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We report the observation of four electron-positron pairs and one muon pair which have the signature of a two-body decay of a particle of mass ∼ 95 GeV/c2. These events fit well the hypothesis that they are produced by the process p ̄ + p → Z0 + X (with Z0 → ℓ+ + ℓ-), where Z0 is the Intermediate Vector Boson postulated by the electroweak theories as the mediator of weak neutral currents. © 1983

We apply the disk-corona evaporation model (Meyer & Meyer-Hofmeister) originally derived for dwarf novae to black hole systems. This model describes the transition of a thin cool outer disk to a hot coronal flow. The mass accretion rate determines the location of this transition. For a number of well-studied black hole binaries, we take the mass flow rates derived from a fit of the advection-dominated accretion flow (ADAF) model to the observed spectra (for a review, see Narayan, Mahadevan, & Quataert) and determine where the transition of accretion via a cool disk to a coronal flow/ADAF would be located for these rates. We compare this with the observed location of the inner disk edge, as estimated from the maximum velocity of the Halpha emission line. We find that the transition caused by evaporation agrees with this determination in stellar disks. We also show that the ADAF and the "thin outer disk + corona" are compatible in terms of the physics in the transition region.

paper we present UBVRI light curves obtained by the WEBT from 1994 to 2002, including the last, extended BL Lac 2001 campaign. A total of about 7500 optical observations performed by 31 telescopes from Japan to Mexico have been collected, to be added to the ∼15 600 observations of the BL Lac Campaign 2000. All these data allow one to follow the source optical emission behaviour with unprecedented detail. The analysis of the colour indices reveals that the flux variability can be interpreted in terms of two components: longer-term variations occurring on a fewday time scale appear as mildly-chromatic events, while a strong bluer-when-brighter chromatism characterizes very fast (intraday) flares. By decoupling the two components, we quantify the degree of chromatism inferring that longer-term flux changes imply moving along a ∼0.1 bluerwhen-brighter slope in the B − R versus R plane; a steeper slope of ∼0.4 would distinguish the shorter-term variations. This means that, when considering the long-term trend, the B-band flux level is related to the R-band one according to a power law of index ∼1.1. Doppler factor variations on a "convex" spectrum could be the mechanism accounting for both the long-term variations and their slight chromatism.

In this paper, historical optical(UBVRI) data and newly observed data from the Yunnan Observatory of China( about100 years) are presented for BL Lacertae. Large variations of ∆U = 5 m .12, ∆B = 5 m .31, ∆V = 4 m .73, ∆R = 2 m .59, ∆I = 2 m .54, and color indices of U − B = −0.11 ± 0.20, B−V = 1.0±0.11, V −R = 0.73±0.19,V −I = 1.42±0.25,R−I = 0.82±0.11,and B − I = 2.44 ± 0.29 have been obtained from the literature; The Jurkevich method is used to investigate the existence of periods in the B band light curve, and a long-term period of 14 years is found. The 0.6 and 0.88 year periods reported by Webb et al.(1988) are confirmed. In addition, a close relation between B-I and B is found, suggesting that the spectra flattens when the source brightens.

h i g h l i g h t s• The green space area reduced by 199 km 2 and became fragmented from 2000 to 2010.• The annual runoff reduction volume ranged from 132 million m 3 to 198 million m 3 .• The rainwater runoff reduction rate decreased by 6% with the land cover changes.• The green space with larger LPI and AI is suitable for flooding risk reduction.a r t i c l e i n f o b s t r a c tThe effects of urban green spaces on stormwater runoff have increasingly attracted attention because of climate change and rapid urbanization conditions. This study investigates the spatial-temporal changes of urban green spaces in Beijing and estimates their effects on rainwater runoff reduction based on an empirical model. Results indicate that green spaces in Beijing decreased by 199 km 2 from 2000 to 2010 and that landscape patches became increasingly isolated and fragmented. The volume of rainwater runoff controlled by urban green spaces first increased and then decreased with the increase in summer rainfall. The runoff reduction rate continuously decreased from 23% in 2000 to 17% in 2010, which is mainly attributed to the composition changes in urban green spaces. In addition, an immense regional difference that is closely related to the changes in the largest patch and aggregation indices of urban green spaces are observed in different regions. This study recommends an optimal landscape pattern of urban green spaces for the planning and management of green spaces in highly urbanized areas.

We present optical monitoring between 1994 February and 1997 December of 10 c-rayÈloud blazars included in our blazar monitoring program. Most of the monitored objects show signiÐcant rapid variations. The typical minimum variability timescale in the optical range is about 1 hour. We have analyzed the relationships between optical variability and c-ray variability, and discussed theoretical models for the c-rayÈloud blazar emission.

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