Nanoparticles for live cell microscopy: A surface-enhanced Raman scattering perspective.

Surface enhanced Raman scattering (SERS) nanoparticles are an attractive alternative to fluorescent probes for biological labeling because of their photostability and multiplexing capabilities. However, nanoparticle size, shape, and surface properties are known to affect nanoparticle-cell interactions. Other issues such as the formation of a protein corona and antibody multivalency interfere with the labeling properties of nanoparticle-antibody conjugates. Hence, it is important to consider these aspects in order to validate such conjugates for live cell imaging applications. Using SERS nanoparticles that target HER2 and CD44 in breast cancer cells, we demonstrate labeling of fixed cells with high specificity that correlates well with fluorescent labels. However, when labeling live cells to monitor surface biomarker expression and dynamics, the nanoparticles are rapidly uptaken by the cells and become compartmentalized into different cellular regions. This behavior is in stark contrast to that of fluorescent antibody conjugates. This study highlights the impact of nanoparticle internalization and trafficking on the ability to use SERS nanoparticle-antibody conjugates to monitor cell dynamics

Thermoelectric transport with electron-phonon coupling and electron-electron interaction in molecular junctions

Within the framework of nonequilibrium Green's functions, we investigate the thermoelectric transport in a single molecular junction with electron-phonon and electron-electron interactions. By transforming into a displaced phonon basis, we are able to deal with these interactions non-perturbatively. Then, by invoking the weak tunneling limit, we are able to calculate the thermoelectricity. Results show that at low temperatures, resonances of the thermoelectric figure of merit ZT occur around the sides of resonances of electronic conductance but drops dramatically to zero at exactly these resonant points. We find ZT can be enhanced by increasing electron-phonon coupling and Coulomb repulsion, and an optimal enhancement is obtained when these two interactions are competing. Our results indicate a great potential for single-molecular-junctions as good thermoelectric devices over a wide range of temperatures.Comment: 7+ pages, 3 figures, with updated appendix. Accepted by PR

Skewed Steel Bridges, Part II: Cross-Frame and Connection Design to Ensure Brace Effectiveness

Skewed bridges in Kansas are often designed such that the cross-frames are carried parallel to the skew angle up to 40°, while many other states place cross-frames perpendicular to the girder for skew angles greater than 20°. Skewed-parallel cross-frames are longer and require different connections than cross-frames oriented perpendicular to the girder. As cross-frames lengthen, they become less stiff and less effective at distributing forces between girders if the same connecting elements are used. For the cross-frame / diaphragm elements to be able to brace the bridge girders, the brace elements must possess both sufficient strength and stiffness to restrain the girder from instability. While strength can be addressed by increasing the cross-sectional properties of the brace elements, providing sufficient stiffness is a more significant challenge. Stiffness of the brace system is dependent on both the brace elements and the type of connection made (Yura et al. 1992; Yura 2001). Therefore it is important to determine whether the cross-frames and their corresponding connecting elements placed in a parallel-to-skew configuration are sufficiently designed to resist lateral torsional buckling demands using current KDOT practices. The authors have performed a study to investigate the effect of cross-frame orientation, skew angle, and cross-frame connection upon bridge system behavior and cross-frame stresses. In a suite of detailed 3D, solid finite element analyses models of skewed bridge systems, cross-frame layout, connection thickness and type, and skew angle were varied. Skewed bridge systems with cross-frames placed parallel to the skew angle as well as systems with cross-frames arranged in a staggered configuration were considered. Varying bent plate connection thicknesses and a half- pipe connection were also analyzed. Cross-frame spacing of 4.6 m [15 ft] and 9.14 [30 ft] were examined; severe cross-frame spacing of 13.7 m [45 ft] was also considered to examine behavior at very long unbraced lengths. The models include geometric nonlinearities to assess the lateral deflection and lateral flange bending stresses in different bridge systems. Material nonlinearities were found to produce insignificant differences in the results and were not included in the full parametric analysis. The findings of this study showed that skew angle, skew configuration, and connection type all influenced the strength and stiffness of system. The skewed-staggered configuration produced higher lateral deflections in the girders compared to the skewed-parallel configuration. With a couple of exceptions, the skewed-staggered configuration also produced higher cross-frame stresses compared to the skewed-parallel configuration. Larger skew angles resulted in lower lateral deflections. As the skew angles increased, cross-frame compression stresses generally remained the same or increased while maximum cross-frame tension stresses generally decreased. Thicker bent plates produced higher lateral displacements, with the 12.7 mm [1/2 in.] and 25.4 mm [1.0 in.] thick bent plates producing similar lateral displacement values. For skewed configurations, cross-frame stress generally increased with thicker bent plates, with 12.7 mm [1/2 in.] and 25.4 mm [1.0 in.] thick bent plates producing similar cross-frame tension stresses. For the non-skewed configuration, cross-frame stresses decreased with thicker bent plates. The half-pipe connection was shown to correspond with smaller magnitudes of lateral deflections than bent plate connections. Finally, the data showed that cross-frame placed parallel to skew up to an angle of 40° performed similar or better than cross-frames oriented perpendicular to skew for every given skew angle and connection type.The Kansas Department of Transportatio

Skewed Steel Bridges, Part I: Effect of Cross-Frame Layout on Lateral Flange Bending Stresses

Lateral flange bending stresses can arise from a number of sources, such as wind loading or eccentric concrete placement, but of particular interest are lateral flange bending stresses, fl, that occur due to skew. Lateral flange bending stresses that occur in skewed bridge systems tend to develop due to lateral forces transferred through cross-frames which may connect adjacent girders at different span points. In lieu of a refined analysis, the AASHTO-LRFD Bridge Design Specifications currently permit engineers examining bridges skewed more than 20° to use a minimum value of fl = 10 ksi for an interior girder and fl = 7.5 ksi for an exterior girder. The estimates for fl provided within the AASHTO-LRFD Bridge Design Specifications are based on a limited data set for skewed bridges. Additionally, since the AASHTO-LRFD Design Specifications state that cross-frames or diaphragms should be placed in a staggered configuration when a bridge is skewed more than 20°, the approximate values provided for fl should not be expected to be indicative of the lateral flange bending stresses experienced when cross-frames are instead carried parallel to the skew in bridges skewed beyond 20°. Carrying cross-frames and diaphragms parallel to the skew angle in bridges skewed more than 20° is a practice implemented by some state DOTs, and is primarily done to minimize problems with cross-frame fit-up during erection. The authors have performed a study to investigate the effects of cross-frame orientation and skew angle upon lateral flange bending stresses, by examining lateral flange bending stresses in a suite of detailed 3D, solid finite element analyses of skewed bridge systems, in which cross- frame layout, spacing, and skew angle were varied. Skewed bridge systems with cross-frames placed parallel to the skew angle as well as systems with cross-frames arranged in a staggered configuration were considered. The models included both material and geometric nonlinearities to assess the lateral flange bending stresses in the different bridge systems. The findings of this study showed that cross-frames placed parallel to the angle of skew produced significantly lower values for fl than cases in which cross-frames were placed perpendicular to the girder line and staggered. Both reducing the skew angle and decreasing cross-frame spacing were found to reduce lateral flange bending stresses. The values of lateral flange bending stress for all configurations were greater than the bounds of the approximate values suggested by AASHTO. Moreover, the minimum values for fl provided in the AASHTO- LRFD Bridge Design Specifications were found to be significantly lower than the results obtained from this study.The Kansas Department of Transportatio

Recognition of 16–18-year-old adolescents for guiding physical activity interventions: a cross-sectional study

Adolescence is a rapid life stage requiring special attention wherein personal autonomy is developed to govern independent lifestyles. Unhealthy lifestyles are integral to prevailing adolescent physical inactivity patterns. Understudied 16–18-year-olds were investigated to establish physical activity prevalences and influencing health-related lifestyle factors. Adolescents were recruited randomly across 2017–2019 from Farnborough College of Technology and North Kent College, UK. Demographic and health-related lifestyle information were gathered anonymously and analysed using SAS® 9.4 software. Among the 414 adolescents included (48.3% male and 51.7% female), the mean (standard deviation (SD)) age was 16.9 (0.77). Approximately 15.2% smoked and 20.8% were overweight/obese. There were 54.8% perceiving themselves unfit and 33.3% spent >4 h/day on leisure-time screen-based activity. Around 80.4% failed to meet the recommended fruit/vegetable daily intake and 90.1% failed to satisfy UK National Physical Activity Guidelines, particularly females (p = 0.0202). Physical activity levels were significantly associated with gender, body mass index, smoking status, leisure sedentary screen-time, fruit/vegetable consumption and fitness perceptions. Those who were female, overweight/obese, non-smoking, having poor fitness perceptions, consuming low fruit/vegetables and engaging in excess screen-based sedentariness were the groups with lowest physical activity levels. Steering physical activity-oriented health interventions toward these at-risk groups in colleges may reduce the UK’s burden of adolescent obesity

A model for mark size dependence on field emission voltage in heat-assisted magnetic probe recording on CoNi/Pt multilayers

A method of heat-assisted magnetic recording (HAMR) potentially suitable for probe-based storage systems is characterized. In this work, field emission current from a scanning tunneling microscope (STM) tip is used as the heating source. Pulse voltages of 2-7 V with a duration of 500 ns were applied to a CoNi/Pt multilayered film. Different types of Ir/Pt and W STM tips were used in the experiment. The results show that thermally recorded magnetic marks are formed with a nearly uniform mark size of 170 nm when the pulse voltage is above a threshold voltage. The threshold voltage depends on the material work function of the tip, with W having a threshold voltage about 1 V lower than Pt. The emission area of our tip-sample system derived from an analytic expression for field emission current is approximately equal to the mark size, and is largely independent of pulse voltage. This emission area is large compared to lateral heat diffusion in the film. Thus higher applied voltages lead to higher peak temperatures in the model of the write process, but the mark diameter remains relatively unchanged

Dynamic domain motion of thermal-magnetically formed marks on CoNi/Pt multilayers

We characterized a method of heat-assisted magnetic recording, which is potentially suitable for probe-based storage systems. The field emission current from a scanning tunneling microscope tip was used as the heating source. Various pulse voltages were applied to two types of CoNi/Pt multilayered films: one is strongly coupled with low coercivity, and the other is weakly coupled with high coercivity. Experimental results show that marks achieved in strongly coupled medium are larger than that in granular one. An external magnetic field was then applied to those marks. For weak fields (lower than the coercivity of the medium) the size of marks changes distinctly in the strongly coupled medium but not in the granular one. A model of magnetic domain dynamics is built to quantitatively explain the experimental results. It agrees with experiments. Based on this model, we will be able to figure out the proposals to achieve small marks for ultrahigh recording density. © 2006 American Institute of Physics.\ud \u

The role of MFM signal in mark size measurement in probe-based magnetic recording on CoNi/Pt multilayers

A method of heat-assisted magnetic recording (HAMR) potentially suitable for probe-based storage systems is characterized. Magnetic marks were formed by a scanning tunneling microscopy (STM)-based thermal magnetic mechanism on a perpendicular CoNi/Pt multilayered film. Magnetic force microscopy (MFM) was applied to display those marks. The MFM signal is dependent of the lift-height during MFM scanning: smaller lift-height leads to higher resolution of the MFM image and a double-peak signal line, while higher lift-height leads to lower resolution and a single-peak signal line. Theoretical calculation of the magnetic field from the mark was executed. It agrees well with experiments, and demonstrates the method of mark size measurement in perpendicular media: full-width half-maximum (FWHM) of the measured MFM signal. \ud \u

Dihydro­myricetin hexa­acetate

In the title compound, C27H24O14, also known as 2,3-di­acetoxy-5-[(2RS,3RS)-3,5,7-triacetoxy-4-oxochromen-2-yl]phenyl acetate, the heterocyclic ring adopts a distorted half-chair conformation, with two C atoms displaced by 0.1775 (16) and −0.5950 (16) Å from the mean plane of the other four atoms. The dihedral angle between the aromatic rings is 57.81 (8)°. In the crystal, the mol­ecules inter­act by C—H⋯O bonds, aromatic π–π stacking [centroid–centroid separation = 3.6206 (9) Å] and C—H⋯π inter­actions

The effect of external magnetic field on mark size during field emission assisted magnetic probe recording on CoNi/Pt multilayers

In this work, we characterize a heat-assisted magnetic recording process potentially suitable for proposed probe-based storage systems. A scanning tunneling microscope (STM) is used to locally heat a uniformly magnetized perpendicular recording medium via field emission current. The recording medium is a 30 nm thick CoNi/Pt multilayer film (H/sub C/ = 100 kA/m [1.2 kOe], M/sub S/ = 360 kA/m) with a 23 nm thick Pt seedlayer, fabricated on a bare Si substrate. Voltage pulses were applied between STM tip (made of Ir/Pt) and the medium to write marks with external magnetic field applied. A magnetic force microscope (MFM) is used to image marks. Mark size was measured as the FWHM of MFM phase signal. Experimental results show that mark size increases with increasing positive field and decreases with increasing negative field. A model is quantitatively simulate our experimental results and we are able to predict tip and medium configurations and applied powers that should permit marks appropriate for recording at 1 Tbit/in/sup 2/ and beyond