Search for Higgs and New Phenomena at Colliders

The present status of searches for the Higgs boson(s) and new phenomena is reviewed. The focus is on analyses and results from the current runs of the HERA and Tevatron experiments. The LEP experiments have released their final combined MSSM Higgs results for this conference. Also included are results from sensitivity studies of the LHC experiments and lepton flavour violating searches from the B factories, KEKB and PEP-II.Comment: XXII International Symposium on Lepton-Photon Interactions at High Energy (11 pages, 16 figures, 2 tables

Formation of Nitrous Acid: Parameterisation and comparison with observations

Nitrous acid formation in the troposphere is described in the light of the most recent advances of knowledge on NOx chemistry on ground and aerosol surfaces. It is suggested to follow the stoichiometry of the reaction 2 NO; + H20 -> HNO2 + HNO3 on all ambient surfaces except those of carbonaceous particles. The influences of ambient humidity on aerosol (water uptake) and ground surface area (surface to area indices) and on water availability for surface reactions are considered. It is concluded that the state of the reacting H20 molecule, chemisorbed to the surface or other, is determining: The ldnetics of the process obeys first order in N02 concentration and eidier pseudo-zeroth order (for low surface coverage with I-12_, using to: - 0.1 - 1 * 10-6 for the various surface types) or first order in water vapour concentration (for water molecules available on the surface in multilayer adsorption, using km =- 1.36 * 10-20 cm4 moles1 s as determined in a laboratory experiment on a humid vessel wall). A reaction mechanism is proposed. The scheme differentiates between 4 ground surface and 4 aerosol surfaces types. Predicted and observed nitrous acid formation rates from two urban sites are compared. For this purpose, observed rates and their' error bars were derived with particular care. Despite large uncertainties for both predicted and observed values, the agreement is good for both low and high humidities (mean predicted/observed = 138 % for 18 nights in Mainz, 1986/87, and 132 % for 9 nights in Milano, 1994)

Fractionation and current time trends of PCB congeners: evolvement of distributions 1950–2010 studied using a global atmosphere-ocean general circulation model

PCBs are ubiquitous environmental pollutants expected to decline in abiotic environmental media in response to decreasing primary emissions since the 1970s. A coupled atmosphere-ocean general circulation model with embedded dynamic sub-models for atmospheric aerosols and the marine biogeochemistry and air-surface exchange processes with soils, vegetation and the cryosphere is used to study the transport and fate of four PCB congeners covering a range of 3–7 chlorine atoms. <br><br> The change of the geographic distribution of the PCB mixture reflects the sources and sinks' evolvement over time. Globally, secondary emissions (re-volatilisation from surfaces) are on the long term increasingly gaining importance over primary emissions. Secondary emissions are most important for the congeners with 5–6 chlorine atoms. Correspondingly, the levels of these congeners are predicted to decrease slowest. Changes in congener mixture composition (fractionation) are characterized both geographically and temporally. In high latitudes enrichment of the lighter, less persistent congeners and more delayed decreasing levels in response to decreasing emissions are found. The delivery of the contaminants to high latitudes is predicted to be more efficient than previously suggested. The results suggest furthermore that the effectiveness of emission control measures may significantly vary among substances. The trends of decline of organic contaminant levels in the abiotic environmental media do not only vary with latitude (slow in high latitudes), but do also show longitudinal gradients

Greenhouse effect of NOx

Through various processes the nitrogen oxides (NO,) interact: with trace gases in the troposphere and stratosphere which do absorb in the spectral range relevant to the greenhouse effect (infrared wavelengths). The net effect is an enhancement of the greenhouse effect. The catalytic role of NO, in the production of tropospheric ozone provides the most prominent contribution. The global waming potential is estimated as GWP (NOx) = 30 - 33 and 7 - 10 for the respective time horizons of 20 and 100 years, and is thereby comparable to chat of methane. NO, emissions in rural areas of anthropogenically influenced regions, or those in the vicinity of the tropopause caused by air traffic, cause the greenhouse effectivity to be substantially more intense. We estimate an additional 5 - 23 % for Germany's contribution to the anthropogenic greenhouse effect as a result of the indirect greenhouse effects stemming from NO,. Furthermore, a small and still inaccurately defined amount of the deposited NO, which has primarily been converted into nitrates is again released from the soil into the atmosphere in the form of the long-lived greenhouse gas nitrous oxide (N2O). Thus, anchropogenically induced NOx emissions contribute to enhanced greenhouse effect and to stratospheric ozone depletion in the time scale of more than a century

Nitrous acid and nitrite in the atmosphere

Nitrous acid is a minor trace gas, yet has an important influence on OH concentrations in the troposphere. Gas phase concentrations in both rural and urban air are larger than predicted from laboratory studies of homogeneous or heterogeneous chemistry. A better understanding of the mechanisms which produce nitrous acid in the atmosphere will lead to improved model of nitrogen oxide and OH chemistry, particularly in polluted air

The significance of the grasshopper effect on the atmospheric distribution of persistent organic substances

Slowly degradable, semivolatile organic compounds (SOCs) may undergo more than one volatilization-transport-deposition cycle through the atmosphere (multi-hopping). The significance of this process for the potential for long-range transport (LRT) is addressed for the first time. We use a multicompartment model which in turn is based on a general circulation model. The results suggest that both transport by single-hopping and multi-hopping contribute significantly to LRT of DDT and γ-HCH (lindane) and to accumulation in high latitudes. A larger fraction of the molecules transported by multi-hopping than of the molecules transported by single-hopping is deposited to the world's oceans. Multi-hopping prevails in the boundary layer far from the source regions. However, single-hopping contributes an almost equal amount to the deposition of DDT and γ-HCH in the Arctic

Impact of regional climate and substance properties on the fate and atmospheric long-range transport of persistent organic pollutants - examples of DDT and g-HCH

A global multicompartment model which is based on a 3-D atmospheric general circulation model (ECHAM5) coupled to 2-D soil, vegetation and sea surface mixed layer reservoirs, is used to simulate the atmospheric transports and total environmental fate of dichlorodiphenyltrichloroethane (DDT) and γ-hexachlorocyclohexane (γ-HCH, lindane). Emissions into the model world reflect the substance's agricultural usage in 1980 and 1990 and same amounts in sequential years are applied. Four scenarios of DDT usage and atmospheric decay and one scenario of γ-HCH are studied over a decade. The global environment is predicted to be contaminated by the substances within ca. 2a (years). DDT reaches quasi-steady state within 3-4a in the atmosphere and vegetation compartments, ca. 6a in the sea surface mixed layer and near to or slightly more than 10a in soil. Lindane reaches quasi-steady state in the atmosphere and vegetation within 2a, in soils within 8 years and near to or slightly more than 10a and in the sea surface mixed layer. The substances' differences in environmental behaviour translate into differences in the compartmental distribution and total environmental residence time, τoverall. τoverall≈0.8a for γ-HCH's and ≈1.0-1.3 a for the various DDT scenarios. Both substances' distributions are predicted to migrate in northerly direction, 5-12° for DDT and 6.7° for lindane between the first and the tenth year in the environment. Cycling in various receptor regions is a complex superposition of influences of regional climate, advection, and the substance's physico-chemical properties. As a result of these processes the model simulations show that remote boreal regions are not necessarily less contaminated than tropical receptor regions. Although the atmosphere accounts for only 1% of the total contaminant burden, transport and transformation in the atmosphere is key for the distribution in other compartments. Hence, besides the physico-chemical properties of pollutants the location of application (entry) affects persistence and accumulation emphasizing the need for georeferenced exposure models

Long-range transport and multimedia partitioning of semivolatile organic compounds: A case study on two modern agrochemicals

The global environmental fate of two modern pesticides was studied using a multimedia model based on a three- dimensional atmosphere general circulation model. The emissions are predicted dynamically based on agricultural application inventories. The insecticide methyl parathion, when assuming properties at the high mobility end of the respective data uncertainties, was found to be distributed on continental and even global scales. This finding implies that based on present knowledge one cannot exclude that methyl parathion reaches regions as far from the sources as e.g. the Arctic. Two scenarios of the environmental cycling of the herbicide atrazine were studied which reflect a lower and an upper estimate of the substance’ mobility. Atrazine largely remains in the source (application) regions and the neighbouring seas. But also atrazine seems to have an albeit limited potential for long-range transport. The findings on substance mobilities are quantified by indicators which address spatial range in the zonal direction in individual media. The seasonal variability of the total environmental burden of both pesticides is governed by the degradation in soil and vegetation which together host 73 % of methyl parathion and 90-99 % of atrazine. Also, the cycling between compartments was studied. Methyl parathion undergoes more deposition and re-emission cycles than atrazine, a characteristics of the environmental fate of semivolatile substances. Persistence is addressed by determination of global total environmental decay times during periods without introduction of new substance into the environment. These are in the range 4-7 months. It is found that the seasonal variability of persistence is pronounced

Low-velocity collisions of centimeter-sized dust aggregates

Collisions between centimeter- to decimeter-sized dusty bodies are important to understand the mechanisms leading to the formation of planetesimals. We thus performed laboratory experiments to study the collisional behavior of dust aggregates in this size range at velocities below and around the fragmentation threshold. We developed two independent experimental setups with the same goal to study the effects of bouncing, fragmentation, and mass transfer in free particle-particle collisions. The first setup is an evacuated drop tower with a free-fall height of 1.5 m, providing us with 0.56 s of microgravity time so that we observed collisions with velocities between 8 mm/s and 2 m/s. The second setup is designed to study the effect of partial fragmentation (when only one of the two aggregates is destroyed) and mass transfer in more detail. It allows for the measurement of the accretion efficiency as the samples are safely recovered after the encounter. Our results are that for very low velocities we found bouncing as could be expected while the fragmentation velocity of 20 cm/s was significantly lower than expected. We present the critical energy for disruptive collisions Q*, which showed up to be at least two orders of magnitude lower than previous experiments in the literature. In the wide range between bouncing and disruptive collisions, only one of the samples fragmented in the encounter while the other gained mass. The accretion efficiency in the order of a few percent of the particle's mass is depending on the impact velocity and the sample porosity. Our results will have consequences for dust evolution models in protoplanetary disks as well as for the strength of large, porous planetesimal bodies

Indoor Navigation with MEMS sensors

AbstractAccurate positioning becomes extremely important for modern application like indoor navigation and location-based services. Standalone GPS cannot meet this accuracy. In this paper a method to couple GPS and a high resolution MEMS pressure sensor is presented to improve vertical as well as horizontal (in urban canyon environment) positioning. Further, a step counter based on an accelerometer is improved with an altimeter for stair detection and automatic step length adaptation for dead reckoning inside buildings. Finally, a stand-alone system accurately tracks floor levels inside buildings, using only a pressure sensor