bluuebunny/crossref_metadata_2025 huggingface dataset:
A Scale Analysis Based Theoretical Force Balance Model for Critical Heat Flux (CHF) During Saturated Flow Boiling in Microchannels and Minichannels
Authors: Kandlikar Satish G.
Published: June 2010

Accurate prediction of critical heat flux (CHF) in microchannels and minichannels is of great interest in estimating the safe operational limits of cooling systems employing flow boiling. Scale analysis is applied to identify the relevant forces leading to the CHF condition. Using these forces, a local parameter model is developed to predict the flow boiling CHF. The theoretical model is an extension of an earlier pool boiling CHF model and incorporates force balance among the evaporation momentum, surface tension, inertia, and viscous forces. Weber number, capillary number, and a new nondimensional group introduced earlier by Kandlikar (2004, “Heat Transfer Mechanisms During Flow Boiling in Microchannels,” ASME J. Heat Transfer, 126, pp. 8–16), K2, representing the ratio of evaporation momentum to surface tension forces, emerged as main groups in quantifying the narrow channel effects on CHF. The constants in the model were calculated from the available experimental data. The mean error with ten data sets is 19.7% with 76% data falling within ±30% error band and 93% within ±50% error band. The length to diameter ratio emerged as a parameter indicating a stepwise regime change. The success of the model indicates that flow boiling CHF can be modeled as a local phenomenon and the scale analysis is able to reveal important information regarding fundamental mechanisms leading to the CHF condition.
Transient Temperature Data Analysis for a Supersonic Flight Test
Authors: Sahoo Niranjan , Peetala Ravi Kumar
Published: June 2010

Determination of transient surface heat flux from the temperature data is one of the traditional techniques applied in many engineering applications. With respect to high speed flight experiments, the time scale of measured temperature data is usually very small (∼ms). So, one-dimensional heat conduction analysis is expensively used to infer surface heating rates on the body. For an analytical modeling, it is necessary to obtain a closed form solution from experimentally measured temperature data. In this paper, a temperature data obtained from a nickel film sensor during a supersonic flight test is considered for analysis. Three different curve fitting techniques are used to recover the temperature history of real time flight, namely, piecewise linear fit, polynomial fitting, and cubic-spline method. A one-dimensional transient heat transfer modeling is used to infer surface heating rates from the closed form temperature solutions. Results obtained from these analysis are compared and it is seen that peak surface heat flux values match very closely for polynomial and cubic-spline fitting of temperature data. But, the piecewise linear fit of temperature data underpredicts the peak surface heat flux value by four times from its counterparts.
Numerical Simulation of Convective Heat Transfer Modes in a Rectangular Area With a Heat Source and Conducting Walls
Authors: Kuznetsov G. V. , Sheremet M. A.
Published: June 2010

Laminar conjugate heat transfer in a rectangular area having finite thickness heat-conducting walls at local heating has been analyzed numerically. The heat source located on the left wall is kept at constant temperature during the whole process. Conjugate heat transfer is complicated by the forced flow. The governing unsteady, two-dimensional flow and energy equations for the gas cavity and unsteady heat conduction equation for solid walls, written in dimensionless form, have been solved using implicit finite-difference method. The solution has been obtained in terms of the stream function and the vorticity vector. The effects of the Grashof number Gr, the Reynolds number Re, and the dimensionless time on the flow structure and heat transfer characteristics have been investigated in detail. Results have been obtained for the following parameters: 103≤Gr≤107, 100≤Re≤1000, and Pr=0.7. Typical distributions of thermohydrodynamic parameters describing features of investigated process have been received. Interference of convective flows (forced, natural, and mixed modes) in the presence of conducting solid walls has been analyzed. The increase in Gr is determined to lead to both the intensification of the convective flow caused by the presence of the heat source and the blocking of the forced flow nearby the upper wall. The nonmonotomic variations in the average Nusselt number with Gr for solid-fluid interfaces have been obtained. The increase in Re is shown to lead to cooling of the gas cavity caused by the forced flow. Evolution of analyzed process at time variation has been displayed. The diagram of the heat convection modes depending on the Grashof and Reynolds numbers has been obtained. The analysis of heat convection modes in a typical subsystem of the electronic equipment is oriented not only toward applied development in microelectronics, but also it can be considered as test database at creation of numerical codes of convective heat transfer simulation in complicated energy systems. Comparison of the obtained results can be made by means of both streamlines and temperature fields at different values of the Grashof number and Reynolds number, and the average Nusselt numbers at solid-fluid interfaces.
Thermohydraulics of Laminar Flow Through Rectangular and Square Ducts With Axial Corrugation Roughness and Twisted Tapes With Oblique Teeth
Authors: Saha Sujoy Kumar
Published: June 2010

The heat transfer and the pressure drop characteristics of laminar flow of viscous oil (175<Pr<538) through rectangular and square ducts with combined internal axial corrugations on all the surfaces of the ducts and with twisted-tape inserts with and without oblique teeth have been studied experimentally. The axial corrugations in combination with both twisted tapes with and without oblique teeth have been found to perform better than either axial corrugations or twisted-tape inserts acting alone. The heat transfer and the pressure drop measurements have been taken in separate test sections. Heat transfer tests were carried out in electrically heated stainless steel ducts incorporating uniform wall heat flux boundary conditions. Pressure drop tests were carried out in acrylic ducts. The flow friction and thermal characteristics are governed by duct aspect ratio, corrugation angle, corrugation pitch, twist ratio, space ratio, length, tooth horizontal length and tooth angle of the twisted tapes, Reynolds number, and Prandtl number. Correlations developed for friction factor and Nusselt number have predicted the experimental data satisfactorily. The performance of the geometry under investigation has been evaluated. It has been found that based on constant pumping power, up to 45% heat duty increase occurs for the combined axial corrugation and twisted-tape insert case compared with the individual axial corrugation and twisted-tape insert cases in the measured experimental parameters space. On the constant heat duty basis, the pumping power has been reduced up to 30% for the combined enhancement geometry than the individual enhancement geometries.
Rendering the Transient Hot Wire Experimental Method for Thermal Conductivity Estimation to Two-Phase Systems—Theoretical Leading Order Results
Authors: Vadasz Peter
Published: June 2010

The transient hot wire experimental method for estimating the thermal conductivity of fluids and solids is well established as the most accurate, reliable, and robust technique. It essentially relies on a simple analytical formula derived from the solution of the heat conduction from a line heat source embedded in the target medium. This simple and elegant analytical formulation was derived for uniform and homogeneous fluids or solids. Its extension to two-phase or composite systems, while in practical application, does not have any theoretical basis, and it is by no means obvious that the latter may be applied without corrections to such heterogeneous systems. When it is actually applied as for single-phase systems, it is clearly incorrect. This paper presents preliminary results at the leading order (in the sense of an expansion of the solution in powers of time, applicable to short time scales, consistent with the validity of the transient hot wire method), which render the transient hot wire method to two-phase and composite systems. While these leading order approximations extend the applicability of the same analytical formula to two-phase systems, they also produce additional conditions that need to be fulfilled for such an application to provide reliable experimental results.
Bubble Dynamics for Nucleate Pool Boiling of Electrolyte Solutions
Authors: Alavi Fazel Seyed Ali , Shafaee Seyed Baher
Published: June 2010

Bubble dynamics is the most important subphenomenon, which basically affects the nucleate pool boiling heat transfer coefficient. Previous investigations state that the effect of physical properties of liquid and vapor phases on bubble departure diameter are often conflicting. In this article, extensive new experimental data are presented for the bubble departure diameter for various electrolyte aqueous solutions over a wide range of heat fluxes and concentrations. Experimental results show that the bubble detachment diameter increase with increasing either boiling heat flux or electrolyte concentration. Experimental results also present a close relation between the dimensionless capillary and bond numbers. A new model for the prediction of vapor bubble departure diameter in nucleate boiling for the electrolyte solutions is proposed, which predicts the experimental data with a satisfactory accuracy.
A Meshless Finite Difference Method for Conjugate Heat Conduction Problems
Authors: Varanasi Chandrashekhar , Murthy Jayathi Y. , Mathur Sanjay
Published: June 2010

A meshless finite difference method is developed for solving conjugate heat transfer problems. Starting with an arbitrary distribution of mesh points, derivatives are evaluated using a weighted least-squares procedure. The resulting system of algebraic equations is sparse and is solved using an algebraic multigrid method. The implementation of the Neumann, Dirichlet, and mixed boundary conditions within this framework is described. For conjugate heat transfer problems, continuity of the heat flux and temperature are imposed on mesh points at multimaterial interfaces. The method is verified through application to classical heat conduction problems with known analytical solutions. It is then applied to the solution of conjugate heat transfer problems in complex geometries, and the solutions so obtained are compared with more conventional unstructured finite volume methods. The method improves on existing meshless methods for conjugate heat conduction by eliminating spurious oscillations previously observed. Metrics for accuracy are provided and future extensions are discussed.
Particle Aspect-Ratio and Agglomeration-State Effects on the Effective Thermal Conductivity of Aqueous Suspensions of Multiwalled Carbon Nanotubes
Authors: Cherkasova Anna S. , Shan Jerry W.
Published: June 2010

The effective thermal conductivities of aqueous nanofluids containing surfactant-stabilized multiwalled carbon nanotubes were measured and compared with the predictions of effective medium theory (Nan, C.-W., et al., 1997, “Effective Thermal Conductivity of Particulate Composites With Interfacial Thermal Resistance,” J. Appl. Phys., 81(10), pp. 6692–6699). Detailed characterization of nanotube morphology was carried out through electron microscopy, while the nanotube agglomeration state was monitored through optical microscopy and absorption measurements. An optimum surfactant-to-nanotube mass ratio was found for the particular surfactant, sodium dodecylbenzene sulfonate, which resulted in the greatest increase in thermal conductivity. Taking into consideration the volume-weighted aspect ratio of the nanotubes, the measured thermal conductivities of the suspensions were shown to be in good agreement with calculations for a reasonable choice of interfacial resistance on the particle/liquid interface. The effect of particle aspect ratio on the suspension’s thermal conductivity was further demonstrated and compared with theory by reducing the nanotube length through intense ultrasonication. The effect of particle aggregation on the thermal conductivity was also investigated by destabilizing previously stable suspensions with ethanol addition, which causes surfactant desorption and bundling of nanotubes. The measured thermal conductivities were correlated with absorption measurements and microscopic visualizations to show that particle aggregation decreases the thermal conductivity of the nanofluid by reducing the effective particle aspect ratio.
On the Use of Lie Group Time Integrators in Multibody Dynamics
Authors: Brüls Olivier , Cardona Alberto
Published: June 2010

This paper proposes a family of Lie group time integrators for the simulation of flexible multibody systems. The method provides an elegant solution to the rotation parametrization problem. As an extension of the classical generalized-α method for dynamic systems, it can deal with constrained equations of motion. Second-order accuracy is demonstrated in the unconstrained case. The performance is illustrated on several critical benchmarks of rigid body systems with high rotation speeds, and second-order accuracy is evidenced in all of them, even for constrained cases. The remarkable simplicity of the new algorithms opens some interesting perspectives for real-time applications, model-based control, and optimization of multibody systems.
Energy Efficient Polymers for Gas-Liquid Heat Exchangers
Authors: Luckow Patrick , Bar-Cohen Avram , Rodgers Peter , Cevallos Juan
Published: June 2010

The compression process necessary for the liquefaction of natural gas on offshore platforms generates large amounts of heat, usually dissipated via sea water cooled plate heat exchangers. To date, the corrosive nature of sea water has mandated the use of metals, such as titanium, as heat exchanger materials, which are costly in terms of life cycle energy expenditure. This study investigates the potential of a commercially available, thermally conductive polymer material, filled with carbon fibers to enhance thermal conductivity by an order of magnitude or more. The thermofluid characteristics of a prototype polymer seawater-methane heat exchanger that could be used in the liquefaction of natural gas on offshore platforms are evaluated based on the total coefficient of performance (COPT), which incorporates the energy required to manufacture a heat exchanger along with the pumping power expended over the lifetime of the heat exchanger, and compared with those of conventional heat exchangers made of metallic materials. The heat exchanger fabricated from a low energy, low thermal conductivity polymer is found to perform as well as, or better than, exchangers fabricated from conventional materials, over its full lifecycle. The analysis suggests that a COPT nearly double that of aluminum, and more than ten times that of titanium, could be achieved. Of the total lifetime energy use, 70% occurs in manufacturing for a thermally enhanced polymer heat exchanger compared with 97% and 85% for titanium and aluminum heat exchangers, respectively. The study demonstrates the potential of thermally enhanced polymer heat exchangers over conventional ones in terms of thermal performance and life cycle energy expenditure.
Exergo-Thermo-Volumes: An Approach for Environmentally Sustainable Thermal Management of Energy Conversion Devices
Authors: Shah Amip J. , Patel Chandrakant D.
Published: June 2010

The design of cooling solutions is an important consideration for the efficient management of different types of energy technologies. In the present work, we adapt the method of thermo-volumes—which has been used for nearly a decade in the design of electronic cooling solutions—for purposes of expeditiously understanding the thermal resistance of a given solution (in terms of cooling performance) along with its flow resistance (an indicator of the pumping power or energy consumption, which will be required by the thermal solution). Furthermore, we expand on thermo-volumes by including the lifetime exergy cost as a means to enable the consideration of resource consumption (and thus the environmental sustainability) of the cooling solution. We apply this framework for evaluation of thermal management solutions in terms of the heat removal capacity per unit lifetime exergy consumption. This paper concludes by illustrating applicability of the method to the design of a fuel cell thermal management solution.
Frictional and Internal Leakage Losses in Rotary-Vane Two-Phase Refrigerating Expanders
Authors: Mahmoud Ahmad M. , Sherif S. A. , Lear W. E.
Published: June 2010

Increasing the coefficient of performance of a vapor compression refrigeration system may be realized by utilizing work recovering expansion devices that additionally lower the enthalpy of the refrigerant at the inlet of the evaporator. Depending on the operational and geometrical parameters of the expander, laminar and viscous two-phase leakage flows within the expander may be present. Single-phase leakage models available in the literature must then be modified or rederived accordingly. A dynamic frictional model for the expander must also be developed for ideal operation (i.e., no internal leakage) and modified to account for internal leakage accordingly. This paper presents a comprehensive component-level model of inherent friction and internal leakage losses in a two-phase circular rotary-vane expander used in a vapor compression refrigeration system. The model establishes the performance of the expander as a function of geometric and fluid parameters. Accurate modeling and prediction of frictional and internal leakage losses is vital to being able to accurately estimate the efficiency, rotational speed, and the torque and power produced by the expander. Directions for future work are also discussed.
A Stretch/Bend Method for In Situ Measurement of the Delamination Toughness of Coatings and Films Attached to Substrates
Authors: He M. Y. , Hutchinson J. W. , Evans A. G.
Published: June 2010

A stretch/bend method for the in situ measurement of the delamination toughness of coatings attached to substrates is described. A beam theory analysis is presented that illustrates the main features of the test. The analysis is general and allows for the presence of residual stress. It reveals that the test produces stable extension of delaminations, rendering it suitable for multiple measurements in a single test. It also provides scaling relations and enables estimates of the loads needed to extend delaminations. Finite element calculations reveal that the beam theory solutions are accurate for slender beams, but overestimate the energy release rate for stubbier configurations and short delaminations. The substantial influence of residual stress on the energy release rate and phase angle is highly dependent on parameters such as the thickness and modulus ratio for the two layers. Its effect must be included to obtain viable measurements of toughness. In a companion paper, the method has been applied to a columnar thermal barrier coating deposited onto a Ni-based super-alloy.
A Passive Model of the Heat, Oxygen and Carbon Dioxide Transport in the Human Body
Authors: Albuquerque-Neto Cyro , Yanagihara Jurandir Itizo
Published: June 2010

The aim of this work is the development of a mathematical model which integrates a model of the human respiratory system and a model of the human thermal system. Both models were previously developed at the same laboratory, based on classical works. The human body was divided in 15 segments: head, neck, trunk, arms, forearms, hands, thighs, legs and feet. Those segments have the form of a cylinder (circular cross-section) or a parallelogram (hands and feet) with the following tissue layers: muscle, fat, skin, bone, brain, lung, heart and viscera. Two different geometries are used to model the transport of mass and heat in the tissues. For the mass transfer, those layers are considered as tissue compartments. For the heat transfer, the body geometry is taken into account. Each segment contains an arterial and a venous compartment, representing the large vessels. The blood in the small vessels are considered together with the tissues. The gases are transported by the blood dissolved and chemically reacted. Metabolism takes place in the tissues, where oxygen is consumed generating carbon dioxide and heat. In the lungs, mass transfer happens by diffusion between an alveolar compartment and several pulmonary capillaries compartments. The skin exchanges heat with the environment by convection, radiation and evaporation. The differential transport equations were obtained by heat and mass balances. The discretization heat equations were obtained applying the finite volume method. The regulation mechanisms were considered as model inputs. The results show three different environment situations. It was concluded that the gas transport is most influenced by the temperature effects on the blood dissociation curves and the metabolism rise in a cold environment by shivering.
Cracked Elastic Layer Under a Compressive Mechanical Load
Authors: Makaryan Vahagn , Sutton Michael , Yeghiazaryan Tatevik , Hasanyan Davresh , Deng Xiaomin
Published: June 2010

In the present work, the problem of an elastic layer weakened by a finite penny shaped crack parallel to a layer’s surface that is loaded in compression is considered. Assuming that the surfaces of the crack have frictional slipping contact, Henkel and Legendre integral transformation techniques are employed to formulate solutions in the form of an infinite system of linear algebraic equations. The regularity of the equations is established and closed-form solutions are obtained for stresses and strains. Assuming shear stress on the crack surfaces is linearly distributed, numerical results show both geometric and physical parameters have an essential influence on the stress distribution around the crack, with specific parameter values indicating the normal stress along the crack surface can change its sign from negative to positive. The implications of the work will be discussed.
The Effect of Surface Over-Aging on the Strength and SCC Susceptibility of 7075 Aluminum Alloy
Authors: Fooladfar Hamidreza , Hashemi Babak , Younesi Mousa
Published: June 2010

A novel heat treatment procedure combining the shot-peening with a two-step aging operation was proposed to improve both the strength and the stress corrosion cracking (SCC) resistance of the high-strength 7075 aluminium alloy. The heat treatment included one shot-peening stage before or between the two stages of aging at 120°C for 24 h and at 160°C for 1 h, respectively. The mechanical properties obtained during the aforementioned operations were extremely similar to those of the T6 sample owing to the unaffected bulk microstructure over such a low over-aging period. The SCC resistance of these samples was considerably improved, compared to that of the T6 sample and of the conventional shot-peened T6 sample due to the over-aging of the surface like the T7 treatment leading from the diffusion acceleration by the dislocations generated in the surface layer during shot-peening. In spite of the further depth of deformation caused by shot-peening prior to the first step of aging, the sample shot-peened after the first step of aging showed no significant decrease in the SCC resistance because of its higher generated dislocation by shot-peening.
A WKB-like approach to Unruh radiation
Authors: de Gill Andrea , Singleton Douglas , Akhmedova Valeria , Pilling Terry
Published: June 2010

Unruh radiation is the thermal flux measured by an accelerated observer moving through Minkowski spacetime. We study Unruh radiation as tunneling through a barrier. We use a WKB-like method to obtain the tunneling rate and the temperature of the Unruh radiation. The gravitational WKB method helps to highlight the subtle points that the tunneling rate should be written as the closed path integral of the canonical momentum, and for the case of the gravitational WKB problem, there is a timelike contribution to the tunneling rate arising from an imaginary change of the time coordinate upon crossing the horizon. This temporal contribution to the tunneling rate has no analog in the usual quantum mechanical WKB calculation. The derivation brings together many topics, including classical mechanics, relativity, relativistic field theory, quantum mechanics, statistical mechanics, and mathematical physics.
Impact of a ball on a surface with tangential compliance
Authors: Cross Rod
Published: June 2010

A simple model is presented to explain how the spin of a ball can be enhanced when the ball is incident obliquely on a flexible surface. The mechanism involves tangential distortion of the surface and a return of the elastic energy stored in the surface via the action of the static friction force on the ball. As an example, we consider the enhancement of the spin that is possible using an appropriate type of tennis racquet string.
Do advanced physics students learn from their mistakes without explicit intervention?
Authors: Mason Andrew , Singh Chandralekha
Published: June 2010

We discuss a case study in which 14 advanced undergraduate physics students taking an honor-level quantum mechanics course were given the same four problems on midterm and final exams. The solutions to the midterm problems were provided to students. Their performance on the final exam shows that although some advanced students performed equally well or improved compared to their performance on the midterm exam on the problems given twice, a comparable number performed less well on the final than on the midterm exam. The wide distribution of students’ performance on problems given again suggests that most advanced students do not automatically use their mistakes as an opportunity for learning, repairing, extending, and organizing their knowledge structure. Interviews with a subset of the students revealed attitudes toward problem solving and gave insight into their approach to learning.
Orientation change of a two-dimensional articulated figure of zero angular momentum
Authors: Di Bartolo S. John
Published: June 2010

This paper examines the motion of a simple system of connected rigid bodies with no net angular momentum. Although it is possible for such a system to move in a way that preserves its orientation, we consider the conditions where orientation of the system changes even in the absence of an external torque. A general formalism is developed for calculating the change of orientation of an articulated figure with two degrees of freedom. This formalism is then used to show that the orientation changes in the absence of an external torque are possible; in particuler it is applied to a simple figure made of three equivalent rods and to a primitive model of the human body. To illustrate how these systems evolve over time, the differential equations governing their movement are solved numerically, and animations of the moving figures are created.
Babinet’s principle in the Fresnel regime studied using ultrasound
Authors: Hitachi Akira , Takata Momo
Published: June 2010

The diffraction of ultrasound by a circular disk and an aperture of the same size has been investigated as a demonstration of Babinet’s principle in the Fresnel regime. The amplitude and the phase of the diffracted ultrasonic waves are measured and a graphical treatment of the results is performed by drawing vectors in the complex plane. The results verify Babinet’s principle. It is also found that the incident wave is π/2 behind the phase of the wave passing through on the central axis of a circular aperture. Because both waves travel the same path and the same distance, they should be in phase. This paradox has previously been regarded as a defect of Fresnel’s theory.
What happens between pre- and post-tests: Multiple measurements of student understanding during an introductory physics course
Authors: Heckler Andrew F. , Sayre Eleanor C.
Published: June 2010

To characterize the evolution of student understanding better than what is possible by pre-and post-testing, we posed simple conceptual questions several times per week to separate, randomly selected groups of introductory physics students. This design avoids issues of retesting and allows for tracking of student understanding of a given topic during the course with a resolution on the order of days. Based on the data from over 1600 students over five quarters, we found significant and interesting changes in performance on time scales of days and weeks. We found that the response curves of performance versus time can be divided into four categories: flat (no change), step-up, step-up and decay, and step-down. We examined changes on a 1 day time scale and found that changes in performance did not coincide with relevant traditional lectures or laboratories, but coincide with due dates of relevant on-line homework that provides immediate feedback. This method is well suited to measuring the effect of particular instructional events as well as providing insight into the nature of student understanding and learning.
The constructal-law origin of the wheel, size, and skeleton in animal design
Authors: Bejan Adrian
Published: June 2010

This paper shows that the emergence of body organs is predictable as an integral part of the design for moving animal mass more easily on Earth, in accord with the constructal law of design in nature: For a finite-size open system to persist in time (to live), it must evolve such that it provides easier access to the imposed (global) currents that flow through it. Every organ destroys useful energy in two ways: Internally by thermodynamic irreversibilities and by having to be carried. From the constructal law follows the necessity of characteristic-size organs and the emergence of solid columns (legs) to facilitate the flow of stresses. This natural “wheel” endows the body with rolling (falling-forward) locomotion, with predicted speeds that agree with the observed speeds in the body mass range of 10−6–103 kg. The constructal law also accounts for animal design features for changing speeds. Skeletons (bones and legs) are solid organs that emerge in accordance with the constructal-law design of moving animal mass: More and stronger material emerges along the lines of highest stresses. A connection between animal wheel movement and swimming, water waves, and tsunamis is also made.
A Giant Planet Imaged in the Disk of the Young Star β Pictoris
Authors: Lagrange A.-M. , Bonnefoy M. , Chauvin G. , Apai D. , Ehrenreich D. , Boccaletti A. , Gratadour D. , Rouan D. , Mouillet D. , Lacour S. , Kasper M.
Published: June 2010

Planet Is Born

The 10-million-year-old star β Pictoris, has long been suspected to host a planet. Through images obtained with the Very Large Telescope, an array of four telescopes located in Chile,

Lagrange
et al.

(p.
57
, published online 10 June) now confirm the presence of a young, giant planet, β Pictoris b, orbiting within the dusty disk that surrounds the star. β Pictoris b orbits closer to its star than Uranus and Neptune do to the Sun in our solar system. This orbital separation is consistent with the in situ formation of the planet via a core accretion mechanism. Thus, giant planets can form within a stellar dust disk in only a few million years.
Bacteremia Due to Extended-Spectrum-β-Lactamase-Producing
Enterobacter cloacae
: Role of Carbapenem Therapy
Authors: Lee Ching-Chi , Lee Nan-Yao , Yan Jing-Jou , Lee Hsin-Chun , Chen Po-Lin , Chang Chia-Ming , Wu Chi-Jung , Ko Nai-Ying , Wang Li-Rong , Chi Chih-Hsien , Ko Wen-Chien
Published: June 2010

Enterobacter cloacae
is an important nosocomial pathogen. However, few studies specifically dealing with the clinical characteristics and outcome of extended-spectrum β-lactamase (ESBL)-producing
E. cloacae
infections have been published. During an 8-year period in a medical center, of 610
E. cloacae
bacteremic isolates, 138 (22.6%) with ESBL genes were designated the ESBL group, and 120 (19.6%) cefotaxime-nonsusceptible isolates without the ESBL phenotype and genes were designated the control group. Of the former group of isolates, 133 (96.3%) carried the
bla
SHV-12
gene, 3 (2.1%) had
bla
CTX-M3
, and 2 (1.4%) had both the
bla
SHV-12
and
bla
CTX-M3
genes. After patients under the age of 18 years were excluded, there were 206 adults with
E. cloacae
bacteremia, and these consisted of 121 patients in the ESBL group and 85 in the control group. More episodes of hospital-onset and polymicrobial bacteremia, increased severity of illness, more cases of bacteremia onset in intensive care units (ICUs), and longer stays in the hospital and ICU after bacteremia onset were noted in the ESBL group. However, the crude and sepsis-related mortality rates in two groups were similar. Of the ESBL group, the in-hospital sepsis-related mortality rate of patients definitively treated by a carbapenem was lower than that of those treated by noncarbapenem β-lactams (5/53, or 9.4%, versus 13/44, or 29.5%;
P
= 0.01) though the difference was not significant in the hierarchical multivariate analysis (
P
= 0.46). Among 62 patients with follow-up blood cultures within 14 days of bacteremia onset, breakthrough bacteremia was more common in those treated by a noncarbapenem β-lactam agent than in those treated by a carbapenem (18/31, or 58.0%, versus 3/31, or 9.6%;
P
< 0.001). Thus, carbapenem therapy for ESBL-producing
E. cloacae
that cause bacteremia may provide therapeutic benefits.
Bile Acids Improve the Antimicrobial Effect of Rifaximin
Authors: Darkoh Charles , Lichtenberger Lenard M. , Ajami Nadim , Dial Elizabeth J. , Jiang Zhi-Dong , DuPont Herbert L.
Published: June 2010

Diarrhea is one of the most common infirmities affecting international travelers, occurring in 20 to 50% of persons from industrialized countries visiting developing regions. Enterotoxigenic
Escherichia coli
(ETEC) is the most common causative agent and is isolated from approximately half of the cases of traveler's diarrhea. Rifaximin, a largely water-insoluble, nonabsorbable (<0.4%) antibiotic that inhibits bacterial RNA synthesis, is approved for use for the treatment of traveler's diarrhea caused by diarrheagenic
E. coli
. However, the drug has minimal effect on the bacterial flora or the infecting
E. coli
strain in the aqueous environment of the colon. The purpose of the present study was to evaluate the antimicrobial effect and bioavailability of rifaximin in aqueous solution in the presence and absence of physiologic concentrations of bile acids. The methods used included growth measurement of ETEC (strain H10407), rifaximin solubility measurements, total bacterial protein determination, and assessment of the functional activity of rifaximin by monitoring inhibition of bacterial β-galactosidase expression. Solubility studies showed rifaximin to be 70- to 120-fold more soluble in bile acids (approximately 30% in 4 mM bile acids) than in aqueous solution. Addition of both purified bile acids and human bile to rifaximin at subinhibitory and inhibitory concentrations significantly improved the drug's anti-ETEC effect by 71% and 73%, respectively, after 4 h. This observation was confirmed by showing a decrease in the overall amount of total bacterial protein expressed during incubation of rifaximin plus bile acids. Rifaximin-treated samples containing bile acids inhibited the expression of ETEC β-galactosidase at a higher magnitude than samples that did not contain bile acids. The study provides data showing that bile acids solubilize rifaximin on a dose-response basis, increasing the drug's bioavailability and antimicrobial effect. These observations suggest that rifaximin may be more effective in the treatment of infections in the small intestine, due to the higher concentration of bile in this region of the gastrointestinal tract than in the colon. The water insolubility of rifaximin is the likely explanation for the drug's minimal effects on colonic flora and fecal pathogens, despite
in vitro
susceptibility.
Role of the Specific Interaction of UL112-113 p84 with UL44 DNA Polymerase Processivity Factor in Promoting DNA Replication of Human Cytomegalovirus
Authors: Kim Young-Eui , Ahn Jin-Hyun
Published: June 2010

The human cytomegalovirus (HCMV) UL112-113 region encodes four phosphoproteins with common amino termini (p34, p43, p50, and p84) via alternative splicing and is thought to be required for efficient viral DNA replication. We have previously shown that interactions among the four UL112-113 proteins regulate their intranuclear targeting and enable the recruitment of the UL44 DNA polymerase processivity factor to viral prereplication foci. Here, we show that in virus-infected cells, the UL112-113 proteins form a complex with UL44 and other replication proteins, such as UL84 and IE2.
In vitro
assays showed that all four phosphoproteins interacted with UL44. Interestingly, p84 required both the shared amino-terminal region and the specific near-carboxy-terminal region for UL44 binding. UL44 required both the carboxy-terminal region and the central region, including the dimerization domain for p84 binding. The production of recombinant virus from mutant Towne bacterial artificial chromosome (BAC) DNA, which encodes intact p34, p43, and p50 and a carboxy-terminally truncated p84 defective in UL44 binding, was severely impaired compared to wild-type BAC DNA. A similar defect was observed when mutant BAC DNA encoded a carboxy-terminally truncated UL44 defective in p84 binding. In cotransfection replication assays using six replication core proteins, UL84, IE2, and UL112-113, the efficient replication of an HCMV
ori
Lyt-containing plasmid required the regions of p84 and UL44 necessary for their interaction. Our data suggest that the UL112-113 proteins form a complex with other replication proteins such as UL44, UL84, and IE2 and that the specific interaction of UL112-113 p84 with UL44 is necessary for efficient viral DNA replication.
Differential Sensitivity of Well-Differentiated Avian Respiratory Epithelial Cells to Infection by Different Strains of Infectious Bronchitis Virus
Authors: Abd El Rahman Sahar , Winter Christine , El-Kenawy Ali , Neumann Ulrich , Herrler Georg
Published: June 2010

Infectious bronchitis virus (IBV) is an avian coronavirus affecting the respiratory tract of chickens. To analyze IBV infection of the lower respiratory tract, we applied a technique that uses precision-cut lung slices (PCLSs). This method allows infection of bronchial cells within their natural tissue composition under
in vitro
conditions. We demonstrate that IBV strains 4/91, Italy02, and QX infect ciliated and mucus-producing cells of the bronchial epithelium, whereas cells of the parabronchial tissue are resistant to infection. This is the first study, using PCLSs of chicken origin, to analyze virus infection. PCLSs should also be a valuable tool for investigation of other respiratory pathogens, such as avian influenza viruses.
Immediate-Early Expression of a Recombinant Antigen by Modified Vaccinia Virus Ankara Breaks the Immunodominance of Strong Vector-Specific B8R Antigen in Acute and Memory CD8 T-Cell Responses
Authors: Baur Karen , Brinkmann Kay , Schweneker Marc , Pätzold Juliane , Meisinger-Henschel Christine , Hermann Judith , Steigerwald Robin , Chaplin Paul , Suter Mark , Hausmann Jürgen
Published: June 2010

Efficient T-cell responses against recombinant antigens expressed by vaccinia virus vectors require expression of these antigens in the early phase of the virus replication cycle. The kinetics of recombinant gene expression in poxviruses are largely determined by the promoter chosen. We used the highly attenuated modified vaccinia virus Ankara (MVA) to determine the role of promoters in the induction of CD8 T-cell responses. We constructed MVA recombinants expressing either enhanced green fluorescent protein (EGFP) or chicken ovalbumin (OVA), each under the control of a hybrid early-late promoter (pHyb) containing five copies of a strong early element or the well-known early-late p7.5 or pS promoter for comparison. In primary or cultured cells, EGFP expression under the control of pHyb was detected within 30 min, as an immediate-early protein, and remained higher over the first 6 h of infection than p7.5- or pS-driven EGFP expression. Repeated immunizations of mice with recombinant MVA expressing OVA under the control of the pHyb promoter led to superior acute and memory CD8 T-cell responses compared to those to p7.5- and pS-driven OVA. Moreover, OVA expressed under the control of pHyb replaced the MVA-derived B8R protein as the immunodominant CD8 T-cell antigen after three or more immunizations. This is the first demonstration of an immediate-early neoantigen expressed by a poxviral vector resulting in superior induction of neoantigen-specific CD8 T-cell responses.
Differential Effects of DNA Double-Strand Break Repair Pathways on Single-Strand and Self-Complementary Adeno-Associated Virus Vector Genomes
Authors: Cataldi Marcela P. , McCarty Douglas M.
Published: June 2010

The linear DNA genomes of recombinant adeno-associated virus (rAAV) gene delivery vectors are acted upon by multiple DNA repair and recombination pathways upon release into the host nucleus, resulting in circularization, concatemer formation, or chromosomal integration. We have compared the fates of single-strand rAAV (ssAAV) and self-complementary AAV (scAAV) genomes in cell lines deficient in each of three signaling factors, ATM, ATR, and DNA-PK
CS
, orchestrating major DNA double-strand break (DSB) repair pathways. In cells deficient in ATM, transduction as scored by green fluorescent protein (GFP) expression is increased relative to that in wild-type (wt) cells by 2.6-fold for ssAAV and 6.6-fold for scAAV vectors, arguing against a mechanism related to second-strand synthesis. The augmented transduction is not reflected in Southern blots of nuclear vector DNA, suggesting that interactions with ATM lead to silencing in normal cells. The additional functional genomes in ATM
−/−
cells remain linear, and the number of circularized genomes is not affected by the mutation, consistent with compartmentalization of genomes into different DNA repair pathways. A similar effect is observed in ATR-deficient cells but is specific for ssAAV vector. Conversely, a large decrease in transduction is observed in cells deficient in DNA-PK
CS
, which is involved in DSB repair by nonhomologous end joining rather than homologous recombination. The mutations also have differential effects on chromosomal integration of ssAAV versus scAAV vector genomes. Integration of ssAAV was specifically reduced in ATM
−/−
cells, while scAAV integration was more profoundly inhibited in DNA-PK
CS
−/−
cells. Taken together, the results suggest that productive rAAV genome circularization is mediated primarily by nonhomologous end joining.
The polarographic and voltammetric determination of 2-amino-5-sulphoamoylnaphthalene-azo-(2’-chloro-4’-nitrobenzene)
Authors: Barek Jiří , Balsiene Jana , Berka Antonín , Hauserová Ivana , Zima Jiří
Published: June 2010

The polarographic reduction of the title azo dye was studied, a mechanism was suggested and optimal conditions were determined for analytical utilization of this process. A detection limit of 3 . 10-7 mol 1-1 was obtained using fast scan differential pulse voltammetry and 0.7 . 10-7 mol 1-1 using linear potential scan voltammetry at a hanging mercury drop electrode. The detection limit can be decreased by adsorptive accumulation of the determined substance on the surface of the hanging mercury drop electrode, to 1 . 10-8 mol 1-1 for fast scan differential pulse voltammetry and 0.6 . 10-8 mol 1-1 for linear scan voltammetry. The selectivity of the determination can be improved by preliminary separation by extraction or thin-layer chromatography.
Syntheses of 5-nitro-2-furyl- and 5-nitro-2-thienylacetonitriles
Authors: Végh Daniel , Kováč Jaroslav , Dandárová Miloslava
Published: June 2010

Syntheses of 5-nitro-2-furyl- and 5-nitro-2-thienylacetonitriles have been accomplished by the reaction of enamines VIII with hydroxylamine-O-sulphonic acid and by nitration of furyl- and thienylacetonitriles V.
A novel cytoskeletal associated protein: Genomic organization and protein pattern
Authors: Zorbas Haralabos , Pöschl Ernst , Pöschl Antonia , Müller Peter K.
Published: June 2010

c-DNA clones were constructed from chicken sternal m-RNA and screened for recognizing those m-RNA species the amount of which decreases during chondrocyte dedifferentiation. One such clone was used to screen a chicken genomic library and, furthermore, to deduce peptide sequences suitable for raising antibodies. Initial results on the genomic structure and on some biochemical and immunochemical properties are presented.
Complexation equilibria between uranium(VI) and 2-(2’-thiazolylazo)-4,6-dimethylphenol and 2-(4’,5’-dimethyl-2’-thiazolylazo)-4,6-dimethylphenol. Extraction-spectrophotometric determination of uranium
Authors: Santana Brígida , Sánchez María J. , Arias Juan J. , García-Montelongo Francisco
Published: June 2010

2-(2’-Thiazolylazo)-4,6-dimethylphenol (TADMP) and 2-(4’,5’-dimethyl-2’-thiazolylazo)-4,6-dimethylphenol (DMTADMP) have been synthesized and their ionization constants determined by spectrophotometric methods and graphical and numerical calculation methods. Both reagents form UO2R+ and UO2R2 complexes with uranium (TADMP: log β101 = 9.18 ± 0.02, log β102 = 17.64 ± 0.01; DMTADMP: log β101 = 8.38 ± 0.02, log β102 = 18.78 ± 0.14) in a 40% (v/v) ethanol-water medium at I = 0.25 (NaClO4). An extraction-spectrophotometric method for the determination of 1.35-9.45 ppm uranium based on its extraction into toluene with TADMP from a pH 6.5 buffered medium has been developed ( ε = 1.6 . 104 l mol-1 cm-1 at 580 nm), and applied to its determination in sulphuric acid leaching residues.
Synthesis of some 3-substituted 4(3H)-quinazolinone and 4(3H)-quinazolinethione derivatives and related fused biheterocyclic ring systems
Authors: Abdel-Megeed Mohamed Farghali , Teniou Abderrahman
Published: June 2010

The reactions of 2-phenyl-4(3H)-quinazoline, 2-phenyl-3-amino-4(3H)-quinazolinone, and corresponding thiones with phenyl isocyanate or phenyl isothiocyanate were investigated. The resulting urea and thiourea quinazolinone or quinazolinethione derivatives reacted with hydrazine hydrate, phenylhydrazine, and urea or thiourea to form fused biheterocyclic ring systems with potential biological activities. The products were identified by IR, 1H NMR, and mass spectroscopy.
Kinetics of oxidation of the bis(ethylenediamine)mercaptoacetatocobalt(III) and cysteinato-bis(ethylenediamine)cobalt(III) ions by hydrogen peroxide in mixed aqueous-nonaqueous solutions
Authors: Benko Ján , Vollárová Oľga , Kovarčík Miroslav
Published: June 2010

The kinetics of oxidation of the coordinatively bonded sulphur in the cysteinato-bis(ethylenediamine)cobalt(III) and bis(ethylenediamine)mercaptoacetatocobalt(III) complexes by hydrogen peroxide to the sulphoxides was examined in HClO4 solutions (c(HClO4) = 1 – 500 mmol l-1) with a view to obtaining data characterizing the effect of the acid-base equilibria of the reactants on the reaction rate. The reaction rate was found affected particularly by the acid-base equilibrium of the oxidant, which plays a role in strongly acid solutions. The oxidation was also studied in water-methyl alcohol, water-tert-butyl alcohol and water-ethylene glycol mixtures, and the effect of the mole fraction of the nonaqueous component on the rate constant and thermodynamic activation parameters was examined.