Incomplete magnetic ordering in Fe2(1−y)Mg1+y Ti y O4 spinels with intermediate compositiony

Static magnetization measurements on the ferrimagnetic spinels Fe_2(1?y)Mg_1+y Ti _y O₄ withy=0.3, 0.4, 0.5, and 0.6 show that these compounds have no well-defined orderdisorder transition temperature and that their ferrimagnetism may not be described in terms of the Néel theory. From the Mössbauer spectra we conclude that a temperature dependent number of the ferric ions does not participate in the ferrimagnetism of those compounds with compositiony≧0.4. The explanation of the observed magnetic and Mössbauer properties is based on the assumption that each ferric ion must have at least two magnetic linkages of the type Fe _A ³⁺ ?O^2??Fe _B ³⁺ in order to couple its magnetic moment to the neighbouring ones over the entire temperature interval between 0 K and the respective Néel temperature.     

Time and temperature dependent three-quantum annihilation and lifetime of positronium in alumina powder

The relative three-quantum yieldP ₃ and the lifetime of ortho-positronium generated by alumina fine powders were studied as a function of temperature and of time. A strong variation in theP ₃ value and a constant value of the long lifetime component are interpreted as the existence of two positronium states, one in the interparticle free volume, the second as positronium absorbed to the surface. The latter state is quenched by surface impurities.     

Positron lifetime measurements inn- andp-type silicon

Positron lifetime measurements were carried out in four different samples of silicon, namelyn-type (P-doped) 75 Ωcm,n-type (Sb-doped) 0.018 Ωcm,p-type (B-doped) 60 Ωcm andp-type (B-doped) 0.02 Ωcm. The measurements were made at room temperature and at 77K. A positron lifetime of τ₁=(230±2) psec was found for all samples, independant of dopant or temperature. Paper A 17 presented at 3 rd Internat'l Conf. Positron Annihilation. Otaniemi, Finland (August 1973).     

Positron trapping by defects in plastically deformed copper

When compared to current theories, positron lifetimes in plastically strained copper are indicative of diffusion limited positron trapping, with diffusion constant D₊ ≈ 4 × 10^?2 cm²/s in dislocations of effective capture radius $\text{r}{}_{\mathrm{<mtext>d</mtext>}}\text{≈ 70}\text{A}\text{?}$.     

Observation of a narrow charm-strange meson D(+)(sJ)(2632)-->D(+)(s)eta and D(0)K(+)

We report the first observation of a charm-strange meson D(+)(sJ)(2632) at a mass of 2632.5+/-1.7 MeV/c(2) in data from SELEX, the charm hadro-production experiment E781 at Fermilab. This state is seen in two decay modes, D(+)(s)eta and D0K+. In the D(+)(s)eta decay mode we observe a peak with 101 events over a combinatoric background of 54.9 events at a mass of 2635.4+/-3.3 MeV/c(2). There is a corresponding peak of 21 events over a background of 6.9 at 2631.5+/-2.0 MeV/c(2) in the decay mode D0K+. The decay width of this state is <17 MeV/c(2) at 90% confidence level. The relative branching ratio Gamma(D0K+)/Gamma(D(+)(s)eta) is 0.14+/-0.06. The mechanism that keeps this state narrow is unclear. Its decay pattern is also unusual, being dominated by the D(+)(s)eta decay mode.     

On some nonself mappings

Let X be a Banach space, let K be a non–empty closed subset of X and let T : K → X be a non–self mapping. The main result of this paper is that if T satisfies the contractive–type condition (1.1) below and maps ?K (?K the boundary of K) into K then T has a unique fixed point in K.     

Jetlike nature of inclusive hadronic interactions

The dominant inclusive systems formed in the beam and target hemispheres of hadronic reactions are explored for jetlike characteristics in terms of sphericity, thrust, and energy and particle flow. We compare $\text{50}\text{GeV}\text{/c π}{}^{\mathrm{?}}\text{p and}\text{p}\text{p and}\text{100}\text{GeV}\text{/c π}{}^{\mathrm{+}}\text{p and pp}$ interactions and find substantial similarities with neutrino-induced hadronic systems and with hadronic jets in e⁺e^? annihilations. We find no strong evidence for differences in angular size between the forward and backward hadronic systems formed in hadron-hadron reactions, and the single-quark jets and the diquark jets which arise variously in lepton-lepton and lepton-hadron reactions.