bluuebunny/crossref_metadata_2025 huggingface dataset:
MALNUTRITION AND INFECTION: AN UPDATE
Authors: Solomons Noel W.
Published: October 2007

The original Scrimshaw, Taylor and Gordon conceptual framework for the interaction of nutrition and infection has well served the scientific community for almost half a century. At its core is the notion of synergistic (mutually reinforcing) and antagonistic (mutually nullifying) influences of the malnourished state on infectious conditions and vice versa. Research on a series of advancing fronts, however, has allowed the incorporation of both relevant public health issues (parasitosis, emerging infectious diseases, obesity and overweight, etc.) and advancing science (molecular immunology, oxidation biology, multiple micronutrient deficiencies, etc.). The present review is an interpretative update on close to 50 years of demographic and epidemiological evolution in the field of human nutrition and the implications for the interaction in the context of microbiological and immunological developments on the infectious side of the dialectic.
The thymus is a common target in malnutrition and infection
Authors: Savino Wilson , Dardenne Mireille , Velloso Licio A. , Dayse Silva-Barbosa Suse
Published: October 2007

Malnutrition, secondary to deficiency in intake of proteins, minerals or vitamins, consistently results in changes in the thymus. This organ undergoes a severe atrophy due to apoptosis-induced thymocyte depletion, particularly affecting the immature CD4+CD8+cells, as well as a decrease in cell proliferation. This feature is apparently linked to a hormonal imbalance, involving a decrease in leptin and consequent increase in glucocorticoid hormone levels in the serum. The thymic microenvironment is also affected in malnutrition: morphological changes in thymic epithelial cells have been found, together with a decrease of thymic hormone production by these cells. Additionally, intrathymic contents of extracellular proteins, such as fibronectin, laminin and collagens, are increased in thymuses from malnourished children. Taken together, these data clearly point to the notion that the thymus is significantly affected in malnutrition. Similar patterns of thymic changes occur in acute infectious diseases, including a severe atrophy of the organ, mainly due to the apoptosis-related depletion of immature CD4+CD8+thymocytes. Additionally, thymocyte proliferation is compromised in acutely-infected subjects. The microenvironmental compartment of the thymus is also affected in acute infections, with an increased density of the epithelial network and an increase in the deposition of extracellular matrix. In conclusion, it seems clear that the thymus is targeted in malnutrition as well as in acute infections. These changes are related to the impaired peripheral immune response seen in malnourished and infected individuals. Thus, strategies inducing thymus replenishment should be considered in therapeutic approaches, in both malnutrition and acute infectious diseases.
Beneficial effects of probiotic bacteria isolated from breast milk
Authors: Lara-Villoslada Federico , Olivares Mónica , Sierra Saleta , Miguel Rodríguez Juan , Boza Julio , Xaus Jordi
Published: October 2007

Breast milk is the best food for the neonate because it provides a unique combination of proteins, carbohydrates, lipids, minerals and vitamins that ensures the correct growth and development of the infant. In addition, it also contains bioactive compounds responsible for a wide range of beneficial effects such as the promotion of immune system maturation and the protection against infections. Among these bioactive agents, probiotic bacteria have been recently isolated from human milk. The present work reviews the beneficial effects of these bacteria both in animal models and in clinical trials. The promotion of immune system maturation and defence against infections as well as the anti-inflammatory properties are among the main healthy effects of these bacteria. The isolation of probiotic bacteria with beneficial effects for the host provides scientific support for the supplementation of infant formula with these bacteria, in order to advance the pursuit of the main goal of formula: to mimic breast milk and its functional effects as closely as possible.
The role of dietary gangliosides on immunity and the prevention of infection
Authors: Rueda Ricardo
Published: October 2007

Gangliosides are acid glycosphingolipids widely distributed in most vertebrate tissues and fluids. They are present in mammalian milk, where they are almost exclusively associated with the membrane fraction of the fat globule. In human milk, the content and individual distribution of gangliosides changes during lactation, GD3being the most abundant ganglioside in colostrum, while in mature milk, GM3is the major individual species. Gangliosides function as “unintended” target receptors for bacterial adhesion in specific tissues. After oral administration, they can be putative decoys that interfere with pathogenic binding in the intestine, this being the main mechanism by which these compounds can prevent infection. Ganglioside-supplemented infant formula has been reported to modify the intestinal ecology of preterm newborns, increasing theBifidobacteriacontent and lowering that ofEscherichia coli. In addition, the influence of dietary gangliosides on several parameters related to the development of intestinal immune system, such as cytokine and intestinal IgA production, has also been described in animal models. Recently, the influence of GM3and GD3on dendritic cell maturation and effector functionalities has also been reported, suggesting a role for these milk gangliosides, especially GD3, in modulating the process of oral tolerance during first stages of life. In summary, dietary gangliosides may have an important role in the modification of intestinal microflora and the promotion of intestinal immunity development in the neonate, and consequently in the prevention of infections during early infancy.
Immune response to nucleotide-supplemented infant formulae: systematic review and meta-analysis
Authors: Gutiérrez-Castrellón Pedro , Mora-Magaña Ignacio , Díaz-García Luisa , Jiménez-Gutiérrez Carlos , Ramirez-Mayans Jaime , Solomon-Santibáñez Guillermo A
Published: October 2007

Human milk is recommended as the only alimentary source for the first six months of life. Additionally there is a medical and social need for safe and effective alternative forms of nutrition for infants who cannot be fed with breast milk. Recently the safety and efficacy of some ingredients in infant formulae, such as nucleotides have been discussed. This systematic review analyzed the available evidence to establish the efficacy, safety and dose-response effect of ribonucleotide-supplemented infant formulae (RSIFs). Randomised controlled clinical trials (RCTs) comparing RSIFs to formulae without nucleotides or breast milk were considered in this review. Outcome measures were: antibody titres to common paediatric vaccinations, total lymphocytes, lymphocyte subclasses and NK-cells, episodes of diarrhoea and acute respiratory infection. Publication quality was determined using Jadad and CONSORT guidelines. Results were combined using a random effects model and reported through standardised mean differences (WMD) or risk ratio (RR). Systematic review and meta-analysis showed that RSIFs were associated with a better antibody response to immunisation withHaemopillus influenzaevaccine [SMD 1·74 (99 %CI 1·43–2·05),P = 0·001], diphtheria toxoid [SMD 0·94 (0·75–1·12),P = 0·001], oral polio vaccine [SMD 0·73 (0·51–0·95),P = 0·001], and fewer episodes of diarrhoea [RR 0·67 (0·58–0·76),P = 0·02]. We did not find a major risk of upper respiratory infections [RR 1·11 (0·90–1·36),P = 0·50]. Available evidence suggests a positive benefit of RSFIs on infant health without any risk. These benefits begin with nucleotide addition of 1·9 mg/418·4 kJ and are maintained or increased with 10·78 mg/418·4 kJ.
Selected vitamins and trace elements support immune function by strengthening epithelial barriers and cellular and humoral immune responses
Authors: Maggini Silvia , Wintergerst Eva S. , Beveridge Stephen , Hornig Dietrich H.
Published: October 2007

Adequate intakes of micronutrients are required for the immune system to function efficiently. Micronutrient deficiency suppresses immunity by affecting innate, T cell mediated and adaptive antibody responses, leading to dysregulation of the balanced host response. This situation increases susceptibility to infections, with increased morbidity and mortality. In turn, infections aggravate micronutrient deficiencies by reducing nutrient intake, increasing losses, and interfering with utilization by altering metabolic pathways. Insufficient intake of micronutrients occurs in people with eating disorders, in smokers (active and passive), in individuals with chronic alcohol abuse, in certain diseases, during pregnancy and lactation, and in the elderly. This paper summarises the roles of selected vitamins and trace elements in immune function. Micronutrients contribute to the body's natural defences on three levels by supporting physical barriers (skin/mucosa), cellular immunity and antibody production. Vitamins A, C, E and the trace element zinc assist in enhancing the skin barrier function. The vitamins A, B6, B12, C, D, E and folic acid and the trace elements iron, zinc, copper and selenium work in synergy to support the protective activities of the immune cells. Finally, all these micronutrients, with the exception of vitamin C and iron, are essential for antibody production. Overall, inadequate intake and status of these vitamins and trace elements may lead to suppressed immunity, which predisposes to infections and aggravates malnutrition. Therefore, supplementation with these selected micronutrients can support the body's natural defence system by enhancing all three levels of immunity.
Fatty acids and immune function: new insights into mechanisms
Authors: Yaqoob Parveen , Calder Philip C.
Published: October 2007

Fatty acids are known to play diverse roles in immune cells. They are important as a source of energy, as structural components of cell membranes, as signaling molecules and as precursors for the synthesis of eicosanoids and similar mediators. Recent research has suggested that the localization and organisation of fatty acids into distinct cellular pools has a direct influence on the behaviour of a number of proteins involved in immune cell activation, including those associated with T cell responses, antigen presentation and fatty acid-derived inflammatory mediator production. This article reviews these studies and places them in the context of existing literature in the field. These studies indicate the existence of several novel mechanisms by which altered fatty acid availability can modulate immune responses and impact upon clinical outcomes.
Assessment of tomato source breeding material through mating designs
Authors: KOUTSIKA-SOTIRIOU M. S. , TRAKA-MAVRONA E. A. , EVGENIDIS G. L.
Published: October 2007

Cultivated tomato has a narrow germplasm base because of several population bottlenecks in the form of founder events, as well as natural and artificial selections that occurred during domestication and evolution of modern cultivars. The F2of commercial single-cross hybrids, as well as locally well-adapted varieties, provide germplasm for developing recombinant lines and exploiting genetic variability, respectively. The present study aims to discriminate the breeding value of tomato source material, i.e. commercial hybrids or well-adapted varieties, by (i) estimating tolerance to inbreeding of hybrids or estimating heterosis of diallel hybrids between varieties, (ii) determining undesirable traits and (iii) determining general combining ability (GCA) and specific combining ability (SCA) effects from diallel crosses between hybrids and between varieties. Two hybrids and four varieties were assessed. One hybrid showed 0·03 inbreeding vigour, which was not combined with undesirable traits in the F2generation. However, negative GCA and positive SCA values did not support the hybrid as source material, provided that hybrids with low inbreeding depression, positive GCA and negative SCA correspond to an F2capable of developing recombinant lines. The assessment of the varieties showed positive GCA and 0·34 heterosis in one variety, indicating agreement between yield and GCA, and that high-yielding varieties may produce high-yielding hybrids. In conclusion, the proposed mating design, taking into account the tolerance to inbreeding for hybrids and the heritability of general worth for both resources, provides a mechanism for ensuring continued improvement in plant performance through plant selection programmes.
Effect of relocation on locomotion and cleanliness in dairy cows
Authors: Wilkes Crafton O , Pence Kristen J , Hurt Amanda M , Becvar Ondrej , Knowlton Katharine F , McGilliard Michael L , Gwazdauskas Francis C
Published: October 2007

This study was conducted to determine the effect that relocation to a new free stall barn had on locomotion and cleanliness of two breeds of dairy cows. The original facility before relocation had cows housed in an 8-row free stall barn. Cows were allocated in a new 4-row free stall facility: cows of two breeds (n=22 Holsteins and 22 Jerseys) were intermixed in the northwest section. Locomotion (scale 1–5) and cleanliness were scored (scale 1–4). Holsteins and Jerseys had no difference in locomotion score throughout 12 weeks following relocation. A lactation number by date interaction showed cows in third and greater lactations had significantly higher locomotion scores (more lameness) by day 86. Locomotion scores increased across breeds during the 86-d observation period, suggesting cows became lamer. Jerseys had cleaner lower legs than Holsteins (2·9±0·1v. 3·5±0·1, respectively). Lactation number affected lower leg cleanliness, with scores decreasing as lactation number increased (3·4v. 3·3v. 2·9±0·10 for first, second and third and greater lactations, respectively;P<0·01). All cows were cleaner (lower scores) after relocation, suggesting that the new facility improved hygiene.
Evidence that primary infection of Charollais sheep withToxoplasma gondiimay not prevent foetal infection and abortion in subsequent lambings
Authors: MORLEY E. K. , WILLIAMS R. H. , HUGHES J. M. , THOMASSON D. , TERRY R. S. , DUNCANSON P. , SMITH J. E. , HIDE G.
Published: October 2007

A study carried out on a sheep farm examined whetherToxoplasma gondiifoetal infection and associated abortion occur in successive lambings. We identified 29 ewes that gave birth to lambs on at least 2 successive years over our study period, 2000–2003. Tissue samples from the progeny of these ewes were analysed by PCR to determine infection status withT. gondii.T. gondii-infected lambs were born in 31% of successive pregnancies.T. gondii-positive lambs were aborted in successive pregnancies in 21% of lambings during study period, 2000–2003. The frequency of successive abortions within this flock over the period 1992–2003 was 18%. If a lamb was congenitally infected there was a high risk (69%) that the successive lamb from that ewe would also be congenitally infected. Similarly, if a lamb was aborted there was a high risk (55%) of abortion in the next lamb produced. These data suggest that life-long immunity toT. gondiiinfections may not always be acquired following an initial infection and raises the question as to whether the mechanisms ofT. gondiitransmission prior to and during ovine pregnancies are fully understood.
Meta-analyses of cognitive functioning in euthymic bipolar patients and their first-degree relatives
Authors: Arts B. , Jabben N. , Krabbendam L. , van Os J.
Published: October 2007

Background

Previous work suggests that impairments in executive function and verbal memory in particular may persist in euthymic bipolar patients and serve as an indicator of genetic risk (endophenotype).

Method

A systematic review of the literature was undertaken. Effects sizes were extracted from selected papers and pooled using meta-analytical techniques.

Results

In bipolar patients, large effect sizes (d>0.8) were noted for executive functions (working memory, executive control, fluency) and verbal memory. Medium effect sizes (0.5<d<0.8) were reported for aspects of executive function (concept shifting, executive control), mental speed, visual memory, and sustained attention. Small effect sizes (d<0.5) were found for visuoperception. In first-degree relatives, effect sizes were small (d<0.5), but significantly different from healthy controls for executive function and verbal memory in particular.

Conclusions

Executive function and verbal memory are candidate bipolar endophenotypes given large deficits in these domains in bipolar patients and small, but intermediate, cognitive impairments in first-degree relatives.
Challenges and growth: the development of the interdisciplinary field of institutional analysis
Authors: OSTROM ELINOR
Published: October 2007

This article briefly describes some of the intellectual challenges during the last half-century to the traditional fields of economics and political science: the public choice approach, the tragedy of the commons debate, the ‘new’ institutional economics, and behavioral game theory. Then, the components of a basic institutional analysis framework are presented that provide a general method for analyzing public economies and diverse forms of collective action. Empirical research related to metropolitan public economies, common-pool resources, and behavioral game theory is summarized that has contributed to the field of institutional analysis. The last section concludes that the macro foundations of institutional analysis appear firmer than the micro foundations related to the model of the individual to be used and discusses this puzzle.
The impact of institutions on the decision how to decide
Authors: ENGEL CHRISTOPH , WEBER ELKE U.
Published: October 2007

Institutions influence and shape behaviour. This paper suggests one way in which they do so that has been largely overlooked in institutional analysis and design. When faced with a decision or problem, people have more than one mechanism at their disposition for addressing it. The human mind offers multiple tools, ranging from conscious deliberation to spontaneous, affective reactions. Relying on technology or experts, decision-makers can also muster additional resources. Often, the meta-choice of which decision-making or problem-solving mode is used has an impact on the output. Some normative goals are more likely met if the decision-maker uses a specific problem-solving mode. We argue that the meta-choice of which problem-solving mode to use for a given decision can be influenced by institutions. In the interest of defining access points for institutions, we develop a conceptual framework for the selection and implementation of decision-making and problem-solving modes.
Naturalizing the market on the road to revisionism: Bruce Caldwell'sHayek's challengeand the challenge of Hayek interpretation
Authors: MIROWSKI PHILIP
Published: October 2007

Bruce Caldwell'sHayek's Challengeshould be welcomed as the first serious book on one of the most important thinkers of the twentieth century. However, this review begins by pointing out a number of curious omissions and silences concerning Hayek's career in the book. We propose that the key to understanding the turns and reversals in his thought lay in his politics, and not as Caldwell has it, in some abstract philosophical doctrines. Central to that thesis is Hayek's fostering the development of Neoliberalism through such institutional structures as the Mont Pèlerin Society.
The Importance and Bioavailability of Phytoferritin-Bound Iron in Cereals and Legume Foods
Authors: Lönnerdal
Published: October 2007

Ferritin is present in several types of plants in low concentrations, but it is possible to enhance this content by plant breeding, or by inserting the gene for ferritin into staple foods. Since each ferritin molecule can bind thousands of iron atoms, this may be a sustainable means to increase the iron content of plants. Before launching such efforts it is important to determine whether ferritin-bound iron is bioavailable. We assessed this in vitro using Caco-2 cells and in vivo using radiolabeled ferritin and whole body counting in human subjects. In Caco-2 cells, we found that dietary factors affecting iron absorption, such as ascorbic acid, phytate, and calcium, had very limited effect on iron uptake from intact ferritin, suggesting that ferritin-bound iron is absorbed via a mechanism different from that of non-heme iron. Using in vitro digestion, we found that ferritin was relatively resistant against proteolytic enzymes. Binding of ferritin to Caco-2 cells was found to be saturable and the kinetics for binding characteristic for a receptor-mediated process. In human subjects, we found that iron absorption from animal ferritin was similar to that from ferrous sulfate, suggesting that iron is well absorbed from ferritin. We did not find any significant difference between iron absorption from ferritin reconstituted with high-phosphate (plant-type) and low-phosphate (animal-type) ferritin mineral, suggesting that plant ferritin-iron is bioavailable. In a subsequent human study we also found that iron from purified soybean ferritin given in a meal was as well absorbed as ferrous iron. In conclusion, iron is well absorbed from phytoferritin and may represent a means of biofortification of staple foods.
Linking the Bioavailability of Iron Compounds to the Efficacy of Iron-Fortified Foods
Authors: Hurrell
Published: October 2007

The bioavailability (relative bioavailability value; RBV) of iron compounds relative to ferrous sulfate has proven useful in ranking the potential of iron compounds for food fortification. The efficacy of iron-fortified foods however depends on the absolute iron absorption from the fortified food and not on the RBV of the iron compound. Compounds of lower RBV can be used to design efficacious fortified foods by adding them at an appropriately higher level. Efficacy thus depends on the amount of iron added to the food vehicle as well as the daily consumption of the fortified food by the target population, the amount of iron lacking in the diet of the target population in relation to their needs, and the prevalence of widespread infections and other micronutrient deficiencies. The World Health Organization has recently published guidelines for food fortification, which include recommendations for iron fortification compounds and a method of how to define the iron fortification level. The same organization has also published guidelines on the iron status methods to be used to monitor interventions. Recent efficacy studies, which have to a large extent followed these guidelines, have shown good efficacy of iron-fortified salt, fish sauce, wheat flour, and rice in improving the iron status of target populations. However, although we now know how to design an efficacious iron-fortified food, efficacy cannot be ensured in populations with widespread infections and other micronutrient deficiencies. In such situations, other public health measures may be necessary before we can ensure an improvement in iron status.
The Bioavailability of (pro) Vitamin A Carotenoids and Maximizing the Contribution of Homestead Food Production to Combating Vitamin A Deficiency
Authors: de Pee  , W. Bloem
Published: October 2007

An estimated 100–140 million children worldwide suffer vitamin A deficiency disorders (VADD). Strategies for combating VADD are best used in combination because they serve particular target groups and none has full coverage. Homestead food production (HFP) can contribute to combating vitamin A deficiency directly, by increasing intake of vitamin A-rich foods, and indirectly through improving health and increasing income. By the late 1990s, conversion factors for estimating vitamin A obtained from plant foods were revised from 6:1 to 12:1 (μg β-carotene:retinol activity equivalent) by the U.S. Institute of Medicine, and by West and colleagues to 21:1 for a mixed diet (12:1 for fruits and 26:1 for vegetables). Thus, plant foods contribute less to vitamin A intake than do other sources. HFP’s contribution can be maximized by increasing the amount of vitamin A-rich food consumed, including animal source foods, choosing foods with higher vitamin A content, and improving bioavailability by adding fat, destroying the matrix of vegetables, and deworming. Since the early 1990s, HFP programs have also included nutrition education and were then generally successful in increasing vitamin A intake. However, impact on vitamin A status was not often accessed. Two examples of evaluating impact using a plausibility approach are described. It is concluded that HFP can make a valuable contribution to combating VADD, especially where dietary diversity is low and when animal husbandry and nutrition education are included. Impact can be further maximized by using program infrastructure to introduce micronutrient-rich cultivars and improved breeds, and by adding other interventions, such as deworming and micronutrient supplementation.
Two‐dimensional distinct element modeling of the structure and growth of normal faults in multilayer sequences: 2. Impact of confining pressure and strength contrast on fault zone geometry and growth
Authors: Schöpfer Martin P. J. , Childs Conrad , Walsh John J.
Published: October 2007

The growth of normal faults in periodically layered sequences with varying strength contrast and at varying confining pressure is modeled using the distinct element method. The normal faulting models are composed of strong layers (bonded particles) and weak layers (nonbonded particles) that are deformed using a predefined fault at the base of the sequence. The model results suggest that faults in sequences with high strength contrast at low confining pressure are highly segmented because of different types of failure (extension versus shear failure) in the different layers. The degree of segmentation decreases as the strength contrast decreases and confining pressure increases. Faults at low confining pressure localize as extension (mode I) fractures within the strong layers and are later linked via shallow dipping faults in the weak ones. This leads to initial staircase geometries that, with increasing displacement, cause space problems that are later resolved by splaying and segmentation. As confining pressure increases, the modeled faults show a transition from extension to hybrid to shear fracture and an associated decrease in fault refraction, with a consequent decrease in fault surface irregularities. Therefore the mode of fracture which is active in the strong layers of a mechanical multilayer at a particular confining pressure exerts an important control on the final fault geometry.
Seasonal rhythms of net primary production and particulate organic carbon flux to depth describe the efficiency of biological pump in the global ocean
Authors: Lutz Michael J. , Caldeira Ken , Dunbar Robert B. , Behrenfeld Michael J.
Published: October 2007

We investigate the functioning of the ocean’s biological pump by analyzing the vertical transfer efficiency of particulate organic carbon (POC). Data evaluated include globally distributed time series of sediment trap POC flux, and remotely sensed estimates of net primary production (NPP) and sea surface temperature (SST). Mathematical techniques are developed to compare these temporally discordant time series using NPP and POC flux climatologies. The seasonal variation of NPP is mapped and shows regional‐ and basin‐scale biogeographic patterns reflecting solar, climatic, and oceanographic controls. Patterns of flux are similar, with more high‐frequency variability and a subtropical‐subpolar pattern of maximum flux delayed by about 5 days per degree latitude increase, coherent across multiple sediment trap time series. Seasonal production‐to‐flux analyses indicate during intervals of bloom production, the sinking fraction of NPP is typically half that of other seasons. This globally synchronous pattern may result from seasonally varying biodegradability or multiseasonal retention of POC. The relationship between NPP variability and flux variability reverses with latitude, and may reflect dominance by the large‐amplitude seasonal NPP signal at higher latitudes. We construct algorithms describing labile and refractory flux components as a function of remotely sensed NPP rates, NPP variability, and SST, which predict POC flux with accuracies greater than equations typically employed by global climate models. Globally mapped predictions of POC export, flux to depth, and sedimentation are supplied. Results indicate improved ocean carbon cycle forecasts may be obtained by combining satellite‐based observations and more mechanistic representations taking into account factors such as mineral ballasting and ecosystem structure.
Control of salinity on the mixed layer depth in the world ocean: 2. Tropical areas
Authors: Mignot Juliette , de Boyer Montégut Clement , Lazar Alban , Cravatte Sophie
Published: October 2007

A new global climatology of the barrier layer (BL) thickness based on the analysis of instantaneous temperature and salinity profiles was presented in the first part of this paper. It is used here to revisit the mean properties of the phenomenon in the tropics. Consistent with previous studies, thick and persistent BLs are detected in the deep tropics of each ocean. Their formation involves various mechanisms such as intense precipitations, oceanic circulation, wind seasonality, and river runoff, in relation with the specific geography and climatology of each basin. The weak seasonal cycle of the BL in the equatorial Pacific is analyzed in particular. Thick BLs are also detected in winter on the equatorial flank of each of the subtropical salinity maxima. They are due to the specific salinity stratification in this area and to the seasonal homogenization of temperature over the vertical under the action of atmospheric heat fluxes. Thick BLs in the western tropical Atlantic that are partly associated with important vertical temperature inversions are furthermore identified and described. More generally, agreement of the BLs mean properties in these areas with previous literature confirms the robustness of the features and validates this new product that uses most available data including the most recent ones issued from the ARGO floats.
Contemporary estimates of Pan‐Arctic freshwater discharge from GRACE and reanalysis
Authors: Syed T. H. , Famiglietti J. S. , Zlotnicki V. , Rodell M.
Published: October 2007

Streamflow from Arctic river basins has been increasing in recent decades in response to warming climate. In addition to being a sensitive indicator of global change, Arctic discharge is a critical component of the freshwater budget of the Arctic Ocean, where increasing freshwater flows may slow rates of North Atlantic Deep Water formation and heat transport by the thermohaline circulation. However, quantifying rates of freshwater discharge from the entire Pan‐Arctic drainage has been troublesome using traditional stream gauging methods. Here we use satellite measurements of variations in continental water storage from the GRACE mission to present first estimates of monthly freshwater discharge from the entire Pan‐Arctic for the period 2003–2005. Results show that rates of Pan‐Arctic discharge for this time period (3588 ± 257 km3 yr−1) are significantly larger than those suggested by gauge‐based estimates (3238 km3 yr−1), and furthermore, may indicate that discharge rates are accelerating.
Rheological study of transient networks with junctions of limited multiplicity
Authors: Indei Tsutomu
Published: October 2007

We theoretically study the viscoelastic and thermodynamic properties of transient gels comprised of telechelic associating polymers. We extend classical theories of transient networks so that correlations among polymer chains through the network junctions are taken into account. This extension enables us to investigate how rheological quantities such as elastic modulus, viscosity, and relaxation time are affected by the association equilibrium, and how these quantities are related to the aggregation number (or multiplicity) of the junctions. In this paper, we assume, in the conventional manner, that chains are elastically effective if both their ends are connected with other chains. It is shown that the dynamic shear moduli are well described in terms of the Maxwell model. As a result of the correlation, the reduced moduli (moduli divided by the polymer concentration) increase with the concentration, but become independent of the concentration in the high-concentration range. The fraction of pairwise junctions is larger at lower concentrations, indicating the presence of concatenated chains in the system, which decreases as the concentration increases. This leads to a network relaxation time that increases with the concentration.
CNDOL: A fast and reliable method for the calculation of electronic properties of very large systems. Applications to retinal binding pocket in rhodopsin and gas phase porphine
Authors: Montero-Cabrera Luis Alberto , Röhrig Ute , Padrón-Garcia Juan A. , Crespo-Otero Rachel , Montero-Alejo Ana L. , Garcia de la Vega José M. , Chergui Majed , Rothlisberger Ursula
Published: October 2007

Very large molecular systems can be calculated with the so called CNDOL approximate Hamiltonians that have been developed by avoiding oversimplifications and only using a priori parameters and formulas from the simpler NDO methods. A new diagonal monoelectronic term named CNDOL/21 shows great consistency and easier SCF convergence when used together with an appropriate function for charge repulsion energies that is derived from traditional formulas. It is possible to obtain a priori molecular orbitals and electron excitation properties after the configuration interaction of single excited determinants with reliability, maintaining interpretative possibilities even being a simplified Hamiltonian. Tests with some unequivocal gas phase maxima of simple molecules (benzene, furfural, acetaldehyde, hexyl alcohol, methyl amine, 2,5 dimethyl 2,4 hexadiene, and ethyl sulfide) ratify the general quality of this approach in comparison with other methods. The calculation of large systems as porphine in gas phase and a model of the complete retinal binding pocket in rhodopsin with 622 basis functions on 280 atoms at the quantum mechanical level show reliability leading to a resulting first allowed transition in 483nm, very similar to the known experimental value of 500nm of “dark state.” In this very important case, our model gives a central role in this excitation to a charge transfer from the neighboring Glu− counterion to the retinaldehyde polyene chain. Tests with gas phase maxima of some important molecules corroborate the reliability of CNDOL/2 Hamiltonians.
Geometric and electronic structure of methane adsorbed on a Pt surface
Authors: Öström H. , Ogasawara H. , Näslund L.-Å. , Andersson K. , Pettersson L. G. M. , Nilsson A.
Published: October 2007

The electronic structure of methane adsorbed on Pt(977) is investigated using angle-resolved x-ray absorption spectroscopy (XAS) in combination with density functional theory spectrum calculations. XAS, which probes the unoccupied states atom specifically, shows the appearance of the symmetry-forbidden gas-phase lowest unoccupied molecular orbital due to s-p rehybridization. In addition new adsorption-induced states appear just above the Fermi level. A systematic investigation, where computed XA spectra are compared with the experiment, indicates elongation of the C–H bond pointing toward the surface to 1.18±0.05Å. The bond elongation arises due to mixing between bonding and antibonding C–H orbitals. Computed charge density difference plots show that no covalent chemical bond is formed between the adsorbate and substrate upon adsorption. The changes in electronic structure arise in order to minimize the Pauli repulsion by polarizing charge away from the surface toward the carbon atom of the methane molecule.
Sagdeev potential analysis for positively charged dust grains in nonthermal dusty plasma near Mars
Authors: El-Taibany W. F. , Wadati Miki
Published: October 2007

The existence of nonlinear dust acoustic (DA) solitary waves for positive dust grains is examined in a dusty plasma (DP). Four charging currents are considered: photoemission, secondary electrons, as well as the electron and ion currents. The nonthermal ion charging current is presented for the first time. Introducing nonthermal ions in the DP system aids in increasing the net positive dust charge, though raising their temperature goes in the opposite direction. There is a maximum value of the ambient plasma potential allowing positive dust charges. The energy equation for the DP system is obtained. The allowed Mach number regime is expanded due to the presence of the nonthermal ions. In the present model, the rarefactive soliton is only permitted. For a constant dust charge, there is a maximum limit of the wave velocity attached to the DA soliton solution. The charging fluctuation always contributes to reducing the amplitude and the width of the produced soliton. The ratio of ion to electron number densities and the nonthermal parameter are two competitors to determine the amplitude and the width of the resultant solitons. Implications of these results to the recorded space phenomena in Martian space and tropical mesosphere are briefly discussed.
The dynamics of pendant droplets on a one-dimensional surface
Authors: Glasner K. B.
Published: October 2007

A sheet of liquid hanging from a solid surface is subject to the Rayleigh-Taylor instability, which leads to the development of pendant droplets. These near-equilibrium structures interact with the liquid film that connects them. The dynamics of the interaction can be rich and leads to large-scale patterning and nonlinear oscillations. We show that droplets move because of an energetically favorable response to asymmetries of the neighboring film thickness. The droplet moves so as to absorb the thicker liquid film and deposits a Landau-Levich film behind. In the case in which a source of fluid is introduced, the film between the droplets does not proceed toward rupture, but rather acts as a driving mechanism for migration and interaction with neighboring droplets. This interaction is shown to always be repulsive in the scaling regime investigated. A reduced system of droplet dynamics is derived asymptotically, and shows how oscillating behavior develops.
The role of magnetic fields on the transport and efficiency of aluminum tris(8-hydroxyquinoline) based organic light emitting diodes
Authors: Desai P. , Shakya P. , Kreouzis T. , Gillin W. P.
Published: October 2007

Magnetoresistance and efficiency measurements of aluminum tris(8-hydroxyquinoline) (Alq3) based organic light emitting diode structures have been made as a function of magnetic field and Alq3 thickness. Both positive and negative magnetoresistances can be observed depending on the thickness of the Alq3 layer, the drive voltage, and the applied field. In all devices, large increases in device efficiency are observed. We suggest that the increase in device efficiency is due to conversion of triplet states into singlets through a hyperfine scale interaction. The changes in the magnetoresistance are a result of the reduction in the triplet concentration and operate either through the reduced role of free carrier trapping at triplet states or through the reduction in triplet dissociation at the cathode interface depending on the Alq3 thickness.
Rapidly rotating Bose-Einstein condensates in homogeneous traps
Authors: Correggi M. , Rindler-Daller T. , Yngvason J.
Published: October 2007

We extend the results of a previous paper on the Gross-Pitaevskii description of rotating Bose-Einstein condensates in two-dimensional traps to confining potentials of the form V(r)=rs, 2<s<∞. Writing the coupling constant as 1∕ε2, we study the limit ε→0. We derive rigorously the leading asymptotics of the ground state energy and the density profile when the rotation velocity Ω tends to infinity as a power of 1∕ε. The case of asymptotically homogeneous potentials is also discussed.
Intensity dependence of relativistic focusing of intense laser beams propagating in plasmas
Authors: Liu Mingwei , Zhou Bingju , Yi Yougen , Liu Xiaojuan , Tang Liqiang
Published: October 2007

Optical guiding of an intense laser beam propagating in uniform plasmas is analyzed by means of the variational method. The focusing properties of the beam are shown to be governed by the laser power as well as the laser intensity. An increase in the laser intensity leads to an enhancement of ponderomotive self-channeling but a stronger weakening of relativistic self-focusing. The oscillations of the beam spot size along the propagation distance come from the variability of the focusing force in terms of the laser intensity; and the dependence on the laser intensity is negligible in the weakly relativistic limit.
Exciton diffusion and relaxation in methyl-substituted polyparaphenylene polymer films
Authors: Gulbinas V. , Minevičiūtė I. , Hertel D. , Wellander R. , Yartsev A. , Sundström V.
Published: October 2007

Exciton diffusion in ladder-type methyl-substituted polyparaphenylene film and solution was investigated by means of femtosecond pump-probe spectroscopy using a combined approach, analyzing exciton-exciton annihilation, and transient absorption depolarization properties. We show that the different views on the exciton dynamics offered by anisotropy decay and annihilation are required in order to obtain a correct picture of the energy transfer dynamics. Comparison of the exciton diffusion coefficient and exciton diffusion radius obtained for polymer film with the two techniques reveals that there is substantial short-range order in the film. Also in isolated chains there is considerable amount of order, as revealed from only partial anisotropy decay, which shows that only a small fraction of the excitons move to differently oriented polymer segments. It is further concluded that interchain energy transfer is faster than intrachain transfer, mainly as a result of shorter interchain distances between chromophoric units.
An equivalent time temperature mapping system with a 320×256pixels full-frame 100kHz sampling rate
Authors: Riccio M. , Breglio G. , Irace A. , Spirito P.
Published: October 2007

In this paper we describe a novel temperature mapping system based on a standard infrared camera with 50Hz frame rate for the measurement of ultrafast temperature transients which, in principle, demand for a much faster acquisition rate. In particular, we base our system on the widely used equivalent time sampling concept which can be adapted to the temperature acquisition system, thanks to a very fast and sensitive camera sensor: an InSb sensor, which allows a reduced integration time of 10μs, and a custom digital synchronization circuit. The latter has been realized by the usage of a fully programmable digital circuit, which generates all the signals needed for the synchronization of the IR camera, of the experiment, and a personal computer needed for data acquisition and storage. We show, with experiments, how this system is capable of detecting temperature transients with an equivalent bandwidth of 100kHz full frame, far beyond the capabilities of the fastest available IR cameras.
Efficient green organic light-Emitting devices with a nondoped dual-functional electroluminescent material
Authors: Tong Qing-Xiao , Lai Shiu-Lun , Chan Mei-Yee , Lai Ka-Ho , Tang Jian-Xin , Kwong Hoi-Lun , Lee Chun-Sing , Lee Shuit-Tong
Published: October 2007

An efficient nondoped green organic light-emitting device was demonstrated by using a dual-functional electroluminescent material, 4,4′,4″-tris[8-(7,10-diphenylfluoranthenyl)] phenylamine (TDPFPA). TDPFPA was shown to be a good hole transporting [with a mobility of (1.1–1.2)×10−4cm2V−1s−1 at (1.8–5.6)×105Vcm−1] and efficient fluorescent material with an exceptionally high glass transition temperature of 237°C. The device with a simple structure of indium tin oxide/TDPFPA/4,7-diphenyl-1,10-phenanthroline/LiF∕Al showed green emission with Commission Internationale de L’Eclairage coordinates of (0.24, 0.54), a current efficiency of 9.9cd∕A, and power efficiency of 10.6lm∕W.
Nanocrystals in silicon photonic crystal standing-wave cavities as spin-photon phase gates for quantum information processing
Authors: Xiao Y.-F. , Gao J. , Yang X. , Bose R. , Guo G.-C. , Wong C. W.
Published: October 2007

By virtue of a silicon high-Q photonic crystal nanocavity, we propose and examine theoretically interactions between a stationary electron spin qubit of a semiconductor nanocrystal and a flying photon qubit. Firstly, we introduce, derive, and demonstrate the explicit conditions toward realization of a spin-photon phase gate, and propose these interactions as a generalized quantum interface for quantum information processing. Secondly, we examine single-spin-induced reflections as direct evidence of intrinsic bare and dressed modes in our coupled nanocrystal-cavity system.
Further Effects of Chain-Length-Dependent Reactivities on Radical Polymerization Kinetics
Authors: Heuts Johan P. A. , Russell Gregory T. , Smith Gregory B.
Published: October 2007

In the present paper, we finalize some threads in our investigations into the effects of chain-length-dependent propagation (CLDP) on radical polymerization kinetics, confirming all our previous conclusions. Additionally, and more significantly, we uncover some unexpected and striking effects of chain-length-dependent chain transfer (CLDTr). It is found that the observed overall rate coefficients for propagation and termination (and therefore the rate of polymerization) are not significantly affected by whether or not chain transfer is chain-length dependent. However, this situation is different when considering the molecular weight distributions of the resulting polymers. In the case of chain-length-independent chain transfer, CLDP results in a considerable narrowing of the distribution at the low molecular weight side of the distribution in a chain-transfer controlled system. However, the inclusion of both CLDP and CLDTr yields identical results to classical kinetics – in these latter two cases, the molecular weight distribution is governed by the same chain-length-independent chain transfer constant, whereas in the case of CLDP only, it is governed by a chain-length-dependent chain transfer constant that decreases with decreasing chain length, thus enhancing the probability of propagation for short radicals. Furthermore, it is shown that the inclusion of a very slow first addition step has tremendous effects on the observed kinetics, increasing the primary radical concentration and thereby the overall termination rate coefficient dramatically. However, including possible penultimate unit effects does not significantly affect the overall picture and can be ignored for the time being. Lastly, we explore the prospects of using molecular weight distributions to probe the phenomena of CLDP and CLDTr. Again, some interesting insights follow.