7,392 research outputs found
The Rise in House Prices in China: Bubbles or Fundamentals?
The dramatic rise of house prices in many cities of China has brought huge attention from both the governmental and academic circles. There is a huge debate on whether the increasing house prices are driven by market fundamentals or just by speculation. Like Levin and Wright (1997a, 1997b), we decompose house prices in China into fundamental and non-fundamental components. We also consider potential nonlinear feedback from the historical growth rate of house prices on the current house prices and propose a semiparametric approach to estimate the speculative components in the model. We demonstrate that the non-fundamental part contributes a relatively small proportion of the rise of house prices in China.
Chiral symmetry analysis and rigid rotational invariance for the lattice dynamics of single-wall carbon nanotubes
In this paper, we provide a detailed expression of the vibrational potential
for the lattice dynamics of the single-wall carbon nanotubes (SWCNT) satisfying
the requirements of the exact rigid translational as well as rotational
symmetries, which is a nontrivial generalization of the valence force model for
the planar graphene sheet. With the model, the low frequency behavior of the
dispersion of the acoustic modes as well as the flexure mode can be precisely
calculated. Based upon a comprehensive chiral symmetry analysis, the calculated
mode frequencies (including all the Raman and infrared active modes),
velocities of acoustic modes and the polarization vectors are systematically
fitted in terms of the chiral angle and radius, where the restrictions of
various symmetry operations of the SWCNT are fulfilled
DNMT3a in the hippocampal CA1 is crucial in the acquisition of morphine selfâadministration in rats
Drugâreinforced excessive operant responding is one fundamental feature of long-lasting addictionâlike behaviors and relapse in animals. However, the transcriptional regulatory mechanisms responsible for the persistent drugâspecific (not natural rewards) operant behavior are not entirely clear. In this study, we demonstrate a key role for one of the de novo DNA methyltransferase, DNMT3a, in the acquisition of morphine selfâadministration (SA) in rats. The expression of DNMT3a in the hippocampal CA1 region but not in the nucleus accumbens shell was significantly upâregulated after 1â and 7âday morphine SA (0.3 mg/kg/infusion) but not after the yoked morphine injection. On the other hand, saccharin SA did not affect the expression of DNMT3a or DNMT3b. DNMT inhibitor 5âazaâ2âdeoxycytidine (5âaza) microinjected into the hippocampal CA1 significantly attenuated the acquisition of morphine SA. Knockdown of DNMT3a also impaired the ability to acquire the morphine SA. Overall, these findings suggest that DNMT3a in the hippocampus plays an important role in the acquisition of morphine SA and may be a valid target to prevent the development of morphine addiction.
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Raman and Infra-red properties and layer dependence of the phonon dispersions in multi-layered graphene
The symmetry group analysis is applied to classify the phonon modes of
-stacked graphene layers (NSGL's) with AB- and AA-stacking, particularly
their infra-red and Raman properties. The dispersions of various phonon modes
are calculated in a multi-layer vibrational model, which is generalized from
the lattice vibrational potentials of graphene to including the inter-layer
interactions in NSGL's. The experimentally reported red shift phenomena in the
layer number dependence of the intra-layer optical C-C stretching mode
frequencies are interpreted. An interesting low frequency inter-layer optical
mode is revealed to be Raman or Infra-red active in even or odd NSGL's
respectively. Its frequency shift is sensitive to the layer number and
saturated at about 10 layers.Comment: enlarged versio
Effects of polymerase, template dilution and cycle number on PCR based 16 S rRNA diversity analysis using the deep sequencing method
A lattice dynamical treatment for the total potential energy of single-walled carbon nanotubes and its applications: relaxed equilibrium structure, elastic properties, and vibrational modes of ultra-narrow tubes
In this paper, we proposed a lattice dynamic treatment for the total
potential energy for single-walled carbon nanotubes (SWCNT's) which is, apart
from a parameter for the non-linear effects, extracted from the vibrational
energy of the planar graphene sheet. Based upon the proposal, we investigated
systematically the relaxed lattice configuration for narrow SWCNT's, the strain
energy, the Young's modulus and Poisson ratio, and the lattice vibrational
properties respected to the relaxed equilibrium tubule structure. Our
calculated results for various physical quantities are nicely in consistency
with existing experimental measurements. Particularly, we verified that the
relaxation effect brings the bond length longer and the frequencies of various
optical vibrational modes softer; Our calculation provides the evidence that
the Young's modulus of armchair tube exceeds that of the planar graphene sheet,
and the large diameter limits of the Young's modulus and Poisson ratio are in
agreement with the experimental values of the graphite; The calculated radial
breathing modes for the ultra narrow tubes with diameter range between 0.2 -
0.5 nm coincide the experimental results and the existing {\it ab initio}
calculations with satisfaction; For narrow tubes of diameter 2 nm, the
calculated frequencies of optical modes in tubule tangential plane as well as
those of radial breathing modes are also in good agreement with the
experimental measurement. In addition, our calculation shows that various
physical quantities of relaxed SWCNT's can actually be expanded in terms of the
chiral angle defined for the correspondent ideal SWCNT's.Comment: 9 pages, 7 figure
The rise in house prices in China: Bubbles or fundamentals?
The dramatic rise of house prices in many cities of China has brought huge attention from both the governmental and academic circles. There is a huge debate on whether the increasing house prices are driven by market fundamentals or just by speculation. Like Levin and Wright (1997a, 1997b), we decompose house prices in China into fundamental and nonâfundamental components. We also consider potential nonlinear feedback from the historical growth rate of house prices on the current house prices and propose a semiparametric approach to estimate the speculative components in the model. We demonstrate that the nonâfundamental part contributes a relatively small proportion of the rise of house prices in China
A new positive relationship between pCO2 and stomatal frequency in Quercus guyavifolia (Fagaceae): a potential proxy for palaeo-CO2 levels
Background and Aims The inverse relationship between atmospheric CO2 partial pressure (pCO2) and stomatal frequency in many species of plants has been widely used to estimate palaeoatmospheric CO2 (palaeo-CO2) levels; however, the results obtained have been quite variable. This study attempts to find a potential new proxy for palaeo-CO2 levels by analysing stomatal frequency in Quercus guyavifolia (Q. guajavifolia, Fagaceae), an extant dominant species of sclerophyllous forests in the Himalayas with abundant fossil relatives. Methods Stomatal frequency was analysed for extant samples of Q. guyavifolia collected from17 field sites at altitudes ranging between 2493 and 4497âm. Herbarium specimens collected between 1926 and 2011 were also examined. Correlations of pCO2-stomatal frequency were determined using samples from both sources, and these were then applied to Q. preguyavaefolia fossils in order to estimate palaeo-CO2 concentrations for two late-Pliocene floras in south-western China. Key Results In contrast to the negative correlations detected for most other species that have been studied, a positive correlation between pCO2 and stomatal frequency was determined in Q. guyavifolia sampled from both extant field collections and historical herbarium specimens. Palaeo-CO2 concentrations were estimated to be approx. 180-240âppm in the late Pliocene, which is consistent with most other previous estimates. Conclusions A new positive relationship between pCO2 and stomatal frequency in Q. guyavifolia is presented, which can be applied to the fossils closely related to this species that are widely distributed in the late-Cenozoic strata in order to estimate palaeo-CO2 concentrations. The results show that it is valid to use a positive relationship to estimate palaeo-CO2 concentrations, and the study adds to the variety of stomatal density/index relationships that available for estimating pCO2. The physiological mechanisms underlying this positive response are unclear, however, and require further researc
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