Quantum ground-state cooling and tripartite entanglement with three-mode optoacoustic interactions

We present a quantum analysis of three-mode optoacoustic parametric interactions in an optical cavity, in which two orthogonal transverse optical-cavity modes are coupled to one acoustic mode through radiation pressure. Due to the optimal frequency matching -- the frequency separation of two cavity modes is equal to the acoustic-mode frequency -- the carrier and sideband fields simultaneously resonate and coherently build up. This mechanism significantly enhances the optoacoustic couplings in the quantum regime. It allows exploration of quantum behavior of optoacoustic interactions in small-scale table-top experiments. We show explicitly that given an experimentally achievable parameter, three-mode scheme can realize quantum ground-state cooling of milligram scale mechanical oscillators and create robust stationary tripartite optoacoustic quantum entanglements.Comment: 20 pages, 5 figure

Impact of Sensor Zenith Angle on MOD10A1 Data Reliability and Modification of Snow Cover Data for the Tarim River Basin

Snow in the mountainous watersheds of the Tarim River Basin is the primary source of water for western China. The Snow Cover Daily L3 Global 500-m Grid (MOD10A1) remote sensing dataset has proven extremely valuable for monitoring the changing snow cover patterns over large spatial areas; however, inherent uncertainty associated with large sensor zenith angles (SZAs) has called its reliability into question. Comparative analysis that utilized a paired-date difference method for parameters such as snow cover frequency, snow cover percentage, and normalized difference snow index (NDSI) has shown that overestimation of snow cover in the Tarim River Basin correlates with high values of SZA. Hence, such overestimation was associated with an increase in the NDSI, attributable to the change in reflectance between Band 4 and Band 6 imagery. A maximum threshold value of SZA of 22.37° was used alongside a multiday refilling method to modify the MOD10A1 dataset to produce a new daily snow cover map of the Tarim River Basin, spanning a 10-year period. A comparison of benchmark results of snow cover classification produced by the HJ-1A/B satellite revealed an increase in the overall accuracy of up to 4%, confirming the usefulness of our modified MOD10A1 data

Electronic Properties of Molecular Silicon

This dissertation explores the electronic characteristics of silicon at the single molecule level. This idea is born as we enter the post-Moore’s law era when the exponential shrinking of conventional silicon microelectronics has begun to stall and an investigation of molecular materials is timely. Single-molecule electronic components have shown promising functionalities such as conductors, switches, and diodes, and single molecule junctions have become a widely used test-bed for probing electron transport properties at the molecular level. In this thesis, we use scanning tunneling microscope break junction method to create single molecule junctions with a variety of silicon molecular wires. Our results demonstrate electronic properties of silicon beyond it being a semiconductor in its bulk form. We begin this work in pursuit of an expanded understanding of low-k dielectric components with an experimental goal on determining the cause of its breakdown. Low-k dielectrics are beneficial as they enable faster switching speeds and lower heat dissipation, however, they tend to breakdown after prolonged usage under an applied voltage. At the atomic level, low-k dielectric breakdown involves bond rupture. To determine which bond breaks easily, we conduct experimental studies on the robustness of individual chemical bonds that are commonly found in low-k dielectrics. We subject the single molecule junctions to a high bias and investigate the breakdown phenomenon of individual Si-Si, Ge-Ge, Si-O, and Si-C bonds. Among these, Si-C proved to be significantly more durable than the others. To further prove our hypothesis that the Si-Si bond ruptures under the applied high bias, we design a two-path molecular structure consisting of a Si-Si bond in parallel with a naphthyl group. The broken junction shows conduction through the naphthyl pathway, strongly indicating that the Si-Si bond is breaking. This demonstrates a method for probing the bond cleavage under an electric field and provides insights to the weak links in low-k dielectrics. Next, we study the fundamental charge transport characteristics of single molecule junctions comprised of Si and Ge-based molecular wires, starting with the simplest form - linear atomic chains. We observe a slower decay of conductance with increasing length in the silanes and germanes than in alkanes, indicating that the electronic delocalization in the Si-Si and Ge-Ge -bonds is stronger than that of the well-studied C-C bonds. Furthermore, we demonstrate that this electronic delocalization in the Si-Si and Ge-Ge bonded backbones enables single-molecule conductance switching. This conductance switch, induced by a mechanical modulation, relies on the nature of the terminal groups and constitutes the first example of a stereoelectronic switch. We also study the molecular conductance of these silanes with metal contacts other than Au, which can potentially open up interesting avenues as metal varies in its electronic states and catalytic activities. We find that Ag electrodes enable higher conductance for thiol-terminated silanes than Au or Pt electrodes. The electrical properties of more complex silicon structures - silicon rings - were probed. We choose a five-membered silicon ring as a target system to investigate the effect of isomerism on single molecule conductance. We find that due to the flexibility of the ring, multiple conformations contribute to the spread in the measured conductance for each isomer. This provides us with a starting point to further compare the conductance of a variety of silicon rings. We find that most of the silicon rings are less conductive than their linear counterparts due to the suboptimal backbone conformation for electronic coupling. In particular, destructive quantum interference appears in one of the bicyclic structures and leads to an exceptionally low conductance. This is the first example of a destructive quantum interference feature ever observed experimentally in a π-bonded rather than a σ-bonded system. Finally, we investigate the impact of strain on molecular conductance of silanes. In one case, we introduce the strain using a silacyclobutane ring in the backbone. Unexpectedly, we find that ring strain enables a new Au-silacycle binding mode, resulting in a much higher conductance state. In another molecular design, we choose disilaacenaphthene in the backbone. This strained disilane is found to constitute an example of a direct Si-to-Au contact in single molecule circuits, thereby demonstrating a new binding motif that is valuable for designing high conducting molecular components. Taken together, this body of work provides important knowledge about the transport properties of silicon at the nano-scale, as well as insights on the design of silicon components for nanoelectronics. This work represents one step forward to create functional silicon molecular components

Production of gamma-aminobutyric acid by Lactobacillus brevis NCL912 using fed-batch fermentation

<p>Abstract</p> <p>Background</p> <p>Gamma-aminobutyric acid is a major inhibitory neurotransmitter in mammalian brains, and has several well-known physiological functions. Lactic acid bacteria possess special physiological activities and are generally regarded as safe. Therefore, using lactic acid bacteria as cell factories for gamma-aminobutyric acid production is a fascinating project and opens up a vast range of prospects for making use of GABA and LAB. We previously screened a high GABA-producer <it>Lactobacillus brevis </it>NCL912 and optimized its fermentation medium composition. The results indicated that the strain showed potential in large-scale fermentation for the production of gamma-aminobutyric acid. To increase the yielding of GABA, further study on the fermentation process is needed before the industrial application in the future. In this article we investigated the impacts of pyridoxal-5'-phosphate, pH, temperature and initial glutamate concentration on gamma-aminobutyric acid production by <it>Lactobacillus brevis </it>NCL912 in flask cultures. According to the data obtained in the above, a simple and effective fed-batch fermentation method was developed to highly efficiently convert glutamate to gamma-aminobutyric acid.</p> <p>Results</p> <p>Pyridoxal-5'-phosphate did not affect the cell growth and gamma-aminobutyric acid production of <it>Lb. brevis </it>NCL912. Temperature, pH and initial glutamate concentration had significant effects on the cell growth and gamma-aminobutyric acid production of <it>Lb. brevis </it>NCL912. The optimal temperature, pH and initial glutamate concentration were 30-35°C, 5.0 and 250-500 mM. In the following fed-batch fermentations, temperature, pH and initial glutamate concentration were fixed as 32°C, 5.0 and 400 mM. 280.70 g (1.5 mol) and 224.56 g (1.2 mol) glutamate were supplemented into the bioreactor at 12 h and 24 h, respectively. Under the selected fermentation conditions, gamma-aminobutyric acid was rapidly produced at the first 36 h and almost not produced after then. The gamma-aminobutyric acid concentration reached 1005.81 ± 47.88 mM, and the residual glucose and glutamate were 15.28 ± 0.51 g L^-1and 134.45 ± 24.22 mM at 48 h.</p> <p>Conclusions</p> <p>A simple and effective fed-batch fermentation method was developed for <it>Lb. brevis </it>NCL912 to produce gamma-aminobutyric acid. The results reveal that <it>Lb. brevis </it>NCL912 exhibits a great application potential in large-scale fermentation for the production of gamma-aminobutyric acid.</p

Predicting hyperlinks via hypernetwork loop structure

While links in simple networks describe pairwise interactions between nodes, it is necessary to incorporate hypernetworks for modeling complex systems with arbitrary-sized interactions. In this study, we focus on the hyperlink prediction problem in hypernetworks, for which the current state-of-art methods are latent-feature-based. A practical algorithm via topological features, which can provide understandings of the organizational principles of hypernetworks, is still lacking. For simple networks, local clustering or loop reflects the correlations among nodes; therefore, loop-based link prediction algorithms have achieved accurate performance. Extending the idea to hyperlink prediction faces several challenges. For instance, what is an effective way of defining loops for prediction is not clear yet; besides, directly comparing topological statistics of variable-sized hyperlinks could introduce biases in hyperlink cardinality. In this study, we address the issues and propose a loop-based hyperlink prediction approach. First, we discuss and define the loops in hypernetworks; then, we transfer the loop-features into a hyperlink prediction algorithm via a simple modified logistic regression. Numerical experiments on multiple real-world datasets demonstrate superior performance compared to the state-of-the-art methods

Exercise blood pressure, cardiorespiratory fitness, fatness and cardiovascular risk in children and adolescents

Cardiovascular disease remains the leading cause of mortality on a global scale. Individuals who possess risk factors for cardiovascular disease, such as high blood pressure (BP) and obesity, face an elevated risk of experiencing organ-specific pathophysiological changes. This damage includes pathophysiological changes in the heart and peripheral vascular systems, such as ventricular hypertrophy, arterial stiffening, and vascular narrowing and stenosis. Consequently, these damages are associated with an increased risk of developing severe cardiovascular outcomes including stroke, myocardial infarction, heart failure, and coronary heart disease. Among all the risk factors associated with cardiovascular disease, high blood pressure emerges as the most prominent. However, conventional resting BP measurement methods such as auscultatory or oscillometric methods may fail to identify many individuals with asymptomatic high BP. Recently, exercise BP has emerged as a valuable diagnostic tool for identifying real (high) blood pressure levels and assessing underlying cardiovascular risk, in addition to resting BP measurements in adults. Furthermore, numerous established factors, such as low cardiorespiratory fitness and high body fatness, have been confirmed to contribute to exercise BP and the associated cardiovascular risk. Modifying these factors may help reduce high exercise BP and, consequently, alleviate the burden of cardiovascular disease. A significant body of evidence has demonstrated cardiovascular disease in later life have their origins in early life. Children and adolescents with these cardiovascular risk factors also possess a greater propensity to develop cardiovascular diseases later in life. Nevertheless, the majority of previous studies on the clinical utility of exercise BP have been conducted in middle-to-older aged populations, often with pre-existing clinical conditions. Therefore, there is a need to investigate further of the factors influencing exercise BP in adolescence and its association with cardiovascular risk in early life. Our previously published work showed that exercise BP is a potential useful method to detect adolescents with increased cardiovascular risk. Children and adolescents with cardiovascular risk factors are more likely to develop cardiovascular diseases later in life. However, previous studies on the clinical utility of exercise BP have largely focused on middle-to-older aged populations with pre-existing clinical conditions. Therefore, there is a need to investigate further the factors influencing exercise BP in adolescence and its association with future cardiovascular risk. Our previous studies, which focused on exercise BP measured at submaximal intensity, have shown that exercise BP is a potentially useful method for identifying adolescents at increased cardiovascular risk. Our previous findings suggest that improving cardio-respiratory fitness and reducing body fatness may help to reduce the risk of developing cardiovascular disease and improve overall cardiovascular health. These findings have important implications for the development of effective prevention and early detection strategies, which can contribute to improved public health outcomes