Nondestructive thickness measurement of biological layers at the nanoscale by simultaneous topography and capacitance imaging

Nanoscale capacitance images of purple membrane layers are obtained simultaneously to topography in a nondestructive manner by operating alternating current sensing atomic force microscopy in jumping mode. Capacitance images show excellent agreement with theoretical modeling and prove to be a noninvasive method for measuring the thickness of purple membrane layers beyond the single monolayer limit with nanoscale lateral spatial resolution. With the ability of spatially resolving the capacitance while preserving the sample from damaging, this technique can be applied for nanoscale thickness measurement of other biological layers and soft materials in general

Nanoscale electrical conductivity of the purple membrane monolayer

Nanoscale electron transport through the purple membrane monolayer, a two-dimensional crystal lattice of the transmembrane protein bacteriorhodopsin, is studied by conductive atomic force microscopy. We demonstrate that the purple membrane exhibits nonresonant tunneling transport, with two characteristic tunneling regimes depending on the applied voltage (direct and Fowler-Nordheim). Our results show that the purple membrane can carry significant current density at the nanometer scale, several orders of magnitude larger than previously estimated by macroscale measurements

Nondestructive thickness measurement of biological layers at the nanoscale by simultaneous topography and capacitance imaging

Nanoscale capacitance images of purple membrane layers are obtained simultaneously to topography in a nondestructive manner by operating alternating current sensing atomic force microscopy in jumping mode. Capacitance images show excellent agreement with theoretical modeling and prove to be a noninvasive method for measuring the thickness of purple membrane layers beyond the single monolayer limit with nanoscale lateral spatial resolution. With the ability of spatially resolving the capacitance while preserving the sample from damaging, this technique can be applied for nanoscale thickness measurement of other biological layers and soft materials in general

Nanoscale electrical conductivity of the purple membrane monolayer

Nanoscale electron transport through the purple membrane monolayer, a two-dimensional crystal lattice of the transmembrane protein bacteriorhodopsin, is studied by conductive atomic force microscopy. We demonstrate that the purple membrane exhibits nonresonant tunneling transport, with two characteristic tunneling regimes depending on the applied voltage (direct and Fowler-Nordheim). Our results show that the purple membrane can carry significant current density at the nanometer scale, several orders of magnitude larger than previously estimated by macroscale measurements

Monitoring of 7Be and gross beta in particulate matter of surface air from Mallorca Island, Spain

[eng] Measurements of airbone radionuclides 7Be and gross beta (Ab) jointly with atmospheric aerosols, i.e. particulate matter (PM) were routinely carried out for 10 years (2004e2014) at the University of the Balearic Islands, Spain. A total of 728 filter (0.8 mm pore size) samples were collected, and in all of them 7Be and Ab specific activities were detected. The maximum and minimum specific activities monitored were 0.73 ± 0.41 e 15.8 ± 1.26 mBq m 3 of 7Be and 0.14 ± 0.02 e 2.55 ± 0.04 mBq m 3 of Ab. PM concentrations were also determined, showing seasonal behavior with the highest concentration in summer and the lowest one in winter. Several meteorological parameters have been considered to explain this intra-annual variation. Principal component analysis (PCA) was applied to the dataset indicating that it is well represented by two principal components that explain 76.6% of total variance. Additionally, a second study with preliminary results of the specific activities of two natural radiotracers (7Be and 210Pb) in PM10 samples was carried out. They were monitored for two years (2013e2015) in air of Mallorca Island. 7Be and 210Pb were detected in most of the PM10 filters, in 100% and 93% of them, respectively. The relationship between activities of both radionuclides and several relevant meteorological parameters was established at 95% confidence level. As a common result to PM and PM10 samples, a strong positive correlation between the evaluated radionuclides and temperature was found

Nanoscale electrical conductivity of the purple membrane monolayer

Nanoscale electron transport through the purple membrane monolayer, a two-dimensional crystal lattice of the transmembrane protein bacteriorhodopsin, is studied by conductive atomic force microscopy. We demonstrate that the purple membrane exhibits nonresonant tunneling transport, with two characteristic tunneling regimes depending on the applied voltage (direct and Fowler-Nordheim). Our results show that the purple membrane can carry significant current density at the nanometer scale, several orders of magnitude larger than previously estimated by macroscale measurements