Platelet deposition studies on copolyether urethanes modified with poly(ethylene oxide)

Pellethane ® 2363 80A films and tubings were chemically modified and the effect of these modifications on platelet deposition was studied. Grafting of high molecular weight poly(ethylene oxide) and graft polymerization of methoxy poly(ethylene glycol) 400 methacrylate resulted in surfaces with a good water wettability. The increased hydrophilicity of these modified surfaces could be demonstrated by contact angle measurements. The platelet deposition was investigated with tubings in a capillary flow system, using different types of perfusates. Platelet deposition from a buffer-containing perfusate on surfaces modified with either high molecular weight poly(ethylene oxide) or methoxy poly(ethylene glycol) 400 methacrylate was almost absent and less than on Pellethane 2363 80A. Using a citrated plasmacontaining perfusate the amount of deposited platelets on Pellethane 2363 80A modified with high molecular weight poly(ethylene oxide) was low and about the same as on unmodified surfaces. However, a marked reduced platelet deposition compared to unmodified Pellethane 2363 80A was found when the platelets were activated by Ca2+ ionophore. The improved blood compatibility of the modified Pellethane 2363 80A tubings obviously indicates the favourable effect of the presence of grafted PEO on the surface

Electric Charge Quantization

Experimentally it has been known for a long time that the electric charges of the observed particles appear to be quantized. An approach to understanding electric charge quantization that can be used for gauge theories with explicit $U(1)$ factors -- such as the standard model and its variants -- is pedagogically reviewed and discussed in this article. This approach uses the allowed invariances of the Lagrangian and their associated anomaly cancellation equations. We demonstrate that charge may be de-quantized in the three-generation standard model with massless neutrinos, because differences in family-lepton--numbers are anomaly-free. We also review the relevant experimental limits. Our approach to charge quantization suggests that the minimal standard model should be extended so that family-lepton--number differences are explicitly broken. We briefly discuss some candidate extensions (e.g. the minimal standard model augmented by Majorana right-handed neutrinos).Comment: 18 pages, LaTeX, UM-P-92/5

Daemons and DAMA: Their Celestial-Mechanics Interrelations

The assumption of the capture by the Solar System of the electrically charged Planckian DM objects (daemons) from the galactic disk is confirmed not only by the St.Petersburg (SPb) experiments detecting particles with V<30 km/s. Here the daemon approach is analyzed considering the positive model independent result of the DAMA/NaI experiment. We explain the maximum in DAMA signals observed in the May-June period to be associated with the formation behind the Sun of a trail of daemons that the Sun captures into elongated orbits as it moves to the apex. The range of significant 2-6-keV DAMA signals fits well the iodine nuclei elastically knocked out of the NaI(Tl) scintillator by particles falling on the Earth with V=30-50 km/s from strongly elongated heliocentric orbits. The half-year periodicity of the slower daemons observed in SPb originates from the transfer of particles that are deflected through ~90 deg into near-Earth orbits each time the particles cross the outer reaches of the Sun which had captured them. Their multi-loop (cross-like) trajectories traverse many times the Earth's orbit in March and September, which increases the probability for the particles to enter near-Earth orbits during this time. Corroboration of celestial mechanics calculations with observations yields ~1e-19 cm2 for the cross section of daemon interaction with the solar matter.Comment: 12 pages including 5 figure

Mirror matter-type dark matter

There are six main things which any non-baryonic dark matter theory should endeavour to explain: (1) The basic dark matter particle properties [mass, stability, darkness]; (2) The similarity in cosmic abundance between ordinary and non-baryonic dark matter, $\Omega_B \sim \Omega_{dark}$; (3) Large scale structure formation; (4) Microlensing (MACHO) events; (5) Asymptotically flat rotation curves in spiral galaxies; (6) The impressive DAMA/NaI annual modulation signal. Only mirror matter-type dark matter is capable of explaining all six of these desirable features. The purpose of this article is to provide an up-to-date and pedagogical review of this dark matter candidate.Comment: about 30 page

Geophysical constraints on mirror matter within the Earth

We have performed a detailed investigation of geophysical constraints on the possible admixture of mirror matter inside the Earth. On the basis of the Preliminary Reference Earth Model (PREM) -- the `Standard Model' of the Earth's interior -- we have developed a method which allows one to compute changes in various quantities characterising the Earth (mass, moment of inertia, normal mode frequencies etc.)due to the presence of mirror matter. As a result we have been able to obtain for the first time the direct upper bounds on the possible concentration of the mirror matter in the Earth. In terms of the ratio of the mirror mass to the Earth mass a conservative upper bound is $3.8\times 10^{-3}$. We then analysed possible mechanisms (such as lunar and solar tidal forces, meteorite impacts and earthquakes) of exciting mirror matter oscillations around the Earth centre. Such oscillations could manifest themselves through global variations of the gravitational acceleration at the Earth's surface. We conclude that such variations are too small to be observed. Our results are valid for other types of hypothetical matter coupled to ordinary matter by gravitation only (e.g. the shadow matter of superstring theories).Comment: 25 pages, in RevTeX, to appear in Phys.Rev.

Active-Sterile neutrino oscillations and BBN+CMBR constraints

We show how active-sterile neutrino oscillations in the early Universe can play an interesting role in explaining the current observations of CMBR anisotropies and light element abundances. We describe different possible phenomenological scenarios in the interpretation of present data and how active-sterile neutrino oscillations can provide a viable theoretical framework.Comment: Some changes, to appear in Phys. Rev.

Detailed study of BBN implications of neutrino oscillation generated neutrino asymmetries in some four neutrino models

We re-examine the evolution of neutrino asymmetries in several four neutrino models. The first case involves the direct creation of $L_{\nu_e}$ by $\nu_e \leftrightarrow \nu_s$ oscillations. In the second case, we consider the mass hierarchy $m_{\nu_\tau} \gg m_{\nu_\mu}, m_{\nu_e}, m_{\nu_s}$ where $\nu_\tau \leftrightarrow \nu_s$ oscillations generate a large $L_{\nu_\tau}$ and some of this asymmetry is converted into $L_{\nu_e}$ by $\nu_{\tau} \leftrightarrow \nu_{e}$ oscillations. We estimate the implications for BBN for a range of cosmologically interesting $\delta m^2$ values. The present paper improves on previous published work by taking into account the finite repopulation rate and the time dependence of the distortions to the neutrino momentum distributions. The treatment of chemical decoupling is also improved.Comment: Expanded discussion on the sign of the neutrino asymmetr

Quark-Lepton Symmetry In Five Dimensions

We construct a complete five dimensional Quark-Lepton symmetric model, with all fields propagating in the bulk. The extra dimension forms an $S^1/Z_2\times Z_2'$ orbifold with the zero mode fermions corresponding to standard model quarks localised at one fixed point. Zero modes corresponding to left(right)-chiral leptons are localised at (near) the other fixed point. This localisation pattern is motivated by the symmetries of the model. Shifting the right-handed neutrinos and charged leptons slightly from the fixed point provides a new mechanism for understanding the absence of relations of the type $m_e=m_u$ or $m_e=m_d$ in Quark-Lepton symmetric models. Flavour changing neutral currents resulting from Kaluza Klein gluon exchange, which typically arise in the quark sector of split fermion models, are suppressed due to the localisation of quarks at one point. The separation of quarks and leptons in the compact extra dimension also acts to suppress the proton decay rate. This permits the extra dimension to be much larger than that obtained in a previous construct, with the bound $1/R\gtrsim30$ TeV obtained.Comment: 12 pages, references added to match published versio

Neutrino physics and the mirror world: how exact parity symmetry explains the solar neutrino deficit, the atmospheric neutrino anomaly and the LSND experiment

Evidence for $\bar \nu_{\mu} \rightarrow \bar \nu_e$ oscillations has been reported at LAMPF using the LSND detector. Further evidence for neutrino mixing comes from the solar neutrino deficit and the atmospheric neutrino anomaly. All of these anomalies require new physics. We show that all of these anomalies can be explained if the standard model is enlarged so that an unbroken parity symmetry can be defined. This explanation holds independently of the actual model for neutrino masses. Thus, we argue that parity symmetry is not only a beautiful candidate for a symmetry beyond the standard model, but it can also explain the known neutrino physics anomalies.Comment: 27 pages, LaTeX, no figures, additional discussion on big bang nucleosynthesis, some additional references, to appear in Phys. Rev.

Cosmology with mirror dark matter I: linear evolution of perturbations

This is the first paper of a series devoted to the study of the cosmological implications of the parallel mirror world with the same microphysics as the ordinary one, but having smaller temperature, with a limit set by the BBN constraints. The difference in temperature of the ordinary and mirror sectors generates shifts in the key epochs for structure formation, which proceeds in the mirror sector under different conditions. We consider adiabatic scalar primordial perturbations as an input and analyze the trends of all the relevant scales for structure formation (Jeans length and mass, Silk scale, horizon scale) for both ordinary and mirror sectors, comparing them with the CDM case. These scales are functions of the fundamental parameters of the theory (the temperature of the mirror plasma and the amount of mirror baryonic matter), and in particular they are influenced by the difference between the cosmological key epochs in the two sectors. Then we used a numerical code to compute the evolution in linear regime of density perturbations for all the components of a Mirror Universe: ordinary baryons and photons, mirror baryons and photons, and possibly cold dark matter. We analyzed the evolution of the perturbations for different values of mirror temperature and baryonic density, and obtained that for x=T'/T less than a typical value x_eq, for which the mirror baryon-photon decoupling happens before the matter-radiation equality, mirror baryons are equivalent to the CDM for the linear structure formation process. Indeed, the smaller the value of x, the closer mirror dark matter resembles standard cold dark matter during the linear regime.Comment: 33 pages, 24 figures; minor corrections in introduction, conclusions and references; accepted for publication in IJMP