Scaling up Dynamic Topic Models

Dynamic topic models (DTMs) are very effective in discovering topics and capturing their evolution trends in time series data. To do posterior inference of DTMs, existing methods are all batch algorithms that scan the full dataset before each update of the model and make inexact variational approximations with mean-field assumptions. Due to a lack of a more scalable inference algorithm, despite the usefulness, DTMs have not captured large topic dynamics. This paper fills this research void, and presents a fast and parallelizable inference algorithm using Gibbs Sampling with Stochastic Gradient Langevin Dynamics that does not make any unwarranted assumptions. We also present a Metropolis-Hastings based $O(1)$ sampler for topic assignments for each word token. In a distributed environment, our algorithm requires very little communication between workers during sampling (almost embarrassingly parallel) and scales up to large-scale applications. We are able to learn the largest Dynamic Topic Model to our knowledge, and learned the dynamics of 1,000 topics from 2.6 million documents in less than half an hour, and our empirical results show that our algorithm is not only orders of magnitude faster than the baselines but also achieves lower perplexity.Comment: 10 pages, 8 figures, to appear in WWW 201

The Emergent Vinifera Wine Industry in North Carolina: A Descriptive Overview

The North Carolina (NC) wine industry has grown rapidly over the past decade and is expected to grow even more as the worldwide wine consumption and export of wines rises. In the United States, the wine market has grown by 13.7 percent since 2002 in volume and by more than 15 percent in dollars as wine has progressed from being a beverage of an elite segment of the market to becoming a mainline beverage, taking its place alongside beer and liquor (MKF Research LLC, 2007; Oches, 2009). The Piedmont Triad Region is uniquely positioned to increase its presence in this industry. Of the 80 wineries in NC that are currently open to the public, nearly half are located in the Piedmont Triad Region. However, growing grapes and making wine is a long term commitment to a community, both financially and physically. The MKF Research report states that the capital-intensive nature of the winery and vineyard sectors is often underestimated, with new entrants to the industry at times unprepared for the extended cash requirements. In addition, only a few local institutions are familiar with the unique needs of the winemaking business. In order to address factors that will impede growth in this nascent industry, it is important to identify the state of the industry and obtain management perspectives on the needs and challenges facing their operations. This study provides information that would help gain a better understanding of the business issues and needs related to the wine and grape industry in North Carolina. Data for this study was drawn from a census of 34 wine producers located in the Yadkin, Swan Creek, and the Haw River valley regions of North Carolina. Descriptive statistics using frequencies and means is used to provide a demographic overview of the industry and to identify the factors that wine producers perceive to be important in affecting their profitability. Results from the study shows that most of the wineries share some common traits: they are small, relatively new to the wine and grape industry and grow grapes other than the traditional native Muscadine grape. Primarily, a majority of the wineries are family-based entrepreneurial businesses that have to behave like mini-conglomerates. These findings are consistent with a study conducted by Taplin and Breckenridge (2008).Profitability Constraints, Financial Management, Marketing, Distribution, Agribusiness, Community/Rural/Urban Development, Farm Management,

In pursuit of β-amino α-nitro β-trifluoromethyl ketones: nitro-Mannich vs Mannich-type reactions

The reactivity of alfa-nitro ketones with trifluoromethyl aldimines is studied for the first time. While under nitro-Mannich conditions only the facial stereoselectivity can be controlled, organocatalysed Mannich-type reactions allowed a complete control of absolute and relative stereoselectivity, leading to highly functionalised β-amino alfa-nitro β-trifluoromethyl compounds as diastereomerically pure compounds. A key role on the geometrical and/or facial stereoselectivity is played by the structure of reactants

Isolation, Structure Elucidation and Total Synthesis of Lajollamide A from the Marine Fungus Asteromyces cruciatus

The marine-derived filamentous fungus Asteromyces cruciatus 763, obtained off the coast of La Jolla, San Diego, USA, yielded the new pentapeptide lajollamide A (1), along with the known compounds regiolone (2), hyalodendrin (3), gliovictin (4), 1N-norgliovicitin (5), and bis-N-norgliovictin (6). The planar structure of lajollamide A (1) was determined by Nuclear Magnetic Resonance (NMR) spectroscopy in combination with mass spectrometry. The absolute configuration of lajollamide A (1) was unambiguously solved by total synthesis which provided three additional diastereomers of 1 and also revealed that an unexpected acid-mediated partial racemization (2:1) of the l-leucine and l-N-Me-leucine residues occurred during the chemical degradation process. The biological activities of the isolated metabolites, in particular their antimicrobial properties, were investigated in a series of assay systems

Relativistic spin hydrodynamics with momentum- and spin-dependent relaxation time

Using the extended relaxation time approximation along with the theory of semiclassical spin, a framework of relativistic dissipative spin hydrodynamics is developed such that the relaxation time can depend on the momenta and spin of the constituent spin-1/2 particles. A general definition of the fluid four-velocity is considered, allowing the theory to be valid in a general frame and matching conditions. Consequently, the frame-invariant bulk, shear, particle diffusion, and spin transport coefficients are obtained, showing that the evolution of fluid remains unaffected by spin in the limit of small polarization as was the case where the relaxation time was independent of spin or momentum

Relativistic spin hydrodynamics from novel relaxation time approximation

With the help of a semiclassical kinetic theory, a new collision kernel is proposed, which simultaneously conserves the energy-momentum tensor and the spin tensor of a relativistic fluid of spin-1/2 particles irrespective of the frame and matching conditions, even when relaxation time is momentum dependent. The relativistic Boltzmann's equation is solved using this new collision kernel that will lead to the transport coefficients with general definitions for the frame and matching conditions. The results indicate the expected existence of Barnett-like effect and the nonexistence of Einstein–de Haas–like effects. For the first time, a local collision kernel is being proposed that can be used to construct relativistic spin hydrodynamics along the line of Bemfica-Disconzi-Noronha-Kovtun (BDNK) formulation, which may lead to a first-order stable and causal theory

MOLECULAR RESOLUTION OF MARINE NEMATODES FOR IMPROVED ASSESSMENT OF BIODIVERSITY

Free-living nematodes are abundant in all marine habitats, highly diverse and can be important ecological indicators for monitoring anthropogenic impacts on the environment. Despite such attributes, nematode diagnostics has traditionally relied on detailed comparison of morphological characters which is often difficult and laborious, and as a result there is an increasing 'black hole' in faunal inventories where the biodiversity of groups such as nematodes is typically underestimated. Molecular methods offer a potentially efficient alternative approach to studying the biodiversity of marine nematode communities, and the main focus of this thesis was to apply molecular ecological tools for improved understanding of nematode diversity in marine and estuarine environments. Denaturing gradient gel electrophoresis (DGGE) has been evaluated as a novel tool for the identification of marine nematodes and for rapid assessment of their diversity based on amplification of the nuclear 18S rRNA gene. This approach successfully identified nematode taxa based on banding pattern and was also able to detect the most abundant taxa in samples from marine and estuarine environments. A DNA barcoding approach based on the 18S rRNA gene was applied for the first time in marine nematology, in an attempt to speed up the identification process. The success rate of this approach, across a range of nematode groups, was found to be close to 97%. A combined morphometrics and molecular approach was also undertaken to investigate cosmopolitanism and cryptic speciation by analysing populations of a cosmopolitan marine nematode, Terschellingia longicaudata, from different geographical regions. Results suggest that Terschellingia longicaudata is indeed truly cosmopolitan, with a wide geographic distribution. Two haplotypes that were divergent from most T. longicaudata were also identified in this study, indicating possible novel cryptic lineages or previously undescribed species of the genus. The final focus of this thesis was to develop methods for the molecular investigation of nematodes stored in formalin and other organic compounds. The effectiveness of formalin as a short term preservative was first evaluated, since this would allow morphological and molecular work to be conducted on the same specimen. Amplifiable DNA could be routinely obtained from specimens stored in formalin for periods of up to nine days. In addition the effectiveness of other organic solvents for the preservation of both molecular and morphological integrity of marine nematodes was investigated. The final part of this study developed and optimized a novel DNA extraction technique that could be employed to recover DNA from archived formalin fixed marine nematode specimens so as to carry out subsequent molecular analysis such as PCR amplification and sequencing.Plymouth Marine Laborator

Salinity from Space Unlocks Satellite-Based Assessment of Ocean Acidification

Approximately a quarter of the carbon dioxide (CO2) that we emit into the atmosphere is absorbed by the ocean. This oceanic uptake of CO2 leads to a change in marine carbonate chemistry resulting in a decrease of seawater pH and carbonate ion concentration, a process commonly called “Ocean Acidification”. Salinity data are key for assessing the marine carbonate system, and new space-based salinity measurements will enable the development of novel space-based ocean acidification assess- ment. Recent studies have highlighted the need to develop new in situ technology for monitoring ocean acidification, but the potential capabilities of space-based measurements remain largely untapped. Routine measurements from space can provide quasi-synoptic, reproducible data for investigating processes on global scales; they may also be the most efficient way to monitor the ocean surface. As the carbon cycle is dominantly controlled by the balance between the biological and solubility carbon pumps, innovative methods to exploit existing satellite sea surface temperature and ocean color, and new satellite sea surface salinity measurements, are needed and will enable frequent assessment of ocean acidification parameters over large spatial scales

Supersymmetric Many-particle Quantum Systems with Inverse-square Interactions

The development in the study of supersymmetric many-particle quantum systems with inverse-square interactions is reviewed. The main emphasis is on quantum systems with dynamical OSp(2|2) supersymmetry. Several results related to exactly solved supersymmetric rational Calogero model, including shape invariance, equivalence to a system of free superoscillators and non-uniqueness in the construction of the Hamiltonian, are presented in some detail. This review also includes a formulation of pseudo-hermitian supersymmetric quantum systems with a special emphasis on rational Calogero model. There are quite a few number of many-particle quantum systems with inverse-square interactions which are not exactly solved for a complete set of states in spite of the construction of infinitely many exact eigen functions and eigenvalues. The Calogero-Marchioro model with dynamical SU(1,1|2) supersymmetry and a quantum system related to short-range Dyson model belong to this class and certain aspects of these models are reviewed. Several other related and important developments are briefly summarized.Comment: LateX, 65 pages, Added Acknowledgment, Discussions and References, Version to appear in Jouranl of Physics A: Mathematical and Theoretical (Commissioned Topical Review Article