4,531 research outputs found
Pseudogap, Superconducting Energy Scale, and Fermi Arcs in Underdoped Cuprate Superconductors
Through the measurements of magnetic field dependence of specific heat in
in zero temperature limit, we determined the nodal slope
of the quasiparticle gap. It is found that has a very
similar doping dependence of the pseudogap temperature or value
. Meanwhile the virtual maximum gap at () derived from
is found to follow the simple relation upon
changing the doping concentration. This strongly suggests a close relationship
between the pseudogap and superconductivity. It is further found that the
superconducting transition temperature is determined by both the residual
density of states of the pseudogap phase and the nodal gap slope in the zero
temperature limit, namely, , where
is the extracted zero temperature value of the normal state
specific heat coefficient which is proportional to the size of the residual
Fermi arc . This manifests that the superconductivity may be formed by
forming a new gap on the Fermi arcs near nodes below . These observations
mimic the key predictions of the SU(2) slave boson theory based on the general
resonating-valence-bond (RVB) picture.Comment: 6 pages, 6 figures, to be published in Phys. Rev.
Monitoring the process of formation of ZnO from ZnO2 using in situ combined XRD/XAS technique
Use of in situ combined X-ray diffraction and X-ray absorption spectroscopy for the study of the thermal decomposition of zinc peroxide to zinc oxide is reported here. Comparison of data extracted from both X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) with thermo gravimetric analysis (TGA) enabled us to follow the nature of the conversion of ZnO2 to ZnO. A temperature range between 230 and 350oC appears to show a very poorly crystalline ZnO is formed prior to the formation of ordered ZnO material. Both the decrease in white line intensity in the Zn K-edge XANES and resulting lower coordination numbers estimated from analysis of Zn K-edge data of ZnO heated at 500oC, in comparison to bulk ZnO, suggest that that the ZnO produced by this method has significant defects in the system
Electronic specific heat and low energy quasiparticle excitations in superconducting state of single crystals
Low temperature specific heat has been measured and extensively analyzed on a
series of single crystals from underdoped to overdoped
regime. From these data the quasiparticle density of states (DOS) in the mixed
state is derived and compared to the predicted scaling law
of d-wave superconductivity. It is found that
the scaling law can be nicely followed by the optimally doped sample (x=0.15)
in quite wide region of (). However, the region
for this scaling becomes smaller and smaller towards more underdoped region: a
clear trend can be seen for samples from x=0.15 to 0.069. Therefore, generally
speaking, the scaling quality becomes worse on the underdoped samples in terms
of scalable region of . This feature in the underdoped region is
explained as due to the low energy excitations from a second order (for
example, anti-ferromagnetic correlation, d-density wave, spin density wave or
charge density wave order) that may co-exist or compete with superconductivity.
Surprisingly, deviations from the d-wave scaling law have also been found for
the overdoped sample (x=0.22). While the scaling law is reconciled for the
overdoped sample when the core size effect is taken into account. An important
discovery of present work is that the zero-temperature data follow the
Volovik's relation quite well for all samples
investigated here although the applicability of the d-wave scaling law to the
data at finite temperatures varies with doped hole concentration. Finally we
present the doping dependence of some parameters, such as, the residual linear
term , the value, etc. ...Comment: 15 pages, 24 figure
Overall Evolution of Realistic Gamma-ray Burst Remnant and Its Afterglow
Conventional dynamic model of gamma-ray burst remnants is found to be
incorrect for adiabatic blastwaves during the non-relativistic phase. A new
model is derived, which is shown to be correct for both radiative and adiabatic
blastwaves during both ultra-relativistic and non-relativistic phase. Our model
also takes the evolution of the radiative efficiency into account. The
importance of the transition from the ultra-relativistic phase to the
non-relativistic phase is stressed.Comment: 9 pages, aasms4 style, 3 ps figures, minor changes, will be published
in Chin. Phys. Let
Citrobacter rodentium induces rapid and unique metabolic and inflammatory responses in mice suffering from severe disease.
The mouse pathogen Citrobacter rodentium is used to model infections with enterohaemorrhagic and enteropathogenic Escherichia coli (EHEC and EPEC). Pathogenesis is commonly modelled in mice developing mild disease (e.g., C57BL/6). However, little is known about host responses in mice exhibiting severe colitis (e.g., C3H/HeN), which arguably provide a more clinically relevant model for human paediatric enteric infection. Infection of C3H/HeN mice with C. rodentium results in rapid colonic colonisation, coinciding with induction of key inflammatory signatures and colonic crypt hyperplasia. Infection also induces dramatic changes to bioenergetics in intestinal epithelial cells, with transition from oxidative phosphorylation (OXPHOS) to aerobic glycolysis and higher abundance of SGLT4, LDHA, and MCT4. Concomitantly, mitochondrial proteins involved in the TCA cycle and OXPHOS were in lower abundance. Similar to observations in C57BL/6 mice, we detected simultaneous activation of cholesterol biogenesis, import, and efflux. Distinctly, however, the pattern recognition receptors NLRP3 and ALPK1 were specifically induced in C3H/HeN. Using cell-based assays revealed that C. rodentium activates the ALPK1/TIFA axis, which is dependent on the ADP-heptose biosynthesis pathway but independent of the Type III secretion system. This study reveals for the first time the unfolding intestinal epithelial cells' responses during severe infectious colitis, which resemble EPEC human infections
The roles of specialist provision for children with specific speech and language difficulties in England and Wales: a model for inclusion?
Children with specific speech and language difficulties pose a challenge to the education and health systems. In addition to their language difficulties they are also at risk of literacy and social, emotional and behavioural difficulties. The main support for children with more severe difficulties has been enhanced provision in mainstream schools (language units or integrated resources) and special schools. The move to an inclusive education system challenges this tradition. The present paper reports the results of interviews with heads of language units/integrated resources and headteachers of special schools (n=57) as part of a larger study within England and Wales. Their views are considered with reference to criteria for entry to specialist provision, the development of collaborative practice between teachers, teaching assistants and speech and language therapists, and the implications for inclusive education
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