bluuebunny/crossref_metadata_2025 huggingface dataset:
Chip Topography for Ductile-Regime Machining of Germanium
Authors: Blackley W. S. , Scattergood R. O.
Published: April 2008

Ductile-regime response during the diamond turning of brittle germanium crystals is evident from the damage-free surfaces obtained. The nature of the ductile-regime processes cannot be determined by examination of the final machined surface itself. Machining chips were characterized using scanning electron microscopy. The chip topography provides insight into the ductile-to-brittle transition that occurs along the tool nose. A detailed examinaiton of the chips provides an independent estimate of the critical cutting depth for the transition.
Stability of Turning Processes with Actively Controlled Linear Motor Feed Drives
Authors: Alter D. M. , Tsao Tsu-Chin
Published: April 2008

Using linear motors as machine tool feed drives has the potential of enhancing machining performance by eliminating gear related mechanical problems and increasing speed and accuracy, but introduces a stability concern due to a strong dynamic feedback interaction between the machining process and the drives. This paper investigates the stability aspect of this dynamic interaction and the use of active damping to achieve machining stability in turning. Various necessary and sufficient conditions for stability at all cutting speeds are derived, and have been used to study the effect of damping and gear reduction in system stability. The interaction of the cutting process with the tool servo loop is seen to have significant instability consequences in systems with small drive gear reductions. Both theoretical stability and experimental cutting results are presented for PD and PID regulation. Results show that actively controlled linear motors can provide sufficient dynamic stiffness for stable turning operation.
Development of a Rational Basis for Design of Advanced Brushing Tools
Authors: Stango R. J. , Shia Chih-Yuan , Henderson J. A.
Published: April 2008

In this paper, issues that are relevant to the design of brushing tool systems are examined and discussed. First, a general framework for brush design is presented that can provide a basis for the synthesis of advanced brushing tools, that is, brushes having predetermined performance characteristics and service life. The proposed general design strategy utilizes an iterative procedure that is based upon applicative considerations, performance requirements, and geometric/materials issues that are peculiar to a specific brush system. Next, an analytical procedure is developed that can facilitate the design of brush stiffness and brush compliance properties. This aspect of the design problem is formulated on the basis of nondimensional parameters that are associated with a quasi-static, large-displacement mechanics analysis for brush/workpart interaction. Numerical examples are presented illustrating the use of this approach for the design of brushing tools that possess unique stiffness/compliance functions. Implications that this design capability can have on the development of advanced brushing processes, as well as product development and brush manufacture, are briefly discussed.
An Analytic Mechanistic Cutting Force Model for Milling Operations: A Theory and Methodology
Authors: Bayoumi A. E. , Yucesan G. , Kendall L. A.
Published: April 2008

An analytic mechanistic force model has been developed to simulate the cutting forces in milling operations. Steps taken to develop the model consisted of cutter surface representation, chip removal kinematics, cutter force definition, and determination of the integration limits from the force equations. The cutter surface is represented by ruled surfaces that are a function of cutter geometry. Cutter forces are determined by integrating the pressure and friction loads acting on these cutter surfaces. The integration limits that are functions of the rotation angle are established. Several techniques dealing with the process parameters are discussed. The model uses process dependent parameters representing normal pressure, chip flow friction, and chip flow kinematics. The paper discusses how process data can be used to establish values for the parameters.
Lumped Multitorch Control of Welding During Production
Authors: Doumanidis C. C.
Published: April 2008

In this article, multiple lumped thermomechanical characteristics of the welding process are regulated by modulation of the welding conditions in real time through feedback control. The controller design is based on three dynamic welding models: a lumped analytical formulation of the weld bead geometry, a numerical simulation of the distributed thermal and phase field, and an experimental linearized model with nonstationary parameters. To account for nonlinearity and thermal drift effects, the weld parameters are identified in-process by the multivariable adaptive controller through surface temperature measurements with an infared pyrometer. Multiple heat inputs, implemented by a single reciprocating, timeshared torch, are employed for simultaneous decoupled control of thermal attributes, such as weld bead size, heat affected zone and cooling rate. The performance of closed-loop controlled welding is tested in setpoint changes and unexpected process disturbances for various welding techniques, materials and geometric arrangements, including new experiments of stainless pipe seam GTA welding.
Neural Network Designs for Partially Known Dynamic Systems
Authors: Mistry S. I. , Nair S. S.
Published: April 2008

Algorithms are investigated for system identification and control using neural networks and validated using on-line hardware implementation. Such algorithms require very little knowledge about the system which, together with their capability of learning, make them attractive for the modeling and control of nonlinear partially known dynamic systems. An implementation architecture for neural dynamic back propagation suitable for application to other machine tools and manufacturing processes, and a network training scheme with more general features are proposed.
Design Concept of an Integrated Vision System for Cost-effective Part-Presentation
Authors: Lee Kok-Meng
Published: April 2008

The cost of feeding parts to a robot for either machine loading or for assembly has been recognized as excessively expensive. The lack of a cost-effective generic part-presenter has prevented the flexibility of the overall manufacturing automation to be fully exploited. For this reason, the design concept of an integrated microprocessor-controlled vision system based on retroreflective vision sensing has been developed at the Material Handling Research Center in Atlanta. Where the orientation of a part can be characterized by its silhouette, outline, or structured “engineering landmarks,” the concept of using retroreflective materials in vision-guided part-presentation system has been proven to have significant potential for improving reliability, reducing computation, and lowering implementation cost. This paper presents optic design concepts for collocated illumination for cost effective part-presentation. The design concepts are illustrated with practical applications and experimental results. The uniformity of the image irradiance across the sensor surface, in general, depends on several factors such as the intensity distribution of the light source, the reflectance characteristics of the object and background, and the geometrical relationship between the imaging sensor, the illumination source, and the target. The trust of this paper focuses on the analytical model which characterizes the influences of these factors for optic design of retro-reflection. This engineering basis is not only necessary for developing practical yet potentially cost-effective optic design concepts, but also provides a useful tool for performance prediction to drive the design for vision-guided part-presentation.
Weldment Evaluation of High Pressure Steam Rotors
Authors: Wojnowski D. , Kasapbasioglu H. , Indacochea J. E. , Galanes G. W. , Spry T. D.
Published: April 2008

Life extension of high pressure and intermediate pressure rotors by weld repair is a viable alternative considering the latest developments. Our objective is to select a filler wire that will produce a weld with mechanical properties compatible with those of the rotor material. Three filler metals, (CrMoV, 12 percent Cr and 5 percent Cr) were used in the investigation. Multipass submerged arc groove welds were produced, post weld heat treated at 677° C (1250°F), and submitted to a series of mechanical tests at room and elevated temperatures. The tests samples were machined parallel to the weld direction (longitudinal), which included only weld metal, and perpendicular to the weld metal (crossweld) so that the test sample includes portions of the weld metal, heat-affected zone (HAZ) and base metal. A limited metallurgical evaluation was also performed. The room temperature tensile properties of the CrMoV and 12 percent Cr crossweld samples exceeded those of the rotor metal, but the tensile properties of the 5 percent Cr crosswelds did not match those of the rotor metal. The 12 percent Cr crossweld samples failed in the weld metal during hot tensile and stress rupture testing, and these failures were attributed to slag entrapment; yet the yield and tensile strengths of these weldments just exceeded those of the rotor base metal. The CrMoV crossweld specimens performed the best at the high temperature testing; the failure for the hot tensile specimens occurred in the weld metal and the values matched those of the all weld metal (longitudinal) specimens which greatly exceeded the rotor base metal strengths. The crossweld stress rupture samples failed outside the weld metal at the heat affected zone (HAZ) near the unaffected base metal with rupture lives lower than the rotor base metal. Microhardness evaluations in the CrMoV and 12 percent Cr cross weldments about the HAZ/base metal boundary identify a soft region at this location. The mechanical properties of the 5 percent weldment were in general inferior to the rotor base metal. The weld metal’s hardness was lower than the rotor base metal given its superior Charpy energy values; however, the creep rupture strength was inferior.
Delamination-Free Drilling of Composite Laminates
Authors: Jain S. , Yang D. C. H.
Published: April 2008

Composite laminates in significant numbers are rendered unacceptable due to delamination that occurs during the drilling operation. Thrust generated during the drilling operation is identified as responsible for delamination. Expressions developed for critical thrusts and critical feed rates, by modeling the delamination zone as an elliptical plate in unidirectional laminates, appear to be fairly accurate. It has been demonstrated that the critical thrusts and feed rates obtained for unidirectional laminates can be conservatively used for multi-directional laminates. With regard to the tool geometry, the chisel edge width appears to be the single most important factor contributing to the thrust force and hence delamination. A diamond-impregnated tubular drill tool was designed and tested. This tool resulted in a much smaller thrust and much better hole quality as compared with the standard twist drills.
Multi-Laser Displacement Sensor Used in Accurate Digitizing Technique
Authors: Smith K. B. , Zheng Y. F.
Published: April 2008

This paper presents a new technique for digitizing an unknown sculptured surface using a new multi-Laser Displacement Sensor (LDS) and an articulated Coordinate Measuring Machine (CMM). The new multi-LDS measures the tangents, curvatures, and displacement of the surface. This local information is utilized in the technique to extrapolate the surface position and normal vector at the next location to be digitized. In addition, this paper derives the relationship between the digitizing error parameters and the ratio of sampling arc length to the radius of maximum curvature. This technique is illustrated experimentally using a six degree-of-freedom PUMA robot and a Keyence LDS.
A Knowledge-Based Diagnostic Approach for the Launch of the Auto-Body Assembly Process
Authors: Ceglarek D. , Shi J. , Wu S. M.
Published: April 2008

This paper is the first attempt to implement a knowledge-based diagnostic approach for the auto-body assembly process launch. This approach enables quick detection and localization of assembly process faults based on in-line dimensional measurements. The proposed approach includes an auto-body assembly knowledge representation and a diagnostic reasoning mechanism. The knowledge representation is comprised of the product, tooling, process, and measurement representations in the form of hierarchical groups. The diagnostic reasoning performs fault diagnostic in three steps. First, an initial statistical analysis of measurement data is performed. Next, the Candidate Component and Candidate Station with the hypothetical fault are searched. Finally, the fault symptom is identified and the root cause is suggested. Two case studies are presented to demonstrate the implementation of the proposed method.
The Min-Max Load Criteria as a Measure of Machining Fixture Performance
Authors: DeMeter E. C.
Published: April 2008

Spherical-tipped locators and clamps are often used for the restraint of castings during machining. For structurally rigid castings, contact region deformation and micro-slippage are the predominant modes of workpiece displacement. In turn contact region deformation and micro-slippage are heavily influenced by contact region loading. This paper presents a linear model for predicting the impact of locator and clamp placement on workpiece displacement throughout a series of machining operations. It illustrates how the continuum of external loads exerted on a workpiece during machining can be bounded within a convex hull, and how the extreme points of this hull are used within the model. Finally it describes the simulation experiments which were used for model validation.
Forecasting Control of Waterborne Basecoat Viscosity
Authors: Fan Hua-Tzu , Hu S. Jack , Wu S. M.
Published: April 2008

Waterborne basecoat is gaining popularity in the automative industry. However, the viscosity of some waterborne basecoats may be unstable while circulating in the paint supply-and-storage system. This instability has caused significant problems in the paintability of the basecoats and the quality of the final finish. An original application of forecasting control is implemented to control the viscosity of certain waterborne basecoat. Both manual and automatic implementations of forecasting control result in significant improvement of process capability.
Influence of Feed Variation on Tool Wear When Milling Stainless Steel 17-4Ph
Authors: Balazinski M. , Ennajimi E.
Published: April 2008

This paper presents the results of experimental studies on the influence of feed variation on tool wear during face milling. Experimental results on milling Stainless Steel 17-4PH show that it is possible to increase tool life substantially with a proper variation of the cutting feed rate throughout the cutting process. Experiments clearly demonstrate this phenomenon and show a decrease of approximately 30 percent of the tool wear. Comparison between constant and variable feed processes is based on the constant volume of material removed in a given time span, therefore maintaining a constant process efficiency for both cases. This paper presents an explanation of this phenomenon by the influence of feed variation on the temperature distribution and on the crater axis position in the tool-chip interface.
Discordant Patterns of Genetic Variation at Two Chloroquine Resistance Loci in Worldwide Populations of the Malaria Parasite
Plasmodium falciparum
Authors: Mehlotra Rajeev K. , Mattera Gabriel , Bockarie Moses J. , Maguire Jason D. , Baird J. Kevin , Sharma Yagya D. , Alifrangis Michael , Dorsey Grant , Rosenthal Philip J. , Fryauff David J. , Kazura James W. , Stoneking Mark , Zimmerman Peter A.
Published: April 2008

Mutations in the chloroquine resistance (CQR) transporter gene of
Plasmodium falciparum
(Pf
crt
; chromosome 7) play a key role in CQR, while mutations in the multidrug resistance gene (Pf
mdr1
; chromosome 5) play a significant role in the parasite's resistance to a variety of antimalarials and also modulate CQR. To compare patterns of genetic variation at Pf
crt
and Pf
mdr1
loci, we investigated 460 blood samples from
P. falciparum
-infected patients from four Asian, three African, and three South American countries, analyzing microsatellite (MS) loci flanking Pf
crt
(five loci [∼40 kb]) and Pf
mdr1
(either two loci [∼5 kb] or four loci [∼10 kb]). CQR Pf
mdr1
allele-associated MS haplotypes showed considerably higher genetic diversity and higher levels of subdivision than CQR Pf
crt
allele-associated MS haplotypes in both Asian and African parasite populations. However, both Pf
crt
and Pf
mdr1
MS haplotypes showed similar levels of low diversity in South American parasite populations. Median-joining network analyses showed that the Pf
crt
MS haplotypes correlated well with geography and CQR Pf
crt
alleles, whereas there was no distinct Pf
mdr1
MS haplotype that correlated with geography and/or CQR Pf
mdr1
alleles. Furthermore, multiple independent origins of CQR Pf
mdr1
alleles in Asia and Africa were inferred. These results suggest that variation at Pf
crt
and Pf
mdr1
loci in both Asian and African parasite populations is generated and/or maintained via substantially different mechanisms. Since Pf
mdr1
mutations may be associated with resistance to artemisinin combination therapies that are replacing CQ, particularly in Africa, it is important to determine if, and how, the genetic characteristics of this locus change over time.
In Vitro Susceptibility of Isolates of
Francisella tularensis
Types A and B from North America
Authors: Urich Sandra K. , Petersen Jeannine M.
Published: April 2008

Due to concern that
Francisella tularensis
, the causative agent of tularemia, may be used as a bioterrorist weapon, the Clinical and Laboratory Standards Institute recently provided a susceptibility testing method with breakpoints. Here, 169 isolates (92 type A and 77 type B) from North America were tested against seven antimicrobial agents (streptomycin, gentamicin, tetracycline, doxycycline, ciprofloxacin, levofloxacin, and chloramphenicol) used for the treatment of tularemia. The MICs for all of the isolates fell within the susceptible range. In addition, all isolates had MICs for erythromycin of 0.5 to 4 μg/ml, in contrast to an MIC of >256 μg/ml for the common laboratory strain LVS (live vaccine strain).
Role for Myosin II in Regulating Positioning ofSalmonella-Containing Vacuoles and Intracellular Replication
Authors: Wasylnka Julie A. , Bakowski Malina A. , Szeto Jason , Ohlson Maikke B. , Trimble William S. , Miller Samuel I. , Brumell John H.
Published: April 2008

Salmonella entericaserovar Typhimurium grows within host cells in a permissive compartment termed theSalmonella-containing vacuole (SCV). These bacteria use two distinct type III secretion systems (T3SS) to deliver virulence proteins (effectors) into cells. Effectors secreted by theSalmonellapathogenicity island 1 (SPI-1)-encoded T3SS mediate invasion and early SCV maturation steps, while those secreted by the SPI-2 T3SS affect the SCV at later stages postinfection. Some SPI-2 effectors modulate microtubule motor activity on the SCV. Here, we show that the actin-based motor myosin II also affects SCV dynamics during infection. Following invasion, myosin II is required for SCV positioning near the nucleus of host cells. Later, myosin II counteracts the activities of the SPI-2 effectors PipB2 and SseJ to maintain SCV positioning and stability, respectively. Myosin II activity was required for maximal bacterial growth in macrophages. Rho kinase activity was required for SCV positioning. The effector SopB, a known activator of Rho GTPases, was found to be required for SCV positioning, and transfection of cells with SopB was sufficient to induce myosin II phosphorylation. These studies reveal a novel role for myosin II in controlling SCV dynamics during infection and suggest that SopB activates myosin II.
The Surface-Exposed Carboxyl Region of
Mycoplasma pneumoniae
Elongation Factor Tu Interacts with Fibronectin
Authors: Balasubramanian Sowmya , Kannan T. R. , Baseman Joel B.
Published: April 2008

Mycoplasma pneumoniae
is a bacterial pathogen of the human respiratory tract that causes a wide range of airway diseases as well as extrapulmonary symptoms. It possesses a distinct, differentiated terminal structure, termed the attachment organelle, that mediates adherence to the host respiratory epithelium. Previously, we reported that surface-associated
M. pneumoniae
elongation factor Tu (EF-Tu, also called MPN665) serves as a fibronectin (Fn)-binding protein, facilitating interactions between mycoplasmas and extracellular matrix. In the present study, we determined that binding of
M. pneumoniae
EF-Tu to Fn is primarily mediated by the EF-Tu carboxyl region. A 179-amino-acid region spanning the carboxyl terminus (designated EC; amino acids 192 to 394) binds Fn in a dose-dependent manner. Further analysis of carboxyl constructs (ED3 and ED4) and their deletion truncations (ED3.1, ED3.2, and ED4.1) revealed that the carboxyl region possessed two distinct sites with different Fn-binding efficiencies. Immunogold electron microscopy using antibodies raised against recombinant ED3 and ED4 demonstrated the surface accessibility of the EF-Tu carboxyl region. Competitive binding assays using intact radiolabeled mycoplasmas and purified recombinant ED3 and ED4 proteins, along with antibody blocking assays, reinforced the role of the surface-exposed EF-Tu carboxyl region in Fn binding. Alkali and high-salt treatment of mycoplasma membranes and Triton X-114-partitioned mycoplasma fractions confirmed the stable association of EF-Tu within the mycoplasma membrane. These observations highlight the unique, multifaceted, and unpredictable role of the classically defined cytoplasmic protein EF-Tu relative to cellular function, compartmentalization, and topography.
The Signal Recognition Particle Pathway Is Required for Virulence in
Streptococcus pyogenes
Authors: Rosch Jason W. , Vega Luis Alberto , Beyer John M. , Lin Ada , Caparon Michael G.
Published: April 2008

The signal recognition particle (SRP) pathway is a universally conserved pathway for targeting polypeptides for secretion via the cotranslational pathway. In particular, the SRP pathway is thought to be the main mechanism for targeting polypeptides in gram-positive bacteria, including a number of important human pathogens. Though widely considered to be an essential cellular component, recent advances have indicated this pathway may be dispensable in gram-positive bacteria of the genus
Streptococcus
under in vitro conditions. However, its importance for the pathogenesis of streptococcal disease is unknown. In this study, we investigated the importance of the SRP pathway for virulence factor secretion in the human pathogen
Streptococcus pyogenes
. While the SRP pathway was not found to be essential for viability in vitro, SRP mutants demonstrated a medium-specific growth defect that could be rescued by the addition of glucose. We also observed that a distinct subset of virulence factors were dependent upon the SRP pathway for secretion, whereas others were completely independent of this pathway. Significantly, deletion of the SRP pathway resulted in mutants that were highly attenuated in both a zebrafish model of necrotic myositis and a murine subcutaneous ulcer model, highlighting the importance of this pathway in vivo. These studies emphasize the importance of the SRP pathway for the in vivo survival and pathogenesis of
S. pyogenes
.
Nasal Vaccination with the 40-Kilodalton Outer Membrane Protein ofPorphyromonas gingivalisand a Nontoxic Chimeric Enterotoxin Adjuvant Induces Long-Term Protective Immunity with Reduced Levels of Immunoglobulin E Antibodies
Authors: Momoi Fumiki , Hashizume Tomomi , Kurita-Ochiai Tomoko , Yuki Yoshikazu , Kiyono Hiroshi , Yamamoto Masafumi
Published: April 2008

In this study, we demonstrated that the 40-kDa outer membrane protein ofPorphyromonas gingivalis(40-kDa OMP) nasally administered with a nontoxic chimeric adjuvant that combines the A subunit of mutant cholera toxin E112K with the pentameric B subunit of heat-labile enterotoxin from enterotoxigenicEscherichia coli(mCTA/LTB) elicited a long-term protective immune response. Immunization with the 40-kDa OMP and mCTA/LTB induced high levels of 40-kDa-OMP-specific immunoglobulin G (IgG) and IgA antibodies (Abs) in sera and elicited a significant IgA anti-40-kDa OMP Ab response in saliva. These Ab responses were maintained for at least 1 year after the immunization. Although using adjuvant mCTA/LTB gave Ab responses in the saliva comparable to those obtained using native cholera toxin (nCT) as the adjuvant, the levels of total IgE and 40-kDa-OMP-specific IgE Abs as well as interleukin-4 levels induced by the immunization with mCTA/LTB were lower than those induced by the immunization with nCT. Importantly, IgG Abs generated by nasal immunization with the 40-kDa OMP plus mCTA/LTB inhibited the coaggregation and hemagglutinin activities ofP. gingivalis. Furthermore, the mice given nasal 40-kDa OMP plus mCTA/LTB showed a significant reduction of alveolar bone loss caused by oral infection withP. gingivaliseven 1 year after the immunization compared to the loss in unimmunized mice. Because mCTA/LTB is nontoxic, nasally administered 40-kDa OMP together with mCTA/LTB should be an effective and safe mucosal vaccine againstP. gingivalisinfection in humans and may be an important tool for the prevention of chronic periodontitis.
Helicobacter hepaticus
Infection Promotes Colon Tumorigenesis in the BALB/c-
Rag2
−/−
Apc

Min
/+

Mouse
Authors: Nagamine Claude M. , Sohn Jane J. , Rickman Barry H. , Rogers Arlin B. , Fox James G. , Schauer David B.
Published: April 2008

Adenomatous polyposis coli (
APC
) mutations are linked to human and mouse colorectal cancers. The
Apc
multiple intestinal neoplasia (Min) mouse mutation causes adenomas to develop throughout the small and large intestines. The BALB-Min (C.B6-
Apc

Min
/+

) congenic strain was generated by backcrossing into BALB/c the
Apc

Min

allele from C57BL/6J-
Apc

Min
/+

mice. BALB-Min mice have a low tumor multiplicity (27.4 small intestine tumors/mouse) and a relatively long life span (>1 year) that makes them amenable to long-term studies. To investigate the interplay of the adaptive immune system and intestinal tumorigenesis, the immunodeficient compound mutant strain BALB-RagMin (C.Cg-
Rag2
−/−
Apc

Min
/+

) was generated. BALB-RagMin mice had a significant increase in tumors in the small, but not large, intestine relative to their BALB-Min counterparts (43.0 versus 24.0 tumors/mouse, respectively). The results suggest that the adaptive immune system plays a role in either the elimination or the equilibrium phase of cancer immunoediting in the small intestine in this model. We investigated the effect of the enterohepatic bacterial pathogen
Helicobacter hepaticus
on liver and intestine tumorigenesis in BALB-RagMin mice.
H. hepaticus
-infected BALB-RagMin mice developed moderate hepatitis, moderate typhlitis, and mild colitis. There were no differences in small intestine and cecal tumor multiplicity, regionality, or size relative to that in uninfected mice. However,
H. hepaticus
-infected BALB-RagMin mice had a significant increase in colon tumor incidence relative to uninfected BALB-RagMin mice (23.5% versus 1.7%, respectively). The data suggest that
H. hepaticus
, which is present in many research colonies, promotes colon tumorigenesis in the BALB-RagMin mouse and that it has the potential to confound colon tumorigenesis studies.
Effects of CO2 in interaction with temperature and soil fertility on the foliar phenology of alder, birch, and maple seedlings
Authors: Koike Takayoshi
Published: April 2008

The foliar phenology of potted 1-year-old seedlings of alder (Alnus hirsuta Turcz.), maple (Acer mono Maxim.), and birch (Betula platyphylla Sukatch. var. japonica Hara) was observed from May to September in eight growth environments: factorial combinations of temperatures (light:dark, 30:20 °C and 26:16 °C), CO2 level (70 and 36 Pa), and nutrient regime (high versus low levels of fertilization). Seedlings grown at high fertility always had more leaves, and under high CO2, shed leaves slightly later than seedlings grown at low fertility. Except for maple, production of newly formed shoots and leaves was accelerated by high CO2. In maple, high CO2 only increased the number of flushes of the leader shoot. Alder and birch accelerated sylleptic shoot and leaf production at high CO2 in fertile conditions. The production of new leaves by alder grown at high CO2 and low fertility was almost the same as that grown under normal CO2, at high fertility. At high CO2, the timing of winter bud formation of monopodial alder and maple was delayed, while that of sympodial birch was almost the same as at ambient CO2. Key words: foliar phenology, elevated atmospheric CO2 and temperature, monopodial versus sympodial growth, nutrient levels, winter bud formation, global change.
Effect of irrigation, fertilization, and artificial drought on basidioma production in a Norway spruce stand
Authors: Wiklund Karin , Nilsson Lars-Owe , Jacobsson Stig
Published: April 2008

A total of 63 mycorrhizal and 49 saprotrophic species was found in a 30-year-old Picea abies stand in southwestern Sweden. Nitrogen addition had an obvious negative effect; all mycorrhizal species ceased to produce basidiomata in the 4th year of supply. Nitrogen-free fertilization resulted in reduced basidioma number and dry mass production by about 50% compared with the control. An increase in basidioma number was observed as result of irrigation, whereas the dry mass production was unaffected compared with the control. No fructification occurred, however, when nutrients were added together with the water. Artificial drought resulted in reduced basidioma production. The 1st year of recovery from drought resulted in an increase in basidioma number and biomass by a factor of 5 and 9 respectively, compared with the control. Production of Cortinarius species, Lactarius theiogalus, and Russula emetica increased as a result of irrigation, while a decrease was observed in Boletus edulis that instead was favoured by earlier drought. The saprotrophic species were only to a minor extent affected by the treatments. It is concluded that increased N deposition would result in decreased basidioma production and species number of mycorrhizal species and that changed precipitation climate would result in another species composition of mycorrhizal basidiomata in coniferous forests. Key words: irrigation, mycorrhizal fungi, nitrogen, saprotrophic fungi, basidioma production, nitrogen-free fertilization (vitalization).
Ultrastructural observations on ascosporogenesis inCiboria betulae(Helotiales : Sclerotiniaceae)
Authors: Schumacher Trond K. , Kamaletdinova Fevzia I. , Vassilyev Andrey E.
Published: April 2008

The ultrastructure of ascospore ontogeny including spore delimitation and spore wall formation is examined in Ciboria betulae. A peripheral delimiting cisterna is derived from the ascus plasmalemma apparently by the self-assembly of subunits in the cytosol. The cisterna is discontinuous and delimits each of eight incipient ascospores in the ascus. The particular, verrucose ascospore ornamentation in C. betulae appears early during primary wall formation. The electron-lucent primary wall differentiates into an endospore of finely fibrillar texture and a two-layered, fibrillar epispore. The ultrastructural changes of ascus epiplasm, sporoplasm, and spore wall are described and compared with previous studies on Ascomycetes. Key words: ascosporogenesis, ascospore ontogeny, Ciboria betulae, ascospore wall differentiation.
The effects of physical damage on seed production in flowering plants of Saponaria officinalis
Authors: Lokker Cynthia , Cavers Paul B.
Published: April 2008

Individual flowering ramets in a large riverbank stand of Saponaria officinalis, bouncingbet, were subjected to three damage treatments at anthesis: removal of most flowers, removal of all leaves, and bending of the stem just below the inflorescence. All seeds were collected from ripened capsules of treated plants as well as from a group shaded by a canopy of Convolvulus sepium and from an untreated control group. Seeds from the defloration treatment were significantly heavier than those from the other treatments. In the control, bent stem, and shaded treatments the seed masses were distributed in a bimodal manner, with most seeds forming a normal distribution around a midpoint of 1.5–1.7 mg and a cohort of heavy seeds having a mean mass of 2.5 mg. This heavy cohort (mode) was missing from the defoliation treatment. Of the total variation in seed mass, 36% was among individuals, 54% was among inflorescences within individuals, and only 10% was within inflorescences. This suggests that resources are allocated differentially between capsules at different positions on the inflorescence but almost uniformly within the individual capsule. Key words: defoliation, defloration, bouncingbet, seed production, Saponaria officinalis.
Time course of anatomical changes to stem vascular tissues of alfalfa, Medicago sativa, from probing injury by the potato leafhopper, Empoasca fabae
Authors: Ecale Carol L. , Backus Elaine A.
Published: April 2008

We used a videomicrography technique to apply standard-duration pulses of leafhopper probing damage to alfalfa stems, or manually punctured stems with an implement resembling leafhopper stylets, to compare damage induction and chronicle the plant's anatomical responses over time. Plants were examined at 0.5, 1, 2, 4, and 8 days after probing. Leafhopper probing occurred primarily in phloem tissue: stylets damaged and deposited sheath saliva primarily in phloem. Between days 1 and 4, collapsed phloem cells and sheath saliva deposits were dissolved and removed as surviving cells adjacent to stylet pathways underwent enlargement and division. By day 8, phloem tissue assumed a near-normal appearance when viewed in cross section, although it is not known whether phloem functionality was restored. In contrast, xylem tissue suffered reduction in size, quantity, and total cross-sectional area of mature tracheary elements. These effects to vascular tissue may be responsible for all subsequent symptoms of hopperburn in alfalfa. Damage to phloem and xylem in mechanically punctured stems was slight and was similar for all time points. Key words: plant wound response, plant vascular development, phloem, xylem, hopperburn, insect feeding behaviour.
Relationships between Suspended Particulate Matter and Sinking Flux along a Trophic Gradient and Implications for the Fate of Planktonic Primary Production
Authors: Baines Stephen B. , Pace Michael L.
Published: April 2008

We measured water column variables and the sinking flux of C, N, P and pigments in 15 lakes which varied in algal biomass to determine (1) the relationship between sinking flux and suspended particulate concentrations, (2) if sinking rates of particles changed as a function of trophic status, and (3) the importance of sinking as a fate for phytoplankton production along a trophic gradient. Sinking flux was well predicted by metalimnetic algal pigment concentrations (chlorophyll + phaeopigments) and epilimnetic C:N ratios (R2 = 83–97%). Sinking rates of algal pigments were not significantly higher in lakes with higher chlorophyll concentrations. Predictions based on observed C sinking fluxes, water column chlorophyll, and an empirical relationship between primary production and chlorophyll concur with published observations in suggesting a slight negative relationship between production and the ratio of sinking flux to production. Our results challenge the notion that plankton communities in oligotrophic lakes are more efficient than those in eutrophic lakes in the retention of nutrients within the water column.
Use of Otolith Microchemistry to Discriminate Oncorhynchus nerka of Resident and Anadromous Origin
Authors: Rieman B. E. , Myers D. L. , Nielsen R. L.
Published: April 2008

We used a wavelength dispersive microprobe to describe patterns in otolith microchemistry of sockeye salmon (Oncorhyncbus nerka). Patterns in Sr/Ca ratios in transects across otoliths were consistent with changes in environmental chemistry associated with life history. The patterns we observed were consistent with those described for other salmonids. We found that Sr/Ca ratios in otolith primordia of fish of known anadromous origin were significantly higher than those in otolith primordia of fish of known resident origin. However, variation among samples was associated with differences in chemistry of the freshwater environments. These differences could confound attempts to discriminate sympatric resident and anadromous forms in lakes where Sr/Ca ratios are high. Samples used to discriminate origin of emigrants from Redfish Lake, Idaho, confirmed the presence of both resident and anadromous fish, but the two groups were not clearly resolved. Otolith microchemistry has the potential to determine the parental origin of O. nerka and to describe life history patterns, but may not clearly identify all individuals in all lakes. More work is needed to determine the inherent variability among individuals and among populations and to determine the influence that migration, spawning, and incubation environments have on the chemistry of otoliths.
Vertical Distribution of Northern Shrimp (Pandalus borealis) Larvae in the Gulf of St Lawrence; Implications for Trophic Interactions and Transport
Authors: Ouellet Patrick , Lefaivre Denis
Published: April 2008

In the northwestern Gulf of St. Lawrence in spring 1987 and 1988, stage I and II northern shrimp (Pandalus borealis) larvae were concentrated in the upper (<30 m) layers above the permanent pycnocline and coincident with subsurface chlorophyll a and suspended particle concentration maxima; this was above other macrozooplankton taxa in the daytime. Shrimp larvae maintained their vertical position relative to the maximum density gradient in the water column in daytime but moved towards the surface at night. Estimation of larval residual transport (~66 km) during the first developmental stage (12 d) corresponded to the horizontal scale of patches of stage I shrimp larvae in the northwest sector of the Gulf. The result is consistent with the suggestion of localized and short-duration larval emergence in the sector. The direction of mass transport and current speed were similar throughout the upper layers of the water column; consequently, the direction and magnitude of larval shrimp transport were not dependent on their vertical position. We suggest that the vertical distribution maintained by shrimp larvae is a mechanism to ensure maximum food availability and to optimize development time in the stratified water of the northwestern Gulf of St. Lawrence.
Structure and Dynamics of Photosynthetic Picoplankton across the Saltwater Transition Zone of the St. Lawrence River
Authors: Bertrand Normand , Vincent Warwick F.
Published: April 2008

Changes in the biomass, community structure, and activity of photosynthetic picoplankton (PP) were measured across the turbid, freshwater–saltwater transition zone (TZ) of the St. Lawrence River. The <2 μm fraction of total Chl a dropped from 20–30% in mid-May to 15% in late June. Photosynthesis by the <2.0 μm fraction in May surface waters contributed 6–38% of the total primary production. Picoplankton dropped from 8.4 × 106 (freshwater zone, FZ) to 3.7 × 106 cells∙L−1 (TZ) in mid-May and from 17 × 106 (FZ) to 5.8 × 106 cells∙L−1 (TZ) in late June. Results implied that the picoplankton were subject to increased losses (e.g., by protozoan grazing) in the TZ. Phycoerythrin-rich cyanobacteria (PEC) dominated the PP counts in mid-May, with phycocyanin-rich forms (PCC) contributing 4–13% of the cell concentrations. Six weeks later the PP community had shifted completely to PCC dominance (60–69% of total counts). In late summer, PP contributed 6–56% of the planktonic Chl a in the St. Lawrence River system. There were large variations in the PEC/PCC ratio and the proportion of eukaryotic PP along certain reaches of the river. These observations underscore the spatially and temporally dynamic character of PP communities in the river–estuary environment.
A data-oriented survey of context models
Authors: Bolchini Cristiana , Curino Carlo A. , Quintarelli Elisa , Schreiber Fabio A. , Tanca Letizia
Published: April 2008

Context-aware systems are pervading everyday life, therefore context modeling is becoming a relevant issue and an expanding research field. This survey has the goal to provide a comprehensive evaluation framework, allowing application designers to compare context models with respect to a given target application; in particular we stress the analysis of those features which are relevant for the problem of data tailoring. The contribution of this paper is twofold: a general analysis framework for context models and an up-to-date comparison of the most interesting, data-oriented approaches available in the literature.
Single-Molecule Studies of Protein Folding
Authors: Borgia Alessandro , Williams Philip M. , Clarke Jane
Published: April 2008

Although protein-folding studies began several decades ago, it is only recently that the tools to analyze protein folding at the single-molecule level have been developed. Advances in single-molecule fluorescence and force spectroscopy techniques allow investigation of the folding and dynamics of single protein molecules, both at equilibrium and as they fold and unfold. The experiments are far from simple, however, both in execution and in interpretation of the results. In this review, we discuss some of the highlights of the work so far and concentrate on cases where comparisons with the classical experiments can be made. We conclude that, although there have been relatively few startling insights from single-molecule studies, the rapid progress that has been made suggests that these experiments have significant potential to advance our understanding of protein folding. In particular, new techniques offer the possibility to explore regions of the energy landscape that are inaccessible to classical ensemble measurements and, perhaps, to observe rare events undetectable by other means.
Pair feeding-mediated changes in metabolism: stress response and pathophysiology in insulin-resistant, atherosclerosis-prone JCR:LA-cp rats
Authors: Russell James C. , Proctor Spencer D. , Kelly Sandra E. , Brindley David N.
Published: April 2008

Rats of the JCR:LA-cp strain, which are homozygous for the cp gene ( cp/ cp), are obese, insulin-resistant, and hyperinsulinemic. They exhibit associated micro- and macrovascular disease and end-stage ischemic myocardial lesions and are highly stress sensitive. We subjected male cp/ cp rats to pair feeding (providing the rats each day with the amount of food eaten by matched freely fed animals), a procedure that alters the diurnal feeding pattern, leading to a state of intermittent caloric restriction. Effects on insulin, glucose, and lipid metabolism, response to restraint stress, aortic contractile/relaxant response, and myocardial lesion frequency were investigated. Pair-fed young (12-wk-old) cp/ cp rats had lower insulin and glucose levels (basal and following restraint), consistent with increased insulin sensitivity, but a greater increase in plasma nonesterified fatty acids in response to restraint. These effects were unrelated to lipolytic rates in adipose tissue but may be related to reduced fatty acid oxidation in skeletal muscle. Older (24-wk-old) pair-fed cp/ cp rats had significantly reduced plasma triglyceride levels, improved micro- and macrovascular function, and reduced severity of ischemic myocardial lesions. These changes indicate a significant amelioration of end-stage disease processes in this animal model and the complexity of metabolic/physiological responses in studies involving alterations in food intake. The effects illustrate the sensitivity of the JCR:LA-cp rat, an animal model for the metabolic syndrome and associated cardiovascular disease, to the environmental and experimental milieu. Similar stress-related mechanisms may play a role in metabolically induced cardiovascular disease in susceptible human beings.
The Quest for the1p36Tumor Suppressor
Authors: Bagchi Anindya , Mills Alea A.
Published: April 2008

Genomic analyses of late-stage human cancers have uncovered deletions encompassing 1p36, thereby providing an extensive body of literature supporting the idea that a potent tumor suppressor resides in this interval. Although several genes have been proposed as 1p36 candidate tumor suppressors, convincing evidence that their encoded products protect from cancer has been scanty. A recent functional study identified chromodomain helicase DNA-binding protein 5 (CHD5) as a novel tumor suppressor mapping to 1p36. Here, we discuss evidence supporting the tumor-suppressive role of CHD5. Together, these findings suggest that strategies designed to enhance CHD5 activity could provide novel approaches for treating a broad range of human malignancies. [Cancer Res 2008;68(8):2551–6]
Gender-Related Survival Differences Associated withEGFRPolymorphisms in Metastatic Colon Cancer
Authors: Press Oliver A. , Zhang Wu , Gordon Michael A. , Yang Dongyun , Lurje Georg , Iqbal Syma , El-Khoueiry Anthony , Lenz Heinz-Josef
Published: April 2008

Evidence is accumulating supporting gender-related differences in the development of colonic carcinomas. Sex steroid hormone receptors are expressed in the colon and interact with epidermal growth factor receptor (EGFR), a gene widely expressed in colonic tissue. Increased EGFR expression is linked with poor prognosis in colon cancer. Within the EGFR gene there are two functional polymorphisms of interest: a polymorphism located at codon 497 (HER-1 R497K) and a dinucleotide (CA)n repeat polymorphism located within intron 1. These germ-line polymorphisms of EGFR were analyzed in genomic DNA from 318 metastatic colon cancer patients, 177 males and 141 females, collected from 1992 to 2003. Gender-related survival differences were associated with the HER-1 R497K polymorphism (Pinteraction = 0.003). Females with the HER-1 497 Arg/Arg variant had better overall survival (OS) when compared with the Lys/Lys and/or Lys/Arg variants. In males the opposite was true. The EGFR dinucleotide (CA)n repeat also trended with a gender-related OS difference (Pinteraction = 0.11). Females with both short <20 (CA)n repeat alleles had better OS than those with any long ≥20 (CA)n repeats. In males the opposite was true. Combination analysis of the two polymorphisms taken together also revealed the same gender-related survival difference (Pinteraction = 0.002). These associations were observed using multivariable analysis. The two polymorphisms were not in linkage disequilibrium and are independent of one another. This study supports the role of functional EGFR polymorphisms as independent prognostic markers in metastatic colon cancer. As a prognostic factor, these variants had opposite prognostic implications based on gender. [Cancer Res 2008;68(8):3037–42]