Time delay as a key to apoptosis induction in the p53 network

A feedback mechanism that involves the proteins p53 and mdm2, induces cell death as a controlled response to severe DNA damage. A minimal model for this mechanism demonstrates that the response may be dynamic and connected with the time needed to translate the mdm2 protein. The response takes place if the dissociation constant k between p53 and mdm2 varies from its normal value. Although it is widely believed that it is an increase in k that triggers the response, we show that the experimental behaviour is better described by a decrease in the dissociation constant. The response is quite robust upon changes in the parameters of the system, as required by any control mechanism, except for few weak points, which could be connected with the onset of cancer. Received 8 May 2002 / Received in final form 9 July 2002 Published online 17 September 2002     

Infinite component field theory as a key to the solution of the gauge hierarchy problem

We construct ultraviolet finite infinite component field theories, in particular we construct the infinite component generalization of the Yang-Mills theory which has an ultraviolet fixed point. We show that the gauge infinite component field theory with the mass of the first excitation M ⩽ (1−10) TeV solves the gauge hierarchy problem.     

Chemical isomerism as a key to explore free-energy landscapes in disordered matter

The effects of a minor chemical modification on the microscopic structure of a material in its glass and crystal phases are investigated by the concurrent use of neutron diffraction and computer simulation. Significant changes in short-, intermediate-, and long-range order are found, resulting from the change in molecular structure. These differences are explainable by a shift in the balance between directional and excluded-volume interactions.     

Dirac string rotations as a key to spin and statistics of dyons

The statistics of the dyonic wave functions in quantum mechanics is crucial in understanding both the fermionic behavior of the dually charged particles and the role played by the Dirac string. The spinstatistics connection for an electric-magnetic system is derived by treating the interchange operation as a 2π rotation of a singularity line of dyons. Furthermore, the invariance under multivalued gauge transformations and under change of canonical momentum representations is established for our method.     

Eight-quark interactions as a chiral thermometer

A NJL Lagrangian extended to six [1–3] and eight quark interactions [4] is applied to study temperature effects [5] (SU(3) flavor limit, massless case), and [6] (realistic massive case). The transition temperature can be considerably reduced as compared to the standard approach, in accordance with recent lattice calculations [7]. The mesonic spectra built on the spontaneously broken vacuum induced by the’ t Hooft interaction strength, as opposed to the commonly considered case driven by the four-quark coupling, undergoes a rapid crossover to the unbroken phase, with a slope and at a temperature which is regulated by the strength of the OZI violating eight-quark interactions. This strength can be adjusted in consonance with the four-quark coupling and leaves the spectra unchanged, except for the sigma meson mass, which decreases. A first order transition behavior is also a possible solution within the present approach.     

Hyperfine interactions as clues to the structure of elementary particles

The history of hyperfine interactions in hadron physics is reviewed. The recent treatment of hyperfine splittings in meson spectroscopy by Frank and O'Donnell is generalized and applied to baryons as well as mesons by the use of techniques developed for treating hyperfine interactions in atomic physics. New relations between meson and baryon mass splittings are obtained following from the assumption that mesons and baryons are made of the same quarks and have the same color hyperfine interactions at the quark level, with corrections due to color factors and differences between baryon and meson wave functions. Work supported by the U.S. Department of Energy, Division of High Energy Physics, Contract W-31-109-ENG-38 and by the Minerva Foundation, Munich, Germany. 1985–86 Argonne Fellow on leave from the Wiezmann Institute of Science, Rehovot, Israel.     

Entanglement as a precondition for secure quantum key distribution

We demonstrate that a necessary precondition for an unconditionally secure quantum key distribution is that both sender and receiver can use the available measurement results to prove the presence of entanglement in a quantum state that is effectively distributed between them. One can thus systematically search for entanglement using the class of entanglement witness operators that can be constructed from the observed data. We apply such analysis to two well-known quantum key distribution protocols, namely, the 4-state protocol and the 6-state protocol. As a special case, we show that, for some asymmetric error patterns, the presence of entanglement can be proven even for error rates above 25% (4-state protocol) and 33% (6-state protocol).     

Zeeman effect as a prototype for intra-atomic interactions

The existence of the familiar product gM_J that occurs in an analysis of the Zeeman effect can be regarded as an example of the Wigner-Eckart theorem for the rotation group R₃. Correspondence is made with the treatment of intra-atomic interactions by means of higher groups, such as R₅ for d electrons. The spin-spin and spin-other-orbit interactions are examined in detail, and an outline is made of the decomposition of the scalar three-particle operators that are required to partially represent the effect on the configuration (nl)^N of excited configurations of the type (nl)^N±1 (nl)^∓1.     

The superfluid as a source of all interactions

The superfluid state of fermion-antifermion fields developed in our previous papers is generalized to include higher orbital and spin states. In addition to single-particle excitations, the system is capable of having real and virtual bound or quasibound composite excitations which are akin to bosons of spinJ ^P equal to0 ^?, 1^?, 2⁺, etc. These pseudoscalar, vector, and tensor bosons can be massive or massless and provide the vehicles for strong, electromagnetic, weak, and gravitational interactions. The concept that the basic (unmanifest) fermion-antifermion interaction can lead to a multiplicity of manifest interactions seems to provide a basis for a unified field theory.     

Quark strong interactions as a possible mechanism of symmetry breaking in weak interactions

A new mechanism for symmetry breaking is suggested which is connected with the negative contribution of quark loops to the vacuum energy and with the strong interactions of quarks with gluons diminishing this effect. The “gluon mechanism” of symmetry breaking makes it possible to estimate the mass of the heaviest quark (～ 60 GeV) and the mass of the Higgs boson (～ 7 GeV).     

Tunneling spectroscopy as a probe of adsorbate-surface interactions

Tunneling spectroscopy is a sensitive probe of two classes of adsorbate-surface interactions: interactions of the adsorbate with the substrate on which it is adsorbed and adsorbate interactions with the top metal electrode that is evaporated on top of it. The talk by Professor Hipps focuses on the first of these classes. This talk focuses on the second. In general, the interaction of the adsorbed molecules with the top metal electrode produces a down-shift in the vibrational mode position ranging in size from 0.1% to 10% depending on the dipole derivative of the mode and the type of top metal electrode.     

Temperature as a key parameter for graphene sono-exfoliation in water

Graphene dispersions in water are highly desirable for a range of applications such as biomedicines, separation membranes, coatings, inkjet printing and more. Recent novel research has been focussed on developing a green approach for scalable production of graphene. However, one important parameter, which is often neglected is the bulk temperature of the processing liquid. This paper follows our earlier work where optimal sono-exfoliation parameters of graphite in aqueous solutions were determined based on the measured acoustic pressure fields at various temperatures and input powers. Here, we take the next step forward and demonstrate using systematic characterisation techniques and acoustic pressure measurements that sonication-assisted liquid phase exfoliation (LPE) of graphite powder can indeed produce high quality few layer graphene flakes in pure water at a specific temperature, i.e. 40 °C, and at an optimised input generator power of 50%, within 2-h of processing. UV–vis analysis also revealed that the exfoliation, stability and uniformity of dispersions were improved with increasing temperature. We further confirmed the successful exfoliation of graphene sheets with minimal level of defects in the optimized sample with the help of Raman microscopy and transmission electron microscopy. This study demonstrated that understanding and controlling processing temperature is one of the key parameters for graphene exfoliation in water which offers a potential pathway for its large-scale production.     

Elastic wave interactions as a principle of vibration measurement

It is known that ultrasound can be used to measure the constant in time deformations and residual stresses, through the acoustoelasticity effect. The method presented here is different from this principle. It is based on the non-resonant parametric interaction of elastic waves and enables measurement of the dynamic deformation in elastic media. The aim of this work is to investigate the interaction of waves in non-linear elastic media with the deformation fields in parametric approximation and to create a method that permits observation (in three-dimensions) of the dynamic stress-state of the opaque elements of a structure. In particular, interest in the solution of this problem arises for high-frequency non-stationary loading on the structure, when it is impossible to determine the internal stress-state of the elastic body by measurement of the vibration of its surface. The solution to this is found by using ultrasonic waves as a type of transducer that can freely penetrate the elastic body in the necessary direction.     

Neutron interactions as seen by a segmented germanium detector

The GERmanium Detector Array (GERDA) is designed for the search for “neutrinoless double-beta decay” ( 0ν2β with germanium detectors enriched in ⁷⁶Ge . An 18-fold-segmented prototype detector for GERDA Phase II was exposed to an AmBe neutron source to improve the understanding of neutron-induced backgrounds. Neutron interactions with the germanium isotopes themselves and in the surrounding materials were studied. Segment information is used to identify neutron-induced peaks in the recorded energy spectra. The Geant4-based simulation package MaGe is used to simulate the experiment. Though many photon peaks from germanium isotopes excited by neutrons are correctly described by Geant4, some physics processes were identified as being incorrectly treated or even missing.     

Charge and spin inhomogeneity as a key to the physics of the high-Tc cuprates

We present a coherent scenario for the physics of cuprate superconductors, which is based on a charge-driven inhomogeneity, i.e. the “stripe phase”. We show that spin and charge critical fluctuations near the stripe instability of strongly correlated electron systems provide an effective interaction between the quasiparticles, which is strongly momentum, frequency, temperature and doping dependent. This accounts for the various phenomena occurring in the overdoped, optimally and underdoped regimes both for the normal and the superconducting phase.     

Quantum key distribution without the transfer of a quantum state as a whole through a communication channel

An example of quantum key distribution on an entangled single photon and in vacuum states is given. In this scheme, the single-photon quantum state is never transferred as a whole through a communication channel.     

High-speed chaotic communication using an optical fibre ring as a key

A chaotic communication scheme with a fibre ring inserted in the optical feedback of the transmitter laser as an additional key is proposed under anticipating synchronization. The numerical results show that the key can enhance the communication security effectively. It is theoretically safe for the communication scheme to transmit messages with a frequency beyond the relaxation oscillation frequency.     

Neutron-deuteron breakup reaction as a tool for studying neutron-neutron interactions

An analysis of the most recent data on the reaction nd → pnn revealed a serious discrepancy between theoretical predictions and cross sections measured for this reaction in various configurations where the role of neutron-neutron interactions is important. In view of this, it seems necessary both to develop theoretical approaches and to obtain new experimental data. For this purpose, a setup for studying the neutron-deuteron breakup reaction was created at the Institute for Nuclear Research on the basis of the neutron beam in the RADEX channel and deuterium targets. This facility makes it possible to perform experiments over a broad region of primary-neutron energies (10–60 MeV) and in various (final-state interaction, quasifree scattering, and spatial-star) configurations. Preliminary results of the respective experiment were obtained for configurations of final-state neutron-neutron interaction and quasifree neutron-neutron scattering.     

Monopolium: the key to monopoles

Dirac showed that the existence of one magnetic pole in the universe could offer an explanation for the discrete nature of the electric charge. Magnetic poles appear naturally in most grand unified theories. Their discovery would be of the greatest importance for particle physics and cosmology. The intense experimental search carried out thus far has not met with success. Moreover, if the monopoles are very massive their production is outside the range of present day facilities. A way out of this impasse would be if the monopoles bind to form monopolium, a monopole–antimonopole bound state, which is so strongly bound that it has a relatively small mass. Under these circumstances it could be produced with present day facilities and the existence of monopoles could be indirectly proven. We study the feasibility of detecting monopolium in present and future accelerators. PACS  14.80.Hv; 95.30.Cq; 98.70.-f; 98.80.-k