher bending rigidity of DPPG/DPPC liposomes. More than 70 mol% of DPPG were needed to induce adhesion-controlled rupture of surface-attached vesicles, while only 30-50% of POPG were sufficient to form planar lipid bilayers on the quartz.

Frequency dependence of a field-induced force between two high dielectric spheres in various fluid media

The frequency dependence of the interaction force f between two identical SrTiO3 spheres has been investigated in various carrying media with different dielectric constants under ac electric field strengths E0. We note that the force f is proportional to E02 and increases with the frequency regardless of the carrying media. The force however, is found to be stronger than that expected theoretically when the interspherical gap is small. The experimental results demonstrate that it is the conductivity that dominates the interaction force at low frequency, while dielectric polarization becomes more important at high frequency, and reveal that stronger interaction force between high dielectric spheres may be obtained in higher dielectric fluids when the frequency of the ac field is high enough. Some anomalous behaviors of f versus frequency are found when the two spheres are nearly touched.

Optical Observation of Gas Bridging between Hydrophobic Surfaces in Water

The very strong and long-ranged interaction force between hydrophobic surfaces in water has been a debated issue for a long time. Recent studies suggest that the long-range attraction is attributable to the bridging of nanoscopic bubbles attached on the surfaces. However, it is still unclear at present whether such a bridging is able to exit stably or not. To clarify the existence of the gas bridge, we conducted the optical observation and the force measurement between the hydrophobic glass particle and plate in water simultaneously, using a combined apparatus of an atomic force microscope and an optical inverted microscope. It is found that (i) the image of the dark ring of ca. 1 μm in diameter appears in the region where the existence of the bridge is confirmed by force curves, but disappears when the separation between surfaces becomes shorter than the low limit of the wavelength of visible light, and (ii) the sudden disappearance of the image coincides well with the breakage of the bridge estimated from the separating force curve. The results obtained here are consistent with the above-mentioned mechanism for the long-range attraction between hydropobic surfaces in water.

Medium-range order in liquid Al 5Fe 2 alloy

The molecular-dynamics (MD) simulation on liquid Al 5Fe 2 is carried out to investigate the structure of medium-range order (MRO), combined with X-ray diffraction experiment. The pre-peak considered as the signature of MRO is observed in the experiment, which is in good agreement with our simulation. According to the structure feature of atomic clusters, we find that there exist many icosahedral clusters in the liquid, which results in the pre-peak of S( Q). It is found from the calculated Ashcroft–Langreth (A–L) structure factors that there exists strong interaction force between Al and Fe atom. Both the Bhatia–Thornton (B–T) structure factors and the chemical short-range order parameter α indicate the preference for unlike-neighbor bonds. It is seen from the low- Q region of S( Q) and the concentration–concentration structure factor S CC( Q) that the pre-peak mainly comes from the first peak of S CC( Q). In other words, the pre-peak originates from the chemical ordering in the liquid.

Removal characteristics of trace compounds of landfill gas by activated carbon adsorption

The removal characteristics of trace compounds and moisture in raw landfill gas (LFG) were studied. The LFG from the extraction well was saturated with water and moisture was eliminated by physical methods including cyclone-type dehydrator and compressor. The moisture removal efficiency of dehydrator and compressor was above 80%. As the moisture contents of LFG decreased, the toxic compounds like aromatics and chlorinated compounds were effectively removed by using the granular activated carbon. The breakthrough time and adsorption capacity of benzene, toluene, and ethyl benzene decreased rapidly when the relative humidity is over 60%. The effect of moisture was more pronounced at lower adsorbate concentrations tested than at higher concentrations. The breakthrough curves for multi-component mixtures show displacement effects. In the course of competing adsorption, adsorbates with strong interaction force to displace weakly bounded substances. Adsorption by activated carbon is in descending order of xylene, ethylbenzene, toluene, tri or tetrachloroethylene, benzene, carbon tetrachloride and chloroform in LFG, respectively.

Mechanical, thermal and morphological properties of glass fiber and carbon fiber reinforced polyamide-6 and polyamide-6/clay nanocomposites

Carbon fiber and glass fiber reinforced polyamide-6 and polyamide-6/clay nanocomposites were prepared. Results show that the mechanical and thermal properties of the polyamide-6/clay nanocomposites are superior to those of polyamide-6 composite in terms of the heat distortion temperature, tensile and flexural strength and modulus without sacrificing their impact strength. This may be due to the nanoscale effects, and the strong interaction force existed between the polyamide-6 matrix and the clay interface. The mechanical properties of neat polyamide-6/clay nanocomposites are better than those of 10 wt.% glass fiber or carbon fiber reinforced polyamide-6. The effect of nanoscale clay on toughness is more significant than that of the fiber.

A model for experimentally-observed high-strain-rate dynamic strain aging in titanium

Recent high-strain-rate experimental results have shown an anomalous response by commercially pure titanium at relatively high temperatures: for a fixed high strain rate and a suitable strain, the flow stress which is a monotonically decreasing function of the temperature, suddenly begins to increase with increasing temperature, and then begins to decrease, displaying a dynamic strain-aging behavior. This phenomenon may be caused by the interaction between moving dislocations and mobile point defects in the dislocation core area. Based on this supposition, a model is developed which, both qualitatively and quantitatively, describes the experimentally observed results. This model assumes that the anomalous response is, in fact, dynamic strain aging caused by the drag of the core atmosphere, the evolution of the dislocation structure, and the associated interaction processes. The model combines the concepts of athermal long-range and thermally activated, short-range barriers, with the model of a “trough” for the thermally activated breakaway of dislocations from the core atmosphere. The evolution of the core atmosphere concentration is included in the model, based on the strong interaction force between dislocations and point defects in the core area. The final product is a unified model which seems to accurately predict the response of commercially pure titanium, over a broad range of strain rates and temperatures.

An experimentalist's highlights

A concise summary of recent experimental data presented at this conference illustrates the progress in our understanding of the photon interactions. The perturbative QCD domain of high Q 2 two-photon events and high p t jet production in both γγ and eγ interactions is well described by NLO calculations and parton density functions. Measurements of diffractive processes and resonance formation provide a detailed information on the difficult field of long range strong interaction forces.

Curved Parametric Segments for the Stress Field of 3-D Dislocation Loops

Under applied mechanical forces, strong mutual interaction or other thermodynamic forces, dislocation shapes become highly curved. We present here a new method for accurate computations of self and mutual interactions between dislocation loops. In this method, dislocation loops of arbitrary shapes are segmented with appropriate parametric equations representing the dislocation line vector. Field equations of infinitesimal linear elasticity are developed on the basis of isotropic elastic Green’s tensor functions. The accuracy and computational speed of the method are illustrated by computing the stress field around a typical (110)-[111] slip loop in a BCC crystal. The method is shown to be highly accurate for close-range dislocation interactions without any loss of computational speed when compared to analytic evaluations of the stress field for short linear segments. Moreover, computations of self-forces and energies of curved segments are guaranteed to be accurate, because of the continuity of line curvature on the loop.

Criterion of polymer-polymer miscibility determined by viscometry

The criteria of polymer-polymer miscibility determined by viscometry are reviewed, and a new criterion is proposed based on the classical Huggins equation and the Huggins coefficient K m in the blends. It was found that, in a ternary (polymer-A)—(polymer-B)-solvent system, ▪ In the absence of strong specific interaction forces between molecules that would encourage aggregation and at sufficiently low concentration, the above equation can be written thus: ▪ This equation can be used to determine the miscibility of polymer blends, when: α ⩾ 0 miscible, α < 0 immiscible. It is found that the new criterion is reasonable and suitable to predict polymer-polymer miscibility by the viscometry method.

Investigations of the adsorption of palladium on carbonaceous adsorbents modified with dimethylglyoxime—I. The adsorption of dimethylglyoxime on selected carbonaceous adsorbents

The adsorption of dimethylglyoxime (DMG) on six commercial activated carbons and on lignite was investigated with the aim to manufacture a modified adsorbent which is capable of separating palladium selectively from metal ion mixtures in nitric acid solutions. The DMG adsorption isotherms and the palladium adsorption behaviour of the modified and unmodified carbonaceous adsorbents indicate strong interaction forces which bring about the adsorption of the reagent. These interactions are probably based on hydrogen bonds.

European Political Cooperation: An Application of Political Reliability Theory to Integration

European Political Cooperation (EPC) denotes the foreign policy integration among members of the European Economic Community (EEC). The extent of political cooperative integration is analyzed by focusing upon the 'political reliability' or probability that EPC events reflect a consistent pattern of integration rather than merely an increasing frequency of interaction. A positive theory of EPC is built from first assumptions about unobservable integrative and disintegrative forces. Observable, politically cooperative events (e.g., European Council meetings, summit meetings, joint declarations, collective sanctions) are the consequence of the system of unobservable political forces which drive EPC activity. Two fundamental variables-political reliability and political interaction force-uniquely determine the EPC event process. Empirical tests strongly support the theory and demonstrate that by the mid1970s the forces of integration acting on the EPC system prevailed over the forces of disintegration. Two underlying processes may contribute to European foreign policy integration, however. The first is governed by a constant (Poisson) force, the other by a strong interaction force. These two subprocesses resemble interactions within the Political Committee of EPC and within the COREU telecommunications network.