bluuebunny/crossref_metadata_2025 huggingface dataset:
Collisional quenching of NO A Σ2+(v′=) between 125 and 294 K
Authors: Settersten Thomas B. , Patterson Brian D. , Carter Campbell D.
Published: May 2009

We report measurements of the temperature-dependent cross sections for the quenching of fluorescence from the A Σ2+(v′=0) state of NO for temperatures between 125 and 294 K. Thermally averaged cross sections were measured for quenching by NO(X Π2), N2, O2, and CO in a cryogenically cooled gas flow cell. Picosecond laser-induced fluorescence was time resolved, and the thermally averaged quenching cross sections were determined from the dependence of the fluorescence decay rate on the quencher-gas pressure. These measurements extend to lower temperature the range of previously published results for NO and O2 and constitute the first reported measurements of the N2 and CO cross sections for temperatures below 294 K. Between 125 and 294 K, a negative temperature dependence is observed for quenching by NO, O2, and CO, implicating collision-complex formation in all three cases. Over the same temperature range, a constant, nonzero cross section is measured for quenching by N2. Updated empirical models for the temperature dependence of the cross sections between 125 and 4500 K are recommended based on weighted least-squares fits to the current low-temperature results and previously published measurements at higher temperature. The results of over 250 measurements presented here indicate that the collisionless lifetime of NO A Σ2+(v′=0) is approximately 192 ns.
Particle-in-cell simulation with Vlasov ions and drift kinetic electrons
Authors: Chen Yang , Parker Scott E.
Published: May 2009

There are certain limitations in using gyrokinetic ions for simulations of turbulent transport in tokamak plasmas. Applications where Vlasov ions might be more appropriate include the electron temperature gradient driven turbulence, edge turbulence with steep density gradient, and magnetic reconnection in a weak guide field. In such cases the ion gyrokinetic model presently used in simulations needs to be extended, but a satisfactory extension valid for fully electromagnetic turbulence is not presently available. Even if an accurate model is found, its numerical implementation could be very challenging. We propose a kinetic model that combines Vlasov ions with gyrokinetic electrons to avoid the difficulties with gyrokinetic ions. The field equations of this model are the Faraday’s equation and the Ampere’s equation without the displacement current. The perturbed fields B1 and E1 rather than the scalar and vector potentials are used to formulate the field equations. We have devised an implicit scheme for this model, demonstrated in three-dimensional slab for the Alfvén waves, the drift Alfvén instability and the ion acoustic waves.
Brownian dynamics of charged particles in a constant magnetic field
Authors: Hou L. J. , Mišković Z. L. , Piel A. , Shukla P. K.
Published: May 2009

Numerical algorithms are proposed for simulating the Brownian dynamics of charged particles in an external magnetic field, taking into account the Brownian motion of charged particles, damping effect, and the effect of magnetic field self-consistently. Performance of these algorithms is tested in terms of their accuracy and long-time stability by using a three-dimensional Brownian oscillator model with constant magnetic field. Step-by-step recipes for implementing these algorithms are given in detail. It is expected that these algorithms can be directly used to study particle dynamics in various dispersed systems in the presence of a magnetic field, including polymer solutions, colloidal suspensions, and, particularly, complex (dusty) plasmas. The proposed algorithms can also be used as thermostat in the usual molecular dynamics simulation in the presence of magnetic field.
A molecular dynamics simulation study of hydrated sulfonated poly(ether ether ketone) for application to polymer electrolyte membrane fuel cells: Effect of water content
Authors: Brunello Giuseppe , Lee Seung Geol , Jang Seung Soon , Qi Yue
Published: May 2009

Sulfonated poly(ether ether ketone) (S-PEEK) with 40% of degree of sulfonation was studied using full atomistic molecular dynamics simulation in order to investigate the nanophase-segregated structures, focusing on the sulfonate group and water phase at various water contents such as 10, 13, and 20 wt %. By analyzing the pair correlation function, it is found that as the water solvation of sulfonate groups proceeds more with increasing water content, the distance between sulfonate groups is increased from 4.4 Å (10 wt %) to 4.8 Å (13 wt %) to 5.4 Å (20 wt %), and the hydronium ions (H3O+) become farther apart from the sulfonate groups. The water coordination number for water and the water diffusion are enhanced with increasing water content because the internal structure of the water phase in S-PEEK approaches that of bulk water. Compared to the Nafion and Dendrion membranes, the S-PEEK membrane shows less internal structure in the water phase and smaller water diffusion, indicating that the S-PEEK has less nanophase segregation than the Nafion and Dendrion membranes.
Flow behind a cylinder forced by a combination of oscillatory translational and rotational motions
Authors: Nazarinia M. , Lo Jacono D. , Thompson M. C. , Sheridan J.
Published: May 2009

The flow behind a cylinder undergoing forced combined oscillatory motion has been studied. The motion consists of two independent oscillations: cross-stream translation and rotation. Previous studies have extensively investigated the effect of these motions individually on cylinder wakes; however, the investigation of their combined effect is new. The motivation lies in its application to vortex-induced vibration and its suppression and to biomimetic motion. The focus is on the effect of the phase difference between the two motions. The results show that there is an unexpected loss of synchronization of the wake for a finite range of phase differences.
Effects of compressibility and heating in magnetohydrodynamics simulations of a reversed field pinch
Authors: Onofri M. , Malara F. , Veltri P.
Published: May 2009

The reversed field pinch is studied using numerical simulations of the compressible magnetohydrodynamics equations. Contrary to what has been done in previous works, the hypotheses of constant density and vanishing pressure are not used. Two cases are investigated. In the first case the pressure is derived from an adiabatic condition and in the second case the pressure equation includes heating terms due to resistivity and viscosity. The evolution of the reversal parameter and the production of single helicity or multiple helicity states are different in the two cases. The simulations show that the results are affected by compressibility and are very sensitive to hypotheses on heat production.
Simple model for wakefield excitation by intense short-pulse laser in underdense plasma
Authors: Wang Xin , Yu Wei , Yu M. Y. , Xu Han , Wang J. W. , Yuan Xiao
Published: May 2009

A simple analytical model for intense-laser interaction with low-density plasma is used to investigate the dependence of the wake structure on the laser parameters and the background plasma density. Many of the properties observed in the existing multidimensional particle-in-cell simulations are qualitatively recovered.
A simple model for studying multilayer adsorption of noninteracting polyatomic species on homogeneous and heterogeneous surfaces
Authors: Sánchez-Varretti F. O. , García G. D. , Ramirez-Pastor A. J. , Romá F.
Published: May 2009

In this work we study a simple model of multilayer adsorption of noninteracting polyatomic species on homogeneous and heterogeneous surfaces. A new approximate analytic isotherm is obtained and validated by comparing with Monte Carlo simulation in one- and two-dimensional lattices. Then, we use the well-known Brunauer–Emmet–Teller (BET) approach to analyze these isotherms and to estimate the monolayer volume, vm. In this way, we confirm previous observations that the value of the vm obtained by the BET equation depends strongly on adsorbate size and surface heterogeneity. In all cases, we find that the use of the BET equation leads to an underestimate of the true monolayer capacity. Nevertheless, a compensation effect is found for the adsorption on a patchwise bivariate surface, but this is not enough to eliminate the decrease of vm caused by the molecular size. In addition, we consider also the possibility to use the model to study the adsorption on nanotube bundles.
Elephant modes and low frequency unsteadiness in a high Reynolds number, transonic afterbody wake
Authors: Meliga Philippe , Sipp Denis , Chomaz Jean-Marc
Published: May 2009

Experiments and large eddy numerical simulation of a fully turbulent afterbody flow in the high subsonic regime, typical of that developing in the wake of a space launcher, exhibit a large-scale low frequency oscillation of the wake. In the present paper, we investigate to what extent the existence of the synchronized oscillations can be interpreted, at the high Reynolds numbers prevailing in this class of flows, by a local stability analysis of the mean flow, as measured in experiments or computed in numerical simulations. This analysis shows the presence of a pocket of absolute instability in the near wake, slightly detached from the body. The global frequency is strikingly well predicted by the absolute frequency at the upstream station of marginal absolute instability, this frequency selection being in agreement with the theory of nonlinear global modes. This result strongly suggests that a so-called elephant mode is responsible for the intense oscillations observed in the lee of space launcher configurations.
Kinematic properties of passive scalar gradient predicted by a stochastic Lagrangian model
Authors: Gonzalez M.
Published: May 2009

A modeled equation for the gradient of a passive scalar is derived consistently with the approach of Chevillard and Meneveau for the velocity gradient tensor [Phys. Rev. Lett. 97, 174501 (2006)] and its predictions are analyzed in three-dimensional, isotropic turbulence. General features of scalar gradient kinematics, namely, production of scalar gradient norm and alignment with respect to strain principal axes and vorticity are rather well described. A strain persistence parameter defined for tight alignment of vorticity with a strain eigenvector is used to bring further insight into geometric properties of the scalar gradient. In particular, the model results lend support to the existence of special alignments of the scalar gradient which are determined by local strain persistence and are different from the directions of strain principal axes as already shown in two-dimensional turbulence.
Ultraviolet photodetectors based on selectively grown ZnO nanorod arrays
Authors: Ji L. W. , Peng S. M. , Su Y. K. , Young S. J. , Wu C. Z. , Cheng W. B.
Published: May 2009

Metal-semiconductor-metal (MSM) ultraviolet (UV) photodetectors with ZnO nanorods (NRs) have been fabricated and characterized in this investigation. The NR arrays were selectively grown on the gap of interdigitated electrodes by chemical solution method through a photolithography process. Compared to a traditional ZnO MSM photodetector with no NRs, the fabricated NR UV photodetector showed much higher photoresponsity. As a result, it can be attributed to high surface-to-volume ratio of ZnO NRs and such a high photoresponse could strongly depend on oxygen adsorption/desorption process in the presence of trap states at the NR surface.
Synergy on catalytic effect of Fe–Zr additives mixed in different proportions on the hydrogen desorption from MgH2
Authors: Kale A. , Bazzanella N. , Checchetto R. , Miotello A.
Published: May 2009

Mg films with mixed Fe and Zr metallic additives were prepared by rf magnetron sputtering keeping the total metal content constant, about 7 at. %, and changing the [Fe]/[Zr] ratio. Isothermal hydrogen desorption curves showed that the kinetics depends on [Fe]/[Zr] ratio and is fastest when the [Fe]/[Zr] ratio is ∼1.8. X-ray diffraction analysis revealed formation of Fe nanoclusters and Mg grain refinement. The improvement of the hydrogen desorption kinetics can be explained by the presence of atomically dispersed Zr and Fe nanoclusters acting as nucleation centers, as well as Mg grain refinement.
Infrared laser-based monitoring of the silane dissociation during deposition of silicon thin films
Authors: Bartlome R. , Feltrin A. , Ballif C.
Published: May 2009

The silane dissociation efficiency, or depletion fraction, is an important plasma parameter by means of which the film growth rate and the amorphous-to-microcrystalline silicon transition regime can be monitored in situ. In this letter we implement a homebuilt quantum cascade laser-based absorption spectrometer to measure the silane dissociation efficiency in an industrial plasma-enhanced chemical vapor deposition system. This infrared laser-based diagnostic technique is compact, sensitive, and nonintrusive. Its resolution is good enough to resolve Doppler-broadened rotovibrational absorption lines of silane. The latter feature various absorption strengths, thereby enabling depletion measurements over a wide range of process conditions.
Hybrid bipolar transistors and inverters of nanoribbon crystals
Authors: Zhang Yajie , Tang Qingxin , Li Hongxiang , Hu Wenping
Published: May 2009

A “hybrid” structure based on organic (p-type) and inorganic (n-type) single crystalline nanoribbons was introduced for the fabrication of organic bipolar field-effect transistors and inverters. The devices were fabricated based on individual organic single crystalline nanoribbon of copper phthalocyanine as p-channel and individual inorganic single crystalline nanoribbon of zinc oxide as n-channel. All transistors exhibited high performance and nice bipolar behavior with hole mobility up to ∼0.62 cm2/V s. With the integration of n- and p- transistors together organic single crystalline complementary inverters were fabricated. The maximum gain of the inverters reached 29. The high performance of the transistors and inverters indicated the potential application of the hybrid structure and nanoribbon crystals for organic electronics.
Two-photon induced amplified spontaneous emission from needlelike triphenylamine-containing derivative crystals with low threshold
Authors: Chen Qi-Dai , Fang Hong-Hua , Xu Bin , Yang Jie , Xia Hong , Chen Fei-Peng , Tian Wen-Jing , Sun Hong-Bo
Published: May 2009

Two-photon induced amplified spontaneous emission (ASE) characteristics of a needlelike crystal were studied. Under two-photon excitation, the upconverted light emission was confined within the crystal and self-waveguided along the needle axis then radiated from the needle tips. The full width at half maximum of the two-photon excited fluorescence reaches 6.5 nm and ASE threshold is as low as 0.29 mJ pulse−1 cm−2 for the N-(4-(4-(4-(diphenylamino)styryl)styryl)phenyl)-N-phenylbenzene amine crystal, comparable with those achieved by single-photon pumping. The needlelike crystal is shown to be a promising candidate for frequency up-converted organic semiconductor microlasers.
Photoalignment effect in a liquid-crystal film doped with nanoparticles and azo-dye
Authors: Chen Wen-Zheng , Tsai Yi-Tai , Lin Tsung-Hsien
Published: May 2009

This study discusses the photoalignment effect in a liquid-crystal (LC) film that is doped with nanoparticles and azo-dye. The vertical alignment induced by nanoparticles of polyhedral oligomeric silsesquioxanes can be changed into homogeneous alignment by the absorption of photoexcited azo-dye. An electrically tunable polarization-dependent LC phase grating is also produced using the method. Both nanoparticle- and azo-dye-induced vertical and homogeneous alignments are noncontact alignment and are highly promising for low-temperature plastic processes.
Integrated continuum-atomistic modeling of nonthermal ablation of gold nanofilms by femtosecond lasers
Authors: Gan Yong , Chen J. K.
Published: May 2009

Ultrafast nonthermal ablation of gold nanofilms is studied using a combined two-temperature model and molecular dynamics method. The results show that for thinner films the tensile stress is directly reversed from the initially generated compressive stress. For thicker films, on the other hand, the tensile stress wave is reflected from the irradiated surface. The key driving force for ultrafast nonthermal material ablation is conventional thermal stress, instead of the hot electron blast force.
Origin of flatband voltage shift and unusual minority carrier generation in thermally grown GeO2/Ge metal-oxide-semiconductor devices
Authors: Hosoi Takuji , Kutsuki Katsuhiro , Okamoto Gaku , Saito Marina , Shimura Takayoshi , Watanabe Heiji
Published: May 2009

Improvement in electrical properties of thermally grown GeO2/Ge metal-oxide-semiconductor (MOS) capacitors, such as significantly reduced flatband voltage (VFB) shift, small hysteresis, and minimized minority carrier response in capacitance-voltage (C-V) characteristics, has been demonstrated by in situ low temperature vacuum annealing prior to gate electrode deposition. Thermal desorption analysis has revealed that not only water but also hydrocarbons are easily infiltrated into GeO2 layers during air exposure and desorbed at around 300 °C, indicating that organic molecules within GeO2/Ge MOS structures are possible origins of electrical defects. The inversion capacitance, indicative of minority carrier generation, increases with air exposure time for Au/GeO2/Ge MOS capacitors, while maintaining an interface state density (Dit) of about a few 1011 cm−2 eV−1. Unusual increase in inversion capacitance was found to be suppressed by Al2O3 capping (Au/Al2O3/GeO2/Ge structures). This suggests that electrical defects induced outside the Au electrode by infiltrated molecules may enhance the minority carrier generation, and thus acting as a minority carrier source just like MOS field-effect transistors.
Symmetry structured correlation in projected Hartree–Fock wavefunctions
Authors: Stuber Jason L.
Published: May 2009

The projected Hartree–Fock wavefunctions are recast within the framework of the coupled cluster approach. Instead of state projection we directly symmetry adapt the broken symmetry correlation operator via the group invariant mean. The algebraic form for the cluster amplitudes is connected to the underlying symmetry group by this analytical projection, resulting in the inclusion of symmetry structured correlation effects into the wavefunction. After truncating the corresponding cluster amplitudes to a given order, equations that exploit this sparsity can be derived through the bivariational functional of the normal coupled cluster method. This prescription fills in a methodological gap in the standard couple cluster hierarchy, providing an additional means to incorporate pairing and higher order amplitude contributions.
Focal adhesion kinase is a blood–testis barrier regulator
Authors: Siu Erica R. , Wong Elissa W. P. , Mruk Dolores D. , Porto Catarina S. , Cheng C. Yan
Published: May 2009

In mammalian testes, such as rats, the mechanism(s) that regulate blood–testis barrier (BTB) restructuring at stages VIII–IX of the seminiferous epithelial cycle of spermatogenesis to facilitate the transit of preleptotene/leptotene spermatocytes is not known. This is due to the lack of information on the regulatory proteins at the BTB. Herein, focal adhesion kinase (FAK), a nonreceptor protein tyrosine kinase, is shown to structurally interact with occludin and ZO-1 to form a functional protein complex at the BTB. Its expression at the BTB in the seminiferous epithelium is stage specific, being lowest at stage VIII–IX tubules, analogous to the expression pattern of occludin. Using primary Sertoli cells cultured in vitro with an established tight junction (TJ) permeability barrier that mimics the BTB in vivo, the knockdown of FAK by RNAi led to a transient disruption of the TJ barrier. This was accompanied by a loss of association between occludin and ZO-1, likely the result of reduced occludin phosphorylation at Tyr and Ser residues, but not Thr, which in turn led to a redistribution of occludin at the Sertoli–Sertoli cell interface, moving from cell membrane into cell cytosol, thereby disrupting the BTB. These findings suggest that a similar mechanism is in place in the testis in vivo to regulate BTB restructuring to facilitate the transit of primary spermatocytes. Furthermore, FAK was shown to be a molecular target of cadmium because its knockdown would desensitize Sertoli cells to cadmium-induced TJ barrier disruption. In summary, FAK is a unique regulator of BTB dynamics in the testis.
A relaxin-like peptide purified from radial nerves induces oocyte maturation and ovulation in the starfish,
Asterina pectinifera
Authors: Mita Masatoshi , Yoshikuni Michiyasu , Ohno Kaoru , Shibata Yasushi , Paul-Prasanth Bindhu , Pitchayawasin Suthasinee , Isobe Minoru , Nagahama Yoshitaka
Published: May 2009

Gonad-stimulating substance (GSS) of starfish is the only known invertebrate peptide hormone responsible for final gamete maturation, rendering it functionally analogous to the vertebrate luteinizing hormone (LH). Here, we purified GSS of starfish,
Asterina pectinifera
, from radial nerves and determined its amino acid sequence. The purified GSS was a heterodimer composed of 2 different peptides, A and B chains, with disulfide cross-linkages. Based on its cysteine motif, starfish GSS was classified as a member of the insulin/insulin-like growth factor (IGF)/relaxin superfamily. The cDNA of GSS encodes a preprohormone sequence with a C peptide between the A and B chains. Phylogenetic analyses revealed that starfish GSS was a relaxin-like peptide. Chemically synthesized GSS induced not only oocyte maturation and ovulation in isolated ovarian fragments, but also unique spawning behavior, followed by release of gametes shortly after the injection. Importantly, the action of the synthetic GSS on oocyte maturation and ovulation was mediated through the production of cAMP by isolated ovarian follicle cells, thereby producing the maturation-inducing hormone of this species, 1-methyladenine. In situ hybridization showed the transcription of GSS to occur in the periphery of radial nerves at the side of tube feet. Together, the structure, sequence, and mode of signal transduction strongly suggest that GSS is closely related to the vertebrate relaxin.
Normal growth of
Arabidopsis
requires cytosolic invertase but not sucrose synthase
Authors: Barratt D. H. Paul , Derbyshire Paul , Findlay Kim , Pike Marilyn , Wellner Nikolaus , Lunn John , Feil Regina , Simpson Clare , Maule Andrew J. , Smith Alison M.
Published: May 2009

The entry of carbon from sucrose into cellular metabolism in plants can potentially be catalyzed by either sucrose synthase (SUS) or invertase (INV). These 2 routes have different implications for cellular metabolism in general and for the production of key metabolites, including the cell-wall precursor UDPglucose. To examine the importance of these 2 routes of sucrose catabolism in
Arabidopsis thaliana
(L.), we generated mutant plants that lack 4 of the 6 isoforms of SUS. These mutants (
sus1/sus2/sus3/sus4
mutants) lack SUS activity in all cell types except the phloem. Surprisingly, the mutant plants are normal with respect to starch and sugar content, seed weight and lipid content, cellulose content, and cell-wall structure. Plants lacking the remaining 2 isoforms of SUS (
sus5/sus6
mutants), which are expressed specifically in the phloem, have reduced amounts of callose in the sieve plates of the sieve elements. To discover whether sucrose catabolism in
Arabidopsis
requires INVs rather than SUSs, we further generated plants deficient in 2 closely related isoforms of neutral INV predicted to be the main cytosolic forms in the root (
cinv1/cinv2
mutants). The mutant plants have severely reduced growth rates. We discuss the implications of these findings for our understanding of carbon supply to the nonphotosynthetic cells of plants.
The fundamental crossed module of the complement of a knotted surface
Authors: Faria Martins João
Published: May 2009

We prove that if

M
M

is a CW-complex and

M
1

M^1

is its 1-skeleton, then the crossed module

Π
2

(
M
,

M
1

)

\Pi _2(M,M^1)

depends only on the homotopy type of

M
M

as a space, up to free products, in the category of crossed modules, with

Π
2

(

D
2

,

S
1

)

\Pi _2(D^2,S^1)

. From this it follows that if

G

\mathcal {G}

is a finite crossed module and

M
M

is finite, then the number of crossed module morphisms

Π
2

(
M
,

M
1

)
→

G

\Pi _2(M,M^1) \to \mathcal {G}

can be re-scaled to a homotopy invariant

I

G

(
M
)

I_{\mathcal {G}}(M)

, depending only on the algebraic 2-type of

M
M

. We describe an algorithm for calculating

π
2

(
M
,

M

(
1
)

)

\pi _2(M,M^{(1)})

as a crossed module over

π
1

(

M

(
1
)

)

\pi _1(M^{(1)})

, in the case when

M
M

is the complement of a knotted surface

Σ
\Sigma

in

S
4

S^4

and

M

(
1
)

M^{(1)}

is the handlebody of a handle decomposition of

M
M

made from its

0
0

- and

1
1

-handles. Here,

Σ
\Sigma

is presented by a knot with bands. This in particular gives us a geometric method for calculating the algebraic 2-type of the complement of a knotted surface from a hyperbolic splitting of it. We prove in addition that the invariant

I

G

I_{\mathcal {G}}

yields a non-trivial invariant of knotted surfaces in

S
4

S^4

with good properties with regard to explicit calculations.
Regularity of subelliptic Monge-Ampère equations in the plane
Authors: Guan Pengfei , Sawyer Eric
Published: May 2009

We establish a

C
∞

C^\infty

regularity result for

C

1
,
1

C^{1,1}

solutions of degenerate Monge-Ampère equation in

R

2

\mathbb R^2

, under the assumption that the trace of the Hessian is bounded from below.
The Milnor Fiber Conjecture and iterated branched cyclic covers
Authors: Lamberson P.
Published: May 2009

In this paper we prove the Milnor Fiber Conjecture of Neumann and Wahl for a class of isolated complete intersection singularities obtained by taking iterated branched cyclic covers of the singularity link. We also show that if the Milnor Fiber Conjecture holds for a given splice diagram, then it holds for any equivalent diagram satisfying the semigroup condition. We illustrate the application of these theorems in an example and discuss the relationship of these singularities with Neumann and Wahl’s Splice Type Conjecture.
Second order cumulants of products
Authors: Mingo James , Speicher Roland , Tan Edward
Published: May 2009

We derive a formula which expresses a second order cumulant whose entries are products as a sum of cumulants where the entries are single factors. This extends to the second order case the formula of Krawczyk and Speicher. We apply our result to the problem of calculating the second order cumulants of a semi-circular and Haar unitary operator.
A construction of numerical Campedelli surfaces with torsion ℤ/6
Authors: Neves Jorge , Papadakis Stavros
Published: May 2009

We produce a family of numerical Campedelli surfaces with

Z

/

6

\mathbb {Z}/6

torsion by constructing the canonical ring of the étale 6 to 1 cover using serial unprojection. In Section 2 we develop the necessary algebraic machinery. Section 3 contains the numerical Campedelli surface construction, while Section 4 contains remarks and open questions.
Existence and Lipschitz regularity of solutions to Bolza problems in optimal control
Authors: Cannarsa P. , Frankowska H. , Marchini E.
Published: May 2009

In this paper we investigate the existence and Lipschitz continuity of optimal trajectories for the autonomous Bolza problem in control theory. The main feature of our results is that they relax the usual fast growth condition for the Lagrangian. Furthermore, we show that optimal solutions do satisfy the maximum principle.
Intersection numbers of polygon spaces
Authors: Agapito José , Godinho Leonor
Published: May 2009

We study the intersection ring of the space

M

(

α
1

,
…
,

α
m

)

\mathcal {M}(\alpha _1,\ldots ,\alpha _m)

of polygons in

R

3

\mathbb {R}^3

. We find homology cycles dual to generators of this ring and prove a recursion relation in

m
m

(the number of edges) for their intersection numbers. This result is an analog of the recursion relation appearing in the work of Witten and Kontsevich on moduli spaces of punctured curves and in the work of Weitsman on moduli spaces of flat connections on two-manifolds of genus

g
g

with

m
m

marked points. Based on this recursion formula we obtain an explicit expression for the computation of the intersection numbers of polygon spaces and use it in several examples. Among others, we study the special case of equilateral polygon spaces (where all

α
i

\alpha _i

’s are the same) and compare our results with the expressions for these particular spaces that have been determined by Kamiyama and Tezuka. Finally, we relate our explicit formula for the intersection numbers with the generating function for intersection pairings of the moduli space of flat connections of Yoshida, as well as with equivalent expressions for polygon spaces obtained by Takakura and Konno through different techniques.
Multiloop realization of extended affine Lie algebras and Lie tori
Authors: Allison Bruce , Berman Stephen , Faulkner John , Pianzola Arturo
Published: May 2009

An important theorem in the theory of infinite dimensional Lie algebras states that any affine Kac-Moody algebra can be realized (that is to say constructed explicitly) using loop algebras. In this paper, we consider the corresponding problem for a class of Lie algebras called extended affine Lie algebras (EALAs) that generalize affine algebras. EALAs occur in families that are constructed from centreless Lie tori, so the realization problem for EALAs reduces to the realization problem for centreless Lie tori. We show that all but one family of centreless Lie tori can be realized using multiloop algebras (in place of loop algebras). We also obtain necessary and sufficient conditions for two centreless Lie tori realized in this way to be isotopic, a relation that corresponds to isomorphism of the corresponding families of EALAs.
Self delta-equivalence for links whose Milnor’s isotopy invariants vanish
Authors: Yasuhara Akira
Published: May 2009

For an

n
n

-component link, Milnor’s isotopy invariants are defined for each multi-index

I
=

i
1

i
2

.
.
.

i
m

 
(

i
j

∈
{
1
,
.
.
.
,
n
}
)

I=i_1i_2...i_m~(i_j\in \{1,...,n\})

. Here

m
m

is called the length. Let

r
(
I
)

r(I)

denote the maximum number of times that any index appears in

I
I

. It is known that Milnor invariants with

r
=
1

r=1

, i.e., Milnor invariants for all multi-indices

I
I

with

r
(
I
)
=
1

r(I)=1

, are link-homotopy invariant. N. Habegger and X. S. Lin showed that two string links are link-homotopic if and only if their Milnor invariants with

r
=
1

r=1

coincide. This gives us that a link in

S
3

S^3

is link-homotopic to a trivial link if and only if all Milnor invariants of the link with

r
=
1

r=1

vanish. Although Milnor invariants with

r
=
2

r=2

are not link-homotopy invariants, T. Fleming and the author showed that Milnor invariants with

r
≤
2

r\leq 2

are self

Δ
\Delta

-equivalence invariants. In this paper, we give a self

Δ
\Delta

-equivalence classification of the set of

n
n

-component links in

S
3

S^3

whose Milnor invariants with length

≤
2
n
−
1

\leq 2n-1

and

r
≤
2

r\leq 2

vanish. As a corollary, we have that a link is self

Δ
\Delta

-equivalent to a trivial link if and only if all Milnor invariants of the link with

r
≤
2

r\leq 2

vanish. This is a geometric characterization for links whose Milnor invariants with

r
≤
2

r\leq 2

vanish. The chief ingredient in our proof is Habiro’s clasper theory. We also give an alternate proof of a link-homotopy classification of string links by using clasper theory.
Spectral analysis of a class of nonlocal elliptic operators related to Brownian motion with random jumps
Authors: Pinsky Ross
Published: May 2009

Let

D
⊂

R
d

D\subset R^d

be a bounded domain and let

P

(
D
)

\mathcal P(D)

denote the space of probability measures on

D
D

. Consider a Brownian motion in

D
D

which is killed at the boundary and which, while alive, jumps instantaneously at an exponentially distributed random time with intensity

γ
>
0

\gamma >0

to a new point, according to a distribution

μ
∈

P

(
D
)

\mu \in \mathcal P(D)

. From this new point it repeats the above behavior independently of what has transpired previously. The generator of this process is an extension of the operator

−

L

γ
,
μ

-L_{\gamma ,\mu }

, defined by

L

γ
,
μ

u
≡
−

1
2

Δ
u
+
γ

V
μ

(
u
)
,

\begin{equation*} L_{\gamma ,\mu }u\equiv -\frac 12\Delta u+\gamma V_\mu (u), \end{equation*}

with the Dirichlet boundary condition, where

V
μ

V_\mu

is a nonlocal “

μ
\mu

-centering” potential defined by

V
μ

(
u
)
=
u
−

∫
D

u
d
μ
.

\begin{equation*} V_\mu (u)=u-\int _Du d\mu . \end{equation*}

The operator

L

γ
,
μ

L_{\gamma ,\mu }

is symmetric only in the case that

μ
\mu

is normalized Lebesgue measure; thus, only in that case can it be realized as a selfadjoint operator. The corresponding semigroup is compact, and thus the spectrum of

L

γ
,
μ

L_{\gamma ,\mu }

consists exclusively of eigenvalues. As is well known, the principal eigenvalue gives the exponential rate of decay in

t
t

of the probability of not exiting the domain by time

t
t

. We study the behavior of the eigenvalues, our main focus being on the behavior of the principal eigenvalue for the regimes

γ
≫
1

\gamma \gg 1

and

γ
≪
1

\gamma \ll 1

. We also consider conditions on

μ
\mu

that guarantee that the principal eigenvalue is monotone increasing or decreasing in

γ
\gamma

.
When is year-class strength determined in western Baltic herring?
Authors: Oeberst Rainer , Klenz Birgitt , Gröhsler Tomas , Dickey-Collas Mark , Nash Richard D. M. , Zimmermann Christopher
Published: May 2009

Oeberst, R., Klenz, B., Gröhsler, T., Dickey-Collas, M., Nash, R. D. M., and Zimmermann, C. 2009. When is year-class strength determined in western Baltic herring? – ICES Journal of Marine Science, 66: 1667–1672. Weekly surveys of larvae in the Strelasund and the Greifswalder Bodden were used to investigate when year-class strength is determined in western Baltic spring-spawning (WBSS) herring. An abundance metric of larvae reaching a length of 20 mm over the entire spawning season was constructed by accounting for increases in daily growth resulting from seasonal increases in temperature (5–20°C). The index was significantly correlated with the acoustic estimates of age-1 herring in the western Baltic Sea (r = 0.88) and with the estimates of year-class strength obtained from stock assessment (r = 0.65). Previous studies of herring elsewhere have reported that year-class strength is determined during the late larval stage, but we show that year-class strength can already be fixed at a larval length of only 20 mm. Although the index obtained may be used in stock assessment and predictions, the intriguing question remains, namely how can the signal of larval productivity from one single spawning component of WBSS herring reflect the year-class dynamics of the entire stock?
Pre-Eclampsia
Authors: Seepana Sreekala , Allamsetty Sudhakar , Simon Chantal
Published: May 2009

Pre-eclampsia is a multisystem syndrome of unknown aetiology peculiar to pregnancy. Between 2003–5, the report on confidential enquiries into maternal and child health (CEMACH) recorded 18 deaths in the UK as a result of pre-eclampsia or eclampsia (0.85 per 100 000 maternities), making this the second leading cause of maternal death. In 72% of these cases, care was deemed substandard.
Bleeding in Early Pregnancy
Authors: Rawal Nikita , Farquharson Roy , Topping Joanne , Simon Chantal
Published: May 2009

Bleeding in pregnancy up to 14 weeks of gestation is common, affecting as many as one in four pregnancies. GPs are expected to distinguish between those women who can be managed at home and those requiring admission.
Acute Breathlessness in Adults
Authors: Zuberi Tahira , Simon Chantal
Published: May 2009

Dyspnoea is the subjective sensation of breathlessness that is excessive for any given level of physical activity. Acute breathlessness is defined as severe dyspnoea evolving rapidly over minutes to hours. The sudden development of dyspnoea heralds, in most cases, a significant cardiopulmonary insult. The aim of this article is to give GPs in training a strategy to deal with acute breathlessness in primary care
Targeted genome editing in human cells with zinc finger nucleases constructed via modular assembly
Authors: Kim Hye Joo , Lee Hyung Joo , Kim Hyojin , Cho Seung Woo , Kim Jin-Soo
Published: May 2009

Broad applications of zinc finger nuclease (ZFN) technology—which allows targeted genome editing—in research, medicine, and biotechnology are hampered by the lack of a convenient, rapid, and publicly available method for the synthesis of functional ZFNs. Here we describe an efficient and easy-to-practice modular-assembly method using publicly available zinc fingers to make ZFNs that can modify the DNA sequences of predetermined genomic sites in human cells. We synthesized and tested hundreds of ZFNs to target dozens of different sites in the humanCCR5gene—a co-receptor required for HIV infection—and found that many of these nucleases induced site-specific mutations in theCCR5sequence. Because human cells that harborCCR5null mutations are functional and normal, these ZFNs might be used for (1) knocking outCCR5to produce T-cells that are resistant to HIV infection in AIDS patients or (2) inserting therapeutic genes at “safe sites” in gene therapy applications.
threo-2-(2,6-Dimethoxyphenoxy)-1-(4-ethoxy-3-methoxyphenyl)propane-1,3-diol
Authors: Ishizuka Kentaro , Ando Daisuke , Watanabe Takashi , Nakamura Masaharu
Published: May 2009

In the crystal structure of the title compound, C20H26O7, a lignin model compound, the asymmetric unit contains two molecules which adopt almost identical overall conformations with some deviation in the region of the terminal hydroxyl groups. The two molecules are linked by an intermolecular O—H...O hydrogen bond. They also develop intramolecular O—H...O hydrogen bonds.
Redetermination of tetrakis(N,N-diethyldithiocarbamato)tin(IV)
Authors: Okio Coco K. Y. A. , Speziali Nivaldo L.
Published: May 2009

The crystal structure of the title compound, [Sn(C5H10NS2)4], was originally determined by Harreld & Schlemper [Acta Cryst.(1971), B27, 1964–1969] using intensity data estimated from Weissenberg films. In comparison with the previous refinement, the current redetermination reveals anisotropic displacement parameters for all non-H atoms, localization of the H atoms, and higher precision of lattice parameters and interatomic distances. The complex features a distorted S6octahedral coordination geometry for tin and acisdisposition of the monodentate dithiocarbamate ligands.
4,5,7-Trimethoxy-2-methyl-3-(2,4,5-trimethoxyphenyl)-1-[3-(2,4,5-trimethoxyphenyl)pentan-2-yl]indane acetone 0.858-solvate
Authors: Liu Chang , Xu Guangyu
Published: May 2009

In the title compound, C36H48O9.0.858C3H6O, the five-membered ring adopts an envelope conformation. The acetone solvent molecule was disordered and was refined over two positions with equal occupancies, giving an overall occupancy of 0.858 (4). There are weak intramolecular C—H...O hydrogen bonds and intermolecular C—H...π interactions in the structure.
2,4-Bis(2-methoxyphenyl)-3-azabicyclo[3.3.1]nonan-9-one
Authors: Parthiban P. , Ramkumar V. , Kim Min Sung , Son Se Mo , Jeong Yeon Tae
Published: May 2009

In the title compound, C22H25NO3, the molecule has a pseudo-mirror plane. The structure is a positional isomer of 2,4-bis(4-methoxyphenyl)-3-azabicyclo[3.3.1]nonan-9-one [Cox, McCabe, Milne & Sim (1985).J. Chem. Soc. Chem. Commun.pp. 626–628]. The 3-azabicyclo[3.3.1]nonan-9-one moiety adopts a double chair conformation with equatorial orientations of both 2-methoxyphenyl substituents on either side of the secondary amino group. The benzene rings are oriented at an angle of 33.86 (4)° with respect to each other and the methoxy groups point towards the carbonyl group. The crystal structure is stabilized by intermolecular N—H...π interactions.
Ethyl 3-nitro-4-(n-propylamino)benzoate
Authors: Zhang Guo-Hua , Wu Yong-Zhong , Li Hao-Yuan , Liu Bo-Nian , Guo Cheng
Published: May 2009

In the molecule of the title compound, C12H16N2O4, an intramolecular N—H...O hydrogen bond results in the formation of a six-membered ring having an envelope conformation. In the crystal structure, a bifurcated intra/intermolecular N—H...(O,O) hydrogen bond generates inversion dimers.
3-(1H-Tetrazol-5-yl)pyridinium chloride
Authors: Dai Jing , Yu Miao-Jia
Published: May 2009

In the cation of the title compound, C6H6N5+·Cl−, the pyridinium and tetrazole rings are nearly coplanar, making a dihedral angle of 5.05 (12)°. The cations and anions are connected by intermolecular N—H...Cl hydrogen bonds, forming a centrosymmetric [2 + 2] aggregate. The aggregates are stacked along theaaxis.
1-[(2-Anilinoethyl)iminiomethyl]-2-naphtholate
Authors: Hao Yu-Mei
Published: May 2009

The title Schiff base compound, C19H18N2O, was prepared by the reaction of equimolar quantities of 2-hydroxy-1-naphthaldehyde withN-phenylethane-1,2-diamine in a methanol solution. The molecule adopts a zwitterionic conformation with the naphthyl OH group deprotonated and the imine N atom protonated. An intramolecular N—H...O hydrogen bond forms between them. The dihedral angle between the benzene ring and the naphthyl system is 86.9 (2)°. In the crystal structure, molecules are linked through intermolecular N—H...O hydrogen bonds, forming chains running along thebaxis.
Polyalanine tracts directly induce the release of cytochrome c, independently of the mitochondrial permeability transition pore, leading to apoptosis
Authors: Toriumi Kazuya , Oma Yoko , Mimoto Ai , Futai Eugene , Sasagawa Noboru , Turk Boris , Ishiura Shoichi
Published: May 2009

In recent years, several novel types of disorder caused by the expansion of triplet repeats in specific genes have been characterized; in the “polyalanine diseases”, these expanded repeats result in proteins with aberrantly elongated polyalanine tracts. In this study, we fused expanded polyalanine tracts to yellow fluorescent protein to examine their physical interaction with mitochondria. Tracts containing more than 23 alanine repeats were found to physically associate with mitochondria, strongly suggesting that an interaction between polyalanine tracts and mitochondria is a contributing factor in the pathology of polyalanine diseases. Furthermore, in in vitro experiments, polyalanine tracts induced release of cytochrome c from mitochondria and caspase‐3 activation, independently of the mitochondrial permeability transition pore. These results suggest that oligomerized polyalanine tracts might induce the rupture of the mitochondrial membrane, the subsequent release of cytochrome c, and apoptosis. This novel mechanism for polyalanine tract cytotoxicity might be common to the pathogenesis of all polyalanine diseases. Further investigation of this mechanism might aid the development of therapies for these diseases.
Effects of chitosan coating and storage position on quality and shelf life of eggs
Authors: Kim Su Hyun , Youn Dal Kyoung , No Hong Kyoon , Choi Sang Won , Prinyawiwatkul Witoon
Published: May 2009

Effects of chitosan coating and storage positions (small‐end down, small‐end up or horizontal) on internal quality and shelf life of eggs were evaluated during 5 weeks of storage at 25 °C. Compared with noncoated eggs, all chitosan‐coated eggs, irrespective of storage positions, had significantly lesser weight loss, higher Haugh units and higher yolk index throughout the storage. Chitosan coating, irrespective of storage positions, extended the egg shelf life by at least 3 weeks at 25 °C compared with noncoated eggs. Noncoated and chitosan‐coated eggs placed small‐end down tentatively showed better quality than eggs placed small‐end up after 3 and 4 weeks of storage. After 5 weeks of storage, storage positions did not significantly affect quality of noncoated and chitosan‐coated eggs. There were no notable differences in total amino acid content of the albumen and fatty acid composition of the yolk between noncoated and chitosan‐coated eggs after 5 weeks of storage.
Potato starch edible films to control oxidative rancidity of polyunsaturated lipids: effects of film composition, thickness and water activity
Authors: Osés Javier , Niza Sandra , Ziani Khalid , Maté Juan I.
Published: May 2009

The objective of this work was to study the effect of potato starch‐based films acting as oxygen barrier on the oxidative rancidity of vegetable oil, as an example of a food rich in polyunsaturated fatty acids. The effect of glycerol (Gly) content (0%, 10%, 20%, 30%), film thickness (30, 60, 100 μm) as well as environmental relative humidity (RH) (50% or 75%) were analysed. Results obtained confirmed that potato starch films delayed the rancidity in vegetable oil. Films without Gly provided the same protection as films with 10% Gly. Films with higher Gly content were not as effective oxygen barrier. It is likely that the fact that film protective capability diminished with increased RH or Gly content was due to the increasing moisture content of the films. Despite that fact, potato starch films can be considered a very efficient oxygen barrier even at RH as high as 75%.
Effect of combining two genes for partial resistance to Barley yellow dwarf virus‐PAV (BYDV‐PAV) derived from Thinopyrum intermedium in wheat
Authors: Jahier J. , Chain F. , Barloy D. , Tanguy A. ‐M. , Lemoine J. , Riault G. , Margalé E. , Trottet M. , Jacquot E.
Published: May 2009

In this study two sources of resistance to Barley yellow dwarf virus (BYDV), both originating from Thinopyrum intermedium, were combined in a single genotype, line ZT, using GISH (genomic in situ hybridization) and a new molecular marker of the partial resistance gene Bdv2. Susceptible wheat cv. Sunstar, the translocation line TC14 carrying Bdv2, the addition line ZH with the group‐2 chromosome arm carrying resistance, and line ZT with both resistances were inoculated with five strains of Barley yellow dwarf virus‐PAV. The tests confirmed the resistance of TC14 and ZH and revealed an additive effect of the two sources of resistance in ZT. The resistance of line ZT was characterized by a proportion of infected plants significantly lower than the parental lines TC14 and ZH (42% vs. a mean of 76% for the parents) and a very low virus titre (area under the virus concentration progress curve of 1·2 vs. a mean on 6·3 for the parents).
Detection of Acidovorax valerianellae in corn‐salad seeds, seed transmission of the pathogen and disease development in the field
Authors: Grondeau C. , Samson R.
Published: May 2009

Acidovorax valerianellae, the causal agent of bacterial black spot of corn salad and responsible for severe economic losses to this vegetable in France, was successfully transmitted to corn‐salad plants by artificially inoculated seeds in glasshouse and field experiments. In the field experiments, climatic data recorded under plastic tunnels indicated that increasing temperature and relative humidity increased symptom development. To investigate the possible contamination of commercial seedlots of corn salad, a seed test was developed consisting of soaking batches of seeds (five batches each of 5000, 1000, 500 and 100 seeds) overnight at 4°C in distilled sterile water, followed by dilution‐plating of seed extracts on TSAV (tryptic soya agar for A. valerianellae) semiselective medium. Suspected colonies were identified by biochemical and pathogenicity tests or, within 24 h, using antibodies specific to A. valerianellae. Acidovorax valerianellae was detected in three lots. Seed infection levels ranged from 0·10 to 0·89% of contaminated seeds and a single seed carried up to 1800 A. valerianellae colony‐forming units.