Improved Performance of Organic Thermoelectric Generators Through Interfacial Energetics.

The interfacial energetics are known to play a crucial role in organic diodes, transistors, and sensors. Designing the metal-organic interface has been a tool to optimize the performance of organic (opto)electronic devices, but this is not reported for organic thermoelectrics. In this work, it is demonstrated that the electrical power of organic thermoelectric generators (OTEGs) is also strongly dependent on the metal-organic interfacial energetics. Without changing the thermoelectric figure of merit (ZT) of polythiophene-based conducting polymers, the generated power of an OTEG can vary by three orders of magnitude simply by tuning the work function of the metal contact to reach above 1000 µW cm-2 . The effective Seebeck coefficient (Seff ) of a metal/polymer/metal single leg OTEG includes an interfacial contribution (Vinter /ΔT) in addition to the intrinsic bulk Seebeck coefficient of the polythiophenes, such that Seff  = S + Vinter /ΔT varies from 22.7 µV K-1 [9.4 µV K-1 ] with Al to 50.5 µV K-1 [26.3 µV K-1 ] with Pt for poly(3,4-ethylenedioxythiophene):p-toluenesulfonate [poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)]. Spectroscopic techniques are used to reveal a redox interfacial reaction affecting locally the doping level of the polymer at the vicinity of the metal-organic interface and conclude that the energetics at the metal-polymer interface provides a new strategy to enhance the performance of OTEGs.

An electronic proton-trapping ion pump for selective drug delivery.

The organic electronic ion pump (OEIP) delivers ions and charged drugs from a source electrolyte, through a charge-selective membrane, to a target electrolyte upon an electric bias. OEIPs have successfully delivered γ-aminobutyric acid (GABA), a neurotransmitter that reduces neuronal excitations, in vitro, and in brain tissue to terminate induced epileptic seizures. However, during pumping, protons (H+), which exhibit higher ionic mobility than GABA, are also delivered and may potentially cause side effects due to large local changes in pH. To reduce the proton transfer, we introduced proton traps along the selective channel membrane. The traps are based on palladium (Pd) electrodes, which selectively absorb protons into their structure. The proton-trapping Pd-OEIP improves the overall performance of the current state-of-the-art OEIP, namely, its temporal resolution, efficiency, selectivity, and dosage precision.

Oxygen-induced doping on reduced PEDOT.

The conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) has shown promise as air electrode in renewable energy technologies like metal-air batteries and fuel cells. PEDOT is based on atomic elements of high abundance and is synthesized at low temperature from solution. The mechanism of oxygen reduction reaction (ORR) over chemically polymerized PEDOT:Cl still remains controversial with eventual role of transition metal impurities. However, regardless of the mechanistic route, we here demonstrate yet another key active role of PEDOT in the ORR mechanism. Our study demonstrates the decoupling of conductivity (intrinsic property) from electrocatalysis (as an extrinsic phenomenon) yielding the evidence of doping of the polymer by oxygen during ORR. Hence, the PEDOT electrode is electrochemically reduced (undoped) in the voltage range of ORR regime, but O2 keeps it conducting; ensuring PEDOT to act as an electrode for the ORR. The interaction of oxygen with the polymer electrode is investigated with a battery of spectroscopic techniques.

What's in an EEM? Molecular signatures associated with dissolved organic fluorescence in boreal Canada.

Dissolved organic matter (DOM) is a master variable in aquatic systems. Modern fluorescence techniques couple measurements of excitation emission matrix (EEM) spectra and parallel factor analysis (PARAFAC) to determine fluorescent DOM (FDOM) components and DOM quality. However, the molecular signatures associated with PARAFAC components are poorly defined. In the current study we characterized river water samples from boreal Québec, Canada, using EEM/PARAFAC analysis and ultrahigh resolution mass spectrometry (FTICR-MS). Spearman's correlation of FTICR-MS peak and PARAFAC component relative intensities determined the molecular families associated with 6 PARAFAC components. Molecular families associated with PARAFAC components numbered from 39 to 572 FTICR-MS derived elemental formulas. Detailed molecular properties for each of the classical humic- and protein-like FDOM components are presented. FTICR-MS formulas assigned to PARAFAC components represented 39% of the total number of formulas identified and 59% of total FTICR-MS peak intensities, and included significant numbers compounds that are highly unlikely to fluoresce. Thus, fluorescence measurements offer insight into the biogeochemical cycling of a large proportion of the DOM pool, including a broad suite of unseen molecules that apparently follow the same gradients as FDOM in the environment.

Computational estimation of fluid mechanical benefits from a fluid deflector at the distal end of artificial vascular grafts.

Intimal hyperplasia at the distal anastomosis is considered to be an important determinant for arterial and arteriovenous graft failure. The connection between unhealthy hemodynamics and intimal hyperplasia motivates the use of computational fluid dynamics modeling to search for improved graft design. However, studies on the fluid mechanical impact on intimal hyperplasia at the suture line intrusion have previously been scanty. In the present work, we focus on intimal hyperplasia at the suture line and illustrate potential benefits from the introduction of a fluid deflector to shield the suture line from unhealthily high wall shear stress.

Non-linear inverse scattering: high resolution quantitative breast tissue tomography.

Recent published results in inverse scattering generally show the difficulty in dealing with moderate to high contrast inhomogeneities when employing linearized or iteratively linearized algorithms (e.g., distorted Born iterative method). This paper presents a fully nonlinear algorithm utilizing full wave field data, that results in ultrasound computed tomographic images from a laboratory breast scanner, and shows several such unique images from volunteer subjects. The forward problem, data collection process and inverse scattering algorithm used are discussed. A functional that represents the "best fit" between predicted and measured data is minimized, and therefore requires a very fast forward problem solver, Jacobian calculation, and gradient estimation, all of which are described. The data collection device is described. The algorithm and device yield quantitative estimates of human breast tissue in vivo. Several high resolution images, measuring ∼150 by 150 wavelengths, obtained from the 2D inverse scattering algorithms, using data collected from a first prototype, are shown and discussed. The quantitative values are compared with previous published work.

Lake secondary production fueled by rapid transfer of low molecular weight organic carbon from terrestrial sources to aquatic consumers.

Carbon of terrestrial origin often makes up a significant share of consumer biomass in unproductive lake ecosystems. However, the mechanisms for terrestrial support of lake secondary production are largely unclear. By using a modelling approach, we show that terrestrial export of dissolved labile low molecular weight carbon (LMWC) compounds supported 80% (34-95%), 54% (19-90%) and 23% (7-45%) of the secondary production by bacteria, protozoa and metazoa, respectively, in a 7-km(2) boreal lake (conservative to liberal estimates in brackets). Bacterial growth on LMWC was of similar magnitude as that of primary production (PP), and grazing on bacteria effectively channelled the LMWC carbon to higher trophic levels. We suggest that rapid turnover of forest LMWC pools enables continuous export of fresh photosynthates and other labile metabolites to aquatic systems, and that substantial transfer of LMWC from terrestrial sources to lake consumers can occur within a few days. Sequestration of LMWC of terrestrial origin, thus, helps explain high shares of terrestrial carbon in lake organisms and implies that lake food webs can be closely dependent on recent terrestrial PP.

Evaluation of a fall-prevention program in older people after femoral neck fracture: a one-year follow-up.

UNLABELLED: A randomized, controlled fall-prevention study including 199 patients operated on for femoral neck fracture reduced inpatient falls and injuries. No statistically significant effects of the intervention program could be detected after discharge. It seems that fall-prevention must be part of everyday life in fall-prone old people. INTRODUCTION: This study evaluates whether a postoperative multidisciplinary, multifactorial fall-prevention program performed by a geriatric team that reduced inpatient falls and injuries had any continuing effect after discharge. The intervention consisted of staff education, systematic assessment and treatment of fall risk factors and vitamin D and calcium supplementation. METHODS: The randomized, controlled trial with a one-year follow-up at Umeå University Hospital, Sweden, included 199 patients operated on for femoral neck fracture, aged > or = 70 years. RESULTS: After one year 44 participants had fallen 138 times in the intervention group compared with 55 participants and 191 falls in the control group. The crude postoperative fall incidence was 4.16/1,000 days in the intervention group vs. 6.43/1,000 days in the control group. The incidence rate ratio was 0.64 (95% CI: 0.40-1.02, p = 0.063). Seven new fractures occurred in the intervention group and 11 in the control group. CONCLUSION: A team applying comprehensive geriatric assessment and rehabilitation, including prevention and treatment of fall-risk factors, reduced inpatient falls and injuries, but no statistically significant effects of the program could be detected after discharge. It seems that fall-prevention must be part of everyday life in fall-prone elderly.

Organic materials for printed electronics.

Organic materials can offer a low-cost alternative for printed electronics and flexible displays. However, research in these systems must exploit the differences - via molecular-level control of functionality - compared with inorganic electronics if they are to become commercially viable.

Characterization of the interface dipole at the paraphenylenediamine-nickel interface: a joint theoretical and experimental study.

In organic-based (opto)electronic devices, charge injection into conjugated materials is governed to a large extent by the metal-organic interface dipole. Controlling the injection of charges requires a better understanding of the fundamental origin of the interface dipole. In this context, photoelectron spectroscopies and density functional theory calculations are used to investigate the interaction between para-phenylenediamine (PPDA), an electron donor, and a polycrystalline nickel surface. The interface dipole formed upon chemisorption of one PPDA monolayer strongly modifies the work function of the nickel surface from 5.10 to 3.55 eV. The work function decrease of 1.55 eV is explained by the electron-donor character of PPDA and the modification of the electronic density at the metal surface. PPDA monolayers are composed of tilted molecules interacting via the nitrogen lone-pair and PPDA molecules chemisorbed parallel to the surface via their pi-electron density. Annealing the monolayer leads to dehydrogenation of PPDA activated by the nickel surface, as found for other amines.