Division of Maternal-Fetal Medicine

The Division of Maternal-Fetal Medicine presently includes nine board certified maternal-fetal specialists. They are: Kimberly K. Leslie, MD (Department Head), Jerome Yankowitz, MD (Division Director), Jennifer R. Niebyl, MD, Asha Rijhsinghani, MD, Janet I. Andrews, MD, Stephen K. Hunter, MD, PhD., Kristi Borowski, MD, Mark Santillan, MD, and Andrea Greiner, MD. Dr. Roger A. Williamson, double boarded in Genetics and Obstetrics, is also a member of the Division. Drs. Yankowitz and Borowski are also board certified in clinical genetics

Evolution of the electronic band structure of twisted bilayer graphene upon doping

The electronic band structure of twisted bilayer graphene develops van Hove singularities whose energy depends on the twist angle between the two layers. Using Raman spectroscopy, we monitor the evolution of the electronic band structure upon doping using the G peak area which is enhanced when the laser photon energy is resonant with the energy separation of the van Hove singularities. Upon charge doping, the Raman G peak area initially increases for twist angles larger than a critical angle and decreases for smaller angles. To explain this behavior with twist angle, the energy of separation of the van Hove singularities must decrease with increasing charge density demonstrating the ability to modify the electronic and optical properties of twisted bilayer graphene with doping.Comment: 10 pages, 4 figure

Pressure-induced commensurate stacking of graphene on boron nitride

Combining atomically-thin van der Waals materials into heterostructures provides a powerful path towards the creation of designer electronic devices. The interaction strength between neighboring layers, most easily controlled through their interlayer separation, can have significant influence on the electronic properties of these composite materials. Here, we demonstrate unprecedented control over interlayer interactions by locally modifying the interlayer separation between graphene and boron nitride, which we achieve by applying pressure with a scanning tunneling microscopy tip. For the special case of aligned or nearly-aligned graphene on boron nitride, the graphene lattice can stretch and compress locally to compensate for the slight lattice mismatch between the two materials. We find that modifying the interlayer separation directly tunes the lattice strain and induces commensurate stacking underneath the tip. Our results motivate future studies tailoring the electronic properties of van der Waals heterostructures by controlling the interlayer separation of the entire device using hydrostatic pressure.Comment: 17 pages, 4 figures and supplementary information. Updated to published versio

Outcomes of pregnancies complicated by maternal tuberous sclerosis

We present three cases of maternal tuberous sclerosis without major complications in pregnancy and several other patients who delivered with a low risk obstetrician, from this we conclude that maternal tuberous sclerosis may not be as high risk for pregnancy as previously reported in the literature. Tuberous sclerosis (TS) is a genetic disorder that is inherited in an autosomal dominant fashion with variable clinical manifestations including seizures, mental retardation, renal failure and pneumothorax. This case series can aid obstetricians in counseling of patients with this rare disorder

Outcomes of pregnancies complicated by maternal tuberous sclerosis

We present three cases of maternal tuberous sclerosis without major complications in pregnancy and several other patients who delivered with a low risk obstetrician, from this we conclude that maternal tuberous sclerosis may not be as high risk for pregnancy as previously reported in the literature. Tuberous sclerosis (TS) is a genetic disorder that is inherited in an autosomal dominant fashion with variable clinical manifestations including seizures, mental retardation, renal failure and pneumothorax. This case series can aid obstetricians in counseling of patients with this rare disorder