bluuebunny/crossref_metadata_2025 huggingface dataset:
Description of Extended Pre‐Harvest PigSalmonellaSurveillance‐and‐Control Programme and its Estimated Effect on Food Safety Related to Pork
Authors: Alban L. , Barfod K. , Petersen J. V. , Dahl J. , Ajufo J. C. , Sandø G. , Krog H. H. , Aabo S.
Published: November 2010

Salmonellain pork can be combated during pre‐ or post‐harvest. For large slaughterhouses, post‐harvest measures like decontamination might be cost‐effective while this is less likely with small‐to‐medium sized slaughterhouses. In this study, pre‐harvest measures might be more relevant. We describe an extended surveillance‐and‐control programme forSalmonellain finisher pigs, which, to establish equivalence to the Swedish control programme, is intended for implementation on the Danish island, Bornholm. The effect of the programme on food safety was estimated by analysingSalmonelladata from pig carcasses originating from herds that would have qualified for the programme during 2006–2008. Food safety was interpreted as prevalence ofSalmonellaon carcasses as well as the estimated number of human cases of salmonellosis related to pork produced within the programme. Data from the DanishSalmonellaprogramme were obtained from Bornholm. We used a simulation model developed to estimate the number of human cases based on the prevalence ofSalmonellaon carcass swabs. Herds are only accepted in the programme if they have one or less seropositive sample within the previous 6 months. In this way, theSalmonellaload is kept to a minimum. The programme is not yet in operation and pigs that qualify for the programme are currently mixed at slaughter with those that do not qualify. Therefore, we had to assess the impact on the carcass prevalence indirectly. The prevalence ofSalmonellain carcass swabs among qualifying herds was 0.46% for the 3 years as a whole, with 2006 as the year with highest prevalence. According to the simulation the expected number of human cases relating to pork produced within the programme was below 10. When the programme is in operation, an extra effect of separating pigs within the programme from those outside is expected to lower the prevalence ofSalmonellaeven further.
Pork Safety: Achievements and Challenges
Authors: Davies P. R.
Published: November 2010

Safepork is a biennial international symposium for researchers investigating the epidemiology and control of foodborne hazards in pork. Current research is heavily weighted towards enteric bacterial pathogens for which development of reliable practical interventions for farmers has proven frustrating. In contrast, modern production practices have greatly reduced the risk of parasitic foodborne pathogens. Better understanding of host adaptation of emerging agents is important for assessing their potential zoonotic and foodborne risks.
Transcriptome analysis of LuxS‐deficient Streptococcus mutans grown in biofilms
Authors: Wen Z.T. , Nguyen A.H. , Bitoun J.P. , Abranches J. , Baker H.V. , Burne R.A.
Published: November 2010

We previously reported that LuxS in Streptococcus mutans is involved in stress tolerance and biofilm formation. In this study, flowcells and confocal laser scanning microscopy were used to further examine the effects of LuxS‐deficiency on biofilm formation. Similar to the wild‐type strain (UA159), a strain deficient in LuxS (TW26D) bound efficiently to the flowcells and formed microcolonies 4 h after inoculation. Unlike UA159, which accumulated and formed compact, evenly distributed biofilms after 28 h, TW26D showed only loose, sporadic, thin biofilms. DNA microarray analysis revealed alterations in transcription of more than 60 genes in TW26D biofilms by at least 1.5‐fold (P < 0.001). Among the upregulated genes were those for sugar‐specific enzymes II of the phosphotransferase (PTS) system and the atp operon, which codes for the proton‐pumping F‐ATPase. Of the downregulated genes, several encode proteins with putative functions in DNA repair. Mutation of selected genes caused severe defects in the ability of the mutants to tolerate low pH and oxidative stress. These results provide additional proof that LuxS‐deficiency causes global alterations in the expression of genes central to biofilm formation and virulence of S. mutans, including those involved in energy metabolism, DNA repair and stress tolerance.
Microbiological and immunological characteristics of young Moroccan patients with aggressive periodontitis with and without detectable Aggregatibacter actinomycetemcomitans JP2 infection
Authors: Rylev M. , Bek‐Thomsen M. , Reinholdt J. , Ennibi O.‐K. , Kilian M.
Published: November 2010

Cross‐sectional and longitudinal studies identify the JP2 clone of Aggregatibacter actinomycetemcomitans as an aetiological agent of aggressive periodontitis (AgP) in adolescents of northwest African descent. To gain information on why a significant part of Moroccan adolescents show clinical signs of periodontal disease in the absence of this pathogen we performed comprehensive mapping of the subgingival microbiota of eight young Moroccans, four of whom were diagnosed with clinical signs of AgP. The analysis was carried out by sequencing and phylogenetic analysis of a total of 2717 cloned polymerase chain reaction amplicons of the phylogenetically informative 16S ribosomal RNA gene. The analyses revealed a total of 173 bacterial taxa of which 39% were previously undetected. The JP2 clone constituted a minor proportion of the complex subgingival microbiota in patients with active disease. Rather than identifying alternative aetiologies to AgP, the recorded infection history of the subjects combined with remarkably high concentrations of antibodies against the A. actinomycetemcomitans leukotoxin suggest that disease activity was terminated in some patients with AgP as a result of elimination of the JP2 clone. This study provides information on the microbial context of the JP2 clone activity in a JP2‐susceptible population and suggests that such individuals may develop immunity to AgP.
Killing of anaerobic pathogens by predatory bacteria
Authors: Van Essche M. , Quirynen M. , Sliepen I. , Loozen G. , Boon N. , Van Eldere J. , Teughels W.
Published: November 2010

Recently, the predation of Bdellovibrio bacteriovorus on a periodontal pathogen has been described. The current study explores the potential antimicrobial activity of a range of predatory bacteria against key periodontal pathogens. A number of representatives from the Bdellovibrio, Bacteriovorax and Peredibacter lineages (called ‘BALOs’) were tested for their activity towards a group of key periodontal pathogens and an optimal multiplicity of infection was established. As the oral cavity contains a wide variety of bacteria that are not preyed upon, it was investigated if they can have an effect on the predation efficiency of BALOs. It was concluded that a number of important variables involved in bacterial predation are found to be compatible with the composition of the oral microbiota. This finding makes the case for continued study of the potential for BALOs to combat periodontal pathogens.
The bcp gene in the bcp‐recA‐vimA‐vimE‐vimF operon is important in oxidative stress resistance in Porphyromonas gingivalis W83
Authors: Johnson N.A. , McKenzie R.M.E. , Fletcher H.M.
Published: November 2010

The ability of Porphyromonas gingivalis to overcome oxidative stress in the inflammatory environment of the periodontal pocket is critical for its survival. We have previously demonstrated that the recA locus, which carries the bacterioferritin co‐migratory protein (bcp) gene and has a unique genetic architecture, plays a role in virulence regulation and oxidative stress resistance in P. gingivalis. To further characterize the bcp gene, which was confirmed to be part of the bcp‐recA‐vimA‐vimE‐vimF operon, we created a P. gingivalis bcp‐defective isogenic mutant (FLL302) by allelic exchange. Compared with the wild‐type, FLL302 had a similar growth rate, black pigmentation, β‐hemolysis and UV sensitivity. Although there was no change in the distribution of gingipain activity, there was a 30% reduction in both Arg‐X and Lys‐X activities in the mutant strain compared with the wild‐type. When exposed to 0.25 mm hydrogen peroxide, P. gingivalis FLL302 was more sensitive than the wild‐type. In addition, the cloned P. gingivalis bcp gene increased resistance to 0.25 mm hydrogen peroxide in a bcp‐defective Escherichia coli mutant. The mutant also demonstrated decreased aerotolerance when compared with the wild‐type. Porphyromonas gingivalis FLL302 and the wild‐type strain had similar virulence profiles in a mouse model of virulence. These observations suggest that the bcp gene may play a role in oxidative stress resistance but has a decreased functional significance in the pathogenic potential of P. gingivalis.
Platelet lysate formulations based on mucoadhesive polymers for the treatment of corneal lesions
Authors: Sandri Giuseppina , Bonferoni Maria Cristina , Rossi Silvia , Ferrari Franca , Mori Michela , Del Fante Claudia , Perotti Cesare , Scudeller Luigia , Caramella Carla
Published: November 2010

Objectives

Growth factors contained in platelet α-granules initiate and modulate tissue repair and are proposed for the treatment of soft and hard-tissue surgical conditions and in the management of non-healing wounds. Platelet lysate is a hemoderivative obtained from platelet-rich plasma and is capable of releasing a pool of growth factors. Many medical and surgical techniques have been proposed for the treatment of corneal lesions; management of these conditions remains problematic and healing with standard protocols is unattainable. The aim of this study was to develop formulations suitable for prolonging the contact of platelet lysate with the damaged cornea for the time necessary to exert a therapeutic effect.

Methods

Two vehicles, one based on polyacrylic acid and one based on chitosan, were autoclaved and loaded with platelet lysate and the resultant formulations were characterized for rheology, mucoadhesion, vehicle compatibility and stability. The proliferation effect was tested on two cell culture types (rabbit corneal epithelial cells and fibroblasts). An in-vitro wound-healing test was performed on fibroblasts. In both cases the formulations were compared with platelet lysate diluted with saline at the same concentration.

Findings

Both formulations maintained the rheological and mucoadhesive properties of the vehicles and the proliferative activity of platelet lysate. The chitosan formulation was able to significantly enhance epithelial cell growth even after storage of up to 2 weeks (in-use conditions), while the polyacrylic acid formulation was less efficient, probably due to the characteristics of the cell model used.

Conclusions

The in-vitro wound-healing test performed on fibroblasts confirmed the differences between the two vehicles. The effect induced by the platelet lysate and chitosan formulation was faster than that of the polyacrylic acid formulation and complete in-vitro wound repair was achieved within 48 h.
Preparation and effects of 2,3-dehydrosilymarin, a promising and potent antioxidant and free radical scavenger
Authors: Tong Shanshan , Chu Chang , Wei Yuan , Wang Li , Gao Xizhe , Xu Ximing , Yu Jiangnan
Published: November 2010

Objectives

Silymarin or silybin has been effectively used for treating liver diseases and acute liver injury partly due to its antioxidant activity. In this study, 2,3-dehydrosilymarin, a compound exhibiting remarkable antiradical/antioxidant activity, was prepared from silymarin for the first time. The solubility, radical scavenging capacity and liver protecting activity of 2,3-dehydrosilymarin were studied and compared with silybin, dehydrosilybin and silymarin.

Methods

The structures of its main components were verified by ultra-performance liquid chromatography/mass spectrometry (UPLC-MS) and other spectral analysis. In addition, a rapid screening method, online high-performance liquid chromatography/1,1-dipheny1-2-picrylhydrazyl (HPLC-DPPH) system, was developed for identifying the individual antioxidants in 2,3-dehydrosilymarin.

Key findings

Both in-vitro and in-vivo results markedly proved that dehydrosilymarin has decent aqueous solubility and remarkable antiradical/antioxidation capacity. Moreover, 2,3-dehydrosilybin and 2,3-dehydrosilychristin were identified to be the two major active compounds contained in 2,3-dehydrosilymarin.

Conclusions

Our results suggest that 2,3-dehydrosilymarin may be a promising and potent alternative for inhibition of free radical and prevention of oxidation.
Signalling pathways responsible for the methylisogermabullone-induced contraction of ileal longitudinal muscles
Authors: Jeong Seung Il , Kwon Oh Deog , Kwon Seung Chun , Jung Kyu Yong
Published: November 2010

Objectives

We have previously reported that methylisogermabullone (MIGB) stimulates small bowel motility through activation of acetylcholinergic receptors. This study investigated the cellular signalling pathways implicated in the regulation of ileal contractility by MIGB.

Methods

The ileal longitudinal muscles prepared from rats were treated with MIGB isolated from radish roots, and muscle contractility and protein expression were measured by force transducer and Western blot, respectively.

Key findings

MIGB at 30 µm induced a sustained phasic contraction of ileal longitudinal muscles. Acetylcholine (ACh, 0.5 µm) and MIGB stimulated translocation of protein kinase C (PKC) to cell membrane of ileal longitudinal muscles, and these stimulatory effects were remarkably attenuated by atropine (0.5 µm). ACh and MIGB induced phosphorylation of ERK 1/2 and p38 MAPKs in ileal longitudinal muscles, and they also phosphorylated the caldesmon and 20-kDa regulatory light chain of myosin (MLC20). Additionally, PD-98058 (10 µm), a selective ERK 1/2 MAPK inhibitor, and SB-203580 (10 µm), a selective p38 MAPK inhibitor, significantly reduced the MIGB-induced contraction of ileal longitudinal muscles.

Conclusions

The muscarinic receptor activated by MIGB translocates the PKC to cell membrane which phosphorylates the ERK 1/2 and p38 MAPKs, resulting in subsequent phosphorylation of caldesmon and MLC20. These cellular events likely converge on the contraction of ileal longitudinal muscles in rats.
Examination of Initialization and Geometric Details on the Results of CFD Simulations of Diesel Engines
Authors: Bergin Michael J. , Musu Ettore , Kokjohn Sage , Reitz Rolf D.
Published: November 2010

Computational fluid dynamic simulations using the AVL FIRE and KIVA 3V codes were performed to examine commonly accepted techniques and assumptions used when simulating direct injection diesel engines. Simulations of a steady-state impulse swirl meter validated the commonly used practice of evaluating the swirl ratio of diesel engines by integrating the valve flow and torque history over discrete valve lift values. The results indicate the simulations capture the complex interactions occurring in the ports, cylinder, and honeycomb cell impulse swirl meter. Geometric details of engines due to valve recesses in the cylinder head and piston cannot be reproduced axisymmetrically. The commonly adopted axisymmetric assumption for an engine with a centrally located injector was tested by comparing the swirl and emissions history for a noncombusting and a double injection low temperature combustion case with varying geometric fidelity. Consideration of the detailed engine geometry including valve recesses in the piston altered the swirl history such that the peak swirl ratio at TDC decreased by approximately 10% compared with the simplified no-recess geometry. An analog to the detailed geometry of the full 3D geometry was included in the axisymmetric geometry by including a groove in the cylinder head of the mesh. The corresponding emissions predictions of the combusting cases showed greater sensitivity to the altered swirl history as the air-fuel ratio was decreased.
Design and Performance Prediction of Hybrid Air Foil Thrust Bearings
Authors: Lee Donghyun , Kim Daejong
Published: November 2010

Air foil bearings (AFBs) have been recognized as the most promising for oil-free turbomachinery. However, the applications of AFBs to the relatively large turbomachinery have many technical challenges due to limited load capacity and wear during start/stops. A hybrid air foil bearing (HAFB), which combines the benefits of AFB and hydrostatic air bearing, was introduced earlier by the authors, and the experimental studies showed much larger load capacity at low speeds and much lesser friction torque during start/stop than hydrodynamic counterpart. The benefit of HAFB was recognized through the experimental studies, and the concept of hybrid operation was further developed to thrust air foil bearings. This paper presents novel design features of the hybrid air foil thrust bearing (HAFTB) with radially arranged bump foils and preformed Rayleigh step contour, and presents simulated static and dynamic characteristics of the HAFTB. A 2D thin plate equation in cylindrical coordinate was solved with the finite difference method for the prediction of the top foil deflection. Parametric studies were performed to evaluate the effect of various design parameters on the static and dynamic performances of HAFTB. At low speeds, a design with orifice located at the center of land region showed the highest load capacity, while a design with orifice located near the leading edge of land region showed the highest load capacity at high speeds. Direct and coupled bearing coefficients were also calculated for various operating conditions. The direct stiffness increases with supply pressure but the direct damping decreases with supply pressure. In addition, typical hardening effect of gas film accompanying increase of stiffness and decrease of damping was predicted in high frequency excitations.
Prediction of Small-Scale Cavitation in a High Speed Flow Over an Open Cavity Using Large-Eddy Simulation
Authors: Shams Ehsan , Apte Sourabh V.
Published: November 2010

Large-eddy simulation of flow over an open cavity corresponding to the experimental setup of Liu and Katz (2008, “Cavitation Phenomena Occurring Due to Interaction of Shear Layer Vortices With the Trailing Corner of a Two-Dimensional Open Cavity,” Phys. Fluids, 20(4), p. 041702) is performed. The filtered, incompressible Navier–Stokes equations are solved using a co-located grid finite-volume solver with the dynamic Smagorinsky model for a subgrid-scale closure. The computational grid consists of around 7×106 grid points with 3×106 points clustered around the shear layer, and the boundary layer over the leading edge is resolved. The only input from the experimental data is the mean velocity profile at the inlet condition. The mean flow is superimposed with turbulent velocity fluctuations generated by solving a forced periodic duct flow at a freestream Reynolds number. The flow statistics, including mean and rms velocity fields and pressure coefficients, are compared with the experimental data to show reasonable agreement. The dynamic interactions between traveling vortices in the shear layer and the trailing edge affect the value and location of the pressure minima. Cavitation inception is investigated using two approaches: (i) a discrete bubble model wherein the bubble dynamics is computed by solving the Rayleigh–Plesset and the bubble motion equations using an adaptive time-stepping procedure and (ii) a scalar transport model for the liquid volume fraction with source and sink terms for phase change. Large-eddy simulation, together with the cavitation models, predicts that inception occurs near the trailing edge similar to that observed in the experiments. The bubble transport model captures the subgrid dynamics of the vapor better, whereas the scalar model captures the large-scale features more accurately. A hybrid approach combining the bubble model with the scalar transport is needed to capture the broad range of scales observed in cavitation.
Swirling Flow in a Fixed Container: Generation and Attenuation of a Vortex Column
Authors: Nahas A. , Calvo A. , Piva M.
Published: November 2010

The development of a columnar vortex and its attenuation using radial rods at the bottom boundary of a stationary container are experimentally studied. The fluid motion is achieved combining two independent flows: a global circulation around the cylinder axis and a meridian flow generated by recirculating fluid through a central nozzle located at the vessel bottom. The resulting velocity field is analyzed under two conditions: with and without the meridian or suction flow. It is shown that in the second condition a columnar vortex merges and that its intensity increases when the suction flow rate is increased. The key role played by the bottom boundary layer in the vortex formation is demonstrated. In the last part of the work, the attenuation of the vortex intensity produced by a set of rods located at the vessel bottom is investigated. It is found that obstacles with heights of the order of the boundary layer thickness are enough to produce the total annihilation of the vortex column.
Wavelength-specific reflections: A decade of extreme ultraviolet actinic mask inspection research
Authors: Goldberg K. A. , Mochi I.
Published: November 2010

Mask inspection is essential for the success of any pattern transfer lithography technology, and extreme ultraviolet lithography (EUVL), in particular, faces unique challenges. EUV masks’ resonant-reflective multilayer coatings have a narrow, wavelength-specific response that dramatically affects the way that defects appear, or disappear, at various illuminating wavelengths. Furthermore, the ever-shrinking size of “critical” defects limits the potential effectiveness of deep ultraviolet inspection techniques over time. Researchers pursuing numerous ways of finding and characterizing defects on extreme ultraviolet (EUV) masks and have met with varying degrees of success. Their lessons inform the current, urgent exploration to select the most effective techniques for high-volume manufacturing. Ranging from basic research and demonstration experiments to commercial inspection tool prototypes, the authors survey the recent history of work in this area, including sixteen projects in Europe, Asia, and America. Solutions range from scanning beams to microscopy, darkfield imaging to pattern transfer.
Assessing the mask clamping ability of a low thermal expansion material chuck
Authors: Zeuske J. R. , Vukkadala P. , Engelstad R. L. , Mikkelson A. R. , Kalkowski G. , Risse S. , Mueller S.
Published: November 2010

The successful implementation of extreme ultraviolet lithography (EUVL) for patterning in the sub-32 nm regime will require significant improvements in image placement (IP) accuracy over the next few years. The IP error budget for the mask system is extremely stringent; consequently, the reduction or elimination of all sources of error is essential. One potential source of IP error is the effect of the residual nonflatness of the patterned surface of the mask during exposure scanning. The focus of this article is to characterize the clamping ability of a Coulombic electrostatic pin-type chuck and to assess its ability to adequately flatten an EUVL mask. The chuck was fabricated from low thermal expansion material, with a nonflatness over the pin area of approximately 74 nm. Experimental results illustrate that a highly bowed substrate (1149 and 1047 nm for the frontside and backside nonflatness, respectively) could be chucked flat to less than 100 nm. Numerical models were also used to simulate electrostatic chucking and to predict the final nonflatness of the pattern surface of the mask. Excellent agreement was found between the experimental and numerical results. In addition, the modeling tools developed here can be used to optimize the chuck design parameters and to establish the requirements on nonflatness of both the EUVL substrate and the surface of the chuck.
Sputtering behavior and evolution of depth resolution upon low energy ion irradiation of GaAs
Authors: Hopstaken M. J. P. , Gordon M. S. , Pfeiffer D. , Sadana D. K. , Topuria T. , Rice P. M. , Gerl C. , Richter M. , Marchiori C.
Published: November 2010

The authors have investigated the sputtering behavior and evolution of depth resolution upon low energy ion irradiation during secondary ion mass spectrometry (SIMS) depth profiling of GaAs. They presented a systematic and quantitative study of the impact of ion species, primary ion impact energy, and incident angle on (evolution of) depth resolution using a well-characterized dedicated InGaAs/GaAs multilayer structure with nearly atomically abrupt heterointerfaces. They demonstrated that for low energy O2+ ion beam irradiation, the SIMS depth resolution is severely degraded by (transient) incorporation of high surface O-concentration into the altered layer, leading to detrimental ion beam induced formation of topography. They provided evidence that topography formation is primarily invoked by the strong angular dependence of the sputter yield on (local) incident angle. In the case of low energy, oblique Cs+ ion beam irradiation, the sputtering behavior of GaAs is well-behaved with no significant transient yield changes and a constant depth resolution. This enables SIMS depth profiling of sharp heteroepitaxial III–V multilayer structures and shallow dopant profiles with sufficiently good depth resolution and good detection efficiency.
Relaxation of misfit strain in silicon-germanium (Si1−xGex) films during dry oxidation
Authors: Yoo Jung-Ho , Kim Sun-Wook , Min Byoung-Gi , Sohn Hyunchul , Ko Dae-Hong , Cho Mann-Ho
Published: November 2010

The effects of oxidation on strain relaxation in Si1−xGex layers on silicon substrates were investigated. Si1−xGex layers, with different Ge fractions (x=0.15 and 0.3), were grown on chemically cleaned silicon substrates by an ultrahigh vacuum chemical vapor deposition process. Oxidation at 800 and 900 °C under O2 ambient in a tube furnace resulted in the production of silicon oxide layers on top and a Ge-rich region in the Si1−xGex films. It was observed that the oxidation of Si0.85Ge0.15 films at 900 °C produced the relaxation of the misfit strain in the remnant Si1−xGex layer and the increase in strain in the Ge pile-up layer with increasing oxidation time, while the oxidation at 800 °C produced no changes in the misfit strain in the Si1−xGex layers. The oxidation of Si0.70Ge0.30 films at 800 °C showed the relaxation of the misfit strain in the remnant Si1−xGex layer with the accumulation of stain in the Ge pile-up layer. However, the oxidation of Si0.70Ge0.30 layers at 900 °C exhibited the strain relaxation in the Ge pile-up layer after the Ge pile-up was extended into the remaining Si1−xGex layer, with the formation of misfit dislocations at the interface between the remaining Si1−xGex and Si substrate.
An experiment on the velocity distribution of thermionic electrons
Authors: Battaglia Onofrio Rosario , Fazio Claudio , Guastella Ivan , Sperandeo-Mineo Rosa Maria
Published: November 2010

This paper describes an undergraduate experiment that yields the velocity distribution of thermionic electrons by analyzing the I-V characteristics of diodes and triodes. The experiment allows students to focus on the distribution function more than on difficulties arising from the complexity of thermionic emission. By using a simple model, the velocity distribution of thermionic electrons emitted by the vacuum tube cathode can be described by Maxwell’s distribution.
Why are the values of the surface tension of most organic liquids similar?
Authors: Bormashenko Edward
Published: November 2010

The values of the surface tension of most organic liquids are of the same order of magnitude. The explanation is that surface tension is governed by London dispersion forces, which are independent of the permanent dipole moment of the molecules. The surface tension of organic liquids (with the exception of polymers and polymer solutions) depends on the ionization potential and the diameter of the molecule only. These parameters vary slightly for organic liquids.
Cooling balloons with liquid nitrogen
Authors: Moreno A. J. , Ferrari H. , Bekeris V.
Published: November 2010

We present an undergraduate level experiment in which the radius of a rubber balloon is measured as it is cooled with liquid nitrogen. For balloons filled with simple gases that condense at liquid nitrogen temperatures, we found that the volume decreases linearly with time. We compared our measurements with a simplified model based on elementary kinetic theory and thermodynamics that explains this behavior. Students are encouraged to test the validity of the model by repeating the experiment using gas mixtures and gases that do not condense at liquid nitrogen temperatures.
Linear transformation method for multinuclide decay calculation
Authors: Yuan Ding
Published: November 2010

A linear transformation method for generic multinuclide decay calculations is presented together with its properties and implications. The method takes advantage of the linear form of the decay solution N(t)=F(t)N0, where N(t) is a column vector that represents the numbers of atoms of the radioactive nuclides in the decay chain, N0 is the initial value vector of N(t), and F(t) is a lower triangular matrix whose time-dependent elements are independent of the initial values of the system.
New experimental method of visualizing the electric field due to surface charges on circuit elements
Authors: Jacobs Rebecca , de Salazar Alex , Nassar Antonio
Published: November 2010

Although static surface charges on circuit elements are of enormous interest, recent papers and textbooks have only discussed the problem theoretically using analytical or numerical approaches. The only well-known experimental method to visualize the structure of electric fields around circuit elements was reported by Jefimenko almost half a century ago. In our paper, we report on a simple method to visualize the electric field produced by static surface charges on current-carrying circuit elements. Our method uses a mixture of PTFE (Teflon) sealant and mineral oil, a copper wire placed in the mixture’s container, and two 6 kV power supplies. We believe that our new method can be used directly in the classroom.
Magnetic black box
Authors: Rezaeezadeh Amin
Published: November 2010

This paper introduces an experiment involving two identical small dipole magnets. One is hidden with arbitrary orientation in a black box. The second is suspended on a string above the box. By studying the horizontal and vertical oscillations of the suspended magnet, it is possible to determine the magnetic moment and the orientation of the hidden magnet, and the horizontal component of the Earth’s magnetic field.
Resource Letter PTG-1: Precision Tests of Gravity
Authors: Will Clifford M.
Published: November 2010

This Resource Letter provides an introduction to some of the main current topics in experimental tests of general relativity as well as to some of the historical literature. It is intended to serve as a guide to the field for upper-division undergraduate and graduate students, both theoretical and experimental, and for workers in other fields of physics who wish learn about experimental gravity. The topics covered include alternative theories of gravity, tests of the principle of equivalence, solar-system and binary-pulsar tests, searches for new physics in gravitational arenas, and tests of gravity in new regimes, involving astrophysics and gravitational radiation.
Smooth double barriers in quantum mechanics
Authors: Dutt Avik , Kar Sayan
Published: November 2010

Quantum mechanical tunneling across smooth double barrier potentials is modeled using Gaussian functions and is analyzed numerically and by using the WKB approximation. The transmission probability, resonances as a function of incident particle energy, and their dependence on the barrier parameters are obtained for various cases. We also discuss the tunneling time, for which we obtain generalizations of the known results for rectangular barriers.
Unusual commutation relations in physics
Authors: Nauts André , Gatti Fabien
Published: November 2010

The angular momentum operator L̂ of a particle obeys the usual commutation rule L̂×L̂=iℏL̂. In contrast, the total angular momentum operator Ĵ of a set of particles relative to moving axes (as, for instance, when mounted on a tumbling molecule) obeys the anomalous commutation rule Ĵ×Ĵ=−iℏĴ. We give a pedagogical and mathematically nonsophisticated description of intermediate cases for which partial angular momentum operators, relative to various moving frames, obey unusual commutation relations that are neither usual nor anomalous. Insight into the origin of these unusual commutation relations provides a means of guessing the type of commutation rule that will be obeyed. In particular, it gives a way to avoid, as far as possible, the unusual commutation relations, which lead to complicated and nonsystematic expressions. Some examples from molecular physics are presented.
Solving the brachistochrone and other variational problems with soap films
Authors: Criado C. , Alamo N.
Published: November 2010

We solve the problem of the brachistochrone and other variational problems with the help of the soap films that are formed between two suitable surfaces. We also discuss the connection between some variational problems of dynamics, statics, optics, and elasticity.
Analytical solution of curvilinear motion on an inclined plane
Authors: Shunyakov V. M. , Lavrik L. V.
Published: November 2010

The problem of rectilinear motion of a body on an inclined plane is well known, but attempts to generalize this problem to two dimensions lead to difficulties, in particular, finding the trajectory of a body under the influence of two forces. We offer a general method for solving this problem. The method introduces a new auxiliary independent variable instead of time and a variable oblique-angle basis replaces a rectangular one. An analogy is shown between curvilinear motion on an inclined plane and the pursuit problem.
Exponential growth of bacteria: Constant multiplication through division
Authors: Hagen Stephen J.
Published: November 2010

The growth of a bacterial culture is one of the most familiar examples of exponential growth, with important consequences in biology and medicine. Bacterial growth involves more than just a rate constant. To sustain exponential growth, the cell must carefully coordinate the accumulation of mass, constant replication of the chromosome, and physical division. Hence, the growth rate is centrally important in any physical and chemical description of a bacterial cell. These aspects of bacterial growth can be described by empirical laws that suggest simple and intuitive models. Therefore, a quantitative discussion of bacterial growth could be a part of any undergraduate biophysics course. We present a general overview of some classic experimental studies and mathematical models of bacterial growth from a mostly physical perspective.
Čerenkov radiation through the Hamiltonian approach
Authors: Razpet Nada , Likar Andrej
Published: November 2010

A calculation of the radiated power and magnetic field of Čerenkov radiation using the Hamiltonian approach is presented. We use this approach to show explicitly how the Čerenkov cone appears in the limit of long times. The Hamiltonian approach is well suited for studying the formation of the cone at the very beginning of the process using numerical integration. The topic is appropriate for advanced courses on electromagnetic fields and in introductory courses on quantum electrodynamics.
A digital oscilloscope setup for the measurement of a transistor’s characteristic curves
Authors: de Buyl Pierre
Published: November 2010

Measuring the I-V characteristics of a transistor constitutes an important step in an introductory electronics course. We demonstrate the use of a digital oscilloscope with a USB connection to perform a measurement of the characteristic curves with no additional custom circuitry. The setup is presented alongside the open-source software that allows the signal acquisition and analysis of the results.
Plant and Animal Sensors of Conserved Microbial Signatures
Authors: Ronald Pamela C. , Beutler Bruce
Published: November 2010

Common Themes

Both plants and animals need to be able to distinguish between their own tissues and the cells and tissues of an invading pathogen. Across kingdoms there exists a range of pattern recognition systems that have become integral to the evolution of innate immune responses.
Ronald and Beutler
(p.
1061
) synthesize recent intellectual progress to bring insights into shared features of animal immunology and plant pathology.
The Uncertainty Principle Determines the Nonlocality of Quantum Mechanics
Authors: Oppenheim Jonathan , Wehner Stephanie
Published: November 2010

Quantum Connection

A system that is quantum mechanically entangled with another distant system can be predicted by measuring the distant system. This form of “action-at-a-distance,” or nonlocality, seemingly contradicts Heisenberg's uncertainty principle, which is one of the fundamental aspects of quantum mechanics.
Oppenheim and Wehner
(p.
1072
) show that the degree of nonlocality in quantum mechanics is actually determined by the uncertainty principle. The unexpected connection between nonlocality and uncertainty holds true for other physical theories besides quantum mechanics.
Interdependence of Cell Growth and Gene Expression: Origins and Consequences
Authors: Scott Matthew , Gunderson Carl W. , Mateescu Eduard M. , Zhang Zhongge , Hwa Terence
Published: November 2010

Theory of Growth Control

Although quantitative studies of growth in bacterial cultures have been made for over 50 years, the relationship between cell proliferation and gene expression has not been clear.

Scott
et al.

(p.
1099
; see the Perspective by

Lerman and Palsson

) have revealed that mass per cell exponentially increased with linear increases in growth rate and that ribosome abundance increased linearly with growth rate depending on the rate of translation. Hence, the systems properties of the biological processes involved in growth can be derived without any molecular understanding of their basis and can be used to establish fundamental properties for the design of biotechnological procedures.
Loss of Carbon from the Deep Sea Since the Last Glacial Maximum
Authors: Yu Jimin , Broecker Wally S. , Elderfield Harry , Jin Zhangdong , McManus Jerry , Zhang Fei
Published: November 2010

Moving Carbon

During the last glacial maximum, approximately 23,000 years ago, both the atmosphere and the terrestrial biosphere contained much less carbon than in the immediately preindustrial era. The carbon must have been stored in the deep ocean, and the transfer of carbon to the air and land during deglaciation must have affected the carbonate chemistry and carbon isotopic composition of the sea.

Yu
et al.

(p.
1084
) estimated how deep-water carbonate concentrations changed over the course of the last deglaciation and combined their results with
13
C/
12
C data to show that carbon released by the deep ocean between 17.5 and 14.5 thousand years ago mostly stayed in the atmosphere as CO
2
, while between 14 and 10 thousand years ago, a substantial fraction was absorbed by the terrestrial biosphere.
Symbiotic Bacterium Modifies Aphid Body Color
Authors: Tsuchida Tsutomu , Koga Ryuichi , Horikawa Mitsuyo , Tsunoda Tetsuto , Maoka Takashi , Matsumoto Shogo , Simon Jean-Christophe , Fukatsu Takema
Published: November 2010

Turncoat Aphids

Aphid color has consequences for the fate of the wearer: Coccinellid beetles prefer to eat red ones and parasitoid wasps attack green ones. What might happen if aphids could change color and outwit their predators?

Tsuchida
et al.

(p.
1102
) have found that a subpopulation of the pea aphid can do this, but not without help from a previously unknown species of bacterium that lives intimately with the aphid as an endosymbiont and makes red aphids turn green. The bacterium interferes with host pigment biosynthesis—itself borrowed from fungi long ago in evolution—to stimulate blue-green pigment production as the aphid larva matures, turning the red nymph into a green adult. The ecological consequences of this about-turn of color have yet to be tested, but other studies have shown a variety of effects on aphid behavior mediated by endosymbionts in response to adaptation to different food plants, temperature tolerance, and predator avoidance.
Comment on “Single-Crystal X-ray Structure of 1,3-Dimethylcyclobutadiene by Confinement in a Crystalline Matrix”
Authors: Scheschkewitz David
Published: November 2010

Legrand
et al
. (Reports, 16 July 2010, p. 299) reported on the photolytic reaction of an α-pyrone confined in a crystalline matrix. Their structural analysis invoked four products: activated precursor, isomeric Dewar β-lactone, and square and rectangular isomers of 1,3-dimethylcyclobutadiene. The reported x-ray data, however, suggest that all observed structures correspond to only one distinct species, the Dewar β-lactone.
Comment on “Single-Crystal X-ray Structure of 1,3-Dimethylcyclobutadiene by Confinement in a Crystalline Matrix”
Authors: Alabugin Igor V. , Gold Brian , Shatruk Michael , Kovnir Kirill
Published: November 2010

Legrand
et al
. (Reports, 16 July 2010, p. 299) reported the experimental observation of square-planar and rectangular-bent geometries of 1,3-dimethylcyclobutadiene (Me
2
CBD) confined within a crystalline matrix. However, we found no evidence for the Me
2
CBD formation. We argue that the experimental x-ray density data are better attributed to the bicyclic β-lactone intermediate where carbon dioxide is covalently bound to cyclobutadiene.
Faster Interprotein Electron Transfer in a [Myoglobin, b
5
] Complex with a Redesigned Interface
Authors: Xiong Peng , Nocek Judith M. , Vura-Weis Josh , Lockard Jenny V. , Wasielewski Michael R. , Hoffman Brian M.
Published: November 2010

Speeding Electron Transfer Between Proteins

Compared to those observed in photosynthetic proteins, electron transfer rates between other large biomolecules, such as myoglobin and cytochrome b
5
, are very slow.

Xiong
et al.

(p.
1075
) show that modifying the acidic amino acid residues in the binding surface of myoglobin to lysine changes the distribution of structures to ones that favor faster electron transfer from the zinc porphyrin in myoglobin to the heme iron of cytochrome b
5
. The rates observed are within an order of magnitude of those observed for the initial step of charge separation in photosynthesis and provide valuable data for scientists interested in designing reactive proteins.
A Law by Any Other Name Would Smell as Sweet
Biology's First Law
The Tendency for Diversity and Complexity to Increase in Evolutionary Systems

by Daniel W. McShea and Robert N. Brandon

University of Chicago Press, Chicago, 2010. 184 pp. $55, £35.50. ISBN 9780226562254. Paper, $20, £13. ISBN 9780226562261.
Authors: Millstein Roberta L.
Published: November 2010

McShea and Brandon argue that biological complexity is the expected outcome of being alive—in the absence of any other forces, both diversity and complexity will increase as the inevitable consequence of cumulative changes.
Structure of the Human Dopamine D3 Receptor in Complex with a D2/D3 Selective Antagonist
Authors: Chien Ellen Y. T. , Liu Wei , Zhao Qiang , Katritch Vsevolod , Won Han Gye , Hanson Michael A. , Shi Lei , Newman Amy Hauck , Javitch Jonathan A. , Cherezov Vadim , Stevens Raymond C.
Published: November 2010

Tweaking Dopamine Reception

Dopamine modulates many cognitive and emotional functions of the human brain by activating G protein–coupled receptors. Antipsychotic drugs that block two of the receptor subtypes are used to treat schizophrenia but have multiple side effects.Chienet al.(p.1091; see the Research Article byWuet al.) resolved the crystal structure of one receptor in complex with a small-molecule inhibitor at 3.15 angstrom resolution. Homology modeling with other receptor subtypes might be a promising route to reveal potential structural differences that can be exploited in the design of selective therapeutic inhibitors having fewer side effects.
Why a Grand Unified Theory Is Neither Feasible nor Desirable
From Populations to Ecosystems
Theoretical Foundations for a New Ecological Synthesis

by Michel Loreau

Princeton University Press, Princeton, NJ, 2010. 316 pp. $99.50, £69.95. ISBN 9780691122694. Paper, $45, £30.95. ISBN 9780691122700. Monographs in Population Biology, 46.
Authors: Fukami Tadashi
Published: November 2010

Seeing a monolithic unified theory of ecology as neither feasible nor desirable, Loreau offers an alternative approach to bridging the fields of evolutionary biology, community ecology, and ecosystems.
π = Visual Cortex
Authors: Miller Kenneth D.
Published: November 2010

Three distantly-related mammals share a brain architecture characterized by a density of π
Key Indicator of Ocean Health May Be Flawed
Authors: Stokstad Erik
Published: November 2010

The most widely used metric of how marine ecosystems are faring worldwide can't be trusted, according to a controversial new analysis of fisheries data.
GM Mosquito Trial Alarms Opponents, Strains Ties in Gates-Funded Project
Authors: Enserink Martin
Published: November 2010

At a press conference in London on 11 November, British company Oxitec announced that it carried out the world's first small trial with transgenic
Aedes aegypti
mosquitoes in Grand Cayman in the fall of 2009, followed by a larger study there last summer.
Russian Science: Waking From Hibernation
Authors: Clery Daniel
Published: November 2010

Russian science has moved beyond survival mode and is trying to recapture its research glory. But as the government backs universities and applied research, what does the future hold for the Russian Academy of Sciences?
Uncertain Future for Academy's Biology Experiment
Authors: Clery Daniel
Published: November 2010

Ask anyone familiar with the Russian Academy of Sciences how the organization can be reformed so that it funds the best researchers, rather than those with the best connections, and the discussion quickly turns to the efforts of Georgii Georgiev, who runs the academy's Molecular and Cell Biology program.
Methicillin-ResistantStaphylococcus aureusin Pork Production Shower Facilities
Authors: Leedom Larson Kerry R. , Harper Abby L. , Hanson Blake M. , Male Michael J. , Wardyn Shylo E. , Dressler Anne E. , Wagstrom Elizabeth A. , Tendolkar Shaliesh , Diekema Daniel J. , Donham Kelley J. , Smith Tara C.
Published: November 2010

As methicillin-resistantStaphylococcus aureus(MRSA) has been found in pigs, we sought to determine if MRSA is present in pork production shower facilities. In two production systems tested, 3% and 26% of shower samples were positive for MRSA.spatypes identified included t034, t189, t753, and t1746.