Stable DHLA–PEG capped PbS quantum dots: from synthesis to near-infrared biomedical imaging

The short shelf-life of water-soluble quantum dots (QDs) due to colloidal instability represents a major drawback to their exploitation. This work examines the colloidal stability of PbS nanoparticles capped with dihydrolipoic acid–polyethylene glycol (DHLA–PEG) ligands terminated with functional groups such as –NH 2 , –COOH, OMe and –N3 and their application for in vivo imaging. We prove a mechanism of colloidal instability and develop a strategy to produce for the first time stable PEG-capped PbS quantum dots with high quantum yield and optical emission in the first and the second near-infrared (NIR) windows of low absorption of biological tissues. The NIR imaging of in vivo biodistribution is demonstrated at wavelengths 4 1000 nm, with benefits of reduced tissue absorption and light scattering. The stability, biocompatibility and potential for further QD functionalization open up realistic prospects for non-invasive bioimaging applications

Grid Keratotomy for Treatment of Atypical Presenting Indolent Corneal Ulceration in a Boxer

Corneal ulcers are one of the highest causes of vision impairment in dogs. The Boxer breed is particularly predisposed to recurrent and refractory corneal ulcers (Whitley and Gigler, 1999). In this report we present an interesting case of indolent corneal ulcer in a Boxer with atypical clinical manifestation and features, and its successful treatment by grid keratotomy. Boxer ulcers which are also synonymously termed as refractory epithelial erosions, indolent ulcers, recurrent corneal erosions syndrome, rodent ulcers, are superficial corneal ulcers that heal either slowly or poorly (Gelatt 1970, Whitley and Gigler, 1999). Some characteristic features that help to recognize the condition are overlapping lip of non adherent epithelium present around the ulcers edge and stain positive to fluorescein stain and usually occurs bilaterally (Whitley and Gigler, 1999). In our present case the above commonly occurring features were however not present, but after making critical differential diagnosis and considering the breed predisposition the case was identified as an indolent corneal ulcer, and was successfully treated following grid keratotomy. This is an interesting case report on atypical presentation of a boxer ulcer; similar findings have not been reported previously. Keywords: Keratotonmy, Treatment, Corneal ulcer, BoxerNigerian Veterinary Journal 32(2) 201

Anesthesia for Intraocular Surgery in Rabbits

The purpose of the study was to assess a ketamine/xylazine combination along with retrobulbar block using  4% lignocaine HCl for performing intraocular surgery in rabbits. To do so ten healthy adult New Zealand  White rabbits aged 1.5-2 years of either sex weighing 2-3 kgs were selected for unilateral cataract extraction  by phacoemulsification . Xylazine HCl was used as preanesthetic at a dose rate of 5 mg/kg, i.m., followed  by Ketamine HCl at a dose rate of 35mg/kg, i.m. A retro bulbar block was performed with 4% lignocaine  HCL. The anesthetic depth was judged by ear pinching reflex. The time for onset and duration of anesthesia  was found to be 7±0.5 minutes and 35.5±1.2 minutes respectively. A central eyeball fixation following  retro bulbar block was obtained in all the cases. The mean values recorded before induction of anesthesia  and during anesthesia of rectal temperature (38.090C±0.2 vs. 37.290C±0.2), heart rate in beats per minute  (276±1.2 vs.272±1.1), arterial blood pH (7.35±0.02 vs. 7.32±0.02), bicarbonate (16.2±1.2 vs. 20.3±1.8),  PaCo2 (26.09±2.3 vs. 27.52±2.3) and PaO2 (84.79±1.9 vs. 80.39±1.1) did not vary significantly (P>0.05).  Recovery was smooth and complete in 32.5±2.8 minutes. Conclusion: the anesthetic regimen provides adequate condition for conducting intraocular surgery in rabbits.

Dome-Shaped Pituitary Enlargement in Primary Hypothyroidism

We describe three cases of primary hypothyroidism which presented initially to neurosurgery department with pituitary hyperplasia. We have found a novel pattern of ‘dome-shaped’ enlargement of pituitary in MRI of these patients. Out of these 3 patients, in two of them, the planned surgery was deferred when endocrinologists were consulted and the pituitary hyperplasia completely resolved with levothyroxine treatment. In the third case, pituitary surgery was already performed before endocrinology consultation and histopathology revealed thyrotroph hyperplasia. The hyperplastic lesions described typically have a homogenous symmetrical ‘dome’ shaped architecture unlike the non-functioning pituitary adenoma (NFPA), which usually might often be of varying shapes and homogeneity. Analysis of pituitary images from similar case reports published in literature, also showed this typical ‘dome’ shaped pituitary enlargement. This imaging characteristic can be a clue to look for underlying hormone deficiency, especially in primary hypothyroidism. Therefore, a thorough endocrine evaluation especially looking for primary hypothyroidism in such dome-shaped pituitary lesions is mandatory to prevent unwarranted neuro-surgical intervention as treatment of primary hypothyroidism may result in resolution of the abnormal enlargement

Divergent Chemistry of Ditetrelynes (E₂R₂, E = Si, Ge) with Late Transition Metals and Low-valent Silicon Precursors

In modern inorganic chemistry, achieving “gram-scale syntheses” of compounds featuring elements in unusually low oxidation states with unconventional bonding modes continues to be a central goal. Successful isolation of such compounds requires novel synthetic approaches and well-designed sterically demanding substituents to provide kinetic protection. The heavy analogues of alkynes, the “ditetrelynes” stand out as notable examples in this category. They exhibit a trans-bent core with a small HOMO–LUMO gap (∼2 eV) and partial diradical character. This unusual bonding of ditetrelynes renders them intriguing in terms of reactivity, and they have proven effective in small molecule activation, C-C coupling reactions, and even in catalysis. Within this framework, efforts will concentrate on pioneering new synthetic methodologies for the formation of heavier tetrel-element multiple bonds via activation/cleavage of ditetrelynes (E2R2, E = Si, Ge). In this work the high synthetic potential of Ge2Tbb2 and Si2Tbb2 was tested towards metal-carbonyls to synthesize and characterize novel unsaturated metallacycles (1-Co, 1-Rh, 5-Co, 9-Rh, 10-Co, 16-Co, 21-Rh) containing low-valent Si and Ge, and exploring their further reactivity, giving the first examples of inverted-carbene complexes (26-Co and 26-Rh) and a disilacyclopropenone complex (27-Rh). Moving further with the ditetrelyne chemistry, unprecedented bis-tetrylidene (31-Ni), tetrylidene-tetrylidyne (29-Co, 32-Ni), and bis-tetrylidyne (30-Co, 33-Fe, 34-Fe) complexes were synthesized and characterized via “Ge≡Ge” triple bond cleavage of a digermyne at a single metal center (M = Fe, Co, Ni). Finally, using a transition metal free metathesis reaction of a “Ge≡Ge” triple bond, a caacMe-supported germasilyne (35-Si) was synthesized and exploring its unique reactivity led to the isolation of novel compounds such as a cationic silagermavinylidene (39-Si) and a potassium silenide (40-Si). The chemistry of silagermavinylidene helped further to isolate the germasilyne (43-Si), which showed a unique isomerization reaction to its vinylidenic form (44-Si) via caacMe and halide migration. This transformation can be considered as an inverse reminiscent of the FBW-rearrangement in context of heavier tetrel chemistry

Investigation of ion dynamics in mixed network former glasses

The work of this thesis is mainly based on the study of structure and ion dynamics of several new ion conducting glasses and to correlate the macroscopic ion transport properties to the glass network structure and the microscopic lengths. The organization of the thesis is as follows Chapter 1 of this thesis deals with the literature review in the field of glasses. A brief introduction to glasses is presented and their exotic features are discussed. The network structures of different type of glasses are briefly discussed. Several theoretical models and concepts used to explain and understand the ion dynamics are pointed out. Finally the scope of the thesis is presented. In chapter 2 a brief description of the preparation technique of glasses and glassnanocomposites and various experimental methods used to characterize them are presented. In the initial part of the chapter the structural characterization such as density, x-ray diffraction (XRD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) and Fourier transform infrared (FTIR) spectroscopy techniques are discussed. In the later part, electrical characterization techniques used to study the ion dynamics are presented. In Chapter 3 the structural and electrical properties of xAgI-(1-x)(0.3Ag2O- 0.7(0.5SeO2-0.5MoO3)) glasses have been investigated. The structural characterizations of these glasses have been carried out using XRD, FTIR spectroscopy etc. and the thermal study has been done using Differential Scanning Calorimeter. The Ag+ ion dynamics in the glasses has been investigated in a broad frequency range from 10Hz – 2MHz and in wide temperature range. The dc conductivity and the microscopic lengths obtained from the linear response theory have been correlated to the glass network structure. Chapter 4 deals with the study of mixed former effect and dynamics of Ag+ ions of xAgI-(1-x)(0.3Ag2O-0.7(ySeO2-(1-y)MoO3)) glasses. The glass formation has been confirmed using XRD. The thermodynamic properties of these glasses have been explored using DSC. The modification of the glass network structure has been analyzed using deconvolution of the FTIR spectra. The ionic conductivity of these glasses has been compared to that of the undoped silver selenomolybdate glasses. The study of relaxation dynamics in these glasses has been performed in the framework of the conductivity and the electric modulus formalism. The characteristic lengths obtained from the conductivity and dielectric spectra have been correlated to the modification of the glass network structure. In chapter 5 the study of mixed former effect and ion dynamics in silver ion conducting mixed network former glasses of composition yAg2O-(1-y)(xSeO2-(1-y))TeO2 are presented in wide composition and temperature ranges. The glass network structures and structural modification depending on composition has been investigated using FTIR spectroscopy. The ion dynamics in these mixed former glasses has been studied using the conductivity formalism as a function of frequency and temperature. The correlation of ion transport properties to the microscopic length scales and the glass network structure has been established. In chapter 6 the Ag+ ion dynamics in xAgI-(1-x)(yAg2O-(1-y)(0.5SeO2-O.5TeO2)) mixed network former glasses for different modifier content is presented. The thermal properties of these glasses have been studied using DSC. The relative concentrations of different network structural units have been determined from the de-convolution of the FTIR spectra. The ac conductivity has been investigated taking the contribution of the electrode-sample interface. The length scales of ion dynamics, such as characteristic mean square displacement and spatial extent of sub-diffusive motion of silver ions have been determined from the ac conductivity and dielectric spectra respectively in the framework of linear response theory. A direct correlation between the ion dynamics and the characteristic length scales and the glass network structure has been established for different compositions of the selenium-tellurite glasses. In Chapter 7 the summary of the thesis is presented. The possible future research in continuation of this work is also highlighted.Research was carried out under the supervision of Prof. Aswini Ghosh of Solid State Division under SPS [School of Physical Sciences]Research was conducted under DST grant and IACS fellowshi