Disentangling the impact of social groups on response times and movement dynamics in evacuations

Crowd evacuations are paradigmatic examples for collective behaviour, as interactions between individuals lead to the overall movement dynamics. Approaches assuming that all individuals interact in the same way have significantly improved our understanding of pedestrian crowd evacuations. However, this scenario is unlikely, as many pedestrians move in social groups that are based on friendship or kinship. We test how the presence of social groups affects the egress time of individuals and crowds in a representative crowd evacuation experiment. Our results suggest that the presence of social groups increases egress times and that this is largely due to differences at two stages of evacuations. First, individuals in social groups take longer to show a movement response at the start of evacuations, and, second, they take longer to move into the vicinity of the exits once they have started to move towards them. Surprisingly, there are no discernible time differences between the movement of independent individuals and individuals in groups directly in front of the exits. We explain these results and discuss their implications. Our findings elucidate behavioural differences between independent individuals and social groups in evacuations. Such insights are crucial for the control of crowd evacuations and for planning mass events.

Wechselwirkungen in Molekülkristallen, 163 [1, 2]. Einfluß der Alkalimetall-Reduktionspotentiale auf die Bildung ihrer Kontaktionenmultipel mit Tetracen- und Decacylen-Polyanionen / Interaction in Molecular Crystals, 163 [ 1,2]. The Influence of Alkaline Metal Reduction Potentials on the Formation of their Contaction Multiples with Tetracene and Decacyclene Polyanions

The reduction of selected π-hydrocarbons tetracene and decacyclene by various alkaline metals allowed the crystallization and structure determination of the following five solvent separated or solvent shared contaction multiples: [Tetracene⊖⊖ (Na⊕Diglyme)2], [Tetracene⊖⊖ - (K⊕ Triglyme)2], [Decacyclene• ⊖] [Cs⊕ (Triglyme)2], [Decacyclene•⊖⊖⊖] [Na⊕ (DME)3]3, [Decacyclene⊖⊖⊖⊖ (K⊕Diglyme)4]. These alkaline salts contain a radicalanion M• ⊖ , dianions M⊖⊖ , a radicaltrianion M•⊖⊖⊖ , and a tetraanion M⊖⊖⊖⊖ generated by single or multiple electron transfer. Their structures are discussed in terms of the difference in alkaline metal reduction potentials, the powerful cation solvation, the effects of the anion charges and of the cation radii. Further aspects concern the solvent-shared or solvent-separated cation coordination to the anions, the polyion aggregation and for the radical trianion the experimentally proven and quantumchemically simulated Jahn/Teller distortion. Altogether the investigation adds facets to the knowledge of multielectrontransfer reactions and of selforganisation phenomena of alkaline salts.

Isolated hepatic perfusion: principles and results

INTRODUCTION

Isolated hepatic perfusion allows the delivery of high dose chemotherapy while decreasing extra-hepatic toxicity, and is used mainly for patients with surgically unresectable liver tumors.

PRINCIPLES

Vascular exclusion of the liver is performed after obtaining satisfactory hemodynamic tolerance, occasionally after cavocaval shunt and/or porto-systemic shunt. Perfusion entry can be arterial and/or portal while the exit is portal or caval. The perfusion circuit can be open or closed, using a circulation pump with or without oxygenation. The chemotherapy regimens used are high dose melphalan (with or without TNF-alpha), oxaliplatin, cisplatin and mitomycin, sometimes associated with moderate hyperthermia. The duration of perfusion ranges between 30 and 90 minutes according to the different protocols used. A percutaneous technique with incomplete liver vascular exclusion is also possible.

RESULTS

The larger series in the literature show a response rate (partial or complete stabilization) between 60 and 80%, with approximately 5% complete morphologic responses. Morbidity and mortality are 40 and 5%, respectively, including specific morbidity related to the perfusion procedure as well as to chemotherapy.

CONCLUSION

Chemotherapy delivered through isolated hepatic perfusion is a new therapeutic alternative, still under development, and can be proposed to patients with surgically unresectable primary or secondary liver tumors within clinical trials. These results seem to be promising, but are still associated with a non-negligible morbidity rate.

Radiation-induced pancreatitis: search for the neoplasm!

The management of a patient with a post-radiation pancreatitis is reported. Several biopsies and imaging failed to diagnose the radiation-induced carcinoma revealed during emergency laparotomy. This diagnosis must be kept in mind, and repeated biopsies are necessary.