bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in objective refraction after pharmacological pupil dilation
Authors: WAKPI DJEUGUE D , TOUZEAU O , BASLI E , GAUJOUX T , BORDERIE VM , LAROCHE L
Published: November 2010

Purpose To analyze the variation of the objective refraction induced by pharmacological pupillary dilation in a normal population.

Methods The objective refraction obtained by an auto‐kerato‐refractometer was analyzed before and after maximum pupillary dilation obtained by 0.5% Tropicamide and 10% Phenylephrine. 200 phakic eyes of 100 patients aged from 15 to 76 years were prospectively included. The refractive data were expressed in a dioptric space by 3 Cartesian coordinates (X, Y, Z).

Results After pupil dilation, the mean refraction ranges from ‐0.08(+0.11)×90.2° to +0.41(+0.10)×90.3° this equal to an astigmatic vectorial variation of (+0.03)×89.6°. The spherical equivalent increases significantly (hyperopization of +0.49D: +0.24D vs +0.74D p<0.001) contrary to the mean keratometry (43.48D vs 43.49 p=0.40) and the cylinder (0.64D vs 0.64D p=0.49) which are unchanged. Change in spherical equivalent is correlated with the age (r=‐0.34 p<0.001) but not with the change in keratometry (r=0.06 p=0.20) or the initial spherical equivalent (r=‐0.05 p=0.23). The mean change in axis between both exams is 15.4° for the ocular astigmatism and 12.2° for the corneal astigmatism. The modification in spherical equivalent of both eyes of a patient are not different (p=0.26) and are strongly correlated (r=0.85 p<0.001) contrary to the modification in axis and in cylinder.

Conclusion Pharmacological pupil dilation modifies primarily the spherical equivalent without significant modification of keratometry and astigmatism. Finally, hyperopization is probably due to the cycloplegic effect of eye drops.
Differentiations in thickness of corneas in high myopic eyes
Authors: BASLI E , TOUZEAU O , BORDERIE VM , LAROCHE L
Published: November 2010

Purpose To compare the corneal thickness of eyes with high myopia with that of emmetropic eyes.

Methods One hundred corneas of 50 myopic patients (axial length >26 mm) and 100 corneas of 50 emmetropic patients (spherical equivalent between –1D and +1D) were prospectively analysed by means of Orbscan and ultrasonic pachymetry. The location of related points to apex, which were quantified using the rectangular coordinates (x, y) of the thinnest point, were used to determinate the location of the quadrant and the distance between this thinnest point and the centre (Pythagoras theorem).

Results In the myopic group, the axial length was 27.2+/‐1.6mm (26.1 to 33.1mm) and the subjective spherical equivalent was –8.17+/‐1.72D (‐19.2 to –5.6D). As compared with emmetropic eyes the corneal thickness was significantly lower (p<0.001) in the myopic group: 526μm vs 543μm (US pachymetry) and 528μm vs 545μm (Orbscan). The distribution of the quadrant in not different for the two groups (p=0.26). The localisation is more frequent in the temporal quadrant (63%), followed by the inferior (23%), superior (9.5%) and finally nasal quadrant (4.5%). The distance of this thinnest point and the apex in not different (0.89 mm vs 0.85 mm, p= 0.30).

Conclusion Corneas of high myopic patients are thinner than corneas of emmetropic patients. However the others characteristics of the corneal thickness including the thinnest point are not different in the two groups.
Ultrasonic biometry of children eyes
Authors: KRIAUCIUNIENE L , AUKSTIKALNIENE R , PAUNKSNIS A
Published: November 2010

Purpose The goal of our work is to evaluate the anatomic measurement of eye using precise ultrasonic biometry for 9‐15 year old children with emmetropic refraction and their changes within the period of accommodation.

Methods The precise ultrasonic eye biometry was performed. The following items were measured: the anterior chamber depth, thickness of crystalline lens, vitreous body length, eye axis length.

Results The 1st group consisted of 32 children of 9‐12 years old.The 2nd group ‐ 44 children, 13‐15 years old. According to the data, the anterior‐posterior eye axis length, the horizontal diameter and vitreous body length of 9‐12 years old children are reliably smaller than the same measurements of the 13‐15 years age group (p=0,000018; p=0,000037; p=0,002483) accordingly. The anterior chamber depth of the 2nd group children is slightly exceeding the same measurements among the 1st group children. While the child is growing the lens crystalline grows a bit flatter, though the difference between those parameters is not essential. When accommodating the length of eye anterio‐posterior axis has not changed among the 1st group children, the extension tendency of the anterio‐posterior axis was observed among the 2nd group children, though it is statistically unreliable. A direct dependence is expressed on the average between anterio‐posterior eye axis length and anterior chamber depth as well as between anterior‐posterior eye axis length and vitreous body length (r=0,316 and r=0483).

Conclusion Precise ultrasonic biometry is an effective method to detect changes of optico‐anatomical parameters of children eyes.
A behavioural method for evaluating depth of focus
Authors: PLAINIS S , BARTELS A , PARRY NRA , PALLIKARIS IG
Published: November 2010

Purpose To develop a technique based on visual reaction times that can evaluate the depth of focus in uncorrected vision or when using different modalities of simultaneous vision correction for presbyopia. Reaction Times (RTs) are known to increase in a predictable way as stimuli become less visible, i.e. as contrast decreases. Contrast reduction, produced by different amounts of defocus blur, was calculated by increased RT.

Methods RTs were measured to the onset of a sinusoidal grating with a spatial frequency of 4 c/deg and a contrast of 10%, displayed on a Sony F‐520 CRT monitor (mean luminance 30 cd/m2), using a VSG2/5 stimulus generator card. All measurements were performed monocularly (dominant eye) and binocularly at 3m viewing distance, with best spectacle sphero‐cylindrical correction for distance and natural pupils. RTs were measured for different degrees of blur, induced using positive powered lenses up to +4.50 D.

Results RT increased with defocus blur, with the effect being more pronounced for monocular compared to binocular viewing conditions. Depth of acceptable perceptual blur (depth of focus) was calculated from the second order polynomials, which fitted the RT vs. defocus blur functions. More specifically, the width of the polynomial fit was estimated for a specific RT. Regardless of the criterion chosen, the depth of acceptable blur was greater under binocular to monocular viewing.

Conclusion The technique described here offers a behavioural measure of the depth of focus, and allows evaluation under both monocular / binocular viewing conditions.
Lutein supplementation and spatial vision in early AMD
Authors: MAKRIDAKI M , BERENDSCHOT TTJM , VAN DER VEEN RLP , CARDEN D , PARRY NRA , MURRAY IJ
Published: November 2010

Purpose To investigate the effect on spatial vision of enhancing macular pigment (MP) with lutein (L) capsules in patients with early AMD.

Methods A randomised, placebo‐controlled two‐centred, 12 months study of the effects of L supplementation was conducted in Manchester, UK and Maastricht, The Netherlands. L capsules (10mg Ester), or a placebo were taken daily. 35 patients (mean age 73.4 ± 8.2, VA>0.5 logMar) were randomly assigned to either L (lutein, n=19) or P (placebo, n=16) groups. Best corrected Log MAR visual acuities, contrast sensitivities (CS) at 0.5, 2, 4, 8,12 and 16 c/deg, and MP were measured at baseline and on three, four month intervals, after the start of the 12 month supplementation period. MP was measured using a flicker‐based technique.

Results An increase in the mean MP levels was found for the L group; from 0.35±0.19 to 0.47±0.22 OD units that was statistically significant (p<0.0003) while no change in MP was found for the P group. A mean improvement from 0.23±0.12 (baseline) to 0.16±0.10 (visit 4) was found in the VA of the L group (statistically significant, p= 0.004). In the P group there was a non‐significant deterioration in VA from 0.18±0.12 to 0.20±0.12. The mean difference in VA between baseline and visit 4 for the L group was 0.07±0.10 and for the P group was ‐0.03±0.10 (statistically significant difference, p= 0.004). No statistically significant changes were found in CS at any of the tested spatial frequencies for either of the 2 groups.

Conclusion Lutein supplementation over a 12 months period improves MP levels in AMD patients and this corresponds to an overall improvement in VA. No such effect is observed in CS.
Regulation of the circadian activity by melanopsin cells in ambient light conditions filtered to wavelengths below to 500 nm
Authors: VICENTE TEJEDOR J , DE LA VILLA P , MARCHENA M , SANCHEZ‐JIMENEZ A , GARCIA‐ORTEGA M , SANCHEZ RAMOS C
Published: November 2010

Purpose To study the variations in the circadian activity in the mouse behaviour with different composition of the luminous spectra. Blue light has been identified as one cause of retinal damage. Nevertheless, these wavelengths (400‐500nm) are important in the process of intrinsically photosensitive ganglion cells (ipRGCs) activation. These cells are essential in not forming images processes such as the pupillary reflex, regulation of the circadian activity and/or release of melatonin. Further, ipRGCs are necessary and sufficient to maintain the synchronization of endogenous cycles with circadian activity of each individual.

Methods By using Circadian Activity cages and different mouse models, we have investigated their behaviour when exposed to the entire light spectrum or to different amounts of the light‐filtered blue component. We have analyzed the behaviour of C57BL6J mice, which have all retinal photosensitive cells, and Rd10 mice, who comprise ipRGCs as the only photosensitive cells in their retinas by postnatal day 100.

Results The use of diverse mouse models has allowed us to investigate the contribution of different photoreceptor classes to the regulation of circadian activity in distinct light conditions. We have observed that ipRGCs are sufficient to maintain the synchronization of endogenous cycles with circadian activity of each individual. Mouse behaviour changes depending on the amount of blue light.

Conclusion The maximum activation of melanopsin‐expressing cells is conditioned by the presence of filters for wavelengths below 500nm. Variations in behaviour exist depending on the amount of visible blue light filtered.
Effect of retinal phototoxicity induced by blue light exposure on the response properties of neurons of the lateral geniculate nucleus of the rat
Authors: GARCíA ORTEGA M , SANCHEZ‐JIMENEZ A , VICENTE‐TEJEDOR J , SANCHEZ RAMOS C
Published: November 2010

Purpose Exposure to bright blue light causes photochemical damage of rodent’s retina via the apoptotic pathway involved in retinitis pigmentosa and age‐related macular degeneration. This photochemical retinal damage occurs with a several different types of morphology and the severity of retinal damage induced by light has great variation among retinal regions. Rather than a mere decrease of the visual response blue light phototoxicity involves important changes on image processing at the retina. Higher visual areas, such as lateral geniculate nucleus (LGN) must adapt their physiology to the new situation. In the present work we will study the changes, and their temporal course, of the response of LGN neurons provoked by acute exposure to bright blue light.

Methods We will stimulate the retina of Wistar rats at 7 different wavelengths and we will record extracellular multiunit activity of these neurons on three different groups: without exposure to bright light (control group), rats exposed to bright (5000 lux) blue light for 72 hours (exposed group) and rats exposed and let a week under control conditions (recovery group).

Results Exposed group showed different profiles of the response parameters measured at the different stimulating wavelengths. These profiles were similar between control and recovery groups.

Conclusion Data shows that retinal damage induced by blue light has a great impact on LGN physiology and that plasticity changes must occur at this area to adapt to the new situation.
COMT Val158Met–Stress Interaction in Psychosis: Role of Background Psychosis Risk
Authors: Collip Dina , van Winkel Ruud , Peerbooms Odette , Lataster Tineke , Thewissen Viviane , Lardinois Marielle , Drukker Marjan , Rutten Bart P.F. , Van Os Jim , Myin‐Germeys Inez
Published: November 2010

Background: The interplay between the catechol‐O‐methyltransferase (COMT) Val158Met polymorphism and environmental stress may have etiological relevance for psychosis, but differential effects have been reported in healthy control and patient groups, suggesting that COMT Val158Met interactions with stress may be conditional on background genetic risk for psychotic disorder. Methods: Patients with a nonaffective psychotic disorder (n = 86) and control participants (n = 109) were studied with the experience sampling method (a structured diary technique) in order to assess stress, negative affect and momentary psychotic symptoms in the flow of daily life. Results: Multilevel analyses revealed significant three‐way interactions between group status (patient or control), COMT genotype and stress in the model of negative affect (χ2(2) = 13.26, P < 0.01) as well as in the model of momentary psychotic symptoms (χ2(2) = 6.92, P < 0.05). Exploration of the three‐way interaction revealed that in patients, COMT genotype moderated the association between stress and negative affect (χ2(4) = 11.50, P < 0.005), as well as the association between stress and momentary psychosis (χ2(4) = 12.79, P < 0.005). Met/Met genotype patients showed significantly increased psychotic and affective reactivity to stress in comparison to the Val/Met and Val/Val genotypes. In contrast, healthy controls did not display large or significant COMT Val158Met X stress interactions. Conclusions: Important differences exist in the effect of COMT Val158Met on stress reactivity, which may depend on background risk for psychotic disorder. Differential sensitivity to environmental stress occasioned by COMT Val158Met may be contingent on higher order interactions with genetic variation underlying psychotic disorder.
Validation of the name Vitis yunnanensis (Vitaceae) endemic to Yunnan, China
Authors: Xiang Chun‐Lei , Liu En‐De
Published: November 2010

Vitis yunnanensis C. L. Li, originally described from Yunnan, southwestern China, was not validly published in 1997, because two type specimens were simultaneously designated. To enable formal use of the name, it is validated here.
Kafka's Grail Castle
Authors: Ullyot Jonathan
Published: November 2010

Kafka's last novel, Das Schloss, borrows structural and thematic elements from the medieval grail quest, especially the first extant grail narrative, Chrétien's incomplete Perceval. In Kafka, however, the symbolic object worthy of the quester's efforts (the grail) is absent. The land surveyor's refusal to be motivated by any object other than “getting to the Castle” is his successful resistance to the oppressive force of authority in the village. Kafka's Das Schloss is a deliberately “stalled” or “failed” version of Perceval, which offers its reader a glimpse of what Benjamin describes as a vision of redemption “on the inner linings” of nothing.
A Note on the Relationship Among Capacity, Pricing, and Inventory in a Make‐to‐Stock System
Authors: Allon Gad , Zeevi Assaf
Published: November 2010

We address the simultaneous determination of pricing, production, and capacity investment decisions by a monopolistic firm in a multi‐period setting under demand uncertainty. We analyze the optimal decision with particular emphasis on the relationship between price and capacity. We consider models that allow for either bi‐directional price changes or models with markdowns only, and in the latter case we prove that capacity and price are strategic substitutes.
Real‐Time Delay Estimation Based on Delay History in Many‐Server Service Systems with Time‐Varying Arrivals
Authors: Ibrahim Rouba , Whitt Ward
Published: November 2010

Motivated by interest in making delay announcements in service systems, we study real‐time delay estimators in many‐server service systems, both with and without customer abandonment. Our main contribution here is to consider the realistic feature of time‐varying arrival rates. We focus especially on delay estimators exploiting recent customer delay history. We show that time‐varying arrival rates can introduce significant estimation bias in delay‐history‐based delay estimators when the system experiences alternating periods of overload and underload. We then introduce refined delay‐history estimators that effectively cope with time‐varying arrival rates together with non‐exponential service‐time and abandonment‐time distributions, which are often observed in practice. We use computer simulation to verify that our proposed estimators outperform several natural alternatives.
Life‐Cycle Channel Coordination Issues in Launching an Innovative Durable Product
Authors: Gutierrez Genaro J. , He Xiuli
Published: November 2010

We analyze the dynamic strategic interactions between a manufacturer and a retailer in a decentralized distribution channel used to launch an innovative durable product (IDP). The underlying retail demand for the IDP is influenced by word‐of‐mouth from past adopters and follows a Bass‐type diffusion process. The word‐of‐mouth influence creates a trade‐off between immediate and future sales and profits, resulting in a multi‐period dynamic supply chain coordination problem. Our analysis shows that while in some environments, the manufacturer is better off with a far‐sighted retailer, there are also environments in which the manufacturer is better off with a myopic retailer. We characterize equilibrium dynamic pricing strategies and the resulting sales and profit trajectories. We demonstrate that revenue‐sharing contracts can coordinate the IDP's supply chain with both far‐sighted and myopic retailers throughout the entire planning horizon and arbitrarily allocate the channel profit.
Antioxidant multi-walled carbon nanotubes by free radical grafting of gallic acid: new materials for biomedical applications
Authors: Cirillo Giuseppe , Hampel Silke , Klingeler Rüdiger , Puoci Francesco , Iemma Francesca , Curcio Manuela , Parisi Ortensia Ilaria , Spizzirri Umile Gianfranco , Picci Nevio , Leonhardt Albrecht , Ritschel Manfred , Büchner Bernd
Published: November 2010

Objectives

To prove the possibility of covalently functionalizing multi-walled carbon nanotubes (CNTs) by free radical grafting of gallic acid on their surface with the subsequent synthesis of materials with improved biological properties evaluated by specific in-vitro assays.

Methods

Antioxidant CNTs were synthesized by radical grafting of gallic acid onto pristine CNTs. The synthesis of carbon nanotubes was carried out in a fixed-bed reactor and, after the removal of the amorphous carbon, the grafting process was performed. The obtained materials were characterized by fluorescence and Fourier transform infrared spectroscopy (FT-IR) analyses. After assessment of the biocompatibility and determination of the disposable phenolic group content, the antioxidant properties were evaluated in terms of total antioxidant activity and scavenger ability against 2,2′-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl and peroxyl radicals. Finally the inhibition activity on acetylcholinesterase was evaluated.

Key findings

The covalent fuctionalization of CNTs with gallic acid was confirmed and the amount of gallic acid bound per g of CNTs was found to be 2.1 ± 0.2 mg. Good antioxidant and scavenging properties were recorded in the functionalized CNTs, which were found to be able to inhibit the acetylcholinesterase with potential improved activity for biomedical and pharmaceutical applications.

Conclusions

For the first time, a free radical grafting procedure was proposed as a synthetic approach for the covalent functionalization of CNTs with an antioxidant polyphenol.
Investigation of Turbine Shroud Distortions on the Aerodynamics of a One and One-Half Stage High-Pressure Turbine
Authors: Crosh Eric A. , Haldeman Charles W. , Dunn Michael G. , Holmes D. Graham , Mitchell Brian E.
Published: November 2010

As part of a proactive effort to investigate the ability of computational fluid dynamics tools to predict time-accurate surface-pressure histories, a combined experimental/computational investigation was performed, examining the effect of rotor shroud (casing) out-of-roundness on the unsteady pressure loading for the blade row of a full-stage turbine. The casing out-of-roundness was idealized by designing a casing ring with a sinusoidal variation. This casing ring was used to replace a flat casing for an existing turbine, and direct comparisons were made between the time-accurate pressure measurements and predictions obtained using the flat and “wavy” casings. For both casing configurations, predictions of the unsteady pressure loading for many locations on the blade and vane were obtained using Numeca’s FINE/TURBO code and General Electric’s turbine and compressor analysis (TACOMA) code. This paper will concentrate on the results obtained for the wavy casing, but the results for the flat casing are presented as a baseline case. The time-accurate surface-pressure measurements were acquired for the vane and blade of a modern, 3D, 1 and 1/2 stage high-pressure turbine operating at the design corrected speed and stage pressure ratio. The research program utilized an uncooled turbine stage for which all three airfoil rows are heavily instrumented at multiple spans to develop a full data set. The vane-blade-vane count for this machine is 38-72-38. The number of waves in the distorted shroud “wavy wall” is approximately 1.5 times the number of vanes. The resulting changes in the aerodynamic surface-pressure measurements were measurable at all blade spanwise locations. Variations in the time-averaged surface pressure of up to 5% of the flat casing values were observed. In addition, the frequency content of the time-resolved blade data for the wavy casing changed substantially from that measured using the flat casing, with changes in both amplitudes and frequencies. Imposing the casing irregularity changed the fundamental physics of the problem from a single frequency and its harmonics to a multifrequency problem with mixed harmonics. The unsteady effects of this type of problem can be addressed using the harmonic method within Numeca’s FINE/TURBO code, which is designed to handle multiple blade passing frequencies and harmonics for one blade row. A more traditional approach is included in this paper by employing the TACOMA code in a linearized mode that produces results for a single frequency. These results show that casing irregularity can have a significant influence on the blade surface-pressure characteristics. Further, it is demonstrated that the FINE/TURBO code experienced difficulty in predicting the unsteady pressure signal attributed to the wavy casing configuration, while at the same time, in capturing the unsteady signal attributed to the vane passing due to limitations in the current methodology.
Prediction of Ingestion Through Turbine Rim Seals—Part I: Rotationally Induced Ingress
Authors: Owen J. Michael
Published: November 2010

The mainstream flow past the stationary nozzle guide vanes and rotating turbine blades in a gas turbine creates an unsteady nonaxisymmetric variation in pressure in the annulus, radially outward of the rim seal. The ingress and egress occur through those parts of the seal clearance where the external pressure is higher and lower, respectively, than that in the wheel-space; this nonaxisymmetric type of ingestion is referred to here as externally induced (EI) ingress. Another cause of ingress is that the rotating air inside the wheel-space creates a radial gradient of pressure so that the pressure inside the wheel-space can be less than that outside; this creates rotationally induced (RI) ingress, which—unlike EI ingress—can occur, even if the flow in the annulus is axisymmetric. Although the EI ingress is usually dominant in a turbine, there are conditions under which both EI and RI ingress are significant, these cases are referred to as combined ingress. In Part I of this two-part paper, the so-called orifice equations are derived for compressible and incompressible swirling flows, and the incompressible equations are solved analytically for the RI ingress. The resulting algebraic expressions show how the nondimensional ingress and egress vary with Θ0, which is the ratio of the flow rate of sealing air to the flow rate necessary to prevent ingress. It is shown that ε, the sealing effectiveness, depends principally on Θ0, and the predicted values of ε are in mainly in good agreement with the available experimental data.
Film Cooling
Effectiveness and Heat Transfer Near Deposit-Laden Film
Holes
Authors: Lewis Scott , Barker Brett , Bons Jeffrey P. , Ai Weiguo , Fletcher Thomas H.
Published: November 2010

Experiments were conducted to determine the impact of synfuel deposits on film cooling effectiveness and heat transfer. Scaled up models were made of synfuel deposits formed on film-cooled turbine blade coupons exposed to accelerated deposition. Three distinct deposition patterns were modeled: a large deposition pattern (maximum deposit peak≅2 hole diameters) located exclusively upstream of the holes, a large deposition pattern (maximum deposit peak≅1.25 hole diameters) extending downstream between the cooling holes, and a small deposition pattern (maximum deposit peak≅0.75 hole diameter) also extending downstream between the cooling holes. The models featured cylindrical holes inclined at 30 deg to the surface and aligned with the primary flow direction. The spacing of the holes were 3, 3.35, and 4.5 hole diameters, respectively. Flat models with the same film cooling hole geometry and spacing were used for comparison. The models were tested using blowing ratios of 0.5–2 with a turbulent approach boundary layer and 0.5% freestream turbulence. The density ratio was approximately 1.1 and the primary flow Reynolds number at the film cooling row location was 300,000. An infrared camera was used to obtain the film cooling effectiveness from steady state tests and surface convective heat transfer coefficients using transient tests. The model with upstream deposition caused the primary flow to lift off the surface over the roughness peaks and allowed the coolant to stay attached to the model. Increasing the blowing ratio from 0.5 to 2 only expanded the region that the coolant could reach and improved the cooling effectiveness. Though the heat transfer coefficient also increased at high blowing ratios, the net heat flux ratio was still less than unity, indicating film cooling benefit. For the two models with deposition between the cooling holes, the freestream air was forced into the valleys in line with the coolant holes and degraded area-averaged coolant performance at lower blowing ratios. It is concluded that the film cooling effectiveness is highest when deposition is limited to upstream of the cooling holes. When accounting for the insulating effect of the deposits between the film holes, even the panels with deposits downstream of the film holes can yield a net decrease in heat flux for some cases.
A Method for Evaluating the Aerodynamic Stability of Multistage
Axial-Flow Compressors
Authors: Nakano Tsuguji , Breeze-Stringfellow Andy
Published: November 2010

A new simple engineering parameter to evaluate the stability of multistage axial compressors has been derived. It is based on the stability analysis for a small circumferential disturbance imposed on the steady-state flow field. The analytical model assumes that the flow field is two dimensional and incompressible in the ducts between blade rows although the steady-state density is permitted to change across the blade rows. The resulting stall parameter contains terms that relate to the slope of the pressure rise characteristic of the blade rows and the inertia effects of the fluid in the blade rows and ducts. The parameter leads to the classical stability criteria based on the slope of the overall total to static pressure rise coefficient in the limit where constant density and constant blade rotational speed are assumed across the compressor. The proposed stall parameter has been calculated for three different multistage axial flow compressors, and the results indicate that the parameter has a strong correlation with the measured stability of the compressors. The good correlation with the test data demonstrates that the newly derived stall parameter captures much of the fundamental physics of instability inception in multistage compressors, and that it can be a good guideline for designers and engineers needing to evaluate the stability boundary of multistage machines.
Predicting Separation and Transitional Flow in Turbine Blades at Low Reynolds Numbers—Part II: The Application to a Highly Separated Turbine Blade Cascade Geometry
Authors: Sanders Darius D. , O’Brien Walter F. , Sondergaard Rolf , Polanka Marc D. , Rabe Douglas C.
Published: November 2010

There has been a need for improved prediction methods for low pressure turbine (LPT) blades operating at low Reynolds numbers. This is known to occur when LPT blades are subjugated to high altitude operations causing a decrease in the inlet Reynolds number. Boundary layer separation is more likely to be present within the flowfield of the LPT stages due to increase in the region adverse pressure gradients on the blade suction surface. Accurate CFD predictions are needed in order to improve design methods and performance prediction of LPT stages operating at low Reynolds numbers. CFD models were created for the flow over two low pressure turbine blade designs using a new turbulent transitional flow model, originally developed by Walters and Leylek (2004, “A New Model for Boundary Layer Transition Using a Single Point RANS Approach,” ASME J. Turbomach., 126(1), pp. 193–202). Part I of this study applied Walters and Leylek’s model to a cascade CFD model of a LPT blade airfoil with a light loading level. Flows were simulated over a Reynolds number range of 15,000–100,000 and predicted the laminar-to-turbulent transitional flow behavior adequately. It showed significant improvement in performance prediction compared to conventional RANS turbulence models. Part II of this paper presents the application of the prediction methodology developed in Part I to both two-dimensional and three-dimensional cascade models of a largely separated LPT blade geometry with a high blade loading level. Comparisons were made with available experimental cascade results on the prediction of the inlet Reynolds number effect on surface static pressure distribution, suction surface boundary layer behavior, and the wake total pressure loss coefficient. The kT-kL-ω transitional flow model accuracy was judged sufficient for an understanding of the flow behavior within the flow passage, and can identify when and where a separation event occurs. This model will provide the performance prediction needed for modeling of low Reynolds number effects on more complex geometries.
A Novel Technique for Assessing Turbine Cooling System Performance
Authors: Luque S. , Povey T.
Published: November 2010

A new experimental technique for the accurate measurement of steady-state metal temperature surface distributions of modern heavily film-cooled turbine vanes has been developed and is described in this paper. The technique is analogous to the thermal paint test but has been designed for fundamental research. The experimental facility consists of an annular sector cascade of high pressure (HP) turbine vanes from a current production engine. Flow conditioning is achieved by using an annular sector of deswirl vanes downstream of the test section, being both connected by a three-dimensionally contoured duct. As a result, a transonic and periodic flow, highly representative of the engine aerodynamic field, is established: Inlet turbulence levels, mainstream Mach and Reynolds numbers, and coolant-to-mainstream total pressure ratio are matched. Since the fully three-dimensional nozzle guide vane (NGV) geometry is used, the correct radial pressure gradient and secondary flow development are simulated and the cooling flow redistribution is engine-realistic. To allow heat transfer measurements to be performed, a mainstream-to-coolant temperature difference (up to 33.5°C) is generated by using two steel-wire mesh heaters, operated in series. NGV surface metal temperatures are measured (between 20°C and 40°C) by wide-band thermochromic liquid crystals. These are calibrated in situ and on a per-pixel basis against vane surface thermocouples, in a heating process that spans the entire color play and during which the turbine vanes can be assumed to slowly follow a succession of isothermal states. Experimental surface distributions of overall cooling effectiveness are presented in this paper. By employing resin vanes of the same geometry and cooling configuration (to implement adiabatic wall thermal boundary conditions) and the transient liquid crystal technique, surface distributions of external heat transfer coefficient and film cooling effectiveness can be acquired. By combining these measurements with those from the metal vanes, the results can be scaled to engine conditions with a good level of accuracy.
Understanding Ignition Delay Effects With Pure Component Fuels in a Single-Cylinder Diesel Engine
Authors: Caton Patrick A. , Hamilton Leonard J. , Cowart Jim S.
Published: November 2010

In order to better understand how future candidate diesel fuels may affect combustion characteristics in diesel engines, 21 pure component hydrocarbon fuels were tested in a single-cylinder diesel engine. These pure component fuels included normal alkanes (C6–C16), normal primary alkenes (C6–C18), isoalkanes, cycloalkanes/-enes, and aromatic species. In addition, seven fuel blends were tested, including commercial diesel fuel, U.S. Navy JP-5 aviation fuel, and five Fischer–Tropsch synthetic fuels. Ignition delay was used as a primary combustion metric for each fuel, and the ignition delay period was analyzed from the perspective of the physical delay period followed by the chemical delay period. While fuel properties could not strictly be varied independently of each other, several ignition delay correlations with respect to physical properties were suggested. In general, longer ignition delays were observed for component fuels with lower liquid fuel density, kinematic viscosity, and liquid-air surface tension. Longer ignition delay was also observed for component fuels with higher fuel volatility, as measured by boiling point and vapor pressure. Experimental data show two regimes of operation: For a carbon chain length of 12 or greater, there is little variation in ignition delay for the tested fuels. For shorter chain lengths, a fuel molecular structure is very important. Carbon chain length was used as a scaling variable with an empirical factor to collapse the ignition delay onto a single trend line. Companion detailed kinetic modeling was pursued on the lightest fuel species set (C6) since this fuel set possessed the greatest ignition delay differences. The kinetic model gives a chemical ignition delay time, which, together with the measured experimental ignition delay, suggests that the physical and chemical delay period have comparable importance. However, the calculated chemical delay periods capture the general variation in the overall ignition delay and could be used to predict the ignition delay of possible future synthetic diesel fuels.
Structure Controlled Synthesis of Vertically Aligned Carbon Nanotubes Using Thermal Chemical Vapor Deposition Process
Authors: Hahm Myung Gwan , Kwon Young-Kyun , Busnaina Ahmed , Jung Yung Joon
Published: November 2010

Due to their unique one-dimensional nanostructure along with excellent mechanical, electrical, and optical properties, carbon nanotubes (CNTs) become a promising material for diverse nanotechnology applications. However, large-scale and structure controlled synthesis of CNTs still have many difficulties due to the lack of understanding of the fundamental growth mechanism of CNTs, as well as the difficulty of controlling atomic-scale physical and chemical reactions during the nanotube growth process. Especially, controlling the number of graphene wall, diameter, and chirality of CNTs are the most important issues that need to be solved to harness the full potential of CNTs. Here we report the large-scale selective synthesis of vertically aligned single walled carbon nanotubes (SWNTs) and double walled carbon nanotubes (DWNTs) by controlling the size of catalyst nanoparticles in the highly effective oxygen assisted thermal chemical vapor deposition (CVD) process. We also demonstrate a simple but powerful strategy for synthesizing ultrahigh density and diameter selected vertically aligned SWNTs through the precise control of carbon flow during a thermal CVD process.
The Experimental and Theoretical Evaluation of an Indirect Cooling System for Machining
Authors: Rozzi Jay C. , Sanders John K. , Chen Weibo
Published: November 2010

Cutting fluids have been used in machining processes for many years to decrease the temperature during machining by spraying the coolant into the machining zone directly on the cutting tool and the part. This has the effect of decreasing the tool temperature, which increases tool life and improves the part quality. These benefits come with significant drawbacks. Cutting fluids are environmentally unfriendly, costly, and potentially toxic. An alternative that has been evaluated in this paper is an internal cooling system (ICS) for lathe turning, which cools the cutting tool using a very small amount of an inert, cryogenic working fluid routed through a microchannel heat exchanger (MHX) that is mounted beneath the cutting tool insert. The working fluid absorbs the heat generated during the machining process after which it is harmlessly vented to the environment. This indirect cooling technique results in an environmentally friendly machining process that uses no cutting fluids, enables increased processing speed, and reduces manufacturing costs. An approximate heat transfer model was developed and used to predict the tool life as a function of the tool cooling approach for various speeds. Machining experiments were completed to validate the heat transfer model and confirm that the ICS can significantly improve tool life relative to conventional flood cooling. The validated model was then used to evaluate alternative cooling approaches using the ICS. It was found that the use of a cryogenic working fluid can significantly improve tool life at all cutting speeds but that the latent heat capacity of the working fluid should exceed the expected maximum heat transfer rate into the tool. This work established that the ICS approach is an effective means to increase tool life without the disadvantages associated with external cryogenic cooling methods.
PneumoniaCheck: A Device for Sampling Lower Airway Aerosols
Authors: Scholz Tamera L. , Midha Prem A. , Anderson Larry J. , Ku David N.
Published: November 2010

The pathogens causing pneumonia are difficult to identify because a high quality specimen from the lower lung is difficult to obtain. A new specimen collection device is designed to collect aerosol specimens selectively from the lower lung generated during deep coughing. The PneumoniaCheck device utilizes a separation reservoir and Venturi valve to segregate contents from the upper and lower airways. The device also includes several specially designed features to exclude oral contaminants from the sample and a filter to collect the aerosolized pathogens. Verification testing of PneumoniaCheck demonstrates effective separation of upper airway gas from the lower airway gas (p<0.0001) and exclusion of both liquid and viscous oral material (p<0.0001) from the collection chamber. The filters can collect 99.9997% of virus and bacteria sized particles from the sampled lower lung aerosols. The selective collection of specimens from the lower airway may aid in the diagnosis of specific pathogens causing pneumonia.
Solution of the Structure of the TNF-TNFR2 Complex
Authors: Mukai Yohei , Nakamura Teruya , Yoshikawa Mai , Yoshioka Yasuo , Tsunoda Shin-ichi , Nakagawa Shinsaku , Yamagata Yuriko , Tsutsumi Yasuo
Published: November 2010

Structural differences in the binding of tumor necrosis factor to its two receptors may aid in the development of receptor-specific therapeutics.
Why Pigeon Doo May Be Bad for You
Authors: Ray L. Bryan
Published: November 2010

A “futile cycle” of transcription allows a pathogenic organism to rapidly respond to conditions favoring sexual reproduction.
Reciprocal Regulation
Authors: Vinson Valda
Published: November 2010

A crystal structure shows how the two components of a central signaling complex regulate each other.
Pharmacodynamic Modeling of
In Vitro
Activity of Marbofloxacin against
Escherichia coli
Strains
Authors: Andraud M. , Chauvin C. , Sanders P. , Laurentie M.
Published: November 2010

A mathematical pharmacodynamic model was developed to describe the bactericidal activity of marbofloxacin against
Escherichia coli
strains with reduced susceptibility levels (determined using MICs) under optimal and intestinal growth conditions. Model parameters were estimated using nonlinear least-square curve-fitting procedures for each
E. coli
strain. Parameters related to bactericidal activity were subsequently analyzed using a maximum-effect (
E
max
) model adapted to account for a direct and a delayed effect. While net growth rates did not vary significantly with strain susceptibility, culture medium had a major effect. The bactericidal activity of marbofloxacin was closely associated with the concentration and the duration of exposure of the bacteria to the antimicrobial agent. The value of the concentration inducing a half-maximum effect (
C
50
) was highly correlated with MIC values (
R
2
= 0.87 and
R
2
= 0.94 under intestinal and optimal conditions, respectively). Our model reproduced the time-kill kinetics with good accuracy (
R
2
of >0.90) and helped explain observed regrowth.
MyD88 Deficiency Leads to Decreased NK Cell Gamma Interferon Production and T Cell Recruitment duringChlamydia muridarumGenital Tract Infection, but a Predominant Th1 Response and Enhanced Monocytic Inflammation Are Associated with Infection Resolution
Authors: Nagarajan Uma M. , Sikes James , Prantner Daniel , Andrews Charles W. , Frazer Lauren , Goodwin Anna , Snowden Jessica N. , Darville Toni
Published: November 2010

We have previously shown that MyD88 knockout (KO) mice exhibit delayed clearance ofChlamydia muridarumgenital infection compared to wild-type (WT) mice. A blunted Th1 response and ineffective suppression of the Th2 response were also observed in MyD88 KO mice. The goal of the present study was to investigate specific mechanisms whereby absence of MyD88 leads to these effects and address the compensatory mechanisms in the genital tract that ultimately clear infection in the absence of MyD88. It was observed that NK cells recruited to the genital tract in MyD88 KO mice failed to produce gamma interferon (IFN-γ) mRNA and protein. This defect was associated with decreased local production of interleukin-17 (IL-17), IL-18, and tumor necrosis factor alpha (TNF-α) but normal levels of IL-12p70. Additionally, recruitment of CD4 T cells to the genital tract was reduced in MyD88 KO mice compared to that in WT mice. Although chronic infection in MyD88 KO mice resulted in oviduct pathology comparable to that of WT mice, increased histiocytic inflammation was observed in the uterine horns. This was associated with increased CCL2 levels and recruitment of macrophages as a potential compensatory mechanism. Further deletion of TLR4-TRIF signaling in MyD88 KO mice, using TLR4/MyD88 double-KO mice, did not further compromise host defense against chlamydiae, suggesting that compensatory mechanisms are Toll-like receptor (TLR) independent. Despite some polarization toward a Th2 response, a Th1 response remained predominant in the absence of MyD88, and it provided equivalent protection against a secondary infection as observed in WT mice.
Rodent dispersal of fungal spores promotes seedling establishment away from mycorrhizal networks on Quercus garryana
Authors: Frank J. L. , Anglin S. , Carrington E. M. , Taylor D. S. , Viratos B. , Southworth D.
Published: November 2010

With global warming and the possible decline of conifers, more habitat may be available to oaks, particularly at higher elevations and more northerly latitudes. Whether oaks expand into new habitats will depend on their ability to disperse and establish at the margins of existing woodlands. Because oaks have a symbiotic relationship with ectomycorrhizal fungi, range expansion requires dispersal of both symbionts: the acorns and the mycorrhizal inoculum. Little is known of this dual dispersal. Here we assess the availability of ectomycorrhizal inoculum as a function of the distance from mature oaks. We examined soil cores for ectomycorrhizal roots and rodent fecal pellets for fungal spores along transects away from mature trees of Quercus garryana Dougl. ex Hook., and planted acorns as bioprobes. We identified spores by microscopy, and mycorrhizas by DNA sequences of the ITS region. Mycorrhizas were present in soil cores 5 m from parent trees, but not beyond. Spores of hypogeous fungi were found in rodent fecal pellets at distances up to 35 m from mature trees. Hypogeous fungi formed ectomycorrhizas with first-year seedlings within the root zone of mature trees and with second-year seedlings beyond the root zone. These data indicate that for seedlings near mature trees, the source of fungal inoculum was the mycorrhizal network of mature trees, and for seedlings beyond that, rodents dispersed the inoculum. We conclude that rodent dispersal of fungal spores promotes seedling establishment away from mycorrhizal networks in Q. garryana.
Hybridization and the reproductive pathways mediating gene flow between nativeMalus coronariaand domestic apple,M. domestica
Authors: Kron Paul , Husband Brian C.
Published: November 2010

Gene flow from crops to wild populations is of increasing scientific and public interest, but the potential effects are not well understood when taxa differ in ploidy. We examined the potential for hybridization and gene flow between the introduced diploid domestic apple, Malus domestica Borkh., and the tetraploid crabapple, Malus coronaria (L.) Miller. Using ploidy and isozyme markers, we inferred the incidence of hybrids in natural populations (adults and open-pollinated seed) and in controlled crosses. Geographic range and flowering time overlapped sufficiently for cross-pollination between domestic apple and M. coronaria. Heterospecific crosses produced as many fruit and seeds as conspecific pollinations on M. coronaria mothers. Some seeds from heterospecific pollinations were hybrids, while others were apomictic in origin. In a natural population, all adult trees tested were tetraploid, but open-pollinated seeds varied in ploidy: 57% tetraploid (sexual or apomictic); 7.7% diploid (apomictic); 7.4% hexaploid or octaploid (sexual); and 27.5% triploid or pentaploid hybrids. Despite previous reports showing that the native and introduced gene pools remain distinct, the high proportion of hybrid seeds suggests there is significant potential for gene flow from domestic apples into native M. coronaria populations.