Unraveling the nature of coherent beatings in chlorosomes.

Coherent two-dimensional (2D) spectroscopy at 80 K was used to study chlorosomes isolated from green sulfur bacterium Chlorobaculum tepidum. Two distinct processes in the evolution of the 2D spectrum are observed. The first being exciton diffusion, seen in the change of the spectral shape occurring on a 100-fs timescale, and the second being vibrational coherences, realized through coherent beatings with frequencies of 91 and 145 cm(-1) that are dephased during the first 1.2 ps. The distribution of the oscillation amplitude in the 2D spectra is independent of the evolution of the 2D spectral shape. This implies that the diffusion energy transfer process does not transfer coherences within the chlorosome. Remarkably, the oscillatory pattern observed in the negative regions of the 2D spectrum (dominated by the excited state absorption) is a mirror image of the oscillations found in the positive part (originating from the stimulated emission and ground state bleach). This observation is surprising since it is expected that coherences in the electronic ground and excited states are generated with the same probability and the latter dephase faster in the presence of fast diffusion. Moreover, the relative amplitude of coherent beatings is rather high compared to non-oscillatory signal despite the reported low values of the Huang-Rhys factors. The origin of these effects is discussed in terms of the vibronic and Herzberg-Teller couplings

F (2004) Formation of selected biogenic amines in carp meat J Sci Food Agr

Abstract: Changes in biogenic amine content in carp (Cyprinus carpio) muscle were studied. Fish halves and minced fish meat were stored at 3 and 15°C. Both the temperature of storage and the type of meat processing had statistically important effects on the amine content. In another set of experiments, temperature and the preservative effects of Purac at various concentrations were tested. Purac can extend the shelf-life of fish halves stored at 3°C by about 5 days. Putrescine concentration is proposed as a chemical indicator of carp meat quality. Decomposition is apparent when the putrescine content in the meat exceeds 20 mg kg À1

Two-Dimensional Electronic Spectroscopy Reveals Ultrafast Energy Diffusion in Chlorosomes.

Chlorosomes are light-harvesting antennae that enable exceptionally efficient light energy capture and excitation transfer. They are found in certain photosynthetic bacteria, some of which live in extremely low-light environments. In this work, chlorosomes from the green sulfur bacterium Chlorobaculum tepidum were studied by coherent electronic two-dimensional (2D) spectroscopy. Previously uncharacterized ultrafast energy transfer dynamics were followed, appearing as evolution of the 2D spectral line-shape during the first 200 fs after excitation. Observed initial energy flow through the chlorosome is well explained by effective exciton diffusion on a sub-100 fs time scale, which assures efficiency and robustness of the process. The ultrafast incoherent diffusion-like behavior of the excitons points to a disordered energy landscape in the chlorosome, which leads to a rapid loss of excitonic coherences between its structural subunits. This disorder prevents observation of excitonic coherences in the experimental data and implies that the chlorosome as a whole does not function as a coherent light-harvester

Národní program ČR na zmírnění dopadů změny klimatu‚ vědecké a technické aspekty vstupu do EU:Národní inventarizace emisí skleníkových plynů pro roky 2001-2004 a zajištění konzistentnosti časových řad, příprava národního systému v souladu s mezinárodními závazky

Zpracování národních inventarizací emisí skleníkových plynů za roky 2001 - 2004 a zpětný přepočet a doplnění emisních řad od roku 1990. Rozbor problematiky a zpracování podkladů pro formulaci Národního programu na zmírnění dopadů změny klimatu. Příprava vstupních emisních dat pro mezinárodní projekty, zaměřené na zjišťování možností emisního obchodování dle čl. 17 Kjótského protokolu. Příprava projekcí emisí skleníkových plynů a vyhodnocení přijatých opatření na snižování emisí skleníkových plynů. Vytvoření a rozvoj nástrojů pro objektivní hodnocení stavu a vývoje emisí skleníkových plynů v souladu s novým zákonem o ovzduší a hodnocení plnění redukčních závazků ČR vůči Kjótskému protokolu. Zpráva za DP 01 obsahuje podklady pro kontrolní den dílčího projektu, studii Rekalkulace emisní řady metanu z enterické fermentace skotu a Metodiku inventarizace emisí CO2 z výroby cementu a emisí a propadů CO2 z výroby a použití vápna