Publications by authors named "Sujan Sarkar"

Skin cancer is a significant global health concern, with timely and accurate diagnosis playing a critical role in improving patient outcomes. In recent years, computer-aided diagnosis systems have emerged as powerful tools for automated skin cancer classification, revolutionizing the field of dermatology. This survey analyzes 107 research papers published over the last 18 years, providing a thorough evaluation of advancements in classification techniques, with a focus on the growing integration of computer vision and artificial intelligence (AI) in enhancing diagnostic accuracy and reliability.

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There are often outbreaks of infectious diseases on farms, which not only disrupt production but also cause significant economic losses. Vaccines are given to prevent the spread of these infectious diseases, but they produce only systemic antibodies or antibodies in the mucosa of a particular system. So, a new mucosal vaccination route is needed where the vaccine will produce antibodies in the systemic circulation as well as in the mucosa of many systems.

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Salinity intrusion into the freshwater system due to climate change and anthropogenic activities is a growing global concern, which has made humans and domesticated animals more susceptible to diseases, resulting in less productivity. However, the effects of salinity on domesticated and wild birds, especially in terms of production and immunity, have not been fully elucidated yet. Therefore, this study was designed to examine the effects of salinity on the production and immunity of birds and the mechanisms by which immunity is compromised.

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Multiple sclerosis (MS) is a neurodegenerative autoimmune disease characterized by the destruction of the myelin sheath of the neuronal axon in the central nervous system. Many risk factors, including environmental, epigenetic, genetic, and lifestyle factors, are responsible for the development of MS. It has long been thought that only adaptive immune cells, especially autoreactive T cells, are responsible for the pathophysiology; however, recent evidence has indicated that innate immune cells are also highly involved in disease initiation and progression.

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An electron has recently been shown to catalyze the cross-coupling reaction of organometallic compounds with aryl halides. In terms of green and sustainable chemistry, the electron catalysis is much more desirable than the inevitably used transition metal catalysis but a high temperature of more than 100°C is required to achieve it. Here, we disclose that visible light photoirradiation accelerates the electron-catalyzed reaction of arylzinc reagents with aryl halides with the aid of a photoredox catalysis.

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Femtosecond laser flash photolysis of 3-(1,9-dihydro-1-cyclopropa[]phenanthren-1-ylidene)tetrahydrofuran produces singlet 3-oxacyclopentylidenecarbene which reacts with acetonitrile solvent to form an ylide. This is the first direct detection of ylide formation by an alkylidenecarbene. This new type of ylide was observed to have a broad absorption band in the visible region with λ ∼450 nm and a lifetime of ∼13.

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Photolysis of a 7,7-difluoro-1,4-diphenyl-2,3-diazabicyclo[2.2.1]hept-2-ene derivative () using a 365 nm light-emitting diode in an Ar matrix at 4 K resulted in the formation of a planar singlet 2,2-difluoro-1,3-diphenylcyclopentane-1,3-diyl diradical derivative, S--pl (λ = 520 nm).

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o-Tolylmethylene 1 is a metastable triplet carbene that rearranges to o-xylylene 2 even at temperatures as low as 2.7 K via [1,4] H atom tunneling. Electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) spectroscopical techniques were used to identify two conformers of 1 (anti and syn) in noble gas matrices and in frozen organic solutions.

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Article Synopsis
  • A new method has been created for generating α-monofluoroalkyl radicals without using metals and with a straightforward process.!
  • The success of this method relies on a combination of a specific photocatalyst and unique fluoroalkylating reagents.!
  • This approach can also be used to synthesize β-monofluoroketones by performing radical monofluoroalkylation on alkenyl acetates.!
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To expand the utility of α-cleavage at cryogenic temperatures, we investigated the photoreactivity of 2-azido-2-phenyl-1,3-indandione (). EPR spectroscopy revealed that irradiating in 2-methyltetrahydrofuran (mTHF) matrices forms alkylnitrene , which has zero-field splitting parameters (/c = 1.5837 cm; /c = 0.

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To clarify the cis-trans isomerization mechanism of simple alkenes on the triplet excited state surface, the photochemistry of acyclic and cyclic vinyl ketones with a -methoxyacetophenone moiety as a built-in triplet sensitizer ( and , respectively) was compared. When irradiated, ketone produces its cis-isomer, whereas ketone does not yield any photoproducts. Laser flash photolysis of ketone yields a transient spectrum with λ ∼ 400 nm (τ ∼ 125 ns).

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Article Synopsis
  • The photolysis of 2,3-diazidonaphthalene-1,4-dione in methyltetrahydrofuran produces vinylnitrene, which has been confirmed using electron paramagnetic resonance spectroscopy.
  • The zfs parameters indicate strong 1,3-biradical character, with specific values for and .
  • Additionally, irradiating vinylnitrene leads to the formation of alkylnitrene, which shows zfs parameters characteristic of cycloalkylnitrene when tested in argon matrices.
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Irradiation of nanocrystals of azide 1 results in a solid-to-solid reaction that forms imine 2 in high chemical yield. In contrast, solution photolysis of azide 1 yields a mixture of products, with 7 as the major one. Laser flash photolysis (LFP) of a nanocrystalline suspension of azide 1 in water shows selective formation of benzoyl radical 4 (λ ∼ 400 nm), which is short-lived (τ = 833 ns) as it intersystem crosses to form imine 2.

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Photolysis of 3-azido-1-indenone (1) with a light-emitting diode (LED, λ = 405 nm) or mercury arc lamp (Pyrex) resulted in the formation of heterodimer 3 in excellent yield, through dimerization of triplet vinylnitrene 2. At ambient temperature, vinylnitrene 2 (λ at 340 and 480 nm) was detected directly with laser flash photolysis of vinyl azide 1. The vinylnitrene intermediate was also characterized directly with IR and ESR spectroscopy in cryogenic matrices.

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The photolysis of 2-azido-1,4-naphthoquinone (1) in argon matrices at 8 K results in the corresponding triplet vinylnitrene (3)2, which was detected directly by IR spectroscopy. Vinylnitrene (3)2 is stable in argon matrices but forms 2-cyanoindane-1,3-dione (3) upon further irradiation. Similarly, the irradiation of azide 1 in 2-methyltetrahydrofuran (MTHF) matrices at 5 K resulted in the ESR spectrum of vinylnitrene (3)2, which is stable up to at least 100 K.

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Nanosecond laser flash photolysis of o-hydroxyacetophenone (1a) and 2,4-dihydroxyacetophenone (1b) in ethanol and acetonitrile results in absorption due to triplet biradicals 2a (λmax 430 nm, τ ≈ 3 μs) and 2b (λmax 400 nm, τ ≈ 1 μs), respectively. Triplet biradical 2a intersystem crosses to form Z-3a (λmax 400 nm, τ ≈ 10 μs), whereas 2b forms both Z-3b and E-3b (λmax 350 nm, τ ≈ 5 and 72 μs). Quenching studies demonstrate that 3a,b are formed on both the singlet and triplet excited surface of 1a and 1b.

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Photolysis of vinylazide 1, which has a built-in acetophenone triplet sensitizer, in argon-saturated toluene results in azirine 2, whereas irradiation in oxygen-saturated toluene yields cyanide derivatives 3 and 4. Laser flash photolysis of azide 1 in argon-saturated acetonitrile shows formation of vinylnitrene 1c, which has a λmax at ∼300 nm and a lifetime of ∼1 ms. Vinylnitrene 1c is formed with a rate constant of 4.

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Article Synopsis
  • Photolysis of 3-methyl-2-phenyl-2H-azirine (1a) in different solvents leads to different products, with oxygen-saturated acetonitrile producing benzaldehyde through the trapping of vinylnitrene 5.
  • In contrast, photolysis of 2-methyl-3-phenyl-2H-azirine (1b) yields heterocycles and a transient ylide with a lifetime of several milliseconds.
  • Advanced density functional theory calculations were utilized to understand the reaction mechanisms and identify intermediates formed during the photolysis of both azirines.
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Photolysis of 1 in argon-saturated acetonitrile yields 2, whereas in oxygen-saturated acetonitrile small amounts of benzoic acid and benzamide are formed in addition to 2. Similarly, photolysis of 2 in argon-saturated acetonitrile results in 1 and a trace amount of 3, whereas in oxygen-saturated acetonitrile the major product is 1 in addition to the formation of small amounts of benzoic acid and benzamide. Laser flash photolysis of 1 results in an absorption due to triplet vinylnitrene 4 (broad absorption with λ(max) at 360 nm, τ = 1.

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