346 research outputs found
Bone orthotropic remodeling as a thermodynamically-driven evolution
International audienceIn this contribution we present and discuss a model of bone remodeling set up in the framework of the theory of generalized continuum mechanics and first introduced by DiCarlo et al.[1]. Bone is described as an orthotropic body experiencing remodeling as a rotation of its microstruc-ture. Thus, the complete kinematic description of a material point is provided by its position in space and a rotation tensor describing the orientation of its microstructure. Material motion is driven by energetic considerations , namely by the application of the Clausius-Duhem inequality to the microstructured material. Within this framework of orthotropic re-modeling, some key features of the remodeling equilibrium configurations are deduced in the case of homogeneous strain or stress loading conditions. First, it is shown that remodeling equilibrium configurations correspond to energy extrema. Second, stability of the remodeling equilibrium configurations is assessed in terms of the local convexity of the strain and complementary energy functionals hence recovering some classical energy theorems. Eventually, it is shown that the remodeling equilibrium configurations are not only highly dependent on the loading conditions, but also on the material properties
When moles became diggers: Tegulariscaptor gen. nov., from the early Oligocene of south Germany, and the evolution of talpid fossoriality
The systematics of Geotrypus is among the most debated within Talpidae, but the recent development of quantitative methods for shape analyses allows us to provide a thorough reconsideration of Geotrypus spp. In the present study, we perform a systematic revision of the species Geotrypus minor from the early Oligocene of Germany using two-dimensional geometric morphometrics on the humerus, and cladistic analyses using two different character matrices. Our results suggest a distinct generic allocation for this species based on its unique humeral shape. Cladistic analyses reveal that G. minor has closer phylogenetic relationships with urotrichine shrew-moles than with other Geotrypus species or highly fossorial moles. Quantitative methods applied in this study support qualitative observations and fully justify a new generic allocation. In light of these results, Tegulariscaptor gen. nov. is proposed to encompass the material previously assigned to G. minor.http://zoobank.org/urn:lsid:zoobank.org:pub:8A839F1E-0EC8-4799-B3AE-1A4E54A95F0
Raptor talon shape and biomechanical performance are controlled by relative prey size but not by allometry
Most birds of prey (raptors), rely heavily on their talons for capturing prey. However, the relationship between talon shape and the ability to take prey is poorly understood. In this study we investigate whether raptor talons have evolved primarily in response to adaptive pressures exerted by different dietary demands, or if talon morphology is largely constrained by allometric or phylogenetic factors. We focus on the hallux talon and include 21 species in total varying greatly in body mass and feeding ecology, ranging from active predation on relatively large prey to obligate scavenging. To quantify the variation in talon shape and biomechanical performance within a phylogenetic framework, we combined three dimensional (3D) geometric morphometrics, finite element modelling and phylogenetic comparative methods. Our results indicate that relative prey size plays a key role in shaping the raptorial talon. Species that hunt larger prey are characterised by both distinct talon shape and mechanical performance when compared to species that predate smaller prey, even when accounting for phylogeny. In contrast to previous results of skull-based analysis, allometry had no significant effect. In conclusion, we found that raptor talon evolution has been strongly influenced by relative prey size, but not allometry and, that talon shape and mechanical performance are good indicators of feeding ecology
Pequeños vertebrados del relleno kárstico del Pleistoceno Superior de Avetrana (Apulia, Sur de Italia)
The fossiliferous deposit (karst cavity) in La Grave, a locality near the small town of Avetrana (Taranto, southÂern Italy), has yielded numerous fossils of vertebrates. The remains of large mammals have been the subject of several studies. This paper examines the remains of small vertebrates and identifies four taxa of amphibians (Bufo bufo, Bufotes gr. B. viridis, Hyla gr. H. Arborea and Rana (s.l.) sp.), four taxa of reptiles (Testudo hermanni, Podarcis sp., Zamenis gr. Z. longissimus, Natrix natrix), and nine taxa of small mammals (Erinaceus europaeus, Crocidura suaveolens, Arvicola italicus, Microtus (Terricola) savii, Microtus (Microtus) arvalis, Apodemus gr. A. sylvaticus - A. flavicollis, Hystrix (Acanthion) vinogradovi, Oryctolagus cuniculus and Lepus corsicanus). From a biochronological point of view, the data on small and large vertebrates indicate an age between the beginning of the Late Pleistocene (MIS 5e) and the central part of MIS 3. The most recent fossiliferous layer (bed 8) is likely to have been deposited during a cooler period when compared to the previous layers.The data from small fossil vertebrates combined with those emerging from the large mammals and birds evidence the presence, near the karstic cavity, of open spaces (prairies) with pools of water, bordered by wooded areas and, not far, the presence of a rocky coastline.El depósito (cavidad kárstica) de La Grave, localidad cercana a la pequeña ciudad de Avetrana (Tarento, Italia meridional), ha dado lugar a numerosos fósiles de vertebrados. Los restos de grandes mamÃferos han sido objeto de varios estudios. En este trabajo se examinan los restos de pequeños vertebrados y se identifican cuatro taxones de anfibios (Bufo bufo, Bufotes gr. B. viridis, Hyla gr. H. Arborea and Rana (s.l.) sp.), cuatro de reptiles (Testudo hermanni, Podarcis sp., Zamenis gr. Z. longissimus, Natrix natrix), y nueve de pequeños mamÃferos (Erinaceus europaeus, Crocidura suaveolens, Arvicola italicus, Microtus (Terricola) savii, Microtus (Microtus) arvaÂlis, Apodemus gr. A. sylvaticus - A. flavicollis, Hystrix (Acanthion) vinogradovi, Oryctolagus cuniculus and Lepus corsicanus). Desde un punto de vista biocronológico, los datos sobre los vertebrados pequeños y grandes indican una edad entre el comienzo del Pleistoceno tardÃo (MIS 5e) y la parte central del MIS 3. Es probable que el estrato fosilÃfero más reciente (nivel 8) se haya depositado durante un perÃodo más frÃo en comparación con las capas anteriores. Los datos de pequeños vertebrados fósiles combinados con los que proceden de los grandes mamÃfeÂros y aves evidencian la presencia, cerca de la cavidad kárstica, de espacios abiertos (praderas) con charcos de agua, bordeados por zonas boscosas y, no muy lejos, la presencia de una costa rocosa
Trapped in the morphospace: The relationship between morphological integration and functional performance
The evolution of complex morphological structures can be characterized by the interplay between different anatomical regions evolving under functional integration in response to shared selective pressures. Using the highly derived humeral morphology of talpid moles as a model, here we test whether functional performance is linked to increased levels of evolutionary integration between humerus subunits and, if so, what the strength is of the relationship. Combining two-dimensional geometric morphometrics, phylogenetic comparative methods, and functional landscape modeling, we demonstrate that the high biomechanical performance of subterranean moles’ humeri is coupled with elevated levels of integration, whereas taxa with low-performance values show intermediate or low integration. Theoretical morphs occurring in high-performance areas of the functional landscape are not occupied by any species, and show a marked drop in covariation levels, suggesting the existence of a strong relationship between integration and performance in the evolution of talpid moles’ humeri. We argue that the relative temporal invariance of the subterranean environment may have contributed to stabilize humeral morphology, trapping subterranean moles in a narrow region of the landscape and impeding any attempt to reposition on a new ascending slope
New systematic insights about Plio-Pleistocene moles from Poland
The generic attribution of the Plio-Pleistocene Polish moles Neurotrichus? polonicus and
Neurotrichus? skoczeni has been questioned several times in the past. The fossil material
belonging to Neurotrichus? polonicus and Neurotrichus? skoczeni is re-evaluated here and a
new diagnosis is provided on the basis of qualitative considerations. In addition, a Geometric
Morphometric analysis of the humerus has been performed including both extant and extinct
Neurotrichini and Urotrichini taxa for comparison. Our results proved the unique morphology
of the Polish material suggesting a distinct taxonomic state. The morphological variations
evidenced by the humeral shape analysis agree with the observed qualitative differences and
support a new generic allocation. The new genus Rzebikia gen. nov. is proposed for all the
material previoulsly ascribed to Neurotrichus? polonicus and Neurotrichus? skoczeni
Utilisation d'indices de pollution pour choisir les procédés de traitement des rejets urbains de temps de pluie dans un bassin versant fortement urbanisé : Liguori de Cosenza, Italie
Repair of sphincter urethral strictures preserving urinary continence: surgical technique and outcomes
Introduction Repair of post-TURP sphincter urethral strictures represents challenging problem, due to the risk of urinary incontinence after the repair. We described a surgical technique we use to repair these strictures preserving urinary continence in patients with incompetent bladder neck. Materials and methods An observational, retrospective, study was conducted to include patients with post-TURP urethral strictures in the area of distal sphincter. We included only patients with complete clinical data and follow-up who previously underwent TURP or HOLEP or TUIP, and subsequently developed proximal bulbar urethral strictures close to the membranous urethra and the related distal urethral sphincter. Patients were included, if they were fully continent after TURP or other procedures to treat BPH. The primary outcome of the study was treatment failure, defined as the need for any post-operative instrumentation. Secondary outcome was post-urethroplasty urinary continence. Patients showing stricture recurrence or post-operative incontinence were classified as failure. Results Overall, 69 patients were included in the study. Median patient's age was 67 years; median stricture length was 4 cm. Thirty-tree patients (47.8%) underwent previous urethrotomy. Median follow-up was 52 months. Out of 69 patients, 55 (79.7%) were classified as success and 14 (20.3%) as failure. Out of the whole cohort, thus, 11/69 (16%) have a risk of recurrent strictures and 3/69 (4.3%) have incontinence. Conclusions The use of modified ventral onlay graft urethroplasty, using particular non-aggressive steps, is a suitable surgical technique for repair of sphincter urethral stricture in patients who underwent BPH transurethral surgery, using different procedures (TURP, HOLEP, TUIP)
Skull shape of a widely distributed, endangered marsupial reveals little evidence of local adaptation between fragmented populations
Risk calculator for prediction of treatment-related urethroplasty failure in patients with penile urethral strictures
Purpose To design a dedicated risk calculator for patients with penile urethra stricture who are scheduled to urethroplasty that might be used to counsel patients according to their pre-operative risk of failure. Methods Patients treated with penile urethroplasty at our center (1994-2018) were included in the study. Patients received 1-stage or staged penile urethroplasty. Patients with failed hypospadias repair, lichen sclerosus or incomplete clinical records were excluded. Treatment failure was defined as any required postoperative instrumentation, including dilation. Univariable Cox regression identified predictors of post-operative treatment failure and Kaplan-Meier analysis plotted the failure-free survival rates according to such predictors. Multivariable Cox regression-based risk calculator was generated to predict the risk of treatment failure at 10 years after surgery. Results 261 patients met the inclusion criteria. Median follow-up was 113 months. Out of 216 patients, 201 (77%) were classified as success and 60 (23%) failures. Former smoker (hazard ratio [HR] 2.12, p = 0.025), instrumentation-derived stricture (HR 2.55, p = 0.006), and use of grafts (HR 1.83, p = 0.037) were predictors of treatment failure. Model-derived probabilities showed that the 10-year risk of treatment failure varied from 5.8 to 41.1% according to patient's characteristics. Conclusions Long-term prognosis in patients who underwent penile urethroplasty is uncertain. To date, our risk-calculator represents the first tool that might help physicians to predict the risk of treatment failure at 10 years. According to our model, such risk is largely influenced by the etiology of the stricture, the use of graft, and patient's smoking habits
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