313 research outputs found
I diari della quarantena. Il lockdown negli appunti visivi degli studenti dell’Università di Pavia
No full textCharacterizing limits and opportunities in speeding up Markov chain mixing
No full textA variety of paradigms have been proposed to speed up Markov chain mixing, ranging from non-backtracking random walks to simulated annealing and lifted Metropolis–Hastings. We provide a general characterization of the limits and opportunities of different approaches for designing fast mixing dynamics on graphs using the framework of “lifted Markov chains”. This common framework allows to prove lower and upper bounds on the mixing behavior of these approaches, depending on a limited set of assumptions on the dynamics. We find that some approaches can speed up the mixing time to diameter time, or a time inversely proportional to the graph conductance, while others allow for no speedup at all
Fattori di patogenicità in ceppi di Escherichia coli isolati da processi infettivi in sedi diverse
No full textEscherichia coli, il batterio commensale più rappresentativo della flora aerobia facoltativa intestinale dell’uomo è anche, paradossalmente, l’organismo isolato più frequentemente come causa di infezioni intestinali e di infezioni extraintestinali da gram-negativi.
Esistono elementi distintivi tra ceppi commensali e ceppi patogeni sia per l’aspetto filogenetico sia per la presenza di specifici fattori di patogenicità (FP).
I geni codificanti molti dei FP noti sono di provenienza esogena, acquisiti, nel corso dell’evoluzione, dal genoma di altre specie. Talvolta sono veicolati da plasmidi e fagi, spesso sono integrati nel cromosoma batterico in associazioni definite isole di patogenicità. La loro presenza è predominante nei ceppi ascrivibili ai due gruppi filogenetici B2 e D.
Nei ceppi di E. coli responsabili di infezioni extraintestinali, diversamente dai ceppi patogeni intestinali, è poco noto il rapporto tra specifici fattori di patogenicità e sindrome.
Per studiare l’influenza di specifici FP nell’insorgere di processi infettivi in determinate sedi extraintestinali, abbiamo esaminato la distribuzione di ventinove FP in 94 isolati clinici di E. coli, 25 provenienti da emocolture, 32 da UTI, 25 da feci e 12 da campioni respiratori (BAL o aspirato endotracheale).
I FP esaminati comprendevano determinanti di adesività, tossine, tipi capsulari, siderofori, fattori di invasività, di resistenza serica ecc. e la loro presenza è stata evidenza mediante amplificazione di specifici marcatori genici.
La distribuzione media dei FP per ceppo è risultata pari a 8 nei gruppi filogenetici B2 e D, e 3 nei gruppi filogenetici B1 ed A.
I filogruppi B2 e D risultano presenti con uguale frequenza nei ceppi di isolamento ematico ma forse con diversa derivazione, se si considera che il gruppo B2 è particolarmente frequente nei ceppi di origine urinaria mentre il D in quelli di isolamento fecale.
Alcuni FP come le fimbrie di tipo S e F1C, il fattore necrotizzante di tipo1 e l’-emolisina sono stati rilevati esclusivamente in ceppi del gruppo B2, mentre le fimbrie di tipo P, alcuni fattori capsulari ed il fattore d’invasione dell’endotelio cerebrale sono presenti anche in ceppi di filotipo D. Altri FP come l’aerobactina ed il fattore di sieroresistenza risultano ugualmente diffusi in tutti i gruppi filogenetici o addirittura ( l’adesina non fimbriale tipo M e la colicina C) prevalenti tra i filotipi commensali B1 ed A
The ESI macroseismic field for the 1624 AD Argenta earthquake (Po Plain – N Italy): an integrated macroseismic approach to overcome MCS misfittings
No full textThe 2012 Emilia seismic sequence (two mainshocks, Mw = 5.86 and Mw = 5.66 on the 20th and 29th of May,
respectively) overclouded the reliability of earthquake parameters derived from MCS Intensity data in the Po Plain. As
highlighted for instance by Galli et al. (2012), Intensity-derived Magnitude, calculated through the BOXER 4 algorithm,
pointed to a Me = 5.23, clearly underestimating the actual energy of the earthquake. Moreover the epicentral Intensity
values (Io VII – VIII MCS) are not fitting well with the peak ground acceleration recorded during the sequence (ca.
0.23 – 0.28 g), consistent with a IX MCS instead.
Livio et al. (2012) applied the same calculations on the ESI Intensity data for the 2012 Emilia seismic sequence
(e.g., Di Manna et al., 2012), obtaining a better fitting between calculated and recorded Magnitude (Me = 5.86 ± 0.38)
and concluding that best results could be obtained integrating both MCS and ESI databases.
In this work we apply BOXER4 to a new dataset coming from an historical earthquake that hit the eastern Po Plain:
the March 19th, 1624 Argenta earthquake. Earthquake parameters, recorded in the CPTI11, report for this earthquake a
MCS Io = VII – VIII and a derived Magnitude Me = 5.47 ± 0.49 (recently revised by Caracciolo et al. 2012).
The epicentral area of this earthquake is characterized by a geological and geomorphological framework similar to
the one of the 2012 sequence, and by many environmental effects including liquefactions, collapse of terrains,
hydrogeological anomalies and seiches. The ESI Intensity near field is characterized by a wider area occupied by high
degrees (in particular by ESI VIII) but is similar to the MCS field in the far field.
For our analysis we used 11 environmental effects, spread over an area of ca. 600 kmq. We integrated them with
17 MCS data points (DMBI catalogue). The calculated derived Magnitude Me = 5.86, obtained from the whole dataset,
is in line with available empirical relations between epicentral intensity and magnitude in Italy (e.g. CPTI11). This
would suggest that, in order to allow comparison between historical and modern strong earthquakes, coseismic
environmental effects should be included in the intensity assessment, both in the Po Plain and in other similar areas of
the Mediterranean region
Epileptic Capgras-Like Delusions in a Patient with Right Frontal Meningioma: Case Report
No full textCapgras syndrome is a condition characterized by the belief that a relative has been replaced by an almost identical imposter. The disorder has been reported in several neurological diseases. We describe the uncommon case of a transient Capgras syndrome manifesting as focal temporal seizures in a woman with a right frontal meningioma. Our patient represents an exceptional case of Capgras syndrome for several reasons, namely, the association with meningioma, very rarely reported before, the transient manifestation of symptoms, and, most importantly, the epileptic etiology of reduplicative paramnesias. Lastly, our report also confirms the importance of frontal and right hemisphere dysfunction in generating Capgras syndrome-like delusions
Testing olfactory dysfunction in acute and recovered COVID-19 patients: a single center study in Italy
No full textBackground: Olfactory dysfunction in coronavirus disease 2019 (COVID-19) is common during acute illness and appears to last longer than other symptoms. The aim of this study was to objectively investigate olfactory dysfunction in two cohorts of patients at two different stages: during acute illness and after a median recovery of 4 months. Methods: Twenty-five acutely ill patients and 26 recovered subjects were investigated. Acute patients had a molecular diagnosis of COVID-19; recovered subjects had a positive antibody assay and a negative molecular test. A 33-item psychophysical olfactory identification test tailored for the Italian population was performed. Results: Median time from symptoms onset to olfactory test was 33 days in acute patients and 122 days in recovered subjects. The former scored a significantly higher number of errors at psychophysical testing (median [IQR]: 8 [13] vs 3 [2], p < 0.001) and were more frequently hyposmic (64% vs 19%, p = 0.002). Recovered subjects reported a variable time to subjective olfactory recovery, from days up to 4 months. Participants included in the study reported no significant nasal symptoms at olfactory testing. Among recovered subject who reported olfactory loss during acute COVID-19, four (27%) were still hyposmic. Demographic and clinical characteristics did not show significant associations with olfactory dysfunction. Conclusion: Moderate-to-severe hospitalized patients showed a high level and frequency of olfactory dysfunction compared to recovered subjects. In the latter group, subjects who reported persisting olfactory dysfunction showed abnormal scores on psychophysical testing, indicating that, at least in some subjects, persistent hyposmia may represent a long-term sequela of COVID-19
Exact and approximate solutions for the quantum minimum-Kullback-entropy estimation problem
No full textThe minimum-Kullback-entropy principle (mKE) is a useful tool to estimate quantum states and operations from incomplete data and prior information. In general, the solution of an mKE problem is analytically challenging and an approximate solution has been proposed and employed in different contexts. Recently, the form and a way to compute the exact solution for finite dimensional systems has been found, and a question naturally arises on whether the approximate solution could be an effective substitute for the exact solution, and in which regimes this substitution can be performed. Here, we provide a systematic comparison between the exact and the approximate mKE solutions for a qubit system when average data from a single observable are available. We address both mKE estimation of states and weak Hamiltonians, and compare the two solutions in terms of state fidelity and operator distance. We find that the approximate solution is generally close to the exact one unless the initial state is near an eigenstate of the measured observable. Our results provide a rigorous justification for the use of the approximate solution whenever the above condition does not occur, and extend its range of application beyond those situations satisfying the assumptions used for its derivation
Spectral Conditions for Stability and Stabilization of Positive Equilibria for a Class of Nonlinear Cooperative Systems
No full textNonlinear cooperative systems associated to vector fields that are concave or subhomogeneous describe well interconnected dynamics that are of key interest for communication, biological, economical, and neural network applications. For this class of positive systems, we provide conditions that guarantee existence, uniqueness and stability of strictly positive equilibria. These conditions can be formulated directly in terms of the spectral radius of the Jacobian of the system. If control inputs are available, then it is shown how to use state feedback to stabilize an equilibrium point in the interior of the positive orthant.Funding Agencies|Swedish Research Council [2015-04390]</p
Detection of Human Polyomavirus 6 DNA in the Cerebrospinal Fluid of HIV negative Patients with Neurological Diseases
No full textIntroduction: The family Polyomaviridae comprises thirteen human viruses that have been detected in various specimen types, mainly urine, skin and blood. Among all of them, only JC Polyomavirus (JCPyV) genome has been detected in Cerebrospinal Fluid (CSF). Recently, the unexpected finding of Human Polyomavirus 6 (HPyV6) DNA in the CSF from an HIV positive patient with leukoencephalopathy was reported. JCPyV being a recognized cause of Progressive Multifocal Leukoencephalopathy (PML) in immunodeficient subjects provides a precedent for polyomavirus causing neurological symptoms, but alternative explanations should be considered. The aims of the study was to explore the prevalence of the newly discovered HPyV6, Human Polyomavirus 7 (HPyV7) and Human Polyomavirus 9 (HPyV9), Merkel Cell Polyomavirus (MCPyV) in neurological diseases, in comparison with those of JCPyV.
Material and methods:CSF have been collected from 51 HIV-positive patients affected with HIV-related leukoencephalopathies and 191 HIV-negative patients affected with other neurological diseases (OND), such as meningitis, encephalitis, and en-cephalomyelitis. DNA was isolated and real-time PCR assays for JCPyV, HPyV6, HPyV7, HPyV9 and MCPyV were conducted.
RESULTS:JCPyV genome was detected in the CSF of 16/51 (31.4%) HIV-related leukoencephalopathies patients, HPyV6 genome in the CSF of 2/51 (3.9%) HIV-related leukoencephalopathies patients and in 37/191 (19.4%) HIV-negative patients with OND. MCPyV DNA was present in 9/191 (4.71%) CSF from HIV-negative OND patients, while HPyV7 and HPyV9 genomes were not amplified in any clinical specimens.
Discussion and Conclusions: HPyV6 genome was found in a high percentage of the CSF of the OND patients, followed by MCPyV, whereas HPyV7 and HPyV9 genomes were not detected. HPyV6 has not been previously associated with any disease, and it is nonetheless possible that the HPyV6 sequences originated from the skin during CSF collection. Whether HPyV6 detection in CSF is associated with patients’s neurological disease, is indicative of contamination with skin microbiota, or reflects increased blood-brain permeability is unknown. Demonstrating a causative role will require further studies
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