183 research outputs found
Study on Isolation and Secondary Metabolite Discovery of Myxobacteria
天然产物是药物的重要来源,目前超过40%的临床药物是天然产物或者是以天然产物为先导化合物改造获得的。近年来,粘细菌由于其次级代谢产物结构新颖,生物活性多样而备受关注,成为发展新药的重要来源。 本论文以河南、安徽、福建、青海等地的土样为研究材料,采用灭活酿酒酵母(Saccharomycescerevisiae)或大肠杆菌(Escherichiacoli)和灭菌滤纸片诱导等方法对粘细菌子实体进行诱导、富集及分离纯化,并采用改进的纯化方法,从而使噬细菌类粘细菌的纯化率达到100%,并且也在一定程度上提高了噬纤维类粘细菌的纯化效率。 通过对95份土样的分离得到117株粘细菌,并从中纯化出54株(包...Nature products are important source of Medicine. More than 40% of important clinical medicines are from microbial secondary metabolites. Nowadays, many types of novel compound with good biological activities are found from Myxobacteri. So Myxobacteria become an important resource of Medicine. The soil samples collected from Henan, Anhui, Fujian, Qinghai and Chongqing, were used as the material...学位:理学硕士院系专业:生命科学学院生物学系_微生物学学号:2172008115253
Entanglement and purity of two-mode Gaussian states in noisy channels
We study the evolution of purity, entanglement and total correlations of
general two--mode Gaussian states of continuous variable systems in arbitrary
uncorrelated Gaussian environments. The time evolution of purity, Von Neumann
entropy, logarithmic negativity and mutual information is analyzed for a wide
range of initial conditions. In general, we find that a local squeezing of the
bath leads to a faster degradation of purity and entanglement, while it can
help to preserve the mutual information between the modes.Comment: 10 pages, 8 figure
Purity of Gaussian states: measurement schemes and time-evolution in noisy channels
We present a systematic study of the purity for Gaussian states of
single-mode continuous variable systems. We prove the connection of purity to
observable quantities for these states, and show that the joint measurement of
two conjugate quadratures is necessary and sufficient to determine the purity
at any time. The statistical reliability and the range of applicability of the
proposed measurement scheme is tested by means of Monte Carlo simulated
experiments. We then consider the dynamics of purity in noisy channels. We
derive an evolution equation for the purity of general Gaussian states both in
thermal and squeezed thermal baths. We show that purity is maximized at any
given time for an initial coherent state evolving in a thermal bath, or for an
initial squeezed state evolving in a squeezed thermal bath whose asymptotic
squeezing is orthogonal to that of the input state.Comment: 9 Pages, 6 Figures; minor errors correcte
QSPcc reduces bottlenecks in computational model simulations
Mathematical models have grown in size and complexity becoming often computationally intractable. In sensitivity analysis and optimization phases, critical for tuning, validation and qualification, these models may be run thousands of times. Scientific programming languages popular for prototyping, such as MATLAB and R, can be a bottleneck in terms of performance. Here we show a compiler-based approach, designed to be universal at handling engineering and life sciences modeling styles, that automatically translates models into fast C code. At first QSPcc is demonstrated to be crucial in enabling the research on otherwise intractable Quantitative Systems Pharmacology models, such as in rare Lysosomal Storage Disorders. To demonstrate the full value in seamlessly accelerating, or enabling, the R&D efforts in natural sciences, we then benchmark QSPcc against 8 solutions on 24 real-world projects from different scientific fields. With speed-ups of 22000x peak, and 1605x arithmetic mean, our results show consistent superior performances.Lombardo and colleagues present QSPcc, a computational code compiler designed to convert code from popular scientific programming languages, such as MATLAB or R, into fast-running C code. This reduces the computational load required for complex modelling approaches and reduces user investment learning additional complex languages
Determining the Quantum Expectation Value by Measuring a Single Photon
Quantum mechanics, one of the keystones of modern physics, exhibits several
peculiar properties, differentiating it from classical mechanics. One of the
most intriguing is that variables might not have definite values. A complete
quantum description provides only probabilities for obtaining various
eigenvalues of a quantum variable. These and corresponding probabilities
specify the expectation value of a physical observable, which is known to be a
statistical property of an ensemble of quantum systems. In contrast to this
paradigm, we demonstrate a unique method allowing to measure the expectation
value of a physical variable on a single particle, namely, the polarisation of
a single protected photon. This is the first realisation of quantum protective
measurements.Comment: Nature Physics, in press (this version corresponds to the one
initially submitted to Nature Physics
The Golden Ratio Prediction for the Solar Angle from a Natural Model with A5 Flavour Symmetry
We formulate a consistent model predicting, in the leading order
approximation, maximal atmospheric mixing angle, vanishing reactor angle and
tan {\theta}_12 = 1/{\phi} where {\phi} is the Golden Ratio. The model is based
on the flavour symmetry A5 \times Z5 \times Z3, spontaneously broken by a set
of flavon fields. By minimizing the scalar potential of the theory up to the
next-to-leading order in the symmetry breaking parameter, we demonstrate that
this mixing pattern is naturally achieved in a finite portion of the parameter
space, through the vacuum alignment of the flavon fields. The leading order
approximation is stable against higher-order corrections. We also compare our
construction to other models based on discrete symmetry groups.Comment: 28 pages, 2 figures. Minor changes, references added. Corrected typos
in Appendix A. Version appeared on JHE
Running Effects on Lepton Mixing Angles in Flavour Models with Type I Seesaw
We study renormalization group running effects on neutrino mixing patterns
when a (type I) seesaw model is implemented by suitable flavour symmetries. We
are particularly interested in mass-independent mixing patterns to which the
widely studied tribimaximal mixing pattern belongs. In this class of flavour
models, the running contribution from neutrino Yukawa coupling, which is
generally dominant at energies above the seesaw threshold, can be absorbed by a
small shift on neutrino mass eigenvalues leaving mixing angles unchanged.
Consequently, in the whole running energy range, the change in mixing angles is
due to the contribution coming from charged lepton sector. Subsequently, we
analyze in detail these effects in an explicit flavour model for tribimaximal
neutrino mixing based on an A4 discrete symmetry group. We find that for
normally ordered light neutrinos, the tribimaximal prediction is essentially
stable under renormalization group evolution. On the other hand, in the case of
inverted hierarchy, the deviation of the solar angle from its TB value can be
large depending on mass degeneracy.Comment: 36 pages, 4 figures; few references added and minor correction
Constraining flavour symmetries at the EW scale II: the fermion processes
We study the set of models in which the Standard Model symmetry is extended with the avour group
AGILE TGFS AND GLOBAL LIGHTNING ACTIVITY
[1] The AGILE satellite detects Terrestrial Gamma-ray Flashes (TGFs) in the 0.35–100 MeV energy range using its Mini-Calorimeter (MCAL) instrument with an average detection rate of 10 TGFs/month. Thanks to its Low Earth Orbit with only 2.5 degree of inclination, AGILE guarantees an unprecedented exposure above the equator, where both lightning activity and TGF detection peak. Here we report the comparison between the AGILE TGFs detected between March 2009 and February 2010 and full climatology lightning worldwide distribution based on satellite optical observations from LIS (Lightning Imaging Sensor) and OTD (Optical Transient Detector) instruments. This approach is complementary to the one-to-one TGF/lightning correlations by ground-based sferics measurements. Based on mono and bi-dimensional Kolmogorov-Smirnov tests, we show that the AGILE TGFs and time-averaged global lightning in the equatorial area are not drawn from the same distribution. However, we find significant regional differences in the degree of correlation as well as in the TGF/lightning ratio. In the case of south east Asia we find a 87% probability for the TGF and lightning being samples of the same distribution. This result supports the idea that the physical conditions at play in TGF generation can have strong geographical and climatological modulation. Based on the assumption that the observed range of TGF/flash ratio holds at all latitudes we can estimate a global rate of ≃ 220 ÷ 570 TGFs per day. The observed TGF/flash geographical modulation as well as the TGF global rate estimate are in agreement with previous observations
- …