bluuebunny/crossref_metadata_2025 huggingface dataset:
Noble gas isotopic fractionation between solar wind and the Sun, and implications for Genesis solar wind oxygen measurements
Authors: OZIMA M. , SUZUKI T. K. , YAMADA A. , PODOSEK F. A.
Published: October 2012

Abstract– We urge that He is the best case for a meaningful estimation of solar composition without measurement of solar wind (SW) composition; the value of such an estimation is that it may then be compared to the actual measurements, thereby leading to an empirical constraint on the degree of isotopic fractionation arising in SW and thence to how much fractionation may have affected the SW composition of other elements. We take primordial 3He/4He to be as identified in the so‐called Q component identified in meteoritic materials. In the Sun, however, 3He/4He is higher because of the augmentation of 3He by D‐burning, the nuclear conversion of primordial deuterium. After accounting for the D‐converted 3He, we estimate 3He/4He in the present Sun (post‐D burning He), and then, from the difference between this and the 3He/4He found in Genesis SW, we estimate the isotopic fractionation between them. Then, from noble gas systematics, we show that Genesis SW noble gases may be related to Q‐noble gases by a mass‐dependent Rayleigh‐type fractionation. We develop a kinetic description of isotopic fractionation of minor components in SW relative to the solar atmosphere, which is consistent with the Rayleigh‐type fractionation. This predicts fractionation in the O mass range, which is significantly different from the value used by Heber et al. (2011). The latter value corresponds to the premise that Ca‐Al‐rich inclusion O is the same as solar O, whence this work does not support that premise.
Computational Modeling of Grain Boundaries in ZrB2: Implications for Lattice Thermal Conductivity
Authors: Lawson John W. , Daw Murray S. , Squire Thomas H. , Bauschlicher Charles W.
Published: October 2012

A combination of ab initio, atomistic, and finite element methods (FEM) was used to investigate fundamental properties of grain boundaries and grain boundary networks and their impact on lattice thermal conductivity in the ultra high‐temperature ceramic ZrB2. The structure, energetics, and lattice thermal conductance of certain low energy grain boundaries were studied. Atomic models of these boundaries were relaxed using density functional theory. Information about bonding across the interfaces was determined from the electron localization function. Interfacial thermal conductances were computed using nonequilibrium molecular dynamics. Microstructural models were used to determine the reduction in lattice thermal conductivity due grain boundary networks where FEM meshes were constructed on top of microstructural images.
Use of dental loupes among dental trainers and trainees in the UK
Authors: Farook Shahme A. , Stokes Richard J. , Davis Anika K. J. , Sneddon Kenneth , Collyer Jeremy
Published: October 2012

Introduction

Magnification loupes are used in dentistry where increased visual performance is needed. The interest and use of loupes among dental practitioners and students appears to be growing. Despite this little quantitative data regarding the use of loupes in clinical practice and factors governing their purchase among dental trainers and trainees is available.

Objective

To determine the extent of use of loupes among dental trainers and trainees in the UK and identify what factors influence their choice of selection.

Method

A proforma questionnaire was designed to collect the information required and was handed out dental trainers and trainees.

Results

Use of loupes is more common among the dental trainers (44%) than trainees (28%). Of the nonusers, increased interest among the trainees (83.6%) and trainers (50%) in purchasing loupes was noted. Price was found to be the most important factor during purchase. The majority of users opted for 2.5×; and a light source was a popular choice. Both users and nonusers in the study group had an affinity towards “through‐the‐lens” type. No significant variation in back/neck discomfort between the users and nonusers was found.

Conclusion

Use of loupes among dental trainers and trainees remains low. Reduction in price and provision of information could increase the number of loupe users.
Strain rates at high temporal resolution from curved inclusion trails in garnet, Passo del Sole, Central Swiss Alps
Authors: BERG C. A. , CARLSON W. D. , CONNELLY J. N.
Published: October 2012

Quantitative strain rates at outcrop scale are very difficult to obtain, but they may be estimated from crystals with curved inclusion trails by calculating rotation rates from growth rates and corresponding deflections of the internal foliation. Garnet in a quartzose pelite at Passo del Sole in the central Swiss Alps is extraordinarily valuable for calculation of strain rates during Alpine orogenesis, because the unusual zoning patterns clearly define the kinetics of its nucleation and growth. Complex concentric zoning patterns can be correlated from one crystal to another in a hand sample, based on compositional and microstructural similarities; the ubiquity of these features demonstrates that all garnet crystals nucleated at nearly the same time. Compositional bands whose radial widths are proportional to crystal size provide evidence for growth governed by the kinetics of intergranular diffusion of locally sourced nutrients. Together, these constraints increase the reliability of estimates of rates of garnet growth, and the strain‐rate calculations that depend on them. To obtain growth rates, P–T conditions during garnet crystallization were modelled in a series of pseudosections, and compositional evolution was connected to rates of garnet growth by means of an independently determined heating rate. These growth rates, combined with measured amounts of curvature of inclusion trails, indicate that the time‐averaged strain rate at Passo del Sole during Alpine metamorphism was on the order of 10−14 s−1. Strain rates calculated using rotational v. non‐rotational models are similar in magnitude. The constraints on crystallization kinetics also allow direct calculation of strain rates during individual stages of garnet growth, revealing short‐term increases to values on the order of 10−13 s−1. These higher strain rates are correlated with the growth of concentric high‐Ca or high‐Mn zones in garnet, which implies that strain softening associated with the transient passage of fluids is responsible for acceleration of deformation during these intervals.
The C‐terminal domain of tetanus toxin protects motoneurons against acute excitotoxic damage on spinal cord organotypic cultures
Authors: Herrando‐Grabulosa Mireia , Casas Caty , Aguilera José
Published: October 2012

The C‐terminal domain of tetanus toxin (Hc‐TeTx) has been suggested to act as a neuroprotective agent by activating signaling pathways related to neurotrophins and also to exert anti‐apoptotic effects. Here, we show the beneficial properties of the recombinant protein Hc‐TeTx to protect spinal motoneurons against excitotoxic damage. In vitro spinal cord organotypic cultures were used to assess acute glutamate excitotoxic damage. Our results indicate that Hc‐TeTx treatment improves motoneuron survival within a short therapeutical window (the first 2 h post‐injury). Within this interval, we found that p44/p42 MAP kinase (ERK1/2) and glycogen synthase kinase‐3 (GSK3β) signaling pathways play a crucial role in the neuroprotective effect. Moreover, we demonstrated that Hc–TeTx treatment initiate autophagy which is ERK1/2‐ and GSK3β‐dependent. These findings suggest a possible therapeutical tool to improve motoneuron survival immediately after excitotoxic insults or during the secondary injury phase that occurs after spinal cord trauma.
Suppression of pain‐related behavior in two distinct rodent models of peripheral neuropathy by a homopolyarginine‐conjugated CRMP2 peptide
Authors: Ju Weina , Li Qi , Allette Yohance M. , Ripsch Matthew S. , White Fletcher A. , Khanna Rajesh
Published: October 2012

The N‐type voltage‐gated calcium channel (CaV2.2) is a clinically endorsed target in chronic pain treatments. As directly targeting the channel can lead to multiple adverse side effects, targeting modulators of CaV2.2 may prove better. We previously identified ST1‐104, a short peptide from the collapsin response mediator protein 2 (CRMP2), which disrupted the CaV2.2–CRMP2 interaction and suppressed a model of HIV‐related neuropathy induced by anti‐retroviral therapy but not traumatic neuropathy. Here, we report ST2‐104 –a peptide wherein the cell‐penetrating TAT motif has been supplanted with a homopolyarginine motif, which dose‐dependently inhibits the CaV2.2–CRMP2 interaction and inhibits depolarization‐evoked Ca2+ influx in sensory neurons. Ca2+ influx via activation of vanilloid receptors is not affected by either peptide. Systemic administration of ST2‐104 does not affect thermal or tactile nociceptive behavioral changes. Importantly, ST2‐104 transiently reduces persistent mechanical hypersensitivity induced by systemic administration of the anti‐retroviral drug 2′,3′‐dideoxycytidine (ddC) and following tibial nerve injury (TNI). Possible mechanistic explanations for the broader efficacy of ST2‐104 are discussed.
The metal transporterSMF‐3/DMT‐1 mediates aluminum‐induced dopamine neuron degeneration
Authors: VanDuyn Natalia , Settivari Raja , LeVora Jennifer , Zhou Shaoyu , Unrine Jason , Nass Richard
Published: October 2012

Aluminum (Al3+) is the most prevalent metal in the earth's crust and is a known human neurotoxicant. Al3+has been shown to accumulate in the substantia nigra of patients with Parkinson's disease (PD), and epidemiological studies suggest correlations between Al3+exposure and the propensity to develop bothPDand the amyloid plaque‐associated disorder Alzheimer's disease (AD). Although Al3+exposures have been associated with the development of the most common neurodegenerative disorders, the molecular mechanism involved in Al3+transport in neurons and subsequent cellular death has remained elusive. In this study, we show that a brief exposure to Al3+decreases mitochondrial membrane potential and cellularATPlevels, and confers dopamine (DA) neuron degeneration in the genetically tractable nematodeCaenorhabditis elegans(C. elegans). Al3+exposure also exacerbatesDAneuronal death conferred by the humanPD‐associated protein α‐synuclein.DAneurodegeneration is dependent onSMF‐3, a homologue to the human divalent metal transporter (DMT‐1), as a functional null mutation partially inhibits the cell death. We also show thatSMF‐3 is expressed inDAneurons, Al3+exposure results in a significant decrease in protein levels, and the neurodegeneration is partially dependent on thePD‐associated transcription factor Nrf2/SKN‐1 and caspase Apaf1/CED‐4. Furthermore, we provide evidence that the deletion ofSMF‐3 confers Al3+ resistance due to sequestration of Al3+into an intracellular compartment. This study describes a novel model for Al3+‐inducedDAneurodegeneration and provides the first molecular evidence of an animal Al3+transporter.
Defining evolutionary boundaries across parapatric ecomorphs of Black Salamanders (Aneides flavipunctatus) with conservation implications
Authors: Reilly Sean B. , Marks Sharyn B. , Jennings W. Bryan
Published: October 2012

The accurate delimitation of evolutionary population units represents an important component in phylogeographic and conservation genetic studies. Here, we used a combined population assignment and historical demographic approach to study a complex of ecomorphologically distinctive populations of Black Salamanders (Aneides flavipunctatus) that are parapatrically distributed and meet at a three‐way contact zone in north‐western California. We used mitochondrial tree‐based and multilocus clustering methods to evaluate a priori two‐ (Northern and Southern) and three (Northern, Coast and Inland) population hypotheses derived from previous studies. Mitochondrial results were consistent with the two‐ and three‐population hypotheses, while the nDNA clustering results supported only the two‐population hypothesis. Historical demographic analyses and mtDNA gene divergence estimates revealed that the Northern and Southern populations split during the Pliocene (2–5 Ma). Subdivision of the Southern population into Coast and Inland populations was estimated to be late Pleistocene (0.24 Ma), although our mtDNA results suggested a Pliocene divergence. Effective gene flow estimates (2Nem) suggest that either the two‐ or three‐population hypotheses remain valid. However, our results unexpectedly revealed that the Northern population might instead represent two parapatric populations that separated nearly 4 Ma. These results are surprising because the Pliocene divergence between these ecomorphologically conservative forms is similar or older than for the ecomorphologically divergent Coast and Inland sister populations. We conclude that Black Salamanders in north‐western California belong to at least three or four populations or species, and these all meet criteria for being Evolutionary Significant Units or ‘ESUs’ and therefore warrant conservation consideration.
Transcriptomics of coping strategies in free‐swimming Lepeophtheirus salmonis (Copepoda) larvae responding to abiotic stress
Authors: Sutherland Ben J. G. , Jantzen Stuart G. , Yasuike Motoshige , Sanderson Dan S. , Koop Ben F. , Jones Simon R. M.
Published: October 2012

The salmon louse Lepeophtheirus salmonis is a marine ectoparasite of wild and farmed salmon in the Northern Hemisphere. Infections of farmed salmon are of economic and ecological concern. Nauplius and copepodid salmon lice larvae are free‐swimming and disperse in the water column until they encounter a host. In this study, we characterized the sublethal stress responses of L. salmonis copepodid larvae by applying a 38K oligonucleotide microarray to profile transcriptomes following 24 h exposures to suboptimal salinity (30–10 parts per thousand (‰)) or temperature (16–4 °C) environments. Hyposalinity exposure resulted in large‐scale gene expression changes relative to those elicited by a thermal gradient. Subsequently, transcriptome responses to a more finely resolved salinity gradient between 30 ‰ and 25 ‰ were profiled. Minimal changes occurred at 29 ‰ or 28 ‰, a threshold of response was identified at 27 ‰, and the largest response was at 25 ‰. Differentially expressed genes were clustered by pattern of expression, and clusters were characterized by functional enrichment analysis. Results indicate larval copepods adopt two distinct coping strategies in response to short‐term hyposaline stress: a primary response using molecular chaperones and catabolic processes at 27 ‰; and a secondary response up‐regulating ion pumps, transporters, a different suite of chaperones and apoptosis‐related transcripts at 26 ‰ and 25 ‰. The results further our understanding of the tolerances of L. salmonis copepodids to salinity and temperature gradients and may assist in the development of salmon louse management strategies.
Vertical partitioning between sister species of Rhizopogon fungi on mesic and xeric sites in an interior Douglas‐fir forest
Authors: Beiler Kevin J. , Simard Suzanne W. , LeMay Valerie , Durall Daniel M.
Published: October 2012

Understanding ectomycorrhizal fungal (EMF) community structure is limited by a lack of taxonomic resolution and autecological information. Rhizopogon vesiculosus and Rhizopogon vinicolor (Basidiomycota) are morphologically and genetically related species. They are dominant members of interior Douglas‐fir (Pseudotsuga menziesii var. glauca) EMF communities, but mechanisms leading to their coexistence are unknown. We investigated the microsite associations and foraging strategy of individual R. vesiculosus and R. vinicolor genets. Mycelia spatial patterns, pervasiveness and root colonization patterns of fungal genets were compared between Rhizopogon species and between xeric and mesic soil moisture regimes. Rhizopogon spp. mycelia were systematically excavated from the soil and identified using microsatellite DNA markers. Rhizopogon vesiculosus mycelia occurred at greater depth, were more spatially pervasive, and colonized more tree roots than R. vinicolor mycelia. Both species were frequently encountered in organic layers and between the interface of organic and mineral horizons. They were particularly abundant within microsites associated with soil moisture retention. The occurrence of R. vesiculosus shifted in the presence of R. vinicolor towards mineral soil horizons, where R. vinicolor was mostly absent. This suggests that competition and foraging strategy may contribute towards the vertical partitioning observed between these species. Rhizopogon vesiculosus and R. vinicolor mycelia systems occurred at greater mean depths and were more pervasive in mesic plots compared with xeric plots. The spatial continuity and number of trees colonized by genets of each species did not significantly differ between soil moisture regimes.
A widely conserved molecular switch controls quorum sensing and symbiosis island transfer in Mesorhizobium loti through expression of a novel antiactivator
Authors: Ramsay Joshua P. , Major Anthony S. , Komarovsky Victor M. , Sullivan John T. , Dy Ron L. , Hynes Michael F. , Salmond George P. C. , Ronson Clive W.
Published: October 2012

ICEMlSymR7A of Mesorhizobium loti is an integrative and conjugative element (ICE) that confers the ability to form a nitrogen‐fixing symbiosis with Lotus species. Horizontal transfer is activated by TraR and N‐acyl‐homoserine lactone (AHL), which can stimulate ICE excision in 100% of cells. However, in wild‐type cultures, the ICE is excised at low frequency. Here we show that QseM, a widely conserved ICE‐encoded protein, is an antiactivator of TraR. Mutation of qseM resulted in TraR‐dependent activation of AHL production and excision, but did not affect transcription of traR. QseM and TraR directly interacted in a bacterial two‐hybrid assay in the presence of AHL. qseM expression was repressed by a DNA‐binding protein QseC, which also activated qseC expression from a leaderless transcript. QseC differentially bound two adjacent operator sites, the lower affinity of which overlapped the −35 regions of the divergent qseC‐qseM promoters. QseC homologues were identified on ICEs, TraR/TraM‐regulated plasmids and restriction‐modification cassettes, suggesting a conserved mode of regulation. Six QseC variants with distinct operators were identified that showed evidence of reassortment between mobile elements. We propose that QseC and QseM comprise a bimodal switch that restricts quorum sensing and ICEMlSymR7A transfer to a small proportion of cells in the population.
The Naive Topology of the Conscious Subject
Authors: Madden Rory
Published: October 2012

What does our naïve conception of a conscious subject demand of the nature of conscious beings? In a series of recent papers David Barnett has argued that a range of powerful intuitions in the philosophy of mind are best explained by the hypothesis that our naïve conception imposes a requirement of mereological simplicity on the nature of conscious beings. It is argued here that there is a much more plausible explanation of the intuitions in question. Our naïve conception of a conscious subject imposes a requirement of topological integrity.
The impact of intrabony lesion size on biopsy preference among oral and maxillofacial surgeons
Authors: Johnson N.R. , Savage N.W. , Kazoullis S. , Batstone M.D.
Published: October 2012

Aim

The management of intrabony lesions of the jaws may be markedly different depending on the exact nature of the pathology. The precise role of a biopsy prior to surgical treatment of mandibular radiolucencies remains controversial. This study aims to document the biopsy practice of oral and maxillofacial surgeons for intrabony lesions of the jaws.

Materials and methods

A survey was mailed to all Australian full or associate members of the Australian and New Zealand Association of Oral and Maxillofacial Surgeons. The first part asked questions in relation to demographic data. The second part asked members to examine orthopantomograms of two different lesions and which, if any, biopsy technique would be used prior to management. Data were analysed using a chi‐square test.

Results

Eighty six of 136 (63.2%) surveys were returned. Only 10.0% of respondents indicated that they would perform a diagnostic incisional biopsy prior to removing the smaller lesion compared with 88.0% of respondents for the larger lesion (P‐value < 0.01). Fine needle aspiration biopsy was only used to exclude vascular lesions by a minority of members. Further investigations would be requested by more than 80.0% of surgeons, with the most popular being three‐dimensional imaging such as computed tomography or cone beam computed tomography.

Conclusion

The use of a preoperative biopsy is not consistent between lesions of different sizes, with the use of fine needle aspiration biopsy continuing to be advocated to exclude vascular lesions. This is despite the widely different management required for various lesions of the jaws that may be identical on imaging.
Sublingual gland ranula secondary to tongue reconstruction with radial forearm flap
Authors: Xiong X. , Shao Z. , Zhang W. , Liu B.
Published: October 2012

Ranula seldom happens as a complication secondary to the surgery surrounding the sublingual gland. Here, we reported that a rare case of sublingual gland ranula after tongue reconstruction with radical forearm flap, saliva extravasation after trauma to the sublingual gland or the ducts was responsible for the occurrence of this ranula.
Effect of Supplementation of Taurine or Trehalose in Extender on Immunolocalization of Tyrosine Phosphoproteins in Buffalo and Cattle (Karan Fries) Cryopreserved Spermatozoa
Authors: Kumar R , Singh VK , Chhillar S , Atreja SK
Published: October 2012

Contents

The present study assessed the effects of incorporation ofTaurine orTrehalose in extender on immunolocalization of tyrosine phosphoproteins, Cryocapacitation and other sperm quality parameters (motility, viability and membrane integrity) in post‐thawed sperm fromBuffalo (Murrah) andCattle (KaranFries). Six ejaculates from six individual bulls from both species were chosen at random and split into four aliquots: one aliquot without dilution (fresh sample), another diluted in egg yolk tris‐citrate (EYTC) extender and the rest of aliquots withEYTCdilution supplemented with taurine (50 mm) or trehalose (100 mm), respectively, and cryopreserved. Following cryopreservation, semen were thawed and assessed for standard semen quality parameters. Extent of capacitation in cryopreserved spermatozoa was measured by inducingin vitroacrosome reaction followed by dual staining. Immunolocalization of tyrosine phosphoproteins was carried out by immunocytochemistry using primary antibody clonepT‐154 (anti‐phosphotyrosine antibody) andFITC‐conjugated secondary antibody. Immunofluorescent signals were analysed for level of protein tyrosine phosphorylation in spermatozoa. Post‐thaw semen evaluation showed supplementation of taurine or trehalose toEYTCextender significantly (p < 0.05) increased motility, viability and membrane integrity of spermatozoa in both species. Percentage of cryocapacitated spermatozoa was significantly (p < 0.05) higher in cattle as compared to buffalo and degree of cryocapacitaion of spermatozoa decreased significantly (p < 0.05) upon supplementation of additives in both the species. It was also found that tyrosine phosphoproteins were localized differentially in fresh and cryopreserved spermatozoa. Supplementation of taurine or trehalose to freezing extender changed the localization of tyrosine phosphoproteins in cryopreserved spermatozoa similar to fresh in both the species. The results obtained clearly indicated that supplementation of taurine or trehalose toEYTCprior to cryopreservation improvesBuffalo andCattle sperm quality in terms of cryocapacitation and immunolocalization of tyrosine phosphoproteins during freezing–thawing process.
Effects of Pre‐Weaning Energy Substitutions on Post‐Weaning Follicle Development, Steroid Hormones and Subsequent Litter Size in Primiparous Sows
Authors: Chen TY , Stott P , Bouwman EG , Langendijk P
Published: October 2012

Contents

The present study investigated the effects of pre‐weaning energy substitutions on follicular development, endocrine characteristics and subsequent litter size in primiparous sows. Sows were fed a standard lactation diet (14.1 DE MJ/kg) and then allocated to a Control (C, n = 24), Fat (F, n = 23), Sugar (S, n = 23) or post‐weaning Regumate (positive control; R, n = 22) treatment at 9 days before weaning of the C, F and S treatments. During the treatment period (8 days), 1 kg of the lactation diet was substituted with 1 kg of a fat‐rich (F, 23.85 DE MJ/kg) or sugar‐rich (S, 15.75 DE MJ/kg) substitution for F and S sows, respectively. For the R treatment, sows were weaned 8 days earlier than other treatments and fed a lactation diet at 3.5 kg with two doses of altrenogest as topdressing from 1 day before weaning until the day on which the other sows were weaned. The F treatment aimed to increase energy intake, and the S treatment aimed to elevate post‐prandial glucose and insulin concentrations. Weaning‐to‐ovulation interval tended to be reduced in the S treatment compared with C (p = 0.06) and F (p = 0.08) treatments. Body weight (BW) loss during the treatment period, post‐weaning follicle development, plasma oestradiol and pre‐weaning leptin did not differ among C, F and S sows, although BW loss was lower and leptin was higher in the R treatment. Post‐ovulatory progesterone concentration in the S treatment was higher (p < 0.05). Sows in the S and R treatments had a greater proportion of litters with larger litter sizes (p < 0.05). The outcome suggests that increasing circulating insulin and glucose concentrations during late lactation or a week of metabolic recovery positively improves subsequent litter size in primiparous sows.
Voronoff to virion: 1920s testis transplantation and AIDS
Authors: Bajic Petar , Selman Steven H. , Rees Michael A.
Published: October 2012

Bajic P, Selman SH., Rees MA. Voronoff to virion: 1920s testis transplantation and AIDS. Xenotransplantation 2012; 19: 337–341. © 2012 John Wiley & Sons A/S.

Abstract:  Background:  We address accusations linking AIDS with testis transplantation performed by a French surgeon, Serge Voronoff (1866–1951), and their implications in the future of animal‐to‐human organ transplantation.

Methods:  Biographical literature on Voronoff and scientific literature on xenotransplantation and the origin of HIV were reviewed.

Results:  In the 1920s, Serge Voronoff transplanted testes from primates into humans to revitalize them sexually and physically, making him one of the first surgeons to perform xenotransplantation–transplanting live tissues between species. In recent years, some have postulated that Voronoff’s transplants may have caused or contributed to the AIDS epidemic. However, consensus among virologists holds that HIV most likely originated from a chimpanzee virus known as simian immunodeficiency viruses (SIV) which many agree was transmitted to humans during the hunting of primates in the early 1900s. As these accusations have never been addressed, evidence is reviewed which refutes the claims. HIV isolate studies are summarized, which show that SIV was most likely transferred to humans from a chimpanzee species different from those used by Voronoff. Furthermore, literature suggests that Voronoff’s experiments were performed in Europe and the United States, not central Africa.

Conclusions:  Over 100 000 people await organ transplants, making the prospect of using animal organs to meet demand increasingly favorable. The accusations against Voronoff and others have led to increased concern over cross‐species disease transfer. The evidence presented refutes those claims and is used to explain the need for further research into xenotransplantation.
Rotor Model Updating and Validation for an Active Magnetic Bearing Based High-Speed Machining Spindle
Authors: Wroblewski Adam C. , Sawicki Jerzy T. , Pesch Alexander H.
Published: October 2012

This paper presents an experimentally driven model updating approach to address the dynamic inaccuracy of the nominal finite element (FE) rotor model of a machining spindle supported on active magnetic bearings. Modeling error is minimized through the application of a numerical optimization algorithm to adjust appropriately selected FE model parameters. Minimizing the error of both resonance and antiresonance frequencies simultaneously accounts for rotor natural frequencies as well as for their mode shapes. Antiresonance frequencies, which are shown to heavily influence the model’s dynamic properties, are commonly disregarded in structural modeling. Evaluation of the updated rotor model is performed through comparison of transfer functions measured at the cutting tool plane, which are independent of the experimental transfer function data used in model updating procedures. Final model validation is carried out with successful implementation of robust controller, which substantiates the effectiveness of the model updating methodology for model correction.
Thrust Control of Small Turbojet Engines Using Fuzzy Logic: Design and Experimental Validation
Authors: Amirante Riccardo , Andrea Catalano Luciano , Tamburrano Paolo
Published: October 2012

The aim of this paper is to propose an effective technique which employs a proportional-integral Fuzzy logic controller for the thrust regulation of small scale turbojet engines, capable of ensuring high performance in terms of response speed, precision and stability. Fuzzy rules have been chosen by logical deduction and some specific parameters of the closed loop control have been optimized using a numerical simulator, so as to achieve rapidity and stability of response, as well as absence of overshoots. The proposed Fuzzy logic controller has been tested on the Pegasus MK3 microturbine: the high response speed and precision of the proposed thrust control, revealed by the simulations, have been confirmed by several experimental tests with step response. Its stability has been demonstrated by means of the frequency response analysis of the system. The proposed thrust control technique has general validity and can be applied to any small-scale turbojet engine, as well as to microturbines for electricity production, provided that thrust being substituted with the net mechanical power.
On the Bagley–Torvik Equation
Authors: Atanackovic T. M. , Zorica D.
Published: October 2012

We propose a new method for finding solution of Bagley–Torvik equation based on recently derived expansion formula for fractional derivatives. The case of nonlinear equations of Bagley–Torvik type is also discussed.
Nonlinear Poro-Elastic Model for Unsaturated Porous Solids
Authors: Carmeliet Jan , Derome Dominique , Dressler Martin , Guyer Robert A.
Published: October 2012

A nonlinear poroelastic constitutive model for unsaturated porous materials is formulated based on a higher order formulation of free energy including mechanical and moisture contributions and the coupling between moisture and mechanics. This orthotropic model leads to the explicit formulation of the dependence of the compliance, moisture capacity, and coupling coefficient on stress and liquid pressure. The nonlinear poroelastic material properties can be easily determined from mechanical testing at different moisture content and free swelling/sorption tests. An academic example illustrates the capacity of the proposed model to describe nonlinear moisture dependent elasticity, stress dependent sorption, and swelling, also called mechano-sorption and moisture expel during mechanical loading. Two materials are analyzed in detail: wood and Berea sandstone. The poroelastic model shows a good agreement with measurements. Different moisture dependence of the elastic properties is found, with wood showing a more complex moisture/mechanical interaction. Berea sandstone is found to show an important nonlinear elastic behavior dependent on stress, similar in dry and wet conditions.
Micromechanics-Derived Scaling Relations for Poroelasticity and
Strength of Brittle Porous Polycrystals
Authors: Fritsch Andreas , Hellmich Christian , Young Philippe
Published: October 2012

There are lots of ceramic geological and biological materials whose microscopic load carrying behavior is not dominated by bending of structural units, but by the three-dimensional interaction of disorderedly arranged single crystals. A particularly interesting solution to capture this so-called polycrystalline behavior has emerged in the form of self-consistent homogenization methods based on an infinite amount of nonspherical (needle or disk-shaped) solid crystal phases and one spherical pore phase. Based on eigenstressed matrix-inclusion problems, together with the concentration and influence tensor concept, we arrive at the following results: Young’s modulus and the poroelastic Biot modulus of the porous polycrystal scale linearly with the Young’s modulus of the single crystals, the former independently of the Poisson’s ratio of the single crystals. Biot coefficients are independent of the single crystals’ Young’s modulus. The uniaxial strength of a pore pressure-free porous polycrystal, as well as the blasting pore pressure of a macroscopic stress-free polycrystal, scale linearly with the tensile strength of the single crystals, independently of all other elastic and strength properties of the single crystals. This is confirmed by experiments on a wide range of bio- and geomaterials, and it is of great interest for numerical simulations of structures built up by such polycrystals.
Biomechanical Measurements of Surgical Drilling Force and Torque in Human Versus Artificial Femurs
Authors: MacAvelia Troy , Salahi Meisam , Olsen Michael , Crookshank Meghan , Schemitsch Emil H. , Ghasempoor Ahmad , Janabi-Sharifi Farrokh , Zdero Rad
Published: October 2012

Few experimental studies have examined surgical drilling in human bone, and no studies have inquired into this aspect for a popular commercially-available artificial bone used in biomechanical studies. Sixteen fresh-frozen human femurs and five artificial femurs were obtained. Cortical specimens were mounted into a clamping system equipped with a thrust force and torque transducer. Using a CNC machine, unicortical holes were drilled in each specimen at 1000 rpm, 1250 rpm, and 1500 rpm with a 3.2 mm diameter surgical drill bit. Feed rate was 120 mm/min. Statistical significance was set at p < 0.05. Force at increasing spindle speed (1000 rpm, 1250 rpm, and 1500 rpm), respectively, showed a range for human femurs (198.4 ± 14.2 N, 180.6 ± 14.0 N, and 176.3 ± 11.2 N) and artificial femurs (87.2 ± 19.3 N, 82.2 ± 11.2 N, and 75.7 ± 8.8 N). For human femurs, force at 1000 rpm was greater than at other speeds (p ≤ 0.018). For artificial femurs, there was no speed effect on force (p ≥ 0.991). Torque at increasing spindle speed (1000 rpm, 1250 rpm, and 1500 rpm), respectively, showed a range for human femurs (186.3 ± 16.9 N·mm, 157.8 ± 16.1 N·mm, and 140.2 ± 16.4 N·mm) and artificial femurs (67.2 ± 8.4 N·mm, 61.0 ± 2.9 N·mm, and 53.3 ± 2.9 N·mm). For human femurs, torque at 1000 rpm was greater than at other speeds (p < 0.001). For artificial femurs, there was no difference in torque for 1000 rpm versus higher speeds (p ≥ 0.228), and there was only a borderline difference between the higher speeds (p = 0.046). Concerning human versus artificial femurs, their behavior was different at every speed (force, p ≤ 0.001; torque, p < 0.001). For human specimens at 1500 rpm, force and torque were linearly correlated with standardized bone mineral density (sBMD) and the T-score used to clinically categorize bone quality (R ≥ 0.56), but there was poor correlation with age at all speeds (R ≤ 0.37). These artificial bones fail to replicate force and torque in human cortical bone during surgical drilling. To date, this is the largest series of human long bones biomechanically tested for surgical drilling.
Three-dimensional capillary force assembly: Fabrication of white light emitters
Authors: Cordeiro Julien , Lecarme Olivier , Osvaldo Dias Guilherme , Peyrade David
Published: October 2012

This work uses convective assisted capillary force assembly from a collection of 100 nm fluorescent polystyrene nanoparticles to fabricate 4 μm wide and 1 μm high localized light-emitting superstructures. Large scale superstructures of about 10 000 particles are transferred on free silicon surfaces by microcontact printing. Optical characterization reveals that these sources emit polychromatic visible light from 400 to 800 nm equivalent to a white spectrum. Finally, single objects are studied to characterize the spatial distribution of the emitted color.
Bimaterial electromechanical systems for a biomimetical acoustic sensor
Authors: Mastropaolo Enrico , Latif Rhonira , Koickal Thomas , Hamilton Alister , Cheung Rebecca , Newton Michael , Smith Leslie
Published: October 2012

Bimaterial planarized micromechanical beams have been designed, simulated, and fabricated with lengths in the range 800–5800 μm and distance to substrate 0.8–4.0 μm. The beams are to be used as vertical-mode resonant gates on p-type field-effect transistors for implementing an adaptable MEMS acoustic sensor inspired by the human ear. A process for fabricating planar bilayer double-clamped beams made of silicon nitride (SiN) and aluminum (Al(1%Si)) has been developed. The planar design and bimaterial approach allow the fabrication of relatively straight beams with length up to 5800 μm with the possibility of controlling the degree of static deflection of the beams. The fabricated beams have shown a maximum deflection of ∼300 nm and a transverse concave shape with respect to the substrate due to the bilayer nature of the structure. From wafer curvature measurements, the stress in the SiN and Al(1%Si) is 200 and 280 MPa, respectively. Finite element simulations and analysis of the profile of the beams have demonstrated that the films’ stress magnitude influences the longitudinal and transverse profile of the beams. The fabricated devices resonate mechanically in the range 15–160 kHz. Preliminary electrical characterization of the devices has shown drain currents in the μA range for gate voltages of −20 to −25 V and drain voltages of −5 V.
Progress toward an aberration-corrected low energy electron microscope for DNA sequencing and surface analysis
Authors: Mankos Marian , Shadman Khashayar , N'Diaye Alpha T. , Schmid Andreas K. , Persson Henrik H. J. , Davis Ronald W.
Published: October 2012

Monochromatic, aberration-corrected, dual-beam low energy electron microscopy (MAD-LEEM) is a novel imaging technique aimed at high resolution imaging of macromolecules, nanoparticles, and surfaces. MAD-LEEM combines three innovative electron–optical concepts in a single tool: a monochromator, a mirror aberration corrector, and dual electron beam illumination. The monochromator reduces the energy spread of the illuminating electron beam, which significantly improves spectroscopic and spatial resolution. The aberration corrector is needed to achieve subnanometer resolution at landing energies of a few hundred electronvolts. The dual flood illumination approach eliminates charging effects generated when a conventional, single-beam LEEM is used to image insulating specimens. The low landing energy of electrons in the range of 0 to a few hundred electronvolts is also critical for avoiding radiation damage, as high energy electrons with kilo-electron-volt kinetic energies cause irreversible damage to many specimens, in particular biological molecules. The performance of the key electron–optical components of MAD-LEEM, the aberration corrector combined with the objective lens and a magnetic beam separator, was simulated. Initial results indicate that an electrostatic electron mirror has negative spherical and chromatic aberration coefficients that can be tuned over a large parameter range. The negative aberrations generated by the electron mirror can be used to compensate the aberrations of the LEEM objective lens for a range of electron energies and provide a path to achieving subnanometer spatial resolution. First experimental results on characterizing DNA molecules immobilized on Au substrates in a LEEM are presented. Images obtained in a spin-polarized LEEM demonstrate that high contrast is achievable at low electron energies in the range of 1–10 eV and show that small changes in landing energy have a strong impact on the achievable contrast. The MAD-LEEM approach promises to significantly improve the performance of a LEEM for a wide range of applications in the biosciences, material sciences, and nanotechnology where nanometer scale resolution and analytical capabilities are required. In particular, the microscope has the potential of delivering images of unlabeled DNA strands with nucleotide-specific contrast. This simplifies specimen preparation and significantly eases the computational complexity needed to assemble the DNA sequence from individual reads.
Quality correction factors of composite IMRT beam deliveries: Theoretical considerations
Authors: Bouchard Hugo
Published: October 2012

Purpose:

In the scope of intensity modulated radiation therapy (IMRT) dosimetry using ionization chambers, quality correction factors of plan‐class‐specific reference (PCSR) fields are theoretically investigated. The symmetry of the problem is studied to provide recommendable criteria for composite beam deliveries where correction factors are minimal and also to establish a theoretical limit for PCSR deliverykQ factors.

Methods:

The concept of virtual symmetric collapsed (VSC) beam, being associated to a given modulated composite delivery, is defined in the scope of this investigation. Under symmetrical measurement conditions, any composite delivery has the property of having akQ factor identical to its associated VSC beam. Using this concept of VSC, a fundamental property of IMRT kQ factors is demonstrated in the form of a theorem. The sensitivity to the conditions required by the theorem is thoroughly examined.

Results:

The theorem states that if a composite modulated beam delivery produces a uniform dose distribution in a volumeVcyl which is symmetric with the cylindrical delivery and all beams fulfills two conditions in Vcyl: (1) the dose modulation function is unchanged along the beam axis, and (2) the dose gradient in the beam direction is constant for a given lateral position; then its associated VSC beam produces no lateral dose gradient in Vcyl, no matter what beam modulation or gantry angles are being used. The examination of the conditions required by the theorem lead to the following results. The effect of the depth‐dose gradient not being perfectly constant with depth on the VSC beam lateral dose gradient is found negligible. The effect of the dose modulation function being degraded with depth on the VSC beam lateral dose gradient is found to be only related to scatter and beam hardening, as the theorem holds also for diverging beams.

Conclusions:

The use of the symmetry of the problem in the present paper leads to a valuable theorem showing thatkQ factors of composite IMRT beam deliveries are close to unity under specific conditions. The theoretical limit is determined based on the property of PCSR deliveries to provide a uniform dose in the target volume. The present approach explains recent experimental observations and proposes ideal conditions for IMRT reference dosimetry. The result of this study could potentially serve as a theoretical basis for reference dosimetry of composite IMRT beam deliveries or for routine IMRT quality assurance.
Prevention of a wrong‐location misadministration through the use of an intradepartmental incident learning system
Authors: Ford Eric C. , Smith Koren , Harris Kendra , Terezakis Stephanie
Published: October 2012

Purpose:

A series of examples are presented in which potential errors in the delivery of radiation therapy were prevented through use of incident learning. These examples underscore the value of reporting near miss incidents.

Methods:

Using a departmental incident learning system, eight incidents were noted over a two‐year period in which fields were treated “out‐of‐sequence,” that is, fields from a boost phase were treated, while the patient was still in the initial phase of treatment. As a result, an error‐prevention policy was instituted in which radiation treatment fields are “hidden” within the oncology information system (OIS) when they are not in current use. In this way, fields are only available to be treated in the intended sequence and, importantly, old fields cannot be activated at the linear accelerator control console.

Results:

No out‐of‐sequence treatments have been reported in more than two years since the policy change. Furthermore, at least three near‐miss incidents were detected and corrected as a result of the policy change. In the first two, the policy operated as intended to directly prevent an error in field scheduling. In the third near‐miss, the policy operated “off target” to prevent a type of error scenario that it was not directly intended to prevent. In this incident, an incorrect digitally reconstructed radiograph (DRR) was scheduled in the OIS for a patient receiving lung cancer treatment. The incorrect DRR had an isocenter which was misplaced by approximately two centimeters. The error was a result of a field from an old plan being scheduled instead of the intended new plan. As a result of the policy described above, the DRR field could not be activated for treatment however and the error was discovered and corrected. Other quality control barriers in place would have been unlikely to have detected this error.

Conclusions:

In these examples, a policy was adopted based on incident learning, which prevented several errors, at least one of which was potentially severe. These examples underscore the need for a rigorous, systematic incident learning process within each clinic. The experiences reported in this technical note demonstrate the value of near‐miss incident reporting to improve patient safety.