Intensity and phase retrieval of IR laser pulse by THz-based measurement and THz waveform modulation

Abstract THz radiation is of great interest for a variety of applications. Simultaneously with the demonstration of high-intensity THz sources the idea to use this radiation for particle acceleration started to be investigated. THz accelerating gradients up to GV/m have been demonstrated in laboratory. THz radiation can be generated through the optical rectification process induced in non-linear crystals by a pump laser. The temporal shape of the pump laser and in general its characteristics are important aspects to be known in order to produce THz radiation via optical rectification in a controlled way. Here we present a technique that can be used to retrieve the temporal profile characteristics (envelope and phase) of the pump laser, starting from the detection of the THz waveform/spectrum and the knowledge of the physical/optical properties of the crystal used to produce it. This work also shows that the THz field can be shaped by properly acting on the pump laser phase. The possibility to opportunely shape the THz field is of great importance for many applications. Therefore this work paves the way to the possibility to coherently and dynamically control the THz field shape

Post-surgical Thyroid Bed Pyoderma Gangrenosum Mimicking Recurrent Papillary Thyroid Carcinoma

Background: Pyoderma gangrenosum (PG) is a rare inflammatory disease presenting with chronic-recurrent cutaneous ulcers histopathologically hallmarked by neutrophilic infiltrates, which may occur more frequently at sites of surgical traumas. The disease is habitually limited to the skin, but it can virtually involve any organ. Nevertheless, no prior cases of PG involving the thyroid bed have ever been reported.Case Report: A bilateral PG of the breast was diagnosed in a 51-year-old woman and treated with intravenous methylprednisolone pulse-therapy and cyclosporine, with partial improvement. During the hospitalization, cytological examination of two hypoechoic thyroid nodules by fine-needle aspiration (FNA) was consistent with thyroid carcinoma. After total thyroidectomy, histopathology confirmed a papillary thyroid cancer (PTC), and radioactive iodine ablation was performed. At 12-month ultrasonographic follow-up, two hypoechoic avascular areas localized in the empty thyroid bed raised the suspect of PTC recurrence. However, (i) undetectable levels of thyroglobulin without anti-thyroglobulin antibodies, (ii) neutrophilia and increased inflammatory marker levels, and (iii) cytological examination of FNA showing numerous neutrophils induced to suspect thyroid bed PG infiltration. An ex juvantibus approach with high-dose methylprednisolone led to dimensional reduction of the hypoechoic areas on ultrasonography, thus confirming the hypothesis of thyroid bed PG.Conclusion: This case of thyroid bed PG supports the idea that PG reflects a cutaneous phenotype encompassed in the spectrum of systemic neutrophilic diseases. Endocrinologists should be aware that thyroid bed PG involvement is an albeit rare differential diagnosis to consider in patients who had undergone thyroid surgery, especially with a history of PG

Therapeutic Induction of Energy Metabolism Reduces Neural Tissue Damage and Increases Microglia Activation in Severe Spinal Cord Injury

: Neural tissue has high metabolic requirements. Following spinal cord injury (SCI), the damaged, tissue suffers from a severe metabolic impairment, which aggravates axonal degeneration and, neuronal loss. Impaired cellular energetic, tricarboxylic acid (TCA) cycle and oxidative, phosphorylation metabolism in neuronal cells has been demonstrated to be a major cause of neural tissue death and regeneration failure following SCI. Therefore, rewiring the spinal cord cell metabolism may be an innovative therapeutic strategy for the treatment of SCI. In this study, we evaluated the therapeutic effect of the recovery of oxidative metabolism in a mouse model of severe contusive SCI. Oral administration of TCA cycle intermediates, co-factors, essential amino acids, and branched-chain amino acids was started 3 days post-injury and continued until the end of the experimental procedures. Metabolomic, immunohistological, and biochemical analyses were performed on the injured spinal cord sections. Administration of metabolic precursors enhanced spinal cord oxidative metabolism. In line with this metabolic shift, we observed the activation of the mTORC1 anabolic pathway, the increase in mitochondrial mass, and ROS defense which effectively prevented the injury-induced neural cell apoptosis in treated animals. Consistently, we found more choline acetyltransferase (ChAT)-expressing motor neurons and increased neurofilament positive corticospinal axons in the spinal cord parenchyma of the treated mice. Interestingly, oral administration of the metabolic precursors increased the number of activated microglia expressing the CD206 marker suggestive of a, pro-resolutive, M2-like phenotype. These molecular and histological modifications observed in treated animals ultimately led to a significant, although partial, improvement of the motor functions. Our data demonstrate that rewiring the cellular metabolism can represent an effective strategy to treat SCI

Effect of Tocilizumab vs Standard Care on Clinical Worsening in Patients Hospitalized With COVID-19 Pneumonia: A Randomized Clinical Trial

The coronavirus disease 2019 (COVID-19) pandemic is threatening billions of people worldwide. Tocilizumab has shown promising results in retrospective studies in patients with COVID-19 pneumonia with a good safety profile

AGILE detection of extreme γ -ray activity from the blazar PKS 1510-089 during March 2009: Multifrequency analysis

We report on the extreme gamma-ray activity from the FSRQ PKS 1510-089 observed by AGILE in March 2009. In the same period a radio-to-optical monitoring of the source was provided by the GASP-WEBT and REM. Moreover, several Swift ToO observations were triggered, adding important information on the source behaviour from optical/UV to hard X-rays. We paid particular attention to the calibration of the Swift/UVOT data to make it suitable to the blazars spectra. Simultaneous observations from radio to gamma rays allowed us to study in detail the correlation among the emission variability at different frequencies and to investigate the mechanisms at work. In the period 9-30 March 2009, AGILE detected an average gamma-ray flux of (311+/-21)x10^-8 ph cm^-2 s^-1 for E>100 MeV, and a peak level of (702+/-131)x10^-8 ph cm^-2 s^-1 on daily integration. The gamma-ray activity occurred during a period of increasing activity from near-IR to UV, with a flaring episode detected on 26-27 March 2009, suggesting that a single mechanism is responsible for the flux enhancement observed from near-IR to UV. By contrast, Swift/XRT observations seem to show no clear correlation of the X-ray fluxes with the optical and gamma-ray ones. However, the X-ray observations show a harder photon index (1.3-1.6) with respect to most FSRQs and a hint of harder-when-brighter behaviour, indicating the possible presence of a second emission component at soft X-ray energies. Moreover, the broad band spectrum from radio-to-UV confirmed the evidence of thermal features in the optical/UV spectrum of PKS 1510-089 also during high gamma-ray state. On the other hand, during 25-26 March 2009 a flat spectrum in the optical/UV energy band was observed, suggesting an important contribution of the synchrotron emission in this part of the spectrum during the brightest gamma-ray flare, therefore a significant shift of the synchrotron peak

Multiwavelength observations of 3C 454.3. III. Eighteen months of agile monitoring of the "crazy diamond"

We report on 18 months of multiwavelength observations of the blazar 3C 454.3 (Crazy Diamond) carried out in the period 2007 July-2009 January. In particular, we show the results of the AGILE campaigns which took place on 2008 May-June, 2008 July-August, and 2008 October-2009 January. During the 2008 May-2009 January period, the source average flux was highly variable, with a clear fading trend toward the end of the period, from an average γ-ray flux F E>100 MeV ≳ 200 × 10-8photonscm -2s-1 in 2008 May-June, to F E>100 MeV 80 × 10-8photonscm-2s-1 in 2008 October-2009 January. The average γ-ray spectrum between 100 MeV and 1 GeV can be fit by a simple power law, showing a moderate softening (from ΓGRID ∼ 2.0 to ΓGRID ∼ 2.2) toward the end of the observing campaign. Only 3σ upper limits can be derived in the 20-60 keV energy band with Super-AGILE, because the source was considerably off-axis during the whole time period. In 2007 July-August and 2008 May-June, 3C 454.3 was monitored by Rossi X-ray Timing Explorer (RXTE). The RXTE/Proportional Counter Array (PCA) light curve in the 3-20 keV energy band shows variability correlated with the γ-ray one. The RXTE/PCA average flux during the two time periods is F 3-20 keV = 8.4 × 10-11ergcm-2s -1, and F 3-20 keV = 4.5 × 10 -11ergcm-2s-1, respectively, while the spectrum (a power law with photon index ΓPCA = 1.65 0.02) does not show any significant variability. Consistent results are obtained with the analysis of the RXTE/High-Energy X-Ray Timing Experiment quasi-simultaneous data. We also carried out simultaneous Swift observations during all AGILE campaigns. Swift/XRT detected 3C 454.3 with an observed flux in the 2-10 keV energy band in the range (0.9-7.5) × 10-11ergcm-2s-1 and a photon index in the range ΓXRT = 1.33-2.04. In the 15-150 keV energy band, when detected, the source has an average flux of about 5mCrab. GASP-WEBT monitored 3C 454.3 during the whole 2007-2008 period in the radio, millimeter, near-IR, and optical bands. The observations show an extremely variable behavior at all frequencies, with flux peaks almost simultaneous with those at higher energies. A correlation analysis between the optical and the γ-ray fluxes shows that the γ-optical correlation occurs with a time lag of τ = -0.4+0.6-0.8 days, consistent with previous findings for this source. An analysis of 15 GHz and 43 GHz VLBI core radio flux observations in the period 2007 July-2009 February shows an increasing trend of the core radio flux, anti-correlated with the higher frequency data, allowing us to derive the value of the source magnetic field. Finally, the modeling of the broadband spectral energy distributions for the still unpublished data, and the behavior of the long-term light curves in different energy bands, allow us to compare the jet properties during different emission states, and to study the geometrical properties of the jet on a time-span longer than one year. © 2010. The American Astronomical Society. All rights reserved

Study and applications of THz and Lasers pulses for accelerator physics

The aim of my work during my PhD course (2016-2019) was to study and develop new applications in the field of accelerator physics using ultrashort lasers and high energy TeraHertz (THz) pulses. Most of my focus was aimed at the generation and control of high energy THz pulses using the Optical Rectification (OR) process. Those pulses are needed both as accelerating source and as diagnostic tool for charged particles. I had characterized in a broadband spectrum (50 to 36000 cm−1) the optical properties of two organic crystals HMQ-TMS and DSTMS, used for the high energy THz generation in OR. Trough an analytical study of the OR process. I had developed a simulation code that reconstructs the THz radiation generated in OR, given a pump laser pulse, and shows how is possible to shape the THz pulse by changing the nonlinear phase of the pump laser. Also inverting the previous technique it is possible to retrieve the laser parameters, resulting in a promising diagnostic tool for ultrafast lasers. I had worked on a new proposal, to use an high energy THz pulse as driver in the Laser WakeField Acceleration (LWFA), using Particle In a Cell (PIC) simulations. The results show how an intense THz pulse can be more efficient than a standard Ti:Sa laser pulse in the excitation of intense wakefield in the quasi-linear regime. The interaction of high energy THz pulses with the plasmas, used for LWFA, shows the possibility to develop a diagnostic tool for the plasma density and temperature along the plasma channel. I will present the model for this diagnostic technique and my work in its experimental application using the THz radiation generated by two color plasma with a plasma filament in air as target. I also developed a start-to-end simulation code to correctly model the THz propagation and interaction with the plasma filament. About the use of high energy ultrafast lasers in particle accelerators, I had studied a laser COMB technique aiming to obtain a good quality flat-top UltraViolet (UV) pulse for the use in a photocathode. The model takes into account the effect of the laser propagation, inside the nonlinear crystal − BBO up to the second order phase, aiming to better characterize the effect of the interference obtaining the best experimental condition for the final flat-top pulse. I carried out a study for different setups and a sensitivity test over the initial parameters for the laser and crystals length. Finally I will show the best setup needed to achieve a flat-top pulse with ripple below the 5% in the flat region. I will present the work done during my stay at CERN in the CLEAR collaboration. During this period, I have worked on the generation and detection of THz radiation, generated by electron bunches at the end of the CLEAR LINAC. THz pulses, generated by Coherent Transition Radiation (CTR), can be used as bunch length diagnostic. Also the radiation generated by different target will be presented along with transverse radial profile of the THz radiation took by a bolometric camera

THz Pulsed Imaging in Biomedical Applications

Recent advances in technology have allowed the production and the coherent detection of sub-ps pulses of terahertz (THz) radiation. Therefore, the potentialities of this technique have been readily recognized for THz spectroscopy and imaging in biomedicine. In particular, THz pulsed imaging (TPI) has rapidly increased its applications in the last decade. In this paper, we present a short review of TPI, discussing its basic principles and performances, and its state-of-the-art applications on biomedical systems

Characterization of volatile organic compounds (VOCs) in their liquid-phase by terahertz time-domain spectroscopy

In this work the terahertz spectra of benzene, toluene, p-xylene and styrene–four volatile organic compounds (VOCs) of interest in environmental pollution studies–have been measured in their liquid phase at room temperature using terahertz time-domain spectroscopy (THz-TDS). Their frequency-dependent refractive index and absorption coefficient have been extracted and analyzed in the spectral range from 0.2 to 2.5 THz. The optical properties of bi-component VOCs mixtures have also been investigated and described in terms of a linear combination of pure VOCs optical components