5,648 research outputs found
Radiative Transfer in a Translucent Cloud Illuminated by an Extended Background Source
We discuss the radiative transfer theory for translucent clouds illuminated
by an extended background source. First we derive a rigorous solution based on
the assumption that multiple scattering produce an isotropic flux. Then we
derive a more manageable analytic approximation showing that it nicely matches
the results of the rigorous approach. To validate our model, we compare our
predictions with accurate laboratory measurements for various types of well
characterized grains, including purely dielectric and strongly absorbing
materials representative of astronomical icy and metallic grains, respectively,
finding excellent agreement without the need of adding free parameters. We use
our model to explore the behavior of an astrophysical cloud illuminated by a
diffuse source with dust grains having parameters typical of the classic ISM
grains of Draine & Lee (1984) and protoplanetary disks, with an application to
the dark silhouette disk 114-426 in Orion Nebula. We find that the scattering
term modifies the transmitted radiation, both in terms of intensity
(extinction) and shape (reddening) of the spectral distribution. In particular,
for small optical thickness our results show that scattering makes reddening
almost negligible at visible wavelengths. Once the optical thickness increases
enough and the probability of scattering events become close to or larger than
1, reddening becomes present but appreciably modified with respect to the
standard expression for line-of-sight absorption. Moreover, variations of the
grain refractive index, in particular the amount of absorption, also play an
important role changing the shape of the spectral transmission curve, with
dielectric grain showing the minimum amount of reddening.Comment: 19 pages, 11 figures, accepted for publication on The Astrophysical
Journa
Metodologie innovative per il supporto alla progettazione e all’analisi delle prestazioni di impianti ad energia solare a concentrazione ed eolici off-shore utilizzando immagini satellitari ottiche e SAR
In questo lavoro presentiamo delle nuove metodologie, sviluppate nell’ambito del progetto SATENERG
(Servizi sATellitari per le ENergie Rinnovabili di nuova Generazione) finanziato dall’Agenzia
Spaziale Italiana, sia per il supporto alla progettazione/pianificazione che per il monitoraggio
quasi in tempo reale e l’analisi delle prestazioni degli impianti ad energia rinnovabile di nuova
generazione (CSP, CPV ed eolici off-shore) utilizzando immagini satellitari.
In particolare per quanto riguarda gli impianti solari a concentrazione (CSP e CPV), abbiamo
sviluppato un metodo per ricavare l’irradianza solare incidente al suolo (in particolare la sua
componente diretta normale rispetto ai raggi solari, fondamentale per questo tipo di impianti) da
immagini ottiche satellitari. Ciò, unito ad un modello di funzionamento di tali impianti e degli
inverter, ci ha resi in grado di poter sviluppare un servizio di supporto nella progettazione e pianificazione
di nuove costruzioni di impianti CSP e CPV (analizzando serie storiche di dati satellitari)
ed anche un servizio di monitoraggio e analisi delle prestazioni per quelli già esistenti (usando
invece immagini satellitari quasi in tempo reale).
In maniera simile, usando immagini SAR (Synthetic Aperture Radar), abbiamo sviluppato un metodo
per ricavare l’intensità e la direzione del vento in aree marine da remoto che ci ha permesso,
utilizzando anche un modello di impianto eolico off-shore (turbina e inverter), di sviluppare sia
un servizio di supporto alla progettazione/pianificazione che un servizio di monitoraggio quasi in
tempo reale della produzione di un impianto eolico off-shore.
Le prime applicazioni di queste nuove metodologie hanno già portato ad avere ottimi risultati in
vari casi di prova sia per quanto concerne il monitoraggio dell’irradianza diretta su piano normale,
in cui l’irradianza misurata e quella ricavata da dato satellitare non si sono discostate più del 10%, sia per quanto riguarda il calcolo dell’intensità e direzione del vento da immagini SAR, in cui l’errore
rispetto al dato misurato è rimasto al di sotto del 15%, fornendo quindi una buona base per il
monitoraggio della energia AC prodotta dagli impianti.In this work we present new methodologies aimed to support both planning and near-real-time
monitoring of new generation solar and wind energy plants (CSP, CPV and wind off-shore) using
satellite imagery. Such methodologies are currently being developed in the scope of SATENERG, a
project funded by ASI (Italian Space Agency).
In particular, for what concerns the concentrating solar energy plants (CSP and CPV) we developed
a method to calculate solar irradiance at ground (and its direct normal component, that has
primary importance in this type of plants) starting from satellite optical images. Then, using also
detailed opto-electronic models of the plants and inverters, we are able to calculate the producible
energy, which can be used to support either the design of potential plants (using historical series
of satellite images) or the monitoring and performance analysis of existing plants (using near-real-
time satellite imagery). Producible energy and other interesting parameters, like production
efficiency, return on investment etc., are delivered through dedicated web services.
In a similar way, we developed also a method to calculate the intensity and the direction of off-shore
wind from satellite SAR (Synthetic Aperture Radar) images that permitted us, together with
detailed models of wind turbine and inverters, to develop a new service in support to both planning
and near-real-time monitoring activities of off-shore wind plants.
The first applications of these methods gave successful results in several test cases: we obtained
a maximum error of 10% for satellite retrieved direct normal solar irradiance and a maximum
error of 15% for wind direction and intensity calculated from SAR images (with respect to in-situ
measured data)
A method for characterizing the stability of light sources
We describe a method for measuring small fluctuations in the intensity of a laser source with a resolution of 10⁻⁴. The current signal generated by a PIN diode is passed to a front-end electronics that discriminates the AC from the DC components, which are physically separated and propagated along circuit paths with different gains. The gain long the AC signal path is set one order of magnitude larger than that along the DC signal path in such a way to optimize the measurement dynamic range. We then derive the relative fluctuation signal by normalizing the input-referred AC signal component to its input-referred DC counterpart. In this way the fluctuation of the optical signal waveform relative to the mean power of the laser is obtained. A "Noise-Scattering-Pattern method" and a "Signal-Power-Spectrum method" are then used to analyze the intensity fluctuations from three different solid-state lasers. This is a powerful tool for the characterization of the intensity stability of lasers. Applications are discussed
Measurement of power spectral density of broad-spectrum visible light with heterodyne near field scattering and its scalability to betatron radiation.
We exploit the speckle field generated by scattering from a colloidal suspension to access both spatial and temporal coherence properties of broadband radiation. By applying the Wiener-Khinchine theorem to the retrieved temporal coherence function, information about the emission spectrum of the source is obtained in good agreement with the results of a grating spectrometer. Experiments have been performed with visible light. We prove more generally that our approach can be considered as a tool for modeling a variety of cases. Here we discuss how to apply such diagnostics to broad-spectrum betatron radiation produced in the laser-driven wakefield accelerator under development at SPARC LAB facility in Frascati
Efficacy of Cemiplimab in a patient affected by Cutaneous Squamous Cell Carcinoma and Myelodysplastic Syndrome
Cutaneous squamous cell carcinoma (cSCC) is a prevalent skin malignancy, often managed through surgical intervention. However, in certain cases, especially when complicated by concurrent hematologic disorders such as myelodysplastic syndrome (MDS), treatment options become more challenging. This abstract highlights a case study examining the efficacy of cemiplimab, a monoclonal antibody targeting programmed cell death protein 1 (PD-1), in a patient diagnosed with both cSCC and MDS.
The patient, initially presenting with an advanced cSCC lesion and underlying MDS, underwent treatment with cemiplimab as a therapeutic approach. Monitoring of the patient's response included clinical evaluation, radiological assessments, and laboratory analyses. Results demonstrated a notable reduction in the size of the cSCC lesion and stabilization of hematologic parameters, suggesting a positive therapeutic effect of cemiplimab in this complex clinical scenario.
This case underscores the potential utility of immunotherapeutic agents, specifically PD-1 inhibitors like cemiplimab, in the management of cutaneous malignancies coexisting with hematologic disorders. Further investigations and larger-scale studies are warranted to validate these findings and establish cemiplimab's role as a viable treatment option in similar clinical contexts
Probing Transverse Coherence with the Heterodyne Speckle Approach: Overview and Perspectives☆
Abstract The properties of spatial coherence of radiation emitted by relativistic electrons is far from being trivial. Assessing the coherence of high-brilliance X-ray sources (3rd generation synchrotrons or free electron lasers) is of crucial importance for machine diagnostics, as well as in planning experiments exploiting coherent techniques. The Heterodyne Speckles method, firstly described by Alaimo et al. (2009), is a valuable alternative to standard methods (e.g. Young's interferometer) which 1) provides a direct measure of transverse coherence without any a-priori assumption, 2) provides a full 2D map of coherence, 3) is capable of one shot, time-resolved measures, 4) is scalable over a wide range of wavelengths. It relies upon the statistical analysis of radiation scattered by spherical particles randomly distributed and suspended in a fluid. Here we give an overview of this method, from the theoretical framework to the operating conditions to be adopted in order to obtain coherence measurements in several conditions
Colloidal aggregation in microgravity by critical Casimir forces
By using the critical Casimir force, we study the attractive strength
dependent aggregation of colloids with and without gravity by means of Near
Field scattering. Significant differences were seen between microgravity and
ground experiments, both in the structure of the formed fractal aggregates as
well as the kinetics of growth. Ground measurements are severely affected by
sedimentation resulting in reaction limited behavior. In microgravity, a purely
diffusive behavior is seen reflected both in the measured fractal dimensions
for the aggregates as well as the power law behavior in the rate of growth.
Formed aggregates become more open as the attractive strength increases.Comment: 4 pages, 3 figure
CCD-based imaging and 3D space--time mapping of terahertz fields via Kerr frequency conversion
We investigate the spatially and temporally resolved four-wave mixing of terahertz (THz) fields and optical pulses in large-bandgap dielectrics, such as diamond. We show that it is possible to perform beam profiling and space–time resolved mapping of THz fields by encoding the spatial information into an optical signal, which can then be recorded by a standard CCD camera
Dynamics of colloidal aggregation in microgravity by critical Casimir forces
Using the critical Casimir force, we study the attractive-strength dependence
of diffusion-limited colloidal aggregation in microgravity. By means of near
field scattering we measure both the static and dynamic structure factor of the
aggregates as the aggregation process evolves. The simultaneous measurement of
both the static and dynamic structure factor under ideal microgravity
conditions allows us to uniquely determine the ratio of the hydrodynamic and
gyration radius as a function of the fractal dimension of the aggregate,
enabling us to elucidate the internal structure of the aggregates as a function
of the interaction potential. We find that the mass is evenly distributed in
all objects with fractal dimension ranging from 2.55 for a shallow to 1.75 for
the deepest potential.Comment: 5 pages, 4 figure
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