bluuebunny/crossref_metadata_2025 huggingface dataset:
A general modelling and control framework for electrostatically actuated mechanical systems
Authors: Maithripala D. H. S. , Kawade B. D. , Berg J. M. , Dayawansa W. P.
Published: September 2005

This paper presents a geometric framework for the stabilization and control of a general class of electrostatically actuated mechanical systems. Microelectromechanical systems (MEMS), such as micromirrors, are one motivating application for this work. There wavelengths of applications of interest lead to positioning requirements on the order of 40–100 nm. Furthermore, electrostatic actuation is poised to be the method of choice for the emerging field of nanoelectromechanical systems (NEMS), and the approach presented should be applicable there as well. The class of devices under study consists of a movable, rigid, grounded electrode, with a variety of allowable rotational and/or translational degrees of freedom, and a set of multiple, fixed, independently addressable, drive electrodes. A key contribution of this paper places general electrostatic forces in a framework suitable for passivity‐based control. The configuration space of the movable body is assumed to have the structure of a simple mechanical system on a Lie group, and stabilizing static and dynamic feedback control laws are derived in terms of co‐ordinate‐independent geometric formulas. To obtain controllers for a specific device it is then necessary only to evaluate these formulas. Appropriate approximations may be applied to make the computations more tractable. The static output feedback controller requires only measurement of the charge and voltage on each drive electrode to provide almost‐global stabilization of a desired feasible configuration, but performance is limited by the natural dynamics of the mechanical subsystem. Performance may be improved using dynamic output feedback, but additional information is needed, typically in the form of a model relating electrode capacitances to the system configuration. We demonstrate the controller computations on a representative MEMS, and validate performance using ANSYS simulations. Copyright © 2005 John Wiley & Sons, Ltd.
Large unselective pore in lipid bilayer membrane formed by positively charged peptides containing a sequence of gramicidin A
Authors: Antonenko Yuri N. , Stoilova Tatyana B. , Kovalchuk Sergey I. , Egorova Natalya S. , Pashkovskaya Alina A. , Sobko Alexander A. , Kotova Elena A. , Sychev Sergey V. , Surovoy Andrey Y.
Published: September 2005

Ion‐channel activity of a series of gramicidin A analogues carrying charged amino‐acid sequences on the C‐terminus of the peptide was studied on planar bilayer lipid membranes and liposomes. It was found that the analogue with the positively charged sequence GSGRRRRSQS forms classical cationic pores at low concentrations and large unselective pores at high concentrations. The peptide was predominantly in the right‐handed β6.3‐helical conformation in liposomes as shown by circular dichroism spectroscopy. The single‐channel conductance of the large pore was estimated to be 320 pS in 100 mM choline chloride as judged from the fluctuation analysis of the multi‐channel current. The analogue with the negatively charged sequence GSGEEEESQS exhibited solely classical cationic channel activity. The ability of a peptide to form different type of channels can be used in the search for broad‐spectrum antibiotics.
REPTILES WITH HOLES
Authors: Jordan Francis , Ngai Sze-Man
Published: September 2005

Croft, Falconer and Guy asked: what is the smallest integer $n$ such that an $n$-reptile in the plane has a hole? Motivated by this question, we describe a geometric method of constructing reptiles in $\mathbb{R}^d$, especially reptiles with holes. In particular, we construct, for each even integer $n\ge4$, an $n$-reptile in $\mathbb{R}^2$ with holes. We also answer some questions concerning the topological properties of a reptile whose interior consists of infinitely many components.
THE RELATIVE PICARD GROUP OF A COMODULE ALGEBRA AND HARRISON COHOMOLOGY
Authors: Caenepeel S. , Guédénon T.
Published: September 2005

Let $A$ be a commutative comodule algebra over a commutative bialgebra $H$. The group of invertible relative Hopf modules maps to the Picard group of $A$, and the kernel is described as a quotient group of the group of invertible group-like elements of the coring $A\otimes H$, or as a Harrison cohomology group. Our methods are based on elementary $K$-theory. The Hilbert 90 theorem follows as a corollary. The part of the Picard group of the coinvariants that becomes trivial after base extension embeds in the Harrison cohomology group, and the image is contained in a well-defined subgroup $E$. It equals $E$ if $H$ is a cosemisimple Hopf algebra over a field.
A CRITERION FOR ERDŐS SPACES
Authors: Dijkstra Jan J.
Published: September 2005

In 1940 Paul Erdős introduced the ‘rational Hilbert space’, which consists of all vectors in the real Hilbert space $\ell^2$ that have only rational coordinates. He showed that this space has topological dimension one, yet it is totally disconnected and homeomorphic to its square. In this note we generalize the construction of this peculiar space and we consider all subspaces $\mathcal{E}$ of the Banach spaces $\ell^p$ that are constructed as ‘products’ of zero-dimensional subsets $E_n$ of $\mathbb{R}$. We present an easily applied criterion for deciding whether a general space of this type is one dimensional. As an application we find that if such an $\mathcal{E}$ is closed in $\ell^p$, then it is homeomorphic to complete Erdős space if and only if $\dim\mathcal{E}>0$ and every $E_n$ is zero dimensional.
THE GENERALIZED GOODWIN–STATON INTEGRAL
Authors: Jones D. S.
Published: September 2005

Some properties of the generalized Goodwin–Staton integral are derived. Explicit error bounds for the asymptotic expansion are determined. In addition, results are obtained for the oscillatory case and when logarithmic factors are present.
Evaluation of cooling strategies for pumping of milk – Impact of fatty acid composition on free fatty acid levels
Authors: Wiking Lars , Bertram Hanne C , Björck Lennart , Nielsen Jacob H
Published: September 2005

Cooling strategies for pumping of raw milk were evaluated. Milk was pumped for 450 s at 31 °C, or pumped after cooling to 4 °C and subsequently subjected to various incubation times. Two types of milk were used; i.e. milk from cows fed a diet high in saturated fat supplements resulting in significantly larger milk fat globules than the other type of milk which comes from cows fed a low-fat diet that stimulates high de novo fat synthesis. The content of liquid fat was determined by low-field 1H NMR, which showed that milk from cows given the saturated fat diet also contained less liquid fat at both 4 ° and 31 °C than the other type of milk. This can be ascribed to the differences in the fatty acid composition of the milk as a result of the fatty acid composition of the diets. After pumping of the milk at 31 °C, measurement of fat globule size distribution revealed a significant coalescence of milk fat globules in the milk obtained from the saturated fat diet due to pumping. Pumping at 4 °C or pumping the other type of milk did not result in coalescence of milk fat globules. Formation of free fatty acids increased significantly in both types of milk by pumping at 31 °C. Cooling the milk to 4 °C immediately before pumping inhibited an increased content of free fatty acids. However, when the milk was incubated at 4 °C for 60 min after cooling and then subjected to pumping, a significant increase in the formation of free fatty acids was observed in both types of milk. It is suggested that this increase in free fatty acids is caused by transition of polymorphic crystal forms or higher level of attached lipoprotein lipases to the milk fat globule before pumping.
PCR-based screening and lineage identification ofTrypanosoma cruzidirectly from faecal samples of triatomine bugs from northwestern Argentina
Authors: MARCET P. L. , DUFFY T. , CARDINAL M. V. , BURGOS J. M. , LAURICELLA M. A. , LEVIN M. J. , KITRON U. , GÜRTLER R. E. , SCHIJMAN A. G.
Published: September 2005

This study applied improved DNA extraction and polymerase chain reaction strategies for screening and identification ofTrypanosoma cruzilineages directly from faeces of triatomines collected in a well-defined rural area in northwestern Argentina. Amplification of the variable regions of the kinetoplastid minicircle genome (kDNA-PCR) was performed in faecal lysates from 33 microscope (MO)-positive and 93 MO-negativeTriatoma infestans, 2 MO-positive and 38 MO-negativeTriatoma guasayanaand 2 MO-positive and 73 MO-negativeTriatoma garciabesi. kDNA-PCR detectedT. cruziin 91% MO-positive and 7·5% MO-negativeT. infestans, which were confirmed by amplification of the minicircle conserved region. In contrast, kDNA-PCR was negative in all faecal samples from the other triatomine species. A panel of PCR-based genomic markers (intergenic region of spliced-leader DNA, 24Sα and 18S rRNA genes and A10 sequence) was implemented to identify the parasite lineages directly in DNA lysates from faeces and culture isolates from 28 infected specimens. Two were found to be infected with TCI, 24 with TCIIe, 1 with TCIId and 1 revealed a mixed TCI+TCII infection in the faecal sample whose corresponding culture only showed TCII, providing evidence of the advantages of direct typing of biological samples. This study provides an upgrade in the current diagnosis and lineage identification ofT. cruziin field-collected triatomines and showsT. cruziII strains as predominant in the region.
fifty years of electronic music in israel
Authors: gluck robert j.
Published: September 2005

the history of electronic music composition, technologies and institutions is traced from the founding of the state of israel in 1948. core developments are followed beginning with the founding generation including joseph tal, tzvi avni and yizhak sadai, continuing with the second and third generations of musicians and researchers, living in israel and the united states. the institutional and political dynamics of the field in this country are explored, with a focus on the challenges of building an audience and institutional support, as well as prospects for the future.
Peano high‐impedance surfaces
Authors: McVay John , Hoorfar Ahmad , Engheta Nader
Published: September 2005

Following our previous work on metamaterial high‐impedance surfaces made of Hilbert curve inclusions, here we theoretically explore the performance of the high‐impedance surfaces made of another form of space‐filling curve known as the Peano curve. This metamaterial surface, formed by a two‐dimensional periodic arrangement of Peano curve inclusions, is located above a conducting ground plane and is shown to exhibit a high surface impedance at certain specific frequencies. Our numerical study reveals the effect of the iteration order of the Peano curve, the surface height above the conducting ground plane, and the separation distance between adjacent inclusions.
Three‐dimensional transient electromagnetic modeling for investigating the spatial sensitivity of time domain reflectometry measurements
Authors: Rejiba Fayçal , Cosenza Philippe , Camerlynck Christian , Tabbagh Alain
Published: September 2005

A three‐dimensional (3‐D) transient electromagnetic modeling based on a full‐wave formulation (Maxwell's equations) has been undertaken in order to study the impact of heterogeneities located near a time domain reflectometry (TDR) probe. We focused on 3‐D heterogeneities located at the ends of rods: (1) interface perpendicular to the probe plane located below the end of rods and (2) 3‐D (cubic and parallelepipedic) heterogeneities whose characteristic lengths are similar to that of the probe. Whatever the rod separation and whatever the dielectric constant contrasts, an interface located just beneath the end of the rod does not affect significantly a simulated TDR signal when the interface is farther than one rod diameter. However, all the simulations carried out with cubic and parallelepipedic heterogeneities located along TDR rods have shown that a significant longitudinal sensitivity exists. The lower the constant dielectric value of heterogeneity, the higher the longitudinal sensitivity. In particular, parallelepipedic heterogeneities parallel to the rods induce significant changes in the travel times, compared to cubic heterogeneities, whose characteristic length is equal to the rod diameter. Moreover, 3‐D numerical calculations have shown that TDR signals are not only sensitive to the heterogeneity volume itself but also to their orientation. Static 2‐D analysis is shown to provide correct qualitative representation of spatial sensitivity analysis, though accurate quantitative estimation of the apparent permittivity requires a complete 4‐D (x, y, z, and time) calculation.
Generation of downshifted oscillations in the electron foreshock: A loss‐cone instability
Authors: Lobzin V. V. , Krasnoselskikh V. V. , Schwartz S. J. , Cairns Iver , Lefebvre B. , Décréau P. , Fazakerley A.
Published: September 2005

Measurements performed aboard Cluster spacecraft near Earth's bow shock on 24 January 2001 provide convincing evidence of a loss‐cone feature within the electron foreshock region. This feature is formed by suprathermal electrons with energies 15–45 eV and pitch angles 130°–150° and is always accompanied by electrostatic waves with frequencies well below the local plasma frequency. An instability analysis shows that these downshifted oscillations can result from a loss‐cone instability of electron cyclotron modes rather than from the beam instability as previously suggested.
Prevention of Ischemic Neuronal Death by Intravenous Infusion of a Ginseng Saponin, Ginsenoside Rb1, That Upregulates Bcl-xL Expression
Authors: Zhang Bo , Hata Ryuji , Zhu Pengxiang , Sato Kohji , Wen Tong-Chun , Yang Lihua , Fujita Hiroko , Mitsuda Noriaki , Tanaka Junya , Samukawa Keiichi , Maeda Nobuji , Sakanaka Masahiro
Published: September 2005

Almost all agents that exhibit neuroprotection when administered into the cerebral ventricles are ineffective or much less effective in rescuing damaged neurons when infused into the blood stream. Search for an intravenously infusible drug with a potent neuroprotective action is essential for the treatment of millions of patients suffering from acute brain diseases. Here, we report that postischemic intravenous infusion of a ginseng saponin, ginsenoside Rb1 (gRb1) (C54H92O23, molecular weight 1109.46) to stroke-prone spontaneously hypertensive rats with permanent occlusion of the middle cerebral artery distal to the striate branches significantly ameliorated ischemia-induced place navigation disability and caused an approximately 50% decrease in the volume of the cortical infarct lesion in comparison with vehicle-infused ischemic controls. In subsequent studies that focused on gRb1-induced expression of gene products responsible for neuronal death or survival, we showed that gRb1 stimulated the expression of the mitochondrion-associated antiapoptotic factor Bcl-xL in vitro and in vivo. Moreover, we revealed that a Stat5 responsive element in the bcl-x promoter became active in response to gRb1 treatment. Ginsenoside Rb1 appears to be a promising agent not only for the treatment of cerebral stroke, but also for the treatment of other diseases involving activation of mitochondrial cell death signaling.
The theoretical study on interaction of hydrogen with single-walled boron nitride nanotubes. I. The reactive force field ReaxFFHBN development
Authors: Han Sang Soo , Kang Jeung Ku , Lee Hyuck Mo , van Duin Adri C. T. , Goddard William A.
Published: September 2005

We present a new reactive force field ReaxFFHBN derived to accurately model large molecular and condensed phase systems of H, B, and N atoms. ReaxFFHBN has been tested against quantum calculation data for B–H, B–B, and B–N bond dissociations and for H–B–H, B–N–B, and N–B–N bond angle strain energies of various molecular clusters. The accuracy of the developed ReaxFFHBN for B–N–H systems is also tested for (i) H–B and H–B bond energies as a function of out of plane in H–B(NH2)3 and H–N(BH2)3, respectively, (ii) the reaction energy for the B3N3H6+H2→B3N3H8, and (iii) crystal properties such as lattice parameters and equations of states for the hexagonal type (h-BN) with a graphite structure and for the cubic type (c-BN) with a zinc-blende structure. For all these systems, ReaxFFHBN gives reliable results consistent with those from quantum calculations as it describes well bond breaking and formation in chemical processes and physical properties. Consequently, the molecular-dynamics simulation based on ReaxFFHBN is expected to give a good description of large systems (>2000 atoms even on the one-CPU machine) with hydrogen, boron, and nitrogen atoms.
Temperature dependence of electron and hole mobilities in heavily impurity-doped SiGe single crystals
Authors: Yonenaga I. , Li W. J. , Akashi T. , Ayuzawa T. , Goto T.
Published: September 2005

Heavily impurity-doped single crystals of SixGe1−x alloy with the composition 0.84<x<1 and large-grained polycrystals with x=0.80 were grown by the Czochralski technique. The Hall-coefficient measurements of the electron and hole mobilities in the grown crystals were carried out in the temperature range of 300–1000K and compared with those in undoped SiGe. The Hall mobilities of electrons and holes in SiGe with a carrier concentration of 1019–1020cm−3 both show a Tn, n∼1, temperature dependence up to elevated temperatures. This indicates that the carrier transport process is mainly rate controlled by charged impurity scattering. In single-crystal SiGe free from grain-boundary effects, the hole mobility increases with decreasing Si content at least up to 0.84 and the electron mobility is greater than in Si and polycrystalline SiGe. These results suggest that scattering processes in alloy semiconductors are more complicated than previously thought.
The impact of charged grain boundaries on thin-film solar cells and characterization
Authors: Metzger W. K. , Gloeckler M.
Published: September 2005

We use two-dimensional computer simulations to examine how charged columnar grain boundaries (GBs) affect transport, recombination, characterization, and performance in polycrystalline Cu(In,Ga)Se2 solar cells. Although the simulations show that charged GBs can increase photocurrent by forming minority-carrier collection channels, this generally occurs at the expense of overall efficiency. Carrier dynamics induced by the GBs significantly alter time-resolved photoluminescence, near-field scanning optical microscopy, electron-beam-induced current microscopy, and quantum efficiency spectra. Consequently, these experiments can place bounds on the role and strength of GB charge in polycrystalline materials. Simulations of these experiments indicate that GB charge sufficient to significantly increase photocurrent collection is generally inconsistent with the actual observations for Cu(In,Ga)Se2 solar cells.
Improved emission of Eu3+ by energy transfer via Tb3+ in coprecipitates TbxEu(1−x)(aspirin)3(phen)
Authors: Zhang T. , Xu Z. , Qian L. , Teng F. , Xu X. R. , Tao D. L.
Published: September 2005

In order to increase the red emission of Eu complex doped in poly(N-vinylcarbazole) (PVK), series of molar ratio coprecipitates [TbxEu(1−x)(aspirin)3(phen)∙H2O] (phen=1,10-phenanthroline) were prepared, in which Tb3+ ion acts as an energy bridge to enhance the energy transfer between the ligands and europium ion. The intramolecular energy transfer from Tb3+ to Eu3+ was studied via a time-resolved spectrum. It gave a direct evidence of the intramolecular energy transfer between the two lanthanide ions of terbium and europium. The photoluminescence and electroluminescence spectra as well as the performance of the device indium tin oxide/poly-(3,4-ethylenedioxythiophene):poly-(styrenesulphonic acid)/PVK:TbxEu(1−x)(aspirin)3(phen)∕Al were also studied. Compared with that of PVK:Eu(aspirin)3phen device, the result showed an enhanced emission of Eu3+ ion due to the energy transfer via Tb3+ ion.
The effects of electrostatic forces on the distribution of drops in a channel flow: Two-dimensional oblate drops
Authors: Fernández Arturo , Tryggvason Gretar , Che Judy , Ceccio Steven L.
Published: September 2005

Numerical simulations are used to examine the effect of an electrostatic field on an emulsion of drops in a channel. The leaky-dielectric theory of Taylor is used to find the electric field, the charge distribution on the drop surface, and the resulting forces. The Navier-Stokes equations are solved using a front-tracking/finite-volume technique. Depending on the ratios of conductivity and permittivity of the drop fluid and the suspending fluid the drops can become oblate or prolate. In addition to normal forces that deform the drops, tangential forces can induce a fluid motion either from the poles of the drops to their equator or from the equator to the poles. In this paper we focus on oblate drops, where both the dielectrophoretic and the electrohydrodynamic interactions of the drops work together to “fibrate” the emulsion by lining the drops up into columns parallel to the electric field. When the flow through the channel is slow, the fibers can extend from one wall to the other. As the flow rate is increased the fibers are broken up and drops accumulate at the channel walls. For high enough flow rate, when the drop interactions are dominated by the fluid shear, the drops remain in suspension. Only two-dimensional systems are examined here, but the method can be used for fully three-dimensional systems as well.
Rectifying “nanohomo” contacts of W–Ga–C composite pad and nanowire fabricated by focused-ion-beam-induced chemical vapor deposition
Authors: Li Wuxia , Shen Tiehan H.
Published: September 2005

We prepared W–Ga–C composite contacts on W–Ga–C composite nanowires by focused-ion-beam-induced chemical vapor deposition using a dual-beam scanning electron microscope∕focused-ion-beam system. The current-voltage (I-V) characteristics of wires were found to change from nonlinear to linear with increasing wire thickness. For wires with small dimensions, which result in strong nonlinear I-V behavior at room temperature, pairs of contacts were fabricated along the wire under different ion energies and scanning modes. Nonlinear and asymmetric rectifying I-V characteristics were observed. The results suggest that nanoscaled W–Ga–C nanowires may behave similarly to semiconductors and that the contact characteristics may be modified using different deposition conditions. Furthermore, ohmiclike junctions could be formed through the use of specific deposition conditions for the contact pads and nanowires.
[
Bi
3
Fe
5
O
12
∕
Gd
3
Ga
5
O
12
]
m
magneto-optical photonic crystals
Authors: Khartsev S. I. , Grishin A. M.
Published: September 2005

A series of one-dimensional heteroepitaxial all-garnet magneto-optical photonic crystals has been synthesized and optically characterized. They are composed of alternating magneto-optically active Bi3Fe5O12 (BIG) and Gd3Ga5O12 (GGG) quarter-wave length layers pulsed laser deposited on to the GGG(001) substrate. Photonic crystals, as designed, exhibit stop band structure and the band gap with the transmittance central peak caused by the light localization in the half-wave length BIG cavity. Compared to previously reported [Bi3Fe5O12∕Y3Fe5O12]m photonic crystal [Appl. Phys. Lett. 84, 1438 (2004)], the replacement of optically dense Y3Fe5O12 garnet by transparent Gd3Ga5O12 enables significant enhancement of light rejection within the stop band. Photonic crystals spectra experience “blue” shift in oblique incidence geometry thus demonstrating feasibility to use this effect for tunable magneto-optical filters.
Branching in electrospinning of nanofibers
Authors: Yarin A. L. , Kataphinan W. , Reneker D. H.
Published: September 2005

Electrospinning of polymer nanofibers often begins with a single, straight, elongating, and electrified fluid jet that emanates from a droplet tip when the electric field at the surface is high enough. After some distance an electrically driven bending instability of the elongating jet occurs. For a polymer solution suitable for electrospinning, capillary instability does not cause the jet to become a spray of droplets. Under some conditions, a sequence of secondary jet branches emanates from the primary jet. This paper describes an experiment in which many closely spaced branches along the jet were observed during the electrospinning of a polycaprolactone solution. A theoretical description of the branching phenomenon is proposed.
Relatively well preserved DNA is present in the crystal aggregates of fossil bones
Authors: Salamon Michal , Tuross Noreen , Arensburg Baruch , Weiner Steve
Published: September 2005

DNA from fossil human bones could provide invaluable information about population migrations, genetic relations between different groups and the spread of diseases. The use of ancient DNA from bones to study the genetics of past populations is, however, very often compromised by the altered and degraded state of preservation of the extracted material. The universally observed postmortem degradation, together with the real possibility of contamination with modern human DNA, makes the acquisition of reliable data, from humans in particular, very difficult. We demonstrate that relatively well preserved DNA is occluded within clusters of intergrown bone crystals that are resistant to disaggregation by the strong oxidant NaOCl. We obtained reproducible authentic sequences from both modern and ancient animal bones, including humans, from DNA extracts of crystal aggregates. The treatment with NaOCl also minimizes the possibility of modern DNA contamination. We thus demonstrate the presence of a privileged niche within fossil bone, which contains DNA in a better state of preservation than the DNA present in the total bone. This counterintuitive approach to extracting relatively well preserved DNA from bones significantly improves the chances of obtaining authentic ancient DNA sequences, especially from human bones.
Molecular origin of time-dependent fluorescence shifts in proteins
Authors: Nilsson Lennart , Halle Bertil
Published: September 2005

Time-resolved fluorescence spectroscopy is used increasingly to probe molecular motions at the aqueous interfaces of biological macromolecules and membranes. By recording the time variation of the fluorescence frequency, thermal atomic fluctuations in the vicinity of the chromophore can be probed. From such fluorescence Stokes shift (FSS) experiments, it has been inferred that water motions in the hydration layer are slowed down by 1–3 orders of magnitude. To provide a more secure foundation for the interpretation of FSS data, we use molecular dynamics simulations to examine the molecular origin of the FSS from a tryptophan residue in a protein. By using linear response theory to decompose the FSS into its water and protein components, we find that the water component dominates the static FSS but decays rapidly. Thus, after a few picoseconds, the FSS essentially reflects protein dynamics, including the self-motion of the chromophore. Because of its collective nature, the FSS response is insensitive to the motion of individual water molecules. Collective water displacement by slowly fluctuating protein groups introduces a long-time tail in the water autocorrelation function, but this dynamic coupling is hardly manifested in the observed FSS. Our analysis reconciles FSS data with the picture of a highly dynamic hydration layer, derived mainly from magnetic relaxation dispersion and simulation studies, and calls for a revision of previous interpretations of FSS decays in terms of slow hydration dynamics at biomolecular and other interfaces.
Biological effects in unirradiated human tissue induced by radiation damage up to 1 mm away
Authors: Belyakov Oleg V. , Mitchell Stephen A. , Parikh Deep , Randers-Pehrson Gerhard , Marino Stephen A. , Amundson Sally A. , Geard Charles R. , Brenner David J.
Published: September 2005

A central tenet in understanding the biological effects of ionizing radiation has been that the initially affected cells were directly damaged by the radiation. By contrast, evidence has emerged concerning “bystander” responses involving damage to nearby cells that were not themselves directly traversed by the radiation. These long-range effects are of interest both mechanistically and for assessing risks from low-dose exposures, where only a small proportion of cells are directly hit. Bystander effects have been observed largely by using single-cell
in vitro
systems that do not have realistic multicellular morphology; no studies have as yet been reported in three-dimensional, normal human tissue. Given that the bystander phenomenon must involve cell-to-cell interactions, the relevance of such single-cell
in vitro
studies is questionable, and thus the significance of bystander responses for human health has remained unclear. Here, we describe bystander responses in a three-dimensional, normal human-tissue system. Endpoints were induction of micronucleated and apoptotic cells. A charged-particle microbeam was used, allowing irradiation of cells in defined locations in the tissue yet guaranteeing that no cells located more than a few micrometers away receive any radiation exposure. Unirradiated cells up to 1 mm distant from irradiated cells showed a significant enhancement in effect over background, with an average increase in effect of 1.7-fold for micronuclei and 2.8-fold for apoptosis. The surprisingly long range of bystander signals in human tissue suggests that bystander responses may be important in extrapolating radiation risk estimates from epidemiologically accessible doses down to very low doses where nonhit bystander cells will predominate.
Quantifying amino acid conformational preferences and side-chain–side-chain interactions in β-hairpins
Authors: Phillips Scott T. , Piersanti Giovanni , Bartlett Paul A.
Published: September 2005

The intrinsic conformational biases of individual amino acids and their interstrand side-chain–side-chain (SC–SC) interactions both contribute to the stability of β-sheets. The relative magnitudes of these effects have been difficult to assess in the context of folded proteins, where tertiary contacts complicate the quantitative analysis of local effects. We now report the results of such an analysis in a much simpler system, a short, stabilized β-hairpin structure where intrastrand (conformational) and interstrand (SC–SC) influences can be distinguished in the absence of competing protein tertiary interactions. A comprehensive comparison of all pairwise combinations of 11 N-terminal and 7 C-terminal amino acids within an 8-residue, @-tide-stabilized [in which @ denotes the 1,2-dihydro-3(6
H
)-pyridinyl unit] β-hairpin reveals distinct differences between the various pairings and shows that the intrastrand and interstrand effects are of comparable magnitude in contributing to the stability of the folded forms over the unfolded forms.
Dichlorination of a pyrrolyl-S-carrier protein by FADH
2
-dependent halogenase PltA during pyoluteorin biosynthesis
Authors: Dorrestein Pieter C. , Yeh Ellen , Garneau-Tsodikova Sylvie , Kelleher Neil L. , Walsh Christopher T.
Published: September 2005

The antifungal natural product pyoluteorin contains a 4,5-dichloropyrrole moiety. The timing of dichlorination in the heteroaromatic ring is now shown to occur after proline is tethered by thioester linkage to the carrier protein PltL and enzymatically desaturated to the pyrrolyl-
S
-PltL. Surprisingly, the FADH
2
-dependent halogenase PltA catalyzes chlorination at both positions of the ring, generating the 5-chloropyrrolyl-
S
-PltL intermediate and then the 4,5-dichloropyrrolyl-
S
-PltL product. PltA activity strictly depends on a heterologous flavin reductase that uses NAD(P)H to produce FADH
2
. Electrospray ionization–Fourier transform MS detected five covalent intermediates attached to the 11-kDa carrier protein PltL. Tandem MS localized the site of covalent modification on the carrier protein scaffold. HPLC analysis of the hydrolyzed products was consistent with the regiospecific chlorination at position 5 and then position 4 of the heteroaromatic ring. A mechanism for dichlorination is proposed involving formation of a FAD-4a-OCl intermediate for capture by the electron-rich C
4
and C
5
of the heteroaromatic pyrrole moiety.
Undernutrition, infection and immune function
Authors: Calder Philip C. , Jackson Alan A.
Published: September 2005

Undernutrition and infection are the major causes of morbidity and mortality in the developing world. These two problems are interrelated. Undernutrition compromises barrier function, allowing easier access by pathogens, and compromises immune function, decreasing the ability of the host to eliminate pathogens once they enter the body. Thus, malnutrition predisposes to infections. Infections can alter nutritional status mediated by changes in dietary intake, absorption and nutrient requirements and losses of endogenous nutrients. Thus, the presence of infections can contribute to the malnourished state. The global burden of malnutrition and infectious disease is immense, especially amongst children. Childhood infections impair growth and development. There is a role for breast-feeding in protection against infections. Key nutrients required for an efficient immune response include vitamin A, Fe, Zn and Cu. There is some evidence that provision of the first three of these nutrients does improve immune function in undernourished children and can reduce the morbidity and mortality of some infectious diseases including measles, diarrhoeal disease and upper and lower respiratory tract infections. Not all studies, however, show benefit of single nutrient supplementation and this might be because the subjects studied have multiple nutrient deficiencies. The situation regarding Fe supplementation is particularly complex. In addition to immunization programmes and improvement of nutrient status, there are important roles for maternal education, improved hygiene and sanitation and increased supply of quality water in the eradication of infectious diseases.
Herbal products: active constituents, modes of action and quality control
Authors: Wills Ron B.H. , Bone Kerry , Morgan Michelle
Published: September 2005

An overview is given of the current position of medicinal herbs in general in relation to usage, market and production, types of pharmacological activity and how they differ from conventional drugs. The increasing importance of quality and manufactured products is also discussed. A more detailed consideration of these issues is given in relation to echinacea, valerian and St John's wort as these herbs are well studied, are market leaders and have widespread community usage.
Plant polyphenols in cancer and heart disease: implications as nutritional antioxidants
Authors: Duthie Garry G. , Duthie Susan J. , Kyle Janet A. M.
Published: September 2005

Certain dietary antioxidants such as vitamin E and vitamin C are important for maintaining optimum health. There is now much interest in polyphenolic products of the plant phenylpropanoid pathway as they have considerable antioxidant activityin vitroand are ubiquitous in our diet. Rich sources include tea, wine, fruits and vegetables although levels are affected by species, light, degree of ripeness, processing and storage. This confounds the formulation of databases for the estimation of dietary intakes. Most attention to date has focused on the flavonoids, a generic term which includes chalcones, flavones, flavanones, flavanols and anthocyanins. There is little convincing epidemiological evidence that intakes of polyphenols are inversely related to the incidence of cancer whereas a number of studies suggest that high intakes of flavonoids may be protective against CHD. In contrast, numerous cell culture and animal models indicate potent anticarcinogenic activity by certain polyphenols mediated through a range of mechanisms including antioxidant activity, enzyme modulation, gene expression, apoptosis, upregulation of gap junction communication and P-glycoprotein activation. Possible protective effects against heart disease may be due to the ability of some polyphenols to prevent the oxidation of LDL to an atherogenic form although anti-platelet aggregation activity and vasodilatory properties are also reported. However, some polyphenols are toxic in mammalian cells. Thus, until more is known about their bioavailability, metabolism and intracellular location, increasing intakes of polyphenols by supplements or food fortification may be unwise.
Phytate and phytase: consequences for protein utilisation
Authors: Selle P H , Ravindran V , Caldwell A , Bryden W. L
Published: September 2005

The excretion of large amounts of P in effluent from intensive pig and poultry units is indicative of the poor availability of phytate-bound P in plant-derived feed ingredients. This environmental problem prompted the development and acceptance of microbial phytase feed enzymes for single-stomached animals. Their introduction led to an increasing recognition that phytate may have adverse effects on protein utilisation in addition to P. Consequently, the nutritional relevance of protein–phytate interactions for pigs and poultry is considered in the present review. Since the current understanding of the effects of protein–phytate interactions comes mainly from responses obtained to added phytase, literature on the influence of microbial phytases on amino acid digestibility and utilisation is summarised, followed by a discussion of possible mechanisms contributing to the negative effects of phytate. However, the rationale for the protein responses to added phytase remains largely speculative, and several modes of action are probably involved. It may be that the release of protein from protein–phytate complexes occurring naturally in feed ingredients, the prevention of formation of binary and ternary protein–phytate complexes within the gut, the alleviation of the negative impact of phytate on digestive enzymes and the reduction in endogenous amino acid losses are all contributing factors. A better understanding of the mechanisms of protein–phytate interactions and the modes of action of exogenous phytase enzymes is clearly desirable. Studies are also needed to identify and quantify the factors that contribute to the variable amino acid responses to added phytase. It appears that the relative solubilities of phytate salts and proteins from different feed ingredients and their effects on the extent of protein–phytate complex formation, coupled with variations in the effectiveness of phytase in different dietary contexts, may be the major factors responsible.
Perspectives on ruminant nutrition and metabolism. II. Metabolism in ruminant tissues
Authors: Annison E. F , Bryden W. L
Published: September 2005

The discovery of the dominance of short-chain fatty acids as energy sources in the 1940s and 1950s, as discussed in part I of this review (Annison & Bryden, 1998) led to uncertainties concerning the interrelationships of glucose and acetate in ruminant metabolism. These were resolved in the following decade largely by use of14C-labelled substrates. Although only small amounts of glucose are absorbed in most dietary situations, glucose availability to ruminant tissues as measured by isotope dilution was shown to be substantial, indicating that gluconeogenesis is a major metabolic activity in both fed and fasted states. Studies with14C-labelled glucose and acetate revealed that in contrast to non-ruminants, acetate and not glucose is the major precursor of long-chain fatty acids in ruminant tissues. Interest in the measurement of energy metabolism in livestock grew rapidly from the 1950s. Most laboratories adopted indirect calorimetry and precise measurements of the energy expenditure of ruminants contributed to the development of new feeding systems. More recently, alternative approaches to the measurement of energy expenditure have included the use of NMR spectroscopy, isotope dilution and the application of the Fick principle to measure O2consumption in the whole animal and in defined tissues. The refinement of the classical arterio-venous difference procedure in the study of mammary gland metabolism in the 1960s, particularly when combined with isotope dilution, encouraged the use of these methods to generate quantitative data on the metabolism of a range of defined tissues. The recent introduction of new methods for the continuous monitoring of both blood flow and blood O2content has greatly increased the precision and scope of arterio-venous difference measurements. The impact of data produced by these and other quantitative procedures on current knowledge of the metabolism of glucose, short-chain fatty acids and lipids, and on N metabolism, is outlined. The role of the portal-drained viscera and liver in N metabolism is discussed in relation to data obtained by the use of multi-catheterized animals. Protein turnover, and the impact of stress (physical, social and disease related) on protein metabolism have been reviewed. The growth of knowledge of mammary gland metabolism and milk synthesis since the first quantitative studies in the 1960s has been charted. Recent findings on the regulation of amino acid uptake and utilization by the mammary gland, and on the control of milk secretion, are of particular interest and importance.
Understanding the nutritional chemistry of lupin (Lupinus spp.) seed to improve livestock production efficiency
Authors: van Barneveld Robert J.
Published: September 2005

In their raw, unprocessed form, lupins have many desirable characteristics for feeding both ruminants and single-stomached animals. An emphasis on these desirable characteristics when formulating diets, combined with an advanced knowledge of how components of lupins can influence nutritional value, will ensure they make a cost-effective contribution to livestock diets. The main lupin species used in livestock diets include Lupinus albus, L. angustifolius and L. luteus. Supplementation of ruminant diets with lupins has been shown to have many positive effects in terms of growth and reproductive efficiency, comparable with supplements of cereal grain. The true value of lupins in ruminants, however, can only be determined following a better definition of animal requirements and a closer match of ration specifications. Pigs can effectively utilize L. angustifolius and L. luteus, but detailed research has yet to reveal the reason for poor utilization of diets containing L. albus. Poultry can tolerate high levels of lupins in their diets but levels are often restricted to avoid problems associated with excess moisture in the excreta. Variable responses to enzymes have been observed when attempting to rectify this problem. Lupins have unique carbohydrate properties characterized by negligible levels of starch, high levels of soluble and insoluble NSP, and high levels of raffinose oligosaccharides, all of which can affect the utilization of energy and the digestion of other nutrients in the diet. In addition to carbohydrates, an understanding of lupin protein, lipid and mineral composition together with a knowledge of potential anti-nutritional compounds is required if the use of this legume is to be optimized.
Dietary protein level alters oxidative phosphorylation in heart and liver mitochondria of chicks
Authors: Toyomizu Masaaki , Kirihara Daisuke , Tanaka Masahiro , Hayashi Kunioki , Tomita Yuichiro
Published: September 2005

To determine the effects of dietary protein level on cardiac and hepatic mitochondrial oxidative phosphorylation, chicks were fed on semi-purified diets of different protein levels (7, 25, 43 and 61% of metabolizable energy content) for 7, 14 and 21 d. All diets were formulated to contain equivalent fat, mineral and vitamin contents on a gross energy basis. Cardiac and hepatic mitochondrial oxidative phosphorylation rates were assessed polarographically with pyruvate and malate as substrates. Cardiac mitochondria isolated from chicks fed on a 43 or 61% protein-energy diet for 7 d exhibited significantly reduced ADP:oxygen (ADP:O) ratios when compared with mitochondria isolated from chicks fed on a lower-protein-energy diet. Feeding low- (7%) protein-energy diets for 14 d resulted in a relatively increased ADP:O ratio in the heart. Responses of ADP:O ratios to protein level in hepatic mitochondria showed more dependency on protein level than in heart muscle; at all feeding periods the ADP:O ratio decreased with an increase in protein level. As a result, ATP synthesized in the liver, expressed as nmol/mg mitochondrial protein per min, significantly decreased with increased dietary protein level. A parallel correlation was observed, in chicks fed on diets with different levels of protein, between ADP:O ratio for liver mitochondria and body fat. These results suggest that the reduction in oxidative phosphorylation in the heart and liver of animals fed on a higher protein-energy diet may partly contribute to the depression of body fat.
Some determinants of postprandial lipaemia in Nigerian diabetic and non-diabetic subjects
Authors: Akanji Abayomi O. , Nzegwu Anali A. , Agbedana E. Olu
Published: September 2005

The efficiency of clearance of plasma triacylglycerols (TAG) after fatty meals in non-diabetic Caucasian subjects is believed to determine the plasma level of high-density-lipoproteins-cholesterol (HDL-C). It is unknown if this observation holds in diabetic subjects and in other racial groups. In assessing the factors that determine TAG responses to acute fat loading in a tropical African population with a low prevalence of atherosclerotic disease, twenty (nine obese) non-insulin-dependent diabetic (NIDDM) patients with optimal glycaemic control and twelve (six obese) age-matched non-diabetic subjects were given meals containing 50 g fat (in butter) and 75 g carbohydrate (in white bread) over 15 min in the morning after a 12 h overnight fast. The fasting plasma levels of glucose, TAG, total cholesterol (total-C), HDL-C, low-density-lipoprotein-cholesterol, insulin and glycosylated haemoglobin (HBAlc) were estimated; glucose and TAG levels were also measured postprandially for 8 h at 2 h intervals. Postprandial lipaemia was consistently higher in the diabetic patients (about 50–100% more than values obtained in the non-diabetic subjects, even when corrected for differences in body mass) and correlated positively with age and postprandial glycaemia. This defect in TAG clearance was even worse (by about 50%) when glucose tolerance became further impaired after ten of the diabetic patients stopped oral hypoglycaemic treatment for 1 week and the fat-tolerance test was repeated. In the obese non-diabetic subjects, but not those of normal weight, there were significant negative relationships between the postprandial lipaemia and fasting plasma levels of HDL-C and the HDL-C: total-C ratio, as reported in Caucasians. It is concluded that age and the ambient glucose concentration appear to be the important determinants of the efficiency of TAG clearance in diabetic subjects. This accords with clinical observations of increased atherogenic liability with increasing age and poorer glycaemic control. The determinants in non-diabetic subjects were less defined, indicating that postprandial lipaemia might be influenced by various factors (obesity as shown here) in different subsets of individuals.