bluuebunny/crossref_metadata_2025 huggingface dataset:
Aggressive course of disease in dementia
Authors: Gauthier Serge , Vellas Bruno , Farlow Martin , Burn David
Published: June 2006

The rate of disease progression in Alzheimer's disease (AD) patients is variable. A significant proportion of AD patients appear to experience an aggressive course of disease, and this has a major impact on prognosis, the patients, and their caregivers and society in general. Here we review the current literature on an aggressive course of disease in dementia and how it can be recognized in clinical practice. We also discuss the options available for treating patients with this condition.
Finding potent drugs for Alzheimer's disease is more important than proving the drugs are disease modifying
Authors: Knopman David
Published: June 2006

There are many who feel that the achievement of a disease‐modifying (DM) designation for a drug is an important goal in Alzheimer disease (AD) therapeutics. Several designs that might prove DM have been proposed, including randomized start, randomized withdrawal, and slope analysis. Using biomarkers such as cerebrospinal fluid assays or imaging features as primary outcome measures have also been considered a way of proving DM. The available methods for establishing DM are fraught with logistical and analytic problems. Unless the drug's benefits are large, attempts to prove DM for a truly effective drug may fail. Therefore, clinical trial designs that are the simplest to conduct and interpret are superior to those more complex approaches intended to prove DM.
Disease modification in multiple sclerosis: Issues with relevance to clinical trial designs in Alzheimer's disease
Authors: Rudick Richard A.
Published: June 2006

The last 13 years have witnessed introduction of disease‐modifying drugs (DMDT) in the multiple sclerosis (MS) field. This remarkable occurrence has not only ushered in an era of therapeutic optimism, it has stimulated change in how the pathogenesis of MS is viewed, how clinical studies should be conducted, and how outcome should be measured. These issues are in a stage of evolution at the time of this writing, but many have great relevance to development of DMDT in Alzheimer's disease (AD).
Optimal design of clinical trials for drugs designed to slow the course of Alzheimer's disease
Authors: Mohs Richard C. , Kawas Claudia , Carrillo Maria C.
Published: June 2006

Compounds now in clinical development are hypothesized to slow the clinical progression and pathogenesis of Alzheimer's disease (AD) by their effects to diminish production, increase clearance, or decrease aggregation of amyloid β protein. Options for investigating the effects of these and other drugs on clinical progression and pathogenesis of AD were examined at a conference that included: (1) a review of experimental methods used to investigate disease‐modifying drugs for multiple sclerosis, rheumatoid arthritis, cardiovascular disease, and osteoporosis; (2) discussion of possible study designs and outcome measures for trials in patients with AD; and (3) discussion of biomarkers available for AD. There is no uniformly best way to investigate a drug's impact on AD progression but characteristics of studies supportive of a disease‐slowing effect can be specified. Relevant clinical outcomes in drug‐treated patients versus placebo‐treated patients should be compared over at least 1 and possibly as long as 2 years with biomarkers reflective of pathogenesis and of the drug's mechanistic effects measured concurrently.
Modifying dementia risk and trajectories of cognitive decline in aging: The Cache County Memory Study
Authors: Welsh‐Bohmer Kathleen A. , Breitner John C.S. , Hayden Kathleen M. , Lyketsos Constantine , Zandi Peter P. , Tschanz JoAnn T. , Norton Maria C. , Munger Ron
Published: June 2006

The Cache County Study of Memory, Health, and Aging, more commonly referred to as the “Cache County Memory Study (CCMS)” is a longitudinal investigation of aging and Alzheimer's disease (AD) based in an exceptionally long‐lived population residing in northern Utah. The study begun in 1994 has followed an initial cohort of 5,092 older individuals (many over age 84) and has examined the development of cognitive impairment and dementia in relation to genetic and environmental antecedents. This article summarizes the major contributions of the CCMS towards the understanding of mild cognitive disorders and AD across the lifespan, underscoring the role of common health exposures in modifying dementia risk and trajectories of cognitive change. The study now in its fourth wave of ascertainment illustrates the role of population‐based approaches in informing testable models of cognitive aging and Alzheimer's disease.
Civil society, Islamism and democratisation: the case of Morocco
Authors: Cavatorta Francesco
Published: June 2006

The positive role that an active civil society plays in processes of democratisation is often highlighted in the literature. However, when it comes to the Middle East and North Africa, such activism is considered to be detrimental to democratisation because the predominant role is played by Islamist groups. The explanation for this rests with the perceived ‘uncivil’ and undemocratic Islamist ethos of such groups. This paper challenges this assumption and argues that Islamist associations can be a potential force for democratisation for three reasons. First, they are capable of political learning; secondly, they generate secular civil society activism as a response to their activities, increasing the number of actors in the political and social system; and finally, they can cooperate with other civil society groups on a number of issues, given that they are all subject to the same authoritarian constraints. The paper focuses in particular on the case of Morocco and the Islamist group Jamiat al-Adl wal-Ihsan.
West Africa versus the United States on cotton subsidies: how, why and what next?
Authors: Heinisch Elinor Lynn
Published: June 2006

Developing countries face considerable disadvantages in trade disputes with their more powerful and wealthier counterparts. Nonetheless, Benin, Burkina Faso and Mali successfully challenged US cotton subsidies, a watershed event in international trade relations. This article explores how the West African governments and cotton farmers confronted US policy, why they succeeded, and the campaign's likely implications. Drawing on interviews with representatives in West Africa and Geneva, public statements, documents filed with the World Trade Organisation (WTO), media coverage, and materials from non-governmental organisations, I analyse the behaviour of four key actors behind this initiative: cotton farmers, producers' unions, governments and the international financial institutions. Tactics included using the WTO's trade-dispute mechanisms, deploying many spokespeople with common messages, enlisting powerful allies, and using the media. The West African campaign is an example of politically weak countries effectively exploiting the liberal economic principles of multilateral institutions to challenge protectionist policies in the industrialised world.
Comment on “A new interpretation of Weimer et al.'s solar wind propagation delay technique” by Bargatze et al.
Authors: Haaland S. , Paschmann G. , Sonnerup B. U. Ö.
Published: June 2006

In a recent article, Bargatze et al. (2005) have identified why the implementation of the minimum variance analysis (MVAB) by Weimer et al. (2003), even though based on an erroneous variance matrix, has been successful in estimating the orientation of the “phase fronts” and the resulting propagation delays of the interplanetary magnetic field (IMF). They recommend further testing of the Weimer analysis as a space weather forecasting tool. In this comment we stress that the Weimer et al. implementation of MVAB closely mimics the results of a well‐known version of MVAB that is constrained by the condition that the average field along the phase front normals is zero. This version of MVAB starts from the correct variance matrix, whereas the Weimer analysis is based on an unphysical matrix resulting from a programming error. We recommend that the constrained MVAB, originally developed by Sonnerup and Cahill (1968) and later recast into a more convenient form by A.V. Khrabrov be used instead. The Khrabrov method, which we refer to as MVAB‐0, has been tested at the Earth's magnetopause by Sonnerup and Scheible (1998) and more recently by Haaland et al. (2004) and Sonnerup et al. (2004).
Empirical orthogonal function analysis of magnetic observatory data: Further evidence for non‐axisymmetric magnetospheric sources for satellite induction studies
Authors: Balasis Georgios , Egbert Gary D.
Published: June 2006

Although satellite electromagnetic induction studies have usually assumed a symmetric magnetospheric ring current source, there is growing evidence for significant source asymmetry. Here we apply empirical orthogonal function methods to mid‐latitude night‐side hourly mean geomagnetic observatory data to search for evidence of non‐zonal low‐frequency source fields. The dominant spatial mode of variability in residuals, obtained by subtracting symmetric ring current and ionospheric fields of the CM4 comprehensive model, has a substantial Y2−1 quadrupole component and is highly correlated with Dst. This pattern of temporal variability, which implies enhanced ring current densities in the dusk sector, persists even when peak storm‐time data are omitted. The observed asymmetry agrees with that inferred previously by Balasis et al. (2004), from the local time dependence of biases in satellite induction transfer functions. Temporal correlation of the leading mode with Dst, and consistency of its spatial structure with recent empirical ring current models, suggest a magnetospheric origin.
Temporal variation of nonmigrating diurnal tide and its relation with the moist convective activity
Authors: Miyoshi Y.
Published: June 2006

By using a general circulation model, behaviors of the eastward propagating diurnal tide with zonal wavenumber 3 (DE3) and their relation with the convective activity in the tropical troposphere are examined. The amplitude of the DE3 is significant in the equatorial mesosphere and lower thermosphere (MLT). Day‐to‐day variations of the DE3 amplitude are evident in the MLT region, and are closely related with temporal variations of the rainfall rate in the tropics. Estimates of the EP flux divergence due to the DE3 indicate that this convective modulated DE3 activity induces day‐to‐day variations of the wave‐induced driving of the zonal mean zonal wind in the MLT region. Our results show that temporal variations of the zonal mean zonal wind in the equatorial MLT region are influenced by the moist convective activity in the tropics.
A geometrical characterization of commutative positive operator valued measures
Authors: Beneduci Roberto
Published: June 2006

We show that a POV measure F on the Borel σ-algebra of the reals B(R) is commutative if and only if there exists a PV measure E on B(R) and, for every λ in the spectrum of E, a probability measure γ(∙)(λ) on B(R) such that the effect F(Δ) coincides with γΔ(A), where A is the self-adjoint operator associated to E. The relevance of this result to the theory of the sharp reconstruction is analyzed.
Role of trivalent La and Nd dopants in lattice distortion and oxygen vacancy generation in cerium oxide nanoparticles
Authors: Patil Swanand , Seal Sudipta , Guo Yu , Schulte Alfons , Norwood John
Published: June 2006

Nanocrystalline Ce1−xRExO2−y (RE=La and Nd) powders were synthesized with a controlled size in the range of 3–5nm using microemulsion technique. The nanoceria retains its cubic fluorite structures for the complete doping range. X-ray diffraction and Raman spectroscopic studies showed that the lattice distortion increased with the doping amount and was found to be higher for La-doped samples compared to the Nd doping. Spatial correlation model used for Raman analysis suggested increased defect concentration for the doped samples compared to nanoceria.
Electron-lattice coupling in bound-to-continuum THz quantum-cascade lasers
Authors: Vitiello Miriam S. , Scamarcio Gaetano , Spagnolo Vincenzo , Losco Tonia , Green Richard P. , Tredicucci Alessandro , Beere Harvey E. , Ritchie David A.
Published: June 2006

We measured the thermal resistance (R=20.1K∕W) and the electrical power dependence of the electronic temperature (Re=27.0K∕W) of THz quantum-cascade lasers (QCLs) with bound-to-continuum active region scheme in the lattice temperature range of 30–100K. This information, obtained from the analysis of microprobe photoluminescence spectra for QCLs operating at 2.5THz, gives an electron-lattice energy relaxation rate (0.1ps−1) ∼50 times lower than THz QCLs with resonant-phonon active region scheme.
Determination of transformation stresses of shape memory alloy thin films: A method based on spherical indentation
Authors: Yan Wenyi , Sun Qingping , Feng Xi-Qiao , Qian Linmao
Published: June 2006

The forward and reverse transformation processes of superelastic shape memory alloys (SMAs) under spherical indentation are analyzed. We found that there exist two characteristic points, the bifurcating point and the returning point, in an indentation curve. The corresponding bifurcation force and return force, respectively, rely on the forward transformation stress and the reverse transformation stress. A method to determine the transformation stresses of SMA from the measure of the bifurcation and return forces is proposed. Additionally, we suggest a slope approach to determine the values of the two forces with high accuracy.
Magnetic/nonmagnetic/magnetic tunnel junction based on hybrid organic Langmuir-Blodgett-films
Authors: Wang T. X. , Wei H. X. , Zeng Z. M. , Han X. F. , Hong Z. M. , Shi G. Q.
Published: June 2006

The magnetic/organic/magnetic spin valve structure has been fabricated with π-conjugated molecular pyrrole derivative 3-hexadecyl pyrrole as the spacer layer by Langmuir-Blodgett (LB) technique. It shows giant magnetoresistance (MR) as large as 20% at room temperature, demonstrating that low-energy electrons can traverse the molecular barrier while remaining spin polarized. The spin transport across organic structures is diffusive from its current-voltage (I-V) curve under bias voltage up to 1V. The MR value decreased when the LB-film layer increased. The telegraph noise and the layer dependent MR value suggest that the spin-polarized transport signals can be degraded by localized states in the molecular barriers and barrier quality.
Regional patterns in reproductive biology of Lethrinus miniatus on the Great Barrier Reef
Authors: Williams A. J. , Davies C. R. , Mapstone B. D.
Published: June 2006

Uniformity in fish population biology is a common assumption in many fishery assessments and management arrangements. Although spatial patterns in population biology are often unknown, ignorance of significant variation within a fished stock has profound implications for fishery assessments and management. In the current paper, the reproductive biology of an exploited reef fish, Lethrinus miniatus, was examined for populations in the northern and southern regions of the Great Barrier Reef (GBR). Significant regional variation was observed in some reproductive parameters, but not others. In the northern region, the proportion of spawning females observed during the spawning season was significantly greater and the size at sex change significantly smaller than in the southern region. However, the spawning season, age at sex change and sex ratios did not differ significantly between the northern and southern regions. Size and age at maturity could not be estimated from either of these regions, but an estimate was obtained from the Capricorn–Bunker region at the southern tip of the GBR. The observed regional patterns in reproductive biology of L. miniatus populations have important implications for specific management arrangements such as size limits and seasonal closures, and for fisheries management in general.
Spatiotemporal reaction kinetics of an ultrafast photoreaction pathway visualized by time-resolved liquid x-ray diffraction
Authors: Kim Tae Kyu , Lorenc Maciej , Lee Jae Hyuk , Lo Russo Manuela , Kim Joonghan , Cammarata Marco , Kong Qingyu , Noel Sylvie , Plech Anton , Wulff Michael , Ihee Hyotcherl
Published: June 2006

We have studied the reaction dynamics for HgI
2
in methanol by using time-resolved x-ray diffraction (TRXD). Although numerous time-resolved spectroscopic studies have provided ample information about the early dynamics of HgI
2
, a comprehensive reaction mechanism in the solution phase spanning from picoseconds up to microseconds has been lacking. Here we show that TRXD can provide this information directly and quantitatively. Picosecond optical pulses triggered the dissociation of HgI
2
, and 100-ps-long x-ray pulses from a synchrotron probed the evolving structures over a wide temporal range. To theoretically explain the diffracted intensities, the structural signal from the solute, the local structure around the solute, and the hydrodynamics of bulk solvents were considered in the analysis. The results in this work demonstrate that the determination of transient states in solution is strongly correlated with solvent energetics, and TRXD can be used as an ultrafast calorimeter. It also is shown that a manifold of structural channels can be resolved at the same time if the measurements are accurate enough and that global analysis is applied. The rate coefficients for the reactions were obtained by fitting our model against the experimental data in one global fit including all
q
-values and time delays. The comparison between all putative reaction channels confirms that two-body dissociation is the dominant dissociation pathway. After this primary bond breakage, two parallel channels proceed. Transient HgI associates nongeminately with an iodine atom to form HgI
2
, and I
2
is formed by nongeminate association of two iodine atoms.
Sustainability issues of reservoir fisheries in Malaysia
Authors: Ambak M. A. , Jalal K. C. A.
Published: June 2006

The main activity in lakes and reservoirs in Malaysia is, and always has been, fishing. The annual fish production from lakes and reservoirs in Malaysia is estimated to be 3,950 metric tons, and freshwater fish are a valuable source of protein for the rural population. Therefore, the fisheries and the fish resources of the lakes and reservoirs should be carefully maintained. In general the fish stocks are degrading and a concerted effort is required to maintain exploitable resources at a sustainable level. This paper describes the existing problems, issues and remedial actions required for the restoration of the fisheries resources in Malaysia. It includes the nature of the resource and environment, conformity to rules and regulations, and consideration of the needs of all stakeholders. The paper also highlights the role of the Local Government Authorities in the upkeep of the lakes' ecosystems, technology developments, legislations, institutions and socio-economic aspects of fisheries for the sustainable development of reservoir fisheries in Malaysia.
Status, impacts and mitigation of hydrocarbon pollution in the Malaysian seas
Authors: Law A. T. , Hii Y. S.
Published: June 2006

Straits of Malacca and South China Sea are vulnerable to oil pollution because of the huge amount of crude oil transported through these waters annually. The present level of oil pollution in these waters is between 150-300 μ g L− 1 in water and 70–100 mg kg− 1 in sediment. Whenever there is an oil spill in the Straits of Malacca, the level of oil in water could be raised to higher than 500 μ g L− 1. Crude oil, especially the aromatic hydrocarbon fraction, is highly toxic to marine organisms. The index of oil pollution for marine environments is set at 1000 μ g L− 1 oil in water and 100 mg kg− 1 oil in sediment. The non-effect level of oil on organisms is about 50 μ g L− 1 in the tropical sea. Toxicological studies demonstrated that the present level of oil pollution in seawater has some chronic effects on the growth and hatching rate of marine organisms. Thus, technologies are being actively pursued and developed for reducing the oil contamination in water to lower than 50 μ g L− 1 to protect marine organisms. This paper will review the status of hydrocarbon pollution in the Malaysian seas and the impacts on Malaysian marine environments, as well as the techniques used to combat oil spills, and the management strategies in place to secure environmental safety in Malaysia.
Distribution and significance of seagrass ecosystems in Malaysia
Authors: Bujang Japar Sidik , Zakaria Muta Harah , Arshad Aziz
Published: June 2006

Seagrasses are the only flowering plants (monocotyledonous Angiosperms) that have adapted themselves to living in marine and estuarine habitats, and are submerged most of the time. They are rooted in sediments on the sea bottom, with shoots appearing above the substrate. Seagrasses occurred at 78 sites scattered in the west and east coasts of Peninsular Malaysia and in Sabah and Sarawak in East Malaysia. They are usually found along the coasts growing in association with shallow inter-tidal, mangroves, coral reefs, semi-enclosed lagoons and shoals. In these habitats, seagrass beds or meadows have distinct species assemblage completely adapted to the submerged life. There are fourteen major species of seagrasses recorded in Malaysia: Enhalus acoroides, Halophila beccarii, H. decipiens, H. ovalis, H. minor, H. spinulosa, Halodule pinifolia, H. uninervis, Cymodocea rotundata, C. serrulata, Thalassia hemprichii, Syringodium isoetifolium, Ruppia maritima and Thalassodendron ciliatum. Although seagrasses make up only a small portion of the marine ecosystem, the physical settings and their interactive community within and from outside account for their high diversity and ensure survival of an assortment of vertebrates (fish), invertebrates (shrimps, starfish, sea cucumbers, bivalves, gastropods), and seaweeds. Seagrass form the food and habitats for the vulnerable dugongs or sea cows (Dugong dugon), seahorses (Hippocampus spp.) and endangered green turtles (Chelonia mydas), and for other fish, and also a feeding ground for seasonal migratory birds, Egretta garzetta. Seagrasses provide conditions for the growth and abundance of invertebrates and fish that many local coastal communities collect and catch for their livelihood. Seagrass ecosystems are sources of food and yet they are continually threatened by human activities, causing their degradation and possible habitat loss. The purpose of this review is to give information on the significant linkages of seagrasses with the coastal inhabitants and to suggest recommendations for the protection and conservation of this important ecosystem and the associated resources.
Heavy metal pollution status in the Malaysian aquatic environment
Authors: Shazili Noor Azhar M. , Yunus Kamaruzaman , Ahmad Ahmad Shamsudin , Abdullah Norantonina , Rashid Mohd Kamil Abd
Published: June 2006

The objective of this paper was to review the status of the Malaysian aquatic environment with respect to heavy metals. Much of the work on metals focused on measurements in biota and sediments, but very little research has been done on dissolved and particulate metals in water, metal speciation in sediments or on the bioavailability of metals. Cadmium (Cd), Copper (Cu), Lead (Pb) and Zinc (Zn) received much attention but due to technical difficulties, Arsenic, (As), Mercury (Hg), Tin (Sn) and other hydride elements have not been well studied.

The sources of metal pollution come from manufacturing, agriculture, sewage and motor vehicle emissions. The few reliable studies on metals in water indicate that some rivers were contaminated with Pb, Cu and Zn. Measurements in fish, bivalves and shrimp indicate no contamination of these resources by metals. However contamination by Cd and Pb was noted in some littoral shore molluscs such as Thais sp. as well as rock oysters (Saccostrea sp.) which may be due to non-anthropogenic sources.

Sediments of the Juru and Langat rivers are contaminated by Pb and Zn, while the Langat River was heavily contaminated by Cd. The concentrations of Zn and Pb in coastal sediments off Juru in Penang, and in the Johor Strait were two and three times higher than global shale values. The source of Pb pollution was thought to be derived from the use of leaded petrol. Metal levels in sediments of the Malacca Strait and the South China Sea were generally similar to global shale values.
Whitney towers and gropes in 4–manifolds
Authors: Schneiderman Rob
Published: June 2006

Many open problems and important theorems in low-dimensional topology have been formulated as statements about certain 2–complexes called gropes. This paper describes a precise correspondence between embedded gropes in 4–manifolds and the failure of the Whitney move in terms of iterated ‘towers’ of Whitney disks. The ‘flexibility’ of these Whitney towers is used to demonstrate some geometric consequences for knot and link concordance connected to

n
n

-solvability,

k
k

-cobordism and grope concordance. The key observation is that the essential structure of gropes and Whitney towers can be described by embedded unitrivalent trees which can be controlled during surgeries and Whitney moves. It is shown that a Whitney move in a Whitney tower induces an IHX (Jacobi) relation on the embedded trees.
On the non-unitary unramified dual for classical 𝑝–adic groups
Authors: Muić Goran
Published: June 2006

In this paper we give a Zelevinsky type classification of unramified irreducible representations of split classical groups.
𝐡-principles for hypersurfaces with prescribed principle curvatures and directions
Authors: Ghomi Mohammad , Kossowski Marek
Published: June 2006

We prove that any compact orientable hypersurface with boundary immersed (resp. embedded) in Euclidean space is regularly homotopic (resp. isotopic) to a hypersurface with principal directions which may have any prescribed homotopy type, and principal curvatures each of which may be prescribed to within an arbitrary small error of any constant. Further we construct regular homotopies (resp. isotopies) which control the principal curvatures and directions of hypersurfaces in a variety of ways. These results, which we prove by holonomic approximation, establish some h-principles in the sense of Gromov, and generalize theorems of Gluck and Pan on embedding and knotting of positively curved surfaces in 3-space.
Growth factor attenuation of IFNγ‐mediated hepatocyte apoptosis requires p21waf−1
Authors: McCullough Christian T. , Tura Benjamin J. , Harrison David J.
Published: June 2006

Interferon gamma (IFNγ) is an important mediator of inflammatory liver damage as part of a complex cytokine network. In vitro, IFNγ induces hepatocyte apoptosis. We hypothesized that the hepatocyte response to IFN signalling is context‐dependent, and that specific growth factors, via phosphatidylinositol 3 kinase (PI(3)K) and protein kinase B/Akt signalling pathways, confer a cytoprotective effect. We established an in vitro model of IFNγ‐mediated primary hepatocyte injury. We show that epidermal growth factor (EGF) and hepatocyte growth factor (HGF) attenuate the IFNγ‐induced hepatocyte apoptosis. IRF‐1, but not p53, is required for IFNγ‐mediated apoptosis. The loss of p21waf−1 not only sensitizes the hepatocyte to IFNγ‐mediated injury but is required for survival factor mediated cytoprotection. We show that the PI(3)K inhibitor, LY294002, partially inhibits the apoptotic response of the hepatocyte to IFNγ. In summary, we present evidence that a component of pro‐apoptotic IFNγ signalling in the primary hepatocyte occurs via the PI(3)K pathway. We show that the hepatocyte response to IFNγ is modulated by external survival factors and that this survival signalling requires p21waf−1.
Detection of pineapple closterovirus in pineapple plants and mealybugs using monoclonal antibodies
Authors: HU J. S. , SETHER D. M. , ULLMAN D. H.
Published: June 2006

Monoclonal antibodies (MAbs) were produced to the pineapple closterovirus (PCV) in Hawaii. These antibodies were shown to be specific for PCV by decoration of the virus particles in immunosorbent electron microscopy (ISEM) and indirect enzyme‐linked immunosorbent assay (ELISA). Several methods of ELISA were compared. An indirect DAS ELISA using a polyclonal antibody to trap virus particles followed by reaction with monoclonal antibody was shown to be the method of choice for detecting PCV in pineapple plants. Pineapple root tissue was found to be most suitable for detecting PCV in crude samples by indirect ELISA. PCV was detected in symptomatic and asymptomatic pineapple plants collected from Oahu and Maui, and pineapple collections in the USDA/ARS National Clonal Germplasm Repository, but was not detected from pineapple plants grown from seed. At least two serotypes of PCV were detected. In addition. PCV was detected from mealybugs collected from wilted pineapple plants, but not from mealybugs of the same species collected from a colony reared on squash. The role of PCV in mealybug wilt of pineapple is being investigated.
Selective sieves in the epidemiology of Melampsora lini
Authors: BURDON J. J. , ELMQVIST T.
Published: June 2006

The effects of various potential selective sieves operating at different stages in the epidemiological cycle of pathogen populations were examined in the context of a natural interaction between Melampsora lini and Linum marginale The establishment of self‐sustaining pathogen populations in previously healthy host stands was significantly lowered only when the size of host populations was extremely low (1‐3 plants). During the endemic phase of growth when interpustule competition was non‐existent, differences in the latent period or size of individual pustules of 10 different pathogen isolates were minor compared to differences due to temperature. A competition experiment between two pathotypes of M. lini detected a marked shift in the relative frequency of the two pathotypes during the course of an epidemic lasting approximately five generations. Finally, the survival of two different pathotypes of the pathogen during off‐season reductions in population size was significantly affected by site, year and pathotypic identity. Interactions between these variables were either marginal or non‐existent. The net effect of the interplay of these genetic and ecological factors is to increase stochasticity and the potential for sustained differences between pathogen denies a feature expected when host pathogen co‐evolution occurs at a metapopulation level.
Temporary partial breakdown of Mlo‐resistance in spring barley by the sudden relief of soil water stress
Authors: NEWTON A. C. , YOUNG I. M.
Published: June 2006

Seedlings of spring barley cultivars expressing mlo genes for resistance to mildew (Erysiphe graminis f.sp. hordei) in different genetic backgrounds were subjected to degrees of water stress under different nutrient and soil conditions. The temporary breakdown in the host of the expression of Mlo‐resistance, reported occasionally under field conditions, was successfully simulated when stress treatments were relieved. Differences in the degree of temporary breakdown were attributable to nutrient status, soil compaction and genetic background of the mlo gene.
RECENT SEDIMENTARY HISTORY OF ST. JOSEPH BAY, FLORIDA1
Authors: STEWART RICHARD A. , GORSLINE DONN S.
Published: June 2006

The history of St. Joseph Bay, on the west coast of Florida, begins with the last rise in sea level about 5,000 years ago. The formation of an extensive cuspate spit has formed a basin which is now in the process of being filled by detrital sands delivered via longshore drift from the eastern Apalachicola River. Prior to or during early stages of spit development, a wedge of fine material was deposited over the old terrace surface from an old distributary of the Apalachicola. Present sedimentation has as yet failed to obscure portions of this older surface within the lagoon.

Clean quartz sand and biological carbonates comprise the bulk of the present sediment contribution. The typical East Gulf “kyanite‐staurolite” heavy mineral suite is present, as is the kaolinite‐montmorillonite‐illite clay mineral suite common to this coast.

Sediments in this area have an average organic content of about 1.4%. A high organic carbon/organic nitrogen average of 15.4 has resulted from the accumulation of highly carbonaceo us plant debris under the restrictive environment of the lagoon.
MINOR STRUCTURES OF UNCONSOLIDATED MARINE SEDIMENTS REVEALED BY X‐RADIOGRAPHY1
Authors: CALVERT S. E. , VEEVERS J. J.
Published: June 2006

Hamblin's (1962) X‐radiographic technique for examining the minor structures of sandstone and siltstone is applied to the study of structures in cores of unconsolidated sediments. The technique is capable of revealing particles not visible on the surface of the core, of resolving structures poorly defined in reflected light, and of revealing latent structures in apparently homogeneous sediments.
SEDIMENTS FROM BAY ST. GEORGE, NEWFOUNDLAND
Authors: CARROLL DOROTHY
Published: June 2006

Sediments cored to a depth of about 1 m in Bay St. George, Newfoundland, were examined for grain‐size distribution and minerals. The sediments are light brown silty clays, the principal minerals of which are chlorite and muscovite mica. The scarce sand consists of fresh detrital grains of blue‐green amphibole, biotite, epidote, zoisite, magnetite, garnet, hypersthene, apatite, chlorite, and scarce zircon. Quartz, plagioclase feldspar, and muscovite are abundant. These minerals are all present in the rocks of the adjacent land areas and have been deposited in the sediments with little alteration or change due to weathering. The clay minerals of the sediments are predominantly muscovite and chlorite with a slight admixture of vermiculite and montmorillonite. There is very little mixed‐layering of these minerals. Montmorillonite may be due to diagenetic changes after deposition of these clays in the marine environment of the bay.
SEDIMENTS FORMING THE BED AND BANKS OF THE LOWER MISSISSIPPI RIVER AND THEIR EFFECT ON RIVER MIGRATION
Authors: KOLB CHARLES R.
Published: June 2006

Physiographic features and depositional history of the sediments forming the bed and banks of the lower 200 miles of the Mississippi River are summarized. From mile 200‐ 160 the river is scouring into coarse substratum sands, between miles 160 and 80 into Pleistocene clays, and between mile 80 and 0 chiefly into prodelta and interdistributary clays. Point‐bar accretion averages 500 acres per river mile in the uppermost segment, 200 acres per river mile in the middle segment, and 30 acres per river mile in the lower‐ most segment. The occurrence of bends caused by faulting or formed during seaward growth of the delta, and the occasional existence of coarse materials in the path of the stream are significant factors in the initiation of meanders. The composition of the bed and banks, and the length of channel occupation are important in the rate and extent of migration. Migration of the river between miles 0 and.160 has been and should continue to be very slow.
POROSITÄT UND VERDICHTUNG REZENTER, MARINER SEDIMENTE
Authors: FÜCHTBAUER HANS , REINECK HANS‐ERICH
Published: June 2006

Sand and clay porosities of foreshore, tidal flat, and shallow sea sediments from the southern North Sea were determined. No definite relationship could be observed between porosity, condensation ratio, and depositional environment.

Porosity increases with increasing clay content. The clay porosity probably depends to some degree on the rate of sedimentation. The porosity of experimentally deposited sands increases with decreasing grain size. The same relation can be observed with fossil sandstones. In Recent sands, this increase may be compensated by a closer packing arrangement of the finer grains, expressed by a higher condensation ratio

image

(P= natural porosity, Pw and Pd are the porosities of the loosest and closest arrangements under water, respectively).

Under certain conditions, the sand(stone) porosity decreases continuously with increasing depth (Fig. 7).
LES REMPLISSAGES KARSTIQUES
Authors: BONTE A.
Published: June 2006

Karst depressions are filled (or lined), at least in the first stages of their development, with material subsiding from permeable deposits that cover the carbonate rocks. Without such a cover no depressions can be formed. In the case of very impure limestones, the fill of the depressions consists for a great part of the insoluble residue from these limestones.

Simultaneously with the morphological evolution of the depressions, their fillings also undergo important changes. The evolution terminates with a denuded karst. The solution processes may be re‐activated if the surface is covered by new (allochthonous) sedimentary material.
UN CURIEUX PHÉNOMÈNE D'ÉROSION FAMENNIENNE: LES “PAINS DE GRÈS” DE CHAMBRALLES (ARDENNE BELGE)
Authors: ET C. EK P. MACAR
Published: June 2006

Vertical walls in quarries of Famennian sandstones near Aywaille (Belgian Ardennes) show in abundance varied sedimentary structures. The most interesting are undoubtedly erosional effects on a few islets (or promontories) of a former sandstone layer that are bordered in several places by microcliffs. Rounded and sub‐circular “wash‐loaves” accompanied by smaller and less regular masses occur near and outside of these cliffs; these are so numerous at one place that they appear as a swarm. Both types are remnants of the islets; they sometimes stand as micro‐stacks, but are also sometimes dragged away some distance, as revealed by the inclined or even vertical laminae that some show in cross‐section. We think that the carving of the microcliffs does not denote an important contemporaneous consolidation of the bed, although its limestone content may have favored firmness. We assume that it is mostly a question of the amount of water in the wet sand. Other examples of microcliffs in ancient formations are known in the vicinity; the swarm of stacks and wash‐debris, on the other hand, seems an exceptional phenomenon.
PETROGENESIS AND PALAEOENVIRONMENT OF DEVONIAN ALGAL LIMESTONES OF NEW SOUTH WALES
Authors: WOLF KARL H.
Published: June 2006

A Lower Devonian algal reef complex, with a basinal algal turbidite facies, offers excellently preserved autochthonous and allochthonous algal textures and structures of the following types: algal calcilutite biolithites of dense, grumous, cellular, tubular, “pelletoid” and “granuloid” textures, algal calcilutite crusts and algal‐bound detritus (e.g., stromatolites), algal pisolites, oolites and circumcrusts, algal pellets and grains (in contrast to faecal and bahamite types), colonial and stem fragments, algal filaments and cells, stromatactis and birdseyes. Encrusting Foraminifera and stromatoporoid colonies were of very subordinate importance in forming the turbulent‐water reefs. Protected pools, crevices, and local lagoons offered a favourable niche for calm‐water Codiaceae, crinoids, polyzoans, Amphipora and some molluscs. Corals occur rarely.

The wave‐resistant calcilutite reefs as well as the high percentage of subsequently introduced fine “internal sediments” within the limestone‐frameworks, indicate that grain‐matrix‐cement ratios do not necessarily reflect degree of turbulence and winnowing.

The algal reefs have no effective primary porosity. Channels and cavities, predominantly horizontally oriented, were filled with internal sediments and early‐formed sparite cement.

Fibrous calcite cement is confined to limestones that seem to have formed in a littoral environment whereas granular sparite appears to be an intra‐stratal product of a later stage.
ASPECTS OF CALCIUM CARBONATE DEPOSITION IN GREAT ONYX CAVE, KENTUCKY1
Authors: SIEGEL FREDERIC R.
Published: June 2006

Speleothems of Great Onyx Cave, Kentucky, are composed of calcite, aragonite, and gypsum. Calcite is present in all carbonate samples, and where aragonite is also present, the speleothem core is always of calcite, overlain by a progression of alter‐ nating shells of aragonite and calcite, calcite being the outermost carbonate shell. In some specimens, gypsum encrusts these other two phases but is never itself enclosed by a carbonate, thus demonstrating that carbonate deposition was complete in these specimens before sulfate deposition began.

Cave temperature is constant at 12.5°C. The pH‐values of standing and dripping water ranged from 7.5 to 8.7, with the value of 8.7 being recorded where precipitation and crystallization of calcite was taking place. At a pH of 8.7, some authors consider that calcium carbonate should normally crystallize as aragonite, but in the cave studied, pH seems to have little effect and temperature may be the controlling factor.

Strontium is measurable in most of the aragonite‐bearing samples and not in the calcite ones. But two calcite stalactites and separated calcitic portions of mixed aragonite‐calcite stalactites contain considerable quantities of strontium. Although the affinity of strontium for the aragonite lattice is demonstrated, it is probable that in these cave deposits, the strontium did not have a primary influence on the poly‐ morph which crystallized.
FLUVIATILE SEDIMENTARY STRUCTURES IN THE WOOD BAY SERIES (DEVONIAN) OF SPITSBERGEN
Authors: FRIEND P. F.
Published: June 2006

A noteworthy feature of parts of the Series is the development of cyclothems which consist of: scoured surface, coarse member, fine member, scoured surface. General environments, suggested by this and fossil evidence, are: erosion in river bed, deposition in river bed, deposition in overbank area, erosion in river bed. Structures within the sets of strata include: no lamination, flat bedding, small and large‐scale cross‐lamination, parting lineation. The significance of each is discussed. Sole structures, occurring on the scoured surfaces, are described. They include: groove casts, crescents, flute casts, a variety of long welts, and unoriented structures. These are mainly scour structures but some may be subaerial marks, and there is also evidence for post‐depositional flowage. The value of these structures as indicators of palaeocurrent and ultimately palaeoslope directions is discussed with examples. Measurements of sole structures, parting lineations and ripples have been more profitable than large‐scale cross‐stratification or contorted lamination.
CROSS‐BEDDING IN THE MERIDIAN SAND
Authors: WERMUND E. G.
Published: June 2006

The Meridian Sand is recognized as neritic bar sand because it is overlain and underlain by prodominantly marine strata, contains a marine microfauna and is glauconitic. Cross‐bedding is the large scale planar type and has a regional variance of 10,302. No maximum is present where dip azimuths of sets are plotted on a stereogram. It is suggested that the wave path, topography of the depositional surface, and local rates of subsidence varied during deposition of the cross‐bedded sand resulting in a uniform distribution of the cross‐bedding sets.
CONVOLUTE LAMINATION AND OTHER STRUCTURES FROM THE LOWER COAL MEASURES OF YORKSHIRE
Authors: DAVIES HUW G.
Published: June 2006

Several deformational sedimentary structures are recorded from the non‐marine sandstones of the Lower Coal Measures of Yorkshire. Some of these structures may be termed convolute lamination and for others the term corrugated lamination is proposed. The scope and synonyms of convolute lamination are discussed and both terms are defined and illustrated. The essential difference between convolute lamination and corrugated lamination is the absence of an overall anticline‐syncline morphology in the latter. Rupture of lamination through most of the thickness of the deformed horizons give rise to rupture structures.

A petrological investigation of the sediments showed slight variations in both grain size and mineralogy within individually deformed horizons. The structures are considered to be the result of load casting, caused by heterogeneity of the sediment, and/or thixotropic behaviour.
A CLASSIFICATION OF SUBAQUEOUS SEDIMENTARY STRUCTURES BASED ON RHEOLOGICAL AND KINEMATICAL PARAMETERS
Authors: ELLIOTT R. E.
Published: June 2006

A wide range of subaqueous sedimentary structures is classified according to the behaviour of sediments at the time of formation of the structures and according to the nature of the motions to which these sediments are subject at that time. Assessments of sediment behaviour and nature of motions are given for each group of structures. The principles and elemental bases of the classification are discussed and its advantages are briefly stated.
LIGHT THROWN ON GENERAL PROBLEMS BY THE ROUMANIAN RESULTS
Authors: KUENEN PH. H.
Published: June 2006

The sedimentological characteristics of typical flysch sediments are confirmed for the Roumanian flysch. The emplacement by turbidity currents of the coarse beds alternating with the shales and marls is again abundantly confirmed by the studies in the area under discussion.
SEDIMENTSTRUKTUREN AUS DEN NIEDERRHEINISCHEN BRAUNKOHLENSCHICHTEN DES MIOZÄNS
Authors: UND K. L. GAURI , KALTERHERBERG J.
Published: June 2006

Sedimentary structures in the Miocene fluviatile deposits of the Lower Rhine Basin, lying immediately beneath the lignite formations have been studied at Tagebau Frechen near Cologne. The structures investigated include slump structures, load casts, clay breccia, cross‐bedding, sand fabric and orientation of driftwood.

The slump structures are composed of alternating laminae of clay and silt and have resulted from sub‐aquatic sliding of a sedimentary sheet over a surface of erosion or of a foreset bed of 10–20° inclination. The slumping has caused folding or brecciation of the strata involved.

The base of a sand bed is difficult to obtain as the sediment is weakly consolidated. Load casts, therefore, have been studied exclusively in their internal structure. It is considered that the load casts of smaller dimensions have suffered a diminution of relief through settlement after the process of load casting had ceased.

Two types of clay breccia have been recognised, namely those which have undergone erosion and transportation by water and those which have resulted from slumping.

In an exposure, tabular‐ and trough‐type of cross‐bedding alternate with each other in geological succession. From these examples sand fabrics have been studied. Both in tabular‐ and trough‐type of cross‐bedding the apparent long axes show two maxima. In the former case, these maxima are disposed to each other at an acute angle, in the latter case, however, they are perpendicular to each other. Imbrication, after tilting the Sf‐to original position, is down‐current in tabular cross‐bedding. In trough type, on the contrary, it may be upcurrent or the long axes of the grains dip symmetrically in up‐ and down‐current direction.