bluuebunny/crossref_metadata_2025 huggingface dataset:
Method optimization and validation for the simultaneous determination of arachidonic acid metabolites in exhaled breath condensate by liquid chromatography-electrospray ionization tandem mass spectrometry
Authors: Gonzalez-Reche Luis M , Musiol Anita K , Müller-Lux Alice , Kraus Thomas , Göen Thomas
Published: May 2006

Background

Determinations of inflammatory markers in exhaled breath condensate were used to assess airway inflammation. The most applied method for this kind of determination is enzyme immunoassay. For research purposes to find new or to relate concrete biomarkers to different pulmonary diseases, a simultaneous determination of different inflammatory markers would be advantageous.

Methods

We developed an analytical method with on-line clean up and enrichment steps to determine 12 different inflammatory markers in exhaled breath condensate. A specific detection method ensures the unequivocally determination of each analyte at the same run. The method was optimized and validated to achieve a low limit of quantification up to 10 pg/mL each analyte. The precision of the method ranged between 4 and 16%.

Conclusion

The presented method should serve as an easy and fast tool to assess the utility of inflammatory markers in exhaled breath condensate to different pulmonary diseases and for several related disciplines in medicine.
"ATR activation in response to ionizing radiation: still ATM territory"
Authors: Cuadrado Myriam , Martinez-Pastor Barbara , Fernandez-Capetillo Oscar
Published: May 2006

Unrepaired DNA double-strand breaks (DSBs) are a major cause for genomic instability. Therefore, upon detection of a DSB a rapid response must be assembled to coordinate the proper repair/signaling of the lesion or the elimination of cells with unsustainable amounts of DNA damage. Three members of the PIKK family of protein kinases -ATM, ATR and DNA-PKcs- take the lead and initiate the signaling cascade emanating from DSB sites. Whereas DNA-PKcs activity seems to be restricted to the phosphorylation of targets involved in DNA repair, ATM and ATR phosphorylate a broad spectrum of cell cycle regulators and DNA repair proteins. In the canonical model, ATM and ATR are activated by two different types of lesions and signal through two independent and alternate pathways. Specifically, ATR is activated by various forms of DNA damage, including DSBs, arising at stalled replication forks ("replication stress"), and ATM is responsible for the signaling of DSBs that are not associated with the replication machinery throughout the cell cycle. Recent evidence suggests that this model might be oversimplified and that coordinated crosstalk between ATM and ATR activation routes goes on at the core of the DNA damage response.
Activation of Dopamine D2 Receptors Lowers Circadian Leptin Concentrations in Obese Women
Authors: Kok Petra , Roelfsema Ferdinand , Frölich Marijke , van Pelt Johannes , Meinders A. Edo , Pijl Hanno
Published: May 2006

Context: Leptin release is regulated by factors other than fat mass alone. Previous observations provide indirect evidence for an inhibitory effect of dopaminergic neurotransmission on leptin secretion. This study was done to establish the effect of bromocriptine treatment on circadian plasma leptin concentrations in obese humans.

Objective: The objective of the study was to study the acute effects of bromocriptine (a D2R agonist) on circadian leptin levels in obese women, whereas body weight and caloric intake remained constant.

Design: This was a prospective, single-blind, crossover study (2004).

Setting: The study was conducted at a clinical research center.

Participants: Eighteen healthy obese women (body mass index 33.2 ± 0.6 kg/m2) were studied twice in the early follicular phase of their menstrual cycle.

Intervention(s): Treatment consisted of bromocriptine or placebo for 8 d.

Main Outcome Measure(s): Blood was collected during 24 h at 20-min intervals for determination of leptin concentrations at the last day of medical treatment (bromocriptine or placebo). Mean 24-h serum concentrations were determined for insulin, glucose, free fatty acids, and triglycerides.

Results: Short-term treatment with bromocriptine reduced leptin concentration (placebo 33.6 ± 2.5 vs. bromocriptine 30.5 ± 2.5 ng/liter, P = 0.03). Free fatty acid concentrations were increased by treatment with bromocriptine. The increase of free fatty acids was inversely related with the decline of leptin levels. The decline of glucose, insulin, or prolactin concentrations in response to bromocriptine was not correlated with the reduction of leptin.

Conclusion: Activation of dopamine D2 receptors by bromocriptine lowers circulating leptin levels in obese women, which suggests that dopaminergic neurotransmission is involved in the control of leptin release in humans.
Reduced Expression of Interleukin-11 and Interleukin-6 in the Periimplantation Endometrium of Excessive Ovarian Responders during in Vitro Fertilization Treatment
Authors: Makkar Guneet , Ng Ernest H. Y. , Yeung William S. B. , Ho P. C.
Published: May 2006

Context: Impaired implantation in assisted reproduction cycles with high serum estradiol (E2) concentrations may be related to abnormal endometrial functions.

Objective: The in vivo expression of T helper type 2 (Th2) cytokines in the periimplantation endometrium of infertile patients was compared between natural and stimulated cycles.

Interventions and Main Outcome Measures: Uterine flushings and endometrial biopsies were collected 7 d after the LH surge in natural cycles or after human chorionic gonadotropin injection in stimulated cycles. Th2 cytokines were determined by immunolocalization and by ELISA. Natural cycles were in group A, whereas stimulated cycles with peak serum E2 of no more than 20,000 pmol/liter (moderate responders) and more than 20,000 pmol/liter (excessive responders) were classified as group B and group C, respectively.

Results: Higher E2 had a negative effect on IL-11 and IL-6 expression in the endometrium and IL-11 concentration in the uterine flushing. In endometrial biopsies, a significantly lower immunostaining of stromal IL-11 (P < 0.001) and glandular IL-6 (P < 0.05) was detected in group C compared with that of groups A and B. IL-11 concentration by ELISA was significantly lower in group C (P < 0.05). Endometrial leukemia inhibitory factor and IL-4 expression was similar in the three groups. In uterine flushings, a significantly higher percentage of women in group C had undetectable IL-11 and a lower IL-11 concentration (P < 0.01) compared with group A, whereas no difference in IL-6 concentration was noted in the three groups.

Conclusion: Reduced expression of IL-11 and IL-6 in periimplantation endometrium may account for lower implantation in excessive responders.
Frequent Finding of the Androgen Receptor A645D Variant in Normal Population
Authors: Lundin Kristina B. , Nordenskjöld Agneta , Giwercman Aleksander , Giwercman Yvonne L.
Published: May 2006

Background: The androgen receptor A645D mutation has been described in one patient with ambiguous genitalia and one boy with normal phenotype.

Objective: Because of this phenotypic variation, we screened a cohort of men from the general population (n = 293) as well as men with the following disorders of the genital tract for the mutation: men with prostate cancer (n = 89), testicular cancer (n = 87), and infertility (n = 103). We also investigated the influence of the polymorphic CAG and GGN repeats on the phenotypic outcome.

Results: The A645D variant was found in three men from the general population (1.0%). These men did not differ regarding testosterone or LH concentrations, compared with the rest of this population. In addition, two men with prostate cancer (2.3%) and one infertile man (1.0%) presented with the mutation. No statistical differences in frequency were noted between the study groups, and none of these individuals had any genital malformations. All men who presented with the mutation carried an extraordinarily short GGN repeat of 10 base triplets in combination with long CAG repeats of 26–28 (average 27.3). In contrast, men with GGN=10, but CAG less than 26 did not have the A645D mutation. A single-nucleotide polymorphism analysis revealed that the A645D variant has emerged from the most common haplogroup in our population.

Conclusions: We conclude that the A645D mutation, which is present in 1% of the general Swedish population, is linked to GGN10 and long CAG repeats. Its effect on androgen receptor function is currently unknown.
Teduglutide for the Treatment of Short Bowel Syndrome
Authors: Ferrone Marcus , Scolapio James S
Published: May 2006

Objective:

To summarize the pharmacology, development, and clinical application of teduglutide (ALX-0600), a glucagon-like peptide-2 (GLP-2) analog for the treatment of short bowel syndrome (SBS).

Data Sources:

Clinical literature, including both primary sources and review articles, was accessed through a search of the MEDLINE databases (1980–March 2006). Key search terms included teduglutide, ALX-0600, glucagon-like peptide-2, short bowel syndrome, short gut, and intestinal adaptation. Clinical trial and drug data were supplied by the manufacturer, NPS Pharmaceuticals.

Study Selection and Data Extraction:

Review articles, abstracts, and clinical studies related to GLP-2 and its analog, teduglutide, were analyzed. An evaluation of the research exploring teduglutide for the management of SBS was conducted. Relevant information was then selected.

Data Synthesis:

Research has revealed that administration of GLP-2 to patients following major small bowel resection improves intestinal adaptation and nutrient absorption. Teduglutide is an enzyme-resistant GLP-2 analog that shows promise in preventing intestinal injury, restoring mucosal integrity, and enhancing intestinal absorptive function.

Conclusions:

Data from ongoing clinical trials indicate that teduglutide may have the ability to enhance intestinal absorptive capacity in patients with SBS. Further studies and the completion of Phase III trials are necessary to determine the appropriate dosage and length of treatment for patients with SBS to gain optimal therapeutic benefit from this drug.
How Many “Me-Too” Drugs are Enough? The Case of Physician Preferences for Specific Statins
Authors: Austin Peter C , Mamdani Muhammad M , Juurlink David N
Published: May 2006

Background:

The increasing availability of “me-too” drugs has provided considerable treatment options for clinicians. However, the number of such drugs within a class that are actually used by clinicians has not been well studied.

Objective:

To determine the number of different statins that individual physicians use in practice.

Methods:

The Ontario Drug Benefit database was used to identify physicians who issued at least 10 incident statin prescriptions between October 2001 and May 2003 for patients aged 66 years and older. A preferred statin was defined for each physician, and the proportion of each physician's incident prescriptions written for that agent was determined. We then determined the number of different statins required to fill each physician's incident prescribing needs.

Results:

A total of 3426 physicians wrote 73 571 incident statin prescriptions. The mean percentage of prescriptions written for each physician's preferred statin formulation was 73.7%. Repeat analysis to examine the proportion of prescriptions filled using each physician's top 2 statin formulations found that the average physician wrote the vast majority of his or her incident prescriptions (94.9%) for only 1 or 2 statins. Half of all physicians used, at most, 2 different statins for all incident prescribing, while 91.3% of physicians used, at most, 3 different statins for all of their incident prescribing.

Conclusions:

A high proportion of Ontario physicians issued the majority of their incident statin prescriptions for the same statin formulation. Most physicians required, at most, 3 different statins for all incident statin prescribing.
The Knowledge-Creating Role of the Internet in International Business: Evidence from Vietnam
Authors: Nguyen Tho D. , Barrett Nigel J.
Published: May 2006

This article examines the knowledge-creating role of the Internet in international business activities of Vietnamese firms. The authors find that both the collection and the transformation of information from the Internet by a firm affect its foreign sales intensity. In addition, market and learning orientations facilitate this process.
Market Share Performance of Foreign and Domestic Brands in China
Authors: Gao Gerald Yong , Pan Yigang , Tse David K. , Yim Chi Kin (Bennett)
Published: May 2006

In this study, the authors examine market share performance of foreign and domestic brands in China. Drawing on the resource-based view and brand management literature, they investigate the impacts of three sets of factors: brands’ competitive advantages, external market environments, and the length of brand existence. The authors also examine the different influences of these factors on foreign versus domestic brands. The empirical testing is based on a survey of senior executives of 408 brands in 52 product categories in China. This study offers new findings on what drives the market share performance in transition economies.
On ovoids of PG(3, q)
Authors: Ball Simeon
Published: May 2006

We give necessary and sufficient conditions that a polynomial f (x, y) gives an ovoid of PG(3, q). Furthermore by considering Rédei polynomials associated to ovoids of PG(3, q) we obtain sets of equations relating the coefficients of f (x, y). One such set of equations implies that if xiyj
occurs as a term in f (x, y) + xy then i and j must have disjoint binary expansions.
Interpolation of homogeneous polynomials over a finite field
Authors: Ballico E
Published: May 2006

We study several interpolation problems for homogeneous polynomials over a finite field.
Extensions of isomorphisms for affine Grassmannians over
Authors: Blok Rieuwert J , Hall Jonathan I
Published: May 2006

In Blok [R. J. Blok, Extensions of isomorphisms for affine dual polar spaces and strong parapolar spaces. Adv. Geom.
5 (2005), 509–532.] affinely rigid classes of geometries were studied. These are classes B of geometries with the following property: Given any two geometries Γ1, Γ2 ∈ B with subspaces 𝒮1 and 𝒮2 respectively, then any isomorphism Γ1 − 𝒮1 → Γ2 − 𝒮2 uniquely extends to an isomorphism Γ1 → Γ2.

Suppose Γ belongs to an affinely rigid class. Then for any subspace 𝒮 we have Aut(Γ − 𝒮) ≤ Aut(Γ). Suppose that, in addition, Γ is embedded into the projective space ℙ(V) for some vector space V. Then one may think of V as a “natural” embedding if every automorphism of Γ is induced by some (semi-) linear automorphism of V. This is for instance true of the projective geometry Γ = ℙ(V) itself by the fundamental theorem of projective geometry. Clearly since Γ belongs to an affinely rigid class and has a natural embedding into ℙ(V), also the embedding Γ − 𝒮 into ℙ(V) is natural.

In Blok [R. J. Blok, Extensions of isomorphisms for affine dual polar spaces and strong parapolar spaces. Adv. Geom.
5 (2005), 509–532.] the notion of a layer-extendable class was introduced and it was shown that layer-extendable classes are affinely rigid. As an application, it was shown that the union of most projective geometries, (dual) polar spaces, and strong parapolar spaces forms an affinely rigid class. However, the geometries motivating that study, the Grassmannians defined over 𝔽2, were not included in this class because they do not form a layer-extendable class. Since affine projective geometries (1-Grassmannians, if you will) are simply complete graphs, clearly they are not affinely rigid at all. In the present note we show that also the class of 2-Grassmannians over 𝔽2 fails to form an affinely rigid class, although in a less dramatic way, whereas the class of k-Grassmannians of projective spaces of dimension n over 𝔽2 where 3 ≤ k ≤ n − 2 is in fact affinely rigid.
Elation generalized quadrangles of order (q, q
2), q even, with a classical subquadrangle of order q
Authors: Thas Koen
Published: May 2006

One of the famous open problems in Finite Geometry is the classification of ovoids in a projective 3-space PG(3, q) over the finite field with q elements, q even. For q odd, this classification was obtained in 1955 by A. Barlotti [
A. Barlotti, Un'estensione del teorema di Segre-Kustaanheimo. Boll. Un. Mat. Ital. (3) 10 (1955), 498–506. MR0075606 (17,776b) Zbl 0066.38901
] and G. Panella [
G. Panella, Caratterizzazione delle quadriche di uno spazio (tridimensionale) lineare sopra un corpo finito. Boll. Un. Mat. Ital. (3) 10 (1955), 507–513. MR0075607 (17,776c) Zbl 0066.38902
]. A breakthrough result was a recent one of M. R. Brown, who showed in [
M. R. Brown, Ovoids of PG (3, q), q even, with a conic section. J. London Math. Soc. (2) 62 (2000), 569–582. MR1783645 (2001i:51012) Zbl 1038.51008 ] that when such an ovoid has a conic plane section, the ovoid must be an elliptic quadric. Even more recently, M. R. Brown and M. Lavrauw [
M. R. Brown, M. Lavrauw, Eggs in PG(4n − 1, q), q even, containing a pseudo-conic.
Bull. London Math. Soc. 36 (2004), 633–639. MR2070439 (2005k:51009)
Zbl 1064.51005
] generalized this theorem by obtaining a similar result for higher dimensions. Both results have equivalent statements in the theory of (translation) generalized quadrangles.

In this note, we improve these results by showing that an elation generalized quadrangle of order (q, q
2), q even, with a

subGQ containing the elation point arises from a non-singular elliptic quadric in PG(5, q).

The theorem itself arises as a corollary of a more general observation which works for all characteristics. There is a wealth of consequences.
Gorenstein liaison in
Authors: Lesperance Joshua
Published: May 2006

One of the main open questions for Gorenstein liaison is whether or not the deficiency module of a curve will determine its even G-liaison class in ℙ
n
, n ≥ 4. In this paper, we show that this is indeed the situation for many degenerate curves in ℙ4. As a special case we are able to show that any two degenerate Buchsbaum curves will belong to the same even G-liaison class if and only if they have isomorphic deficiency modules (up to shifts). We then explore when this may also be true for curves which are obtained as hypersurface sections of Buchsbaum surfaces in ℙ4.
Flat manifolds, harmonic spinors, and eta invariants
Authors: Sadowski M , Szczepañski A
Published: May 2006

The aim of this paper is to calculate the eta invariants and the dimensions of the spaces of harmonic spinors of an infinite family of closed flat manifolds ℱ
CHD
. It consists of some flat manifolds M with cyclic holonomy groups. If M ∈ ℱ
CHD
, then we give explicit formulas for η(M) and 𝔥(M). They are expressed in terms of solutions of appropriate congruences in {−1, 1}
k
. As an application we investigate the integrability of some η invariants of ℱ
CHD
-manifolds.
Cremona convexity, frame convexity and a theorem of Santaló
Authors: Goodman J. E , Holmsen A , Pollack R , Ranestad K , Sottile F
Published: May 2006

In 1940, Luis Santaló proved a Helly-type theorem for line transversals to boxes in ℝ
d
. An analysis of his proof reveals a convexity structure for ascending lines in ℝ
d
that is isomorphic to the ordinary notion of convexity in a convex subset of ℝ2d−2. This isomorphism is through a Cremona transformation on the Grassmannian of lines in ℙ
d
, which enables a precise description of the convex hull and affine span of up to d ascending lines: the lines in such an affine span turn out to be the rulings of certain classical determinantal varieties. Finally, we relate Cremona convexity to a new convexity structure that we call frame convexity, which extends to arbitrary-dimensional flats in ℝ
d
.
Two-transitive ovals
Authors: Maschietti Antonio
Published: May 2006

An oval 𝒪 of a projective plane is called two-transitive if there is a collineation group G fixing 𝒪 and acting 2-transitively on its points. If the plane has odd order, then the plane is desarguesian and the oval is a conic. In the present paper we prove that if a plane has order a power of two and admits a two-transitive oval, then either the plane is desarguesian and the oval is a conic, or the plane is dual to a Lüneburg plane.
The direct product theorem for profinite groups
Authors: Goldstein Daniel , Guralnick Robert M
Published: May 2006

Let A and B be finitely generated profinite groups. If G is isomorphic to A × B, then any short exact sequence 1 → A → G → B → 1 splits as a direct product.
The quasi-variety of groups with trivial fourth dimension subgroup
Authors: Mikhailov Roman , Passi Inder Bir S
Published: May 2006

We prove that the quasi-variety consisting of the groups with trivial fourth dimension subgroup is not finitely based. This answers a problem of B. I. Plotkin.
Subsemigroups of groups: presentations, Malcev presentations, and automatic structures
Authors: Cain Alan J , Robertson Edmund F , Ruškuc Nik
Published: May 2006

All finitely generated subsemigroups of virtually nilpotent groups admit finite Malcev presentations. (A Malcev presentation is a presentation of a special type for a semigroup that can be embedded in a group.) All automatic or asynchronous automatic semigroups embeddable into groups admit finite Malcev presentations. Finitely generated subsemigroups of virtually free groups are automatic. A finitely generated subsemigroup of the free product of a free group and an abelian group that fails to have a finite Malcev presentation is exhibited. Therefore the class of groups all of whose finitely generated subsemigroups admit finite Malcev presentations is properly contained in the class of coherent groups. Finitely generated subsemigroups of the free product of a free monoid and an abelian group are asynchronously automatic and therefore have finite Malcev presentations.
Effects of wastewater filtration on geotextile permeability
Authors: Yaman C. , Martin J. P. , Korkut E.
Published: May 2006

The purpose of this study was to show how the permeability of different types of geotextile behaved when they were subjected to municipal wastewater filtration. The tests were intended to show the clogging potential of geotextiles if they were used for wastewater treatment. The geotextiles filtered organic suspended solids and hosted growth of microorganisms. The test liquid was primary treatment effluent that treated combined sewage (wastewater plus stormwater runoff). The project used 10.16 cm diameter packed columns containing alternating layers of gravel, sand and geotextile filters. The study included four phases. The first phase was intended to measure the baseline permeability of each geotextile used. The second phase was a screening phase to see how the permeability of woven and nonwoven geotextiles changes when they are subjected to wastewater. Phase III was a parametric study to assess the effects of variables on residual permeability. These variables were the number of geotextile filter layers, the hydraulic loading rate (HLR) or flow rate, and provision for passive re-aeration. It was found in the first two phases that only nonwoven geotextiles with complex structures and high internal porosity retained more biomass yet preserved sustainable permeability. A confirmatory final phase was conducted using the best combination of operating variables indicated by the parametric study. It was shown that these variables influence the residual permeability of the geotextile filters tested. The confirmatory final phase included two layers of continuous filament geotextile filters in a granular matrix of decreasing coarseness with depth, maintaining an unsaturated subgrade, and twice daily dose and drain application of primary treatment effluent at a net rate of 365 L/m2/day. With this HLR, the composite filter permeability of 0.925 cm/s was sustained with little loss, 0.2%, whereas the control column with no geotextile layer indicated 13% permeability loss. Scanning electron microscope images showed that the biomass morphology was a discontinuous floc entrapped within the geotextile pore structure.
Effect of geotextiles on the load-carrying capacity and deformation characteristics of sabkha soil
Authors: Aiban S. A. , Siddiqi Z. U. , Baghabra Al-Amoudi O. S. , Al-Ahmadi H. M. , Asi I. M.
Published: May 2006

Road construction on sabkha terrain along the coastal regions of the Arabian Gulf and the Red Sea is often faced with different types of damage due to the low bearing capacity of sabkha deposits, especially when they are wetted. Such conditions necessitate the improvement of sabkha prior to any construction. The purpose of this investigation was to upgrade the load-carrying capacity of sabkha soil using geotextiles by varying the geotextile type, base thickness, moisture condition and the magnitude of the deviatoric stress. To achieve these objectives, a special mould was fabricated to accommodate the soil-fabric-aggregate (SFA) systems. The performance of SFA systems was evaluated by measuring the permanent deformation under the applied ‘dynamic’ load. Results of this study indicate that the selection of an appropriate geotextile type can bring about significant improvement in the load-carrying capacity of the water-sensitive sabkha soils, particularly under soaked conditions. The inclusion of a geotextile layer on top of the sabkha subgrade reduced the thickness of the graded base layer by 34%. In addition, the geotextile increased the stiffness of the sabkha subgrade and reduced the permanent deformation after a certain number of load reputations.
Proteasome activity in experimental diabetes
Authors: Alexandrova Albena , Petrov Lubomir , Kirkova Margarita
Published: May 2006

Numerous studies have indicated that oxidative stress contributes to the development and progression of diabetes and other related complications. Since the ubiquitin-proteasome pathway is involved in degradation of oxidized proteins, it is to be expected that alterations in proteasome-dependent proteolysis accompany diabetes. This paper focuses on the role of the proteasome in alloxan-induced experimental diabetes. The changes in proteasomal activity and oxidative stress indices (protein oxidation and lipid peroxidation) were evaluated. The obtained results revealed increased protein oxidation and lipid peroxidation, as well as alterations in proteasomal activities in diabetic rats. Our data indicates a significant decrease in chymotryptic-like activity; increased tryptic-like activity; and unchanged post-glutamyl peptide hydrolytic-like activity. These findings suggest the presence of oxidative stress in diabetes that appears to result in changes to the ubiquitin-proteasome pathway.
Three‐dimensional architecture of the left ventricular myocardium
Authors: Lunkenheimer Paul P. , Redmann Klaus , Kling Natalie , Jiang Xiaoji , Rothaus Kai , Cryer Colin W. , Wübbeling Frank , Niederer Peter , Heitz Philipp U. , Yen Ho Siew , Anderson Robert H.
Published: May 2006

Concepts for ventricular function tend to assume that the majority of the myocardial cells are aligned with their long axes parallel to the epicardial ventricular surface. We aimed to validate the existence of aggregates of myocardial cells orientated with their long axis intruding obliquely between the ventricular epicardial and endocardial surfaces and to quantitate their amount and angulation. To compensate for the changing angle of the long axis of the myocytes relative to the equatorial plane of the ventricles with varying depths within the ventricular walls, the so‐called helical angle, we used pairs of cylindrical knives of different diameters to punch semicircular slices from the left ventricular wall of pigs, the slices extending from the epicardium to the endocardium. The slices were pinned flat, fixed in formaldehyde, embedded in paraffin, sectioned, stained with azan or hematoxilin and eosin, and analyzed by a new semiautomatic procedure. We made use of new techniques in informatics to determine the number and angulation of the aggregates of myocardial cells cut in their long axis. The alignment of the myocytes cut longitudinally varied markedly between the epicardium and the endocardium. Populations of myocytes, arranged in strands, diverge by varying angles from the epicardial surface. When paired knives of decreasing diameter were used to cut the slices, the inclination of the diagonal created by the arrays increases, while the lengths of the array of cells cut axially decreases. The visualization of the size, shape, and alignment of the myocytic arrays at any side of the ventricular wall is determined by the radius of the knives used, the range of helical angles subtended by the alignment of the myocytes throughout the thickness of the wall, and their angulation relative to the epicardial surface. Far from the majority of the ventricular myocytes being aligned at angles more or less tangential to the epicardial lining, we found that three‐fifths of the myocardial cells had their long axes diverging at angles between 7.5 and 37.5° from an alignment parallel to the epicardium. This arrangement, with the individual myocytes supported by connective tissue, might control the cyclic rearrangement of the myocardial fibers. This could serve as an important control of both ventricular mural thickening and intracavitary shape. Anat Rec Part A 288A:565–578, 2006. © 2006 Wiley‐Liss, Inc.
Origin of cosmic magnetic fields
Authors: Rees M. J.
Published: May 2006

The first significant cosmic fields, and the seed field for galactic dynamos probably developed after the formation of the first non‐linear structures. The history of star formation and the intergalactic medium is controlled, at least in part, by how and when galaxies and their precursors acquired their fields. The amplification of fields behind shocks, and the diffusivity of the magnetic flux, are crucial to the interpretation of radio sources, gamma ray burst afterglows, and other energetic cosmic phenomena. The build‐up of magnetic fields is an important aspect of the overall cosmogonic process. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cosmological magnetic helicity
Authors: Sokoloff D. , Semikoz V. B.
Published: May 2006

We argue that magnetic helicity conservation is violated at the lepton stage in the evolution of the early Universe. As a result, a cosmological magnetic field which can be a seed for the galactic dynamo obtains a substantial magnetic helicity from the beginning which has to be taken into account on later stages of galactic evolution. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Primordial magnetic fields and gravitational waves
Authors: Caprini C.
Published: May 2006

We analyse the generation of tensor metric perturbations by the anisotropic stresses of a primordial magnetic field. First we present the implication of causality on the initial spectrum of the magnetic field, and then derive strong limits on its amplitude by applying the nucleosynthesis bound on the gravitational waves (GW) induced by the field. Finally we discuss the CMB tensor spectrum generated by the magnetic field, presenting analytical approximations for the temperature anisotropies and polarisation signal by a possible helical component in the magnetic field. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cyclotron emission effect on CMB spectral distortions
Authors: Burigana C. , Zizzo A.
Published: May 2006

We investigated the role of the cyclotron emission (CE) associated to cosmic magnetic fields (MF) on the evolution of cosmic microwave background (CMB) spectral distortions. We computed the photon and energy injection rates by including spontaneous and stimulated emission and absorption. These CE rates have been compared with those of bremsstrahlung (BR) and double Compton scattering (DC), for realistic CMB distorted spectra at various cosmic epochs. For reasonable MF strengths we found that the CE contribution to the evolution of the CMB spectrum is much smaller than the BR and DC contributions. The constraints on the energy exchanges at various redshifts can be then derived, under quite general assumptions, by considering only Compton scattering (CS), BR, and DC, other than the considered dissipation process. Upper limits to the CMB polarization degree induced by CE have been estimated. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Amplification of primordial magnetic fields by anisotropic gravitational collapse
Authors: King E. J. , Coles P.
Published: May 2006

If a magnetic field, B , is frozen into a plasma that undergoes spherical compression then B varies with the plasma density ρ according to B ∝ ρ 2/3. In the gravitational collapse of cosmological density perturbations, however, quasi‐spherical evolution is very unlikely. In anisotropic collapses the magnetic field can be a much steeper function of gas density than in the isotropic case. We investigate the distribution of amplifications in realistic gravitational collapses from Gaussian initial fluctuations using the Zel'dovich approximation. Representing our results using a relation of the form B ∝ ρ α , we show that the median value of α can be much larger than the α = 2/ 3 resulting from spherical collapse, even if there is no initial correlation between magnetic .eld and principal collapse directions. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The generation of magnetic fields by the Weibel instability
Authors: Fujita Y. , Kato T. N.
Published: May 2006

We show that strong magnetic fields can be generated at shock waves associated with formation of galaxies or clusters of galaxies by the Weibel instability, an instability in collisionless plasmas. The estimated strength of the magnetic field generated through this mechanism is close to the order of values observed in galaxies or clusters of galaxies at present, which indicates that strong amplification of magnetic fields after formation of galaxies or clusters of galaxies is not required. This mechanism could have worked even at a redshift of ∼10, and therefore the generated magnetic fields may have affected the formation of stars at the early Universe. This model will be tested by future observations of nearby clusters of galaxies. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Environment and luminosity of supernova remnants
Authors: Hunt L. K. , Reynolds S. P.
Published: May 2006

The explosion of supernovae and the evolution of their remnants (SNRs) accelerate cosmic rays over a vast range of timescales. Magnetic fields can be investigated indirectly through one of the observational signatures of this acceleration, namely radio synchrotron emission. With the aim of better understanding the role of the magnetic field in supernova evolution, we explore the variation of SNR radio luminosities with physical conditions in the surrounding interstellar medium. With a data set that comprises more than 90 individual SNRs in 10 galaxies, and a range of 3000 in ISM density and 104 in radio synchrotron luminosity, we find a significant correlation between the two quantities. The observed trends support the hypothesis that adiabatic compression of magnetic fields by itself is insuf.cient to explain the radio emission of the brighter and more luminous in SNRs. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamo and hydromagnetic liquid metal experiments
Authors: Colgate S. A.
Published: May 2006

Magnetic dynamo experiments are being performed in many laboratories throughout the world. The most successful have been at Karlsruhe and Riga, where liquid sodium has been forced in constrained flows and has produced the predicted positive dynamo gain. The unconstrained flows are being investigated at Wisconsin, Cadarache, and Maryland. These experiments have not reached the critical values of the magnetic Reynolds number,Rm, necessary for dynamo gain, despite the positive predictions of laminar flow theory. Experiments in understanding the relationship of turbulence to MHD are being performed in addition to these at Perm, Princeton, and Swarthmore. A naturally constrained dynamo, using angular momentum gradient, Couette flow, to suppress turbulence is being attempted at New Mexico Tech. Flow constrained by ridged walls is likely to have less turbulence than unconstrained flow where the criterion of constraint is the degree of suppression of the Helmholtz shear flow instability. The study of MHD in conjunction with fluid turbulence has become of major importance in dynamo experiments as well as to future dynamo theory. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cosmic ray driven dynamo in galactic disks: effects of resistivity, SN rate and spiral arms
Authors: Hanasz M. , Otmianowska‐Mazur K. , Kowal G. , Lesch H.
Published: May 2006

We present a further development of the first numerical model of the magnetohydrodynamical dynamo, driven by cosmic rays in the interstellar medium (Hanasz et al. 2004). The cosmic rays are produced in randomly occurring supernova remnants. Our model is described by equations of magnetohydrodynamics supplemented with the diffusion‐advection equation governing the propagation of cosmic rays. The other essential elements of the model are: vertical gravity of the disk, differential rotation and resistivity leading to reconnection of magnetic field lines. We obtain amplification of the large‐scale magnetic field on a timescale of galactic rotation. The model represents a kind of fast, cosmic ray driven galactic dynamo proposed by Parker (1992). The amplification of the large‐scale magnetic field results from the buoyancy of the cosmic ray component in the interstellar medium. We describe five models characterized by different resistivity magnitudes, supply rates of cosmic rays and discuss in more detail a model with periodic SN activity, which mimics the presence of spiral arms in the disk. We find that both the resistivity and spiral arms enhance the efficiency of the cosmic–ray dynamo. The timescale of magnetic field amplification in this model is as short as 140 Myr. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A multi‐scale disk dynamo model
Authors: Stepanov R. , Frick P. , Sokoloff D.
Published: May 2006

We suggest to combine the mean‐field description of the galactic dynamo with a shell description of small‐scale turbulence for high values of hydrodynamic and magnetic Reynolds numbers. The model allows us to keep the balance of energy and realizes the kinematic and non‐linear regimes of the magnetic field generation. The suggested approach gives a possibility to study the role of magnetic helicity in the generation process. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Radio polarization and RM structure at high Galactic latitudes
Authors: de Bruyn A. G. , Katgert P. , Haverkorn M. , Schnitzeler D. H. F. M.
Published: May 2006

We present WSRT observations at low frequencies (315–388 MHz) of the diffuse polarized emission in an area of 6° × 6° at high Galactic latitude. Polarized emission is found to be ubiquitous with typical levels of about 3–5 K brightness temperature with a generally mottled structure. The Rotation Measure (RM) of the emission varies between values of –5 to +20 rad m–2. Most of the polarized emission appears Faraday thin with a single unresolved valued for the RM. The data suggest both inhomogeneous as well as dissimilar distribution functions of the synchrotron emitting and Faraday rotating media along the line of sight. The systematic patterns in the RM at this high Galactic latitude of +71° also provide evidence for significant variations in the vertical component of the local Galactic magnetic field at a level of 1 μ Gauss. The potential for Galactic polarimetry at even lower frequencies using LOFAR and SKA is briefly discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic fields in halos of spiral galaxies
Authors: Dettmar R.‐J. , Soida M.
Published: May 2006

Observations of magnetic fields in halos of edge‐on disk galaxies are discussed in relation to the interstellar disk‐halo interface in disk galaxies. The distribution of extra‐planar diffuse ionized gas correlates on local and global scales with cosmic rays and magnetic fields as inferred from observations of the non‐thermal radio continuum radiation and its polarisation. From the polarisation a large‐scale and well‐ordered magnetic field in these gaseous halos can be deduced. For several objects a significant poloidal component of the halo field is likely. These observations indicate the presence of physical processes which generate and maintain magnetic fields on galactic scales. The importance of differential rotation of the gaseous halos for such processes is briefly discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strong magnetic asymmetries in weakly interacting spirals
Authors: Chyży K. T. , Ehle M. , Beck R.
Published: May 2006

We investigate the influence of cluster environment on the structure and evolution of magnetic fields and the interstellar medium in the Virgo cluster spiral NGC 4254. Our sensitive interferometric (VLA) and single dish (Effelsberg) radio polarimetric observations reveal several magnetic spiral arms displaced from optical ones. However, the southern arm, particularly bright in polarized emission, lacks an optical counterpart. In this area the magnetic pitch angle is very small. On the contrary, the northern part of the galaxy with more diffuse total radio emission shows a significant radial component of the magnetic field. At 1.4 GHz the galaxy shows an extended polarized envelope with a highly regular magnetic field extending further than any star‐forming region. The regular component enters the cluster environment and can enrich the cluster‐scale magnetic field. Our XMM‐Newton observations reveal that the broadband X‐ray emission of the hot gas emerges from almost the whole galaxy disk and is tightly associated with regions of star formation. The distribution of Xrays does not show any sign of stripped hot gas around the galaxy disk and rules out strong ram pressure of the hot cluster gas. Magnetic asymmetries and slightly perturbed H I and optical emission probably manifest weak tidal interactions of NGC 4254 with other Virgo cluster members: the dark galaxy VIRGOHI 21 or NGC 4262. We also compare polarimetric properties of NGC 4254 with other Virgo cluster spirals which we currently observe systematically with the Effelsberg radio telescope. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Radio sources and the evolution of the intracluster medium
Authors: De Young D. , Jones T. W.
Published: May 2006

The energy available from active galactic nuclei and their accompanying radio sources in clusters of galaxies have been suggested as energy sources that can solve the “cooling flow problem” in rich clusters of galaxies. In particular, fragmentation and subsequent mixing of buoyant radio source bubbles and relics has been proposed as a mechanism for mixing and reheating the intracluster medium. However, inclusion of the effects of the magnetic field present in the ICM of most clusters shows that the situation is more complex than might have been thought. Using self consistent 2‐D and 3‐D MHD calculations of the evolution of radio source bubbles in clusters, including their formation and including both galaxy and cluster gravitational potentials, it is shown that the buoyant bubbles are stable against fragmentation over times comparable to their buoyant risetimes and to the cooling times in clusters. In addition, lifting and mixing of the ICM is confined to volumes directly below the rising bubble and thus does not include an appreciable fraction of the overall volume of the ICM in the inner regions of clusters. Hence some additional mixing and fragmentation mechanisms may be required in order to effectively use radio sources in clusters as a means of general reheating of the ICM on times comparable in inner cluster cooling times. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polarization and magnetic fields of giant radio galaxies
Authors: Jamrozy M.
Published: May 2006

Giant double radio galaxies with a linear size greater than 1 Mpc (H 0 = 50 km s–1 Mpc–1) are the largest individual objects in the Universe. They are of particular interest in studying a number of astrophysical problems. One of them are magnetic fields associated with these sources, which play a crucial physical rôle in plasma processes over very large scales. In this paper, we report new VLA observations and show high‐frequency total‐power and polarization maps of the sources from the Machalski, Jamrozy & Zola (2001) sample. This sample and a comparison set of ‘normal‐size’ radio galaxies are used to study correlations between different physical properties of the lobes of FRII‐type sources. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Linear polarization in small radio sources
Authors: Rossetti A. , Mantovani F. , Dallacasa D.
Published: May 2006

Polarimetric observations at 5 and 8.4 GHz have been performed for 3 CSS quasars. These observations are part of a programme aimed at studying the polarization characteristics of the core regions, jets, and lobes in such objects and at possibly finding of jet‐cloud interactions in CSSs. The behaviour of the fractional polarization and of the observed polarization angle as a function of λ 2 provides information on the density distribution of the ISM embedding the radio source, on its clumpiness and on the ordered and random components of the interstellar magnetic field. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Unbiased studies of diffuse extragalactic radio sources
Authors: Rudnick L. , Delain K. M. , Lemmerman J. A.
Published: May 2006

We present an overview of unbiased studies of diffuse extragalactic radio sources. We use a previously developed filtering technique to remove compact sources from large surveys such as WENSS, WISH, and NVSS and examine the residual diffuse emission. A search of these residuals, unbiased by optical or X‐ray selection, has uncovered a wide variety of diffuse sources, including those associated with groups of galaxies, “blank” fields, and previously unrecognized diffuse radio galaxy emission, as well as halos and relics of rich clusters. A second, targeted survey of the brightest X‐ray clusters results in a number of new sources, and illuminates some important selection effects. When the well‐established relationship between X‐ray and radio halo luminosities is extrapolated to lower levels, the apparent correlation holds quite well for any type of diffuse source, even background noise. The observed correlations must therefore be scrutinized for possible selection effects before physical interpretations are made. We briefly mention a wide‐field mapping project to search for large‐scale structures, and goals for the next generation of studies in magnetic field ‐ angular size parameter space. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mergers, relics and magnetic fields: The complex case of A2256
Authors: Clarke T. E. , Ensslin T.
Published: May 2006

Clusters of galaxies undergo multiple mergers during their lifetimes. Each merger drives shocks into the intracluster medium (ICM) which can heat the thermal gas, accelerate relativistic particles, and compress magnetic fields. Radio observations toward a number of clusters reveal large regions of diffuse synchrotron emission (halos and relics) which are not associated with individual host galaxies but are general properties of the ICM. Clusters host to this diffuse emission reveal significant evidence of recent or on‐going merger activity. We present deep VLA observations of the diffuse radio halo and relic emission in Abell 2256. Our new observations provide the first detailed image of the central diffuse radio halo emission in this cluster. The high fractional polarization of the relic allow us to use Faraday rotation measure observations to place constraints on the merger geometry of the system. In addition, the relic is composed of a number of synchrotron filaments which suggest the presence of spatially intermittent magnetic fields in this cluster. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)