Local time-resolved measurements of fast reversal of the magnetization of single crystals of Mn12-acetate indicate that the magnetization avalanche spreads as a narrow interface that propagates through the crystal at a constant velocity that is roughly two orders of magnitude smaller than the speed of sound. We argue that this phenomenon is closely analogous to the propagation of a flame front (deflagration) through a flammable chemical substance. 1 . Arranged in a centered tetragonal lattice, the spin of the Mn 12 clusters is subject to strong magnetic anisotropy along the symmetry axis (the c-axis of the crystal). Below the blocking temperature of ≈ 3.5 K, the crystal exhibits remarkable staircase magnetic hysteresis due to resonant quantum spin tunneling between energy levels on opposite sides of the anisotropy barrier corresponding to different spin projections, as illustrated in Fig. 1(a).2 This and other interesting properties of Mn 12 -ac have been intensively studied in the last decade (see Refs. 3,4,5,6 for reviews).It has been known for some time 7 that Mn 12 -ac crystals exhibit an abrupt reversal of their magnetic moment under certain conditions. This phenomenon, also observed in other molecular magnets, has been attributed to a thermal runaway (avalanche) in which the initial relaxation of the magnetization toward the direction of the field results in the release of heat that further accelerates the magnetic relaxation. Direct measurements of the heat emitted by Mn 12 -ac crystals, 8 as well as measurements of the magnetization reversal in pulsed magnetic fields, 9 have confirmed the thermal nature of the avalanches. More recently, the electromagnetic signal associated with avalanches was detected 10,11 and it was argued that if the radiation is of thermal origin it would indicate a significant increase in the temperature of the crystal. This has not been confirmed by direct bulk measurements of the temperature using a thermometer. Evidence has been obtained 12 that the avalanche may not be a uniform process throughout the sample. No clear understanding of the avalanche process has emerged to date.In this Letter we report local time-resolved measurements of fast magnetization reversal (avalanches) in mmsize single crystals of Mn 12 -ac. We show that a magnetic avalanche takes the form of a thin interface between regions of opposite magnetization which propHall Sensors (a) (b)Spin-up

To elucidate the role of NK cells and TCR + ˇ + T cells in acute experimental autoimmune encephalomyelitis (EAE) induced in Lewis rats, the distribution, number and function of these cells were studied using several methods. Immunohistochemical and flow cytometric analysis revealed that a certain number of NK cells (17 % of the total inflammatory cells) infiltrated the central nervous system (CNS) at the peak stage of EAE and were mainly located in the perivascular region. On the other hand, virtually no TCR + ˇ + T cells were found in the CNS. NK-T (NKR-P1 + TCR § g +) cells were few and did not increase in number in the CNS and lymphoid organs. In the cytotoxic assay using YAC-1 cells, effector cells isolated from the spleen of rats at the peak of EAE showed essentially the same cytotoxicity as those isolated from normal controls although the total number of NK cells decreased to one fifth of that of normal rats. Furthermore, in vivo administration of anti-NK cell (3.2.3 and anti-asialo GM1), but not of anti-TCR + ˇ (V65), antibodies exacerbated the clinical features of EAE and induced fatal EAE in some rats. These findings suggest that NK cells play a suppressive role in acute EAE whereas TCR + ˇ + T cells are not involved in the development of or recovery from the disease.

The Legendre transformation is one of the ways to rewrite the theory by small number of selected variables. It leads naturally to the generalized action functional called the effective action and everything starts from this generating functional. It is applied to various problems of physics ranging from the relativistic field theory to the condensed matter physics. The main techniques used here are the on-shell expansion and the inversion method. The scheme presented in this article is thus a generating functional formalism of the many particle systems.

In magnetic fields applied parallel to the anisotropy axis, the relaxation of the magnetization of a Mn12-acetate single crystal measured for different sweep rates is shown to collapse onto a single scaled curve. The form of the scaling implies that the dominant symmetry-breaking process that gives rise to tunneling is a locally varying second-order anisotropy, forbidden by tetragonal symmetry in the perfect crystal, which gives rise to a broad distribution of tunnel splittings in a real crystal of Mn12-acetate. Different forms applied to even and odd-numbered steps provide a clear distinction between even step resonances (associated with crystal anisotropy) and odd resonances (which require a transverse component of magnetic field). , generally referred to as Mn 12 -acetate, is a particularly interesting and much-studied example of this class. The Mn 12 clusters are composed of twelve Mn atoms tightly coupled to give a sizable S = 10 spin magnetic moment that is stable at temperatures of the order of 10 K and below [1]. These identical weaklyinteracting magnetic molecules are regularly arranged on a tetragonal crystal. As illustrated by the double well potential shown in the inset to Fig. 1, strong uniaxial anisotropy (of the order of 65 K) yields a set of energy levels corresponding to different projections m = ±10, ±9, ....., 0 of the total spin along the easy c-axis of the crystal. Measurements [2,3] below the blocking temperature of 3 K have revealed a series of steep steps in the curves of M versus H at roughly equal intervals of magnetic field due to enhanced relaxation of the magnetization whenever levels on opposite sides of the anisotropy barrier coincide in energy. Below ≈ 0.56K the magnetization curves are independent of temperature, and the tunneling proceeds from the ground state of the metastable well (see inset to Fig. 1).The spin Hamiltonian for Mn 12 is given by:where D = 0.65 K is the longitudinal anisotropy, the second term is the Zeeman energy with g z ≈ 1.94, and the third on the right-hand side represents the next higherorder term in longitudinal anisotropy. In order for tunneling to occur, the Hamiltonian must also include terms that do not commute with S z . In a perfect crystal, the lowest transverse anisotropy term allowed by the tetragonal symmetry of Mn 12 is proportional to (S 4 + + S 4 − ). For ground state tunneling, such a term only permits every fourth step. In contrast, all steps are observed with no clear differences in amplitude between them. This suggests that transverse internal magnetic fields, which would allow all steps to occur on an equal footing, provide the dominant symmetry-breaking term that drives the tunneling in Mn 12 . However, dipolar fields [4][5][6][7] and 1

The use of bidirectional barbed suture appears to be safe for closing the vaginal cuff in a total laparoscopic hysterectomy and for closing the hysterotomy site during laparoscopic myomectomy.