bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermo-Economic Comparisons of Different Types of Solar Desalination Processes
Authors: Sharaf Mohamed A.
Published: April 2012

Many types of desalination technologies are widely used around the worldwide. Thermal and membrane types dominated the market share among the other technologies (freezing, electrodialysis, and ion-exchange). Currently, multistage flash considered the power house of desalination technologies; however, in the last few decades, multi effect distillation and reverse osmosis (RO) technologies were proven as reliable and cost efficient processes. But comparing and electing the most efficient type between conventional desalination technologies is still under scope. It is very hard to decide which type or technique is reliable and thermo-economically efficient. Also, it becomes harder to decide which type is thermo-economically efficient when desalination process is combined with solar energy. In this work, different types of solar desalination processes are thermo-economically compared and analyzed. Results revel that RO and multi effect distillation-thermal vapor compression are recommended according to specific solar area (SSA m2/(m3/d)), total water price (TWP $/m3), thermo-economic product cost (cp $/GJ), and the gain ratio (GR). The comparisons were performed based on two scenarios: (1) different operating conditions due to each individual technology and (2) uniform operating conditions.
Microstructural Modeling and Dynamic Process Simulation of Laser-Assisted Machining of Silicon Nitride Ceramics With Distinct Element Method
Authors: Shen Xinwei , Yang Budong , Lei Shuting
Published: April 2012

The distinct element method (or discrete element method, DEM) is applied to simulate the dynamic process of laser-assisted machining (LAM) of silicon nitride ceramics. This is motivated by the fact that LAM of ceramics shows a few complicated characteristics such as spontaneous crack formation, discontinuous chips, etc. Thus, using the two-dimensional distinct element code, PFC2D, the microstructure of a β-type silicon nitride ceramic is modeled, and the resulting temperature-dependent synthetic specimens are created first, and then, machining simulations are conducted. The DEM model is validated through comparing the predicted results with those from the experiments under different cutting temperatures in terms of cutting force, chip size, and depth of subsurface damage. Furthermore, the mechanisms of LAM are analyzed from the aspects of material removal, chip segments, surface/subsurface damage, as well as crack initiation, propagation, and coalescence.
Effects of Terrain Slope on Nacelle Anemometry
Authors: Ameur Khaled , Masson Christian
Published: April 2012

A numerical analysis of the effects of sloped terrain on the reading of a nacelle anemometer is investigated. Simulations of the turbulent flow around a 2.5 MW wind turbine in an atmospheric boundary layer are made by resolving 3D RANS equations. In addition to flat terrain, four escarpments (at slopes of 7.5%, 11%, 14%, and 20%) are studied for various inlet velocities in three cases: terrains with no wind turbine, with nonoperating turbines and with operating turbines. The slope of the ground has two major effects on flow: speed-up and an increase in flow inclination. The presence of the nacelle enhances the flow speed-up caused by the escarpment, especially outside the anemometer’s position. However, the horizontal velocity at the location of the anemometer tends to decrease with increasing ground slope. This trend is due in large part to the nacelle wake. This disturbed area is characterized by the presence of separated flow and two opposing vortices which are sensitive to the flow inclination. The evaluated nacelle transfer function is influenced by the terrain slope but this sensitivity is reduced by displacing the position of the anemometer upward the nacelle body.
Mathematical Modeling and Implementation of Residual Stress Mapping From Microscale to Macroscale Finite Element Models
Authors: Afazov S. M. , Becker A. A. , Hyde T. H.
Published: April 2012

The paper reviews a development of mathematical algorithms and implementation of mapping residual stress profiles from microscale to macroscale finite element (FE) models. A shot-peening simulation of Inconel 718 is conducted using the finite element method (FEM) to obtain the residual stress profiles which are used as an input in the developed mapping algorithms. Residual stress profiles induced by the shot-peening processes are mapped into different FE models including a perforated plate, a model with a complex surface, and an aero-engine vane component. The mathematical mapping algorithms and formulations are developed for 2D and 3D FE models where residual stress profiles obtained experimentally, numerically, or analytically for different manufacturing processes including shot-peening, water jet machining, milling, turning, roller burnishing, laser machining and peening, electro discharge machining, etc., can be mapped on FE models with complex geometries. The implementation and the results for the mapping techniques are presented and discussed in detail.
New Continuous Dynamic Coupling for Three Component Modeling of Tool–Holder–Spindle Structure of Machine Tools With Modified Effected Tool Damping
Authors: Faraji Ghanati Mohammad , Madoliat Reza
Published: April 2012

In machine dynamics, the tool point frequency response functions (FRFs) are employed to predict the stable machining conditions. In this paper, a combined analytical–experimental substructuring procedure is proposed to determine the tool point FRFs usable for different holder–tool configurations. Contact interface of holder–spindle and tool–holder is modeled using translational and rotational springs and dampers spread in the length of contact surface. These joint parameters are defined using finite element method. This enables the analyst to introduce the contact stiffness and damping in more detail with taking into consideration the variations of normal pressure in the tool–holder and holder–spindle joints. The dynamic analysis of the holder is done using Timoshenko beam theory by Tchebyshev method. The tool dynamics is modeled based on Euler–Bernoulli beam theory using the method of equivalent diameter. For the purpose of shifting the tool stability lobes to a higher level, tool damping parameter is modified by internal frictional damper and the effect is analyzed by analytical methods and experimental study. After joint parameters are defined continuously by finite element method, a new method for continuous dynamic coupling is presented. The method employs the measured spindle-machine FRFs and analytical models of the tool and holder to predict the tool tip FRFs. In this new method, continuous coupling in two separate domains of response model and modal model is presented. Such structural modeling avoids us to do complex modal tests for a different set of combinations of the holder and tool with specific milling machine. An experimental case study is provided to demonstrate the applicability of the proposed method in dynamic modeling of machine tool.
Start-Up Modeling for Annual CSP Yield Calculations
Authors: Hirsch Tobias , Fabian Feldhoff Jan , Schenk Heiko
Published: April 2012

In solar thermal power plants, at least the solar part undergoes a daily start-up process. Since duration and energy consumption of the start-up depend on irradiance and temperature boundary conditions, differences occur between the individual days and especially between the seasons. For a good representation in annual electricity yield calculations, the start-up process should be modeled on a daily basis. This paper presents a closed approach for the calculation of start-up and cool-down in solar thermal power plants especially designed for annual calculations. It is demonstrated by one example how the required parameters can be obtained and how the methodology is applied. A sensitivity analysis reveals the large impact of start-up consumption on the annual yield.
Structural and magnetic properties of epitaxial In1–xMnxSb semiconductor alloys with x > 0.08
Authors: Feeser Caitlin E. , Lari Leonardo , Lazarov Vlado K. , Peters John A. , Wessels Bruce W.
Published: April 2012

High temperature ferromagnetic In1−xMnxSb semiconductor alloys with a Curie temperature (TC) above 400 K were investigated. Alloys with x ranging from 0.08 to 0.22 deposited by metalorganic vapor phase epitaxy were examined. X-ray diffraction indicated alloys are primarily two phase consisting of a zinc blende InMnSb solid solution and hexagonal MnSb precipitates. Transmission electron microscopy analysis confirmed the presence of hex-MnSb nanoprecipitates as well as the presence of the additional minority phases Mn3Sb, metallic Mn, and MnAs1−xSbx. Magnetization measurements indicate that the alloy films are ferromagnetic, showing clear hysteresis in field dependent measurements from 5 to 400 K. Magnetization values as high as 47 emu/cm3 for an alloy with x = 0.22 were measured at room temperature. Irreversibility is observed between field-cooled and zero-field-cooled magnetization curves that is attributed to inhomogeneous magnetic order arising from randomly distributed ferromagnetic nanoprecipitates. Temperature dependent magnetization indicates at least two magnetic phases are present, one with a nominal TC of 300 K that is attributed to MnAs1−xSbx nanoprecipitates which form at the GaAs substrate interface, and a second with a TC > 400 K that is attributed to hex-MnSb nanoprecipitates and to the InMnSb matrix. The majority of magnetization arises from the high TC phase, where fitting the temperature dependent magnetization curve with a Brillouin function indicated a TC of 570 K. Magnetization measurements indicate that there is an interparticle magnetic interaction. Large saturation magnetization at 300 K and TC of 570 K make these multiphase InMnSb epitaxial films excellent candidates for ferromagnetic layers in semiconductor spintronic devices that operate at room temperature.
Fabrication of nickel diffractive phase elements for x-ray microscopy at 8 keV photon energy
Authors: Grenci Gianluca , Pozzato Alessandro , Sovernigo Enrico , Prasciolu Mauro , Tormen Massimo
Published: April 2012

The ability to resolve small details using x-ray microscopy is critically dependent on the properties of the optical elements used in the microscope’s setup. Today, Fresnel zone plates (ZPs) are widely used at synchrotron radiation sources, due to their ability to concentrate x-ray beams to spots with diameters in the tens of nanometers range. Unfortunately, fabricating ZPs with high efficiencies and sharp foci proves to be extremely challenging technologically, especially in the range of hard x-rays. A widely recognized fabrication issue is the mechanical instability of narrow and tall features made up of polymeric resists. These features often collapse either during the development or the drying of the structures due to the action of capillary forces, or in the step of electroplating because of the stress applied to them by the growing metal. The authors demonstrate a fabrication strategy that solves such issues by forming high-aspect-ratio templates in materials as hard and mechanically stable as silicon. The strategy is implemented by a combination of high-resolution lithography techniques, electroplating and plasma etching. In the present work, Fresnel zone plates with 200 nm outermost zone widths were demonstrated by electroplating nickel up to 2.1 μm height using 3.5 μm deep template structures.
Effects of detailing on panel zone seismic behaviour in special moment resisting frames with unequal beam depths
Authors: Jazany Roohollah Ahmady , Hashemi Behrokh Hosseini
Published: April 2012

Special moment resisting frames (SMRF) are commonly used as lateral-load resisting systems in seismic design. The results of recent studies have shown that the seismic performance of such frames can be improved by paying particular attention to the detailing of their panel zones (PZ) and beams. Panel zones with unequal beam depths appear to be a special case of connection detailing, which has not received sufficient attention so far and could lead to complications in everyday engineering practice. Some full-scale experiments of connections with unequal beam depths were performed, using different continuity plate arrangements (inclined and straight plates), and different corner clip lengths. A companion analytical study was also conducted, for which results have shown that the correct selection of inclined or straight continuity plates, with special detailing of the PZ, could keep the behaviour of the latter within safe margins. Such considerations could prevent the occurrence of failure in the PZ, and significantly improve the seismic resistance of SMRF with unequal beam depths.
Assessment of CSA A23.3 structural integrity requirements for two-way slabs
Authors: Habibi Farshad , Redl Erin , Egberts Michael , Cook William D. , Mitchell Denis
Published: April 2012

This paper investigates the post-punching behaviour of reinforced concrete slab–column connections with a goal of providing adequate structural integrity reinforcement. The test results of seven interior slab–column connections are presented. A study was made of the effects of slab thickness, length of structural integrity reinforcing bars, distribution of structural integrity reinforcement in slabs with rectangular columns, and the placement of structural integrity reinforcement in slabs with drop panels. Results from this test series and other researchers were compared with predictions using the CSA A23.3-04 design equations for both punching shear and post-punching resistance. The test results demonstrated that the provision of structural integrity reinforcement in accordance with the requirements of CSA A23.3-04 resulted in significant post-punching resistance and the design equations provide a reasonable estimate of this resistance.
A new performance based design approach for moment resisting frames
Authors: Grigorian Mark , Grigorian Carl E.
Published: April 2012

This paper proposes a simple, relatively new elastic–plastic design method for earthquake resisting frames that enables the engineer to directly control the essential aspects of the future behavior of certain structural forms, through basic statics and imposition of predetermined modes of behavior. The method is particularly applicable to the preliminary design of low to mid-rise buildings where the fundamental period of vibrations dominates the response of the system to seismic loading. The focus of this paper is directed towards simplified but accurate manual design rather than sophisticated structural analysis. The premise of the proposed solution is that the constituent elements of the system can be selected in such a way as to cause both the elastic as well as the plastic drift functions to follow linearly varying straight line profiles during all phases of loading. Frameworks designed by this method act not only as structures of uniform response (UR), i.e., uniform strength and stiffness, where the demand/capacity ratios of its members remain the same, both before and after formation of plastic hinges, but they also result in unique solutions, satisfying the prescribed yield criteria, the boundary support, as well as the of static equilibrium conditions.
Effects of reduced aeration in a biological aerated filter
Authors: Ray Rajan , Henshaw Paul , Biswas Nihar
Published: April 2012

Aeration is a major part of the operating cost in biological aerated filtration (BAF) systems for wastewater treatment. This study investigated the effect of reducing aeration at the City of Windsor’s Lou Romano Water Reclamation Plant to find the lowest possible airflow rate while maintaining a satisfactory ammonia and biological oxygen demand (BOD) in the BAF effluent. Profiles of temperature, dissolved oxygen, pH, BOD, ammonia and nitrate concentration were measured along the height of cell No. 7 at the plant, at different time intervals during filtration, at airflow rates varying from 1300 to 1700 m3/h per cell. This study found that the BOD and ammonium removal were satisfactory at the lowest airflow rate.
Prevalence of bacteriocin activities and bacteriocin-encoding genes in enterococcal clinical isolates in Iran
Authors: Hassan Maryam , Diep Dzung B. , Javadzadeh Yousef , Dastmalchi Siavash , Nes Ingolf F. , Sharifi Yaeghob , Yari Saber , Farajnia Safar , Lotfipour Farzaneh
Published: April 2012

The aim of the project was to isolate and characterize bacteriocin-producing enterococci, as well as determine the prevalence of enterocin structural genes in 187 enterococcal clinical isolates from the northwest of Iran. The isolates were screened for antibacterial activity against 15 different indicator strains. The proteinaceous nature of the antimicrobial substances was confirmed by sensitivity to proteinase K; their stability to heat treatment was tested at 60 °C and 100 °C for 20 and 10 min, respectively. The PCR method was applied to detect previously identified enterocin genes. Our results showed that 38 (20.3%) of the enterococcal isolates were considered to be potential bacteriocinogenic strains. Furthermore, genes encoding diverse bacteriocin are highly distributed among clinical enterococci, and the strains with multi-bacteriocin genes displayed high antimicrobial activity. Enterocin A, enterolysin A, and enterocin L50A/B were the most abundant structural genes detected in bacteriocinogenic strains. This work is the first survey on the prevalence of bacteriocin genes among clinical enterococci in Iran that has isolated a strain with high antimicrobial activity and sensitivity to clinically relevant antibiotics.
Importance of theicmNgene in the growth ofLegionella pneumophilain amoebic cells at low temperature
Authors: Qin Tian , Iida Ken-ichiro , Piao Zhenyu , Shiota Susumu , Ren Hongyu , Shao Zhujun , Yoshida Shin-ichi
Published: April 2012

Legionella pneumophila grows in amoebae and has achieved the ability to grow at various temperatures, although the mechanisms controlling this ability remain poorly understood. The Icm/Dot type IVB secretion system is composed of more than 25 proteins and is known to be essential for intracellular growth. The role of the icmN gene in intracellular multiplication and the effects of culture temperatures on it are not precisely understood. We conducted our investigation using an icmN mutant made by gene replacement mutagenesis. Intracellular growth of the mutant was impaired both in mammalian macrophages and amoeba at 37 °C. In particular, intracellular growth in amoebae was completely impaired at 25 °C. It was found that genes from icmN to icmC formed an operon, i.e., icmN, -M, -L, -E, -G, -C,, and the promoter activity of the icmN operon was stronger at 25 than at 37 °C. It was suggested that icmM and its downstream genes had a secondary promoter that enables icmN mutant grow in amoebae at lower temperatures and macrophages at 37 °C. These results show that the icmN promoter has a low temperature inducible nature, and gene products of the icmN operon require high expression for bacterial proliferation at low temperatures within amoeba.
A comparison of the clavam biosynthetic gene clusters in Streptomyces antibioticus Tü1718 and Streptomyces clavuligerus
Authors: Goomeshi Nobary Sarah , Jensen Susan E.
Published: April 2012

The production of clavam metabolites has been studied previously in Streptomyces clavuligerus , a species that produces clavulanic acid as well as 4 other clavam compounds, but the late steps of the pathway leading to the specific end products are unclear. The present study compared the clavam biosynthetic gene cluster in Streptomyces antibioticus , chosen because it produces only 2 clavam metabolites and no clavulanic acid, with that of S. clavuligerus. A cosmid library of S. antibioticus genomic DNA was screened with a clavaminate synthase-specific probe based on the corresponding genes from S. clavuligerus, and 1 of the hybridizing cosmids was sequenced in full. A clavam gene cluster was identified that shows similarities to that of S. clavuligerus but also contains a number of novel genes. Knock-out mutation of the clavaminate synthase gene abolished clavam production in S. antibioticus, confirming the identity of the gene cluster. Knock-out mutation of a novel gene encoding an apparent oxidoreductase also abolished clavam production. A potential clavam biosynthetic pathway consistent with the genes in the cluster and the metabolites produced by S. antibioticus, and correspondingly different from that of S. clavuligerus, is proposed.
Phylogenetic analysis of antimicrobial lactic acid bacteria from farmed seabass Dicentrarchus labrax
Authors: Bourouni Ouissal Chahad , El Bour Monia , Calo-Mata Pilar , Mraouna Radhia , Abedellatif Boudabous , Barros-Velàzquez Jorge
Published: April 2012

The use of lactic acid bacteria (LAB) in the prevention or reduction of fish diseases is receiving increasing attention. In the present study, 47 LAB strains were isolated from farmed seabass ( Dicentrarchus labrax ) and were phenotypically and phylogenetically analysed by 16S rDNA and randomly amplified polymorphic DNA – polymerase chain reaction (RAPD–PCR). Their antimicrobial effect was tested in vitro against a wide variety of pathogenic and spoilage bacteria. Most of the strains isolated were enterococci belonging to the following species: Enterococcus faecium (59%), Enterococcus faecalis (21%), Enterococcus sanguinicola (4 strains), Enterococcus mundtii (1 strain), Enterococcus pseudoavium (1 strain), and Lactococcus lactis (1 strain). An Aerococcus viridans strain was also isolated. The survey of their antimicrobial susceptibility showed that all isolates were sensitive to vancomycin and exhibited resistance to between 4 and 10 other antibiotics relevant for therapy in human and animal medicine. Different patterns of resistance were noted for skin and intestines isolates. More than 69% (32 strains) of the isolates inhibited the growth of the majority of pathogenic and spoilage bacteria tested, including Listeria monocytogenes , Staphylococcus aureus , Aeromonas hydrophila , Aeromonas salmonicida , Vibrio anguillarum , and Carnobacterium sp. To our knowledge, this is the first report of bioactive enterococcal species isolated from seabass that could potentially inhibit the undesirable bacteria found in food systems.
Phylogenetic diversity of nitrogen-fixing bacteria and thenifHgene from mangrove rhizosphere soil
Authors: Liu Jianyin , Peng Mengjun , Li Youguo
Published: April 2012

Nine types of nitrogen-fixing bacterial strains were isolated from 3 rhizosphere soil samples taken from mangrove plants in the Dongzhaigang National Mangrove Nature Reserve of China. Most isolates belonged to Gammaproteobacteria Pseudomonas , showing that these environments constituted favorable niches for such abundant nitrogen-fixing bacteria. New members of the diazotrophs were also found. Using a soil DNA extraction and PCR-cloning-sequencing approach, 135 clones were analyzed by restriction fragment length polymorphism (RFLP) analysis, and 27 unique nifH sequence phylotypes were identified, most of which were closely related to sequences from uncultured bacteria. The diversity of nitrogen-fixing bacteria was assessed by constructing nifH phylogenetic trees from sequences of all isolates and clones in this work, together with related nifH sequences from other mangrove ecosystems in GenBank. The nifH diversity varied among soil samples, with distinct biogeochemical properties within a mangrove ecosystem. When comparing different mangrove ecosystems, the nifH gene sequences from a specific site tended to cluster as individual groups. The results provided interesting data and novel information on our understanding of diazotroph community diversity in the mangrove ecosystems.
Optimized expression of dual reporter genes in transient transfection of purifiedToxoplasma gondiiusing different promoters
Authors: Hao Yongxin , Yang Jianmin , Li Xuelian , Ding Jun , Zhang Wei , Liu Qun
Published: April 2012

Fluorescent protein and luciferase genes are valuable reporter genes and have been widely used for noninvasive monitoring of gene expression in living tissues and cells. We tested expression of the dual reporter genes in transient transfection of purified Toxoplasma gondii tachyzoites. Two copies of the enhanced yellow fluorescent protein (EYFP) gene were put under the control of 3 representative T. gondii promoters (GRA1, SAG1, and DHFR). Fluorescence from each EYFP reporter was significantly higher than that from a green fluorescent protein (GFP) reporter. The GRA1-EYFP reporter gave the highest fluorescence. Although both fluorescence and luciferase were expressed in the dual reporter system, the luciferase reporter was more efficient than either the EYFP or GFP reporters, and it required fewer parasites to be successfully used.
FUZZY-PID CONTROLLER APPLIED TO A REFRIGERATION SYSTEM
Authors: SCHMITZ JONES ERNI , DA SILVA FLAVIO VASCONCELOS , FILETI ANA MARIA FRATTINI , FILHO LINCOLN CAMARGO NEVES , SILVEIRA JÚNIOR VIVALDO
Published: April 2012

A refrigeration system exhibits a dynamic behavior on which the variables are interdependent and subjected to oscillation, hence, implicating necessity of changes on operating conditions and undesirable energy expenses. These characteristics ratify the importance of adequate dimensioning and equipment selection to find pre-defined operating conditions such as, the maximum cooling capacity and the evaporating and condensing temperatures. The application of fuzzy control in industrial processes is growing fast in the last decades, mainly in processes whose first principle models require complex methods to be simulated. In these cases, the fuzzy controllers’ capacity of acting correctly based only on expert knowledge and on the capacity of inter-relating all the variables of the process are attractive features. This work presents the experimental development and evaluation of fuzzy-PID controllers for the maintenance of the evaporating temperature in a chiller. The system was submitted to load and set-point disturbances accomplishing an analysis based upon error parameters and transient response. The results showed that fuzzy controllers were adapted satisfactorily.
Orthogonal Intermolecular Interactions of CO Molecules on a One-Dimensional Substrate
Authors: Feng Min , Lin Chungwei , Zhao Jin , Petek Hrvoje
Published: April 2012

By low-temperature scanning tunneling microscopy, we study CO molecule chemisorption on a quasi–one-dimensional Cu(110)-(2×1)-O surface. Atom-resolved images reveal how the interaction of CO with the surface Cu-O- chains gives rise to orthogonal attractive and repulsive intermolecular interactions. First-principles calculations show that CO molecules induce unprecedented lifting of the host Cu atoms by 1 Å from the Cu-O- chains, enabling the Cu-CO unit to tilt by 45° from the surface normal. Contrary to the behavior of CO on metal surfaces, this structural distortion enables unprecedented, orthogonal, short-range intermolecular dipole-dipole attraction and long-range, surface-mediated repulsion. These interactions lead to self-assembly into molecular nanograting structures consisting of arrays of single-molecule-wide CO rows. The origin of the novel behavior of CO molecules in the electronic and geometrical properties of the quasi–one-dimensional substrate suggests that similar molecule-molecule and molecule-substrate interactions could play an important role at catalytic sites on reactive surfaces.
The Physical Chemistry of Mass-Independent Isotope Effects and Their Observation in Nature
Authors: Thiemens Mark H. , Chakraborty Subrata , Dominguez Gerardo
Published: April 2012

Historically, the physical chemistry of isotope effects and precise measurements in samples from nature have provided information on processes that could not have been obtained otherwise. With the discovery of a mass-independent isotopic fractionation during the formation of ozone, a new physical chemical basis for isotope effects required development. Combined theoretical and experimental developments have broadened this understanding and extended the range of chemical systems where these unique effects occur. Simultaneously, the application of mass-independent isotopic measurements to an extensive range of both terrestrial and extraterrestrial systems has furthered the understanding of events such as solar system origin and evolution and planetary atmospheric chemistry, present and past.
Model Catalysts: Simulating the Complexities of Heterogeneous Catalysts
Authors: Gao Feng , Goodman D. Wayne
Published: April 2012

Surface-science investigations have contributed significantly to heterogeneous catalysis in the past several decades. Fundamental studies of reactive systems on metal single crystals have aided researchers in understanding the effect of surface structure on catalyst reactivity and selectivity for a number of important reactions. Recently, model systems, consisting of metal clusters deposited on planar oxide surfaces, have facilitated the study of metal particle-size and support effects. These model systems not only are useful for carrying out kinetic investigations, but are also amenable to surface spectroscopic techniques, thus enabling investigations under realistic pressures and at working temperatures. By combining surface-science characterization methods with kinetic measurements under realistic working conditions, researchers are continuing to advance the molecular-level understanding of heterogeneous catalysis and are narrowing the pressure and material gap between model and real-world catalysts.
The Influence of Pain Distribution on Walking Velocity and Horizontal Ground Reaction Forces in Patients with Low Back Pain
Authors: Simmonds Maureen J. , Lee C. Ellen , Etnyre Bruce R. , Morris G. Stephen
Published: April 2012

Objective. The primary purpose of this paper was to evaluate the influence of pain distribution on gait characteristics in subjects with low back problems (LBP) during walking at preferred and fastest speeds. Design. Cross-sectional, observational study. Setting. Gait analysis laboratory in a health professions university. Participants. A convenience age- and gender-matched sample of 20 subjects with back pain only (BPO), 20 with referred leg pain due to back problems (LGP), and 20 pain-free individuals (CON). Methods and Measures. Subjects completed standardized self-reports on pain and disability and were videotaped as they walked at their preferred and fastest speeds along a walkway embedded with a force plate. Temporal and spatial gait characteristics were measured at the midsection of the walkway, and peak medial, lateral, anterior, and posterior components of horizontal ground reaction forces (hGRFs) were measured during the stance phase. Results. Patients with leg pain had higher levels of pain intensity and affect compared to those with back pain only (t=4.91, P<.001 and t=5.80, P<0.001, resp.) and walking had an analgesic effect in the BPO group. Gait velocity was highest in the control group followed by the BPO and LGP group and differed between groups at both walking speeds (F2.57=13.62, P<.001 and F2.57=9.09, P<.001, for preferred and fastest speed condition, resp.). When normalized against gait velocity, the LGP group generated significantly less lateral force at the fastest walking speed (P=.005) and significantly less posterior force at both walking speeds (P≤.01) compared to the control group. Conclusions. Pain intensity and distribution differentially influence gait velocity and hGRFs during gait. Those with referred leg pain tend to utilize significantly altered gait strategies that are more apparent at faster walking speeds.
Hormone Replacement Therapy and Risk for Neurodegenerative Diseases
Authors: Dye Richelin V. , Miller Karen J. , Singer Elyse J. , Levine Andrew J.
Published: April 2012

Over the past two decades, there has been a significant amount of research investigating the risks and benefits of hormone replacement therapy (HRT) with regards to neurodegenerative disease. Here, we review basic science studies, randomized clinical trials, and epidemiological studies, and discuss the putative neuroprotective effects of HRT in the context of Alzheimer’s disease, Parkinson’s disease, frontotemporal dementia, and HIV-associated neurocognitive disorder. Findings to date suggest a reduced risk of Alzheimer’s disease and improved cognitive functioning of postmenopausal women who use 17β-estradiol. With regards to Parkinson’s disease, there is consistent evidence from basic science studies for a neuroprotective effect of 17β-estradiol; however, results of clinical and epidemiological studies are inconclusive at this time, and there is a paucity of research examining the association between HRT and Parkinson’s-related neurocognitive impairment. Even less understood are the effects of HRT on risk for frontotemporal dementia and HIV-associated neurocognitive disorder. Limits to the existing research are discussed, along with proposed future directions for the investigation of HRT and neurodegenerative diseases.
Model Predictive Control of Uncertain Constrained Linear System Based on Mixed ℋ2/ℋ∞Control Approach
Authors: Orukpe Patience E.
Published: April 2012

Uncertain constrained discrete-time linear system is addressed using linear matrix inequality based optimization techniques. The constraints on the inputs and states are specified as quadratic constraints but are formulated to capture hyperplane constraints as well. The control action is of state feedback and satisfies the constraints. Uncertainty in the system is represented by unknown bounded disturbances and system perturbations in a linear fractional transform (LFT) representation. Mixed ℋ2/ℋ∞method is applied in a model predictive control strategy. The control law takes account of disturbances and uncertainty naturally. The validity of this approach is illustrated with two examples.
Paternal Benzo[a]pyrene Exposure Modulates MicroRNA Expression Patterns in the Developing Mouse Embryo
Authors: Brevik Asgeir , Lindeman Birgitte , Brunborg Gunnar , Duale Nur
Published: April 2012

Little attention has been given to how microRNA expression is affected by environmental contaminants exposure. We investigate the effects of paternal exposure to benzo[a]pyrene (B[a]P) on miRNA expression in the developing mouse embryo. Male mice were exposed to B[a]P (150 mg/kg i.p.), and their sperm was used four days later inin-vitrofertilization experiments. Twenty embryos each from 2-, 8-cell and the blastocyst stage were used for genome-wide miRNA expression profiling. Paternal exposure to B[a]P affected the expression of several miRNAs, and the target genes for some of the dysregulated miRNAs were enriched in many different pathways that are likely to be relevant for the developing mouse embryo. By linking the miRNA target genes to publicly available databases, we identified some miRNA target genes that may serve as global markers of B[a]P-mediated genotoxic stress. The dysregulated miRNAs may provide valuable knowledge about potential transgenerational effects of sublethal exposure to chemicals.
The Masquerades of a Childhood Ciliary Body Medulloepithelioma: A Case of Chronic Uveitis, Cataract, and Secondary Glaucoma
Authors: Chua Jocelyn , Muen Wisam J. , Reddy Ashwin , Brookes John
Published: April 2012

Ciliary body medulloepitheliomas in childhood often masquerade other intraocular conditions due to its insidious nature as well as its secondary effects on proximal intraocular tissues in the anterior chamber. We report a case where a ciliary body medulloepithelioma in a two-year-old boy presents with chronic uveitis, cataract, and an uncontrolled secondary glaucoma after an innocuous blunt ocular trauma. The diagnosis was only made after the occurrence of a ciliary body mass. We discuss the clinical features of ciliary body medulloepitheliomas, the implications of a delayed diagnosis and treatment as well as the concern of periorbital tumor seeding with the use of an aqueous shunt implant in this case.
Acute Fibrinous and Organizing Pneumonia and Undifferentiated Connective Tissue Disease: A Case Report
Authors: Valim Valéria , Rocha Roberta Hora , Couto Roberta Barcelos , Paixão Thaysa Simões , Serrano Érica Vieira
Published: April 2012

Acute fibrinous and organizing pneumonia (AFOP), recently described, is a histologic pattern characterized by the presence of fibrin “balls” within alveolar spaces. The term undifferentiated connective tissue disease (UCTD) is used to identify autoimmune systemic diseases that do not fulfill the criteria to be classified as a definitive connective tissue disease. The AFOP has never been reported in association with UCTD. The present reported case is a 39-year-old Caucasian, female with dry cough and progressive dyspnea. Eight months later, she was diagnosed with “organizing pneumonia” based on clinical history and radiologic images. She manifested Raynaud’s Phenomenon, sicca syndrome, boot and gloves neuropathic pain, and previous hypothyroidism. Antinuclear antibody, rheumatoid factor, and specific autoantibodies were negative. Salivary gland biopsy and electroneuromyiography were normal. The capillaroscopy showed a “scleroderma” pattern with capillary deletion and ectasia. She experienced clinical and radiologic worsening. Despite being submitted to cyclophosphamide pulse, she developed hemorrhage and then died. Thoracotomy pulmonary specimen showed histological pattern of AFOP. This paper shows a rare association of AFOP with UCTD.
Patient-Derived Xenografts of Non Small Cell Lung Cancer: Resurgence of an Old Model for Investigation of Modern Concepts of Tailored Therapy and Cancer Stem Cells
Authors: Moro Massimo , Bertolini Giulia , Tortoreto Monica , Pastorino Ugo , Sozzi Gabriella , Roz Luca
Published: April 2012

Current chemotherapy regimens have unsatisfactory results in most advanced solid tumors. It is therefore imperative to devise novel therapeutic strategies and to optimize selection of patients, identifying early those who could benefit from available treatments. Mouse models are the most valuable tool for preclinical evaluation of novel therapeutic strategies in cancer and, among them, patient-derived xenografts models (PDX) have made a recent comeback in popularity. These models, obtained by direct implants of tissue fragments in immunocompromised mice, have great potential in drug development studies because they faithfully reproduce the patient’s original tumor for both immunohistochemical markers and genetic alterations as well as in terms of response to common therapeutics They also maintain the original tumor heterogeneity, allowing studies of specific cellular subpopulations, including their modulation after drug treatment. Moreover PDXs maintain at least some aspects of the human microenvironment for weeks with the complete substitution with murine stroma occurring only after 2-3 passages in mouse and represent therefore a promising model for studies of tumor-microenvironment interaction. This review summarizes our present knowledge on mouse preclinical cancer models, with a particular attention on patient-derived xenografts of non small cell lung cancer and their relevance for preclinical and biological studies.
Apo A1 Mimetic Rescues the Diabetic Phenotype of HO-2 Knockout Mice via an Increase in HO-1 Adiponectin and LKBI Signaling Pathway
Authors: Cao Jian , Puri Nitin , Sodhi Komal , Bellner Lars , Abraham Nader G. , Kappas Attallah
Published: April 2012

Insulin resistance, with adipose tissue dysfunction, is one of the hallmarks of metabolic syndrome. We have reported a metabolic syndrome-like phenotype in heme oxygenase (HO)-2 knockout mice, which presented with concurrent HO-1 deficiency and were amenable to rescue by an EET analog. Apo A-I mimetic peptides, such as L-4F, have been shown to induce HO-1 expression and decrease oxidative stress and adiposity. In this study we aimed to characterize alleviatory effects of HO-1 induction (if any) on metabolic imbalance observed in HO-2 KO mice. In this regard, HO-2(−/−)mice were injected with 2 mg/kg/day L-4F, or vehicle, i.p., for 6 weeks. As before, compared to WT animals, the HO-2 null mice were obese, displayed insulin resistance, and had elevated blood pressure. These changes were accompanied by enhanced tissue (hepatic) oxidative stress along with attenuation of HO-1 expression and activity and reduced adiponectin, pAMPK, and LKB1 expression. Treatment with L-4F restored HO-1 expression and activity and increased adiponectin, LKB1, and pAMPK in the HO-2(−/−)mice. These alterations resulted in a decrease in blood pressure, insulin resistance, blood glucose, and adiposity. Taken together, our results show that a deficient HO-1 response, in a state with reduced HO-2 basal levels, is accompanied by disruption of metabolic homeostasis which is successfully restored by an HO-1 inducer.
Cone-Beam Computed Tomography and Radiographs in Dentistry: Aspects Related to Radiation Dose
Authors: Lorenzoni Diego Coelho , Bolognese Ana Maria , Garib Daniela Gamba , Guedes Fabio Ribeiro , Sant’Anna Eduardo Franzotti
Published: April 2012

Introduction. The aim of this study was to discuss the radiation doses associated with plain radiographs, cone-beam computed tomography (CBCT), and conventional computed tomography (CT) in dentistry, with a special focus on orthodontics.Methods. A systematic search for articles was realized by MEDLINE from 1997–March 2011.Results. Twenty-seven articles met the established criteria. The data of these papers were grouped in a table and discussed.Conclusions. Increases in kV, mA, exposure time, and field of view (FOV) increase the radiation dose. The dose for CT is greater than other modalities. When the full-mouth series (FMX) is performed with round collimation, the orthodontic radiographs transmit higher dose than most of the large FOV CBCT, but it can be reduced if used rectangular collimation, showing lower effective dose than large FOV CBCT. Despite the image quality, the CBCT does not replace the FMX. In addition to the radiation dose, image quality and diagnostic needs should be strongly taken into account.
Pilot Study of an Individualised Early Postpartum Intervention to Increase Physical Activity in Women with Previous Gestational Diabetes
Authors: McIntyre Harold David , Peacock Ann , Miller Yvette D. , Koh Denise , Marshall Alison L.
Published: April 2012

Optimal strategies to prevent progression towards overt diabetes in women with recent gestational diabetes remain ill defined. We report a pilot study of a convenient, home based exercise program with telephone support, suited to the early post-partum period. Twenty eight women with recent gestational diabetes were enrolled at six weeks post-partum into a 12 week randomised controlled trial of Usual Care (n=13) versus Supported Care (individualised exercise program with regular telephone support;n=15). Baseline characteristics (Mean ± SD) were: Age  33±4  years; Weight 80 ± 20 kg and Body Mass Index (BMI)30.0±9.7 kg/m2. The primary outcome, planned physical activity {Median (Range)}, increased by 60 (0–540) mins/week in the SC group versus 0 (0–580) mins/week in the UC group (P=0.234). Walking was the predominant physical activity. Body weight, BMI, waist circumference, % body fat, fasting glucose and insulin did not change significantly over time in either group. This intervention designed to increase physical activity in post-partum women with previous gestational diabetes proved feasible. However, no measurable improvement in metabolic or biometric parameters was observed over a three month period.
Secular Trends in Ischemic Stroke Characteristics in a Rapidly Developed Country
Authors: Jung Keun-Hwa , Lee Seung-Hoon , Kim Beom Joon , Yu Kyung-Ho , Hong Keun-Sik , Lee Byung-Chul , Roh Jae-Kyu ,   Korean Stroke Registry Study Group
Published: April 2012

Background—

A dynamic change in industry, lifestyle, and healthcare structure brings a corresponding change in disease patterns. Limited data exist with respect to secular trends in stroke epidemiology in Korea, a rapidly developed country.

Methods and Results—

We analyzed individual patient data registered the Korean Stroke Registry, a nationwide hospital-based stroke database, between January 2002 and November 2010. Mortality data were obtained from a national death certificate system. Linear or logistic regression analyses were performed to assess secular trends. A total of 46 098 patients were included in this study. Mean±SD age was 66.1±12.3 years, and 57.6% of the patients were men. Over the 9-year period, patient ages steadily increased by 0.24 year annually (
P
<0.001). Risk factor proportions of hypertension, diabetes, smoking, and prior stroke declined slightly (
P
<0.05 for all). However, dyslipidemia frequency showed a complex pattern of an initial decline and then an increase. For relative proportions of subtypes, cardioembolism increased, small vessel occlusion decreased, and large artery atherosclerosis remained stable. Still, intracranial stenosis overwhelms extracranial stenosis, but extracranial stenosis is on the rise. Arrival within 3 hours increased from 20% to 29%, and reperfusion therapy increased from 5.3% to 7.0%. Age-adjusted all-cause mortality did not decrease at 30 days but decreased at 1 year over time.

Conclusions—

During the first decade of 21st century, stroke characteristics in Korea changed, likely because of increased lifespan, westernized lifestyle, and improved public awareness. Stroke experts need to cope with these distinguishing trends to establish a better strategy for prevention and acute therapy.
Loss of Angiotensin-Converting Enzyme-2 Exacerbates Diabetic Cardiovascular Complications and Leads to Systolic and Vascular Dysfunction
Authors: Patel Vaibhav B. , Bodiga Sreedhar , Basu Ratnadeep , Das Subhash K. , Wang Wang , Wang Zuocheng , Lo Jennifer , Grant Maria B. , Zhong JiuChang , Kassiri Zamaneh , Oudit Gavin Y.
Published: April 2012

Rationale:

Diabetic cardiovascular complications are reaching epidemic proportions. Angiotensin-converting enzyme-2 (ACE2) is a negative regulator of the renin-angiotensin system. We hypothesize that loss of ACE2 exacerbates cardiovascular complications induced by diabetes.

Objective:

To define the role of ACE2 in diabetic cardiovascular complications.

Methods and Results:

We used the well-validated Akita mice, a model of human diabetes, and generated double-mutant mice using the ACE2 knockout (KO) mice (Akita/ACE2
−/y
). Diabetic state was associated with increased ACE2 in Akita mice, whereas additional loss of ACE2 in these mice leads to increased plasma and tissue angiotensin II levels, resulting in systolic dysfunction on a background of impaired diastolic function. Downregulation of SERCA2 and lipotoxicity were equivalent in Akita and Akita/ACE2KO hearts and are likely mediators of the diastolic dysfunction. However, greater activation of protein kinase C and loss of Akt and endothelial nitric oxide synthase phosphorylation occurred in the Akita/ACE2KO hearts. Systolic dysfunction in Akita/ACE2KO mice was linked to enhanced activation of NADPH oxidase and metalloproteinases, resulting in greater oxidative stress and degradation of the extracellular matrix. Impaired flow-mediated dilation in vivo correlated with increased vascular oxidative stress in Akita/ACE2KO mice. Treatment with the AT1 receptor blocker, irbesartan rescued the systolic dysfunction, normalized altered signaling pathways, flow-mediated dilation, and the increased oxidative stress in the cardiovascular system.

Conclusions:

Loss of ACE2 disrupts the balance of the renin-angiotensin system in a diabetic state and leads to an angiotensin II/AT1 receptor-dependent systolic dysfunction and impaired vascular function. Our study demonstrates that ACE2 serves as a protective mechanism against diabetes-induced cardiovascular complications.