368 research outputs found
Consequences of scarcity: the impact of perceived scarcity on executive functioning and its neural basis
IntroductionPrevious studies have found a causal relationship between scarcity and the adverse impact it has on executive functioning. However, few studies have directly examined perceived scarcity, and cognitive flexibility (the third component of executive functions) has rarely been included.MethodsUsing a 2 (group: scarcity group vs. control group) × 2 (trial type: repeat trial vs. switch trial) mixed design, this study directly explored perceived scarcity’s impact on cognitive flexibility and revealed its neural basis in the switching tasks. Seventy college students participated in this study through open recruitment in China. A priming task was used to induce perceived scarcity, thus exploring the impact of perceived scarcity on participants’ performance in switching tasks and enabling the analysis of the neural activity of the brain, combined with electroencephalograph (EEG) technology.ResultsIn terms of behavioral outcomes, perceived scarcity led to poorer performance and a greater switching cost of reaction time in the switching tasks. Regarding neural activity, perceived scarcity led to an increase in the amplitude of P3 differential wave (repeat trials minus switch trials) in the parietal cortex during the target-locked epochs in the switching tasks.DiscussionPerceived scarcity can lead to changes in the neural activity of the brain regions related to executive functioning, resulting in a temporary decrease in cognitive flexibility. It may lead to individuals unable to adapt well to the changing environment, unable to quickly devote themselves to new tasks, and reduce work and learning efficiency in daily life
Improving fatty acids production by engineering dynamic pathway regulation and metabolic control
Global energy demand and environmental concerns have stimulated increasing efforts to produce carbon-neutral fuels directly from renewable resources. Microbially derived aliphatic hydrocarbons, the petroleum-replica fuels, have emerged as promising alternatives to meet this goal. However, engineering metabolic pathways with high productivity and yield requires dynamic redistribution of cellular resources and optimal control of pathway expression. Here we report a genetically encoded metabolic switch that enables dynamic regulation of fatty acids (FA) biosynthesis in Escherichia coli. The engineered strains were able to dynamically compensate the critical enzymes involved in the supply and consumption of malonyl-CoA and efficiently redirect carbon flux toward FA biosynthesis. Implementation of this metabolic control resulted in an oscillatory malonyl-CoA pattern and a balanced metabolism between cell growth and product formation, yielding 15.7- and 2.1-fold improvement in FA titer compared with the wild-type strain and the strain carrying the uncontrolled metabolic pathway. This study provides a new paradigm in metabolic engineering to control and optimize metabolic pathways facilitating the high-yield production of other malonyl-CoA–derived compounds.National Science Foundation (U.S.) (Award CBET1144226)National Science Foundation (U.S.) (Award CBET0836513)Rensselaer Polytechnic Institute. Biocatalysis and Metabolic Engineering Constellatio
Enhancement of shot noise due to the fluctuation of Coulomb interaction
We have developed a theoretical formalism to investigate the contribution of
fluctuation of Coulomb interaction to the shot noise based on Keldysh
non-equilibrium Green's function method. We have applied our theory to study
the behavior of dc shot noise of atomic junctions using the method of
nonequilibrium Green's function combined with the density functional theory
(NEGF-DFT). In particular, for atomic carbon wire consisting 4 carbon atoms in
contact with two Al(100) electrodes, first principles calculation within
NEGF-DFT formalism shows a negative differential resistance (NDR) region in I-V
curve at finite bias due to the effective band bottom of the Al lead. We have
calculated the shot noise spectrum using the conventional gauge invariant
transport theory with Coulomb interaction considered explicitly on the Hartree
level along with exchange and correlation effect. Although the Fano factor is
enhanced from 0.6 to 0.8 in the NDR region, the expected super-Poissonian
behavior in the NDR regionis not observed. When the fluctuation of Coulomb
interaction is included in the shot noise, our numerical results show that the
Fano factor is greater than one in the NDR region indicating a super-Poissonian
behavior
Unified framework of the microscopic Landau-Lifshitz-Gilbert equation and its application to Skyrmion dynamics
The Landau-Lifshitz-Gilbert (LLG) equation is widely used to describe
magnetization dynamics. We develop a unified framework of the microscopic LLG
equation based on the nonequilibrium Green's function formalism. We present a
unified treatment for expressing the microscopic LLG equation in several
limiting cases, including the adiabatic, inertial, and nonadiabatic limits with
respect to the precession frequency for a magnetization with fixed magnitude,
as well as the spatial adiabatic limit for the magnetization with slow
variation in both its magnitude and direction. The coefficients of those terms
in the microscopic LLG equation are explicitly expressed in terms of
nonequilibrium Green's functions. As a concrete example, this microscopic
theory is applied to simulate the dynamics of a magnetic Skyrmion driven by
quantum parametric pumping. Our work provides a practical formalism of the
microscopic LLG equation for exploring magnetization dynamics
Mach cone induced by -triggered jets in high-energy heavy-ion collisions
MMedium excitation by jet shower propagation inside a quark-gluon plasma is
studied within a linear Boltzmann transport and a multiphase transport model.
Contrary to the naive expectation, it is the deflection of both the jet shower
and the Mach-cone-like excitation in an expanding medium that is found to gives
rise to a double-peak azimuthal particle distribution with respect to the
initial jet direction. Such deflection is the strongest for hadron-triggered
jets which are often produced close to the surface of dense medium due to
trigger-bias and travel against or tangential to the radial flow. Without such
trigger bias, the effect of deflection on -jet showers and their medium
excitation is weaker. Comparative study of hadron and -triggered
particle correlations can therefore reveal the dynamics of jet-induced medium
excitation in high-energy heavy-ion collisions.Comment: 4 pages in RevTeX with 5 figures, finally version in PR
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Identification of Metastasis Associated Antigen 1 (MTA1) by Serological Screening of Prostate Cancer cDNA Libraries
Over the past 10 years the serological analysis of recombinant cDNA expression libraries (SEREX) has proved to be an effective method for the identification of tumour antigens. In the present study, two prostate cancer libraries were constructed and screened using autologous sera. Fifty five genes were isolated, including 46 known genes and 9 previously uncharacterised genes. Among the known genes, a metastasis-associated gene, MTA1, previously identified by differential cDNA hybridisation, was preferentially expressed in a panel of malignant tissues compared with normal tissues, as analysed by reverse transcriptase-polymerase chain reaction (RT-PCR). MTA1 transcripts were observed to be over-expressed in normal human testes as well as various cancer tissues when compared to the panel of normal tissues. MTA1 antigen reacted with 2 of 13 allogeneic prostate cancer patient sera tested, but no sera reactivity was observed to any of the normal adult sera tested. Furthermore, a similar distribution and expression level of MTA-1 was observed in murine tissues and cancer cell lines. Based on these findings and previous reports on the literature on this gene, MTA-1 can be considered not only as a “biomarker” of aggressive disease but also as a potential therapeutic target
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