Observation of hard scattering in photoproduction events with a large rapidity gap at HERA

Events with a large rapidity gap and total transverse energy greater than 5 GeV have been observed in quasi-real photoproduction at HERA with the ZEUS detector. The distribution of these events as a function of the $\gamma p$ centre of mass energy is consistent with diffractive scattering. For total transverse energies above 12 GeV, the hadronic final states show predominantly a two-jet structure with each jet having a transverse energy greater than 4 GeV. For the two-jet events, little energy flow is found outside the jets. This observation is consistent with the hard scattering of a quasi-real photon with a colourless object in the proton.Comment: 19 pages, latex, 4 figures appended as uuencoded fil

Measurement of Charged and Neutral Current e-p Deep Inelastic Scattering Cross Sections at High Q2

Deep inelastic e-p scattering has been studied in both the charged current (CC) and neutral current (NC) reactions at momentum transfers squared Q(2) above 400 GeV2 using the ZEUS detector at the HERA ep collider. The CC and NC total cross sections, the NC to CC cross section ratio, and the differential cross sections d sigma/dQ(2) are presented. From the Q(2) dependence of the CC cross section, the mass term in the CC propagator is determined to be M(W) = 76 +/- 16 +/- 13 GeV

Untersuchungen und Entwicklungen zur Spurerkennung in den Vorwaertsdriftkammern des ZEUS Detektors

SIGLECopy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

El hombre como animal cultural en el tratamiento de Carlos París

Crítica del libro París Amador, Carlos, "El animal cultural: Biologia y cultura en la realidad humana"; Barcelona: Crítica, 1994.Es Carlos París uno de los filósofos españoles que se han ido preocupando más -a lo largo de muchas obras sobradamente conocidas del público filosófico- en analizar, desde diversas perspectivas, al ser humano, su peculiaridad, sus facetas, siempre en tanto en cuanto ello comporta problemas genuinamente filosóficos y necesita un tratamiento que trasciende al de los saberes particulares y de los especialistas; mas también siempre en diálogo con cuanto tengan que aportar esos mismos especialistas, sin ruptura ninguna entre el quehacer filosófico y el de las disciplinas que -cada una según sus métodos y su delimitación temática, mejor o peor acotada- se empeñan en alcanzar resultados sin duda más rigurosos que aquellos a los que puede aspirar la filosofía; más rigurosos, sí, mejor apuntalados por la evidencia disponible, pero también, como es natural, menos ambiciosos.Ambicioso, y penetrado por el prurito de aprender de los especialistas científicos de las diversas disciplinas relacionadas con el estudio de lo humano, lo es con creces este nuevo libro (El animal cultural: Biologia y cultura en la realidad humana, Barcelona, Crítica, 1994).Peer reviewe

Field assisted sintering consolidation of Al-Si-Fe-X alloy powder/flakes produced through air atomization/melt spinning

Melt-spun flakes and air atomised powder of a multi-component Al-Si-Fe-X alloy were consolidated by field assisted (FAST) or spark plasma sintering (SPS) in vacuum using steel dies and punches. Experiments were carried out at 350, 400, 450 and 500°C under applied loads ranging from 81 to 283 MPa. The resulting compacts were microstructurally and mechanically characterized. Ultimate strength values up to 1000 MPa and plastic strains up to 20% were observed during compression tests. The effect of the powder shape on the sintering behaviour is compared. The effect of process parameters such as temperature and applied load on the densification and mechanical properties is discussed. It was found that compacts sintered from melt-spun flakes resulted in a higher strength and ductility than compacts produced from air-atomized powder, sintered under identical conditions.Book subtitle: RESEARCH THROUGH INNOVATION AND TECHNOLOGYstatus: publishe

Mechanical milling and field assisted sintering consolidation of nanocrystalline Al-Si-Fe-X alloy powder

Rapidly solidified pre-alloyed Al-17Si-5Fe-3.5Cu-1.1Mg-0.6Zr (wt.%) powder was mechanically milled using stearic acid and ethyl acetate as process control agents. The resulting nanocrystalline powder was degassed in a furnace at 350 degreesC for 5 hrs in vacuum. Both as-milled and degassed powders were consolidated using field-assisted sintering (FAST) in steel dies in vacuum at 375 to 500 degreesC. Some experiments were also carried out with an additional in-situ degassing step at 470-500 degreesC for 1 to 5 minutes. Shrinkage along the pressure axis, temperature and applied pressure were automatically stored through a data acquisition system. As-milled powder and sintered compacts were characterized using optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and microhardness measurements. The crystal size, calculated from the line broadening of the X-ray diffraction peaks using Williamsonhall plots, of the mechanically alloyed powders and FAST sintered mechanically alloyed materials was in the range of 23-70 nm, depending on the type and amount of process control agent used during milling and the FAST parameters. As-milled powders with furnace degassing (350 C/5h) could not be fully densified due to remaining entrapped gasses. An in-situ degassing (500 degreesC/5min) step included during FAST sintering however resulted in the consolidation of fully densified bulk nanostructured compacts. Microstructure and hardness showed strong dependency on the type of process control agent used during milling.status: publishe