Showing papers by "Jun Lu published in 1993"

Daily melatonin administration synchronizes circadian patterns of brain metabolism and behavior in pinealectomized house sparrows,Passer domesticus

Abstract: Recent research in our laboratory has indicated that in sparrows the visual suprachiasmatic nucleus (vSCN) is metabolically rhythmic such that 2-deoxy[14C]glucose (2DG) uptake and specific binding of 2[125I]iodomelatonin (IMEL) are high during subjective day for up to 10 circadian cycles in constant darkness (DD) These rhythms damp to arrhythmicity in pinealectomized birds (PINX) The present study was designed to test the hypothesis that exogenous melatonin rhythmically applied can restore disrupted behavioral and cerebral rhythmicity Pinealectomized house sparrows were placed in constant dim light and allowed to become arrhythmic Experimental birds received 086 mM melatonin in 001% ethanol (ETOH) to drink for 12 of every 24 h for 14 days Control birds received 001% ETOH only Behavioral rhythmicity was restored by melatonin but not by ETOH Birds were injected with 2DG 6 or 18 h following the beginning of melatonin (for experimental birds: MT06 and MT18 respectively) or ETOH (for control birds: ET06 and ET18 respectively) administration, allowed to survive 1 h and killed for 2DG and IMEL autoradiography The data indicated 2DG rhythmicity such that uptake was high at MT18 in vSCN and several visual, auditory and limbic system structures in birds receiving melatonin but not in birds receiving ETOH Similarly, IMEL binding rhythms were restored in vSCN and other visual, auditory and limbic system structures in birds receiving melatonin but not in those receiving ETOH These data indicate that melatonin cycles are responsible for generating and/or driving a wide array of cerebral metabolic rhythms and that this influence is inhibitory

Pineal regulation of circadian rhythms of 2-deoxy[14C]glucose uptake and 2[125I]iodomelatonin binding in the visual system of the house sparrow, Passer domesticus

Abstract: The pineal gland and its hormone melatonin are crucial for the generation of circadian rhythms in several species of passerine birds. The sites and mechanisms by which they influence avian behavior are therefore of particular interest. Recent research employing several brain imaging techniques has indicated that the sites of melatonin action within the avian brain are wide-spread within the 4 major visual pathways. In this study, we have investigated whether the avian homologue of the mammalian suprachiasmatic nucleus, the visual suprachiasmatic nucleus (vSCN), and other visually sensitive structures express circadian rhythms of 2-deoxy[14C]glucose (2DG) uptake and 2[125I]iodomelatonin (IMEL) binding in house sparrows,Passer domesticus, under constant environmental conditions in the presence or absence of the pineal gland. The results indicate that 2DG uptake in the vSCN is oscillatory in sham-operated sparrows but damps to arrhythmicity in pinealectomized birds, suggesting this structure contains a damped circadian oscillator independent of pineal input. We have also asked whether IMEL binding is rhythmic under these conditions in the same brains. These results indicate IMEL binding is rhythmic in several structures in the circadian, tectofugal, thalamofugal visual pathways and that pinealectomy increases the level of IMEL binding 2–4 fold suggesting that IMEL binding is down regulated by endogenous melatonin. However, the circadian rhythm of this binding is only gradually abolished, suggesting it too is regulated by a non-pineal circadian clock. These data are discussed in the context of the behavioral neurobiology of avian circadian systems and the neuroendocrine loop model.

Search for quark compositeness, axigluons, and heavy particles using the dijet invariant mass spectrum observed in pp¯ collisions

Abstract: The dijet invariant mass distribution has been measured in the region between 140 and 1000 GeV/${\mathit{c}}^{2}$, in 1.8 TeV p p\ifmmode\bar\else\textasciimacron\fi{} collisions. Data collected with the Collider Detector at Fermilab show agreement with QCD calculations. A limit on quark compositeness of ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}$g1.3 TeV is obtained. Axigluons with masses between 240 and 640 GeV/${\mathit{c}}^{2}$ are excluded at 95% C.L. if we assume ten open decay channels. Model-independent limits on the production of heavy particles decaying into two jets are also presented.

Observation of the decay Bs0J/ in p»p collisions at s =1.8 TeV

Abstract: This Letter reports the observation and mass measurement of fully reconstructed [ital B][sub [ital s]][sup 0] mesons through the decay chain [ital B][sub [ital s]][sup 0][r arrow][ital J]/[psi] [psi], [ital J]/[psi][r arrow][mu][sup +][mu][sup [minus]], [phi][r arrow][ital K][sup +][ital K[minus]] using data obtained at the Collider Detector at Fermilab in [ital [bar p]p] collisions at [radical][ital s] =1.8 TeV. A signal of 14.0[plus minus]4.7 events is observed. Comparison of the [ital B][sub [ital s]][sup 0] signal with the kinematically similar decays [ital B][sup +][r arrow][ital J]/[psi] [ital K][sup +] and [ital B][sup 0][r arrow][ital J]/[psi] K[sup *](892)[sup 0] is presented. The mass of the [ital B][sub [ital s]][sup 0] meson is determined to be 5383.3[plus minus]4.5(stat)[plus minus]5.0(syst) MeV/[ital c][sup 2].

Improved wear resistance of ceramics through the use of coatings

Abstract: Ceramic materials operating in a mild wear regime display extremely low wear rates. However, a transition to a severe wear regime results in the formation of wear debris, the presence of which may contribute to the formation of protective surface films. Aluminas represent ceramics with very high wear rates in the severe regime which generally result in failure of the system. Thus there is a potential for extending the mild wear regimes of aluminas by applying a surface coating. Tribological properties of uncoated and WC/C-coated alumina in plane, close contact sliding in air and water were characterized before and after testing utilizing advanced electron microscopy techniques. It is concluded that the WC/C-coated Al 2 O 3 can have a wear resistance several orders of magnitude higher than uncoated Al 2 O 3 couples when tested in both air and water. The explanation for this is believed to be that teh WC/C coating protects the alumina surface by reducing the magnitude of the local contact stresses and thus the tendency for wear by brittle fracture.