bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication of nanogapped single-electron transistors for transport studies of individual single-molecule magnets
Authors: Henderson J. J. , Ramsey C. M. , del Barco E. , Mishra A. , Christou G.
Published: April 2007

Three-terminal single-electron transistor devices utilizing Al∕Al2O3 gate electrodes were developed for the study of electron transport through individual single-molecule magnets (SMMs). The devices were patterned via multiple layers of optical and electron beam lithography. Electromigration induced breaking of the nanowires reliably produces 1–3nm gaps between which the SMM can be situated. Conductance through a single Mn12 (3-thiophenecarboxylate) displays the Coulomb blockade effect with several excitations within ±40meV.
Magnetic properties of an Fe(II) meso-tetra(4-pyridyl)porphyrin network
Authors: Danilovic D. , Lin C. L. , Yuen Tan , Pan Long , Li Jing
Published: April 2007

Magnetic properties of Fe(II) meso-tetra(4-pyridyl)porphyrin [Fe(TpyP)], a recently discovered metalloporphyrin network, were investigated using magnetic susceptibility M(T)∕H, isothermal magnetization M(H), and heat capacity C(T) measurements. The crystal structure of Fe(TpyP) at room temperature is orthorhombic with a space group Cmca (No. 64). This network gives rise to an unprecedented two-dimensional paddle-wheel-like pattern (a 44 topology). The results of M(T)∕H on powder samples of Fe(TpyP) show that the effective moment μeff of Fe2+ is 5.52μB at 340K, close to the expected value for a high spin Fe2+ (S=2) ion. μeff increases to 5.90μB as T decreases to the range of 170K<T<220K, and then decreases monotonically as T decreases further. The behavior of μeff in the high temperature region may be attributed to a positive Fe2+–Fe2+ coupling. The low field (H⩽4kG) M(T)∕H data reveal an anomalous behavior of this compound in the low temperature region which seems spin-glass-like. A small hysteresis was observed in M(H) measured at 2K. No anomaly was seen in the C(T) data from 1.6to25K.
Antiferromagnetic fluctuations in the quantum phase transition of the one-dimensional electron system
Authors: Tomita Norikazu
Published: April 2007

Quantum antiferromagnetic (AF) fluctuations that promote the charge-density-wave (CDW)-AF state phase transition in the one-dimensional (1D) extended Hubbard model are clarified for the strong correlation regime. It is clearly shown that the CDW wave function contains quantum fluctuations due to the AF domains near the phase boundary. Though the size of these AF domains stays finite, its density to the system size becomes asymptotically zero in the infinite-size limit. This indicates the quantum decoherence, or the first order phase transition between the CDW and AF state. On the other hand, the survived AF domains would naturally evolve into the quantum nucleation that triggers the CDW-AF state phase transition.
A molecular beam optical Stark study of the [15.8] and [16.0] Π1∕22-XΣ−4 (0,0) band systems of rhodium monoxide, RhO
Authors: Gengler Jamie , Ma Tongmei , Adam Allan G. , Steimle Timothy C.
Published: April 2007

The R11S(0) and R11S(1) branch features of the [15.8] and [16.0]Π1∕22-XΣ−4 (0,0) subband systems of rhodium monoxide, RhO, have been studied at near the natural linewidth limit of resolution by optical Stark spectroscopy using laser induced fluorescence detection. The Stark shifts and splittings were analyzed to produce the magnitude of the permanent electric dipole moment, ∣μ∣, of 3.81(2)D for the XΣ3∕2−4 (v=0) state. The results are compared to density functional theory calculations. Trends in observed values of ∣μ∣ across the 4d series of transition metal monoxides are interpreted in terms of simple single configuration molecular orbital correlation diagrams.
X-ray scattering intensities of water at extreme pressure and temperature
Authors: Goldman Nir , Fried Laurence E.
Published: April 2007

We have calculated the coherent x-ray scattering intensity of several phases of water under high pressure using the ab initio density functional theory (DFT). Our calculations span the molecular liquid, ice VII, and superionic solid phases, including the recently predicted symmetrically hydrogen bonded region. We compute simulated spectra for ice VII and superionic water. We provide new atomic scattering form factors for water at extreme conditions, which take into account frequently neglected changes in ionic charge and electron delocalization. We show that our modified atomic form factors allow for a nearly exact comparison with the total x-ray scattering intensities calculated from DFT. Finally, we analyze the effect of their new form factors have on the determination of the oxygen-oxygen radial distribution function from experiment.
Interplay of explosive thermal reaction dynamics and structural confinement
Authors: Perry W. Lee , Zucker Jonathan , Dickson Peter M. , Parker Gary R. , Asay Blaine W
Published: April 2007

Explosives play a significant role in human affairs; however, their behavior in circumstances other than intentional detonation is poorly understood. Accidents may have catastrophic consequences, especially if additional hazardous materials are involved. Abnormal ignition stimuli, such as impact, spark, friction, and heat may lead to a very violent outcome, potentially including detonation. An important factor influencing the behavior subsequent to abnormal ignition is the strength and inertia of the vessel confining the explosive, i.e., the near-field structural/mechanical environment, also known as confinement (inertial or mechanical). However, a comprehensive and quantified understanding of how confinement affects reaction violence does not yet exist. In the research discussed here, we have investigated a wide range of confinement conditions and related the explosive response to the fundamentals of the combustion process in the explosive. In our experiments, a charge of an octahydrotetranitrotetrazine-based plastic bonded explosive (PBX 9501) was loaded into a gun assembly having variable confinement conditions and subjected to a heating profile. The exploding charge breached the confinement and accelerated a projectile down the gun barrel. High bandwidth pressure and volume measurements were made and a first-law analysis was used to obtain enthalpy and power from the raw data. These results were then used to quantify reaction violence. Enthalpy change and power ranged from 0−1.8 kJ and 0−12 MW for 300 mg charges, respectively. Below a confinement strength of 20 MPa, violence was found to decline precipitously with decreasing confinement, while the violence for the heaviest confinement experiments was found to be relatively constant. Both pressure and pressurization rate were found to have critical values to induce and sustain violent reaction.
Exact analytical evaluation of time dependent transmission coefficient from the method of reactive flux for an inverted parabolic barrier
Authors: Chakrabarti Rajarshi
Published: April 2007

The paper demonstrates an elegant way of combining the normal mode analysis and the method of reactive flux to evaluate the time dependent transmission coefficient for a classical particle coupled to a set of harmonic oscillators, surmounting a one dimensional barrier. The author’s analysis reproduces the results of Kohen and Tannor [J. Chem. Phys. 103, 6013 (1995)] and Bao [J. Chem. Phys. 124, 114103 (2006)]. Moreover the use of normal mode analysis has a better physical meaning.
Hot precursor reactions during the collisions of gas-phase oxygen atoms with deuterium chemisorbed on Pt(100)
Authors: Kan Heywood H. , Shumbera R. Bradley , Weaver Jason F.
Published: April 2007

We utilized direct rate measurements and temperature programmed desorption to investigate reactions that occur during the collisions of gaseous oxygen atoms with deuterium-covered Pt(100). We find that both D2O and D2 desorb promptly when an oxygen atom beam impinges upon D-covered Pt(100) held at surface temperatures ranging from 90to150K, and estimate effective cross sections of 12 and 1.8Å2, respectively, for the production of gaseous D2O and D2 at 90K. The yields of D2O and D2 that desorb at 90K are about 13% and 2%, respectively, of the initial D atom coverage, though most of the D2O product molecules (∼80%) thermalize to the surface rather than desorb at the surface temperatures studied. Increasing the surface temperature from 90to150K causes the D2O desorption rate to decay more quickly during O atom exposures to the surface and results in lower yields of gaseous D2O. We attribute the production of D2O and D2 in these experiments to reactions involving intermediates that are not thermally accommodated to the surface, so-called hot precursors. The results are consistent with the production of hot D2O involving first the generation of hot OD groups from the reaction O*+D(a)→OD*, where the asterisk denotes a hot precursor, followed by the parallel pathways OD*+D(a)→D2O* and OD*+OD(a)→D2O*+O(a). The final reaction contributes significantly to hot D2O production only later in the reaction period when thermalized OD groups have accumulated on the surface, and it becomes less important at higher temperature due to depletion of the OD(a) concentration by thermally activated D2O production.
Density functional theory for copolymers confined in a nanoslit
Authors: Ye Zhencheng , Chen Houyang , Liu Honglai , Hu Ying , Jiang Jianwen
Published: April 2007

A density functional theory is developed for copolymers confined in a nanoslit on the basis of our previous work for homopolymers. The theory accurately captures the structural characteristics for diblock and alternating copolymers composed of hard-sphere or square-well segments. Satisfactory agreement is obtained between the theoretical predictions and simulation results in segment density profiles, segment fractions, and partition coefficients. Structures under confinement strongly depend on the substituent segment sizes for the hard-sphere copolymers and also on the segment-wall attractions for the square-well copolymers. Alternating copolymers are found to behave as homopolymers with effective segment size, and effective segment-segment and segment-wall interactions.
Diffusive diffraction phenomenon in a porous polymer material observed by NMR using radio-frequency field gradients
Authors: Kuntz J.-F. , Trausch G. , Palmas P. , Mutzenhardt P. , Canet D.
Published: April 2007

Pulsed field gradient NMR diffusion experiments can, in principle, lead to the “diffusive diffraction” phenomenon. In practice, its observation by gradients of the static magnetic field is difficult in real systems because they involve internal gradients due to the static magnetic field (necessary for polarizing nuclear spins). This latter drawback can be circumvented by using gradients of the radio-frequency (rf) field (the other magnetic field used in any NMR experiment). For the first time, by means of rf gradients, a so-called diffusive diffraction peak has been observed in a real porous system and its position provides a value of the mean distance between pores; this can be further complemented by the mean pore size determined from the dependence of the apparent diffusion coefficient with respect to the diffusion interval.
Surface tension and scaling of critical nuclei in diatomic and triatomic fluids
Authors: Napari Ismo , Laaksonen Ari
Published: April 2007

Density functional theory has been used to investigate surface tension and scaling of critical clusters in fluids consisting of diatomic and rigid triatomic molecules. The atomic sites are hard spheres with attractive interactions obtained from the tail part of the Lennard-Jones potential. Asymmetry in attractive interactions between the atomic sites has been introduced to cause molecular orientation and oscillatory density profiles at liquid-vapor interfaces. The radial dependence of cluster surface tension in fluids showing modest orientation in unimolecular layer at the interface or no orientation at all resembles the surface tension behavior of clusters in simple monoatomic fluids, although the surface tension maximum becomes more pronounced with increasing chain length of the molecule. Surface tension of clusters having multiple oscillatory layers at the interface shows a prominent maximum at small cluster sizes; however, the surface tension of large clusters is lower than the planar value. The scaling relation for the number of molecules in the critical cluster and the nucleation barrier height developed by McGraw and Laaksonen [Phys. Rev. Lett. 76, 2754 (1996)] are well obeyed for fluids with little structure at liquid-vapor interface. However, fluids having enhanced interfacial structure show some deviation from the particle number scaling, and the barrier height scaling breaks up seriously.
A study of the growth of Lu2O3 on Si(001) by synchrotron radiation photoemission and transmission electron microscopy
Authors: Malvestuto M. , Pedio M. , Nannarone S. , Pavia G. , Scarel G. , Fanciulli M. , Boscherini F.
Published: April 2007

Rare-earth oxides are among the materials which are presently studied as possible replacements of amorphous silicon dioxide as gate insulators in nanometric Si devices; in fact, they generally exhibit high values of the dielectric constant (“high κ”), a necessary requirement to obtain a high capacitance with layer thickness greater than the value below which tunneling currents become unacceptably high. Lu2O3 is one of the rare-earth oxides which may have the required properties in view of its quite high values of κ and forbidden band gap. Since the envisaged dielectric layers are only a few nanometers thick, a description and a physical understanding of the atomic and electronic structure of the interface are of great importance. In this paper, we report a study by synchrotron radiation photoemission and transmission electron microscopy of the growth of Lu2O3 on Si(001). Thanks to the high spectral and spatial resolution, we provide clear evidence of a rather complex structure in which all silicon suboxides and SiO2 are present at the same time, along with a silicatelike phase and Lu2O3 itself; moreover, some grains and both crystalline and amorphous portions are present. In the photoemission experiment, the contribution of the Si surface to the core level line shapes has been taken into account; in the electron microscopy measurements, we present line scans on the nanometer scale of O, Si, and Lu concentrations and a Fourier transform discussion of the structure of the crystalline portions of the overlayer. The valence band discontinuity, which is measured in situ and is relative to the structurally well characterized interface, is found to be 3.16±0.16eV. These findings are discussed in relation to the suitability of Lu2O3 as a high-κ dielectric and in the context of available theoretical predictions of thermodynamic stability versus the formation of silicon oxide, silicates, and silicides and of the band discontinuity problem.
Spin diffusion/transport in n-type GaAs quantum wells
Authors: Cheng J. L. , Wu M. W.
Published: April 2007

The spin diffusion/transport in a n-type (001) GaAs quantum well at high temperatures (≥120 K) is studied by setting up and numerically solving the kinetic spin Bloch equations together with the Poisson equation self-consistently. All the scattering, especially the electron-electron Coulomb scattering, is explicitly included and solved in the theory. This enables us to study the system far away from the equilibrium, such as the hot-electron effect induced by the external electric field parallel to the quantum well. We find that the spin polarization/coherence oscillates along the transport direction even when there is no external magnetic field. We show that when the scattering is strong enough, electron spins with different momentums oscillate in the same phase which leads to an equal transversal spin injection length and an ensemble transversal injection length. It is also shown that the intrinsic scattering is already strong enough for such a phenomena. The oscillation period is almost independent on the external electric field which is in agreement with the latest experiment in the bulk system at a very low temperature [M. Beck, C. Metzner, S. Malzer, and G. H. Döhler, Europhys. Lett. 75, 597 (2006)]. The spin relaxation/dephasing along the diffusion/transport can be well understood by the inhomogeneous broadening, which is caused by the momentum-dependent diffusion and the spin-orbit coupling, and the scattering. The scattering, temperature, quantum well width, and external magnetic/electric field dependence of the spin diffusion is studied in detail.
Observation of whispering-gallery modes in Si microdisks at room temperature
Authors: Xia J. S. , Ikegami Y. , Nemoto K. , Shiraki Y.
Published: April 2007

Whispering-gallery modes are observed at room temperature in silicon microdisk resonators fabricated on silicon-on-insulator substrates. Sharp luminescent peaks originating from the crystalline silicon film, corresponding to the whispering-gallery modes, are observed to change in microdisks with different diameters. Over 30 times enhancement of the photoluminescence from bulk silicon is observed due to the microdisk.
Identification of a bone marrow precursor of the earliest thymocytes in adult mouse
Authors: Lai Anne Y. , Kondo Motonari
Published: April 2007

The thymus requires continuous replenishment of progenitors from the bone marrow (BM) to sustain T cell development. However, it remains unclear which hematopoietic progenitors downstream from hematopoietic stem cells in the BM home to the thymus in adult mice. In this work, we demonstrate that although multiple BM populations have intrinsic T lineage differentiation potential, a small subset of multipotent progenitors (MPPs) expressing CCR9 preferentially homes to the thymus. These CCR9+MPPs are phenotypically similar to the most immature early T lineage progenitors (ETPs) in the thymus and are present in the peripheral blood. Similar to ETPs, CCR9+MPPs undergo Notch signaling, as indicated by higher expression of Notch1 and downstream target Hes1 genes compared with other MPP subsets. Furthermore, CCR9+MPPs possess differentiation potential similar to that of ETPs, with very limited granulocyte/macrophage differentiation potential, but they can differentiate into T, B, and dendritic cells. These characteristics implicate CCR9+MPPs as the BM precursors of the earliest thymic progenitors. In addition, our data suggest that before transition from BM to thymus, MPPs are lymphoid-specified and primed for T lineage differentiation.
Regulation of ryanodine receptor-dependent calcium signaling by polycystin-2
Authors: Anyatonwu Georgia I. , Estrada Manuel , Tian Xin , Somlo Stefan , Ehrlich Barbara E.
Published: April 2007

Mutations in polycystin-2 (PC2) cause autosomal dominant polycystic kidney disease. A function for PC2 in the heart has not been described. Here, we show that PC2 coimmunoprecipitates with the cardiac ryanodine receptor (RyR2) from mouse heart. Biochemical assays showed that the N terminus of PC2 binds the RyR2, whereas the C terminus only binds to RyR2 in its open state. Lipid bilayer electrophysiological experiments indicated that the C terminus of PC2 functionally inhibited RyR2 channel activity in the presence of calcium (Ca2+).Pkd2−/−cardiomyocytes had a higher frequency of spontaneous Ca2+oscillations, reduced Ca2+release from the sarcoplasmic reticulum stores, and reduced Ca2+content compared withPkd2+/+cardiomyocytes. In the presence of caffeine,Pkd2−/−cardiomyocytes exhibited decreased peak fluorescence, a slower rate of rise, and a longer duration of Ca2+transients compared withPkd2+/+. These data suggest that PC2 is important for regulation of RyR2 function and that loss of this regulation of RyR2, as occurs when PC2 is mutated, results in altered Ca2+signaling in the heart.
Rubisco large-subunit translation is autoregulated in response to its assembly state in tobacco chloroplasts
Authors: Wostrikoff Katia , Stern David
Published: April 2007

Plants rely on ribulose bisphosphate carboxylase/oxygenase (Rubisco) for carbon fixation. Higher plant Rubisco possesses an L
8
S
8
structure, with the large subunit (LS) encoded in the chloroplast by
rbcL
and the small subunit encoded by the nuclear
RBCS
gene family. Because its components accumulate stoichiometrically but are encoded in two genetic compartments,
rbcL
and
RBCS
expression must be tightly coordinated. Although this coordination has been observed, the underlying mechanisms have not been defined. Here, we use tobacco to understand how LS translation is related to its assembly status. To do so, two transgenic lines deficient in LS biogenesis were created: a chloroplast transformant expressing a truncated and unstable LS polypeptide, and a line where a homolog of the maize Rubisco-specific chaperone,
BSD2
, was repressed by RNAi. We found that in both lines, LS translation is no longer regulated by the availability of small subunit (SS), indicating that LS translation is not activated by the presence of its assembly partner but, rather, undergoes an autoregulation of translation. Pulse labeling experiments indicate that LS is synthesized but not accumulated in the transgenic lines, suggesting that accumulation of a repressor motif is required for LS assembly-dependent translational regulation.
Lipoprotein SmpA is a component of the YaeT complex that assembles outer membrane proteins in
Escherichia coli
Authors: Sklar Joseph G. , Wu Tao , Gronenberg Luisa S. , Malinverni Juliana C. , Kahne Daniel , Silhavy Thomas J.
Published: April 2007

A major role of the outer membrane (OM) of Gram-negative bacteria is to provide a protective permeability barrier for the cell, and proper maintenance of the OM is required for cellular viability. OM biogenesis requires the coordinated assembly of constituent lipids and proteins via dedicated OM assembly machineries. We have previously shown that, in
Escherichia coli
, the multicomponent YaeT complex is responsible for the assembly of OM β-barrel proteins (OMPs). This complex contains the OMP YaeT and three OM lipoproteins. Here, we report another component of the YaeT complex, the OM lipoprotein small protein A (SmpA). Strains carrying loss-of-function mutations in
smpA
are viable but exhibit defects in OMP assembly. Biochemical experiments show that SmpA is involved in maintaining complex stability. Taken together, these experiments establish an important role for SmpA in both the structure and function of the YaeT complex.
12R-lipoxygenase deficiency disrupts epidermal barrier function
Authors: Epp Nikolas , Fürstenberger Gerhard , Müller Karsten , de Juanes Silvia , Leitges Michael , Hausser Ingrid , Thieme Florian , Liebisch Gerhard , Schmitz Gerd , Krieg Peter
Published: April 2007

12R-lipoxygenase (12R-LOX) and the epidermal LOX-3 (eLOX-3) constitute a novel LOX pathway involved in terminal differentiation in skin. This view is supported by recent studies showing that inactivating mutations in 12R-LOX and eLOX-3 are linked to the development of autosomal recessive congenital ichthyosis. We show that 12R-LOX deficiency in mice results in a severe impairment of skin barrier function. Loss of barrier function occurs without alterations in proliferation and stratified organization of the keratinocytes, but is associated with ultrastructural anomalies in the upper granular layer, suggesting perturbance of the assembly/extrusion of lamellar bodies. Cornified envelopes from skin of 12R-LOX–deficient mice show increased fragility. Lipid analysis demonstrates a disordered composition of ceramides, in particular a decrease of ester-bound ceramide species. Moreover, processing of profilaggrin to monomeric filaggrin is impaired.

This study indicates that the 12R-LOX–eLOX-3 pathway plays a key role in the process of epidermal barrier acquisition by affecting lipid metabolism, as well as protein processing.
Isoform specificity of protein kinase Cs in synaptic plasticity
Authors: Sossin Wayne S.
Published: April 2007

Protein kinase Cs (PKCs) are implicated in many forms of synaptic plasticity. However, the specific isoform(s) of PKC that underlie(s) these events are often not known. We have used Aplysia as a model system in order to investigate the isoform specificity of PKC actions due to the presence of fewer isoforms and a large number of documented physiological roles for PKC in synaptic plasticity in this system. In particular, we have shown that distinct isoforms mediate distinct types of synaptic plasticity induced by the same neurotransmitter: The novel calcium-independent PKC Apl II is required for actions mediated by serotonin (5-HT) alone, while the classical calcium-dependent PKC Apl I is required for actions mediated when 5-HT is coupled to activity. We will discuss the reasons for PKC isoform specificity, assess the tools used to uncover isoform specificity, and discuss the implications of isoform specificity for understanding the roles of PKC in regulating synaptic plasticity.
Opioid receptors mediate direct predictive fear learning: Evidence from one-trial blocking
Authors: Cole Sindy , McNally Gavan P.
Published: April 2007

Pavlovian fear learning depends on predictive error, so that fear learning occurs when the actual outcome of a conditioning trial exceeds the expected outcome. Previous research has shown that opioid receptors, including μ-opioid receptors in the ventrolateral quadrant of the midbrain periaqueductal gray (vlPAG), mediate such predictive fear learning. Four experiments reported here used a within-subject one-trial blocking design to study whether opioid receptors mediate a direct or indirect action of predictive error on Pavlovian association formation. In Stage I, rats were trained to fear conditioned stimulus (CS) A by pairing it with shock. In Stage II, CSA and CSB were co-presented once and co-terminated with shock. Two novel stimuli, CSC and CSD, were also co-presented once and co-terminated with shock in Stage II. The results showed one-trial blocking of fear learning (Experiment 1) as well as one-trial unblocking of fear learning when Stage II training employed a higher intensity footshock than was used in Stage I (Experiment 2). Systemic administrations of the opioid receptor antagonist naloxone (Experiment 3) or intra-vlPAG administrations of the selective μ-opioid receptor antagonist CTAP (Experiment 4) prior to Stage II training prevented one-trial blocking. These results show that opioid receptors mediate the direct actions of predictive error on Pavlovian association formation.
Teaching Milton: Some Thoughts on Manipulation and Mapping
Authors: Huntley John
Published: April 2007

Two readings of Paradise Lost are an obligatory minimum before the parts of that complex poem can begin to make sense, and the pattern of the whole shades into view for new explorers. I like to teach the poem in the last half of a semester. During the first half we read and discuss the shorter poems while students give Paradise Lost a first, independent read‐through. After that we seem to be ready for an intensive, book‐by‐book rereading and a close discussion of parts and patterns.
Dynamical Computation of the Equatorial Current System of the Pacific, with Special Application to the Equatorial Undercurrent
Authors: Hidaka Koji , Nagata Yutaka
Published: April 2007

The currents near the equator are treated by solving the dynamical equations for the steady-state involving terms of Coriolis force, pressure gradient, and horizontal and vertical mixing. The coefficients of horizontal and vertical mixing are estimated at 108 and 102 c.g.s. respectively and are constant everywhere. The distribution of mean wind-stress and mean pressure are computed from observed data. The result shows an eastward current below the surface near the equator, and it seems to give an explanation of the equatorial undercurrent.
Determination of the Earth's Gravitational Potential from Observations on Sputnik 2 (1957β)
Authors: Cook A.H.
Published: April 2007

R.A.E. observations of the rate of rotation of the orbital plane of Sputnik 2 are combined with Jeffreys's (1943, 1952) equations for the coefficients J and D in the spherical harmonic expansion of the Earth's gravitational field to give revised estimates of J and D. The relative uncertainties of the results emphasize the great value of satellite observations and the need for a revision of the spherical harmonic analysis of surface gravity. Comparison of the value of e−1 with that deduced from the constant of precession indicates that the Earth is not in a hydrostatic state.
Confidence Set Inference with a Prior Quadratic Bound
Authors: Backus George E.
Published: April 2007

In the uniqueness part of a geophysical inverse problem, the observer wants to predict all likely values of P unknown numerical properties z = (z1 ,…, zp ) of the earth from measurement of D other numerical properties y  (0)= (y  1  (0),…, y   D  (0)), using full or partial knowledge of the statistical distribution of the random errors in y  (0). the data space Y containing y  (0) is D-dimensional, so when the model space X is infinite-dimensional the linear uniqueness problem usually is insoluble without prior information about the correct earth model x. If that information is a quadratic bound on x (e.g. energy or dissipation rate), Bayesian inference (BI) and stochastic inversion (SI) inject spurious structure into x, implied by neither the data nor the quadratic bound. Confidence set inference (CSI) provides an alternative inversion technique free of this objection. the first step in CSI is to estimate unmodelled systematic errors in y  (0) and z. the second step is to choose any finite-dimensional subspace XN of X, and to use the prior quadratic bound to estimate the truncation error when the full data function F:X→ Y in the forward problem is approximated by restricting it to XN to give a finite-dimensional function FN :XN → Y. Step three calculates the eigenstructure (singular value decomposition) of FN . Step 4 uses this eigenstructure to find for each positive ρ≤ 1 a Neyman subset Kz (ρ) of the P-dimensional prediction space Z such that either the correct value of the prediction vector z is a member of the confidence set Kz (ρ) or an event has occurred whose probability was no more than ρ. In contrast to SI and BI, CSI offers no incentive for considering any value of P except 1. CSI is illustrated in the problem of estimating the geomagnetic field B at the core-mantle boundary (CMB) from components of B measured on or above the earth's surface. Neither the heat flow nor the energy bound is strong enough to permit estimation of Br at single points on the CMB, but the heat flow bound permits estimation of uniform averages of Br over discs on the CMB, and both bounds permit weighted disc-averages with continuous weighting kernels. Both bounds also permit estimation of low-degree Gauss coefficients at the CMB. the heat flow bound resolves them up to degree 8 if the crustal field at satellite altitudes must be treated as a systematic error, but can resolve to degree 11 under the most favorable statistical treatment of the crust. These two limits produce circles of confusion on the CMB with diameters of 25° and 19° respectively.
Least-squares collocation, geophysical inverse theory and geostatistics: a bird's eye view
Authors: Herzfeld Ute Christina
Published: April 2007

Geodetical least-squares prediction and collocation, geophysical inverse theory, and geostatistics (the theory of regionalized variables) provide methods that from a theoretical point of view solve a common problem: a continuously defined spatial model is supported by only finitely many observations. The synopsis focuses on common methodological aspects as well as on differences in the underlying mathematical assumptions and their geological implications. Introductory examples familiarize with approaches specific to three earth science applications (least-squares collocation of gravity anomalies, geostatistical estimation of mineral resources, and spectral interpolation of marine magnetic anomalies).
Degeneracy, singularity and multiple solutions in geophysical inversion
Authors: Vasco D. W.
Published: April 2007

The relationship between the parameters describing a geophysical experiment and the number of solutions to the inverse problem is explored. It is found that degenerate situations, such as an inherent symmetry in an experimental set up, can give rise to multiple or even an infinite number of solutions. Techniques are developed to determine the simplest multivariable polynomial which represents the essential properties of the misfit functional. From the polynomial, the stability of a given solution to an inverse problem may be evaluated. It is shown how to calculate additional terms necessary to represent all the possible perturbations of a given minima due to changes in the description of the geophysical experiment. These terms indicate the number and types of solutions to the inverse problem which result from such changes. An example, the earthquake location problem, is considered. For differering station configurations the nature of the solutions to the location problem behave dramatically different with respect to changes in station position.
Applied geophysical inversion
Authors: Ellis R. G. , Oldenburg D. W.
Published: April 2007

Using the 2-D DC-resistivity tomography experiment as an example, we examine some of the difficulties inherently associated with constructing a single maximally smooth model as a solution to a geophysical inverse problem. We argue that this conventional approach yields at best only a single model from a myriad of possible models and at worst produces a model which, although having minimum structure, frequently has little useful relation to the earth that gave rise to the observed data. In fact in applied geophysics it is usual to have significant prior information which is to be supplemented by further geophysical experiments. With this perspective we suggest an alternate approach to geophysical inverse problems which emphasizes the prior information and includes the data from the geopysical experiment as a supplementary constraint. To this end we take all available prior information and construct an inversion algorithm which, given an arbitrary starting model and the absence of any data, will produce a preconceived earth model and then introduce the observed data into the inversion to determine how the prior earth model is influenced by the supplementary geophysical data.
The liver in coeliac disease
Authors: POLLOCK D. J.
Published: April 2007

The pathology of the liver in 19 cases of malabsorption in reported. Five of these were proven to have adult coeliac disease, in the others that diagnosis was presumed by exclusion of other causes of malabsorption and by the coincidence of other conditions known to be associated with coeliac disease. Of these cases, three had liver changes of chronic hepatitis and two of these were in the proven coeliac group, including a case with cirrhosis and a hepatoma. In addition, less severe liver changes such as portal tract fibrosis and portal tract infiltration by inflammatory cells were present greatly in excess to that of the controls. The reasons for the occurrence of liver damage in coeliac disease are outlined and discussed in relation to the liver disorders associated with jejunoileal bypass used in the treatment of obesity. Possible mechanisms of liver injury in coeliac disease are described.
Blue naevi of lymph node capsule
Authors: AZZOPARDI J. G. , ROSS C. M. D. , FRIZZERA G.
Published: April 2007

Blue naevi are reported for what is believed to be the first time in the capsule and fibrous trabeculae of lymph nodes. In one of the two cases the nodal blue naevus was accompanied by an ordinary blue naevus in the regional skin. These blue naevi are compared with the ‘naevus‐cell aggregates’ in nodal capsule, the histogenesis of which is currently disputed. A developmental migratory arrest of melanocytes is thought to be the histogenetic mechanism involved in the production of these blue naevi in lymph nodes.
The hyaline cell: a distinctive feature of ‘mixed’ salivary tumours
Authors: LOMAX‐SMITH J. D. , AZZOPARDI J. G.
Published: April 2007

We have identified and described a distinctive type of cell which is characteristic of the ‘mixed’ salivary tumour. This ‘hyaline cell’ or plasmacytoid cell is particularly common and conspicuous in ‘mixed’ tumours of the palate and other sites in the mouth. It occurs also in tumours of the major glands, but with much lesser frequency. The hyaline cell is found in ‘mixed’ salivary‐type tumours in other sites, e.g. the skin. It is not present in the other types of salivary tumour, notably adenoid cystic carcinoma, adenolymphoma, mucoepidermoid and acinic tumour. Ultrastructural study suggests that the hyaline cell is an indicator of myoepithelial differentiation. Current concepts of the acceptable pathways of myoepithelial differentiation in ‘mixed’ tumours are discussed briefly. The specificity of the hyaline cell will probably prove valuable in separating ‘mixed’ tumours from monomorphic adenomas, thus retaining the identity of the latter. The hyaline cell is almost as distinctive a feature of ‘mixed’ tumours as is myxochondroid tissue and its specificity is of practical value in the diagnosis and classification of salivary tumours.
A fixation‐decalcification procedure for bone biopsies
Authors: BUSSOLATI G.
Published: April 2007

A procedure for the simultaneous fixation and decalcification of bone biopsies is described. Mild acidic fixatives (such as Bouin's fluid) are effective decalcifying agents when made calcium‐free by a continuous circulation through a column of anion‐binding ion exchange resin. The procedure has been found relatively fast, safe, economic and to provide excellent histology of biopsies containing cancellous bone.
A light and electron microscopic study of an ovarian and rectal carcinoid
Authors: WILLIAMS R. M.
Published: April 2007

An ovarian and rectal carcinoid within the same person is described. The ovarian carcinoid is non‐argentaffinic with typical regular granules. The rectal tumour consists of two types of APUD cells, some argentaffinic and diazo‐positive, whilst others are non‐argyrophilic. These features are mirrored ultrastructurally, some cells containing the large pleomorphic argentaffinic granules while others have smaller regular granules. In addition, focal aggregates of microfilaments were found in both tumour types. These findings are discussed in terms of the APUD concept. The similarities of the APUD tumour cells to D1 APUD cells of the duodenum is highlighted, and an alternative explanation for their derivation is proposed.
Metastatic tumours in the testis
Authors: TILTMAN A. J.
Published: April 2007

In a prospective autopsy study of male subjects with solid malignant neoplasms, six were shown to have metastatic deposits within the testis (2.5%). These were metastases from carcinoma of the prostate (two cases), melanoma (two cases), bronchial carcinoma (one case) and pleural mesothelioma (one case). In addition, four of 29 leukaemic patients and six of 28 with non‐Hodgkin's lymphoma showed testicular involvement. The metastases from the solid tumours presented in solitary nodules, as multiple nodules or as a diffuse involvement. Microscopically, these were represented by tumour cells within the interstitial tissue without involvement of the seminiferous tubules; interstitial tissue and tubular involvement, and tumour confined to the seminiferous tubules respectively.
The nature of retest reaction in delayed hypersensitivity. I. Light microscopic changes in the skin of the eyelid
Authors: GOGI R. , RAHI A. H. S. , GARNER A.
Published: April 2007

The retest reaction is a variant of delayed hypersensitivity wherein repeated application of an antigen at the same site leads to an intense eosinophil leucocytic infiltration. This reaction has been produced experimentally for the first time in the eyelids of rabbits and guinea‐pigs and it is possible that such a mechanism is implicated in a variety of clinical ocular conditions in which IgE does not appear to feature. It was also found that tissue reaction was modified in the absence of suppressor cells, these having been temporarily inhibited by pretreatment of the animals with cyclophosphamide.
Oxyuris granulomas of pelvic peritoneum and appendicular wall
Authors: VIÑUELA A. , FERNANDEZ‐ROJO F. , MARTINEZ‐MERINO A.
Published: April 2007

Infestation with Enterobius (Oxyuris) vermicularis is very common but seldom produces lesions and even more rarely causes granulomas. Two cases of oxyuris granulomas (nodules), one in the serosa of ovaries and left fallopian tube in a female of 32 years and the other in the submucosa of the appendix in a IO‐year‐old girl are identified by the presence of true necrotizing granulomas containing the parasite. The pathogenesis and differential diagnosis of abdominal granulomas is discussed.
Postmastectomy lymphangiosarcoma: a reappraisal of the concept—a critical review and report of an illustrative case
Authors: SCHAFLER KATHRINE , McKENZIE C. G. , SALM R.
Published: April 2007

The syndrome of postmastectomy lymphangiosarcoma (LAS) has been universally accepted since it was first outlined by Stewart & Treves (1948), except for a small number of authors who concluded that the neoplasms arising in the chronic lymphoedematous arms were in fact due to retrograde spread from the original breast carcinoma (Laffargue, Pinet & le Go 1960, Giannardi, Pelù & Zampi 1960, Giannardi & Pelù 1961, Delarue 1962, Salm 1963, Laugier, Olmos, Hunziker & Orusco 1973), but their views have been largely ignored. A case is reported in whom neoplastic arm lesions appeared 27 years after mastectomy and were due, in our opinion, to recent metastases from a new primary Carcinoma of the lung. The validity of the entire concept of LAS is re‐examined.
Hodgkin's disease with lymphocytic predominance, nodular type (nodular paragranuloma) and progressively transformed germinal centres—a cytohistological study
Authors: POPPEMA S. , KAISERLING E. , LENNERT K.
Published: April 2007

The histology, cytology, and enzyme cytochemistry of a nodular variant of Hodgkin's disease with lymphocytic predominance, called ‘nodular paragranuloma’, are presented. The histological features of nodular paragranuloma are compared with those of progressively transformed germinal centres, which are enlarged follicles showing a predominance of small lymphocytes and some residual germinal centre cells. Progressively transformed germinal centres are sometimes found in nonspecific lymphadenitis (reactive hyperplasia). The histological similarity and the association between lymph nodes with nodular paragranuloma and lymph nodes with progressively transformed germinal centres in the same patient at different moments or at the same time, suggest that progressively transformed germinal centres are the origin of nodular paragranuloma. Hence, it must be concluded that nodular paragranuloma takes place in B‐cell areas of the lymph node, unlike the other, or at least most of the other, types of Hodgkin's disease.
Observations on the results of specific histochemical techniques and empirical staining methods on several tissue/organ types using a variety of fixing fluids
Authors: DAVENPORT W. D. , BALL C. R.
Published: April 2007

Several histotechniques (Harris hematoxylin and alcoholic eosin, Gomori's reticulum method, Verhoeff's elastic stain; Gomori's trichrome, Mallory's aniline blue collagen stain and the Cameron and Steele method) were each used with a number of fixatives (Lavdowsky's chromic acid, Karnovsky's glutaral‐dehyde/paraformaldehyde, neutral buffered formalin, Lavdowsky's formalin‐acetic acid‐alcohol, Zenker's and Helley's). Lavdowsky's chromic acid fixative provided superior results as compared to the other fixing fluids and its use was critical with respect to the trichrome or connective tissue staining procedures. The Cameron and Steele modification used with Lavdowsky's chromic acid fixative gave the best differentiation of tissue types and was also the most reproducible.
The trachea in children with tracheo‐oesophageal fistula
Authors: WAILOO M. P. , EMERY J. L.
Published: April 2007

Forty tracheas from children with tracheo‐oesophageal fistulae were histologically analysed for structural deformity. Thirty (75%) had a deficiency of cartilage; 24 (60%) showed an increase in the length of the transverse muscle, and 26 (65%) had a longer than average internal perimeter. Only six tracheas were entirely normal. The position of the fistula bore little relationship to the abnormalities found. Since in only nine patients were abnormalities restricted to the site of the fistula, we believe that careful examination of the whole length of the trachea is needed at the time of surgery to determine the extent of the anomaly and to anticipate tracheal problems. This is also relevant to autopsy studies and to elucidate the cause of death.
Foetal remnants in the uterus and their relation to other uterine heterotopia
Authors: TYAGI S. P. , SAXENA K. , RIZVI R. , LANGLEY F. A.
Published: April 2007

Foetal remnants were found in uterine curettings obtained from three women complaining of irregular vaginal bleeding. These findings are discussed in relation to other cases in the literature in which heterotopic tissues have been found in curettings and also for the light they throw on the origin of the so‐called uterine teratomas.
Sclerosing stromal tumours of the ovary
Authors: GEE D. C. , RUSSELL P.
Published: April 2007

Sclerosing stromal tumours of the ovary have recently been described as a histologically and clinically distinct subgroup within the thecoma‐fibroma spectrum of benign ovarian sex cord stromal tumours. Reported cases occurred predominantly in young women and only occasional tumours showed evidence of hormonal activity. The present series of five cases expands the spectra of both histological patterns and clinical presentations and suggests that the entity of sclerosing stromal tumours may not be as clearly circumscribed as has been previously reported.
Immunohistochemical identification of renal lysozyme during allograft rejection in man
Authors: KLOCKARS M. , REITAMO S. , COLLAN Y.
Published: April 2007

An immunoperoxidase staining method was used to identify lysozyme in biopsy or transplantectomy specimens of human renal allografts during reversible and irreversible rejection of the grafts. Proximal tubules in apparently functioning nephrons showed lysozyme staining. In irreversibly rejected grafts, infiltrating mononuclear phagocytes in and near peritubular and glomerular capillaries also stained intensely for lysozyme. In acute necrotizing arteritis, lysozyme‐positive cells (mononuclear phagocytes) infiltrated the blood vessel wall. The presence of infiltrating lysozyme‐positive cells in the transplant was consistent with poor graft survival.

The variation in lysozyme staining of proximal tubular cells apparently was a reflection of the differences in the reabsorption capacity of the tubular cells, attributable to the tubular dysfunction of renal allografts. The infiltrating lysozyme‐positive cells probably contribute to the increased urinary excretion of lysozyme during acute rejection.
Adenocarcinoma of the pancreas of childhood: a report of two cases
Authors: BENJAMIN E. , WRIGHT D.H.
Published: April 2007

The clinical, gross anatomical, light microscopic and ultrastructural features of two cases of adenocarcinoma of the pancreas of childhood are presented and compared with adult carcinoma of the pancreas. Both tumours showed acinar differentiation and zymogen granules were demonstrated by electron microscopy. A limited immunohistochemical study suggests that staining for α1‐antitrypsin may provide a marker for acinar differentiation. The histogenesis of this tumour is discussed in relation to the possible origins of islet cells.