2,591 research outputs found
Development of novel separation techniques for biological samples in capillary electrophoresis
This dissertation includes three different topics, general introduction of capillary electrophoresis (CE), gradient in CE and CE in biological separations, and capillary gel electrophoresis (CGE) for DNA separation;Factors such as temperature, viscosity, pH and the surface of capillary wall affecting the separation performance have been well demonstrated in Chapters 2 to 4. A pH gradient between 3.0 and 5.2 is useful to improve the resolution among eight different organic acids. Flow gradient due to the change in the concentration of surfactant which is able to coat to the capillary wall to change the flow rate and its direction is also shown as a good way to improve the resolution for organic compounds. Temperature gradient caused by joule heat has been shown by voltage programming to enhance the resolution and shorten the separation time for several phenolic compounds. We also showed that self-regulating dynamic control of electroosmotic flow in CE by simply running separation in different concentration of surfactant has less matrix effect on the separation performance. One of the most important demonstrations in this dissertation is that we proposed on-column reaction which gives several advantages including the use of small amount of sample, low risk of contamination, time saving and kinetic feature. We used this idea with laser induced fluorescence (LIF) as a detection mode to detect an on-column digestion of sub-ng of protein. This technique also has been applied to single cell analysis in our group;An entangled polymer, poly(ethylene oxide), was used to separate 11 fragments of Hae III digest of [phi]X174RF DNA. The effects of voltage, gel concentration and molecular weight of polymer are well studied. Also, the effects of the nature and concentration of labeling dyes, and the capillary length on the resolution of DNA fragments has been studied with different lasers. DNA sequence of PGEM/U with four different terminal dyes has been shown. Mixed gel matrices provides single-base resolution and better separation performance for DNA fragments up to 500 base pairs have been shown;Lastly, CE with LIF has been shown as a powerful technique to detect attomol levels of amine compounds, which are neurotransmitters. This method also has been used to determine the norepinephrine and epinephrine at femtomole level in single adrenomedullary cells
Understanding and Predicting Delay in Reciprocal Relations
Reciprocity in directed networks points to user's willingness to return
favors in building mutual interactions. High reciprocity has been widely
observed in many directed social media networks such as following relations in
Twitter and Tumblr. Therefore, reciprocal relations between users are often
regarded as a basic mechanism to create stable social ties and play a crucial
role in the formation and evolution of networks. Each reciprocity relation is
formed by two parasocial links in a back-and-forth manner with a time delay.
Hence, understanding the delay can help us gain better insights into the
underlying mechanisms of network dynamics. Meanwhile, the accurate prediction
of delay has practical implications in advancing a variety of real-world
applications such as friend recommendation and marketing campaign. For example,
by knowing when will users follow back, service providers can focus on the
users with a potential long reciprocal delay for effective targeted marketing.
This paper presents the initial investigation of the time delay in reciprocal
relations. Our study is based on a large-scale directed network from Tumblr
that consists of 62.8 million users and 3.1 billion user following relations
with a timespan of multiple years (from 31 Oct 2007 to 24 Jul 2013). We reveal
a number of interesting patterns about the delay that motivate the development
of a principled learning model to predict the delay in reciprocal relations.
Experimental results on the above mentioned dynamic networks corroborate the
effectiveness of the proposed delay prediction model.Comment: 10 page
Cold quarks in medium: an equation of state
We derive a compact, semi-algebraic expression for the cold quark matter
equation of state (EoS) in a covariant model that exhibits coincident
deconfinement and chiral symmetry restoring transitions in-medium. Along the
way we obtain algebraic expressions for: the number- and scalar-density
distributions in both the confining Nambu and deconfined Wigner phases; and the
vacuum-pressure difference between these phases, which defines a bag constant.
The confining interaction materially alters the distribution functions from
those of a Fermi gas and consequently has a significant impact on the model's
thermodynamic properties, which is apparent in the EoS.Comment: 5 pages, 5 figure
Attributed Network Embedding for Learning in a Dynamic Environment
Network embedding leverages the node proximity manifested to learn a
low-dimensional node vector representation for each node in the network. The
learned embeddings could advance various learning tasks such as node
classification, network clustering, and link prediction. Most, if not all, of
the existing works, are overwhelmingly performed in the context of plain and
static networks. Nonetheless, in reality, network structure often evolves over
time with addition/deletion of links and nodes. Also, a vast majority of
real-world networks are associated with a rich set of node attributes, and
their attribute values are also naturally changing, with the emerging of new
content patterns and the fading of old content patterns. These changing
characteristics motivate us to seek an effective embedding representation to
capture network and attribute evolving patterns, which is of fundamental
importance for learning in a dynamic environment. To our best knowledge, we are
the first to tackle this problem with the following two challenges: (1) the
inherently correlated network and node attributes could be noisy and
incomplete, it necessitates a robust consensus representation to capture their
individual properties and correlations; (2) the embedding learning needs to be
performed in an online fashion to adapt to the changes accordingly. In this
paper, we tackle this problem by proposing a novel dynamic attributed network
embedding framework - DANE. In particular, DANE first provides an offline
method for a consensus embedding and then leverages matrix perturbation theory
to maintain the freshness of the end embedding results in an online manner. We
perform extensive experiments on both synthetic and real attributed networks to
corroborate the effectiveness and efficiency of the proposed framework.Comment: 10 page
Phase diagram and critical endpoint for strongly-interacting quarks
We introduce a method based on the chiral susceptibility, which enables one
to draw a phase diagram in the chemical-potential/temperature plane for
strongly-interacting quarks whose interactions are described by any reasonable
gap equation, even if the diagrammatic content of the quark-gluon vertex is
unknown. We locate a critical endpoint (CEP) at (\mu^E,T^E) ~ (1.0,0.9)T_c,
where T_c is the critical temperature for chiral symmetry restoration at \mu=0;
and find that a domain of phase coexistence opens at the CEP whose area
increases as a confinement length-scale grows.Comment: 4 pages, 3 figure
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