C.R. Chang

The duration of pre-ovulatory serum progesterone elevation before hCG administration affects the outcome of IVF/ICSI cycles

STUDY QUESTIONnDuring controlled ovarian stimulation (COS), does the duration of premature serum progesterone (P) elevation before administration of hCG affect the outcomes of IVF/ICSI embryo transfer (-ET) cycles?nnnSUMMARY ANSWERnThe duration of the premature serum P elevation is inversely related to the clinical pregnancy rate of IVF/ICSI-ET cycles.nnnWHAT IS KNOWN AND WHAT THIS PAPER ADDSnThe majority of the previous studies only considered a single serum P measurement made on the day of hCG administration and the results of attempts to relate this to IVF/ICSI-ET outcomes were controversial. However, the effect of the duration of premature serum P elevation before the hCG administration on the outcomes of IVF/ICSI-ET cycles has not been studied well. Here we demonstrate that the duration of premature serum P elevation has a more significant inverse correlation than the absolute serum P concentration on the day of hCG administration with IVF/ICSI-ET outcomes.nnnDESIGNnIt is a retrospective, single-centre cohort study. A total of 1784 IVF and/or ICSI-ET cycles were included from October 2005 to June 2011.nnnPARTICIPANTS AND SETTINGnA total of 1784 patients underwent their IVF and/or ICSI-ET cycles in a university hospital IVF unit. The inclusion criteria include (i) age between 20 and 42 years and (ii) eligible indications for COS before IVF/ICSI.nnnMAIN RESULTS AND THE ROLE OF CHANCEnThe duration of premature serum P elevation to >1 ng/ml is significantly inversely associated with the probability of clinical pregnancy (odds ratio = 0.773, 95% confidence interval: 0.660-0.891, P < 0.001), after adjustment for possible confounders with multivariate logistic regression analysis. However, the significance of inverse correlation between the absolute serum P concentration on the day of hCG administration with clinical pregnancy rate decreased after adjustment.nnnBIAS, CONFOUNDING AND OTHER REASONS FOR CAUTIONnThe cutoff value we chose to define premature serum P elevation (P > 1.0 ng/ml) might not be able to be applied to different immunoassay kits and study population. The retrospective nature of this study inevitably might be influenced by some selection bias.nnnGENERALIZABILITY TO OTHER POPULATIONSnOlder patients (>42 years) are excluded from our study.

Superconducting and transport properties of YBa2Cu3O7∕La0.7Sr0.3MnO3 bilayers

Temperature-dependent resistivity, thermoelectric power, and magnetoresistance (MR) are investigated in YBa2Cu3O7∕La0.7Sr0.3MnO3 (YBCO/LSMO) bilayers with the thickness of YBCO fixed at 150 nm and that of LSMO varying from t=0 to 50 nm. It is found that the onset temperature Tc of the superconducting transition retains at a constant value of 74 K for t<50nm, but reduces to 20 K at t=50nm. In conjunction with the existence of a critical thickness of 50 nm for delocalizing charge carriers in the LSMO layer, we attribute the Tc suppression to the diffusion of spin-polarized carriers from the metallic LSMO to the YBCO layer. Furthermore, we observe a sign reversal of MR with temperature in the YBCO(150 nm)/LSMO(50 nm) bilayer, indicating a competition between a positive MR of YBCO and a negative MR of LSMO.

Influences of the aspect ratio and film thickness on switching properties of elliptical Permalloy elements

The size dependence on the switching properties of microstructured Permalloy (Ni/sub 80/Fe/sub 20/) ellipses were investigated by magnetoresistance measurements and magnetic force microscopy. Elements with fixed short axes of 1 /spl mu/m, long axes varying from 2 to 10 /spl mu/m, and film thickness varying from 8 to 55 nm were fabricated by electron beam lithography through a lift-off technique. A single-domain configuration was observed in the elements with the range of aspect ratios (long/short axis) from 5 to 10. More complex domain structures appear in the lower aspect ratio and thicker samples. The switching properties show a strong dependence on the film thickness as well as the aspect ratio. The switching fields of uniform magnetization reversal increase with increasing thickness up to a critical value (24<t/sub c/<40 nm), whereas they decrease with increasing thickness above t/sub c/. Nevertheless, the switching fields only show weak dependency on aspect ratio.

Annealing effect on magnetic properties of Si-modified γFe2O3 particles

Abstract Acicular γue5f8Fe2O3 particles are synthesized by dehydration, reduction and oxidation of acicular γue5f8FeOOH particles. The annealing treatment has been added preceding the reduction step in the preparation of acicular γue5f8Fe2O3 particles. We studied the annealing effect from the investigation of particle morphology, coercive force as well as magnetization. It has been found that Si adsorption on the surface of the particle will significantly improve the annealing effect. Furthermore, it causes an anomalous increase in the coercive force. The origins of annealing effect and Hc enhancement are discussed.

Field evolution of multivortex and cross-tie states in Permalloy thin films

Field evolution of vortex and cross-tie states is investigated by magnetic force microscopy imaging experimentally. We found that the vortices move perpendicular to the field direction. For the multivortex states, as the external field is perpendicular to the magnetization direction of the rhombic domain, which is enclosed by two neighboring vortices, the rhombic domain tilts. When the external field is parallel/antiparallel to the magnetization direction of the rhombic domain, this domain is extended/contracted. For the cross-tie state, the vortex and antivortex cores annihilate pair by pair in series when the field is applied along the short axis. When the magnetic field is applied along the long axis, the Bloch line moves along the short-axis direction till it, as a whole, annihilates near the edge of the elliptical thin film.

Frequency of low serum LH is associated with increased early pregnancy loss in IVF/ICSI cycles

The role of LH during ovarian stimulation remains uncertain. Previous studies defined the low LH group using a single LH measurement on a predefined day of stimulation possibly not reflecting the entire follicular phase. This study retrospectively collected data from 619 IVF/ICSI cycles with GnRH antagonist and recombinant FSH. The low LH group was defined as LH concentration ≤0.8u2009mIU/ml at any time during the cycle. Pregnancy results were compared between patients with one episode of low LH or more than two episodes of low LH (study group) and those without low LH (control group). There was no difference in fertilization rates between the two groups (67.5 ± 1.7% versus 68.8 ± 1.0%, respectively). The implantation rates (20.4% versus 25.2%), clinical pregnancy rates (43.9% versus 45.2%) and live-birth rates (LBR) (23.7% versus 30.4%) appeared lower in the study group, but the differences were not significant. In the study group, there were significantly increased early pregnancy loss rates (31.1% versus 16.3%, P = 0.012). The odds of early pregnancy loss increases by 1.55 fold for increased episodes of low serum LH (P = 0.029). Whether the adverse outcome is due to impaired oocyte quality or an endometrial component deserves further investigation.

Relaxation effects in magnetic recording

Master equation formalism is employed to describe the effect of a recording head on an initially demagnetized particulate medium. It is found that transition noise and transition shift along the track are inversely correlated and that large transition noise is found to be associated with high recording frequencies, low recording temperatures (large particles) and particle misalignment. Interparticle coupling is discussed.

Experimental and simulation of magnetic hysteresis loops of [Co3(pyz)(HPO4)2F2]

Pure phase of [Co3(pyz)(HPO4)2F2] crystal powder was successfully synthesized. The structure consisted of neutral sheets of [Co3(HPO4)2F2], which were pillared through pyrazine ligand to form three-dimensional frameworks. Below 20 K, the magnetic hysteresis loops showed a ferromagnetic part superimposed with an antiferromagnetic (AF) part. With increasing field magnitude, the AF part showed sharp steps at 5 kOe. Micromagnetic simulation, taking into account the Co ions as AF coupled sublattices and as suggested by the negative Weiss temperature extrapolated by the inverse susceptibility versus temperature behavior, explained the hysteresis loops the temperature dependence qualitatively.Pure phase of [Co3(pyz)(HPO4)2F2] crystal powder was successfully synthesized. The structure consisted of neutral sheets of [Co3(HPO4)2F2], which were pillared through pyrazine ligand to form three-dimensional frameworks. Below 20 K, the magnetic hysteresis loops showed a ferromagnetic part superimposed with an antiferromagnetic (AF) part. With increasing field magnitude, the AF part showed sharp steps at 5 kOe. Micromagnetic simulation, taking into account the Co ions as AF coupled sublattices and as suggested by the negative Weiss temperature extrapolated by the inverse susceptibility versus temperature behavior, explained the hysteresis loops the temperature dependence qualitatively.

Lower rate of early pregnancy loss in patients experiencing early-onset low LH in GnRH antagonist cycles supplemented with menotropin

BACKGROUND/PURPOSEnThe role of LH during controlled ovarian stimulation (COS) in the general population remains contentious. There is no consensus on the indications for LH supplementation during COS. The purpose of this study is to determine whether menotropin supplement is associated with decreases in early pregnancy loss rates in patients exhibiting low endogenous LH during COS.nnnMETHODnThis is a single-center, retrospective cohort from a university-affiliated hospital. Patients were enrolled from the in-vitro fertilization center from January, 2011 to December, 2014. Patients who experienced a LH levelxa0≦xa00.8xa0mIU/mL during stimulation were identified, and patients that received menotropin supplementation were compared to those without menotropin supplementation. Outcome variables, including the number of oocytes retrieved, embryos obtained, implantation rates, pregnancy rates and early pregnancy loss rates, were compared.nnnRESULTSnPatients that experienced low LH during GnRH antagonist protocol and were supplemented with menotropin were associated with lower early pregnancy loss when compared with patients without menotropin supplementation (26.7% vs. 11.5%, pxa0=xa00.045). More specifically, in patients who exhibited early-onset low LH, before the use of GnRH antagonists, menotropin supplementation was associated with significantly lower early pregnancy loss compared with non-supplemented patients (3.3% vs. 29.0%, OR: 0.08, pxa0=xa00.012). Beneficial effects persisted after adjusting for confounders (aOR: 0.103, 95% CI: 0.011-0.933).nnnCONCLUSIONnMenotropin supplementation is associated with decreased early pregnancy loss in patient who exhibited low LH during GnRH antagonist cycles. This effect is especially prominent in patients who experience low LH before the start of GnRH antagonists.

Advantages of cumulative pregnancy outcomes in freeze-all strategy in high responders – A case-control matching analysis of a large cohort

BACKGROUND/PURPOSEnThe freeze-all strategy in high responders is considered to be a safe and effective strategy for inxa0vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) treatment; however, the cumulative pregnancy outcomes have not been established.nnnMETHODSnA retrospective, single-center cohort study was conducted and 1311 high-responder patients (>20 oocytes retrieved and/or a serum estradiol levelxa0>xa03000xa0pg/ml on the triggering day) were recruited from 2006 to 2015. The study group (nxa0=xa0351) underwent the freeze-all strategy with subsequent thawed embryo transfer (ET), and the control group (nxa0=xa0960) received fresh-cycle ET and subsequent thawed ET if needed. A case-control matching analysis was performed to match the two groups for the number of retrieved oocytes. The primary outcomes were the ongoing pregnancy rate (OPR) of the first ET cycle and the cumulative OPR.nnnRESULTSnAfter matching, there was a significantly higher OPR in the first ET cycle (49.5% vs. 32.2%, pxa0<xa00.0001; nxa0=xa0301 in each group) and the cumulative OPR (69.4% vs. 55.1%, pxa0<xa00.0001) in the study group, with significantly fewer total transferred embryos and cycles. The advantages of the freeze-all strategy for the OPR in the first ET cycle (OR: 1.97, pxa0<xa00.0001) and the cumulative OPR (OR: 1.49, pxa0=xa00.032) remained statistically significant after adjusting for other possible confounding factors in multivariate logistic regression analysis.nnnCONCLUSIONnFor high responders, the freeze-all strategy with thawed ET achieved a significantly higher OPR in the first ET cycle and a higher cumulative OPR than the fresh ET strategy.