381 research outputs found
Power-Law Decay of Standing Waves on the Surface of Topological Insulators
We propose a general theory on the standing waves (quasiparticle interference
pattern) caused by the scattering of surface states off step edges in
topological insulators, in which the extremal points on the constant energy
contour of surface band play the dominant role. Experimentally we image the
interference patterns on both BiTe and BiSe films by measuring
the local density of states using a scanning tunneling microscope. The observed
decay indices of the standing waves agree excellently with the theoretical
prediction: In BiSe, only a single decay index of -3/2 exists; while in
BiTe with strongly warped surface band, it varies from -3/2 to -1/2 and
finally to -1 as the energy increases. The -1/2 decay indicates that the
suppression of backscattering due to time-reversal symmetry does not
necessarily lead to a spatial decay rate faster than that in the conventional
two-dimensional electron system. Our formalism can also explain the
characteristic scattering wave vectors of the standing wave caused by
non-magnetic impurities on BiTe.Comment: 4 pages, 3 figure
Magnetic phase transitions in the triangular-lattice spin-1 dimer compound K2Ni2(SeO3)3
In our study, we conduct magnetization and heat capacity measurements to
investigate field-induced magnetic phase transitions within the newly
synthesized compound K2Ni2(SeO3)3, a spin-1 dimer system arranged on a
triangular lattice. The Ni-Ni dimers exhibit a ferromagnetic intra-dimer
interaction, effectively behaving as an ensemble with a total spin of S=2. In
contrast, antiferromagnetic interactions manifest between these dimers on the
triangular lattice. The trigonal distortion of the NiO6 octahedra introduces
easy-axis magnetic anisotropy, accounting for the distinct magnetic phase
diagrams observed when applying c-axis directional and in-plnae magnetic
fields. Notably, our investigation unveils a two-step phase transition with the
magnetic field aligned with the c direction. We propose that the system at the
first transition is from a paramagnetic state to an up-up-down state,
characterized by the Z3 lattice-symmetry breaking. Subsequently, a
Berezinskii-Kosterlitz-Thouless transition, involving the breaking of the
c-axis spin-rotation symmetry, leads to the formation of the "Y state" at low
temperatures. These findings yield valuable insights into the magnetic phase
transitions inherent to geometrically frustrated magnetic systems featuring
dimer structures.Comment: 10 pages, 11 figure
2,3-Diaminopyridinium sorbate–sorbic acid (1/1)
In the title molecular salt–adduct, C5H8N3
+·C6H7O2
−·C6H8O2, the 2,3-diaminopyridinium cation is essentially planar, with a maximum deviation of 0.013 (2) Å, and is protanated at its pyridine N atom. The sorbate anion and sorbic acid molecules exist in extended conformations. In the crystal, the protonated N atom and one of the two amino-group H atoms are hydrogen bonded to the sorbate anion through a pair of N—H⋯O hydrogen bonds, forming an R
1
2(6) ring motif. The carboxyl groups of the sorbic acid molecules and the carboxylate groups of the sorbate anions are connected via O—H⋯O hydrogen bonds. Furthermore, the ion pairs and neutral molecules are connected via intermolecular N—H⋯O hydrogen bonds, forming sheets lying parallel to (100)
Pharmacokinetics, safety and tolerability of L-3-n-butylphthalide tablet after single and multiple oral administrations in healthy Chinese volunteers
L-3-n-butylphthalide (L-NBP) is a naturally occurring antioxidant, which can be used for the treatment of acute ischemic stroke and vascular dementia. This study evaluated the safety, tolerability and pharmacokinetics of L-NBP tablets in healthy Chinese volunteers. This was a single-center, randomized, double-blind, placebo-controlled, single- and multiple-dose study. Subjects were assigned to receive a single dose of L-NBP tablet at either 80, 160, 320, or 480 mg (n=40), or multiple doses of 160 mg twice daily for 7 days (n=12). Plasma samples were analyzed with LC-MS/MS. Pharmacokinetic parameters of L-NBP were calculated using non-compartmental analysis with WinNonlin software. Statistical analysis was performed using SPSS software. All adverse events (AEs) were mild and of limited duration; AEs in this study occurred less frequently and more mildly than AEs listed for the DL-NBP soft capsule. No serious adverse event (SAE), death or withdrawal from the study was observed. In the single-dose study, Cmax was reached at about 1 h, and the mean t1/2 was approximately 13.76 h. Area under curve (AUC) and Cmax increased with dose escalation, but dose proportionality was not observed over the range of 160 to 480 mg. In the multiple-dose study, the steady-state was reached within 3 days with slight accumulation. In summary, the L-NBP tablet was well tolerated in healthy Chinese subjects. Slight accumulation appeared after repeated doses.L-3-n-butilftalida (L-NMP) é um antioxidante natural, que pode ser utilizado para o tratamento do acidente isquêmico agudo e demência vascular. Este estudo avaliou segurança, tolerância e farmacocinética de comprimidos de L-NBP em chineses voluntários sadios. Este foi um estudo monocêntrico, randomizado, duplo cego, com controle por placebo e doses única e múltipla. Os indivíduos receberam dose única de comprimido de L-NBP de 80, 160, 320 ou 480 mg (n=40) e doses múltiplas de 160 mg duas vezes ao dia, por sete dias (n=12). Amostras de plasma foram analisadas com LC-MS/MS. Os parâmetros farmacocinéticos do L-NBP foram calculados utilizando análise não compartimental, com o programa WinNonlin. A análise estatística foi realizada utilizando-se o programa SPSS. Todos os eventos adversos (EAs) foram moderados e de duração limitada. EAs nesse estudo ocorreram menos frequentemente e mais moderadamente do que os EAs relacionados para cápsulas moles de DL-NBP. Não se observaram eventos adversos graves (EAG), morte ou abandono do estudo. Com dose única, atingiu-se o Cmax em cerca de 1 hora e o t1/2 médio foi de, aproximadamente, 13,76 h. A área sob a curva (ASC) e o Cmax aumentaram com o aumento da dose, mas não se observou proporcionalidade na faixa acima de 160 a 480 mg. No estudo de dose múltipla, o equilíbrio foi alcançado em três dias, com pequeno acúmulo. Em resumo, o comprimido de L-NMP foi bem tolerado em indivíduos chineses saudáveis. O acúmulo pequeno apareceu após doses repetidas
Constraints on the cosmological parameters with three-parameter correlation of Gamma-ray bursts
As one of the most energetic and brightest events, gamma-ray bursts (GRBs)
can be treated as a promising probe of the high-redshift universe. Similar to
type Ia supernovae (SNe Ia), GRBs with same physical origin could be treated as
standard candles. We select GRB samples with the same physical origin, which
are divided into two groups. One group is consisted of 31 GRBs with a plateau
phase feature of a constant luminosity followed by a decay index of about -2 in
the X-ray afterglow light curves, and the other has 50 GRBs with a shallow
decay phase in the optical light curves. For the selected GRB samples, we
confirm that there is a tight correlation between the plateau luminosity ,
the end time of plateau and the isotropic energy release
. We also find that the correlation is
insensitive to the cosmological parameters and no valid limitations on the
cosmological parameters can be obtained using this correlation. We explore a
new three-parameter correlation , , and the spectral peak energy in
the rest frame (), and find that this correlation
can be used as a standard candle to constrain the cosmological parameters. By
employing the optical sample only, we find the constraints of for a flat CDM model. For the
non-flat CDM model, the best-fitting results are , . For the combination of the X-ray and optical
smaples, we find for a flat
CDM model, and , for a non-flat CDM model.Comment: Accepted for publication in The Astrophysical Journal, 13 pages, 9
figures and 2 table
Electron interaction-driven insulating ground state in Bi2Se3 topological insulators in the two dimensional limit
We report a transport study of ultrathin Bi2Se3 topological insulators with
thickness from one quintuple layer to six quintuple layers grown by molecular
beam epitaxy. At low temperatures, the film resistance increases
logarithmically with decreasing temperature, revealing an insulating ground
state. The sharp increase of resistance with magnetic field, however, indicates
the existence of weak antilocalization, which should reduce the resistance as
temperature decreases. We show that these apparently contradictory behaviors
can be understood by considering the electron interaction effect, which plays a
crucial role in determining the electronic ground state of topological
insulators in the two dimensional limit.Comment: 4 figure
Visualizing the elongated vortices in -Ga nanostrips
We study the magnetic response of superconducting -Ga via low
temperature scanning tunneling microscopy and spectroscopy. The magnetic vortex
cores rely substantially on the Ga geometry, and exhibit an unexpectedly-large
axial elongation with aspect ratio up to 40 in rectangular Ga nano-strips
(width 100 nm). This is in stark contrast with the isotropic circular
vortex core in a larger round-shaped Ga island. We suggest that the unusual
elongated vortices in Ga nanostrips originate from geometric confinement effect
probably via the strong repulsive interaction between the vortices and Meissner
screening currents at the sample edge. Our finding provides novel conceptual
insights into the geometrical confinement effect on magnetic vortices and forms
the basis for the technological applications of superconductors.Comment: published in Phys. Rev. B as a Rapid Communicatio
Radio Plateaus in Gamma-Ray Burst Afterglows and Their Application in Cosmology
The plateau phase in the radio afterglows has been observed in very few
gamma-ray bursts (GRBs), and 27 radio light curves with plateau phase were
acquired from the published literature in this article. We obtain the related
parameters of the radio plateau, such as temporal indexes during the plateau
phase ( and ), break time (\Tbz) and the corresponding
radio flux (). The two parameter Dainotti relation between the break
time of the plateau and the corresponding break luminosity (\Lbz) in radio
band is \Lbz \propto \Tbz^{-1.20\pm0.24}. Including the isotropic energy
\Eiso and the peak energy \Epi, the three parameter correlations for the
radio plateaus are written as \Lbz \propto \Tbz^{-1.01 \pm 0.24} \Eiso^{0.18
\pm 0.09} and \Lbz \propto \Tbz^{-1.18 \pm 0.27} \Epi^{0.05 \pm 0.28},
respectively. The correlations are less consistent with that of X-ray and
optical plateaus, implying that radio plateaus may have a different physical
mechanism. The typical frequencies crossing the observational band may be a
reasonable hypothesis that causes the breaks of the radio afterglows. We
calibrate GRBs empirical luminosity correlations as standard candle for
constraining cosmological parameters, and find that our samples can constrain
the flat CDM model well, while are not sensitive to non-flat
CDM model. By combining GRBs with other probes, such as SN and CMB,
the constraints on cosmological parameters are \om = 0.297\pm0.006 for the
flat CDM model and \om = 0.283\pm0.008, \oL = 0.711\pm0.006 for
the non-flat CDM model, respectively.Comment: 16 pages, 6 figures and 6 tables, accepted for publication in Ap
Diagnostic value of urine sCD163 levels for sepsis and relevant acute kidney injury: a prospective study
BACKGROUND: Sepsis is a common syndrome in critically ill patients and easily leads to the occurrence of acute kidney injury (AKI), with high mortality rates. This study aimed to investigate the diagnostic value of urine soluble CD163 (sCD163) for identification of sepsis, severity of sepsis, and for secondary AKI, and to assess the patients’ prognosis. METHODS: We enrolled 20 cases with systemic inflammatory response syndrome (SIRS), 40 cases with sepsis (further divided into 17 sepsis cases and 23 severe sepsis cases) admitted to the intensive care unit (ICU), and 20 control cases. Results for urine sCD163 were recorded on the day of admission to the ICU, and AKI occurrence was noted. RESULTS: On the day of ICU admission, the sepsis group exhibited higher levels of urine sCD163 (74.8 ng/ml; range: 47.9-148.3 ng/ml) compared with those in the SIRS group (31.9 ng/ml; 16.8-48.0, P < 0.001). The area under the curve (AUC) was 0.83 (95% confidence interval [CI]: 0.72-0.94, P < 0.001) the sensitivity was 0.83, and the specificity was 0.75 (based on a cut-off point of 43.0 ng/ml). Moreover, the severe sepsis group appeared to have a higher level of sCD163 compared with that in the sepsis group (76.2; 47.2-167.5 ng/ml vs. 74.2; 46.2-131.6 ng/ml), but this was not significant. For 15 patients with AKI, urine sCD163 levels at AKI diagnosis were significantly higher than those of the remaining 35 sepsis patients upon ICU admission (121.0; 74.6-299.1 ng/ml vs. 61.8; 42.8-128.3 ng/ml, P = 0.049). The AUC for urine sCD163 was 0.688 (95% CI: 0.51-0.87, P = 0.049). Sepsis patients with a poor prognosis showed a higher urine sCD163 level at ICU admission (98.6; 50.3-275.6 ng/ml vs. 68.0; 44.8-114.5 ng/ml), but this was not significant. Patients with AKI with a poor prognosis had higher sCD163 levels than those in patients with a better prognosis (205.9; 38.6-766.0 ng/ml vs. 80.9; 74.9-141.0 ng/ml), but this was not significant. CONCLUSIONS: This study shows, for the first time, the potential value of urine sCD163 levels for identifying sepsis and diagnosing AKI, as well as for assessment of patients’ prognosis. TRIAL REGISTRATION: ChiCTR-ONC-1000081
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