Editorial

In the years leading to the handover on 1 July 1997, there were both pessimists and optimists among the observers of the process of decolonisation and the establishment of the so-called “One Country, Two systems” arrangement in Hong Kong. For the pessimists, their main concerns were two. First, the socialist system in China could hardly accommodate a free market, capitalist Hong Kong; conflict was inevitable. Second, the encounter between an authoritarian China and a highly liberalised Hong Kong would also be a source of conflict and contention; personal freedom in Hong Kong would quickly be contained. For the optimists, with China eager to carry out market reform and Hong Kong being well placed to facilitate its economic reform and modernisation, capitalism would continue to prosper in the former British colony. The return of Hong Kong to China would therefore be no more than business as usual. Changes, if any, would be minimal. Both the pessimists and the optimists failed to anticipate the kind of problems encountered by Hong Kong since 1997.

Éditorial

Dans les années qui ont précédé la rétrocession de Hong Kong à la Chine le 1er juillet 1997, les observateurs du processus de décolonisation du territoire et de l’instauration de la formule « un pays, deux systèmes » étaient partagés en optimistes et pessimistes. Les pessimistes avaient deux inquiétudes principales. Ils pensaient tout d’abord que le système socialiste chinois pourrait difficilement intégrer le capitalisme de marché de Hong Kong et que le conflit était donc inévitable. Ensuite, la rencontre entre un pays autoritaire et une ville très libérale serait également une source de tension et de conflit, qui entrainerait rapidement la limitation des libertés individuelles à Hong Kong. Pour les optimistes, Hong Kong était en revanche bien placé pour faciliter les réformes économiques et la modernisation que la Chine était impatiente de renforcer et poursuivre. En conséquence, le capitalisme allait pour eux continuer à prospérer dans l’ancienne colonie britannique et la rétrocession ne provoquerait que peu de changements. En réalité, ni les pessimistes ni les optimistes n’ont anticipé les nouveaux défis qui se posent à Hong Kong depuis 1997

Editorial

In the years leading to the handover on 1 July 1997, there were both pessimists and optimists among the observers of the process of decolonisation and the establishment of the so-called “One Country, Two systems” arrangement in Hong Kong. For the pessimists, their main concerns were two. First, the socialist system in China could hardly accommodate a free market, capitalist Hong Kong; conflict was inevitable. Second, the encounter between an authoritarian China and a highly liberalised Hong Kong would also be a source of conflict and contention; personal freedom in Hong Kong would quickly be contained. For the optimists, with China eager to carry out market reform and Hong Kong being well placed to facilitate its economic reform and modernisation, capitalism would continue to prosper in the former British colony. The return of Hong Kong to China would therefore be no more than business as usual. Changes, if any, would be minimal. Both the pessimists and the optimists failed to anticipate the kind of problems encountered by Hong Kong since 1997.

DNA Damage Mediated S and G2 Checkpoints in Human Embryonal Carcinoma Cells

For mouse embryonic stem (ES) cells, the importance of the S and G2 cell cycle checkpoints for genomic integrity is increased by the absence of the G1 checkpoint. We have investigated ionizing radiation (IR)-mediated cell cycle checkpoints in undifferentiated and retinoic acid-differentiated human embryonal carcinoma (EC) cells. Like mouse ES cells, human EC cells did not undergo G1 arrest after IR but displayed a prominent S-phase delay followed by a G2-phase delay. In contrast, although differentiated EC cells also failed to arrest at G1-phase after IR, they quickly exited S-phase and arrested in G2-phase. In differentiated EC cells, the G2-M-phase cyclin B1/CDC2 complex was upregulated after IR, but the G1-S-phase cyclin E and the cyclin E/CDK2 complex were expressed at constitutively low levels, which could be an important factor distinguishing DNA damage responses between undifferentiated and differentiated EC cells. S-phase arrest and expression of p21 could be inhibited by 7-hydroxystaurosporine, suggesting that the ataxia-telangiectasia and Rad-3-related-checkpoint kinase 1 (ATR-CHK1), and p21 pathways might play a role in the IR-mediated S-phase checkpoint in EC cells. IR-mediated phosphorylation of ataxia-telangiectasia mutated, (CHK1), and checkpoint kinase 2 were distinctly higher in undifferentiated EC cells compared with differentiated EC cells. Combined with the prominent S and G2 checkpoints and a more efficient DNA damage repair system, these mechanisms operate together in the maintenance of genome stability for EC cells. Stem Cells 2009;27:568–57

Search for Higgs Bosons in e+e- Collisions at 183 GeV

The data collected by the OPAL experiment at sqrts=183 GeV were used to search for Higgs bosons which are predicted by the Standard Model and various extensions, such as general models with two Higgs field doublets and the Minimal Supersymmetric Standard Model (MSSM). The data correspond to an integrated luminosity of approximately 54pb-1. None of the searches for neutral and charged Higgs bosons have revealed an excess of events beyond the expected background. This negative outcome, in combination with similar results from searches at lower energies, leads to new limits for the Higgs boson masses and other model parameters. In particular, the 95% confidence level lower limit for the mass of the Standard Model Higgs boson is 88.3 GeV. Charged Higgs bosons can be excluded for masses up to 59.5 GeV. In the MSSM, mh > 70.5 GeV and mA > 72.0 GeV are obtained for tan{beta}>1, no and maximal scalar top mixing and soft SUSY-breaking masses of 1 TeV. The range 0.8 < tanb < 1.9 is excluded for minimal scalar top mixing and m{top} < 175 GeV. More general scans of the MSSM parameter space are also considered.Comment: 49 pages. LaTeX, including 33 eps figures, submitted to European Physical Journal

A Measurement of the Product Branching Ratio f(b->Lambda_b).BR(Lambda_b->Lambda X) in Z0 Decays

The product branching ratio, f(b->Lambda_b).BR(Lambda_b->Lambda X), where Lambda_b denotes any weakly-decaying b-baryon, has been measured using the OPAL detector at LEP. Lambda_b are selected by the presence of energetic Lambda particles in bottom events tagged by the presence of displaced secondary vertices. A fit to the momenta of the Lambda particles separates signal from B meson and fragmentation backgrounds. The measured product branching ratio is f(b->Lambda_b).BR(Lambda_b->Lambda X) = (2.67+-0.38(stat)+0.67-0.60(sys))% Combined with a previous OPAL measurement, one obtains f(b->Lambda_b).BR(Lambda_b->Lambda X) = (3.50+-0.32(stat)+-0.35(sys))%.Comment: 16 pages, LaTeX, 3 eps figs included, submitted to the European Physical Journal

Measurement of the Michel Parameters in Leptonic Tau Decays

The Michel parameters of the leptonic tau decays are measured using the OPAL detector at LEP. The Michel parameters are extracted from the energy spectra of the charged decay leptons and from their energy-energy correlations. A new method involving a global likelihood fit of Monte Carlo generated events with complete detector simulation and background treatment has been applied to the data recorded at center-of-mass energies close to sqrt(s) = M(Z) corresponding to an integrated luminosity of 155 pb-1 during the years 1990 to 1995. If e-mu universality is assumed and inferring the tau polarization from neutral current data, the measured Michel parameters are extracted. Limits on non-standard coupling constants and on the masses of new gauge bosons are obtained. The results are in agreement with the V-A prediction of the Standard Model.Comment: 32 pages, LaTeX, 9 eps figures included, submitted to the European Physical Journal

Energetic particle influence on the Earth's atmosphere

This manuscript gives an up-to-date and comprehensive overview of the effects of energetic particle precipitation (EPP) onto the whole atmosphere, from the lower thermosphere/mesosphere through the stratosphere and troposphere, to the surface. The paper summarizes the different sources and energies of particles, principally galactic cosmic rays (GCRs), solar energetic particles (SEPs) and energetic electron precipitation (EEP). All the proposed mechanisms by which EPP can affect the atmosphere are discussed, including chemical changes in the upper atmosphere and lower thermosphere, chemistry-dynamics feedbacks, the global electric circuit and cloud formation. The role of energetic particles in Earth’s atmosphere is a multi-disciplinary problem that requires expertise from a range of scientific backgrounds. To assist with this synergy, summary tables are provided, which are intended to evaluate the level of current knowledge of the effects of energetic particles on processes in the entire atmosphere