217 research outputs found
Mathematical modelling and numerical bifurcation analysis of inbreeding and interdisciplinarity dynamics in academia
We address a mathematical model to approximate in a coarse qualitative the interaction between inbreeding-lobbying and interdisciplinarity in academia and perform a one and two-parameter numerical bifurcation analysis to analyse its dynamics. Disciplinary diversity is a necessary condition for the development of interdisciplinarity, which is being recognized today as the key to establish a vibrant academic environment with bigger potential for breakthroughs/innovation in research and technology. However, the interaction of several factors including institutional policies, and behavioural attitudes put significant barriers on advancing interdisciplinarity. A âcognitive rigidityâ may rise due to reactive academic lobby behaviours favouring inbreeding. The proposed model consists of four coupled non-linear Ordinary Differential Equations simulating the interaction between certain types of academic behaviour and the rate of knowledge advancement which is related to the level of disciplinary diversity. The effect of a control policy that inhibits inbreeding-lobbying is also investigated. The numerical bifurcation analysis reveals a rich nonlinear behaviour including multistability, sustained oscillations, limit points of limit cycles, homoclinic bifurcations as well as codimension-two bifurcations and in particular BogdanovâTakens and Bautin bifurcations
Tracing day-zero and forecasting the COVID-19 outbreak in Lombardy, Italy: A compartmental modelling and numerical optimization approach
Introduction Italy became the second epicenter of the novel coronavirus disease 2019 (COVID-19) pandemic after China, surpassing by far Chinaâs death toll. The disease swept through Lombardy, which remained in lockdown for about two months, starting from the 8th of March. As of that day, the isolation measures taken in Lombardy were extended to the entire country. Here, assuming that effectively there was one case âzeroâ that introduced the virus to the region, we provide estimates for: (a) the day-zero of the outbreak in Lombardy, Italy; (b) the actual number of asymptomatic infected cases in the total population until March 8; (c) the basic (R0)and the effective reproduction number (Re) based on the estimation of the actual number of infected cases. To demonstrate the efficiency of the model and approach, we also provide a tentative forecast two months ahead of time, i.e. until May 4, the date on which relaxation of the measures commenced, on the basis of the COVID-19 Community Mobility Reports released by Google on March 29. Methods To deal with the uncertainty in the number of the actual asymptomatic infected cases in the total population Volpert et al. (2020), we address a modified compartmental Susceptible/ Exposed/ Infectious Asymptomatic/ Infected Symptomatic/ Recovered/ Dead (SEIIRD) model with two compartments of infectious persons: one modelling the cases in the population that are asymptomatic or experience very mild symptoms and another modelling the infected cases with mild to severe symptoms. The parameters of the model corresponding to the recovery period, the time from the onset of symptoms to death and the time from exposure to the time that an individual starts to be infectious, have been set as reported from clinical studies on COVID-19. For the estimation of the day-zero of the outbreak in Lombardy, as well as of the âeffectiveâ per-day transmission rate for which no clinical data are available, we have used the proposed SEIIRD simulator to fit the numbers of new daily cases from February 21 to the 8th of March. This was accomplished by solving a mixed-integer optimization problem. Based on the computed parameters, we also provide an estimation of the basic reproduction number R0 and the evolution of the effective reproduction number Re. To examine the efficiency of the model and approach, we ran the simulator to âforecastâ the epidemic two months ahead of time, i.e. from March 8 to May 4. For this purpose, we considered the reduction in mobility in Lombardy as released on March 29 by Google COVID-19 Community Mobility Reports, and the effects of social distancing and of the very strict measures taken by the government on March 20 and March 21, 2020. Results Based on the proposed methodological procedure, we estimated that the expected day-zero was January 14 (min-max rage: January 5 to January 23, interquartile range: January 11 to January 18). The actual cumulative number of asymptomatic infected cases in the total population in Lombardy on March 8 was of the order of 15 times the confirmed cumulative number of infected cases, while the expected value of the basic reproduction number R0 was found to be 4.53 (min-max range: 4.40- 4.65). On May 4, the date on which relaxation of the measures commenced the effective reproduction number was found to be 0.987 (interquartiles: 0.857, 1.133). The model approximated adequately two months ahead of time the evolution of reported cases of infected until May 4, the day on which the phase I of the relaxation of measures was implemented over all of Italy. Furthermore the model predicted that until May 4, around 20% of the population in Lombardy has recovered (interquartile range: *10% to *30%)
Exotic radiation from a photonic crystal excited by an ultra-relativistic electron beam
We report the observation of an exotic radiation (unconventional
Smith-Purcell radiation) from a one-dimensional photonic crystal. The physical
origin of the exotic radiation is direct excitation of the photonic bands by an
ultra-relativistic electron beam. The spectrum of the exotic radiation follows
photonic bands of a certain parity, in striking contrast to the conventional
Smith-Purcell radiation, which shows solely a linear dispersion. Key
ingredients for the observation are the facts that the electron beam is in an
ultra-relativistic region and that the photonic crystal is finite. The origin
of the radiation was identified by comparison of experimental and theoretical
results.Comment: 4 pages, 5 figure
Obstructive sleep apnea syndrome in the pediatric age: the role of the otorhinolaryngologist
OBJECTIVE: Obstructive sleep apnea (OSA) is the primary indication for tonsillectomy, one of the most common pediatric surgical procedures, commonly performed in association with adenoidectomy. The objective of this review article is to evaluate the role of the otorhinolaryngologist in pediatric OSA. MATERIALS AND METHODS: A literature review has been performed on the following topics: peculiarities of sleep-disordered breathing in pediatric age; discrimination of sleep disorders; adenotonsillar hypertrophy; surgical techniques; adjuvant surgical procedures. RESULTS: The role of the otorhinolaryngologist in pediatric OSA is important for the evaluation of the upper airways and of essential biometric and polysomnographic data and for indication and execution of appropriate surgical treatment. In the majority of healthy children, adenotonsillectomy for OSA results in a dramatic improvement in respiratory parameters as measured by polysomnography. When post-surgical residual OSA occurs, it is essential to monitor patients by means of drug-induced sleep endoscopy (DISE). CONCLUSIONS: Otolaryngologic assessment is of paramount importance to correctly classify a child with OSA. Correct inspection of the upper airway and quantification of the quality of sleep through polysomnography lead to the right therapeutic choice. Knowledge of different surgical techniques helps to deal with residual OSA after studying the obstruction sites by drug-induced sedation endoscopy
Cost-effectiveness strategies in OSAS management: a short review
Lapnea ostruttiva del sonno (OSAS) Ăš una malattia cronica eccessivamente sotto-diagnosticata con unalta prevalenza negli adulti. LOSAS sta diventando un problema sociale significativo perchĂ© associata ad un peggioramento della qualitĂ della vita ed un aumento della mortalitĂ . Il rapporto costo-efficacia nella gestione diagnostica e terapeutica dellOSAS Ăš un problema strategico per contrastare la crescente domanda di test oggettivi. I pazienti OSAS che non presentano comorbilitĂ clinicamente evidenti devono essere studiati utilizzando un sistema semplificato e poco costoso, come lHome Sleep Testing (HST). Al contrario, la Sleep Laboratory Polisomnography (PSG) rimane il gold standard per la gestione dei pazienti con OSAS in presenza di comorbiditĂ . Occorre sottolineare che luso di HST potrebbe portare ad una diagnosi errata in soggetti OSAS non ben selezionati. Questa breve rassegna si propone di offrire argomenti di riflessione sulla corretta diagnosi e trattamento dellOSAS, in rapporto ai dati di prevalenza e alle ricadute sui costi/benefici sociali della malattia. Attualmente non puĂČ essere solo il rapporto costo/efficacia a definire il modello organizzativo adottato per la gestione dellOSAS, in quanto si rendono necessari ulteriori studi prospettici a lungo termine, volti a validare in maniera definitiva tale rapporto nonchĂ© il confronto tra il trattamento con modelli di gestione ospedaliera versus lassistenza domiciliare
Temporary Acceleration of Electrons While Inside an Intense Electromagnetic Pulse
A free electron can temporarily gain a very significant amount of energy if
it is overrun by an intense electromagnetic wave. In principle, this process
would permit large enhancements in the center-of-mass energy of
electron-electron, electron-positron and electron-photon interactions if these
take place in the presence of an intense laser beam. Practical considerations
severely limit the utility of this concept for contemporary lasers incident on
relativistic electrons. A more accessible laboratory phenomenon is
electron-positron production via an intense laser beam incident on a gas.
Intense electromagnetic pulses of astrophysical origin can lead to very
energetic photons via bremsstrahlung of temporarily accelerated electrons
Is complement alternative pathway disregulation involved in veno-occlusive disease of the liver?
From continuum analytical description to discrete numerical modelling of localized fluidization in granular media
Bone invading NSCLC cells produce IL-7: mice model and human histologic data
<p>Abstract</p> <p>Background</p> <p>Bone metastases are a common and dismal consequence of lung cancer that is a leading cause of death. The role of IL-7 in promoting bone metastases has been previously investigated in NSCLC, but many aspects remain to be disclosed. To further study IL-7 function in bone metastasis, we developed a human-in-mice model of bone aggression by NSCLC and analyzed human bone metastasis biopsies.</p> <p>Methods</p> <p>We used NOD/SCID mice implanted with human bone. After bone engraftment, two groups of mice were injected subcutaneously with A549, a human NSCLC cell line, either close or at the contralateral flank to the human bone implant, while a third control group did not receive cancer cells. Tumor and bone vitality and IL-7 expression were assessed in implanted bone, affected or not by A549. Serum IL-7 levels were evaluated by ELISA. IL-7 immunohistochemistry was performed on 10 human bone NSCLC metastasis biopsies for comparison.</p> <p>Results</p> <p>At 12 weeks after bone implant, we observed osteogenic activity and neovascularization, confirming bone vitality. Tumor aggressive cells implanted close to human bone invaded the bone tissue. The bone-aggressive cancer cells were positive for IL-7 staining both in the mice model and in human biopsies. Higher IL-7 serum levels were found in mice injected with A549 cells close to the bone implant compared to mice injected with A549 cells in the flank opposite to the bone implant.</p> <p>Conclusions</p> <p>We demonstrated that bone-invading cells express and produce IL-7, which is known to promote osteoclast activation and osteolytic lesions. Tumor-bone interaction increases IL-7 production, with an increase in IL-7 serum levels. The presented mice model of bone invasion by contiguous tumor is suitable to study bone-tumor cell interaction. IL-7 plays a role in the first steps of metastatic process.</p
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