Quantitative image analysis and polymer blend coalescence

grantor: University of TorontoAn objective method of conducting accurate image segmentation for the measurement of objects of interest in images obtained off-line, as well as in-line, was developed. The method first entails image enhancement to eliminate noise and to enhance the edges of the objects. Next, a sample of the grayscale values that define the object boundaries in the image are selected, and are averaged to yield a global average grayscale value for image segmentation. Off-line images obtained from the Laser Confocal Fluorescence Microscope of the coarsening of quiescent polystyrene/poly(methyl methacrylate) (PS-PMMA) blends were analyzed by image analysis. Evidence for the occurrence of coalescence and Ostwald ripening of the PMMA droplets was found, as well as differences in coalescence for two different PS matrix viscosities. In-line images obtained using the Particle Vision Monitor (PVM), of three size classes of particles representing contaminants, added to polymer flow during extrusion, were studied by image analysis.M.A.Sc

Clinical and histological correlation of diabetic nephropathy

Renal failure in diabetes is a common cause of renal replacement therapy. The affected kidney goes through various changes in all compartments progressively. The classification of diabetic nephropathy is based on glomerular lesions and displays a heterogeneous morphology. Abnormalities in tubulointerstitial and vascular compartments are important in assessing the outcome of these patients. We applied the new pathologic classification of diabetic nephropathy by Tervaert et al to classify the renal damage in diabetes. This is a prospective study over two years. We analyzed 74 renal biopsies in diabetic patients, both type-1 and type-2. Indications for biopsy were rapid onset of proteinuria, absence of retinopathy, presence of hematuria, active urine sediment, and rapid unexplained deterioration of renal function. Biopsy was done to rule out nondiabetic renal disease or any other associated pathology with diabetic nephropathy. In our study, 53 patients were male and 21 patients were female. Age ranged from 27 to 82 years. The mean ± standard deviation age at the time of the biopsy was 54.09 ± 11.59 years. Mean duration of diabetes was 10.2 years. Proteinuria ranged from 1 to 26 g. Type-111 histopathological lesion was the most common lesion observed in our series. There was a correlation between the degree of tubulo-interstitial damage with renal function. There was no correlation between the fundal changes and degree of proteinuria with the histological class of diabetic nephropathy. Application of the classification by Tervaert et al to diabetic lesions reduces the inter-observer variability and also helps in prognosticating and management of patients

Activation of Benzyl Aryl Carbonates: The Role of Cation−π Interactions

Benzyl aryl carbonates can react with a nucleophile to yield an activated electrophile and an aryloxide anion. Previously, we had utilized this in the synthesis of α-nitro esters from nitroalkanes. To further understand the process of activation of these carbonates by nucleophiles, we have performed kinetic studies on the hydrolysis of carbonates using nucleophiles. Rate constants for the hydrolysis were obtained under pseudo-first-order conditions with DABCO as the nucleophile. A comparison of rate constant for hydrolysis of isobutyl phenyl carbonate with benzyl phenyl carbonate shows that the presence of benzyl group results in a 16-fold acceleration of hydrolysis rate. This indicates that the transition state for activation of carbonate is stabilized by cation−π interactions. A comparison of the rate constant for various aromatic rings indicates that electron-donating substituents on the benzyl groups accelerate the rate of hydrolysis. Studies were also carried out with DMAP as nucleophile and the results are presented. Our studies show that stable carbonates can be activated using nucleophiles. Activated acyl groups generated from acid anhydrides have been used in several enantioselective reactions. Our studies show that carbonates can be stable alternatives to acid anhydrides

Focal segmental glomerulosclerosis in renal allografts: Is it possible to diagnose the etiology?

Recurrence of FSGS in renal allo grafts is a major cause of graft loss. In this context, we tried to diagnose and classify FSGS in renal allografts. Indications for biopsy included graft dysfunction and/or proteinuria. Three hundred and sixty-three graft biopsies were studied over a period of 2 years. We classified FSGS into recurrent FSGS, new-onset primary FSGS and FSGS secondary to chronic humoral rejection, calcineurin inhibitor toxicity, and nephron loss and hyperfiltration injury. Twenty-four cases were diagnosed as FSGS, constituting 6.6%. Secondary FSGS was the most common FSGS in grafts in our study. Incidence of recurrent FSGS may not be accurate as pretransplant biopsy is available in very few cases

Thrombotic microangiopathy in renal allografts

Thrombotic microangiopathy (TMA) is a serious complication of renal transplantation. It is a morphological expression of various etiological factors. In a renal allograft, TMA can occur de novo or be a recurrent disease. The aim of this study was to analyze the etiological factors and observe the changing trends of TMA with respect to emerging new etiological factors. We evaluated 131 graft biopsies over a period of 2½ years (2010-2012). All the renal biopsies were formalin fixed, paraffin embedded. Twenty serial sections were studied. Stains routinely used were Hematoxylin and Eosin, Periodic Acid Schiff, Massons Trichrome and Silver Methenamine stains. C4d by immunohistochemical method was done on all graft biopsies. Incidence of TMA in our series was 9.1%. Out of the 12 cases, five were associated with calcineurin inhibitor toxicity, three were diagnosed as acute antibody-mediated rejection, and two were recurrent haemolytic uremic syndrome. One patient developed haemolytic uremic syndrome on treatment with sirolimus and one patient was cytomegalovirus positive on treatment with ganciclovir, developed haemolytic uremic syndrome during treatment course. This study describes a spectrum of etiological factors for thrombotic mciroangiopathy ranging from common cause like calcineurin inhibitor toxicity to rare cause like ganciclovir induced TMA

Nonplanar Perylene Diimides as Potential Alternatives to Fullerenes in Organic Solar Cells

Perylene diimides (PDIs) are attractive alternatives to fullerenes as electron transporters because of their optoelectronic properties, durability, and ease of synthesis. Belying this promise, devices that utilize PDIs as electron acceptors have low efficiencies. The primary deficiency in such cells is the low short circuit current density (<i>J</i>_SC), which is traceable to the crystallinity of PDIs. Therefore, disrupting the crystallinity without adversely impacting the charge-transfer properties of PDIs is proposed as an important design principle. This has been achieved using a nonplanar perylene. In combination with a hole transporting polymer, a device efficiency of 2.77% has been achieved. A 10-fold increase in <i>J</i>_SC is observed in comparison with a planar PDI, resulting in one of the highest <i>J</i>_SC values for a solution processed device featuring a PDI. Indeed, this is one of the highest efficiencies for devices featuring a nonfullerene as the electron transporter

Unusual Reactivity of Nitronates with an Aryl Alkyl Carbonate: Synthesis of α‑Amino Esters

The monoanions of nitroalkanes are ambident nucleophiles that react with carbonate electrophiles through the oxygen atom. Products arising from reactivity at the carbon atom will yield α-nitro esters, which are precursors for α-amino esters. We demonstrate this in the reactions of nitroalkanes with benzyl phenyl carbonate and DABCO where α-nitro esters are obtained instead of nitrile oxides. The products are readily reduced to α-amino esters. This pathway could be a safe alternative to the Strecker reaction

Ferroelectric Polymer Matrix for Probing Molecular Organization in Perylene Diimides

Ferroelectric films of poly­(vinylidene fluoride-<i>co</i>-trifluoroethylene) (PVDF-TrFE) provide a controlled environment to study the aggregation tendency of functional molecules such as perylene diimides (PDIs). The local electric field and free volume confinement parameters offered by the matrix are tailored to study the organizational and assembly characteritics of molecular acceptors. The optical properties of planar and nonplanar PDIs in the ferroelectric polymer matrix were studied systematically over a wide range that encompassed the ferroelectric transition temperature. This approach provides valuable insight into the properties of molecular materials used in applications ranging from bulk heterostructure-based photovoltaics to nonlinear optical materials