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Quantum systems whose classical counterparts are chaotic typically have highly correlated eigenvalues and level statistics that coincide with those from ensembles of full random matrices. A dynamical manifestation of these correlations comes in the form of the so-called correlation hole, which is a dip below the saturation point of the survival probability's time evolution. In this work, we study the correlation hole in the spin-boson (Dicke) model, which presents a chaotic regime and can be realized in experiments with ultracold atoms and ion traps. We derive an analytical expression that describes the entire evolution of the survival probability and allows us to determine the time scales of its relaxation to equilibrium. This expression shows remarkable agreement with our numerical results. While the initial decay and the time to reach the minimum of the correlation hole depend on the initial state, the dynamics beyond the hole up to equilibration is universal. We find that the relaxation time of the survival probability for the Dicke model increases linearly with system size.

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In the Pampa region of Argentina, farming activities have been performed since the beginning of the 20th century, but in the 1990s, land-use patterns rapidly changed towards intensive agriculture and poultry breeding. This study compares the helminth community of Akodon azarae (Rodentia) among three habitats with different land use in pampean agroecosystems: poultry farms, mono-cultivated fields and abandoned fields (not used for 35 years), under the prediction that there will be greater helminth richness and diversity in mice from abandoned fields compared to those from the other habitats. Nevertheless, the highest abundance of A. azarae occurred on poultry farms, the habitat most disturbed by human activity, while cultivated fields showed the lowest. Helminth richness and diversity were significantly higher on poultry farms than in the other habitats, due to the presence of Trichuris laevitestis, Protospirura numidica criceticola and cysts of Taenia taeniaeformis. We suggest that the helminth fauna of A. azarae can survive on poultry farms despite disturbance from farming activities, because rodents can move and get shelter within farm perimeter fences, where dense and high vegetation grows. This farm area could offer good conditions for geohelminth development, while chicken sheds could attract insects that are intermediate hosts of helminths with indirect life cycles. On the contrary, agrochemicals applied in cultivated fields would negatively influence helminth diversity and composition, by decreasing host populations (arthropods and rodents) and affecting free larval stages of geohelminths.

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A main feature of a chaotic quantum system is a rigid spectrum where the levels do not cross. We discuss how the presence of level repulsion in lattice many-body quantum systems can be detected from the analysis of their time evolution instead of their energy spectra. This approach is advantageous to experiments that deal with dynamics, but have limited or no direct access to spectroscopy. Dynamical manifestations of avoided crossings occur at long times. They correspond to a drop, referred to as correlation hole, below the asymptotic value of the survival probability and to a bulge above the saturation point of the von Neumann entanglement entropy and the Shannon information entropy. By contrast, the evolution of these quantities at shorter times reflects the level of delocalization of the initial state, but not necessarily a rigid spectrum. The correlation hole is a general indicator of the integrable-chaos transition in disordered and clean models and as such can be used to detect the transition to the many-body localized phase in disordered interacting systems.This article is part of the themed issue 'Breakdown of ergodicity in quantum systems: from solids to synthetic matter'.

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Introducción: El cierre de cuero cabelludo en neurocirugías supratentoriales mediante sutura intradérmica es una técnica poco difundida en la actualidad. En contraste, es común que se efectúen suturas de alta tensión con el fin de evitar dehiscencias, fístula de líquido cefalorraquídeo (LCR) y sangrado durante el período posquirúrgico, pero que no tienen buen resultado estético. Objetivo: Comparar las complicaciones relacionadas al cierre de cuero cabelludo que se presentaron en neurocirugías supratentoriales en un período de 19 meses, para determinar si utilizar un cierre de menor tensión y con mejor resultado estético, es igual de seguro que las técnicas de cierre habituales. Materiales y Métodos: Se incluyeron 84 casos de neurocirugías supratentoriales electivas. En 43 casos (control) se realizó el cierre mediante sutura continua tipo surget y en 41 casos (experimental) el cierre fue mediante sutura intradérmica. Resultados: Se presentaron 2 casos de infecciones, 1 en cada grupo (p= 0,97) y 1 caso de sangrado en el grupo control (p= 0,32). No se presentaron dehiscencias ni casos de fístula de LCR. Conclusiones: El cierre de cuero cabelludo mediante sutura intradérmica fue un método seguro que no generó una mayor incidencia de complicaciones y logró un mejor resultado estético a corto y largo plazo.

Background: Scalp closure by means of intradermal suture in patients who underwent supratentorial neurosurgeries is currently an uncommon technique. In contrast, it is usual to perform high tension sutures to avoid skin dehiscence, cerebrospinal fluid leak (CSF) and postoperative bleeding; however it usually results in unsatisfactory aesthetic results. Aim: Comparing complications, over a two year period, related to scalp closure occurred in supratentorial neurosurgeries. The goal is to establish if the intradermal suture is as safe as the current high tension closure technique.Materials and Methods: Eighty-four patients were included. In forty-three cases (control) continuous high tension suture (surget) was performed. The other forty-one cases (experimental) underwent intradermal suture. Results: Two infection cases occurred, one from each group (p= 0, 97). There was one case of bleeding that took place in the control group (p= 0,32). Neither dehiscence nor CSF leak occurred in any of the trial cases.Conclusions: Intradermal suture performed for scalp closure was as safe as surget in terms of complications occurrence and obtained better cosmetic results in the short and long term.

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OBJETIVO: Presentar nuestra experiencia en el manejo de los cavernomas de tronco cerebral, de tálamo y de ganglios basales. MATERIAL Y MÉTODO: Analizamos una serie de 16 pacientes asistidos en nuestra Institución, entre enero de 1990 y diciembre del año 2013. De ellos, 9 fueron varones y 7 mujeres. El rango de edad osciló entre 3 y 61 años. RESULTADOS: Siete debutaron con hemorragia cerebral, de ellos 4 se localizaban en protuberancia y 3 en el bulbo raquídeo. Siete pacientes tuvieron cavernomas múltiples, de ellos 3 tenían familiares con la misma enfermedad. El procedimiento diagnóstico de elección fue la resonancia nuclear magnética de cerebro en todos, y en los pacientes con cavernomas múltiples se completó el estudio con resonancia nuclear magnética de médula espinal. El tratamiento fue conservador en 9 enfermos, quirúrgico en 6 y radiocirugía estereotáctica en 1 enfermo; a éste paciente hubo necesidad de operarlo 6 meses después del tratamiento radiante por un resangrado voluminoso en la protuberancia. DISCUSIÓN: La cirugía es exitosa cuando el cavernoma se ubica a 2 mm de la piamadre, o del epéndimo. La radiocirugía puede ser causante de resangrado y de mayor volumen que las hemorragias previas. Por último, el tratamiento conservador sigue teniendo vigencia en los pacientes que se recuperaron neurológicamente y cuando se ubican en la profundidad del tronco cerebral, tálamo óptico o ganglios basales. CONCLUSIÓN: Cada paciente debe evaluarse individualmente para decidir el tipo de tratamiento, teniendo en cuenta la edad, la recuperación de los signos neurológicos, el volumen y la localización precisa del cavernoma

Objective: To present our experience in the management of brainstem, thalamus and basal ganglia cavernous malformations. Material and Method: We analyzed a series of 16 patients admitted to our Institution between January 1990 and December 2013. Nine of them were male and 7 female. Age ranged between 3 and 61. Results: Seven patients presented brainstem hemorrhage, 4 being pontine and the remaining 3 were medullary. Seven patients had multiple cavernomas, and 3 of them had a family background with the disease. The chosen diagnostic procedure was brain MRI in all patients; in patients with multiple cavernomas spine MRI was also requested. Nine patients received conservative treatment, 6 patients underwent surgery and one was treated with stereotactic radiosurgery but had to be operated on six months after radiation treatment due to voluminous re-bleeding at protuberance. Discussion: Surgery is successful when the cavernous malformation is placed 2 mm away from pia mater or ependyma. Radiosurgery can cause re-bleeding and of a greater volume than previous hemorrhages. Finally, conservative treatment is useful in patients who get neurologically recovered and when malformations are placed deep in brainstem, optic thalamus or basal ganglia. Conclusion: Each patient has to be individually assessed to individually assessed to make a decision regarding the type of treatment, taking into account age, recovery of neurological signs, volume, and precise location of cavernous malformation

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Numerically, we study the time fluctuations of few-body observables after relaxation in isolated dynamical quantum systems of interacting particles. Our results suggest that they decay exponentially with system size in both regimes, integrable and chaotic. The integrable systems considered are solvable with the Bethe ansatz and have a highly nondegenerate spectrum. This is in contrast with integrable Hamiltonians mappable to noninteracting ones. We show that the coefficient of the exponential decay depends on the level of delocalization of the initial state with respect to the energy shell.

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This paper describes the helminth community of the Pampean grassland mouse (Akodon azarae) inhabiting poultry farms in central Argentina. Winter diversity (season of high rodent abundance) has been compared to spring diversity (season of low rodent abundance). Species richness was seven in both seasons: five nematodes (Syphacia carlitosi, Stilestrongylus spp., Trichuris laevitestis, Pterygodermatites (Paucipectines) azarai and Protospirura numidica criceticola) and two cestodes (adults of Cyclophyllidea and Taenia taeniaeformis hepatic cysts). No difference in richness was detected between host sexes in each season or among host age classes. However, the helminth community showed 67% similarity between winter and spring, with diversity being significantly higher in spring (H = 0.873) than in winter (H = 0.546; P < 0.0005). This could be attributed to different factors, such as host abundance, host diet or environmental factors, that affect the transmission of each species differently. On the other hand, Stilestrongylus spp. and S. carlitosi showed higher dominance and intensity in both seasons compared to their cohabiting species, P. (P.) azarai and T. laevitestis, respectively. The lower values of the latter two species may be related to a crowding effect due to their large body sizes. This is the first report of cestodes in A. azarae. The finding of T. taeniaeformis strobilocerci could be important in the epidemiology of parasitosis in domestic animals of the farms.

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OBJECTIVE: To evaluate the clinical presentation, tumour response, clinical improvement and complications in 12 children and young people with a pilocytic astrocytoma, WHO I grade 1, who were treated with interstitial radiosurgery using Iodine-125 seed implants. PATIENTS AND METHODS: Retrospective analysis of 12 patients aged under 18 years (mean 8.4 years, ranging from 8 months to 17 years of age) with a pilocytic astrocytoma treated between 1993 and 2006. Iodine-125 seeds were used as temporary implants with low-dose rate (

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OBJECTIVE: To present our experience in the treatment of child optic pathway gliomas in the last 25 years. MATERIAL AND METHODS: Seventeen children under 10 years of age have been analyzed and assessed from clinic, ophthalmologic, endocrinologic, neurological, neuropathologic, and imaginologic points of view. RESULTS: Predominance of female patients, 10 girls and 7 boys between 6 and 122 months old; mean age was 3 years and 8 months. The most frequent symptoms have been ophthalmologic and visual alterations in all 17 patients, endocrine alterations in 10, and neurological signs in 6. One of the patients presented neurofibromatosis type 1 (NF1), another patient had Down syndrome. Diagnosed using computed tomography or/and magnetic resonance imaging, histological studies showed pilocytic astrocytomas in 13 cases and a fibrillary astrocytoma grade II in 1 case. There were three patients without histological diagnosis; one of them had NF1. The treatment consisted of surgery, external beam radiotherapy, chemotherapy, and brachytherapy with iodine 125, separately or combined. Five patients died; the causes were secondary tumors in two children, tumor recurrence in one, sepsis secondary to respiratory and urinary tract infections in the child with Down syndrome, and finally, hydrocephaly due to hyperproteinorachia of tumor origin in one. Average survival was 89 months. CONCLUSION: Chemotherapy and brachytherapy are therapeutic methods to be considered, especially in children under 5. Marsupialization of the residual cyst into the ventricular system postradio or oncolytic treatment through endoscopic or stereotactic techniques is useful in the treatment of endocranial hypertension and/or hypothalamic compression in these patients.

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