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1.
Pierre-Alain Monnard H.-J. Ziock 《Origins of life and evolution of the biosphere》2007,37(4-5):469-472
The construction of artificial cells or protocells that are a simplified version of contemporary cells will have implications
for both the understanding of the origins of cellular Life and the design of “cell-like” chemical factories. In this short
communication, we discuss the progress and remaining issues related to the construction of protocells from metabolic products.
We further outline the de novo design of a simple chemical system that mimics the functional properties of a living cell without
being composed of molecules of biological origin, thereby addressing issues related to Life’s origins.
Presented at: International School of Complexity—4th Course: Basic Questions on the Origins of Life; “Ettore Majorana” Foundation
and Centre for Scientific Culture, Erice, Italy, 1–6 October 2006. 相似文献
2.
Francois Raulin 《Origins of life and evolution of the biosphere》2007,37(4-5):345-349
For understanding the origin(s) of life on Earth it is essential to search for and study extraterrestrial environments where
some of the processes which participated in the emergence of Life on our planet are still occurring. This is one of the goals
of astrobiology. In that frame, the study of extraterrestrial organic matter is essential and is certainly not of limited
interest regarding prebiotic molecular evolution. Titan, the largest satellite of Saturn and the only planetary body with
an atmosphere similar to that of the Earth is one of the places of prime interest for these astrobiological questions. It
presents many analogies with the primitive Earth, and is a prebiotic-like laboratory at the planetary scale, where a complex
organic chemistry in is currently going on.
Presented at: International School of Complexity – 4th Course: Basic Questions on the Origins of Life; “Ettore Majorana” Foundation and Centre for Scientific Culture, Erice, Italy, 1–6 October 2006. 相似文献
3.
Summary. Gravity plays an important role for the evolution, orientation and development of organisms. Most of us, however, tend to
overlook its importance because – due to its constant presence from the beginning of evolution some 4 billion years ago –
this environmental parameter is almost hardwired into our interpretation of reality. This negligence of gravity is the more
surprising as we all have our strong fights with this factor, especially during the very early and again during the late phases
of our lives. On the other hand, scientists have been fascinated to observe the effects of gravity especially on plants and
microorganisms for more than a hundred years, since Darwin and Sachs demonstrated the role of the root cap for downward growing
plants. Different experimental approaches are nowadays available in order to change the influence of gravity and to study
the corresponding influences on the physiology of biological systems. With the advent of spaceflight, a long-term nearly nullification
of gravity is possible. Utilisation of this so-called “microgravity” condition for research in life sciences thus became an
important asset in the space programs of various space agencies around the world. The German Space Life Sciences Program is
managed – like all other space programs and activities in Germany – by the German Aerospace Center (DLR) in its role as space
agency for Germany. Within the current space program, approved by the German government in May 2001, the overall goal for
its life sciences part was defined as to gain scientific knowledge and to disclose new application potential by research under
space conditions, especially by utilising the microgravity environment of the International Space Station. Three main scientific
fields have been identified in collaboration with the scientific community: integrative human physiology, biotechnological
applications of the microgravity environment, and fundamental biology of gravity and radiation responses (i.e., gravitational
and radiation biology). In the present contribution, specific goals as well as achievements and perspectives of research in
gravitational biology are given. In addition, some information is provided on spaceflight opportunities available.
Correspondence and reprints: German Aerospace Center (DLR), Space Agency, P.O. Box 300364, 53183 Bonn, Federal Republic of
Germany. 相似文献
4.
Vic Norris Axel Hunding Francois Kepes Doron Lancet Abraham Minsky Derek Raine Robert Root-Bernstein K. Sriram 《Origins of life and evolution of the biosphere》2007,37(4-5):429-432
Five common assumptions about the first cells are challenged by the pre-biotic ecology model and are replaced by the following
propositions: firstly, early cells were more complex, more varied and had a greater diversity of constituents than modern
cells; secondly, the complexity of a cell is not related to the number of genes it contains, indeed, modern bacteria are as
complex as eukaryotes; thirdly, the unit of early life was an ‘ecosystem’ rather than a ‘cell’; fourthly, the early cell needed
no genes at all; fifthly, early life depended on non-covalent associations and on catalysts that were not confined to specific
reactions. We present here the outlines of a theory that connects findings about modern bacteria with speculations about their
origins.
Presented at the International School of Complexity – 4th Course: Basic Questions on the Origins of Life; “Ettore Majorana”
Foundation and Centre for Scientific Culture, Erice, Italy, 1–6 October 2006. 相似文献
5.
Sandra Pizzarello 《Origins of life and evolution of the biosphere》2007,37(4-5):341-344
Astrobiological studies of abiotic organic chemistry, such as it is observed in interstellar molecular clouds or found in
comets and meteorites, offer a glimpse of the chemical evolution that preceded the onset of life. They also allow to evaluate
the possibility that the molecules produced through the long cosmic history of the biogenic elements contributed to the early
Earth organic pool and facilitated prebiotic molecular evolution.
Presented at: International School of Complexity – 4th Course: Basic Questions on the Origins of Life; “Ettore Majorana” Foundation and Centre for Scientific Culture, Erice, Italy, 1–6 October 2006. 相似文献
6.
Peter E. Nielsen 《Origins of life and evolution of the biosphere》2007,37(4-5):323-328
The possibilities of pseudo peptide DNA mimics like PNA (peptide nucleic acid) having a role for the prebiotic origin of life
prior to an RNA world is discussed. In particular a scenario is proposed in which protocells with an achiral genetic material
through several generations stepwise is converted into a chiral genetic material, e.g., by incorporation of RNA units. Provided
that a sufficiently large sequence space is occupied, a selection process based on catalytic function in which a single cell
(first common ancestor) has a definite evolutionary advantage, selection of this cell would by contingency also lock it into
homochirality.
Presented at: International School of Complexity – 4th Course: Basic Questions on the Origins of Life; “Ettore Majorana” Foundation
and Centre for Scientific Culture, Erice, Italy, 1–6 October 2006. 相似文献
7.
E. Walter Helbling M. Eugenia Farías M. Verónica Fernández Zenoff Virginia E. Villafañe 《Hydrobiologia》2006,559(1):123-134
In situ experiments were conducted at various depths in the water column to determine the effects of solar ultraviolet radiation
(UVR, 280–400 nm) on photosynthesis of natural phytoplankton assemblages from the subtropical Lake La Angostura (Argentina,
26°45′ S; 65°37° W, 1980 m asl.). Water samples were taken daily and incubated under three radiation treatments: (a) Samples
exposed to UVR + Photosynthetic Available Radiation (PAR) – PAB treatment (280–700 nm); (b) Samples exposed to ultraviolet-A
radiation (UV-A) + PAR – PA treatment (320–700 nm), and, (c) Samples exposed to PAR only – P treatment (400–700 nm). Additionally,
depth profiles were done to determine different physical (i.e., temperature and underwater radiation field) and biological
characteristics of the water column – photosynthetic pigments, UV-absorbing compounds, cell concentration, deoxyribonucleic
acid (DNA) and cyclobutane pyrimidine dimers (CPDs). The effects of UVR on natural phytoplankton assemblages were significant
only in the first 50 cm of the water column, causing a decrease in photosynthetic rates of 36 and 20% due to UV-A and ultraviolet-B
radiation (UV-B), respectively; below this depth, however, there were no significant differences between radiation treatments.
Concentration of CPDs per mega base of DNA in natural phytoplankton was low, <27 CPDs MB−1 between 0 and 4 m. Data on net DNA damage, together with that on mixing conditions of the water column, suggest that mixing
can favour phytoplankton by allowing cells to be transported to depths where active repair can take place. This mechanism
to reduce UVR-induced DNA damage would be of great advantage for these assemblages dominated by small cyanobacteria and chlorophytes
where UV-absorbing compounds that could act as sunscreens are virtually absent. 相似文献
8.
Enzo Gallori Elisa Biondi Sergio Branciamore 《Origins of life and evolution of the biosphere》2006,36(5-6):493-499
All life forms on Earth share the same biological program based on the DNA/RNA genomes and proteins. The genetic information,
recorded in the nucleotide sequence of the DNA and RNA molecule, supplies the language of life which is transferred through
the different generations, thus ensuring the perpetuation of genetic information on Earth. The presence of a genetic system
is absolutely essential to life. Thus, the appearance in an ancestral era of a nucleic acid-like polymer able to undergo Darwinian
evolution indicates the beginning of life on our planet. The building of primordial genetic molecules, whatever they were,
required the presence of a protected environment, allowing the synthesis and concentration of precursors (nucleotides), their
joining into larger molecules (polynucleotides), the protection of forming polymers against degradation (i.e. by cosmic and
UV radiation), thus ensuring their persistence in a changing environment, and the expression of the “biological” potential
of the molecule (its capacity to self-replicate and evolve). Determining how these steps occurred and how the primordial genetic
molecules originated on Earth is a very difficult problem that still must be resolved. It has long been proposed that surface
chemistry, i.e. on clay minerals, could have played a crucial role in the prebiotic formation of molecules basic to life.
In the present work, we discuss results obtained in different fields that strengthen the hypothesis of a clay-surface-mediated
origin of genetic material.
Presented at: National Workshop on Astrobiology: Search for Life in the Solar System, Capri, Italy, 26 to 28 October, 2005. 相似文献
9.
With growing evidence for a heavy bombardment period ending 4–3.8 billion years ago, meteorites and comets may have been an
important source of prebiotic carbon, nitrogen, and phosphorus on the early Earth. Life may have originated shortly after
the late-heavy bombardment, when concentrations of organic compounds and reactive phosphorus were enough to “kick life into
gear”. This work quantifies the sources of potentially prebiotic, extraterrestrial C, N, and P and correlates these fluxes
with a comparison to total Ir fluxes, and estimates the effect of atmosphere on the survival of material. We find (1) that
carbonaceous chondrites were not a good source of organic compounds, but interplanetary dust particles provided a constant,
steady flux of organic compounds to the surface of the Earth, (2) extraterrestrial metallic material was much more abundant
on the early Earth, and delivered reactive P in the form of phosphide minerals to the Earth’s surface, and (3) large impacts
provided substantial local enrichments of potentially prebiotic reagents. These results help elucidate the potential role
of extraterrestrial matter in the origin of life. 相似文献
10.
Wanda L. Davis Christopher P. McKay 《Origins of life and evolution of the biosphere》1996,26(1):61-73
The field of study that deals with the origins of life does not have a consensus for a theory of life's origin. An analysis of the range of theories offered shows that they share some common features that may be reliable predictors when considering the possible origins of life on another planet. The fundamental datum dealing with the origins of life is that life appeared early in the history of the Earth, probably before 3.5 Ga and possibly before 3.8 Ga. What might be called the standard theory (the Oparin-Haldane theory) posits the production of organic molecules on the early Earth followed by chemical reactions that produced increased organic complexity leading eventually to organic life capable of reproduction, mutation, and selection using organic material as nutrients. A distinct class of other theories (panspermia theories) suggests that life was carried to Earth from elsewhere — these theories receive some support from recent work on planetary impact processes. Other alternatives to the standard model suggest that life arose as an inorganic (clay) form and/or that the initial energy source was not organic material but chemical energy or sunlight. We find that the entire range of current theories suggests that liquid water is the quintessential environmental criterion for both the origin and sustenance of life. It is therefore of interest that during the time that life appeared on Earth we have evidence for liquid water present on the surface of Mars. 相似文献
11.
Karen Olsson-Francis Rosa de la Torre Martin C. Towner Charles S. Cockell 《Origins of life and evolution of the biosphere》2009,39(6):565-579
Cyanobacteria are photosynthetic organisms that have been considered for space applications, such as oxygen production in
bioregenerative life support systems, and can be used as a model organism for understanding microbial survival in space. Akinetes
are resting-state cells of cyanobacteria that are produced by certain genera of heterocystous cyanobacteria to survive extreme
environmental conditions. Although they are similar in nature to endospores, there have been no investigations into the survival
of akinetes in extraterrestrial environments. The aim of this work was to examine the survival of akinetes from Anabaena cylindrica in simulated extraterrestrial conditions and in Low Earth Orbit (LEO). Akinetes were dried onto limestone rocks and sent
into LEO for 10 days on the ESA Biopan VI. In ground-based experiments, the rocks were exposed to periods of desiccation,
vacuum (0.7 × 10−3 kPa), temperature extremes (−80 to 80°C), Mars conditions (−27°C, 0.8 kPa, CO2) and UV radiation (325–400 nm). A proportion of the akinete population was able to survive a period of 10 days in LEO and
28 days in Mars simulated conditions, when the rocks were not subjected to UV radiation. Furthermore, the akinetes were able
to survive 28 days of exposure to desiccation and low temperature with high viability remaining. Yet long periods of vacuum
and high temperature were lethal to the akinetes. This work shows that akinetes are extreme-tolerating states of cyanobacteria
that have a practical use in space applications and yield new insight into the survival of microbial resting-state cells in
space conditions. 相似文献
12.
To establish a relation between biologically effective erythemal radiation (EER) and global solar radiation, the hourly and
daily clear-sky broadband (310–2,800 nm) global solar radiation (G) and spectral ultraviolet radiation incident on a horizontal
surface at Esfahan, Iran (32°37′N, 51°40′E) were measured during the period 2001–2005. Good correlations at statistically
significant levels between the daily values of EER and the daily G were found. The seasonal variability of EER/G is also discussed
and the correction factors are determined for inclusion of vertical column ozone and solar zenith angle (SZA) cycles. The
comparison of the estimated daily EER against the independent observed EER revealed that under clear sky conditions the estimations
are accurate to 10% or better over SZA of 10–60° and column ozone of 250–350 Dobson. The comparison of the results with the
similar works that have used shorter period of experimental data showed more accurate estimates. The deduced relations could
be used to a rough estimate of the daily EER from G in arid climate regions, where there is no measured UV radiation or there
are instrumental and other difficulties encountered in measuring UV radiation. 相似文献
13.
G. G. Bentini M. Bianconi A. Cerutti A. Nubile P. Cerabolini M. Chiarini G. Pennestrì W. Dinicolantonio R. Guzzi 《Origins of life and evolution of the biosphere》2006,36(5-6):597-603
Absorption or emission spectroscopy is a powerful tool for detecting chemical compounds, diluted in fluid media: the sensitivity
of this technique depends on the optical path of the source radiation, on the spectral window used for analysis and on the
spectrometer performances. In this view, we designed and produced the first prototypes of an integrated scanning Fourier Transform
Microinterferometer with Mach–Zehnder geometry, by using MEOS (Micro Electro Optical Systems) technologies. The microdevice,
obtained by fabricating integrated optical waveguides on LiNbO3 (LN) crystals, is electrically driven, without moving parts, by exploiting the electrooptical properties of the material.
The microdevice operates the Fourier Transform of the input radiation spectral distribution, which can be reconstructed starting
from the output signal by means of Fast Fourier Transform (FFT) techniques. The microinterferometer weights few grams, the
power consumption is of a few mW and, in principle, can operate in the LN transmittance range (0.36–4.5 μm). The microinterferometer
performances were preliminary tested in the (0.4–1.7 μm) spectral window. In the Visible region (0.4–0.7 μm) this microsystem
demonstrated a spectral resolution suitable for detecting the characteristic lines of the solar spectrum together with the
absorption bands of common gases present in Earth’s atmosphere. In a further experiment we tested its performances for gas
trace detection by using a calibrated NO2 optical gas cell, showing the possibility to reveal up to 10 ppb, when suitable optical paths are used. Finally, colorimetry
tests for the titration of an organic dye (E131) in alcohol solution are presented.
Presented at: National Workshop on Astrobiology: Search for Life in the Solar System, Capri, Italy, 26 to 28 October, 2005. 相似文献
14.
Living cells are powered by intricate networks of chemical reactions of thousands of molecules. Understanding how living systems emerged through the assembly of chemical processes is one of the biggest challenges in science. Subject Categories: Biotechnology & Synthetic Biology, Evolution & Ecology, MetabolismHow can chemistry turn into biology? How can living cells be built from molecules? These are fundamental questions in biology and, despite much research efforts, remain unanswered. Yet, the past two decades have seen considerable advances in our knowledge of how and which (bio)physical and (bio)chemical processes could have driven the emergence of the first living cells. These achievements have led not only to a better understanding of the molecular origins of life, but also spurred significant developments in synthetic biology, biophysics and supramolecular chemistry. Although the exact events that sparked life on Earth will quite likely remain a mystery, at least partially, exploring the chemical origins of life offers clues about our primordial past and could contribute to shaping our future.
Although the exact events that sparked life on Earth will quite likely remain a mystery […] exploring the chemical origins of life offers clues about our primordial past and could contribute to shaping our future.相似文献
15.
Davide De Lucrezia Fabrizio Anella Cristiano Chiarabelli 《Origins of life and evolution of the biosphere》2007,37(4-5):379-385
The discovery of catalytic RNA has revolutionised modern molecular biology and bears important implications for the origin
of Life research. Catalytic RNA, in particular self-replicating RNA, prompted the hypothesis of an early “RNA world” where
RNA molecules played all major roles such information storage and catalysis. The actual role of RNA as primary actor in the
origin of life has been under debate for a long time, with a particular emphasis on possible pathways to the prebiotic synthesis
of mononucleotides; their polymerization and the possibility of spontaneous emergence of catalytic RNAs synthesised under
plausible prebiotic conditions. However, little emphasis has been put on the chemical reality of an RNA world; in particular
concerning the chemical constrains that such scenario should have met to be feasible. This paper intends to address those
concerns with regard to the achievement of high local RNA molecules concentration and the aetiology of unique sequence under
plausible prebiotic conditions.
Presented at: International School of Complexity – 4th Course: Basic Questions on the Origins of Life; “Ettore Majorana” Foundation and Centre for Scientific Culture, Erice, Italy, 1–6 October 2006. 相似文献
16.
Witold Szaflarski Knud H. Nierhaus 《Origins of life and evolution of the biosphere》2007,37(4-5):423-428
In our previous contribution (Nierhaus, Orig Life Evol Biosph, this volume, 2007) we mentioned that life had solved the problem
of energy supply in three major steps, and that these steps also mark major stages during the development of life. We further
outlined a possible scenario concerning a minimal translational apparatus focusing on the essential components necessary for
protein synthesis. Here we continue that consideration by addressing on one of the main problems of early life, namely avoiding
wasteful energy loss. With regard to the limiting energy supply of early living systems, i.e. those of say more than 3,000 Ma,
a carefully controlled and product oriented energy consumption was in demand. In recent years we learned how a bacterial cell
avoids energy drain, thus being able to pump most of the energy into protein synthesis. These lessons must be followed by
the design of a minimal living system, which is surveyed in this short article.
Presented at the International School of Complexity – 4th Course: Basic Questions on the Origins of Life; “Ettore Majorana”
Foundation and Centre for Scientific Culture, Erice, Italy, 1–6 October 2006. 相似文献
17.
G. Galletta F. Ferri G. Fanti M. D’Alessandro G. Bertoloni D. Pavarin C. Bettanini P. Cozza P. Pretto G. Bianchini S. Debei 《Origins of life and evolution of the biosphere》2006,36(5-6):625-627
The Martian Environment Simulator (SAM “Simulatore di Ambiente Marziano”) is a interdisciplinary project of Astrobiology done at University of Padua. The research is aimed to the study of the survival
of the microorganisms exposed to the “extreme” planetary environment. The facility has been designed in order to simulate
Mars’ environmental conditions in terms of atmospheric pressure, temperature cycles and UV radiation dose. The bacterial cells,
contained into dedicated capsules, will be exposed to thermal cycles simulating diurnal and seasonal Martian cycles. The metabolism
of the different biological samples will be analysed at different phases of the experiment, to study their survival and eventual
activity of protein synthesis (mortality, mutations and capability of DNA reparing). We describe the experimental facility
and provide the perspectives of the biological experiments we will perform in order to provide hints on the possibility of
life on Mars either autochthonous or imported from Earth.
Presented at: National Workshop on Astrobiology: Search for Life in the Solar System, Capri, Italy, 26 to 28 October, 2005. 相似文献
18.
Francesco Saverio Ambesi Impiombato Francesco Curcio Antonella Meli Anna Maria Zambito 《Origins of life and evolution of the biosphere》2006,36(5-6):577-585
The present project has been developed because of the desire to unify the research lines in the A.S.I. ‘Medicine & Biotechnology’
area into one research line that could satisfy the interests of all of the collaborative groups and at the same time could
pursue a relevant social goal. A 6 month feasibility study (SF) called MoMa was carried out in the ASI framework. During the
SF the know-how and the tools already available in the national scientific community have been assessed, selected and evaluated
even with the important contribution of Small and Medium-size Enterprises (SME) and of Italian industries already involved
in Space Research. As result of the SF MoMa, all of the participants decided to combine all the efforts together and define,
with all the know-how and the available technologies, one strategic topic, the “Aging” with a special attention to the Quality
of Life (QoL).
The space environment is a unique laboratory to study the reaction of living organisms (especially humans) to microgravity
and cosmic radiation. The study of the effects of these two variables at the molecular and cellular levels will shed light
on the response of cells and living organisms to adverse stimulations that are always present even on Earth and will help
us able to develop the best strategies to protect the organisms from the progressive structural and functional decline related
to Aging. Relevant spin-offs on Earth and also relevant industrial applications are the expected outputs of this project.
Presented at: National Workshop on Astrobiology: Search for Life in the Solar System, Capri, Italy, 26 to 28 October, 2005. 相似文献
19.
The European light dosimeter network of over 40 stations has been established in Europe and other continents equipped with
three-channel filter dosimeters to measure solar radiation in three channels, UV-B (280–315 nm), UV-A (315–400 nm) and photosynthetically
active radiation (PAR). The recorded data have been evaluated, and the monthly doses in all three channels show a strong latitudinal
dependence from northern Sweden to the Canary Islands. There are a few remarkable exceptions such as the data recorded at
the high mountain station on the Zugspitze (German Alps) and unequal doses at stations at comparable latitudes which indicate
the impact of local weather conditions and mean sunshine hours. While generally peak values are recorded in the months of
June and July, the UV-B maxima are shifted later into the year, which is due to the antagonistic functions of decreasing solar
angles and increasing transparency of the atmosphere as the total column ozone decreases in the second half of the year for
the Northern Hemisphere. This is supported by comparison with modelled total column ozone and satellite-based measurements.
Also the ratios of UV-B:UV-A and UV-B:PAR as well as UV-A:PAR peak during the summer months, with the exception of the northernmost
station at Abisko (north Sweden) where the UV-A:PAR ratio peaks in the winter months which is due to the specific photoclimatic
conditions north of the polar circle. The penetration of solar radiation into the water column was found to strongly depend
on the transparency of the water column. In Gran Canaria more than 10% of the surface UV-B penetrated to 4–5 m depth. The
path of the solar eclipse on 11 August 1999 could be followed in several stations with different degrees of occlusion of the
sun disk.
Received in revised form: 12 May 2000
Electronic Publication 相似文献
20.
Kellerer AM 《Radiation and environmental biophysics》2000,39(1):17-24
The risk of low-dose radiation exposures has – for a variety of reasons – been highly politicised. This has led to a frequently
exaggerated perception of the potential health effects, and to lasting public controversies. A balanced view requires a critical
reassessment of the epidemiological basis of current assumptions. There is reliable quantitative information available on
the increase of cancer rates due to moderate and high doses. This provides a firm basis for the derivation of probabilities
of causation, e.g. after high radiation exposures. For small doses or dose rates, the situation is entirely different: potential
increases of cancer rates remain hidden below the statistical fluctuations of normal rates, and the molecular mechanisms of
cancerogenesis are not sufficiently well known to allow numerical predictions. Risk coefficients for radiation protection
must, therefore, be based on the uncertain extrapolation of observations obtained at moderate or high doses. While extrapolation
is arbitrary, it is, nevertheless, used and mostly with the conservative assumption of a linear dose dependence with no threshold
(LNT model). All risk estimates are based on this hypothesis. They are, thus, virtual guidelines, rather than firm numbers.
The observations on the A-bomb survivors are still the major source of information on the health effects of comparatively
small radiation doses. A fairly direct inspection of the data shows that the solid cancer mortality data of the A-bomb survivors
are equally consistent with linearity in dose and with reduced effectiveness at low doses. In the leukemia data a reduction
is strongly indicated. With one notable exception – leukemia after prenatal exposure – these observations are in line with
a multitude of observations in groups of persons exposed for medical reasons. The low-dose effects of densely ionizing radiations
– such as alpha-particles from radon decay products or high-energy neutrons – are a separate important issue. For neutrons,
there is little epidemiological information. This has facilitated exaggerated claims of high neutron effects with reference
to alleged dangers from transports of reactor fuel. However, in spite of limited information, it can be shown that the data
from Hiroshima exclude the stated claims. New dosimetric information on neutrons may turn out to be highly informative with
regard to an upper limit for the potential effects of neutrons and equally with regard to a reassessment – and a possible
reduction – of risk estimates for gamma-rays.
Received: 13 November 1999 / Accepted in revised form: 13 December 1999 相似文献