bluuebunny/crossref_metadata_2025 huggingface dataset:
Immunostimulatory Effects of Mesenchymal Stem Cell‐Derived Neurons: Implications for Stem Cell Therapy in Allogeneic Transplantations
Authors: Castillo Marianne D. , Trzaska Katarzyna A. , Greco Steven J. , Ponzio Nicholas M. , Rameshwar Pranela
Published: May 2008

Mesenchymal stem cells (MSCs) differentiate along various lineages to specialized mesodermal cells and also transdifferentiate into cells such as ectodermal neurons. MSCs are among the leading adult stem cells for application in regenerative medicine. Advantages include their immune‐suppressive properties and reduced ethical concerns. MSCs also show immune‐enhancing functions. Major histocompatibility complex II (MHC‐II) is expected to be downregulated in MSCs during neurogenesis. Ideally, “off the shelf” MSCs would be suited for rapid delivery into patients. The question is whether these MSC‐derived neurons can reexpress MHC‐II in a milieu of inflammation. Western analyses demonstrated gradual decrease in MHC‐II during neurogenesis, which correlated with the expression of nuclear CIITA, the master regulator of MHC‐II expression. MHC‐II expression was reversed by exogenous IFNY. One‐way mixed lymphocyte reaction with partly differentiated neurons showed a stimulatory effect, which was partly explained by the release of the proinflammatory neurotransmitter substance P (SP), cytokines, and decreases in miR‐130a and miR‐206. The anti‐inflammatory neurotransmitters VIP and CGRP were decreased at the peak time of immune stimulation. In summary, MSC‐derived neurons show decreased MHC‐II expression, which could be reexpressed by IFNY. The release of neurotransmitters could be involved in initiating inflammation, underscoring the relevance of immune responses as consideration for stem cell therapies.
Hyaluronan (HA) Deposition Precedes and Promotes Leukocyte Recruitment in Intestinal Inflammation
Authors: Kessler Sean , Rho Hyunjin , West Gail , Fiocchi Claudio , Drazba Judith , De La Motte Carol
Published: May 2008

Increased hyaluronan (HA) deposition is a common feature of inflamed tissues, including inflammatory bowel disease (IBD)‐involved intestines. However, whether HA accumulation promotes or is the result of intestinal inflammation is unknown. Using the mouse dextran sulfate sodium (DSS)‐induced experimental model of colitis, we investigated changes in HA deposition in the colon over time in conjunction with evolving pathological changes of tissue architecture. Profound changes in colon HA deposition occurred within 3–7 days of oral DSS administration and, more important, they preceded the inflammatory infiltrate. Interestingly, HA deposition within blood vessels of the colon is observed as early as 3 days during the course of colitis induction, well before any significant inflammatory infiltrate. HA deposition is also observed in blood vessels of inflamed human colon of IBD patients. We determined that human intestinal endothelial cells generate HA in response to proinflammatory stimuli by demonstrating a TNF‐α‐induced increase in hyaluronan synthase‐3 mRNA expression and the accumulation of HA cable‐like structures that are adhesive for leukocytes. Additionally, IBD mucosal endothelial cells produce higher levels of cell surface HA in response to TNF‐α than non‐IBD control cells. Therefore, HA deposition is an early event in inflamed gut tissue, preceding and likely promoting leukocyte infiltration.
Risk indicators of caries experience among young adults
Authors: Roberts‐Thomson K , Stewart JF
Published: May 2008

Background:  Significant gains have been documented on the oral health of Australian children. However, the question remains as to whether improvements have extended to the oral health of young adults. This study aimed to determine the risk indicators associated with oral health status in young adults aged 20–25 years.

Methods:  A random sample of young adults was selected from the South Australian electoral roll. Telephone interviews were conducted for 1261 young adults. These provided socio‐demographic, health behaviour and dental visiting data. Dental examinations were carried out on 644 subjects by three calibrated examiners in clinical settings.

Results:  The mean number of tooth surfaces affected by dental caries (DMFS) was 6.05 with the presence of untreated cavitated decayed surfaces (DS) evident in 28.6 per cent. In regression models the risk indicators associated with DS were being on government benefits, unemployed, usually visiting for a problem rather than a check, visiting a public clinic, drinking 5+ acidic drinks per day and being a current smoker. Risk indicators for higher DMFS scores were usually visiting for a problem, visiting a public clinic, being on government benefits and having made a dental visit in the previous 2 years.

Conclusions:  Socio‐demographic factors, dental visiting patterns and general health behaviours are risk indicators for caries in young adults.
Effect of ozone and Tooth MousseTM on the efficacy of peroxide bleaching
Authors: Manton DJ , Bhide R , Hopcraft MS , Reynolds EC
Published: May 2008

Background:  The aim of this in vitro study was to investigate the effect of Tooth Mousse™ (TM) and ozone on the bleaching effectiveness of peroxide (P).

Methods:  Sixty enamel specimens were stained by tea infusion. P (8% carbamide peroxide solution) and the P/TM (50:50) blend were prepared freshly as required. The specimens were divided randomly into six groups: Group A – ozone followed by P; Group B – ozone concurrently with P; Group C – P alone; Group D – ozone followed by P/TM; Group E – ozone concurrently with P/TM; and Group F – P/TM alone. Ozone exposure was of 40 seconds duration. Digital photographic images were recorded at baseline and endpoint under standardized lighting and desiccation conditions. CIELAB L*a*b* values were determined.

Results:  The addition of TM to P or the application of ozone with P did not significantly affect bleaching effectiveness compared with P alone. The application of ozone prior to P significantly decreased bleaching effectiveness as indicated by the ΔL*, Δa*, ΔE and %L* values. The addition of TM to the P did enhance the aesthetic by increasing the lustre and translucency of the treated enamel.

Conclusions:  The results of this study suggest that Tooth Mousse may be applied concurrently with the bleach, and not reduce bleaching effectiveness.
Comparative analysis of three commercial saliva testing kits with a standard saliva buffering test
Authors: Kitasako Y , Burrow MF , Stacey M , Huq L , Reynolds EC , Tagami J
Published: May 2008

Background:  In 1959, Ericsson developed a laboratory buffer capacity test. Because the Ericsson test is not practical for use as a chair‐side test, commercially available saliva buffering capacity tests have been developed for use in the dental office. The purpose of this study was to evaluate the correlation between a modified Ericsson test and three commercially available quantitative and colourimetric tests.

Methods:  Stimulated saliva (by chewing paraffin wax) was collected from 113 patients. Individual saliva buffering capacity was assessed with the following four different methods: modified Ericsson test; quantitative test using a hand‐held pH meter; paper strip; or liquid colourimetric test. The correlations of ranking results among the different tests were analysed using the Spearman Rank Correlation Test, p < 0.001.

Results:  Spearman Rank Correlation indicated significant positive coefficients between the modified Ericsson test and the quantitative test (ρ = 0.857), the paper strip colourimetric test (ρ = 0.621) and the liquid‐type colourimetric test (ρ = 0.689).

Conclusion:  The detection level of medium and high buffering capacity was test dependent. The quantitative test using a hand‐held pH meter showed a stronger positive correlation with the modified Ericsson test. The qualitative tests seemed less reliable, particularly for patients classified as having a medium buffering capacity.
Molar incisor hypomineralization: a survey of members of the Australian and New Zealand Society of Paediatric Dentistry
Authors: Crombie FA , Manton DJ , Weerheijm KL , Kilpatrick NM
Published: May 2008

Background:  Worldwide, molar incisor hypomineralization (MIH) affects a substantial number of children and impacts greatly on treatment need and dental anxiety, yet there is little information regarding its prevalence, aetiology, presentation and management. The aims of this survey were to assess awareness and perceptions of the Australian paediatric dental community concerning MIH, and to describe current treatment strategies.

Methods:  A questionnaire, based upon a previous European study, was sent to all Australian members of the Australian and New Zealand Society of Paediatric Dentistry. The questionnaire sought information on clinical experience of MIH, knowledge of prevalence, aetiology and contemporary management strategies for MIH.

Results:  One hundred and thirty useable responses were received (58.8 per cent response rate) of which 36 were paediatric dentists, 6 paediatric dentistry postgraduate students, 59 general dentists, 14 dental therapists and 14 specialists in other fields. Most (98.5 per cent) respondents were familiar with MIH and encountered it in their practice. The majority (73.1 per cent) estimated that MIH occurred in between 5 to 25 per cent of their clinical practice and almost all (96.9 per cent) considered it to be a clinical problem. Only 16.9 per cent of respondents were aware of existing prevalence data and 96.9 per cent valued investigating the prevalence of MIH. No consensus existed regarding the aetiology of MIH or its restorative management. Paediatric dentists used preformed crowns significantly more than non‐specialists, however glass ionomer cements were popular with all groups.

Conclusions:  MIH is a well recognized and widely encountered clinical condition. MIH presents several clinical problems and is worthy of further investigation. Currently, no consistent clinical management strategies are utilized.
Microleakage of composite resin restorations in cervical cavities prepared by Er,Cr:YSGG laser radiation
Authors: Shahabi S , Ebrahimpour L , Walsh LJ
Published: May 2008

Background:  Evaluation of microleakage is important for assessing the success of new methods for surface preparation and new adhesive restorative materials. The aim of this laboratory study was to assess microleakage at the margins of composite restorations in Er,Cr:YSGG laser prepared cavities on the cervical aspects of teeth by means of dye penetration, and compare this with conventionally prepared and conditioned cavities.

Methods:  Class V cavities were produced on sound extracted human teeth, which had been assigned randomly to one of three groups (N = 10 each), as follows: Group 1 – prepared using a diamond cylindrical bur and then treated with 37% phosphoric acid; Group 2 – irradiated with an Er,Cr:YSGG laser (Biolase Waterlase) and then treated with 37% phosphoric acid; Group 3 – irradiated only with the laser. After application of bonding agent (Excite, Ivoclar Vivadent), all cavities were restored with composite resin (Heliomolar). After polishing the restorations, the teeth were thermocycled from 5–50°C for 500 cycles. Dye leakage was assessed after immersion in methylene blue, by examining longitudinal sections in a stereomicroscope at ×30 magnification.

Results:  The extent of dye penetration was lowest in the laser only group (Group 3). Penetration of dye to dentine and axial walls occurred in 80 per cent of conventionally prepared (bur + acid) specimens, but in the laser group, dye penetration to the axial wall occurred in only 30 per cent of cases. There was a strong statistical association between treatment group and the distribution of microleakage scores (Chi‐square, P = 0.0023).

Conclusions:  For Class V cavities, with the adhesive materials employed, higher microleakage occurs with phosphoric acid etching of bur‐ or laser‐cut surfaces, than with the surface created by use of the laser alone without additional conditioning.
Cohomology of topological groups with applications to the Weil group
Authors: Flach M.
Published: May 2008

We establish various properties of the definition of cohomology of topological groups given by Grothendieck, Artin and Verdier in SGA4, including a Hochschild–Serre spectral sequence and a continuity theorem for compact groups. We use these properties to compute the cohomology of the Weil group of a totally imaginary field, and of the Weil-étale topology of a number ring recently introduced by Lichtenbaum (both with integer coefficients).
Petri map for rank two bundles with canonical determinant
Authors: Teixidor i Bigas Montserrat
Published: May 2008

We prove the Bertram–Feinberg–Mukai conjecture for a generic curve C of genus g and a semistable vector bundle E of rank two and determinant K on C, namely we prove the injectivity of the Petri-canonical map S2(H0(E))→H0(S2(E)).
Post-buckling and Snap-Through Behavior of Inclined Slender Beams
Authors: Zhao Jian , Jia Jianyuan , He Xiaoping , Wang Hongxi
Published: May 2008

Based on the geometrical nonlinear theory of large deflection elastic beams, the governing differential equations of post-buckling behavior of clamped-clamped inclined beams subjected to combined forces are established. By using the implicit compatibility conditions to solve the nonlinear statically indeterminate problems of elastic beams, the strongly nonlinear equations formulated in terms of elliptic integrals are directly solved in the numerical sense. When the applied force exceeds the critical value, the numerical simulation shows that the inclined beam snaps to the other equilibrium position automatically. It is in the snap-through process that the accurate configurations of the post-buckling inclined beam with different angles are presented, and it is found that the nonlinear stiffness decreases as the midpoint displacement is increased according to our systematical analysis of the inward relations of different buckling modes. The numerical results are in good agreement with those obtained in the experiments.
Transient Response of Submerged Plates Subject to Underwater Shock Loading: An Analytical Perspective
Authors: Liu Zhanke , Young Yin L.
Published: May 2008

In this paper, Taylor’s floating air-backed plate (ABP) model is extended to the case of a submerged water-backed plate (WBP) within the acoustic range. The solution of the WBP is cast into the same format as that of the ABP with a modified fluid-structure interaction (FSI) parameter, which allows a unified analysis of the ABP and WBP using the same set of formulas. The influence of back conditions on fluid and structural dynamics, including fluid cavitation, is systematically investigated. Asymptotic limits are mathematically identified and physically interpolated. Results show that the WBP experiences lower equivalent pressure loading, reduced structural response, and hence lower peak momentum gaining. The time to reach peak momentum is shorter for the WBP than for the ABP. Cavitation is found to be almost inevitable for the ABP, while relevant to the WBP only for a small range of the FSI parameter. Implications to shock response of submerged structures are briefly discussed.
Aeroelastic Stability of Wide Webs and Narrow Ribbons in Cross Flow
Authors: Bidkar Rahul A. , Raman Arvind , Bajaj Anil K.
Published: May 2008

Aeroelastic flutter can lead to large amplitude oscillations of tensioned wide webs and narrow ribbons commonly used in the paper-handling, textile, sheet-metal, and plastics industries. In this article, we examine the aeroelastic stability of a web or a ribbon, which is submerged in an incompressible and inviscid fluid flow across its free edges. The web or ribbon is modeled as a uniaxially tensioned Kirchhoff plate with vanishingly small bending stiffness. A Galerkin discretization for the structural dynamics together with panel methods for the unsteady three dimensional potential flow are used to cast the coupled system into the form of a gyroscopic, nonconservative dynamical system. It is found that wide webs mainly destabilize through a divergence instability due to the cross-flow-induced conservative centrifugal effects. However, for certain values of applied tension, the wake-induced nonconservative effects can destabilize the web via a weak flutter instability. Contrarily, narrow ribbons in cross flow are nearly equally likely to undergo flutter or divergence instability depending on the value of applied tension.
An Alternative to F. Y. M. Wan’s Single Equation for an Elastic Right Circular Conical Shell
Authors: Simmonds J. G.
Published: May 2008

In 1970, F. Y. M. Wan derived a single, complex-valued ordinary differential equation for an elastically isotropic right circular conical shell (“On the Equations of the Linear Theory of Elastic Conical Shells,” Studies Appl. Math., 49, pp. 69–83). The unknown was the nth Fourier component of a complex combination of the midsurface normal displacement and its static-geometric dual, a stress function. However, an attempt to formally replace the Fourier index n by a partial derivative in the circumferential angle θ results in a partial differential equation, which is eighth order in θ. The present paper takes as unknowns the traces of the bending strain and stress resultant tensors, respectively, and derives static-geometric dual partial differential equations of fourth order in both the axial and circumferential variables. Because of the explicit appearance of Poisson ratios of bending and stretching, these two equations cannot be combined into a single complex-valued equation. Reduced equations for beamlike (axisymmetric and lateral) deformations are also derived.
Performance of the Various Sn Approximations of DOM in a 3D Combustion Chamber
Authors: Paul Manosh C.
Published: May 2008

We have carried out a three-dimensional numerical study to investigate the radiative heat transfer in a model gas turbine combustor. The combustion chamber is a representative of the Rolls-Royce Tay engine combustor. The discrete ordinate method (Sn) in general body-fitted coordinate system is developed and then applied to solve the filtered radiative transfer equation for the radiation modeling, and this has been combined with a large eddy simulation of the flow, temperature, and composition fields within the combustion chamber. Various approximations of Sn have been considered and their performances in the investigation of the radiative heat transfer are presented in the paper. The radiation considered in this work is due only to the hot combustion gases, notably carbon dioxide (CO2) and water vapor (H2O) also known as nonluminous radiation. The instantaneous results of the radiation properties such as the incident radiation and the radiative energy source or sink as the divergence of the radiative heat fluxes are computed inside the combustion chamber and presented graphically. Effects of the wall emissivity on the incident radiation inside the combustion chamber have been examined, and it has been found that the radiative energy is enhanced with the increment of the wall emissivity.
Monte Carlo Simulation of Steady-State Microscale Phonon Heat Transport
Authors: Randrianalisoa Jaona , Baillis Dominique
Published: May 2008

Heat conduction in submicron crystalline materials can be well modeled by the Boltzmann transport equation (BTE). The Monte Carlo method is effective in computing the solution of the BTE. These past years, transient Monte Carlo simulations have been developed, but they are generally memory demanding. This paper presents an alternative Monte Carlo method for analyzing heat conduction in such materials. The numerical scheme is derived from past Monte Carlo algorithms for steady-state radiative heat transfer and enables us to understand well the steady-state nature of phonon transport. Moreover, this algorithm is not memory demanding and uses very few iteration to achieve convergence. It could be computationally more advantageous than transient Monte Carlo approaches in certain cases. Similar to the famous Mazumder and Majumdar’s transient algorithm (2001, “Monte Carlo Study of Phonon Transport in Solid Thin Films Including Dispersion and Polarization,” ASME J. Heat Transfer, 123, pp. 749–759), the dual polarizations of phonon propagation, the nonlinear dispersion relationships, the transition between the two polarization branches, and the nongray treatment of phonon relaxation times are accounted for. Scatterings by different mechanisms are treated individually, and the creation and/or destruction of phonons due to scattering is implicitly taken into account. The proposed method successfully predicts exact solutions of phonon transport across a gallium arsenide film in the ballistic regime and that across a silicon film in the diffusion regime. Its capability to model the phonon scattering by boundaries and impurities on the phonon transport has been verified. The current simulations agree well with the previous predictions and the measurement of thermal conductivity along silicon thin films and along silicon nanowires of widths greater than 22nm. This study confirms that the dispersion curves and relaxation times of bulk silicon are not appropriate to model phonon propagation along silicon nanowires of 22nm width.
Heat Transfer Analysis Through Solar and Rooted Fins
Authors: Khaled A.-R. A.
Published: May 2008

Heat transfer through solar fins and rooted fins is analyzed theoretically in this work. The terminology of “solar fin” is used to refer to fins that are subject to external irradiations while the terminology “rooted fin” is used to refer to fins partially embedded in the base wall. One-dimensional heat transfer analysis is conducted and heat transfer rate through the fin, fin efficiency, as well as other performance indicators are obtained. It is found that the fin efficiency of the solar fins is maximized at certain fin indices and that rooted fins are preferable over ordinary fins for a wide range of fin indices. This range of fin indices is summarized in a correlation for insulated walls or insulated fin roots. Moreover, the minimum fin length that maximizes fin heat transfer is found to increase as solar irradiation intensity increases for solar fins subjected partially to solar irradiations. Finally, this work provides new passive methods for enhancing heat transfer in thermal systems.
Numerical Experiments in Turbulent Natural Convection Using Two-Equation Eddy-Viscosity Models
Authors: Albets-Chico X. , Oliva A. , Pérez-Segarra C. D.
Published: May 2008

This work is focused on the simulation and prediction of turbulent natural convection flows by means of two-equation eddy-viscosity models. In order to show the generality, precision, and numerical issues related to these models under natural convection, three different buoyancy-driven cavities have been simulated: a tall cavity with a 30:1 aspect ratio, a cavity with a 5:1 aspect ratio, and, finally, a 4:1 aspect ratio cavity. All cases are solved under moderate and∕or transitional Rayleigh numbers (2.43×1010, 5×1010, and 1×1010, respectively) and all simulations are compared to experimental and∕or direct numerical simulation data available in literature. These different situations allow to check the applicability of two-equation eddy-viscosity models in buoyancy-driven flows, giving criteria on computational effort∕precision and their physical behavior.
Modeling of Thermophysical Processes in Liquid Ceramic Precursor Droplets Heated by Monochromatic Irradiation
Authors: Basu Saptarshi , Cetegen Baki M.
Published: May 2008

A transient heat and mass transfer model is formulated to describe radiative heating of ceramic precursor droplets in a nonconvective environment. Heating causes vaporization of solvent from the droplet and concentration of the solute within the droplet leading to precipitation of the solute. It is found that the temperatures within the droplets are fairly uniform, but show different spatial profiles depending on the characteristics of solute absorptivity and duration of radiative heating. Incident laser irradiance and wavelength were found to play a significant role in the temperature profiles within droplets due to the absorption characteristics of the solute and the solvent. Lower levels of incident laser irradiation allows longer times for mass diffusion within a droplet leading to a gradual increase of the solute concentration from its center to its surface. Based on an equilibrium homogeneous precipitation hypothesis, it is found that the droplets heated with low laser irradiance tend to form thick precipitate shells as compared to those exposed to higher irradiances and consequently faster rates of vaporization. Large droplets form thin shells through surface precipitation, while small droplets may precipitate into shells of varying thickness depending on the magnitude of irradiance. Comparisons with convective heating in a high temperature plasma indicate that, with proper tuning of the laser irradiance, similar internal temperatures and solute concentration distributions are achievable. These modeling results suggest that different particle morphologies can be obtained from processing of liquid ceramic precursor containing droplets by proper tailoring of radiation parameters (wavelength and irradiance level).
Computational Study of Heat Transfer in a Conjugate Turbulent Wall Jet Flow at High Reynolds Number
Authors: Vishnuvardhanarao E. , Das Manab Kumar
Published: May 2008

In the present case, the conjugate heat transfer involving the cooling of a heated slab by a turbulent plane wall jet has been numerically solved. The bottom of the solid slab is maintained at a hot uniform temperature, whereas the wall jet temperature, is equal to the ambient temperature. The Reynolds number considered is 15,000 because it has already been experimentally found and reported that the flow becomes fully turbulent and is independent of the Reynolds number. The high Reynolds number two-equation model (κ‐ϵ) has been used for the turbulence modeling. The parameters chosen for the study are the conductivity ratio of the solid-fluid (K), the solid slab thickness (S), and the Prandtl number (Pr). The ranges of parameters are K=1–1000, S=1–10, and Pr=0.01–100. Results for the solid-fluid interface temperature, local Nusselt number, local heat flux, average Nusselt number, and average heat transfer are presented and discussed.
Flow Boiling Instabilities in Microchannels and Means for Mitigation by Reentrant Cavities
Authors: Kuo C.-J. , Peles Y.
Published: May 2008

The ability of reentrant cavities to suppress flow boiling oscillations and instabilities in microchannels was experimentally studied. Suppression mechanisms were proposed and discussed with respect to various instability modes previously identified in microchannels. It was found that structured surfaces formed inside channel walls can assist mitigating the rapid bubble growth instability, which dominates many systems utilizing flow boiling in microchannels. This, in turn, delayed the parallel channel instability and the critical heat flux (CHF) condition. Experiments were conducted using three types of 200×253μm2 parallel microchannel devices: with reentrant cavity surface, with interconnected reentrant cavity surface, and with plain surface. The onset of nucleate boiling, CHF condition, and local temperature measurements were obtained and compared in order to study and identify flow boiling instability.
Analysis of the Thermal Behavior of a Multilayer Slab With Imperfect Contact Using the Dual-Phase-Lag Heat Conduction Model
Authors: Ramadan K. , Al-Nimr M. A.
Published: May 2008

The thermal behavior of a multilayered slab in imperfect contact using the dual-phase-lag heat conduction model is numerically analyzed, considering a range of heat flux-phase lag, temperature gradient-phase lag, and thermal contact resistance. Wave reflections from both insulated boundaries and contact surfaces take place when the phase lag of the temperature gradient is less than the phase lag of the heat flux. Due to the wave nature of energy transport in composite slabs having much less temperature gradient-phase lag than heat flux-phase lag and with a low thermal contact resistance, an initially low-temperature layer can attain a higher temperature than that of the initially high-temperature layer. For composite slabs with temperature gradient-phase lag higher than the heat flux-phase lag and due to the absence of the wave nature of energy transport and the enhancement of heat diffusion, a thermal disturbance is more quickly felt in the whole domain when the temperature gradient-phase lag increases, although in terms of the interfacial temperature difference, the contact surface shows lower response with increasing temperature gradient-phase lag during early stages of the transient energy transport.
Effect of Pin Tip Clearance on Flow and Heat Transfer at Low Reynolds Numbers
Authors: Rozati Ali , Tafti Danesh K. , Blackwell Neal E.
Published: May 2008

Cylindrical pin fins with tip clearances are investigated in the low Reynolds number range 5<ReD<400 in a plane minichannel. Five tip gaps are investigated ranging from a full pin fin (t*=0.0) to a clearance of t*=0.4D*, where D* is the pin diameter. It is established that unlike high Reynolds number flows, the flow and heat transfer are quite sensitive to tip clearance. A number of unique flow effects, which increase the heat transfer performance, are identified. The tip gap affects the heat transfer coefficient by eliminating viscosity dominated end wall effects on the pin, by eliminating the pin wake shadow on the end walls, by inducing accelerated flow in the clearance, by reducing or impeding the development of recirculating wakes, and by redistributing the flow along the height of the channel. In addition, tip gaps also reduce form losses and friction factor. A clearance of t*=0.3D* was found to provide the best performance at ReD<100; however, for ReD>100, both t*=0.2D* and 0.3D* were comparable in performance.
Experimental Investigation of the Painlevé Paradox in a Robotic System
Authors: Zhao Zhen , Liu Caishan , Ma Wei , Chen Bin
Published: May 2008

This paper aims at experimentally investigating the dynamical behaviors when a system of rigid bodies undergoes so-called paradoxical situations. An experimental setup corresponding to the analytical model presented in our prior work Liu et al. [2007, “The Bouncing Motion Appearing in a Robotic System With Unilateral Constraint,” Nonlinear Dyn., 49(1–2), 217–232] is developed, in which a two-link robotic system comes into contact with a moving rail. The experimental results show that a tangential impact exists at the contact point and takes a peculiar property that well coincides with the maximum dissipation principle stated in the work of Moreau [1988, “Unilateral Contact and Dry Friction in Finite Freedom Dynamics,” Nonsmooth Mechanics and Applications, Springer-Verlag, Vienna, pp. 1–82] the relative tangential velocity of the contact point must immediately approach zero once a Painlevé paradox occurs. After the tangential impact, a bouncing motion may be excited and is influenced by the speed of the moving rail. We adopt the tangential impact rule presented by Liu et al. to determine the postimpact velocities of the system, and use an event-driven algorithm to perform numerical simulations. The qualitative comparisons between the numerical and experimental results are carried out and show good agreements. This study not only presents an experimental support for the shock assumption related to the problem of the Painlevé paradox, but can also find its applications in better understanding the instability phenomena appearing in robotic systems.
Marginal Instability and Intermittency in Stochastic Systems—Part I: Systems With Slow Random Variations of Parameters
Authors: Dimentberg M. F. , Hera A. , Naess A.
Published: May 2008

Dynamic systems with lumped parameters, which experience random temporal variations, are considered. The variations may “smear” boundary between the system’s states, which are dynamically stable and unstable in the classical sense. The system’s response within such a “twilight zone” of marginal instability is found to be of an intermittent nature, with alternating periods of zero (or almost-zero) response and rare short outbreaks. As long as it may be impractical to preclude completely such outbreaks for a designed system, subject to highly uncertain dynamic loads, the corresponding system’s response should be analyzed. Results of such analyses are presented for cases of slow and rapid (broadband) parameter variations in Parts I and II, respectively. In the former case, the “nominal” system—one without variations of parameter(s)—is stable in the classical sense. Its transient response during the “slow” short-term excursions of the parameter(s) into the instability domain is described by a linear model. The analysis is based on Krylov–Bogoliubov averaging over “rapid” time within the response period together with parabolic approximation for the parameter variations in the vicinity of their peaks (so-called Slepian model). Solution to the resulting deterministic transient response problem with random initial condition(s) at the instant of upcrossing the stability boundary yields a relation between peak value(s) of the response(s) and that of the parameter(s); in this way, reliability study for the system is reduced to a probabilistic analysis of the parameter variations. The solutions are obtained for the cases of negative-damping-type instability in a SDOF system and for TDOF systems with potential dynamic instability due to coalescing or merging of natural frequencies; the illustrating examples of applications are rotating shafts with internal damping, two-dimensional galloping of a rigid body in a fluid flow and a row of tubes in a cross flow of fluid. The response is of the intermittent nature due to the way it is generated, with alternating relatively long periods of zero (or almost-zero) response and short outbreaks due to temporary excursions into the instability domain.
Experimental Data Have to Decide Which of the Nonprobabilistic Uncertainty Descriptions—Convex Modeling or Interval Analysis—to Utilize
Authors: Wang Xiaojun , Elishakoff Isaac , Qiu Zhiping
Published: May 2008

This study shows that the type of the analytical treatment that should be adopted for nonprobabilistic analysis of uncertainty depends on the available experimental data. The main idea is based on the consideration that the maximum structural response predicted by the preferred theory ought to be minimal, and the minimum structural response predicted by the preferred theory ought to be maximal, to constitute a lower overestimation. Prior to the analysis, the existing data ought to be enclosed by the minimum-volume hyper-rectangle V1 that contains all experimental data. The experimental data also have to be enclosed by the minimum-volume ellipsoid V2. If V1 is smaller than V2 and the response calculated based on it R(V1) is smaller than R(V2), then one has to prefer interval analysis. However, if V1 is in excess of V2 and R(V1) is greater than R(V2), then the analyst ought to utilize convex modeling. If V1 equals V2 or these two quantities are in close vicinity, then two approaches can be utilized with nearly equal validity. Some numerical examples are given to illustrate the efficacy of the proposed methodology.
An Alternative Two-Variable Model for Bending Problems of Multilayered Beams
Authors: Zhang Neng-Hui , Chen Jian-Zhong
Published: May 2008

A closed-form analytical solution to thermoelastic bending problems of multilayered beams is obtained by an alternative two-variable method. There are only two unknowns to be solved and two equilibrium conditions to be satisfied in the present analysis. Differences among zero-strain axis, zero-stress axis, bending axis and centroidal axis are compared.
Screw Dislocations in a Three-Phase Composite Cylinder Model With Interface Stress
Authors: Fang Q. H. , Liu Y. W. , Wen P. H.
Published: May 2008

A three-phase composite cylinder model is utilized to study the interaction between screw dislocations and nanoscale inclusions. The stress boundary condition at the interface between nanoscale inclusion and the matrix is modified by incorporating surface/interface stress. The explicit solution to this problem is derived by means of the complex variable method. The explicit expressions of image forces exerted on screw dislocations are obtained. The mobility and the equilibrium positions of the dislocation near one of the inclusions are discussed. The results show that, compared to the classical solution (without interface stress), more equilibrium positions of the screw dislocation may be available when the dislocation is close to the nanoscale inclusion due to consider interface stress. Also, the mobility of the dislocation in the matrix will become more complex than the classical case.
Basidiocarps, annelloconidia, and sclerotia in agar cultures of Pistillaria (Clavariadelphaceae)
Authors: Koske Jr. Richard E. , Perrin Peter W.
Published: May 2008

Pistillaria micans Fr. and Pistillaria setipes Grev. produced fertile sporophores in agar culture. Light was necessary for production of fertile basidiocarps in both species and for pigment production and conidium formation in P. micans. Annelloconidia were produced by P. micans. Viable sclerotia were formed by P. setipes. The taxonomic significance of sclerotia in Pistillaria and Typhula is discussed. Neither species demonstrated geotropism, but the fruit body of P. setipes was positively phototropic. Temperature optima for growth and sporophore production were ca. 15 °C for P. setipes and ca. 20–22 °C for P. micans.
Germination of Polyporus tomentosus basidiospores on extracts from diseased and healthy trees
Authors: Whitney R. D. , Bohaychuk W. P.
Published: May 2008

High percentages of P. tomentosus spores germinated on media supplemented with bark extracts from roots of white and black spruce. Best germination was on extracts from the inner bark of black spruce. Spore germination was significantly higher on extracts from root bark of diseased trees than on those from healthy trees.
Translocation of sugars in Cucurbita melopepo. VI. The reversible low temperature inhibition of 14C movement and cold acclimation of phloem tissue
Authors: Webb J. A.
Published: May 2008

14C translocation through the node ceases immediately the tissue is chilled (0°) and 14C export from the blade is considerably reduced within the next 5 min, while the assimilation rate remains unchanged. The ratio of 14C distribution among the translocated compounds indicates a uniform deceleration of the entire longitudinal flow through the unchilled length of petiole. Immediately after node chilling an increasing restraint is imposed on the rate of 14C translocation throughout the length of the petiole. This second inhibitory effect of cold treatment is maximally expressed between 30 and 60 min after node chilling and may reflect an accentuated accumulation of translocates within the phloem under these conditions. Translocation through the node resumes immediately the tissue is returned to 25°. Initially the rate is slow but within 90 min of warming the node, when all prechilling restraints on longitudinal movement appear to be removed, the rate of 14C translocation approaches that of control plants. Rapid resumption of transport through the node is matched by a rapid loss of 14C from the blade, again indicating that the entire longitudinal flow moves as a continuum. The longitudinal transport in the phloem and radial movement into the surrounding tissues are both rapidly inhibited at 0 °C. Longitudinal movement will acclimate and within 6 h of continuous cold (1 °C) appreciable transport is resumed through the chilled zone while after 19 to 20 h almost complete recovery of translocation is achieved. There was no evidence for acclimation of the radial movement. If radial movement of 14C reflects cytoplasmic streaming then longitudinal movement likely proceeds by some other mechanism. An evaluation of the extensive cytological observations of phloem tissue produced no clues to explain the mechanism of low temperature inhibition of translocation at the structural level.
Ultrastructure of conidiogenesis in Scopulariopsis brevicaulis
Authors: Cole Garry T. , Aldrich H. C.
Published: May 2008

An ultrastructural study of conidia and conidiogenous cells of Scopulariopsis brevicaulis (Sacc.) Bain. in various stages of development is presented using transmission and scanning electron microscope and freeze-etching techniques. Septa between both fertile and vegetative cells are examined. The development of the double septum is outlined and mechanisms are suggested to explain conidium secession. Cytological changes which occur in the developing conidium initial are illustrated and their possible association with wall synthesis and deposition is noted. Change in the orientation of rodlets occurs on the walls of frozen-etched conidia at different stages of formation. The relationship of this phenomenon to conidium development is discussed. Description of the nature of wall relations during conidium ontogeny is stressed because of its importance in a classification of Fungi Imperfecti based on developmental characters of the reproductive cells. A diagrammatic interpretation of the sequence of formation of wall layers of the developing conidium is presented.
Cytomorphological studies of the pycnial and aecial stages of Cerotelium dicentrae
Authors: Berkson Burton M.
Published: May 2008

The development of the monokaryotic and dikaryotic mycelia was studied cytologically. The monokaryotic mycelium of Cerotelium dicentrae appears to be systemic within the Dicentra cucullaria host plant and the dikaryotic mycelium is initiated upon pycniospore germ-tube penetration of the Dicentra leaf.
Pollen longevity in birch (Betula)
Authors: Alam M. T. , Grant W. F.
Published: May 2008

To carry out reciprocal crosses between birch species which vary by several weeks in their time of anthesis, the period of pollen viability has been determined for three species, Betula populifolia, B. cordifolia, and B. papyrifera. Pollen viability decreased from 85–95% at the time collected to 32–44% after being stored at room temperature (23–27 °C) for 30 days and to 1.0–1.5% after 60 days. In contrast, pollen germination for pollen stored at 2–5 °C for 105 days fell only to 46.0% for B. populifolia and 20.5% and 21.5% for B. cordifolia and B. papyrifera, respectively.
Recent history of fire and vegetation from laminated sediment of Greenleaf Lake, Algonquin Park, Ontario
Authors: Cwynar Les C.
Published: May 2008

Laminated sediment (presumed varved) from Greenleaf Lake was examined for evidence of forest fires. A 500-year section dating approximately 770–1270 A.D. was analysed for influx of pollen, charcoal, aluminum, and vanadium using decadal samples. Intervals showing concurrent peaks in charcoal, aluminum, and vanadium influx, varve thickness, and charcoal:pollen ratio were interpreted as representing major fires within the drainage basin of Greenleaf Lake. By these criteria, six fires occurred within 500 years, or one fire approximately every 80 years. The pollen diagram indicates a stable forest composition for the past 1200 years. This, coupled with abundant charcoal fragments in all sediment samples, suggests that fire has been a frequent, natural phenomenon affecting the landscape during this period. There is a significant positive correspondence between peak charcoal influxes and peak influxes of aluminum and vanadium, indicating that increased soil erosion is responsible for their deposition.
Zygosporangium and zygospore formation in Phycomyces nitens
Authors: O'Donnell K. L. , Flegler S. L. , Hooper G. R.
Published: May 2008

Zygosporangium and zygospore formation in Phycomyces nitens was followed by correlative light microscopy and scanning and transmission electron microscopy. Compatible multibranched zygophores became interlocked by the interdigitation of their lobes. Progametangia grew up from the substratum in pairs and then differentiated into gametangia and tongs-shaped suspensors. Plasmogamy was deferred until the gametangia were delimited. Development of rings of hyaline appendages on the suspensors was concomitant with plasmogamy. The appendages originated from the tertiary suspensor wall layer and ruptured the outer primary and secondary wall layers prior to development of their terminal thornlike processes.Developing zygosporangia contained a large central vacuole and some organelle zonation; however, these features were not discernible in more mature zygosporangia. A reticulum of electron-opaque fluted warts developed within the secondary zygosporangial wall layer. Cryofractured zygosporangia revealed a smooth hyaline zygospore with truncate ends. Wall layer relations of mature zygosporangia and zygospores were presented. Information obtained was correlated with existing ultrastructural observations on zygosporangiogenesis in the Mucorales.
Apothecial ontogeny in Pulvinula tetraspora (Pezizales: Ascomycetes)
Authors: O'Donnell K. L. , Hooper G. R.
Published: May 2008

Apothecial ontogeny in Pulvinula tetraspora, an operculate Discomycete (Pezizales, Pyronemataceae), was followed by correlative light microscopy and scanning electron microscopy. Hymenial development was paragymnohymenial; opening occurred in the prohymenial phase. A functional ascogonium gave rise to ascogenous hyphae which by sympodial and centrifugal growth, produced typical croziers. Developmental aspects of the sterile and fertile portions of the apothecia were described and illustrated.
Effect of salinity on photosynthesis and photorespiration of two wheat species (Triticum durum cv. PEPE 2122 and Triticum aestivum cv. Marzotto)
Authors: Passera Calvino , Albuzio Antonio
Published: May 2008

Effects of NaCl toxicity were examined in two wheat species (Triticum durum L. cv. PEPE 2122 and Triticum aestivum L. cv. Marzotto). At NaCl concentration up to 50 mM growth, dry weight, succulence, and O2 evolution decreased while chlorophyll and protein content increased. 14CO2 fixation increased at 25 mM and decreased at 50 mM NaCl; also, carboxylating and photorespiratory enzyme activities were differently affected by increased salinity. The ratio between ribulose 1, 5-diphosphate carboxylase and phosphoenolpyruvate carboxylase activities decreased, photorespiration rate was stimulated, and the O2 evolving mechanism was inhibited.
The potential effect of drop size on efficiency of splash-cup and springboard dispersal devices
Authors: Savile D. B. O. , Hayhoe H. N.
Published: May 2008

An equation was derived that gives the velocity of a water drop of given size after a given distance of fall. A 4-mm drop develops nearly 11 times the momentum of a 2-mm drop such as commonly occurs in rain. A 4-mm drop reaches about 47% terminal velocity after 1 m and about 91% after 8 m. It is suggested that most splash-cup and springboard mechanisms evolved under the canopies of humid forests where large drops can exert a very great selective stimulus.
Sequential degeneration of mycoplasma-like bodies in plant tissue cultures infected with aster yellows
Authors: Jacoli G. G.
Published: May 2008

In carrot explants infected with aster yellows, mycoplasma-like bodies (MLBs) were seen only in the phloem of the primary cultures. During subsequent transfers of the cultures, MLBs underwent gradual degeneration and disappeared within 80 days. Electron microscopy showed three stages of degeneration. In the first stage, which started after about 30 days in culture, MLBs changed from a round to a filamentous shape and became electron opaque. During the second stage, the MLB membrane ruptured, and numerous unusual structures were observed. In the final stage, the MLB particles disrupted and the cells plasmolysed. Differentiation occurred earlier in infected than in healthy cultures, and the new phloem tissue contained no MLBs.