Feasibility of a Treatment Protocol for Parkinson's Fatigue Management Using a Cognitive Behavioral Approach.

OBJECTIVES: Fatigue affects half of people with Parkinson's disease, but treatment options remain limited. A treatment protocol was developed for Parkinson's fatigue management. It aims to explore protocol feasibility and effectiveness and inform the design of subsequent larger study. METHODS: People with Parkinson's fatigue (n=10) participated in six weekly meetings. Participant enrollment and retention rate assess program feasibility. Program effectiveness was measured by perceived fatigue, sleep rating and quality of life at week 0, 6, and 12. RESULTS: Participant retention rate was 100%. Attendance mean was 90%. No statistical difference was found in outcome measures. 40% exceeded minimal clinically important difference in fatigue from week 0 to 12. Effect size was medium. CONCLUSIONS: This protocol is feasible. Future studies should address psychosocial factors with interprofessional collaboration.

Arrays of high quality SAM-based junctions and their application in molecular diode based logic.

This paper describes a method to fabricate a microfluidic top-electrode that can be utilized to generate arrays of self-assembled monolayer (SAM)-based junctions. The top-electrodes consist of a liquid-metal of GaOx/EGaIn mechanically stabilized in microchannels and through-holes in polydimethylsiloxane (PDMS); these top-electrodes form molecular junctions by directly placing them onto the SAM supported by template-stripped (TS) Ag or Au bottom-electrodes. Unlike conventional techniques to form multiple junctions, our method does not require lithography to pattern the bottom-electrode and is compatible with TS bottom-electrodes, which are ultra-flat with large grains, free from potential contamination of photoresist residues, and do not have electrode-edges where the molecules are unable to pack well. We formed tunneling junctions with n-alkanethiolate SAMs in yields of ∼80%, with good reproducibility and electrical stability. Temperature dependent J(V) measurements indicated that the mechanism of charge transport across the junction is coherent tunneling. To demonstrate the usefulness of these junctions, we formed molecular diodes based on SAMs with Fc head groups. These junctions rectify currents with a rectification ratio R of 45. These molecular diodes were incorporated in simple electronic circuitry to demonstrate molecular diode-based Boolean logic.

Probing the nature and resistance of the molecule-electrode contact in SAM-based junctions.

It is challenging to quantify the contact resistance and to determine the nature of the molecule-electrode contacts in molecular two-terminal junctions. Here we show that potentiodynamic and temperature dependent impedance measurements give insights into the nature of the SAM-electrode interface and other bottlenecks of charge transport (the capacitance of the SAM (C(SAM)) and the resistance of the SAM (R(SAM))), unlike DC methods, independently of each other. We found that the resistance of the top-electrode-SAM contact for junctions with the form of Ag(TS)-SC(n)//GaO(x)/EGaIn with n = 10, 12, 14, 16 or 18 is bias and temperature independent and hence Ohmic (non-rectifying) in nature, and is orders of magnitude smaller than R(SAM). The C(SAM) and R(SAM) are independent of the temperature, indicating that the mechanism of charge transport in these SAM-based junctions is coherent tunneling and the charge carrier trapping at the interfaces is negligible.

Equivalent circuits of a self-assembled monolayer-based tunnel junction determined by impedance spectroscopy.

The electrical characteristics of molecular tunnel junctions are normally determined by DC methods. Using these methods it is difficult to discriminate the contribution of each component of the junctions, e.g., the molecule-electrode contacts, protective layer (if present), or the SAM, to the electrical characteristics of the junctions. Here we show that frequency-dependent AC measurements, impedance spectroscopy, make it possible to separate the contribution of each component from each other. We studied junctions that consist of self-assembled monolayers (SAMs) of n-alkanethiolates (S(CH2)(n-1)CH3 ≡ SC(n) with n = 8, 10, 12, or 14) of the form Ag(TS)-SC(n)//GaO(x)/EGaIn (a protective thin (~0.7 nm) layer of GaO(x) forms spontaneously on the surface of EGaIn). The impedance data were fitted to an equivalent circuit consisting of a series resistor (R(S), which includes the SAM-electrode contact resistance), the capacitance of the SAM (C(SAM)), and the resistance of the SAM (R(SAM)). A plot of R(SAM) vs n(C) yielded a tunneling decay constant ß of 1.03 ± 0.04 n(C)(-1), which is similar to values determined by DC methods. The value of C(SAM) is similar to previously reported values, and R(S) (2.9-3.6 × 10(-2) Ω·cm(2)) is dominated by the SAM-top contact resistance (and not by the conductive layer of GaO(x)) and independent of n(C). Using the values of R(SAM), we estimated the resistance per molecule r as a function of n(C), which are similar to values obtained by single molecule experiments. Thus, impedance measurements give detailed information regarding the electrical characteristics of the individual components of SAM-based junctions.

Preparation, size control, surface deposition, and catalytic reactivity of hydrophobic corrolazine nanoparticles in an aqueous environment.

Nanoparticles, each consisting of one of the three molecular corrolazine (Cz) compounds, H(3)(TBP(8)Cz), Mn(III)(TBP(8)Cz), and Fe(III)(TBP(8)Cz) (TBP(8)Cz = octakis(4-tert-butylphenyl)corrolazinato), were prepared via a facile mixed-solvent technique. The corrolazine nanoparticles (MCz-NPs) were formed in H(2)O/THF (10:1) in the presence of a small amount of a polyethylene glycol derivative (TEG-ME) added as a stabilizer. This technique allows highly hydrophobic Czs to be "dissolved" in an aqueous environment as nanoparticles, which remain in solution for several months without visible precipitation. The MCz-NPs were characterized by UV-visible spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM) imaging, and shown to be spherical particles from 100-600 nm in diameter with low polydispersity indices (PDI = 0.003-0.261). Particle size is strongly dependent on Cz concentration. The H(3)Cz-NPs were adsorbed on to a modified self-assembled monolayer (SAM) surface and imaged by atomic force microscopy (AFM). Adsorption resulted in disassembly of the larger H(3)Cz-NPs to smaller H(3)Cz-NPs, whereby the resulting particle size can be controlled by the surface energy of the monolayer. The Fe(III)Cz-NPs were shown to be competent catalysts for the oxidation of cyclohexene with either PFIB or H(2)O(2) as external oxidant. The reactivity and product selectivity seen for Fe(III)Cz-NPs differs dramatically from that seen for the molecular species in organic solvents, suggesting that both the nanoparticle structure and the aqueous conditions may contribute to significant changes in the mechanism of action of the Fe(III)Cz catalyst.

Parallel effects of cations on PNIPAM graft wettability and PNIPAM solubility.

Stimuli-responsive surfaces grafted with thermoresponsive polymers switch from hydrophilic to hydrophobic thermally, making these surfaces attractive in applications such as in microfluidics devices, as antifouling surfaces, and in cell culture and tissue engineering. These materials exhibit changes in wettability as the polymer undergoes a phase transition above its lower critical solution temperature (LCST). Because the presence of salts affects LCSTs in accordance to the Hofmeister series, salt effects on the wettability of these thermoresponsive surfaces will dramatically impact device performance. Prior studies of such effects have focused on the influence of anions. Detailed studies of the effects of cations have not been carried out. Here, the influence of varying cation identity in a series of mono-, di-, and trivalent sulfate salts on the wettability of a stimuli-responsive grafted surface was investigated by measuring advancing water contact angle (Theta(a)) changes. The cation-induced changes in Theta(a) were correlated with corresponding changes in surface morphology examined by AFM. The results showed that the effects of varying cations on surface wettability are as large as the effects of varying anion identity and concentration (i.e., Theta(a) changes of up to 90 degrees). Parallel studies of the effects of varying the cation identity and concentration for these same cation sulfate salts in solution show that cation variation also has a large effect on the LCST of PNIPAM, the stimuli responsive polymer component of the nanocomposite grafts that were studied. Moreover, analyses of the Theta(a) and LCST data using activity showed that the Theta(a) or LCST versus cation activity/concentration could be readily grouped by charge. Such differences are not seen in similar studies where anion identity, charge, and concentration are changed.

Designing surfaces with wettability that varies in response to solute identity and concentration.

Surfaces with solute responsive wettability can be prepared by covalent layer-by-layer assembly of PNIPAM-c-PNASI with 10 and 100 nm diameter aminated silica nanoparticles. These surfaces are found to exhibit reversible changes in surface wetting in response to solute anion identity and concentration, allowing surfaces to be switched from hydrophilic (advancing water contact angle 68 degrees ) to hydrophobic (advancing water contact angle 145 degrees ). The extent of the response to solute salts is found to be consistent with the Hofmeister series and with associated changes in surface roughness which result from varying degrees of polymer swelling in response to solute ion identity and concentration. The observed wettability changes on these surfaces are reversible.

Superhydrophobic surfaces formed using layer-by-layer self-assembly with aminated multiwall carbon nanotubes.

A convenient and simple route to functionalized multiwall carbon nanotubes (MWNTs) using the reaction of the amine (NH) groups of polyethyleneimine (PEI) with MWNTs in N,N-dimethylformamide (DMF) at 50 degrees C is described. The product functionalized MWNTs (MWNT-NH-PEI) contain 6-8% by weight PEI based on elemental analysis, thermal gravimetric analysis, and titration. The products form stable emulsions in water below pH 9 and can be derivatized to form alkylated MWNTs that are dispersible in organic media. Such MWNT-NH-PEI nanoparticles can also be used in covalent or ionic layer-by-layer assembly to form nanocomposite thin films on functionalized polyethylene (PE) films and powders. Such nanocomposite films were analyzed by contact angle analysis, atomic force microscopy (AFM), and confocal Raman microscopy. These analyses show that these superhydrophilic surfaces have micro/nanoroughness with a roughly uniform distribution of MWNT nanoparticles. Superhydrophobic PE films can be formed either from ionic layer-by-layer self-assembly of MWNT-NH-PEIs and poly(acrylic acid) or from covalent layer-by-layer self-assembly of MWNT-NH-PEIs and Gantrez if the final graft is acrylated with a mixed anhydride prepared from ethyl chloroformate and octadecanoic acid. The resulting octadecylated surface produced by five covalent layer-by-layer deposition steps has a water contact angle of 165 degrees and a sliding angle of less than 5 degrees. The corresponding surface produced by five ionic layer-by-layer deposition steps has a water contact angle of 155 degrees but exhibits water pinning. The ionically assembled nanocomposite graft is labile under acidic conditions. The covalently assembled graft is more chemically robust.