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Quantum anomalous Hall effect—the appearance of quantized Hall conductance at zero magnetic field—has been observed in thin films of the topological insulator Bi 2 Se 3 doped with magnetic atoms. The doping, however, introduces inhomogeneity, reducing the temperature at which the effect occurs. Two groups have now observed quantum anomalous Hall effect in intrinsically magnetic materials (see the Perspective by Wakefield and Checkelsky). Serlin et al. did so in twisted bilayer graphene aligned to hexagonal boron nitride, where the effect enabled the switching of magnetization with tiny currents. In a complementary work, Deng et al. observed quantum anomalous Hall effect in the antiferromagnetic layered topological insulator MnBi 2 Te 4 . Science , this issue p. 900 , p. 895 ; see also p. 848 Transport measurements indicate quantized Hall conductance without a magnetic field. The quantum anomalous Hall (QAH) effect combines topology and magnetism to produce precisely quantized Hall resistance at zero magnetic field. We report the observation of a QAH effect in twisted bilayer graphene aligned to hexagonal boron nitride. The effect is driven by intrinsic strong interactions, which polarize the electrons into a single spin- and valley-resolved moiré miniband with Chern number C = 1. In contrast to magnetically doped systems, the measured transport energy gap is larger than the Curie temperature for magnetic ordering, and quantization to within 0.1% of the von Klitzing constant persists to temperatures of several kelvin at zero magnetic field. Electrical currents as small as 1 nanoampere controllably switch the magnetic order between states of opposite polarization, forming an electrically rewritable magnetic memory.

Magnetism typically arises from the joint effect of Fermi statistics and repulsive Coulomb interactions, which favours ground states with non-zero electron spin. As a result, controlling spin magnetism with electric fields—a longstanding technological goal in spintronics and multiferroics 1 , 2 —can be achieved only indirectly. Here we experimentally demonstrate direct electric-field control of magnetic states in an orbital Chern insulator 3 – 6 , a magnetic system in which non-trivial band topology favours long-range order of orbital angular momentum but the spins are thought to remain disordered 7 – 14 . We use van der Waals heterostructures consisting of a graphene monolayer rotationally faulted with respect to a Bernal-stacked bilayer to realize narrow and topologically non-trivial valley-projected moiré minibands 15 – 17 . At fillings of one and three electrons per moiré unit cell within these bands, we observe quantized anomalous Hall effects 18 with transverse resistance approximately equal to h /2 e 2 (where h is Planck’s constant and e is the charge on the electron), which is indicative of spontaneous polarization of the system into a single-valley-projected band with a Chern number equal to two. At a filling of three electrons per moiré unit cell, we find that the sign of the quantum anomalous Hall effect can be reversed via field-effect control of the chemical potential; moreover, this transition is hysteretic, which we use to demonstrate non-volatile electric-field-induced reversal of the magnetic state. A theoretical analysis 19 indicates that the effect arises from the topological edge states, which drive a change in sign of the magnetization and thus a reversal in the favoured magnetic state. Voltage control of magnetic states can be used to electrically pattern non-volatile magnetic-domain structures hosting chiral edge states, with applications ranging from reconfigurable microwave circuit elements to ultralow-power magnetic memories. Non-volatile electrical switching of magnetic order in an orbital Chern insulator is experimentally demonstrated using a moiré heterostructure and analysis shows that the effect is driven by topological edge states.

Pulmonary hypertension is a known complication of sarcoidosis and is associated with increased mortality. Little is known about the outcome of sarcoidosis-associated pulmonary hypertension, including response to treatment. To determine the characteristics and outcome of patients with sarcoidosis-associated pulmonary hypertension treated with IV epoprostenol. Retrospective chart review of all cases of pulmonary hypertension with a concomitant diagnosis of sarcoidosis evaluated in the Boston University Pulmonary Hypertension Center from 2000 to 2004. Data collected included patient demographics, sarcoidosis stage, pulmonary function, echocardiography results, treatment, baseline and posttreatment hemodynamic measurements, and clinical outcome. Eight patients were identified; four of the patients had stage IV pulmonary sarcoidosis. Pulmonary function test results were notable for severe diffusion impairment (mean diffusion capacity of the lung for carbon monoxide, 30% of predicted), with only mild-to-moderate restrictive physiology (mean FVC, 59% of predicted). Seventy-five percent of patients required supplemental oxygen at the time of presentation. All patients had moderate or severe pulmonary hypertension and were New York Heart Association (NYHA)/World Health Organization (WHO) class III or IV. A vasodilator trial with epoprostenol was performed in seven of the eight patients; six of the seven patients had a significant hemodynamic response (> 25% reduction in pulmonary vascular resistance). All but one of the responders (five of six patients) continued on therapy. Average clinical improvement was one to two NYHA/WHO classes at a mean follow-up of 29 months (range, 15 to 49 months). In patients with sarcoidosis-associated pulmonary hypertension, the severity of pulmonary vascular disease occurs out of proportion to lung function abnormalities. The majority of our patients responded to epoprostenol; survival may be improved in this group.

The quantum anomalous Hall (QAH) effect combines topology and magnetism to produce precisely quantized Hall resistance at zero magnetic field. We report the observation of a QAH effect in twisted bilayer graphene aligned to hexagonal boron nitride. The effect is driven by intrinsic strong interactions, which polarize the electrons into a single spin- and valley-resolved moiré miniband with Chern number C = 1. In contrast to magnetically doped systems, the measured transport energy gap is larger than the Curie temperature for magnetic ordering, and quantization to within 0.1% of the von Klitzing constant persists to temperatures of several kelvin at zero magnetic field. Electrical currents as small as 1 nanoampere controllably switch the magnetic order between states of opposite polarization, forming an electrically rewritable magnetic memory.

The quantum anomalous Hall (QAH) effect combines topology and magnetism to produce precisely quantized Hall resistance at zero magnetic field. We report the observation of a QAH effect in twisted bilayer graphene aligned to hexagonal boron nitride. The effect is driven by intrinsic strong interactions, which polarize the electrons into a single spin- and valley-resolved moiré miniband with Chern numberC= 1. In contrast to magnetically doped systems, the measured transport energy gap is larger than the Curie temperature for magnetic ordering, and quantization to within 0.1% of the von Klitzing constant persists to temperatures of several kelvin at zero magnetic field. Electrical currents as small as 1 nanoampere controllably switch the magnetic order between states of opposite polarization, forming an electrically rewritable magnetic memory.

Pulmonary hypertension is a known complication of sarcoidosis and is associated with increased mortality. Little is known about the outcome of sarcoidosis-associated pulmonary hypertension, including response to treatment. To determine the characteristics and outcome of patients with sarcoidosis-associated pulmonary hypertension treated with IV epoprostenol. Retrospective chart review of all cases of pulmonary hypertension with a concomitant diagnosis of sarcoidosis evaluated in the Boston University Pulmonary Hypertension Center from 2000 to 2004. Data collected included patient demographics, sarcoidosis stage, pulmonary function, echocardiography results, treatment, baseline and posttreatment hemodynamic measurements, and clinical outcome. Eight patients were identified; four of the patients had stage IV pulmonary sarcoidosis. Pulmonary function test results were notable for severe diffusion impairment (mean diffusion capacity of the lung for carbon monoxide, 30% of predicted), with only mild-to-moderate restrictive physiology (mean FVC, 59% of predicted). Seventy-five percent of patients required supplemental oxygen at the time of presentation. All patients had moderate or severe pulmonary hypertension and were New York Heart Association (NYHA)/World Health Organization (WHO) class III or IV. A vasodilator trial with epoprostenol was performed in seven of the eight patients; six of the seven patients had a significant hemodynamic response (> 25% reduction in pulmonary vascular resistance). All but one of the responders (five of six patients) continued on therapy. Average clinical improvement was one to two NYHA/WHO classes at a mean follow-up of 29 months (range, 15 to 49 months). In patients with sarcoidosis-associated pulmonary hypertension, the severity of pulmonary vascular disease occurs out of proportion to lung function abnormalities. The majority of our patients responded to epoprostenol; survival may be improved in this group.

Evidence suggests that documentation support provided by scribes can help relieve physician burnout and increase practice productivity.

Gestational diabetes occurs in 5 to 9 percent of pregnancies in the United States and is growing in prevalence. It is a controversial entity, with conflicting guidelines and treatment protocols. Recent studies show that diagnosis and management of this disorder have beneficial effects on maternal and neonatal outcomes, including reduced rates of shoulder dystocia, fractures, nerve palsies, and neonatal hypoglycemia. Diagnosis is made using a sequential model of universal screening with a 50-g one-hour glucose challenge test, followed by a diagnostic 100-g three-hour oral glucose tolerance test for women with a positive screening test. Treatment consists of glucose monitoring, dietary modification, exercise, and, when necessary, pharmacotherapy to maintain euglycemia. Insulin therapy is the mainstay of treatment, although glyburide and metformin may become more widely used. In women receiving pharmacotherapy, antenatal testing with nonstress tests and amniotic fluid indices beginning in the third trimester is generally used to monitor fetal well-being. The method and timing of delivery are controversial. Women with gestational diabetes are at high risk of subsequent development of type 2 diabetes. Lifestyle modification should therefore be encouraged, along with regular screening for diabetes. ( Am Fam Physician . 2009;80(1):57-62. Copyright © 2009 American Academy of Family Physicians.)