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The three body fragmentation of methane dication has been studied using the technique of cold target recoil ion momentum spectroscopy. The process is initiated by impact of energetic Ar9+ ions on neutral methane and the data is subsequently collected in coincidence with Ar8+ projectile. By analysing the dissociation channels leading to (H + H+ + CH 2 + ) and (H + H 2 + + CH+) fragments, it is concluded that these fragments are formed in a sequential manner via formation of molecular intermediates CH 3 + and CH 2 + respectively. It is shown that these molecular intermediates carry a few eVs as their internal energies, part of which is released when they emit an H-atom with the open possibility that the final detected fragments may still be internally excited. This was accomplished by analysing the two-steps of the sequential process in their own native frames. For a molecular system having three-dimensional structure, our results prove to be an ideal example to highlight the importance of using native frames for correct interpretation of the obtained results. Our results indicate that the dissociation of methane dication can be a major source of production of H-atoms in addition to H+ fragments with the probability of the two being of similar order. [ABSTRACT FROM AUTHOR]

Guar gum is a specialty galactomannan that serves as an abundant, renewable and sustainable feedstock. Nevertheless, its films cannot be used for sustained drug delivery due to certain drawbacks such as susceptibility towards microbial contamination, high swelling rate, non-porous structure, and brittleness. Therefore, functionalization of galactomannan has been achieved by crosslinking with malonic acid, a green, water-soluble, simple organic dicarboxylic acid with minimum chain length possessing natural plasticizer properties using a green chemistry approach. Interestingly, malonic acid also acts as an auto catalyst during acylation and subsequent crosslinking. The reaction conditions were optimized by varying the concentrations of malonic acid (0.5%, 1.5%, and 2% w/v), temperature (55 °C, 100 °C, 120 °C, and 140 °C) and time (5, 10, and 15 min) to introduce 1,3-propane dioates in the galactomannan chains resulting in flexible crosslinked films of galactomannans. Furthermore, the effect of low and high curing temperatures on crosslinking has been investigated by the analysis of the degree of crosslinking for the first time. The mechanism of crosslinking with a dicarboxylic acid has also been proposed. Detailed analysis of films has been achieved by NMR (1D & 2D), FTIR, XRD, TGA and DSC. Furthermore, curcumin has been loaded in these crosslinked films and kinetic studies via the Korsmeyer--Peppas model demonstrate that curcumin has a non-Fickian diffusion controlled release (DCR) mechanism. The antibacterial, antifungal and antioxidant studies show that the prepared formulation has potential utility in sustained drug delivery and other biomedical applications. Altogether, these studies provide a foundation to develop a sustained drug release system using crosslinked films for wound healing, anticancer therapy and many more. [ABSTRACT FROM AUTHOR]

The three-body breakup of [ C 2 H 2 ] 3 + formed in collision with Xe9+ moving at 0.5 atomic units of velocity is studied by using recoil ion momentum spectroscopy. Three-body breakup channels leading to (H+, C+, CH+) and (H+, H+, C 2 + ) fragments are observed in the experiment and their kinetic energy release is measured. The breakup into (H+, C+, CH+) occurs via concerted and sequential modes, whereas the breakup into (H+, H+, C 2 + ) shows only the concerted mode. By collecting events coming exclusively from the sequential breakup leading to (H+, C+, CH+), we have determined the kinetic energy release for the unimolecular fragmentation of the molecular intermediate, [ C 2 H ] 2 + . By using ab initio calculations, the potential energy surface for the lowest electronic state of [ C 2 H ] 2 + is generated, which shows the existence of a metastable state with two possible dissociation pathways. A discussion on the agreement between our experimental results and these ab initio calculations is presented. [ABSTRACT FROM AUTHOR]

Purpose: Chemical eye injury is an acute emergency that can result in vision loss. Neurotrophic keratitis (NK) is the most common long-term manifestation of chemical injury. NK due to alkali burn affects ocular surface health and is one of its most common causes. Here, we established a rabbit model of corneal alkali burns to evaluate the severity of NK-associated changes. Material methods: Alkali burns were induced in NZ rabbits by treating the cornea with (i) a 5 mm circular filter paper soaked in 0.75 N NaOH for 10 s (Mild NK) and (ii) trephination using a guarded trephine (5 mm diameter and 150-micron depth), followed by alkali burn, with a 5 mm circular filter paper soaked in 0.75 N NaOH for 10 s (a severe form of NK). Immediately after, the cornea was rinsed with 10 mL of normal saline to remove traces of NaOH. Clinical features were evaluated on Day 0, Day 1, Day 7, Day 15, and Day 21 post-alkali burn using a slit lamp, Pentacam, and anterior segment optical coherence tomography (AS-OCT). NK-like changes in epithelium, sub-basal nerve plexus, and stroma were observed using in vivo confocal microscopy (IVCM), and corneal sensation were measured using an aesthesiometer post alkali injury. After 21 days, pro-inflammatory cytokines were evaluated for inflammation through ELISA. Results: Trephination followed by alkali burn resulted in the loss of epithelial layers (manifested using fluorescein stain), extensive edema, and increased corneal thickness (550 µm compared to 380 µm thickness of control) evaluated through AS-OCT and increased opacity score in alkali-treated rabbit (80 compared to 16 controls). IVCM images showed complete loss of nerve fibers, which failed to regenerate over 30 days, and loss of corneal sensation—conditions associated with NK. Cytokines evaluation of IL6, VEGF, and MMP9 indicated an increased angiogenic and pro-inflammatory milieu compared to the milder form of NK and the control. Discussion: Using clinical parameters, we demonstrated that the alkali-treated rabbit model depicts features of NK. Using IVCM in the NaOH burn animal model, we demonstrated a complete loss of nerve fibers with poor self-healing capability associated with sub-basal nerve degeneration and compromised corneal sensation. This pre-clinical rabbit model has implications for future pre-clinical research in neurotrophic keratitis. [ABSTRACT FROM AUTHOR]

We report on the direct experimental evidence of hydrogen migration in triply charged acetylene. The roaming hydrogen atom in a triply charged molecular ion is counter intuitive. The three body breakup channel C 2 H 2 3 + → H + + C + + C H + is studied using the technique of recoil ion momentum spectroscopy. The triply charged ion was generated in collisions of the neutral parent with a slow highly charged Xe9+ ion. Three different dissociation pathways have been identified and separated, namely, concerted breakup in an acetylene configuration, concerted breakup in a vinylidene configuration, and sequential breakup via a [ C 2 H ] 2 + intermediate, and the branching ratio for all three pathways are determined. [ABSTRACT FROM AUTHOR]

The ion-induced fragmentation of C H 4 2 + into H+ and C H 3 + is studied using a cold target recoil ion momentum spectroscopy in coincidence with the charge state of the post-collision projectile. Using constant velocity Ar9+ and N3+, results from four different datasets are presented, with a selection on the final charge state of the projectile (Ar8+ or Ar7+ and N2+ or N+). Three distinct dissociation pathways (I, II, and III) are observed for each dataset, with the mean kinetic energy release values of around 4.7, 5.8, and 7.9 eV, respectively. The electronic states that are populated correspond to electronic configurations (1 t 2 ) − 2 and (2 a 1 ) − 1 (1 t 2 ) − 1 of the methane dication, C H 4 2 + . The relative branching ratios between the three pathways are discussed as a function of the charge state of the post-collision projectile, and a strong correlation with the specific nature of the ion–molecule interaction is found. The existing ab initio calculations have provided an explanation only for pathway II. In this article, we propose an explanation for pathway III, but pathway I still remains unexplained and requires further theoretical efforts. A discussion of the dependence of dissociation on the mode of excitation is presented. [ABSTRACT FROM AUTHOR]

Electron acceleration due to the beating of two linearly polarized lasers of finite spot size at an arbitrary angle in a vacuum has been investigated. The interference at certain angles due to these lasers with slightly different frequencies interacting at any arbitrary angle has been studied. Due to the constructive interference between these lasers, their resultant electric and magnetic field points out in a particular direction, where the electron is injected for effective trapping and noticeable acceleration has been observed. Sensitiveness of chirp parameters on electron acceleration have been observed. Along with this, a periodic frequency chirp plays a crucial role in the improved acceleration of electron. In this way, electron energy is enhanced more conveniently. [ABSTRACT FROM AUTHOR]