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Showing papers by "Radboud University Nijmegen published in 1996"


Journal ArticleDOI
TL;DR: In this paper, the authors present a theory of self-organization of behaviour in the human brain, focusing on the brain's ability to learn and adapt to the external world.
Abstract: Part 1 How nature handles complexity: what is a pattern? kinds of patterns principles of dynamic pattern formation the messages of self-organized patterns new laws to be expected in the organism matters of mind and matter the mind revealed? or, what this book's about. Part 2 Self-organization of behaviour - the basic picture: some historical remarks about the science of psychology are actions self-organized? if so, how? from synergies to synergetics requirements of a theory of self-organized behaviour. Part 3 Self-organization of behaviour - first steps of generalization: Hubris tempered? on Harvard horses and Russian cats coordination between components of an organism coordination between organisms on coupling. Part 4 Extending the basic picture - breaking away: relative coordination relative coordination explained absolute and relative coordination unified related models - fireflies, lampreys, and lasers instability and the nature of life - the intermittency mechanism exposed postscript. Part 5 Intentional dynamics: goal-directness in biology the second cornerstone of biological self-organization - informational specificity intentional behaviourial change related views - termites, predator-prey cycles, and quantum mechanics summing up. Part 6 Learning dynamics: issues in learning the main concepts the 'seagull effect' - competition and cooperation questions of learning transfer and generalization - symmetry again behaviourial development evolution and morphogenesis summary and conclusions. Part 7 perceptual dynamics: the barrier of meaning - perceptual dynamics I the barrier of meaning - perceptual dynamics II metastability of mind principles of perceiving - calculating, settling, resonating, and twinkling. Part 8 Self-organizing dynamics of the nervous system: microscale events mesoscale events macroscale events extending the basic picture...again postscript on etymology. Part 9 Self-organization of the human brain: prolegomenon obstacles to understanding the brain is not a static machine the 'brain dynamics' approach - fractural dimension spatiotemporal patterns of the brain models of brain behaviour - coupled modes and Sil'nikov chaos summary and conclusions - brain behaviour.

2,486 citations


Journal Article
TL;DR: It is concluded that heterozygosity for CBS deficiency does not appear to be involved in premature cardiovascular disease, however, a frequent homozygous mutation in the MTHFR gene is associated with a threefold increase in risk for prematurely cardiovascular disease.
Abstract: Mild hyperhomocysteinemia is an established risk factor for cardiovascular disease. Genetic aberrations in the cystathionine beta-synthase (CBS) and methylenetetrahydrofolate reductase (MTHFR) genes may account for reduced enzyme activities and elevated plasma homocysteine levels. In 15 unrelated Dutch patients with homozygous CBS deficiency, we observed the 833T-->C (I278T) mutation in 50% of the alleles. Very recently, we identified a common mutation (677C-->T; A-->V) in the MTHFR gene, which, in homozygous state, is responsible for the thermolabile phenotype and which is associated with decreased specific MTHRF activity and elevated homocysteine levels. We screened 60 cardiovascular patients and 111 controls for these two mutations, to determine whether these mutations are risk factors for premature cardiovascular disease. Heterozygosity for the 833T-->C mutation in the CBS gene was observed in one individual of the control group but was absent in patients with premature cardiovascular disease. Homozygosity for the 677C-->T mutation in the MTHFR gene was found in (15%) of 60 cardiovascular patients and in only 6 (approximately 5%) of 111 control individuals (odds ratio 3.1 [95% confidence interval 1.0-9.2]). Because of both the high prevalence of the 833T-->C mutation among homozygotes for CBS deficiency and its absence in 60 cardiovascular patients, we may conclude that heterozygosity for CBS deficiency does not appear to be involved in premature cardiovascular disease. However, a frequent homozygous mutation in the MTHFR gene is associated with a threefold increase in risk for premature cardiovascular disease.

672 citations


Journal ArticleDOI
TL;DR: Cowden disease (CD) (MIM 158350), or multiple hamartoma syndrome, is a rare autosomal dominant familial cancer syndrome with a high risk of breast cancer and central nervous system manifestations of CD were emphasized only recently.
Abstract: Cowden disease (CD) (MIM 158350), or multiple hamartoma syndrome, is a rare autosomal dominant familial cancer syndrome with a high risk of breast cancer. Its clinical features include a wide array of abnormalities but the main characteristics are hamartomas of the skin, breast, thyroid, oral mucosa and intestinal epithelium. The pathognomonic hamartomatous features of CD include multiple smooth facial papules, acral keratosis and multiple oral papillomas. The pathological hallmark of the facial papules are multiple trichilemmomas. Expression of the disease is variable and penetrance of the dermatological lesions is assumed to be virtually complete by the age of twenty. Central nervous system manifestations of CD were emphasized only recently and include megalencephaly, epilepsy and dysplastic gangliocytomas of the cerebellum (Lhermitte-Duclos disease, LDD). Early diagnosis is important since female patients with CD are at risk of developing breast cancer. Other lesions include benign and malignant disease of the thyroid, intestinal polyps and genitourinary abnormalities. To localize the gene for CD, an autosomal genome scan was performed. A total of 12 families were examined, resulting in a maximum lod score of 8.92 at theta = 0.02 with the marker D10S573 located on chromosome 10q22-23.

622 citations


Journal ArticleDOI
TL;DR: Current experiments aim to unravel the adaptive mechanisms whereby terrestrial plants cope with the peculiar conditions of the floodplain, from the whole plant down to the cell.
Abstract: Floodplains and wetlands are highly suitable for plant ecological studies, whether for agricultural interests, nature conservation or basic science. Traditional work has entailed a descriptive approach at the community or individual plant level. Nowadays these studies are evolving into physiological research on relationships between flooding stress and vegetation zonation. Current experiments aim to unravel the adaptive mechanisms whereby terrestrial plants cope with the peculiar conditions of the floodplain, from the whole plant down to the cell.

457 citations


Journal ArticleDOI
TL;DR: In a prospective follow-up study of patients with early-onset rheumatoid arthritis, the prevalence of remission according to the 1981 American Rheumatism Association (ARA) preliminary criteria was evaluated and the DAS was proposed as a tool to define remission.
Abstract: In a prospective follow-up study of patients with early-onset rheumatoid arthritis, the prevalence of remission according to the 1981 American Rheumatism Association (ARA) preliminary criteria was evaluated. A total of 227 patients with a median follow-up of 3.9 yr and a total of 2832 follow-up visits were studied. The ARA remission criteria were fulfilled in 9.5% of these visits. The percentage of patients with at least one visit fulfilling the ARA criteria was for years 2-6 approximately 25%. Each year, approximately 15% of the patients were in remission for at least two consecutive visits. A comparison was made between the ARA remission criteria and the Disease Activity Score (DAS). DAS < 1.6 corresponded with being in remission according to the ARA criteria. The DAS is being proposed as a tool to define remission because absence of disease activity should be measured using the same method as for higher levels of disease activity, preferably on a continuous scale.

399 citations


Journal ArticleDOI
TL;DR: The clinical, immunological, chromosomal, and cell biological findings resemble those in AT, but the clinical findings are quite different and NBS appears to be a separate entity not allelic with AT.
Abstract: Nijmegen breakage syndrome (NBS), a rare autosomal recessive condition also known as ataxia telangiectasia (AT) variants V1 and V2, is characterised by microcephaly, typical facies, short stature, immunodeficiency, and chromosomal instability. We report the clinical, immunological, chromosomal, and cell biological findings in 42 patients who are included in the NBS Registry in Nijmegen. The immunological, chromosomal, and cell biological findings resemble those in AT, but the clinical findings are quite different. NBS appears to be a separate entity not allelic with AT.

365 citations


Journal ArticleDOI
TL;DR: The contention that simple loss– or gain–of–expression of DMPK is not the only crucial requirement for development of the disease is strengthened.
Abstract: Myotonic dystrophy (DM) is commonly associated with CTG repeat expansions within the gene for DM–protein kinase (DMPK). The effect of altered expression levels of DMPK, which is ubiquitously expressed in all muscle cell lineages during development, was examined by disrupting the endogenous Dmpk gene and overexpressing a normal human DMPK transgene in mice. Nullizygous (−/−) mice showed only inconsistent and minor size changes in head and neck muscle fibres at older age, animals with the highest DMPK transgene expression showed hypertrophic cardiomyopathy and enhanced neonatal mortality. However, both models lack other frequent DM symptoms including the fibre–type dependent atrophy, myotonia, cataract and male–infertility. These results strengthen the contention that simple loss– or gain–of–expression of DMPK is not the only crucial requirement for development of the disease.

344 citations


Proceedings Article
03 Dec 1996
TL;DR: This work proposes a new method to compute prediction intervals that is better than existing methods with regard to extrapolation and interpolation in data regimes with a limited amount of data, and yields prediction intervals which actual confidence levels are closer to the desired confidence levels.
Abstract: We propose a new method to compute prediction intervals. Especially for small data sets the width of a prediction interval does not only depend on the variance of the target distribution, but also on the accuracy of our estimator of the mean of the target, i.e., on the width of the confidence interval. The confidence interval follows from the variation in an ensemble of neural networks, each of them trained and stopped on bootstrap replicates of the original data set. A second improvement is the use of the residuals on validation patterns instead of on training patterns for estimation of the variance of the target distribution. As illustrated on a synthetic example, our method is better than existing methods with regard to extrapolation and interpolation in data regimes with a limited amount of data, and yields prediction intervals which actual confidence levels are closer to the desired confidence levels.

339 citations


Journal ArticleDOI
TL;DR: The findings suggest that the long-sought RP3 gene is cloned, and that it may encode the GEF of a retina-specific GTP-binding protein, the guanine-nucleotide-exchange factor of the Ras-like GTPase Ran.
Abstract: The gene for retinitis pigmentosa 3 (RP3), the most frequent form of X-linked RP (XLRP), has been mapped previously to a chromosome interval of less than 1000 kbp between the DXS1110 marker and the OTC locus at Xp21.1-p11.4. Employing a novel technique, YAC Representation Hybridization (YRH)', we have recently identified a small XLRP associated microdeletion in this interval, as well as several putative exons including the 3' end of a gene that was truncated by the deletion. cDNA library screening and sequencing of a cosmid centromeric to the deletion has now enabled us to identify numerous additional exons and to detect several point mutations in patients with XLRP. The predicted gene product shows homology to RCC1, the guanine-nucleotide-exchange factor (GEF) of the Ras-like GTPase Ran. Our findings suggest that we have cloned the long-sought RP3 gene, and that it may encode the GEF of a retina-specific GTP-binding protein.

329 citations


Journal ArticleDOI
TL;DR: Experimental data on particle correlations and fluctuations in various high-energy multiparticle collisions are presented, with special emphasis on evidence for scaling-law evolution in small phase-space domains as mentioned in this paper.

309 citations


Journal ArticleDOI
TL;DR: A mutation of the human gene for endothelin 3 (EDN3), homozygously present in a patient with a combined Waardenburg syndrome type 2 and HSCR phenotype, is described and a novel mutation detected in one of 40 unselected H SCR patients is reported.
Abstract: Hirschsprung disease (HSCR) or colonic agan-glionosis is a congenital disorder characterized by an absence of intramural ganglia along variable lengths of the colon resulting in intestinal obstruction. The incidence of HSCR is 1 in 5,000 live births. Mutations in the RET gene1–2, which codes for a receptor tyrosine kinase, and in EDNRB3 which codes for the endothelin-B receptor, have been shown to be associated with HSCR in humans. The lethal-spotted mouse which has pigment abnormalities, but also colonic aganglionosis, carries a mutation in the gene coding for endothelin 3 (Edn3)4, the ligand for the receptor protein encoded by EDNRB. Here, we describe a mutation of the human gene for endothelin 3 (EDN3), homozygously present in a patient with a combined Waardenburg syndrome type 2 (WS2) and HSCR phenotype (Shah-Waardenburg syndrome5). The mutation, Cys159Phe, in exon 3 in the ET-3-like domain of EDN3, presumably affects the proteolytic processing of the preproendothelin to the mature peptide EDN3. The patient's parents were first cousins. A previous child in this family had been diagnosed with a similar combination of HSCR, depigmentation and deafness. Depigmentation and deafness were present in other relatives. Moreover, we present a further indication for the involvement of EDNRB in HSCR by reporting a novel mutation detected in one of 40 unselected HSCR patients.

Journal ArticleDOI
TL;DR: In patients with severe heart failure, high dose furosemide administered as a continuous infusion is more efficacious than bolus injection and causes less ototoxic side effects.

Journal Article
TL;DR: KAI1 protein expression is consistently down-regulated during the progression of human prostatic cancer and that this down-regulation does not commonly involve either mutation or allelic loss of the KAI1 gene.
Abstract: The KAI1 gene, located on human chromosome 11p11.2, suppresses tumor metastasis when expressed in certain cancer cells. To evaluate whether dysregulation of KAI1 occurs during the progression of human prostatic cancer, protein expression, mutation, and allelic loss of KAI1 were analyzed using a tissue bank of 98 primary cancers and 32 metastases. By immunohistochemical staining, high levels of KAI1 protein are detected in the epithelial but not stromal compartment of normal prostatic and benign prostatic hyperplasia tissue. In epithelial cells, KAI1 protein is expressed on the plasma membrane. KAI1 protein expression is downregulated in more than 70% of the 49 primary prostatic cancers from untreated patients. In 10 such untreated patients, down-regulation of KAI1 protein occurred in all of the lymph node metastases examined. In 15 patients with metastatic disease who had failed androgen ablation therapy, more than 90% of the primary prostatic cancers had downregulation, with 60% having no KAI1 protein expression. Primers derived from the sequences flanking each exon of KAI1 were used to analyze KAI1 mutation and allelic loss by the method of PLR-single-strand conformational polymorphism. Using this method, no point mutation or allelic loss was detected in metastases from 10 patients. No allelic loss was detected in an additional 34 primary and 12 lymph node metastases via microsatellite analysis using the marker D11S1344, which is located in the region of KAI1. These results demonstrate that KAI1 protein expression is consistently down-regulated during the progression of human prostatic cancer and that this down-regulation does not commonly involve either mutation or allelic loss of the KAI1 gene.

Journal ArticleDOI
TL;DR: Results suggest that in a group of patients with active systemic sclerosis, low-dose MTX seems to be more effective than placebo according to pre-defined response criteria.
Abstract: In this study, methotrexate (MTX) was compared with placebo in the treatment of systemic sclerosis (scleroderma, SSc) in a 24 week randomized double-blind trial, followed by an observational trial of 24 weeks duration. Twenty-nine scleroderma patients were allocated to receive weekly injections of either 15 mg MTX or placebo. Patients who responded favourably after 24 weeks continued with the same regimen for a further 24 weeks; those who showed a poor response on placebo were allocated to further treatment with 15 mg MTX weekly, and those who responded poorly to treatment with 15 mg MTX had their doses increased to 25 mg. A favourable response was defined as an improvement of total skin score (TSS) by > or = 30%, of single breath diffusion capacity (DLCO) by > or = 15%, or of the score on a visual analogue scale of general well-being (VAS) by > or = 30%, provided that such improvements were not accompanied by persistent digital ulcerations or worsening of DLCO > or = 15%. Seventeen patients were allocated to MTX treatment and 12 to treatment with placebo. After 24 weeks, a significantly larger number of patients receiving MTX (n = 8, 53%) who completed the first 24 weeks of the study had responded favourably compared to patients receiving placebo (n = 1, 10%, P = 0.03). Comparison of separate variables between the two treatment groups by intention-to-treat analysis at week 24 showed improvement in the MTX group of TSS (P = 0.06) and creatinine clearance (P = 0.07). At week 48, 13 patients received MTX from the start of the study and nine during 24 weeks. From these 22 patients, 15(68%) responded favourably and compared with the start of the study they showed significant improvement of TSS (P = 0.04), VAS (P = 0.02), grip strength of the right hand (P = 0.02) and ESR (P = 0.01). Although the number of patients enrolled in this study is small, these results suggest that in a group of patients with active systemic sclerosis, low-dose MTX seems to be more effective than placebo according to pre-defined response criteria.

Journal ArticleDOI
TL;DR: The techniques developed here can be used to obtain a complete characterization of the mechanical properties of trabecular architecture and with the development of in vivo reconstruction techniques, even in vivo measurements will be possible.

Journal ArticleDOI
TL;DR: Differences between females and males were detected in the phases of sexual activity that resulted in Fos immunoreactivity in these brain areas, allowing more insight in the nature of the sensory and hormonal stimuli leading to the induction of Fos Immunoreactivity.

Journal ArticleDOI
TL;DR: It may be concluded that future research of health risks of nursing work should have a wider focus than the relation between physical workload and low back pain.
Abstract: OBJECTIVES: To determine the prevalence of musculoskeletal complaints of the back, arms or neck, and legs among nurses, and to investigate the relation between these complaints and various work related and personal variables. METHODS: A questionnaire survey was carried out in four nursing homes in The Netherlands. RESULTS: The response was 95% and resulted in 846 completed questionnaires. It was found that a large proportion of the subjects regularly had back complaints (36%) but also had arm or neck (30%) and leg complaints (16%). Almost all respondents (89%) considered nursing work as physically strenuous. Most of them complained of working under time pressure (69%), increased work pressure (70%), and having no opportunity to take a break from the work (70%). The physical variables which seem to trouble the subjects most were lifting (65%), working in awkward postures (47%), and stooping (34%). Moreover, 53% of the subjects responded that the ergonomic lay out of the ward was disagreeable. Most of the work related variables under study seemed to be associated with musculoskeletal complaints. For all types of complaints the strongest associations were found with having to lift heavy loads. Apart from physical stress various aspects of work pressure showed strong associations with the occurrence of musculoskeletal complaints. The variables on the ergonomy of the ward showed less clear associations with musculoskeletal complaints than were found for physical stress and work pressure. CONCLUSIONS: From these results it may be concluded that future research of health risks of nursing work should have a wider focus than the relation between physical workload and low back pain.

Journal ArticleDOI
TL;DR: Two-dimensional (2D) spin-diffusion experiments show that the alanine-rich domains of the protein form β-sheet structures in agreement with one-dimensional NMR results from a different species of the genus Nephila but at variance with diffraction results.
Abstract: The local structure of dragline silk from the spider Nephila madagascariensis is investigated by solid-state nuclear magnetic resonance. Two-dimensional (2D) spin-diffusion experiments show that th...

Journal ArticleDOI
01 Feb 1996-Bone
TL;DR: It was found that osteocyte death was not related to age, nor was it increased in osteoporosis compared with the controls, which are compatible with the hypothesis that, in osteopsorosis, osteoblasts produce less bone per cell.

Journal ArticleDOI
TL;DR: It is concluded that under the circumstances of this study magnitude of force is not decisive in determining the rate of bodily tooth movement, but individual characteristics are.

Journal ArticleDOI
TL;DR: It is shown that longevity and length of connection covary negatively, yielding two distinct clonal growth strategies (fragmenting versus compact, persistent clones) with a preference for the more common habitat trait combinations: nutrient-rich, shaded and/or wet versus nutrient-poor, open and/ or dry, respectively.
Abstract: Somatic embryogenesis is a phylogenetically ancient trait that allows sessile plants to grow in a modular fashion and to respond plastically to different environmental cues. It facilitates damage repair and permits clonal growth, the capacity to produce potentially independent but genetically identical offspring. Clonal growth is observed to originate from both the shoot or the root part of the plant body and it has been assigned various ecological functions such as reproduction, exploitation and persistence. These functions are rooted in two basic morphological characteristics of clonal growth: the longevity and the length of the connection between clonal parts. Clonality, although an ancient trait, shows a polyphyletic distribution among plant taxa with a strong representation especially among monocots. Phylogenetically controlled comparisons show that clonality is more common among species that occur in cold or nutrient-poor habitats and under poor light conditions. The frequent occurrence of clonals among aquatic species is confounded by the fact that many aquatics are monocots. This however does not necessarily preclude a functional ecological explanation. It is further shown that longevity and length of connection covary negatively, yielding two distinct clonal growth strategies (fragmenting versus compact, persistent clones) with a preference for the more common habitat trait combinations: nutrient-rich, shaded and/or wet versus nutrient-poor, open and/or dry, respectively.

Journal ArticleDOI
TL;DR: The isolation and characterization of the human AQP4 cDNAs and genomic DNA is reported, and RNase protection revealed distinct transcripts corresponding to M1 and M23 mRNAs, and AQP 4 immunoblots of cerebellum demonstrated reactive polypeptides of 31 and 34 kDa.
Abstract: The aquaporin family of membrane water transport proteins are expressed in diverse tissues, and in brain the predominant water channel protein is AQP4. Here we report the isolation and characterization of the human AQP4 cDNAs and genomic DNA. Two cDNAs were isolated corresponding to the two initiating methionines (M1 in a 323-aa polypeptide and M23 in a 301-aa polypeptide) previously identified in rat [Jung, J.S., Bhat, R.V., Preston, G.M., Guggino, W.B. & Agre, P. (1994) Proc. Natl. Acad. Sci. USA 91, 13052-13056]. Similar to other aquaporins, the AQP4 gene is composed of four exons encoding 127, 55, 27, and 92 amino acids separated by introns of 0.8, 0.3, and 5.2 kb. Unlike other aquaporins, an alternative coding initiation sequence (designated exon 0) was located 2.7 kb upstream of exon 1. When spliced together, M1 and the subsequent 10 amino acids are encoded by exon 0; the next 11 amino acids and M23 are encoded by exon 1. Transcription initiation sites have been mapped in the proximal promoters of exons 0 and 1. RNase protection revealed distinct transcripts corresponding to M1 and M23 mRNAs, and AQP4 immunoblots of cerebellum demonstrated reactive polypeptides of 31 and 34 kDa. Using a P1 and a lambda EMBL subclone, the chromosomal site of the human AQP4 gene was mapped to chromosome 18 at the junction of q11.2 and q12.1 by fluorescence in situ hybridization. These studies may now permit molecular characterization of AQP4 during human development and in clinical disorders.

Journal ArticleDOI
TL;DR: The authors argue that output plays an important role in second language acquisition, in particular because it generates highly specific input the cognitive system needs to build up a coherent set of knowledge, and that output also plays a direct role in enhancing fluency by turning declarative knowledge into procedural knowledge.
Abstract: In this article I attempt to elucidate the psycholinguistic mechanics of Swain’s “output hypothesis.” Taking the information processing approach as a starting point and relating that to Levelt’s model of language production and Anderson’s learning theory, I argue that output serves an important role in second language acquisition, in particu­ lar because it generates highly specific input the cognitive system needs to build up a coherent set of knowledge. Output also plays a direct role in enhancing fluency by turning declarative knowledge into procedural knowledge. Output can also play an indirect role in the acquisition of declarative knowledge by triggering input that the learner can use for the generation of new declarative knowledge. On the basis of an analysis of think-aloud protocols, I hypothesize that the locus of the effect of output is in the transition of declarative to procedural knowledge.

Journal ArticleDOI
TL;DR: From the results of this study it is suggested that 600 degrees C is probably the best annealing temperature to obtain a better characterization and understanding of the coating.

Journal ArticleDOI
TL;DR: The present knee model can realistically simulate the passive motion characteristics of the human knee joint and compensated for the lack of menisci and capsular structures by higher prestrains, thereby overestimating the ligament forces.

Journal ArticleDOI
TL;DR: Results showed that the ridge width is the most important parameter, since varying the groove width and groove depth did not affect the RDF size, shape, nor the angle of cellular orientation.

Journal ArticleDOI
TL;DR: The (X;1)(p11;q21) translocation is a recurrent chromosomal abnormality in a subset of human papillary renal cell carcinomas, and is sometimes the sole cytogenetic abnormality present.
Abstract: The (X;1)(p11;q21) translocation is a recurrent chromosomal abnormality in a subset of human papillary renal cell carcinomas, and is sometimes the sole cytogenetic abnormality present. Via positional cloning, we were able to identify the genes involved. The translocation results in a fusion of the transcription factor TFE3 gene on the X chromosome to a novel gene, designated PRCC, on chromosome 1. Through this fusion, reciprocal translocation products are formed, which are both expressed in papillary renal cell carcinomas. PRCC is ubiquitously expressed in normal adult and fetal tissues and encodes a putative protein of 491 aa with a relatively high content of prolines. No relevant homologies with known sequences at either the DNA or the protein level were found.

Journal ArticleDOI
TL;DR: In order to quantify the effect of the substrata surface topography on cellular behaviour, planar and micro-textured silicon substrata were produced and made suitable for cell culture by radio frequency glow discharge treatment and RDF size, shape and orientation proved to be almost comparable to the SilD00 substrata.

Journal ArticleDOI
TL;DR: Cavity ring down absorption spectroscopy with a continuous light source is used to measure the transition frequencies and absolute absorption coefficient of the weak b1Σg+(v′ = 2) ← X 3 Σg−(v″ = 0) transition of 18O2.

Journal ArticleDOI
TL;DR: The reaction of iron sulfide with H2S in water, in presence of CO2 under anaerobic conditions was found to yield H2 and a variety of organic sulfur compounds, mainly thiols and small amounts of CS2 and dimethyldisulfide, which could replace the need for a reducing atmosphere on the primitive earth.
Abstract: The reaction of iron sulfide (FeS) with H2S in water, in presence of CO2 under anaerobic conditions was found to yield H2 and a variety of organic sulfur compounds, mainly thiols and small amounts of CS2 and dimethyldisulfide. The same compounds were produced when H2S was replaced by HCl, in the H2S-generating system FeS/HCl/CO2. The identification of the products was confirmed by GC-MS analyses and the incorporation of H2 in the organic sulfur compounds was demonstrated by experiments in which all hydrogen compounds were replaced by deuterium compounds. Generation of H2 and the synthesis of thiols were both dependent upon the relative abundance of FeS and HCl or H2S, i.e. the FeS/HCl- or FeS/H2S-proportions. Whether thiols or CS2 were formed as the main products depended also on the FeS/HCl-ratio: All conditions which create a H2 deficiency were found to initiate a proportional increase in the amount of CS2. The quantities of H2 and thiols generated depended on temperature: the production of H2 was significantly accelerated from 50 degrees C onward and thiol synthesis above 75 degrees C. The yield of thiols increased with the amount of FeS and HCl (H2S), given a certain FeS/HCl-ratio and a surplus of CO2. A deficiency of CO2 results in lower thiol synthesis. The end product, pyrite (FeS2), was found to appear as a silvery granular layer floating on the aqueous surface. The identity of the thiols was confirmed by mass spectrometry, and the reduction of CO2 demonstrated by the determination of deuterium incorporation with DCl and D2O. The described reactions can principally proceed under the conditions comparable to those obtaining around submarine hydrothermal vents, or the global situation about 4 billion years ago, before the dawn of life, and could replace the need for a reducing atmosphere on the primitive earth.