bluuebunny/crossref_metadata_2025 huggingface dataset:
Sea level change and the area of shallow-marine habitat: implications for marine biodiversity
Authors: Holland Steven M.
Published: March 2012

Analysis of a global elevation database to measure changes in shallow-marine habitat area as a function of sea level reveals an unexpectedly complicated relationship. In contrast to prevailing views, sea level rise does not consistently generate an increase in shelf area, nor does sea level fall consistently reduce shelf area. Different depth-defined habitats on the same margin will experience different changes in area for the same sea level change, and different margins will likewise experience different changes in area for the same sea level change. Simple forward models incorporating a species-area relationship suggest that the diversity response to sea level change will be largely idiosyncratic. The change in habitat area is highly dependent on the starting position of sea level, the amount and direction of sea level change, and the habitat and region in question. Such an idiosyncratic relationship between diversity and sea level reconciles the widespread evidence from the fossil record for a link between diversity and sea level change with the lack of quantitative support for such a relationship throughout the Phanerozoic.
Stonecutters Bridge: design of foundations
Authors: Thompson Peter A. , Lee Daman , Kite Steve , Colwill Richard D.
Published: March 2012

For Stonecutters Bridge, Hong Kong, the foundation support is most efficiently provided by bored piles utilising end bearing and friction in the hard rock stratum, which is typically between 45 m and 67 m below ground level on the east side and between 48 m and 75 m below ground level on the west side. Local areas of deeper weathering are observed beneath the west tower and the adjacent back-span pier. The foundations for each pier and tower comprise a thick reinforced concrete cap supported on a grid of large-diameter, bored piles. The bored piles are socketted in rock and typically enlarged at the base up to 1·5 times the pile shaft diameter to provide resistance through both shaft friction and end bearing with no contribution from the overlying superficial deposits. The design used an iterative process to achieve compatibility between the bridge superstructure and substructure. Additional considerations for seismic loads and ship impact were also taken into account.
Stonecutters Bridge, Hong Kong: design of steel deck
Authors: Hauge Lars , Carter Matt , Vejrum Tina
Published: March 2012

This paper describes the detailed design of the steel deck of Stonecutters Bridge in Hong Kong. The 1018 m main span deck and first 49·75 m of each back-span deck are steel, whereas the remaining lengths of back-span decks are prestressed concrete. The 53·3 m wide bridge deck consists of twin box girders connected by cross girders. The aerodynamic performance of the steel deck is fundamental to the overall behaviour of the bridge and the design is dominated by the dynamic effects of typhoon winds. Other design considerations including intense fatigue loading from heavy goods traffic and high summer temperatures were also influential in the design.
Evaluation of shear strength in self-compacting fibre-reinforced concrete and conventional concrete deep beams
Authors: Shah Dinesh L. , Modhera Chetankumar D.
Published: March 2012

Self-compacting concrete (SCC) offers several benefits over conventional concrete (CC), mainly the ease in placement and lack of vibration. The uses of SCC with fibres extend its possibilities. As fibres are known to significantly affect the workability of concrete, primarily investigation was carried out to finalise the possible content of steel and polyester fibres by various fresh property tests of SCC as per EFNARC specifications. The use of concrete deep beams is gaining rapid popularity in modern construction industry owing to the requirement of column-free space. There is some concern among researchers and designers that SCC may not be strong enough in shear because of the smaller amount, smaller size and the weak interlock mechanism of coarse aggregate. In the case of deep beams, shear failure is prominent and the aim of further research is to investigate the shear strength and deformation characteristics of SCC with and without fibres for various span-to-depth ratios of deep beams in comparison with conventional concrete. Based on the fresh property test results of SCC with fibres, steel fibres produced more hindrance in flow than polyester fibres, whereas in the hardened state steel fibres showed better strength. In deep beams, the shear capacity of SCC was 35–45% lower than that of CC. The shear capacity of the SCC deep beams was increased 25–35% by the inclusion of steel fibres. However, insignificant and unrewarding results were produced by polyester fibres.
Photographic mark–recapture analysis of local dynamics within an open population of dolphins
Authors: Fearnbach H. , Durban J. , Parsons K. , Claridge D.
Published: March 2012

Identifying demographic changes is important for understanding population dynamics. However, this requires long‐term studies of definable populations of distinct individuals, which can be particularly challenging when studying mobile cetaceans in the marine environment. We collected photo‐identification data from 19 years (1992–2010) to assess the dynamics of a population of bottlenose dolphins (Tursiops truncatus) restricted to the shallow (<7 m) waters of Little Bahama Bank, northern Bahamas. This population was known to range beyond our study area, so we adopted a Bayesian mixture modeling approach to mark–recapture to identify clusters of individuals that used the area to different extents, and we specifically estimated trends in survival, recruitment, and abundance of a “resident” population with high probabilities of identification. There was a high probability (p = 0.97) of a long‐term decrease in the size of this resident population from a maximum of 47 dolphins (95% highest posterior density intervals, HPDI = 29–61) in 1996 to a minimum of just 24 dolphins (95% HPDI = 14–37) in 2009, a decline of 49% (95% HPDI = −5% to −75%). This was driven by low per capita recruitment (average ∼0.02) that could not compensate for relatively low apparent survival rates (average ∼0.94). Notably, there was a significant increase in apparent mortality (∼5 apparent mortalities vs. ∼2 on average) in 1999 when two intense hurricanes passed over the study area, with a high probability (p = 0.83) of a drop below the average survival probability (∼0.91 in 1999; ∼0.94, on average). As such, our mark–recapture approach enabled us to make useful inference about local dynamics within an open population of bottlenose dolphins; this should be applicable to other studies challenged by sampling highly mobile individuals with heterogeneous space use.
Environmental Predictors of Pathogenic Vibrios in South Florida Coastal
Waters
Authors: Yamazaki Koske , Esiobu Nwadiuto
Published: March 2012

In 2007, diseases caused by Vibrio vulnificus and other Vibrio species became nationally notifiable in the
United States because of the potential severity of bloodstream infections. Direct contact of open wound with seawater and
the ingestion of contaminated oysters are the principal modes of transmission. Presently, no clear environmental
predictors of oyster contamination are known. This study is the first to report an apparent association between rainfall and
Vibrio counts at five South Florida beaches. Using multiple regression and ANOVA, the relationship between Vibrio
populations and various environmental factors were examined. Vibrio counts ranged from 135 CFU/100 mL at Hollywood
Beach to 186,000 CFU/100 mL at North Miami Beach. Vibrio vulnificus and parahemolyticus were detected (less than
1% of all identified isolates) at two and four beaches respectively. Temperature and rainfall dates were the most
significant correlates of the incidence of pathogenic Vibrio species.
Advance Care Planning in CKD/ESRD
Authors: Holley Jean L.
Published: March 2012

Advance care planning was historically considered to be simply the completion of a proxy (health care surrogate designation) or instruction (living will) directive that resulted from a conversation between a patient and his or her physician. We now know that advance care planning is a much more comprehensive and dynamic patient-centered process used by patients and families to strengthen relationships, achieve control over medical care, prepare for death, and clarify goals of care. Some advance directives, notably designated health care proxy documents, remain appropriate expressions of advance care planning. Moreover, although physician orders, such as do-not-resuscitate orders and Physician Orders for Life-Sustaining Treatment, may not be strictly defined as advance directives, their completion, when appropriate, is an integral component of advance care planning. The changing health circumstances and illness trajectory characteristic of ESRD mandate that advance care planning discussions adapt to a patient’s situation and therefore must be readdressed at appropriate times and intervals. The options of withholding and withdrawing dialysis add ESRD-specific issues to advance care planning in this population and are events each nephrologist will at some time confront. Advance care planning is important throughout the spectrum of ESRD and is a part of nephrology practice that can be rewarding to nephrologists and beneficial to patients and their families.
Association of Statin Use with Risk and Outcome of Acute Kidney Injury in Community-Acquired Pneumonia
Authors: Murugan Raghavan , Weissfeld Lisa , Yende Sachin , Singbartl Kai , Angus Derek C. , Kellum John A.
Published: March 2012

Background and objectives

Sepsis is a leading cause of AKI. Animal studies suggest that the pleiotropic effect of statins attenuates the risk for AKI and decreases mortality. This study examined whether statin use was associated with a lower risk for pneumonia-induced AKI and 1-year and cause-specific mortality in patients with AKI.

Design, setting, participants, & measurements

Multicenter, prospective cohort study of 1836 patients hospitalized with community-acquired pneumonia.

Results

Baseline characteristics differed among statin users and nonusers. Of the 413 patients (22.5%) who received a statin before hospitalization, statin treatment, when adjusted for differences in age, severity of pneumonia, admission from nursing home, health insurance, and propensity for statin use, did not reduce the risk for AKI (odds ratio [OR], 1.32 [95% confidence interval (CI), 1.02–1.69]; P=0.05). Of patients with AKI (n=631), statin use was associated with a lower risk for death at 1 year (27.8% versus 38.8%; P=0.01), which was not significant when adjusted for differences in age, severity of pneumonia and AKI, use of mechanical ventilation, and propensity score (OR, 0.72 [95% CI, 0.50–1.06]; P=0.09). Among patients with AKI, cardiovascular disease accounted for one third of all deaths.

Conclusions

In a large cohort of patients hospitalized with pneumonia, statins did not reduce the risk for AKI. Among patients with AKI, statin use was not associated with lower risk for death at 1 year. The higher risk for AKI observed among statin users may be due to indication bias.
Electrocardiogram Abnormalities and Cardiovascular Mortality in Elderly Patients with CKD
Authors: Dobre Mirela , Brateanu Andrei , Rashidi Arash , Rahman Mahboob
Published: March 2012

Background and objectives

Cardiovascular disease is the most common cause of death in CKD. This study evaluated whether electrocardiogram (ECG) abnormalities are predictors of cardiovascular death in CKD.

Design, setting, participants, & measurements

The Cardiovascular Health Study limited database (1989–2005) was used to identify a cohort with CKD at baseline (estimated GFR < 60 mL/min per 1.73 m2). The patients were categorized as having major, minor, or no ECG abnormalities. Rates of adjudicated cardiovascular events and mortality were compared among the groups using proportional hazards regression models.

Results

A total of 1192 participants had CKD at baseline; mean age ± SD was 74.7±6.2 years. Of these patients, 452 (38.8%) had major, 346 (29.7%) had minor, and 367 (31.5%) had no ECG abnormalities. Participants with estimated GFR < 60 mL/min per 1.73 m2 were more likely to have ECG abnormalities at baseline (adjusted prevalence odds ratio, 1.23 [95% confidence interval (CI), 1.06–1.43]) than those with GFR ≥ 60 mL/min per 1.73 m2. During mean follow-up of 10.3±3.8 years, 814 (68.3%) participants died. Compared with participants without ECG abnormalities, participants with major abnormalities had the highest risk for cardiovascular events and death; adjusted hazard ratios were 2.15 (95% CI, 1.56–2.98) and 2.27 (95% CI, 1.56–3.30), respectively. For minor ECG abnormalities, hazard ratios were 1.24 (95% CI, 0.91–1.70) and 1.48 (95% CI, 1.00–2.18), respectively.

Conclusions

In patients with CKD, major ECG abnormalities are frequently present and predict a significantly higher risk for death and adverse cardiovascular outcomes.
Bilateral Changes in Forearm Oxygen Consumption at Rest and After Exercise in Patients With Unilateral Repetitive Strain Injury: A Case-Control Study
Authors: Brunnekreef Jaap J.J. , Thijssen Dick H.J. , Oosterhof Jan , Hopman Maria T.E.
Published: March 2012

Study Design

Case-control study.

Objectives

To investigate whether oxygen consumption and blood flow at rest and after exercise are lower in the affected arm of patients with repetitive strain injury (RSI) compared to controls, and lower in the healthy nonaffected forearm within patients with unilateral RSI.

Background

RSI is considered an upper extremity overuse injury. Despite the local presentation of complaints, RSI may be represented by systemic adaptations. Insight into the pathophysiology of RSI is important to better understand the development of RSI complaints and to develop effective treatment and prevention strategies.

Methods

Twenty patients with unilateral RSI and 20 gender-matched control subjects participated in this study. Forearm muscle blood flow and oxygen consumption were measured using near-infrared spectroscopy at baseline and immediately after isometric handgrip exercises at 10%, 20%, and 40% of the individual maximal voluntary contraction.

Results

Unilateral RSI resulted in a lower oxygen consumption and blood flow in the affected forearm at baseline and lower oxygen consumption after incremental handgrip exercises compared to controls (P<.05). In addition, exercise-induced blood flow and oxygen consumption in the nonaffected forearm in patients with RSI were similarly reduced.

Conclusion

Blood flow and oxygen consumption after exercise are similarly attenuated in the affected and nonaffected arms of patients with unilateral RSI. Our findings suggest that, despite the unilateral character in clinical symptoms, RSI demonstrates systemic adaptations in forearm blood flow and oxygen consumption at rest and after exercise.
Suggestions From the Field for Return-to-Sport Rehabilitation Following Anterior Cruciate Ligament Reconstruction: Alpine Skiing
Authors: Kokmeyer Dirk , Wahoff Michael , Mymern Matt
Published: March 2012

Synopsis

Alpine skiing is a high-risk sport for injuries to the anterior cruciate ligament (ACL). While descending a hill, a skier must resist large centrifugal forces at a high velocity, while the knees are positioned in postures that place the ACL at risk of injury. Skiers who undergo ACL reconstructive surgery are prone to a high rate of reinjury to the same knee and even ACL injury in the uninjured knee. A rehabilitation program that integrates the best current evidence of ACL rehabilitation and the science of skiing is essential to a successful return to alpine skiing. Unlike rehabilitation programs developed for court or field athletes, a skiing program must place a large emphasis on slow eccentric-loading and weight-bearing (closed-chain) power and endurance. The purpose of this clinical commentary is to provide the rehabilitation specialist such a program directed toward safely returning the athlete to alpine skiing.

Level of Evidence

Therapy, level 5.
Hunting influences the diel patterns in habitat selection by northern pintails Anas acuta
Authors: Casazza Michael L. , Coates Peter S. , Miller Michael R. , Overton Cory T. , Yparraguirre Daniel R.
Published: March 2012

Northern pintail Anas acuta (hereafter pintail) populations wintering within Suisun Marsh, a large estuarine managed wetland near San Francisco Bay, California, USA, have declined markedly over the last four decades. The reasons for this decline are unclear. Information on how hunting and other factors influence the selection of vegetation types and sanctuaries would be beneficial to manage pintail populations in Suisun Marsh. During 1991‐1993, we radio‐marked and relocated female pintails (individuals: N = 203, relocations: N = 7,688) within Suisun Marsh to investigate habitat selection during the non‐breeding months (winter). We calculated selection ratios for different vegetation types and for sanctuaries, and examined differences in those ratios between hunting season (i.e. hunting and non‐hunting), age (hatch‐year and after‐hatch‐year), and time of day (daylight or night hours). We found that diel patterns in selection were influenced by hunting disturbance. For example, prior to the hunting season and during daylight hours, pintails selected areas dominated by brass buttons Cotula coronopifolia, a potentially important food source, usually outside of sanctuary boundaries. However, during the hunting season, pintails did not select brass buttons during daylight hours, but instead highly selected permanent pools, mostly within sanctuaries. Also, during the hunting season, pintails showed strong selection for brass buttons at night. Sanctuaries provided more area of permanent water pools than within hunting areas and appeared to function as important refugia during daylight hours of the hunting season. Wildlife managers should encourage large protected permanent pools adjacent to hunted wetlands to increase pintail numbers within wetland environments and responsibly benefit hunting opportunities while improving pintail conservation.
Keeping bats cool in the winter: hibernating bats and their exposure to ‘hot’ incandescent lamplight
Authors: Haarsma Anne‐Jifke , de Hullu Eva
Published: March 2012

In order to monitor bat population trends, an annual census is performed of all known underground hibernacula in Europe. During these censuses, bats are sometimes found to show signs of arousal, presumably from non‐tactile stimuli caused by the observer, e.g. air currents, sound, light or an increase in temperature. We assume that heat and/or light from a torch can play a role in awaking hibernating bats. Observers use different light sources, which produce different amounts of heat. We experimentally tested the heat produced by three commonly used torches: two incandescent torches (krypton and halogen) and one LED torch. We performed the experiment on 28 January 2007 in an old brick kiln in Windesheim (Overijssel Province, the Netherlands), which is used by hibernating bats. The results show that temperatures in a crevice significantly increased when using the ‘hot’ incandescent torch types. The effect of these torches on both air and surface temperature was significant after both 10 and 30 seconds. Under the assumption that an increase of the ambient temperature by 5°C or more can cause a bat to arouse from torpor, we conclude that using ‘hot’ torches such as incandescent (halogen) lights poses a risk to the animals under study. To minimise heat disturbance from light sources, we recommend LED torches as the best available alternative.
Can Landsat data detect variations in snow cover within habitats of arctic ungulates?
Authors: Maher Andrew I. , Treitz Paul M. , Ferguson Michael A.D.
Published: March 2012

With climate change, modelling has suggested that increased inaccessibility of forage through snow may endanger some populations of arctic ungulates; however, contemporaneous data on snow‐cover conditions, other ecological factors and ungulate responses are lacking at the landscape scale. Researchers have increasingly used remote sensing to map snow cover with higher accuracy, but such tools have not been utilized in research and management of arctic ungulate populations. We estimated field‐measured percent snow‐covered area (F‐SCA) in wintering areas of endangered Peary caribou Rangifer tarandus pearyi in the Bathurst Island complex (BIC) and developed a threshold for a normalized difference snow index (NDSI) using Landsat data. We used our NDSI threshold and another threshold to estimate snow‐covered area (SCA) in Peary caribou habitats in the BIC during 1993‐2003, compared these estimates with snow data from the nearest weather station and assessed the adequacy of Landsat data for arctic ungulate research. Our calculated NDSI threshold of 0.70 reflected field observations better than the published threshold, and our estimated SCAs showed greater variation between study areas, between years and during snow melt. Estimated SCAs were not correlated with total snowfall or snow depth at the nearest weather station. We conclude that SCA using remotely‐sensed data for ungulate habitats would be more useful than weather‐station data. Our methods could detect winters with relatively mild snow‐cover conditions, but not those with very severe conditions; therefore, we recommend development of NDSI thresholds corresponding to ≥ 75% F‐SCA, instead of ≥ 50%. NDSI‐derived SCA methods should prove more useful for southerly arctic regions where sun angles would be less limiting than in the BIC. Higher resolution imagery may be more suited than Landsat for the assessment of snow cover in arctic ungulate ecology. With climate change, further development of remotely‐sensed indices of snow cover, such as NDSI and SCA, should enhance our understanding of how arctic ungulates may or may not adapt.
Effect of Ti addition on the wettability of Al–B4C metal matrix composites
Authors: Kocaefe Duygu , Sarkar Arunima , Chen X-Grant
Published: March 2012

In this study, the wettability of B4C by molten Al, as well as Al–Ti alloys, with different Ti contents has been studied using the sessile-drop method. In general, the contact angle decreases with increasing temperature and time. The results show that an appropriate amount of Ti addition improves the wettability of B4C by Al. Analyses of the interfaces of solidified drops revealed that Al3BC and AlB2 particles form around the B4C particles when they are in contact with pure Al. However, when Ti is added to Al, AlB2 particles disappear and a new Ti-rich layer composed of TiB2 particles forms around B4C surfaces. In addition, the effect of Ti addition on the surface tension of aluminum has also been examined.
Microstructure characterization in the weld joint of a high nickel austenitic alloy and Cr18-Ni8 stainless steel
Authors: Wu Na , Li Yajiang , Wang Juan
Published: March 2012

High nickel austenitic alloy, 6 mm thick, and Cr18-Ni8 stainless steel with a thickness of 0.6 mm were joined by pulsed current tungsten inert gas arc welding without filler metal in this work. Metallographic examination, micro-hardness measurement and electron microprobe analysis were used to reveal microstructural characteristics in the joint. The results indicated that the weld metal consisted of γ-austenite, δ-ferrite and carbides without the appearance of martensite. There were dendrite crystals at the edge of the weld metal near the high nickel austenitic alloy and isometric crystals in the center of the weld metal. The micro-hardness of the weld metal was the highest due to the existence of carbides and its finer structure. Graphite flakes were still embedded in the austenite matrix of the heat-affected zone without the formation of martensite.
Microstructure evolution in a 2618 aluminium alloy during creep-fatigue tests
Authors: Nový František , Janeček Miloš , Král Robert , Hadzima Branislav
Published: March 2012

Microstructure changes in the 2618 aluminium alloy during creep-fatigue tests were studied. These tests simulate the conditions of the application of this alloy in devices for the exhaustion of hot gasses generated during fire in closed or difficultly accessible areas. Creep-fatigue tests result in high dislocation density in subgrains and narrow subgrain boundaries, in contrast to creep tests reported in our previous work where large subgrains were observed with relatively wide subgrain boundaries and relatively low dislocation density in grains. Extensive precipitation occurred with denuded (precipitate-free) zones along grain boundaries. The coherent S-phase (Al2CuMg) transformed into partially coherent needle-shaped S′ precipitates. Superior stress amplitude caused reduced lifetime and wider denuded zones. A model of the formation of denuded zones along (sub)grain boundaries was proposed.
Melting temperature of metallic nanoparticles embedded in a rigid matrix
Authors: Vollath Dieter
Published: March 2012

Phase transformations of freestanding nanoparticles are well analyzed. The situation is different for particles embedded in a second matrix. The special case of melting and crystallizing of nanoparticles in a rigid matrix is the topic of this study based on the energy balance, resulting in a size dependency of these phase transformations primarily on variation of the materials properties with the particle size. Therefore, an important outcome of this study is the result that thermodynamic data of bulk materials are insufficient to describe phenomena connected to nanoparticles. The differences may be significant.
Non-covalent assembly of hybrid nanostructures of gold and palladium nanoparticles with carbon nanotubes
Authors: del Río Rodrigo Segura
Published: March 2012

Hybrid nanostructures were prepared by mixing gold and palladium nanoparticles with multi- and single-walled carbon nanotubes. The approach to prepare these nanohybrid implies the interaction of long hydrocarbon chains chemisorbed at the nanoparticles surface and the graphitic walls of nanotubes. Transmission electron microscopy results show the efficiency of this simple method to assemble these nanostructures. The electron microscopy images show that nanoparticles are effectively absorbed on the nanotube surfaces homogeneously but without any particular order. These nanostructures have proven to be stable after a moderate ultrasonic treatment.
Adsorption of bovine serum albumin onto titanium dioxide nanotube arrays
Authors: Shi Jie , Feng Bo , Lu Xiong , Weng Jie
Published: March 2012

Titanium dioxide nanotube arrays on titanium were fabricated via anodic oxidation and heat treatment. The diameters of nanotubes ranged from 20 to 200 nm, and the lengths were 500 and 1000 nm. The adsorption behavior of bovine serum albumin onto the nanotube arrays was investigated. Surface characterization for samples was carried out using scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Adsorbance of bovine serum albumin was detected with an ultraviolet spectrophotometer. The results showed that the nanotube arrays on titanium surfaces significantly enhanced bovine serum albumin adsorption. The nanotube arrays with larger diameter could adsorb more bovine serum albumin, but longer nanotubes showed less adsorbance than shorter nanotubes. In the present work, the nanotube arrays with 160–200 nm diameter, the largest diameter, showed the highest adsorption ability, and the maximum adsorption capacity q
m was 31.40 mg · cm−2. In addition, the adsorbance of bovine serum albumin increased with increase of initial bovine serum albumin concentrations, and a saturation value was achieved at the initial bovine serum albumin concentration of 2.0 mg · ml−1.
Effect of solid content on performance of conductive silver paste for crystalline silicon solar cells
Authors: Guo Guiquan , Gan Weiping , Liu Huan , Chen Yinglong , Xiang Feng , Luo Jian , Chen Zhibo , Li Jianqiu
Published: March 2012

The effect of solid content of conductive silver paste on the film thickness, microstructure of screen-printed front contact, and electrical performance of crystalline silicon solar cells was investigated. Three different solid content pastes were tested. It is found that the solid content of silver paste strongly affects the film thickness, microstructure of the thick film, and electrical performance of the cells. The paste with 84 wt.% solid content has higher viscosity and density than the ones with 82 wt.% and 83 wt.%. After sintering, the front Ag electrode thick film prepared using the paste with 84 wt.% solid content has a larger film thickness and the corresponding cell exhibits higher photoelectric conversion efficiency than the ones with 82 wt.% and 83 wt.% under the same conditions. This indicates that increasing film thickness can improve the conversion efficiency.
Microstructural and mechanical properties of dual-phase steels welded using GMAW with solid and flux-cored welding wires
Authors: Hayat Fatih , Uzun Hüseyin
Published: March 2012

The aim of this study is to demonstrate the transformation of grade-A steel into dual-phase steel by heat treatment, and the joint performance of dual-phase steels welded by means of the gas metal arc welding process using both solid and flux-cored welding wires. Dual-phase steels with different contents of martensite were obtained by intercritical annealing in different temperature ranges of a grade-A shipbuilding steel, followed by water quenching. The experimental results revealed that the tensile strength of the dual-phase steels joined by solid wire is higher than that of the flux-cored wire joints. The microstructure of grade-A steel consists of ferrite and pearlite, while the dual-phase steels consist of ferrite and martensite. On the other hand, while the martensitic phase is especially encountered in the weld metal of the dual-phase steels joined with the solid wire, the ferrite phase is more common in the weld metal of the flux-cored wire joints.
Combustion synthesis and characterization of bulk nanostructured Ni50Al17Fe33 alloy
Authors: Ma Jiqiang , Yang Jun , Zhang Xinghua , Bi Qinling , Fu Licai , Kang Yonghai , Liu Weimin
Published: March 2012

A bulk nanostructured Ni50Al17Fe33 alloy was produced by combustion synthesis associated with rapid solidification. The microstructure and mechanical properties of the as-fabricated material were investigated by means of scanning electron microscopy, X-ray diffraction, and mechanical tests. The Ni50Al17Fe33 alloy was composed of eutectic matrix and precipitated phase. The eutectic matrix consisted of 30–50 nm globular γ′-(Ni,Fe)3Al and 5–10 nm γ-Ni(Fe) boundary. The precipitate was comprised of 100–150 nm γ′-(Ni,Fe)3Al, γ-Fe, and α-Fe solid solution phases. The nanostructured Ni50Al17Fe33 alloy exhibited simultaneously high yield stress (about 900 MPa), high fracture strength (over 3860 MPa), and good ductility (over 75%) in compression.
Steady-state creep analysis of a functionally graded thick cylinder subjected to internal pressure and thermal gradient
Authors: Singh Tejeet , Gupta Vinay
Published: March 2012

The steady-state creep behavior in an isotropic functionally graded composite cylinder subjected to internal pressure has been analyzed in the presence of a thermal gradient. The cylinder is assumed to be made of a functionally graded composite containing silicon carbide particles in a matrix of pure aluminum. The effect of imposing a linear particle as well as a thermal gradient on the distribution of creep stresses and creep rates in the functionally graded cylinder has been investigated. The study shows that in the presence of both thermal and particle gradients, the radial stress decreases throughout the cylinder, whereas the tangential, axial, and effective stresses increase significantly near the inner radius but show a significant decrease towards the outer radius. The strain rates as well as strain-rate inhomogeneity in the composite cylinder could be reduced to a significant extent by imposing thermal and particle gradients alone or together, while keeping the same average amount of reinforcement.
Modelling of metal nano-particle condensation and growth in a reactive atmosphere
Authors: Greppi Paolo , Arato Elisabetta
Published: March 2012

The control of the particle size distribution of metal nano-particles produced via aerosol condensation is a technologically relevant open problem, constrained by the limits of the construction materials and by the desire to minimise carrier gas consumption.

As reactive impurities can be present in the carrier gas, we have reviewed the physical chemistry and reactivity of nano-particles and developed a quantitative, continuous model of the nucleation and particle growth processes in the presence of a reactive impurity. The model has been applied to nickel as the metal and oxygen as the impurity, but could equally well be applied to other metals and other impurities such as nitrogen, sulphur, or the halogens.

In certain conditions oxygen is only stochastically present in the nucleating nickel droplets, resulting in oxide inclusions that cannot be described by a continuous model. In other conditions the oxidation occurs simultaneously with the metal condensation and can be studied qualitatively using the developed continuous model. The model indicates that the concentration of a reactive contaminant in the gas phase could be used as an additional operating parameter to control the final particle size.
Thermodynamic properties of liquid copper–antimony–tin alloys determined from e.m.f. measurements
Authors: Jendrzejczyk-Handzlik Dominika , Gierlotka Wojciech , Fitzner Krzysztof
Published: March 2012

The thermodynamics properties of liquid Cu–Sn–Sb alloys were determined using solid-oxide galvanic cells with zirconia electrolyte:
(1)

Re
+
kanthal
,

Cu

x

−

Sb

y

−

Sn

(
1
−
x
−
y
)

,

SnO

2

/
/

ZrO

2

+
(

Y

2

O

3

)
/
/
NiO
,
Ni
,
Pt

in the temperature range from 998 to 1223 K.

The Gibbs free energy of formation of pure solid SnO2 from pure elements was derived. Using electromotive force values measured for the cell with x
Sn = 1.0, the following temperature dependence was obtained:

Δ

G

f
,

SnO

2

0

=
−
567903
+
200
.
33
T
(
±
1000
J
)
[
J

mol

−
1

]

Activities of tin were determined along three sections of the ternary system specified by the ratio of mole fractions x
Cu/x
Sb = 1:3, 1:1, and 3:1. Thermodynamic properties of the liquid phase were described by the Redlich–Kister–Muggianu formula. Using commercial software, phase relations in the ternary system were calculated. The results of the calculations are compared with experimental data available from literature.
Study of the structural evolution of crystalline zinc oxide films prepared by PLD
Authors: Peng Xiaoyan , Chu Jin , Muhammad Sajjad , Feng Peter
Published: March 2012

The structural evolution of nanocrystalline ZnO films on copper substrates synthesized via pulsed laser deposition was observed with increasing thickness controlled by deposition time. Scanning electron microscopy images indicate an increase in the average grain size. All the films are polycrystalline with the hexagonal wurtzite structure. X-ray diffraction patterns prove the orientation of the crystals to become better with an increase in film thickness. Raman measurements show three optical normal modes of crystalline ZnO indicating wurtzite structure. The line-width variation of the E2high mode reveals the structural improvement of the nanocrystalline ZnO films. The spatial correlation model was applied to analyze the structure evolution of the films. Different electron field-emission current densities are observed during the structural evolution of nanocrystalline ZnO films.
Rheology and microstructure of polymer-modified asphalt nanocomposites
Authors: Topal Ali , Sureshkumar Markanday Subramanian , Sengoz Burak , Polacco Giovanni
Published: March 2012

Asphalt modification with polymers has utilized the advantages of nanotechnology including nanoclays as one of the components in addition to polymers. This led to the metamorphosis of polymer-modified asphalts into a new class of material called polymer-modified asphalt nanocomposites which offer the cumulative characteristic features obtained by the polymer modification of asphalt as well as the innovative properties experienced from polymer nanocomposites. Polymer-modified asphalt nanocomposites including styrene butadiene and ethylene vinyl acetate have revealed additional features which were not available in polymer-modified asphalts. The compositional complexity provides a great challenge in addressing the structure–property relations prevailing in these materials. This paper describes microstructural features as determined by Qwin Plus Software analysis and the rheological properties on compositional changes.
Numerical study of equal-channel angular pressing based on the element-free Galerkin method
Authors: Yanjin Guan , Guoqun Zhao , Ping Lu
Published: March 2012

Based on the flow formulation for rigid–plastic/viscoplastic materials, a rigid–plastic/viscoplastic element-free Galerkin method is established to realize the simulation of massive metal-forming processes. Stiffness equations and solution formulae are derived in terms of the incomplete generalized variational principle. The transformation method is employed to exert the essential boundary condition in the local coordinate system. The arctangent frictional model is used to implement the frictional boundary conditions, and the transform matrix from the global coordinate system to local coordinate system is given. Being similar to finite-element simulations, the key techniques for metal-forming meshless analysis such as the treatment of the rigid region, dynamic adjustment of the boundary nodes, and treatment of volumetric locking are developed. The analysis software is developed. The equal-channel angular pressing process is simulated numerically using the software. The effective strains become larger and more uniform with increasing curve angle Ψ. On the other hand, the forming load increases greatly with the increase in the curve angle Ψ. The effective strains change slightly with the change of the frictional status between the die and the workpiece. However, the frictional status influences greatly the forming load.
Preparation and characterization of polyaniline/Fe3O4–polyacrylonitrile composite nanofibers
Authors: Huang Fenglin , Zhang Huidan , Shi Jinsong , Chen Fang , Cai Yibing , Wei Qufu
Published: March 2012

Polyaniline/Fe3O4 nanocomposite was synthesized via micro-emulsion polymerization of aniline in the presence of Fe3O4 nanoparticles. The experimental results revealed that a core-shell structure composite was obtained successfully. Electrospinning of Fe3O4-polyaniline/polyacrylonitrile (Fe3O4–PANI/PAN) blended with different composition ratios were performed using N, N-Dimethylformamide as solvent. Morphology and fiber diameters were investigated by means of scanning electron microscopy. Electrospun fibers with diameters ranging from 168 to 300 nm were obtained. Scanning electron microscopy images indicated that the diameter of the composite nanofiber increases with the content of Fe3O4. It was also found that the permittivity was decreased by the addition of Fe3O4, but the permittivity was increased relevantly if the Fe3O4 mass fraction in the Fe3O4/PANI was increased. The thermal stability of the composite nanofibers is also examined in this paper.
Clinical, radiological, and genetic similarities between patients with Chiari Type I and Type 0 malformations
Authors: Markunas Christina A. , Tubbs R. Shane , Moftakhar Roham , Ashley-Koch Allison E. , Gregory Simon G. , Oakes W. Jerry , Speer Marcy C. , Iskandar Bermans J.
Published: March 2012

Object

Although Chiari Type I (CM-I) and Type 0 (CM-0) malformations have been previously characterized clinically and radiologically, there have been no studies focusing on the possible genetic link between these disorders. The goal of this study was to identify families in whom CM-0 and CM-I co-occurred and to further assess the similarities between these disorders.

Methods

Families were ascertained through a proband with CM-I. Detailed family histories were obtained to identify first-degree relatives diagnosed with CM-0. Several criteria were used to exclude individuals with acquired forms of CM-I and/or syringomyelia. Individuals were excluded with syndromic, traumatic, infectious, or tumor-related syringomyelia, as well as CM-I due to a supratentorial mass, hydrocephalus, history of cervical or cranial surgery unrelated to CM-I, or development of symptoms following placement of a lumbar shunt. Medical records and MR images were used to characterize CM-I and CM-0 individuals clinically and radiologically.

Results

Five families were identified in which the CM-I proband had a first-degree relative with CM-0. Further assessment of affected individuals showed similar clinical and radiological features between CM-0 and CM-I individuals, although CM-I patients in general had more severe symptoms and skull base abnormalities than their CM-0 relatives. Overall, both groups showed improvement in symptoms and/or syrinx size following craniocervical decompression surgery.

Conclusions

There is accumulating evidence suggesting that CM-0 and CM-I may be caused by a common underlying developmental mechanism. The data in this study are consistent with this hypothesis, showing similar clinical and radiological features between CM-0 and CM-I individuals, as well as the occurrence of both disorders within families. Familial clustering of CM-0 and CM-I suggests that these disorders may share an underlying genetic basis, although additional epigenetic and/or environmental factors are likely to play an important role in the development of CM-0 versus CM-I.
Intractable episodic bradycardia resulting from progressive lead traction in an epileptic child with a vagus nerve stimulator: a delayed complication
Authors: Clark Aaron J. , Kuperman Rachel A. , Auguste Kurtis I. , Sun Peter P.
Published: March 2012

Vagus nerve stimulation (VNS) is used as palliation for adult and pediatric patients with intractable epilepsy who are not candidates for curative resection. Although the treatment is generally safe, complications can occur intraoperatively, perioperatively, and in a delayed time frame. In the literature, there are 2 reports of pediatric patients with implanted VNS units who had refractory bradycardia that resolved after the stimulation was turned off. The authors report the case of a 13-year-old boy with a history of vagus nerve stimulator placement at 2 years of age, who developed intractable episodic bradycardia that persisted despite the cessation of VNS and whose imaging results suggested vagus nerve tethering by the leads. He was subsequently taken to the operating room for exploration, where it was confirmed that the stimulator lead was exerting traction on the vagus nerve, which was displaced from the carotid sheath. After the vagus nerve was untethered and the leads were replaced, the bradycardia eventually resolved with continual effective VNS therapy. When placing a VNS unit in a very young child, accommodations must be made for years of expected growth. Delayed intractable bradycardia can result from a vagus nerve under traction by tethered stimulator leads.
Subdural hemorrhage as a first symptom in an infant with a choledochal cyst
Authors: Chen Te-Yuan , Wang Hao-Kuang , Yeh Ming-Lun , Wei Shu-Hao , Lu Kang
Published: March 2012

Choledochal cysts are not rare in East Asia. The classic symptoms of these cysts are intermittent abdominal pain, jaundice, and a right upper quadrant abdominal mass. The authors report the case of an infant with a choledochal cyst presenting with intracranial hemorrhage. This 2-month-old girl with a partial coma presented at the authors' hospital. A brain CT scan revealed right-sided subdural hemorrhage. The routine preoperative survey found coagulopathy. After correcting the bleeding disorder, an emergency craniectomy was performed. Further examination found a choledochal cyst during abdominal ultrasonography and CT. Choledochal cysts are a cause of neonatal cholestasis but rarely produce vitamin K deficiency bleeding.
Intraventricular lesions in tuberous sclerosis complex: a possible association with the caudate nucleus
Authors: Katz Joel S. , Milla Sarah S. , Wiggins Graham C. , Devinsky Orrin , Weiner Howard L. , Roth Jonathan
Published: March 2012

Object

Tuberous sclerosis complex (TSC) can manifest with 3 principal intracranial pathological entities: cortical tubers, subependymal nodules (SENs), and subependymal giant cell astrocytomas (SEGAs). The authors analyzed the location and growth of intraventricular lesions in a large cohort of patients with TSC.

Methods

After institutional review board protocol approval, the authors retrospectively reviewed brain MRI scans of TSC patients for whom at least 1 electronically stored cranial MRI study was available. Collected data included location, size, and growth over time of all intraventricular lesions.

Results

The authors reviewed 560 scans in 103 patients, who harbored 496 intraventricular lesions. Of the 496 lesions, 157 lesions were located along the caudate-thalamic groove (CTG) in 88 patients. Twenty SEGAs were operated on. The remaining 339 lesions were distributed along the lateral ventricle, always in contact with the course of the caudate nucleus, and were presumed to be SENs. Twenty-two patients with more than 4 years of follow-up had 34 lesions along the CTG, of which 23 were stable in size and 11 grew. All other intraventricular lesions were stable. Seven-Tesla MRI showed the intimate association of SENs and the caudate nucleus in 1 patient.

Conclusions

Intraventricular lesions in TSC patients are located throughout the lateral ventricular wall. Their location exclusively follows the course of the caudate nucleus. Only lesions along the CTG showed the potential to grow, and these were then identified as SEGAs. The remaining lesions were SENs. Understanding why these lesions develop in relation to the caudate nucleus may offer insights into therapy.
Spontaneous occlusion of the circle of Willis in children: pediatric moyamoya summary with proposed evidence-based practice guidelines
Authors: Smith Edward R. , Scott R. Michael
Published: March 2012

Moyamoya is a progressive arteriopathy of unknown origin affecting the branches of the internal carotid artery (ICA). The arteriopathy can present as an isolated medical condition, affecting both sides of the brain (“moyamoya disease”) or can be unilateral or found in association with systemic disorders (“moyamoya syndrome”). The ischemia resulting from luminal narrowing predisposes children to transient ischemic attacks and stroke—the primary presentations of affected patients. Although it is rare—affecting 1 in 1 million children in the US—moyamoya is implicated in 6% of all childhood strokes. Diagnosis is defined by characteristic findings on arteriograms, including stenosis of the branches of the ICA and a pathognomonic spray of small collateral vessels in this region, descriptively likened to a “puff of smoke” (“moyamoya” in Japanese). Treatment is predicated on restoration of cerebral blood flow by surgical revascularization. The rarity of this disorder has limited research and the development of evidence-based clinical management. While acknowledging these limitations, in this article the authors aim to summarize current studies of pediatric moyamoya, with the objective of providing a framework for construction of evidence-based guidelines for treatment. The compilation of current data in these guidelines should serve as a resource to aid pediatric neurosurgeons in their role as advocates for providing appropriate care to affected children.