Interpenetrating polymer networks based on carboxylated nitrile rubber and poly(alkyl methacrylate)s

A series of interpenetrating polymer networks (IPNs) based on carboxylated nitrile rubber (XNBR) and poly(alkyl methacrylate)s such as poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA) and poly(butyl methacrylate) (PBuMA) were synthesized. The compositions of the IPNs were also varied by changing the swelling time of the rubber in the methacrylate monomer. The tensile and dynamic mechanical properties of the IPNs were studied. The dynamic mechanical properties in the range of 1–10⁵ Hz were obtained by the time‐temperature superposition of the data under multifrequency mode, which indicated high tanδ with good storage modulus in the entire frequency range. This indicates the suitability of these IPNs as vibration and acoustic dampers.     

GABAergic influences on plus-maze behaviour in mice

Manipulations of GABA function have been found to produce highly variable effects in animal models of anxiety. In the present series, an ethological version of the murine elevated plus-maze was used to examine in detail the behavioural profiles of diazepam (1.5 mg/kg; positive control) and a range of GABA-related compounds: valproic acid (100-400 mg/kg), No-711 (1.25-10.0 mg/kg), muscimol (0.5-3.0 mg/kg), (+)bicuculline (4.0-8.0 mg/kg), picrotoxin (0.25-2.0 mg/kg), R(+)baclofen (0.375-3.0 mg/kg) and CGP 35348 (25-200 mg/kg). On both conventional and ethological indices, results confirmed the anxiolytic profile of diazepam under present test conditions, and revealed substantially similar effects for the GABA-T inhibitor, valproic acid (100-400 mg/kg), and the GABAA receptor agonist, muscimol (2 mg/kg). The GABA reuptake inhibitor, No-711, produced weak anxiolytic-like effects at low doses (1.25-2.5 mg/kg) but disrupted behaviour at the highest dose tested (10 mg/ kg). Although the GABAA receptor antagonists, (+)bicuculline and picrotoxin, produced changes indicative of anxiety enhancement, concomitant behavioural suppression was evident at high doses (8 mg/kg and 1-2 mg/kg, respectively). Further studies suggested that the effects observed with bicuculline may be mediated by an active metabolite, such as bicucine. In contrast to the effects of valproic acid and direct GABAA receptor manipulations, the GABAB receptor agonist, R(+) baclofen, non-specifically disrupted behaviour at the highest dose tested (3 mg/kg) while the GABAB receptor antagonist, CGP 35348, was inactive over the dose range studied. Although present data confirm the sensitivity of the plus-maze to agents which modify GABAA receptor function, further studies will be required in order more fully to characterize this relationship.     

Myocardial infarction following electric shock

A 17 year old man presented with a five-month history of swelling of the distal phalanx and a small ulcer on the pulp of the right fifth finger. Despite biopsy the diagnosis was missed until more than six months after onset, when the lesion was excised and histological examination showed a dermal leiomyosarcoma.     

Shape memory properties and unusual optical behaviour of an interpenetrating network of poly(ethylene oxide) and poly(2‐hydroxyethyl methacrylate)

An interpenetrating polymer network (IPN) with shape memory properties was prepared by using poly(2‐hydroxyethyl methacrylate) (PHEMA) and poly(ethylene oxide) (PEO). PHEMA acts as a fixed phase and PEO as a switching phase. The switching action of PEO is due to the reversible process of melting and crystallization. It was observed that the shape recovery of the IPN increases with increasing crosslinker concentration up to an optimum value and decreases thereafter. In addition to the shape memory property, the IPNs show a reversible change in optical properties from translucent to opaque. The change in optical properties is quite different from that observed in a semicrystalline polymer system where the transparency increases as a result of the melting of crystals. This behaviour of the IPN is explained in terms of H‐bonding of PEO with PHEMA. Fourier transform infrared spectroscopy was used to study the H‐bonding between PEO and PHEMA. © 2019 Society of Chemical Industry     

Understanding stability relationships among three curcumin polymorphs

Understanding thermodynamic stability relationship among polymorphs of any active pharmaceutical ingredient (API) is a necessary step for drug formulation development. Knowledge of such relationship enables identification of a stable polymorphic form at the prevalent conditions. Curcumin, a pharmaceutically active ingredient found in herbal spice turmeric, exists in three polymorphic forms; a monoclinic form (Form 1) and two orthorhombic forms (Form 2 and Form 3). However, thermodynamic stability relationships among curcumin polymorphs have not been ascertained yet. This work therefore, was focused on understanding thermodynamic stability relationships among curcumin polymorphs. During purification of curcumin, the pressure applied for vacuum evaporation of organic solvent was found to significantly affect the polymorphic outcome. Form 1 was obtained at pressures ranging from 300 to 400?mbar whereas Form 2 was obtained at pressures ranging from 100 to 200?mbar. Form 3 was obtained by liquid antisolvent precipitation using ultrasound and Bovine Serum Albumin (BSA) as an additive. The obtained polymorphs were characterized by X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC) techniques. Relative stability of polymorphs was established by conducting solvent mediated transformation studies, thermal analysis through DSC and variable temperature X-ray diffraction studies (VT-XRD). It was observed that Form 2 and Form 3 irreversibly convert to Form 1 upon heating. Further, Form 2 and Form 3 convert to Form 1 in aqueous organic solutions at temperatures ranging from 0?°C to 50?°C. Thus, the curcumin polymorphs were found to be monotropically related to each other with the monoclinic form (Form 1) being the most stable form.     

Humidity sensing properties of spray deposited Fe doped TiO2 thin film

In the present work,ferrite (Fe) doped TiO2 thin films with different volume percentage (vol％) were synthesized us-ing a spray pyrolysis technique.The effect of Fe doping on structural properties such as crystallite size,texture coefficient,mi-crostrain,dislocation densities etc.were evaluated from the X ray diffratometry (XRD) data.XRD data revealed a polycrystalline anatase TiO2 phase for sample synthesized up to 2 vol％ and mixed anatase and rutile crystalline phase for sample synthesized at 4 vol％ Fe doped TiO2.The crystalline size was observed to decrease with increase in Fe dopant vol％ and also other structur-al parameters changes with Fe dopant percentage.In the present work,electrical resistance was observed to decrease with a rise in Fe dopant vol％ and temperature of the sample.Thermal properties like temperature coefficient of resistance and activa-tion energy also showed strong correlation with Fe dopant vol％.Humidity sensing properties of the synthesized sample altered with a change in Fe dopant vol％.In the present paper,maximum sensitivity of about 88.7％ for the sample synthes-ized with 2 vol％ Fe doped TiO2 and also the lowest response and recovery time of about 52 and 3 s were reported for the same sample.