The surface conditions on the Moon are extremely harsh with high doses of ultraviolet (UV) irradiation (26.8 W · m-2 UVC/UVB), wide temperature extremes (-171°C to 140°C), low pressure (10-10 Pa), and high levels of ionizing radiation. External spacecraft surfaces on the Moon are generally >100°C during daylight hours and can reach as high as 140°C at local noon. A Lunar Microbial Survival (LMS) model was developed that estimated (1) the total viable bioburden of all spacecraft landed on the Moon as ∼4.57 × 1010 microbial cells/spores at contact, (2) the inactivation kinetics of Bacillus subtilis spores to vacuum as approaching -2 logs per 2107 days, (3) the inactivation of spores on external surfaces due to concomitant low-pressure and high-temperature conditions as -6 logs per 8 h for local noon conditions, and (4) the ionizing radiation by solar wind particles as approaching -3 logs per lunation on external surfaces only. When the biocidal factors of solar UV, vacuum, high-temperature, and ionizing radiation were combined into an integrated LMS model, a -231 log reduction in viable bioburden was predicted for external spacecraft surfaces per lunation at the equator. Results indicate that external surfaces of landed or crashed spacecraft are unlikely to harbor viable spores after only one lunation, that shallow internal surfaces will be sterilized due to the interactive effects of vacuum and thermal cycling from solar irradiation, and that deep internal surfaces would be affected only by vacuum with a degradation rate of -0.02 logs per lunation.
- MeSH
- Bacillus subtilis fyziologie účinky záření MeSH
- biologické modely * MeSH
- kosmická loď MeSH
- kosmické záření škodlivé účinky MeSH
- Měsíc * MeSH
- mikrobiální viabilita účinky záření MeSH
- mimozemské prostředí MeSH
- simulace kosmického prostředí metody MeSH
- spory bakteriální fyziologie účinky záření MeSH
- ultrafialové záření škodlivé účinky MeSH
- vakuum MeSH
- vysoká teplota MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
Magnetic sensing is used to structure every-day, non-migratory behaviours in many animals. We show that crayfish exhibit robust spontaneous magnetic alignment responses. These magnetic behaviours are altered by interactions with Branchiobdellidan worms, which are obligate ectosymbionts. Branchiobdellidan worms have previously been shown to have positive effects on host growth when present at moderate densities, and negative effects at relatively high densities. Here we show that crayfish with moderate densities of symbionts aligned bimodally along the magnetic northeast-southwest axis, similar to passive magnetic alignment responses observed across a range of stationary vertebrates. In contrast, crayfish with high symbiont densities failed to exhibit consistent alignment relative to the magnetic field. Crayfish without symbionts shifted exhibited quadramodal magnetic alignment and were more active. These behavioural changes suggest a change in the organization of spatial behaviour with increasing ectosymbiont densities. We propose that the increased activity and a switch to quadramodal magnetic alignment may be associated with the use of systematic search strategies. Such a strategy could increase contact-rates with conspecifics in order to replenish the beneficial ectosymbionts that only disperse between hosts during direct contact. Our results demonstrate that crayfish perceive and respond to magnetic fields, and that symbionts influence magnetically structured spatial behaviour of their hosts.
The molecules of life were created by a continuous physicochemical process on an early Earth. In this hadean environment, chemical transformations were driven by fluctuations of the naturally given physical parameters established for example by wet-dry cycles. These conditions might have allowed for the formation of (self)-replicating RNA as the fundamental biopolymer during chemical evolution. The question of how a complex multistep chemical synthesis of RNA building blocks was possible in such an environment remains unanswered. Here we report that geothermal fields could provide the right setup for establishing wet-dry cycles that allow for the synthesis of RNA nucleosides by continuous synthesis. Our model provides both the canonical and many ubiquitous non-canonical purine nucleosides in parallel by simple changes of physical parameters such as temperature, pH and concentration. The data show that modified nucleosides were potentially formed as competitor molecules. They could in this sense be considered as molecular fossils.
Recent results in prebiotic chemistry implicate hydrogen cyanide (HCN) as the source of carbon and nitrogen for the synthesis of nucleotide, amino acid and lipid building blocks. HCN can be produced during impact events by reprocessing of carbonaceous and nitrogenous materials from both the impactor and the atmosphere; it can also be produced from these materials by electrical discharge. Here we investigate the effect of high energy events on a range of starting mixtures representative of various atmosphere-impactor volatile combinations. Using continuously scanning time-resolved spectrometry, we have detected ·CN radical and excited CO as the initially most abundant products. Cyano radicals and excited carbon monoxide molecules in particular are reactive, energy-rich species, but are resilient owing to favourable Franck-Condon factors. The subsequent reactions of these first formed excited species lead to the production of ground-state prebiotic building blocks, principally HCN.
- Klíčová slova
- geomagnetické pole, elektrostatické pole,
- MeSH
- elektromagnetické jevy MeSH
- hojení ran MeSH
- lidé MeSH
- magnetické pole MeSH
- magnetoterapie * dějiny klasifikace MeSH
- magnety dějiny MeSH
- management bolesti MeSH
- vazodilatace MeSH
- významné osobnosti MeSH
- Země (planeta) MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- biografie MeSH
- historické články MeSH
- práce podpořená grantem MeSH
- O autorovi
- Maxwell, James Clerk, 1831-1879 Autorita
- Paracelsus, 1493-1541 Autorita
- Gilbert, William, 1544-1603 Autorita
- Mesmer, Franz Anton, 1734-1815 Autorita
- Hell, Maximilián, 1720-1792 Autorita
- Charcot, Jean Martin, 1825-1893 Autorita
- Arsonval, Jacques Arsene d', 1851-1940 Autorita
- Ørsted, Hans-Christian, 1777-1851 Autorita
- Thalés, asi 624 př. Kr.-asi 548 př. Kr Autorita
- Ampère, André Marie, 1775-1836 Autorita
Recent synthetic efforts aimed at reconstructing the beginning of life on our planet point at the plausibility of scenarios fueled by extraterrestrial energy sources. In the current work we show that beyond nucleobases the sugar components of the first informational polymers can be synthesized in this way. We demonstrate that a laser-induced high-energy chemistry combined with TiO2 catalysis readily produces a mixture of pentoses, among them ribose, arabinose and xylose. This chemistry might be highly relevant to the Late Heavy Bombardment period of Earth's history about 4-3.85 billion years ago. In addition, we present an in-depth theoretical analysis of the most challenging step of the reaction pathway, i.e., the TiO2-catalyzed dimerization of formaldehyde leading to glycolaldehyde.
- MeSH
- arabinosa chemická syntéza MeSH
- dimerizace MeSH
- formaldehyd chemie MeSH
- katalýza MeSH
- planetární evoluce MeSH
- původ života MeSH
- ribosa chemická syntéza MeSH
- sacharidy chemická syntéza MeSH
- titan chemie MeSH
- xylosa chemická syntéza MeSH
- Země (planeta) MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The end of the late heavy bombardment era coincides with the emergence of life on the Earth 4 billion years ago. This coincidence suggests that the impacts of extraterrestrial bodies might have contributed to the formation of the first molecules involved in early living structures. We have simulated a high-energy synthesis of nucleic acid bases from formamide in the impact of an extraterrestrial body. The high-power laser system PALS was employed in simulation of impact plasma by inducing a laser dielectric breakdown in formamide. In hot and dense plasma, formamide decomposed producing reactive radicals. The radicals reacted with formamide and nucleic acid bases were produced. Formamide was pretreated with laser plasma in the presence of catalysts. The products were analyzed by FTIR spectrometry and GC-MS. Time-resolved emission spectra of formamide discharge plasma were measured. Kinetic models and formation pathways for nucleic acid bases were calculated. The results show that the nucleic acid bases can be synthesized in impact plasma involving CN and NH radicals and formamide.
- MeSH
- biogeneze organel MeSH
- formamidy * chemie MeSH
- katalýza MeSH
- lasery využití MeSH
- nukleové kyseliny * chemie MeSH
- plynová chromatografie s hmotnostně spektrometrickou detekcí přístrojové vybavení MeSH
- spektroskopie infračervená s Fourierovou transformací přístrojové vybavení MeSH
- Země (planeta) MeSH
This paper provides an overview of analytical methods frequently used to identify terrestrial radionuclides in samples. While radioactivity is normally measured through the ionising radiation produced during the spontaneous decay of unstable atoms, selected radionuclides or their chemical elements can be quantified with instrumental techniques based on stimulated emission or counting of atoms. The advantages and disadvantages of these analytical methods are discussed. Particular attention is paid to X-ray fluorescence analysis of materials containing uranium and thorium. It is also possible to determine the area distributions of these chemical elements in samples with the use of scanning X-ray fluorescence systems.
- MeSH
- hmotnostní spektrometrie MeSH
- mikroanalýza elektronovou sondou MeSH
- neutronová aktivační analýza MeSH
- poločas MeSH
- radiační pozadí * MeSH
- radioizotopy draslíku analýza MeSH
- radiometrie metody MeSH
- radionuklidy analýza MeSH
- spektrometrie rentgenová emisní * přístrojové vybavení MeSH
- thorium analýza MeSH
- uran analýza MeSH
- Země (planeta) * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Rockström et al. (2009a, 2009b) have warned that humanity must reduce anthropogenic impacts defined by nine planetary boundaries if "unacceptable global change" is to be avoided. Chemical pollution was identified as one of those boundaries for which continued impacts could erode the resilience of ecosystems and humanity. The central concept of the planetary boundary (or boundaries) for chemical pollution (PBCP or PBCPs) is that the Earth has a finite assimilative capacity for chemical pollution, which includes persistent, as well as readily degradable chemicals released at local to regional scales, which in aggregate threaten ecosystem and human viability. The PBCP allows humanity to explicitly address the increasingly global aspects of chemical pollution throughout a chemical's life cycle and the need for a global response of internationally coordinated control measures. We submit that sufficient evidence shows stresses on ecosystem and human health at local to global scales, suggesting that conditions are transgressing the safe operating space delimited by a PBCP. As such, current local to global pollution control measures are insufficient. However, while the PBCP is an important conceptual step forward, at this point single or multiple PBCPs are challenging to operationalize due to the extremely large number of commercial chemicals or mixtures of chemicals that cause myriad adverse effects to innumerable species and ecosystems, and the complex linkages between emissions, environmental concentrations, exposures and adverse effects. As well, the normative nature of a PBCP presents challenges of negotiating pollution limits amongst societal groups with differing viewpoints. Thus, a combination of approaches is recommended as follows: develop indicators of chemical pollution, for both control and response variables, that will aid in quantifying a PBCP(s) and gauging progress towards reducing chemical pollution; develop new technologies and technical and social approaches to mitigate global chemical pollution that emphasize a preventative approach; coordinate pollution control and sustainability efforts; and facilitate implementation of multiple (and potentially decentralized) control efforts involving scientists, civil society, government, non-governmental organizations and international bodies.
Blesk Zdraví ; Ročník 7, číslo 12, příloha prosinec 2014
32 stran : ilustrace ; 15 cm
- MeSH
- interpersonální vztahy MeSH
- krása MeSH
- Měsíc MeSH
- zahradničení MeSH
- zdraví MeSH
- zdravotní výchova MeSH
- Publikační typ
- populární práce MeSH
- Konspekt
- Hygiena. Lidské zdraví
- NLK Obory
- zdravotní výchova
