Thermal control system corrosion study

During the development of an expert system for autonomous control of the Space Station Thermal Control System (TCS), the thermal performance of the Brassboard TCS began to gradually degrade. This degradation was due to filter clogging by metallic residue. A study was initiated to determine the source of the residue and the basic cause of the corrosion. The investigation focused on the TCS design, materials compatibility, Ames operating and maintenance procedures, and chemical analysis of the residue and of the anhydrous ammonia used as the principal refrigerant. It was concluded that the corrosion mechanisms involved two processes: the reaction of water alone with large, untreated aluminum parts in a high pH environment and the presence of chlorides and chloride salts. These salts will attack the aluminum oxide layer and may enable galvanic corrosion between the aluminum and the more noble stainless steel and other metallic elements present. Recommendations are made for modifications to the system design, the materials used, and the operating and maintenance procedures, which should largely prevent the recurrence of these corrosion mechanisms

Genetic analysis of milk urea nitrogen and relationships with yield and fertility across lactation

AbstractThe aim of this project was to investigate the relationship of milk urea nitrogen (MUN) with 3 milk production traits [milk yield (MY), fat yield (FY), protein yield (PY)] and 6 fertility measures (number of inseminations, calving interval, interval from calving to first insemination, interval from calving to last insemination, interval from first to last insemination, and pregnancy at first insemination). Data consisted of 635,289 test-day records of MY, FY, PY, and MUN on 76,959 first-lactation Swedish Holstein cows calving from 2001 to 2003, and corresponding lactation records for the fertility traits. Yields and MUN were analyzed with a random regression model followed by a multi-trait model in which the lactation was broken into 10 monthly periods. Heritability for MUN was stable across lactation (between 0.16 and 0.18), whereas MY, FY, and PY had low heritability at the beginning of lactation, which increased with time and stabilized after 100 d in milk, at 0.47, 0.36, and 0.44, respectively. Fertility traits had low heritabilities (0.02 to 0.05). Phenotypic correlations of MUN and milk production traits were between 0.13 (beginning of lactation) and 0.00 (end of lactation). Genetic correlations of MUN and MY, FY, and PY followed similar trends and were positive (0.22) at the beginning and negative (−0.15) at the end of lactation. Phenotypic correlations of MUN and fertility were close to zero. A surprising result was that genetic correlations of MUN and fertility traits suggest a positive relationship between the 2 traits for most of the lactation, indicating that animals with breeding values for increased MUN also had breeding values for improved fertility. This result was obtained with a random regression model as well as with a multi-trait model. The analyzed group of cows had a moderate level of MUN concentration. In such a population MUN concentration may increase slightly due to selection for improved fertility. Conversely, selection for increased MUN concentration may improve fertility slightly

Vibrational Spectroscopy of Glycans in Helium Nanodroplets

A central theme among the glycosciences is the Janus-faced nature ofglycans. Their tremendous structural diversity enables a myriad ofbiological functions ranging from energy storage to molecular recogni-tion processes. But at the same time, this structural diversity poses aformidable challenge for glycan analysis that impedes the full develop-ment of structural glycobiology. In contrast to genomics and proteomics,glycomics lacks generic sequencing methods that allow reliable, high-throughput analyses with low sample consumption. Instead, a variety ofsophisticated methods is used for glycan analysis, including mass spec-trometry. A general challenge using mass spectrometry alone, however,is the unambiguous identification of isomeric glycans. Therefore, it isoften coupled to orthogonal techniques, such as liquid chromatography.In the last two decades, the combination of mass spectrometry andgas-phase action spectroscopy emerged for glycan analysis. Variouschallenges, however, limited gas-phase spectroscopy to smaller glycans.In particular, the thermal activation of ions during the measurement ininfrared multiple-photon dissociation spectroscopy leads to significantline-broadening, which limits the amount of structural information thatcan be obtained by this method.This work overcomes these limitations by combining mass spectrom-etry and cryogenic vibrational spectroscopy using superfluid helium nanodroplets. The unique low-temperature environment of heliumdroplets allows the acquisition of vibrational spectra in the absenceof significant thermal contributions. A systematic study of isomericglycans demonstrates the outstanding resolving power that provides avariety of well-resolved absorption bands that are unique to each isomer:a true spectral fingerprint. The unique optical signatures allow theresolution of even minute structural details, such as the stereochemicalorientation of a single hydroxy group.The exceptional ability of this method to resolve structural detailswas used to investigate an elusive rearrangement reaction, called fu-cose migration, which frequently leads to the detection of misleadingfragment ions and erroneous sequence assignments in tandem massspectrometry. Because fucose migration was only observed in fragmentions, it was strictly associated with the fragmentation process. In thiswork, cryogenic vibrational spectroscopy reveals that fucose migrationis not restricted to fragment ions, and instead occurs in intact ions aswell. These results generalize fucose migration to a universal issue inmass spectrometry as a whole.In another study, the combination of cryogenic vibrational spec-troscopy and first-principles theory was used to unravel the structureof glycosyl cations, the key intermediates during chemical glycosyla-tion reactions. Various reaction pathways were postulated many yearsago, but the exact structure of glycosyl cations remained obscure dueto their short-lived and reactive nature in the condensed phase. Inthis work, the fragmentation of precursor ions was used to generateglycosyl cations in the gas phase, which provides a unique clean-roomenvironment that stabilizes these transient intermediates. The highlyresolved vibrational spectra obtained for various glycosyl cations allowan in-depth structural analysis that reveals detailed insights into the two fundamental structural motifs that enable stereoselective glycosylationreactions: neighboring group participation and remote participation.These results facilitate the mechanistic understanding of glycosylationreactions and will eventually lead to a more rational design of buildingblocks that is based on structural rather than anecdotal evidence.Een centraal thema in de glyco-wetenschappen is het dubbele karaktervan glycanen. Enerzijds maakt de enorme structurele diversiteit vanglycanen een groot aantal biologische functies mogelijk, variërend vanenergieopslag tot moleculaire herkenningsprocessen. Maar tegelijkertijdvormt deze structurele diversiteit een enorme uitdaging voor de ana-lyse van glycanen, wat de ontwikkeling van structurele glycobiologiebelemmert. In tegenstelling tot genomics en proteomics, ontbreekthet glycomics aan een generieke sequentiemethode die betrouwbare,high-throughput analyses van kleine hoeveelheden glycanen mogelijkmaakt. In plaats daarvan wordt een verscheidenheid aan geavanceerdemethoden gebruikt, waaronder massaspectrometrie. Met uitsluitendmassa-spectrometrische methoden, is een eenduidige identificatie vanverschillende isomeren van glycanen echter slechts beperkt mogelijk.Daarom wordt massaspectrometrie vaak gekoppeld aan orthogonale tech-nieken, zoals vloeistofchromatografie. In de laatste twee decennia is ookde combinatie van massaspectrometrie met gasfase-actiespectroscopieopgekomen voor glycaan analyse. Deze combinatie is tot dusver metname gebruikt voor de analyse van kleinere glycanen. In het bijzonderleidt de thermische activering van ionen gedurende infrarood multifotondissociatie spectroscopie tot een significante lijnverbreding, hetgeen de hoeveelheid structurele informatie beperkt die met deze methodeverkregen kan worden.Het onderzoek beschreven in dit proefschrift lost deze beperkingenop door massaspectrometrie te combineren met cryogene vibratiespec-troscopie, gebruikmakend van superfluïde helium nanodruppels. Delage temperatuur in de heliumdruppels maakt de opname van vibratie-spectra mogelijk in afwezigheid van significante thermische bijdragen.Een systematische studie van isomere glycanen toont het uitstekendeoplossend vermogen van deze techniek. De spectra bevatten volledigopgeloste absorptiebanden die uniek zijn voor een specifiek isomeer:een echte spectrale vingerafdruk. Deze spectra maken een identificatiemogelijk van zeer subtiele structurele details, zoals de stereochemie vaneen enkele hydroxygroep.Het uitzonderlijke vermogen van deze methode om structurele de-tails te onderscheiden is gebruikt om een lastige migratie-reactie, dezogenaamde fucose migratie, te onderzoeken. Deze migratie-reactie leidtvaak tot de detectie van misleidende fragmentionen en foutieve sequen-tietoewijzingen in tandem massaspectrometrie. Omdat fucose migratiealleen werd waargenomen in fragmentionen, werd het enkel geassoci-eerd met het fragmentatieproces. Zoals beschreven in dit proefschrift,onthult cryogene vibratiespectroscopie dat fucose migratie niet beperktis tot fragmentionen maar dat dit ook voorkomt in intacte ionen. Dezeresultaten maken duidelijk dat fucose migratie een universele kwestie isin de massaspectrometrie.In een andere studie is de combinatie van cryogene vibratiespectro-scopie en ab initio theorie gebruikt om de structuur van glycosylkationen,de belangrijkste tussenproducten tijdens chemische glycosyleringsreac-ties, te ontrafelen. Verschillende reactiepaden zijn vele jaren geledengepostuleerd, maar de exacte structuur van glycosylkationen bleef onduidelijk vanwege hun kortstondige en reactieve aard in de gecondenseerdefase. In dit werk is de fragmentatie van precursor-ionen gebruikt omglycosylkationen te genereren in de gasfase. Dit creëert een unieke“clean-room” omgeving die deze tijdelijke tussenproducten stabiliseert.De vibratiespectra verkregen voor verschillende glycosylkationen makeneen diepgaande structurele analyse mogelijk. Dit onthult gedetailleerdeinzichten in de twee fundamentele structurele motieven die stereoselec-tieve glycosyleringsreacties mogelijk maken: participatie van naburigegroepen en participatie op afstand. Deze resultaten maken een mecha-nistisch begrip van glycosyleringsreacties mogelijk en zullen uiteindelijkleiden tot een rationeler ontwerp van de benodigde bouwstenen, geba-seerd op structureel in plaats van anekdotisch bewijs

Community Structure in the United States House of Representatives

We investigate the networks of committee and subcommittee assignments in the United States House of Representatives from the 101st--108th Congresses, with the committees connected by ``interlocks'' or common membership. We examine the community structure in these networks using several methods, revealing strong links between certain committees as well as an intrinsic hierarchical structure in the House as a whole. We identify structural changes, including additional hierarchical levels and higher modularity, resulting from the 1994 election, in which the Republican party earned majority status in the House for the first time in more than forty years. We also combine our network approach with analysis of roll call votes using singular value decomposition to uncover correlations between the political and organizational structure of House committees.Comment: 44 pages, 13 figures (some with multiple parts and most in color), 9 tables, to appear in Physica A; new figures and revised discussion (including extra introductory material) for this versio

Clarification of the role of the TBC1D24 gene in human genetic conditions

Des variants pathogéniques du gène TBC1D24 sont associés à des maladies génétiques dont la majorité sont transmises d’une façon autosomique récessive. Les phénotypes sont variables en termes de présentation clinique et de sévérité. Les formes les plus sévères causent une encéphalopathie épileptique (EIEE16) ou le syndrome DOORS qui est marqué par une surdité, des anomalies des ongles et des doigts, un déficit intellectuel et des convulsions qui sont souvent difficiles à contrôler. D’autres formes d’épilepsie incluent EPRPDC (Rolandic epilepsy with paroxysmal exercise-induce dystonia and writer's cramp), FIME (familial infantile myoclonic epilepsy), et PME (progressive myoclonus epilepsy). Une variant faux-sens spécifique est associée à une surdité autosomique dominante (DFNA65) qui se développe à l’âge adulte. Nous avons écrit un guide de pratique clinique qui inclut une revue de la littérature sur les phénotypes publiés chez les individus avec des variantes pathogénique du gène TBC1D24 avec de recommandations pour le suivi clinique de ces patients. De plus, une cohorte de huit patients avec déficience intellectuelle et épilepsie qui partagent une microdélétion sur le chromosome 16p13.3 contenant le gène TBC1D24 a été assemblée et caractérisée afin de définir un nouveau syndrome génétique. La région critique contient TBC1D24, ATP6V0C et PDPK1. Le phénotype similaire entre les huit individus suggère que l’haploinsuffisance pour TBC1D24, ATP6V0C et PDPK1 cause un nouveau syndrome génétique. L’etude des gènes essentiels pour le phénotype dans cette cohorte aide dans l’identification des nouveaux gènes candidates pour la déficience intellectuelle et épilepsie.Pathogenic variants in the TBC1D24 gene are associated with genetic disorders, the majority of which are transmitted in an autosomal recessive manner. The phenotypes are variable in terms of clinical presentation and severity. The most severe forms cause epileptic encephalopathy (EIEE16) or DOORS syndrome which is marked by deafness, abnormalities of the nails and fingers, intellectual deficit and convulsions which are often difficult to control. Other forms of epilepsy include EPRPDC (Rolandic epilepsy with paroxysmal exercise-induce dystonia and writer's cramp), FIME (familial infantile myoclonic epilepsy), and PME (progressive myoclonus epilepsy). A specific missense variant is associated with autosomal dominant deafness (DFNA65) which develops in adulthood. A review of the literature of the published phenotypes observed in individuals with pathogenic variants in the TBC1D24 gene is presented here with recommendations for the clinical management of these patients. In addition, a group of eight patients with intellectual disability and epilepsy who share a microdeletion on chromosome 1613.3 containing the TBC1D24 gene were characterized in order to define a new genetic syndrome. The critical region contains TBC1D24, ATP6V0C and PDPK1. The significantly similar phenotype shared by the eight individuals suggests that haploinsufficiency for TBC1D24, ATP6V0C and PDPK1 causes a new genetic syndrome. Knowledge of the genes essential for the phenotype in this cohort helps in the identification of new candidate genes for intellectual disability and epilepsy

Approximate solutions to a model of two-component reactive flow

We consider a model of motion of binary mixture, based on the compressible Navier-Stokes system. The mass balances of chemically reacting species are described by the reaction-diffusion equations with generalized form of multicomponent difiusion ux. Under a special relation between the two density dependent viscosity coefficients and for singular cold pressure we construct the weak solutions passing through several levels of approximation

Heat-Conducting, Compressible Mixtures with Multicomponent Diffusion: Construction of a Weak Solution

We investigate a coupling between the compressible Navier'stokes-Fourier system and the full Maxwell'stefan equations. This model describes the motion of a chemically reacting heat-conducting gaseous mixture. The viscosity coefficients are density-dependent functions vanishing in a vacuum and the internal pressure depends on species concentrations. By several levels of approximation we prove the global-in-time existence of weak solutions on the three-dimensional torus

A caricature of a singular curvature flow in the plane

We study a singular parabolic equation of the total variation type in one dimension. The problem is a simplification of the singular curvature flow. We show existence and uniqueness of weak solutions. We also prove existence of weak solutions to the semi-discretization of the problem as well as convergence of the approximating sequences. The semi-discretization shows that facets must form. For a class of initial data we are able to study in details the facet formation and interactions and their asymptotic behavior. We notice that our qualitative results may be interpreted with the help of a special composition of multivalued operators

Remote participation during glycosylation reactions of galactose building blocks: Direct evidence from cryogenic vibrational spectroscopy

The stereoselective formation of 1,2‐cis‐glycosidic bonds is challenging. However, 1,2‐cis‐selectivity can be induced by remote participation of C4 or C6 ester groups. Reactions involving remote participation are believed to proceed via a key ionic intermediate, the glycosyl cation. Although mechanistic pathways were postulated many years ago, the structure of the reaction intermediates remained elusive owing to their short‐lived nature. Herein, we unravel the structure of glycosyl cations involved in remote participation reactions via cryogenic vibrational spectroscopy and first principles theory. Acetyl groups at C4 ensure α‐selective galactosylations by forming a covalent bond to the anomeric carbon in dioxolenium‐type ions. Unexpectedly, also benzyl ether protecting groups can engage in remote participation and promote the stereoselective formation of 1,2‐cis‐glycosidic bonds

Role of social environment and social clustering in spread of opinions in co-evolving networks

Taking a pragmatic approach to the processes involved in the phenomena of collective opinion formation, we investigate two specific modifications to the co-evolving network voter model of opinion formation, studied by Holme and Newman [1]. First, we replace the rewiring probability parameter by a distribution of probability of accepting or rejecting opinions between individuals, accounting for the asymmetric influences in relationships among individuals in a social group. Second, we modify the rewiring step by a path-length-based preference for rewiring that reinforces local clustering. We have investigated the influences of these modifications on the outcomes of the simulations of this model. We found that varying the shape of the distribution of probability of accepting or rejecting opinions can lead to the emergence of two qualitatively distinct final states, one having several isolated connected components each in internal consensus leading to the existence of diverse set of opinions and the other having one single dominant connected component with each node within it having the same opinion. Furthermore, and more importantly, we found that the initial clustering in network can also induce similar transitions. Our investigation also brings forward that these transitions are governed by a weak and complex dependence on system size. We found that the networks in the final states of the model have rich structural properties including the small world property for some parameter regimes. [1] P. Holme and M. Newman, Phys. Rev. E 74, 056108 (2006)