Temporal modes of hub synchronization at rest.

The brain is a dynamic system that generates a broad repertoire of perceptual, motor, and cognitive states by the integration and segregation of different functional domains represented in large-scale brain networks. However, the fundamental mechanisms underlying brain network integration remain elusive. Here, for the first time to our knowledge, we found that in the resting state the brain visits few synchronization modes defined as clusters of temporally aligned functional hubs. These modes alternate over time and their probability of switching leads to specific temporal loops among them. Notably, although each mode involves a small set of nodes, the brain integration seems highly vulnerable to a simulated attack on this temporal synchronization mechanism. In line with the hypothesis that the resting state represents a prior sculpted by the task activity, the observed synchronization modes might be interpreted as a temporal brain template needed to respond to task/environmental demands .

The potential role of magnetic resonance brain relaxometry in veterinary medicine: a preliminary study.

Magnetic Resonance (MR) is a non-invasive modality of choice for the evaluation of brain morphology, with superior performance as compared to other techniques. However, MR images are typically assessed qualitatively, thus relying on the experience of the involved radiologist. This may lead to errors of interpretation in the presence of subtle alterations and does not exploit the full potential of this technique as a quantitative diagnostic tool. To this end Magnetic Resonance Relaxometry (MRR), which is able to quantitively characterize the tissues under investigation through their relaxation rates, seems extremely promising. Many studies assessed the feasibility of relaxometry as a diagnostic tool in human brain disorders, with the most promising results obtained in the evaluation of neurodegenerative diseases and in the oncologic field. However, despite such extensive literature in human medicine, due to the lack of standardized protocols and the need of high-field MRI scanners, to date few studies have been performed on companion animals. In this work, first we describe relaxometry applications in human neuropathology and their possible extension to companion animals both in the experimental and clinical fields. Then, we present two experiments performed on a typical standard clinical scanner operating at 0.25 T to show that, despite the low field intensity, this technique may be promising even in the clinical setup. We tested the relaxometry protocol in a phantom study and then applied it to a real clinical case study. The results showed that this protocol used on a phantom led to a higher contrast, as compared to the standard approach. Furthermore, when applied to a real case study, this protocol revealed brain lesions undetected by the standard technique which were confirmed by a histopathological examination. These preliminary results are encouraging and support the development of this approach as an advanced diagnostic tool even in a clinical setting where low field MRI scanners are typically employed.

Cortical cores in network dynamics.

Spontaneous brain activity at rest is spatially and temporally organized in networks of cortical and subcortical regions specialized for different functional domains. Even though brain networks were first studied individually through functional Magnetic Resonance Imaging, more recent studies focused on their dynamic 'integration'. Integration depends on two fundamental properties: the structural topology of brain networks and the dynamics of functional connectivity. In this scenario, cortical hub regions, that are central regions highly connected with other areas of the brain, play a fundamental role in serving as way stations for network traffic. In this review, we focus on the functional organization of a set of hub areas that we define as the 'dynamic core'. In the resting state, these regions dynamically interact with other regions of the brain linking multiple networks. First, we introduce and compare the statistical measures used for detecting hubs. Second, we discuss their identification based on different methods (functional Magnetic Resonance Imaging, Diffusion Weighted Imaging, Electro/Magneto Encephalography). Third, we show that the degree of interaction between these core regions and the rest of the brain varies over time, indicating that their centrality is not stationary. Moreover, alternating periods of strong and weak centrality of the core relate to periods of strong and weak global efficiency in the brain. These results indicate that information processing in the brain is not stable, but fluctuates and its temporal and spectral properties are discussed. In particular, the hypothesis of 'pulsed' information processing, discovered in the slow temporal scale, is explored for signals at higher temporal resolution.

A Dynamic Core Network and Global Efficiency in the Resting Human Brain.

Spontaneous brain activity is spatially and temporally organized in the absence of any stimulation or task in networks of cortical and subcortical regions that appear largely segregated when imaged at slow temporal resolution with functional magnetic resonance imaging (fMRI). When imaged at high temporal resolution with magneto-encephalography (MEG), these resting-state networks (RSNs) show correlated fluctuations of band-limited power in the beta frequency band (14-25 Hz) that alternate between epochs of strong and weak internal coupling. This study presents 2 novel findings on the fundamental issue of how different brain regions or networks interact in the resting state. First, we demonstrate the existence of multiple dynamic hubs that allow for across-network coupling. Second, dynamic network coupling and related variations in hub centrality correspond to increased global efficiency. These findings suggest that the dynamic organization of across-network interactions represents a property of the brain aimed at optimizing the efficiency of communication between distinct functional domains (memory, sensory-attention, motor). They also support the hypothesis of a dynamic core network model in which a set of network hubs alternating over time ensure efficient global communication in the whole brain.

Modeling the dispersion of viable and total Escherichia coli cells in the artificial semi-enclosed bathing area of Santa Marinella (Latium, Italy).

Coastal areas are strongly affected by episodes of fecal contamination due to polluted water inflows from inadequately treated sewages. The present study aims to investigate the dispersion of Escherichia coli in the artificial semi-enclosed bathing area of Santa Marinella (Latium, Italy) through in situ samplings carried out in summer 2012 and the application of a dynamic model. Collected samples were analyzed by the Culture-Based technique and the Fluorescent Antibody method in order to estimate both the viable culturable cells and the total E. coli population, respectively. The in situ datasets were used to test the proposed modeling approach and simulate the behavior of bacteria as particles subjected, or not, to decay. Next, the flushing time and the computation of the Microbiological Potential Risk Area allowed the evaluation of the contribution of physical and biological processes to coliform dispersion and the related potential risk for bathers.

Changes in digestive enzyme activities of red porgy Pagrus pagrus during a fasting-refeeding experiment.

An experiment was carried out in red porgy, Pagrus pagrus (Teleostei, Sparidae), to assess the effects of a 14-day fasting period, followed by refeeding to apparent satiation, on the contents of digestive enzymes (total proteases, and particularly pepsin, trypsin, chymotrypsin, carboxypeptidases A and B; amylase and lipase). Two fish groups were considered: one (indicated as fasted/refed group) was fasted for 14 days and then refed during further 7 and 15 days, and the other was fed throughout the study and was taken as a control group. The measured enzymatic values showed that fasting resulted in a generalized, not significant decrease, of the activity of digestive enzymes. Refeeding caused a significant increase for most of the assayed enzymes: total proteases both in the middle and distal intestine, pepsin in the stomach, trypsin in the middle intestine, and amylase and lipase in the proximal intestine. Nevertheless, the detection in the fasted/refed fish of enzymatic values still lower than those measured in the control fish suggested that fish experiencing short-term fasting were partially impaired in their digestive capacity.

Frequency specific interactions of MEG resting state activity within and across brain networks as revealed by the multivariate interaction measure.

Resting state networks (RSNs) are sets of brain regions exhibiting temporally coherent activity fluctuations in the absence of imposed task structure. RSNs have been extensively studied with fMRI in the infra-slow frequency range (nominally <10(-1)Hz). The topography of fMRI RSNs reflects stationary temporal correlation over minutes. However, neuronal communication occurs on a much faster time scale, at frequencies nominally in the range of 10(0)-10(2)Hz. We examined phase-shifted interactions in the delta (2-3.5 Hz), theta (4-7 Hz), alpha (8-12 Hz) and beta (13-30 Hz) frequency bands of resting-state source space MEG signals. These analyses were conducted between nodes of the dorsal attention network (DAN), one of the most robust RSNs, and between the DAN and other networks. Phase shifted interactions were mapped by the multivariate interaction measure (MIM), a measure of true interaction constructed from the maximization of imaginary coherency in the virtual channels comprised of voxel signals in source space. Non-zero-phase interactions occurred between homologous left and right hemisphere regions of the DAN in the delta and alpha frequency bands. Even stronger non-zero-phase interactions were detected between networks. Visual regions bilaterally showed phase-shifted interactions in the alpha band with regions of the DAN. Bilateral somatomotor regions interacted with DAN nodes in the beta band. These results demonstrate the existence of consistent, frequency specific phase-shifted interactions on a millisecond time scale between cortical regions within RSN as well as across RSNs.

Adding dynamics to the Human Connectome Project with MEG.

The Human Connectome Project (HCP) seeks to map the structural and functional connections between network elements in the human brain. Magnetoencephalography (MEG) provides a temporally rich source of information on brain network dynamics and represents one source of functional connectivity data to be provided by the HCP. High quality MEG data will be collected from 50 twin pairs both in the resting state and during performance of motor, working memory and language tasks. These data will be available to the general community. Additionally, using the cortical parcellation scheme common to all imaging modalities, the HCP will provide processing pipelines for calculating connection matrices as a function of time and frequency. Together with structural and functional data generated using magnetic resonance imaging methods, these data represent a unique opportunity to investigate brain network connectivity in a large cohort of normal adult human subjects. The analysis pipeline software and the dynamic connectivity matrices that it generates will all be made freely available to the research community.

Different types of thoracic endografts.

The emerging role of stent-graft strategies for the management of thoracic aortic diseases has attracted growing acceptance, especially in considering the sobering results of open repair in thoracic high-risk settings (e.g., acute dissection, trauma, rupture). Aortic endograft technology for thoracic diseases has rapidly improved after the early use of first generation devices, and the new models show very promising early and mid-term success rates. To date there is no evidence of the superiority of any single device model over the others. Indeed, each device has some peculiarities that makes it more useful in specific settings. Current limitations in thoracic stent-grafts will hopefully be addressed with new designs of highly-individualized low-profile devices in order to extend the applicability of stent-graft technology in the thoracic aorta. Despite progress in configuration and flexibility and the greater availability of different devices compared to a decade ago, shortcomings of specific endovascular grafts including collapse, migration, or dislodgment have not been fully resolved. Nowadays the selection of patients on the basis of favourable anatomy and pathology is the key for the success of the procedure. Not all patients have lesions amenable to stent-graft repair (contraindications for endovascular treatment of thoracic aorta are still not marginal and mainly defined by anatomical constraints) and thoracic endografting is technically challenging, requiring dedicated facilities and experienced specialists. This paper discusses the different configurations and models of stent-graft for thoracic aortic disease as well as the still existing shortcomings.

Empirical Markov Chain Monte Carlo Bayesian analysis of fMRI data.

In this work an Empirical Markov Chain Monte Carlo Bayesian approach to analyse fMRI data is proposed. The Bayesian framework is appealing since complex models can be adopted in the analysis both for the image and noise model. Here, the noise autocorrelation is taken into account by adopting an AutoRegressive model of order one and a versatile non-linear model is assumed for the task-related activation. Model parameters include the noise variance and autocorrelation, activation amplitudes and the hemodynamic response function parameters. These are estimated at each voxel from samples of the Posterior Distribution. Prior information is included by means of a 4D spatio-temporal model for the interaction between neighbouring voxels in space and time. The results show that this model can provide smooth estimates from low SNR data while important spatial structures in the data can be preserved. A simulation study is presented in which the accuracy and bias of the estimates are addressed. Furthermore, some results on convergence diagnostic of the adopted algorithm are presented. To validate the proposed approach a comparison of the results with those from a standard GLM analysis, spatial filtering techniques and a Variational Bayes approach is provided. This comparison shows that our approach outperforms the classical analysis and is consistent with other Bayesian techniques. This is investigated further by means of the Bayes Factors and the analysis of the residuals. The proposed approach applied to Blocked Design and Event Related datasets produced reliable maps of activation.

Ion diffusion modelling of Fricke-agarose dosemeter gels.

In Fricke-agarose gels, an accurate determination of the spatial dose distribution is hindered by the diffusion of ferric ions. In this work, a model was developed to describe the diffusion process within gel samples of finite length and, thus, permit the reconstruction of the initial spatial distribution of the ferric ions. The temporal evolution of the ion concentration as a function of the initial concentration is derived by solving Fick's second law of diffusion in two dimensions with boundary reflections. The model was applied to magnetic resonance imaging data acquired at high spatial resolution (0.3 mm) and was found to describe accurately the observed diffusion effects.

Optical imaging of dose distributions in Fricke gels.

Ferrous-sulphate infused gels, or 'Fricke gels', encounter great interest in the field of radiation dosimetry, due to their potential for 3D radiation dose mapping. Typically, magnetic resonance (MR) relaxation rates are determined in these systems in order to derive the absorbed dose. However, when large concentration gradients are present, diffusion effects before and during the MR imaging may not be negligible. In these cases, optical techniques may represent a viable alternative. This paper describes research aimed at measuring 3D dose distributions in a Fricke-xylenol orange gel by measuring optical density with a CCD camera. This method is inexpensive and fast. A series of early experiments is described, in which optical density profiles were measured with a commercial microdensitometer for film dosimetry. The light box of the device was modified to work at 567 nm, close to the maximum absorbance of the ferric ion-xylenol orange complex. Under these conditions, the gel shows linearity with dose and high sensitivity.

Fluorescent antibody-viability staining and beta-glucuronidase assay as rapid methods for monitoring Escherichia coli viability in coastal marine waters.

A faecal pollution monitoring of coastal Messina waters was performed by comparing three (microscopic, enzyme, and culture) methods. Evidence of Escherichia coli cells (29.99 to 96.79% of the total enteropathogenic serotypes) retaining their viability into the marine environment was shown. beta-Glucuronidase activity rates suggested that living cells were also metabolically active. Heavily polluted sites were detected, where improperly treated urban wastes were discharged. Significant relationships between microscopic and enzymatic data proved both methods to be suitable alternatives to the culture method for E. coli detection, improving environmental quality assessment.

Cerebrospinal fluid and serum neuron-specific enolase concentrations in a normal population.

The aim of this study was to determine cerebrospinal fluid (CSF) and serum neuron-specific enolase (NSE) concentrations in a normal population and to analyse their relationship with sex and age. The sample was recruited among patients undergoing spinal anaesthesia, without neurological diseases. NSE was determined by means of immunometric assay. One hundred and eight patients (68 men) were recruited. CSF-NSE concentration was (mean +/- SD) 17.3 +/- 4.6 ng/ml (men 17.4 +/- 4.2, women 17.0 +/- 5.2, P = 0.62); serum concentration was 8.7 +/- 3.9 ng/ml (men 8.9 +/- 3.9, women 8.3 +/- 4.0, P = 0.06). The mean CSF/serum NSE ratio was 2.3 +/- 0.8 (men 2.2 +/- 0.8, women 2.4 +/- 0.9, P = 0.22). In both sexes, simple regression analysis showed not significantly increasing concentrations with advancing age for both CSF and serum NSE. Serum and CSF concentrations did not correlate in both sexes. In our study, CSF-NSE was twice the serum concentration; both were not influenced by sex or age. Serum and CSF-NSE values vary widely among different studies on normal populations because of different determination methods; therefore, each laboratory should obtain its own reference values. Finally, serum NSE should be used with caution as an indicator of CSF concentration as no correlation could be demonstrated between them in our study.

Teleportation on a quantum dot array.

We present a model of quantum teleportation protocol based on a double quantum dot array. The unknown qubit is encoded using a pair of quantum dots, with one excess electron, coupled by tunneling. It is shown how to create a maximally entangled state using an adiabatically increasing Coulomb repulsion between different dot pairs. This entangled state is exploited to perform teleportation again using an adiabatic coupling between itself and the incoming unknown state. Finally, a sudden separation of Bob's qubit allows a time evolution of Alice's, which amounts to a modified version of standard Bell measurement. A transmission over a long distance could be obtained by considering the entangled state of a chain of N coupled double quantum dots. The system is shown to be increasingly robust with N against decoherence due to phonons.

Zygotic and nucellar embryo survival following dehydration and cryopreservation of citrus intact seeds.

A cryopreservation procedure by dehydration and direct immersion in liquid nitrogen was developed for seeds of four polyembryonic Citrus species, and the sexual or nucellar origin of the recovered seedlings was investigated. Seeds of three species could be desiccated in a sterile air flow to 16 percent (C. sinensis) or 10 percent (C. aurantium and C. limon) moisture content with a negligible reduction in germination levels. Differently, the germinability of C. deliciosa seeds dropped to 50 percent after drying to 15 percent moisture content. Following dehydration treatments, a reduction in the average number of seedlings per germinated seed was always observed. However, all four species benefited from desiccation in terms of protection during immersion in liquid nitrogen, with C. sinensis and C. aurantium showing the greatest survival (93 percent germination) after cryopreservation. The Inter-Simple Sequence Repeat analysis of seedlings recovered from cryopreserved seeds showed that the dehydration/cryopreservation procedure promotes the germination of zygotic embryos and reduces the number of apomictic seedlings per seed.

Dose reconstruction in irradiated Fricke-agarose gels by means of MRI and optical techniques: 2D modelling of diffusion of ferric ions.

Fricke-agarose gels have elicited much interest in the field of radiation dosimetry, as tissue-equivalent dosemeters. magnetic resonance (MR) relaxation rates are measured for dose reconstruction. A major problem of Fricke-agarose gels is the diffusion of the ferric ions formed after irradiation. Knowledge of the diffusion coefficient of ferric ions may be necessary. Xylene orange, a dye that specifically chelates ferric ions, was added to the Fricke gel system to reduce ion diffusion and, as the binding gives a coloured complex, to allow optical detection of ferric ions. Diffusion of ferric ions in two dimensions and time evolution of ion concentration were evaluated. MR images were obtained at different times after irradiation. Ferric ion distribution, the corresponding images and the doses at different times after irradiation were reconstructed taking into account the calculated diffusion coefficients. Diffusion was then estimated by means of two different optical methods. The agreement obtained supports the reliability of the MRI method and of the model.

[General anesthesia and cervical anesthesia. What changes in carotid surgery]. / Anestesia generale ed anestesia plessica. Cosa cambia in chirurgia carotidea.

Carotid surgery must be preventive; therefore cerebral protection procedures have been the centre of interest for a decade. Nowadays local cervical block anaesthesia seems to have changed the terms of the problem allowing achieve the aim of "no risk surgery". Therefore we considered our 16 year experience (352 carotids operated on 290 patients). Since 1990 we employed cervical block anaesthesia. In order to ratify as much as possible the two groups of comparison, considering that we adopted some exclusion criteria, we compared the results of the first hundred carotids that underwent surgery with general anaesthesia and the first hundred operated using cervical block anaesthesia. Since we adopted cervical block anaesthesia there was no need of intra-operative monitoring systems because we considered exclusively the patients' clinical answer to preclamping. The use of shunt decreased from 9% to 3%. Surgery performed in cervical block anaesthesia gives a positive impression. This is due to the fact that there is not only a significant reduction of the morbidity rate, especially from a neurologic point of view, but also a reduction of the post-operation hospital stay. Furthermore there is also a better organization of the surgical phases. Direct monitoring of the cerebral function allows a precise analysis of the peri-operatory neurological events. In conclusion our study suggests that cervical block anaesthesia allows clinical benefits for the patient as far as safety is concerned being also more convenient under the economic point of view.

Bayesian estimation of relaxation times T(1) in MR images of irradiated Fricke-agarose gels.

The authors present a novel method for processing T(1)-weighted images acquired with Inversion-Recovery (IR) sequence. The method, developed within the Bayesian framework, takes into account a priori knowledge about the spatial regularity of the parameters to be estimated. Inference is drawn by means of Markov Chains Monte Carlo algorithms. The method has been applied to the processing of IR images from irradiated Fricke-agarose gels, proposed in the past as relative dosimeter to verify radiotherapeutic treatment planning systems. Comparison with results obtained from a standard approach shows that signal-to noise ratio (SNR) is strongly enhanced when the estimation of the longitudinal relaxation rate (R1) is performed with the newly proposed statistical approach. Furthermore, the method allows the use of more complex models of the signal. Finally, an appreciable reduction of total acquisition time can be obtained due to the possibility of using a reduced number of images. The method can also be applied to T(1) mapping of other systems.

[Cardiovascular neuroregulation and rhythms of the autonomic nervous system: frequency domain analysis]. / La neuroregolazione cardiovascolare ed i ritmi del sistema nervoso autonomo: analisi nel dominio della frequenza.

Studies using spectral analysis of cardiovascular variability series, as a non invasive tool for assessing the autonomic nervous system activity, have attracted growing interest in the last 20 years. Short-term recordings of heart rate variability distinguish two main spectral components: a high-frequency (HF) component (ranging between 0.15-0.40 Hz), and a low-frequency (LF) component (ranging between 0.04-0.15 Hz), respectively considered markers of parasympathetic and sympathetic control. Spectral analysis of microcirculatory blood flow, by using laser Doppler flowmetry, recently disclosed the presence of similar rhythms. Although a general agreement about the amplitude and frequency of these spectral components has not been gained yet, evidences of an autonomic nervous system role have been collected. Also the pupil diameter spontaneously fluctuates in the HF range. The aim of this study was to design an experimental set up for the simultaneous and continuous recording of heart rate, blood pressure, respiratory activity, peripheral blood flow, and pupil diameter fluctuations in order to investigate whether common spontaneous rhythms could be detected into the variability series. We enrolled 10 normal volunteers (range 24-28 years). The variability series of heart rate, blood pressure, respiratory activity, peripheral blood flow and pupil diameter were obtained at rest and during sympathetic activation by head-up tilt test 70 degrees. Subjects were instructed to breath at 15 breath/min following an audio signal and adjusting their tidal volume to a comfortable level. Peripheral blood flow was non invasively monitored with laser Doppler technique, with the two probes located in the palmar site of the hand and in the sternum. We continuously assess the pupil diameter fluctuations by a custom, portable, infrared TV pupillometer. Spectral density was estimated by autoregressive modeling on 250-point segments. The respiratory rhythm was clearly detected in all the variability series. Oscillations in the LF band were detected in heart rate, blood pressure and in the laser Doppler signals of the hand, as well as in the pupil diameter, but not always in the laser Doppler flow of the sternum. In this last signal an harmonic component at 0.16-0.17 Hz was detected. A reduction in the total variability, with a relative increase in the LF component was observed during head-up tilt test in the heart rate, blood pressure, peripheral blood flow and pupil diameter signals. These findings are consistent with the increased sympathetic modulation induced by the head-up tilt test. These data confirm previous findings and observations, collected with different techniques and for different purposes. Whether these rhythms can be expression of central common oscillators or reflex mechanical factors is of primary importance for possible clinical applications of this approach.