Moving from the most recent results on Foxg1 biology,we first summarize the available information on some special pleiotropic effectors of neurodevelopmental interest,involved in controlling both transcription and pos...Moving from the most recent results on Foxg1 biology,we first summarize the available information on some special pleiotropic effectors of neurodevelopmental interest,involved in controlling both transcription and post-transcriptional steps of gene expression.Then,after further analysis of the literature,we report evidence that,not strictly limited to neurodevelopmental effectors,such pleiotropy also applies to other transcription factors,involved in physiology and homeostasis.Furthermore,through the systematic analysis of a major public protein-protein interaction database,we gather strong evidence that the involvement of“canonical”transcription factors in post-transcriptional control of gene expression could be a pervasive phenomenon,characterizing hundreds of effectors.Finally,we discuss the biological significance of these findings and propose three evolutionary mechanisms that may have contributed to such an unexpected scenario.展开更多
Nosocomial infections are also known as hospital-acquired/associated infections. National Healthcare Safety Network along with Centers for Disease Control for surveillance has classified nosocomial infection sites int...Nosocomial infections are also known as hospital-acquired/associated infections. National Healthcare Safety Network along with Centers for Disease Control for surveillance has classified nosocomial infection sites into 13 types with 50 infection sites, which are specific on the basis of biological and clinical criteria. The agents that are usually involved in hospitalacquired infections include Streptococcus spp., Acinetobacter spp., enterococci, Pseudomonas aeruginosa, coagulase-negative staphylococci, Staphylococcus aureus, Bacillus cereus, Legionella and Enterobacteriaceae family members, namely, Proteus mirablis, Klebsiella pneumonia, Escherichia coli, Serratia marcescens. Nosocomial pathogens can be transmitted through person to person, environment or contaminated water and food, infected individuals, contaminated healthcare personnel's skin or contact via shared items and surfaces. Mainly, multi-drug-resistant nosocomial organisms include methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, Pseudomonas aeruginosa and Klebsiella pneumonia, whereas Clostridium difficile shows natural resistance. Excessive and improper use of broadspectrum antibiotics, especially in healthcare settings, is elevating nosocomial infections, which not only becomes a big health care problem but also causes great economic and production loss in the community. Nosocomial infections can be controlled by measuring and comparing the infection rates within healthcare settings and sticking to the best healthcare practices. Centers for Disease Control and Prevention provides the methodology for surveillance of nosocomial infections along with investigation of major outbreaks. By means of this surveillance, hospitals can devise a strategy comprising of infection control practices.展开更多
One of the major problems of modern neurobiology is how to replace dead or damaged neurons in the human brain or spinal cord after injury or as a consequence of neurodegenerative dis- eases. In fact, because adult mam...One of the major problems of modern neurobiology is how to replace dead or damaged neurons in the human brain or spinal cord after injury or as a consequence of neurodegenerative dis- eases. In fact, because adult mammalian neurons are post-mi- totic cells that cannot divide to replace dead cells, loss due to lesion or disease is permanent. Furthermore, surviving neurons have modest capacity to regenerate their damaged axons and re-establish functional connections. Thus, a gradual neurode- generative scenario with certain similarities in stroke, brain or spinal cord injuries and neurological diseases like Alzheimer＇s disease is produced. These conditions represent the major disease burden of the modern world in terms of mortality, dis- ability, productivity loss and health-care costs （World Health Organization, 2008）. While much effort has been directed to understand the molecular and cellular mechanisms involved in the pathology of these diseases to set new effective treatments, many neuroprotective and regenerative approaches, although showing positive results in preclinical studies, have so far failed to provide strong benefit to patients.展开更多
The problem of the presence of Cantor part in the derivative of a solution to a hyperbolic system of conservation laws is considered. An overview of the techniques involved in the proof is given, and a collection of r...The problem of the presence of Cantor part in the derivative of a solution to a hyperbolic system of conservation laws is considered. An overview of the techniques involved in the proof is given, and a collection of related problems concludes the paper.展开更多
Under the Flaschka-Newell Lax pair,the Darboux transformation for the Painlevé-Ⅱequation is constructed by the limiting technique.With the aid of the Darboux transformation,the rational solutions are represented...Under the Flaschka-Newell Lax pair,the Darboux transformation for the Painlevé-Ⅱequation is constructed by the limiting technique.With the aid of the Darboux transformation,the rational solutions are represented by the Gram determinant,and then we give the large y asymptotics of the determinant and the rational solutions.Finally,the solution of the corresponding Riemann-Hilbert problem is obtained from the Darboux matrices.展开更多
Generation of astrocytes within the murine developing cerebral cortex mainly takes place during the first postnatal week, after neuronogenesis and prior to the bulk of oligogenesis. This process involves a great varie...Generation of astrocytes within the murine developing cerebral cortex mainly takes place during the first postnatal week, after neuronogenesis and prior to the bulk of oligogenesis. This process involves a great variety of highly complex regulatory mechanisms. Astrocytic outputs depend on two primary factors： progressive commitment of multipotent precursors to astroglial fates and proper tuning of proliferation of astrocyte-committed progenitors. To date, several regulatory mechanisms have been identified for the former process, while very little is known about modulation of astroblast proliferation （reviewed in Mallamaci,展开更多
The deferred correction(DeC)is an iterative procedure,characterized by increasing the accuracy at each iteration,which can be used to design numerical methods for systems of ODEs.The main advantage of such framework i...The deferred correction(DeC)is an iterative procedure,characterized by increasing the accuracy at each iteration,which can be used to design numerical methods for systems of ODEs.The main advantage of such framework is the automatic way of getting arbitrarily high order methods,which can be put in the Runge-Kutta(RK)form.The drawback is the larger computational cost with respect to the most used RK methods.To reduce such cost,in an explicit setting,we propose an efcient modifcation:we introduce interpolation processes between the DeC iterations,decreasing the computational cost associated to the low order ones.We provide the Butcher tableaux of the new modifed methods and we study their stability,showing that in some cases the computational advantage does not afect the stability.The fexibility of the novel modifcation allows nontrivial applications to PDEs and construction of adaptive methods.The good performances of the introduced methods are broadly tested on several benchmarks both in ODE and PDE contexts.展开更多
Utilizing a BzK-selecfion technique, we obtain 14 550 star-forming galaxies （sBzKs） and 1763 passive galaxies （pBzKs） at z - 2 from the K-selected （KAB 〈 22.5） catalog in the COSMOS/UltraVISTA field. The differ...Utilizing a BzK-selecfion technique, we obtain 14 550 star-forming galaxies （sBzKs） and 1763 passive galaxies （pBzKs） at z - 2 from the K-selected （KAB 〈 22.5） catalog in the COSMOS/UltraVISTA field. The differential number counts of sBzKs and pBzKs are consistent with the results from the literature. Compared to the observed results, semi-analytic models of galaxy formation and evolution provide too few （many） galaxies at the high （low） mass end. Moreover, we find that the star formation rate and stellar mass of sBzKs follow the relation of the main sequence. Based on HST/Wide Field Camera 3 F160W imaging, we find a wide range of morphological diversities for sBzKs, from diffuse to early-type spiral structures, with relatively high M20, large size and low G, while pBzKs have elliptical-like compact morphologies with lower M20, smaller size and higher G, indicating a more concentrated and symmetric spatial extent of stellar population distribution in pBzKs than sBzKs. Furthermore, the sizes of pBzKs （sBzKs） at z - 2 are on average two to three （one to two） times smaller than those of local early-type （late-type） galaxies with similar stellar mass. Our findings imply that the two classes have different evolution models and mass assembly histories.展开更多
Reduced order modeling(ROM)techniques are numerical methods that approximate the solution of parametric partial differential equation(PED)by properly combining the high-fidelity solutions of the problem obtained for s...Reduced order modeling(ROM)techniques are numerical methods that approximate the solution of parametric partial differential equation(PED)by properly combining the high-fidelity solutions of the problem obtained for several configurations,i.e.for several properly chosen values of the physical/geometrical parameters characterizing the problem.By starting from a database of high-fidelity solutions related to a certain values of the parameters,we apply the proper orthogonal decomposition with interpolation(PODI)and then reconstruct the variables of interest for new values of the parameters,i.e.different values from the ones included in the database.Furthermore,we present a preliminary web application through which one can run the ROM with a very user-friendly approach,without the need of having expertise in the numerical analysis and scientific computing field.The case study we have chosen to test the efficiency of our algorithm is represented by the aortic blood flow pattern in presence of a left ventricular(LVAD)assist device when varying the pump flow rate.展开更多
Using high-resolution HST/Wide Field Camera 3 F125W imaging from the CANDELS-COSMOS field, we report the structural and morphological properties of extremely red objects （EROs） at -z 1. Based on the UVJ color crite...Using high-resolution HST/Wide Field Camera 3 F125W imaging from the CANDELS-COSMOS field, we report the structural and morphological properties of extremely red objects （EROs） at -z 1. Based on the UVJ color criteria, we sepa- rate EROs into two types： old passive galaxies （OGs） and dusty star-forming galaxies （DGs）. For a given stellar mass, we find that the mean size of OGs （DGs） is smaller by a factor of - 2 （1.5） than that of present-day early-type （late-type） galaxies at a rest-frame optical wavelength. We derive the average effective radii of OGs and DGs, corresponding to 2.09 ± 1.13 kpc and 3.27± 1.14 kpc, respectively. Generally, the DGs are heterogeneous, with mixed features including bulges, disks and irregular structures, with relatively high M20, large size and low G. By contrast, OGs have elliptical-like compact morphologies with lower M20, smaller size and higher G, indicating a more concentrated and symmetric spatial extent of the stellar population distribution in OGs than DGs. These findings imply that OGs and DGs have different evolutionary processes, and that the minor merger scenario is the most likely mechanism for the structural properties of OGs. However, the size evolution of DGs is possibly due to the secular evolution of galaxies.展开更多
We build a sample of 298 spectroscopically-confirmed galaxies at redshift z - 2, selected in the z850-band from the GOODS-MUSIC catalog. By utilizing the rest frame 8 p.m luminosity as a proxy of the star formation ra...We build a sample of 298 spectroscopically-confirmed galaxies at redshift z - 2, selected in the z850-band from the GOODS-MUSIC catalog. By utilizing the rest frame 8 p.m luminosity as a proxy of the star formation rate （SFR）, we check the accuracy of the standard SED-fitting technique, finding it is not accurate enough to provide reliable estimates of the physical parameters of galaxies. We then develop a new SED-fitting method that includes the IR luminosity as a prior and a generalized Calzetti law with a variable Rv. Then we exploit the new method to re-analyze our galaxy sample, and to robustly determine SFRs, stellar masses and ages. We find that there is a general trend of increasing attenuation with the SFR. Moreover, we find that the SFRs range between a few to 103 M~ yr-1, the masses from 109 to 4 ~ 1011 Mo, and the ages from a few tens of Myr to more than 1 Gyr. We discuss how individual age measurements of highly attenuated objects indicate that dust must have formed within a few tens of Myr and already been copious at 〈 100 Myr. In addition, we find that low luminosity galaxies harbor, on average, significantly older stellar populations and are also less massive than brighter ones; we discuss how these findings and the well known ＇downsizing＇ scenario are consistent in a framework where less massive galaxies form first, but their star formation lasts longer. Finally, we find that the near-IR attenuation is not scarce for luminous objects, contrary to what is customarily assumed; we discuss how this affects the interpretation of the observed M,/L ratios.展开更多
We propose a new paradigm for designing efcient p-adaptive arbitrary high-order meth-ods.We consider arbitrary high-order iterative schemes that gain one order of accuracy at each iteration and we modify them to match...We propose a new paradigm for designing efcient p-adaptive arbitrary high-order meth-ods.We consider arbitrary high-order iterative schemes that gain one order of accuracy at each iteration and we modify them to match the accuracy achieved in a specifc iteration with the discretization accuracy of the same iteration.Apart from the computational advan-tage,the newly modifed methods allow to naturally perform the p-adaptivity,stopping the iterations when appropriate conditions are met.Moreover,the modifcation is very easy to be included in an existing implementation of an arbitrary high-order iterative scheme and it does not ruin the possibility of parallelization,if this was achievable by the original method.An application to the Arbitrary DERivative(ADER)method for hyperbolic Par-tial Diferential Equations(PDEs)is presented here.We explain how such a framework can be interpreted as an arbitrary high-order iterative scheme,by recasting it as a Deferred Correction(DeC)method,and how to easily modify it to obtain a more efcient formula-tion,in which a local a posteriori limiter can be naturally integrated leading to the p-adap-tivity and structure-preserving properties.Finally,the novel approach is extensively tested against classical benchmarks for compressible gas dynamics to show the robustness and the computational efciency.展开更多
Despite governing heat management in any realistic device,the microscopic mechanisms of heat transport in all-solid-state electrolytes are poorly known:existing calculations,all based on simplistic semi-empirical mode...Despite governing heat management in any realistic device,the microscopic mechanisms of heat transport in all-solid-state electrolytes are poorly known:existing calculations,all based on simplistic semi-empirical models,are unreliable for superionic conductors and largely overestimate their thermal conductivity.In this work,we deploy a combination of state-of-the-art methods to calculate the thermal conductivity of a prototypical Li-ion conductor,the Li_(3)ClO antiperovskite.By leveraging ab initio,machine learning,and force-field descriptions of interatomic forces,we are able to reveal the massive role of anharmonic interactions and diffusive defects on the thermal conductivity and its temperature dependence,and to eventually embed their effects into a simple rationale which is likely applicable to a wide class of ionic conductors.展开更多
In the last years much progress has been achieved in KAM theory concerning bifurcation of quasi-periodic solutions of Hamiltonian or reversible partial differential equations.We provide an overview of the state of the...In the last years much progress has been achieved in KAM theory concerning bifurcation of quasi-periodic solutions of Hamiltonian or reversible partial differential equations.We provide an overview of the state of the art in this field.展开更多
We report on an extensive study of the viscosity of liquid water at near-ambient conditions,performed within the Green-Kubo theory of linear response and equilibrium ab initio molecular dynamics(AIMD),based on density...We report on an extensive study of the viscosity of liquid water at near-ambient conditions,performed within the Green-Kubo theory of linear response and equilibrium ab initio molecular dynamics(AIMD),based on density-functional theory(DFT).In order to cope with the long simulation times necessary to achieve an acceptable statistical accuracy,our ab initio approach is enhanced with deep-neural-network potentials(NNP).This approach is first validated against AIMD results,obtained by using the Perdew–Burke–Ernzerhof(PBE)exchange-correlation functional and paying careful attention to crucial,yet often overlooked,aspects of the statistical data analysis.Then,we train a second NNP to a dataset generated from the Strongly Constrained and Appropriately Normed(SCAN)functional.Once the error resulting from the imperfect prediction of the melting line is offset by referring the simulated temperature to the theoretical melting one,our SCAN predictions of the shear viscosity of water are in very good agreement with experiments.展开更多
In this work,two approaches,based on the certified Reduced Basis method,have been developed for simulating the movement of nuclear reactor control rods,in time-dependent non-coercive settings featuring a 3D geometrica...In this work,two approaches,based on the certified Reduced Basis method,have been developed for simulating the movement of nuclear reactor control rods,in time-dependent non-coercive settings featuring a 3D geometrical framework.In particular,in a first approach,a piece-wise affine transformation based on subdomains division has been implemented for modelling the movement of one control rod.In the second approach,a“staircase”strategy has been adopted for simulating themovement of all the three rods featured by the nuclear reactor chosen as case study.The neutron kinetics has been modelled according to the so-called multi-group neutron diffusion,which,in the present case,is a set of ten coupled parametrized parabolic equations(two energy groups for the neutron flux,and eight for the precursors).Both the reduced order models,developed according to the two approaches,provided a very good accuracy comparedwith high-fidelity results,assumed as“truth”solutions.At the same time,the computational speed-up in the Online phase,with respect to the fine“truth”finite element discretization,achievable by both the proposed approaches is at least of three orders of magnitude,allowing a real-time simulation of the rod movement and control.展开更多
The Eliashberg theory of superconductivity accounts for the fundamental physics of conventional superconductors,including the retardation of the interaction and the Coulomb pseudopotential,to predict the critical temp...The Eliashberg theory of superconductivity accounts for the fundamental physics of conventional superconductors,including the retardation of the interaction and the Coulomb pseudopotential,to predict the critical temperature T_(c).McMillan,Allen,and Dynes derived approximate closed-form expressions for the critical temperature within this theory,which depends on the electron–phonon spectral functionα^(2)F(ω).Here we show that modern machine-learning techniques can substantially improve these formulae,accounting for more general shapes of theα^(2)F function.Using symbolic regression and the SISSO framework,together with a database of artificially generatedα^(2)F functions and numerical solutions of the Eliashberg equations,we derive a formula for T_(c)that performs as well as Allen–Dynes for low-T_(c)superconductors and substantially better for higher-T_(c)ones.This corrects the systematic underestimation of Tc while reproducing the physical constraints originally outlined by Allen and Dynes.This equation should replace the Allen–Dynes formula for the prediction of higher-temperature superconductors.展开更多
Background:Parkinson’s disease(PD)is a neurodegenerative disorder whose diagnosis is often challenging because symptoms may overlap with neurodegenerative parkinsonisms.PD is characterized by intraneuronal accumulati...Background:Parkinson’s disease(PD)is a neurodegenerative disorder whose diagnosis is often challenging because symptoms may overlap with neurodegenerative parkinsonisms.PD is characterized by intraneuronal accumulation of abnormalα-synuclein in brainstem while neurodegenerative parkinsonisms might be associated with accumulation of eitherα-synuclein,as in the case of Multiple System Atrophy(MSA)or tau,as in the case of Corticobasal Degeneration(CBD)and Progressive Supranuclear Palsy(PSP),in other disease-specific brain regions.Definite diagnosis of all these diseases can be formulated only neuropathologically by detection and localization ofα-synuclein or tau aggregates in the brain.Compelling evidence suggests that trace-amount of these proteins can appear in peripheral tissues,including receptor neurons of the olfactory mucosa(OM).Methods:We have set and standardized the experimental conditions to extend the ultrasensitive Real Time Quaking Induced Conversion(RT-QuIC)assay for OM analysis.In particular,by using human recombinantα-synuclein as substrate of reaction,we have assessed the ability of OM collected from patients with clinical diagnoses of PD and MSA to induceα-synuclein aggregation,and compared their seeding ability to that of OM samples collected from patients with clinical diagnoses of CBD and PSP.Results:Our results showed that a significant percentage of MSA and PD samples inducedα-synuclein aggregation with high efficiency,but also few samples of patients with the clinical diagnosis of CBD and PSP caused the same effect.Notably,the final RT-QuIC aggregates obtained from MSA and PD samples owned peculiar biochemical and morphological features potentially enabling their discrimination.Conclusions:Our study provide the proof-of-concept that olfactory mucosa samples collected from patients with PD and MSA possess important seeding activities forα-synuclein.Additional studies are required for(i)estimating sensitivity and specificity of the technique and for(ii)evaluating its application for the diagnosis of PD and neurodegenerative parkinsonisms.RT-QuIC analyses of OM and cerebrospinal fluid(CSF)can be combined with the aim of increasing the overall diagnostic accuracy of these diseases,especially in the early stages.展开更多
A parametric reduced order model based on proper orthogonal decomposition with Galerkin projection has been developed and applied for the modeling of heat transport in T-junction pipes which are widely found in nuclea...A parametric reduced order model based on proper orthogonal decomposition with Galerkin projection has been developed and applied for the modeling of heat transport in T-junction pipes which are widely found in nuclear power reactor cooling systems.Thermal mixing of different temperature coolants in T-junction pipes leads to temperature fluctuations and this could potentially cause thermal fatigue in the pipe walls.The novelty of this paper is the development of a parametric ROM consider-ing the three dimensional,incompressible,unsteady Navier-Stokes equations coupled with the heat transport equation in a finite volume regime.Two different parametric cases are presented in this paper:parametrization of the inlet temperatures and parametrization of the kinematic viscosity.Different training spaces are considered and the results are compared against the full order model.The first test case results to a computational speed-up factor of 374 while the second test case to one of 211.展开更多
基金supported by SISSA(intramural funding to AM)International FOXG1 Research Foundation(Grant to AM)+1 种基金Italian Ministery of University and Research(Grant PRIN222022M95RC7 to AM)Fondazione Telethon(Grant GMR22T2018 to AM).
文摘Moving from the most recent results on Foxg1 biology,we first summarize the available information on some special pleiotropic effectors of neurodevelopmental interest,involved in controlling both transcription and post-transcriptional steps of gene expression.Then,after further analysis of the literature,we report evidence that,not strictly limited to neurodevelopmental effectors,such pleiotropy also applies to other transcription factors,involved in physiology and homeostasis.Furthermore,through the systematic analysis of a major public protein-protein interaction database,we gather strong evidence that the involvement of“canonical”transcription factors in post-transcriptional control of gene expression could be a pervasive phenomenon,characterizing hundreds of effectors.Finally,we discuss the biological significance of these findings and propose three evolutionary mechanisms that may have contributed to such an unexpected scenario.
文摘Nosocomial infections are also known as hospital-acquired/associated infections. National Healthcare Safety Network along with Centers for Disease Control for surveillance has classified nosocomial infection sites into 13 types with 50 infection sites, which are specific on the basis of biological and clinical criteria. The agents that are usually involved in hospitalacquired infections include Streptococcus spp., Acinetobacter spp., enterococci, Pseudomonas aeruginosa, coagulase-negative staphylococci, Staphylococcus aureus, Bacillus cereus, Legionella and Enterobacteriaceae family members, namely, Proteus mirablis, Klebsiella pneumonia, Escherichia coli, Serratia marcescens. Nosocomial pathogens can be transmitted through person to person, environment or contaminated water and food, infected individuals, contaminated healthcare personnel's skin or contact via shared items and surfaces. Mainly, multi-drug-resistant nosocomial organisms include methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, Pseudomonas aeruginosa and Klebsiella pneumonia, whereas Clostridium difficile shows natural resistance. Excessive and improper use of broadspectrum antibiotics, especially in healthcare settings, is elevating nosocomial infections, which not only becomes a big health care problem but also causes great economic and production loss in the community. Nosocomial infections can be controlled by measuring and comparing the infection rates within healthcare settings and sticking to the best healthcare practices. Centers for Disease Control and Prevention provides the methodology for surveillance of nosocomial infections along with investigation of major outbreaks. By means of this surveillance, hospitals can devise a strategy comprising of infection control practices.
文摘One of the major problems of modern neurobiology is how to replace dead or damaged neurons in the human brain or spinal cord after injury or as a consequence of neurodegenerative dis- eases. In fact, because adult mammalian neurons are post-mi- totic cells that cannot divide to replace dead cells, loss due to lesion or disease is permanent. Furthermore, surviving neurons have modest capacity to regenerate their damaged axons and re-establish functional connections. Thus, a gradual neurode- generative scenario with certain similarities in stroke, brain or spinal cord injuries and neurological diseases like Alzheimer＇s disease is produced. These conditions represent the major disease burden of the modern world in terms of mortality, dis- ability, productivity loss and health-care costs （World Health Organization, 2008）. While much effort has been directed to understand the molecular and cellular mechanisms involved in the pathology of these diseases to set new effective treatments, many neuroprotective and regenerative approaches, although showing positive results in preclinical studies, have so far failed to provide strong benefit to patients.
文摘The problem of the presence of Cantor part in the derivative of a solution to a hyperbolic system of conservation laws is considered. An overview of the techniques involved in the proof is given, and a collection of related problems concludes the paper.
基金Project supported by the National Natural Science Foundation of China (Grant No.12101246)。
文摘Under the Flaschka-Newell Lax pair,the Darboux transformation for the Painlevé-Ⅱequation is constructed by the limiting technique.With the aid of the Darboux transformation,the rational solutions are represented by the Gram determinant,and then we give the large y asymptotics of the determinant and the rational solutions.Finally,the solution of the corresponding Riemann-Hilbert problem is obtained from the Darboux matrices.
文摘Generation of astrocytes within the murine developing cerebral cortex mainly takes place during the first postnatal week, after neuronogenesis and prior to the bulk of oligogenesis. This process involves a great variety of highly complex regulatory mechanisms. Astrocytic outputs depend on two primary factors： progressive commitment of multipotent precursors to astroglial fates and proper tuning of proliferation of astrocyte-committed progenitors. To date, several regulatory mechanisms have been identified for the former process, while very little is known about modulation of astroblast proliferation （reviewed in Mallamaci,
文摘The deferred correction(DeC)is an iterative procedure,characterized by increasing the accuracy at each iteration,which can be used to design numerical methods for systems of ODEs.The main advantage of such framework is the automatic way of getting arbitrarily high order methods,which can be put in the Runge-Kutta(RK)form.The drawback is the larger computational cost with respect to the most used RK methods.To reduce such cost,in an explicit setting,we propose an efcient modifcation:we introduce interpolation processes between the DeC iterations,decreasing the computational cost associated to the low order ones.We provide the Butcher tableaux of the new modifed methods and we study their stability,showing that in some cases the computational advantage does not afect the stability.The fexibility of the novel modifcation allows nontrivial applications to PDEs and construction of adaptive methods.The good performances of the introduced methods are broadly tested on several benchmarks both in ODE and PDE contexts.
基金Supported by the National Natural Science Foundation of China
文摘Utilizing a BzK-selecfion technique, we obtain 14 550 star-forming galaxies （sBzKs） and 1763 passive galaxies （pBzKs） at z - 2 from the K-selected （KAB 〈 22.5） catalog in the COSMOS/UltraVISTA field. The differential number counts of sBzKs and pBzKs are consistent with the results from the literature. Compared to the observed results, semi-analytic models of galaxy formation and evolution provide too few （many） galaxies at the high （low） mass end. Moreover, we find that the star formation rate and stellar mass of sBzKs follow the relation of the main sequence. Based on HST/Wide Field Camera 3 F160W imaging, we find a wide range of morphological diversities for sBzKs, from diffuse to early-type spiral structures, with relatively high M20, large size and low G, while pBzKs have elliptical-like compact morphologies with lower M20, smaller size and higher G, indicating a more concentrated and symmetric spatial extent of stellar population distribution in pBzKs than sBzKs. Furthermore, the sizes of pBzKs （sBzKs） at z - 2 are on average two to three （one to two） times smaller than those of local early-type （late-type） galaxies with similar stellar mass. Our findings imply that the two classes have different evolution models and mass assembly histories.
基金supported by the European Research Council Executive Agency by the Consolidator Grant project AROMA-CFD“Advanced Reduced Order Methods with Applications in Computational Fluid Dynamics”--GA 681447,H2020-ERC CoG 2015 AROMA-CFD and INdAM-GNCS 2020 project“Tecniche Numeriche Avanzate per Applicazioni Industriali”。
文摘Reduced order modeling(ROM)techniques are numerical methods that approximate the solution of parametric partial differential equation(PED)by properly combining the high-fidelity solutions of the problem obtained for several configurations,i.e.for several properly chosen values of the physical/geometrical parameters characterizing the problem.By starting from a database of high-fidelity solutions related to a certain values of the parameters,we apply the proper orthogonal decomposition with interpolation(PODI)and then reconstruct the variables of interest for new values of the parameters,i.e.different values from the ones included in the database.Furthermore,we present a preliminary web application through which one can run the ROM with a very user-friendly approach,without the need of having expertise in the numerical analysis and scientific computing field.The case study we have chosen to test the efficiency of our algorithm is represented by the aortic blood flow pattern in presence of a left ventricular(LVAD)assist device when varying the pump flow rate.
基金Supported by the National Natural Science Foundation of China
文摘Using high-resolution HST/Wide Field Camera 3 F125W imaging from the CANDELS-COSMOS field, we report the structural and morphological properties of extremely red objects （EROs） at -z 1. Based on the UVJ color criteria, we sepa- rate EROs into two types： old passive galaxies （OGs） and dusty star-forming galaxies （DGs）. For a given stellar mass, we find that the mean size of OGs （DGs） is smaller by a factor of - 2 （1.5） than that of present-day early-type （late-type） galaxies at a rest-frame optical wavelength. We derive the average effective radii of OGs and DGs, corresponding to 2.09 ± 1.13 kpc and 3.27± 1.14 kpc, respectively. Generally, the DGs are heterogeneous, with mixed features including bulges, disks and irregular structures, with relatively high M20, large size and low G. By contrast, OGs have elliptical-like compact morphologies with lower M20, smaller size and higher G, indicating a more concentrated and symmetric spatial extent of the stellar population distribution in OGs than DGs. These findings imply that OGs and DGs have different evolutionary processes, and that the minor merger scenario is the most likely mechanism for the structural properties of OGs. However, the size evolution of DGs is possibly due to the secular evolution of galaxies.
基金Supported by the National Natural Science Foundation of China
文摘We build a sample of 298 spectroscopically-confirmed galaxies at redshift z - 2, selected in the z850-band from the GOODS-MUSIC catalog. By utilizing the rest frame 8 p.m luminosity as a proxy of the star formation rate （SFR）, we check the accuracy of the standard SED-fitting technique, finding it is not accurate enough to provide reliable estimates of the physical parameters of galaxies. We then develop a new SED-fitting method that includes the IR luminosity as a prior and a generalized Calzetti law with a variable Rv. Then we exploit the new method to re-analyze our galaxy sample, and to robustly determine SFRs, stellar masses and ages. We find that there is a general trend of increasing attenuation with the SFR. Moreover, we find that the SFRs range between a few to 103 M~ yr-1, the masses from 109 to 4 ~ 1011 Mo, and the ages from a few tens of Myr to more than 1 Gyr. We discuss how individual age measurements of highly attenuated objects indicate that dust must have formed within a few tens of Myr and already been copious at 〈 100 Myr. In addition, we find that low luminosity galaxies harbor, on average, significantly older stellar populations and are also less massive than brighter ones; we discuss how these findings and the well known ＇downsizing＇ scenario are consistent in a framework where less massive galaxies form first, but their star formation lasts longer. Finally, we find that the near-IR attenuation is not scarce for luminous objects, contrary to what is customarily assumed; we discuss how this affects the interpretation of the observed M,/L ratios.
文摘We propose a new paradigm for designing efcient p-adaptive arbitrary high-order meth-ods.We consider arbitrary high-order iterative schemes that gain one order of accuracy at each iteration and we modify them to match the accuracy achieved in a specifc iteration with the discretization accuracy of the same iteration.Apart from the computational advan-tage,the newly modifed methods allow to naturally perform the p-adaptivity,stopping the iterations when appropriate conditions are met.Moreover,the modifcation is very easy to be included in an existing implementation of an arbitrary high-order iterative scheme and it does not ruin the possibility of parallelization,if this was achievable by the original method.An application to the Arbitrary DERivative(ADER)method for hyperbolic Par-tial Diferential Equations(PDEs)is presented here.We explain how such a framework can be interpreted as an arbitrary high-order iterative scheme,by recasting it as a Deferred Correction(DeC)method,and how to easily modify it to obtain a more efcient formula-tion,in which a local a posteriori limiter can be naturally integrated leading to the p-adap-tivity and structure-preserving properties.Finally,the novel approach is extensively tested against classical benchmarks for compressible gas dynamics to show the robustness and the computational efciency.
基金This work was partially funded by the EU through the MAX Centre of Excellence for supercomputing applications(Project No.824143)the Italian Ministry of Research and education through the PRIN 2017 FERMAT grant.F.G.acknowledges funding from the Swiss National Science Foundation(SNSF),through Project No.200021-182057from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Action IF-EF-ST,grant agreement No.101018557(TRANQUIL)。
文摘Despite governing heat management in any realistic device,the microscopic mechanisms of heat transport in all-solid-state electrolytes are poorly known:existing calculations,all based on simplistic semi-empirical models,are unreliable for superionic conductors and largely overestimate their thermal conductivity.In this work,we deploy a combination of state-of-the-art methods to calculate the thermal conductivity of a prototypical Li-ion conductor,the Li_(3)ClO antiperovskite.By leveraging ab initio,machine learning,and force-field descriptions of interatomic forces,we are able to reveal the massive role of anharmonic interactions and diffusive defects on the thermal conductivity and its temperature dependence,and to eventually embed their effects into a simple rationale which is likely applicable to a wide class of ionic conductors.
基金supported by PRIN 2015 Variational methods with applications to problems in mathematical physics and geometry
文摘In the last years much progress has been achieved in KAM theory concerning bifurcation of quasi-periodic solutions of Hamiltonian or reversible partial differential equations.We provide an overview of the state of the art in this field.
基金This work was partially funded by the EU through the MAX Centre of Excellence for supercomputing applications(Project No.824143)the Italian MUR,through the PRIN grant FERMATThe work at Princeton University was supported by the Computational Chemical Sciences Center“Chemistry in Solution and at Interfaces”funded by the US Department of Energy under Award No.DE-SC0019394.
文摘We report on an extensive study of the viscosity of liquid water at near-ambient conditions,performed within the Green-Kubo theory of linear response and equilibrium ab initio molecular dynamics(AIMD),based on density-functional theory(DFT).In order to cope with the long simulation times necessary to achieve an acceptable statistical accuracy,our ab initio approach is enhanced with deep-neural-network potentials(NNP).This approach is first validated against AIMD results,obtained by using the Perdew–Burke–Ernzerhof(PBE)exchange-correlation functional and paying careful attention to crucial,yet often overlooked,aspects of the statistical data analysis.Then,we train a second NNP to a dataset generated from the Strongly Constrained and Appropriately Normed(SCAN)functional.Once the error resulting from the imperfect prediction of the melting line is offset by referring the simulated temperature to the theoretical melting one,our SCAN predictions of the shear viscosity of water are in very good agreement with experiments.
基金We acknowledge CINECA and Regione Lombardia LISA computational initiative,for the availability of high performance computing resources and support.G.Rozza acknowledges INDAM-GNCS national activity group and NOFYSAS program of SISSA.
文摘In this work,two approaches,based on the certified Reduced Basis method,have been developed for simulating the movement of nuclear reactor control rods,in time-dependent non-coercive settings featuring a 3D geometrical framework.In particular,in a first approach,a piece-wise affine transformation based on subdomains division has been implemented for modelling the movement of one control rod.In the second approach,a“staircase”strategy has been adopted for simulating themovement of all the three rods featured by the nuclear reactor chosen as case study.The neutron kinetics has been modelled according to the so-called multi-group neutron diffusion,which,in the present case,is a set of ten coupled parametrized parabolic equations(two energy groups for the neutron flux,and eight for the precursors).Both the reduced order models,developed according to the two approaches,provided a very good accuracy comparedwith high-fidelity results,assumed as“truth”solutions.At the same time,the computational speed-up in the Online phase,with respect to the fine“truth”finite element discretization,achievable by both the proposed approaches is at least of three orders of magnitude,allowing a real-time simulation of the rod movement and control.
基金The work presented here was performed under the auspice of Basic Energy Sciences,United States Department of Energy,contract number DE-SC0020385.
文摘The Eliashberg theory of superconductivity accounts for the fundamental physics of conventional superconductors,including the retardation of the interaction and the Coulomb pseudopotential,to predict the critical temperature T_(c).McMillan,Allen,and Dynes derived approximate closed-form expressions for the critical temperature within this theory,which depends on the electron–phonon spectral functionα^(2)F(ω).Here we show that modern machine-learning techniques can substantially improve these formulae,accounting for more general shapes of theα^(2)F function.Using symbolic regression and the SISSO framework,together with a database of artificially generatedα^(2)F functions and numerical solutions of the Eliashberg equations,we derive a formula for T_(c)that performs as well as Allen–Dynes for low-T_(c)superconductors and substantially better for higher-T_(c)ones.This corrects the systematic underestimation of Tc while reproducing the physical constraints originally outlined by Allen and Dynes.This equation should replace the Allen–Dynes formula for the prediction of higher-temperature superconductors.
基金This study was supported in part by the Italian Ministry of Health(GR-2013-02355724)the Michael J.Fox Foundation,Alzheimer’s Association,Alzheimer’s Research UK and the Weston Brain Institute(BAND 11035)+1 种基金Associazione Italiana Encefalopatie da Prioni(AIEnP)to FMItalian Ministry of Health(GR-2009-1607326)to AEE,Italian Ministry of Health(NET-2011-02346784)to FT and NIH/NIA(P30 AG10133)to Bernardino Ghetti.
文摘Background:Parkinson’s disease(PD)is a neurodegenerative disorder whose diagnosis is often challenging because symptoms may overlap with neurodegenerative parkinsonisms.PD is characterized by intraneuronal accumulation of abnormalα-synuclein in brainstem while neurodegenerative parkinsonisms might be associated with accumulation of eitherα-synuclein,as in the case of Multiple System Atrophy(MSA)or tau,as in the case of Corticobasal Degeneration(CBD)and Progressive Supranuclear Palsy(PSP),in other disease-specific brain regions.Definite diagnosis of all these diseases can be formulated only neuropathologically by detection and localization ofα-synuclein or tau aggregates in the brain.Compelling evidence suggests that trace-amount of these proteins can appear in peripheral tissues,including receptor neurons of the olfactory mucosa(OM).Methods:We have set and standardized the experimental conditions to extend the ultrasensitive Real Time Quaking Induced Conversion(RT-QuIC)assay for OM analysis.In particular,by using human recombinantα-synuclein as substrate of reaction,we have assessed the ability of OM collected from patients with clinical diagnoses of PD and MSA to induceα-synuclein aggregation,and compared their seeding ability to that of OM samples collected from patients with clinical diagnoses of CBD and PSP.Results:Our results showed that a significant percentage of MSA and PD samples inducedα-synuclein aggregation with high efficiency,but also few samples of patients with the clinical diagnosis of CBD and PSP caused the same effect.Notably,the final RT-QuIC aggregates obtained from MSA and PD samples owned peculiar biochemical and morphological features potentially enabling their discrimination.Conclusions:Our study provide the proof-of-concept that olfactory mucosa samples collected from patients with PD and MSA possess important seeding activities forα-synuclein.Additional studies are required for(i)estimating sensitivity and specificity of the technique and for(ii)evaluating its application for the diagnosis of PD and neurodegenerative parkinsonisms.RT-QuIC analyses of OM and cerebrospinal fluid(CSF)can be combined with the aim of increasing the overall diagnostic accuracy of these diseases,especially in the early stages.
文摘A parametric reduced order model based on proper orthogonal decomposition with Galerkin projection has been developed and applied for the modeling of heat transport in T-junction pipes which are widely found in nuclear power reactor cooling systems.Thermal mixing of different temperature coolants in T-junction pipes leads to temperature fluctuations and this could potentially cause thermal fatigue in the pipe walls.The novelty of this paper is the development of a parametric ROM consider-ing the three dimensional,incompressible,unsteady Navier-Stokes equations coupled with the heat transport equation in a finite volume regime.Two different parametric cases are presented in this paper:parametrization of the inlet temperatures and parametrization of the kinematic viscosity.Different training spaces are considered and the results are compared against the full order model.The first test case results to a computational speed-up factor of 374 while the second test case to one of 211.
