bluuebunny/crossref_metadata_2025 huggingface dataset:
The magnetic field of a circular turn
Authors: Erlichson Herman
Published: March 2005

This article presents the numerical solution for the magnetic field of a current-carrying circular turn at any point. Textbook solutions usually confine themselves to the solution on the axis of the turn because the on-axis Biot–Savart law integration is easy to do in closed form. As the knowledge and use of hand-held calculators and computers has increased, the numerical solution of this problem for off-axis points has become possible by students in the introductory calculus-based course. A good way to do this problem is in the physics laboratory where actual measurements can be compared with the values obtained from a numerical solution.
On the magnetic field generated by a short segment of current
Authors: Hovey Arthur
Published: March 2005

This article describes a series of simple experiments with which students can discover the well-known formula for the magnetic field generated by an infinitesimal current segment. No such procedure seems to have been described previously in the literature.
Gauge fields
Authors: Mills Robert
Published: March 2005

This article is a survey of the history and ideas of gauge theory. Described here are the gradual emergence of symmetry as a driving force in the shaping of physical theory; the elevation of Noether’s theorem, relating symmetries to conservation laws, to a fundamental principle of nature; and the force of the idea (‘‘the gauge principle’’) that the symmetries of nature, like the interactions themselves, should be local in character. The fundamental role of gauge fields in mediating the interactions of physics springs from Noether’s theorem and the gauge principle in a remarkably clean and elegant way, leaving, however, some tantalizing loose ends that might prove to be the clue to a future deeper level of understanding. The example of the electromagnetic field as the prototype gauge theory is discussed in some detail and serves as the basis for examining the similarities and differences that emerge in generalizing to non-Abelian gauge theories. The article concludes with a brief examination of the dream of total unification—all the forces of nature in a single unified gauge theory, with the differences among the forces due to the specific way in which the fundamental symmetries are broken in the local environment.
Space-time software: Computer graphics utilities in special relativity
Authors: Taylor Edwin F.
Published: March 2005

No one can experience directly the world of the very fast, described by special relativity. Interactive graphics displays have been developed for personal computers that help students visualize this world. They are in the form of interactive graphics utilities that students use to carry out homework exercises and take-home projects. Sequential versions of these programs have been used for 3 years in classes in various institutions. This article describes the programs and reports on the educational outcomes of these computer uses.
Gauge kinematics of deformable bodies
Authors: Shapere Alfred , Wilczek Frank
Published: March 2005

The treatment of the motion of deformable bodies requires a specification of axes for each shape. A natural kinematic formulation of this problem is presented in terms of a gauge structure over the space of shapes that the body may assume. Within this framework, one may compute the net change in orientation of a body with angular momentum zero, resulting from a given sequence of deformations.
Delta-function identities and electromagnetic field singularities
Authors: Weiglhofer Werner
Published: March 2005

An identity for the second-order derivative of the Green’s function of Helmholtz’ equation is presented. Application of this identity permits the derivation of the correct delta-function singularity of the corresponding electromagnetic Green’s tensor and the electromagnetic fields at the source points.
Reconciling the ‘‘strange’’ and ‘‘ordinary’’ polarizations of the classical atom
Authors: Solem Johndale C.
Published: March 2005

The counterintuitive transverse electric−field response of a hydrogenic atom is reconciled with the customary notion of dielectric polarization.
On classical and quantal measurements
Authors: Likar A.
Published: March 2005

A measurement always has two parts; first, detection of the signal from a set of sensors, and second, an interpretation of the signals in light of known dynamic laws governing the system under investigation. It is shown that interpretation requires a model system whose dynamic properties are essentially different from the original system. In the model system, damping is unavoidable so it must always be described with infinite degrees of freedom, although the original system could be very simple. This holds both for classical as well as for quantal measurements.
Motion in noninertial systems: Theory and demonstrations
Authors: Kugler M.
Published: March 2005

The problem of motion in accelerated frames is discussed by using the concept of a locally inertial frame. This method is often used in general relativity, but it is useful in classical mechanics as well. The use of such frames simplifies the equations of motion. Some simple experiments that help to illustrate the physical phenomena involved are presented.
Boltzmann’s constant: A laboratory experiment
Authors: Kruglak Haym
Published: March 2005

The mean-square displacement of a latex microsphere is determined from its projection on a TV monitor. The distribution of displacement is shown to be Gaussian. Boltzmann’s constant, calculated from the pooled data of several observers, is in excellent agreement with the accepted value. The experiment is designed for one laboratory period in the advanced undergraduate laboratory.
The two cycles of the rotary Curie-point heat engine
Authors: Barnes George
Published: March 2005

The behavior of a heat engine’s working substance, as it passes through a set of thermodynamic processes and returns to its original state, is called its cycle. Most heat engines have a single cycle, and, for most, the working substance is steam, a gas, or a gas–vapor mixture. The Curie-point heat engine is a solid-state device having only one moving part in which two simultaneous cycles occur, but neither needs to involve a gas or vapor. One cycle describes work done by a magnetic torque τ, which causes an angular displacement θ. The second is a hysteresis cycle of magnetic field intensity H and intensity of magnetization M. Some positive and some negative work is produced during both cycles.
One-dimensional scattering by a locally periodic potential
Authors: Lee Hai-Woong , Zysnarski Adam , Kerr Phillip
Published: March 2005

One-dimensional scattering of a particle or a wave packet by a finite number of periodic potential barriers is studied. The fundamental physical mechanism that determines the transmission coefficient is shown to be quantum interference between waves with different numbers of inner reflections. The tendency of the transmission coefficient to saturate with respect to an increase in the number of barriers is due to the free-particle nature of a particle subject to a completely periodic potential.
Curvature in orbital dynamics
Authors: Nauenberg Michael
Published: March 2005

The physical basis and the geometrical significance of the equation for the orbit of a particle moving under the action of external forces is exhibited by deriving this equation in a coordinate-independent representation in terms of the radius of curvature of the orbit. Although this formulation appeared in Newton’s Principia, it has been ignored in contemporary classical mechanics textbooks. For small eccentricities, the orbit equation is used to obtain approximate solutions that illustrate the role of curvature. It is shown that this approach leads to a simple graphical method for determining the orbits for central forces. This method is similar to one attributed to Newton, who applied it to a constant central force, and sent a diagram of the orbit to Hooke in 1679. The result is compared to the corresponding orbit of a ball revolving inside an inverted cone which Hooke described in his response to Newton.
Feline Calicivirus VP2 Is Essential for the Production of Infectious Virions
Authors: Sosnovtsev Stanislav V. , Belliot Gaël , Chang Kyeong-Ok , Onwudiwe Oge , Green Kim Y.
Published: March 2005

The third open reading frame (ORF3) located at the 3′ end of the genomic RNA of feline calicivirus (FCV) encodes a small (12.2-kDa) minor structural protein of 106 amino acids designated VP2. Point mutations and deletions were introduced into an infectious FCV cDNA clone in order to evaluate the functional importance of ORF3 and its encoded protein, VP2. Deletion of the entire ORF3 sequence was lethal for the virus, and evidence was found for strong selective pressure to produce the VP2 protein. Extended deletions in the 5′ end and small deletions in the 3′ end of ORF3, as well as the introduction of stop codons into the ORF3 sequence, were tolerated by the viral replication machinery, but infectious virus could not be recovered. Infectious virus particles could be rescued from a full-length FCV cDNA clone encoding a nonfunctional VP2 when VP2 was provided in
trans
from a eukaryotic expression plasmid. Our data indicate that VP2, a protein apparently unique to the caliciviruses, is essential for productive replication that results in the synthesis and maturation of infectious virions and that the ORF3 nucleotide sequence itself overlaps a
cis
-acting RNA signal at the genomic 3′ end.
Antigenic Domain 1 Is Required for Oligomerization of Human Cytomegalovirus Glycoprotein B
Authors: Britt William J. , Jarvis Michael A. , Drummond Derek D. , Mach Michael
Published: March 2005

Human cytomegalovirus (HCMV) glycoprotein B (gB) is an abundant virion envelope protein that has been shown to be essential for the infectivity of HCMV. HCMV gB is also one of the most immunogenic virus-encoded proteins, and a significant fraction of virus neutralizing antibodies are directed at gB. A linear domain of gB designated AD-1 (antigenic domain 1) represents a dominant antibody binding site on this protein. AD-1 from clinical isolates of HCMV exhibits little sequence variation, suggesting that AD-1 plays an essential role in gB structure or function. We investigated this possibility by examining the role of AD-1 in early steps of gB synthesis. Our results from studies using eukaryotic cells indicated that amino acid (aa) 635 of the gB sequence represented the carboxyl-terminal limit of this domain and that deletion of aa 560 to 640 of the gB sequence resulted in loss of AD-1 expression. AD-1 was shown to be required for oligomerization of gB. Mutation of cysteine at either position 573 or 610 in AD-1 resulted in loss of its reactivity with AD-1-specific monoclonal antibodies and gB oligomerization. Infectious virus could not be recovered from HCMV bacterial artificial chromosomes following introduction of these mutations into the HCMV genome, suggesting that AD-1 was an essential structural domain required for gB function in the replicative cycle of HCMV. Sequence alignment of AD-1 with homologous regions of gBs from other herpesviruses demonstrated significant relatedness, raising the possibility that this domain may contribute to multimerization of gBs in other herpesviruses.
Acid-Resistant Bovine Pestivirus Requires Activation for pH-Triggered Fusion during Entry
Authors: Krey Thomas , Thiel Heinz-Jürgen , Rümenapf Till
Published: March 2005

The route of internalization of the pestivirus bovine viral diarrhea virus (BVDV) was studied by using different chemical and biophysical inhibitors of endocytosis. Expression of the dominant-negative mutant Dyn
K44A
of the GTPase dynamin in MDBK cells, as well as the treatment of the cells with chlorpromazine and β-methyl-cyclodextrin inhibited BVDV entry. BVDV infection was also abolished by potassium (K
+
) depletion, hyperosmolarity, and different inhibitors of endosomal acidification. We conclude that BVDV likely enters the cell by clathrin-dependent endocytosis and that acidification initiates fusion with the endosomal membrane. Further studies revealed that BVDV was unable to undergo “fusion from without” at low pH. The finding that low pH is not sufficient to force adsorbed BVDV into fusion with the plasma membrane is compatible with the remarkable resistance of pestiviruses to inactivation by low pH. The importance of the abundant intra- and intermolecular disulfide bonds in BVDV glycoproteins for virus stability was studied by the use of reducing agents. The combination of dithiothreitol and acidic pH led to partial inactivation of BVDV and allowed fusion from without at low efficiency. Evidence is provided here that acid-resistant BVDV is destabilized during endocytosis to become fusogenic at an endosomal acidic pH. We suggest that destabilization of the virion occurs by breakage of disulfide bonds in the glycoproteins by an unknown mechanism.
Critical Role of Epstein-Barr Virus (EBV)-Encoded RNA in Efficient EBV-Induced B-Lymphocyte Growth Transformation
Authors: Yajima Misako , Kanda Teru , Takada Kenzo
Published: March 2005

It was demonstrated that Epstein-Barr virus (EBV)-encoded small RNAs (EBERs) were nonessential for B-lymphocyte growth transformation. We revisited this issue by producing a large quantity of EBER-deleted EBV by using an Akata cell system. Although the EBER-deleted virus efficiently infected B lymphocytes, its 50% transforming dose was approximately 100-fold less than that of the EBER-positive EBV. We then engineered the genome of EBER-deleted virus and generated a recombinant virus with the EBER genes reconstituted at their native locus. The resultant EBER-reconstituted EBV exhibited restored transforming ability. In addition, lymphoblastoid cell lines established with the EBER-deleted EBV grew significantly more slowly than those established with wild-type or EBER-reconstituted EBV, and the difference between the growth rates was especially highlighted when the cells were plated at low cell densities. These results clearly demonstrate that EBERs significantly contribute to the efficient growth transformation of B lymphocytes by enhancing the growth potential of transformed lymphocytes.
Consequences of Immunodominant Epitope Deletion for Minor Influenza Virus-Specific CD8+-T-Cell Responses
Authors: Andreansky Samita S. , Stambas John , Thomas Paul G. , Xie Weidong , Webby Richard J. , Doherty Peter C.
Published: March 2005

The extent to which CD8+T cells specific for other antigens expand to compensate for the mutational loss of the prominent DbNP366and DbPA224epitopes has been investigated using H1N1 and H3N2 influenza A viruses modified by reverse genetics. Significantly increased numbers of CD8+KbPB1703+, CD8+KbNS2114+, and CD8+DbPB1-F262+T cells were found in the spleen and in the inflammatory population recovered by bronchoalveolar lavage from mice that were first given the −NP−PA H1N1 virus intraperitoneally and then challenged intranasally with the homologous H3N2 virus. The effect was less consistent when this prime-boost protocol was reversed. Also, though the quality of the response measured by cytokine staining showed some evidence of modification when these minor CD8+-T-cell populations were forced to play a more prominent part, the effects were relatively small and no consistent pattern emerged. The magnitude of the enhanced clonal expansion following secondary challenge suggested that the prime-boost with the −NP−PA viruses gave a response overall that was little different in magnitude from that following comparable exposure to the unmanipulated viruses. This was indeed shown to be the case when the total response was measured by ELISPOT analysis with virus-infected cells as stimulators. More surprisingly, the same effect was seen following primary challenge, though individual analysis of the CD8+KbPB1703+, CD8+KbNS2114+, and CD8+DbPB1-F262+sets gave no indication of compensatory expansion. A possible explanation is that novel, as yet undetected epitopes emerge following primary exposure to the −NP−PA deletion viruses. These findings have implications for both natural infections and vaccines.
Variants of Human Immunodeficiency Virus Type 1 That Efficiently Use CCR5 Lacking the Tyrosine-Sulfated Amino Terminus Have Adaptive Mutations in gp120, Including Loss of a Functional N-Glycan
Authors: Platt Emily J. , Shea Danielle M. , Rose Patrick P. , Kabat David
Published: March 2005

By selecting the R5 human immunodeficiency virus type 1 (HIV-1) strain JR-CSF for efficient use of a CCR5 coreceptor with a badly damaged amino terminus [i.e., CCR5(Y14N)], we previously isolated variants that weakly utilize CCR5(Δ18), a low-affinity mutant lacking the normal tyrosine sulfate-containing amino-terminal region of the coreceptor. These previously isolated HIV-1
JR-CSF
variants contained adaptive mutations situated exclusively in the V3 loop of their gp120 envelope glycoproteins. We now have weaned the virus from all dependency on the CCR5 amino terminus by performing additional selections with HeLa-CD4 cells that express only a low concentration of CCR5(Δ18). The adapted variants had additional mutations in their V3 loops, as well as one in the V2 stem (S193N) and four alternative mutations in the V4 loop that eliminated the same N-linked oligosaccharide from position N403. Assays using pseudotyped viruses suggested that these new gp120 mutations all made strong contributions to use of CCR5(Δ18) by accelerating a rate-limiting CCR5-dependent conformational change in gp41 rather than by increasing viral affinity for this damaged coreceptor. Consistent with this interpretation, loss of the V4 N-glycan at position N403 also enhanced HIV-1 use of a different low-affinity CCR5 coreceptor with a mutation in extracellular loop 2 (ECL2) [i.e., CCR5(G163R)], whereas the double mutant CCR5(Δ18,G163R) was inactive. We conclude that loss of the N-glycan at position N403 helps to convert the HIV-1 envelope into a hair-trigger form that no longer requires strong interactions with both the CCR5 amino terminus and ECL2 but efficiently uses either site alone. These results demonstrate a novel functional role for a gp120 N-linked oligosaccharide and a high degree of adaptability in coreceptor usage by HIV-1.
Effects of Foot-and-Mouth Disease Virus Nonstructural Proteins on the Structure and Function of the Early Secretory Pathway: 2BC but Not 3A Blocks Endoplasmic Reticulum-to-Golgi Transport
Authors: Moffat Katy , Howell Gareth , Knox Caroline , Belsham Graham J. , Monaghan Paul , Ryan Martin D. , Wileman Thomas
Published: March 2005

Infection of cells by picornaviruses leads to the generation of intracellular membrane vesicles. The expression of poliovirus (PV) 3A protein causes swelling of the endoplasmic reticulum (ER) and inhibition of protein trafficking between the ER and the Golgi apparatus. Here, we report that the nonstructural proteins of a second picornavirus, foot-and-mouth disease virus (FMDV), also perturb the secretory pathway. FMDV proteins 3A, 2B, 2C, and 2BC expressed alone in cells were recovered from crude membrane fractions, indicating membrane association. Immunofluorescence microscopy showed that 3A was located in a reticular structure and 2B was located in the ER, while 2C was located in both the ER and the bright punctate structures within the Golgi apparatus. 2BC gave punctate cytoplasmic staining and also caused accumulation of ER proteins in large vesicular structures located around the nuclei. The effect of the FMDV proteins on the trafficking of the vesicular stomatitis virus glycoprotein (G protein) from the ER to the cell surface was determined. Unlike its PV counterpart, the 3A protein of FMDV did not prevent trafficking of the G protein to the cell surface. Instead, surface expression of the G protein was blocked by 2BC, with retention of the G protein in a modified ER compartment staining for 2BC. The results suggest that the nonstructural proteins of different picornaviruses may vary in their ability to perturb the secretory pathway. Since FMDV 2BC can block the delivery of proteins to the cell surface, it may, as shown for PV 3A, play a role in immune evasion and contribute to the persistent infections observed in ruminants.
The Nuclear Shuttle Protein ofTomato Leaf Curl New Delhi VirusIs a Pathogenicity Determinant
Authors: Hussain Mazhar , Mansoor Shahid , Iram Shazia , Fatima Ayesha Naureen , Zafar Yusuf
Published: March 2005

The role of the movement protein (MP) and nuclear shuttle protein (NSP) in the pathogenicity ofTomato leaf curl New Delhi virus(ToLCNDV), a bipartite begomovirus, was studied. Both genes were expressed inNicotiana benthamiana,Nicotiana tabacum, andLycopersicon esculentumplants with thePotato virus X(PVX) expression vector or by stable transformation of gene constructs under the control of the 35S promoter inN. tabacum. No phenotypic changes were observed in any of the three species when the MP was expressed from the PVX vector or constitutively expressed in transgenic plants. Expression of the ToLCNDV NSP from the PVX vector inN. benthamianaresulted in leaf curling that is typical of the disease symptoms caused by ToLCNDV in this species. Expression of NSP from PVX inN. tabacumandL. esculentumresulted in a hypersensitive response (HR), demonstrating that the ToLCVDV NSP is a target of host defense responses in these hosts. The NSP, when expressed as a transgene under the control of the 35S promoter, resulted in necrotic lesions in expanded leaves that initiated from a point and then spread across the leaf. The necrotic response was systemic in all the transgenic plants. Deletion of 100 amino acids from the C terminus did not compromise the HR response, suggesting that this region has no role in HR. Deletion of 60 or 100 amino acids from the N terminus of NSP abolished the HR response, suggesting that these sequences are required for the HR response. These findings demonstrate that the ToLCNDV NSP is a pathogenicity determinant as well as a target of host defense responses.
Mumps Virus V Protein Antagonizes Interferon without the Complete Degradation of STAT1
Authors: Kubota Toru , Yokosawa Noriko , Yokota Shin-ichi , Fujii Nobuhiro , Tashiro Masato , Kato Atsushi
Published: March 2005

Mumps virus (MuV) has been shown to antagonize the antiviral effects of interferon (IFN) through proteasome-mediated complete degradation of STAT1 by using the viral V protein (T. Kubota et al., Biochem. Biophys. Res. Commun. 283:255-259, 2001). However, we found that MuV could inhibit IFN signaling and the generation of a subsequent antiviral state long before the complete degradation of cellular STAT1 in infected cells. In MuV-infected cells, nuclear translocation and phosphorylation of STAT1 and STAT2 tyrosine residue (Y) at 701 and 689, respectively, by IFN-β were significantly inhibited but the phosphorylation of Jak1 and Tyk2 was not inhibited. The transiently expressed MuV V protein also inhibited IFN-β-induced Y701-STAT1 and Y689-STAT2 phosphorylation, suggesting that the V protein could block IFN-β-induced signal transduction without the aid of other viral components. Finally, a substitution of an alanine residue in place of a cysteine residue in the C-terminal V-unique region known to be required for STAT1 degradation and inhibition of anti-IFN signaling resulted in the loss of V protein function to inhibit the Y701-STAT1 and Y689-STAT2 phosphorylation.
The Alpha/Beta Interferon Response Controls Tissue Tropism and Pathogenicity of Poliovirus
Authors: Ida-Hosonuma Miki , Iwasaki Takuya , Yoshikawa Tomoki , Nagata Noriyo , Sato Yuko , Sata Tetsutaro , Yoneyama Mitsutoshi , Fujita Takashi , Taya Choji , Yonekawa Hiromichi , Koike Satoshi
Published: March 2005

Poliovirus selectively replicates in neurons in the spinal cord and brainstem, although poliovirus receptor (PVR) expression is observed in both the target and nontarget tissues in humans and transgenic mice expressing human PVR (PVR-transgenic mice). We assessed the role of alpha/beta interferon (IFN) in determining tissue tropism by comparing the pathogenesis of the virulent Mahoney strain in PVR-transgenic mice and PVR-transgenic mice deficient in the alpha/beta IFN receptor gene (PVR-transgenic/Ifnarknockout mice). PVR-transgenic/Ifnarknockout mice showed increased susceptibility to poliovirus. After intravenous inoculation, severe lesions positive for the poliovirus antigen were detected in the liver, spleen, and pancreas in addition to the central nervous system. These results suggest that the alpha/beta IFN system plays an important role in determining tissue tropism by protecting nontarget tissues that are potentially susceptible to infection. We subsequently examined the expression of IFN and IFN-stimulated genes (ISGs) in the PVR-transgenic mice. In the nontarget tissues, ISGs were expressed even in the noninfected state, and the expression level increased soon after poliovirus infection. On the contrary, in the target tissues, ISG expression was low in the noninfected state and sufficient response after poliovirus infection was not observed. The results suggest that the unequal IFN response is one of the important determinants for the differential susceptibility of tissues to poliovirus. We consider that poliovirus replication was observed in the nontarget tissues of PVR-transgenic/Ifnarknockout mice because the IFN response was null in all tissues.
The Epstein-Barr Virus EBNA-LP Protein Preferentially Coactivates EBNA2-Mediated Stimulation of Latent Membrane Proteins Expressed from the Viral Divergent Promoter
Authors: Peng RongSheng , Moses Stephanie C. , Tan Jie , Kremmer Elisabeth , Ling Paul D.
Published: March 2005

The mechanistic contribution of the Epstein-Barr virus (EBV) EBNA-LP protein to B-cell immortalization remains an enigma. However, previous studies have indicated that EBNA-LP may contribute to immortalization by enhancing EBNA2-mediated transcriptional activation of the LMP-1 gene. To gain further insight into the potential role EBNA-LP has in EBV-mediated B-cell immortalization, we asked whether it is a global or gene-specific coactivator of EBNA2 and whether coactivation requires interaction between these proteins. In type I Burkitt's lymphoma cells, we found that EBNA-LP strongly coactivated EBNA2 stimulation of LMP-1 and LMP2B RNAs, which are expressed from the viral divergent promoter. Surprisingly, the viral LMP2A gene and cellular CD21 and Hes-1 genes were induced by EBNA2 but showed no further induction after EBNA-LP coexpression. We also found that EBNA-LP did not stably interact with EBNA2 in coimmunoprecipitation assays, even though the conditions were adequate to observe specific interactions between EBNA2 and its cellular cofactor, CBF1. Colocalization between EBNA2 and EBNA-LP was not detectable in EBV-transformed cell lines or transfected type I Burkitt's cells. Finally, no significant interactions between EBNA2 and EBNA-LP were found with mammalian two-hybrid assays. From this data, we conclude that EBNA-LP is not a global coactivator of EBNA2 targets, but it preferentially coactivates EBNA2 stimulation of the viral divergent promoter. While this may require specific transient interactions between these proteins that only occur in the context of the divergent promoter, our data strongly suggest that EBNA-LP also cooperates with EBNA2 through mechanisms that do not require direct or indirect complex formation between these proteins.
Dual Role of the Lymphocytic Choriomeningitis Virus Intergenic Region in Transcription Termination and Virus Propagation
Authors: Pinschewer Daniel D. , Perez Mar , de la Torre Juan Carlos
Published: March 2005

Each genome segment of the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV), encodes two genes in ambisense orientation, separated by an intergenic region (IGR). The 3′ ends of subgenomic viral mRNAs have been mapped to a stem-loop structure within the IGR, suggesting structure-dependent transcription termination. We have studied the role of the LCMV IGR by using a minigenome (MG) rescue system based on RNA analogues of the short genome segment. An ambisense MG coding for chloramphenicol acetyltransferase (CAT) and green fluorescent protein reporter genes instead of the nucleoprotein and glycoprotein open reading frames, respectively, served as a template for synthesis of full-length anti-MG (aMG) replicate and subgenomic size mRNA for reporter gene expression. An analogous MG without IGR was amplified by the virus polymerase with equal efficiency, but subgenomic mRNA was undetectable. Reporter gene expression from IGR-deficient aMG CAT-sense RNA of genomic length was approximately 5-fold less efficient than that from subgenomic CAT mRNA derived from an IGR-containing MG, but at least 100-fold more efficient than that from a T7 RNA polymerase transcript with the same sequence. Therefore, in the absence of IGR-mediated transcription termination, a fraction of full-length aMG RNA appears to behave as bona fide mRNA. Unexpectedly, MGs without IGR were dramatically impaired in their ability to passage reporter gene activity via infectious virus-like particles. These data suggest that the LCMV IGR serves individual functions in transcription termination for enhanced gene expression and in the virus assembly and/or budding, which are required for the efficient propagation of LCMV infectivity.
UNIT KILLING VECTOR FIELDS ON NEARLY KÄHLER MANIFOLDS
Authors: MOROIANU ANDREI , NAGY PAUL-ANDI , SEMMELMANN UWE
Published: March 2005

We study 6-dimensional nearly Kähler manifolds admitting a Killing vector field of unit length. In the compact case, it is shown that up to a finite cover there is only one geometry possible, that of the 3-symmetric space S3 × S3.
DALITZ PLOT ANALYSES FROM FOCUS
Authors:   FOR THE FOCUS COLLABORATION., DINI PAOLO
Published: March 2005

Charm meson decay-dynamics has been extensively studied in the last decade. Dalitz plot analysis has revealed as a powerful tool for investigating effects of resonant substructures, interference patterns and final-state-interactions in the charm sector. Recent results from FOCUS on D+ and Ds decays will be presented with particular emphasis on the decay amplitude formalism; Isobar model and K-matrix model results will be compared and discussed.
DETERMINATION OF |Vcb| AND RELATED RESULTS FROM BABAR
Authors:   REPRESENTING THE BABAR COLLABORATION., MORII MASAHIRO
Published: March 2005

The CKM matrix element amplitude |Vcb| was determined using the data collected by the BABAR detector. The partial branching fraction, lepton-energy moments, and hadron-mass moments were measured in inclusive semileptonic decays B→Xcℓν. A global fit to a Heavy-Quark-Expansion calculation allowed precise determination of |Vcb|, mb, mc, ℬ(B→Xcℓν) and four non-perturbative parameters.
THRESHOLD HYPERON PRODUCTION AT COSY-11
Authors: ROŻEK T. , GRZONKA D. , KILIAN K. , KOWINA P. , OELERT W. , SEFZICK T. , WINTER P. , WOLKE M. , WÜSTNER P. , SIEMASZKO M. , ZIPPER W. , CZYŻYKIEWICZ R. , JANUSZ M. , JARCZYK L. , KAMYS B. , KLAJA P. , MOSKAL P. , PISKOR-IGNATOWICZ C. , PRZERWA J. , SMYRSKI J. , ADAM H. H. , KHOUKAZ A. , SANTO R. , TÄSCHNER A. , BUDZANOWSKI A.
Published: March 2005

The Λ, Σ0 and Σ+ hyperon production in NN collisions is studied at the COSY – 11 installation in order to investigate the production mechanism as well as to extract information about the Y-N interaction.
η AND η′ PHOTOPRODUCTION OFF THE NUCLEON
Authors:   FOR THE CBELSA/TAPS COLLABORATION., KOTULLA MARTIN
Published: March 2005

We have measured the reaction γp→η′p from threshold up to 2.6 GeV incident beam energy using the Crystal Barrel and TAPS detectors at the ELSA accelerator. At present the knowledge about the resonance contribution to this process is very limited. Our measurement is a significant improvement of the data basis. We will present preliminary results.
The crystal structure of KCaF3 at 4.2 and 300 K: A re-evaluation using high-resolution powder neutron diffraction
Authors: Knight K. S. , Darlington C. N. W. , Wood I. G.
Published: March 2005

The crystal structure of the perovskite phase KCaF3 has been redetermined at 4.2 and 300 K using powder neutron diffraction collected at the highest resolution. At both temperatures the phase was found to be orthorhombic in space group Pnma, with lattice parameters a=0.622 879(5) nm, b=0.870 031(7) nm, c=0.611 210(5) nm at 4.2 K, and a=0.621 488(6) nm, b=0.876 360(8) nm, c=0.616 481(6) nm at 300 K. The CaF6 octahedron is regular at both temperatures with octahedral rotations of 9.6° and 13.2° for the in-phase and anti-phase tilts, respectively, at 4.2 K. No evidence was found to support the recent revision of the space group from Pnma to the monoclinic space group B21∕m.
The crystal structure of (Ho0.50Ca0.50)MnO3and its evolution with Cr doping: A Rietveld refinement investigation
Authors: Martinelli A. , Ferretti M.
Published: March 2005

Single-phase (Ho0.50Ca0.50)MnO3has been successfully prepared by means of solid state reaction at high temperature. Its crystal structure, as well as those of Cr-doped samples(Ho1−xCax)(Mn1−yCry)O3, has been refined by the Rietveld method, using X-ray powder diffraction data. All the examined compounds crystallize in thePnmaspace group with a distorted perovskite-type structure. The distortion of the BO6octahedra, due to the Jahn–Teller Mn3+ionic species, decreases with the Cr content. Bond valence sum calculations were carried out using the refined results.
Role of the Right and Left Hemispheres in Recovery of Function during Treatment of Intention in Aphasia
Authors: Crosson Bruce , Moore Anna Bacon , Gopinath Kaundinya , White Keith D. , Wierenga Christina E. , Gaiefsky Megan E. , Fabrizio Katherine S. , Peck Kyung K. , Soltysik David , Milsted Christina , Briggs Richard W. , Conway Tim W. , Rothi Leslie J. Gonzalez
Published: March 2005

Two patients with residual nonfluent aphasia after ischemic stroke received an intention treatment that was designed to shift intention and language production mechanisms from the frontal lobe of the damaged left hemisphere to the right frontal lobe. Consistent with experimental hypotheses, the first patient showed improvement on the intention treatment but not on a similar attention treatment. In addition, in keeping with experimental hypotheses, the patient showed a shift of activity to right presupplementary motor area and the right lateral frontal lobe from pre-to post-intention treatment functional magnetic resonance imaging (fMRI) of language production. In contrast, the second patient showed improvement on both the intention and attention treatments. During pre-treatment fMRI, she already showed lateralization of intention and language production mechanisms to the right hemisphere that continued into post-intention treatment imaging. From pre-to post-treatment fMRI of language production, both patients demonstrated increased activity in the posterior perisylvian cortex, although this activity was lateralized to left-hemisphere language areas in the second but not the first patient. The fact that the first patient's lesion encompassed almost all of the dominant basal ganglia and thalamus whereas the second patient's lesion spared these structures suggests that the dominant basal ganglia could play a role in spontaneous reorganization of language production functions to the right hemisphere. Implications regarding the theoretical framework for the intention treatment are discussed.
Behavioral and Electrophysiological Evidence of a Right Hemisphere Bias for the Influence of Negative Emotion on Higher Cognition
Authors: Simon-Thomas Emiliana R. , Role Kemi O. , Knight Robert T.
Published: March 2005

We examined how responses to aversive pictures affected performance and stimulus-locked event-related potentials (ERPs) recorded during a demanding cognitive task. Numeric Stroop stimuli were briefly presented to either left or right visual hemifield (LVF and RVF, respectively) after a centrally presented aversive or neutral picture from the International Affective Picture System. Subjects indicated whether a quantity value from each Stroop stimulus matched the preceding Stroop stimulus while passively viewing the pictures. After aversive pictures, responses were more accurate for LVF Stroops and less accurate for RVF Stroops. Early-latency extrastriate attention-dependent visual ERPs were enhanced for LVF Stroops. The N2 ERP was enhanced for LVF Stroops over the right frontal and parietal scalp sites. Slow potentials (300–800 msec) recorded over the frontal and parietal regions showed enhanced picture related modulation and amplitude for LVF Stroops. These results suggest that emotional responses to aversive pictures selectively facilitated right hemisphere processing during higher cognitive task performance.
Expectation and the Vestibular Control of Balance
Authors: Guerraz Michel , Day Brian L.
Published: March 2005

Recent experiments have shown that the visual channel of balance control is susceptible to cognitive influence. When a subject is aware that an upcoming visual disturbance is likely to arise from an external agent, that is, movement of the visual environment, rather than from self-motion, the whole-body response is suppressed. Here we ask whether this is a principle that generalizes to the vestibular channel of balance control. We studied the whole-body response to a pure vestibular perturbation produced by galvanic vestibular stimulation (GVS; 0.5 mA for 3 sec). In the first experiment, subjects stood with vision occluded while stimuli were delivered either by the subject himself (self-triggered) or by the experimenter. For the latter, the stimulus was delivered either without warning (unpredictable) or at a fixed interval following an auditory cue (predictable). Results showed that GVS evoked a whole-body response that was not affected by whether the stimulus was self-triggered, predictable, or unpredictable. The same results were obtained in a second experiment in which subjects had access to visual information during vestibular stimulation. We conclude that the vestibular-evoked balance response is automatic and immune to knowledge of the source of the perturbation and its timing. We suggest the reason for this difference between visual and vestibular channels stems from a difference in their natural abilities to signal self-motion. The vestibular system responds to acceleration of the head in space and therefore always signals self-motion. Visual flow, on the other hand, is ambiguous in that it signals object motion and eye motion, as well as self-motion.
The Randomized Sample Tree: A Data Structure for Interactive Walk-Throughs in Externally Stored Virtual Environments
Authors: Klein Jan , Krokowski Jens , Fischer Matthias , Wand Michael , Wanka Rolf , Heide Friedhelm Meyer auf der
Published: March 2005

We present a new data structure for rendering highly complex virtual environments of arbitrary topology. The special feature of our approach is that it allows an interactive navigation in very large scenes (30 GB/400 million polygons in our benchmark scenes) that cannot be stored in main memory, but only on a local or remote hard disk. Furthermore, it allows interactive rendering of substantially more complex scenes by instantiating objects.

The sampling process is done in the preprocessing. There, the polygons are randomly distributed in our hierarchical data structure, the randomized sample tree. This tree uses only space that is linear in the number of polygons. In order to produce an approximate image of the scene, the tree is traversed and polygons stored in the visited nodes are rendered. During the interactive walk-through, parts of the sample tree are loaded from a local or remote hard disk.

We implement our algorithm in a prototypical walk-through system. Analysis and experiments show that the quality of our images is comparable to images computed by the conventional z-buffer algorithm regardless of the scene topology.
Material Representations: From the Genetic Code to the Evolution of Cellular Automata
Authors: Rocha Luis Mateus , Hordijk Wim
Published: March 2005

We present a new definition of the concept of representation for cognitive science that is based on a study of the origin of structures that are used to store memory in evolving systems. This study consists of novel computer experiments in the evolution of cellular automata to perform nontrivial tasks as well as evidence from biology concerning genetic memory. Our key observation is that representations require inert structures to encode information used to construct appropriate dynamic configurations for the evolving system. We propose criteria to decide if a given structure is a representation by unpacking the idea of inert structures that can be used as memory for arbitrary dynamic configurations. Using a genetic algorithm, we evolved cellular automata rules that can perform nontrivial tasks related to the density task (or majority classification problem) commonly used in the literature. We present the particle catalogs of the new rules following the computational mechanics framework. We discuss if the evolved cellular automata particles may be seen as representations according to our criteria. We show that while they capture some of the essential characteristics of representations, they lack an essential one. Our goal is to show that artificial life can be used to shed new light on the computation-versus-dynamics debate in cognitive science, and indeed function as a constructive bridge between the two camps. Our definitions of representation and cellular automata experiments are proposed as a complementary approach, with both dynamics and informational modes of explanation.
The Development of Embodied Cognition: Six Lessons from Babies
Authors: Smith Linda , Gasser Michael
Published: March 2005

The embodiment hypothesis is the idea that intelligence emerges in the interaction of an agent with an environment and as a result of sensorimotor activity. We offer six lessons for developing embodied intelligent agents suggested by research in developmental psychology. We argue that starting as a baby grounded in a physical, social, and linguistic world is crucial to the development of the flexible and inventive intelligence that characterizes humankind.
New Robotics: Design Principles for Intelligent Systems
Authors: Pfeifer Rolf , Iida Fumiya , Bongard Josh
Published: March 2005

New robotics is an approach to robotics that, in contrast to traditional robotics, employs ideas and principles from biology. While in the traditional approach there are generally accepted methods (e.g., from control theory), designing agents in the new robotics approach is still largely considered an art. In recent years, we have been developing a set of heuristics, or design principles, that on the one hand capture theoretical insights about intelligent (adaptive) behavior, and on the other provide guidance in actually designing and building systems. In this article we provide an overview of all the principles but focus on the principles of ecological balance, which concerns the relation between environment, morphology, materials, and control, and sensory-motor coordination, which concerns self-generated sensory stimulation as the agent interacts with the environment and which is a key to the development of high-level intelligence. As we argue, artificial evolution together with morphogenesis is not only “nice to have” but is in fact a necessary tool for designing embodied agents.
Flexible Couplings: Diffusing Neuromodulators and Adaptive Robotics
Authors: Philippides Andy , Husbands Phil , Smith Tom , O'Shea Michael
Published: March 2005

Recent years have seen the discovery of freely diffusing gaseous neurotransmitters, such as nitric oxide (NO), in biological nervous systems. A type of artificial neural network (ANN) inspired by such gaseous signaling, the GasNet, has previously been shown to be more evolvable than traditional ANNs when used as an artificial nervous system in an evolutionary robotics setting, where evolvability means consistent speed to very good solutions—here, appropriate sensorimotor behavior-generating systems. We present two new versions of the GasNet, which take further inspiration from the properties of neuronal gaseous signaling. The plexus model is inspired by the extraordinary NO-producing cortical plexus structure of neural fibers and the properties of the diffusing NO signal it generates. The receptor model is inspired by the mediating action of neurotransmitter receptors. Both models are shown to significantly further improve evolvability. We describe a series of analyses suggesting that the reasons for the increase in evolvability are related to the flexible loose coupling of distinct signaling mechanisms, one “chemical” and one “electrical.”
Predicting red muscle performance
Authors: Curtin  , Lou  , Woledge
Published: March 2005

The active force production during contraction of bundles of red muscle fibres from myotomal muscle of dogfish Scyliorhinus canicula (L.) has been predicted by a numerical model based on Hill's 2-component model of the mechanical properties of muscle, with the addition of a simple model for the kinetics of activation. When all of these factors are included, the model makes good predictions for the force and power during stimulation. There are, however, significant discrepancies during relaxation after the end of stimulation, from which we conclude that additional processes have a large influence on force during relaxation. This has functional relevance for fish swimming because during relaxation the muscle fibre continues its sinusoidal pattern of movement and thus continues to either produce power if shortening, or require power input from other structures to cause lengthening.
Alien Species Stay Home: The International Convention for the Control and Management of Ships' Ballast Water and Sediments 2004
Authors: Tsimplis Michael
Published: March 2005

The transfer of organisms by ships has been altering the ecosystems for many decades. Living organisms within ballast water is part of this problem. Where ballast water has been taken from heavily polluted areas then potential risks for human health are also created. The International Convention for the Control and Management of Ships' Ballast Water (the Ballast Water Convention—referred to hereafter as the BWC) is the first international attempt to provide a legal and technical instrument for a risk that was not so far covered by any legal regime. The BWC imposes obligations both on the flag and the port states and provides for a certification system that will eventually be able to regulate ballast water management. Ambitious ballast water quality standards are included but they will not be imposed until 2016 when a new generation of ships having the required new technology will be developed. These strict standards are subject to review on the basis of their feasibility and cost implications. In the meantime only some basic precautions and restrictions, together with a complex surveying and certification system, will be imposed. Moreover, these restrictions will only be imposed if they do not cause delay or deviation for the ships, arguably making one wonder whether the problem is indeed a serious and imminent threat to the environment.