120 research outputs found
Beyond the Linearity of Current-Voltage Characteristics in Multiwalled Carbon Nanotubes
We present local and non-local electron transport measurements on individual
multi-wall nanotubes for bias voltage between 0 and about 4 V. Local
current-voltage characteristics are quite linear. In contrast, non-local
measurements are highly non-linear; the differential non-local conductance can
even become negative in the high-bias regime. We discuss the relationship
between these results and transport parameters such as the elastic length, the
number of current carrying shells, and the number of conducting modes.Comment: 5 pages, 5 figure
Determination of the Intershell Conductance in Multiwalled Carbon Nanotubes
We report on the intershell electron transport in multiwalled carbon
nanotubes (MWNT). To do this, local and nonlocal four-point measurements are
used to study the current path through the different shells of a MWNT. For
short electrode separations 1 m the current mainly flows
through the two outer shells, described by a resistive transmission line with
an intershell conductance per length of ~(10 k\Omega)^{-1}/m. The
intershell transport is tunnel-type and the transmission is consistent with the
estimate based on the overlap between -orbitals of neighboring shells.Comment: 5 pages, 4 figure
Geometrical Dependence of High-Bias Current in Multiwalled Carbon Nanotubes
We have studied the high-bias transport properties of the different shells
that constitute a multiwalled carbon nanotube. The current is shown to be
reduced as the shell diameter is decreased or the length is increased. We
assign this geometrical dependence to the competition between electron-phonon
scattering process and Zener tunneling.Comment: 4 pages, 4 figure
Ab Initio Calculations of the Walls Shear Strength of Carbon Nanotubes
The dependence of the energy of interwall interaction in double-walled carbon
nanotubes (DWNT) on the relative position of walls has been calculated using
the density functional method. This dependence is used to evaluate forces that
are necessary for the relative telescopic motion of walls and to calculate the
shear strength of DWNT for the relative sliding of walls along the nanotube
axis and for their relative rotation about this axis. The possibility of
experimental verification of the obtained results is discussed.Comment: 4 pages, 1 figur
Nanomechanical Properties and Phase Transitions in a Double-Walled (5,5)@(10,10) Carbon Nanotube: ab initio Calculations
The structure and elastic properties of (5,5) and (10,10) nanotubes, as well
as barriers for relative rotation of the walls and their relative sliding along
the axis in a double-walled (5,5)@(10,10) carbon nanotube, are calculated using
the density functional method. The results of these calculations are the basis
for estimating the following physical quantities: shear strengths and diffusion
coefficients for relative sliding along the axis and rotation of the walls, as
well as frequencies of relative rotational and translational oscillations of
the walls. The commensurability-incommensurability phase transition is
analyzed. The length of the incommensurability defect is estimated on the basis
of ab initio calculations. It is proposed that (5,5)@(10,10) double-walled
carbon nanotube be used as a plain bearing. The possibility of experimental
verification of the results is discussed.Comment: 14 page
Evaluation of drug administration errors in a teaching hospital
<p>Abstract</p> <p>Background</p> <p>Medication errors can occur at any of the three steps of the medication use process: prescribing, dispensing and administration. We aimed to determine the incidence, type and clinical importance of drug administration errors and to identify risk factors.</p> <p>Methods</p> <p>Prospective study based on disguised observation technique in four wards in a teaching hospital in Paris, France (800 beds). A pharmacist accompanied nurses and witnessed the preparation and administration of drugs to all patients during the three drug rounds on each of six days per ward. Main outcomes were number, type and clinical importance of errors and associated risk factors. Drug administration error rate was calculated with and without wrong time errors. Relationship between the occurrence of errors and potential risk factors were investigated using logistic regression models with random effects.</p> <p>Results</p> <p>Twenty-eight nurses caring for 108 patients were observed. Among 1501 opportunities for error, 415 administrations (430 errors) with one or more errors were detected (27.6%). There were 312 wrong time errors, ten simultaneously with another type of error, resulting in an error rate without wrong time error of 7.5% (113/1501). The most frequently administered drugs were the cardiovascular drugs (425/1501, 28.3%). The highest risks of error in a drug administration were for dermatological drugs. No potentially life-threatening errors were witnessed and 6% of errors were classified as having a serious or significant impact on patients (mainly omission). In multivariate analysis, the occurrence of errors was associated with drug administration route, drug classification (ATC) and the number of patient under the nurse's care.</p> <p>Conclusion</p> <p>Medication administration errors are frequent. The identification of its determinants helps to undertake designed interventions.</p
Hindered rolling and friction anisotropy in supported carbon nanotubes
Carbon nanotubes (CNTs) are well known for their exceptional thermal,
mechanical and electrical properties. For many CNT applications it is of the
foremost importance to know their frictional properties. However, very little
is known about the frictional forces between an individual nanotube and a
substrate or tip. Here, we present a combined theoretical and experimental
study of the frictional forces encountered by a nanosize tip sliding on top of
a supported multiwall CNT along a direction parallel or transverse to the CNT
axis. Surprisingly, we find a higher friction coefficient in the transverse
direction compared with the parallel direction. This behaviour is explained by
a simulation showing that transverse friction elicits a soft 'hindered rolling'
of the tube and a frictional dissipation that is absent, or partially absent
for chiral CNTs, when the tip slides parallel to the CNT axis. Our findings can
help in developing better strategies for large-scale CNT assembling and sorting
on a surface.Comment: 8 pages, 5 figure
Overview and characterization of penile cancer content across social media platforms
BackgroundSocial media platforms (SMP) are an emerging resource that allows physicians, patients, and families to converse on cancer prevention, diagnosis, and treatment. We aimed to characterize penile cancer (PC) content shared on SMP.MethodsWe searched PC posts on Twitter, Facebook, and Instagram from July 1st, 2021, through June 30th, 2022. Two independent, blinded reviewers analyzed the hashtags: #PenileCancer, #PenileCancerAwareness, and #PenileNeoplasm. Descriptive statistics were used for posts characterization, Pearson´s correlation coefficient for associations, and Cohen’s weighted kappa coefficient for inter-rater agreement rate.ResultsA total of 791 posts were analyzed, with Twitter accounting for 52%, Facebook for 12.2%, and Instagram for 35.5%, and. Most posts originated from high-income countries, such as the United Kingdom (48.8%). We found no correlation between the number of posts with PC incidence (p = 0.64) or users on SMP (p = 0.27). Most accounts were classified as “support and awareness communities” (43.6%) and “physicians and clinical researchers” (38.2%). Urology was the most common medical specialty to post (60.9%), followed by oncology (11.3%). Most posts were classified as “prevention and awareness for users” (45.1%). Global inter-reviewer agreement rate was almost perfect (k=0.95; p ≤ 0.01). On Twitter, “physicians and clinical researchers” shared more content on “treatment updates and medical papers published in medical journals,” while on Facebook and Instagram, “support and awareness communities” focused on “personal and support comments.”ConclusionOverall, the number of PC posts was low compared to other neoplasms across the SMP evaluated in this study. “Physicians and clinical researchers” shared more content on Twitter, while “support and awareness communities” on Facebook and Instagram. Encouraging the use of a common SMP among the medical community and general users could lead to a more effective communication between physicians, patients, and support groups, and to increased awareness of PC
Graphene Transistor as a Probe for Streaming Potential
We explore the dependence of electrical transport in a graphene field effect
transistor (GraFET) on the flow of the liquid within the immediate vicinity of
that transistor. We find large and reproducible shifts in the charge neutrality
point of GraFETs that are dependent on the fluid velocity and the ionic
concentration. We show that these shifts are consistent with the variation of
the local electrochemical potential of the liquid next to graphene that are
caused by the fluid flow (streaming potential). Furthermore, we utilize the
sensitivity of electrical transport in GraFETs to the parameters of the fluid
flow to demonstrate graphene-based mass flow and ionic concentration sensing.
We successfully detect a flow as small as~70nL/min, and detect a change in the
ionic concentration as small as ~40nM.Comment: 6 pages, 4 figure
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