Controllable Spin-Orbit Torque Induced by Interfacial Ion Absorption in Ta/CoFeB/MgO Multilayers with Canted Magnetizations.

Electrically generated spin-orbit torque (SOT) has emerged as a powerful pathway to control magnetization for spintronic applications including memory, logic, and neurocomputing. However, the requirement of external magnetic fields, together with the ultrahigh current density, is the main obstacle for practical SOT devices. In this paper, we report that the field-free SOT-driven magnetization switching can be successfully realized by interfacial ion absorption in perpendicular Ta/CoFeB/MgO multilayers. Besides, the tunable SOT efficiency exhibits a strong dependence on interfacial Ti insertion thicknesses. Polarized neutron reflection measurements demonstrate the existence of canted magnetization with Ti inserted, which leads to deterministic magnetization switching. In addition, interfacial characterization and first-principles calculations reveal that B absorption by the Ti layer is the main cause behind the enhanced interfacial transparency, which determines the tunable SOT efficiency. Our findings highlight an attractive scheme to a purely electric control spin configuration, enabling innovative designs for SOT-based spintronics via interfacial engineering.

Magnetic Skyrmions in a Hall Balance with Interfacial Canted Magnetizations.

Magnetic skyrmions are attracting interest as efficient information-storage devices with low energy consumption, and have been experimentally and theoretically investigated in multilayers including ferromagnets, ferrimagnets, and antiferromagnets. The 3D spin texture of skyrmions demonstrated in ferromagnetic multilayers provides a powerful pathway for understanding the stabilization of ferromagnetic skyrmions. However, the manipulation mechanism of skyrmions in antiferromagnets is still lacking. A Hall balance with a ferromagnet/insulating spacer/ferromagnet structure is considered to be a promising candidate to study skyrmions in synthetic antiferromagnets. Here, high-density Néel-type skyrmions are experimentally observed at zero field and room temperature by Lorentz transmission electron microscopy in a Hall balance (core structure [Co/Pt]n /NiO/[Co/Pt]n ) with interfacial canted magnetizations because of interlayer ferromagnetic/antiferromagnetic coupling between top and bottom [Co/Pt]n multilayers, where the Co layers in [Co/Pt]n are always ferromagnetically coupled. Micromagnetic simulations show that the generation and density of skyrmions are strongly dependent on interlayer exchange coupling (IEC) and easy-axis orientation. Direct experimental evidence of skyrmions in synthetic antiferromagnets is provided, suggesting that the proposed approach offers a promising alternative mechanism for room-temperature spintronics.

Tunable Giant Anomalous Hall Angle in Perpendicular Multilayers by Interfacial Orbital Hybridization.

A spintronic device based on the spin-dependent Hall effect has attracted great interest because of its great potential applications in the multivalue storage and logic gate, which is a promising candidate to break the bottleneck of the information industry in the big data period. It is a technological challenge to implant spintronic devices into semiconductor integrated circuits. The anomalous Hall angle (θ), defined as the deviation of the electron flow from the current direction, is the key parameter to evaluate the capacity of Hall device compatibility. However, the bottleneck for the device is low θ (less than 5%) at room temperature (RT), making it difficult to directly complement with the semiconductor circuit which limits its potential application. Here, we report a simple perpendicular multilayered structure with θ up to 5.1% at RT. Wide working temperature (250-350 K) across RT for our samples will accelerate the potential applications in spintronic memory. A giant Hall angle at RT originates from the enhanced side-jump scattering at the atomic-scale-modified interfacial structure. The high θ at RT together with wide working temperature is practically significant and may provide the way for further 3D spintronic devices based on the spin-dependent Hall effect with ultrahigh storage density and ultralow power consumption.

Live birth after transfer of a twice-vitrified warmed blastocyst that had undergone trophectoderm biopsy.

A 28-year-old patient presented for preimplantation genetic screening (PGS) for family balancing utilizing previously vitrified blastocysts and day-2 embryos. To synchronize endometrial development with the embryos to be transferred, five embryos vitrified on day 2 were warmed 3 days prior to scheduled transfer. Three of them developed to 8-, 8- and 7-cell stages, respectively, and were biopsied the next day, during which three vitrified blastocysts were warmed and the two surviving blastocysts underwent trophectoderm biopsy. The five biopsied embryos were subjected to two-probe fluorescence in-situ hybridization for chromosomes X and Y. As there were still 2 days before the scheduled embryo transfer following biopsy, the two biopsied blastocysts were re-vitrified. One blastocyst and two of the embryos vitrified on day 2 were normal for sex chromosomes; of these, one of the day-2 vitrified embryos was arrested and the other did not favour the patient's wish. The re-vitrified blastocyst, which was normal for sex chromosomes, was therefore warmed and transferred, resulting in delivery of one healthy boy. As far as is known, this is the first-reported live birth developed from a re-vitrified blastocyst that had been previously vitrified, warmed and undergone trophectoderm biopsy.

Pregnancy and live birth following the transfer of vitrified-warmed blastocysts derived from zona- and corona-cell-free oocytes.

This study reports two clinical pregnancies and one live birth following the transfer of vitrified blastocysts developed from oocytes with neither zona pellucida nor corona cells. Two zona-free oocytes obtained from two patients of advanced maternal age undergoing minimal stimulation were normally fertilized after intracytoplasmic sperm injection. In case 1, all four blastomeres of the zona-free embryo were loosely associated and inserted back into ruptured zona on day 2. Zona-free embryo from case 2 had tight contacts between blastomeres and was cultured without zona. Both embryos derived from zona-free oocytes progressed to blastocyst stage and were cryopreserved by vitrification. When patients came back for a cryopreserved embryo transfer, both vitrified blastocysts survived warming. In case 1, transfer of a warmed blastocyst with reconstructed zona resulted in a clinical pregnancy that ended in a spontaneous abortion at 22 weeks. In case 2, live birth was achieved with a normal healthy baby (male) weighing 2381 g at 40 weeks' gestation. This report emphasizes the importance of maintenance of normal cell arrangement on the subsequent embryonic development for a zona-free oocyte. Zona-free oocytes may provide a valuable source of embryos for infertility patients, especially for those with a limited number of oocytes.

Visualization of meiotic spindle and subsequent embryonic development in in vitro and in vivo matured human oocytes.

PURPOSE: The aim of this study is to investigate the relationship between spindle location and embryonic development of in vivo and in vitro matured human oocytes. METHODS: The spindles of 134 in vivo matured, 105 in vitro matured oocytes were examined by Polscope at the time of ICSI. RESULTS: The spindles were visualized in 83.6 and 77.1% of in vivo and in vitro matured oocytes respectively. The rate of fertilization of in vivo matured oocytes with spindles beneath or adjacent to the first polar body (angle of 0-5 degrees) was significantly higher (93.3%) than all other groups. The proportions of various spindle positions did not differ statistically in in vivo and in vitro matured oocytes. CONCLUSIONS: Meiotic spindle location with regard to the first polar body appears to influence fertilization rate.

Successful preimplantation genetic diagnosis for alpha- and beta-thalassemia in China.

METHODS & RESULTS: In southern China, the average carrier rates of alpha-thalassemia and beta-thalassemia in the population are as high as 10.3% and 2.8%, respectively. Because of the high rates, they are known as 'social diseases' in some regions. In this study, the fluorescent gap PCR, which can detect the alpha-thalassemia Southeast Asia deletion (SEA deletion), was applied in four clinical applications of preimplantation genetic diagnosis (PGD) on four couples, among whom both partners were alpha-thalassemia carriers. Two patients became pregnant and two healthy babies were born, which confirmed the PGD results. The single cell multiplex nested PCR followed by reverse dot blot (RDB), which can simultaneously detect the 16 beta-thalassemia mutations in the Chinese population, was applied in four clinical PGD cycles on four couples among whom both partners were beta-thalassemia carriers. One pregnancy was achieved and it resulted in a live healthy birth, which confirmed the results of PGD. The amplification efficiencies of the two protocols described above were 89.5% and 93.9%, respectively. The allele drop-out (ADO) rates of these two protocols were 5.9% and 10.9%, respectively. CONCLUSION: These studies represent the successful applications of PGD protocols that can detect more than 95% of alpha- and beta -thalassemia mutations in the Chinese population.

[Successful preimplantation genetic diagnosis for alpha-thalassemia using fluorescent polymerase chain reaction].

OBJECTIVE: To develop single-cell fluorescent gap polymerase chain reaction (PCR) assay for preimplantation genetic diagnosis (PGD) in couples at risk of having child with alpha-thalassemia. METHODS: Single cell fluorescent gap PCR which can detect the alpha-thalassemia Southeast Asia deletion (-SEA deletion), was applied to single lymphocytes and blastomeres which coming from four clinical PGD cycles. RESULTS: The Single cell fluorescent gap PCR can detect the alpha-thalassemia -SEA deletion, which account for 94% of hydrop fetalis in Chinese population with an amplification efficiency of 90.0% (72/80) and allele drop-out (ADO) rate of 8.3% (6/72) in lymphocytes. In four clinical PGD cycles, a total 38 embryos were detected and 38 blastomeres were obtained. Thirty-four blastomeres were amplified with the amplification efficiency of 89.5% (34/38) and ADO rate of 5.9% (2/34). Eleven embryos were shown to be normal homozygous, eight embryos were shown to be heterozygous and 15 embryos were shown to be affected homozygous. Eleven embryos were transferred back to the uterus of the patients. Two pregnancy achieved, resulting in two live healthy births, which confirmed the results of PGD. CONCLUSION: This first reported unaffected pregnancy resulting from PGD using fluorescent gap PCR for alpha-thalassemia demonstrates that this technique, as an alternative to prenatal diagnosis, is a reliable and effective way to help those carrier couples to get a healthy baby.

Closely linked polymorphic marker: successful application in preimplantation genetic diagnosis for beta-thalassemia.

OBJECTIVE: To evaluate the applicability of the polymorphic marker closely linked with beta-globin gene for the preimplantation genetic diagnosis (PGD) in couples at risk of having child with beta-thalassemia. METHODS: Single cell multiplex nested PCR which coamplifies the beta-globin gene and the closely linked polymorphic marker, HumTHO1 gene, was applied in six clinical PGD cycles for four couples with beta-thalassemia. RESULTS: In six clinical PGD cycles, a total of 44 embryos were biopsied and 44 blastomeres were obtained. Forty-one blastomeres were amplified and thirty-five embryos were given definite diagnoses. Fourteen embryos were transferred back to the uterus of the patients and one pregnancy went on well and ended with one live healthy birth, which confirmed the results of PGD. The average amplification efficiency of single blastomere was 89.7% and the average allele drop-out(ADO) rate was 14.4%. The coamplification of HumTHO1 could help to detect the existence of ADO and contamination. CONCLUSION: This is the first report on unaffected pregnancy resulting from PGD using multiplex nested PCR in China. The simultaneous amplification of polymorphic marker closely linked to beta-globin gene(HumTHO1) could help to resist the risk of misdiagnosis in PGD caused by ADO and contamination.

[Successful preimplantation genetic diagnosis for beta-thalassemia using multiplex nested polymerase chain reaction].

OBJECTIVE: To develop single-cell multiplex nested polymerase chain reaction (PCR) assays for preimplantation genetic diagnosis (PGD) in couples at risk of having child with beta-thalassemia. METHODS: Primers were designed and synthesized according to the documented mutation sites common among Chinese. Venous blood was collected from 4 pairs of husband and wife, all heterozygotes for beta-thalassemia, and underwent multiple nested PCR. Intraooplasmic sperm injection and mechanical bio psy was used to obtain single blastomere. Multiplex nested PCR was used to detect the CD41-42 mutation and the closely linked polymorphic marker, HumTHO1 gene or CD41-42, CD41-28, IVSII654 mutation and HumTHO1 gene in the single blastomeres from four clinical PGD cycles. The normal embryos with high scores capable of continuing to divide were transplanted into the uteri. The process of gestation was observed. RESULTS: 200 lymphocytes were amplified by nested PCR. The average amplification rate of the most common 16 beta-thalassemia mutations in Chinese population was 91.3% and the average rate of allele drop out for different sites was 17.0% without differences between any 2 sites. During the 4 PGD cycles 33 embryos underwent bioassay with a success rate of 100%. 33 blastomeres were obtained to undergo PCR, of which 30 were successfully amplified with an amplification rate of 90.9%. Explicit diagnosis was obtained in 26 of the 30 embryos: 7 normal homozygotes, 11 heterozygotes, and 8 abnormal or complex heterozygotes. One or more embryos were transferred back into the uteri of the 4 women and clinical pregnancy occurred in one woman. Five weeks after the implantation B-mode ultrasonography showed monocyesis, and in the 17th week of gestational period paracentesis of cord blood showed normal homozygote. At last a normal female infant confirming the PGD result had been born, which was the first reported unaffected pregnancy resulting from PGD using multiplex nested PCR for couples as beta-thalassemia gene carriers. The results of diagnosis for embryo all corresponded to those for blastomere. The average ADO rate of blastomere was 13.3% (4/30). CONCLUSION: PGD using multiplex nested PCR, as an alternative to prenatal diagnosis, is a reliable and effective way to help couples-carriers of pathogenetic genes to get a healthy baby.

[Outcome of repeated epididymal sperm aspiration or testicular sperm extraction in azoospermic patients].

OBJECTIVE: To review the outcome of repeated percutaneous sperm aspiration (PESA) and testicular sperm extraction (TESE) for intracytoplasmic sperm injection (ICSI). METHODS: Forty-three cycles of 31 cases of azoospermic patients which underwent at least two PESA or TESE for ICSI from January 2001 to December 2002 were collected. The sperm retrieval, fertilization, implantation and clinical pregnancy were analyzed. RESULTS: Twenty-four cases underwent PESA and 7 cases underwent TESE. There were not any complications in these patients. Compared with the first cycle of 154 cases, the fertilization rate, implantation rate and clinical pregnancy rate were 78.39% vs 73.64%, 19.68% vs 18.38% and 34.88% vs 37.91%, respectively(P > 0.05). CONCLUSIONS: Repeated PESA or TESE is safe and well tolerated in azoospermic patients. Compared with the first cycle, the differences of repeated PESA or TESE cycles in fertilization rate, implantation rate and clinical pregnancy rate were not statistically significant.

[Clinical application of a modified pronuclear stage scoring system following conventional in-vitro fertilization].

OBJECTIVE: To assess the clinical value of pronuclear stage scoring system in human conventional in vitro fertilization-embryo transfer (IVF-ET) program. METHODS: A modified pronuclear scoring system was used to score zygotes 16 - 18 hours after insemination during conventional IVF. RESULTS: A total of 178 IVF cycles were recruited in this study. Cycles with mean pronuclear score (sum of pronuclear scores of all transferred embryos divided by total number of transferred embryos) > or = 13 had significant high pregnancy and implantation rate, as compared to those with less than 13 (49.1% and 26.5% Vs 29.4% and 15.0% respectively). Although the pregnancy, implantation rate and multiple pregnancy rate tend to increase with the increasing number of zygotes with full pronuclear score (= 15) among transferred embryos, no significant difference could be found (P > 0.05). When all embryos were analyzed, 77.2% zygotes with pronuclear score > or = 11 could be transferred or cryopreserved, while those with pronuclear score less than 11 decreased to 46.1%. CONCLUSIONS: Pronuclear stage scoring system provides additional parameter for embryo selection. However, pronuclear morphology could only partly represent embryonic viability. Combination with the scoring of both pronuclear stage and cleavage stage embryos for selecting transferred embryos is indispensable.

[Sperm retrieval methods and pregnancy outcome of 100 azoospermia patients].

OBJECTIVES: To review the retrospective treatment results of the azoospermia patients during January 2001 to January 2002 in the fertility center. METHODS: One hundred males attempted intracytoplasmic sperm injection (ICSI) cycle for treatment of azoospermia. All patients were undergone sperm retrieval by percutaneous epididymal sperm aspiration (PESA) or testicular sperm extraction (TESE) while their wives received conventional ovarian hyperstimulation. The hormone levels, testicular histology, the rates of sperm retrieval, fertilization, implantation and pregnancy were analysed and evaluated. RESULTS: Sperm were retrieved by PESA in 76 of 100 (76%) and by TESE in 23 of 100 (23%) men of azoospermia. The fertilization rate, implantation rate and clinical pregnancy rate were 71.3%, 20.35% and 42.11% respectively in PESA group, and 75.18%, 22.05% and 41.60% respectively in TESA group. Thirty-two clinical pregnancies were achieved with 15 ongoing pregnancies and subsequent live delivery for 15 cases in PESA group, and 2 cases of miscarriage, while 10 clinical pregnancies were achieved with 6 ongoing pregnancies, 2 cases of live delivery and 2 cases of miscarriage in TESA group. One case failed to retrieve sperm by TESE and canceled. CONCLUSIONS: Hormonal levels and testicular histology are unable to predict which men with azoospermia will have sperm retrieved by PESA and TESE. PESA and TESE with ICSI are effective methods to treat azoospermia. There were no significant differences in fertilization, implantation and clinical pregnancy rate between two groups.