TY  - JOUR
A1  - Varykhalov, A.
A1  - Marchenko, D.
A1  - Sánchez-Barriga, J.
A1  - Scholz, M. R.
A1  - Verberck, B.
A1  - Trauzettel, B.
A1  - Wehling, T. O.
A1  - Carbone, C.
A1  - Rader, O.
T1  - Intact Dirac Cones at Broken Sublattice Symmetry: Photoemission Study of Graphene on Ni and Co
JF  - Physical Review X
N2  - The appearance of massless Dirac fermions in graphene requires two equivalent carbon sublattices of trigonal shape. While the generation of an effective mass and a band gap at the Dirac point remains an unresolved problem for freestanding extended graphene, it is well established by breaking translational symmetry by confinement and by breaking sublattice symmetry by interaction with a substrate. One of the strongest sublattice-symmetry-breaking interactions with predicted and measured band gaps ranging from 400 meV to more than 3 eV has been attributed to the interfaces of graphene with Ni and Co, which are also promising spin-filter interfaces. Here, we apply angle-resolved photoemission to epitaxial graphene on Ni (111) and Co(0001) to show the presence of intact Dirac cones 2.8 eV below the Fermi level. Our results challenge the common belief that the breaking of sublattice symmetry by a substrate and the opening of the band gap at the Dirac energy are in a straightforward relation. A simple effective model of a biased bilayer structure composed of graphene and a sublattice-symmetry-broken layer, corroborated by density-functional-theory calculations, demonstrates the general validity of our conclusions.
KW  - NI(111)
KW  - ultrasoft pseudopotentials
KW  - monolayer graphite
KW  - electronic states
KW  - transistors
KW  - surface
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-135732
VL  - 2
IS  - 041017
ER  - 
TY  - JOUR
A1  - Haring, Bernhard
A1  - Crandall, Carolyn J
A1  - Carbone, Laura
A1  - Liu, Simin
A1  - Li, Wenjun
A1  - Johnson, Karen C
A1  - Wactawski-Wende, Jean
A1  - Shadyab, Aladdin H
A1  - Gass, Margery L
A1  - Kamensky, Victor
A1  - Cauley, Jane A
A1  - Wassertheil-Smoller, Sylvia
T1  - Lipoprotein(a) plasma levels, bone mineral density and risk of hip fracture: a post hoc analysis of the Women’s Health Initiative, USA
JF  - BMJ Open
N2  - Objectives 
Elevated Lipoprotein(a) (Lp[a]) is a well-known risk factor for cardiovascular disease. However, its roles in bone metabolism and fracture risk are unclear. We therefore investigated whether plasma Lp(a) levels were associated with bone mineral density (BMD) and incident hip fractures in a large cohort of postmenopausal women.

Design 
Post hoc analysis of data from the Women’s Health Initiative (WHI), USA.

Setting 
40 clinical centres in the USA.

Participants 
The current analytical cohort consisted of 9698 white, postmenopausal women enrolled in the WHI, a national prospective study investigating determinants of chronic diseases including heart disease, breast and colorectal cancers and osteoporotic fractures among postmenopausal women. Recruitment for WHI took place from 1 October 1993 to 31 December 1998.

Exposures 
Plasma Lp(a) levels were measured at baseline.

Outcome measures 
Incident hip fractures were ascertained annually and confirmed by medical records with follow-up through 29 August 2014. BMD at the femoral neck was measured by dual X-ray absorptiometry in a subset of participants at baseline.

Statistical analyses 
Cox proportional hazards and logistic regression models were used to evaluate associations of quartiles of plasma Lp(a) levels with hip fracture events and hip BMD T-score, respectively.

Results 
During a mean follow-up of 13.8 years, 454 incident cases of hip fracture were observed. In analyses adjusting for confounding variables including age, body mass index, history of hysterectomy, smoking, physical activity, diabetes mellitus, general health status, cardiovascular disease, use of menopausal hormone therapy, use of bisphosphonates, calcitonin or selective-oestrogen receptor modulators, baseline dietary and supplemental calcium and vitamin D intake and history of fracture, no significant association of plasma Lp(a) levels with low hip BMD T-score or hip fracture risk was detected.

Conclusions 
These findings suggest that plasma Lp(a) levels are not related to hip BMD T-score or hip fracture events in postmenopausal women.
KW  - hip fracture
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-201139
VL  - 9
ER  -