A Biomimetic Total Synthesis of the Alkaloid Gracilamine

In 2005 Ünver and Kaya reported that ethanolic extraction of the dried and powdered total plant material derived from Galanthus gracilis, a Turkish member of the Amaryllidaceae family, lead to the isolation of gracilamine and to which the unprecedented structure 1.1 was assigned on the basis of extensive NMR spectroscopic and mass spectrometric analyses. This compound represents the first example of a pentacyclic dinitrogenous alkaloid isolated from the Amaryllidaceae family. It embodies five rings and seven stereocentres. The ethyl ester moiety associated with compound 1.1 is almost certainly an artifact of the isolation process, the naturally occurring alkaloid presumably being either another ester or the corresponding free acid. This rather complex structure together with the author’s previous [BSc(Hons.)] studies made its total synthesis a topic of considerable interest. Chapter One provides a brief introduction to the isolation, structural elucidation, proposed biogenesis, and previous total syntheses of gracilamine. It also details earlier relevant work carried out by the author. Chapter Two details a model study involving a Pd-catalysed intramolecular Alder-ene (IMAE) reaction that delivers a substrate used for testing the crucial intramolecular [3+2]cycloaddition process. By such means the basic framework, 2.24, of gracilamine was established. Chapter Three outlines the difficulties encountered in efforts to extend the abovementioned model studies in establishing a total synthesis of gracilamine. Despite this, one of these “difficulties” could be parlayed in the establishment of a ten-step total synthesis of the racemic modification of the alkaloid (±)-3-O-demethylmacronine (1.68). Chapter Four details the completion of a total synthesis of gracilamine. The final route proceeded in just eleven steps and so representing the shortest route to the title alkaloid reported thus far in this active area of research. Chapter Five presents the experimental procedures and data underpinning all of the work and conclusions detailed in Chapters Two, Three and Four

Many-box locality

There is an ongoing search for a physical or operational definition for quantum mechanics. Several informational principles have been proposed which are satisfied by a theory less restrictive than quantum mechanics. Here, we introduce the principle of "many-box locality", which is a refined version of the previously proposed "macroscopic locality". These principles are based on coarse-graining the statistics of several copies of a given box. The set of behaviors satisfying many-box locality for $N$ boxes is denoted $MBL_N$. We study these sets in the bipartite scenario with two binary measurements, in relation with the sets $\mathcal{Q}$ and $\mathcal{Q}_{1+AB}$ of quantum and "almost quantum" correlations. We find that the $MBL_N$ sets are in general not convex. For unbiased marginals, by working in the Fourier space we can prove analytically that $MBL_{N}\subsetneq\mathcal{Q}$ for any finite $N$, while $MBL_{\infty}=\mathcal{Q}$. Then, with suitably developed numerical tools, we find an example of a point that belongs to $MBL_{16}$ but not to $\mathcal{Q}_{1+AB}$. Among the problems that remain open, is whether $\mathcal{Q}\subset MBL_{\infty}$.Comment: 10 pages, 4 figures, 2 ancillary files; v2: similar to published versio

Demands and Development Strategies for Support Services of Autonomous Learning at Chinese Universities

In recent years, autonomous learning has become one of the most popular ways for Chinese university students to obtain new knowledge and skills, which requires more support services from their affiliated institutions. However, few previous studies combined investigation of the students’ needs and learning support services. Our study conducted online survey to analyze the status quo of Chinese students’ autonomous learning and the much-needed support services from their schools. We sent out the survey in October 2019 and received 458 valid responses. All participants were undergraduate students from 195 universities/colleges in China. The following information was collected: 1. School/Grade/Major of participant; 2. Autonomous learning time/goals/methods/main concerns of these students; 3. Existing support services, e.g., spaces, resources, counseling, procedures, activities; 4. The students’ degree of satisfaction with the available support services. Chinese students showed strong and diversified needs of support services to fulfill their autonomous learning tasks, which cannot be met by their schools. We proposed a development framework and some strategies for higher education institutions in China to launch more innovative learning support services

gem-Dibromocyclopropanes and enzymatically derived cis-1,2-dihydrocatechols as building blocks in alkaloid synthesis

The application of the title building blocks, the 6,6-dibromobicyclo[3.1.0]hexanes and the cis-1,2-dihydrocatechols, to the total synthesis of crinine and lycorinine alkaloids is described.We thank the Australian Research Council and the Institute of Advanced Studies for generous financial support

Biomimetic total synthesis of the pentacyclic Amaryllidaceae alkaloid derivative gracilamine

The illustrated azomethine ylide, produced through a Schiff base condensation of the corresponding aldehyde-containing C3a-arylhexahydroindole with ethyl l-leucinate, engages in a stereoselective intramolecular cycloaddition reaction to give adduct 23 that has been elaborated, over eight steps, into the racemic modification of the alkaloid derivative gracilamine (1). The formation of this ylide and its conversion into isomer 23 mimics the proposed biogenesis of the pentacyclic framework of compound 1.We thank the Australian Research Council and the Institute of Advanced Studies for financial support. N.(Y.)G. is the grateful recipient of a Postgraduate Award provided by the ANU. Dr Benoit Bolte (ANU) is warmly thanked for his invaluable advice throughout the duration of this project

Horizontal Pyramid Matching for Person Re-identification

Despite the remarkable recent progress, person re-identification (Re-ID) approaches are still suffering from the failure cases where the discriminative body parts are missing. To mitigate such cases, we propose a simple yet effective Horizontal Pyramid Matching (HPM) approach to fully exploit various partial information of a given person, so that correct person candidates can be still identified even even some key parts are missing. Within the HPM, we make the following contributions to produce a more robust feature representation for the Re-ID task: 1) we learn to classify using partial feature representations at different horizontal pyramid scales, which successfully enhance the discriminative capabilities of various person parts; 2) we exploit average and max pooling strategies to account for person-specific discriminative information in a global-local manner. To validate the effectiveness of the proposed HPM, extensive experiments are conducted on three popular benchmarks, including Market-1501, DukeMTMC-ReID and CUHK03. In particular, we achieve mAP scores of 83.1%, 74.5% and 59.7% on these benchmarks, which are the new state-of-the-arts. Our code is available on GithubComment: Accepted by AAAI 201

TAG: Boosting Text-VQA via Text-aware Visual Question-answer Generation

Text-VQA aims at answering questions that require understanding the textual cues in an image. Despite the great progress of existing Text-VQA methods, their performance suffers from insufficient human-labeled question-answer (QA) pairs. However, we observe that, in general, the scene text is not fully exploited in the existing datasets -- only a small portion of the text in each image participates in the annotated QA activities. This results in a huge waste of useful information. To address this deficiency, we develop a new method to generate high-quality and diverse QA pairs by explicitly utilizing the existing rich text available in the scene context of each image. Specifically, we propose, TAG, a text-aware visual question-answer generation architecture that learns to produce meaningful, and accurate QA samples using a multimodal transformer. The architecture exploits underexplored scene text information and enhances scene understanding of Text-VQA models by combining the generated QA pairs with the initial training data. Extensive experimental results on two well-known Text-VQA benchmarks (TextVQA and ST-VQA) demonstrate that our proposed TAG effectively enlarges the training data that helps improve the Text-VQA performance without extra labeling effort. Moreover, our model outperforms state-of-the-art approaches that are pre-trained with extra large-scale data. Code is available at https://github.com/HenryJunW/TAG.Comment: BMVC 202

Effects of dispersed fibres in myocardial mechanics, Part I: passive response

It is widely acknowledged that an imbalanced biomechanical environment can have significant effects on myocardial pathology, leading to adverse remodelling of cardiac function if it persists. Accurate stress prediction essentially depends on the strain energy function which should have competent descriptive and predictive capabilities. Previous studies have focused on myofibre dispersion, but not on fibres along other directions. In this study, we will investigate how fibre dispersion affects myocardial biomechanical behaviours by taking into account both the myofibre dispersion and the sheet fibre dispersion, with a focus on the sheet fibre dispersion. Fibre dispersion is incorporated into a widely-used myocardial strain energy function using the discrete fibre bundle approach. We first study how different dispersion affects the descriptive capability of the strain energy function when fitting to ex vivo experimental data, and then the predictive capability in a human left ventricle during diastole. Our results show that the chosen strain energy function can achieve the best goodness-of-fit to the experimental data by including both fibre dispersion. Furthermore, noticeable differences in stress can be found in the LV model. Our results may suggest that it is necessary to include both dispersion for myofibres and the sheet fibres for the improved descriptive capability to the ex vivo experimental data and potentially more accurate stress prediction in cardiac mechanics

A Total Synthesis of (±)-3-O-Demethylmacronine through Rearrangement of a Precursor Embodying the Haemanthidine Alkaloid Framework

A total synthesis of the racemic modification, (±)-2, of the tazettine-type alkaloid 3-O-demethylmacronine is described. The key steps are an intramolecular Alder-ene (IMAE) reaction and a lactam-to-lactone rearrangement of tetracycle 13, a compound that embodies the haemanthidine alkaloid framework.We thank the Australian Research Council for financial support. X.M. is the grateful recipient of a PhD Scholarship provided by the Guangzhou Elite Project of the Guangzhou Municipal Government, People’ s Republic of China

AI Nushu: An Exploration of Language Emergence in Sisterhood -Through the Lens of Computational Linguistics

This paper presents "AI Nushu," an emerging language system inspired by Nushu (women's scripts), the unique language created and used exclusively by ancient Chinese women who were thought to be illiterate under a patriarchal society. In this interactive installation, two artificial intelligence (AI) agents are trained in the Chinese dictionary and the Nushu corpus. By continually observing their environment and communicating, these agents collaborate towards creating a standard writing system to encode Chinese. It offers an artistic interpretation of the creation of a non-western script from a computational linguistics perspective, integrating AI technology with Chinese cultural heritage and a feminist viewpoint.Comment: Accepted for publication at SIGGRAPH Asia 202