bluuebunny/crossref_metadata_2025 huggingface dataset:
Early pancreatic development requires the vertebrate Suppressor of Hairless (RBPJ) in the PTF1 bHLH complex
Authors: Masui Toshihiko , Long Qiaoming , Beres Thomas M. , Magnuson Mark A. , MacDonald Raymond J.
Published: October 2007

PTF1a is an unusual basic helix–loop–helix (bHLH) transcription factor that is required for the development of the pancreas. We show that early in pancreatic development, active PTF1a requires interaction with RBPJ, the vertebrate Suppressor of Hairless, within a stable trimeric DNA-binding complex (PTF1). Later, as acinar cell development begins, RBPJ is swapped for RBPJL, the constitutively active, pancreas-restricted paralog of RBPJ. Moreover, the Rbpjl gene is a direct target of the PTF1 complex: At the onset of acinar cell development when the Rbpjl gene is first induced, a PTF1 complex containing RBPJ is bound to the Rbpjl promoter. As development proceeds, RBPJL gradually replaces RBPJ in the PTF1 complex bound to Rbpjl and appears on the binding sites for the complex in the promoters of other acinar-specific genes, including those for the secretory digestive enzymes. A single amino acid change in PTF1a that eliminates its ability to bind RBPJ (but does not affect its binding to RBPJL) causes pancreatic development to truncate at an immature stage, without the formation of acini or islets. These results indicate that the interaction between PTF1a and RBPJ is required for the early stage of pancreatic growth, morphogenesis, and lineage fate decisions. The defects in pancreatic development phenocopy those of Ptf1a-null embryos; thus, the first critical function of PTF1a is in the context of the PTF1 complex containing RBPJ. Action within an organ-specific transcription factor is a previously unknown function for RBPJ and is independent of its role in Notch signaling.
SIRT1 controls endothelial angiogenic functions during vascular growth
Authors: Potente Michael , Ghaeni Laleh , Baldessari Danila , Mostoslavsky Raul , Rossig Lothar , Dequiedt Franck , Haendeler Judith , Mione Marina , Dejana Elisabetta , Alt Frederick W. , Zeiher Andreas M. , Dimmeler Stefanie
Published: October 2007

The nicotinamide adenine dinucleotide (NAD+)-dependent histone deacetylase Sir2 regulates life-span in various species. Mammalian homologs of Sir2 are called sirtuins (SIRT1–SIRT7). In an effort to define the role of sirtuins in vascular homeostasis, we found that among the SIRT family, SIRT1 uniquely regulates angiogenesis signaling. We show that SIRT1 is highly expressed in the vasculature during blood vessel growth, where it controls the angiogenic activity of endothelial cells. Loss of SIRT1 function blocks sprouting angiogenesis and branching morphogenesis of endothelial cells with consequent down-regulation of genes involved in blood vessel development and vascular remodeling. Disruption of SIRT1 gene expression in zebrafish and mice results in defective blood vessel formation and blunts ischemia-induced neovascularization. Through gain- and loss-of-function approaches, we show that SIRT1 associates with and deacetylates the forkhead transcription factor Foxo1, an essential negative regulator of blood vessel development to restrain its anti-angiogenic activity. These findings uncover a novel and unexpected role for SIRT1 as a critical modulator of endothelial gene expression governing postnatal vascular growth.
Reiterated WG/GW motifs form functionally and evolutionarily conserved ARGONAUTE-binding platforms in RNAi-related components
Authors: El-Shami Mahmoud , Pontier Dominique , Lahmy Sylvie , Braun Laurence , Picart Claire , Vega Danielle , Hakimi Mohamed-Ali , Jacobsen Steven E. , Cooke Richard , Lagrange Thierry
Published: October 2007

Two forms of RNA Polymerase IV (PolIVa/PolIVb) have been implicated in RNA-directed DNA methylation (RdDM) in Arabidopsis. Prevailing models imply a distinct function for PolIVb by association of Argonaute4 (AGO4) with the C-terminal domain (CTD) of its largest subunit NRPD1b. Here we show that the extended CTD of NRPD1b-type proteins exhibits conserved Argonaute-binding capacity through a WG/GW-rich region that functionally distinguishes Pol IVb from Pol IVa, and that is essential for RdDM. Site-specific mutagenesis and domain-swapping experiments between AtNRPD1b and the human protein GW182 demonstrated that reiterated WG/GW motifs form evolutionarily and functionally conserved Argonaute-binding platforms in RNA interference (RNAi)-related components.
Niccolo Machiavelli: 1527–1927
Authors: Bugeja Henry
Published: October 2007

On the 22nd of June, four hundred years ago, Niccolo Machiavelli died at San Casciano, not far from Florence, where he had lived since his dismissal from the office of Secretary to the Florentine Republic in 1512. A typical representative of his times, although his life, habits and ideals were those of a pagan, he died a Christian death : all the neo-pag'ans of the Italian Renaissance did the same. It was the fashion.

A broken and disappointed man, discarded by the Medici, to whom in vain he had offered his services and experience, ready to sacrifice his political convictions if they could employ him, were it only in rolling a stone,’ suspected by his old political friends as one who fawned on princes and a traitor to the Republican cause, Machiavelli passed the last few years of his life cursing fate, fighting against poverty and chafing under this enforced idleness, which to a man of his undoubted capabilities, accustomed for many a year to transact diplomatic business with the most renowned princes of the epoch, must have been truly unbearable. It is with pity and sympathy, not unmingled with a sense of disgust, that one reads Machiavelli’s own account of how he used to pass his days in the semiexile of San Casciano. Rising at dawn, after passing a couple of hours in the woods of the estate he used to go and sit by a spring reading Dante, Petrarch, Tibullus and Ovid, meditating pleasantly on ‘their amorous transports and the history of their loves’ ; thence betaking himself to an inn by the roadside to gossip with passers-by and ‘note the varied tastes and diverse fancies of mankind. . . . Dinner over, I go back to the inn.
Poles and Parallels of Culture
Authors: Kincaid Dennis
Published: October 2007

It is not often that a book excites such comment as did Spengler’s Decline of the West in postwar Germany. Only the first volume of this has been translated into English, as yet. It is an exposition of determinism involving the methodic rise and fall of cultures. And in spite of some exaggerations, and the arbitrariness of its thesis, it is of the greatest interest. Possibly its greatest value lies in this, that the author contrives to awaken in his reader an understanding of the diversity of civilizations. We are so accustomed to look from out our own culture without adjusting our prejudices, and to form judgments in a moment of time upon an almost eternal phenomenon. We take no account of the changes in culture, of the shifting perspectives, and alien outlook in countries which are spiritually as remote as another world. We condemn or praise with no real sympathy. In the hope of deepening understanding a few comparisons between civilizations are suggested in this article.

The natural opposite of Europe has been always the East. But Roman Europe was, and modem Europe is, confronted by an Orient feverish and decadent. Syria and Egypt then can be compared to India now. We can find parallels between the local cults of those countries that rose to sudden prominence as fashions at Rome and those that do the same to-day; or between the atmosphere of the Trismegistists and that of the followers of Shankara. Between that period and the present the true East and true West were separated by the vigorous world of Arab culture, alien alike to its eastern and its western neighbours.
Dickens and Spirituallsm
Authors: Clayton Joseph
Published: October 2007

Quite a number of books have been published lately containing, so the spiritualists declare, messages from another world. The reading of these books does not suggest that the ‘spirits or their messages are any livelier or more intelligent than they were nearly seventy years ago, when Charles Dickens came across them.

In The Haunted House, a Christmas story written for All the Year Round, 1859, Dickens begins with the revelations provided by a travelling companion in a railway train. The journey was by night, and the fellow passenger, armed with a pencil and pocket-book, was perpetually listening and taking notes.

‘I have passed the night—as indeed I pass the whole of my time now—in spiritual intercourse,’ explained the man—’ a goggle-eyed gentleman of a perplexed aspect’—in the cold light of morning.

The messages had not been rapped on any table, but had been deciphered in the jolts and bumps of the carriage. (Many of us are familiar with the rhythmic utterance of railway engines.) The seance— ‘conference’ the goggle-eyed gentleman preferred to call it—began with the greeting :’ Evil communications corrupt good manners.’

‘“Sound,” said I; “but, absolutely new?”’

‘“New from spirits,” returned the gentleman.’ The last entry in the notebook was : ‘A bird in the hand is worth two in the Bosh.’

‘“Truly I am of the same opinion,” said I; “ but shouldn’t it be Bush?”’

‘“It came to me, Bosh,” returned the gentle... n , )> )
St. Peter, St. Paul and St. Thomas
Authors: McNabb Vincent
Published: October 2007

The following extracts from the Summa Theologica of St. Thomas may be of interest and value to our readers. They are found in the Secunda Secundae.

Question 33. Article 4.

Whether a man is bound to correct his prelate.

Obj. 2. A gloss on Gal. II, 11 : ‘/ withstood him to the face adds : as an equal. Therefore since a subject is not equal to his prelate, he ought not to correct him ....

.... I answer that a subject is not competent to administer to his prelate the correction which is an act of justice through the coercive nature of punishment.

But the fraternal correction which is an act of charity is within the competency of everyone in respect of any person towards whom he is bound by charity, provided there be something in that person which requires correction.

Now an act which proceeds from a habit or power extends to whatever is contained under the object of that power or habit. Thus vision extends to all things comprised in the object of sight. Since, however, a virtuous act needs to be moderated by due circumstances, it follows that when a subject corrects his prelate he ought to do so in a becoming manner; not with impudence and harshness, but with gentleness and respect. Hence the Apostle says (I Tim. v, 1), An ancient man rebuke not, but entreat as a father. Wherefore Dionysius finds fault with Demophilus, a monk (Ep. viii), for rebuking a priest with insolence by striking and turning him out of the church.
The Book of St. Catherine of Siena
Authors: Curtayne Alice
Published: October 2007

The Church has produced much spiritual writing in the five and a half centuries which have elapsed since this extraordinary genius of the Middle Ages, this woman of strenuous action, left us the written expression of her contemplative life. She, and the friends who wrote it for her, always spoke of it simply as ‘The Book,’ and after five hundred and fifty years it may well retain the title, for it has lost none of its unique character in Christian literature. It was written under peculiarly arresting circumstances : dictated by a woman of thirty-one, while in ecstasy, to three or four members of her famous circle: Barduccio, Stephen, Neri, Tuscan youths of noble family, who were her ardent disciples, and Christopher, a Sienese notary. This is the Saint’s own description of her mental and bodily state when in ecstasy:

. . . . the bodily powers alone departed, becoming united to Me through affection of Love. Then is the memory full of nought but Me; the understanding uplifted � to contemplate My truth as object; the will, that follows the understanding, loves and unites itself to what the eye of the understanding sees. These powers, being united and gathered together and immersed and inflamed in Me, the body loses its feeling, so that the seeing eye sees not, and the hearing ear hears not, and the tongue does not speak, except as the abundance of the heart will sometimes permit it for the alleviation of the heart and the praise and glory of My name.’
Convolvulus
Authors: Sedgwick R.L.
Published: October 2007

The rain had fallen drearily From the grey sky,

And past the wet trees heavily The wine-cart rumbled by.

The goodman doffed his coloured cap At every shrine,

And prayed to God that no mishap Might overtake his wine.

But the ruts grew deeper as They crossed the lea :

The cart struck fast, the goodman was Powerless to free.

The sinking wheels and stumbling horse Whose piteous neigh

Shook the damp woods and the pale gorse That fringed the tortuous way.

It chanced Our Lady was the first To cross the burn :

Said she, ‘Give me some wine, I thirst— I’ll help thee in return.’

The goodman bowed, and looking up—

‘Right willingly,’

He said : ‘But Lady, I’ve no cup Or glass to offer thee.’

She picked a flower in the grass,

Shaped like a bowl,

Which served her as a little glass Not as a buttonhole.

Our Lady drank the wine, and lo!

The cart was free.

And once more on their way they go Praising God joyfully.

The flower still blossoms in the grass: Folk call it thus,

Either Our Lady’s little glass,

Or wild convolvulus.

R. L. Sedgwick.
Martyrs
Authors: Hill Philip Maurice
Published: October 2007

‘Apellabo martyrem; praedicavi satis.’

—St. Ambrose.

With what emotion must he who travels from the south first break upon the Campagna, and see presently the Appian Way. Here, on the outskirts of the City, is the heart of Rome. Not the centre of her grandeur and dominion, not the seat of justice and power, but the cradle of Christianity suffering and victorious.

‘Now—the single little turret that remains On the plains,

By the caper over-rooted, by the gourd Overscored . . . .

Here is ‘love among the ruins.’ But divine, not human, love. Along the line marked by the cypresses lie the catacombs, untouched by any pious transformation. These were the sleeping places of the martyrs. Who were they, and what have they done for Christianity?

First, they have supplied certain proofs needful for the understanding of the nature and continuity of the Faith and of the Church.

No cause was ever so hopeless as that of Christianity on the morning after the Crucifixion. No religion has ever won a wider dominion in a shorter time.

The Holy Spirit prepared the soil for Christianity and made sure its growth and harvesting. The universal Empire of Pagan Rome forshadowed the Universal Church. It brought peace, order and unity of government to peoples as various in mind as in colour and race, and helped that ‘empire within the Empire’ to gather men of every condition and in all places under one rule of thought and life. Guided by the Church, religious licence was exchanged for spiritual liberty, and thousands embraced a creed which made all men equal before God.
Investigation of Unsteady Flow Field in a Vaned Diffuser of a Transonic Centrifugal Compressor
Authors: Ibaraki Seiichi , Matsuo Tetsuya , Yokoyama Takao
Published: October 2007

Transonic centrifugal compressors are used with high-load turbochargers and turboshaft engines. These compressors usually have a vaned diffuser to increase the efficiency and the pressure ratio. To improve the performance of such a centrifugal compressor, it is required to optimize not only the impeller but also the diffuser. However the flow field of the diffuser is quite complex and unsteady because of the impeller located upstream. Although some research on vaned diffusers has been published, the diffuser flow is strongly dependent on the particular impeller exit flow, and some of the flow physics remain to be elucidated. In the research reported here, detailed flow measurements within a vaned diffuser were conducted using a particle image velocimetery (PIV). The vaned diffuser was designed with high subsonic inlet conditions marked by an inlet Mach number of 0.95 for the transonic compressor. As a result, a complex three-dimensional flow with distortion between the shroud and the hub was observed. Also, unsteady flow accompanying the inflow of the impeller wake was confirmed. Steady computational flow analysis was performed and compared with the experimental results.
Heat Transfer Measurements in a First-Stage Nozzle Cascade Having Endwall Contouring: Misalignment and Leakage Studies
Authors: Piggush J. D. , Simon T. W.
Published: October 2007

This work supports new gas turbine designs for improved performance by evaluating endwall heat transfer rates in a cascade that is representative of a first-stage stator passage and incorporates endwall assembly features and leakage. Assembly features, such as gaps in the endwall and misalignment of those gaps, disrupt the endwall boundary layer, typically leading to enhanced heat transfer rates. Leakage flows through such gaps within the passage can also affect endwall boundary layers and may induce additional secondary flows and vortex structures in the passage near the endwall. The present paper documents leakage flow and misalignment effects on the endwall heat transfer coefficients within a passage which has one axially contoured and one straight endwall. In particular, features associated with the combustor-to-turbine transition piece and the assembly joint on the vane platform are addressed.
An Experimental and Numerical Study of Heat Transfer and Pressure Loss in a Rectangular Channel With V-Shaped Ribs
Authors: Maurer Michael , von Wolfersdorf Jens , Gritsch Michael
Published: October 2007

An experimental and numerical study was conducted to determine the thermal performance of V-shaped ribs in a rectangular channel with an aspect ratio of 2:1. Local heat transfer coefficients were measured using the steady state thermochromic liquid crystal technique. Periodic pressure losses were obtained with pressure taps along the smooth channel sidewall. Reynolds numbers from 95,000 to 500,000 were investigated with V-shaped ribs located on one side or on both sides of the test channel. The rib height-to-hydraulic diameter ratios (e∕Dh) were 0.0625 and 0.02, and the rib pitch-to-height ratio (P∕e) was 10. In addition, all test cases were investigated numerically. The commercial software FLUENT™ was used with a two-layer k-ε turbulence model. Numerically and experimentally obtained data were compared. It was determined that the heat transfer enhancement based on the heat transfer of a smooth wall levels off for Reynolds numbers over 200,000. The introduction of a second ribbed sidewall slightly increased the heat transfer enhancement whereas the pressure penalty was approximately doubled. Diminishing the rib height at high Reynolds numbers had the disadvantage of a slightly decreased heat transfer enhancement, but benefits in a significantly reduced pressure loss. At high Reynolds numbers small-scale ribs in a one-sided ribbed channel were shown to have the best thermal performance.
Double-Jet Ejection of Cooling Air for Improved Film Cooling
Authors: Kusterer Karsten , Bohn Dieter , Sugimoto Takao , Tanaka Ryozo
Published: October 2007

Film cooling in gas turbines leads to aerodynamic mixing losses and reduced temperatures of the gas flow. Improvements of the gas turbine thermal efficiency can be achieved by reducing the cooling fluid amount and by establishing a more equal distribution of the cooling fluid along the surface. It is well known that vortex systems in the cooling jets are the origin of reduced film-cooling effectiveness. For the streamwise ejection case, kidney vortices result in a liftoff of the cooling jets; for the lateral ejection case, usually only one dominating vortex remains, leading to hot gas flow underneath the jet from one side. Based on the results of numerical analyses, a new cooling technology has been introduced by the authors, which reaches high film-cooling effectiveness as a result of a well-designed cooling hole arrangement for interaction of two neighboring cooling jets (double-jet film cooling (DJFC)). The results show that configurations exist, where an improved film-cooling effectiveness can be reached because an anti-kidney vortex pair is established in the double-jet. The paper aims at the following major contributions: (1) to introduce the DJFC as an alternative film-cooling technology to conventional film-cooling design; (2) to explain the major phenomena, which leads to the improvement of the film-cooling effectiveness by application of the DJFC; and (3) to prove basic applicability of the DJFC to a realistic blade cooling configuration and present the first test results under machine operating conditions.
Transport of Particulates in an Internal Cooling Ribbed Duct
Authors: Shah Anant , Tafti Danesh K.
Published: October 2007

A ribbed square duct (P∕e=10, e∕Dh=0.10) subjected to sand ingestion is studied using large-eddy simulations (LES). Particle sizes of 10μm, 50μm, and 100μm with nondimensional response times (normalized by friction velocity and hydraulic diameter) of 0.06875, 1.71875, and 6.875, respectively are considered. The calculations are performed for a nominal bulk Reynolds number of 20,000 under fully-developed conditions. Distributions of impingement density, impingement velocities and angles, together with fractional energy transfer are presented for each surface. It is found that about 40% of the total number of 10micron particles are concentrated in the vicinity (within 0.05 Dh) of the duct surfaces, compared to 25–30% of the 50 and 100micron particles. The 10micron particles are more sensitive to the primary and secondary flow velocities than the larger particles. While the 10micron particles exhibit high energy transfer to the surface near the rib side-wall junction and immediately upstream of the rib, the larger particles exhibit more uniform distributions. The largest fraction of incoming particulate energy is transferred to the front face of the rib and is between one to two orders of magnitude larger than the other surfaces. As particle size increases, substantial particle energy is also transferred to the back face of the rib by particles bouncing off the front face and carrying enough momentum to impinge on the back face of the preceding rib.
Predicting Transition on Concave Surfaces
Authors: Johnson Mark W.
Published: October 2007

Boundary layers on concave surfaces differ from those on flat plates due to the presence of Taylor-Goertler (T-G) vortices. These vortices cause momentum transfer normal to the blade’s surface and hence result in a more rapid development of the laminar boundary layer and a fuller profile than is typical of a flat plate. Transition of boundary layers on concave surfaces also occurs at a lower Rex than on a flat plate. Concave surface transition correlations have been formulated previously from experimental data, but they are not comprehensive and are based on relatively sparse data. The purpose of the current work was to attempt to model the physics of both the laminar boundary layer development and transition process in order to produce a transition model suitable for concave surface boundary layers. The development of the laminar boundary layer on a concave surface was modeled by considering the profiles at the upwash and downwash locations separately. The profiles of the boundary layers at these two locations were then combined to successfully approximate the spanwise averaged profile. The ratio of the boundary layer thicknesses at the two locations was found to be as great as 50 and this leads to laminar boundary layer shape factors as low as 1.3 and skin friction coefficients up to 12 times the value for a flat plate laminar boundary layer. Boundary layers therefore grow much more rapidly on concave surfaces than on flat plates. The transition model assumed that transition commenced in the upwash location boundary layer at the same transition inception Reθ observed on a flat plate. Transition at the downwash location then results from the growth of turbulent spots from the upwash location rather than through the initiation of spots. The model showed that initially curvature promotes transition because of the thickened upwash boundary layer, but for strong curvature the T-G vortices effectively stabilize the boundary layer and transition then occurs at a higher Reθ than on a flat plate. Results from the transition model were in broad agreement with experimental observations. The current work therefore provides a basis for the modeling of transition on concave surfaces.
Coriolis Forces in Forced Response Analysis of Mistuned Bladed Disks
Authors: Nikolic M. , Petrov E. P. , Ewins D. J.
Published: October 2007

The problem of estimating the mutual interaction of the effects of Coriolis forces and of blade mistuning on the vibration characteristics of bladed disks is addressed in this paper. The influence of different degrees of mistuning on forced response and amplification factors are studied in the presence of Coriolis forces and then compared to their non-Coriolis counterparts using a computationally inexpensive, yet representative, model of a bladed disk. The primary objective of the study reported in this paper is to establish whether current mistuned bladed disk analyses should incorporate Coriolis effects in order to represent accurately all the significant factors that affect the forced response levels.
Experimental Results
From Controlled Blade Tip/Shroud Rubs at Engine
Speed
Authors: Padova Corso , Barton Jeffery , Dunn Michael G. , Manwaring Steve
Published: October 2007

Experimental results obtained for an Inconel® compressor blade rubbing a steel casing at engine speed are described. Load cell, strain gauge, and accelerometer measurements are discussed and then applied to analyze the metal-on-metal interaction resulting from sudden incursions of varying severity, defined by incursion depths ranging from 13μm to 762μm (0.0005in. to 0.030in.). The results presented describe the transient dynamics of rotor and casing vibro-impact response at engine operational speed similar to those experienced in flight. Force components at the blade tip in axial and circumferential directions for a rub of moderate incursion depth (140μm) are compared to those for a severe rub (406μm). Similar general trends of variation during the metal-to-metal contact are observed. However, in the nearly threefold higher incursion the maximum incurred circumferential load increases significantly, while the maximum incurred axial load increases much less, demonstrating the non-linear nature of the rub phenomena. Concurrently, the stress magnification on the rubbing blade at root mid-chord, at tip leading edge, and at tip trailing edge is discussed. The results point to the possibility of failure occurring first at the airfoil trailing edge. Such a failure was in fact observed in the most severe rub obtained to date in the laboratory, consistent with field observations. Computational models to analyze the non-linear dynamic response of a rotating beam with periodic pulse loading at the free-end are currently under development and are noted.
A Simplified Method for Predicting the Stability of Aerodynamically Excited Turbomachinery
Authors: Storace Albert F.
Published: October 2007

A modal stability (MS) method is presented for the quick and accurate prediction of the stability of aerodynamically excited turbomachinery using real eigenvalue/eigenvector data obtained from a rotordynamics model. The modal stability method provides a means to compare the work of stabilizing damping forces to the work of destabilizing aerodynamic cross-coupled stiffness forces to predict the onset of whirl instability. The MS method thus indicates that unstable or self-excited whirling (sometimes called whipping) at one of the system’s natural frequencies is initiated when the destabilizing work equals or exceeds the stabilizing work. This approach provides a powerful design tool to quickly ascertain the effects of squeeze-film dampers, and turbine engine architecture, including bearing locations and bearing support structure stiffness, on system stability.
High-Pressure Pocket
Damper Seals: Leakage Rates and Cavity
Pressures
Authors: Gamal Ahmed
M. , Ertas Bugra
H. , Vance John M.
Published: October 2007

The turbomachinery component of interest in this paper, the pocket damper seal, has the dual purpose of limiting leakage and providing an additional source of damping at the seal location. The rotordynamic coefficients of these seals (primarily the direct stiffness and damping) are highly dependent on the leakage rates through the seals and the pressures in the seals’ cavities. This paper presents both numerical predictions and experimentally obtained results for the leakage and the cavity pressures of pocket damper seals operating at high pressures. The seals were tested with air, at pressures up to 1000psi(6.92MPa), as the working fluid. Earlier flow-prediction models were modified and used to obtain theoretical reference values for both mass flow rates and pressures. Leakage and static pressure measurements on straight-through and diverging-clearance configurations of eight-bladed and twelve-bladed seals were used for code validation and for calculation of seal discharge coefficients. Higher than expected leakage rates were measured in the case of the twelve-bladed seal, while the leakage rates for the eight-bladed seals were predicted with reasonable accuracy. Differences in the axial pitch lengths of the cavities and the blade profiles of the seals are used to explain the discrepancy in the case of the twelve-bladed seal. The analysis code used also predicted the static cavity pressures reasonably well. Tests conducted on a six-bladed pocket damper seal to further investigate the effect of blade profile supported the results of the eight-bladed and twelve-bladed seal tests and matched theoretical predictions with satisfactory accuracy.
High-Frequency Effects in the Aspirating Probe
Authors: Payne S. J. , Moxon A. J. W.
Published: October 2007

The aspirating probe has recently been successfully used to measure entropy within a turbomachine; however, it was found that its sensitivity to total pressure and total temperature fluctuations was significantly altered at high frequencies. If the aspirating probe is to be used to measure unsteady flow fields accurately, these high-frequency effects must be better understood. The analysis of this behavior presented here shows that there are three effects that must be considered: the frequency response of the hot wires, the presence of Mach number fluctuations inside the probe, and the change in heat transfer from the hot wires at high frequencies. A theoretical analysis of the first effect has provided a correction factor that can be used for any hot wire, dependent solely on the baseline heat transfer ratio, the overheat ratio, and the time constant of the hot wires. The second and third effects have been examined numerically, since no theoretical solution is known to exist. The Mach number fluctuations are found to be well predicted by a simple one-dimensional solver and to show a variation of ±2.4% in Mach number at the hot-wire plane for the geometry and flow field considered here. The variation in heat transfer with frequency is found to be negligible at high overheat ratios, but significant at overheat ratios below ∼0.4. Coefficients that determine how the measured total pressure and total temperature depend on the actual total pressure, total temperature, and Mach number have been derived, and these show significant variation with the values of the two overheat ratios. Using synthetic data, based on previous experimental data, the effects on the probe measurement accuracy are analyzed. This shows that the amplitudes of total pressure and total temperature are reduced. At widely spaced overheat ratios, the amplitudes are reduced by similar amounts, but at smaller spacing the reductions become dissimilar, resulting in highly erroneous entropy∕R measurements. High-frequency effects thus have a significant effect on the performance of the aspirating probe and should be carefully considered when using it in a highly unsteady flow field.
Numerical Study of the Heat Transfer in Micro Gas Turbines
Authors: Verstraete T. , Alsalihi Z. , Van den Braembussche R. A.
Published: October 2007

This paper presents a numerical investigation of the heat transfer inside a micro gas turbine and its impact on the performance. The large temperature difference between turbine and compressor in combination with the small dimensions results in a high heat transfer causing a drop in efficiency of both components. Present study aims to quantify this heat transfer and to reveal the different mechanisms that contribute to it. A conjugate heat transfer solver has been developed for this purpose. It combines a three-dimensional (3D) conduction calculation inside the rotor and the stator with a 3D flow calculation in the radial compressor, turbine and gap between stator and rotor. The results for micro gas turbines of different size and shape and different material characteristics are presented and the impact on performance is evaluated.
Mechanism of the Interaction of a Ramped Bleed Slot With the Primary Flow
Authors: Leishman B. A. , Cumpsty N. A.
Published: October 2007

An experimental and computational study of the ramped bleed slot in a compressor cascade is presented. The geometry is a circumferential slot downstream of the stator blade trailing edge, with endwall ramps inside the blade passage, and the paper builds on work previously reported for different bleed off-take geometries (Leishman et al., 2007, ASME J. Turbomach., 129, pp. 645–658; Leishman et al., 2007, ASME J. Turbomach., 129, pp. 659–668). The strong interaction between any bleed slot and the primary flow through the cascade can be strong, thereby causing the levels of loss and blockage in the primary flow leaving the blade passage to be increased at some bleed flow rates. Radial flow into the bleed slot is highly nonuniform because the blade-to-blade pressure field causes flow to enter the bleed slot preferentially where the static pressure is high, and to spill out into the primary flow where the static pressure is low. The mechanism for the ramped bleed slot is different from that described in the earlier papers for other geometries. For the ramped bleed slot a static pressure field, with large variations of static pressure in the circumferential direction, is set up in the slot because the endwall flow entering the slot has higher stagnation pressure downstream of the pressure surface than downstream of the suction surface of the upstream blades. The flow entering the slot with high stagnation pressure is brought to rest in a stagnation point on the downstream surface of the slot, and the consequent variation in static pressure on the rear surface sets tangential and radial components of velocity which are a large fraction of the freestream velocity. As well as demonstrating the mechanism for the flow behavior, the paper presents results of experiments and calculations to demonstrate the behavior and gives guidance for the design of bleed slots by stressing the fundamental features of the flow.
A Network Approach to Define Modularity of Components in Complex Products
Authors: Sosa Manuel E. , Eppinger Steven D. , Rowles Craig M.
Published: October 2007

Modularity has been defined at the product and system levels. However, little effort has gone into defining and quantifying modularity at the component level. We consider complex products as a network of components that share technical interfaces (or connections) in order to function as a whole and define component modularity based on the lack of connectivity among them. Building upon previous work in graph theory and social network analysis, we define three measures of component modularity based on the notion of centrality. Our measures consider how components share direct interfaces with adjacent components, how design interfaces may propagate to nonadjacent components in the product, and how components may act as bridges among other components through their interfaces. We calculate and interpret all three measures of component modularity by studying the product architecture of a large commercial aircraft engine. We illustrate the use of these measures to test the impact of modularity on component redesign. Our results show that the relationship between component modularity and component redesign depends on the type of interfaces connecting product components. We also discuss directions for future work.
Design of a Novel Two Degree-of-Freedom Ankle-Foot Orthosis
Authors: Agrawal Abhishek , Sangwan Vivek , Banala Sai K. , Agrawal Sunil K. , Binder-Macleod Stuart A.
Published: October 2007

An ankle-foot orthosis (AFO) is commonly used to help subjects with weakness of ankle dorsiflexor muscles due to peripheral or central nervous system disorders. Both these disorders are due to the weakness of the tibialis anterior muscle, which results in the lack of dorsiflexion assist moment. The deformity and muscle, weakness of one joint in the lower extremity influences the stability of the adjacent joints, thereby requiring compensatory adaptations. We present an innovative ankle-foot orthosis (AFO). The prototype AFO would introduce greater functionality over currently marketed devices by means of its pronation-supination degree of freedom in addition to flexion/extension. This orthosis can be used to measure joint forces and moments applied by the human at both joints. In the future, by incorporation of actuators in the device, it will be used as a training device to restore a normal walking pattern.
Function Generation With Finitely Separated Precision Points Using Geometric Constraint Programming
Authors: Kinzel Edward C. , Schmiedeler James P. , Pennock Gordon R.
Published: October 2007

This paper extends geometric constraint programming (GCP) to function generation problems involving large numbers of finitely separated precision points and complex mechanisms. In parametric design software, GCP uses the sketching mode to graphically impose geometric constraints in kinematic diagrams and the numerical solvers to solve the relevant nonlinear equations without the user explicitly formulating them. For function generation, the same approach can be applied to any mechanism, requiring no unique algorithms. Implementation is straightforward, so the designer can quickly generate solutions for a large number of precision points and/or with complex mechanisms to accurately match the function. Examples of function generation with a four-bar linkage, a Stephenson III six-bar linkage, and a seven-bar linkage with a mobility of two are presented.
Design, Simulation, and Fabrication of a Quadstable Monolithic Mechanism With X- and Y-Directional Bistable Curved Beams
Authors: Han Jeong Sam , Müller Claas , Wallrabe Ulrike , Korvink Jan G.
Published: October 2007

This paper demonstrates a novel quadstable monolithic mechanism (QsMM), which provides four stable equilibrium positions within its planar operation range. The QsMM has been realized from the use of both X- and Y-directional bistable structures, which utilize curved snapping beams. Two pairs of curved beams were attached to an inner frame in both X and Y directions to present an independent bistable behavior in the directions. It was found out that the design of the inner frame is crucial for the quadstability and dynamic responses of the mechanism. A millimeter-scale brass mechanism was actually fabricated by ultraprecision milling to test the quadstability and the force-displacement behavior. The prototype clearly demonstrates four distinct stable positions in its millimeter-scale operation range. The design concept, finite element simulation, fabrication, and experimental measurement of the proposed multistable mechanism have been presented. The mechanical multistability of the proposed QsMM can be utilized for multiple switching and optical networking applications, yielding low power consumption operations.
The Late Palaeocene–Early Eocene and Toarcian (Early Jurassic) carbon isotope excursions: a comparison of their time scales, associated environmental changes, causes and consequences
Authors: Cohen Anthony S. , Coe Angela L. , Kemp David B.
Published: October 2007

Although the Earth's environment is constantly changing, there have been a few unusual episodes over the last
c
. 200 Ma when change was extreme in terms of its rapidity, severity, long-lasting consequences and unpredictability. The geochemical and biotic records for two of these episodes, the Palaeocene–Eocene thermal maximum and the Toarcian Oceanic Anoxic Event (Early Jurassic), possess many significant similarities. Each event was associated with a major carbon isotope excursion, significant levels of biotic extinctions, severe global warming, an enhanced hydrological cycle, and evidence for widespread seawater anoxia. Both carbon isotope excursions can be subdivided into distinct stages with broadly similar characteristics and durations; based on a detailed comparison, the Palaeocene–Eocene thermal maximum may have been an incipient Oceanic Anoxic Event. The geochemical and biotic changes during these two events are most readily explained by the abrupt, large-scale dissociation of methane hydrate that followed a period of more gradual environmental change linked to the emplacement of a large igneous province. Carbon release rates at those times were of the same order of magnitude as the current anthropogenic release rate of carbon to the atmosphere, indicating that ancient events such as these may usefully serve as analogues for present-day environmental change.
Early Palaeozoic initial-rift volcanism in the Central European Variscides (the Kaczawa Mountains, Sudetes, SW Poland): evidence from SIMS dating of zircons
Authors: Kryza R. , Zalasiewicz J.A. , Mazur S. , Aleksandrowski P. , Sergeev S. , Presnyakov S.
Published: October 2007

Early Palaeozoic volcanic suites are widespread throughout the Variscan Belt, and have commonly been ascribed to incipient rifting along the northern periphery of Gondwana in Cambrian to Ordovician times. Their distribution across Europe defines the present-day extent of Gondwana-derived terranes and constrains the timing of their separation from the Gondwanan margin. The Kaczawa Mountains in the West Sudetes, at the eastern termination of the Variscan Belt, include bimodal rift-related rocks, but their protolith age and, hence, their significance have been highly uncertain. We have applied secondary ionization mass spectrometry zircon geochronology to a metarhyodacite and a metatrachyte from this suite, yielding ages of 502.4 ± 2.6 Ma and 485.7 ± 1.6 Ma, respectively. This constrains the initial rift magmatism to
c
. 500–485 Ma in this part of the European Variscides. The rift-related Early Palaeozoic volcanism thus seems to have been broadly synchronous throughout the peri-Gondwanan terranes of Europe.
A 1.16 Ma record of carbon accumulation in western European peatland during the Oligocene from the Ballymoney lignite, Northern Ireland
Authors: Large David J.
Published: October 2007

The Oligocene Ballymoney lignite in Northern Ireland is one of the thickest lignites in Europe and provides the potential for comparing Holocene and pre-Holocene peatland evolution and its response to long-term climate change on time scales much greater than 10 ka. Samples were collected from 50 m of lignite and analysed for δ
13
C. Spectral analysis of the δ
13
C record reveals that the record contains significant frequencies at 0.21 m
−1
and 1.12 m
−1
. These cycles are interpreted as the
c
. 100 ka eccentricity and 20 ka precession cycles, respectively. These cycles were then tuned and the duration was determined as 1.16 Ma with a carbon accumulation rate of 27 g C m
−2
a
−1
. If long-term changes in lignite δ
13
C are related to changes in the δ
13
C of the exogenic carbon reservoir, and if the lignite Chattian age is accepted, then the lignite probably formed between 24.6 and 25.8 Ma. Comparison of the estimated carbon accumulation rate with other Cenozoic peatland carbon accumulation rates indicates that this rate appears to be insensitive to changes in the concentration of atmospheric CO
2
.
Morphological development of basin-scale silica diagenetic fronts revealed with 2D seismic reflection data: offshore Sakhalin, Russian Far East
Authors: Meadows David , Davies Richard J.
Published: October 2007

Two-dimensional (2D) seismic reflection data reveal two silica diagenetic boundaries located in the North Sakhalin Basin, offshore Sakhalin Island. These boundaries form distinctive high-amplitude seismic reflections that predominantly cross-cut Miocene stratigraphy. The boundaries represent the opal-A to opal-CT (cristobalite and tridymite) transition and the subsequent deeper opal-CT to quartz transition and cover an area of
c
. 107 000 km
2
. The reflections represent diagenetic reaction fronts that advance through silica-rich host sediments during burial. The oldest strata within which the diagenetic fronts have been identified are of Miocene age and the fronts commonly show a parallel relationship to a Late Miocene unconformity. These diagenetic fronts develop a variety of morphological forms. In the North Sakhalin Basin these front geometries are probably the result of the interference of the diagenetic fronts with inclined and folded stratigraphy together with lateral changes in the composition and, therefore, depth of transformation of the sediment. We define criteria for the recognition of these 2D cross-sectional morphological elements and by so doing provide the basis for the objective description and categorization of diagenetic front geometry.
Petrology and geochemistry of a cumulate xenolith suite from Bute: evidence for late Palaeozoic crustal underplating beneath SW Scotland
Authors: Downes H. , Upton B.G.J. , Connolly J. , Beard A.D. , Bodinier J.-L.
Published: October 2007

Xenoliths from Hawk's Nib (Bute, SW Scotland), entrained in alkali basalt of late Carboniferous–early Permian age, generally possess unrecrystallized igneous cumulate textures. Most are inferred to derive from lower crustal (20–30 km) depths, with a small minority from the underlying restitic mantle. Compositions range from ultramafic cumulates (dunite, wehrlite, websterite, clinopyroxenite) to gabbros and anorthosites. The suite is unique in being dominated by poikilitic wehrlites and olivine clinopyroxenites. Major element variation in the cumulates is controlled by modal mineral variations. The ultramafic cumulates all have high REE contents and light REE (LREE)-enriched patterns, with websterites being the least enriched. Gabbroic xenoliths have uniform patterns in which both LREE and heavy REE are depleted relative to the middle REE, with small positive Eu anomalies. Present-day Sr–Nd isotopic data for the suite are the most depleted among Scottish xenoliths. The xenoliths are inferred to be products of young replenishments of the lower crust by basaltic magmas during continental underplating. Orthopyroxene-bearing lithologies crystallized from tholeiitic magmas whereas alkali basalts formed the clinopyroxene-rich samples; both parental magma-types were derived from similar mantle sources.
Ecology of earliest reptiles inferred from basal Pennsylvanian trackways
Authors: Falcon-Lang Howard J. , Benton Michael J. , Stimson Matthew
Published: October 2007

Trackways representing the earliest evidence for the origin of reptiles (amniotes) are reported from the basal Pennsylvanian Grande Anse Formation, New Brunswick, Canada. Amniote characters include pentadactyl manus and pes, slender digits whose relative lengths approximate a phalangeal formula of 23453 (manus) and 23454 (pes), narrow digit splay (40–63°), putative transverse scale impressions on digit pads, and straight tail drag. The trackways occur in the deposits of a seasonally active dryland river channel. Sedimentological context suggests, for the first time, that early amniotes existed in water-stressed environments, where the cleidoic egg would have presumably conferred reproductive advantage.