Is nonlinear propagation responsible for the brassiness of elephant trumpet calls?

African elephants (Loxodonta africana) produce a broad diversity of sounds ranging from infrasonic rumbles to much higher frequency trumpets. Trumpet calls are very loud voiced signals given by highly aroused elephants, and appear to be produced by a forceful expulsion of air through the trunk. Some trumpet calls have a very distinctive quality that is unique in the animal kingdom, but resemble the "brassy" sounds that can be produced with brass musical instruments such as trumpets or trombones. Brassy musical sounds are characterised by a flat spectral slope caused by the nonlinear propagation of the source wave as it travels through the long bore of the instrument. The extent of this phenomenon, which normally occurs at high intensity levels (e.g. fortissimo), depends on the fundamental frequency (F0) of the source as well as on the length of the resonating tube. Interestingly, the length of the vocal tract of the elephant (as measured from the vocal folds to the end of the trunk) approximates the critical length for shockwave formation, given the fundamental frequency and intensity of trumpet calls. We suggest that this phenomenon could explain the unique, distinctive brassy quality of elephant trumpet calls

Léon Walras et le statut de la concurrence : une étude à partir des Elements d'économie politique pure

On a trop tendance encore aujourd'hui à assimiler la « libre concurrence » chez Léon Walras et la « concurrence pure et parfaite » comme structure de marché de la vulgate néo-classique. Nous chercherons à montrer dans cette étude que chez Walras, la libre concurrence, quel que soit le niveau auquel on l'appréhende (certains marchés concrets, marché type réel, marché type idéal), est essentiellement un comportement spécifique et naturel d'individus rationnels et libres, et disposant d'institutions leur permettant d'exercer pleinement ces libertés. Elle découle de trois libertés : celle de proposer les prix à l'enchère et au rabais, celle de faire varier sa production selon les situations de bénéfice ou de perte, celle d'entrer ou de sortir du marché. Trois libertés, qui produisent un comportement naturel, mais qui doivent pouvoir s'exercer pleinement, d'où l'existence de deux règles suivantes : - les échangistes doivent rendre publiques leurs propositions en les criant, - les processus d'enchères et rabais doivent être terminés et le prix d'équilibre atteint, avant qu'il y ait des transactions effectives. Notre étude comprendra deux sections. La première section, La concurrence et la méthode walrasienne, met en relation la méthode de l'auteur des Eléments et les divers niveaux auxquels il appréhende la concurrence et les marchés concurrentiels. La deuxième section, Marché, concurrence et libre concurrence absolue, examine comment Walras prend en compte les marchés concrets, construit son marché type réel et passe ensuite au marché type idéal. On peut ainsi caractériser la concurrence walrasienne par opposition aux conceptions standard.représentations du marché ; Léon Walras ; libre-concurrence ; marchés concurrentiels ; marché type idéal

Non-linearized amplifier and advanced mitigation techniques: DVB-S2X spectral efficiency improvement

The latest standardization DVB-S2X increases the achievable spectral efficiency of the satellite communications by around 15% in AWGN channel. In order to benefit from those improvements, the strong non-linear distortions introduced by the payload have to be overcome, mostly taking high back-off on the amplifier operation point. Nowadays, on- board amplifiers are linearized before being deployed, allowing low-complexity transmitters and receivers at the detriment of the payload's cost and reduced energy efficiency. In this paper, various techniques are investigated for the purpose of spectral efficiency improvement while releasing the amplifier linearization constraint. Iterative pre-distortion at the transmitter, turbo- equalization at the receiver and appropriate waveforms for transmission through non-linearized payload appear as strong candidates considering the results of this study

Voltage-gated sodium channels: new targets in cancer therapy?

Early detection and treatment of cancers have increased survival and improved clinical outcome. The development of metastases is often associated with a poor prognostic of survival. Finding early markers of metastasis and developing new therapies against their development is a great challenge. Since a few years, there is more evidence that ionic channels are involved in the oncogenic process. Among these, voltage-gated sodium channels expressed in non-nervous or non-muscular organs are often associated with the metastatic behaviour of different cancers. The aim of this review is to describe the current knowledge on the functional expression of voltage-gated sodium channels and their biological roles in different cancers such as prostate, breast, lung (small cells and non-small cells) and leukaemia. In the conclusion, we develop conceptual approaches to understand how such channels can be involved in the metastatic process and conclude that blockers targeted toward these channels are promising new therapeutic solutions against metastatic cancers

Duplication processes in Saccharomyces cerevisiae haploid strains

Duplication is thought to be one of the main processes providing a substrate on which the effects of evolution are visible. The mechanisms underlying this chromosomal rearrangement were investigated here in the yeast Saccharomyces cerevisiae. Spontaneous revertants containing a duplication event were selected and analyzed. In addition to the single gene duplication described in a previous study, we demonstrated here that direct tandem duplicated regions ranging from 5 to 90 kb in size can also occur spontaneously. To further investigate the mechanisms in the duplication events, we examined whether homologous recombination contributes to these processes. The results obtained show that the mechanisms involved in segmental duplication are RAD52-independent, contrary to those involved in single gene duplication. Moreover, this study shows that the duplication of a given gene can occur in S.cerevisiae haploid strains via at least two ways: single gene or segmental duplication

Influence of genetic background on the occurrence of chromosomal rearrangements in Saccharomyces cerevisiae

<p>Abstract</p> <p>Background</p> <p>Chromosomal rearrangements such as duplications and deletions are key factors in evolutionary processes because they promote genomic plasticity. Although the genetic variations in the <it>Saccharomyces cerevisiae </it>species have been well documented, there is little known to date about the impact of the genetic background on the appearance of rearrangements.</p> <p>Results</p> <p>Using the same genetic screening, the type of rearrangements and the mutation rates observed in the S288c <it>S. cerevisiae </it>strain were compared to previous findings obtained in the FL100 background. Transposon-associated rearrangements, a major chromosomal rearrangement event selected in FL100, were not detected in S288c. The mechanisms involved in the occurrence of deletions and duplications in the S288c strain were also tackled, using strains deleted for genes implicated in homologous recombination (HR) or non-homologous end joining (NHEJ). Our results indicate that an Yku80p-independent NHEJ pathway is involved in the occurrence of these rearrangements in the S288c background.</p> <p>Conclusion</p> <p>The comparison of two different <it>S</it>. <it>cerevisiae </it>strains, FL100 and S288c, allowed us to conclude that intra-species genomic variations have an important impact on the occurrence of chromosomal rearrangement and that this variability can partly be explained by differences in Ty1 retrotransposon activity.</p

Health and frailty among older spousal caregivers:an observational cohort study in Belgium

Abstract Background Among older couples, spouses are first in line to provide care, and they are key elements in the home support of dependent older persons. In this context, ensuring the health of these older spousal caregivers should be an important issue for all of the providers who care for older adults. The aim of this study was to longitudinally assess the health of older spousal caregivers considering frailty, nutrition, cognition, physical performance and mood disorders. Methods In this longitudinal, observational cohort study, participants were assessed at home in Wallonia, Belgium. At baseline, 82 community-dwelling spouses of older patients with cognitive deficits or functional impairment were assessed; 78 caregivers were assessed at follow-up (16 months). The clinical instruments used included Frailty Phenotype (Fried), the Mini Nutritional Assessment-short form (MNA-SF), Short Physical Performance Battery (SPPB), Geriatric Depression Scale (GDS-15), clock drawing test, medications, Zarit Burden Index (ZBI), and Caregiver Reaction Assessment (CRA). Biological assessments included plasma interleukin-6 (IL-6), ultrasensitive C-reactive protein (CRP), cortisol, albumin and insulin growth factor-1 (IGF-1). Results Among caregivers, 54% were women, and the mean age was 80 years. Among care-receivers, 83% had cognitive impairment. Caregivers were more likely to be in a pre-frail stage. In one-third of the caregivers, the frailty status worsened. Transitions were observed between each of the states, except from frail to robust. In contrast to frailty, items including nutrition, cognitive status, SPPB and mood assessments were stable over time, with approximately 70% of the caregivers not experiencing significant change at follow-up. Caregiver experiences assessed with the Zarit Burden Interview and CRA were relatively stable over 16 months. Conclusion Many caregivers of geriatric patients are spouses who are old themselves. A failure in the health of the caregiver may anticipate an undesired care breakdown. Caregiver health and its determinants should be explored in future longitudinal studies that cover a longer time period