bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of columbite ceramics A1–xNb2O6 by positron annihilation spectroscopy
Authors: Grebennikov Dmytro , Ovchar Oleg , Neretina Svetlana , Belous Anatolii , Mascher Peter
Published: August 2007

Columbite ceramics A1–xNb2O6 (where A = Mg, Co, Zn and x = 0, ‐0.005, ‐0.01, ‐0.03, ‐0.04) were studied by means of positron annihilation spectroscopy. The lifetime spectra revealed the presence of two lifetime components. The first component originates from positron annihilation inside of the grains. The second component is due to annihilations in the grain boundary regions. From the intensity of the second component and simulations (C. Hübner, T. Staab, and R. Krause‐Rehberg, Appl. Phys A 61, 203 (1995) [1]) the diameter of the grains is estimated as 2‐5 μm, ∼ 10 μm and 5‐7 μm, respectively for Mg‐, Co‐, and Zn‐containing columbites, in agreement with the results of microscopy measurements. In order to facilitate explanation of experimental results, theoretical calculations were conducted on columbite samples. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adsorbed hydrogen on Ni(111) surface studied by slow positron beam
Authors: Hirota K. , Osawa M. , Suzuki H. , Oishi Y. , Kanazawa I. , Fukutani K. , Nozawa K. , Komori F.
Published: August 2007

Reemitted slow positrons from clean Ni(111) surface and hydrogen‐adsorbed Ni(111) one have been measured. We have estimated experimentally the positron work functions, ‐0.60±0.05 and ‐0.82±0.07 eV of clean Ni(111) surface and the hydrogen‐adsorbed Ni(111) surface, respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of Fe‐doping and electrical load on the defect structure of Pb(ZrxTi1–x)O3 ferroelectric ceramics
Authors: Puff W. , Balke N. , Kungl H. , Hoffmann M. J. , Balogh A. G.
Published: August 2007

Vacancy related defects in undoped and 1 mol% Fe doped Pb(Zr54Ti46)O3 ferroelectric ceramic samples have been investigated by means of positron lifetime spectroscopy. Temperature dependent measure‐ments between 10 K and room temperature have been performed to study the influence of the acceptor type doping on the defect structure and on the charge states of the defects. On commercial Pb(Zr0.54Ti0.47(Ni0.33Sb0.67)0.08)O3 samples the influence of different electrical loading have been studied. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vacancy‐induced minority‐spin states in half‐metallic Heusler alloys
Authors: Özdoğan Kemal , Şaşıoğlu Ersoy , Galanakis Iosif
Published: August 2007

Ferromagnetic full Heusler alloys containing Co are amongst the most studied half‐metallic systems. Several studies recently have been concentrated on the effect of defects and impurities. We focus in this Letter on the case of vacancies in these alloys. We show that the occurrence of vacancies at the sites occupied by Co atoms can destroy half‐metallicity and alters the Slater–Pauling rule. Such defects are likely to occur since they result to the C1b lattice structure of the semi‐Heusler alloys. Contrary, the appearance of vacancies at the other sites keeps the half‐metallic character of the parent alloys. Thus for realistic devices it is important to prevent the appearance of vacancies during the growth of thin films. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐Abelian homomorphism testing, and distributions close to their self‐convolutions
Authors: Ben‐or Michael , Coppersmith Don , Luby Mike , Rubinfeld Ronitt
Published: August 2007

In this paper, we study two questions related to the problem of testing whether a function is close to a homomorphism. For two finite groupsG,H(not necessarily Abelian), an arbitrary mapf:G,H, and a parameter 0 <ε< 1, say thatfisε‐close to a homomorphism if there is some homomorphismgsuch thatgandfdiffer on at mostε|G| elements ofG, and say thatfisε‐far otherwise. For a givenfandε, a homomorphism tester should distinguish whetherfis a homomorphism, or iffisε‐far from a homomorphism. WhenGis Abelian, it was known that the test which picksO(1/ε) random pairsx,yand tests thatf(x) +f(y) =f(x+y) gives a homomorphism tester. Our first result shows that such a test works for all groupsG.

Next, we consider functions that are close to their self‐convolutions. LetA= {ag|gεG} be a distribution onG. The self‐convolution ofA,A′= {a|gεG}, is defined byIt is known thatA=A′exactly whenAis the uniform distribution over a subgroup ofG. We show that there is a sense in which this characterization is robust—that is, ifAis close in statistical distance toA′, thenAmust be close to uniform over some subgroup ofG.

Finally, we show a relationship between the question of testing whether a function is close to a homomorphism via the above test and the question of characterizing functions that are close to their self‐convolutions. © 2007 Wiley Periodicals, Inc. Random Struct. Alg., 2008
The random planar graph process
Authors: Gerke Stefanie , Schlatter Dirk , Steger Angelika , Taraz Anusch
Published: August 2007

We consider the following variant of the classical random graph process introduced by Erdős and Rényi. Starting with an empty graph on n vertices, choose the next edge uniformly at random among all edges not yet considered, but only insert it if the graph remains planar. We show that for all ε > 0, with high probability, θ(n2) edges have to be tested before the number of edges in the graph reaches (1 + ε)n. At this point, the graph is connected with high probability and contains a linear number of induced copies of any fixed connected planar graph, the first property being in contrast and the second one in accordance with the uniform random planar graph model. © 2007 Wiley Periodicals, Inc. Random Struct. Alg., 2008
Octylphenol reduces the expressions of steroidogenic enzymes and testosterone production in mouse testis
Authors: Kim Suel‐Kee , Kim Jong‐Hoon , Lee Ho‐Joon , Yoon Yong‐Dal
Published: August 2007

4‐tert‐octylphenol (OP) is known to disrupt testicular development and reduce male fertility. In the present study, male mice were exposed to OP at two different developmental stages, and the expression of steroidogenic enzymes and testosterone production were evaluated. Juvenile (15‐day‐old) and adult (8‐week‐old) male mice were injected with 2, 20, or 200 mg/kg of OP or 0.2 μg/kg of estradiol valerate for 5 days. Testosterone concentration was measured by radioimmunoassay and the expressions of the testicular genes were determined by RT‐PCR analysis and immunohistochemistry. In the animals exposed with 20 mg/kg of OP during juvenile stage, histochemical analysis of the testis showed that number of pyknotic germ cells inside the tubule was increased, while the number of oil red O positive Leydig cells was decreased. Moreover, the lumen formation was remarkably delayed. A reduced serum testosterone concentration and down‐regulated expressions of the mRNAs for steroidogenic acute regulatory protein (StAR), cholesterol side‐chain cleavage enzyme (P450scc), and 17α‐hydroxylase/C17–20 lyase (P45017α) were also observed after juvenile exposure to OP. Immunohistochemical staining for P450scc was mainly detected in interstitial Leydig cells, and a slightly reduced expression of P450scc protein was observed in the testis exposed to 20 mg/kg of OP during juvenile stage. The present study demonstrates that juvenile exposure to OP inhibits steroidogenesis by decreasing the expressions of steroidogenic enzymes in the testis. Diminished lipid content in Leydig cells and reduced transcriptional expression of the cholesterol transport gene, StAR, also support altered cholesterol metabolism and/or transport as a potential mechanism for the decreased testosterone production following exposure to OP. Altogether, the alteration of steroidogenesis by exposure to OP may adversely affect the normal development of the testis and spermatogenesis. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 449–458, 2007.
Serologic evaluation of human microcystin exposure
Authors: Hilborn E. D. , Carmichael W. W. , Soares R. M. , Yuan M. , Servaites J. C. , Barton H. A. , Azevedo S. M. F. O.
Published: August 2007

Microcystins are among the most commonly detected toxins associated with cyanobacteria blooms worldwide. Two episodes of intravenous microcystin exposures occurred among kidney dialysis patients during 1996 and 2001. Analysis of serum samples collected during these episodes suggests that microcystins are detectable as free and bound forms in human serum. Our goal was to characterize the biochemical evidence for human exposure to microcystins, to identify uncertainties associated with interpretation of these observed results, and to identify research needs. We analyzed serum samples using enzyme‐linked immunosorbent assay (ELISA) methods to detect free microcystins, and gas chromatography/mass spectrometry (GC/MS) to detect 2‐methyl‐3‐methoxy‐4‐phenylbutyric acid (MMPB). MMPB is derived from both free and protein‐bound microcystins by chemical oxidation, and it appears to represent total microcystins present in serum. We found evidence of free microcystins in patient serum for more than 50 days after the last documented exposure. Serum concentrations of free microcystins were consistently lower than MMPB quantification of total microcystins: free microcystins as measured by ELISA were only 8–51% of total microcystin concentrations as detected by the GC/MS method. After intravenous exposure episodes, we found evidence of microcystins in human serum in free and protein‐bound forms, though the nature of the protein‐bound forms is uncertain. Free microcystins appear to be a small but variable subset of total microcystins present in human serum. Research is needed to elucidate the human toxicokinetics of microcystins, in part to determine how observed serum concentrations can be used to estimate previous microcystin exposure. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 459–463, 2007.
Seasonal evaluation of reproductive status and exposure to environmental estrogens in hornyhead turbot at the municipal wastewater outfall of Orange County, CA
Authors: Deng Xin , Rempel Mary Ann , Armstrong Jeff , Schlenk Daniel
Published: August 2007

Seasonal changes in developmental stages, condition factor (CF), gonadosomatic index, and plasma vitellogenin (Vtg) concentrations in male and female hornyhead turbot were examined at the wastewater outfall (T1) of the Orange County Sanitation District, and two farfield sites T11 (7.7 km northwest of the outfall) and Dana Point (35 km south of the outfall) between February 2005 and May 2006. Fish collected from the three sites exhibited male‐oriented sex ratios. With few exceptions, developmental stages, CF, and GSI of both genders and plasma Vtg concentrations of females were not significantly different in samples collected from different sites at the same sampling period. More advanced gonad developmental stages and higher plasma Vtg concentrations in females were observed in August, indicating the seasonality of the reproductive cycle for this species. Plasma Vtg concentrations in males were observed in all of the sampling sites with the highest prevalence at T11 relative to T1 and Dana Point. The Vtg expression in males from the three sampling sites indicated widespread exposure to estrogenic compounds in waters of coastal California. However, the histopathological and reproductive relevance of the responses appeared to be insignificant and may not affect the population in these locations. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 464–471, 2007.
Acute toxicities of trace metals and common xenobiotics to the marine copepod Tigriopus japonicus: Evaluation of its use as a benchmark species for routine ecotoxicity tests in Western Pacific coastal regions
Authors: Lee K.‐W. , Raisuddin S. , Hwang D.‐S. , Park H. G. , Lee J.‐S.
Published: August 2007

Marine copepods have recently been recognized as important organisms in ecotoxicity testing for regulatory purposes. The harpacticoid copepod Tigriopus japonicus has a wide geographical distribution along the coast in the Western Pacific including Japan, South Korea, Taiwan, and Hong Kong. This study evaluated the acute toxicity sensitivity profile of Tigriopus japonicus against 12 common toxic substances including six endocrine disrupting chemicals (EDCs), three biocides and three trace metals. Through standard acute toxicity test procedures, toxicity endpoints LC50, LC10, and no observed effect concentration (NOEC) of each chemical were obtained. Although T. japonicus depicted different sensitivities towards different chemicals, a dose‐response relationship was consistent in all cases. T. japonicus was particularly sensitive to most of the EDCs, but relatively less sensitive to molinate (a thiocarbate herbicide). Across all tested chemicals, tributyltin (TBT) was the most toxic to the copepod with the LC50, LC10, and NOEC of 0.05, 0.03, and 0.02 mg/L, respectively. A comparison made with available data on acute toxicities of these chemicals to other marine copepod species revealed that T. japonicus is generally more sensitive to EDCs and in particular to TBT. We, therefore, strongly advocate that T. japonicus shall be adopted as a benchmark marine species for routine ecotoxicity testing and ecotoxicological studies in Western Pacific coasts. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 532–538, 2007.
Release of hydrogen sulfide by asteroidimpacts in black sea and risks for inland human population
Authors: Badescu Viorel
Published: August 2007

The hydrogen sulfide rich waters of the Black Sea pose a potential danger for the surrounding land regions. The impact of an asteroid may cause a catastrophic poisonous gas release in the atmosphere. Some effects of this last phenomenon on the Eastern Black Sea coastal regions are evaluated in this article. Two simple models are proposed to describe the generation of the H2S cloud. The initial diameter of the cloud depends on asteroid size. The initial thickness of the cloud depends, in addition, on sea depth at impact location. The wind speed plays an important role in H2S cloud dynamics. At 10 m/s wind‐speed the cloud margins may be seen at about 150 km from impact location in about 3.2 h. The maximum distance traveled by the hydrogen sulfide cloud increases by increasing the asteroid size and wind speed. The influence of the impact position on the distance traveled by hydrogen sulfide clouds is rather weak, as far as the seawater depth does not change significantly. Two values are considered when referring to the effect of hydrogen sulfide concentrations on humans: the lower concentration limit of 19.88 ppm (which corresponds to fatigue, loss of appetite, headache, irritability, poor memory, dizziness) and the upper concentration limit of 497 ppm (which corresponds to death after single exposures). The land surface area covered by the H2S cloud generated by a 1000 m size asteroid during the run‐in ranges between about 6080 and 11 520 km2. This may affect between 145 000 and 276 000 people. When a 250 m size asteroid is considered, the covered land surface area ranges between about 840 and 1890 km2 and between 20 000 and 45 000 people may be affected. In case of a 70 m size asteroid, the cloud covers up to 105 km2 of land during the run‐in. This may affect about 2500 people. These are moderate estimates. They do not include the urban population and may be 10 times underestimated for some particular wind directions. General recommendations to diminish the social effects of the impacts are presented. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 510–524, 2007.
Levator co‐activation is a significant confounder of pelvic organ descent on Valsalva maneuver
Authors: Örnö A. K. , Dietz H. P.
Published: August 2007

Objective

A Valsalva maneuver is used clinically and on imaging in order to determine female pelvic organ prolapse. We have examined the potential confounding effect of levator co‐activation at the time of a Valsalva maneuver and the impact of repetition with biofeedback instruction.

Methods

Fifty nulliparous women at 36–38 weeks' gestation received 3D/4D translabial ultrasound investigation in the dorsal resting position after bladder emptying. Valsalva maneuvers were recorded initially and after repeated attempts with visual biofeedback both during the maneuver and after, with the operator demonstrating findings on the ultrasound monitor, in order to abolish levator co‐activation. Offline analysis was subsequently undertaken.

Results

Significant differences between first and optimal Valsalva maneuver were found for bladder neck position, bladder neck descent, hiatal sagittal diameter and hiatal area on Valsalva. In a minority of women (22/50) we observed a reduction in the sagittal hiatal diameter on first Valsalva maneuver, indicating levator co‐activation. A reduction in sagittal diameter was seen in only 11/50 after instruction. Levator co‐activation was associated with significantly lower bladder neck descent.

Conclusion

The Valsalva maneuver is frequently accompanied by a pelvic floor muscle contraction. Levator co‐activation may be a substantial confounder, reducing pelvic organ descent. Without repetition and digital, auditory or visual biofeedback, women may not perform a correct Valsalva maneuver. Biofeedback markedly reduces the likelihood of levator co‐activation but does not abolish it completely. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.
Newborn screening in Latin America at the beginning of the 21st century
Authors: Borrajo G. J. C.
Published: August 2007

Newborn screening (NBS) in Latin America took its first steps in the mid‐1970s. Nevertheless, many years elapsed before it achieved its integration within the public health care system and its systematic and continuous implementation under a programme structure. Latin American countries can be characterized not only by their great geographic, demographic, ethnic, economic and health system diversity, but also by their heterogeneity in NBS activities, which gives rise to variation in degree of organization: countries with optimal fulfilment (Cuba, Costa Rica, Chile, Uruguay); others rapidly expanding their coverage (Brazil, Mexico, Argentina); some others in a recent implementation phase (Colombia, Paraguay, Venezuela, Nicaragua, Peru); others with minimal, isolated and non‐organized activities (Guatemala, Dominican Republic, Bolivia, Panama, Ecuador); and finally others without any NBS activities at all (El Salvador, Honduras, Haiti). Despite this disparity, a sustained and significant growth in NBS activities has become evident during the last decade, highlighted by implementation of new programmes, increase in coverage, expansion of NBS panels, increasing involvement of governmental and public health authorities, and integration of NBS teams through scientific societies and External Quality Assurance Schemes. Currently, congenital hypothyroidism (CH) is the most widely screened disease, followed by phenylketonuria, with organized NBS programmes for CH in 14 countries. Other diseases usually included in NBS programmes are screened in a lower rate. Every year, around 11.2 million infants are born in Latin America. During 2005, 49.3% of newborns were screened for CH, indicating that around 5.7 million newborns still did not have access to the benefits of NBS.
Distress and Family Functioning in Oncogenetic Counselling for Hereditary and Familial Breast and/or Ovarian Cancers
Authors: Condello C. , Gesuita R. , Pensabene M. , Spagnoletti I. , Capuano I. , Baldi C. , Carle F. , Contegiacomo A.
Published: August 2007

We conducted a psychological assessment during oncogenetic counseling for hereditary breast/ovarian cancer. Anxiety and depression were assessed with the HAD scale, and family functioning and satisfaction with FACES III. HAD was administered at baseline (t1), at risk communication (t2), at genetic test result communication, or at first surveillance in not tested subjects (t3); FACES III was administered at baseline only. We analysed a total of 185 questionnaires administered to the 37 subjects studied. Although not pathological, distress was significantly higher at t2 and t3 (p = 0.027 and p = 0.039, respectively). Health and marital status were significantly associated with distress. In a disease‐free condition, anxiety was higher (p = 0.027) at t2, and for single status, depression increased from t1 to t2 (p = 0.026). Families were perceived to be well functioning, and subjects were satisfied with their families. The data collected in this analysis could help to improve the quality of oncogenetic counselling in clinical practice.
Factors Influencing Perceptions of Breast Cancer Genetic Counseling among Women in an Urban Health Care System
Authors: Ford Marvella E. , Alford Sharon Hensley , Britton Diandra , McClary Beth , Gordon Howard S.
Published: August 2007

The study assessed perceptions of breast cancer genetic counseling. Focus groups were conducted with twenty women (ages < = 50 years) in a Midwestern, urban health system identified as at above average risk of developing hereditary breast cancer and referred for breast cancer genetic counseling following mammography. All participants associated the words “breast cancer” with fear. African American women who received breast cancer genetic counseling may have channeled their fear into increased vigilance related to breast health. African American women who did not receive breast cancer genetic counseling were most knowledgeable about it. In contrast, Caucasian women who did not receive it reported uncertainty about the role of genetic counseling and testing in assessing breast cancer risk, mistrust in medical professionals, and lack of trust in the accuracy of genetic tests. The results could be used to help develop interventions to improve informed decision‐making regarding breast cancer genetic counseling.
A trematode infection with no effect on reproductive success of a sand‐bubbler crab
Authors: Koga Tsunenori
Published: August 2007

The infection effects of the parasitic digenean trematode on the body weight and reproductive success of the sand‐bubbler crab were examined.Gynaecotyla squatarolae(Trematoda: Microphallidae) infects the body cavity ofScopimera globosa(Decapoda: Scopimeridae) and uses the crab as its second intermediate host. The parasites infected all reproductive crabs examined to varying degrees. Larger crabs of both sexes had more parasites than smaller ones, probably because body size reflects age, and older crabs had a longer period of exposure to infection. Males had more parasites than females, probably because of sexual difference in acting time on the surface. Ovigerous females stay in closed burrows and do not act on the surface during incubation, and so have less chance of infection than males. The quantity of infecting parasites did not explain variations in either body weight or reproductive success of individual crabs in a field experiment. The life history of this parasite, relative body size of the crabs, and cost and the possible benefit of manipulation for the parasite may explain these results.
Nanoparticles for Applications in Cellular Imaging
Authors: Thurn K Ted , Brown EricMB , Wu Aiguo , Vogt Stefan , Lai Barry , Maser Jörg , Paunesku Tatjana , Woloschak Gayle E
Published: August 2007

In the following review we discuss several types of nanoparticles (such as TiO2, quantum dots, and gold nanoparticles) and their impact on the ability to image biological components in fixed cells. The review also discusses factors influencing nanoparticle imaging and uptake in live cells in vitro. Due to their unique size-dependent properties nanoparticles offer numerous advantages over traditional dyes and proteins. For example, the photostability, narrow emission peak, and ability to rationally modify both the size and surface chemistry of Quantum Dots allow for simultaneous analyses of multiple targets within the same cell. On the other hand, the surface characteristics of nanometer sized TiO2allow efficient conjugation to nucleic acids which enables their retention in specific subcellular compartments. We discuss cellular uptake mechanisms for the internalization of nanoparticles and studies showing the influence of nanoparticle size and charge and the cell type targeted on nanoparticle uptake. The predominant nanoparticle uptake mechanisms include clathrin-dependent mechanisms, macropinocytosis, and phagocytosis.
Combination of TLC Blotting and Gas Chromatography–Mass Spectrometry for Analysis of Peroxidized Cholesterol
Authors: Minami Yuko , Yokoi Sayuri , Setoyama Mari , Bando Noriko , Takeda Sayaka , Kawai Yoshichika , Terao Junji
Published: August 2007

We have established a sensitive and convenient method for analysis of cholesterol hydroperoxides (Chol‐OOHs) as trimethylsilyloxyl derivatives using diphenylpyrenylphosphine (DPPP)‐thin‐layer chromatography (TLC) blotting and gas chromatography–electron ionization–mass spectrometry/selected‐ion monitoring (GC–EI–MS/SIM). Chol‐OOH standards were prepared by photosensitized oxidation and azo radical‐induced peroxidation of cholesterol. Trimethylsilyloxyl derivatives of cholesterol 5α‐hydroperoxide (Chol 5α‐OOH), cholesterol 7α‐hydroperoxide (Chol 7α‐OOH), and cholesterol 7β‐hydroperoxide (Chol 7β‐OOH) could be separated from one another in the SIM chromatogram using a fragment ion with elimination of trimethylsilanol from the molecular ion. This method was used to characterize peroxidized cholesterol from azo radical‐exposed human low‐density lipoprotein and UVA‐irradiated human keratinocytes in the presence of hematoporphyrin. Finally, we succeeded in the quantification of each Chol‐OOH isomer present in hairless mouse skin with and without UVA irradiation by use of β‐sitosterol hydroperoxide as internal standard. The accumulation of Chol 5α‐OOH with Chol 7α/βOOH in the skin indicates that singlet molecular oxygen (1O2) participated in the peroxidation of skin cholesterol, because Chol 5α‐OOH is known to be a 1O2 specific cholesterol peroxidation product. We concluded that the combination of DPPP‐TLC blotting and GC–EI–MS/SIM is useful for quantifying peroxidized cholesterol in biological samples and confirming the participation of 1O2 in oxidative stress.
Altered neuropeptide profile of Caenorhabditis elegans lacking the chaperone protein 7B2 as analyzed by mass spectrometry
Authors: Husson Steven J. , Schoofs Liliane
Published: August 2007

Cellular synthesis of naturally occurring, bioactive peptides requires the proprotein convertase PC2/EGL‐3 for cleavage from the larger peptide precursors. A neuroendocrine chaperone 7B2 is needed for the proteolytical activation of proPC2, as extensively studied in mouse models. To determine the role of its orthologue in Caenorhabditis elegans, we analyzed wild‐type and 7B2‐null strains by HPLC and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry, which allowed the identification of a novel neuropeptide gene, flp‐33. The presence and/or absence of some neuropeptides in 7B2‐null animals strongly differs form the peptide profile in wild‐type, suggesting a specific and determined action of 7B2 in C. elegans.
Structural element responsible for the Fe(III)–phytosiderophore specific transport by HvYS1 transporter in barley
Authors: Harada Emiko , Sugase Kenji , Namba Kosuke , Iwashita Takashi , Murata Yoshiko
Published: August 2007

Hordeum vulgare L. yellow stripe 1 (HvYS1) is a selective transporter for Fe(III)–phytosiderophores, involved in primary iron acquisition from soils in barley roots. In contrast, Zea mays yellow stripe 1 (ZmYS1) in maize possesses broad substrate specificity, despite a high homology with HvYS1. Here we revealed, by assessing the transport activity of a series of HvYS1–ZmYS1 chimeras, that the outer membrane loop between the sixth and seventh transmembrane regions is essential for substrate specificity. Circular dichroism spectra indicated that a synthetic peptide corresponding to the loop of HvYS1 forms an α‐helix in solution, whereas that of ZmYS1 is flexible. We propose that the structural difference at this particular loop determines the substrate specificity of the HvYS1 transporter.
tRNA import into yeast mitochondria is regulated by the ubiquitin‐proteasome system
Authors: Brandina Irina , Smirnov Alexandre , Kolesnikova Olga , Entelis Nina , Krasheninnikov Igor A. , Martin Robert P. , Tarassov Ivan
Published: August 2007

In Saccharomyces cerevisiae, one of two cytosolic lysine‐tRNAs is partially imported into mitochondria. We demonstrate that three components of the ubiquitin/26S proteasome system (UPS), Rpn13p, Rpn8p and Doa1p interact with the imported tRNA and with the essential factor of its mitochondrial targeting, pre‐Msk1p. Genetic and biochemical assays demonstrate that UPS plays a dual regulatory role, since the overall inhibition of cellular proteasome activity reduces tRNA import, while specific depletion of Rpn13p or Doa1p increases it. This result suggests a functional link between UPS and tRNA mitochondrial import in yeast and indicates on the existence of negative and positive import regulators.
Differential maturation of chloride homeostasis in primary afferent neurons of the somatosensory system
Authors: Gilbert Daniel , Franjic‐Würtz Christina , Funk Katharina , Gensch Thomas , Frings Stephan , Möhrlen Frank
Published: August 2007

Recent research into the generation of hyperalgesia has revealed that both the excitability of peripheral nociceptors and the transmission of their afferent signals in the spinal cord are subject to modulation by Cl− currents. The underlying Cl− homeostasis of nociceptive neurons, in particular its postnatal maturation, is, however, poorly understood. Here we measure the intracellular Cl− concentration, [Cl−]i, of somatosensory neurons in intact dorsal root ganglia of mice. Using two‐photon fluorescence‐lifetime imaging microscopy, we determined [Cl−]i in newborn and adult animals. We found that the somatosensory neurons undergo a transition of Cl− homeostasis during the first three postnatal weeks that leads to a decline of [Cl−]i in most neurons. Immunohistochemistry showed that a major fraction of neurons in the dorsal root ganglia express the cation–chloride co‐transporters NKCC1 and KCC2, indicating that the molecular equipment for Cl− accumulation and extrusion is present. RT‐PCR analysis showed that the transcription pattern of electroneutral Cl− co‐transporters does not change during the maturation process.

These findings demonstrate that dorsal root ganglion neurons undergo a developmental transition of chloride homeostasis during the first three postnatal weeks. This process parallels the developmental “chloride switch” in the central nervous system. However, while most CNS neurons achieve homogeneously low [Cl−]i levels – which is the basis of GABAergic and glycinergic inhibition – somatosensory neurons maintain a heterogeneous pattern of [Cl−]i values. This suggests that Cl− currents are excitatory in some somatosensory neurons, but inhibitory in others. Our results are consistent with the hypothesis that Cl− homeostasis in somatosensory neurons is regulated through posttranslational modification of cation–chloride co‐transporters.
Prevalence of Cryptosporidium, Giardia and Isospora species infections in pet cats with clinical signs of gastrointestinal disease
Authors: Tzannes Sophia , Batchelor Daniel J. , Graham Peter A. , Pinchbeck Gina L. , Wastling Jonathan , German Alexander J.
Published: August 2007

This study reports the prevalence of Cryptosporidium, Giardia and Isospora species in cats showing signs of gastrointestinal disease. Records from a United Kingdom commercial diagnostic laboratory between December 2003 and December 2005 were reviewed. Of 1355 cats, Cryptosporidium species oocysts were found in 13 cats (1%), Giardia species trophozoites in 74 (6%), and Isospora felis oocysts in 46 (3%). In a second group of 48 cats, prevalence of Giardia species was 15% using an immunoassay for detection of antigen compared to 4% detected with microscopy. Prevalence of Giardia (9%) and Isospora (9%) species was higher in cats less than 6 months old. Gender and breed did not affect prevalence. There was a trend for Cryptosporidium and Isospora species infections to be detected in late autumn and early winter. Regional differences in prevalence were not detected. None of these organisms show a characteristic pattern of clinical signs. This study demonstrates that enteric protozoal infection is common in domestic cats showing signs of alimentary disease.
Bacteriuria in cats with feline lower urinary tract disease: A clinical study of 134 cases in Norway
Authors: Eggertsdóttir Anna V. , Lund Heidi S. , Krontveit Randi , Sørum Henning
Published: August 2007

Feline lower urinary tract disease (FLUTD) is considered to be one of the most common diagnoses in feline patients. Several authors have concluded that feline idiopathic cystitis is the most common cause of FLUTD, whereas infectious cystitis is diagnosed in only 2% of the cases. In the period from January 2003 to February 2005, 134 cats that presented with signs of lower urinary tract disorders were included in a study at the Norwegian School of Veterinary Science. Ninety-seven percent were first opinion cases. All the cats went through a physical examination, and blood samples were collected for haematology and clinical chemistry. The urine analysis included urine stix, specific gravity, microscopic examination of the sediment and microbiological culturing. The urine samples were collected as voided mid-stream urine samples, by catheter or by cystocentesis and the method used was registered. Of the 134 cats included in the study, 37% were diagnosed as having obstructive and 63% as having non-obstructive FLUTD. In total 44 cats (33%) were diagnosed with bacteriuria, exceeding 103 colony forming units per millilitre (cfu/ml) and 33 (25%) of these cats had bacterial growth exceeding 104 cfu/ml, either alone or in combination with crystals and/or uroliths. Six cats (18%) with bacterial growth exceeding 104 cfu/ml were older than 8 years. No significant difference was found between the sampling methods performed with regard to bacteriuria. This study indicates that bacteriuria may have been underdiagnosed in Norwegian cats with clinical signs of FLUTD. It also confirms the importance of microbiological culturing in first opinion cases with FLUTD and that a skilled operator can get representative samples regardless the choice of method.
On the front velocity of gravity currents
Authors: CANTERO MARIANO I. , LEE J. R. , BALACHANDAR S. , GARCIA MARCELO H.
Published: August 2007

Highly resolved three-dimensional and two-dimensional simulations of gravity currents in planar and cylindrical configurations are presented. The volume of release of the heavy fluid is varied and the different phases of spreading, namely acceleration, slumping, inertial and viscous phases, are studied. The incompressible Navier–Stokes equations are solved assuming that the Boussinesq approximation is valid for small density difference. The simulations are performed for three different Reynolds numbers (Re): 895, 3450 and 8950 (this particular choice corresponds to values of Grashof number: 105, 1.5 × 106 and 107, respectively). Following their sudden release, the gravity currents are observed to go through an acceleration phase in which the maximum front velocity is reached. As the interface of the current rolls up, the front velocity slightly decreases from the maximum and levels off to a nearly constant value. At higher Re, three-dimensional disturbances grow rapidly and the currents become strongly turbulent. In contrast, in two-dimensional simulations, the rolled-up vortices remain coherent and very strong. Depending on the initial Re of the flow and on the size of the release, the current may transition from the slumping to the inertial phase, or directly to the viscous phase without an inertial phase. New criteria for the critical Re are introduced for the development of the inertial phase. Once the flow transitions to the inertial or viscous phase, it becomes fully three-dimensional. During these phases of spreading, two-dimensional approximations underpredict the front location and velocity. The enhanced vortex coherence of the two-dimensional simulations leads to strong vortex interaction and results in spurious strong time variations of the front velocity. The structure and dynamics of the three-dimensional currents are in good agreement with previously reported numerical and experimental observations.
Convection by a horizontal thermal gradient
Authors: GRAMBERG H. J. J. , HOWELL P. D. , OCKENDON J. R.
Published: August 2007

This paper considers a paradigm large-Prandtl-number, large-Rayleigh-number forced convection problem suggested by the batch melting process in the glass industry. Although the fluid is heated from above, non-uniform heating in the horizontal direction induces thermal boundary layers in which colder liquid is driven over hotter liquid. This leads to an interesting selection problem in the boundary layer analysis, whose resolution is suggested by a combination of analytical and numerical evidence.
Conditions under which a supercritical turbidity current traverses an abrupt transition to vanishing bed slope without a hydraulic jump
Authors: KOSTIC SVETLANA , PARKER GARY
Published: August 2007

Turbidity currents act to sculpt the submarine environment through sediment erosion and deposition. A sufficiently swift turbidity current on a steep slope can be expected to be supercritical in the sense of the bulk Richardson number; a sufficiently tranquil turbidity current on a mild slope can be expected to be subcritical. The transition from supercritical to subcritical flow is accomplished through an internal hydraulic jump. Consider a steady turbidity current flowing from a steep canyon onto a milder fan, and then exiting the fan down another steep canyon. The flow might be expected to undergo a hydraulic jump to subcritical flow near the canyon–fan break, and then accelerate again to critical flow at the fan–canyon break downstream. The problem of locating the hydraulic jump is here termed the ‘jump problem’. Experiments with fine-grained sediment have confirmed the expected behaviour outlined above. Similar experiments with coarse-grained sediment suggest that if the deposition rate is sufficiently high, this ‘jump problem’ may have no solution with the expected behaviour, and in particular no solution with a hydraulic jump. In such cases, the flow either transits the length of the low-slope fan as a supercritical flow and shoots off the fan–canyon break without responding to it, or dissipates as a supercritical flow before exiting the fan. The analysis presented below confirms the existence of a range associated with rapid sediment deposition where no solution to the ‘jump problem’ can be found. The criterion for this range is stated in terms of an order-one dimensionless parameter involving the fall velocity of the sediment. The criterion is tested and confirmed against the experiments mentioned above. A sample field application is presented.
Large-eddy simulation analysis of mechanisms for viscous losses in a turbomachinery tip-clearance flow
Authors: YOU DONGHYUN , WANG MENG , MOIN PARVIZ , MITTAL RAJAT
Published: August 2007

The tip-leakage flow in a turbomachinery cascade is studied using large-eddy simulation with particular emphasis on understanding the underlying mechanisms for viscous losses in the vicinity of the tip gap. Systematic and detailed analysis of the mean flow field and turbulence statistics has been made in a linear cascade with a moving endwall. Gross features of the tip-leakage vortex, tip-separation vortices, and blade wake have been revealed by investigating their revolutionary trajectories and mean velocity fields. The tip-leakage vortex is identified by regions of significant streamwise velocity deficit and high streamwise and pitchwise vorticity magnitudes. The tip-leakage vortex and the tip-leakage jet which is generated by the pressure difference between the pressure and suction sides of the blade tip are found to produce significant mean velocity gradients along the spanwise direction, leading to the production of vorticity and turbulent kinetic energy. The velocity gradients are the major causes for viscous losses in the cascade endwall region. The present analysis suggests that the endwall viscous losses can be alleviated by changing the direction of the tip-leakage flow such that the associated spanwise derivatives of the mean streamwise and pitchwise velocity components are reduced.
The contribution of shock tubes to simplified analysis of gas filtration through granular media
Authors: BRITAN A. , SHAPIRO H. , BEN-DOR G.
Published: August 2007

A hybrid method for the problem of transient shock-induced filtration of the gas flow through granular media is developed. The hybrid method combines a controlled shock-tube test and Morrison's simplified approach to the problem of gas filtration. It is demonstrated that most pressure traces that have been recorded in various laboratories with a large variety of granular material samples and under different conditions are limited to situations in which the pressure losses in the flow are dominated by the Forchheimer mechanism. The hybrid method enables these results to be described by a single, universal pressure curve, and specification of the Forchheimer coefficient which is one of the two key parameters responsible for the correct simulation of the filtration-flow behaviour. The second key parameter, the Darcy coefficient, cannot be evaluated by the available experimental results. To overcome this shortcoming, a new controlled laboratory test that provides a wider range of the flow conditions, from the Forchheimer to the developed mixed flow, was conducted. In turn, a comprehensive gas dynamic analysis of the transient flow inside the shock tube enables us to define, from the single controlled laboratory test, the two coefficients of the Forchheimer resistance law, a and b.
Experimental observations of the merger of co-rotating wake vortices
Authors: BERTÉNYI T. , GRAHAM W. R.
Published: August 2007

The interaction and merger of a pair of co-rotating vortices has been studied experimentally in a wind tunnel. The vortices are generated using two separate wings, allowing both initial circulation ratio and initial separation to be varied. At the nominal test speed of 30 ms−1, the circulation-based Reynolds number is typically 6.4 × 104. Mean crossflow velocities at stations downstream are obtained with a traverse-mounted yaw meter. The vortex interaction is characterized by fitting Lamb–Oseen profiles to the measured, azimuthally averaged, tangential velocity profiles.

It is found that the merger process differs in several important respects from lower-Reynolds-number studies. First, the separation of the vortices decreases continually throughout the initial, ‘viscous growth’, phase, instead of remaining constant. Second, the vortex core growth in this phase appears to be greater than can be accounted for by turbulent diffusivity, even after correcting for the effects of wandering. Finally, the time to merger lies well below that predicted by expressions based on the lower-Reynolds-number observations, and is further reduced when the circulation ratio departs from unity. We conclude that the enhanced core growth is probably due to the short-wavelength ‘elliptic’ instability that has already been observed in some high-Reynolds-number experiments. The mechanism behind the decrease in separation, which is a crucial factor in the reduced merger time, is three-dimensional, but, beyond this, remains unknown.
Direct numerical simulations of two- and three-dimensional turbulent natural convection flows in a differentially heated cavity of aspect ratio 4
Authors: TRIAS F. X. , SORIA M. , OLIVA A. , PÉREZ-SEGARRA C. D.
Published: August 2007

A set of complete two- and three-dimensional direct numerical simulations (DNS) in a differentially heated air-filled cavity of aspect ratio 4 with adiabatic horizontal walls is presented in this paper. Although the physical phenomenon is three-dimensional, owing to its prohibitive computational costs the majority of the previous DNS of turbulent and transition natural convection flows in enclosed cavities assumed a two-dimensional behaviour. The configurations selected here (Rayleigh number based on the cavity height 6.4 × 108, 2 × 109 and 1010, Pr = 0.71) are an extension to three dimensions of previous two-dimensional problems.

An overview of the numerical algorithm and the methodology used to verify the code and the simulations is presented. The main features of the flow, including the time-averaged flow structure, the power spectra and probability density distributions of a set of selected monitoring points, the turbulent statistics, the global kinetic energy balances and the internal waves motion phenomenon are described and discussed.

As expected, significant differences are observed between two- and three-dimensional results. For two-dimensional simulations the oscillations at the downstream part of the vertical boundary layer are clearly stronger, ejecting large eddies to the cavity core. In the three-dimensional simulations these large eddies do not persist and their energy is rapidly passed down to smaller scales of motion. It yields on a reduction of the large-scale mixing effect at the hot upper and cold lower regions and consequently the cavity core still remains almost motionless even for the highest Rayleigh number. The boundary layers remain laminar in their upstream parts up to the point where these eddies are ejected. The point where this phenomenon occurs clearly moves upstream for the three-dimensional simulations. It is also shown that, even for the three-dimensional simulations, these eddies are large enough to permanently excite an internal wave motion in the stratified core region. All these differences become more marked for the highest Rayleigh number.
Three-dimensional spatial normal modes in compressible boundary layers
Authors: TUMIN ANATOLI
Published: August 2007

Three-dimensional spatially growing perturbations in a two-dimensional compressible boundary layer are considered within the scope of linearized Navier–Stokes equations. The Cauchy problem is solved under the assumption of a finite growth rate of the disturbances. It is shown that the solution can be presented as an expansion into a biorthogonal eigenfunction system. The result can be used in a decomposition of flow fields derived from computational studies when pressure, temperature, and all the velocity components, together with some of their derivatives, are available. The method can also be used if partial data are available when a priori information may be utilized in the decomposition algorithm.
Model problems for the tear film in a blink cycle: single-equation models
Authors: BRAUN R. J. , KING-SMITH P. E.
Published: August 2007

We consider model problems for the tear film over multiple blink cycles in limits that yield a single equation for the tear film; the single nonlinear partial differential equation that governs the film thickness arises from lubrication theory. The two models arise from considering the absence of naturally occurring surfactant and the case when the surfactant strongly affects the surface tension. The film is considered on a sinusoidally varying domain length with specified film thickness and volume flux at each end; only one end of the domain is moving, which is analogous to the upper eyelid moving with each blink. A main contribution of this article is computation of solutions for multiple complete blink cycles; the results of these non-trivial computations show a distinct similarity to quantitative in vivo observations of the tear film under partial blink conditions. A transition between periodic and non-periodic solutions has been estimated and this may be a criterion for what is effectively a full blink according to fluid dynamic considerations.