Abstract
STUDY QUESTION
What is the prevalence of multiple pregnancy with zygotic splitting after single embryo transfer (SET)?
SUMMARY ANSWER
The prevalence of multiple pregnancy with zygotic ...splitting after SET was 1.36%.
WHAT IS KNOWN ALREADY
In 2008, the Japan Society of Obstetrics and Gynaecology (JSOG) recommended the adoption of SET to reduce multiple births. Since then, to improve the clinical pregnancy rate, elective SET using blastocyst transfer and frozen-warmed ET has increased. Blastocyst culture and zona pellucida manipulation, including ICSI and AH, have been widely reported as risk factors for monozygotic twinning. However, all these studies may have included cases with dizygotic pregnancies produced by a transferred embryo and a spontaneous conception.
STUDY DESIGN, SIZE, DURATION
A retrospective observational study was performed, based on 937 848 SET cycles in registered ART data from the JSOG between 2007 and 2014. The study was approved by the Registration and Research Subcommittee of the JSOG and Juntendo University Ethics Committee.
PARTICIPANTS/MATERIALS, SETTING, METHODS
To identify possible factors affecting the prevalence of zygotic splitting, we identified pregnancies, in which the number of foetuses exceeded the number of gestational sacs (GSs), to restrict our analysis to 'true' zygotic splitting. Multiple logistic regression analysis was performed using singleton pregnancy after SET, as control. P < 0.05 was considered statistically significant.
MAIN RESULTS AND THE ROLE OF CHANCE
Fresh and frozen-warmed SET produced 276 934 clinical pregnancies (29.5%/SET), including 4310 twins (1.56% of pregnancies) and 109 triplets (0.04% of pregnancies). Based on sex analysis of dichorionic twins after SET, the prevalence of multiple pregnancy with zygotic splitting was 1.36%. Statistical analysis revealed that compared to singleton pregnancies zygotic splitting pregnancies were associated with frozen-warmed ET cycles (odds ratio OR = 1.34; 95% CI: 1.16-1.55), blastocyst culture (OR = 1.79; 95% CI: 1.54-2.09) or AH (OR = 1.21; 95% CI: 1.08-1.35). In fresh ET cycles, the prevalence rate of zygotic splitting pregnancy after single blastocyst transfer was significantly higher than that after SET cycles with cleavage embryos (OR = 2.20; 95% CI: 1.83-2.66). However, no significant difference in ovarian stimulation and fertilization methods was recognized.
LIMITATIONS, REASONS FOR CAUTION
In the current Japanese ART registry system, data regarding frozen-warmed ET do not include information about ovarian stimulation and fertilization methods. Registration for AH only began in 2010. There is no way of validating if data submitted by clinics is correct
WIDER IMPLICATIONS OF THE FINDINGS
Clinicians should consider whether to counsel couples about the small increase in the risk of zygotic splitting associated with some embryo manipulations.
STUDY FUNDING/COMPETING INTEREST(S)
No external funds were used for the study. The authors have no competing interests to declare.
TRIAL REGISTRATION NUMBER
None.
Charge ordering (CO) is a phenomenon in which electrons in solids crystallize into a periodic pattern of charge-rich and charge-poor sites owing to strong electron correlations. This usually results ...in long-range order. In geometrically frustrated systems, however, a glassy electronic state without long-range CO has been observed. We found that a charge-ordered organic material with an isosceles triangular lattice shows charge dynamics associated with crystallization and vitrification of electrons, which can be understood in the context of an energy landscape arising from the degeneracy of various CO patterns. The dynamics suggest that the same nucleation and growth processes that characterize conventional glass-forming liquids guide the crystallization of electrons. These similarities may provide insight into our understanding of the liquid-glass transition.
We report the test results of the first series beam separation dipole, MBXF1, for the HL-LHC project. The magnet has a full length of 7 m and is designed to generate a field integral of 35 T ...<inline-formula><tex-math notation="LaTeX">\cdot</tex-math></inline-formula> m at a nominal operating current (<inline-formula><tex-math notation="LaTeX">I_\text{nominal}</tex-math></inline-formula>) of 12.11 kA. The cold test is performed at the test facility in High Energy Accelerator Research Organization (KEK) using a 9-m deep vertical cryostat. The test consists of two test cycles with one thermal cycle. In each of the test cycles MBXF1 is energized in superfluid helium at 1.9 K and subjected to a series of quench training and magnetic field evaluation. The test shows that the magnet has a good training performance as it reaches <inline-formula><tex-math notation="LaTeX">I_\text{nominal}</tex-math></inline-formula> with two quenches and an ultimate operating current (<inline-formula><tex-math notation="LaTeX">I_\text{ultimate}</tex-math></inline-formula>) of 13.231 kA with seven quenches. Furthermore we observe no quench during the training of the second test cycle, indicating MBXF1 has a good training memory. Magnetic measurements of MBXF1 show that the discrepancy between the measured and computed harmonics at the magnetic center is 3.9 units for normal sextupole and less than 0.5 units for the other allowed-normal multipoles. Finally sextupole integral (<inline-formula><tex-math notation="LaTeX">\bar{b}_{3}</tex-math></inline-formula>) and decapole integral (<inline-formula><tex-math notation="LaTeX">\bar{b}_{5}</tex-math></inline-formula>), which are major systematic field errors in MBXF, respectively are estimated to be 2.0 units and 1.7 units for an actual environmental condition with ferromagnetic materials in the LHC accelerator tunnel.
The infrared synchrotron radiation (IR-SR) beamline of SPring-8 as an IR light source was applied to characterize boron (B) atoms in silicon nanowires (SiNWs). The use of an IR-SR beam with much ...higher brilliance than conventional IR light sources and a wide range of wavenumbers from visible to far IR regions made it possible to detect a local vibrational mode of B in SiNWs. The use of this technique has also made it possible to detect other IR peaks related to transitions of a bound hole from the ground state of a B acceptor atom to excited states, clarifying the electronic state of B acceptors in SiNWs.
As a Japanese contribution to the High-Luminosity Large Hadron Collider (HL-LHC) upgrade, KEK is in charge of developing the beam separation dipole cold masses. The full-scale prototype magnet ...(MBXFP1) was constructed in Hitachi and powering test at cold was conducted at KEK. After the test, the magnet was returned to Hitachi for the final assembly of the cold mass. The pressure vessel design of the cold mass was carried out by KEK in accordance with ASME code. A new design of bus leads was proposed to satisfy the requirement of flexibility as well as mechanical support and electrical insulation. Welding of the extremity pipes was challenging due to tight position tolerance. This article reports the structure, pressure vessel design, and assembly of the LMBXF prototype cold mass (LMBXFP1) including bus work, instrumentation, and welding works with geometrical measurements.
High Energy Research Organization (KEK) has engaged in development of the beam separation dipole, MBXF, toward the HL-LHC project. The magnet has a full length of 7 m and generates a magnetic field ...of 5.6 T in the magnet center at nominal operating condition of 12 kA and 1.9 K. Optimization of the magnetic model is performed through two and three dimensional studies and iterated until resultant field quality is within required tolerance. Field quality of the first full-scale prototype of MBXF (a.k.a. MBXFP1) is measured first at room temperature on the premises of the manufacturer, Hitachi Ltd. This result is used for comparison with the numerical models and the first validation of our design methodology. After then a further model tuning is considered for the magnetic design of the first series. The final validation of our design methodology is performed after the cold test of MBXFP1 in the vertical cryostat in KEK facilities. Finally we determine a magnetic design of the first series production with an expected sextupole integral and decapole integral, which are major systematic contributions to the field quality of MBXF, estimated to be <inline-formula><tex-math notation="LaTeX">0.0 \pm 1.6</tex-math></inline-formula> units and <inline-formula><tex-math notation="LaTeX">1.1 \pm 0.2</tex-math></inline-formula> units, respectively.
High Energy Accelerator Research Organization (KEK) is developing Nb-Ti based beam separation dipole (MBXF) for the high-luminosity Large Hadron Collider (HL-LHC) upgrade within the framework of ...CERN-KEK collaboration. This magnet produces field integral of 35 T*m in a 150 mm bore at 12 kA and 1.9 K. KEK has fabricated and tested three 2 m-long model magnets as in-house activities. After the technologies cultivated in these model magnet development was transferred from KEK to a manufacture, construction of the first full-scale prototype (MBXFP1) started in Hitachi. This paper reports test result of cold test for MBXFP1 including training, mechanical behavior, magnetic field quality and quench protection.
A large aperture beam separation dipole (D1 magnet) is required to generate a field integral of 35 Tm at 12 kA and 1.9 K for the high luminosity upgrade of the large hadron collider (HL-LHC). ...High-energy accelerator Research Organization (KEK) fabricated the first 2 m model (MBXFS1) and a magnet test was performed in 2015-2016. Although the quench current reached the nominal operating current, training performance was not satisfactory. The measured azimuthal coil pre-stress was completely released below the nominal current, and this was suggested to be the main reason for the insufficient training performance. After the magnet test, MBXFS1 was disassembled and reassembled as MBXFS1b after increasing the coil pre-stress. In this paper, we report the reassembly of the magnet and test results focusing on the training performance.
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