Extended two-level quantum dissipative system from bosonization of the elliptic spin-1/2 Kondo model

We study the elliptic spin-1/2 Kondo model (spin-1/2 fermions in one dimension with fully anisotropic contact interactions with a magnetic impurity) in the light of mappings to bosonic systems using the fermion-boson correspondence and associated unitary transformations. We show that for fixed fermion number, the bosonic system describes a two-level quantum dissipative system with two noninteracting copies of infinitely-degenerate upper and lower levels. In addition to the standard tunnelling transitions, and the transitions driven by the dissipative coupling, there are also bath-mediated transitions between the upper and lower states which simultaneously effect shifts in the horizontal degeneracy label. We speculate that these systems could provide new examples of continuous time quantum random walks, which are exactly solvable.Comment: 7 pages, 1 figur

Making Cheese on The Farm

Cottage cheese should be used by every farm household because of the low cost of preparation and high food value. Cottage cheese ranks well with meat and eggs in food value, and when it can be made from surplus skim milk it costs practically nothing except the time required for its preparation. (See more in text.

Low-loss photonic crystal fibers for transmission systems and their dispersion properties

We report on a single-mode photonic crystal fiber with attenuation and effective area at 1550 nm of 0.48 dB/km and 130 square-micron, respectively. This is, to our knowledge, the lowest loss reported for a PCF not made from VAD prepared silica and at the same time the largest effective area for a low-loss (< 1 dB/km) PCF. We briefly discuss the future applications of PCFs for data transmission and show for the first time, both numerically and experimentally, how the group velocity dispersion is related to the mode field diameterComment: 5 pages including 3 figures + 1 table. Accepted for Opt. Expres

Methods of Cream Separator Sanitation

Cream quality surveys repeatedly have revealed the farm separator as an important factor affecting the flavor of cream. The relation between the unwashed separator and off-flavored cream has been pointed out and the remedy has appeared to be obvious. The labor required to wash the machine twice daily, however, often has appeared unreasonable when a small value of milk is separated as is the case on many farms. The present work was designed to test the effectiveness of methods which likely would require less labor but might maintain satisfactory cream quality. As early as 1904 the United States Department of Agriculture pointed out that serious cream quality troubles might be encountered unless farmers followed detailed instructions regarding the use and care of cream separators on the farm. Bacterial numberst were reduced greatly when unwashed separators were thoroughly flushed with water, both before and after use, when the bowl was held below 65 degrees F. When it was held at 85 degrees F. profuse fermentation occurred. It has been generally recognized that the separator should be properly washed after being used. This is important because of its influence on (1) cream quality; (2) efficient separation, and (3) the life of the machine. Chlorine solutions have merits when used as germicidal rinses for separators. Other experimenters have used trisodium phosphate or lye, or trisodium phosphate containing 0.25 percent sodium chromate as a corrosion inhibitor. The first two are quite corrosive and trisodium phosphate with chromate solution may be corrosive if solution strengths are not carefully controlled. With these factors in mind, several chemicals were used in these trials, some germicidal, others largely growth retarders. The concentration used was such that effective antiseptic action might be expected without harmful effect on the metal parts of the separator. The number of trials and the concentration of chemicals used in this work were rather limited. Therefore, results are not conclusive

Critical behavior of loops and biconnected clusters on fractals of dimension d < 2

We solve the O(n) model, defined in terms of self- and mutually avoiding loops coexisting with voids, on a 3-simplex fractal lattice, using an exact real space renormalization group technique. As the density of voids is decreased, the model shows a critical point, and for even lower densities of voids, there is a dense phase showing power-law correlations, with critical exponents that depend on n, but are independent of density. At n=-2 on the dilute branch, a trivalent vertex defect acts as a marginal perturbation. We define a model of biconnected clusters which allows for a finite density of such vertices. As n is varied, we get a line of critical points of this generalized model, emanating from the point of marginality in the original loop model. We also study another perturbation of adding local bending rigidity to the loop model, and find that it does not affect the universality class.Comment: 14 pages,10 figure

A study of 15N14N isotopic exchange over cobalt molybdenum nitrides

The 14N/15N isotopic exchange pathways over Co3Mo3N, a material of interest as an ammonia synthesis catalyst and for the development of nitrogen transfer reactions, have been investigated. Both the homomolecular and heterolytic exchange processes have been studied, and it has been shown that lattice nitrogen species are exchangeable. The exchange behavior was found to be a strong function of pretreatment with ca. 25% of lattice N atoms being exchanged after 40 min at 600 °C after N2 pretreatment at 700 °C compared to only 6% following similar Ar pretreatment. This observation, for which the potential contribution of adsorbed N species can be discounted, is significant in terms of the application of this material. In the case of the Co6Mo6N phase, regeneration to Co3Mo3N under 15N2 at 600 °C occurs concurrently with 14N15N formation. These observations demonstrate the reactivity of nitrogen in the Co–Mo–N system to be a strong function of pretreatment and worthy of further consideration

Neutron scattering study of spin ordering and stripe pinning in superconducting La1.93_{1.93}Sr0.07_{0.07}CuO4_4

The relationships among charge order, spin fluctuations, and superconductivity in underdoped cuprates remain controversial. We use neutron scattering techniques to study these phenomena in La$_{1.93}$Sr$_{0.07}$CuO$_4$, a superconductor with a transition temperature of $T_c = 20$~K. At $T\ll T_c$, we find incommensurate spin fluctuations with a quasielastic energy spectrum and no sign of a gap within the energy range from 0.2 to 15 meV. A weak elastic magnetic component grows below $\sim10$~K, consistent with results from local probes. Regarding the atomic lattice, we have discovered unexpectedly strong fluctuations of the CuO$_6$ octahedra about Cu-O bonds, which are associated with inequivalent O sites within the CuO$_2$ planes. Furthermore, we observed a weak elastic $(3\bar{3}0)$ superlattice peak that implies a reduced lattice symmetry. The presence of inequivalent O sites rationalizes various pieces of evidence for charge stripe order in underdoped \lsco. The coexistence of superconductivity with quasi-static spin-stripe order suggests the presence of intertwined orders; however, the rotation of the stripe orientation away from the Cu-O bonds might be connected with evidence for a finite gap at the nodal points of the superconducting gap function.Comment: 13 pages, 11 figures; accepted versio