bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Investigation of Micro-Channeled Louver Fin Aluminum Heat Exchangers at Low Reynolds Number
Authors: Shinde Pradeep , Schäfer Mirko , Lin Cheng-Xian
Published: November 2016

Extensive studies are being carried out by several researchers on the performance prediction of aluminum heat exchangers with different fin and tube geometrical configurations mostly for Reynolds number higher than 100. In the present study, the air-side heat transfer and pressure drop characteristics of the louvered fin micro-channeled, Aluminum heat exchangers are systematically analyzed by a 3D numerical simulation for very low Reynolds number from 25 to 200. Three different heat exchanger geometries obtained for the experimental investigation purposes with constant fin pitch (14 fins per inch) but varied fin geometrical parameters (fin height, fin thickness, louver pitch, louver angle, louver length and flow depth) are numerically investigated. The performance of the heat exchangers is predicted by calculating Colburn j factor and Fanning friction f factor. The effect of fin geometrical parameters on the heat exchanger performance at the Reynolds number range specified is evaluated. The air-side performance of the studied heat exchangers for the specified Reynolds number range is compared with experimental heat exchanger performance data available in the open literature and a good agreement is observed. The present results show that at the studied range of Reynolds number the flow through the heat exchanger is fin directed rather than the louver directed and therefore the heat exchanger shows poor performance. The effect of geometrical parameters on the average heat transfer coefficient is computed and design curves are obtained which can be used to predict the heat transfer performance for a given geometry.
Heat Transfer in Non-Newtonian Laminar Impinging Jets
Authors: Chatterjee Ajay , Fabris Drazen
Published: November 2016

Numerical results are presented for laminar impinging flow and heat transfer with a non-Newtonian inelastic fluid in a planar two dimensional geometry. Bifurcation diagrams are computed to characterize flow separation and reattachment in steady flow. For a range of rheological parameters calculations show that the dimensionless wall jet heat transfer rate Q may be correlated as RP1.3 where RP is the reattachment coordinate of the primary vortex scaled with the jet half-width, thus quantifying the extent of enhancement with shear thinning. For Re = 200 the unsteady time periodic flow is computed for both fluids and employed in the heat transfer calculations. The Newtonian flow Nusselt numbers at the stagnation point and in the wall jet region, although periodic, show an oscillation in magnitude less than 10% of the mean and time averages similar to steady flow. For the shear thinning fluid the wall jet Nusselt number displays an oscillation amplitude of about half the mean value, and the Nusselt number profile shows considerably improved uniformity over a length scale extending several nozzle widths into the wall jet region. However, unlike steady flow, heat transfer rates are not significantly increased in the oscillatory flow regime.
Liquid Layering and the Enhanced Thermal Conductivity of Ar-Cu Nanofluids: A Molecular Dynamics Study
Authors: Paul Jithu , Madhu A. K. , Jayadeep U. B. , Sobhan C. B.
Published: November 2016

Nanofluids — colloidal suspensions of nanoparticles in base fluids — are known to possess superior thermal properties compared to the base fluids. Various theoretical models have been suggested to explain the often anomalous enhancement of these properties. Liquid layering around the nanoparticle is one of such reasons. The effect of the particle size on the extent of liquid layering around the nanoparticle has been investigated in the present study. Classical molecular dynamics simulations have been performed in the investigation, considering the case of a copper nanoparticle suspended in liquid argon. The results show a strong dependence of thickness of the liquid layer on the particle size, below a particle diameter of 4nm. To establish the role of liquid layering in the enhancement of thermal conductivity, simulations have been performed at constant volume fraction for different particle sizes using Green Kubo formalism. The thermal conductivity results show 100% enhancement at 3.34% volume fraction for particle size of 2nm. The results establish the dominant role played by liquid layering in the enhanced thermal conductivity of nanofluids at the low particle sizes used. Contrary to the previous findings, the molecular dynamics simulations also predict a strong dependence of the liquid layer thickness on the particle size in the case of small particles.
A Novel Double-Pipe Heat Storage Unit
Authors: Rozenfeld A. , Kozak Y. , Rozenfeld T. , Ziskind G.
Published: November 2016

This research is an experimental investigation of a double-pipe heat storage unit. The inner pipe of the unit, through which a heat-transfer fluid (HTF) is supplied, is made of aluminum and has an outer helix-like fin. The annular space between the pipes is filled with a phase change material (PCM). Actually, this research presents a novel design of the heat storage unit, which, unlike traditional designs with e.g. radial (circumferential) or longitudinal fins, has a single fin which does not divide the shell volume into separated cells. Moreover, this research focuses on close-contact melting (CCM), a process which is characterized by detachment of the solid bulk from the unit envelope and its sinking towards the hot fin surface. In previous investigations, performed in our laboratory, this effect has been achieved in units with above-mentioned traditional fin configurations. It was demonstrated that CCM reduces the overall melting time, i.e. the rate of unit charging, significantly as compared with commonly encountered melting in which the fins serve just to enlarge the heat transfer area. The experimental system employed in this study includes a vertically-oriented double-pipe heat storage unit and thermostatic baths capable of providing hot or cold HTF. The unit has a transparent Perspex shell which makes visualization possible. The entire unit may be placed in a heated water tank with transparent walls. In the latter case, close-contact melting is achieved by detaching the solid phase from the envelope and thus allowing its gravity-induced motion. Regular melting is compared to CCM and advantages of the latter are demonstrated. Also demonstrated are the advantages of the novel fin, including in solidification. Possible mathematical and numerical modeling of the melting processes is discussed.
Toward Modular Prediction of Free-Surface Jet Array Cooling: The Hydraulic Jump Location and Non-Monotonous Heat Transfer
Authors: Haustein Herman D.
Published: November 2016

The present study develops the ground work for modular prediction of free-surface jet arrays. Jet arrays generate one of the highest single-phase heat transfer rates, while covering reasonably large areas with good thermal uniformity, relevant to electronics cooling. However, due to liquid evacuation problems, free-jet arrays suffer from flooding, cross-flow and jet interaction, together with the large amount of influencing geometrical parameters, this makes them very difficult to predict.

For the modular prediction approach to be applied, key issues are here addressed: experiments were conducted employing de-ionized water in both single and basic multiple-jet array (2×2, with local liquid extraction in the jet interaction zones) configurations. Modular conditions, wherein all jets are similar to each other, were created experimentally in a consistent fashion, by use of liquid extraction in the jet-interaction zones. Based on present and previous experimental data the influencing parameters on the pre-jump depth were identified. This description was then used to predict the location of the hydraulic jump (as dependant on the measured post-jump depth). The model combines elements of two previous approaches the shallow-water vs. jump conservation model, and obtains good agreement with available data. In addition conditions were shown for maximizing the distance at which the hydraulic jump occurs — to the point that the supercritical flows of adjacent jets touch (standing fountain type jump). This not only permits prediction of the supercritical flow heat transfer distribution over almost the entire array area, but also reduces the low heat transfer post-jump regions to a minimum. Finally, a more universal single-jet heat transfer model was developed incorporating inherent self-similarities recently identified by the authors and considering all relevant parameters: jet velocity profiles, nozzle-plate spacing, and inclination relative to gravity, to predict stagnation heat transfer as well as its radial decay. It is further identified that the influence of inclination is also of vital importance to free-surface jets (breakage of symmetry) and must be examined in future studies.

By addressing these three key issues the foundation for a modular prediction of heat transfer under a free jet array is laid.
Laser Induced Implantation Doping of Glass Substrates
Authors: Sadeh Sepehr , Mitra Kunal
Published: November 2016

Lasers are widely used as high-accuracy tools for material processing. Different types of lasers such as CO2, Nd:YAG, and excimer lasers are used in different operating modes such as continuous wave, pulsed or Q-switched. Volumes of materials and their composition, structure, and properties can be controlled or modified by varying laser pulses.

In this research, by using laser as a material processing tool, an experimental method was developed for laser induced implantation doping of glass substrates with conductive metals. Experiments were performed on glass samples using Q-switched Nd:YAG lasers. Gold, silver, and copper were used as conductive dopant materials. Initial experiments were performed using nickel as a catalyst. Effect of the catalyst on the composition of implanted dopant material was observed using Large Area Rapid Imaging Analytical Tool (LARIAT). Through further experiment, the effect of several parameters such as beam fluence, scanning speed, pulse repetition frequency, wavelength, substrate temperature, dopant material, and glass substrate material on the morphology of heat affected zones were investigated by optical microscopy (OM). Depth of penetration in doped glass samples was measured for different substrate temperatures by means of a laser displacement sensor. The effect of beam fluence and glass substrate thickness on depth of penetration was investigated. The results of these non-destructive measurements were verified using scanning electron microscopy (SEM). Based on optical observations, morphological characteristics of the heat affected zone were assessed in order to obtain the best parameter settings in different experiments. These settings were defined by factors such as the number and size of cracks in glass substrates, and the quality of the distribution of dopant metal over the scanned pattern. While using a catalyst with substrates at room temperature, the best parameter settings were obtained at wavelength of 532 nm, pulse repetition frequency of 6 kHz, beam fluence of 0.36 J/cm2, and scanning speed of 0.10 m/s. By removing the catalyst, these settings were changed to 355 nm, 10 kHz, 0.09 J/cm2, and 0.01 m/s for gold sputtered soda-lime glass substrate at 500 °C. For beam fluence values ranging from 0.06 J/cm2 to 0.38 J/cm2, the obtained values for average depth of penetration were 255 μm and 187 μm in 1 mm and 3 mm thick soda-lime glass substrates respectively.

Further development of this implantation method could lead to implantation of electronic circuits in transparent substrates, inspiring the evolution of transparent electronic devices such as transparent smart phones, smart windows and displays, and lighting products in the future.
Numerical Investigation of the Freezing of a Phase Change Material in a Thermal Storage Device With an Embedded Evaporator
Authors: Khalifa H. Ezzat , Koz Mustafa
Published: November 2016

Two time-dependent mathematical and numerical models with different levels of complexity and fidelity were developed to investigate the freezing of a PCM configured as a slab with an embedded serpentine microchannel evaporator of a vapor compression refrigeration system. The time-dependent PCM freezing process was first analyzed using finite-element modeling (FEM) of a representative 2-D domain. This model incorporates 2-D conduction and natural convection within the molten PCM. The FEM revealed that natural convection is negligible and that the freezing front advances in essentially 1-D fashion. However, the long execution time of FEM makes it unsuitable for repetitive design optimization of thermal storage devices. Consequently, a fast-executing quasi 2-D reduced-order model (ROM) was developed. The ROM is then utilized to study the freezing process in a multi-slab thermal storage device that is designed to store ∼500 W-h of “cooling” during ∼8 h of freezing operation at night, to be subsequently released for local cooling of room air during the day. The results show that (1) freezing rate is strongly affected by the frozen PCM thermal conductivity; (2) freezing almost ceases once the refrigerant is fully evaporated; (3) refrigerant exit quality drops precipitously toward the end of the freezing cycle.
Thermal Interfacial Resistance Reduction Between Metal and Dielectric Materials by Inserting Intermediate Metal Layer
Authors: Li Xiangyu , Park Wonjun , Chen Yong P. , Ruan Xiulin
Published: November 2016

In this work, we have observed 60% reduction in total interfacial resistance by adding an intermediate metal layer nickel between gold and aluminum oxide. Two temperature model is applied to explain the change of interfacial resistance, including both lattice mismatch with diffuse mismatch model and electron-phonon coupling effect. Simulation result agrees reasonably well with experimental data. Even though interfacial resistance due to electron-phonon coupling effect for Au-aluminum oxide is much larger than that of Ni-aluminum oxide interface, lattice mismatch is still the dominant factor for interfacial resistance.
Numerical Investigation of Heat Transfer Characteristics of a Novel Wavy-Tapered Microchannel Heat Sink
Authors: Eltaweel Ahmed , Baobeid Abdulla , Tompkins Brian , Hassan Ibrahim
Published: November 2016

In the present study, a multi-variable comparative study of the effect of microchannel heat sink configurations on their thermal performance is conducted by numerically simulating three-dimensional fluid flow and heat transfer in multiple microchannel heat sink configurations. Thermal analysis is performed to investigate a novel wavy-tapered channel configuration of microchannel heat sinks with directionally alternating coolant flow for high-end electronics cooling. Simulations were conducted at different tapering and aspect ratios, focusing on how effectively previously proven geometric enhancements combine with one another in novel ways. Results confirmed the superiority of wavy channels over straight channels due to the development of the secondary flow (Dean Vortices), which enhance the advection mixing and consequently the overall heat sink thermal performance. Moreover, width-tapering of the wavy channel showed improved channel performance in terms of thermal resistance compared to untapered wavy channels. Almost 10% improvement in thermal resistance is obtained with width tapering. Also, the thermal performance showed a strong dependency on channel aspect ratio. Overall performance suggests that optimum tapering and aspect ratio conditions exist. The numerical investigations are then extended to novel heat sink design includes wavy tapered microchannels with directionally alternating flow to improve heat sink thermal performance. A 15% reduction in thermal resistance and highly improved substrate surface temperature distribution uniformity are obtained using alternating flow compared to corresponding parallel flow channels.
The Mass Burning Rate of n-Heptane Pool Fire Under Dynamic Pressure
Authors: Ma Qiuju , Liu Quanyi , Tian Runhe , Ye Junjian , Yang Rui , Zhang Hui
Published: November 2016

Fire safety is critical for safety of airplane operation. During an emergency landing, airplane goes through dramatic external pressure change from cruise altitude to sea level, considering the impact caused by low pressure atmosphere. The objective of this work is to examine the effect of dynamic pressure on the behavior of a horizontally burning diffusion flame over a pool fuel surface based on experimental approach. The experiments were conducted in a large-scale altitude chamber of size 2 m × 3 m × 4.65 m. The pressure rise process was examined under different dynamic pressures from respectively 38 kPa, 64 kPa and 75 kPa to 90 kPa with various pressure rise rates of 100 Pa/s, 150 Pa/s, 200 Pa/s, 250 Pa/s and 300 Pa/s, which is to simulate the airplane landing process from different altitudes. The whole system of the altitude chamber is of unique capability that the pressure in the chamber can be exactly controlled by a powerful pressure controlling system, and the oxygen concentration can maintain at the level about 20%, which are achieved through controlling inlet air flow for oxygen level and outlet gas flow for pressure (static or dynamic) level. A round steel fuel pans of 34 cm in diameter and 15 cm in height were chosen for the pool fire tests. The fuel pan was filled with 99% pure liquid n-Heptane. Cold water is added beneath the fuel layer to cool the pan and minimize the temperature rise in the fuel. Parameters such as mass, mass burning rate, chamber pressure were measured. The results of those tests demonstrated the significant impact to fire behaviors caused by high altitude or low pressure atmosphere.
Numerical and Experimental Study of Lead-Acid Battery
Authors: Munoz-Carpio Vicente D. , Mason Jerry , Celik Ismail , Elizalde-Blancas Francisco , Alatorre-Ordaz Alejandro
Published: November 2016

Lead-Acid battery was the earliest secondary battery to be developed. It is the battery that is most widely used in applications ranging from automotive to industrial storage. Nowadays it is often used to store energy from renewable energy sources. There is a growing interest to continue using Lead-Acid batteries in the energy systems due to the recyclability and the manufacturing infrastructure which is already in place. Due to this rising interest, there is also a need to improve the efficiency and extend the life cycle of Lead-Acid batteries. To achieve these objectives, it is necessary to gain a better understanding of the physics taking place within individual batteries. A physics based computational model can be used to simulate the mechanisms of the battery accurately and describe all the processes that are happening inside; including the interactions between the battery elements, based upon the physical processes that the model takes into account.

In the present paper, we present a discharge/charge experimental study that has been carried out with small Lead-Acid batteries (with a capacity of 7 Ah). The experiments were performed with a constant current rate of 0.1C [A]1 for two different battery arrangements.

An in-house zero dimensional model was developed to perform simulations of Lead-Acid batteries under different operating conditions. A validation analysis of the model was executed to confirm the accuracy of the results obtained by the model compared to the aforementioned experiments. Additional simulations of the battery were carried out under different current rates and geometry modifications in order to study how the performance of the battery may change under these conditions.
Spectral Tuning of Radiative Heat Transfer Using Nanoparticles
Authors: Ghanekar Alok , Zheng Yi , Lin Laura , Zhang Zongqin , Sun Mingdi
Published: November 2016

Microscopic thin films are known to have narrow band selective thermal radiation whch have potential applications in selective emitter and absorbers. We propose a methodology to shift the wavelength selectivity in the desired location. Calculation of emissivity and near field radiation for different materials and structures is presented. Emissivity calculations are performed using the standard expressions for Fresnel reflection coefficients. For the near field thermal radiation, we use the analytical expression for transitivity between two half spaces obtained using the dyadic Greens function formalism. We use Maxwell-Garnett-Mie theory to calculate effective dielectric function of media doped with nanoparticles. We observe that spectrum of thermal radiation in far-field and in near-field can be altered using nanoparticles. Moreover spectral properties of mixtures can be characterized using refractive indices. Influence of nanoparticle size and concentration is also studied.
Selective Emission Properties and vdW Energy of Micro/Nano-Sized Spherical Shapes
Authors: Ghanekar Alok , Zheng Yi , Zhang Weixing , Zhang Zongqin
Published: November 2016

Near-field thermal radiation and van der Waal force between flat plates and curved surfaces have been probed in the past; however the peculiarities of radiative heat transfer and van der Waals stress due to fluctuations of electromagnetic fields for micro/nano-sized spherical objects have not been studied in great details. We demonstrate how fluctuational electrodynamics can be used to determine emissivity and van der Waals contribution to surface energy for various spherical shapes in a homogeneous and isotropic medium. The dyadic Green’s function formalism of radiative energy and fluctuation-induced van der Waals stress for different spherical configurations has been developed. We present the calculations for a single sphere, a bubble, a spherical shell and a coated sphere. We observe that emission spectrum ofmicro/nanoscale spheres displays several sharp peaks as the size of object reduces. Our calculations indicate that surface energy becomes size dependent (r-3) due to van der Waals phenomena for small radii.
The structure of Hindi stop consonants
Authors: Singh Kushagra , Tiwari Nachiketa
Published: November 2016

The pronunciation of stop consonants varies markedly with age, gender, accent, etc. Yet by extracting appropriate cues common to these varying pronunciations, it is possible to correctly identify the spoken consonant. In this paper, the structure underlying Hindi stop consonants is presented. This understanding may potentially be used as a “recipe” for their artificial synthesis. Hindi alphabet stops were analyzed for this purpose. This alphabet has an organized and comprehensive inventory of stop consonants, and its consonants invariably terminate with the neutral vowel schwa. While the former consideration makes the findings potentially applicable to many languages including English, the latter rationale helped reduce the endeavor's analytical complexity. The alphabet has velar, palatal, retroflex, dental and bilabial stops in voiceless-unaspirated, voiceless-aspirated, voiced-unaspirated, voiced-aspirated, and nasal flavors. It is shown that additive combinations of relatively simple acoustic functions can be used to generate most of the 20 non-nasal stops. This work will potentially help speech therapists improve diagnosis and rectification of speech and hearing disabilities, speed up electronic communication of audio data, and improve voice recognition.
Cetacean acoustic detections from free-floating vertical hydrophone arrays in the southern California Current
Authors: Griffiths Emily T. , Barlow Jay
Published: November 2016

Drifting acoustic recorders were deployed in the southern California Current during Fall 2014. Two hydrophones configured as a 2-m vertical array at 100 m depth recorded using a 192 kHz sample rate on a 10% duty cycle (2 min/20 min). Beaked whales were detected in 33 of 8618 two-minute recordings. Sperm whales were detected in 185 recordings, and dolphins in 2291 recordings. Many beaked whales detected were over an abyssal plain and not associated with slope or seamount features. Results show the feasibility of using free-floating recording systems to detect a variety of cetacean species over periods of several months.
Test-Retest Reliability and Reproducibility of Laser- versus Contact-Displacement Sensors in Mechanomyography: Implications for Musculoskeletal Research
Authors: Seidl Laura , Tosovic Danijel , Brown J. Mark
Published: November 2016

Whole muscle mechanomyography (MMG) has gained considerable interest in recent years for its ability to noninvasively determine muscle contractile properties (ie, contraction time [Tc], half-relaxation time [1/2Tr], and maximal displacement [Dmax)]). The aim of this study was to evaluate the test-retest reliability of two fairly novel MMG transducers: a laser-displacement sensor (LDS) and contact-displacement sensor (CDS). MMG was conducted on the rectus femoris muscle of 30 healthy individuals on 4 separate occasions. Test-retest reliability was quantified using intraclass correlation coefficients (ICCs). Both sensors were reliable for time-derived parameters Tc (ICCs, 0.85–0.88) and 1/2Tr (0.77–0.89), with Dmax identified as the most reproducible parameter (0.89–0.94). The 2 sensors produced similar Tc and Dmax measures, although significant (P < .05) systematic bias was identified with the CDS recording higher mean values, on average. However, these differences may not be considered clinically significant. The wide limits of agreement identified between 1/2Tr measures (–19.0 ms and 25.2 ms) are considered unreliable from a clinical perspective. Overall, MMG demonstrated good-to-excellent reliability for the assessment of muscle contractile properties with no significant differences identified between sessions, thus further validating its applicability as a noninvasive measure of muscle contractile properties.
Epistemic Communities and Knowledge-Based Professional Networks in Sport Policy and Governance: A Case Study of the Canadian Sport for Life Leadership Team
Authors: Dowling Mathew , Washington Marvin
Published: November 2016

This investigation examined how a network of knowledge-based professionals—the Canadian Sport for Life Leadership Team (CS4LLT)—as a newly emerging organizational form was able to influence the Canadian sport policy and governance process in an attempt to reshape Canadian sport. The analysis draws upon the epistemic community approach (Haas, 1992; Haas & Adler, 1992) and empirical data collected as part of an in-depth case study examination into the leadership team and senior Sport Canada officials. The findings support the notion that the CS4LLT, as a network of knowledge-based professionals with legitimated and authoritative and policy-relevant expertise (epistemic community), was able to influence the Canadian sport policy process through (i) influencing key governmental actors by (re)framing policy-relevant issues and (ii) establishing knowledge/truth claims surrounding athlete development, which, in turn, enabled direct and indirect involvement in and influence over the sport policy renewal process. More broadly, the study draws attention to the potential role and importance of knowledge-based professional networks as a fluid, dynamic, and responsive approach to organizing and managing sport that can reframe policy debates, insert ideas, and enable policy learning.
The Effectiveness of Hyperbaric Oxygen Therapy as a Treatment for Postconcussion Symptoms
Authors: Hawkins Jeremy R. , Gonzalez Kayla E. , Heumann Kristin J.
Published: November 2016

Clinical Scenario:

Concussions are a prevalent topic in medicine. Concussion symptoms include headaches, dizziness, nausea, neuropsychiatric symptoms, and cognitive impairments, the persistence of which is referred to as postconcussion syndrome. Hyperbaric oxygen therapy (HBOT) has been proposed and evaluated as an additional treatment of these symptoms. HBOT is an innovative approach that has been considered by many but has received both criticism and acceptance.

Clinical Question:

Is HBOT an effective means of reducing symptoms for individuals suffering from postconcussion syndrome (persistence of symptoms for >3 mo)?

Summary of Search:

The literature was searched for studies that were relevant to the clinical question. Literature provided 5 level 1 studies that were relevant enough to be considered.

Clinical Bottom Line:

Based on the research that is available, the authors conclude that there is more evidence to refute the use of HBOT for postconcussion syndrome than to support it.

Strength of Recommendation:

Four studies disprove the use of HBOT; 1 study supported the use of HBOT. These 5 studies are the same level of evidence (level 1) and provide significant findings in their studies. The strength of this recommendation is a B according to the Centre for Evidence-Based Medicine.
Clinical Effects of Dry Needling Among Asymptomatic Individuals With Hamstring Tightness: A Randomized Controlled Trial
Authors: Geist Kathleen , Bradley Claire , Hofman Alan , Koester Rob , Roche Fenella , Shields Annalise , Frierson Elizabeth , Rossi Ainsley , Johanson Marie
Published: November 2016

Study Design:

Randomized controlled trial.

Objectives:

The aim of this study was to determine the effects of dry needling on hamstring extensibility and functional performance tests among asymptomatic individuals with hamstring muscle tightness.

Background:

Dry needling has been shown to increase range of motion in the upper quarter and may have similar effects in the lower quarter.

Methods:

27 subjects with hamstring extensibility deficits were randomly assigned to side of treatment (dominant or nondominant) and group (blunt needling or dry needling). The first session included measurement of hamstring extensibility and performance on 4 unilateral hop tests, instruction in home hamstring stretching exercises and needling distal to the ischial tuberosity and midbellies of the medial and lateral hamstrings. A second session, 3–5 days following the first session, included outcome measures and a second needling intervention, and a third session, 4–6 weeks following the first session, included outcome measures only. A 2 × 3 × 2 ANOVA was used to statistically analyze the data.

Results:

Hamstring extensibility showed a significant side × time interaction (P < .05). The single hop for distance, timed 6-meter hop, and the crossover hop test had a significant main effect of time (P < .05). The triple hop for distance showed a significant side × time × group interaction (P < .05).

Conclusions:

It does not appear dry needling results in increased extensibility beyond that of stretching alone in asymptomatic individuals. Our study findings suggest that dry needling may improve certain dimensions of functional performance, although no clear conclusion can be made. Level of Evidence: Intervention, level 2b.
For chronic fatigue syndrome, a ‘shifting tide’ at NIH
Authors: Wadman Meredith
Published: November 2016

New funding shows increased commitment to mystery illness, but not everyone trusts the agency's sincerity.
Complete Genome Sequence of a Genomovirus Associated with Common Bean Plant Leaves in Brazil
Authors: Lamas Natalia Silva , Fontenele Rafaela Salgado , Melo Fernando Lucas , Costa Antonio Felix , Varsani Arvind , Ribeiro Simone Graça
Published: November 2016

A new genomovirus has been identified in three common bean plants in Brazil. This virus has a circular genome of 2,220 nucleotides and 3 major open reading frames. It shares 80.7% genome-wide pairwise identity with a genomovirus recovered from Tongan fruit bat guano.
Draft Genome Sequence of Corynebacterium amycolatum Strain ICIS 53 Isolated from a Female Urogenital Tract
Authors: Gladysheva Irina V. , Cherkasov Sergey V. , Khlopko Yuriy A. , Plotnikov Andrey O. , Gogoleva Natalya E.
Published: November 2016

This report describes the draft genome sequence of
Corynebacterium amycolatum
strain ICIS 53, isolated from the reproductive tract of a healthy woman. The size of the genome was 2,460,257 bp (58.98% G+C content). Annotation revealed 2,173 coding sequences, including 2,076 proteins, 7 rRNA genes, and 53 tRNA genes.
Molecular structure and immunity specificity of colicin E6, an evolutionary intermediate between E-group colicins and cloacin DF13
Authors: Akutsu A , Masaki H , Ohta T
Published: November 2016

The primary structure of a 3.1-kilobase E6 or E3 segment carrying colicin and related genes was determined. Plasmid ColE6-CT14 showed striking homology to ColE3-CA38 throughout this segment, including homology to the secondary immunity gene, immE8, downstream of the E6 or E3 immunity gene. The ColE3-CA38 and ColE6-CT14 sequences, however, contained an exceptional hot spot region encoding both the colicin-active domain (RNase region) and the immunity protein, reflecting their different immunity specificities. On the other hand, some chimeric plasmids were constructed through homologous recombination between colicin E3 and cloacin DF13 operons. The resulting plasmids were deduced to produce chimeric colicins with a colicin E3-type N-terminal part, a cloacin DF13-type C-terminal-active domain, and the DF13 immunity protein. The killing spectra of the chimeric colicins and the immunities of the plasmids were identical to those of colicin E6 and ColE6-CT14, respectively, showing that the colicin E6 immunity specificity is completely equivalent to that of cloacin DF13. Nevertheless, colicin E6 has been found to show a sequence diversity from cloacin DF13 almost to the same extent as that from colicin E3 in their RNase and immunity regions, indicating that only a small number of amino acids defines the immunity specificity for discrimination between colicins E3 and E6 (or cloacin DF13).
A phylogenetic analysis of the mycoplasmas: basis for their classification
Authors: Weisburg W G , Tully J G , Rose D L , Petzel J P , Oyaizu H , Yang D , Mandelco L , Sechrest J , Lawrence T G , Van Etten J
Published: November 2016

Small-subunit rRNA sequences were determined for almost 50 species of mycoplasmas and their walled relatives, providing the basis for a phylogenetic systematic analysis of these organisms. Five groups of mycoplasmas per se were recognized (provisional names are given): the hominis group (which included species such as Mycoplasma hominis, Mycoplasma lipophilum, Mycoplasma pulmonis, and Mycoplasma neurolyticum), the pneumoniae group (which included species such as Mycoplasma pneumoniae and Mycoplasma muris), the spiroplasma group (which included species such as Mycoplasma mycoides, Spiroplasma citri, and Spiroplasma apis), the anaeroplasma group (which encompassed the anaeroplasmas and acholeplasmas), and a group known to contain only the isolated species Asteroleplasma anaerobium. In addition to these five mycoplasma groups, a sixth group of variously named gram-positive, walled organisms (which included lactobacilli, clostridia, and other organisms) was also included in the overall phylogenetic unit. In each of these six primary groups, subgroups were readily recognized and defined. Although the phylogenetic units identified by rRNA comparisons are difficult to recognize on the basis of mutually exclusive phenotypic characters alone, phenotypic justification can be given a posteriori for a number of them.
Effect of variation of charged and uncharged tRNA(Trp) levels on ppGpp synthesis in Escherichia coli
Authors: Rojiani M V , Jakubowski H , Goldman E
Published: November 2016

We introduced into a stringent Escherichia coli tryptophan auxotroph a plasmid bearing the tRNA(Trp) gene under the control of an inducible promoter. This allows us to manipulate the total concentration of tRNA(Trp) in the cell according to whether and when inducer is added to the culture. We also manipulated the concentration of Trp-tRNA(Trp) in vivo since the strain used bears a mutation in the Trp-tRNA synthetase affecting the Km for tryptophan, such that varying the exogenous concentration of tryptophan led to variation in the level of Trp-tRNA(Trp) in the cell. With this system, we found that the signal eliciting ppGpp synthesis during a stringent response triggered by tryptophan limitation did not depend on the absolute concentration of either charged or uncharged tRNA(Trp) but rather depended on a decline in the ratio of charged/uncharged tRNA(Trp). In addition, we found that the amplitude of the response, once triggered by tryptophan limitation, was determined by the total concentration of tRNA(Trp) present in the cell (which is mostly uncharged at that point in time). However, excess uncharged tRNA(Trp) did not amplify ppGpp synthesis triggered by limitation of a different amino acid. These data provide in vivo support for the in vitro-derived model of ppGpp synthesis on ribosomes.
Genetic selection and DNA sequences of 4.5S RNA homologs
Authors: Brown S , Thon G , Tolentino E
Published: November 2016

A general strategy for cloning the functional homologs of an Escherichia coli gene was used to clone homologs of 4.5S RNA from other bacteria. The genes encoding these homologs were selected by their ability to complement a deletion of the gene for 4.5S RNA. DNA sequences of the regions encoding the homologs were determined. Since this approach does not require that the homologous genes hybridize with probes generated from the E. coli sequence, the sequences of the homologs were not all similar to the sequence of the E. coli gene. Despite the dissimilarity of the primary sequences of some of the homologs, all could be folded to obtain a similar structure.
Gyrase inhibitors can increase gyrA expression and DNA supercoiling
Authors: Franco R J , Drlica K
Published: November 2016

Treatment of bacterial cells with inhibitors of gyrase at high concentration leads to relaxation of DNA supercoils, presumably through interference with the supercoiling activity of gyrase. Under certain conditions, however, the inhibitors can also increase supercoiling. In the case of coumermycin A1, this increase occurs at low drug concentrations. Oxolinic acid increases supercoiling in a partially resistant mutant. We found that increases in chromosomal DNA supercoiling, which were blocked by treatment with chloramphenicol, were accompanied by an increased expression rate of gyrA. This result is consistent with gyrase being responsible for the increase in supercoiling. In wild-type cells, increases in gyrA expression were transient, suggesting that when supercoiling reaches sufficiently high levels, gyrase expression declines. Oxolinic acid studies carried out with a delta topA strain showed that drug treatment also increased plasmid supercoiling. The levels of supercoiling and topoisomer heterogeneity were much higher when the plasmid contained one of several promoters fused to galK. Since oxolinic acid causes an increase in gyrA expression, it appears that gyrase levels may be important in transcription-mediated changes in supercoiling even when topoisomerase I is absent.
Purification of a new dihydrolipoamide dehydrogenase from Escherichia coli
Authors: Richarme G
Published: November 2016

I purified a new dihydrolipoamide dehydrogenase from a lpd mutant of Escherichia coli deficient in the lipoamide dehydrogenase (EC 1.6.4.3) common to the pyruvate dehydrogenase (EC 1.2.4.1) and 2-oxoglutarate dehydrogenase complexes. The occurrence of the new lipoamide dehydrogenase in lpd mutants, including a lpd deletion mutant and the immunological properties of the enzyme, showed that it is different from the lpd gene product. The new dihydrolipoamide dehydrogenase had a molecular weight of 46,000, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It was expressed in low amounts. It catalyzed the NAD+-dependent reduction of dihydrolipoamide with a maximal activity of 20 mumol/min per mg of protein and exhibited a hyperbolic dependence of catalytic activity on the concentration of both dihydrolipoamide and NAD+. The possible implication of the new dihydrolipoamide in the function of 2-oxo acid dehydrogenase complexes is discussed, as is its relation to binding protein-dependent transport.
Phosphate regulon in members of the family Enterobacteriaceae: comparison of the phoB-phoR operons of Escherichia coli, Shigella dysenteriae, and Klebsiella pneumoniae
Authors: Lee T Y , Makino K , Shinagawa H , Amemura M , Nakata A
Published: November 2016

The structure and function of the phoB and phoR genes of Shigella dysenteriae strains and Klebsiella pneumoniae, which are involved in regulation of the phosphate regulon, were analyzed. Complementation tests among the genes of Escherichia coli, S. dysenteriae strains, and K. pneumoniae for production of alkaline phosphatase indicate that S. dysenteriae serotype 2 and serotype 3 strains and K. pneumoniae are phoA+ phoB+ phoR+ but S. dysenteriae Sh and serotype 1 strains are phoA phoB+ phoR. Nucleotide sequences of phoB and phoR of S. dysenteriae Sh and K. pneumoniae are highly homologous to those of E. coli, except for a single base insertion found in phoR of S. dysenteriae Sh.
Characterization of a dynamic S layer on Bacillus thuringiensis
Authors: Luckevich M D , Beveridge T J
Published: November 2016

The surfaces of three Bacillus thuringiensis strains possess an S layer composed of linear arrays of small particles arranged with p2 symmetry and with a = 8.5 nm, b = 7.2 nm, and gamma = 73 degrees. Platinum shadows of whole cells and S-layer fragments revealed the outer surface of the array to be smooth and the inner surface to be corrugated. Treatment with 2 M guanidine hydrochloride at pH 2.5 to 4 best removed the S layer for chemical characterization; it was a relatively hydrophilic 91.4-kilodalton protein with a pI of 5, no detectable carbohydrate, cysteine, methionine or tryptophan, and 21.2% nonpolar residues. No N-terminal homology with other S-layer proteins was evident. Antibody labeling experiments confirmed that the amount of S layer was proportional to the growth phase in broth cultures. Late-exponential- and stationary-growth-phase cells typically sloughed off fragments of S layer, and this may be the result of wall turnover. Indigenous autolytic activity in isolated walls rapidly digested the wall fabric, liberating soluble S-layer protein. At the same time, proteases frequently reduced the molecular weight of the 91.4-kilodalton protein, but these polypeptides could still be identified as S-layer components by immunoblotting. As cultures were serially subcultured, the frequency of appearance of the S layer diminished, and it was eventually lost. The dynamic nature of this S layer makes it atypical of most previously identified S layers and made it unusually difficult to characterize.
Effects of medium composition on penicillin-induced hydrolysis and loss of RNA and culture turbidity in group A streptococci
Authors: McDowell T D , Reed K E
Published: November 2016

Exposure to penicillin G of exponentially growing cultures of group A streptococci growing in chemically defined medium (CDM) can lead to extensive loss of culture turbidity. Significant reductions in culture turbidity did not accompany comparable treatments of group A streptococci growing in Todd-Hewitt broth (THB). Studies with THB and a high-molecular-weight (greater than 12,000) fraction of THB demonstrated that components in this complex medium inhibited the efflux of RNA hydrolysis products from otherwise intact cells. Hydrolysis products accumulated intracellularly and inhibited the extensive hydrolysis of RNA and consequently the loss of culture turbidity. Results of survival studies with cultures of group A streptococci exposed to penicillin G in THB demonstrated that this treatment protocol produces conditions of phenotypic tolerance relative to exposure in CDM. In combination, these findings provide further support for the hypothesis of RNA hydrolysis as the bactericidal mechanism of penicillin G action in this nonlytic death phenotype.
Redox regulation of the genes for cobinamide biosynthesis in Salmonella typhimurium
Authors: Andersson D I , Roth J R
Published: November 2016

Transcription of the cobinamide biosynthetic genes (the CobI operon) was induced under three different physiological conditions: anaerobiosis (anaerobic respiration or fermentation), aerobic respiration at low oxygen levels, and aerobic respiration with a partial block of the electron transport chain. After a shift to inducing conditions, there was a time lag of approximately 50 min before the onset of CobI induction. Under conditions of anaerobic respiration, the level of CobI transcription was dependent on the nature of both the electron donor (carbon and energy source) and the acceptor. Cells grown with electron acceptors with a lower midpoint potential showed higher CobI expression levels. The highest level of CobI transcription observed was obtained with glycerol as the carbon source and fumarate as the electron acceptor. The high induction seen with glycerol was reduced by mutational blocks in the glycerol catabolic pathway, suggesting that glycerol does not serve as a gratuitous inducer but must be metabolized to stimulate CobI transcription. In the presence of oxygen, CobI operon expression was induced 6- to 20-fold by the following: inhibition of cytochrome o oxidase with cyanide, mutational blockage of ubiquinone biosynthesis, and starvation of mutant cells for heme. We suggest that the CobI operon is induced in response to a reducing environment within the cell and not by the absence of oxygen per se.
Nucleotide sequences and operon structure of plasmid-borne genes mediating uptake and utilization of raffinose in Escherichia coli
Authors: Aslanidis C , Schmid K , Schmitt R
Published: November 2016

The plasmid-borne raf operon encodes functions required for inducible uptake and utilization of raffinose by Escherichia coli. Raf functions include active transport (Raf permease), alpha-galactosidase, and sucrose hydrolase, which are negatively controlled by the Raf repressor. We have defined the order and extent of the three structural genes, rafA, rafB, and rafD; these are contained in a 5,284-base-pair nucleotide sequence. By comparisons of derived primary structures with known subunit molecular weights and an N-terminal peptide sequence, rafA was assigned to alpha-galactosidase (708 amino acids), rafB was assigned to Raf permease (425 amino acids), and rafD was assigned to sucrose hydrolase (476 amino acids). Transcription was shown to initiate 13 nucleotides upstream of rafA; a putative promoter, a ribosome-binding site, and a transcription termination signal were identified. Striking similarities between Raf permease and lacY-encoded lactose permease, revealed by high sequence conservation (76%), overlapping substrate specificities, and similar transport kinetics, suggest a common origin of these transport systems. alpha-Galactosidase and sucrose hydrolase are not related to host enzymes but have their counterparts in other species. We propose a modular origin of the raf operon and discuss selective forces that favored the given gene organization also found in the E. coli lac operon.