bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of docosahexaenoic acid administration on plasma lipid profile and metabolic parameters of children with methylmalonic acidaemia
Authors: Aldámiz‐Echevarría L. , Sanjurjo P. , Elorz J. , Prieto J. A. , Pérez C. , Andrade F. , Rodríguez‐Soriano J.
Published: April 2006

Aim. To evaluate the effect of administration of docosahexaenoic acid (DHA) on dyslipidaemia, plasma fatty acid composition and metabolic parameters of children with isolated methylmalonic acidaemia (MMA) (McKusick 25100).

Methods. Four children (3 male, 1 female) with MMA (mut(0)), participated in a crossover, randomized study of DHA administration (25 mg/kg per day, divided into three daily doses). The control group comprised 56 healthy children, aged 10± 2.7 years, (51 male, 5 female), who were followed in our clinic owing to possible familial risk of cardiovascular disease.

Results. The comparison of plasma fatty acid composition of children with MMA versus control children demonstrated that the patients had significantly higher values for oleic acid (p = 0.004) and linolenic acid (p = 0.008). No differences were observed in the levels of DHA and arachidonic acid. Plasma concentrations of insulin, glycine, ammonia, total cholesterol and cholesterol fractions did not change with DHA administration. No significant changes were observed in urinary excretion of methylmalonic acid. As expected, the percentage of DHA and n−3 fatty acids in plasma increased significantly after therapy (p = 0.005 and 0.014, respectively). The most remarkable result was a decrease of plasma levels of triglycerides after DHA therapy (p = 0.014).

Conclusion. As previously found in normal children, dietary supplementation with DHA decreases the triglyceride levels, normalizing the hypertriglyceridaemia of these children without any evidence of short‐term adverse effects.
Isolated 3‐methylcrotonyl‐coenzyme A carboxylase deficiency in a child with metabolic stroke
Authors: Pinto L. , Zen P. , Rosa R. , Paskulin G. , Perla A. , Barea L. , Baumgartner M. R. , Dantas M. F. , Fowler B. , Giugliani R. , Vargas C. , Wajner M. , Graziadio C.
Published: April 2006

We report a 3‐year‐old boy with isolated 3‐methylcrotonyl‐coenzyme A deficiency with unexpectedly severe presentation, seizures and history of cerebral ischae‐mic episode.
Manifestations of Fabry disease in placental tissue
Authors: Vedder A. C. , Strijland A. , Weerman M. A. vd Bergh , Florquin S. , Aerts J. M. F. G. , Hollak C. E. M.
Published: April 2006

Fabry disease is an X‐linked lysosomal storage disorder caused by deficiency of the lysosomal enzyme α‐galactosidase A. Manifestations of the disease in placental tissue have been reported only twice. We report for the first time on the biochemical, histological and genetic features of two cases: placenta A derived from a mother heterozygous for Fabry disease who gave birth to a hemizygous son, and placenta B obtained from a healthy mother who carried a heterozygous daughter. Biopsies of placentae A, B and of four healthy controls were taken directly after birth. Assessment of α‐galactosidase A (α‐Gal) activity was performed both in fetal leukocytes (derived from umbilical cord blood) and in the biopsy specimens. The tissue was further examined by electron microscopy, immunohistochemistry and biochemical analysis for the presence of storage material (ceramide trihexoside (CTH)). In placenta A, characteristic zebra bodies reflecting accumulated storage material were seen in all biopsies evaluated. CTH values were markedly elevated as compared to the controls and α‐Gal activity in both fetal leukocytes and placental tissue was very low. Placenta B showed no storage material at all. CTH values were within the control range. α‐Gal activity ranged from intermediate to near normal; enzyme activity in fetal leukocytes was significantly decreased. As placental tissue is mainly derived from fetal cells, we may conclude that, in a boy suffering from Fabry disease, extensive storage of CTH is already present at birth. As complications develop only around the age of 10 years, it may be not the CTH itself but secondary processes that cause cellular and organ damage.
Genetic heterogeneity of the GLDC gene in 28 unrelated patients with glycine encephalopathy
Authors: Conter C. , Rolland M. O. , Cheillan D. , Bonnet V. , Maire I. , Froissart R.
Published: April 2006

Glycine encephalopathy, or nonketotic hyperglycinaemia (NKH; McKusick 238300) is a severe autosomal recessive disease due to a defect in the glycine cleavage system (GCS), which is a complex of four subunits: P‐, T‐, H‐ and L‐proteins. A P‐protein (glycine decarboxylase or GLDC) deficiency was reported in about 80% of NKH patients. We performed mutation analysis of the complete coding sequence of the GLDC gene in 28 unrelated patients with neonatal NKH using denaturing high‐performance liquid chromatography (DHPLC) and sequencing. Forty different gene alterations were identified, confirming the large molecular heterogeneity of the GLDC gene. Eighteen alterations were clearly disease‐causing: two large deletions, four one‐base deletions (c.28delC, c.1175delC, c.2186delC, c.2422delA), one 1‐base insertion (c.1002_1003insT), one 4‐base insertion (c.1285_1286insCAAA), one insertion/deletion (c.2153_2155delinsTCCTGGTTTA), five nonsense mutations (p.E153X, p.R236X, p.E270X, p.R337X, p.R424X) and four splice site mutations (c.861+1G > T, c.1402−1C > G, c.2316−1G > A, c.2919+1G > A). Additionally, we identified one intronic mutation outside the consensus splice sites (c.2838+5G > A) and 21 nucleotide substitutions leading to amino acid change (including three previously described mutations: p.T269M, p.R461Q, p.G771R), the pathogenicity of which should be confirmed by expression studies (p.S132W, p.Y138F, p.G171A, p.T187K, p.R212K, p.T269M, p.R373W, p.I440N, p.R461Q, p.N533Y, p.C644F, p.H651R, p.V705M, p.N732K, p.G771R, p.H775R, p.T830M, p.A841P, p.D880V, p.S957P and p.R966G). Mutation analysis allowed us to identify sequence alterations in both alleles for 19 patients and in one allele for 7 patients One patient was carrying three mutations (p.Y138F, p.T269M and p.E153X) and one patient was carrying two amino acid substitutions on the same allele (p.V705M and p.R212K) and an unidentified mutation on the other allele. No mutation could be found in two patients, suggesting possible defects in the H‐protein or gene alterations that could not be identified by our technique. The potential use of genotype determination for prenatal diagnosis is emphasized.
Cardiomyopathy in tyrosinaemia type I is common but usually benign
Authors: Arora N. , Stumper O. , Wright J. , Kelly D. A. , McKiernan P. J.
Published: April 2006

Tyrosinaemia type I (TTI) is an inherited multisystemic disorder of tyrosine metabolism. In addition to hepatic and renal involvement, cardiomyopathy is an important clinical manifestation. Objective: To evaluate the incidence and outcome of cardiomyopathy in TTI. Subjects and methods: A retrospective study was performed of 20 consecutive children with TTI (12 male, 8 female) referred to a single centre between 1986 and 2002. All were initially treated with standard dietary therapy and, since 1992, with nitisinone. The indications for orthotopic liver transplantation (LT) changed during the study. Serial echocardiography was undertaken in all subjects. Results: 9/20 (45%) children had an acute hepatic presentation. Five (25%) received dietary treatment followed by LT, and 14 (70%) were treated with nitisinone at presentation. 6/20 (30%) had cardiomyopathy at initial assessment, with interventricular septal hypertrophy being the commonest finding (5/6). Cardiomyopathy was significantly less common in those treated initially with nitisinone. After a median follow‐up of 3.6 (0.45–13.5) years, 5/6 (83%) had complete resolution of cardiomyopathy and 1/6 showed significant improvement. No child with a normal initial echocardiography subsequently developed cardiomyopathy. Conclusion: Cardiomyopathy is a common manifestation of TTI and it has a favourable long‐term outcome. Children initially treated with nitisinone are less likely to develop this complication.
Stabilization of hypoglycosylation in a patient with congenital disorder of glycosylation type Ia
Authors: Hahn S. H. , Minnich S. J. , O'Brien J. F.
Published: April 2006

A follow‐up over 7 years on a patient with congenital disorder of glycosylation type Ia showed a significant normalization of hypoglycosylated transferrin. Isoelectric focusing for serum transferrin is a widely used screening method but there could be a limit of detection and the subtle changes can be also overlooked. Re‐test with a different method is desirable, especially when the clinical suspicion for congenital disorder of glycosylation is high.
Refining the diagnosis of mitochondrial HMG‐CoA synthase deficiency
Authors: Aledo R. , Mir C. , Dalton R. N. , Turner C. , Pié J. , Hegardt F. G. , Casals N. , Champion M. P.
Published: April 2006

Mitochondrial HMG‐CoA synthase deficiency is an inherited metabolic disorder caused by a defect in the enzyme that regulates the formation of ketone bodies. Patients present with hypoketotic hypoglycaemia, encephalopathy and hepatomegaly, usually precipitated by an intercurrent infection or prolonged fasting. The diagnosis may easily be missed as previously reported results of routine metabolic investigations, urinary organic acids and plasma acylcarnitines may be nonspecific or normal, and a high index of suspicion is required to proceed to further confirmatory tests. We describe a further acute case in which the combination of urinary organic acids, low free carnitine and changes in the plasma acylcarnitine profile on carnitine supplementation were very suggestive of a defect in ketone synthesis. The diagnosis of mitochondrial HMG‐CoA synthase deficiency was confirmed on genotyping, revealing two novel mutations: c.614G > A (R188H) and c.971T > C (M307T). A further sibling, in whom the diagnosis had not been made acutely, was also found to be affected. The possible effects of these mutations on enzyme activity are discussed.
Atypical phenotype in a boy with a maple syrup urine disease
Authors: Ben‐Omran T. I. , Blaser S. , Phillips H. , Callahan J. , Feigenbaum A.
Published: April 2006

Maple syrup urine disease (MSUD) is a metabolic disorder due to a block in the decarboxylation step in the catabolic pathways of the branched‐chain amino acids (BCAAs). We describe an atypical presentation in an infant male. The patient presented with psychomotor retardation, profound hypotonia and elevated plasma levels of BCAAs, but no elevation of alloisoleucine. Cranial magnetic resonance imaging showed prominent diffuse CSF spaces, delayed myelin maturation and symmetrical signal abnormality within the globi pallidi, midbrain, dorsal pons and medulla. The cerebellar white matter was specifically spared. A mitochondrial disorder was suggested. After correction of feeding problems with G‐tube feeds, his high BCAAs persisted and, on fourth analysis, alloisoleucine was seen. Subsequent fibroblast enzyme and mutation analysis confirmed MSUD due to E1‐α subunit deficiency. After starting dietary treatment, there was no significant improvement in his hypotonia or his psychomotor development. However, the high signal within the globi pallidi had resolved. MSUD may have diverse clinical presentations, and should be considered in children who present with chronic psychomotor delay but no acute encephalopathic episodes. BCAA levels may not be very high, alloisoleucine may not always be detected in MSUD even with severe enzyme deficiency, and imaging may be misleading if seen in the chronic phase only.
The effect of L‐alanine therapy in a patient with adult onset glycogen storage disease type II
Authors: Mundy H. R. , Williams J. E. , Cousins A. J. , Lee P. J.
Published: April 2006

Adult‐onset glycogen storage disease type II (GSD II) (McKusick 232300) is a progressive disabling myopathy. At present there is no treatment of proven clinical efficacy. Enzyme replacement therapy may in the future provide benefit but it will be costly and is not yet freely available. L‐Alanine, a simple and relatively cheap therapy, has been shown to reduce protein degradation in GSD II patients but has not previously been assessed for clinical benefit in a controlled study. In this study L‐alanine was assessed in a double blind, placebo‐controlled, crossover n = 1 study. Assessments consisted of spirometry, cardiopulmonary exercise testing, quality of life measurements, biochemical markers and assessment by the criterion 4‐component model of body composition. Alanine therapy was associated with a 15% gain in total body protein. However, the patient showed no functional improvement and reported feeling worse after treatment. Further controlled studies in a small group may be warranted, but not widespread use of this therapy.
D‐2‐Hydroxyglutaric aciduria: Unravelling the biochemical pathway and the genetic defect
Authors: Struys Eduard A.
Published: April 2006

D‐2‐Hydroxyglutaric aciduria (D‐2‐HGA) is a neurometabolic inherited disorder first described in 1980. In the following years, it became clear that the clinical phenotype of the disease varies widely from severe neonatal to asymptomatic. However, the sparse biochemical knowledge made D‐2‐HGA a poorly understood disease. Much progress has been made in the last five years in various studies, revealing two human enzymes that play a role in the metabolism of D‐2‐hydroxyglutarate (D‐2‐HG): hydroxyacid‐oxoacid transhydrogenase (HOT) and D‐2‐HG dehydrogenase. HOT is expected to be responsible for the formation of D‐2‐HG, while D‐2‐HG dehydrogenase converts D‐2‐HG into 2‐ketoglutarate. We demonstrated pathogenic mutations in the D2HGD gene in patients with D‐2‐HGA, helping to unravel the primary defect causing D‐2‐HGA. However, in approximately 50% of the patients with D‐2‐HGA examined, no pathogenic mutations have yet been found.
Surgical approach for tentorial meningiomas in cats: A review of six cases
Authors: Forterre Franck , Fritsch Guido , Kaiser Stephan , Matiasek Kaspar , Brunnberg Leo
Published: April 2006

The surgical technique for removal of tentorial meningiomas is described on six cats using a unilateral temporal supracerebellar transtentorial approach. Complete gross tumour resection was achieved in four of six cats. In one cat, only subtotal resection was achieved. One cat died shortly after surgery because of extensive cerebral haemorrhage. The surgical approach, combined with cisternal or ventricular cerebrospinal fluid puncture and an open-window technique (tumour fenestration and enucleation) provided sufficient visibility and tumour accessibility without excessive manipulation of the brain parenchyma. In all patients, a postoperative transient worsening of the clinical signs was observed. The neurological signs resolved with time with the exception of blindness in two cats. All five surviving cats were monitored for a mean follow-up time of 19 months (median 20 months; range 6–30 months). All patients died or were euthanased because of tumour regrowth within the follow-up period. Although challenging, surgical treatment is a useful therapeutic measure in the treatment of cats presenting with tentorial meningiomas.
Lipid microdomains in model and biological membranes: how strong are the connections?
Authors: Silvius John
Published: April 2006

1. Introduction 373

2. Are rafts probable? 374

3. Micro-, nano- or ephemeral domains? 375

4. How can we reliably assess ‘raft’ composition? 376

5. Are rafts plausible? 379

6. What more can model systems contribute to ‘raft’ studies? 381

7. References 382

The concept of ‘lipid rafts’ and related liquid-ordered membrane microdomains has attracted great attention in the field of membrane biology, both as a novel paradigm in models of membrane organization and for the potential importance of such domains in phenomena such as membrane signaling and the differential trafficking of various membrane components. Studies of biological and of model membranes have gone hand in hand in shaping our current picture of the possible organization and functions of liquid-ordered lipid microdomains in membranes. This essay discusses some important current questions concerning the existence and functional importance of lipid microdomains in mammalian cell membranes, and the potential as well as the limitations of using model systems to help to address such questions.
Impact of Galileo on Global Ionosphere Map Estimation
Authors: Le Anh Quan
Published: April 2006

The upcoming GNSS Galileo, with its new satellite geometry and frequency plan, will not only bring many benefits for navigation and positioning but also help to improve ionosphere delay estimation. This paper investigates ionosphere estimation with Galileo and compares it with the results from GPS-only and combined GPS-Galileo. The standard deviation of the Vertical Total Electron Content (VTEC) at a certain location can improve significantly by 40 per cent. Various Galileo configurations are considered to assess the differences in frequency plan and signals to be used. The IGS network, which is involved in producing the current IGS Global Ionosphere Map (GIM) is used in the simulation for more realistic results. A more accurate GIM will in its turn improve navigation and positioning performance.
Winged Auxiliaries: Women Pilots in the UK and US during World War Two
Authors: Schrader Helena P.
Published: April 2006

During World War II women in the US and the UK were given the then unprecedented opportunity to fly military aircraft. Yet while the women flying in the UK soon gained the privileges and status enjoyed by their male colleagues, the American women pilots were expressly denied the same status, rank, pay, and benefits as USAAF pilots. In fact, after an ugly slander campaign against the women pilots' organisation, the US programme was discontinued and the women were sent home before their job was done. The American women pilots were not less dedicated or inherently less capable than the women flying in Britain. Rather, key environmental and organisational differences and above all a failure of leadership accounts for their fate. This paper summarises the differences and their impact. The complete findings of the comparative research on the experiences of women pilots in the US and the UK during WWII will be published by Pen & Sword Books Inc early in 2006 under the title Sisters in Arms.
Low Cost Intelligent Pervasive Location Tracking (iPLOT) in All Environments for the Management of Crime
Authors: Mautz Rainer , Ochieng Washington , Walsh David , Brodin Gary , Kemp Andy , Cooper John , Son Le Thanh
Published: April 2006

This paper details the current status of the development of an ‘automatic’ low-cost system based on wireless communications technology to provide continuous tracking of the location of devices in all environments. This task requires a multi-disciplinary approach combining communications systems design, digital signal processing to extract ranges and, importantly, approaches from the field of geodesy to develop novel network positioning techniques for ad-hoc networks. Such a network will support a number of services relevant to crime management where seamless tracking is required. The paper discusses the process for developing the system, christened intelligent pervasive location tracking (iPLOT), with a particular reference to user and system requirements, and how these have been used to explore a network positioning strategy.
Assessment of Hydrographic Data Uncertainty for Seamless Reference Surface
Authors: El-Rabbany Ahmed
Published: April 2006

The development of a seamless vertical reference surface is accompanied by a number of challenges pertinent to the availability, volume and uncertainty of bathymetric and topographic data. Data uncertainty, which is by far the most difficult to deal with, is attributed to various sources of errors including those of geodetic and hydrographic origin. The uncertainties in the geodetic measurements originate mainly from the limitations in the geodetic technique employed, i.e. terrestrial or space. Old nautical charts and topographic maps were based on terrestrial techniques, which are far less accurate than modern space techniques. In addition, the distribution of the positioning uncertainty is not expected to follow a consistent pattern across the chart (map). This is mainly due to the inconsistent datum distortion as well as the discrepancies in the measuring techniques in the subsequent chart (map) versions. The existing paper (and digitized) charts in many areas of the world were also based on old hydrographic surveying methods, for example the lead-line, which are far less accurate than modern techniques such as multibeam echo-sounding surveys. This creates inconsistent depth uncertainty across the chart. As uncertainties are propagated into the estimated transformation parameters, estimated positions and their covariance matrix, it is of utmost importance that they are properly modelled. This paper addresses the issue of uncertainty in hydrographic data and suggests ways to account for it.
On-the-Fly Prediction of Orbit Corrections for RTK Positioning
Authors: El-Mowafy Ahmed
Published: April 2006

In this study, a method is presented to maintain real-time positioning at the decimetre-level accuracy during breaks in reception of the measurement corrections from multiple reference stations. The method is implemented at the rover by estimating prediction coefficients of the corrections during normal RTK positioning, and uses these coefficients to predict the corrections when reception of the corrections is temporarily lost. The paper focuses on one segment of this method, the on-the-fly prediction of orbital corrections. Frequently, only a few minutes of data representing short orbit ‘arcs’ are available to the user before losing radio transmission. Thus, it would be hard for the rover to predict the satellite positions using equations of motion. An alternative method is proposed. In this method, GPS orbital corrections are predicted as a time series and are added to the initial positions computed from the broadcast ephemeris to compute relatively accurate satellite positions. Different prediction approaches were investigated. Results show that the double exponential smoothing method and Winters' method can be successfully applied. The latter, however, has a better performance. The impact of the data length used for estimation of the prediction coefficients and the selection of seasonal lengths in Winters' method were investigated and some values were recommended. In general, the method can give orbital correction estimation accuracy of less than 5 cm after 15 minutes of prediction. This will result in a positioning accuracy better than 5 cm.
Automatic Identification Systems – the Effects of Class B on the Use of Class A Systems
Authors: Norris Andy
Published: April 2006

The standards for CSTDMA Class B AIS will shortly be published by the International Electrotechnical Commission and equipment will become available during 2006. The perceived benefits that Class B brings to leisure craft users and its relatively low cost will make it attractive in the market place. A rapid take-up of Class B use can therefore be expected. This paper considers the impact that increased use of Class B will have on users of Class A AIS that are compulsorily fitted to larger vessels to meet the requirements of the International Maritime Organization Safety of Life at Sea convention. The CSTDMA Class B system has been designed to prevent overloading of the AIS VHF data link. This is briefly reviewed but there are a number of other aspects that need to be considered. These include: the increased garbling of Class B messages compared to those of Class A; the problems accruing from the low update rate of Class B information; the increase in display information that will need to be managed; and the possible increase in inappropriate manoeuvres of leisure craft caused by misplaced reliance on AIS. As a result of the investigation the paper highlights the fact that Class B users must not assume that their own presence, in the form of Class B transmissions, will be particularly visible on the bridge of many SOLAS vessels. This will continue to be the case for many years into the future, until such vessels are mandated to carry radar with AIS target overlay capability.
Can the Shipping-Aviation Analogy be used as an Argument to decrease the need for Maritime Pilotage?
Authors: van Erve Patrick , Bonnor Norman
Published: April 2006

The aviation-shipping analogy cannot be used as an argument for a decrease in the need for maritime pilotage. The increasing complexity and upsizing of modern ships, in combination with a vast variety in ship types, economic maximisation, crewing and technical standards, lead to marginal ship operations that require specialist knowledge and skill. On the other hand, modern commercial aircraft have very standardised equipment and operating procedures and they approach and land at airports which also use standard radio-navigation aids and procedures.
La structure en de quoi
Authors: LEFEUVRE FLORENCE
Published: April 2006

Dans cet article, nous examinons la structure en de quoi + infinitif qui peut être régie par un verbe:

(i) Il y a de quoi s'interroger!

ou ne pas l'être:

(ii) Jamais la France du très haut ne s'est aussi bien portée que sous Jospin. De quoi irriter l'ex-Premier ministre

Nous envisageons deux possibilités d'analyse, selon la valeur de de. Soit celui-ci est considéré comme un article partitif. Mais alors de quelle façon l'infinitif s'articulet-il à de quoi? Soit il constitue une préposition. On se rapproche alors d'énoncés tels que:

(iii) Il a de qui tenir

mais ici, de quoi prend une fonction inhabituelle, celle de circonstant, alors que dans un exemple tel que (iii), de qui remplit la fonction de complément essentiel indirect par rapport à l'infinitif. Dans un dernier temps, nous avons étudié les emplois en discours de cette structure, selon que la proforme quoi anaphorise ou non une structure prédicative de l'énoncé précédent et selon les infinitifs utilisés.
Le datif en français: un cas structural
Authors: VAN PETEGHEM MARLEEN
Published: April 2006

Cet article discute la dichotomie cas structural vs non structural par rapport au datif français. Plusieurs faits semblent plaider en faveur du caractère non structural de ce datif, comme le marquage des datifs nominaux par une préposition (cf. cas oblique) et l'existence de datifs non argumentaux (cf. cas sémantique). Néanmoins l'examen des différents types de datif dont dispose le français montre que l'apparition de ce datif est soumise en premier lieu à des facteurs configurationnels. Dans la grande majorité des cas la présence du datif n'est en effet pas possible sans celle d'un autre argument interne dans le VP, qui a un rôle thématique inférieur à celui du datif.
Technology, social space and environmental justice in Swedish cities: water distribution to suburban Norrköping and Linköping, 1860–90
Authors: HALLSTRÖM JONAS
Published: April 2006

The aim of this article is to study how the Swedish cities Linköping and Norrköping treated new working-class suburbs during the period from 1860 to 1890, by looking at the extension of piped water supply. The author concludes that working-class suburbs were located in poor, geographically unfavourable and unsanitary places, to which extensions of water could be technically demanding and expensive, which led to frequent urban inability or unwillingness to help. It is also suggested that by denying water cities separated spatially between city and suburb, thereby underlining already existing environmental and even spatial injustice between the two.
National city, human city: the reimagining and revitalization of Beiping, 1928–37
Authors: DRYBURGH MARJORIE
Published: April 2006

The reimagining of Beiping – now ‘Beijing’ – reveals the limits of community in early twentieth-century China. Despite the centrality of the crowd to the imagining, construction and management of other Chinese cities, and despite an emerging local advocacy of ‘revitalization’ for Beiping and the Beiping crowd, literary and official understandings of the city that marginalized the mass of Beiping residents remained dominant, highlighting the tension between symbol and community in the construction of place and nation.
Abundant hydrothermal venting along melt‐rich and melt‐free ridge segments in the Lau back‐arc basin
Authors: Baker Edward T. , Resing Joseph A. , Walker Sharon L. , Martinez Fernando , Taylor Brian , Nakamura Ko‐ichi
Published: April 2006

The relationship between the spatial density of hydrothermal venting (ph) and spreading rate (us) is undefined along back‐arc ridges. Here we report a continuous survey of hydrothermal plumes along the ∼400‐km‐long Eastern Lau Spreading Center. The mean ph/us ratio for each of three tectonic segments followed the global midocean ridge trend, with ph doubling as us increased northward from 39 to 96 mm/yr. However, we found little correlation between ph and the previously imaged distribution of axial melt lenses, which are near‐continuous along the southern two segments but wholly absent along the northernmost segment. We infer that venting on the southern segments is melt driven, whereas venting on the northern ELSC is entirely powered with heat extracted by deep circulation through hot rock. This segment may be a rare example of an entire fast‐spreading segment where hydrothermal convection cells are powered by downward‐migrating cracking fronts.
New interpretation of magnetospheric energy circulation
Authors: Pulkkinen T. I. , Palmroth M. , Tanskanen E. I. , Janhunen P. , Koskinen H. E. J. , Laitinen T. V.
Published: April 2006

New results from the global MHD simulation GUMICS‐4 show that the energy transfer rate from the solar wind into the magnetosphere is a function of also the past values of the IMF. Furthermore, comparison of the energy input rate with the conversion and dissipation rates in the magnetosphere and ionosphere shows that the energy entering the magnetosphere is processed by the system without delay. This and earlier observations lead us to suggest that the role of energy input during the substorm growth phase is to facilitate the configuration change rather than to store energy for later dissipation. While the change of magnetotail stability requires configuration change, the substorm energetics after the onset is quite directly driven by the solar wind energy input.
Electronic spin transitions and the seismic properties of ferrous iron‐bearing MgSiO3 post‐perovskite
Authors: Stackhouse Stephen , Brodholt John P. , Dobson David P. , Price G. David
Published: April 2006

The elastic constants of post‐perovskite of chemical composition Mg0.9375Fe0.0625SiO3 and Mg0.8750Fe0.1250SiO3 have been calculated at 0 K and 136 GPa using ab initio methods. For both compositions studied, iron remains in a high‐spin state below 180 GPa at 0 K. The effect of spin state on elastic properties is small. Logarithmic derivations of isotropic wave velocities and density with respect to ferrous iron content are similar to those predicted from pure end‐members.
Thermospheric densities derived from spacecraft orbits: Application to the Starshine satellites
Authors: Lean J. L. , Picone J. M. , Emmert J. T. , Moore G.
Published: April 2006

The amplitude and variability of the total mass density of the Earth's atmosphere at altitudes between 200 and 475 km are analyzed for the period from June 1999 to January 2003, around the maximum of solar activity in cycle 23. The densities are derived with uncertainties of order ±6% from analysis of the approximately circular orbits of three Starshine spacecraft of known ballistic coefficients. Local densities averaged over all three Starshine missions are ∼4% lower than the corresponding NRLMSISE‐00 model values, which may reflect a secular decrease from thermospheric cooling. Differences of order ±15% occur on timescales of days to weeks, and larger differences of as much as 30% can persist on timescales of several months. Some differences are traceable to the NRLMSIS model's use of the 10.7 cm proxy of EUV radiation, since they are reduced when NRLMSIS is evaluated using the Mg II index, which is a better proxy of variations in EUV irradiance that heats the thermosphere. Comparisons of 27‐day density cycles extracted by complex demodulation indicate that NRLMSIS underestimates upper atmospheric density increases associated with solar rotational modulation of EUV radiation by as much as a factor of two.
Validation of Atmospheric Infrared Sounder temperature and water vapor retrievals with matched radiosonde measurements and forecasts
Authors: Divakarla Murty G. , Barnet Chris D. , Goldberg Mitchell D. , McMillin Larry M. , Maddy Eric , Wolf Walter , Zhou Lihang , Liu Xingpin
Published: April 2006

An evaluation of the temperature and moisture profile retrievals from the Atmospheric Infrared Sounder (AIRS) data is performed using more than 2 years of collocated data sets. The Aqua‐AIRS retrievals, global radiosonde (RAOB) measurements, forecast data from the National Center for Environmental Prediction Global Forecasting System (NCEP_GFS), the European Center for Medium Range Forecast (ECMWF), and the operational retrievals from the NOAA 16 satellite Advanced TIROS Operational Vertical Sounder (ATOVS) instrument are used in this validation. Using RAOB observations as the reference, bias and RMS differences are computed for “sea,” “land,” and “all” categories for the AIRS retrievals and other collocated data sets. The results of the intercomparison reveal that temperature and water vapor retrievals from the AIRS are in very good agreement with the RAOBs. The RMS difference for clear‐only cases over “sea” and “all” categories is close to the expected goal accuracies, namely, 1°K in 1 km layers for the temperature and better than 15% in 2‐km layers for the water vapor in the troposphere. The overall RMS difference for the cloud‐cleared cases is also close to the expected product goal accuracy except for a slight degradation at the surface. When AIRS and ATOVS retrievals are compared with the RAOBs, the AIRS temperature retrievals show an improvement over ATOVS of at least 0.5°K for all the accepted cases. Both the ECMWF and the NCEP_GFS forecasts match the RAOB temperatures within 1°K and water vapor within 14%. With respect to biases, the AIRS final retrieval shows a larger bias with the RAOBs relative to ATOVS, NCEP_GFS, and ECMWF. The bias is highly influenced by a larger bias contribution from “land” samples and shows a month‐to‐month and annual variation that correlates with the CO2 variations. This coupling suggests a need to include CO2 and possibly other trace gas climatologies in the AIRS initial guess to partially mitigate the effects in the final physical retrieval.
Carbon isotope fractionation by methane‐oxidizing bacteria in tropical rain forest soils
Authors: Teh Yit Arn , Silver Whendee L. , Conrad Mark E. , Borglin Sharon E. , Carlson Charlotte M.
Published: April 2006

Humid tropical forests have the potential to be significant sources or sinks of atmospheric methane (CH4), a radiatively important trace gas. Methane oxidation can consume a large fraction of the CH4 produced in tropical soils, although controls on this process are poorly understood. Using soil incubation experiments, we investigated the effects of CH4 and oxygen (O2) concentrations on C isotope fractionation and CH4 oxidation in tropical rain forest soils. We also explored the effects of these environmental variables on the isotope fractionation factor for CH4 oxidation (α), which is widely used to evaluate the relative contributions of CH4 production and oxidation to the atmospheric CH4 pool. Methane oxidation was sensitive to CH4 at lower CH4 concentrations (<850 ppmv) and insensitive to O2 concentrations between 3 and 21%. Maximum rates of CH4 oxidation were between 8.2 ± 1.2 and 11.3 ± 1.5 nmol CH4 hour−1 g dry soil−1. Measured values for α were sensitive to both CH4 oxidation rate and CH4 concentration. Alpha was inversely proportional to CH4 oxidation rate (r2 = 0.86, P < 0.001) and positively correlated with CH4 concentration (r2 = 0.52, P < 0.01). A multiple regression model that included CH4 oxidation rate, CH4 concentration, and the interaction of the two terms explained a high proportion of the variability in α (r2 = 0.94, P < 0.0001). These data suggest that it is possible to accurately determine α, allowing for more precise estimates of CH4 oxidation by isotope mass balance.
Finite-difference time-domain simulation of heterostructures with inclusion of arbitrarily complex geometry
Authors: Mejdoubi Abdelilah , Brosseau Christian
Published: April 2006

Currently, there is a great interest in tailoring the polarization properties of composite materials with the goal of controlling the dielectric behavior. This paper reports finite-difference time-domain (FDTD) modeling of the dielectric behavior of two-dimensional (2D) lossless two-phase heterostructures. More specifically, we present extensive results of 2D FDTD computations on the quasistatic effective permittivity of a single inclusion, with arbitrarily complex geometry (regular polygons and fractals), embedded in a plane. The uniaxial perfectly matched layer-absorbing boundary condition is found adequate for truncating the boundary of the 2D space because it leads to only very small backreflections. The effectiveness of the method is demonstrated by the variety of geometries modeled, i.e., regular polygons and fractals, and permittivity contrast ratios which allows us to distinguish between effects of surface fraction and effects of morphology. Our calculations show that geometrical effects can give rise to significant modifications of the surface fraction dependence of the permittivity. The results are compared with Maxwell-Garnett (MG) and symmetric Bruggeman (SBG) formulas. As expected the effective permittivity in the situations considered here deviates from the MG and SBG results at high surface fractions and/or high permittivity ratios between the inclusion and the host medium. In addition, the results show that a two-phase composite containing a fractal-boundary inclusion, e.g., Koch’s snowflake, can have a permittivity which is several tens of percent lower between the first and the fourth iteration of the structure at a fixed perimeter-to-surface ratio. This feature is consistent with the fact that as the surface fraction becomes higher, the inclusion rough boundaries dominate the overall geometry. We believe that simplified modeling such as the modeling done here can serve as a useful purpose in understanding the interplay between the structure and dielectric function and in engineering multifunctional materials at the nanoscale.
A wind-tunnel experiment on real-time opposition control of turbulence
Authors: Rebbeck Henry , Choi Kwing-So
Published: April 2006

Real-time, opposition control of near-wall turbulence has been carried out in physical experiments by selectively canceling the downwash of high-speed fluid during the sweep events. The control strategy that we employed in this study was a combination of in-phase u-velocity and out-of-phase v-velocity control, where the wall-ward advancement of sweep events with positive u and negative v velocity was blocked by wall-normal jets. Changes made to the sequence of sweep events by opposition control in the near-wall region of turbulent boundary layer were examined using hot-wire measurement with conditional sampling technique.
Proton core imaging of the nuclear burn in inertial confinement fusion implosions
Authors: DeCiantis J. L. , Séguin F. H. , Frenje J. A. , Berube V. , Canavan M. J. , Chen C. D. , Kurebayashi S. , Li C. K. , Rygg J. R. , Schwartz B. E. , Petrasso R. D. , Delettrez J. A. , Regan S. P. , Smalyuk V. A. , Knauer J. P. , Marshall F. J. , Meyerhofer D. D. , Roberts S. , Sangster T. C. , Stoeckl C. , Mikaelian K. , Park H. S. , Robey H. F.
Published: April 2006

A proton emission imaging system has been developed and used extensively to measure the nuclear burn regions in the cores of inertial confinement fusion implosions. Three imaging cameras, mounted to the 60-beam OMEGA laser facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)], use the penetrating 14.7MeV protons produced from DHe3 fusion reactions to produce emission images of the nuclear burn spatial distribution. The technique relies on penumbral imaging, with different reconstruction algorithms for extracting the burn distributions of symmetric and asymmetric implosions. The hardware and design considerations required for the imaging cameras are described. Experimental data, analysis, and error analysis are presented for a representative symmetric implosion of a fuel capsule with a 17-μm-thick plastic shell and 18atm DHe3 gas fill. The radial burn profile was found to have characteristic radius Rburn, which we define as the radius containing half the DHe3 reactions, of 32±2μm (burn radii measured for other capsule types range from 20to80μm). Potential sources of error due to proton trajectory changes from interactions with electric fields and scattering in capsule and camera hardware are estimated with simple analytic and Monte Carlo calculations; they are predicted to be small compared with statistical errors. Experimental tests were performed to look for any inconsistencies between results from different cameras and different imaging geometries, or evidence of error due to ambient electric or magnetic fields, and none were found.
On the validity range of the Born-Oppenheimer approximation: A semiclassical study for all-particle quantization of three-body Coulomb systems
Authors: Takahashi Satoshi , Takatsuka Kazuo
Published: April 2006

The validity range of the Born-Oppenheimer (BO) approximation is studied with respect to the variation of the mass (m) of negatively charged particle by substituting an electron (e) with muon (μ) and antiproton (p¯) in hydrogen molecule cation. With the use of semiclassical quantization applied to these (ppe), (ppμ), and (ppp¯) under a constrained geometry, we estimate the energy difference of the non-BO vibronic ground state from the BO counterpart. It is found that the error in the BO approximation scales to the power of 3∕2 to the mass of negative particles, that is, m1.5. The origin of this clear-cut relation is analyzed based on the original perturbation theory due to Born and Oppenheimer, with which we show that the fifth order term proportional to m5∕4 is zero and thereby the first correction to the BO approximation should arise from the sixth order term that is proportional to m6∕4. Therefore, the validity range of the Born-Oppenheimer approximation is wider than that often mistakenly claimed to be proportional to m1∕4.
Laser synthesis and magnetism of amorphous iron and cobalt carbide nanoparticles with carbon onion
Authors: Huh Seung H. , Nakajima Atsushi
Published: April 2006

Amorphous iron or cobalt carbide nanoparticles with a carbon onion structure were produced using a pulsed laser ablation of metallocene powders at room temperature. While they are ferromagnetic at room temperature, they exhibit a drastic change in magnetic spin moments at 20–30 K. These magnetic properties are ascribed to a considerable magnetic contribution of superparamagnetism for the amorphous iron or cobalt carbide nanoparticles with a carbon onion and the origin of the magnetic properties is discussed.
Ferromagnetic GaN:MnAlSi nanowires
Authors: Xu Congkang , Chun Junghwan , Rho Keehan , Kim Dong Eon , Kim Beom Jim , Yoon Seokwon , Han Seong-Eok , Kim Ju-Jin
Published: April 2006

The fabrication of crystalline Al-codoped GaN:Mn nanowires with a Mn doping rate of approximately 7at.% is reported. The magnetism measurements show that the Curie temperature is above 350K. X-ray and electron diffractions do not show the presence of any secondary magnetic phases. The electrical transport measurement indicates that the nanowires are of n-type semiconductor.
Effect of pulsing parameters on laser ablative cleaning of copper oxides
Authors: Zhang Jie , Wang Youneng , Cheng Peng , Yao Y. Lawrence
Published: April 2006

The characteristics of copper oxide removal are comparably investigated under different pulsing strategies. A two-dimensional model is utilized to numerically simulate the laser ablative cleaning process. In the model, property discontinuity and Stephan and kinetic boundary conditions are taken into account, and the moving phase interface in the material is evaluated with the enthalpy method. Experiments are carried out on copper samples having different oxide layer thicknesses. The copper oxide layer thicknesses determined by ellipsometer and the chemical constituents of the copper oxide layer determined via x-ray photoelectron spectroscopy are incorporated into this numerical model. Under the single-pulse irradiation strategy, a higher laser intensity threshold is determined by the model based on the criterion of removing the oxide film as much as possible without damaging the substrate. Under the multipulse irradiation strategy, a lower threshold is employed to remove the oxide layer, while the appropriate pulse numbers under different laser intensities and different laser pulse repetition rates are the key issues investigated. A reasonable agreement is obtained between the experimental and simulated results.
Monitoring the addition of molecular species to electrodes utilizing inherent electronic properties
Authors: McCarty Gregory S.
Published: April 2006

The ability to accurately, efficiently, and inexpensively detect biological species is critical to the diagnosis and treatment of disease. In this work, electrode pairs featuring nanometer scale junctions are utilized to detect the addition of an amino acid to nanogap sensors through variations in their electronic properties. A series of nanogap sensors was monitored as succinimide groups and then the amino acid phenylalanine was added to functionalized nanogap sensors. The addition of these species caused a statistically significant increase in charge transfer through the nanogap sensors. This flexible detection scheme has the potential of offering a powerful, nonoptical alternative for biological monitoring in extremely small volumes and of extremely low concentrations.
Pearling instability of nanoscale fluid flow confined to a chemical channel
Authors: Koplik J. , Lo T. S. , Rauscher M. , Dietrich S.
Published: April 2006

We investigate the flow of a nanoscale incompressible ridge of low-volatility liquid along a “chemical channel”: a long, straight, and completely wetting stripe embedded in a planar substrate, and sandwiched between two extended less wetting solid regions. Molecular dynamics simulations, a simple long-wavelength approximation, and a full stability analysis based on the Stokes equations are used, and give qualitatively consistent results. While thin liquid ridges are stable both statically and during flow, a (linear) pearling instability develops if the thickness of the ridge exceeds half of the width of the channel. In the flowing case, periodic bulges propagate along the channel and subsequently merge due to nonlinear effects. However, the ridge does not break up even when the flow is unstable, and the qualitative behavior is unchanged even when the fluid can spill over onto a partially wetting exterior solid region.