bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Hyperdispersant on the Mechanical Properties and Morphology of Sisal Fiber/Polypropylene Composites
Authors: Yu Chun He , Lu Shao Rong , Yang Zhi You , Liu Kuo , Fan Xin
Published: May 2011

In order to enhance the interfacial interactions between the sisal fiber (SF) and the polypropylene (PP) matrix, a water-solubility hyperdispersant which has amphipathic structure and flexible segment was used. Experimental results revealed that when the content of hyperdispersant is 5 percent, the impact strength of the composites was 27.4 kJ·m-2 and the flexural strength of SF/PP composites was 40.1 MPa, which was 64 and 34 wt% higher than that of unmodified systems, respectively. Meanwhile, the crystallinity of the composites also leads to an increase.
Evaluating the Influence of Mix Proportion Parameters on Anti-Permeability of Green High Performance Concrete with Grey Relational Analysis
Authors: Guan Qiao Yan , Zhang Peng
Published: May 2011

The aim of this study was to evaluate the influence of mix proportion parameters on anti-permeability of green high performance concrete (GHPC) and find out the main influencing factors. Applying grey relational analysis method, the relational grades between the influencing factors and diffusion coefficient of Cl- of GHPC were calculated. Besides, the sequence result of influencing degree of the factors to affect the anti-permeability was obtained. The result shows that the importance of the factors affecting anti-permeability of GHPC has following sequence: water-binder ratio> sand ratio > dosage of cement> dosage of water reducing admixture > dosage of mineral fillers > dosage of fly ash. In order to improve anti-permeability of GHPC, water-binder ratio and sand ratio must be controlled strictly.
Study on Interface Properties of EVA-Modified Cement Mortar
Authors: Wu Yuan Yuan , Ma Bao Guo , Wang Jun , Zhang Feng Chen , Jian Shou Wei
Published: May 2011

Ethylene - vinyl acetate copolymer (EVA)-modified mortar is widely used in China because of better adhesion strength and flexibility as compared to traditional one. This paper, based on a laboratory program, evaluated the effects of EVA-cement and different fillers on interface properties of EVA-modified cement mortar such as adhesive strength and dynamic cracking resistance, and the mechanism was also analyzed by scanning electron microscopy (SEM). The results showed that under laboratory condition, adhesion strength and dynamic cracking resistance of EVA-modified cement mortar increased with EVA-cement rising. Interface performance of the EVA-modified mortar improved greatly as EVA-cement increased from 0% to 12% and amplification slowed down when it increased further. EVA-cement around 12% was the optimal proportion considering all factors in this study. Fillers of different particle grade contributed to interface properties of EVA-modified cement mortar, A/fillers around 1/6~2/3 is the optimal proportion in this study.
The Effect of Process Conditions on the Preparation of α-Calcium Sulfate Hemihydrate from FGD Gypsum Using the Hydrothermal Method under Atmospheric Pressure
Authors: Liu Xian Feng , Peng Jia Hui , Zou Chen Yang , Bai Leng , Li Mei
Published: May 2011

This paper studies the laws of crystal growth, percent conversion and the rate of reaction of α-calcium sulfate hemihydrate from FGD gypsum under different conditions using the hydrothermal method under atmospheric pressure. The crystal morphology was observed by using SEM, polarizing microscope profile, and percent conversion and the rate of reaction were obtained by assaying crystal water content and calculating. The results showed, (1) with the increase of reaction temperature, the dehydration rate increased and the formed α-calcium sulfate hemihydrate crystal had a larger particle size; (2) with the increase of salt concentration or slurry concentration, the formed α-calcium sulfate hemihydrate crystal was smaller, percent conversion and the rate of reaction was nearly unchanged; (3) with the increase of pH value of solution, the rate of reaction increased and percent conversion was nearly unchanged, and with pH value ranging from 5 to 7 the formed α-calcium sulfate hemihydrate crystal was crassitude. In conclusion, the perfect technological parameters were as follows: reaction temperature ranging from 95°C to 100°C, salt concentration ranging from 15% to 20%, slurry concentration ranging from 15% to 20%, pH value ranging from 5 to 7, and reaction time not exceeding 90min.
Property of High Volume Industrial Residue Concrete
Authors: Li Ke Liang , Yang Zhong Zheng , Huang Guo Hong , Tang Xiu Sheng
Published: May 2011

To protect circumstance and improve of structure durability of Cao’e River floodgate, high volume industrial residue concrete (HVIRC) was prepared, and its mechanical property and durability were studied systematically. 10% of fly ash and 40% of ground granulated blast-furnace slag was used to replace 50% of cement in HVIRC. HVIRC had better anti-carking ability with larger tensile strength, larger ultimate tensile strain, larger tensile-compressive strength ratio and smaller elastic modulus-to-strength ratio. Dry shrinkage rate of HVIRC was similar with that of ordinary Portland concrete (OPC). HVIRC had higher compactness with smaller gas diffusion coefficient and relative permeability coefficient. Expansion caused by alkali-silica reaction reduced greatly by using high volume industrial residue and alkali-silica reaction was controlled markedly. HVIRC had better property of chloride ion penetration resistance with low effective diffusion coefficient. HVIRC could protect steel-bar from premature corrosions. Properties of sulfate resistance and frost resistance of HVIRC were also favorable. It’s proved that high volume industrial residue can enhance greatly mechanical property and durability of concrete and HVIRC can be used in Cao’e River floodgate.
The Application of Glazed Hollow Beads in Thermal Insulation Structure of Gallery and its Energy Conservation Effect
Authors: Guo Xiu Hua , Li Zhu , Zhu Guo Qiang
Published: May 2011

Insulation grout of glazed hollow beads is injected into the support structure of high temperature gallery. By this way, thermal insulation structure system is constructed. The paper measures the thermal conductivity of this material and sums up the calculating model and formulas of the heat transfer quantity from surrounding rock to airflow in a gallery. The paper provides the theoretical basis for energy conservation prediction, construction and design of this structure system.
Discussions on Fracture Factors of Brittle Materials under the Shear-Compression Condition
Authors: Li Zhi Hui , Shi Jun Ping , Tang An Min
Published: May 2011

Based on fundamental ideas in tribology and basic concept of stress state in solid mechanics, the existence of frictional force on shear plane is discussed under uniaxial compression of brittle materials. On account of macroscopic fracture forms and mesoscopic fracture mechanisms, the key factors influencing shear fracture angle are analyzed. The results show that, when brittle materials are compressed and shear fracture occurs, shear fracture surface at the crack initiation point is consistent with the maximum shear stress. But the reason of shear fracture angle examined in experiment greater than 45º lies in that, the existence of frictional force between endface of specimen and pressure head of testing machine, and additional tensile stress produced in the materials when harder crystalline grain wedge in softer medium have changed original uniaxial compression stress state and the direction of maximum shear stress on next fracture path.
Modulus of Rupture Test and Numerical Fitting of Plybamboo Form
Authors: Li Ben Gui , Yu Yun Shui , Chen Jun Min , Peng Liang , Zhou Wei Hong
Published: May 2011

Longitudinal and transverse modulus of rupture(MOR) tests of plybamboo form with different moisture content were performed. The results show that both longitudinal MOR and transverse MOR decrease with the increasing of the moisture content of the plybamboo form. At low moisture content stage MOR of the plybamboo form decrease linearly with the increasing of the moisture content of the plybamboo form. Curve regression equations of longitudinal and transverse MOR of plybamboo form were constructed by the method of numerical fitting, and linear regression equations at low moisture content stage were also constructed. Decline of plybamboo form strength itself and bonding invalidation lead to the decrease of MOR. The results of variance analysis and significance test of four regression equations show that all the regression equations achieve very significant level.
Effect of Processing Parameters on Properties of Wheat-Straw Boards with FRW
Authors: Zhu Xiao Dong , Wang Feng Hu , Liu Yu
Published: May 2011

This paper explored the effect of MDI, UF and FRW content on the mechanical and fire retardant property of straw based panels with surface alkali liquor processing. In order to manufacture the straw based panel with high quality, low toxic and fire retardant, the interface of wheat-straw was treated with alkaline liquid under the optimal treating condition: alkaline liquid concentration was 0.4-0.8%, alkaline dosage was 1:2.5-1:4.5, alkaline-treated time was 12h-48h.The physical and mechanical properties of wheat-straw boards after treated could satisfy the China national standard. And the variance analysis of the fire retardant property of straw based panel showed that TTI, pkHRR and peak value appearance time were not affected by the MDI, UF and FRW content significantly. The results of orthogonal test showed that the optimized processing condition was MDI content as 4%, UF resin content as 7% and the FRW content as 10%.
Review of Study on Polyurethane Foams from Biomass
Authors: Zhang Meng , Zhou Yong Hong , Yang Xiao Hui , Hu Li Hong
Published: May 2011

Due to the versatility of the biomass, this article reviews the research and development of polyurethane foams based on starch, rosin, oil, cellulose and lignin. The study on biodegradable polyurethane foams become hotspot in recent years. An awareness of the various structures and compositions of renewable resource can be used to make a strong case for an increase in its production as a vital raw material for the polyurethane industries.
Experiment Research on Basic Mechanic Property of Recycled Concrete with Different Ratio of Recycled Aggregate
Authors: Sun Yue Dong , Xiao Xiang
Published: May 2011

The test confects C20, C25, C30, C35 and C40 recycled aggregate concrete, and the percentage of recycled aggregate are 0%, 20%, 30%, 50%, 70% and 100%,the test age of sample are 7d,28d and 56d.Through test, the cube crushing strength,prismatical compressive strength and elasticity modulus of recycled aggregate concrete with different recycled aggregate percentage and different ages are studied, and compare with general concrete. Test show that, with the development of age, the strength development law of recycled aggregate concrete is similar to general concrete; with the increase of amount of recycled aggregate, the strength and elasticity modulus of recycled aggregate concrete shows the trend of decline, and the basic mechanic property of recycled concrete meet the demand of existing criterion.
Probing the Activation Migration Enthalpies of Dislocations in 2024 Aircraft Material Using Nuclear and Electrical Techniques
Authors: Abdel-Rahman M.A. , Kamel N.A. , Refeay Abdullah A. , Badawi Emad A.
Published: May 2011

Positron annihilation lifetime (PAL) measurement is one of the most important nuclear techniques used in materials science. Electrical measurements are also used in materials science. Both PAL and electrical measurements were used here to determine the activation energy of migration of dislocations in one of the most important engineering aluminum alloys: 2024. Samples of 25% deformed (thickness reduction) material have been used for these studies. The isothermal annealing measurements were performed at 583, 603, 623 and 643K for both techniques. The activation energy of migration of the dislocation was found to be equal to 1.24 ± 0.08eV by using PAL measurements and to 1.35 ± 0.01eV by using the electrical technique.
A Numerical Simulation Approach to Convection, Buoyancy Effect, Microfiltration and Flow Analysis as an Influential Lead for Designing and Dimensioning in MEMS
Authors: Malik M. Rizwan , Shi Tie Lin , Tang Zi Rong , Liao Guang Lan
Published: May 2011

Multiphysics numerical simulation (MPNS) has certainly acquired a wide acceptance in the modeling, designing and fabrication fields and has been validated for various research applications. But it is important that the method should be thoroughly understood by students of the various fields. Keeping this aim in view, we demonstrate here the MPNS process as applied in several fields, such as: electrostatics, mechanics, chemistry, heat transfer and fluid flow. Four tasks are performed for fifteen hours in order to analyze simulation approaches such as modeling with geometrical parameters, meshing, solution and post-processing methods. Convection, buoyancy effects, microfiltration and flow analysis are investigated. This comprehensive study will enhance appreciation of the basic concepts of design and dimensioning of an object in MEMS for engineers, and help to guide workers in these fields when performing these tasks.
Effect of Film Thickness on Some Optical Properties of Sprayed Pyrolysis Cobalt Oxide Thin Films
Authors: Aly S.A.
Published: May 2011

The optical properties of cobalt oxide samples prepared by spray pyrolysis technique on glass substrates with different film thicknesses have been studied. The structural characteristics of the samples were investigated using X-ray diffraction. The optical properties of the prepared films were studied by transmittance and reflectance measurements, and the integrated transmittance (TVIS, and TNIR) and absorptance (AVIS and ANIR) in VIS and NIR regions was calculated and found to be affected by film thickness. The dependence of absorption coefficient on wave length was also reported. The energy gap was calculated and two energies have been observed at 2.15 and 1.5 eV suggesting that the deposited films are semi-conducting with allowed direct transitions.
Study of the Glass Transition Temperature of (Se100-xBix)90Te10 (x = 0, 0.5, 1, 1.5, 2, 2.5, 3) Alloys
Authors: Sharma Deepshikha , Thakur Saneel K.
Published: May 2011

Alloys of (Se100-xBix)90Te10 (x =0, 0.5, 1, 1.5, 2, 2.5, 3 at.%) were prepared by using a conventional melt-quench technique. The samples under investigation were characterized using X-ray diffraction (XRD) and differential analysis (DTA) at a heating rate of 10K/min. It was found, from the XRD studies, that the alloys were amorphous in nature. The glass transition temperatures of the alloys were found to increase with increasing bismuth content. This increase in the glass transition temperature was explained on the basis of a chemically ordered network model.
Surface Composition Transformation of Thin Film Based on Al Grown by CBE on the (001) GaAs Surface Due to Laser Assistance
Authors: Lioubtchenko Dmitri V. , Briantseva Tatiana A. , Lebedeva Z.M. , Bullough Tim J.
Published: May 2011

It is shown that laser-assisted growth of Al films using the CBE method results in remarkable surface composition transformations. The values of the laser reflectivity are slightly correlated with the composition or with the metal thickness. The energy characteristics of the reactions guide the reflectivity changes, together with thickness changes. It was shown that the composition within the laser spot is different from that outside the laser spot due to the destruction of compounds under laser exposure.
Characterization and Properties of Iron/Silica-Sand-Nanoparticle Composites
Authors: Ahmad Tahir , Mamat Othman
Published: May 2011

Metal matrix-particulate composites fabricated by using powder metallurgy possess a higher dislocation density, a small sub-grain size and limited segregation of particles, which, when combined, result in superior mechanical properties. The present study aims to develop iron based silica sand nanoparticles composites with improved mechanical properties. An iron based silica sand nanoparticles composite with 5, 10, 15 and 20 wt.% of nanoparticles silica sand were developed through powder metallurgy technique. It was observed that by addition of silica sand nanoparticles with 20 wt.% increased the hardness up to 95HRB and tensile strength up to 690MPa. Sintered densities and electrical conductivity of the composites were improved with an optimum value of 15 wt.% silica sand nanoparticles. Proposed mechanism is due to diffusion of silica sand nanoparticles into porous sites of the composites.
Influence of Annealing on the Microstructure and Mechanical Properties of Electrodeposited Nanocrystalline Nickel
Authors: Yang B.
Published: May 2011

The evolution of the microstructure and mechanical properties of electrodeposited nanocrystalline Ni with different annealing procedures was studied systematically. For the annealed specimens hardness decreases with increasing average grain size but the dependence changes at different grain size ranges. The specimens annealed at a low temperature show higher hardness compared to the as-deposited nanocrystalline Ni, despite an increased measured average grain size. In association with this hardening an increase in elastic modulus and a decrease in microstrain was observed after annealing. With increasing annealing temperature both the tensile strength and the fracture strain were observed to decrease, this is companied with a transition from ductile to brittle in the fracture surfaces. These results indicated that the mechanical behaviour of nanocrystalline Ni depends not only on the average grain size but also on the grain boundary structure. A change in the grain boundary state arising from annealing may be responsible for the observed increase in hardness and elastic modulus as well as the deterioration of tensile properties.
Mechanical Behaviors of Electrodeposited Bulk Nanocrystalline Metals and Alloys
Authors: Han S. , Lian Jian She , Mu J.W. , Shen X.X. , Qin L.Y. , Jiang Z.H. , Jiang Qing
Published: May 2011

Nanocrystalline (NC) metals and alloys always exhibit extremely high strength but quite limited ductility. This disappointing ductility might be caused by the preparation artifacts and the weak strain hardening ability of NC materials. In order to optimize the mechanical properties of NC metals and alloys , especially to enhance their ductility, and investigate the underlying deformation mechanism, nanocrystalline Ni, dual phase Ni-Co alloy and Cu were synthesized via electrodeposition and electro-brush deposition respectively, and then a series of mechanical tests were carried out. The results show that all the materials exhibit a combination of high strength and remarkable ductility. The high strength can be attributed to the “true” nanocrystalline grain sizes ranges from 15 to 30 nm. In addition, three factors are revealed to contribute to the enhanced ductility of these materials, respectively: (a) modified deformation mode (the tensile-relaxation cycle test) for nanocrystalline Ni, (b) high strain hardening and cooperative deformation for dual-phase Ni-Co alloy, and (c) high strain rate sensitivity for nanocrystalline Cu.
Stages of Plastic Deformation in Metallic Nanocrystals
Authors: Koneva Nina , Kozlov Eduard
Published: May 2011

In this paper, analysis of work hardening laws for grains with sizes on nano- and microlevel is carried out. The work is based on experimental data of deformation behavior of mainly pure copper at room temperature (RT). A special attention is given to the interval of grains with the average size between 20 nm and 230 nm. Work hardening stages of active plastic deformation during tension and compression are characterized. The dependence of work hardening coefficients on the average grains size at the nanoscale in the II, IV and VI stages is revealed for the first time. Mechanisms of deformation in the range of grains sizes between 10 nm and 1000 nm are categorized. The relationship between work hardening stages and deformation mechanisms is discussed. The stage of deformation where deformation localization takes place is determined.
Deformation Mechanisms in Nanocrystalline Nickel at Low Temperatures
Authors: Hollang L. , Reuther K. , Dey S.R. , Hieckmann E. , Skrotzki Werner
Published: May 2011

It is the aim of the present paper to quantify and visualise the grain size induced transition of the deformation mechanism in metal polycrystals from the conventional dislocation–dislocation interaction at large grain sizes to (probably) dislocation–grain boundary interaction in the “nano” region. Since both types of interaction are thermally activated, thermal activation analysis can be used to discriminate between them. For this purpose dynamic tensile tests with stress relaxation tests were performed on pure pulsed electrodeposited nickel with 140 nm grain size at temperatures between 4 and 320 K. The results clearly indicate the transition temperature to be around 77 K. A rather unexpected result is the existence of a second transition of the deformation mechanism, which is only observable at very low temperatures namely from the homogeneous deformation mode governed by conventional dislocation–dislocation interaction towards localized deformation by “catastrophic shear”.
Kinetic Modeling of the Deformation Behavior of High-Strength Nanostructured Al-Mg Alloys
Authors: Alexandrov Igor V. , Chembarisova Roza G. , Latypov M.I.
Published: May 2011

Basing on the kinetic modeling, the role of microstructure peculiarities in formation of a revealed experimentally high-strength state of the nanostructured Al 6061 (Mg 0.8…1.2, Si 0.4…0.8, Cu 0.15…0.40, Cr 0.15…0.35, Mn 0.15, Fe 0.7, Zn 0.25, Ti 0.15 wt. %) alloy was analyzed, Possible strengthening mechanisms of the alloy subjected to high pressure torsion at room temperature have been considered. It has been shown that the grain size and segregation of Si, Cu and Mg atoms from the solid solution in the grain boundaries area are the main factors that enhance the alloy strength. Conclusions on the deformation mechanisms acting in the considered alloy have been made. They can be helpful for predicting the mechanical properties of materials. Quantitative estimation of the dislocation density, the stress of dislocation strengthening, and the stress of dislocation pinning by Mg atoms has been made.
On the Conflicts in the Experimental Results Concerning the Mechanical Properties of Ultra-Fine Grained and Nanostructured Materials: Effects of Processing Routes and Experimental Conditions
Authors: Padmanabhan K. Anantha , Prabu S. Balasivanandha
Published: May 2011

Different routes of severe plastic deformation (SPD) processing employed for the production of ultrafine grained and nanostructured materials are identified. The structural changes accompanying SPD that lead to improved mechanical properties are noted. Some uncertainties associated with the processing, which cause variations in the mechanical properties, are highlighted. Special attention is paid to equi-channel angular pressing/ extrusion, high pressure torsion, accumulative roll bonding/fold - roll processing, reciprocating extrusion – compression, cyclic close die forging, and repetitive corrugation and straightening- processes many of which can be adapted to suit standard metal working equipment, fitted with inexpensive devices and tools. The conflicting observations on the mechanical properties of ultrafine grained and nanostructured materials are discussed.
Effects of Surface Pinning, Locking and Adaption of Twins on the Performance of Magnetic Shape-Memory Alloys
Authors: Chmielus Markus , Müllner Peter
Published: May 2011

We study the effect of surface modifications and constraints on the mechanical properties of Ni-Mn- Ga single crystals, which are imposed by (i) structural modifications near the surface, (ii) mounting to a solid surface, and (iii) guiding the stroke. Spark eroded samples were electropolished and characterized before and after each polishing treatment. Surface damage was then produced with spark erosion and abrasive wearing. Surface damage stabilizes and pins a dense twin-microstructure and prevents twins from coarsening. The density of twins increases with increasing degree of surface deformation. Twinning stress and hardening rate during mechanical loading increase with increasing surface damage and twin density. In contrast, when a damaged surface layer is removed, twinning stresses, hardening rate, and twin density decrease. Constraining the sample by mounting and guiding reduces the magnetic-field-induced strain by locking twins at the constrained surfaces. . For single-domain crystals and for hard magnetic shape-memory alloys, external constraints strongly reduce the magnetic-field-induced strain and the fatigue lifetime is short. In contrast, for selfaccommodated martensite and for soft magnetic shape-memory alloys, the twin-microstructure adapts well to external constraints and the fatigue lifetime is long. The performance of devices with MSMA transducers requires managing stress distributions through design and control of surface properties, microstructure, and constraints.
Room Temperature Ferromagnetism and its "Switch" Behaviour in some Dilute Magnetic Oxides: an Electronic Structure and Magnetization Study
Authors: Singhal R.K.
Published: May 2011

ZnO doped with a few per cent of magnetic ions such as Ni, Fe, Co exhibits room temperature ferromagnetism (RTFM), transforming it into a very promising candidate for future spintronic applications. Two samples i.e. ZnO doped with Ni and Cr (5% each) have been investigated in the present work. The samples were characterized by Rietveld refinement of X-ray diffraction (XRD) patterns and the superconducting quantum interference device (SQUID) magnetometry. Rietveld analysis confirms that both the polycrystalline samples possess wurtzite structure with no evidence of any secondary phase. The SQUID measurements exhibit a diamagnetic state for the pristine ZnO and a paramagnetic state for the as-synthesized (Cr and Ni)-doped ZnO samples. However, the post annealing in H2 and vacuum drive them to a remarkable ferromagnetic state at room temperature. No element specific signature for ferromagnetism was seen. Then the X-ray photoelectron spectroscopic (XPS) measurements were performed to investigate their electronic structure and exploring the origin of ferromagnetism in these diluted magnetic semiconductor materials. The XPS results confirm the creation of oxygen vacancies upon Hydrogen/ vacuum annealing, owned to the (Ni/Cr) 3d¬−O 2p hybridization. The findings suggest oxygen vacancies as the intrinsic origin for ferromagnetism in doped ZnO. The important feature of this work is that the ferromagnetism and the consequent electronic property changes are found to be reversible with regard to re-heating the samples in air, showing a switch “on” and “off” ferromagnetic ordering in the ZnO matrix.
First-Principles Study of Structural, Electronic, Elastic, Phonon, and Thermodynamical Properties of the Niobium Carbide
Authors: Rathod Nikita , Gupta S.D. , Gupta Sanjeev K. , Jha Prafulla K.
Published: May 2011

A detailed theoretical study of structural, electronic and vibrational properties of niobium carbide are carried out in rocksalt phase using the density functional theory implemented in ABINIT code. The calculated structural parameters like lattice constant and bulk modulus agree well with the available data. The Zener anisotropy factor (A), Poison's ratio (v), Young’s modulus (Y) and shear modulus (C’) are also presented. The electronic band structure and density of states are presented and discussed in light of bonding nature in NbC. The band structure indicates its metallic nature. The calculated phonon dispersion curves show that the NbC in rocksalt phase has all positive phonons throughout the Brillouin zone. The thermodynamical properties are also presented and discussed.
Bovine Tuberculosis and the Establishment of an Eradication Program in the United States: Role of Veterinarians
Authors: Palmer Mitchell V. , Waters W. Ray
Published: May 2011

The significance of the identification ofMycobacterium bovisas a zoonotic pathogen in 1882 was not initially recognized. After years of research by veterinarians, and other scientists, the importance ofM. bovisas a pathogen and the public health ramifications, were appreciated. Veterinarians played pivotal roles in the creation of improved meat and milk inspection, diagnosis ofM. bovisinfected cattle, and in time, a bovine tuberculosis eradication program that would impact every cattle producer in the country. After overcoming many challenges, the 93-year-long program has decreased disease prevalence from 5% to <0.001%. Today, years of hard work by practitioners, researchers and regulatory officials alike, have yielded a program with a net benefit of almost $160 million per year.
Correlation of Chimerism with Acute Graft-versus-Host Disease in Rats following Liver Transplantation
Authors: Xue Fei , Chen Wei , Bai Xue-Li , Xu Guo-Dong , Liang Liang , Liang Ting-Bo
Published: May 2011

The accurate diagnosis of acute graft-versus-host disease following liver transplantation (LTx-aGVHD) has been hampered. Chimerism appears in the majority of recipients after LT and its significance in the diagnosis of LTx-aGVHD has not been clearly established. To demonstrate the significance of chimerism on the diagnosis of LTx-aGVHD, we compared the change of chimerism in syngeneic LT recipients, semiallogeneic LT recipients, and LTx-aGVHD induced recipients. Chimerism in PBMCs following sex-mismatched LT was identified by real-time PCR based on a rat Y-chromosome-specific primer. All recipients in semiallogeneic group grew in a normal pattern. However, when donor splenocytes were transferred simultaneously during LT, the morbidity of lethal aGVHD was 100%. The chimerism appeared slightly higher in the semiallogeneic group than in the syngeneic LT group, but the difference was not significant. However, when the recipients developed lethal aGVHD after LT, chimerism in the PBMCs increased progressively, and even at an early time, a significant increase in chimerism was observed. In conclusion, high level chimerism correlated well with LTx-aGVHD, and detection of chimerism soon after transplantation may be of value in the diagnosis of LTx-aGVHD prior to the onset of symptoms.
Upregulation of cardiac NO/NOS system during short-term hypoxia and the subsequent reoxygenation period
Authors: Rus A. , Del Moral M.L. , Molina F. , Peinado M.A.
Published: May 2011

Hypoxia/reoxygenation (H/R) reportedly influences nitric oxide (NO) production and NO synthase (NOS) expression in the heart. Nonetheless, a number of works have shown controversial results regarding the changes that the cardiac NO/NOS system undergoes under such situations. Therefore, this study aims to clarify the behaviour of this system in the hypoxic heart by investigating seven different reoxygenation times. Wistar rats were submitted to H/R (hypoxia for 30 min; reoxygenation of 0, 2, 12, 24, 48, 72 h, and 5 days) in a novel approach to address the events provoked by assaults under such circumstances. Endothelial and inducible NOS (eNOS and iNOS) mRNA and protein expression, as well as enzymatic activity and enzyme location were determined. NO levels were indirectly quantified as nitrate/nitrite, and other S-nitroso compounds (NOx), which would act as NO-storage molecules. The results showed a significant increase in eNOS mRNA, protein and activity, as well as in NOx levels immediately after hypoxia, while iNOS protein and activity were induced throughout the reoxygenation period. These findings indicate that, not only short-term hypoxia, but also the subsequent reoxygenation period upregulate cardiac NO/NOS system until at least 5 days after the hypoxic stimulus, implying major involvement of this system in the changes occurring in the heart in response to H/R.
Teenagers’ experiences of sexual health dialogue in the rural villages of the Vhembe District, Limpopo Province
Authors: Tsakani Lebese R. , Davhana- Maselesele Mashudu , Obi Larry C.
Published: May 2011

Dialogue with teenagers about sexual health is of global concern, as it is found mostly to be minimal, if not absent. This limitation is influenced by the cultural values, beliefs and norms of teenagers. To a great extent, culture influences which and how sexual health issues can be discussed between teenagers and adults. The purpose of this study was to explore and describe teenagers’ experiences of sexual health dialogue in the rural areas of the Vhembe district in Limpopo province, South Africa. A qualitative, explorative, descriptive and contextual research approach was used. Data were collected by means of in-depth, individual interviews and focus-group discussions. A purposive sampling method was used to select the 57 participating teenagers, based on criteria that were set. The findings of the study indicated that there was minimal dialogue between adults and teenagers about sexual health. Most teenagers reported that they learned about issues related to sexual health from friends, the media, initiation schools and relatives who, most often, were aunts. It was also noted with concern that the teenagers always equated sexual health to the act of intercourse and that no attention was paid to other aspects of sexual health. Recommendations to improve the current situation were made.OpsommingDialoog met tienerjariges rakende seksuele gesondheid is ’n wêreldwye probleem omdat daar gevind is dat dit meestal minimaal is of glad nie plaasvind nie. Hierdie beperking word beïnvloed deur die tienerjariges se kulturele waardes, oortuigings en norme. Kultuur beïnvloed in ’n groot mate watter seksuele gesondheidsake tussen tienerjariges en volwassenes bespreek kan word, en hoe dit gedoen kan word. Die doel van hierdie studie was om tienerjariges se ondervindings van seksuele gesondheidsdialoog in die landelike gebiede van die Vhembedistrik in die Limpopo-provinsie van Suid-Afrika te ondersoek en te bespreek. ’n Kwalitatiewe,ondersoekende, beskrywende en kontekstuele navorsingsbenadering is gevolg.Data is versamel deur middel van grondige individuele onderhoude en fokusgroep-besprekings.’n Doelbewuste steekproefmetode is gebruik om die 57 deelnemende tienerjariges op grond van bepaalde kriteria te selekteer.Die bevindings van die studie het aangedui dat daar minimale dialoog oor seksuele gesondheid tussen tienerjariges en volwassenes is. Die meeste tienerjariges het gerapporteer dat hulle by vriende, die media, inisiasieskole en familielede, meestal ’n tante, van seksuele gesondheid geleer het. Daar is met kommer opgemerk dat tienerjariges seksuele gesondheid aan die daad van omgang gelykstel en dat geen aandag aan ander aspekte van seksuele gesondheid geskenk is nie. Aanbevelings ter verbetering van die situasie is gemaak.
Physical activity levels and energy expenditure of 9-year-old – 12-year-old overweight and obese children
Authors: Kemp Chanelle , Pienaar Anita E.
Published: May 2011

The high occurrence of overweight and obesity amongst children is a disturbing health problem worldwide. Possible causes of increasing childhood obesity are inactivity and energy imbalances. The aim of this study was to analyse the total energy expenditure (TEE)and physical activity levels in 9-year-old – 12-year-old overweight and obese children during a weekday and a weekend day, as well as during a weekday morning and afternoon. Twenty-four 9-year-old – 12-year-old children (seven boys and 17 girls), of whom nine were overweight and 15 were obese, were selected from seven public primary schools for this study. Body mass index (BMI) cut-off points were used to distinguish between overweight and obese. Each participant wore an ACTICAL™ monitor to determine their physical activity levels and TEE. It was found that the TEE of the children did not differ between a week day and a weekend day, although the TEE of the week day afternoon differed significantly from that of the weekday morning. Unlike the overweight children, none of the obese children met the requirements of 60 minutes of moderate-intensity physical activity per day. Strategies should be found to increase the activity levels of overweight and, especially, obese children, specifically during the mornings and over weekends.OpsommingDie hoë voorkoms van oorgewig en obesiteit onder kinders is wêreldwyd ’n kommerwekkende gesondheidsprobleem. Fisieke onaktiwiteit en energiewanbalanse word as moontlike oorsake van die probleem beskou. Die doel van hierdie studie was om die totale energieverbruik (TEV) en fisieke-aktiwiteitsvlakke van 9-jarige – 12-jarige oorgewig- en obese kinders tydens ‘n totale weeksdag en naweekdag te ontleed, asook tydens die oggend en middag van ‘n weeksdag. Vier-en-twintig 9-jarige – 12-jarige kinders (sewe seuns en 17 dogters), waarvan nege oorgewig en 15 obees was, is uit sewe publieke laerskole vir die studie gekies. Afsnypunte volgens die liggaamsmassa-indeks (LMI) is gebruik om tussen oorgewig en obees te onderskei. Elke deelnemer het ‘n ACTICAL™ monitor gedra om hul fisieke-aktiwiteitsvlakke en TEV te bepaal. Die studie het getoon dat die TEV van die kinders op ’n weeksdag en naweekdag nie verskil het nie, alhoewel TEV tydens die middag van die weeksdag betekenisvol verskil het van die oggend s’n. Anders as die oorgewig kinders, het geen van die obese kinders aan die voorgestelde riglyn van 60 minute se matig intensiewe fisieke aktiwiteit per dag voldoen nie. Strategieë moet gevind word om die vlakke van aktiwiteit van oorgewig en veral obese kinders te verhoog, spesifiek gedurende die oggende en oor naweke.
The avifauna of Kwandwe Private Game Reserve, Eastern Cape, South Africa
Authors: Craig Adrian J.F.K. , Bissett Charlene , Galpin Mark D. , Olver Bryan , Hulley Pat E.
Published: May 2011

A protected area since 1999, Kwandwe Private Game Reserve incorporates several former farms, for which past records of bird occurrences are available. No bird species appear to have been lost from the area. Between 2001 and 2005, a group of observers conducted systematic bird surveys in most months, which allowed the status (resident, migrant or irregular visitor) of most bird species to be determined. At least three species have established breeding populations in the reserve over the past 10 years. Of 302 species reliably recorded to date, 182 (60.3%) appear to be resident, 46 (15.2%) are seasonal migrants and 74 (24.5%) are vagrant visitors. Eight vulnerable and eight near-threatened bird species have been recorded; Blue Crane, Kori Bustard and African Crowned Eagle have bred in the reserve. Together with other state-owned and private protected areas in this region, this reserve holds a significant portion of the inland bird species recorded from the Eastern Cape.Conservation implications: The varied thicket vegetation types of the Great Fish River Valley support a considerable diversity of bird species. If these habitats are managed for biodiversity conservation, they can support a large component of the terrestrial avifauna of the Eastern Cape region.
Advances and challenges in the implementation of strategic adaptive management beyond the Kruger National Park – Making linkages between science and biodiversity management
Authors: Gaylard Angela , Ferreira Sam
Published: May 2011

South African National Parks (SANParks) makes use of strategic adaptive management (SAM) to achieve its primary mandate of biodiversity conservation. This involves an iterative adaptive planning, management and review cycle to ensure appropriate alignment of stakeholder values with conservation objectives, to address the uncertainty inherent in complex social– economic–ecological systems and to learn explicitly whilst doing so. Adaptive management is recognised as the most logical framework for continuous improvement in natural resource management; nevertheless, several challenges in its implementation remain. This paper outlined these challenges and the various modifications to SANParks’ adaptive planning and management process that have emerged during its development. We demonstrated how the establishment of a regular Science–Management Forum provides opportunities for social colearning amongst resource managers and scientists of a particular park, whilst providing other positive spin-offs that mature the SAM process across the organisation. We discussed the use of particular conceptual constructs that clarify the link between monitoring, management requirements and operational endpoints, providing the context within which Thresholds of Potential Concern (TPCs) should be set, prioritised and measured. The evolution of the TPC concept was also discussed in the context of its use by other organisations, whilst recognising its current limitations within SANParks. Finally, we discussed remaining implementation challenges and uncertainties, and suggested a way forward for SAM.Conservation implications: This paper outlined practical methods of implementing SAM in conservation areas, beyond what has already been learnt within, and documented for, the Kruger National Park. It also highlighted several implementation challenges that prove useful to other conservation agencies planning to adopt this approach to managing complex ecosystems.
Implementing invasive species management in an adaptive management framework
Authors: Foxcroft Llewellyn C. , McGeoch Melodie
Published: May 2011

Adaptive management theory has attracted substantial interest in recent years, in natural resource management in general and also for invasive alien species management. However, whilst many theoretical and conceptual advances have been made, documented cases of practical applications are rare. Coupling invasive species management components with adaptive feedback processes is not without challenges, requiring a substantial change in the thinking and practice of all those involved. Drawing on a decade of experience in South African National Parks, we suggest an approach to implementing adaptive management for controlling invasive alien species. Whilst efforts have been made to advance components of the overall management strategy, the absence of a framework for decision making and feedback mechanisms, inflexibility in the system and shortcomings in the governance structure are all identified as barriers to learning and knowledge integration for the purposes of effective invasive alien species management. The framework provided here, encompassing documents, committees and processes, is aimed at addressing these shortcomings.Conservation implication: Adaptive management theory offers a robust tool for managing inherently complex systems. Its practical application, however, requires distilling the theory into useable functions. We offer a framework to advance implementation of strategic adaptive management for the control of invasive alien species using experiences gained from South African National Parks.
SANParks, people and adaptive management: Understanding a diverse field of practice during changing times
Authors: Swemmer Louise K. , Taljaard Sandra
Published: May 2011

Biodiversity conservation is often measurable and achievable and has been reasonably successful within the boundaries of national parks. However, the concept of parks providing tangible benefits and hence being seen as ‘valuable’ to the majority of the nation has been more difficult to define, measure and, importantly, deliver on. This function has traditionally fallen under what is currently known as the People and Conservation Department, which has a rich history in South African National Parks (SANParks) of change and adaptive learning in terms of defining core functions and associated management strategies, spanning from its original inception as the Information Services Department over 80 years ago. Learning from and in some cases, adapting to change, is evident throughout this broad scale national evolution of the department, from an initial focus on information sharing and education in the 1930s, to what we see today. This includes the primary focus areas of cultural resource management and indigenous knowledge, community relations, environmental education, awareness, youth outreach, interpretation and training. At a more local, park scale, there is a current drive to formalise the adaptive management and learning process for the people component of protected areas through the alignment of relevant project, programme and park objectives with those at a corporate or national level. Associated with this is an attempt to further align the associated monitoring, evaluation and reporting processes, thereby completing the formal adaptive management loops in order to facilitate and stimulate co-learning within and between relevant responsible departments within the organisation.Conservation implications: Benefit sharing through biodiversity conservation has been shown to be crucial for the long-term success of protected areas, but the practicalities of implementing this are thwart with challenges. Despite this, SANParks is attempting to facilitate and promote benefits through conservation, specifically in the sense of benefits that support livelihoods whilst reducing vulnerability. With this in mind, we acknowledge the importance of the concepts of scale, resilience, complexity and adaptive learning for, and during, this process.
Towards adaptive fire management for biodiversity conservation: Experience in South African National Parks
Authors: Van Wilgen Brian W. , Govender Navashni , Forsyth Gregory G. , Kraaij Tineke
Published: May 2011

This paper reviews the experience gained in three South African national parks (Kruger, Table Mountain and Bontebok) with regard to the adaptive management of fire for the conservation of biodiversity. In the Kruger National Park, adaptive approaches have evolved over the past 15 years, beginning initially as a form of ‘informed trial and error’, but progressing towards active adaptive management in which landscape-scale, experimental burning treatments are being applied in order to learn. In the process, significant advances in understanding regarding the role and management of fire have been made. Attempts have been made to transfer the approaches developed in Kruger National Park to the other two national parks. However, little progress has been made to date, both because of a failure to provide an agreed context for the introduction of adaptive approaches, and because (in the case of Bontebok National Park) too little time has passed to be able to make an assessment. Fire management interventions, ultimately, will manifest themselves in terms of biodiversity outcomes, but definite links between fire interventions and biodiversity outcomes have yet to be made.Conservation implications: Significant challenges face the managers of fire-prone and fire adapted ecosystems, where the attainment of ecosystem goals may require approaches (like encouraging high-intensity fires at hot and dry times of the year) that threaten societal goals related to safety. In addition, approaches to fire management have focused on encouraging particular fire patterns in the absence of a sound understanding of their ecological outcomes. Adaptive management offers a framework for addressing these issues, but will require higher levels of agreement, monitoring and assessment than have been the case to date.