			Home About us Contact

Inner Core (inner + core)

Distribution by Scientific Domains

Earth and Environmental Science	24%
Polymers and Materials Science	20%
Physics and Astronomy	20%
Chemistry	16%
Life Sciences	8%
Humanities and Social Sciences	8%

Selected Abstracts

Tenement City: The Emergence of Multi-storey Districts Through Large-scale Private Landlordism in Nairobi

INTERNATIONAL JOURNAL OF URBAN AND REGIONAL RESEARCH, Issue 4 2007
MARIE HUCHZERMEYER
Abstract Large-scale private landlordism dominates low-income housing provision in Nairobi, with extreme residential densities in districts where rooming tenements reach seven floors above ground. This trend differs from the small-scale private landlordism, predominantly with owner occupation, which has been documented for the developing world. Nairobi's large-scale multi-storey private rental has remained unmentioned in housing and tenure literature on the developing world. The terms ,tenement' and ,tenement city' are largely associated with nineteenth and early twentieth century rental investment in Europe and the US when cities were shaped by the profit-making interests of landlords. In this article, two case studies of tenement areas in Nairobi, low-income Huruma and middle-income Umoja Inner Core, are analysed in terms of the evolution of the tenement investment and current residential densities. The ongoing, mostly unauthorized construction of tenements suggests that Nairobi could be termed a tenement city, a reality that is not currently addressed by the urban discourse. Résumé A Nairobi, la propriété privée à grande échelle domine l'offre de logements à faible loyer, avec des densités résidentielles extrêmes dans des quartiers où les immeubles de rapport proposant des chambres s'élèvent sur sept étages. Cette tendance se distingue de la propriété privée à petite échelle, occupée essentiellement par le propriétaire, décrite pour les pays en développement. La location à grande échelle dans les immeubles privés à plusieurs étages de Nairobi n'a jamais été abordée dans les travaux sur le logement ou ses modes d'occupation dans les pays en développement. ,Immeuble de rapport' et ,cité ouvrière' sont des expressions associées d'abord aux investissements pratiqués dans le logement locatif au XIXe et au début du XXe siècle, en Europe et aux Etats-Unis, lorsque l'urbanisme était dicté par les intérêts mercantiles des propriétaires. Cet article présente deux études de cas de quartiers locatifs de Nairobi, l'un à faible revenu (Huruma), l'autre à revenu moyen (Umoja Inner Core). L'analyse s'appuie sur l'évolution de l'investissement dans les immeubles de rapport et sur les densités résidentielles courantes. Compte tenu de la construction actuelle , sauvage le plus souvent , d'immeubles de rapport, Nairobi pourrait être qualifiée de cité ouvrière, une réalité ignorée pour le moment par les débats urbains. [source]

A female-specific pentraxin, CrOctin, bridges pattern recognition receptors to bacterial phosphoethanolamine

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 12 2007
Yue Li
Abstract Pathogen recognition and binding are crucial functions of innate immunity. It has been observed that the short pentraxin superfamily including C-reactive protein (CRP) and serum amyloid,P component are pathogen pattern recognition receptors (PRR) in the plasma. We isolated and characterized a novel and distinctive pentraxin from the plasma of horseshoe crab, Carcinoscorpius rotundicauda, henceforth named CrOctin, which binds to bacteria via phosphoethanolamine (PE), a chemical component present on lipid,A and core polysaccharide moieties of bacterial lipopolysaccharide (LPS). Infection enhances the formation of the PRR interactome constituting CrOctin, CRP and galactose-binding protein. In particular, infection increases the affinity of CRP to CrOctin by 1000-fold. Furthermore, we observed that by binding to PE, CrOctin acts as a linker that bridges the PRR interactome to the inner core of LPS. On the other hand, under normal physiological conditions, binding of CrOctin to PE appears to obscure other PRR from interacting directly with PE. Interestingly, the cluster of "CrOctin-interactive PRR" is sex specific. We report, for the first time, the change in PRR protein profiles with a distinctive gender difference during Pseudomonas infection. [source]

Thiophene,Benzothiadiazole Co-Oligomers: Synthesis, Optoelectronic Properties, Electrical Characterization, and Thin-Film Patterning

ADVANCED FUNCTIONAL MATERIALS, Issue 3 2010
Manuela Melucci
Abstract Newly synthesized thiophene (T) and benzothiadiazole (B) co-oligomers of different size, alternation motifs, and alkyl substitution types are reported. Combined spectroscopic data, electrochemical analysis, and theoretical calculations show that the insertion of a single electron-deficient B unit into the aromatic backbone strongly affects the LUMO energy level. The insertion of additional B units has only a minor effect on the electronic properties. Cast films of oligomers with two alternated B rings (B,T,B inner core) display crystalline order. Bottom-contact FETs based on films cast on bare SiO2 show hole-charge mobilities of 1,×,10,3,5,×,10,3,cm2 V,1s,1 and Ion/Ioff ratios of 105,106. Solution-cast films of cyclohexyl-substituted compounds are amorphous and do not show FET behavior. However, the lack of order observed in these films can be overcome by nanorubbing and unconventional wet lithography, which allow for fine control of structural order in thin deposits. [source]

A glassy lowermost outer core

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2009
Vernon F. Cormier
SUMMARY New theories for the viscosity of metallic melts at core pressures and temperatures, together with observations of translational modes of oscillation of Earth's solid inner core, suggest a rapid increase in the dynamic viscosity near the bottom of the liquid outer core. If the viscosity of the lowermost outer core (F region) is sufficiently high, it may be in a glassy state, characterized by a frequency dependent shear modulus and increased viscoselastic attenuation. In testing this hypothesis, the amplitudes of high-frequency PKiKP waves are found to be consistent with an upper bound to shear velocity in the lowermost outer core of 0.5 km s,1 at 1 Hz. The fit of a Maxwell rheology to the frequency dependent shear modulus constrained by seismic observations at both low and high-frequency favours a model of the F region as a 400-km-thick chemical boundary layer. This layer has both a higher density and higher viscosity than the bulk of the outer core, with a peak viscosity on the order of 109 Pa s or higher near the inner core boundary. If lateral variations in the F region are confirmed to correlate with lateral variations observed in the structure of the uppermost inner core, they may be used to map differences in the solidification process of the inner core and flow in the lowermost outer core. [source]

Variations in the Earth's gravity field caused by torsional oscillations in the core

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2004
Mathieu Dumberry
SUMMARY We investigate whether a component of the flow in the Earth's fluid core, namely torsional oscillations, could be detected in gravity field data at the surface and whether it could explain some of the observed time variations in the elliptical part of the gravity field (J2). Torsional oscillations are azimuthal oscillations of rigid coaxial cylindrical surfaces and have typical periods of decades. This type of fluid motion supports geostrophic pressure gradients, which produce deformations of the core,mantle boundary. Because of the density discontinuity between the core and the mantle, such deformations produce changes in the gravity field that, because of the flow geometry, are both axisymmetric and symmetric about the equator. Torsional oscillations are thus expected to produce time variations in the zonal harmonics of even degree in the gravity field. Similarly, the changes in the rotation rates of the mantle and inner core that occur to balance the change in angular momentum carried by the torsional oscillations also produce zonal variations in gravity. We have built a model to calculate the changes in the gravity field and in the rotation rates of the mantle and inner core produced by torsional oscillations. We show that the changes in the rotation rate of the inner core produce changes in J2 that are a few orders of magnitude too small to be observed. The amplitudes of the changes in J2 from torsional oscillations are 10 times smaller than the temporal changes that are observed to occur about a linear secular trend. However, provided the mechanism responsible for these changes in J2 is identified and that this contribution is removed from the data, it may be possible in the future to detect the lowest harmonic degrees of the torsional oscillations in the gravity field data. We also show that torsional oscillations have contributed to the linear secular change in J2 by about ,0.75 × 10,12 per year in the last 20 years. Finally, the associated change in the vertical ground motion at the surface of the Earth that is predicted by our mechanism is of the order of 0.2 mm, which is too small to be detected with the current precision in measurements. [source]

Can the Earth's dynamo run on heat alone?

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2003
David Gubbins
SUMMARY The power required to drive the geodynamo places significant constraints on the heat passing across the core,mantle boundary and the Earth's thermal history. Calculations to date have been limited by inaccuracies in the properties of liquid iron mixtures at core pressures and temperatures. Here we re-examine the problem of core energetics in the light of new first-principles calculations for the properties of liquid iron. There is disagreement on the fate of gravitational energy released by contraction on cooling. We show that only a small fraction of this energy, that associated with heating resulting from changes in pressure, is available to drive convection and the dynamo. This leaves two very simple equations in the cooling rate and radioactive heating, one yielding the heat flux out of the core and the other the entropy gain of electrical and thermal dissipation, the two main dissipative processes. This paper is restricted to thermal convection in a pure iron core; compositional convection in a liquid iron mixture is considered in a companion paper. We show that heat sources alone are unlikely to be adequate to power the geodynamo because they require a rapid secular cooling rate, which implies a very young inner core, or a combination of cooling and substantial radioactive heating, which requires a very large heat flux across the core,mantle boundary. A simple calculation with no inner core shows even higher heat fluxes are required in the absence of latent heat before the inner core formed. [source]

Preparation and in vitro release of D,L -tetrahydropalmatine-loaded graft copolymer nanoparticles

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008
Yinglei Zhai
Abstract D,L -tetrahydropalmatine (THP)-loaded poly{[,-maleic anhydride-,-methoxy-poly(ethylene glycol)]- co -(ethy cyanoacrylate)} (PEGECA) amphiphilic graft copolymer nanoparticles (PEGECAT NPs) were prepared by the nanoprecipitation technique. The effects of solvent property, temperature, copolymer composition, and drug feeding on the drug-loaded amount and size of PEGECAT NPs were investigated. The morphological structure of PEGECAT NPs was characterized by transmission electron microscopy (TEM), proton nuclear magnetic resonance (1H NMR), and the size was measured by laser particle size analyzer (LPSA). In vitro release behaviors of drug from PEGECAT NPs were examined by high-pressure liquid chromatography (HPLC). The results demonstrate that PEGECAT NPs take on a spherical morphology with an inner core and outer shell before and after in vitro release. THP can be incorporated into the hydrophobic core of PEGECAT NPs and the drug-loaded amount is higher than 5%. The release of THP from PEGECAT NPs is initially fast and then slows down. The accumulated release is lower than 40% after 48 h. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Spatial insulin signalling in isolated skeletal muscle preparations

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 5 2010
Peter Sogaard
Abstract During in vitro incubation in the absence or presence of insulin, glycogen depletion occurs in the inner core of the muscle specimen, concomitant with increased staining of hypoxia-induced-factor-1-alpha and caspase-3, markers of hypoxia and apoptosis, respectively. The aim of this study was to determine whether insulin is able to diffuse across the entire muscle specimen in sufficient amounts to activate signalling cascades to promote glucose uptake and glycogenesis within isolated mouse skeletal muscle. Phosphoprotein multiplex assay on lysates from muscle preparation was performed to detect phosphorylation of insulin-receptor on Tyr1146, Akt on Ser473 and glycogen-synthases-kinase-3 on Ser21/Ser9. To address the spatial resolution of insulin signalling, immunohistochemistry studies on cryosections were performed. Our results provide evidence to suggest that during the in vitro incubation, insulin sufficiently diffuses into the centre of tubular mouse muscles to promote phosphorylation of these signalling events. Interestingly, increased insulin signalling was observed in the core of the incubated muscle specimens, correlating with the location of oxidative fibres. In conclusion, insulin action was not restricted due to insufficient diffusion of the hormone during in vitro incubation in either extensor digitorum longus or soleus muscles from mouse under the specific experimental settings employed in this study. Hence, we suggest that the glycogen depleted core as earlier observed is not due to insufficient insulin action. J. Cell. Biochem. 109: 943,949, 2010. © 2010 Wiley-Liss, Inc. [source]

Tastier and Healthier Alternatives to French Fries

JOURNAL OF FOOD SCIENCE, Issue 4 2010
Caius M. Rommens
ABSTRACT:, The effect of both the origin and shape of potato cuts on fry quality was investigated in this study. Linear strips from the inner core of tubers were compared to those from outer tissues, both before and after processing, and strips from either specific tissues or whole peeled tubers were also evaluated against ring-shaped cuts. Both strips and rings had 0.7 cm sides and, in most cases, a volume of 4.9 cm3. They were analyzed for moisture content, antioxidants, asparagine, and reducing sugars. The material was then blanched, dipped in 0.5% disodium acid pyrophosphate and 0.3% glucose, dried at 77 °C, par-fried in soybean oil at 191 °C, and finish-fried at 168 °C. The fried product was analyzed for sensory characteristics and oil, salt, and acrylamide content. Our results showed that strips from the inner core absorbed 28% more oil and exhibited inferior sensory characteristics compared to strips from the outer parts. The extended drying and frying times needed to match the crispness and flavor of inner strips to those of regularly fried outer strips resulted in a further increased absorption of oil and, importantly, triggered a 163% increase in levels of the toxic Maillard reaction product acrylamide. Potato rings consisted of higher dry matter material, contained more antioxidants, and had a lower surface-to-volume ratio than the conventional linear strips. Upon processing, they also absorbed 22% less oil, contained 26% less salt, and displayed superior sensory properties. Thus, ring fries may represent an attractive alternative to French fries as processed staple food. [source]

Fat Uptake in French Fries as Affected by Different Potato Varieties and Processing

JOURNAL OF FOOD SCIENCE, Issue 6 2001
C.J. O'Connor
ABSTRACT: The uptake of lipid into French fries was investigated using two varieties of potato (,Russet Burbank' and ,Agria') and the New Zealand sweet potato, Ipomoea batatas, (kumara). The variety of potato used had a significant effect on lipid uptake, with ,Agria' having the lowest lipid content. The different cellular structures may have affected the fat uptake in the French fries by influencing either the loss of moisture during finish-frying or the damage done to the original anatomy during processing before pre-frying. The French fries that had undergone frozen storage had a higher amount of lipid contained in their inner core than did those that had been either chilled or prepared freshly for frying. [source]

Study of the solubilization of gliclazide by aqueous micellar solutions

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2003
Khouloud A. Alkhamis
Abstract It was of interest to increase the solubility of gliclazide in aqueous media. Therefore, solubilization of gliclazide in a variety of surfactants was investigated. Anionic and cationic surfactants exhibited dramatic solubilizing ability for gliclazide, whereas nonionic surfactants showed significantly lower solubilizing ability. It was found that gliclazide solubility increases with increasing the carbon chain length of cationic surfactants and decreases with increasing the carbon chain length of anionic surfactants. The solubilization data were analyzed on the basis of a pseudo-phase model with gliclazide exhibiting moderate partition coefficients into the micellar phase. The possible sites of solubilization of gliclazide in the micelle were examined by studying the effect of NaCl on solubilization and by comparing the absorption spectra of gliclazide in different solvents. The results obtained from these two experiments indicated that gliclazide is solubilized mainly in the inner core of the cationic surfactant micelles and in the outer regions of the anionic surfactant micelles. © 2003 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 92:839,846, 2003 [source]

Synthesis and characterization of amphiphilic block copolymers with allyl side-groups

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2007
Xiuli Hu
Abstract The synthesis of a new cyclic carbonate monomer containing an allyl group was reported and its biodegradable amphiphilic block copolymer, poly(ethylene glycol)- block -poly(L -lactide- co -5-methyl-5-allyloxycarbonyl-propylene carbonate) [PEG- b -P(LA- co -MAC)] was synthesized by ring-opening polymerization (ROP) of L -lactide (LA) and 5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one (MAC) in the presence of poly (ethylene glycol) as a macroinitiator, with diethyl zinc as a catalyst. 13C NMR and 1H NMR were used for microstructure identification of the copolymers. The copolymer could form micelles in aqueous solution. The core of the micelles is built of the hydrophobic P(LA- co -MAC) chains, whereas the shell is set up by the hydrophilic PEG blocks. The micelles exhibited a homogeneous spherical morphology and unimodal size distribution. By using the cyclic carbonate monomer containing allyl side-groups, crosslinking of the PEG- b -P(LA- co -MAC) inner core was possible. The adhesion and spreading of ECV-304 cells on the copolymer were better than that on PLA films. Therefore, this biodegradable amphiphilic block copolymer is expected to be used as a biomaterial for drug delivery and tissue engineering. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5518,5528, 2007 [source]

Synthesis and characterization of core,shell-type polymeric micelles from diblock copolymers via reversible addition,fragmentation chain transfer

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2006
Ping Zhang
Abstract A method was developed to enable the formation of nanoparticles by reversible addition,fragmentation chain transfer polymerization. The thermoresponsive behavior of polymeric micelles was modified by means of micellar inner cores and an outer shell. Polymeric micelles comprising AB block copolymers of poly(N -isopropylacrylamide) (PIPAAm) and poly(2-hydroxyethylacrylate) (PHEA) or polystyrene (PSt) were prepared. PIPAAm- b -PHEA and PIPAAm- b -PSt block copolymers formed a core,shell micellar structure after the dialysis of the block copolymer solutions in organic solvents against water at 20 °C. Upon heating above the lower critical solution temperature (LCST), PIPAAm- b -PHEA micelles exhibited an abrupt increase in polarity and an abrupt decrease in rigidity sensed by pyrene. In contrast, PIPAAm- b -PSt micelles maintained constant values with lower polarity and higher rigidity than those of PIPAAm- b -PHEA micelles over the temperature range of 20,40 °C. Structural deformations produced by the change in the outer polymer shell with temperature cycles through the LCST were proposed for the PHEA core, which possessed a lower glass-transition temperature (ca. 20 °C) than the LCST of the PIPAAm outer shell (ca. 32.5 °C), whereas the PSt core with a much higher glass-transition temperature (ca. 100 °C) retained its structure. The nature of the hydrophobic segments composing the micelle inner core offered an important control point for thermoresponsive drug release and the drug activity of the thermoresponsive polymeric micelles. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3312,3320, 2006 [source]

The parameterization of solid metal-liquid metal partitioning of siderophile elements

METEORITICS & PLANETARY SCIENCE, Issue 10 2003
Nancy L. CHABOT
We present a method for parameterizing solid metal-liquid metal partition coefficients for siderophile (metal-loving) elements as a function of the metallic liquid composition. Our parameterization method is based on an older theory of Jones and Malvin (1990), which stated that the metallic liquid is composed of metal and non-metal-bearing domains, and the domains are the dominant influence on the partitioning behavior. By revising the means by which the metal domains are calculated, our revised parameterization method is able to match experimental partitioning data from the Fe-Ni-S, Fe-Ni-P, Fe-Ni-S-P, and Fe-Ni-C systems. Mathematical expressions were derived for the solid metal-liquid metal partitioning of 13 siderophile elements. Elements that are chalcophile (S-loving), P-loving, or C-loving prefer the non-metal-bearing domains in the metallic liquid and, consequently, aren't fit by the parameterization method presented here. Possible applications for our parameterization method include modeling the crystallization of iron meteorites, planetary differentiation, and the solidification of Earth's inner core. [source]

Identification of a gene (lpt-3) required for the addition of phosphoethanolamine to the lipopolysaccharide inner core of Neisseria meningitidis and its role in mediating susceptibility to bactericidal killing and opsonophagocytosis

MOLECULAR MICROBIOLOGY, Issue 4 2002
Fiona G. Mackinnon
Summary We have identified a gene, lpt-3, that is required for the addition of phosphoethanolamine to the 3-position (PEtn-3) on the , -chain heptose (HepII) of the inner core lipopolysaccharide (LPS) of Neisseria meningitidis (Nm). The presence of this PEtn-3 substituent is characteristic of the LPS of a majority (, 70%) of hypervirulent Nm strains, irrespective of capsular serogroup, and is required for the binding of a previously described monoclonal antibody (mAb B5) to a surface-accessible epitope. All strains of Nm that have PEtn-3 possess the lpt-3 gene. In some lpt-3 -containing strains, the 3-position on HepII is preferentially substituted by glucose instead of PEtn, the result of lgtG phase variation mediated by slippage of a homopolymeric tract of cytidines. Inactivation of lpt-3 resulted in loss of PEtn-3, lack of reactivity with mAb B5 and conferred relative resistance to bactericidal killing and opsonophagocytosis by mAb B5 in vitro. Thus, the identification of lpt-3 has facilitated rigorous genetic, structural and immunobiological definition of an immunodominant epitope that is a candidate immunogen for inclusion in an LPS-based vaccine to protect against invasive meningococcal disease. [source]

FMR study of amorphous Co68Mn7Si10B15 glass-coated microwires

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003
R. Zuberek
Abstract The magnetic properties of Co68Mn7Si10B15 glass coated amorphous microwires of about 16.5 ,m in diameter have been investigated from liquid helium up to room temperature by ferromagnetic resonance at 9.243 GHz. Based on the results of measurements both the magnetic anisotropy constants, the first arising from the stress at the interface between the metallic surface and the coating and the second one of the inner core have been obtained for the room temperature. The effective anisotropy field was determined in the range from the liquid helium to the room temperature. [source]

Explaining Fascism and Ethnic Cleansing: The Three Dimensions of Charisma and the Four Dark Sides of Nationalism

POLITICAL STUDIES REVIEW, Issue 3 2006
Roger Eatwell
Ideas and leaders matter. Fascism's syncretic ideology is crucial to understanding its rise and support. So too is the coterie charisma exerted by leaders like Hitler over an inner core even in the wilderness years; his centripetal charisma went on to help attract the masses to the ,Führer party' for very diverse reasons; and the cultic charisma leaders developed especially when in power further helps explain their appeal. The four dark sides of nationalism , namely, its ethnic, religious, scientific and economic dimensions , are also crucial to understanding genocide. So too is leadership: no Hitler, no Holocaust. Genocide also points to the importance of lower levels of leaders, who were sometimes influenced by the charisma of the ,great' leader, although in other cases, such as Milosevic's Serbia, the charismatisation of the national idea was more influential. [source]

SHRIMP U-Pb Zircon Age of the Inishi Migmatite around the Kamioka Mining Area, Hida Metamorphic Complex, Central Japan

RESOURCE GEOLOGY, Issue 1 2006
Masatoshi Sakoda
Abstract. SHRIMP U-Pb ages were determined on single zircons separated from the Inishi migmatite in the Kamioka mining area, Hida metamorphic complex, central Japan. Twenty one determinations were distributed within the age of 234.2±1.8 Ma, excluding one inner core of a grain. As the analyzed crystals were mostly euhedral igneous zircons, the age indicates the crystallization of zircons from granitic melt during the formation of Inishi migmatite. The age of ca. 234 Ma corresponded to the later stage of the major regional metamorphic event in the Hida complex, while the age of ca. 265 Ma determined in a grain suggested the inherited age of the earlier phase of the metamorphism. [source]

Hydrogen-bonding controls the solid-state and enantiomeric comformations of the amino alcohol ligand 2-[(2-hydroxyethyl)amino]cyclohexanol

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2010
Alvaro S. de Sousa
The crystal structure of the title compound, C8H17NO2, consists of (R,R) and (S,S) enantiomeric pairs packed in adjacent double layers which are characterized by centrosymmetric hydrogen-bonded dimers, generated via N,H...O and O,H...O interactions, respectively. Intermolecular interactions, related to acceptor and donor molecule chirality, link the achiral double layers into tubular columns, which consist of a staggered hydrophilic inner core surrounded by a hydrophobic cycloalkyl outer surface and extend in the [011] direction. [source]

Secular changes of LOD associated with a growth of the inner core

ASTRONOMISCHE NACHRICHTEN, Issue 4 2006
C. Denis
Abstract From recent estimates of the age of the inner core based on the theory of thermal evolution of the core, we estimate that nowadays the growth of the inner core may perhaps contribute to the observed overall secular increase of LOD caused mainly by tidal friction (i.e., 1.72 ms per century) by a relative decrease of 2 to 7 µs per century. Another, albeit much less plausible, hypothesis is that crystallization of the inner core does not produce any change of LOD, but makes the inner core rotate differentially with respect to the outer core and mantle. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

The cause of superchrons

ASTRONOMY & GEOPHYSICS, Issue 6 2001
J A Jacobs
Superchrons , long periods in the geomagnetic record when the Earth's magnetic field did not reverse its polarity , are a challenge to observers and theorists. Jack Jacobs outlines the problems and some possible solutions. Reversals of polarity are a feature of the geomagnetic record for all the time it has been documented. Although not regular, reversals are sufficiently frequent for their absence to be noticeable. When the Earth's magnetic field retains the same polarity for over 20 million years, a superchron is established. Superchrons demand the attention of geophysicists concerned with the generation of the Earth's field: either they must result from an intrinsic feature of the geodynamo, or they reflect the influence of some external force. Here I discuss internal and external mechanisms for the formation of superchrons, including the role of the inner core, true polar wander, Earth's orbital variations and tides. [source]