The emergence of multifrequency force microscopy

Atomic force microscopy uses the deflection of a cantilever with a sharp tip to examine surfaces, and conventional dynamic force microscopy involves the excitation and detection of a single frequency component of the tip’s motion. Information about the properties of a sample is, however, encoded in the motion of the probe and the dynamics of the cantilever are highly nonlinear. Therefore, information included in the other frequency components is irreversibly lost. Multifrequency force microscopy involves the excitation and/or detection of several frequencies of the probe’s oscillation, and has the potential to overcome limitations in spatial resolution and acquisition times of conventional force microscopes. It could also provide new applications in fields such as energy storage and nanomedicine. Here we review the development of multifrequency force microscopy methods, highlighting the five most prominent approaches. We also examine the range of applications offered by the technique, which include mapping the flexibility of proteins, imaging the mechanical vibrations of carbonbased resonators, mapping ion diffusion, and imaging the subsurface of cells.We are grateful for financial support from the Ministerio de Ciencia e Innovación (CSD2010-00024, MAT2009-08650).Peer reviewe

Combining early postoperative parathyroid hormone and serum calcium levels allows for an efficacious selective post-thyroidectomy supplementation treatment

BACKGROUND: Optimal treatment protocol to prevent symptomatic hypocalcemia following total thyroidectomy is still matter of debate. We prospectively evaluated the efficacy of a selective supplementation protocol based on both early postoperative intact parathyroid hormone (iPTH) and serum calcium levels. METHODS: Two hundred thirty consecutive patients were divided in three different groups of treatment according to iPTH levels 4 h after total thyroidectomy (4 h-iPTH) and serum calcium levels in the first postoperative day (1PO-Ca): group A (4 h-iPTH > 10 pg/ml, 1PO-Ca 65 8.5 mg/dl), no treatment; group B (4 h-iPTH > 10 pg/ml, 1PO-Ca < 8.5 mg/dl), oral calcium (OC) 3 g per day; and group C (4 h-iPTH 64 10 pg/ml), OC 3 g + calcitriol (VD) 1 \u3bcg per day. Development of biochemical and/or symptomatic hypocalcemia was evaluated. RESULTS: Fifty-nine patients (25.6%) had subnormal 4 h-iPTH levels ( 6410 pg/ml) (group C). Among patients with normal 4 h-iPTH levels, 25 (10.9%) had subnormal 1PO-Ca (<8.5 mg/dl) (group B). The remaining 146 patients (63.5%) had normal 4 h-iPTH and 1PO-Ca levels (group A). One patient in group A, 2 in group B, and 18 in group C developed biochemical hypocalcemia. Only one patient in group C experienced major symptoms. Treatment was discontinued within 1 month in all the patients in group B. At a mean follow-up of 303 days, five patients in group C were still under supplementation treatment. CONCLUSION: The proposed supplementation protocol seems efficacious in preventing symptomatic hypocalcemia. It could allow a safe and early discharge of most patients, thus avoiding the constraints and the costs of routine supplementation