5,164 research outputs found
Parity-violating coupling constant from the flavor-conserving effective weak chiral Lagrangian
We investigate the parity-violating pion-nucleon-nucleon coupling constant
, based on the chiral quark-soliton model. We employ an effective
weak Hamiltonian that takes into account the next-to-leading order corrections
from QCD to the weak interactions at the quark level. Using the gradient
expansion, we derive the leading-order effective weak chiral Lagrangian with
the low-energy constants determined. The effective weak chiral Lagrangian is
incorporated in the chiral quark-soliton model to calculate the
parity-violating constant . We obtain a value of about
at the leading order. The corrections from the next-to-leading order
reduce the leading order result by about 20~\%.Comment: 12 page
Adiabatic Electroweak Baryogenesis Driven by an Axion-like Particle
An axion-like particle (ALP) offers a new direction in electroweak
baryogenesis because the periodic nature enables it to trigger a strong
first-order phase transition insensitively to the decay constant . For
much above TeV, the ALP-induced electroweak phase transition is approximately
described by adiabatic processes, distinguishing our scenario for electroweak
baryogenesis from the conventional ones. We show that, coupled to the
electroweak anomaly, the ALP can naturally realize spontaneous electroweak
baryogenesis to solve the matter-antimatter asymmetry problem for in the
range between about GeV and GeV. In such an ALP window, the
violation for baryogenesis is totally free from the experimental constraints,
especially from the recently improved limit on the electron electric dipole
moment. Future searches for ALPs could probe our scenario while revealing the
connection between electroweak symmetry breaking and baryogenesis.Comment: 12 pages, 5 figures, appendices added, published versio
Dark matter filtering-out effect during a first-order phase transition
If the mass of dark matter is generated from a cosmological phase transition
involving the nucleation of bubbles, the corresponding bubble walls can filter
out dark matter particles during the phase transition. Only particles with
sufficient momentum to overcome their mass inside the bubbles can pass through
the walls. As a result, the dark matter number density after the phase
transition has a suppression factor , where
is the dark matter mass, and and are the Lorentz
factor and temperature of the incoming fluid in the bubble wall rest frame,
respectively. Under certain assumptions, we show that the filtering-out process
can naturally provide a large suppression consistent with the observed dark
matter density for a wide range of dark matter masses up to the Planck scale.
Since the first-order phase transition is the decisive ingredient in our
mechanism, a new connection is made between heavy dark matter scenarios and
gravitational wave observations.Comment: 6 pages, 2 figures, minor change, presentation improve
Nasopharynx as a Microbiologic Reservoir in Chronic Suppurative Otitis Media: Preliminary Study
ObjectivesThe present study was designed to identify the correlations of bacterial strains of the middle ear and the nasopharynx in chronic suppurative otitis media (CSOM) patients who were scheduled for operations.MethodsSixty-three patients with CSOM were enrolled in the study. Culture specimens were collected from the middle ear and nasopharynx of patients who were admitted for operation. Samples collections were performed 3 times; from the middle ear and nasophaynx at the admission day, from the middle ear during the operation, and from the external auditory canal post-operatively. Bacteria were identified by gram staining and biochemical tests. The correspondence rate of organisms which simultaneously exist in the middle ear and the nasopharynx was measured.ResultsSixty-eight organisms were isolated from the middle ear and 57 organisms from the nasopharynx among 63 patients. Of 68 bacteria identified in middle ear, 26.52% (18 bacteria) corresponded with those of nasopharynx. MRSA had the high correspondence rate, and of 18 methicillin-resistant Staphylococcus aureus (MRSA) isolated from middle ear, 33.3% (6 bacteria) corresponded with nasophaynx. Meanwhile, 3 organisms of MRSA were detected from the external auditory canal post-operatively, although they were only found in nasopharynx pre-operatively.ConclusionThe current trend of middle ear swab alone for bacterial detection would be insufficient to identify the potent MRSA and impede early antibiotic intervention for the effective middle ear surgery. Therefore, it is necessary to perform nasopharynx cultures together with conventional middle ear culture to control potent risk for infection pre-operatively
Ionothermal Synthesis of Metal-Organic Framework
Ionothermal synthesis employs ionic liquids for synthesis of metal organic frameworks (MOFs) as solvent and template. The cations and anions of ionic liquids may be finely adjusted to produce a great variety of reaction environments and thus frameworks. Organisation of the structures synthesised from related ionic liquid combinations give rise to provocative chemical trends that may be used to predict future outcomes. Further analysis of their structures is possible by reducing the complex framework to its underlying topology, which by itself brings more precision to prediction. Through reduction, many seemingly different, but related classes of structures may be merged into larger groups and provide better understanding of the nanoscopic structures and synthesis conditions that gave rise to them. Ionothermal synthesis has promised to enable us to effectively plan the synthesis ahead for a given purpose. However, for its promise to be kept, several difficult limitations must be overcome, including the inseparable cations from the solvent that reside in the framework pore
The Influence of Tibial Positioning on the Diagnostic Accuracy of Combined Posterior Cruciate Ligament and Posterolateral Rotatory Instability of the Knee
Background: To determine if tibial positioning affects the external rotation of the tibia in a dial test for posterolateral rotatory instability combined with posterior cruciate ligament (PCL) injuries. Methods: Between April 2007 and October 2007, 16 patients with a PCL tear and posterolateral rotatory instability were diagnosed using a dial test. The thigh-foot angle was measured at both 30 ° and 90 ° of knee fl exion with an external rotation stress applied to the tibia in 2 different positions (reduction and posterior subluxation). The measurements were performed twice by 2 orthopedic surgeons. Results: In posterior subluxation, the mean side-to-side difference in the thigh-foot angle was 11.56 ± 3.01 ° at 30 ° of knee fl exion and 11.88 ± 4.03 ° at 90 ° of knee flexion. In the sequential dial test performed with the tibia reduced, the mean side-to-side difference was 15.94 ± 4.17 ° (p < 0.05) at 30 ° of knee fl exion and 16.88 ± 4.42 ° (p = 0.001) at 90 ° of knee fl exion. The mean tibial external rotation was 5.31 ± 2.86 ° and 6.87 ± 3.59 ° higher in the reduced position than in the posterior subluxation at both 30° and 90 ° of knee fl exion. Conclusions: In the dial test, reducing the tibia with an anterior force increases the ability of an examiner to detect posterolateral rotary instability of the knee combined with PCL injuries
Cessation of Gonadotropin-Releasing Hormone Antagonist on Triggering Day: An Alternative Method for Flexible Multiple-Dose Protocol
This study was performed to analyze retrospectively outcomes of stimulated in vitro fertilization (IVF) cycles where the gonadotropin-releasing hormone (GnRH) antagonist was omitted on ovulation triggering day. A total of 92 consecutive IVF cycles were included in 65 women who are undergoing ovarian stimulation with recombinant FSH. A GnRH antagonist, cetrorelix 0.25 mg/day, was started when leading follicle reached 14 mm in diameter until the day of hCG administration (Group A, 66 cycles) or until the day before hCG administration (Group B, 26 cycles). The duration of ovarian stimulation, total dose of gonadotropins, serum estradiol levels on hCG administration day, and the number of oocytes retrieved were not significantly different between the two groups. The total dose of GnRH antagonist was significantly lower in Group B compared to Group A (2.7±0.8 vs. 3.2±0.9 ampoules). There was no premature luteinization in the subjects. The proportion of mature oocytes (71.4% vs. 61.7%) and fertilization rate of mature (86.3±19.7% vs. 71.8±31.7%) was significantly higher in Group B. There were no significant differences in embryo quality and clinical pregnancy rates. Our results suggest that cessation of the GnRH antagonist on the day of hCG administration during a flexible multiple-dose protocol could reduce the total dose of GnRH antagonist without compromising IVF results
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