bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of exogenous hormones on the ovulation of primary and secondary oocytes in LT/Sv strain mice
Authors: Speirs S. , Kaufman M. H.
Published: February 2005

LT/Sv strain mice ovulate both primary and secondary oocytes. These are fertilizable and give rise to digynic triploid and normal diploid conceptuses, respectively. A previous study [Kaufman and Speirs, 1987] had indicated that just over 20% of embryos recovered on the 10th day of gestation from spontaneously ovulating females had a triploid chromosome constitution. This value was considerably lower than might have been expected by extrapolation from earlier studies in which LT/Sv mice had been given exogenous gonadotrophins. In the present study, therefore, cytogenetic analysis of fertilized eggs was performed at the first cleavage mitosis in (1) spontaneously ovulating females mated to F1 hybrid males, and (2) superovulated females mated to similar males. Additional females from group (1) were autopsied on the 10th day of gestation, and the ploidy of embryos isolated at this stage of gestation was determined. Exposure to exogenous gonadotrophins significantly increased the proportion of eggs that were ovulated as primary oocytes (34.4%), compared to the situation observed following spontaneous ovulation (24.4%). All the triploids encountered in both series were of the digynic type and characteristically (for LT/Sv mice) had an oocyte‐derived set with 40 chromosomes present, and a sperm‐derived set containing 20 chromosomes. Similar numbers of eggs were recovered from spontaneously ovulating females on the 1st and 10th days of gestation, and the incidence of triploidy observed on the 10th day was 22.1%. The influence of exogenous hormones in increasing the “spontaneous” level of triploidy in LT/Sv and in other strains of mice is briefly reviewed.
Lipid interactions with in vitro development of mammalian zygotes
Authors: Waterman R. A. , Wall R. J.
Published: February 2005

Rabbit zygotes were tested for their ability to sequester radiolabeled acetate, oleate, and arachidonate in intracellular lipid. Radiolabeled arachidonic acid was concentrated 170 ± 28‐fold (mean ± SEM) and oleic acid was concentrated 105 ± 26‐fold in zygotic lipids during 6 hr of culture when compared with the initial concentrations in culture medium. Acetate was not concentrated into lipids by cultured zygotes. Both long chain fatty acids were incorporated mainly as triglyceride. Polydimethylsiloxane fluid, used to cover the microdroplets of medium during culture, demonstrated lipophilic properties. This characteristic was utilized to indirectly transfer lipids to culture medium, permitting examination only of lipoidal properties of test extracts on embryonal development. For rabbit zygotes, blood plasma extract was detrimental and whole blood extract was beneficial for embryonal cleavage rates during the first 24 hr of culture. A higher proportion of mouse zygotes developed to blastocysts when cultured in modified Ham's F‐10 medium compared to BMOC medium, and this difference was negated by inclusion of a lipid extract prepared from rabbit oviductal fluid in the culture system. Comparison of fatty acid analyses of the lipid extracts with development rates of zygotes suggests that modified rates of embryo development may be associated with ratios of individual fatty acids presented to the culture medium rather than with the presence of any single fatty acid.
Ultrastructural observations on gamete interactions using micromanipulated mouse oocytes
Authors: Cummins J. M. , Edirisinghe W. R. , Odawara Y. , Wales R. G. , Yovich J. L.
Published: February 2005

Cumulus‐free mouse oocytes were subjected to zona opening by cracking with microhooks (ZC) or acid drilling (ZD) and fixed 30–90 min after insemination (105 pre‐capacitated motile sperms/ml). Ultrastructural observations were made on serially thin‐sectioned oocytes: 15 ZC and 12 ZD. The zona lesion in ZC oocytes was a clean cut, whereas in ZD oocytes it formed a patchy area of partial zona loss, with reduced microvillar height on the underlying oocyte surface. Spermatozoa were observed within the perivitelline space and partially fusing with the oocyte after 30 min in both situations. Only acrosome‐reacted sperm heads were observed to fuse: acrosome intact forms were generally in contact with the zona pellucida, either with the inner or outer surface. Acrosome‐intact spermatozoa were also observed deeply embedded in the zona matrix, possibly indicating surface enzyme activity preceding the membrane fusion events of the acrosome reaction proper. The observations are consistent with the need for spermatozoa to make contact preferentially with the zona pellucida during the course of the acrosome reaction.
Some benefits of Fe doped less dislocated GaN templates for AlGaN/GaN HEMTs grown by MOVPE
Authors: Bougrioua Z. , Azize M. , Lorenzini P. , Laügt M. , Haas H.
Published: February 2005

Strategies for maintaining a low threading dislocation density in highly resistive GaN layers grown by MOVPE on sapphire or SiC substrates using Fe modulation doping are presented. Sheet resistances as high as 108 Ω□ for dislocation densities lower than 8 × 108 cm–2 have been obtained. 2DEGs created at the AlGaN/GaN:Fe interface have good confinement while the low dislocation density benefits the mobility: room temperature values up to 2170 cm2 V–1 s–1 have been obtained for a carrier density of 9.3 × 1012 cm–2. A simplified transport model is proposed to fit the experimental data. Processed transistors showed good channel control and DC performance. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defect morphology and strain of CVD grown 3C–SiC layers: effect of the carbonization process
Authors: Méndez D. , Aouni A. , Morales F. M. , Pacheco F. J. , Araújo D. , Bustarret E. , Ferro G. , Monteil Y.
Published: February 2005

The heterostructure formed by cubic silicon carbide/silicon (3C–SiC/Si) is very promising as substrate for cubic III‐N growth and for SiC devices. Optimized Si substrate carbonization process before the epitaxial growth of SiC, leads to a higher quality of the layer. In this paper, transmission electron microscopy is used to analyze the defect morphology and strain of SiC layers grown by chemical vapor deposition on two differently carbonized substrates, with tensile and compressive strain state. Misfit dislocations, stack‐ ing faults and antiphase domains are observed in this heteroepitaxial system. Irrespective of the substrate used, the epitaxial relationship between Si and SiC is good. However, the grain misorientation of the mosaic structure and the strain of the overgrowth layer depend drastically on the carbonization conditions of the silicon substrate. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the relationship of thermodynamic parameters with the buried surface area in protein-ligand complex formation
Authors: Singha Netai C. , Surolia Namita , Surolia A.
Published: February 2005

Prediction of thermodynamic parameters of protein-protein and antigen-antibody complex formation from high resolution structural parameters has recently received much attention, since an understanding of the contributions of different fundamental processes like hydrophobic interactions, hydrogen bonding, salt bridge formation, solvent reorganization etc. to the overall thermodynamic parameters and their relations with the structural parameters would lead to rational drug design. Using the results of the dissolution of hydrocarbons and other model compounds the changes in heat capacity (ΔCp), enthalpy (ΔH) and entropy (ΔS) have been empirically correlated with the polar and apolar surface areas buried during the process of protein folding/unfolding and protein-ligand complex formation. In this regard, the polar and apolar surfaces removed from the solvent in a protein-ligand complex have been calculated from the experimentally observed values of changes in heat capacity (ΔCp) and enthalpy (ΔH) for protein-ligand complexes for which accurate thermodynamic and high resolution structural data are available, and the results have been compared with the x-ray crystallographic observations. Analyses of the available results show poor correlation between the thermodynamic and structural parameters. Probable reasons for this discrepancy are mostly related with the reorganization of water accompanying the reaction which is indeed proven by the analyses of the energetics of the binding of the wheat germ agglutinin to oligosaccharides.
Modulation of islet G-proteins, α-glucosidehydrolase inhibition and insulin release stimulated by various secretagogues
Authors: Salehi A. , Lundquist I.
Published: February 2005

Guanine nucleotide-binding proteins (G-proteins) are known to act as important modulators of insulin release from the islets of Langerhans. We have recently found that the deoxynojirimycin-derivative emiglitate, a recognized inhibitor of intestinal α-glucosidehydrolase activity, is a powerful inhibitor of glucose-induced insulin release. With the use of isolated mouse islets the present investigation was performed in a primary attempt to elucidate whether this inhibitory mechanism in some way was linked to the β-cell G-protein system. Treatment of freshly isolated islets with pertussis toxin (PTX), which is known to inactivate the Gi-proteins, abolished the inhibitory effect of the α2-adrenoceptor agonist clonidine on insulin release stimulated by the phosphodiesterase inhibitor IBMX in the presence of the protein kinase C activator TPA and even changed it into an increase. Emiglitate did not display any inhibitory action on insulin release induced by these secretagogues. Similarly, clonidine-induced inhibition of glucose stimulated insulin release was reversed by PTX. However, PTX did not influence the suppressive action of emiglitate on glucose-induced insulin secretion. In contrast, the adenylate cyclase activator forskolin totally abolished the inhibitory effect of emiglitate, but not that of the glucose analogue mannoheptulose, on glucose-induced insulin release. Moreover, the stimulatory effect of forskolin and cholera toxin (CTX) (activator of Gs-proteins) on the secretion of insulin was markedly enhanced in the presence of emiglitate. In conclusion, our results suggest that the inhibitory effect of emiglitate on glucose-induced insulin release is not directly related to the Gj-proteins, but most likely exerted solely through the selective suppression of lysosomal α-glucosidehydrolase activity, a step in between the proximal and the distal Gi-proteins, in glucose-induced stimulus-secretion mechanisms. Our data also suggests that the inhibitory action of emiglitate on glucose stimulated insulin release can be compensated for by an increased sensitivity of the cyclic AMP-protein kinase A pathway. Hence, emiglitate might indirectly elicit an increased activity of the Gs-proteins to facilitate the secretory process.
Electrical conductivity dispersion as a probe of membrane modifications in mouse polyomavirus infected cells in culture
Authors: Bonincontro Adalberto , Iacoangeli Anna , Risuleo Gianfranco
Published: February 2005

In this report we investigate the inhibition of membrane conductivity, due to the murine polyomavirus infection in permissive cells in culture. We define experimental conditions to have reproducible results and demonstrate that the intensity of the effects on the cell membrane, depends upon the virus titer used in the infection. Finally, the virus dependent effects disappear if the infection is performed in the presence of a drug that inhibits polymavirus DNA replication.
Catalytic and structural modifications of sarcoplasmic reticulum and plasma membrane (Ca2+ + Mg2+)ATPases induced by organic solutes that accumulate in living systems
Authors: Vieyra Adalberto
Published: February 2005

Organic solutes such as urea, methylamines, polyols and amino acid can accumulate in the cytoplasm of cells to compensate for hyperosmotic conditions in the external medium. Whereas urea is considered to be typical of solutes that destabilize structure and function of proteins, methylamines, polyols and some amino acids appear to have the opposite effect, and can also compensate for the perturbing effects of urea. These effects have been extensively analyzed for a variety of proteins in terms of global changes in enzyme structure and acceleration or inhibition of overall reaction rates. Here the influence of these solutes on sarcoplasmic reticulum and plasma membrane (Ca2+ + Mg2+)ATPases is reviewed. The focus is on the changes induced by “perturbing” and “stabilizing” solutes at specific steps of the catalytic cycles of these enzymes, which can run forward (leading to ATP hydrolysis) and backward (leading to ATP synthesis). Structural changes promoted by osmolytes are correlated with functional changes, especially those that are related to energy coupling.
Signal transduction: Evolution of an idea
Authors: Rodbell Martin
Published: February 2005

“In general there is no set of observations conceivable which can give enough information about the past of a system to give complete information as to its future”: Norbert Wiener. “Think simplicity; then discard it”: Alfred North Whitehead
Semantics of under-determined expressions
Authors: Larsen Peter Gorm , Hansen Bo Stig
Published: February 2005

Some specification languages, such as VDM-SL, allow expressions whose values are not fully determined. This may be convenient in cases where the choice of value should be left to a later stage of development.

We consider a simple functional language including such under-determined expressions and present a denotational semantics for the language along with a set of proof rules for reasoning about properties of under-determined expressions. One of the specific problems considered is the combination of under-determinedness and a least fixed point semantics of recursion. Soundness of the proof rules is also discussed.
Structured development of a virtual shared memory system
Authors: Seidel Karen , Gardiner Paul
Published: February 2005

In this paper we formalise three different views of a virtual shared memory system and show that they are equivalent. The formalisation starts with five basic component processes specified in the language of CSP [Hoa85], which can be adapted as necessary by two operations called labelling and clamping, and are combined in two basic ways: either they are chained, so that the output of one component becomes the input of the next, or they are put in parallel, so that their communications are arbitrarily interleaved. Using the laws of CSP we show that these basic processes and operators satisfy a number of algebraic equivalences, which enable us to prove equivalence of the different models of the memory system by reasoning entirely at the level of processes, instead of at the lower and more complicated level of events. As a result the proofs of equivalence of the different models are purely algebraic and very simple.

The specification is intended to provide a general framework for any architecture using an interconnection network, such as the on-chip interconnect between macrocells or the networks of processor nodes connected by bit-serial interconnect which are described in [Jon93]. It addresses architecture independent design issues such as access transparency, connectivity, addressing models and serialisability. By structuring it as a hierarchy of models it is hoped that the treatment of these many issues is made as clear and tractable as possible, whilst the proofs of equivalence ensure consistency.
The co-invariant generator: An aid in deriving loop bodies
Authors: Billington David , Dromey R. Geoff
Published: February 2005

Given a loop invariant,
I
, and an assignment,
α
, which decreases the variant, we define a constructive function, cg, called the co-invariant generator, which has the property that
I
Λ cg (
α, I
) ⇒ wp (
α, I
), where wp (
α, I
) is the weakest precondition for
α
to establish I. Several results about the co-invariant generator are proved, important special cases are considered, and a non-trivial example of its use in deriving the body of a loop is given. We also define a function which performs a related constructive action on terms formed from binary operations. The coinvariant generator makes a useful contribution to formalising and automating a key step in program derivation.
Event refinement in state-based concurrent systems
Authors: Sinclair Jane , Woodcock Jim
Published: February 2005

Operations on action systems may be defined corresponding to CSP hiding and renaming. These are of particular use in describing the refinement between action systems in which the granularity of actions is altered. We derive a simplified expression for hiding sets of actions and present sufficient conditions for forwards simulation in which the concrete system uses hiding and renaming. Both of these reduce the complexity of proofs of refinement. We present a case study in specification and refinement using action systems which makes use of the operations and refinement rules previously defined.
Some facile chemistry
Authors: Leth Lone , Thomsen Bent
Published: February 2005

In this paper we use the chemical abstract machine (CHAM) framework [BeB90, BeB92, Bou94] for discussing various semantics for the Facile programming language [GMP89, GMP90, FAR93] and for formalising (parts of) its implementations. We use these formal descriptions to argue (informally) about implementability and cost of implementation in terms of low level machinery needed to implement the given semantics.

We take the Facile language as source for discussion, but the results also apply to several other new languages such as CML [Rep91, BMT92] and Poly/ML [Mat91]. Characteristic for all these languages is that they combine ideas from the λ-calculus and process algebra, such as CCS [Mil80, Mil89], to support high level constructs for programming concurrent, parallel and/or distributed systems.

The full version of this extended summary can be found in [LeT94].
Using units of measurement in formal specifications
Authors: Hayes Ian J. , Mahony Brendan P.
Published: February 2005

In the physical sciences and engineering, units of measurement provide a valuable aid to both the exposition and comprehension of physical systems. In addition, they provide an error checking facility comparable to static type checking commonly found with programming languages. It is argued that units of measurement can provide similar benefits in the specification and design of software and computer systems.

To demonstrate this, we present an extension of the Z specification notation with support for the incorporation of units in specifications and demonstrate the feasibility of static dimensional analysis of the resulting language.
Type inference in stack based languages
Authors: Stoddart Bill , Knaggs Peter J.
Published: February 2005

We consider a language of operations which pass parameters by means of a stack. An algebra over the set of type signatures is introduced, which allows the type signature of a program to be obtained from the type signatures of its constituent operations.

Although the theories apply in principle to any stack based language, they have been evolved with particular regard to the proposed ANSI Standard Forth language, which is currently implemented in a type free manner. We hope this work will stimulate an interest in Forth amongst those applying algebraic techniques in software engineering, and we hope to lay the theoretical foundations for implementing practical type checkers to support Forth.
The formal specification of safety requirements for storing explosives
Authors: Mukherjee Paul , Stavridou Victoria
Published: February 2005

In this paper we consider the current practices involved in the storage of explosive articles and substances. In the spirit of Defence standard 00-55, we formalize the safety requirements of the ACS software which is used to manage certain MOD holdings in the United Kingdom using the specification language VDM. We also prove some properties of these safety requirements and comment on a similar OBJ3 specification.
Categorical ML — Category-theoretic modular programming
Authors: Dennis-Jones Esther , Rydeheard David E.
Published: February 2005

We consider an extension of the functional programming language Standard ML with a modular structure based upon concepts in category theory such as categories, functors, natural transformations and adjunctions. In essence, we are following the categorical imperative of considering arrows as well as objects. This is intended to enforce a certain mathematical rigour on the programmer, so that the only programs that can be expressed are those with a categorical significance. The essentially algebraic nature of category theory means that we may generate equational correctness conditions for the modular structure of programs, thus separating the correctness of individual functions from that of modules. We describe this programming language, give examples of its use, and explain how it is implemented in a type system.
The same old process? Older people, participation and deliberation
Authors: BARNES MARIAN
Published: February 2005

Opportunities for older people to take part in decision making about public policies and services are expanding in the United Kingdom and elsewhere. This paper considers the potential of older people's participation in policy processes for both transforming the policy process and for achieving socially just outcomes. It argues that the way in which such participation takes place, in particular the nature of the deliberative processes, affects both who will feel able to take part and the capacity to develop new policy discourses which can challenge official perspectives and assumptions. It draws from critical perspectives on deliberative democracy to provide a theoretical framework. This work emphasises the importance of story telling and forms of exchange designed to offer recognition to others, as well as the rational argument more usually associated with deliberation on matters of public policy. The argument is illustrated with examples of participation initiatives that have involved ‘active’ older people and those who are users of social care services. Different styles and processes of exchange are distinguished in the three case studies. In one, active facilitation enables individual stories of ageing and of service use to be woven into collective narratives that offer an alternative vision of care services. In another, a strong emphasis on ‘greeting’ enables conflicting views to be expressed without participants falling out. In the third, styles of exchange familiar in formal debate limit the development of an alternative discourse. The conclusion suggests that attention needs to be given to the process of participation as well as to outcomes.
The potential impact of changes in public funding for residential and nursing-home care in the United Kingdom: the Residential Allowance
Authors: CLARKSON PAUL , HUGHES JANE , CHALLIS DAVID
Published: February 2005

The pursuit of independence and avoidance of unnecessary care-home admissions are key elements of British government policy for the care of older people. The present government's objective to maintain independence has been compromised by the ‘Residential Allowance’ which, as a component of social security payable to residents in independent-sector homes, could be seen as an incentive to place people in care-homes rather than seek care-at-home. In order to remove this incentive, the government proposed to abolish the allowance and instead transfer resources by a grant to local authorities. This was intended to promote independence by making available funds with which social services departments could support domiciliary care. This paper examines the potential impact of the proposal from the perspective of front line practitioners and managers. Calculations of the proposal's likely effects in five authorities were made from a simulation of their usual decision-making processes. The results, applied to the national picture, showed only a marginal effect of the change upon admissions to care homes. The potential effect of the change in diverting admissions from care homes was seen to be hampered by organisational influences which vary between authorities.
The impact of retirement on physical activity
Authors: BERGER URSULA , DER GEOFF , MUTRIE NANETTE , HANNAH MARY KATE
Published: February 2005

Most adults do not achieve the levels of physical activity currently recommended for a healthy lifestyle. Population surveys suggest that there is a linear decline of activity levels with age, yet physical activity has many health benefits for older adults. If these are to be more widely adopted among older people, health policy and promotion require an understanding of the factors that influence decreasing activity with age. This study examined the patterns of physical activity of 699 participants in the West of Scotland Twenty-07 Study who were aged 60 years when interviewed in 1991 and followed up four to five years later. It examined the factors that influenced whether or not the subjects achieved currently recommended levels of activity, by applying random effects models with a seasonal adjustment. It was found that higher levels of physical activity associated with a healthier lifestyle, and that socio-economic factors played a minor role in determining the level of physical activity. A substantial amount of physical activity occurred at work but was lost by those who had retired, for while those who were not working were more physically active at home or at leisure than those in work, the majority of the sample did too little physical activity outside work to compensate for the loss of work-based activity. One conclusion is that health promotion initiatives that encourage people to become more physically active should be targeted at those who are about to retire.
Dementia from the inside: how people with early-stage dementia evaluate their quality of life
Authors: KATSUNO TOWAKO
Published: February 2005

The purposes of this study were to explore the self-rated and objectively measured quality of life of people with early-stage dementia and to describe their personal experiences and reactions to the negative public view of dementia. Information was collected from 23 participants who lived in a mid-western United States metropolitan area. Self-ratings were collected by semi-structured and structured interviews, and the objective measures were the Quality of Life Index (QLI) and the Single Item Quality of Life Scale (SIQLS). It was found that 21 of the participants perceived their current QOL as ‘good’ or better, and that the mean scores for the QLI and the SIQLS were 22.8 and 7.3 respectively. Triangulation of the subjective and objective data established their congruence. The QLI scores suggested that people with early-stage dementia often perceived their current life as good and that the participants were as satisfied with their life as the general population. Their accounts also revealed that many had experienced stigma and that this appreciably affected their psychosocial wellbeing. The findings of this study provide new insights into the ways in which health-care professionals and the general public can and should view and treat people with dementia.
Boarded out by auction: poor children and their families in nineteenth-century northern Sweden
Authors: ENGBERG ELISABETH
Published: February 2005

Boarding out and fostering poor children was a favoured method of poor relief in many rural areas in northern Europe. This article discusses children who were boarded out to foster-parents by public auction in a rural parish in northern nineteenth-century Sweden. Poverty was the main reason why children were boarded out, frequently associated with loss of parents and difficulties in providing for a large household. It is suggested that the Swedish system of boarding out poor children must be understood in the context of a welfare system where cost efficiency was important. The auction method was used in spite of the risks involved because it was considered to be the best way to provide poor children with food, clothes, shelter and care, while keeping the compensation to the foster-parents at a reasonably low level.
Teleological Egalitarianism vs. the Slogan
Authors: RAMSAY MARC
Published: February 2005

The Slogan holds that one situation cannot be worse (or better) than another unless there is someone for whom it is worse (or better). This principle appears to provide the basis for the levelling-down objection to teleological egalitarianism. Larry Temkin, however, argues that the Slogan is not a plausible moral ideal, since it stands against not just teleological egalitarianism, but also values such as freedom, rights, autonomy, virtue and desert. I argue that the Slogan is a plausible moral principle, one that provides a suitable moral basis for the levelling-down objection to teleological egalitarianism. Contrary to Temkin, freedom, autonomy, virtue, and rights can all be understood in person-affecting terms, while equality of outcome cannot. Moreover, the Slogan is open to a variety of different ideas about how we should weight or rank people's gains and losses. This flexibility allows the Slogan to accommodate ideals such as prioritarianism and desert.
Detection of a long‐term decrease in thermospheric neutral density
Authors: Marcos Frank A. , Wise John O. , Kendra Michael J. , Grossbard Neil J. , Bowman Bruce R.
Published: February 2005

Long‐term thermospheric neutral density trends near 400 km altitude are analyzed using high accuracy satellite drag measurements over the common time period 1970–2000. Data coverage is over all latitudes and local times and an extensive range of solar and geomagnetic conditions. Densities are compared to empirical models that remove known variations related to solar activity, latitude, local time, day of year and altitude. An average unmodeled secular neutral density decrease of 1.7% per decade is detected. This result is qualitatively consistent with predictions of thermospheric cooling related to anthropogenic causes deduced by theoretical models, and in general agreement with global cooling estimates determined from previous analyses of satellite orbital decay.
Painting a picture of gas hydrate distribution with thermal images
Authors: Weinberger Jill L. , Brown Kevin M. , Long Philip E.
Published: February 2005

A study of cold thermal anomalies identified in continuous down‐core records of thermal structure acquired by an infrared (IR) camera during Ocean Drilling Program (ODP) Leg 204 to southern Hydrate Ridge, is combined with core‐based observations of structure and lithology, to present new insights into the influence of lithology on hydrate distribution in an accretionary margin. Hydrate distribution is spatially associated with <0.5 cm–thick, laterally discontinuous sand horizons that compose <1% of the sedimentary section at all sites. Proximity to the fractured ridge crest determines the extent to which individual sand horizons host hydrate, with 70% of the horizons hosting hydrate at the crest and only 29% in the basin. This trend is consistent with focused up‐dip migration of fluids along permeable lithologic conduits, and shows that lateral flow may be as important as vertical diffusion and fracture flow in determining gas hydrate distribution at Hydrate Ridge.
Tracking the Arctic's shrinking ice cover: Another extreme September minimum in 2004
Authors: Stroeve J. C. , Serreze M. C. , Fetterer F. , Arbetter T. , Meier W. , Maslanik J. , Knowles K.
Published: February 2005

Satellite passive microwave observations document an overall downward trend in Arctic sea ice extent and area since 1978. While the record minimum observed in September 2002 strongly reinforced this downward trend, extreme ice minima were again observed in 2003 and 2004. Although having three extreme minimum years in a row is unprecedented in the satellite record, attributing these recent trends and extremes to greenhouse gas loading must be tempered by recognition that the sea ice cover is variable from year to year in response to wind, temperature and oceanic forcings.
The telomerase RNA component Terc is required for the tumour‐promoting effects of Tert overexpression
Authors: Cayuela María Luisa , Flores Juana M , Blasco María A
Published: February 2005

A role for the telomerase reverse transcriptase subunit (Tert) in tumorigenesis independent of telomere length is emerging. K5‐Tert mice, which overexpress Tert in the skin, show increased tumorigenesis and faster wound healing than wild‐type controls. Here, we demonstrate that the telomerase RNA component Terc is necessary to mediate these effects of Tert overexpression. In contrast to K5‐Tert mice, K5‐Tert mice in a Terc‐deficient background, K5‐Tert/Terc−/−, do not show increased tumorigenesis or increased wound healing compared with wild‐type controls. Indeed, K5‐Tert/Terc−/− mice show a reduction in tumour growth compared with Terc−/− controls, indicating an inhibitory effect of Tert overexpression in the absence of Terc. These results indicate that the tumour‐promoting effects of Tert overexpression require the formation of Tert–Terc complexes. In addition, we show that the increased expression of Tert in the absence of Terc has an inhibitory effect on tumorigenesis, independently of telomere length and telomerase activity. These findings highlight Terc as a target for telomerase‐based anticancer therapies.
The effect of density on the properties of short chain fluids
Authors: Porter J. A. , Lipson J. E. G.
Published: February 2005

We incorporate density dependence into continuum Born–Green–Yvon (BGY) theory through calculation of the end-to-end intramolecular correlation function. Whereas in previous studies we had only performed this calculation for the case of an isolated (zero-density) square-well chain of m segments (3⩽m⩽7), here we consider this single chain to have been placed in a square-well monomeric fluid of variable density. We find that the results obtained by this more sophisticated approach are in good agreement with the predictions of both other theories and simulation concerning the structural properties of short chains. Using a homologous series of n-alkanes as a test case, we also conclude that BGY theory, with the current modifications, is capable of describing fluid properties for heptane (n-C7) through nonadecane (n-C19).
Temperature-dependent dielectric and electro-optic properties of a ZnO-BaTiO3-ZnO heterostructure grown by pulsed-laser deposition
Authors: Mbenkum B. N. , Ashkenov N. , Schubert M. , Lorenz M. , Hochmuth H. , Michel D. , Grundmann M. , Wagner G.
Published: February 2005

Temperature-dependent dielectric and electro-optic properties of a ZnO-BaTiO3-ZnO heterostructure grown by pulsed-laser deposition on (0001) sapphire are reported. The wurtzite-structure ZnO layers serve as transparent conducting electrodes. Previously observed coupling effects within the wurtzite-perovskite heterostructure by spectroscopic electro-optic ellipsometry birefringence measurements manifest themselves as a “pinning” of the ferroelectric polarization in the BaTiO3 layer by the cladding ZnO layers. Temperature-controlled electro-optic Raman measurements assign the electro-optic birefringence results to a temperature-driven phase transition resulting from the leakage current within the sample. High-temperature small-signal capacitance measurements exploiting the conductive electrode properties of the cladding layers reveal occurrence of the Curie temperature of the BaTiO3 layer at 384 K.
Influence of variable thermal conductivity and viscosity for nonisothermal fluid flow
Authors: Pinarbasi Ahmet , Ozalp Coskun , Duman Selim
Published: February 2005

This Brief Communication investigates the effect of variable viscosity and thermal conductivity of a nonisothermal, incompressible Newtonian fluid flowing under the effect of a constant pressure gradient in plane Poiseuille flow. The viscosity and thermal conductivity of the fluid exhibit linear temperature dependence and the effect of viscous heating is included in the analysis. Channel walls are kept at constant temperatures. Discretization is performed using a pseudospectral technique based on Chebyshev polynomial expansions. The resulting nonlinear, coupled boundary value problem is solved iteratively using Chebyshev pseudospectral method.
Temperature dependence of the tangential momentum accommodation coefficient for gases
Authors: Cao Bing-Yang , Chen Min , Guo Zeng-Yuan
Published: February 2005

The temperature dependence of the tangential momentum accommodation coefficient (TMAC) is investigated by examining gas flows in a submicron channel using molecular dynamics simulations. The results show that the TMAC decreases with the increasing temperature following an exponential decay law, and is more sensitive to lower temperatures than to higher ones. The molecular trapping-desorption behaviors near the channel surface are found to be responsible for this dependence.
A New Pathway for Activation of C - C and C - H Bonds by Transition Metals in the Gas Phase
Authors: Zhang Dongju , Wang Ruoxi , Zhu Rongxiu
Published: February 2005

C–H and C–C bond activation of hydrocarbons at metal centres are of fundamental importance in biochemistry, organometallic chemistry, and catalysis. The present work aims to search for novel mechanisms for activation of C–C and C–H bonds by transition metals in the gas phase. Using high-level density functional calculations, we systemically studied the reactions of Ti+, V+, and Fe+ with ethane, and proposed new pathways of C–C and C–H bond activation—concerted activation of C–C and C–H bonds, and 1,2-H2 elimination. These two pathways clearly differ from the general addition–elimination mechanism.
The Synthesis and Biological Evaluation of Two Analogues of the C-Riboside Showdomycin
Authors: Renner Jens , Kruszelnicki Irma , Adamiak Beata , Willis Anthony C. , Hammond Edward , Su Stephen , Burns Christopher , Trybala Edward , Ferro Vito , Banwell Martin G.
Published: February 2005

Two novel analogues, 2 and 3, of the C-riboside showdomycin (1) have been prepared by exploiting the N-TIPS-substituted pyrrole 7 as a synthetic equivalent for the maleimide C3 anion. The tetraacetate precursor, 12, of target 2 as well as target 3 itself were subjected to single-crystal X-ray analyses. Analogues 2 and 3 as well as showdomycin and its anomer (4) have each been evaluated in various assays for their cytotoxic, anti-bacterial, and anti-viral effects.
Thermal regimes and diel activity patterns of four species of small elapid snakes from south-eastern Australia
Authors: Llewelyn John , Shine Richard , Webb Jonathan K.
Published: February 2005

Two of the most basic biological attributes for any ectothermic animal are the times of day that it is active and the body temperatures that it exhibits. Published studies on reptile biology display a heavy bias towards diurnal lizards from Northern Hemisphere habitats. To help redress this imbalance, we quantified thermal regimes and activity times in four species of small Australian elapid snakes. Mean selected body temperature in a thermal gradient was affected by the time of testing (i.e. night v. day), with snakes choosing higher body temperatures at night than by day. In outdoor enclosures, whip snakes (Demansia psammophis) were shuttling heliotherms active only during daylight hours at relatively high body temperatures; in a laboratory thermal gradient these animals selected high body temperatures (mean 31.3°C during the day and 33.2°C at night). The other three taxa – golden-crowned snakes (Cacophis squamulosus), small-eyed snakes (Cryptophis nigrescens) and marsh snakes (Hemiaspis signata) – were active mostly at night at relatively low body temperatures, and selected low body temperatures in a thermal gradient (18.1–23.4°C). Thus, mean selected body temperatures differ substantially among sympatric elapid species in south-eastern Australia and are correlated with times of activity.
On the role of Cro in λ prophage induction
Authors: Svenningsen Sine L. , Costantino Nina , Court Donald L. , Adhya Sankar
Published: February 2005

The lysogenic state of bacteriophage λ is exceptionally stable yet the prophage is readily induced in response to DNA damage. This delicate epigenetic switch is believed to be regulated by two proteins; the lysogenic maintenance promoting protein CI and the early lytic protein Cro. First, we confirm, in the native configuration, the previous observation that the DNA loop mediated by oligomerization of CI bound to two distinct operator regions (
O
L
and
O
R
), increases repression of the early lytic promoters and is important for stable maintenance of lysogeny. Second, we show that the presence of the
cro
gene might be unimportant for the lysogenic to lytic switch during induction of the λ prophage. We revisit the idea that Cro's primary role in induction is instead to mediate weak repression of the early lytic promoters.
Inhibition of NUDEL (nuclear distribution element-like)-oligopeptidase activity by disrupted-in-schizophrenia 1
Authors: Hayashi Mirian A. F. , Portaro Fernanda C. V. , Bastos Marta F. , Guerreiro Juliano R. , Oliveira Vitor , Gorrão Silvia S. , Tambourgi Denise V. , Sant'Anna Osvaldo A. , Whiting Paul J. , Camargo L. Miguel , Konno Katsuhiro , Brandon Nicholas J. , Camargo Antonio C. M.
Published: February 2005

Recently, nuclear distribution element-like (NUDEL) has been implicated to play a role in lissencephaly and schizophrenia through interactions with the lissencephaly gene 1 (Lis1) and disrupted-in-schizophrenia 1 (DISC1) products, respectively. Interestingly, NUDEL is the same protein as endooligopeptidase A (EOPA), a thiol-activated peptidase involved in conversion and inactivation of a number of bioactive peptides. In this study, we have cloned EOPA from the human brain and have confirmed that it is equivalent to NUDEL, leading us to suggest a single name, NUDEL-oligopeptidase. In the brain, the monomeric form of NUDEL-oligopeptidase is responsible for the peptidase activity whose catalytic mechanism is likely to involve a reactive cysteine, because mutation of Cys-273 fully abolished NUDEL-oligopeptidase activity without disrupting the protein's secondary structure. Cys-273 is very close to the DISC1-binding site on NUDEL-oligopeptidase. Intriguingly, DISC1 inhibits NUDEL-oligopeptidase activity in a competitive fashion. We suggest that the activity of NUDEL-oligopeptidase is under tight regulation through protein–protein interactions and that disruption of these interactions, as postulated in a Scottish DISC1 translocation schizophrenia cohort, may lead to aberrant regulation of NUDEL-oligopeptidase, perhaps providing a substrate for the pathology of schizophrenia.
HTLV-1 Associated Motor Neuron Disease Mimicking “Man-in-the-Barrel” Syndrome
Authors: Vainstein Gabriel , Gordon Carlos R , Gadoth Natan
Published: February 2005

The “man-in-the-barrel” syndrome is a descriptive term that was used in the past for patients with complete flaccid paralysis of the upper extremities caused by symmetric “watershed” brain infarction after cardiovascular arrest or cardiac surgery. However, it is now evident that this syndrome can occur in acute and chronic diseases of the upper and lower motor neuron. We describe a 48-year-old woman with rapid and severe progressive weakness and wasting of both upper extremities mimicking the “man-in-the-barrel” syndrome. The neurologic and electrophysiological findings were compatible with anterior horn cell disease affecting the cervical spinal cord segments. There were only minimal signs suggesting the presence of myelopathy. After the initial rapid onset, progression during the 7 years of follow up was minimal. An extensive etiologic workup disclosed infection with HTLV-1.
Magnetic Resonance Imaging and Computed Tomography of Skeletal Muscles in Oculopharyngeal Muscular Dystrophy
Authors: King Molly K , Lee Roland R , Davis Larry E
Published: February 2005

Objective:

To determine the spectrum of skeletal muscle involvement by neuroimaging in patients with oculopharyngeal muscular dystrophy (OPMD).

Methods:

A neuroradiologist, blinded to severity of patients' dystrophy, retrospectively read 22 magnetic resonance or computed tomography images of the head, neck, chest, abdomen, pelvis, and proximal leg from 13 patients with OPMD. Imaged muscles were evaluated for degree of fatty infiltration and bulk in a semiquantitative fashion using similar images from age-matched patients lacking neuromuscular disease. Neurologic examinations were performed without knowledge of imaging results.

Results:

We found abnormal tongue fatty infiltration in all patients and widespread infiltration in many other muscles. Over 50% of masseter, posterior neck, shoulder girdle, lumbar paraspinous, and gluteus muscles had abnormal fat.

Conclusion:

Although patients with OPMD have dysphagia with weak lids and proximal limbs, they have neuroimaging evidence of widespread fatty infiltration of many muscles. Excessive fatty infiltration of the tongue may help identify atypical patients with OPMD.
The Electromyographic Features of Acute Rhabdomyolysis
Authors: Al-Shekhlee Amer , Hachwi Rami , Jaberi Mohamed M , Katirji Bashar
Published: February 2005

Rhabdomyolysis and acute polymyositis share a similar clinical profile with elevated serum creatine kinase (CK). Unlike polymyositis, the electromyography (EMG) findings of acute rhabdomyolysis with myoglobinuria are not well defined. We retrospectively evaluated 15 patients during the acute phase of rhabdomyolysis. All patients (age range, 10-84 years) underwent electrodiagnostic studies, including needle EMG, during the first 2 weeks from the onset of symptoms. All patients presented with acute myalgia, muscle tenderness, and severe generalized weakness. The median peak CK was 48.0 k u/L (25th and 75th percentiles, 11.0 and 68.0 k u/L), whereas the median CK elevation at the time of EMG examination was 10.0 k u/L (25th and 75th percentiles, 4.5 and 48.5 k u/L). Nerve conduction studies were normal in all except 1 patient who had a preexisting mild polyneuropathy. Needle EMG was performed on 117 muscles. Eighty-seven of 117 (74%) muscles were normal, and 19 of 117 (16%) showed variable proximal myopathic motor unit action potentials. None had persistent fibrillation potentials. One third of patients (5 of 15) had myopathic EMG that was present in 1 to 3 sampled proximal muscles. We conclude that the EMG findings during rhabdomyolysis are often normal and when abnormal, the changes are subtle and are in contrast to the often-prominent EMG findings in polymyositis and dermatomyositis.