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  • Humans  (26,754)
  • Analytical Chemistry and Spectroscopy  (25,033)
  • 1
    facet.materialart.
    Unknown
    Frontiers Media SA
    Publication Date: 2024-03-31
    Description: Echolocation has evolved in different groups of animals, from bats and cetaceans to birds and humans, and enables localization and tracking of objects in a dynamic environment, where light levels may be very low or absent. Nature has shaped echolocation, an active sense that engages audiomotor feedback systems, which operates in diverse environments and situations. Echolocation production and perception vary across species, and signals are often adapted to the environment and task. In the last several decades, researchers have been studying the echolocation behavior of animals, both in the air and underwater, using different methodologies and perspectives. The result of these studies has led to rich knowledge on sound production mechanisms, directionality of the sound beam, signal design, echo reception and perception. Active control over echolocation signal production and the mechanisms for echo processing ultimately provide animals with an echoic scene or image of their surroundings. Sonar signal features directly influence the information available for the echolocating animal to perceive images of its environment. In many echolocating animals, the information processed through echoes elicits a reaction in motor systems, including adjustments in subsequent echolocation signals. We are interested in understanding how echolocating animals deal with different environments (e.g. clutter, light levels), tasks, distance to targets or objects, different prey types or other food sources, presence of conspecifics or certain predators, ambient and anthropogenic noise. In recent years, some researchers have presented new data on the origins of echolocation, which can provide a hint of its evolution. Theoreticians have addressed several issues that bear on echolocation systems, such as frequency or time resolution, target localization and beam-forming mechanisms. In this Research Topic we compiled recent work that elucidates how echolocation – from sound production, through echolocation signals to perception- has been shaped by nature functioning in different environments and situations. We strongly encouraged comparative approaches that would deepen our understanding of the processes comprising this active sense.
    Keywords: QP1-981 ; Q1-390 ; bats ; Biosonar ; Humans ; marine mammals ; sensory biology ; Birds ; Behavior ; Communication ; thema EDItEUR::M Medicine and Nursing::MF Pre-clinical medicine: basic sciences::MFG Physiology
    Language: English
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  • 2
    facet.materialart.
    Unknown
    Frontiers Media SA
    Publication Date: 2024-03-30
    Description: In the ancient past, cocoa has been appreciated as a high-calorie food to boost energy in soldiers and for its undefined medicinal and mystical properties. During other times, chocolate has been considered as the forbidden “food of God”: a treasure of pleasure for the mind and the soul. The overall perception of the consumer for chocolate was of a “charming” and appealing food with lots of negative aspects related to high sugar content leading to consider chocolate as “junk food” for its “obesigen” calories. Recently, in association with the renewed interest of nutrition science in alternative source of health-promoting foods and ingredients, a large body of research has been conducted to unravel the pro and cons of cocoa in relation to human health. Epidemiological evidences indicate that cocoa consumption helps preventing cardiovascular disease for its high content in bioactive flavonoids. Clinical trials show that chocolate consumption might improve vascular function, decreasing platelet aggregation and display an antioxidant and anti-inflammatory effect. The putative protective action of cocoa seems to be multi-factorial and involving different aspects of vascular, antioxidant and endothelial function. However, the mechanism(s) that account for the benefits of cocoa it is still unclear. The aim of this Research Topic is therefore to provide the reader with an objective picture of the state of art on the association between cocoa and health, mainly through the evidences of human trials; overwhelmingly considered the golden standard for nutritional science. The Research Topic will cover the analysis of the manufacturing processes of the chocolate and the antioxidant effects in humans as well as the majority of the putative health effects of chocolate and cocoa, such as anti-inflammatory properties, effect on immunity, platelet aggregation, blood pressure, endothelial function and cognitive behavior. Unraveling the functional properties of cocoa will help to understand if the 'food of God' is a primordial gift for the health of mankind.
    Keywords: R5-920 ; RC581-607 ; TX341-641 ; Antioxidants ; Obesity ; Flavonoids ; Humans ; Chocolate ; Blood pressure ; Inflammation ; Cognitive function ; Cocoa ; Immunity
    Language: English
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  • 3
    Publication Date: 2024-04-05
    Description: This eBook comprises s series of original research and review articles dealing with the anatomical, genetic, and physiological organization of the auditory system from humans to monkeys and mice.
    Keywords: RC321-571 ; Q1-390 ; audition ; monkeys ; gens ; translational ; Humans ; Rodents ; Memory ; Perception ; Physiology ; functional imaging ; Anatomy ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAN Neurosciences
    Language: English
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  • 4
    Publication Date: 2024-04-05
    Description: The global population aged over 60 is set to rise dramatically in the coming decades. In many countries, the older population now faces the prospect of spending a quarter of their lives aged over 65, and a significant proportion will have to cope with cognitive decline associated with normal ageing or with dementia disorders. Given that these fundamental demographic changes will pose a significant challenge to health care systems, a detailed understanding of age-related cognitive and neurobiological changes is essential in helping elderly populations maintain cognitive performance. In addition, developing sensitive biomarkers to identify those at risk of developing dementia is crucial for early and effective interventions. To make inferences about the ageing process from the animal model back to the human, rigorous behavioral paradigms must be used to ensure that the same function is being examined across species. Given that similar navigational paradigms can easily be applied to humans and animals, recent years have seen an expansion of studies attempting to bridge the gap between age-related changes in animal and human spatial cognition. These studies begin to suggest that disruptions in spatial computations are among the earliest indicators of impending cognitive decline. In addition, although many animal studies have identified pathological mechanisms with paradigms involving spatial navigation, these mechanisms support many nonspatial cognitive functions as well. As a consequence, a successful characterization of how spatial processing changes in the ageing brain could reveal fundamental effects of cognitive ageing that could inform about general mechanisms underlying decline in perception, mnemonic processing and multisensory integration.
    Keywords: RC321-571 ; Q1-390 ; Neuroscience ; spatial navigation ; Humans ; Aging ; Animal Models ; Dementia ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAN Neurosciences
    Language: English
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  • 5
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    Unknown
    White Rose University Press | White Rose University Press
    Publication Date: 2022-12-06
    Description: In Hidden Depths, Professor Penny Spikins explores how our emotional connections have shaped human ancestry. Focusing on three key transitions in human origins, Professor Spikins explains how the emotional capacities of our early ancestors evolved in response to ecological changes, much like similar changes in other social mammals. For each transition, dedicated chapters examine evolutionary pressures, responses in changes in human emotional capacities and the archaeological evidence for human social behaviours. Starting from our earliest origins, in Part One, Professor Spikins explores how after two million years ago, movement of human ancestors into a new ecological niche drove new types of collaboration, including care for vulnerable members of the group. Emotional adaptations lead to cognitive changes, as new connections based on compassion, generosity, trust and inclusion also changed our relationship to material things. Part Two explores a later key transition in human emotional capacities occurring after 300,000 years ago. At this time changes in social tolerance allowed ancestors of our own species to further reach out beyond their local group and care about distant allies, making human communities resilient to environmental changes. An increasingly close relationship to animals, and even to cherished possessions, appeared at this time, and can be explained through new human vulnerabilities and ways of seeking comfort and belonging. Lastly, Part Three focuses on the contrasts in emotional dispositions arising between ourselves and our close cousins, the Neanderthals. Neanderthals are revealed as equally caring yet emotionally different humans, who might, if things had been different, have been in our place today. This new narrative breaks away from traditional views of human evolution as exceptional or as a linear progression towards a more perfect form. Instead, our evolutionary history is situated within similar processes occurring in other mammals, and explained as one in which emotions, rather than ‘intellect’, were key to our evolutionary journey. Moreover, changes in emotional capacities and dispositions are seen as part of differing pathways each bringing strengths, weaknesses and compromises. These hidden depths provide an explanation for many of the emotional sensitivities and vulnerabilities which continue to influence our world today.
    Keywords: Human demography ; Group size ; Lithic transfers ; Raw material movements ; Bonobos ; Dog burial ; Comfort ; Symbolic objects ; Symbolism ; Mobiliary art ; Attachment fluidity ; Hypersociability ; Human-animal relationships ; Dog domestication ; Attachment object ; Approachability ; Approach behaviour ; Avoidance behaviour ; Androgens ; Physiological responses ; Cognitive Archaeology ; Autism Spectrum Condition ; Handaxe ; Biface ; Neurodiversity ; Palaeolithic stone tools ; Evolution of neurodiversity ; Rock art ; Ice age art ; Material Culture ; Cultural transmission ; Emotional commitment ; Biopsychosocial approach ; Social tolerance ; Attachment ; Genus Homo ; Acheulian ; Cultural evolution ; Skeletal abnormality ; Injury ; Illness ; Interdependence ; Emotional sensitivity ; Moral emotions ; Evolution of Altruism ; Hominins ; Upper Palaeolithic ; Lower Palaeolithic ; Ecological niche ; Selective pressure ; Behavioural ecology ; Wolves ; Affective empathy ; Cognitive empathy ; Theory of mind ; Human Cognition ; Vulnerability ; Evolutionary Psychology ; Developmental psychology ; Helping behaviours ; Social cognition ; Social mammals ; Human Emotion ; Human social collaboration ; Generosity ; Emotional brain ; Social emotions ; Comparative behaviour ; Evolution ; Social carnivores ; Primate behavioural ecology ; Primate social systems ; Human Evolution ; Human ancestors ; Collaboration ; Evolutionary Biology ; Emotional vulnerability ; Social connection ; Decolonisation ; Social networks ; Middle Palaeolithic ; Community resilience ; Convergent evolution ; Chimpanzee ; Origin of modern humans ; Social safeness ; Wolf domestication ; Cherished possessions ; Compensatory attachment ; Loneliness ; Palaeolithic art ; Stress reactivity ; Bonding hormones ; Humans ; Hunter-gatherers ; Intergroup collaboration ; Tolerance ; Emotional connection ; Autism ; Trust ; Early Prehistory ; Palaeopathology ; Origins of healthcare ; Human self-domestication ; Palaeolithic Archaeology ; Social brain ; Care-giving ; Empathy ; Neanderthals ; Compassion ; Social Connection ; Evolution of Emotions ; Human Origins ; Adaptation ; Prehistory ; bic Book Industry Communication::J Society & social sciences::JH Sociology & anthropology::JHM Anthropology ; bic Book Industry Communication::H Humanities::HD Archaeology ; bic Book Industry Communication::P Mathematics & science::PS Biology, life sciences ; bic Book Industry Communication::P Mathematics & science::PS Biology, life sciences::PSA Life sciences: general issues::PSAF Ecological science, the Biosphere ; bic Book Industry Communication::P Mathematics & science::PS Biology, life sciences::PSA Life sciences: general issues::PSAJ Evolution ; bic Book Industry Communication::J Society & social sciences::JP Politics & government::JPW Political activism::JPWQ Revolutionary groups & movements ; bic Book Industry Communication::J Society & social sciences::JM Psychology
    Language: English
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  • 6
    Publication Date: 2024-04-04
    Description: This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact
    Keywords: drugs ; Behavior ; Memory tasks ; pre-clinical ; clinical ; Humans ; Animals ; thema EDItEUR::P Mathematics and Science::PD Science: general issues ; thema EDItEUR::M Medicine and Nursing::MK Medical specialties, branches of medicine::MKG Pharmacology
    Language: English
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  • 7
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    Unknown
    De Gruyter | De Gruyter Open Poland
    Publication Date: 2022-11-22
    Description: This edited volume examines the opportunities to think, do, and/or create jointly afforded by digital storytelling. The contributors discuss digital storytelling in the context of educational programs, teaching anthropology, and ethnographic research involving a variety of populations and subjects that will appeal to researchers and practitioners engaged with qualitative methods and pedagogies that rely on media technology.
    Keywords: Discourse ; Climate Change ; Humans ; Nature ; Oceania ; Resilience ; Environmental Ethics ; Environmental Change ; Worldview ; bic Book Industry Communication::J Society & social sciences::JF Society & culture: general::JFF Social issues & processes::JFFC Social impact of disasters ; bic Book Industry Communication::J Society & social sciences::JF Society & culture: general::JFH Popular beliefs & controversial knowledge::JFHF Folklore, myths & legends ; bic Book Industry Communication::J Society & social sciences::JF Society & culture: general::JFS Social groups::JFSL Ethnic studies::JFSL9 Indigenous peoples ; bic Book Industry Communication::J Society & social sciences::JH Sociology & anthropology::JHB Sociology::JHBD Population & demography ; bic Book Industry Communication::J Society & social sciences::JH Sociology & anthropology::JHM Anthropology ; bic Book Industry Communication::P Mathematics & science::PS Biology, life sciences::PSX Human biology::PSXM Medical anthropology
    Language: English
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 34 (1992), S. 336-344 
    ISSN: 1432-1432
    Keywords: Humans ; Mitochondrial DNA ; Nuclear polymorphisms ; Heteroplasmy ; Genetic differentiation ; Sickle cell ; Rain forest refuges
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The identification of genetically coherent populations is essential for understanding human evolution. Among the culturally uniform ethnic groups of west Africa, there are two geographically distinct populations with high frequencies of sickle-cell hemoglobin (HbS). Although the HbS mutation in each group is found on distinguishable chromosomes 11, these populations have been assumed to be parts of a single population. Analysis of mitochondrial DNA (mtDNA) in these populations demonstrated that the two populations identified by alternative chromosomes 11 bearing HbS have distinct distributions of mitochondrial genotypes, i.e., they are maternally separate. These studies also showed that, contrary to expectation, the mtDNA of some individuals is heteroplasmic. For nuclear loci, a comparison of the frequency of alternative alleles established that these populations are genetically distinct. Both the mitochondrial and nuclear data indicate that these populations have been separate for approximately 50,000 years. Although HbS in the two populations is usually attributed to recent, independent mutations, the duration of the separation and the observed geographic distribution of the population allow for the possibility of an ancient origin of HbS. Assuming an ancient mutation and considering the known biogeography, we suggest that HbS protected selected populations from malaria in rain forest refuges during the most recent ice age.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 35 (1992), S. 7-16 
    ISSN: 1432-1432
    Keywords: Alu source genes ; Humans ; Gorillas ; Retrotransposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A member of the young PV Alu sub-family is detected in chimpanzee DNA showing that the PV subfamily is not specific to human DNA. This particular Alu is absent from the orthologous loci in both human and gorilla DNAs, indicating that PV subfamily members transposed within the chimpanzee lineage following the divergence of chimpanzee from both gorilla and human. These findings and previous reports describing the transpositional activity of other Alu sequences within the human, gorilla, and chimpanzee lineages provide phylogenetic evidence for the existence of multiple Alu source genes. Sequences surrounding this particular Alu resemble known transcriptional control elements associated with RNA polymerase III, suggesting a mechanism by which cis-acting elements might be acquired upon retrotransposition.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 33 (1991), S. 442-449 
    ISSN: 1432-1432
    Keywords: Humans ; Mouse ; Rat ; Codon usage ; Mutation bias ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A new statistical test has been developed to detect selection on silent sites. This test compares the codon usage within a gene and thus does not require knowledge of which genes are under the greatest selection, that there exist common trends in codon usage across genes, or that genes have the same mutation pattern. It also controls for mutational biases that might be introduced by the adjacent bases. The test was applied to 62 mammalian sequences, the significant codon usage biases were detected in all three species examined (humans, rats, and mice). However, these biases appear not to be the consequence of selection, but of the first base pair in the codon influencing the mutation pattern at the third position.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 27 (1988), S. 311-320 
    ISSN: 1432-1432
    Keywords: Genome composition ; Coding sequences ; Isochores ; Humans ; Murids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The compositional distributions of coding sequences and DNA molecules (in the 50-100-kb range) are remarkably narrower in murids (rat and mouse) compared to humans (as well as to all other mammals explored so far). In murids, both distributions begin at higher and end at lower GC values. A comparison of homologous coding sequences from murids and humans revealed that their different compositional distributions are due to differences in GC levels in all three codon positions, particularly of genes located at both ends of the distribution. In turn, these differences are responsible for differences in both codon usage and amino acids. When GC levels at first+second codon positions and third codon positions, respectively, of murid genes are plotted against corresponding GC levels of homologous human genes, linear relationships (with very high correlation coefficients and slopes of about 0.78 and 0.60, respectively) are found. This indicates a conservation of the order of GC levels in homologous genes from humans and murids. (The same comparison for mouse and rat genes indicates a conservation of GC levels of homologous genes.) A similar linear relationship was observed when plotting GC levels of corresponding DNA fractions (as obtained by density gradient centrifugation in the presence of a sequence-specific ligand) from mouse and human. These findings indicate that orderly compositional changes affecting not only coding sequences but also noncoding sequences took place since the divergence of murids. Such directional fixations of mutations point to the existence of selective pressures affecting the genome as a whole.
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  • 12
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Mutation Research DNAging 237 (1990), S. 123-130 
    ISSN: 0921-8734
    Keywords: Aging ; Humans ; Ionizing radiation ; Single cell electrophoresis
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
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  • 13
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Free Radical Biology and Medicine 10 (1991), S. 177-184 
    ISSN: 0891-5849
    Keywords: Free radicals ; Humans ; Noninvasive analytical techniques ; Oxidative stress status
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine
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  • 14
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Ethology and Sociobiology 6 (1985), S. 183-187 
    ISSN: 0162-3095
    Keywords: Assortative mating ; Genetic similarity ; Heritability ; Humans ; Kin recognition
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
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  • 15
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Ethology and Sociobiology 8 (1987), S. 215-220 
    ISSN: 0162-3095
    Keywords: Humans ; Paternity confidence ; Relatedness
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
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  • 16
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Mutation Research DNAging 256 (1991), S. 45-48 
    ISSN: 0921-8734
    Keywords: Ageing ; Humans ; Skin cells ; Telomeres
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
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  • 17
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Peptides 1 (1980), S. 55-57 
    ISSN: 0196-9781
    Keywords: ACTH ; Aging ; Attention ; Cognition ; Humans ; MSH ; Peptide ; Visual retention
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
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  • 18
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Peptides 4 (1983), S. 451-455 
    ISSN: 0196-9781
    Keywords: Biliary system ; Cat ; Guinea-pig ; Humans ; Mucosa ; Rabbit ; Radioimmunoassay ; Respiratory system ; Skin ; Substance P ; Sympathetic nervous system ; Urinary system
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
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  • 19
    ISSN: 0196-9781
    Keywords: Autocrine feedback mechanism ; Cholecystokinin ; Feeding ; Humans ; Radioimmunoassay
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
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  • 20
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Peptides 10 (1989), S. 489-492 
    ISSN: 0196-9781
    Keywords: Angiotensin II ; Blood ; Humans ; Radioimmunoassay ; Rats ; [des-Leu^1^0]-angiotensin I
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
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  • 21
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Peptides 5 (1984), S. 319-323 
    ISSN: 0196-9781
    Keywords: Blood flow ; Circulation ; Electromagnetic flowmetry ; Humans ; VIP
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
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  • 22
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Applied Animal Behaviour Science 39 (1994), S. 141-150 
    ISSN: 0168-1591
    Keywords: Cats ; Foraging ; Humans ; Livestock ; Predators ; Vampire bats
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
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  • 23
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Applied Animal Behaviour Science 41 (1994), S. 101-114 
    ISSN: 0168-1591
    Keywords: Fear ; Handling ; Humans ; Poultry ; Productivity
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
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  • 24
    ISSN: 0165-7992
    Keywords: Cytochrome P-450 ; Dogs ; Humans ; Monkeys ; P-448-H ; Rats
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
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  • 25
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 304 (1994), S. 285-294 
    ISSN: 0027-5107
    Keywords: Cotinine ; Genetic monitoring ; Hprt mutation ; Humans ; Lymphocytes ; Pregnancy ; Smoking ; Tobacco
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
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  • 26
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Thermal Biology 5 (1980), S. 249-251 
    ISSN: 0306-4565
    Keywords: Humans ; exercise ; hyperthermia ; oesophageal temperature
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
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  • 27
    Electronic Resource
    Electronic Resource
    Springer
    International journal of biometeorology 34 (1990), S. 42-48 
    ISSN: 1432-1254
    Keywords: Briths ; Humans ; Solar wind ; Geomagnetism ; Melatonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract Data obtained from the literature on the annual pattern of human conceptions and plasma melatonin at high latitudes indicated that simple annual rhythms do not exist. Instead, prominent semiannual rhythms are found, with equinoctial troughs and solsticial peaks. A prominent semiannual environmental event is the magnetic disturbance induced by the solar wind. The semiannual magnetic disturbances are worldwide, but most pronounced in the auroral zones where the corpuscular radiation enters the atmosphere. Magnetic indices that predominantly reflect these events were obtained from the literature and correlated with the melatonin and conception data. Significant and inverse correlations were found for Inuit conceptions and the melatonin data. The correlations obtained for 48 contiguous states of the United States indicated that only the extreme northern states exhibited this relationship. These data were compared with a previous correlational study in the United States which established that sunshine was correlated with conceptions in the middle latitude and southern states. An hypothesis of dual control by electromagnetic and magnetic energies is proposed: melatonin is a progonadal hormone in humans controlled by both factors, depending on their relative strength. Other studies are reviewed regarding the possible factors involved in determining the annual pattern of human conceptions. Demographic studies of geographic variation in temporal patterns of conceptions, with particular regard to variations of the magnetic fields on the earth's surface, may provide some insight into the efficacy of these different factors.
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  • 28
    Electronic Resource
    Electronic Resource
    Springer
    Animal cognition 1 (1998), S. 25-35 
    ISSN: 1435-9456
    Keywords: Key words Shape from shading ; Visual search ; Texture segregation ; Chimpanzees ; Humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The perception of shape from shading was tested in two chimpanzees (Pan troglodytes) and five humans (Homo sapiens), using visual search tasks. Subjects were required to select and touch an odd item (target) from among uniform distractors. Humans found the target faster when shading was vertical than when it was horizontal, consistent with results of previous research. Both chimpanzees showed the opposite pattern: they found the target faster when shading was horizontal. The same difference in response was found in texture segregation tasks. This difference between the species could not be explained by head rotation or head shift parallel to the surface of the monitor. Furthermore, when the shaded shape was changed from a circle to a square, or the shading type was changed from gradual to stepwise, the difference in performance between vertical and horizontal shading disappeared in chimpanzees, but persisted in humans. These results suggest that chimpanzees process shading information in a different way from humans.
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  • 29
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 124 (1993), S. 73-77 
    ISSN: 1573-0832
    Keywords: Assessment ; Cancer ; Humans ; Hydrazines ; Mushroom
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract This assessment focuses on the concentrations of some chemicals present in theAgaricus bisporus mushroom, the cancer-inducing doses of these chemicals or mushroom used in the animal experiments, the total amounts of these chemicals or mushroom needed to induce cancer in these mice, and the estimated total amounts of these chemicals or mushroom needed to induce cancer in humans. By adding the estimated amounts of chemicals needed to induce cancer and by comparing it with the amount of raw mushroom needed to induce the same effect, it becomes obvious that we have accounted for less than 2% of the carcinogenic components of theAgaricus bisporus mushroom. Since some unavailable data handicapped this assessment, it should be regarded as tentative and subject to further adjustment.
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  • 30
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 23 (2000), S. 511-514 
    ISSN: 0935-6304
    Keywords: CZE ; indirect UV detection ; metal ions ; ecological samples ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 5 Ill.
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  • 31
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 23 (2000), S. 561-564 
    ISSN: 0935-6304
    Keywords: Retention factors ; Cinnamomi ramulus ; high-performance liquid chromatography ; capillary electrophoresis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 3 Ill.
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  • 32
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 23 (2000), S. 590-594 
    ISSN: 0935-6304
    Keywords: Ion chromatography ; graphitic carbon stationary phases ; anions ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Inorganic anions could be separated on porous graphitic carbon stationary phases in ion chromatography. Ion exchange between eluent anions and sample anions on the stationary phase was confirmed by the retention behavior and the possibility of indirect photometric detection. The elution order of anions was different from that observed for commercially available anion exchangers. Chloride, nitrate, and sulfate contained in tap water could be determined in 7 min.
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    Journal of High Resolution Chromatography 23 (2000), S. 603-608 
    ISSN: 0935-6304
    Keywords: Solvation parameter model ; ystem constants for poly(dimethyldiphenylsiloxane) HP-5 and poly(ethylene glycol) HP-INNOWax stationary phases ; temperature ; molecular interaction ; retention models ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
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  • 34
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    Journal of High Resolution Chromatography 23 (2000), S. 656-658 
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis (CE) ; laser induced fluorescence detection (LIFD) ; fluorescein isothiocyanate (FITC) ; inulin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
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  • 35
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    Journal of High Resolution Chromatography 23 (2000), S. 699-701 
    ISSN: 0935-6304
    Keywords: Phenol derivatives ; RP-HPLC separation ; short RP column ; gradient elution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
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  • 36
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    Journal of High Resolution Chromatography 23 (2000), S. 485-488 
    ISSN: 0935-6304
    Keywords: Pyrethroids ; solid-phase microextraction ; water analysis ; temperature ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Synthetic pyrethroids are increasingly being used for insect control on field crops because of their advantageous environmental properties such as short field life, broad spectrum of insecticide activity, and relatively low mammalian toxicity. In the present work, experimental conditions were optimized for trace analysis of pyrethroids in water by using solid-phase microextraction followed by capillary gas chromatography. Effects of temperature, SPME-fiber diameter, and matrix were studied. SPME used off-line with a gas chromatograph electron-capture detection (GC-ECD) showed a linear response over a wide concentration range. Our results showed a strong temperature effect on pyrethroid extraction yield. The detection limit after 5 min of SPME-fiber exposure to the samples changed from 1 ppb (at 30°C) to 0.1 ppt (at 90°C), which is a 10000 increase in pyrethroid detection. The standard deviations of the analyte peak area ratios were typically in the range of 1-7% at 30°C and of 3 to 15% at 90°C. Best conditions for pyrethroids analysis were achieved using high temperature solution and a 100 μm polydimethylsiloxane fiber. No matrix (river water) influence was observed on detection of the investigated pyrethroids.
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  • 37
    ISSN: 0935-6304
    Keywords: Comprehensive two-dimensional GC ; time-of-flight ; oil analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In this work a comprehensive two-dimensional system (GC×GC) was coupled to a time-of-flight mass spectrometer (TOF/MS) for the analysis of oil samples. Group-types like the alkanes and saturated cyclic compounds (naphthenes), which are present in oil, are shown separately by selecting their unique masses. On selecting appropriate ion fragments, this method also permits the determination of sulfur- and oxygen-containing species in oil. Former results obtained by FID detection could be confirmed. After proper selection of unique ions in GC×GC-TOF both selectivity and sensitivity increase.
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  • 38
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    Journal of Chemometrics 8 (1994), S. 263-272 
    ISSN: 0886-9383
    Keywords: Molecular descriptors ; Principal component analysis ; Chemometrics ; Pattern recognition ; Total surface area ; PCDD PCDF ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New theoretical molecular indices are defined. They contain information about the whole molecular structure in terms of size, shape, symmetry and atom distribution. These indices are calcualted from the (x, y, z) co-ordinates of a molecule within different weighting schemes in a straightforward manner and represent a very general approach to describe molecules, molecular fragments, macromolecules and molecular conformations in a unitary conceptual framework. Their interpretability is quite evident and is defined by the same mathematical properties as the algorithm used for their calculation. Examples on the total surface area, toxicity of PCDD and PCDF and reaction rate of catalysed reactions show a high modelling power of these indices.
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  • 39
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 40
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 41
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    Journal of Chemometrics 9 (1995), S. 229-229 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 42
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    Journal of Chemometrics 9 (1995), S. 230-231 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 43
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    Journal of Chemometrics 9 (1995), S. 232-236 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 44
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    Journal of Chemometrics 8 (1994), S. 273-285 
    ISSN: 0886-9383
    Keywords: GRAM ; Least-squares problem ; Eigenvalue problem ; NIPALS ; Performance index ; Condition number ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper we discuss the practical implementation of the generalized rank annihilation method (GRAM). The practical implementation comes down to developing a computer program where two critical steps can be distinguished: the construction of the factor space and the oblique rotation of the factors. The construction of the factor space is a least-squares (LS) problem solved by singular value decomposition (SVD), whereas the rotation of the factors is brought about by solving an eigenvalue problem. In the past several formulations for GRAM have been published. The differences essentially come down to solving either a standard eigenvalue problem or a generalized eigenvalue problem. The first objective of this paper is to discuss the numerical stability of the algorithms resulting from these formulations. It is found that the generalized eigenvalue problem is only to be preferred if the construction of the factor space is not performed with maximum precision. This is demonstrated for the case where the dominant factors are calculated by the non-linear iterative partial least-squares (NIPALS) algorithm. Several performance measures are proposed to investigate the numerical accuracy of the computed solution. The previously derived bias and variance are proposed to estimate the number of physically significant digits in the computed solution. The second objective of this paper is to discuss the relevance of theoretical considerations for application of GRAM in the presence of model errors.
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  • 45
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    Journal of Chemometrics 9 (1995), S. 343-362 
    ISSN: 0886-9383
    Keywords: straight line calibration ; errors in both axes ; uncertainties ; linear regression ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Calibration is a fundamental step in the calculation of the unknown concentration of analyte in most analytical methods. It is known that for certain methodologies, if only the errors in the independent variable are taken into account, there may be considerable errors in the estimation of the value of the regression coefficients, the derived statistical parameters and in some cases the sought for response and concentration values. This paper reviews the calibration methods including some references to procedures for the detection of outliers and robust regression when there are errors in both axes. The advantages and limitations of the different approaches are discussed and a comparative study is made of the approaches of several techniques for which computer programmes have been developed based on the algorithms put forward by the different authors. Finally, some trends of future development in this field are envisaged.
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  • 46
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    Journal of Chemometrics 9 (1995), S. 363-372 
    ISSN: 0886-9383
    Keywords: PLS regression ; orthogonal expansion ; optimization ; Lagrange multipliers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple iteration algorithm that is faster and less memory-intensive than the NIPALS iteration algorithm for PLS regression is presented. The iteration algorithm is obtained by treating the orthogonal expansion or decomposition of a matrix X as an extremum problem subject to normalization and orthogonality constraint conditions and then solving the problem by use of the method of Lagrange multipliers. The main idea in this method is to find the transformation vector r. The latent variable t is expressed exactly as the linear combination of X-variables with the vector r so that the final regression coefficients can be conveniently provided. In the algorithm the recursion of the orthogonal projection is needed, which is derived by use of a matrix inverse formula. Algorithms are established from the equation for calculating the vector r that are suitable for dealing with three cases of large data sets. The first case is when the number of objects is very large, the number of variables is relatively small and the number of Y-variables is equal to or greater than the number of X-variables. The second case is when the number of objects is very large, the number of variables is relatively small and the number of X-variables is greater than the number of Y-variables. The last case is when the number of variables, either X- or Y-variables, or both, is very large and the number of objects is small.
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  • 47
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    Journal of Chemometrics 9 (1995), S. 431-432 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 48
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    Journal of Chemometrics 9 (1995), S. 451-457 
    ISSN: 0886-9383
    Keywords: non-linear regression ; optimization ; robust methods ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several robust regression methods, including a new proposal, are described and their properties discussed. Resistance to various types of outliers and non-normality is demonstrated. The techniques are applied to non-linear regression models from chemical kinetics and calibration. Optimization of the types of objective functions encountered when applying robust regression is considered.
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  • 49
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    Keywords: PLS ; kernel algorithm ; multivariate calibration ; EM algorithm ; cross-validation ; missing data ; Chemistry ; Analytical Chemistry and Spectroscopy
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    Topics: Chemistry and Pharmacology
    Notes: This is Part II of a series concerning the PLS kernel algorithm for data sets with many variables and few objects. Here the issues of cross-validation and missing data are investigated. Both partial and full crossvalidation are evaluated in terms of predictive residuals and speed and are illustrated on real examples. Two related approaches to the solution of the missing data problem are presented. One is a full EM algorithm and the second a reduced EM algorithm which applies when the number of missing values is small. The two examples are multivariate calibration data sets. The first set consists of UV-visible data measured on mixtures of four metal ions. The second example consists of FT-IR measurements on mixtures consisting of four different organic substances.
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    Journal of Chemometrics 9 (1995), S. 439-439 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Journal of Chemometrics 9 (1995) 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 52
    ISSN: 0886-9383
    Keywords: sequential response surface modelling ; Williamson ether synthesis ; SN2 ; optimization ; reaction kinetics ; reaction mechanism ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this work the utility of a new method for determining kinetic parameters by sequential response surface modelling, previously described (Part 1), is shown by applying it to an experimental study of a reaction with known kinetics. The nucleophilic substitution reaction between ethoxide and benzyl chloride, the Williamson ether synthesis, was selected as a model reaction. This reaction is known to proceed with second-order kinetics. The method gives access to estimates of initial reaction rate which can be further used to obtain estimates of activation energy and reaction order of reactants. The results obtained are in good agreement with the estimated values of these parameters obtained with conventional kinetic experiments.
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  • 53
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    Journal of Chemometrics 9 (1995), S. 483-487 
    ISSN: 0886-9383
    Keywords: fractional factorial design ; multiresponse ; PLS ; PCA ; reduced-rank regression ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper presents an interpretation of PLS applied to orthogonal explanatory variables. In particular, it is shown that in fractional factorial multiresponse experiments PLS2 gives identical results to ordinary least squares applied to principal components of the response variables. The general relationship is that the reduced-rank regression algorithm which first projects Y onto the X-space and then truncates this matrix by principal component analysis before performing ordinary least squares estimation gives the same predictor as PLS2 and SIMPLS if all the non-zero eigenvalues of XTX are identical.
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  • 54
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    Journal of Chemometrics 9 (1995), S. 471-481 
    ISSN: 0886-9383
    Keywords: batch prediction ; continuum regression ; multivariate calibration ; sequential prediction ; simultaneous prediction ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In analytical chemistry a single fitted calibration model is used repeatedly to predict the level of the analyte of interest for the specimens comprising the prediction set. Unlike the calibration (or training) set, which is often limited in size, the prediction set can be very large.In the case of multivariate calibration a number of methods such as PLS and PCR are commonly used to construct the calibration model. The set of instrumental measurements and the reference analyte level are available for each specimen in the calibration set. For specimens in the prediction set, only the instrumental measurements are available, since the problem is to predict the analyte level for these specimens. It is not widely recognized that predictions of the analyte levels for individual specimens can be improved by utilizing seemingly unrelated information from the instrumental measurements associated with the other members of the prediction set. In the case of PCR there exists a very straightforward procedure for doing this. A description of the various sources of prediction errors is provided to explain the ability of PCR to utilize this additional information. The use of PCR in this context is illustrated with both a synthetic and a real example.
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    Journal of Chemometrics 9 (1995), S. 531-531 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 57
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    Journal of Chemometrics 9 (1995), S. 509-520 
    ISSN: 0886-9383
    Keywords: canonical variates ; discriminant analysis ; partial least squares ; principal components ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new set of derived variables is proposed for exhibiting group separation in multivariate data on for preprocessing such data prior to discriminant analysis. The technique combines optimal features of canonical variate analysis and principal component analysis: the derived variables are linear combinations of the original variables that optimize the canonical variate criterion (ratio of between-group to within-group variance) but subject to the orthogonality constraints of principal components. In this formulation the canonical variates can be derived even when the within-group matrix is singular (i.e. when there are more variables than objects in the data matrix). A simple computational algorithm for extraction of these variables is proposed. The methods are illustrated on several data sets and compared with alternative techniques such as principal component analysis and partial least squares.
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    Journal of Chemometrics 9 (1995), S. 489-507 
    ISSN: 0886-9383
    Keywords: QSAR ; partial least squares ; robust regression ; CoMFA ; weighted regression ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A robust implementation of partial least squares (PLS) is developed in which the method of iteratively reweighted least squares is adapted for use with PLS. The result is a PLS algorithm which is robust to outliers and is easy to implement. Examples and case studies are presented, followed by two Monte Carlo studies designed to explore the behavior of the method.The paper begins with the motivation and intended applications for the procedure. A discussion is given of the method of interatively reweighted least squares (IRLS) for outlier detection. The procedure, given the name IRPLS, is then presented. Three case studies illustrate how the procedure works on various types of data and how it should be used. The first Monte Carlo study is designed to determine whether the IRPLS procedure correctly identifies multiple outliers in a wide variety of configurations. The second Monte Carlo study is designed to estimate the breakdown bound of the procedure.
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 60
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    Journal of Chemometrics 8 (1994), S. 287-292 
    ISSN: 0886-9383
    Keywords: Rank annihilation ; Principal components ; Procrustes rotation ; Multivariate analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that the DATa ANalysis (DATAN) algorithm can be expressed in terms of rank annihilation factor analysis (RAFA). Subsequent advances in RAFA are applied to DATAN to eliminate the problems and restrictions associated with DATAN. The extension of DATAN in terms of the trilinear decomposition algorithm is discussed.
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    Journal of Chemometrics 9 (1995), S. 309-322 
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    Keywords: simulated annealing ; messy genetic algorithms ; optimization of multimodal objective functions ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The method of simulated annealing is modified so that the concept of messy chromosomes is applied. Constituent genes of messy chromosomes are specified by their respective names (indices) and values (alleles) simultaneously. Unlike simple chromosomes (binary vectors), messy chromosomes may be either under- or overspecified with respect to the problem being solved. The messy simulated annealing algorithm is a very robust and efficient stochastic optimization method which is able to find correct minima of deceptive or highly multimodal objective functions. This is shown by way of a number of simulations.
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    Journal of Chemometrics 9 (1995), S. 323-326 
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    Keywords: partial least squares ; biased regression ; ordinary least squares ; minimum length least squares ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An algebraic proof is given that in partial least squares (PLS) regression the Euclidean length of the estimator is shrunk in comparison with the ordinary least squares estimator or with PLS estimators based on a larger number of dimensions.
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    Journal of Chemometrics 9 (1995), S. 329-330 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Journal of Chemometrics 9 (1995) 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Journal of Chemometrics 9 (1995), S. 389-409 
    ISSN: 0886-9383
    Keywords: multivariate image analysis ; principal component analysis ; exploratory data analysis ; projection in multivariate space ; graphical visualization ; noise ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Multivariate image analysis (MIA) is a powerful tool for many image segmentation and classification problems, but the interpretation and understanding of the original and resulting multidimensional (multivariate) data are not always easy. A strategy for MIA has been proposed which describes its usage on multivariate images for segmentation tasks. MIA starts with principal component analysis (PCA) and then continues with interactive analysis of the output from PCA. In this paper a number of extensions to MIA are proposed. The extensions are the suggestion to incorporate preprocessing of the multivariate image in MIA, the suggestion to use synthetic multivariate image models which create a clear-cut situation, and new visualization tools which improve the interactivity and understanding of the results. Extended MIA is applied on synthetic multivariate image data simulating a possible application with large noise, positron emission tomography (PET). As a result of the interactive analysis, suggestions for preprocessing emerge. The developed methodology for handling the noise is then applied on real PET image data with good results.
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Journal of Chemometrics 1 (1987) 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Journal of Chemometrics 1 (1987), S. 75-75 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Journal of Chemometrics 1 (1987), S. 74-74 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Journal of Chemometrics 1 (1987), S. 77-77 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Journal of Chemometrics 1 (1987), S. 79-90 
    ISSN: 0886-9383
    Keywords: Numerical deconvolution ; Peak resolution ; Peak separation ; Iterative deconvolution ; Jansson's method ; Super-resolution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Severely overlapped gas chromatographic peaks can be resolved using Jansson's method. Jansson's method is an iterative nonlinear deconvolution technique and consists of Van Cittert's algorithm with the relaxation factor a function of the kth estimate of the peak shape. The maximum peak amplitude of the instrument and peak non-negativity serve as constraints to improve the peak estimate. Super-resolution is achieved without significantly degrading the chromatogram signal-to-noise ratio. The method only requires a knowledge of the instrument impulse response function and maximum peak height.
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    Journal of Chemometrics 1 (1987), S. 111-120 
    ISSN: 0886-9383
    Keywords: Principal component analysis ; Submatrix analysis ; Spectroscopy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the treatment of spectroscopic data by principal component analysis, correct determination of the dimensionality of the data is essential. Submatrix analysis, which involves preliminary analysis of subsets of the data matrix, is described, and shown to be valuable in determining both the size of the factor space and estimates of equilibrium constants in the system, even for data containing abnormally large experimental error.
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  • 74
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    Journal of Chemometrics 1 (1987), S. 91-101 
    ISSN: 0886-9383
    Keywords: Factor analysis ; Retention indices ; Model ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Retention indices for 18 monomeric stationary-phase solvents and 33 organic solutes are factor analyzed. Six factors reproduce the data matrix near experimental error. The solvents diglycerol and zonyl E-7 are shown to be highly unique, whereas none of the solutes behaves uniquely. Combination sets of solvent vectors and of solute vectors from the data matrix lead to models having errors within experimental error. Basic factors which might influence the solute - solvent interactions are identified by the least-squares method of target testing. For the solvents, a number of properties, including McReynolds' constants and molecular weight, test successfully. For the solutes, carbon number and group dipole moment are representative properties which test successfully. The best combination of solvent basic factors gives errors about twice the experimental error. Combination sets composed only of McReynolds' constants do not model the data well.
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  • 75
    ISSN: 0886-9383
    Keywords: NIR ; Fast Fourier transform ; Principal component analysis ; Discrimination ; Baking quality ; Wheat ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Digitalized continuous near infra-red reflectance (NIR) spectra are composed of a great number of data which must be reduced for microcomputer mathematical treatment. The sequence ‘fast Fourier transform preceding principal component analysis’ was tested to perform data size reduction without a large loss of information. The method was applied on a collection of wheat spectra composed of 351 data. Ten resulting data, which described 99.5% of the total variance, were kept. The relevance of the method was estimated by the ability of the resulting data (i) to regenerate the original signal, and (ii) to discriminate the baking quality of the wheat by stepwise multiple discriminant analysis. The average difference between initial and regenerated spectra was -2.4 × 10-3 log (1/R) units and the standard deviation was 1.16 × 10-3 log (1/R) units. The discrimination treatments gave 89.9% of well classified samples for the calibration test and 90.5% for the prediction test. The application of these mathematical treatments to other continuous signals is discussed.
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    Journal of Chemometrics 1 (1987), S. 135-135 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 77
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 78
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    Journal of Chemometrics 1 (1987), S. 1-2 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 79
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    Journal of Chemometrics 1 (1987), S. 3-6 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 80
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    Journal of Chemometrics 2 (1988), S. 67-79 
    ISSN: 0886-9383
    Keywords: Experimental design ; Multivariate calibration ; Variable selection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methods of multivariate calibration use models that relate spectral data or sensor array responses to the concentrations of analytes. The goal is to insure that the calibration model can accurately estimate analyte concentrations in unknown samples not contained in the calibration set. The sensors or spectral channels (e.g. wavelengths) selected for incorporation in the model, as well as the samples selected for the calibration step, are known to have an effect on the accuracy of analysis for unknown samples. This work provides a fundamental treatment of this effect and derives criteria for optimal selection. Additionally, a proof is given for the advantage of having more sensors and calibration samples than analytes - the overdetermined case.
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  • 81
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 82
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 83
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    Journal of Chemometrics 1 (1987), S. 250-254 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 84
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    Journal of Chemometrics 2 (1988) 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 85
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    Journal of Chemometrics 2 (1988), S. i 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 86
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    Journal of Chemometrics 2 (1988), S. 1-10 
    ISSN: 0886-9383
    Keywords: Linear discriminant functions ; Pattern recognition ; Monte Carlo simulations ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In applications of pattern recognition techniques to problems in chemical fingerprinting, only limited knowledge about the underlying statistical distribution of the data is generally available. This means that non-parametric methods must be used. Non-parametric discriminant functions have been used to provide insight into relationships contained within sets of chemical measurements. However, classification based on random or chance separation can be a serious problem. Monte Carlo simulation studies have been carried out to assess the probability of chance classification for non-parametric linear discriminants. The level of expected chance classification is a function of the number of observations (the number of samples), the dimensionality of the problem (the number of independent variables per observation), class membership distribution and the covariance structure of the data being examined. An approach for assessing the level of significance of classification scores obtained from real training sets will be presented. These simulation studies establish limits on the approaches that can be taken with real data sets so that chance classification are improbable, and provide information necessary for integrating the data analysis into the overall experimental design.
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  • 87
    ISSN: 0886-9383
    Keywords: Oligosaccharides ; Glycoproteins ; Identification ; Substructure analysis ; High-resolution ; 1H-NMR spectra ; Computer retrieval ; Reproducibility ; Chemical shifts ; Similarity index ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Based on a statistical model of the reproducibility of NMR spectral features, a system for computer retrieval of high-resolution 1H-NMR spectra of glycoprotein carbohydrates has been developed. For corresponding peaks in an unknown and a reference spectrum, a similarity index based on the reproducibility of the chemical shifts is calculated. In addition, a second similarity index, based on the probability distribution of the percentage of non-matching peaks, has been developed. From these two similarity indices, a combined similarity index using the recall-reliability function as the optimizing criterion has been derived.First results indicate that the ‘1H-NMR reproducibility-based retrieval’ (‘1HRR’) system offers good perspectives for both identification and substructure analysis.
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  • 88
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    Journal of Chemometrics 3 (1989), S. 431-441 
    ISSN: 0886-9383
    Keywords: Resolution of mixtures ; Excitation-emission matrices ; Eigenanalysis ; Wavelength component vectorgram ; Total luminescence spectroscopy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We consider the problem of resolving the total luminescence spectra of two-component mixtures. Non-negativity of the constituent spectra is commonly used as a criterion to accomplish this resolution, but its application seldom leads to unique answers. Sometimes, the condition must be relaxed because no solution satisfying non-negativity exists. In these cases judgments must be made concerning which parts of the spectra will be allowed to go negative and by how much.The wavelength component vectorgramn (WCV) is presented here as a tool for assisting the experimenter in making these judgments. Even when non-negative resolutions exist, it may happen that resolutions with slight negative elements will more closely match the spectra of the pure constituents. The WCV can also be used as a tool for detecting these cases. The methodology is illustrated with real data from a two-component mixture.
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    Journal of Chemometrics 3 (1989), S. 453-453 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Topics: Chemistry and Pharmacology
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  • 90
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    Journal of Chemometrics 3 (1989), S. 451-452 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Topics: Chemistry and Pharmacology
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  • 91
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    Journal of Chemometrics 3 (1989), S. 443-449 
    ISSN: 0886-9383
    Keywords: Multicomponent analysis ; Iterative refinement ; Simplex method ; Condition numbers ; Linear programming ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Concentration estimates of components present in a sample mixture can be obtained using matrix mathematics. In the past, the condition number of the calibration matrix has been used to give an amplification factor by which uncertainties in data can work through to errors in the concentration estimates. This paper explores an additional interpretation of condition numbers with regards to significant figures and rounding errors. A procedure is suggested which will always give the most accurate concentration estimates provided the calibration matrix is not too ill-conditioned. Condition numbers have also been used by analytical chemists to discuss the error bounds for concentration estimates. Unfortunately, only one representative error bound can be approximated for all the components. This paper will show how to compute bounds for individual concentration estimates obtained as solutions to a system of m equations and n unknowns. The procedure is appropriate when calibration data and sample responses are inaccurate.
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  • 92
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 93
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    Journal of Chemometrics 3 (1989) 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 94
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    Journal of Chemometrics 3 (1989), S. 21-32 
    ISSN: 0886-9383
    Keywords: Kalman filter ; Multicomponent analysis ; Fluorescence spectral shifts ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of peak shifts on the performance of a Kalman filter multicomponent analysis algorithm has been investigated. A series of Gaussian test systems were employed to characterize the concentration estimation errors and the morphology of the on-line residuals (the innovations sequence). Both forward and reverse filters were used in the generation of the innovations sequences. It was found that the difference between the forward and reverse innovations sequences gave an accurate indication of the direction and magnitude of the peak shift. A series of overlapped two-component systems were also investigated. Again, a correlation between the difference innovations and the degree of the response shift was observed. The behavior of the Kalman filter in fitting the shifted fluorescence emission spectrum of benzo[a]pyrene was also examined. The response for benzo[a]pyrene in cyclohexane solution was compared to that obtained on the surface surface of a reversed phase thin layer chromatography plate. A red shift of 4 nm was detected for the surface spectrum by observing the difference innovations sequence. This approach holds promise for correction of response shifts in multicomponent systems.
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  • 95
    ISSN: 0886-9383
    Keywords: Principal component analysis ; Factor analysis ; Singular value decomposition ; Eigenvalue analysis ; Multivariate analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fisher variance ratio tests are developed for determining (1) the number of statistically significant abstract factors responsible for a data matrix and (2) the significance of target vectors projected into the abstract factor space. F-tests, developed from the viewpoint of vector distributions, are applied to various data sets taken from the chemical literature.
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  • 96
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    Keywords: Parameter estimation ; Cyclic voltammetry ; Quasi-reversible electron transfer reactions ; Cerium (IV) bis(octaethylporphyrinate) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Values of the peak potential, the peak current function and the peak potential difference are extracted from simulated cyclic voltammograms of a quasi-reversible electron transfer reaction. Variations of the feature values are described by empirical functions of the model parameters α (transfer coefficient) and ψ′ (dimensionless form of the heterogeneous electron transfer rate constant ks) using multiple linear regression. These functions are used to determine the system parameters α and ks from test data sets of feature values. The predictive power of the features is discussed. It is shown that several features can be used simultaneously in the analysis. Also, α, ks, the formal potential E0 and the diffusion coefficient D can be estimated simultaneously. Experimental data from the metal-centered one-electron reduction of cerium (IV) bis(octaethylporphyrinate), Ce(OEP)2, are analyzed using the technique, and values of the system parameters for this electrochemical reaction are determined.
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  • 97
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 98
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    Journal of Chemometrics 2 (1988), S. 247-263 
    ISSN: 0886-9383
    Keywords: Calibration ; Tensor ; Multivariate ; PCR ; MLR ; PLS ; Regression ; Multidimensional arrays ; Order ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Many analytical instruments now produce one-, two- or n-dimensional arrays of data that must be used for the analysis of samples. An integrated approach to linear calibration of such instruments is presented from a tensorial point of view. The data produced by these instruments are seen as the components of a first-, second- or nth-order tensor respectively. In this first paper, concepts of linear multivariate calibration are developed in the framework of first-order tensors, and it is shown that the problem of calibration is equivalent to finding the contravariant vector corresponding to the analyte being calibrated. A model of the subspace spanned by the variance in the calibration must be built to compute the contravarian vectors. It is shown that the only difference between methods such as least squares, principal components regression, latent root regression, ridge regression and partial least squres resides in the choice of the model.
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    Journal of Chemometrics 2 (1988), S. 265-280 
    ISSN: 0886-9383
    Keywords: Calibration ; Tensor ; Multivariate ; Order ; Regression ; Generalized rank annihilation ; GRAM ; Multi order ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tensorial calibration provides a useful approach to calibration in general. For calibration of instruments that produce two-dimensional (second-order) arrays of data per sample, tensoial concepts are as natural a way of solving the calibration problem as vectorial concepts are for the multivariate problem. Similarly, for third- and higher-order data, the tensorial description of calibration is also useful. This paper introduces second-order calibration from a tensorial point of view. Univariate, multivariate and bilinear approaches to calibration are presented. The generalized rank annihilation method (GRAM) is described from the tensorial perspective, and it is shown that GRAM is equivalent to finding a second-order tensorial base that spans both tensors (calibration and unknown) with respective diagonal component matrices. GRAM uses a single calibration sample for multicomponent analysis even in the presence of interference. Second-order bilinear calibration is extended to multiple calibration samples where the effect of collinearities is reduced.
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    Journal of Chemometrics 5 (1991), S. 68-69 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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