bluuebunny/crossref_metadata_2025 huggingface dataset:
Smitin, a novel smooth muscle titin–like protein, interacts with myosin filaments in vivo and in vitro
Authors: Kim Kyoungtae , Keller Thomas C.S.
Published: July 2002

Smooth muscle cells use an actin–myosin II-based contractile apparatus to produce force for a variety of physiological functions, including blood pressure regulation and gut peristalsis. The organization of the smooth muscle contractile apparatus resembles that of striated skeletal and cardiac muscle, but remains much more poorly understood. We have found that avian vascular and visceral smooth muscles contain a novel, megadalton protein, smitin, that is similar to striated muscle titin in molecular morphology, localization in a contractile apparatus, and ability to interact with myosin filaments. Smitin, like titin, is a long fibrous molecule with a globular domain on one end. Specific reactivities of an anti-smitin polyclonal antibody and an anti-titin monoclonal antibody suggest that smitin and titin are distinct proteins rather than differentially spliced isoforms encoded by the same gene. Smitin immunofluorescently colocalizes with myosin in chicken gizzard smooth muscle, and interacts with two configurations of smooth muscle myosin filaments in vitro. In physiological ionic strength conditions, smitin and smooth muscle myosin coassemble into irregular aggregates containing large sidepolar myosin filaments. In low ionic strength conditions, smitin and smooth muscle myosin form highly ordered structures containing linear and polygonal end-to-end and side-by-side arrays of small bipolar myosin filaments. We have used immunogold localization and sucrose density gradient cosedimentation analyses to confirm association of smitin with both the sidepolar and bipolar smooth muscle myosin filaments. These findings suggest that the titin-like protein smitin may play a central role in organizing myosin filaments in the contractile apparatus and perhaps in other structures in smooth muscle cells.
Viral Escape by Selection of Cytotoxic T Cell–Resistant Variants in Influenza a Virus Pneumonia
Authors: Price Graeme E. , Ou Rong , Jiang Hong , Huang Lei , Moskophidis Demetrius
Published: July 2002

Antigenic variation is a strategy exploited by influenza viruses to promote survival in the face of the host adaptive immune response and constitutes a major obstacle to efficient vaccine development. Thus, variation in the surface glycoproteins hemagglutinin and neuraminidase is reflected by changes in susceptibility to antibody neutralization. This has led to the current view that antibody-mediated selection of influenza A viruses constitutes the basis for annual influenza epidemics and periodic pandemics. However, infection with this virus elicits a vigorous protective CD8+ cytotoxic T lymphocyte (CTL) response, suggesting that CD8+ CTLs might exert selection pressure on the virus. Studies with influenza A virus–infected transgenic mice bearing a T cell receptor (TCR) specific for viral nucleoprotein reveal that virus reemergence and persistence occurs weeks after the acute infection has apparently been controlled. The persisting virus is no longer recognized by CTLs, indicating that amino acid changes in the major viral nucleoprotein CTL epitope can be rapidly accumulated in vivo. These mutations lead to a total or partial loss of recognition by polyclonal CTLs by affecting presentation of viral peptide by class I major histocompatibility complex (MHC) molecules, or by interfering with TCR recognition of the mutant peptide–MHC complex. These data illustrate the distinct features of pulmonary immunity in selection of CTL escape variants. The likelihood of emergence and the biological impact of CTL escape variants on the clinical outcome of influenza pneumonia in an immunocompetent host, which is relevant for the design of preventive vaccines against this and other respiratory viral infections, are discussed.
Interferon Regulatory Factor (Irf)-1 and Irf-2 Regulate Interferon γ–Dependent Cyclooxygenase 2 Expression
Authors: Blanco Jorge C. G. , Contursi Cristina , Salkowski Cindy A. , DeWitt David L. , Ozato Keiko , Vogel Stefanie N.
Published: July 2002

Cyclooxygenases (Cox) are rate-limiting enzymes that initiate the conversion of arachidonic acid to prostanoids. Cox-2 is the inducible isoform that is upregulated by proinflammatory agents, initiating many prostanoid-mediated pathological aspects of inflammation. In this study, we demonstrate that interferon (IFN)-γ alone or in synergy with lipopolysaccharide (LPS) or interleukin 1α induces Cox-2 expression in mouse peritoneal macrophages, which is paralleled by changes in Cox-2 protein levels and prostaglandin E2 (PGE2) release. Induction of Cox-2 was abrogated in macrophages that lack IFN regulatory factor (IRF)-1, consistent with an attenuated hepatic mRNA response in IRF-1−/− mice injected with LPS. Conversely, the absence of IRF-2 in macrophages resulted in a significant increase in both basal and inducible Cox-2 gene and protein expression as well as IFN-γ–stimulated PGE2 release, identifying IRF-2 as negative regulator of this promoter. Two IFN stimulation response elements were identified in the mouse Cox-2 promoter that were highly conserved in the human Cox-2 gene. Both bind endogenous IRF-1 and IRF-2 and regulate transcription in an IRF-1/2–dependent manner. Our data demonstrate conclusively the importance of IFN-γ as a direct activator and coactivator of the Cox-2 gene, and the central role of IRF-1/2 family members in this process.
Opposing Effects of Transmembrane and Soluble FAS Ligand Expression on Inflammation and Tumor Cell Survival
Authors: Hohlbaum Andreas M. , Moe Signa , Marshak-Rothstein Ann
Published: July 2002

Fas ligand (FasL) has been shown to mediate both apoptotic and inflammatory reactions. To rigorously assess the physiological role of different forms of the FasL molecule with regard to these two distinct processes, we isolated stably transfected lymphoma cell lines that expressed either murine wild-type FasL, membrane-only FasL, or functionally distinct forms of soluble FasL. First, the ability of these lines to induce an inflammatory response was assessed in vivo by injecting the transfectants intraperitoneally and measuring subsequent neutrophil extravasation into the peritoneal cavity. Second, lines were assessed by injecting the transfectants subcutaneously and monitoring their growth as solid tumors. Our study clearly demonstrated that the extent of inflammation induced by the transfectants directly correlated with their relative cytotoxic activities. A neutrophil response could only be elicited in mice with intact Fas death domains although Fas expression by the neutrophils was not essential. Lymphoma cells expressing the soluble FasL form corresponding to the natural cleavage product could not trigger apoptosis and did not induce a neutrophil response. In contrast to the other FasL transfectants, these cells survived as tumor transplants. However, expression of soluble FasL was not benign, but actually suppressed the inflammatory response and protected other transfectants from the effector mechanisms elicted by membrane-bound FasL.
A Soluble Form of B Cell Maturation Antigen, a Receptor for the Tumor Necrosis Factor Family Member April, Inhibits Tumor Cell Growth
Authors: Rennert Paul , Schneider Pascal , Cachero Teresa G. , Thompson Jeffrey , Trabach Luciana , Hertig Sylvie , Holler Nils , Qian Fang , Mullen Colleen , Strauch Kathy , Browning Jeffrey L. , Ambrose Christine , Tschopp Jürg
Published: July 2002

A proliferation-inducing ligand (APRIL) is a ligand of the tumor necrosis factor (TNF) family that stimulates tumor cell growth in vitro and in vivo. Expression of APRIL is highly upregulated in many tumors including colon and prostate carcinomas. Here we identify B cell maturation antigen (BCMA) and transmembrane activator and calcium modulator and cyclophilin ligand (CAML) interactor (TACI), two predicted members of the TNF receptor family, as receptors for APRIL. APRIL binds BCMA with higher affinity than TACI. A soluble form of BCMA, which inhibits the proliferative activity of APRIL in vitro, decreases tumor cell proliferation in nude mice. Growth of HT29 colon carcinoma cells is blocked when mice are treated once per week with the soluble receptor. These results suggest an important role for APRIL in tumorigenesis and point towards a novel anticancer strategy.
Resistance to Experimental Autoimmune Encephalomyelitis in Mice Lacking the Cc Chemokine Receptor (Ccr2)
Authors: Izikson Leonid , Klein Robyn S. , Charo Israel F. , Weiner Howard L. , Luster Andrew D.
Published: July 2002

Monocyte recruitment to the central nervous system (CNS) is a necessary step in the development of pathologic inflammatory lesions in experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis. Monocyte chemoattractant protein (MCP)-1, a potent agonist for directed monocyte migration, has been implicated in the pathogenesis of EAE. Here we report that deficiency in CC chemokine receptor (CCR)2, the receptor for MCP-1, confers resistance to EAE induced with a peptide derived from myelin oligodendrocyte glycoprotein peptide 35–55 (MOGp35–55). CCR2−/− mice immunized with MOGp35–55 failed to develop mononuclear cell inflammatory infiltrates in the CNS and failed to increase CNS levels of the chemokines RANTES (regulated on activation, normal T cell expressed and secreted), MCP-1, and interferon (IFN)-inducible protein 10 (IP-10) as well the chemokine receptors CCR1, CCR2, and CCR5. Additionally, T cells from CCR2−/− immunized mice showed decreased antigen-induced proliferation and production of IFN-γ compared with wild-type immunized controls, suggesting that CCR2 enhances the T helper cell type 1 immune response in EAE. These data indicate that CCR2 plays a necessary and nonredundant role in the pathogenesis of EAE.
Donor-Derived Ip-10 Initiates Development of Acute Allograft Rejection
Authors: Hancock Wayne W. , Gao Wei , Csizmadia Vilmos , Faia Kerrie L. , Shemmeri Nida , Luster Andrew D.
Published: July 2002

An allograft is often considered an immunologically inert playing field on which host leukocytes assemble and wreak havoc. However, we demonstrate that graft-specific physiologic responses to early injury initiate and promulgate destruction of vascularized grafts. Serial analysis of allografts showed that intragraft expression of the three chemokine ligands for the CXC chemo-kine receptor CXCR3 was induced in the order of interferon (IFN)-γ–inducible protein of 10 kD (IP-10, or CXCL10), IFN-inducible T cell α-chemoattractant (I-TAC; CXCL11), and then monokine induced by IFN-γ (Mig, CXCL9). Initial IP-10 production was localized to endothelial cells, and only IP-10 was induced by isografting. Anti–IP-10 monoclonal antibodies prolonged allograft survival, but surprisingly, IP-10–deficient (IP-10−/−) mice acutely rejected allografts. However, though allografts from IP-10+/+ mice were rejected by day 7, hearts from IP-10−/− mice survived long term. Compared with IP-10+/+ donors, use of IP-10−/− donors reduced intragraft expression of cytokines, chemokines and their receptors, and associated leukocyte infiltration and graft injury. Hence, tissue-specific generation of a single chemokine in response to initial ischemia/reperfusion can initiate progressive graft infiltration and amplification of multiple effector pathways, and targeting of this proximal chemokine can prevent acute rejection. These data emphasize the pivotal role of donor-derived IP-10 in initiating alloresponses, with implications for tissue engineering to decrease immunogenicity, and demonstrate that chemokine redundancy may not be operative in vivo.
T Cell–Independent Interleukin 15rα Signals Are Required for Bystander Proliferation
Authors: Lodolce James P. , Burkett Patrick R. , Boone David L. , Chien Marcia , Ma Averil
Published: July 2002

Cytokine driven or “bystander” proliferation of T cells occurs in vivo independently of major histocompatibility complex–T cell receptor interactions. This process may be important for supporting T cell homeostasis and facilitating T cell responses to microbial antigens, and may involve the cytokine interleukin (IL)-15. In this study, we find that IL-15Rα–deficient (IL-15Rα−/−) mice fail to undergo poly I:C or IL-15 driven bystander proliferation of CD8+ T cells. Surprisingly, IL-15Rα−/− CD8+ T cells proliferate in response to poly I:C when adoptively transferred into normal mice, and normal CD8+ T cells fail to proliferate in IL-15Rα−/− mice. Normal mice reconstituted with IL-15Rα−/− bone marrow cells also fail to exhibit bystander responses. Thus, CD8+ T cell independent IL-15Rα signals from radiation sensitive hematopoietic cells are likely required for bystander responses. Moreover, normal CD8+ T cells proliferate in IL-15Rα−/− mice after treatment with IL-15. Therefore, IL-15Rα signals may mediate a positive feedback loop involving the further physiological production of IL-15. These findings provide new insights into how IL-15Rα supports memory phenotype CD8+ T cell proliferation, and suggest novel mechanisms by which memory CD8+ T cells are maintained in vivo.
Repetitive Injections of Dendritic Cells Matured with Tumor Necrosis Factor α Induce Antigen-specific Protection of Mice from Autoimmunity
Authors: Menges Mauritius , Rößner Susanne , Voigtländer Constanze , Schindler Heike , Kukutsch Nicole A. , Bogdan Christian , Erb Klaus , Schuler Gerold , Lutz Manfred B.
Published: July 2002

Mature dendritic cells (DCs) are believed to induce T cell immunity, whereas immature DCs induce T cell tolerance. Here we describe that injections of DCs matured with tumor necrosis factor (TNF)-α (TNF/DCs) induce antigen-specific protection from experimental autoimmune encephalomyelitis (EAE) in mice. Maturation by TNF-α induced high levels of major histocompatibility complex class II and costimulatory molecules on DCs, but they remained weak producers of proinflammatory cytokines. One injection of such TNF/DCs pulsed with auto-antigenic peptide ameliorated the disease score of EAE. This could not be observed with immature DCs or DCs matured with lipopolysaccharide (LPS) plus anti-CD40. Three consecutive injections of peptide-pulsed TNF/DCs derived from wild-type led to the induction of peptide-specific predominantly interleukin (IL)-10–producing CD4+ T cells and complete protection from EAE. Blocking of IL-10 in vivo could only partially restore the susceptibility to EAE, suggesting an important but not exclusive role of IL-10 for EAE prevention. Notably, the protection was peptide specific, as TNF/DCs pulsed with unrelated peptide could not prevent EAE. In conclusion, this study describes that stimulation by TNF-α results in incompletely matured DCs (semi-mature DCs) which induce peptide-specific IL-10–producing T cells in vivo and prevent EAE.
Molecular Architecture of Full-Length KcsA
Authors: Cortes D. Marien , Cuello Luis G. , Perozo Eduardo
Published: July 2002

The molecular architecture of the NH2 and COOH termini of the prokaryotic potassium channel KcsA has been determined using site-directed spin-labeling methods and paramagnetic resonance EPR spectroscopy. Cysteine mutants were generated (residues 5–24 and 121–160) and spin labeled, and the X-band CW EPR spectra were obtained from liposome-reconstituted channels at room temperature. Data on probe mobility (ΔHo−1), accessibility parameters (ΠO2 and ΠNiEdda), and inter-subunit spin-spin interaction (Ω) were used as structural constraints to build a three-dimensional folding model of these cytoplasmic domains from a set of simulated annealing and restrained molecular dynamics runs. 32 backbone structures were generated and averaged using fourfold symmetry, and a final mean structure was obtained from the eight lowest energy runs. Based on the present data, together with information from the KcsA crystal structure, a model for the three-dimensional fold of full-length KcsA was constructed. In this model, the NH2 terminus of KcsA forms an α-helix anchored at the membrane–water interface, while the COOH terminus forms a right-handed four-helix bundle that extend some 40–50 Å towards the cytoplasm. Functional analysis of COOH-terminal deletion constructs suggest that, while the COOH terminus does not play a substantial role in determining ion permeation properties, it exerts a modulatory role in the pH-dependent gating mechanism.
The 1979 Cerro El Roble Supernova Search
Authors: MAZA J.
Published: July 2002

A new systematic program to search for supernova in southern galaxies, being carried out at the University of Chile, is described. Data for three supernovae discovered during 1979 are presented.
On the period variation of the Delta Scurti star VZ CANCRI
Authors: Arellano Ferro A.
Published: July 2002

New photometric photometry and new times of maximum light are reported for the delta Scuti-type star VZ Cancri. Times of maximum light available for the last five decades have been studied. The times of maximum from the last decade, however, indicate that the period has not been steadily increasing as believed until now. To allow for this discrepancy several interpretations of the O-C diagram are discussed. However, the scatter in the (O-C) residuals is large and it is difficult to favor a case between a sloping linear fit and a sinusoidal fit. The former indicates that the main period needs to be revised and a predicted value of 0.17836365 days is obtained. The later suggests the presence of an unseen companion whose nature and implications are briefly discussed. In either case it can be concluded that VZ Cancri is not undergoing any secular period variation. Other possibilities like abrupt period changes and long-term effects of nonlinear combinations of short frequencies are discussed but found unrealistic.
Candidate RR Lyrae Stars Found in Sloan Digital Sky Survey
Commissioning Data*
Authors: Ivezić Željko , Peek J. E. G. , Finlator Kristian , Knapp Gillian R. , Yanny Brian , McKay Timothy A. , Amrose Susan , Krisciunas Kevin , Willman Beth , Anderson Scott , Schaber Chris , Erb Dawn , Logan Chelsea , Stubbs Chris , Chen Bing , Neilsen Eric , Uomoto Alan , Pier Jeffrey R. , Fan Xiaohui , Gunn James E. , Lupton Robert H. , Rockosi Constance M. , Schlegel David , Strauss Michael A. , Annis James , Brinkmann Jon , Csabai István , Doi Mamoru , Fukugita Masataka , Hennessy Gregory S. , Hindsley Robert B. , Margon Bruce , Munn Jeffrey A. , Newberg Heidi Jo , Schneider Donald P. , Smith J. Allyn , Szokoly Gyula P. , Thakar Aniruddha R. , Vogeley Michael S. , Waddell Patrick , Yasuda Naoki , York Donald G.
Published: July 2002

We present a sample of 148 candidate RR Lyrae stars selected from Sloan Digital Sky Survey (SDSS) commissioning data for about 100 deg2 of sky surveyed twice with Δt = 1.9946 days. Although the faint-magnitude limit of the SDSS allows us to detect RR Lyrae stars to large Galactocentric distances (∼100 kpc, or r* ∼ 21), we find no candidates fainter than r* ∼ 20, i.e., farther than ∼65 kpc from the Galactic center. On the assumption that all 148 candidates are indeed RR Lyrae stars (contamination by other species of variable star is probably less than 10%), we find that their volume density has roughly a power-law dependence on Galactocentric radius, R
-2.7±0.2, between 10 and 50 kpc and drops abruptly at R ∼ 50–60 kpc, possibly indicating a sharp edge to the stellar halo as traced by RR Lyrae stars. The Galactic distribution of stars in this sample is very inhomogeneous and shows a clump of over 70 stars at about 45 kpc from the Galactic center. This clump is also detected in the distribution of nonvariable objects with RR Lyrae star colors. When sources in the clump are excluded, the best power-law fit becomes consistent with the R
-3 distribution found from surveys of bright RR Lyrae stars. These results imply that the halo contains clumpy overdensities inhomogeneously distributed within a smooth R
-3 background, with a possible cutoff at ∼50 kpc.
X-ray attenuation coefficients and atomic photoelectric absorption cross sections of silicon
Authors: L Gerward
Published: July 2002

The X-ray linear attenuation coefficient of single-crystal silicon has been measured to within 0.5% using an energy dispersive method. Atomic photoelectric cross sections are derived from the experimental results and compared with theoretical calculations. Results are given for the Cu and Mo K lines.
High-resolution studies of the Stark effect in even-purity Rydberg states of Ca I
Authors: K A H van Leeuwen  , W Hogervorst
Published: July 2002

High-resolution laser-atomic-beam spectroscopy has been applied to the study of the quadratic Stark effect in calcium 4sns3S states with principal quantum number n ranging from 14 to 45 and 4snd3D states with n=10 to 30. For the3D states the electric-field-induced splittings are comparable with the fine-structure splittings. The analysis takes account of both field-induced fine-structure mixing and zero-field deviations from LS coupling. The resulting polarisabilities are compared with calculations based on the Coulomb approximation. Satisfactory agreement is obtained. Accurate values of the fine-structure intervals in the 4snd3D series (n=14 to 30) and of the44Ca-40Ca isotope shift in a number of transitions from the 4s4p3P2state to 4sns3S1and 4snd3D3states have also been determined. From the latter data the residual level isotope shift in the 4s4p3P2state is derived. Fine-structure and Stark effect data for the 4snd levels near n=15, where the singlet and triplet series cross, indicate a stronger singlet-triplet mixing than previously assumed. This is explained in terms of small admixtures of doubly excited configurations in the 4snd levels resulting in a strong off-diagonal spin-orbit interaction.
Feasibility of the use of three-dimensional anemometers in a simulated tornado flow measurement
Authors: B Fattahi  , C T Hsu
Published: July 2002

A Thermo Systems Incorporated 1080 vector anemometer was used to map the general flow pattern of a complicated laboratory model of a tornado. Three-dimensional velocity vectors were measured with the aid of a low-pass filter for smoothing the fluctuating signal due to the inherent flow instability. The resulting pattern was in good agreement with visual observations (motion picture) of this laboratory model. The split film anemometer with its direction-finding capacity proved to be a useful instrument for this purpose, although the detailed flow structure was extremely difficult to obtain, owing to the application of a signal averaging technique. Sources of occasional error in determining the flow direction in association with this instrument are discussed.
A two-component dynamic wind tunnel balance for mounted insects
Authors: R H Buckholz
Published: July 2002

A dynamic force balance has been developed for the measurement of the instantaneous lift and drag components of an insect flying fixed in a wind tunnel. The force balance is a simple taut 'string' with fixed ends; in this work a live insect is mounted near the string midpoint. The miniscule wire displacements due to imposed forces are optically detected and interpreted as forces by an electromagnetic calibration procedure. The system response is strongly frequency-dependent, but this posed no serious problem for the measurement of periodic forces such as lift and drag fluctuations due to wing beat.
Magnesium fluoride windowed deuterium lamps as radiance transfer standards between 115 and 370 nm
Authors: P J Key  , R C Preston
Published: July 2002

Deuterium discharge lamps with magnesium fluoride windows sealed to envelopes by means of pure glass-blowing techniques have been developed at NPL as radiance transfer standards between 115 and 370 nm. It is shown how the problems of the complex molecular emission spectrum of deuterium below 165 nm are overcome at the calibration stage provided the bandwidth of the spectroradiometric system to be calibrated is known. Total power dissipation of about 15 W, compact construction, ease of use, high radiance and aging rates less than 0.05% h-1are some of the advantages discussed.
A transmission line cell for measuring the permittivity of liquids over the frequency range 90 MHz to 2 GHz
Authors: S Szwarnowski
Published: July 2002

A coaxial line transmission cell is described which allows accurate permittivity measurements to be made on lossy liquids over the frequency range 90 MHz to 2 GHz. To test the performance of the cell, measurements were made on water, methanol and ethanol at 293K.
Cu II laser with a helical hollow cathode discharge
Authors: H Koch
Published: July 2002

A novel design of a water-cooled helical hollow cathode device (HCD) is presented. The simple construction, that is conveniently manufactured, offers discharge and laser properties superior to those obtained with conventional HCDs. This is demonstrated for a CW IR Cu II laser.
A compact ignitor for spectroscopic arcs
Authors: C A Schmidt-Harms
Published: July 2002

A novel ignitor is described for cascade arcs with long electrode gaps, permitting rapid, reliable and repetitive ignition with minimal contamination of the arc plasma. It employs an eddy-current disc attached to a sliding electrical contact. The operation of an eddy-current drive can be understood in terms of the pressure exerted on the conducting disc by a trapped magnetic field.
Apparatus for observing dynamic nuclear polarization at low magnetic fields
Authors: J C Collingwood  , J W White
Published: July 2002

An electron-nuclear double resonance spectrometer to study the Overhauser effect at magnetic fields near 30 G and over a wide temperature range is described. A combination of high Q in the electron resonance cavity with sensitive nuclear resonance detection makes observations on high dielectric loss samples practical. Examples of enhanced nuclear resonance sensitivity (for protons, fluorine, lithium and phosphorus nuclei) are given with an application of the apparatus for very accurate measurements of electron spin resonance parameters at low fields.
The retrieval of low current pulses from noise for attachment measurements in weakly attaching gases
Authors: J Dutton  , A Goodings  , A K Lucas  , A W Williams
Published: July 2002

Describes the use of a digital storage oscilloscope linked to a microprocessor via a GPIB digital interface for the improvement of the signal-to-random-noise ratio of low-level ( approximately 10-10A) repetitive current waveforms obtained from drift tubes. The analysis of such signals allows attachment coefficient to be calculated for very weakly attaching gas mixtures.
Apparatus for correlation of magnetic and metallurgical properties of metals
Authors: N Davis  , P A Norris
Published: July 2002

This note describes laboratory equipment designed to make simultaneous and continuous measurements of magnetic and metallurgical properties of a steel specimen over a large temperature range. Details are given of the associated electronics, including a rugged and very sensitive system to replace conventional dilatometry techniques. The application of the electronic systems to a noncontact probe to make similar measurements is mentioned.
A note on Unsworth's voltage-to-frequency converter
Authors: P Y Ho  , A R G Lang
Published: July 2002

A low cost, voltage-to-frequency converter was examined. Measurements, made on a batch of 31 units, showed a linearity and long term stability of 0.3%, and a temperature coefficient of 0.05% K-1. The converters proved very satisfactory for field measurements requiring an accuracy of 1%.
Infrared spectroscopy of adsorbed layers. II. Investigation of calorimetric infrared spectroscopy
Authors: H Gentsch  , J C Snaith
Published: July 2002

For Pt.I see ibid., vol.5, no.1 28. Calorimetric detection of absorbed radiation was used to measure spectra on gold and nickel films. Detector calorimeters were prepared from thin mica wafers bearing evaporated metal film thermocouples. Initial tests with microgram deposits of polystyrene on gold films indicate that absorptions of a few per cent are readily measured. Spectra were obtained for the nickel-carbon monoxide system comparable to data in the literature, confirming the suitability of the technique for measurements on adsorbed layers on metal films.
A miniature conifuge
Authors: R Poynting
Published: July 2002

A new version of an established aerosol sampling instrument is described. As in previous models, analysis of the sample is simplified by size separation of the collected particles. The miniature conifuge is self-aspirated and being battery operated and less than half the previous size, is completely portable. The instrument is constructed of stainless steel and is mounted directly on to the driving motor. It will sample unit density particles of diameters between 1 and 8 mu m and has been successfully used with particles of density up to 10 g cm-3. Wind speeds of up to 5 m s-1 have no significant effect on its sampling rate and it may be operated either upright or horizontally.
Parallel plate analyser with second order focusing property
Authors: W Schmitz  , W Mehlhorn
Published: July 2002

The optical properties are studied of three different parallel plate analysers using point sources, the usual pi /4 analyser with first order focusing and two versions of the pi /6 analyser with second order focusing. It is shown that the ratio of the transmission to the resolution of a modified pi /6 analyser, constructed in a 2 pi geometry, is superior to all other electrostatic analysers having a 2 pi geometry. Because parallel plate analysers with 2 pi geometry have the disadvantage of large ring detectors, sector shaped analysers with Delta phi <<2 pi , requiring only commercially available particle detectors, have also been investigated. The modified pi /6 analyser is also superior to the other parallel plate analysers.
Interferometry using a laser as radiation source, amplifier and detector
Authors: C B Wheeler  , S J Fielding
Published: July 2002

The photon induced current changes in a DC laser produced by optical feedback from an external cavity are shown to be a convenient means of monitoring interference in the laser interferometer. Experiments are carried out using a helium-neon laser operated at 0.6328 and 3.39 mu m wavelengths with variation in path length of the external cavity produced by piezoelectric movement of the external mirror. The frequency response of the voltage fringes appearing across the laser tube is shown to be somewhat less than that of the conventional optical fringes; however in the present case fringing frequencies of 500 kHz were readily observed. Closer investigation using very narrow optical fringes showed that the frequency response of the voltage fringes was determined by their 4 mu s decay time. This technique could be a great asset to laser interferometry in the infrared where radiation detectors are expensive and of low sensitivity.
A focusing monochromator for producing a very narrow band of X-ray wavelengths
Authors: J Cermak  , M Cernansky
Published: July 2002

A monochromator is described that produces a very narrow band of X-ray wavelengths-only about one-fifth of the width of the spectral K alpha1line. It makes use of high-angle reflections ( theta >70 degrees ) from a quartz crystal. With it, extremely accurate measurement of line profiles is possible. An assessment of its performance is given.
Ion beam systems for surface analysis
Authors: R E Hurley
Published: July 2002

Ion beam systems and their component parts used for analysis of solid surfaces are reviewed. The energy range under consideration for the primary beam system is of the order of a few keV to several hundred keV with ion currents up to 1 mA. Ion production, acceleration and focusing, analysis, beam handling and detection facilities are discussed together with some examples of complete systems.
A laser interferometric differential refractometer for detection of chromatographic effluent and measurement of volume elasticity of liquids
Authors: H F Hazebroek
Published: July 2002

A recording liquid interferometer with a sensing volume of only 4 mu l and a lower detection limit of refractive index of less than 2*10-7 has been developed using the narrow beam of a small helium-neon gas laser. The instrument was originally designed for the detection of liquid chromatographic effluents in small-diameter packed capillary columns. It is suitable for use at high liquid pressures (e.g. 50 kg cm-2), as in the study of volume elasticity, and probably also as a detector in supercritical fluid-phase chromatography, using a separation technique recently developed in our laboratory. A special and more versatile phase-to-voltage converter was devised to record the optical phase shift in the interferometer. The instrument and some experimental results obtained with it are described.
Optimum coupling of a microtron accelerator cavity in the case of variable electron beam loading
Authors: H W Haag
Published: July 2002

A waveguide section beyond cut-off, having variable length and immediately preceding the cavity resonator of a microtron, is used as a variable coupling device in order to match the cavity resonator to the waveguide transmission line in the case of variable electron beam loading of the accelerator cavity. The condition for critical coupling of the cavity resonator can be experimentally found by determining the minimum in the measured curve of the cavity reflection coefficient as a function of the cut-off length, and the magnitude of the cavity peak voltage can be estimated from the measured value of the minimum reflection coefficient for any value of the electron beam loading.
Field ionization mass spectrometry
Authors: A J B Robertson
Published: July 2002

Field ionization and field desorption are described and distinguished. Field ion and field desorption emitters of various types are available, and activation processes for these emitters have been devised. Ion sources and mass spectrometers for field ionization, and the mass spectra produced, are discussed. The investigation of surfaces and surface processes by field ionization mass spectrometry is considered, and the importance of chemical reactions on the emitter surface is emphasized. Field ionization can be used to investigate the kinetics and mechanisms of ionic dissociation reactions. The uses of field ionization mass spectra for analytical and structural investigations are briefly summarized.
The tungsten filament gun in the scanning electron microscope
Authors: C W Oatley
Published: July 2002

The characteristics of electron guns with tungsten filaments are investigated in some detail, with particular reference to their use in electron probe instruments, and an improved method of measuring brightness is described. Consideration is given to the conditions that must be fulfilled if optimum performance is to be obtained and it is shown that current densities as high as 10 A cm-2 can be drawn from the tip of the filament without exceeding a total gun current of 1 mA.
An infrared sensitive stopped-flow apparatus (for studying fast chemical reactions)
Authors: S E Brady  , J P Maher  , J Bromfield  , K Stewart  , M Ford
Published: July 2002

A Perkin-Elmer 237 infrared spectrophotometer has been modified to enable stopped-flow kinetic measurements to be made. The machine has a single-beam system, with the radiation chopped at 2 kHz; the detector is a liquid nitrogen cooled InSb photoconductive device; a new form of sampling circuit associated with this detector is described. A new form of 'diaphragm syringe' has been developed for the fluid handling system. The machine is sensitive from 4000 cm-1to 1800 cm-1with a signal to noise level less than 0.3%; kinetics of reactions may be studied with half lives ranging from ca. 10 ms to 10 s; it is purged of CO2and H2O and may be thermostated between 10 degrees C and 40 degrees C. The apparatus is being applied to the study of the reactions of various organometallic and transition metal complexes containing ligands with infrared absorptions in the region of 2000 cm-1.
Partitions with parts in a finite set
Authors: Nathanson Melvyn
Published: July 2002

LetAAbe a nonempty finite set of relatively prime positive integers, and letpA(n)p_A(n)denote the number of partitions ofnnwith parts inAA. An elementary arithmetic argument is used to prove the asymptotic formula\[<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="p Subscript upper A Baseline left-parenthesis n right-parenthesis equals left-parenthesis StartFraction 1 Over product Underscript a element-of upper A Endscripts a EndFraction right-parenthesis StartFraction n Superscript k minus 1 Baseline Over left-parenthesis k minus 1 right-parenthesis factorial EndFraction plus upper O left-parenthesis n Superscript k minus 2 Baseline right-parenthesis period">pA(n)=(1∏a∈Aa)nk−1(k−1)!+O(nk−2).p_A(n) = \left (\frac {1}{\prod _{a\in A}a}\right ) \frac {n^{k-1}}{(k-1)!} + O\left ( n^{k-2}\right ).\]
Non-isomorphism of 𝐿_{𝑝}-spaces associated with finite and infinite von Neumann algebras
Authors: Sukochev F.
Published: July 2002

If

(

M

1

,

τ

1

)

(M_{1},\tau _{1})

is a finite von Neumann algebra and if

(

M

2

,

τ

2

)

(M_{2},\tau _{2})

is an infinite (semifinite) von Neumann algebra, then

L

p

(

M

1

,

τ

1

)

L_{p}(M_{1},\tau _{1})

and

L

p

(

M

2

,

τ

2

)

L_{p}(M_{2},\tau _{2})

are non-isomorphic for all

p
∈
(
1
,
∞
)
,
p
≠
2

p\in (1,\infty ), p\neq 2

.
The supremum of the difference between the big and little finitistic dimensions is infinite
Authors: Smalø Sverre
Published: July 2002

For each natural number

n
n

, an example of a finite dimensional algebra

Λ
n

\Lambda _n

is given, which has left little finitistic dimension equal to 1 and left big finitistic dimension equal to

n
n

.
The space of invariant functions on a finite Lie algebra
Authors: Lehrer G.
Published: July 2002

We show that the operations of Fourier transform and duality on the space of adjoint-invariant functions on a finite Lie algebra commute with each other. This result is applied to give formulae for the Fourier transform of a “Brauer function”—i.e. one whose value at

X
X

depends only on the semisimple part

X
s

X_s

of

X
X

and for the dual of the convolution of any function with the Steinberg function. Geometric applications include the evaluation of the characters of the Springer representations of Weyl groups and the study of the equivariant cohomology of local systems on

G

/

T

G/T

, where

T
T

is a maximal torus of the underlying reductive group

G
G

.
Cylindric Partitions
Authors: Gessel Ira , Krattenthaler C.
Published: July 2002

A new object is introduced into the theory of partitions that generalizes plane partitions: cylindric partitions. We obtain the generating function for cylindric partitions of a given shape that satisfy certain row bounds as a sum of determinants of

q
q

-binomial coefficients. In some special cases these determinants can be evaluated. Extending an idea of Burge (J. Combin. Theory Ser. A 63 (1993), 210–222), we count cylindric partitions in two different ways to obtain several known and new summation and transformation formulas for basic hypergeometric series for the affine root system

A
~

r

\widetilde A_{r}

. In particular, we provide new and elementary proofs for two

A
~

r

\widetilde A_{r}

basic hypergeometric summation formulas of Milne (Discrete Math. 99 (1992), 199–246).
Asymptotic height optimization for topical IFS, Tetris heaps, and the finiteness conjecture
Authors: Bousch Thierry , Mairesse Jean
Published: July 2002

Given an Iterated Function System (IFS) of topical maps verifying some conditions, we prove that the asymptotic height optimization problems are equivalent to finding the extrema of a continuous functional, the average height, on some compact space of measures. We give general results to determine these extrema, and then apply them to two concrete problems. First, we give a new proof of the theorem that the densest heaps of two Tetris pieces are sturmian. Second, we construct an explicit counterexample to the Lagarias-Wang finiteness conjecture for the joint spectral radius of a set of matrices.

Résumé. Etant donné un système itéré de fonctions (IFS) topicales, vérifiant certaines conditions, nous montrons que les questions d’optimisation asymptotique de la hauteur sont équivalentes à la recherche des extrema d’une fonctionnelle continue, la hauteur moyenne, sur un certain espace compact de mesures. Nous présentons des résultats généraux permettant de déterminer ces extrema, puis appliquons ces méthodes à deux problèmes concrets. Premièrement, nous redémontrons que les empilements les plus denses de deux pièces de Tetris sont sturmiens. Deuxièmement, nous construisons un contre-exemple effectif à la conjecture de finitude de Lagarias et Wang sur le rayon spectral joint d’un ensemble de matrices.
Bott’s formula and enumerative geometry
Authors: Ellingsrud Geir , Strømme Stein
Published: July 2002

We outline a strategy for computing intersection numbers on smooth varieties with torus actions using a residue formula of Bott. As an example, Gromov-Witten numbers of twisted cubic and elliptic quartic curves on some general complete intersection in projective space are computed. The results are consistent with predictions made from mirror symmetry computations. We also compute degrees of some loci in the linear system of plane curves of degrees less than 10, like those corresponding to sums of powers of linear forms, and curves carrying inscribed polygons.
Contracting modules and standard monomial theory for symmetrizable Kac-Moody algebras
Authors: Littelmann Peter
Published: July 2002

The aim of this article is to attach to the set of L-S paths of type

λ
\lambda

in a canonical way a basis of the corresponding representation

V
(
λ
)

V(\lambda )

. This basis has some nice algebraic-geometric properties. For example, it is compatible with restrictions to Schubert varieties and has the “standard monomial property”. As a consequence we get new simple proofs of the normality of Schubert varieties, the surjectivity of the multiplication map or the restriction map for sections of a line bundle on Schubert varieties. Other applications to the defining ideal of Schubert varieties and associated Groebner basis will be discussed in a forthcoming paper.
Periods of automorphic forms
Authors: Jacquet Hervé , Lapid Erez , Rogawski Jonathan
Published: July 2002

Let

E

/

F

E/F

be a quadratic extension of number fields and

G
=

Res

E

/

F

⁡
H

G= \operatorname {Res}_{E/F}H

, where

H
H

is a reductive group over

F
F

. We define the integral (in general, non-convergent) of an automorphic form on

G
G

over

H
(
F
)
∖
H
(

A

)
1

H(F)\backslash H(\mathbb A)^1

via regularization. This regularized integral is used to derive a formula for the integral over

H
(
F
)
∖
H
(

A

)
1

H(F)\backslash H(\mathbb A)^1

of a truncated Eisenstein series on

G
G

. More explicit results are obtained in the case

H
=
G
L
(
n
)

H=GL(n)

. These results will find applications in the expansion of the spectral side of the relative trace formula.
Minimal varieties of algebras of exponential growth
Authors: Giambruno A. , Zaicev M.
Published: July 2002

The exponent of a variety of algebras over a field of characteristic zero has been recently proved to be an integer. Through this scale we can now classify all minimal varieties of a given exponent and of finite basic rank. As a consequence we describe the corresponding T-ideals of the free algebra, and we compute the asymptotics of the related codimension sequences. We then verify in this setting some known conjectures.
Operator 𝐾-theory for groups which act properly and isometrically on Hilbert space
Authors: Higson Nigel , Kasparov Gennadi
Published: July 2002

Let

G
G

be a countable discrete group which acts isometrically and metrically properly on an infinite-dimensional Euclidean space. We calculate the

K
K

-theory groups of the

C

∗

C^{*}

-algebras

C

max

∗

(
G
)

C^{*}_{\max }(G)

and

C

red

∗

(
G
)

C^{*}_{ \smash {\text {red}}}(G)

. Our result is in accordance with the Baum-Connes conjecture.
A RAPID algorithm for sequence database comparisons: application to the identification of vector contamination in the EMBL databases.
Authors: Miller C , Gurd J , Brass A
Published: July 2002

MOTIVATION: Word-matching algorithms such as BLAST are routinely used for sequence comparison. These algorithms typically use areas of matching words to seed alignments which are then used to assess the degree of sequence similarity. In this paper, we show that by formally separating the word-matching and sequence-alignment process, and using information about word frequencies to generate alignments and similarity scores, we can create a new sequence-comparison algorithm which is both fast and sensitive. The formal split between word searching and alignment allows users to select an appropriate alignment method without affecting the underlying similarity search. The algorithm has been used to develop software for identifying entries in DNA sequence databases which are contaminated with vector sequence. RESULTS: We present three algorithms, RAPID, PHAT and SPLAT, which together allow vector contaminations to be found and assessed extremely rapidly. RAPID is a word search algorithm which uses probabilities to modify the significance attached to different words; PHAT and SPLAT are alignment algorithms. An initial implementation has been shown to be approximately an order of magnitude faster than BLAST. The formal split between word searching and alignment not only offers considerable gains in performance, but also allows alignment generation to be viewed as a user interface problem, allowing the most useful output method to be selected without affecting the underlying similarity search. Receiver Operator Characteristic (ROC) analysis of an artificial test set allows the optimal score threshold for identifying vector contamination to be determined. ROC curves were also used to determine the optimum word size (nine) for finding vector contamination. An analysis of the entire expressed sequence tag (EST) subset of EMBL found a contamination rate of 0.27%. A more detailed analysis of the 50 000 ESTs in est10.dat (an EST subset of EMBL) finds an error rate of 0.86%, principally due to two large-scale projects. AVAILABILITY: A Web page for the software exists at http://bioinf.man.ac.uk/rapid, or it can be downloaded from ftp://ftp.bioinf.man.ac.uk/RAPID CONTACT: crispin@cs.man.ac.uk
Identification of novel families of membrane proteins from the

model plant Arabidopsis thaliana
Authors: Ward John M.
Published: July 2002

Motivation: The completion of the Arabidopsis genome offers the first opportunity to analyze all of the membrane protein sequences of a plant. The majority of integral membrane proteins including transporters, channels, and pumps contain hydrophobic \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({\alpha}\) \end{document}-helices and can be selected based on TransMembrane Spanning (TMS) domain prediction. By clustering the predicted membrane proteins based on sequence, it is possible to sort the membrane proteins into families of known function, based on experimental evidence or homology, or unknown function. This provides a way to identify target sequences for future functional analysis.

Results: An automated approach was used to select potential membrane protein sequences from the set of all predicted proteins and cluster the sequences into related families. The recently completed sequence of Arabidopsis thaliana , a model plant, was analyzed. Of the 25470 predicted protein sequences 4589 (18%) were identified as containing two or more membrane spanning domains. The membrane protein sequences clustered into 628 distinct families containing 3208 sequences. Of these, 211 families (1764 sequences) either contained proteins of known function or showed homology to proteins of known function in other species. However, 417 families (1444 sequences) contained only sequences with no known function and no homology to proteins of known function. In addition, 1381 sequences did not cluster with any family and no function could be assigned to 1337 of these.

Availability: Results from the analysis of all proteins of A.thaliana , source code for the programs, and links to primary data are available at the following WWW site: http://www.cbs.umn.edu/arabidopsis

Contact: jward@tc.umn.edu