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Showing papers by "Aarhus University published in 1994"


Book ChapterDOI
21 Aug 1994
TL;DR: In this paper, the authors show how to transform a proof of knowledge P into a witness indistinguishable protocol, in which the prover demonstrates knowledge of the solution to some subset of n problem instances out of a collection of subsets denned by a secret sharing scheme S on n participants.
Abstract: Suppose we are given a proof of knowledge P in which a prover demonstrates that he knows a solution to a given problem instance. Suppose also that we have a secret sharing scheme S on n participants. Then under certain assumptions on P and S, we show how to transform P into a witness indistinguishable protocol, in which the prover demonstrates knowledge of the solution to some subset of n problem instances out of a collection of subsets denned by S. For example, using a threshold scheme, the prover can show that he knows at least d out of n solutions without revealing which d instances are involved. If the instances axe independently generated, we get a witness hiding protocol, even if P did not have this property. Our results can be used to efficiently implement general forms of group oriented identification and signatures. Our transformation produces a protocol with the same number of rounds as P and communication complexity n times that of P. Our results use no unproven complexity assumptions.

1,299 citations


Journal ArticleDOI
TL;DR: It is concluded that the neurodegenerative processes associated with normal ageing and with Alzheimer's disease are qualitatively different and that Alzheimer's Disease is not accelerated by ageing but is a distinct pathological process.

1,207 citations


Book ChapterDOI
14 Dec 1994
TL;DR: The concept of truncated differentials is introduced and it is shown how to find a minimum nonlinear order of a block cipher using higher order differentials.
Abstract: In [6] higher order derivatives of discrete functions were considered and the concept of higher order differentials was introduced. We introduce the concept of truncated differentials and present attacks on ciphers presumably secure against differential attacks, but vulnerable to attacks using higher order and truncated differentials. Also we give a differential attack using truncated differentials on DES reduced to 6 rounds using only 46 chosen plaintexts with an expected running time of about the time of 3,500 encryptions. Finally it is shown how to find a minimum nonlinear order of a block cipher using higher order differentials.

771 citations


Book
01 Jan 1994
TL;DR: In this article, the authors introduce the notions of higher order theory and likelihood combinants, and some further results and tools for the analysis of higher-order theory with respect to probability.
Abstract: Introduction Preliminaries Some general concepts First order theory Higher order theory:preliminaries Mathematical basis of higher order theory Higher order theory: likelihood combinants higher order theory: some further results and tools Various notions of likelihood and higher order theory Further aspects References Index

649 citations


Journal ArticleDOI
TL;DR: The Responsibil-ity Hypothesis as mentioned in this paper states that voters hold the government responsible for economic conditions, and that voting is retrospective as expectations are static, thus it costs the average government almost 2% of the vote to rule.
Abstract: VP-functions explain the support for the government at votes and polls by economic and political variables. Most studies analyze macro time series. We also cover studies of individual voters, socio-economic groups and regional cross-sections. The theory starts from the Responsibil- ity Hypothesis: voters hold the government responsible for economic conditions. It works in two party/block systems, but not else. Voters in most countries are found to be sociotropic. Egotropic voting also occurs. Voters' myopia is well established. Voting is retrospective as expectations are static. It costs the average government almost 2% of the vote to rule.

639 citations


Journal ArticleDOI
Hans Brix1
TL;DR: Macrophytes stabilise the surface of the beds, provide good conditions for physical filtration, prevent vertical flow systems from clogging, insulate against frost during winter, and provide a huge surface area for attached microbial growth.

612 citations


Journal ArticleDOI
TL;DR: Self-consistent linear muffin-tin-orbital band-structure calculations are used to investigate the optical and structural properties of III-V semiconducting nitrides under hydrostatic pressure and suggest that all the nitride under pressure transform to the semiconducted rocksalt phase.
Abstract: Self-consistent linear muffin-tin-orbital band-structure calculations are used to investigate the optical and structural properties of III-V semiconducting nitrides under hydrostatic pressure. The pressure behavior of the energy band structures is discussed in the context of the postulated chemical trends in III-V semiconductors. The regions in k space of dominant interband contributions to the elements of structure in the dielectric functions are identified. The total-energy calculations suggest that all the nitrides under pressure transform to the semiconducting rocksalt phase. The calculated transition pressures are 21.6 GPA (InN), 51.8 GPa (GaN), 16.6 GPa (AlN), and 850 GPa (BN). Experimental values that agree well with this have been found for the first three compounds. The fact that GaN and AlN have such different transition pressures in spite of their very similar ionicities is explained by the presence of 3d states on Ga.

554 citations


Journal ArticleDOI
TL;DR: All cases of MBP deficiency may be explained by these three variants: dominant action of a point mutation at codon 54 of the MBP gene in Eskimos, partially in Caucasians, but not in Africans, and Hardy-Weinberg equilibrium is seen in the investigated ethnic groups.
Abstract: Human mannan-binding protein (MBP) is a serum lectin participating in the innate immune defence. Low MBP concentrations are explained by the dominant action of a point mutation at codon 54 of the MBP gene in Eskimos, partially in Caucasians, but not in Africans. A previously described point mutation at codon 57 was very frequent (0.23) in East Africans, low in Caucasians (0.02), and absent in Eskimos. The African population only conformed to Hardy-Weinberg expectation when assuming the existence of an unknown allele, which was subsequently found as a point mutation at codon 52. This allele appeared with a relatively high frequency (0.05) in both Africans and Caucasians, but was absent in Eskimos. Hardy-Weinberg equilibrium is now seen in the investigated ethnic groups. All cases of MBP deficiency may be explained by these three variants.

522 citations


Journal ArticleDOI
TL;DR: Collectin domains bind carbohydrates on microorganisms, while the collagenous regions are ligands for the collectin receptor on phagocytes and also mediate C1q-independent activation of the classical complement pathway.

490 citations


Journal ArticleDOI
TL;DR: The widely available information on protein sequences cannot, a priori, be assumed to be sufficient for calculating pI values because post‐translational modifications, in particular N‐terminal blockage, pose a major problem.
Abstract: A highly reproducible, commercial and nonlinear, wide-range immobilized pH gradient (IPG) was used to generate two-dimensional (2-D) gel maps of [35S]methionine-labeled proteins from noncultured, unfractionated normal human epidermal keratinocytes. Forty one proteins, common to most human cell types and recorded in the human keratinocyte 2-D gel protein database were identified in the 2-D gel maps and their isoelectric points (pI) were determined using narrow-range IPGs. The latter established a pH scale that allowed comparisons between 2-D gel maps generated either with other IPGs in the first dimension or with different human protein samples. Of the 41 proteins identified, a subset of 18 was defined as suitable to evaluate the correlation between calculated and experimental pI values for polypeptides with known composition. The variance calculated for the discrepancies between calculated and experimental pI values for these proteins was 0.001 pH units. Comparison of the values by the t-test for dependent samples (paired test) gave a p-level of 0.49, indicating that there is no significant difference between the calculated and experimental pI values. The precision of the calculated values depended on the buffer capacity of the proteins, and on average, it improved with increased buffer capacity. As shown here, the widely available information on protein sequences cannot, a priori, be assumed to be sufficient for calculating pI values because post-translational modifications, in particular N-terminal blockage, pose a major problem. Of the 36 proteins analyzed in this study, 18–20 were found to be N-terminally blocked and of these only 6 were indicated as such in databases. The probability of N-terminal blockage depended on the nature of the N-terminal group. Twenty six of the preteins had either M, S or A as N-terminal amino acids and of these 17–19 were blocked. Only 1 in 10 proteins containing other N-terminal groups were blocked.

483 citations


Journal ArticleDOI
15 Dec 1994-Nature
TL;DR: The assignment of a family of tightly related proteins from lower and higher eukaryotes which are structurally and functionally similar to rabbit eRF are reported, concluding that the eRFl proteins are directly implicated in the termination of translation in eukARYotes.
Abstract: THE termination of protein synthesis in ribosomes is governed by termination (stop) codons in messenger RNAs and by polypeptide chain release factors (RFs). Although the primary structure of prokaryotic RFs and yeast mitochrondrial RF is established1–4, that of the only known eukaryotic RF (eRF)5 remains obscure. Here we report the assignment of a family of tightly related proteins (designated eRFl) from lower and higher eukaryotes which are structurally and functionally similar to rabbit eRF. Two of these proteins, one from human6 and the other from Xenopus laevis7 , have been expressed in yeast and Escherichia coli, respectively, purified and shown to be active in the in vitro RF assay. The other protein of this family, sup45 (supl) of Saccharomyces cerevisiae, is involved in omnipotent suppression during translation8–12. The amino-acid sequence of the eRFl family is highly conserved. We conclude that the eRFl proteins are directly implicated in the termination of translation in eukaryotes.

Journal ArticleDOI
TL;DR: It is concluded that long-term infusion of AVP, acting either directly or indirectly, regulates expression of the AQP-CD water channel and AQP -CD is the predominant AVP-regulated water channel.
Abstract: AQP-CD is a vasopressin-regulated water channel expressed exclusively in the renal collecting duct. We have previously shown that AQP-CD is present in the apical plasma membrane and subapical vesicles of collecting duct cells, consistent with membrane-shuttling mechanisms that have been proposed to explain the short-term action of [Arg8] vasopressin (AVP) to regulate apical water permeability. We propose here that AVP may also have long-term actions on the collecting duct to regulate the expression of the AQP-CD water channel. We used immunoblotting, immunohistochemistry, and in vitro perfusion of renal tubules to investigate water channel regulation in collecting ducts of diabetes insipidus (Brattleboro) rats treated with a 5-day infusion of AVP or vehicle. Immunoblotting and immunohistochemistry demonstrated that collecting ducts of vehicle-infused Brattleboro rats had markedly reduced expression of AQP-CD relative to normal rats. In response to AVP infusion there was a nearly 3-fold increase in AQP-CD expression as detected by immunoblotting. Immunocytochemistry demonstrated that the increased expression was predominantly in the apical plasma membrane and subapical vesicles of collecting duct cells. Inner medullary collecting ducts of AVP-infused Brattleboro rats displayed a 3-fold increase in osmotic water permeability relative to vehicle-infused controls, in parallel with the change in AQP-CD expression. Based on these findings, we conclude that (i) long-term infusion of AVP, acting either directly or indirectly, regulates expression of the AQP-CD water channel and (ii) AQP-CD is the predominant AVP-regulated water channel.

Journal ArticleDOI
Steinar Kvale1
TL;DR: The qualitative research interview has tended to evoke rather stereotyped objections from the mainstream of social science: it is not scientific, not objective, not trustworthy, nor reliable, not intersubjective, not a formalized method, not hypothesis testing, not quantitative, not generalizable, and not valid as mentioned in this paper.
Abstract: Qualitative research has tended to evoke rather stereotyped objections from the mainstream of social science. Ten standardized responses to the stimulus "qualitative research interview" are discussed: it is not scientific, not objective, not trustworthy, nor reliable, not intersubjective, not a formalized method, not hypothesis testing, not quantitative, not generalizable, and not valid. With the objections to qualitative interviews highly predictable, they may be taken into account when designing, reporting, and defending an interview study. As a help for new qualitative researchers, some of the issues, concepts, and arguments involved are outlined, and the relevancy of the standard objections is discussed. Alternative conceptions of qualitative research, coming from phenomenological and hermeneutical traditions, are suggested. The qualitative interview based on conversation and interaction here appears as a privileged access to a linguistically constituted social world.

Journal ArticleDOI
TL;DR: This is the highest number of tree species ever recorded for a tropical rain forest sample of this size and in both dbh classes, the most species-rich families were: Fabaceae sensu lato (including Mimosaceae and Caesalpiniaceae), Lauraceae and Sapotaceae; the most Species-rich genera, were Pouteria, Inga and Protium.
Abstract: In a 1 ha square plot of terra firme forest at 260 m elevation in Amazonian Ecuador, all trees with diameter at breast height (dbh) ≥5 cm were studied. There were 1561 individuals, 473 species, 187 genera and 54 families. Of these, 693 individuals, 307 species, 138 genera and 46 families had a dbh ≥10 cm. This is the highest number of tree species ever recorded for a tropical rain forest sample of this size. In both dbh classes, the most species-rich families were: Fabaceae sensu lato (including Mimosaceae and Caesalpiniaceae), Lauraceae and Sapotaceae; the most species-rich genera, were Pouteria, Inga and Protium. The vertical space was partitioned among species: 166 species were found only in the 5–10 dbh cm class and were mostly sub-canopy treelets, and 307 species with dbh ≥10 cm were mostly large canopy trees.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the effect of oxygen regulation of nitrification and denitrification in sediments with 15N-isotope techniques and found that higher O2 levels in the overlying water will stimulate denitification, while the opposite will occur in systems containing high NO3- concentrations.
Abstract: Oxygen regulation of nitrification and denitrification in sediments was investigated with 15N-isotope techniques. Sediment cores were incubated in a continuous flowthrough system in which the 0, concen- tration was varied in the overlying water while the NO,- concentration was kept constant. Nitrification was stimulated with increasing 0, concentrations in the overlying water from 0 to 100% of atmospheric saturation, whereas only a slight stimulation was observed above 100%. At 0, concentrations below 100% of atmospheric saturation, NO,- from the overlying water was the most important source of N for denitrification, whereas above 100% of atmospheric saturation, NO,- produced by nitrification was the main source of N for denitrification. The converse effects of the O2 levels on the source of NO3- can be explained by applying a simple one-dimensional model: 0, in the overlying water controls the difisional distance of NO,- to the anoxic zone of denitrification and consequently the location of NO,- vertically in the sediment as well as the magnitude of the nitrification activity. Our results suggest that in aquatic environments containing low NO,- concentrations in the overlying water (such as coastal waters), higher 0, conditions will stimulate denitrification, while the opposite will occur in systems containing high NO,- concentrations (such as eutrophic lakes and streams).

Journal ArticleDOI
Hans Brix1
TL;DR: In this article, the authors summarized the state-of-the-art of the uses of constructed wetlands in water pollution control by reviewing the basics of the technology, the historical development, and the performance expectations with focus on the use of free water surface and subsurface flow constructed wetlands for municipal wastewater treatment.

Journal ArticleDOI
TL;DR: An increase of the rate of metabolism of an exogenous dopa tracer in the neostriatum of a subgroup of patients with a history of psychosis is discovered, consistent with the theory that a state of psychosis arises when episodic dopamine excess is superimposed on a trait of basic dopamine deficiency in the striatum.
Abstract: The hypofrontality theory of the pathogenesis of schizophrenia predicts that cortical lesions cause psychosis. During a search for abnormalities of catecholaminergic neurotransmission in patients with complex partial seizures of the mesial temporal lobe, we discovered an increase of the rate of metabolism of an exogenous dopa tracer (6-[18F]fluoro-L-dopa) in the neostriatum of a subgroup of patients with a history of psychosis. When specifically assayed for this abnormality, patients with schizophrenia revealed the same significant increase of the rate of metabolism in the striatum. The finding is consistent with the theory that a state of psychosis arises when episodic dopamine excess is superimposed on a trait of basic dopamine deficiency in the striatum. The finding is explained by the hypothesis that cortical insufficiency, a proposed pathogenetic mechanism of both disorders, causes an up-regulation of the enzymes responsible for dopa turnover in the neostriatum as well as the receptors mediating dopaminergic neurotransmission.

Journal ArticleDOI
TL;DR: Direct measurements at room temperature of the conductance of a point contact between a scanning tunneling microscope tip and Ni, Cu, and Pt surfaces and atomistic simulations show that the observed behavior is due to the quantization of the transverse electron motion in a contact which contains between one and ten atoms.
Abstract: We present direct measurements at room temperature of the conductance of a point contact between a scanning tunneling microscope tip and Ni, Cu, and Pt surfaces. As the contact is stretched the conductance jumps in units of 2${\mathit{e}}^{2}$/h. Atomistic simulations of the stretch of the contact combined with calculations of the conductance using the Landauer formula show that the observed behavior is due to the quantization of the transverse electron motion in a contact which contains between one and ten atoms.

Journal ArticleDOI
01 Nov 1994
TL;DR: In this paper, the diffusion of O 2 fluxes through the diffusive boundary layer and the depth distribution of consumption rates within the sediment were calculated from the obtained microprofiles, and the difference correlated with the abundance of macrofauna in the sediment.
Abstract: Total O 2 uptake rates were measured by the benthic flux chamber lander ELINOR, and O 2 microprofiles were measured by the profiling lander PROFILUR in the eastern South Atlantic. Diffusive O 2 fluxes through the diffusive boundary layer and the depth distribution of O 2 consumption rates within the sediment were calculated from the obtained microprofiles. The depth integrated O 2 consumption rate agreed closely with the diffusive O 2 uptake at all stations. Total O 2 uptake was 1.2–4.2 times the diffusive O 2 uptake, and the difference correlated with the abundance of macrofauna in the sediment. Diffusive O 2 uptake and O 2 -penetration depths correlated with the organic content of the sediments and exhibited an inverse correlation with water depth. Total and diffusive rates of in situ O 2 uptake were higher than previously published data for shelf and abyssal sediments in the Atlantic, but were comparable to rates from upwelling areas in the eastern Pacific. Laboratory measurements on recovered sediment cores showed lower O 2 penetration depths and higher diffusive uptake rates than in situ measurements. The differences increased with increasing water depth. We primarily ascribe this compression of O 2 profiles to a transiently increased temperature during recovery and enhanced microbial activity in decompressed sediment cores. Total O 2 uptake rates measured in the laboratory on macrofauna-rich stations were, in contrast, lower than those measured in situ because of underrepresentation and disturbance of the macrofauna.

Journal ArticleDOI
TL;DR: A causal analysis of secondary variables showed that the formation of FB memories was primarily associated with the level of importance attached to the event and level of affective response to the news.
Abstract: A large group of subjects took part in a multinational test-retest study to investigate the formation of flashbulb (FB) memories for learning the news of the resignation of the British prime minister, Margaret Thatcher. Over 86% of the U.K. subjects were found to have FB memories nearly 1 year after the resignation; their memory reports were characterized by spontaneous, accurate, and full recall of event details, including minutiae. In contrast, less than 29% of the non-U.K. subjects had FB memories 1 year later; memory reports in this group were characterized by forgetting, reconstructive errors, and confabulatory responses. A causal analysis of secondary variables showed that the formation of FB memories was primarily associated with the level of importance attached to the event and level of affective response to the news. These findings lend some support to the study by R. Brown and Kulik (1977), who suggest that FB memories may constitute a class of autobiographical memories distinguished by some form of preferential encoding.

Journal ArticleDOI
TL;DR: The piracetam-like nootropics are capable of achieving reversal of amnesia induced by scopolamine, electroconvulsive shock and hypoxia and much evidence points in the direction of a modulated ion flux by, e.g., potentiated calcium influx through non-L-type voltage-dependent calcium channels, potentiated sodium influx through alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor gated channels or

Journal ArticleDOI
TL;DR: This analysis is a formulation in terms of coupled Langevin equations which allows in a natural way for the inclusion of external force fields and finds that this result is independent of the presence of weak quenched disorder.
Abstract: We consider the combined effects of a power law L\'evy step distribution characterized by the step index f and a power law waiting time distribution characterized by the time index g on the long time behavior of a random walker. The main point of our analysis is a formulation in terms of coupled Langevin equations which allows in a natural way for the inclusion of external force fields. In the anomalous case for f2 and g1 the dynamic exponent z locks onto the ratio f/g. Drawing on recent results on L\'evy flights in the presence of a random force field we also find that this result is independent of the presence of weak quenched disorder. For d below the critical dimension ${\mathit{d}}_{\mathit{c}}$=2f-2 the disorder is relevant, corresponding to a nontrivial fixed point for the force correlation function.

Journal ArticleDOI
TL;DR: Mat samples incubated anaerobically in the presence of acetate or succinate exhibited significant potential for iron reduction, suggesting the possibility that a localized iron cycle could occur within the mat community.
Abstract: We constructed a small flow chamber in which suboxic medium containing 60 to 120 muM FeCl(2) flowed up through a sample well into an aerated reservoir, thereby creating an suboxic-oxic interface similar to the physicochemical conditions that exist in natural iron seeps. When microbial mat material from the Marselisborg iron seep that contained up to 10 bacterial cells per cm (D. Emerson and N. P. Revsbech, Appl. Environ. Microbiol. 60:4022-4031, 1994) was placed in the sample well of the chamber, essentially all of the Fe flowing through the sample well was oxidized at rates of up to 1,200 nmol of Fe oxidized per h per cm of mat material. The oxidation rates of samples of the mat that were pasteurized prior to inoculation were only about 20 to 50% of the oxidation rates of unpasteurized samples. Sodium azide also significantly inhibited oxidation. These results suggest that at least 50% and up to 80% of the Fe oxidation in the chamber were actively mediated by the microbes in the mat. It also appeared that Fe stimulated the growth of the community since chambers fed with FeCl(2) accumulated masses of either filamentous or particulate growth, both in the sample well and attached to the walls of the chamber. Control chambers that did not receive FeCl(2) showed no sign of such growth. Furthermore, after 4 to 5 days the chambers fed with FeCl(2) contained 35 to 75% more protein than chambers not supplemented with FeCl(2). Leptothrix ochracea and, to a lesser extent, Gallionella spp. were responsible for the filamentous growth, and the sheaths and stalks, respectively, of these two organisms harbored large numbers of Fe-encrusted, nonappendaged unicellular bacteria. In chambers where particulate growth predominated, the unicellular bacteria alone appeared to be the primary agents of iron oxidation. These results provide the first clear evidence that the "iron bacteria" commonly found associated with neutral-pH iron seeps are responsible for most of the iron oxidation and that the presence of ferrous iron appears to stimulate the growth of these organisms.

Journal ArticleDOI
TL;DR: In this article, a 15N isotope-pairing technique was used to distinguish between coupled nitrification-denitrification and denitrification of nitrate supplied from the water column.
Abstract: Diurnal variation of denitrification in sediments with benthic microphytes was investigated by a 15N isotope-pairing technique in order to distinguish between coupled nitrification-denitrification and denitrification of nitrate supplied from the water column. Sediments were incubated in a continuous flowthrough system and exposed to diurnal light and dark cycles. Illumination of both limnetic and estuarine sediments doubled the rate of coupled nitrification-denitrification but reduced the rate of denitrification of nitrate supplied from the water column by -50%. Photosynthesis in the uppermost sediment layers during illumination led to deeper oxygen penetration and a resultant stimulation of nitrification. This stimulation may explain the increased rate of coupled nitrification-denitrification during illumination. The rate of denitrification of nitrate supplied from the water column was reduced during illumination due to a longer diffusion path between water and the anoxic denitrification zone. Denitrification, the bacterial reduction of nitrate to nitrogen gas via nitrite, is an important nitrogen sink in aquatic environments. There are two main sources of nitrate for sediment denitrification: nitrate diffusing into the sediment from the water column and nitrate produced by nitrification in the sediment (Jenkins and Kemp 1984; Seitzinger 1988). The processes of nitrification and denitrification are usually vertically separated within the sediment (Vanderborght and Billen 1975). Nitrification is strictly aerobic and therefore restricted to a thin oxic zone in the upper few millimeters of the sediment. Denitrification takes place in anoxic environments, and in many sediments, most activity is found just below the oxic-anoxic interface (Sweerts and de Beer 1989). The rates of nitrification and denitrification in the active microenvironments are controlled by the availability of substrates, which to a large extent are supplied by diffusion along

Book ChapterDOI
09 May 1994
TL;DR: In this paper, a new group signature scheme was proposed, which hides the identity of the signer unconditionally and (unlike previous similar suggestions) allows new members to join the group.
Abstract: Group signatures, introduced by Chaum and van Heijst, allow individual members of a group to sign messages on behalf of the group. The identity of the signer is kept secret except that a group authority can identify the signer if needed. This note presents a new group signature scheme, which hides the identity of the signer unconditionally and (unlike previous similar suggestions) allows new members to join the group. Simplifying this scheme a somewhat more efficient scheme giving computational anonymity is obtained. The group authority identifies the signer using a general method. This method can also be used to simplify three of the schemes suggested by Chaum and van Heijst. Finally, the schemes suggested here can be used to solve an open problem posed by Chaum and van Heijst.

BookDOI
TL;DR: In this article, the authors provide a systematic introduction to probability theory, and in particular, those parts that are used in statistics, and discuss the law of large numbers for independent and non-independent random variables, transforms, special distributions, convergence in law, the central limit theorem for normal and infinitely divisible laws, conditional expectations and martingales.
Abstract: Volume I of this two-volume text and reference work begins by providing a foundation in measure and integration theory. It then offers a systematic introduction to probability theory, and in particular, those parts that are used in statistics. This volume discusses the law of large numbers for independent and non-independent random variables, transforms, special distributions, convergence in law, the central limit theorem for normal and infinitely divisible laws, conditional expectations and martingales. Unusual topics include the uniqueness and convergence theorem for general transforms with characteristic functions, Laplace transforms, moment transforms and generating functions as special examples. The text contains substantive applications, e.g., epidemic models, the ballot problem, stock market models and water reservoir models, and discussion of the historical background. The exercise sets contain a variety of problems ranging from simple exercises to extensions of the theory.

Journal ArticleDOI
TL;DR: It is concluded that dental fluorosis is a sensitive way of recording past fluoride exposure because, so far, no other agent or condition in man is known to create changes within the dentition similar to those induced by fluoride.
Abstract: It is now well-established that a linear relationship exists between fluoride dose and enamel fluorosis in human populations. With increasing severity, the subsurface enamel all along the tooth becomes increasingly porous (hypomineralized), and the lesion extends toward the inner enamel. In dentin, hypomineralization results in an enhancement of the incremental lines. After eruption, the more severe forms are subject to extensive mechanical breakdown of the surface. The continuum of fluoride-induced changes can best be classified by the TF index, which reflects, on an ordinal scale, the histopathological features and increases in enamel fluoride concentrations. Human and animal studies have shown that it is possible to develop dental fluorosis by exposure during enamel maturation alone. It is less apparent whether an effect of fluoride on the stage of enamel matrix secretion, alone, is able to produce changes in enamel similar to those described as dental fluorosis in man. The clinical concept of post-eruptive maturation of erupting sound human enamel, resulting in fluoride uptake, most likely reflects subclinical caries. Incorporation of fluoride into enamel is principally possible only as a result of concomitant enamel dissolution (caries lesion development). At higher fluoride concentrations, calcium-fluoride-like material may form, although the formation, identification, and dissolution of this compound are far from resolved. It is concluded that dental fluorosis is a sensitive way of recording past fluoride exposure because, so far, no other agent or condition in man is known to create changes within the dentition similar to those induced by fluoride. Since the predominant cariostatic effect of fluoride is not due to its uptake by the enamel during tooth development, it is possible to obtain extensive caries reductions without a concomitant risk of dental fluorosis.

Journal ArticleDOI
TL;DR: Two studies on otherwise unselected patients support the hypothesis that in vitro radiosensitivity of normal human skin fibroblasts correlated with clinical normal tissue reactions, and some of the methodological problems involved in this field are discussed.

Journal ArticleDOI
TL;DR: It is demonstrated that CHIP proteoliposomes exhibit all known characteristics of water channels in native red cells and therefore provide a defined system for biophysical analysis of transmembrane water movements.
Abstract: Reconstitution of highly purified aquaporin CHIP (channel-forming integral protein) into proteoliposomes was previously shown to confer high osmotic water permeability (Pf) to the membranes [Zeidel et al. (1992) Biochemistry 31, 7436-7440]. Here we report detailed ultrastructural, pharmacologic, and transport studies of human red cell CHIP in proteoliposomes. Freeze-fracture and transmission electron microscopy revealed a uniform distribution of CHIP which was incorporated into the membranes in both native and inverse orientations. Morphometric analysis of membranes reconstituted at three different concentrations of CHIP revealed that the intramembrane particles correspond to tetramers or possible higher order oligomers, and the Pf increased in direct proportion to the CHIP density. Proteolytic removal of the 4-kDa C-terminal cytoplasmic domain of CHIP did not alter the Pf or oligomerization in red cell membranes. CHIP exhibited a similar conductance for water when reconstituted into membranes of varied lipid compositions. The sensitivities of CHIP-mediated Pf to specific sulfhydryl reagents were identical to known sensitivities of red cell Pf, including a delayed response to p-(chloromercuri)benzenesulfonate. CHIP did not increase the permeability of the proteoliposome membranes to H+/OH- or NH3. These studies demonstrate that CHIP proteoliposomes exhibit all known characteristics of water channels in native red cells and therefore provide a defined system for biophysical analysis of transmembrane water movements.

Book
01 Jan 1994
TL;DR: Object-Oriented Languages and Type Systems The BOPL Language The Rest of this Book Type Checking Type Inference Inheritance Genericity The BopL Grammar The Workbench.
Abstract: Object-Oriented Languages and Type Systems The BOPL Language The Rest of this Book Type Checking Type Inference Inheritance Genericity The BOPL Grammar The Workbench.