Search for Millicharged Particles at SLAC

Particles with electric charge q < 10^(-3)e and masses in the range 1--100 MeV/c^2 are not excluded by present experiments. An experiment uniquely suited to the production and detection of such "millicharged" particles has been carried out at SLAC. This experiment is sensitive to the infrequent excitation and ionization of matter expected from the passage of such a particle. Analysis of the data rules out a region of mass and charge, establishing, for example, a 95%-confidence upper limit on electric charge of 4.1X10^(-5)e for millicharged particles of mass 1 MeV/c^2 and 5.8X10^(-4)e for mass 100 MeV/c^2.Comment: 4 pages, REVTeX, multicol, 3 figures. Minor typo corrected. Submitted to Physical Review Letter

A New Deformed Supersymmetric Oscillator

We construct and discuss the Fock-space representation for a deformed oscillator with "peculiar" statistics. We show that corresponding algebra represents deformed supersymmetric oscillator.Comment: LATEX, 10 pages, no figures, to appear in Europhys.Let

Broad-band gravitational-wave pulses from binary neutron stars in eccentric orbits

Maximum gravitational wave emission from binary stars in eccentric orbits occurs near the periastron passage. We show that for a stationary distribution of binary neutron stars in the Galaxy, several high-eccentricity systems with orbital periods in the range from tens of minutes to several days should exist that emit broad gravitational-wave pulses in the frequency range 1-100 mHz. The space interferometer LISA could register the pulsed signal from these system at a signal-to-noise ratio level $S/N>5\sqrt{5}$ in the frequency range $\sim 10^{-3}-10^{-1}$ Hz during one-year observational time. Some detection algorithms for such a signal are discussed.Comment: 17 pages, LATEX, 3 figures, Astronomy Letters, 2002, in press; typos corrected, refference adde

Algebraic approach to time-delay data analysis for LISA

Cancellation of laser frequency noise in interferometers is crucial for attaining the requisite sensitivity of the triangular 3-spacecraft LISA configuration. Raw laser noise is several orders of magnitude above the other noises and thus it is essential to bring it down to the level of other noises such as shot, acceleration, etc. Since it is impossible to maintain equal distances between spacecrafts, laser noise cancellation must be achieved by appropriately combining the six beams with appropriate time-delays. It has been shown in several recent papers that such combinations are possible. In this paper, we present a rigorous and systematic formalism based on algebraic geometrical methods involving computational commutative algebra, which generates in principle {\it all} the data combinations cancelling the laser frequency noise. The relevant data combinations form the first module of syzygies, as it is called in the literature of algebraic geometry. The module is over a polynomial ring in three variables, the three variables corresponding to the three time-delays around the LISA triangle. Specifically, we list several sets of generators for the module whose linear combinations with polynomial coefficients generate the entire module. We find that this formalism can also be extended in a straight forward way to cancel Doppler shifts due to optical bench motions. The two modules are infact isomorphic. We use our formalism to obtain the transfer functions for the six beams and for the generators. We specifically investigate monochromatic gravitational wave sources in the LISA band and carry out the maximisiation over linear combinations of the generators of the signal-to-noise ratios with the frequency and source direction angles as parameters.Comment: 27 Pages, 6 figure

Tumor microenvironment: the formation of the immune profile

Tumor microenvironment (TME) is formed as a result of interaction and cross-linking between the tumor cell and different types of surrounding cells. Recent studies have shown that the tumor reprograms the microenvironment so that TME promotes the development of primary tumors, their metastasis and becomes an important regulator of oncogenesis. Under the influence of the tumor, the immune profile in the TME undergoes significant changes, “editing". An immunosuppressive network is formed, which suppresses the activity of the main effector of cellular immunity — T lymphocytes. T cells in TMA are in a state of anergy and exhaustion. T cells in TME are characterized by increased expression of inhibitory receptors, decreased secretion of cytokines and cytolytic activity. Blocking inhibitory receptors with specific antibodies can lead to the restoration of the functions of exausted T cells. Therefore, the restoration of the functional activity of T lymphocytes is one of the important strategies in cancer immunotherapy. The formation of the immune profile is influenced by genetic aberrations accumulating in the tumor. They play an important role in creating a specific, characteristic only for this tumor immune environment in the TME. Genetic changes in tumor cells lead to phenotypic and functional rearrangements of lymphocytes, which allows the tumor to escape the reaction of immune cells. Since many tumors occur after prolonged inflammation or exhibit characteristics of chronic inflammation as they progress, inflammation is considered an important factor in the formation of immune profile in TME. Immune infiltrates from different human tumors associated with inflammation may contain valuable prognostic and pathophysiological information. Macrophages in the TME now began to be regarded as descriptive marker and as a therapeutic target. One of the main mechanisms by which tumor cells reprogram surrounding cells is the release of exosomes — small vesicles that carry and deliver proteins and nucleic acids to other cells. When exosomal cargo is absorbed, molecular, transcriptional and translational changes occur in the recipient non-tumor cells in the TME. Therefore, tumor exosomes are an effective means by which the functions of immune cells in TME are purposefully changed. Thus, along with individual molecular and genomic testing of the tumor, attention should be paid to a deeper analysis of the immune profile of TME. It is a large resource of biomarkers and targets for immunotherapy

Millisecond-range electron spin memory in singly-charged InP quantum dots

We report millisecond-range spin memory of resident electrons in an ensemble of InP quantum dots (QDs) under a small magnetic field of 0.1 T applied along the optical excitation axis at temperatures up to about 5 K. A pump-probe photoluminescence (PL) technique is used for optical orientation of electron spins by the pump pulses and for study of spin relaxation over the long time scale by measuring the degree of circular polarization of the probe PL as a function of pump-probe delay. Dependence of spin decay rate on magnetic field and temperature suggests two-phonon processes as the dominant spin relaxation mechanism in this QDs at low temperatures.Comment: 3 pages, 4 figures, submitted to Appl. Phys. Let