Essays on financial frictions: China and rest of the world

This thesis studies the role of financial frictions in shaping the consumption and investment behavior in China and its implications on rest of the world. The first chapter uses a panel of Chinese individual level data to show that the inability to borrow against future labour income forces a significant portion of individuals to deviate from a smooth consumption path over the life cycle, which they would otherwise follow. Financial frictions also affect the Chinese corporate sector. The second chapter relates China's current account surplus, as well as productivity differential between state-owned (SOEs) and privately-owned enterprises (POEs), to differences in access to finance. I consider an open- economy DSGE model of the Chinese economy with two productive sectors. I model SOEs and POEs as start-ups which need to borrow in order to begin production. Following a policy-induced asymmetric shock to the borrowing constraints, SOEs are on average less productive than POEs. Because of the lower hurdle rate for investment they face, SOEs end up creating more investable assets than POEs, while, due to more constrained credit availability, POEs save more and invest less than SOEs. In aggregate, this simple mechanism implies investment (driven by less productive SOEs) does not keep up with savings (driven by more productive POEs), resulting in a current ac- count surplus. Furthermore, the savings of Chinese POEs owners in search of investable foreign assets put downward pressure on the world long run real interest rate. In the third chapter, I move from China to an international perspective. This chapter constructed a measure of financial frictions for 41 emerging economies (EMs) between 1995 and 2008 in order to shed light on common factors across countries. Finally, Chapter four shows econometrically that financial frictions pose a serious danger to EMs, by reducing long run economic growth, raising the probability of a crisis, and leading to asset bubbles. Consistent with Chapter 2, I confirm that financial fractions can also help explain the current account position of EMs

Weighted gene co-expression network analysis and CIBERSORT screening of key genes related to m6A methylation in Hirschsprung’s disease

Hirschsprung’s disease (HSCR) is a neural crest disease that results from the failure of enteric neural crest cells (ENCCs) to migrate to the corresponding intestinal segment. The RET gene, which regulates enteric neural crest cell proliferation and migration, is considered one of the main risk factors for HSCR and is commonly used to construct HSCR mouse models. The epigenetic mechanism of m6A modification is involved in HSCR. In this study, we analyzed the GEO database (GSE103070) for differentially expressed genes (DEGs) and focused on m6A–related genes. Comparing the RNA-seq data of Wide Type and RET Null, a total of 326 DEGs were identified, of which 245 genes were associated with m6A. According to the CIBERSORT analysis, the proportion of Memory B-cell in RET Null was significantly higher than that of Wide Type. Venn diagram analysis was used to identify key genes in the selected memory B-cell modules and DEGs associated with m6A. Enrichment analysis showed that seven genes were mainly involved in focal adhesion, HIV infection, actin cytoskeleton organization and regulation of binding. These findings could provide a theoretical basis for molecular mechanism studies of HSCR

DUET: A Generic Framework for Finding Special Quadratic Elements in Data Streams

Finding special items, like heavy hitters, top-k, and persistent items, has always been a hot issue in data stream processing for web analysis. While data streams nowadays are usually high-dimensional, most prior works focus on special items according to a certain primary dimension and yield little insight into the correlations between dimensions. Therefore, we propose to find special quadratic elements to reveal close correlations. Based on the items mentioned above, we extend our problem to three applications related to heavy hitters, top-k, and persistent items, and design a generic framework DUET to process them. Besides, we analyze the error bound of our algorithm and conduct extensive experiments on four data sets. Our experimental results show that DUET can achieve 3.5 times higher throughput and three orders of magnitude lower average relative error compared with cutting-edge algorithms

N6-methyladenosine RNA modification promotes viral genomic RNA stability and infection

Molecular manipulation of susceptibility (S) genes that are antipodes to resistance (R) genes has been adopted as an alternative strategy for controlling crop diseases. Here, we show the S gene encoding Triticum aestivum m(6)A methyltransferase B (TaMTB) is identified by a genome-wide association study and subsequently shown to be a positive regulator for wheat yellow mosaic virus (WYMV) infection. TaMTB is localized in the nucleus, is translocated into the cytoplasmic aggregates by binding to WYMV NIb to upregulate the m(6)A level of WYMV RNA1 and stabilize the viral RNA, thus promoting viral infection. A natural mutant allele TaMTB-SNP176C is found to confer an enhanced susceptibility to WYMV infection through genetic variation analysis on 243 wheat varieties. Our discovery highlights this allele can be a useful target for the molecular wheat breeding in the future

Managing External Volatility: Policy Frameworks in Non-Reserve-Issuing Economies

Since the Global Financial Crisis, non-reserve-issuing economies (NREs) have been highly sensitive to episodes of external pressures. With monetary policy independence constrained by this sensitivity, many NREs have utilized other policy instruments. This paper confirms the vulnerability of NREs to external shocks and finds that, in some circumstances, managing such shocks with multiple instruments can both lessen the policy response required from any one policy tool to financial and external shocks and increase the effectiveness of policies in stabilizing macrofinancial conditions. Effectiveness, however, does not always imply appropriateness, which rests on an evaluation of potential trade-offs and unintended consequences

Genome Assembly and Annotation of a High-Polymalic Acid (PMLA) Producing Strain Aureobasidium melanogenum CGMCC18996 and Analysis of Its Key Proteins Related to PMLA Synthesis

In this study, we applied PacBio Sequel II and Illumina NovaSeq 6000 sequencing platforms to sequence the genome of a high-polymalic acid (PMLA)-producing strain, Aureobasidium melanogenum CGMCC18996, and used different assemblers to obtain a high-quality genome assembly, which was then annotated using transcriptomic data. The results indicated a total of 6 202 genes were found in the A. melanogenum genome, mainly involved in carbohydrate transport and metabolism, amino acid transport and metabolism, post-translational modification, RNA processing and modification. Meanwhile, functional annotation revealed that most genes in the genome were related to peroxisome in the strain. Transmission electron microscopy (TEM) indicated the existence of a circular peroxisome-like (glyoxysome) structure in the cells, demonstrating the ability to malic acid through the glyoxylate cycle. Finally, we predicted the protein structures of two enzymes related to PMLA biosynthesis, phosphoenolpyruvate carboxykinase (PCKA) and malate synthase (MASY). It was found that the enzymes could have the ability to synthesize malic acid. This study could provide a reference for metabolism regulation in A. melanogenum for improved PMLA production, and the assembled genome has been uploaded to the database, which could provide the basis for the future development and utilization of A. melanogenum CGMCC18996

Spatiotemporal dynamic of subtropical forest carbon storage and its resistance and resilience to drought in China

Subtropical forests are rich in vegetation and have high photosynthetic capacity. China is an important area for the distribution of subtropical forests, evergreen broadleaf forests (EBFs) and evergreen needleleaf forests (ENFs) are two typical vegetation types in subtropical China. Forest carbon storage is an important indicator for measuring the basic characteristics of forest ecosystems and is of great significance for maintaining the global carbon balance. Drought can affect forest activity and may even lead to forest death and the stability characteristics of different forest ecosystems varied after drought events. Therefore, this study used meteorological data to simulate the standardized precipitation evapotranspiration index (SPEI) and the Biome-BGC model to simulate two types of forest carbon storage to quantify the resistance and resilience of EBF and ENF to drought in the subtropical region of China. The results show that: 1) from 1952 to 2019, the interannual drought in subtropical China showed an increasing trend, with five extreme droughts recorded, of which 2011 was the most severe one; 2) the simulated average carbon storage of the EBF and ENF during 1985-2019 were 130.58 t·hm-2 and 78.49 t·hm-2, respectively. The regions with higher carbon storage of EBF were mainly concentrated in central and southeastern subtropics, where those of ENF mainly distributed in the western subtropic; 3) The median of resistance of EBF was three times higher than that of ENF, indicating the EBF have stronger resistance to extreme drought than ENF. Moreover, the resilience of two typical forest to 2011 extreme drought and the continuous drought events during 2009 - 2011 were similar. The results provided a scientific basis for the response of subtropical forests to drought, and indicating that improve stand quality or expand the plantation of EBF may enhance the resistance to drought in subtropical China, which provided certain reference for forest protection and management under the increasing frequency of drought events in the future

Polycrystalline {\gamma}-boron: As hard as polycrystalline cubic boron nitride

The Vickers hardness of polycrystalline {\gamma}-B was measured using a diamond indentation method. The elastic properties of polycrystalline {\gamma}-B (B=213.9 GPa, G=227.2 GPa, and E=503.3 GPa) were determined using ultrasonic measurement at ambient condition. Under the loading force up to 20 N, our test gave an average Vickers hardness in the asymptotic-hardness region of 30.3 GPa. The average fracture toughness was measured as 4.1MPa m1/2. Additionally, We also measured the hardness and elastic properties of polycrystalline {\beta}-B and PcBN for comparison. The hardness and elastic properties for polycrystalline {\gamma}-B was found to be very close to that of PcBN. Our results suggest that the polycrystalline {\gamma}-B could be a superhard polycrystalline material for industrial applications.Comment: 16 page

Genomic Analyses Reveal Mutational Signatures and Frequently Altered Genes in Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most common cancers worldwide and the fourth most lethal cancer in China. However, although genomic studies have identified some mutations associated with ESCC, we know little of the mutational processes responsible. To identify genome-wide mutational signatures, we performed either whole-genome sequencing (WGS) or whole-exome sequencing (WES) on 104 ESCC individuals and combined our data with those of 88 previously reported samples. An APOBEC-mediated mutational signature in 47% of 192 tumors suggests that APOBEC-catalyzed deamination provides a source of DNA damage in ESCC. Moreover, PIK3CA hotspot mutations (c.1624G>A [p.Glu542Lys] and c.1633G>A [p.Glu545Lys]) were enriched in APOBEC-signature tumors, and no smoking-associated signature was observed in ESCC. In the samples analyzed by WGS, we identified focal (<100 kb) amplifications of CBX4 and CBX8. In our combined cohort, we identified frequent inactivating mutations in AJUBA, ZNF750, and PTCH1 and the chromatin-remodeling genes CREBBP and BAP1, in addition to known mutations. Functional analyses suggest roles for several genes (CBX4, CBX8, AJUBA, and ZNF750) in ESCC. Notably, high activity of hedgehog signaling and the PI3K pathway in approximately 60% of 104 ESCC tumors indicates that therapies targeting these pathways might be particularly promising strategies for ESCC. Collectively, our data provide comprehensive insights into the mutational signatures of ESCC and identify markers for early diagnosis and potential therapeutic targets

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead