bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical characterization of p-type N-polar and Ga-polar GaN grown by metalorganic chemical vapor deposition
Authors: Fichtenbaum N. A. , Schaake C. , Mates T. E. , Cobb C. , Keller S. , DenBaars S. P. , Mishra U. K.
Published: October 2007

We report on Mg-doped N-polar and Ga-polar GaN films grown by metal organic chemical vapor deposition (MOCVD). The bis-cyclopentadienyl magnesium flow was varied from 64to640nmol∕min, for N-polar and Ga-polar samples, while other growth conditions were held constant. The sample surfaces were characterized by atomic force microscopy. Electrical measurements were made to determine the resistivity, specific contact resistance, carrier concentrations, mobilities, and activation energies. Finally, current-voltage measurements were used to characterize the properties of N-polar p-n diodes. Comparisons between both polarities demonstrate that p-type N-polar GaN can be grown by MOCVD with comparable properties to Ga-polar GaN.
Structural and electrical characteristics of a high-k NdTiO3 gate dielectric
Authors: Pan Tung-Ming , Shu Wei-Hao
Published: October 2007

In this letter, we study the structural and electrical properties of high-k neodymium titanium oxide (NdTiO3) gate dielectrics deposited on Si (100) substrates by reactive rf sputtering. We find that the capacitance value of NdTiO3 gate dielectric prepared at a 6nm Ti metal film is higher than other thicknesses and exhibits a lower hysteresis voltage and interface trap density in capacitance-voltage curves. This result is attributed to an amorphous NdTiO3 structure and the suppression of the interfacial layer observed from x-ray diffraction and x-ray photoelectron spectroscopy, respectively.
Relative abundance of single and double vacancies in irradiated single-walled carbon nanotubes
Authors: Tolvanen A. , Kotakoski J. , Krasheninnikov A. V. , Nordlund K.
Published: October 2007

Double and single vacancies differently affect the conductance of carbon nanotubes [G. Gómez-Navarro et al., Nat. Mater. 4, 534 (2005)], so that the exact knowledge of the abundance of these defects is mandatory for an unambiguous interpretation of irradiation-induced changes in nanotube conductance. We calculate concentrations of defects produced by Ar ions using the molecular dynamics method combined with kinetic Monte Carlo simulations. Carefully taking into account the annealing of defects, we show that the ratio of single to double vacancies has a minimum at ion energies of about 0.5keV and that the ratio saturates toward a constant value at high ion energies.
An atomic level model for silicon anisotropic etching processes: Cellular automaton simulation and experimental verification
Authors: Zhou Zai-Fa , Huang Qing-An , Li Wei-Hua
Published: October 2007

An atomic level model with comprehensive physical and chemical concepts is developed, and the model can accurately simulate silicon anisotropic etching processes with high-index planes. The model describes the contributions from the first nearest atoms, the direct second nearest atoms, the indirect second nearest atoms, and their locations with respect to the etching surface to the etching processes of surface atoms. The atomic level model, combining with a dynamic algorithm, has been extended to a simulation system based on a cellular automaton method and the simulation results demonstrate to be in good agreement with the experimental results.
Significant reduction of coercivity without reduction of tunneling magnetoresistance ratio of CoFeB∕MgO∕CoFeB-based magnetic tunnel junction using sandwich-structured free layer
Authors: Choi Young-suk , Tsunekawa Koji
Published: October 2007

We report the significant reduction of coercivity (Hc) without huge drop of tunneling magnetoresistance ratio (TMR) in the CoFeB∕MgO∕CoFeB-based magnetic tunnel junction by employing sandwich-structured free layer of CoFeB/metallic spacer/NiFe. Strong magnetostatic coupling without physical contact induces magnetic softness from NiFe to CoFeB and avoids considerable reduction of TMR. This achievement satisfies the requirements given to the magnetic read head in hard disk drive and the spin torque transfer magnetic random access memory for the application to the higher areal density and the reduction of critical current density for current-induced magnetization switching, respectively.
Surface plasmon coupling effect in an InGaN∕GaN single-quantum-well light-emitting diode
Authors: Yeh Dong-Ming , Huang Chi-Feng , Chen Cheng-Yen , Lu Yen-Cheng , Yang C. C.
Published: October 2007

The authors demonstrate the coupling effects between the quantum well (QW) and surface plasmon (SP) generated nearby on the p-type side in an InGaN∕GaN single-QW light-emitting diode (LED). The QW-SP coupling leads to the enhancement of the electroluminescence (EL) intensity in the LED sample designed for QW-SP coupling and reduced SP energy leakage, when compared to a LED sample of weak QW-SP coupling or significant SP energy loss. In the LED samples of significant QW-SP coupling, the blueshifts of the photoluminescence and EL emission spectra are observed, indicating one of the important features of such a coupling process. The device performance can be improved by using the n-type side for SP generation such that the device resistance can be reduced and the QW-SP coupling effect can be enhanced (by further decreasing the distance between the QW and metal) because of the higher carrier concentration in the n-type layer.
Separation of the strain and finite size effect on the ferromagnetic properties of La0.5Sr0.5CoO3 thin films
Authors: Xie Changkun , Budnick J. I. , Wells B. O. , Woicik J. C.
Published: October 2007

The ferromagnetic properties of epitaxial La0.5Sr0.5CoO3 thin films have been studied. The magnetic transition is affected by both strain and finite thickness. We have used a series of films of different thicknesses and on different substrates in order to quantitatively determine the change in Curie temperature contributed by each effect. The phase diagram of TC versus in-plane strain suggests that the ferromagnetic transition temperature is suppressed by tensile strain and enhanced by compressive strain. The general method of separating strain and finite thickness effects should be applicable to any ordering phase transition in thin films.
The Print Media in South Africa: Paving the Way for ‘Privatisation’
Authors: Mayher Anne , Mcdonald David
                      A.
Published: October 2007

Since the end of apartheid, national and local governments in South Africa have been involved in the commercialisation and marketisation of a wide range of public services. This article examines the responses of the mainstream media to these neo-liberal initiatives, looking specifically at English-language newspapers and their coverage of water, electricity and waste management services. We explore the extent to which the print media can be deemed to be in favour of privatisation as well as the more subtle, discursive ways in which it covers these issues. We argue that these corporate media outlets in South Africa generate and perpetuate a neo-liberal discourse on privatisation, but that this dialogue is neither omnipotent nor monolithic. Nevertheless, it is exactly this façade of objectivity which gives neo-liberalism its hegemony. By appearing to give equal space to different points of view there is a perception of balance in the press that obscures the more subtle, opinionmaking discourses that generate neo-liberal biases. We conclude with a brief discussion of what might be done to counter this neo-liberal authority.
Somaliland: A New Democracy in the Horn of Africa?
Authors: Hansen Stig
                      Jarle , Bradbury Mark
Published: October 2007

With a constitutionally-based and popularly elected government, the Republic of Somaliland, which broke away from Somalia in 1991, has a democratic system matched by few other countries in Africa and the Middle East. However, Somaliland's independence has not been recognised internationally. Moreover developments in neighbouring countries suggest that people in Somaliland will face serious challenges in entrenching a democratic political system. This article takes as its point of departure Georg Sorensen's (1998:3) definition of democracy. His definition is employed, together with the history of elections in the region, to explore the challenges people in Somaliland face in establishing a democratic political system, in this sense the article aims to explore the challenges of the future, rather than analyse the processes of the past. These include, among others, the shift from a clan-based form of political representation and competition to one based on political partiesas forums for political representation and competition, the urban-based nature of political discourse in a still predominantly rural society, and the absence of a strong independent media.
Structural interactions of conjugacy closed loops
Authors: Drápal Aleš
Published: October 2007

We study conjugacy closed loops by means of their multiplication groups. Let

Q
Q

be a conjugacy closed loop,

N
N

its nucleus,

A
A

the associator subloop, and

L

\mathcal L

and

R

\mathcal R

the left and right multiplication groups, respectively. Put

M
=
{
a
∈
Q
;

M = \{a\in Q;

L
a

∈

R

}

L_a \in \mathcal R\}

. We prove that the cosets of

A
A

agree with orbits of

[

L

,

R

]

[\mathcal L, \mathcal R]

, that

Q

/

M
≅
(
Inn
⁡
Q
)

/

L

1

Q/M \cong (\operatorname {Inn} Q)/\mathcal L_1

and that one can define an abelian group on

Q

/

N
×

Mlt
1

Q/N \times \operatorname {Mlt}_1

. We also explain why the study of finite conjugacy closed loops can be restricted to the case of

N

/

A

N/A

nilpotent. Group

[

L

,

R

]

[\mathcal {L},\mathcal {R}]

is shown to be a subgroup of a power of

A
A

(which is abelian), and we prove that

Q

/

N

Q/N

can be embedded into

Aut
⁡
(
[

L

,

R

]
)

\operatorname {Aut}([\mathcal {L}, \mathcal {R}])

. Finally, we describe all conjugacy closed loops of order

p
q

pq

.
Pure subrings of regular rings are pseudo-rational
Authors: Schoutens Hans
Published: October 2007

We prove a generalization conjectured by Aschenbrenner and Schoutens (2003) of the Hochster-Roberts-Boutot-Kawamata Theorem: let

R
→
S

R\to S

be a pure homomorphism of equicharacteristic zero Noetherian local rings. If

S
S

is regular, then

R
R

is pseudo-rational, and if

R
R

is moreover

Q

\mathbb Q

-Gorenstein, then it is pseudo-log-terminal.
Geometry of regular modules over canonical algebras
Authors: Bobiński Grzegorz
Published: October 2007

We classify canonical algebras such that for every dimension vector of a regular module the corresponding module variety is normal (respectively, a complete intersection). We also prove that for the dimension vectors of regular modules normality is equivalent to irreducibility.
Quantum symmetric 𝐿^{𝑝} derivatives
Authors: Ash J. , Catoiu Stefan
Published: October 2007

For

1
≤
p
≤
∞

1\leq p\leq \infty

, a one-parameter family of symmetric quantum derivatives is defined for each order of differentiation as are two families of Riemann symmetric quantum derivatives. For

1
≤
p
≤
∞

1\leq p\leq \infty

, symmetrization holds, that is, whenever the

L

p

L^{p}

k
k

th Peano derivative exists at a point, all of these derivatives of order

k
k

also exist at that point. The main result, desymmetrization, is that conversely, for

1
≤
p
≤
∞

1\leq p\leq \infty

, each

L

p

L^{p}

symmetric quantum derivative is a.e. equivalent to the

L

p

L^{p}

Peano derivative of the same order. For

k
=
1

k=1

and

2
2

, each

k
k

th

L

p

L^{p}

symmetric quantum derivative coincides with both corresponding

k
k

th

L

p

L^{p}

Riemann symmetric quantum derivatives, so, in particular, for

k
=
1

k=1

and

2
2

, both

k
k

th

L

p

L^{p}

Riemann symmetric quantum derivatives are a.e. equivalent to the

L

p

L^{p}

Peano derivative.
Gromov-Witten invariants of jumping curves
Authors: Coskun Izzet
Published: October 2007

Given a vector bundle

E
E

on a smooth projective variety

X
X

, we can define subschemes of the Kontsevich moduli space of genus-zero stable maps

M

0
,
0

(
X
,
β
)

M_{0,0}(X, \beta )

parameterizing maps

f
:

P

1

→
X

f: \mathbb {P}^1 \rightarrow X

such that the Grothendieck decomposition of

f
∗

E

f^*E

has a specified splitting type. In this paper, using a “compactification” of this locus, we define Gromov-Witten invariants of jumping curves associated to the bundle

E
E

. We compute these invariants for the tautological bundle of Grassmannians and the Horrocks-Mumford bundle on

P

4

\mathbb {P}^4

. Our construction is a generalization of jumping lines for vector bundles on

P

n

\mathbb {P}^n

. Since for the tautological bundle of the Grassmannians the invariants are enumerative, we resolve the classical problem of computing the characteristic numbers of unbalanced scrolls.
Schreier sets in Ramsey theory
Authors: Farmaki V. , Negrepontis S.
Published: October 2007

We show that Ramsey theory, a domain presently conceived to guarantee the existence of large homogeneous sets for partitions on

k
k

-tuples of words (for every natural number

k
k

) over a finite alphabet, can be extended to one for partitions on Schreier-type sets of words (of every countable ordinal). Indeed, we establish an extension of the partition theorem of Carlson about words and of the (more general) partition theorem of Furstenberg-Katznelson about combinatorial subspaces of the set of words (generated from

k
k

-tuples of words for any fixed natural number

k
k

) into a partition theorem about combinatorial subspaces (generated from Schreier-type sets of words of order any fixed countable ordinal). Furthermore, as a result we obtain a strengthening of Carlson’s infinitary Nash-Williams type (and Ellentuck type) partition theorem about infinite sequences of variable words into a theorem, in which an infinite sequence of variable words and a binary partition of all the finite sequences of words, one of whose components is, in addition, a tree, are assumed, concluding that all the Schreier-type finite reductions of an infinite reduction of the given sequence have a behavior determined by the Cantor-Bendixson ordinal index of the tree-component of the partition, falling in the tree-component above that index and in its complement below it.
On the essential commutant of 𝒯(𝒬𝒞)
Authors: Xia Jingbo
Published: October 2007

Let

T

{\mathcal T}

(QC) (resp.

T

{\mathcal T}

) be the

C
∗

C^\ast

-algebra generated by the Toeplitz operators

{

T
φ

:
φ
∈

\{T_\varphi : \varphi \in

QC

}
\}

(resp.

{

T
φ

:
φ
∈

L
∞

}

\{T_\varphi : \varphi \in L^\infty \}

) on the Hardy space

H
2

H^2

of the unit circle. A well-known theorem of Davidson asserts that

T

{\mathcal T}

(QC) is the essential commutant of

T

{\mathcal T}

. We show that the essential commutant of

T

{\mathcal T}

(QC) is strictly larger than

T

{\mathcal T}

. Thus the image of

T

{\mathcal T}

in the Calkin algebra does not satisfy the double commutant relation. We also give a criterion for membership in the essential commutant of

T

{\mathcal T}

(QC).
High Performance Motion Tracking Control for Electronic Manufacturing
Authors: Potsaid Benjamin , Wen John Ting-Yung , Unrath Mark , Watt David , Alpay Mehmet
Published: October 2007

Motion control requirements in electronic manufacturing demand both higher speeds and greater precision to accommodate continuously shrinking part/feature sizes and higher densities. However, improving both performance criteria simultaneously is difficult because of resonances that are inherent to the underlying positioning systems. This paper presents an experimental study of a feedforward controller that was designed for a point-to-point motion control system on a modern and state of the art laser processing system for electronics manufacturing. We systematically apply model identification, inverse dynamics control, iterative refinement (to address modeling inaccuracies), and adaptive least mean square to achieve high speed trajectory tracking. The key innovations lie in using the identified model to generate the gradient descent used in the iterative learning control, encoding the result from the learning control in a finite impulse response filter and adapting the finite impulse response coefficients during operation using the least-mean-square update based on position, velocity, and acceleration feedforward signals. Experimental results are provided to show the efficacy of the proposed approach, a variation of which has been implemented on the production machine.
Analysis and Strategy for Superharmonics With Semiactive Suspension Control Systems
Authors: Song Xubin , Ahmadian Mehdi , Southward Steve
Published: October 2007

This paper focuses on an experimental implementation of a semiactive seat suspension using magnetorheological (MR) dampers. We first introduce the nonlinear dynamics phenomena induced by skyhook control. Skyhook control has been widely applied to applications ranging from structural vibration suppression to commercialized vehicle suspensions. Unfortunately, skyhook control generates superharmonic dynamics; yet, this issue has not been clearly addressed in such vibration control systems. This paper will attempt to explain how superharmonics are created with skyhook controls through analysis of test data. Furthermore, a nonlinear model-based adaptive control algorithm is developed and evaluated for reducing the negative impact of the superharmonics. Based on an empirical MR damper model, the adaptive algorithm is expanded mathematically, and the system stability is discussed. Then in the following sections, this paper describes implementation procedures such as modeling simplification and validation, and testing results. Through the laboratory testing, the adaptive suspension is compared to two passive suspensions: hard-damping (stiff) suspension with a maximum current of 1A to the MR damper and low-damping (soft) suspension with a low current of 0A, while broadband random excitations are applied with respect to the seat suspension resonant frequency in order to test the adaptability of the adaptive control. In two separate studies, both mass and spring rate are assumed known and unknown in order to investigate the capability of the adaptive algorithm with the simplified model. Finally, the comparison of test results is presented to show the effectiveness and feasibility of the proposed adaptive algorithm to eliminate the superharmonics from the MR seat suspension response.
Noise Tolerant Iterative Learning Control and Identification for Continuous-Time Systems With Unknown Bounded Input Disturbances
Authors: Kim Tae-Hyoung , Zheng Xiaoguang , Sugie Toshiharu
Published: October 2007

This paper considers the problems of both noise tolerant iterative learning control (ILC) and iterative identification for a class of continuous-time systems with unknown bounded input disturbance and measurement noise. To this aim, we first propose a formulation of an extended ILC scheme using sampled input∕output (I∕O) data. The proposed ILC method has distinctive features as follows. Its learning law works in a prescribed finite-dimensional parameter space and employs I∕O data of all past trials efficiently. Also, the time derivative of tracking error is not required. Then, it is presented how the uncertain parameters can be identified by using the proposed ILC algorithm and how robust it is against measurement noise through a numerical example. Furthermore, its experimental evaluation is performed to demonstrate the effectiveness of the proposed identification scheme.
Teaching To the Test: Some SSS-Based TTTTT
Authors: Korsunsky Boris
Published: October 2007

“Teaching to the test” is an expression that has a decidedly derogatory connotation in the world of education. It is usually used to describe relentless and mindless drills with the expectation that the tasks on the test will resemble the drill exercises. However, “teaching to the test” can be understood in a broader—and much more positive—sense. A learning cycle always includes assessment tasks (well, tests)—and it seems a reasonable goal for an instructor to help the students take those tests successfully. In a way, one is always “teaching to the test.”
Frost in the Solar System
Authors: McIntosh Gordon
Published: October 2007

As an astronomy instructor, I am always looking for commonly observed phenomena on Earth that also appear elsewhere. Frost is an example of such a phenomenon, and this paper discusses frosts of various materials that occur on Mars and on other bodies throughout the solar system.
Work, Energy Transfer, and Sliding Friction
Authors: Poon Dick C. H.
Published: October 2007

In the analysis of work done by sliding friction, there are complications that arise from the deformations of the points of contact where friction originates. This paper presents a physical picture of the energy processes in which these complications are sidestepped and the traditional simple textbook explanation becomes acceptable.
Why Do We Feel Weightless in Free Fall?
Authors: Mohazzabi Pirooz
Published: October 2007

Using a very simple model, we explain why in free fall we do not feel our own weight or acceleration due to gravity, whereas in an accelerating vehicle not only do we feel our acceleration and the inflicting force, if they are high enough, they can be fatal.
An Old Favorite: The Noncircular “Wheel”
Authors: Greenslade Thomas B.
Published: October 2007

For many years, Prof. H.R. Crane of the University of Michigan wrote a wonderful series of notes for The Physics Teacher under the running title “How Things Work.” I find myself going back regularly to them for inspiration and remembrance.
Relativistic Effects on Clocks Aboard GPS Satellites
Authors: Mungan Carl E.
Published: October 2007

Consider a clock aboard a satellite orbiting the Earth, such as a Global Positioning System (GPS) transmitter. There are two major relativistic influences upon its rate of timekeeping: a special relativistic correction for its orbital speed and a general relativistic correction for its orbital altitude. Both of these effects can be treated at an introductory level, making for an appealing application of relativity to everyday life.
Kelvin and the Trans-Atlantic Cable
Authors: Erlichson Herman
Published: October 2007

Physics professors are well-acquainted with the accomplishments of Kelvin in physics. They are also aware that he was involved with the laying of the trans-Atlantic cable. But they are usually unaware about the details of his involvement with the cable.
The Energetics of Bouncing (Revisited): A Quantitative Demonstration of Energy Conversion During Bouncing
Authors: Gettrust Eric
Published: October 2007

A previous article1 described the gravitational potential energy and the kinetic energy of a bouncing ball and showed that the total of the two actually dropped below the “rest energy” situation of the stationary ball on the floor. The missing energy is in the form of elastic potential energy of the ball and floor. This paper describes the use of probes and sensors to help quantify all three energy forms in order to more completely demonstrate the conservation of mechanical energy.
Creating and Analyzing a Mirage
Authors: Richey Lauren , Stewart Bailey , Peatross Justin
Published: October 2007

Most people have witnessed mirages such as the distant “puddles” that appear on a highway when the pavement is warmed by the Sun. The warmed surface heats the nearby air creating a temperature gradient with the cooler (and more dense) air above. The apparent displacement of distant objects occurs as light refracts through the different air densities. Rays of light from the sky that are originally directed toward the ground can be bent upward, appearing to a viewer as though coming from the ground. This effect is known as an inferior mirage; a superior mirage occurs when cooler air is underneath.1,2 In this paper, a mirage is created indoors using an electric hotplate and a saucepan filled with ice water.
Physiological upper limits of left ventricular dimensions in highly trained junior tennis players
Authors: Basavarajaiah Sandeep , Wilson Mathew , Naghavi Reza , Whyte Gregory , Turner Mike , Sharma Sanjay
Published: October 2007

Background:

The differentiation between physiological cardiac enlargement and cardiomyopathy is crucial, considering that most young non-traumatic deaths in sport are due to cardiomyopathy. Currently, there are few data relating to cardiac dimensions in junior elite tennis players. The aim of this study was to define the upper limits of left ventricular dimensions in a large cohort of national adolescent tennis players.

Methods:

Between 1996 and 2003, 259 adolescent tennis players (152 males), mean (SD) age 14.8 (1.4) years (range 13–19) and 86 healthy age, gender and body surface matched sedentary controls underwent 12-lead ECG and 2D-transthoracic echocardiography.

Results:

Inter-ventricular septal end diastolic dimension (IVSd), left ventricular end diastolic dimension (LVEDd) and left ventricular end diastolic posterior wall dimension (LVPWd) in tennis players were significantly higher than in controls (8.9 mm vs 8.3 mm p<0.001, 48.9 mm vs 47.9 mm p<0.05 and 9 mm vs 8.3 mm p<0.001 respectively), however in absolute terms, the difference did not exceed 7%. None of the tennis players had a wall thickness exceeding 12 mm or a left ventricular cavity size exceeding 60 mm.

Conclusions:

Tennis players exhibit modest increases in cardiac dimensions, which do not resemble those seen in individuals with cardiomyopathy affecting the left ventricle.
An uncommon ankle sprain: Figure 1
Authors: van Zoest Wart J F , Janssen Rob P A , Tseng Carroll M E S
Published: October 2007

Objective:

Ankle sprain is the most frequently occurring acute injury in tennis, accounting for 20–25% of all injuries. In the current paper, we assess the cause of ankle sprain and suggest possibilities to be considered during diagnosis.

Methods:

We assessed a professional tennis player with a partial tear of the long peroneal tendon after an ankle sprain by physical exam, X-ray and MRI.

Results:

Conservative treatment by means of soft cast and propriocepsis training led to full recovery.

Conclusion:

Peroneal tendon disorders must be part of the differential diagnosis after ankle sprain in the professional athlete.
Rectus abdominis muscle strains in tennis players
Authors: Maquirriain Javier , Ghisi Juan P , Kokalj Antonio M
Published: October 2007

Rectus abdominis muscle strains are common and debilitating injuries among competitive tennis players. Eccentric overload, followed by forced contraction of the non-dominant rectus abdominis during the cocking phase of the service motion is the accepted injury mechanism. A tennis-specific rehabilitation program emphasising eccentrics and plyometric strengthening of the abdominal wall muscles, contributes to the complete functional recovery in tennis players, and could help reduce recurrences.
Short-term effects of light and heavy load interventions on service velocity and precision in elite young tennis players
Authors: Ferrauti Alexander , Bastiaens Kenneth
Published: October 2007

Objective:

This study was conducted to investigate the acute effects of a complex throwing intervention set-up, with light or heavy loads, on the service velocity of elite junior tennis players.

Methods:

On 3 separate test days, 13 elite juniors (mean (SD) 12.3 (0.8) years, 149 (9) cm, 37.5 (5.5) kg) performed four sets of six serves with different between-set conditions. In a cross-over design, the players performed respectively 6, 4 and 2 maximum effort throws with a 200 g ball (LI, light intervention), 6, 4 and 2 maximum effort throws with a 600 g ball (HI, heavy intervention) and no throws (NI, no intervention) during the 2 min in between-set period. Participants were instructed to serve, with maximum speed, to a target near the midline of the deuce court service box. A two-factor analysis of variance was used to determine the effects of intervention type and set number on “service velocity”, “service precision” (eg, percentage of serves in) and “service touch” (11 point rating scale).

Results:

Mean (SD) service velocity decreased significantly in HI (124.3 (7.8) km/h) as compared to NI (126.6 (9.3) km/h, p<0.05, effect size d = 0.26), yet no such differences were found between LI (125.2 (7.9) km/h) and NI. Service velocity also remained constant between sets (p = 0.406). Service precision and service touch were unaffected by the interventions.

Conclusions:

Under the conditions of our study, a heavy throwing intervention during service training has no beneficial effect on service velocity in young elite tennis players (under 14).
Exercise-induced homeostatic perturbations provoked by singles tennis match play with reference to development of fatigue
Authors: Mendez-Villanueva Alberto , Fernandez-Fernandez Jaime , Bishop David
Published: October 2007

This review addresses metabolic, neural, mechanical and thermal alterations during tennis match play with special focus on associations with fatigue. Several studies have provided a link between fatigue and the impairment of tennis skills proficiency. A tennis player’s ability to maintain skilled on-court performance and/or optimal muscle function during a demanding match can be compromised as a result of several homeostatic perturbations, for example hypoglycaemia, muscle damage and hyperthermia. Accordingly, an important physiological requirement to succeed at competitive level might be the player’s ability to resist fatigue. However, research evidence on this topic is limited and it is unclear to what extent players experience fatigue during high-level tennis match play and what the physiological mechanisms are that are likely to contribute to the deterioration in performance.
Muscle activation in coupled scapulohumeral motions in the high performance tennis serve
Authors: Kibler William B , Chandler T Jeff , Shapiro Robert , Conuel Michael
Published: October 2007

Objective:

To evaluate muscle activation patterns in selected scapulohumeral muscles in the tennis serve. These patterns of muscle activation have not been evaluated in other studies of the tennis serve. Fine wire and surface EMG was used to calculate onset and offset timing of muscle activation.

Design:

Controlled laboratory study.

Setting:

Biomechanical laboratory.

Subjects:

16 tennis players (age 18–40) with rated skills (National Tennis Rating Program (NTRP) rating 4.5–6.5; club tournament level or higher) were subjects.

Main outcomes measure:

Dependent variables of muscle activation onset and offset as well as sequencing of the stabilising muscles of the scapula (upper trapezius, lower trapezius, serratus anterior; the muscles that position the arm) anterior deltoid and posterior deltoid; and the muscles of the rotator cuff muscles (supraspinatus, infraspinatus, teres minor) during the tennis serve motion.

Results:

Patterns of muscle activation were observed during the tennis serve motion. The serratus anterior (−287 ms before ball impact) and upper trapezius (−234 ms) were active in the early cocking phase, while the lower trapezius (−120 ms) was activated in the late cocking phase just before the acceleration phase. The anterior deltoid (−250 ms) was activated in early cocking, while the posterior deltoid (−157 ms) was activated later. The teres minor (−214 ms) was activated early in the cocking phase. The supraspinatus (−103 ms) was activated in late cocking. The infraspinatus (+47 ms after ball impact) was activated in follow-through. All muscles except infraspinatus were activated in duration of more than 50% of the service motion.

Conclusions:

This study demonstrates that there are patterns of activation of muscles around the scapulohumeral articulation in the normal accomplished tennis serve. Rehabilitation and conditioning programs for tennis players should be structured to restore and optimise the activation sequences (scapular stabilisers before rotator cuff), task specific functions (serratus anterior as a retractor of the scapula, lower trapezius as a scapular stabiliser in the elevated rotating arm) and duration of activation of these muscles.
Site regions revisited: a climatic analysis of Hills' site regions for the province of Ontario using a parametric method
Authors: MacKey Brendan G. , McKenney Daniel W. , Yang Yin-Qian , McMahon June P. , Hutchinson Michael F.
Published: October 2007

A climatic analysis was conducted` of Hills' site regions for Ontario using spatially distributed models of long-term, mean monthly climate data. Gridded estimates of eight climatic variables were generated by coupling thin-plate smoothing spline surfaces (fitted as a trivariate function of longitude, latitude, and elevation) to a 1-km resolution digital elevation model of Ontario. The gridded climate estimates were used to characterize the climate of each site region. New climatic classifications for the province were calculated from these data using a clustering algorithm. They were also compared with the existing site region boundaries. The analyses confirm many of the general climatic gradients established by Hills, but also suggest where major revisions should be made. The climatic models present new analytical opportunities for mapping plant–climate response in the context of forest planning and management.
Relationships between crown dimensions and stem development in Fraxinusexcelsior
Authors: Ottorini Jean-Marc , Goff Noël Le , Cluzeau Catherine
Published: October 2007

In this study, the relationships between crown development and stem volume increment of ash (Fraxinusexcelsior L.) were considered in the framework of a project where modelling and computer simulation should be used to gain insight into the dynamics of even-aged ash stands. Twenty trees, of various development stages and competition status, were felled and subjected to stem and branch analysis. The relationships established in a previous study between stem elongation, branch growth, and branching angle (based on these measurements), together with the characteristic pattern of variation of stem cross-sectional area increment along the stem (Pressler's Law), allowed the reconstruction of the past development of tree crowns. The quantity of foliage in tree crowns was estimated by a "foliar volume" calculated as the product of crown surface projection area and height growth, for each growing year considered. This foliar volume was used together with a relative foliar volume based on the stem surface area to obtain a prediction equation for annual stem volume increment.
Spectral reflectance characteristics and digital imagery of a pine needle blight in the southeastern United States
Authors: Carter Gregory A. , Cibula William G. , Dell Tommy R.
Published: October 2007

A field study determined an optimal approach for the remote sensing of a pine needle blight of unknown cause that occurs frequently in the southeastern United States. Needle spectral reflectance was measured in five pairs of slash pines (Pinuselliottii Engelm. var. elliottii), each comprising a blighted and a nonblighted tree. Reflectance of blighted needles generally was greater within the 400–700 nm wavelength range and less in the 720–850 nm range compared with nonblighted needles (p ≤ 0.050). The relative change in reflectance, or reflectance sensitivity to the blight, was greatest near 680 nm. As predicted by the reflectance sensitivity, a black and white digital image at 680 ± 5 nm revealed strong contrast of a blighted compared with a nonblighted tree; the blighted canopy was nearly white in the image, while the nonblighted canopy was dark grey. Contrasts were much less at 560 ± 5, 694 ± 3, and 700 ± 5 nm, in the panchromatic visible spectrum (410–740 nm), and at 760 ± 5 nm. Remote sensing of southeastern pine forests at 680 ± 5 nm ultimately could provide regional estimates of blight occurrence and distribution, and thus contribute to determining its cause.
Effects of organic horizon removal, ash, watering regime, and shading on red pine seedling emergence
Authors: Herr David G. , Duchesne Luc C.
Published: October 2007

Soil monoliths were used to determine the effects of organic horizon removal, ash, water regime, and shading on red pine (Pinusresinosa Ait.) seedling emergence. Soil monoliths were collected from a jack pine (Pinusbanksiana Lamb.) stand and taken to the laboratory for prescribed burning, leading to 25%, 50%, 75%, and 100% organic horizon removal. One half of each monolith contained ash generated from burning, while the other half was kept ash-free. Each half of every monolith was sown with red pine seeds. The monoliths were then placed in a greenhouse and, in separate experiments, were exposed to different water regimes and shade regimes. Red pine seedling emergence was highest under high water regimes, increased shade regimes, and increased organic horizon removal. Seedling emergence was reduced by the presence of ash.
Using nuclear and organelle DNA markers to discriminate among PicearubensPiceamariana, and their hybrids
Authors: Bobola Michael S. , Guenette Denis , Eckert Robert T. , Klein Anita S. , Stapelfeldt Karen , Smith Dirk E.
Published: October 2007

The pattern of nuclear ribosomal alleles in controlled-cross black spruce × red spruce hybrids was compared with that of samples from provenance tests of the entire range of red spruce (Picearubens Sarg.) and the eastern complex of black spruce (Piceamariana (Mill.) BSP). In addition, restriction fragment length polymorphisms were identified for the organelle genomes of red spruce and black spruce. Organelle haplotypes were closely associated with species, but were not species specific. Data from controlled-cross hybrids suggest that mitochondria are maternally inherited and chloroplasts are paternally inherited in these spruce species. Organelle markers were combined with restriction fragment length polymorphism data from the nuclear rDNA repeat to derive a simple three-character index capable of identifying red spruce, black spruce, and hybrids of the two species.
Tree-ring analysis of wetlands of the upper St. Lawrence River, Quebec: response to hydrology and climate
Authors: Jean Martin , Bouchard André
Published: October 2007

A dendrochronological analysis of three tree species colonizing a swamp along the St. Lawrence River was undertaken to (a) study the extent to which water-level fluctuations have an impact on tree growth in comparison to climatic variations; (b) compare the responses of three species (Acerrubrum L., Larixlaricina (Du Roi) K. Koch, and Thujaoccidentalis L.) with hydrologic and climatic variations; and (c) examine the duration of the influence of water-level fluctuations on tree growth. Tree cores from 78 stands were cross-dated and verified with COFECHA and a master chronology for each species was produced using ARSTAN. Response function analyses were used to measure the influence of climate (temperature and precipitation) and water level on tree growth. Water-level fluctuations have a significant influence on A. rubrum growth, accounting for 30% of the tree growth variation. A significant relationship exists between L. laricina and water-level fluctuations, but only 9% of the tree growth is explained by hydrology. No significant relationship was found between water levels and T. occidentalis growth. Climatic fluctuations are a more important influence on growth for all three species, accounting for 46% to 51% of the tree growth variation not explained by water levels.
Growth of planted lodgepole pine and hybrid spruce following chemical and manual vegetation control on a frost-prone site
Authors: LePage Phil , Coates K. Dave
Published: October 2007

The 5-year height and diameter growth response of a frost-tolerant species, (lodgepole pine, Pinuscontorta var. latifolia Dougl. ex Loud.) and a frost-susceptible species (hybrid spruce, Piceaglauca (Moench) Voss × Piceasitchensis (Bong.) Carr.) to different vegetation-control site-preparation treatment and timing combinations was examined using a factorial experiment. The site chosen for the experiment is subject to frequent summer growing season frosts. The vegetation control treatments were: an untreated control, manual cutting, and glyphosate applied at the rates of 1.4 and 2.1 kg active ingredient (a.i.) per hectare. Each vegetation-control treatment was applied at four dates (timing) that covered the active growing season of the vegetation on the study area. Vegetation-control method had a major impact on the growth of the planted seedlings. The influence of timing of control treatments on growth was found to be minor. Fifth-year height and diameter in the manual cutting and control treatments were equally poor. Growth was significantly improved by both levels of chemical vegetation control and after 5 years, no differences were apparent between the two. Pine height and diameter and spruce diameter continually improved as the level of thimbleberry (Rubusparviflorus Nutt.) was reduced. Below 5% thimbleberry cover, this growth increased dramatically, suggesting a response threshold. As vegetation cover was lowered, however, spruce seedlings were damaged by frost, resulting in reduced total height. In this case, better height growth was associated with either very low or moderately high thimbleberry cover than with moderate to low levels.
An evaluation of selected spruce bark beetle infestation dynamics using point in time extensive forest inventory data, Kenai Peninsula, Alaska
Authors: van Hees Wlllem W.S. , Holsten Edward H.
Published: October 2007

Forest inventory data collected in 1987 from the Kenai Peninsula, Alaska, were used to explore whether or not such data can be used to evaluate dynamics of a spruce bark beetle (Dendroctonusrufipennis (Kirby)) infestation there. The utility of the inventory data as an evaluation tool is shown by performing analyses equivalent to those performed by other researchers in smaller scale studies conducted on the Kenai Peninsula and comparing results. Analyses showed that extensive forest inventory data can be used to estimate areas of infestation and to establish relations among tree diameter, recent radial growth, tree stocking, state of beetle attack, and stage of infestation. Understanding of spruce bark beetle infestation dynamics on broad, regional scales, can be achieved while also obtaining extensive forest inventory data.
Effects of adding tree, stand, and site variables to Kozak's variable-exponent taper equation
Authors: Muhairwe Charles K. , LeMay Valerie M. , Kozak Antal
Published: October 2007

Crown class, site class, and breast-height age were incorporated into Kozak's variable-exponent taper equation (A. Kozak. 1988. Can. J. For. Res. 18: 1363–1368) for three species: Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), western red cedar (Thujaplicata Donn), and aspen (Populustremuloides Michx.). For lodgepole pine (Pinuscontorta Dougl.), crown ratio, breast-height age, and quadratic mean diameter were incorporated into Kozak's taper equation. The effects of adding these variables to the exponent part of the taper equation on the prediction abilities of the taper model were assessed for prediction of diameter inside bark along the stem, total tree volume, and tree merchantable height. It was found that apart from the use of crown ratio for lodgepole pine, the additional variables resulted in only marginal improvements to the published version of Kozak's taper function. Therefore, the cost of measuring these additional variables is not justifiable.
Analysis of Sitka spruce–interior spruce introgression in British Columbia using cytoplasmic and nuclear DNA probes
Authors: Sutton B.C.S. , Pritchard S.C. , Gawley J.R. , Newton C.H. , Kiss G.K.
Published: October 2007

Restriction fragment length polymorphisms of the nuclear ribosomal RNA genes were used to define species-specific patterns for interior spruce (a complex of white spruce, Piceaglauca (Moench) Voss, and Engelmann spruce, Piceaengelmannii Parry) and Sitka spruce (Piceasitchensis (Bong.) Carr.) populations in British Columbia. These patterns are highly conserved among seed lots and individual trees of each species from diverse geographic origins. Both the ribosomal RNA gene probe and species-specific probes for the chloroplast and mitochondrion, described previously, were used to analyze 164 dominant trees from 19 locations in a zone of presumed Sitka–interior spruce introgression in northwestern British Columbia. Hybrid fraction was estimated from an index based on the relative abundance of polymorphic ribosomal RNA hybridizing bands for each tree and was in good agreement with the proportion of trees exhibiting either interior or Sitka spruce specific chloroplast bands. The results demonstrate that complex hybrids occur frequently in this zone, indicative of true introgression. Furthermore, the trend of variation in species mix is consistent with the topographical trends. It is anticipated that the results of this survey will be useful in defining seed transfer guidelines for reforestation of this region.
Bud and cambial zone phenology of lateral branches from Douglas-fir (Pseudotsugamenziesii) seedlings
Authors: Rensing K.H. , Owens J.N.
Published: October 2007

Bud and cambial zone phenologies of outdoor-grown, containerized seedlings of Pseudotsugamenziesii (Mirb.) Franco (Douglas-fir) were determined and compared. Morphological characteristics of the live primordial shoots were related to known stages of bud development, while cambial zone phenology was based on anatomical characteristics. Secondary growth in branches of P. menziesii seedlings was separated into six stages: (i) early wood formation; (ii) latewood formation; (iii) cessation of cambial cell division; (iv) dormancy; (v) cambial cell expansion; and (vi) resumption of cell division. Early wood formation by the cambial zone, and primary leaf initiation in the shoot tips occurred until July. During this time of maximal activity, differences in wall thickness and shape distinguished cambial cells from vascular cells in early differentiation stages. By late July, earlywood formation was changing to latewood formation and bud-scale initiation had begun. The transition to preformed leaf initiation in the buds occurred over a period of 1 month in August and September. Cambial cell division ceased in early September but tracheid differentiation continued until about the end of October. Preformed leaf initiation lasted until the buds became dormant in mid-November. The cambial zone was dormant from the end of November until the beginning of March, and in transverse section was characterized by a distinct boundary at the border of the xylem and regular, cigar-shaped cambial cells with thick radial walls. Resumption of cambial activity in the 1st week of April began with radial expansion, followed about 2 weeks later by cell division. Differentiation of earlywood tracheids and bud swelling began in early April. The majority of buds flushed in the 3rd week of April. Rays in the lateral shoots were composed of monoseriate files of radially elongated cells. Ray initials were not observed. Ultrastructural features indicated that the dictyosomes of the cambial cells were active during the winter period.