Silicone oil tamponade induced vasculitis- a rare manifestation of toxic posterior segment syndrome.

AIM: To report silicone oil tamponade induced vasculitis in the early post operative period - a rare manifestation of 'Toxic Posterior Segment Syndrome' after pars plana vitrectomy for rhegmatogenous retinal detachment. CASE DESCRIPTION: A 50-year-old gentleman presented with vasculitis after a pars plana vitrectomy with silicone oil tamponade on the first post-operative day. He was started on oral steroids (1 mg/ kg) tapered sequentially every week. All signs of vasculitis resolved over a period of one month after which the silicone oil was removed. The patient maintained a visual acuity of 20/90 even after 3 months. There was no recurrence of vasculitis observed thereafter. CONCLUSION: Silicone oil induced vasculitis is a rarely described entity, especially as a manifestation of toxic posterior segment syndrome. This differential must be kept in mind even on the first post-operative day in cases where silicone oil has been used for tamponade.

Unilateral solitary choroidal tuberculoma as the presenting sign in disseminated tuberculosis in an immunocompetent patient.

INTRODUCTION: Tuberculosis can involve any organ in the body including ocular tissue of which the uveal tissue is most commonly infected. Choroidal involvement ranges from choroidal tubercles to granulomas. This is one of the few cases of a solitary choroidal granuloma with no other systemic symptoms in an immunocompetent child. METHOD: A case report. RESULTS: A 12-year-old female, presented with diminution of vision in the left eye for a month. The anterior segment of her left eye was normal. A fundus examination revealed an isolated orangish-yellow choroidal mass, 4 DD in size, involving the posterior pole with overlying subretinal exudation. CT scan of the thorax showed large pulmonary, cervical and pancreatic lymph nodes, along with lytic lesions of the thoracic vertebrae. Excision biopsy of the cervical lymph nodes showed caseating granulomas with no e/o malignancies on histopathology. The patient was started on anti-tubercular therapy. Six months after the treatment, the lesion had reduced in size and her vision had improved. CONCLUSION: Isolated choroidal tuberculomas can be present in eyes with little associated ocular inflammation and no other symptoms of systemic tuberculosis. High suspicion, early diagnosis and rapid initiation of medication are important for the treatment of ocular and systemic tuberculosis.

Application of the Milan System for Reporting Salivary Gland Lesions and Its Cytohistological Correlation for Risk Stratification: A Single-Institution Experience.

INTRODUCTION:  Salivary gland tumors are known to have a heterogeneous profile with variable clinical presentation and a wide variety of histological subgroups of prognostic significance. Immunocytochemical markers that aid in the diagnosis and characterization of the cell type of origin are critical for this heterogeneous group of malignancies. AIMS AND OBJECTIVES: To study the application of The 'Milan System' for Reporting Salivary Gland Cytology and the diagnostic utility of a panel of immunocytochemical markers in the diagnosis of salivary gland neoplasms and their cytohistological correlation for their risk stratification. MATERIALS AND METHODS: This was a prospective study carried out in which a total of 60 patients were enrolled in the study. Fine-needle aspiration cytology (FNAC) smears and cell blocks were prepared with standard techniques and staining procedures. Immunocytochemistry (ICC) was performed on cell block sections by immunoperoxidase procedure. Immunocytochemical (ICC) stains were used for the differentiation of the lesions in cell blocks. Histopathology was also studied if the patient underwent excision of salivary gland lesions. DISCUSSION AND RESULTS: Almost 60 cases were studied under FNAC and cell block evaluation, as well as ICC, among those five (8.33%) samples were inadequate, eight (13.3%) were non-neoplastic, 27 (45%) were benign, one (1.7%) was neoplasm with uncertain malignancy potential, one (1.7%) was suspected of malignancy, and 19 (31.7%) were malignant. The histopathological diagnosis was confirmed in 47 cases. Of these, 24 (51.1%) were benign and 23 (48.9%) were malignant. The malignancy rate for Milan Categories I, II, III, IVa, IVb, V, and VI was 0%, 0%, 100%, 24%, 50%, 80%, and 84.6%, respectively. The study showed that malignancy risk stratification could be further improved by using cell block with immunocytochemistry as a complementary diagnostic modality. CONCLUSIONS: The present study was carried out to assess the usefulness of the Milan system to report salivary gland cytology results. Thus, the findings of the present study show that the Milan system is helpful in stratifying the risk of malignancy in salivary gland tumors.

Expression of immune checkpoint protein in oral squamous cell carcinoma and its clinicopathological correlation: A tertiary care center cross-sectional study.

Background: Recent evidence suggests that oral squamous cell carcinoma (OSCC) patients who exhibit the immunohistochemical expression of immune checkpoint protein programmed cell death ligand 1 (PD-L1) are more likely to have a poor clinical outcome and may serve as an independent prognostic marker. Aims and Objectives: This study aimed to assess the immunohistochemical expression of immune checkpoint protein PD-L1 in OSCC and its clinicopathological correlation. Materials and Methods: OSCC cases were included in the study. This was a tertiary care center cross-sectional one-year duration study. Histomorphological diagnosis and immunohistochemical expression of PD-L1 were performed after taking ethical clearance. The statistical analysis was performed using Statistical Package for Social Sciences (SPSS) version 21.0 statistical analysis software. Results: A total of 106 cases of OSCC were included in the study. Histologically, the majority of cases (58.5%) were graded as well differentiated, followed by moderately differentiated (58.5%) and poorly differentiated (4.7%), respectively. In PD-L1 immunohistochemical expression, score 1+ was accorded to 37 (34.9%), 2+ was accorded to 31 (29.2%), and score 3+ was accorded to 33 (31.1%) cases. Tumor size, pattern, depth of invasion lymphovascular invasion (LVI), and perineural invasion (PNI) were found to be significantly associated with PD-L1 immunohistochemical scores. Conclusions: We concluded that the immunohistochemical expression of immune checkpoint protein PD-L1 positivity in tumor cells was seen in the majority of the cases (60.37%) in our patient. This suggests that the PD-1 or PD-L1 pathway plays a significant role in tumor immune evasion in OSCC.

A Comparative Analysis of Liquid-Based Cytology and Conventional Smears in Fine-Needle Aspirates of Thyroid Lesions.

Background Palpable nodules in the thyroid are present in 4-7% of the general population. Fine-needle aspiration cytology is a safe and cost-effective method of choice for evaluating thyroid nodules. Aspirated samples can be manually spread directly onto the slide and stained in the conventional smear method. The liquid-cased cytology method has been recently introduced, which is an automated machine-based method, yielding a single slide with a clean background and greater preservation of cells and consuming less time for screening. This study aimed to compare the cytomorphological features and diagnostic accuracy of conventional smears and liquid-based cytology smears. Methodology This prospective study comprised 250 cases of thyroid lesions. Fine-needle aspiration cytology using conventional smears and liquid-based cytology smears was reported per the Bethesda system of reporting thyroid cytopathology. Detailed cytomorphological features were evaluated and compared in both techniques. Results The cellularity of conventional smears was significantly higher for scores 2+ and 3+ than paired liquid-based cytology smears (paired t-test, p < 0.001). The overall diagnostic efficacy of conventional smears and liquid-based cytology smears was equivalent in the majority of cases (n = 171, 68.4%). Conventional smears were better than liquid-cased cytology smears in 34 (13.6%) cases, and liquid-based cytology smears were better than conventional smears in eight (3.2%) cases. Liquid-based cytology smears showed a higher unsatisfactory rate compared to conventional Smears (15.6% vs. 5.2%). The sensitivity and specificity of conventional smears were 84.6% and 94.4%, respectively, compared to 68.7% and 92.4%, respectively, of liquid-based cytology smears. Conclusions Conventional smears are a cost-effective and easy method for diagnosing thyroid nodules. Liquid-based cytology smears can be used in association with conventional smears to enhance the accuracy of the evaluation of malignant thyroid nodules.

Barriers related to Oral Cancer Screening, Diagnosis and Treatment in Karnataka, India.

BACKGROUND: The most predominant cancer in India is Oral cancer. Annually 130,000 people yield to oral cancer in India, which translates into about 14 deaths per hour and 60-80% of patients present with advanced disease as compared to 40% in developed countries. AIM: To decide factors associated with primary, secondary and tertiary delays and identify reasons for a lack of follow-up. MATERIALS AND METHODS: This study was conducted at the Kidwai Memorial Institute of Oncology, Bengaluru. A hospitalbased cross-sectional study using the direct personal interview method was done. A total of 200 oral cancer patients were included in the study. RESULTS: 34.5% were men and 65.5% were women. About 97.5% of patients were engaged with either one of the habits like smoking, chewing or alcohol consumption. 84% of patients were not aware of the risk of getting oral cancer. 29% of people agreed that tobacco and alcohol are risk factors for oral cancer and they know about the signs of oral cancer. If detected early, cure rates were higher compared to illiterate people and this difference is statistically significant p< 0.05. 83.5% of patients did not know that oral cancer can be diagnosed early by regular screening of the oral cavity. The cost of staying near a Regional cancer centre, job security, and the social and economic burden on relatives were significant barriers to incomplete treatment and a decreased follow-up rate. CONCLUSION: Low awareness is the main barrier to oral cancer detection. Conducting cancer awareness and screening camps frequently will detect oral cancers at an early stage. KEY WORDS: Oral Cancer, Barriers, Cancer awareness, Oral Screening.

Armchair silicon carbide nanoribbon for potential anode material in lithium-ion batteries (LIBs).

In this work, we have investigated the electrochemical characteristics of armchair silicon carbide nanoribbon (ASiCNR) for its potential deployment as 2D lithium-ion battery anode material. Density functional theory approach is used to calculate the adsorption energy, storage capacity, and open circuit voltage of ASiCNR for LIB. Adsorption of Li atoms introduces the new energy bands which cross the Fermi level; this results in semiconductor to metallic transition of ASiCNR. It indicates the strong interaction of Li atoms towards the ASiCNR. When adsorption of Li atoms increases one by one, the adsorption energy (E[Formula: see text]) per Li atoms increases gradually. When all favourable sites are adsorbed by Li atoms E[Formula: see text] reached its maximum value and it results in maximum storage capacity of 818 mAhg[Formula: see text] and open circuit voltage of 1.15 V. Diffusion barrier of Li atoms for the substrate is 0.42 eV. Our computational results suggest that ASiCNR can be used as an anode material for Li-ion batteries, and it provides the theoretical background for the future study on ASiCNR and other Li storage structures.

Immunohistochemical Expression of p16 and CDK4 in Soft Tissue Tumors.

BACKGROUND AND OBJECTIVES:  The aim of this study was to determine the immunohistochemical expression of p16 (p16INK4a) and cyclin-dependent kinase 4 (CDK4) and CDK4 markers in various lineages of soft tissue tumors and to evaluate their role in differentiating atypical lipomatous tumors/well-differentiated liposarcomas from benign lipomas. MATERIAL AND METHODS: A total of 70 cases of both excisional and incisional biopsies of soft tissue tumors were included in this study. Histopathological examination was done by using formalin-fixed, paraffin-embedded tissue samples. After that, we performed IHC expressions of p16 and CDK4 markers on the unstained slides of these soft tissue tumors.  Results: Immunohistochemical study showed that positive expressions of p16, CDK4, and combined (p16+CDK4) markers were 51.4%, 10.0%, and 12.9%, respectively in soft tissue tumors. Positive p16 expression was observed among a higher proportion of malignant cases (66.7%) as compared to benign (20.0%) and intermediate (50.0%) cases. This difference was found to be statistically significant (p=0.009). Negative expression of only CDK4 and combined (p16 and CDK4) were observed among a higher proportion of benign as compared to malignant and intermediate cases (90.0% vs. 78.6% & 75.0%, p=0.393 and 65.0% vs. 26.2% & 37.5%, p=0.028, respectively). This difference was not found to be statistically significant. For adipocytic tumors, the majority of malignant and intermediate tumors had positive p16 (7/7; 100%) and CDK4 (6/7; 85.7%) immunohistochemical expression. These differences were found to be statistically significant. CONCLUSION: Immunohistochemical marker p16 can be used to differentiate between malignant and benign soft tissue tumors. Amongst adipocytic tumors, combination of p16 and CDK4 immunohistochemical expression can be used to differentiate liposarcomas from benign ones.

Role of anchoring groups on the light harvesting and optoelectronic properties of triphenylamine derivatives: insights from theory.

BACKGROUND: In the present work, DFT and time-dependent DFT calculations were performed to investigate the role of anchoring groups on the photophysical properties and reveal structure-property correlations of triphenylamine (TPA) derivatives. The selected anchoring groups are tetrazole, acrylamide, hydantoin, and rhodanine. RESULTS: Our results show that the different anchoring groups employed alter the planarity, intramolecular charge transfer properties, and HOMO-LUMO gap and hence influence the optoelectronic properties of the dyes. Although all molecules fulfill the basic requirements with suitable energy levels, band gap, absorption, and charge transfer properties, the dye with rhodanine acceptor (TPA4) was the most promising candidate due to its lowest HOMO-LUMO gap, red-shifted highest λmax absorption value, better ICT pattern, low total reorganization energy, and good electron injection properties. Overall, it is anticipated that the results of this investigation will point to new avenues for the experimental fabrication of remarkably effective metal-free organic dyes for solar cell applications.

Anti-oxidative and anti-neuroinflammatory role of Necrostatin-1s and docosahexaenoic acid in RIP-1-mediated neurotoxicity in MPTP-induced Parkinson's disease model.

Parkinson's disease (PD) is a neuromuscular ailment that affects people in their later years and causes both motor and non-motor deficits. Receptor-interacting protein-1 (RIP-1) is a critical participant in necroptotic cell death, possibly through an oxidant-antioxidant imbalance and cytokine cascade activation in PD pathogenesis. The present study examined the role of RIP-1-mediated necroptosis and neuroinflammation in the MPTP-induced PD mouse model, as well as their protection by Necrostatin-1s (an RIP signalling inhibitor), antioxidant DHA and their functional interaction. BALB/c mice were given acute MPTP therapy (4 injections of 15 mg/kg i.p. at 2-h intervals) on day 1. After MPTP intoxication, Necrostatin-1s (Nec-1s; 8 mg/kg/day, i.p.) and DHA (300 mg/kg/day, p.o.) treatments were given once daily for 7 days. The Nec-1s treatment prevented MPTP-induced behavioural, biochemical and neurochemical alterations, and the addition of DHA increases Nec-1s' neuroprotective impact. In addition, Nec-1s and DHA significantly improve the survival of TH-positive dopaminergic neurons and lower expression levels of the inflammatory cytokines, IL-1ß and TNF-α. Furthermore, Nec-1s dramatically reduced RIP-1 expression, whereas DHA had little effect. Our research raises the possibility that neuroinflammatory signalling and acute MPTP-induced necroptosis are both mediated by TNFR1-driven RIP-1 activity. In this study, RIP-1 ablation through Nec-1s and the addition of DHA showed a reduction in the levels of pro-inflammatory and oxidative markers, as well as protection from MPTP-driven dopaminergic degeneration and neurobehavioural changes, suggesting potential therapeutic applications. For a better understanding, additional research about the mechanism(s) behind Nec-1s and DHA is required.

Immunohistochemical appraisal of epithelial mesenchymal transition type III in gall bladder cancer.

Background: Epithelial-mesenchymal transition (EMT) is the heart of invasion. EMT associated with cancer progression and metastasis is known as type III EMT. Beta-catenin, E-cadherin, and MMP9 markers of EMT are routinely employed for diagnostic purposes. Aims: We employed these markers to study EMT by immunohistochemistry (IHC) in gall bladder cancer (GBC) with respect to depth of tumor invasion, clinical outcome, and disease-free survival. Settings and Design: This was a prospective case-control study. Material and Methods: Seventy gall bladders were included (50 GBC and 20 CC). After detailed histology, immunoexpression was studied in terms of percentage and strength of expression. Statistics Analysis Used: Expression was compared between CC and GBC by Student t test and analysis of variance. Kaplan-Meier was used for survival analysis, and the extent of agreement ("Kappa") was calculated. Results and Conclusions: The age of incidence of GBC was 49.40 (+11.6) years with female predominance (F:M = 4:1). In 88% (44/50) of GBC, the fundus was involved. Moderately differentiated adenocarcinoma was most frequent [54%; 27/50]. Significant downregulation of E-cadherin (P = 0.022) and beta-catenin (P < 0.001) and upregulation in MMP9 (P < 0.001) were seen in GBC with respect to CC with significant association among them. MMP9 expression was significantly associated with higher tumor stage but with chemotherapeutic response. Our results display that epithelial-mesenchymal transition type III plays a role in GBC invasion. MMP9 overexpression and loss of membranous beta-catenin may be considered a marker for poor clinical outcomes and advanced disease.

Neuroprotective role of chloroquine via modulation of autophagy and neuroinflammation in MPTP-induced Parkinson's disease.

Parkinson's disease (PD) is a neuro-motor ailment that strikes adults in their older life and results in both motor and non-motor impairments. In neuronal and glial cells, PD has recently been linked to a dysregulated autophagic system and cerebral inflammation. Chloroquine (CQ), an anti-malarial drug, has been demonstrated to suppress autophagy in a variety of diseases, including cerebral ischemia, Alzheimer's disease (AD), and Traumatic brain injury (TBI), while its involvement in PD is still unclear. BALB/c mice were randomly allocated to one of four groups: 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP), CQ treatment with or without MPTP, or control. The CQ treatment group received CQ (intraperitoneally, 8 mg/kg body weight) after 1 h of MPTP induction on day 1, and it lasted for 7 days. CQ therapy preserves dopamine levels stable, inhibits tyrosine hydroxylase (TH) positive dopaminergic cell death, and lowers oxidative stress. CQ reduces the behavioural, motor, and cognitive deficits caused by MPTP after injury. Furthermore, CQ therapy slowed aberrant neuronal autophagy (microtubule-associated protein-1 light chain 3B; LC3B & Beclin1) and lowered expression levels of the inflammatory cytokines interleukin 1 (IL-1ß) and tumour necrosis factor (TNF-α) in the mice brain. In addition, CQ's antioxidant and anti-inflammatory effects were also tested in MPTP-mediated cell death in PC12 cells, demonstrating that CQ has a neurorestorative impact by successfully rescuing MPTP-induced ROS generation and cell loss. Our findings show that CQ's can help to prevent dopaminergic degeneration and improve neurological function after MPTP intoxication by lowering the harmful effects of neuronal autophagy and cerebral inflammation.

A malignant transformation of borderline phyllodes tumor to fibrosarcoma breast: A rare case report.

ABSTRACT: Phyllodes tumor of the breast with malignant transformation to fibrosarcoma of the breast is a rare entity. Breast fibrosarcoma is uncommon, accounting for less than 1% of all breast tumors. Prognosis of fibrosarcoma of the breast is poor. Due to its rarity, survival rates are not defined. A 23-year-old woman presented with a mass in the left breast, and another 48-year-old woman presented with right breast mass. Both patients underwent for surgery. The histological & immunohistochemical examination confirms the diagnosis of a malignant transformation from borderline phyllodes tumor to fibrosarcoma. We concluded that the phyllodes tumor is mostly benign but local recurrence is common. As the tumor progresses toward malignancy, due to the difficulty in the diagnosis of borderline phyllodes tumors, total mastectomy with axillary resection must be recommended.

Histological Spectrum of Post Covid Debridement Tissues: Salient Histomorphological Features With Respect to Identification Fungal Elements.

Background: Secondary bacterial and fungal infections in COVID patients have been documented during current pandemic. The present study provides detailed account of histomorphology of debridement tissue received for suspected fungal infections. The primary objective was to determine the morphological characteristics that must be recognized for the identification of fungal hyphae. Methods: The detailed histological examination of debridement tissue was performed. Demographic and clinical findings with treatment provided was recorded. Presence or absence of necrosis and lecocytoclasis was noted. Results: A total of 110 cases of debrided tissues were included in the study. Eosinophilic granular necrosis with lecocytoclasis was observed in 103cases; fungal elements were identified in 89.3% (92/103) of these. Eleven cases where necrosis was observed, strong suspicion of fungus was reported, 6 of them displayed fungus on KOH preparation, 3 on repeat biopsy. However, in 2 of these cases, neither KOH nor repeat biopsies identified the fungus. Mucor with aspergillus was observed in 7 cases and actinomyces in 3. In all these 10 cases dense fungal colonies were evident. In 7 cases careful observation revealed fruiting bodies of aspergillus. Cotton ball appearance of actinomyces was evident. Mucor infection in current disease was so rampant that aseptate ribbon like branching mucor hyphae were evident on H&E sections. Diabetes was significantly associated with fungal infection (97.2%; 70/72; P < .005). 90% [19/21] of the patients who were on room air and diagnosed with fungal infection were diabetic. Conclusions: Eosinophilic granular necrosis with the presence of neutrophilic debris in a case of suspected fungal disease suggests the presence of fungal elements. This warrants processing of the entire tissue deposited for examination, careful observation, application of fungal stains, and repeat biopsy if clinical suspicion is strong. Moreover, uncontrolled diabetes is more frequently associated with secondary fungal infection in COVID patients as compared to oxygen therapy.

Expression of aldehyde dehydrogenase 1A1 in oral squamous cell carcinoma and its correlation with clinicopathological parameters.

Background: Aldehyde dehydrogenase 1A1 (ALDH1A1) is a key aldehyde dehydrogenase (ALDH) isozyme, related to the cancer stem cells which are responsible for initiating tumor growth, progression, and recurrence. High expression of ALDH1A1 has been reported in several tumor types in humans and its expression is associated with poor prognosis. The aim of this study was to assess the expression of the ALDH1A1 in oral squamous cell carcinoma (SCC) and its correlation with various clinicopathological parameters. Materials and Methods: ALDH1A1 expression was analyzed by using immunohistochemistry on paraffin blocks of 112 cases of primary oral SCC and their corresponding 68 lymph nodes with metastatic deposits. ALDH1A1 expression was also correlated with various clinicopathological parameters. Statistical analysis was done with statistical analysis software, the Statistical Package for the Social Sciences version 21.0. Results: High ALDH1A1 expression was observed in 31.2% of cases of primary oral SCC as compared to 73.5% in lymph node metastasis. A statistically significant difference (P = 0.04) was observed in high TNM stages (68.6%) of the tumor as compared to low TNM stages (31.4%). However, histopathological grades of tumor showed nonsignificant correlation with ALDH1A1 expression (P = 0.093). 40.2% of patients were expired at the end of the study, and the rate of mortality was significantly higher (P = 0.01) in patients with high ALDH1A1 expression as compared to low expression (60.0% vs. 31.2%). Conclusion: High ALDH1A1 expression was associated with higher TNM tumor stage and high nodal stage. It was also associated with high mortality rate which validates it as a marker of invasiveness and poor prognosis in oral SCC.

Anaplastic Intraventricular Meningioma with Rhabdoid Features: An Unusual Tumor with Usual Clinical Presentation.

Meningiomas are tumors arising from leptomeninges. Malignant counterpart of them is known as anaplastic meningioma which are WHO grade III tumors. Intraventricular location of these tumors is rare and is clinic-radiologically challenging. Histopathology and immunohistochemistry are confirmatory. We present case of a 27-year-old girl, who presented with usual symptoms of intraventricular mass in emergency. After shunt surgery, clinical diagnosis of ependymoma was formed with differential of high-grade glioma. Squash tissue was difficult to crush displaying tight clusters of spindle cells with necrosis in background. Definitive histology revealed high grade spindle cell neoplasm disposed in sheets with brisk and atypical mitosis. Only focal whorling pattern was seen. Large cells with eccentric cytoplasm, reminiscent of rhabdoid cells were also seen. Immunohistochemistry was positive for vimentin and EMA, negative for GFAP. Final diagnosis of Anaplastic meningioma was dispatched. The histological pattern of the present case, young age of presentation and presence of Rhabdoid cells make it unusual. Though rare but intraventricular meningiomas must also be kept in clinical radiological differentials apart from the usual ependymoma at this location.

Gastric immature teratoma arising from the lesser curvature of the stomach: A rare case report.

Immature gastric teratoma is an uncommon germ cell tumor of the stomach. A 6-month-old male child was born through full-term vaginal delivery. After 1 month presented with a history of abdominal distension and palpable mass along with a history of Malena for the past 10 days. Computed tomography scan showed the presence of a large well-defined multilobulated solid cystic lesion with multiple calcifications in the abdominopelvic region. Radiological findings were suggestive of germ cell tumors. The exploratory laparotomy findings showed a large tumor mass with variegated consistency arising from the lesser curvature of the posterior wall of the stomach. The total excision of mass and primary closure of the gastric wall was done. Histopathology of excised specimens showed immature teratoma of the stomach. The child is still on follow-up regularly visited as outpatient, doing well day-to-day activity. We report a very rare case of immature gastric teratoma in an infant on the basis of clinicoradiological and pathological findings.

Substituent Effect on the Photophysics and ESIPT Mechanism of N,N'-Bis(salicylidene)-p-phenylenediamine: A DFT/TD-DFT Analysis.

Excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT) processes are widely exploited in the designing of organic materials for multifarious applications. This work explores the aftereffects of combining both ESIPT and ICT events in a single molecule, namely, N,N'-bis(salicylidene)-p-phenylenediamine (BSP) exploiting DFT and TD-DFT formalisms. The PBE0 functional employed in the present study is found to yield results with better accuracy for excited-state calculations. The results reveal that introduction of electron donor (-NH2) and electron acceptor (-NO2) substituents on BSP produces a strikingly red-shifted emission with respect to the corresponding emission from the unsubstituted analogue in polar solvents. This red-shifted emission originated due to the coupled effect of ESIPT and planar-ICT (PICT) processes from the coplanar geometry adopted by the substituted molecule (s-BSP). Based on the computed potential energy curves, the ground-state intramolecular proton transfer (GSIPT) was found to take place more favorably in s-BSP than in BSP under all solvent conditions. In the case of ESIPT, the barrier and relative energies of the phototautomers of s-BSP were slightly higher than BSP, which shows that simultaneous substitution of -NH2 and -NO2 groups causes slight perturbation to the ESIPT process. Overall, the computed results show that simultaneous substitution of suitable electron donor and acceptor substituents provides profitable changes in the photophysical properties of ESIPT molecules like BSP. These molecular-level insights will pave way for designing better materials for diverse applications.

The keto-enol tautomerization of ethyl acetoacetate in choline ionic liquids: the role of cation and anion in switching the tautomeric equilibrium.

In this work, density functional theory (DFT) calculations were carried out to study the role of the explicit treatment of four different choline-based ionic liquids (CS, CP, NS, and NP) by utilizing two different cations and anions in the tautomeric equilibrium of ethyl acetoacetate (EAA). The involvement of the acidic N-H proton from the cationic part of NS and NP ionic liquid offers the possibility to have two more additional transition states for the tautomeric equilibrium of EAA. The computed results demonstrated that a high activation free energy barrier (ΔG = 49.4 kcal mol-1) is associated with the direct enol to keto (E → K) interconversion via a 4-membered ring transition state. Upon explicit involvement of the cationic part of ionic liquids in the tautomeric equilibrium via a 6-membered ring transition state (CAT), ΔG is substantially reduced to 21.88 kcal mol-1. Further, ΔG is drastically reduced to 10.57 kcal mol-1 upon the involvement of the anionic part of the ionic liquid explicitly via an 8-membered ring transition state (AAT). The W-shaped TS in the CAT pathway causes steric hindrance and increases the energy penalty, while the sickle-shaped TS in AAT facilitates easy proton transfer without the influence of the steric factor. In addition, the RDG scatter graphs predict large negative values of ρ*, which indicate that the hydrogen bonding network in AAT is stronger, enhancing the delocalization of the electron density. The QTAIM analysis substantiated the role of intermolecular hydrogen bonding interactions between the ionic liquid and EAA and within the anion-cation pair in stabilizing the keto group of EAA. Besides, the involvement of the acidic N-H proton in the transition state is the key factor in influencing the energetics of the keto-enol tautomerization reaction. The present study illustrates molecular-level insights into the role of individual ions of ionic liquids and also provides adequate ideas for designing novel ionic liquid-based catalysts for industrially relevant chemical reactions.