Functionalisable cyclopolymers by ring-closing metathesis

Post‐polymerisation modification of polymers is extremely beneficial in terms of designing brand new synthetic pathways toward functional complex polymers. While many chemical groups could provide a platform for chemical functionalisation, arguably one of the most versatile groups is the olefin functionality. This could be significant as the olefins do not readily interfere with common polymerisation techniques such as ring-opening polymerisation (ROP) but can be transformed into a broad range of functional groups. Ring-Closing Metathesis (RCM) is a powerful method for the preparation of cyclic compounds by the formation of new carbon-carbon double bonds. The aim of this project is utilising RCM as a post-polymerisation modification tool for preparing novel functionalisable cyclopolymers. This work includes monomer synthesis, ring-opening polymerisation and post-polymerisation modification. Whereas aliphatic polyethers are highly established polymers and used for an immense variety of applications, stereoregular cyclic architectures of polyethers mimic natural polymers remain rare in synthetic polymer chemistry. Herein we disclosed the formation of a stereocontrolled 1,4-linked six-membered functionalisable cyclopolyether (FCPE) prepared by RCM. Further post-polymerisation modification by diastereoselective dihydroxylation (DH) afforded a novel polymer family encompassing a poly(ethylene glycol) backbone and sugar-like functionalities “PEGose”. The high stereoregularity of FCPE and PEGose produced helical conformation structures. In particular, (R,R) cis PEGose structure has an extended pseudohelical structure similar to amylose. Different ring sizes of cyclopolyethers were sought from two other different starting polymers; poly(epoxy-hexene) (PEH) and poly(divinyl-oxirane) (PDVO). While divinyl oxirane (DVO) and epoxy hexene (EH) were successfully polymerised by ROP, the RCM of PEH gave mainly a cross-linked polymer. The project also attempted to expand the principle to polyesters to afford 1,4-linked six-membered functionalisable cyclopolyesters. To have the desired structure, a novel polymer of poly(vinyl glycolic acid) (PVGA) was made by ROP of a new monomer, 5-vinyl-1,3-dioxolan-4-ones (vinyl-Dox), using an aluminium salen catalyst system. However, the RCM of the last polymer was not completed even after two days of the reaction and gave mainly a cross-linked polymer. Finally, in a collaborative project, ROP of L-thionolactide was reported for the first time using aluminium salen catalysts. The polymerisation was controlled, regioselective and completed within a few hours

Evaluation the effect of high and low viscosity Nano-hydroxylapatite gel in repairing of an induced critical-size tibial bone defect in dogs: Radiolographical study

Many types of bioactive materials are categorized as bone tissue substitutes for reconstruction and regeneration of bone defects, such as nano-hydroxyapatite. The objective of the present study was to radiologically evaluate the bone healing process in experimentally induced tibial defects in dogs treated with two different viscosity concentrations of nano-hydroxyapatite gel. Twelve adult, healthy Mongrel dogs were included. A critical size bone defect of 3–0.7 cm was induced surgically in the lateral border of the tibial bone of the right limb of all dogs enrolled in this study. The dogs were then categorized into two treatment groups: Group 1 (6 dogs): The defect was filled with prepared hydroxyapatite nanogel at a concentration of 33%, and Group 2 (6 dogs) hydroxyapatite nanogel at a concentration of 24% was used as a filling material. The healing process of the tibial defect and associated clinical and radiolographical findings were recorded in all studied groups at 30 and 60 days postoperatively. The results of the current study showed complete healing of the induced defect in the absence of any signs of pain or discomfort. Radiographically, there was an increase in radiographic density in the first group at 60 days. There is continuing healing in the late stage of the bone segment with the surrounding area and a crossing callus with cortical irregularities, denoting a chronic periosteal reaction and a good healing process. In the second group, the defect was completely filled with cortical thickening, which appears denser, denoting a periosteal reaction. In conclusion, using hydroxyapatite nanogel with high viscosity as a bone substitute contributed to progressing bone tissue regeneration with good callus formation and giving perfect mechanical support to defective bone

Cerebrospinal fluid microRNAs as potential biomarkers in Alzheimer’s disease

Alzheimer’s disease (AD) is the leading form of dementia worldwide, but its early detection and diagnosis remain a challenge. MicroRNAs (miRNAs) are a group of small endogenous RNA molecules that regulate mRNA expression. Recent evidence suggests miRNAs play an important role in the five major hallmarks of AD pathophysiology: amyloidogenesis, tauopathy, neuroinflammation, synaptic dysfunction, and neuronal death. Compared to traditional biomarkers of AD, miRNAs display a greater degree of stability in cerebrospinal fluid. Moreover, aberrant changes in miRNA expression can be measured over time to monitor and guide patient treatment. Specific miRNA profiles and combinations may also be used to distinguish AD subjects from normal controls and other causes of dementia. Because of these properties, miRNAs are now being considered as promising and potential biomarkers of AD. This review comprehensively summarizes the diagnostic potential and regulatory roles miRNAs play in AD

Three dimensional echocardiographic imaging of multiple recurrent myxomas

We report a case of a recurrence of 5 cardiac myxomas in both atria with atypical anatomical features difficult to image. Although a multimodality imaging was performed, three-dimensional echocardiography (3DE) was the only technique able to correctly identify all the recurrences and the anatomical characteristics of the myxomas. MRI detected the blood supply of the mass but even after careful review was able to identify only 4 of the 5 lesions. Even though it was already reported the usefulness of 3DE to better delineate the site of attachment of cardiac tumors, it was never reported its sensibility in the setting of multiple myxomas; this case highlights the ability of the 3DE in this challenging scenario and its potential for being considered the key adjunctive modality for the anatomy when advanced surgical plan is required

Olefin cross metathesis and ring-closing metathesis in polymer chemistry

The use of olefin cross metathesis in preparing functional polymers, through either pre-functionalisation of monomers or post-polymerisation functionalisation is growing in both scope and breadth. The broad functional group tolerance of olefin metathesis offers a wealth of opportunities for introducing a broad range of functional groups into the polymer backbone, tuning polymer properties and expanding potential applications. Similarly, ring-closing metathesis offers the ability to tune the polymer macrostructure and microstructure to similar effect. In this review, we explore the importance of understanding selectivity in olefin cross metathesis in designing functional polymers, the manipulation of this reactivity to prepare (multi)functional polymers, and show how polymer systems can be constructed to favour ring closing and change backbone structure and properties

Estimate the Sediment Load Entering the Left Side of Mosul Dam Lake Using Four Methods

Mosul Dam is one of the important dams in Iraq, it suffers like other dams from the problem of sediment accumulation in the lake. The daily surface runoff was estimated from seven main valleys in the left bank of the lake during the period (1/1/1988-31/8/2016) by applying SWAT model. The model performance was assessed using the statistical criteria R2, IOA, NSE and T-Test, the results were good. The averages annual surface runoff from the main valleys to the lake ranged between 3.3*106 m3 to 42.1*106 m3. The daily sediment load was estimated by four methods, Bagnold method was used in SWAT sediments transport simulation, while Yang, Toffaletti methods and Excess Shear Theory were programed by MATLAB, The performance of sediments transport simulation using Bagnlod, Yang and Excess Shear Theory methods was assessed using the same four statistical criteria and the results were good, The averages annual sediment load from the main valleys to the lake were (5.78*103 - 68.62*103), (1.49*104 - 42.13*104), (8.46*103 - 160.77*103) and (4.26*104 - 78.6*104) tons for Bagnold, Yang, Excess Shear Theory and Toffaletti methods, respectively. The valley Jardiam is the main supplier of sediments to the left side of the dam lake with 56%

Gut-Modulating Agents and Amyotrophic Lateral Sclerosis: Current Evidence and Future Perspectives

Amyotrophic Lateral Sclerosis (ALS) is a highly fatal neurodegenerative disorder characterized by the progressive wasting and paralysis of voluntary muscle. Despite extensive research, the etiology of ALS remains elusive, and effective treatment options are limited. However, recent evidence implicates gut dysbiosis and gut–brain axis (GBA) dysfunction in ALS pathogenesis. Alterations to the composition and diversity of microbial communities within the gut flora have been consistently observed in ALS patients. These changes are often correlated with disease progression and patient outcome, suggesting that GBA modulation may have therapeutic potential. Indeed, targeting the gut microbiota has been shown to be neuroprotective in several animal models, alleviating motor symptoms and mitigating disease progression. However, the translation of these findings to human patients is challenging due to the complexity of ALS pathology and the varying diversity of gut microbiota. This review comprehensively summarizes the current literature on ALS-related gut dysbiosis, focusing on the implications of GBA dysfunction. It delineates three main mechanisms by which dysbiosis contributes to ALS pathology: compromised intestinal barrier integrity, metabolic dysfunction, and immune dysregulation. It also examines preclinical evidence on the therapeutic potential of gut-microbiota-modulating agents (categorized as prebiotics, probiotics, and postbiotics) in ALS