15 research outputs found

    Emerging Memory System Design to Improve Memory Reliability and Energy Efficiency

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    Fabrication technology scaling has drastically improved DRAM cell density and thus capacity. However, because shrinking memory cells are less stable and reliable than before, the trend also negatively impacts memory system reliability, security, energy efficiency, and performance. This thesis defense will present three research works to help address those challenges. First, we have designed discreet-PARA, a novel defense mechanism against DRAM rowhammer attacks. The latter is a new security attack that exploits weak DRAM cells by disturbing them with intensive memory accesses to their neighbor rows. The proposed design uses a hybrid of the existing counter-based approach and probabilistic approach. It has very high defense strength, low performance overhead, meanwhile, a small and fixed hardware overhead. It is the first one of this type. Second, we identified a disturbance correlation problem for ECC memory under the rowhammer attack and then proposed a highly efficient scheme to break this correlation. With this new scheme, ECC becomes another layer of defense against rowhammer attacks, drastically improving the overall defense strength. Finally, to address the ever-increasing DRAM refresh energy consumption in high-density DRAM memories, we have designed adaptive dual-refresh, a retention-aware DRAM refresh mechanism. It uses dual and independent refresh mechanisms, namely auto-refresh and target refresh, for DRAM cells of short and long retention times, respectively. The design is novel in that it can make fine-grain adjustments to the auto-refresh period for a given DRAM memory system to maximize energy-saving

    Transcriptomic Analysis of Red-Fleshed Apples Reveals the Novel Role of MdWRKY11 in Flavonoid and Anthocyanin Biosynthesis

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    In plants, flavonoids are important secondary metabolites that contribute to the nutritional quality of many foods. Apple is a popular and frequently consumed food because of its high flavonoid content. In this study, flavonoid composition and content were detected and compared between red- and white-fleshed apples in a BC<sub>1</sub> hybrid population using ultraperformance liquid chromatography–quadrupole time-of-flight mass spectrometry. Transcriptomic analysis of the red- and white-fleshed apples was then performed using RNA-seq technology. By screening differentially expressed genes encoding transcription factors, we unearthed a WRKY-family transcription factor designated MdWRKY11. Overexpression of MdWRKY11 promoted the expression of <i>F3H</i>, <i>FLS</i>, <i>DFR</i>, <i>ANS</i>, and <i>UFGT</i> and increased the accumulation of flavonoids and anthocyanin in apple calli. Our findings explored the novel role of MdWRKY11 in flavonoid biosynthesis and suggest several other genes that may also be potentially involved. This provides valuable information on flavonoid synthesis for the breeding of elite red-fleshed apples

    Transcriptomic Analysis of Red-Fleshed Apples Reveals the Novel Role of MdWRKY11 in Flavonoid and Anthocyanin Biosynthesis

    No full text
    In plants, flavonoids are important secondary metabolites that contribute to the nutritional quality of many foods. Apple is a popular and frequently consumed food because of its high flavonoid content. In this study, flavonoid composition and content were detected and compared between red- and white-fleshed apples in a BC<sub>1</sub> hybrid population using ultraperformance liquid chromatography–quadrupole time-of-flight mass spectrometry. Transcriptomic analysis of the red- and white-fleshed apples was then performed using RNA-seq technology. By screening differentially expressed genes encoding transcription factors, we unearthed a WRKY-family transcription factor designated MdWRKY11. Overexpression of MdWRKY11 promoted the expression of <i>F3H</i>, <i>FLS</i>, <i>DFR</i>, <i>ANS</i>, and <i>UFGT</i> and increased the accumulation of flavonoids and anthocyanin in apple calli. Our findings explored the novel role of MdWRKY11 in flavonoid biosynthesis and suggest several other genes that may also be potentially involved. This provides valuable information on flavonoid synthesis for the breeding of elite red-fleshed apples

    Phylogenetic tree of ubiquitin-conjugating (UBC) domains from <i>Carica papaya</i>, <i>Arabidopsis</i>, <i>Solanum lycopersicum</i>, and <i>Saccharomyces cerevisiae</i>.

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    <p>The neighbor-joining tree includes 34 UBC proteins from papaya (squares), 15 from <i>S</i>. <i>cerevisiae</i> (rhombi), 48 from <i>A</i>. <i>thaliana</i> (circles), and 52 from <i>S</i>. <i>lycopersicum</i> (triangles). The different colors indicate different CpUBC subgroups.</p

    Structure of CpUBC genes.

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    <p>Untranslated 5′ and 3′ regions, exons, and introns are indicated by red, blue, and gray, respectively. The scale bar represents 1000 bp.</p

    Analysis of the Xyloglucan Endotransglucosylase/Hydrolase Gene Family during Apple Fruit Ripening and Softening

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    Ethylene and xyloglucan endotransglucosylase/hydrolase (<i>XTH</i>) genes were important for fruit ripening and softening in ‘Taishanzaoxia’ apple. In this study, we found it was <i>ACS1-1/-1</i> homozygotes in ‘Taishanzaoxia’ apple, which determined the higher transcription activity of <i>ACS1</i>. <i>XTH1</i>, <i>XTH3</i>, <i>XTH4</i>, <i>XTH5</i>, and <i>XTH9</i> were mainly involved in the early fruit softening independent of ethylene, while <i>XTH2</i>, <i>XTH6</i>, <i>XTH7</i>, <i>XTH8</i>, <i>XTH10</i>, and <i>XTH11</i> were predominantly involved in the late fruit softening dependent on ethylene. Overexpression of <i>XTH2</i> and <i>XTH10</i> in tomato resulted in the elevated expression of genes involved in ethylene biosynthesis (<i>ACS2</i>, <i>ACO1</i>), signal transduction (<i>ERF2</i>), and fruit softening (<i>XTHs</i>, <i>PG2A</i>, <i>Cel2</i>, and <i>TBG4</i>). In summary, the burst of ethylene in ‘Taishanzaoxia’ apple was predominantly determined by <i>ACS1-1/-1</i> genotype, and the differential expression of <i>XTH</i> genes dependent on and independent of ethylene played critical roles in the fruit ripening and softening. <i>XTH2</i> and <i>XTH10</i> may act as a signal switch in the feedback regulation of ethylene signaling and fruit softening

    Synthesis of WS<sub>2<i>x</i></sub>Se<sub>2–2<i>x</i></sub> Alloy Nanosheets with Composition-Tunable Electronic Properties

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    Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have recently emerged as a new class of atomically thin semiconductors for diverse electronic, optoelectronic, and valleytronic applications. To explore the full potential of these 2D semiconductors requires a precise control of their band gap and electronic properties, which represents a significant challenge in 2D material systems. Here we demonstrate a systematic control of the electronic properties of 2D-TMDs by creating mixed alloys of the intrinsically p-type WSe<sub>2</sub> and intrinsically n-type WS<sub>2</sub> with variable alloy compositions. We show that a series of WS<sub>2<i>x</i></sub>Se<sub>2–2<i>x</i></sub> alloy nanosheets can be synthesized with fully tunable chemical compositions and optical properties. Electrical transport studies using back-gated field effect transistors demonstrate that charge carrier types and threshold voltages of the alloy nanosheet transistors can be systematically tuned by adjusting the alloy composition. A highly p-type behavior is observed in selenium-rich alloy, which gradually shifts to lightly p-type, and then switches to lightly n-type characteristics with the increasing sulfur atomic ratio, and eventually evolves into highly n-doped semiconductors in sulfur-rich alloys. The synthesis of WS<sub>2<i>x</i></sub>Se<sub>2–2<i>x</i></sub> nanosheets with tunable optical and electronic properties represents a critical step toward rational design of 2D electronics with tailored spectral responses and device characteristics

    Study design for modeling the risk of an inpatient hospital readmission 30 days post discharge.

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    <p>There were three steps in model development: 1) two independent cohorts were constructed for retrospective modeling and prospective validation; 2) the retrospective cohort was split into two subgroups with each incorporating non-overlapped care facilities. The first subgroup was further split into model training and calibration sub cohorts, and the second subgroup was used as the blind-test cohort; and 3) the model was validated using the prospective cohort. Unsupervised clustering pattern analysis that included demographic and clinical data was performed. The prospectively validated model was then deployed in production to support healthcare quality monitoring and improvement efforts.</p
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