True Closure Research Articles

Rabbit as model for osteoporosis research.

Osteoporosis is a major public health problem affecting more than 200 million people worldwide. The use of different animal models, for the study of its pathophysiology and treatments, is important being actually the ovariectomized rat the most widely used; although this model has several problems due its small size, lack of true closure of epiphyseal plate and bone differences with humans. This review is aimed at summarizing the most common methods published for osteoporosis induction in rabbits as model for human disease with their advantages and disadvantages. The paper shows the advantages of the use of this specie compared with the rat. All the techniques seemed to achieve the osteoporotic condition, but the one which obtained the most consistent bone mineral reduction in less time was the combination of surgery and corticoid treatment. The conclusion of the review was that rabbits are promising as a model of osteoporosis research because of their size, haversian remodelling and closure of epiphyseal plate, which solve some of the problems of the rat model. There are different techniques in the literature used to achieve the osteoporotic condition with diverse results, but there is a lack of consensus as to the best one.

Bias in detrital fission track grain-age populations: Implications for reconstructing changing erosion rates

The sedimentary record is our principal archive of mass transfer across the Earth's surface in response to tectonic and climatic changes in the geologic past. The thermochronology of individual sediment grains (detrital thermochronology) has emerged as a critical tool to infer erosion rates and track mountain belt evolution. Such inferences are reliant upon the statistical inversion of detrital grain ages to unbiasedly approximate the cooling history of the source areas from which the sediment originated. However, it is challenging to critique the reliability and consistency of modelled ages. These arise both from fundamental measurement uncertainties and the assumptions we employ in inverting the data. For detrital fission track modelling of young detrital samples, this problem is particularly acute since the uncertainty on the track counts produces uncertainty in the age estimates. We apply Monte-Carlo modelling to generate synthetic detrital data conditioned on known closure age models, and then invert the grain data to assess the reliability of different inversion schemes. The results clearly demonstrate that existing practice can be subject to large uncertainty, to systematic bias and to non-uniqueness of interpretation. We then show how to map such regions of systematic bias in the population modelling as a function of the true closure ages, and how this bias propagates through into the lag-time modelling. Applying the method to real data from the Siwalik group sediments in western Nepal, we find no evidence for a change in the underlying climate or tectonic processes, since the apparent change in lag coincides with a thresholded change in the resolution of the population modelling. This paper shows how to map regions of systematic bias in the population modelling as a function of the true closure ages, and how this bias propagates through into the lag-time modelling and can be applied retrospectively to existing studies. However, it is equally applicable to other age inversion schemes such as minimum age modelling. The application of these methods will enhance current practice and facilitate more robust interpretation of grain ages, in particular in discriminating between stationary and non-stationary geological and climatic processes.

Monitoring socioeconomic impacts of Hawai‘i's 2010 bigeye tuna closure: Complexities of local management in a global fishery

This paper presents the results of a study to monitor the socioeconomic impacts of the first extended closure of the western and central Pacific Ocean (WCPO) bigeye tuna (bigeye) fishery to US longliners from the state of Hawai‘i. We applied qualitative and quantitative approaches to examine how diverse members of Hawai‘i's bigeye fishery community, including fishermen, a large fish auction, dealers, processors, retailers, consumers, and support industries, perceived and were affected by the constraints of the 40-day closure of the WCPO bigeye fishery at the end of 2010. Our analysis found that there was reduced supply and reduced quality of bigeye landed along with increased prices for bigeye during the closure period. In addition, Hawai‘i longliners were forced to travel longer distances to fish during the closure. These factors contributed to increased stress and in some cases lost revenue for a variety of individuals and businesses connected to the fishery. We also found that different stakeholder groups responded to the closure in different ways and fish dealers were among those most affected by the closure. However, overall impacts to the bigeye community were not as severe as what had been anticipated at the outset. Several mitigating factors meant this was not a true closure, as US boats could continue to fish for bigeye in the Eastern Pacific Ocean and foreign and dual permitted vessels could still fish in the WCPO. Hawai‘i's longline fleet has since benefited from US legislation and federal rules that have prevented any subsequent closures of the fishery. While this relief from closures could stall short term socioeconomic impacts to Hawai‘i bigeye community, some worry that it could set back global efforts towards sustainable management of the fishery. This study highlights the challenges and equity considerations inherent in efforts to achieve meaningful conservation benefits from localized management actions within a global fishery. It also demonstrates the importance of interdisciplinary socioeconomic monitoring to examine how global fisheries policies scale down to individual fishing communities.

Decapitate or Strangulate?

HomeCirculationVol. 123, No. 23Decapitate or Strangulate? Free AccessBrief ReportPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessBrief ReportPDF/EPUBDecapitate or Strangulate? Philippe Debruyne, MD and Tom Rossenbacker, MD, PhD Philippe DebruynePhilippe Debruyne From the Department of Cardiology, Imeldaziekenhuis, Bonheiden, Belgium. Search for more papers by this author and Tom RossenbackerTom Rossenbacker From the Department of Cardiology, Imeldaziekenhuis, Bonheiden, Belgium. Search for more papers by this author Originally published14 Jun 2011https://doi.org/10.1161/CIRCULATIONAHA.110.016618Circulation. 2011;123:2748A 79-year-old woman with paroxysmal atrial fibrillation and severe mitral regurgitation underwent a mitral valve plasty and suture ligation of the left atrial appendage. Because of the patient's refractoriness to antiarrhythmic drugs, a transcutaneous pulmonary vein isolation was scheduled 17 months after the initial surgery. During the selective angiography (Figure 1) of the right superior pulmonary vein a saccular structure was surprisingly visualized, anteriorly and superiorly located to the mitral ring, corresponding to the previously presumed excluded left atrial appendage. A computed tomography scan, performed 2 days before ablation, also revealed that the left atrial appendage was not excluded (Figure 2). An incomplete exclusion of the left atrial appendage could correspond to a proembolic status, and can be documented by transesophageal echocardiography. Fortunately, oral anticoagulation has never been interrupted in our patient, and no thromboembolic complications have occurred. Different epicardial, endocardial, and combined epicardial-endocardial methods are currently being clinically investigated to close the left atrial appendage to ensure a true closure or excision of the left atrial appendage.Download figureDownload PowerPointFigure 1. Incomplete occlusion of the left atrial appendage after suture ligation. * indicates the right superior pulmonary vein; **, saccular structure; and ***, mitral ring.Download figureDownload PowerPointFigure 2. Frontal view showing that the left atrial appendage (LAA) was not excluded after ligation. ** indicates LAA.DisclosuresNone.FootnotesCorrespondence to Philippe Debruyne, MD, Department of Cardiology, Imeldaziekenhuis, Bonheiden, Belgium. E-mail Philippe.[email protected]be Previous Back to top Next FiguresReferencesRelatedDetails June 14, 2011Vol 123, Issue 23 Advertisement Article InformationMetrics © 2011 American Heart Association, Inc.https://doi.org/10.1161/CIRCULATIONAHA.110.016618PMID: 21670243 Originally publishedJune 14, 2011 PDF download Advertisement SubjectsArrhythmiasCardiovascular SurgeryCerebrovascular Procedures

I–Xe dating: From adolescence to maturity

The I–Xe chronometer is based upon decay of now-extinct 129I where the ratio of accumulated daughter 129Xe to stable 127I reflects the iodine isotopic ratio at closure of the host mineral. Since none of the parent remains, I–Xe is by nature a relative chronometer but, when referenced by a standard mineral of known age, the I–Xe system becomes an absolute chronometer reflecting true closure times. Most iodine hosts are secondary minerals so the I–Xe system is unique in providing details of post-formational chronometry not readily available with other chronometers. The short half-life of 129I gives it exceptional precision. However, the secondary nature of iodine host minerals, combined with the inherent precision of I–Xe, were responsible for a large database of “whole-rock” I–Xe ages that were not easily interpreted. As this problem evolved historically, doubts were cast upon the viability of the I–Xe system as a chronometer which persisted until it was tested against other chronometers in single-mineral systems. Properly calibrated, absolute I–Xe ages reflect the true closure time of the host minerals, and sequences of closure times in different hosts provide cooling rates for the parent object.

A New Version of α-Tight Closure

AbstractHara and Yoshida introduced a notion of α-tight closure in 2003, and they proved that the test ideals given by this operation correspond to multiplier ideals. However, their operation is not a true closure. The alternative operation introduced here is a true closure. Moreover, we define a joint Hilbert-Kunz multiplicity that can be used to test for membership in this closure. We study the connections between the Hara-Yoshida operation and the one introduced here, primarily from the point of view of test ideals. We also consider variants with positive real exponents.

Spatially correlated anomalous 40Ar/ 39Ar “age” variations in biotites about a lithologic contact near Simplon Pass, Switzerland: a mechanistic explanation for excess Ar

Forty-four biotite samples collected about a lithologic contact between pelite and amphibolite were analyzed for 40Ar/ 39Ar and demonstrate the importance of bulk Ar diffusivity and system geometry—factors not usually considered in the interpretation and collection of 40Ar/ 39Ar age data. The resulting 40Ar/ 39Ar apparent ages range from 11.30 ± 0.05 Ma to 17.90 ± 0.10 Ma. The ages (and excess argon contents) are spatially and lithologically correlated. The pelite samples all yield ages clustering around ∼12 Ma, the age expected for cooling through biotite closure (∼360°C) in this region of the Alps. Ages in the amphibolite biotites are older, showing a smooth trend between 15 Ma at the contact with the pelite to 18 Ma, 34 cm from the contact. This data shows that characterization of the Ar closure age for biotite in a given system should not rest on a single sample, as otherwise irresolvable differences in age between samples within the same outcrop can exist. A generalized mechanistic model for excess argon is presented. The presence (or absence) of excess Ar depends on an intrinsic system parameter, τ T, the transmissive timescale, which is the characteristic time for 40Ar to escape through the local intergranular transporting medium (ITM) to some sink for argon. To prevent buildup of geochronologically significant excess 40Ar, τ T must be very short relative to the true closure age of the mineral. A FORTRAN code including radiogenic Ar production, diffusive loss of Ar from biotite, and bulk Ar diffusion through the ITM has been developed. Application of numerical modeling suggests that the time-averaged effective bulk diffusivity, D eff Ar , in the biotite-amphibolite rock during early retrograde cooling is 2.2 ± 1.0 × 10 −8 m 2/yr (assuming steady state conditions) - the first such measurement available. Numerical modeling also provides information about the transmissivity and geologic history specific to the field site, including a drop in D eff Ar at 15.5 ± 1.0 Ma. The timing of this drop is related to coincident rheological changes and the onset of rapid exhumation of the nappe stack.

Empirical constraints on closure temperatures from a single diffusion coefficient

The elucidation of thermal histories by geochronological and isotopic means is based fundamentally on solid-state diffusion and the concept of closure temperatures. Because diffusion is thermally activated, an analytical solution of the closure temperature (Tc*) can only be obtained if the diffusion coefficient D of the diffusion process is measured at two or more different temperatures. If the diffusion coefficient is known at only one temperature, however, the true closure temperature (Tc*) cannot be calculated analytically because there exist an infinite number of possible (apparent) closure temperatures (T¯c) which can be generated by this single datum. By introducing further empirical constraints to limit the range of possible closure temperatures, however, mathematical analysis of a modified form of the closure temperature equation shows that it is possible to make both qualitative and quantitative estimates of Tc* given knowledge of only one diffusion coefficient DM measured at one temperature TM. Qualitative constraints of the true closure temperature Tc* are obtained from the shapes of curves on a graph of the apparent Tc (T¯c) vs. activation energy E, in which each curve is based on a single diffusion coefficient measurement DM at temperature TM. Using a realistic range of E, the concavity of the curve shows whether TM is less than, approximately equal to, or greater than Tc*. Quantitative estimates are obtained by considering two dimensionless parameters [lnERT^c vs. Tc*/TM] derived from these curves. When these parameters are plotted for known argon diffusion data and for a given diffusion size and cooling rate, it is found that the resultant curves are almost identical for all of the commonly dated K–Ar minerals – biotite, phlogopite, muscovite, hornblende and orthoclase – in spite of differences in their diffusion parameters. A common curve for Ar diffusion can be derived by least-squares fitting of all the Ar diffusion data and provides a way of predicting a “model” closure temperature Tcm from a single diffusion coefficient DM at temperature TM. Preliminary diffusion data for a labradorite lead to a Tcm of 507 ± 17 °C and a corresponding activation energy of about 65 kcal/mol, given a grain size of 200 μm and a cooling rate of 5 °C/Ma. Curves for He diffusion in silicates (augite, quartz and sanidine) also overlap to a significant degree, both among themselves and with the Ar model curve, suggesting that a single model curve may be a good representation of noble gas closure temperatures in silicates. An analogous model curve for a selection of 18O data can also be constructed, but this curve differs from the Ar model curve. A single model curve for cationic species does not appear to exist, however, suggesting that chemical bonding relationships between the ionic size/charge and crystal structure may influence the closure temperatures of diffusing cations. An indication of the degree of overlap among the various curves for Ar, He, 18O and cations is also obtained by considering the dimensionless parameter E/RTc*; for the noble gases and 18O, E/RTc* values for the respective minerals are very similar, whereas for cations, there is significant dispersion. Given these constraints, this may be a potential method of estimating closure temperatures for certain diffusing species when there are limited diffusion data.

Evidence for excess argon during high pressure metamorphism in the dora maira massif (Western Alps, Italy), using an ultra-violet laser ablation microprobe 40Ar-39Ar technique

Ultra-high pressure eclogite/amphibolite grade metamorphism of the Dora Maira Massif in the western Alps is a well established and intensively studied event. However, the age of peak metamorphism and early cooling remains controversial. The 40Ar-39 Ar step-heating and laser spot ages from high pressure phengites yield plateau ages as old as 110 Ma which have been interpreted as the time of early cooling after the high pressure event. Recent U/Pb and Sm/Nd results challenge this assertion, indicating a much younger age for the event, around 45 Ma, and hence a radically different timing for the tectonic evolution of the western Alps. In a new approach to the problem, samples from the undeformed Hercynian metagranite, Brossasco, were studied using an ultra-violet laser ablation microprobe technique for 40Ar-39 Ar dating. The new technique allowed selective in situ analysis, at a spatial resolution of 50 urn, of quartz, phengite, biotite and K-feldspar. The results demonstrate the frequent occurrence of excess argon with high 40Ar-39 Ar ratios (1000–10000) and a strong relationship between apparent ages and metamorphic textures. The highest excess argon ratios are always associated with high closure temperature minerals or large diffusion domains within single mineral phases. The best interpretation of this relationship seems to be that excess argon was incorporated in all phases during the high pressure event, then mixed with an atmospheric component during rapid cooling and retrogression, producing a wide range of argon concentrations and 40Ar/36Ar ratios. Step-heating analysis of minerals with this mixture would produce linear arrays on a40Ar/36Ar versus 40Ar/36 Ar correlation diagram, leading to geologically meaningless plateau ages, older than the true closure age. In the present case, some ages in the range 60–110 Ma could be explained by the presence of excess argon incorporated around 40–50 Ma ago. Similar results found in other high pressure terrains in the Alps may reconcile the argon geochronometer with other systems such as Rb/Sr, U/Pb or Sm/Nd. This study therefore calls for an increasing use of high resolution in situ sampling techniques to clarify the meaning of 40Ar/ 36 Ar ages in many high pressure terrains.

" Las Donas e las femnas, las tozas avinens" : Women in La Canso de la Crozada

"LAS DONAS E LAS FEMNAS, LAS TOZAS AVINENS" WOMEN IN LA CANSO DE LA CROZADA La Canso de la Crozada, the epic narrative ofthirteenth-century war and destruction in Southern France, challenges the modern reader to see both sides of a real war and both sides of a literary struggle to expand the boundaries of an established genre, the chanson de geste. The story, which relates the events dating from 1208 to 1219 of the Catholic church's crusade against the Cathar heretics and their aristocratic protectors, istold by two authorswith two different points of view, two different reasons for writing, and, ultimately, two different stories, which, together, are known as La Canso de la Crozada (or. in French, La Chanson de la Croisade albigeoise).1 In examining this textmodern scholarshave compared its disparate messages and the poetic quality of its two authors and considered its place in the literature of the time. One aspect, however, has escaped the attention of most scholars: namely, the role of women. Compared to most epic accounts, the Canso allows women to appear with relative frequency, giving them an active role and a voice. In this article 1 shall analyze the passages in which women are mentioned in order to compare the two authors, their attitudes about women, the narrative function of women in their texts. and. finally, their attitudes about the genre adopted for their subject. Little is known about the two authors ofthe Canso. The first poet introduces himselfin the text: "Maestre Guilhelms la fist a Montalba on fo" (9, 26). His name is Guilhem de Tudela, a clerk from Navarre protected by Count Baudoin. He is openly hostile towards the heretics (2, 4-9) and a staunch supporter ofthe crusaders, attributing their success to divine intervention (56, 44-46, 57). He states that he began writing in 1210 (9, 24).2 His part of the poem, 2749 verses, recounts the events from the initial invasion of 1209 to the Batttle of Muret in 12 13.3 The continuator of his poem remains anonymous: no mention ofhis name is made in the text, but it has been surmised that he was a clerk from Toulouse, possibly even the troubadour. Peire Cardenal.4 He continueswhere the otherpoetleft off, with the Battle of Muret, and ends with the arrival of Louis, son of the King of France, Philip Augustus, in Toulouse in 1219. His portion of the text amounts to 6,811 verses, or roughly threequarters of the entire work. The anonymous poet is clearly sympathetic to the cause ofthe South and supports the house ofToulouse. WOMEN IN CANSO DE LA CROZADA He deplores the destruction ofcities and land, the death ofso many people, and the French presence on land rightfully belonging to Southerners. That does not, however, mean that he espouses heretical religious ideas. His theology is quite orthodox, except for his hatred ofthe Bishop ofToulouse, whom he sees as acollaborator. Even though the Canso is written by two different authors, the plot, which is arranged chronologically, continues without interruption, ending with a sense of true closure.5 The only outward sign of the shift from one poet to the other is the abrupt change of political perspective and the transformation ofthe rhyme schemefrom cablas capcaudadas to cablas capfinidas.6 Both authors followthe basic lines ofthe chanson degestemodel in crafting their respective sections of the Canso. They develop the typical motifs and formulas of the genre: descriptions of arms, knights, battles, the siege of cities, mobilization of troops, one-onone combat using swords and other weapons, insults and threats, prayers, pursuit ofthe enemy, meetings ofwar councils and ambassadors .7 Guilhem de Tudela explains that the specific model for his poem is the Canso d'Antiocha: "Senhors. esta canso es faita d'aitai guia / Com sela d'Antiocha" (Lords, this song is composed according to the same form / As that of Antioch) [2. 1-2], which was a well known chanson de geste about the first Crusade.8 Thus. Tudela builds his poem on a textwhich supplies the form and melody for his own. a text which is couched in a generic tradition with well-defined themes and particular modes of expression, such as...