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Catecholamines (epinephrine, norepinephrine and dopamine) are considered toxic to the melanocytes and may play an important role in the development of depigmented patches on the skin. This study was done to evaluate the levels of catecholamines in skin and plasma samples of active vitiligo patients' and gene expression changes in catecholamines' metabolism regulatory genes (COMT and GTPCH1), immunoregulatory genes (CTLA4 and PTPN22), and Catalase in active vitiligo patients. In this single-centre, prospective, case-control study, 30 patients with active vitiligo were recruited and skin biopsies from the perilesional site and plasma samples were collected. Skin biopsies from the normal site in vitiligo patients and healthy controls (n = 15) and plasma samples from controls were also obtained. Catecholamines' estimation was done via high-performance liquid chromatography. Gene expression variations were investigated via reverse transcription-polymerase chain reaction (PCR) and real-time PCR. Epinephrine, norepinephrine and dopamine levels were significantly higher in perilesional skin biopsies as compared to controls (P = 0.035, 0.024, and 0.006, respectively). However, epinephrine, norepinephrine and dopamine levels observed in patients' plasma samples were comparable to controls. The mRNA expression level of the Catalase gene was found to be upregulated at the perilesional site of patients as compared to the non-affected site of same patients (P 0.001) and healthy controls (P = 0.037). Transcriptional expression of GTPCH1 and COMT were observed to be increased significantly at the perilesional site of patients in comparison to controls (P = 0.004 and P = 0.046, respectively). Our results support the presence of oxidative stress, inflammation and induced immune response in vitiligo patients at the perilesional sites. The increased inflammatory response may lead to catecholamines upregulation resulting in oxidative stress and melanocyte damage.

Critical applications of satellite data products include monitoring vegetation dynamics and assessing vegetation health conditions. Some indicators like normalized difference vegetation index (NDVI) and land surface temperature (LST) are used to assess the status of vegetation growth and health. But one of the major problems with passive remote sensing satellite data products is cloud and shadow cover that leads to data gaps in the images. The present study proposes temporal aggregation of images over a short time span and developing short span harmonic analysis of time series (SS-HANTS) and pixel-wise multiple linear regression (PMLR) algorithms for retrieving cloud contaminated NDVI and LST information from Landsat-8 (L8) data products, respectively. The developed algorithms were applied in the northeastern part of Thailand to recover the missing NDVI and LST values from time series L8 images acquired in 2018. The predicted NDVI and LST values at artificially clouded locations were compared with the corresponding clear pixel values. Additionally, the model predicted LST and NDVI values were also compared with MODIS LST and NDVI datasets. The calculated root mean square (RMSE) values were ranging from 0.03 to 0.11 and 1.50 to 2.98 °C for NDVI and LST variables, respectively. The validation statistics show that these models can be satisfactorily applied to retrieve NDVI and LST values from cloud-contaminated pixels of L8 images. Furthermore, a vegetation health index (VHI) computed from cloud retrieved continuous NDVI and LST images at province level shows that most of the western provinces have healthy vegetation condition than other provinces in the northeast of Thailand.

In this novel scheme, a theoretical analysis of resonant terahertz (THz) generation in the array of magnetized anharmonic carbon nanotubes (CNTs) is presented. Two laser beams with frequencies ( $${\omega }_{1}, {\omega }_{2}$$ ) and wavenumbers ( $${k}_{1}, {k}_{2}$$ ) propagate through the array of vertically aligned anharmonic CNTs in the presence of an applied static magnetic field. It provides different displacements to the various electrons of CNTs. Due to this, restoration force varies nonlinearly with the displacements of electrons and hence results in anharmonicity. This anharmonicity plays a significant role in the enhancement of absorption of laser beams by the electrons of CNTs. The nonlinear restoration force produces the current which is responsible for the THz generation. It is observed that the applied magnetic field $$(170\mathrm{ to }235\mathrm{ kG})$$ helps in the enhancement of the THz generation by increasing the nonlinearity of the system. The impact of dimensions, inter-tube separation, and density of CNTs on the THz amplitude has also been analyzed.

Present work focuses on Hermite-cosh-Gaussian (HchG) laser-induced third harmonic generation (THG) in plasma on account of self-focusing. HchG laser beam gets self-focused due to ponderomotive force while propagating in plasma. Interaction of intense laser pulse results ponderomotive force on electrons and induce density perturbation that produces density oscillations at second harmonic frequency. Induced density perturbation beats with quiver velocity of electrons at laser frequency to produce a third harmonic nonlinear current. Application of wiggler magnetic field satisfies the phase matching condition which results resonant THG. Significant enhancement in the efficiency of THG is observed by using HchG laser profile for mode index m = 2. Small variation in decentered parameter also affects the THG efficiency which shows the sensitivity of decentered parameter.

The present analysis develops a novel theory of terahertz radiation generation by beating of two laser beams, incident obliquely on the array of vertically aligned carbon nanotubes (CNTs) in the presence of an external wiggler magnetic field. The array of CNTs behaves as nanoantenna to generate THz radiations. The incident lasers exert a ponderomotive force on the electrons of the CNTs to produce nonlinear oscillatory velocity, which beats with the applied wiggler magnetic field. This beating produces a nonlinear current at (ω2 − ω1, k2 − k1 + k0) which acts as an antenna to produce the THz radiation. We observe that when the beat frequency (ω2 − ω1) lies near the effective plasmon frequency of the CNTs, strong THz radiation is produced due to a resonant interaction of the laser with CNT electrons. The externally applied wiggler magnetic field enhances the efficiency of THz radiation of nanoantenna by providing the necessary momentum to the generated THz radiation. We explore the impact of radius and length of nanotubes on the efficiency of THz generation. The generated THz power is enhanced at an optimum angle of incidence of lasers with an array of CNTs.

A new scheme of terahertz (THz) generation from laser filaments in plasma in the presence of static electric and magnetic fields is proposed. Two femtosecond laser pulses of different frequencies ( $$\omega_{1} ,\omega_{2}$$ ) and wave numbers ( $$k_{1} ,k_{2}$$ ) are co-propagating under the action of filamentation in a magnetized collisional plasma. THz wave is generated due to the nonlinear coupling between nonlinear velocity and electron density in magnetized collisional plasma. For suitable laser and plasma parameters, the nonlinear coupling results in enhanced nonlinear current density which leads to resonant THz waves. The external D.C. electric and magnetic fields are applied perpendicular to each other and mutually perpendicular to the direction of co-propagating lasers. We have obtained the expression of a dielectric tensor with anisotropic nature, and it is found very useful in the study of THz generation. The applied magnetic field also aids to enhance the transverse components of nonlinear current. This nonlinear current is responsible to generate enhanced terahertz waves at frequency ( $$\omega_{1} - \omega_{2}$$ ). We have found that the normalized THz amplitude increases significantly with the increase in applied D.C. electric field from 10 to 30 kV/cm and magnetic field from 10 to 50kG. Our scheme with numerical analysis may open the door for efficient and cost-effective way to generate THz radiation.

An analysis of the self-focusing of Hermite Gaussian chirped pulse laser in the relativistic and ponderomotive regime under the influence of exponential plasma density ramp and linear absorption has been done. Differential equation for beam width parameter is derived by using paraxial ray approximation and then solved numerically. It is observed that self-focusing of the chirped pulse laser is strongly influenced by linear absorption. Also it is seen that with the increase in intensity of laser beam, plasma density ramp and chirped parameter value, self-focusing becomes more effective. Current work may be useful in understanding laser induced fusion, quantum dots etc.

In the present paper, second harmonic generation (SHG) of cosh-Gaussian laser in a magnetized plasma is analyzed. During laser propagation through plasma, electrons acquire the oscillatory velocity and result density perturbation. The density oscillations beat with the oscillatory velocity to produce second harmonic current which drives SHG. Wiggler magnetic field adds the additional momentum to the photons of second harmonic and fulfills the phase matching condition which results in resonant SHG. Wiggler magnetic field also helps to maintain the cyclotron frequency due to which plasma electrons remain confined within the plasma region and results SHG of higher efficiency. Using paraxial approximation, we have derived the equation for the amplitude of SHG and studied its variation for different values of intensity parameter of incident laser, wiggler magnetic field, decentered parameter and plasma density. The efficiency of SHG is significant at higher values of intensity of incident laser, wiggler field, and plasma density as observed in our analysis.

The resonant third-harmonic generation of a self-focusing laser in plasma with a density transition was investigated. Because of self-focusing of the fundamental laser pulse, a transverse intensity gradient was created, which generated a plasma wave at the fundamental wave frequency. Phase matching was satisfied by using a Wiggler magnetic field, which provided additional angular momentum to the third-harmonic photon to make the process resonant. An enhancement was observed in the resonant third-harmonic generation of an intense short-pulse laser in plasma embedded with a magnetic Wiggler with a density transition. A plasma density ramp played an important role in the self-focusing, enhancing the third-harmonic generation in plasma. We also examined the effect of the Wiggler magnetic field on the pulse slippage of the third-harmonic pulse in plasma. The pulse slippage was due to the group-velocity mismatch between the fundamental and third-harmonic pulses.