Stereoselective Synthesis Of Legionaminic Acid And Pseudaminic Acid Glycosides

Legionaminic acid (Leg) and pseudaminic acid (Pse) are deoxy acetamido analogues of the most common sialic acid, N-acetylneuraminic acid (NeuAc) that are found in microorganisms. Leg and Pse are rare but important class of sialic acids, as their glycosides are found in lipopolysaccharides and glycoproteins of several pathogenic Gram-negative bacteria including Pseudomonas aeruginosa, Legionella pneumophila serogroup 1, Campylobacter jejuni, and Campylobacter coli. As such, the stereoselective glycosylation of the equatorial Leg and Pse donors, and the role played by their side chain conformations in anomeric reactivity and selectivity are the focus of this thesis. Chapter two describes the synthesis of a Leg donor in 15 straightforward steps and 17% overall yield from the commercially available N-acetylneuraminic acid. The synthesized legionaminic acid donor showed excellent equatorial selectivity when glycosylated with various primary, secondary and tertiary acceptors when using NIS/TfOH as activator at -78 ºC in 1:2 acetonitrile/dichloromethane. The selectivity was, nevertheless, less than the 5-azido NeuAc donro synthesized in Chpater three. The 9-deoxy nature of the side chain made the donor less disarming and afforded greater oxocarbenium-like character in the transition state, a major factor attributing to some loss in the glycosylation selectivity. Chapter three describes the synthesis of an intermediate 5-epi-NeuAc donor having the same C-5 configuration as pseudaminic acid. The glycosylation reactions of various primary and secondary alcohols including a sialic acid based acceptor with this donor under the standard glycosylation reaction conditions gave exquisite equatorial selectivity. Conformational analysis reveals the side chain of the donor to have undergone a conformational change from the predominant gg- to the less active gt-conformation in order to avoid the steric and dipolar repulsion between the C5-N5 bond and the side chain. This change in conformation offsets the negative effect of the axial azide at the 5-position. Additionally, the stereoselective synthesis of the NeuAc glycosides obtained from the 5-azido NeuAc donor was in apparent contradiction to the selectivity observed for the various literature 5-azido NeuAc donors, and showcased the importance of low temperature (-78 ºC) in the control of glycosylation selectivity. Chapter four describes the synthesis of a pseudaminic acid donor in 20 steps and 5% overall yield from the commercially available N-acetylneuraminic acid. Glycosylation reactions of various primary and hindered secondary alcohols under the standard glycosylation reaction conditions gave exquisite equatorial selectivity and good to excellent yields. The excellent selectivity observed is attributed to the inversion of configuration at the 5- and 7-positions, which creates a strong dipolar and steric repulsion between the C5-N5 bond and the side chain. To avoid this, the donor undergoes a conformational change from the predominant gg- to the least active tg-conformation and and is rendered more selective in the glycosylation reaction. For selected glycosides, regioselective reductions of the azides were performed to afford deprotected glycosides with differentially blocked amines, suitable for accessing the bacterial lipopolysaccharides. Chapter five includes the overall conclusion of the dissertation, which is followed by the detailed experimental procedures employed in synthesizing all the sialic acid derivatives in chapter six

A trade-based approach for defects management in residential construction

This project aims to understand how to manage defects in single and two storey residential projects in Queensland taking a trade-based approach given that most work is subcontracted. Despite various construction acts, regulations, standards, codes, licensing regimes, other management approaches such as quality management, risk management, defect management, building are still handed with defects. In developed countries such as Australia, subcontractors do most of the on-site work. However, despite subcontractor or trade contractor being the specialists in the specific area, there are yet many problems associated with subcontractors. It is this phenomenon that led to the further investigation in this area. Although Queensland Building and Construction Commission (QBCC) produces the list of top ten defects each year in its annual report, due to some of its limitations, it does not provide the whole picture of defects actually occurring in this industry. Thus it was deemed necessary to conduct a risk analysis of various trades used in residential construction. An online questionnaire survey was chosen as a research method, which was further divided into two stages. For the first stage, a qualitative risk analysis adopted from Project Management Body of Knowledge was undertaken to identify the troublesome trades. After the identification of the troublesome trades, second stage survey was undertaken to identify the strategies that would assist in minimising defects for those troublesome trades. After receiving the ethics approval from University of Southern Queensland ethics committee, the questionnaire was distributed to approximately 500 participants. Unfortunately only 24 (4.8%) responses were received for the first stage survey and only 14 (2.8%) responses were received for the second stage survey. The main finding from the first stage survey was the identification of high-risk trades. Out of thirty-four trades used in the first stage survey, three trades were identified as high-risk trades, which are as follows: • Waterproofing • Concreting • Swimming pool construction, maintenance and installation With this knowledge, potential mitigation techniques could be implemented in construction to assist in minimising defects. The second survey identified that the majority of respondents believe that the licensing regime should be tightened for trades such as waterproofing and Swimming pool construction, installation and maintenance. For Concreting trade majority of respondents choose payment of work done should only be made after receiving relevant certificates from building certifier. For Painting and Decorating trade respondent believed that there is a need to grade trade contractor as Grade 1,2 etc. (to motivate subcontractors for better performance). Further research on the feasibility of introducing the grading system for subcontractors and further study on how licencing system could be tightened for high-risk trades is proposed through this project

Ancient Himalayan wolf (Canis lupus chanco) lineage in Upper Mustang of the Annapurna Conservation Area, Nepal

The taxonomic status of the wolf (Canis lupus) in Nepal’s Trans-Himalaya is poorly understood. Recent genetic studies have revealed the existence of three lineages of wolves in the Indian sub-continent. Of these, the Himalayan wolf, Canis lupus chanco, has been reported to be the most ancient lineage historically distributed within the Nepal Himalaya. These wolves residing in the Trans-Himalayan region have been suggested to be smaller and very different from the European wolf. During October 2011, six fecal samples suspected to have originated from wolves were collected from Upper Mustang in the Annapurna Conservation Area of Nepal. DNA extraction and amplification of the mitochondrial (mt) control region (CR) locus yielded sequences from five out of six samples. One sample matched domestic dog sequences in GenBank, while the remaining four samples were aligned within the monophyletic and ancient Himalayan wolf clade. These four sequences which matched each other, were new and represented a novel Himalayan wolf haplotype. This result confirms that the endangered ancient Himalayan wolf is extant in Nepal. Detailed genomic study covering Nepal’s entire Himalayan landscape is recommended in order to understand their distribution, taxonomy and, genetic relatedness with other wolves potentially sharing the same landscape

Experimental demonstration of diffusion limitations on resolution and SNR in MR microscopy

Magnetic resonance microscopy images at cellular resolution (< 10 microns) are limited by diffusion. SNR and spatial resolution suffer from the dephasing of transverse magnetization caused by diffusion of spins in strong gradients. Such effects may be reduced by using phase encoding instead of frequency encoding readout gradients. Demonstration of the benefits of phase encoding are lacking, and the conditions in which it is preferred are not clearly established. We quantify when phase encoding outperforms a readout gradient with emphasis on the detrimental effects of diffusion on SNR and resolution. A 15.2T MRI scanner, with 1 T/m gradients, and micro solenoid RF coils < 1 mm in diameter, were used to quantify diffusion effects on resolution and SNR of frequency and phase encoded acquisitions. Frequency and phase encoding resolution and SNR per square root time were calculated and measured for images at the diffusion limited resolution. The point-spread-function was measured for phase and frequency encoding using additional constant time gradients with voxels 3-15 microns. The effect of diffusion during the readout gradient on SNR was experimentally demonstrated. The achieved resolutions of frequency and phase encoded acquisitions were measured via the point-spread-function. SNR per square root time and actual resolution were calculated for a wide range of gradient amplitudes, diffusion coefficients, and relaxation properties. The results provide a practical guide on how to choose between phase and frequency encoding. Images of excised rat spinal cord at 10 x 10 microns in-plane demonstrate benefits of phase encoding in the form of higher measured resolution and SNR vs the same image acquired with a conventional readout. We demonstrate the extent to which phase encoding outperforms readout gradients in SNR and resolution over a wide range of voxel sizes, sample, and hardware properties.Comment: 36 pages, 9 figures, 1 table, and 4 supplemental figures. Submitted to Journal of Magnetic Resonance; cleaned up metadata, fixed heading typ

Role of AIM2 Inflammasome in Pulmonary Host Defense Against Staphylococcus aureus-induced Pneumonia

Bacterial pneumonia is the leading cause of death in children under the age of five, claiming the lives of two million children each year. Staphylococcus aureus is the extracellular Gram-positive bacteria that causes necrotizing pneumonia. Moreover, the spread of antibiotic-resistant and hypervirulent strains has made treatment more challenging. Absent in melanoma 2 (AIM2) is a dsDNA-sensing cytosolic innate immune receptor that activates inflammasomes and is crucial for host defense against intracellular bacteria and DNA viruses. However, its role in extracellular bacterial pathogen-induced pneumonia is unclear. Therefore, understanding how AIM2 initiates host responses during Staphylococcus aureus is crucial for the development of novel therapeutics as well as prevention strategies. To investigate more about how the AIM2 inflammasomes regulate host defense against S. aureus infection, we used C57BL6 (wild-type) and AIM2 gene-deficient (AIM2-/-) mice in an S. aureus-induced pneumonia model. In this model, AIM2-/- mice exhibit lower bacterial counts in lungs, BALF, and extrapulmonary organs (liver and spleen) compared to wild-type (WT) mice. In addition, there was an increase in immune cells (neutrophils and macrophages) in BALF of AIM2-/- mice compared to WT. Pro-inflammatory cytokines, including IFN-γ and TNF-α, were also found to be increased in AIM2-/- mice; however, interestingly, IL-6 was found to be lower in AIM2-/- mice than in WT. Further, an intracellular killing experiment revealed that AIM2-/- bone marrow macrophages and neutrophils have an increased ability to clear bacteria compared to their WT counterparts. These findings suggest that the AIM2 inflammasome has a negative regulatory role in S. aureus-induced pneumonia

A trade-based risk management approach towards the elimination of defects in residential construction

The construction industry seems to have settled down to a level of inefficiency saddled with a culture of handing over buildings with defects with mechanisms for dealing with patent, latent, serial and other defects. While it is important to understand direct and root causes of defects, the key to success lies in implementing strategic solutions in an environment where subcontracting is rampant: Accordingly, this study takes a trade-based risk management approach to identify problematic trades by undertaking a risk assessment. While Queensland Building Construction Commission’s top ten defects provide an indication of what such trades may be, this study argues that it fails to provide a comprehensive overview of the defects regime related to single and two-storey houses, therefore, this study focusses on all 34 trades that requires a license to practice. Trades that are high risk, moderately high risk, and moderately risky have been identified through an on-line questionnaire survey sent to approximately 500 respondents which seek information on the likelihood and the impact of defects for each licensed trade including reasons for high risks. The scores received are translated to risk levels and multiplied together to arrive an overall risk score which is classified into high, moderate, and low risk using a risk classification matrix. Accordingly, 14 problematic trades have been identified with Waterproofing being the riskiest trade followed by Swimming Pool Construction and Concreting. The study emphasises the value of this approach to practitioners and regulators to develop strategies for ensuring buildings are defect free

Vision-based intelligent path planning for SCARA arm

This paper proposes a novel algorithm combining object detection and potential field algorithm for autonomous operation of SCARA arm. The start, obstacles, and goal states are located and detected through the RetinaNet Model. The model uses standard pre-trained weights as checkpoints which is trained with images from the working environment of the SCARA arm. The potential field algorithm then plans a suitable path from start to goal state avoiding obstacle state based on results from the object detection model. The algorithm is tested with a real prototype with promising results

Correlation of Imaging Findings with Molecular Subtypes of Breast Cancer

Background: Ultrasound and Mammography are first-line imaging in breast cancer. The management of malignant breast lesions depends on molecular biomarkers in the tumor cells. This study aims to correlate different imaging findings in breast carcinoma with immune-histology subtypes. Methods: The study was a retrospective study conducted between 2018 January to 2021 December. Patients with malignant breast lesions who underwent USG-guided biopsy of breast lesions were included in the study. Ultrasound and mammographic findings of these patients were retrieved in PACS and analyzed. Malignant breast lesions were classified according to molecular markers into Luminal A, Luminal B, Her- 2 enriched, and triple-negative breast cancers. The correlation between imaging findings and molecular subtypes of breast cancer was analyzed. Results: A total of 42 patients were included in the study. The mean age of the patients in our study was 52.24+/-13.54 years with median of 51 years (IQ range-19.5 years). The most common IHC subtype was Luminal type B (22, 52.4%), followed by triple negative (15, 35.7%), luminal type A (4, 9.5%) and least common was Her-2 enriched (1, 2.4%). Mammogram was non-diagnostic in 9.5% of case. Oval shape and well marginated margin in ultrasound were more frequently associated with triple negative breast cancer than other subtypes (P<0.05). Rest of the characteristics of triple negative and other malignancies were not significantly difference in our study. No significant difference is noted between mammographic findings between various subtypes. Conclusions: Triple negative breast cancer was more common in our population than in the west. Triple-negative breast cancers are more frequently well-defined and oval in shape mimicking benign lesions. Keywords: Breast cancer; mammography; molecular subtypes; ultrasoun

Stereoselective Synthesis of the Equatorial Glycosides of Legionaminic Acid

The synthesis of a legionaminic acid donor from <i>N</i>-acetylneuraminic acid in 15 steps and 17% overall yield is described. Activation of the adamantanyl thioglycoside in the donor with <i>N</i>-iodosuccinimide and trifluoromethanesulfonic acid in dichloromethane and acetonitrile at −78 °C in the presence of primary, secondary and tertiary alcohols affords the corresponding glycosides in excellent yield and good to excellent equatorial selectivity. In particular, coupling to the 4-OH of a suitably protected neuraminic acid derivative affords a disaccharide that closely resembles the glycosidic linkage in the polylegionaminic acid from the lipopolysaccharide of the <i>Legionella pneumophila</i> virulence factor. A straightforward deprotection sequence enables conversion of the protected glycosides to the free <i>N</i>,<i>N</i>-diacetyllegionaminic acid glycosides

Multiple tracheobronchial diverticula in a post‐TB patient: A case report

Abstract The presence of multiple tracheal and bronchial diverticula is a rare condition. We present a case of a 22‐years old non‐smoker male with a history of pulmonary tuberculosis, having multiple tracheal and bronchial diverticula along with other common sequelae such as stenosed and collapsed upper lobe bronchi