Engineering topological phases in triple HgTe/CdTe quantum wells.

Quantum wells formed by layers of HgTe between Hg[Formula: see text]Cd[Formula: see text]Te barriers lead to two-dimensional (2D) topological insulators, as predicted by the BHZ model. Here, we theoretically and experimentally investigate the characteristics of triple HgTe quantum wells. We describe such heterostructure with a three dimensional [Formula: see text] Kane model, and use its eigenstates to derive an effective 2D Hamiltonian for the system. From these we obtain a phase diagram as a function of the well and barrier widths and we identify the different topological phases composed by zero, one, two, and three sets of edge states hybridized along the quantum wells. The phase transitions are characterized by a change of the spin Chern numbers and their corresponding band inversions. Complementary, transport measurements are experimentally investigated on a sample close to the transition line between the phases with one and two sets of edges states. Accordingly, for this sample we predict a gapless spectrum with low energy bulk conduction subbands given by one parabolic and one Dirac subband, and with edge states immersed in the bulk valence subbands. Consequently, we show that under these conditions, local and non-local transport measurements are inconclusive to characterize a sole edge state conductivity due to bulk conductivity. On the other hand, Shubnikov-de Haas (SdH) oscillations show an excellent agreement with our theory. Particularly, we show that the measured SdH oscillation frequencies agrees with our model and show clear signatures of the coexistence of a parabolic and Dirac subbands.

Acceleration of the precession frequency for optically-oriented electron spins in ferromagnetic/semiconductor hybrids.

Time-resolved Kerr rotation measurements were performed in InGaAs/GaAs quantum wells nearby a doped Mn delta layer. Our magneto-optical results show a typical time evolution of the optically-oriented electron spin in the quantum well. Surprisingly, this is strongly affected by the Mn spins, resulting in an increase of the spin precession frequency in time. This increase is attributed to the variation in the effective magnetic field induced by the dynamical relaxation of the Mn spins. Two processes are observed during electron spin precession: a quasi-instantaneous alignment of the Mn spins with photo-excited holes, followed by a slow alignment of Mn spins with the external transverse magnetic field. The first process leads to an equilibrium state imprinted in the initial precession frequency, which depends on pump power, while the second process promotes a linear frequency increase, with acceleration depending on temperature and external magnetic field. This observation yields new information about exchange process dynamics and on the possibility of constructing spin memories, which can rapidly respond to light while retaining information for a longer period.

Current-Controlled Spin Precession of Quasistationary Electrons in a Cubic Spin-Orbit Field.

Space- and time-resolved measurements of spin drift and diffusion are performed on a GaAs-hosted two-dimensional electron gas. For spins where forward drift is compensated by backward diffusion, we find a precession frequency in the absence of an external magnetic field. The frequency depends linearly on the drift velocity and is explained by the cubic Dresselhaus spin-orbit interaction, for which drift leads to a spin precession angle twice that of spins that diffuse the same distance.

Failure of intravenous immunoglobulin to prevent congenital heart block: Findings of a multicenter, prospective, observational study.

OBJECTIVE: Congenital heart block (CHB) is presumed to be caused by transplacental passage of maternal immunoglobulin against Ro and La ribonucleoproteins. The recurrence rate in subsequent pregnancies following the birth of a child with CHB is approximately 19%. The purpose of this study was to determine whether intravenous immunoglobulin (IVIG) therapy could prevent the development of CHB in the fetuses of high-risk pregnant women. METHODS: A total of 24 pregnancies in 22 women who had a previous pregnancy in which CHB developed, were over the age of 18 years, were <12 weeks pregnant, and had anti-Ro, anti-La, or both antibodies were monitored in this multicenter, prospective, observational study. Fifteen patients received infusions of IVIG. The 9 pregnancies in the remaining 7 patients served as controls. IVIG was administered at a dose of 400 mg/kg at weeks 12, 15, 18, 21, and 24 of pregnancy. Echocardiograms were performed at least every 3 weeks from week 15 to week 30 of gestation. Electrocardiograms were obtained at birth. The outcome measure was the development of third-degree CHB detected by fetal echocardiogram. RESULTS: CHB developed in 3 babies among the 15 pregnancies in the treatment group (20%) and in 1 baby among the 9 pregnancies in the control group (11%). CHB was detected at weeks 18, 23, and 26, respectively, in the 3 babies in the treated group and at week 19 in the baby in the control group. Three of the affected pregnancies ended in termination; 2 for reasons related to the fetal disease and 1 for reasons related to both maternal (severe pulmonary hypertension) and fetal disease (at 21 weeks of gestation). CONCLUSION: IVIG at the dose and frequency used in this study was not effective as prophylactic therapy for CHB in high-risk mothers.

Landé g tensor in semiconductor nanostructures.

Understanding the electronic structure of semiconductor nanostructures is not complete without a detailed description of their corresponding spin-related properties. Here we explore the response of the shell structure of InAs self-assembled quantum dots to magnetic fields oriented in several directions, allowing mapping of the g-tensor modulus for the s and p shells. We find that the g tensors for the s and p shells exhibit a very different behavior. The s state, being more localized, probes the confinement potential details by sweeping the magnetic-field orientation from the growth direction towards the in-plane direction. For the p state, the g-tensor modulus is closer to that of the surrounding GaAs, consistent with a larger delocalization. In addition to the assessment of the g tensor, these results reveal further details of the confining potentials of self-assembled quantum dots that have not yet been probed.

Thawed cryoprecipitate stored for 6 h at room temperature: a potential alternative to factor VIII concentrate for continuous infusion.

Continuous infusion (CI) of factor VIII concentrates has been demonstrated to be cost-effective method in maintaining stable levels of FVIII activity in haemophilia A patients with major bleeding or undergoing major surgery. Cryoprecipitates remain the major source of FVIII in developing countries-like the Philippines because of limited availability and high cost of concentrates. To support the use of cryoprecipitate as alternative to FVIII concentrate for CI in centres with no factor concentrates, FVIII levels in 37 bags of random cryoprecipitate were measured at 0, 2, 4 and 6 h after thawing, kept at room temperature with bacteriological culture studies performed on the sixth hour. The mean FVIII content at hour 0 was 108.10 U per bag. Type ORh+ blood had lower FVIII content (+/-78.91 U per bag) compared with blood types ARh+ (+/-121.64 U per bag) and BRh+ (+/-117.04 U per bag). The units stored <6 months had higher FVIII content (+/-117.74 U per bag) compared with those stored for over 6- but <12-months (+/-66.77 U per bag). The mean rate of decline of FVIII activity at 2, 4 and 6 h was statistically significant at 10.35% (P = 0.000), 21.49% (P = 0.000) and 29.41% (P = 0.000) from baseline, respectively, using the paired t-test. Similar finding was found across different blood types and storage duration. Only one of 37 bags grew Staphylococcus aureus on day 10 of incubation.

Cryoprecipitate-removed plasma 'cryo-removed plasma' as a source of factor IX in the treatment of haemophilia B.

Fresh frozen plasma (FFP) is the main source of factor IX (FIX) in the treatment of bleeding episodes of haemophilia B in the Philippines. Cryoprecipitate-removed plasma otherwise known in the Philippines as cryosupernate, is a by-product of cryoprecipitate preparation. These blood products expire in storage or are just thrown- away because of less demand for clinical use. By theory, this product should have almost the same amount of FIX as in FFP, therefore can be used in the treatment of haemophilia B. There is no local data on the actual FIX content of the cryoprecipitate-removed plasma. Hence, the authors established these data to support the use of this product. Eighty-three bags of cryoprecipitate-removed plasma received from three different blood banks in Manila, Philippines were tested for FIX activity using an activated partial thromboplastin time (APTT)-based one-stage FIX assay. The FIX content in each bag of cryoprecipitate-removed plasma was calculated by multiplying its volume in mL with that of FIX activity per mL of plasma measured in vitro. The total mean FIX content per bag was 212.20 U (+/-88.98) exceeding the contents set by the American Association of Blood Banks (AABB, 70-90 U). The mean FIX activity per bag was 127.62% (+/-38.23) with the mean volume of 164.28 mL (+/-52.23). Statistically significant difference on volume (P = 0.000) was found across the three sources resulting to a significant variation of the actual FIX content (P = 0.000).