bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-dimensional ring-like vortex and multisoliton nonlinear structures at the upper-hybrid resonance
Authors: Lashkin V. M.
Published: October 2007

Two-dimensional (2D) equations describing the nonlinear interaction between upper-hybrid and dispersive magnetosonic waves are presented. Nonlocal nonlinearity in the equations results in the possibility of the existence of stable 2D nonlinear structures. A rigorous proof of the absence of collapse in the model is given. Different types of nonlinear localized structures such as fundamental solitons, radially symmetric vortices, nonrotating multisolitons (two-hump solitons, dipoles, and quadrupoles), and rotating multisolitons (azimuthons) have been found numerically. It is shown by direct numerical simulations that 2D fundamental solitons with a negative Hamiltonian are stable.
Complex trajectories sans isochrones: Quantum barrier scattering with rectilinear constant velocity trajectories
Authors: Rowland Brad A. , Wyatt Robert E.
Published: October 2007

One of the major obstacles in employing complex-valued trajectory methods for quantum barrier scattering calculations is the search for isochrones. In this study, complex-valued derivative propagation method trajectories in the arbitrary Lagrangian-Eulerian frame are employed to solve the complex Hamilton-Jacobi equation for quantum barrier scattering problems employing constant velocity trajectories moving along rectilinear paths whose initial points can be in the complex plane or even along the real axis. It is shown that this effectively removes the need for isochrones for barrier transmission problems. Model problems tested include the Eckart, Gaussian, and metastable quadratic+cubic potentials over a variety of wave packet energies. For comparison, the “exact” solution is computed from the time-dependent Schrödinger equation via pseudospectral methods.
The effective viscosity of a channel-type porous medium
Authors: Breugem W.-P.
Published: October 2007

An expression for the effective viscosity (μe) of a homogeneous channel-type porous medium has been derived by matching the Brinkman solution for the macroscopic flow with the volume average of the corresponding Stokes solution for the microscopic flow. In a least-squares error sense, the optimal value for μe is equal to μ(ϵ−3∕7)∕2 for ϵ⩾3∕7 and 0 for ϵ<3∕7, where ϵ is the porosity and μ is the fluid viscosity. Thus, μe<μ for all ϵ. For μe=0, the Brinkman equation reduces to Darcy’s law.
Self-sustained oscillations with acoustic feedback in flows over a backward-facing step with a small upstream step
Authors: Yokoyama Hiroshi , Tsukamoto Yuichi , Kato Chisachi , Iida Akiyoshi
Published: October 2007

Self-sustained oscillations with acoustic feedback take place in a flow over a two-dimensional two-step configuration: a small forward-backward facing step, which we hereafter call a bump, and a relatively large backward-facing step (backstep). These oscillations can radiate intense tonal sound and fatigue nearby components of industrial products. We clarify the mechanism of these oscillations by directly solving the compressible Navier-Stokes equations. The results show that vortices are shed from the leading edge of the bump and acoustic waves are radiated when these vortices pass the trailing edge of the backstep. The radiated compression waves shed new vortices by stretching the vortex formed by the flow separation at the leading edge of the bump, thereby forming a feedback loop. We propose a formula based on a detailed investigation of the phase relationship between the vortices and the acoustic waves for predicting the frequencies of the tonal sound. The frequencies predicted by this formula are in good agreement with those measured in the experiments we performed.
Theoretical understanding of the increment of β upon protonation of pyridine peripheral octupolar molecules: Toward nonlinear optical sensors
Authors: Ruiz Delgado M. Carmen , Orduna Jesús , Moreno Oliva Maria , Casado Juan , López Navarrete Juan T.
Published: October 2007

In this article, we present a computational study of the nonlinear optical properties of pyridine-based octupolar molecules in their neutral and fully triprotonated states. The effect of the core substitution and the degree of conjugation with the periphery has been also established and confirms the possibility of fine-tuning the nonlinear optical response. Computations involving the time-dependent density-functional theory approach serve to further explore the existence of excited states with nonzero dipole moment. From these results, the origin of the high second-order nonlinear optical activity upon protonation is addressed.
Phase lenses and mirrors created by laser micronanofabrication via two-photon photopolymerization
Authors: Chen Qi-Dai , Wu Dong , Niu Li-Gang , Wang Juan , Lin Xiao-Feng , Xia Hong , Sun Hong-Bo
Published: October 2007

The phase lens, also called kinoform, a promising focusing component in an integrated micro-optical system, was produced by femtosecond laser fabrication via two-photon photopolymerization. Kinoforms consisting of two-, four-, eight-level subzones with level thicknesses of 475, 238, and 119nm demonstrate diffraction efficiencies of 30%, 54%, and 68%, respectively, which are comparable with the theoretical limit and with those from the commercial phase lenses. In addition, a reflective diffractive micromirror was proposed and realized with the aid of electroless plating. These works show the promising prospect of femtosecond laser fabrication in manufacturing optical micronanodevices and their integrated system with optical quality.
Nanoscale phase separation in ultrafast pulsed laser deposited arsenic trisulfide (As2S3) films and its effect on plasma etching
Authors: Choi Duk-Yong , Madden Steve , Rode Andrei , Wang Rongping , Luther-Davies Barry
Published: October 2007

We have observed nanoscale phase separation in amorphous arsenic trisulfide (As2S3) films produced by ultrafast pulsed laser deposition and its effect on the surface morphology of the film after plasma etching. When the film was etched in CF4–O2 plasma, a grainy structure was observed on the surface. From Raman and x-ray photoelectron spectroscopies, we concluded that the grainy structure of the etched surfaces comes from the differential chemical attack between different phases in the film.
Doping effect on complex permeability and permittivity for W-type barium ferrite composites
Authors: Li Z. W. , Wu Y. P , Lin G. Q.
Published: October 2007

Doping effects on crystal structure, static, and dynamic magnetic properties have been investigated for BaCoZnFe16O27 doped with 0.5 wt % CaO, Bi2O3, SiO2, 0.5 and 1.0 wt % Nb2O5 and V2O5, as well as their ferrite/epoxy composites. The results show that the doping can greatly modify the high-frequency dynamic properties of the composites. As compared to the undoped composite, doping of CaO, Bi2O3, and SiO2 significantly increases complex permittivities ϵ′ and ϵ″. The increase has its origin in the formation of Fe2+ ions caused by the doping. Doping of CaO, Bi2O3, Nb2O5, and V2O5 leads to a considerable increase in static permeability μ0′. Further, the doping of V2O5 can significantly increase the maximum imaginary permeability μmax″. Based on the curve-fitted results to complex permeability spectra, the former is attributed to the enhanced wall permeability and the latter is related to the decrease in effective damping coefficient. However, the resonance is shifted to lower frequency for all composites doped with various oxides.
Study of one-dimensional Bragg structures with localized defect
Authors: Konoplev I. V. , MacInnes P. , Cross A. W. , Phelps A. D. R. , Ronald K.
Published: October 2007

The results of studies of one-dimensional Bragg structures (one-dimensional periodic lattice) with localized defects are presented. The defects considered are localized, step changes (shifts) of the lattice phase (corrugation). The influence of the defects on the periodic lattice band-gap parameters has been analyzed. The presence of the defect resulted in the appearance of a pass band, associated with the defect eigenmode, inside the lattice band gap and it was demonstrated that the position of the pass band depended strongly on the parameters of the defect as well as the field structure. The experimental and theoretical results obtained are compared and discussed.
Proton dynamics in ZnO nanorods quantified by in situ solid-state H1 nuclear magnetic resonance spectroscopy
Authors: Wang Li-Qiong , Zhou Xiao-Dong , Exarhos Gregory J. , Pederson Larry R. , Wang Chongmin , Windisch Charles F. , Yao Chunhua
Published: October 2007

In situ solid-state H1 NMR spectroscopy was employed to investigate the local chemical environments and dynamic details of protons in ZnO nanorods. The mean correlation time for the 4.8ppm resonance was found to be ∼2.1×10−10s at 500K and the activation energy for proton hopping was ∼0.15eV. Both the small activation energy and short correlation time suggest that the protons are mobile. In contrast to nanometer micrometer particles of ZnO, γ-Al2O3, and CeO2, a stable resonance at 4.8ppm indicates that these proton species are most likely associated with the defect sites in the lattice of ZnO nanorods.
Transport of light in amorphous photonic materials
Authors: Reufer Mathias , Rojas-Ochoa Luis Fernando , Eiden Stefanie , Sáenz Juan José , Scheffold Frank
Published: October 2007

Amorphous photonic materials based on dense assemblies of high refractive index spherical particles are presented. Light transmission through these photonic glasses shows a nontrivial wavelength dependence. The transmission spectra can be quantitatively reproduced by modeling the optical properties starting from their building blocks. Our results emphasize the relevance of including short range order correlations and an appropriate effective refractive index in the analysis of light transmission through amorphous photonic materials.
Vibrational property and Raman spectrum of carbon nanoribbon
Authors: Zhou Jian , Dong Jinming
Published: October 2007

The vibrational property and Raman spectra of carbon nanoribbons (CNRs) have been systematically studied by the density functional theory in the local density approximation. It is found that for all CNRs there are three typical Raman-active modes, i.e., the radial-breathing-like mode (RBLM), the localized mode and the graphene E2g-like one, which are helpful to identify different CNRs in the Raman experiments. Among them, the RBLM is the most characteristic one, whose frequency decreases with the increasing CNR width in a linear proportion to the inverse square root of the width, making it very useful to determine the CNR width experimentally.
PbS colloidal quantum dot photoconductive photodetectors: Transport, traps, and gain
Authors: Konstantatos Gerasimos , Sargent Edward H.
Published: October 2007

We investigate experimentally the origins of gain in PbS colloidal quantum dot photodetectors. We employ measurements of photocurrent, its transient behavior, and dark current over a wide range of temperatures. We find the hole mobility to have an activation energy of 0.16eV, and we identify photosensitizing centers at ∼0.1, 0.2, and 0.3eV below the conduction band edge. These centers account for the 60, 300, and 2000ms fall times observed in the transient response of the photocurrent at room temperature. These centers enable us to account for the constancy of photoconductive gain across the wide temperature range of 250–340K.
Carrier capture cross sections of deep gap states at the interfacial grain boundary in a (110)∕(100) bonded silicon wafer
Authors: Lu Jinggang , Rozgonyi George
Published: October 2007

This letter examines hole emission processes at a (110)∕(100) grain boundary in a hybrid orientation direct-silicon-bonded p-type Si wafer. The near surface boundary position permits easy control of the charge density at the grain boundary via an applied reverse bias and simultaneous monitoring of the hole emission rate by the leakage current. It was found that, for states below the middle bandgap, those close to the valance band edge have relatively smaller hole capture cross sections than those at higher energy position, and electron capture cross sections are at least two or three orders larger than the corresponding hole capture cross sections.
The sensitivity of gas sensor based on single ZnO nanowire modulated by helium ion radiation
Authors: Liao L. , Lu H. B. , Li J. C. , Liu C. , Fu D. J. , Liu Y. L.
Published: October 2007

In this letter, we present a gas sensor using a single ZnO nanowire as a sensing unit. This ZnO nanowire-based sensor has quick and high sensitive response to H2S in air at room temperature. It has also been found that the gas sensitivity of the ZnO nanowires could be modulated and enhanced by He+ implantation at an appropriate dose. A possible explanation is given based on the modulation model of the depletion layer.
Size-dependent thermal instability and melting behavior of Sn nanowires
Authors: Shin Ho Sun , Yu Jin , Song Jae Yong
Published: October 2007

Thermal instability and melting behavior of tin nanowires were studied with a decrease of wire radius(rNW=7–30nm) via differential scanning calorimetry (DSC). Two sequential DSC measurements showed a 1∕rNW dependency of the melting temperature depression; the first melting temperature decreased from 502to486K with 1∕rNW whereas the second one was more depressed between 0.8 and 5K. The melting temperature difference between the first and second cycles increased linearly with 1∕rNW. This variation was attributed to fragmentation of nanowires due to Rayleigh instability. Here, fragmentation of long nanowires was suppressed by a template confinement, resulting in the formation of short nanorods.
D. R. Congo: Explaining Peace Building Failures, 2003-2006
Authors: Autesserre Séverine
Published: October 2007

As a corrective to the emphasis on national and international reconciliation during peace building processes, I develop here a conceptual analysis of the dynamics of violence during the transition from war to peace and democracy in the Democratic Republic of Congo between 2003 and 2006. I locate the sources, at the local, national, and regional levels, of continued local violence during this transition. Through an analysis of the situation in the provinces of North Kivu and North Katanga, I illustrate how local dynamics interacted with the national and regional dimensions of the conflict. I demonstrate that, after a national and regional settlement was reached, some local conflicts over land and political power increasingly became self-sustaining, autonomous, and disconnected from the national and regional tracks. Thus, peace building action was required not only at the national and regional levels but also locally.
The Auslander-Reiten translation in submodule categories
Authors: Ringel Claus , Schmidmeier Markus
Published: October 2007

Let

Λ
\Lambda

be an artin algebra or, more generally, a locally bounded associative algebra, and

S

(
Λ
)

\mathcal {S}(\Lambda )

the category of all embeddings

(
A
⊆
B
)

(A\subseteq B)

where

B
B

is a finitely generated

Λ
\Lambda

-module and

A
A

is a submodule of

B
B

. Then

S

(
Λ
)

\mathcal {S}(\Lambda )

is an exact Krull-Schmidt category which has Auslander-Reiten sequences. In this manuscript we show that the Auslander-Reiten translation in

S

(
Λ
)

\mathcal {S}(\Lambda )

can be computed within

mod

Λ

\operatorname {mod}\,\Lambda

by using our construction of minimal monomorphisms. If in addition

Λ
\Lambda

is uniserial, then any indecomposable nonprojective object in

S

(
Λ
)

\mathcal {S}(\Lambda )

is invariant under the sixth power of the Auslander-Reiten translation.
Intransitive Cartesian decompositions preserved by innately transitive permutation groups
Authors: Baddeley Robert , Praeger Cheryl , Schneider Csaba
Published: October 2007

A permutation group is innately transitive if it has a transitive minimal normal subgroup, which is referred to as a plinth. We study the class of finite, innately transitive permutation groups that can be embedded into wreath products in product action. This investigation is carried out by observing that such a wreath product preserves a natural Cartesian decomposition of the underlying set. Previously we classified the possible embeddings in the case where the innately transitive group projects onto a transitive subgroup of the top group. In this article we prove that the transitivity assumption we made in the previous paper was not too restrictive. Indeed, the image of the projection into the top group can only be intransitive when the finite simple group that is involved in the plinth comes from a small list. Even then, the innately transitive group can have at most three orbits on an invariant Cartesian decomposition. A consequence of this result is that if

G
G

is an innately transitive subgroup of a wreath product in product action, then the natural projection of

G
G

into the top group has at most two orbits.
Filtrations in semisimple Lie algebras, II
Authors: Barnea Y. , Passman D.
Published: October 2007

In this paper, we continue our study of the maximal bounded

Z

\mathbb {Z}

-filtrations of a complex semisimple Lie algebra

L
L

. Specifically, we discuss the functionals which give rise to such filtrations, and we show that they are related to certain semisimple subalgebras of

L
L

of full rank. In this way, we determine the “order” of these functionals and count them without the aid of computer computations. The main results here involve the Lie algebras of type

E
6

E_6

,

E
7

E_7

and

E
8

E_8

, since we already know a good deal about the functionals for the remaining types. Nevertheless, we reinterpret our previous results into the new context considered here. Finally, we describe the associated graded Lie algebras of all of the maximal filtrations obtained in this manner.
On symplectic fillings of lens spaces
Authors: Lisca Paolo
Published: October 2007

Let

ξ
¯

st

\overline \xi _\textrm {st}

be the contact structure naturally induced on the lens space

L
(
p
,
q
)
=

S
3

/

Z

/

p

Z

L(p,q)=S^3/\mathbb {Z}/p\mathbb {Z}

by the standard contact structure

ξ

st

\xi _\textrm {st}

on the three–sphere

S
3

S^3

. We obtain a complete classification of the symplectic fillings of

(
L
(
p
,
q
)
,

ξ
¯

st

)

(L(p,q),\overline \xi _\textrm {st})

up to orientation–preserving diffeomorphisms. In view of our results, we formulate a conjecture on the diffeomorphism types of the smoothings of complex two–dimensional cyclic quotient singularities.
Asymptotic spectral analysis of growing regular graphs
Authors: Hora Akihito , Obata Nobuaki
Published: October 2007

We propose the quantum probabilistic techniques to obtain the asymptotic spectral distribution of the adjacency matrix of a growing regular graph. We prove the quantum central limit theorem for the adjacency matrix of a growing regular graph in the vacuum and deformed vacuum states. The condition for the growth is described in terms of simple statistics arising from the stratification of the graph. The asymptotic spectral distribution of the adjacency matrix is obtained from the classical reduction.
Linear differential equations with coefficients in weighted Bergman and Hardy spaces
Authors: Heittokangas Janne , Korhonen Risto , Rättyä Jouni
Published: October 2007

Complex linear differential equations of the form
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartLayout 1st Row with Label left-parenthesis reverse-solidus dagger right-parenthesis EndLabel f Superscript left-parenthesis k right-parenthesis Baseline plus a Subscript k minus 1 Baseline left-parenthesis z right-parenthesis f Superscript left-parenthesis k minus 1 right-parenthesis Baseline plus midline-horizontal-ellipsis plus a 1 left-parenthesis z right-parenthesis f Superscript prime Baseline plus a 0 left-parenthesis z right-parenthesis f equals 0 EndLayout">

(\dagger)

f

(
k
)

+

a

k
−
1

(
z
)

f

(
k
−
1
)

+
⋯
+

a
1

(
z
)

f
′

+

a
0

(
z
)
f
=
0

\begin{equation}\tag {\dagger } f^{(k)}+a_{k-1}(z)f^{(k-1)}+\cdots +a_1(z)f’+a_0(z)f=0 \end{equation}

with coefficients in weighted Bergman or Hardy spaces are studied. It is shown, for example, that if the coefficient

a
j

(
z
)

a_j(z)

of

(
†
)

(\dagger )

belongs to the weighted Bergman space

A
α

1

k
−
j

A^\frac {1}{k-j}_\alpha

, where

α
≥
0

\alpha \ge 0

, for all

j
=
0
,
…
,
k
−
1

j=0,\ldots ,k-1

, then all solutions are of order of growth at most

α
\alpha

, measured according to the Nevanlinna characteristic. In the case when

α
=
0

\alpha =0

all solutions are shown to be not only of order of growth zero, but of bounded characteristic. Conversely, if all solutions are of order of growth at most

α
≥
0

\alpha \ge 0

, then the coefficient

a
j

(
z
)

a_j(z)

is shown to belong to

A
α

p
j

A^{p_j}_\alpha

for all

p
j

∈
(
0
,

1

k
−
j

)

p_j\in (0,\frac {1}{k-j})

and

j
=
0
,
…
,
k
−
1

j=0,\ldots ,k-1

. Analogous results, when the coefficients belong to certain weighted Hardy spaces, are obtained. The non-homogeneous equation associated to

(
†
)

(\dagger )

is also briefly discussed.
Level sets of scalar Weyl invariants and cohomogeneity
Authors: Console Sergio , Olmos Carlos
Published: October 2007

We prove that the cohomogeneity of a Riemannian manifold coincides locally with the codimension of the foliation by regular level sets of the scalar Weyl invariants.
A Minkowski-style theorem for focal functions of compact convex reflectors
Authors: Oliker Vladimir
Published: October 2007

This paper continues the study of a class of compact convex hypersurfaces in

R

n

,
 
n
≥
1
,

\mathbf {R}^n, ~n \geq 1,

which are boundaries of compact convex bodies obtained by taking the intersection of (solid) confocal paraboloids of revolution. Such hypersurfaces are called reflectors. In

R

3

\mathbb {R}^3

reflectors arise naturally in geometrical optics and are used in design of light reflectors and reflector antennas. They are also important in rendering problems in computer graphics. The notion of a focal function for reflectors plays a central role similar to that of the Minkowski support function for convex bodies. In this paper the basic question of when a given function is a focal function of a convex reflector is answered by establishing necessary and sufficient conditions. In addition, some smoothness properties of reflectors and of the associated directrix hypersurfaces are also etablished.
Guidelines for Prevention of Cardiovascular Disease in Women: A Summary of Recommendations
Authors: Mosca Lori
Published: October 2007

Cardiovascular disease (CVD) is a major cause of mortality in women. The first evidence‐based guidelines for the prevention of CVD in women were developed in 2004 and updated this year. The 2007 guidelines place more emphasis on women's overall lifetime coronary heart disease risk, as opposed to short‐term absolute risk, than did the 2004 recommendations. Depending on the criteria met, women are classified as being at high risk, at risk, or at optimal risk. The authors provide an overview of the recommendations in the 3 different categories: lifestyle interventions, major risk factor interventions, and preventive drug interventions.
PRO: Should Aspirin Be Used in All Women Older Than 65 Years to Prevent Stroke?
Authors: Hsia Judith
Published: October 2007

A number of studies have reported that aspirin is beneficial in the prevention of cardiovascular disease. A meta‐analysis of data from 3 studies of the cardioprotective effect of aspirin in women has reported that use of aspirin reduces the risk of coronary events mainly by reducing the risk of ischemic stroke. Results of the Women's Health Study showed that although there is a risk of bleeding events with aspirin use, overall this risk is outweighed by the number of strokes prevented.
H
2

∕

H
∞

Robust Static Output Feedback Control Design Without Solving Linear Matrix Inequalities
Authors: Toscano R.
Published: October 2007

In this paper, we investigate the problem of robust synthesis of a static output feedback controller, with guaranteed H2∕H∞ cost, in the context of multiple parametric uncertainties. To solve this problem, a random optimization technique based on a bisection method is proposed. The principle is as follows: For a given initial stabilizing controller of the nominal system, the proposed approach iteratively generates a sequence of matrices with a decreasing H2∕H∞ cost. By a bisection method, this procedure is stopped when the controller reaches the best possible nominal performance that satisfies a given guaranteed H2∕H∞ cost. Numerical examples show the practical applicability of the proposed method.
A New Development of Internal Combustion Engine Air-Fuel Ratio Control With Second-Order Sliding Mode
Authors: Wang Shiwei , Yu D. L.
Published: October 2007

A novel application of a second-order sliding mode control (SMC) scheme to the air-fuel ratio (AFR) control of automobile internal combustion engines is developed in this paper. In this scheme, the sliding surface S[x(t)] is steered to zero in finite time by using the discontinuous first-order derivative of a control variable u̇c(t), and the corresponding actual control variable uc(t) turns out to be continuous, which significantly reduces the undesired chattering. Its sliding gain is adjusted by a novel radial basis function network based adaptation method derived using the Lyapunov theory. It not only avoids handling the unavailable parameters and variables, but also saves the unnecessary manual adjusting time of the second-order SMC. The proposed method is applied to a widely used engine benchmark, the mean value engine model for evaluation. The simulation results show substantially improved AFR control performance compared with the conventional SMC.
Sliding Mode Output Feedback Control of Vibration in a Flexible Structure
Authors: Pai M. C. , Sinha A.
Published: October 2007

This paper presents a new approach for the robust control of vibration in a flexible structure in the presence of uncertain parameters and residual modes. The technique is based on the sliding mode control algorithm using direct output feedback and assumes that actuators and sensors are not collocated. The uncertainty matrix need not satisfy the invariance or matching conditions. The small gain theorem/μ analysis is applied to analyze the asymptotic behavior of the closed-loop system with parametric uncertainties inside boundary layers. The model of a flexible tetrahedral truss structure is used to conduct numerical verification of the theoretical analysis.
Specified-Deflection Command Shapers for Second-Order Position Input Systems
Authors: Robertson Michael J. , Singhose William E.
Published: October 2007

This paper documents new command shapers designed to both eliminate the residual vibration and reduce the transient deflection of a flexible system. Equations are derived to predict both the residual vibration and the transient deflection for a mass-spring-damper system with position input, or equivalently, a mass under PD control. The solution of equations containing constraints on both the transient deflection and the residual vibration leads to the creation of specified-deflection, zero-vibration command shapers. These specified-deflection shapers limit the transient deflection to a predetermined ratio of the base line deflection resulting from an arbitrary reference command. Computer simulations and experiments on a bridge crane verify the efficacy of the new command shapers.
Radius of Gyration of a Sphere and a Barrel
Authors: Leung Alfred F.
Published: October 2007

This paper describes a method for measuring the radius of gyration of a circular object. In the experiment a circular object rolls down an elevated incline and then falls freely to the ground. Its radius of gyration is determined by its initial height on the incline, as well as the height and range of the free fall. The determination relies on many basic concepts, such as rolling without slipping, relationship between translation and rotational kinetic energies, conservation of energy, and equations of motion for free fall. The method is applied to measure the radius of gyration of a sphere and a barrel. The apparatus is so simple that students can do the experiment at home.
Two Physical Phenomena in One Experiment
Authors: Torres José Naranjo
Published: October 2007

In the physics laboratory, apparatus is normally used to illustrate a single theory or physical law. The apparatus used to study the principle of linear thermal expansion of solids, such as that manufactured by PASCO scientific,1 provides a bonus. In addition to using this apparatus for its original purpose, it can also be used to illustrate Newton's law of cooling in the course of a single laboratory period.
Stress reaction of the humerus in tennis players
Authors: Silva Rogerio Teixeira , Hartmann Luis Guilherme , de Souza Laurino Cristiano Frota
Published: October 2007

Background:

Overuse injuries are a frequent occurrence among competitive athletes. When analysing the incidence of overuse injuries in tennis players, it has been determined that a significant number of these injures occur in the upper limb area. In this study, we describe five cases of a stress-induced injury to the middle and distal humerus occurring mainly due to repetitive serving.

Methods:

Athletes studied were competitive tennis players and elite junior players, two of whom played at international level. Four of the five were male. In all cases, diagnosis was confirmed by magnetic resonance imaging examination. The treatment of middle and distal humeral stress reactions consisted of physical therapy, which focused on analgesia and muscle strengthening. In addition, we analysed each tennis player’s strokes in order to identify modifications that would decrease the amount of stress that the upper limbs were subjected to during the service motion.

Results:

The players in our study missed on average 3 weeks of play and at follow-up after 1 year were able to play symptom free.

Conclusions:

Our study highlights the need for coaches, physicians and players to be aware of distal humeral pain and understand treatment options in order to prevent further injury, including stress fractures.
The continuing story of nutritional supplements and doping infractions: Table 1
Authors: de Hon Olivier , Coumans Bart
Published: October 2007

Nutritional supplements can be a source of positive doping cases as some supplements contain prohibited substances without showing this on their label. This problem has existed for some time and has been extensively studied in the past 8 years. The sport of tennis has played a particular role in this problem because of some peculiar doping cases within its community.

This article focuses on this particular doping problem, explaining the background and reviewing the available literature. It presents the first 3 years of experience within the Netherlands Security System Nutritional Supplements Elite Sports (“Nederlands Zekerheidssysteem Voedingssupplementen Topsport” or NZVT) and explains the most extensive system established to combat this particular doping problem.

The NZVT experience has shown that paper-based quality systems are still prone to possible contaminations, which leads to the conclusion that the best possible solution for athletes who wish to use nutritional supplements must include laboratory-based analysis for doping substances, preferably repeated for every new batch. The most important educational message, however, is to use a nutritional supplement only if it is deemed of benefit by a nutritional expert.
Effects of girdling and gibberellin A4/7 on flowering of European and Japanese larch grafts in an outdoor clone bank
Authors: Philipson J.J.
Published: October 2007

Field-grown European larch (Larixdecidua Mill.) and Japanese larch (Larixkaempferi (Lamb.) Carr.) grafts were treated with main-stem girdling applied with or without injection of gibberellin A4/7 (GA4/7). The level of female coning was low in the untreated trees and was significantly increased by girdling; the mean number of seed cones per tree, on trees receiving girdling alone, was 71 for the European larch and 50 for the Japanese larch. There was considerable male flowering on the untreated trees, (701 and 1208 cones per tree on the European and Japanese larch, respectively), and on trees receiving girdling alone there were 1356 pollen cones per tree on the European larch, and 2035 on the Japanese larch, representing increases of 94 and 68%, respectively, compared with the untreated trees. The overall girdling effect on male flowering, however, was not statistically significant for either species. GA4/7 application produced no significant increases in coning, and in fact fewer pollen cones were observed on GA4/7-treated grafts than on grafts without GA4/7. Between 6 and 12% of the pollen-cone buds on untreated trees did not flush successfully, and the GA4/7 application significantly increased this proportion of unflushed buds. Girdling is an easy and effective treatment to increase female coning of European and Japanese larch and may also result in increases in pollen cones; thus, it would be a useful treatment to assist in the breeding of these species and the production of their hybrid (Larix ×eurolepis A. Henry).
Inoculum concentration and time of application of Gliocladiumroseum in relation to biocontrol of Botrytiscinerea in black spruce seedlings
Authors: Zhang P.G. , Sutton J.C. , Hopkin A.A.
Published: October 2007

Inoculum concentration and time of application of Gliocladiumroseum Bainier were examined in relation to sporulation of Botrytiscinerea Pers.:Fr. in container-grown seedlings of black spruce (Piceamariana (Mill.) BSP) in greenhouses. Gliocladiumroseum concentrations ranging from 102 to 108 conidia/mL water plus surfactant, applied four times at 2- to 4-week intervals starting when the seedling canopies closed, increasingly suppressed the proportion of seedlings with sporulation of B. cinerea (YI) during early and midphases of epidemics, and the proportion of shoot length with sporulation of the pathogen (YS) throughout the epidemics. Concentrations of 106 and 108 conidia/mL suppressed YI and YS as or more effectively than did chlorothalonil (1.4 g active ingredient/L water) applied at the same times. One application of G. roseum (106 conidia/mL) when the seedling canopies were closing suppressed YS as effectively as did programs of two to six applications of the antagonist, or six of chlorothalonil, all at 1- and 2-week intervals beginning at canopy closure. The various programs generally did not affect YI. Logistic and Gompertz regression models were developed that adequately described YI and YS as functions of inoculum concentration and (or) time. It is concluded that G. roseum has potential as a biological control agent against B. cinerea in production systems of black spruce seedlings.
Hydrology and microtopography effects on northern white-cedar regeneration in Michigan's Upper Peninsula
Authors: Chimner Rodney A. , Hart James B.
Published: October 2007

Many harvested northern white-cedar (Thujaoccidentalis L.) sites have not regenerated to cedar but have become dominated by other species such as balsam fir (Abiesbalsamea (L.) Mill.) and tag alder (Alnusrugosa (Du Roi) Spreng.) A regenerating cedar fen near Escanaba, Mich., was used to study factors related to regeneration success and failure. Twelve plots (6.1 × 6.1 m) were established on the site to collect data on hydrology, microtopography, stand composition, and stem density. Abundance of cedar regeneration was positively correlated with percentage of hummocks. There were more cedar on microsites with drier conditions (numerous hummocks) while more shrubs and hardwoods were found on the wetter areas (fewer hummocks) of the fen. The shallow depth to groundwater and unsaturated soil thickness early in the growing season are suggested to be factors.
Comparison of small-mammal community responses to broadcast burning and herbicide application in cutover forest habitats
Authors: Sullivan Thomas P. , Boateng Jacob O.
Published: October 2007

This study was designed to compare the responses of small-mammal communities to broadcast burning and herbicide-induced alteration of forest habitats. Study areas were located in south-coastal British Columbia, Canada, in the Coastal Western Hemlock (CWHdm) biogeoclimatic zone, and in west-central British Columbia in the Sub-boreal Spruce (SBSmk) and Engelmann Spruce–Subalpine Fir (ESSFmc) zones. Control–treatment comparisons for a herbicide application or a broadcast burning treatment were conducted at the coastal study area from 1982 to 1984. Replicate control–treatment comparisons between these two silvicultural practices were conducted at the interior study area within the period 1989 to 1992. Small-mammal populations were intensively livetrapped in all control and treatment blocks. Deer mouse (Peromyscusmaniculatus Wagner) populations showed short-term (1–2 months) declines after treatments at the coastal study area but appeared little affected by these habitat alterations at the interior area. Voles of the genus Microtus disappeared from burned blocks at the interior area but Microtusoregoni (Merriam) persisted on the burned block at the coastal area; however, the red-backed vole (Clethrionomysgapperi Vigors) did not. Chipmunks (Eutamiastownsendii Bachman and Eutamiasamoenus Allen) were little affected by either treatment. Neither treatment seemed to affect species diversity of these small-mammal communities. In terms of abundance of small-mammal populations, it is likely that broadcast burning is a more extreme means of habitat alteration than herbicide treatment.
Temperature changes along the Gulf of Alaska and the Pacific Northwest coast modeled from coastal tree rings
Authors: Wiles Gregory C. , D'Arrigo Rosanne D. , Jacoby Gordon C.
Published: October 2007

Warm-season (April–September) temperature models based on a network of coastal ring-width and maximum latewood density tree-ring chronologies are the first reconstructions for coastal stations along the Gulf of Alaska and the Pacific Northwest. These well-verified temperature models are consistent with long climatic series from coastal stations and other proxy data from the Pacific coast. Cool summers during the 1850s and late 1800s in the Gulf of Alaska correspond to general glacier advance from the region. The Pacific Northwest reconstruction shows summer temperatures cooling in the early 1800s, coincident with a maximum of glacier activity in the coastal Olympic Mountains, Washington. The two warm-season temperature records show intervals when anomalies are opposite in sign, most notably during the 1850s, when cooling is inferred for the Gulf and warming is inferred for the Pacific Northwest. The records are coherent, however, during other intervals, with both showing cooling in the early 1800s and warming around 1870. The phase of these two records may reflect decadal changes in large-scale circulation in the northeastern Pacific. These land temperature reconstructions are strongly correlated with nearby sea surface temperatures, indicating large-scale oceanic–atmospheric influences.
pH distribution in radial sections of the stem and root of Cryptomeriajaponica
Authors: Satake Kenichi , Nakaya Ken , Takamatsu Takejiro
Published: October 2007

The pH distribution in the outer bark, inner bark, cambium, and xylem layer of a conifer, Cryptomeriajaponica, was measured using an iridium oxide electrode and a flat-type glass electrode. The outer bark of C. japonica was strongly acidic, and there was a difference in pH between the outer and inner bark. The outer bark had a pH of about 3 from the surface to the inside. The inner bark pH was about 4 at the outer bark side and about 6 near the cambium side. The pH was maximal (about 6.3) in the cambium, and slightly lower in the outer xylem. pH values determined in subsections of the outer bark after chemical washing with pure water, hydrochloric acid, barium chloride, and formic acid suggested that water-insoluble carboxyl (—COOH) groups bound to organic polymers contribute to the strong acidity of the outer bark.
A comparison of crown asymmetry between Piceaabies and Betulamaximowicziana
Authors: Umeki Kiyoshi
Published: October 2007

not available
Technical efficiency and industry evolution in southern U.S. pulpwood harvesting
Authors: Carter Douglas R. , Cubbage Frederick W.
Published: October 2007

This research measures technical efficiency among methods of pulpwood harvesting in the southern United States in 1979 and 1987. An econometric frontier production function is modeled using analysis of covariance methods, which results in consistent estimates of method effects. Employed efficiency measures isolate economies of scale from what can be termed pure technical efficiency. Harvesting methods utilizing either extremely low or high capitalization levels were the most technically efficient. Longwood grapple skidder systems were the most efficient, and intermediate systems least efficient. This suggests a noncontinuous improvement in harvesting technology that has investment implications for small producers interested in upgrading low capitalization systems. Scale economies represented only a small percentage of the total efficiency effect, the rest being attributed to efficiency of method. Thus, too much emphasis may be placed on the impacts of scale economies when analyzing structural change in the industry. Efficiency measures correlate well with the observed evolution of the industry over the period and conform with the predictions of economic theory.
Age and size structure of natural and second-growth peatland Piceamariana stands
Authors: Groot Arthur , Horton Brian J.
Published: October 2007

Age and size structures were determined in 40 stands of black spruce (Piceamariana (Mill.) B.S.P.) growing on peatlands and transitional peatlands in northeastern Ontario, Canada. Natural and second-growth stands representing several site types were examined. The age structure of natural black spruce stands varied from even aged in young stands (<160 years) to uneven aged in older stands. Uneven-aged black spruce stands on nutrient-poor peats appear to be self perpetuating in the absence of intense disturbance. Natural stands on more fertile peats or on transitional peatlands are less likely to escape disturbance and more likely to undergo succession to other species. Second-growth stands, which originated after forest harvesting 50–70 years ago, were uneven-aged, although a high frequency of stems commonly occurred in the age-class associated with the time of harvesting. The age and size structures of second-growth stands currently differ from that of natural stands, but will likely become similar to natural stands over time.
Relationship of snowshoe hare feeding preferences to nutrient and tannin content of four conifers
Authors: Rangen Sheila A. , Hawley Alex W.L. , Hudson Robert J.
Published: October 2007

The relative preferences of snowshoe hares for native and exotic tree species and the relationship of these preferences to nutritional constituents and phenols have important forestry management implications. Thus, feeding preferences of confined snowshoe hares (Lepusamericanus Erxleben) for Siberian larch (Larixsibericus (Endl.) Sabine ex Trautv.), Norway spruce (Piceaabies (L.) Karst.), white spruce (Piceaglauca (Moench) Voss), and black spruce (Piceamariana (Mill.) B.S.R) were examined under two experimental ad libitum feeding conditions. At the end of experiment 1, two-year-old Siberian larch and Norway spruce were equally selected by hares. Twigs and stems of Siberian larch, however, were browsed almost exclusively during the first few days of the experiment, while white spruce was browsed very little at all. Siberian larch was richer in crude protein and lower in fiber than white spruce and Norway spruce, whereas Norway spruce was lower in condensed tannins and total phenols than the other two species. In experiment 2, twigs and stems of 4-year-old black spruce were preferred to those of white spruce. Black spruce contained significantly higher concentrations of crude protein, calcium, and phosphorus and lower concentrations of cellulose and total phenols than white spruce. Overall, white spruce was most resistant to hare damage, though the lack of preference was not reflected in either low nutrient or high tannin values. In fact, concentrations of condensed tannins and total phenols had no antifeedant effects.
Seasonal changes in shoot and root production and in carbohydrate content of salmonberry (Rubusspectabilis) rhizome segments from the central Oregon Coast Ranges
Authors: Zasada John C. , Tappeiner III John C. , Maxwell Bruce D. , Radwan M.A.
Published: October 2007

An extensive rhizome system is an important aspect of the morphology and architecture of salmonberry (Rubusspectabilis Pursh) and of its potential for regrowth following disturbance. Seasonal activity of the rhizome system was studied by collecting rhizome segments monthly from February through October 1988 and February 1989 from four sites. Total nonstructural carbohydrate content was determined and segments were incubated in a growth chamber to determine periodicity of shoot and root production. The number and dry weight of shoots peaked in February and March, declined from April through June when aboveground shoot growth was greatest and were generally low through the dry summer months. Root production was highest from August through October and generally lower the rest of the year. Total nonstructural carbohydrate content was highest during the dormant season and dropped to the lowest level in midsummer. Shoot production was more closely associated with total nonstructural carbohydrate content than was root production. The significant reduction in shoot production potential suggests a time in the annual growth cycle when the species capacity for regrowth following disturbance is at a relatively low level.
Growth and foliar nutrition of western red cedar fertilized with sewage sludge, pulp sludge, fish silage, and wood ash on northern Vancouver Island
Authors: McDonald M.A. , Hawkins B.J. , Prescott C.E. , Kimmins J.P.
Published: October 2007

The fertilizer efficacy of a variety of organic wastes was tested in a 9-year-old plantation of western red cedar (Thujaplicata Donn ex D. Don) growing on a cutover of cedar–hemlock (Tsugaheterophylla (Raf.) Sarg.) forest on northern Vancouver Island. Seven treatments were compared: municipal sewage sludge, sewage sludge plus pulp sludge, fish silage and wood ash, silage and ash plus pulp sludge, wood ash alone, ammonium nitrate with triple super phosphate, and control (untreated). Each treatment was replicated three times. Rates of application were 225 kg N•ha−1 in the inorganic fertilizer and about 500 kg N•ha−1 in the organic wastes (except wood ash). The height and diameter of the cedar trees 2 years after fertilization were greatest in the plots treated with inorganic fertilizer (average height was 274 cm, vs. 211 cm in control plots; average diameter at 30 cm was 49 mm, vs. 34 mm in control plots). Smaller but significant growth responses were achieved with sewage sludge and fish silage plus ash. Mixtures of sewage sludge or silage with pulp sludge produced smaller height growth responses, but did not affect diameter growth. Wood ash alone had no effect on tree growth. All treatments except wood ash increased the concentrations of macronutrients in foliage. Foliar N concentrations were greatest in trees treated with fish silage or inorganic fertilizer. Stagnated plantations of western red cedar appear to provide an opportunity for recycling these organic wastes.